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Sample records for intermolecular systems formed

  1. Thermodynamics of systems with different geometric constraints and intermolecular correlations.

    PubMed

    Chen, Y; Kilburg, R R; Donohue, M D

    2009-09-17

    Four types of systems with different degrees of geometric constraint and intermolecular correlations were studied to determine the differences in their thermodynamics. The average configurational internal energies of these systems were calculated using Monte Carlo simulations, and the results are compared at the same temperatures and constant average bulk density. From the energy profiles for the four systems, the effects of geometry and intermolecular correlations on the systems' phase behavior are discussed. It was observed that indirect intermolecular correlations, rather than geometric constraints, are the key to achieving a first-order phase transition.

  2. Investigations of Diffuse Intermolecular Electronic Systems

    NASA Astrophysics Data System (ADS)

    Muguet, Francis Fabien Michel

    1992-01-01

    Diffuse intermolecular electronic systems, such as the hydrated electron or the ammonia and water dimers, present both a theoretical and a practical computational challenge. The hydrated electron was discovered more than 25 years ago, yet there is still no consensus on an explanation of this phenomenon. A novel model is presented here, whereby the hydrated electron consists in an itinerant diHydronium radical structure. Although electrostatically neutral, the itinerant radical is shown to behave as a negative charge carrier under the influence of an electric field. Within this perspective, the hydrated electron may be considered a quasiparticle. Contrary to the absence of agreement between many experiments and the old but still popular cavity model description, the energetics in the new model are shown to be consistent with photophysical experimental data. In order to understand negatively charged water clusters, it is also proposed that a metastable bifurcated water dimer structure is able to bind an extra electron. Prior to our studies, no ab initio computations had been able to reproduce the experimental geometry of the ammonia dimer or to predict any water dimer anion with the Franck-Condon factors agreeing with those recently found in molecular beam experiments. In both cases the potential energy surface is determined by attractors corresponding to nonlinear and linear hydrogen bonded geometries, respectively. One attractor receives an unfair advantage in the computational procedure mainly because of the basis set superposition error (BSSE). There is still no agreement on a scheme for correcting the BSSE. A widely employed error estimation method is the counterpoise correction. A completely different new method is proposed using reorthonormalization of purified localized molecular orbitals. In terms of a BSSE corrected potential energy surface of the water dimer, a multi-attractor model of liquid water is briefly discussed. For further water molecular dynamics

  3. Inter-molecular crosslinking activity is engendered by the dimeric form of transglutaminase 2.

    PubMed

    Kim, Nayeon; Lee, Won-Kyu; Lee, Seon-Hyeong; Jin, Kyeong Sik; Kim, Kyung-Hee; Lee, Younho; Song, Minsoo; Kim, Soo-Youl

    2017-03-01

    Transglutaminase 2 (TGase 2) catalyzes a crosslink between protein bound-glutamine and -lysine. We proposed the mechanism of TGase 2 activation depends on conformation change from unfolded monomer to unfolded dimer. We found that TGase 2 has temperature-sensitive conformation change system at 30 °C. Small-angle X-ray scattering analysis showed that the enzyme was maintained as an unfolded monomer at temperatures below 30 °C, but changed to an unfolded dimer at over 30 °C. Mass analysis revealed that the C-terminus of TGase 2 was the critical region for dimerization. Furthermore, this conformational switch creates new biochemical reactivity that catalyzed inter-molecular crosslink at above 30 °C as an unfolded dimer of TGase 2 while catalyzed intra-molecular crosslink at below 30 °C as an unfolded monomer of TGase 2. The mechanism of TGase 2 activation depends on temperature-sensitive conformation change from unfolded monomer to unfolded dimer at over 30 °C. Furthermore, inter-molecular crosslinking activity is generated by the dimeric form of TGase 2. TGase 2 switches its conformation from a monomer to a dimer following a change in temperature, which engendered unique catalytic function of enzyme as inter-molecular crosslinking activity with calcium.

  4. Glass-Forming Tendency of Molecular Liquids and the Strength of the Intermolecular Attractions

    NASA Astrophysics Data System (ADS)

    Koperwas, Kajetan; Adrjanowicz, Karolina; Wojnarowska, Zaneta; Jedrzejowska, Agnieszka; Knapik, Justyna; Paluch, Marian

    2016-11-01

    When we cool down a liquid below the melting temperature, it can either crystallize or become supercooled, and then form a disordered solid called glass. Understanding what makes a liquid to crystallize readily in one case and form a stable glass in another is a fundamental problem in science and technology. Here we show that the crystallization/glass-forming tendencies of the molecular liquids might be correlated with the strength of the intermolecular attractions, as determined from the combined experimental and computer simulation studies. We use van der Waals bonded propylene carbonate and its less polar structural analog 3-methyl-cyclopentanone to show that the enhancement of the dipole-dipole forces brings about the better glass-forming ability of the sample when cooling from the melt. Our finding was rationalized by the mismatch between the optimal temperature range for the nucleation and crystal growth, as obtained for a modeled Lennard-Jones system with explicitly enhanced or weakened attractive part of the intermolecular 6–12 potential.

  5. Glass-Forming Tendency of Molecular Liquids and the Strength of the Intermolecular Attractions

    PubMed Central

    Koperwas, Kajetan; Adrjanowicz, Karolina; Wojnarowska, Zaneta; Jedrzejowska, Agnieszka; Knapik, Justyna; Paluch, Marian

    2016-01-01

    When we cool down a liquid below the melting temperature, it can either crystallize or become supercooled, and then form a disordered solid called glass. Understanding what makes a liquid to crystallize readily in one case and form a stable glass in another is a fundamental problem in science and technology. Here we show that the crystallization/glass-forming tendencies of the molecular liquids might be correlated with the strength of the intermolecular attractions, as determined from the combined experimental and computer simulation studies. We use van der Waals bonded propylene carbonate and its less polar structural analog 3-methyl-cyclopentanone to show that the enhancement of the dipole-dipole forces brings about the better glass-forming ability of the sample when cooling from the melt. Our finding was rationalized by the mismatch between the optimal temperature range for the nucleation and crystal growth, as obtained for a modeled Lennard-Jones system with explicitly enhanced or weakened attractive part of the intermolecular 6–12 potential. PMID:27883011

  6. Rattusin structure reveals a novel defensin scaffold formed by intermolecular disulfide exchanges

    PubMed Central

    Min, Hye Jung; Yun, Hyosuk; Ji, Sehyeon; Rajasekaran, Ganesan; Kim, Jae Il; Kim, Jeong-Sun; Shin, Song Yub; Lee, Chul Won

    2017-01-01

    Defensin peptides are essential for innate immunity in humans and other living systems, as they provide protection against infectious pathogens and regulate the immune response. Here, we report the solution structure of rattusin (RTSN), an α-defensin-related peptide, which revealed a novel C2-symmetric disulfide-linked dimeric structure. RTSN was synthesized by solid-phase peptide synthesis (SPPS) and refolded by air oxidation in vitro. Dimerization of the refolded RTSN (r-RTSN) resulted from five intermolecular disulfide (SS) bond exchanges formed by ten cysteines within two protomer chains. The SS bond pairings of r-RTSN were determined by mass analysis of peptide fragments cleaved by trypsin digestion. In addition to mass analysis, nuclear magnetic resonance (NMR) experiments for a C15S mutant and r-RTSN confirmed that the intermolecular SS bond structure of r-RTSN showed an I-V’, II-IV’, III-III’, IV-II’, V-I’ arrangement. The overall structure of r-RTSN exhibited a cylindrical array, similar to that of β-sandwich folds, with a highly basic surface. Furthermore, fluorescence spectroscopy results suggest that r-RTSN exerts bactericidal activity by damaging membrane integrity. Collectively, these results provide a novel structural scaffold for designing highly potent peptide-based antibiotics suitable for use under various physiological conditions. PMID:28345637

  7. Evaluation of intermolecular forces in a circulating system.

    PubMed

    Guo, Qiuquan; Liu, Mei; Yang, Jun

    2011-11-01

    Intercellular interactions, which are mediated by a variety of complex intercellular molecules through the processes of formation and dissociation of molecular bonds, play a critical role in regulating cellular functions in biological systems. Various approaches are applied to evaluate intercellular or molecular bonding forces. To quantify the intermolecular interaction forces, flow chamber has become a meaningful technique as it can ultimately mimic the cellular microenvironment in vivo under physiological flow conditions. Hydrodynamic forces are usually used to predict the intercellular forces down to the single molecular level. However, results show that only using hydrodynamic force will overestimate up to 30% of the receptor-ligand strength when the non-specific forces such as Derjaguin-Landau-Verway-Overbeek (DLVO) forces become un-neglected. Due to the nature of high ion concentration in the physiological condition, electrostatic force is largely screened which will cause DLVO force unbalanced. In this study, we propose to take account of the DLVO force, including van der Waals (VDW) force and electrostatic force, to predict the intermolecular forces of a cell doublet and cell-substrate model in a circulating system. Results also show that the DLVO force has a nonlinear effect as the cell-cell or cell-substrate distance changes. In addition, we used the framework of high accuracy hydrodynamic theories proved in colloidal systems. It is concluded that DLVO force could not be ignored in quantitative studies of molecular interaction forces in circulating system. More accurate prediction of intercellular forces needs to take account of both hydrodynamic force and DLVO force. Copyright © 2011 Elsevier Ireland Ltd. All rights reserved.

  8. Electronic Structure Theory for Radicaloid Systems and Intermolecular Interactions

    NASA Astrophysics Data System (ADS)

    Kurlancheek, Westin

    associated with unrestriction. Second, the relaxed density matrix itself fails to be N-representable, with natural orbital occupation numbers less than zero and greater than one. Therefore, it is desirable to use a method that is not dependent on the inverse of the Hessian like orbital optimized MP2 (O2). Another system which requires the use of orbital optimization is a neutral soliton on a polyacetylene chain. In this system, the Hartree-Fock reference suffers from severe spin-polarization making the wavefunction physically unreasonable unless a very sophisticated treatment of electron correlation is used to correct this problem. Originally, it was found that computationally expensive methods like CCSD(T) and CASSCF could adequately describe small model chain but not the full system. The O2 method is found to be an dramatic improvement over traditional MP2 which can be feasibly applied to polyenyl chains long enough to characterize the soliton. It is also discovered that density functionals are generally inadequate in describing the half-width of the soliton. Finally, the last chapter takes a slightly different perspective and focuses on the addition of correlation energy to a successful energy decomposition analysis based on absolutely localized molecular orbitals. It is discovered that the resulting new method can adequately describe systems with dispersive intermolecular interactions and large amounts of charge transfer. This scheme is then applied to the water dimer systems and it is found that all of the intermolecular interactions similar in size with the electrostatic interaction being the largest and the dispersive interaction being the smallest. This method is also contrasted with other EDA schemes.

  9. Preparation and characterisation of novel chlorothiazide potassium solid-state salt forms: Intermolecular self assembly suprastructures.

    PubMed

    Paluch, Krzysztof J; Tajber, Lidia; McCabe, Thomas; O'Brien, John E; Corrigan, Owen I; Healy, Anne Marie

    2011-02-14

    Chlorothiazide (CTZ) is a poorly soluble diuretic agent. The aim of the present work was to produce and characterise a potassium salt form of chlorothiazide which has the potential advantages of improved aqueous solubility and potassium supplementation. A number of novel potassium salt forms of CTZ (CTZK) were prepared: CTZK monohydrate (form I), CTZK dihydrate (form II), anhydrous CTZK (form III), CTZK monohydrate hemiethanolate (form IV) and a desolvate of CTZK monohydrate hemiethanolate (form V). These salt forms were characterised by thermal analysis, PXRD, NMR, elemental analysis, FTIR, Karl Fisher titrimetry, ICP-MS and GC-MS. The ethanol-free CTZK forms were also characterised by dynamic vapour sorption analysis (DVS). CTZK form I was stable (in the DVS) over the range 0-60% RH. The dihydrate form of the salt was stable (in the DVS) over a broader range of relative humidities, 10-90% RH at 25°C. CTZK form II was less hygroscopic at high humidities (70-90% RH) than the previously reported CTZNa dihydrate. Single crystal X-ray analysis indicated that chlorothiazide potassium, crystallised from water or water/acetone mixture, formed a dihydrated polymeric-like intermolecular self-assembly (ISA) suprastructure. The ISA coordination was determined to be: (CTZ)(3)·K·(H(2)O)(2)(CTZ)(2)·(H(2)O)(2)·K·(CTZ)(3) (monoclinic, space group: C2/c, single crystal cell parameters: a=18.328(4)Å, b=7.3662(16)Å, c=19.993(5)Å, α=90°, β=99.729(3)°, γ=90°). When CTZK was crystallised from ethanol, a monohydrate hemiethanolate ISA was formed, described as (CTZ)(3)·K·CTZ·(H(2)O)(2)·CTZ·K·(CTZ)(2) (triclinic, space group: P-1, single crystal cell parameters: a=7.078(3)Å, b=9.842(5)Å, c=21.994(11)Å, α=87.522(13)°, β=84.064(14)°, γ=78.822(12)°). The aqueous solubility of CTZK dihydrate, was determined to be 78.71±1.82mg/ml, approximately 400-fold higher than chlorothiazide, indicating a biopharmaceutical advantage associated with the potassium salt

  10. Development of a flexible intra- and intermolecular empirical potential function for large molecular systems

    SciTech Connect

    Oie, T.; Maggiora, M.; Christoffersen, R.E.; Duchamp, D.J.

    1981-01-01

    The development of a flexible intra- and intermolecular empirical potential function is described, which is designed for investigating the geometric structure of large molecular systems. The intramolecular components in the potential consist of harmonic bond stretching and angle bending terms, out-of-plane deformation terms, and torsional terms; intermolecular components include nonbonding, hydrogen bonding, and electrostatic germs. Bond lengths, angles, and torsional angles are predicted to within 2% of experiment, with most cases being within 1%. The suitability of the intermolecular potential was tested by crystal packing calculations; in all cases the results obtained were in excellent agreement with experiment.

  11. Intermolecular interactions and solvent diffusion in ordered nanostructures formed by self-assembly of block copolymers

    NASA Astrophysics Data System (ADS)

    Gu, Zhiyong

    Hydrogels formed by Poloxamer poly(ethylene oxide)-poly(propylene oxide) (PEO-PPO) block copolymers find various pharmaceutical and biomedical applications. A variety of ordered structures can be exhibited by Poloxamer block copolymers in selective solvents such as water, for example, micellar cubic phase, hexagonal phase, lamellar phase, etc. We are interested in the thermodynamic and transport properties of water in such hydrogels that have an ordered (lyotropic liquid crystalline) structure. We have investigated the time evolution of water loss from Poloxamer gel films under a driving force of known water vapor pressure in the air in contact with the film. The experimental data on the drying process have been fitted to the diffusion equation for water in the film, under a boundary condition that includes the water concentration in the gel at infinite time; the water diffusion coefficient and other parameters have thus been obtained. The water chemical potential and osmotic pressure in the gel have been obtained from osmotic stress measurements. The osmotic pressure (force), together with data on the corresponding lyotropic liquid crystal spacing (distance) that we obtained from Small Angle X-Ray Scattering (SAXS) measurements, have been analyzed to provide information on the prevailing intermolecular (inter-assembly) forces in the gel. The forces in the gel reveal interactions that occur at two levels, that of the PEO coil and that of the PEO segment.

  12. Crystallographic Structure, Intermolecular Packing Energetics, Crystal Morphology and Surface Chemistry of Salmeterol Xinafoate (Form I).

    PubMed

    Moldovan, Alexandru A; Rosbottom, Ian; Ramachandran, Vasuki; Pask, Christopher M; Olomukhoro, Oboroghene; Roberts, Kevin J

    2017-03-01

    Single crystals of salmeterol xinafoate (form I), prepared from slow cooled supersaturated propan-2-ol solutions, crystallize in a triclinic P1¯ symmetry with 2 closely related independent salt pairs within the asymmetric unit, with an approximately double-unit cell volume compared with the previously published crystal structure. Synthonic analysis of the bulk intermolecular packing confirms the similarity in packing energetics between the 2 salt pairs. The strongest synthons, as expected, are dominated by coulombic interactions. Morphologic prediction reveals a plate-like morphology, dominated by the {001}, {010}, and {100} surfaces, consistent with experimentally grown crystals. Although surface chemistry of the slow-growing {001} face comprises large sterically hindering phenyl groups, although weaker coulombic interactions still prevail from the alcohol group present on the phenyl and hydroxymethyl groups. The surface chemistry of the faster growing {010} and {100} faces are dominated by the significantly stronger cation/anion interactions occurring between the carboxylate and protonated secondary ammonium ion groups. The importance of understanding the cohesive and adhesive nature of the crystal surfaces of an active pharmaceutical ingredient, with respect to their interaction with other active pharmaceutical ingredient crystals and how that may affect formulation design, is highlighted.

  13. Dielectric spectroscopy investigation of ion-containing and intermolecular hydrogen-bonded polymer systems

    NASA Astrophysics Data System (ADS)

    Atorngitjawat, Pornpen

    Ion-containing and intermolecular hydrogen-bonded polymers are used widely in a variety of industrial and commercial applications, from food packaging to battery electrolytes to pharmaceuticals. Yet the dynamics of these polymers, which are both complex and important to the application, are poorly understood. This thesis provides the first systematic study of the dynamics of several ion-containing and intermolecular hydrogen-bonded polymers by broadband dielectric relaxation spectroscopy. The systems under consideration include sulfonated polystyrene (SPS) in acid (SPS-H) and neutralized forms, and mixtures of poly(2-vinylpyridine) (P2VPy) with lithium perchlorate (LiClO4) and low molecular weight phenolic molecules. Dynamic mechanical analysis, Fourier transform infrared spectroscopy, differential scanning calorimetry, small-angle X-ray scattering and wide-angle X-ray diffraction were employed in a complementary role. Multiple relaxations were generally observed at high temperatures. For SPS ionomers, the segmental process, Maxwell-Wagner-Sillars interfacial polarization, and electrode polarization were detected. Three relaxations were also found in spectra of SPS-H, attributed to the segmental process, hydrogen bond association/dissociation, and electrode polarization. Three dielectric relaxations above the segmental process were observed for P2VPy-LiClO4 mixtures: ion-mode relaxation, slow hindered segmental relaxation and electrode polarization. However, only electrode polarization was observed above the segmental relaxation for all P2VPy--small phenolic molecule mixtures, except P2VPy + 10 mol% 2,3,3,4,4,5-hexahydroxybenzophenone. This mixture exhibited an additional relaxation due to Maxwell-Wagner-Sillars interfacial polarization, arising from the existence of phase-separated complexes within the P2VPy matrix. Sub-Tg local relaxations were suppressed by ionic intermolecular interactions for SPS ionomers and P2VPy-LiClO4 mixtures. Intermolecular hydrogen

  14. a General Transformation to Canonical Form for Potentials in Pairwise Intermolecular Interactions

    NASA Astrophysics Data System (ADS)

    Walton, Jay R.; Rivera-Rivera, Luis A.; Lucchese, Robert R.; Bevan, John W.

    2015-06-01

    A generalized formulation of explicit transformations is introduced to investigate the concept of a canonical potential in both fundamental chemical and intermolecular bonding. Different classes of representative ground electronic state pairwise interatomic interactions are referenced to a single canonical potential illustrating application of explicit transformations. Specifically, accurately determined potentials of the diatomic molecules H_2, H_2^+, HF, LiH, argon dimer, and one-dimensional dissociative coordinates in Ar-HBr, OC-HF, and OC-Cl_2 are investigated throughout their bound potentials. The advantages of the current formulation for accurately evaluating equilibrium dissociation energies and a fundamentally different unified perspective on nature of intermolecular interactions will be emphasized. In particular, this canonical approach has relevance to previous assertions that there is no very fundamental distinction between van der Waals bonding and covalent bonding or for that matter hydrogen and halogen bonds.

  15. Permutationally invariant fitting of intermolecular potential energy surfaces: A case study of the Ne-C2H2 system

    NASA Astrophysics Data System (ADS)

    Li, Jun; Guo, Hua

    2015-12-01

    The permutation invariant polynomial-neural network (PIP-NN) approach is extended to fit intermolecular potential energy surfaces (PESs). Specifically, three PESs were constructed for the Ne-C2H2 system. PES1 is a full nine-dimensional PIP-NN PES directly fitted to ˜42 000 ab initio points calculated at the level of CCSD(T)-F12a/cc-pCVTZ-F12, while the other two consist of the six-dimensional PES for C2H2 [H. Han, A. Li, and H. Guo, J. Chem. Phys. 141, 244312 (2014)] and an intermolecular PES represented in either the PIP (PES2) or PIP-NN (PES3) form. The comparison of fitting errors and their distributions, one-dimensional cuts and two-dimensional contour plots of the PESs, as well as classical trajectory collisional energy transfer dynamics calculations shows that the three PESs are very similar. We conclude that full-dimensional PESs for non-covalent interacting molecular systems can be constructed efficiently and accurately by the PIP-NN approach for both the constituent molecules and intermolecular parts.

  16. Thermal diffusion factors and intermolecular potentials for noble gas-SF sub 6 systems

    SciTech Connect

    Taylor, W.L.; Hurly, J.J. Cincinnati Univ., OH . Dept. of Chemistry)

    1990-01-01

    Experimental thermal diffusion factors for equimolar mixtures of He-, Ne-, Ar-, Kr-, and Xe-SF{sub 6} have been measured in the temperature range from 225 to 500 K. The data were obtained in a 20-tube trennschaukel, or swing separator.'' The systems containing the four lighter noble gases all exhibited a normal'' thermal diffusion factor, {alpha}{sub T}, that is concentration of the heavy species, SF{sub 6}, in the cold region of the apparatus and increase of {alpha}{sub T} with temperature. Xe-SF{sub 6}, the system with the smallest mass difference, exhibited abnormal'' behavior. The spherically symmetric Pack potentials were used to calculate the thermal diffusion factor with reasonable success. Recently published dipole-dipole dispersion coefficients were used to construct intermolecular potentials of the Hartree-Fock-Dispersion functional form with individually damped attractive terms. The potentials, when tested against the available transport and thermodynamic data, improved the fit to experiment in almost all cases. 35 refs., 7 figs., 2 tabs.

  17. Pharmaceutical cocrystals, salts and multicomponent systems; intermolecular interactions and property based design.

    PubMed

    Berry, David J; Steed, Jonathan W

    2017-03-23

    As small molecule drugs become harder to develop and less cost effective for patient use, efficient strategies for their property improvement become increasingly important to global health initiatives. Improvements in the physical properties of Active Pharmaceutical Ingredients (APIs), without changes in the covalent chemistry, have long been possible through the application of binary component solids. This was first achieved through the use of pharmaceutical salts, within the last 10-15years with cocrystals and more recently coamorphous systems have also been consciously applied to this problem. In order to rationally discover the best multicomponent phase for drug development, intermolecular interactions need to be considered at all stages of the process. This review highlights the current thinking in this area and the state of the art in: pharmaceutical multicomponent phase design, the intermolecular interactions in these phases, the implications of these interactions on the material properties and the pharmacokinetics in a patient.

  18. New openings for porous systems research from intermolecular double-quantum NMR.

    PubMed

    Capuani, S; Alesiani, M; Branca, R T; Maraviglia, B

    2004-01-01

    It has been recently recognized that residual intermolecular double-quantum coherences (iDQcs) provide a novel contrast mechanism to study heterogeneity in liquid systems. This is of much interest in the field of the physics of matter and biomedicine. Nowadays, literature concerning the behaviour of the iDQc signal originated by highly heterogeneous systems such as fluids in porous media is scarce. In this paper, we report and discuss our principal results about iDQc signal behaviour in confined liquid systems (trabecular bone, travertine, porous standard systems) and also some new results obtained on doped water in glass capillary pipes.

  19. A functional fragment of Tau forms fibers without the need for an intermolecular cysteine bridge

    SciTech Connect

    Huvent, Isabelle; Kamah, Amina; Cantrelle, François-Xavier; Barois, Nicolas; Slomianny, Christian; Smet-Nocca, Caroline; Landrieu, Isabelle; Lippens, Guy

    2014-03-07

    Highlights: • A functional fragment of Tau forms bundled ribbon-like fibrils. • Nucleation of its fibril formation is faster than for full-length Tau. • In contrast to full-length Tau, without cysteines, the fragment still forms fibers. - Abstract: We study the aggregation of a fragment of the neuronal protein Tau that contains part of the proline rich domain and of the microtubule binding repeats. When incubated at 37 °C with heparin, the fragment readily forms fibers as witnessed by Thioflavin T fluorescence. Electron microscopy and NMR spectroscopy show bundled ribbon like structures with most residues rigidly incorporated in the fibril. Without its cysteines, this fragment still forms fibers of a similar morphology, but with lesser Thioflavin T binding sites and more mobility for the C-terminal residues.

  20. Copper(I)-catalyzed aryl bromides to form intermolecular and intramolecular carbon-oxygen bonds.

    PubMed

    Niu, Jiajia; Guo, Pengran; Kang, Juntao; Li, Zhigang; Xu, Jingwei; Hu, Shaojing

    2009-07-17

    A highly efficient Cu-catalyzed C-O bond-forming reaction of alcohol and aryl bromides has been developed. This transformation was realized through the use of copper(I) iodide as a catalyst, 8-hydroxyquinoline as a ligand, and K(3)PO(4) as a base. A variety of functionalized substrates were found to react under these reaction conditions to provide products in good to excellent yields.

  1. Calculation of the absolute thermodynamic properties of association of host-guest systems from the intermolecular potential of mean force.

    PubMed

    Ghoufi, Aziz; Malfreyt, Patrice

    2006-12-14

    The authors report calculations of the intermolecular potential of mean force (PMF) in the case of the host-guest interaction. The host-guest system is defined by a water soluble calixarene and a cation. With an organic cation such as the tetramethylammonium cation, the calixarene forms an insertion complex, whereas with the Lanthane cation, the supramolecular assembly is an outer-sphere complex. The authors apply a modified free energy perturbation method and the force constraint technique to establish the PMF profiles as a function of the separation distance between the host and guest. They use the PMF profile for the calculation of the absolute thermodynamic properties of association that they compare to the experimental values previously determined. They finish by giving some structural features of the insertion and outer-sphere complexes at the Gibbs free energy minimum.

  2. Brief history of intermolecular and intersurface forces in complex fluid systems.

    PubMed

    Israelachvili, Jacob; Ruths, Marina

    2013-08-06

    We review the developments of ideas, concepts, and theories of intermolecular and intersurface forces and how these were influenced (or ignored) by observations of nature and, later, systematic experimentation. The emphasis of this review is on the way things gradually changed: experimentation replaced rhetoric, measurement and quantification replaced hand waving, energy replaced force in calculations, discrete atoms replaced the (continuum) aether, thermodynamics replaced mechanistic models, randomness and probability replaced certainty, and delicate experiments on the subnanoscale revealed fascinating self-assembling structures and complex behavior of even the simplest systems. We conclude by discussing today's unresolved challenges: how complex "dynamic" multicomponent--especially living biological--systems that receive a continuous supply of energy can be far from equilibrium and not even in any steady state. Such systems, never static but evolving in both space and time, are still far from being understood both experimentally and theoretically.

  3. Low-valent niobium-catalyzed intermolecular [2 + 2 + 2] cycloaddition of tert-butylacetylene and arylnitriles to form 2,3,6-trisubstituted pyridine derivatives.

    PubMed

    Satoh, Yasushi; Obora, Yasushi

    2013-08-02

    A catalytic system based on low-valent niobium has been developed, consisting of NbCl5, Zn, and an alkoxysilane. This combination has been shown to be an efficient catalyst for the synthesis of pyridine derivatives from the intermolecular cycloaddition of alkynes and nitriles via a niobacyclopentadiene intermediate.

  4. Desensitization of metastable intermolecular composites

    SciTech Connect

    Busse, James R.; Dye, Robert C.; Foley, Timothy J.; Higa, Kelvin T.; Jorgensen, Betty S.; Sanders, Victor E.; Son, Steven F.

    2011-04-26

    A method to substantially desensitize a metastable intermolecular composite material to electrostatic discharge and friction comprising mixing the composite material with an organic diluent and removing enough organic diluent from the mixture to form a mixture with a substantially putty-like consistency, as well as a concomitant method of recovering the metastable intermolecular composite material.

  5. Ground state analytical ab initio intermolecular potential for the Cl{sub 2}-water system

    SciTech Connect

    Hormain, Laureline; Monnerville, Maurice Toubin, Céline; Duflot, Denis; Pouilly, Brigitte; Briquez, Stéphane; Bernal-Uruchurtu, Margarita I.; Hernández-Lamoneda, Ramón

    2015-04-14

    The chlorine/water interface is of crucial importance in the context of atmospheric chemistry. Modeling the structure and dynamics at this interface requires an accurate description of the interaction potential energy surfaces. We propose here an analytical intermolecular potential that reproduces the interaction between the Cl{sub 2} molecule and a water molecule. Our functional form is fitted to a set of high level ab initio data using the coupled-cluster single double (triple)/aug-cc-p-VTZ level of electronic structure theory for the Cl{sub 2} − H{sub 2}O complex. The potential fitted to reproduce the three minima structures of 1:1 complex is validated by the comparison of ab initio results of Cl{sub 2} interacting with an increasing number of water molecules. Finally, the model potential is used to study the physisorption of Cl{sub 2} on a perfectly ordered hexagonal ice slab. The calculated adsorption energy, in the range 0.27 eV, shows a good agreement with previous experimental results.

  6. Effect of donor orientation on ultrafast intermolecular electron transfer in coumarin-amine systems

    SciTech Connect

    Singh, P. K.; Nath, S.; Bhasikuttan, A. C.; Kumbhakar, M.; Mohanty, J.; Sarkar, S. K.; Mukherjee, T.; Pal, H.

    2008-09-21

    Effect of donor amine orientation on nondiffusive ultrafast intermolecular electron transfer (ET) reactions in coumarin-amine systems has been investigated using femtosecond fluorescence upconversion measurements. Intermolecular ET from different aromatic and aliphatic amines used as donor solvents to the excited coumarin-151 (C151) acceptor occurs with ultrafast rates such that the shortest fluorescence lifetime component ({tau}{sub 1}) is the measure of the fastest ET rate ({tau}{sub 1}={tau}{sub ET}{sup fast}=(k{sub ET}{sup fast}){sup -1}), assigned to the C151-amine contact pairs in which amine donors are properly oriented with respect to C151 to maximize the acceptor-donor electronic coupling (V{sub el}). It is interestingly observed that as the amine solvents are diluted by suitable diluents (either keeping solvent dielectric constant similar or with increasing dielectric constant), the {tau}{sub 1} remains almost in the similar range as long as the amine dilution does not cross a certain critical limit, which in terms of the amine mole fraction (x{sub A}) is found to be {approx}0.4 for aromatic amines and {approx}0.8 for aliphatic amines. Beyond these dilutions in the two respective cases of the amine systems, the {tau}{sub 1} values are seen to increase very sharply. The large difference in the critical x{sub A} values involving aromatic and aliphatic amine donors has been rationalized in terms of the largely different orientational restrictions for the ET reactions as imposed by the aliphatic (n-type) and aromatic ({pi}-type) nature of the amine donors [A. K. Satpati et al., J. Mol. Struct. 878, 84 (2008)]. Since the highest occupied molecular orbital (HOMO) of the n-type aliphatic amines is mostly centralized at the amino nitrogen, only some specific orientations of these amines with respect to the close-contact acceptor dye [also of {pi}-character; A. K. Satpati et al., J. Mol. Struct. 878, 84 (2008) and E. W. Castner et al., J. Phys. Chem. A 104, 2869

  7. Intermolecular forces.

    PubMed

    Buckingham, A D

    1975-11-06

    The nature of molecular interactions is examined. Intermolecular forces are divided into long-range and short-range components; the former operate at distances where the effects of electron exchange are negligible and decrease as an inverse power of the separation. The long-range interactions may be subdividied into electrostatic, induction and dispersion contributions, where the electrostatic component is the interaction of the permanent charge distributions and the others originate in the fluctuations in the distributions. Typical magnitudes of the various contributions are given. The forces between macroscopic bodies are briefly considered, as are the effects of a medium. Some of the manifestations of molecular interactions are discussed.

  8. Broadband Microwave Spectroscopy as a Tool to Study Intermolecular Interactions in the Diphenyl Ether - Water System

    NASA Astrophysics Data System (ADS)

    Fatima, Mariyam; Perez, Cristobal; Schnell, Melanie

    2017-06-01

    Many biological processes, such as chemical recognition and protein folding, are mainly controlled by the interplay of hydrogen bonds and dispersive forces. This interplay also occurs between organic molecules and solvent water molecules. Broadband rotational spectroscopy studies of weakly bound complexes are able to accurately reveal the structures and internal dynamics of molecular clusters isolated in the gas phase. Amongst them, water clusters with organic molecules are of particular interest. In this work, we investigate the interplay between different types of weak intermolecular interactions and how it controls the preferred interaction sites of aromatic ethers, where dispersive interactions may play a significant role. We present our results on diphenyl ether (C_{12}H_{10}O, 1,1'-Oxydibenzene) complexed with up to three molecules of water. Diphenyl ether is a flexible molecule, and it offers two competing binding sites for water: the ether oxygen and the aromatic π system. In order to determine the structure of the diphenyl ether-water complexes, we targeted transitions in the 2-8 GHz range using broadband rotational spectroscopy. We identify two isomers with one water, one with two water, and one with three water molecules. Further analysis from isotopic substitution measurements provided accurate structural information. The preferred interactions, as well as the observed structural changes induced upon complexation, will be presented and discussed.

  9. Evidence of anomalous behavior of intermolecular interactions at low concentration of methanol in ethanol-methanol binary system.

    PubMed

    Nilavarasi, K; Kartha, Thejus R; Madhurima, V

    2018-01-05

    At low concentrations of methanol in a binary system of ethanol and methanol, uniquely complex molecular interactions are reported here. Previous studies indicate that ethanol molecules form aggregates held together by hydrogen bonding (O-H-O) and also dispersive forces. Addition of small amount of methanol tends to break the hydrogen bond network of ethanol due to the larger polarity of methanol. This leads to the ethanol molecules becoming somewhat isolated from each other within a scaffolding network of methanol molecules, as seen from the present molecular dynamics simulations. This is an indication of a repulsive force that dominates among the two different alcohols. At higher molar concentration of methanol (Xm > 0.3817), the strength and extent (number) of formation of hydrogen bonds between ethanol and methanol increase. The geometry of molecular structure at high concentration favors the fitting of component molecules with each other. Intermolecular interactions in the ethanol-methanol binary system over the entire concentration range were investigated in detail using broadband dielectric spectroscopy, FTIR, surface tension and refractive index studies. Molecular dynamics simulations show that the hydrogen bond density is a direct function of the number of methanol molecules present, as the ethanol aggregates are not strictly hydrogen-bond constructed which is in agreement with the experimental results. Copyright © 2017 Elsevier B.V. All rights reserved.

  10. Universal scaling of potential energy functions describing intermolecular interactions. I. Foundations and scalable forms of new generalized Mie, Lennard-Jones, Morse, and Buckingham exponential-6 potentials.

    PubMed

    Xantheas, Sotiris S; Werhahn, Jasper C

    2014-08-14

    Based on the formulation of the analytical expression of the potential V(r) describing intermolecular interactions in terms of the dimensionless variables r* = r/r(m) and ɛ* = V/ɛ, where r(m) is the separation at the minimum and ɛ the well depth, we propose more generalized scalable forms for the commonly used Mie, Lennard-Jones, Morse, and Buckingham exponential-6 potential energy functions. These new generalized forms have an additional parameter from the original forms and revert to the original ones for some choice of that parameter. In this respect, the original forms of those potentials can be considered as special cases of the more general forms that are introduced. We also propose a scalable, non-revertible to the original one, 4-parameter extended Morse potential.

  11. Universal scaling of potential energy functions describing intermolecular interactions. I. Foundations and scalable forms of new generalized Mie, Lennard-Jones, Morse, and Buckingham exponential-6 potentials

    SciTech Connect

    Xantheas, Sotiris S.; Werhahn, Jasper C.

    2014-08-14

    Based on the formulation of the analytical expression of the potential V(r) describing intermolecular interactions in terms of the dimensionless variables r*=r/rm and !*=V/!, where rm is the separation at the minimum and ! the well depth, we propose more generalized scalable forms for the commonly used Lennard-Jones, Mie, Morse and Buckingham exponential-6 potential energy functions (PEFs). These new generalized forms have an additional parameter from and revert to the original ones for some choice of that parameter. In this respect, the original forms can be considered as special cases of the more general forms that are introduced. We also propose a scalable, but nonrevertible to the original one, 4-parameter extended Morse potential.

  12. Chemical force spectroscopy in heterogeneous systems: intermolecular interactions involving epoxy polymer, mixed monolayers, and polar solvents.

    PubMed

    Vezenov, Dmitri V; Zhuk, Andrew V; Whitesides, George M; Lieber, Charles M

    2002-09-04

    We used chemical force microscopy (CFM) to study adhesive forces between surfaces of epoxy resin and self-assembled monolayers (SAMs) capable of hydrogen bonding to different extents. The influence of the liquid medium in which the experiments were carried out was also examined systematically. The molecular character of the tip, polymer, and liquid all influenced the adhesion. Complementary macroscopic contact angle measurements were used to assist in the quantitative interpretation of the CFM data. A direct correlation between surface free energy and adhesion forces was observed in mixed alcohol-water solvents. An increase in surface energy from 2 to 50 mJ/m(2) resulted in an increase in adhesion from 4-8 nN to 150-300 nN for tips with radii of 50-150 nm. The interfacial surface energy for identical nonpolar surface groups of SAMs was found not to exceed 2 mJ/m(2). An analysis of adhesion data suggests that the solvent was fully excluded from the zone of contact between functional groups on the tip and sample. With a nonpolar SAM, the force of adhesion increased monotonically in mixed solvents of higher water content; whereas, with a polar SAM (one having a hydrogen bonding component), higher water content led to decreased adhesion. The intermolecular force components theory was used for the interpretation of adhesion force measurements in polar solvents. Competition between hydrogen bonding within the solvent and hydrogen bonding of surface groups and the solvent was shown to provide the main contribution to adhesion forces. We demonstrate how the trends in the magnitude of the adhesion forces for chemically heterogeneous systems (solvents and surfaces) measured with CFM can be quantitatively rationalized using the surface tension components approach. For epoxy polymer, inelastic deformations also contributed heavily to measured adhesion forces.

  13. Exploring the Details of Intermolecular Interactions via a Systematic Characterization of the Structures of the Bimolecular Heterodimers Formed Between Protic Acids and Haloethylenes

    NASA Astrophysics Data System (ADS)

    Leung, Helen O.

    2017-06-01

    In the early 2000's, the work of Cole and Legon, combined with that done earlier by Kisiel, Fowler, and Legon, demonstrated that comparisons among the complexes of HF, HCl, and HCCH each with vinyl fluoride could provide information concerning the strength of intermolecular interactions. Specifically, that the length of the hydrogen bond and its deviation from linearity as a result of a secondary interaction with the nucleophilic portion of the protic acid could be correlated with the hydrogen bond strength. Building on this foundation, we undertook a systematic characterization of the molecular structures of complexes formed between these three acids and the remaining polar fluoroethylenes, seeking to unravel the nature of their intermolecular interactions. What started out as a simple confirmation of chemical intuition regarding relative interaction strengths developed into a fuller appreciation of the competition between electrostatic and steric forces in determining the lowest energy configuration for the heterodimer. Additional surprises were in store for us as we expanded the study to chlorofluoroethylenes. Although the first few examples again served to confirm earlier conclusions, subsequent complexes provided unexpected results that signaled an increasing importance of the dispersion interaction in determining the geometry of the complex as well as the fundamental differences in the electron distributions surrounding the halogens in a C-F versus C-Cl bond. Our work with these species has not only allowed us to investigate fundamental questions regarding intermolecular interactions, but obtaining and analyzing the spectra of these complexes along with those of the various haloethylene monomers and their complexes with the argon atom have provided an introduction to molecular spectroscopy and structure determination for many undergraduate students. G.C. Cole and A.C. Legon, Chem. Phys. Lett. 369, 31-40 (2003). G.C. Cole and A.C. Legon, Chem. Phys. Lett. 400

  14. Shell forming system

    NASA Technical Reports Server (NTRS)

    Kendall, Jr., James M. (Inventor); Wang, Taylor G. (Inventor); Elleman, Daniel D. (Inventor)

    1987-01-01

    An apparatus is provided for forming gas-filled spheres of metal, glass or other material, which produces spheres (12) of uniform size and wall thickness in a relatively simple system. The system includes concentric nozzles, including an inner nozzle (18) through which gas flows and and an outer nozzle (20), which jointly define an annular passageway (50) through which a liquid flows. The flow rates are adjusted so that the gas flows at greater velocity than does the liquid, out of their respective nozzles, e.g. three times as great, in order to produce an extrusion (30) which undergoes axisymmetric oscillations resulting in the pinch off into hollow spheres with very uniform spacing. The system is useful not only where gas-filled spheres are required, but also is useful to accurately control the dispensing of solid, liquid, or gaseous materials.

  15. Development of an intermolecular transposition assay system in Bacillus subtilis 168 using IS4Bsu1 from Bacillus subtilis (natto).

    PubMed

    Takahashi, Kiwamu; Sekine, Yasuhiko; Chibazakura, Taku; Yoshikawa, Hirofumi

    2007-08-01

    Most of the spontaneous poly-gamma-glutamate (gamma-PGA)-deficient mutants of Bacillus subtilis (natto) appear to have resulted from the insertion of IS4Bsu1 exclusively into the comP gene. However, complete genomic analysis of B. subtilis 168, a close relative of B. subtilis (natto), revealed no IS4Bsu1 insertion. Preliminary experiments using a transformable 'natto' strain indicated that the frequency of transposition of IS4Bsu1 was exceptionally high under competence-developing conditions. On the other hand, such high-frequency transposition was not observed when cells were grown in a rich medium, such as LB medium, suggesting that there must be suitable environmental conditions that give rise to the transposition of IS4Bsu1. To assess the behaviour of IS4Bsu1 and explore any host factors playing roles in IS transposition, an intermolecular transposition assay system was constructed using a modified IS4Bsu1 element in B. subtilis 168. Here, the details of the intermolecular transposition assay system are given, and the increase in transposition frequency observed under high-temperature and competence-inducing conditions is described.

  16. Insights into the Complexity of Weak Intermolecular Interactions Interfering in Host-Guest Systems.

    PubMed

    Zhang, Dawei; Chatelet, Bastien; Serrano, Eloisa; Perraud, Olivier; Dutasta, Jean-Pierre; Robert, Vincent; Martinez, Alexandre

    2015-10-05

    The recognition properties of heteroditopic hemicryptophane hosts towards anions, cations, and neutral pairs, combining both cation-π and anion-π interaction sites, were investigated to probe the complexity of interfering weak intermolecular interactions. It is suggested from NMR experiments, and supported by CASSCF/CASPT2 calculations, that the binding constants of anions can be modulated by a factor of up to 100 by varying the fluorination sites on the electron-poor aromatic rings. Interestingly, this subtle chemical modification can also reverse the sign of cooperativity in ion-pair recognition. Wavefunction calculations highlight how short- and long-range interactions interfere in this recognition process, suggesting that a disruption of anion-π interactions can occur in the presence of a co-bound cation. Such molecules can be viewed as prototypes for examining complex processes controlled by the competition of weak interactions.

  17. Direct, Intermolecular, Enantioselective, Iridium-Catalyzed Allylation of Carbamates to Form Carbamate-Protected, Branched Allylic Amines

    PubMed Central

    Weix, Daniel J.; Marković, Dean; Ueda, Mitsuhiro; Hartwig, John F.

    2009-01-01

    The direct reaction between carbamates and achiral allylic carbonates to form branched, conveniently protected primary allylic amines with high regioselectivity and enantioselectivity is reported. This process occurs without base or with 0.5 equiv K3PO4 in the presence of a metalacyclic iridium catalyst containing a labile ethylene ligand. The reactions of aryl, heteroaryl and alkyl-substituted allylic carbonates with BocNH2, FmocNH2, CbzNH2, TrocNH2, TeocNH2, and 2-oxazolidinone occur in good yields, with high selectivity for the branched isomer, and high enantioselectivities (98% average ee). PMID:19552468

  18. Direct, intermolecular, enantioselective, iridium-catalyzed allylation of carbamates to form carbamate-protected, branched allylic amines.

    PubMed

    Weix, Daniel J; Marković, Dean; Ueda, Mitsuhiro; Hartwig, John F

    2009-07-02

    The direct reaction between carbamates and achiral allylic carbonates to form branched, conveniently protected primary allylic amines with high regioselectivity and enantioselectivity is reported. This process occurs without base or with 0.5 equiv K(3)PO(4) in the presence of a metalacyclic iridium catalyst containing a labile ethylene ligand. The reactions of aryl-, heteroaryl-, and alkyl-substituted allylic carbonates with BocNH(2), FmocNH(2), CbzNH(2), TrocNH(2), TeocNH(2), and 2-oxazolidinone occur in good yields, with high selectivity for the branched isomer and high enantioselectivities (98% average ee).

  19. The HC fragment of tetanus toxin forms stable, concentration-dependent dimers via an intermolecular disulphide bond.

    PubMed

    Qazi, Omar; Bolgiano, Barbara; Crane, Dennis; Svergun, Dmitri I; Konarev, Petr V; Yao, Zhong-Ping; Robinson, Carol V; Brown, Katherine A; Fairweather, Neil

    2007-01-05

    Protein oligomerisation is a prerequisite for the toxicity of a number of bacterial toxins. Examples include the pore-forming cytotoxin streptolysin O, which oligomerises to form large pores in the membrane and the protective antigen of anthrax toxin, where a heptameric complex is essential for the delivery of lethal factor and edema factor to the cell cytosol. Binding of the clostridial neurotoxins to receptors on neuronal cells is well characterised, but little is known regarding the quaternary structure of these toxins and the role of oligomerisation in the intoxication process. We have investigated the oligomerisation of the receptor binding domain (H(C)) of tetanus toxin, which retains the binding and trafficking properties of the full-length toxin. Electrophoresis, size exclusion chromatography and mass spectrometry were used to demonstrate that H(C) undergoes concentration-dependent oligomerisation in solution. Reducing agents were found to affect H(C) oligomerisation and, using mutagenesis, Cys869 was shown to be essential for this process. Furthermore, the oligomeric state and quaternary structure of H(C) in solution was assessed using synchrotron small-angle X-ray scattering. Ab initio shape analysis and rigid body modelling coupled with mutagenesis data allowed the construction of an unequivocal model of dimeric H(C) in solution. We propose a possible mechanism for H(C) oligomerisation and discuss how this may relate to toxicity.

  20. Methyl group dynamics in paracetamol and acetanilide: probing the static properties of intermolecular hydrogen bonds formed by peptide groups

    NASA Astrophysics Data System (ADS)

    Johnson, M. R.; Prager, M.; Grimm, H.; Neumann, M. A.; Kearley, G. J.; Wilson, C. C.

    1999-06-01

    Measurements of tunnelling and librational excitations for the methyl group in paracetamol and tunnelling excitations for the methyl group in acetanilide are reported. In both cases, results are compared with molecular mechanics calculations, based on the measured low temperature crystal structures, which follow an established recipe. Agreement between calculated and measured methyl group observables is not as good as expected and this is attributed to the presence of comprehensive hydrogen bond networks formed by the peptide groups. Good agreement is obtained with a periodic quantum chemistry calculation which uses density functional methods, these calculations confirming the validity of the one-dimensional rotational model used and the crystal structures. A correction to the Coulomb contribution to the rotational potential in the established recipe using semi-emipircal quantum chemistry methods, which accommodates the modified charge distribution due to the hydrogen bonds, is investigated.

  1. Shell forming system

    NASA Technical Reports Server (NTRS)

    Kendall, Jr., James M. (Inventor); Wang, Taylor G. (Inventor); Elleman, Daniel D. (Inventor)

    1990-01-01

    Hollow shells of high uniformity are formed by emitting liquid through an outer nozzle and gas through an inner nozzle, to form a hollow extrusion, by flowing the gas at a velocity between about 1.3 and 10 times the liquid velocity. The natural breakup rate of the extrusion can be increased to decrease shell size by applying periodic perturbations to one of the materials prior to exiting the nozzles, to a nozzle, or to the extrusion.

  2. An Efficient Method to Evaluate Intermolecular Interaction Energies in Large Systems Using Overlapping Multicenter ONIOM and the Fragment Molecular Orbital Method

    PubMed Central

    Asada, Naoya; Fedorov, Dmitri G.; Kitaura, Kazuo; Nakanishi, Isao; Merz, Kenneth M.

    2012-01-01

    We propose an approach based on the overlapping multicenter ONIOM to evaluate intermolecular interaction energies in large systems and demonstrate its accuracy on several representative systems in the complete basis set limit at the MP2 and CCSD(T) level of theory. In the application to the intermolecular interaction energy between insulin dimer and 4′-hydroxyacetanilide at the MP2/CBS level, we use the fragment molecular orbital method for the calculation of the entire complex assigned to the lowest layer in three-layer ONIOM. The developed method is shown to be efficient and accurate in the evaluation of the protein-ligand interaction energies. PMID:23050059

  3. Desensitization and recovery of metastable intermolecular composites

    DOEpatents

    Busse, James R [South Fork, CO; Dye, Robert C [Los Alamos, NM; Foley, Timothy J [Los Alamos, NM; Higa, Kelvin T [Ridgecrest, CA; Jorgensen, Betty S [Jemez Springs, NM; Sanders, Victor E [White Rock, NM; Son, Steven F [Los Alamos, NM

    2010-09-07

    A method to substantially desensitize a metastable intermolecular composite material to electrostatic discharge and friction comprising mixing the composite material with an organic diluent and removing enough organic diluent from the mixture to form a mixture with a substantially putty-like consistency, as well as a concomitant method of recovering the metastable intermolecular composite material.

  4. An approach to the origin of self-replicating system. I - Intermolecular interactions

    NASA Technical Reports Server (NTRS)

    Macelroy, R. D.; Coeckelenbergh, Y.; Rein, R.

    1978-01-01

    The present paper deals with the characteristics and potentialities of a recently developed computer-based molecular modeling system. Some characteristics of current coding systems are examined and are extrapolated to the apparent requirements of primitive prebiological coding systems.

  5. Intramolecular Flexibility of Relatively Rigid Polymers, and Intermolecular Interactions in Ordered Polymer Systems. Part II.

    DTIC Science & Technology

    1981-01-26

    rials, the ordering of the chains, and the mechanical strenth of the resulting films or fibers . The basic goals are thus a molecular understanding of...polymers, cis and trans polybenzoxazoles (PBO) and polybenzothiazoles (PBT), form such phases, and energy calculations were therefore carried out to...Phys., 18, 000 (1981). 2. Phenylene Group Rotations and Nonplanar Conformations in Some Cis and Trans Polybenzoxazoles and Polybenzothiazoles, W. J

  6. Many-body effects in intermolecular forces.

    PubMed

    Elrod, M J; Saykally, R J

    1994-11-01

    The authors provide a review and literature survey of many-body effects in intermolecular forces. Topics include experimental methods, theoretical methods, many-body effects in atomic systems, and many-body effects in aqueous and nonaqueous molecular systems.

  7. Inelastic intermolecular exchange of vibrational quanta and relaxation of vibrationally excited states in binary solid systems

    NASA Astrophysics Data System (ADS)

    Aliev, A. R.; Akhmedov, I. R.; Kakagasanov, M. G.; Aliev, Z. A.; Gafurov, M. M.; Rabadanov, K. Sh.; Amirov, A. M.

    2017-04-01

    The processes of molecular relaxation in the binary nitrate-perchlorate solid systems LiNO3-LiClO4, NaNO3-NaClO4, and KNO3-KClO4 have been investigated using Raman spectroscopy. It has been found that the relaxation time of the ν1( A) vibration of the NO3 - anion in the binary solid system is shorter than that in the pure metal nitrates. It has been shown that an increase in the relaxation rate is caused by the existence of an additional mechanism of relaxation of vibrationally excited states of the nitrate ion in the system. This mechanism is associated with the excitation of a vibration of another anion (ClO4 -), as well as with the "creation" of a lattice phonon. It has been established that the condition for the realization of the relaxation mechanism is that the difference between the frequencies of the aforementioned vibrations should correspond to the range of sufficiently high densities of states of the phonon spectrum.

  8. The role of intermolecular interactions: studies on model systems for bacterial biofilms.

    PubMed

    Mayer, C; Moritz, R; Kirschner, C; Borchard, W; Maibaum, R; Wingender, J; Flemming, H C

    1999-10-01

    The mechanical stability of biofilms and other microbial aggregates is of great importance for both the maintenance of biofilm processes and the removal of undesired biofilms. The binding forces are weak interactions such as London dispersion forces, electrostatic interactions and hydrogen bonds. In a first attempt to rank their contribution, the viscosity of solutions of extracellular polymeric substances (EPS) from a mucoid strain of Pseudomonas aeruginosa is measured. In order to distinguish the binding forces, substances are chosen which individually address the different types of bonds. Polyacrylic acid is identified as a suitable model system for EPS when molecular interactions are studied. Electrostatic interactions and hydrogen bonds are found to be the dominating forces among macromolecules within the biofilm.

  9. Substrate system for spray forming

    DOEpatents

    Chu, Men G.; Chernicoff, William P.

    2002-01-01

    A substrate system for receiving a deposit of sprayed metal droplets including a movable outer substrate on which the sprayed metal droplets are deposited. The substrate system also includes an inner substrate disposed adjacent the outer substrate where the sprayed metal droplets are deposited on the outer substrate. The inner substrate includes zones of differing thermal conductivity to resist substrate layer porosity and to resist formation of large grains and coarse constituent particles in a bulk layer of the metal droplets which have accumulated on the outer substrate. A spray forming apparatus and associated method of spray forming a molten metal to form a metal product using the substrate system of the invention is also provided.

  10. Substrate system for spray forming

    DOEpatents

    Chu, Men G.; Chernicoff, William P.

    2000-01-01

    A substrate system for receiving a deposit of sprayed metal droplets including a movable outer substrate on which the sprayed metal droplets are deposited. The substrate system also includes an inner substrate disposed adjacent the outer substrate where the sprayed metal droplets are deposited on the outer substrate. The inner substrate includes zones of differing thermal conductivity to resist substrate layer porosity and to resist formation of large grains and coarse constituent particles in a bulk layer of the metal droplets which have accumulated on the outer substrate. A spray forming apparatus and associated method of spray forming a molten metal to form a metal product using the substrate system of the invention is also provided.

  11. Molecular-beam study of the ammonia-noble gas systems: characterization of the isotropic interaction and insights into the nature of the intermolecular potential.

    PubMed

    Pirani, Fernando; Roncaratti, Luiz F; Belpassi, Leonardo; Tarantelli, Francesco; Cappelletti, D

    2011-11-21

    We report new high resolution molecular beam experiments aimed at characterizing the intermolecular interaction in the NH(3)-Ng (Ng = He, Ne, Ar, Kr, Xe) weakly bound complexes. Integral cross section data are obtained over a sufficiently wide velocity range and with rotationally hot NH(3) molecules to produce (except for the NH(3)-He case) a well resolved "glory" quantum interference pattern. Data analysis, carried out by employing a recently proposed potential model, allows unique information on the absolute scale of the intermolecular interaction to be obtained both at long range and at the equilibrium distance. An extensive and internally consistent comparison with the behavior of the corresponding Kr-Ng systems is exploited in order to identify those cases where an interaction component due to charge transfer effects provides an appreciable intermolecular bond stabilization that is clearly distinct from and must be added to the standard van der Waals plus induction picture. The results of the present investigation extend the phenomenology of perturbative charge transfer effects in gas phase complexes involving hydrogenated molecules.

  12. Morphology and the Strength of Intermolecular Contact in Protein Crystals

    NASA Technical Reports Server (NTRS)

    Matsuura, Yoshiki; Chernov, Alexander A.

    2002-01-01

    The strengths of intermolecular contacts (macrobonds) in four lysozyme crystals were estimated based on the strengths of individual intermolecular interatomic interaction pairs. The periodic bond chain of these macrobonds accounts for the morphology of protein crystals as shown previously. Further in this paper, the surface area of contact, polar coordinate representation of contact site, Coulombic contribution on the macrobond strength, and the surface energy of the crystal have been evaluated. Comparing location of intermolecular contacts in different polymorphic crystal modifications, we show that these contacts can form a wide variety of patches on the molecular surface. The patches are located practically everywhere on this surface except for the concave active site. The contacts frequently include water molecules, with specific intermolecular hydrogen-bonds on the background of non-specific attractive interactions. The strengths of macrobonds are also compared to those of other protein complex systems. Making use of the contact strengths and taking into account bond hydration we also estimated crystal-water interfacial energies for different crystal faces.

  13. A test of the significance of intermolecular vibrational coupling in isotopic fractionation

    NASA Astrophysics Data System (ADS)

    Herman, Michael F.; Currier, Robert P.; Peery, Travis B.; Clegg, Samuel M.

    2017-09-01

    Intermolecular coupling of dipole moments is studied for a model system consisting of two diatomic molecules (AB monomers) arranged co-linearly and which can form non-covalently bound dimers. The dipolar coupling is a function of the bond length in each molecule as well as of the distance between the centers-of-mass of the two molecules. The calculations show that intermolecular coupling of the vibrations results in an isotope-dependent modification of the AB-AB intermolecular potential. This in turn alters the energies of the low-lying bound states of the dimers, producing isotope-dependent changes in the AB-AB dimer partition function. Explicit inclusion of intermolecular vibrational coupling then changes the predicted gas-dimer isotopic fractionation. In addition, a mass dependence in the intermolecular potential can also result in changes in the number of bound dimer states in an equilibrium mixture. This in turn leads to a significant dimer population shift in the model monomer-dimer equilibrium system considered here. The results suggest that intermolecular coupling terms should be considered when probing the origins of isotopic fractionation.

  14. A test of the significance of intermolecular vibrational coupling in isotopic fractionation

    DOE PAGES

    Herman, Michael F.; Currier, Robert P.; Peery, Travis B.; ...

    2017-07-15

    Intermolecular coupling of dipole moments is studied for a model system consisting of two diatomic molecules (AB monomers) arranged co-linearly and which can form non-covalently bound dimers. The dipolar coupling is a function of the bond length in each molecule as well as of the distance between the centers-of-mass of the two molecules. The calculations show that intermolecular coupling of the vibrations results in an isotope-dependent modification of the AB-AB intermolecular potential. This in turn alters the energies of the low-lying bound states of the dimers, producing isotope-dependent changes in the AB-AB dimer partition function. Explicit inclusion of intermolecular vibrationalmore » coupling then changes the predicted gas-dimer isotopic fractionation. In addition, a mass dependence in the intermolecular potential can also result in changes in the number of bound dimer states in an equilibrium mixture. This in turn leads to a significant dimer population shift in the model monomer-dimer equilibrium system considered here. Finally, the results suggest that intermolecular coupling terms should be considered when probing the origins of isotopic fractionation.« less

  15. Intermolecular Hydrogen Bonding in Peptide and Modified Jeffamine Organogels

    NASA Astrophysics Data System (ADS)

    Savin, Daniel; Richardson, Adam

    2011-03-01

    In these studies, we present two systems whereby supramolecular assembly results in rigid organogels. First, a series of AB diblock copolymers consisting of poly(Lysine(Z)) (P(Lys(Z)) blocks were synthesized and found to form stable, rigid organogels in THF (ca. 1 - 1.5 wt.% solutions) and chloroform at room temperature. In these systems, the protecting group on the P(Lys) side-chains remains intact and gel formation results from the assembly of the solventphobic P(Lys(Z)) chains through intermolecular beta-sheet formation. The non-peptide block was found to have an effect on organogel properties due to interfacial frustration, which disrupts H-bonding. Second, Jeffamine polymers were modified in a facile way to incorporate intermolecular H-bonding groups to yield networks able to gel various solvents as well as mineral and canola oil. We present the physical and rheological properties of the organogels produced.

  16. Induced Smectic X Phase Through Intermolecular Hydrogen-Bonded Liquid Crystals Formed Between Citric Acid and p- n-(Octyloxy)Benzoic Acid

    NASA Astrophysics Data System (ADS)

    Sundaram, S.; Subhasri, P.; Rajasekaran, T. R.; Jayaprakasam, R.; Senthil, T. S.; Vijayakumar, V. N.

    2017-08-01

    Hydrogen-bonded liquid crystal (HBLC) is synthesized from citric acid (CA) and 4-(octyloxy)benzoic acid (8OBA) with different mole ratios. Fourier transform infrared spectroscopy (FT-IR) confirms the presence of hydrogen bond between CA and 8OBA. Nuclear magnetic resonance (NMR) spectroscopic studies validate the intermolecular complementary, cyclic type of hydrogen bond, and molecular environment in the designed HBLC complex. Powder X-ray diffraction analysis reveals the monoclinic nature of liquid crystal complex in solid phase. Liquid crystal parameters such as phase transition temperature and enthalpy values for the corresponding mesogenic phases are investigated using a polarizing optical microscope (POM) and differential scanning calorimetry (DSC). It is observed that the change in chain length and steric hindrance while increasing the mole ratio in HBLC complex induces a new smectic X (Sm X) along with higher-order smectic G (Sm G) phases by quenching of smectic C (Sm C). From the experimental observations, induced Sm X phase has been identified as a finger print texture. Also, Sm G is a multi-colored mosaic texture in 1:1, 1:2, and 1:3 mol ratios. The optical tilt angle, thermal stability factor, and enhanced thermal span width of CA + 8OBA complex are discussed.

  17. Solid state synthesis, structural, physicochemical and optical properties of an inter-molecular compound: 2-hydroxy-1, 2-diphenylethanone-4-nitro-o-phenylenediamine system

    NASA Astrophysics Data System (ADS)

    Rai, U. S.; Singh, Manjeet; Rai, R. N.

    2017-09-01

    The phase diagram of 2-hydroxy-1, 2-diphenylethanone (HDPE)-4-nitro-o-phenylenediamine (NOPDA) system, determined by the thaw-melt method, gives two eutectics E1 (m p = 66.0 °C) and E2 (m p = 155.0 °C) with 0.30 and 0.55 mol fractions of NOPDA, respectively, and an 1:1 inter-molecular compound (IMC) (m p 162.0 °C). This IMC was synthesized by adopting the green synthetic method of solid state reaction. While its formation and structure were confirmed by the X-ray diffraction and spectroscopic methods, the ORTEP view gives mode of crystal packing, C‒H…O, C‒H…N, π-π stacking and the inter-molecular hydrogen bonding in the compound. The single crystal of the IMC shows 53% transmission and emits significantly higher dual fluorescence, and the band gap was computed to be 3.04 eV. The values of solubility of the IMC, measured in the temperature range 304-322 K, satisfy the mole fraction (X) and temperature equation: Xeq= 5.1324 × 10-7 e 0.01356T.

  18. A canonical form for nonlinear systems

    NASA Technical Reports Server (NTRS)

    Su, R.; Hunt, L. R.

    1985-01-01

    The conceptions of transformation and canonical form have been much used to analyze the structure of linear systems. A coordinate system and a corresponding canonical form are developed for general nonlinear control systems. Their usefulness is demonstrated by showing that every feedback linearizable system becomes a system with only feedback paths in the canonical form.

  19. System for forming janus particles

    DOEpatents

    Hong, Liang [Midland, MI; Jiang, Shan [Champaign, IL; Granick, Steve [Champaign, IL

    2011-01-25

    The invention is a method of forming Janus particles, that includes forming an emulsion that contains initial particles, a first liquid, and a second liquid; solidifying the first liquid to form a solid that contains at least a portion of the initial particles on a surface of the solid; and treating the exposed particle sides with a first surface modifying agent, to form the Janus particles. Each of the initial particles on the surface has an exposed particle side and a blocked particle side.

  20. Orthogonal adsorption onto nano-graphene oxide using different intermolecular forces for multiplexed delivery.

    PubMed

    Wang, Feng; Liu, Biwu; Ip, Alexander C-F; Liu, Juewen

    2013-08-14

    Nano-graphene oxide can adsorb both doxorubicin and zwitterionic dioleoyl-sn-glycero-3-phosphocholine (DOPC) liposomes in an orthogonal and non-competing manner with high capacities based on different surface and intermolecular forces taking place on the heterogeneous surface of the graphene oxide. The system forms stable colloids, allowing co-delivery of both cargos to cancer cells.

  1. A canonical form for nonlinear systems

    NASA Technical Reports Server (NTRS)

    Su, R.; Hunt, L. R.

    1986-01-01

    The concepts of transformation and canonical form have been used in analyzing linear systems. These ideas are extended to nonlinear systems. A coordinate system and a corresponding canonical form are developed for general nonlinear control systems. Their usefulness is demonstrated by showing that every feedback linearizable system becomes a system with only feedback paths in the canonical form. For control design involving a nonlinear system, one approach is to put the system in its canonical form and approximate by that part having only feedback paths.

  2. Mapping intermolecular bonding in C₆₀.

    PubMed

    Sundqvist, Bertil

    2014-08-22

    The formation of intermolecular bonds in C₆₀ has been investigated in detail at pressures below 2.2 GPa and up to 750 K. Fullerene samples were heated in a temperature gradient to obtain data on the formation of dimers and low-dimensional polymers along isobars. Intermolecular bonding was analyzed ex situ by Raman scattering, using both intramolecular modes and intermolecular stretching modes. Semi-quantitative reaction maps are given for the formation of dimers and chains. The activation energy for dimer formation decreases by 0.2 meV pm(-1) when intermolecular distances decrease and dimer formation is noticeably affected by the rotational state of molecules. Above 400-450 K larger oligomers are formed; below 1.4 GPa most of these are disordered, with small domains of linear chains, but above this the appearance of stretching modes indicates the existence of ordered one-dimensional polymers. At the highest pressures and temperatures two-dimensional polymers are also observed.

  3. Mapping intermolecular bonding in C60

    PubMed Central

    Sundqvist, Bertil

    2014-01-01

    The formation of intermolecular bonds in C60 has been investigated in detail at pressures below 2.2 GPa and up to 750 K. Fullerene samples were heated in a temperature gradient to obtain data on the formation of dimers and low-dimensional polymers along isobars. Intermolecular bonding was analyzed ex situ by Raman scattering, using both intramolecular modes and intermolecular stretching modes. Semi-quantitative reaction maps are given for the formation of dimers and chains. The activation energy for dimer formation decreases by 0.2 meV pm−1 when intermolecular distances decrease and dimer formation is noticeably affected by the rotational state of molecules. Above 400–450 K larger oligomers are formed; below 1.4 GPa most of these are disordered, with small domains of linear chains, but above this the appearance of stretching modes indicates the existence of ordered one-dimensional polymers. At the highest pressures and temperatures two-dimensional polymers are also observed. PMID:25145952

  4. Ladder Forms in Estimation and System Identification.

    DTIC Science & Technology

    1977-01-01

    system identification . Many record applications, such as in geophysical signal processing, high resolution (’maximum entropy’) spectral estimation and speech encoding, justify the interest in these forms. They appear in many contexts, such as scattering and network theory and the theory of orthogonal polynomials. The state-space model ladder realizations are very closely related in (block) Schwarz matrix canonical forms, which generally appear in the context of stability analysis. In fact they are the natural ’stability canonical form’ for

  5. Enthalpies of mixing and intermolecular interactions in the 1-octanol-dimethylformamide system at 298-318 K

    NASA Astrophysics Data System (ADS)

    Smirnova, N. L.; Kustov, A. V.

