Science.gov

Sample records for intermolecular systems formed

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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. PMID:14698403

  7. 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.

  8. 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.

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

    PubMed

    Israelachvili, Jacob; Ruths, Marina

    2013-08-01

    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.

  10. 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

    2013-08-01

    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.

  11. 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

    2013-08-01

    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. PMID:23848456

  12. Desensitization of metastable intermolecular composites

    DOEpatents

    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.

  13. 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.

  14. Intermolecular interactions and 3D structure in cellulose-NaOH-urea aqueous system.

    PubMed

    Jiang, Zhiwei; Fang, Yan; Xiang, Junfeng; Ma, Yanping; Lu, Ang; Kang, Hongliang; Huang, Yong; Guo, Hongxia; Liu, Ruigang; Zhang, Lina

    2014-08-28

    The dissolution of cellulose in NaOH/urea aqueous solution at low temperature is a key finding in cellulose science and technology. In this paper, (15)N and (23)Na NMR experiments were carried out to clarify the intermolecular interactions in cellulose/NaOH/urea aqueous solution. It was found that there are direct interactions between OH(-) anions and amino groups of urea through hydrogen bonds and no direct interaction between urea and cellulose. Moreover, Na(+) ions can interact with both cellulose and urea in an aqueous system. These interactions lead to the formation of cellulose-NaOH-urea-H2O inclusion complexes (ICs). (23)Na relaxation results confirmed that the formation of urea-OH(-) clusters can effectively enhance the stability of Na(+) ions that attracted to cellulose chains. Low temperature can enhance the hydrogen bonding interaction between OH(-) ions and urea and improve the binding ability of the NaOH/urea/H2O clusters that attached to cellulose chains. Cryo-TEM observation confirmed the formation of cellulose-NaOH-urea-H2O ICs, which is in extended conformation with mean diameter of about 3.6 nm and mean length of about 300 nm. Possible 3D structure of the ICs was proposed by the M06-2X/6-31+G(d) theoretical calculation, revealing the O3H···O5 intramolecular hydrogen bonds could remain in the ICs. This work clarified the interactions in cellulose/NaOH/urea aqueous solution and the 3D structure of the cellulose chain in dilute cellulose/NaOH/urea aqueous solution.

  15. 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.

  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

    2015-10-01

    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. 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.

  18. Desensitization and recovery of metastable intermolecular composites

    DOEpatents

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

    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.

  19. Synthesis, crystal growth and physicochemical studies on a novel organic inter-molecular compound; 3,5-dinitrobenzoic acid and salicylamide system

    NASA Astrophysics Data System (ADS)

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

    2015-06-01

    The phase diagram of salicylamide (SAM) and 3,5-dinitrobenzoic acid (DNBA) system was determined by the thaw-melt method. Results show the formation of an inter-molecular compound and two eutectics. The values of heat of mixing, entropy of fusion, roughness parameter, interfacial energy, and the excess thermodynamic functions were calculated from the enthalpy of fusion data determined by the differential scanning calorimetric (DSC) method. The spectroscopic investigations (IR and NMR) suggest the presence of hydrogen bonding between the components of the compound. A single crystal of the inter-molecular compound was grown using slow cooling technique from the mixed solvent of ethanol and triple distilled water in 2:1 volume ratio. The single crystal analysis and the atomic packing pattern of the grown crystal confirm the monoclinic crystal structure with P21/c space group. The solubility of the inter-molecular compound was determined in the mixed solvent at different temperatures. Using solubility and entropy of fusion data, the entropy of dissolution and heat of mixing were calculated. The optical transmittance spectra of the crystal of the inter-molecular compound show 75% transmittance and the band gap of the crystal was found to be 3.00 eV. The refractive index of the crystal was computed to be 2.50 at the cut off wavelength.

  20. 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.

  1. Surface activity at the planar interface in relation to the thermodynamics of intermolecular interactions in the ternary system: maltodextrin-small-molecule surfactant-legumin.

    PubMed

    Myasoedova, M S.; Semenova, M G.; Belyakova, L E.; Antipova, A S.

    2001-07-01

    We report on the effect of potato maltodextrins with variable dextrose equivalent (Paselli SA-2, SA-6 and SA-10) on the surface behavior at the air-water interface of the mixture: legumin+small-molecule surfactant. Distinct in nature small-molecule surfactants (model: sodium salt of capric acid, Na-caprate; and commercially important: a citric acid ester of monoglyceride, CITREM) have been under our consideration. The role of the structure of both of the maltodextrins and the small-molecule surfactants in the effect studied has been elucidated by measurements in a bulk aqueous medium of the enthalpy of their interaction from mixing calorimetry, value of weight average molecular weight of the maltodextrins and the thermodynamics of the pair maltodextrin-solvent and maltodextrin-protein interactions from laser static light scattering. The combined data of mixing calorimetry and light scattering suggest some complex formation between the small-molecule surfactants and the maltodextrins. Predominantly hydrophobic interactions along with hydrogen bonding form the basis of the complexes. The effect of the maltodextrins on the thermodynamics of the protein heat denaturation and thereby on the protein conformational stability in the presence of the small-molecule surfactants has been studied by differential scanning calorimetry. The interrelation between the thermodynamics of intermolecular interactions in a bulk and the surface behavior at the planar air-water interface of the ternary systems (maltodextrin+legumin+small-molecule surfactant) has been elucidated by tensiometry. The effect of the maltodextrins on the surface activity of mixtures of legumin with the small-molecule surfactants is governed by the competitive in relation to the protein interactions with the small-molecule surfactants and a subsequent change in the thermodynamic properties of the both biopolymers, which are favorable to the ternary complex formation.

  2. 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.

  3. 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.

  4. [Kinin forming system and ovulation].

    PubMed

    Seki, M

    1984-06-01

    The aim of the study is to clarify the role of the kinin forming system on ovulation. The results were as follows, Plasma prekallikrein of superovulated prepubertal rats was decreased to 50-60% of the normal level after PMS injection and 80-90% of the normal level after hCG injection. The lowest level was 33.8% 39 hours after PMS injection. Aprotinin suppressed the superovulation of prepubertal rats at doses of 16.7 X 10(4) KIE and 37.8 X 10(4) KIE (p less than 0.01). These results showed that the kinin production system has an effect on ovulation. As the sex steroid hormone, estradil benzoate, progesterone and testosterone propinate were used in oophorectomized mice. They had no effect on the plasma prekallikrein level. The plasma prekallikrein level during the estrus cycle of mature female mice was 85.5% of the control level in preestrus, 80.3% in estrus, 83.7% in metestrus and 89.8% in diestrus. The mean was 83.9%, which was significantly lower than that for oophorectomized mice (94.1%). It is proved that plasma prekallikrein was consumed and the kinin forming system was accelerated in the ovary with ovulation. PMID:6205107

  5. Effect of intermolecular hydrogen bonding and proton transfer on fluorescence of salicylic acid

    NASA Astrophysics Data System (ADS)

    Denisov, G. S.; Golubev, N. S.; Schreiber, V. M.; Shajakhmedov, Sh. S.; Shurukhina, A. V.

    1997-12-01

    Effects of intermolecular interactions, in particular the influence of intermolecular hydrogen bonds formed by salicylic acid (SA) as a proton donor with proton acceptors of different strength, on fluorescence spectra of SA in non-aqueous solutions have been investigated. Infrared spectra of studied systems have been analyzed in order to elucidate the ground state structure of the complexes formed. It has been found that at the room temperature in dilute solutions in non-polar or slightly polar aprotic solvents, where the SA molecule is not involved in intermolecular hydrogen bonding, the position of the main (blue) fluorescence component is determined by the excited state intramolecular proton transfer (ESIPT) in the lowest singlet excited state S 1. With increasing proton acceptor ability of the environment, when formation of weak or middle strength intermolecular H-bonds is possible, the emission band shifts gradually to lower frequency, the quantum yield falls and poorly resolved doublet structure becomes more pronounced, especially in the solvents containing heavy bromine atoms. As a possible reason for these effects, coupling between the S 1 and closely lying triplet term is considered. With the strongest proton acceptors like aliphatic amines, intermolecular proton transfer with ionic pair formation in the ground state and double (intra- and intermolecular) proton transfer in the excited state take place, resulting in a blue shift of the emission band. Similar emission is typical for the SA anion in aqueous solutions. The p Ka value of SA in S 1 state has been found to be 3.1. Such a small value can be explained taking into account the ESIPT reaction following the excitation. The SA complex with pyridine exhibits emission spectrum containing both molecular-like and anion-like bands with relative intensities strongly dependent on the temperature and solvent properties. The most probable origin of this dual emission is the molecular-ionic tautomerism caused by

  6. 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.

  7. The structure of a tetrameric α-carbonic anhydrase from Thermovibrio ammonificans reveals a core formed around intermolecular disulfides that contribute to its thermostability.

    PubMed

    James, Paul; Isupov, Michail N; Sayer, Christopher; Saneei, Vahid; Berg, Svein; Lioliou, Maria; Kotlar, Hans Kristian; Littlechild, Jennifer A

    2014-10-01

    Carbonic anhydrase enzymes catalyse the reversible hydration of carbon dioxide to bicarbonate. A thermophilic Thermovibrio ammonificans α-carbonic anhydrase (TaCA) has been expressed in Escherichia coli and structurally and biochemically characterized. The crystal structure of TaCA has been determined in its native form and in two complexes with bound inhibitors. The tetrameric enzyme is stabilized by a unique core in the centre of the molecule formed by two intersubunit disulfides and a single lysine residue from each monomer that is involved in intersubunit ionic interactions. The structure of this core protects the intersubunit disulfides from reduction, whereas the conserved intrasubunit disulfides are not formed in the reducing environment of the E. coli host cytosol. When oxidized to mimic the environment of the periplasmic space, TaCA has increased thermostability, retaining 90% activity after incubation at 70°C for 1 h, making it a good candidate for industrial carbon-dioxide capture. The reduction of all TaCA cysteines resulted in dissociation of the tetrameric molecule into monomers with lower activity and reduced thermostability. Unlike other characterized α-carbonic anhydrases, TaCA does not display esterase activity towards p-nitrophenyl acetate, which appears to result from the increased rigidity of its protein scaffold. PMID:25286845

  8. White polymer light-emitting electrochemical cells using emission from exciplexes with long intermolecular distances formed between polyfluorene and π-conjugated amine molecules

    NASA Astrophysics Data System (ADS)

    Nishikitani, Y.; Takeuchi, H.; Nishide, H.; Uchida, S.; Yazaki, S.; Nishimura, S.

    2015-12-01

    The authors present white polymer light-emitting electrochemical cells (PLECs) fabricated with polymer blend films of poly(9,9-di-n-dodecylfluorenyl-2,7-diyl) (PFD) and π-conjugated triphenylamine molecules. The PLECs have bulk heterojunction structures composed of van der Waals interfaces between the PFD segments and the amine molecules. White-light electroluminescence (EL) can be achieved via light-mixing of the blue exciton emission from PFD and long-wavelength exciplex emission from excited complexes consisting of PFD segments (acceptors (As)) and the amine molecules (donors (Ds)). Precise control of the distances between the PFD and the amine molecules, affected through proper choice of the concentrations of PFD, amine molecules, and polymeric solid electrolytes, is critical to realizing white emission. White PLECs can be fabricated with PFD and amine molecules whose highest occupied molecular orbital (HOMO) levels range from -5.3 eV to -5.0 eV. Meanwhile, PLECs fabricated with amine molecules whose HOMO levels are lower than -5.6 eV cannot produce exciplex emission. The distances between the PFD and amine molecules of the exciplexes appear to be larger than 0.4 nm. These experimental data are explained by perturbation theory using the charge-transfer state ( A - D + ), the locally excited state ( A * D ), which is assumed to be the locally excited acceptor state in which there is no interaction with the donor molecule; and the energy gap between the HOMO levels of the PFD and the amine molecules. Color-stable white PLECs were fabricated using 4,4',4″-tris[N-(2-naphthyl)-N-phenylamino]-triphenylamine, which has a HOMO level of -5.2 eV, as the amine molecule, and the color stability of the device is a function of the fact that PFD forms exciplexes with these molecules.

  9. 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.

  10. Intermolecular dimerization with pillared layered clay templates.

    SciTech Connect

    Wiederrecht, G. P.; Sandi, G.; Carrado, K. A.; Seifert, S.; Chemistry

    2001-11-19

    Solutions of pyrene in the presence of a pillared, layered montmorillonite clay produce hybrid organic-inorganic materials with substantial molecular loading in the gallery regions between the clay layers. The results are in sharp contrast to other aromatics, such as benzene, naphthalene, or perylene, which show minimal incorporation of the molecules into the gallery regions of the clay. We present evidence that the unusual affinity for pyrene to form intermolecular dimers is the reason for the high loading. Pyrene monomers are easily introduced to the layers. Through steric hindrance, subsequent intermolecular dimer formation is allowed, and they are captured by the pillared, layered structure. CW and time-resolved emission spectra strongly indicate the presence of face-to-face intermolecular dimers (excimers) within the clay galleries. The combination of the ease of high molecular loading into an inorganic, high aspect ratio template and the collective optical properties of the organic layer may be useful as a new means to create hybrid structures.

  11. Frontier orbital symmetry control of intermolecular electron transfer

    SciTech Connect

    Stevens, B.

    1990-11-01

    Research continued on the study of intermolecular electron transfer. This report discusses the following topics: fluorescence quenching by electron transfer and the modification of quenching dynamics by solvent properties and net free energy change; transient absorption measurements following selective excitation of 1:1 EDA complex isomers; selective quenching of dual fluorescence from linked EDA systems; electron-transfer sensitized cycloreversion of rubrene endoperoxide; and vibronic modification of adiabatic requirements for intermolecular electron transfer. (CBS)

  12. Perturbation analyses of intermolecular interactions.

    PubMed

    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

  13. 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

  14. 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…

  15. Intermolecular electrostatic energies using density fitting.

    PubMed

    Cisneros, G Andrés; Piquemal, Jean-Philip; Darden, Thomas A

    2005-07-22

    A method is presented to calculate the electron-electron and nuclear-electron intermolecular Coulomb interaction energy between two molecules by separately fitting the unperturbed molecular electron density of each monomer. This method is based on the variational Coulomb fitting method which relies on the expansion of the ab initio molecular electron density in site-centered auxiliary basis sets. By expanding the electron density of each monomer in this way the integral expressions for the intermolecular electrostatic calculations are simplified, lowering the operation count as well as the memory usage. Furthermore, this method allows the calculation of intermolecular Coulomb interactions with any level of theory from which a one-electron density matrix can be obtained. Our implementation is initially tested by calculating molecular properties with the density fitting method using three different auxiliary basis sets and comparing them to results obtained from ab initio calculations. These properties include dipoles for a series of molecules, as well as the molecular electrostatic potential and electric field for water. Subsequently, the intermolecular electrostatic energy is tested by calculating ten stationary points on the water dimer potential-energy surface. Results are presented for electron densities obtained at four different levels of theory using two different basis sets, fitted with three auxiliary basis sets. Additionally, a one-dimensional electrostatic energy surface scan is performed for four different systems (H2O dimer, Mg2+-H2O, Cu+-H2O, and n-methyl-formamide dimer). Our results show a very good agreement with ab initio calculations for all properties as well as interaction energies.

  16. 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.

  17. 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

  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. 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.

  20. 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…

  1. Reducing quasilinear systems to block triangular form

    SciTech Connect

    Tunitsky, Dmitry V

    2013-03-31

    The paper is concerned with systems of n quasilinear partial differential equations of the first order with 2 independent variables. Using a geometric formalism for such equations, which goes back to Riemann, it is possible to assign a field of linear operators on an appropriate vector bundle to this type of quasilinear system. Several tests for a quasilinear system to be reducible to triangular or block triangular form are obtained in terms of this field; they supplement well known results on diagonalization and block diagonalization due to Haantjes and Bogoyavlenskij. Bibliography: 10 titles.

  2. Intramolecular versus intermolecular disulfide bonds in prion proteins.

    PubMed

    Welker, Ervin; Raymond, Lynne D; Scheraga, Harold A; Caughey, Byron

    2002-09-01

    Prion protein (PrP) is the major component of the partially protease-resistant aggregate that accumulates in mammals with transmissible spongiform encephalopathies. The two cysteines of the scrapie form, PrP(Sc), were found to be in their oxidized (i.e. disulfide) form (Turk, E., Teplow, D. B., Hood, L. E., and Prusiner, S. B. (1988) Eur. J. Biochem. 176, 21-30); however, uncertainty remains as to whether the disulfide bonds are intra- or intermolecular. It is demonstrated here that the monomers of PrP(Sc) are not linked by intermolecular disulfide bonds. Furthermore, evidence is provided that PrP(Sc) can induce the conversion of the oxidized, disulfide-intact form of the monomeric cellular prion protein to its protease-resistant form without the temporary breakage and subsequent re-formation of the disulfide bonds in cell-free reactions.

  3. 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.

  4. Correlation functions for glass-forming systems

    PubMed

    Jacobs

    2000-07-01

    We present a simple, linear, partial-differential equation for the density-density correlation function in a glass-forming system. The equation is written down on the basis of fundamental and general considerations of linearity, symmetry, stability, thermodynamic irreversibility and consistency with the equation of continuity (i.e. , conservation of matter). The dynamical properties of the solutions show a change in behavior characteristic of the liquid-glass transition as a function of one of the parameters (temperature). The equation can be shown to lead to the simplest mode-coupling theory of glasses and provides a partial justification of this simplest theory. It provides also a method for calculating the space dependence of the correlation functions not available otherwise. The results suggest certain differences in behavior between glassy solids and glass-forming liquids which may be accessible to experiment. A brief discussion is presented of how the method can be applied to other systems such as sandpiles and vortex glasses in type II superconductors. PMID:11088609

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

    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)....

  6. Ionic strength and intermolecular contacts in protein crystals

    NASA Astrophysics Data System (ADS)

    Iyer, Ganesh H.; Dasgupta, Swagata; Bell, Jeffrey A.

    2000-08-01

    The ionic strengths of crystallization solutions for 206 proteins were observed to form a bimodal distribution. The data was divided into two sets at an ionic strength of 4.4 M, and knowledge-based potentials were calculated to determine contact preferences at intermolecular crystal interfaces. Consistent with previous observations over all ionic strengths, intermolecular crystal contacts tend to exclude nonpolar amino acids; lysine is the least favored polar amino acid at crystal contacts; and arginine and glutamine are the two most favored amino acid at crystal contacts. However, some aspects of intermolecular contact preferences within protein crystals are significantly dependent on ionic strength. Arginine is the most favored residue at low ionic strength, but it takes second place to glutamine at high ionic strength. Other major ionic strength-dependent differences in protein crystal contacts can be explained by the binding of cations or anions. While others have shown the importance of ion binding experimentally in selected protein crystals, these statistical results indicate that intermolecular interface formation must involve ion-mediated contacts in a large number of protein crystals.

  7. Some mathematical models of intermolecular autophosphorylation.

    PubMed

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

    2015-04-01

    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.

  8. Kinetic theory for flows of nonhomogeneous rodlike liquid crystalline polymers with a nonlocal intermolecular potential.

    PubMed

    Wang, Qi; E, Weinan; Liu, Chun; Zhang, Pingwen

    2002-05-01

    The Doi kinetic theory for flows of homogeneous, rodlike liquid crystalline polymers (LCPs) is extended to model flows of nonhomogeneous, rodlike LCPs through a nonlocal (long-range) intermolecular potential. The theory features (i) a nonlocal, anisotropic, effective intermolecular potential in an integral form that is consistent with the chemical potential, (ii) short-range elasticity as well as long-range isotropic and anisotropic elasticity, (iii) a closed-form stress expression accounting for the nonlocal molecular interaction, and (iv) an extra elastic body force exclusively associated with the integral form of the intermolecular potential. With the effective intermolecular potential, the theory is proven to be well posed in that it warrants a positive entropy production and thereby the second law of thermodynamics. Approximate theories are obtained by gradient expansions of the number density function in the free energy density.

  9. Kinetic theory for flows of nonhomogeneous rodlike liquid crystalline polymers with a nonlocal intermolecular potential.

    PubMed

    Wang, Qi; E, Weinan; Liu, Chun; Zhang, Pingwen

    2002-05-01

    The Doi kinetic theory for flows of homogeneous, rodlike liquid crystalline polymers (LCPs) is extended to model flows of nonhomogeneous, rodlike LCPs through a nonlocal (long-range) intermolecular potential. The theory features (i) a nonlocal, anisotropic, effective intermolecular potential in an integral form that is consistent with the chemical potential, (ii) short-range elasticity as well as long-range isotropic and anisotropic elasticity, (iii) a closed-form stress expression accounting for the nonlocal molecular interaction, and (iv) an extra elastic body force exclusively associated with the integral form of the intermolecular potential. With the effective intermolecular potential, the theory is proven to be well posed in that it warrants a positive entropy production and thereby the second law of thermodynamics. Approximate theories are obtained by gradient expansions of the number density function in the free energy density. PMID:12059561

  10. 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.

  11. 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.

  12. 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; 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,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

  13. 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....

  14. 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....

  15. 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....

  16. 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....

  17. 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....

  18. 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.

  19. 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

  20. 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

  1. Intramolecular screening of intermolecular forces

    NASA Astrophysics Data System (ADS)

    Liang, Ying Q.; Hunt, K. L. C.

    1993-03-01

    By use of nonlocal polarizability densities, we analyze the intramolecular screening of intermolecular fields. For two interacting molecules A and B with weak or negligible charge overlap, we show that the reaction field and the field due to the unperturbed charge distribution of the neighboring molecule are screened identically via the Sternheimer shielding tensor and its generalizations to nonuniform fields and nonlinear response. The induction force on nucleus I in molecule A, derived from perturbation theory, results from linear screening of the reaction field due to B and nonlinear screening of the field from the permanent charge distribution of B. In general, at first or second order in the molecular interaction, the screening-tensor expressions for the force on nucleus I involve susceptibilities of one order higher than the expressions derived from perturbation theory. The first-order force from perturbation theory involves permanent charge moments, while the first-order screened force involves linear response tensors; and the second-order screened force depends on hyperpolarizabilities, while second-order induction effects are specified in terms of static, lowest-order susceptibilities. The equivalence of the two formulations for these forces, order by order, is a new illustration of the interrelations we have found among permanent moments, linear-response tensors, and nonlinear response. This work also provides new insight into the dispersion forces on an individual nucleus I in molecule A by separating the forces into two distinct terms—the first term results from changes in the reaction of A to the fluctuating charge distribution of the neighboring molecule B, when nucleus I shifts infinitesimally, and the second term stems from changes in correlations of the fluctuating charge distribution of A itself. Changes in the fluctuation correlations are determined by changes in the classical Coulomb field of nucleus I and by the imaginary part of the

  2. Fluorescence photoactivation by intermolecular proton transfer.

    PubMed

    Swaminathan, Subramani; Petriella, Marco; Deniz, Erhan; Cusido, Janet; Baker, James D; Bossi, Mariano L; Raymo, Françisco M

    2012-10-11

    We designed a strategy to activate fluorescence under the influence of optical stimulations based on the intermolecular transfer of protons. Specifically, the illumination of a 2-nitrobenzyl derivative at an activating wavelength is accompanied by the release of hydrogen bromide. In turn, the photogenerated acid encourages the opening of an oxazine ring embedded within a halochromic compound. This structural transformation extends the conjugation of an adjacent coumarin fluorophore and enables its absorption at an appropriate excitation wavelength. Indeed, this bimolecular system offers the opportunity to activate fluorescence in liquid solutions, within rigid matrixes and inside micellar assemblies, relying on the interplay of activating and exciting beams. Furthermore, this strategy permits the permanent imprinting of fluorescent patterns on polymer films, the monitoring of proton diffusion within such materials in real time on a millisecond time scale, and the acquisition of images with spatial resolution at the nanometer level. Thus, our operating principles for fluorescence activation can eventually lead to the development of valuable photoswitchable probes for imaging applications and versatile mechanisms for the investigation of proton transport. PMID:22994311

  3. The search for forming planetary systems

    NASA Astrophysics Data System (ADS)

    Sargent, A. I.; Beckwith, S. V. W.

    1993-04-01

    The paper considers the probable sequence of events in the evolution of the solar system and examines examples of other stars observed in some of the gestational stages of planetary formation, which was made possible by recently developed technology, such as the Caltech's millimeter-wave array and IRAM millimeter-wave telescope. Indirect evidence obtained on the formation and evolution of a planetary system is described. Today's evidence strongly suggests that the solar system is not unique and that planetary systems are abundant in the Galaxy.

  4. 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

  5. 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.

  6. 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

  7. 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.

  8. 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

  9. 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

  10. 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.

  11. System and method for incremental forming

    SciTech Connect

    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.

  12. Estimation of intermolecular interactions in polymer networks

    SciTech Connect

    Subrananian, P.R.; Galiatsatos, V.

    1993-12-31

    Strain-birefringence measurements have been used to estimate intermolecular interactions in polymer networks. The intensity of the interaction has been quantified through a theoretical scheme recently proposed by Erman. The results show that these interactions diminish with decreasing molecular weight between cross-links and decreasing cross-link functionality.

  13. 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

  14. Spatio-spectral infrared vibrational nano-imaging of intermolecular coupling

    NASA Astrophysics Data System (ADS)

    Pollard, Benjamin; Muller, Eric; Raschke, Markus

    2014-03-01

    Molecular self-assembly, the function of biomembranes, and the performance of organic solar cells rely on molecular interactions on the nanoscale. The understanding and design of such heterogeneous functional soft matter has long been impeded by a lack of spectroscopic tools with sufficient nanometer spatial resolution, attomolar sensitivity, and intermolecular spectroscopic specificity. We implement vibrational scattering-scanning near-field optical microscopy (s-SNOM) in a multi-spectral modality to investigate the structure-function relationship in PS- b-PMMA block copolymers. Using a vibrational resonance as a sensitive reporter of local structure, coupling, and dynamics, we resolve spectral Stark shifts and line broadening correlated with molecular-scale morphologies. By creating images of solvatochromic vibrational shifts we discriminate local variations in electric fields between nanoscale bulk and interface regions, with quantitative agreement to dielectric continuum models. This new nano-chemometric 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.

  15. 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.

  16. 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.

  17. Co-operative intermolecular kinetics of 2-oxoglutarate dependent dioxygenases may be essential for system-level regulation of plant cell physiology

    PubMed Central

    Kundu, Siddhartha

    2015-01-01

    Can the stimulus-driven synergistic association of 2-oxoglutarate dependent dioxygenases be influenced by the kinetic parameters of binding and catalysis?In this manuscript, I posit that these indices are necessary and specific for a particular stimulus, and are key determinants of a dynamic clustering that may function to mitigate the effects of this trigger. The protein(s)/sequence(s) that comprise this group are representative of all major kingdoms of life, and catalyze a generic hydroxylation, which is, in most cases accompanied by a specialized conversion of the substrate molecule. Iron is an essential co-factor for this transformation and the response to waning levels is systemic, and mandates the simultaneous participation of molecular sensors, transporters, and signal transducers. Here, I present a proof-of-concept model, that an evolving molecular network of 2OG-dependent enzymes can maintain iron homeostasis in the cytosol of root hair cells of members of the family Gramineae by actuating a non-reductive compensatory chelation by the phytosiderophores. Regression models of empirically available kinetic data (iron and alpha-ketoglutarate) were formulated, analyzed, and compared. The results, when viewed in context of the superfamily responding as a unit, suggest that members can indeed, work together to accomplish system-level function. This is achieved by the establishment of transient metabolic conduits, wherein the flux is dictated by kinetic compatibility of the participating enzymes. The approach adopted, i.e., predictive mathematical modeling, is integral to the hypothesis-driven acquisition of experimental data points and, in association with suitable visualization aids may be utilized for exploring complex plant biochemical systems. PMID:26236316

  18. 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.

  19. 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…

  20. 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.

  1. 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.

  2. 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.

  3. Masking reveals parallel form systems in the visual brain

    PubMed Central

    Lo, Yu Tung; Zeki, Semir

    2014-01-01

    It is generally supposed that there is a single, hierarchically organized pathway dedicated to form processing, in which complex forms are elaborated from simpler ones, beginning with the orientation-selective cells of V1. In this psychophysical study, we undertook to test another hypothesis, namely that the brain’s visual form system consists of multiple parallel systems and that complex forms are other than the sum of their parts. Inspired by imaging experiments which show that forms of increasing perceptual complexity (lines, angles, and rhombuses) constituted from the same elements (lines) activate the same visual areas (V1, V2, and V3) with the same intensity and latency (Shigihara and Zeki, 2013, 2014), we used backward masking to test the supposition that these forms are processed in parallel. We presented subjects with lines, angles, and rhombuses as different target-mask pairs. Evidence in favor of our supposition would be if masking is the most effective when target and mask are processed by the same system and least effective when they are processed in different systems. Our results showed that rhombuses were strongly masked by rhombuses but only weakly masked by lines or angles, but angles and lines were well masked by each other. The relative resistance of rhombuses to masking by low-level forms like lines and angles suggests that complex forms like rhombuses may be processed in a separate parallel system, whereas lines and angles are processed in the same one. PMID:25120460

  4. 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.

  5. Bile salt-induced intermolecular disulfide bond formation activates Vibrio cholerae virulence.

    PubMed

    Yang, Menghua; Liu, Zhi; Hughes, Chambers; Stern, Andrew M; Wang, Hui; Zhong, Zengtao; Kan, Biao; Fenical, William; Zhu, Jun

    2013-02-01

    To be successful pathogens, bacteria must often restrict the expression of virulence genes to host environments. This requires a physical or chemical marker of the host environment as well as a cognate bacterial system for sensing the presence of a host to appropriately time the activation of virulence. However, there have been remarkably few such signal-sensor pairs identified, and the molecular mechanisms for host-sensing are virtually unknown. By directly applying a reporter strain of Vibrio cholerae, the causative agent of cholera, to a thin layer chromatography (TLC) plate containing mouse intestinal extracts, we found two host signals that activate virulence gene transcription. One of these was revealed to be the bile salt taurocholate. We then show that a set of bile salts cause dimerization of the transmembrane transcription factor TcpP by inducing intermolecular disulfide bonds between cysteine (C)-207 residues in its periplasmic domain. Various genetic and biochemical analyses led us to propose a model in which the other cysteine in the periplasmic domain, C218, forms an inhibitory intramolecular disulfide bond with C207 that must be isomerized to form the active C207-C207 intermolecular bond. We then found bile salt-dependent effects of these cysteine mutations on survival in vivo, correlating to our in vitro model. Our results are a demonstration of a mechanism for direct activation of the V. cholerae virulence cascade by a host signal molecule. They further provide a paradigm for recognition of the host environment in pathogenic bacteria through periplasmic cysteine oxidation.

  6. Computational studies on intermolecular interactions in solvation

    NASA Astrophysics Data System (ADS)

    Song, Weiping

    This thesis presents the results of computational studies of intermolecular interactions in various contexts. We first investigated the relation between solute-solvent intermolecular interactions and local density augmentation in supercritical solvation. The phenomenon of interest is the excess density that exists in the neighborhood of an attractive solute in a supercritical solvent in the vicinity of the critical point. In Chapter 2, we examined the ability of various measures of the strength of solute-solvent interactions, calculated from all-atom potential functions, to correlate the extent of local density augmentation in both experimental and model solvents. The Gibbs Ensemble Monte Carlo (GEMC) method enables us to calculate phase equilibrium in pure substances and mixtures. It provides a convenient way to test and develop model potentials. In Chapter 3 we present some methodological aspects of such calculations, the issues related to approach to critical points and finite-size effects and applications to simple fluids. Chapter 4 then describes a simplified 2-site potential model for simulating supercritical fluoroform. The GEMC method was used to simulate the vapor-liquid coexistence curve of the model fluid and the dynamic properties were studied by performing NVT molecular dynamics (MD) simulations. The results show that despite its simplicity, this model is able to reproduce many important properties of supercritical fluoroform, making it useful in molecular simulations of supercritical solvation. In the above two studies, the intermolecular interactions are described by a sum of pair-wise additive Lennard-Jones + Coulomb terms. The standard Lorentz-Berthelot combining rules (geometric mean rule for well depth and arithmetic mean rule for collision diameter) are commonly applied to account for the unlike pair Lennard-Jones parameters. In Chapter 5, we examined the applicability of the combining rules for modeling alkane-perfluoroalkane interactions. It

  7. Interplay between molecular conformation and intermolecular interactions in conformational polymorphism: a molecular perspective from electronic calculations of tolfenamic acid.

    PubMed

    Mattei, Alessandra; Li, Tonglei

    2011-10-14

    Tolfenamic acid exhibits conformational polymorphism. The molecules in its two commonly occurred crystal structures form similar hydrogen-bonded dimers but differ in conformation. The conformational variance was analyzed by electronic calculation methods with the aim to unravel intrinsic connection between the conformational flexibility and intermolecular interactions in the polymorphs. The study was conducted mainly by conceptual density functional theory (DFT) and natural bond orbital (NBO) analysis. It is found that the conformational polymorphism is resulted from the energy competition between intramolecular π-conjugation and intermolecular hydrogen bonding. By adapting conformation that departs from being the most energetically stable, tolfenamic acid molecules can strengthen the intermolecular hydrogen-bonding interactions in the crystals. The study illustrates how the molecule's electronic properties are influenced by conformational variation and, inherently, how the intermolecular interactions become regulated. Moreover, understanding molecular interaction and crystal packing necessitates electronic structure calculation and analysis, which can be further facilitated by utilizing DFT and NBO concepts.

  8. New Tooling System for Forming Aluminum Beverage Can End Shell

    NASA Astrophysics Data System (ADS)

    Yamazaki, Koetsu; Otsuka, Takayasu; Han, Jing; Hasegawa, Takashi; Shirasawa, Taketo

    2011-08-01

    This paper proposes a new tooling system for forming shells of aluminum beverage can ends. At first, forming process of a conversional tooling system has been simulated using three-dimensional finite element models. Simulation results have been confirmed to be consistent with those of axisymmetric models, so simulations for further study have been performed using axisymmetric models to save computational time. A comparison shows that thinning of the shell formed by the proposed tooling system has been improved about 3.6%. Influences of the tool upmost surface profiles and tool initial positions in the new tooling system have been investigated and the design optimization method based on the numerical simulations has been then applied to search optimum design points, in order to minimize thinning subjected to the constraints of the geometrical dimensions of the shell. At last, the performance of the shell subjected to internal pressure has been confirmed to meet design requirements.

  9. 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.

  10. 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

  11. 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

  12. 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.

  13. The diversity of physical forces and mechanisms in intermolecular interactions.

    PubMed

    Berezovsky, Igor N

    2011-06-01

    Intermolecular interactions became an inherent part of the structure-function paradigm. Therefore, the generalized concept of protein stability and interactions should consider the balance of stabilizing forces working in different types of intermolecular interactions. We consider here two 'extremes' of protein interactions, viral protein with high intrinsic disorder and hyperthermostable protein complexes. Intermolecular interactions provide folding upon binding as a part of function in the viral case, while they secure and stabilize specific native interfaces as a prerequisite for function in hyperthermostable complexes. We propose a generalized concept of protein stability and interactions, which includes intermolecular interactions comprising distinct combinations of stabilizing forces depending on the types of interacting partners.

  14. 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.

  15. Van der Waals Interactions in Density Functional Theory: Intermolecular Complexes

    NASA Astrophysics Data System (ADS)

    Kannemann, Felix; Becke, Axel

    2010-03-01

    Conventional density functional theory (GGA and hybrid functionals) fails to account for dispersion interactions and is therefore not applicable to systems where van der Waals interactions play a dominant role, such as intermolecular complexes and biomolecules. The exchange-hole dipole moment (XDM) dispersion model of Becke and Johnson [A. D. Becke and E. R. Johnson, J. Chem. Phys. 127, 154108 (2007)] corrects for this deficiency. We have previously shown that the XDM dispersion model can be combined with standard GGA functionals (PW86 for exchange and PBE for correlation) to give accurate binding energy curves for rare-gas diatomics [F. O. Kannemann and A. D. Becke, J. Chem. Theory Comput. 5, 719 (2009)]. Here we present further tests of the GGA-XDM method using benchmark sets including hydrogen bonding, electrostatic, dispersion and stacking interactions, and systems ranging from rare-gas diatomics to biomolecular complexes.

  16. 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.

  17. 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.

  18. High-energy-rate magnetohydraulic metal forming system

    NASA Technical Reports Server (NTRS)

    1967-01-01

    In the magnetohydraulic metal forming system, a sonic shock wave is generated in a liquid medium by a coil energized by an electrical discharge. These waves transfer energy from a metal diaphragm, actuated by a pulsed magnetic field, to a metal workpiece. In the development a study was made of the pressure pulse phenomenon in a liquid medium.

  19. The acid free asymmetric intermolecular α-alkylation of aldehydes in fluorinated alcohols.

    PubMed

    Xiao, Jian; Zhao, Kai; Loh, Teck-Peng

    2012-04-11

    The acid free asymmetric intermolecular α-alkylation of aldehydes with alcohols has been discovered using trifluoroethanol as solvent. This unprecedented system affords the enantioenriched functionalized primary alcohols (after NaBH(4) reduction) in high yields and good to excellent enantioselectivities with wide substrate scope in the absence of any acid additive.

  20. 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.

  1. 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

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

    PubMed

    Colmenero, J

    2015-03-18

    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 mixtures with

  3. 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.

  4. 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

  5. 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

  6. 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

  7. 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.

  8. A corresponding-states framework for the description of the Mie family of intermolecular potentials

    NASA Astrophysics Data System (ADS)

    Ramrattan, N. S.; Avendaño, C.; Müller, E. A.; Galindo, A.

    2015-05-01

    The Mie (λr, λa) intermolecular pair potential has been suggested as an alternative to the traditional Lennard-Jones (12-6) potential for modelling real systems both via simulation and theory as its implementation leads to an accuracy and flexibility in the determination of thermophysical properties that cannot be obtained when potentials of fixed range are considered. An additional advantage of using variable-range potentials is noted in the development of coarse-grained models where, as the superatoms become larger, the effective potentials are seen to become softer. However, the larger number of parameters that characterise the Mie potential (λr, λa, σ, ɛ) can hinder a rational study of the particular effects that each individual parameter have on the observed thermodynamic properties and phase equilibria, and higher degeneracy of models is observed. Here a three-parameter corresponding states model is presented in which a cohesive third parameter α is proposed following a perturbation expansion and assuming a mean-field limit. It is shown that in this approximation the free energy of any two Mie systems sharing the same value of α will be the same. The parameter α is an explicit function of the repulsive and attractive exponents and consequently dictates the form of the intermolecular pair potential. Molecular dynamics simulations of a variety of Mie systems over a range of values of α are carried out and the solid-liquid, liquid-vapour and vapour-solid phase boundaries for the systems considered are presented. Using the simulation data, we confirm that systems of the same α exhibit conformal phase behaviour for the fluid-phase properties as well as for the solid-fluid boundary, although larger differences are noted in the solid region; these can be related to the approximations in the definition of the parameter. Furthermore, it is found that the temperature range over which the vapour-liquid envelope of a given Mie system is stable follows a linear

  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. Invited Article: Digital beam-forming imaging riometer systems

    NASA Astrophysics Data System (ADS)

    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.

