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1

Phenomena induced by intermolecular interactions  

International Nuclear Information System (INIS)

This is concerned with recent experimental and theoretical work dealing with phenomena created by the transient dipoles and polarizabilities produced by intermolecular interactions. The former produce absorption from the microwave to the optical regions of the spectrum and the latter produce Rayleigh and Raman scattering; such absorption and scattering would be absent without collisions. Static properties, such as dielectric constant, refractive index, and Kerr effect, also exhibit the effects of induced dipoles and polarizabilities

2

Intermolecular interactions in solid benzene.  

Science.gov (United States)

The lattice dynamics and molecular vibrations of benzene and deuterated benzene crystals are calculated from force constants derived from density-functional theory (DFT) calculations and compared with measured inelastic neutron-scattering spectra. A very small change (0.5%) in lattice parameter is required to obtain real lattice-mode frequencies across the Brillouin zone. There is a strong coupling between wagging and breathing modes away from the zone center. This coupling and sensitivity to cell size arises from two basic interactions. Firstly, comparatively strong interactions that hold the benzene molecules together in layers. These include an intermolecular interaction in which H atoms of one molecule link to the center of the aromatic ring of a neighboring molecule. The layers are held to each other by weaker interactions, which also have components that hold molecules together within a layer. Small changes in the lattice parameters change this second type of interaction and account for the changes to the lattice dynamics. The calculations also reveal a small auxetic effect in that elongation of the crystal along the b axis leads to an increase in internal pressure in the ac plane, that is, elongation in the b direction induces expansion in the a and c directions. PMID:16460192

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

2006-01-28

3

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

Science.gov (United States)

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. PMID:18554003

Korona, Tatiana

2008-06-14

4

Model calculations of intermolecular interactions in the lowest energy Rydberg state of ammonia  

International Nuclear Information System (INIS)

Ab initio calculations on the triplet n3S Rydberg state of ammonia and the ammonia + two hydrogen molecule encounter complex indicate that contrary to expectations the system undergoes increasing rydbergization without great energy cost at close approaches. (orig.)

5

Computational studies on intermolecular interactions in solvation  

Science.gov (United States)

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 was found that the geometric combining rule fails to predict the "weaker-than-expected" alkane-perfluoroalkane interactions, as illustrated by the systematic disagreements with experiment in the case of cross second pressure viral coefficients, gas solubilities, and liquid-liquid mixing properties. In Chapter 6, this study was extended to the investigation on combining rules and potential functions by looking extensively at the limit of accuracy of using some 2-parameter potential functions with some combining rules to represent a wide range of nonpolar interactions by fitting to experimental 2nd pressure virial coefficients. Overall, no pairing of potential function and any combining rules were found to represent simultaneously the intermolecular interactions within the provided experimental uncertainties for the range of molecules involved in the study. The limit of accuracy of representing the interactions using transferable parameters was found to be approximately 10--15%.

Song, Weiping

6

Probing intermolecular protein-protein interactions in the calcium-sensing receptor homodimer using bioluminescence resonance energy transfer (BRET)  

DEFF Research Database (Denmark)

The calcium-sensing receptor (CaR) belongs to family C of the G-protein coupled receptor superfamily. The receptor is believed to exist as a homodimer due to covalent and non-covalent interactions between the two amino terminal domains (ATDs). It is well established that agonist binding to family C receptors takes place at the ATD and that this causes the ATD dimer to twist. However, very little is known about the translation of the ATD dimer twist into G-protein coupling to the 7 transmembrane moieties (7TMs) of these receptor dimers. In this study we have attempted to delineate the agonist-induced intermolecular movements in the CaR homodimer using the new bioluminescence resonance energy transfer technique, BRET2, which is based on the transference of energy from Renilla luciferase (Rluc) to the green fluorescent protein mutant GFP2. We tagged CaR with Rluc and GFP2 at different intracellular locations. Stable and highly receptor-specific BRET signals were obtained in tsA cells transfected with Rluc- and GFP2-tagged CaRs under basal conditions, indicating that CaR is constitutively dimerized. However, the signals were not enhanced by the presence of agonist. These results could indicate that at least parts of the two 7TMs of the CaR homodimer are in close proximity in the inactivated state of the receptor and do not move much relative to one another upon agonist activation. However, we cannot exclude the possibility that the BRET technology is unable to register putative conformational changes in the CaR homodimer induced by agonist binding because of the bulk sizes of the Rluc and GFP2 molecules.

Jensen, Anders A.; Hansen, Jakob L

2002-01-01

7

Effects of the higher electron correlation correction on the calculated intermolecular interaction energies of benzene and naphthalene dimers: comparison between MP2 and CCSD(T) calculations  

Science.gov (United States)

Intermolecular interaction energies of parallel and T-shape benzene dimers and parallel naphthalene dimer were calculated with MP2, MP3, MP4(SDQ), MP4(SDTQ), CCSD and CCSD(T) electron correlation corrections using several basis sets. The MP2 calculations considerably overestimated the attraction compared to the CCSD(T) ones. The MP2 correlation interaction energies, the differences between the HF and MP2 interaction energies, were 21-38% larger than the corresponding CCSD(T) ones. The MP4(SDQ) and CCSD calculations substantially underestimated the attraction compared to MP4(SDTQ) and CCSD(T), which indicated the importance of triple excitation. The estimated CCSD(T) interaction energies of the three dimers with reasonably large basis sets were -1.74, -2.50 and -5.69 kcal/mol, respectively.

Tsuzuki, Seiji; Uchimaru, Tadafumi; Matsumura, Kazunari; Mikami, Masuhiro; Tanabe, Kazutoshi

2000-03-01

8

Energy-dispersive NEXAFS. A novel tool for the investigation of intermolecular interaction and structural phase dynamics  

Energy Technology Data Exchange (ETDEWEB)

In the context of this thesis, the novel method soft X-ray energy-dispersive NEXAFS spectroscopy was explored and utilized to investigate intermolecular coupling and post-growth processes with a temporal resolution of seconds. 1,4,5,8- naphthalene tetracarboxylic acid dianhydride (NTCDA)multilayer films were the chosen model system for these investigations. The core hole-electron correlation in coherently coupled molecules was studied by means of energy-dispersive near-edge X-ray absorption fine-structure spectroscopy. A transient phase was found which exists during the transition between a disordered condensed phase and the bulk structure. This phase is characterized by distinct changes in the spectral line shape and energetic position of the X-ray absorption signal at the C K-edge. The findings were explained with the help of theoretical models based on the coupling of transition dipole moments, which are well established for optically excited systems. In consequence, the experimental results provides evidence for a core hole-electron pair delocalized over several molecules. Furthermore, the structure formation of NTCDA multilayer films on Ag(111) surfaces was investigated. With time-resolved and energy-dispersive NEXAFS experiments the intensity evolution in s- and p-polarization showed a very characteristic behavior. By combining these findings with the results of time-dependent photoemission measurements, several sub-processes were identified in the post- growth behavior. Upon annealing, the amorphous but preferentially flat-lying molecules flip into an upright orientation. After that follows a phase characterized by strong intermolecular coupling. Finally, three-dimensional islands are established. Employing the Kolmogorov-Johnson-Mehl-Avrami model, the activation energies of the sub-processes were determined.

Scholz, Markus

2013-06-27

9

Energy-dispersive NEXAFS. A novel tool for the investigation of intermolecular interaction and structural phase dynamics  

International Nuclear Information System (INIS)

In the context of this thesis, the novel method soft X-ray energy-dispersive NEXAFS spectroscopy was explored and utilized to investigate intermolecular coupling and post-growth processes with a temporal resolution of seconds. 1,4,5,8- naphthalene tetracarboxylic acid dianhydride (NTCDA)multilayer films were the chosen model system for these investigations. The core hole-electron correlation in coherently coupled molecules was studied by means of energy-dispersive near-edge X-ray absorption fine-structure spectroscopy. A transient phase was found which exists during the transition between a disordered condensed phase and the bulk structure. This phase is characterized by distinct changes in the spectral line shape and energetic position of the X-ray absorption signal at the C K-edge. The findings were explained with the help of theoretical models based on the coupling of transition dipole moments, which are well established for optically excited systems. In consequence, the experimental results provides evidence for a core hole-electron pair delocalized over several molecules. Furthermore, the structure formation of NTCDA multilayer films on Ag(111) surfaces was investigated. With time-resolved and energy-dispersive NEXAFS experiments the intensity evolution in s- and p-polarization showed a very characteristic behavior. By combining these findings with the results of time-dependent photoemission measurements, several sub-processes were identified in the post- growth behavior. Upon annealing, the amorphous but preferentially flat-lying molecules flip into an upright orientation. After that follows a phase characterized by strong intermolecular coupling. Finally, three-dimensional islands are established. Employing the Kolmogorov-Johnson-Mehl-Avrami model, the activation energies of the sub-processes were determined.

10

Density matrix based microscopic theory of molecule metal-nanoparticle interactions: Linear absorbance and plasmon enhancement of intermolecular excitation energy transfer  

Science.gov (United States)

A microscopic theory of interacting molecule metal-nanoparticle (MNP) systems is presented and used to compute absorption spectra and the plasmon enhancement of intermolecular excitation energy transfer (EET). The approach is based on a nonperturbative consideration of the Coulomb coupling matrix elements responsible for EET between the molecules and the MNP. In this way, the need to determine the local fields induced by surface plasmon excitations of the MNP is removed, but the whole description is restricted to distances among the interacting species less than the wavelength of absorbed photons. Based on a density matrix theory, the approach accounts for the vibrational level structure of the molecules, intramolecular vibrational energy redistribution (IVR), and plasmon damping. Numerical results for linear absorbance spectra and EET dynamics are offered. In this respect the importance of energy dissipation in the MNP due to rapid surface plasmon decay is emphasized.

Kyas, Gerold; May, Volkhard

2011-01-01

11

Effects of aromatic trifluoromethylation, fluorination, and methylation on intermolecular ?-? interactions.  

Science.gov (United States)

Marcus theory states that the rate of charge transfer is directly proportional to the amount of intermolecular orbital overlap. Theoretically optimizing the electronic coupling through the orientation and distance which both can increase the frontier orbital overlap between molecules is an attractive route to potentially provide theoretical insight for discovering new high performance semiconductor materials. To investigate how these parameters qualitatively affect charge transfer of model systems, unconstrained dimer optimizations with MP2 and dispersion-corrected DFT methods were used to probe the ?-? interactions of methylated, fluorinated, and trifluoromethylated benzene, pyridine, and bipyridine dimers. These systems can serve as simplified models representing weak noncovalent interactions in organic semiconductor materials. Enhanced intermolecular interaction energies, reduced ?-? distances, and more favorable cofacial orientations were found with the trifluoromethylated dimers compared to fluorinated and methylated dimers studied. Similar effects were found with donor-acceptor pairs that represent organic p-n heterojunction systems. These enhanced ?-? interactions are likely caused by increased molecular quadrupole moment and dispersion interaction associated with trifluoromethylation. This computational study illustrates the strong potential of trifluoromethylation and, possibly perfluoroalkylation of acenes and heteroacenes, leading qualitatively to enhanced electron transfer through better ?-? stacked structures, making them viable candidates for use as n-type organic semiconductor materials. The findings also provide insight for fundamental interactions between drug molecules that include fluorinated and trimethylfluorinated aromatics binding to protein receptors. PMID:23906416

Mottishaw, Jeffery D; Sun, Haoran

2013-08-22

12

Small and efficient basis sets for the evaluation of accurate interaction energies: aromatic molecule-argon ground-state intermolecular potentials and rovibrational States.  

Science.gov (United States)

By evaluating a representative set of CCSD(T) ground state interaction energies for van der Waals dimers formed by aromatic molecules and the argon atom, we test the performance of the polarized basis sets of Sadlej et al. (J. Comput. Chem. 2005, 26, 145; Collect. Czech. Chem. Commun. 1988, 53, 1995) and the augmented polarization-consistent bases of Jensen (J. Chem. Phys. 2002, 117, 9234) in providing accurate intermolecular potentials for the benzene-, naphthalene-, and anthracene-argon complexes. The basis sets are extended by addition of midbond functions. As reference we consider CCSD(T) results obtained with Dunning's bases. For the benzene complex a systematic basis set study resulted in the selection of the (Z)Pol-33211 and the aug-pc-1-33321 bases to obtain the intermolecular potential energy surface. The interaction energy values and the shape of the CCSD(T)/(Z)Pol-33211 calculated potential are very close to the best available CCSD(T)/aug-cc-pVTZ-33211 potential with the former basis set being considerably smaller. The corresponding differences for the CCSD(T)/aug-pc-1-33321 potential are larger. In the case of the naphthalene-argon complex, following a similar study, we selected the (Z)Pol-3322 and aug-pc-1-333221 bases. The potentials show four symmetric absolute minima with energies of -483.2 cm(-1) for the (Z)Pol-3322 and -486.7 cm(-1) for the aug-pc-1-333221 basis set. To further check the performance of the selected basis sets, we evaluate intermolecular bound states of the complexes. The differences between calculated vibrational levels using the CCSD(T)/(Z)Pol-33211 and CCSD(T)/aug-cc-pVTZ-33211 benzene-argon potentials are small and for the lowest energy levels do not exceed 0.70 cm(-1). Such differences are substantially larger for the CCSD(T)/aug-pc-1-33321 calculated potential. For naphthalene-argon, bound state calculations demonstrate that the (Z)Pol-3322 and aug-pc-1-333221 potentials are of similar quality. The results show that these surfaces differ substantially from the available MP2/aug-cc-pVDZ potential. For the anthracene-argon complex it proved advantageous to calculate interaction energies by using the (Z)Pol and the aug-pc-1 basis sets, and we expect it to be increasingly so for complexes containing larger aromatic molecules. PMID:25317989

Cybulski, Hubert; Baranowska-??czkowska, Angelika; Henriksen, Christian; Fernández, Berta

2014-11-01

13

Intermolecular interactions and the thermodynamic properties of supercritical fluids  

Science.gov (United States)

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

Yigzawe, Tesfaye M.; Sadus, Richard J.

2013-05-01

14

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

Science.gov (United States)

A new formulation of the second-order exchange-induction energy of symmetry-adapted perturbation theory is presented. In the proposed formalism the exchange-induction energy is expressed through one- and two-particle reduced density matrices of monomers, which are of zeroth and first order with respect to the effective electrostatic potential of another monomer. The resulting expression is further modified by using the partition of two-particle density matrices into the antisymmetrized product of one-particle density matrices and the remaining cumulant part. The proposed formalism has been applied to the case of closed-shell monomers and for density matrices obtained from the expectation-value expression with coupled cluster singles and doubles wave functions. The performance of the new approach has been demonstrated on several benchmark van der Waals systems, including dimers of argon, water, and ethyne. PMID:18979036

Korona, Tatiana

2008-11-21

15

Direct observation of intermolecular interactions mediated by hydrogen bonding  

Science.gov (United States)

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.

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

2014-07-01

16

Anion response of organogels: dependence on intermolecular interactions between gelators.  

Science.gov (United States)

Being different from common sensing molecules existing as monomer in solution, the gelators as sensing molecules self-assembled together in gels. Therefore, the interaction strength between gelators is believed as an important factor for gels to recognize selectively anions. In this paper, we choose two gelators, presenting similar binding sites for anions, but different strengths in intermolecular interaction. Moreover, their anion responsive behaviors in organogels were examined by observing phase state and measuring UV-vis and fluorescence spectra. We found that the organogel formed by 2 with strong intermolecular interaction could selectively recognize fluoride anion. However, the gels of 1 could be transformed into sol phases by addition of F(-), Cl(-), Br(-), AcO(-) and H(2)PO(4)(-) because of the small aggregate constant of 1 in o-dichlorobenzene, presenting poor selectivity. Moreover, their UV-vis and emission spectra acting as testing methods also suggested the same conclusion. PMID:23380938

Xue, Pengchong; Sun, Jiabao; Xu, Qiuxia; Lu, Ran; Takafuji, Makoto; Ihara, Hirotaka

2013-03-21

17

Intermolecular interactions of reduced nicotinamide adenine dinucleotide (NADH) in solution  

Science.gov (United States)

Nicotinamide adenine dinucleotide (NAD^+/NADH) is a coenzyme involved in cellular respiration as an electron transporter. In aqueous solution, the molecule exhibits a folding transition characterized by the stacking of its aromatic moieties. A transition to an unfolded conformation is possible using chemical denaturants like methanol. Because the reduced NADH form is fluorescent, the folding transition can be monitored using fluorescence spectroscopy, e.g., via a blue-shift in the UV-excited emission peak upon methanol unfolding. Here we present evidence of interactions between NADH molecules in solution. We measure the excited-state emission from NADH at various concentrations (1-100 ?M in MOPS buffer, pH 7.5; 337-nm wavelength excitation). Unlike for the folded form, the emission peak wavelength of the unfolded form is concentration dependent, exhibiting a red-shift with higher NADH concentration, suggesting the presence of intermolecular interactions. An understanding of NADH spectra in solution would assist in interpreting intercellular NADH measurements used for the in vivo monitoring cellular energy metabolism.

Jasensky, Joshua; Junaid Farooqi, M.; Urayama, Paul

2008-10-01

18

Electronic Structure Theory for Radicaloid Systems and Intermolecular Interactions  

Science.gov (United States)

A radical molecule contains one or more electrons that are unpaired. A radicaloid may be defined as a molecule in which there are that are partially unpaired. As a result, the electronic structure of the radicaloid can be quite complicated for a variety of reasons. For a singlet biradicaloid, the singlet and triplet wavefunction can be quite close energetically which can lead to problems when trying to describe the system with a single determinant. The simplest solution to this problem is to allow the wavefunction to break spin-symmetry in order to get a lower energy. Unfortunately this action can lead to wavefunctions that are no longer eigenfunctions of the operator. In the second chapter we investigate a distannyne which has a biradicaloid resonance structure. By examining the orbital Hessian, it is discovered that the spin-symmetric solution is a saddle-point in wavefunction space and is structurally different than the spin-polarized solution. We then increase the complexity of the model system and see that the spin-symmetric solution is only a minimum for the exact experimental system and not for a simplified model system in which bulky organic substituents are replaced by simpler phenyl groups. Therefore, the breaking of spin-symmetry is absolutely critical in the small model systems and the full substituents play a non-trivial role. However, the breaking of the spin-symmetry can have consequences for physical quantities when correlated methods are used. At the point of spin polarization or unrestriction the orbital Hessian will have one eigenvalue which is zero. Since the relaxed density matrix in correlated methods like Second-Order Mo ller-Plesset theory (MP2) depend on the inverse of the Hessian, at the unrestriction point this quantity will be undefined. Some unphysical artifacts are identified as a direct consequence of this fact. First, discontinuities in first order molecular properties such as the dipole moment are seen at the geometries 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.

Kurlancheek, Westin

19

Incisive probing of intermolecular interactions in molecular crystals: core level spectroscopy combined with density functional theory.  

Science.gov (United States)

The ?-form of crystalline para-aminobenzoic acid (PABA) has been examined as a model system for demonstrating how the core level spectroscopies X-ray photoelectron spectroscopy (XPS) and near-edge X-ray absorption fine-structure (NEXAFS) can be combined with CASTEP density functional theory (DFT) to provide reliable modeling of intermolecular bonding in organic molecular crystals. Through its dependence on unoccupied valence states NEXAFS is an extremely sensitive probe of variations in intermolecular bonding. Prediction of NEXAFS spectra by CASTEP, in combination with core level shifts predicted by WIEN2K, reproduced experimentally observed data very well when all significant intermolecular interactions were correctly taken into account. CASTEP-predicted NEXAFS spectra for the crystalline state were compared with those for an isolated PABA monomer to examine the impact of intermolecular interactions and local environment in the solid state. The effects of the loss of hydrogen-bonding in carboxylic acid dimers and intermolecular hydrogen bonding between amino and carboxylic acid moieties are evident, with energy shifts and intensity variations of NEXAFS features arising from the associated differences in electronic structure and bonding. PMID:25248405

Stevens, Joanna S; Seabourne, Che R; Jaye, Cherno; Fischer, Daniel A; Scott, Andrew J; Schroeder, Sven L M

2014-10-23

20

Intermolecular interactions and phase structures of plasticized wheat proteins materials.  

Science.gov (United States)

The intermolecular interactions and phase structures of thermally processed wheat proteins with glycerol and water as plasticizers were studied by dynamic mechanical analysis and solid-state high-resolution NMR spectroscopy. The results of phase structures at scales of molecular level to tens of nanometers were correlated with the mechanical properties of the materials. The strong hydrogen bonding intermolecular interactions between the components in wheat proteins and the plasticizers resulted in a significant change in molecular motions of wheat protein materials. The plasticized systems, however, still presented a wide distribution of chain mobility at a scale from the molecular level to 20-30 nm, and the plasticizing effect was different for each wheat protein system. High protein content systems tended to be plasticized relatively easily especially when lipid content is high, but the existence of residual starch would require more plasticizers to reach a similar level of chain mobility. On a scale of 20-30 nm, plasticized vital wheat gluten (WG) and the deamidated wheat proteins (WP-I) were heterogeneous with each component exhibiting its individual mobility, whereas the plasticized insoluble protein system (WP-II) with poor mechanical properties was homogeneous. Both WG and WP-I systems showed excellent mechanical polymeric properties in tensile strength and elasticity despite the heterogeneity. The strong intermolecular hydrogen bonding interactions and soluble protein components in the materials could provide an adhesion among different components and act as a continuous matrix in the systems. Therefore, these materials displayed excellent mechanical properties via coordination effects among different components. PMID:15877392

Zhang, Xiaoqing; Burgar, Iko; Do, My Dieu; Lourbakos, Eleni

2005-01-01

 
 
 
 
21

Towards the biaxial nematic phase via specific intermolecular interactions  

International Nuclear Information System (INIS)

The work described in this thesis has been focussed on the search of an elusive liquid crystal phase, known as the biaxial nematic phase. Indeed, despite nearly thirty years of intense research, no-one has been able to characterise unambiguously a biaxial nematic phase in a low-molar-mass thermotropic system. Our research is based on the concept of molecular biaxiality as distinct from shape biaxiality. Thus, we are seeking to design palladium complexes where specific intermolecular interactions could exist. Therefore, a few original synthetic strategies were developed to tackle the challenge of discovering the biaxial nematic phase

22

Intermolecular Interactions in Biomolecular Systems Examined by Mass Spectrometry  

Science.gov (United States)

With the development of electrospray and matrix-assisted laser desorption ionization, mass spectrometry (MS) evolved into a powerful tool in the field of biochemistry. Whereas MS is primarily analytical in nature, an increasing number of MS research groups employ the method to address fundamental biochemical questions. Probing the interaction of noncovalently bound molecules in the mass spectrometer is one of the most interesting MS-based experiments possible today, with the potential of making a significant contribution to the basic understanding of the structure and function of biochemical complexes. Here we review a number of current research efforts employing primarily MS techniques to investigate intermolecular interactions in biochemical systems. Examples chosen include the interaction of biomolecules with solvent molecules; interactions between nucleic-acid molecules, in particular, interactions in duplex and quadruplex structures; and interactions between proteins involved in neurodegenerative diseases. Finally we conclude by presenting a few examples of very large biomolecular assemblies in the mega-Dalton range analyzed by MS.

Wyttenbach, Thomas; Bowers, Michael T.

2007-05-01

23

Intra- and intermolecular energy transfer in H2+OH collisions  

International Nuclear Information System (INIS)

We have used the method of quasiclassical dynamics to investigate intra- and intermolecular energy transfer in H2+OH collisions. Energy transfer has been investigated as function of translational temperature, rotational energy, and vibrational energy. The energy transfer mechanism is complex with ten types of energy transfer possible, and evidence was found for all types. There is much more exchange between the translational degree of freedom and the H2 vibrational degree of freedom than there is between translation and OH vibration. Translational energy is transferred to the rotational degrees of freedom of each molecule, and this occurs more readily for OH than H2. Both molecules exhibited intramolecular energy transfer from vibration to rotation, and this was a major pathway for vibrational deactivation. Evidence was also found for the intermolecular transfer of energy from vibration to the rotational and vibrational degrees of freedom of the other molecule

24

Infrared absorption by H2-Ar collisional complexes and the anisotropy of the intermolecular interaction potential  

International Nuclear Information System (INIS)

H2-Ar scattering processes in the presence of a weak photon field are considered. Calculations are based on an accurate ab initio interaction-induced electric dipole surface and an anisotropic intermolecular potential energy surface. The close-coupled scheme of integrating the Schroedinger equation is employed to calculate the rototranslational absorption spectrum of H2-Ar pairs in the far-infrared region of the electromagnetic spectrum. The results are compared with previous work where the weak anisotropy of the intermolecular interaction potential was suppressed. Under the conditions considered, accounting for the anisotropy modifies the rototranslational absorption spectrum discernibly, but only at some frequency bands where the corrections are negative, typically below 10%

25

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

Science.gov (United States)

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 sheets which suggests a switch from very small corrugation to stick-slip behavior at interlayer distances smaller than 6 Å. Our results for gas phase clusters agree reasonably with methods using more demanding quantum chemical methods to treat the van der Waals interactions, thus providing support for the relatively fast density functional theory methods used here for studying water-graphene interactions in nanoscale systems. PMID:25356833

McKenzie, S; Kang, H C

2014-12-21

26

Hierarchical intermolecular interaction models of N-heteroaromatic STM adlayer structures  

Science.gov (United States)

The molecular scale electronic device concept was initiated in 1974 with the semi-quantitative analysis of a hemiquinone molecule. Because of the molecule's electron donor and acceptor properties, and ability to transfer electrons along the pi-network, it was proposed that the molecule could perform as a circuit rectifier. Many investigations of molecular scale systems have occurred since then, in particular, of organic molecules with large, fused ring systems that spontaneously self-organize after deposition onto a substrate. The directionality and molecular specificity of hydrogen bonding differentiates it from the other weak interactions, driving molecules into specific arrangements and enabling spontaneous rearrangement after addition of only a small amount of enthalpic energy. A direct application of molecular recognition through self-assembly has been the design of patterned self-assembled monolayers (SAMs) for the construction of microelectrodes and supramolecular templates. However, the intermolecular interactions that drive ordered structures to form, including molecular chains and large aggregates, has not been well understood. To elucidate a quantitative description of the intermolecular forces of pi network systems of aromatics that control such features as packing density and porosity, two individual model heteroaromatic systems of 9-acridinecarboxylic acid and isonicotinic acid are investigated using both experimental and computational resources. Supported by scanning tunneling microscopy (STM) topographies, x-ray diffraction (XRD) data and x-ray photoelectron (XPS) spectra, this class of N-heteroaromatics adsorbed on Ag (111) serves as a model system to systematically investigate 2-dimensional intermolecular (2-D) interactions and their impact on forming different structural phases of molecular chain domains. To approach an understanding of the dynamics of N-heteroaromatic film growth, an intermolecular interaction model of 1-D single phase chains and clusters is performed. The model considers the anisotropy of the electrostatic force interactions to determine what charge arrangements (dipole, quadrupole, etc.) better characterize the molecular interactions. Furthermore, the competition between phase chain types is shown to be length dependent and in qualitative agreement with the coverage dependent STM structural phase composition.

Evans, Diane

27

The effects of P-T changes on intermolecular interactions in crystal structure of iodoform  

Science.gov (United States)

The structural transition at different pressures of a halogen and hydrogen bonded molecular structure (iodoform, CHI3) is described. The pressures analyzed up to sample decomposition are 0.85 GPa (P1RT) and 2.15 GPa (P2RT); also room conditions (P0RT) and low temperature (106 K, P0LT) structures have been reported for comparison. The observed disorder-order phase transition, from P63/m to P63 space group, can be rationalized by the intermolecular interaction analysis. The shortening of the distances among iodoform planes, observed during the compression and the temperature decreasing, determines an ordering of molecular dipoles in a parallel arrangement: this phase transition causes a shortening of I⋯I halogen bondings. The BSSE corrected cohesive energies have been calculated for all structures at DFT/B3LYP level of theory using a periodic boundary condition code and the Grimme dispersion correction. Hirshfeld surfaces and electrostatic potential mapped on charge density isosurfaces have been computed and their features have been analyzed, in order to better understand the halogen intermolecular interactions that control the structural modification of iodoform crystal.

Bertolotti, Federica; Curetti, Nadia; Benna, Piera; Gervasio, Giuliana

2013-06-01

28

About intermolecular interactions in binary and ternary solutions of some azo-benzene derivatives.  

Science.gov (United States)

The nature and strength of the intermolecular interactions in the solutions of three azo-benzene derivatives (ADi, i=1, 2, 3) were established by solvatochromic effects in solvents with different electric permittivities, refractive indices and Kamlet-Taft constants. A quantum mechanical analysis corroborated with spectral data offered information about the excited state dipole moments and polarizabilities of the studied compounds. The separation of the supply of universal and specific interactions to the total spectral shift was made based on the regression coefficients from the equations describing the solvatochromic effect. Supplementary information about the composition of the first solvation shell and the energy in the solute-solvent molecular pairs were obtained analyzing the ternary solutions of ADi, i=1, 2, 3 compounds in solvent mixture Methanol (M)+n-Hexane (H). PMID:25168003

Ivan, Liliana Mihaela; Closca, Valentina; Burlea, Marin; Rusu, Elena; Airinei, Anton; Dorohoi, Dana Ortansa

2015-02-01

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MODELS OF AMPHOTERICIN MEMBRANE CHANNEL BASED ON CONCERTED INTERMOLECULAR =C-H…O INTERACTIONS  

Directory of Open Access Journals (Sweden)

Full Text Available To study the possibility for amphotericin to form membrane channel via intermolecular interactions mimicing the association mode of polyene macrolides in crystal structures we have built two channel models in vacuo: amphotericin B octamer and hexamer. The octamer model does not reproduce the concerted weak =C-H…O intermolecular interactions within the whole aggregate structure and has too large pore diameter. For hexamer model, the pore diameter is within experimental estimates. The hexamer model rather well reproduces characteristic features of a channel with such concerted weak interactions: association mode, H-bonding pattern within the whole assembly and accessibility of polyene hydroxyl groups for hydrophyllic interactions in the pore.

Lisnyak Yu. V

2012-10-01

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Reversible electron-induced cis-trans isomerization mediated by intermolecular interactions  

International Nuclear Information System (INIS)

Reversible isomerization processes are rarely found when organic molecular switches are adsorbed on metal surfaces. One obstacle is the large energy difference of the isomeric forms, since usually the most planar conformer has the largest adsorption energy. In the example of an imine derivative, we show a strategy for also stabilizing the non-planar isomer by intermolecular bonding to its neighbors. Tunneling electrons from the tip of a scanning tunneling microscope can then be used to induce reversible switching between the trans and cis-like state. Supported by model force-field calculations, we illustrate that the most probable cause of the enhanced stability of the three-dimensional cis state at specific adsorption sites is the electrostatic interaction with N sites of the neighboring molecule.

31

Range-separated density-functional theory with random phase approximation applied to noncovalent intermolecular interactions  

CERN Document Server

Range-separated methods combining a short-range density functional with long-range random phase approximations RPAs with or without exchange response kernel are tested on rare-gas dimers and the S22 benchmark set of weakly interacting complexes of Jurecka et al. [Phys. Chem. Chem. Phys. 8, 1985 (2006 )] . The methods are also compared to full-range RPA approaches. Both range separation and inclusion of the Hartree-Fock exchange kernel largely improve the accuracy of intermolecular interaction energies. The best results are obtained with the method called RSH+RPAx, which yields interaction energies for the S22 set with an estimated mean absolute error of about 0.5-0.6 kcal/mol, corresponding to a mean absolute percentage error of about 7%-9% depending on the reference interaction energies used. In particular, the RSH+RPAx method is found to be overall more accurate than the range-separated method based on long-range second-order M{\\o}ller-Plesset MP2 perturbation theory RSH+MP2 .

Zhu, Wuming; Savin, Andreas; Angyán, János G

2014-01-01

32

Modulation of the intermolecular interaction of myoglobin by removal of the heme  

Science.gov (United States)

Toward understanding intermolecular interactions governing self-association of proteins, the present study investigated a model protein, myoglobin, using a small-angle X-ray scattering technique. It has been known that removal of the heme makes myoglobin aggregation-prone. The interparticle interferences of the holomyoglobin and the apomyoglobin were compared in terms of the structure factor. Analysis of the structure factor using a model potential of Derjaguin–Laudau–Verwey–Overbeek (DLVO) suggests that the intermolecular interaction potential of apomyoglobin is more attractive than that of holomyoglobin at short range from the protein molecule. PMID:24121340

Imamura, Hiroshi; Morita, Takeshi; Sumi, Tomonari; Isogai, Yasuhiro; Kato, Minoru; Nishikawa, Keiko

2013-01-01

33

Isolating the non-polar contributions to the intermolecular potential for water-alkane interactions.  

Science.gov (United States)

Intermolecular potential models for water and alkanes describe pure component properties fairly well, but fail to reproduce properties of water-alkane mixtures. Understanding interactions between water and non-polar molecules like alkanes is important not only for the hydrocarbon industry but has implications to biological processes as well. Although non-polar solutes in water have been widely studied, much less work has focused on water in non-polar solvents. In this study we calculate the solubility of water in different alkanes (methane to dodecane) at ambient conditions where the water content in alkanes is very low so that the non-polar water-alkane interactions determine solubility. Only the alkane-rich phase is simulated since the fugacity of water in the water rich phase is calculated from an accurate equation of state. Using the SPC/E model for water and TraPPE model for alkanes along with Lorentz-Berthelot mixing rules for the cross parameters produces a water solubility that is an order of magnitude lower than the experimental value. It is found that an effective water Lennard-Jones energy ?(W)/k = 220?K is required to match the experimental water solubility in TraPPE alkanes. This number is much higher than used in most simulation water models (SPC/E-?(W)/k = 78.2?K). It is surprising that the interaction energy obtained here is also higher than the water-alkane interaction energy predicted by studies on solubility of alkanes in water. The reason for this high water-alkane interaction energy is not completely understood. Some factors that might contribute to the large interaction energy, such as polarizability of alkanes, octupole moment of methane, and clustering of water at low concentrations in alkanes, are examined. It is found that, though important, these factors do not completely explain the anomalously strong attraction between alkanes and water observed experimentally. PMID:25134597

Ballal, Deepti; Venkataraman, Pradeep; Fouad, Wael A; Cox, Kenneth R; Chapman, Walter G

2014-08-14

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Intermolecular interactions of aromatic hydrocarbons in carbonaceous materials - a molecular and quantum mechanics  

Energy Technology Data Exchange (ETDEWEB)

Aromatic hydrocarbons (PAHs and oligomers) that are models of carbonaceous materials components were studied using MM + All Atom Force Field and the semi-empirical methods (MINDO3 and ZINDO1) of quantum chemistry. The following intermolecular interactions were studied through potential energy function: (1) Among PAH molecules; (2) among oligomeric molecules; and (3) among oligomer and PAH molecules. It was found: (1) The potential energy minimized stacks of PAHs showed interlayer distances which correspond to the experimentally measured distances in carbonaceous materials. (2) Interactions among oligomers, in general, resulted in aggregates that showed random space orientation of aromatic units. Only few aromatic units of separate oligomers were parallel to each other. (3) Interactions among the oligomer and PAH molecules resulted in parallel orientation of PAH molecules relative to aromatic units of the oligomer. Common orbitals were found in stacks of parallel oriented aromatic planes,no matter whether the planes belonged to individual molecules forming PAH crystallites, oligomeric aggregates, or PAH/oligomer aggregates. Conclusions refer to the chemical structure of the optical isotropy phase occurring in carbonaceous materials, electrical conductivity of the materials, and X-ray measurements of the average size of the aromatic units (La).

Marzec, A. [Polish Academy of Science, Gliwice (Poland). Inst. of Coal Chemistry

2000-07-01

35

Molecular dynamics simulations of fluid methane properties using ab initio intermolecular interaction potentials.  

Science.gov (United States)

Intermolecular interaction energy data for the methane dimer have been calculated at a spectroscopic accuracy and employed to construct an ab initio potential energy surface (PES) for molecular dynamics (MD) simulations of fluid methane properties. The full potential curves of the methane dimer at 12 symmetric conformations were calculated by the supermolecule counterpoise-corrected second-order Møller-Plesset (MP2) perturbation theory. Single-point coupled cluster with single and double and perturbative triple excitations [CCSD(T)] calculations were also carried out to calibrate the MP2 potentials. We employed Pople's medium size basis sets [up to 6-311++G(3df, 3pd)] and Dunning's correlation consistent basis sets (cc-pVXZ and aug-cc-pVXZ, X = D, T, Q). For each conformer, the intermolecular carbon-carbon separation was sampled in a step 0.1 A for a range of 3-9 A, resulting in a total of 732 configuration points calculated. The MP2 binding curves display significant anisotropy with respect to the relative orientations of the dimer. The potential curves at the complete basis set (CBS) limit were estimated using well-established analytical extrapolation schemes. A 4-site potential model with sites located at the hydrogen atoms was used to fit the ab initio potential data. This model stems from a hydrogen-hydrogen repulsion mechanism to explain the stability of the dimer structure. MD simulations using the ab initio PES show quantitative agreements on both the atom-wise radial distribution functions and the self-diffusion coefficients over a wide range of experimental conditions. PMID:19090563

Chao, Shih-Wei; Li, Arvin Huang-Te; Chao, Sheng D

2009-09-01

36

Intermolecular vibrational energy exchange directly probed with ultrafast two dimensional infrared spectroscopy  

Science.gov (United States)

Ultrafast two dimensional infrared (2D IR) spectroscopy has been applied to probe the intermolecular vibrational energy exchange between two model molecules, benzonitrile and acetonitrile-d3. The vibrational energy exchange between these two molecules is manifested through the growth of cross peaks in their 2D IR spectra. In experiments, their nitrile groups (CN) are not involved in the energy exchange but serve as reporters of the process. Our experiments demonstrate that intermolecular vibrational energy transfer can be directly probed with the 2D IR method. Results also show that the mode specific energy transfer can be important in intermolecular vibrational energy transfers.

Bian, Hongtao; Zhao, Wei; Zheng, Junrong

2009-09-01

37

Kinetic model of the Boltzmann equation for a power-law intermolecular interaction potential  

Science.gov (United States)

A model kinetic equation approximating the Boltzmann equation with a linearized collision integral is constructed to describe rarefied gas flows at moderate and low Knudsen numbers. The kinetic model describes gas flows with a power-law intermolecular interaction potential and involves five relaxation parameters. The structure of a shock wave is computed, and the results are compared with an experiment for argon.

Larina, I. N.; Rykov, V. A.

2010-03-01

38

Liquid chloroform structure from computer simulation with a full ab initio intermolecular interaction potential  

International Nuclear Information System (INIS)

We have calculated the intermolecular interaction energies of the chloroform dimer in 12 orientations using the second-order Møller-Plesset perturbation theory. Single point energies of important geometries were calibrated by the coupled cluster with single and double and perturbative triple excitation method. Dunning's correlation consistent basis sets up to aug-cc-pVQZ have been employed in extrapolating the interaction energies to the complete basis set limit values. With the ab initio potential data we constructed a 5-site force field model for molecular dynamics simulations. We compared the simulation results with recent experiments and obtained quantitative agreements for the detailed atomwise radial distribution functions. Our results were also consistent with previous results using empirical force fields with polarization effects. Moreover, the calculated diffusion coefficients reproduced the experimental data over a wide range of thermodynamic conditions. To the best of our knowledge, this is the first ab initio force field which is capable of competing with existing empirical force fields for liquid chloroform

39

Liquid chloroform structure from computer simulation with a full ab initio intermolecular interaction potential  

Energy Technology Data Exchange (ETDEWEB)

We have calculated the intermolecular interaction energies of the chloroform dimer in 12 orientations using the second-order Møller-Plesset perturbation theory. Single point energies of important geometries were calibrated by the coupled cluster with single and double and perturbative triple excitation method. Dunning's correlation consistent basis sets up to aug-cc-pVQZ have been employed in extrapolating the interaction energies to the complete basis set limit values. With the ab initio potential data we constructed a 5-site force field model for molecular dynamics simulations. We compared the simulation results with recent experiments and obtained quantitative agreements for the detailed atomwise radial distribution functions. Our results were also consistent with previous results using empirical force fields with polarization effects. Moreover, the calculated diffusion coefficients reproduced the experimental data over a wide range of thermodynamic conditions. To the best of our knowledge, this is the first ab initio force field which is capable of competing with existing empirical force fields for liquid chloroform.

Yin, Chih-Chien; Li, Arvin Huang-Te; Chao, Sheng D., E-mail: sdchao@spring.iam.ntu.edu.tw [Institute of Applied Mechanics, National Taiwan University, Taipei 106, Taiwan (China)

2013-11-21

40

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

Science.gov (United States)

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

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

2014-09-01

 
 
 
 
41

Supramolecular patterns controlled by electron interference and direct intermolecular interactions.  

Science.gov (United States)

Whereas all 230 three-dimensional space groups occur in organic crystals, out of only 17 plane groups some highly symmetric ones such as p31m have not yet been observed in two-dimensional (2D) crystals of organic molecules. Here a kagome network with p31m symmetry is reported for cobalt phthalocyanine on Cu(111). This unusual structure results from substrate-induced reduction of molecular symmetry and substrate-mediated interaction via quantum interference of surface electrons. These interactions provide additional control over the symmetry of 2D crystals of phthalocyanines and lead to a variety of other symmetries in self-assembled arrays. PMID:19594153

Wang, Yongfeng; Ge, Xin; Manzano, Carlos; Kröger, Jörg; Berndt, Richard; Hofer, Werner A; Tang, Hao; Cerda, Jorge

2009-08-01

42

The Study of Intermolecular Interactions Using Optical Biosensors Operating on the Effect of Surface Plasmon Resonance  

Directory of Open Access Journals (Sweden)

Full Text Available Present knowledge of the technology of optical biosensors based on the effect of surface plasmon resonance (SPR is presented. SPR enables to register almost all molecular interactions in real time without any labels or associated processes. There are considered the main technical characteristics of SPR biosensors and the principles of analysis of kinetic, equilibrium and thermodynamic parameters of intermolecular interactions.There are presented a number of examples of Biacore biosensors (GE Healthcare, USA application in post-genomic researches carried out in the Institute of Biomedical Chemistry (Moscow, Russia: SPR technology has been used in the analysis of intermolecular interactions, like protein-protein, protein-low-molecular-weight compounds, protein-DNA; in the analysis of protein oligomerization and the search of dimerization inhibitors; in the search of drug prototype compounds interacting with a target protein; and in biosensor analysis of disease biomarkers.The technology of optical biosensors operating on the effect of surface ?lasmon resonance is getting one of the approaches in researching various intermolecular interactions. It is of universal character and enables to record the interactions between almost any molecular objects in a wide range of concentrations. SPR-biosensors have very high accuracy, capability of reproducing and sensitivity; due to these characteristics their application is growing both in fundamental and applied researches.