    2013-05-01

    The heat effects of solution of N,N-dimethylformamide (DMF) and 1-octanol (OctOH) in the DMF (1)-OctOH (2) system are measured over the range of compositions using a variable-temperature isothermal-shell calorimeter at 298, 308, and 318 K. The partial molar enthalpies of the binary mixture components and the enthalpies and heat capacities of mixing are determined. It is found that the amide-alcohol mixing is strongly endothermic and very weakly depends on temperature. The enthalpy and specific heat parameters of binary and ternary interactions between the DMF molecules in OctOH and the OctOH molecules in DMF are determined in terms of the virial expansion technique, and it is shown that the two nonelectrolytes exhibit a tendency to homoassociation.

  6. Direct evaluation of individual hydrogen bond energy in situ in intra- and intermolecular multiple hydrogen bonds system.

    PubMed

    Liu, Cui; Zhao, Dong-Xia; Yang, Zhong-Zhi

    2012-02-05

    The results of evaluating the individual hydrogen bond (H-bond) strength are expected to be helpful for the rational design of new strategies for molecular recognition or supramolecular assemblies. Unfortunately, there is few obvious and unambiguous means of evaluating the energy of a single H-bond within a multiple H-bonds system. We present a local analytic model, ABEEMσπ H-bond energy (HBE) model based on ab initio calculations (MP2) as benchmark, to directly and rapidly evaluate the individual HBE in situ in inter- and intramolecular multiple H-bonds system. This model describes the HBE as the sum of electrostatic and van der Waals (vdW) interactions which all depend upon the geometry and environment, and the ambient environment of H-bond in the model is accounted fairly. Thus, it can fairly consider the cooperative effect and secondary effect. The application range of ABEEMσπ HBE model is rather wide. This work has discussed the individual H-bond in DNA base pair and protein peptide dimers. The results indicate that the interactions among donor H atom, acceptor atom as well as those atoms connected to them with 1,2 or 1,3 relationships are all important for evaluating the HBE, although the interaction between the donor H atom and the acceptor atom is large. Furthermore, our model quantitatively indicates the polarization ability of N, O, and S in a new style, and gives the percentage of the polarization effect in HBE, which can not be given by fixed partial charge force field.

  7. Structures and Intermolecular Interactions in Dimethyl Sulfoxide-Water System Studied by All-atom Molecular Simulations

    NASA Astrophysics Data System (ADS)

    Zhang, Rong; Wu, Wen-juan

    2010-10-01

    An all-atom dimethyl sulfoxide (DMSO) and water model have been used for molecular dynamics simulation. The NMR and IR spectra are also performed to study the structures and interactions in the DMSO-water system. And there are traditional strong hydrogen bonds and weak C-H ··· O contacts existing in the mixtures according to the analysis of the radial distribution functions. The insight structures in the DMSO-water mixtures can be classified into different regions by the analysis of the hydrogen-bonding network. Interestingly, the molar fraction of DMSO 0.35 is found to be a special concentration by the network. It is the transitional region which is from the water rich region to the DMSO rich region. The stable aggregates of (DMSO)m·S=O···HW-OW·(H2O)n might play a key role in this region. Moreover, the simulation is compared with the chemical shifts in NMR and wavenumbers in IR with concentration dependence. And the statistical results of the average number hydrogen bonds in the MD simulations are in agreement with the experiment data in NMR and IR spectra.

  8. Plasma formed ion beam projection lithography system

    DOEpatents

    Leung, Ka-Ngo; Lee, Yung-Hee Yvette; Ngo, Vinh; Zahir, Nastaran

    2002-01-01

    A plasma-formed ion-beam projection lithography (IPL) system eliminates the acceleration stage between the ion source and stencil mask of a conventional IPL system. Instead a much thicker mask is used as a beam forming or extraction electrode, positioned next to the plasma in the ion source. Thus the entire beam forming electrode or mask is illuminated uniformly with the source plasma. The extracted beam passes through an acceleration and reduction stage onto the resist coated wafer. Low energy ions, about 30 eV, pass through the mask, minimizing heating, scattering, and sputtering.

  9. Evaluation of Questions in General Chemistry Textbooks According to the Form of the Questions and the Question-Answer Relationship (QAR): The Case of Intra-and Intermolecular Chemical Bonding

    ERIC Educational Resources Information Center

    Pappa, Eleni T.; Tsaparlis, Georgios

    2011-01-01

    One way of checking to what extent instructional textbooks achieve their aim is to evaluate the questions they contain. In this work, we analyze the questions that are included in the chapters on chemical bonding of ten general chemistry textbooks. We study separately the questions on intra- and on intermolecular bonding, with the former…

  10. Evaluation of Questions in General Chemistry Textbooks According to the Form of the Questions and the Question-Answer Relationship (QAR): The Case of Intra-and Intermolecular Chemical Bonding

    ERIC Educational Resources Information Center

    Pappa, Eleni T.; Tsaparlis, Georgios

    2011-01-01

    One way of checking to what extent instructional textbooks achieve their aim is to evaluate the questions they contain. In this work, we analyze the questions that are included in the chapters on chemical bonding of ten general chemistry textbooks. We study separately the questions on intra- and on intermolecular bonding, with the former…

  11. Perturbation analyses of intermolecular interactions

    NASA Astrophysics Data System (ADS)

    Koyama, Yohei M.; Kobayashi, Tetsuya J.; Ueda, Hiroki R.

    2011-08-01

    Conformational fluctuations of a protein molecule are important to its function, and it is known that environmental molecules, such as water molecules, ions, and ligand molecules, significantly affect the function by changing the conformational fluctuations. However, it is difficult to systematically understand the role of environmental molecules because intermolecular interactions related to the conformational fluctuations are complicated. To identify important intermolecular interactions with regard to the conformational fluctuations, we develop herein (i) distance-independent and (ii) distance-dependent perturbation analyses of the intermolecular interactions. We show that these perturbation analyses can be realized by performing (i) a principal component analysis using conditional expectations of truncated and shifted intermolecular potential energy terms and (ii) a functional principal component analysis using products of intermolecular forces and conditional cumulative densities. We refer to these analyses as intermolecular perturbation analysis (IPA) and distance-dependent intermolecular perturbation analysis (DIPA), respectively. For comparison of the IPA and the DIPA, we apply them to the alanine dipeptide isomerization in explicit water. Although the first IPA principal components discriminate two states (the α state and PPII (polyproline II) + β states) for larger cutoff length, the separation between the PPII state and the β state is unclear in the second IPA principal components. On the other hand, in the large cutoff value, DIPA eigenvalues converge faster than that for IPA and the top two DIPA principal components clearly identify the three states. By using the DIPA biplot, the contributions of the dipeptide-water interactions to each state are analyzed systematically. Since the DIPA improves the state identification and the convergence rate with retaining distance information, we conclude that the DIPA is a more practical method compared with the

  12. Cross linking molecular systems to form ultrathin dielectric layers

    NASA Astrophysics Data System (ADS)

    Feng, Danqin

    Dehydrogenation leads to cross linking of polymer or polymer like formation in very different systems: self-assembled monolayers and in closo -carboranes leading to the formation of semiconducting and dielectric boron carbide. We find evidence of intermolecular interactions for a self-assembled monolayer (SAM) formed from a large molecular adsorbate, [1,1';4',1"-terphenyl]-4,4"-dimethanethiol, from the dispersion of the molecular orbitals with changing the wave vector k and from the changes with temperature. With the formation self assembled molecular (SAM) layer, the molecular orbitals hybridize to electronic bands, with indications of significant band dispersion of the unoccupied molecular orbitals. Although organic adsorbates and thin films are generally regarded as "soft" materials, the effective Debye temperature, indicative of the dynamic motion of the lattice normal to the surface, can be very high, e.g. in the multilayer film formed from [1,1'-biphenyl]-4,4'-dimethanethiol (BPDMT). Depending on molecular orientation, the effective Debye temperature can be comparable to that of graphite due to the 'stiffness' of the benzene rings, but follows the expected Debye-Waller behavior for the core level photoemission intensities with temperature. This is not always the case. We find that a monomolecular film formed from [1,1';4',1"-terphenyl]-4,4"-dimethanethiol deviates from Debye-Waller temperature behavior and is likely caused by temperature dependent changes in molecular orientation. We also find evidence for the increase in dielectric character with polymerization (cross-linking) in spite of the decrease in the HOMO-LUMO gap upon irradiation of TPDMT. The changes in the HOMO-LUMO gap, with cross-linking, are roughly consistent with the band dispersion. The decomposition and cross-linking processes are also accompanied by changes in molecular orientation. The energetics of the three isomeric carborane cage compounds [ closo-1,2-orthocarborane, closo-1

  13. Form and function in systems neuroscience.

    PubMed

    Kristan, William B; Katz, Paul

    2006-10-10

    'Form follows function' is an architectural philosophy attributed to the great American architect Louis Sullivan, and later taken up by the Bauhaus movement. It stresses that the form of a building should reflect its function. Neuroscientists have used the converse of this dictum to learn the functions of neural circuits, believing that if we study neural architecture, it will lead us to an understanding of how neural systems function. New tools for studying the structure of neural circuits are being developed, so it is important to discuss what the old techniques have taught us about how to derive function from the form of a neural circuit.

  14. Slab edge insulating form system and methods

    DOEpatents

    Lee, Brain E.; Barsun, Stephan K.; Bourne, Richard C.; Hoeschele, Marc A.; Springer, David A.

    2009-10-06

    A method of forming an insulated concrete foundation is provided comprising constructing a foundation frame, the frame comprising an insulating form having an opening, inserting a pocket former into the opening; placing concrete inside the foundation frame; and removing the pocket former after the placed concrete has set, wherein the concrete forms a pocket in the placed concrete that is accessible through the opening. The method may further comprise sealing the opening by placing a sealing plug or sealing material in the opening. A system for forming an insulated concrete foundation is provided comprising a plurality of interconnected insulating forms, the insulating forms having a rigid outer member protecting and encasing an insulating material, and at least one gripping lip extending outwardly from the outer member to provide a pest barrier. At least one insulating form has an opening into which a removable pocket former is inserted. The system may also provide a tension anchor positioned in the pocket former and a tendon connected to the tension anchor.

  15. Studies on intermolecular interaction on binary mixtures of methyl orange-water system: excess molar functions of ultrasonic parameters at different concentrations and at different temperatures.

    PubMed

    Thanuja, B; Kanagam, Charles; Sreedevi, S

    2011-11-01

    Density (ρ), viscosity (η) and ultrasonic velocity (u) of binary mixtures of methyl orange and water were measured at different concentrations and at different temperatures; several useful parameters such as excess volume, excess velocity, and excess adiabatic compressibility have been calculated. These parameters are used to explain the nature of intermolecular interactions taking place in the binary mixture. The above study is helpful in understanding the dye/solvent interaction at different concentration and temperatures.

  16. In Situ Forming Polymeric Drug Delivery Systems

    PubMed Central

    Madan, M.; Bajaj, A.; Lewis, S.; Udupa, N.; Baig, J. A.

    2009-01-01

    In situ forming polymeric formulations are drug delivery systems that are in sol form before administration in the body, but once administered, undergo gelation in situ, to form a gel. The formation of gels depends on factors like temperature modulation, pH change, presence of ions and ultra violet irradiation, from which the drug gets released in a sustained and controlled manner. Various polymers that are used for the formulation of in situ gels include gellan gum, alginic acid, xyloglucan, pectin, chitosan, poly(DL-lactic acid), poly(DL-lactide-co-glycolide) and poly-caprolactone. The choice of solvents like water, dimethylsulphoxide, N-methyl pyrrolidone, triacetin and 2-pyrrolidone for these formulations depends on the solubility of polymer used. Mainly in situ gels are administered by oral, ocular, rectal, vaginal, injectable and intraperitoneal routes. The in situ gel forming polymeric formulations offer several advantages like sustained and prolonged action in comparison to conventional drug delivery systems. The article presents a detailed review of these types of polymeric systems, their evaluation, advancements and their commercial formulations. From a manufacturing point of view, the production of such devices is less complex and thus lowers the investment and manufacturing cost. PMID:20490289

  17. The intermolecular interaction in D2 - CX4 and O2 - CX4 (X = F, Cl) systems: Molecular beam scattering experiments as a sensitive probe of the selectivity of charge transfer component.

    PubMed

    Cappelletti, David; Falcinelli, Stefano; Pirani, Fernando

    2016-10-07

    Gas phase collisions of a D2 projectile by CF4 and by CCl4 targets have been investigated with the molecular beam technique. The integral cross section, Q, has been measured for both collisional systems in the thermal energy range and oscillations due to the quantum "glory" interference have been resolved in the velocity dependence of Q. The analysis of the measured Q(v) data provided novel information on the anisotropic potential energy surfaces of the studied systems at intermediate and large separation distances. The relative role of the most relevant types of contributions to the global interaction has been characterized. Extending the phenomenology of a weak intermolecular halogen bond, the present work demonstrates that while D2 - CF4 is basically bound through the balance between size (Pauli) repulsion and dispersion attraction, an appreciable intermolecular bond stabilization by charge transfer is operative in D2 - CCl4. We also demonstrated that the present analysis is consistent with that carried out for the F((2)P)-D2 and Cl((2)P)-D2 systems, previously characterized by scattering experiments performed with state-selected halogen atom beams. A detailed comparison of the present and previous results on O2-CF4 and O2-CCl4 systems pinpointed striking differences in the behavior of hydrogen and oxygen molecules when they interact with the same partner, mainly due to the selectivity of the charge transfer component. The present work contributes to cast light on the nature and role of the intermolecular interaction in prototype systems, involving homo-nuclear diatoms and symmetric halogenated molecules.

  18. The intermolecular interaction in D2 - CX4 and O2 - CX4 (X = F, Cl) systems: Molecular beam scattering experiments as a sensitive probe of the selectivity of charge transfer component

    NASA Astrophysics Data System (ADS)

    Cappelletti, David; Falcinelli, Stefano; Pirani, Fernando

    2016-10-01

    Gas phase collisions of a D2 projectile by CF4 and by CCl4 targets have been investigated with the molecular beam technique. The integral cross section, Q, has been measured for both collisional systems in the thermal energy range and oscillations due to the quantum "glory" interference have been resolved in the velocity dependence of Q. The analysis of the measured Q(v) data provided novel information on the anisotropic potential energy surfaces of the studied systems at intermediate and large separation distances. The relative role of the most relevant types of contributions to the global interaction has been characterized. Extending the phenomenology of a weak intermolecular halogen bond, the present work demonstrates that while D2 - CF4 is basically bound through the balance between size (Pauli) repulsion and dispersion attraction, an appreciable intermolecular bond stabilization by charge transfer is operative in D2 - CCl4. We also demonstrated that the present analysis is consistent with that carried out for the F(2P)-D2 and Cl(2P)-D2 systems, previously characterized by scattering experiments performed with state-selected halogen atom beams. A detailed comparison of the present and previous results on O2-CF4 and O2-CCl4 systems pinpointed striking differences in the behavior of hydrogen and oxygen molecules when they interact with the same partner, mainly due to the selectivity of the charge transfer component. The present work contributes to cast light on the nature and role of the intermolecular interaction in prototype systems, involving homo-nuclear diatoms and symmetric halogenated molecules.

  19. Vibrational nano-spectroscopic imaging correlating structure with intermolecular coupling and dynamics.

    PubMed

    Pollard, Benjamin; Muller, Eric A; Hinrichs, Karsten; Raschke, Markus B

    2014-04-11

    Molecular self-assembly, the function of biomembranes and the performance of organic solar cells rely on nanoscale molecular interactions. Understanding and control of such materials have been impeded by difficulties in imaging their properties with the desired nanometre spatial resolution, attomolar sensitivity and intermolecular spectroscopic specificity. Here we implement vibrational scattering-scanning near-field optical microscopy with high spectral precision to investigate the structure-function relationship in nano-phase separated block copolymers. A vibrational resonance is used as a sensitive reporter of the local chemical environment and we image, with few nanometre spatial resolution and 0.2 cm(-1) spectral precision, solvatochromic Stark shifts and line broadening correlated with molecular-scale morphologies. We discriminate local variations in electric fields between nano-domains with quantitative agreement with dielectric continuum models. This ability to directly resolve nanoscale morphology and associated intermolecular interactions can form a basis for the systematic control of functionality in multicomponent soft matter systems.

  20. Intermolecular interactions in rifabutin—2-hydroxypropyl-β-cyclodextrin—water solutions

    NASA Astrophysics Data System (ADS)

    Anshakova, A. V.; Yermolenko, Yu. V.; Konyukhov, V. Yu.; Polshakov, V. I.; Maksimenko, O. O.; Gelperina, S. E.

    2015-05-01

    The possibility of a intermolecular complex rifabutin (RB)-2-hydroxypropyl-β-cyclodextrin (HP-β-CD) formed as a result of the interaction of the piperidine fragment of the RB molecule and the hydrophobic cavity of the HP-β-CD molecule was found. The stability constant of the intermolecular complex was determined.

  1. Pediatric scleroderma: systemic or localized forms.

    PubMed

    Torok, Kathryn S

    2012-04-01

    Pediatric scleroderma includes 2 major groups of clinical entities, systemic sclerosis (SSc) and localized scleroderma (LS). Although both share a common pathophysiology, their clinical manifestations differ. LS is typically confined to the skin and underlying subcutis, with up to a quarter of patients showing extracutaneous disease manifestations such as arthritis and uveitis. Vascular, cutaneous, gastrointestinal, pulmonary, and musculoskeletal involvement are most commonly seen in children with SSc. Treatment of both forms targets the active inflammatory stage and halts disease progression; however, progress needs to be made toward the development of more effective antifibrotic therapy to help reverse disease damage. Copyright © 2012 Elsevier Inc. All rights reserved.

  2. 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…

  3. 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…

  4. Intermolecular potentials for hexafluoride gases

    SciTech Connect

    Aziz, R.A. . Dept. of Physics); Taylor, W.L. )

    1989-10-31

    Second virial coefficient and viscosity data were used to evaluate intermolecular potential functions proposed in the literature for SF{sub 6}, UF{sub 6}, and WF{sub 6}. It was found that none of the potentials could predict the properties simultaneously. By suitable adjustment of the repulsive wall, we constructed an inverse power (n{minus}7) potential which correlates second virial coefficient and viscosity data at the same time. The best integer repulsive exponent for SF{sub 6} was found to be n = 40, while that for UF{sub 6} and WF{sub 6} was n = 46. 41 refs., 10 figs., 11 tabs.

  5. 46 CFR 108.474 - Aqueous film forming foam systems.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 46 Shipping 4 2011-10-01 2011-10-01 false Aqueous film forming foam systems. 108.474 Section 108... DESIGN AND EQUIPMENT Fire Extinguishing Systems Foam Extinguishing Systems § 108.474 Aqueous film forming foam systems. Aqueous film forming foam systems may be installed if approved by the Commandant....

  6. 46 CFR 108.474 - Aqueous film forming foam systems.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 46 Shipping 4 2012-10-01 2012-10-01 false Aqueous film forming foam systems. 108.474 Section 108... DESIGN AND EQUIPMENT Fire Extinguishing Systems Foam Extinguishing Systems § 108.474 Aqueous film forming foam systems. Aqueous film forming foam systems may be installed if approved by the Commandant....

  7. 46 CFR 108.474 - Aqueous film forming foam systems.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 46 Shipping 4 2014-10-01 2014-10-01 false Aqueous film forming foam systems. 108.474 Section 108... DESIGN AND EQUIPMENT Fire Extinguishing Systems Foam Extinguishing Systems § 108.474 Aqueous film forming foam systems. Aqueous film forming foam systems may be installed if approved by the Commandant....

  8. 46 CFR 108.474 - Aqueous film forming foam systems.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 46 Shipping 4 2010-10-01 2010-10-01 false Aqueous film forming foam systems. 108.474 Section 108... DESIGN AND EQUIPMENT Fire Extinguishing Systems Foam Extinguishing Systems § 108.474 Aqueous film forming foam systems. Aqueous film forming foam systems may be installed if approved by the Commandant....

  9. 46 CFR 108.474 - Aqueous film forming foam systems.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 46 Shipping 4 2013-10-01 2013-10-01 false Aqueous film forming foam systems. 108.474 Section 108... DESIGN AND EQUIPMENT Fire Extinguishing Systems Foam Extinguishing Systems § 108.474 Aqueous film forming foam systems. Aqueous film forming foam systems may be installed if approved by the Commandant....

  10. Green synthesis, characterization and some physico-chemical studies on a novel intermolecular compound; 4-nitro-o-phenylenediamine-N, N-dimethylaminobenzaldehyde system

    NASA Astrophysics Data System (ADS)

    Rai, U. S.; Singh, Manjeet; Rai, R. N.

    2017-09-01

    An inter-molecular compound (IMC) L1 was synthesized by taking 1:1 molar ratio of p-nitro-o-phenylenediamine (NOPDA) and N, N-dimethylaminobenzaldehyde (DMAB) via thermally initiated solid state reaction. It was characterized by X-ray diffraction, spectral and optical studies. The single crystal of the (L1) was grown from saturated solution of ethanol using slow evaporation technique at 29 °C. From the single crystal X-ray diffraction analysis, it can be inferred that it crystallizes in triclinic unit cell with P-1 space group (CCDC No 1422765). Absorption spectrum of IMC (L1) shows a band at 318 nm attributed to the intra-molecular charge-transfer (ICT) excited state absorption and the other band at 376 nm is due to n→π* transition. The IMC (L1) shows a strong fluorescence at 418 nm with a Stokes shift (≈100 nm) and quantum efficiency (0.22) upon excitation in methyl alcohol at 318 nm.

  11. FormEd: An X Window System application for managing first-order formulas

    SciTech Connect

    Henry, T.L.; McCune, W.W.

    1990-11-01

    FormEd is a window-based program for constructing, displaying, and managing first-order logic formulas. The main motivation for constructing FormEd was the desire to have formulas displayed in a readable, two-dimensional format. Users of FormEd can make two kinds of transformation on formulas: logic transformations, such as negation normal form translation, which preserve the meaning of a formula, and edit transformations, which can be used to make arbitrary changes, such as adding a hypothesis to a subformula. FormEd was written by using the X Window System, Version 11, and code from the theorem prover OTTER. 4 refs.

  12. Identification and measurement of intermolecular interaction in polyester/polystyrene blends by FTIR-photoacoustic spectrometry

    USDA-ARS?s Scientific Manuscript database

    Fourier transform infrared photoacoustic spectrometry was used to reveal and identify n-p type intermolecular interaction formed in plastic comprising binary blends of polystyrene and a biodegradable polymer, either polylactic acid, polycaprolactone or poly(tetramethyleneadipate-co-terephthalate)....

  13. Some mathematical models of intermolecular autophosphorylation.

    PubMed

    Doherty, Kevin; Meere, Martin; Piiroinen, Petri T

    2015-04-07

    Intermolecular autophosphorylation refers to the process whereby a molecule of an enzyme phosphorylates another molecule of the same enzyme. The enzyme thereby catalyses its own phosphorylation. In the present paper, we develop two generic models of intermolecular autophosphorylation that also include dephosphorylation by a phosphatase of constant concentration. The first of these, a solely time-dependent model, is written as one ordinary differential equation that relies upon mass-action and Michaelis-Menten kinetics. Beginning with the enzyme in its dephosphorylated state, it predicts a lag before the enzyme becomes significantly phosphorylated, for suitable parameter values. It also predicts that there exists a threshold concentration for the phosphorylation of enzyme and that for suitable parameter values, a continuous or discontinuous switch in the phosphorylation of enzyme are possible. The model developed here has the advantage that it is relatively easy to analyse compared with most existing models for autophosphorylation and can qualitatively describe many different systems. We also extend our time-dependent model of autophosphorylation to include a spatial dependence, as well as localised binding reactions. This spatio-temporal model consists of a system of partial differential equations that describe a soluble autophosphorylating enzyme in a spherical geometry. We use the spatio-temporal model to describe the phosphorylation of an enzyme throughout the cell due to an increase in local concentration by binding. Using physically realistic values for model parameters, our results provide a proof-of-concept of the process of activation by local concentration and suggest that, in the presence of a phosphatase, this activation can be irreversible.

  14. An approach to the averaged intermolecular potential field of methane from viscosity

    NASA Astrophysics Data System (ADS)

    Zhang, Ailian; Yang, Xiaohong; Zhang, Shunxi

    2017-08-01

    A novel approach to averaged intermolecular potential field (AIPF) of methane from viscosity was developed. Using symmetric molecular interaction approximation and Maxwell-Boltzmann distribution function of velocity, equations relating the AIPF and viscosity have been derived. Applying the equations to methane, good agreements were found between high quality viscosity data and the equations via fitting method. Then a formula for methane's AIPF as a function of temperature and density was determined. Obtained results not only give a new method to estimate the AIPF for fluidic system, but also may form a novel base to study the viscosity of other alkane mixtures.

  15. Intermolecular interaction approach for TADF (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Wong, Ken-Tsung

    2016-09-01

    Materials with thermally activated delayed fluorescence (TADF) have recently emerged as new fluorescent emitters for highly efficient organic light-emitting diodes (OLEDs). Molecule with TADF behavior needs to have a small singlet-triplet energy difference (ΔES-T) that allows the up-conversion from nonradiative triplet state (T1) to radiative singlet state (S1) via reverse intersystem crossing (RISC) process. Generally, molecules with small ΔES-T can be obtained via carefully manipulate the degree of "intramolecular" charge transfer (ICT) between electron-donating and -accepting components, such that the electron exchange energy that contributes to ΔES-T, can be minimized. Alternatively, excited state with small ΔES-T can be feasibly realized via "intermolecular" charge transfer occurring at the interface between spatially separating donor (D) and acceptor (A) molecules. Because the exchange energy decreases as the HOMO-LUMO separation distance increases, theoretically, the intermolecular D/A charge transfer state (or exciplex) should have rather small ΔES-T, leading to efficient TADF. However, it is still a challenge to access highly efficient exciplex systems. This is mainly because exciplex formation is commonly accompanied with a large red shift of emission spectra and long radiative lifetime, which tend to diminish photoluminescence quantum yield (PLQY) as well as electroluminescence (EL) performance. Until now, exciplex-based OLEDs with external quantum efficiency (EQE) above 10% are still limited. By judicious selection of donor and acceptor, the formation of efficient exciplex can be feasibly achieved. In this conference, our recent efforts on highly efficient exciplexes using C3-symmetry triazine acceptors and various donors, and their device characteristics will be presented.

  16. Intermolecular interactions in solid benzene.

    PubMed

    Kearley, G J; Johnson, M R; Tomkinson, J

    2006-01-28

    The lattice dynamics and molecular vibrations of benzene and deuterated benzene crystals are calculated from force constants derived from density-functional theory (DFT) calculations and compared with measured inelastic neutron-scattering spectra. A very small change (0.5%) in lattice parameter is required to obtain real lattice-mode frequencies across the Brillouin zone. There is a strong coupling between wagging and breathing modes away from the zone center. This coupling and sensitivity to cell size arises from two basic interactions. Firstly, comparatively strong interactions that hold the benzene molecules together in layers. These include an intermolecular interaction in which H atoms of one molecule link to the center of the aromatic ring of a neighboring molecule. The layers are held to each other by weaker interactions, which also have components that hold molecules together within a layer. Small changes in the lattice parameters change this second type of interaction and account for the changes to the lattice dynamics. The calculations also reveal a small auxetic effect in that elongation of the crystal along the b axis leads to an increase in internal pressure in the ac plane, that is, elongation in the b direction induces expansion in the a and c directions.

  17. Mechanism of Intermolecular Electron Transfer in Bionanostructures

    NASA Astrophysics Data System (ADS)

    Gruodis, A.; Galikova, N.; Šarka, K.; Saulė, R.; Batiuškaitė, D.; Saulis, G.

    Hepatocellular carcinoma (HCC) is one of the most common malignant tumors worldwide. Most patients are inoperable and hepatoma cells are resistant to conventional chemotherapies. Thus, the development of novel therapies for HCC treatment is of paramount importance. Amongst different alimentary factors, vitamin C and vitamin K3 In the present work, it has been shown that the treatment of mouse hepatoma MH-22A cells by vitamin C and vitamin K3 at the ratio of 100:1 greatly enhanced their cytotoxicity. When cells were subjected to vitamin C at 200 μM or to vitamin K3 at 2 μM separately, their viability reduced by only about 10%. However, when vitamins C and K3 were combined at the same concentrations, they killed more than 90% of cells. To elucidate the mechanism of the synergistic cytotoxicity of the C&K3 mixture, theoretical quantum-chemical analysis of the dynamics of intermolecular electron transfer (IET) processes within the complexes containing C (five forms) and K3 (one form) has been carried out. Optimization of the ground state complex geometry has been provided by means of GAUSSIAN03 package. Simulation of the IET has been carried out using NUVOLA package, in the framework of molecular orbitals (MO). The rate of IET has been calculated using Fermi Golden rule. The results of simulations allow us to create the preliminary model of the reaction pathway.

  18. Electric Field Effects on the Intermolecular Interactions in Water Whiskers: Insight from Structures, Energetics, and Properties

    DOE PAGES

    Bai, Yang; He, Hui-Min; Li, Ying; ...

    2015-02-19

    Modulation of intermolecular interactions in response to external electric fields could be fundamental to the formation of unusual forms of water, such as water whiskers. However, a detailed understanding of the nature of intermolecular interactions in such systems is lacking. In this study, we present novel theoretical results based on electron correlation calculations regarding the nature of H-bonds in water whiskers, which is revealed by studying their evolution under external electric fields with various field strengths. We find that the water whiskers consisting of 2-7 water molecules all have a chain-length dependent critical electric field. Under the critical electric field,more » the most compact chain structures are obtained, featuring very strong H-bonds, herein referred to as covalent H-bonds. In the case of a water dimer whisker, the bond length of the novel covalent H-bond shortens by 25%, the covalent bond order increases by 9 times, and accordingly the H-bond energy is strengthened by 5 times compared to the normal H-bond in a (H2O)2 cluster. Below the critical electric field, it is observed that with increasing field strength, H-bonding orbitals display gradual evolutions in the orbital energy, orbital ordering, and orbital nature (i.e., from typical -style orbital to unusual -style double H-bonding orbital). We also show that beyond the critical electric field, a single water whisker may disintegrate to form a loosely bound zwitterionic chain due to a relay-style proton transfer, whereas two water whiskers may undergo intermolecular cross-linking to form a quasi-two-dimensional water network. In conclusion, these results help shed new insight on the effects of electric fields on water whisker formation.« less

  19. Electric Field Effects on the Intermolecular Interactions in Water Whiskers: Insight from Structures, Energetics, and Properties

    SciTech Connect

    Bai, Yang; He, Hui-Min; Li, Ying; Zhou, Zhong-Jun; Wang, Jia-Jun; Wu, Di; Chen, Wei; Gu, Feng-Long; Sumpter, Bobby G.; Huang, Jingsong

    2015-02-19

    Modulation of intermolecular interactions in response to external electric fields could be fundamental to the formation of unusual forms of water, such as water whiskers. However, a detailed understanding of the nature of intermolecular interactions in such systems is lacking. In this study, we present novel theoretical results based on electron correlation calculations regarding the nature of H-bonds in water whiskers, which is revealed by studying their evolution under external electric fields with various field strengths. We find that the water whiskers consisting of 2-7 water molecules all have a chain-length dependent critical electric field. Under the critical electric field, the most compact chain structures are obtained, featuring very strong H-bonds, herein referred to as covalent H-bonds. In the case of a water dimer whisker, the bond length of the novel covalent H-bond shortens by 25%, the covalent bond order increases by 9 times, and accordingly the H-bond energy is strengthened by 5 times compared to the normal H-bond in a (H2O)2 cluster. Below the critical electric field, it is observed that with increasing field strength, H-bonding orbitals display gradual evolutions in the orbital energy, orbital ordering, and orbital nature (i.e., from typical -style orbital to unusual -style double H-bonding orbital). We also show that beyond the critical electric field, a single water whisker may disintegrate to form a loosely bound zwitterionic chain due to a relay-style proton transfer, whereas two water whiskers may undergo intermolecular cross-linking to form a quasi-two-dimensional water network. In conclusion, these results help shed new insight on the effects of electric fields on water whisker formation.

  20. Probing Intermolecular Coupled Vibrations between Two Molecules

    NASA Astrophysics Data System (ADS)

    Han, Zhumin; Czap, Gregory; Xu, Chen; Chiang, Chi-lun; Yuan, Dingwang; Wu, Ruqian; Ho, W.

    2017-01-01

    Intermolecular interactions can induce energy shifts and coupling of molecular vibrations. However, the detection of intermolecular coupled vibrations has not been reported at the single molecule level. Here we detected an intermolecular coupled vibration between two CO molecules, one on the surface and another on the tip within the gap of a subkelvin scanning tunneling microscope, and analyzed the results by density functional calculations. We attribute the evolution of the energy and intensity of this coupled vibration as a function of tip-sample distance to the tilting and orbital alignment of the two CO molecules.

  1. Broadband reconfigurable optical beam-forming systems

    NASA Astrophysics Data System (ADS)

    Toughlian, Edward N.; Zmuda, Henry; Carter, Charity A.

    1994-06-01

    It is shown that by applying spatial frequency dependent optical phase compensation in an optical heterodyne process, variable RF delay can be achieved over a prescribed frequency band. Experimental results that demonstrate the performance of the delay line with regard to both maximum delay and resolution over a broad bandwidth are presented. Additionally, a spatially integrated optical system is proposed for control of phased array antennas, providing mechanical stability, essentially eliminating the drift problems associated with free-space optical systems, and providing high packing density. This approach uses a class of SLM known as a deformable mirror device and leads to a steerable arbitrary antenna radiation pattern of the true time-delay type. Also considered is the ability to utilize the delay line as a general photonic signal processing element in an adaptive (reconfigurable) transversal frequency filter configuration. Such systems are widely applicable in jammer/noise canceling systems, broadband ISDN, spread spectrum secure communications and the like.

  2. Temporal arteritis: a form of systemic panarteritis.

    PubMed Central

    Sendino, A; Barbado, F J; González-Anglada, I; Antón, E; López-Barea, F; Vázquez, J J

    1992-01-01

    The case is reported of a patient with giant cell arteritis affecting several organs. The triggering cause of death was a brainstem infarction due to basilar artery thrombosis. The necropsy showed the systemic character of the disease affecting the coronary, bronchial, and ovarian arteries. Images PMID:1417143

  3. Interpolation of intermolecular potentials using Gaussian processes

    NASA Astrophysics Data System (ADS)

    Uteva, Elena; Graham, Richard S.; Wilkinson, Richard D.; Wheatley, Richard J.

    2017-10-01

    A procedure is proposed to produce intermolecular potential energy surfaces from limited data. The procedure involves generation of geometrical configurations using a Latin hypercube design, with a maximin criterion, based on inverse internuclear distances. Gaussian processes are used to interpolate the data, using over-specified inverse molecular distances as covariates, greatly improving the interpolation. Symmetric covariance functions are specified so that the interpolation surface obeys all relevant symmetries, reducing prediction errors. The interpolation scheme can be applied to many important molecular interactions with trivial modifications. Results are presented for three systems involving CO2, a system with a deep energy minimum (HF-HF), and a system with 48 symmetries (CH4-N2). In each case, the procedure accurately predicts an independent test set. Training this method with high-precision ab initio evaluations of the CO2-CO interaction enables a parameter-free, first-principles prediction of the CO2-CO cross virial coefficient that agrees very well with experiments.

  4. Intermolecular domain docking in the hairpin ribozyme

    PubMed Central

    Sumita, Minako; White, Neil A.; Julien, Kristine R.; Hoogstraten, Charles G.

    2013-01-01

    The hairpin ribozyme is a prototype small, self-cleaving RNA motif. It exists naturally as a four-way RNA junction containing two internal loops on adjoining arms. These two loops interact in a cation-driven docking step prior to chemical catalysis to form a tightly integrated structure, with dramatic changes occurring in the conformation of each loop upon docking. We investigate the thermodynamics and kinetics of the docking process using constructs in which loop A and loop B reside on separate molecules. Using a novel CD difference assay to isolate the effects of metal ions linked to domain docking, we find the intermolecular docking process to be driven by sub-millimolar concentrations of the exchange-inert Co(NH3)63+. RNA self-cleavage requires binding of lower-affinity ions with greater apparent cooperativity than the docking process itself, implying that, even in the absence of direct coordination to RNA, metal ions play a catalytic role in hairpin ribozyme function beyond simply driving loop-loop docking. Surface plasmon resonance assays reveal remarkably slow molecular association, given the relatively tight loop-loop interaction. This observation is consistent with a “double conformational capture” model in which only collisions between loop A and loop B molecules that are simultaneously in minor, docking-competent conformations are productive for binding. PMID:23324606

  5. Cobalt complex of cinchonine: intermolecular interactions in two crystalline modifications.

    PubMed

    Skórska, Agnieszka; Oleksyn, Barbara J; Sliwiński, Jan

    2002-01-01

    Two crystalline modifications of cinchonine cobalt complex, C19H23Cl3CoN2O, were obtained from mixture of saturated alcohol solutions of CoCl3 x 6H2O and cinchonine. The X-ray structure analysis revealed that the asymmetric unit of one modification, CoCn1, contains only zwitterionic molecules of the complex. In the asymmetric unit of the other, CoCn2, there are two molecules of the title compound and two molecules of ethanol. The influence of the absolute configuration, the CoCl3 coordination with quinoline, and the presence of alcohol molecules on the studied structures was established by comparison of the crystal and molecular structures of both cobalt complexes with the analogous quinine complex and zinc complex of cinchonine. The interactions that dominate in the packing of the molecules in both structures are intermolecular hydrogen bonds. They form characteristic ring systems, depending on the presence of the alcohol molecules. The ring features are also related to the absolute configuration of the alkaloid.

  6. Quantitative tomographic imaging of intermolecular FRET in small animals

    PubMed Central

    Venugopal, Vivek; Chen, Jin; Barroso, Margarida; Intes, Xavier

    2012-01-01

    Forster resonance energy transfer (FRET) is a nonradiative transfer of energy between two fluorescent molecules (a donor and an acceptor) in nanometer range proximity. FRET imaging methods have been applied to proteomic studies and drug discovery applications based on intermolecular FRET efficiency measurements and stoichiometric measurements of FRET interaction as quantitative parameters of interest. Importantly, FRET provides information about biomolecular interactions at a molecular level, well beyond the diffraction limits of standard microscopy techniques. The application of FRET to small animal imaging will allow biomedical researchers to investigate physiological processes occurring at nanometer range in vivo as well as in situ. In this work a new method for the quantitative reconstruction of FRET measurements in small animals, incorporating a full-field tomographic acquisition system with a Monte Carlo based hierarchical reconstruction scheme, is described and validated in murine models. Our main objective is to estimate the relative concentration of two forms of donor species, i.e., a donor molecule involved in FRETing to an acceptor close by and a nonFRETing donor molecule. PMID:23243567

  7. System and method for incremental forming

    DOEpatents

    Beltran, Michael; Cao, Jian; Roth, John T.

    2015-12-29

    A system includes a frame configured to hold a workpiece and first and second tool positioning assemblies configured to be opposed to each other on opposite sides of the workpiece. The first and second tool positioning assemblies each include a toolholder configured to secure a tool to the tool positioning assembly, a first axis assembly, a second axis assembly, and a third axis assembly. The first, second, and third axis assemblies are each configured to articulate the toolholder along a respective axis. Each axis assembly includes first and second guides extending generally parallel to the corresponding axis and disposed on opposing sides of the toolholder with respect to the corresponding axis. Each axis assembly includes first and second carriages articulable along the first and second guides of the axis assembly, respectively, in the direction of the corresponding axis.

  8. Cutting tool form compensaton system and method

    DOEpatents

    Barkman, William E.; Babelay, Jr., Edwin F.; Klages, Edward J.

    1993-01-01

    A compensation system for a computer-controlled machining apparatus having a controller and including a cutting tool and a workpiece holder which are movable relative to one another along a preprogrammed path during a machining operation utilizes a camera and a vision computer for gathering information at a preselected stage of a machining operation relating to the actual shape and size of the cutting edge of the cutting tool and for altering the preprogrammed path in accordance with detected variations between the actual size and shape of the cutting edge and an assumed size and shape of the cutting edge. The camera obtains an image of the cutting tool against a background so that the cutting tool and background possess contrasting light intensities, and the vision computer utilizes the contrasting light intensities of the image to locate points therein which correspond to points along the actual cutting edge. Following a series of computations involving the determining of a tool center from the points identified along the tool edge, the results of the computations are fed to the controller where the preprogrammed path is altered as aforedescribed.

  9. Cutting tool form compensation system and method

    DOEpatents

    Barkman, W.E.; Babelay, E.F. Jr.; Klages, E.J.

    1993-10-19

    A compensation system for a computer-controlled machining apparatus having a controller and including a cutting tool and a workpiece holder which are movable relative to one another along a preprogrammed path during a machining operation utilizes a camera and a vision computer for gathering information at a preselected stage of a machining operation relating to the actual shape and size of the cutting edge of the cutting tool and for altering the preprogrammed path in accordance with detected variations between the actual size and shape of the cutting edge and an assumed size and shape of the cutting edge. The camera obtains an image of the cutting tool against a background so that the cutting tool and background possess contrasting light intensities, and the vision computer utilizes the contrasting light intensities of the image to locate points therein which correspond to points along the actual cutting edge. Following a series of computations involving the determining of a tool center from the points identified along the tool edge, the results of the computations are fed to the controller where the preprogrammed path is altered as aforedescribed. 9 figures.

  10. Highly Stereoselective Intermolecular Haloetherification and Haloesterification of Allyl Amides

    PubMed Central

    Soltanzadeh, Bardia; Jaganathan, Arvind; Staples, Richard J.

    2016-01-01

    An organocatalytic and highly regio-, diastereo-, and enantioselective intermolecular haloetherification and haloesterification reaction of allyl amides is reported. A variety of alkene substituents and substitution patterns are compatible with this chemistry. Notably, electronically unbiased alkene substrates exhibit exquisite regio- and diastereoselectivity for the title transformation. We also demonstrate that the same catalytic system can be used in both chlorination and bromination reactions of allyl amides with a variety of nucleophiles with little or no modification. PMID:26110812

  11. On Goursat Normal Forms, Prolongations, and Control Systems

    DTIC Science & Technology

    2007-11-02

    form, we also show how the exact linearization conditions for control systems can be restated in the language of Pfaffian systems. In addition, we give...area. We show that all of the main results in exact linearization of nonlinear systems can be restated in terms of exterior differential systems, and...to Goursat form can be specialized to give conditions for exact linearization . Theorem 6. Exact Linearization [5]. If a control system I defined

  12. Tooth form design supporting system in module design

    NASA Astrophysics Data System (ADS)

    Nagasawa, Junji; Namiki, Ryou; Tanaka, Souichi; Aoyama, Shigeru

    A lot of time was spent in designing the tooth form because there was no Computer Aided Design (CAD) system suitable for designing the tooth form of gears. A CAD system to support the tooth form design to promote efficiency of the tooth form design of gears for a wristwatch was developed. This system can perform calculation of torque transmission factor of gears, automatic drawing of tooth form drawing, and engagement simulation, and by utilizing this system the tooth form can be designed in less than one fourth of the time required by the conventional method. The characteristics of the system used to calculate the torque transmission factor of a pair of gears are summarized and the displayed results are shown.

  13. Efficient activation of a visible light-activatable CA4 prodrug through intermolecular photo-unclick chemistry in mitochondria.

    PubMed

    Bio, Moses; Rajaputra, Pallavi; Lim, Irene; Thapa, Pritam; Tienabeso, Bomaonye; Hurst, Robert E; You, Youngjae

    2017-02-07

    Photo-unclick chemistry mediates visible and near IR-controlled drug release via a singlet oxygen (SO)-cleavable linker. Due to the limited diffusion distance of SO in biological systems, a photosensitizer and the SO-cleavable linker have been conjugated in one molecule or mixed in nano-drug delivery systems. In this communication, we demonstrate a new strategy to activate prodrugs with photo-unclick chemistry in an intermolecular fashion using an SO-cleavable CA4 prodrug and a mitochondria-specific photosensitizer, protoporphyrin IX, formed from prodrug hexyl-5-aminolevulinate.

  14. Rorschach Form Quality in Two Editions of Exner's Comprehensive System.

    ERIC Educational Resources Information Center

    Barley, William D.; And Others

    Form level is a major element in the scoring and interpretation of Rorschach responses. Exner's 1974 text and 1976 comprehensive system workbook provided helpful norms and scoring conventions for determining form quality, but its 1985 revision appeared to lead to generally lower levels of form quality. To examine this clinical impression, the…

  15. Rorschach Form Quality in Two Editions of Exner's Comprehensive System.

    ERIC Educational Resources Information Center

    Barley, William D.; And Others

    Form level is a major element in the scoring and interpretation of Rorschach responses. Exner's 1974 text and 1976 comprehensive system workbook provided helpful norms and scoring conventions for determining form quality, but its 1985 revision appeared to lead to generally lower levels of form quality. To examine this clinical impression, the…

  16. Covalent intermolecular interaction of the nitric oxide dimer (NO)2

    NASA Astrophysics Data System (ADS)

    Zhang, Hui; Zheng, Gui-Li; Lv, Gang; Geng, Yi-Zhao; Ji, Qing

    2015-09-01

    Covalent bonds arise from the overlap of the electronic clouds in the internucleus region, which is a pure quantum effect and cannot be obtained in any classical way. If the intermolecular interaction is of covalent character, the result from direct applications of classical simulation methods to the molecular system would be questionable. Here, we analyze the special intermolecular interaction between two NO molecules based on quantum chemical calculation. This weak intermolecular interaction, which is of covalent character, is responsible for the formation of the NO dimer, (NO)2, in its most stable conformation, a cis conformation. The natural bond orbital (NBO) analysis gives an intuitive illustration of the formation of the dimer bonding and antibonding orbitals concomitant with the breaking of the π bonds with bond order 0.5 of the monomers. The dimer bonding is counteracted by partially filling the antibonding dimer orbital and the repulsion between those fully or nearly fully occupied nonbonding dimer orbitals that make the dimer binding rather weak. The direct molecular mechanics (MM) calculation with the UFF force fields predicts a trans conformation as the most stable state, which contradicts the result of quantum mechanics (QM). The lesson from the investigation of this special system is that for the case where intermolecular interaction is of covalent character, a specific modification of the force fields of the molecular simulation method is necessary. Project supported by the National Natural Science Foundation of China (Grant Nos. 90403007 and 10975044), the Key Subject Construction Project of Hebei Provincial Universities, China, the Research Project of Hebei Education Department, China (Grant Nos. Z2012067 and Z2011133), the National Natural Science Foundation of China (Grant No. 11147103), and the Open Project Program of State Key Laboratory of Theoretical Physics, Institute of Theoretical Physics, Chinese Academy of Sciences, China (Grant No. Y5

  17. Density functional calculation of intermolecular potentials.

    PubMed

    Nyeland, Carl

    2011-06-30

    Calculations of intermolecular potentials following the density functional theory (DFT) turn out to be very complicated without using some appropriate approximations. Most often the following three approximations have been considered. In one approximation the disturbed charge distributions during collisions are reduced to sums of undisturbed charge distributions from the colliding species. In another approximation, the so-called local density approximation (LDA), one neglects the fact that the intermolecular potentials that depend on charge densities also depend on gradients in the densities. In a third approximation one assumes that the intermolecular potential can be considered as a sum of two terms: a term for the long-range geometry and a term for the short-range geometry. In this Article the three approximations mentioned will be discussed for numerical accuracy for calculations of potentials between inert gas atoms and for calculations of potentials between surfaces and inert gas atoms. In the discussion a few other approximations will be mentioned too.

  18. Controlling the growth of multiple ordered heteromolecular phases by utilizing intermolecular repulsion

    NASA Astrophysics Data System (ADS)

    Henneke, Caroline; Felter, Janina; Schwarz, Daniel; Stefan Tautz, F.; Kumpf, Christian

    2017-06-01

    Metal/organic interfaces and their structural, electronic, spintronic and thermodynamic properties have been investigated intensively, aiming to improve and develop future electronic devices. In this context, heteromolecular phases add new design opportunities simply by combining different molecules. However, controlling the desired phases in such complex systems is a challenging task. Here, we report an effective way of steering the growth of a bimolecular system composed of adsorbate species with opposite intermolecular interactions--repulsive and attractive, respectively. The repulsive species forms a two-dimensional lattice gas, the density of which controls which crystalline phases are stable. Critical gas phase densities determine the constant-area phase diagram that describes our experimental observations, including eutectic regions with three coexisting phases. We anticipate the general validity of this type of phase diagram for binary systems containing two-dimensional gas phases, and also show that the density of the gas phase allows engineering of the interface structure.

  19. Intermolecular Vibrations of Hydrophobic Amino Acids

    NASA Astrophysics Data System (ADS)

    Williams, Michael Roy Casselman

    Hydrophobic amino acids interact with their chemical environment through a combination of electrostatic, hydrogen bonding, dipole, induced dipole, and dispersion forces. These interactions all have their own characteristic energy scale and distance dependence. The low-frequency (0.1-5 THz, 5-150 cm-1) vibrational modes of amino acids in the solid state are a direct indicator of the interactions between the molecules, which include interactions between an amino acid functional group and its surroundings. This information is central to understanding the dynamics and morphology of proteins. The alpha-carbon is a chiral center for all of the hydrophobic amino acids, meaning that they exist in two forms, traditionally referred to as L- and D-enantiomers. This nomenclature indicates which direction the molecule rotates plane-polarized visible light (levorotory and dextrorotory). Chiral a-amino acids in proteins are exclusively the L-variety In the solid state, the crystal lattice of the pure L-enantiomer is the mirror image of the D-enantiomer crystal lattice. These solids are energetically identical. Enantiomers also have identical spectroscopic properties except when the measurement is polarization sensitive. A mixture of equal amounts D- and L-amino acid enantiomers can crystallize into a racemic (DL-) structure that is different from that of the pure enantiomers. Whether a solution of both enantiomers will crystallize into a racemic form or spontaneously resolve into a mixture of separate D- and L-crystals largely depends on the interactions between molecules available in the various possible configurations. This is an active area of research. Low-frequency vibrations with intermolecular character are very sensitive to changes in lattice geometry, and consequently the vibrational spectra of racemic crystals are usually quite distinct from the spectra of the crystals of the corresponding pure enantiomers in the far-infrared (far-IR). THz time-domain spectroscopy (THz

  20. Separation of intra- and intermolecular contributions to the PELDOR signal

    NASA Astrophysics Data System (ADS)

    Schöps, Philipp; Plackmeyer, Jörn; Marko, Andriy

    2016-08-01

    Pulsed Electron-electron Double Resonance (PELDOR) is commonly used to measure distances between native paramagnetic centers or spin labels attached to complex biological macromolecules. In PELDOR the energies of electron magnetic dipolar interactions are measured by analyzing the oscillation frequencies of the recorded time resolved signal. Since PELDOR is an ensemble method, the detected signal contains contributions from intramolecular, as well as intermolecular electron spin interactions. The intramolecular part of the signal contains the information about the structure of the studied molecules, thus it is very important to accurately separate intra- and intermolecular contributions to the total signal. This separation can become ambiguous, when the length of the PELDOR signal is not much longer than twice the oscillation period of the signal. In this work we suggest a modulation depth scaling method, which can use short PELDOR signals in order to extract the intermolecular contribution. Using synthetic data we demonstrate the advantages of the new approach and analyze its stability with regard to signal noise. The method was also successfully tested on experimental data of three systems measured at Q-Band frequencies, two model compounds in deuterated and protonated solvents and one biological sample, namely BetP. The application of the new method with an assigned value of the signal modulation depth enables us to determine the interspin distances in all cases. This is especially interesting for the model compound with an interspin distance of 5.2 nm in the protonated solvent and the biological sample, since an accurate separation of the intra- and intermolecular PELDOR signal contributions would be difficult with the standard approach in those cases.

  1. Competing Intramolecular vs. Intermolecular Hydrogen Bonds in Solution

    PubMed Central

    Nagy, Peter I.

    2014-01-01

    A hydrogen bond for a local-minimum-energy structure can be identified according to the definition of the International Union of Pure and Applied Chemistry (IUPAC recommendation 2011) or by finding a special bond critical point on the density map of the structure in the framework of the atoms-in-molecules theory. Nonetheless, a given structural conformation may be simply favored by electrostatic interactions. The present review surveys the in-solution competition of the conformations with intramolecular vs. intermolecular hydrogen bonds for different types of small organic molecules. In their most stable gas-phase structure, an intramolecular hydrogen bond is possible. In a protic solution, the intramolecular hydrogen bond may disrupt in favor of two solute-solvent intermolecular hydrogen bonds. The balance of the increased internal energy and the stabilizing effect of the solute-solvent interactions regulates the new conformer composition in the liquid phase. The review additionally considers the solvent effects on the stability of simple dimeric systems as revealed from molecular dynamics simulations or on the basis of the calculated potential of mean force curves. Finally, studies of the solvent effects on the type of the intermolecular hydrogen bond (neutral or ionic) in acid-base complexes have been surveyed. PMID:25353178

  2. Investigation on intermolecular interaction between two solutes where one solute occurs in two states

    NASA Astrophysics Data System (ADS)

    Kang, Xiaoyan; He, Anqi; Guo, Ran; Chen, Jing; Zhai, Yanjun; Xu, Yizhuang; Noda, Isao; Wu, Jinguang

    2016-11-01

    The spectral behavior of a pair of 2D asynchronous spectra generated by using the double asynchronous orthogonal sample design (DAOSD) approach on a chemical system is investigated. Two solutes (P and Q) are dissolved in the solution and intermolecular interaction between P and Q is characterized. In this particular system, P occurs in two exchangeable states when it is dissolved in the solutions. Results on mathematical analysis and computer simulation demonstrated that interference unrelated to the intermolecular interaction can be completely removed. Hence the resultant 2D asynchronous spectra generated by using the DAOSD approach can reflect intermolecular interaction reliably. Moreover, properties of cross peaks in different regions of the pair of asynchronous spectra are discussed. In our previous works, cross peaks generated by using the DAOSD and relevant techniques reflect variations on peak position, bandwidth or absorptivity of the characteristic peaks of solutes caused by intermolecular interaction. However, we find that cross peak can still be produced even if intermolecular interaction do not bring about any changes on the characteristic peaks of solutes. Mathematical analysis demonstrates that cross peaks are related to the variations of chemical systems caused by intermolecular interaction at a network level.

  3. Vibrational nano-spectroscopic imaging correlating structure with intermolecular coupling and dynamics

    PubMed Central

    Pollard, Benjamin; Muller, Eric A.; Hinrichs, Karsten; Raschke, Markus B.

    2014-01-01

    Molecular self-assembly, the function of biomembranes and the performance of organic solar cells rely on nanoscale molecular interactions. Understanding and control of such materials have been impeded by difficulties in imaging their properties with the desired nanometre spatial resolution, attomolar sensitivity and intermolecular spectroscopic specificity. Here we implement vibrational scattering-scanning near-field optical microscopy with high spectral precision to investigate the structure–function relationship in nano-phase separated block copolymers. A vibrational resonance is used as a sensitive reporter of the local chemical environment and we image, with few nanometre spatial resolution and 0.2 cm−1 spectral precision, solvatochromic Stark shifts and line broadening correlated with molecular-scale morphologies. We discriminate local variations in electric fields between nano-domains with quantitative agreement with dielectric continuum models. This ability to directly resolve nanoscale morphology and associated intermolecular interactions can form a basis for the systematic control of functionality in multicomponent soft matter systems. PMID:24721995

  4. An improved intermolecular potential for sulfur hexafluoride

    SciTech Connect

    Aziz, R.A.; Slaman, M.J. ); Taylor, W.L.; Hurly, J.J. Department of Chemistry, University of Cincinnati, Cincinnati, Ohio 45221 )

    1991-01-15

    Second virial coefficient data and viscosity were used to evaluate effective isotropic intermolecular potential functions proposed in the literature for sulfur hexafluoride. It was found that none of the potentials could predict the properties simultaneously. We have constructed a Morse--Morse--Spline--van der Waals (MMSV) potential which satisfactorily correlates second virial coefficient and viscosity data at the same time.

  5. Catalytic intermolecular alkene oxyamination with nitrenes.

    PubMed

    Dequirez, Geoffroy; Ciesielski, Jennifer; Retailleau, Pascal; Dauban, Philippe

    2014-07-14

    The Rh(II)-catalyzed intermolecular addition of nitrenes to aromatic and aliphatic alkenes provides vicinal amino alcohols with yields of up to 95 % and complete regioselectivity. This 1,2-oxyamination reaction involves the formation of an aziridine intermediate that undergoes in situ ring opening. The latter is induced by the Rh-bound nitrene that behaves as a Lewis acid.

  6. Intermolecular Slip Mechanism in Tropocollagen Nanofibrils

    DTIC Science & Technology

    2009-01-01

    our studies could advance our knowledge of mechan- isms underlying important collagen-related diseases like Osteogenesis Imperfecta or Ehlers-Danlos...collagen mutations, these studies could advance our knowledge of mechanisms underlying important collagen-related diseases like Osteogenesis ... Imperfecta or Ehlers-Danlos Syndrome. REPORT DOCUMENTATION PAGE (SF298) (Continuation Sheet) Continuation for Block 13 ARO Report Number Intermolecular slip

  7. Transformations of PTCDA structures on rutile TiO2 induced by thermal annealing and intermolecular forces.

    PubMed

    Godlewski, Szymon; Prauzner-Bechcicki, Jakub S; Glatzel, Thilo; Meyer, Ernst; Szymoński, Marek

    2015-01-01

    Transformations of molecular structures formed by perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA) molecules on a rutile TiO2(110) surface are studied with low-temperature scanning tunnelling microscopy. We demonstrate that metastable molecular assemblies transform into differently ordered structures either due to additional energy provided by thermal annealing or when the influence of intermolecular forces is increased by the enlarged amount of deposited molecules. Proper adjustment of molecular coverage and substrate temperature during deposition allows for fabrication of desired assemblies. Differences between PTCDA/TiO2(110) and PTCDA/TiO2(011) systems obtained through identical experimental procedures are discussed.

  8. Methanol-methanol and methanol-water systems: the intermolecular interactions controlling the transition from small clusters to the liquid phase.

    PubMed

    Albertí, Margarita; Amat, Anna; Aguilar, Antonio; Pirani, Fernando

    2017-06-28

    The present paper focuses on the characterization of the properties of methanol and water molecules in gas and liquid environments. A force field for methanol-methanol and methanol-water interactions, useful to be applied in Molecular Dynamics (MD) simulations, is proposed. The electrostatic interaction contributions, arising from permanent charge and/or from anisotropic charge distributions originating from permanent electric multipoles (Vel), different in gas and in liquid phases, are combined with the non electrostatic ones (Vnel), defined by means of Improved Lennard-Jones (ILJ) functions [F. Pirani et al., Phys. Chem. Chem. Phys., 2008, 10, 5489-5503]. Interestingly, the relevant parameters of the ILJ functions are not fitted to reproduce the selected properties of the systems but calculated from the molecular polarizability, which is considered the key property to define size (or Pauli) repulsion and dispersion and induction attractions. The constructed force field predicts binding energies and geometries of the methanol-methanol and methanol-water dimers, in good agreement with available data. On the other hand, several bulk and structural properties of liquid methanol, such as densities, vaporization enthalpies, diffusion coefficients, coefficients of cubic thermal expansion, heat capacities at constant pressure and some relevant radial distribution functions, calculated considering 2744 molecules and different conditions of pressure and temperature, have also been found to be in good agreement with experimental data. The study has been completed by calculating the density values at 298 K and 1 bar of some methanol-water mixtures, which have also been found to be in good agreement with experimental data.

  9. Altering intra- to inter-molecular hydrogen bonding by dimethylsulfoxide: A TDDFT study of charge transfer for coumarin 343

    NASA Astrophysics Data System (ADS)

    Liu, Xiaochun; Yin, Hang; Li, Hui; Shi, Ying

    2017-04-01

    DFT and TDDFT methods were carried out to investigate the influences of intramolecular and intermolecular hydrogen bonding on excited state charge transfer for coumarin 343 (C343). Intramolecular hydrogen bonding is formed between carboxylic acid group and carbonyl group in C343 monomer. However, in dimethylsulfoxide (DMSO) solution, DMSO 'opens up' the intramolecular hydrogen bonding and forms solute-solvent intermolecular hydrogen bonded C343-DMSO complex. Analysis of frontier molecular orbitals reveals that intramolecular charge transfer (ICT) occurs in the first excited state both for C343 monomer and complex. The results of optimized geometric structures indicate that the intramolecular hydrogen bonding interaction is strengthened while the intermolecular hydrogen bonding is weakened in excited state, which is confirmed again by monitoring the shifts of characteristic peaks of infrared spectra. We demonstrated that DMSO solvent can not only break the intramolecular hydrogen bonding to form intermolecular hydrogen bonding with C343 but also alter the mechanism of excited state hydrogen bonding strengthening.

  10. Cooling system optimization analysis for hot forming processes

    NASA Astrophysics Data System (ADS)

    Ghoo, Bonyoung; Umezu, Yasuyoshi; Watanabe, Yuko

    2013-12-01

    Hot forming technology was developed to produce automotive panels having ultra-high tensile stress over 1500MPa. The elevated temperature corresponds with decreased flow stress and increased ductility. Furthermore, hot forming products have almost zero springback amounts. This advanced forming technology accelerates the needs for numerical simulations coupling with thermal-mechanical formulations. In the present study, 3-dimensional finite element analyses for hot forming processes are conducted using JSTAMP/NV and LS-DYNA considering cooling system. Special attention is paid to the optimization of cooling system using thermo-mechanical finite element analysis through the influence of various cooling parameters. The presented work shows an adequate cooling system functions and microstructural phase transformation material model together with a proper set of numerical parameters can give both efficient and accurate design insight in hot forming manufacturing process. JSTAMP/NV and LS-DYNA can become a robust combination set for complex hot forming analysis which needs thermo-mechanical and microstructural material modeling and various process modeling. The use of the new JSTAMP/NV function for multishot manufacturing process is shown good capabilities in cooling system evaluation. And the use of the advanced LS-DYNA microstructural phase transformation model is shown good evaluation results in martensite amount and Vickers hardness after quenching.

  11. A New Sheet Metal Forming System Based on Incremental Punching

    NASA Astrophysics Data System (ADS)

    Luo, Yuanxin

    Stamping is one of the most commonly used manufacturing processes. Everyday, millions of parts are formed by this process. The conventional stamping is to form a part in one or several operations with a press machine and a set/sets of dies. It is very efficient but is not cost effective for small batch production parts and prototypes as the dies are expensive and time consuming to make. Recently, with the increasing demands for low-volume and customer-made products, a die-less forming method, Incremental Sheet Metal Forming (ISMF), has become one of the leading R&D topics in the industry. ISMF uses a small generic tool to apply a sequence of operations along the given path to deform the sheet incrementally. These small deformations accumulate to form the final shape of the part. As a result, different parts can be made by the same setup. Despite of some 30 years of research and development, however, ISMF technology is still premature for industrial applications due to the following reasons: The accuracy of the part is limited; the surface roughness is poor; and the productivity is low. This motivates the presented research. In this research, a new incremental forming system based on incremental punching is designed and built. The system consists of a 3-axes CNC platform, a high speed hydraulic cylinder with a hemispherical forming tool, and a PC-based CNC control system. The hydraulic system provides the forming force to deform the sheet metal with constant stokes, while the CNC system positions the part. When forming a part, the forming tool punches the sheet metal along the given contour of the part punch by punch; when one layer of the part is completed, the forming tool moves down to the next layer; and the process is finished till all layers are completed. The CNC control system works with standard NC code, and hence, is easy to use. In order to ensure the desirable performance of the machine, dynamic analysis of the machine is necessary. The analysis is

  12. Effects of intermolecular interaction on inelastic electron tunneling spectra

    NASA Astrophysics Data System (ADS)

    Kula, Mathias; Luo, Yi

    2008-02-01

    We have examined the effects of intermolecular interactions on the inelastic electron tunneling spectroscopy (IETS) of model systems: a pair of benzenethiol or a pair of benzenedithiol sandwiched between gold electrodes. The dependence of the IETS on the mutual position of and distance between the paired molecules has been predicted and discussed in detailed. It is shown that, although in most cases, there are clear spectral fingerprints present which allow identification of the actual structures of the molecules inside the junction. Caution must be exercised since some characteristic lines can disappear at certain symmetries. The importance of theoretical simulation is emphasized.

  13. The NMR Chemical Shift: - and Intermolecular Effects

    NASA Astrophysics Data System (ADS)

    de Dios, Angel Cagandahan

    1992-01-01

    Gas phase NMR measurements were performed to provide a more accurate description of the shielding. These experiments were aimed to provide the finer details of shielding: its dependence on the geometry of the molecule and intermolecular factors. Together with these experiments were ab initio calculations of the shielding designed to deepen our understanding of how the shielding is affected by the internal motions of the molecule as well as interactions among the molecules. The exceptional cases of ^{15 }N in NH_3 and ^{31}P in PH_3 were rigorously studied. The deuterium-induced isotope shifts were found to be dominated by contributions arising from bond extension. The temperature dependence is found to be a combination of contributions coming from centrifugal stretching and bond angle distortion. These cases were compared with ^{13}C in CH_4 and ^{17 }O in H_2O revealing some general characteristics of shielding surfaces. As a model for the intermolecular shift for rare gas atoms, the argon dimer was used. Through a scaling scheme, measured second virial coefficients of the shielding of ^{129}Xe in various collision partners were satisfactorily reproduced from the ab initio shielding function of the argon dimer. The intermolecular shielding function also helped in interpreting gas-to-solution shifts of rare gases and the ^ {129}Xe NMR results from adsorption studies. Lastly, an attempt was made to develop a theory that would explain both intramolecular and intermolecular effects on the chemical shifts. It was discovered that a general shape for the shielding function was possible.

  14. Intermolecular Michael reactions: a computational investigation.

    PubMed

    Kwan, Eugene E; Evans, David A

    2010-11-19

    Computational studies have suggested that η(3)-lithium enolates in which the cation is partially bound to both carbon and oxygen may be important reactive intermediates. DFT calculations are used to demonstrate that explicitly solvated acetone enolates are largely O-bound. With this premise in mind, the stereochemical course of intermolecular Michael additions is examined. The results are generally consistent with what is observed experimentally and the model advanced by Heathcock and co-workers.

  15. Prevalence of chaos in planetary systems formed through embryo accretion

    NASA Astrophysics Data System (ADS)

    Clement, Matthew S.; Kaib, Nathan A.

    2017-05-01

    The formation of the solar system's terrestrial planets has been numerically modeled in various works, and many other studies have been devoted to characterizing our modern planets' chaotic dynamical state. However, it is still not known whether our planets fragile chaotic state is an expected outcome of terrestrial planet accretion. We use a suite of numerical simulations to present a detailed analysis and characterization of the dynamical chaos in 145 different systems produced via terrestrial planet formation in Kaib and Cowan (2015). These systems were created in the presence of a fully formed Jupiter and Saturn, using a variety of different initial conditions. They are not meant to provide a detailed replication of the actual present solar system, but rather serve as a sample of similar systems for comparison and analysis. We find that dynamical chaos is prevalent in roughly half of the systems we form. We show that this chaos disappears in the majority of such systems when Jupiter is removed, implying that the largest source of chaos is perturbations from Jupiter. Chaos is most prevalent in systems that form 4 or 5 terrestrial planets. Additionally, an eccentric Jupiter and Saturn is shown to enhance the prevalence of chaos in systems. Furthermore, systems in our sample with a center of mass highly concentrated between ∼0.8-1.2 AU generally prove to be less chaotic than systems with more exotic mass distributions. Through the process of evolving systems to the current epoch, we show that late instabilities are quite common in our systems. Of greatest interest, many of the sources of chaos observed in our own solar system (such as the secularly driven chaos between Mercury and Jupiter) are shown to be common outcomes of terrestrial planetary formation. Thus, consistent with previous studies such as Laskar (1996), the solar system's marginally stable, chaotic state may naturally arise from the process of terrestrial planet formation.