  11. 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.

  12. Explicit solutions of normal form of driven oscillatory systems

    NASA Astrophysics Data System (ADS)

    Tsarouhas, George E.; Ross, John

    1987-12-01

    We consider an oscillatory dissipative system driven by external sinusoidal perturbations of given amplitude Q and frequency ω. The kinetic equations are transformed to normal form and solved for small Q, near a Hopf bifurcation to oscillations in the autonomous system, for ratios ωn to the autonomous frequency of irrational so that the response of the system is quasiperiodic. The system is assumed to have either two variables or is adequately described by two variables near the bifurcation, and we obtain explicit solutions for this general case. The equations show interesting effects of external perturbations on limit cycles, both stable and unstable. Next we treat a specific model (Brusselator) and show by comparison with results of numerical integration that the theory predicts well the shape of the perturbed limit cycle, its variation with changes in constraints and parameters, and the point of transition from quasiperiodic to periodic response.

  13. ASLForm: an adaptive self learning medical form generating system.

    PubMed

    Zheng, Shuai; Wang, Fusheng; Lu, James J

    2013-01-01

    To facilitate the process of extracting information from narrative medical reports and transforming extracted data into standardized structured forms, we present an interactive, incrementally learning based information extraction system - ASLForm. ASLForm provides users a convenient interface that can be used as a simple data extraction and data entry system. It is unique, however, in its ability to transparently analyze and quickly learn, from users' interactions with a small number of reports, the desired values for the data fields. Additional user feedback (through acceptance decision or edits on the generated values) can incrementally refine the decision model in real-time, which further reduces users' interaction effort thereafter. The system eventually achieves high accuracy on data extraction with minimal effort from users. ASLForm requires no special configuration or training sets, and is not constrained to specific domains, thus it is easy to use and highly portable. Our experiments demonstrate the effectiveness of the system.

  14. 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)

  15. Strong orbital interaction in a weak CH-π hydrogen bonding system.

    PubMed

    Li, Jianfu; Zhang, Rui-Qin

    2016-03-01

    For the first time, the intermolecular orbital interaction between benzene and methane in the benzene-methane complex, a representative of weak interaction system, has been studied by us using ab initio calculations based on different methods and basis sets. Our results demonstrate obvious intermolecular orbital interaction between benzene and methane involving orbital overlaps including both occupied and unoccupied orbitals. Similar to interatomic orbital interaction, the intermolecular interaction of orbitals forms "bonding" and "antibonding" orbitals. In the interaction between occupied orbitals, the total energy of the complex increases because of the occupation of the antibonding orbital. The existence of the CH-π hydrogen bond between benzene and methane causes a decrease in rest energy level, leading to at least -1.51 kcal/mol intermolecular interaction energy. Our finding extends the concept of orbital interaction from the intramolecular to the intermolecular regime and gives a reliable explanation of the deep orbital reformation in the benzene-methane complex.

  16. 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.

  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. Propagation studies of metastable intermolecular composites (MIC).

    SciTech Connect

    Son, S. F.; Busse, J. R.; Asay, B. W.; Peterson, P. D.; Mang, J. T.; Bockmon, B.; Pantoya, M.

    2002-01-01

    Thermite materials are attractive energetic materials because the reactions are highly exothermic, have high energy densities, and high temperatures of combustion. However, the application of thermite materials has been limited because of the relative slow release of energy compared to other energetic materials. Engineered nano-scale composite energetic materials, such as Al/MoO{sub 3}, show promise for additional energetic material applications because they can react very rapidly. The composite material studied in this work consists of tailored, ultra-fine grain (30-200 nm diameter) aluminum particles that dramatically increase energy release rates of these thermite materials. These reactant clusters of fuel and oxidizer particles are in nearly atomic scale proximity to each other but are constrained from reaction until triggered. Despite the growing importance of nano-scale energetic materials, even the most basic combustion characteristics of these materials have not been thoroughly studied. This paper reports initial studies of the ignition and combustion of metastable intermolecular composites (MIC) materials. The goals were lo obtain an improved understanding of flame propagation mechanisms and combustion behaviors associated with nano-structured energetic materials. Information on issues such as reaction rate and behavior as a function of composition (mixture ratio), initial static charge, and particle size are essential and will allow scientists to design applications incorporating the benefits of these compounds. The materials have been characterized, specifically focusing on particle size, shape, distribution and morphology.

  19. 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.

  20. Total Synthesis and Structural Reassignment of Lyngbyaloside C Highlighted by Intermolecular Ketene Esterification.

    PubMed

    Chang, Chia-Fu; Stefan, Eric; Taylor, Richard E

    2015-07-20

    Lyngbyaloside C, a classic macrolide, isolated from Lyngbya bouilloni, has shown moderate anticancer activity against several cancer cell lines. Here, we report the first total synthesis and stereochemical configuration reassignment of lyngbyaloside C. The synthesis highlights a one-pot intermolecular ketene esterification reaction to form the crucial tertiary ester and tetrahydropyran. In addition, a novel and concise synthetic pathway towards the 1,3-syn secondary, tertiary diol fragment is described using a regio- and stereospecific electrophilic ether transfer reaction.

  1. 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

  2. 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

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

    PubMed

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

    2016-01-01

    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. PMID:26010349

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

    PubMed

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

    2016-01-01

    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.

  5. Interatomic (Intermolecular) Decay Processes in Clusters: Current Status and Outlook

    SciTech Connect

    Averbukh, V.; Cederbaum, L. S.

    2007-11-29

    Since their theoretical prediction a decade ago, interatomic (intermolecular) Coulombic decay (ICD) and related processes have been in the focus of intensive theoretical and experimental research. The spectacular progress in this direction has been stimulated both by the fundamental importance of the new electronic decay phenomena and by the exciting possibility of their practical application, for example in spectroscopy. We review the current status of the research of interatomic (intermolecular) decay phenomena in clusters and discuss some perspectives of this new field.

  6. Simulation of Absorption Systems in Flexible and Modular Form

    1994-09-23

    The computer code has been developed for simulation of absorption systems at steady-state in a flexible and modular form, making 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. When all the equations have been established, a mathematical solver routine is employed to solve them simultaneously. Property subroutines contained in a separate data base serve to provide thermodynamicmore » properties of the working fluids. 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 the cycle by specifying the different components and their interconnections. Based on this information, the program calculates the temperature, flowrate, concentration, pressure and vapor fraction at each state point in the system and the heat duty at each unit, from which the coefficient of performance may be determined. A graphical user-interface is provided to facilitate interactive input and study of the output.« less

  7. Evolutionary meandering of intermolecular interactions along the drift barrier.

    PubMed

    Lynch, Michael; Hagner, Kyle

    2015-01-01

    Many cellular functions depend on highly specific intermolecular interactions, for example transcription factors and their DNA binding sites, microRNAs and their RNA binding sites, the interfaces between heterodimeric protein molecules, the stems in RNA molecules, and kinases and their response regulators in signal-transduction systems. Despite the need for complementarity between interacting partners, such pairwise systems seem to be capable of high levels of evolutionary divergence, even when subject to strong selection. Such behavior is a consequence of the diminishing advantages of increasing binding affinity between partners, the multiplicity of evolutionary pathways between selectively equivalent alternatives, and the stochastic nature of evolutionary processes. Because mutation pressure toward reduced affinity conflicts with selective pressure for greater interaction, situations can arise in which the expected distribution of the degree of matching between interacting partners is bimodal, even in the face of constant selection. Although biomolecules with larger numbers of interacting partners are subject to increased levels of evolutionary conservation, their more numerous partners need not converge on a single sequence motif or be increasingly constrained in more complex systems. These results suggest that most phylogenetic differences in the sequences of binding interfaces are not the result of adaptive fine tuning but a simple consequence of random genetic drift. PMID:25535374

  8. Cation-π interactions: accurate intermolecular potential from symmetry-adapted perturbation theory.

    PubMed

    Ansorg, Kay; Tafipolsky, Maxim; Engels, Bernd

    2013-09-01

    Symmetry-adapted perturbation theory (SAPT) is used to decompose the total intermolecular interaction energy between the ammonium cation and a benzene molecule into four physically motivated individual contributions: electrostatics, exchange, dispersion, and induction. Based on this rigorous decomposition, it is shown unambiguously that both the electrostatic and the induction energy components contribute almost equally to the attractive forces stabilizing the dimer with a nonnegligible contribution coming from the dispersion term. A polarizable potential model for the interaction of ammonium cation with benzene is parametrized by fitting these four energy components separately using the functional forms of the AMOEBA force field augmented with the missing charge penetration energy term calculated as a sum over pairwise electrostatic energies between spherical atoms. It is shown that the proposed model is able to produce accurate intermolecular interaction energies as compared to ab initio results, thus avoiding error compensation to a large extent.

  9. 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.

  10. 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).

  11. Intermolecular interactions, nucleation, and thermodynamics of crystallization of hemoglobin C.

    PubMed Central

    Vekilov, Peter G; Feeling-Taylor, Angela R; Petsev, Dimiter N; Galkin, Oleg; Nagel, Ronald L; Hirsch, Rhoda Elison

    2002-01-01

    The mutated hemoglobin HbC (beta 6 Glu-->Lys), in the oxygenated (R) liganded state, forms crystals inside red blood cells of patients with CC and SC diseases. Static and dynamic light scattering characterization of the interactions between the R-state (CO) HbC, HbA, and HbS molecules in low-ionic-strength solutions showed that electrostatics is unimportant and that the interactions are dominated by the specific binding of solutions' ions to the proteins. Microscopic observations and determinations of the nucleation statistics showed that the crystals of HbC nucleate and grow by the attachment of native molecules from the solution and that concurrent amorphous phases, spherulites, and microfibers are not building blocks for the crystal. Using a novel miniaturized light-scintillation technique, we quantified a strong retrograde solubility dependence on temperature. Thermodynamic analyses of HbC crystallization yielded a high positive enthalpy of 155 kJ mol(-1), i.e., the specific interactions favor HbC molecules in the solute state. Then, HbC crystallization is only possible because of the huge entropy gain of 610 J mol(-1) K(-1), likely stemming from the release of up to 10 water molecules per protein intermolecular contact-hydrophobic interaction. Thus, the higher crystallization propensity of R-state HbC is attributable to increased hydrophobicity resulting from the conformational changes that accompany the HbC beta 6 mutation. PMID:12124294

  12. Characterizing Warm Molecular Hydrogen in Active Star-Forming Systems

    NASA Astrophysics Data System (ADS)

    Rangwala, Naseem

    2014-10-01

    Herschel observations of nearby star-forming galaxies have determined that the warm component of the molecular gas traced by the high-J CO lines dominates the luminosity (~90% of the total CO luminosity) and hence the energetics of the molecular ISM. At the temperatures (T = 300 - 2000 K) and densities (n_H < 1E6 per cubic cm) typically found in our survey, H2 emission is the dominant gas coolant, much more important than CO. A fundamental assumption of all analyses of CO emission has been that CO emission traces H2 over the entire range of physical conditions in the observed sources. However, a direct observational comparison of spatial distributions and kinematics of CO and H2 has never been made for the warm molecular gas. We propose to observe the warm H2, in S(1) and S(2) transitions, with the SOFIA-EXES instrument in a diverse sample of star-forming systems: NGC 253 (starburst nucleus), NGC 6240 (luminous infrared galaxy), NGC 1068 (Seyfert-2), and SgrB2(M)/(N) (Galactic hot cores). The primary goal is to compare these measurements with the warm CO (J = 6-5 transition) observed with the Atacama Large Millimeter Array (ALMA) to investigate differences in the kinematics and spatial distributions (for the extended targets) of the two molecules and thereby confirm whether CO is a reliable tracer of H2 in the warm gas.

  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. 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.

  15. 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. PMID:22021851

  16. 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. PMID:23364742

  17. 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.

  18. Long range intermolecular forces in change-of-phase heat transfer

    SciTech Connect

    Wayner, P.C. Jr.

    1999-07-01

    The variation of long range intermolecular forces near interfaces profoundly affects the performance of change-of-phase heat exchangers. Starting with the fundamental electromagnetic force between molecules (dielectric properties), the effects of shape, temperature and concentration on the heat transfer characteristics and stability of thin films and larger systems are reviewed. A judicious selection of literature gives a consistent set of models of particular use in heat transfer. Examples of experimental verification in this rapidly developing field are also presented.

  19. Intermolecular Interactions and Cooperative Effects from Electronic Structure Calculations: An Effective Means for Developing Interaction Potentials for Condensed Phase Simulations

    SciTech Connect

    Xantheas, Sotiris S.

    2004-05-01

    The modeling of the macroscopic properties of homogeneous and inhomogeneous systems via atomistic simulations such as molecular dynamics (MD) or Monte Carlo (MC) techniques is based on the accurate description of the relevant solvent-solute and solvent-solvent intermolecular interactions. The total energy (U) of an n-body molecular system can be formally written as [1,2,3

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

    NASA Astrophysics Data System (ADS)

    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.

    2014-01-01

    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 20femtoseconds 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. 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

  2. Intermolecular artifacts in probe microscope images of C60 assemblies

    NASA Astrophysics Data System (ADS)

    Jarvis, Samuel Paul; Rashid, Mohammad Abdur; Sweetman, Adam; Leaf, Jeremy; Taylor, Simon; Moriarty, Philip; Dunn, Janette

    2015-12-01

    Claims that dynamic force microscopy has the capability to resolve intermolecular bonds in real space continue to be vigorously debated. To date, studies have been restricted to planar molecular assemblies with small separations between neighboring molecules. Here we report the observation of intermolecular artifacts over much larger distances in 2D assemblies of C60 molecules, with compelling evidence that in our case the tip apex is terminated by a C60 molecule (rather than the CO termination typically exploited in ultrahigh resolution force microscopy). The complete absence of directional interactions such as hydrogen or halogen bonding, the nonplanar structure of C60, and the fullerene termination of the tip apex in our case highlight that intermolecular artifacts are ubiquitous in dynamic force microscopy.

  3. 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.

  4. Visualizing coherent intermolecular dipole–dipole coupling in real space

    NASA Astrophysics Data System (ADS)

    Zhang, Yang; Luo, Yang; Zhang, Yao; Yu, Yun-Jie; Kuang, Yan-Min; Zhang, Li; Meng, Qiu-Shi; Luo, Yi; Yang, Jin-Long; Dong, Zhen-Chao; Hou, J. G.

    2016-03-01

    Many important energy-transfer and optical processes, in both biological and artificial systems, depend crucially on excitonic coupling that spans several chromophores. Such coupling can in principle be described in a straightforward manner by considering the coherent intermolecular dipole–dipole interactions involved. However, in practice, it is challenging to directly observe in real space the coherent dipole coupling and the related exciton delocalizations, owing to the diffraction limit in conventional optics. Here we demonstrate that the highly localized excitations that are produced by electrons tunnelling from the tip of a scanning tunnelling microscope, in conjunction with imaging of the resultant luminescence, can be used to map the spatial distribution of the excitonic coupling in well-defined arrangements of a few zinc-phthalocyanine molecules. The luminescence patterns obtained for excitons in a dimer, which are recorded for different energy states and found to resemble σ and π molecular orbitals, reveal the local optical response of the system and the dependence of the local optical response on the relative orientation and phase of the transition dipoles of the individual molecules in the dimer. We generate an in-line arrangement up to four zinc-phthalocyanine molecules, with a larger total transition dipole, and show that this results in enhanced ‘single-molecule’ superradiance from the oligomer upon site-selective excitation. These findings demonstrate that our experimental approach provides detailed spatial information about coherent dipole–dipole coupling in molecular systems, which should enable a greater understanding and rational engineering of light-harvesting structures and quantum light sources.

  5. Visualizing coherent intermolecular dipole-dipole coupling in real space

    NASA Astrophysics Data System (ADS)

    Zhang, Yang; Luo, Yang; Zhang, Yao; Yu, Yun-Jie; Kuang, Yan-Min; Zhang, Li; Meng, Qiu-Shi; Luo, Yi; Yang, Jin-Long; Dong, Zhen-Chao; Hou, J. G.

    2016-03-01

    Many important energy-transfer and optical processes, in both biological and artificial systems, depend crucially on excitonic coupling that spans several chromophores. Such coupling can in principle be described in a straightforward manner by considering the coherent intermolecular dipole-dipole interactions involved. However, in practice, it is challenging to directly observe in real space the coherent dipole coupling and the related exciton delocalizations, owing to the diffraction limit in conventional optics. Here we demonstrate that the highly localized excitations that are produced by electrons tunnelling from the tip of a scanning tunnelling microscope, in conjunction with imaging of the resultant luminescence, can be used to map the spatial distribution of the excitonic coupling in well-defined arrangements of a few zinc-phthalocyanine molecules. The luminescence patterns obtained for excitons in a dimer, which are recorded for different energy states and found to resemble σ and π molecular orbitals, reveal the local optical response of the system and the dependence of the local optical response on the relative orientation and phase of the transition dipoles of the individual molecules in the dimer. We generate an in-line arrangement up to four zinc-phthalocyanine molecules, with a larger total transition dipole, and show that this results in enhanced ‘single-molecule’ superradiance from the oligomer upon site-selective excitation. These findings demonstrate that our experimental approach provides detailed spatial information about coherent dipole-dipole coupling in molecular systems, which should enable a greater understanding and rational engineering of light-harvesting structures and quantum light sources.

  6. Theory of specific heat in glass-forming systems.

    PubMed

    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

  7. Inelastic x-ray scattering of dense solid oxygen: Evidence for intermolecular bonding

    SciTech Connect

    Meng, Yue; Eng, Peter J.; Tse, John S.; Shaw, Dawn M.; Hu, Michael Y.; Shu, Jinfu; Gramsch, Stephen A.; Kao, Chichang; Hemley, Russell J.; Mao, Ho-kwang

    2008-08-14

    The detailing of the intermolecular interactions in dense solid oxygen is essential for an understanding of the rich polymorphism and remarkable properties of this element at high pressure. Synchrotron inelastic x-ray scattering measurements of oxygen K-edge excitations to 38 GPa reveal changes in electronic structure and bonding on compression of the molecular solid. The measurements show that O{sub 2} molecules interact predominantly through the half-filled 1{pi}{sub g}* orbital <10 GPa. Enhanced intermolecular interactions develop because of increasing overlap of the 1{pi}{sub g}* orbital in the low-pressure phases, leading to electron delocalization and ultimately intermolecular bonding between O{sub 2} molecules at the transition to the {epsilon}-phase. The {epsilon}-phase, which consists of (O{sub 2}){sub 4} clusters, displays the bonding characteristics of a closed-shell system. Increasing interactions between (O{sub 2}){sub 4} clusters develop upon compression of the {epsilon}-phase, and provide a potential mechanism for intercluster bonding in still higher-pressure phases.

  8. 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.

  9. Tic disorders: when habit forming neural systems form habits of their own?

    PubMed

    Leckman, J F; Yeh, C B; Cohen, D J

    2001-12-01

    Tourette syndrome (TS), obsessive-compulsive disorder (OCD) and related conditions are prevalent disorders affecting as many as 0.3-3% of the population. They are frequently chronic and can be associated with marked impairment and disability. Although clinical care has improved over the past decade, a significant number of patients fail to respond adequately or experience intolerable side effects. The etiology of these disorders is unknown. Compelling evidence suggests that the vulnerability to develop TS and OCD is mediated by both genetic and environmental factors, and that neural systems located in the basal ganglia and functionally related brain structures are involved in their pathogenesis. Based on explicit models of pathogenesis for TS and OCD and building on work accomplished over the past two decades, an array of clinical, neuropsychological, genetic, neuroimaging, epidemiological neurobiological, and treatment studies have been completed or are underway at the Child Study Center at Yale University. A multidisciplinary team of investigators has joined forces to test specific hypotheses through the integration and translation of basic and clinical neuroscience research. All subjects have been studied using identical clinical, neuropsychological, genetic, neurobiological, and pharmacological techniques. Current conceptualizations of TS have been shaped by advances in clinical phenomenology, genetics, systems neuroscience and the emerging understanding of the role of the basal ganglia in implicit learning and habit formation, neuroimmunology and psychopharmacology. An appreciation of the premonitory urges that precede tics and temporal dynamics of tics have provided useful viewpoints from which to regard the natural history of TS. While the long-term outcome of TS can be relatively benign, the presence of comorbid conditions such as attention deficit/hyperactivity disorder (ADHD), OCD or a major affective disorder can have lasting untoward consequences. The

  10. 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.

  11. 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…

  12. 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.

  13. 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…

  14. Direct observation of intermolecular interactions mediated by hydrogen bonding

    NASA Astrophysics Data System (ADS)

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

    2014-07-01

    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.

  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. 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…

  17. 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.

  18. Intermolecular G-quadruplex-based universal quencher free molecular beacon.

    PubMed

    Zhou, Hui; Xie, Su-Jin; Li, Ji-Shan; Wu, Zai-Sheng; Shen, Guo-Li

    2012-11-11

    A simple and universal quencher-free molecular beacon (MB) with low background fluorescence is developed based on an intermolecular G-quadruplex signaling probe. Unlike previous fluorescent MB strategies, it can function without any fluorophore and quencher modifications on its hairpin sequence.

  19. Copper-catalyzed intermolecular asymmetric propargylic dearomatization of indoles.

    PubMed

    Shao, Wen; Li, He; Liu, Chuan; Liu, Chen-Jiang; You, Shu-Li

    2015-06-22

    The first copper-catalyzed intermolecular dearomatization of indoles by an asymmetric propargylic substitution reaction was developed. This method provides a highly efficient synthesis of versatile furoindoline and pyrroloindoline derivatives containing a quaternary carbon stereogenic center and a terminal alkyne moiety with up to 86 % yield and 98 % ee. PMID:25968474

  20. 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.

  1. 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

  2. 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. PMID:16573013

  3. Intermolecular disulfide bond formation promotes immunoglobulin aggregation: investigation by fluorescence correlation spectroscopy.

    PubMed

    Nag, Moupriya; Bera, Kallol; Basak, Soumen

    2015-01-01

    Protein aggregation generally results from association between hydrophobic regions of individual monomers. However, additional mechanisms arising from specific interactions, such as intermolecular disulfide bond formation, may also contribute to the process. The latter is proposed to be the initiating pathway for aggregation of immunoglobulin (IgG), which is essential for triggering its immune response. To test the veracity of this hypothesis, we have employed fluorescence correlation spectroscopy to measure the kinetics of aggregation of IgG in separate experiments either allowing or inhibiting disulfide formation. Fluorescence correlation spectroscopy measurements yielded a diffusion time (τ(D)) of ∼200 µsec for Rhodamine-labeled IgG, corresponding to a hydrodynamic radius (R(H)) of 56 Å for the IgG monomer. The aggregation kinetics of the protein was followed by monitoring the time evolution of τ(D) under conditions in which its cysteine residues were either free or blocked. In both cases, the progress curves confirmed that aggregation proceeded via the nucleation-dependent polymerization pathway. However, for aggregation in the presence of free cysteines, the lag times were shorter, and the aggregate sizes bigger, than their respective counterparts for aggregation in the presence of blocked cysteines. This result clearly demonstrates that formation of intermolecular disulfide bonds represents a preferred pathway in the aggregation process of IgG. Fluorescence spectroscopy showed that aggregates formed in experiments where disulfide formation was prevented denatured at lower concentration of guanidine hydrochloride than those obtained in experiments where the disulfides were free to form, indicating that intermolecular disulfide bridging is a valid pathway for IgG aggregation. PMID:25371040

  4. 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.

  5. Geometric method for forming periodic orbits in the Lorenz system

    NASA Astrophysics Data System (ADS)

    Nicholson, S. B.; Kim, Eun-jin

    2016-04-01

    Many systems in nature are out of equilibrium and irreversible. The non-detailed balance observable representation (NOR) provides a useful methodology for understanding the evolution of such non-equilibrium complex systems, by mapping out the correlation between two states to a metric space where a small distance represents a strong correlation [1]. In this paper, we present the first application of the NOR to a continuous system and demonstrate its utility in controlling chaos. Specifically, we consider the evolution of a continuous system governed by the Lorenz equation and calculate the NOR by following a sufficient number of trajectories. We then show how to control chaos by converting chaotic orbits to periodic orbits by utilizing the NOR. We further discuss the implications of our method for potential applications given the key advantage that this method makes no assumptions of the underlying equations of motion and is thus extremely general.

  6. Isotopic enrichment of forming planetary systems from supernova pollution

    NASA Astrophysics Data System (ADS)

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

    2016-08-01

    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 disk 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 disks 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.

  7. 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.

  8. Intermolecular vs molecule–substrate interactions: A combined STM and theoretical study of supramolecular phases on graphene/Ru(0001)

    PubMed Central

    Roos, Michael; Uhl, Benedikt; Künzel, Daniela; Hoster, Harry E; Groß, Axel

    2011-01-01

    Summary The competition between intermolecular interactions and long-range lateral variations in the substrate–adsorbate interaction was studied by scanning tunnelling microscopy (STM) and force field based calculations, by comparing the phase formation of (sub-) monolayers of the organic molecules (i) 2-phenyl-4,6-bis(6-(pyridin-3-yl)-4-(pyridin-3-yl)pyridin-2-yl)pyrimidine (3,3'-BTP) and (ii) 3,4,9,10-perylene tetracarboxylic-dianhydride (PTCDA) on graphene/Ru(0001). For PTCDA adsorption, a 2D adlayer phase was formed, which extended over large areas, while for 3,3'-BTP adsorption linear or ring like structures were formed, which exclusively populated the areas between the maxima of the moiré structure of the buckled graphene layer. The consequences for the competing intermolecular interactions and corrugation in the adsorption potential are discussed and compared with the theoretical results. PMID:22003444

  9. Intermolecular vs molecule-substrate interactions: A combined STM and theoretical study of supramolecular phases on graphene/Ru(0001).

    PubMed

    Roos, Michael; Uhl, Benedikt; Künzel, Daniela; Hoster, Harry E; Groß, Axel; Behm, R Jürgen

    2011-01-01

    The competition between intermolecular interactions and long-range lateral variations in the substrate-adsorbate interaction was studied by scanning tunnelling microscopy (STM) and force field based calculations, by comparing the phase formation of (sub-) monolayers of the organic molecules (i) 2-phenyl-4,6-bis(6-(pyridin-3-yl)-4-(pyridin-3-yl)pyridin-2-yl)pyrimidine (3,3'-BTP) and (ii) 3,4,9,10-perylene tetracarboxylic-dianhydride (PTCDA) on graphene/Ru(0001). For PTCDA adsorption, a 2D adlayer phase was formed, which extended over large areas, while for 3,3'-BTP adsorption linear or ring like structures were formed, which exclusively populated the areas between the maxima of the moiré structure of the buckled graphene layer. The consequences for the competing intermolecular interactions and corrugation in the adsorption potential are discussed and compared with the theoretical results.

  10. 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.

  11. Stereometric Measurement System For Quantification Of Object Forms

    NASA Astrophysics Data System (ADS)

    Fischer, P.; Mesqui, F.; Kaeser, F.

    1986-07-01

    A three-dimensional camera unit has been developed at the Dental School of the University of Zurich for jaw motion recording. Since the system is designed to detect and reconstruct the spatial position of a light source, it can easily be used to digitize an object surface being scanned by a laser beam. This is performed by an additional device which has been developed in order to enlarge the application field of the camera unit as well as to prove the feasibility and find out the limits of such a simple and low-cost quantification system.

  12. 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

  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. Intra- and intermolecular hydrogen bonding in acetylacetone and benzoylacetone derived enaminone derivatives

    NASA Astrophysics Data System (ADS)

    Lazić, Vedrana; Jurković, Mihaela; Jednačak, Tomislav; Hrenar, Tomica; Vuković, Jelena Parlov; Novak, Predrag

    2015-01-01

    The structure and hydrogen bonding in solution of acetylacetone and benzoylacetone derived enaminone derivatives, 1a-1d and 2a-2d, have been studied by a combination of experimental (NMR and UV spectroscopies) and theoretical (PM6 and DFT) methods. It has been shown that all studied compounds predominantly existed in the localised keto-amine tautomeric form in solution as found also in the solid state. Significant line-broadening and down-field chemical shifts of NH and OH protons have strongly indicated that both groups formed hydrogen bonds, which has further been supported by quantum chemical calculations. Temperature and concentration dependent NMR measurements have pointed towards the fact that NH protons are engaged in strong intramolecular hydrogen bonds of the NH⋯Odbnd C type in both solvents. On the other hand, OH protons are involved in weaker intermolecular hydrogen bonding with solvent molecules in DMSO, while in chloroform intermolecular interactions between two molecules dominate. The results presented in this paper can be used for better understanding and further exploiting properties these ligands possess, especially their bioactivity.

  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. 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.

  17. 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.

  18. 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.

  19. 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.

  20. Intermolecular vibrations in hydrophobic amino acid crystals: experiments and calculations.

    PubMed

    Williams, Michael R C; Aschaffenburg, Daniel J; Ofori-Okai, Benjamin K; Schmuttenmaer, Charles A

    2013-09-12

    Intermolecular vibrations of amino acid crystals occur in the THz, or far-infrared, region of the electromagnetic spectrum. We have measured the THz and Raman spectra of DL-leucine as well as two polymorphs of DL-valine, the spectroscopic properties of which have not previously been compared. Theoretical modeling of intermolecular vibrations in hydrophobic amino acids is challenging because the van der Waals interactions between molecules are not accounted for in standard density functional theory. Therefore, to calculate the vibrational modes, we used a recently developed approach that includes these nonlocal electron correlation forces. We discuss methods for comparing results from different theoretical models using metrics other than calculated vibrational frequency and intensity, and we also report a new approach enabling concise comparison of vibrational modes that involve complicated mixtures of inter- and intramolecular displacements.

  1. 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.

  2. Intermolecular forces in phase-change heat transfer: 1998 Kern award review

    SciTech Connect

    Wayner, P.C. Jr.

    1999-10-01

    The variation of long-range intermolecular forces near interfaces profoundly affects the performance of change-of-phase heat exchangers. Starting with the fundamental electromagnetic force between molecules (dielectric properties), the effects of shape (Kelvin effect), temperature (Clapeyron effect) and concentration on the heat-transfer characteristics of thin films and larger systems are reviewed and connected. A judicious selection of literature gives a consistent set of models of particular use in heat transfer. Examples of experimental verification of these interfacial models in this rapidly developing field are also presented.

  3. Transient grating study of the intermolecular dynamics of liquid nitrobenzene

    NASA Astrophysics Data System (ADS)

    Wu, Hong-Lin; Song, Yun-Fei; Yu, Guo-Yang; Yang, Yan-Qiang

    2016-10-01

    Femtosecond time-resolved transient grating (TG) technique is used to study the intermolecular dynamics in liquid phase. Non-resonant excitation of the sample by two crossing laser pulses results in a transient Kerr grating, and the molecular motion of liquid can be detected by monitoring the diffraction of a third time-delayed probe pulse. In liquid nitrobenzene (NB), three intermolecular processes are observed with lifetimes of 37.9±1.4 ps, 3.28±0.11 ps, and 0.44±0.03 ps, respectively. These relaxations are assigned to molecular orientational diffusion, dipole/induced dipole interaction, and libration in liquid cage, respectively. Such a result is slightly different from that obtained from OKE experiment in which the lifetime of the intermediate process is measured to be 1.9 ps. The effects of electric field on matter are different in TG and optical Kerr effect (OKE) experiments, which should be responsible for the difference between the results of these two types of experiments. The present work demonstrates that TG technique is a useful alternative in the study of intermolecular dynamics. Project supported by the National Natural Science Foundation of China (Grant Nos. 11304058 and 11404307) and NSAF (Grant No. U1330106).

  4. Morphology development in polymer blends exhibiting strong intermolecular interactions

    SciTech Connect

    Weiss, R.A.; Feng, Y.; Han, C.C.; Karim, A.

    1996-12-31

    He et al. measured the spinodal decomposition (SD) kinetics of a blend of poly(butyl methacrylate) with a polystyrene modified with 1.5 mol% of a hydroxy-containing comonomer that exhibited intermolecular hydrogen bonding, who studied blends. For small excursions into the spinodal region, multiple structures developed in the blend, which suggested that multiple mechanisms may be involved in the phase separation process. For most cases, however, the kinetics of phase separation followed Cahn-Hilliard theory in the early stage of spinodal decomposition and a self-similar mechanism in the later stages, similar to non-associating polymer blends such as PS/PVME. The failure to observe an effect of a specific intermolecular interaction on SD kinetics may be a consequence of the low concentration of hydroxyl groups on the polystyrene, ca. five per chain, and the weakening of the hydrogen bond at the elevated temperatures used to study phase separation where the crosslink effect of hydrogen bonding may not be significant. At elevated temperatures, the association-dissociation equilibrium shifts towards non-associated hydroxyl and ester groups. An objective of the present study was to use a polymer blend having a relatively higher degree of intermolecular association at the phase separation temperature and to investigate how physical crosslinks affect the phase separation kinetics accompanying spinodal decomposition.

  5. Forming Stereogenic Centers in Acyclic Systems from Alkynes.

    PubMed

    Vabre, Roxane; Island, Biana; Diehl, Claudia J; Schreiner, Peter R; Marek, Ilan

    2015-08-17

    The combined carbometalation/zinc homologation followed by reactions with α-heterosubstituted aldehydes and imines proceed through a chair-like transition structure with the substituent of the incoming aldehyde residue preferentially occupying a pseudo-axial position to avoid the two gauche interactions. The heteroatom in the axial position produces a chelated intermediate (and not a Cornforth-Evans transition structure for α-chloro aldehydes and imines) leading to a face differentiation in the allylation reaction. This method provides access to functionalized products in which three new carbon-carbon bonds and two to three stereogenic centers, including a quaternary one, were created in acyclic systems in a single-pot operation from simple alkynes. PMID:26130570

  6. Forming Stereogenic Centers in Acyclic Systems from Alkynes.

    PubMed

    Vabre, Roxane; Island, Biana; Diehl, Claudia J; Schreiner, Peter R; Marek, Ilan

    2015-08-17

    The combined carbometalation/zinc homologation followed by reactions with α-heterosubstituted aldehydes and imines proceed through a chair-like transition structure with the substituent of the incoming aldehyde residue preferentially occupying a pseudo-axial position to avoid the two gauche interactions. The heteroatom in the axial position produces a chelated intermediate (and not a Cornforth-Evans transition structure for α-chloro aldehydes and imines) leading to a face differentiation in the allylation reaction. This method provides access to functionalized products in which three new carbon-carbon bonds and two to three stereogenic centers, including a quaternary one, were created in acyclic systems in a single-pot operation from simple alkynes.

  7. Single-molecule studies of DNA dynamics and intermolecular forces

    NASA Astrophysics Data System (ADS)

    Robertson, Rae Marie

    DNA molecules were used as a model system to investigate fundamental problems in polymer physics; namely, how molecular length, topology and concentration influence the dynamical properties of polymers. A set of DNA molecules suitable for polymer studies was prepared using molecular biology techniques. Video fluorescence microscopy and single-molecule tracking were used to determine self-diffusion coefficients of DNA molecules. Optical tweezers were used to measure the intermolecular forces confining entangled DNA molecules. Scaling of diffusion with molecular length was in agreement with the Zimm model for dilute solutions of linear and circular DNA, indicating that excluded volume effects are appreciable for both topologies. Scaling of diffusion with concentration was also determined for the four possible topological combinations of linear and circular molecules: linear DNA diffusing in a solution of linear DNA, linear DNA in circular DNA, circular in circular, and circular in linear. For lower concentrations molecular topology had little effect and scaling was in agreement with that of the Rouse model. As concentration was increased topology played a much larger role and scaling crossed over to that of the reptation model, predicted to describe the dynamics of entangled polymers. The notable exception was the strongly hindered diffusion observed for a circular molecule diffusing in an entangled linear solution, suggesting the importance of constraint release. Using a new experimental approach with optical tweezers, a tube-like field confining a single entangled molecule was measured, in accord with the key assumption of the reptation model. A time-dependent harmonic potential opposed displacement transverse to the molecular contour, and the force relaxations following displacement were composed of three distinct modes. A characteristic tube radius of the entangled solution was also determined, close to the classically predicted value. The dependence of the above

  8. The forms of knowledge mobilized in some machine vision systems.

    PubMed Central

    Brady, M

    1997-01-01

    This paper describes a number of computer vision systems that we have constructed, and which are firmly based on knowledge of diverse sorts. However, that knowledge is often represented in a way that is only accessible to a limited set of processes, that make limited use of it, and though the knowledge is amenable to change, in practice it can only be changed in rather simple ways. The rest of the paper addresses the questions: (i) what knowledge is mobilized in the furtherance of a perceptual task?; (ii) how is that knowledge represented?; and (iii) how is that knowledge mobilized? First we review some cases of early visual processing where the mobilization of knowledge seems to be a key contributor to success yet where the knowledge is deliberately represented in a quite inflexible way. After considering the knowledge that is involved in overcoming the projective nature of images, we move the discussion to the knowledge that was required in programs to match, register, and recognize shapes in a range of applications. Finally, we discuss the current state of process architectures for knowledge mobilization. PMID:9304690

  9. Exploring the extent of magnetic field effect on intermolecular photoinduced electron transfer in different organized assemblies.

    PubMed

    Choudhury, Sharmistha Dutta; Basu, Samita

    2005-09-15

    Magnetic field effect (MFE) on the photoinduced electron transfer (PET) between phenazine (PZ) and the amines, N,N-dimethylaniline , N,N-diethylaniline, 4,4'-bis(dimethylamino)diphenylmethane (DMDPM), and triethylamine, has been studied in micelles, reverse micelles, and small unilamellar vesicles (SUVs) with a view to understand the effect of spatial location of the donor and acceptor moieties on the magnetic field behavior. The structure of the assembly is found to influence greatly the PET dynamics and hence the MFE of all the systems studied. The magnetic field behavior in micelles is consistent with the hyperfine mechanism, but high B(1/2) values have been obtained which have been ascribed to hopping and lifetime broadening. The variation of MFE with W(0), in reverse micelles, proves yet again that the MFE maximizes at an optimum separation distance between the acceptor and donor. This is the first example of such behavior for intermolecular PET in heterogeneous medium. We have also reported for the first time MFE on intermolecular PET in SUVs. In this case, the PZ-DMDPM system responds most appreciably to an external field compared to the other acceptor-donor systems because it is appropriately positioned in the bilayer. The differential behavior of the amines has been discussed in terms of their confinement in different zones of the organized assemblies depending on their bulk, hydrophobic, and electrostatic effects.