?.S. Ivanov

2012-12-01

43

Atom depth analysis delineates mechanisms of protein intermolecular interactions  

International Nuclear Information System (INIS)

Highlights: •3D atom depth analysis is proposed to identify different layers in protein structures. •Amino acid contents for each layers have been analyzed for a large protein dataset. •Charged amino acids in the most external layer are present at very different extents. •Atom depth indexes of K residues reflect their side chains flexibility. •Mobile surface charges can be responsible for long range protein–protein recognition. -- Abstract: The systematic analysis of amino acid distribution, performed inside a large set of resolved protein structures, sheds light on possible mechanisms driving non random protein–protein approaches. Protein Data Bank entries have been selected using as filters a series of restrictions ensuring that the shape of protein surface is not modified by interactions with large or small ligands. 3D atom depth has been evaluated for all the atoms of the 2,410 selected structures. The amino acid relative population in each of the structural layers formed by grouping atoms on the basis of their calculated depths, has been evaluated. We have identified seven structural layers, the inner ones reproducing the core of proteins and the outer one incorporating their most protruding moieties. Quantitative analysis of amino acid contents of structural layers identified, as expected, different behaviors. Atoms of Q, R, K, N, D residues are increasingly more abundant in going from core to surfaces. An opposite trend is observed for V, I, L, A, C, and G. An intermediate behavior is exhibited by P, S, T, M, W, H, F and Y. The outer structural layer hosts predominantly E and K residues whose charged moieties, protruding from outer regions of the protein surface, reorient free from steric hindrances, determining specific electrodynamics maps. This feature may represent a protein signature for long distance effects, driving the formation of encounter complexes and the eventual short distance approaches that are required for protein–protein functional interactions

44

Atom depth analysis delineates mechanisms of protein intermolecular interactions  

Energy Technology Data Exchange (ETDEWEB)

Highlights: •3D atom depth analysis is proposed to identify different layers in protein structures. •Amino acid contents for each layers have been analyzed for a large protein dataset. •Charged amino acids in the most external layer are present at very different extents. •Atom depth indexes of K residues reflect their side chains flexibility. •Mobile surface charges can be responsible for long range protein–protein recognition. -- Abstract: The systematic analysis of amino acid distribution, performed inside a large set of resolved protein structures, sheds light on possible mechanisms driving non random protein–protein approaches. Protein Data Bank entries have been selected using as filters a series of restrictions ensuring that the shape of protein surface is not modified by interactions with large or small ligands. 3D atom depth has been evaluated for all the atoms of the 2,410 selected structures. The amino acid relative population in each of the structural layers formed by grouping atoms on the basis of their calculated depths, has been evaluated. We have identified seven structural layers, the inner ones reproducing the core of proteins and the outer one incorporating their most protruding moieties. Quantitative analysis of amino acid contents of structural layers identified, as expected, different behaviors. Atoms of Q, R, K, N, D residues are increasingly more abundant in going from core to surfaces. An opposite trend is observed for V, I, L, A, C, and G. An intermediate behavior is exhibited by P, S, T, M, W, H, F and Y. The outer structural layer hosts predominantly E and K residues whose charged moieties, protruding from outer regions of the protein surface, reorient free from steric hindrances, determining specific electrodynamics maps. This feature may represent a protein signature for long distance effects, driving the formation of encounter complexes and the eventual short distance approaches that are required for protein–protein functional interactions.

Alocci, Davide, E-mail: alodavide@gmail.com [Department of Biotechnology, Chemistry and Pharmacy, University of Siena, via A. Fiorentina 1, 53100 Siena (Italy); Bernini, Andrea, E-mail: andrea.bernini@unisi.it [Department of Biotechnology, Chemistry and Pharmacy, University of Siena, via A. Fiorentina 1, 53100 Siena (Italy); Niccolai, Neri, E-mail: neri.niccolai@unisi.it [Department of Biotechnology, Chemistry and Pharmacy, University of Siena, via A. Fiorentina 1, 53100 Siena (Italy); SienaBioGrafix Srl, via A. Fiorentina 1, 53100 Siena (Italy)

2013-07-12

45

X-ray photoelectron spectroscopy as a probe of intermolecular interactions in porphyrin polymer thin films.  

Science.gov (United States)

High-resolution X-ray photoelectron spectroscopy (XPS) has been applied to a series of free-base and Zn-porphyrin polymers in which the macrocycles are separated by oligo(phenylene vinylene) units (OPV) of different, controllable lengths. Neat films of all the Zn-porphyrin polymers unexpectedly reveal two peaks in the N 1s XPS region ( approximately 400 eV). The peak areas vary with the length of the OPV bridge, suggesting an intermolecular interaction between the porphyrin and linker subunits. A series of XPS analyses were performed to identify the different interactions taking place in these thin films. To inhibit interpolymer interactions, one of the polymers was incorporated into a nonconjugated PMMA matrix, collapsing the N1s spectrum to a single peak at 398.0 eV, relative to the neat film signals at 397.8 and 400.1 eV. In a conjugated matrix of OPV, two peaks remain at 401.7 and 399.5 eV. Extensive vacuum drying of the neat film leads to a single peak at 398.3 eV, suggesting loss of trapped solvent molecules. Ultimately, we attribute the lower energy signal of the neat films to solvent ligation, and the higher energy peak is attributed to interactions between the porphyrins and conjugated bridges on nearby polymer chains. This interpretation is successfully applied to the N 1s XPS data from a previously reported Zn-porphyrin oligomer-based multilayer array. PMID:11703135

Sarno, D M; Matienzo, L J; Jones, W E

2001-11-19

46

Redetermined structure, intermolecular interactions and absolute configuration of royleanone  

Directory of Open Access Journals (Sweden)

Full Text Available The structure of the title diterpenoid, C20H28O3, {systematic name: (4bS,8aS-3-hydroxy-2-isopropyl-4b,8,8-trimethyl-4b,5,6,7,8,8a,9,10-octahydrophenanthrene-1,4-dione} is confirmed [Eugster et al. (1993. Private communication (refcode HACGUN. CCDC, Union Road, Cambridge] and its packing is now described. Its absolute structure was established by refinement against data collected with Cu radiation: the two stereogenic centres both have S configurations. One cyclohexane ring adopts a chair conformation whereas the other cyclohexane ring is in a half-chair conformation and the benzoquinone ring is slightly twisted. An intramolecular O—H...O hydrogen bond generates an S(5 ring motif. In the crystal, molecules are linked into chains along [010] by O—H...O hydrogen bonds and weak C—H...O interactions. The packing also features C...O [3.131?(3?Å] short contacts.

Hoong-Kun Fun

2011-05-01

47

The electronic structure and the ferromagnetic intermolecular interactions in the crystal of TEMPO radicals  

International Nuclear Information System (INIS)

Based on the generalized gradient approximation, full potential linearized augmented plane wave (FP-LAPW) calculations have been performed to study the electronic band structure and the intermolecular ferromagnetic (FM) interactions for the two TEMPO radicals 4-Benzylideneamino-2,2,6,6-tetramethylpiperidin-1-oxyl (1) and 4-(2-naphtylmethyleneamino)-2,2,6,6-tetramethylpiperidin-1-oxyl (2). The total and the partial density of states and the atomic spin magnetic moments are calculated and discussed. The calculation revealed that the two TEMPO radicals have the intermolecular FM interactions, and the spontaneous magnetic moment is 1.0 ? B per molecule of each crystal, which is in good agreement with the experimental value. It is found that the unpaired electrons in these compounds are localized in a molecular orbital constituted primarily of ?* (NO) orbital, and the main contribution of the spin magnetic moment comes from the NO-free radical. The origin of FM is also studied in detail

48

Investigation of intermolecular interactions in aqueous solutions using the effective fragment potential  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Intermolecular interactions in aqueous solutions are extremely important for many chemical phenomena, but are not completely understood. This thesis describes computer simulations of aqueous solutions with different small molecule solutes using the effective fragment potential (EFP) method, classical simulations, and ab initio calculations. ^ Structure and bonding patterns in tert-butanol (TBA) – water mixtures are investigated by using molecular dynamics simulations with EFP. EFP is a mo...

Hands, Michael David

2012-01-01

49

Ferromagnetic intermolecular interactions and magnetically ordered states in some organic radical crystals  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Recent results of magnetization, susceptibility and muon spin rotation (mu SR) measurements and crystal structure determinations of the organic radicals based on cl-nitronyl nitroxide are described. Temperature variation of mu SR and a.c. susceptibility reveals that the organic radicals, which are found to exhibit ferromagnetic intermolecular interactions, undergo magnetic phase transitions at around 0.1 similar to 0.7 K. The organic radicals have not only a simply ferromagnetic ordered state...

Sugano, T.; Kurmoo, M.; Day, P.; Pratt, Fl; Blundell, Sj; Hayes, W.; Ishikawa, M.; Kinoshita, M.; Ohashi, Y.

1995-01-01

50

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

Energy Technology Data Exchange (ETDEWEB)

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 ?–? 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.

González, M.; Lemus-Santana, A.A. [Centro de Investigación en Ciencia Aplicada y Tecnología Avanzada, Unidad Legaria, Instituto Politécnico Nacional, México, DF (Mexico); Rodríguez-Hernández, J. [Centro de Investigación en Ciencia Aplicada y Tecnología Avanzada, Unidad Legaria, Instituto Politécnico Nacional, México, DF (Mexico); Instituto de Ciencia y Tecnología de Materiales, Universidad de La Habana, Havana (Cuba); Aguirre-Velez, C.I. [Centro de Investigación en Ciencia Aplicada y Tecnología Avanzada, Unidad Legaria, Instituto Politécnico Nacional, México, DF (Mexico); Knobel, M. [Institute of Physics “Gleb Wataghin”, UNICAMP, 13083-970 Campinas, SP (Brazil); Reguera, E., E-mail: edilso.reguera@gmail.com [Centro de Investigación en Ciencia Aplicada y Tecnología Avanzada, Unidad Legaria, Instituto Politécnico Nacional, México, DF (Mexico)

2013-08-15

51

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

International Nuclear Information System (INIS)

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)4] layers to form a solid of formula unit T(ImD)2[Ni(CN)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)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 ?–? 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

52

Understanding thermodynamic competitivity between biopolymer folding and misfolding under large-scale intermolecular interactions.  

Science.gov (United States)

Cooperativity is a hallmark of spontaneous biopolymer folding. The presence of intermolecular interactions could create off-pathway misfolding structures and suppress folding cooperativity. This raises the hypothesis that thermodynamic competitivity between off-pathway misfolding and on-pathway folding may intervene with cooperativity and govern biopolymer folding dynamics under conditions permitting large-scale intermolecular interactions. Here we report direct imaging and theoretical modeling of thermodynamic competitivity between biopolymer folding and misfolding under such conditions, using a two-dimensional array of proton-fueled DNA molecular motors packed at the maximal density as a model system. Time-resolved liquid-phase atomic force microscopy with enhanced phase contrast revealed that the misfolding and folding intermediates transiently self-organize into spatiotemporal patterns on the nanoscale in thermodynamic states far away from equilibrium as a result of thermodynamic competitivity. Computer simulations using a novel cellular-automaton network model provide quantitative insights into how large-scale intermolecular interactions correlate the structural dynamics of individual biomolecules together at the systems level. PMID:22126310

Mao, Youdong; Zhang, Jinzhong

2012-01-11

53

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

International Nuclear Information System (INIS)

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-1 power-law behavior with separation distance, while the far zone has a modulatdistance, while the far zone has a modulated R-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

54

Intermolecular interactions between a Ru complex and organic dyes in cosensitized solar cells: a computational study.  

Science.gov (United States)

Intermolecular interactions in cyclometalated Ru complex dye (FT89) dimers, carbazole organic dye (MK-45 and MK-111) dimers, FT89-MK-45 complexes, and FT89-MK-111 complexes were investigated using density functional theory (DFT) and time-dependent DFT (TD-DFT) to elucidate the improvement mechanism of dye-sensitized solar cell (DSSC) performance due to cosensitization with FT89 and MK dyes. All of the dimers and complexes form intermolecular cyclic hydrogen bonds via the carboxyl groups. The FT89 dimer and complexes with the TiO2Na model system promote intermolecular interactions with I2via the NCS ligand of the FT89 monomer. The computational results verify that MK-111 behaves not only as a sensitizer but also inhibits FT89 aggregation by effectively serving as a coadsorbent similar to deoxycholic acid (DCA) in the dye solution, suppressing recombination of the injected electrons in TiO2 with I2, improving DSSC performance. PMID:24968132

Kusama, Hitoshi; Funaki, Takashi; Koumura, Nagatoshi; Sayama, Kazuhiro

2014-08-14

55

Intermolecular interactions and electrostatic properties of the ?-hydroquinone apohost: implications for supramolecular chemistry.  

Science.gov (United States)

The crystal structure of the ?-polymorph of hydroquinone (?-HQ), the apohost of a large family of clathrates, is reported with a specific focus on intermolecular interactions and the electrostatic nature of its cavity. Hirshfeld surface analysis reveals subtle close contacts between two interconnecting HQ networks, and the local packing and related close contacts were examined by breakdown of the fingerprint plot. An experimental multipole model containing anisotropic thermal parameters for hydrogen atoms has been successfully refined against 15(2) K single microcrystal synchrotron X-ray diffraction data. The experimental electron density model has been compared with a theoretical electron density calculated with the molecule embedded in its own crystal field. Hirshfeld charges, interaction energies and the electrostatic potential calculated for both models are qualitatively in good agreement, but small differences in the electrostatic potential persist due to charge transfer from all hydrogen atoms to the oxygen atoms in the theoretical model. The electrostatic potential in the center of the cavity is positive, very shallow and highly symmetric, suggesting that the inclusion of polar molecules in the void will involve a balance between opposing effects. The electric field is by symmetry zero in the center of the cavity, increasing to a value of 0.0185 e/Å(2) (0.27 V/Å) 1 Å along the 3-fold axis and 0.0105 e/Å(2) (0.15 V/Å) 1 Å along the perpendicular direction. While these values are substantial in a macroscopic context, they are quite small for a molecular cavity and are not expected to strongly polarize a guest molecule. PMID:21809888

Clausen, Henrik F; Chen, Yu-Sheng; Jayatilaka, Dylan; Overgaard, Jacob; Koutsantonis, George A; Spackman, Mark A; Iversen, Bo B

2011-11-17

56

Intermolecular potential energy surface and thermophysical properties of ethylene oxide  

Science.gov (United States)

A six-dimensional potential energy hypersurface (PES) for two interacting rigid ethylene oxide (C2H4O) molecules was determined from high-level quantum-chemical ab initio calculations. The counterpoise-corrected supermolecular approach at the MP2 and CCSD(T) levels of theory was utilized to determine interaction energies for 10178 configurations of two molecules. An analytical site-site potential function with 19 sites per ethylene oxide molecule was fitted to the interaction energies and fine tuned to agree with data for the second acoustic virial coefficient from accurate speed of sound measurements. The PES was validated by computing the second virial coefficient, shear viscosity, and thermal conductivity. The values of these properties are substantiated by the best experimental data as they tend to fall within the uncertainty intervals and also obey the experimental temperature functions, except for viscosity, where experimental data are insufficient. Due to the lack of reliable data, especially for the transport properties, our calculated values are currently the most accurate estimates for these properties of ethylene oxide.

Crusius, Johann-Philipp; Hellmann, Robert; Hassel, Egon; Bich, Eckard

2014-10-01

57

Intermolecular potential energy surface and thermophysical properties of ethylene oxide.  

Science.gov (United States)

A six-dimensional potential energy hypersurface (PES) for two interacting rigid ethylene oxide (C2H4O) molecules was determined from high-level quantum-chemical ab initio calculations. The counterpoise-corrected supermolecular approach at the MP2 and CCSD(T) levels of theory was utilized to determine interaction energies for 10178 configurations of two molecules. An analytical site-site potential function with 19 sites per ethylene oxide molecule was fitted to the interaction energies and fine tuned to agree with data for the second acoustic virial coefficient from accurate speed of sound measurements. The PES was validated by computing the second virial coefficient, shear viscosity, and thermal conductivity. The values of these properties are substantiated by the best experimental data as they tend to fall within the uncertainty intervals and also obey the experimental temperature functions, except for viscosity, where experimental data are insufficient. Due to the lack of reliable data, especially for the transport properties, our calculated values are currently the most accurate estimates for these properties of ethylene oxide. PMID:25362314

Crusius, Johann-Philipp; Hellmann, Robert; Hassel, Egon; Bich, Eckard

2014-10-28

58

Intermolecular interactions in solid-state metalloporphyrins and their impacts on crystal and molecular structures.  

Science.gov (United States)

A variable-temperature (VT) crystal structure study of [Fe(TPP)Cl] (TPP(2-) = meso-tetraphenylporphyrinate) and Hirshfeld surface analyses of its structures and previously reported structures of [M(TPP)(NO)] (M = Fe, Co) reveal that intermolecular interactions are a significant factor in structure disorder in the three metalloporphyrins and phase changes in the nitrosyl complexes. These interactions cause, for example, an 8-fold disorder in the crystal structures of [M(TPP)(NO)] at room temperature that obscures the M-NO binding. Hirshfeld analyses of the structure of [Co(TPP)(NO)] indicate that the phase change from I4/m to P1? leads to an increase in void-volume percentage, permitting additional structural compression through tilting of the phenyl rings to offset the close-packing interactions at the interlayer positions in the crystal structures with temperature decrease. X-ray and neutron structure studies of [Fe(TPP)Cl] at 293, 143, and 20 K reveal a tilting of the phenyl groups away from being perpendicular to the porphyrin ring as a result of intermolecular interactions. Structural similarities and differences among the three complexes are identified and described by Hirshfeld surface and void-volume calculations. PMID:25338536

Hunter, Seth C; Smith, Brenda A; Hoffmann, Christina M; Wang, Xiaoping; Chen, Yu-Sheng; McIntyre, Garry J; Xue, Zi-Ling

2014-11-01

59

Vibrational predissociation of Van der Waals molecules and intermolecular potential energy surfaces  

International Nuclear Information System (INIS)

Spectroscopic experiments yield information about energy transfer processes in van der Waals molecules, for which we do not have reliable guides for geometries. Important properties of the molecules are included in the areas of intermolecular potential energy curves, structure, and energy transfer processes. Vibrational predissociation is more fully explored through experimental studies, a theoretical model, numerical results, momentum gap, and relaxation channels

60

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

Science.gov (United States)

We perform an ab initio computational study of molecular complexes with the general formula CF3X—B that involve one trifluorohalomethane CF3X (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 (NH3 and PH3), two n-pairs (H2O and H2S), two n-pairs with an unsaturated bond (H2CO and H2CS), and a single ?-pair (C2H4) and two ?-pairs (C2H2). 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 ?-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 ?-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.

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

2014-10-01

 
 
 
 
61

Intermolecular Interactions between Eosin Y and Caffeine Using 1H-NMR Spectroscopy  

Science.gov (United States)

DETECHIP has been used in testing analytes including caffeine, cocaine, and tetrahydrocannabinol (THC) from marijuana, as well as date rape and club drugs such as flunitrazepam, gamma-hydroxybutyric acid (GHB), and methamphetamine. This study investigates the intermolecular interaction between DETECHIP sensor eosin Y (DC1) and the analyte (caffeine) that is responsible for the fluorescence and color changes observed in the actual array. Using 1H-NMR, 1H-COSY, and 1H-DOSY NMR methods, a proton exchange from C-8 of caffeine to eosin Y is proposed. PMID:25018772

Okuom, Macduff O.; Wilson, Mark V.; Jackson, Abby; Holmes, Andrea E.

2014-01-01

62

Relativistic effects in the intermolecular interaction-induced nuclear magnetic resonance parameters of xenon dimer  

DEFF Research Database (Denmark)

Relativistic effects on the 129Xe nuclear magnetic resonance shielding and 131Xe nuclear quadrupole coupling (NQC) tensors are examined in the weakly bound Xe2 system at different levels of theory including the relativistic four-component Dirac-Hartree-Fock (DHF) method. The intermolecular interaction-induced binary chemical shift d, the anisotropy of the shielding tensor ?s, and the NQC constant along the internuclear axis ?ll are calculated as a function of the internuclear distance. DHF shielding calculations are carried out using gauge-including atomic orbitals. For comparison, the full leading-order one-electron Breit-Pauli perturbation theory (BPPT) is applied using a common gauge origin. Electron correlation effects are studied at the nonrelativistic (NR) coupled-cluster singles and doubles with perturbational triples [CCSD(T)] level of theory. The fully relativistic second-order Møller-Plesset many-body perturbation (DMP2) theory is used to examine the cross coupling between correlation and relativityon NQC. The same is investigated for d and ?s by BPPT with a density functional theory model. A semiquantitative agreement between the BPPT and DHF binary property curves is obtained for d and ?s in Xe2. For these properties, the currently most complete theoretical description is obtained by a piecewise approximation where the uncorrelated relativistic DHF results obtained close to the basis-set limit are corrected, on the one hand, for NR correlation effects and, on the other hand, for the BPPT-based cross coupling of relativity and correlation. For ?ll, the fully relativistic DMP2 results obtain a correction for NR correlation effects beyond MP2. The computed temperature dependence of the second virial coefficient of the 129Xe nuclear shielding is compared to experiment in Xe gas. Our best results, obtained with the piecewise approximation for the binary chemical shift combined with the previously published state of the art theoretical potential energy curve for Xe2, are in excellent agreement with the experiment for the first time. © 2007 American Institute of Physics. [DOI: 10.1063/1.2777143

Hanni, Matti; Lantto, Perttu

2007-01-01

63

Theoretical study of intermolecular interactions in nanoporous networks on boron doped silicon surface  

Science.gov (United States)

Supramolecular networks on a doped boron silicon surface under ultra high vacuum (UHV) have been recently obtained (Makoudi et al., 2013). The used molecule contains different end-groups, bearing either bromine, iodine or hydrogen atoms denoted 1,3,5-tri(4?-bromophenyl)benzene (TBB), 1,3,5-tri(4-iodophenyl)benzene (TIB) and 1,3,5-triphenyl-benzene (THB). To explain the formation of the nanoporous structures, interactions of the type aryl-X⋯H hydrogen bonds (X being a halogen atom) have been proposed. In order to obtain a complete insight of the stabilizing interaction in these networks adsorbed on the Si(1 1 1)?3x?3R30°-boron surface, we present a full density-functional-theory study taking the van der Waals interactions into account. We investigated the energetic and structural properties of three different nanoporous networks constituted by TBB, TIB and THB molecules. The electronic studies allow us to identify hydrogen bond and dipole-dipole intermolecular interactions in the supramolecular halogen networks, whereas only dipole-dipole interactions are present in the 1,3,5-triphenyl-benzene nanoporous network.

Boukari, Khaoula; Duverger, Eric; Hanf, Marie-Christine; Stephan, Régis; Sonnet, Philippe

2014-11-01

64

Spectroscopic studies on weak intermolecular interactions of fluoranthene derivatives with benzene or ethanol in cyclohexane  

International Nuclear Information System (INIS)

Complete text of publication follows. We have published on the spectroscopic study on the formation of a 1:1 molecular complex of fluoranthene (F) with benzene (B) in cyclohexane and estimated the equilibrium constant K(F-B) (0.147 dm3 mol-1 at 298 K), enthalpy change DH(F-B) (-5.9 kJ mol-1) and entropy change DS(F-B) (-36 JK-1mol-1 at 298 K) for this complex formation (S. Enomoto et al., Bull. Chem. Soc. Jpn., 75 (2002) 689-693). In this study, the electronic absorption spectra have been observed for the fluoranthene derivatives in cyclohexane-benzene and/or cyclohexane-ethanol mixed solvents to investigate the weak intermolecular interactions between fluoranthene derivatives and benzene or ethanol. The electronic absorption spectra of 3-aminofluoranthene (AF) in the mixed solvent mentioned above showed isosbestic points with varying B and ethanol (E) concentrations. These observations indicate that AF forms a 1:1 molecular complex with B or E, the K(AF-B) and K(AF-E) values for these complex formations being estimated as 0.146 and 0.647 dm3 mol-1 at 298 K, respectively. Temperature dependence of K(AF-B) and K(AF-E) yielded ?H(AF-B) and ?H(AF-E) values of -6.3 and -14.2 kJ mol-1, respectively, ?S(AF-B) and ?S(AF-E) values being respectively calculated as -40 and -51 JK-1mol-1 at 298 K. Applying similar experimental and calculational procedures to 3-nitrofd calculational procedures to 3-nitrofluoranthene (NF) in cyclohexane-B mixed solvent, K(NF-B), ?H(NF-B) and ?S(NF-B) values were estimated as 0.064 dm3 mol-1 at 298 K, -14.6 kJ mol-1 and -72 JK-1 mol1 at 298 K, respectively, for the 1:1 molecular complex formation of NF with B. It is interesting to note that the amino group has almost no effect on the stability of F-B molecular complex since K(AF-B) is comparable to K(F-B) value. It is, further, noted that AF-E and NF-B complexes are enthalpically easier and entropically harder to be formed, respectively, than AF-B one. Assuming that the dispersion energy involved in ?H(NF-B) is the same in magnitude as ?H(F-B) which is considered to be purely dispersion energy, the induction energy contributed to ?H(NF-B) is calculated as -8.7 kJ mol-1. Concerning the conformations of AF-B and NF-B molecular complexes, both the ab initio and PPP calculations support the sandwich- or parallel-type.

65

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

Science.gov (United States)

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. PMID:25111839

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

2014-08-28

66

Ab initio potential energy surface and intermolecular vibrations of the naphthalene-argon van der Waals complex  

Science.gov (United States)

The intermolecular potential energy surface (PES) of the naphthalene-argon (NpAr) complex is constructed using an ab initio method. The molecule-argon interaction energy is computed at the level of the second-order Møller-Plesset (MP2) theory combined with the augmented correlation consistent polarized valence double-? basis set. The analytical PES fitted to a large set of single energy values is further improved with the help of correction functions determined by calculations of the interaction energy at the coupled cluster level including single and double excitations supplemented by triple excitations performed for a limited set of intermolecular configurations. The PES determined is very flat near its four equivalent global minima of -493 cm-1 located from both sides of the Np plane at a distance of 3.435 A? and shifted from the center of Np by +/-0.43 A? along its long symmetry axis. The large-amplitude motion of Ar in the complex is investigated, and dynamical consequence of a strong intermode coupling is discovered in the excited vibrational states. The theoretical results obtained allow for the reassignment of the spectral bands observed in the electronic transition S1 <-- S0 of the NpAr complex.

Makarewicz, Jan

2011-02-01

67

Effects of Weak Intermolecular Interactions on the Molecular Isomerism of Tricobalt Metal Chains  

International Nuclear Information System (INIS)

Depending on the number of interstitial solvent molecules, n, crystals of the linear chain compound Co3(dipyridylamide)4Cl2·nCH2Cl2 adopt either symmetrical or unsymmetrical metal chain structures. We explore here the possible reasons for such behavior using Hirshfeld surface analysis of intermolecular interactions as well as the charge density determined from 100(1) K X-ray diffraction data on the unsymmetrical complex Co3(dipyridylamide)4Cl2·2.11CH2Cl2, u-1, and crystal structures of u-1 determined from single crystal synchrotron X-ray diffraction data at 20, 150, and 300 K. The new crystal structures are compared with previous structural results on a crystal with slightly different solvent content. This change in solvent content only affects the bond distances to atom Co(3), which are also strongly affected by temperature changes due to a spin crossover transition. Large differences in intermolecular interactions are revealed by the Hirshfeld surface analysis between symmetrical (s-1) and unsymmetrical (u-1) crystal solvates, suggesting that the molecular isomerism is strongly influenced by crystal packing effects. Topological analysis of the static electron density of u-1 suggests that there is direct metal-metal bonding for both the shorter Co(1)-Co(2) and the longer Co(2)-Co(3) contact. The approximate description of the system as a (Co2)2+-dimer and an isolated Co2+-ion is reflected in the character of the metal-ligand interactions, which are more ionic for tinteractions, which are more ionic for the isolated Co(3) atom, and the topological charges Co(1)+0.50, Co(2)+0.77, and Co(3)+1.36. The two termini of u-1 are found to be very different, both in terms of structural surroundings as well as topology. The central Co(2) atom is similar to a cobalt atom in a tetragonally distorted octahedral environment resulting in preferred occupancy in the t2g orbitals. The Co(1) atom has significant deformation in the xz and yz planes (z along the chain axis, x and y toward ligands) reflecting covalent interactions with the terminal chlorine atom Cl(1). The Co(3) atom has a relatively high occupancy of the dx2-y2 orbital and a relatively low occupancy of the dxy orbital confirming that these orbitals are involved in the spin crossover process and predominantly responsible for the observed variation in bond lengths with temperature.

68

Effects of Weak Intermolecular Interactions on the Molecular Isomerism of Tricobalt Metal Chains  

Energy Technology Data Exchange (ETDEWEB)

Depending on the number of interstitial solvent molecules, n, crystals of the linear chain compound Co3(dipyridylamide)4Cl2{center_dot}nCH2Cl2 adopt either symmetrical or unsymmetrical metal chain structures. We explore here the possible reasons for such behavior using Hirshfeld surface analysis of intermolecular interactions as well as the charge density determined from 100(1) K X-ray diffraction data on the unsymmetrical complex Co3(dipyridylamide)4Cl2{center_dot}2.11CH2Cl2, u-1, and crystal structures of u-1 determined from single crystal synchrotron X-ray diffraction data at 20, 150, and 300 K. The new crystal structures are compared with previous structural results on a crystal with slightly different solvent content. This change in solvent content only affects the bond distances to atom Co(3), which are also strongly affected by temperature changes due to a spin crossover transition. Large differences in intermolecular interactions are revealed by the Hirshfeld surface analysis between symmetrical (s-1) and unsymmetrical (u-1) crystal solvates, suggesting that the molecular isomerism is strongly influenced by crystal packing effects. Topological analysis of the static electron density of u-1 suggests that there is direct metal-metal bonding for both the shorter Co(1)-Co(2) and the longer Co(2)-Co(3) contact. The approximate description of the system as a (Co2)2+-dimer and an isolated Co2+-ion is reflected in the character of the metal-ligand interactions, which are more ionic for the isolated Co(3) atom, and the topological charges Co(1)+0.50, Co(2)+0.77, and Co(3)+1.36. The two termini of u-1 are found to be very different, both in terms of structural surroundings as well as topology. The central Co(2) atom is similar to a cobalt atom in a tetragonally distorted octahedral environment resulting in preferred occupancy in the t2g orbitals. The Co(1) atom has significant deformation in the xz and yz planes (z along the chain axis, x and y toward ligands) reflecting covalent interactions with the terminal chlorine atom Cl(1). The Co(3) atom has a relatively high occupancy of the dx2-y2 orbital and a relatively low occupancy of the dxy orbital confirming that these orbitals are involved in the spin crossover process and predominantly responsible for the observed variation in bond lengths with temperature.

Poulsen, R.; Overgaard, J; Schulman, A; Østergaard, C; Murillo, C; Spackman, M; Iversen, B

2009-01-01

69

Intermolecular interactions in binary mixtures of 2-Chloroethanol with 2-Dimethylaminoethanol and 2-Diethylaminoethanol at different temperatures  

Science.gov (United States)

The ultrasonic velocity (u) and density (?) of binary mixtures of 2-Chloroethanol (2-CletOH) with 2-Dimethylaminoethanol (DMAE) and 2-Diethylaminoethanol (DEAE) have been measured over the entire concentration range at temperatures 293.15, 303.15 and 313.15 K. The ultrasonic velocity and density data are used to estimate adiabatic compressibility (?S), intermolecular free length (Lf), molar sound velocity (R), molar compressibility (B) and specific acoustic impedance (Z) along with excess values of ultrasonic velocity (uE), adiabatic compressibility (?SE), intermolecular free length (LfE), acoustic impedance (ZE) and molar volume (VmE). The infrared spectra of both of the systems, 2-CletOH + DMAE and 2-CletOH + DEAE, have also been recorded at room temperature (298.15 K). The observed variations of these parameters, with concentration and temperature, are discussed in terms of the intermolecular interactions between the unlike molecules of the binary mixtures.

Pandey, Puneet Kumar; Awasthi, Anjali; Awasthi, Aashees

2013-09-01

70

Sensitivity of predicted gas hydrate occupancies on treatment of intermolecular interactions.  

Science.gov (United States)

The sensitivity of gas hydrate occupancies predicted on the basis of van der Waals-Platteeuw theory is investigated, as a function of the intermolecular guest-water interaction potential model, and of the number of water molecules taken into account. Simple analytical correction terms that account for the interactions with the water molecules beyond the cutoff distance are introduced, and shown to improve significantly the convergence rate, and hence the efficiency of the computation of the Langmuir constants. The predicted cage occupancies in pure methane and pure carbon dioxide clathrates, calculated using different recent guest-water pair potentials models derived from ab initio calculations, can vary significantly depending on the model. That sensitivity becomes especially strong in the case of multiple guest clathrates. It is shown that the abundances of coenclathrated molecules in multiple guest clathrate hydrates potentially formed on the surface of Mars can vary by more than two orders of magnitude depending on the model. These results underline the strong need for experimental data on pure and multiple guest clathrate hydrates, in particular in the temperature and pressure range that are relevant in extreme environment conditions, to discriminate among the theoretical models. PMID:20232974

Thomas, Caroline; Picaud, Sylvain; Ballenegger, Vincent; Mousis, Olivier

2010-03-14

71

Ferroelectric ordering in chiral smectic-C* liquid crystals determined by nonchiral intermolecular interactions.  

Science.gov (United States)

General microscopic mechanism of ferroelectric ordering in chiral smectic-C* liquid crystals is considered. It is shown that if the mesogenic molecules have a sufficiently low symmetry, the spontaneous polarization is proportional to one of the biaxial vector order parameters of the smectic-C phase. This order parameter may be determined by intermolecular interactions which are not sensitive to molecular chirality. At the same time, the polarization is also proportional to a pseudoscalar parameter which vanishes if the molecules are nonchiral. The general statistical theory of ferroelectric ordering is illustrated by two particular models. The first model is based on electrostatic quadrupole-quadrupole interactions, and it enables one to obtain explicit analytical expressions for the spontaneous polarization. In the second model, the molecular chirality and polarity are determined by a pair of off-center nonparallel dipoles. For this case, the spontaneous polarization is calculated numerically as a function of temperature. The theory provides a more general interpretation of the previous approaches including the classical Boulder model. PMID:18517400

Osipov, M A; Gorkunov, M V

2008-03-01

72

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

Science.gov (United States)

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. PMID:24890320

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

2014-09-01

73

Intermolecular interactions in ternary solutions of some 1,2,4-triazolium ylids studied by spectral means  

Science.gov (United States)

Triazolium ylids are dipolar molecules with separated charges in their ground electronic state; the positive charge is located on one Nitrogen atom belonging to the heterocycle and the negative charge is located near the ylid carbanion. The intramolecular charge transfer from the carbanion to heterocycle gives a visible electronic absorption band, very sensitive to the solvent nature. Its position in the wavenumber scale offers information about the intermolecular interactions in which the ylid molecules are engaged. The spectral study revealed the presence of both universal and specific interactions in solutions of 1,2,4-triazolium ylids with protic solvents. By choosing adequate binary solvents, the contribution of the specific interaction of the weak hydrogen bond between the -OH atomic group of the protic solvents and the ylid carbanion can be estimated. Ternary solutions of the studied ylids achieved with Methanol +Benzene, Water + Ethanol and 1,3 Propanediol + Dimethyl formamide binary solvents are analyzed from spectral point of view and the difference between the potential energies in molecular pairs of the types: 1,2,4-triazolium ylid-protic solvent and 1,2,4-triazolium ylid-non protic were estimated on the basis of the statistic cell model of ternary solutions.

Closca, Valentina; Melniciuc-Puica, Nicoleta; Dorohoi, Dana Ortansa; Benchea, A. C.

2014-08-01

74

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

Science.gov (United States)

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.

Gu, Zhiyong

75

A combined experimental and quantum chemical studies on molecular structure, spectral properties, intra and intermolecular interactions and first hyperpolarizability of 4-(benzyloxy)benzaldehyde thiosemicarbazone and its dimer  

Science.gov (United States)

In the present work, a detailed spectroscopic analysis of 4-(benzyloxy)benzaldehyde thiosemicarbazone (3) has been carried out using 1H NMR, 13C NMR, UV-Visible and FT-IR spectroscopic techniques. The quantum chemical calculations have been carried out using DFT level of theory, B3LYP functional and 6-31G(d,p) basis set. The calculated thermodynamic parameters show that the formation of 3 is an exothermic and spontaneous reaction at 25 °C. The vibrational analysis indicates the formation of dimer in the solid state by intermolecular hydrogen bonding (Nsbnd H⋯Sdbnd C) and the binding energy of dimer is calculated to be 11.2 kcal/mol, using DFT calculation. NBO analysis is carried out to investigate the charge transfer in various intra and intermolecular interactions involved in dimer. Topological parameters at bond critical points (BCPs) are calculated to analyze the strength and nature of various intra and intermolecular interactions in dimer by Bader's 'Atoms in molecules' AIM theory in detail. The local reactivity descriptors such as Fukui functions (fk+, fk-), local softnesses (sk+, sk-) and electrophilicity indices (?k+, ?k-) analysis are performed to determine the reactive sites within molecule. Non linear optical (NLO) behavior of title compound is investigated by the computed value of first hyperpolarizability (?0).

Kumar, Amit; Rawat, Poonam; Baboo, Vikas; Verma, Divya; Singh, R. N.; Saxena, Deepti; Gauniyal, H. M.; Pandey, Anoop Kumar; Pal, Harish

2013-02-01

76

Intermolecular Interactions in Ternary Glycerol–Sample–H2O : Towards Understanding the Hofmeister Series (V)  

DEFF Research Database (Denmark)

We studied the intermolecular interactions in ternary glycerol (Gly)–sample (S)–H2O systems at 25?°C. By measuring the excess partial molar enthalpy of Gly, HGlyEHEGly, we evaluated the Gly–Gly enthalpic interaction, HGly-GlyEHEGly--Gly, in the presence of various samples (S). For S, tert-butanol (TBA), 1-propanol (1P), urea (UR), NaF, NaCl, NaBr, NaI, and NaSCN were used. It was found that hydrophobes (TBA and 1P) reduce the values of HGly-GlyEHEGly--Gly considerably, but a hydrophile (UR) had very little effect on HGly-GlyEHEGly--Gly. The results with Na salts indicated that there have very little effect on HGly-GlyEHEGly--Gly. This contrasts with our earlier studies on 1P–S–H2O in that Na+, F? and Cl? are found as hydration centers from the induced changes on HIP-IPEHEIP--IP in the presence of S, while Br?, I?, and SCN? are found to act as hydrophiles. In comparison with the Hofmeister ranking of these ions, the kosmotropes are hydration centers and the more kosmotropic the higher the hydration number, consistent with the original Hofmeister’s concept of “H2O withdrawing power.” Br?, I? and SCN?, on the other hand, acted as hydrophiles and the more chaotropic they are the more hydrophilic. These observations hint that whatever effect each individual ion has on H2O, it is sensitive only to hydrophobes (such as 1P) but not to hydrophiles (such as Gly). This may have an important bearing towards understanding the Hofmeister series, since biopolymers are amphiphilic and their surfaces are covered by hydrophobic as well as hydrophilic parts.

Westh, Peter; Rasmussen, Erik Lumby

2011-01-01

77

Theoretical study of the Ar-, Kr-, and Xe-CH4, -CF4 intermolecular potential-energy surfaces.  

Science.gov (United States)

We present a theoretical study of the intermolecular potentials for the Ar, Kr, and Xe-CH4, -CF4 systems. The potential-energy surfaces of these systems have been calculated utilizing second-order Möller-Plesset perturbation theory and coupled-cluster theory in combination with correlation-consistent basis sets (aug-cc-pvnz; n = d, t, q). The calculations show that the stabilizing interactions between the rare gases and the molecules are slightly larger for CF4 than for CH4. Moreover, the rare-gas-CX4 (X = H, F) potentials are more attractive for Xe than for Kr and Ar. Our highest quality ab initio data (focal-point-CCSD(T) extrapolated to the complete basis set limit) have been used to develop pairwise analytical potentials for rare-gas-hydrocarbon (-fluorocarbon) systems. These potentials can be applied in classical-trajectory studies of rare gases interacting with hydrocarbon surfaces. PMID:16970379

Alexander, William A; Troya, Diego

2006-09-21

78

Theory of intermolecular forces  

CERN Document Server

Theory of Intermolecular Forces deals with the exposition of the principles and techniques of the theory of intermolecular forces. The text focuses on the basic theory and surveys other aspects, with particular attention to relevant experiments. The initial chapters introduce the reader to the history of intermolecular forces. Succeeding chapters present topics on short, intermediate, and long range atomic interactions; properties of Coulomb interactions; shape-dependent forces between molecules; and physical adsorption. The book will be of good use to experts and students of quantum mechanics

Margenau, H; Ter Haar, D

1971-01-01

79

Collecting high-order interactions in an effective pairwise intermolecular potential using the hydrated ion concept: the hydration of Cf³?.  