  16. Rational targeting of subclasses of intermolecular interactions: elimination of nonspecific binding for analyte sensing.

    PubMed

    Lane, Jordan S; Richens, Joanna L; Vere, Kelly-Ann; O'Shea, Paul

    2014-08-12

    The ability to target and control intermolecular interactions is crucial in the development of several different technologies. Here we offer a tool to rationally design liquid media systems that can modulate specific intermolecular interactions. This has broad implications in deciphering the nature of intermolecular forces in complex solutions and offers insight into the forces that govern both specific and nonspecific binding in a given system. Nonspecific binding still continues to be a problem when dealing with analyte detection across a range of different detection technologies. Here, we exemplify the problem of nonspecific binding on model membrane systems and when dealing with low-abundance protein detection on commercially available SPR technology. A range of different soluble reagents that target specific subclasses of intermolecular interactions have been tested and optimized to virtually eliminate nonspecific binding while leaving specific interactions unperturbed. Thiocyanate ions are used to target nonpolar interactions, and small reagents such as glycylglycylglycine are used to modulate the dielectric constant, which targets charge-charge and dipole interactions. We show that with rational design and careful modulation these reagents offer a step forward in dissecting the intermolecular forces that govern binding, alongside offering nonspecific binding elimination in detection systems.

  17. Tannin oxidation: intra- versus intermolecular reactions.

    PubMed

    Poncet-Legrand, Céline; Cabane, Bernard; Bautista-Ortín, Ana-Belén; Carrillo, Stéphanie; Fulcrand, Hélène; Pérez, Javier; Vernhet, Aude

    2010-09-13

    Grape and apple condensed tannin fractions were autoxidized at high concentrations (5 g/L) in aqueous solutions and analyzed by thiolysis (depolymerization followed by HPLC analysis) and small angle X-ray scattering (SAXS). Structural parameters of native (unoxidized) tannin polymers were derived from SAXS according to the wormlike chain model: the length per monomer is 15 A, the length of the statistical segment 17 A, and the cross section of the macromolecule has a radius within the range 3-4.5 A. The rather short length of the statistical segment is an effect of the different location of interflavanol linkages, which cause a loss of orientational correlation between successive monomers. Oxidation created new bonds that were resistant to thiolysis, and, according to thiolysis, some of these new bonds were intramolecular. However, according to SAXS, oxidation at high tannin concentration caused the weight average degree of polymerization to increase, indicating that intermolecular reactions took place as well, creating larger macromolecules. In the case of the smaller grape seed tannins, these intermolecular reactions took place "end to end" leading to the formation of longer linear macromolecules, at least in the earlier stages of oxidation. In the case of the larger apple tannins, the SAXS patterns were characteristic of larger branched macromolecules. Accordingly, the intermolecular reactions were mainly "end to middle". This is in agreement with the higher probabilities of "end to middle" reactions arising from a higher ratio extension unit/terminal unit in the latter case.

  18. Computing free energy hypersurfaces for anisotropic intermolecular associations.

    PubMed

    Strümpfer, Johan; Naidoo, Kevin J

    2010-01-30

    We previously used an adaptive reaction coordinate force biasing method for calculating the free energy of conformation (Naidoo and Brady, J Am Chem Soc 1999, 121, 2244) and chemical reactions (Rajamani et al., J Comput Chem 2003, 24, 1775) amongst others. Here, we describe a generalized version able to produce free energies in multiple dimensions, descriptively named the free energies from adaptive reaction coordinate forces method. To illustrate it, we describe how we calculate a multidimensional intermolecular orientational free energy, which can be used to investigate complex systems such as protein conformation and liquids. This multidimensional intermolecular free energy W(r, theta(1), theta(2), phi) provides a measure of orientationally dependent interactions that are appropriate for applications in systems that inherently have molecular anisotropic features. It is a highly informative free energy volume, which can be used to parameterize key terms such as the Gay-Berne intermolecular potential in coarse grain simulations. To demonstrate the value of the information gained from the W(r, theta(1), theta(2), phi) hypersurfaces we calculated them for TIP3P, TIP4P, and TIP5P dimer water models in vacuum. A comparison with a commonly used one-dimensional distance free energy profile is made to illustrate the significant increase in configurational information. The W(r) plots show little difference between the three models while the W(r, theta(1), theta(2), phi) hypersurfaces reveal the underlying energetic reasons why these potentials reproduce tetrahedrality in the condensed phase so differently from each. Copyright 2009 Wiley Periodicals, Inc.

  19. An isotopic mass effect on the intermolecular potential

    SciTech Connect

    Herman, Michael F.; Currier, Robert Patrick; Clegg, Samuel M.

    2015-09-28

    The impact of isotopic variation on the electronic energy and intermolecular potentials is often suppressed when calculating isotopologue thermodynamics. Intramolecular potential energy surfaces for distinct isotopologues are in fact equivalent under the Born–Oppenheimer approximation, which is sometimes used to imply that the intermolecular interactions are independent of isotopic mass. In this paper, the intermolecular dipole–dipole interaction between hetero-nuclear diatomic molecules is considered. It is shown that the intermolecular potential contains mass-dependent terms even though each nucleus moves on a Born–Oppenheimer surface. Finally, the analysis suggests that mass dependent variations in intermolecular potentials should be included in comprehensive descriptions of isotopologue thermodynamics.

  20. Spray forming system for producing molds, dies and related tooling

    DOEpatents

    McHugh, Kevin M.

    2000-01-01

    A system for the spray forming manufacturing of near-net-shape molds, dies and related toolings, wherein liquid material such as molten metal, metallic alloys, or polymers are atomized into fine droplets by a high temperature, high velocity gas and deposited onto a pattern. Quenching of the atomized droplets provides a heat sink, thereby allowing undercooled and partially solidified droplets to be formed in-flight. Composites can be formed by combining the atomized droplets with solid particles such as powders, whiskers or fibers.

  1. Beam-Forming Concentrating Solar Thermal Array Power Systems

    NASA Technical Reports Server (NTRS)

    Cwik, Thomas A. (Inventor); Dimotakis, Paul E. (Inventor); Hoppe, Daniel J. (Inventor)

    2016-01-01

    The present invention relates to concentrating solar-power systems and, more particularly, beam-forming concentrating solar thermal array power systems. A solar thermal array power system is provided, including a plurality of solar concentrators arranged in pods. Each solar concentrator includes a solar collector, one or more beam-forming elements, and one or more beam-steering elements. The solar collector is dimensioned to collect and divert incoming rays of sunlight. The beam-forming elements intercept the diverted rays of sunlight, and are shaped to concentrate the rays of sunlight into a beam. The steering elements are shaped, dimensioned, positioned, and/or oriented to deflect the beam toward a beam output path. The beams from the concentrators are converted to heat at a receiver, and the heat may be temporarily stored or directly used to generate electricity.

  2. Experimental and computational investigation of intermolecular interactions in cyclopentanone with methanol mixture

    NASA Astrophysics Data System (ADS)

    Zhang, Yu-Feng; Huang, Rong-Yi; Wang, Jun-Wei; Geng, Tong-Mou; Zhao, Shun-Ping; Wu, Gen-Hua

    2014-09-01

    In this Letter, excess molar volumes, refractive index deviations, Raman spectra and quantum-chemical calculations have been used to explore the underlying intermolecular interactions in the binary mixture containing cyclopentanone (CPN) and methanol. The experimental data reveal that the 1:1 (Ia) and 1:2 (Ib) cross-associations between CPN and methanol are formed in the studied binary mixture. This result has been further corroborated via theoretical calculations. In addition, the observed 1747 and 1732 cm-1 bands can be assigned to the Cdbnd O stretching vibrations of the intermolecular cross-associations Ia and Ib, respectively, in distinct contradiction with the previous explanations.

  3. Study of gelatin-agar intermolecular aggregates in the supernatant of its coacervate.

    PubMed

    Singh, S Santinath; Bohidar, H B; Bandyopadhyay, S

    2007-05-15

    Intermolecular interaction leading to formation of aggregates between gelatin, a polyampholyte, and agar, a polysaccharide was studied in the supernatant of the complex coacervate formed by these biopolymers. Electrophoresis, laser light scattering and viscometry data were used to determine the interaction and the physical structure of these intermolecular soluble complexes by modeling these to be prolate ellipsoids of revolution (rod-like structures with well defined axial ratio and Perrin's factor). Solution ionic strength was found to reduce the axial ratio of these complexes implying the presence of screened polarization-induced electrostatic interaction between the two biopolymers.

  4. Closed-form solutions of performability. [in computer systems

    NASA Technical Reports Server (NTRS)

    Meyer, J. F.

    1982-01-01

    It is noted that if computing system performance is degradable then system evaluation must deal simultaneously with aspects of both performance and reliability. One approach is the evaluation of a system's performability which, relative to a specified performance variable Y, generally requires solution of the probability distribution function of Y. The feasibility of closed-form solutions of performability when Y is continuous are examined. In particular, the modeling of a degradable buffer/multiprocessor system is considered whose performance Y is the (normalized) average throughput rate realized during a bounded interval of time. Employing an approximate decomposition of the model, it is shown that a closed-form solution can indeed be obtained.

  5. Sources of Chaos in Planetary Systems Formed Through Numerical Methods

    NASA Astrophysics Data System (ADS)

    Clement, Matthew S.

    2017-01-01

    The formation of the solar system’s terrestrial planets has been numerically modeled in countless works, and many other studies have been devoted to char- acterizing our modern planets’ chaotic dynamical state. However, it is still not known whether our planets fragile chaotic state is an expected outcome of terrestrial planet accretion. We use a large suite of numerical simulations to present a detailed analysis and characterization of the dynamical chaos in 145 different systems produced via terrestrial planet formation in Kaib & Cowan (2015). These systems were created in the presence of a fully formed Jupiter and Saturn, using a variety of different initial conditions. We provide the first analysis of the dynamical states of fully evolved (4.5 Gyr) planetary systems formed using numerical simulations. We find that dynamical chaos is preva- lent in roughly half of the systems, with the largest source of the chaos being perturbations from Jupiter. Chaos is most prevalent in systems that form 4 or 5 terrestrial planets. Additionally, an eccentric Jupiter and Saturn is shown to enhance the prevalence of chaos in systems. Furthermore, systems with a center of mass highly concentrated between 0.8-1.2 AU generally prove to be less chaotic than systems with more exotic mass distributions. Through the process of evolving systems to the current epoch, we show that late instabilities are quite common in our systems. Of greatest interest, many of the sources of chaos observed in our own solar system (such as the secularly driven chaos between Mercury and Jupiter) are shown to be common outcomes of terrestrial planetary formation. Thus, the solar system’s marginally stable, chaotic state may naturally arise from the process of terrestrial planet formation.

  6. Advanced manufacturing by spray forming: Aluminum strip and microelectromechanical systems

    SciTech Connect

    McHugh, K.M.

    1994-12-31

    Spray forming is an advanced materials processing technology that converts a bulk liquid metal to a near-net-shape solid by depositing atomized droplets onto a suitably shaped substrate. By combining rapid solidification processing with product shape control, spray forming can reduce manufacturing costs while improving product quality. INEL is developing a unique spray-forming method based on de Laval (converging/diverging) nozzle designs to produce near-net-shape solids and coatings of metals, polymers, and composite materials. Properties of the spray-formed material are tailored by controlling the characteristics of the spray plume and substrate. Two examples are described: high-volume production of aluminum alloy strip, and the replication of micron-scale features in micropatterned polymers during the production of microelectromechanical systems.

  7. NMR detection of intermolecular interaction sites in the dimeric 5'-leader of the HIV-1 genome.

    PubMed

    Keane, Sarah C; Van, Verna; Frank, Heather M; Sciandra, Carly A; McCowin, Sayo; Santos, Justin; Heng, Xiao; Summers, Michael F

    2016-11-15

    HIV type-1 (HIV-1) contains a pseudodiploid RNA genome that is selected for packaging and maintained in virions as a noncovalently linked dimer. Genome dimerization is mediated by conserved elements within the 5'-leader of the RNA, including a palindromic dimer initiation signal (DIS) that has been proposed to form kissing hairpin and/or extended duplex intermolecular contacts. Here, we have applied a (2)H-edited NMR approach to directly probe for intermolecular interactions in the full-length, dimeric HIV-1 5'-leader (688 nucleotides; 230 kDa). The interface is extensive and includes DIS:DIS base pairing in an extended duplex state as well as intermolecular pairing between elements of the upstream Unique-5' (U5) sequence and those near the gag start site (AUG). Other pseudopalindromic regions of the leader, including the transcription activation (TAR), polyadenylation (PolyA), and primer binding (PBS) elements, do not participate in intermolecular base pairing. Using a (2)H-edited one-dimensional NMR approach, we also show that the extended interface structure forms on a time scale similar to that of overall RNA dimerization. Our studies indicate that a kissing dimer-mediated structure, if formed, exists only transiently and readily converts to the extended interface structure, even in the absence of the HIV-1 nucleocapsid protein or other RNA chaperones.

  8. Are polymers standard glass-forming systems? The role of intramolecular barriers on the glass-transition phenomena of glass-forming polymers

    NASA Astrophysics Data System (ADS)

    Colmenero, J.

    2015-03-01

    Traditionally, polymer melts have been considered archetypal glass-formers. This has been mainly due to the fact that these systems can easily be obtained as glasses by cooling from the melt, even at low cooling rates. However, the macromolecules, i.e. the structural units of polymer systems in general, are rather different from the standard molecules. They are long objects (‘chains’) made by repetition of a given chemical motif (monomer) and have intra-macromolecular barriers that limit their flexibility. The influence of these properties on, for instance, the glass-transition temperature of polymers, is a topic that has been widely studied by the polymer community almost from the early times of polymer science. However, in the framework of the glass-community, the relevant influence of intra-macromolecular barriers and chain connectivity on glass-transition phenomena of polymers has started to be recognized only recently. The aim of this review is to give an overview and to critically revise the results reported on this topic over the last years. From these results, it seems to be evident that there are two different mechanisms involved in the dynamic arrest in glass-forming polymers: (i) the intermolecular packing effects, which dominate the dynamic arrest of low molecular weight glass-forming systems; and (ii) the effect of intra-macromolecular barriers combined with chain connectivity. It has also been shown that the mode coupling theory (MCT) is a suitable theoretical framework to discuss these questions. The values found for polymers for the central MCT parameter—the so-called λ-exponent—are of the order of 0.9, clearly higher than the standard values (λ ≈ 0.7) found in systems where the dynamic arrest is mainly driven by packing effects (‘standard’ glass-formers). Within the MCT, this is a signature of the presence of two competing mechanisms of dynamic arrest, as it has been observed in short-ranged attractive colloids or two component

  9. Invited article: Digital beam-forming imaging riometer systems.

    PubMed

    Honary, Farideh; Marple, Steve R; Barratt, Keith; Chapman, Peter; Grill, Martin; Nielsen, Erling

    2011-03-01

    The design and operation of a new generation of digital imaging riometer systems developed by Lancaster University are presented. In the heart of the digital imaging riometer is a field-programmable gate array (FPGA), which is used for the digital signal processing and digital beam forming, completely replacing the analog Butler matrices which have been used in previous designs. The reconfigurable nature of the FPGA has been exploited to produce tools for remote system testing and diagnosis which have proven extremely useful for operation in remote locations such as the Arctic and Antarctic. Different FPGA programs enable different instrument configurations, including a 4 × 4 antenna filled array (producing 4 × 4 beams), an 8 × 8 antenna filled array (producing 7 × 7 beams), and a Mills cross system utilizing 63 antennas producing 556 usable beams. The concept of using a Mills cross antenna array for riometry has been successfully demonstrated for the first time. The digital beam forming has been validated by comparing the received signal power from cosmic radio sources with results predicted from the theoretical beam radiation pattern. The performances of four digital imaging riometer systems are compared against each other and a traditional imaging riometer utilizing analog Butler matrices. The comparison shows that digital imaging riometer systems, with independent receivers for each antenna, can obtain much better measurement precision for filled arrays or much higher spatial resolution for the Mills cross configuration when compared to existing imaging riometer systems.

  10. Emulsion forming drug delivery system for lipophilic drugs.

    PubMed

    Wadhwa, Jyoti; Nair, Anroop; Kumria, Rachna

    2012-01-01

    In the recent years, there is a growing interest in the lipid-based formulations for delivery of lipophilic drugs. Due to their potential as therapeutic agents, preferably these lipid soluble drugs are incorporated into inert lipid carriers such as oils, surfactant dispersions, emulsions, liposomes etc. Among them, emulsion forming drug delivery systems appear to be a unique and industrially feasible approach to overcome the problem of low oral bioavailability associated with the BCS class II drugs. Self-emulsifying formulations are ideally isotropic mixtures of oils, surfactants and co-solvents that emulsify to form fine oil in water emulsions when introduced in aqueous media. Fine oil droplets would pass rapidly from stomach and promote wide distribution of drug throughout the GI tract, thereby overcome the slow dissolution step typically observed with solid dosage forms. Recent advances in drug carrier technologies have promulgated the development of novel drug carriers such as control release self-emulsifying pellets, microspheres, tablets, capsules etc. that have boosted the use of "self-emulsification" in drug delivery. This article reviews the different types of formulations and excipients used in emulsion forming drug delivery system to enhance the bioavailability of lipophilic drugs.

  11. Embedding the Form Generator in a Content Management System

    NASA Astrophysics Data System (ADS)

    Delgado, A.; Wicenec, A.; Delmotte, N.; Tejero, A.

    2008-08-01

    Given the tremendous amount of data generated by ESO's telescopes and the rapid evolution of the World Wide Web, the ESO archive web interface needs to offer more flexible services and advanced functionalities to a growing community of users all over the world. To achieve this endeavour, a query form generator is being developed inside a Content Management System. We present here a progress report.

  12. Dissecting Anion Effects in Gold(I)-Catalyzed Intermolecular Cycloadditions

    PubMed Central

    Homs, Anna; Obradors, Carla; Lebœuf, David; Echavarren, Antonio M

    2014-01-01

    From a series of gold complexes of the type [t-BuXPhosAu(MeCN)]X (X=anion), the best results in intermolecular gold(I)-catalyzed reactions are obtained with the complex with the bulky and soft anion BAr4F− [BAr4F−=3,5-bis(trifluoromethyl)phenylborate] improving the original protocols by 10–30% yield. A kinetic study on the [2+2] cycloaddition reaction of alkynes with alkenes is consistent with an scenario in which the rate-determining step is the ligand exchange to generate the (η2-phenylacetylene)gold(I) complex. We have studied in detail the subtle differences that can be attributed to the anion in this formation, which result in a substantial decrease in the formation of unproductive σ,π-(alkyne)digold(I) complexes by destabilizing the conjugated acid formed. PMID:26190958

  13. Bistability Controlled by Convection in a Pattern-Forming System

    NASA Astrophysics Data System (ADS)

    Marsal, Nicolas; Weicker, Lionel; Wolfersberger, Delphine; Sciamanna, Marc

    2017-01-01

    We analyze the transition from convective to absolute dynamical instabilities in a nonlinear optical system forming patterns, i.e., a photorefractive crystal in a single feedback configuration. We demonstrate that the convective regime is directly related to the bistability area in which the homogeneous steady state coexists with a pattern solution. Outside this domain, the system exhibits either a homogeneous steady state or an absolute dynamical regime. We evidence that the bistability area can be greatly increased by adjusting the mirror tilt angle and/or by applying an external background illumination on the photorefractive crystal.

  14. VSCF calculations for the intra- and intermolecular vibrational modes of the water dimer and its isotopologs

    NASA Astrophysics Data System (ADS)

    Monteiro, João G. S.; Barbosa, André G. H.

    2016-11-01

    In this work we show how the VSCF method may be successfully used to describe all fundamental vibrational transitions of several isotopologs of water dimer. By expressing the normal mode displacements in terms of appropriate delocalized internal coordinates we are able to minimize the mode-mode coupling in the PES and thus yield PT2-VSCF frequencies in good agreement with the experiment. The use of curvilinear normal modes is of paramount importance to describe vibrational transitions of the very soft intermolecular modes. Within our approach the maximum calculated error for the (H2O)2 intermolecular frequencies are reduced from 311 cm-1 (Cartesian normal modes) to just 56 cm-1 (curvilinear normal modes). Plots of the diagonal intermolecular potential and of the vibrational wave function illustrate the remarkable effect of different coordinate systems. In conclusion, our PT2-VSCF calculations provide a fair anharmonic description of the fundamental transitions of water dimers.

  15. From dimers to the solid-state: Distributed intermolecular force-fields for pyridine

    NASA Astrophysics Data System (ADS)

    Aina, Alexander A.; Misquitta, Alston J.; Price, Sarah L.

    2017-10-01

    An anisotropic atom-atom force-field for pyridine, using distributed atomic multipoles, polarizabilities, and dispersion coefficients and an anisotropic atom-atom repulsion model derived from symmetry-adapted perturbation theory (density functional theory) dimer calculations, is used to model pyridine crystal structures. Here we show that this distributed intermolecular force-field (DIFF) models the experimental crystal structures as accurately as modelling all but the electrostatic term with an isotropic repulsion-dispersion potential that has been fitted to experimental crystal structures. In both cases, the differences are comparable to the changes in the crystal structure with temperature, pressure, or neglect of zero-point vibrational effects. A crystal structure prediction study has been carried out, and the observed polymorphs contrasted with hypothetical thermodynamically competitive crystal structures. The DIFF model was able to identify the structure of an unreported high pressure phase of pyridine, unlike the empirically fitted potential. The DIFF model approach therefore provides a model of the underlying pair potential energy surface that we have transferred to the crystalline phase with a considerable degree of success, though the treatment of the many-body terms needs improvement and the pair potential is slightly over-binding. Furthermore, this study of a system that exhibits isotopic polymorphism highlights that the use of an empirical potential has partially absorbed temperature and zero-point motion effects as well as the intermolecular forces not explicitly represented in the functional form. This study therefore highlights the complexity in modelling crystallization phenomena from a realistic pair potential energy surface.

  16. [Introduction of an accreditation system for hospital informed consent forms].

    PubMed

    López-Picazo, J J; Tomás-Garcia, N; Calle-Urra, J E; Parra-Hidalgo, P; Valverde-Iniesta, J J

    2015-01-01

    To describe an accreditation system for informed consent forms (ICF) in a tertiary hospital, as an intervention to improve their quality, and to check the improvements achieved. Following an external evaluation of the ICF quality in a public hospital in Murcia (Spain), an accreditation committee set the ICF requirements and associated procedures. Effectiveness is assessed by comparing two external evaluations carried out by the EMCA Program (2011 and 2013) and based on 19 criteria and a sample of 60 ICF for every public hospital in Murcia Region. To be accredited, every ICF must meet the 19 external criteria plus 5 based on legibility, readability and scientific and technical validity. A form to fill in the contents of every ICF was agreed, which would be reviewed, approved and validated for five years. Before the implementation, 8.2 defects/ICF were detected. The accreditation system obtained an 89% improvement (0.9 defects/ICF) and achieved significant improvements in 18 criteria, 16 of which are benchmarked. The accreditation system achieved a substantial improvement in the ICF (obtaining a better result in external evaluations) and guarantees their contents, legibility and readability. This system needs to be extended to other hospitals, since it is not clear whether common ICFs would be suitable. However, this improvement is structural and does not guarantee that the overall information/consent procedure is done properly, thus complementary strategies for measurement and improvement are required. Copyright © 2014 SECA. Published by Elsevier Espana. All rights reserved.

  17. Control and monitoring method and system for electromagnetic forming process

    DOEpatents

    Kunerth, Dennis C.; Lassahn, Gordon D.

    1990-01-01

    A process, system, and improvement for a process for electromagnetic forming of a workpiece in which characteristics of the workpiece such as its geometry, electrical conductivity, quality, and magnetic permeability can be determined by monitoring the current and voltage in the workcoil. In an electromagnet forming process in which a power supply provides current to a workcoil and the electromagnetic field produced by the workcoil acts to form the workpiece, the dynamic interaction of the electromagnetic fields produced by the workcoil with the geometry, electrical conductivity, and magnetic permeability of the workpiece, provides information pertinent to the physical condition of the workpiece that is available for determination of quality and process control. This information can be obtained by deriving in real time the first several time derivatives of the current and voltage in the workcoil. In addition, the process can be extended by injecting test signals into the workcoil during the electromagnetic forming and monitoring the response to the test signals in the workcoil.

  18. Portable Electron-Beam Free-Form Fabrication System

    NASA Technical Reports Server (NTRS)

    Watson, J. Kevin; Petersen, Daniel D.; Taminger, Karen M.; Hafley, Robert A.

    2005-01-01

    A portable electron-beam free-form fabrication (EB F3) system, now undergoing development, is intended to afford a capability for manufacturing metal parts in nearly net sizes and shapes. Although the development effort is oriented toward the eventual use of systems like this one to supply spare metal parts aboard spacecraft in flight, the basic system design could also be adapted to terrestrial applications in which there are requirements to supply spare parts on demand at locations remote from warehouses and conventional manufacturing facilities. Prior systems that have been considered for satisfying the same requirements (including prior free-form fabrication systems) are not easily portable because of their bulk and massive size. The mechanical properties of the components that such systems produce are often inferior to the mechanical properties of the corresponding original, conventionally fabricated components. In addition, the prior systems are not efficient in the utilization of energy and of feedstock. In contrast, the present developmental system is designed to be sufficiently compact and lightweight to be easily portable, to utilize both energy and material more efficiently, and to produce components that have mechanical properties approximating those of the corresponding original components. The developmental EB F3 system will include a vacuum chamber and associated vacuum pumps, an electron-beam gun and an associated power supply, a multiaxis positioning subsystem, a precise wire feeder, and an instrumentation system for monitoring and control. The electron-beam gun, positioning subsystem, and wire feeder will be located inside the vacuum chamber (see figure). The electron beam gun and the wire feeder will be mounted in fixed positions inside the domed upper portion of the vacuum chamber. The positioning subsystem and ports for the vacuum pumps will be located on a base that could be dropped down to provide full access to the interior of the chamber

  19. Frontier orbital symmetry control of intermolecular electron transfer. Final report, September 15, 1988--December 31, 1994

    SciTech Connect

    Stevens, B.

    1997-07-01

    This report discusses the following topics: the recovery of intermolecular transfer parameters from fluorescence quenching in liquids; photoinduced intramolecular electron transfer in flexible donor/space/acceptor systems containing an extended unsaturated spacer; electron transfer sensitized reaction; the recovery of solute and fractal dimensions from electron transfer quenching data; and frontier orbital symmetry control of back electron transfer.

  20. Ultrasonic and IR study of intermolecular association through hydrogen bonding in ternary liquid mixtures.

    PubMed

    Awasthi, Aashees; Shukla, J P

    2003-08-01

    Complex formation in ternary liquid mixtures of dimethylsulfoxide (DMSO) with phenol and o-cresol in carbontetrachloride has been studied by measuring ultrasonic velocity at 2 MHz, in the concentration range of 0.019-0.162 (in mole fraction of DMSO) at varying temperatures of 20, 30 and 40 degrees C. Using measured values of ultrasonic velocity, other parameters such as adiabatic compressibility, intermolecular free length, molar sound velocity, molar compressibility, specific acoustic impedance and molar volume have been evaluated. These parameters have been utilized to study the solute-solute interactions in these systems. The ultrasonic velocity shows a maxima and adiabatic compressibility a corresponding minima as a function of concentration for these mixtures. The results indicate the occurrence of complex formation between unlike molecules through intermolecular hydrogen bonding between oxygen atom of DMSO molecule and hydrogen atom of phenol and o-cresol molecules. The excess values of adiabatic compressibility and intermolecular free length have also been evaluated. The variation of both these parameters with concentration also indicates the possibility of the complex formation in these systems. Further, to investigate the presence of O-HO bond complexes and the strength of molecular association with concentrations, the infrared spectra of both the systems, DMSO-phenol and DMSO-o-cresol, have been recorded for various concentrations at room temperature (20 degrees C). The results obtained using infrared spectroscopy for both the systems also support the occurrence of complex formation through intermolecular hydrogen bonding in these ternary liquid mixtures.

  1. Intermolecular vibrations and fast relaxations in supercooled ionic liquids

    NASA Astrophysics Data System (ADS)

    Ribeiro, Mauro C. C.

    2011-06-01

    Short-time dynamics of ionic liquids has been investigated by low-frequency Raman spectroscopy (4 < ω < 100 cm-1) within the supercooled liquid range. Raman spectra are reported for ionic liquids with the same anion, bis(trifluoromethylsulfonyl)imide, and different cations: 1-butyl-3-methylimidazolium, 1-hexyl-3-methylimidazolium, 1-butyl-1-methylpiperidinium, trimethylbutylammonium, and tributylmethylammonium. It is shown that low-frequency Raman spectroscopy provides similar results as optical Kerr effect (OKE) spectroscopy, which has been used to study intermolecular vibrations in ionic liquids. The comparison of ionic liquids containing aromatic and non-aromatic cations identifies the characteristic feature in Raman spectra usually assigned to librational motion of the imidazolium ring. The strength of the fast relaxations (quasi-elastic scattering, QES) and the intermolecular vibrational contribution (boson peak) of ionic liquids with non-aromatic cations are significantly lower than imidazolium ionic liquids. A correlation length assigned to the boson peak vibrations was estimated from the frequency of the maximum of the boson peak and experimental data of sound velocity. The correlation length related to the boson peak (˜19 Å) does not change with the length of the alkyl chain in imidazolium cations, in contrast to the position of the first-sharp diffraction peak observed in neutron and X-ray scattering measurements of ionic liquids. The rate of change of the QES intensity in the supercooled liquid range is compared with data of excess entropy, free volume, and mean-squared displacement recently reported for ionic liquids. The temperature dependence of the QES intensity in ionic liquids illustrates relationships between short-time dynamics and long-time structural relaxation that have been proposed for glass-forming liquids.

  2. Intermolecular vibrations and fast relaxations in supercooled ionic liquids.

    PubMed

    Ribeiro, Mauro C C

    2011-06-28

    Short-time dynamics of ionic liquids has been investigated by low-frequency Raman spectroscopy (4 < ω < 100 cm(-1)) within the supercooled liquid range. Raman spectra are reported for ionic liquids with the same anion, bis(trifluoromethylsulfonyl)imide, and different cations: 1-butyl-3-methylimidazolium, 1-hexyl-3-methylimidazolium, 1-butyl-1-methylpiperidinium, trimethylbutylammonium, and tributylmethylammonium. It is shown that low-frequency Raman spectroscopy provides similar results as optical Kerr effect (OKE) spectroscopy, which has been used to study intermolecular vibrations in ionic liquids. The comparison of ionic liquids containing aromatic and non-aromatic cations identifies the characteristic feature in Raman spectra usually assigned to librational motion of the imidazolium ring. The strength of the fast relaxations (quasi-elastic scattering, QES) and the intermolecular vibrational contribution (boson peak) of ionic liquids with non-aromatic cations are significantly lower than imidazolium ionic liquids. A correlation length assigned to the boson peak vibrations was estimated from the frequency of the maximum of the boson peak and experimental data of sound velocity. The correlation length related to the boson peak (∼19 Å) does not change with the length of the alkyl chain in imidazolium cations, in contrast to the position of the first-sharp diffraction peak observed in neutron and X-ray scattering measurements of ionic liquids. The rate of change of the QES intensity in the supercooled liquid range is compared with data of excess entropy, free volume, and mean-squared displacement recently reported for ionic liquids. The temperature dependence of the QES intensity in ionic liquids illustrates relationships between short-time dynamics and long-time structural relaxation that have been proposed for glass-forming liquids.

  3. Intermolecular Interactions in Crystalline Theobromine as Reflected in Electron Deformation Density and (13)C NMR Chemical Shift Tensors.

    PubMed

    Bouzková, Kateřina; Babinský, Martin; Novosadová, Lucie; Marek, Radek

    2013-06-11

    An understanding of the role of intermolecular interactions in crystal formation is essential to control the generation of diverse crystalline forms which is an important concern for pharmaceutical industry. Very recently, we reported a new approach to interpret the relationships between intermolecular hydrogen bonding, redistribution of electron density in the system, and NMR chemical shifts (Babinský et al. J. Phys. Chem. A, 2013, 117, 497). Here, we employ this approach to characterize a full set of crystal interactions in a sample of anhydrous theobromine as reflected in (13)C NMR chemical shift tensors (CSTs). The important intermolecular contacts are identified by comparing the DFT-calculated NMR CSTs for an isolated theobromine molecule and for clusters composed of several molecules as selected from the available X-ray diffraction data. Furthermore, electron deformation density (EDD) and shielding deformation density (SDD) in the proximity of the nuclei involved in the proposed interactions are calculated and visualized. In addition to the recently reported observations for hydrogen bonding, we focus here particularly on the stacking interactions. Although the principal relations between the EDD and CST for hydrogen bonding (HB) and stacking interactions are similar, the real-space consequences are rather different. Whereas the C-H···X hydrogen bonding influences predominantly and significantly the in-plane principal component of the (13)C CST perpendicular to the HB path and the C═O···H hydrogen bonding modulates both in-plane components of the carbonyl (13)C CST, the stacking modulates the out-of-plane electron density resulting in weak deshielding (2-8 ppm) of both in-plane principal components of the CST and weak shielding (∼ 5 ppm) of the out-of-plane component. The hydrogen-bonding and stacking interactions may add to or subtract from one another to produce total values observed experimentally. On the example of theobromine, we demonstrate

  4. Thermodynamic curvature for attractive and repulsive intermolecular forces.

    PubMed

    May, Helge-Otmar; Mausbach, Peter; Ruppeiner, George

    2013-09-01

    The thermodynamic curvature scalar R for the Lennard-Jones system is evaluated in phase space, including vapor, liquid, and solid state. We paid special attention to the investigation of R along vapor-liquid, liquid-solid, and vapor-solid equilibria. Because R is a measure of interaction strength, we traced out the line R=0 dividing the phase space into regions with effectively attractive (R<0) or repulsive (R>0) interactions. Furthermore, we analyzed the dependence of R on the strength of attraction applying a perturbation ansatz proposed by Weeks-Chandler-Anderson. Our results show clearly a transition from R>0 (for poorly repulsive interaction) to R<0 when loading attraction in the intermolecular potential.

  5. Resolving Intra- and Inter-Molecular Structure with Non-Contact Atomic Force Microscopy

    PubMed Central

    Jarvis, Samuel Paul

    2015-01-01

    A major challenge in molecular investigations at surfaces has been to image individual molecules, and the assemblies they form, with single-bond resolution. Scanning probe microscopy, with its exceptionally high resolution, is ideally suited to this goal. With the introduction of methods exploiting molecularly-terminated tips, where the apex of the probe is, for example, terminated with a single CO, Xe or H2 molecule, scanning probe methods can now achieve higher resolution than ever before. In this review, some of the landmark results related to attaining intramolecular resolution with non-contact atomic force microscopy (NC-AFM) are summarised before focussing on recent reports probing molecular assemblies where apparent intermolecular features have been observed. Several groups have now highlighted the critical role that flexure in the tip-sample junction plays in producing the exceptionally sharp images of both intra- and apparent inter-molecular structure. In the latter case, the features have been identified as imaging artefacts, rather than real intermolecular bonds. This review discusses the potential for NC-AFM to provide exceptional resolution of supramolecular assemblies stabilised via a variety of intermolecular forces and highlights the potential challenges and pitfalls involved in interpreting bonding interactions. PMID:26307976

  6. Resolving Intra- and Inter-Molecular Structure with Non-Contact Atomic Force Microscopy.

    PubMed

    Jarvis, Samuel Paul

    2015-08-21

    A major challenge in molecular investigations at surfaces has been to image individual molecules, and the assemblies they form, with single-bond resolution. Scanning probe microscopy, with its exceptionally high resolution, is ideally suited to this goal. With the introduction of methods exploiting molecularly-terminated tips, where the apex of the probe is, for example, terminated with a single CO, Xe or H2 molecule, scanning probe methods can now achieve higher resolution than ever before. In this review, some of the landmark results related to attaining intramolecular resolution with non-contact atomic force microscopy (NC-AFM) are summarised before focussing on recent reports probing molecular assemblies where apparent intermolecular features have been observed. Several groups have now highlighted the critical role that flexure in the tip-sample junction plays in producing the exceptionally sharp images of both intra- and apparent inter-molecular structure. In the latter case, the features have been identified as imaging artefacts, rather than real intermolecular bonds. This review discusses the potential for NC-AFM to provide exceptional resolution of supramolecular assemblies stabilised via a variety of intermolecular forces and highlights the potential challenges and pitfalls involved in interpreting bonding interactions.

  7. The B-box module of CYLD is responsible for its intermolecular interaction and cytoplasmic localization.

    PubMed

    Xie, Songbo; Chen, Miao; Gao, Siqi; Zhong, Tao; Zhou, Peng; Li, Dengwen; Zhou, Jun; Gao, Jinmin; Liu, Min

    2017-02-07

    The tumor suppressor protein cylindromatosis (CYLD), as a microtubule-associated deubiquitinase, plays a pivotal role in a wide range of cellular activities, including innate immunity, cell division, and ciliogenesis. Structural characterization reveals a small zinc-binding B-box inserted within the ubiquitin specific protease (USP) domain of CYLD; however, the exact role for this module remains yet to be elucidated. Here we identify a critical role for the B-box in facilitating the intermolecular interaction and subcellular localization of CYLD. By co-immunoprecipitation assays we uncover that CYLD has the ability to form an intermolecular complex. Native gel electrophoresis analysis and pull down assays show that the USP domain of CYLD is essential for its intermolecular interaction. Further investigation reveals that deletion of the B-box from the USP domain disrupts the intermolecular interaction of CYLD. Importantly, although loss of the B-box has no obvious effect on the deubiquitinase activity of CYLD, it abolishes the USP domain-mediated retention of CYLD in the cytoplasm. Collectively, these data demonstrate an important role for the B-box module of CYLD in mediating its assembly and subcellular distribution, which might be related to the functions of CYLD in various biological processes.

  8. An isotopic mass effect on the intermolecular potential

    DOE PAGES

    Herman, Michael F.; Currier, Robert Patrick; Clegg, Samuel M.

    2015-09-28

    The impact of isotopic variation on the electronic energy and intermolecular potentials is often suppressed when calculating isotopologue thermodynamics. Intramolecular potential energy surfaces for distinct isotopologues are in fact equivalent under the Born–Oppenheimer approximation, which is sometimes used to imply that the intermolecular interactions are independent of isotopic mass. In this paper, the intermolecular dipole–dipole interaction between hetero-nuclear diatomic molecules is considered. It is shown that the intermolecular potential contains mass-dependent terms even though each nucleus moves on a Born–Oppenheimer surface. Finally, the analysis suggests that mass dependent variations in intermolecular potentials should be included in comprehensive descriptions of isotopologuemore » thermodynamics.« less

  9. X-ray Intermolecular Structure Factor (XISF): separation of intra- and intermolecular interactions from total X-ray scattering data

    SciTech Connect

    Mou, Q.; Benmore, C. J.; Yarger, J. L.

    2015-06-01

    XISF is a MATLAB program developed to separate intermolecular structure factors from total X-ray scattering structure factors for molecular liquids and amorphous solids. The program is built on a trust-region-reflective optimization routine with the r.m.s. deviations of atoms physically constrained. XISF has been optimized for performance and can separate intermolecular structure factors of complex molecules.

  10. Intermolecular Sulfur···Oxygen Interactions: Theoretical and Statistical Investigations.

    PubMed

    Zhang, Xuejin; Gong, Zhen; Li, Jian; Lu, Tao

    2015-10-26

    Intermolecular S···O interactions are very common and are important in biological systems, but until recently, the presence of these contacts in protein-ligand systems largely depended on serendipitous discovery instead of rational design. Here we provide insight into the phenomenon of intermolecular S···O contacts by focusing on three sulfur-containing aromatic rings. Quantum mechanics is employed to characterize the strength and directionality of the S···O interactions and to determine their energy dependence on their geometric parameters. Protein Data Bank mining is performed to systematically determine the occurrence and geometry of intermolecular S···O interactions, and several representative examples are discussed. Three typical cases are investigated using a combined quantum mechanics/molecular mechanics approach to demonstrate the potential of these interactions in improving binding affinities and physiochemical properties. Overall, our work elucidates the structures and energy features of intermolecular S···O interactions and addresses their use in molecular design.

  11. Distinguishability and chiral stability in solution: Effects of decoherence and intermolecular interactions

    SciTech Connect

    Han, Heekyung; Wardlaw, David M.; Frolov, Alexei M.

    2014-05-28

    We examine the effect of decoherence and intermolecular interactions (chiral discrimination energies) on the chiral stability and the distinguishability of initially pure versus mixed states in an open chiral system. Under a two-level approximation for a system, intermolecular interactions are introduced by a mean-field theory, and interaction between a system and an environment is modeled by a continuous measurement of a population difference between the two chiral states. The resultant equations are explored for various parameters, with emphasis on the combined effects of the initial condition of the system, the chiral discrimination energies, and the decoherence in determining: the distinguishability as measured by a population difference between the initially pure and mixed states, and the decoherence process; the chiral stability as measured by the purity decay; and the stationary state of the system at times long relative to the time scales of the system dynamics and of the environmental effects.

  12. Intermolecular potential functions from spectroscopic properties of weakly bound complexes

    SciTech Connect

    Muenter, J.S.

    1992-01-01

    Goal is to consolidate the information from high resolution spectroscopy of weakly bound cluster molecules through a theoretical model of intermolecular potential energy surfaces. The ability to construct analytic intermolecular potential functions that accurately predict the interaction energy between small molecules will have a major impact in chemistry, biochemistry, and biology. This document presents the evolution and capabilities of a potential function model developed here, and then describes plans for future developments and applications. This potential energy surface (PES) model was first used on (HCCH){sub 2}, (CO{sub 2}){sub 2}, HCCH - CO{sub 2}; it had to be modified to work with HX dimers and CO{sub 2}-HX complexes. Potential functions have been calculated for 15 different molecular complexes containing 7 different monomer molecules. Current questions, logical extensions and new applications of the model are discussed. The questions are those raised by changing the repulsion and dispersion terms. A major extension of the PES model will be the inclusion of induction effects. Projects in progress include PES calculations on (HCCH){sub 3}, CO{sub 2} containing complexes, (HX){sub 2}, HX - CO{sub 2}, CO{sub 2} - CO, (CO{sub 2}){sub 3}, and (OCS){sub 2}. The first PES calculation for a nonlinear molecule will be for water and ammonia complexes. Possible long-term applications for biological molecules are discussed. Differences between computer programs used for molecular mechanics and dynamics in biological systems are discussed, as is the problem of errors. 12 figs, 74 refs. (DLC)

  13. Chemotaxis and Autotaxis in Biofilm-Forming Systems

    NASA Astrophysics Data System (ADS)

    Strain, Shinji; Bienvenu, Samuel; Thatcher, Travis; Cooley, Benjamin; Gordon, Vernita

    2011-03-01

    Biofilms are multicellular, surface-bound communities of interacting unicellular organisms. In the initial stages of biofilm formation, discrete cells populate the surface and eventually form microcolonies (dense surface-bound clusters of cells). How much these microcolonies arise from clonal growth and how much they arise from attraction and active motility of non-clonal cells is not well-understood. One potentially important form of attraction is autotaxis, movement of cells toward like cells. Another is chemotaxis, movement of cells toward an attractive chemical, which could act to concentrate cells with no direct intercellular interaction. While both autotaxis and chemotaxis have been studied for three-dimensional, swimming, dense bacterial systems, they remain largely unstudied in sparse, surface-bound populations that initiate biofilms. Using microscopy and automated tracking and analysis algorithms, we will study how bacteria respond to each other and to chemoattractants, in a spatially-dependent manner. We will determine how variations in neighbor density and arrangement stimulate changes in the motility of E. coli and P. aeruginosa cells on a surface.

  14. Detection of the water reservoir in a forming planetary system.

    PubMed

    Hogerheijde, Michiel R; Bergin, Edwin A; Brinch, Christian; Cleeves, L Ilsedore; Fogel, Jeffrey K J; Blake, Geoffrey A; Dominik, Carsten; Lis, Dariusz C; Melnick, Gary; Neufeld, David; Panić, Olja; Pearson, John C; Kristensen, Lars; Yildiz, Umut A; van Dishoeck, Ewine F

    2011-10-21

    Icy bodies may have delivered the oceans to the early Earth, yet little is known about water in the ice-dominated regions of extrasolar planet-forming disks. The Heterodyne Instrument for the Far-Infrared on board the Herschel Space Observatory has detected emission lines from both spin isomers of cold water vapor from the disk around the young star TW Hydrae. This water vapor likely originates from ice-coated solids near the disk surface, hinting at a water ice reservoir equivalent to several thousand Earth oceans in mass. The water's ortho-to-para ratio falls well below that of solar system comets, suggesting that comets contain heterogeneous ice mixtures collected across the entire solar nebula during the early stages of planetary birth.

  15. The speakers’ bureau system: a form of peer selling

    PubMed Central

    Reid, Lynette; Herder, Matthew

    2013-01-01

    Abstract In the speakers’ bureau system, physicians are recruited and trained by pharmaceutical, biotechnology, and medical device companies to deliver information about products to other physicians, in exchange for a fee. Using publicly available disclosures, we assessed the thesis that speakers’ bureau involvement is not a feature of academic medicine in Canada, by estimating the prevalence of participation in speakers’ bureaus among Canadian faculty in one medical specialty, cardiology. We analyzed the relevant features of an actual contract made public by the physician addressee and applied the Canadian Medical Association (CMA) guidelines on physician–industry relations to participation in a speakers’ bureau. We argue that speakers’ bureau participation constitutes a form of peer selling that should be understood to contravene the prohibition on product endorsement in the CMA Code of Ethics. Academic medical institutions, in conjunction with regulatory colleges, should continue and strengthen their policies to address participation in speakers’ bureaus. PMID:24348883

  16. System and method for accumulative double sided incremental forming

    DOEpatents

    Cao, Jian; Malhotra, Rajiv

    2015-10-27

    A forming system includes first and second tools, moving assemblies, and a control unit. The moving assemblies move the first tool and the second tool relative to the sheet. The control unit is configured to control movement of the first tool and the second tool by the one or more moving assemblies by moving at least one of the first tool or the second tool in a first deformation direction to deform the sheet, then moving the first and second tools laterally relative to the sheet to a subsequent location while engaging the sheet, then moving at least one of the first tool or the second tool in the first deformation direction or an opposite second deformation direction to deform the sheet, and then continue moving the first and second tools to deform the sheet in order to create a three-dimensional component from the sheet.

  17. The speakers' bureau system: a form of peer selling.

    PubMed

    Reid, Lynette; Herder, Matthew

    2013-01-01

    In the speakers' bureau system, physicians are recruited and trained by pharmaceutical, biotechnology, and medical device companies to deliver information about products to other physicians, in exchange for a fee. Using publicly available disclosures, we assessed the thesis that speakers' bureau involvement is not a feature of academic medicine in Canada, by estimating the prevalence of participation in speakers' bureaus among Canadian faculty in one medical specialty, cardiology. We analyzed the relevant features of an actual contract made public by the physician addressee and applied the Canadian Medical Association (CMA) guidelines on physician-industry relations to participation in a speakers' bureau. We argue that speakers' bureau participation constitutes a form of peer selling that should be understood to contravene the prohibition on product endorsement in the CMA Code of Ethics. Academic medical institutions, in conjunction with regulatory colleges, should continue and strengthen their policies to address participation in speakers' bureaus.

  18. An old disk still capable of forming a planetary system.

    PubMed

    Bergin, Edwin A; Cleeves, L Ilsedore; Gorti, Uma; Zhang, Ke; Blake, Geoffrey A; Green, Joel D; Andrews, Sean M; Evans, Neal J; Henning, Thomas; Oberg, Karin; Pontoppidan, Klaus; Qi, Chunhua; Salyk, Colette; van Dishoeck, Ewine F

    2013-01-31

    From the masses of the planets orbiting the Sun, and the abundance of elements relative to hydrogen, it is estimated that when the Solar System formed, the circumstellar disk must have had a minimum mass of around 0.01 solar masses within about 100 astronomical units of the star. (One astronomical unit is the Earth-Sun distance.) The main constituent of the disk, gaseous molecular hydrogen, does not efficiently emit radiation from the disk mass reservoir, and so the most common measure of the disk mass is dust thermal emission and lines of gaseous carbon monoxide. Carbon monoxide emission generally indicates properties of the disk surface, and the conversion from dust emission to gas mass requires knowledge of the grain properties and the gas-to-dust mass ratio, which probably differ from their interstellar values. As a result, mass estimates vary by orders of magnitude, as exemplified by the relatively old (3-10 million years) star TW Hydrae, for which the range is 0.0005-0.06 solar masses. Here we report the detection of the fundamental rotational transition of hydrogen deuteride from the direction of TW Hydrae. Hydrogen deuteride is a good tracer of disk gas because it follows the distribution of molecular hydrogen and its emission is sensitive to the total mass. The detection of hydrogen deuteride, combined with existing observations and detailed models, implies a disk mass of more than 0.05 solar masses, which is enough to form a planetary system like our own.

  19. A pneumatic transfer system for special form {sup 252}Cf

    SciTech Connect

    Gehrke, R.J.; Berry, S.M.; Grafwallner, E.G.; Hoggan, J.M.

    1996-09-01

    A pneumatic transfer system has been developed for use with series 100 Special Form {sup 252}Cf. It was developed to reduce the exposure to personnel handling sources of {sup 252}Cf with masses up to 150 {micro}g by permitting remotely activated two-way transfer between the storage container and the irradiation position. The pneumatic transfer system also permits transfers for reproducible repetitive irradiation periods. In addition to the storage container equipped with quick-release fittings, the transfer system consists of an irradiation station, a control box with momentary contact switches to activate the air-pressure control valves and indicators to identify the location of the source, and connecting air hose and electrical wire. A source of 20 psig air and 110 volt electrical power are required for operation of the transfer system which can be easily moved and set up by one individual in 5 to 10 minutes. Tests have shown that rarely does a source become lodged in the transfer tubing, but two methods have been developed to handle incomplete transfers of the {sup 252}Cf source. The first method consists of closing one air vent to allow a pressure impulse to propel the source to the opposite side. The second method applies to those {sup 252}Cf capsules with a threaded or tapped end to which a small ferromagnetic piece can be attached; an incompletely transferred source in the transfer tube can then be guided to a position of safety by surrounding the transfer tubing containing the capsule with a horseshoe magnet attached to the end of a long pole.

  20. High-frequency intermolecular homologous recombination during herpes simplex virus-mediated plasmid DNA replication.

    PubMed

    Fu, Xinping; Wang, Hua; Zhang, Xiaoliu

    2002-06-01

    Homologous recombination is a prominent feature of herpes simplex virus (HSV) type 1 DNA replication. This has been demonstrated and traditionally studied in experimental settings where repeated sequences are present or are being introduced into a single molecule for subsequent genome isomerization. In the present study, we have designed a pair of unique HSV amplicon plasmids to examine in detail intermolecular homologous recombination (IM-HR) between these amplicon plasmids during HSV-mediated DNA replication. Our data show that IM-HR occurred at a very high frequency: up to 60% of the amplicon concatemers retrieved from virion particles underwent intermolecular homologous recombination. Such a high frequency of IM-HR required that both plasmids be replicated by HSV-mediated replication, as IM-HR events were not detected when either one or both plasmids were replicated by simian virus 40-mediated DNA replication, even with the presence of HSV infection. In addition, the majority of the homologous recombination events resulted in sequence replacement or targeted gene repair, while the minority resulted in sequence insertion. These findings imply that frequent intermolecular homologous recombination may contribute directly to HSV genome isomerization. In addition, HSV-mediated amplicon replication may be an attractive model for studying intermolecular homologous recombination mechanisms in general in a mammalian system. In this regard, the knowledge obtained from such a study may facilitate the development of better strategies for targeted gene correction for gene therapy purposes.

  1. Intermolecular interaction studies of glyphosate with water

    NASA Astrophysics Data System (ADS)

    Manon, Priti; Juglan, K. C.; Kaur, Kirandeep; Sethi, Nidhi; Kaur, J. P.

    2017-07-01

    The density (ρ), viscosity (η) and ultrasonic velocity (U) of glyphosate with water have been measured on different ultrasonic frequency ranges from 1MHz, 2MHz, 3MHz & 5MHz by varying concentrations (0.05%, 0.10%, 0.15%, 0.20%, 0.25%, 0.30%, 0.35%, & 0.40%) at 30°C. The specific gravity bottle, Ostwald's viscometer and quartz crystal interferometer were used to determine density (ρ), viscosity (η) and ultrasonic velocity (U). These three factors contribute in evaluating the other parameters as acoustic impedance (Z), adiabatic compressibility (β), relaxation time (τ), intermolecular free length (Lf), free volume (Vf), ultrasonic attenuation (α/f2), Rao's constant (R), Wada's constant (W) and relative strength (R). Solute-solvent interaction is confirmed by ultrasonic velocity and viscosity values, which increases with increase in concentration indicates stronger association between solute and solvent molecules. With rise in ultrasonic frequency the interaction between the solute and solvent particles decreases. The linear variations in Rao's constant and Wada's constant suggest the absence of complex formation.

  2. A Catalytic, Brønsted Base Strategy for Intermolecular Allylic C—H Amination

    PubMed Central

    Reed, Sean A.; Mazzotti, Anthony R.; White, M. Christina

    2009-01-01

    A Brønsted base activation mode for oxidative, Pd(II)/sulfoxide catalyzed, intermolecular C—H allylic amination is reported. N,N-diisopropylethylamine was found to promote amination of unactivated terminal olefins, forming the corresponding linear allylic amine products with high levels of stereo-, regio-, and chemoselectivity. The predictable and high selectivity of this C—H oxidation method enables late-stage incorporation of nitrogen into advanced synthetic intermediates and natural products. PMID:19645492

  3. Intermolecular interactions in rifabutin-2-hydroxypropyl-β-cyclodextrin-water solutions, according to solubility data

    NASA Astrophysics Data System (ADS)

    Anshakova, A. V.; Vinogradov, E. V.; Sedush, N. G.; Kurtikyan, T. S.; Zhokhov, S. S.; Polshakov, V. I.; Ermolenko, Yu. V.; Konyukhov, V. Yu.; Maksimenko, O. O.; Gelperin, S. E.

    2016-05-01

    The formulations of rifabutin (RB) and 2-hydroxypropyl-β-cyclodextrin (HP-β-CD), obtained using different preparation techniques, are studied by means of differential scanning calorimetry and molecular spectroscopy (FTIR, NMR, Raman scattering, and photon correlation light scattering). It is established that molecules of RB do not form inclusion complexes with the molecules of HP-β-CD, and an increase in the solubility of RB determined earlier is caused by the formation of weak intermolecular associates.

  4. Form and toxicity of copper released into marine systems from ...

    EPA Pesticide Factsheets

    The fate and effects of pristine engineered nanomaterials (ENMs) in simplified systems have been widely studied; however, little is known about the potential release and impact of ENMs from consumer goods, especially lumber that has been treated with micronized copper. Micronized copper solutions contain copper complexes predominately in the 10-700 nm size range, and are used in lumber to prevent microbial degradation and fouling. In this work, the goal was to determine the rate, concentration, and form of copper released from commercially available pressure treated lumber samples (blocks and sawdust) exposed to an aqueous system. Lumber tested included Southern Yellow Pine (SYP) treated with micronized copper azole (MCA) at 0.96 and 2.4 Kg/m3, alkaline copper quaternary (ACQ) at 0.30 and 9.6 Kg/m3, and chromated copper arsenate (CCA) at 40 Kg/m3. Of the different chemical treatments, only MCA included nano- and micro-sized copper complexes. The experimental system included wood cubes cut from the outer 2 cm surface of the lumber or the equivalent mass (4 g) of sawdust submerged in 250 mL of media (0, 1, 10, and 30 ppt filtered natural seawater) in polyethylene bottles, and mixed on a shaker table at 120 rpm. Water samples were taken at 8 hours, and on days 1, 2, 7, 14, and 28 for the blocks and days 1, 2, 3, 7, 17, and 28 for the sawdust. Subsamples included unfiltered water (defined as 0.45 µm - filtered water for the sawdust), and water filtered through a 0.

  5. Transformations of PTCDA structures on rutile TiO2 induced by thermal annealing and intermolecular forces

    PubMed Central

    Godlewski, Szymon; Glatzel, Thilo; Meyer, Ernst; Szymoński, Marek

    2015-01-01

    Summary Transformations of molecular structures formed by perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA) molecules on a rutile TiO2(110) surface are studied with low-temperature scanning tunnelling microscopy. We demonstrate that metastable molecular assemblies transform into differently ordered structures either due to additional energy provided by thermal annealing or when the influence of intermolecular forces is increased by the enlarged amount of deposited molecules. Proper adjustment of molecular coverage and substrate temperature during deposition allows for fabrication of desired assemblies. Differences between PTCDA/TiO2(110) and PTCDA/TiO2(011) systems obtained through identical experimental procedures are discussed. PMID:26199854

  6. From intra- to inter-molecular hydrogen bonds with the surroundings: steady-state and time-resolved behaviours.

    PubMed

    Alarcos, Noemí; Gutiérrez, Mario; Liras, Marta; Sánchez, Félix; Douhal, Abderrazzak

    2015-07-01

    We report on the photodynamics of 2-(2'-hydroxyphenyl)benzoxazole (HBO), compared to its amino derivatives, 6-amino-2-(2'-hydroxypheny)benzoxazole (6A-HBO) and 5-amino-2-(2'-hydroxypheny)benzoxazole (5A-HBO) in N,N-dimethylformamide (DMF) solutions. HBO at S0 shows a reversible deprotonation reaction leading to the production of anionic forms. However, for 6A-HBO and 5A-HBO, DMF containing KOH is necessary to produce the anions. Excited HBO in DMF exhibits intra- as well as inter-molecular proton transfer (ESIPT and ESPT) reactions. With excitation at 330 nm, we observed the open-enol, anti-enol and keto forms with different emission and lifetimes (620 ps, 1.5 ns, and 74 ps, respectively), while with the excitation at 433 nm, only the anionic species emission was detected (3.7 ns). Contrary to HBO, 6A-HBO and 5A-HBO do not exhibit any proton transfer process, and only the emissions of the open-enol charge-transferred forms (open-ECT) were observed, which are comparable to those of their methylated derivatives (6A-MBO and 5A-MBO). Femtosecond studies of 6A-MBO and 6A-HBO in DMF indicate that an intramolecular charge-transfer (ICT) reaction (∼80 fs) and solvent relaxation process (2 ps) take place at S1. Remarkably, the photoinduced breaking of the intramolecular hydrogen bond of 6A-HBO and the formation of an intermolecular hydrogen bond with DMF molecules occurs in 80 ps, while for 5A-HBO, this process occurs in less than 10 ps. In this study, we have demonstrated that the presence and position of the amino group in the HBO framework change both the S0 and S1 behaviours of the intramolecular H-bonds; a result which might be useful for the design and better understanding of supramolecular systems based on intra- and intermolecular H-bonds.

  7. The origins of the directionality of noncovalent intermolecular interactions.

    PubMed

    Wang, Changwei; Guan, Liangyu; Danovich, David; Shaik, Sason; Mo, Yirong

    2016-01-05

    The recent σ-hole concept emphasizes the contribution of electrostatic attraction to noncovalent bonds, and implies that the electrostatic force has an angular dependency. Here a set of clusters, which includes hydrogen bonding, halogen bonding, chalcogen bonding, and pnicogen bonding systems, is investigated to probe the magnitude of covalency and its contribution to the directionality in noncovalent bonding. The study is based on the block-localized wavefunction (BLW) method that decomposes the binding energy into the steric and the charge transfer (CT) (hyperconjugation) contributions. One unique feature of the BLW method is its capability to derive optimal geometries with only steric effect taken into account, while excluding the CT interaction. The results reveal that the overall steric energy exhibits angular dependency notably in halogen bonding, chalcogen bonding, and pnicogen bonding systems. Turning on the CT interactions further shortens the intermolecular distances. This bond shortening enhances the Pauli repulsion, which in turn offsets the electrostatic attraction, such that in the final sum, the contribution of the steric effect to bonding is diminished, leaving the CT to dominate the binding energy. In several other systems particularly hydrogen bonding systems, the steric effect nevertheless still plays the major role whereas the CT interaction is minor. However, in all cases, the CT exhibits strong directionality, suggesting that the linearity or near linearity of noncovalent bonds is largely governed by the charge-transfer interaction whose magnitude determines the covalency in noncovalent bonds.

  8. Are Fossil Groups Early-forming Galaxy Systems?

    NASA Astrophysics Data System (ADS)

    Kundert, A.; D'Onghia, E.; Aguerri, J. A. L.

    2017-08-01

    Using the Illustris cosmological simulation, we investigate the origin of fossil groups in the {M}200={10}13{--}{10}13.5 {M}⊙ {h}-1 mass regime. We examine the formation of the two primary features of fossil groups: the large magnitude gap between their two brightest galaxies and their exceptionally luminous brightest group galaxy (BGG). For fossils and nonfossils identified at z = 0, we find no difference in their halo mass assembly histories at early times, departing from previous studies. However, we do find a significant difference in the recent accretion history of fossil and nonfossil halos; in particular, fossil groups show a lack of recent accretion and have in majority assembled 80% of their {M}200(z=0) mass before z˜ 0.4. For fossils, massive satellite galaxies accreted during this period have enough time to merge with the BGG by the present day, producing a more massive central galaxy. In addition, the lack of recent group accretion prevents replenishment of the bright satellite population, allowing for a large magnitude gap to develop within the past few Gyr. We thus find that the origin of the magnitude gap and overmassive BGG of fossils in Illustris depends on the recent accretion history of the groups and merger history of the BGGs after their collapse at z˜ 1. This indicates that selecting galaxy groups by their magnitude gap does not guarantee obtaining either early-forming galaxy systems or undisturbed central galaxies.

  9. Pediatric Scleroderma –Systemic and Localized Forms

    PubMed Central

    Torok, Kathryn S.

    2012-01-01

    Synopsis statement Pediatric scleroderma includes two major groups of clinical entities, systemic sclerosis (SSc) and localized scleroderma (LS). Although both share a common pathophysiology, with an initial inflammatory phase associated with endothelial activation, and a later fibrotic phase evidenced by collagenization of tissue and appreciable skin thickness, their clinical manifestations differ. LS is typically confined to the skin and underlying subcutis, and though not fatal like SSc, up to a quarter of the patients may have extracutaneous disease manifestations, such as arthritis and uveitis. While any organ may be affected in SSc, vascular (Raynaud’s phenomenon), cutaneous (skin thickening), GI, pulmonary and musculoskeletal involvement are most commonly seen in children. Auto-antibody profiles in childhood onset SSc can assist in predicting internal organ involvement. Treatment for both forms of scleroderma targets the active inflammatory stage and halts disease progression; however, progress still needs to be made towards the development of a more effective anti-fibrotic therapy to help reverse disease damage. PMID:22560576

  10. Synthesis and intermolecular interactions of N-benzylidenetyramines

    NASA Astrophysics Data System (ADS)

    Maldonado, Mauricio; Pérez-Redondo, Adrián; Quevedo, Rodolfo

    2017-01-01

    In this paper, the synthesis and intermolecular interactions between N-benzylidenetyramine molecules were investigated. The crystal structure of N-(4-nitrobenzylidene)tyramine shows a molecular organization in zigzag chains with intermolecular O-H⋯N hydrogen bonds between the azomethine and phenolic hydroxyl groups. Those chains are held together by C-H⋯O hydrogen bonds to generate layers, which are connected by C-H⋯O, π⋯π and NO2⋯π interactions.

  11. Intermolecular forces between the motor protein and the filament.

    PubMed

    Suda, H; Taylor, T W

    1993-03-07

    Intermolecular forces between motor proteins and filaments were evaluated on the basis of the experimental data of an in vitro motility assay by considering the molecular friction in the movement system. The molecular friction was caused by a different mechanism from that of the hydrodynamic drag. However, the molecular frictional forces apparently gave the same expression as the hydrodynamic frictional forces. The resulting equation was very effective in examining the physical properties of the weak interaction in the dynein-microtubules system from basic experiments carried out by Vale et al. (1989). From careful analysis of their experimental data, it was concluded that the hydrodynamic friction was not dominant, even in the weak binding state. The electrostatic interaction between dynein-heads and microtubules in the weak binding state was analyzed by applying the DLVO (Derjaguin-Landau-Verway-Overbeek) theory in colloid science through the ionic dependence of one-dimensional diffusion. The interacting distance between charges which took part in the weak adhesion was estimated to be 3 nm. In the present study, the molecular mechanism of the sliding velocity was also investigated for the myosin-actin filaments and the kinesin-microtubules systems by fitting the ATP-dependence and the ionic dependence in ATP-driven active sliding.

  12. Investigation of intermolecular interactions in perylene films on Au(111) by infrared spectroscopy

    NASA Astrophysics Data System (ADS)

    Ding, Li; Schulz, Philip; Farahzadi, Azadeh; Shportko, Kostiantyn V.; Wuttig, Matthias

    2012-02-01

    Intermolecular interactions in crystalline perylene films on Au(111) have been investigated by Fourier transform infrared spectroscopy. Dimer modes of vibrations are observed in the crystalline film, in contrast to the monomer modes found for isolated perylene molecules. These dimers are formed via hydrogen bonding in the sandwich herringbone structure of the crystalline α-phase. Davydov splitting of both the monomer and the dimer modes is observed due to resonance dynamic intermolecular interaction. The splitting of monomer modes into three distinct vibrations and the occurrence of the dimer modes confirm that the film crystallizes in the α phase, which is in line with the x-ray diffraction results. The frequency shift and band broadening at elevated temperature have been attributed to the cubic and quartic anharmonic interactions.

  13. Probing acid-amide intermolecular hydrogen bonding by NMR spectroscopy and DFT calculations

    NASA Astrophysics Data System (ADS)

    Chaudhari, Sachin Rama; Suryaprakash, N.

    2012-05-01

    Benzene carboxylic acids and benzamide act as their self-complement in molecular recognition to form inter-molecular hydrogen bonded dimers between amide and carboxylic acid groups, which have been investigated by 1H, 13C and 15N NMR spectroscopy. Extensive NMR studies using diffusion ordered spectroscopy (DOSY), variable temperature 1D, 2D NMR, established the formation of heterodimers of benzamide with benzoic acid, salicylic acid and phenyl acetic acid in deuterated chloroform solution. Association constants for the complex formation in the solution state have been determined. The results are ascertained by X-ray diffraction in the solid state. Intermolecular interactions in solution and in solid state were found to be similar. The structural parameters obtained by X-ray diffraction studies are compared with those obtained by DFT calculations.