  10. The effect of intermolecular hydrogen bonding on the planarity of amides.

    PubMed

    Platts, James A; Maarof, Hasmerya; Harris, Kenneth D M; Lim, Gin Keat; Willock, David J

    2012-09-14

    Ab initio and density functional theory (DFT) calculations on some model systems are presented to assess the extent to which intermolecular hydrogen bonding can affect the planarity of amide groups. Formamide and urea are examined as archetypes of planar and non-planar amides, respectively. DFT optimisations suggest that appropriately disposed hydrogen-bond donor or acceptor molecules can induce non-planarity in formamide, with OCNH dihedral angles deviating by up to ca. 20° from planarity. Ab initio energy calculations demonstrate that the energy required to deform an amide molecule from the preferred geometry of the isolated molecule is more than compensated by the stabilisation due to hydrogen bonding. Similarly, the NH(2) group in urea can be made effectively planar by the presence of appropriately positioned hydrogen-bond acceptors, whereas hydrogen-bond donors increase the non-planarity of the NH(2) group. Small clusters (a dimer, two trimers and a pentamer) extracted from the crystal structure of urea indicate that the crystal field acts to force planarity of the urea molecule; however, the interaction with nearest neighbours alone is insufficient to induce the molecule to become completely planar, and longer-range effects are required. Finally, the potential for intermolecular hydrogen bonding to induce non-planarity in a model of a peptide is explored. Inter alia, the insights obtained in the present work on the extent to which the geometry of amide groups may be deformed under the influence of intermolecular hydrogen bonding provide structural guidelines that can assist the interpretation of the geometries of such groups in structure determination from powder X-ray diffraction data. PMID:22847473

  11. 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

    2014-08-01

    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. PMID:25011055

  12. 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.

  13. 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.

  14. Optimization of intermolecular potential parameters for the CO2/H2O mixture.

    PubMed

    Orozco, Gustavo A; Economou, Ioannis G; Panagiotopoulos, Athanassios Z

    2014-10-01

    Monte Carlo simulations in the Gibbs ensemble were used to obtain optimized intermolecular potential parameters to describe the phase behavior of the mixture CO2/H2O, over a range of temperatures and pressures relevant for carbon capture and sequestration processes. Commonly used fixed-point-charge force fields that include Lennard-Jones 12-6 (LJ) or exponential-6 (Exp-6) terms were used to describe CO2 and H2O intermolecular interactions. For force fields based on the LJ functional form, changes of the unlike interactions produced higher variations in the H2O-rich phase than in the CO2-rich phase. A major finding of the present study is that for these potentials, no combination of unlike interaction parameters is able to adequately represent properties of both phases. Changes to the partial charges of H2O were found to produce significant variations in both phases and are able to fit experimental data in both phases, at the cost of inaccuracies for the pure H2O properties. By contrast, for the Exp-6 case, optimization of a single parameter, the oxygen-oxygen unlike-pair interaction, was found sufficient to give accurate predictions of the solubilities in both phases while preserving accuracy in the pure component properties. These models are thus recommended for future molecular simulation studies of CO2/H2O mixtures. PMID:25198539

  15. 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

    2014-08-01

    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.

  16. Quantifying the anisotropy of intermolecular potential energy surfaces: a critical assessment of available N2-N2 potentials.

    PubMed

    Karimi-Jafari, M H; Ashouri, M

    2011-05-28

    Based on definition of angular central moments, a quantitative measure is proposed for comparative assessment of the anisotropy of different intermolecular potential energy surfaces at different intermolecular distances. Angular spreadness, skewness and peakedness are three features of anisotropy that are used here to describe the distribution of values of interaction energy around its isotropic component. In agreement with qualitative interpretations, the proposed measure exhibits a sharp change in the R-dependent pattern of anisotropy at an intermediate distance where the repulsive forces on the average overcome the attractive ones. The R-dependence of anisotropy of available N(2)-N(2) potentials is examined in comparison with bare ab initio data and considerable discrepancies are found at distances shorter than the onset of repulsion. It is shown that the full experimentally derived potentials with simplified functional forms do not reproduce the correct anisotropy of interaction energy.

  17. Subunit–subunit interactions are critical for proton sensitivity of ROMK: Evidence in support of an intermolecular gating mechanism

    PubMed Central

    Leng, Qiang; MacGregor, Gordon G.; Dong, Ke; Giebisch, Gerhard; Hebert, Steven C.

    2006-01-01

    The tetrameric K channel ROMK provides an important pathway for K secretion by the mammalian kidney, and the gating of this channel is highly sensitive to changes in cytosolic pH. Although charge–charge interactions have been implicated in pH sensing by this K channel tetramer, the molecular mechanism linking pH sensing and the gating of ion channels is poorly understood. The x-ray crystal structure KirBac1.1, a prokaryotic ortholog of ROMK, has suggested that channel gating involves intermolecular interactions of the N- and C-terminal domains of adjacent subunits. Here we studied channel gating behavior to changes in pH using giant patch clamping of Xenopus laevis oocytes expressing WT or mutant ROMK, and we present evidence that no single charged residue provides the pH sensor. Instead, we show that N–C- and C–C-terminal subunit–subunit interactions form salt bridges, which function to stabilize ROMK in the open state and which are modified by protons. We identify a highly conserved C–C-terminal arginine–glutamate (R-E) ion pair that forms an intermolecular salt bridge and responds to changes in proton concentration. Our results support the intermolecular model for pH gating of inward rectifier K channels. PMID:16446432

  18. Transition Metal Free Intermolecular Direct Oxidative C-N Bond Formation to Polysubstituted Pyrimidines Using Molecular Oxygen as the Sole Oxidant.

    PubMed

    Guo, Wei; Li, Chunsheng; Liao, Jianhua; Ji, Fanghua; Liu, Dongqing; Wu, Wanqing; Jiang, Huanfeng

    2016-07-01

    Various polysubstituted pyrimidines are smoothly formed via a base-promoted intermolecular oxidation C-N bond formation of allylic C(sp(3))-H and vinylic C(sp(2))-H of allyllic compounds with amidines using O2 as the sole oxidant. This protocol features protecting group free nitrogen sources, good functional group tolerance, high atom economy, and environmental advantages.

  19. 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.

  20. 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.

  1. 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.

  2. 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…

  3. Photon Antibunching in Complex Intermolecular Fluorescence Quenching Kinetics.

    PubMed

    Sharma, Arjun; Enderlein, Jörg; Kumbhakar, Manoj

    2016-08-18

    We present a novel fluorescence spectroscopic method, which combines fluorescence antibunching, time-correlated single-photon counting (TCSPC), and steady-state emission spectroscopy, to study chemical reactions at the single molecule level. We exemplify our method on investigating intermolecular fluorescence quenching of Rhodamine110 by aniline. We demonstrate that the combination of measurements of fluorescence antibunching, fluorescence lifetime, and fluorescence steady state intensity, captures the full picture of the complex quenching kinetics, which involves static and dynamics quenching, and which cannot be seen by steady-state or lifetime measurements alone. PMID:27468007

  4. 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

  5. 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.

  6. The Effect of Intermolecular Modes on the Xh-Stretching Vibrations in Hydrogen Bonded Complexes

    NASA Astrophysics Data System (ADS)

    Mackeprang, Kasper; Kjaergaard, Henrik G.

    2016-06-01

    Vibrational spectra of hydrogen bonded bimolecular complexes (XH\\cdotsY, where X is the hydrogen bond donor atom, and Y is the acceptor atom) have long been a theoretical challenge. Specifically, the XH-stretching motion is difficult to describe due to the effect of the large amplitude intermolecular modes inherent to complexes. We have developed a vibrational model, the Local Mode Perturbation Theory (LMPT) model, to accurately determine the transition wavenumber and oscillator strength of the XH-stretching transition in hydrogen bonded bimolecular complexes. The model is based on a local mode (LM) model of the XH-stretching transition and the effect of the intermolecular modes is included via Rayleigh-Schrödinger perturbation theory. Our model has significantly improved results obtained using the LM model (see Figure). Additionally, our LMPT model does not require a full-dimensional anharmonic calculation, which enables application to large systems and the usage of higher level ab initio theory for the required potential energy surfaces. This work was inspired by our recent efforts to accurately determine equilibrium constants of complex formation, which rely on an accurate determination of the oscillator strength of the XH-stretching transition.

  7. 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.

  8. Thermal-sensitive viscosity transition of elongated micelles induced by breaking intermolecular hydrogen bonding of amide groups.

    PubMed

    Morita, Clara; Imura, Yoshiro; Ogawa, Tetsuya; Kurata, Hiroki; Kawai, Takeshi

    2013-05-01

    A heat-induced viscosity transition of novel worm-like micelles of a long alkyl-chain amidoamine derivative (C18AA) bearing intermolecular hydrogen-bonding group was investigated by cryo-TEM, FT-IR, and rheological measurements. At lower temperature, C18AA forms straight elongated micelles with a length on the order of micrometers due to strong intermolecular hydrogen-bonded packing of the amide groups, although the micelles rarely entangle and have low value of zero-shear viscosity. The straight elongated micelles likely became flexible and underwent a morphological transition from straight structure to worm-like structure at a certain temperature, which caused a drastic increase in viscosity due to entanglement of the micelles. This morphological transition was caused by a defect of intermolecular hydrogen bonding between the amide groups on heating. Furthermore, addition of LiCl, which acts as hydrogen-bond breaker, also promoted the viscosity transition, leading to a lowering of the transition temperature.

  9. Oriented covalent immobilization of antibodies for measurement of intermolecular binding forces between zipper-like contact surfaces of split inteins.

    PubMed

    Sorci, Mirco; Dassa, Bareket; Liu, Hongwei; Anand, Gaurav; Dutta, Amit K; Pietrokovski, Shmuel; Belfort, Marlene; Belfort, Georges

    2013-06-18

    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 intermolecular force measurement of 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 1 μm/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 nonpolar attraction between multiple aligned ion pairs and hydrophobic residues. Also, we tested the Jarzynski's equality and demonstrated, as expected, that nonequilibrium 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.

  10. 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.

  11. 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.

  12. Intermolecular Hybridization Creating Nanopore Orbital in a Supramolecular Hydrocarbon Sheet.

    PubMed

    Zhang, Yi-Qi; Björk, Jonas; Barth, Johannes V; Klappenberger, Florian

    2016-07-13

    Molecular orbital engineering is a key ingredient for the design of organic devices. Intermolecular hybridization promises efficient charge carrier transport but usually requires dense packing for significant wave function overlap. Here we use scanning tunneling spectroscopy to spatially resolve the electronic structure of a surface-confined nanoporous supramolecular sheet of a prototypical hydrocarbon compound featuring terminal alkyne (-CCH) groups. Surprisingly, localized nanopore orbitals are observed, with their electron density centered in the cavities surrounded by the functional moieties. Density functional theory calculations reveal that these new electronic states originate from the intermolecular hybridization of six in-plane π-orbitals of the carbon-carbon triple bonds, exhibiting significant electronic splitting and an energy downshift of approximately 1 eV. Importantly, these nanopore states are distinct from previously reported interfacial states. We unravel the underlying connection between the formation of nanopore orbital and geometric arrangements of functional groups, thus demonstrating the generality of applying related orbital engineering concepts in various types of porous organic structures.

  13. 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.

  14. 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

  15. Quantitative analysis of intermolecular interactions in orthorhombic rubrene

    DOE PAGES

    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,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

  16. Quantitative analysis of intermolecular interactions in orthorhombic rubrene.

    PubMed

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

    2015-09-01

    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

  17. Dynamics of intermolecular interactions in CCl4via the isotope effect by femtosecond time-resolved spectroscopy.

    PubMed

    Konarska, Jadwiga; Gadomski, Wojciech; Ratajska-Gadomska, Bożena; Polok, Kamil; Pudłowski, Grzegorz; Kardaś, Tomasz M

    2016-06-21

    We report our study on the ultrafast dynamics of intermolecular interactions in liquid CCl4. A transient transmission time domain signal, obtained in the 40 ps delay range, exhibits beating at the difference frequency of the totally symmetric stretching vibrations of the tetrachloride isotopologues. We show that the spectra obtained as the windowed Fourier transform of different parts of the time domain signal in the range of this totally symmetric vibration, split due to the isotope effect, carry the information about the dynamics of the coherently excited, coupled molecules. We use a simple theoretical model in order to prove that the intermolecular interaction influences the relative amplitudes of the isotopologue peaks in the spectrum. Moreover, we demonstrate that the pump induced coherence in the system leads to additional strengthening of the interaction, which can be observed in the spectra obtained from the experimental time domain signal. PMID:27244535

  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. First-order exchange energy of intermolecular interactions from coupled cluster density matrices and their cumulants.

    PubMed

    Korona, Tatiana

    2008-06-14

    A new method for the calculation of the first-order intermolecular exchange energy is proposed. It is based on the partition of two-particle density matrices of monomers into the antisymmetrized product of one-particle density matrices and the remaining cumulant part. This partition is used to modify the formula for the first-order exchange energy developed by Moszynski et al. [J. Chem. Phys. 100, 5080 (1994)]. The new expression has been applied for the case of monomer density matrices derived from the expectation value expression for the coupled cluster singles and doubles wave function. In this way an accurate method of calculation of the first-order exchange energy for many-electron systems has been obtained, where both monomers are described on the coupled cluster level. Numerical results are presented for several benchmark van der Waals systems to illustrate the performance of the new approach.

  20. Exploring How Technology Mediates the Types of Relationships Formed in Sociotechnical Systems

    ERIC Educational Resources Information Center

    Chu, Kar-Hai

    2012-01-01

    This work presents an exploratory study of how technology mediates the different types of relationships that are formed in sociotechnical systems. More people each day are connecting with each other through social networks, online communities, and other forms of virtual environments. Whether for education, information seeking, friendship,…

  1. 78 FR 5477 - Agency Information Collection Activities: InfoPass System, No Form Number; Extension, Without...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-01-25

    ... information collection notice was previously published in the Federal Register on October 31, 2012, at 77 FR... 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...

  2. 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…

  3. 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

    ... the Chief Information Officer. BILLING CODE 4210-67-P ... URBAN DEVELOPMENT Enterprise Income Verification (EIV) System User Access Authorization Form and Rules of Behavior and User Agreement AGENCY: Office of the Chief Information Officer, HUD. ACTION:...

  4. Carleman linearization and normal forms for differential systems with quasi-periodic coefficients.

    PubMed

    Chermnykh, Sergey V

    2016-01-01

    We study the matrix representation of Poincaré normalization using the Carleman linearization technique for non-autonomous differential systems with quasi-periodic coefficients. We provide a rigorous proof of the validity of the matrix representation of the normalization and obtain a recursive algorithm for computing the normalizing transformation and the normal form of the differential systems. The algorithm provides explicit formulas for the coefficients of the normal form and the corresponding transformation. PMID:27588240

  5. Atomic force microscopy measurements of intermolecular binding forces.

    PubMed

    Misevic, Gradimir N; Karamanos, Yannis; Misevic, Nikola J

    2009-01-01

    Atomic force microscopy (AFM) measurements of intermolecular binding strength between a single pair of complementary cell adhesion molecules in physiological solutions provided the first quantitative evidence for their cohesive function. This novel AFM-based nanobiotechnology opens a molecular mechanic approach for studying structure- to function-related properties of any type of individual biological macromolecules. The presented example of Porifera cell adhesion glyconectin proteoglycans showed that homotypic carbohydrate to carbohydrate interactions between two primordial proteoglycans can hold the weight of 1,600 cells. Thus, glyconectin type carbohydrates, as the most peripheral cell surface molecules of sponges (today's simplest living Metazoa), are proposed to be the primary cell adhesive molecules essential for the evolution of the multicellularity.

  6. Visualizing the orientational dependence of an intermolecular potential

    NASA Astrophysics Data System (ADS)

    Sweetman, Adam; Rashid, Mohammad A.; Jarvis, Samuel P.; Dunn, Janette L.; Rahe, Philipp; Moriarty, Philip

    2016-02-01

    Scanning probe microscopy can now be used to map the properties of single molecules with intramolecular precision by functionalization of the apex of the scanning probe tip with a single atom or molecule. Here we report on the mapping of the three-dimensional potential between fullerene (C60) molecules in different relative orientations, with sub-Angstrom resolution, using dynamic force microscopy (DFM). We introduce a visualization method which is capable of directly imaging the variation in equilibrium binding energy of different molecular orientations. We model the interaction using both a simple approach based around analytical Lennard-Jones potentials, and with dispersion-force-corrected density functional theory (DFT), and show that the positional variation in the binding energy between the molecules is dominated by the onset of repulsive interactions. Our modelling suggests that variations in the dispersion interaction are masked by repulsive interactions even at displacements significantly larger than the equilibrium intermolecular separation.

  7. Intermolecular-charge-transfer-induced fluorescence quenching in protic solvent

    NASA Astrophysics Data System (ADS)

    Lin, Tao; Liu, Xiaojun; Lou, Zhidong; Hou, Yanbing; Teng, Feng

    2016-11-01

    The fluorescence quenching of fluorenone in protic solvent has been extensively investigated, and the intermolecular hydrogen bond was found to play a crucial role. Unfortunately, the mechanism at atomic level is still not clear. In the present work, we theoretically put forward the charge transfer along the hydrogen bond in the excited states. The vertical excitation energies of the fluorenone-methanol complex as well as the potential energy profiles and surfaces of the vertical excited states and charge transfer states were calculated by using the ab initio electronic-structure methods. The photochemical reactions occurring in the diverse charge transfer states were compared and their decisiveness to the fluorescence quenching was discussed in the paper.

  8. Visualizing the orientational dependence of an intermolecular potential

    PubMed Central

    Sweetman, Adam; Rashid, Mohammad A.; Jarvis, Samuel P.; Dunn, Janette L.; Rahe, Philipp; Moriarty, Philip

    2016-01-01

    Scanning probe microscopy can now be used to map the properties of single molecules with intramolecular precision by functionalization of the apex of the scanning probe tip with a single atom or molecule. Here we report on the mapping of the three-dimensional potential between fullerene (C60) molecules in different relative orientations, with sub-Angstrom resolution, using dynamic force microscopy (DFM). We introduce a visualization method which is capable of directly imaging the variation in equilibrium binding energy of different molecular orientations. We model the interaction using both a simple approach based around analytical Lennard–Jones potentials, and with dispersion-force-corrected density functional theory (DFT), and show that the positional variation in the binding energy between the molecules is dominated by the onset of repulsive interactions. Our modelling suggests that variations in the dispersion interaction are masked by repulsive interactions even at displacements significantly larger than the equilibrium intermolecular separation. PMID:26879386

  9. 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.

  10. 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

  11. 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.

  12. 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.

  13. Interplay of Halogen and π-π Charge-Transfer Bondings in Intermolecular Associates of Bromo- or Iododinitrobenzene with Tetramethyl-p-phenylenediamine.

    PubMed

    Rosokha, Sergiy V; Loboda, Eric A

    2015-04-23

    Two modes of intermolecular interactions (halogen and π-π charge-transfer bonding) between bromo- or iododinitrobenzene (XDNB) and tetramethyl-p-phenylenediamine (TMPD) are compared. X-ray crystallography revealed that TMPD·XDNB cocrystals comprise alternating donors/acceptors stacks formed by π-bonded (cofacial) TMPD and XDNB molecules. These structures also show two-point (C-X···O-N) halogen bonding between XDNB molecules resulting in formation of (XDNB)2 dimers. In solutions, XDNB and TMPD molecules formed 1:1 complexes showing strong absorption bands near 550 nm which followed the same Mulliken correlation as the associates of TMPD with the (halogen-free) nitro- and cyanobenzenes. In accord with the experimental data, density functional theory calculations with the M062X functional showed that TMPD·XDNB associates formed via π-π charge-transfer bonding are more stable (by 6-12 kcal/mol) than their halogen-bonded analogues. If XDNB is replaced with iodo- or bromoperfluorinated benzenes, or TMPD is replaced with pyridine, the energy gap between the π-π and halogen-bonded associates decreased. The analysis of the molecular-orbital interactions and surface electrostatic potentials of the interacting species indicated that charge-transfer contributions represent a critical component which determines variations of the strength of halogen bonding in these systems.

  14. 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.

  15. 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.

  16. 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…

  17. 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.

  18. 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

  19. 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

  20. 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.

  1. 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.

  2. Experimental evolution of complexity: in vitro emergence of intermolecular ribozyme interactions.

    PubMed Central

    Hanczyc, M M; Dorit, R L

    1998-01-01

    In the course of evolving variants of the Tetrahymena thermophila Group I ribozyme for improved DNA cleavage in vitro, we witnessed the unexpected emergence of a derived molecular species, capable of acting as a partner for the ribozyme, but no longer autocatalytic. This new RNA species exhibits a deletion in the catalytic core and participates in a productive intermolecular interaction with an active ribozyme, thus insuring its survival in the population. These novel RNA molecules have evolved a precise catalytic interaction with the Group I ribozyme and depend for their survival on the continued presence of active catalysts. This interaction hints at the complexity that may inevitably arise even in simple evolving systems. PMID:9510329

  3. Graphene-enhanced intermolecular interaction at interface between copper- and cobalt-phthalocyanines.

    PubMed

    Dou, Wei-Dong; Huang, Shu-Ping; Lee, Chun-Sing

    2015-10-01

    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. PMID:26450327

  4. 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.

  5. Graphene-enhanced intermolecular interaction at interface between copper- and cobalt-phthalocyanines

    NASA Astrophysics Data System (ADS)

    Dou, Wei-Dong; Huang, Shu-Ping; Lee, Chun-Sing

    2015-10-01

    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.

  6. 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.

  7. Ethyl 4-dodecyl-3,5-dimethyl-1H-pyrrole-2-carboxylate: intermolecular interactions in an amphiphilic pyrrole.

    PubMed

    Ramos Silva, Manuela; Matos Beja, Ana; Paixão, Jose Antonio; Sobral, Abilio J F N; Lopes, Susana H; Rocha Gonsalves, A M d'A

    2002-09-01

    The title compound, C(21)H(37)NO(2), is a new amphiphilic pyrrole with a long hydrocarbon chain, which will be used as a precursor for the synthesis of Langmuir-Blodgett films of porphyrins. Molecules related by an inversion centre are joined head-to-head into dimers by strong N-H.O hydrogen bonds. The dimers pack in the structure with their carbon chains parallel to one another, thereby forming alternating layers of carbon chains and pyrrole heads. The structure is further stabilized by two weak C-H.pi intermolecular interactions, thereby saturating the hydrogen-bonding capability of the aromatic pi-electron clouds.

  8. Intermolecular Tl···H-C anagostic interactions in luminescent pyridyl functionalized thallium(I) dithiocarbamates.

    PubMed

    Kumar, Vinod; Singh, Vikram; Gupta, Ajit N; Drew, Michael G B; Singh, Nanhai

    2015-01-28

    Crystal structures of novel pyridyl functionalised [Tl(L)]∞ (L = (N-benzyl-N-methylpyridyl) dithiocarbamate(L1) 1, bis(N-methylpyridyl) dithiocarbamate(L2) 2, (N-methyl(1,4-benzodioxane-6-yl)-N-methylpyridyl)dithiocarbamate(L3) 3, (N-ferrocenyl-N-methylpyridyl) dithiocarbamate(L4) 4) complexes revealed rare intermolecular C-H···Tl anagostic and C-S···Tl interactions forming a six-membered chelate ring about the metal center, which have been assessed by DFT calculations. The strong thallophilic bonding is responsible for the strong luminescent characteristics of the complexes in the solid phase. PMID:25461980

  9. 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.

  10. 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.

  11. 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.

  12. Squeezing water clusters between graphene sheets: energetics, structure, and intermolecular interactions.

    PubMed

    McKenzie, S; Kang, H C

    2014-12-21

    The behavior of water confined at the nanoscale between graphene sheets has attracted much theoretical and experimental attention recently. However, the interactions, structure, and energy of water at the molecular scale underpinning the behavior of confined water have not been characterized by first-principles calculations. In this work we consider small water clusters up to the hexamer adsorbed between graphene sheets using density functional theory calculations with van der Waals corrections. We investigate the effects on structure, energy, and intermolecular interactions due to confinement between graphene sheets. For interlayer distances of about one nanometer or more, the cluster adsorption energy increases approximately linearly with the cluster size by 0.1 eV per molecule in the cluster. As the interlayer distance decreases, the cluster adsorption energy reaches a maximum at 6 to 7 Å with approximately 0.16 eV stabilization energy relative to large interlayer distances. This suggests the possibility of controlling the amount of adsorption in graphene nanomaterials by varying the interlayer distance. We also quantify the intermolecular hydrogen bonding in the clusters by calculating the dissociation energy required to remove one molecule from each cluster. For each cluster size, this is constant for interlayer distances larger than approximately 6 to 8 Å. For smaller distances the intermolecular interaction decreases rapidly thus leading to weaker cohesion between molecules in a squeezed cluster. We expect a mechanism of concerted motion for hydrogen-bonded water molecules confined between graphene sheets, as has been observed for water confined within the carbon nanotubes. Thus, the decrease in the dissociation energy we observed here is consistent with experimental results for water transport through graphene and related membranes that are of interest in nanofiltration. We also calculate the corrugation in the interaction potential between graphene

  13. 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

    2014-07-01

    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

  14. Pick and Pack: a just-in-time forms order and delivery system.

    PubMed

    Stewart, M

    1993-01-01

    Since the University of Alabama Hospital at Birmingham (UAB) had an in-plant print shop, the idea of purchasing forms from an outside supplier on a JIT order and delivery system didn't occur to them. But after establishing a successful medical/surgical JIT system at University of Alabama Hospital at Birmingham (UAB), the Director of Support Services and the Director of Purchasing looked at and developed a program to have a JIT forms inventory system by using their own print shop in conjunction with an outside supplier. The system, called Pick and Pack, basically works like this: An outside supplier buys flat-bed forms printed by the UAB Print Shop for resale back to UAB, and also produces their own custom, continuous forms to sell to UAB. The supplier warehouses, then picks and packs per individual UAB patient care unit order and delivers the forms to the UAB Material Management loading dock. Requisitioning is on-line for each patient care unit, Materiel Management and the supplier. Success was achieved in a step-by-step manner, reducing a time-consuming, labor-intensive receiving process to a one-person process. Inventory of forms is estimated to have been reduced by $90,000 and approximately 2,160 cubic feet of space freed for other uses.

  15. 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

  16. Principles of optical system construction for forming a cylindrical light tube

    NASA Astrophysics Data System (ADS)

    Ezhova, Kseniia; Zverev, Victor

    2016-04-01

    In this paper the basic principles of the optical system construction for forming a cylindrical light tube of assigned diameter are formulated. It is based on the principle of agreement aperture and field angle of the optical system and the possibility of converting the transverse dimensions of the cylindrical light tubes by using the afocal optical system. In general, the task of converting a formed cylindrical light tube with the desired dimensions in the reverse path of the rays can be solved with a help of the single afocal system consisting of two positive components. In paper some variants of the optical system scheme for preliminary (initial) conversion of light tubes with an indication of their main advantages and disadvantages are presented. Aberration analysis of optical systems was carried out.

  17. Normal form solutions of dynamical systems in the basin of attraction of their fixed points

    NASA Astrophysics Data System (ADS)

    Bountis, Tassos; Tsarouhas, George; Herman, Russell

    1998-10-01

    The normal form theory of Poincaré, Siegel and Arnol'd is applied to an analytically solvable Lotka-Volterra system in the plane, and a periodically forced, dissipative Duffing's equation with chaotic orbits in its 3-dimensional phase space. For the planar model, we determine exactly how the convergence region of normal forms about a nodal fixed point is limited by the presence of singularities of the solutions in the complex t-plane. Despite such limitations, however, we show, in the case of a periodically driven system, that normal forms can be used to obtain useful estimates of the basin of attraction of a stable fixed point of the Poincaré map, whose ``boundary'' is formed by the intersecting invariant manifolds of a second hyperbolic fixed point nearby.

  18. 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…

  19. 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.

  20. A Colloidal Description of Intermolecular Interactions Driving Fibril-Fibril Aggregation of a Model Amphiphilic Peptide.

    PubMed

    Owczarz, Marta; Motta, Anna C; Morbidelli, Massimo; Arosio, Paolo

    2015-07-14

    We apply a kinetic analysis platform to study the intermolecular interactions underlying the colloidal stability of dispersions of charged amyloid fibrils consisting of a model amphiphilic peptide (RADA 16-I). In contrast to the aggregation mechanisms observed in the large majority of proteins and peptides, where several elementary reactions involving both monomers and fibrils are present simultaneously, the system selected in this work allows the specific investigation of the fibril-fibril aggregation process. We examine the intermolecular interactions driving the aggregation reaction at pH 2.0 by changing the buffer composition in terms of salt concentration, type of ion as well as type and concentration of organic solvent. The aggregation kinetics are followed by dynamic light scattering, and the experimental data are simulated by Smoluchowski population balance equations, which allow to estimate the energy barrier between two colliding fibrils in terms of the Fuchs stability ratio (W). When normalized on a dimensionless time weighted on the Fuchs stability ratio, the aggregation profiles under a broad range of conditions collapse on a single master curve, indicating that the buffer composition modifies the aggregation kinetics without affecting the aggregation mechanism. Our results show that the aggregation process does not occur under diffusion-limited conditions. Rather, the reaction rate is limited by the presence of an activation energy barrier that is largely dominated by electrostatic repulsive interactions. Such interactions could be reduced by increasing the concentration of salt, which induces charge screening, or the concentration of organic solvent, which affects the dielectric constant. It is remarkable that the dependence of the activation energy on the ionic strength can be described quantitatively in terms of charge screening effects in the frame of the DLVO theory, although specific anion and cation effects are also observed. While anion

  1. Selenoprotein K form an intermolecular diselenide bond with unusually high redox potential

    PubMed Central

    Liu, Jun; Zhang, Zhengqi; Rozovsky, Sharon

    2014-01-01

    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. PMID:25117454

  2. [Inflammatory and autoimmune reactions in different forms of nervous system functioning disorders].

    PubMed

    Otman, I N; Zozulya, S A; Sarmanova, Z V; Klushnik, T P

    2015-01-01

    Parameters of innate (the leukocyte elastase (LE) and alpha1-proteinase inhibitor (α-1-PI) activity) and adaptive immunity (the level of autoantibodies to neuroantigens nerve growth factor (NGF) and myelin basic protein (MPB)) were studied over time in the blood serum of 107 children with perinatal hypoxic-ischemic encephalopathy; 188 children with autism spectrum disorder; 108 patients with schizophrenia. The correlations between immunological parameters and clinical status assessment in all groups of patients using psychometric scales were analyzed. The involvement of innate immunity, i.e. inflammatory reactions, in pathogenesis of all analyzed forms of nervous system functioning disorders was confirmed. The activation of adaptive immunity, i.e. autoimmune reactions, was found only in the group of patients with the most severe forms of nervous system functioning endogenous disorders. The results indicate that the inflammatory and autoimmune reactions are pathogenic mechanism of all studied forms of nervous system functioning disorders. PMID:26852601

  3. 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.

  4. 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

  5. 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.

  6. 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.

  7. Design of compact and smooth free-form optical system with uniform illuminance for LED source.

    PubMed

    Luo, Yi; Feng, Zexin; Han, Yanjun; Li, Hongtao

    2010-04-26

    A feedback modification method based on variable separation mapping is proposed in the design of free-form optical system with uniform illuminance for LED source. In this method, the non-negligible size of LED source is taken into account, and a smooth optical system is established with single freeform surface regenerated by adding feedback to the lens design for a point light source. More rounds of feedback can improve the lens performance. As an example, a smooth free-form lens with rectangular illuminance distribution is designed, and the illuminance uniformity is improved from 18.75% to 81.08% after eight times feedback.

  8. 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.

  9. 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.

  10. 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

    2016-01-01

    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.

  11. When do we need attractive-repulsive intermolecular potentials?

    SciTech Connect

    Venkattraman, Ayyaswamy

    2014-12-09

    The role of attractive-repulsive interactions in direct simulation Monte Carlo (DSMC) simulations is studied by comparing with traditional purely repulsive interactions. The larger collision cross section of the long-range LJ potential is shown to result in a higher collision frequency and hence a lower mean free path, by at least a factor of two, for given conditions. This results in a faster relaxation to equilibrium as is shown by comparing the fourth and sixth moments of the molecular velocity distribution obtained using 0-D DSMC simulations. A 1-D Fourier-Couette flow with a large temperature and velocity difference between the walls is used to show that matching transport properties will result in identical solutions using both LJPA and VSS models in the near-continuum regime. However, flows in the transitional regime with Knudsen number, Kn ∼ 0.5 show a dependence on the intermolecular potential in spite of matching the viscosity coefficient due to differences in the collision frequency. Attractive-repulsive potentials should be used when both transport coefficients and collision frequencies should be matched.

  12. Carbon dioxide-methanol intermolecular complexes in interstellar grain mantles

    NASA Astrophysics Data System (ADS)

    Dartois, E.; Demyk, K.; d'Hendecourt, L.; Ehrenfreund, P.

    1999-11-01

    We present new laboratory data to interpret the Infrared Space Observatory (ISO) spectra of protostellar objects, and particularly RAFGL7009S. Our experimental results show that solid methanol and carbon dioxide exhibit specific intermolecular interactions. We propose the formation of a Lewis acid-base complex between carbon dioxide and methanol molecules to explain specific substructure of the 15.2 mu m CO_2 bending mode observed in different objects. The various CO_2 bending mode patterns observed in many lines of sight can be interpreted as a combination of both this complex formation and the temperature evolution of the ices. The temperature induced segregation of ice mantles containing CO_2 can be monitored by the 13CO_2 stretching mode shift toward the pure CO_2 ice position. The large width observed for this mode towards interstellar sources partly results from the different temperatures sampled along the line of sight. Given the amount of methanol involved in RAFGL7009S, on the basis of ground based observations, we derive that about half of the so called ``6.85 mu m'' band and a quarter of the 4.9 mu m bands can be accounted for by the deformation modes and 2nu_8 transitions of CH_3OH. Based on observations with ISO, an ESA project with instruments funded by ESA Member States (especially the PI countries: France, Germany, the Netherlands and the United Kingdom) and with the participation of ISAS and NASA

  13. 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

  14. Externally controlled anisotropy in pattern-forming reaction-diffusion systems.

    PubMed

    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. Understanding antibody-antigen associations by molecular dynamics simulations: detection of important intra- and inter-molecular salt bridges.

    PubMed

    Sinha, Neeti; Li, Yili; Lipschultz, Claudia A; Smith-Gill, Sandra J

    2007-01-01

    1 NSec molecular dynamics (MD) simulation of anti-hen egg white antibody, HyHEL63 (HH63), complexed with HEL reveals important molecular interactions, not revealed in its X-ray crystal structure. These molecular interactions were predicted to be critical for the complex formation, based on structure-function studies of this complex and 3-other anti-HEL antibodies, HH8, HH10 and HH26, HEL complexes. All four antibodies belong to the same structural family, referred to here as HH10 family. Ala scanning results show that they recognize 'coincident epitopes'. 1 NSec explicit, with periodic boundary condition, MD simulation of HH63- HEL reveals the presence of functionally important saltbridges. Around 200 ps in vacuo and an additional 20 ps explicit simulation agree with the observations from 1 Nsec simulation. Intra-molecular salt-bridges predicted to play significant roles in the complex formation, were revealed during MD simulation. A very stabilizing saltbridge network, and another intra-molecular salt-bridge, at the binding site of HEL, revealed during the MD simulation, is proposed to predipose binding site geometry for specific binding. All the revealed saltbridges are present in one or more of the other three complexes and/or involve \\"hot-spot\\" epitope and paratope residues. Most of these charged epitope residues make large contribution to the binding free energy. The "hot spot" epitope residue Lys97Y, which significantly contributes to the free energy of binding in all the complexes, forms an intermolecular salt-bridge in several MD conformers. Our earlier computations have shown that this inter-molecular salt-bridge plays a significant role in determining specificity and flexibility of binding in the HH8-HEL and HH26-HEL complexes. Using a robust criterion of salt-bridge detection, this intermolecular salt-bridge was detected in the native structures of the HH8-HEL and HH26-HEL complexes, but was not revealed in the crystal structure of HH63-HEL complex

  16. Theoretical study on the effect of solvent and intermolecular fluctuations in proton transfer reactions: General theory

    SciTech Connect

    Kato, Nobuhiko; Ida, Tomonori; Endo, Kazunaka

    2004-04-30

    We present a theory of proton transfer reactions which incorporate the modulation of the proton's potential surface by intermolecular vibrations and the effect of coupling to solvent degree of freedom. The proton tunnels between states corresponding to it being localized in the wells of a double minimum potential. The resulting tunnel splitting depends on the intermolecular separation. The solvent response to the proton's charge is modeled as that of a continuous distribution of harmonic oscillators and the intermolecular stretching mode is also damped because of the interaction with solvent degree of freedom. The transition rate is given by the Fermi Gorlden Rule expression.

  17. Na + concentration dependence of intermolecular distance in 3,4,9,10-perylenetetracarboxylic dianhydride dimer

    NASA Astrophysics Data System (ADS)

    Fujii, Kazuhito

    2010-01-01

    We have discussed the Na + concentration dependence of the intermolecular distance of 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) dimers in aqueous solution of NaOH. We have particularly focused on the S10-S00 transition of the PTCDA dimers which is sensitive to the intermolecular distance and we have found that the S10 state is split for the higher lying sublevel and the lower lying sublevel with the increase of the Na + concentrations. From the energy shift of the lower lying sublevel, we have estimated the intermolecular distance of the PTCDA dimer, that changes from 7.5 to 4.9 Å by the Na + concentration.

  18. [Familial forms of central nervous system cavernomas: from recognition to gene therapy].