Science.gov (United States)

This work proposes a new methodology to build interaction potentials between a highly charged metal cation and water molecules. These potentials, which can be used in classical computer simulations, have been fitted to reproduce quantum mechanical interaction energies (MP2 and BP86) for a wide range of [M(H2O)n](m+)(H2O)? clusters (n going from 6 to 10 and ? from 0 to 18). A flexible and polarizable water shell model (Mobile Charge Density of Harmonic Oscillator) has been coupled to the cation-water potential. The simultaneous consideration of poly-hydrated clusters and the polarizability of the interacting particles allows the inclusion of the most important many-body effects in the new polarizable potential. Applications have been centered on the californium, Cf(III) the heaviest actinoid experimentally studied in solution. Two different strategies to select a set of about 2000 structures which are used for the potential building were checked. Monte Carlo simulations of Cf(III)+500 H2O for three of the intermolecular potentials predict an aquaion structure with coordination number close to 8 and average R(Cf-O) in the range 2.43-2.48 Å, whereas the fourth one is closer to 9 with R(Cf-O) = 2.54 Å. Simulated EXAFS spectra derived from the structural Monte Carlo distribution compares fairly well with the available experimental spectrum for the simulations bearing 8 water molecules. An angular distribution similar to that of a square antiprism is found for the octa-coordination. PMID:24907987

Galbis, Elsa; Hernández-Cobos, Jorge; Pappalardo, Rafael R; Sánchez Marcos, Enrique

2014-06-01

80

REFINEMENT OF THE OH A2(SIGMA+)(V=0)+AR INTERMOLECULAR POTENTIAL-ENERGY SURFACE  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Several intermolecular vibrational levels of the excited electronic state of OH-Ar correlating with OH A 2?+(v=0)+Ar have been characterized by laser-induced fluorescence and hole-burning experiments. The OH-Ar levels identified include the lowest intermolecular level, an intermolecular bending level with a lower degree of stretching excitation than previously observed, and intermolecular levels with two quanta of bending excitation. The intensities of electronic transitions to these levels ...

Lester, M.; Loomis, R.; Giancarlo, L.; Berry, M.; Chakravarty, C.; Clary, D.

1993-01-01

 
 
 
 
81

THE INTERACTION OF PARAMAGNETIC RELAXATION REAGENTS WITH INTRA- AND INTERMOLECULAR HYDROGEN BONDED PHENOLS  

Science.gov (United States)

Intermolecular electron-nuclear 13-C relaxation times (T(1)sup e's) from solutions containing the paramagnetic relaxation reagent (PARR), Cr(acac)3, used in conjunction with 13-C T(1)'s in diamagnetic solutions (intramolecular 13-C - (1)H dipolar T(1)'s) provide a significant inc...

82

Luminescent goldI carbenes from 2-pyridylisocyanide complexes: structural consequences of intramolecular versus intermolecular hydrogen-bonding interactions.  

Science.gov (United States)

Isocyanide [AuX(CNPy-2)] (X = Cl, C6F5, fluoromesityl, 1/2 octafluorobiphenyl) and carbene [AuX{C(NR1R2)(NHPy-2)}] (R1R2NH = primary or secondary amines or 1/2 primary diamine) gold(I) complexes have been synthesized and characterized. For X = Cl, the carbene complexes show aurophilic interactions. The fragment NHPy-2, formed in the carbenes, can give rise to intra- (for primary amines) or intermolecular (for secondary amines) hydrogen bonds, depending on the amine used. These bonds and contacts have been studied in the solid state and in solution. The intermolecular hydrogen bonds are split in an acetone solution, but the intramolecular ones, which close a six-membered ring, survive in solution. Except for the fluoromesityl derivatives, the carbene complexes display luminescent properties. PMID:18237121

Bartolomé, Camino; Carrasco-Rando, Marta; Coco, Silverio; Cordovilla, Carlos; Martín-Alvarez, Jose M; Espinet, Pablo

2008-03-01

83

The effect of the intermolecular potential formulation on the state-selected energy exchange rate coefficients in N2-N2 collisions.  

Science.gov (United States)

The rate coefficients for N2-N2 collision-induced vibrational energy exchange (important for the enhancement of several modern innovative technologies) have been computed over a wide range of temperature. Potential energy surfaces based on different formulations of the intramolecular and intermolecular components of the interaction have been used to compute quasiclassically and semiclassically some vibrational to vibrational energy transfer rate coefficients. Related outcomes have been rationalized in terms of state-to-state probabilities and cross sections for quasi-resonant transitions and deexcitations from the first excited vibrational level (for which experimental information are available). On this ground, it has been possible to spot critical differences on the vibrational energy exchange mechanisms supported by the different surfaces (mainly by their intermolecular components) in the low collision energy regime, though still effective for temperatures as high as 10,000 K. It was found, in particular, that the most recently proposed intermolecular potential becomes the most effective in promoting vibrational energy exchange near threshold temperatures and has a behavior opposite to the previously proposed one when varying the coupling of vibration with the other degrees of freedom. PMID:24590423

Kurnosov, Alexander; Cacciatore, Mario; Laganà, Antonio; Pirani, Fernando; Bartolomei, Massimiliano; Garcia, Ernesto

2014-04-01

84

Penning ionization of N2O molecules by He*(2(3,1)S) and Ne*(3P2,0) metastable atoms: theoretical considerations about the intermolecular interactions.  

Science.gov (United States)

A theoretical investigation of the intermolecular interaction, operative in collision complexes of He*(2 3S1), He*(2 1S0), and Ne*(3P2,0) with N2O, is carried out to explain the main results of the experimental study reported in the preceding paper. The analysis is carried out by means of a semiempirical method based on the identification, modeling, and combination of the leading interaction components, including the effect of the selective polarization of the more external electronic cloud of the metastable atom in the intermolecular electric field. These and other crucial aspects of our approach have been quantitatively verified by ab initio calculations. The proposed method permits to evaluate the interaction at any configuration of the complexes and provides a useful and inexpensive representation of the intermolecular potential energy for dynamics studies. The main experimental findings can be rationalized taking into account the critical balancing between molecular orientation effects in the intermolecular interaction field and the ionization probability. These orientation effects tend to become less pronounced with increasing collision energy. PMID:15945685

Biondini, Francesco; Brunetti, Brunetto G; Candori, Pietro; De Angelis, Filippo; Falcinelli, Stefano; Tarantelli, Francesco; Pirani, Fernando; Vecchiocattivi, Franco

2005-04-22

85

Cooperativity of anion⋯? and ?⋯? interactions regulates the self-assembly of a series of carbene proligands: Towards quantitative analysis of intermolecular interactions with Hirshfeld surface  

Science.gov (United States)

The cooperative effect of weak non-covalent forces between anions and electron deficient aromatics by ?⋯? stacking of a series of carbene proligands (1-3) have been thoroughly explored by crystallographic studies. Structural analysis revealed that the anion⋯? and ?⋯? interactions along with intermolecular hydrogen bonding mutually cooperate to facilitate the assembling of the supramolecular framework. The ?⋯? and corresponding anion⋯? interactions have been investigated in the title carbene proligands despite their association with counter ions. The presence of the anion in the vicinity of the ?-system leads to the formation of anion⋯?/?⋯?/?⋯anion network for an inductive stabilization of the assemblies. To assess the dimensionality of the supramolecular framework consolidated by cooperative anion⋯?/?⋯? interactions and hydrogen bonding, different substituent effects in the carbene backbone have been considered to tune these interactions. These facts show that the supramolecular framework based on these cooperative weak forces may be robust enough for application in molecular recognition. The investigation of close intermolecular interactions between the molecules via Hirshfeld surface analyses is presented in order to reveal subtle differences and similarities in the crystal structures. The decomposition of the fingerprint plot area provides a percentage of each intermolecular interaction, allowing for a quantified analysis of close contacts within each crystal.

Samanta, Tapastaru; Dey, Lingaraj; Dinda, Joydev; Chattopadhyay, Shyamal Kumar; Seth, Saikat Kumar

2014-06-01

86

Tailoring intermolecular interactions for efficient room-temperature phosphorescence from purely organic materials in amorphous polymer matrices.  

Science.gov (United States)

Herein we report a rational design strategy for tailoring intermolecular interactions to enhance room-temperature phosphorescence from purely organic materials in amorphous matrices at ambient conditions. The built-in strong halogen and hydrogen bonding between the newly developed phosphor G1 and the poly(vinyl alcohol) (PVA) matrix efficiently suppresses vibrational dissipation and thus enables bright room-temperature phosphorescence (RTP) with quantum yields reaching 24?%. Furthermore, we found that modulation of the strength of halogen and hydrogen bonding in the G1-PVA system by water molecules produced unique reversible phosphorescence-to-fluorescence switching behavior. This unique system can be utilized as a ratiometric water sensor. PMID:25044368

Kwon, Min Sang; Lee, Dongwook; Seo, Sungbaek; Jung, Jaehun; Kim, Jinsang

2014-10-13

87

Intermolecular interactions between molecules in various conformational states: the dimer of oxalic acid.  

Science.gov (United States)

We considered stability of the dimer of oxalic acid. The global minimum energy structure identified by us is stabilized by two inter- and four intramolecular hydrogen bonds, whereas the most stable structure identified in previous studies is supported by two inter- and three intramolecular hydrogen bonds. The latter structure proves to be less stable by 25 meV than the former. The global minimum stability results from a balancing act between a moderately attractive two-body interaction energy and small repulsive one-body terms. We have analyzed zero-point vibrational corrections to the stability of various conformers of oxalic acid and their dimers. We have found that minimum energy structures with the most stabilizing sets of hydrogen bonds have the largest zero-point vibrational energy, contrary to a naive anticipation based on red shifts of OH stretching modes involved in hydrogen bonds. PMID:24923870

Keolopile, Zibo G; Ryder, Matthew R; Gutowski, Maciej

2014-09-01

88

Structural aspects of intermolecular interactions in the solid state of 1,4-dibenzylpiperazines bearing nitrile or amidine groups.  

Science.gov (United States)

The crystal structures of the title 1,4-bis(4-cyanobenzyl)piperazine (1) and 1,4-bis(4-amidinobenzyl)piperazine tetrahydrochloride tetrahydrate (2) are reported. Compound (1) crystallizes in the triclinic space group P\\bar 1 and compound (2) in the monoclinic space group P21/n. In both (1) and (2) the asymmetric unit contains one half of the molecule because the central piperazine rings were located across a symmetry center. The packing of both molecules was dominated by hydrogen bonds. The crystal lattice of (1) was formed by weak C-H...N and C-H...? interactions. The crystal structure of (2) was completely different, with cations as well as chloride anions and water molecules taking part in intermolecular interactions. Single-crystal X-ray diffraction studies combined with density functional theory (DFT) calculations allowed the characterization of the intermolecular interactions in those two systems having different types of very strong electrophilic groups: non-ionic nitrile and ionic amidine. Chemical shift data from (13)C CP/MAS (Cross Polarization Magic Angle Spinning) NMR spectra were analyzed using the different procedures for the theoretical computation of shielding constants. PMID:25274515

Rezler, Mateusz; ?o?ek, Teresa; Wolska, Irena; Maciejewska, Dorota

2014-10-01

89

Intermolecular Sb···Sb interactions in crystalline tetramethyldistibane (Element element bonds ; 3)  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Tetramethyldistibane which shows a colour change from deep red to pale yellow upon melting, has been subjected to single-crystal x-ray diffraction analyses at -21° and -139°C (orthorhombic, Pnma, Z = 4, -139°C: a = 1150.9(3); b = 1136.8(2); c = 651.6(2) pm). The molecules adopt the antiperiplanar conformation with the crystallographically imposed symmetry m (c 3) and are aligned in extended linear antimony chains with short intermolecular contacts (-139 °C: Sb-Sb 283.8(1), Sb···Sb 367....

Mundt, Otto; Riffel, Heinz; Becker, Gerd; Simon, Arndt

1984-01-01

90

Intermolecular interactions in mixtures of poly (ethylene glycol) with methoxybenzene and ethoxybenzene: Volumetric and viscometric studies  

International Nuclear Information System (INIS)

Highlights: • Density and viscosity values of PEG400 + methoxybenzene or + ethoxybenzene were measured. • The excess molar volume and thermodynamic functions of activation were calculated. • The results were interpreted in light of polymer–solvent interactions. • The changes in activation function indicate the viscous flow process. • The thermodynamic functions were correlated with the suitable equations. -- Abstract: The density and viscosity values of the binary mixtures of {poly (ethylene glycol) (PEG400) + methoxybenzene, or + ethoxybenzene} have been measured at T = (298.15, 308.15, and 318.15) K. From these experimental values, the excess molar volume, apparent specific volume, partial specific volume of solute, partial specific volume of solvent and excess Gibbs free energy of activation have been computed over the entire range of composition at three temperatures. From the experimental data, the thermodynamic functions of activation have been estimated for each binary mixture. The obtained results have been interpreted in light of polymer–solvent interactions and packing effects. The signs of excess molar volume and deviations of excess Gibbs free energy of activation have been used to obtain some information in regard to existence of specific interactions between PEG400 and solvents molecules. The changes in entropy and enthalpy of activation from the initial state to the transition state were also calculated in order to see which one of these functions controls viscous flow process in the studied polymer solutions. The excess molar volume and excess Gibbs free energy of activation values have been adequately fitted to the Redlich–Kister polynomial. Apparent specific volume values were correlated with the suitable equation. The different models proposed for correlating the viscosity of polymer solutions or liquid mixtures (segment-based-Eyring–NRTL, segment-based-Eyring–Wilson, Grunbreg–Nissan, Frenkel, Hind et al., Katti–Chauddhri, Tamura–Kurata, Auslander and McAllister) have also been used to fit the viscosity values

91

Characterization of self-assembled structure of discotic liquid crystal molecules using small-angle X-ray scattering and computer simulation methods based on intermolecular interactions  

Science.gov (United States)

This study aimed at elucidating the self-assembly structure of newly synthesized three-armed discotic liquid crystal molecules (DLCs) which give rise to small-angle X-ray scattering (SAXS) profiles that have difficulties in the direct determination of the symmetry of long-range intercolumnar lattice. The self-assembly structure of newly synthesized two analogues of DLCs, viz. 1,3,5-tris[2-(4-dodecyloxyphenyl)-oxadiazol-5-yl]benzene (TDOB) and 1,3,5-tris[2-(3,4,5-tris-dodecyloxyphenyl)-oxadiazol-5-yl]benzene (TTDOB), being discerned only in the number of dodecyloxyphenyl tails on each oxadiazol arm, were elucidated by comparative analyzes between experimentally observed SAXS profiles and those generated from a computational method. TTDOB molecules exhibited a typical SAXS profile of a hexagonal columnar mesophase, but TDOB molecules showed an ambiguous one hard to analyze. We found that, in TDOB molecules, the low degree of branching caused the localized conjugated electrons, which leads to weakening of interdisc interactions of core part and loosing the packing of disc molecules. And the free space between arms, afforded by a single branch on each arm, and electrostatic interactions between opposite charges on neighboring molecules which come from the localized electrons, allow TDOB columns to pack more closely than the disc diameter, then to form an interdigitated columnar structure. Such self-assembly structure is thought to be the result of the balance of various intermolecular interactions, so the self-assembly structures were tried to explain through a relative contribution of each intermolecular interaction component, that is, individual interaction energy values that we can calculate. With our proposed approaches, it is expected to widen our understanding of the self-assembly structures of various materials including DLCs.

Gihm, Se Hoon; Kim, Bong Gi; Kim, Sehoon; Seo, Jangwon; Park, Soo Young; Park, Chong Rae

2010-12-01

92

Tuning intermolecular interactions to enhance solid-state nanopore force spectroscopy  

Science.gov (United States)

Nanopores, nanometer sized holes in membranes, have recently come into prominence as tools for single molecule sensing. A technique called nanopore force spectroscopy uses the nanopore to probe energy landscapes between molecules. With the development of this technique, it will be possible for molecular recognition in complex fluids, such as blood. However, before that can be possible, solid-state nanopores, commonly fabricated in silicon nitride membranes, and having very confined sizes and charged surfaces, need to be optimized to minimize unwanted interactions between solution-phase molecules and the surface. DNA, for example, a crucial part of nanopore force spectroscopy, frequently sticks to the nanopore surface. Surface functionalization techniques, both on the nanopore and molecular surface, were attempted in this thesis work. These surface functionalization methods aimed to reduce surface charge or alter molecular properties in order to minimize the unwanted surface interactions, and they include silane modification, fluid lipid bilayer coating, and surfactant self-assembly on the DNA phosphate backbone. Results from some of these methods yield insights to improve nanopore force spectroscopy performance that will minimize the unwanted surface interactions and deliver on the promise of nanopore sensing.

Foun, Elaine

93

Perturbation theory of intermolecular interactions: What is the problem, are there solutions?  

International Nuclear Information System (INIS)

We review the nature of the problem in the framework of Rayleigh-Schroedinger perturbation theory (the polarization approximation) considering explicitly two examples: the interaction of two hydrogen atoms and the interaction of Li with H. We show, in agreement with the work of Claverie and of Morgan and Simon, that the LiH problem is dramatically different from the H2 problem. In particular, the physical states of LiH are higher in energy than an infinite number of discrete, unphysical states and they are buried in a continuum of unbound, unphysical states, which starts well below the lowest physical state. Clavrie has shown that the perturbation expansion, under these circumstances, is likely to converge to an unphysical state of lower energy than the physical ground state, if it converges at all. We review, also, the application of two classes of exchange perturbation theory to LiH and larger systems. We show that the spectra of three Eisenschitz-London (EL) class, exchange perturbation theories have no continuum of unphysical states overlaying the physical states and no discrete, unphysical states below the lowest physical state. In contrast, the spectra of two Hirschfelder-Silbey class theories differ hardly at all from that found with the polarization approximation. Not one of the EL class of perturbation theories, however, eliminates all of the discrete unphysical states

94

Relação entre transferência de carga e as interações intermoleculares em complexos de hidrogênio heterocíclicos Relationship between charge transfer and intermolecular interactions in heterocyclic hydrogen-bonded complexes  

Directory of Open Access Journals (Sweden)

Full Text Available Hydrogen-bonded complexes formed by the interaction of the heterocyclic molecules C2H4O and C2H5N with HF, HCN, HNC and C2H2 have been studied using density functional theory. The hydrogen bond strength has been analyzed through electron density charge transfer from the proton acceptor to the proton donor. The density charge transfer has been estimated using different methods such as Mulliken population analysis, CHELPG, GAPT and AIM. It has been shown that AIM-estimated charge transfer correlates very well with the hydrogen bond energy and the infrared bathochromic effect of the proton donor stretching frequencies.

Boaz G. Oliveira

2007-08-01

95

Intermolecular C–H?O interactions in cyclopentanone: An inelastic neutron scattering study  

International Nuclear Information System (INIS)

Highlights: • The inelastic neutron spectrum of cyclopentanone was obtained. • The neutron spectrum of the pure compound reveals presence of C–H?O hydrogen bonds. • Almost exact match between simulated C–H?O bonded dimer and experimental spectra. • Anti-translational ?H?O mode assigned to band at 95 cm?1 and confirmed by DFT results. - Abstract: The inelastic neutron scattering (INS) spectra of cyclopentanone were obtained for pure and 50% CCl4 solution forms. Spectra are compared with infrared and Raman data, and with DFT calculated eigenvectors. This exercise aims to find spectroscopic evidence in the neutron spectra for the presence of C–H?O hydrogen bonds. These are weak interactions with an energy of ca. ?6 kJ mol?1 as predicted by DFT. The neutron spectra show narrow and sharp bands which allows for an assignment of the vibrational modes. The simulated neutron spectrum of C–H?O bonded cyclopentanone dimers matches the experimental spectrum of the pure compound, whereas the monomer simulation monomer matches the experimental spectrum of the diluted solution, meaning that such interaction can be probed by INS. Assignment of the 95 cm?1 band to the ?H?O anti-translational mode, being supported by DFT results and in agreement with previous literature data, is considered and discussed

96

Intermolecular interactions as controlling factor for water sorption into polymer membranes.  

Science.gov (United States)

A multidisciplinary approach was used for delineating the mechanisms controlling water sorption into modified block co-poly-(ether/amide) (PEBAX) membranes. In particular, incorporation of aromatic sulfonamide (KET) into the polymer matrix led to a nonlinear increase of water sorption in the membrane. The modification in sorption was accompanied by a nonlinear behavior in membrane surface energies. Infrared analysis revealed a different availability and accessibility of free polar groups supporting the formation of hydrogen bonding as a function of modifier concentration. A combination of both experimental and theoretical procedures was used to analyze the molecular processes of water sorption on PEBAX membranes. Molecular dynamics (MD) and quantum chemical (QC) calculations demonstrated that the formation of KET-KET dimers in the polymeric matrix led to a decrease in the interaction energy between water and modifiers. In addition, no variations in the dipole moments of water-dimer structures were found in comparison to a single KET and water-KET molecule. The formation of water-dimer complexes at higher concentration of modifier decreases the number of the dipole moment, thus preventing the polarization of polymer chains. PMID:17608518

Gugliuzza, A; Luca, G De; Tocci, E; Lorenzo, L De; Drioli, E

2007-08-01

97

Relação entre transferência de carga e as interações intermoleculares em complexos de hidrogênio heterocíclicos / Relationship between charge transfer and intermolecular interactions in heterocyclic hydrogen-bonded complexes  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: Portuguese Abstract in portuguese [...] Abstract in english Hydrogen-bonded complexes formed by the interaction of the heterocyclic molecules C2H4O and C2H5N with HF, HCN, HNC and C2H2 have been studied using density functional theory. The hydrogen bond strength has been analyzed through electron density charge transfer from the proton acceptor to the proton [...] donor. The density charge transfer has been estimated using different methods such as Mulliken population analysis, CHELPG, GAPT and AIM. It has been shown that AIM-estimated charge transfer correlates very well with the hydrogen bond energy and the infrared bathochromic effect of the proton donor stretching frequencies.

Boaz G., Oliveira; Regiane C. M. U. de, Araújo.

2007-08-01

98

Sensitivity analysis of rotational energy transfer processes to the intermolecular potential  

International Nuclear Information System (INIS)

This paper considers the sensitivity of rotational energy transfer processes to the variation of parameters within an assumed model intermolecular potential. The following cross sections are considered here: integral state to state, pressure broadening, effective diffusion and viscosity, and final state summed integral cross sections. In order to simplify the calculation of cross sections, attention is restricted to the scattering of an atom and linear rigid rotor. Furthermore, the collision dynamics are approximated by using the infinite order sudden (IOS) method. It is shown that use of the IOS method allows for the very simple generation of first order sensitivity coefficients (i.e., the partial derivative of cross sections with respect to potential parameters). Particular attention is focused upon the sensitivities of different cross sections and combinations of cross sections to the various parameters. The first order sensitivities are also used to derive new coefficients which describe how the potential parameters correlate given a limited set of cross section measurements. These coefficients are shown to be particularly important in determining the degree to which a set of measurements is able to define various parameters of the assumed potential

99

Transport properties in mixtures involving carbon dioxide at low and moderate density: test of several intermolecular potential energies and comparison with experiment  

Energy Technology Data Exchange (ETDEWEB)

It is the purpose of this paper to extract unlike intermolecular potential energies of five carbon dioxide-based binary gas mixtures including CO{sub 2}-He, CO{sub 2}-Ne, CO{sub 2}-Ar, CO{sub 2}-Kr, and CO{sub 2}-Xe from viscosity data and compare the calculated potentials with other models potential energy reported in literature. Then, dilute transport properties consisting of viscosity, diffusion coefficient, thermal diffusion factor, and thermal conductivity of aforementioned mixtures are calculated from the calculated potential energies and compared with literature data. Rather accurate correlations for the viscosity coefficient of afore-cited mixtures embracing the temperature range 200 Kintermolecular potentials energy. Our estimated accuracies for the viscosity are to within {+-}2%. In addition, the calculated potential energies are used to present smooth correlations for other transport properties. The accuracies of the binary diffusion coefficients are of the order of {+-}3%. Finally, the unlike interaction energy and the calculated low density viscosity have been employed to calculate high density viscosities using Vesovic-Wakeham method. (orig.)

Moghadasi, Jalil; Yousefi, Fakhri [Shiraz University, Department of Chemistry, Shiraz (Iran); Papari, Mohammad Mehdi; Faghihi, Mohammad Ali [Shiraz University of Technology, Department of Chemistry, Shiraz (Iran); Mohsenipour, Ali Asghar [University of Waterloo, Department of Chemical Engineering, Waterloo (Canada)

2009-09-15

100

Intermolecular interactions and thermodynamic properties of 3,6-diamino-1,2,4,5-tetrazine-1,4-dioxide dimers: A density functional theoretical study  

Scientific Electronic Library Online (English)

Full Text Available SciELO South Africa | Language: English Abstract in english Three fully optimized structures of 3,6-diamino-1,2,4,5-tetrazine-1,4-dioxide (LAX-112) dimers have been obtained with the density functional theory (DFT) method at the B3LYP/6-311++G level. Vibrational frequency calculations were carried out to ascertain that each structure is a minimum (no imagina [...] ry frequencies). The intermolecular interaction energy is calculated with the basis set superposition error (BSSE) correction and zero point energy (ZPE) correction. The greatest corrected binding energy among the three dimers is -42.38 kJ mol-1. The charge redistribution mainly occurs on the adjacent O(N)......H atoms between submolecules and the charge transfer between two subsystems is very small. Natural bond orbital (NBO) analysis was performed to reveal the origin of the interaction. Based on the vibrational analysis, the standard thermodynamic functions (heat capacities (cºp), entropies (S°m) and enthalpies (H°m)) and the changes of thermodynamic properties from the monomer to dimer with the temperature ranging from 200.00 K to 800.00 K have been obtained using statistical thermodynamics. The results show that the strong hydrogen bonds dominantly contribute to the dimers, while the bonding energies are not only determined by the hydrogen bonding. The dimerization process of dimer II can occur spontaneously at room temperature.

Ning Ning, Zhao; Ya Ling, Zhao; Yin, Hu; Hai Xia, Ma; Feng Qi, Zhao; Ji Rong, Song.

2013-08-01

 
 
 
 
101

The theory of intermolecular forces  

CERN Document Server

The theory of intermolecular forces has advanced very greatly in recent years. It has become possible to carry out accurate calculations of intermolecular forces for molecules of useful size, and to apply the results to important practical applications such as understanding protein structure and function, and predicting the structures of molecular crystals. The Theory of Intermolecular Forces sets out the mathematical techniques that are needed to describe and calculate intermolecular interactions and to handle the more elaborate mathematical models. It describes the methods that are used to calculate them, including recent developments in the use of density functional theory and symmetry-adapted perturbation theory. The use of higher-rank multipole moments to describe electrostatic interactions is explained in both Cartesian and spherical tensor formalism, and methods that avoid the multipole expansion are also discussed. Modern ab initio perturbation theory methods for the calculation of intermolecular inte...

Stone, Anthony J

2013-01-01

102

plasma desorption mass spectrometry of quinolinium salts and method of estimation of their intermolecular interactions with phospholipids  

Science.gov (United States)

Using plasma desorption mass spectrometry, the fragmentation of 1-phenyl-2(p-aminostyryl)quinolinium and 1-phenyl-2(p-aminostyryl)benzo(f)quinolinium derivatives, with various substituents at the amino nitrogen, was studied. With plasma desorption ionization, the fragmentation features of the compounds studied are mainly determined by the nature of the N',N'' substituents. The behaviour of some quinolinium derivatives in the presence of lecithin, a basic component of the phospholipid fraction of cell membranes, was investigated. For the benzo(f)quinolinium derivative, the analysis of changes in the mass spectra indicates a strong interaction between these substances, leading to the formation of a molecular complex stabilized by the interactions of the negatively charged phosphate group of lecithin with the quinolinium quaternary nitrogen and the lecithin quaternary nitrogen with the benzene part of the aminophenyl fragment. The effect of the third aromatic ring of the benzoquinolinium system on complex stabilization is discussed. For the benzoquinolinium derivative with lecithin, the changes in the mass spectrometric fragmentation pattern of the molecule can be used as a sensitive and informative method for the characterization of intermolecular interactions which may result in molecular complex formation.

Andrievsky, Grigory V.; Lisnyak, Yury V.; Klochkov, Vladimir K.; Volyansky, Yury L.; Malaya, Lubov T.

1997-06-01

103

Weak Chemical Interaction and van der Waals Forces: A Combined Density Functional and Intermolecular Perturbation Theory - Application to Graphite and Graphitic Systems  

Science.gov (United States)

In this contribution we address the theoretical underst anding of weak chemical interactions and of the van der Waals forces, in conjunction with the last developments in this area and selected applications to nanostructures. In the first section, we highlight the importance of these interactions, in physics and chemistry and also in biology, and we recall early treatments of these issues, as those by van der Waals and London. After a brief review of the existing methods to treat such interactions, we present a model based on DFT (for each van der Waals-interacting independent system) and an intermolecular perturbation theory that uses a localized orbitals basis set. We will first detail a weak overlap expansion (LCAO-S 2) as a perturbation treatment to determine the weak chemical interaction. Then we will show how to implement the van der Waals interaction in the DFT solution, from the dipolar approximation in a perturbation theory. We apply this model to a reference system for weak interactions, i.e., the interaction between two planes of graphene. In the framework of a minimal basis set that describes each independent system and the weak chemical repulsion, we show that it is necessary to take into account atomic dipole transitions involving high excited states like 3d orbitals to properly describe the van der Waals interaction. We demonstrate how the delicate balance between chemical repulsion and van der Waals attractive interaction gives the equilibrium geometry and the binding energy of the system. Moreover, as an extension of this work, we obtain the adsorption energy of a carbon nanotube on graphene, the adsorption energy of a C60 molecule on a carbon nanotube, and the energy of a C60 molecule encapsulated in a carbon nanotube. This gives us the opportunity to discuss incommensurable systems. A complete study of C60 dimers is also presented with future perspective for the study of C60 molecular crystals. We will conclude with an overview of this work, discussing interaction and transport at metal-organics interfaces from the point of view of applications in the field of molecular electronics.

Dappe, Y. J.; Ortega, J.; Flores, F.

104

Intermolecular interactions in binary and ternary solutions of two cycloimmonium-carboethoxy-anilido-methylids  

Science.gov (United States)

Two cycloimmonium ylids with pyridinium and iso-quinolinium as heterocycle and having common carbanion were studied from the point of view of the solvent influence on electronic absorption spectra in binary and ternary solutions. The supplies of the universal and specific interactions to the spectral shifts in the electronic absorption spectra of hydroxyl solutions were separated. The strength of the specific interactions of the ylid molecules with octanol was estimated by using ternary solutions in binary solvent Octanol + Dichloroethane, in which the universal interactions have similar strengths. Quantum mechanical calculations and also the solvatochromic effect allowed us estimating the values of the molecular dipole moments in the excited state of the studied ylids. The conclusions showed that by excitation the molecular dipole moment of the studied ylids decreases or changes its sense, due to the electronic charge transport from the carbanion towards the heterocycle.

Closca, Valentina; Ivan, Liliana Mihaela; Dorohoi, Dana Ortansa

2014-03-01

105

12C/13C and H/D vapor pressure isotope effects of fluoroform: intermolecular interactions in liquid fluoroform  

International Nuclear Information System (INIS)

A precision cryostat of the Bigeleisen-Brooks-Ribnikar-Ishida (BBIR) type with associated vacuum systems has been constructed and the appropriate temperature/pressure measurement and control systems designed and implemented. Various improvements in the cryostat design were incorporated in order to facilitate the assembly and repair processes. A major design change involved the incorporation of a digital stand alone computer to control cryostat operations. This apparatus was used to measure the 12C/13C and H/D Vapor Pressure Isotope Effects of Fluoroform. Analysis of the measured VPIE results, in light of existing experimental data and theories, has demonstrated the need of a temperature dependent liquid force field, specifically a temperature-dependent interaction force constant between the C-H stretching motion and translational motion in the direction of the figure axis of CHF3. This result is consistent with the observed spectroscopic data and vibrational and configurational models of fluoroform dimers. The intermolecular interaction is believed to be a weak hydrogen-bond in nature

106

Investigating Intermolecular Interactions via Scanning Tunneling Microscopy: An Experiment for the Physical Chemistry Laboratory  

Science.gov (United States)

A scanning tunneling microscope (STM) project designed as a module for the undergraduate physical chemistry laboratory is described. The effects of van der Waals interactions on the condensed-phase structure are examined by the analysis of the pattern of the monolayer structures.

Pullman, David; Peterson, Karen I.

2004-01-01

107

Weak carbonyl-methyl intermolecular interactions in acetone clusters explored by IR plus VUV spectroscopy  

International Nuclear Information System (INIS)

Highlights: ? The carbonyl overtone of acetone clusters is observed by IR-VUV spectroscopy. ? Acetone molecules in the dimer are stacked with an antiparallel way. ? The structure of the acetone trimer and the tetramer are the cyclic structures. ? The carbonyl groups would interact with the methyl groups in acetone clusters. ? These weak interactions are further confirmed by H/D substitution experiment. -- Abstract: Size-selected IR–VUV spectroscopy is employed to detect vibrational characteristics in the region 2850 ? 3550 cm?1 of neutral acetone and its clusters (CH3COCH3)n (n = 1–4). Features around 3440 cm?1 in the spectra of acetone monomer and its clusters are assigned to the carbonyl stretch (CO) overtone. These features red-shift from 3455 to 3433 cm?1 as the size of the clusters increases from the monomer to the tetramer. Based on calculations, the experimental IR spectra in the C=O overtone region suggest that the dominant structures for the acetone trimer and tetramer should be cyclic in the supersonic expansion sample. This study also suggests that the carbonyl groups interact with the methyl groups in the acetone clusters. These weak interactions are further confirmed by the use of deuterium substitution.

108

Redetermined structure of diphenylphosphonimidotriphenylphosphorane: location of the hydrogen atoms and analysis of the intermolecular interactions  

Directory of Open Access Journals (Sweden)

Full Text Available The title compound, C30H25NOP2, is a bulky phosphazene derivative. Its previous crystal structure [Cameron et al. (1979. Acta Cryst. B35, 1373–1377] is confirmed and its H atoms have been located in the present study. The formal P=N double bond is about 0.05?Å shorter than the P—N single bond and the large P=N—P bond angle reflects the steric strain in the molecule. An intramolecular C—H...O interaction occurs. In the crystal, short C—H...O contacts connect the molecules into chains propagating in [011], which are cross-linked via C—H...? interactions, generating a three-dimensional network. Aromatic ?–? stacking also occurs [shortest centroid–centroid separation = 3.6012?(11?Å].

Richard Betz

2011-05-01

109

Prediction of polymer mixture compatibility by Monte Carlo simulation of intermolecular binary interactions  

CERN Document Server

We have evaluated conformational and orientational averages of binary interaction integrals for pairs of chains constituting atomistic representations of short polymer molecules. By considering A-A, B-B and A-B pairs, we relate these results with the Flory-Huggins parameter for the A-B mixtures. This parameter is commonly accepted as a good indicator of compatibility. Since the method ignores the simultaneous interactions with other molecules in the mixture, the local environment is approximately described by introducing an effective medium dielectric constant whose value is conveniently parameterized. The results for four different real systems are compared with data obtained from experimental neutron scattering data. The method qualitatively predicts the sign and variation with temperature in the four different cases, also showing a reasonable quantitative agreement in some of the cases. Its performance is discussed in comparison with a standard method that evaluates the Flory-Huggins parameter by calculati...

Ahmadi, Amirhossein

2009-01-01

110

Determination of stepsize parameters for intermolecular vibrational energy transfer: Progress report, May 1, 1987-April 30, 1988  

International Nuclear Information System (INIS)

Intermolecular vibrational energy transfer for highly excited polyatomic molecules is involved in any mechanism in which excitation energy is required (pyrolysis) or in which energy must be removed from a hot source (cooling). The average energy removed per collision, , is a useful quantity to compare efficiency for energy transfer. The objectives of this work are: to determine the dependence of on excitation energy and on the molecular complexity (number of vibrational modes) of substrate and deactivator; to assess the importance of intermolecular attractions (complex formation) on vibrational energy transfer; to obtain detailed information on the energy distribution after collision and to evaluate the importance of on high-temperature unimolecular reactions. This information will be obtained by monitoring the time dependence of the infrared emission, ultraviolet absorption, refractive index and pressure. The results from these complementary techniques will be benchmarked with values from previous studies on the relaxation of chemically activated alkyl and fluoroalkyl radicals. Trajectory calculations simulating energy transfer are being performed for ''generic'' substrate/deactivator pairs to provide additional details and insight on the important parameters. Model calculations are also being performed to determine the feasibility of obtaining information from experimental data for high-temperature unimolecular reactions

111

Conductance switching in a molecular device: The role of side groups and intermolecular interactions  

DEFF Research Database (Denmark)

We report first-principles studies of electronic transport in monolayers of Tour wires functionalized with different side groups. An analysis of the scattering states and transmission eigenchannels suggests that the functionalization does not strongly affect the resonances responsible for current flow through the monolayer. However, functionalization has a significant effect on the interactions within the monolayer, so that monolayers with NO2 side groups exhibit local minima associated with twisted conformations of the molecules. We use our results to interpret observations of negative differential resistance and molecular memory in monolayers of NO2 functionalized molecules in terms of a twisting of the central ring induced by an applied bias potential.

Taylor, Jeremy Philip; Brandbyge, Mads

2003-01-01

112

Co-amorphous simvastatin and glipizide combinations show improved physical stability without evidence of intermolecular interactions.  

Science.gov (United States)

The objective of this study was to prepare a co-amorphous drug/drug combination between two BCS class II drugs, simvastatin (SVS) and glipizide (GPZ). This pharmacologically relevant combination of two drugs could produce a promising candidate for formulations intended for combination therapy of metabolic disorders. The co-amorphous SVS-GPZ mixtures (molar ratios 2:1, 1:1 and 1:2) were prepared by mechanical activation (ball milling or cryomilling) and characterized with respect to their thermal properties, possible molecular interactions, dissolution properties and physical stability, and compared to the behaviour of pure amorphous forms and their physical mixtures. It was found that even though a molecular mixture was achieved with all SVS-GPZ mixture ratios, no molecular interactions between the drugs could be detected. By formation of co-amorphous single-phase mixtures, only the dissolution rate of GPZ could be improved. The co-amorphous mixtures showed improved stability compared to the pure amorphous forms and the amorphous physical mixtures. It was concluded that this was attributable to the molecular level mixing of SVS with GPZ upon milling, and GPZ is acting as an anti-plasticizer in these mixtures. PMID:22353489

Löbmann, Korbinian; Strachan, Clare; Grohganz, Holger; Rades, Thomas; Korhonen, Ossi; Laitinen, Riikka

2012-05-01

113

Co-amorphous simvastatin and glipizide combinations show improved physical stability without evidence of intermolecular interactions  

DEFF Research Database (Denmark)

The objective of this study was to prepare a co-amorphous drug/drug combination between two BCS class II drugs, simvastatin (SVS) and glipizide (GPZ). This pharmacologically relevant combination of two drugs could produce a promising candidate for formulations intended for combination therapy of metabolic disorders. The co-amorphous SVS-GPZ mixtures (molar ratios 2:1, 1:1 and 1:2) were prepared by mechanical activation (ball milling or cryomilling) and characterized with respect to their thermal properties, possible molecular interactions, dissolution properties and physical stability, and compared to the behaviour of pure amorphous forms and their physical mixtures. It was found that even though a molecular mixture was achieved with all SVS-GPZ mixture ratios, no molecular interactions between the drugs could be detected. By formation of co-amorphous single-phase mixtures, only the dissolution rate of GPZ could be improved. The co-amorphous mixtures showed improved stability compared to the pure amorphous forms and the amorphous physical mixtures. It was concluded that this was attributable to the molecular level mixing of SVS with GPZ upon milling, and GPZ is acting as an anti-plasticizer in these mixtures.

Löbmann, Korbinian; Strachan, Clare

2012-01-01

114

Study of Intermolecular Interactions of Acetophenone and Benzene at 303.15, 313.15 and 323.15 K  

Directory of Open Access Journals (Sweden)

Full Text Available The behaviour of mixture of acetophenone  and  benzene  as a function of temperature and composition  has been investigated by measuring sound velocity in conjunction with density at 303.15, 313.15and 323.15 K. Derived parameters computed from density (? and sound velocity (U have been used to determine excess molar volumes (VME, excess isentropic compressibilities (KSE and excess inter molecular free length (LfE.The excess functions have been discussed in terms of intermolecular interactions between the components of binary mixture. The validity of various theoretical approaches of liquids has been tested for the system by comparing theoretical sound speeds with those experimentally determined over the entire composition range in the temperature range 303.15-323.15K. The computed results have been fitted to the Redlich-Kister polynomial equation to estimate the smoothening coefficients and standard deviations for this system. The validity of various theoretical approaches of liquids has been tested for the system by comparing theoretical sound speeds with those experimentally determined over the entire composition range in the temperature303.15-323.15K.

K. Saravanakumar

2010-05-01

115

Solid-State [2+2] Photodimerization and Photopolymerization of ?,?-Diarylpolyene Monomers: Effective Utilization of Noncovalent Intermolecular Interactions in Crystals  

Directory of Open Access Journals (Sweden)

Full Text Available [2+2] Photocycloaddition of olefins is a very useful reaction in synthetic organic chemistry to obtain cyclobutane-containing molecules, which are almost inaccessible by other methods. The reaction, when performed in the crystalline state, occurs more efficiently and selectively than in homogeneous solution due to tight and regular molecular arrangement in the crystal state. Despite numerous examples for the solid-state [2+2] photodimerization of monoenes, however, it is still a challenge to prepare not only dimers but also higher oligomers and polymers from conjugated polyenes, which have multiple reactive double bonds in a molecule. In our recent studies of the solid-state photoreactions of ?,?-diarylpolyenes, noncovalent intermolecular interactions in crystals were effectively utilized to prealign molecules in stacking arrangements, suitable for the [2+2] reaction. With appropriate ring-substituents, [2+2] photodimerization and photopolymerization of the polyenes took place, although the degree of polymerization was relatively low. This review will describe the details of these reactions.

Yoriko Sonoda

2010-12-01

116

Theoretical analysis of the intermolecular interactions in naphthalene diimide and pyrene complexes.  

Science.gov (United States)

Supramolecular assembly of donor-acceptor complexes as the key component in organic functional nanomaterials is a promising approach for future electronic devices. One representative example of the donor-acceptor complexes is the naphthalene diimide-pyrene (NDI-Py) system, which shows fascinating photoelectric properties. Herein, the analysis of the ?-? interactions between NDI and Py has been investigated using the DFT/M06-2X and reduced density gradient methods. According to the calculations, the attractive forces for the stabilization of the NDI-Py dimer are dependent on the rotation angles, which provide physical insight into the experimental data reported by Wilson and co-workers (Langmuir, 2011, 27, 6554). Our results not only provide computational evidence for the origin of the rotation in the crystal structure of the NDI-Py but also address the role of the charge-transfer attractions in the complexes. PMID:25294626

Yeh, Mei-Yu; Lin, Hsin-Chieh

2014-10-21

117

Direct observation of the intermolecular triplet-triplet energy transfer from UV-A absorber 4- tert -butyl-4?-methoxydibenzoylmethane to UV-B absorber octyl methoxycinnamate  

Science.gov (United States)

Triplet energy transfer (TET) is an important photostabilization process for organic UV absorbers, such as 4- tert-butyl-4'-methoxydibenzoylmethane (BM-DBM) and octyl methoxycinnamate (OMC). To characterize interactions between UV absorbers as TET the interactions between BM-DBM and OMC have been studied through measurements of EPR and time-resolved phosphorescence spectra. The EPR Bmin signals and the phosphorescence of OMC were observed through the selective excitation of BM-DBM at 365 nm in EtOH at 77 K. These results indicate that the intermolecular TET occurs from BM-DBM to OMC. This is the first report of the experimental evidence of the TET between the organic UV absorbers.