  14. Theory of specific heat in glass-forming systems

    NASA Astrophysics Data System (ADS)

    Hentschel, H. G. E.; Ilyin, Valery; Procaccia, Itamar; Schupper, Nurith

    2008-12-01

    Experimental measurements of the specific heat in glass-forming systems are obtained from the linear response to either slow cooling (or heating) or to oscillatory perturbations with a given frequency about a constant temperature. The latter method gives rise to a complex specific heat with the constraint that the zero frequency limit of the real part should be identified with thermodynamic measurements. Such measurements reveal anomalies in the temperature dependence of the specific heat, including the so called “specific heat peak” in the vicinity of the glass transition. The aim of this paper is to provide theoretical explanations of these anomalies in general and a quantitative theory in the case of a simple model of glass formation. We first present interesting simulation results for the specific heat in a classical model of a binary mixture glass former. We show that in addition to the formerly observed specific heat peak there is a second peak at lower temperatures which was not observable in earlier simulations. Second, we present a general relation between the specific heat, a caloric quantity, and the bulk modulus of the material, a mechanical quantity, and thus offer a smooth connection between the liquid and amorphous solid states. The central result of this paper is a connection between the micromelting of clusters in the system and the appearance of specific heat peaks; we explain the appearance of two peaks by the micromelting of two types of clusters. We relate the two peaks to changes in the bulk and shear moduli. We propose that the phenomenon of glass formation is accompanied by a fast change in the bulk and the shear moduli, but these fast changes occur in different ranges of the temperature. Last, we demonstrate how to construct a theory of the frequency dependent complex specific heat, expected from heterogeneous clustering in the liquid state of glass formers. A specific example is provided in the context of our model for the dynamics of

  15. Polyelectrolyte brushes in mixed ionic medium studied via intermolecular forces

    NASA Astrophysics Data System (ADS)

    Farina, Robert; Laugel, Nicolas; Pincus, Philip; Tirrell, Matthew

    2011-03-01

    The vast uses and applications of polyelectrolyte brushes make them an attractive field of research especially with the growing interest in responsive materials. Polymers which respond via changes in temperature, pH, and ionic strength are increasingly being used for applications in drug delivery, chemical gating, etc. When polyelectrolyte brushes are found in either nature (e.g., surfaces of cartilage and mammalian lung interiors) or commercially (e.g., skin care products, shampoo, and surfaces of medical devices) they are always surrounded by mixed ionic medium. This makes the study of these brushes in varying ionic environments extremely relevant for both current and future potential applications. The polyelectrolyte brushes in this work are diblock co-polymers of poly-styrene sulfonate (N=420) and poly-t-butyl styrene (N=20) which tethers to a hydrophobic surface allowing for a purely thermodynamic study of the polyelectrolyte chains. Intermolecular forces between two brushes are measured using the SFA. As multi-valent concentrations are increased, the brushes collapse internally and form strong adhesion between one another after contact (properties not seen in a purely mono-valent environment).

  16. Cartilage matrix protein forms a type II collagen-independent filamentous network: analysis in primary cell cultures with a retrovirus expression system.

    PubMed Central

    Chen, Q; Johnson, D M; Haudenschild, D R; Tondravi, M M; Goetinck, P F

    1995-01-01

    Cartilage matrix protein (CMP) is expressed specifically in mature cartilage and consists of two von Willebrand factor A domains (CMP-A1 and CMP-A2) that are separated by an epidermal growth factor-like domain, and a coiled-coil tail domain at the carboxyl terminal end. We have shown previously that CMP interacts with type II collagen-containing fibrils in cartilage. In this study, we describe a type II collagen-independent CMP filament and we analyze the structural requirement for the formation of this type of filament. Recombinant wild-type CMP and two mutant forms were expressed in chick primary cell cultures using a retrovirus expression system. In chondrocytes, the wild-type virally encoded CMP is able to form disulfide bonded trimers and to assemble into filaments. Filaments also form with CMP whose Cys455 and Cys457 in the tail domain were mutagenized to prevent interchain disulfide bond formation. Therefore, intermolecular disulfide bonds are not necessary for the assembly of CMP into filaments. Both the wild-type and the double cysteine mutant also form filaments in fibroblasts, indicating that chondrocyte-specific factors are not required for filament formation. A truncated form of CMP that consists only of the CMP-A2 domain and the tail domain can form trimers but fails to form filaments, indicating that the deleted CMP-A1 domain and/or the epidermal growth factor domain are necessary for filament assembly but not for trimer formation. Furthermore, the expression of the virally encoded truncated CMP in chondrocyte culture disrupts endogenous CMP filament formation. Together these data suggest a role for CMP in cartilage matrix assembly by forming filamentous networks that require participation and coordination of individual domains of CMP. Images PMID:8590802

  17. Interpreting the widespread nonlinear force spectra of intermolecular bonds

    PubMed Central

    Friddle, Raymond W.; Noy, Aleksandr; De Yoreo, James J.

    2012-01-01

    Single molecule force spectroscopy probes the strength, lifetime, and energetic details of intermolecular interactions in a simple experiment. A growing number of these studies have reported distinctly nonlinear trends in rupture force with loading rate that are typically explained in conventional models by invoking complex escape pathways. Recent analyses suggested that these trends should be expected even for simple barriers based on the basic assumptions of bond rupture dynamics and thus may represent the norm rather than the exception. Here we explore how these nonlinear trends reflect the two fundamental regimes of bond rupture: (i) a near-equilibrium regime, produced either by bond reforming in the case of a single bond or by asynchronized rupture of multiple individual bonds, and (ii) a kinetic regime produced by fast, non-equilibrium bond rupture. We analyze both single- and multi-bonded cases, describe the full evolution of the system as it transitions between near- and far-from-equilibrium loading regimes, and show that both interpretations produce essentially identical force spectra. Data from 10 different molecular systems show that this model provides a comprehensive description of force spectra for a diverse suite of bonds over experimentally relevant loading rates, removes the inconsistencies of previous interpretations of transition state distances, and gives ready access to both kinetic and thermodynamic information about the interaction. These results imply that single-molecule binding free energies for a vast number of bonds have already been measured. PMID:22869712

  18. Localized-overlap approach to calculations of intermolecular interactions

    NASA Astrophysics Data System (ADS)

    Rob, Fazle

    Symmetry-adapted perturbation theory (SAPT) based on the density functional theory (DFT) description of the monomers [SAPT(DFT)] is one of the most robust tools for computing intermolecular interaction energies. Currently, one can use the SAPT(DFT) method to calculate interaction energies of dimers consisting of about a hundred atoms. To remove the methodological and technical limits and extend the size of the systems that can be calculated with the method, a novel approach has been proposed that redefines the electron densities and polarizabilities in a localized way. In the new method, accurate but computationally expensive quantum-chemical calculations are only applied for the regions where it is necessary and for other regions, where overlap effects of the wave functions are negligible, inexpensive asymptotic techniques are used. Unlike other hybrid methods, this new approach is mathematically rigorous. The main benefit of this method is that with the increasing size of the system the calculation scales linearly and, therefore, this approach will be denoted as local-overlap SAPT(DFT) or LSAPT(DFT). As a byproduct of developing LSAPT(DFT), some important problems concerning distributed molecular response, in particular, the unphysical charge-flow terms were eliminated. Additionally, to illustrate the capabilities of SAPT(DFT), a potential energy function has been developed for an energetic molecular crystal of 1,1-diamino-2,2-dinitroethylene (FOX-7), where an excellent agreement with the experimental data has been found.

  19. NMR detection of intermolecular interaction sites in the dimeric 5′-leader of the HIV-1 genome

    PubMed Central

    Keane, Sarah C.; Van, Verna; Frank, Heather M.; Sciandra, Carly A.; McCowin, Sayo; Santos, Justin; Heng, Xiao; Summers, Michael F.

    2016-01-01

    HIV type-1 (HIV-1) contains a pseudodiploid RNA genome that is selected for packaging and maintained in virions as a noncovalently linked dimer. Genome dimerization is mediated by conserved elements within the 5′-leader of the RNA, including a palindromic dimer initiation signal (DIS) that has been proposed to form kissing hairpin and/or extended duplex intermolecular contacts. Here, we have applied a 2H-edited NMR approach to directly probe for intermolecular interactions in the full-length, dimeric HIV-1 5′-leader (688 nucleotides; 230 kDa). The interface is extensive and includes DIS:DIS base pairing in an extended duplex state as well as intermolecular pairing between elements of the upstream Unique-5′ (U5) sequence and those near the gag start site (AUG). Other pseudopalindromic regions of the leader, including the transcription activation (TAR), polyadenylation (PolyA), and primer binding (PBS) elements, do not participate in intermolecular base pairing. Using a 2H-edited one-dimensional NMR approach, we also show that the extended interface structure forms on a time scale similar to that of overall RNA dimerization. Our studies indicate that a kissing dimer-mediated structure, if formed, exists only transiently and readily converts to the extended interface structure, even in the absence of the HIV-1 nucleocapsid protein or other RNA chaperones. PMID:27791166

  20. Resonant Auger decay driving intermolecular Coulombic decay in molecular dimers.

    PubMed

    Trinter, F; Schöffler, M S; Kim, H-K; Sturm, F P; Cole, K; Neumann, N; Vredenborg, A; Williams, J; Bocharova, I; Guillemin, R; Simon, M; Belkacem, A; Landers, A L; Weber, Th; Schmidt-Böcking, H; Dörner, R; Jahnke, T

    2014-01-30

    In 1997, it was predicted that an electronically excited atom or molecule placed in a loosely bound chemical system (such as a hydrogen-bonded or van-der-Waals-bonded cluster) could efficiently decay by transferring its excess energy to a neighbouring species that would then emit a low-energy electron. This intermolecular Coulombic decay (ICD) process has since been shown to be a common phenomenon, raising questions about its role in DNA damage induced by ionizing radiation, in which low-energy electrons are known to play an important part. It was recently suggested that ICD can be triggered efficiently and site-selectively by resonantly core-exciting a target atom, which then transforms through Auger decay into an ionic species with sufficiently high excitation energy to permit ICD to occur. Here we show experimentally that resonant Auger decay can indeed trigger ICD in dimers of both molecular nitrogen and carbon monoxide. By using ion and electron momentum spectroscopy to measure simultaneously the charged species created in the resonant-Auger-driven ICD cascade, we find that ICD occurs in less time than the 20 femtoseconds it would take for individual molecules to undergo dissociation. Our experimental confirmation of this process and its efficiency may trigger renewed efforts to develop resonant X-ray excitation schemes for more localized and targeted cancer radiation therapy.

  1. Determination of stepsize parameters for intermolecular vibrational energy transfer

    SciTech Connect

    Tardy, D.C.

    1992-03-01

    Intermolecular energy transfer of highly excited polyatomic molecules plays an important role in many complex chemical systems: combustion, high temperature and atmospheric chemistry. By monitoring the relaxation of internal energy we have observed trends in the collisional efficiency ({beta}) for energy transfer as a function of the substrate's excitation energy and the complexities of substrate and deactivator. For a given substrate {beta} increases as the deactivator's mass increase to {approximately}30 amu and then exhibits a nearly constant value; this is due to a mass mismatch between the atoms of the colliders. In a homologous series of substrate molecules (C{sub 3}{minus}C{sub 8}) {beta} decreases as the number of atoms in the substrate increases; replacing F with H increases {beta}. All substrates, except for CF{sub 2}Cl{sub 2} and CF{sub 2}HCl below 10,000 cm{sup {minus}1}, exhibited that {beta} is independent of energy, i.e. <{Delta}E>{sub all} is linear with energy. The results are interpreted with a simple model which considers that {beta} is a function of the ocillators energy and its vibrational frequency. Limitations of current approximations used in high temperature unimolecular reactions were evaluated and better approximations were developed. The importance of energy transfer in product yields was observed for the photoactivation of perfluorocyclopropene and the photoproduction of difluoroethyne. 3 refs., 18 figs., 4 tabs.

  2. Data assimilation and determining forms for weakly damped, dispersive systems

    NASA Astrophysics Data System (ADS)

    Sadigov, Tural

    In this work, we show that the global attractor of the 1D damped, driven, nonlinear Schrodinger equations (NLS) is embedded in the long-time dynamics of a determining form. The determining form for the NLS is an ordinary differential equation in a space of trajectories X = Cb 1(R,PmH2) where Pm is the L2-projector onto the span of the ?rst m Fourier modes. Similarly, we also find a determining form for the damped, driven Korteweg de-Vries equations (KdV). This time, the determining form for the KdV is an ordinary differential equation in a space of trajectories X = Cb 1(R,PmH2). In both cases, there is a one-to-one identi?cation with the trajectories in the global attractor of the underlying equations and the steady states of the determining form for the that equation. The determining form for both of these equations is dv(s, t)/ dt= - sup{s∈R} |v( s, t) - PmW (v( s, t))|2(v(s, t) - Pmu* (s, t)), where v( s) ∈ X, u* is a steady state of the underlying equation and W is a special map from X to a different Banach space which contains the relation between the underlying partial differential equation and the determining form. Additionally, we prove that the determining modes property holds for both of these equations. We give an improved estimate for the number of the determining modes for the NLS and we give an estimate for the number of determining modes for the KdV. Moreover, we give a continuous data assimilation algorithm via feedback control approach for the NLS and the KdV using only definitely many modes. The NLS and the KdV equations are ius + uxx + |u|2u + gammau = f, (NLS) us + uux + uxxx + gamma u = f, (KdV) respectively. We prove the following theorem: Theorem. Let u be a solution of the following equation us = F( u), with an initial data u(s 0), where the above equation is either (NLS) or (KdV), and let w be the solution of the corresponding data assimilation equation ws = F(w) - micro Pm(w - u), with an arbitrary initial data w(s0). For micro large

  3. Forming design teams to develop healthcare information systems.

    PubMed

    Saleem, Naveed; Jones, Donald R; Van Tran, Hien; Moses, Beulah

    2006-01-01

    Healthcare information systems are assuming an increasingly critical role in providing quality patient care in an effective and efficient manner. However, the success of these systems in achieving these goals remains a lingering concern. Consequently, investigating and devising strategies to enhance the likelihood of success of a healthcare information system continues to draw research interest. One strategy recommended by both researchers and practitioners alike is the participation of the target users in the design and development of the information system. However, practical considerations mandate representative, rather than universal, participation of users. Unfortunately, the information systems literature offers few guidelines for selecting user representatives to serve on a design team. This lack of guidelines easily results in system designers talking with the wrong users or managers assigning the wrong users to the design team. On the basis of the theoretical paradigms underlying the user participation and design team concepts, the authors examined and derived user characteristics that are considered the most critical criteria for selecting user members of a design team. They then report on a field survey they conducted to validate the derived criteria in healthcare information systems context. The authors conclude that the system-related functional expertise should be the primary criterion employed to select healthcare personnel to participate in system design and development. Other criteria, such as users' communication skills, computing backgrounds, and personality traits, should be given secondary considerations. Ignoring these guidelines can render user participation superfluous, resulting in system failures.

  4. Heterotetrameric forms of human phenylalanine hydroxylase: co-expression of wild-type and mutant forms in a bicistronic system.

    PubMed

    Leandro, João; Leandro, Paula; Flatmark, Torgeir

    2011-05-01

    Hybrid forms of human phenylalanine hydroxylase (hPAH) mutants have been found to present catalytic activities lower than predicted from the individual recombinant forms, indicating that interallelic complementation could be a major determinant of the metabolic phenotype of compound heterozygous phenylketonuric (PKU) patients. To provide a molecular explanation for interallelic complementation we have here developed a bicistronic expression system and a purification strategy to obtain isolated hPAH heteromeric forms. On co-expression of WT-hPAH (~50% tetramer; ~10% dimer) and the N- and C-terminally truncated form ΔN102/ΔC24-hPAH (~80% dimer) no heterodimers were recovered. Moreover, by co-expression of WT-hPAH and the N-terminally truncated form ΔN102-hPAH (~95% tetramer), heterotetramers, as a result of an assembly of two different homodimers, were isolated. The recovered (WT)/(ΔN102)-hPAH heterotetramers revealed a catalytic activity deviating significantly from that calculated by averaging the respective recombinant homotetrameric forms. The heterotetramer assembly also results in conformational changes in the WT-hPAH protomer, as detected by trypsin limited proteolysis. The finding that the presence of two homodimers with different kinetic parameters influences the properties of the resulting heterotetrameric protein indicates that the dimers exhibit interactions which are transmitted across the assembled tetramer. The bicistronic expression system developed here allowed the isolation of hybrid forms that exhibit negative interallelic complementation, and may represent a model system for studying the molecular pathogenic mechanisms of PAH gene mutations in compound heterozygous PKU patients, providing the rationale to understand the observed inconsistencies both in genotype/phenotype correlations and in the response to BH(4) supplementation.

  5. Greenhouse effect in planetary atmospheres caused by molecular symmetry breaking in intermolecular interactions

    NASA Astrophysics Data System (ADS)

    Vigasin, A. A.; Mokhov, I. I.

    2017-03-01

    It is believed that the greenhouse effect is related to the parameters of absorption spectra of polyatomic molecules, usually trace gases, in planetary atmospheres. The main components of all known atmospheres of celestial bodies are symmetrical molecules that do not possess the dipole-allowed purely rotational (and in the case of diatomic molecules, vibrational-rotational) absorption spectrum. Upon increased pressure, a weak absorption appears, induced by intermolecular interaction, which can lead to a greenhouse effect. The contribution of the induced absorption in radiative forcing of a dense atmosphere may amount to a few or even tens of W/m2. In conditions typical for the atmospheres of terrestrial planets (including paleoatmospheres), the collision-induced absorption and associated greenhouse effect may lead to an increase in surface temperature above the freezing point of water. There is a correlation between the temperature of an atmosphere and the intermolecular bonding energy of gases that dominate in planetary atmospheres of the Solar System.

  6. Tip relaxation in atomic force microscopy imaging simulations to resolve intermolecular bonds

    NASA Astrophysics Data System (ADS)

    Lee, Alex; Sakai, Yuki; Chelikowsky, Jim

    Experimental noncontact atomic force microscopy (AFM) studies have reported distinct lines in regions with no electron density for a variety of systems. The appearance of these lines is unexpected because Pauli repulsion is thought to be the dominant factor in the AFM imaging mechanism. These lines have been proposed to represent intermolecular bonding. Recent theoretical studies have shown that accounting for tip probe relaxation can sharpen images and highlight features that make simulations more comparable to experiment. We will apply a similar tip relaxation scheme to our computational method-which uses an ab initio real-space pseudopotential formalism with frozen density embedding theory added-to the study of dibenzo[a,h]thianthrene and an 8-hydroxyquinoline dimer to develop our interpretation of imaged intermolecular bonds. Work is supported by the DOE under DOE/DE-FG02-06ER46286 and by the Welch Foundation under Grant F-1837. Computational resources were provided by NERSC and XSEDE.

  7. Thermal history of caldera-forming magmatic systems

    NASA Astrophysics Data System (ADS)

    Bradshaw, R. W.; Kent, A. J.; Cooper, K. M.; Huber, C.

    2015-12-01

    Large, caldera-forming silicic eruptions require the assembly and storage of a large volume of magma, and are though to result from either (1) rare high magma flux events needed to maintain melt-rich (eruptible) magma for extended timescales, or (2) magma accumulation at lower magma fluxes, storage for extended timescales as low temperature crystal mushes and rapid rejuvenation prior to eruption. The thermal history of these magmas prior to eruption thus provides an important clue into the processes that lead to eruption, but has been difficult to quantify. However in-situ measurement of Sr and other trace elements in plagioclase, coupled with diffusion models, can be used to constrain the time magmas spend at different temperatures. Progressive differentiation of plagioclase from a silicic magma produces plagioclase with lower Sr at low An—producing a positive correlation between Sr and An, which is the opposite of what is predicted by equilibrium partitioning. Forward modeling of the temperature-dependent diffusion of Sr from this initial disequilibrium condition toward equilibrium concentrations, based on partitioning relationships of An and Sr, gives an estimate of the time individual crystals spend at specific temperatures. Preliminary high spatial resolution LA-ICP-MS analysis of Sr in plagioclase from five caldera-forming eruptions show overall positive correlations of Sr and An, suggesting that little diffusive re-equilibration has occurred. Thus, over the lifetime that these magmas reside in the upper crust (>10 k.y.) they likely spend less than a few thousand years at temperatures above 750 °C (the approximate temperature of rheological lockup). These results suggest that the magmas that feed many large caldera-forming eruptions are kept in cold storage for long timescales, and that rapid rejuvenation of mush occurs without extended thermal conditioning prior to eruption.

  8. Isotopic enrichment of forming planetary systems from supernova pollution

    NASA Astrophysics Data System (ADS)

    Lichtenberg, Tim; Parker, Richard J.; Meyer, Michael R.

    2016-11-01

    Heating by short-lived radioisotopes (SLRs) such as 26Al and 60Fe fundamentally shaped the thermal history and interior structure of Solar system planetesimals during the early stages of planetary formation. The subsequent thermo-mechanical evolution, such as internal differentiation or rapid volatile degassing, yields important implications for the final structure, composition and evolution of terrestrial planets. SLR-driven heating in the Solar system is sensitive to the absolute abundance and homogeneity of SLRs within the protoplanetary disc present during the condensation of the first solids. In order to explain the diverse compositions found for extrasolar planets, it is important to understand the distribution of SLRs in active planet formation regions (star clusters) during their first few Myr of evolution. By constraining the range of possible effects, we show how the imprint of SLRs can be extrapolated to exoplanetary systems and derive statistical predictions for the distribution of 26Al and 60Fe based on N-body simulations of typical to large clusters (103-104 stars) with a range of initial conditions. We quantify the pollution of protoplanetary discs by supernova ejecta and show that the likelihood of enrichment levels similar to or higher than the Solar system can vary considerably, depending on the cluster morphology. Furthermore, many enriched systems show an excess in radiogenic heating compared to Solar system levels, which implies that the formation and evolution of planetesimals could vary significantly depending on the birth environment of their host stars.

  9. Effect of the electronic structure of quinoline and its derivatives on the capacity for intermolecular interactions

    SciTech Connect

    Privalova, N.Yu.; Sokolova, I.V.

    1985-05-01

    Calculations of the ground and excited states of quinoline and its 20H-, 70H-, 7NH2-, 7N(CH3)2-, and 7N(C2H5)2- substituted derivatives were undertaken by the INDO method, and the effect of intramolecular proton transfer (IPT) on their electronic structure was studied. The proton-accepting capacity of the compounds for intermolecular interactions was estimated by the molecular electrostatic potential method. It was shown that the proton-accepting capacity with respect to intermolecular interactions increases during the tautomeric transformation of the enolic form of 2-OH-quinoline to its keto form. The change in the basicity of the two forms of the molecules is affected by the orbital nature, and the multiplicity of the state is also important for the keto form. Substitution by electron-donating groups leads to increase in the proton-accepting capacity of both forms of the compounds in the S0, S/sub */, and T/sub */ states.

  10. Intermolecular disulfide bond influences unphosphorylated STAT3 dimerization and function.

    PubMed

    Butturini, Elena; Gotte, Giovanni; Dell'Orco, Daniele; Chiavegato, Giulia; Marino, Valerio; Canetti, Diana; Cozzolino, Flora; Monti, Maria; Pucci, Piero; Mariotto, Sofia

    2016-10-01

    Signal transducer and activator of transcription 3 (STAT3) is a transcription factor activated by the phosphorylation of tyrosine 705 in response to many cytokines and growth factors. Recently, the roles for unphosphorylated STAT3 (U-STAT3) have been described in response to cytokine stimulation, in cancers, and in the maintenance of heterochromatin stability. It has been reported that U-STAT3 dimerizes, shuttles between the cytoplasm and nucleus, and binds to DNA, thereby driving genes transcription. Although many reports describe the active role of U-STAT3 in oncogenesis in addition to phosphorylated STAT3, the U-STAT3 functional pathway remains elusive.In this report, we describe the molecular mechanism of U-STAT3 dimerization, and we identify the presence of two intermolecular disulfide bridges between Cys367 and Cys542 and Cys418 and Cys426, respectively. Recently, we reported that the same cysteines contribute to the redox regulation of STAT3 signaling pathway both in vitro and in vivo The presence of these disulfides is here demonstrated to largely contribute to the structure and the stability of U-STAT3 dimer as the dimeric form rapidly dissociates upon reduction in the S-S bonds. In particular, the Cys367-Cys542 disulfide bridge is shown to be critical for U-STAT3 DNA-binding activity. Mutation of the two Cys residues completely abolishes the DNA-binding capability of U-STAT3. Spectroscopic investigations confirm that the noncovalent interactions are sufficient for proper folding and dimer formation, but that the interchain disulfide bonds are crucial to preserve the functional dimer. Finally, we propose a reaction scheme of U-STAT3 dimerization with a first common step followed by stabilization through the formation of interchain disulfide bonds. © 2016 The Author(s); published by Portland Press Limited on behalf of the Biochemical Society.

  11. Intermolecular Vibrational Modes Speed Up Singlet Fission in Perylenediimide Crystals.

    PubMed

    Renaud, Nicolas; Grozema, Ferdinand C

    2015-02-05

    We report numerical simulations based on a non-Markovian density matrix propagation scheme of singlet fission (SF) in molecular crystals. Ab initio electronic structure calculations were used to parametrize the exciton and phonon Hamiltonian as well as the interactions between the exciton and the intramolecular and intermolecular vibrational modes. We demonstrate that the interactions of the exciton with intermolecular vibrational modes are highly sensitive to the stacking geometry of the crystal and can, in certain cases, significantly accelerate SF. This result may help in understanding the fast SF experimentally observed in a broad range of molecular crystals and offers a new direction for the engineering of efficient SF sensitizers.

  12. Towards a Functionally-Formed Air Traffic System-of-Systems

    NASA Technical Reports Server (NTRS)

    Conway, Sheila R.; Consiglio, Maria C.

    2005-01-01

    Incremental improvements to the national aviation infrastructure have not resulted in sufficient increases in capacity and flexibility to meet emerging demand. Unfortunately, revolutionary changes capable of substantial and rapid increases in capacity have proven elusive. Moreover, significant changes have been difficult to implement, and the operational consequences of such change, difficult to predict due to the system s complexity. Some research suggests redistributing air traffic control functions through the system, but this work has largely been dismissed out of hand, accused of being impractical. However, the case for functionally-based reorganization of form can be made from a theoretical, systems perspective. This paper investigates Air Traffic Management functions and their intrinsic biases towards centralized/distributed operations, grounded in systems engineering and information technology theories. Application of these concepts to a small airport operations design is discussed. From this groundwork, a robust, scalable system transformation plan may be made in light of uncertain demand.

  13. System and method of forming nanostructured ferritic alloy

    DOEpatents

    Dial, Laura Cerully; DiDomizio, Richard; Alinger, Matthew Joseph; Huang, Shenyan

    2016-07-26

    A system for mechanical milling and a method of mechanical milling are disclosed. The system includes a container, a feedstock, and milling media. The container encloses a processing volume. The feedstock and the milling media are disposed in the processing volume of the container. The feedstock includes metal or alloy powder and a ceramic compound. The feedstock is mechanically milled in the processing volume using metallic milling media that includes a surface portion that has a carbon content less than about 0.4 weight percent.

  14. Novel RNA modifications in the nervous system: form and function.

    PubMed

    Satterlee, John S; Basanta-Sanchez, Maria; Blanco, Sandra; Li, Jin Billy; Meyer, Kate; Pollock, Jonathan; Sadri-Vakili, Ghazaleh; Rybak-Wolf, Agnieszka

    2014-11-12

    Modified RNA molecules have recently been shown to regulate nervous system functions. This mini-review and associated mini-symposium provide an overview of the types and known functions of novel modified RNAs in the nervous system, including covalently modified RNAs, edited RNAs, and circular RNAs. We discuss basic molecular mechanisms involving RNA modifications as well as the impact of modified RNAs and their regulation on neuronal processes and disorders, including neural fate specification, intellectual disability, neurodegeneration, dopamine neuron function, and substance use disorders.

  15. Novel RNA Modifications in the Nervous System: Form and Function

    PubMed Central

    Basanta-Sanchez, Maria; Blanco, Sandra; Li, Jin Billy; Meyer, Kate; Pollock, Jonathan; Sadri-Vakili, Ghazaleh; Rybak-Wolf, Agnieszka

    2014-01-01

    Modified RNA molecules have recently been shown to regulate nervous system functions. This mini-review and associated mini-symposium provide an overview of the types and known functions of novel modified RNAs in the nervous system, including covalently modified RNAs, edited RNAs, and circular RNAs. We discuss basic molecular mechanisms involving RNA modifications as well as the impact of modified RNAs and their regulation on neuronal processes and disorders, including neural fate specification, intellectual disability, neurodegeneration, dopamine neuron function, and substance use disorders. PMID:25392485

  16. Systems and methods for forming microchannel plate (MCP) photodetector assemblies

    DOEpatents

    Xia, Lei; Zhao, Huyue; Wagner, Robert G.; Gregar, Joseph S.; Xie, Junqi; Wang, Jingbo

    2017-07-11

    A MCP photodetector assembly includes an anode plate including a plurality of electrical traces positioned thereon, a plurality of MCPs and a plurality of grid spacers. The MCPs are positioned between the grid spacers. The grid spacers have a grid spacer shape defining at least one aperture. A plurality of shims are positioned between the grid spacers and the MCPs so as to form a stack positioned on the anode plate. Each of the plurality of shims have a shim shape which is the same as the grid spacer shape such that each of the plurality of shims and each of the plurality of grid spacers overlap so as to define at least one MCP aperture. At least a portion of the plurality of MCPs are positioned within the MCP aperture. The shims are structured to electrically couple the MCPs to the anode plate.

  17. The intermolecular hydrogen-hydrogen structure of chain-molecule liquids from neutron diffraction

    NASA Astrophysics Data System (ADS)

    Londono, J. D.; Annis, B. K.; Turner, J. Z.; Soper, A. K.

    1994-11-01

    Neutron diffraction isotopic substitution experiments on liquid n-decane (C10H22) and n-eicosane (C20H42) are described. The intermolecular H-H structure function hHH(Q) and the intermolecular H-H correlation function ginterHH(r) are obtained without recourse to models of the intramolecular structure. The structure of the ginterHH(r) found at 2.5, 5.0, and 7.0 Å corresponds to different shells in the H-H pair correlation function. In addition, ginterHH(r)<1 for a considerable range, due to the screening of intermolecular correlations by intramolecular correlations. This ``correlation hole'' effect is accentuated by extrapolation of the structure functions to the expected infinite wavelength limit, and shows good agreement with values determined from small-angle neutron scattering (SANS) data. All of these features are in good agreement with the results of molecular dynamics simulations for the closely related system C13H28.

  18. Information systems form large part of strategic plan.

    PubMed

    Landis, D

    1991-02-01

    Strategic planning is often a low priority for community hospitals because it is often too impractical. The difference for Ed McFall, chief information officer at Pitt County Memorial Hospital (PCMH) in Greenville, N.C., is that his hospital's and affiliated medical school's information systems plans work.

  19. Highly enantioselective and anti-diastereoselective catalytic intermolecular glyoxylate-ene reactions: effect of the geometrical isomers of alkenes.

    PubMed

    Zhang, Xiang; Wang, Min; Ding, Ran; Xu, Yun-He; Loh, Teck-Peng

    2015-06-05

    An efficient method for the synthesis of homoallylic alcohols with high enantioselectivities and anti-diastereoselectivities via an In(III)-catalyzed intermolecular glyoxylate-ene reaction has been developed. The geometrical isomers of alkenes were shown to have different reactivities. Only the isomers of the alkenes having a proton β-cis to the substituent reacted in this catalytic system.

  20. Methods of forming thermal management systems and thermal management methods

    DOEpatents

    Gering, Kevin L.; Haefner, Daryl R.

    2012-06-05

    A thermal management system for a vehicle includes a heat exchanger having a thermal energy storage material provided therein, a first coolant loop thermally coupled to an electrochemical storage device located within the first coolant loop and to the heat exchanger, and a second coolant loop thermally coupled to the heat exchanger. The first and second coolant loops are configured to carry distinct thermal energy transfer media. The thermal management system also includes an interface configured to facilitate transfer of heat generated by an internal combustion engine to the heat exchanger via the second coolant loop in order to selectively deliver the heat to the electrochemical storage device. Thermal management methods are also provided.

  1. Lake phosphorus loading form septic systems by seasonally perched groundwater

    USGS Publications Warehouse

    Gilliom, R.J.; Patmont, C.R.

    1983-01-01

    The movement of effluent phosphorus (P) from old septic systems by seasonally perched groundwater was investigated. A previous study indicated a correlation between P loadings and the presence of old homes. Water samples were taken from shallow wells installed 10 to 50 m downgradient from seven septic systems 20 to 40 years old. The equivalent volumetric fraction of each sample consisting of undiluted effluent was estimated from chloride concentration. A Monte Carlo analysis was used to account for the various sources of uncertainty. Movement of diluted septic effluent to the lake was common, but transport of more than 1% of effluent P through the soil was probable for only 4 of 26 samples. The greatest apparent P movement was associated with persistently saturated conditions.

  2. Rodlike localized structure in isotropic pattern-forming systems.

    PubMed

    Bordeu, Ignacio; Clerc, Marcel G

    2015-10-01

    Stationary two-dimensional localized structures have been observed in a wide variety of dissipative systems. The existence, stability properties, dynamical evolution, and bifurcation diagram of an azimuthal symmetry breaking, rodlike localized structure in the isotropic prototype model of pattern formation, the Swift-Hohenberg model, is studied. These rodlike structures persist under the presence of nongradient perturbations. Interaction properties of the rodlike structures are studied. This allows us to envisage the possibility of different crystal-like configurations.

  3. Light scattering studies of clathrate hydrate forming systems

    NASA Astrophysics Data System (ADS)

    Zachary, Ralph Karl

    The current importance of clathrate hydrates lies primarily in the problems they pose for the oil and gas industry; in the future they may represent an important source of energy. These studies were persued in an effort to determine the utility of light scattering for elucidating changes in the dynamical structure of aqueous solutions that occur prior to hydrate formation. Such an understanding has direct relevance to the kinetics of clathrate hydrate formation, and may contribute to our knowledge of the many other systems in which water plays an important role. Aqueous solutions of tetrahydrofuran were at the center of this research which included experimental spectroscopic studies of such solutions as a function of temperature and system composition. Light scattering spectra were found to contain important information concerning the extent and nature of hydrogen bonding, and the structural changes that precede hydrate nucleation. Specifically, the OH stretching band due to water and the COC stretch band due to tetrahydrofuran were seen to vary in a predictable manner with changes in the composition, temperature, and thermal history of the system. Computer simulation studies were performed and used to aid in the interpretation of experimental spectra. Low wavenumber polarizability fluctuations were calculated and found to give reorientation times in good agreement with those found using other methods.

  4. Invariants reveal multiple forms of robustness in bifunctional enzyme systems.

    PubMed

    Dexter, Joseph P; Dasgupta, Tathagata; Gunawardena, Jeremy

    2015-08-01

    Experimental and theoretical studies have suggested that bifunctional enzymes catalyzing opposing modification and demodification reactions can confer steady-state concentration robustness to their substrates. However, the types of robustness and the biochemical basis for them have remained elusive. Here we report a systematic study of the most general biochemical reaction network for a bifunctional enzyme acting on a substrate with one modification site, along with eleven sub-networks with more specialized biochemical assumptions. We exploit ideas from computational algebraic geometry, introduced in previous work, to find a polynomial expression (an invariant) between the steady state concentrations of the modified and unmodified substrate for each network. We use these invariants to identify five classes of robust behavior: robust upper bounds on concentration, robust two-sided bounds on concentration ratio, hybrid robustness, absolute concentration robustness (ACR), and robust concentration ratio. This analysis demonstrates that robustness can take a variety of forms and that the type of robustness is sensitive to many biochemical details, with small changes in biochemistry leading to very different steady-state behaviors. In particular, we find that the widely-studied ACR requires highly specialized assumptions in addition to bifunctionality. An unexpected result is that the robust bounds derived from invariants are strictly tighter than those derived by ad hoc manipulation of the underlying differential equations, confirming the value of invariants as a tool to gain insight into biochemical reaction networks. Furthermore, invariants yield multiple experimentally testable predictions and illuminate new strategies for inferring enzymatic mechanisms from steady-state measurements.

  5. Divergent dynamics and the Kauzmann temperature in glass forming systems

    PubMed Central

    Martinez-Garcia, Julio Cesar; Rzoska, Sylwester J.; Drzozd-Rzoska, Aleksandra; Martinez-Garcia, Jorge; Mauro, John C.

    2014-01-01

    In the last decade the challenging analysis of previtreous behavior of relaxation time (τ(T)) in ultraviscous low molecular weight liquids led to the conceptual shift of the glass transition physics toward theories not predicting a “finite-temperature” divergence. This “breakthrough” experimental finding was strengthened by the discovery that “dynamic” (i.e. from τ(T) fitting) and “thermodynamic” estimations of the “ideal glass” (Kauzmann) temperature do not match, what in fact questioned its existence. In this report, due to the novel way of analysis based on the transformation of τ(T) experimental data to the activation energy temperature index form, the clear prevalence of the “finite-temperature” divergence is proved. The obtained “dynamic” singular temperatures clearly coincide with “thermodynamic” estimations of the Kauzmann temperature, thus solving also the second mystery. The comprehensive picture was obtained due to the analysis of 55 experimental data-sets, ranging from low molecular weight liquids and polymers to liquid crystal and plastic crystals. PMID:24895028

  6. Spatial rogue waves in a photorefractive pattern-forming system.

    PubMed

    Marsal, N; Caullet, V; Wolfersberger, D; Sciamanna, M

    2014-06-15

    We have experimentally analyzed pattern formation in an optical system composed of a bulk photorefractive crystal subjected to a single optical feedback. In a highly nonlinear regime far above the modulational instability threshold, we are reporting on turbulent spatiotemporal dynamics that leads to rare, intense localized optical peaks. We have proven that the statistics and features of those peaks correspond to the signatures of two-dimensional spatial rogue events. These optical rogue waves occur erratically in space and time and live typically the same amount of time as the response time of the photorefractive material.

  7. Interatomic and intermolecular Coulombic decay: the coming of age story

    NASA Astrophysics Data System (ADS)

    Jahnke, T.

    2015-04-01

    In pioneering work by Cederbaum et al an excitation mechanism was proposed that occurs only in loosely bound matter (Cederbaum et al 1997 Phys. Rev. Lett. 79 4778): it turned out, that (in particular) in cases where a local Auger decay is energetically forbidden, an excited atom or molecule is able to decay in a scheme which was termed ‘interatomic Coulombic decay’ (or ‘intermolecular Coulombic decay’) (ICD). As ICD occurs, the excitation energy is released by transferring it to an atomic or molecular neighbor of the initially excited particle. As a consequence the neighboring atom or molecule is ionized as it receives the energy. A few years later the existence of ICD was confirmed experimentally (Marburger et al 2003 Phys. Rev. Lett. 90 203401; Jahnke et al 2004 Phys. Rev. Lett. 93 163401; Öhrwall et al 2004 Phys. Rev. Lett. 93 173401) by different techniques. Since this time it has been found that ICD is not (as initially suspected) an exotic feature of van der Waals or hydrogen bonded systems, but that ICD is a very general and common feature occurring after a manifold of excitation schemes and in numerous weakly bound systems, as revealed by more than 200 publications. It was even demonstrated, that ICD can become more efficient than a local Auger decay in some system. This review will concentrate on recent experimental investigations on ICD. It will briefly introduce the phenomenon and give a short summary of the ‘early years’ of ICD (a detailed view on this episode of investigations can be found in the review article by U Hergenhahn with the same title (Hergenhahn 2011 J. Electron Spectrosc. Relat. Phenom. 184 78)). More recent articles will be presented that investigate the relevance of ICD in biological systems and possible radiation damage of such systems due to ICD. The occurrence of ICD and ICD-like processes after different excitation schemes and in different systems is covered in the middle section: in that context the helium dimer (He2

  8. Global feedback control for pattern-forming systems.

    PubMed

    Stanton, L G; Golovin, A A

    2007-09-01

    Global feedback control of pattern formation in a wide class of systems described by the Swift-Hohenberg (SH) equation is investigated theoretically, by means of stability analysis and numerical simulations. Two cases are considered: (i) feedback control of the competition between hexagon and roll patterns described by a supercritical SH equation, and (ii) the use of feedback control to suppress the blowup in a system described by a subcritical SH equation. In case (i), it is shown that feedback control can change the hexagon and roll stability regions in the parameter space as well as cause a transition from up to down hexagons and stabilize a skewed (mixed-mode) hexagonal pattern. In case (ii), it is demonstrated that feedback control can suppress blowup and lead to the formation of spatially localized patterns in the weakly nonlinear regime. The effects of a delayed feedback are also investigated for both cases, and it is shown that delay can induce temporal oscillations as well as blowup.

  9. Intermolecular interaction and the extended wormlike chain conformation of chitin in NaOH/urea aqueous solution.

    PubMed

    Fang, Yan; Duan, Bo; Lu, Ang; Liu, Maili; Liu, Huili; Xu, Xiaojuan; Zhang, Lina

    2015-04-13

    The intra- and intermolecular interactions of chitin in NaOH/urea aqueous system were studied by a combination of NMR measurements (including (13)C NMR, (23)Na NMR, and (15)N NMR) and differential scanning calorimetry. The results revealed that the NaOH and chitin formed a hydrogen-bonded complex that was surrounded by the urea hydrates to form a sheath-like structure, leading to the good dissolution. The optimal concentration range, in which chitin was molecularly dispersed in NaOH/urea aqueous, was found to investigate the chain conformation in the dilute solution with a combination of static and dynamic light scattering. The weight-average molecular weight (Mw), radii of gyration (⟨Rg⟩z), and hydrodynamic radii (⟨Rh⟩z) values of chitin were determined, and the structure-sensitive parameter (ρ) and persistent length (Lp) were calculated to be >2.0 and ∼30 nm, respectively, suggesting an extended wormlike chain conformation. The visualized images from TEM, cryo-TEM, and AFM indicated that, chitin nanofibers were fabricated from the parallel aggregation of chitin chains in NaOH/urea system. This work would provide a theoretical guidance for constructing novel chitin-based nanomaterials via "bottom-up" method at the molecular level.

  10. Weak Intermolecular Hydrogen Bonds with Fluorine: Detection and Implications for Enzymatic/Chemical Reactions, Chemical Properties, and Ligand/Protein Fluorine NMR Screening.

    PubMed

    Dalvit, Claudio; Vulpetti, Anna

    2016-05-23

    It is known that strong hydrogen-bonding interactions play an important role in many chemical and biological systems. However, weak or very weak hydrogen bonds, which are often difficult to detect and characterize, may also be relevant in many recognition and reaction processes. Fluorine serving as a hydrogen-bond acceptor has been the subject of many controversial discussions and there are different opinions about it. It now appears that there is compelling experimental evidence for the involvement of fluorine in weak intramolecular or intermolecular hydrogen bonds. Using established NMR methods, we have previously characterized and measured the strengths of intermolecular hydrogen-bond complexes involving the fluorine moieties CH2 F, CHF2 , and CF3 , and have compared them with the well-known hydrogen-bond complex formed between acetophenone and the strong hydrogen-bond donor p-fluorophenol. We now report evidence for the formation of hydrogen bonds involving fluorine with significantly weaker donors, namely 5-fluoroindole and water. A simple NMR method is proposed for the simultaneous measurement of the strengths of hydrogen bonds between an acceptor and a donor or water. Important implications of these results for enzymatic/chemical reactions involving fluorine, for chemical and physical properties, and for ligand/protein (19) F NMR screening are analyzed through experiments and theoretical simulations.

  11. Vibrational Circular Dichroism (VCD) Reveals Subtle Conformational Aspects and Intermolecular Interactions in the Carnitine Family.

    PubMed

    Mazzeo, Giuseppe; Abbate, Sergio; Longhi, Giovanna; Castiglioni, Ettore; Villani, Claudio

    2015-12-01

    Vibrational circular dichroism spectra (VCD) in the mid-IR region and electronic circular dichroism (ECD) spectra for three carnitine derivatives in the form of hydrochloride salts were recorded in deuterated methanol solutions. Density Functional Theory calculations help one to understand the significance of the observed VCD bands. VCD and ECD spectra are informative about the absolute configuration of the molecule, but VCD data reveal also some conformational aspects in the N,N,N-trimethyl moiety and inform us about intermolecular interactions gained from the carbonyl stretching region for the acyl substituted carnitines.

  12. Student Understanding of Intermolecular Forces: A Multimodal Study

    ERIC Educational Resources Information Center

    Cooper, Melanie M.; Williams, Leah C.; Underwood, Sonia M.

    2015-01-01

    The ability to use representations of molecular structure to predict the macroscopic properties of a substance is central to the development of a robust understanding of chemistry. Intermolecular forces (IMFs) play an important role in this process because they provide a mechanism for how and why molecules interact. In this study, we investigate…

  13. Intermolecular atom-atom bonds in crystals - a chemical perspective.

    PubMed

    Thakur, Tejender S; Dubey, Ritesh; Desiraju, Gautam R

    2015-03-01

    Short atom-atom distances between molecules are almost always indicative of specific intermolecular bonding. These distances may be used to assess the significance of all hydrogen bonds, including the C-H⋯O and even weaker C-H⋯F varieties.

  14. Connecting Protein Structure to Intermolecular Interactions: A Computer Modeling Laboratory

    ERIC Educational Resources Information Center

    Abualia, Mohammed; Schroeder, Lianne; Garcia, Megan; Daubenmire, Patrick L.; Wink, Donald J.; Clark, Ginevra A.

    2016-01-01

    An understanding of protein folding relies on a solid foundation of a number of critical chemical concepts, such as molecular structure, intra-/intermolecular interactions, and relating structure to function. Recent reports show that students struggle on all levels to achieve these understandings and use them in meaningful ways. Further, several…

  15. Direct observation of intermolecular interactions mediated by hydrogen bonding

    SciTech Connect

    De Marco, Luigi; Reppert, Mike; Thämer, Martin; Tokmakoff, Andrei

    2014-07-21

    Although intermolecular interactions are ubiquitous in physicochemical phenomena, their dynamics have proven difficult to observe directly, and most experiments rely on indirect measurements. Using broadband two-dimensional infrared spectroscopy (2DIR), we have measured the influence of hydrogen bonding on the intermolecular vibrational coupling between dimerized N-methylacetamide molecules. In addition to strong intramolecular coupling between N–H and C=O oscillators, cross-peaks in the broadband 2DIR spectrum appearing upon dimerization reveal strong intermolecular coupling that changes the character of the vibrations. In addition, dimerization changes the effects of intramolecular coupling, resulting in Fermi resonances between high and low-frequency modes. These results illustrate how hydrogen bonding influences the interplay of inter- and intramolecular vibrations, giving rise to correlated nuclear motions and significant changes in the vibrational structure of the amide group. These observations have direct impact on modeling and interpreting the IR spectra of proteins. In addition, they illustrate a general approach to direct molecular characterization of intermolecular interactions.

  16. Intermolecular potentials from shock structure experiments. [for monatomic gases

    NASA Technical Reports Server (NTRS)

    Sturtevant, B.; Steinhilper, E. A.

    1974-01-01

    Ground-state intermolecular interaction potentials determined from shock structure experiments with four monatomic gases are reported. These potentials are assessed for self-consistency, using the law of corresponding states, and their suitability for engineering applications in rarefied gas dynamics is discussed.

  17. Learning about Intermolecular Interactions from the Cambridge Structural Database

    ERIC Educational Resources Information Center

    Battle, Gary M.; Allen, Frank H.

    2012-01-01

    A clear understanding and appreciation of noncovalent interactions, especially hydrogen bonding, are vitally important to students of chemistry and the life sciences, including biochemistry, molecular biology, pharmacology, and medicine. The opportunities afforded by the IsoStar knowledge base of intermolecular interactions to enhance the…

  18. Learning about Intermolecular Interactions from the Cambridge Structural Database

    ERIC Educational Resources Information Center

    Battle, Gary M.; Allen, Frank H.

    2012-01-01

    A clear understanding and appreciation of noncovalent interactions, especially hydrogen bonding, are vitally important to students of chemistry and the life sciences, including biochemistry, molecular biology, pharmacology, and medicine. The opportunities afforded by the IsoStar knowledge base of intermolecular interactions to enhance the…

  19. Connecting Protein Structure to Intermolecular Interactions: A Computer Modeling Laboratory

    ERIC Educational Resources Information Center

    Abualia, Mohammed; Schroeder, Lianne; Garcia, Megan; Daubenmire, Patrick L.; Wink, Donald J.; Clark, Ginevra A.

    2016-01-01

    An understanding of protein folding relies on a solid foundation of a number of critical chemical concepts, such as molecular structure, intra-/intermolecular interactions, and relating structure to function. Recent reports show that students struggle on all levels to achieve these understandings and use them in meaningful ways. Further, several…

  20. Student Understanding of Intermolecular Forces: A Multimodal Study

    ERIC Educational Resources Information Center

    Cooper, Melanie M.; Williams, Leah C.; Underwood, Sonia M.

    2015-01-01

    The ability to use representations of molecular structure to predict the macroscopic properties of a substance is central to the development of a robust understanding of chemistry. Intermolecular forces (IMFs) play an important role in this process because they provide a mechanism for how and why molecules interact. In this study, we investigate…

  1. Hydrogen-hydrogen intermolecular structure of polyethylene in the melt

    NASA Astrophysics Data System (ADS)

    Londono, J. D.; Annis, B. K.; Habenschuss, A.; Smith, G. D.; Borodin, O.; Tso, C.; Hsieh, E. T.; Soper, A. K.

    1999-05-01

    Three polyethylene samples, which differed in their degree of deuteration, were studied in neutron diffraction isotopic substitution (NDIS) experiments at 428 K. These results were complemented at small wavevectors by small angle neutron measurements. The intermolecular hydrogen-hydrogen (HH) structure function, hHH(Q), was obtained without recourse to intramolecular structure models, as demonstrated in a prior report. The PE experimental results are compared to computer simulation results for the alkanes C100 at 509 K and C44 at 350, 400, and 450 K. The small temperature dependence of the HH intermolecular radial distribution functions, gHH(r) for C44 indicates that the differences observed between the PE, C100, and C44 (450 K) results are, for the most part, not due to just temperature differences. It is shown that the string model, an analytic result from an integral equation theory of polymers (PRISM), can account approximately for the overall shape of the gHH(r) functions, and that this overall shape is dependent on the radius of gyration of the molecule. Further analysis shows that there are two other contributions to gHH(r), both of which are independent of chain length to first order. The first is due to chain-chain packing, and the second is due to local HH intermolecular correlations. These results are significant because they demonstrate that hHH(Q) is a useful function for studying intermolecular polymer structure, which has been shown to underpin phase behavior in polyolefin blends.

  2. Are there environmental forms of systemic autoimmune diseases?

    PubMed Central

    Hess, E V

    1999-01-01

    A large number of drugs and an increasing number of environmental agents reportedly result in the appearance of a number of autoantibodies and in many instances in the appearance of a range of autoimmune clinical syndromes. The major disorders so recognized have marked resemblances to the autoimmune disease systemic lupus erythematosus. The commonly used term is drug-induced lupus; a better term is drug-related lupus. There is considerable interest at the present time in an increasing number of environmental agents. There have been two epidemics in recent years--one in Spain to a contaminant of rapeseed oil and one in the United States to a contaminant of l-tryptophan that caused an eosinophilic myositis. It is important for physicians and others involved in health care to recognize the potential associations of these diseases of unknown cause or causes. PMID:10502535

  3. Microwave Imaging Radar Reflectometer System Utilizing Digital Beam Forming

    NASA Astrophysics Data System (ADS)

    Hu, Fengqi; Li, Meijiao; Domier, Calvin W.; Liu, Xiaoguang; Luhmann, Neville C., Jr.

    2016-10-01

    Microwave Imaging Reflectometry is a radar-like technique developed to measure the electron density fluctuations in fusion plasmas. Phased Antenna Arrays can serve as electronically controlled ``lenses'' that can generate the required wavefronts by phase shifting and amplitude scaling, which is being realized in the digital domain with higher flexibility and faster processing speed. In the transmitter, the resolution of the phase control is 1.4 degrees and the amplitude control is 0.5 dB/ step. A V-band double-sided, printed bow tie antenna which exhibits 49% bandwidth (46 - 76 GHz) is employed. The antenna is fed by a microstrip transmission line for easy impedance matching. The simple structure and the small antenna are suitable for low cost fabrication, easy circuit integration, and phased antenna array multi-frequency applications. In the receiver part, a sub-array of 32 channels with 200 mil spacing is used to collect the scattered reflected signal from one unit spot on the plasma cutoff surface. Pre-amplification is used to control the noise level of the system and wire bondable components are used to accommodate the small spacing between each channel. After down converting, base band signals are digitized and processed in an FPGA module. U.S. Department of Energy Grant No. DE-FG02-99ER54531.

  4. Intermolecular forces and scaling relations between heterogeneous macromolecular surfaces

    NASA Astrophysics Data System (ADS)

    Rosenberg, Kenneth J.

    Most theories regarding the behavior of intermolecular forces assume perfectly smooth surfaces with well-defined chemical and material properties. In this thesis, three separate systems are studied to explore the accuracy of this assumption in very different situations. In the first system, the effects of milli-molar amounts of dissolved gas (the amount typically present in normal atmospheric conditions) have been studied at a pristine oil/water interface. It was found that the removal of the dissolved gas significantly increased the lifetime of the oil droplets, effectively reducing the long-range hydrophobic attractive force present under standard conditions. In the second system, the effect of varying normal and lateral roughness of solid surfaces in understanding the long-range steric forces and shorter-range adhesive (van der Waals) forces are studied. Various techniques to reproducibly control and vary the roughness were developed for a number of different types of polymeric surfaces. A strong correlation between the roughness and the repulsive steric force was observed for randomly rough surfaces. Similar scaling relations between the roughness and the magnitude of the adhesive force were measured. Friction measurements between these surfaces show that even a few nanometers of roughness significantly reduces the critical shear stress required to initiate sliding. However, the coefficient of friction was relatively unaffected by the range of roughness considered, in agreement with the macroscopic Amontons' law. The third and final system dealt with the properties of adsorbed layers of polyampholytes (containing both positively and negatively charged groups), as opposed to the more common classes of neutral polymers or polyelectrolytes. These measurements took advantage of a naturally occurring family of proteins (a class of polyampholytes), known as tau, which exist in six different well-defined lengths and charge densities. Force measurements were made with

  5. Intermolecular forces: a solution to dispersion interactions.

    PubMed

    Shimizu, Ken D

    2013-12-01

    London dispersion forces have been cited as an important factor in protein folding, drug–receptor interactions, and catalyst selectivities. However, careful analysis of a model system finds that the dispersion interactions are only minor contributors to the formation of complexes in solution.

  6. Tuning intermolecular non-covalent interactions for nanowires of organic semiconductors

    NASA Astrophysics Data System (ADS)

    Jiang, Lang; Gao, Jianhua; Fu, Yanyan; Dong, Huanli; Zhao, Huaping; Li, Hongxiang; Tang, Qingxin; Chen, Keqiu; Hu, Wenping

    2010-12-01

    Anthracene and its derivatives are used to demonstrate a simple way to cast assemble nanowires of organic semiconductors with tuning of intermolecular non-covalent interactions by molecular design. The tuning of intermolecular interactions could be achieved by (i) decreasing intermolecular hydrophobic interactions by linking hydrophilic side chains to anthracene rings, (ii) increasing intermolecular interaction for self-assembly with the assistance of hydrogen bonds, and (iii) enhancing molecular π-π interaction by increasing the conjugated dimension of the compounds.

  7. Tuning intermolecular non-covalent interactions for nanowires of organic semiconductors.

    PubMed

    Jiang, Lang; Gao, Jianhua; Fu, Yanyan; Dong, Huanli; Zhao, Huaping; Li, Hongxiang; Tang, Qingxin; Chen, Keqiu; Hu, Wenping

    2010-12-01

    Anthracene and its derivatives are used to demonstrate a simple way to cast assemble nanowires of organic semiconductors with tuning of intermolecular non-covalent interactions by molecular design. The tuning of intermolecular interactions could be achieved by (i) decreasing intermolecular hydrophobic interactions by linking hydrophilic side chains to anthracene rings, (ii) increasing intermolecular interaction for self-assembly with the assistance of hydrogen bonds, and (iii) enhancing molecular π-π interaction by increasing the conjugated dimension of the compounds.

  8. The integration of solid-form informatics into solid-form selection.

    PubMed

    Feeder, Neil; Pidcock, Elna; Reilly, Anthony M; Sadiq, Ghazala; Doherty, Cheryl L; Back, Kevin R; Meenan, Paul; Docherty, Robert

    2015-06-01

    To demonstrate how the use of structural informatics during drug development assists with the assessment of the risk of polymorphism and the selection of a commercial solid form. The application of structural chemistry knowledge derived from the hundreds of thousands of crystal structures contained in the Cambridge Structural Database to drug candidates is described. Examples given show the comparison of intermolecular geometries to database-derived statistics, the use of Full Interaction Maps to assess polymorph stability and the calculation of hydrogen bond propensities to provide assurance of a stable solid form. The software tools used are included in the Cambridge Structural Database System and the Solid Form Module of Mercury. The early identification of an unusual supramolecular motif in the development phase of maraviroc led to further experimental work to find the most stable polymorph. Analyses of two polymorphs of a pain candidate drug demonstrated how consideration of molecular conformation and intermolecular interactions were used for the assessment of relative stability. Informatics analysis confirmed that the solid form of crizotinib, a monomorphic system, had a low risk of polymorphism. The application of informatics-based assessment of new chemical entities complements experimental studies and provides a deeper understanding of the qualities of the structure. The information provided by structural analyses is incorporated into the assessment of risk. Informatics techniques are quick to apply and are straightforward to use, allowing an assessment of progressing drug candidates. © 2015 Royal Pharmaceutical Society.

  9. Systemic study on fluorescent switching systems composed of naphthopyran and benzimidazole in solution and film forms

    NASA Astrophysics Data System (ADS)

    He, Yi; Wang, Guang; Wang, Mingxin

    2016-07-01

    The fluorescent photo-switching systems were prepared based on fluorescent benzimidazole and photochromic naphthopyran. Naphthopyran in this systems displayed excellent photochromic performance in tetrahydrofuran solutions and in PMMA films. The fluorescent emission of benzimidazole was modulated between "on" and "off" via the photoisomerization of naphthopyran in high-contrast due to the photoinduced energy transfer from benzimidazole to the open-form naphthopyran. Both the fluorescent photoswitching and the photochromism of benzimidazole-naphthopyran dyads in solutions and films displayed excellent fatigue resistance. The spaces between benzimidazole and naphthopyran affect the absorbance and fluorescence spectra of benzimidazole-naphthopyran dyads. The non-destructive readout ability of synthesized dyads in doped PMMA film was achieved.

  10. Systems and methods for forming defects on graphitic materials and curing radiation-damaged graphitic materials

    DOEpatents

    Ryu, Sunmin; Brus, Louis E.; Steigerwald, Michael L.; Liu, Haitao

    2012-09-25

    Systems and methods are disclosed herein for forming defects on graphitic materials. The methods for forming defects include applying a radiation reactive material on a graphitic material, irradiating the applied radiation reactive material to produce a reactive species, and permitting the reactive species to react with the graphitic material to form defects. Additionally, disclosed are methods for removing defects on graphitic materials.

  11. Magneto-dielectric effects induced by optically-generated intermolecular charge-transfer states in organic semiconducting materials.

    PubMed

    Zang, Huidong; Yan, Liang; Li, Mingxing; He, Lei; Gai, Zheng; Ivanov, Ilia; Wang, Min; Chiang, Long; Urbas, Augustine; Hu, Bin

    2013-10-02

    Traditionally, magneto-dielectric effects have been developed by combining ferroelectric and magnetic materials. Here, we show a magneto-dielectric effect from optically-generated intermolecular charge-transfer states in an organic semiconducting donor:acceptor (PVK:TCNB) system. We observe in magnetic field effects of photoluminescence that a magnetic field can change singlet/triplet population ratio in intermolecular charge-transfer states. Furthermore, our theoretical analysis and experimental evidence indicate that the singlets and triplets in charge-transfer states have stronger and weaker electrical polarizations, respectively. Therefore, the observed magneto-dielectric effect can be attributed to magnetically-dependent singlet/triplet ratio in intermolecular charge-transfer states. In principle, a magneto-dielectric effect can be generated through two different channels based on magneto-polarization and magneto-current effects when the singlet/triplet ratio in intermolecular charge-transfer states is changed by a magnetic field. We find, from the simulation of dielectric effects, that magneto-polarization and magneto-current effects play primary and secondary roles in the generation of magneto-dielectric effect.

  12. Intermolecular Aryne Ene Reaction of Hantzsch Esters: Stable Covalent Ene Adducts from a 1,4-Dihydropyridine Reaction.

    PubMed

    Trinchera, Piera; Sun, Weitao; Smith, Jane E; Palomas, David; Crespo-Otero, Rachel; Jones, Christopher R

    2017-09-01

    The reaction of arynes with 1,4-dihydropyridines affords 2-aryl-1,2-dihydropyridines or 2-methylene-3-aryl-1,2,3,4-tetrahydropyridines via a regioselective C-2 or C-3 arylation. These compounds are the first series of isolable and bench-stable covalent ene adducts formed between dihydropyridines and unsaturated substrates. Experimental studies and DFT calculations provide mechanistic support for a concerted intermolecular aryne ene process, which may have implications for NAD(P)H model reactions.

  13. Validation of intermolecular transfer integral and bandwidth calculations for organic molecular materials.

    PubMed

    Huang, Jingsong; Kertesz, Miklos

    2005-06-15

    We present an interpretation of the intermolecular transfer integral that is independent from the origin of the energy scale allowing convergence studies of this important parameter of organic molecular materials. We present extensive numerical studies by using an ethylene pi dimer to investigate the dependence of transfer integrals on the level of theory and intermolecular packing. Transfer integrals obtained from semiempirical calculations differ substantially from one another and from ab initio results. The ab initio results are consistent across all the levels used including Hartree-Fock, outer valence Green's function, and various forms of density functional theory (DFT). Validation of transfer integrals and bandwidths is performed by comparing the calculated values with the experimental values of tetrathiafulvalene-tetracyanoquinodimethane (TTF-TCNQ), bis[1,2,5]thiadiazolo-p-quinobis(1,3-dithiole), (BTQBT) K-TCNQ, and hexagonal graphite. DFT in one of its presently popular forms, such as Perdew-Wang functionals (PW91), in combination with sufficient basis sets provides reliable transfer integrals, and therefore can serve as a basis for energy band calculations for soft organic materials with van der Waals gaps.

  14. Foot-and-mouth disease virus leader proteinase: structural insights into the mechanism of intermolecular cleavage.

    PubMed

    Steinberger, Jutta; Grishkovskaya, Irina; Cencic, Regina; Juliano, Luiz; Juliano, Maria A; Skern, Tim

    2014-11-01

    Translation of foot-and-mouth disease virus RNA initiates at one of two start codons leading to the synthesis of two forms of leader proteinase L(pro) (Lab(pro) and Lb(pro)). These forms free themselves from the viral polyprotein by intra- and intermolecular self-processing and subsequently cleave the cellular eukaryotic initiation factor (eIF) 4 G. During infection, Lb(pro) removes six residues from its own C-terminus, generating sLb(pro). We present the structure of sLb(pro) bound to the inhibitor E64-R-P-NH2, illustrating how sLb(pro) can cleave between Lys/Gly and Gly/Arg pairs. In intermolecular cleavage on polyprotein substrates, Lb(pro) was unaffected by P1 or P1' substitutions and processed a substrate containing nine eIF4GI cleavage site residues whereas sLb(pro) failed to cleave the eIF4GI containing substrate and cleaved appreciably more slowly on mutated substrates. Introduction of 70 eIF4GI residues bearing the Lb(pro) binding site restored cleavage. These data imply that Lb(pro) and sLb(pro) may have different functions in infected cells.

  15. Conformational diversity in prion protein variants influences intermolecular [beta]-sheet formation

    SciTech Connect

    Lee, Seungjoo; Antony, Lizamma; Hartmann, Rune; Knaus, Karen J.; Surewicz, Krystyna; Surewicz, Witold K.; Yee, Vivien C.

    2010-04-19

    A conformational transition of normal cellular prion protein (PrP{sup C}) to its pathogenic form (PrP{sup Sc}) is believed to be a central event in the transmission of the devastating neurological diseases known as spongiform encephalopathies. The common methionine/valine polymorphism at residue 129 in the PrP influences disease susceptibility and phenotype. We report here seven crystal structures of human PrP variants: three of wild-type (WT) PrP containing V129, and four of the familial variants D178N and F198S, containing either M129 or V129. Comparison of these structures with each other and with previously published WT PrP structures containing M129 revealed that only WT PrPs were found to crystallize as domain-swapped dimers or closed monomers; the four mutant PrPs crystallized as non-swapped dimers. Three of the four mutant PrPs aligned to form intermolecular {beta}-sheets. Several regions of structural variability were identified, and analysis of their conformations provides an explanation for the structural features, which can influence the formation and conformation of intermolecular {beta}-sheets involving the M/V129 polymorphic residue.

  16. A new criterion for bar-forming instability in rapidly rotating gaseous and stellar systems. 2: Nonaxisymmetric form

    NASA Technical Reports Server (NTRS)

    Christodoulou, Dimitris M.; Shlosman, Isaac; Tohline, Joel E.

    1995-01-01

    We have previously introduced the parameter alpha as an indicator of stability to m = 2 nonaxisymmetric modes in rotating, self-gravitating, axisymmetric, gaseous (alpha less than or approximately equal to 0.34) and stellar (alpha less than or approximately equal to 0.25) systems. This parameter can be written as alpha = (ft/2)(exp 1/2), where t is defined as T/(absolute value of W), T is the total rotational kinetic energy, W is the total gravitational potential energy, and f is a function characteristic of the topology/connectedness and the geometric shape of a system. In this paper, we extend the stability criterion to nonaxisymmetric equilibrium systems by determining empirically the appropriate form of the function f for ellipsoids and elliptical disks and cylinders. We test the validity of this extension of the stability indicator alpha by considering its predictions for previously published, gaseous and stellar, nonaxisymmetric models. The formulation and critical values account accurately for the stability properties of m =2 modes in gaseous Riemann S-type ellipsoids (including the Jacobi and Dedekind ellipsoids) and elliptical Riemann disks as well as in stellar elliptical Freeman disks and cylinders: all these systems are dynamically stable except the stellar elliptical Freeman disks that exhibit a relatively small region of m = 2 dynamical instability. A partial disagreement in the case of stellar Freeman ellipsoids in maximum rotation may be due to the fact that the region of instability has not been previously determined with sufficient accuracy.

  17. A new criterion for bar-forming instability in rapidly rotating gaseous and stellar systems. 1: Axisymmetric form

    NASA Technical Reports Server (NTRS)

    Christodoulou, Dimitris M.; Shlosman, Isaac; Tohline, Joel E.

    1995-01-01

    We analyze previous results on the stability of uniformly and differentialy rotating, self-gravitating, gaseous and stellar, axisymmetric systems to derive a new stability criterion for the appearance of torodial, m = 2 intermediate or I-modes and bar modes. In the process, we demonstrate that the bar modes in stellar systems and the m = 2 I-modes in gaseous systems have many common physical characteristics and only one substantial difference: because of the anisotropy of the stress tensor, dynamical instability sets in at lower rotation in stellar systems. This difference is reflected also in the new stability criterion. The new stability parameter alpha equals (T(sub J))/(absolute value of W) is formulated first for uniformly rotating systems and is based on the angular momentum content rather than on the energy content of a system. (T(sub J) is defined as ((L)(Omega(sub J)))/2; L is the total angular momentum; Omega(sub J) is the Jeans frequency introduced by self-gravity; and W is the total gravitational potential energy.) For stability of stellar systems alpha less than or equal to 0.254-0.258 while alpha less than or equal to 0.341-0.354 for stability of gaseous systems. For uniform rotation, one can write alpha = ((ft)/2)(exp 1/2), where t is defined as T/(absolute value of W), T is the total kinetic energy due to rotation, and f is a function characteristic of the topology/connectedness and the geometric shape of a system. Equivalently, alpha equals t/(chi), where chi is defined as Omega/Omega(sub J) and Omega is the rotation frequency. Using these forms, alpha can be extended to and calculated for a variety of differentially rotating, gaseous and stellar, axisymmetric disk and spheroidal models whose equilibrium structures and stability characteristics are known. In this paper, we also estimate alpha for gaseous torodial models and for stellar disk systems embedded in an inert or responsive 'halo.' We find that the new stability criterion holds equally

  18. 78 FR 5477 - Agency Information Collection Activities: InfoPass System, No Form Number; Extension, Without...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-01-25

    ... SECURITY U.S. Citizenship and Immigration Services Agency Information Collection Activities: InfoPass... Collection. (2) Title of the Form/Collection: InfoPass System. (3) Agency form number, if any, and the.... The InfoPass system allows an applicant or petitioner to schedule an interview appointment with...