    PubMed

    Labauge, P

    2007-06-01

    Ten percent of all cavernomas are familial forms. 300 independent families have been identified in France since 1995. Clinical manifestations are more frequent in familial (50%) than in sporadic forms (5%). The symptoms are the same in both forms: epilepsy, hemorrhages, neurological focal deficits and headache, but hemorrhages are more frequent and the age of revelation is younger, before 30 years. It is also frequent to observe extraneural location, cutaneous and retinal. On MRI, four types of lesional aspects were described and lesions are multiple in all cases with numerous "de novo" cavernomas. The prognostic does not depend on the number of lesions, but on their topography, especially in the brain stem. Familial forms may be considered not only as a neurological but as a systemic disease for which global management with a genetic counseling should be considered. Gene therapy is not today available, but perhaps in the future. PMID:17498752

  19. Normal and quasinormal forms for systems of difference and differential-difference equations

    NASA Astrophysics Data System (ADS)

    Kashchenko, Ilya; Kaschenko, Sergey

    2016-09-01

    The local dynamics of systems of difference and singularly perturbed differential-difference equations is studied in the neighborhood of a zero equilibrium state. Critical cases in the problem of stability of its state of equilibrium have infinite dimension. Special nonlinear evolution equations, which act as normal forms, are set up. It is shown that their dynamics defines the behavior of solutions to the initial system.

  20. 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.

  1. Inter-molecular β-sheet structure facilitates lung-targeting siRNA delivery.

    PubMed

    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

  2. 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

  3. 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

  4. 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.

  5. 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

    2014-05-01

    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.

  6. O-ring tube fittings form leakproof seal in hydraulic systems

    NASA Technical Reports Server (NTRS)

    1966-01-01

    Leakproof fittings for hydraulic systems are designed to be welded to the ends of the tubing to be joined and mated to form a seal with one o-ring at the joint. Since the fittings are coupled at only one joint, they tend to be more reliable than standard fittings coupled at two joints.

  7. 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.

  8. 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.

  9. Asymmetric crystallization during cooling and heating in model glass-forming systems

    NASA Astrophysics Data System (ADS)

    Wang, Minglei; Zhang, Kai; Li, Zhusong; Liu, Yanhui; Schroers, Jan; Shattuck, Mark D.; O'Hern, Corey S.

    2015-03-01

    We perform molecular dynamics (MD) simulations of the crystallization process in binary Lennard-Jones systems during heating and cooling to investigate atomic-scale crystallization kinetics in glass-forming materials. For the cooling protocol, we prepared equilibrated liquids above the liquidus temperature Tl and cooled each sample to zero temperature at rate Rc. For the heating protocol, we first cooled equilibrated liquids to zero temperature at rate Rp and then heated the samples to temperature T >Tl at rate Rh. We measured the critical heating and cooling rates Rh* and Rc*, below which the systems begin to form a substantial fraction of crystalline clusters during the heating and cooling protocols. We show that Rh*>Rc* and that the asymmetry ratio Rh*/Rc* includes an intrinsic contribution that increases with the glass-forming ability (GFA) of the system and a preparation-rate dependent contribution that increases strongly as Rp→Rc* from above. We also show that the predictions from classical nucleation theory (CNT) can qualitatively describe the dependence of the asymmetry ratio on the GFA and preparation rate Rp from the MD simulations and results for the asymmetry ratio measured in Zr- and Au-based bulk metallic glasses (BMG). This work emphasizes the need for and benefits of an improved understanding of crystallization processes in BMGs and other glass-forming systems.

  10. 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.

  11. Asymmetric crystallization during cooling and heating in model glass-forming systems.

    PubMed

    Wang, Minglei; Zhang, Kai; Li, Zhusong; Liu, Yanhui; Schroers, Jan; Shattuck, Mark D; O'Hern, Corey S

    2015-03-01

    We perform molecular dynamics (MD) simulations of the crystallization process in binary Lennard-Jones systems during heating and cooling to investigate atomic-scale crystallization kinetics in glass-forming materials. For the cooling protocol, we prepared equilibrated liquids above the liquidus temperature Tl and cooled each sample to zero temperature at rate Rc. For the heating protocol, we first cooled equilibrated liquids to zero temperature at rate Rp and then heated the samples to temperature T>Tl at rate Rh. We measured the critical heating and cooling rates Rh* and Rc*, below which the systems begin to form a substantial fraction of crystalline clusters during the heating and cooling protocols. We show that Rh*>Rc* and that the asymmetry ratio Rh*/Rc* includes an intrinsic contribution that increases with the glass-forming ability (GFA) of the system and a preparation-rate dependent contribution that increases strongly as Rp→Rc* from above. We also show that the predictions from classical nucleation theory (CNT) can qualitatively describe the dependence of the asymmetry ratio on the GFA and preparation rate Rp from the MD simulations and results for the asymmetry ratio measured in Zr- and Au-based bulk metallic glasses (BMG). This work emphasizes the need for and benefits of an improved understanding of crystallization processes in BMGs and other glass-forming systems.

  12. Reliability and Validity of a Spanish Version of the Social Skills Rating System--Teacher Form

    ERIC Educational Resources Information Center

    Jurado, Michelle; Cumba-Aviles, Eduardo; Collazo, Luis C.; Matos, Maribel

    2006-01-01

    The aim of this study was to examine the psychometric properties of a Spanish version of the Social Skills Scale of the Social Skills Rating System-Teacher Form (SSRS-T) with a sample of children attending elementary schools in Puerto Rico (N = 357). The SSRS-T was developed for use with English-speaking children. Although translated, adapted, and…

  13. 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…

  14. 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…

  15. 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.

  16. 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).

  17. Push it to the limit: Characterizing the convergence of common sequences of basis sets for intermolecular interactions as described by density functional theory

    NASA Astrophysics Data System (ADS)

    Witte, Jonathon; Neaton, Jeffrey B.; Head-Gordon, Martin

    2016-05-01

    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.

  18. 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.

  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. Embryonic Origins of a Motor System:Motor Dendrites Form a Myotopic Mapin Drosophila

    PubMed Central

    2003-01-01

    The organisational principles of locomotor networks are less well understood than those of many sensory systems, where in-growing axon terminals form a central map of peripheral characteristics. Using the neuromuscular system of the Drosophila embryo as a model and retrograde tracing and genetic methods, we have uncovered principles underlying the organisation of the motor system. We find that dendritic arbors of motor neurons, rather than their cell bodies, are partitioned into domains to form a myotopic map, which represents centrally the distribution of body wall muscles peripherally. While muscles are segmental, the myotopic map is parasegmental in organisation. It forms by an active process of dendritic growth independent of the presence of target muscles, proper differentiation of glial cells, or (in its initial partitioning) competitive interactions between adjacent dendritic domains. The arrangement of motor neuron dendrites into a myotopic map represents a first layer of organisation in the motor system. This is likely to be mirrored, at least in part, by endings of higher-order neurons from central pattern-generating circuits, which converge onto the motor neuron dendrites. These findings will greatly simplify the task of understanding how a locomotor system is assembled. Our results suggest that the cues that organise the myotopic map may be laid down early in development as the embryo subdivides into parasegmental units. PMID:14624243

  1. Interactions between motion and form processing in the human visual system

    PubMed Central

    Mather, George; Pavan, Andrea; Bellacosa Marotti, Rosilari; Campana, Gianluca; Casco, Clara

    2013-01-01

    The predominant view of motion and form processing in the human visual system assumes that these two attributes are handled by separate and independent modules. Motion processing involves filtering by direction-selective sensors, followed by integration to solve the aperture problem. Form processing involves filtering by orientation-selective and size-selective receptive fields, followed by integration to encode object shape. It has long been known that motion signals can influence form processing in the well-known Gestalt principle of common fate; texture elements which share a common motion property are grouped into a single contour or texture region. However, recent research in psychophysics and neuroscience indicates that the influence of form signals on motion processing is more extensive than previously thought. First, the salience and apparent direction of moving lines depends on how the local orientation and direction of motion combine to match the receptive field properties of motion-selective neurons. Second, orientation signals generated by “motion-streaks” influence motion processing; motion sensitivity, apparent direction and adaptation are affected by simultaneously present orientation signals. Third, form signals generated by human body shape influence biological motion processing, as revealed by studies using point-light motion stimuli. Thus, form-motion integration seems to occur at several different levels of cortical processing, from V1 to STS. PMID:23730286

  2. Faint Lyα Emitters, Star-forming Galaxies, and Damped Lyα Systems

    NASA Astrophysics Data System (ADS)

    Rauch, M.; Haehnelt, M.; Bunker, A.; Becker, G.; Marleau, F.; Graham, J.; Cristiani, S.; Jarvis, M.; Lacey, C.; Morris, S.; Peroux, C.; Roettgering, H.; Theuns, T.

    2008-10-01

    We have discovered a population of faint single line emitters, likely to be identified with faint z˜ 3 Lyα emitters and with the host galaxies of damped Lyman alpha systems. The objects appear to constitute the bulk of the star-forming galaxies detected so far from the ground, and are likely to provide the gaseous reservoir from which present-day Milky way type galaxies have formed. Unlike color-selected (yman break galaxies, these objects appear to have low star-formation rates, relatively strong Lyalpha emission, and low masses, metallicities, and dust content (s.a. arXiv:0711.1354).

  3. The ``primitive'' wave function in the theory of intermolecular interactions

    NASA Astrophysics Data System (ADS)

    Kutzelnigg, Werner

    1980-07-01

    The concept of the primitive wave function for a supermolecule consisting of interacting subsystems is critically analyzed. The distinction between formal and genuine primitive functions is stressed. The concept of uniformly complete basis sets as contrasted to simply complete basis is introduced. Primitive basis sets are defined and shown not to be uniformly complete for the expansion of the supersystem wave function while 'full supersystem basis sets' are. The conditions are specified under which a supersystem wave function can be decomposed into its 'primitive components' corresponding to different partitions of the electrons among the subsystems. These primitive components satisfy the Schrödinger equation asymptotically. The matrix representation of the Hamiltonian (both the full supersystem Hamiltonian H and the zeroth order Hamiltonian Ho) in terms of these partitions is analyzed. It is shown that in the standard application of RS-perturbation theory to intermolecular forces (the polarization approximation) the limiting processes λ→1 and R→∞ do not commute, that the λ-series is not uniformly convergent with respect to R and that the wave function to any finite order in λ is genuinely primitive. The symmetrized polarization approximation is justified for the 'coasymptotic ground state' in certain cases and a 'symmetrized polarization approximation with shifted eigenvalues' is proposed that connects the lowest eigenvalue of Ho with the physical ground state. A justification of simplified schemes in the region of 'small exchange' is given and alternative perturbation schemes are discussed. Finally the use of the primitive function in variational treatments is outlined. One advantage is that a genuinely (not a formally) primitive function is uniformly expandable in a primitive basis set.

  4. Interpretation of intermolecular geometric isotope effect in hydrogen bonds: nuclear orbital plus molecular orbital study.

    PubMed

    Ikabata, Yasuhiro; Imamura, Yutaka; Nakai, Hiromi

    2011-03-01

    The intermolecular geometric isotope effect (GIE) in hydrogen bond A-X···B (X = H and D) is investigated theoretically using the nuclear orbital plus molecular orbital (NOMO) theory. To interpret the GIE in terms of physically meaningful energy components such as electrostatic and exchange-repulsion interactions, the reduced variational space self-consistent-field method is extended to the NOMO scheme. The intermolecular GIE is analyzed as a two-stage process: the intramolecular bond shrinkage and the intermolecular bond elongation. According to the isotopic shifts of energy components described by the NOMO/MP2 method, the intermolecular GIE is approximately interpreted as a process reducing the exchange-repulsion interaction after the decrease of electrostatic interaction. PMID:21306139

  5. The palladium-catalyzed intermolecular C-H chalcogenation of arenes.

    PubMed

    Qiu, Renhua; Reddy, Vutukuri Prakash; Iwasaki, Takanori; Kambe, Nobuaki

    2015-01-01

    Palladium catalyzes the intermolecular chalcogenation of carbazole, 2-phenylpyridine, benzo[h]quinolone, and indole derivatives with disulfides and diselenides via selective C-H bond cleavage, providing a convenient route to thio and selenoethers. PMID:25437148

  6. 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)

  7. Reduction in burst release of PLGA microparticles by incorporation into cubic phase-forming systems.

    PubMed

    Ahmed, Abid Riaz; Dashevsky, Andrei; Bodmeier, Roland

    2008-11-01

    A high initial burst release of an phosphorothioate oligonucleotide drug from poly(lactide-co-glycolide) (PLGA) microparticles prepared by the w/o/w solvent extraction/evaporation was reduced by incorporating the microparticles into the following glycerol monooleate (GMO) formulations: 1) pure molten GMO, 2) preformed cubic phase (GMO+water) or 3) low viscosity in situ cubic phase-forming formulations (GMO+water+cosolvent). The in situ cubic phase-forming formulations had a low viscosity in contrast to the first two formulations resulting in good dispersability of the microparticles and good syringability/injectability. Upon contact with an aqueous phase, a highly viscous cubic phase formed immediately entrapping the microparticles. A low initial burst and a continuous extended release over several weeks was obtained with all investigated formulations. The drug release profile could be well controlled by the cosolvent composition with the in situ systems.

  8. 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.

  9. Finding new strength in unity. Four Cincinnati-area Mercy hospitals form an integrated regional system.

    PubMed

    Hanser, J

    1997-01-01

    In early 1993 the leaders of the Sisters of Mercy in Cincinnati decided to form their four area hospitals into a new integrated regional system, The creation of this system--Mercy Regional Health System Greater Cincinnati--was made difficult by the fact that each of its four facilities had its own culture. Change, moreover, can be threatening to even the boldest. As a result of these factors, formation of the new system did not proceed as smoothly as we had planned. Things improved after we began to acquaint ourselves with the histories and cultures of the four hospitals. After that, we created a new regional leadership structure that enabled us to form administrators and employees into teams, breaking down the compartmentalization traditional in healthcare. We showed our employees that the system would open opportunities for them. We also created a new regional board of trustees to develop the system's strategic plan, manage its business infrastructure, and draw up its budget. We established a holistic health and wellness center to encourage focus on the connections between body, mind, and spirit. Through new corporate publications, newspaper advertisements, and lobby displays, we have explained our evolution both to our employees and the residents of the region. As a result, we are now in virtually all of greater Cincinnati's managed care plans.

  10. 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.

  11. Intra- and Inter-Molecular Cross-Linking of Peptide Ions in the Gas Phase: Reagents and Conditions

    NASA Astrophysics Data System (ADS)

    Mentinova, Marija; McLuckey, Scott A.

    2011-05-01

    Intra-molecular and inter-molecular cross-linking of protonated polypeptide ions in the gas phase via ion/ion reactions have been demonstrated using N-hydroxysulfosuccinimide (sulfo-NHS)- based reagent anions. The initial step in the ion/ion reaction involves the formation of a long-lived complex between the peptide and reagent, which is a prerequisite for the covalent bioconjugation chemistry. The sulfonate groups on the NHS rings of the homo-bifunctional cross-linking reagents have high affinity for the protonated sites in the peptide and, therefore, facilitate the long-lived complex formation. In addition to the formation of a long-lived chemical complex, intra-molecular cross-linking also requires two unprotonated primary amine sites within a molecule where the covalent modification takes place. Alternatively, inter-molecular cross-linking demands the availability of one neutral primary amine site in each of the two peptides that are being cross-linked. Nucleophilic displacement of two sulfo-NHS groups by the amine functionalities in the peptide is a signature of the covalent cross-linking chemistry in the gas phase. Upon removal of the two sulfo-NHS groups, two amide bonds are formed between an unprotonated, primary amine group of a lysine side chain in the peptide and the carboxyl group in the reagent.

  12. Intermolecular electron transfer promoted by directional donor-acceptor attractions in self-assembled diketopyrrolopyrrole-thiophene films.

    PubMed

    Liu, Huiying; Jia, Hui; Wang, Lanfen; Wu, Yishi; Zhan, Chuanlang; Fu, Hongbing; Yao, Jiannian

    2012-11-01

    The photophysics of a symmetric triad consisting of two bithiophene (BT) units covalently linked to a central diketopyrrolopyrrole unit (DPP) has been investigated both in dichloromethane and in the thin film. The DPP-BT film exhibits a red-shifted low-energy absorption band compared to its solution, which is indicative of efficient π-π interactions in the solid-state phase. The steady-state and time-resolved fluorescence results revealed that the photoluminescence was subjected to severe emission quenching when DPP-BT changes from its solution phase to its film form. Further femtosecond transient absorption studies clarified that rapid intermolecular electron transfer accounts for the considerable fluorescence quenching event. The structural characterization of DPP-BT nanobelts, based on GIXRD and SAED patterns, suggested that the composite may be self-assembled into a slipped face-to-face configuration in the film, providing compact interlayer D-A interactions. As a result, intermolecular electron transfer is promoted by the favorable donor-acceptor attractions between the adjacent molecules. Moreover, this packing configuration provides a moderate channel for charge transportation. The hole mobility, which was measured based on a single-belt field-effect transistor, was found to be around 0.07 cm(2) V(-1) s(-1). Our observation reveals the role of spatial orientation in photophysical processes and the consequential semiconductor performance, providing guidance for the development and self-assembly of new opto-electronic molecules. PMID:22951990

  13. 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.

  14. Precursors of dangerous substances formed in the loss of control of chemical systems.

    PubMed

    Cozzani, V; Zanelli, S

    1999-03-01

    Article 2 of Directive 96/82/EC on the control of major accident hazards caused by dangerous substances requires to consider also the hazards due to the dangerous substances "which it is believed may be generated during loss of control of an industrial chemical process", although no generally accepted guidelines are available for the identification of these substances. In the present study, the accidents involving the unwanted formation of dangerous substances as a consequence of the loss of control of chemical systems were investigated. A specifically developed database was used, containing data on more than 400 of these accidents and on the substances involved. The hazardous substances formed in the accidents and the precursors of these substances were identified. The influence of accident characteristics on the substances formed was investigated. In the context of the application of Directive 96/82/EC, an accident severity index and a hazard rating of the precursors of dangerous substances formed in the accidents were proposed. A lumping approach was used in order to develop schemes for the preliminary identification of substances that may be formed in the loss of control of chemical system. The results of accident analysis were used to test the schemes developed. PMID:10337407

  15. Architecture based on the integration of intermolecular G-quadruplex structure with sticky-end pairing and colorimetric detection of DNA hybridization

    NASA Astrophysics Data System (ADS)

    Li, Hongbo; Wu, Zai-Sheng; Shen, Zhifa; Shen, Guoli; Yu, Ruqin

    2014-01-01

    An interesting discovery is reported in that G-rich hairpin-based recognition probes can self-assemble into a nano-architecture based on the integration of an intermolecular G-quadruplex structure with the sticky-end pairing effect in the presence of target DNAs. Moreover, GNPs modified with partly complementary DNAs can intensively aggregate by hybridization-based intercalation between intermolecular G-quadruplexes, indicating an inspiring assembly mechanism and a powerful colorimetric DNA detection. The proposed intermolecular G-quadruplex-integrated sticky-end pairing assembly (called GISA)-based colorimetric system allows a specific and quantitative assay of p53 DNA with a linear range of more than two orders of magnitude and a detection limit of 0.2 nM, suggesting a considerably improved analytical performance. And more to the point, the discrimination of single-base mismatched target DNAs can be easily conducted via visual observation. The successful development of the present colorimetric system, especially the GISA-based aggregation mechanism of GNPs is different from traditional approaches, and offers a critical insight into the dependence of the GNP aggregation on the structural properties of oligonucleotides, opening a good way to design colorimetric sensing probes and DNA nanostructure. An interesting discovery is reported in that G-rich hairpin-based recognition probes can self-assemble into a nano-architecture based on the integration of an intermolecular G-quadruplex structure with the sticky-end pairing effect in the presence of target DNAs. Moreover, GNPs modified with partly complementary DNAs can intensively aggregate by hybridization-based intercalation between intermolecular G-quadruplexes, indicating an inspiring assembly mechanism and a powerful colorimetric DNA detection. The proposed intermolecular G-quadruplex-integrated sticky-end pairing assembly (called GISA)-based colorimetric system allows a specific and quantitative assay of p53 DNA

  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. Intermolecular chiral assemblies in R(-) and S(+) 2-butanol detected by microcalorimetry measurements.

    PubMed

    Cogan, Uri; Shpigelman, Avi; Portnaya, Irina; Rutenberg, Abraham; Scolnik, Yosef; Shinitzky, Meir

    2012-07-01

    Supramolecular chiral assemblies of R(-) and S(+) 2-butanol, in their neat form or when dissolved in their nonchiral isomer isobutanol, were evaluated by isothermal titration calorimetry (ITC) ensuing mixing. Dilution of 0.5 M solution of R(-) 2-butanol in isobutanol into the latter liberated heat of several calories per mole, which was approximately double than that obtained in parallel dilutions of S(+) 2-butanol in isobutanol. The ITC dilution profiles indicated an estimate of about 100 isobutanol solvent molecules surrounding each of the 2-butanol enantiomers, presumably arranged in chiral configurations, with different adopted order between the isomers. Mixings of neat R and S 2-butanol were followed by endothermic ITC profiles, indicating that, in racemic 2-butanol, both the supramolecular order and the intermolecular binding energies are lower than in each of the neat chiral isomers. The diversion from symmetrical ITC patterns in these mixings indicated again a subtle difference in molecular organization between the neat enantiomers. It should be noted that the presence of impurities, α-pinene and teterhydrofuran, at a level totaling 0.5%, did not influence the ITC heat flow profiles. The findings of this study demonstrate for the first time that chiral solutes in organic solvents are expected to acquire asymmetric solvent envelopes that may be different between the enantiomers, thus broadening this phenomenon beyond the previously demonstrated cases in aqueous solutions.

  18. Anti-plasticizing effect of amorphous indomethacin induced by specific intermolecular interactions with PVA copolymer.

    PubMed

    Ueda, Hiroshi; Aikawa, Shohei; Kashima, Yousuke; Kikuchi, Junko; Ida, Yasuo; Tanino, Tadatsugu; Kadota, Kazunori; Tozuka, Yuichi

    2014-09-01

    The mechanism of how poly(vinyl alcohol-co-acrylic acid-co-methyl methacrylate) (PVA copolymer) stabilizes an amorphous drug was investigated. Solid dispersions of PVA copolymer, poly(vinyl pyrrolidone) (PVP), and poly(vinyl pyrrolidone-co-vinyl acetate) (PVPVA) with indomethacin (IMC) were prepared. The glass transition temperature (Tg)-proportion profiles were evaluated by differential scanning calorimetry (DSC). General Tg profiles decreasing with the IMC ratio were observed for IMC-PVP and IMC-PVPVA samples. An interesting antiplasticizing effect of IMC on PVA copolymer was observed; Tg increased up to 20% IMC ratio. Further addition of IMC caused moderate reduction with positive deviation from theoretical values. Specific hydrophilic and hydrophobic interactions between IMC and PVA copolymer were revealed by infrared spectra. The indole amide of IMC played an important role in hydrogen bonding with PVA copolymer, but not with PVP and PVPVA. X-ray diffraction findings and the endotherm on DSC profiles suggested that PVA copolymer could form a semicrystalline structure and a possibility of correlation of the crystallographic nature with its low hygroscopicity was suggested. PVA copolymer was able to prevent crystallization of amorphous IMC through both low hygroscopicity and the formation of a specific intermolecular interaction compared with that with PVP and PVPVA.

  19. Experimental results of water film formation on various fuel forms from a fire suppression system

    SciTech Connect

    Ross, R.H.; Davis, J.R.

    1993-12-31

    The purpose of the study was to determine the thickness and coverage of water film formations on various materials during fire sprinkler deluge. An exhaustive literature search revealed that no applicable research data exists that governs water film formations from fire protection systems. Therefore, a controlled, infield, mockup was created to predict the thickness and coverage of water film on fissile material forms. This paper discusses the background, experimental procedure and the characterization of these water films.

  20. 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.

  1. Stochastic maximum principle in the Pontryagin's form for wide band noise driven systems

    NASA Astrophysics Data System (ADS)

    Bashirov, Agamirza E.

    2015-03-01

    The control problems for wide band noise driven systems have the following specific feature. A wide band noise is given by its autocovariance function. At the same time, different wide band noises may have the same autocovariance function. Therefore, it is important to obtain the results which are invariant under the change of wide band noises, corresponding to the same autocovariance function. In this paper, one such result is obtained: a stochastic maximum principle in the Pontryagin's form is proved for a control system driven by a state-dependent wide band noise. The result is demonstrated on an example of controlled stochastic differential equation of risky asset price.

  2. 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.

  3. 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.

  4. Differentiating lexical form, meaning, and structure in the neural language system.

    PubMed

    Tyler, L K; Marslen-Wilson, W D; Stamatakis, E A

    2005-06-01

    A technique for studying the relationship between brain and language, which involves correlating scores on two continuous variables, signal intensity across the entire brains of brain-damaged patients and behavioral priming scores, was used to investigate a central issue in cognitive neuroscience: Are the components of the neural language system organized as a single undifferentiated process, or do they respond differentially to different types of linguistic structure? Differences in lexical structure, in the form of the regular and irregular past tense, have proven to be critical in this debate by contrasting a highly predictable rule-like process (e.g., jump-jumped) with an unpredictable idiosyncratic process typified by the irregulars (e.g., think-thought). The key issue raised by these contrasts is whether processing regular and irregular past tense forms differentially engages different aspects of the neural language system or whether they are processed within a single system that distinguishes between them purely on the basis of phonological and semantic differences. The correlational analyses provide clear evidence for a functional differentiation between different brain regions associated with the processing of lexical form, meaning, and morphological structure. PMID:15923263

  5. 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. PMID:26111400

  6. Strong orbital interaction in a weak CH-π hydrogen bonding system

    PubMed Central

    Li, Jianfu; Zhang, Rui-Qin

    2016-01-01

    For the first time, the intermolecular orbital interaction between benzene and methane in the benzene-methane complex, a representative of weak interaction system, has been studied by us using ab initio calculations based on different methods and basis sets. Our results demonstrate obvious intermolecular orbital interaction between benzene and methane involving orbital overlaps including both occupied and unoccupied orbitals. Similar to interatomic orbital interaction, the intermolecular interaction of orbitals forms “bonding” and “antibonding” orbitals. In the interaction between occupied orbitals, the total energy of the complex increases because of the occupation of the antibonding orbital. The existence of the CH-π hydrogen bond between benzene and methane causes a decrease in rest energy level, leading to at least −1.51 kcal/mol intermolecular interaction energy. Our finding extends the concept of orbital interaction from the intramolecular to the intermolecular regime and gives a reliable explanation of the deep orbital reformation in the benzene-methane complex. PMID:26927609

  7. A new approach to generate arbitrary pulsatile pressure wave forms in mechanical circulatory support systems.

    PubMed

    Aghababaei, Amin; Hexamer, Martin

    2015-01-01

    Pulsatile pressure/flow wave forms reproduction of blood in mechanical circulatory systems are still an open topic. Regarding the periodic behavior of pulsatile hemodynamics, a repetitive control algorithm was adopted as a potential methodology for rotary blood pumps. The developed algorithm was tested on a mock system including an oxygenator, a resistance, and a compliance. The post-oxygenator pressure served as the feedback of the control system. Initially, a model of the whole system was developed in order to use repetitive control algorithm. Then the performance of the developed algorithm was evaluated in three different scenarios. The experimental results indicated that the proposed method was able to accurately reproduce any pattern of pulsatile pressure. Moreover, it demonstrated an acceptable robustness in terms of model uncertainty and nonlinearity.

  8. Improving activity of minicellulosomes by integration of intra- and intermolecular synergies

    PubMed Central

    2013-01-01

    Background Complete hydrolysis of cellulose to glucose requires the synergistic action of three general types of glycoside hydrolases; endoglucanases, exoglucanases, and cellobiases. Cellulases that are found in Nature vary considerably in their modular diversity and architecture. They include: non-complexed enzymes with single catalytic domains, independent single peptide chains incorporating multiple catalytic modules, and complexed, scaffolded structures, such as the cellulosome. The discovery of the latter two enzyme architectures has led to a generally held hypothesis that these systems take advantage of intramolecular and intermolecular proximity synergies, respectively, to enhance cellulose degradation. We use domain engineering to exploit both of these concepts to improve cellulase activity relative to the activity of mixtures of the separate catalytic domains. Results We show that engineered minicellulosomes can achieve high levels of cellulose conversion on crystalline cellulose by taking advantage of three types of synergism; (1) a complementary synergy produced by interaction of endo- and exo-cellulases, (2) an intramolecular synergy of multiple catalytic modules in a single gene product (this type of synergism being introduced for the first time to minicellulosomes targeting crystalline cellulose), and (3) an intermolecular proximity synergy from the assembly of these cellulases into larger multi-molecular structures called minicellulosomes. The binary minicellulosome constructed in this study consists of an artificial multicatalytic cellulase (CBM4-Ig-GH9-X11-X12-GH8-Doc) and one cellulase with a single catalytic domain (a modified Cel48S with the structure CBM4-Ig-GH48-Doc), connected by a non-catalytic scaffoldin protein. The high level endo-exo synergy and intramolecular synergies within the artificial multifunctional cellulase have been combined with an additional proximity-dependent synergy produced by incorporation into a minicellulosome

  9. Diverse supramolecular arrangement of substituted oxopyrrolidine analogues influenced by weak intermolecular interactions (Csbnd H⋯O/Csbnd H⋯π/H⋯H)

    NASA Astrophysics Data System (ADS)

    Samipillai, Marivel; Bhatt, Nilay; Kruger, Hendrik G.; Govender, Thavendran; Naicker, Tricia

    2016-10-01

    Three analogues of 3-oxopyrrolidines; (S)-1-tert-butyl 2-ethyl-2-((S)-2-nitro-1-p-tolylethyl)-3-oxopyrrolidine-1,2-dicarboxylate, 1, (S)-1-tert-butyl 2-ethyl 2-((S)-1-(4-methoxyphenyl)-2-nitroethyl)-3-oxopyrrolidine-1,2-dicarboxylate 2, and Ethyl 1-((S)-2-(((benzyloxy)carbonyl)amino)-3-phenylpropanoyl)-2-(2-nitro-1-phenylethyl)-3-oxopyrrolidine-2-carboxylate 3, were synthesized and crystallized in suitable solvents. Crystal structure analysis was carried out by single crystal X-ray diffraction to provide a detailed investigation of the packing and supramolecular arrangement of these analogues. The weak interactions such as Csbnd H⋯O/Csbnd H⋯π present in the crystal structure of all these analogues (1-3) played a vital role in controlling the conformation of the molecules and construction of dissimilar supramolecular assemblies. This study provides some insight; that even though these oxopyrrolidine analogues, lack a hydrogen bond donor and acceptor system, that upon bulky substitutions, this scaffold can still form fascinating supramolecular assemblies through various weak interactions. The surface interaction was carried out by means of Hirshfeld surface analysis, which depicted the significant intermolecular interactions of a molecule with its neighbor within the structures.

  10. 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

  11. Strong intermolecular vibrational coupling through cyclic hydrogen-bonded structures revealed by ultrafast continuum mid-IR spectroscopy.

    PubMed

    Stingel, Ashley M; Calabrese, Carmella; Petersen, Poul B

    2013-12-12

    Cyclic hydrogen-bonded structures are common motifs in biological systems, providing structural stability and mediating proton transfer for redox reactions. The mechanism of proton transfer across hydrogen-bonded interfaces depends on the strength of the intermolecular coupling between bridging OH/NH vibrational modes. Here we present a novel ultrafast continuum mid-IR spectroscopy experiment to study the vibrational dynamics of the 7-azaindole-acetic acid (7AI-Ac) heterodimer as a model system for asymmetric cyclic hydrogen-bonded structures. In addition to spreading of the excitation across the whole OH band within the time resolution of the experiment, excitation of a 300 cm(-1) region of the ∼1000 cm(-1) broad OH stretching mode of the acetic acid monomer leads to a frequency shift in the NH stretching mode of the 7AI monomer. This indicates that the NH and OH stretching modes located on the two monomers are strongly coupled despite being separated by 750 cm(-1). The strong coupling further causes the OH and NH bands to decay with a common decay time of ∼2.5 ps. This intermolecular coupling is mediated through the hydrogen-bonded structure of the 7AI-Ac heterodimer and is likely a general property of cyclic hydrogen-bonded structures. Characterizing the vibrational dynamics of and the coupling between the high-frequency OH/NH modes will be important for understanding proton transfer across such molecular interfaces.

  12. 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.

  13. Intermolecular forces in spread phospholipid monolayers at oil/water interfaces.

    PubMed

    Mingins, James; Pethica, Brian A

    2004-08-31

    The lateral intermolecular forces between phospholipids are of particular relevance to the behavior of biomembranes, and have been approached via studies of monolayer isotherms at aqueous interfaces, mostly restricted to air/water (A/W) systems. For thermodynamic properties, the oil/water (O/W) interface has major advantages but is experimentally more difficult and less studied. A comprehensive reanalysis of the available thermodynamic data on spread monolayers of phosphatidyl cholines (PC) and phosphatidyl ethanolamines (PE) at O/W interfaces is conducted to identify the secure key features that will underpin further development of molecular models. Relevant recourse is made to isotherms of single-chain molecules and of mixed monolayers to identify the contributions of chain-chain interactions and interionic forces. The emphasis is on the properties of the phase transitions for a range of oil phases. Apparent published discrepancies in thermodynamic properties are resolved and substantial agreement emerges on the main features of these phospholipid monolayer systems. In compression to low areas, the forces between the zwitterions of like phospholipids are repulsive. The molecular model for phospholipid headgroup interactions developed by Stigter et al. accounts well for the virial coefficients in expanded phospholipid O/W monolayers. Inclusion of the changes in configuration and orientation of the zwitterion headgroups on compression, which are indicated by the surface potentials in the phase transition region, and inclusion of the energy of chain demixing from the oil phase will be required for molecular modeling of the phase transitions.

  14. Modeling intermolecular interactions of physisorbed organic molecules using pair potential calculations

    SciTech Connect

    Kroeger, Ingo; Stadtmueller, Benjamin; Wagner, Christian; Weiss, Christian; Temirov, Ruslan; Tautz, F. Stefan; Kumpf, Christian

    2011-12-21

    The understanding and control of epitaxial growth of organic thin films is of crucial importance in order to optimize the performance of future electronic devices. In particular, the start of the submonolayer growth plays an important role since it often determines the structure of the first layer and subsequently of the entire molecular film. We have investigated the structure formation of 3,4,9,10-perylene-tetracarboxylic dianhydride and copper-phthalocyanine molecules on Au(111) using pair-potential calculations based on van der Waals and electrostatic intermolecular interactions. The results are compared with the fundamental lateral structures known from experiment and an excellent agreement was found for these weakly interacting systems. Furthermore, the calculations are even suitable for chemisorptive adsorption as demonstrated for copper-phthalocyanine/Cu(111), if the influence of charge transfer between substrate and molecules is known and the corresponding charge redistribution in the molecules can be estimated. The calculations are of general applicability for molecular adsorbate systems which are dominated by electrostatic and van der Waals interaction.

  15. Intra- vs. intermolecular hydrogen bonding: dimers of alpha-hydroxyesters with methanol.

    PubMed

    Borho, Nicole; Suhm, Martin A; Le Barbu-Debus, Katia; Zehnacker, Anne

    2006-10-14

    Intermolecular hydrogen bonding competes with an intramolecular hydrogen bond when methanol binds to an alpha-hydroxyester. Disruption of the intramolecular OH...O=C contact in favour of a cooperative OH...OH...O=C sequence is evidenced by FTIR spectroscopy for the addition of methanol to the esters methyl glycolate, methyl lactate and methyl alpha-hydroxyisobutyrate in seeded supersonic jet expansions. Comparison of the OH stretching modes with quantum-chemical harmonic frequency calculations and 18O labelling of methanol unambiguously prove the insertion of methanol into the intramolecular hydrogen bond. This is in marked contrast to UV/IR hole burning studies of the homologous system methyl lactate: (+/-)-2-naphthyl-1-ethanol, where only addition complexes were found and the intramolecular hydrogen bond was conserved. This switch in hydrogen bond pattern from aliphatic to aromatic heterodimers is thought to reflect not only a kinetic propensity but also a thermodynamic preference for addition complexes when dispersion forces become more important in aromatic systems. PMID:17001413

  16. 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. PMID:27007455

  17. 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.

  18. Self-assembling supramolecular systems of different symmetry formed by wedged macromolecular dendrons

    SciTech Connect

    Shcherbina, M. A. Bakirov, A. V.; Yakunin, A. N.; Percec, V.; Beginn, U.; Moeller, M.; Chvalun, S. N.

    2012-03-15

    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.

  19. 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.

  20. 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. PMID:23744115

  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. 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.

  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. PMID:24922417

  4. Characterization of a new anhydrous form of Rotundine and its monohydrate

    NASA Astrophysics Data System (ADS)

    Yang, Shiying; Du, Guanhua; Lu, Yang

    2015-09-01

    Rotundine is a chemical drug developed from Chinese traditional medicines that exhibits pseudopolymorphism. The anhydrous form and monohydrate are isolated and prepared via systemic crystallization screening, and the anhydrous form is reported for the first time. In this article single crystal X-ray diffractometry, powder X-ray diffractometry and FT-IR spectroscopy are used to characterize the Rotundine modifications. The analysis results show that the factors of crystal symmetry, intermolecular arrangements, conformational flexibility, hydrogen bonding interactions, and the incorporation of water finally lead to produce the polymorphic phenomenon. Via the in-vivo bioavailability of two forms, it is found that the new anhydrous form presents absorbable superiority relative to monohydrate, specifically Cmax and AUC of anhydrous form were approximately 1.5 times those of monohydrate. Study on the transformation of two forms show that they can convert to each other in certain conditions at solid state.

  5. A paper form processing system with an error correcting function for reading handwritten Kanji strings

    SciTech Connect

    Katsumi Marukawa; Kazuki Nakashima; Masashi Koga; Yoshihiro Shima; Hiromichi Fujisawa

    1994-12-31

    This paper presents a paper form processing system with an error correcting function for reading handwritten kanji strings. In the paper form processing system, names and addresses are important key data, and especially this paper takes up an error correcting method for name and address recognition. The method automatically corrects errors of the kanji OCR (Optical Character Reader) with the help of word dictionaries and other knowledge. Moreover, it allows names and addresses to be written in any style. The method consists of word matching {open_quotes}furigana{close_quotes} verification for name strings, and address approval for address strings. For word matching, kanji name candidates are extracted by automaton-type word matching. In {open_quotes}furigana{close_quotes} verification, kana candidate characters recognized by the kana OCR are compared with kana`s searched from the name dictionary based on kanji name candidates, given by the word matching. The correct name is selected from the results of word matching and furigana verification. Also, the address approval efficiently searches for the right address based on a bottom-up procedure which follows hierarchical relations from a lower placename to a upper one by using the positional condition among the placenames. We ascertained that the error correcting method substantially improves the recognition rate and processing speed in experiments on 5,032 forms.