Kikuchi, Azusa; Yagi, Mikio

2011-09-01

118

Fabrication and Intermolecular Interactions of Silk Fibroin/Hydroxybutyl Chitosan Blended Nanofibers  

Directory of Open Access Journals (Sweden)

Full Text Available The native extracellular matrix (ECM is composed of a cross-linked porous network of multifibril collagens and glycosaminoglycans. Nanofibrous scaffolds of silk fibroin (SF and hydroxybutyl chitosan (HBC blends were fabricated using 1,1,1,3,3,3-hexa?uoro-2-propanol (HFIP and trifluoroacetic acid (TFA as solvents to biomimic the native ECM via electrospinning. Scanning electronic microscope (SEM showed that relatively uniform nanofibers could be obtained when 12% SF was blended with 6% HBC at the weight ratio of 50:50. Meanwhile, the average nano?brous diameter increased when the content of HBC in SF/HBC blends was raised from 20% to 100%. Fourier transform infrared spectra (FTIR and 13C nuclear magnetic resonance (NMR showed SF and HBC molecules existed in hydrogen bonding interactions but HBC did not induce conformation of SF transforming from random coil form to ?-sheet structure. X-ray diffraction (XRD confirmed the different structure of SF/HBC blended nanofibers from both SF and HBC. Thermogravimetry-Differential thermogravimetry (TG-DTG results demonstrated that the thermal stability of SF/HBC blend nanofibrous scaffolds was improved. The results indicated that the rearrangement of HBC and SF molecular chain formed a new structure due to stronger hydrogen bonding between SF and HBC. These electrospun SF/HBC blended nanofibers may provide an ideal tissue engineering scaffold and wound dressing.

Xiu-Mei Mo

2011-03-01

119

Self-assembly of carboranethiol isomers on Au111: intermolecular interactions determined by molecular dipole orientations.  

Science.gov (United States)

Self-assembled monolayer (SAM) structures and properties are dominated by two interactions: those between the substrate and adsorbate and those between the adsorbates themselves. We have fabricated self-assembled monolayers of m-1-carboranethiol (M1) and m-9-carboranethiol (M9) on Au[111]. The two isomers are nearly identical geometrically, but calculated molecular dipole moments show a sizable difference at 1.06 and 4.08 D for M1 and M9 in the gas phase, respectively. These molecules provide an opportunity to investigate the effect of different dipole moments within SAMs without altering the geometry of the assembly. Pure and co-deposited SAMs of these molecules were studied by scanning tunneling microscopy (STM). The molecules are indistinguishable in STM images, and the hexagonally close-packed adlayer structures were found to have ((square root of 19) x (square root of 19))R23.4 degrees unit cells. Both SAMs display rotational domains without the protruding or depressed features in STM images associated with domain boundaries in other SAM systems. Differing orientations of molecular dipole moments influence SAM properties, including the stability of the SAM and the coverage of the carboranethiolate in competitive binding conditions. These properties were investigated by dynamic contact angle goniometry, Kelvin probe force microscopy, and grazing incidence Fourier transform infrared spectroscopy. PMID:19243128

Hohman, J Nathan; Zhang, Pengpeng; Morin, Elizabeth I; Han, Patrick; Kim, Moonhee; Kurland, Adam R; McClanahan, Patrick D; Balema, Viktor P; Weiss, Paul S

2009-03-24

120

New solvation free energy function comprising intermolecular solvation and intramolecular self-solvation terms  

Directory of Open Access Journals (Sweden)

Full Text Available Abstract Solvation free energy is a fundamental thermodynamic quantity that should be determined to estimate various physicochemical properties of a molecule and the desolvation cost for its binding to macromolecular receptors. Here, we propose a new solvation free energy function through the improvement of the solvent-contact model, and test its applicability in estimating the solvation free energies of organic molecules with varying sizes and shapes. This new solvation free energy function is constructed by combining the existing solute-solvent interaction term with the self-solvation term that reflects the effects of intramolecular interactions on solvation. Four kinds of atomic parameters should be determined in this solvation model: atomic fragmental volume, maximum atomic occupancy, atomic solvation, and atomic self-solvation parameters. All of these parameters for total 37 atom types are optimized by the operation of a standard genetic algorithm in such a way to minimize the difference between the experimental solvation free energies and those calculated by the solvation free energy function for 362 organic molecules. The solvation free energies estimated from the new solvation model compare well with the experimental results with the associated squared correlation coefficients of 0.88 and 0.85 for training and test sets, respectively. The present solvation model is thus expected to be useful for estimating the solvation free energies of organic molecules.

Choi Hwanho

2013-02-01

 
 
 
 
121

Intermolecular interactions and charge transfer transitions in aromatic hydrocarbon-tetracyanoethylene complexes.  

Science.gov (United States)

A comprehensive theoretical study of the electronically excited states in complexes between tetracyanoethylene (TCNE) and three aromatic electron donors, benzene, naphthalene and anthracene, was performed with a focus on charge transfer (CT) transitions. The results show that the algebraic diagrammatic construction method to second order (ADC(2)) provides excellent possibilities for reliable calculations of CT states. Significant improvements in the accuracy of the computed transition energies are obtained by using the scaled opposite-spin (SOS) variant of ADC(2). Solvent effects were examined on the basis of the conductor-like screening model (COSMO) which has been implemented recently in the ADC(2) method. The dielectric constant and the refractive index of dichloromethane have been chosen in the COSMO calculations to compare with experimental solvatochromic effects. The computation of optimized ground state geometries and enthalpies of formation has been performed at the second-order Møller-Plesset perturbation theory (MP2) level. By comparison with experimental data and with high-level coupled-cluster methods including explicitly correlated (F12) wave functions, the importance of the SOS approach is demonstrated for the ground state as well. In the benzene-TCNE complex, the two lowest electronic excitations are of CT character whereas in the naphthalene and anthracene TCNE complexes three low-lying CT states are observed. As expected, they are strongly stabilized by the solvent. Geometry optimization in the lowest excited state allowed the calculation of fluorescence transitions. Solvent effects lead to a zero gap between S1 and S0 for the anthracene-TCNE complex. Therefore, in the series of benzene-TCNE to anthracene a change from a radiative to a nonradiative decay mechanism to the ground state is to be expected. PMID:25156236

Aquino, Adélia A J; Borges, Itamar; Nieman, Reed; Köhn, Andreas; Lischka, Hans

2014-10-14

122

Asynchronous orthogonal sample design scheme for two-dimensional correlation spectroscopy (2D-COS) and its application in probing intermolecular interactions from overlapping infrared (IR) bands.  

Science.gov (United States)

This paper introduces a new approach to analysis of spectra called asynchronous orthogonal sample design (AOSD). Specifically designed concentration series are selected according to mathematical analysis of orthogonal vectors. Based on the AOSD approach, the interfering portion of the spectra arising strictly from the concentration effect can be completely removed from the asynchronous spectra. Thus, two-dimensional (2D) asynchronous spectra can be used as an effective tool to characterize intermolecular interactions that lead to apparent deviations from the Beer-Lambert law, even if the characteristic peaks of two compounds are substantially overlapped. A model solution with two solutes is used to investigate the behavior of the 2D asynchronous spectra under different extents of overlap of the characteristic peaks. Simulation results demonstrate that the resulting spectral patterns can reflect subtle spectral variations in bandwidths, peak positions, and absorptivities brought about by intermolecular interaction, which are barely visualized in the conventional one-dimensional (1D) spectra. Intermolecular interactions between butanone and dimethyl formamide (DMF) in CCl(4) solutions were investigated using the proposed AOSD approach to prove the applicability of the AOSD method in real chemical systems. PMID:21819780

Li, Xiaopei; Pan, Qinghua; Chen, Jing; Liu, Shaoxuan; He, Anqi; Liu, Cuige; Wei, Yongju; Huang, Kun; Yang, Limin; Feng, Juan; Zhao, Ying; Xu, Yizhuang; Ozaki, Yukihiro; Noda, Isao; Wu, Jinguang

2011-08-01

123

Intermolecular interactions, charge-density distribution and the electrostatic properties of pyrazinamide anti-TB drug molecule: an experimental and theoretical charge-density study.  

Science.gov (United States)

An experimental charge-density analysis of pyrazinamide (a first line antitubercular drug) was performed using high-resolution X-ray diffraction data [(sin??/?)max = 1.1?Å(-1)] measured at 100?(2)?K. The structure was solved by direct methods using SHELXS97 and refined by SHELXL97. The total electron density of the pyrazinamide molecule was modeled using the Hansen-Coppens multipole formalism implemented in the XD software. The topological properties of electron density determined from the experiment were compared with the theoretical results obtained from CRYSTAL09 at the B3LYP/6-31G** level of theory. The crystal structure was stabilized by N-H...N and N-H...O hydrogen bonds, in which the N3-H3B...N1 and N3-H3A...O1 interactions form two types of dimers in the crystal. Hirshfeld surface analysis was carried out to analyze the intermolecular interactions. The fingerprint plot reveals that the N...H and O...H hydrogen-bonding interactions contribute 26.1 and 18.4%, respectively, of the total Hirshfeld surface. The lattice energy of the molecule was calculated using density functional theory (B3LYP) methods with the 6-31G** basis set. The molecular electrostatic potential of the pyrazinamide molecule exhibits extended electronegative regions around O1, N1 and N2. The existence of a negative electrostatic potential (ESP) region just above the upper and lower surfaces of the pyrazine ring confirm the ?-electron cloud. PMID:24892603

Rajalakshmi, Gnanasekaran; Hathwar, Venkatesha R; Kumaradhas, Poomani

2014-06-01

124

Collecting high-order interactions in an effective pairwise intermolecular potential using the hydrated ion concept: The hydration of Cf3+  

Science.gov (United States)

This work proposes a new methodology to build interaction potentials between a highly charged metal cation and water molecules. These potentials, which can be used in classical computer simulations, have been fitted to reproduce quantum mechanical interaction energies (MP2 and BP86) for a wide range of [M(H2O)n]m+(H2O)? clusters (n going from 6 to 10 and ? from 0 to 18). A flexible and polarizable water shell model (Mobile Charge Density of Harmonic Oscillator) has been coupled to the cation-water potential. The simultaneous consideration of poly-hydrated clusters and the polarizability of the interacting particles allows the inclusion of the most important many-body effects in the new polarizable potential. Applications have been centered on the californium, Cf(III) the heaviest actinoid experimentally studied in solution. Two different strategies to select a set of about 2000 structures which are used for the potential building were checked. Monte Carlo simulations of Cf(III)+500 H2O for three of the intermolecular potentials predict an aquaion structure with coordination number close to 8 and average R_{{Cf-O}} in the range 2.43-2.48 Å, whereas the fourth one is closer to 9 with R_{{Cf-O}} = 2.54 Å. Simulated EXAFS spectra derived from the structural Monte Carlo distribution compares fairly well with the available experimental spectrum for the simulations bearing 8 water molecules. An angular distribution similar to that of a square antiprism is found for the octa-coordination.

Galbis, Elsa; Hernández-Cobos, Jorge; Pappalardo, Rafael R.; Marcos, Enrique Sánchez

2014-06-01

125

On the representation of the electric charge distribution in ethane for calculations of the molecular quadrupole moment and intermolecular electrostatic energy  

DEFF Research Database (Denmark)

It is shown that a simple atom-site monopole model is inferior to one which includes higher-order local multipoles to represent the intramolecular charge distribution of ethane. Unlike the latter model, the local monopole representation predicts the wrong sign for the molecular quadrupole moment and gives a repulsive rather than an attractive electrostatic interaction at typical intermolecular distances. In the local multipole model, the atom-site dipoles give the largest contribution to both the molecular quadrupole moment and the intermolecular interaction. The Journal of Chemical Physics is copyrighted by The American Institute of Physics.

Hansen, Flemming Yssing

1985-01-01

126

Crystal habits of cubic insulin from porcine pancreas and evaluation of intermolecular interactions by macrobond and EET analyses  

Science.gov (United States)

Experimental and theoretical investigations of the crystal growth of cubic insulin from porcine pancreas were carried out. Three different crystal habits, cube, cube and dodecahedron, and rhombic dodecahedron forms, were obtained. Judging from the results of macroseeding, the most stable of these forms would be the rhombic dodecahedron surrounded by {1 1 0} faces. Molecular interactions in the crystal were evaluated by the macrobond analysis and electrostatic energy of transfer (EET) analysis. The calculated surface energy of {1 1 0} was lower than {1 0 0} by around 40%, which was consistent with the experimental results. Atomic EET supported the macrobond analysis, where the number of hydrogen bonds was primarily evaluated. At the same time, it was suggested that the parameters of the interaction energies of electrically neutral pairs would be smaller than those of charged pairs. The contribution from the bound water molecules to the crystal stabilization was discussed.

Ootaki, Masanori; Endo, Shigeru; Sugawara, Yoko; Takahashi, Takuya

2009-08-01

127

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

International Nuclear Information System (INIS)

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: A498, non fluorescent and B462, 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., A498 becomes B462), and a intermolecular and unidirectional Forster-type energy transfer. During the FRET process, the fluorescent B462 form acts as donor for the non-fluorescent A498 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.

128

Comparison of Cluster, Slab, and Analytic Potential Models for the Dimethyl Methylphosphonate (DMMP)/TiO2 (110) Intermolecular Interaction  

Energy Technology Data Exchange (ETDEWEB)

In a previous study (J. Phys. Chem. C 2011, 115, 12403) cluster models for the TiO2 rutile (110) surface and MP2 calculations were used to develop an analytic potential energy function for dimethyl methylphosphonate (DMMP) interacting with this surface. In the work presented here, this analytic potential and MP2 cluster models are compared with DFT "slab" calculations for DMMP interacting with the TiO2 (110) surface and with DFT cluster models for the TiO2 (110) surface. The DFT slab calculations were performed with the PW91 and PBE functionals. The analytic potential gives DMMP/ TiO2 (110) potential energy curves in excellent agreement with those obtained from the slab calculations. The cluster models for the TiO2 (110) surface, used for the MP2 calculations, were extended to DFT calculations with the B3LYP, PW91, and PBE functional. These DFT calculations do not give DMMP/TiO2 (110) interaction energies which agree with those from the DFT slab calculations. Analyses of the wave functions for these cluster models show that they do not accurately represent the HOMO and LUMO for the surface, which should be 2p and 3d orbitals, respectively, and the models also do not give an accurate band gap. The MP2 cluster models do not accurately represent the LUMO and that they give accurate DMMP/TiO2 (110) interaction energies is apparently fortuitous, arising from their highly inaccurate band gaps. Accurate cluster models, consisting of 7, 10, and 15 Ti-atoms and which have the correct HOMO and LUMO properties, are proposed. The work presented here illustrates the care that must be taken in "constructing" cluster models which accurately model surfaces.

Yang, Li; Tunega, Daniel; Xu, Lai; Govind, Niranjan; Sun, Rui; Taylor, Ramona; Lischka, Hans; De Jong, Wibe A.; Hase, William L.

2013-08-29

129

New solvation free energy function comprising intermolecular solvation and intramolecular self-solvation terms  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Abstract Solvation free energy is a fundamental thermodynamic quantity that should be determined to estimate various physicochemical properties of a molecule and the desolvation cost for its binding to macromolecular receptors. Here, we propose a new solvation free energy function through the improvement of the solvent-contact model, and test its applicability in estimating the solvation free energies of organic molecules with varying sizes and shapes. This new solvation free energy...

Choi Hwanho; Kang Hongsuk; Park Hwangseo

2013-01-01

130

Polyelectrolyte and non-polyelectrolyte polyacrylamide copolymer solutions: the role of salt on the intra- and intermolecular interactions  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in portuguese Poli(acrilamida-co-dihexilacrilamida) (PAHM-0) e poli(acrilamida-co-acrilato de sódio-co-dihexilacrilamida) (PAHM-21) foram estudadas por espalhamento de raios-X a baixos ângulos (SAXS), espalhamento de luz (LS) e reologia. Os resultados de SAXS ressaltaram o caráter polieletrolítico da PAHM-21, com [...] uma conformação altamente estendida em solução aquosa devido às repulsões entre as cargas, enquanto a PAHM-0 tem uma conformação em novelo aleatório. As medidas de LS indicaram que a PAHM-0 forma aglomerados intermoleculares em solução, na presença e na ausência de sal, mesmo com um conteúdo hidrofóbico menor que o descrito na literatura para poliacrilamidas associativas. Contudo, os resultados reológicos mostraram que, apesar de haver associação hidrofóbica, não há um aumento da viscosidade. Os resultados de LS da PAHM-21 sugerem que esse polímero forma, predominantemente, associações intramoleculares na presença de sais. Além disso, as medidas viscosimétricas mostram que a sua viscosidade diminui com a blindagem das cargas pela adição de sais. Abstract in english Poly(acrylamide-co-dihexylacrylamide) (PAHM-0) and poly(acrylamide-co-sodium acrylate-co-dihexylacrylamide) (PAHM-21) were studied through small-angle X-ray scattering (SAXS), light scattering (LS) and rheology. SAXS results highlighted the polyelectrolyte character of PAHM-21, with highly extended [...] conformation in aqueous solution owing to charge repulsion, while the PAHM-0 has a coil conformation. LS measurements indicated that PAHM-0 makes intermolecular clusters in solution, in presence and absence of salt, even with a lower hydrophobic content than that described in the literature to the associative polyacrylamides. However, the rheological results showed that there is not an enhancement of the viscosity although hydrophobic association takes place. LS results for PAHM-21 suggest that this polymer makes intramolecular associations mainly in the presence of salts. Furthermore, the viscosity measurements show that its viscosity decreases due to screening of the charges by the addition of salts.

Ana M. S., Maia; Marcos A., Villetti; Redouane, Borsali; Rosangela C., Balaban.

1871-18-01

131

Intermolecular dynamics of hexamethylenetetramine  

International Nuclear Information System (INIS)

The technique of coherent inelastic neutron scattering has been used to measure the dispersion curves of intermolecular modes propagating along various high symmetry directions in the organic molecular crystal deuterated hexamethylenetetramine, at 100 and 298 K. The results are analysed in terms of phenomenological models involving interactions between supposedly rigid molecules. Interactions with both first and second nearest-neighbour molecules are found to be necessary for an adequate description. A simplified five-parameter model, which assumes centrosymmetric molecules, provides almost as good a fit to the results as that given by a generalized twelve-parameter model. Group theory shows that the effects of assuming centrosymmetry may be significant in the [??0] or ? direction. Assuming that the replacement of deuterium by hydrogen does not change the intermolecular forces, the frequency distribution of function and the heat capacity of hydrogenous hexamethylenetetramine are calculated. The agreement between the computed and measured heat capacities is good. The frequency distribution function shows many obvious critical points and other singular features. The existence of logarithmically infinite singularities in this function is investigated. The elastic constants computed from the force models show discrepancies from those measured ultrasonically, and these discrepancies are thought to be significant. The long wavelength optical librational frequency measureh optical librational frequency measured in the present work differs considerably from that deduced from optical measurements, and an explanation of this apparent discrepancy is suggested. The 2% hydrogen content in the specimen results in the presence of hydrogenous 'defect' molecules, and the effects of these on the normal vibrations of the host lattice are shown to be very small. (author)

132

INTER-MOLECULAR INTERACTIONS OF TETRAHYDROPYRAN + 1-BUTANOL BINARY SYSTEM AT T= (298.15, 303.15, 308.15, 313.15 & 318.15 K  

Directory of Open Access Journals (Sweden)

Full Text Available The evaluation of the different thermo dynamical parameters such as isentropic compressibility, molar volume, free length, acoustic impedance, internal pressure with their excess E E values, excess velocity (u , deviations of isentropic compressibility (? K , excess molar volume (V , s m E E E excess free length (L , excess acoustic impedance (Z and excess internal pressure (ð over the entire f i range of composition have been carried out at T = (298.15, 303.15, 308.15, 313.15 & 318.15 K from the measurements of ultrasonic velocity (u and density (ñ of pure & binary liquid mixtures of tetrahydropyran (THP with 1-butanol. The results thus obtained are discussed for molecular interaction. The nature of these values as seen from the plots of these ultrasonic parameters with the composition range indicates presence of the intermolecular interaction between the components of molecules of the mixture.

Anil Kumar K

2014-06-01

133

Regulation of crystal structure in organic redox systems by using intermolecular interactions induced by annelation of heterocycles; Hetero kan no shukugo ni yotte reikisareru bunshikan sogo sayo wo mochiita yukibutsu sanka kangenkei no kessho kozo no seigyo  

Energy Technology Data Exchange (ETDEWEB)

Discussions were given on regulations of the crystal structure of an organic redox system using intermolecular interactions induced by comdensation of heterocycles. The study contains the following three themes: chalcogenadiazole (chalcogen atoms: O, S, Se) was condensed as an intermolecular interaction unit in tetramethyl P-phenilendiamine and P-dipyrrolizinylbenzene; one electron reduction can occur easily; S-N interaction was found weaker than Se-N interaction by analyzing the crystals; a benzidine derivative in which chalcogenadiazole is condensed was synthesized; its electrochemical amphotericity is high; in a structure in which these molecular and intermolecular CT interactions are lowered, electrostatic interaction between the chalcogen atoms and N is concealed as a result of intermolecular CT interaction; and it was revealed from a structural analysis of 4,7-dihalobenzochalcogenadizaole that diiodo substances are similar in shape irrespective of the kinds of chalcogen atoms, and a network including non-covalent bonded dimers generated by the electrostatic actions of chalcogen and N has been formed as a result of the interaction between I atoms. 3 refs., 1 fig.

Suzuki, T. [Tohoku University, Sendai (Japan). Faculty of Science

1994-12-15

134

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

Energy Technology Data Exchange (ETDEWEB)

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.

Mercatelli, Raffaella; Quercioli, Franco [Istituto Sistemi Complessi, CNR, Via Madonna del Piano 10, 50019 Sesto Fiorentino (Italy); Barsanti, Laura; Evangelista, Valter [Istituto di Biofisica, CNR, Via Moruzzi 1, 56124 Pisa (Italy); Coltelli, Primo [ISTI, CNR, Via Moruzzi 1, 56124 Pisa (Italy); Passarelli, Vincenzo; Frassanito, Anna Maria [Istituto di Biofisica, CNR, Via Moruzzi 1, 56124 Pisa (Italy); Gualtieri, Paolo, E-mail: paolo.gualtieri@pi.ibf.cnr.it [Istituto di Biofisica, CNR, Via Moruzzi 1, 56124 Pisa (Italy)

2009-07-24

135

Intermolecular energy transfer from UO22+ to Eu3+ in solutions  

International Nuclear Information System (INIS)

The quenching constants for the UO22+ ion fluorescence by the Eu3+ ion in H2O, D2O, potassium formate and acetic acid media were determined by measuring the decrease in intensity of the 5050 A fluorescence peak and the lifetime of the UO22+ ion fluorescence. The energy transferred to the Eu3+ ion was found to be a small fraction of the energy lost by the UO22+ ion by the non-radiative processes. The variations of the quenching constants of the UO22+ ion and the fluorescence lifetimes were determined for different concentrations of potassium formate and acetic acid. These results indicate that the UO22+ ion forms inner sphere complexes with the two ligands mentioned

136

In-vitro anti-proliferative and anti-oxidant activity of galangin, fisetin and quercetin: role of localization and intermolecular interaction in model membrane.  

Science.gov (United States)

Flavonols are an important class of naturally occurring molecules and are known for their pharmacological activity. The activity is associated with the ability of flavonols to influence membrane-dependent processes. We have investigated the in-vitro anti-proliferative and anti-oxidant activity of galangin (GLN), fisetin (FTN) and quercetin (QTN), which possess variable number of phenolic hydroxyl groups. An attempt has been made to correlate the biological activity of these molecules with their interaction and localization in dipalmitoyl phosphatidyl choline (DPPC) bilayers, using differential dcanning calorimetry (DSC) and nuclear magnetic resonance (NMR) methods. Results indicate that GLN interacts to the alkyl chains of the lipid bilayer involving hydrophobic interactions. FTN and QTN interact with head region and sn-1-glycero region involving hydrogen bonding. Ring current induced chemical shifts of lipid protons, due to intermolecular interaction indicate that GLN acquires a parallel orientation with respect to the bilayer normal whereas FTN and QTN resume a mixed orientation. The membrane binding constants of these molecules are in the order GLN > QTN > FTN. It has been shown that the number and position of hydroxyl groups in these molecules play an important role in membrane binding and thereby in biological activity. PMID:24727463

Sinha, Ragini; Srivastava, Sudha; Joshi, Akshada; Joshi, Urmila J; Govil, Girjesh

2014-05-22

137

Intra- and intermolecular Se···X (X = Se, O) interactions in selenium-containing heterocycles: 3-benzoylimino-5-(morpholin-4-yl)-1,2,4-diselenazole.  

Science.gov (United States)

In the selenium-containing heterocyclic title compound {systematic name: N-[5-(morpholin-4-yl)-3H-1,2,4-diselenazol-3-ylidene]benzamide}, C13H13N3O2Se2, the five-membered 1,2,4-diselenazole ring and the amide group form a planar unit, but the phenyl ring plane is twisted by 22.12 (19)° relative to this plane. The five consecutive N-C bond lengths are all of similar lengths [1.316 (6)-1.358 (6) Å], indicating substantial delocalization along these bonds. The Se···O distance of 2.302 (3) Å, combined with a longer than usual amide C=O bond of 2.252 (5) Å, suggest a significant interaction between the amide O atom and its adjacent Se atom. An analysis of related structures containing an Se-Se···X unit (X = Se, S, O) shows a strong correlation between the Se-Se bond length and the strength of the Se···X interaction. When X = O, the strength of the Se···O interaction also correlates with the carbonyl C=O bond length. Weak intermolecular Se···Se, Se···O, C-H···O, C-H···? and ?-? interactions each serve to link the molecules into ribbons or chains, with the C-H···O motif being a double helix, while the combination of all interactions generates the overall three-dimensional supramolecular framework. PMID:24816018

Linden, Anthony; Zhou, Yuehui; Heimgartner, Heinz

2014-05-01

138

Electron dynamics and intermolecular energy transfer in aqueous solutions studied by X-ray electron spectroscopy  

Science.gov (United States)

X-ray photoelectron spectroscopy measurements from a vacuum liquid microjet are performed to investigate the electronic structure of aqueous solutions. Here, focus is on the excited-state dynamics of chloride and hydroxide anions in water, following core-level excitation. A series of Cl^-(aq) charge-transfer-to-solvent (CTTS) states, and their ultrafast relaxation, on the time scale of the core hole, is identified from the occurrence of spectator Auger decay. Resonant oxygen 1s excitation of aqueous hydroxide, in contrast, leads to non-local decay, involving energy transfer into a neighboring water molecule. This channel is argued to arise from the weak hydrogen donor bond of OH^-(aq), and thus identifies a special transient hydration configuration, which can explain hydroxide's unusual and fast transport in water. Analogous measurements from pure water point to a similar relaxation channel, which is concluded from a strong isotope effect. The characteristic resonance spectral features are considerably stronger for H2O(aq) than for D2O(aq). As for OH^-(aq) the results can be understood in terms of energy transfer from the excited water molecule to a neighbor water molecule.

Winter, Bernd

2009-03-01

139

Intermolecular effects in the pulsed field ionization zero kinetic energy photoelectron spectra of molecular  

International Nuclear Information System (INIS)

Pulsed field ionization zero kinetic energy electron spectroscopy (PFI-ZEKE) involves the electric field ionization of high principal quantum number Rydberg states approximately one microsecond after optical excitation. Only recently has it been appreciated that in most cases these Rydberg states should have lifetimes much shorter than one microsecond if purely intramolecular behavior is considered (due to the autoionization and predissociation decay channels). It has been hypothesized that weak electric DC-fields and surrounding ions can stabilize these states against decay. The PFI-ZEKE spectra corresponding to highly vibrationally excited ionic cores of H2+ (v+ = 13, 15) have been observed. In this case the Rydberg states responsible for the field ionization signal require some form of stabilization against vibrational autoionization. In this talk it is reported that ion-density influence the H2 PFI-ZEKE lineshapes in a dramatic manner. This is shown to be consistent with the ion-density stabilization mechanism

140

The "excited state C-C bond cleavage-luminescence" phenomenon of a biphenyl-substituted methylenecyclopropane triggered by intermolecular energy transfer from triplet benzophenone.  

Science.gov (United States)

Existence of the "excited state C-C bond cleavage-luminescence" phenomenon was demonstrated by utilizing intermolecular energy transfer from the excited-triplet benzophenone to 2,2-di(4-biphenylyl)-1-methylenecyclopropane (3). An excellent linear relationship between the intensity of the excitation laser light and that of luminescence clearly shows that formation of the corresponding excited trimethylenemethane biradical (3)4??* proceeds via a one-photon route. PMID:25267075

Matsui, Yasunori; Kido, Taiki; Ohta, Eisuke; Ikeda, Hiroshi

2014-11-21

 
 
 
 
141

Intermolecular, ion-molecular and interionic interactions in solutions of lithium and tetrabutylammonium salts in mixtures of methanol with propylene carbonate  

International Nuclear Information System (INIS)

Interparticle interactions are investigated in solutions of LiI, LiBr, LiCl, LiNCS, (C4H9)4NI, (C4H9)4NBr, (C4H9)4NCl in mixtures of methanol with propylene carbonate in absence of self-association of molecules of methanol and in different salt concentrations by the methods of IR spectroscopy. Intermolecular and ion-molecular interactions are studied on IR absorption lines of valent vibrations of OH-groups of methanol (3300-3500 cm-1), interionic interaction - on lines of valent CN (2000-2100 cm-1) and deformation O-Cl-O (625 cm-1) vibrations of NVS- and ClO4- correspondingly. Concentrations of lithium complexes forming in solutions are calculated on intensities of valent absorption lines of OH-groups of methanol. In the case of salt concentration increase the content of complexes decreases. Ousting of solvent molecule by anions in complex happens so faster as electron-donor ability of it is higher

142

Black Hole Interaction Energy  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The interaction energy between two black holes at large separation distance is calculated. The first term in the expansion corresponds to the Newtonian interaction between the masses. The second term corresponds to the spin-spin interaction. The calculation is based on the interaction energy defined on the two black holes initial data. No test particle approximation is used. The relation between this formula and cosmic censorship is discussed.

Dain, Sergio

2002-01-01

143

Interaction of Pyrrolobenzodiazepine (PBD) Ligands with Parallel Intermolecular G-Quadruplex Complex Using Spectroscopy and ESI-MS  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Studies on ligand interaction with quadruplex DNA, and their role in stabilizing the complex at concentration prevailing under physiological condition, has attained high interest. Electrospray ionization mass spectrometry (ESI-MS) and spectroscopic studies in solution were used to evaluate the interaction of PBD and TMPyP4 ligands, stoichiometry and selectivity to G-quadruplex DNA. Two synthetic ligands from PBD family, namely pyrene-linked pyrrolo[2,1-c][1,4]benzodiazepine hybrid (PBD1), mix...

Raju, Gajjela; Srinivas, Ragampeta; Santhosh Reddy, Vangala; Idris, Mohammed M.; Kamal, Ahmed; Nagesh, Narayana

2012-01-01

144

Relationship between molecular weight of poly(ethylene)glycol and intermolecular interaction of Taka-amylase A monomers  

Science.gov (United States)

Dynamic and static light scattering investigations of Taka-amylase A (TAA) protein monomers were done using solutions containing poly(ethylene)glycol (PEG) with molecular weights of 1500, 4000, 8000, and 20 000. The anomalies observed in a previous study using a weight of 8000, in which the hydrodynamic TAA monomer radius at a zero protein concentration and the molecular weight of the monomers decreased when the PEG concentration was increased, were observed for all four weights. These anomalies became more pronounced as the PEG molecular weight was increased. The overall interaction parameter did not move further in the direction of the attractive force despite an increase in the PEG concentration from 6% to 12.5% for the PEG 8000 and 20 000 solutions. This was due to the change in the relative contributions of the static structure factor (direct interaction) and the hydrodynamic interaction factor (indirect interaction) against the overall interaction parameter. For the PEG 1500 and 4000 solutions, the change in the overall interaction parameter with an increase in the PEG concentration was controlled by changing the static structure factor. For the PEG 8000 and 20 000 solutions, a change in the hydrodynamic interaction factor with an increase in the PEG concentration offset the change in the static structure factor, unexpectedly resulting in the overall interaction parameter being independent of the PEG concentration. This suggests that the scale and density of a PEG network structure, which are thought to be the origin of the observed anomalies, change nonlinearly with the PEG molecular weight.

Onuma, Kazuo; Furubayashi, Naoki; Shibata, Fujiko; Kobayashi, Yoshiko; Kaito, Sachiko; Ohnishi, Yuki; Inaka, Koji

2010-04-01

145

Electronic transitions and intermolecular forces  

International Nuclear Information System (INIS)

This thesis describes two different subjects - electronic transitions and intermolecular forces - that are related mainly by the following observation: The wavenumber at which an electronic transition in an atom or molecule occurs, depends on the environment of that atom or molecule. This implies, for instance, that when a molecule becomes solvated its absorption spectrum may be shifted either to the blue or to the red side of the original gasphase spectrum. In part I attention is paid to the experimental aspects of VUV spectroscopy, both in the gasphase and in the condensed phase. In part II a series of papers are presented, dealing with the calculation of intermolecular forces (and some related topics) both for the ground state and for the excited state interactions, using different non-empirical methods. The calculations provide, among other results, a semiquantitative interpretation of the spectral blue shifts encountered in our experiments. (Auth.)

146

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

Science.gov (United States)

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

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

2002-05-01

147

Synthesis, crystal structure and intermolecular magnetic interactions of a new N-TEMPO-3,5-di- tert-butylsalicylaldimine radical  

Science.gov (United States)

A new N-TEMPO-3,5-di- tert-butylsalicylaldimine radical ( 1) has been synthesized and characterized by single crystal X-ray diffraction, elemental analysis, IR, UV-vis, and EPR spectroscopy and temperature dependent magnetic susceptibility. X-ray diffraction revealed that H-atoms of ?-CH in TEMPO and CH 3 in salicylaldimine moieties, are located in close contact with the neighboring N-O radical group in crystal 1. The temperature dependence of the magnetic susceptibility ( ?m) of 1 has been fitted by the Curie-Weiss law with ? = -0.3 K within 10-300 K, suggesting the presence of a weak intermolecular antiferromagnetic interaction between radical centers at T < 10 K. It has been demonstrated that radical 1 possesses crystal structure involving co-existence of antiferromagnetic and ferromagnetic interactions through C-H⋯O-N rad contacts of ?-CH and tBu groups hydrogen atoms, in which the former path dominates over the latter.

Kasumov, Veli T.; Uçar, Ibrahim; Bulut, Ahmet; Yerli, Yusuf

2011-10-01

148

Interaction of Pyrrolobenzodiazepine (PBD) Ligands with Parallel Intermolecular G-Quadruplex Complex Using Spectroscopy and ESI-MS  

Science.gov (United States)

Studies on ligand interaction with quadruplex DNA, and their role in stabilizing the complex at concentration prevailing under physiological condition, has attained high interest. Electrospray ionization mass spectrometry (ESI-MS) and spectroscopic studies in solution were used to evaluate the interaction of PBD and TMPyP4 ligands, stoichiometry and selectivity to G-quadruplex DNA. Two synthetic ligands from PBD family, namely pyrene-linked pyrrolo[2,1-c][1,4]benzodiazepine hybrid (PBD1), mixed imine-amide pyrrolobenzodiazepine dimer (PBD2) and 5,10,15,20-tetrakis(N-methyl-4-pyridyl)porphyrin (TMPyP4) were studied. G-rich single-stranded oligonucleotide d(5?GGGGTTGGGG3?) designated as d(T2G8), from the telomeric region of Tetrahymena Glaucoma, was considered for the interaction with ligands. ESI-MS and spectroscopic methods viz., circular dichroism (CD), UV-Visible, and fluorescence were employed to investigate the G-quadruplex structures formed by d(T2G8) sequence and its interaction with PBD and TMPyP4 ligands. From ESI-MS spectra, it is evident that the majority of quadruplexes exist as d(T2G8)2 and d(T2G8)4 forms possessing two to ten cations in the centre, thereby stabilizing the complex. CD band of PBD1 and PBD2 showed hypo and hyperchromicity, on interaction with quadruplex DNA, indicating unfolding and stabilization of quadruplex DNA complex, respectively. UV-Visible and fluorescence experiments suggest that PBD1 bind externally where as PBD2 intercalate moderately and bind externally to G-quadruplex DNA. Further, melting experiments using SYBR Green indicate that PBD1 unfolds and PBD2 stabilizes the G-quadruplex complex. ITC experiments using d(T2G8) quadruplex with PBD ligands reveal that PBD1 and PBD2 prefer external/loop binding and external/intercalative binding to quadruplex DNA, respectively. From experimental results it is clear that the interaction of PBD2 and TMPyP4 impart higher stability to the quadruplex complex. PMID:22558271

Raju, Gajjela; Srinivas, Ragampeta; Santhosh Reddy, Vangala; Idris, Mohammed M.; Kamal, Ahmed; Nagesh, Narayana

2012-01-01

149

STUDY OF INTERMOLECULAR FORCES AND INTERACTIONS IN BINARY LIQUID MIXTURE CHLOROFORM, ACETONE, M-XYLENE, AND CYCLOHEXANE IN DMSO  

Directory of Open Access Journals (Sweden)

Full Text Available Thermodynamic studies like density ( ? , ultrasonic speed ( u and excess molar volume ( Vm E of binary liquid mixture of Chloroform ,Acetone, m- Xylene ,Cyclohexane+ DMSO have been carried out over the different range of composition at 308.15 K. Thermodynamic parameters like isentropic compressibility Ks , interaction parameter, ?12 , Flory parameters, coefficients, Ai and standard deviations, ? (Y E have been computed from experimental findings.

Dheeraj Kumar

2014-05-01

150

Intra and inter-molecular interactions dictate the aggregation state of irinotecan co-encapsulated with floxuridine inside liposomes  

DEFF Research Database (Denmark)

PURPOSE: The inter/intramolecular interactions between drugs (floxuridine, irinotecan) and excipients (copper gluconate, triethanolamine) in the dual-drug liposomal formulation CPX-1 were elucidated in order to identify the physicochemical properties that allow coordinated release of irinotecan and floxuridine and maintenance of the two agents at a fixed, synergistic 1:1 molar ratio. METHODS: Release of irinotecan and floxuridine from the liposomes was assessed using an in vitro-release assay. Fluorescence, Nuclear Magnetic Resonance spectroscopy (NMR) and UV-Vis were used to characterize the aggregation state of the drugs within the liposomes. RESULTS: Coordinated release of the drugs from liposomes was disrupted by removing copper gluconate. Approximately 45% of the total irinotecan was detectable in the copper-containing CPX-1 formulation by NMR, which decreased to 19% without copper present in the liposomal interior. Formation of higher order, NMR-silent aggregates was associated with slower and uncoordinated irinotecan release relative to floxuridine and loss of the synergistic drug/drug ratio. Solution spectroscopy and calorimetry revealed that while all formulation components were required to achieve the highest solubility of irinotecan, direct drug-excipient binding interactions were absent. CONCLUSIONS: Long-range interactions between irinotecan, floxuridine and excipients modulate the aggregation state of irinotecan, allowing for simultaneous release of both drugs from the liposomes Udgivelsesdato: 2008/7

Dicko, A.; Frazier, A.A.

2008-01-01

151

Intermolecular interaction of voriconazole analogues with model membrane by DSC and NMR, and their antifungal activity using NMR based metabolic profiling.  

Science.gov (United States)

The development of novel antifungal agents with high susceptibility and increased potency can be achieved by increasing their overall lipophilicity. To enhance the lipophilicity of voriconazole, a second generation azole antifungal agent, we have synthesized its carboxylic acid ester analogues, namely p-methoxybenzoate (Vpmb), toluate (Vtol), benzoate (Vbz) and p-nitrobenzoate (Vpnb). The intermolecular interactions of these analogues with model membrane have been investigated using nuclear magnetic resonance (NMR) and differential scanning calorimetric (DSC) techniques. The results indicate varying degree of changes in the membrane bilayer's structural architecture and physico-chemical characteristics which possibly can be correlated with the antifungal effects via fungal membrane. Rapid metabolite profiling of chemical entities using cell preparations is one of the most important steps in drug discovery. We have evaluated the effect of synthesized analogues on Candida albicans. The method involves real time (1)H NMR measurement of intact cells monitoring NMR signals from fungal metabolites which gives Metabolic End Point (MEP). This is then compared with Minimum Inhibitory Concentration (MIC) determined using conventional methods. Results indicate that one of the synthesized analogues, Vpmb shows reasonably good activity. PMID:24012381

Kalamkar, Vaibhav; Joshi, Mamata; Borkar, Varsha; Srivastava, Sudha; Kanyalkar, Meena

2013-11-01

152

Local conformation and intermolecular interaction of rigid ring polymers are not always the same as the linear analogue: cyclic amylose tris(phenylcarbamate) in ? solvents.  