  19. Factor Structure of the BASC-2 Behavioral and Emotional Screening System Student Form

    ERIC Educational Resources Information Center

    Dowdy, Erin; Twyford, Jennifer M.; Chin, Jenna K.; DiStefano, Christine A.; Kamphaus, Randy W.; Mays, Kristen L.

    2011-01-01

    The BASC-2 Behavioral and Emotional Screening System (BESS) Student Form (Kamphaus & Reynolds, 2007) is a recently developed youth self-report rating scale designed to identify students at risk for behavioral and emotional problems. The BESS Student Form was derived from the Behavior Assessment System for Children-Second Edition Self-Report of…

  20. Pd-catalyzed intermolecular amidation of aryl halides: the discovery that xantphos can be trans-chelating in a palladium complex.

    PubMed

    Yin, Jingjun; Buchwald, Stephen L

    2002-05-29

    A general method for the intermolecular coupling of aryl halides and amides using a Xantphos/Pd catalyst is described. This system displays good functional group compatibility, and the desired C-N bond forming process proceeds in good to excellent yields with 1-4 mol % of the Pd catalyst. Additionally, the arylation of sulfonamides, oxazolidinones, and ureas is reported. The efficiency of these transformations was found to be highly dependent on reaction concentrations and catalyst loadings. A Pd complex resulting from oxidative addition of 4-bromobenzonitrile, (Xantphos)Pd(4-cyanophenyl)(Br) (II), was prepared in one step from Xantphos, Pd(2)(dba)(3), and the aryl bromide. Complex II proved to be an active catalyst for the coupling between 4-bromobenzonitrile and benzamide. X-ray crystallographic analysis of II revealed a rare trans-chelating bisphosphine-Pd(II) structure with a large bite angle of 150.7 degrees.

  1. Joint Tactical Radio System Handheld, Manpack, and Small Form Fit Radios (JTRS HMS)

    DTIC Science & Technology

    2015-12-01

    Selected Acquisition Report (SAR) RCS: DD-A&T(Q&A)823-385 Joint Tactical Radio System Handheld, Manpack, and Small Form Fit Radios (JTRS HMS) As...2014 Program Information Program Name Joint Tactical Radio System Handheld, Manpack, and Small Form Fit Radios (JTRS HMS) DoD Component Army Joint...18:21:36 UNCLASSIFIED 5 Mission and Description The Handheld, Manpack, and Small Form Fit (HMS) radio program is a materiel solution meeting the

  2. Intermolecular interactions between imidazole derivatives intercalated in layered solids. Substituent group effect

    SciTech Connect

    González, M.; Lemus-Santana, A.A.; Rodríguez-Hernández, J.; Aguirre-Velez, C.I.; Knobel, M.; Reguera, E.

    2013-08-15

    This study sheds light on the intermolecular interactions between imidazole derive molecules (2-methyl-imidazole, 2-ethyl-imidazole and benzimidazole) intercalated in T[Ni(CN){sub 4}] layers to form a solid of formula unit T(ImD){sub 2}[Ni(CN){sub 4}]. These hybrid inorganic–organic solids were prepared by soft chemical routes and their crystal structures solved and refined from X-ray powder diffraction data. The involved imidazole derivative molecules were found coordinated through the pyridinic N atom to the axial positions for the metal T in the T[Ni(CN){sub 4}] layer. In the interlayers region ligand molecules from neighboring layers remain stacked in a face-to-face configuration through dipole–dipole and quadrupole–quadrupole interactions. These intermolecular interactions show a pronounced dependence on the substituent group and are responsible for an ImD-pillaring concatenation of adjacent layers. This is supported by the structural information and the recorded magnetic data in the 2–300 K temperature range. The samples containing Co and Ni are characterized by presence of spin–orbit coupling and pronounced temperature dependence for the effective magnetic moment except for 2-ethyl-imidazole related to the local distortion for the metal coordination environment. For this last one ligand a weak ferromagnetic ordering ascribed to a super-exchange interaction between T metals from neighboring layers through the ligands π–π interaction was detected. - Graphical abstract: In the interlayers region imidazole derivative molecules are oriented according to their dipolar and quadrupolar interactions and minimizing the steric impediment. Highlights: • Imidazole derivatives intercalation compounds. • Intermolecular interaction between intercalated imidazole derivatives. • Hybrid inorganic–organic solids. • Pi–pi interactions and ferromagnetic coupling. • Dipolar and quadrupolar interactions between intercalated imidazole derivatives.

  3. Using corresponding state theory to obtain intermolecular potentials to calculate pure liquid shock Hugoniots

    SciTech Connect

    Hobbs, M.L.

    1997-12-01

    Determination of product species, equations-of-state (EOS) and thermochemical properties of high explosives and pyrotechnics remains a major unsolved problem. Although, empirical EOS models may be calibrated to replicate detonation conditions within experimental variability (5--10%), different states, e.g. expansion, may produce significant discrepancy with data if the basic form of the EOS model is incorrect. A more physically realistic EOS model based on intermolecular potentials, such as the Jacobs Cowperthwaite Zwisler (JCZ3) EOS, is needed to predict detonation states as well as expanded states. Predictive capability for any EOS requires a large species data base composed of a wide variety of elements. Unfortunately, only 20 species have known JCZ3 molecular force constants. Of these 20 species, only 10 have been adequately compared to experimental data such as molecular scattering or shock Hugoniot data. Since data in the strongly repulsive region of the molecular potential is limited, alternative methods must be found to deduce force constants for a larger number of species. The objective of the present study is to determine JCZ3 product species force constants by using a corresponding states theory. Intermolecular potential parameters were obtained for a variety of gas species using a simple corresponding states technique with critical volume and critical temperature. A more complex, four parameter corresponding state method with shape and polarity corrections was also used to obtain intermolecular potential parameters. Both corresponding state methods were used to predict shock Hugoniot data obtained from pure liquids. The simple corresponding state method is shown to give adequate agreement with shock Hugoniot data.

  4. Long-range intermolecular interaction between broken DNA fragments

    NASA Astrophysics Data System (ADS)

    Pinchuk, Anatoliy O.; Vysotskii, Vladimir I.

    2001-03-01

    We analyzed the long-range intermolecular interaction between fragments of broken DNA. We considered two constituents of long-range intermolecular interaction. The first is a net electrostatic Coulomb interaction between charges, involved in a structure of opposite nucleotides, which we evaluate using Debye-Huckel theory. The second one is the Van der Waals interaction between the nucleotides. The general Lifshitz theory of Van der Waals forces was used to evaluate this interaction. Numerical calculations showed that a repulsive force between broken DNA fragments can arise in specific cases. This repulsion can prevent DNA from repairing itself after a double-strand break. The height of the barrier decreases with an increase of the ionic strength of the intracellular milieu, or with a reduction of its viscosity.

  5. Long range intermolecular interactions between the alkali diatomics Na2, K2, and NaK

    NASA Astrophysics Data System (ADS)

    Zemke, Warren T.; Byrd, Jason N.; Michels, H. Harvey; Montgomery, John A.; Stwalley, William C.

    2010-06-01

    Long range interactions between the ground state alkali diatomics Na2-Na2, K2-K2, Na2-K2, and NaK-NaK are examined. Interaction energies are first determined from ab initio calculations at the coupled-cluster with singles, doubles, and perturbative triples [CCSD(T)] level of theory, including counterpoise corrections. Long range energies calculated from diatomic molecular properties (polarizabilities and dipole and quadrupole moments) are then compared with the ab initio energies. A simple asymptotic model potential ELR=Eelec+Edisp+Eind is shown to accurately represent the intermolecular interactions for these systems at long range.

  6. Long range intermolecular interactions between the alkali diatomics Na(2), K(2), and NaK.

    PubMed

    Zemke, Warren T; Byrd, Jason N; Michels, H Harvey; Montgomery, John A; Stwalley, William C

    2010-06-28

    Long range interactions between the ground state alkali diatomics Na(2)-Na(2), K(2)-K(2), Na(2)-K(2), and NaK-NaK are examined. Interaction energies are first determined from ab initio calculations at the coupled-cluster with singles, doubles, and perturbative triples [CCSD(T)] level of theory, including counterpoise corrections. Long range energies calculated from diatomic molecular properties (polarizabilities and dipole and quadrupole moments) are then compared with the ab initio energies. A simple asymptotic model potential E(LR)=E(elec)+E(disp)+E(ind) is shown to accurately represent the intermolecular interactions for these systems at long range.

  7. Correlated and cooperative motions in segmental relaxation: Influence of constitutive unit weight and intermolecular interactions.

    PubMed

    Rijal, Bidur; Soto Puente, Jorge Arturo; Atawa, Bienvenu; Delbreilh, Laurent; Fatyeyeva, Kateryna; Saiter, Allisson; Dargent, Eric

    2016-12-01

    This work clarifies the notion of correlated and cooperative motions appearing during the α-relaxation process through the role of the molecular weight of the constitutive units and of the interchain dipolar interactions. By studying amorphous copolymers of poly(ethylene-co-vinyl acetate) with different vinyl acetate contents, we show that the correlated motions are not sensitive to the interchain dipolar interactions, in contrast to the cooperative motions, which increase with a strengthening of the intermolecular interactions for this sample family. Concerning the influence of the molecular weight m_{0}, the notion of "correlated motions" seems to be equivalent to the notion of "cooperative motions" only for low m_{0} systems.

  8. Catalytic Asymmetric Synthesis of 8-Oxabicyclooctanes by Intermolecular [5+2] Pyrylium Cycloadditions**

    PubMed Central

    Witten, Michael R.

    2014-01-01

    Highly enantioselective intermolecular [5+2] cycloadditions of pyrylium ion intermediates with electron-rich alkenes are promoted by a dual catalyst system composed of an achiral thiourea and a chiral primary aminothiourea. The observed enantioselectivity is highly dependent on the substitution pattern of the 5π component, and the basis for this effect is analyzed using experimental and computational evidence. The resultant 8-oxabicyclo[3.2.1]octane derivatives possess a scaffold common in natural products and medicinally active compounds and are also versatile chiral building blocks for further manipulations. Several stereoselective complexity-generating transformations of the 8-oxabicyclooctane products are presented. PMID:24782332

  9. Correlated and cooperative motions in segmental relaxation: Influence of constitutive unit weight and intermolecular interactions

    NASA Astrophysics Data System (ADS)

    Rijal, Bidur; Soto Puente, Jorge Arturo; Atawa, Bienvenu; Delbreilh, Laurent; Fatyeyeva, Kateryna; Saiter, Allisson; Dargent, Eric

    2016-12-01

    This work clarifies the notion of correlated and cooperative motions appearing during the α-relaxation process through the role of the molecular weight of the constitutive units and of the interchain dipolar interactions. By studying amorphous copolymers of poly(ethylene-co-vinyl acetate) with different vinyl acetate contents, we show that the correlated motions are not sensitive to the interchain dipolar interactions, in contrast to the cooperative motions, which increase with a strengthening of the intermolecular interactions for this sample family. Concerning the influence of the molecular weight m0, the notion of "correlated motions" seems to be equivalent to the notion of "cooperative motions" only for low m0 systems.

  10. Rational design of cyclopropane-based chiral PHOX ligands for intermolecular asymmetric Heck reaction

    PubMed Central

    Rubina, Marina; Sherrill, William M; Barkov, Alexey Yu

    2014-01-01

    Summary A novel class of chiral phosphanyl-oxazoline (PHOX) ligands with a conformationally rigid cyclopropyl backbone was synthesized and tested in the intermolecular asymmetric Heck reaction. Mechanistic modelling and crystallographic studies were used to predict the optimal ligand structure and helped to design a very efficient and highly selective catalytic system. Employment of the optimized ligands in the asymmetric arylation of cyclic olefins allowed for achieving high enantioselectivities and significantly suppressing product isomerization. Factors affecting the selectivity and the rate of the isomerization were identified. It was shown that the nature of this isomerization is different from that demonstrated previously using chiral diphosphine ligands. PMID:25161709

  11. Calciate-mediated intermolecular hydroamination of diphenylbutadiyne with secondary anilines.

    PubMed

    Glock, Carsten; Görls, Helmar; Westerhausen, Matthias

    2012-07-18

    Calciate-mediated intermolecular hydroamination of diphenylbutadiyne with N-phenyl and N-isopropyl-substituted anilines yields E- and Z-isomers of the corresponding 1-anilino-1,4-diphenylbut-1-ene-3-yne. In the case of HNPh(2) solely heterobimetallic K(2)Ca(NPh(2))(4) is able to effectively catalyze this hydroamination reaction in tetrahydrofuran at elevated temperatures.

  12. Energetics of Intermolecular Hydrogen Bonds in a Hydrophobic Protein Cavity

    NASA Astrophysics Data System (ADS)

    Liu, Lan; Baergen, Alyson; Michelsen, Klaus; Kitova, Elena N.; Schnier, Paul D.; Klassen, John S.

    2014-05-01

    This work explores the energetics of intermolecular H-bonds inside a hydrophobic protein cavity. Kinetic measurements were performed on the gaseous deprotonated ions (at the -7 charge state) of complexes of bovine β-lactoglobulin (Lg) and three monohydroxylated analogs of palmitic acid (PA): 3-hydroxypalmitic acid (3-OHPA), 7-hydroxypalmitic acid (7-OHPA), and 16-hydroxypalmitic acid (16-OHPA). From the increase in the activation energy for the dissociation of the (Lg + X-OHPA)7- ions, compared with that of the (Lg + PA)7- ion, it is concluded that the -OH groups of the X-OHPA ligands participate in strong (5 - 11 kcal mol-1) intermolecular H-bonds in the hydrophobic cavity of Lg. The results of molecular dynamics (MD) simulations suggest that the -OH groups of 3-OHPA and 16-OHPA act as H-bond donors and interact with backbone carbonyl oxygens, whereas the -OH group of 7-OHPA acts as both H-bond donor and acceptor with nearby side chains. The capacity for intermolecular H-bonds within the Lg cavity, as suggested by the gas-phase measurements, does not necessarily lead to enhanced binding in aqueous solution. The association constant (Ka) measured for 7-OHPA [(2.3 ± 0.2) × 105 M-1] is similar to the value for the PA [(3.8 ± 0.1) × 105 M-1]; Ka for 3-OHPA [(1.1 ± 0.3) × 106 M-1] is approximately three-times larger, whereas Ka for 16-OHPA [(2.3 ± 0.2) × 104 M-1] is an order of magnitude smaller. Taken together, the results of this study suggest that the energetic penalty to desolvating the ligand -OH groups, which is necessary for complex formation, is similar in magnitude to the energetic contribution of the intermolecular H-bonds.

  13. Bimorpholine-mediated enantioselective intramolecular and intermolecular aldol condensation.

    PubMed

    Kanger, Tõnis; Kriis, Kadri; Laars, Marju; Kailas, Tiiu; Müürisepp, Aleksander-Mati; Pehk, Tõnis; Lopp, Margus

    2007-07-06

    Monosalts of N-substituted bimorpholine derivatives are efficient organocatalysts in intramolecular and intermolecular aldol reactions. The properties of the catalysts can be tuned either by the selection of an appropriate acid for the salt formation or by the change of a substituent at the nitrogen atom. In aldol condensation, i-Pr-substituted bimorpholine is the most stereoselective catalyst affording products in high yield with enantioselectivities up to 95% ee.

  14. Stability of linear systems in second-order form based on structure preserving similarity transformations

    SciTech Connect

    Stoustrup, Jakob; Pommer, Christian; Kliem, Wolfhard

    2015-10-31

    This paper deals with two stability aspects of linear systems of the form I ¨ x +B˙ x +Cx = 0 given by the triple (I;B;C). A general transformation scheme is given for a structure and Jordan form preserving transformation of the triple. We investigate how a system can be transformed by suitable choices of the transformation parameters into a new system (I;B1;C1) with a symmetrizable matrix C1. This procedure facilitates stability investigations. We also consider systems with a Hamiltonian spectrum which discloses marginal stability after a Jordan form preserving transformation.

  15. Production of low kinetic energy electrons and energetic ion pairs by Intermolecular Coulombic Decay.

    PubMed

    Hergenhahn, Uwe

    2012-12-01

    The paper gives an introduction into Interatomic and Intermolecular Coulombic Decay (ICD). ICD is an autoionization process, which contrary to Auger decay involves neighbouring sites of the initial vacancy as an integral part of the decay transition. As a result of ICD, slow electrons are produced which generally are known to be active in radiation damage. The author summarizes the properties of ICD and reviews a number of important experiments performed in recent years. Intermolecular Coulombic Decay can generally take place in weakly bonded aggregates in the presence of ionizing particles or ionizing radiation. Examples collected here mostly use soft X-rays produced by synchrotron radiation to ionize, and use rare-gas clusters, water clusters or solutes in a liquid jet to observe ICD after irradiation. Intermolecular Coulombic Decay is initiated by single ionization into an excited state. The subsequent relaxation proceeds via an ultra-fast energy transfer to a neighbouring site, where a second ionization occurs. Secondary electrons from ICD have clearly been identified in numerous systems. ICD can take place after primary ionization, as the second step of a decay cascade which also involves Auger decay, or after resonant excitation with an energy which exceeds the ionization potential of the system. ICD is expected to play a role whenever particles or radiation with photon energies above the ionization energies for inner valence electrons are present in weakly bonded matter, e.g., biological tissue. The process produces at the same time a slow electron and two charged atomic or molecular fragments, which will lead to structural changes around the ionized site.

  16. Molecular-beam study of the water-helium system: features of the isotropic component of the intermolecular interaction and a critical test for the available potential-energy surfaces.

    PubMed

    Cappelletti, David; Aquilanti, Vincenzo; Cornicchi, Elena; Teixidor, Marc Moix; Pirani, Fernando

    2005-07-08

    We report molecular-beam measurements of the total integral cross sections for the scattering of water molecules by helium atoms. A combined analysis of the new experimental data together with available differential cross section results has allowed an accurate determination of the isotropic component of the interaction potential for this prototypical system. The potential well shows a depth of 0.265 +/- 0.010 kJ/mol at a distance between He and the center of mass of the water molecule of 0.345 +/- 0.02 nm. An effective isotropic long-range attraction constant C(LR) = (6.3+/-0.3) x 10(-4) kJ mol(-1) nm(-6), including both dispersion and induction contributions, has also been determined. The most recent and accurate ab initio potential-energy surfaces have been tested against these new experimental results.

  17. Intermolecular Modes between LH2 Bacteriochlorophylls and Protein Residues: The Effect on the Excitation Energies.

    PubMed

    Anda, André; De Vico, Luca; Hansen, Thorsten

    2017-06-08

    Light-harvesting system 2 (LH2) executes the primary processes of photosynthesis in purple bacteria; photon absorption, and energy transportation to the reaction center. A detailed mechanistic insight into these operations is obscured by the complexity of the light-harvesting systems, particularly by the chromophore-environment interaction. In this work, we focus on the effects of the protein residues that are ligated to the bacteriochlorophylls (BChls) and construct potential energy surfaces of the ground and first optically excited state for the various BChl-residue systems where we in each case consider two degrees of freedom in the intermolecular region. We find that the excitation energies are only slightly affected by the considered modes. In addition, we see that axial ligands and hydrogen-bonded residues have opposite effects on both excitation energies and oscillator strengths by comparing to the isolated BChls. Our results indicate that only a small part of the chromophore-environment interaction can be associated with the intermolecular region between a BChl and an adjacent residue, but that it may be possible to selectively raise or lower the excitation energy at the axial and planar residue positions, respectively.

  18. On the symmetric form of systems of conservation laws with entropy

    NASA Technical Reports Server (NTRS)

    Harten, A.

    1983-01-01

    The present investigation has the objective to review the general structure of system of conservation laws with entropy, giving particular attention to a presentation of symmetric formulations of the equations of gas dynamics. Systems of hyperbolic conservation laws are considered, taking into account the case in which a system of equations is symmetric hyperbolic, questions of symmetrization, and entropy functions. The Euler equations for a polytropic gas in conservation form are considered. The symmetric form retains the conservation properties of the equations. Weak solutions remain, therefore, unchanged. Of particular computational interest is the possibility of using the symmetric form.

  19. On the symmetric form of systems of conservation laws with entropy

    NASA Technical Reports Server (NTRS)

    Harten, A.

    1983-01-01

    The present investigation has the objective to review the general structure of system of conservation laws with entropy, giving particular attention to a presentation of symmetric formulations of the equations of gas dynamics. Systems of hyperbolic conservation laws are considered, taking into account the case in which a system of equations is symmetric hyperbolic, questions of symmetrization, and entropy functions. The Euler equations for a polytropic gas in conservation form are considered. The symmetric form retains the conservation properties of the equations. Weak solutions remain, therefore, unchanged. Of particular computational interest is the possibility of using the symmetric form.

  20. Effect of intermolecular hydrogen bonding, vibrational analysis and molecular structure of 4-chlorobenzothioamide

    NASA Astrophysics Data System (ADS)

    Çırak, Çağrı; Sert, Yusuf; Ucun, Fatih

    2013-09-01

    In the present work, the experimental and theoretical vibrational spectra of 4-chlorobenzothioamide were investigated. The FT-IR (400-4000 cm-1) and μ-Raman spectra (100-4000 cm-1) of 4-chlorobenzothioamide in the solid phase were recorded. The geometric parameters (bond lengths and bond angles), vibrational frequencies, Infrared and Raman intensities of the title molecule in the ground state were calculated using ab initio Hartree-Fock and density functional theory (B3LYP) methods with the 6-311++G(d,p) basis set for the first time. The optimized geometric parameters and the theoretical vibrational frequencies were found to be in good agreement with the corresponding experimental data and with the results found in the literature. The vibrational frequencies were assigned based on the potential energy distribution using the VEDA 4 program. The dimeric form of 4-chlorobenzothioamide was also simulated to evaluate the effect of intermolecular hydrogen bonding on the vibrational frequencies. It was observed that the Nsbnd H stretching modes shifted to lower frequencies, while the in-plane and out-of-plane bending modes shifted to higher frequencies due to the intermolecular Nsbnd H⋯S hydrogen bond. Also, the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energies and diagrams were presented.

  1. Effect of intermolecular hydrogen bonding, vibrational analysis and molecular structure of 4-chlorobenzothioamide.

    PubMed

    Çırak, Çağrı; Sert, Yusuf; Ucun, Fatih

    2013-09-01

    In the present work, the experimental and theoretical vibrational spectra of 4-chlorobenzothioamide were investigated. The FT-IR (400-4000 cm(-1)) and μ-Raman spectra (100-4000 cm(-1)) of 4-chlorobenzothioamide in the solid phase were recorded. The geometric parameters (bond lengths and bond angles), vibrational frequencies, Infrared and Raman intensities of the title molecule in the ground state were calculated using ab initio Hartree-Fock and density functional theory (B3LYP) methods with the 6-311++G(d,p) basis set for the first time. The optimized geometric parameters and the theoretical vibrational frequencies were found to be in good agreement with the corresponding experimental data and with the results found in the literature. The vibrational frequencies were assigned based on the potential energy distribution using the VEDA 4 program. The dimeric form of 4-chlorobenzothioamide was also simulated to evaluate the effect of intermolecular hydrogen bonding on the vibrational frequencies. It was observed that the N-H stretching modes shifted to lower frequencies, while the in-plane and out-of-plane bending modes shifted to higher frequencies due to the intermolecular N-H···S hydrogen bond. Also, the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energies and diagrams were presented.

  2. Effect of intermolecular hydrogen bonding, vibrational analysis and molecular structure of a biomolecule: 5-Hydroxymethyluracil

    NASA Astrophysics Data System (ADS)

    Çırak, Çağrı; Sert, Yusuf; Ucun, Fatih

    2014-06-01

    In the present work, the experimental and theoretical vibrational spectra of 5-hydroxymethyluracil were investigated. The FT-IR (4000-400 cm-1) spectrum of the molecule in the solid phase was recorded. The geometric parameters (bond lengths and bond angles), vibrational frequencies, Infrared intensities of the title molecule in the ground state were calculated using density functional B3LYP and M06-2X methods with the 6-311++G(d,p) basis set for the first time. The optimized geometric parameters and theoretical vibrational frequencies were found to be in good agreement with the corresponding experimental data, and with the results found in the literature. The vibrational frequencies were assigned based on the potential energy distribution using the VEDA 4 program. The dimeric form of 5-hydroxymethyluracil molecule was also simulated to evaluate the effect of intermolecular hydrogen bonding on its vibrational frequencies. It was observed that the Nsbnd H stretching modes shifted to lower frequencies, while its in-plane and out-of-plane bending modes shifted to higher frequencies due to the intermolecular Nsbnd H⋯O hydrogen bond. Also, the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energies and diagrams were presented.

  3. Effect of intermolecular hydrogen bonding, vibrational analysis and molecular structure of a biomolecule: 5-Hydroxymethyluracil.

    PubMed

    Çırak, Çağrı; Sert, Yusuf; Ucun, Fatih

    2014-06-05

    In the present work, the experimental and theoretical vibrational spectra of 5-hydroxymethyluracil were investigated. The FT-IR (4000-400cm(-1)) spectrum of the molecule in the solid phase was recorded. The geometric parameters (bond lengths and bond angles), vibrational frequencies, Infrared intensities of the title molecule in the ground state were calculated using density functional B3LYP and M06-2X methods with the 6-311++G(d,p) basis set for the first time. The optimized geometric parameters and theoretical vibrational frequencies were found to be in good agreement with the corresponding experimental data, and with the results found in the literature. The vibrational frequencies were assigned based on the potential energy distribution using the VEDA 4 program. The dimeric form of 5-hydroxymethyluracil molecule was also simulated to evaluate the effect of intermolecular hydrogen bonding on its vibrational frequencies. It was observed that the NH stretching modes shifted to lower frequencies, while its in-plane and out-of-plane bending modes shifted to higher frequencies due to the intermolecular NH⋯O hydrogen bond. Also, the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energies and diagrams were presented.

  4. Intermolecular Singlet and Triplet Exciton Transfer Integrals from Many-Body Green's Functions Theory.

    PubMed

    Wehner, Jens; Baumeier, Björn

    2017-03-08

    A general approach to determine orientation and distance-dependent effective intermolecular exciton transfer integrals from many-body Green's functions theory is presented. On the basis of the GW approximation and the Bethe-Salpeter equation (BSE), a projection technique is employed to obtain the excitonic coupling by forming the expectation value of a supramolecular BSE Hamiltonian with electron-hole wave functions for excitations localized on two separated chromophores. Within this approach, accounting for the effects of coupling mediated by intermolecular charge transfer (CT) excitations is possible via perturbation theory or a reduction technique. Application to model configurations of pyrene dimers shows an accurate description of short-range exchange and long-range Coulomb interactions for the coupling of singlet and triplet excitons. Computational parameters, such as the choice of the exchange-correlation functional in the density-functional theory (DFT) calculations that underly the GW-BSE steps and the convergence with the number of included CT excitations, are scrutinized. Finally, an optimal strategy is derived for simulations of full large-scale morphologies by benchmarking various approximations using pairs of dicyanovinyl end-capped oligothiophenes (DCV5T), which are used as donor material in state-of-the-art organic solar cells.

  5. Curcumin amorphous solid dispersions: the influence of intra and intermolecular bonding on physical stability.

    PubMed

    Wegiel, Lindsay A; Zhao, Yuhong; Mauer, Lisa J; Edgar, Kevin J; Taylor, Lynne S

    2014-12-01

    We have investigated the physical stability of amorphous curcumin dispersions and the role of curcumin-polymer intermolecular interactions in delaying crystallization. Curcumin is an interesting model compound as it forms both intra and intermolecular hydrogen bonds in the crystal. A structurally diverse set of amorphous dispersion polymers was investigated; poly(vinylpyrrolidone), Eudragit E100, carboxymethyl cellulose acetate butyrate, hydroxypropyl methyl cellulose (HPMC) and HPMC-acetate succinate. Mid-infrared spectroscopy was used to determine and quantify the extent of curcumin-polymer interactions. Physical stability under different environmental conditions was monitored by powder X-ray diffraction. Curcumin chemical stability was monitored by UV-Vis spectroscopy. Isolation of stable amorphous curcumin was difficult in the absence of polymers. Polymers proved to be effective curcumin crystallization inhibitors enabling the production of amorphous solid dispersions; however, the polymers showed very different abilities to inhibit crystallization during long-term storage. Curcumin intramolecular hydrogen bonding reduced the extent of its hydrogen bonding with polymers; hence most polymers were not highly effective crystallization inhibitors. Overall, polymers proved to be crystallization inhibitors, but inhibition was limited due to the intramolecular hydrogen bonding in curcumin, which leads to a decrease in the ability of the polymers to interact at a molecular level.

  6. Intermolecular Stabilization of 3,3'-Diamino-4,4'-azoxyfurazan (DAAF) Compressed to 20 GPa

    SciTech Connect

    Chellappa, Raja S.; Dattelbaum, Dana M.; Coe, Joshua D.; Velisavljevic, Nenad; Stevens, Lewis L.; Liu, Zhenxian

    2014-07-10

    The room temperature stability of 3,3'-diamino-4,4'-azoxyfurazan (DAAF) has been investigated using synchrotron far-infrared, mid-infrared, Raman spectroscopy, and synchrotron X-ray diffraction (XRD) up to 20 GPa. The as-loaded DAAF samples exhibited subtle pressure-induced ordering phenomena (associated with positional disorder of the azoxy “O” atom) resulting in doubling of the a-axis, to form a superlattice similar to the low-temperature polymorph. Neither high pressure synchrotron XRD, nor high pressure infrared or Raman spectroscopies indicated the presence of structural phase transitions up to 20 GPa. Compression was accommodated in the unit cell by a reduction of the c-axis between the planar DAAF layers, distortion of the β-angle of the monoclinic lattice, and an increase in intermolecular hydrogen bonding. Changes in the ring and -NH2 deformation modes and increased intermolecular hydrogen bonding interactions with compression suggest molecular reorganizations and electronic transitions at ~5 GPa and ~10 GPa that are accompanied by a shifting of the absorption band edge into the visible. A fourth-order Birch–Murnaghan fit to the room temperature isotherm afforded an estimate of the zero-pressure isothermal bulk modulus, K0 = 12.4 ± 0.6 GPa and its pressure derivative K0' = 7.7 ± 0.3.

  7. Intermolecular stabilization of 3,3'-diamino-4,4'-azoxyfurazan (DAAF) compressed to 20 GPa.

    PubMed

    Chellappa, Raja S; Dattelbaum, Dana M; Coe, Joshua D; Velisavljevic, Nenad; Stevens, Lewis L; Liu, Zhenxian

    2014-08-07

    The room temperature stability of 3,3'-diamino-4,4'-azoxyfurazan (DAAF) has been investigated using synchrotron far-infrared, mid-infrared, Raman spectroscopy, and synchrotron X-ray diffraction (XRD) up to 20 GPa. The as-loaded DAAF samples exhibited subtle pressure-induced ordering phenomena (associated with positional disorder of the azoxy "O" atom) resulting in doubling of the a-axis, to form a superlattice similar to the low-temperature polymorph. Neither high pressure synchrotron XRD, nor high pressure infrared or Raman spectroscopies indicated the presence of structural phase transitions up to 20 GPa. Compression was accommodated in the unit cell by a reduction of the c-axis between the planar DAAF layers, distortion of the β-angle of the monoclinic lattice, and an increase in intermolecular hydrogen bonding. Changes in the ring and -NH2 deformation modes and increased intermolecular hydrogen bonding interactions with compression suggest molecular reorganizations and electronic transitions at ∼ 5 GPa and ∼ 10 GPa that are accompanied by a shifting of the absorption band edge into the visible. A fourth-order Birch-Murnaghan fit to the room temperature isotherm afforded an estimate of the zero-pressure isothermal bulk modulus, K0 = 12.4 ± 0.6 GPa and its pressure derivative K0' = 7.7 ± 0.3.

  8. Intermolecular crosslinking of fatty acyl chains in phospholipids: use of photoactivable carbene precursors.

    PubMed Central

    Gupta, C M; Radhakrishnan, R; Gerber, G E; Olsen, W L; Quay, S C; Khorana, H G

    1979-01-01

    Phospholipids containing photolysable carbene precursors (beta-trifluoro-alpha-diazopropionoxy and m-diazirinophenoxy groups) in omega-positions of sn-2 fatty acyl chains were prepared. Photolysis of their vesicles produced crosslinked products in 40-60% yields. Crosslinking was mostly intermolecular and occurred by carbene insertion into the C-H bonds of a second fatty acyl chain. Crosslinking products were characterized by (i) their gel permeation behavior, (ii) analysis of products formed by base-catalyzed transesterification, (iii) degradation with phospholipases A2 and C, (iv) gas chromatography/mass spectrometry, and (v) use of mixtures of phospholipids carrying the carbene precursors and a phospholipid containing radioactively labeled fatty acyl groups. Nitrenes generated from the aliphatic or aromatic azido groups in phospholipids were unsatisfactory for forming crosslinks by insertion in C-H bonds. PMID:288050

  9. Weak intermolecular interactions in 11-chloro-2,3,4,5-tetrahydro-1H-cyclohepta[b]quinoline.

    PubMed

    Novaković, Sladjana B; Vitorović-Todorović, Maja D; Bogdanović, Goran A; Drakulić, Branko J

    2008-09-01

    The title compound, C(14)H(14)ClN, is a chloro analogue of tacrine, an acetylcholinesterase inhibitor. The compound comprises a seven-membered alicyclic ring whose CH donor groups are engaged in extensive intermolecular interactions. The important feature of this crystal structure is that, regardless of the presence of two typical hydrogen-bonding acceptors, viz. chlorine and nitrogen, the corresponding C-H...Cl and C-H...N interactions take no significant role in crystal stabilization. The molecules form dimers through pi-pi interactions with an interplanar distance between interacting pyridine rings of 3.576 (1) A. Within the dimers, the molecules are additionally interconnected by four C-H...pi interactions. The dimers arrange into regular columns via further intermolecular C-H...pi interactions.

  10. Intermolecular hydrogen bonds in hetero-complexes of biologically active aromatic molecules probed by the methods of vibrational spectroscopy

    NASA Astrophysics Data System (ADS)

    Semenov, M. A.; Blyzniuk, Iu. N.; Bolbukh, T. V.; Shestopalova, A. V.; Evstigneev, M. P.; Maleev, V. Ya.

    2012-09-01

    By the methods of vibrational spectroscopy (Infrared and Raman) the investigation of the hetero-association of biologically active aromatic compounds: flavin-mononucleotide (FMN), ethidium bromide (EB) and proflavine (PRF) was performed in aqueous solutions. It was shown that between the functional groups (Cdbnd O and NH2) the intermolecular hydrogen bonds are formed in the hetero-complexes FMN-EB and FMN-PRF, additionally stabilizing these structures. An estimation of the enthalpy of Н-bonding obtained from experimental shifts of carbonyl vibrational frequencies has shown that the H-bonds do not dominate in the magnitude of experimentally measured total enthalpy of the hetero-association reactions. The main stabilization is likely due to intermolecular interactions of the molecules in these complexes and their interaction with water environment.

  11. Intermolecular hydrogen bonds in hetero-complexes of biologically active aromatic molecules probed by the methods of vibrational spectroscopy.

    PubMed

    Semenov, M A; Blyzniuk, Iu N; Bolbukh, T V; Shestopalova, A V; Evstigneev, M P; Maleev, V Ya

    2012-09-01

    By the methods of vibrational spectroscopy (Infrared and Raman) the investigation of the hetero-association of biologically active aromatic compounds: flavin-mononucleotide (FMN), ethidium bromide (EB) and proflavine (PRF) was performed in aqueous solutions. It was shown that between the functional groups (CO and NH(2)) the intermolecular hydrogen bonds are formed in the hetero-complexes FMN-EB and FMN-PRF, additionally stabilizing these structures. An estimation of the enthalpy of Н-bonding obtained from experimental shifts of carbonyl vibrational frequencies has shown that the H-bonds do not dominate in the magnitude of experimentally measured total enthalpy of the hetero-association reactions. The main stabilization is likely due to intermolecular interactions of the molecules in these complexes and their interaction with water environment.

  12. Selective detection of intermolecular response in benzonitrile through double-pulse excitation in optical Kerr effect spectroscopy

    NASA Astrophysics Data System (ADS)

    Nikiforov, V. G.; Zharkov, D. K.; Shmelev, A. G.; Leontyev, A. V.; Lobkov, V. S.

    2017-07-01

    We report on the decomposition of the molecular contribution to the optically heterodyne-detected optical Kerr effect (OHD-OKE) in benzonitrile C6H5CN in the process of double-pulse laser excitation. The pump pulses with linear orthogonal polarizations, controllable intensities and timing enable us to manipulate the amplitudes of various molecular responses due to the fact that the OHD-OKE signal is formed by the superposition of independent third-order responses associated with each pump pulse. We apply this technique to detect the intermolecular response selectively by using an excitation scenario with suppression of orientational and intramolecular responses. A detailed comparative analysis of third-order optical responses indicates strongly that the double-pulse excitation of the OHD-OKE is the useful spectroscopic technique to obtain precise information on the intermolecular spectrum in liquids.

  13. A general intermolecular force field based on tight-binding quantum chemical calculations

    NASA Astrophysics Data System (ADS)

    Grimme, Stefan; Bannwarth, Christoph; Caldeweyher, Eike; Pisarek, Jana; Hansen, Andreas

    2017-10-01

    A black-box type procedure is presented for the generation of a molecule-specific, intermolecular potential energy function. The method uses quantum chemical (QC) information from our recently published extended tight-binding semi-empirical scheme (GFN-xTB) and can treat non-covalently bound complexes and aggregates with almost arbitrary chemical structure. The necessary QC information consists of the equilibrium structure, Mulliken atomic charges, charge centers of localized molecular orbitals, and also of frontier orbitals and orbital energies. The molecular pair potential includes model density dependent Pauli repulsion, penetration, as well as point charge electrostatics, the newly developed D4 dispersion energy model, Drude oscillators for polarization, and a charge-transfer term. Only one element-specific and about 20 global empirical parameters are needed to cover systems with nuclear charges up to radon (Z = 86). The method is tested for standard small molecule interaction energy benchmark sets where it provides accurate intermolecular energies and equilibrium distances. Examples for structures with a few hundred atoms including charged systems demonstrate the versatility of the approach. The method is implemented in a stand-alone computer code which enables rigid-body, global minimum energy searches for molecular aggregation or alignment.

  14. Work Organisation, Forms of Employee Learning and National Systems of Education and Training

    ERIC Educational Resources Information Center

    Lorenz, Edward; Lundvall, Bengt-Åke; Kraemer-Mbula, Erika; Rasmussen, Palle

    2016-01-01

    This article uses a multi-level framework to investigate for 17 European nations the links between forms of work organisation and style of employee learning at the workplace on the one hand, and the characteristics of national educational and training systems on the other. The analysis shows that forms of work organisation characterised by…

  15. Work Organisation, Forms of Employee Learning and National Systems of Education and Training

    ERIC Educational Resources Information Center

    Lorenz, Edward; Lundvall, Bengt-Åke; Kraemer-Mbula, Erika; Rasmussen, Palle

    2016-01-01

    This article uses a multi-level framework to investigate for 17 European nations the links between forms of work organisation and style of employee learning at the workplace on the one hand, and the characteristics of national educational and training systems on the other. The analysis shows that forms of work organisation characterised by…

  16. 75 FR 4101 - Enterprise Income Verification (EIV) System User Access Authorization Form and Rules of Behavior...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-01-26

    ... of Behavior and User Agreement AGENCY: Office of the Chief Information Officer, HUD. ACTION: Notice... (EIV) System User Access, Authorization Form and Rules Of Behavior and User Agreement. OMB Approval...

  17. Structure of the Minnesota Developmental Programming System Behavioral Scales, Alternate Form C.

    ERIC Educational Resources Information Center

    Silverman, Wayne P.; And Others

    1983-01-01

    The Minnesota Developmental Programming System Behavioral Scales, Alternate Form C, designed to assess adaptive behavior of profoundly developmentally disabled individuals, was evaluated using data from 3,487 individuals. (Author/CL)

  18. CCR Certification Form for Wyoming or EPA R8 Tribal Community Water Systems

    EPA Pesticide Factsheets

    The CCR Certification Form can be used to certify that community water systems in Wyoming or on Tribal Lands in EPA Region 8 have completed and distributed their annual Consumer Confidence Report (CCR) or water quality report.

  19. From H2+ to the multidimensional potential of the intermolecular interaction Ar·HBr: A canonical approach

    NASA Astrophysics Data System (ADS)

    Walton, Jay R.; Rivera-Rivera, Luis A.; Lucchese, Robert R.; Bevan, John W.

    2015-10-01

    A proof-of-concept for the accurate generation of multidimensional intermolecular interaction potentials is demonstrated. The basis for evaluating this application is the available very accurate 3-D morphed potential of Ar·HBr. Starting from the well-defined potential of the simplest molecule, the diatomic H2+, a recently developed 1-D canonical potential is used with selected 2-D polyatomic data to generate the adiabatic intermolecular interaction potential in Ar·HBr, with HBr in the vibrational ground state. This represents the first application of canonical transformations to a higher vibrationally dimensional molecular system, in this case, Ar·HBr. Results indicate intrinsic bonding characteristics inherent to both systems.

  20. Free-form surface measuring method based on optical theodolite measuring system

    NASA Astrophysics Data System (ADS)

    Yu, Caili

    2012-10-01

    The measurement for single-point coordinate, length and large-dimension curved surface in industrial measurement can be achieved through forward intersection measurement by the theodolite measuring system composed of several optical theodolites and one computer. The measuring principle of flexible large-dimension three-coordinate measuring system made up of multiple (above two) optical theodolites and composition and functions of the system have been introduced in this paper. Especially for measurement of curved surface, 3D measured data of spatial free-form surface is acquired through the theodolite measuring system and the CAD model is formed through surface fitting to directly generate CAM processing data.

  1. Intermolecular interactions in the bilirubin-cholate-silica system

    NASA Astrophysics Data System (ADS)

    Vlasova, N. N.; Golovkova, L. P.; Severinovskaya, O. V.

    2007-06-01

    Bilirubin-cholate interactions in aqueous solutions were studied. The constants of binding of bilirubin with taurocholate dimers and taurodeoxycholate trimers were calculated. The adsorption of bilirubin and cholates on the surface of highly dispersed silica was studied. It was shown that taurine-conjugated cholates are poorly adsorbed from micellar solutions on the silica surface, the specific amount of bilirubin adsorbed decreases with increasing concentration of cholates in the solution, the affinity of free bilirubin for the silica surface is independent of the nature of the cholic acid, and that the affinity of cholate-bilirubin complexes for the silica surface is lower than the affinity of free bilirubin.

  2. Signatures of Solvation Thermodynamics in Spectra of Intermolecular Vibrations

    PubMed Central

    2017-01-01

    This study explores the thermodynamic and vibrational properties of water in the three-dimensional environment of solvated ions and small molecules using molecular simulations. The spectrum of intermolecular vibrations in liquid solvents provides detailed information on the shape of the local potential energy surface, which in turn determines local thermodynamic properties such as the entropy. Here, we extract this information using a spatially resolved extension of the two-phase thermodynamics method to estimate hydration water entropies based on the local vibrational density of states (3D-2PT). Combined with an analysis of solute–water and water–water interaction energies, this allows us to resolve local contributions to the solvation enthalpy, entropy, and free energy. We use this approach to study effects of ions on their surrounding water hydrogen bond network, its spectrum of intermolecular vibrations, and resulting thermodynamic properties. In the three-dimensional environment of polar and nonpolar functional groups of molecular solutes, we identify distinct hydration water species and classify them by their characteristic vibrational density of states and molecular entropies. In each case, we are able to assign variations in local hydration water entropies to specific changes in the spectrum of intermolecular vibrations. This provides an important link for the thermodynamic interpretation of vibrational spectra that are accessible to far-infrared absorption and Raman spectroscopy experiments. Our analysis provides unique microscopic details regarding the hydration of hydrophobic and hydrophilic functional groups, which enable us to identify interactions and molecular degrees of freedom that determine relevant contributions to the solvation entropy and consequently the free energy. PMID:28783431

  3. Combination Bands of the Nonpolar OCS Dimer Involving Intermolecular Modes

    NASA Astrophysics Data System (ADS)

    Rezaei, M.; Oliaee, J. Norooz; Moazzen-Ahmadi, N.; McKellar, A. R. W.

    2012-06-01

    Spectra of the nonpolar carbonyl sulfide in the region of the OCS ν_1 fundamental band were observed in a supersonic slit-jet apparatus. The expansion gas was probed using radiation from a tunable diode laser employed in a rapid-scan signal averaging mode. Three bands centered at 2085.906, 2103.504, and 2114.979 cm-1 were observed and anlysed. The rotational assignment and fitting of the bands were made by fixing the lower state parameters to those for the ground state of nonpolar (OCS)_2, thus confirming that they were indeed combination bands of the of the most stable isomer of OCS dimer. The band centered at 2085.906 cm-1 is a combination of the forbidden A_g intramolecular mode plus the geared bend intermolecular mode and that centered at 2114.979 cm-1 is a combination of the allowed B_u intramolecular mode plus the intermolecular van der Waals stretch. The combination at 2103.504 cm-1 can be assigned as a band whose upper state involves four quanta of the intramolecular bend or the B_u intramolecular mode plus two quanta of the intermolecular torsional mode. Isotopic work is needed to conclusively identify the vibrational assignment of this band. Our experimental frequencies for the geared bend and van der Waals modes are in good agreement with a recent high level ab initio calculation by Brown et al. J. Brown, Xiao-Gang Wang, T. Carrington Jr. and Richard Dawes, Journal of Chemical Physics, submitted.

  4. Intermolecular interactions of 4-pyrrolidino pyridine: a simulation study

    NASA Astrophysics Data System (ADS)

    Ranjan Bangal, Prakriti; Chakravorti, Sankar

    1999-10-01

    Simulations of intermolecular interaction by the AM1 method have been performed. The hydrogen bonding complex between and 4-pyrrolidino pyridine (PP) and water molecules with 1: n complexes have been considered to investigate possible stable complex configurations and to calculate the stable interaction energy. These calculations confirm the influence of water molecules on twisting of the pyrrolidino group in ground state. The excited state simulation predicts that the energy minimized geometry of the PP molecule takes an almost sandwich like structure, confirming the formation of an intramolecular exciplex in the gas phase as well as in nonpolar or in weakly polar solvents in line with the experimental findings.

  5. INTERMOLECULAR FORCES IN ASSOCIATION OF PURINES WITH POLYBENZENOID HYDROCARBONS.

    PubMed

    PULLMAN, B; CLAVERIE, P; CAILLET, J

    1965-03-12

    The interactions in solution between purine or pyrimidine bases and polybenzenoid aromatic hydrocarbons probably consist in a vertical, stacking-type physical association. By molecular orbital calculations the role of the Van der Waals-London intermolecular forces in these interactions is determined. The electrostatic dipole-dipole forces are negligible, the polarization (or induction) dipole-induced dipole forces are contributory, but most important are the dispersion (or fluctuation) forces. This loose, physical type of interaction should not show any specificity with respect to the carcinogenic activity of the hydrocarbons.

  6. Structurally Defined Molecular Hypervalent Iodine Catalysts for Intermolecular Enantioselective Reactions

    PubMed Central

    Haubenreisser, Stefan; Wöste, Thorsten H.; Martínez, Claudio; Ishihara, Kazuaki

    2015-01-01

    Abstract Molecular structures of the most prominent chiral non‐racemic hypervalent iodine(III) reagents to date have been elucidated for the first time. The formation of a chirally induced supramolecular scaffold based on a selective hydrogen‐bonding arrangement provides an explanation for the consistently high asymmetric induction with these reagents. As an exploratory example, their scope as chiral catalysts was extended to the enantioselective dioxygenation of alkenes. A series of terminal styrenes are converted into the corresponding vicinal diacetoxylation products under mild conditions and provide the proof of principle for a truly intermolecular asymmetric alkene oxidation under iodine(I/III) catalysis. PMID:26596513

  7. Accurate temperature imaging based on intermolecular coherences in magnetic resonance.

    PubMed

    Galiana, Gigi; Branca, Rosa T; Jenista, Elizabeth R; Warren, Warren S

    2008-10-17

    Conventional magnetic resonance methods that provide interior temperature profiles, which find use in clinical applications such as hyperthermic therapy, can develop inaccuracies caused by the inherently inhomogeneous magnetic field within tissues or by probe dynamics, and work poorly in important applications such as fatty tissues. We present a magnetic resonance method that is suitable for imaging temperature in a wide range of environments. It uses the inherently sharp resonances of intermolecular zero-quantum coherences, in this case flipping up a water spin while flipping down a nearby fat spin. We show that this method can rapidly and accurately assign temperatures in vivo on an absolute scale.

  8. Output feedback control of a class of discrete MIMO nonlinear systems with triangular form inputs.

    PubMed

    Zhang, Jin; Ge, Shuzhi Sam; Lee, Tong Heng

    2005-11-01

    In this paper, adaptive neural network (NN) control is investigated for a class of discrete-time multi-input-multi-output (MIMO) nonlinear systems with triangular form inputs. Each subsystem of the MIMO system is in strict feedback form. First, through two phases of coordinate transformation, the MIMO system is transformed into input-output representation with the triangular form input structure unchanged. By using high-order neural networks (HONNs) as the emulators of the desired controls, effective output feedback adaptive control is developed using backstepping. The closed-loop system is proved to be semiglobally uniformly ultimate bounded (SGUUB) by using Lyapunov method. The output tracking errors are guaranteed to converge into a compact set whose size is adjustable, and all the other signals in the closed-loop system are proved to be bounded. Simulation results show the effectiveness of the proposed control scheme.

  9. Corrigendum: New Form of Kane's Equations of Motion for Constrained Systems

    NASA Technical Reports Server (NTRS)

    Roithmayr, Carlos M.; Bajodah, Abdulrahman H.; Hodges, Dewey H.; Chen, Ye-Hwa

    2007-01-01

    A correction to the previously published article "New Form of Kane's Equations of Motion for Constrained Systems" is presented. Misuse of the transformation matrix between time rates of change of the generalized coordinates and generalized speeds (sometimes called motion variables) resulted in a false conclusion concerning the symmetry of the generalized inertia matrix. The generalized inertia matrix (sometimes referred to as the mass matrix) is in fact symmetric and usually positive definite when one forms nonminimal Kane's equations for holonomic or simple nonholonomic systems, systems subject to nonlinear nonholonomic constraints, and holonomic or simple nonholonomic systems subject to impulsive constraints according to Refs. 1, 2, and 3, respectively. The mass matrix is of course symmetric when one forms minimal equations for holonomic or simple nonholonomic systems using Kane s method as set forth in Ref. 4.

  10. Cooperative control design for non-holonomic chained-form systems

    NASA Astrophysics Data System (ADS)

    Cao, Ke-Cai; Jiang, Bin; Chen, YangQuan

    2015-07-01

    Consensus and formation control problems for multiple non-holonomic chained-form systems are solved in this paper. For consensus problem, based on cascaded structure of the chained-form systems, it amounts to solving two consensus subproblems of two linear subsystems transformed from the original system. With the obtained consensus protocols and the method of virtual structure, decentralised formation controllers can then be designed. According to different desired motion patterns of the entire group, both the formation tracking and formation stabilisation problems can be considered. The significance of this paper lies in adapting theories from non-autonomous cascaded systems for cooperative control design for non-holonomic chained-form systems. A unique feature of our proposed solution is that all states can be cooperatively controlled to achieve the desired references for non-holonomic chained-form system. Simulation results are included to illustrate the effectiveness of the proposed methods in solving cooperative control problems of non-holonomic chained-form systems.

  11. Is Student Performance on the Information Systems Analyst Certification Exam Affected by Form of Delivery of Information Systems Coursework?

    ERIC Educational Resources Information Center

    Haga, Wayne; Moreno, Abel; Segall, Mark

    2012-01-01

    In this paper, we compare the performance of Computer Information Systems (CIS) majors on the Information Systems Analyst (ISA) Certification Exam. The impact that the form of delivery of information systems coursework may have on the exam score is studied. Using a sample that spans three years, we test for significant differences between scores…

  12. Polarizable intermolecular potentials for water and benzene interacting with halide and metal ions

    PubMed Central

    Archambault, Fabien; Soteras, Ignacio; Luque, F. Javier; Schulten, Klaus

    2010-01-01

    A complete derivation of polarizable intermolecular potentials based on high-level, gas-phase quantum-mechanical calculations is proposed. The importance of appreciable accuracy together with inherent simplicity represents a significant endeavor when enhancement of existing force fields for biological systems is sought. Toward this end, symmetry-adapted perturbation theory (SAPT) can provide an expansion of the total interaction energy into physically meaningful e.g. electrostatic, induction and van der Waals terms. Each contribution can be readily compared with its counterpart in classical force fields. Since the complexity of the different intermolecular terms cannot be fully embraced using a minimalist description, it is necessary to resort to polyvalent expressions capable of encapsulating overlooked contributions from the quantum-mechanical expansion. This choice results in consistent force field components that reflect the underlying physical principles of the phenomena. This simplified potential energy function is detailed and definitive guidelines are drawn. As a proof of concept, the methodology is illustrated through a series of test cases that include the interaction of water and benzene with halide and metal ions. In each case considered, the total energy is reproduced accurately over a range of biologically relevant distances. PMID:21113276

  13. Intermolecular hydrogen bonding in chlorine dioxide photochemistry: A time-resolved resonance Raman study

    NASA Astrophysics Data System (ADS)

    Philpott, Matthew P.; Hayes, Sophia C.; Thomsen, Carsten L.; Reid, Philip J.

    2001-01-01

    The geminate-recombination and vibrational-relaxation dynamics of chlorine dioxide (OClO) dissolved in ethanol and 2,2,2-trifluoroethanol (TFE) are investigated using time-resolved resonance Raman spectroscopy. Stokes spectra are measured as a function of time following photoexcitation using degenerate pump and probe wavelengths of 398 nm. For OClO dissolved in ethanol, subpicosecond geminate recombination occurs resulting in the reformation of ground-state OClO with a quantum yield of 0.5±0.1. Following recombination, intermolecular-vibrational relaxation of OClO occurs with a time constant of 31±10 ps. For OClO dissolved in TFE, recombination occurs with a time constant of 1.8±0.8 ps and a quantum yield of only 0.3±0.1. The intermolecular-vibrational-relaxation time constant of OClO in TFE is 79±27 ps. The reduced geminate-recombination quantum yield, delayed recombination, and slower vibrational relaxation for OClO in TFE is interpreted in terms of greater self-association of the solvent. Degenerate pump-probe experiments are also presented that demonstrate decay of the Cl-solvent charge-transfer complex on the ˜1-ns time scale in ethanol and TFE. This time is significantly longer than the abstraction times observed for other systems demonstrating that Cl hydrogen abstraction from alcohols occurs in the presence of a significant energy barrier.

  14. Intermolecular Alignment in Y145Stop Human Prion Protein Amyloid Fibrils Probed by Solid-State NMR Spectroscopy

    PubMed Central

    Helmus, Jonathan J.; Surewicz, Krystyna; Apostol, Marcin I.; Surewicz, Witold K.; Jaroniec, Christopher P.

    2011-01-01

    The Y145Stop mutant of human prion protein, huPrP23-144, has been linked to PrP cerebral amyloid angiopathy, an inherited amyloid disease, and also serves as a valuable in vitro model for investigating the molecular basis of amyloid strains. Prior studies of huPrP23-144 amyloid by magic-angle spinning (MAS) solid-state NMR revealed a compact β-rich amyloid core region near the C-terminus and an unstructured N-terminal domain. Here, with the focus on understanding the higher order architecture of huPrP23-144 fibrils, we probe the intermolecular alignment of β-strands within the amyloid core using MAS NMR techniques and fibrils formed from equimolar mixtures of 15N-labeled protein and 13C-huPrP23-144 prepared with [1,3-13C] or [2-13C]glycerol. Numerous intermolecular correlations involving backbone atoms observed in 2D 15N-13C spectra unequivocally suggest an overall parallel in-register alignment of the β-sheet core. Additional experiments that report on intermolecular 15N-13CO and 15N-13Cα dipolar couplings yield an estimated strand spacing that is within ~10% of the ~4.7–4.8 Å distances typical for parallel β-sheets. PMID:21827207

  15. Intermolecular alignment in Y145Stop human prion protein amyloid fibrils probed by solid-state NMR spectroscopy.

    PubMed

    Helmus, Jonathan J; Surewicz, Krystyna; Apostol, Marcin I; Surewicz, Witold K; Jaroniec, Christopher P

    2011-09-07

    The Y145Stop mutant of human prion protein, huPrP23-144, has been linked to PrP cerebral amyloid angiopathy, an inherited amyloid disease, and also serves as a valuable in vitro model for investigating the molecular basis of amyloid strains. Prior studies of huPrP23-144 amyloid by magic-angle-spinning (MAS) solid-state NMR spectroscopy revealed a compact β-rich amyloid core region near the C-terminus and an unstructured N-terminal domain. Here, with the focus on understanding the higher-order architecture of huPrP23-144 fibrils, we probed the intermolecular alignment of β-strands within the amyloid core using MAS NMR techniques and fibrils formed from equimolar mixtures of (15)N-labeled protein and (13)C-huPrP23-144 prepared with [1,3-(13)C(2)] or [2-(13)C]glycerol. Numerous intermolecular correlations involving backbone atoms observed in 2D (15)N-(13)C spectra unequivocally suggest an overall parallel in-register alignment of the β-sheet core. Additional experiments that report on intermolecular (15)N-(13)CO and (15)N-(13)Cα dipolar couplings yielded an estimated strand spacing that is within ∼10% of the distances of 4.7-4.8 Å typical for parallel β-sheets.

  16. Intermolecular symmetry-adapted perturbation theory study of large organic complexes

    SciTech Connect

    Heßelmann, Andreas; Korona, Tatiana

    2014-09-07

    Binding energies for the complexes of the S12L database by Grimme [Chem. Eur. J. 18, 9955 (2012)] were calculated using intermolecular symmetry-adapted perturbation theory combined with a density-functional theory description of the interacting molecules. The individual interaction energy decompositions revealed no particular change in the stabilisation pattern as compared to smaller dimer systems at equilibrium structures. This demonstrates that, to some extent, the qualitative description of the interaction of small dimer systems may be extrapolated to larger systems, a method that is widely used in force-fields in which the total interaction energy is decomposed into atom-atom contributions. A comparison of the binding energies with accurate experimental reference values from Grimme, the latter including thermodynamic corrections from semiempirical calculations, has shown a fairly good agreement to within the error range of the reference binding energies.

  17. Intermolecular symmetry-adapted perturbation theory study of large organic complexes.

    PubMed

    Heßelmann, Andreas; Korona, Tatiana

    2014-09-07

    Binding energies for the complexes of the S12L database by Grimme [Chem. Eur. J. 18, 9955 (2012)] were calculated using intermolecular symmetry-adapted perturbation theory combined with a density-functional theory description of the interacting molecules. The individual interaction energy decompositions revealed no particular change in the stabilisation pattern as compared to smaller dimer systems at equilibrium structures. This demonstrates that, to some extent, the qualitative description of the interaction of small dimer systems may be extrapolated to larger systems, a method that is widely used in force-fields in which the total interaction energy is decomposed into atom-atom contributions. A comparison of the binding energies with accurate experimental reference values from Grimme, the latter including thermodynamic corrections from semiempirical calculations, has shown a fairly good agreement to within the error range of the reference binding energies.

  18. In situ gel-forming system: an attractive alternative for nasal drug delivery.

    PubMed

    Wang, Xiaoqing; Liu, Guiyang; Ma, Jianli; Guo, Shaolai; Gao, Lei; Jia, Yanhua; Li, Xiang; Zhang, Qingzhe

    2013-01-01

    Intranasal delivery is one of the most interesting and challenging endeavors facing pharmaceutical scientists. The conventional nasal drug delivery systems including solutions, suspensions, and ointments show drawbacks such as short residence in the nasal cavity, highly variable efficiency, low permeability, and inconvenient administration. In situ gel-forming systems are an interesting polymeric system that exists as flowing aqueous solution before administration and undergoes phase transition to form a viscoelastic gel in a physiologic environment. Benefiting from the merits of both a solution and a gel, an impressive number of in situ gel-forming systems induced by temperature, pH, and ions have been prepared for use in nasal drug delivery in the past few years. In situ gel-forming systems increase the retention of drugs in the nasal cavity, and some of them also show permeation-enhancing capabilities. This article reviews the in situ gel-forming systems used for nasal drug delivery and introduces their gelling mechanisms and other favorable features for intranasal delivery. It also describes the release patterns and drug stability of in situ gels as well as their in vivo performances and local safety following nasal administration.

  19. 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.

  20. Optical properties of azobenzene-functionalized self-assembled monolayers: Intermolecular coupling and many-body interactions

    NASA Astrophysics Data System (ADS)

    Cocchi, Caterina; Moldt, Thomas; Gahl, Cornelius; Weinelt, Martin; Draxl, Claudia

    2016-12-01

    In a joint theoretical and experimental work, the optical properties of azobenzene-functionalized self-assembled monolayers (SAMs) are studied at different molecular packing densities. Our results, based on density-functional and many-body perturbation theory, as well as on differential reflectance (DR) spectroscopy, shed light on the microscopic mechanisms ruling photo-absorption in these systems. While the optical excitations are intrinsically excitonic in nature, regardless of the molecular concentration, in densely packed SAMs intermolecular coupling and local-field effects are responsible for a sizable weakening of the exciton binding strength. Through a detailed analysis of the character of the electron-hole pairs, we show that distinct excitations involved in the photo-isomerization at low molecular concentrations are dramatically broadened by intermolecular interactions. Spectral shifts in the calculated DR spectra are in good agreement with the experimental results. Our findings represent an important step forward to rationalize the excited-state properties of these complex materials.

  1. Gibb's energy and intermolecular free length of 'Borassus Flabellifier' (BF) and Adansonia digitata (AnD) aqueous binary mixture

    NASA Astrophysics Data System (ADS)

    Phadke, Sushil; Darshan Shrivastava, Bhakt; Ujle, S. K.; Mishra, Ashutosh; Dagaonkar, N.

    2014-09-01

    One of the potential driving forces behind a chemical reaction is favourable a new quantity known as the Gibbs free energy (G) of the system, which reflects the balance between these forces. Ultrasonic velocity and absorption measurements in liquids and liquid mixtures find extensive application to study the nature of intermolecular forces. Ultrasonic velocity measurements have been successfully employed to detect weak and strong molecular interactions present in binary and ternary liquid mixtures. After measuring the density and ultrasonic velocity of aqueous solution of 'Borassus Flabellifier' BF and Adansonia digitata And, we calculated Gibb's energy and intermolecular free length. The velocity of ultrasonic waves was measured, using a multi-frequency ultrasonic interferometer with a high degree of accuracy operating Model M-84 by M/s Mittal Enterprises, New Delhi, at a fixed frequency of 2MHz. Natural sample 'Borassus Flabellifier' BF fruit pulp and Adansonia digitata AnD powder was collected from Dhar, District of MP, India for this study.

  2. Intermolecular interactions and the thermodynamic properties of supercritical fluids

    NASA Astrophysics Data System (ADS)

    Yigzawe, Tesfaye M.; Sadus, Richard J.

    2013-05-01

    The role of different contributions to intermolecular interactions on the thermodynamic properties of supercritical fluids is investigated. Molecular dynamics simulation results are reported for the energy, pressure, thermal pressure coefficient, thermal expansion coefficient, isothermal and adiabatic compressibilities, isobaric and isochoric heat capacities, Joule-Thomson coefficient, and speed of sound of fluids interacting via both the Lennard-Jones and Weeks-Chandler-Andersen potentials. These properties were obtained for a wide range of temperatures, pressures, and densities. For each thermodynamic property, an excess value is determined to distinguish between attraction and repulsion. It is found that the contributions of intermolecular interactions have varying effects depending on the thermodynamic property. The maxima exhibited by the isochoric and isobaric heat capacities, isothermal compressibilities, and thermal expansion coefficient are attributed to interactions in the Lennard-Jones well. Repulsion is required to obtain physically realistic speeds of sound and both repulsion and attraction are necessary to observe a Joule-Thomson inversion curve. Significantly, both maxima and minima are observed for the isobaric and isochoric heat capacities of the supercritical Lennard-Jones fluid. It is postulated that the loci of these maxima and minima converge to a common point via the same power law relationship as the phase coexistence curve with an exponent of β = 0.32. This provides an explanation for the terminal isobaric heat capacity maximum in supercritical fluids.

  3. Quantitative analysis of intermolecular interactions in orthorhombic rubrene

    PubMed Central

    Hathwar, Venkatesha R.; Sist, Mattia; Jørgensen, Mads R. V.; Mamakhel, Aref H.; Wang, Xiaoping; Hoffmann, Christina M.; Sugimoto, Kunihisa; Overgaard, Jacob; Iversen, Bo Brummerstedt

    2015-01-01

    Rubrene is one of the most studied organic semiconductors to date due to its high charge carrier mobility which makes it a potentially applicable compound in modern electronic devices. Previous electronic device characterizations and first principles theoretical calculations assigned the semiconducting properties of rubrene to the presence of a large overlap of the extended π-conjugated core between molecules. We present here the electron density distribution in rubrene at 20 K and at 100 K obtained using a combination of high-resolution X-ray and neutron diffraction data. The topology of the electron density and energies of intermolecular interactions are studied quantitatively. Specifically, the presence of Cπ⋯Cπ interactions between neighbouring tetracene backbones of the rubrene molecules is experimentally confirmed from a topological analysis of the electron density, Non-Covalent Interaction (NCI) analysis and the calculated interaction energy of molecular dimers. A significant contribution to the lattice energy of the crystal is provided by H—H interactions. The electron density features of H—H bonding, and the interaction energy of molecular dimers connected by H—H interaction clearly demonstrate an importance of these weak interactions in the stabilization of the crystal structure. The quantitative nature of the intermolecular interactions is virtually unchanged between 20 K and 100 K suggesting that any changes in carrier transport at these low temperatures would have a different origin. The obtained experimental results are further supported by theoretical calculations. PMID:26306198

  4. Hybrid materials from intermolecular associations between cationic lipid and polymers.

    PubMed

    Pereira, Edla M A; Kosaka, Priscila M; Rosa, Heloísa; Vieira, Débora B; Kawano, Yoshio; Petri, Denise F S; Carmona-Ribeiro, Ana M

    2008-08-07

    Intermolecular associations between a cationic lipid and two model polymers were evaluated from preparation and characterization of hybrid thin films cast on silicon wafers. The novel materials were prepared by spin-coating of a chloroformic solution of lipid and polymer on silicon wafer. Polymers tested for miscibility with the cationic lipid dioctadecyldimethylammonium bromide (DODAB) were polystyrene (PS) and poly(methyl methacrylate) (PMMA). The films thus obtained were characterized by ellipsometry, wettability, optical and atomic force microscopy, Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), and activity against Escherichia coli. Whereas intermolecular ion-dipole interactions were available for the PMMA-DODAB interacting pair producing smooth PMMA-DODAB films, the absence of such interactions for PS-DODAB films caused lipid segregation, poor film stability (detachment from the silicon wafer) and large rugosity. In addition, the well-established but still remarkable antimicrobial DODAB properties were transferred to the novel hybrid PMMA/DODAB coating, which is demonstrated to be highly effective against E. coli.