  6. 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.

  7. 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.

  8. [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.

  9. 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.

  10. Explicit solutions of normal form of driven oscillatory systems in entrainment bands

    NASA Astrophysics Data System (ADS)

    Tsarouhas, George E.; Ross, John

    1988-11-01

    As in a prior article (Ref. 1), we consider an oscillatory dissipative system driven by external sinusoidal perturbations of given amplitude Q and frequency ω. The kinetic equations are transformed to normal form and solved for small Q near a Hopf bifurcation to oscillations in the autonomous system. Whereas before we chose irrational ratios of the frequency of the autonomous system ωn to ω, with quasiperiodic response of the system to the perturbation, we now choose rational coprime ratios, with periodic response (entrainment). The dissipative system has either two variables or is adequately described by two variables near the bifurcation. We obtain explicit solutions and develop these in detail for ωn/ω=1; 1:2; 2:1; 1:3; 3:1. We choose a specific dissipative model (Brusselator) and test the theory by comparison with full numerical solutions. The analytic solutions of the theory give an excellent approximation for the autonomous system near the bifurcation. The theoretically predicted and calculated entrainment bands agree very well for small Q in the vicinity of the bifurcation (small μ); deviations increase with increasing Q and μ. The theory is applicable to one or two external periodic perturbations.

  11. 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

  12. 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

  13. 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

  14. 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.

  15. Density-based Energy Decomposition Analysis for Intermolecular Interactions with Variationally Determined Intermediate State Energies

    SciTech Connect

    Wu, Q.; Ayers, P.W.; Zhang, Y.

    2009-10-28

    The first purely density-based energy decomposition analysis (EDA) for intermolecular binding is developed within the density functional theory. The most important feature of this scheme is to variationally determine the frozen density energy, based on a constrained search formalism and implemented with the Wu-Yang algorithm [Q. Wu and W. Yang, J. Chem. Phys. 118, 2498 (2003) ]. This variational process dispenses with the Heitler-London antisymmetrization of wave functions used in most previous methods and calculates the electrostatic and Pauli repulsion energies together without any distortion of the frozen density, an important fact that enables a clean separation of these two terms from the relaxation (i.e., polarization and charge transfer) terms. The new EDA also employs the constrained density functional theory approach [Q. Wu and T. Van Voorhis, Phys. Rev. A 72, 24502 (2005)] to separate out charge transfer effects. Because the charge transfer energy is based on the density flow in real space, it has a small basis set dependence. Applications of this decomposition to hydrogen bonding in the water dimer and the formamide dimer show that the frozen density energy dominates the binding in these systems, consistent with the noncovalent nature of the interactions. A more detailed examination reveals how the interplay of electrostatics and the Pauli repulsion determines the distance and angular dependence of these hydrogen bonds.

  16. Modeling and simulation of magnetic resonance imaging based on intermolecular multiple quantum coherences

    NASA Astrophysics Data System (ADS)

    Cai, Congbo; Dong, Jiyang; Cai, Shuhui; Cheng, En; Chen, Zhong

    2006-11-01

    Intermolecular multiple quantum coherences (iMQCs) have many potential applications since they can provide interaction information between different molecules within the range of dipolar correlation distance, and can provide new contrast in magnetic resonance imaging (MRI). Because of the non-localized property of dipolar field, and the non-linear property of the Bloch equations incorporating the dipolar field term, the evolution behavior of iMQC is difficult to deduce strictly in many cases. In such cases, simulation studies are very important. Simulation results can not only give a guide to optimize experimental conditions, but also help analyze unexpected experimental results. Based on our product operator matrix and the K-space method for dipolar field calculation, the MRI simulation software was constructed, running on Windows operation system. The non-linear Bloch equations are calculated by a fifth-order Cash-Karp Runge-Kutta formulism. Computational time can be efficiently reduced by separating the effects of chemical shifts and strong gradient field. Using this software, simulation of different kinds of complex MRI sequences can be done conveniently and quickly on general personal computers. Some examples were given. The results were discussed.

  17. Spatiotemporal patterns enhanced by intra- and inter-molecular fluctuations in arrays of allosterically regulated enzymes

    NASA Astrophysics Data System (ADS)

    Togashi, Yuichi; Casagrande, Vanessa

    2015-03-01

    Enzymatic reactions often involve slow conformational changes, with reaction cycles that sometimes require milliseconds or seconds to complete. The dynamics are strongly affected by fluctuations at the nanoscale. However, such enzymes often occur in small numbers in a cell; hence, the fluctuations caused by finite numbers of molecules should also be substantial. Because of these factors, the behavior of the system is likely to deviate from that of classical reaction-diffusion equations, in which immediate reaction events are assumed to occur without memory and between a huge number of molecules. In this work, we model each enzyme as a unit represented by a phase variable to investigate the effects of fluctuations in arrays of enzymes. Using an analysis based on partial differential equations and stochastic simulations, we show that fluctuations arising from internal states of enzymes (intramolecular fluctuations) and those arising from the stochastic nature of interactions between molecules (intermolecular fluctuations) have distinctive effects on spatiotemporal patterns; the former generally disturb synchronization at high frequencies, whereas the latter can enhance synchronization. The balance of the two types of fluctuations may determine the spatiotemporal behavior of biochemical processes.

  18. Resolution enhancement in MR spectroscopy of red bone marrow fat via intermolecular double-quantum coherences

    NASA Astrophysics Data System (ADS)

    Bao, Jianfeng; Cui, Xiaohong; Huang, Yuqing; Zhong, Jianhui; Chen, Zhong

    2015-08-01

    High-resolution 1H magnetic resonance spectroscopy (MRS) is generally inaccessible in red bone marrow (RBM) tissues using conventional MRS techniques. This is because signal from these tissues suffers from severe inhomogeneity in the main static B0 field originated from the intrinsic honeycomb structures in trabecular bone. One way to reduce effects of B0 field inhomogeneity is by using the intermolecular double quantum coherence (iDQC) technique, which has been shown in other systems to obtain signals insensitive to B0 field inhomogeneity. In the present study, we employed an iDQC approach to enhance the spectral resolution of RBM. The feasibility and performance of this method for achieving high resolution MRS was verified by experiments on phantoms and pig vertebral bone samples. Unsaturated fatty acid peaks which overlap in the conventional MRS were well resolved and identified in the iDQC spectrum. Quantitative comparison of fractions of three types of fatty acids was performed between iDQC spectra on the in situ RMB and conventional MRS on the extracted fat from the same RBM. Observations of unsaturated fatty acids with iDQC MRS may provide valuable information and may hold potential in diagnosis of diseases such as obesity, diabetes, and leukemia.

  19. Calibration of a trinocular system formed with wide angle lens cameras.

    PubMed

    Ricolfe-Viala, Carlos; Sanchez-Salmeron, Antonio-Jose; Valera, Angel

    2012-12-01

    To obtain 3D information of large areas, wide angle lens cameras are used to reduce the number of cameras as much as possible. However, since images are high distorted, errors in point correspondences increase and 3D information could be erroneous. To increase the number of data from images and to improve the 3D information, trinocular sensors are used. In this paper a calibration method for a trinocular sensor formed with wide angle lens cameras is proposed. First pixels locations in the images are corrected using a set of constraints which define the image formation in a trinocular system. When pixels location are corrected, lens distortion and trifocal tensor is computed.

  20. Cu-Cl-Salt-Hydrate Melts and Their Possible Role in Ore-forming Systems

    NASA Astrophysics Data System (ADS)

    Renno, A. D.; Franz, L.; Witzke, T.; Herzig, P. M.

    2004-12-01

    We found direct evidence for a Cu-Cl-salt-hydrate melt in equilibrium with a complex system of silicate melts in a magnesiohastingsite-dominant cumulate from the TUBAF Seamount near Lihir Island (Papua New Guinea). We observed four distinct exsolution-induced features in the trachyandesitic intercumulus melt: 1) exsolution of a Cu-Fe sulfide melt, 2) exsolution of a Cu-salt-hydrate melt, 3) exsolution of a second foiditic silicate melt, and 4) exsolution of a vapor phase. The Cu-Cl-salt-hydrate melt crystallized into polycrystalline monomineralic aggregates of clinoatacamite. The features, which testify the formation of the clinoatacamite as an exsolution from the silicate melt, are presented. There is no indication of late hydrothermal alteration or weathering in the sample. We compare different possibilities to explain the formation of the xenolith and show, that the xenolith had formed independently from its parent magma in the oceanic crust. Even though no data on the solubility in Cu-Cl-silicate melt systems are available we suggest, with respect to other salt-melt - silicate-melt systems, an upper temperature limit of 800 ° C for the unmixing of the salt-hydrate-melt. The observation of these unmixing processes sheds new light on the modus operandi of how metal-enriched magmatic fluids enter hydrothermal systems. We present different scenarios, how these fluids may affect the formation of ore deposits, like epithermal gold deposits or copper porphyry systems.

  1. 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

  2. 17 CFR 249.821 - Form PILOT, information required of self-regulatory organizations operating pilot trading systems...

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... (CONTINUED) FORMS, SECURITIES EXCHANGE ACT OF 1934 Forms for Self-Regulatory Organization Rule Changes and... required of self-regulatory organizations operating pilot trading systems pursuant to § 240.19b-5 of this... Associations § 249.821 Form PILOT, information required of self-regulatory organizations operating...

  3. In situ forming nimodipine depot system based on microparticles for the treatment of posthemorrhagic cerebral vasospasm.

    PubMed

    Bege, Nadja; Renette, Thomas; Endres, Thomas; Beck-Broichsitter, Moritz; Hänggi, Daniel; Kissel, Thomas

    2013-05-01

    The present study was conducted to examine the feasibility of nimodipine-loaded PLGA microparticles suspended in Tisseel fibrin sealant as an in situ forming depot system. This device locally placed can be used for the treatment of vasospasm after a subarachnoid hemorrhage. Microparticles were prepared via spray-drying by using the vibration mesh spray technology of Nano Spray Dryer B-90. Spherically shaped microparticles with different loadings and high encapsulation efficiencies of 93.3-97.8% were obtained. Depending on nimodipine loading (10-40%), the particle diameter ranged from 1.9 ± 1.2 μm to 2.4 ± 1.3 μm. Thermal analyses using DSC revealed that nimodipine is dissolved in the PLGA matrix. Also, fluorescent dye loaded microparticles were encapsulated in Tisseel to examine the homogeneity of particles. 3D-pictures of the in situ forming devices displayed uniform particle homogeneity in the sealant matrix. Drug release was examined by fluorescence spectrophotometry which demonstrated a drug release proportional to the square root of time. A prolonged drug release of 19.5h was demonstrated under in vitro conditions. Overall, the nimodipine in situ forming device could be a promising candidate for the local treatment of vasospasm after a subarachnoid hemorrhage.

  4. 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.

  5. 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. PMID:25336757

  6. 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.

  7. Extracellular matrix-associated proteins form an integral and dynamic system during Pseudomonas aeruginosa biofilm development

    PubMed Central

    Zhang, Weipeng; Sun, Jin; Ding, Wei; Lin, Jinshui; Tian, Renmao; Lu, Liang; Liu, Xiaofen; Shen, Xihui; Qian, Pei-Yuan

    2015-01-01

    Though the essential role of extracellular matrix in biofilm development has been extensively documented, the function of matrix-associated proteins is elusive. Determining the dynamics of matrix-associated proteins would be a useful way to reveal their functions in biofilm development. Therefore, we applied iTRAQ-based quantitative proteomics to evaluate matrix-associated proteins isolated from different phases of Pseudomonas aeruginosa ATCC27853 biofilms. Among the identified 389 proteins, 54 changed their abundance significantly. The increased abundance of stress resistance and nutrient metabolism-related proteins over the period of biofilm development was consistent with the hypothesis that biofilm matrix forms micro-environments in which cells are optimally organized to resist stress and use available nutrients. Secreted proteins, including novel putative effectors of the type III secretion system were identified, suggesting that the dynamics of pathogenesis-related proteins in the matrix are associated with biofilm development. Interestingly, there was a good correlation between the abundance changes of matrix-associated proteins and their expression. Further analysis revealed complex interactions among these modulated proteins, and the mutation of selected proteins attenuated biofilm development. Collectively, this work presents the first dynamic picture of matrix-associated proteins during biofilm development, and provides evidences that the matrix-associated proteins may form an integral and well regulated system that contributes to stress resistance, nutrient acquisition, pathogenesis and the stability of the biofilm. PMID:26029669

  8. 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.

  9. Pore-forming Activity of the Escherichia coli Type III Secretion System Protein EspD.

    PubMed

    Chatterjee, Abhishek; Caballero-Franco, Celia; Bakker, Dannika; Totten, Stephanie; Jardim, Armando

    2015-10-16

    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.

  10. Two molecular weight forms of muscarinic acetylcholine receptors in the avian central nervous system: switch in predominant form during differentiation of synapses.

    PubMed Central

    Large, T H; Rauh, J J; De Mello, F G; Klein, W L

    1985-01-01

    Muscarinic acetylcholine receptors from the avian central nervous system were examined for developmental changes that correlated with the differentiation of cholinergic synapses. In contrast to previous studies that showed a single molecular weight form of muscarinic receptors in the mature central nervous system, the current study of receptors from embryonic and newly hatched chick retina showed the presence of two electrophoretic forms having apparent molecular weights of 86,200 +/- 400 and 72,200 +/- 300. Two receptor forms also were observed in embryonic cerebrum, optic tectum, and cerebellum. Each form was present, although decreased in molecular weight by 6000, after treatment with deglycosylating enzymes, consistent with molecular differences occurring in the protein portions, rather than the carbohydrate portions, of the molecules. The relative proportions of the high and low molecular weight receptors in retina showed a striking inversion during development. Before synaptogenesis, receptors were mainly of Mr 86,000, whereas after synaptogenesis, receptors were mainly of Mr 72,000. Development of a predominantly low molecular weight receptor population also occurred in aggregate, but not monolayer, cell culture, suggesting a possible role for cell-cell interactions in triggering the change. Pulse-chase labeling of receptors on cultured cells indicated that both forms were present on the cell surface; the labeled Mr 86,000 population had a half-life of 5 hr, whereas the labeled Mr 72,000 population had a half-life of 19 hr. The change in size of muscarinic receptors during development may reflect the action of regulatory mechanisms critical to the proper assembly and function of synapses in the central nervous system. Images PMID:3866251

  11. Comment on 'Intermolecular interaction potentials of the methane dimer from the local density approximation'

    SciTech Connect

    Li, Arvin H.-T.; Chao, S.D.

    2006-01-15

    To verify the recently calculated intermolecular interaction potentials of the methane dimer within the density functional theory using the (Perdew) local density approximation (LDA) [Chen et al., Phys. Rev. A 69, 034701 (2004)], we have performed a parallel series of calculations using the LDA/6-311++G (3df, 3pd) level of theory with selected exchange functionals (B, G96, MPW, O, PBE, PW91, S, and XA). None of the above calculated intermolecular interaction potentials from the local density approximation reproduce the results reported in the commented paper. In addition, we point out the inappropriateness of using the Lennard-Jones function to model the long-range parts of the calculated intermolecular interaction potentials, as suggested positively by Chen et al.

  12. Localization of the dominant non-enzymatic intermolecular cross-linking sites on fibrous collagen.

    PubMed

    Chiue, Hiroko; Yamazoye, Tsutako; Matsumura, Sueo

    2015-06-01

    Previous studies have shown that fibrous collagen undergoes intermolecular cross-linking at multiple sites of the elongated triple-helical regions among adjacent juxtaposed collagen molecules on incubation with a very high concentration of reducing sugar such as 200 mM ribose, and the similarity of the changes in its physicochemical properties to that of senescent collagen aged in vivo has been emphasized. In the present study, however, it was found that when incubated with less than 30 mM ribose, fibrous collagen underwent intermolecular cross-linking primarily between the telopeptide region of a collagen molecule and the triple-helical region of another adjacent collagen molecule, and intermolecular cross-linking between the triple-helical regions of adjacent collagen molecules was very small. Physiological significance of the previous studies thus needs to be reevaluated.

  13. Intermolecular and intramolecular contributions to the relaxation process in sorbitol and maltitol

    NASA Astrophysics Data System (ADS)

    Sixou, B.; Faivre, A.; David, L.; Vigier, G.

    Molecular mobility in sorbitol and maltitol is studied with spectroscopic techniques and molecular dynamics simulations in order to evaluate the relative contributions of the intermolecular and intramolecular interactions involved in the relaxation processes. The results of the molecular dynamics simulations performed on the polyols in the bulk or in vacuum compares well with the results of the analysis of the relaxation diagrams in the framework of the Perez et al . model. They both imply that the difference in the relative contributions of the intermolecular and intramolecular interactions associated with the different chemical architectures of the two polyols must be taken into account. The intermolecular interactions cannot be neglected and they are stronger in sorbitol than in maltitol in relation with the linear structure of this polyol. The intramolecular barrier, higher in the maltitol molecule with a more complex structure, could be at the origin of the higher junction temperature between the αand βrelaxation processes.

  14. SEM evaluation of resin-carious dentin interfaces formed by two dentin adhesive systems

    PubMed Central

    Hsu, Kuang-Wei; Marshall, Sally J.; Pinzon, Lilliam M.; Watanabe, Larry; Saiz, Eduardo; Marshall, Grayson W.

    2008-01-01

    Objectives We investigated the influence of dentin tubule direction and identifiable zone of carious dentin on the microstructure and the thickness of the hybrid-like layer (HL) formed by self-etch and etch-rinse adhesive systems. Methods An etch-rinse and a self-etching adhesive were bonded to dentin carious zones divided into groups with parallel or perpendicular orientation relative to the dentin tubules at the resin-carious dentin interface (N = 5/variable). Bonds were prepared to each of the four zones of carious dentin apparent after staining with Caries Detector: pink, light pink, transparent and apparently normal Six non-carious third molars were controls. The microstructure and thickness of the HL were determined by SEM.and compared using three-way ANOVA and Tukey's multiple comparisons (p<0.05). Results Etch-rinse controls gave thicker HLs than self-etching systems; ; orientation did not affect thickness for the self-etch system. Perpendicular orientations gave thicker HLs than parallel for the pink zone bonded with the etch-rinse system. For both adhesives, HL thickness in the pink zone were significantly greater than in light pink for the perpendicular group, but no significant differences were found among other variables. HL microstructure was more granular and rougher for the etch rinse than for the self etching system. Pores and cracks were obvious in the more demineralized zones, Resin tags were shorter and irregular in the transparent zone and often were completely absent in the outer demineralized zones (pink, light pink). Significance Microstructure of bonded interfaces varies markedly depending on adhesive system, tubule orientation and carious zone. PMID:18155289

  15. Length scales in glass-forming liquids and related systems: a review

    NASA Astrophysics Data System (ADS)

    Karmakar, Smarajit; Dasgupta, Chandan; Sastry, Srikanth

    2016-01-01

    The central problem in the study of glass-forming liquids and other glassy systems is the understanding of the complex structural relaxation and rapid growth of relaxation times seen on approaching the glass transition. A central conceptual question is whether one can identify one or more growing length scale(s) associated with this behavior. Given the diversity of molecular glass-formers and a vast body of experimental, computational and theoretical work addressing glassy behavior, a number of ideas and observations pertaining to growing length scales have been presented over the past few decades, but there is as yet no consensus view on this question. In this review, we will summarize the salient results and the state of our understanding of length scales associated with dynamical slow down. After a review of slow dynamics and the glass transition, pertinent theories of the glass transition will be summarized and a survey of ideas relating to length scales in glassy systems will be presented. A number of studies have focused on the emergence of preferred packing arrangements and discussed their role in glassy dynamics. More recently, a central object of attention has been the study of spatially correlated, heterogeneous dynamics and the associated length scale, studied in computer simulations and theoretical analysis such as inhomogeneous mode coupling theory. A number of static length scales have been proposed and studied recently, such as the mosaic length scale discussed in the random first-order transition theory and the related point-to-set correlation length. We will discuss these, elaborating on key results, along with a critical appraisal of the state of the art. Finally we will discuss length scales in driven soft matter, granular fluids and amorphous solids, and give a brief description of length scales in aging systems. Possible relations of these length scales with those in glass-forming liquids will be discussed.

  16. Length scales in glass-forming liquids and related systems: a review.

    PubMed

    Karmakar, Smarajit; Dasgupta, Chandan; Sastry, Srikanth

    2016-01-01

    The central problem in the study of glass-forming liquids and other glassy systems is the understanding of the complex structural relaxation and rapid growth of relaxation times seen on approaching the glass transition. A central conceptual question is whether one can identify one or more growing length scale(s) associated with this behavior. Given the diversity of molecular glass-formers and a vast body of experimental, computational and theoretical work addressing glassy behavior, a number of ideas and observations pertaining to growing length scales have been presented over the past few decades, but there is as yet no consensus view on this question. In this review, we will summarize the salient results and the state of our understanding of length scales associated with dynamical slow down. After a review of slow dynamics and the glass transition, pertinent theories of the glass transition will be summarized and a survey of ideas relating to length scales in glassy systems will be presented. A number of studies have focused on the emergence of preferred packing arrangements and discussed their role in glassy dynamics. More recently, a central object of attention has been the study of spatially correlated, heterogeneous dynamics and the associated length scale, studied in computer simulations and theoretical analysis such as inhomogeneous mode coupling theory. A number of static length scales have been proposed and studied recently, such as the mosaic length scale discussed in the random first-order transition theory and the related point-to-set correlation length. We will discuss these, elaborating on key results, along with a critical appraisal of the state of the art. Finally we will discuss length scales in driven soft matter, granular fluids and amorphous solids, and give a brief description of length scales in aging systems. Possible relations of these length scales with those in glass-forming liquids will be discussed.

  17. Computational Analysis of Intermolecular Coulombic Decay Effects in DNA nucleotide Photoionization

    NASA Astrophysics Data System (ADS)

    Vargas, E. L.; Robertson, J.; Andrianarijaona, V. M.

    2016-03-01

    Intermolecular Coulombic Decay (ICD) is the process of how electrons return to their original state after excitation and how this affects their immediate environment. In a previous research presentationwe had considered the hypothetical applications of Intermolecular Coulombic Decay on the adhesiveness of coding proteins within DNA molecules. This presentation is a continuation of the previous in that the results of our DFT-based computational calculations of the ionization potentials of nucleotides and their excitation energies will be presented, as well as how they influence their surroundings. Author would like to acknowledge the PUC Student Senate for financial assistance.

  18. Intermolecular potential functions and high resolution molecular spectroscopy of weakly bound complexes. Final progress report

    SciTech Connect

    Muenter, J.S.

    1997-04-01

    This report describes accomplishments over the past year in research supported by this grant. Two papers published in this period are briefly discussed. The general goal of the work is to consolidate the understanding of experimental results through a theoretical model of intermolecular potential energy surfaces. Progress in the experimental and theoretical phases of the program are presented and immediate goals outlined. The ability to construct analytic intermolecular potential functions that accurately predict the energy of interaction between small molecules will have great impact in many areas of chemistry, biochemistry, and biology.

  19. Effects of competition for charge capture from the matrix on intermolecular electron-tunneling reactions

    SciTech Connect

    Huddleston, R.K.; Miller, J.R.

    1982-04-15

    A general method is presented for correcting for the direct capture of matrix charges by the acceptor in an intermolecular electron-transfer reaction in a rigid medium. The method is based on a two-step electron-tunneling model that takes into account the correlation between matrix charge capture and intermolecular electron transfer. As an experimental test of the method, electron transfer from the anion of cinnamaldehyde to neutral pryomellitic dianhydride was studied in 2-methyltetrahydrofuran glass at 77/sup 0/K. Good agreement between the model and the experimental kinetic results was obtained.

  20. The role of entropy and polarity in intermolecular contacts in protein crystals

    SciTech Connect

    Cieślik, Marcin; Derewenda, Zygmunt S.

    2009-05-01

    Logistic regression was used to study the amino-acid composition and structure of crystal contacts in monomeric proteins. Crystal contacts are generally depleted of large flexible amino acids and enriched in small and hydrophobic residues such as Gly and Leu; additionally, larger contacts have cores depleted of polar residues. The integrity and X-ray diffraction quality of protein crystals depend on the three-dimensional order of relatively weak but reproducible intermolecular contacts. Despite their importance, relatively little attention has been paid to the chemical and physical nature of these contacts, which are often regarded as stochastic and thus not different from randomly selected protein surface patches. Here, logistic regression was used to analyze crystal contacts in a database of 821 unambiguously monomeric proteins with structures determined to 2.5 Å resolution or better. It is shown that the propensity of a surface residue for incorporation into a crystal contact is not a linear function of its solvent-accessible surface area and that amino acids with low exposed surfaces, which are typically small and hydrophobic, have been underestimated with respect to their contact-forming potential by earlier area-based calculations. For any given solvent-exposed surface, small and hydrophobic residues are more likely to be involved in crystal contacts than large and charged amino acids. Side-chain entropy is the single physicochemical property that is most negatively correlated with the involvement of amino acids in crystal contacts. It is also shown that crystal contacts with larger buried surfaces containing eight or more amino acids have cores that are depleted of polar amino acids.

  1. BeSocratic: An Intelligent Tutoring System for the Recognition, Evaluation, and Analysis of Free-Form Student Input

    ERIC Educational Resources Information Center

    Bryfczynski, Samuel Paul

    2012-01-01

    This dissertation describes a novel intelligent tutoring system, BeSocratic, which aims to help fill the gap between simple multiple-choice systems and free-response systems. BeSocratic focuses on targeting questions that are free-form in nature yet defined to the point which allows for automatic evaluation and analysis. The system includes a set…

  2. In situ gel-forming AP-57 peptide delivery system for cutaneous wound healing.

    PubMed

    Li, Xiaoling; Fan, Rangrang; Tong, Aiping; Yang, Meijia; Deng, Jiaojiao; Zhou, Liangxue; Zhang, Xiaoning; Guo, Gang

    2015-11-10

    In situ gel-forming system as local drug delivery system in dermal traumas has generated a great interest. Accumulating evidence shows that antimicrobial peptides play pivotal roles in the process of wound healing. Here in this study, to explore the potential application of antimicrobial peptide in wound healing, biodegradable poly(L-lactic acid)-Pluronic L35-poly(L-lactic acid) (PLLA-L35-PLLA) was developed at first. Then based on this polymer, an injectable in situ gel-forming system composed of human antimicrobial peptides 57 (AP-57) loaded nanoparticles and thermosensitive hydrogel was prepared and applied for cutaneous wound healing. AP-57 peptides were enclosed with biocompatible nanoparticles (AP-57-NPs) with high drug loading and encapsulation efficiency. AP-57-NPs were further encapsulated in a thermosensitive hydrogel (AP-57-NPs-H) to facilitate its application in cutaneous wound repair. As a result, AP-57-NPs-H released AP-57 in an extended period and exhibited quite low cytotoxicity and high anti-oxidant activity in vitro. Moreover, AP-57-NPs-H was free-flowing liquid at room temperature, and can form non-flowing gel without any crosslink agent upon applied on the wounds. In vivo wound healing assay using full-thickness dermal defect model of SD rats indicated that AP-57-NPs-H could significantly promote wound healing. At day 14 after operation, AP-57-NPs-H treated group showed nearly complete wound closure of 96.78 ± 3.12%, whereas NS, NPs-H and AP-57-NPs group recovered by about 68.78 ± 4.93%, 81.96 ± 3.26% and 87.80 ± 4.62%, respectively. Histopathological examination suggested that AP-57-NPs-H could promote cutaneous wound healing through enhancing granulation tissue formation, increasing collagen deposition and promoting angiogenesis in the wound tissue. Therefore, AP-57-NPs-H might have potential application in wound healing.

  3. Numerical Modeling of Multiphase Fluid Flow in Ore-Forming Hydrothermal Systems

    NASA Astrophysics Data System (ADS)

    Weis, P.; Driesner, T.; Coumou, D.; Heinrich, C. A.

    2007-12-01

    Two coexisting fluid phases - a variably saline liquid and a vapor phase - are ubiquitous in ore-forming and other hydrothermal systems. Understanding the dynamics of phase separation and the distinct physical and chemical evolution of the two fluids probably plays a key role in generating different ore deposit types, e.g. porphyry type, high and low sulfidation Cu-Mo-Au deposits. To this end, processes within hydrothermal systems have been studied with a refined numerical model describing fluid flow in transient porous media (CSP~5.0). The model is formulated on a mass, energy and momentum conserving finite-element-finite-volume (FEFV) scheme and is capable of simulating multiphase flow of NaCl-H20 fluids. Fluid properties are computed from an improved equation of state (SOWAT~2.0). It covers conditions with temperatures of up to 1000 degrees~C, pressures of up to 500 MPa, and fluid salinities of 0~to 100%~NaCl. In particular, the new set-up allows for a more accurate description of fluid phase separation during boiling of hydrothermal fluids into a vapor and a brine phase. The geometric flexibility of the FEFV-meshes allows for investigations of a large variety of geological settings, ranging from ore-forming processes in magmatic hydrothermal system to the dynamics of black smokers at mid-ocean ridges. Simulations demonstrated that hydrothermal convection patterns above cooling plutons are primarily controlled by the system-scale permeability structure. In porphyry systems, high fluid pressures develop in a stock rising from the magma chamber which can lead to rock failure and, eventually, an increase in permeability due to hydrofracturing. Comparisons of the thermal evolution as inferred from modeling studies with data from fluid inclusion studies of the Pb-Zn deposits of Madan, Bulgaria are in a strikingly good agreement. This indicates that cross-comparisons of field observations, analytical data and numerical simulations will become a powerful tool towards a

  4. Efficacy of various chemical disinfectants on biofilms formed in spacecraft potable water system components.

    PubMed

    Wong, Wing C; Dudinsky, Lynn A; Garcia, Veronica M; Ott, Charlie M; Castro, Victoria A

    2010-07-01

    As the provision of potable water is critical for successful habitation of the International Space Station (ISS), life support systems were installed in December 2008 to recycle both humidity from the atmosphere and urine to conserve available water in the Station. In-flight pre-consumption testing from the dispensing needle at the Potable Water Dispenser (PWD) indicated that bacterial concentrations exceeded the current ISS specifications of 50 colony-forming units (CFU) ml(-1). Subsequent investigations revealed that a corrugated stainless steel flex hose upstream of the dispensing needle in the PWD was filled with nonsterile water and left at room temperature for more than 1 month before launch. To simulate biofilm formation that was suspected in the flight system, sterile flex hoses were seeded with a consortium of bacterial isolates previously recovered from other ISS water systems, including Ralstonia pickettii, Burkholderia multivorans, Caulobacter vibrioides, and Cupriavidus pauculus. After incubation for 5 days, the hoses were challenged with various chemical disinfectants including hydrogen peroxide (H2O2), colloidal silver, and buffered pH solutions to determine the ability of the disinfectants to decrease and maintain bacterial concentrations below ISS specifications. The disinfection efficacy over time was measured by collecting daily heterotrophic plate counts after exposure to the disinfectants. A single flush with either 6% H2O2 solution or a mixture of 3% H2O2 and 400 ppb colloidal silver effectively reduced the bacterial concentrations to <1 CFU ml(-1) for a period of up to 3 months.

  5. Current Thoughts on Reactive Element Effects in Alumina-Forming Systems: In Memory of John Stringer

    DOE PAGES

    Naumenko, D.; Pint, B. A.; Quadakkers, W. J.

    2016-05-06

    In memory of John Stringer (1934–2014), one of the leaders in studying the reactive element (RE) effects, this paper reviews the current status of understanding of the effect of RE dopants on high-temperature oxidation behavior, with an emphasis on recent research related to deploying alumina-forming alloys and coatings with optimal performance in commercial systems. Additionally, to the well-known interaction between indigenous sulfur and RE additions, effects have been observed with C, N, and O found in commercial alloys and coatings. While there are many similarities between alumina-forming alloys and coatings, the latter bring additional complicating factors such as the effectsmore » of O incorporation during thermal spraying MCrAlY coatings, coating roughness, and heat treatments that must be considered in optimizing the beneficial dopant addition. We can see analogies between RE effects in alloys and in the substrates beneath diffusion M–Al coatings. Recently, there has been more interest in the influence of mixed oxidant environments, since these may modify the manifestation of the RE effect. Some thoughts are provided on optimizing the RE benefit and modeling oxidation of RE-doped alloys.« less

  6. Lyotropic liquid crystalline phases formed from glycerate surfactants as sustained release drug delivery systems.

    PubMed

    Boyd, Ben J; Whittaker, Darryl V; Khoo, Shui-Mei; Davey, Greg

    2006-02-17

    A new class of surfactants with glycerate headgroups, that form viscous lyotropic liquid crystalline phases in excess water, have been investigated for their potential to provide sustained release matrices for depot drug delivery. Oleyl glycerate and phytanyl glycerate were used as representative surfactants of this new class, and their behaviour compared with that of glyceryl monooleate (GMO). The surfactants were found to form reverse hexagonal phase (H(II)) in excess water, and the matrices were loaded with a series of model hydrophobic and hydrophilic drugs, (paclitaxel, irinotecan, glucose, histidine and octreotide), and the release kinetics determined. In all cases, the release behaviour obeyed Higuchi kinetics, with linear drug release versus square root of time. The H(II) phases released model drugs slower than the GMO cubic phase matrix. The oleyl glycerate matrix was found to consistently release drug faster than the phytanyl glycerate matrix, despite both matrices being based on H(II) phase. To further demonstrate the potential utility of these materials as drug depot delivery systems, an injectable precursor formulation for octreotide was also prepared and demonstrated to provide controlled release for the peptide. The stability of the H(II) phase to likely in vivo breakdown products was also assessed.

  7. On the Shape of Meissner Solutions to a Limiting Form of Ginzburg-Landau Systems

    NASA Astrophysics Data System (ADS)

    Xiang, Xingfei

    2016-07-01

    In this paper we study a semilinear system involving the curl operator, which is a limiting form of the Ginzburg-Landau model for superconductors in R^3 for a large value of the Ginzburg-Landau parameter. We consider the locations of the maximum points of the magnitude of solutions, which are associated with the nucleation of instability of the Meissner state for superconductors when the applied magnetic field is increased in the transition between the Meissner state and the vortex state. For small penetration depth, we prove that the location is not only determined by the tangential component of the applied magnetic field, but also by the normal curvatures of the boundary in some directions. This improves the result obtained by Bates and Pan in Commun. Math. Phys. 276, 571-610 (2007). We also show that the solutions decay exponentially in the normal direction away from the boundary if the penetration depth is small.

  8. [Rabies virus study by the plaque forming system. A simplified technique].

    PubMed

    Salaun, J J

    1978-01-01

    The author describes here a simplified and economical plaque forming system for rabies virus study. It is achieved in three steps (cells preparation and infection, apply of overlay, staining). It presents more advantages than previous techniques: time as well as culture media and handling spearing, easy and durable reading. Cells prepared with di-ethyl-amino-ethyl-dextran are added to equal quantities of diluted virus (for titration) or to virus-serum mixing (for seroneutralization) and overlaid after 4 hours with a carboxymethylcellulose medium. Reading is carried out after 6 days incubation and staining with amido black. Plaques obtained are to 2-3 mm in diameter, regularly reproductible, clear and easy to read. This technique enables titration and seroneutralization and even a rabies virus cloning.

  9. An altered form of pp60/sup c-src/ is expressed primarily in the central nervous system

    SciTech Connect

    Le Beau, J.M.; Wiestler, O.D.; Walter, G.

    1987-11-01

    The expression of two forms of pp60/sup c-scr/, pp60 and pp60/sup +/, was measured in the central nervous system (CNS) and the peripheral nervous system. Both forms were expressed in the CNS, whereas only pp60 was primarily detected in the peripheral nervous system. Our findings suggest that pp60/sup +/ may play a role in events important to the CNS.

  10. Efficacy of Various Chemical Disinfectants on Biofilms Formed in Spacecraft Potable Water System Component

    NASA Technical Reports Server (NTRS)

    Wong, Willy; Garcia, Veronica; Castro, Victoria; Ott, Mark; Duane

    2009-01-01

    As the provision of potable water is critical for successful habitation of the International Space Station (ISS), life support systems were installed in December 2008 to recycle both humidity from the atmosphere and urine to conserve available water in the vehicle. Pre-consumption testing from the dispensing needle at the Potable Water Dispenser (PWD) indicated that bacterial concentrations exceeded the current ISS specifications of 50 colony forming units (CFU) per ml. Subsequent investigations revealed that a corrugated stainless steel flex hose upstream of the dispensing needle in the PWD was filled with non-sterile water and left at room temperature for over one month before launch. To simulate biofilm formation that was suspected in the flight system, sterile flex hoses were seeded with a consortium of bacterial isolates previously recovered from other ISS water systems, which included Ralstonia pickettii, Burkholderia multivorans, Caulobacter vibrioides., and Cupriavidus pauculus. After 5 days of incubation, these hoses were challenged with various chemical disinfectants including hydrogen peroxide, colloidal silver, and buffered pH solutions to determine the ability of the disinfectants to decrease and maintain bacterial concentrations below ISS specifications. Disinfection efficacy over time was measured by collecting daily heterotrophic plate counts following exposure to the disinfectants. A single flush with either 6% hydrogen peroxide solution or a mixture of 3% hydrogen peroxide and 400 ppb colloidal silver effectively reduced the bacterial concentrations to less than 1 CFU/ml for a period of up to 2 months. Testing results indicated that hydrogen peroxide and mixtures of hydrogen peroxide and colloidal silver have tremendous potential as alternative disinfectants for ISS water systems.

  11. Evidence for a noncovalent intermolecular interaction of opiates with thiamine.

    PubMed

    Misra, A L; Vadlamani, N L; Pontani, R B

    1977-11-01

    Opiate agonists and antagonists formed reversible molecular complexes with thiamine. The absorption maxima of these complexes were at wavelengths longer than those of the individual components and their intensities depended on the concentration and nature of the opiate component. The possible implications of such an interaction are discussed. PMID:928957

  12. Effects of Extreme Monsoon Precipitation on River Systems Form And Function, an Early Eocene Perspective

    NASA Astrophysics Data System (ADS)

    Plink-Bjorklund, P.; Birgenheier, L.