Science.gov (United States)

Small-angle X-ray scattering and static and dynamic light scattering measurements were made for cyclic amylose tris(phenylcarbamate) (cATPC) of which weight-average molar mass M(w) ranges from 1.3 × 10(4) to 1.5 × 10(5) to determine their z-average mean square radius of gyration z, particle scattering function P(q), hydrodynamic radius R(H), and second virial coefficient A2 in methyl acetate (MEA), ethyl acetate (EA), and 4-methyl-2-pentanone (MIBK). The obtained z, P(q), and R(H) data were analyzed in terms of the wormlike ring to estimate the helix pitch per residue h and the Kuhn segment length ?(-1) (the stiffness parameter, twice the persistence length). Both h and ?(-1) for cATPC in MEA, EA, and MIBK are smaller than those for linear amylose tris(phenylcarbamate) (ATPC) in the corresponding solvent and the discrepancy becomes more significant with increasing the molar volume of the solvent. This indicates that not every rigid ring has the same local helical structure and chain stiffness as that for the linear polymer in the M(w) range investigated while infinitely long ring chains should have the same local conformation. This conformational difference also affects A2. In actuality, negative A2 was observed for cATPC in MIBK at the ? temperature of linear ATPC whereas intermolecular topological interaction of ring polymers increases A2. PMID:23879791

Asano, Natsuki; Kitamura, Shinichi; Terao, Ken

2013-08-15

153

Anisotropic intermolecular interactions and rotational ordering in hydrogen containing solids. Final report, January 1, 1972--June 30, 1978  

Energy Technology Data Exchange (ETDEWEB)

Thermodynamic properties, order-disorder phenomena, optical, electric and magnetic properties of hydrogen-containing molecular solids have been investigated. A summary of the findings of this 6 year research program is presented here. The approach in these studies was (a) thermodynamic and transport studies extending to very low temperatures, (b) pulsed NMR studies for determination of structural parameters important to spin-lattice relaxation, and (c) pulsed laser studies for the investigation of excitations and energy transfer mechanisms in solids. (GHT)

White, D.

1978-01-01

154

Controlling gold atom penetration through alkanethiolate self-assembled monolayers on Au{111} by adjusting terminal group intermolecular interactions.  

Science.gov (United States)

The penetration behavior of thermally evaporated Au on S(CH(2))(15)CH(3), S(CH(2))(15)CO(2)CH(3), S(CH(2))(15)CO(2)H, K-modified S(CH(2))(15)CO(2)CH(3), and K-modified S(CH(2))(15)CO(2)H self-assembled monolayers (SAM) on Au substrates is investigated. Gold is a particularly interesting metal since vapor-deposited Au atoms are known to pass through alkanethiolate SAMs on Au{111} substrates at room temperature. Here we show that it is possible to control Au penetration by adjusting the interactions between terminal groups. It is found that Au atoms evenly penetrate into the CH(3) and CO(2)CH(3) films, forming smooth buried layers below the organic thin films. For the CO(2)H film, although Au atoms can still penetrate through it, filaments and mushroomlike clusters form due to H-bonding between film molecules. In the case of the K-modified CO(2)CH(3) or CO(2)H films, however, most Au atoms form islands at the vacuum interface. These results suggest that van der Waals forces and H-bonds are not strong enough to block Au from going through but that ionic interactions are able to block Au penetration. The measurements were performed primarily using time-of-flight secondary ion mass spectrometry (ToF-SIMS) and atomic force microscopy (AFM). The combination of these highly complementary probes provides a very useful strategy for the study of metal atom behavior on SAMs. PMID:17044698

Zhu, Zihua; Daniel, Thomas A; Maitani, Masato; Cabarcos, Orlando M; Allara, David L; Winograd, Nicholas

2006-10-25

155

Refined ab initio intermolecular ground-state potential energy surface for the He-C2H2 van der Waals complex  

DEFF Research Database (Denmark)

A refined CCSD(T) intermolecular potential energy surface is developed for the He-C2H2 van der Waals complex. For this, 206 points on the intermolecular potential energy surface, evaluated using the CCSD(T) method and the aug-cc-pVQZ basis set extended with a set of 3s3p2d1f1g midbond functions, are fitted to a 15-parameter analytic function. The potential is characterised by minima of-24.21 cm-1 at distances between the rare gas atom and the C2H2 centre of mass of 4.3453 A?, and with the complex in a linear configuration. At intermediate distances the surface is rather similar to that developed previously by Munteanu and Ferna?ndez (J. Chem. Phys., 123, 014309, 2005) but differs notably at short range. The improved potential energy surface should, therefore, be particularly useful for computations of collision line broadening. Dynamical calculations of a number of rovibrational bound state energies and wave functions are presented. Inspection of the nodal surfaces of several low lying excited states shows that the complex is close to the free rotor limit.

Ferna?ndez, Berta; Henriksen, Christian

2013-01-01

156

Intermolecular Contrast in Atomic Force Microscopy Images without Intermolecular Bonds  

Science.gov (United States)

Intermolecular features in atomic force microscopy images of organic molecules have been ascribed to intermolecular bonds. A recent theoretical study [P. Hapala et al., Phys. Rev. B 90, 085421 (2014)] showed that these features can also be explained by the flexibility of molecule-terminated tips. We probe this effect by carrying out atomic force microscopy experiments on a model system that contains regions where intermolecular bonds should and should not exist between close-by molecules. Intermolecular features are observed in both regions, demonstrating that intermolecular contrast cannot be directly interpreted as intermolecular bonds.

Hämäläinen, Sampsa K.; van der Heijden, Nadine; van der Lit, Joost; den Hartog, Stephan; Liljeroth, Peter; Swart, Ingmar

2014-10-01

157

Intermolecular and surface forces  

CERN Document Server

This reference describes the role of various intermolecular and interparticle forces in determining the properties of simple systems such as gases, liquids and solids, with a special focus on more complex colloidal, polymeric and biological systems. The book provides a thorough foundation in theories and concepts of intermolecular forces, allowing researchers and students to recognize which forces are important in any particular system, as well as how to control these forces. This third edition is expanded into three sections and contains five new chapters over the previous edition.· starts fr

Israelachvili, Jacob N

2011-01-01

158

Intermolecular and Surface Forces  

CERN Document Server

This reference describes the role of various intermolecular and interparticle forces in determining the properties of simple systems such as gases, liquids and solids, with a special focus on more complex colloidal, polymeric and biological systems. The book provides a thorough foundation in theories and concepts of intermolecular forces, allowing researchers and students to recognize which forces are important in any particular system, as well as how to control these forces. This third edition is expanded into three sections and contains five new chapters over the previous edition.· starts fr

Israelachvili, Jacob N

2010-01-01

159

Readout system for delay line detectors with a time stamp TDC and a small angle scattering study of intermolecular interactions in protein solutions  

Energy Technology Data Exchange (ETDEWEB)

The present work consists of two parts: The first part is a contribution to instrumentation and more particularly the development of a readout system for gas detectors used in small angle X-ray scattering (SAXS) and the second part covers the results of an investigation of interactions between proteins in solution. One aim of the instrumentation part was to investigate the role of fluorescence in gas proportional detector with delay line readout, a phenomenon that leads to events, unrelated to the actual scattering pattern. For this purpose a time stamp (TS-) TDC readout was developed that is able to detect simultaneous events in the detector by using all timing information in the anode and cathode signals (check-sum). It was found that the fluorescence of the gas clearly limits the spatial and time resolution in gas detection. The present observations confirm the influence of argon fluorescence on the point-spread function (PSF) and demonstrate that a rejection mechanism that analyses single events only cannot entirely eliminate these effects. The signal-to-noise ratio can, however, be improved by taking the drift time of the electrons and the check-sum of the signals into account. Drift time measurements are made possible by the unique ability of the TS-TDC to correlate the observation of scattered photons with individual radiation bunches in the storage ring. This feature could also facilitate time-resolved measurements with nanosecond-resolution. In the second part of this thesis gas detectors were used in a contribution to an important topic in biophysics: the study of intermolecular interactions in protein solutions. This was done by measuring the structure factors of protein solutions. According to the DLVO theory the main interactions between spherical particles are the hard-sphere interactions, a short range attraction, due to surface-surface forces, and a long range repulsion caused by the fact that the particles are charged. A computer program was written, which calculates the structure factors from the pair potentials and was shown to reproduce some results in the literature as well as all the main observations in our experiments. Several measurements were made on solutions of the proteins glucose oxidase and lysozyme under various conditions in order to investigate the interactions of these proteins in the presence of co-solutes such as salts, urea, TMAO, glycine or at different protein concentrations. The influence of variables like temperature and pH on the attractive and repulsive interactions and in particular the pair potentials was also studied. The main features of the structure factors observed in the protein concentration series are correctly predicted with the program. (orig.)

Niebuhr, M.

2004-07-01

160

Competing Intramolecular vs. Intermolecular Hydrogen Bonds in Solution  

Directory of Open Access Journals (Sweden)

Full Text Available 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.

Peter I. Nagy

2014-10-01

 
 
 
 
161

Preparation and characterization of co-amorphous Ritonavir-Indomethacin systems by solvent evaporation technique: improved dissolution behavior and physical stability without evidence of intermolecular interactions.  

Science.gov (United States)

The aim of this study was to stabilize the amorphous form of Ritonavir (RTV) a BCS class-II drug with known amorphous stabilizing small molecule Indomethacin (IND) by co-amorphous technology. The co-amorphous samples were prepared by solvent evaporation technique in the molar ratios RTV:IND (2:1), RTV:IND (1:1), RTV:IND (1:2) and their amorphous nature was confirmed by XRPD, DSC and FT-IR. Physical stability studies were carried out at temp 25°C and 40°C for maximum up to 90 days under dry conditions. Solubility and dissolution testing were carried out to investigate the dissolution advantage of prepared co-amorphous systems. The amorphous mixtures of all tested molar ratios were found to become amorphous after solvent evaporation. The same was confirmed by detecting halo pattern in diffractograms of co-amorphous mixtures. The Tg values of all three systems were found to be more than 40°C, the highest being 51.88°C for RTV:IND (2:1) system. Theoretical Tg values were calculated by Gordon-Taylor equation. Insignificant deviation of theoretical Tg values from that of practical one, corroborated by FT-IR studies showed no evidence of intermolecular interactions between RTV and IND. Almost 3-folds increase in the solubility for both amorphous RTV and IND was found as compared to their respective crystalline counterparts. The study demonstrated significant increase in the dissolution rate as well as increase in the total amount of drug dissolved for amorphous RTV, however it failed to demonstrate any significant improvement in the dissolution behavior of IND. PMID:24878386

Dengale, Swapnil J; Ranjan, Om Prakash; Hussen, Syed Sajjad; Krishna, B S M; Musmade, Prashant B; Gautham Shenoy, G; Bhat, Krishnamurthy

2014-10-01

162

Effect of phase behavior and pressure on the constant-volume heat capacity and intermolecular interaction of CO2-ethanol and CO2-n-pentane mixtures in the critical region.  

Science.gov (United States)

Study on the properties of the fluids near the critical point of mixed systems is a key for the development of supercritical (SC) technology and for the further understanding of the features of supercritical fluids (SCFs). The constant-volume molar heat capacity (Cv) of a solution is directly related to the internal energy, intermolecular interaction, and the microstructure of the solution. In this work, the Cv of CO2-n-pentane and CO2-ethanol systems was determined at 308.15 K in different phase regions. This work focuses on how the properties of the mixtures change with pressure, composition, and the structure of the components near the critical point of the mixtures. It was found that at fixed composition, a maximum in Cv versus pressure curve exists (Cv(max)) that occurs at the pressure at which the isothermal compressibility (K(T)) is the largest. We deduced that breaking the "clusters" in the SC mixtures is an endothermic process. It is very interesting that Cv increases sharply as the pressure approaches the critical point (CP) or bubble point (BP), while Cv is nearly independent of pressure and composition at the pressures well above the CP or BP pressure, and that the Cv at CP or BP can be several times larger than that at the high pressures. It can be deduced that at fixed composition the degree of "clustering" changes significantly with pressure near the CP or BP, and is the largest at CP and BP. PMID:11843157

Li, Hongping; Zhang, Xiaogang; Han, Buxing; Liu, Jun; He, Jun; Liu, Zhimin

2002-01-18

163

Intermolecular interactions: basis set and intramolecular correlation effects on semiempirical methods. Application to (C2H2)2, (C2H2)3 and (C2H4)2  

International Nuclear Information System (INIS)

A detailed study of the intrinsic consistency of the semiempirical method of P. Claverie namely, the effects of the basis set and intramolecular correlation on the multipole distributions of molecular subunits and the influence of the electronic population of each atom in the molecular subunit on its van der Waals radius, is performed on some van der Waals dimers. The validity, limits of this model and the appropriate way to use it is established. In particular, the dependence of the geometry and the interaction energy on the basis set chosen and the intramolecular correlation shows that the multipole distribution involved in the calculation of the electrostatic and polarization terms must be derived from a correlated wave function within an extended basis set. Associated to non local methods for finding stationary points, the method of P. Claverie reproduce reliably the intermolecular geometrical parameters observed for the equilibrium structures and the transition states of the dimer and trimer of acetylene. In addition, a study of the equilibrium structures of the ethylene dimer is presented, the aim of being to clarify the considerable uncertainty in their number and their geometry. (orig.)

164

Theoretical study of intermolecular energy transfer involving electronically excited molecules: He(1S) + H2(B 1?/sub u/+)  

International Nuclear Information System (INIS)

To further understanding of gas phase collision dynamics involving electronically-excited molecules, a fully quantum mechanical study of He + H2(B 1?/sub u/+) was undertaken. Iterative natural orbital configuration interaction (CI) calculations were performed to obtain the interaction potential between He and H2(B 1?/sub u/+). The potential energy surface (PES) is highly anisotropic and has a van der Waals well of about 0.03 eV for C/sub 2v/ approach. Avoided PES crossings occur with He + H2(E,F 1?/sub g/+) and with He + H2(X 1?/sub g/+) and cause a local maximum and a deep minimum in the He + H2(B 1?/sub u/+) PES, respectively. The crossing with He + H2(X 1?/sub g/+) provides a mechanism for fluorescence quenching. The computed CI energies were combined with previous multi-reference double excitation CI calculations and fit with analytic functions for convenience in scattering calculations. Accurate dipole polarizabilities and quadrupole moment of H2(B 1?/sub u/+) were computed for use in the multipole expansion, which is the analytic form of the long-range PES. 129 refs., 28 figs., 35 tabs

165

New Type of Dual Solid-State Thermochromism: Modulation of Intramolecular Charge Transfer by Intermolecular ?-? Interactions, Kinetic Trapping of the Aci-Nitro Group, and Reversible Molecular Locking  

Science.gov (United States)

When heated above room temperature, some crystalline polymorphs of the 1,3-bis(hydroxyalkylamino)-4,6-dinitrobenzenes (BDBn, n = 2-5), bis(hydroxyalkyl) analogues of the intramolecular charge-transfer molecule 1,3-diamino-4,6-dinitrobenzene, exhibit "dual" thermochromism: gradual color change from yellow to orange at lower temperatures, and sharp color change from orange to red at higher temperatures. These two thermochromic changes are related to different solid-state processes. When allowed to cool to room temperature, the yellow color of the thermochromic molecules with different alkyl length (n) is recovered with unexpectedly different kinetics, the order of the respective rate constants ranging from 10-7-10-6 s-1 for BDB2 to about 0.1 s-1 in the case of BDB3. The thermochromic mechanism and the reasons behind the different kinetics were clarified on the basis of detailed crystallographic characterization, kinetic thermoanalysis, and spectroscopic study of eight crystalline forms (seven polymorphs and one solvate). It was found that the polymorphism is due to the possibility of "locking" and "unlocking" of the alkyl arms by formation of a strong intramolecular hydrogen bond between the hydroxyl groups at their hydroxyl termini. The locking of BDB2, with shortest alkyl arms, is reversible and it can be controlled thermally; either of the two conformations can be obtained in the solid state by proper thermal treatment. By use of high temperature in situ single crystal X-ray diffraction analysis of BDB3, direct evidence was obtained that the gradual thermochromic change is related to increased distance and weakened ?-? interactions between the stacked benzene rings: the lattice expands preferably in the stacking direction, causing enhanced oscillator strength and red shift of the absorption edge of the intramolecular charge transfer transition. The second, sharp thermochromic change had been assigned previously to solid-solid phase transition triggered by intramolecular proton transfer of one amino proton to the nitro group, whereupon an aci-nitro form is thermally populated. Contrary to the numerous examples of solid thermochromic molecules based on either pericyclic reactions or keto-enol tautomerism, this system appears to be the first organic thermochromic family where the thermochromic change appears as an effect of intermolecular ?-? interactions and thermal intramolecular proton transfer to aromatic nitro group.

Naumov, Pan?e; Lee, Sang Cheol; Ishizawa, Nobuo; Jeong, Young Gyu; Chung, Ihn Hee; Fukuzumi, Shunichi

2009-09-01

166

Energetics of Intermolecular Hydrogen Bonds in a Hydrophobic Protein Cavity  

Science.gov (United States)

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

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

2014-05-01

167

Intermolecular dispersion interactions of normal alkanes with rare gas atoms: van der Waals complexes of n-pentane with helium, neon, and argon  

International Nuclear Information System (INIS)

Interaction energies of normal pentane with three rare gas atoms (helium, neon, and argon) were calculated using ab initio methods: the second-order Moller-Plesset (MP2), the fourth-order Moller-Plesset (MP4), and coupled cluster with single and double substitutions with noniterative triple excitation (CCSD(T)) levels of theory. Dunning's correlation consistent basis sets up to aug-cc-pVQZ were applied. Eight profiles (246 points for each rare gas atom) of potential energy surface (PES) of all-trans (anti-anti) conformation of n-pentane were scanned. Optimal distances for complex formation were found. MP2 interaction energies at the basis set limit were evaluated by three different methods (Feller's, Helgaker's, and Martin's). The MP2 interaction energy at the basis set limit for a global minimum of n-pentane complex with argon was more than 400 cm-1, so formation of a stable complex (at least at low temperature) can be expected. A comparison with previously published data on propane complexes with rare gas atoms (both computational and experimental) was done. The MP4 level of theory was found to be sufficient for a description of C5H12 complexes with helium, neon, and argon

168

Intermolecular interactions in nuclear magnetic resonance: medium shifts of the 1H and 13C nuclei in methane in the gas phase and in solution and of gaseous 3He  

International Nuclear Information System (INIS)

An analysis has been carried out of the continuum and the binary collision models used in the description of NMR solvent shifts caused by Van der Waals intermolecular interactions. The basic assumption underlying the models, i.e. ? sub(w)= -BE2 (I) is examined. The possible effects on I of such phenomena as B anisotropy and field gradients are discussed, as well as the inadequacy of I in representing the true intermolecular shielding. A new expression for E2 is proposed, which in connection with I forms the bais of a modified binary collision model. The new E2 expression takes into account the dynamic character of the interaction. The major obstacle to the binary collision model, the requirement for accurate parameters for the intermolecular potential employed in the statistical-mechanical averaging, is alleviated by the establishment of priority rules to be used in the selection of these paramters. The proposed binary collision model and a collision model are used to interpret the 1H and 13C medium shifts of methane in the gas phase and in solution. The proton shift data conform equally well to either model; the 13C data indicate that a large solvent-dependent term contributes to the observed medium shifts in addition to I. Proton and 13C B parameters of methane in the gas phase and in solution are discussed. Preliminary results of 3He medium shifts as a function of gas density aium shifts as a function of gas density are presented. An extracted B parameter based on the proposed binary collision model appears to agree well with the result of a quantum-mechanical calculation of B for a 3He atom in a uniform static electric field. (LL)

169

Desensitization of metastable intermolecular composites  

Science.gov (United States)

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.

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

2011-04-26

170

Inhomogeneous and interacting vacuum energy  

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Vacuum energy is a simple model for dark energy driving an accelerated expansion of the universe. If the vacuum energy is inhomogeneous in spacetime then it must be interacting. We present the general equations for a spacetime-dependent vacuum energy in cosmology, including inhomogeneous perturbations. We show how any dark energy cosmology can be described by an interacting vacuum+matter. Different models for the interaction can lead to different behaviour (e.g., sound speed...

De-santiago, Josue; Wands, David; Wang, Yuting

2012-01-01

171

Intermolecular potential energy surface, microwave and infrared spectra of the Kr-CO 2 complex from ab initio calculations  

Science.gov (United States)

We present a new potential energy surface for Kr-CO 2 which incorporates its dependence on the asymmetric Q3 normal mode with CO 2 in both ground ( ?3 = 0) and the first excited ( ?3 = 1) states were generated by integration of this potential over the Q3 coordinate. Each potential is found to have a T-shaped global minimum. The radial DVR/angular FBR method are applied to calculate the rovibrational energy levels. The calculated band origin shifts, microwave and infrared spectra are in good agreement with the available experiment values.

Chen, Rong; Zhu, Hua; Xie, Daiqian

2011-08-01

172

Intermolecular Forces: A Jigsaw Activity  

Science.gov (United States)

This jigsaw activity is designed as a cooperative learning activity used to introduce the idea of intermolecular forces. Intermolecular forces are the types of attractive forces that occur between molecules in a solid, liquid, or gas. Each force causes different physical properties of matter. Each member of the group will become an expert on one type of force and then teach the rest of the group.

Edu., Boise S.

2011-09-20

173

The role of intermolecular coupling in the photophysics of disordered organic semiconductors: Aggregate emission in regioregular polythiophene  

CERN Document Server

We address the role of intermolecular interactions in determining the nature of photoexcitations in the conjugated polymer regioregular poly(3-hexylthiophene). By means of temperature-dependent absorption and photoluminescence spectroscopy, we show that optical emission is overwhelmingly dominated by weakly coupled H-aggregates. The relative absorbance of the 0-0 and 0-1 vibronic peaks provides a powerfully simple means to extract the magnitude of the intermolecular coupling energy, which was found to be on the order of 15 meV.

Clark, J; Friend, R H; Spano, F C; Clark, Jenny; Silva, Carlos; Friend, Richard H.; Spano, Frank C.

2007-01-01

174

Intermolecular correlation in a new approximation scheme  

International Nuclear Information System (INIS)

It is demonstrated for a spin-free, nonrelativistic, complete molecular Hamiltonian that there is an optimal solution to the separation of electronic and nuclear motions. The adiabatic approximation is obtained as a special limiting case. A fruitful interpretation of intermolecular correlation results from the assumption that such correlation involves the degeneracy of a molecular-energy state of one molecule with that of another chemical species, e.g., cubane and cyclooctatetraene. As a consequence, rigorous relations are establiehed for the influence of nodal patterns of the electronic functions on intermolecular correlation. Also derived are stringent symmetry rules which both electronic and nuclear functions involved in the correlation must obey. Throughout the treatment is a many-electron one. 10 references

175

Bioluminescence resonance energy transfer (BRET) imaging of protein–protein interactions within deep tissues of living subjects  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Identifying protein–protein interactions (PPIs) is essential for understanding various disease mechanisms and developing new therapeutic approaches. Current methods for assaying cellular intermolecular interactions are mainly used for cells in culture and have limited use for the noninvasive assessment of small animal disease models. Here, we describe red light-emitting reporter systems based on bioluminescence resonance energy transfer (BRET) that allow for assaying PPIs both in cell cultu...

Dragulescu-andrasi, Anca; Chan, Carmel T.; De, Abhijit; Massoud, Tarik F.; Gambhir, Sanjiv S.

2011-01-01

176

Intermolecular symmetry-adapted perturbation theory study of large organic complexes  

Science.gov (United States)

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.

Heßelmann, Andreas; Korona, Tatiana

2014-09-01

177

Direct measurements of intermolecular forces by chemical force microscopy  

Science.gov (United States)

Detailed description of intermolecular forces is key to understanding a wide range of phenomena from molecular recognition to materials failure. The unique features of atomic force microscopy (AFM) to make point contact force measurements with ultra high sensitivity and to generate spatial maps of surface topography and forces have been extended to include measurements between well-defined organic molecular groups. Chemical modification of AFM probes with self-assembled monolayers (SAMs) was used to make them sensitive to specific molecular interactions. This novel chemical force microscopy (CFM) technique was used to probe forces between different molecular groups in a range of environments (vacuum, organic liquids and aqueous solutions); measure surface energetics on a nanometer scale; determine pK values of the surface acid and base groups; measure forces to stretch and unbind a short synthetic DNA duplex and map the spatial distribution of specific functional groups and their ionization state. Studies of adhesion forces demonstrated the important contribution of hydrogen bonding to interactions between simple organic functionalities. The chemical identity of the tip and substrate surfaces as well as the medium had a dramatic effect on adhesion between model monolayers. A direct correlation between surface free energy and adhesion forces was established. The adhesion between epoxy polymer and model mixed SAMs varied with the amount of hydrogen bonding component in the monolayers. A consistent interpretation of CFM measurements in polar solvents was provided by contact mechanics models and intermolecular force components theory. Forces between tips and surfaces functionalized with SAMs terminating in acid or base groups depended on their ionization state. A novel method of force titration was introduced for highly local characterization of the pK's of surface functional groups. The pH-dependent changes in friction forces were exploited to map spatially the changes in ionization state on SAM surfaces. The phase contrast in tapping mode AFM between chemically distinct monolayer regions and corresponding adhesion forces were found to be directly correlated. Thus, both friction and intermittent contact CFM images could be interpreted in terms of the strength of intermolecular interactions. CFM was also used to probe biomolecular interactions. Separation forces between complementary oligonucleotide strands were significantly larger than the forces measured between noncomplementary strands and were consistent with the unbinding of a single DNA duplex. CFM data provided a direct measure of the forces required to elastically deform, structurally-transform and separate well-defined, synthetic duplexes into single strand oligonucleotides.

Vezenov, Dmitri Vitalievich

1999-12-01

178

Quantum mechanical calculations on weakly interacting complexes  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Symmetry-adapted perturbation theory (SAPT) has been applied to compute the intermolecular potential energy surfaces and the interaction-induced electrical properties of weakly interacting complexes. Asymptotic (large R) expressions have been derived for the contributions to the collision-induced properties up to and including second order in the intermolecular potential. The computed interaction-induced polarizability for the helium diatom has been used in quantum-dynamical calculations of t...

Heijmen, Theodorus Gerardus Albertus

1998-01-01

179

Single-molecule force spectroscopic studies on intra- and intermolecular interactions of G-quadruplex aptamer with target Shp2 protein.  

Science.gov (United States)

With widespread applications in biosensors, diagnostics, and therapeutics, much investigation has been made in the structure of the G-quadruplexes and mechanism of their interactions with protein targets. However, in view of AFM based single-molecule force spectroscopic (SMFS) studies of G-quadruplex systems, only bimolecular approaches have been employed. In this article, we present an improved dual-labeling approach for surface immobilization of G-quadruplex DNA apatmers for investigation of intramolecular interaction from an integral unimolecular G-quadruplex system. The melting force of HJ24 G-quadruplex aptamer in the presence of K(+) has been successfully measured. It has been found that dynamic equilibrium exists between unfolding and folding structures of the HJ24 aptamer even in pure water. We also investigated the interactions between the HJ24 aptamer and its target protein (Shp2) under the same solution condition. The HJ24/Shp2 unbinding force in the absence of K(+), 42.0 pN, is about 50% smaller than that in the presence of K(+), 61.7 pN. The great reduction in force in the absence of K(+) suggests that the stability of G-quadruplex secondary structure is important for a stable HJ24/Shp2 binding. The methodology developed and demonstrated in this work is applicable for studying the stability of secondary structures of other unimolecular G-quadruplex aptamers and their interactions with target proteins. PMID:22924632

Zhao, Xue-Qin; Wu, Jie; Liang, Jing-Hong; Yan, Jia-Wei; Zhu, Zhi; Yang, Chaoyong James; Mao, Bing-Wei

2012-09-20

180

Intermolecular potential functions from spectroscopic properties of weakly bound complexes  

Energy Technology Data Exchange (ETDEWEB)

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)

Muenter, J.S.

1992-01-01

 
 
 
 
181

Carbon dioxide hydrate phase equilibrium and cage occupancy calculations using ab initio intermolecular potentials.  

Science.gov (United States)

Gas hydrate deposits are receiving increased attention as potential locations for CO2 sequestration, with CO2 replacing the methane that is recovered as an energy source. In this scenario, it is very important to correctly characterize the cage occupancies of CO2 to correctly assess the sequestration potential as well as the methane recoverability. In order to predict accurate cage occupancies, the guest–host interaction potential must be represented properly. Earlier, these potential parameters were obtained by fitting to experimental equilibrium data and these fitted parameters do not match with those obtained by second virial coefficient or gas viscosity data. Ab initio quantum mechanical calculations provide an independent means to directly obtain accurate intermolecular potentials. A potential energy surface (PES) between H2O and CO2 was computed at the MP2/aug-cc-pVTZ level and corrected for basis set superposition error (BSSE), an error caused due to the lower basis set, by using the half counterpoise method. Intermolecular potentials were obtained by fitting Exponential-6 and Lennard-Jones 6-12 models to the ab initio PES, correcting for many-body interactions. We denoted this model as the “VAS” model. Reference parameters for structure I carbon dioxide hydrate were calculated using the VAS model (site–site ab initio intermolecular potentials) as ??(w)(0) = 1206 ± 2 J/mol and ?H(w)(0) = 1260 ± 12 J/mol. With these reference parameters and the VAS model, pure CO2 hydrate equilibrium pressure was predicted with an average absolute deviation of less than 3.2% from the experimental data. Predictions of the small cage occupancy ranged from 32 to 51%, and the large cage is more than 98% occupied. The intermolecular potentials were also tested by calculating the pure CO2 density and diffusion of CO2 in water using molecular dynamics simulations. PMID:24328234

Velaga, Srinath C; Anderson, Brian J

2014-01-16

182

Multiplicities in high energy interactions  

International Nuclear Information System (INIS)

This paper reviews the data on multiplicities in high energy interactions. Results from e+e- annihilation, from neutrino interactions, and from hadronic collisions, both diffractive and nondiffractive, are compared and contrasted. The energy dependence of the mean charged multiplicity, , as well as the rapidity density at Y = 0 are presented. For hadronic collisions, the data on neutral pion production shows a strong correlation with . The heavy particle fractions increase with ?s up to the highest energies. The charged particle multiplicity distributions for each type of reaction show a scaling behavior when expressed in terms of the mean. Attempts to understand this behavior, which was first predicted by Koba, Nielsen, and Olesen, are discussed. The multiplicity correlations and the energy variation of the shape of the KNO scaling distribution provide important constraints on models. Some extrapolations to the energies of the Superconducting Super Collider are made. 51 refs., 27 figs

183

Molecular near-field antenna effect in resonance hyper-Raman scattering: Intermolecular vibronic intensity borrowing of solvent from solute through dipole-dipole and dipole-quadrupole interactions  

Science.gov (United States)

We quantitatively interpret the recently discovered intriguing phenomenon related to resonance Hyper-Raman (HR) scattering. In resonance HR spectra of all-trans-?-carotene (?-carotene) in solution, vibrations of proximate solvent molecules are observed concomitantly with the solute ?-carotene HR bands. It has been shown that these solvent bands are subject to marked intensity enhancements by more than 5 orders of magnitude under the presence of ?-carotene. We have called this phenomenon the molecular-near field effect. Resonance HR spectra of ?-carotene in benzene, deuterated benzene, cyclohexane, and deuterated cyclohexane have been measured precisely for a quantitative analysis of this effect. The assignments of the observed peaks are made by referring to the infrared, Raman, and HR spectra of neat solvents. It has been revealed that infrared active and some Raman active vibrations are active in the HR molecular near-field effect. The observed spectra in the form of difference spectra (between benzene/deuterated benzene and cyclohexane/deuterated cyclohexane) are quantitatively analyzed on the basis of the extended vibronic theory of resonance HR scattering. The theory incorporates the coupling of excited electronic states of ?-carotene with the vibrations of a proximate solvent molecule through solute-solvent dipole-dipole and dipole-quadrupole interactions. It is shown that the infrared active modes arise from the dipole-dipole interaction, whereas Raman active modes from the dipole-quadrupole interaction. It is also shown that vibrations that give strongly polarized Raman bands are weak in the HR molecular near-field effect. The observed solvent HR spectra are simulated with the help of quantum chemical calculations for various orientations and distances of a solvent molecule with respect to the solute. The observed spectra are best simulated with random orientations of the solvent molecule at an intermolecular distance of 10 Å.

Shimada, Rintaro; Hamaguchi, Hiro-o.

2014-05-01

184

Structural modeling and intermolecular correlation of liquid chlorine dioxide  

International Nuclear Information System (INIS)

Chlorine dioxide (ClO2) is water-soluble yellow gas at room temperature. It has long been used as a disinfectant of tap water and various commodities owing to its strong oxidizing activity against various microbial proteins. The oxidizing activity is believed to be due to the presence of unpaired electron in its molecular orbital. Despite wealth of physicochemical studies of gaseous ClO2, little is known about liquid ClO2, especially about fine molecular structure and intermolecular interactions of liquid ClO2. The purpose of this study is to elucidate the fine structure and intermolecular orientations of ClO2 molecules in its liquid state using a high-energy X-ray diffraction technique. The measurements of liquid ClO2 were carried out at -50 to 0 degree Celsius using a two-axis diffractometer installed at the BL04B2 beamline in the third-generation synchrotron radiation facility SPring-8 (Hyogo, Japan). The incident X-ray beamline was 113.4 keV in energy and 0.1093 Armstrong in wavelength from a Si(111) monochromator with the third harmonic reflection. Liquid ClO2 held in a quartz capillary tube was placed in a temperature-controlled vacuum chamber. We obtained a structure factor S(Q) to a range of Q = 0.3-30 Amstrong-1 and a pair distribution function g(r) upon Fourier transform of the S(Q). The total g(r) showed peaks at 1.46, 2.08, 2.48, 3.16 and 4.24 Armstrong. From intramolecular bond lengths of 1.46 Armstrong for Cl-O and 2.48 Armstrong for O-O, O-Cl-O bond angle was estimated to be 116.1 degrees. Peaks at 3.16 and 4.24 Armstrong in the total g(r) strongly indicate presence of specific intermolecular orientations of ClO2 molecules that are distinct from those observed as a dimer in the solid phase ClO2. This view was further supported by molecular simulation using a reverse Monte Carlo method (RMC). (author)

185

Influence both of radiation and peroxide cross-linking on inter-chain interaction for polyethylene  

International Nuclear Information System (INIS)

The activation energy values of thermal oxidative destruction obtained in a temperature range corresponding to initiation of polymer oxidation have been proposed to be used in calculation of intermolecular interaction energy in polyethylene

186

Intermolecular potential for binding of protonated peptide ions with perfluorinated hydrocarbon surfaces.  

Science.gov (United States)

An analytic potential energy function was developed to model both short-range and long-range interactions between protonated peptide ions and perfluorinated hydrocarbon chains. The potential function is defined as a sum of two-body potentials of the Buckingham form. The parameters of the two-body potentials were obtained by fits to intermolecular potential energy curves (IPECs) calculated for CF4, which represents the F and C atoms of a perfluoroalkane chain, interacting with small molecules chosen as representatives of the main functional groups and atoms present in protonated peptide ions: specifically, CH4, NH3, NH4(+), and HCOOH. The IPECs were calculated at the MP2/aug-cc-pVTZ level of theory, with basis set superposition error (BSSE) corrections. Good fits were obtained for an energy range extending up to about 400 kcal/mol. It is shown that the pair potentials derived from the NH3/CF4 and HCOOH/CF4 fits reproduce acceptably well the intermolecular interactions in HCONH2/CF4, which indicates that the parameters obtained for the amine and carbonyl atoms may be transferable to the corresponding atoms of the amide group. The derived potential energy function may be used in chemical dynamics simulations of collisions of peptide-H(+) ions with perfluorinated hydrocarbon surfaces. PMID:24779856

Pratihar, Subha; Kohale, Swapnil C; Vázquez, Saulo A; Hase, William L

2014-05-22

187

Bulk and molecular compressibilities of organic-inorganic hybrids [(CH?)?N]?MnX? (X = Cl, Br); role of intermolecular interactions.  

Science.gov (United States)

This work reports an X-ray diffraction, X-ray absorption, and Raman spectroscopy study of [(CH?)?N]?MnX? (X = Cl, Br) under pressure. We show that both compounds share a similar phase diagram with pressure. A P2?/c monoclinic structure describes precisely the [(CH?)?N]?MnCl? crystal in the 0.1-6 GPa range, prior to crystal decomposition and amorphization, while [(CH?)?N]?MnBr? can be described by a Pmcn orthorhombic structure in its stability pressure range of 0-3 GPa. These materials are attractive systems for pressure studies since they are readily compressible through the weak interaction between organic/inorganic [(CH?)?N?/MnX?²?] tetrahedra through hydrogen bonds and contrast with the small compressibility of both tetrahedra. Here we determine the equation-of-state (EOS) of each crystal and compare it with the corresponding local EOS of the MnX?²? and (CH?)?N? tetrahedra, the compressibility of which is an order and 2 orders of magnitude smaller than the crystal compressibility, respectively, in both chloride and bromide. The variations of the Mn-Cl bond distance obtained by extended X-ray absorption fine structure and the frequency of the totally symmetric ??(A?) Raman mode of MnCl?²? with pressure in [(CH?)?N]?MnCl? allowed us to determine the associated Grüneisen parameter (?(loc) = 1.15) and hence an accurate local EOS. On the basis of a local compressibility model, we obtained the Grüneisen parameters and corresponding variations of the intramolecular Mn–Br and C–N bond distances of MnBr?²? (?(loc) = 1.45) and (CH?)?N? (?(loc) = 3.0) in [(CH?)?N]?MnBr?. PMID:25244664

Barreda-Argüeso, Jose Antonio; Nataf, Lucie; Rodríguez-Lazcano, Yamilet; Aguado, Fernando; González, Jesús; Valiente, Rafael; Rodríguez, Fernando; Wilhelm, Heribert; Jephcoat, Andrew P

2014-10-01

188

Theoretical investigation of the ethylene dimer: interaction energy and dipole moment.  

Science.gov (United States)

The interaction potential energy and the interaction-induced dipole moment surfaces of the van der Waals C(2)H(4)-C(2)H(4) complex has been calculated for a broad range of intermolecular separations and configurations in the approximation of rigid interacting molecules. The calculations have been carried out using high-level ab initio theory with the aug-cc-pVTZ basis set and within the framework of the analytical description of long-range interactions between ethylene molecules. Binding energy for the most stable configuration of the C(2)H(4)-C(2)H(4) complex was calculated at the CCSD(T)/CBS level of theory. The harmonic fundamental vibrational frequencies for this complex were calculated at the MP2 level of theory. PMID:22102329

Kalugina, Yulia N; Cherepanov, Victor N; Buldakov, Mikhail A; Zvereva-Loëte, Natalia; Boudon, Vincent

2012-01-30

189

Quantitative tomographic imaging of intermolecular FRET in small animals.  

Science.gov (United States)

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

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

2012-12-01

190

Substrate binding-dissociation and intermolecular electron transfer in cytochrome c oxidase are driven by energy-dependent conformational changes in the enzyme and substrate.  

Science.gov (United States)

Reduction of O? by cytochrome c oxidase (COX) is critical to the cellular production of adenosine-5'-triphosphate; COX obtains the four electrons required for this process from ferrocytochrome c. The COX-cytochrome c enzyme-substrate complex is stabilized by electrostatic interactions via carboxylates on COX and lysines on cytochrome c. Conformational changes are believed to play a role in ferrocytochrome c oxidation and release and in rapid intramolecular transfer of electrons within COX, but the details are unclear. To gather specific information about the extent and relevance of conformational changes, we performed bioinformatics studies using the published structures of both proteins. For both proteins, we studied the surface accessibility and energy, as a function of the proteins' oxidation state. The residues of reduced cytochrome c showed greater surface accessibility and were at a higher energy than those of the oxidized cytochrome c. Also, most residues of the core subunits (I, II, and III) of COX showed low accessibility, ?35%, and compared to the oxidized subunits, the reduced subunits had higher energies. We concluded that substrate binding and dissociation is modulated by specific redox-dependent conformational changes. We further conclude that high energy and structural relaxation of reduced cytochrome c and core COX subunits drive their rapid electron transfer. PMID:23586831

Ashe, Damian; Alleyne, Trevor; Sampson, Valerie

2012-01-01

191

Topological characterisation of intermolecular lithium bonding  

International Nuclear Information System (INIS)

Bader's atoms in molecules topological theory was employed to analyse the B3LYP/6-311++G(3d2f,3p2d) electron distributions of several adducts that contain LiF. The results indicate significant differences between lithium bonding (LB) and hydrogen bonding (HB): (i) in spite of their larger stability, the charge density at the intermolecular critical points of LB complexes is about half of its value in the corresponding HB complexes, suggesting a dominant role of electrostatic interactions in the former; (ii) the Li atom in LB compounds is more shared between the base atom and the attached fluorine than hydrogen in HB complexes; and (iii) the Li atom gains electron charge from the hydrogens in all the complexes here studied, undergoing energetic stabilisation

192

The study of intermolecular energy transfers in electronic energy quenching for molecular collisions N{sub 2}-N{sub 2}, N{sub 2}-O{sub 2}, O{sub 2}-O{sub 2}  

Energy Technology Data Exchange (ETDEWEB)

Contributions of intermolecular electron energy transfers in the electronic quenching are calculated for molecular collisions N{sub 2}(A{sup 3}{sigma}{sub u}{sup +}, W{sup 3}{delta}{sub u})+N{sub 2}(X{sup 1}{sigma}{sub g}{sup +}, v=0), N{sub 2}(A{sup 3}{sigma}{sub u}{sup +})+N{sub 2}(X{sup 1}{sigma}{sub g}{sup +}, v{>=}0), N{sub 2}(A{sup 3}{sigma}{sub u}{sup +})+O{sub 2}(X{sup 3}{sigma}{sub g}{sup -}, v=0-2), O{sub 2}(a{sup 1}{delta}{sub g}, b{sup 1}{sigma}{sub g}{sup +})+O{sub 2}(X{sup 3}{sigma}{sub g}{sup -}, v=0-2). The calculation has allowed one to estimate the product branching ratios. It is shown that there is a dependence of the calculated rate coefficients on the vibrational excitation of N{sub 2}(X{sup 1}{sigma}{sub g}{sup +}) and O{sub 2}(X{sup 3}{sigma}{sub g}{sup -}) molecules. In many cases, the calculated rate coefficients have a good agreement with available experimental data. (orig.)

Kirillov, A.S. [Kola Science Centre RAS, Apatity (Russian Federation). Polar Geophysical Inst.

2008-07-01

193

New type of dual solid-state thermochromism: modulation of intramolecular charge transfer by intermolecular pi-pi interactions, kinetic trapping of the aci-nitro group, and reversible molecular locking.  