  5. Intermolecular interactions and the thermodynamic properties of supercritical fluids.

    PubMed

    Yigzawe, Tesfaye M; Sadus, Richard J

    2013-05-21

    The role of different contributions to intermolecular interactions on the thermodynamic properties of supercritical fluids is investigated. Molecular dynamics simulation results are reported for the energy, pressure, thermal pressure coefficient, thermal expansion coefficient, isothermal and adiabatic compressibilities, isobaric and isochoric heat capacities, Joule-Thomson coefficient, and speed of sound of fluids interacting via both the Lennard-Jones and Weeks-Chandler-Andersen potentials. These properties were obtained for a wide range of temperatures, pressures, and densities. For each thermodynamic property, an excess value is determined to distinguish between attraction and repulsion. It is found that the contributions of intermolecular interactions have varying effects depending on the thermodynamic property. The maxima exhibited by the isochoric and isobaric heat capacities, isothermal compressibilities, and thermal expansion coefficient are attributed to interactions in the Lennard-Jones well. Repulsion is required to obtain physically realistic speeds of sound and both repulsion and attraction are necessary to observe a Joule-Thomson inversion curve. Significantly, both maxima and minima are observed for the isobaric and isochoric heat capacities of the supercritical Lennard-Jones fluid. It is postulated that the loci of these maxima and minima converge to a common point via the same power law relationship as the phase coexistence curve with an exponent of β = 0.32. This provides an explanation for the terminal isobaric heat capacity maximum in supercritical fluids.

  6. Quantitative analysis of intermolecular interactions in orthorhombic rubrene

    DOE PAGES

    Hathwar, Venkatesha R.; Sist, Mattia; Jørgensen, Mads R. V.; ...

    2015-08-14

    Rubrene is one of the most studied organic semiconductors to date due to its high charge carrier mobility which makes it a potentially applicable compound in modern electronic devices. Previous electronic device characterizations and first principles theoretical calculations assigned the semiconducting properties of rubrene to the presence of a large overlap of the extended π-conjugated core between molecules. We present here the electron density distribution in rubrene at 20 K and at 100 K obtained using a combination of high-resolution X-ray and neutron diffraction data. The topology of the electron density and energies of intermolecular interactions are studied quantitatively. Specifically,more » the presence of Cπ...Cπinteractions between neighbouring tetracene backbones of the rubrene molecules is experimentally confirmed from a topological analysis of the electron density, Non-Covalent Interaction (NCI) analysis and the calculated interaction energy of molecular dimers. A significant contribution to the lattice energy of the crystal is provided by H—H interactions. The electron density features of H—H bonding, and the interaction energy of molecular dimers connected by H—H interaction clearly demonstrate an importance of these weak interactions in the stabilization of the crystal structure. Finally, the quantitative nature of the intermolecular interactions is virtually unchanged between 20 K and 100 K suggesting that any changes in carrier transport at these low temperatures would have a different origin. The obtained experimental results are further supported by theoretical calculations.« less

  7. He-, Ne-, and Ar-phosgene intermolecular potential energy surfaces.

    PubMed

    Munteanu, Cristian R; Henriksen, Christian; Felker, Peter M; Fernández, Berta

    2013-05-09

    Using the CCSD(T) model, we evaluated the intermolecular potential energy surfaces of the He-, Ne-, and Ar-phosgene complexes. We considered a representative number of intermolecular geometries for which we calculated the corresponding interaction energies with the augmented (He complex) and double augmented (Ne and Ar complexes) correlation-consistent polarized valence triple-ζ basis sets extended with a set of 3s3p2d1f1g midbond functions. These basis sets were selected after systematic basis set studies carried out at geometries close to those of the surface minima. The He-, Ne-, and Ar-phosgene surfaces were found to have absolute minima of -72.1, -140.4, and -326.6 cm(-1) at distances between the rare-gas atom and the phosgene center of mass of 3.184, 3.254, and 3.516 Å, respectively. The potentials were further used in the evaluation of rovibrational states and the rotational constants of the complexes, providing valuable results for future experimental investigations. Comparing our results to those previously available for other phosgene complexes, we suggest that the results for Cl2-phosgene should be revised.

  8. Quantitative analysis of intermolecular interactions in orthorhombic rubrene

    SciTech Connect

    Hathwar, Venkatesha R.; Sist, Mattia; Jørgensen, Mads R. V.; Mamakhel, Aref H.; Wang, Xiaoping; Hoffmann, Christina M.; Sugimoto, Kunihisa; Overgaard, Jacob; Iversen, Bo Brummerstedt

    2015-08-14

    Rubrene is one of the most studied organic semiconductors to date due to its high charge carrier mobility which makes it a potentially applicable compound in modern electronic devices. Previous electronic device characterizations and first principles theoretical calculations assigned the semiconducting properties of rubrene to the presence of a large overlap of the extended π-conjugated core between molecules. We present here the electron density distribution in rubrene at 20 K and at 100 K obtained using a combination of high-resolution X-ray and neutron diffraction data. The topology of the electron density and energies of intermolecular interactions are studied quantitatively. Specifically, the presence of Cπ...Cπinteractions between neighbouring tetracene backbones of the rubrene molecules is experimentally confirmed from a topological analysis of the electron density, Non-Covalent Interaction (NCI) analysis and the calculated interaction energy of molecular dimers. A significant contribution to the lattice energy of the crystal is provided by H—H interactions. The electron density features of H—H bonding, and the interaction energy of molecular dimers connected by H—H interaction clearly demonstrate an importance of these weak interactions in the stabilization of the crystal structure. Finally, the quantitative nature of the intermolecular interactions is virtually unchanged between 20 K and 100 K suggesting that any changes in carrier transport at these low temperatures would have a different origin. The obtained experimental results are further supported by theoretical calculations.

  9. Intermolecular control of thermoswitching and photoswitching phenomena in two spin-crossover polymorphs

    NASA Astrophysics Data System (ADS)

    Buron-Le Cointe, M.; Hébert, J.; Baldé, C.; Moisan, N.; Toupet, L.; Guionneau, P.; Létard, J. F.; Freysz, E.; Cailleau, H.; Collet, E.

    2012-02-01

    We discuss here the important role of intermolecular coupling for the thermal- and light-induced molecular state switching in the solid state. Investigations were performed on the two crystalline polymorphs of the spin-crossover [Fe-(PM-BIA)2(NCS)2] material. In addition to structural studies at thermal equilibrium, light-induced phenomena were investigated through photocrystallography, photomagnetic, and dynamical optical measurements. Strong similarities between the thermal-equilibrium and the out-of-equilibrium light-induced transformations are observed in each polymorph: strong cooperative phenomena in one polymorph versus weak cooperative ones in the second polymorph. These different responses of the two crystalline forms of the compound to external perturbations are discussed at the microscopic level in terms of Ising-like model and two-mode description of on-site molecular potentials.

  10. Spinning Hierarchical Gold Nanowire Microfibers by Shear Alignment and Intermolecular Self-Assembly.

    PubMed

    Reiser, Beate; Gerstner, Dominik; Gonzalez-Garcia, Lola; Maurer, Johannes H M; Kanelidis, Ioannis; Kraus, Tobias

    2017-05-23

    Hierarchical structures lend strength to natural fibers made of soft nanoscale building blocks. Intermolecular interactions connect the components at different levels of hierarchy, distribute stresses, and guarantee structural integrity under load. Here, we show that synthetic ultrathin gold nanowires with interacting ligand shells can be spun into biomimetic, free-standing microfibers. A solution spinning process first aligns the wires, then lets their ligand shells interact, and finally converts them into a hierarchical superstructure. The resulting fiber contained 80 vol % organic ligand but was strong enough to be removed from the solution, dried, and mechanically tested. Fiber strength depended on the wire monomer alignment. Shear in the extrusion nozzle was systematically changed to obtain process-structure-property relations. The degree of nanowire alignment changed breaking stresses by a factor of 1.25 and the elongation at break by a factor of 2.75. Plasma annealing of the fiber to form a solid metal shell decreased the breaking stress by 65%.

  11. ORGANIC CHEMISTRY. Iron-catalyzed intermolecular [2+2] cycloadditions of unactivated alkenes.

    PubMed

    Hoyt, Jordan M; Schmidt, Valerie A; Tondreau, Aaron M; Chirik, Paul J

    2015-08-28

    Cycloadditions, such as the [4+2] Diels-Alder reaction to form six-membered rings, are among the most powerful and widely used methods in synthetic chemistry. The analogous [2+2] alkene cycloaddition to synthesize cyclobutanes is kinetically accessible by photochemical methods, but the substrate scope and functional group tolerance are limited. Here, we report iron-catalyzed intermolecular [2+2] cycloaddition of unactivated alkenes and cross cycloaddition of alkenes and dienes as regio- and stereoselective routes to cyclobutanes. Through rational ligand design, development of this base metal-catalyzed method expands the chemical space accessible from abundant hydrocarbon feedstocks. Copyright © 2015, American Association for the Advancement of Science.

  12. Development and validation of the Diabetes Medication System Rating Questionnaire-Short Form.

    PubMed

    Peyrot, M; Xu, Y; Rubin, R R

    2014-10-01

    To develop and validate a short form of the 54-item Diabetes Medication System Rating Questionnaire that maintains the domains and performance characteristics of the long-form questionnaire. Data from the Diabetes Medication System Rating Questionnaire validation study were analysed to select items representing the nine scales (convenience, negative events, interference, self-monitoring of blood glucose burden, efficacy, social burden, psychological well-being, treatment satisfaction and treatment preference). The resulting 20-item Diabetes Medication System Rating Questionnaire Short-Form was administered online, with validated criterion measures of treatment satisfaction and medication adherence, with a retest within 2 weeks. Participants were US adults (N = 413) with Type 2 diabetes using oral agents alone; insulin by syringe and/or pen with or without oral agents; or glucagon-like peptide-1 agents. Most participants (82%) completed the retest. The median inter-item agreement of scales was 0.76 and the total composite (mean of all items except treatment preference) was 0.88. The median test-retest reliability of scales was 0.86, and of the total composite was 0.95. All statistically significant correlations between Diabetes Medication System Rating Questionnaire Short-Form scales and criterion measures of treatment satisfaction and adherence were in the expected direction. The median correlation of the Diabetes Medication System Rating Questionnaire Short-Form with corresponding criterion measures of treatment satisfaction was 0.59; the mean correlation of the same Diabetes Medication System Rating Questionnaire Short-Form measures with adherence was 0.42. The Diabetes Medication System Rating Questionnaire Short-Form scales were more powerful predictors of adherence than were the criterion measures of treatment satisfaction. The Diabetes Medication System Rating Questionnaire Short-Form scales differentiated between those taking different medications and

  13. Effects of quenched disorder on critical transitions in pattern-forming systems

    NASA Astrophysics Data System (ADS)

    Yizhaq, Hezi; Bel, Golan

    2016-02-01

    Critical transitions are of great interest to scientists in many fields. Most knowledge about these transitions comes from systems exhibiting the multistability of spatially uniform states. In spatially extended and, particularly, in pattern-forming systems, there are many possible scenarios for transitions between alternative states. Quenched disorder may affect the dynamics, bifurcation diagrams and critical transitions in nonlinear systems. However, only a few studies have explored the effects of quenched disorder on pattern-forming systems, either experimentally or by using theoretical models. Here, we use a fundamental model describing pattern formation, the Swift-Hohenberg model and a well-explored mathematical model describing the dynamics of vegetation in drylands to study the effects of quenched disorder on critical transitions in pattern-forming systems. We find that the disorder affects the patterns formed by introducing an interplay between the imposed pattern and the self-organized one. We show that, in both systems considered here, the disorder significantly increases the durability of the patterned state and makes the transition between the patterned state and the uniform state more gradual. In addition, the disorder induces hysteresis in the response of the system to changes in the bifurcation parameter well before the critical transition occurs. We also show that the cross-correlation between the disordered parameter and the dynamical variable can serve as an early indicator for an imminent critical transition.

  14. The rotational spectrum, geometry, and intermolecular force constant of the heterodimer of hydrogen cyanide and fluoroform

    NASA Astrophysics Data System (ADS)

    Goodwin, Elizabeth J.; Legon, A. C.

    1986-02-01

    The ground-state rotational spectra of six isotopic species of an intermolecular complex formed by hydrogen cyanide and fluoroform have been measured using the pulsed-nozzle, Fourier-transform microwave technique. The rotational constant B0, the centrifugal distortion constants DJ,DJK,HJ, HJK, and HKJ, and, where appropriate, the nuclear quadrupole coupling constants χ(14N) and χ(D) have been determined for each of the species HC14NṡṡṡHCF3, DC14NṡṡṡHCF3, HC14ṡṡṡDCF3, HC15NṡṡṡHCF3, HC15NṡṡṡDCF3, and DC15NṡṡṡHCF3. For HC14NṡṡṡHCF3 the values are as follows: B0=1151.2991(4) MHz, DJ=1.91(1) kHz, DJK=282.75(6) kHz, HJ=-0.1(1) Hz, HJK=44.3(5) Hz, HKJ=53(5) Hz, and χ(14N)=3.948(8) MHz. The form of the spectra and magnitudes of the rotational constants allow the conclusion that the geometry of the complex is of C3V symmetry with the nuclei in the order HCNṡṡṡHCF3 and lead to r(NṡṡṡC)=3.489(2) Å for HCF3 species but 3.483(1) Å for DCF3 species. The intermolecular stretching force constant determined from DJ is kσ=3.52 N m-1.

  15. Predicting Behavior Assessment System for Children-Second Edition Self-Report of Personality Child Form Results Using the Behavioral and Emotional Screening System Student Form: A Replication Study with an Urban, Predominantly Latino/a Sample

    ERIC Educational Resources Information Center

    Kiperman, Sarah; Black, Mary S.; McGill, Tia M.; Harrell-Williams, Leigh M.; Kamphaus, Randy W.

    2014-01-01

    This study assesses the ability of a brief screening form, the Behavioral and Emotional Screening System-Student Form (BESS-SF), to predict scores on the much longer form from which it was derived: the Behavior Assessment System for Children-Second Edition Self-Report of Personality-Child Form (BASC-2-SRP-C). The present study replicates a former…

  16. Alternatives for high-level waste forms, containers, and container processing systems

    SciTech Connect

    Crawford, T.W.

    1995-09-22

    This study evaluates alternatives for high-level waste forms, containers, container processing systems, and onsite interim storage. Glass waste forms considered are cullet, marbles, gems, and monolithic glass. Small and large containers configured with several combinations of overpack confinement and shield casks are evaluated for these waste forms. Onsite interim storage concepts including canister storage building, bore holes, and storage pad were configured with various glass forms and canister alternatives. All favorable options include the monolithic glass production process as the waste form. Of the favorable options the unshielded 4- and 7-canister overpack options have the greatest technical assurance associated with their design concepts due to their process packaging and storage methods. These canisters are 0.68 m and 0.54 m in diameter respectively and 4.57 m tall. Life-cycle costs are not a discriminating factor in most cases, varying typically less than 15 percent.

  17. [Intermolecular hydrogen bond between protein and flavonoid and its contribution to the stability of the flavonoids].

    PubMed

    Fang, Ru; Leng, Xiao-jing; Wu, Xia; Li, Qi; Hao, Rui-fang; Ren, Fa-zheng; Jing, Hao

    2012-01-01

    The interactions between three proteins (BSA, lysozyme and myoglobin) and three flavonoids (quercetin, kaempferol and rutin) were analyzed, using three-dimensional fluorescence spectrometry in combination with UV-Vis spectrometry and Fourier transform infrared (FTIR) spectroscopy. The stabilities of unbound flavonoids and protein-bound flavonoids were compared. The correlation between the interaction and stability was analyzed. The results showed that the hydrophobic interaction was the main binding code in all proteins and flavonoids systems. However, the hydrogen bond has been involved merely in the BSA system. The stability of all three flavonoids (quercetin, kaempferol and rutin) was improved by BSA. There was a great correlation between the hydrogen bonding and the stability of the flavonoids in the presence of BSA. It suggested that the protection of BSA on the flavonoids was due to the intermolecular hydrogen bonding between BSA and flavonoid, and the stronger hydrogen bonding resulted in more protection.

  18. Biaxial Dielectrophoresis Force Spectroscopy: A Stoichiometric Approach for Examining Intermolecular Weak Binding Interactions.

    PubMed

    Park, In Soo; Kwak, Tae Joon; Lee, Gyudo; Son, Myeonggu; Choi, Jeong Woo; Choi, Seungyeop; Nam, Kihwan; Lee, Sei-Young; Chang, Woo-Jin; Eom, Kilho; Yoon, Dae Sung; Lee, Sangyoup; Bashir, Rashid; Lee, Sang Woo

    2016-04-26

    The direct quantification of weak intermolecular binding interactions is very important for many applications in biology and medicine. Techniques that can be used to investigate such interactions under a controlled environment, while varying different parameters such as loading rate, pulling direction, rupture event measurements, and the use of different functionalized probes, are still lacking. Herein, we demonstrate a biaxial dielectrophoresis force spectroscopy (BDFS) method that can be used to investigate weak unbinding events in a high-throughput manner under controlled environments and by varying the pulling direction (i.e., transverse and/or vertical axes) as well as the loading rate. With the BDFS system, we can quantitatively analyze binding interactions related to hydrogen bonding or ionic attractions between functionalized microbeads and a surface within a microfluidic device. Our BDFS system allowed for the characterization of the number of bonds involved in an interaction, bond affinity, kinetic rates, and energy barrier heights and widths from different regimes of the energy landscape.

  19. Interfacial and intermolecular interactions determining the rotational orientation of C60 adsorbed on Au(111)

    NASA Astrophysics Data System (ADS)

    Paßens, Michael; Karthäuser, Silvia

    2015-12-01

    Close-packed monolayers of fullerenes on metallic substrates are very rich systems with respect to their rotational degrees of freedom and possible interactions with different adsorption sites or next neighbours. In this connection, we report in detail on the (2√3 × 2√3)R30°-superstructure of C60 with respect to the Au(111)-surface. We use molecular orbital imaging in systematic UHV-STM studies to reveal the delicate balance of interfacial and intermolecular interactions in this system. Thus, bright C60-molecules in 5:6-top and 6:6-top geometries are observed depending on the respective next neighbours. Moreover, tiny changes in the appearance of the unoccupied molecular orbitals of dim C60-molecules in hex-vac positions are identified which are caused by the respective interaction with the facets surrounding the Au-vacancy.

  20. Correlations of life form, pollination mode and sexual system in aquatic angiosperms.

    PubMed

    Du, Zhi-Yuan; Wang, Qing-Feng

    2014-01-01

    Aquatic plants are phylogenetically well dispersed across the angiosperms. Reproductive and other life-history traits of aquatic angiosperms are closely associated with specific growth forms. Hydrophilous pollination exhibits notable examples of convergent evolution in angiosperm reproductive structures, and hydrophiles exhibit great diversity in sexual system. In this study, we reconstructed ancestral characters of aquatic lineages based on the phylogeny of aquatic angiosperms. Our aim is to find the correlations of life form, pollination mode and sexual system in aquatic angiosperms. Hydrophily is the adaptive evolution of completely submersed angiosperms to aquatic habitats. Hydroautogamy and maleflower-ephydrophily are the transitional stages from anemophily and entomophily to hydrophily. True hydrophily occurs in 18 submersed angiosperm genera, which is associated with an unusually high incidence of unisexual flowers. All marine angiosperms are submersed, hydrophilous species. This study would help us understand the evolution of hydrophilous pollination and its correlations with life form and sexual system.

  1. Correlations of Life Form, Pollination Mode and Sexual System in Aquatic Angiosperms

    PubMed Central

    Du, Zhi-Yuan; Wang, Qing-Feng

    2014-01-01

    Aquatic plants are phylogenetically well dispersed across the angiosperms. Reproductive and other life-history traits of aquatic angiosperms are closely associated with specific growth forms. Hydrophilous pollination exhibits notable examples of convergent evolution in angiosperm reproductive structures, and hydrophiles exhibit great diversity in sexual system. In this study, we reconstructed ancestral characters of aquatic lineages based on the phylogeny of aquatic angiosperms. Our aim is to find the correlations of life form, pollination mode and sexual system in aquatic angiosperms. Hydrophily is the adaptive evolution of completely submersed angiosperms to aquatic habitats. Hydroautogamy and maleflower-ephydrophily are the transitional stages from anemophily and entomophily to hydrophily. True hydrophily occurs in 18 submersed angiosperm genera, which is associated with an unusually high incidence of unisexual flowers. All marine angiosperms are submersed, hydrophilous species. This study would help us understand the evolution of hydrophilous pollination and its correlations with life form and sexual system. PMID:25525810

  2. Construction of Darboux coordinates and Poincaré-Birkhoff normal forms in noncanonical Hamiltonian systems

    NASA Astrophysics Data System (ADS)

    Junginger, Andrej; Main, Jörg; Wunner, Günter

    2017-06-01

    We demonstrate a general method to construct Darboux coordinates via normal form expansions in noncanonical Hamiltonian system obtained from e.g. a variational approach to quantum systems. The procedure serves as a tool to naturally extract canonical coordinates out of the variational parameters and at the same time to transform the energy functional into its Poincaré-Birkhoff normal form. The method is general in the sense that it is applicable for arbitrary degrees of freedom, in arbitrary orders of the local expansion, and it is independent of the precise form of the Hamilton operator. The method presented allows for the general and systematic investigation of quantum systems in the vicinity of fixed points, which e.g. correspond to ground, excited or transition states. Moreover, it directly allows to calculate classical and quantum reaction rates by applying transition state theory.

  3. Genetically engineered photoinducible homodimerization system with improved dimer-forming efficiency.

    PubMed

    Nihongaki, Yuta; Suzuki, Hideyuki; Kawano, Fuun; Sato, Moritoshi

    2014-03-21

    Vivid (VVD) is a photoreceptor derived from Neurospora Crassa that rapidly forms a homodimer in response to blue light. Although VVD has several advantages over other photoreceptors as photoinducible homodimerization system, VVD has a critical limitation in its low dimer-forming efficiency. To overcome this limitation of wild-type VVD, here we conduct site-directed saturation mutagenesis in the homodimer interface of VVD. We have found that the Ile52Cys mutation of VVD (VVD-52C) substantially improves its homodimer-forming efficiency up to 180%. We have demonstrated the utility of VVD-52C for making a light-inducible gene expression system more robust. In addition, using VVD-52C, we have developed photoactivatable caspase-9, which enables optical control of apoptosis of mammalian cells. The present genetically engineered photoinducible homodimerization system can provide a powerful tool to optically control a broad range of molecular processes in the cell.

  4. Semiclassical form factor for spectral and matrix element fluctuations of multidimensional chaotic systems.

    PubMed

    Turek, Marko; Spehner, Dominique; Müller, Sebastian; Richter, Klaus

    2005-01-01

    We present a semiclassical calculation of the generalized form factor Kab(tau) which characterizes the fluctuations of matrix elements of the operators a and b in the eigenbasis of the Hamiltonian of a chaotic system. Our approach is based on some recently developed techniques for the spectral form factor of systems with hyperbolic and ergodic underlying classical dynamics and f = 2 degrees of freedom, that allow us to go beyond the diagonal approximation. First we extend these techniques to systems with f > 2. Then we use these results to calculate Kab(tau). We show that the dependence on the rescaled time tau (time in units of the Heisenberg time) is universal for both the spectral and the generalized form factor. Furthermore, we derive a relation between Kab(tau) and the classical time-correlation function of the Weyl symbols of a and b.

  5. Adaptive Fuzzy Tracking Control for a Class of MIMO Nonlinear Systems in Nonstrict-Feedback Form.

    PubMed

    Chen, Bing; Lin, Chong; Liu, Xiaoping; Liu, Kefu

    2015-12-01

    This paper focuses on the problem of fuzzy adaptive control for a class of multiinput and multioutput (MIMO) nonlinear systems in nonstrict-feedback form, which contains the strict-feedback form as a special case. By the condition of variable partition, a new fuzzy adaptive backstepping is proposed for such a class of nonlinear MIMO systems. The suggested fuzzy adaptive controller guarantees that the proposed control scheme can guarantee that all the signals in the closed-loop system are semi-globally uniformly ultimately bounded and the tracking errors eventually converge to a small neighborhood around the origin. The main advantage of this paper is that a control approach is systematically derived for nonlinear systems with strong interconnected terms which are the functions of all states of the whole system. Simulation results further illustrate the effectiveness of the suggested approach.

  6. Process of forming compounds using reverse micelle or reverse microemulsion systems

    DOEpatents

    Linehan, John C.; Fulton, John L.; Bean, Roger M.

    1998-01-01

    The present invention is directed to a process for producing a nanometer-sized metal compound. The process comprises forming a reverse micelle or reverse microemulsion system comprising a polar fluid in a non-polar or low-polarity fluid. A first reactant comprising a multi-component, water-soluble metal compound is introduced into the polar fluid in a non-polar or low-polarity fluid. This first reactant can be introduced into the reverse micelle or reverse microemulsion system during formation thereof or subsequent to the formation of the reverse micelle or microemulsion system. The water-soluble metal compound is then reacted in the reverse micelle or reverse microemulsion system to form the nanometer-sized metal compound. The nanometer-sized metal compound is then precipitated from the reverse micelle or reverse microemulsion system.

  7. Technology maturation project on optimization of sheet metal forming of aluminum for use in transportation systems

    NASA Astrophysics Data System (ADS)

    Johnson, Ken I.; Smith, Mark T.; Lavender, Curt A.; Khalell, Mohammad A.

    1994-10-01

    Using aluminum instead of steel in transportation systems could dramatically reduce the weight of vehicles, an effective way of decreasing energy consumption and emissions. The current cost of sheet metal formed (SMF) aluminum alloys (about $4 per pound) and the relatively long forming times of current materials are serious drawbacks to the widespread use of SMF in industry. The interdependence of materials testing and model development is critical to optimizing SMF since the current process is conducted in a heated, pressurized die where direct measurement of critical SMF parameters is extremely difficult. Numerical models provide a means of tracking the forming process, allowing the applied gas pressure to be adjusted to maintain the optimum SMF behavior throughout the forming process. Thus, models can help produce the optimum SMF component in the least amount of time. The Pacific Northwest Laboratory is integrating SMF model development with research in improved aluminum alloys for SMF. The objectives of this research are: develop and characterize competitively priced aluminum alloys for SMF applications in industry; improve numerical models to accurately predict the optimum forming cycle for reduced forming time and improved quality; and verify alloy performance and model accuracy with forming tests conducted in PNL's Superplastic Forming User Facility. The activities performed in this technology maturation project represent a critical first step in achieving these objectives through cooperative research among industry, PNL, and universities.

  8. Design of a Precast Concrete Stay-in-Place Forming System for Lock Wall Rehabilitation

    DTIC Science & Technology

    1987-07-01

    RE-HABILITATION RESEARCH PROGNtAN ai ,_TECHNICAL REPORT REMR-CS-7 DESIGN OF A PRECAST CONCRETE AD-A 185 0 8 1 STAY-IN-PLACE FORMING SYSTEM FOR LOCK...ie report was prepred: Problem Area Probim Area CS Concrete snd Stee Structures EM Electrical end Mechanical GT Giotechnical El Environmentso Impacts...ment concrete , cracking problems can be eliminated. This report descr-bes the design of such a forming system. A range of design ’alternatives was

  9. Instructions for the preparation of Resource Allocation Support System (RASS) data forms

    SciTech Connect

    Baldwin, T.E.; Buehring, W.A.; Jusko, M.J.; Keisler, J.M.; Whitfield, R.G.; Wolsko, T.D.

    1994-03-01

    The Resource Allocation Support System (RASS) is a decision-aiding system being developed to assist the US Department of Energy`s Office of Waste Management in program and budget decision making. Information about proposed work, developed by DOE program managers and contractors, comprises what is called the RASS database. A set of data forms and worksheets (paper copies) are provided to record information that will be entered into the RASS database. This report contains instructions for preparing the data forms and worksheets.

  10. Announcement: Implementation of the Vaccine Adverse Event Reporting System 2.0 Reporting Form.

    PubMed

    2017-07-14

    The Vaccine Adverse Event Reporting System (VAERS), co-managed by CDC and the Food and Drug Administration (FDA), is the national postmarketing safety monitoring system that accepts reports about adverse events that occur after administration of U.S.-licensed vaccines (1,2). On June 30, 2017, CDC and FDA implemented a revised reporting form and a new process for submitting reports to VAERS. Persons reporting adverse events are now able to use the VAERS 2.0 online reporting tool to submit reports directly online; alternatively, they may download and complete the writable and savable VAERS 2.0 form and submit it using an electronic document upload feature.

  11. Programmable display of DNA-protein chimeras for controlling cell-hydrogel interactions via reversible intermolecular hybridization.

    PubMed

    Zhang, Zhaoyang; Li, Shihui; Chen, Niancao; Yang, Cheng; Wang, Yong

    2013-04-08

    Extensive studies have been recently carried out to achieve dynamic control of cell-material interactions primarily through physicochemical stimulation. The purpose of this study was to apply reversible intermolecular hybridization to program cell-hydrogel interactions in physiological conditions based on DNA-antibody chimeras and complementary oligonucleotides. The results showed that DNA oligonucleotides could be captured to and released from the immobilizing DNA-functionalized hydrogels with high specificity via DNA hybridization. Accordingly, DNA-antibody chimeras were captured to the hydrogels, successfully inducing specific cell attachment. The cell attachment to the hydrogels reached the plateau at approximately half an hour after the functionalized hydrogels and the cells were incubated together. The attached cells were rapidly released from the bound hydrogels when triggering complementary oligonucleotides were introduced to the system. However, the capability of the triggering complementary oligonucleotides in releasing cells was affected by the length of intermolecular hybridization. The length needed to be at least more than 20 base pairs in the current experimental setting. Notably, because the procedure of intermolecular hybridization did not involve any harsh condition, the released cells maintained the same viability as that of the cultured cells. The functionalized hydrogels also exhibited the potential to catch and release cells repeatedly. Therefore, this study demonstrates that it is promising to regulate cell-material interactions dynamically through the DNA-programmed display of DNA-protein chimeras.

  12. Ground test bed design for self-forming network in disaggregated satellites system

    NASA Astrophysics Data System (ADS)

    Liu, Pengfei; Yang, Lei; Chen, Xiaoqian

    2016-02-01

    Disaggregated spacecraft architecture arouses an increasing attention in the realm of distributed space systems in recent years. One of the main technical challenges for disaggregated spacecraft system is self-forming network, in which new satellite nodes are allowed to join in a 'plug-and-play' fashion. To facilitate the protocol design for self-forming network, high-fidelity simulation tools are required. To that end, with the aid of OPNET Modeler's co-simulation mechanism provided by the external system (Esys) module, a ground test bed solution for self-forming network in disaggregated satellites system is presented, and then tested in a self-forming network scenario during the ingress process of a new-added satellite module. Simulation results show that this test bed can support for the evaluation of network performance, as well as mobility modeling which enables reflecting both the effects of orbital dynamic behaviors and in-orbit maneuver or control efforts. Though this test bed is mainly developed for the purpose of further study in disaggregated satellites system, its architecture can also be extended to other satellite network applications.

  13. Document recognition and XML generation of tabular form discharge summaries for analogous case search system.

    PubMed

    Kawanaka, H; Sumida, T; Yamamoto, K; Shinogi, T; Tsuruoka, S

    2007-01-01

    This paper discusses and develops a document image recognition, keyword extraction and automatic XML generation system to search analogous cases from paper-based documents. In this paper, we propose the document structure recognition method and automatic XML generation method for the tabular form discharge summary documents. This paper also develops the prototype system using the proposed method. Evaluation experiments using actual documents are done to discuss the effectiveness of the developed system. The developed system consists of the following methods. Paper-based summary documents are scanned by a scanner using 300 dpi first. Noise and tilt of the image are reduced by pre-processing, and the table structures are identified. Characters in the table are recognized and converted to text data by the OCR engine. XML documents are automatically generated using obtained results. In this paper, patient discharge summary documents archived at Mie University Hospital were used. The results show that XML documents can be automatically generated when standard tabular form documents are input into the developed system. In this experiment, it takes about 20 seconds to generate an XML document using the general personal computer. This paper also compares the developed system with a commercial product to discuss the effectiveness of the present system. Experimental results also show that the accuracy of table structure recognition is high and it can be used in a practical situation. This paper showed the effectiveness of the proposed method to recognize the tabular form document images to generate XML documents.

  14. Externally controlled anisotropy in pattern-forming reaction-diffusion systems

    NASA Astrophysics Data System (ADS)

    Escala, Dario M.; Guiu-Souto, Jacobo; Muñuzuri, Alberto P.

    2015-06-01

    The effect of centrifugal forces is analyzed in a pattern-forming reaction-diffusion system. Numerical simulations conducted on the appropriate extension of the Oregonator model for the Belousov-Zhabotinsky reaction show a great variety of dynamical behaviors in such a system. In general, the system exhibits an anisotropy that results in new types of patterns or in a global displacement of the previous one. We consider the effect of both constant and periodically modulated centrifugal forces on the different types of patterns that the system may exhibit. A detailed analysis of the patterns and behaviors observed for the different parameter values considered is presented here.

  15. [Systemic production of cytokines and growth factors in various forms of syndrome of delayed fetal growth].

    PubMed

    Makarenko, M V

    2014-11-01

    The syndrome of delayed fetal growth (SDFG) is one of the most wide-spread pathological conditions while course of pregnancy; it is characterized by disorder of the feto-placental system function. Its incidence is from 3 to 8%. The studying of peculiarities of the system and local immune disorders, coinciding with SDFG, would permit to establish the immune mechanisms of its formation. Revealing of immunoregulation disorders on systemic and local levels would promote the creation of a concept, depicting participation of the immune system in formation of asymmetrical and symmetrical forms of SDFG, to elaborate new approaches for prognosis and diagnosis.

  16. Intermolecular forces and energies between ligands and receptors.

    PubMed

    Moy, V T; Florin, E L; Gaub, H E

    1994-10-14

    The recognition mechanisms and dissociation pathways of the avidin-biotin complex and of actin monomers in actin filaments were investigated. The unbinding forces of discrete complexes of avidin or streptavidin with biotin analogs are proportional to the enthalpy change of the complex formation but independent of changes in the free energy. This result indicates that the unbinding process is adiabatic and that entropic changes occur after unbinding. On the basis of the measured forces and binding energies, an effective rupture length of 9.5 +/- 1 angstroms was calculated for all biotin-avidin pairs and approximately 1 to 3 angstroms for the actin monomer-monomer interaction. A model for the correlation among binding forces, intermolecular potential, and molecular function is proposed.

  17. Transetherification on Polyols by Intra- and Intermolecular Nucleophilic Substitutions

    PubMed Central

    Muraoka, Takahiro; Adachi, Kota; Chowdhury, Rainy; Kinbara, Kazushi

    2014-01-01

    Transetherification on polyols involving intra- and intermolecular nucleophilic substitutions is reported. Di- or trialkoxide formation of propane-1,3-diol or 2-(hydroxymethyl)propane-1,3-diol derivatives by NaH triggers the reaction via oxetanes formation, where the order to add NaH and a polyol significantly influences the yields of products. It was demonstrated that the protective group on the pentaerythritol skeleton is apparently transferred to the hydrophilic and hydrophobic chain molecules bearing a leaving group in one-step, and a protective group conversion from tosyl to benzyl was successful using a benzyl-appending triol to afford a desired product in 67% yield. PMID:24663293

  18. An assay for intermolecular exchange of alpha crystallin

    NASA Technical Reports Server (NTRS)

    Gopalakrishnan, S.; Takemoto, L.; Spooner, B. S. (Principal Investigator)

    1992-01-01

    An affinity column of alpha crystallin linked to cyanogen bromide-activated Sepharose was developed to study the exchange of alpha subunits. Alpha crystallin bound to the Sepharose-alpha complex was dissociated with 8 mol/l urea, followed by quantitation using high-performance reverse-phase liquid chromatography. The time course of binding at 37 degrees C showed a hyperbolic binding pattern reaching equilibrium between 6-18 hr. Under these conditions, binding of beta and gamma crystallins to the same matrix was less than 10% of the alpha values, as was binding of alpha to glycine-coupled Sepharose. This assay was used to demonstrate changes in the subunit exchange of alpha crystallins present in high molecular weight versus lower molecular weight aggregates of the human lens. These results show that this binding procedure was a specific reproducible assay that might be used to study intermolecular interactions of the alpha crystallins.

  19. An assay for intermolecular exchange of alpha crystallin

    NASA Technical Reports Server (NTRS)

    Gopalakrishnan, S.; Takemoto, L.; Spooner, B. S. (Principal Investigator)

    1992-01-01

    An affinity column of alpha crystallin linked to cyanogen bromide-activated Sepharose was developed to study the exchange of alpha subunits. Alpha crystallin bound to the Sepharose-alpha complex was dissociated with 8 mol/l urea, followed by quantitation using high-performance reverse-phase liquid chromatography. The time course of binding at 37 degrees C showed a hyperbolic binding pattern reaching equilibrium between 6-18 hr. Under these conditions, binding of beta and gamma crystallins to the same matrix was less than 10% of the alpha values, as was binding of alpha to glycine-coupled Sepharose. This assay was used to demonstrate changes in the subunit exchange of alpha crystallins present in high molecular weight versus lower molecular weight aggregates of the human lens. These results show that this binding procedure was a specific reproducible assay that might be used to study intermolecular interactions of the alpha crystallins.

  20. Intermolecular vibrational energy transfers in liquids and solids.

    PubMed

    Chen, Hailong; Wen, Xiewen; Guo, Xunmin; Zheng, Junrong

    2014-07-21

    Resonant and nonresonant intermolecular vibrational energy transfers in KSCN/KSC(13)N/KS(13)C(15)N aqueous and DMF solutions and crystals are studied. Both energy-gap and temperature dependent measurements reveal some surprising results, e.g. inverted energy-gap dependent energy transfer rates and opposite temperature dependences of resonant and nonresonant energy transfer rates. Two competing mechanisms are proposed to be responsible for the experimental observations. The first one is the dephasing mechanism in which the measured energy transfer rate originates from the dephasing of the energy donor-acceptor coherence, and the second one is the phonon-compensation mechanism derived from the second order perturbation. It is found that both the nonresonant energy transfers in the liquids and resonant energy transfers in both liquids and solids can be well described by the first mechanism. The second mechanism explains the nonresonant energy transfers in one series of the solid samples very well.

  1. Multi-referenced excited states and intermolecular forces from the anti-Hermitian contracted Schrodinger equation

    NASA Astrophysics Data System (ADS)

    Sturm, Erica J.

    Strong correlation due to multi-referenced electronic states of quantum chemical systems are crucial for a proper understanding of important phenomena including excited states, bond breakage and formation, singlet fission and biological transport. By solving for the 2-electron reduced density matrix (2-RDM) directly via the anti-Hermitian contracted Schrodinger equation (ACSE) we provide a balanced treatment of single and multi-referenced correlation effects without utilizing the N-electron wave function. This significantly reduces the computational expense while still maintaining near full configuration interaction accuracy when available. When provided with an initial 2-RDM guess from an active-space multi-configuration self consistent field wave function the ACSE scales as [special characters omitted] where ra is the number of active molecular orbitals (MOs) and ra is the number of external MOs. This work demonstrates the energetic accuracy of ACSE calculations with several small multi-referenced systems and presents a novel approach for investigating intermolecular interactions, using a simple dimer test case. In this monomer-optimized basis set approach we compute each monomer's properties in isolation and obtain a set of natural orbitals that best describe the monomer. We then remove or truncate orbitals deemed excessive as a function of occupation number, defining a monomer molecular orbital basis uniquely suited to that monomer. Combining two such monomers yields a super-system expressed in the monomer basis which we then rotate to a dimer basis at a desired geometry before creating a new initial 2-RDM for the final optimization by an ACSE calculation. It is found that the intermolecular properties calculated in this fashion from larger atomic basis sets maintain their high accuracy but at a fraction of the computational cost. Furthermore this basis set optimization is free of basis set superposition error, circumventing the need for an expensive

  2. Testing electronic structure methods for describing intermolecular H...H interactions in supramolecular chemistry.

    PubMed

    Casadesús, Ricard; Moreno, Miquel; González-Lafont, Angels; Lluch, José M; Repasky, Matthew P

    2004-01-15

    In this article a wide variety of computational approaches (molecular mechanics force fields, semiempirical formalisms, and hybrid methods, namely ONIOM calculations) have been used to calculate the energy and geometry of the supramolecular system 2-(2'-hydroxyphenyl)-4-methyloxazole (HPMO) encapsulated in beta-cyclodextrin (beta-CD). The main objective of the present study has been to examine the performance of these computational methods when describing the short range H. H intermolecular interactions between guest (HPMO) and host (beta-CD) molecules. The analyzed molecular mechanics methods do not provide unphysical short H...H contacts, but it is obvious that their applicability to the study of supramolecular systems is rather limited. For the semiempirical methods, MNDO is found to generate more reliable geometries than AM1, PM3 and the two recently developed schemes PDDG/MNDO and PDDG/PM3. MNDO results only give one slightly short H...H distance, whereas the NDDO formalisms with modifications of the Core Repulsion Function (CRF) via Gaussians exhibit a large number of short to very short and unphysical H...H intermolecular distances. In contrast, the PM5 method, which is the successor to PM3, gives very promising results. Our ONIOM calculations indicate that the unphysical optimized geometries from PM3 are retained when this semiempirical method is used as the low level layer in a QM:QM formulation. On the other hand, ab initio methods involving good enough basis sets, at least for the high level layer in a hybrid ONIOM calculation, behave well, but they may be too expensive in practice for most supramolecular chemistry applications. Finally, the performance of the evaluated computational methods has also been tested by evaluating the energetic difference between the two most stable conformations of the host(beta-CD)-guest(HPMO) system.

  3. X-ray Intermolecular Structure Factor ( XISF ): separation of intra- and intermolecular interactions from total X-ray scattering data

    SciTech Connect

    Mou, Q.; Benmore, C. J.; Yarger, J. L.

    2015-05-09

    XISFis a MATLAB program developed to separate intermolecular structure factors from total X-ray scattering structure factors for molecular liquids and amorphous solids. The program is built on a trust-region-reflective optimization routine with the r.m.s. deviations of atoms physically constrained.XISFhas been optimized for performance and can separate intermolecular structure factors of complex molecules.

  4. Intermolecular potential energy surface for CS2 dimer.

    PubMed

    Farrokhpour, Hossein; Mombeini, Zainab; Namazian, Mansoor; Coote, Michelle L

    2011-04-15

    A new four-dimensional intermolecular potential energy surface for CS(2) dimer is obtained by ab initio calculation of the interaction energies for a range of configurations and center-of-mass separation distances for the first time. The calculations were performed using the supermolecular approach at the Møller-Plesset second-order perturbation (MP2) level of theory with the augmented correlation consistent basis sets (aug-cc-pVxZ, x = D, T) and corrected for the basis-set superposition error using the full counterpoise correction method. A two-point extrapolation method was used to extrapolate the calculated energy points to the complete basis set limit. The effect of using the higher levels of theory, quadratic configuration interaction containing single, double, and perturbative triple excitations QCISD(T) and coupled cluster singles, doubles and perturbative triples excitations CCSD(T), on the shape of potential energy surface was investigated. It is shown that the MP2 level of theory apparently performs extremely poorly for describing the intermolecular potential energy surface, overestimating the total energy by a factor of nearly 1.73 in comparison with the QCISD(T) and CCSD(T) values. The value of isotropic dipole-dipole dispersion coefficient (C(6) ) of CS(2) fluid was obtained from the extrapolated MP2 potential energy surface. The MP2 extrapolated energy points were fitted to well-known analytical potential functions using two different methods to represent the potential energy surface analytically. The most stable configuration of the dimer was determined at R = 6.23 au, α = 90°, β = 90°, and γ = 90°, with a well depth of 3.980 kcal mol(-1) at the MP2 level of theory. Finally, the calculated second virial coefficients were compared with experimental values to test the quality of the presented potential energy surface. Copyright © 2010 Wiley Periodicals, Inc.

  5. A new form measurement system based on subaperture stitching with a line-scanning interferometer

    NASA Astrophysics Data System (ADS)

    Laubach, Sören; Ehret, Gerd; Riebeling, Jörg; Lehmann, Peter

    2016-12-01

    A new optical form measurement system for almost rotational symmetric surfaces has been set up. It is based on an interferometric line sensor applying sinusoidal path length modulation in combination with a movement system. With this system, ring-shaped subapertures of the specimens are measured. The system is especially suitable for measuring spheres and aspheres with a broad range of radii (r>50 mm). The individual subapertures are stitched together to yield the full 3D topography. Because the rotation of the specimen by more than 360° has to yield the same results, inherent consistency tests are possible. Example measurements of a sphere are shown and discussed. Reproducibility measurements for one ring scan performed with the system show a standard deviation of 14 nm. The system can be set up at a moderate price as off-the-shelf mechanical and optoelectronic devices can be used. Future improvements of the system are discussed.

  6. Formulation and evaluation of an in situ gel forming system for controlled delivery of triptorelin acetate.

    PubMed

    Abashzadeh, Sh; Dinarvand, R; Sharifzadeh, M; Hassanzadeh, G; Amini, M; Atyabi, F

    2011-11-20

    The novel physical hydrogels composed of chitosan or its water soluble derivatives such as carboxymethyl chitosan (CMCh) and sodium carboxymethyl chitosan (NaCMCh) and opened ring polyvinyl pyrrolidone (OP-PVP) were used as a controlled delivery system for triptorelin acetate, a luteinizing-releasing hormone agonist. The in situ gel forming system designed according to physical interactions such as chains entanglements and hydrophilic attractions especially h-bonds of chitosan and/or NaCMCh and OR-PVP. In order to increase in situ gel forming rate the chitosan microspheres prepared through spray drying technique. The chitosan or NaCMCh/OR-PVP blends prepared at different ratios (0.05, 0.10, 0.12, 0.16, 0.20 and 0.24) and suspended in sesame oil as non-aqueous vehicle at different solid content (10-30%). The suitable ratio of polymers with faster in situ gel forming rate was selected for in vivo studies. The gel formation and drug release from the system was evaluated both in vitro and in vivo. In vitro and in vivo results were compared with Diphereline SR 3.75mg, a commercially available controlled delivery system of triptorelin. In vitro release studies showed a sustained release profile for about 192h with first order kinetics. In vivo studies on male rats by determination of serum testosterone were confirmed the acceptable performance of in situ gel forming system compared with Diphereline SR in decreasing the serum testosterone level for 35days, demonstrating the potential of the novel in situ gel forming system for controlled delivery of peptides. Copyright © 2011 Elsevier B.V. All rights reserved.

  7. Thermodynamic analysis of glass-forming ability in a Ca-Mg-Zn ternary alloy system

    SciTech Connect

    Gorsse, S.; Orveillon, G.; Senkov, O. N.; Miracle, D. B.

    2006-06-01

    A thermodynamic analysis of the onset driving force for crystallization of super-cooled liquid has been conducted to explain strong composition dependency of the glass forming ability in the Ca-Mg-Zn ternary alloy system observed experimentally. In addition to the onset driving force, other energetic and kinetic factors are discussed to explain the observed glass stabilities. The universality of this method is discussed, thus establishing an analytic approach for determining the most stable glass in a given alloy system.

  8. Arginine-phosphate salt bridges between histones and DNA: intermolecular actuators that control nucleosome architecture.

    PubMed

    Yusufaly, Tahir I; Li, Yun; Singh, Gautam; Olson, Wilma K

    2014-10-28

    Structural bioinformatics and van der Waals density functional theory are combined to investigate the mechanochemical impact of a major class of histone-DNA interactions, namely, the formation of salt bridges between arginine residues in histones and phosphate groups on the DNA backbone. Principal component analysis reveals that the configurational fluctuations of the sugar-phosphate backbone display sequence-specific directionality and variability, and clustering of nucleosome crystal structures identifies two major salt-bridge configurations: a monodentate form in which the arginine end-group guanidinium only forms one hydrogen bond with the phosphate, and a bidentate form in which it forms two. Density functional theory calculations highlight that the combination of sequence, denticity, and salt-bridge positioning enables the histones to apply a tunable mechanochemical stress to the DNA via precise and specific activation of backbone deformations. The results suggest that selection for specific placements of van der Waals contacts, with high-precision control of the spatial distribution of intermolecular forces, may serve as an underlying evolutionary design principle for the structure and function of nucleosomes, a conjecture that is corroborated by previous experimental studies.

  9. Arginine-phosphate salt bridges between histones and DNA: Intermolecular actuators that control nucleosome architecture

    NASA Astrophysics Data System (ADS)

    Yusufaly, Tahir I.; Li, Yun; Singh, Gautam; Olson, Wilma K.

    2014-10-01

    Structural bioinformatics and van der Waals density functional theory are combined to investigate the mechanochemical impact of a major class of histone-DNA interactions, namely, the formation of salt bridges between arginine residues in histones and phosphate groups on the DNA backbone. Principal component analysis reveals that the configurational fluctuations of the sugar-phosphate backbone display sequence-specific directionality and variability, and clustering of nucleosome crystal structures identifies two major salt-bridge configurations: a monodentate form in which the arginine end-group guanidinium only forms one hydrogen bond with the phosphate, and a bidentate form in which it forms two. Density functional theory calculations highlight that the combination of sequence, denticity, and salt-bridge positioning enables the histones to apply a tunable mechanochemical stress to the DNA via precise and specific activation of backbone deformations. The results suggest that selection for specific placements of van der Waals contacts, with high-precision control of the spatial distribution of intermolecular forces, may serve as an underlying evolutionary design principle for the structure and function of nucleosomes, a conjecture that is corroborated by previous experimental studies.

  10. Self-formed cavity quantum electrodynamics in coupled dipole cylindrical-waveguide systems.

    PubMed

    Afshar V, S; Henderson, M R; Greentree, A D; Gibson, B C; Monro, T M

    2014-05-05

    An ideal optical cavity operates by confining light in all three dimensions. We show that a cylindrical waveguide can provide the longitudinal confinement required to form a two dimensional cavity, described here as a self-formed cavity, by locating a dipole, directed along the waveguide, on the interface of the waveguide. The cavity resonance modes lead to peaks in the radiation of the dipole-waveguide system that have no contribution due to the skew rays that exist in longitudinally invariant waveguides and reduce their Q-factor. Using a theoretical model, we evaluate the Q-factor and modal volume of the cavity formed by a dipole-cylindrical-waveguide system and show that such a cavity allows access to both the strong and weak coupling regimes of cavity quantum electrodynamics.

  11. Correlation techniques to determine model form in robust nonlinear system realization/identification

    NASA Technical Reports Server (NTRS)

    Stry, Greselda I.; Mook, D. Joseph

    1991-01-01

    The fundamental challenge in identification of nonlinear dynamic systems is determining the appropriate form of the model. A robust technique is presented which essentially eliminates this problem for many applications. The technique is based on the Minimum Model Error (MME) optimal estimation approach. A detailed literature review is included in which fundamental differences between the current approach and previous work is described. The most significant feature is the ability to identify nonlinear dynamic systems without prior assumption regarding the form of the nonlinearities, in contrast to existing nonlinear identification approaches which usually require detailed assumptions of the nonlinearities. Model form is determined via statistical correlation of the MME optimal state estimates with the MME optimal model error estimates. The example illustrations indicate that the method is robust with respect to prior ignorance of the model, and with respect to measurement noise, measurement frequency, and measurement record length.

  12. Selecting a response form for nonverbal persons: Facilitated communication, pointing systems, or sign language?

    PubMed Central

    Sundberg, Mark L.

    1993-01-01

    The three major types of augmentative communication for nonverbal persons consist of writing (or typing), pointing, and signing. These alternative response forms are examined in terms of their advantages and disadvantages for establishing effective verbal behavior. In addition, these systems are examined using the concepts from Skinner's (1957) analysis of verbal behavior (i.e., mand, tact, intraverbal, and autoclitic). The results of this analysis show that sign language has the most advantages and the fewest disadvantages, and more closely parallels speech in terms of the verbal operants. Although, the current trend is to favor facilitated communication (typing) and pointing systems, both of these response forms have several disadvantages that impede the development of the verbal operants. It is suggested that for many nonverbal individuals sign language is a better alternative response form, and has a better chance of improving speech. PMID:22477084

  13. Factor structure of the BASC-2 Behavioral and Emotional Screening System Student Form.

    PubMed

    Dowdy, Erin; Twyford, Jennifer M; Chin, Jenna K; DiStefano, Christine A; Kamphaus, Randy W; Mays, Kristen L

    2011-06-01

    The BASC-2 Behavioral and Emotional Screening System (BESS) Student Form (Kamphaus & Reynolds, 2007) is a recently developed youth self-report rating scale designed to identify students at risk for behavioral and emotional problems. The BESS Student Form was derived from the Behavior Assessment System for Children-Second Edition Self-Report of Personality (BASC-2 SRP; Reynolds & Kamphaus, 2004) using principal component analytic procedures and theoretical considerations. Using 3 samples, the authors conducted exploratory factor analyses (EFA) and confirmatory factor analyses (CFA) to understand the underlying factor structure of the BESS Student Form. The results of the EFA suggested that the SRP contained a 4-factor (i.e., Personal Adjustment, Inattention/Hyperactivity, Internalizing, School Problems) emergent structure, which was supported by CFA in 2 additional samples. Practical and research implications are discussed.

  14. Second law considerations in Fourier heat conduction of a lattice chain in relation to intermolecular potentials

    NASA Astrophysics Data System (ADS)

    Jesudason, Christopher G.

    2017-01-01

    Two aspects of conductive heat are focused here (i) the nature of conductive heat, defined as that form of energy that is transferred as a result of a temperature difference and (ii) the nature of the intermolecular potentials that induces both thermal energy flow and the temperature profile at the steady state for a 1-D lattice chain. It is found that the standard presuppositions of people like Benofy and Quay (BQ) following Joseph Fourier do not obtain for at least a certain specified regime of intermolecular potential parameters related to harmonic (quadratic) potentials for nearest neighbor interactions. For these harmonic potentials, it appears from the simulation results that steady state solutions exist utilizing non-synthetic thermostats that couple not just the two particles at the extreme ends of the lattice chain, but to a control volume of N particles located at either ends of the chain that does not accord with the unique analytical solutions that obtains for single particle thermostatting at the ends of the lattice with a different thermostatting algorithm that utilizes coupling coefficients. If the method used here is considered a more "realistic" or feasible model of the physical reality, then a re-evaluation of some aspects of the standard theoretical methodology is warranted since the standard model solution profile does not accord with the simulation temperature profile determined here for this related model. We also note that the sinusoidal temperature profile generated suggests that thermal integrated circuits with several thermal P-N junctions may be constructed, opening a way to create more complex thermal transistor circuits. A stationary principle is proposed for regions that violate the Fourier principle Jq.∇T ≤ 0, where Jq is the heat current vector and T the temperature.

  15. 77 FR 65898 - Agency Information Collection Activities: InfoPass System, No Form Number; Extension, Without...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-10-31

    ... SECURITY U.S. Citizenship and Immigration Services Agency Information Collection Activities: InfoPass...: Extension, Without Change, of a Currently Approved Collection. (2) Title of the Form/Collection: InfoPass... as a brief abstract: Primary: Individuals or households. The InfoPass system allows an applicant...

  16. Modeling Multiple Human-Automation Distributed Systems using Network-form Games

    NASA Technical Reports Server (NTRS)

    Brat, Guillaume

    2012-01-01

    The paper describes at a high-level the network-form game framework (based on Bayes net and game theory), which can be used to model and analyze safety issues in large, distributed, mixed human-automation systems such as NextGen.

  17. Waste vitrification: prediction of acceptable compositions in a lime-soda-silica glass-forming system

    SciTech Connect

    Gilliam, T.M.; Jantzen, C.M.

    1996-10-01

    A model is presented based upon calculated bridging oxygens which allows the prediction of the region of acceptable glass compositions for a lime-soda-silica glass-forming system containing mixed waste. The model can be used to guide glass formulation studies (e.g., treatability studies) or assess the applicability of vitrification to candidate waste streams.

  18. Forms of Mediation: The Case of Interpreter-Mediated Interactions in Medical Systems

    ERIC Educational Resources Information Center

    Baraldi, Claudio

    2009-01-01

    This paper analyses the forms of mediation in interlinguistic interactions performed in Italian healthcare services and in contexts of migration. The literature encourages dialogic transformative mediation, empowering participants' voices and changing cultural presuppositions in social systems. It may be doubtful, however, whether mediation can…

  19. Using Form and Function Analogy Object Boxes to Teach Human Body Systems

    ERIC Educational Resources Information Center

    Rule, Audrey C.; Furletti, Charles

    2004-01-01

    This study compares the use of form and function analogy object boxes to more traditional lecture and worksheet instruction during a 10th-grade unit on human body systems. The study was conducted with two classes (N = 32) of mixed ability students at a high-needs rural high school in central New York State. The study used a pretest/posttest…

  20. A program to form a multidisciplinary data base and analysis for dynamic systems

    NASA Technical Reports Server (NTRS)

    Taylor, L. W.; Suit, W. T.; Mayo, M. H.

    1984-01-01

    Diverse sets of experimental data and analysis programs have been assembled for the purpose of facilitating research in systems identification, parameter estimation and state estimation techniques. The data base analysis programs are organized to make it easy to compare alternative approaches. Additional data and alternative forms of analysis will be included as they become available.

  1. Using Form and Function Analogy Object Boxes to Teach Human Body Systems

    ERIC Educational Resources Information Center

    Rule, Audrey C.; Furletti, Charles

    2004-01-01

    This study compares the use of form and function analogy object boxes to more traditional lecture and worksheet instruction during a 10th-grade unit on human body systems. The study was conducted with two classes (N = 32) of mixed ability students at a high-needs rural high school in central New York State. The study used a pretest/posttest…

  2. Intermolecularly-induced conformational disorder in ferrocene, 1-bromoferrocene and 1,1‧-dibromoferrocene

    NASA Astrophysics Data System (ADS)

    Silva, Patrícia A.; Maria, Teresa M. R.; Nunes, Cláudio M.; Eusébio, Maria Ermelinda S.; Fausto, Rui

    2014-12-01

    Conformational preferences for isolated molecules of ferrocene, 1-bromoferrocene and 1,1‧-dibromoferrocene were obtained by combined use of matrix-isolation infrared spectroscopy and quantum chemical calculations. Monomeric ferrocene and 1-dibromoferrocene were found to exist in a low temperature argon matrix (T = 15 K) exclusively in the eclipsed configuration, which corresponds to their most stable conformation in gas phase. On the other hand, for the neat compounds in crystalline phase, intermolecular interactions induce conformational disorder, leading to presence in the room temperature polymorphic forms of monomeric units with the staggered (or nearly staggered) conformation. 1,1‧-Dibromoferrocene exists in both gas phase and low temperature argon matrix in two conformers of C2 symmetry (C2-I and C2-II), with eclipsed cyclopentadienyl moieties and Br atoms opposed to H atoms. The populations of the two conformers trapped in the as-deposited matrix were found to correspond to those estimated from theory for the room temperature equilibrium gas phase. By increasing the temperature of the matrix (up to 35 K), the gas phase lower energy form (C2-I) converted to the C2-II form. Besides allowing the precise structural and spectroscopic characterization of the two forms, these studies also revealed that the C2-II conformer (having a largest dipole moment) is stabilized in the matrix media, thus becoming more stable than the C2-I form under these conditions. Very interestingly, the room temperature stable polymorph of the compound (Tfus = 325.4 ± 0.1 K) is composed by 1,1‧-dibromoferrocene units exhibiting the C2v symmetry eclipsed conformation with opposed bromine atoms, which for the isolated molecule corresponds to the highest energy conformation along the ring torsional coordinate and is the transition state structure between the two symmetry equivalent C2-II minima. Differential scanning calorimetry, polarized light thermomicroscopy and infrared

  3. Meeting the Challenge of Intermolecular Gold(I)-Catalyzed Cycloadditions of Alkynes and Allenes

    PubMed Central

    Muratore, Michael E; Homs, Anna; Obradors, Carla; Echavarren, Antonio M

    2014-01-01

    The development of gold(I)-catalyzed intermolecular carbo- and hetero-cycloadditions of alkynes and allenes has been more challenging than their intramolecular counterparts. Here we review, with a mechanistic perspective, the most fundamental intermolecular cycloadditions of alkynes and allenes with alkenes. PMID:25048645

  4. The use of intermolecular potential functions in fitting pressure induced spectra

    NASA Technical Reports Server (NTRS)

    Goorvitch, D.; Silvaggio, P. M.; Boese, R. W.

    1981-01-01

    An example is presented which demonstrates the importance of using physically realistic derivatives of the intermolecular potential when fitting pressure-induced spectra. The use of nonrealistic derivatives may mask second-order temperature effects in the theory. As the temperature decreases, the intermolecular potential may have an important angular dependence.

  5. Quantifying intra- and intermolecular phenomena: challenging yet exciting territory for quantum chemistry.

    PubMed

    Corminboeuf, Clémence

    2014-01-01

    van der Waals interactions occur in all molecules and intermolecular complexes but are poorly described by the most widely used electronic structure framework. This paper addresses the efforts pursued in our laboratory to improve the performance of standard density functional approximations and deliver modern strategies to analyze and fine-tune the underlying physics of intra- and intermolecular interactions.

  6. Problem-Based Learning in 9th Grade Chemistry Class: "Intermolecular Forces"

    ERIC Educational Resources Information Center

    Tarhan, Leman; Ayar-Kayali, Hulya; Urek, Raziye Ozturk; Acar, Burcin

    2008-01-01

    This research study aims to examine the effectiveness of a problem-based learning (PBL) on 9th grade students' understanding of intermolecular forces (dipole-dipole forces, London dispersion forces and hydrogen bonding). The student's alternate conceptions about intermolecular bonding and their beliefs about PBL were also measured. Seventy-eight…

  7. Problem-Based Learning in 9th Grade Chemistry Class: "Intermolecular Forces"

    ERIC Educational Resources Information Center

    Tarhan, Leman; Ayar-Kayali, Hulya; Urek, Raziye Ozturk; Acar, Burcin

    2008-01-01

    This research study aims to examine the effectiveness of a problem-based learning (PBL) on 9th grade students' understanding of intermolecular forces (dipole-dipole forces, London dispersion forces and hydrogen bonding). The student's alternate conceptions about intermolecular bonding and their beliefs about PBL were also measured. Seventy-eight…

  8. Crystal structures and intermolecular interactions of two novel antioxidant triazolyl-benzimidazole compounds

    SciTech Connect

    Karayel, A. E-mail: yccaoh@hotmail.com; Özbey, S.; Ayhan-Kılcıgil, G.; Kuş, C.

    2015-12-15

    The crystal structures of 5-(2-(p-chlorophenylbenzimidazol-1-yl-methyl)-4-(3-fluorophenyl)-2, 4-dihydro-[1,2,4]-triazole-3-thione (G6C) and 5-(2-(p-chlorophenylbenzimidazol-1-yl-methyl)-4-(2-methylphenyl)-2, 4-dihydro-[1,2,4]-triazole-3-thione (G4C) have been determined by single-crystal X-ray diffraction. Benzimidazole ring systems in both molecules are planar. The triazole part is almost perpendicular to the phenyl and the benzimidazole parts of the molecules in order to avoid steric interactions between the rings. The crystal structures are stabilized by intermolecular hydrogen bonds between the amino group of the triazole and the nitrogen atom of benzimidazole of a neighboring molecule.

  9. Intermolecular forces in bovine serum albumin solutions exhibiting solidlike mechanical behaviors.

    PubMed

    Ikeda, S; Nishinari, K

    2000-01-01

    Mechanical properties of bovine serum albumin (BSA) solutions were analyzed to gain information on intermolecular forces that stabilize the system under normal physiological conditions. BSA solutions showed unexpectedly large zero shear viscosity values under steady shear flows but responded like solids to sinusoidal linear strains: the storage shear moduli were always larger than the loss shear moduli in the frequency range 1-100 rad/s. These results suggest that BSA solutions are so-called colloidal crystals in which colloidal particles are ordered in an array due to strong repulsive forces among particles. However, the pair potential between BSA molecules predicted based on the conventional Derjaguin-Landau-Verwey-Overbeek theory failed to explain these remarkable mechanical properties of BSA solutions. Additional repulsive forces other than electrostatic must be introduced to explain stability of BSA aqueous dispersions.

  10. Crystal structures and intermolecular interactions of two novel antioxidant triazolyl-benzimidazole compounds

    NASA Astrophysics Data System (ADS)

    Karayel, A.; Özbey, S.; Ayhan-Kılcıgil, G.; Kuş, C.

    2015-12-01

    The crystal structures of 5-(2-( p-chlorophenylbenzimidazol-1-yl-methyl)-4-(3-fluorophenyl)-2,4-dihydro-[1,2,4]-triazole-3-thione (G6C) and 5-(2-( p-chlorophenylbenzimidazol-1-yl-methyl)-4-(2-methylphenyl)-2,4-dihydro-[1,2,4]-triazole-3-thione (G4C) have been determined by single-crystal X-ray diffraction. Benzimidazole ring systems in both molecules are planar. The triazole part is almost perpendicular to the phenyl and the benzimidazole parts of the molecules in order to avoid steric interactions between the rings. The crystal structures are stabilized by intermolecular hydrogen bonds between the amino group of the triazole and the nitrogen atom of benzimidazole of a neighboring molecule.

  11. Graphene-enhanced intermolecular interaction at interface between copper- and cobalt-phthalocyanines

    SciTech Connect

    Dou, Wei-Dong; Huang, Shu-Ping; Lee, Chun-Sing

    2015-10-07

    Interfacial electronic structures of copper-phthalocyanine (CuPc), cobalt-phthalocyanine (CoPc), and graphene were investigated experimentally by using photoelectron spectroscopy. While the CuPc/graphene interface shows flat band structure and negligible interfacial dipole indicating quite weak molecule-substrate interaction, the CuPc/CoPc/graphene interface shows a large interfacial dipole and obvious energy level bending. Controlled experiments ruled out possible influences from the change in film structure of CuPc and pure π–π interaction between CoPc and CuPc. Analysis based on X-ray photoelectron spectroscopy and density functional theory reveals that the decrease in the work function for the CuPc/CoPc/graphene system is induced by the intermolecular interaction between CuPc and CoPc which is enhanced owning to the peculiar electronic properties at the CoPc-graphene interface.

  12. Graphene-enhanced intermolecular interaction at interface between copper- and cobalt-phthalocyanines.

    PubMed

    Dou, Wei-Dong; Huang, Shu-Ping; Lee, Chun-Sing

    2015-10-07

    Interfacial electronic structures of copper-phthalocyanine (CuPc), cobalt-phthalocyanine (CoPc), and graphene were investigated experimentally by using photoelectron spectroscopy. While the CuPc/graphene interface shows flat band structure and negligible interfacial dipole indicating quite weak molecule-substrate interaction, the CuPc/CoPc/graphene interface shows a large interfacial dipole and obvious energy level bending. Controlled experiments ruled out possible influences from the change in film structure of CuPc and pure π-π interaction between CoPc and CuPc. Analysis based on X-ray photoelectron spectroscopy and density functional theory reveals that the decrease in the work function for the CuPc/CoPc/graphene system is induced by the intermolecular interaction between CuPc and CoPc which is enhanced owning to the peculiar electronic properties at the CoPc-graphene interface.

  13. Density Analysis of Intra- and Intermolecular Vibronic Couplings toward Bath Engineering for Singlet Fission.

    PubMed

    Ito, Soichi; Nagami, Takanori; Nakano, Masayoshi

    2015-12-17

    Vibronic coupling plays a crucial role in singlet fission whereby a singlet exciton splits into two triplet excitons. In order to reveal the physicochemical origin of the vibronic coupling associated with singlet fission as well as to clarify its relationship with chemical structure, we evaluate relevant vibronic couplings from the viewpoint of their spatial contributions described by vibronic coupling density. From the analysis using a model tetracene dimer, a typical singlet fission system, the frequency dependence of vibronic couplings in each electronic state is found to be significantly different from that of another depending on the nature of the electronic structure (intra/intermolecular excitation) and the related vibrational motion. These findings contribute not only to the fundamental understanding of the singlet fission mechanism from the viewpoint of vibronic couplings but also to opening a new path to designing highly efficient singlet fission materials through phonon-bath engineering.