    2013-12-01

    Here we document effects of extreme monsoon precipitation on river systems with mountainous drainage basin. We discuss the effects of individual extreme monsoon seasons, as well as long-term changes in Earth surface system's form and function. The dataset spans across 1000 m of stratigraphy across ca 200 km of Paleocene and Early Eocene river deposits. The excessive 3-dimensional outcrops, combined with our new Carbon isotope, ichnological and paleosols record allow reconstruction of long-term river system's evolution during the Paleocene-Eocene Thermal Maximum (PETM) ca 56 million years ago, the transient global warming events during Early Eocene Climate Optimum (EECO) ca 53 to 51.5 million years ago, as well as the effects of highly peaked precipitation events during single monsoon seasons. On the single season scale, the increase in precipitation peakedness causes high discharge flooding events that remove large quantities of sediment from the drainage basin, due to stream erosion and landslide initiation. The initiation of landslides is especially significant, as the drainage basin is of high gradient, the monsoon intensification is accompanied by significant vegetation decline, as the monsoon cycle changes to multi-year droughts interrupted by extreme monsoon precipitation. These large discharge floods laden with sediment cause rapid deposition from high-velocity currents that resemble megaflood deposits in that they are dominated by high-velocity and high deposition rate sedimentary structures and thick simple depositional packages (unit bars). Such high deposition rates cause locally rapid channel bed aggradation and thus increase frequency of channel avulsions and cause catastrophic high-discharge terrestrial flooding events across the river basin. On long time scales, fluvial megafan systems, similar to those, e.g. in the Himalayan foreland, developed across the ca 200 km wide river basin, causing significant sediment aggradation and a landscape with high

  13. A triple protostar system formed via fragmentation of a gravitationally unstable disk

    NASA Astrophysics Data System (ADS)

    Tobin, John J.; Kratter, Kaitlin M.; Persson, Magnus V.; Looney, Leslie W.; Dunham, Michael M.; Segura-Cox, Dominique; Li, Zhi-Yun; Chandler, Claire J.; Sadavoy, Sarah I.; Harris, Robert J.; Melis, Carl; Pérez, Laura M.

    2016-10-01

    Binary and multiple star systems are a frequent outcome of the star formation process and as a result almost half of all stars with masses similar to that of the Sun have at least one companion star. Theoretical studies indicate that there are two main pathways that can operate concurrently to form binary/multiple star systems: large-scale fragmentation of turbulent gas cores and filaments or smaller-scale fragmentation of a massive protostellar disk due to gravitational instability. Observational evidence for turbulent fragmentation on scales of more than 1,000 astronomical units has recently emerged. Previous evidence for disk fragmentation was limited to inferences based on the separations of more-evolved pre-main sequence and protostellar multiple systems. The triple protostar system L1448 IRS3B is an ideal system with which to search for evidence of disk fragmentation as it is in an early phase of the star formation process, it is likely to be less than 150,000 years old and all of the protostars in the system are separated by less than 200 astronomical units. Here we report observations of dust and molecular gas emission that reveal a disk with a spiral structure surrounding the three protostars. Two protostars near the centre of the disk are separated by 61 astronomical units and a tertiary protostar is coincident with a spiral arm in the outer disk at a separation of 183 astronomical units. The inferred mass of the central pair of protostellar objects is approximately one solar mass, while the disk surrounding the three protostars has a total mass of around 0.30 solar masses. The tertiary protostar itself has a minimum mass of about 0.085 solar masses. We demonstrate that the disk around L1448 IRS3B appears susceptible to disk fragmentation at radii between 150 and 320 astronomical units, overlapping with the location of the tertiary protostar. This is consistent with models for a protostellar disk that has recently undergone gravitational instability

  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. PMID:27208948

  15. Did the Solar system form in a sequential triggered star formation event?

    NASA Astrophysics Data System (ADS)

    Parker, Richard J.; Dale, James E.

    2016-02-01

    The presence and abundance of the short-lived radioisotopes (SLRs) 26Al and 60Fe during the formation of the Solar system is difficult to explain unless the Sun formed in the vicinity of one or more massive star(s) that exploded as supernovae. Two different scenarios have been proposed to explain the delivery of SLRs to the protosolar nebula: (i) direct pollution of the protosolar disc by supernova ejecta, and (ii) the formation of the Sun in a sequential star formation event in which supernovae shockwaves trigger further star formation which is enriched in SLRs. The sequentially triggered model has been suggested as being more astrophysically likely than the direct pollution scenario. In this paper, we investigate this claim by analysing a combination of N-body and smoothed particle hydrodynamics simulations of star formation. We find that sequential star formation would result in large age spreads (or even bi-modal age distributions for spatially coincident events) due to the dynamical relaxation of the first star formation event(s). Secondly, we discuss the probability of triggering spatially and temporally discrete populations of stars and find this to be only possible in very contrived situations. Taken together, these results suggest that the formation of the Solar system in a triggered star formation event is as improbable, if not more so, than the direct pollution of the protosolar disc by a supernova.

  16. The properties of immune complex-forming systems. A new theoretical approach.

    PubMed Central

    Steensgaard, J; Liu, B M; Cline, G B; Møller, N P

    1977-01-01

    A new mathematical model for antigen-antibody interactions has been developed. The new model is based on the assumption that the formation of complexes between a bivalent antibody and a multivalent antigen is determined thermodynamically by the concentrations and valences of antigen as well as antibody, together with one association constant which is common to all mutual interactions. Formulae have been derived for calculation of the distributions of compositionally different antigen-antibody complexes either from knowledge of equilibrium concentrations of free antigen and antibody, or from knowledge of total amounts of antigen and antibody in the system. A computer program for these calculation is described. The model is found to yield precise predictions of the formation of soluble immune complexes, as studied by zonal centrifugation. It is found through use of the model that 'complex formation' as such differs in binding characteristics from adsorption, especially for high concentrations of antigens and antibodies. 'Complex formation' implies that association constants estimated through a Sips plot method will vary with antibody concentration, and that certain curvatures of the lines in a Sips plot reflect inherent properties of complex-forming systems. PMID:608678

  17. Distributive Fluvial Systems of the Chaco Plain - Satellite Image Assessment of Fluvial Form and Facies Distributions

    NASA Astrophysics Data System (ADS)

    Weissmann, G. S.; Hartley, A. J.; Scuderi, L.; Bhattacharyya, P.; Buehler, H.; Leleu, S.; Mather, A.

    2009-12-01

    Distributive fluvial systems (DFS) dominate fluvial deposition inside modern continental sedimentary basins and are particularly extensive in modern foreland basins. The largest of these DFS are found in the Chaco Plain, Andean Foreland Basin, South America. We use published literature, field and satellite data (Landsat, Modis, and SRTM) to construct preliminary hypotheses about the geomorphic form and fluvial facies distributions on the DFSs in this basin. The Pilcomayo River DFS extends over 700 km from apex to toe. The river enters the DFS apex as a large braided river with a bankfull channel width of 2500 m. Gravels and cobbles occur in terraces cut through the apex. At ~70-km downstream the bankfull channel width is ~2000 m and the channel is dominated by fine sand with cut banks 2-3 m high. The proximal channel belt is surrounded by floodplain sediments, however many sandy abandoned channel belts are present across the DFS, indicating a mobile channel system. Abandoned channels have a similar form to the modern channel, with minor reworking by underfit meandering streams. At ~75-km downfan, the river system diminishes in size (bankfull channel width up to 2 km but generally <1.5 km) and becomes increasingly sinuous in planform. This point appears to serve as a node for a series of recently abandoned meander belts and splays associated with discrete channels surrounded by floodplain material. At 100 km downstream the planform is highly sinuous and bankfull width has decreased to 1500 m or less. Downstream of this area abandoned meander belts dominate along the flanks of the modern channel with oxbow lakes present adjacent to the active channel. At 150 km downstream the bankfull channel belt width is 500 m or less and the river bifurcates into splays and multiple active channels which extend downstream for a further 200 km. Vegetation maps derived from Modis imagery indicate an increase in tree density around the DFS at this elevation (230 m). Along the distal

  18. Waterhole form and process in the anastomosing channel system of Cooper Creek, Australia

    NASA Astrophysics Data System (ADS)

    Knighton, A. David; Nanson, Gerald C.

    2000-10-01

    One of the most distinctive features of Cooper Creek's anastomosing channel system is the preponderance of waterholes, enlarged segments of channel ranging in length from 100 m to over 20 km. Enlargement occurs in both the width and depth dimensions to give bankfull cross-sectional areas four to eight times the average size of individual anastomosing channels. The anastomosing system is cut into a floodplain of subtle relief but depths of incision can be highly variable, giving rise to changes in the degree of anastomosis as different sets of channels are activated during the filling stage of a flood. Also, cross-sectional form and bed topography can vary markedly over short channel distances, which has implications for local flow conditions and erosive potential. Hydraulic geometry analyses suggest that cross-sectional area adjusts much more readily than velocity to increasing discharge in waterholes, particularly if there is limited lateral confinement. Consequently, velocities tend to be rather modest across a wide spectrum of flows, with average values rarely reaching 1 m s -1. Nevertheless, observations made during a 1:20-year flood reveal a deeply penetrative band of relatively high velocity in one waterhole, suggesting that localized values of bed shear could be quite large even when sectional averages are moderate. Waterholes appear to be a product of the present regime, since they concentrate flow from both feeder channels and the floodplain during flood discharges. In several respects they resemble chains-of-ponds morphology [Eyles, R.J., 1977. Birchams Creek: the transition from a chain of ponds to a gully. Aust. Geogr. Stud. 15, 146-157.], and could represent the discontinuous sections of a present-day channel, which cannot be maintained in that form over its entire length. That the one waterhole to accommodate the entire cross-valley flow at bankfull stage (Meringhina Waterhole) has cross-sectional dimensions similar to those predicted by appropriate

  19. Copper-catalyzed intermolecular chloroazidation of α,β-unsaturated amides.

    PubMed

    Chen, Long; Xing, Haotian; Zhang, Huaibin; Jiang, Zhong-Xing; Yang, Zhigang

    2016-08-21

    A highly practical copper-catalyzed intermolecular chloroazidation of α,β-unsaturated amides has been described, giving a series of azidochlorides in good-to-excellent yields. The stable azidoiodine(iii) reagent and SOCl2 were used as azide and chlorine sources, respectively. The synthetic applications of this protocol were also explored by a variety of synthetically useful transformations. PMID:27462802

  20. An Analysis of Two Textbooks on the Topic of Intermolecular Forces

    ERIC Educational Resources Information Center

    Tan, Daniel Kim Chwee; Seng, Chan Kim

    2004-01-01

    This paper describes the analysis of two commonly used high school (Grades 11 and 12) chemistry textbooks in Singapore to determine if the content presented in the topic of intermolecular forces is consistent with the concepts and propositional knowledge identified by the authors as essential for the learning and understanding of the topic…

  1. Intermolecular forces and nonbonded interactions: Superoperator nonlinear time-dependent density-functional-theory response approach

    SciTech Connect

    Harbola, Upendra; Mukamel, Shaul

    2004-11-01

    Electrostatic and dispersive interactions of polarizable molecules are expressed in terms of generalized (nonretarded) charge-density response functions of the isolated molecules, which in turn are expanded using the collective electronic oscillator (CEO) eigenmodes of linearized time-dependent density-functional theory. Closed expressions for the intermolecular energy are derived to sixth order in charge fluctuation amplitudes.

  2. Salting Effects as an Illustration of the Relative Strength of Intermolecular Forces

    ERIC Educational Resources Information Center

    Person, Eric C.; Golden, Donnie R.; Royce, Brenda R.

    2010-01-01

    This quick and inexpensive demonstration of the salting of an alcohol out of an aqueous solution illustrates the impact of intermolecular forces on solubility using materials familiar to many students. Ammonium sulfate (fertilizer) is added to an aqueous 35% solution of isopropyl alcohol (rubbing alcohol and water) containing food coloring as a…

  3. Instantaneous normal mode analysis for intermolecular and intramolecular vibrations of water from atomic point of view

    SciTech Connect

    Chen, Yu-Chun; Tang, Ping-Han; Wu, Ten-Ming

    2013-11-28

    By exploiting the instantaneous normal mode (INM) analysis for models of flexible molecules, we investigate intermolecular and intramolecular vibrations of water from the atomic point of view. With two flexible SPC/E models, our investigations include three aspects about their INM spectra, which are separated into the unstable, intermolecular, bending, and stretching bands. First, the O- and H-atom contributions in the four INM bands are calculated and their stable INM spectra are compared with the power spectra of the atomic velocity autocorrelation functions. The unstable and intermolecular bands of the flexible models are also compared with those of the SPC/E model of rigid molecules. Second, we formulate the inverse participation ratio (IPR) of the INMs, respectively, for the O- and H-atom and molecule. With the IPRs, the numbers of the three species participated in the INMs are estimated so that the localization characters of the INMs in each band are studied. Further, by the ratio of the IPR of the H atom to that of the O atom, we explore the number of involved OH bond per molecule participated in the INMs. Third, by classifying simulated molecules into subensembles according to the geometry of their local environments or their H-bond configurations, we examine the local-structure effects on the bending and stretching INM bands. All of our results are verified to be insensible to the definition of H-bond. Our conclusions about the intermolecular and intramolecular vibrations in water are given.

  4. Instantaneous normal mode analysis for intermolecular and intramolecular vibrations of water from atomic point of view.

    PubMed

    Chen, Yu-Chun; Tang, Ping-Han; Wu, Ten-Ming

    2013-11-28

    By exploiting the instantaneous normal mode (INM) analysis for models of flexible molecules, we investigate intermolecular and intramolecular vibrations of water from the atomic point of view. With two flexible SPC/E models, our investigations include three aspects about their INM spectra, which are separated into the unstable, intermolecular, bending, and stretching bands. First, the O- and H-atom contributions in the four INM bands are calculated and their stable INM spectra are compared with the power spectra of the atomic velocity autocorrelation functions. The unstable and intermolecular bands of the flexible models are also compared with those of the SPC/E model of rigid molecules. Second, we formulate the inverse participation ratio (IPR) of the INMs, respectively, for the O- and H-atom and molecule. With the IPRs, the numbers of the three species participated in the INMs are estimated so that the localization characters of the INMs in each band are studied. Further, by the ratio of the IPR of the H atom to that of the O atom, we explore the number of involved OH bond per molecule participated in the INMs. Third, by classifying simulated molecules into subensembles according to the geometry of their local environments or their H-bond configurations, we examine the local-structure effects on the bending and stretching INM bands. All of our results are verified to be insensible to the definition of H-bond. Our conclusions about the intermolecular and intramolecular vibrations in water are given.

  5. Instantaneous normal mode analysis for intermolecular and intramolecular vibrations of water from atomic point of view

    NASA Astrophysics Data System (ADS)

    Chen, Yu-Chun; Tang, Ping-Han; Wu, Ten-Ming

    2013-11-01

    By exploiting the instantaneous normal mode (INM) analysis for models of flexible molecules, we investigate intermolecular and intramolecular vibrations of water from the atomic point of view. With two flexible SPC/E models, our investigations include three aspects about their INM spectra, which are separated into the unstable, intermolecular, bending, and stretching bands. First, the O- and H-atom contributions in the four INM bands are calculated and their stable INM spectra are compared with the power spectra of the atomic velocity autocorrelation functions. The unstable and intermolecular bands of the flexible models are also compared with those of the SPC/E model of rigid molecules. Second, we formulate the inverse participation ratio (IPR) of the INMs, respectively, for the O- and H-atom and molecule. With the IPRs, the numbers of the three species participated in the INMs are estimated so that the localization characters of the INMs in each band are studied. Further, by the ratio of the IPR of the H atom to that of the O atom, we explore the number of involved OH bond per molecule participated in the INMs. Third, by classifying simulated molecules into subensembles according to the geometry of their local environments or their H-bond configurations, we examine the local-structure effects on the bending and stretching INM bands. All of our results are verified to be insensible to the definition of H-bond. Our conclusions about the intermolecular and intramolecular vibrations in water are given.

  6. Using Molecular Dynamics Simulation to Reinforce Student Understanding of Intermolecular Forces

    ERIC Educational Resources Information Center

    Burkholder, Phillip R.; Purser, Gordon H.; Cole, Renee S.

    2008-01-01

    Intermolecular forces play an important role in many aspects of chemistry ranging from inorganic to biological chemistry. These forces dictate molecular conformation, species aggregation (including self-assembly), trends in solubility and boiling points, adsorption characteristics, viscosity, phase changes, surface tension, capillary action, vapor…

  7. Intermolecular C-H Quaternary Alkylation of Aniline Derivatives Induced by Visible-Light Photoredox Catalysis.

    PubMed

    Cheng, Jie; Deng, Xia; Wang, Guoqiang; Li, Ying; Cheng, Xu; Li, Guigen

    2016-09-16

    The intermolecular direct C-H alkylation of aniline derivatives with α-bromo ketones to build a quaternary carbon center was reported with a visible-light catalysis procedure. The reaction covers a variety of functional groups with good to excellent yields. A regioselectivity favoring the ortho position for the amine group was observed and investigated with Fukui indices and spectral methods.

  8. Optical BEAMTAP beam-forming and jammer-nulling system for broadband phased-array antennas.

    PubMed

    Kriehn, G; Kiruluta, A; Silveira, P E; Weaver, S; Kraut, S; Wagner, K; Weverka, R T; Griffiths, L

    2000-01-10

    We present an approach to receive-mode broadband beam forming and jammer nulling for large adaptive antenna arrays as well as its efficient and compact optical implementation. This broadband efficient adaptive method for true-time-delay array processing (BEAMTAP) algorithm decreases the number of tapped delay lines required for processing an N-element phased-array antenna from N to only 2, producing an enormous savings in delay-line hardware (especially for large broadband arrays) while still providing the full NM degrees of freedom of a conventional N-element time-delay-and-sum beam former that requires N tapped delay lines with M taps each. This allows the system to adapt fully and optimally to an arbitrarily complex spatiotemporal signal environment that can contain broadband signals of interest, as well as interference sources and narrow-band and broadband jammers--all of which can arrive from arbitrary angles onto an arbitrarily shaped array--thus enabling a variety of applications in radar, sonar, and communication. This algorithm is an excellent match with the capabilities of radio frequency (rf) photonic systems, as it uses a coherent optically modulated fiber-optic feed network, gratings in a photorefractive crystal as adaptive weights, a traveling-wave detector for generating time delay, and an acousto-optic device to control weight adaptation. Because the number of available adaptive coefficients in a photorefractive crystal is as large as 10(9), these photonic systems can adaptively control arbitrarily large one- or two-dimensional antenna arrays that are well beyond the capabilities of conventional rf and real-time digital signal processing techniques or alternative photonic techniques.

  9. Optical BEAMTAP Beam-Forming and Jammer-Nulling System for Broadband Phased-Array Antennas

    NASA Astrophysics Data System (ADS)

    Kriehn, Gregory; Kiruluta, Andrew; Silveira, Paulo E. X.; Weaver, Sam; Kraut, Shawn; Wagner, Kelvin; Weverka, R. Ted; Griffiths, Lloyd

    2000-01-01

    We present an approach to receive-mode broadband beam forming and jammer nulling for large adaptive antenna arrays as well as its efficient and compact optical implementation. This broadband efficient adaptive method for true-time-delay array processing (BEAMTAP) algorithm decreases the number of tapped delay lines required for processing an N -element phased-array antenna from N to only 2, producing an enormous savings in delay-line hardware (especially for large broadband arrays) while still providing the full NM degrees of freedom of a conventional N -element time-delay-and-sum beam former that requires N tapped delay lines with M taps each. This allows the system to adapt fully and optimally to an arbitrarily complex spatiotemporal signal environment that can contain broadband signals of interest, as well as interference sources and narrow-band and broadband jammers all of which can arrive from arbitrary angles onto an arbitrarily shaped array thus enabling a variety of applications in radar, sonar, and communication. This algorithm is an excellent match with the capabilities of radio frequency (rf) photonic systems, as it uses a coherent optically modulated fiber-optic feed network, gratings in a photorefractive crystal as adaptive weights, a traveling-wave detector for generating time delay, and an acousto-optic device to control weight adaptation. Because the number of available adaptive coefficients in a photorefractive crystal is as large as 10 9 , these photonic systems can adaptively control arbitrarily large one- or two-dimensional antenna arrays that are well beyond the capabilities of conventional rf and real-time digital signal processing techniques or alternative photonic techniques.

  10. Characterization of Microemulsion Systems Formed by a Mixed 1,3-Dioxolane Ethoxylate / Octyl Glucoside Surfactant System

    SciTech Connect

    Alkhatib, Mayson H; Hayes, Douglas G; Urban, Volker S

    2009-01-01

    The phase behavior of microemulsion systems containing water (or 1.0 wt% NaCl{sub aq}), isooctane, and the binary surfactant system consisting of n-octyl-{beta}-D-glucopyranoside, C{sub 8}{beta}G{sub 1}, and the acid-cleavable alkyl ethoxylate, 4-CH{sub 3}O (CH{sub 2}CH{sub 2}O){sub 7.2}, 2-(CH{sub 2}){sub 12}CH{sub 3}, 2-(CH{sub 2})CH{sub 3}, 1,3-dioxolane, or 'cyclic ketal' ('CK-2,13'), was determined. Large temperature-insensitive one, two, and three-phase microemulsion-phase regions were obtained when equal masses of the two surfactants were employed, suggesting that C{sub 8}{beta}G{sub 1} reduces the temperature sensitivity of CK-2,13's ethoxylate group. Addition of C{sub 8}{beta}G{sub 1} to CK-2,13 greatly improves the latter's low efficiency, evidenced by the formation of a three-phase microemulsion system for surfactant concentrations at low fractions of total surfactants for systems with equal mass ratios of water to oil and CK-2,13 to C{sub 8}{beta}G{sub 1}. Analysis of the phase diagrams also suggests that CK-2,13 and C{sub 8}{beta}G{sub 1} impart hydrophobic and hydrophilic character, respectively, to the surfactant mixture, and that addition of salt further increases the hydrophilicity of C{sub 8}{beta}G{sub 1}, presumably because of the salting-in of the latter. Analysis of small-angle neutron scattering data revealed that the mixed surfactant system formed spherical oil-in-water microemulsions, and that increasing the CK-2,13 fraction among the surfactants reduced the critical microemulsion concentration but slightly increased the nanodroplet size.

  11. Laboratory flume experiments for characterising Martian channels formed by distinct groundwater systems

    NASA Astrophysics Data System (ADS)

    Marra, Wouter A.; Kleinhans, Maarten G.; McLelland, Stuart J.; Murphy, Brendan J.; Parsons, Daniel R.; Conway, Susan J.; Hauber, Ernst

    2013-04-01

    Channels on Mars have been found in many locations and across all possible scales, suggesting the presence of flowing water in the past. Several hypotheses for the formation of these channels have been proposed, including a role for groundwater. In this study we explored the development of channel morphology for three types of groundwater systems: 1) seepage from a regional groundwater system, 2) seepage from local precipitation and 3) groundwater release from a pressurised aquifer. We performed a series of scale experiments to study the morphological development of different scenarios. Smaller scale experiments were conducted in a setup of 1x3x0.25 m (at UU) using lightweight plastic sediment. Larger scale experiments were conducted in a setup of 4x6x1 m (at UoH) using sand. To simulate the three aforementioned hydrological conditions, 1) a constant sub-surface hydraulic head was applied using a header tank connected to the sediment, 2) a series of rainfall simulator nozzles were used (UoH setup only) and 3) a super-surface hydraulic pressure was applied to a perforated pipe beneath the sediment. The two scales of experiments allow us to assess the scalability to real-world conditions. We collected detailed DEMs and time-lapse imagery of the morphological development of the sediment surface. In the regional groundwater experiments, elongated valleys with circular, steep head walls developed, with depths down to the groundwater table. The valley heads and sides developed as a result of mass wasting processes; within the valley material was transported by fluvial processes. Multiple parallel valleys formed initially, but one or two eventually capture most of the outflow and became larger than the pirated valleys. In the precipitation-fed seepage experiments, groundwater flowed from all directions into valleys rather than just from upstream. Again, multiple parallel valleys with semi-circular heads formed but the valleys were shallower and wider. Channel formation by

  12. Frontier orbital symmetry control of intermolecular electron transfer

    SciTech Connect

    Stevens, B.

    1991-09-01

    This report contains sections describing the selection of electron donor-acceptor systems, the synthesis and photophysical properties of linked electron-donor-acceptor systems, the estimation of photoinduced charge-separation rate constants from fluorescence quenching data, and radical ion-pair recombination by picosecond transient absorption spectroscopy. 9 refs., 1 fig., 7 tabs.

  13. A novel bioprinting method and system for forming hybrid tissue engineering constructs.

    PubMed

    Shanjani, Y; Pan, C C; Elomaa, L; Yang, Y

    2015-01-01

    Three dimensional (3D) bioprinting is a promising approach to form tissue engineering constructs (TECs) via positioning biomaterials, growth factors, and cells with controlled spatial distribution due to its layer-by-layer manufacturing nature. Hybrid TECs composed of relatively rigid porous scaffolds for structural and mechanical integrity and soft hydrogels for cell- and growth factor-loading have a tremendous potential to tissue regeneration under mechanical loading. However, despite excessive progress in the field, the current 3D bioprinting techniques and systems fall short in integration of such soft and rigid multifunctional components. Here we present a novel 3D hybrid bioprinting technology (Hybprinter) and its capability enabling integration of soft and rigid components for TECs. Hybprinter employs digital light processing-based stereolithography (DLP-SLA) and molten material extrusion techniques for soft and rigid materials, respectively. In this study, poly-ethylene glycol diacrylate (PEGDA) and poly-(ε-caprolactone) (PCL) were used as a model material for soft hydrogel and rigid scaffold, respectively. It was shown that geometrical accuracy, swelling ratio and mechanical properties of the hydrogel component can be tailored by DLP-SLA module. We have demonstrated the printability of variety of complex hybrid construct designs using Hybprinter technology and characterized the mechanical properties and functionality of such constructs. The compressive mechanical stiffness of a hybrid construct (90% hydrogel) was significantly higher than hydrogel itself (∼6 MPa versus 100 kPa). In addition, viability of cells incorporated within the bioprinted hybrid constructs was determined approximately 90%. Furthermore, a functionality of a hybrid construct composed of porous scaffold with an embedded hydrogel conduit was characterized for vascularized tissue engineering applications. High material diffusion and high cell viability in about 2.5 mm distance

  14. A novel bioprinting method and system for forming hybrid tissue engineering constructs.

    PubMed

    Shanjani, Y; Pan, C C; Elomaa, L; Yang, Y

    2015-01-01

    Three dimensional (3D) bioprinting is a promising approach to form tissue engineering constructs (TECs) via positioning biomaterials, growth factors, and cells with controlled spatial distribution due to its layer-by-layer manufacturing nature. Hybrid TECs composed of relatively rigid porous scaffolds for structural and mechanical integrity and soft hydrogels for cell- and growth factor-loading have a tremendous potential to tissue regeneration under mechanical loading. However, despite excessive progress in the field, the current 3D bioprinting techniques and systems fall short in integration of such soft and rigid multifunctional components. Here we present a novel 3D hybrid bioprinting technology (Hybprinter) and its capability enabling integration of soft and rigid components for TECs. Hybprinter employs digital light processing-based stereolithography (DLP-SLA) and molten material extrusion techniques for soft and rigid materials, respectively. In this study, poly-ethylene glycol diacrylate (PEGDA) and poly-(ε-caprolactone) (PCL) were used as a model material for soft hydrogel and rigid scaffold, respectively. It was shown that geometrical accuracy, swelling ratio and mechanical properties of the hydrogel component can be tailored by DLP-SLA module. We have demonstrated the printability of variety of complex hybrid construct designs using Hybprinter technology and characterized the mechanical properties and functionality of such constructs. The compressive mechanical stiffness of a hybrid construct (90% hydrogel) was significantly higher than hydrogel itself (∼6 MPa versus 100 kPa). In addition, viability of cells incorporated within the bioprinted hybrid constructs was determined approximately 90%. Furthermore, a functionality of a hybrid construct composed of porous scaffold with an embedded hydrogel conduit was characterized for vascularized tissue engineering applications. High material diffusion and high cell viability in about 2.5 mm distance

  15. Copper-Catalyzed Intermolecular Amidation and Imidation of Unactivated Alkanes

    PubMed Central

    2015-01-01

    We report a set of rare copper-catalyzed reactions of alkanes with simple amides, sulfonamides, and imides (i.e., benzamides, tosylamides, carbamates, and phthalimide) to form the corresponding N-alkyl products. The reactions lead to functionalization at secondary C–H bonds over tertiary C–H bonds and even occur at primary C–H bonds. [(phen)Cu(phth)] (1-phth) and [(phen)Cu(phth)2] (1-phth2), which are potential intermediates in the reaction, have been isolated and fully characterized. The stoichiometric reactions of 1-phth and 1-phth2 with alkanes, alkyl radicals, and radical probes were investigated to elucidate the mechanism of the amidation. The catalytic and stoichiometric reactions require both copper and tBuOOtBu for the generation of N-alkyl product. Neither 1-phth nor 1-phth2 reacted with excess cyclohexane at 100 °C without tBuOOtBu. However, the reactions of 1-phth and 1-phth2 with tBuOOtBu afforded N-cyclohexylphthalimide (Cy-phth), N-methylphthalimide, and tert-butoxycyclohexane (Cy-OtBu) in approximate ratios of 70:20:30, respectively. Reactions with radical traps support the intermediacy of a tert-butoxy radical, which forms an alkyl radical intermediate. The intermediacy of an alkyl radical was evidenced by the catalytic reaction of cyclohexane with benzamide in the presence of CBr4, which formed exclusively bromocyclohexane. Furthermore, stoichiometric reactions of [(phen)Cu(phth)2] with tBuOOtBu and (Ph(Me)2CO)2 at 100 °C without cyclohexane afforded N-methylphthalimide (Me-phth) from β-Me scission of the alkoxy radicals to form a methyl radical. Separate reactions of cyclohexane and d12-cyclohexane with benzamide showed that the turnover-limiting step in the catalytic reaction is the C–H cleavage of cyclohexane by a tert-butoxy radical. These mechanistic data imply that the tert-butoxy radical reacts with the C–H bonds of alkanes, and the subsequent alkyl radical combines with 1-phth2 to form the corresponding N-alkyl imide product

  16. Intermolecular interactions in a radiation field via the method of induced moments

    SciTech Connect

    Salam, A.

    2006-01-15

    Molecular quantum electrodynamics is employed to calculate a generalized formula for the energy shift between a pair of molecules that have electric polarizability of arbitrary multipole order and are in the presence of an intense electromagnetic field. In contrast to a previous calculation of the dipole-dipole contribution, which required fourth-order time-dependent perturbation theory for its evaluation, the present approach involves calculating the interaction between the multipole moments induced at each center by the incident beam and the resonant multipole-multipole coupling tensor together with the average value of the spatial correlation function of the displacement field for an N-photon state. The theory developed applies to the situation where the molecular pair is held fixed relative to the direction of propagation of the radiation field or is allowed to be completely randomly oriented. Explicit results are obtained for dipole-quadrupole and quadrupole-quadrupole polarizable molecules. For oriented systems the energy shift for linear and circular polarizations is examined for incident radiation propagating in directions parallel and perpendicular to the intermolecular join, and the asymptotic behavior is obtained at the limits of short and large separation distance. After performing a pair orientation average, the energy shift in the near zone is found to exhibit an R{sup -1} power-law behavior with separation distance, while the far zone has a modulated R{sup -2} dependence in all of the cases considered. None of the energy shifts obtained display discriminatory characteristics, with respect to either the handedness of the incident beam or the individual species.

  17. Cross-dehydrogenative coupling for the intermolecular C–O bond formation

    PubMed Central

    Krylov, Igor B; Vil’, Vera A

    2015-01-01

    Summary The present review summarizes primary publications on the cross-dehydrogenative C–O coupling, with special emphasis on the studies published after 2000. The starting compound, which donates a carbon atom for the formation of a new C–O bond, is called the CH-reagent or the C-reagent, and the compound, an oxygen atom of which is involved in the new bond, is called the OH-reagent or the O-reagent. Alcohols and carboxylic acids are most commonly used as O-reagents; hydroxylamine derivatives, hydroperoxides, and sulfonic acids are employed less often. The cross-dehydrogenative C–O coupling reactions are carried out using different C-reagents, such as compounds containing directing functional groups (amide, heteroaromatic, oxime, and so on) and compounds with activated C–H bonds (aldehydes, alcohols, ketones, ethers, amines, amides, compounds containing the benzyl, allyl, or propargyl moiety). An analysis of the published data showed that the principles at the basis of a particular cross-dehydrogenative C–O coupling reaction are dictated mainly by the nature of the C-reagent. Hence, in the present review the data are classified according to the structures of C-reagents, and, in the second place, according to the type of oxidative systems. Besides the typical cross-dehydrogenative coupling reactions of CH- and OH-reagents, closely related C–H activation processes involving intermolecular C–O bond formation are discussed: acyloxylation reactions with ArI(O2CR)2 reagents and generation of O-reagents in situ from C-reagents (methylarenes, aldehydes, etc.). PMID:25670997

  18. Photo-induced spin transition of Iron(III) compounds with pi-pi intermolecular interactions.

    PubMed

    Hayami, Shinya; Hiki, Kenji; Kawahara, Takayoshi; Maeda, Yonezo; Urakami, Daisuke; Inoue, Katsuya; Ohama, Mitsuo; Kawata, Satoshi; Sato, Osamu

    2009-01-01

    Iron(III) spin-crossover compounds [Fe(pap)(2)]ClO(4) (1), [Fe(pap)(2)]BF(4) (2), [Fe(pap)(2)]PF(6) (3), [Fe(qsal)(2)]NCS (4), and [Fe(qsal)(2)]NCSe (5) (Hpap=2-(2-pyridylmethyleneamino)phenol and Hqsal=2-[(8-quinolinylimino)methyl]phenol) were prepared and their spin-transition properties investigated by magnetic susceptibility and Mössbauer spectroscopy measurements. The iron(III) compounds exhibited spin transition with thermal hysteresis. Single crystals of the iron(III) compounds were obtained as suitable solvent adducts for X-ray analysis, and structures in high-spin (HS) and low-spin (LS) states were revealed. Light-induced excited-spin-state trapping (LIESST) effects of the iron(III) compounds were induced by light irradiation at 532 nm for 1-3 and at 800 nm for 4 and 5. The activation energy E(a) and the low-temperature tunneling rate k(HL)(T-->0) of iron(III) LIESST compound 1 were estimated to be 1079 cm(-1) and 2.4x10(-8) s(-1), respectively, by HS-->LS relaxation experiments. The Huang-Rhys factor S of 1 was also estimated to be 50, which was similar to that expected for iron(II) complexes. It is thought that the slow relaxation in iron(III) systems is achieved by the large structural distortion between HS and LS states. Introduction of strong intermolecular interactions, such as pi-pi stacking, can also play an important role in the relaxation behavior, because it can enhance the structural distortion of the LIESST complex. PMID:19191246

  19. Enhancing intermolecular benzoyl-transfer reactivity in crystals by growing a "reactive" metastable polymorph by using a chiral additive.

    PubMed

    Murali, Chebrolu; Shashidhar, Mysore S; Gonnade, Rajesh G; Bhadbhade, Mohan M

    2009-01-01

    Racemic 2,4-di-O-benzoyl-myo-inositol-1,3,5-orthoacetate, which normally crystallizes in a monoclinic form (form I, space group P2(1)/n) could be persuaded to crystallize out as a metastable polymorph (form II, space group C2/c) by using a small amount of either D- or L- 2,4-di-O-benzoyl-myo-inositol-1,3,5-orthoformate as an additive in the crystallization medium. The structurally similar enantiomeric additive was chosen by the scrutiny of previous experimental results on the crystallization of racemic 2,4-di-O-benzoyl-myo-inositol-1,3,5-orthoacetate. Form II crystals can be thermally transformed to form I crystals at about 145 degrees C. The relative organization of the molecules in these dimorphs vary slightly in terms of the helical assembly of molecules, that is, electrophile (El)...nucleophile (Nu) and C-H...pi interactions, but these minor variations have a profound effect on the facility and specificity of benzoyl-group-transfer reactivity in the two crystal forms. While form II crystals undergo a clean intermolecular benzoyl-group-transfer reaction, form I crystals are less reactive and undergo non-specific benzoyl-group transfer leading to a mixture of products. The role played by the additive in fine-tuning small changes that are required in the molecular packing opens up the possibility of creating new polymorphs that show varied physical and chemical properties. Crystals of D-2,6-di-O-benzoyl-myo-inositol-1,3,5-orthoformate (additive) did not show facile benzoyl-group-transfer reactivity (in contrast to the corresponding racemic compound) due to the lack of proper juxtaposition and assembly of molecules.

  20. 17 CFR 249.821 - Form PILOT, information required of self-regulatory organizations operating pilot trading systems...

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 17 Commodity and Securities Exchanges 3 2010-04-01 2010-04-01 false Form PILOT, information required of self-regulatory organizations operating pilot trading systems pursuant to § 240.19b-5 of this... Associations § 249.821 Form PILOT, information required of self-regulatory organizations operating...

  1. Intermolecular forces in acetonitrile + ethanol binary liquid mixtures

    NASA Astrophysics Data System (ADS)

    Elangovan, A.; Shanmugam, R.; Arivazhagan, G.; Mahendraprabu, A.; Karthick, N. K.

    2015-10-01

    FTIR spectral measurements have been carried out on the binary mixtures of acetonitrile with ethanol at 1:0 (acetonitrile:ethanol), 1:1, 1:2, 1:3 and 0:1 at room temperature. DFT and isosurface calculations have been performed. The acetonitrile + ethanol binary mixtures consist of 1:1, 1:2, 1:3 and 1:4 complexes formed through both the red and blue shifting H-bonds. Inter as well as intra molecular forces are found to exist in 1:3 and 1:4 complexes.

  2. The origins of intra- and inter-molecular vibrational couplings: A case study of H2O-Ar on full and reduced-dimensional potential energy surface.

    PubMed

    Hou, Dan; Ma, Yong-Tao; Zhang, Xiao-Long; Li, Hui

    2016-01-01

    The origin and strength of intra- and inter-molecular vibrational coupling is difficult to probe by direct experimental observations. However, explicitly including or not including some specific intramolecular vibrational modes to study intermolecular interaction provides a precise theoretical way to examine the effects of anharmonic coupling between modes. In this work, a full-dimension intra- and inter-molecular ab initio potential energy surface (PES) for H2O-Ar, which explicitly incorporates interdependence on the intramolecular (Q1,  Q2,  Q3) normal-mode coordinates of the H2O monomer, has been calculated. In addition, four analytic vibrational-quantum-state-specific PESs are obtained by least-squares fitting vibrationally averaged interaction energies for the (v1,  v2,  v3) =  (0,  0,  0), (0,  0,  1), (1,  0,  0), (0,  1,  0) states of H2O to the three-dimensional Morse/long-range potential function. Each vibrationally averaged PES fitted to 442 points has root-mean-square (rms) deviation smaller than 0.15 cm(-1), and required only 58 parameters. With the 3D PESs of H2O-Ar dimer system, we employed the combined radial discrete variable representation/angular finite basis representation method and Lanczos algorithm to calculate rovibrational energy levels. This showed that the resulting vibrationally averaged PESs provide good representations of the experimental infrared data, with rms discrepancies smaller than 0.02 cm(-1) for all three rotational branches of the asymmetric stretch fundamental transitions. The infrared band origin shifts associated with three fundamental bands of H2O in H2O-Ar complex are predicted for the first time and are found to be in good agreement with the (extrapolated) experimental values. Upon introduction of additional intramolecular degrees of freedom into the intermolecular potential energy surface, there is clear spectroscopic evidence of intra- and intermolecular vibrational couplings.