Science.gov (United States)

When heated above room temperature, some crystalline polymorphs of the 1,3-bis(hydroxyalkylamino)-4,6-dinitrobenzenes (BDBn, n = 2-5), bis(hydroxyalkyl) analogues of the intramolecular charge-transfer molecule 1,3-diamino-4,6-dinitrobenzene, exhibit "dual" thermochromism: gradual color change from yellow to orange at lower temperatures, and sharp color change from orange to red at higher temperatures. These two thermochromic changes are related to different solid-state processes. When allowed to cool to room temperature, the yellow color of the thermochromic molecules with different alkyl length (n) is recovered with unexpectedly different kinetics, the order of the respective rate constants ranging from 10(-7)-10(-6) s(-1) for BDB2 to about 0.1 s(-1) in the case of BDB3. The thermochromic mechanism and the reasons behind the different kinetics were clarified on the basis of detailed crystallographic characterization, kinetic thermoanalysis, and spectroscopic study of eight crystalline forms (seven polymorphs and one solvate). It was found that the polymorphism is due to the possibility of "locking" and "unlocking" of the alkyl arms by formation of a strong intramolecular hydrogen bond between the hydroxyl groups at their hydroxyl termini. The locking of BDB2, with shortest alkyl arms, is reversible and it can be controlled thermally; either of the two conformations can be obtained in the solid state by proper thermal treatment. By use of high temperature in situ single crystal X-ray diffraction analysis of BDB3, direct evidence was obtained that the gradual thermochromic change is related to increased distance and weakened pi-pi interactions between the stacked benzene rings: the lattice expands preferably in the stacking direction, causing enhanced oscillator strength and red shift of the absorption edge of the intramolecular charge transfer transition. The second, sharp thermochromic change had been assigned previously to solid-solid phase transition triggered by intramolecular proton transfer of one amino proton to the nitro group, whereupon an aci-nitro form is thermally populated. Contrary to the numerous examples of solid thermochromic molecules based on either pericyclic reactions or keto-enol tautomerism, this system appears to be the first organic thermochromic family where the thermochromic change appears as an effect of intermolecular pi-pi interactions and thermal intramolecular proton transfer to aromatic nitro group. PMID:19780605

Naumov, Pance; Lee, Sang Cheol; Ishizawa, Nobuo; Jeong, Young Gyu; Chung, Ihn Hee; Fukuzumi, Shunichi

2009-10-22

194

Weak interactions at high energies  

International Nuclear Information System (INIS)

Review lectures are presented on the phenomenological implications of the modern spontaneously broken gauge theories of the weak and electromagnetic interactions, and some observations are made about which high energy experiments probe what aspects of gauge theories. Basic quantum chromodynamics phenomenology is covered including momentum dependent effective quark distributions, the transverse momentum cutoff, search for gluons as sources of hadron jets, the status and prospects for the spectroscopy of fundamental fermions and how fermions may be used to probe aspects of the weak and electromagnetic gauge theory, studies of intermediate vector bosons, and miscellaneous possibilities suggested by gauge theories from the Higgs bosons to speculations about proton decay. 187 references

195

Desensitization and recovery of metastable intermolecular composites  

Science.gov (United States)

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.

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

2010-09-07

196

High-Energy Neutrino Interactions  

CERN Multimedia

This experiment studies neutrino interactions in iron at the highest available energies using the narrow-band neutrino beam N3 and the wide-band neutrino beam N1. The basis of the detector is a massive target-calorimeter in which the energy deposited by a neutrino (or antineutrino) is measured by electronic techniques and the momentum of outgoing muons is determined by magnetic deflection. The detector is constructed in the form of a 20 m long iron-cored toroidal magnet, composed of modules of length 70~cm and 90~cm, and of 3.75~m diameter. Drift chambers placed in between each module measure the trajectory of muons from the neutrino interactions. The modules are of three types. The first ten modules are constructed of 2.5~cm iron plates with 20~scintillator planes inserted between the plates. The next five modules are constructed of 5~cm plates with 15~planes of scintillator and the last six modules are constructed of 15~cm plates with 5~planes of scintillators. The total mass of the detector is @=~1400 tons...

2002-01-01

197

Interacting agegraphic tachyon model of dark energy  

International Nuclear Information System (INIS)

Scalar-field dark energy models like tachyon are often regarded as an effective description of an underlying theory of dark energy. In this Letter, we implement the interacting agegraphic dark energy models with tachyon field. We demonstrate that the interacting agegraphic evolution of the universe can be described completely by a single tachyon scalar field. We thus reconstruct the potential as well as the dynamics of the tachyon field according to the evolutionary behavior of interacting agegraphic dark energy.

198

Probing ion/molecule interactions in aqueous solutions with vibrational energy transfer.  

Science.gov (United States)

Interactions between model molecules representing building blocks of proteins and the thiocyanate anion, a strong protein denaturant agent, were investigated in aqueous solutions with intermolecular vibrational energy exchange methods. It was found that thiocyanate anions are able to bind to the charged ammonium groups of amino acids in aqueous solutions. The interactions between thiocyanate anions and the amide groups were also observed. The binding affinity between the thiocyanate anion and the charged amino acid residues is about 20 times larger than that between water molecules and the amino acids and about 5-10 times larger than that between the thiocyanate anion and the neutral backbone amide groups. The series of experiments also demonstrates that the chemical nature, rather than the macroscopic dielectric constant, of the ions and molecules plays a critical role in ion/molecule interactions in aqueous solutions. PMID:22984821

Li, Jiebo; Bian, Hongtao; Wen, Xiewen; Chen, Hailong; Yuan, Kaijun; Zheng, Junrong

2012-10-11

199

Propagation studies of metastable intermolecular composites (MIC).  

Energy Technology Data Exchange (ETDEWEB)

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.

Son, S. F. (Steven F.); Busse, J. R. (James R.); Asay, B. W. (Blaine W.); Peterson, P. D. (Paul D.); Mang, J. T. (Joseph T.); Bockmon, B. (Bryan); Pantoya, M. (Michelle)

2002-01-01

200

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

Science.gov (United States)

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 ?m/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. PMID:23679912

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

2013-06-18

 
 
 
 
201

Simple non-empirical procedure for spin-component-scaled MP2 methods applied to the calculation of dissociation energy curve of noncovalently-interacting systems  

CERN Document Server

We present a simple and non-empirical method to determine optimal scaling coefficients, within the (spin-component)-scaled MP2 approach, for calculating intermolecular potential energies of noncovalently-interacting systems. The method is based on an observed proportionality between (spin-component) MP2 and CCSD(T) energies for a wide range of intermolecular distances and allows to compute with high accuracy a large portion of the dissociation curve at the cost of a single CCSD(T) calculation. The accuracy of the present procedure is assessed for a series of noncovalently-interacting test systems: the obtained results reproduce CCSD(T) quality in all cases and definitely outperform conventional MP2, CCSD and SCS-MP2 results. The difficult case of the Beryllium dimer is also considered.

Grabowski, I; Della Sala, F

2013-01-01

202

Inelastic scattering calculations in polyatomic systems using an ab initio intermolecular potential energy surface: The CO2* (0,0,1,0)+H2(D2) ?CO2(0,0,0,0)+H2(D2) systems  

International Nuclear Information System (INIS)

An ab initio computation of the energy transfer dynamics in the (CO2,H2) and (CO2,D2) systems has been carried out. The intermolecular potential energy hypersurface has been obtained from the results of ab initio SCF computations using extended Gaussian basis sets. The potential energy has been computed for 1053 different geometries. Previously formulated cubic spline fitting procedures are employed to effect surface interpolation and to extract surface gradients. At small CO2--H2 center-of-mass separations, the potential energy is repulsive and nearly exponential in form. At larger separations, small attractive wells are found. At a given separation, the most stable conformation is a planar, parallel structure of C2/sub v/ symmetry. Vibrational deexcitation probabilities, energy transfer mechanisms, and isotope ratios for the relaxation of the first excited state of the doubly degenerate bending mode of CO2 have been computed as a function of temperature by quasiclassical trajectories. In the temperature range below 600 K, the computed deexcitation probabilities are in fair to good agreement with the experimental shock tube data. At higher temperatures up to 1500 K, the computed results are too large by a factor of 3 or less. This error is interpreted to result at least partly from the assumption of classical motion. Computed isotope ratios are in fair accord with experiment over a 1000 K temperature range. The major relaxation mechanism is found to be V?R energy transfer for T< or =700 K and V?T transfer for 700 K< T< or =1500 K

203

Origin of the low-viscosity of [emim][(FSO2)2N] ionic liquid and its lithium salt mixture: experimental and theoretical study of self-diffusion coefficients, conductivities, and intermolecular interactions.  

Science.gov (United States)

The temperature-dependent viscosity, ionic conductivity, and self-diffusion coefficients of an ionic liquid, 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)amide ([emim][FSA]), and its Li salt mixture were studied with reference to emim bis(trifluoromethyl-sulfonyl)amide ([emim][TFSA]) systems. The stabilization energies for the formation of the FSA(-) complexes with emim(+) and Li(+) were calculated by the MP2/6-311G** level ab initio method. The stabilization energies calculated for the FSA(-) complexes with emim(+) and Li(+) (-77.0 and -134.3 kcal/mol) were smaller than those for the corresponding TFSA(-) complexes (-78.8 and -137.2 kcal/mol). The weaker electrostatic and induction interactions are the causes of the smaller interaction energies for the FSA(-) complexes. The weaker interaction between the FSA(-) and emim(+) can be one of the causes of the lower viscosity of the [emim][FSA] ionic liquid compared with that of the [emim][TFSA] ionic liquid. The weaker interaction between the FSA(-) and Li(+) compared with that between the TFSA(-) and Li(+) explains the fact that the addition of Li salt to the [emim][FSA] ionic liquid induces a little increase of the viscosity and a little decrease of the ionic conductivity and self-diffusion coefficients of ions. The FSA(-) in the Li[FSA] complex prefers the cis form due to the stronger attraction and smaller deformation energy of the cis-FSA(-) compared with the trans-FSA(-). PMID:21080680

Tsuzuki, Seiji; Hayamizu, Kikuko; Seki, Shiro

2010-12-16

204

Interatomic and intermolecular coulombic decay: The early years  

International Nuclear Information System (INIS)

Research highlights: ? Autoionization in weakly bonded systems can involve energy transfer between sites. ? These channels have been termed intermolecular coulombic decay (ICD). ? Here, I review the experimental research on ICD from its discovery until 2010. - Abstract: Autoionization is an important pathway for the relaxation of electronically excited states. In weakly bonded matter, efficient autoionization channels have been found, in which not only the initially excited state, but also neighbouring atoms or molecules take part. Since their theoretical prediction in 1997 these processes are known as interatomic or intermolecular coulombic decay (ICD). The author summarizes the experimental research on ICD up to the presence. Experiments on inner valence ICD in rare gas clusters, on cascade ICD after Auger decay and on ICD of satellite states are explicitly discussed. First experiments on water clusters and on solutes will be reviewed. An outlook on other non-local autoionization processes and on future directions of ICD research closes the article.

205

Nonadditive intermolecular forces from the spectroscopy of van der Waals trimers: A theoretical study of Ar2-HF  

International Nuclear Information System (INIS)

Calculations of vibrational energies and rotational constants are carried out for the van der Waals trimer Ar2-HF. The calculations include all five intermolecular degrees of freedom. The different intramolecular vibrational states v of the HF molecule are separated out adiabatically, so that the calculations are carried out on effective intermolecular potentials for each HF vibrational state separately. Calculations are performed both on pairwise-additive potentials, derived from the well-known Ar-Ar and Ar-HF potentials, and on nonadditive potentials, incorporating various different contributions to the three-body forces. The results are compared with experimental results from high-resolution spectroscopy, and provide detailed information on the anisotropy of the nonadditive intermolecular forces. As in previous work on Ar2-HCl, it is found that a very important nonadditive term arises from the interaction between the permanent multipoles of the HF molecule and the exchange quadrupole caused by distortion of the two Ar atoms as they overlap. An improved model of this term is described

206

Configuration Interactions Constrained by Energy Density Functionals  

CERN Document Server

A new method for constructing a Hamiltonian for configuration interaction calculations with constraints to energies of spherical configurations obtained with energy-density-functional (EDF) methods is presented. This results in a unified model that reproduced the EDF binding-energy in the limit of single-Slater determinants, but can also be used for obtaining energy spectra and correlation energies with renormalized nucleon-nucleon interactions. The three-body and/or density-dependent terms that are necessary for good nuclear saturation properties are contained in the EDF. Applications to binding energies and spectra of nuclei in the region above 208Pb are given.

Brown, B Alex; Hjorth-Jensen, Morten

2010-01-01

207

High-energy cosmic ray interactions  

International Nuclear Information System (INIS)

Research into hadronic interactions and high-energy cosmic rays are closely related. On one hand--due to the indirect observation of cosmic rays through air showers--the understanding of hadronic multiparticle production is needed for deriving the flux and composition of cosmic rays at high energy. On the other hand the highest energy particles from the universe allow us to study the characteristics of hadronic interactions at energies far beyond the reach of terrestrial accelerators. This is the summary of three introductory lectures on our current understanding of hadronic interactions of cosmic rays.

208

Intra- and intermolecular vibrational energy transfer in tungsten carbonyl complexes W(CO)5(X) (X=CO, CS, CH3CN, and CD3CN)  

Science.gov (United States)

Vibrational energy relaxation of degenerate CO stretches of four tungsten carbonyl complexes, W(CO)6, W(CO)5(CS), W(CO)5(CH3CN), and W(CO)5(CD3CN), is observed in nine alkane solutions by subpicosecond time-resolved infrared (IR) pump-probe spectroscopy. Between 0 and 10 ps after the vibrational excitation, the bleaching signal of the ground-state IR absorption band shows anisotropy. Decay of the anisotropic component corresponds either to the rotational diffusion of the molecule or to the intramolecular vibrational energy transfer among the degenerate CO stretch modes. The time constant of the anisotropy decay, ?aniso, shows distinct solvent dependence. By comparing the results for the T1u CO stretch of W(CO)6 and the A1 CO stretch of W(CO)5(CS), the time constant of the rotational diffusion, ?r, and the time constant of the intramolecular energy transfer among the three degenerate vibrational modes, ?e, are determined as 12 and 8 ps, respectively. The ?aniso value increases as the number of carbon atoms in the alkane solvent increases. After 10 ps, the recovery of the bleaching becomes isotropic. The isotropic decay represents the vibrational population relaxation, from v=1 to v=0. In heptane, the time constant for the isotropic decay, ?1, for W(CO)5(CS) and W(CO)6 was 140 ps. The ?1 for the two acetonitrile-substituted complexes, however, shows a smaller value of 80 ps. The vibrational energy relaxation of W(CO)5(CH3CN) and W(CO)5(CD3CN) is accelerated by the intramolecular energy redistribution from the CO ligand to the acetonitrile ligand. In the nine alkane solutions, the ?1 value of W(CO)6 ranges between 124 and 158 ps, showing the apparent V-shaped solvent dependence with its minimum in decane, while the ?1 value shows little solvent dependence for W(CO)5(CH3CN) and W(CO)5(CD3CN).

Banno, Motohiro; Iwata, Koichi; Hamaguchi, Hiro-O.

2007-05-01

209

Polynomial identities for ternary intermolecular recombination  

CERN Document Server

The operation of binary intermolecular recombination, originating in the theory of DNA computing, permits a natural generalization to n-ary operations which perform simultaneous recombination of n molecules. In the case n = 3, we use computer algebra to determine the polynomial identities of degree <= 9 satisfied by this trilinear nonassociative operation. Our approach requires computing a basis for the nullspace of a large integer matrix, and for this we compare two methods: (i) the row canonical form, and (ii) the Hermite normal form with lattice basis reduction. In the conclusion, we formulate some conjectures for the general case of n-ary intermolecular recombination.

Bremner, Murray R

2010-01-01

210

Finding a unifying motif of intermolecular cooperativity in protein associations  

CERN Document Server

At the molecular level, most biological processes entail protein associations which in turn rely on a small fraction of interfacial residues called hot spots. Here we show that hot spots share a unifying molecular attribute: they provide a third-body contribution to intermolecular cooperativity. Such motif, based on the wrapping of interfacial electrostatic interactions, is essential to maintain the integrity of the interface and can be exploited in rational drug design since such regions may serve as blueprints to engineer small molecules disruptive of protein-protein interfaces.

Accordino, Sebastián R; Appignanesi, Gustavo A; Fernández, Ariel

2011-01-01

211

Thermodynamic laws in interacting dark energy scenario  

Science.gov (United States)

We discuss the laws of thermodynamics in interacting dark energy scenario. Entropy of the universe is calculated assuming that universe is a closed system. The components of the tachyonic scalar field in the universe are taken to exist in the state of non-equilibrium initially, but due to interaction they undergo a transition towards the equilibrium state. We show that the zeroth law of thermodynamics demands interaction among the components of cosmic field. During such interaction the second law of thermodynamics is governing dynamics in transfer of energy among the three components of the proposed field with local violation of conservation of energy for individual components. It is further shown that, in our proposed mechanism, the interaction itself generates an increase of entropy in an evolving universe and thus it might indicate a possible solution to the well-known entropy problem.

Pathak, Shankar Dayal; Verma, Murli

212

Pion nucleon interaction at low energy  

International Nuclear Information System (INIS)

A theory of the ?N interaction at low energy is described. An analogy is made with an unusual approach to potential scattering theory. Phase shifts, cross sections, and scattering amplitudes and lengths are calculated. 28 references

213

High Energy Cosmic Ray Interactions -- an Overview  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The status of present theoretical description of very high energy hadronic interactions is reviewed. The impact of new results of accelerator and cosmic ray experiments on hadronic interaction model constructions is discussed in detail. Special attention is payed to remaining uncertainties in model extrapolations into the ultra-high energy domain, in particular, concerning model predictions for the muon component of extensive air showers. New promising theoretical approaches...

Ostapchenko, Sergey

2006-01-01

214

Thermodynamics of interacting holographic dark energy  

CERN Document Server

The thermodynamics of a scheme of dark matter-dark energy interaction is studied considering a holographic model for the dark energy in a flat Friedmann-Lemaitre-Robertson-Walker background. We obtain a total entropy rate for a general horizon and study the Generalized Second Law of Thermodynamics. In addition, we study two horizons related to the Ricci and Ricci-like model and its effect on an interacting system.

Arevalo, Fabiola; Pena, Francisco

2014-01-01

215

Catalytic intermolecular alkene oxyamination with nitrenes.  

Science.gov (United States)

The Rh(II)-catalyzed intermolecular addition of nitrenes to aromatic and aliphatic alkenes provides vicinal amino alcohols with yields of up to 95?% and complete regioselectivity. This 1,2-oxyamination reaction involves the formation of an aziridine intermediate that undergoes in situ ring opening. The latter is induced by the Rh-bound nitrene that behaves as a Lewis acid. PMID:24939636

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

2014-07-14

216

Vacuum energies and multipole interactions  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in english In this paper, we present a quantum-field-theoretical description of the interaction between stationary and localized external sources linearly coupled to bosonic fields (specifically, we study models with a scalar and the Maxwell field). We consider external sources that simulate not only point cha [...] rges but also higher-multipole distributions along D-dimensional branes. Our results complement the ones previously obtained in reference [1].

F.A., Barone; G., Flores-Hidalgo.

2010-06-01

217

Monopole interaction and single-particle energies  

International Nuclear Information System (INIS)

The importance of the monopole component of effective NN interaction has been pointed out since 1960's in the context of energy difference between different shell-model configurations [1-3]. It has been more emphasized in recent studies on shell structure evolution in neutron-rich nuclei [4-6]. The definition of single-particle (s.p.) energy is not trivial, especially for open-shell nuclei. According to the prescription of Baranger [7], we derived an expression of s.p. energies by employing a shell-model sum rule technique [5]. The result is very simple and reasonable. The s.p. energy can be evaluated for any state by a sum of ?jcore with respect to the core nucleus and a part which arises from interaction between valence nucleons by calculating occupation numbers of s.p. orbits. The s.p. energies are determined only by the monopole strengths of NN interaction. This formulation allows us, for the first time, to discuss quantitatively changes of s.p. energies from a nucleus to another due to the monopole interaction, and, consequently, the evolution of shell structure. We have studied the monopole interaction in detail [6]. It is the lowest order term in the multipole expansion of NN interactions. The spin-tensor decomposition revealed that the monopole strengths are dominated by the triplet-even attraction of the central force, which contains second-order effects of the tensor force. The two-body monopole interaction is renormalized, as a very good approximation, to the one-body s.p. energies, which indicates that the above formulation of s.p. energies is consistent with the two-body interaction. The monopole, therefore, dominates the nuclear binding due to NN interactions. However, since the monopole interaction is expressed by number operators, it is diagonal with respect to shell-model configurations, and further binding is gained mainly by the quadrupole component. A study is under progress on the roles of central, tensor and spin-orbit components of NN interactions in a wide range of nuclear chart, with an emphasis on the monopole interaction.(author)

218

String interactions at high energy  

International Nuclear Information System (INIS)

In this lecture I discuss briefly a few topics that I have worked on in the last year, largely dealing with what one can learn from a study of the high energy behavior of string theory. I argue that weak coupling perturbation theory is clearly insufficient by discussing a recent result that string perturbation theory diverges and is non Borel-summable. I then discuss how string theory looks at energies large compared to the Planck mass. I argue this is a semiclassical limit of the first quantized theory and exhibits very simply but stringy behavior which might give us a clue to the conceptual foundations of the theory. In particular it suggests that there is a very large symmetry present in string theory which is not visible at low energies but is restored at very high energies. Finally I show that if one tries to use high energy strings as microscopes to probe short distances that there are indications that this possibility breaks down close to the Planck length, at what might be called a minimal length. (orig./HSI)

219

Thermodynamic curvature for attractive and repulsive intermolecular forces.  

Science.gov (United States)

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 (R0) 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. PMID:24125229

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

2013-09-01

220

Expectations for ultra-high energy interactions  

International Nuclear Information System (INIS)

Strong interactions at ultra-high energies are discussed with emphasis on the hadrons produced in high energy collisions. Evidence is considered that quantum chromodynamics might be the right theory, and also some estimates are given of quantum chromodynamics asymptotic-freedom phenomena, the work under discussion being very preliminary. 6 references

 
 
 
 
221

Dark energy interacting with two fluids  

Energy Technology Data Exchange (ETDEWEB)

A cosmological model of dark energy interacting with dark matter and another general component of the universe is investigated. We found general constraints on these models imposing an accelerated expansion. The same is also studied in the case for holographic dark energy.

Cruz, Norman [Departamento de Fisica, Facultad de Ciencia, Universidad de Santiago, Casilla 307, Santiago (Chile)], E-mail: ncruz@lauca.usach.cl; Lepe, Samuel [Instituto de Fisica, Facultad de Ciencias Basicas y Matematicas, Universidad Catolica de Valparaiso, Avenida Brasil 2950, Valparaiso (Chile)], E-mail: slepe@ucv.cl; Pena, Francisco [Departamento de Ciencias Fisicas, Facultad de Ingenieria, Ciencias y Administracion, Universidad de La Frontera, Avda. Francisco Salazar 01145, Casilla 54-D Temuco (Chile)], E-mail: fcampos@ufro.cl

2008-05-29

222

Casimir energy of frequency dependent interactions  

Science.gov (United States)

Vacuum polarization (or Casimir) energies can be straightforwardly computed from scattering data for static field configurations whose interactions with the fluctuating field are frequency independent. In effective theories, however, such interactions are typically frequency dependent. As a consequence, the relationship between scattering data and the Green's function is modified, which may or may not induce additional contributions to the vacuum polarization energy. We discuss several examples that naturally include frequency dependent interactions: (i) scalar electrodynamics with a static background potential, (ii) an effective theory that emerges from integrating out a heavy degree of freedom, and (iii) quantum electrodynamics coupled to a frequency dependent dielectric material. In the latter case, we argue that introducing dissipation as required by the Kramers-Kronig relations requires the consideration of the Casimir energy within a statistical mechanics formalism, while in the absence of dissipation, we can work entirely within field theory, using an alternative formulation of the energy density.

Graham, N.; Quandt, M.; Weigel, H.

2014-10-01

223

Problems with Ultrahigh-energy Neutrino Interactions  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The IceCube collaboration has recently identified events due to ultrahigh-energy neutrino interactions. Predictions of the neutrino-nucleon cross section at ultrahigh energies require a huge extrapolation of the cross sections experimentally measured at laboratory energies. Upon relating neutrino scattering to deep inelastic electron scattering, we show that the empirically verified color dipole picture is well suited for such an extrapolation. The dominant contribution to t...

Schildknecht, Dieter

2014-01-01

224

Tachyon Reconstruction of Interacting Ghost Dark Energy  

CERN Document Server

Recently it has been argued that a possible source for the dark energy may arise due to the contribution to the vacuum energy of the QCD ghost in a time-dependent background. In this paper we establish a connection between interacting ghost dark energy and tachyon field. It is demonstrated that the evolution of the ghost dark energy dominated universe can be described completely by a single tachyon scalar field. The potential and the dynamics of the tachyon field are reconstructed according to the evolutionary behavior of ghost energy density.

Sheykhi, A; Ebrahimi, E

2011-01-01

225

Electroweak interactions at LEP energies  

International Nuclear Information System (INIS)

Some of the processes that have been observed at LEP energies, particularly the decay rate for Z0?ff-bar, and the forward-backward asymmetry in the process e+e-?ff-bar are presented. It is also discussed how measurement of Z0 width counts the number of light neutrinos and how one can look for the Higgs particle and for other exotic particles in the decay of the Z0 and calculate some of the expected rates. The important role played by radiative corrections in the analysis of data is emphasised. 33 refs., 5 tabs., 7 figs

226

Problems with Ultrahigh-energy Neutrino Interactions  

CERN Document Server

The IceCube collaboration has recently identified events due to ultrahigh-energy neutrino interactions. Predictions of the neutrino-nucleon cross section at ultrahigh energies require a huge extrapolation of the cross sections experimentally measured at laboratory energies. Upon relating neutrino scattering to deep inelastic electron scattering, we show that the empirically verified color dipole picture is well suited for such an extrapolation. The dominant contribution to the total neutrino-nucleon cross section, even at ultrahigh energies, is due to the kinematic range where color transparency is valid for the color dipole interaction. We deviate from various claims in the literature on the presence of screening effects due to non-linear evolution at ultrahigh neutrino energies.

Schildknecht, Dieter

2014-01-01

227

Energy and entropy of interacting dislocations  

International Nuclear Information System (INIS)

The energy and entropy of interacting edge dislocations have been calculated by atomistic simulations, with the use of piecewise-linear forces in a two-dimensional triangular lattice. We conclude that the interaction energy between small groups of dislocations is well described by continuum mechanics for separations greater than a few lattice spacings. Our calculations enable us to make a precise determination of the core energy, which is an essential parameter in determining dislocation multiplication rates. We find also that continuum mechanics gives an accurate representation of the interaction of a dislocation pair with a homogeneous elastic stress field. The vibrational contribution to the entropy of such a pair is small, about 0.3k

228

Interacting holographic dark energy with logarithmic correction  

International Nuclear Information System (INIS)

The holographic dark energy (HDE) is considered to be the most promising candidate of dark energy. Its definition is motivated from the entropy-area relation which depends on the theory of gravity under consideration. Recently a new definition of HDE is proposed with the help of quantum corrections to the entropy-area relation in the setup of loop quantum cosmology. Employing this new definition, we investigate the model of interacting dark energy and derive its effective equation of state. Finally we establish a correspondence between generalized Chaplygin gas and entropy-corrected holographic dark energy

229

High energy electron beam interaction with tantalum  

International Nuclear Information System (INIS)

Preliminary studies were performed on the interaction of high energy electron beams (HEEB) with commercially pure tantalum (Ta). Small Ta bars, nominally 2 x 0.5 x 0.1 cm were irradiated with HEEBs of energies ranging from 2.5 to 3 MeV, 1.5 kA, 1 to 2 micros pulse with a beam radius of 0.3 cm and larger. These HEEBs had a gaussian energy distribution. Following exposure in a vacuum, the bars were examined visually, with light optical microscopy and scanning electron microscopy which also provided energy dispersive x-rays (EDX) analysis. Weight and dimensional measurements were made on some of the bars. Based on the results of these examinations, a model for the interaction of HEEBs with Ta was developed and is presented

230

Interacting Ricci Dark Energy with Logarithmic Correction  

CERN Document Server

Motivated by the holographic principle, it has been suggested that the dark energy density may be inversely proportional to the area $A$ of the event horizon of the universe. However, such a model would have a causality problem. In this work, we consider the entropy-corrected version of the holographic dark energy model in the non-flat FRW universe and we propose to replace the future event horizon area with the inverse of the Ricci scalar curvature. We obtain the equation of state (EoS) parameter $\\omega_{\\Lambda}$, the deceleration parameter $q$ and $\\Omega_D'$ in the presence of interaction between Dark Energy (DE) and Dark Matter (DM). Moreover, we reconstruct the potential and the dynamics of the tachyon, K-essence, dilaton and quintessence scalar field models according to the evolutionary behavior of the interacting entropy-corrected holographic dark energy model.

Pasqua, Antonio; Jamil, Mubasher; Myrzakulov, R

2011-01-01

231

Interacting holographic tachyon model of dark energy  

CERN Document Server

We propose a holographic tachyon model of dark energy with interaction between the components of the dark sector. The correspondence between the tachyon field and the holographic dark energy densities allows the reconstruction of the potential and the dynamics of the tachyon scalar field in a flat Friedmann-Robertson-Walker universe. We show that this model can describe the observed accelerated expansion of our universe with a parameter space given by the most recent observational results.

Rozas-Fernández, Alberto; Cruz, Norman

2010-01-01

232

Low energy atomic collision with dipole interactions  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We apply quantum defect theory to study low energy ground state atomic collisions including aligned dipole interactions such as those induced by an electric field. Our results show that coupled even ($l$) relative orbital angular momentum partial wave channels exhibit shape resonance structures while odd ($l$) channels do not. We analyze and interpret these resonances within the framework of multichannel quantum defect theory (MQDT).

Deb, B.; You, L.

2001-01-01

233

Charged current weak interactions at high energy  

International Nuclear Information System (INIS)

We review high energy neutrino and antineutrino charged current interactions. An overview of the experimental data is given, including a discussion of the experimental status of the y anomaly. Locality tests, ?-e universality and charge symmetry invariance tests are discussed. Charm production is discussed. The experimental status of trimuon events and possible phenomenological models for these events are presented. (orig.)

234

The key role of the intermolecular pi-pi interactions in the presence of spin crossover in neutral [Fe(abpt)2A2] complexes (A = terminal monoanion N ligand).  

Science.gov (United States)

New iron(II) complexes of formulas [Fe(abpt) 2(tcm) 2] ( 1), [Fe(abpt) 2(tcnome) 2] ( 2), and [Fe(abpt) 2(tcnoet) 2] ( 3) (abpt = 4-amino-3,5-bis(pyridin-2-yl)-1,2,4-triazole, tcm (-) = [C(CN) 3] (-) = tricyanomethanide anion; tcnome (-) = [(NC) 2CC(OCH 3)C(CN) 2] (-) = 1,1,3,3-tetracyano-2-methoxypropenide anion; tcnoet (-) = [(NC) 2CC(OC 2H 5)C(CN) 2] (-) = 1,1,3,3-tetracyano-2-ethoxypropenide anion) have been synthesized and characterized by infrared spectroscopy, magnetic properties and by variable-temperature single-crystal X-ray diffraction. The crystal structure determinations of 1 and 2 reveal in both cases centrosymmetric discrete iron(II) monomeric structures in which two abpt chelating ligands stand in the equatorial plane and two terminal polynitrile ligands complete the distorted octahedral environment in trans positions. For 3, the crystallographic studies revealed two polymorphs, 3- A and 3- B, exhibiting similar discrete molecular structures to those found for 1 and 2 but with different molecular arrangements. In agreement with the variable-temperature single-crystal X-ray diffraction, the magnetic susceptibility measurements, performed in the temperature range 2-400 K, showed a spin-crossover phenomenon above room temperature for complexes 1, 3- A, and 3- B with a T 1/2 of 336, 377, and 383 K, respectively, while complex 2 remains in the high-spin ground state ( S = 2) in the whole temperature range. To understand further the magnetic behaviors of 1, 3-A, and 3-B, single-crystal X-ray diffraction measurements were performed at high temperatures. The crystal structures of both polymorphs could not be obtained above 400 K because the crystals decomposed. However, single-crystal X-ray data have been collected for compound 1, which reaches the full high-spin state at lower temperatures. Its crystal structure, solved at 400 K, showed a strong modification of the iron coordination sphere (average Fe-N = 2.157(3) A vs 1.986(3) A at 293 K). In agreement with the magnetic properties. Such structural behavior is a signature of the spin-state transition from low-spin (LS) to high-spin (HS). On the basis of the intermolecular pi stacking observed for the series described in this paper and for related complexes involving similar discrete structures, we have shown that complexes displaying frontal pi stacking present spin transition such as 1, 3-A, and 3-B and those involving sideways pi stacking such as complex 2 remain in the HS state. PMID:18686945

Dupouy, Gaelle; Marchivie, Mathieu; Triki, Smail; Sala-Pala, Jean; Salaün, Jean-Yves; Gómez-García, Carlos J; Guionneau, Philippe

2008-10-01

235

Interacting vacuum energy in the dark sector  

CERN Document Server

We analyse three cosmological scenarios with interaction in the dark sector, which are particular cases of a general expression for the energy flux from vacuum to matter. In the first case the interaction leads to a transition from an unstable de Sitter phase to a radiation dominated universe, avoiding in this way the initial singularity. In the second case the interaction gives rise to an inflationary expansion without inflaton, with desired features of standard inflation. Finally, the third scenario is a concordance model for the late-time universe, with the vacuum term decaying into cold dark matter. We identify the physics behind these forms of interaction, and we show that they can be described as particular types of the modified Chaplygin gas.

Chimento, L P

2014-01-01

236

Halo events in superhigh energy nuclear interactions  

International Nuclear Information System (INIS)

Gamma family events with visible energies higher than 1015 eV usually form halos in the emulsion chambers, which bring up some problems for further investigating the characteristics of superhigh energy nuclear interactions. At present, only a few gross quantities are used for describing the halo events. On the other hand, there are some fine structures inside the halo, which can give us more information. We have measured all the showers one by one in the superhigh energy family events and compared the results with those obtained by the method of halo measurements. Analyses and discussions are made for some special events

237

Nonlinear interaction involving zero energy wave  

International Nuclear Information System (INIS)

Three-wave interactions involving one or two modes with non-definite sign of wave energy, treated by second order differential equations in time, are studied. The third mode is assumed to suffer heavy linear damping, and is treated by means of Tang's adiabatic approximation. The possibility of negative pump energy and positive decay mode energy is shown to lead to an explosive situation. Self-similar explosive solutions are derived, and it is shown that almost any solution asymptotically approaches, in some sense, these self-similar solutions

238

High energy theory of strong interactions  

International Nuclear Information System (INIS)

Development of strong interaction theory can be overlooked by two following supplementary directions: surveying the current theoretical approaches and models, and analysing recent experimental results. Asymptotic energies are not yet reached, polarization in pp scattering is still nonzero. Nature of the vacuum exchange (the Pomeranchuk singularity) is still an enigma. A close relationship between the t-dependent SU3-structure of the vacuum exchange and the OZI-rule regularities in the heavy meson decays, apparently, exists. This makes deeper the Regge idea on relationship of high energy behaviour and particle properties with the relevant quantum numbers. Situation with quark confinement in Dimensional Quark Counting is still puzzling. Measuring angular dependence, polarizations and phases of scattering amplitudes of the binary reactions at large angles, it is important to understand, how far are really good predictions of the Dimensional Quark Counting. Quark degrees of freedom seem to be important for a description of nucleus interactions at high energies and large transferred momenta. Presence of the fundamental length or new energy scale could change drastically the picture of particle interactions at extremal energies

239

Interactive Joint Transfer of Energy and Information  

DEFF Research Database (Denmark)

In some communication networks, such as passive RFID systems, the energy used to transfer information between a sender and a recipient can be reused for successive communication tasks. In fact, from known results in physics, any system that exchanges information via the transfer of given physical resources, such as radio waves, particles and qubits, can conceivably reuse, at least part, of the received resources. This paper aims at illustrating some of the new challenges that arise in the design of communication networks in which the signals exchanged by the nodes carry both information and energy. To this end, a baseline two-way communication system is considered in which two nodes communicate in an interactive fashion. In the system, a node can either send an “on” symbol (or “1”), which costs one unit of energy, or an “off” signal (or “0”), which does not require any energy expenditure. Upon reception of a “1” signal, the recipient node “harvests”, with some probability, the energy contained in the signal and stores it for future communication tasks. Inner and outer bounds on the achievable rates are derived. Numerical results demonstrate the effectiveness of the proposed strategies and illustrate some key design insights. Index Terms— Two-way channel, interactive communication, energy transfer, energy harvesting.

Popovski, Petar; Fouladgar, A. M.

2013-01-01

240

Spatial assignment of symmetry adapted perturbation theory interaction energy components: The atomic SAPT partition.  

Science.gov (United States)

We develop a physically-motivated assignment of symmetry adapted perturbation theory for intermolecular interactions (SAPT) into atom-pairwise contributions (the A-SAPT partition). The basic precept of A-SAPT is that the many-body interaction energy components are computed normally under the formalism of SAPT, following which a spatially-localized two-body quasiparticle interaction is extracted from the many-body interaction terms. For electrostatics and induction source terms, the relevant quasiparticles are atoms, which are obtained in this work through the iterative stockholder analysis (ISA) procedure. For the exchange, induction response, and dispersion terms, the relevant quasiparticles are local occupied orbitals, which are obtained in this work through the Pipek-Mezey procedure. The local orbital atomic charges obtained from ISA additionally allow the terms involving local orbitals to be assigned in an atom-pairwise manner. Further summation over the atoms of one or the other monomer allows for a chemically intuitive visualization of the contribution of each atom and interaction component to the overall noncovalent interaction strength. Herein, we present the intuitive development and mathematical form for A-SAPT applied in the SAPT0 approximation (the A-SAPT0 partition). We also provide an efficient series of algorithms for the computation of the A-SAPT0 partition with essentially the same computational cost as the corresponding SAPT0 decomposition. We probe the sensitivity of the A-SAPT0 partition to the ISA grid and convergence parameter, orbital localization metric, and induction coupling treatment, and recommend a set of practical choices which closes the definition of the A-SAPT0 partition. We demonstrate the utility and computational tractability of the A-SAPT0 partition in the context of side-on cation-? interactions and the intercalation of DNA by proflavine. A-SAPT0 clearly shows the key processes in these complicated noncovalent interactions, in systems with up to 220 atoms and 2845 basis functions. PMID:25084889

Parrish, Robert M; Sherrill, C David

2014-07-28

 
 
 
 
241

Energy landscape of all-atom protein-protein interactions revealed by multiscale enhanced sampling.  

Science.gov (United States)

Protein-protein interactions are regulated by a subtle balance of complicated atomic interactions and solvation at the interface. To understand such an elusive phenomenon, it is necessary to thoroughly survey the large configurational space from the stable complex structure to the dissociated states using the all-atom model in explicit solvent and to delineate the energy landscape of protein-protein interactions. In this study, we carried out a multiscale enhanced sampling (MSES) simulation of the formation of a barnase-barstar complex, which is a protein complex characterized by an extraordinary tight and fast binding, to determine the energy landscape of atomistic protein-protein interactions. The MSES adopts a multicopy and multiscale scheme to enable for the enhanced sampling of the all-atom model of large proteins including explicit solvent. During the 100-ns MSES simulation of the barnase-barstar system, we observed the association-dissociation processes of the atomistic protein complex in solution several times, which contained not only the native complex structure but also fully non-native configurations. The sampled distributions suggest that a large variety of non-native states went downhill to the stable complex structure, like a fast folding on a funnel-like potential. This funnel landscape is attributed to dominant configurations in the early stage of the association process characterized by near-native orientations, which will accelerate the native inter-molecular interactions. These configurations are guided mostly by the shape complementarity between barnase and barstar, and lead to the fast formation of the final complex structure along the downhill energy landscape. PMID:25340714

Moritsugu, Kei; Terada, Tohru; Kidera, Akinori

2014-10-01

242

Energy Landscape of All-Atom Protein-Protein Interactions Revealed by Multiscale Enhanced Sampling  

Science.gov (United States)

Protein-protein interactions are regulated by a subtle balance of complicated atomic interactions and solvation at the interface. To understand such an elusive phenomenon, it is necessary to thoroughly survey the large configurational space from the stable complex structure to the dissociated states using the all-atom model in explicit solvent and to delineate the energy landscape of protein-protein interactions. In this study, we carried out a multiscale enhanced sampling (MSES) simulation of the formation of a barnase-barstar complex, which is a protein complex characterized by an extraordinary tight and fast binding, to determine the energy landscape of atomistic protein-protein interactions. The MSES adopts a multicopy and multiscale scheme to enable for the enhanced sampling of the all-atom model of large proteins including explicit solvent. During the 100-ns MSES simulation of the barnase-barstar system, we observed the association-dissociation processes of the atomistic protein complex in solution several times, which contained not only the native complex structure but also fully non-native configurations. The sampled distributions suggest that a large variety of non-native states went downhill to the stable complex structure, like a fast folding on a funnel-like potential. This funnel landscape is attributed to dominant configurations in the early stage of the association process characterized by near-native orientations, which will accelerate the native inter-molecular interactions. These configurations are guided mostly by the shape complementarity between barnase and barstar, and lead to the fast formation of the final complex structure along the downhill energy landscape. PMID:25340714

Moritsugu, Kei; Terada, Tohru; Kidera, Akinori

2014-01-01

243

Interactions between dark energy and dark matter  

Energy Technology Data Exchange (ETDEWEB)

We have investigated interacting dark energy cosmologies both concerning their impact on the background evolution of the Universe and their effects on cosmological structure growth. For the former aspect, we have developed a cosmological model featuring a matter species consisting of particles with a mass that increases with time. In such model the appearance of a Growing Matter component, which is negligible in early cosmology, dramatically slows down the evolution of the dark energy scalar field at a redshift around six, and triggers the onset of the accelerated expansion of the Universe, therefore addressing the Coincidence Problem. We propose to identify this Growing Matter component with cosmic neutrinos, in which case the present dark energy density can be related to the measured average mass of neutrinos. For the latter aspect, we have implemented the new physical features of interacting dark energy models into the cosmological N-body code GADGET-2, and we present the results of a series of high-resolution simulations for a simple realization of dark energy interaction. As a consequence of the new physics, cold dark matter and baryon distributions evolve differently both in the linear and in the non-linear regime of structure formation. Already on large scales, a linear bias develops between these two components, which is further enhanced by the non-linear evolution. We also find, in contrast with previous work, that the density profiles of cold dark matter halos are less concentrated in coupled dark energy cosmologies compared with {lambda}{sub CDM}. Also, the baryon fraction in halos in the coupled models is significantly reduced below the universal baryon fraction. These features alleviate tensions between observations and the {lambda}{sub CDM} model on small scales. Our methodology is ideally suited to explore the predictions of coupled dark energy models in the fully non-linear regime, which can provide powerful constraints for the viable parameter space of such scenarios. (orig.)