  14. Rh-Catalyzed Intermolecular Reactions of α-Alkyl-α-Diazo Carbonyl Compounds with Selectivity over β-Hydride Migration

    PubMed Central

    DeAngelis, Andrew; Panish, Robert; Fox, Joseph M.

    2016-01-01

    CONSPECTUS Rh-carbenes derived from α-diazocarbonyl compounds have found broad utility across a remarkable range of reactivity, including cyclopropanation, cyclopropenation, C–H insertions, heteroatom–H insertions, and ylide forming reactions. However, in contrast to α-aryl or α-vinyl-α-diazocarbonyl compounds, the utility of α-alkyl-α-diazocarbonyl compounds had been moderated by the propensity of such compounds to undergo intramolecular β-hydride migration to give alkene products. Especially challenging had been intermolecular reactions involving α-alkyl-α-diazocarbonyl compounds. PMID:26689221

  15. Noncovalent intermolecular interactions between dehydroepiandrosterone and the active site of human dehydroepiandrosterone sulphotransferase: A density functional theory based treatment

    NASA Astrophysics Data System (ADS)

    Astani, Elahe; Heshmati, Emran; Chen, Chun-Jung; Hadipour, Nasser L.; Shekarsaraei, Setareh

    2016-04-01

    A theoretical study was performed to characterize noncovalent intermolecular interactions, especially hydrogen bond (HB), in the active site of enzyme human dehydroepiandrosterone sulphotransferase (SULT2A1/DHEA) using the local (M06-L) and hybrid (M06, M06-2X) meta-GGA functionals of density functional theory (DFT). Results revealed that DHEA is able to form HBs with residues His99, Tyr231, Met137 and Met16 in the active site of the SULT2A1/DHEA. It was found that DHEA interacts with the other residues through electrostatic and Van der Waals interactions.

  16. Importance of the donor:fullerene intermolecular arrangement for high-efficiency organic photovoltaics.

    PubMed

    Graham, Kenneth R; Cabanetos, Clement; Jahnke, Justin P; Idso, Matthew N; El Labban, Abdulrahman; Ngongang Ndjawa, Guy O; Heumueller, Thomas; Vandewal, Koen; Salleo, Alberto; Chmelka, Bradley F; Amassian, Aram; Beaujuge, Pierre M; McGehee, Michael D

    2014-07-09

    The performance of organic photovoltaic (OPV) material systems are hypothesized to depend strongly on the intermolecular arrangements at the donor:fullerene interfaces. A review of some of the most efficient polymers utilized in polymer:fullerene PV devices, combined with an analysis of reported polymer donor materials wherein the same conjugated backbone was used with varying alkyl substituents, supports this hypothesis. Specifically, the literature shows that higher-performing donor-acceptor type polymers generally have acceptor moieties that are sterically accessible for interactions with the fullerene derivative, whereas the corresponding donor moieties tend to have branched alkyl substituents that sterically hinder interactions with the fullerene. To further explore the idea that the most beneficial polymer:fullerene arrangement involves the fullerene docking with the acceptor moiety, a family of benzo[1,2-b:4,5-b']dithiophene-thieno[3,4-c]pyrrole-4,6-dione polymers (PBDTTPD derivatives) was synthesized and tested in a variety of PV device types with vastly different aggregation states of the polymer. In agreement with our hypothesis, the PBDTTPD derivative with a more sterically accessible acceptor moiety and a more sterically hindered donor moiety shows the highest performance in bulk-heterojunction, bilayer, and low-polymer concentration PV devices where fullerene derivatives serve as the electron-accepting materials. Furthermore, external quantum efficiency measurements of the charge-transfer state and solid-state two-dimensional (2D) (13)C{(1)H} heteronuclear correlation (HETCOR) NMR analyses support that a specific polymer:fullerene arrangement is present for the highest performing PBDTTPD derivative, in which the fullerene is in closer proximity to the acceptor moiety of the polymer. This work demonstrates that the polymer:fullerene arrangement and resulting intermolecular interactions may be key factors in determining the performance of OPV material

  17. Molecular simulation of fluids with non-identical intermolecular potentials: Thermodynamic properties of 10-5 + 12-6 Mie potential binary mixtures

    NASA Astrophysics Data System (ADS)

    Stiegler, Thomas; Sadus, Richard J.

    2015-02-01

    General methods for combining interactions between particles characterised by non-identical intermolecular potentials are investigated. The combination methods are tested by performing molecular dynamics simulations to determine the pressure, energy, isochoric and isobaric heat capacities, thermal expansion coefficient, isothermal compressibility, Joule-Thomson coefficient, and speed of sound of 10-5 + 12-6 Mie potential binary mixtures. In addition to the two non-identical Mie potentials, mixtures are also studied with non-identical intermolecular parameters. The combination methods are compared with results obtained by simply averaging the Mie exponents. When either the energy or size parameters are non-identical, very significant differences emerge in the thermodynamic properties predicted by the alternative combination methods. The isobaric heat capacity is the thermodynamic property that is most affected by the relative magnitude of the intermolecular potential parameters and the method for combining non-identical potentials. Either the arithmetic or geometric combination of potentials provides a simple and effective way of performing simulations involving mixtures of components characterised by non-identical intermolecular potentials, which is independent of their functional form.

  18. Molecular simulation of fluids with non-identical intermolecular potentials: thermodynamic properties of 10-5 + 12-6 Mie potential binary mixtures.

    PubMed

    Stiegler, Thomas; Sadus, Richard J

    2015-02-28

    General methods for combining interactions between particles characterised by non-identical intermolecular potentials are investigated. The combination methods are tested by performing molecular dynamics simulations to determine the pressure, energy, isochoric and isobaric heat capacities, thermal expansion coefficient, isothermal compressibility, Joule-Thomson coefficient, and speed of sound of 10-5 + 12-6 Mie potential binary mixtures. In addition to the two non-identical Mie potentials, mixtures are also studied with non-identical intermolecular parameters. The combination methods are compared with results obtained by simply averaging the Mie exponents. When either the energy or size parameters are non-identical, very significant differences emerge in the thermodynamic properties predicted by the alternative combination methods. The isobaric heat capacity is the thermodynamic property that is most affected by the relative magnitude of the intermolecular potential parameters and the method for combining non-identical potentials. Either the arithmetic or geometric combination of potentials provides a simple and effective way of performing simulations involving mixtures of components characterised by non-identical intermolecular potentials, which is independent of their functional form.

  19. Molecular simulation of fluids with non-identical intermolecular potentials: Thermodynamic properties of 10-5 + 12-6 Mie potential binary mixtures

    SciTech Connect

    Stiegler, Thomas; Sadus, Richard J.

    2015-02-28

    General methods for combining interactions between particles characterised by non-identical intermolecular potentials are investigated. The combination methods are tested by performing molecular dynamics simulations to determine the pressure, energy, isochoric and isobaric heat capacities, thermal expansion coefficient, isothermal compressibility, Joule-Thomson coefficient, and speed of sound of 10-5 + 12-6 Mie potential binary mixtures. In addition to the two non-identical Mie potentials, mixtures are also studied with non-identical intermolecular parameters. The combination methods are compared with results obtained by simply averaging the Mie exponents. When either the energy or size parameters are non-identical, very significant differences emerge in the thermodynamic properties predicted by the alternative combination methods. The isobaric heat capacity is the thermodynamic property that is most affected by the relative magnitude of the intermolecular potential parameters and the method for combining non-identical potentials. Either the arithmetic or geometric combination of potentials provides a simple and effective way of performing simulations involving mixtures of components characterised by non-identical intermolecular potentials, which is independent of their functional form.

  20. Expression, purification and characterization of inactive and active forms of ERK2 from insect expression system.

    PubMed

    Yan, Kelly; Merritt, Hanne; Crawford, Kenneth; Pardee, Gwynn; Cheng, Jan Marie; Widger, Stephania; Hekmat-Nejad, Mohammad; Zaror, Isabel; Sim, Janet

    2015-06-01

    Extracellular signal-regulated kinase 2 (ERK2) is a serine/threonine protein kinase involved in many cellular programs, such as cell proliferation, differentiation, motility and programed cell-death. It is therefore considered an important target in the treatment of cancer. In an effort to support biochemical screening and small molecule drug discovery, we established a robust system to generate both inactive and active forms of ERK2 using insect expression system. We report here, for the first time, that inactive ERK2 can be expressed and purified with 100% homogeneity in the unphosphorylated form using insect system. This resulted in a significant 20-fold yield improvement compared to that previously reported using bacterial expression system. We also report a newly developed system to generate active ERK2 in insect cells through in vivo co-expression with a constitutively active MEK1 (S218D S222D). Isolated active ERK2 was confirmed to be doubly phosphorylated at the correct sites, T185 and Y187, in the activation loop of ERK2. Both ERK2 forms, inactive and active, were well characterized by biochemical activity assay for their kinase function. Inactive and active ERK2 were the two key reagents that enabled successful high through-put biochemical assay screen and structural drug discovery studies.

  1. Evidence for production of oxidizing radicals by the particulate O-2-forming system from human neutrophils.

    PubMed

    Tauber, A I; Gabig, T G; Babior, B M

    1979-04-01

    The particulate O-2-forming system from human neutrophils was found to oxidize methional and 2-keto-4-methylthiobutyric acid (KMB) to ethylene, indicating the formation by this system of strongly oxidizing radicals. Conforming this interpretation was the observation that ethylene production was inhibited by the radical scavengers benzoate, ethanol, and mannitol. Ethylene production was also sharply reduced by superoxide dismutase, implicatin O-2 as a precursor of oxidizing radicals. In our system catalase only partially inhibited ethylene generation from either methional or KMB, suggesting that oxidizing radicals are generated at least in part by the reacton of O-2 with compounds other than H2O2. We propose that in neutrophils oxidizing radicals are formed in a reaction between O-2 and a peroxide according to the following equation: O-2 + ROOH leads to RO . + OH- + O2, in which ROOH may be hydrogen peroxide, an alkyl peroxide, or an acyl peroxide (i.e., a peroxy acid).

  2. Early Campanian coastal progradational systems and their coal-forming environments, Wyoming to New Mexico

    SciTech Connect

    Marley, W.E.; Flores, R.M.; Ethridge, F.G.; Cavaroc, V.V.

    1985-05-01

    Ammonite zones (Baculites obtusus-Scaphites hippocrepis) in the marine facies associated with the Mesaverde Formation in the Bighorn basin, Wyoming, Star Point Sandstone and Blackhawk Formation in the Wasatch Plateau, Utah, and the Point Lookout Sandstone, Menefee Formation, and Crevasse Canyon Formation in the Gallup coalfield, New Mexico, indicate that these formations were deposited during early Campanian time (80-84 Ma). The coal-forming environments of these early Campanian formations were located landward of wave-reworked coastal sand complexes of progradational systems along the western margin of the Cretaceous seaway from Wyoming to New Mexico. The Mesaverde coals accumulated in swamps of the lower delta plain and coeval interdeltaic strandplain environments. The Star Point-Blackhawk coals accumulated in swamps of the lower delta plains of laterally shifting, prograding deltas and associated barrier ridge plains. The Point Lookout, Menefee, and Crevasse canyon coals formed in swamps of the lower delta plain and infilled lagoons behind barrier islands. Although the common coal-forming environments of these progradational systems are back barrier and delta plain, the former setting was the more conducive for accumulation of thick, laterally extensive coals. Economic coal deposits formed in swamps built on abandoned back-barrier platforms that were free of detrital influx and marine influence. Delta-plain coals tend to be lenticular and laterally discontinuous and thus uneconomic. The early Campanian coal-forming coastal-plain environments are analogous to modern peat-forming environments along the coast of Belize, Central America. Deltaic sediments deposited along the Belize coast by short-headed streams are reworked by waves into coastal barrier systems.

  3. Selenoprotein K form an intermolecular diselenide bond with unusually high redox potential.

    PubMed

    Liu, Jun; Zhang, Zhengqi; Rozovsky, Sharon

    2014-09-17

    Selenoprotein K (SelK) is a membrane protein involved in antioxidant defense, calcium regulation and the ER-associated protein degradation pathway. We found that SelK exhibits a peroxidase activity with a rate that is low but within the range of other peroxidases. Notably, SelK reduced hydrophobic substrates, such as phospholipid hydroperoxides, which damage membranes. Thus, SelK might be involved in membrane repair or related pathways. SelK was also found to contain a diselenide bond-the first intramolecular bond of that kind reported for a selenoprotein. The redox potential of SelK was -257 mV, significantly higher than that of diselenide bonds in small molecules or proteins. Consequently, SelK can be reduced by thioredoxin reductase. These finding are essential for understanding SelK activity and function. Copyright © 2014 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.

  4. GT1_vgeers_1: Tracing Remnant Gas in Planet Forming Debris Disk Systems

    NASA Astrophysics Data System (ADS)

    Geers, V.

    2010-03-01

    Recent studies of gas emission lines with Spitzer and sub-millimeter telescopes have shown that 10-100 Myr old stars with debris disks have too little gas left to form Jupiter like gas giant planets. Whether enough gas remains in these systems to form ice giant planets is still unanswered. The [OI] emission line at 63 micron is one of the most sensitive tracers of gas mass in the ice-giant region of 10-50 AU in disks, and Herschel PACS is therefore uniquely suited to trace the remnant gas in planet-forming disks. We propose to obtain PACS line spectroscopy of [OI] (63 micron) for two nearby young stars, HR 8799 and HD 15115, which are two systems with detected giant planets or signs of planet formation, while still harbouring prominent debris disks that could be in the process of forming ice giants such as Neptune and Uranus. The proposed observations will probe down to gas masses of 0.01 Earth masses, and allow us to constrain prospects for ice giant formation, measure gas-to-dust ratios in evolved disks to compare with planet formation / disk evolution models, and put constraints on whether the dust dynamics in these systems is driven by the remnant gas or by the radiation. Note: this proposal is submitted under the Swiss part of the HIFI Guaranteed Time program; HIFI PI: Frank Helmich, HIFI Swiss Lead CoI: Arnold Benz.

  5. Glass transition in binary eutectic systems: best glass-forming composition.

    PubMed

    Wang, Li-Min; Li, Zijing; Chen, Zeming; Zhao, Yue; Liu, Riping; Tian, Yongjun

    2010-09-23

    The glass transition and glass-forming ability in a binary eutectic system of methyl o-toluate (MOT) versus methyl p-toluate (MPT) are studied across the whole composition range. The phase diagram is constructed to explore the best glass-forming composition as the characteristic temperatures of the glass transition, crystallization, eutectic, and liquidus are determined. The best vitrification region is found to locate between the eutectic and the midpoint compositions of the eutectic line, indicating a remarkable deviation from the eutectic composition. The compilation of various simple binary eutectic systems covering inorganic, metallic, ionic, and molecular glass-forming liquids reproduces the rule. Kinetics and thermodynamics in binary systems are investigated to associate with the rule. The composition dependence of the structural relaxation time and the kinetic fragility are presented with dielectric measurements. It is found that whereas mixing of binary miscible liquids kinetically favors glass formation, thermodynamic contribution to the deviation of the best glass-forming composition from eutectics is implied.

  6. Piecewise smooth dynamical systems: Persistence of periodic solutions and normal forms

    NASA Astrophysics Data System (ADS)

    Gouveia, Márcio R. A.; Llibre, Jaume; Novaes, Douglas D.; Pessoa, Claudio

    2016-04-01

    We consider an n-dimensional piecewise smooth vector field with two zones separated by a hyperplane Σ which admits an invariant hyperplane Ω transversal to Σ containing a period annulus A fulfilled by crossing periodic solutions. For small discontinuous perturbations of these systems we develop a Melnikov-like function to control the persistence of periodic solutions contained in A. When n = 3 we provide normal forms for the piecewise linear case. Finally we apply the Melnikov-like function to study discontinuous perturbations of the given normal forms.

  7. Rh-Catalyzed Intermolecular Reactions of α-Alkyl-α-Diazo Carbonyl Compounds with Selectivity over β-Hydride Migration.

    PubMed

    DeAngelis, Andrew; Panish, Robert; Fox, Joseph M

    2016-01-19

    Rh-carbenes derived from α-diazocarbonyl compounds have found broad utility across a remarkable range of reactivity, including cyclopropanation, cyclopropenation, C-H insertions, heteroatom-hydrogen insertions, and ylide forming reactions. However, in contrast to α-aryl or α-vinyl-α-diazocarbonyl compounds, the utility of α-alkyl-α-diazocarbonyl compounds had been moderated by the propensity of such compounds to undergo intramolecular β-hydride migration to give alkene products. Especially challenging had been intermolecular reactions involving α-alkyl-α-diazocarbonyl compounds. This Account discusses the historical context and prior limitations of Rh-catalyzed reactions involving α-alkyl-α-diazocarbonyl compounds. Early studies demonstrated that ligand and temperature effects could influence chemoselectivity over β-hydride migration. However, effects were modest and conflicting conclusions had been drawn about the influence of sterically demanding ligands on β-hydride migration. More recent advances have led to a more detailed understanding of the reaction conditions that can promote intermolecular reactivity in preference to β-hydride migration. In particular, the use of bulky carboxylate ligands and low reaction temperatures have been key to enabling intermolecular cyclopropenation, cyclopropanation, carbonyl ylide formation/dipolar cycloaddition, indole C-H functionalization, and intramolecular bicyclobutanation with high chemoselectivity over β-hydride migration. Cyclic α-diazocarbonyl compounds have been shown to be particularly resilient toward β-hydride migration and are the first class of compounds that can engage in intermolecular reactivity in the presence of tertiary β-hydrogens. DFT calculations were used to propose that for cyclic α-diazocarbonyl compounds, ring constraints relieve steric interaction for intermolecular reactions and thereby accelerate the rate of intermolecular reactivity relative to intramolecular

  8. High pressure rheology of gas hydrate formed from multiphase systems using modified Couette rheometer

    NASA Astrophysics Data System (ADS)

    Pandey, Gaurav; Linga, Praveen; Sangwai, Jitendra S.

    2017-02-01

    Conventional rheometers with concentric cylinder geometries do not enhance mixing in situ and thus are not suitable for rheological studies of multiphase systems under high pressure such as gas hydrates. In this study, we demonstrate the use of modified Couette concentric cylinder geometries for high pressure rheological studies during the formation and dissociation of methane hydrate formed from pure water and water-decane systems. Conventional concentric cylinder Couette geometry did not produce any hydrates in situ and thus failed to measure rheological properties during hydrate formation. The modified Couette geometries proposed in this work observed to provide enhanced mixing in situ, thus forming gas hydrate from the gas-water-decane system. This study also nullifies the use of separate external high pressure cell for such measurements. The modified geometry was observed to measure gas hydrate viscosity from an initial condition of 0.001 Pa s to about 25 Pa s. The proposed geometries also possess the capability to measure dynamic viscoelastic properties of hydrate slurries at the end of experiments. The modified geometries could also capture and mimic the viscosity profile during the hydrate dissociation as reported in the literature. The present study acts as a precursor for enhancing our understanding on the rheology of gas hydrate formed from various systems containing promoters and inhibitors in the context of flow assurance.

  9. Economic consequences of aviation system disruptions: A reduced-form computable general equilibrium analysis

    SciTech Connect

    Chen, Zhenhua; Rose, Adam Z.; Prager, Fynnwin; Chatterjee, Samrat

    2017-01-01

    The state of the art approach to economic consequence analysis (ECA) is computable general equilibrium (CGE) modeling. However, such models contain thousands of equations and cannot readily be incorporated into computerized systems used by policy analysts to yield estimates of economic impacts of various types of transportation system failures due to natural hazards, human related attacks or technological accidents. This paper presents a reduced-form approach to simplify the analytical content of CGE models to make them more transparent and enhance their utilization potential. The reduced-form CGE analysis is conducted by first running simulations one hundred times, varying key parameters, such as magnitude of the initial shock, duration, location, remediation, and resilience, according to a Latin Hypercube sampling procedure. Statistical analysis is then applied to the “synthetic data” results in the form of both ordinary least squares and quantile regression. The analysis yields linear equations that are incorporated into a computerized system and utilized along with Monte Carlo simulation methods for propagating uncertainties in economic consequences. Although our demonstration and discussion focuses on aviation system disruptions caused by terrorist attacks, the approach can be applied to a broad range of threat scenarios.

  10. Enhancement of oxygen transfer efficiency in diffused aeration systems using liquid-film-forming apparatus.

    PubMed

    Zhu, H; Imai, T; Tani, K; Ukita, M; Sekine, M; Higuchi, T; Zhang, Z J

    2007-05-01

    Surface transfer and bubble transfer both contribute significantly to oxygen transfer in a diffused aeration system. In the present study, liquid-film-forming apparatus is successfully developed on a laboratory scale to improve considerably the surface transfer via the unique liquid film transfer technique. The experimental results show that the volumetric mass transfer coefficient for liquid-film-forming apparatus alone is found to be as much as 5.3 times higher than that for water surface and that the total volumetric mass transfer coefficient for liquid film aeration system increases by 37 % in comparison with conventional aeration system. Additionally, by tuning finely the structural parameters of the liquid-film-forming apparatus, it can also lead to high dissolved oxygen water with the dissolved oxygen percent saturation greater than 90 %. More importantly, this result is accomplished by simply offering a single-pass aeration at the depth as shallow as 26 cm. As a result, the objective of economical energy consumption in diffused aeration systems can be realized by lowering the aeration depth without sacrificing the aeration efficiency.

  11. High pressure rheology of gas hydrate formed from multiphase systems using modified Couette rheometer.

    PubMed

    Pandey, Gaurav; Linga, Praveen; Sangwai, Jitendra S

    2017-02-01

    Conventional rheometers with concentric cylinder geometries do not enhance mixing in situ and thus are not suitable for rheological studies of multiphase systems under high pressure such as gas hydrates. In this study, we demonstrate the use of modified Couette concentric cylinder geometries for high pressure rheological studies during the formation and dissociation of methane hydrate formed from pure water and water-decane systems. Conventional concentric cylinder Couette geometry did not produce any hydrates in situ and thus failed to measure rheological properties during hydrate formation. The modified Couette geometries proposed in this work observed to provide enhanced mixing in situ, thus forming gas hydrate from the gas-water-decane system. This study also nullifies the use of separate external high pressure cell for such measurements. The modified geometry was observed to measure gas hydrate viscosity from an initial condition of 0.001 Pa s to about 25 Pa s. The proposed geometries also possess the capability to measure dynamic viscoelastic properties of hydrate slurries at the end of experiments. The modified geometries could also capture and mimic the viscosity profile during the hydrate dissociation as reported in the literature. The present study acts as a precursor for enhancing our understanding on the rheology of gas hydrate formed from various systems containing promoters and inhibitors in the context of flow assurance.

  12. Hidden role of intermolecular proton transfer in the anomalously diffuse vibrational spectrum of a trapped hydronium ion.

    PubMed

    Craig, Stephanie M; Menges, Fabian S; Duong, Chinh H; Denton, Joanna K; Madison, Lindsey R; McCoy, Anne B; Johnson, Mark A

    2017-06-13

    We report the vibrational spectra of the hydronium and methyl-ammonium ions captured in the C3v binding pocket of the 18-crown-6 ether ionophore. Although the NH stretching bands of the CH3NH3(+) ion are consistent with harmonic expectations, the OH stretching bands of H3O(+) are surprisingly broad, appearing as a diffuse background absorption with little intensity modulation over 800 cm(-1) with an onset ∼400 cm(-1) below the harmonic prediction. This structure persists even when only a single OH group is present in the HD2O(+) isotopologue, while the OD stretching region displays a regular progression involving a soft mode at about 85 cm(-1) These results are rationalized in a vibrationally adiabatic (VA) model in which the motion of the H3O(+) ion in the crown pocket is strongly coupled with its OH stretches. In this picture, H3O(+) resides in the center of the crown in the vibrational zero-point level, while the minima in the VA potentials associated with the excited OH vibrational states are shifted away from the symmetrical configuration displayed by the ground state. Infrared excitation between these strongly H/D isotope-dependent VA potentials then accounts for most of the broadening in the OH stretching manifold. Specifically, low-frequency motions involving concerted motions of the crown scaffold and the H3O(+) ion are driven by a Franck-Condon-like mechanism. In essence, vibrational spectroscopy of these systems can be viewed from the perspective of photochemical interconversion between transient, isomeric forms of the complexes corresponding to the initial stage of intermolecular proton transfer.

  13. Potential mesogens based on pyridine derivatives: The geometric structure, conformational properties and characteristics of intermolecular hydrogen bonds

    NASA Astrophysics Data System (ADS)

    Fedorov, Mikhail S.; Giricheva, Nina I.; Shpilevaya, Kseniya E.; Lapykina, Elena A.; Syrbu, Svetlana A.

    2017-03-01

    Conformational properties of the main part (excluding sbnd OC3H7 radicals) of the p-n-propyloxybenzoic (A1) and p-n-propyloxycinnamic (A2) acids molecules (relating to mesomorphic compounds) as well as p-n-propyloxybenzoic acid pyridine ester (B1) and p-n-propyloxyphenylazopyridine (B2) molecules (relating to non-mesomorphic compounds) were studied by DFT(B3LYP)/cc-pVTZ method. It was shown that the main parts of A1 and A2 acids are rigid. The barrier to internal rotation of pyridine fragment in the B1 and B2 molecules depends on the nature of the bridging group. It was determined that all studied A1⋯B1, A2⋯B1 and A2⋯B2 complexes are characterized by a strong hydrogen bond. The binding energy of complexes (≈14 kcal/mol, with BSSE corrections, DFT(B97D)/6-311++G**) exceeds the energy per hydrogen bond in the corresponding acid dimers (≈10 kcal/mol). The structural non-rigidity of A⋯B complexes is mainly caused by possibility of sbnd OC3H7 radicals internal rotation and A and B molecules rotation about the (H)O⋯N line. The characteristics of intermolecular hydrogen bonds were determined by NBO-analysis. The obtained results indicate that examined complexes correspond to the basic requirements to mesogen molecular forms. The thermodynamic functions of the gas-phase complexation reactions (idealized model of the complexes formation in the condensed state) were calculated. Preliminary studies of mesogen-non-mesogen A1⋯B2 system by differential scanning calorimetry and polarizing optical microscopy, showed that it has mesomorphic properties.

  14. Control of nonlinear systems represented in quasilinear form. Ph.D. Thesis, 1994 Final Report

    NASA Technical Reports Server (NTRS)

    Coetsee, Josef A.

    1993-01-01

    Methods to synthesize controllers for nonlinear systems are developed by exploiting the fact that under mild differentiability conditions, systems of the form: x-dot = f(x) + G(x)u can be represented in quasilinear form, viz: x-dot = A(x)x + B(x)u. Two classes of control methods are investigated. The first is zero-look-ahead control, where the control input depends only on the current values of A(x) and B(x). For this case the control input is computed by continuously solving a matrix Riccati equation as the system progresses along a trajectory. The second is controllers with look-ahead, where the control input depends on the future behavior of A(x) and B(x). These controllers use the similarity between quasilinear systems and linear time varying systems to find approximate solutions to optimal control type problems. The methods that are developed are not guaranteed to be globally stable. However in simulation studies they were found to be useful alternatives for synthesizing control laws for a general class of nonlinear systems.

  15. Two-dimensional infrared spectroscopy of intermolecular hydrogen bonds in the condensed phase.

    PubMed

    Elsaesser, Thomas

    2009-09-15

    Hydrogen bonding plays a key role in the structural, physical, and chemical properties of liquids such as water and in macromolecular structures such as proteins. Vibrational spectroscopy is an important tool for understanding hydrogen bonding because it provides a way to observe local molecular geometries and their interaction with the environment. Linear vibrational spectroscopy has mapped characteristic changes of vibrational spectra and the occurrence of new bands that form upon hydrogen bonding. However, linear vibrational spectroscopy gives very limited insight into ultrafast dynamics of the underlying molecular interactions, such as the motions of hydrogen-bonded groups, energy dissipation and delocalization, and the fluctuations within hydrogen-bonded structures that occur in the ultrafast time domain. Nonlinear vibrational spectroscopy with its femtosecond time resolution can discern these dynamic processes in real time and has emerged as an important tool for unraveling molecular dynamics and for quantifying interactions that govern the vibrational and structural dynamics of hydrogen bonds. This Account reviews recent progress originating from third-order nonlinear methods of coherent multidimensional vibrational spectroscopy. Ultrafast dynamics of intermolecular hydrogen bonds are addressed for a number of prototype systems: hydrogen-bonded carboxylic acid dimers in an aprotic liquid environment, the disordered fluctuating hydrogen-bond network of liquid water, and DNA oligomers interacting with water. Cyclic carboxylic acid dimers display a rich scheme of vibrational couplings, resulting in OH stretching absorption bands with highly complex spectral envelopes. Two-dimensional spectroscopy of acetic acid dimers in a nonpolar liquid environment demonstrates that multiple Fermi resonances of the OH stretching mode with overtones and combination tones of fingerprint vibrations dominate both the 2D and linear absorption spectra. The coupling of the OH

  16. Closed-form solutions of performability. [modeling of a degradable buffer/multiprocessor system

    NASA Technical Reports Server (NTRS)

    Meyer, J. F.

    1981-01-01

    Methods which yield closed form performability solutions for continuous valued variables are developed. The models are similar to those employed in performance modeling (i.e., Markovian queueing models) but are extended so as to account for variations in structure due to faults. In particular, the modeling of a degradable buffer/multiprocessor system is considered whose performance Y is the (normalized) average throughput rate realized during a bounded interval of time. To avoid known difficulties associated with exact transient solutions, an approximate decomposition of the model is employed permitting certain submodels to be solved in equilibrium. These solutions are then incorporated in a model with fewer transient states and by solving the latter, a closed form solution of the system's performability is obtained. In conclusion, some applications of this solution are discussed and illustrated, including an example of design optimization.

  17. An expert system for ensuring the reliability of the technological process of cold sheet metal forming

    NASA Astrophysics Data System (ADS)

    Kashapova, L. R.; Pankratov, D. L.; Utyaganov, P. P.

    2016-06-01

    In order to exclude periodic defects in the parts manufacturing obtained by cold sheet metal forming a method of automated estimation of technological process reliability was developed. The technique is based on the analysis of reliability factors: detail construction, material, mechanical and physical requirements; hardware settings, tool characteristics, etc. In the work the expert system is presented based on a statistical accumulation of the knowledge of the operator (technologist) and decisions of control algorithms.

  18. 15N Fractionation in Star-Forming Regions and Solar System Objects

    NASA Technical Reports Server (NTRS)

    Wirstrom, Eva; Milam, Stefanie; Adande, GIlles; Charnley, Steven; Cordiner, Martin

    2015-01-01

    A central issue for understanding the formation and evolution of matter in the early Solar System is the relationship between the chemical composition of star-forming interstellar clouds and that of primitive Solar System materials. The pristinemolecular content of comets, interplanetary dust particles and carbonaceous chondrites show significant bulk nitrogen isotopic fractionation relative to the solar value, 14N15N 440. In addition, high spatial resolution measurements in primitive materials locally show even more extreme enhancements of 14N15N 100.

  19. Practical output tracking of switched nonlinear systems in p-normal form with unstable subsystems

    NASA Astrophysics Data System (ADS)

    Long, Lijun; Zhao, Jun

    2016-08-01

    This paper studies practical output tracking of switched nonlinear systems in p-normal form. No solvability of the practical output tracking problem for subsystems is required. A constructive scheme to solve the problem for a switched nonlinear system is set up by exploiting the single Lyapunov function method and the tool of adding a power integrator. Also, we design a proper switching law and construct state-feedback controllers of subsystems. A two inverted pendulums as a practical example, which cannot be handled by the existing approaches, illustrates our theoretical result.

  20. Optimal control of nonlinear continuous-time systems in strict-feedback form.

    PubMed

    Zargarzadeh, Hassan; Dierks, Travis; Jagannathan, Sarangapani

    2015-10-01

    This paper proposes a novel optimal tracking control scheme for nonlinear continuous-time systems in strict-feedback form with uncertain dynamics. The optimal tracking problem is transformed into an equivalent optimal regulation problem through a feedforward adaptive control input that is generated by modifying the standard backstepping technique. Subsequently, a neural network-based optimal control scheme is introduced to estimate the cost, or value function, over an infinite horizon for the resulting nonlinear continuous-time systems in affine form when the internal dynamics are unknown. The estimated cost function is then used to obtain the optimal feedback control input; therefore, the overall optimal control input for the nonlinear continuous-time system in strict-feedback form includes the feedforward plus the optimal feedback terms. It is shown that the estimated cost function minimizes the Hamilton-Jacobi-Bellman estimation error in a forward-in-time manner without using any value or policy iterations. Finally, optimal output feedback control is introduced through the design of a suitable observer. Lyapunov theory is utilized to show the overall stability of the proposed schemes without requiring an initial admissible controller. Simulation examples are provided to validate the theoretical results.

  1. Student construction of differential length elements in multivariable coordinate systems: A symbolic forms analysis

    NASA Astrophysics Data System (ADS)

    Thompson, John; Schermerhorn, Benjamin

    2017-01-01

    Analysis of properties of physical quantities represented by vector fields often involves symmetries and spatial relationships best expressed in non-Cartesian coordinate systems. Many important quantities are determined by integrals that can involve multivariable vector differential quantities. Four pairs of students in junior-level Electricity and Magnetism (E&M) were interviewed to investigate their understanding of the structure of non-Cartesian coordinate systems and the associated differential elements. Pairs were asked to construct differential length elements for an unconventional spherical coordinate system. In order to explore how student conceptual understanding interacts with their understanding of the specific structures of these expressions, a symbolic forms framework was used. Analysis of student reasoning revealed both known and novel forms as well as the general progression of students--use and combination of symbol templates during the construction process. Each group invoked and combined symbolic forms in a similar sequence. Difficulties with the construction of expressions seem to be related almost exclusively to the conceptual schema (e.g., neglecting the role of projection) rather than with symbol templates. Supported in part by NSF Grant PHY-1405726.

  2. Still-Forming Solar System May Have Planets Orbiting Star in Opposite Directions, Astronomers Say

    NASA Astrophysics Data System (ADS)

    2006-02-01

    Astronomers studying a disk of material circling a still-forming star inside our Galaxy have found a tantalizing result -- the inner part of the disk is orbiting the protostar in the opposite direction from the outer part of the disk. Protostar Graphic Disk Around Young Star Rotating in Opposite Directions CREDIT: Bill Saxton, NRAO/AUI/NSF More Graphics "This is the first time anyone has seen anything like this, and it means that the process of forming planets from such disks is more complex than we previously expected," said Anthony Remijan, of the National Radio Astronomy Observatory, who with his colleague Jan M. Hollis, of the NASA Goddard Space Flight Center, used the National Science Foundation's Very Large Array radio telescope to make the discovery. "The solar system that likely will be formed around this star will include planets orbiting in different directions, unlike our own solar system in which all the planets orbit the Sun in the same direction," Hollis explained. Stars and planets, scientists believe, are formed when giant clouds of gas and dust collapse. As the cloud collapses, a flattened, rotating disk of material develops around the young star. This disk provides the material from which planets form. The disk and the resulting planets rotate in the same direction as the original cloud, with the rotation speed increasing closer to the center, much as a spinning figure skater spins faster when they draw their arms inward. If all the material in the star and disk come from the same prestellar cloud, they all will rotate in the same direction. That is the case with our own solar system, in which the planets all orbit the Sun in the same direction as the Sun itself rotates on its axis. In the case of a young star some 500 light-years from Earth in the direction of the constellation Ophiuchus, Remijan and Hollis found the inner and outer parts of the disk rotating in opposite directions. "We think this system may have gotten material from two clouds

  3. A IR Diode Laser Spectroscopic Study of Adsorption and Intermolecular Interactions on Stepped Metal Surfaces: Carbon Monoxide on Vicinal COPPER(100)

    NASA Astrophysics Data System (ADS)

    Borguet, Eric Urbain

    The kinetics of elementary surface processes, intermolecular interactions and stepped surfaces are intrinsic scientific interest, as well as being important to industrially relevant processes such as catalysis. A novel time-resolved surface sensitive technique, Transient Diode Laser Infrared Reflection-Absorption Spectroscopy, has been developed to investigate adsorption on stepped metal surfaces. The IR spectra display anomalous intensity behavior resulting in a minority step-CO species accounting for a disproportionate fraction of the spectral intensity. A model has been elaborated which successfully accounts for, and simulates, the observed spectra. This enables site specific concentrations to be determined, even in the presence of strong dynamic-dipole coupling. These methods allow the spectroscopy, kinetics and intermolecular interactions of CO on a stepped Cu(100) surface to be probed. In particular, it has been possible to observe a dynamic equilibrium between CO adsorbed at step and terrace sites and to investigate the kinetics of site exchange on this surface. The IR spectra also reveal the nature and range of the intermolecular interactions and the local order which results. The CO/Cu(100) system is characterized by repulsive first and second nearest neighbor interactions. As a consequence, the adsorbates adopt a configuration which maximizes the intermolecular distance. Additionally, a non-resonant, broadband, adsorbate induced change in surface reflectivity is observed both in the IR and visible. This linear dependence of this signal with coverage provides a simple method of determining total adsorbed CO concentration.

  4. An IR diode laser spectroscopic study of adsorption and intermolecular interactions on stepped metal surfaces: CO on vicinal Cu(100). [IR (infrared)

    SciTech Connect

    Borguet, E.R.

    1993-01-01

    The kinetics of elementary surface processes, intermolecular interactions and stepped surfaces are intrinsic scientific interest, as well as being important to industrially relevant processes such as catalysis. A novel time-resolved surface sensitive technique. Transient Diode Laser Infrared Reflection-Absorption Spectroscopy, has been developed to investigate adsorption on stepped metal surfaces. The IR spectra display anomalous intensity behavior resulting in a minority step-CO species accounting for a disporportionate fraction of the spectral intensity. A model has been elaborated which successfully accounts for, and simulates, the observed spectra. This enables site specific concentrations to be determined, even in the presence of strong dynamic-dipole coupling. These methods allow the spectroscopy, kinetics and intermolecular interactions of CO on a stepped Cu(100) surface to be probed. In particular, it has been possible to observe a dynamic equilibrium between CO adsorbed at step and terrace sites and to investigate the kinetics of site exchanges on this surface. The IR spectra also reveal the nature and range of the intermolecular interactions and the local order which results. The CO/Cu(100) system is characterized by repulsive first and second nearest neighbor interactions. As a consequence, the adsorbates adopt a configuration which maximizes the intermolecular distance. Additionally, a non-resonant, broadband, adsorbate induced change in surface reflectivity is observed both in the IR and visible. This linear dependence of this signal with coverage provides a simple method of determining total absorbed CO concentration.

  5. Phosphite-oxazole/imidazole ligands in asymmetric intermolecular Heck reaction.

    PubMed

    Mazuela, Javier; Tolstoy, Paivi; Pàmies, Oscar; Andersson, Pher G; Diéguez, Montserrat

    2011-02-07

    We describe the application of a new class of ligands--the phosphite-oxazole/imidazole (L1-L5a-g)--in asymmetric intermolecular Pd-catalyzed Heck reactions under thermal and microwave conditions. These ligands combine the advantages of the oxazole/imidazole moiety with those of the phosphite moiety: they are more stable than their oxazoline counterparts, less sensitive to air and other oxidizing agents than phosphines and phosphinites, and easy to synthesize from readily available alcohols. The results indicate that activities, regio- and enantioselectivities, are highly influenced by the type of nitrogen donor group (oxazole or imidazole), the oxazole and biaryl-phosphite substituents and the axial chirality of the biaryl moiety of the ligand. By carefully selecting the ligand components, we achieved high activities, regio- (up to 99%) and enantioselectivities (up to 99%) using several triflate sources. Under microwave-irradiation conditions, reaction times were considerably shorter (from 24 h to 30 min) and regio- and enantioselectivities were still excellent.

  6. Thermal selectivity of intermolecular versus intramolecular reactions on surfaces.

    PubMed

    Cirera, Borja; Giménez-Agulló, Nelson; Björk, Jonas; Martínez-Peña, Francisco; Martin-Jimenez, Alberto; Rodriguez-Fernandez, Jonathan; Pizarro, Ana M; Otero, Roberto; Gallego, José M; Ballester, Pablo; Galan-Mascaros, José R; Ecija, David

    2016-03-11

    On-surface synthesis is a promising strategy for engineering heteroatomic covalent nanoarchitectures with prospects in electronics, optoelectronics and photovoltaics. Here we report the thermal tunability of reaction pathways of a molecular precursor in order to select intramolecular versus intermolecular reactions, yielding monomeric or polymeric phthalocyanine derivatives, respectively. Deposition of tetra-aza-porphyrin species bearing ethyl termini on Au(111) held at room temperature results in a close-packed assembly. Upon annealing from room temperature to 275 °C, the molecular precursors undergo a series of covalent reactions via their ethyl termini, giving rise to phthalocyanine tapes. However, deposition of the tetra-aza-porphyrin derivatives on Au(111) held at 300 °C results in the formation and self-assembly of monomeric phthalocyanines. A systematic scanning tunnelling microscopy study of reaction intermediates, combined with density functional calculations, suggests a [2+2] cycloaddition as responsible for the initial linkage between molecular precursors, whereas the monomeric reaction is rationalized as an electrocyclic ring closure.

  7. Thermal selectivity of intermolecular versus intramolecular reactions on surfaces

    PubMed Central

    Cirera, Borja; Giménez-Agulló, Nelson; Björk, Jonas; Martínez-Peña, Francisco; Martin-Jimenez, Alberto; Rodriguez-Fernandez, Jonathan; Pizarro, Ana M.; Otero, Roberto; Gallego, José M.; Ballester, Pablo; Galan-Mascaros, José R.; Ecija, David

    2016-01-01

    On-surface synthesis is a promising strategy for engineering heteroatomic covalent nanoarchitectures with prospects in electronics, optoelectronics and photovoltaics. Here we report the thermal tunability of reaction pathways of a molecular precursor in order to select intramolecular versus intermolecular reactions, yielding monomeric or polymeric phthalocyanine derivatives, respectively. Deposition of tetra-aza-porphyrin species bearing ethyl termini on Au(111) held at room temperature results in a close-packed assembly. Upon annealing from room temperature to 275 °C, the molecular precursors undergo a series of covalent reactions via their ethyl termini, giving rise to phthalocyanine tapes. However, deposition of the tetra-aza-porphyrin derivatives on Au(111) held at 300 °C results in the formation and self-assembly of monomeric phthalocyanines. A systematic scanning tunnelling microscopy study of reaction intermediates, combined with density functional calculations, suggests a [2+2] cycloaddition as responsible for the initial linkage between molecular precursors, whereas the monomeric reaction is rationalized as an electrocyclic ring closure. PMID:26964764

  8. Intermolecular Structural Change for Thermo-Switchable Polymeric photosensitizer

    SciTech Connect

    Park, Wooram; Park, Sin-Jung; Cho, Soojeong; Shin, Heejun; Jung, Young-Seok; Lee, Byeongdu; Na, Kun; Kim, Dong-Hyun

    2016-08-31

    A switchable photosensitizer (PS), which can be activated at a spe-cific condition beside light, has tremendous advantages for photo-dynamic therapy (PDT). Herein, we developed a thermo-switchable polymeric photosensitizer (T-PPS) by conjugating PS (Pheophor-bide-a, PPb-a) to a temperature-responsive polymer backbone of biocompatible hydroxypropyl cellulose (HPC). Self-quenched PS molecules linked in close proximity by pi-pi stacking in T-PPS were easily transited to an active monomeric state by the tempera-ture induced phase transition of polymer backbones. The tempera-ture responsive inter-molecular interaction changes of PS molecules in T-PPS were demonstrated in synchrotron small-angle X-ray scattering (SAXS) and UV-Vis spectrophotometer analysis. The T-PPS allowed switchable activation and synergistically enhanced cancer cell killing effect at the hyperthermia temperature (45 °C). Our developed T-PPS has the considerable potential not only as a new class of photomedicine in clinics but also as a biosensor based on temperature responsiveness.

  9. Thermal selectivity of intermolecular versus intramolecular reactions on surfaces

    NASA Astrophysics Data System (ADS)

    Cirera, Borja; Giménez-Agulló, Nelson; Björk, Jonas; Martínez-Peña, Francisco; Martin-Jimenez, Alberto; Rodriguez-Fernandez, Jonathan; Pizarro, Ana M.; Otero, Roberto; Gallego, José M.; Ballester, Pablo; Galan-Mascaros, José R.; Ecija, David

    2016-03-01

    On-surface synthesis is a promising strategy for engineering heteroatomic covalent nanoarchitectures with prospects in electronics, optoelectronics and photovoltaics. Here we report the thermal tunability of reaction pathways of a molecular precursor in order to select intramolecular versus intermolecular reactions, yielding monomeric or polymeric phthalocyanine derivatives, respectively. Deposition of tetra-aza-porphyrin species bearing ethyl termini on Au(111) held at room temperature results in a close-packed assembly. Upon annealing from room temperature to 275 °C, the molecular precursors undergo a series of covalent reactions via their ethyl termini, giving rise to phthalocyanine tapes. However, deposition of the tetra-aza-porphyrin derivatives on Au(111) held at 300 °C results in the formation and self-assembly of monomeric phthalocyanines. A systematic scanning tunnelling microscopy study of reaction intermediates, combined with density functional calculations, suggests a [2+2] cycloaddition as responsible for the initial linkage between molecular precursors, whereas the monomeric reaction is rationalized as an electrocyclic ring closure.

  10. Noncovalent Intermolecular Forces in Phycobilisomes of Porphyridium cruentum.

    PubMed

    Zilinskas, B A; Glick, R E

    1981-08-01

    Using sensitized fluorescence as a measure of intactness of phycobilisomes isolated from Porphyridium cruentum, the effects of various environmental perturbations on phycobilisome integrity were investigated. The rate of phycobilisome dissociation in 0.75 ionic strength sodium salts proceeds in the order: SCN(-) > NO(3) (-) > Cl(-) > C(6)H(5)O(7) (3-) > SO(4) (2-) > PO(4) (3-), as predicted from the lyotropic series of anions and their effects on hydrophobic interactions in proteins. Similarly, increasing temperature (to 30 C) and pH values approaching the isoelectric points of the biliproteins stabilize phycobilisomes. Deuterium substitution at exchangeable sites on the phycobiliproteins decreases the rate of phycobilisome dissociation, while substitution at nonexchangeable sites increases rates of dissociation. It is concluded that hydrophobic intermolecular interactions are the most important forces in maintaining the phycobilisome structure. Dispersion forces also seem to contribute to phycobilisome stabilization. The adverse effects of electrostatic repulsion must not be ignored; however, it seems that the requirement of phycobilisomes of high salt concentrations is not simply countershielding of charges on the proteins.

  11. Metallicity gradients and newly created star-forming systems in interacting galaxies

    NASA Astrophysics Data System (ADS)

    Mendes de Oliveira, Claudia L.

    2015-08-01

    Interactions play an extremely important role in the evolution of galaxies, changing their morphologies and kinematics. Galaxy collisions may result in the formation of intergalactic star-forming objects, such as HII regions, young clusters and/or tidal dwarf galaxies. Several studies have found a wealth of newly created objects in interacting systems. We will exemplify the problems and challenges in this field and will describe observations of the interacting group NGC 6845, which contains four bright galaxies, two of which have extended tidal tails. We obtained Gemini/GMOS spectra for 28 of the regions located in the galaxies and in the tails. All regions in the latter are star-forming objects according to their line ratios, with ages younger than 10 Myr. A super luminous star forming complex is found in the brightest member of the group, NGC 6845A. Its luminosity reveals a star formation density of 0.19 solar masses, per year, per kpc^2, suggesting that this object is a localized starburst. We derived the gas-phase metallicity gradients across NGC 6845A and its two tails and we find that these are shallower than those for isolated galaxies. We speculate that the observed metallicity gradient may be related to one or more of the following mechanisms: (1) interaction induced inflow of fresh gas to the galaxy center, as seen in simulations, which is expected to dilute the metallicity of the central burst, (2) the formation of young metal-rich star forming regions in the tidal tails, which were born out of enriched gas expelled from the central regions of the system during the interaction and (3) the incremental growth of metals accumulated over time, due to the successful generations of star forming regions along the tails. Finally we will describe our plans to do a search for such objects on Halpha images that will soon be available for 17.5k degrees of the sky, with the A-PLUS survey.

  12. Composition-insensitive highly viscous wormlike micellar solutions formed in anionic and cationic surfactant systems.

    PubMed

    Aramaki, Kenji; Iemoto, Suzuka; Ikeda, Naoaki; Saito, Keitaro

    2010-01-01

    We investigated phase behavior and rheological properties of aqueous micellar phase formed in water/cocoyl glutamate neutralized with triethanol amine (CGT-n)/hexadecyl trimethylammonium salt (CTAB or CTAC) systems, where n is a degree of neutralization. Micellar phase appears in wide composition range with respect to the surfactant mixing fraction in ternary phase diagrams at 25 degrees C. At high mixing fraction of cationic surfactant in the water/CGT-n/CTAB systems, one can observe a highly viscous micellar phase in which worm-like micelles are expected to form. Contrary to conventional systems in which worm-like micelles are formed, the zero-shear viscosity of the micellar solution in the water/CGT-n/CTAB system with n=1.2 increases with the addition of cationic cosurfactant and once decreases after a maximum, then increases again and decreases after the second maximum. At n=1.5 and 2, highly viscous solution is observed in the relatively wide range of surfactant mixing fraction instead of two maxima of the viscosity curve observed at n=1.2. In the case of CTAC instead of CTAB we can observe narrow composition range for the maximum viscosity. Frequency sweep measurements were performed on the highly viscous samples in the water/CGT-1.5/CTAB system. Typical viscoelastic behavior of worm-like micellar solutions is observed; i.e. the curves of storage (G') and loss (G") moduli make a crossover and the data points of G' and G" can be fitted to the Maxwell model. Relaxation time against the mixing fraction of two surfactants behaves similarly to the zero-shear viscosity change, whereas the plateau modulus continuously increases in the plateau region for the zero-shear viscosity curve.

  13. A quantum chemical insight to intermolecular hydrogen bonding interaction between cytosine and nitrosamine: Structural and energetic investigations

    NASA Astrophysics Data System (ADS)

    Khalili, Behzad

    2016-03-01

    Hydrogen bond interactions which are formed during complex formation between cytosine and nitrosamine have been fully investigated using B3LYP, B3PW91 and MP2 methods in conjunction with various basis sets including 6-311++G (d,p), 6-311++G (2d,2p), 6-311++G (df,pd) and AUG-cc-pVDZ. Three regions around the most stable conformer of cytosine in the gas phase with six possible double H-bonded interactions were considered. Two intermolecular hydrogen bonds of type NC-N-HNA and O-H(N-H)C-ONA were found on the potential energy surface in a cyclic system with 8-member in CN1, CN3, CN5 and 7-member in CN2, CN4, CN6 systems. Results of binding energy calculation at all applied methods reveal that the CN1 structure is the most stable one which is formed by interaction of nitrosamine with cytosine in S1 region. The BSSE-corrected binding energy for six complex system is ranging from -23.8 to -43.6 kJ/mol at MP2/6-311++G (df,pd) level and the stability order is as CN1 > CN2 > CN3 > CN4 > CN5 > CN6 in all studied levels of theories. The NBO results reveal that the charge transfer occurred from cytosine to nitrosamine in CN1, CN3, CN5 and CN6 whereas this matter in the case of CN2 and CN4 was reversed. The relationship between BEs with red shift of H-bond involved bonds vibrational frequencies, charge transfer energies during complex formation and electron densities at H-bond BCPs were discussed. In addition activation energetic properties related to the proton transfer process between cytosine and nitrosamine have been calculated at MP2/6-311++G (df,pd) level. AIM results imply that H-bond interactions are electrostatic with partially covalent characteristic in nature.

  14. Intramolecular photo-switching and intermolecular energy transfer as primary photoevents in photoreceptive processes: the case of Euglena gracilis.

    PubMed

    Mercatelli, Raffaella; Quercioli, Franco; Barsanti, Laura; Evangelista, Valter; Coltelli, Primo; Passarelli, Vincenzo; Frassanito, Anna Maria; Gualtieri, Paolo

    2009-07-24

    In this paper we report the results of measurements performed by FLIM on the photoreceptor of Euglenagracilis. This organelle consists of optically bistable proteins, characterized by two thermally stable isomeric forms: A(498,) non fluorescent and B(462), fluorescent. Our data indicate that the primary photoevent of Euglena photoreception upon photon absorption consists of two contemporaneous different phenomena: an intramolecular photo-switch (i.e., A(498) becomes B(462)), and a intermolecular and unidirectional Forster-type energy transfer. During the FRET process, the fluorescent B(462) form acts as donor for the non-fluorescent A(498) form of the protein nearby, which acts as acceptor. We hypothesize that in nature these phenomena follow each other with a domino progression along the orderly organized and closely packed proteins in the photoreceptor layer(s), modulating the isomeric composition of the photoreceptive protein pool. This mechanism guarantees that few photons are sufficient to produce a signal detectable by the cell.

  15. Intermolecular proton-transfer in acetic acid clusters induced by vacuum-ultraviolet photoionization

    NASA Astrophysics Data System (ADS)

    Ohta, Keisuke; Matsuda, Yoshiyuki; Mikami, Naohiko; Fujii, Asuka

    2009-11-01

    Infrared (IR) spectroscopy based on vacuum-ultraviolet one-photon ionization detection was carried out to investigate geometric structures of neutral and cationic clusters of acetic acid: (CH3COOH)2, CH3COOH-CH3OH, and CH3COOH-H2O. All the neutral clusters have cyclic-type intermolecular structures, in which acetic acid and solvent molecules act as both hydrogen donors and acceptors, and two hydrogen-bonds are formed. On the other hand, (CH3COOH)2+ and (CH3COOH-CH3OH)+ form proton-transferred structures, where the acetic acid moiety donates the proton to the counter molecule. (CH3COOH-H2O)+ has a non-proton-transferred structure, where CH3COOH+ and H2O are hydrogen-bonded. The origin of these structural differences among the cluster cations is discussed with the relative sizes of the proton affinities of the cluster components and the potential energy curves along the proton-transfer coordinate.

  16. Inter-molecular β-sheet structure facilitates lung-targeting siRNA delivery

    PubMed Central

    Zhou, Jihan; Li, Dong; Wen, Hao; Zheng, Shuquan; Su, Cuicui; Yi, Fan; Wang, Jue; Liang, Zicai; Tang, Tao; Zhou, Demin; Zhang, Li-He; Liang, Dehai; Du, Quan

    2016-01-01

    Size-dependent passive targeting based on the characteristics of tissues is a basic mechanism of drug delivery. While the nanometer-sized particles are efficiently captured by the liver and spleen, the micron-sized particles are most likely entrapped within the lung owing to its unique capillary structure and physiological features. To exploit this property in lung-targeting siRNA delivery, we designed and studied a multi-domain peptide named K-β, which was able to form inter-molecular β-sheet structures. Results showed that K-β peptides and siRNAs formed stable complex particles of 60 nm when mixed together. A critical property of such particles was that, after being intravenously injected into mice, they further associated into loose and micron-sized aggregates, and thus effectively entrapped within the capillaries of the lung, leading to a passive accumulation and gene-silencing. The large size aggregates can dissociate or break down by the shear stress generated by blood flow, alleviating the pulmonary embolism. Besides the lung, siRNA enrichment and targeted gene silencing were also observed in the liver. This drug delivery strategy, together with the low toxicity, biodegradability, and programmability of peptide carriers, show great potentials in vivo applications. PMID:26955887

  17. Inter-molecular β-sheet structure facilitates lung-targeting siRNA delivery

    NASA Astrophysics Data System (ADS)

    Zhou, Jihan; Li, Dong; Wen, Hao; Zheng, Shuquan; Su, Cuicui; Yi, Fan; Wang, Jue; Liang, Zicai; Tang, Tao; Zhou, Demin; Zhang, Li-He; Liang, Dehai; Du, Quan

    2016-03-01

    Size-dependent passive targeting based on the characteristics of tissues is a basic mechanism of drug delivery. While the nanometer-sized particles are efficiently captured by the liver and spleen, the micron-sized particles are most likely entrapped within the lung owing to its unique capillary structure and physiological features. To exploit this property in lung-targeting siRNA delivery, we designed and studied a multi-domain peptide named K-β, which was able to form inter-molecular β-sheet structures. Results showed that K-β peptides and siRNAs formed stable complex particles of 60 nm when mixed together. A critical property of such particles was that, after being intravenously injected into mice, they further associated into loose and micron-sized aggregates, and thus effectively entrapped within the capillaries of the lung, leading to a passive accumulation and gene-silencing. The large size aggregates can dissociate or break down by the shear stress generated by blood flow, alleviating the pulmonary embolism. Besides the lung, siRNA enrichment and targeted gene silencing were also observed in the liver. This drug delivery strategy, together with the low toxicity, biodegradability, and programmability of peptide carriers, show great potentials in vivo applications.

  18. [Influence of double rice cropping system innovation on paddy soil profile form and soil characteristics].

    PubMed

    Zeng, Xi-Bai; Sun, Nan; Gao, Ju-Sheng; Li, Lian-Fang; Wang, Bo-Ren; Bai, Ling-Yu

    2008-05-01

    Field experiments were conducted on the double rice cropping paddy field in red soil area to evaluate the influence of cropping system innovation on soil profile form and related soil characteristics. Four cropping systems of rice-rice-Chinese Milkvetch (Astragalus sinicus Linn.), forage, paddy-upland rotation, and upland were substituted for the double rice cropping system. The results indicated that compared with those under double rice cropping system, the thickness of cultivated horizon under upland cropping system increased by 4 cm, that of plow pan declined by 2 cm, > 2 mm aggregates in wet-sieved particle-size fractions increased by 6.94%, wet-sieved mean-mass diameter increased by 0.37 mm, contents of humic acid carbon and fulvic acid carbon increased by 0.15 and 0.49 g kg(-1), respectively, and quotient of aggregates water stability was 0.78 times higher. Under paddy-upland rotation, the quotient of aggregates water stability was higher (95.86), while soil nutrient contents changed a little. Under rice-rice-Chinese Milkvetch system, soil organic matter content increased by 1.3 g kg(-1), quotient of aggregates water stability declined by 8.82, but other parameters had less changes. Under forage system, the thickness of cultivated and transitional horizons increased by 2 cm and 9 cm, respectively, quotient of aggregates water stability increased by 1.39, while the contents of soil organic matter and total potassium decreased by 5.6 and 2.8 g kg(-1), respectively. Among all test cropping systems, forage system had the greatest changes in soil characteristics. It was completely feasible to substitute the local double rice cropping system for paddy-upland rotation or upland cropping, particularly in the areas where full irrigation was not available. However, attention should be paid to the decrease of soil potassium content when the cropping system innovation was practiced.

  19. Simulated imaging of intermolecular bonds using high throughput real-space density functional calculations

    NASA Astrophysics Data System (ADS)

    Lee, Alex; Kim, Minjung; Chelikowsky, James

    2015-03-01

    Recent experimental noncontact atomic force microscopy (AFM) studies on 8-hydroxyquinoline (8-hq) assemblies have imaged distinct lines between molecules that are thought to represent intermolecular bonding. To aid the interpretation of these images, we calculate simulated AFM images of an 8-hq dimer with a CO functionalized tip using a real-space pseudopotential formalism. We examine the effects of Pauli repulsion and tip probe relaxation as explanations for the enhanced resolution that resolves these intermolecular force lines. Our study aims to compute ab initio real-space images of intermolecular interactions.

  20. Ground state intermolecular proton transfer in the supersystems thymine-(H2O)n and thymine-(CH3OH)n, n = 1,2: a theoretical study.

    PubMed

    Delchev, Vassil B; Shterev, Ivan G

    2009-04-01

    Twelve binary and eight ternary supersystems between thymine and methanol, and water were investigated in the ground state at the B3LYP and MP2 levels of theory using B3LYP/6-311 + + G(d,p) basis functions. The thermodynamics of complex formations and the mechanisms of intermolecular proton transfers were clarified in order to find out the most stable H-boned system. It was established that the energy barriers of the water/methanol-assisted proton transfers are several times lower than those of the intramolecular proton transfers in the DNA/RNA bases. The X-ray powder spectra of thymine, and this precrystallized from water and methanol showed that water molecules are incorporated in the crystal lattice of thymine forming H-bridges between thymine molecules.

  1. A computer model for simulation of absorption systems in flexible and modular form

    SciTech Connect

    Grossman, G; Gommed, K; Gadoth, D

    1991-08-01

    A computer code in a flexible and modular form developed for simulation of absorption systems makes it possible to investigate various cycle configurations with different working fluids. The code is based on unit subroutines containing the governing equations for the system's components. The equations are linked by a main program according to the user's specifications to form the complete system. The equations are solved simultaneously, and fluid properties are taken from a property data base. The code is user oriented and requires a relatively simple input containing the given operating conditions and the working fluid at each state point. The user conveys to the computer an image of his or her cycle by specifying the different subunits and their interconnection. Based on this information, the program calculates (1) the temperature, flow rate, concentration, pressure, and vapor fraction at each state point in the system and (2) the heat duty at each unit, from which the coefficient of performance may be determined. The program has been used successfully to simulate a variety of single-stage, double-stage, and dual-loop heat pumps and heat transformers, with the working fluids LiBr-H{sup 2}O,H{sub 2}O-NH{sub 3}, LiBr/H{sub 2}O-NH{sub 3}, LiBr/ZnBr{sub 2}-CH{sub 3}OH, and more. 23 refs., 10 figs., 13 tabs.

  2. Kinetics of color development of melanoidins formed from fructose/amino acid model systems.

    PubMed

    Echavarría, A P; Pagán, J; Ibarz, A

    2014-03-01

    The formation of soluble melanoidins from a single combination of sugar (fructose) and amino acid model systems were evaluated kinetically. The selected amino acids, commonly found in apple juice and highly reactive in the Maillard reaction, were asparagine, aspartic acid, and glutamic acid. The effect of these reagents and the treatment at different temperatures (50 , 85 , and 100 ) during 96 h on the color intensity of the melanoidin formed was measured by absorbance at different wavelengths (280, 325, 405, and 420 nm). The absorbance of the melanoidin formed from all model systems was located on the wavelength of 405 nm, that is, the area of the visible spectrum close to the UV region. The color of the melanoidins was directly measured using the CIELAB color space system. A first-order kinetic model was applied to the evolution of the ΔE * (color difference) and L * (lightness) of the color. The fructose/aspartic acid model system values of a * (redness) and b * (yellowness) were found in the brown-red zone. Therefore, the color development of the melanoidins was influenced by the type of amino acid and temperature. Especially, it is thought that the a * and b * values can be used to explain the differences among the amino acids in the color development of melanoidins.

  3. LED surgical lighting system with multiple free-form surfaces for highly sterile operating theater application.

    PubMed

    Liu, Peng; Zhang, Yaqin; Zheng, Zhenrong; Li, Haifeng; Liu, Xu

    2014-06-01

    Although the ventilation system is widely employed in the operating theater, a strictly sterile surgical environment still cannot be ensured because of laminar disturbance, which is mainly caused by the surgical lighting system. Abandoning traditional products, we propose an LED surgical lighting system, which can alleviate the laminar disturbance and provide an appropriate lighting condition for surgery. It contains a certain amount of LED lens units, which are embedded in the ceiling and arranged around the air supply smallpox. The LED lens unit integrated with an LED light source and a free-form lens is required to produce a uniform circular illumination with a large tolerance to the change of lighting distance. To achieve such a dedicated lens, two free-form refractive surfaces, which are converted into two ordinary differential equations by the design method presented in this paper, are used to deflect the rays. The results show that the LED surgical lighting system can provide an excellent illumination environment for surgery, and, apparently, the laminar disturbance also can be relieved.

  4. Self-assembling supramolecular systems of different symmetry formed by wedged macromolecular dendrons

    NASA Astrophysics Data System (ADS)

    Shcherbina, M. A.; Bakirov, A. V.; Yakunin, A. N.; Percec, V.; Beginn, U.; Möller, M.; Chvalun, S. N.

    2012-03-01

    The main stages of the self-assembling of supramolecular ensembles have been revealed by studying different functional wedged macromolecules: polymethacrylates with tapered side chains based on gallic acid, their macromonomers, and salts of 2,3,4- and 3,4,5-tris(dodecyloxy)benzenesulphonic acid. The first stage is the formation of individual supramolecular aggregates (long cylinders or spherical micelles) due to the weak noncovalent interactions of mesogenic groups and the subsequent ordering in these aggregates, which is accompanied by a decrease in the free energy of the system. Supramolecular aggregates, in turn, form 2D or 3D lattices. The shape of supramolecular aggregates and its change with temperature are delicate functions of the mesogen chemical structure; this circumstance makes it possible to rationally design complex self-assembling systems with the ability to respond smartly to external stimuli. X-ray diffraction analysis allows one to study the structure of supramolecular systems with different degrees of order, determine the type of mesophases formed by these systems, and reveal the phase behavior of the material. Particular attention has been paid to the method for reconstruction of electron density distribution from the relative reflection intensity. The application of a suite of experimental methods, including wide- and small-angle X-ray diffraction, molecular modeling, differential scanning calorimetry, and polarization optical microscopy, allows one to establish the relationship between the shape of the structural unit (molecule or molecular aggregate), the nature of the interaction, and the phase behavior of the material.

  5. Closed-form solutions for linear regulator design of mechanical systems including optimal weighting matrix selection

    NASA Technical Reports Server (NTRS)

    Hanks, Brantley R.; Skelton, Robert E.

    1991-01-01

    Vibration in modern structural and mechanical systems can be reduced in amplitude by increasing stiffness, redistributing stiffness and mass, and/or adding damping if design techniques are available to do so. Linear Quadratic Regulator (LQR) theory in modern multivariable control design, attacks the general dissipative elastic system design problem in a global formulation. The optimal design, however, allows electronic connections and phase relations which are not physically practical or possible in passive structural-mechanical devices. The restriction of LQR solutions (to the Algebraic Riccati Equation) to design spaces which can be implemented as passive structural members and/or dampers is addressed. A general closed-form solution to the optimal free-decay control problem is presented which is tailored for structural-mechanical system. The solution includes, as subsets, special cases such as the Rayleigh Dissipation Function and total energy. Weighting matrix selection is a constrained choice among several parameters to obtain desired physical relationships. The closed-form solution is also applicable to active control design for systems where perfect, collocated actuator-sensor pairs exist.

  6. New Closed-Form of the Largest Eigenvalue PDF for Max-SNR MIMO System Performances

    NASA Astrophysics Data System (ADS)

    Letessier, Jonathan; Vrigneau, Baptiste; Rostaing, Philippe; Burel, Gilles

    Multiple-input multiple-output (MIMO) maximum-SNR (max-SNR) system employs the maximum ratio combiner (MRC) at the receiver side and the maximum ratio transmitter (MRT) at the transmitter side. Its performances highly depend on MIMO channel characteristics, which vary according to both the number of antennas and their distribution between the transmitter and receiver sides. By using the decomposition of the ordered Wishart distribution in the uncorrelated Rayleigh case, we derived a closed-form expression of the largest eigenvalue probability density function (PDF). The final result yields to an expression form of the PDF where polynomials are multiplied by exponentials; it is worth underlining that, though this form had been previously observed for given couples of antennas, to date no formally-written closed-form was available in the literature for an arbitrary couple. Then, this new expression permits one to quickly and easily get the well known largest eigenvalue PDF and use it to determine the binary error probability (BEP) of the max-SNR.