  3. Intramolecular photo-switching and intermolecular energy transfer as primary photoevents in photoreceptive processes: The case of Euglena gracilis

    SciTech Connect

    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{sub 498,} non fluorescent and B{sub 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{sub 498} becomes B{sub 462}), and a intermolecular and unidirectional Forster-type energy transfer. During the FRET process, the fluorescent B{sub 462} form acts as donor for the non-fluorescent A{sub 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.

  4. An intermolecular electrostatic interaction controls the prepore-to-pore transition in a cholesterol-dependent cytolysin

    PubMed Central

    Wade, Kristin R.; Hotze, Eileen M.; Kuiper, Michael J.; Morton, Craig J.; Parker, Michael W.; Tweten, Rodney K.

    2015-01-01

    β-Barrel pore-forming toxins (βPFTs) form an obligatory oligomeric prepore intermediate before the formation of the β-barrel pore. The molecular components that control the critical prepore-to-pore transition remain unknown for βPFTs. Using the archetype βPFT perfringolysin O, we show that E183 of each monomer within the prepore complex forms an intermolecular electrostatic interaction with K336 of the adjacent monomer on completion of the prepore complex. The signal generated throughout the prepore complex by this interaction irrevocably commits it to the formation of the membrane-inserted giant β-barrel pore. This interaction supplies the free energy to overcome the energy barrier (determined here to be ∼19 kcal/mol) to the prepore-to-pore transition by the coordinated disruption of a critical interface within each monomer. These studies provide the first insight to our knowledge into the molecular mechanism that controls the prepore-to-pore transition for a βPFT. PMID:25646411

  5. Universal scaling of potential energy functions describing intermolecular interactions. II. The halide-water and alkali metal-water interactions

    SciTech Connect

    Werhahn, Jasper C.; Akase, Dai; Xantheas, Sotiris S.

    2014-08-14

    The scaled versions of the newly introduced [S. S. Xantheas and J. C. Werhahn, J. Chem. Phys.141, 064117 (2014)] generalized forms of some popular potential energy functions (PEFs) describing intermolecular interactions – Mie, Lennard-Jones, Morse, and Buckingham exponential-6 – have been used to fit the ab initio relaxed approach paths and fixed approach paths for the halide-water, X-(H2O), X = F, Cl, Br, I, and alkali metal-water, M+(H2O), M = Li, Na, K, Rb, Cs, interactions. The generalized forms of those PEFs have an additional parameter with respect to the original forms and produce fits to the ab initio data that are between one and two orders of magnitude better in the χ2 than the original PEFs. They were found to describe both the long-range, minimum and repulsive wall of the respective potential energy surfaces quite accurately. Overall the 4-parameter extended Morse (eM) and generalized Buckingham exponential-6 (gBe-6) potentials were found to best fit the ab initio data for these two classes of ion-water interactions. Finally, the fitted values of the parameter of the (eM) and (gBe-6) PEFs that control the repulsive wall of the potential correlate remarkably well with the ionic radii of the halide and alkali metal ions.

  6. Method and system for constructing a rechargeable battery and battery structures formed with the method

    DOEpatents

    Hobson, David O.; Snyder, Jr., William B.

    1995-01-01

    A method and system for manufacturing a thin-film battery and a battery structure formed with the method utilizes a plurality of deposition stations at which thin battery component films are built up in sequence upon a web-like substrate as the substrate is automatically moved through the stations. At an initial station, cathode and anode current collector film sections are deposited upon the substrate, and at another station, a thin cathode film is deposited upon the substrate so to overlie part of the cathode current collector section. At another station, a thin electrolyte film is deposited upon so as to overlie the cathode film and part of the anode current collector film, at yet another station, a thin lithium film is deposited upon so as to overlie the electrolyte film and an additional part of the anode current collector film. Such a method accommodates the winding of a layup of battery components into a spiral configuration to provide a thin-film, high capacity battery and also accommodates the build up of thin film battery components onto a substrate surface having any of a number of shapes.

  7. Sparse electrocardiogram signals recovery based on solving a row echelon-like form of system.

    PubMed

    Cai, Pingmei; Wang, Guinan; Yu, Shiwei; Zhang, Hongjuan; Ding, Shuxue; Wu, Zikai

    2016-02-01

    The study of biology and medicine in a noise environment is an evolving direction in biological data analysis. Among these studies, analysis of electrocardiogram (ECG) signals in a noise environment is a challenging direction in personalized medicine. Due to its periodic characteristic, ECG signal can be roughly regarded as sparse biomedical signals. This study proposes a two-stage recovery algorithm for sparse biomedical signals in time domain. In the first stage, the concentration subspaces are found in advance. Then by exploiting these subspaces, the mixing matrix is estimated accurately. In the second stage, based on the number of active sources at each time point, the time points are divided into different layers. Next, by constructing some transformation matrices, these time points form a row echelon-like system. After that, the sources at each layer can be solved out explicitly by corresponding matrix operations. It is noting that all these operations are conducted under a weak sparse condition that the number of active sources is less than the number of observations. Experimental results show that the proposed method has a better performance for sparse ECG signal recovery problem. PMID:26816398

  8. A proposal for a drug product Manufacturing Classification System (MCS) for oral solid dosage forms.

    PubMed

    Leane, Michael; Pitt, Kendal; Reynolds, Gavin

    2015-01-01

    This paper proposes the development of a drug product Manufacturing Classification System (MCS) based on processing route. It summarizes conclusions from a dedicated APS conference and subsequent discussion within APS focus groups and the MCS working party. The MCS is intended as a tool for pharmaceutical scientists to rank the feasibility of different processing routes for the manufacture of oral solid dosage forms, based on selected properties of the API and the needs of the formulation. It has many applications in pharmaceutical development, in particular, it will provide a common understanding of risk by defining what the "right particles" are, enable the selection of the best process, and aid subsequent transfer to manufacturing. The ultimate aim is one of prediction of product developability and processability based upon previous experience. This paper is intended to stimulate contribution from a broad range of stakeholders to develop the MCS concept further and apply it to practice. In particular, opinions are sought on what API properties are important when selecting or modifying materials to enable an efficient and robust pharmaceutical manufacturing process. Feedback can be given by replying to our dedicated e-mail address (mcs@apsgb.org); completing the survey on our LinkedIn site; or by attending one of our planned conference roundtable sessions.

  9. Discovery of a solid solution of enantiomers in a racemate-forming system by seeding.

    PubMed

    Huang, Jun; Chen, Shuang; Guzei, Ilia A; Yu, Lian

    2006-09-13

    A racemic liquid of opposite enantiomers usually crystallizes as a racemic compound (racemate), rarely as a conglomerate, and even more rarely as a solid solution. We discovered a Type II solid solution (mixed crystal) of the enantiomers of the chiral drug tazofelone (TZF) by seeding its racemic liquid with enantiomerically pure crystals (enantiomorphs). Without seeding, the racemic liquid crystallized as a racemic compound. The crystal structure of this solid solution resembles that of the enantiomorph but has static disorder arising from the random substitution of enantiomers. This solid solution is a kinetic product of crystallization made possible by its faster growth rate compared to that of the competing racemate (by 4- to 40-fold between 80 and 146 degrees C). The free energy of the solid solution continuously varies with the enantiomeric composition between those of the conglomerate and the racemates. The existence of the TZF solid solution explains the absence of eutectic melting between crystals of different enantiomeric compositions. The ability of TZF to simultaneously form racemate and solid solution originates from its conformational flexibility. Similar solid solutions of enantiomers may exist in other systems and may be discovered in similar ways. The study demonstrates the use of cross-nucleation for discovering and engineering crystalline materials to optimize physical properties.

  10. Circulating colony-forming units of granulocytes and monocytes/macrophages in systemic lupus erythematosus.

    PubMed Central

    López-Karpovitch, X; Cardiel, M; Cardenas, R; Piedras, J; Alarcón-Segovia, D

    1989-01-01

    In systemic lupus erythematosus (SLE) patients, in vitro bone marrow (BM) colony-forming units of granulocytes and monocytes/macrophages (CFU-GM) are decreased, suggesting that granulomonopoietic failure may play an important role in the mechanism of peripheral blood (PB) depletion of neutrophils and monocytes. No information concerning CFU-GM in PB of patients with SLE is available. The present study was undertaken in order to determine whether SLE itself and the inactive or active stage of disease would modify the number of GFU-GM in PB samples from 20 treatment-free SLE women, 12 inactive and eight active. CFU-GM growth was significantly decreased in both inactive (P = 0.018) and active (P = 0.008) SLE patients as compared with controls (n = 8). The difference in CFU-GM growth between SLE groups was not significant. These results indicate that the number of circulating CFU-GM is significantly reduced in patients with SLE regardless of disease activity or remission. PMID:2766577

  11. Droplet-based microfluidic system to form and separate multicellular spheroids using magnetic nanoparticles.

    PubMed

    Yoon, Sungjun; Kim, Jeong Ah; Lee, Seung Hwan; Kim, Minsoo; Park, Tai Hyun

    2013-04-21

    The importance of creating a three-dimensional (3-D) multicellular spheroid has recently been gaining attention due to the limitations of monolayer cell culture to precisely mimic in vivo structure and cellular interactions. Due to this emerging interest, researchers have utilized new tools, such as microfluidic devices, that allow high-throughput and precise size control to produce multicellular spheroids. We have developed a droplet-based microfluidic system that can encapsulate both cells and magnetic nanoparticles within alginate beads to mimic the function of a multicellular tumor spheroid. Cells were entrapped within the alginate beads along with magnetic nanoparticles, and the beads of a relatively uniform size (diameters of 85% of the beads were 170-190 μm) were formed in the oil phase. These beads were passed through parallel streamlines of oil and culture medium, where the beads were magnetically transferred into the medium phase from the oil phase using an external magnetic force. This microfluidic chip eliminates additional steps for collecting the spheroids from the oil phase and transferring them to culture medium. Ultimately, the overall spheroid formation process can be achieved on a single microchip. PMID:23426090

  12. Intermolecular potential functions from spectroscopic properties of weakly bound complexes. Third progress report, July 1, 1991--June 30, 1992

    SciTech Connect

    Muenter, J.S.

    1992-08-01

    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. Helping Students Assess the Relative Importance of Different Intermolecular Interactions

    ERIC Educational Resources Information Center

    Jasien, Paul G.

    2008-01-01

    A semi-quantitative model has been developed to estimate the relative effects of dispersion, dipole-dipole interactions, and H-bonding on the normal boiling points ("T[subscript b]") for a subset of simple organic systems. The model is based upon a statistical analysis using multiple linear regression on a series of straight-chain organic…

  14. Tracking the energy input form the magnetosphere to the ionosphere-thermosphere system

    NASA Astrophysics Data System (ADS)

    Zesta, E.; Connor, H.; Shi, Y.; Raeder, J.; Fedrizzi, M.; Fuller-Rowell, T. J.; Codrescu, M.

    2014-12-01

    During geomagnetically active times, the ionosphere - thermosphere (IT) system is strongly affected by magnetospheric energy that comes in the form of auroral particle precipitation and Poynting flux. This ultimately results in the increase of the thermospheric mass density, a critical parameter not only for determining and predicting air drag on satellites, but also for understanding the solar wind - magnetosphere- IT coupling. We use observations and model simulations to explore when, where and how energy transfers from the solar wind through the magnetosphere and is deposited into the IT system during solar wind disturbances. We observe and simulate dynamic pressure impacts on the magnetosphere and a magnetic storm main phase. We use thermospheric density observations from the CHAMP and GRACE satellites and Poynting flux measurements from Defense Meteorological Satellite Platform (DMSP) satellites. We show that the thermosphere density as well as the downward Poynting flux intensified shortly after (within ~20 min) the sudden enhancement of the solar wind dynamic pressure mostly in the dayside auroral zone and polar cap regions with the peaks in the vicinity of the cusp. Simulations from the two-way coupled OpenGGCM-CTIM magnetosphere-ionosphere-thermosphere model show that the ionospheric Joule heating also increases abruptly along with the sudden enhancement of the dynamic pressure in the same regions. The modeling results show that the pair of high-latitude localized cusp field-aligned currents (FACs) are intensified and extended azimuthally as a result of the enhanced dayside high-latitude reconnection caused by the sudden increase of the solar wind dynamic pressure. They are likely the source of the enhanced Joule heating and the ensuing thermospheric heating in that region. We also look at the first hours of a magnetic storm main phase where the picture is significantly more complex, but Poynting flux and thermospheric density first enhance at polar

  15. The L723 Low-Mass Star Forming Protostellar System: Resolving a Double Core

    NASA Astrophysics Data System (ADS)

    Girart, J. M.; Rao, R.; Estalella, R.

    2009-03-01

    We present 1.35 mm Submillimeter Array (SMA) observations around the low-mass Class 0 source IRAS 19156+1906, at the center of the LDN 723 (L723) dark cloud. We detected emission from dust as well as emission from H2CO 30,3-20,2, DCN 3-2, and CN 2-1 lines, which arise from two cores, SMA 1 and SMA 2, separated by 2farcs9 (880 AU in projected distance). SMA 2 is associated with the previously detected source VLA 2. Weak SiO 5-4 emission is detected, possibly tracing a region of interaction between the dense envelope and the outflow. We modeled the dust and H2CO emission from the two cores. The results from the modeling show that the cores have similar physical properties (density and temperature distribution) but that SMA 2 has a larger p-H2CO abundance (by a factor of 3-10) than SMA 1. The p-H2CO abundances' findings are compatible with the value of the outer part of the circumstellar envelopes associated with Class 0 sources. SMA 2 is harboring an active multiple low-mass protostellar system and powering at least one molecular outflow. In contrast, there are no known signs of outflow activity toward SMA 1. This suggests that SMA 2 is more evolved than SMA 1. The kinematics of the two sources show marginal evidence of infall and rotation motions. The mass detected by the SMA observation, which trace scales of lsim1000 AU, is only a small fraction of the mass contained in the large-scale molecular envelope, which suggests that L723 is still in a very early phase of star formation. Despite the apparent quiescent nature of the L723, fragmentation is occurring at the center of the cloud at different scales. Thus, at sime1000 AU, the cloud has fragmented in two cores: SMA 1 and SMA 2. At the same time, at least one of these cores, SMA 2, has undergone additional fragmentation at scales of sime150 AU, forming a multiple stellar system.

  16. 49 CFR Appendix H to Part 40 - DOT Drug and Alcohol Testing Management Information System (MIS) Data Collection Form

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ..., App. H Appendix H to Part 40—DOT Drug and Alcohol Testing Management Information System (MIS) Data... 49 Transportation 1 2011-10-01 2011-10-01 false DOT Drug and Alcohol Testing Management Information System (MIS) Data Collection Form H Appendix H to Part 40 Transportation Office of the...

  17. 49 CFR Appendix H to Part 40 - DOT Drug and Alcohol Testing Management Information System (MIS) Data Collection Form

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 49 Transportation 1 2010-10-01 2010-10-01 false DOT Drug and Alcohol Testing Management Information System (MIS) Data Collection Form H Appendix H to Part 40 Transportation Office of the Secretary..., App. H Appendix H to Part 40—DOT Drug and Alcohol Testing Management Information System (MIS)...

  18. 49 CFR Appendix H to Part 40 - DOT Drug and Alcohol Testing Management Information System (MIS) Data Collection Form

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ..., App. H Appendix H to Part 40—DOT Drug and Alcohol Testing Management Information System (MIS) Data... 49 Transportation 1 2014-10-01 2014-10-01 false DOT Drug and Alcohol Testing Management Information System (MIS) Data Collection Form H Appendix H to Part 40 Transportation Office of the...

  19. 49 CFR Appendix H to Part 40 - DOT Drug and Alcohol Testing Management Information System (MIS) Data Collection Form

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ..., App. H Appendix H to Part 40—DOT Drug and Alcohol Testing Management Information System (MIS) Data... 49 Transportation 1 2013-10-01 2013-10-01 false DOT Drug and Alcohol Testing Management Information System (MIS) Data Collection Form H Appendix H to Part 40 Transportation Office of the...

  20. 49 CFR Appendix H to Part 40 - DOT Drug and Alcohol Testing Management Information System (MIS) Data Collection Form

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ..., App. H Appendix H to Part 40—DOT Drug and Alcohol Testing Management Information System (MIS) Data... 49 Transportation 1 2012-10-01 2012-10-01 false DOT Drug and Alcohol Testing Management Information System (MIS) Data Collection Form H Appendix H to Part 40 Transportation Office of the...

  1. Hydrogeochemistry Of A Modern Dolomite-Forming Lagoon System, Cabo Frio-RJ, Brazil

    NASA Astrophysics Data System (ADS)

    Moreira, N. F.; Walter, L. M.

    2004-12-01

    Two hypersaline, dolomite-forming lagoons near Cabo Frio, Brazil, and associated ground- and surface waters were sampled in a comparative sediment and fluid geochemical (solutes, stable isotopes) investigation. Although microbial mediation via sulfate reducers has been invoked to explain dolomite formation in these lagoons, we showed that dolomites are associated with sulfide oxidation (Moreira et al., 2004). Sulfide oxidation is thought to promote dolomite formation by causing undersaturation for competing carbonate phases such as Mg-calcite. Herein, we consider the larger hydrogeologic and temporal setting to further elucidate hydrogeochemical and geochemical constraints on rates and mechanisms of dolomite formation in the two lagoons. The lagoons, Brejo do Espinho (BE) and Lagoa Vermelha (LV), are shallow marginal marine systems flanked by quartz sand dunes separating them from Atlantic open seawater to the south and from Araruama lagoon, a large, hypersaline water body, to the north. In both lagoons, about 1 m of high Mg-calcite and dolomite mud has accumulated over the last 5,000 years on an underlying aquifer composed of highly permeable, quartz-rich coquinas. BE has a proximal relation to recharge from Araruama lagoon, while LV is more closely associated with meteoric recharge from lacustrine and riverine systems. BE is shallower, at 0.5 m water depth, than LV (2 m), permitting BE waters to remain oxic. Oxygen isotope values and chloride mass balances of pore waters and of fluids sampled from shallow ground water wells identify the different water and solute sources the lagoons. BE overlying brines and pore waters appear to be produced by evapoconcentration of Araruama source brines and meteoric precipitation. In contrast, LV derives from evapoconcentrated seawater mixed with regional lake and ground water sources. We envision a scenario in which dense, Mg-SO4-rich brines from Araruama migrate along a permeable flowpath in limited contact with the atmosphere

  2. Intermolecular interactions of trifluorohalomethanes with Lewis bases in the gas phase: An ab initio study

    SciTech Connect

    Wang, Yi-Siang; Yin, Chih-Chien; Chao, Sheng D.

    2014-10-07

    We perform an ab initio computational study of molecular complexes with the general formula CF{sub 3}X—B that involve one trifluorohalomethane CF{sub 3}X (X = Cl or Br) and one of a series of Lewis bases B in the gas phase. The Lewis bases are so chosen that they provide a range of electron-donating abilities for comparison. Based on the characteristics of their electron pairs, we consider the Lewis bases with a single n-pair (NH{sub 3} and PH{sub 3}), two n-pairs (H{sub 2}O and H{sub 2}S), two n-pairs with an unsaturated bond (H{sub 2}CO and H{sub 2}CS), and a single π-pair (C{sub 2}H{sub 4}) and two π-pairs (C{sub 2}H{sub 2}). The aim is to systematically investigate the influence of the electron pair characteristics and the central atom substitution effects on the geometries and energetics of the formed complexes. The counterpoise-corrected supermolecule MP2 and coupled-cluster single double with perturbative triple [CCSD(T)] levels of theory have been employed, together with a series of basis sets up to aug-cc-pVTZ. The angular and radial configurations, the binding energies, and the electrostatic potentials of the stable complexes have been compared and discussed as the Lewis base varies. For those complexes where halogen bonding plays a significant role, the calculated geometries and energetics are consistent with the σ-hole model. Upon formation of stable complexes, the C–X bond lengths shorten, while the C–X vibrational frequencies increase, thus rendering blueshifting halogen bonds. The central atom substitution usually enlarges the intermolecular bond distances while it reduces the net charge transfers, thus weakening the bond strengths. The analysis based on the σ-hole model is grossly reliable but requires suitable modifications incorporating the central atom substitution effects, in particular, when interaction components other than electrostatic contributions are involved.

  3. Development and evaluation of gastroretentive raft forming systems incorporating curcumin-Eudragit® EPO solid dispersions for gastric ulcer treatment.

    PubMed

    Kerdsakundee, Nattha; Mahattanadul, Sirima; Wiwattanapatapee, Ruedeekorn

    2015-08-01

    Novel raft forming systems incorporating curcumin-Eudragit® EPO solid dispersions were developed to prolong the gastric residence time and provide for a controlled release therapy of curcumin to treat gastric ulcers. The solid dispersions of curcumin with Eudragit® EPO were prepared by the solvent evaporation method at various ratios to improve the solubility and the dissolution of curcumin. The optimum weight ratio of 1:5 for curcumin to Eudragit® EPO was used to incorporate into the raft forming systems. The raft forming formulations were composed of curcumin-Eudragit® EPO solid dispersions, sodium alginate as a gelling polymer and calcium carbonate for generating divalent Ca(2+) ions and carbon dioxide to form a floating raft. All formulations formed a gelled raft in 1min and sustained buoyancy on the 0.1N hydrochloric acid (pH 1.2) surface with a 60-85% release of curcumin within 8h. The curative effect on the acetic acid-induced chronic gastric ulcer in rats was determined. The curcumin raft forming formulations at 40mg/kg once daily showed a superior curative effect on the gastric ulcer in terms of the ulcer index and healing index than the standard antisecretory agent: lansoprazole (1mg/kg, twice daily) and a curcumin suspension (40mg/kg, twice daily). These studies demonstrated that the new raft forming systems containing curcumin solid dispersions are promising carriers for a stomach-specific delivery of poorly soluble lipophilic compounds.

  4. Actinide-Catalyzed Intermolecular Addition of Alcohols to Carbodiimides.

    PubMed

    Batrice, Rami J; Kefalidis, Christos E; Maron, Laurent; Eisen, Moris S

    2016-02-24

    The unprecedented actinide-catalyzed addition of alcohols to carbodiimides is presented. This represents a rare example of thorium-catalyzed transformations of an alcoholic substrate and the first example of uranium complexes showing catalytic reactivity with alcohols. Using the uranium and thorium amides U[N(SiMe3)2]3 and [(Me3Si)2N]2An[κ(2)-(N,C)-CH2Si(CH3)2N(SiMe3)] (An = Th or U), alcohol additions to unsaturated carbon-nitrogen bonds are achieved in short reaction times with excellent selectivities and high to excellent yields. Computational studies, supported by experimental thermodynamic data, suggest plausible models of the profile of the reaction which allow the system to overcome the high barrier of scission of the actinide-oxygen bond. Accompanied by experimentally determined kinetic parameters, a plausible mechanism is proposed for the catalytic cycle. PMID:26844823

  5. Intermolecular vibrational frequencies of the C-bonded CO2sbnd CO dimer and observation of Hesbnd CO2sbnd CO trimers

    NASA Astrophysics Data System (ADS)

    Barclay, A. J.; Sheybani-Deloui, S.; Michaelian, K. H.; McKellar, A. R. W.; Moazzen-Ahmadi, N.

    2016-05-01

    Infrared spectra of the CO2sbnd CO dimer are observed in the carbon monoxide CO stretch region (≈2150 cm-1). Combination bands yield the first experimental determinations of intermolecular mode frequencies for the planar T-shaped C-bonded form ('isomer 1'): 24.34 cm-1 for the in-plane CO rock and 43.96 cm-1 for the out-of-plane CO rock. These values are significantly higher than the analogous modes of the O-bonded form ('isomer 2'), previously determined to be 14.19 and 22.68 cm-1, respectively. New results are also reported for both isomers of the 12C18O2-substituted form of the dimer. Weak 'satellite bands' observed for both isomers are tentatively assigned to the trimer Hesbnd CO2sbnd CO.

  6. Coupled effects of substrate adhesion and intermolecular forces on polymer thin film glass-transition behavior.

    PubMed

    Xia, Wenjie; Keten, Sinan

    2013-10-15

    Intermolecular noncovalent forces between polymer chains influence the mobility and glass-transition temperature (Tg), where weaker interchain interactions, all else being the same, typically results in lower bulk polymer Tg. Using molecular dynamics simulations, here we show that this relation can become invalid for supported ultrathin films when the substrate-polymer interaction is extremely strong and the polymer-polymer interactions are much weaker. This contrasting trend is found to be due to a more pronounced substrate-induced appreciation of the film Tg for polymers with weaker intermolecular interactions and low bulk Tg. We show that optimizing this coupling between substrate adhesion and bulk Tg maximizes thin film Tg, paving the way for tuning film properties through interface nanoengineering.

  7. Changes of microstructure characteristics and intermolecular interactions of preserved egg white gel during pickling.

    PubMed

    Zhao, Yan; Chen, Zhangyi; Li, Jianke; Xu, Mingsheng; Shao, Yaoyao; Tu, Yonggang

    2016-07-15

    Changes in gel microstructure characteristics and in intermolecular interactions of preserved egg whites during pickling were investigated. Spin-spin relaxation times of preserved egg whites significantly decreased in the first 8 days and remained unchanged after the 16th day. SEM images revealed a three-dimensional gel network, interwoven with a loose linear fibrous mesh structure. The protein gel mesh structure became more regular, smaller, and compacted with pickling time. Free sulfhydryl contents in the egg whites increased significantly, while total sulfhydryl contents dramatically decreased during pickling. The primary intermolecular forces in the preserved egg white gels were ionic and disulfide bonds. Secondary forces included hydrophobic interaction and relatively few hydrogen bonds. During the first 8 days, the proportion of ionic bonds sharply decreased, and that of disulfide bonds increased over the first 24 days.

  8. Charge dependence of solvent-mediated intermolecular Coster-Kronig decay dynamics of aqueous ions.

    PubMed

    Ohrwall, G; Ottosson, N; Pokapanich, W; Legendre, S; Svensson, S; Björneholm, O

    2010-12-30

    The 2s and 2p photoelectron spectra have been measured for Na(+), Mg(2+), and Al(3+) ions in aqueous solution. In all cases, the 2s lines are significantly broader than the 2p features, which is attributed to a shorter lifetime of the respective 2s hole. Since intraionic Coster-Kronig decay channels from the (2s)(-1) state are closed for free Na(+), Mg(2+), and Al(3+) ions, this is evidence for an intermolecular Coster-Kronig-like process, reminiscent of intermolecular Coulombic decay (ICD), involving neighboring water solvent molecules. The observed 2s Lorentzian line widths correspond to lifetimes of the (2s)(-1) state of 3.1, 1.5, and 0.98 fs for the solvated Na, Mg, and Al ions, respectively.

  9. Theoretical study on intermolecular interactions in BrF/H nX adducts

    NASA Astrophysics Data System (ADS)

    Wu, Junyong; Zhang, Jingchang; Wang, Zhaoxu; Cao, Weiliang

    2007-09-01

    Equilibrium geometries, interaction energies, and charge transfer for the intermolecular interactions between BrF and H nX (HF, H 2O, and NH 3) were studied at the MP2/6-311++G(3d,3p) level. The halogen-bonded geometry and hydrogen-bonded geometry are observed in these interactions. The calculated interaction energies show that the halogen-bonded structures are more stable than the corresponding hydrogen-bonded structures. To study the nature of the intermolecular interactions, symmetry-adapted perturbation theory (SAPT) calculations were carried out and the results indicate that the halogen bonding interactions are dominantly inductive energy in nature, while electrostatic energy governs the hydrogen bonding interactions.

  10. A quantitative analysis of weak intermolecular interactions & quantum chemical calculations (DFT) of novel chalcone derivatives

    NASA Astrophysics Data System (ADS)

    Chavda, Bhavin R.; Gandhi, Sahaj A.; Dubey, Rahul P.; Patel, Urmila H.; Barot, Vijay M.

    2016-05-01

    The novel chalcone derivatives have widespread applications in material science and medicinal industries. The density functional theory (DFT) is used to optimized the molecular structure of the three chalcone derivatives (M-I, II, III). The observed discrepancies between the theoretical and experimental (X-ray data) results attributed to different environments of the molecules, the experimental values are of the molecule in solid state there by subjected to the intermolecular forces, like non-bonded hydrogen bond interactions, where as isolated state in gas phase for theoretical studies. The lattice energy of all the molecules have been calculated using PIXELC module in Coulomb -London -Pauli (CLP) package and is partitioned into corresponding coulombic, polarization, dispersion and repulsion contributions. Lattice energy data confirm and strengthen the finding of the X-ray results that the weak but significant intermolecular interactions like C-H…O, Π- Π and C-H… Π plays an important role in the stabilization of crystal packing.

  11. Changes of microstructure characteristics and intermolecular interactions of preserved egg white gel during pickling.

    PubMed

    Zhao, Yan; Chen, Zhangyi; Li, Jianke; Xu, Mingsheng; Shao, Yaoyao; Tu, Yonggang

    2016-07-15

    Changes in gel microstructure characteristics and in intermolecular interactions of preserved egg whites during pickling were investigated. Spin-spin relaxation times of preserved egg whites significantly decreased in the first 8 days and remained unchanged after the 16th day. SEM images revealed a three-dimensional gel network, interwoven with a loose linear fibrous mesh structure. The protein gel mesh structure became more regular, smaller, and compacted with pickling time. Free sulfhydryl contents in the egg whites increased significantly, while total sulfhydryl contents dramatically decreased during pickling. The primary intermolecular forces in the preserved egg white gels were ionic and disulfide bonds. Secondary forces included hydrophobic interaction and relatively few hydrogen bonds. During the first 8 days, the proportion of ionic bonds sharply decreased, and that of disulfide bonds increased over the first 24 days. PMID:26948621

  12. Optical Activity Enhanced by Strong Inter-molecular Coupling in Planar Chiral Metamaterials

    PubMed Central

    Kim, Teun-Teun; Oh, Sang Soon; Park, Hyun-Sung; Zhao, Rongkuo; Kim, Seong-Han; Choi, Wonjune; Min, Bumki; Hess, Ortwin

    2014-01-01

    The polarization of light can be rotated in materials with an absence of molecular or structural mirror symmetry. While this rotating ability is normally rather weak in naturally occurring chiral materials, artificial chiral metamaterials have demonstrated extraordinary rotational ability by engineering intra-molecular couplings. However, while in general, chiral metamaterials can exhibit strong rotatory power at or around resonances, they convert linearly polarized waves into elliptically polarized ones. Here, we demonstrate that strong inter-molecular coupling through a small gap between adjacent chiral metamolecules can lead to a broadband enhanced rotating ability with pure rotation of linearly polarized electromagnetic waves. Strong inter-molecular coupling leads to nearly identical behaviour in magnitude, but engenders substantial difference in phase between transmitted left and right-handed waves. PMID:25209452

  13. The structure and intermolecular forces of DNA condensates.

    PubMed

    Yoo, Jejoong; Aksimentiev, Aleksei

    2016-03-18

    Spontaneous assembly of DNA molecules into compact structures is ubiquitous in biological systems. Experiment has shown that polycations can turn electrostatic self-repulsion of DNA into attraction, yet the physical mechanism of DNA condensation has remained elusive. Here, we report the results of atomistic molecular dynamics simulations that elucidated the microscopic structure of dense DNA assemblies and the physics of interactions that makes such assemblies possible. Reproducing the setup of the DNA condensation experiments, we measured the internal pressure of DNA arrays as a function of the DNA-DNA distance, showing a quantitative agreement between the results of our simulations and the experimental data. Analysis of the MD trajectories determined the DNA-DNA force in a DNA condensate to be pairwise, the DNA condensation to be driven by electrostatics of polycations and not hydration, and the concentration of bridging cations, not adsorbed cations, to determine the magnitude and the sign of the DNA-DNA force. Finally, our simulations quantitatively characterized the orientational correlations of DNA in DNA arrays as well as diffusive motion of DNA and cations.

  14. Influence of intermolecular forces at critical-point wedge filling.

    PubMed

    Malijevský, Alexandr; Parry, Andrew O

    2016-04-01

    We use microscopic density functional theory to study filling transitions in systems with long-ranged wall-fluid and short-ranged fluid-fluid forces occurring in a right-angle wedge. By changing the strength of the wall-fluid interaction we can induce both wetting and filling transitions over a wide range of temperatures and study the order of these transitions. At low temperatures we find that both wetting and filling transitions are first order in keeping with predictions of simple local effective Hamiltonian models. However close to the bulk critical point the filling transition is observed to be continuous even though the wetting transition remains first order and the wetting binding potential still exhibits a small activation barrier. The critical singularities for adsorption for the continuous filling transitions depend on whether retarded or nonretarded wall-fluid forces are present and are in excellent agreement with predictions of effective Hamiltonian theory even though the change in the order of the transition was not anticipated.

  15. The structure and intermolecular forces of DNA condensates

    PubMed Central

    Yoo, Jejoong; Aksimentiev, Aleksei

    2016-01-01

    Spontaneous assembly of DNA molecules into compact structures is ubiquitous in biological systems. Experiment has shown that polycations can turn electrostatic self-repulsion of DNA into attraction, yet the physical mechanism of DNA condensation has remained elusive. Here, we report the results of atomistic molecular dynamics simulations that elucidated the microscopic structure of dense DNA assemblies and the physics of interactions that makes such assemblies possible. Reproducing the setup of the DNA condensation experiments, we measured the internal pressure of DNA arrays as a function of the DNA–DNA distance, showing a quantitative agreement between the results of our simulations and the experimental data. Analysis of the MD trajectories determined the DNA–DNA force in a DNA condensate to be pairwise, the DNA condensation to be driven by electrostatics of polycations and not hydration, and the concentration of bridging cations, not adsorbed cations, to determine the magnitude and the sign of the DNA–DNA force. Finally, our simulations quantitatively characterized the orientational correlations of DNA in DNA arrays as well as diffusive motion of DNA and cations. PMID:26883635

  16. The structure and intermolecular forces of DNA condensates.

    PubMed

    Yoo, Jejoong; Aksimentiev, Aleksei

    2016-03-18

    Spontaneous assembly of DNA molecules into compact structures is ubiquitous in biological systems. Experiment has shown that polycations can turn electrostatic self-repulsion of DNA into attraction, yet the physical mechanism of DNA condensation has remained elusive. Here, we report the results of atomistic molecular dynamics simulations that elucidated the microscopic structure of dense DNA assemblies and the physics of interactions that makes such assemblies possible. Reproducing the setup of the DNA condensation experiments, we measured the internal pressure of DNA arrays as a function of the DNA-DNA distance, showing a quantitative agreement between the results of our simulations and the experimental data. Analysis of the MD trajectories determined the DNA-DNA force in a DNA condensate to be pairwise, the DNA condensation to be driven by electrostatics of polycations and not hydration, and the concentration of bridging cations, not adsorbed cations, to determine the magnitude and the sign of the DNA-DNA force. Finally, our simulations quantitatively characterized the orientational correlations of DNA in DNA arrays as well as diffusive motion of DNA and cations. PMID:26883635

  17. Intermolecular C-H Quaternary Alkylation of Aniline Derivatives Induced by Visible-Light Photoredox Catalysis.

    PubMed

    Cheng, Jie; Deng, Xia; Wang, Guoqiang; Li, Ying; Cheng, Xu; Li, Guigen

    2016-09-16

    The intermolecular direct C-H alkylation of aniline derivatives with α-bromo ketones to build a quaternary carbon center was reported with a visible-light catalysis procedure. The reaction covers a variety of functional groups with good to excellent yields. A regioselectivity favoring the ortho position for the amine group was observed and investigated with Fukui indices and spectral methods. PMID:27571116

  18. Estimation of Some Parameters from Morse-Morse-Spline-Van Der Waals Intermolecular Potential

    SciTech Connect

    Coroiu, I.

    2007-04-23

    Some parameters such as transport cross-sections and isotopic thermal diffusion factor have been calculated from an improved intermolecular potential, Morse-Morse-Spline-van der Waals (MMSV) potential proposed by R.A. Aziz et al. The treatment was completely classical and no corrections for quantum effects were made. The results would be employed for isotope separations of different spherical and quasi-spherical molecules.

  19. Enantioselective Intermolecular Cyclopropanations for the Synthesis of Chiral Pyrimidine Carbocyclic Nucleosides.

    PubMed

    Xie, Ming-Sheng; Zhou, Peng; Niu, Hong-Ying; Qu, Gui-Rong; Guo, Hai-Ming

    2016-09-01

    A direct route to chiral cyclopropylpyrimidine carbocyclic nucleoside analogues has been reported via highly enantioselective intermolecular cyclopropanation reactions of N1-vinylpyrimidines with α-diazoesters. With chiral ruthenium(II)-phenyloxazoline complex (2 mol %) as the catalyst, cyclopropyl pyrimidine nucleoside analogues could be obtained in good yields (71-96% yields) with high levels of diastereo- and enantioselectivities (10:1 to >20:1 dr and 96-99% ee) in 1 min. PMID:27526779

  20. Cupric-Superoxo Mediated Inter-Molecular C-H Activation Chemistry

    PubMed Central

    Peterson, Ryan L.; Himes, Richard A.; Kotani, Hiroaki; Suenobu, Tomoyoshi; Tian, Li; Siegler, Maxime A.; Solomon, Edward I.; Fukuzumi, Shunichi; Karlin, Kenneth D.

    2011-01-01

    A new cupric-superoxo complex [LCuII(O2•−)]+, which possesses particularly strong O–O and Cu–O bonding, is capable of intermolecular C-H activation of the NADH analogue 1-benzyl-1,4-dihydronicotinamide (BNAH). Kinetic studies indicate a first-order dependence on both the Cu-complex and BNAH with a deuterium kinetic isotope effect (KIE) of 12.1, similar to that observed for certain copper monooxygenases. PMID:21265534

  1. Intermolecular electronic coupling in organic molecular thin films measured by temperature modulation spectroscopy

    SciTech Connect

    Yadav, Abhishek; Jin, Y; Chan, P. K. L.; Shtein, Max; Pipe, Kevin P.