Baldi, Marco

2009-03-20

244

Determination of a silane intermolecular force field potential model from an ab initio calculation  

International Nuclear Information System (INIS)

Intermolecular interaction potentials of the silane dimer in 12 orientations have been calculated by using the Hartree-Fock (HF) self-consistent theory and the second-order Moeller-Plesset (MP2) perturbation theory. We employed basis sets from Pople's medium-size basis sets [up to 6-311++G(3df, 3pd)] and Dunning's correlation consistent basis sets (up to the triply augmented correlation-consistent polarized valence quadruple-zeta basis set). We found that the minimum energy orientations were the G and H conformers. We have suggested that the Si-H attractions, the central silicon atom size, and electronegativity play essential roles in weakly binding of a silane dimer. The calculated MP2 potential data were employed to parametrize a five-site force field for molecular simulations. The Si-Si, Si-H, and H-H interaction parameters in a pairwise-additive, site-site potential model for silane molecules were regressed from the ab initio energies.

245

An assay for intermolecular exchange of alpha crystallin  

Science.gov (United States)

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.

Gopalakrishnan, S.; Takemoto, L.; Spooner, B. S. (Principal Investigator)

1992-01-01

246

Nano-spectroscopic imaging of intermolecular structure, coupling and dynamics  

CERN Document Server

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 intrinsic or engineered 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 with unprecedented spectral precision to investigate the structure-function relationship in nano-phase separated block-copolymers. We use a vibrational resonance as a sensitive reporter of the local chemical environment and resolve, with few nanometer spatial resolution and 0.2 cm$^{-1}$ spectral precision, spectral Stark shifts and line broadening correlated with molecular-scale morphologies. By creating images of solvatochromic vibrational shifts we discriminate local variations in elect...

Pollard, Benjamin; Hinrichs, Karsten; Raschke, Markus B

2013-01-01

247

Laser energy deposition in Edney IV interaction  

Science.gov (United States)

Hypersonic vehicles are subject to intense local aerothermodynamic loading associated with specific local flow phenomena. An example is the well-known Edney IV interaction which can result in peak heat transfer rates which are orders of magnitude above the already high stagnation point heat transfer. Failure to alleviate or control such local aerothermodynamic loading can leading to serious degradation of vehicle aerodynamic integrity and performance, and even to catastrophic failure. In this paper, we explore the capability of pulsed laser energy deposition to favorably modify the shock structure associated with an Edney IV interaction generated by the intersection of an oblique shock with the blunt body shock associated with a sphere at Mach 3.45. Surface pressure measurements indicate a signicant modification of the surface pressure during the interaction including substantial reduction in peak surface pressure.

Knight, D.; Adelgren, R.; Elliott, G.; Yan, H.; Beutner, T.

248

Low energy weak interactions and decays  

International Nuclear Information System (INIS)

Results presented during sessions B5 to 7 at the XXth International Conference on High Energy Physics (University of Wisconsin, Madison, July 17 to 23, 1980) are discussed. Essentially all the material presented is summarized. The sessions covered various aspects of low-energy weak interactions. The following topics are addressed: CP-invariance violation, high-statistics study of ? beta decay, parity violation in proton-nucleus scattering at 6 GeV/c, new results on the tau, charm particle decays (direct lifetime determinations, semileptonic branching ratios, comparison of semileptonic rate with theoretical expectations, further study of charm meson decays, F decays), and neutrino oscillations. 6 figures, 9 tables

249

Effect of intermolecular hydrogen bonding on the micro-mechanical properties of high performance organic fibers  

Science.gov (United States)

Since their introduction in the early 1970s, high performance organic fibers have gained an increasingly significant role in a wide range of weight-sensitive applications. However, the use of organic fibers in structural applications has been restricted by their performance under compression. Organic fibers have a fibrillar structure in which the lack of strong lateral support between fibrils results in failure at low compressive loads. Despite the relevance of lateral interactions on organic fiber mechanical properties, there is not a reliable method to measure and quantify the effect of hydrogen bonding on fiber compressive properties. The mechanisms by which intermolecular hydrogen bonding affects fiber compressive properties have been elucidated by analyzing the state of hydrogen bonding in M5, a poly-pyridobisimidazole experimental fiber developed by Akzo Nobel. An experimental methodology based on FTIR microspectroscopy has been developed in order to detect and quantify the state of hydrogen bonding in M5 fibers with varying degrees of heat treatment. The methodology has shown that in the as-spun material, 72% of the N-H vibration groups are hydrogen-bonded to water, while in the fully heat-treated fiber more than 90% of the N-H vibration groups develop intermolecular hydrogen bonds. Saturation of previously annealed M5 fiber has been shown to result in a reduction of the measured degree of intermolecular hydrogen bonding from 93 to 64%, providing the first direct evidence of partial reversibility of hydrogen bonding in high performance organic fibers. The compressive properties of five high performance organic fibers with varying degrees of lateral molecular interactions have been analyzed. A novel micro-mechanical technique applies an axial compressive load on a segment of free fiber in order to quantify the axial compressive modulus of single filaments. The resulting ratios of axial compressive to tensile modulus show values ranging between 0.3--1.0, depending on the type and degree of intermolecular interactions present in the fiber. The assumption of equal tensile and compressive modulus necessary to determine single fiber axial compressive strength from the elastica loop test has been relaxed by deriving a compressive strength equation based on the analysis of the flexural response of a fiber with different modulus in tension and compression. Using the FTIR methodology to quantify the degree of intermolecular hydrogen bonding in M5 fiber as a function of annealing conditions, and the micro-mechanical techniques suitable for the evaluation of the effect of intermolecular interactions on fiber compressive properties, a direct relationship between the degree of intermolecular hydrogen bonding in the fiber and the measured compressive strength values is established.

Leal Ayala, Angel Andres

250

An Intermolecular Vibration Model for Lattice Ice  

Directory of Open Access Journals (Sweden)

Full Text Available Lattice ice with tetrahedral arrangement is studied using a modified Einstein’s model that incorporates the hindered translational and rotational vibration bands into a harmonic oscillation system. The fundamental frequencies for hindered translational and rotational vibrations are assigned based on the intermolecular vibration bands as well as thermodynamic properties from existing experimental data. Analytical forms for thermodynamic properties are available for the modified model, with three hindered translational bands at (65, 229, 229 cm-1 and three effective hindered rotational bands at 560 cm-1. The derived results are good for temperatures higher than 30 K. To improve the model below 30 K, Lorentzian broadening correction is added. This simple model helps unveil the physical picture of ice lattice vibration behavior.

Quinn M. Brewster

2010-06-01

251

An Intermolecular Vibration Model for Lattice Ice  

Directory of Open Access Journals (Sweden)

Full Text Available Lattice ice with tetrahedral arrangement is studied using a modified Einstein’s model that incorporates the hinderedtranslational and rotational vibration bands into a harmonic oscillation system. The fundamental frequencies forhindered translational and rotational vibrations are assigned based on the intermolecular vibration bands as well asthermodynamic properties from existing experimental data. Analytical forms for thermodynamic properties areavailable for the modified model, with three hindered translational bands at (65, 229, 229 cm-1 and three effectivehindered rotational bands at 560 cm-1. The derived results are good for temperatures higher than 30 K. To improvethe model below 30 K, Lorentzian broadening correction is added. This simple model helps unveil the physicalpicture of ice lattice vibration behavior.

Kuo-Ting Wang

2010-06-01

252

Intermolecular bonding and vibrations of phenol?H2O (D2O)  

Science.gov (United States)

Extensive ab initio calculations of the phenol?H2O complex were performed at the Hartree-Fock level, using the 6-31G(d,p) and 6-311++G(d,p) basis sets. Fully energy-minimized geometries were obtained for (a) the equilibrium structure, which has a translinear H bond and the H2O plane orthogonal to the phenol plane, similar to (H2O)2; (b) the lowest-energy transition state structure, which is nonplanar (C1 symmetry) and has the H2O moiety rotated by ±90°. The calculated MP2/6-311G++(d,p) binding energy including basis set superposition error corrections is 6.08 kcal/mol; the barrier for internal rotation around the H bond is only 0.4 kcal/mol. Intra- and intermolecular harmonic vibrational frequencies were calculated for a number of different isotopomers of phenol?H2O. Anharmonic intermolecular vibrational frequencies were computed for several intermolecular vibrations; anharmonic corrections are very large for the ?2 intermolecular wag. Furthermore, the H2O torsion ? around the H-bond axis, and the ?2 mode are strongly anharmonically coupled, and a two-dimensional ?/?2 potential energy surface was explored. The role of tunneling splitting due to the torsional mode is discussed and tunnel splittings are estimated for the calculated range of barriers. The theoretical studies were complemented by a detailed spectroscopic study of h-phenol?H2O and d-phenol?D2O employing two-color resonance-two-photon ionization and dispersed fluorescence emission techniques, which extends earlier spectroscopic studies of this system. The ?1 and ?2 wags of both isotopomers in the S0 and S1 electronic states are newly assigned, as well as several other weaker transitions. Tunneling splittings due to the torsional mode may be important in the S0 state in conjunction with the excitation of the intermolecular ? and ?2 modes.

Schütz, Martin; Bürgi, Thomas; Leutwyler, Samuel; Fischer, Thomas

1993-03-01

253

[High-energy electron-positron interactions  

International Nuclear Information System (INIS)

The purpose of the research was the study of electron-positron interactions at high energies using the Time Projection Chamber (TPC) at the Positron Electron Project (PEP) at SLAC. The TPC detector had an initial data gathering from 1982 until 1986 and accumulated a data sample with an integrated luminosity of -150 pb-1 at an electron-positron energy of 29 GeV. The data runs in the 1988--1990 time period (yielding ? pb-1) were abbreviated, due to the need of the laboratory to give highest priority to the new Stanford Linear Collider (SLC). The TPC collaboration decided in 1991 to discontinue data taking, but has continued the collaboration for the purpose of completing the analysis of the data. When UMass joined the SLD project, it was being designed as a new state-of-the-art detector for studying electron-positron interactions at energies in the vicinity of 91 GeV, the Z0 mass. The detector was completed and installed at the interaction point of the SLC in 1991, at which time an initial, ''engineering run'' allowed the debugging of detector components and provided a data sample of ?1,000 events with hadronic Z0 decays. In 1992 the SLC provided beams of polarized electrons and the SLD collected a data sample in excess of 11,000 hadronic Z0 events produced by polarized electrons, allowing unique measurements of some of the parameters of the standard model. This project is continuing to take data in 1993 with increased polarization and higher luminosity. This report reviews the research work performed under the contract, and survey's the physics results

254

IMPROPER HYDROGEN BONDS - A THEORETICAL STUDY ABOUT THE MOLECULAR STRUCTURE OF INTERMOLECULAR SYSTEMS FORMED BY H3C-H+?...X AND H3C+?...H-Y WITH X = CL- OR F- AND Y = CL OR F  

Directory of Open Access Journals (Sweden)

Full Text Available In this work is presented a theoretical study of the molecular properties of the H3C-H...X and H3C+?...H-Y intermolecular systems with X = CL- or F- and Y = Cl or F. In the H3C-H...X complex, it is formed a traditional hydrogen bond between the CL- or F- anions and the hydrogen atom of the methyl. About the H3C+?...H-Y complex, it was observed an improper hydrogen bond because the carbon atom of the methyl cation function as a proton acceptor. In this insight, the capacity of methane to interact with halogen anions (CL- or F- and molecular acids (HCl or HF was examined at the B3LYP/6-311++G(3df,3dp level of calculation. Moreover, the interaction strengths of the H3C-H...X and H3C+?...H-Y complexes was evaluated by computing their intermolecular distances and binding energies. Finally, QTAIM calculations also were executed with the purpose to examine the intermolecular interactions through the quantification of their electronic densities (p as well as by the interpretation of the Laplacian operators (.

B.G OLIVEIRA

2009-01-01

255

IMPROPER HYDROGEN BONDS - A THEORETICAL STUDY ABOUT THE MOLECULAR STRUCTURE OF INTERMOLECULAR SYSTEMS FORMED BY H3C-H+?...X AND H3C+?...H-Y WITH X = CL- OR F- AND Y = CL OR F  

Scientific Electronic Library Online (English)

Full Text Available SciELO Chile | Language: English Abstract in english In this work is presented a theoretical study of the molecular properties of the H3C-H...X and H3C+?...H-Y intermolecular systems with X = CL- or F- and Y = Cl or F. In the H3C-H...X complex, it is formed a traditional hydrogen bond between the CL- or F- anions and the hydrogen atom of the methyl. A [...] bout the H3C+?...H-Y complex, it was observed an improper hydrogen bond because the carbon atom of the methyl cation function as a proton acceptor. In this insight, the capacity of methane to interact with halogen anions (CL- or F-) and molecular acids (HCl or HF) was examined at the B3LYP/6-311++G(3df,3dp) level of calculation. Moreover, the interaction strengths of the H3C-H...X and H3C+?...H-Y complexes was evaluated by computing their intermolecular distances and binding energies. Finally, QTAIM calculations also were executed with the purpose to examine the intermolecular interactions through the quantification of their electronic densities (p) as well as by the interpretation of the Laplacian operators ().

B.G, OLIVEIRA.

256

Weak interactions at high energies. [Lectures, review  

Energy Technology Data Exchange (ETDEWEB)

Review lectures are presented on the phenomenological implications of the modern spontaneously broken gauge theories of the weak and electromagnetic interactions, and some observations are made about which high energy experiments probe what aspects of gauge theories. Basic quantum chromodynamics phenomenology is covered including momentum dependent effective quark distributions, the transverse momentum cutoff, search for gluons as sources of hadron jets, the status and prospects for the spectroscopy of fundamental fermions and how fermions may be used to probe aspects of the weak and electromagnetic gauge theory, studies of intermediate vector bosons, and miscellaneous possibilities suggested by gauge theories from the Higgs bosons to speculations about proton decay. 187 references. (JFP)

Ellis, J.

1978-08-01

257

Study of Intermolecular Interactions of Binary Liquid Mixtures by Measuring Intensive Macroscopic Properties at (303.15, 313.15 and 323.15 K and at Ambient Pressure  

Directory of Open Access Journals (Sweden)

Full Text Available Measurements of thermodynamic and transport properties have been adequately employed in understanding the nature of molecular systems and physico-chemical behavior in liquid mixtures. These properties are important from practical and theoretical point of view to understand liquid theory. In the present study density (? and viscosity (?, have been measured for a binary liquid mixture of Diacetone alcohol with benzene and chlorobenzene, over the entire composition range at 303.15 K, 313.15 K and 323.15 K and the evaluation of different excess properties. The viscosity values and excess values were fitted to respective models. It was found that in all cases, the data obtained fitted with the values correlated by the corresponding models very well. The molecular interactions existing between the components and comparison of liquid mixtures were also discussed.

T.R Kubendran

2009-02-01

258

Theoretical study of intermolecular energy transfer involving electronically excited molecules: He(/sup 1/S) + H/sub 2/(B /sup 1/. sigma. /sub u//sup +/). [Solution for coupled channel equations  

Energy Technology Data Exchange (ETDEWEB)

To further understanding of gas phase collision dynamics involving electronically-excited molecules, a fully quantum mechanical study of He + H/sub 2/(B /sup 1/..sigma../sub u//sup +/) was undertaken. Iterative natural orbital configuration interaction (CI) calculations were performed to obtain the interaction potential between He and H/sub 2/(B /sup 1/..sigma../sub u//sup +/). The potential energy surface (PES) is highly anisotropic and has a van der Waals well of about 0.03 eV for C/sub 2v/ approach. Avoided PES crossings occur with He + H/sub 2/(E,F /sup 1/..sigma../sub g//sup +/) and with He + H/sub 2/(X /sup 1/..sigma../sub g//sup +/) and cause a local maximum and a deep minimum in the He + H/sub 2/(B /sup 1/..sigma../sub u//sup +/) PES, respectively. The crossing with He + H/sub 2/(X /sup 1/..sigma../sub g//sup +/) provides a mechanism for fluorescence quenching. The computed CI energies were combined with previous multi-reference double excitation CI calculations and fit with analytic functions for convenience in scattering calculations. Accurate dipole polarizabilities and quadrupole moment of H/sub 2/(B /sup 1/..sigma../sub u//sup +/) were computed for use in the multipole expansion, which is the analytic form of the long-range PES. 129 refs., 28 figs., 35 tabs.

Grimes, R.M.

1986-11-01

259

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

Science.gov (United States)

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.

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

2014-04-01

260

Resonant Auger decay driving intermolecular Coulombic decay in molecular dimers  

Science.gov (United States)

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.

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

 
 
 
 
261

Differential requirements for retinal degeneration slow intermolecular disulfide-linked oligomerization in rods versus cones  

Digital Repository Infrastructure Vision for European Research (DRIVER)

It is commonly assumed that the ultrastructural organization of the rim region of outer segment (OS) discs in rods and lamellae in cones requires functional retinal degeneration slow/rod outer segment membrane protein 1 (Rds/Rom-1) complexes. Cysteine-150 (C150) in Rds has been implicated in intermolecular disulfide bonding essential for functional Rds complexes. Transgenic mice containing the Rds C150S mutation (C150S-Rds) failed to form higher-order Rds oligomers, although interactions betw...

Chakraborty, Dibyendu; Ding, Xi-qin; Conley, Shannon M.; Fliesler, Steven J.; Naash, Muna I.

2009-01-01

262

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

Energy Technology Data Exchange (ETDEWEB)

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)

Muenter, J.S.

1992-08-01

263

Intermolecularly-induced conformational disorder in ferrocene, 1-bromoferrocene and 1,1?-dibromoferrocene  

Science.gov (United States)

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 measurements on 1,1?-dibromoferrocene allowed to identify a new polymorph of the compound, with Tfus = 320.2 ± 0.1 K. On the whole, the results presented in this article represent illuminating examples of intermolecularly-induced conformational disorder in solid phase and of its relevance to polymorphism.

Silva, Patrícia A.; Maria, Teresa M. R.; Nunes, Cláudio M.; Eusébio, Maria Ermelinda S.; Fausto, Rui

2014-12-01

264

Tuning Aryl?CH···O Intermolecular Interactions on Pt(111)  

DEFF Research Database (Denmark)

Scanning tunneling microscopy (STM) data are reported for the room-temperature adsorption of 2,2,2-trifluoroacetophenone (TFAP), 2,2,2-trifluorovinylbenzene (TFVB), octafluoroacetophenone (OFAP), and methyl benzoate (MB) on Pt(111). The objective of the study is to establish the role of aryl?CH···O bonding in forming self-assembled low-nuclearity structures at room temperature and to compare aryl?CH···O bonding by ester and ketone carbonyl functions. The STM images clearly evidence the formation of homochiral dimers and trimers of TFAP, and density functional theory (DFT) calculations reveal aryl?CH···O bonding as the driving force for dimer formation. In contrast to TFAP, chemisorbed TFVB and OFAP do not form such self-assembled structures as they lack carbonyl and aryl?CH groups, respectively. The self-assembly of MB on Pt(111) differs from that of TFAP, in that it can form structures stabilized by one, as distinct from two, aryl?CH···O bonds. The results are discussed with respect to the enantioselective hydrogenation of ?-ketoesters on cinchona modified Pt catalysts.

Demers-Carpentier, Vincent; Laliberte, Marc-Andre?

2011-01-01

265

Analytical and Numerical Calculations of Diffusion Effects on the Intermolecular Multiple Quantum Coherences in Solution NMR  

International Nuclear Information System (INIS)

We calculated the analytical solutions to evaluate the effects of diffusion on the iMQCs in CRAZED pulse sequences. The obtained solution has been verified using the results of numerical simulation. The diffusional behaviors of the iMQCs during both the evolution and detection time periods could be examined by the analytical solution, which was quite different from those of the conventional NMR experiments. Understanding the difference in diffusional behaviors could lead to useful applications such as diffusion MRI based on the detection of iMQCs. The intermolecular multiple quantum coherences (iMQCs) that are generated by intermolecular dipolar interactions between distant spins on different molecules, have recently gained considerable attention because their properties are intrinsically different from those of conventional single quantum coherences (SQCs) in solution NMR. This feature allows for a wider range of applications in NMR and MR imaging

266

Chemical Exchange Saturation Transfer by Intermolecular Double Quantum Coherence  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A number of contrast enhancement effects based on the use of intermolecular multiple-quantum coherences, or distant dipolar field effects are known. This phenomenon is based on the dependence on the m-th power of the initial magnetization (where m is the coherence order used). In this article we describe the contrast enhancement based on chemical exchange saturation transfer and NOE, which is achieved by the use of intermolecular double-quantum coherences (iDQC). The method was validated usin...

Ling, Wen; Eliav, Uzi; Navon, Gil; Jerschow, Alexej

2008-01-01

267

Statefinder diagnosis for the interacting model of holographic dark energy  

CERN Document Server

In this paper, we investigate the holographic dark energy model with interaction between dark energy and dark matter, from the statefinder viewpoint. We plot the trajectories of the interacting holographic dark energy model for different interaction cases as well as for different values of the parameter $c$ in the statefinder-plane. The statefinder diagrams characterize the properties of the holographic dark energy and show the discrimination between the two cases with and without interaction. As a result, we show the influence of the interaction to the evolution of the universe in the statefinder diagrams. Moreover, as a complement to the statefinder diagnosis, we study the interacting holographic dark energy model in the $w-w'$ plane, which can provide us with a dynamical diagnosis.

Zhang, Jingfei; Liu, Hongya

2008-01-01

268

Energy Conscious Interactive Communication for Sensor Networks  

CERN Document Server

In this work, we are concerned with maximizing the lifetime of a cluster of sensors engaged in single-hop communication with a base-station. In a data-gathering network, the spatio-temporal correlation in sensor data induces data-redundancy. Also, the interaction between two communicating parties is well-known to reduce the communication complexity. This paper proposes a formalism that exploits these two opportunities to reduce the number of bits transmitted by a sensor node in a cluster, hence enhancing its lifetime. We argue that our approach has several inherent advantages in scenarios where the sensor nodes are acutely energy and computing-power constrained, but the base-station is not so. This provides us an opportunity to develop communication protocols, where most of the computing and communication is done by the base-station. The proposed framework casts the sensor nodes and base-station communication problem as the problem of multiple informants with correlated information communicating with a recipi...

Agnihotri, Samar

2007-01-01

269

Interaction between DBI-essence and other Dark Energies  

CERN Document Server

The present work considers interaction between DBI-essence and other candidates of dark energies like modified Chaplygin gas, hessence, tachyonic field, and new agegraphic dark energy. The potentials of the fields have been reconstructed under interaction and their evolutions have been viewed against cosmic time $t$ and scalar field $\\phi$. Equation of state parameters have also been obtained. The nature of potentials and the equation of state parameters of the dark energies have been found graphically in presence of interaction (both small and large interaction).

Chattopadhyay, Surajit

2010-01-01

270

Explosives sensing by using electron-rich supramolecular polymers: role of intermolecular hydrogen bonding in significant enhancement of sensitivity.  

Science.gov (United States)

We demonstrate here that supramolecular interactions enhance the sensitivity towards detection of electron-deficient nitro-aromatic compounds (NACs) over discrete analogues. NACs are the most commonly used explosive ingredients and are common constituents of many unexploded landmines used during World War?II. In this study, we have synthesised a series of pyrene-based polycarboxylic acids along with their corresponding discrete esters. Due to the electron richness and the fluorescent behaviour of the pyrene moiety, all the compounds act as sensors for electron-deficient NACs through a fluorescence quenching mechanism. A Stern-Volmer quenching constant determination revealed that the carboxylic acids are more sensitive than the corresponding esters towards NACs in solution. The high sensitivity of the acids was attributed to supramolecular polymer formation through hydrogen bonding in the case of the acids, and the enhancement mechanism is based on an exciton energy migration upon excitation along the hydrogen-bond backbone. The presence of intermolecular hydrogen bonding in the acids in solution was established by solvent-dependent fluorescence studies and dynamic light scattering (DLS) experiments. In addition, the importance of intermolecular hydrogen bonds in solid-state sensing was further explored by scanning tunnelling microscopy (STM) experiments at the liquid-solid interface, in which structures of self-assembled monolayer of the acids and the corresponding esters were compared. The sensitivity tests revealed that these supramolecular sensors can even detect picric acid and trinitrotoluene in solution at levels as low as parts per trillion (ppt), which is much below the recommended permissible level of these constituents in drinking water. PMID:25187022

Gole, Bappaditya; Song, Wentao; Lackinger, Markus; Mukherjee, Partha Sarathi

2014-10-13

271

An analysis of two textbooks on the topic of intermolecular forces  

Directory of Open Access Journals (Sweden)

Full Text Available 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 according to the Singapore high school chemistry syllabus. The authors found that the two textbooks did not adequately discuss the electrostatic nature of intermolecular forces, and the factors influencing the polarity of bonds/molecules, hydrogen bonding and instantaneous dipole-induced dipole interactions. The insufficient coverage of the above areas may lead to students having alternative conceptions of intermolecular forces as they may have incomplete or little understanding of the concepts involved and relationships between these concepts. Thus, teachers need to analyse textbooks carefully before using the textbooks so that they can be more aware of the difficulties that students may face when reading the textbooks, and attend to these areas by careful elaboration and integration of concepts in their lessons.

Tan Kim Chwee, Daniel

2004-04-01

272

Breaking parameter degeneracy in interacting dark energy models from observations  

International Nuclear Information System (INIS)

We study the interacting dark energy model with time varying dark energy equation of state. We examine the stability in the perturbation formalism and the degeneracy among the coupling between dark sectors, the time-dependent dark energy equation of state and dark matter abundance in the cosmic microwave background radiation. Further we discuss the possible ways to break such degeneracy by doing global fitting using the latest observational data and we get a tight constraint on the interaction between dark sectors.

273

Energies and physicochemical properties of cation-? interactions in biological structures.  

Science.gov (United States)

The cation-? interactions occur frequently within or between proteins due to six (Phe, Tyr, Trp, Arg, Lys, and His) of the twenty natural amino acids potentially interacting with metallic cations via these interactions. In this study, quantum chemical calculations and molecular orbital (MO) theory are used to study the energies and properties of cation-? interactions in biological structures. The cation-? interactions of H? and Li? are similar to hydrogen bonds and lithium bonds, respectively, in which the small, naked cations H? and Li? are buried deep within the ?-electron density of aromatic molecules, forming stable cation-? bonds that are much stronger than the cation-? interactions of other alkali metal cations. The cation-? interactions of metallic cations with atomic masses greater than that of Li? arise mainly from the coordinate bond comprising empty valence atomic orbitals (AOs) of metallic cations and ?-MOs of aromatic molecules, though electrostatic interactions may also contribute to the cation-? interaction. The binding strength of cation-? interactions is determined by the charge and types of AOs in the metallic cations. Cation-? interaction energies are distance- and orientation-dependent; energies decrease with the distance (r) and the orientation angle (?). In solution, the cation-? energies decrease with the increase of the dielectric constant (?) of the solvent; however, solvation has less influence on the H?-? and H?O?-? interactions than on interactions with other cations. The conclusions from this study provide useful theoretical insights into the nature of cation-? interactions and may contribute to the development of better force field parameters for describing the molecular dynamics of cation-? interactions within and between proteins. PMID:22306412

Du, Qi-Shi; Meng, Jian-Zong; Liao, Si-Ming; Huang, Ri-Bo

2012-04-01

274

Exactly solved models of interacting dark matter and dark energy  

CERN Document Server

We introduce an effective one-fluid description of the interacting dark sector in a spatially flat Friedmann-Robertson-Walker space-time and investigate the stability of the power-law solutions. We find the "source equation" for the total energy density and determine the energy density of each dark component. We study linear and nonlinear interactions which depend on the dark matter and dark energy densities, their first derivatives, the total energy density with its derivatives up to second order and the scale factor. We solve the evolution equations of the dark components for both interactions, examine exhaustively several examples and show cases where the problem of the coincidence is alleviated. We show that a generic nonlinear interaction gives rise to the "relaxed Chaplygin gas model" whose effective equation of state includes the variable modified Chaplygin gas model while some others nonlinear interactions yield de Sitter and power-law scenarios.

Chimento, Luis P

2012-01-01

275

Protein-Protein Interaction Analysis by Docking  

Directory of Open Access Journals (Sweden)

Full Text Available Based on a protein-protein docking approach we have developed a procedure to verify or falsify protein-protein interactions that were proposed by other methods such as yeast-2-hybrid assays. Our method currently utilizes intermolecular energies but can be expanded to incorporate additional terms such as amino acid based pair-potentials. We show some early results that demonstrate the general applicability of our approach.

Stephan Ederer

2009-03-01

276

Vibrational Spectra of ??-Type BEDT-TTF Salts: Relationship between Conducting Property, Time-Averaged Site Charge and Inter-Molecular Distance  

Directory of Open Access Journals (Sweden)

Full Text Available The relationship between the conducting behavior and the degree of charge fluctuation in the ??-type BEDT-TTF salts is reviewed from the standpoints of vibrational spectroscopy and crystal structure. A group of ??-type ET salts demonstrates the best model compounds for achieving the above relationship because the two-dimensional structure is simple and great diversity in conducting behavior is realized under ambient pressure. After describing the requirement for the model compound, the methodology for analyzing the results of the vibrational spectra is presented. Vibrational spectroscopy provides the time-averaged molecular charge, the charge distribution in the two-dimensional layer, and the inter-molecular interactions, etc. The experimental results applied to 2/3-filled and 3/4-filled ??-type ET salts are reported. These experimental results suggest that the conducting property, the difference in the time-averaged molecular charges between the ionic and neutral-like sites, the alternation in the inter-molecular distances and the energy levels in the charge distributions are relevant to one another. The difference in the time-averaged molecular charges, ??, is a useful criterion for indicating conducting behavior. All superconductors presented in this review are characterized as small but finite ??.

Takashi Yamamoto

2012-07-01

277

Interacting Holographic dark energy in chameleon tachyon cosmology  

CERN Document Server

We propose in this paper an interacting holographic dark energy (IHDE) model in chameleon--tachyon cosmology by interaction between the components of the dark sectors. In the formalism, the interaction term emerges from the scalar field coupling matter lagrangian in the model rather than being inserted into the formalism as an external source for the interaction. The correspondence between the tachyon field and the holographic dark energy (HDE) densities allows to reconstruct the tachyon scalar field and its potential in a flat FRW universe. The model can show the accelerated expansion of the universe and satisfies the observational data.

Farajollahi, H; Fadakar, G Farpour

2011-01-01

278

Cosmological Evolution With Interaction Between Dark Energy And Dark Matter  

CERN Document Server

In this review we consider in detail different theoretical topics associated with interaction in the dark sector. We study linear and nonlinear interactions which depend on the dark matter and dark energy densities. We consider a number of different models (including the holographic dark energy and dark energy in a fractal universe) with interacting dark energy (DE) and dark matter (DM), have done a thorough analysis of these models. The main task of this review was not only to give an idea about the modern set of different models of dark energy, but to show how much can be diverse dynamics of the universe in these models. We find that the dynamics of a Universe that contains interaction in the dark sector can differ significantly from the Standard Cosmological Model (SCM).

Bolotin, Yu L; Lemets, O A; Yerokhin, D A

2013-01-01

279

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

Science.gov (United States)

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

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

2014-10-01

280

Load Matching and Grid Interaction of Net Zero Energy Buildings  

DEFF Research Database (Denmark)

“Net Zero Energy Building” has become a prominent wording to describe the synergy of energy efficient building and renewable energy utilization to reach a balanced energy budget over a yearly cycle. Taking into account the energy exchange with a grid infrastructure overcomes the limitations of seasonal energy storage on-site. Even though the wording “Net Zero Energy Building” focuses on the annual energy balance, large differences may occur between solution sets in the amount of grid interaction needed to reach the goal. The paper reports on the analysis of example buildings concerning the load matching and grid interaction. Indices to describe both issues are proposed and foreseen as part of a harmonized definition framework. The work is part of subtask A of the IEA SHCP Task40/ECBCS Annex 52: “Towards Net Zero Energy Solar Buildings”.

Voss, Karsten; Sartori, Igor

2010-01-01

 
 
 
 
281

Understanding of nuclear quadrupole interactions of 35Cl, 79Br and 129I and binding energies of solid halogens at first-principles level  

International Nuclear Information System (INIS)

This paper deals with the understanding at a first-principles level of the nuclear quadrupole interaction (NQI) parameters of solid chlorine, bromine and iodine as well as the intermolecular binding of these molecules in the solid. The electronic structure investigations that we have carried out to study these properties of the solid halogens are based on the Hartree-Fock Cluster approach using the Roothaan variational procedure with electron correlation effects included using many-body perturbation theory with the empty orbitals used in the perturbation theory investigations for the excited states. The results of our investigations provide good agreement with the measured NQI parameters primarily from the Hartree-Fock one electron wave-functions with many-body effects making minor contributions. The binding (dissociation) energies for the molecules with the solid state environment on the other hand arises from intermolecular many body effects identified as the Van der Waals attraction with one-electron Hartree-Fock contribution being repulsive in nature.

282

Intermolecular Casimir-Polder Forces in Water and near Surfaces  

CERN Document Server

The Casimir-Polder force is an important long range interaction involved in adsorption and desorption of molecules in fluids. We explore Casimir-Polder interactions between methane molecules in water, and between a molecule in water near SiO2 and hexane surfaces. Inclusion of the finite molecular size in the expression for the Casimir-Polder energy leads to estimates of the dispersion contribution to the binding energies between molecules and between one molecule and a planar surface.

Thiyam, Priyadarshini; Sernelius, Bo E; Parsons, Drew F; Malthe-Sørenssen, Anders; Boström, Mathias

2014-01-01

283

Chirality of weakly bound complexes: The potential energy surfaces for the hydrogen-peroxide-noble-gas interactions  

Science.gov (United States)

We consider the analytical representation of the potential energy surfaces of relevance for the intermolecular dynamics of weakly bound complexes of chiral molecules. In this paper we study the H2O2-Ng (Ng=He, Ne, Ar, Kr, and Xe) systems providing the radial and the angular dependence of the potential energy surface on the relative position of the Ng atom. We accomplish this by introducing an analytical representation which is able to fit the ab initio energies of these complexes in a wide range of geometries. Our analysis sheds light on the role that the enantiomeric forms and the symmetry of the H2O2 molecule play on the resulting barriers and equilibrium geometries. The proposed theoretical framework is useful to study the dynamics of the H2O2 molecule, or other systems involving O-O and S-S bonds, interacting by non-covalent forces with atoms or molecules and to understand how the relative orientation of the O-H bonds changes along collisional events that may lead to a hydrogen bond formation or even to selectivity in chemical reactions.

Roncaratti, L. F.; Leal, L. A.; Pirani, F.; Aquilanti, V.; e Silva, G. M.; Gargano, R.

2014-10-01

284

Electron-gas plus damped-dispersion model for intermolecular forces: the rare-gas and H2-He, H2-Ne, and H2-Ar potentials  

International Nuclear Information System (INIS)

The modified Gordon-Kim (MGK) electron-gas model for the calculation of the short-range repulsive interactions between closed-shell atoms and molecules is used with a damped-dispersion term of a form suggested by Hepburn et al. to calculate the intermolecular potentials between the rare-gas atoms and H2-He, H2-Ne, and H2-Ar. The damping function for the dispersion energies is found by comparison with the experimental Ar-Ar potential and is then used without change for all other interactions. Except for interactions involving Ne atoms, the results for the atom-atom interactions are uniformly quite good, with an average deviation from experiment in the position of the minimum (neglecting those involving Ne atoms) of only 0.7%. Both the radical V0(r) and anisotropic V2(r) terms of the atom-molecule results are compared with experiment. The calculated V0(r) potentials for He-H2 and Ar-H2 show close agreement with experiment, though the V2 terms are less well determined. All interactions involving Ne atoms are too repulsive. The errors in the potentials involving Ne atoms are attributed to errors in the treatment of the exchange energy in the MGK model. 29 references, 11 figures, 5 tables

285

Pollution prevention and energy conservation: Understanding the interactions  

International Nuclear Information System (INIS)

The traditional view holds that pollution prevention is good for energy conservation and vice versa. Analysis of pollution prevention and energy conservation activities indicates, however, that interactions and synergies between environmental and energy factors can mean that pollution prevention can be energy intensive and, conversely, that energy conservation can lead to increased pollution. Full cost accounting, taking into account all media, must be performed before precise pollution prevention-energy conservation interrelationships can be characterized and quantified. Use of a pollution prevention-energy conservation matrix can further this understanding

286

Hadron-nucleus interactions at high energy  

International Nuclear Information System (INIS)

Properties of energetic secondaries produced at large angles using 800 GeV incident protons are presented. H2, Be, C, Al, Cu and Pb targets were used for the study. The yields for producing such secondaries vary as A/sup ?/ where A is the atomic mass number of the target and ? attains values as large as 1.6. There is evidence that jet-like events have ? values approaching unity, indicating a hard scattering mechanism may be occurring. Events with large values of target-fragmentation energy have, on average, large values of energy in the central region and small values of forward-going energy. Energy flows and number of secondaries are independent of the target when events with similar amounts of energy in the central region are studied

287

High energy e+e- interactions  

International Nuclear Information System (INIS)

A review is given about the experimental studies of e+e- interactions. After a description of the PETRA and PEP storage rings the structure of leptons and the weak neutral current contributions to lepton pair production are discussed. Then experiments for the search for new particles, the jet formation in e+e- annihilation, and the quark and gluon fragmentation are described. (HSI)

288

Magnon energies and exchange interactions in terbium  

DEFF Research Database (Denmark)

The magnon density of states, and hence the magnetic contribution to the specific heat, and also the exchange interaction between ions in the same sublattice have been calculated for Tb at 90°K, using experimental results obtained by inelastic neutron scattering.

Houmann, Jens Christian Gylden

1968-01-01

289

Magnon energies and exchange interactions in terbium  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The magnon density of states, and hence the magnetic contribution to the specific heat, and also the exchange interaction between ions in the same sublattice have been calculated for Tb at 90°K, using experimental results obtained by inelastic neutron scattering.

Houmann, Jens Christian Gylden

2011-01-01

290

Interacting holographic dark energy models: A general approach  

CERN Document Server

Dark energy models inspired by the cosmological holographic principle are studied in homogeneous isotropic spacetime with a general choice for the dark energy density $\\rho_d=3(\\alpha H^2+\\beta\\dot{H})$. Special choices of the parameters enable us to obtain three different holographic models, including the holographic Ricci dark energy(RDE) model. Effect of interaction between dark matter and dark energy on the dynamics of those models are investigated for different popular forms of interaction. It is found that crossing of phantom divide can be avoided in RDE models for $\\beta>0.5$ irrespective of the presence of interaction. A choice of $\\alpha=1$ and $\\beta=2/3$ leads to a varying $\\Lambda$-like model introducing an IR cutoff length $\\Lambda^{-1/2}$. It is concluded that among the popular choices an interaction of the form $Q\\propto H\\rho_m$ suits the best in avoiding the coincidence problem in this model.

Som, S

2014-01-01

291

Non-flat universe and interacting dark energy model  

International Nuclear Information System (INIS)

For non-flat universe of k0, we investigate a model of the interacting holographic dark energy with cold dark matter (CDM). There exists a mixture of two components arisen from decaying of the holographic dark energy into CDM. In this case we use the effective equations of state (??eff,?meff) instead of the native equations of state (??,?m). Consequently, we show that interacting holographic energy models in non-flat universe cannot accommodate a transition from the dark energy to the phantom regime

292

?-? interaction energy in sub(??)6He and OBE potentials  

International Nuclear Information System (INIS)

In this paper we evaluate the ?-? interaction energy in sub(??)6He by using OBE ?-? potentials constructed on the basis of the Nijmegen models. The structure of sub(??)6He was reinvestigated by solving the ? + ? + ? three-body equation, although simple effective interactions were used. (orig./HSI)

293

Interacting Ghost Dark Energy Models in the Higher Dimensional Cosmology  

CERN Document Server

We investigate interacting ghost dark energy models in higher dimensional cosmology. We attempt to model dark matter within a barotropic fluid with $P_{b}=\\omega(t)_{b}\\rho$. In this work we consider four different models based on choosing equation of state parameter and interaction term. We confirm that our models agree with observational data.

Sadeghi, J; Movsisyan, A; Farahani, H

2014-01-01

294

INTERACTION ENERGIES IN NON WATSON-CRICK PAIRS: AN AB INITIO STUDY OF G·U AND U·U PAIRS  

Directory of Open Access Journals (Sweden)

Full Text Available Ab initio calculations at the MP2/6-31G** level have been carried out on the non-Watson-Crick nucleic acids pairs G·U and U·U to obtain the interaction energies and to see whether the derived values are comparable or not with the canonical G-C, A-T and A-U pairs. Optimized geometries of the pairs show that the structural parameters of the isolated bases differ very little on pairing. The guanine -NH2 group does not participate in the hydrogen bonding formation and possesses a pyramidal structure; its intrinsic nonplanarity plays an important role in the out-of-plane intermolecular interactions. Thus, the G·U pair projects three hydrogen bonding acceptor sites, namely, N7(G, O6(G and O4(U to the RNA major groove. The interaction energy (DHºint calculated for the G·U pair (-13.6 kcal/mol is comparable to that determined for A-T (-13.0 kcal/mol, but considerable smaller than the experimental value reported for G-C (-21.0 kcal/mol. The U·U pair follows the trend that pairing between pyrimidines bases should have lower interacting energies than purine-pyrimidine pairs

SANDRA T MADARIAGA

2005-03-01

295

Impact parameters of inelastic hadron interaction at high energies  

International Nuclear Information System (INIS)

The expression for impact parameters of inelastic hadron-hadron interaction with the defined number of charged particles in the final state is obtained from the absorptive model. The model satisfy the unitary condition in the direct reaction channel. The impact parameters of the inelastic pp interaction at ISR energies are calculated. It is found that the impact parameters of multiple production processes decrease with multiplicity growth and at fixed multiplicity they increase with energy

296

Interacting agegraphic quintessence dark energy in non-flat universe  

International Nuclear Information System (INIS)

We establish a correspondence between interacting agegraphic dark energy model and the quintessence scalar field in a non-flat universe. We demonstrate that the agegraphic evolution of the universe can be described completely by a single quintessence scalar field. We also reconstruct the potential of the interacting agegraphic quintessence dark energy as well as the dynamics of the quintessence scalar field which describe the quintessence cosmology

297

Varying vacuum energy of a self-interacting scalar field  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Understanding mechanisms capable of altering the vacuum energy is currently of interest in field theories and cosmology. We consider an interacting field and show that the vacuum energy naturally takes any value between its maximum and zero because interaction affects the number of operating field modes, the assertion that involves no assumptions or postulates. The mechanism is similar to the recently discussed temperature evolution of collective modes in liquids. The cosmol...