  7. Form of an evolutionary tradeoff affects eco-evolutionary dynamics in a predator-prey system.

    PubMed

    Kasada, Minoru; Yamamichi, Masato; Yoshida, Takehito

    2014-11-11

    Evolution on a time scale similar to ecological dynamics has been increasingly recognized for the last three decades. Selection mediated by ecological interactions can change heritable phenotypic variation (i.e., evolution), and evolution of traits, in turn, can affect ecological interactions. Hence, ecological and evolutionary dynamics can be tightly linked and important to predict future dynamics, but our understanding of eco-evolutionary dynamics is still in its infancy and there is a significant gap between theoretical predictions and empirical tests. Empirical studies have demonstrated that the presence of genetic variation can dramatically change ecological dynamics, whereas theoretical studies predict that eco-evolutionary dynamics depend on the details of the genetic variation, such as the form of a tradeoff among genotypes, which can be more important than the presence or absence of the genetic variation. Using a predator-prey (rotifer-algal) experimental system in laboratory microcosms, we studied how different forms of a tradeoff between prey defense and growth affect eco-evolutionary dynamics. Our experimental results show for the first time to our knowledge that different forms of the tradeoff produce remarkably divergent eco-evolutionary dynamics, including near fixation, near extinction, and coexistence of algal genotypes, with quantitatively different population dynamics. A mathematical model, parameterized from completely independent experiments, explains the observed dynamics. The results suggest that knowing the details of heritable trait variation and covariation within a population is essential for understanding how evolution and ecology will interact and what form of eco-evolutionary dynamics will result.

  8. Coordination compounds of tetravalent silicon, germanium and tin: the structure, chemical bonding and intermolecular interactions in them

    NASA Astrophysics Data System (ADS)

    Korlyukov, A. A.

    2015-04-01

    The review is devoted to analysis and generalization of the results of (i) quantum chemical studies on the structure, chemical bonding and intermolecular interactions in coordination compounds of tetravalent silicon, germanium and tin in crystals, in solutions and in the gas phase and (ii) experimental investigations of the electron density distribution in these systems. The bibliography includes 147 references. In memoriam of Corresponding Member of the Russian Academy of Sciences M Yu Antipin (1951 - 2013), Academician of the Russian Academy of Sciences M G Voronkov (1921 - 2014) and Dr. S P Knyazev, Lomonosov Moscow University of Fine Chemical Technology (1949 - 2012).

  9. Effect of retinal ischemia on the non-image forming visual system.

    PubMed

    González Fleitas, María Florencia; Bordone, Melina; Rosenstein, Ruth E; Dorfman, Damián

    2015-03-01

    Retinal ischemic injury is an important cause of visual impairment. The loss of retinal ganglion cells (RGCs) is a key sign of retinal ischemic damage. A subset of RGCs expressing the photopigment melanopsin (mRGCs) regulates non-image-forming visual functions such as the pupillary light reflex (PLR), and circadian rhythms. We studied the effect of retinal ischemia on mRGCs and the non-image-forming visual system function. For this purpose, transient ischemia was induced by raising intraocular pressure to 120 mm Hg for 40 min followed by retinal reperfusion by restoring normal pressure. At 4 weeks post-treatment, animals were subjected to electroretinography and histological analysis. Ischemia induced a significant retinal dysfunction and histological alterations. At this time point, a significant decrease in the number of Brn3a(+) RGCs and in the anterograde transport from the retina to the superior colliculus and lateral geniculate nucleus was observed, whereas no differences in the number of mRGCs, melanopsin levels, and retinal projections to the suprachiasmatic nuclei and the olivary pretectal nucleus were detected. At low light intensity, a decrease in pupil constriction was observed in intact eyes contralateral to ischemic eyes, whereas at high light intensity, retinal ischemia did not affect the consensual PLR. Animals with ischemia in both eyes showed a conserved locomotor activity rhythm and a photoentrainment rate which did not differ from control animals. These results suggest that the non-image forming visual system was protected against retinal ischemic damage.

  10. Small-angle neutron scattering study of a dense microemulsion system formed with an ionic liquid.

    PubMed

    Kang, T; Qian, S; Smith, G S; Do, C; Heller, W T

    2017-09-12

    Mixtures of water, octane and 1-octanol with 1-tetradecyl-3-methylimidazolium chloride (C14MIM·Cl), often referred to as a surface active ionic liquid (SAIL), form water-in-oil microemulsions that have potential application as extraction media for various metal ions. Here, we present a structural study by small-angle neutron scattering (SANS) of dense microemulsions formed by surfactant-rich mixtures of these four compounds to understand how the SAIL can be used to tune the structures and properties of the microemulsions. The SANS experiments revealed that the microemulsions formed are composed of two phases, a water-in-oil microemulsion and a bicontinuous microemulsion, which becomes the dominant phase at high surfactant concentration. In this concentration regime, the surfactant film becomes more rigid, having a higher bending modulus that results from the parallel stacking of the imidazolium ring of the SAIL. At lower surfactant concentrations, the molecular packing of the SAIL does not change with the water content of the microemulsion. The results presented here correlate well with previously observed changes in the interaction between the IL cation and metal ions (Y. Tong, L. Han and Y. Yang, Ind. Eng. Chem. Res., 2012, 51, 16438-16443), while the capacity of the microemulsion system for water remains high enough for using the system as an extraction medium.

  11. An effective desiccant system to regulate the humidity inside the chambers of the solid dosage forms.

    PubMed

    Lehto, Vesa-Pekka; Erling, Ida

    2007-11-01

    The most common way to protect moisture-sensitive pharmaceutical powders is to utilize protective packaging. However, the most convenient package materials are all permeable to water molecules to some extent and limited protection is normally achieved with this arrangement even though desiccants are employed. In the present study we introduce a novel system that can regulate the internal humidity of the containers used with solid dosage forms for a desired time at a requested level. Instead of the widely used solid adsorbents the system utilizes saturated salt solutions loaded in desiccant bags made of various polymer materials with appropriate permeation properties. By utilizing salt solutions the size of the desiccant bag can be further reduced. A wide variety of commonly used powder chambers and desiccant bags are tested, proving the effectiveness of the introduced system.

  12. Forming system of strategic innovation management at high-tech engineering enterprises

    NASA Astrophysics Data System (ADS)

    Ergunova, O. T.; Lizunkov, V. G.; Malushko, E. Yu; Marchuk, V. I.; Ignatenko, A. Yu

    2017-02-01

    The article considers the processes of forming the strategic system of innovative activity management at the enterprises of a high-tech mechanical engineering complex (MEC) that are traditionally decisive in shaping the economic base of Russia. The authors proposed a method of designing a strategic system of innovative activity management at the MEC’s enterprises of the region which is based on the consideration of means and opportunities of the enterprise to implement intellectual activity. The proposed methodology and the empirical results constituted a ground for developing a system of strategic innovation management when performing the state-guaranteed order at the hi-tech MEC enterprises. Its implementation will help to reduce the level of uncertainty throughout the entire life cycle of an innovative activity product.

  13. Multi-system Nernst-Michaelis-Menten model applied to bioanodes formed from sewage sludge.

    PubMed

    Rimboud, Mickaël; Desmond-Le Quemener, Elie; Erable, Benjamin; Bouchez, Théodore; Bergel, Alain

    2015-11-01

    Bioanodes were formed under constant polarization at -0.2 V/SCE from fermented sewage sludge. Current densities reached were 9.3±1.2 A m(-2) with the whole fermented sludge and 6.2±0.9 A m(-2) with the fermented sludge supernatant. The bioanode kinetics was analysed by differentiating among the contributions of the three redox systems identified by voltammetry. Each system ensured reversible Nernstian electron transfer but around a different central potential. The global overpotential required to reach the maximum current plateau was not imposed by slow electron transfer rates but was due to the potential range covered by the different redox systems. The microbial communities of the three bioanodes were analysed by 16S rRNA gene pyrosequencing. They showed a significant microbial diversity around a core of Desulfuromonadales, the proportion of which was correlated with the electrochemical performance of the bioanodes. Copyright © 2015 Elsevier Ltd. All rights reserved.

  14. Push it to the limit: Characterizing the convergence of common sequences of basis sets for intermolecular interactions as described by density functional theory.

    PubMed

    Witte, Jonathon; Neaton, Jeffrey B; Head-Gordon, Martin

    2016-05-21

    With the aim of systematically characterizing the convergence of common families of basis sets such that general recommendations for basis sets can be made, we have tested a wide variety of basis sets against complete-basis binding energies across the S22 set of intermolecular interactions-noncovalent interactions of small and medium-sized molecules consisting of first- and second-row atoms-with three distinct density functional approximations: SPW92, a form of local-density approximation; B3LYP, a global hybrid generalized gradient approximation; and B97M-V, a meta-generalized gradient approximation with nonlocal correlation. We have found that it is remarkably difficult to reach the basis set limit; for the methods and systems examined, the most complete basis is Jensen's pc-4. The Dunning correlation-consistent sequence of basis sets converges slowly relative to the Jensen sequence. The Karlsruhe basis sets are quite cost effective, particularly when a correction for basis set superposition error is applied: counterpoise-corrected def2-SVPD binding energies are better than corresponding energies computed in comparably sized Dunning and Jensen bases, and on par with uncorrected results in basis sets 3-4 times larger. These trends are exhibited regardless of the level of density functional approximation employed. A sense of the magnitude of the intrinsic incompleteness error of each basis set not only provides a foundation for guiding basis set choice in future studies but also facilitates quantitative comparison of existing studies on similar types of systems.

  15. Hopf normal form with SN symmetry and reduction to systems of nonlinearly coupled phase oscillators

    NASA Astrophysics Data System (ADS)

    Ashwin, Peter; Rodrigues, Ana

    2016-06-01

    Coupled oscillator models where N oscillators are identical and symmetrically coupled to all others with full permutation symmetry SN are found in a variety of applications. Much, but not all, work on phase descriptions of such systems consider the special case of pairwise coupling between oscillators. In this paper, we show this is restrictive-and we characterize generic multi-way interactions between oscillators that are typically present, except at the very lowest order near a Hopf bifurcation where the oscillations emerge. We examine a network of identical weakly coupled dynamical systems that are close to a supercritical Hopf bifurcation by considering two parameters, ɛ (the strength of coupling) and λ (an unfolding parameter for the Hopf bifurcation). For small enough λ > 0 there is an attractor that is the product of N stable limit cycles; this persists as a normally hyperbolic invariant torus for sufficiently small ɛ > 0. Using equivariant normal form theory, we derive a generic normal form for a system of coupled phase oscillators with SN symmetry. For fixed N and taking the limit 0 < ɛ ≪ λ ≪ 1, we show that the attracting dynamics of the system on the torus can be well approximated by a coupled phase oscillator system that, to lowest order, is the well-known Kuramoto-Sakaguchi system of coupled oscillators. The next order of approximation generically includes terms with up to four interacting phases, regardless of N. Using a normalization that maintains nontrivial interactions in the limit N → ∞, we show that the additional terms can lead to new phenomena in terms of coexistence of two-cluster states with the same phase difference but different cluster size.

  16. Devices, systems, and methods for harvesting energy and methods for forming such devices

    DOEpatents

    Kotter, Dale K.; Novack, Steven D.

    2012-12-25

    Energy harvesting devices include a substrate coupled with a photovoltaic material and a plurality of resonance elements associated with the substrate. The resonance elements are configured to collect energy in at least visible and infrared light spectra. Each resonance element is capacitively coupled with the photovoltaic material, and may be configured to resonate at a bandgap energy of the photovoltaic material. Systems include a photovoltaic material coupled with a feedpoint of a resonance element. Methods for harvesting energy include exposing a resonance element having a resonant electromagnetic radiation having a frequency between approximately 20 THz and approximately 1,000 THz, absorbing at least a portion of the electromagnetic radiation with the resonance element, and resonating the resonance element at a bandgap energy of an underlying photovoltaic material. Methods for forming an energy harvesting device include forming resonance elements on a substrate and capacitively coupling the resonance elements with a photovoltaic material.

  17. Disks, Young Stars, and Radio Waves: The Quest for Forming Planetary Systems

    NASA Astrophysics Data System (ADS)

    Chandler, C. J.; Shepherd, D. S.

    2008-08-01

    Kant and Laplace suggested the Solar System formed from a rotating gaseous disk in the 18th century, but convincing evidence that young stars are indeed surrounded by such disks was not presented for another 200 years. As we move into the 21st century the emphasis is now on disk formation, the role of disks in star formation, and on how planets form in those disks. Radio wavelengths play a key role in these studies, currently providing some of the highest-spatial-resolution images of disks, along with evidence of the growth of dust grains into planetesimals. The future capabilities of EVLA and ALMA provide extremely exciting prospects for resolving disk structure and kinematics, studying disk chemistry, directly detecting protoplanets, and imaging disks in formation.

  18. [Forming a community at risk for circulatory system diseases among workers engaged into underground mining].

    PubMed

    Shliapnikov, D M; Shur, P Z; Kostarev, V G; Alexeyev, V B; Vlasova, E M; Uhabov, V M

    2015-01-01

    Forming a community at risk for circulatory system diseases will increase efficiency of medical and prophylactic measures on managing risk of arterial hypertension. Epidemiologic analysis helped to reveal reliable connection between arterial hypertension predictors and work conditions of mining machine operators and supported actualization of high occupational risk suggested in a priori evaluation. Mathematic modelling helped to forecast increase in the disease probability: with noise level of 94 dB after 10 years of work, 17.9% of workers are expected to have arterial hypertension preventing from further occupational activity. Forecasting results of arterial hypertension probability help to form risk groups for medical and preventive technologies managing occupational risk, and predictors enable to specify necessity of individual medical preventive measures.

  19. Direct Fluorescent Detection of Blood Potassium by Ion-Selective Formation of Intermolecular G-Quadruplex and Ligand Binding.

    PubMed

    Yang, Le; Qing, Zhihe; Liu, Changhui; Tang, Qiao; Li, Jishan; Yang, Sheng; Zheng, Jing; Yang, Ronghua; Tan, Weihong

    2016-09-20

    G-quadruplex analogues have been widely used as molecular tools for detection of potassium ion (K(+)). However, interference from a higher concentration of sodium ion (Na(+)), enzymatic degradation of the oligonucleotide, and background absorption and fluorescence of blood samples have all limited the use of G-quadruplex for direct detection of K(+) in blood samples. Here, we reported, for the first time, an intermolecular G-quadruplex-based assay capable of direct fluorescent detection of blood K(+). Increased stringency of intermolecular G-quadruplex formation based on our screened G-rich oligonucleotide (5'-TGAGGGA GGGG-3') provided the necessary selectivity for K(+) against Na(+) at physiological ion level. To increase long-term stability of oligonucleotide in blood, the screened oligonucleotide was modified with an inverted thymine nucleotide whose 3'-terminus was connected to the 3'-terminus of the upstream nucleotide, acting as a blocking group to greatly improve antinuclease stability. Lastly, to avoid interference from background absorption and autofluorescence of blood, a G-quadruplex-binding, two-photon-excited ligand, EBMVC-B, was synthesized and chosen as the fluorescence reporter. Thus, based on selective K(+) ion-induced formation of intermolecular G-quadruplex and EBMVC-B binding, this approach could linearly respond to K(+) from 0.5 to 10 mM, which matches quite well with the physiologically relevant concentration of blood K(+). Moreover, the system was highly selective for K(+) against other metal ions, including Na(+), Ca(2+), Mg(2+), Zn(2+) common in blood. The practical application was demonstrated by direct detection of K(+) from real blood samples by two-photon fluorescence technology. To the best of our knowledge, this is the first attempt to exploit molecular G-quadruplex-based fluorescent sensing for direct assay of blood target. As such, we expect that it will promote the design and practical application of similar DNA-based sensors in

  20. Intra- and intermolecular interaction ECL study of novel ruthenium tris-bipyridyl complexes with different amine reductants.

    PubMed

    Sun, Shiguo; Yang, Yang; Liu, Fengyu; Fan, Jiangli; Peng, Xiaojun; Kehr, Jan; Sun, Licheng

    2009-10-14

    A series of ruthenium(II) tris-bipyridyl complexes covalently linked with different amine reductants such as tripropylamine (TPrA), ethanolamine and diethanolamine for an electrochemiluminescence (ECL) system have been synthesized. Their ECL property at different working electrodes has been studied with and without the presence of TPrA, triethanolamine (TEOA) and 2-(dibutylamino) ethanol (DBAE) as the coreactant, respectively. The results demonstrate that the conjugated ruthenium complex alone can generate ECL through intramolecular interaction at a relatively low concentration, while with intermolecular interaction the ECL intensity increases progressively and becomes increasingly dominant with increasing complex concentration. For the coreactant system ECL, the amine coreactant needed for the conjugate complexes can be significantly lowered in comparison with that of the well known [Ru(bpy)(3)](2+)/TPrA system. One amine substituent is better for the system in order to diminish the steric hindrance, and the intramolecular amine reductant employed should have a similar structure with that of the additive amine coreactant to achieve a good ECL performance, which can pave a new route to further improving the ECL efficiency and increase the sensitivity of detection through combining both intra- and intermolecular interaction.

  1. Good's buffers as novel phase-forming components of ionic-liquid-based aqueous biphasic systems.

    PubMed

    Luís, Andreia; Dinis, Teresa B V; Passos, Helena; Taha, Mohamed; Freire, Mara G

    2015-09-15

    Aiming at the development of self-buffering and benign extraction/separation processes, this work reports a novel class of aqueous biphasic systems (ABS) composed of ionic liquids (ILs) and organic biological buffers (Good's buffers, GBs). A large array of ILs and GBs was investigated, revealing than only the more hydrophobic and fluorinated ILs are able to form ABS. For these systems, the phase diagrams, tie-lines, tie-line lengths, and critical points were determined at 25 °C. The ABS were then evaluated as alternative liquid-liquid extraction strategies for two amino acids (L-phenylalanine and L-tryptophan). The single-step extraction efficiencies for the GB-rich phase range between 22.4 and 100.0 % (complete extraction). Contrarily to the most conventional IL-salt ABS, in most of the systems investigated, the amino acids preferentially migrate for the most biocompatible and hydrophilic GB-rich phase. Remarkably, in two of the studied ABS, L-phenylalanine completely partitions to the GB-rich phase while L-tryptophan shows a preferential affinity for the opposite phase. These results show that the extraction efficiencies of similar amino acids can be tailored by the design of the chemical structures of the phase-forming components, creating thus new possibilities for the use of IL-based ABS in biotechnological separations.

  2. Papular sarcoidosis of the knees. A frequent form of presentation of systemic sarcoidosis.

    PubMed

    Marcoval, Joaquim; Mañá, Juan

    2016-03-29

    In recent years we have observed with increasing frequency granulomatous papular lesions involving the knees, for which we proposed the term papular sarcoidosis of knees. To evaluate the clinicopathological features of papular sarcoidosis of the knees. Patients with papular lesions of the knees and histopathologically sarcoid granulomas were included in the study. Systemic sarcoidosis was investigated in all cases. Clinical charts were retrospectively retrieved. Biopsy specimens were evaluated under polarized light to detect foreign bodies. Fifty-three patients fulfilled inclusion criteria. In 36 cases systemic sarcoidosis was diagnosed and these cases were considered as papular sarcoidosis of the knees. Foreign particles were observed in 21 of these 36 patients. In only 9/36 patients did the activity of systemic disease persist over two years. In 17 cases sarcoidosis could not be demonstrated during follow-up. Papular sarcoidosis of the knees can be considered a relatively frequent form of cutaneous sarcoidosis usually present at the beginning of the disease that can be useful for the diagnosis of sarcoidosis. It is mainly observed in acute forms of sarcoidosis and can be considered a sign of good prognosis.

  3. Nutraceutical delivery systems: resveratrol encapsulation in grape seed oil nanoemulsions formed by spontaneous emulsification.

    PubMed

    Davidov-Pardo, Gabriel; McClements, David Julian

    2015-01-15

    The aim of this work was to fabricate nanoemulsions-based delivery systems to encapsulate resveratrol. Nanoemulsions were formed using spontaneous emulsification method: 10% oil phase (grape seed oil plus orange oil) and 10% surfactant (Tween 80) were titrated into 80% aqueous phase. An optimum orange oil-to-grape seed oil ratio of 1:1(w/w) formed small droplets (d ≈ 100 nm) with good stability to droplet growth. The maximum amount of resveratrol that could be dissolved in the oil phase was 120 ± 10 μg/ml. The effect of droplet size on the chemical stability of encapsulated resveratrol was examined by preparing systems with different mean droplet diameters of 220 ± 2; 99 ± 3; and 45 ± 0.4 nm. Encapsulation of resveratrol improved its chemical stability after exposure to UV-light: 88% retention in nanoemulsions compared to 50% in dimethylsulphoxide (DMSO). This study showed that resveratrol could be encapsulated within low-energy nanoemulsion-based delivery systems and protected against degradation. Copyright © 2014 Elsevier Ltd. All rights reserved.

  4. Composites Formed from Thermoresponsive Polymers and Conductive Nanowires for Transient Electronic Systems.

    PubMed

    Zhang, Xin; Bellan, Leon M

    2017-07-05

    The disintegration of transient electronic systems after a preprogrammed time or a particular stimulus (e.g., water, light, or temperature) is fundamentally linked to the properties and behavior of the materials used for their construction. Herein, we demonstrate that polymers exhibiting lower critical solution temperature (LCST) behavior can work as thermoresponsive substrates for circuitry and that these materials can be coupled with conductive nanowires to form a transient electronics platform with unique, irreversible temperature-responsive behavior. The transient systems formed from composites of LCST polymers and conductive nanowires exhibit stable electrical performance in solution (Tsolution > LCST) for over 24 h until a cooling stimulus triggers a rapid (within 5 min) and gigantic (3-4 orders of magnitude) transition in electrical conductance due to polymer dissolution. Using a parylene mask, we are able to fabricate thermoresponsive electrical components, such as conductive traces and parallel-plate capacitors, demonstrating the versatility of this material and patterning technique. With this unique stimulus-responsive transient system and polymers with LCSTs above room temperature (e.g., poly(N-isopropylacrylamide), methyl cellulose), we have developed a platform in which a circuit requires a source of heat to remain viable and is destroyed and vanishes once this heat source is lost.

  5. Aqueous-Based Latex Systems for Producing Durable Waste Forms-Initial Characterization

    SciTech Connect

    Terry, Troy N.; Russell, Renee L. ); Smith, Harry D. ); Liang, Liang ); Smith, Gary L. )

    2000-11-01

    The overall objective of this project is to identify and successfully demonstrate a water-based polyceram system suitable for producing an environmentally stable waste form highly loaded with salt wastes. The backbone for this idea is the development of aqueous based sol-gel technology. Most interest in sol-gel synthesis of ceramics in recent years has concentrated on the hydrolysis of metal alkoxides in organic media, but the alternative sol-gel process in aqueous media may offer acceptable results without the need for hazardous precursors or waste products. To accomplish this, water micelle (like an emulsion) systems will be substituted for the organic based systems already identified. Preliminary tests show that emulsions such as Styrene/Butadiene and Acrylic latex are good candidates for the aqueous media. Both of these materials when mixed with a percentage of natural latex have been shown to effectively immobilize salt wastes with loadings over 10 wt%. The low cost, availability, and ease of preparation (low temperature of cure) of these products makes them strong contenders as a waste form. Techniques for improving both chemical and physical properties, such as adding cross-linking agents and fine-tuning the curing process, are currently in development at Pacific Northwest National Laboratories along with collaboration with staff from the University of Arizona.

  6. Enhanced tunability afforded by aqueous biphasic systems formed by fluorinated ionic liquids and carbohydrates.

    PubMed

    Ferreira, Ana M; Esteves, Pedro D O; Boal-Palheiros, Isabel; Pereiro, Ana B; Rebelo, Luís Paulo N; Freire, Mara G

    2016-02-21

    This work unveils the formation of novel aqueous biphasic systems (ABS) formed by perfluoroalkylsulfonate-based ionic liquids (ILs) and a large number of carbohydrates (monosaccharides, disaccharides and polyols) aiming at establishing more benign alternatives to the salts commonly used. The respective ternary phase diagrams were determined at 298 K. The aptitude of the carbohydrates to induce phase separation closely follows their hydration capability, while the length of the IL cation/anion fluorinated chain also plays a crucial role. Finally, these systems were investigated as liquid-liquid extraction strategies for four food dyes. Single-step extraction efficiencies for the carbohydrate-rich phase up to 94% were obtained. Remarkably and contrarily to the most investigated IL-salt ABS, most dyes preferentially migrate for the most hydrophilic and biocompatible carbohydrate-rich phase - an outstanding advantage when envisaging the products recovery and further use. On the other hand, more hydrophobic dyes preferentially partition to the IL-rich phase, disclosing therefore these novel systems as highly amenable to be tuned by the proper choice of the phase-forming components.

  7. Enhanced tunability afforded by aqueous biphasic systems formed by fluorinated ionic liquids and carbohydrates†

    PubMed Central

    Boal-Palheiros, Isabel; Pereiro, Ana B.; Rebelo, Luís Paulo N.; Freire, Mara G.

    2016-01-01

    This work unveils the formation of novel aqueous biphasic systems (ABS) formed by perfluoroalkylsulfonate-based ionic liquids (ILs) and a large number of carbohydrates (monosaccharides, disaccharides and polyols) aiming at establishing more benign alternatives to the salts commonly used. The respective ternary phase diagrams were determined at 298 K. The aptitude of the carbohydrates to induce phase separation closely follows their hydration capability, while the length of the IL cation/anion fluorinated chain also plays a crucial role. Finally, these systems were investigated as liquid–liquid extraction strategies for four food dyes. Single-step extraction efficiencies for the carbohydrate-rich phase up to 94% were obtained. Remarkably and contrarily to the most investigated IL-salt ABS, most dyes preferentially migrate for the most hydrophilic and biocompatible carbohydrate-rich phase – an outstanding advantage when envisaging the products recovery and further use. On the other hand, more hydrophobic dyes preferentially partition to the IL-rich phase, disclosing therefore these novel systems as highly amenable to be tuned by the proper choice of the phase-forming components. PMID:27667966

  8. Effects of intermolecular interactions on the stability of carbon nanotube–gold nanoparticle conjugates in solution

    PubMed Central

    Konczak, Lukasz; Narkiewicz-Michalek, Jolanta; Pastorin, Giorgia; Panczyk, Tomasz

    2016-01-01

    This work deals with the role of intermolecular interactions in the stability of a carbon nanotube (CNT) capped by functionalized gold nanoparticles (AuNPs). The importance of such a system is due to its potential application as a pH-controlled drug carrier. Our preliminary experimental studies showed that fabrication of such a nanobottle/nanocontainer is feasible and it is possible to encapsulate the anticancer drug cisplatin inside the inner space of a CNT and seal its ends by functionalized AuNPs. The expected behavior, that is, detachment of AuNPs at acidic pH and the release of cisplatin, was, however, not observed. On the other hand, our theoretical studies of chemically identical system led to the conclusion that the release of cisplatin at acidic pH should be observed. Therefore, in this work, a deeper theoretical analysis of various factors that could be responsible for the disagreement between experimental and theoretical results were performed. The study found that the major factor is a large dispersion interaction component acting between CNT and AuNP in solution in the case of the experimental system. This factor can be controlled to some extent by tuning the system size or the ratio between AuNP diameter and CNT diameter. Thus, such kind of a pH-sensitive drug carrier is still of great interest, but its structural parameters need to be properly adjusted. PMID:27853368

  9. How Do Multiple-Star Systems Form? VLA Study Reveals "Smoking Gun"

    NASA Astrophysics Data System (ADS)

    2006-12-01

    Astronomers have used the National Science Foundation's Very Large Array (VLA) radio telescope to image a young, multiple-star system with unprecedented detail, yielding important clues about how such systems are formed. Most Sun-sized or larger stars in the Universe are not single, like our Sun, but are members of multiple-star systems. Astronomers have been divided on how such systems can form, producing competing theoretical models for this process. Multiple Star Formation Graphic Proposed Formation Process for L1551 IRS5 CREDIT: Bill Saxton, NRAO/AUI/NSF Click on image for page of graphics and full information The new VLA study produced a "smoking gun" supporting one of the competing models, said Jeremy Lim, of the Institute of Astronomy & Astrophysics, Academia Sinica, in Taipei, Taiwan, whose study, done with Shigehisa Takakuwa of the National Astronomical Observatory of Japan, is published in the December 10 issue of the Astrophysical Journal. Ironically, their discovery of a third, previously-unknown, young star in the system may support a second theoretical model. "There may be more than one way to make a multiple-star system," Lim explained. The astronomers observed an object called L1551 IRS5, young, still-forming protostars enshrouded in a cloud of gas and dust, some 450 light-years from Earth in the direction of the constellation Taurus. Invisible to optical telescopes because of the gas and dust, this object was discovered in 1976 by astronomers using infrared telescopes. A VLA study in 1998 showed two young stars orbiting each other, each surrounded by a disk of dust that may, in time, congeal into a system of planets. Lim and Takakuwa re-examined the system, using improved technical capabilities that greatly boosted the quality of their images. "In the earlier VLA study, only half of the VLA's 27 antennas had receivers that could collect the radio waves, at a frequency of 43 GigaHertz (GHz), coming from the dusty disks. When we re-observed this

  10. Challenges in forming the solar system's giant planet cores via pebble accretion

    SciTech Connect

    Kretke, K. A.; Levison, H. F.

    2014-12-01

    Though ∼10 M {sub ⊕} mass rocky/icy cores are commonly held as a prerequisite for the formation of gas giants, theoretical models still struggle to explain how these embryos can form within the lifetimes of gaseous circumstellar disks. In recent years, aerodynamic-aided accretion of 'pebbles', objects ranging from centimeters to meters in size, has been suggested as a potential solution to this long-standing problem. While pebble accretion has been demonstrated to be extremely effective in local simulations that look at the detailed behavior of these pebbles in the vicinity of a single planetary embryo, to date there have been no global simulations demonstrating the effectiveness of pebble accretion in a more complicated, multi-planet environment. Therefore, we have incorporated the aerodynamic-aided accretion physics into LIPAD, a Lagrangian code that can follow the collisional/accretional/dynamical evolution of a protoplanetary system, to investigate how pebble accretion manifests itself in the larger planet formation picture. We find that under generic circumstances, pebble accretion naturally leads to an 'oligarchic' type of growth in which a large number of planetesimals grow to similar-sized planets. In particular, our simulations tend to form hundreds of Mars- and Earth-mass objects between 4 and 10 AU. While merging of some oligarchs may grow massive enough to form giant planet cores, leftover oligarchs lead to planetary systems that cannot be consistent with our own solar system. We investigate various ideas presented in the literature (including evaporation fronts and planet traps) and find that none easily overcome this tendency toward oligarchic growth.

  11. Challenges in Forming the Solar System's Giant Planet Cores via Pebble Accretion

    NASA Astrophysics Data System (ADS)

    Kretke, K. A.; Levison, H. F.

    2014-12-01

    Though ~10 M ⊕ mass rocky/icy cores are commonly held as a prerequisite for the formation of gas giants, theoretical models still struggle to explain how these embryos can form within the lifetimes of gaseous circumstellar disks. In recent years, aerodynamic-aided accretion of "pebbles," objects ranging from centimeters to meters in size, has been suggested as a potential solution to this long-standing problem. While pebble accretion has been demonstrated to be extremely effective in local simulations that look at the detailed behavior of these pebbles in the vicinity of a single planetary embryo, to date there have been no global simulations demonstrating the effectiveness of pebble accretion in a more complicated, multi-planet environment. Therefore, we have incorporated the aerodynamic-aided accretion physics into LIPAD, a Lagrangian code that can follow the collisional/accretional/dynamical evolution of a protoplanetary system, to investigate how pebble accretion manifests itself in the larger planet formation picture. We find that under generic circumstances, pebble accretion naturally leads to an "oligarchic" type of growth in which a large number of planetesimals grow to similar-sized planets. In particular, our simulations tend to form hundreds of Mars- and Earth-mass objects between 4 and 10 AU. While merging of some oligarchs may grow massive enough to form giant planet cores, leftover oligarchs lead to planetary systems that cannot be consistent with our own solar system. We investigate various ideas presented in the literature (including evaporation fronts and planet traps) and find that none easily overcome this tendency toward oligarchic growth.

  12. Development of a Leave-in-Place Slab Edge Insulating Form System

    SciTech Connect

    Marc Hoeschele; Eric Lee

    2009-08-31

    Concrete slabs represent the primary foundation type in residential buildings in the fast-growing markets throughout the southern and southwestern United States. Nearly 75% of the 2005 U.S. population growth occurred in these southern tier states. Virtually all of these homes have uninsulated slab perimeters that transfer a small, but steady, flow of heat from conditioned space to outdoors during the heating season. It is estimated that new home foundations constructed each year add 0.016 quads annually to U.S. national energy consumption; we project that roughly one quarter of this amount can be attributed to heat loss through the slab edge and the remaining three quarters to deep ground transfers, depending upon climate. With rising concern over national energy use and the impact of greenhouse gas emissions, it is becoming increasingly imperative that all cost-effective efforts to improve building energy efficiency be implemented. Unlike other building envelope components that have experienced efficiency improvements over the years, slab edge heat loss has largely been overlooked. From our vantage point, a marketable slab edge insulation system would offer significant benefits to homeowners, builders, and the society as a whole. Conventional slab forming involves the process of digging foundation trenches and setting forms prior to the concrete pour. Conventional wood form boards (usually 2 x 10's) are supported by vertical stakes on the outer form board surface, and by supporting 'kickers' driven diagonally from the top of the form board into soil outside the trench. Typically, 2 x 10's can be used only twice before they become waste material, contributing to an additional 400 pounds of construction waste per house. Removal of the form boards and stakes also requires a follow-up trip to the jobsite by the concrete subcontractor and handling (storage/disposal) of the used boards. In the rare cases where the slab is insulated (typically custom homes with radiant

  13. Hydrogen-Bonding Polarizable Intermolecular Potential Model for Water.

    PubMed

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

    2016-12-08

    A polarizable intermolecular potential model with short-range directional hydrogen-bonding interactions was developed for water. The model has a rigid geometry, with bond lengths and angles set to experimental gas-phase values. Dispersion interactions are represented by the Buckingham potential assigned to the oxygen atom, whereas electrostatic interactions are modeled by Gaussian charges. Polarization is handled by a Drude oscillator site, using a negative Gaussian charge attached to the oxygen atom by a harmonic spring. An explicit hydrogen-bonding term is included in the model to account for the effects of charge transfer. The model parameters were optimized to density, configurational energy, pair correlation function, and the dielectric constant of water under ambient conditions, as well as the minimum gas-phase dimer energy. Molecular dynamics and Gibbs ensemble Monte Carlo simulations were performed to evaluate the new model with respect to the thermodynamic and transport properties over a wide range of temperature and pressure conditions. Good agreement between model predictions and experimental data was found for most of the properties studied. The new model yields better performance relative to the majority of existing models and outperforms the BK3 model, which is one of the best polarizable models, for vapor-liquid equilibrium properties, whereas the new model is not better than the BK3 model for representation of other properties. The model can be efficiently simulated with the thermalized Drude oscillator algorithm, resulting in computational costs only 3 times higher than those of the nonpolarizable TIP4P/2005 model, whereas having significantly improved properties. Because it involves only a single Drude oscillator site, the new model is significantly faster than polarizable models with multiple sites. With the explicit inclusion of hydrogen-bond interactions, the model may provide a better description of the phase behavior of aqueous mixtures.

  14. Competing intermolecular interactions in some 'bridge-flipped' isomeric phenylhydrazones.

    PubMed

    Ojala, William H; Arola, Trina M; Brigino, Ann M; Leavell, Jeremy D; Ojala, Charles R

    2012-07-01

    To examine the roles of competing intermolecular interactions in differentiating the molecular packing arrangements of some isomeric phenylhydrazones from each other, the crystal structures of five nitrile-halogen substituted phenylhydrazones and two nitro-halogen substituted phenylhydrazones have been determined and are described here: (E)-4-cyanobenzaldehyde 4-chlorophenylhydrazone, C(14)H(10)ClN(3), (Ia); (E)-4-cyanobenzaldehyde 4-bromophenylhydrazone, C(14)H(10)BrN(3), (Ib); (E)-4-cyanobenzaldehyde 4-iodophenylhydrazone, C(14)H(10)IN(3), (Ic); (E)-4-bromobenzaldehyde 4-cyanophenylhydrazone, C(14)H(10)BrN(3), (IIb); (E)-4-iodobenzaldehyde 4-cyanophenylhydrazone, C(14)H(10)IN(3), (IIc); (E)-4-chlorobenzaldehyde 4-nitrophenylhydrazone, C(13)H(10)ClN(3)O(2), (III); and (E)-4-nitrobenzaldehyde 4-chlorophenylhydrazone, C(13)H(10)ClN(3)O(2), (IV). Both (Ia) and (Ib) are disordered (less than 7% of the molecules have the minor orientation in each structure). Pairs (Ia)/(Ib) and (IIb)/(IIc), related by a halogen exchange, are isomorphous, but none of the 'bridge-flipped' isomeric pairs, viz. (Ib)/(IIb), (Ic)/(IIc) or (III)/(IV), is isomorphous. In the nitrile-halogen structures (Ia)-(Ic) and (IIb)-(IIc), only the bridge N-H group and not the bridge C-H group acts as a hydrogen-bond donor to the nitrile group, but in the nitro-halogen structures (III) (with Z' = 2) and (IV), both the bridge N-H group and the bridge C-H group interact with the nitro group as hydrogen-bond donors, albeit via different motifs. The occurrence here of the bridge C-H contact with a hydrogen-bond acceptor suggests the possibility that other pairs of `bridge-flipped' isomeric phenylhydrazones may prove to be isomorphous, regardless of the change from isomer to isomer in the position of the N-H group within the bridge.

  15. The effects of intramolecular and intermolecular coordination on (31)P nuclear shielding: phosphorylated azoles.

    PubMed

    Chernyshev, Kirill A; Larina, Ludmila I; Chirkina, Elena A; Krivdin, Leonid B

    2012-02-01

    The effects of intramolecular and intermolecular coordination on (31)P nuclear shielding have been investigated in the series of tetracoordinated, pentacoordinated and hexacoordinated N-vinylpyrazoles and intermolecular complexes of N-vinylimidazole and 1-allyl-3,5-dimethylpyrazole with phosphorous pentachloride both experimentally and theoretically. It was shown that either intramolecular or intermolecular coordination involving phosphorous results in a dramatic (31)P nuclear shielding amounting to approximately 150 ppm on changing the phosphorous coordination number by one. A major importance of solvent effects on (31)P nuclear shielding of intramolecular and intermolecular complexes involving N → P coordination bond has been demonstrated. It was found that the zeroth-order regular approximation-gauge-including atomic orbital-B1PW91/DZP method was sufficiently accurate for the calculation of (31)P NMR chemical shifts, provided relativistic corrections are taken into account, the latter being of crucial importance in the description of (31)P nuclear shielding.

  16. Determining the Intermolecular Potential Energy in a Gas: A Physical Chemistry Experiment

    ERIC Educational Resources Information Center

    Olbregts, J.; Walgraeve, J. P.

    1976-01-01

    Describes an experiment in which gas viscosity coefficients over a large temperature range are used to determine the parameters of the intermolecular potential energy and other properties such as virial coefficients. (MLH)

  17. Intermolecular Forces in Introductory Chemistry Studied by Gas Chromatography, Computer Models, and Viscometry

    NASA Astrophysics Data System (ADS)

    Wedvik, Jonathan C.; McManaman, Charity; Anderson, Janet S.; Carroll, Mary K.

    1998-07-01

    An experiment on intermolecular forces for first-term introductory college chemistry is presented. The experiment integrates traditional viscometry-based measurements with modern chromatographic analysis and use of computer-based molecular models. Students performing gas chromatographic (GC) analyses of mixtures of n-alkanes and samples that simulate crime scene evidence discover that liquid mixtures can be separated rapidly into their components based upon intermolecular forces. Each group of students is given a liquid sample that simulates one collected at an arson scene, and the group is required to determine the identity of the accelerant. Students also examine computer models to better visualize how molecular structure affects intermolecular forces: London forces, dipole-dipole interactions, and hydrogen bonding. The relative viscosities of organic liquids are also measured to relate physical properties to intermolecular forces.

  18. Determining the Intermolecular Potential Energy in a Gas: A Physical Chemistry Experiment

    ERIC Educational Resources Information Center

    Olbregts, J.; Walgraeve, J. P.

    1976-01-01

    Describes an experiment in which gas viscosity coefficients over a large temperature range are used to determine the parameters of the intermolecular potential energy and other properties such as virial coefficients. (MLH)

  19. Universal Form of Stochastic Evolution for Slow Variables in Equilibrium Systems

    NASA Astrophysics Data System (ADS)

    Itami, Masato; Sasa, Shin-ichi

    2017-04-01

    Nonlinear, multiplicative Langevin equations for a complete set of slow variables in equilibrium systems are generally derived on the basis of the separation of time scales. The form of the equations is universal and equivalent to that obtained by Green. An equation with a nonlinear friction term for Brownian motion turns out to be an example of the general results. A key method in our derivation is to use different discretization schemes in a path integral formulation and the corresponding Langevin equation, which also leads to a consistent understanding of apparently different expressions for the path integral in previous studies.

  20. Optimization of topical gels with betamethasone dipropionate: selection of gel forming and optimal cosolvent system.

    PubMed

    Băiţan, Mariana; Lionte, Mihaela; Moisuc, Lăcrămioara; Gafiţanu, Eliza

    2011-01-01

    The purpose of these studies was to develop a 0.05% betamethasone gel characterized by physical-chemical stability and good release properties. The preliminary studies were designed to select the gel-forming agents and the excipients compatible with betamethasone dipropionate. In order to formulate a clear gel without particles of drug substances in suspension, a solvent system for the drug substance was selected. The content of drug substance released, the rheological and in vitro release tests were the tools used for the optimal formulation selection. A stable carbomer gel was obtained by solubilization of betamethasone dipropionate in a vehicle composed by 40% PEG 400, 10% ethanol and 5% Transcutol.

  1. Compound Natural Gas Hydrate: A Natural System for Separation of Hydrate-Forming Gases

    NASA Astrophysics Data System (ADS)

    Max, M. D.; Osegovic, J. P.

    2007-12-01

    Natural processes that separate materials from a mixture may exert a major influence on the development of the atmospheres and surfaces of planets, moons, and other planetary bodies. Natural distillation and gravity separation, amongst others, are well known means of differentiating materials through liquid-gas partitioning. One of the least known attributes of clathrate (gas) hydrates is their potential effect on the evolution of planetary system oceans and atmospheres. Gas hydrates separate gases from mixtures of gases by concentrating preferred hydrate-forming materials (HFM) guests within the water-molecule cage structure of crystalline hydrate. Different HFMs have very different fields of stability. When multiple hydrate formers are present, a preference series based on their selective uptake exists. Compound hydrate, which is formed from two or more species of HFM, extract preferred HFM from a mixture in very different proportions to their relative percentages of the original mixture. These compound hydrates can have different formation and dissociation conditions depending on the evolution of the environment. That is, the phase boundary of the compound hydrate that is required for dissociation lies along a lower pressure - higher temperature course. Compound hydrates respond to variations in temperature, pressure, and HFM composition. On Earth, the primary naturally occurring hydrate of interest to global climate modeling is methane hydrate. Oceanic hydrate on Earth is the largest store of carbon in the biosphere that is immediately reactive to environmental change, and is capable of releasing large amounts of methane into the atmosphere over a short geological time span. Hydrate formation is essentially metastable and is very sensitive to environmental change and to gas flux. Where natural variations in temperature and pressure varies so that hydrate will form and dissociate in some cyclical manner, such as in oceans where sea level is capable of rising and

  2. Universal Form of Stochastic Evolution for Slow Variables in Equilibrium Systems

    NASA Astrophysics Data System (ADS)

    Itami, Masato; Sasa, Shin-ichi

    2017-02-01

    Nonlinear, multiplicative Langevin equations for a complete set of slow variables in equilibrium systems are generally derived on the basis of the separation of time scales. The form of the equations is universal and equivalent to that obtained by Green. An equation with a nonlinear friction term for Brownian motion turns out to be an example of the general results. A key method in our derivation is to use different discretization schemes in a path integral formulation and the corresponding Langevin equation, which also leads to a consistent understanding of apparently different expressions for the path integral in previous studies.

  3. Aqueous Two-Phase Systems formed by Biocompatible and Biodegradable Polysaccharides and Acetonitrile

    PubMed Central

    de Brito Cardoso, Gustavo; Souza, Isabela Nascimento; Pereira, Matheus M.; Freire, Mara G.; Soares, Cleide Mara Faria; Lima, Álvaro Silva

    2015-01-01

    In this work, it is shown that novel aqueous two-phase systems can be formed by the combination of acetonitrile and polysaccharides, namely dextran. Several ternary phase diagrams were determined at 25 °C for the systems composed of water + acetonitrile + dextran. The effect of the dextran molecular weight (6,000, 40,000 and 100,000 g.mol−1) was ascertained toward their ability to undergo liquid-liquid demixing. An increase in the dextran molecular weight favors the phase separation. Furthermore, the effect of temperature (25, 35 and 45 °C) was evaluated for the system constituted by the dextran of higher molecular weight. Lower temperatures are favorable for phase separation since lower amounts of dextran and acetonitrile are required for the creation of aqueous two-phase systems. In general, acetonitrile is enriched in the top phase while dextran is majorly concentrated in the bottom phase. The applicability of this new type of two-phase systems as liquid-liquid extraction approaches was also evaluated by the study of the partition behavior of a well-known antioxidant – vanillin - and used here as a model biomolecule. The optimized conditions led to an extraction efficiency of vanillin of 95% at the acetonitrile-rich phase. PMID:25729320

  4. Aqueous Two-Phase Systems formed by Biocompatible and Biodegradable Polysaccharides and Acetonitrile.

    PubMed

    de Brito Cardoso, Gustavo; Souza, Isabela Nascimento; Pereira, Matheus M; Freire, Mara G; Soares, Cleide Mara Faria; Lima, Álvaro Silva

    2014-11-05

    In this work, it is shown that novel aqueous two-phase systems can be formed by the combination of acetonitrile and polysaccharides, namely dextran. Several ternary phase diagrams were determined at 25 °C for the systems composed of water + acetonitrile + dextran. The effect of the dextran molecular weight (6,000, 40,000 and 100,000 g.mol(-1)) was ascertained toward their ability to undergo liquid-liquid demixing. An increase in the dextran molecular weight favors the phase separation. Furthermore, the effect of temperature (25, 35 and 45 °C) was evaluated for the system constituted by the dextran of higher molecular weight. Lower temperatures are favorable for phase separation since lower amounts of dextran and acetonitrile are required for the creation of aqueous two-phase systems. In general, acetonitrile is enriched in the top phase while dextran is majorly concentrated in the bottom phase. The applicability of this new type of two-phase systems as liquid-liquid extraction approaches was also evaluated by the study of the partition behavior of a well-known antioxidant - vanillin - and used here as a model biomolecule. The optimized conditions led to an extraction efficiency of vanillin of 95% at the acetonitrile-rich phase.

  5. Synergy between twisted conformation and effective intermolecular interactions: strategy for efficient mechanochromic luminogens with high contrast.

    PubMed

    Yuan, Wang Zhang; Tan, Yeqiang; Gong, Yongyang; Lu, Ping; Lam, Jacky W Y; Shen, Xiao Yuan; Feng, Cunfang; Sung, Herman H-Y; Lu, Yawei; Williams, Ian D; Sun, Jing Zhi; Zhang, Yongming; Tang, Ben Zhong

    2013-05-28

    A strategy towards efficient mechanochromic luminogens with high contrast is developed. The twisted propeller-like conformations and effective intermolecular interactions not only endow the luminogens with AIE characteristics and high efficiency in the crystalline state, but also render them to undergo conformational planarization and disruption in intermolecular interactions upon mechanical stimuli, resulting in remarkable changes in emission wavelength and efficiency. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Systemic effects of urban form on air pollution and environmental quality

    SciTech Connect

    Okamoto, P.C.

    1997-12-31

    The form and design of cities and towns have a direct impact on the quality of the natural environment, particularly air and water quality. This paper illustrates some of the dynamic relationships between the form of urban environments and air and water pollution. Recent research suggests how urban form affects environmental quality in at least three ways: (a) how suburban development and its dependency on the private motor vehicle increases air pollution, (b) how exterior building materials help to generate urban heat islands and ozone precursors, and (c) how conventional stormwater drainage systems transport polluted urban runoff into waterways. Today`s aging urban infrastructure provides an important and timely opportunity to re-examine the design of cities and towns with a goal of enhancing overall environmental quality. Many miles of roads, freeways, bridges, and stormwater culverts and pipes are in poor condition and need to be repaired or replaced, while many cities are now failing to meet air and water quality standards designed to protect human and environmental health. This paper also explores seven urban planning and design concepts that could reduce the magnitude of air and water pollution in urban environments and help to improve the health of both cities and their residents.

  7. A General Closed-Form Solution for the Lunar Reconnaissance Orbiter (LRO) Antenna Pointing System

    NASA Technical Reports Server (NTRS)

    Shah, Neerav; Chen, J. Roger; Hashmall, Joseph A.

    2010-01-01

    The National Aeronautics and Space Administration s (NASA) Lunar Reconnaissance Orbiter (LRO) launched on June 18, 2009 from the Cape Canaveral Air Force Station aboard an Atlas V launch vehicle into a direct insertion trajectory to the Moon LRO, designed, built, and operated by the NASA Goddard Space Flight Center in Greenbelt, MD, is gathering crucial data on the lunar environment that will help astronauts prepare for long-duration lunar expeditions. During the mission s nominal life of one year its six instruments and one technology demonstrator will find safe landing site, locate potential resources, characterize the radiation environment and test new technology. To date, LRO has been operating well within the bounds of its requirements and has been collecting excellent science data images taken from the LRO Camera Narrow Angle Camera (LROC NAC) of the Apollo landing sites have appeared on cable news networks. A significant amount of information on LRO s science instruments is provided at the LRO mission webpage. LRO s Attitude Control System (ACS), in addition to controlling the orientation of the spacecraft is also responsible for pointing the High Gain Antenna (HGA). A dual-axis (or double-gimbaled) antenna, deployed on a meter-long boom, is required to point at a selected Earth ground station. Due to signal loss over the distance from the Moon to Earth, pointing precision for the antenna system is very tight. Since the HGA has to be deployed in spaceflight, its exact geometry relative to the spacecraft body is uncertain. In addition, thermal distortions and mechanical errors/tolerances must be characterized and removed to realize the greatest gain from the antenna system. These reasons necessitate the need for an in-flight calibration. Once in orbit around the moon, a series of attitude maneuvers was conducted to provide data needed to determine optimal parameters to load onboard, which would account for the environmental and mechanical errors at any

  8. Children with dyslexia lack multiple specializations along the visual word-form (VWF) system.

    PubMed

    van der Mark, Sanne; Bucher, Kerstin; Maurer, Urs; Schulz, Enrico; Brem, Silvia; Buckelmüller, Jsabelle; Kronbichler, Martin; Loenneker, Thomas; Klaver, Peter; Martin, Ernst; Brandeis, Daniel

    2009-10-01

    Developmental dyslexia has been associated with a dysfunction of a brain region in the left inferior occipitotemporal cortex, called the "visual word-form area" (VWFA). In adult normal readers, the VWFA is specialized for print processing and sensitive to the orthographic familiarity of letter strings. However, it is still unclear whether these two levels of occipitotemporal specialization are affected in developmental dyslexia. Specifically, we investigated whether (a) these two levels of specialization are impaired in dyslexic children with only a few years of reading experience and (b) whether this impairment is confined to the left inferior occipitotemporal VWFA, or extends to adjacent regions of the "VWF-system" with its posterior-anterior gradient of print specialization. Using fMRI, we measured brain activity in 18 dyslexic and 24 age-matched control children (age 9.7-12.5 years) while they indicated if visual stimuli (real words, pseudohomophones, pseudowords and false-fonts) sounded like a real word. Five adjacent regions of interest (ROIs) in the bilateral occipitotemporal cortex covered the full anterior-posterior extent of the VWF-system. We found that control and dyslexic children activated the same main areas within the reading network. However, a gradient of print specificity (higher anterior activity to letter strings but higher posterior activity to false-fonts) as well as a constant sensitivity to orthographic familiarity (higher activity for unfamiliar than familiar word-forms) along the VWF-system could only be detected in controls. In conclusion, analyzing responses and specialization profiles along the left VWF-system reveals that children with dyslexia show impaired specialization for both print and orthography.

  9. Oriented covalent immobilization of antibodies for measurement of intermolecular binding forces between zipper-like contact surfaces of split inteins

    PubMed Central

    Sorci, Mirco; Dassa, Bareket; Liu, Hongwei; Anand, Gaurav; Dutta, Amit K.; Pietrokovski, Shmuel; Belfort, Marlene; Belfort, Georges

    2013-01-01

    In order to measure the intermolecular binding forces between two halves (or partners) of naturally split protein splicing elements called inteins, a novel thiol-hydrazide linker was designed and used to orient immobilized antibodies specific for each partner. Activation of the surfaces was achieved in one step allowing direct force measurements of the formation of a peptide bond catalyzed by the binding of the two partners of the split intein (called protein trans-splicing). Through this binding process, a whole functional intein is formed resulting in subsequent splicing. Atomic force microscopy (AFM) was used to directly measure the split intein partner binding at 1µm/s between native (wild-type) and mixed pairs of C- and N-terminal partners of naturally occurring split inteins from three cyanobacteria. Native and mixed pairs exhibit similar binding forces within the error of the measurement technique (~52 pN). Bioinformatic sequence analysis and computational structural analysis discovered a zipper-like contact between the two partners with electrostatic and non-polar attraction between multiple aligned ion pairs and hydrophobic residues. Also, we tested the Jarzynski’s equality and demonstrated, as expected, that non-equilibrium dissipative measurements obtained here gave larger energies of interaction as compared with those for equilibrium. Hence, AFM coupled with our immobilization strategy and computational studies provides a useful analytical tool for the direct measurement of intermolecular association of split inteins and could be extended to any interacting protein pair. PMID:23679912

  10. Molecular structure and effects of intermolecular hydrogen bonding on the vibrational spectrum of trifluorothymine, an antitumor and antiviral agent.

    PubMed

    Cırak, Cağrı; Koç, Nurettin

    2012-09-01

    In the present work, the experimental and the theoretical vibrational spectra of trifluorothymine were investigated. The FT-IR (400-4000 cm(-1)) and μ-Raman spectra (100-4000 cm(-1)) of trifluorothymine in the solid phase were recorded. The geometric parameters (bond lengths and bond angles) and vibrational frequencies of the title molecule in the ground state were calculated using ab initio Hartree-Fock (HF) method and density functional theory (B3LYP) method with the 6-31++G(d,p) and 6-311++G(d,p) basis sets for the first time. The optimized geometric parameters and the theoretical vibrational frequencies were found to be in good agreement with the corresponding experimental data and with results found in the literature. Vibrational frequencies were assigned based on the potential energy distribution using the VEDA 4 program. The dimeric form of trifluorothymine was also simulated to evaluate the effect of intermolecular hydrogen bonding on the vibrational frequencies. It was observed that the stretching modes shifted to lower frequencies, while the in-plane and out-of-plane bending modes shifted to higher frequencies due to the intermolecular N-H⋯O hydrogen bonds.

  11. Influence of intermolecular amide hydrogen bonding on the geometry, atomic charges, and spectral modes of acetanilide: An ab initio study

    NASA Astrophysics Data System (ADS)

    Binoy, J.; Prathima, N. B.; Murali Krishna, C.; Santhosh, C.; Hubert Joe, I.; Jayakumar, V. S.

    2006-08-01

    Acetanilide, a compound of pharmaceutical importance possessing pain-relieving properties due to its blocking the pulse dissipating along the nerve fiber, is subjected to vibrational spectral investigation using NIR FT Raman, FT-IR, and SERS. The geometry, Mulliken charges, and vibrational spectrum of acetanilide have been computed using the Hartree-Fock theory and density functional theory employing the 6-31G (d) basis set. To investigate the influence of intermolecular amide hydrogen bonding, the geometry, charge distribution, and vibrational spectrum of the acetanilide dimer have been computed at the HF/6-31G (d) level. The computed geometries reveal that the acetanilide molecule is planar, while twisting of the secondary amide group with respect to the phenyl ring is found upon hydrogen bonding. The trans isomerism and “amido” form of the secondary amide, hyperconjugation of the C=O group with the adjacent C-C bond, and donor-acceptor interaction have been investigated using computed geometry. The carbonyl stretching band position is found to be influenced by the tendency of the phenyl ring to withdraw nitrogen lone pair, intermolecular hydrogen bonding, conjugation, and hyperconjugation. A decrease in the NH and C=O bond orders and increase in the C-N bond orders due to donor-acceptor interaction can be observed in the vibrational spectra. The SERS spectral analysis reveals that the flat orientation of the molecule on the adsorption plane is preferred.

  12. Spectral Moments of Collision-Induced Absorption of CO2 Pairs: The Role of the Intermolecular Potential

    NASA Technical Reports Server (NTRS)

    Gruszka, Marcin; Borysow, Aleksandra

    1994-01-01

    In this paper we examine the role of the anisotropy of the intermolecular potential in the rototranslational collision-induced absorption of the CO2 pairs. Using newly developed formulas that include the effects of anisotropy of the potential to all orders, we calculate the two lowest spectral moments gamma(prime), and alpha(prime), for four different classes of C02 pair potentials and compare the results with the experimental values. We assumed only multipolar induction in the process of forming the induced dipole, with the second-order contributions included. Using a site-site LJ and a site-site semi-ab initio intermolecular potentials we were able to reproduce the experimental values of gamma(prime), and alpha(prime) moments over entire temperature range from 230 to 330 K. Also, the role of an electrostatic interaction between two C02 molecules and its impact on the spectral moments is thoroughly investigated. An isotropic core with a point quadrupole centered at each molecule is shown to be an inadequate representation of the C02-CO2 potential. Additionally, we show the results obtained with the first- and second-order perturbation theory to be more than twice too small.

  13. Topological characterization of electron density, electrostatic potential and intermolecular interactions of 2-nitroimidazole: an experimental and theoretical study.

    PubMed

    Kalaiarasi, Chinnasamy; Pavan, Mysore S; Kumaradhas, Poomani

    2016-10-01

    An experimental charge density distribution of 2-nitroimidazole was determined from high-resolution X-ray diffraction and the Hansen-Coppens multipole model. The 2-nitroimidazole compound was crystallized and a high-angle X-ray diffraction intensity data set has been collected at low temperature (110 K). The structure was solved and further, an aspherical multipole model refinement was performed up to octapole level; the results were used to determine the structure, bond topological and electrostatic properties of the molecule. In the crystal, the molecule exhibits a planar structure and forms weak and strong intermolecular hydrogen-bonding interactions with the neighbouring molecules. The Hirshfeld surface of the molecule was plotted, which explores different types of intermolecular interactions and their strength. The topological analysis of electron density at the bond critical points (b.c.p.) of the molecule was performed, from that the electron density ρbcp(r) and the Laplacian of electron density ∇(2)ρbcp(r) at the b.c.p.s of the molecule have been determined; these parameters show the charge concentration/depletion of the nitroimidazole bonds in the crystal. The electrostatic parameters like atomic charges and the dipole moment of the molecule were calculated. The electrostatic potential surface of the molecule has been plotted, and it displays a large electronegative region around the nitro group. All the experimental results were compared with the corresponding theoretical calculations performed using CRYSTAL09.

  14. pH-controlled carbon nanotube aggregation/dispersion based on intermolecular i-motif DNA formation.

    PubMed

    Cheng, Enjun; Yang, Yang; Liu, Dongsheng

    2010-11-01

    In this work, we report a new strategy to manipulate the aggregation and dispersion of carbon nanotube in solution via formation of intermolecular i-motif (four-stranded C-quadruplex) structures in a pH dependent manner. Firstly, single-stranded (ss) DNAs containing two stretches of cytosine (C)-rich domains are covalently linked to carbon nanotubes. At pH 8.0, DNAs are at random coil state, which enhance the dispersion of multi-wall carbon nanotubes (MWNTs) in water; after changing pH to 5.0, the intermolecular i-motif structures formed by the C-rich ssDNAs on neighboring carbon nanotube could drive the MWNTs aggregate. This process is reversible and the transition process has been verified by circular dichroism (CD) spectroscopy, gel electrophoresis and transmission electron microscopy (TEM). Considering the mechanical properties of carbon nanotube, this finding will benefit many application research fields, such as artificial muscle, functional nano-devices and so on.

  15. A method for the quantification of model form error associated with physical systems.

    SciTech Connect

    Wallen, Samuel P.; Brake, Matthew Robert

    2014-03-01

    In the process of model validation, models are often declared valid when the differences between model predictions and experimental data sets are satisfactorily small. However, little consideration is given to the effectiveness of a model using parameters that deviate slightly from those that were fitted to data, such as a higher load level. Furthermore, few means exist to compare and choose between two or more models that reproduce data equally well. These issues can be addressed by analyzing model form error, which is the error associated with the differences between the physical phenomena captured by models and that of the real system. This report presents a new quantitative method for model form error analysis and applies it to data taken from experiments on tape joint bending vibrations. Two models for the tape joint system are compared, and suggestions for future improvements to the method are given. As the available data set is too small to draw any statistical conclusions, the focus of this paper is the development of a methodology that can be applied to general problems.

  16. Improving R-value in brick systems using various pore-forming agents

    NASA Astrophysics Data System (ADS)

    Shepherd, Graham Miller

    Energy efficiency and energy savings are two topics that have continued to gain momentum over the last decade. This topic is extremely important when it comes to the construction of buildings and homes. Efforts have been ongoing to increase the insulation value of brick systems to hinder the conductive heat transfer through the material. The use of pore-forming agents (PFA's have been studied to increase the porosity within a ceramic system, through sacrificial burnout or place-holder method, which leave a residual, defined pore size distribution. This increase in porosity leads to better insulating capabilities and inherently lower conductivity values. In this study, varying types and sizes of pore-forming agents were investigated, such as organic fuels/wastes such as peanut hulls, commercially produced ceramic hollow spheres, and aluminum hydroxide. After extrusion and firing, the physical properties (bulk density, cold water absorption, flexural strength, pore size distribution) were investigated to relate to the effect on the thermal conductivity. Both size fractions of peanut hulls (-24/+50 M & -50/+100 M) suggested the lowest recorded thermal conductivity fired to 1100°C at 15% weight addition level at 0.399+/-;0.010 and 0.422+/-0.011 W/m K, respectively.

  17. Effect of experimental glaucoma on the non-image forming visual system.

    PubMed

    de Zavalía, Nuria; Plano, Santiago A; Fernandez, Diego C; Lanzani, María Florencia; Salido, Ezequiel; Belforte, Nicolás; Sarmiento, María I Keller; Golombek, Diego A; Rosenstein, Ruth E

    2011-06-01

    Glaucoma is a leading cause of blindness worldwide, characterized by retinal ganglion cell degeneration and damage to the optic nerve. We investigated the non-image forming visual system in an experimental model of glaucoma in rats induced by weekly injections of chondroitin sulphate (CS) in the eye anterior chamber. Animals were unilaterally or bilaterally injected with CS or vehicle for 6 or 10 weeks. In the retinas from eyes injected with CS, a similar decrease in melanopsin and Thy-1 levels was observed. CS injections induced a similar decrease in the number of melanopsin-containing cells and superior collicular retinal ganglion cells. Experimental glaucoma induced a significant decrease in the afferent pupil light reflex. White light significantly decreased nocturnal pineal melatonin content in control and glaucomatous animals, whereas blue light decreased this parameter in vehicle- but not in CS-injected animals. A significant decrease in light-induced c-Fos expression in the suprachiasmatic nuclei was observed in glaucomatous animals. General rhythmicity and gross entrainment appear to be conserved, but glaucomatous animals exhibited a delayed phase angle with respect to lights off and a significant increase in the percentage of diurnal activity. These results indicate the glaucoma induced significant alterations in the non-image forming visual system. © 2011 The Authors. Journal of Neurochemistry © 2011 International Society for Neurochemistry.

  18. Pore-forming Activity of the Escherichia coli Type III Secretion System Protein EspD*

    PubMed Central

    Chatterjee, Abhishek; Caballero-Franco, Celia; Bakker, Dannika; Totten, Stephanie; Jardim, Armando

    2015-01-01

    Enterohemorrhagic Escherichia coli is a causative agent of gastrointestinal and diarrheal diseases. Pathogenesis associated with enterohemorrhagic E. coli involves direct delivery of virulence factors from the bacteria into epithelial cell cytosol via a syringe-like organelle known as the type III secretion system. The type III secretion system protein EspD is a critical factor required for formation of a translocation pore on the host cell membrane. Here, we show that recombinant EspD spontaneously integrates into large unilamellar vesicle (LUV) lipid bilayers; however, pore formation required incorporation of anionic phospholipids such as phosphatidylserine and an acidic pH. Leakage assays performed with fluorescent dextrans confirmed that EspD formed a structure with an inner diameter of ∼2.5 nm. Protease mapping indicated that the two transmembrane helical hairpin of EspD penetrated the lipid layer positioning the N- and C-terminal domains on the extralumenal surface of LUVs. Finally, a combination of glutaraldehyde cross-linking and rate zonal centrifugation suggested that EspD in LUV membranes forms an ∼280–320-kDa oligomeric structure consisting of ∼6–7 subunits. PMID:26324713

  19. Injectable long-acting in situ forming systems for Radix Ophiopogonis polysaccharide.

    PubMed

    Shi, XiaoLi; Lin, Xiao; Yao, ChunXia; Shen, Lan; Feng, Yi

    2015-01-01

    In the area of injectable long-acting formulations, the in situ forming system (ISFS) is an attractive alternative for its various superiorities. In this study, both hydrophilic and hydrophobic in situ forming systems, using Poloxamer and sucrose acetate isobutyrate (SAIB) or poly(D,L-lactide-co-glycolide) copolymer (PLGA) as carrier, respectively, were investigated for Radix Ophiopogonis polysaccharide (ROP), a natural anti-myocardial ischemic fructan. A reasonable and applicable range of formulations were selected from each carrier for in vivo study by investigating their rheological property. The results from in vivo evaluation show that relatively promising sustained behaviors were achieved by formulations 24% P407/10% P188, 40% PLGA30k/NMP, and 30% PLGA50k/NMP. Significant differences of drug release kinetics were observed between in situ thermally-induced Poloxamer-based hydrogels and in situ solvent exchange-induced hydrophobic PLGA depots. This suggests that different ISFS could be chosen to provide different application purpose for polysaccharide drugs. In the case of ROP, Poloxamer-based ISFS is promising for short-term acute therapies; however, PLGA-based ISFS might be promising for long-term precaution or/and cure of myocardial ischemia.

  20. In situ-forming hydrogels--review of temperature-sensitive systems.

    PubMed

    Ruel-Gariépy, Eve; Leroux, Jean-Christophe

    2004-09-01

    In the past few years, an increasing number of in situ-forming systems have been reported in the literature for various biomedical applications, including drug delivery, cell encapsulation, and tissue repair. There are several possible mechanisms that lead to in situ gel formation: solvent exchange, UV-irradiation, ionic cross-linkage, pH change, and temperature modulation. The thermosensitive approach can be advantageous for particular applications as it does not require organic solvents, co-polymerization agents, or an externally applied trigger for gelation. In the last 2 decades, several thermosensitive formulations have been proposed. This manuscript focuses on aqueous polymeric solutions that form implants in situ in response to temperature change, generally from ambient to body temperature. It mainly reviews the characterization and use of polysaccharides, N-isopropylacrylamide copolymers, poly(ethylene oxide-b-propylene oxide-b-ethylene oxide) (poloxamer) and its copolymers, poly(ethylene oxide)/(D,L-lactic acid-co-glycolic acid) copolymers, and thermosensitive liposome-based systems.