    2010-01-01

    Temperature modulation spectroscopy is used to obtain the temperature dependences of oscillator strength, exciton transition energy, and line width for a copper phthalocyanine thin film. With increasing temperature, the oscillator strength exhibits a pronounced decrease for charge transfer (CT) excitons, making this technique suitable for differentiating exciton types. From the measured magnitude and temperature dependence of the CT oscillator strength, we obtain estimates for the intermolecular electronic coupling and its exponential decay coefficient.

  2. Copper-catalyzed regio- and stereoselective intermolecular three-component oxyarylation of allenes.

    PubMed

    Itoh, Taisuke; Shimizu, Yohei; Kanai, Motomu

    2014-05-16

    A copper(II)-catalyzed intermolecular three-component oxyarylation of allenes using arylboronic acids as a carbon source and TEMPO as an oxygen source is described. The reaction proceeded under mild conditions with high regio- and stereoselectivity and functional group tolerance. A plausible reaction mechanism is proposed, involving carbocupration of allenes, homolysis of the intervening allylcopper(II), and a radical TEMPO trap. PMID:24766635

  3. Metal-free intermolecular formal cycloadditions enable an orthogonal access to nitrogen heterocycles

    PubMed Central

    Xie, Lan-Gui; Niyomchon, Supaporn; Mota, Antonio J.; González, Leticia; Maulide, Nuno

    2016-01-01

    Nitrogen-containing heteroaromatic cores are ubiquitous building blocks in organic chemistry. Herein, we present a family of metal-free intermolecular formal cycloaddition reactions that enable highly selective and orthogonal access to isoquinolines and pyrimidines at will. Applications of the products are complemented by a density functional theory mechanistic analysis that pinpoints the crucial factors responsible for the selectivity observed, including stoichiometry and the nature of the heteroalkyne. PMID:26975182

  4. Blind test of density-functional-based methods on intermolecular interaction energies

    NASA Astrophysics Data System (ADS)

    Taylor, DeCarlos E.; Ángyán, János G.; Galli, Giulia; Zhang, Cui; Gygi, Francois; Hirao, Kimihiko; Song, Jong Won; Rahul, Kar; Anatole von Lilienfeld, O.; Podeszwa, Rafał; Bulik, Ireneusz W.; Henderson, Thomas M.; Scuseria, Gustavo E.; Toulouse, Julien; Peverati, Roberto; Truhlar, Donald G.; Szalewicz, Krzysztof

    2016-09-01

    In the past decade, a number of approaches have been developed to fix the failure of (semi)local density-functional theory (DFT) in describing intermolecular interactions. The performance of several such approaches with respect to highly accurate benchmarks is compared here on a set of separation-dependent interaction energies for ten dimers. Since the benchmarks were unknown before the DFT-based results were collected, this comparison constitutes a blind test of these methods.

  5. Solid-State NMR Identification and Quantification of Newly Formed Aluminosilicate Phases in Weathered Kaolinite Systems

    SciTech Connect

    Crosson, Garry S.; Choi, Sunkyung; Chorover, Jon; Amistadi, Mary K.; O'Day, Peggy A.; Mueller, Karl T.

    2006-01-19

    The weathering of a specimen kaolinite clay was studied over the course of 369 d via solid-state 29Si magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy and high-field 27Al MAS NMR. The chosen baseline solution conditions (0.05 mol kg-1 of Al, 2 mol kg-1 of Na+, 1 mol kg-1 of NO3 -, 1 mol kg-1 of OH-, and pH ~13.8) approximate those of solutions leaking from waste tanks at the Hanford Site in Richland, WA. Nonradioactive Cs and Sr cations were added to this synthetic tank waste leachate (STWL) solution at concentrations of 10-3, 10-4, and 10-5 molal (m) to represent their radionuclide counterparts. The transformations of silicon- and aluminum-containing solid phase species were monitored quantitatively by using NMR spectroscopy, with the resulting spectra directly reporting the influence of the initial Cs and Sr on formation and transformation of the neo-formed solids. At the lowest concentration of Cs and Sr employed (10-5 m in each cation) peaks consistent with the formation of zeolite-like minerals were detected via 29Si and 27Al MAS NMR as early as 33 d. At concentrations of 10-3 m in each cation, new silicon species are not detected until 93 d, although neophases containing four-coordinate aluminum were detectable at earlier reaction times via 27Al MAS NMR. At the highest magnetic field strengths employed in this NMR study, deconvolutions of resonances detected in the tetrahedral region of the 27Al MAS spectra yielded multiple components, indicating the existence of at least four new aluminum-containing phases. Two of these phases are identified as sodalite and cancrinite through comparison with diffuse-reflectance infrared (DRIFT) spectra and powder X-ray diffraction (XRD) results, while a third phase may correlate with a previously detected aluminum-rich chabazite phase. All measurable solid reaction products have been quantified via their 27Al MAS resonances acquired at high magnetic field strengths (17.6 T), and the quantitative

  6. Solution and solid-state study of the structure of azo-coupling products from isomeric enaminones possessing tert-butyl group: An unprecedented observation of pure hydrazo form in azo coupled N-alkyl β-enaminones

    NASA Astrophysics Data System (ADS)

    Šimůnek, Petr; Padělková, Zdeňka; Macháček, Vladimír

    2014-10-01

    The structure of the azo-coupling products from enaminones derived from 4,4-dimethyl-1-phenylpentane-1,3-dione has been studied by means of solution-state 1H, 13C and 15N NMR spectroscopy and X-ray diffractometry. The presence of bulky tert-butyl group hinders or even prevents from the formation of planar conjugated heterodiene system Hsbnd Nsbnd Cdbnd Csbnd Ndbnd N with an intramolecular hydrogen bond Nsbnd H⋯Ndbnd which is the prerequisite for fast tautomeric exchange imino-hydrazo - enamino-azo. The minor amount of azo compounds is formed by a proton exchange through a hydrogen bond Nsbnd H⋯N, which is either intramolecular (in solution) or intermolecular (solid state). The intermolecular exchange proceeds via the dimers of the azo coupling products. This is unprecedented result among the similar molecules hitherto studied.

  7. Intermolecular interactions in multi-component crystals of acridinone/thioacridinone derivatives: Structural and energetics investigations

    NASA Astrophysics Data System (ADS)

    Wera, Michał; Storoniak, Piotr; Trzybiński, Damian; Zadykowicz, Beata

    2016-12-01

    A single crystal X-ray analysis of two multi-component crystals consisting of an acridinone/thioacridinone moiety and a solvent moiety - water and ammonia (1 and 2), respectively, was carried out to determine the crystal structures of obtained crystals. A theoretical approach was undertaken - using the DFT method, lattice energies calculations and Hirshfeld surfaces (HS) - to qualitatively and quantitatively assess the intermolecular interactions within the crystal. HS analysis was showed that the H⋯H, C⋯H/H⋯C and C⋯C contacts for both structures (altogether 81.6% of total Hirshfeld surface area for 1 and 79.3% for 2) and the O⋯H/H⋯O (14.3%) for 1 and the S⋯H/H⋯S (15.2%) contacts for 2 were the characteristic intermolecular contacts in the related crystal structures. Using a computational methods were confirmed that the main contribution to the stabilization of the crystal lattice of compound 1 comes from the Coulombic interactions, whereas in compound 2 electrostatic and van der Waals appear to have similar contribution to the crystal lattice energy. Theoretical calculations of the investigated compounds have also allowed to determine the energy of a single specific intermolecular interaction.

  8. Boiling points of halogenated ethanes: an explanatory model implicating weak intermolecular hydrogen-halogen bonding.

    PubMed

    Beauchamp, Guy

    2008-10-23

    This study explores via structural clues the influence of weak intermolecular hydrogen-halogen bonds on the boiling point of halogenated ethanes. The plot of boiling points of 86 halogenated ethanes versus the molar refraction (linked to polarizability) reveals a series of straight lines, each corresponding to one of nine possible arrangements of hydrogen and halogen atoms on the two-carbon skeleton. A multiple linear regression model of the boiling points could be designed based on molar refraction and subgroup structure as independent variables (R(2) = 0.995, standard error of boiling point 4.2 degrees C). The model is discussed in view of the fact that molar refraction can account for approximately 83.0% of the observed variation in boiling point, while 16.5% could be ascribed to weak C-X...H-C intermolecular interactions. The difference in the observed boiling point of molecules having similar molar refraction values but differing in hydrogen-halogen intermolecular bonds can reach as much as 90 degrees C.

  9. Human DNA ligase III bridges two DNA ends to promote specific intermolecular DNA end joining

    PubMed Central

    Kukshal, Vandna; Kim, In-Kwon; Hura, Gregory L.; Tomkinson, Alan E.; Tainer, John A.; Ellenberger, Tom

    2015-01-01

    Mammalian DNA ligase III (LigIII) functions in both nuclear and mitochondrial DNA metabolism. In the nucleus, LigIII has functional redundancy with DNA ligase I whereas LigIII is the only mitochondrial DNA ligase and is essential for the survival of cells dependent upon oxidative respiration. The unique LigIII zinc finger (ZnF) domain is not required for catalytic activity but senses DNA strand breaks and stimulates intermolecular ligation of two DNAs by an unknown mechanism. Consistent with this activity, LigIII acts in an alternative pathway of DNA double strand break repair that buttresses canonical non-homologous end joining (NHEJ) and is manifest in NHEJ-defective cancer cells, but how LigIII acts in joining intermolecular DNA ends versus nick ligation is unclear. To investigate how LigIII efficiently joins two DNAs, we developed a real-time, fluorescence-based assay of DNA bridging suitable for high-throughput screening. On a nicked duplex DNA substrate, the results reveal binding competition between the ZnF and the oligonucleotide/oligosaccharide-binding domain, one of three domains constituting the LigIII catalytic core. In contrast, these domains collaborate and are essential for formation of a DNA-bridging intermediate by adenylated LigIII that positions a pair of blunt-ended duplex DNAs for efficient and specific intermolecular ligation. PMID:26130724

  10. Physicochemical properties, form, and formulation selection strategy for a biopharmaceutical classification system class II preclinical drug candidate.

    PubMed

    Lohani, Sachin; Cooper, Harriet; Jin, Xiaoling; Nissley, Becky P; Manser, Kimberly; Rakes, Linda Huong; Cummings, John J; Fauty, Scott E; Bak, Annette

    2014-10-01

    This work summarizes the pharmaceutical evaluation of a preclinical drug candidate with poor physicochemical properties. Compound 1 is a weakly basic, GPR-119 agonist designated to Biopharmaceutics Classification System Class II because of good permeability in a Caco-2 cell line model and poor solubility. Compound 1 showed good oral bioavailability from a solution formulation at low doses and oral exposure sufficient for toxicological evaluation at high doses from a nanosuspension of Form A-the only known polymorph of 1 during drug discovery. The identification of the thermodynamically stable polymorph, Form B, during early development adversely affected the bioperformance of the nanosuspension. The poor solubility of Form B resulted in a significant reduction in the oral exposure from a nanosuspension to a level that was insufficient for toxicological evaluation of compound 1. Subsequent to the discovery of Form B, multiple form and formulation engineering strategies were evaluated for their ability to enhance the oral exposure of 1. Formulations based on cocrystals and amorphous solid dispersions showed a statistically significant increase in exposure, sixfold and sevenfold, respectively, over the benchmark formulation, a suspension of Form B. The physicochemical characterization of 1, and the solid form and formulation engineering approaches explored to address the insufficient oral exposure of Form B are discussed along with insights on improving the physicochemical properties of the follow-on drug candidates in discovery.

  11. Newly formed minerals of the Fe-P-S system in Kolyma fulgurite

    NASA Astrophysics Data System (ADS)

    Plyashkevich, A. A.; Minyuk, P. S.; Subbotnikova, T. V.; Alshevsky, A. V.

    2016-04-01

    Newly obtained data from microscopic, geochemical, and thermomagnetic studies of the large Kolyma fulgurite are presented here: the fulgurite was formed in the Holocene as a result of lightning affected black shale alluvium. The composition is very close to that of glass formed from a melt. The glass has elevated concentrations of Y, Zr, Nb, and REEs. The newly formed mineral phases have been identified: those are Al-Si glass, α-cristobalite, moissanite, native iron with a phosphorus admixture, nickel-less shreibersite (?), troilite, and possibly cohenite. The formation of these minerals is related to the melt fractionation and the effects of element concentration and segregation of ore components under conditions of the rock melting caused by the effect of high-energy plasma (lightning strike).

  12. Molecular orientation transition of organic thin films on graphite: the effect of intermolecular electrostatic and interfacial dispersion forces.

    PubMed

    Chen, Wei; Huang, Han; Thye, Andrew; Wee, Shen

    2008-09-28

    In situ low-temperature scanning tunnelling microscopy investigation reveals a molecular orientation transition of organic thin films of pentacene and p-sexiphenyl on graphite, arising from the delicate balance between the intermolecular electrostatic and interfacial dispersion forces.

  13. Simulations of the THz spectrum of liquid water incorporating the effects of intermolecular charge fluxes through hydrogen bonds

    SciTech Connect

    Torii, Hajime

    2015-12-31

    The intensity of the band at ∼200 cm{sup −1} (∼6 THz) in the Terahertz spectrum of liquid water mainly arises from the modulations of the extent of intermolecular charge transfer through hydrogen bonds, called intermolecular charge fluxes, occurring upon molecular translations along the O…H hydrogen bonds. To obtain reasonable spectral profiles from simulations, it is necessary to effectively incorporate the effects of those intermolecular charge fluxes, but apparently it is not possible by simple classical molecular dynamics simulations with fixed atomic partial charges even if they are amended by molecular induced dipoles due to intermolecular electrostatic interactions. The present paper shows how we can do reasonably correct spectral simulations, without resorting to fully ab initio molecular dynamics.

  14. Halistaurin, phialidin and modified forms of aequorin as Ca2+ indicator in biological systems.

    PubMed Central

    Shimomura, O; Shimomura, A

    1985-01-01

    Two kinds of aequorin-type photoproteins, i.e., halistaurin and phialidin, and four kinds of modified forms of aequorin, i.e., products of acetylation, ethoxycarbonylation, fluorescamine-modification and fluorescein labelling, were prepared. The modified forms of aequorin were more sensitive to Ca2+ than was aequorin in their Ca2+-triggered luminescence reactions, whereas halistaurin and phialidin were less sensitive. The emission maxima of luminescence were all within a wavelength range 450-464 nm, except for fluorescein-labelled aequorin, which emitted yellowish light (lambda max. 520 nm). A new technique of measuring Ca2+ concentration is suggested. PMID:4026808

  15. 15N-15N spin-spin coupling constants through intermolecular hydrogen bonds in the solid state.

    PubMed

    Claramunt, Rosa M; Pérez-Torralba, Marta; María, Dolores Santa; Sanz, Dionisia; Elena, Bénédicte; Alkorta, Ibon; Elguero, José

    2010-10-01

    A 2hJNN intermolecular spin-spin coupling constant (SSCC) of 10.2±0.4 Hz has been measured for the powdered tetrachlorogallate salt of pyridinium solvated by pyridine (pyridine-H+⋯pyridine cation 3). Density Functional Theory (DFT) calculations at the B3LYP/6-311++G(d,p) level reproduced this value and two others reported in the literature for 2hJ intermolecular SSCCs, which were measured for complexes in solution.

  16. Encouraging Multiple Forms of Scholarship in Faculty Reward Systems: Influence on Faculty Work Life

    ERIC Educational Resources Information Center

    O'Meara, KerryAnn

    2006-01-01

    This article presents findings from a national study of Chief Academic Officers (CAOs) of four-year institutions on the effect of policy efforts that encourage multiple forms of scholarship on faculty involvement and satisfaction. Findings show that institutions that initiated reforms were significantly more likely than their counterparts to have…

  17. Encouraging Multiple Forms of Scholarship in Faculty Reward Systems: Does It Make a Difference?

    ERIC Educational Resources Information Center

    O'Meara, Kerry Ann

    2005-01-01

    This article presents findings from a national study of Chief Academic Officers of 4-year institutions on the impact of policy efforts to encourage multiple forms of scholarship in faculty roles and rewards. The extent of reform, kinds of reform and influence of initiating reform is examined in four areas: expectations for faculty evaluation, the…

  18. On-line Technology Information System (OTIS): Solid Waste Management Technology Information Form (SWM TIF)

    NASA Technical Reports Server (NTRS)

    Levri, Julie A.; Boulanger, Richard; Hogan, John A.; Rodriguez, Luis

    2003-01-01

    Contents include the following: What is OTIS? OTIS use. Proposed implementation method. Development history of the Solid Waste Management (SWM) Technology Information Form (TIF) and OTIS. Current development state of the SWM TIF and OTIS. Data collection approach. Information categories. Critiques/questions/feedback.

  19. A lithologic data-recording form for a computer-based well-data system

    USGS Publications Warehouse

    Conley, C.D.; Hea, J.P.

    1972-01-01

    Well-data files maintained by petroleum companies and service companies are important sources of data for exploration geologists. To make these data readily accessible and useful for computer studies, three preliminary steps are necessary: (1) systematic data gathering and recording, (2) storage for ready retrieval, and (3) preparation of analysis programs. One important source of geologic data is lithologic descriptions of well cuttings and cores. The practical lithologic data-recording form described here is used routinely at the well site and in the laboratory. It is designed in an 80-column format and uses codes for lithologic characteristics, porosity, and hydrocarbon shows, and forms part of an integrated well-data file. This datarecording form has the advantages that descriptions are made according to a standardized format convenient to use at the well site, and the data are subsequently available in raw form relatively free from interpretive bias. A library of analysis and display programs can be assembled for utilization of the data. ?? 1972 Plenum Publishing Corporation.

  20. Bioadhesive film formed from a novel organic-inorganic hybrid gel for transdermal drug delivery system.

    PubMed

    Guo, Ruiwei; Du, Xiaoyan; Zhang, Rui; Deng, Liandong; Dong, Anjie; Zhang, Jianhua

    2011-11-01

    A novel organic-inorganic hybrid film-forming agent for TDDS was developed by a modified poly(vinyl alcohol) (PVA) gel using γ-(glycidyloxypropyl)trimethoxysilane (GPTMS) as an inorganic-modifying agent, poly(N-vinyl pyrrolidone) (PVP) as a tackifier and glycerol (GLY) as a plasticizer. The prepared gels can be applied to the skin by a coating method and in situ form very thin and transparent films with good performance, comfortable feel and cosmetic attractiveness. The key properties of the bioadhesive films produced from the hybrid gels were investigated and the results showed that the incorporation of appropriate GPTMS (GPTMS/(PVA+GPTMS) in the range of 20-30%) into the PVA matrix not only can significantly enhance mechanical strength and skin adhesion properties of the resultant film, but also can decrease the crystalline regions of PVA and hence facilitate the diffusion of water vapor and drug. Furthermore, the investigations into in vivo skin irritation suggested the films caused non-irritation to skin after topical application for 120 h. In conclusion, the bioadhesive films formed from organic-inorganic hybrid gels possessed very good qualities for application on the skin and may provide a promising formulation for TDDS, especially when the patient acceptability from an aesthetic perspective of the dosage form is a prime consideration. PMID:21723945

  1. The method of normal forms for singularly perturbed systems of Fredholm integro-differential equations with rapidly varying kernels

    SciTech Connect

    Bobodzhanov, A A; Safonov, V F

    2013-07-31

    The paper deals with extending the Lomov regularization method to classes of singularly perturbed Fredholm-type integro-differential systems, which have not so far been studied. In these the limiting operator is discretely noninvertible. Such systems are commonly known as problems with unstable spectrum. Separating out the essential singularities in the solutions to these problems presents great difficulties. The principal one is to give an adequate description of the singularities induced by 'instability points' of the spectrum. A methodology for separating singularities by using normal forms is developed. It is applied to the above type of systems and is substantiated in these systems. Bibliography: 10 titles.

  2. How coupled elementary units determine the dynamics of macroscopic glass-forming systems

    NASA Astrophysics Data System (ADS)

    Rehwald, Christian; Heuer, Andreas

    2012-11-01

    We investigate the dynamics of a binary mixture Lennard-Jones system of different system sizes with respect to the importance of the properties of the underlying potential energy landscape (PEL). We show that the dynamics of small systems can be very well described within the continuous time random walk formalism, which is determined solely by PEL parameters. Finite size analysis shows that the diffusivity of large and small systems are very similar. This suggests that the PEL parameters of the small system also determine the local dynamics in large systems. The structural relaxation time, however, displays significant finite size effects. Furthermore, using a nonequilibrium configuration of a large system, we find that causal connections exist between nearby regions of the system. These findings can be described by the coupled landscape model for which a macroscopic system is described by a superposition of elementary systems, each described by its PEL. A minimum coupling is introduced which accounts for the finite size behavior. The coupling strength, as the single adjustable parameter, becomes smaller closer to the glass transition.

  3. Purification and characterization of multiple forms of rat liver xanthine oxidoreductase expressed in baculovirus-insect cell system.

    PubMed

    Nishino, Tomoko; Amaya, Yoshihiro; Kawamoto, Susumu; Kashima, Yuji; Okamoto, Ken; Nishino, Takeshi

    2002-10-01

    cDNA of rat liver xanthine oxidoreductase (XOR), a molybdenum-containing iron-sulfur flavoprotein, was expressed in a baculovirus-insect cell system. The expressed XOR consisted of a heterogeneous mixture of native dimeric, demolybdo-dimeric, and monomeric forms, each of which was separated and purified to homogeneity. All the expressed forms contained flavin, of which the semiquinone form was stable during dithionite titration after dithiothreitol treatment, indicating that the flavin domains of all the expressed molecules have the intact conformations interconvertible between NAD(+)-dependent dehydrogenase (XDH) and O(2)-dependent oxidase (XO) types. The absorption spectrum and metal analyses showed that the monomeric form lacks not only molybdopterin but also one of the iron-sulfur centers. The reductive titration of the monomer with dithionite showed that the monomeric form required only three electrons for complete reduction, and the redox potential of the iron-sulfur center in the monomeric form is a lower value than that of FAD. In contrast to native or demolybdo-dimeric XDHs, the monomer showed a very slow reductive process with NADH under anaerobic conditions, although the conformation around FAD is a dehydrogenase form, suggesting the important role of the iron-sulfur center in the reductive process of FAD with the reduced pyridine nucleotide.

  4. Technology maturation project on optimization of sheet metal forming of aluminum for use in transportation systems: Final project report

    SciTech Connect

    Johnson, K.I.; Smith, M.T.; Lavender, C.A.; Khalell, M.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 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; 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.

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

    PubMed

    Huang, Jingsong; Kingsbury, Stephanie; Kertesz, Miklos

    2008-05-21

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

  6. CB-TE2A(+)·Cl(-)·3H2O: a short intermolecular hydrogen bond between zwitterionic bicyclo[6.6.2]tetraamine macrocycles.

    PubMed

    Jurek, Paul; Reibenspies, Joseph H; Kiefer, Garry E

    2016-02-01

    1,4,8,11-Tetraazabicyclo[6.6.2]hexadecane-4,11-diacetic acid (CB-TE2A) is of much interest in nuclear medicine for its ability to form copper complexes that are kinetically inert, which is beneficial in vivo to minimize the loss of radioactive copper. The structural chemistry of the hydrated HCl salt of CB-TE2A, namely 11-carboxymethyl-1,8-tetraaza-4,11-diazoniabicyclo[6.6.2]hexadecane-4-acetate chloride trihydrate, C16H31N4O4(+)·Cl(-)·3H2O, is described. The compound crystallized as a positively charged zwitterion with a chloride counter-ion. Two of the amine groups in the macrocyclic ring are protonated. Formally, a single negative charge is shared between two of the carboxylic acid groups, while one chloride ion balances the charge. Two intramolecular hydrogen bonds are observed between adjacent pairs of N atoms of the macrocycle. Two intramolecular hydrogen bonds are also observed between the protonated amine groups and the pendant carboxylate groups. A short intermolecular hydrogen bond is observed between two partially negatively charged O atoms on adjacent macrocycles. The result is a one-dimensional polymeric zigzag chain that propagates parallel to the crystallographic a direction. A second intermolecular interaction is a hydrogen-bonding network in the crystallographic b direction. The carbonyl group of one macrocycle is connected through the three water molecules of hydration to the carbonyl group of another macrocycle. PMID:26846499

  7. Role of Intramolecular Aromatic π-π Interactions in the Self-Assembly of Di-l-Phenylalanine Dipeptide Driven by Intermolecular Interactions: Effect of Alanine Substitution.

    PubMed

    Reddy, Samala Murali Mohan; Shanmugam, Ganesh

    2016-09-19

    Although the role of intermolecular aromatic π-π interactions in the self-assembly of di-l-phenylalanine (l-Phe-l-Phe, FF), a peptide that is known for hierarchical structure, is well established, the influence of intramolecular π-π interactions on the morphology of the self-assembled structure of FF has not been studied. Herein, the role of intramolecular aromatic π-π interactions is investigated for FF and analogous alanine (Ala)-containing dipeptides, namely, l-Phe-l-Ala (FA) and l-Ala-l-Phe (AF). The results reveal that these dipeptides not only form self-assemblies, but also exhibit remarkable differences in structural morphology. The morphological differences between FF and the analogues indicate the importance of intramolecular π-π interactions, and the structural difference between FA and AF demonstrates the crucial role of the nature of intramolecular side-chain interactions (aromatic-aliphatic or aliphatic-aromatic), in addition to intermolecular interactions, in deciding the final morphology of the self-assembled structure. The current results emphasise that intramolecular aromatic π-π interaction may not be essential to induce self-assembly in smaller peptides, and π (aromatic)-alkyl or alkyl-π (aromatic) interactions may be sufficient. This work also illustrates the versatility of aromatic and a combination of aromatic and aliphatic residues in dipeptides in the formation of structurally diverse self-assembled structures.

  8. α- And β Pahases of oxalic acid, H 2C 2O 4: Vibrational spectra, normal-coordinate calculations, and intermolecular forces

    NASA Astrophysics Data System (ADS)

    De Villepin, J.; Novak, A.; Bougeard, D.

    1982-12-01

    Infrared (4000-30 cm -1) and Raman (4000-0 cm -) spectra of single crystals of α-oxalic acid (Pcab, Z=4) have been investigated at 100 and 300 K. A complete assignment of all modes in terms of symmetry species and to internal, librational, translational, and hydrogen bond motions is given. In order to interpret the spectra and to determine the crystal field, several normal-coordinate calculations (free molecule, rigid body model, unit cell as a supermolecule) have been carried out. The calculations are in good agreement with the experimental results and show the importance of different intermolecular forces: OH … O hydrogen bonds and very short C … O interactions lead to both unusually strong correlation field splitting and high lattice frequencies while quadrupole-quadrupole and CO dipole-dipole interactions influence lattice and some internal vibrations, respectively. The intermolecular potentials obtained for α-oxalic acid are transferable to the β form having a different crystal structure (P2 1/c, Z = 2) and stronger hydrogen bonds.

  9. Structure of an acidic phospholipase A2 from Indian saw-scaled viper (Echis carinatus) at 2.6 A resolution reveals a novel intermolecular interaction.

    PubMed

    Jasti, Jayasankar; Paramasivam, M; Srinivasan, A; Singh, T P

    2004-01-01

    The crystal structure of an acidic phospholipase A(2) from the venom of Echis carinatus (saw-scaled viper; scPLA(2)) has been determined at 2.6 A resolution and refined to a crystallographic R factor of 0.192. Although the overall structure of scPLA(2) is essentially similar to those of other group II acidic PLA(2)s from different species, it shows unique features in several parts. Particularly noteworthy is the C-terminal part, which folds differently to those of other group II PLA(2)s. This part is considered to be responsible for inhibition of the platelet-aggregation activity. The calcium-binding loop is tightly organized with sevenfold coordination. Another striking feature of scPLA(2) is the involvement of Asn79 O(delta1) of a symmetry-related molecule in a coordination linkage with Ca(2+) of the calcium-binding loop. This is the first observation of an internal metal ion participating in an intermolecular interaction. The beta-wing of a molecule is deeply inserted into the hydrophobic channel of another molecule and forms several intermolecular interactions. This results in the formation of an infinite chain of molecules. These chains are stacked in an antiparallel arrangement in the crystals. PMID:14684894

  10. Normal forms for some classes of sequential spiking neural P systems.

    PubMed

    Song, Tao; Pan, Linqiang; Jiang, Keqin; Song, Bosheng; Chen, Wei

    2013-09-01

    Spiking neural P systems (SN P systems, for short) are a class of distributed parallel computing devices inspired from the way neurons communicate by means of spikes, where each neuron can have several spiking rules and forgetting rules and neurons work in parallel in the sense that each neuron that can fire should fire at each computation step. In this work, we consider SN P systems with the restrictions: 1) systems are simple (resp. almost simple) in the sense that each neuron has only one rule (resp. except for one neuron); 2) at each step the neuron(s) with the maximum number of spikes among the neurons that can spike will fire. These restrictions correspond to that the systems are simple or almost simple and a global view of the whole network makes the systems sequential. The computation power of simple SN P systems and almost simple SN P systems working in the sequential mode induced by maximum spike number is investigated. Specifically, we prove that such systems are Turing universal as both number generating and accepting devices. The results improve the corresponding ones in Theor. Comput. Sci., 410 (2009), 2982-2991. PMID:23974661

  11. Multiple-access phased array antenna simulator for a digital beam forming system investigation

    NASA Technical Reports Server (NTRS)

    Kerczewski, Robert J.; Yu, John; Walton, Joanne C.; Perl, Thomas D.; Andro, Monty; Alexovich, Robert E.

    1992-01-01

    Future versions of data relay satellite systems are currently being planned by NASA. Being given consideration for implementation are on-board digital beamforming techniques which will allow multiple users to simultaneously access a single S-band phased array antenna system. To investigate the potential performance of such a system, a laboratory simulator has been developed at NASA's Lewis Research Center. This paper describes the system simulator, and in particular, the requirements, design, and performance of a key subsystem, the phased array antenna simulator, which provides realistic inputs to the digital processor including multiple signals, noise, and nonlinearities.

  12. Mucoadhesive system formed by liquid crystals for buccal administration of poly(hexamethylene biguanide) hydrochloride.

    PubMed

    Souza, Carla; Watanabe, Evandro; Borgheti-Cardoso, Livia Neves; De Abreu Fantini, Márcia Carvalho; Lara, Marilisa Guimarães

    2014-12-01

    Antimicrobial approaches are valuable in controlling the development of buccal diseases, but some antibacterial agents have a short duration of activity. Therefore, the development of prolonged delivery systems would be advantageous. Liquid crystalline systems comprising monoolein (GMO)/water have been considered to be a potential vehicle to deliver drugs to the buccal mucosa because of the phase properties that allow for controlled drug release as well as its mucoadhesive properties. Therefore, the aim of this study was to develop a GMO/water system for the slow release of poly(hexamethylene biguanide) hydrochloride (PHMB) on the buccal mucosa and test the properties of this system with regard to swelling, release profile, antimicrobial activity, and strength of mucoadhesion, with the overall goal of treating buccal infections. The tested systems were capable of modulating drug release, which is controlled by diffusion of the drug throughout the system. Furthermore, PHMB appeared to improve the mucoadhesive properties of the system and may synergistically act with the drug to promote antimicrobial activity against S. mutas and C. albicans, indicating that liquid crystals may be suitable for the administration of PHMB on the buccal mucosa. Therefore, this system could be proposed as a novel system for mucoadhesive drug delivery.

  13. Comparison between Synthesized Lead Particles and Lead Solids Formed on Surfaces in Real Drinking Water Distribution Systems

    EPA Science Inventory

    The objective of this work is to compare the properties of lead solids formed during bench-scale precipitation experiments to solids found on lead pipe removed from real drinking water distribution systems and metal coupons used in pilot scale corrosion testing. Specifically, so...

  14. Pattern formation in spatially extended nonlinear systems: Toward a foundation for meaning in symbolic forms

    NASA Astrophysics Data System (ADS)

    DeMaris, David

    1998-07-01

    This paper brings together observations from a variety of fields to point toward what the author believes to be the most promising computational approach to the modeling of brain-like symbol formation, unifying perceptual and linguistic domains under a common computational physics. It brings Cassirer's Gestalt era evolutionary theory of language and symbolic thought to the attention of the situated cognition community, and describes how recent observations in experimental brain dynamics and computational approaches can be brought to bear on the problem. Research by the author and others in oscillatory network models of ambiguous perception with an attentional component is emphasised as a starting point for exploring increasingly complex pattern formation processes leading to simple forms of linguistic performance. These forms occupy a space between iconic representations and grammar. The dynamic pattern network framework suggests that to separate perception, representation or models and action in a realistic biophysics of situated organisms may be problematic.

  15. Method of Forming a Hot Film Sensor System on a Model

    NASA Technical Reports Server (NTRS)

    Tran, Sang Q. (Inventor)

    1998-01-01

    A method of forming a hot film sensor directly on a model is provided. A polyimide solution is sprayed onto the model. The model so sprayed is then heated in air. The steps of spraying and heating are repeated until a polyimide film of desired thickness is achieved on the model. The model with the polyimide film thereon is then thoroughly dried in air. One or more hot film sensors and corresponding electrical conducting leads are then applied directly onto the polyimide film.

  16. System and method for forming synthetic protein crystals to determine the conformational structure by crystallography

    DOEpatents

    Craig, George D.; Glass, Robert; Rupp, Bernhard

    1997-01-01

    A method for forming synthetic crystals of proteins in a carrier fluid by use of the dipole moments of protein macromolecules that self-align in the Helmholtz layer adjacent to an electrode. The voltage gradients of such layers easily exceed 10.sup.6 V/m. The synthetic protein crystals are subjected to x-ray crystallography to determine the conformational structure of the protein involved.

  17. System and method for forming synthetic protein crystals to determine the conformational structure by crystallography

    DOEpatents

    Craig, G.D.; Glass, R.; Rupp, B.

    1997-01-28

    A method is disclosed for forming synthetic crystals of proteins in a carrier fluid by use of the dipole moments of protein macromolecules that self-align in the Helmholtz layer adjacent to an electrode. The voltage gradients of such layers easily exceed 10{sup 6}V/m. The synthetic protein crystals are subjected to x-ray crystallography to determine the conformational structure of the protein involved. 2 figs.

  18. Intermolecular electron transfer from intramolecular excitation and coherent acoustic phonon generation in a hydrogen-bonded charge-transfer solid.

    PubMed

    Rury, Aaron S; Sorenson, Shayne; Dawlaty, Jahan M

    2016-03-14

    Organic materials that produce coherent lattice phonon excitations in response to external stimuli may provide next generation solutions in a wide range of applications. However, for these materials to lead to functional devices in technology, a full understanding of the possible driving forces of coherent lattice phonon generation must be attained. To facilitate the achievement of this goal, we have undertaken an optical spectroscopic study of an organic charge-transfer material formed from the ubiquitous reduction-oxidation pair hydroquinone and p-benzoquinone. Upon pumping this material, known as quinhydrone, on its intermolecular charge transfer resonance as well as an intramolecular resonance of p-benzoquinone, we find sub-cm(-1) oscillations whose dispersion with probe energy resembles that of a coherent acoustic phonon that we argue is coherently excited following changes in the electron density of quinhydrone. Using the dynamical information from these ultrafast pump-probe measurements, we find that the fastest process we can resolve does not change whether we pump quinhydrone at either energy. Electron-phonon coupling from both ultrafast coherent vibrational and steady-state resonance Raman spectroscopies allows us to determine that intramolecular electronic excitation of p-benzoquinone also drives the electron transfer process in quinhydrone. These results demonstrate the wide range of electronic excitations of the parent of molecules found in many functional organic materials that can drive coherent lattice phonon excitations useful for applications in electronics, photonics, and information technology.

  19. Molecular and intermolecular effects in collagen fibril mechanics: a multiscale analytical model compared with atomistic and experimental studies.

    PubMed

    Marino, Michele

    2016-02-01

    Both atomistic and experimental studies reveal the dependence of collagen fibril mechanics on biochemical and biophysical features such as, for instance, cross-link density, water content and protein sequence. In order to move toward a multiscale structural description of biological tissues, a novel analytical model for collagen fibril mechanics is herein presented. The model is based on a multiscale approach that incorporates and couples: thermal fluctuations in collagen molecules; the uncoiling of collagen triple helix; the stretching of molecular backbone; the straightening of the telopeptide in which covalent cross-links form; slip-pulse mechanisms due to the rupture of intermolecular weak bonds; molecular interstrand delamination due to the rupture of intramolecular weak bonds; the rupture of covalent bonds within molecular strands. The effectiveness of the proposed approach is verified by comparison with available atomistic results and experimental data, highlighting the importance of cross-link density in tuning collagen fibril mechanics. The typical three-region shape and hysteresis behavior of fibril constitutive response, as well as the transition from a yielding-like to a brittle-like behavior, are recovered with a special insight on the underlying nanoscale mechanisms. The model is based on parameters with a clear biophysical and biochemical meaning, resulting in a promising tool for analyzing the effect of pathological or pharmacological-induced histochemical alterations on the functional mechanical response of collagenous tissues.

  20. [Intermolecular Interactions between Cytisine and Bovine Serum Albumin A Synchronous Fluorescence Spectroscopic Analysis and Molecular Docking Research].

    PubMed

    Wu, Yu-hang; Han, Zhong-bao; Ma, Jia-ze; He, Yan; Liu, Li-yan; Xin, Shi-gang; Yu, Zhan

    2016-03-01

    Cytisine (Cy) is one of the alkaloids that exist naturally in the plant genera Laburnum of the family Fabaceae. With strong bioactivities, Cy is commercialized for smoking cessation for years. In this work, the study of intermolecular interactions between Cy and bovine serum albumin (BSA) was performed by applying fluorescence spectroscopic methods under simulated physiological conditions. The mechanism of fluorescence quenching of BSA by Cy was also studied. Parameters such as bathing temperature, time and solution pH were investigated to optimize the fluorescence quenching. The binding type, binding ratio and binding constant between BSA and Cy were calculated by using the Stem-Volmer equation. Experimental results indicated that Cy can quench the fluorescent emission of BSA statically by forming a 1 : 1 type non-covalent complex and the binding constant is 5.6 x 10(3) L x mol(-1). Synchronous fluorescence spectral research shows Cy may affect the fluorescence emission of Trp residues of BSA. Furthermore, molecular docking is utilized to model the complex and probe the plausible quenching mechanism. It can be noted that the hydrogen bindings and hydrophobic interactions between Cy and BSA change the micro-environment of Trp213, which leads to the fluorescence quenching of BSA. PMID:27400521