Trachenko, Kostya

2014-01-01

298

Bioluminescence resonance energy transfer (BRET) imaging of protein-protein interactions within deep tissues of living subjects.  

Science.gov (United States)

Identifying protein-protein interactions (PPIs) is essential for understanding various disease mechanisms and developing new therapeutic approaches. Current methods for assaying cellular intermolecular interactions are mainly used for cells in culture and have limited use for the noninvasive assessment of small animal disease models. Here, we describe red light-emitting reporter systems based on bioluminescence resonance energy transfer (BRET) that allow for assaying PPIs both in cell culture and deep tissues of small animals. These BRET systems consist of the recently developed Renilla reniformis luciferase (RLuc) variants RLuc8 and RLuc8.6, used as BRET donors, combined with two red fluorescent proteins, TagRFP and TurboFP635, as BRET acceptors. In addition to the native coelenterazine luciferase substrate, we used the synthetic derivative coelenterazine-v, which further red-shifts the emission maxima of Renilla luciferases by 35 nm. We show the use of these BRET systems for ratiometric imaging of both cells in culture and deep-tissue small animal tumor models and validate their applicability for studying PPIs in mice in the context of rapamycin-induced FK506 binding protein 12 (FKBP12)-FKBP12 rapamycin binding domain (FRB) association. These red light-emitting BRET systems have great potential for investigating PPIs in the context of drug screening and target validation applications. PMID:21730157

Dragulescu-Andrasi, Anca; Chan, Carmel T; De, Abhijit; Massoud, Tarik F; Gambhir, Sanjiv S

2011-07-19

299

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

Science.gov (United States)

We have investigated the physical stability of amorphous curcumin dispersions and the role of curcumin-polymer intermolecular interactions in delaying crystallization. Curcumin is an interesting model compound as it forms both intra and intermolecular hydrogen bonds in the crystal. A structurally diverse set of amorphous dispersion polymers was investigated; poly(vinylpyrrolidone), Eudragit E100, carboxymethyl cellulose acetate butyrate, hydroxypropyl methyl cellulose (HPMC) and HPMC-acetate succinate. Mid-infrared spectroscopy was used to determine and quantify the extent of curcumin-polymer interactions. Physical stability under different environmental conditions was monitored by powder X-ray diffraction. Curcumin chemical stability was monitored by UV-Vis spectroscopy. Isolation of stable amorphous curcumin was difficult in the absence of polymers. Polymers proved to be effective curcumin crystallization inhibitors enabling the production of amorphous solid dispersions; however, the polymers showed very different abilities to inhibit crystallization during long-term storage. Curcumin intramolecular hydrogen bonding reduced the extent of its hydrogen bonding with polymers; hence most polymers were not highly effective crystallization inhibitors. Overall, polymers proved to be crystallization inhibitors, but inhibition was limited due to the intramolecular hydrogen bonding in curcumin, which leads to a decrease in the ability of the polymers to interact at a molecular level. PMID:24192454

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

2014-12-01

300

Strong impact of protonation and deprotonation on intermolecular Coulombic decay  

International Nuclear Information System (INIS)

Intermolecular Coulombic decay (ICD) is an ultrafast relaxation mechanism of a highly excited system embedded in a chemical environment. Our theoretical investigation of ammonia clusters shows that the ICD efficiency can be regulated by protonation or deprotonation. It is suggested that by varying ICD rate through changing the environmental pH value a control over the relaxation dynamics can be achieved.

 
 
 
 
301

Intermolecular Hydrogen Transfer in Isobutane Hydrate  

Directory of Open Access Journals (Sweden)

Full Text Available Electron spin resonance (ESR spectra of butyl radicals induced with ?-ray irradiation in the simple isobutane (2-methylpropane hydrate (prepared with deuterated water were investigated. Isothermal annealing results of the ?-ray-irradiated isobutane hydrate reveal that the isobutyl radical in a large cage withdraws a hydrogen atom from the isobutane molecule through shared hexagonal-faces of adjacent large cages. During this “hydrogen picking” process, the isobutyl radical is apparently transformed into a tert-butyl radical, while the sum of isobutyl and tert-butyl radicals remains constant. The apparent transformation from isobutyl to tert-butyl radicals is an irreversible first-order reaction and the activation energy was estimated to be 35 ± 3 kJ/mol, which was in agreement with the activation energy (39 ± 5 kJ/mol of hydrogen picking in the ?-ray-irradiated propane hydrate with deuterated water.

Takeshi Sugahara

2012-05-01

302

Noncovalent cation-? interactions - their role in nature.  

Science.gov (United States)

Non-covalent interactions play an extremely important role in organisms. The main non-covalent interactions in nature are: ion-ion interactions, dipole-dipole interactions, hydrogen bonds, and van der Waals interactions. A new kind of intermolecular interactions - cation-? interactions - is gaining increasing attention. These interactions occur between a cation and a ? system. The main contributors to cation-? interactions are electrostatic, polarization and, to a lesser extent, dispersion interactions. At first, cation-? interactions were studied in a gas phase, with metal cation-aromatic system complexes. The characteristics of these complexes are as follows: an increase of cation atomic number leads to a decrease of interaction energy, and an increase of cation charge leads to an increase of interaction energy. Aromatic amino acids bind with metal cations mainly through interactions with their main chain. Nevertheless, cation-? interaction with a hydrophobic side chain significantly enhances binding energy. In water solutions most cations preferentially interact with water molecules rather than aromatic systems. Cation-? interactions occur in environments with lower accessibility to a polar solvent. Cation-? interactions can have a stabilizing role on the secondary, tertiary and quaternary structure of proteins. These interactions play an important role in substrate or ligand binding sites in many proteins, which should be taken into consideration when the screening of effective inhibitors for these proteins is carried out. Cation-? interactions are abundant and play an important role in many biological processes. PMID:25380210

Fink, Krzysztof; Boraty?ski, Janusz

2014-01-01

303

Phase-space analysis on interactions in dark energy models  

Energy Technology Data Exchange (ETDEWEB)

To alleviate the ''cosmic triple coincidence'' problem, we add two kinds of interacting term in scalar field models which make radiation, matter and dark energy causally connected. Specifically, the interacting term ({gamma}{phi}{sup 2}) is being used in dark energy models for the first time. By the phase-space analysis, the evolution of our universe is investigated. We find that the eigenvalues in the radiation dominated phases could be all positive and the interactions help alleviate the ''cosmic triple coincidence'' problem in quintessence model. (orig.)

Zhang, Yi [Chongqing University of Posts and Telecommunications, College of Mathematics and Physics, Chongqing (China); Beijing Normal University, Department of Astronomy, Beijing (China); Li, Hui [Yantai University, Department of Physics, Yantai (China); Gong, Yungui [Chongqing University of Posts and Telecommunications, College of Mathematics and Physics, Chongqing (China); Zhu, Zong-Hong [Beijing Normal University, Department of Astronomy, Beijing (China)

2012-06-15

304

Interacting dark sector with variable vacuum energy  

Science.gov (United States)

We examine a cosmological scenario where dark matter is coupled to a variable vacuum energy while baryons and photons are two decoupled components for a spatially flat Friedmann-Robertson-Walker spacetime. We apply the ?2 method to the updated observational Hubble data for constraining the cosmological parameters and analyze the amount of dark energy in the radiation era. We show that our model fulfills the severe bound of ?x(z?1100)survey, the Atacama Cosmology Telescope, and the South Pole Telescope along with the future constraints achievable by the Euclid and CMBPol experiments, and fulfills the stringent bound ?x(z?1010)big-bang nucleosynthesis epoch.

Chimento, Luis P.; Richarte, Martín G.; García, Iván E. Sánchez

2013-10-01

305

New energy performance indexes for energy-efficient interactive buildings  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This paper argues that promoting energy supply by Renewable Energy Sources (RES) in buildings, namely residential, requires additional informative indexes to be included in buildings Energy Performance Certificates. The load-generation approach for the energy balance is here discussed, and compared with the current recommended by CEN/TR 15615, i.e. the delivered-exported approach. Besides the Energy Performance Index, which takes the same value for both approaches, other indexes are studied. ...

Pana?o, Marta Oliveira; Camelo, Susana; Gonc?alves, Helder

2013-01-01

306

Calculations of Potential Energy Surfaces Using Monte Carlo Configuration Interaction  

CERN Document Server

We apply the method of Monte Carlo configuration interaction (MCCI) to calculate ground-state potential energy curves for a range of small molecules and compare the results with full configuration interaction. We show that the MCCI potential energy curve can be calculated to relatively good accuracy, as quantified using the non-parallelity error, using only a very small fraction of the FCI space. In most cases the potential curve is of better accuracy than its constituent single-point energies. We finally test the MCCI program on systems with basis sets beyond full configuration interaction: a lattice of fifty hydrogen atoms and ethylene. The results for ethylene agree fairly well with other computational work while for the lattice of fifty hydrogens we find that the fraction of the full configuration interaction space we were able to consider appears to be too small as, although some qualitative features are reproduced, the potential curve is less accurate.

Coe, J P; Paterson, M J; 10.1063/1.4767052

2012-01-01

307

Hadronic interactions and cosmic rays at ultra high energies  

Directory of Open Access Journals (Sweden)

Full Text Available Observations of ultra high energy cosmic rays allow in principle to obtain information about the properties of hadronic interactions in an energy range not accessible with particle accelerators. This task is however complicated by the fact that the composition of the primary CR is not known and must be estimated from the same data set. Solving the ambiguity between composition and hadronic interaction modeling is a central problem for UHECR observations. Recently the Pierre Auger collaboration has presented an estimate of the p–air interaction length at a laboratory energy E0 ? 1018.24?eV. The interaction length is inferred from the shape of the tail of the Xmax distribution of the observed showers, following a method pioneered by the Fly's Eye group. In this work we want to analyse critically this method, and discuss its potential for further studies.

Lipari Paolo

2013-06-01

308

Intermediate-energy hadron interactions, II  

International Nuclear Information System (INIS)

The topics to be covered are as follows. I'll begin with new developments in NN ? NN? reactions. This will provide a natural lead-in to the main topic of this talk, which is dibaryons. This will be followed by discussion of elastic proton-deuteron and inelastic proton-alpha scattering. Then there will be a brief mention of two technical developments. Finally, I'll close by giving short remarks about two peculiarities that were found by theorists looking at strong interaction amplitudes. 15 refs., 3 figs

309

Energy Centroids in the presence of random interactions  

CERN Document Server

In this paper we study energy centroids such as those with fixed spin and isospin, those with fixed irreducible representations for bosons, in the presence of random two-body and/or three-body interactions. Our results show that regularities of energy centroids of fixed spin states reported in earlier works are more robust than expected.

Zhao, Y M; Yoshida, N; Ogawa, K; Yoshinaga, N; Kota, V K B

2005-01-01

310

Strong interactions studies with medium energy probes  

International Nuclear Information System (INIS)

This report discusses work on: charmonium spectroscopy; proton form- factor in the time-like region; proton-antiproton forward scattering; QCD scaling laws; light quark spectroscopy; high resolutions electron scattering; quasi-free electron scattering; and low energy pion double charge exchange

311

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

Science.gov (United States)

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

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

2012-09-01

312

Interacting Viscous Dark Energy in Bianchi Type-III Universe  

CERN Document Server

In this paper we study the evolution of the equation of state of viscous dark energy in the scope of Bianchi type III space-time. We consider the case when the dark energy is minimally coupled to the perfect fluid as well as direct interaction with it. The viscosity and the interaction between the two fluids are parameterized by constants $\\zeta_{0}$ and $\\sigma$ respectively. We have made a detailed investigation on the cosmological implications of this parametrization. To differentiate between different dark energy models, we have performed a geometrical diagnostic by using the statefinder pair $\\{s, r\\}$.

Amirhashchi, Hassan

2014-01-01

313

Proton tunnelling in intermolecular hydrogen bonds  

International Nuclear Information System (INIS)

The wavefunctions of particles extend beyond the classically accessible regions of potential energy-surfaces (PES). A manifestation of this partial delocalization is the quantum-mechanical tunneling effect which enables a particle to escape from a metastable potential-well. Tunnelling is most important for the lightest atoms, so that the determination of its contribution to proton transfer, one of the most fundamental chemical reactions, is an important issue. QENS and NMR techniques have been employed to study the motion of protons in the hydrogen bond of benzoic-acid crystals, a system which has emerged as a particularly suitable model since proton transfer occurs in a near symmetric double-well potential. The influence of quantum tunnelling was revealed and investigated in these experiments. This work provides an experimental benchmark for theoretical descriptions of translational proton-tunnelling. (author)

314

Self-energies and the interactions of particles with surfaces  

International Nuclear Information System (INIS)

We have in this paper reviewed the method of treating many-body problems by means of an effective interaction self-energy. We have developed an alternatvie approach to the self-energy which is simpler and more straight-forward than standard methods, and we have illustrated its use with two examples of a charge interacting with a metal surface. In each case the self-energy produces the classical image potential together with corrections due to quantum mechanical effects. This method has also been successfully applied to the problem of an atom interacting with a surface. Corrections to the Van der Waals dispersion force are obtained, and via the non-conservative imaginary parts to /summation//sub i/(z) we discuss transition rates and energy exchange. 14 refs., 1 fig

315

Self-energies and the interactions of particles with surfaces  

Energy Technology Data Exchange (ETDEWEB)

We have in this paper reviewed the method of treating many-body problems by means of an effective interaction self-energy. We have developed an alternatvie approach to the self-energy which is simpler and more straight-forward than standard methods, and we have illustrated its use with two examples of a charge interacting with a metal surface. In each case the self-energy produces the classical image potential together with corrections due to quantum mechanical effects. This method has also been successfully applied to the problem of an atom interacting with a surface. Corrections to the Van der Waals dispersion force are obtained, and via the non-conservative imaginary parts to /summation//sub i/(z) we discuss transition rates and energy exchange. 14 refs., 1 fig.

Manson, J.R.; Ritchie, R.H.; Echenique, P.M.; Gras-Marti, A.

1987-01-01

316

Interacting dark sector with variable vacuum energy  

CERN Document Server

We examine a cosmological scenario where dark matter is coupled to a variable vacuum energy while baryons and photons are two decoupled components for a spatially flat Friedmann-Robertson-Walker spacetime. We apply the $\\chi^{2}$ method to the updated observational Hubble data for constraining the cosmological parameters and analyze the amount of dark energy in the radiation era. We show that our model fulfills the severe bound of $\\Omega_{x}(z\\simeq 1100)<0.009$ at the $2\\sigma$ level, so it is consistent with the recent analysis that includes cosmic microwave background anisotropy measurements from the Planck survey, the Atacama Cosmology Telescope, and the South Pole Telescope along with the future constraints achievable by the Euclid and CMBPol experiments, and fulfills the stringent bound $\\Omega_{x}(z\\simeq 10^{10})<0.04$ at the $2\\sigma$ level in the big-bang nucleosynthesis epoch.

Chimento, Luis P; García, Iván E Sánchez

2013-01-01

317

Low-energy antiproton-neon interaction  

International Nuclear Information System (INIS)

By means of a streamer chamber exposed to the LEAR antiproton beams, the total reaction cross sections, the charged-prong multiplicity distributions and lower limits for the production of negative pions and Ksub(s)0 in the anti p-Ne interaction were measured at 19.6, 48.7 and 179.6 MeV. Annihilation was found to be dominant over all other non-elastic anti p-Ne processes. An analysis of Ne and other nuclei data in the frame of the Glauber theory allowed us to determine the ratio between the anti p-n and the anti p-p cross sections. An analysis in the light of INC model predictions allowed us to show up events which can be interpreted as annihilations having occurred deeply inside the nuclei. (orig.)

318

Intermolecular forces and scaling relations between heterogeneous macromolecular surfaces  

Science.gov (United States)

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

Rosenberg, Kenneth J.

319

Weber-like interactions and energy conservation  

CERN Document Server

Velocity dependent forces varying as $k(\\hat{r}/r)(1 - \\mu \\dot{r}^2 + \\gamma r \\ddot{r})$ (such as Weber force), here called Weber-like forces, are examined from the point of view of energy conservation and it is proved that they are conservative if and only if $\\gamma=2\\mu$. As a consequence, it is shown that gravitational theories employing Weber-like forces cannot be conservative and also yield both the precession of the perihelion of Mercury as well as the gravitational deflection of light.

Bunchaft, F

1997-01-01

320

THz absorption spectrum of the CO2–H2O complex: Observation and assignment of intermolecular van der Waals vibrations  

DEFF Research Database (Denmark)

Terahertz absorption spectra have been recorded for the weakly bound CO2–H2O complex embedded in cryogenic neon matrices at 2.8 K. The three high-frequency van der Waals vibrational transitions associated with out-of-plane wagging, in-plane rocking, and torsional motion of the isotopic H2O subunit have been assigned and provide crucial observables for benchmark theoretical descriptions of this systems’ flat intermolecular potential energy surface. A (semi)-empirical value for the zero-point energy of 273 ± 15 cm?1 from the class of intermolecular van der Waals vibrations is proposed and the combination with high-level quantum chemical calculations provides a value of 726 ± 15 cm?1 for the dissociation energy D0

Andersen, Jonas; Wallin Mahler Andersen, Denise

2014-01-01

 
 
 
 
321

Kaon nucleon interaction at intermediate energies  

International Nuclear Information System (INIS)

The kaon nucleon system in I = 0 and I = 1 states is studied in terms of a model lagrangian containing Yukawa terms and contact terms which represent effective short range forces in both isospin states. We compute all Feynman diagrams contributions up to the fourth order and use the Pade approximants method to construct S matrix elements satisfying unitarity. Using values already determined for the Yukawa coupling constants g sub(N?K) and g sub(N?K) and the well-known value for the scattering length in I = 1, it remains as the only free parameter in the model the strength of the contact term in I = 0. Results are discussed and compared with available experimental data at low and intermediate energies, for K0P ? K+n, K+p ? K+p and K+d ? K0pp processes. (Author)

322

Mutually interacting Tachyon dark energy with variable $G$ and $\\Lambda$  

CERN Document Server

In this paper we consider Tachyonic scalar field as dark energy with interaction between components in the case of variable $G$ and $\\Lambda$. We assume a flat Universe with specific form of scale factor and study cosmological parameters numerically and graphically. Statefinder analysis also performed as well. In the special choice of interaction parameters we succeed to obtain analytical expression of densities. We find that our model will be stable in the late stage but there is an instability at the early Universe.

Hakobyan, J Sadeghi M Khurshudyan M

2013-01-01

323

Balancing Local Order and Long-Ranged Interactions in the Molecular Theory of Liquid Water  

CERN Document Server

A molecular theory of liquid water is identified and studied on the basis of computer simulation of the TIP3P model of liquid water. This theory would be exact for models of liquid water in which the intermolecular interactions vanish outside a finite spatial range, and therefore provides a precise analysis tool for investigating the effects of longer-ranged intermolecular interactions. We show how local order can be introduced through quasi-chemical theory. Long-ranged interactions are characterized generally by a conditional distribution of binding energies, and this formulation is interpreted as a regularization of the primitive statistical thermodynamic problem. These binding-energy distributions for liquid water are observed to be unimodal. The gaussian approximation proposed is remarkably successful in predicting the Gibbs free energy and the molar entropy of liquid water, as judged by comparison with numerically exact results. The remaining discrepancies are subtle quantitative problems that do have si...

Shah, J K; Pratt, L R; Paulaitis, M E

2007-01-01

324

Intermolecular Hydrogen Bonding in Peptide and Modified Jeffamine Organogels  

Science.gov (United States)

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

Savin, Daniel; Richardson, Adam

2011-03-01

325

Simulated Galaxy Interactions as Probes of Merger Spectral Energy Distributions  

CERN Document Server

We present the first systematic comparison of ultraviolet-millimeter spectral energy distributions (SEDs) of observed and simulated interacting galaxies. Our sample is drawn from the Spitzer Interacting Galaxy Survey, and probes a range of galaxy interaction parameters. We use 31 galaxies in 14 systems which have been observed with Herschel, Spitzer, GALEX, and 2MASS. We create a suite of GADGET-3 hydrodynamic simulations of isolated and interacting galaxies with stellar masses comparable to those in our sample of interacting galaxies. Photometry for the simulated systems is then calculated with the SUNRISE radiative transfer code for comparison with the observed systems. For most of the observed systems, one or more of the simulated SEDs match reasonably well. The best matches recover the infrared luminosity and the star formation rate of the observed systems, and the more massive systems preferentially match SEDs from simulations of more massive galaxies. The most morphologically distorted systems in our sa...

Lanz, Lauranne; Zezas, Andreas; Smith, Howard A; Ashby, Matthew L N; Brassington, Nicola; Fazio, Giovanni G; Hernquist, Lars

2014-01-01

326

Decoherence of intermolecular entanglement in exchange-coupled nanomagnets  

CERN Document Server

We theoretically investigate the hyperfine-induced decoherence in a pair of spin-cluster qubits, consisting of two exchange-coupled heterometallic wheels. We identify two distinct regimes in the decoherence of intermolecular entanglement and show that this can be substantially recovered through dynamical decoupling. Different chemical elements and physical processes are responsible for the decoherence of the singlet-triplet superposition, resulting in a wider tunability of its decoherence time.

Szallas, A

2010-01-01

327

Covariantizing the interaction between dark energy and dark matter  

Science.gov (United States)

Coupling dark energy and dark matter through an effective fluid description is a very common procedure in cosmology; however, it always remains in comoving coordinates in the special FLRW space. We construct a consistent, general, and covariant formulation, where the interaction is a natural implication of the imperfectness of the fluids. This imperfectness makes difficult the final step towards a robust formulation of interacting fluids, namely the construction of a Lagrangian whose variation would give rise to the interacting equations. Nevertheless, we present a formal solution to this problem for a single fluid, through the introduction of an effective metric.

Faraoni, Valerio; Dent, James B.; Saridakis, Emmanuel N.

2014-09-01

328

Interaction between Tachyon and Hessence (or Hantom) dark energies  

CERN Document Server

In this paper, we have considered that the universe is filled with tachyon, hessence (or hantom) dark energies. Subsequently we have investigated the interactions between tachyon and hessence (hantom) dark energies and calculated the potentials considering the power law form of the scale factor. It has been revealed that the tachyonic potential always decreases and hessence (or hantom) potential increases with corresponding fields. Furthermore, we have considered a correspondence between the hessence (or hantom) dark energy density and new variable modified Chaplygin gas energy density. From this, we have found the expressions of the arbitrary positive constants B0 and C of new variable modified Chaplygin gas.

Chattopadhyay, Surajit

2010-01-01

329

Flat Cosmology with Interacting Matter and Dark Energies  

CERN Document Server

Three models of a flat universe of interacting matter and dark energies with different low-redshift parameterizations of the dark energy equation of state are considered. The dark energy is assumed to vary with time like the trace of the energy-momentum tensor of cosmic matter. In the radiation-dominated era the models reduce to standard cosmology. In the matter-dominated era they are, for often quoted values of the cosmological parameters, consistent with data from supernovae Ia searches and with the data of Gurvits et al.(1999) for angular sizes of ultra compact radio sources.

Abdel-Rahman, A M M; Riad, Ihab F.

2005-01-01

330

Partonic description of soft high energy pp interactions  

CERN Document Server

We discuss how the main features of high-energy `soft' and `semihard' pp collisions may be described in terms of parton cascades and multi-Pomeron exchange. The interaction between Pomerons produces an effective infrared cutoff, k_sat, by the absorption of low k_t partons. This provides the possibility of extending the parton approach, used for `hard' processes, to also describe high-energy soft and semihard interactions. We outline a model which incorporates these features. Finally, we discuss what the most recent LHC measurements in the soft domain imply for the model.

Martin, A D; Ryskin, M G

2012-01-01

331

Thomas precession and spin interaction energy in very special relativity  

Science.gov (United States)

Very Special Relativity (VSR), proposed by Cohen and Glashow, considers one of the subgroups of Poincaré group as the symmetry of spacetime. This paper investigates the transformations of electromagnetic fields under boosts of VSR, and by the aid of them studies the interaction energy between spin of an electron and external electromagnetic fields. Here, we argue that Thomas precession, one of the consequences of Special Relativity (SR), does not exist in HOM(2) avatar of VSR. The predictions of SR and VSR about the spin interaction energy in a certain case are compared, and despite the absence of Thomas precession in VSR, no noticeable departure is seen.

Ganjitabar, Hassan; Shojai, Ali

2014-08-01

332

Comparison of classical, distorted wave, and straight path methods of evaluating the integrals over the intermolecular trajectory during molecular collisions  

International Nuclear Information System (INIS)

The integrals over the intermolecular trajectory, relevant to pressure-broadening and energy transfer calculations, are evaluated for the classical path, straight path, and distorted wave approximations. The present work, coupled with previous published work, leads to the conclusion that the three approximations agree to within 25% for near-resonant collisions involving reduced energies E*approximately-greater-than1. For nonresonant collisions the classical calculation, which does not conserve energy, is in surprisingly good agreement with the distorted wave results even when the energy mismatch is one-half of the incident energy

333

Interacting agegraphic dark energy models in phase space  

International Nuclear Information System (INIS)

Agegraphic dark energy, has been recently proposed, based on the so-called Karolyhazy uncertainty relation, which arises from quantum mechanics together with general relativity. In the first part of the article we study the original agegraphic dark energy model by including the interaction between agegraphic dark energy and pressureless (dark) matter. The phase space analysis was made and the critical points were found, one of which is the attractor corresponding to an accelerated expanding Universe. Recent observations of near supernova show that the acceleration of Universe decreases. This phenomenon is called the transient acceleration. In the second part of Article we consider the 3-component Universe composed of a scalar field, interacting with the dark matter on the agegraphic dark energy background. We show that the transient acceleration appears in frame of such a model. The obtained results agree with the observations

334

Exact zero-point interaction energy between cylinders  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We calculate the exact Casimir interaction energy between two perfectly conducting, very long, eccentric cylindrical shells using a mode summation technique. Several limiting cases of the exact formula for the Casimir energy corresponding to this configuration are studied both analytically and numerically. These include concentric cylinders, cylinder-plane, and eccentric cylinders, for small and large separations between the surfaces. For small separations we recover the pro...

Mazzitelli, F. D.; Dalvit, D. A. R.; Lombardo, F. C.

2006-01-01

335

Distributed energy resources in grid interactive AC microgrids  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Increased penetration of distributed energy resources (DER) and large-scale deployment of renewable energy sources are challenging the entire architecture of traditional power system. Microgrid, featuring higher flexibility and reliability, becomes an attractive candidate for the configuration of future electrical power system. This paper gives an overview of DER units in the grid interactive ac microgrid. The options in structures and control methods of power electronics interfaced DER units...

Wang, Xiongfei; Guerrero, Josep; Chen, Zhe; Blaabjerg, Frede

2010-01-01

336

Transition of the dark energy equation of state in an interacting holographic dark energy model  

International Nuclear Information System (INIS)

A model of holographic dark energy with an interaction with matter fields has been investigated. Choosing the future event horizon as an IR cutoff, we have shown that the ratio of energy densities can vary with time. With the interaction between the two different constituents of the universe, we observed the evolution of the universe, from early deceleration to late time acceleration. In addition, we have found that such an interacting dark energy model can accommodate a transition of the dark energy from a normal state where wD>-1 to wD<-1 phantom regimes. Implications of interacting dark energy model for the observation of dark energy transition has been discussed

337

Parametrized post-Friedmann framework for interacting dark energy  

Science.gov (United States)

Dark energy might directly interact with cold dark matter. However, in such a scenario, an early-time large-scale instability occurs occasionally, which may be due to the incorrect treatment for the pressure perturbation of dark energy as a nonadiabatic fluid. To avoid this nonphysical instability, we establish a new framework to correctly calculate the cosmological perturbations in the interacting dark energy models. Inspired by the well-known parametrized post-Friedmann approach, the condition of the dark energy pressure perturbation is replaced with the relationship between the momentum density of dark energy and that of other components on large scales. By reconciling the perturbation evolutions on the large and small scales, one can complete the perturbation equations system. The large-scale instability can be successfully avoided and the well-behaved density and metric perturbations are obtained within this framework. Our test results show that this new framework works very well and is applicable to all the interacting dark energy models.

Li, Yun-He; Zhang, Jing-Fei; Zhang, Xin

2014-09-01

338

Effects of pair correlation functions on intermolecular nuclear relaxation by translational and rotational diffusion in liquids  

International Nuclear Information System (INIS)

In order to study the intermolecular relaxation due to magnetic dipolar interactions, we calculate the spectral densities resulting from random translational and rotational motions of spherical molecules carrying off-centre spins. The relative translational motion is treated in the frame-work of a general diffusion equation (the Smoluchowski equation) which takes into account the existence of effective forces between the molecules. This model implies a pair correlation function. i.e. a non unifom relative distribution of the molecules. The analytical calculations are carried out by taking correctly into account the hard sphere boundary conditions for the molecules. Explicit numerical calculations of the spectral densities are performed using finite difference methods and the pair correlation function of Verlet and Weiss obtained by computer experiments. The resulting calculations allow one to interpret the relaxation exhibited by benzene and some of its monohalogen derivatives which has been measured by Jonas et al. at various pressures. The effects of pair correlation and eccentricity contribute to a noticeable enhancement of the spectral densities, especially as the frequency increases. The translational correlation times calculated from the Stokes formula and those deduced from intermolecular relaxation studies are compared. It is shown that in order to distinguish which of the dynamical models is appropriate, measurements must be made as a function of frequency

339

Electrochemical study of the intermolecular electron transfer to Pseudomonas aeruginosa cytochrome cd1 nitrite reductase  

International Nuclear Information System (INIS)

The kinetics of electron transfer reaction between cytochrome cd1 nitrite reductase (NiR) from Pseudomonas aeruginosa and various physiological/non physiological redox partners was investigated using cyclic voltammetry at the pyrolytic graphite electrode. While NiR did not exchange electron with the electrode, cytochrome c551 and azurin, both from Ps. aeruginosa, behaved as fast electrochemical systems. The intermolecular electron transfers between NiR and cytochrome c551 or azurin as electron shuttles, in the presence of nitrite, were studied. Second order rate constants of 2x106 and 1.4x105 M-1 s-1 are calculated for cytochrome c551 and azurin, respectively. The dependence of the second-order rate constant on ionic strength and pH is discussed. Finally, the effect of the global charge of the electron shuttles was explored using differently charged species (proteins or small ions). The experimental results suggest involvement of polar interactions as well as of hydrophobic contacts in the protein recognition prior to the intermolecular electron transfer. As the cross-reaction between Ps. nautica cytochrome c552 and Ps. aeruginosa NiR was shown to be as efficient as the catalytic reaction involving the physiological partners, it is concluded to a 'pseudo-specificity' in the recognition between NiR and the electron donor

340

Analysis of Intermolecular Coordinate Contributions to Third-order Ultrafast Spectroscopy of Liquids in the Harmonic Oscillator  

Energy Technology Data Exchange (ETDEWEB)

The apparently-multicomponent subpicosecond intermolecular dynamics of carbon disulfide liquid are addressed in a unified manner in terms of an inhomogeneously broadened quantum mechanical harmonic oscillator model for a single vibrational coordinate. For an inhomogeneously broadened (Gaussian) distribution of oscillators, the model predicts naturally the bimodal character of the subpicosecond intermolecular dynamics of carbon disulfide liquid, and also the spectral evolution effects (spectral narrowing and saturation) that are observed for solutions of carbon disulfide in weakly interacting alkane solvents. The unique dynamical signature of these low-frequency vibrational coordinates is determined largely by the physical constraints on the coordinates (near equality of oscillator frequency, dephasing frequency, and inhomogeneous bandwidth), such that constructive and destructive interference effects play a dominant role in shaping the experimental observable.

Thantu, Napoleon; McMorrow, D.; Melinger, J. S.; Kleiman, V.; Lotshaw, W. T.

2001-07-01

 
 
 
 
341

Experimental studies of pion-nucleus interactions at intermediate energies  

International Nuclear Information System (INIS)

This report summarizes the work on experimental research in intermediate energy nuclear physics carried out at New Mexico State University in 1991 under a great from the US Department of Energy. Most of these studies have involved investigations of various pion-nucleus interactions. The work has been carried out both with the LAMPF accelerator at the Los Alamos National Laboratory and with the cyclotron at the Paul Scherrer Institute (PSI) near Zurich, Switzerland. Part of the experimental work involves measurements of new data on double-charge-exchange scattering, using facilities at LAMPF which we helped modify, and on pion absorption, using a new detector system at PSI that covers nearly the full solid-angle region which we helped construct. Other work involved preparation for future experiments using polarized nuclear targets and a new high-resolution spectrometer system for detecting ?0 mesons. We also presented several proposals for works to be done in future years, involving studies related to pi-mesonic atoms, fundamental pion-nucleon interactions, studies of the difference between charged and neutral pion interactions with the nucleon, studies of the isospin structure of pion-nucleus interactions, and pion scattering from polarized 3He targets. This work is aimed at improving our understanding of the pion-nucleon interaction, of the pion-nucleus interaction mechanism, and of nuclear structure

342

Wormhole solutions supported by interacting dark matter and dark energy  

Science.gov (United States)

We show that the presence of a nonminimal interaction between dark matter and dark energy may lead to a violation of the null energy condition and to the formation of a configuration with nontrivial topology (a wormhole). In this it is assumed that both dark matter and dark energy satisfy the null energy condition, a violation of which takes place only in the inner high-density regions of the configuration. This is achieved by assuming that, in a high-density environment, a nonminimal coupling function changes its sign in comparison with the case where dark matter and dark energy have relatively low densities which are typical for a cosmological background. For this case, we find regular static, spherically symmetric solutions describing wormholes supported by dark matter nonminimally coupled to dark energy in the form of a quintessence scalar field.

Folomeev, Vladimir; Dzhunushaliev, Vladimir

2014-03-01

343

MINT - A Simple Model for Low Energy Hadronic Interactions  

CERN Document Server

The bulk of inelastic hadronic interactions is characterized by longitudinal phase space and exponentially damped transverse momentum spectra. A simple model with only a single adjustable parameter is presented, making it a very convenient tool for systematic studies, which gives a surprisingly good description of pA-collisions at 920 GeV beam energy.

Schmelling, M

2005-01-01

344

Open beauty production in high energy ?--tungsten interactions  

International Nuclear Information System (INIS)

We present a study of Banti B meson pair production in ?--tungsten interactions at 140, 194 and 286 GeV incident pion energy. At 286 GeV, where we have the best statistics, we find a model-dependent Banti B production cross-section ?Banti B = 14(+17-6)nb/nucleon. (orig.)

345

Comment on open-quotes Accuracy of counterpoise corrections in second-order intermolecular potential calculations. 1. Hellum dimerclose quotes  

International Nuclear Information System (INIS)

A recent paper on the validity of counterpoise corrections in the intermolecular energy calculations was published by Yang and Kestner. The authors are particularly interested in this work since they previously worked on the same topic with a different approach. While the authors generally agree with their arguments and conclusions in the paper, the authors have found a few problems in some of the calculational results. It is the purpose of this comment to point out the possible errors in that paper

346

A unique quinolineboronic acid-based supramolecular structure that relies on double intermolecular B-N bonds for self-assembly in solid state and in solution  

Science.gov (United States)

The boronic acid functional group plays very important roles in sugar recognition, catalysis, organic synthesis, and supramolecular assembly. Therefore, understanding the unique properties of this functional group is very important. 8-Quinolineboronic acid (8-QBA) is found to be capable of self-assembling in solid state through a unique intermolecular B-N bond mechanism reinforced by intermolecular boronic anhydride formation, ?-? stacking, and hydrogen bond formation. NMR NOE and diffusion studies indicate that intermolecular B-N interaction also exists in solution with 8-QBA. In contrast, a positional isomer of 8-QBA, 5-quinolineboronic acid (5-QBA) showed very different behaviors in crystal packing and in solution and therefore different supramolecular network. Understanding the structural features of this unique 8-QBA assembly could be very helpful for the future design of new sugar sensors, molecular catalysts, and supramolecular assemblies. PMID:18414645

Zhang, Yanling; Li, Minyong; Chandrasekaran, Sekar; Gao, Xingming; Fang, Xikui; Lee, Hsiau-Wei; Hardcastle, Kenneth; Yang, Jenny; Wang, Binghe

2007-01-01

347

Hadron production in proton-proton interactions at medium energies  

International Nuclear Information System (INIS)

Hadron production in proton-proton interactions is described in the framework of a collision model, which aims at describing simultaneously all reaction channels in a wide energy region. An empirical matrix element based on the present knowledge of the partonic structure of hadrons is combined with the concept of intermediate subsystems and the calculation of modified statistical weights of the various final states. It is demonstrated that the energy dependence of total cross sections between threshold and about 50 GeV incident energy can be satisfactorily reproduced. This is the basis for considering theoretical and experimental problems of K-, ? and ?' production in more detail. (orig.)

348

Interactions of quarks and gluons with nuclei at intermediate energies  

Energy Technology Data Exchange (ETDEWEB)

Some processes involving the interaction of medium energy quarks and gluons with nuclear matter are described. Possible mechanisms for the A-dependence of the energy loss of leading protons produced in proton-nucleus collisions are given, and an experiment which may help to distinguish these mechanisms is described. A possible color transparency experiment at CEBAF is described. Experiments to measure energy loss of quarks in nuclear matter and the formation time of hadrons are discussed along with the possibilities of measuring {sigma}{sub J}/{psi} and {sigma}{sub {psi}{prime}} at CEBAF.

Mueller, A.H. [Columbia Univ., New York, NY (United States)

1994-04-01

349

Schematic potential energy for interaction between isobutene and zeolite mordenite  

International Nuclear Information System (INIS)

A schematic representation of the potential energy for the interaction between isobutene and H mordenite was presented by using eight different positions (P1-P8) of C1 or C2 atoms located in front of the acid hydrogen (H+). In all cases a ? complex was formed yielding different values of the adsorption energy. In some cases of the adsorption point in P1-P8 the frontier orbitals are shown. The P8 position exhibits the highest value obtained for the adsorption energy, where the C1 atom is in front of the H+. Calculations were of all electron type employing HF/6-31G**

350

Simulations of structure formation in interacting dark energy cosmologies  

International Nuclear Information System (INIS)

The evidence in favor of a dark energy component dominating the Universe, and driving its presently accelerated expansion, has progressively grown during the last decade of cosmological observations. If this dark energy is given by a dynamic scalar field, it may also have a direct interaction with other matter fields in the Universe, in particular with cold dark matter. Such interaction would imprint new features on the cosmological background evolution as well as on the growth of cosmic structure, like an additional long-range fifth-force between massive particles, or a variation in time of the dark matter particle mass. We present here the implementation of these new physical effects in the N-body code GADGET-2, and we discuss the outcomes of a series of high-resolution N-body simulations for a selected family of interacting dark energy models. We interestingly find, in contrast with previous claims, that the inner overdensity of dark matter halos decreases in these models with respect to ?CDM, and consistently halo concentrations show a progressive reduction for increasing couplings. Furthermore, the coupling induces a bias in the overdensities of cold dark matter and baryons that determines a decrease of the halo baryon fraction below its cosmological value. These results go in the direction of alleviating tensions between astrophysical observations and the predictions of the ?CDM model on small scales, thereby opening new room for coupled dark energy models as room for coupled dark energy models as an alternative to the cosmological constant.

351

Low-energy pion interaction with lightest nuclei  

International Nuclear Information System (INIS)

The present state of low-energy pion interaction with 2H, 3He, 4He nuclei is considered. Calculation of differential cross sections (??/d?)?± of elastic scattering of positive and negative pions on 4He nucleus with the energy of T?=30 MeV (in lab.syst.) and variation of inelasticity parameters with angular moment l=0 and 1 are presented. Highcriticality of estimations of total cross section for (?, 4He) reaction extracted from elastic scattering analysis to (d?/d?)?± behaviour in minimum range is detected. Some actual problems of experimental and theoretial studies of low-energy pion interaction with the lightest nuclei are discussed. 25 refs.; 10 figs.; 1 tab

352

Meson production in two-photon interactions at LHC energies  

Energy Technology Data Exchange (ETDEWEB)

The LHC opens a new kinematical regime at high energy, where several questions related to the description of the high-energy regime of the Quantum Chromodynamics (QCD) remain without satisfactory answers. Some open questions are the search for non-q-bar q resonances, the determination of the spectrum of q-bar q states and the identification of states with anomalous {gamma}{gamma} couplings. A possible way to study these problems is the study of meson production in two-photon interactions. In this contribution we calculate the meson production in two-photon interactions at LHC energies considering proton - proton collisions and estimate the total cross section for the production of the mesons {pi}, a, f, {eta} and {chi}.

Da Silva, D. T.; Goncalves, V. P.; Sauter, W. K. [Instituto de Fisica e Matematica, Universidade Federal de Pelotas, Campus Universitario UFPel, CP 354, 96010-900, Capao do Leao-RS (Brazil)

2013-03-25

353

SHINIE: Simulation of High Energy Neutrinos Interacting with the Earth  

International Nuclear Information System (INIS)

SHINIE is acronym for Simulation of High-energy Neutrinos Interacting with the Earth, which is a Monte-Carlo simulation code for the interactions and propagations of neutrinos and leptons inside the Earth at energy greater than 1014 eV. This code can be used for underground or above-ground neutrino telescopes. Since 2004, we had made several major updates, which include stochastic energy loss for ? and ?, modification for underground detector, addition of ??, ?e, ?, and electron, and a new material salt for simulation of underground salt dome neutrino detector. Details of this code are described here. A benchmark test of tau lepton flux passing through 100 km of standard rock are performed and concluded that all processes behave properly and consistent with previous versions

354

HIGH ENERGY NUCLEAR INTERACTIONS AND QCD : AN INTRODUCTION.  

Energy Technology Data Exchange (ETDEWEB)

The goal of these lectures, oriented towards the students just entering the field, is to provide an elementary introduction to QCD and the physics of nuclear interactions at high energies. We first introduce the general structure of QCD and discuss its main properties. Then we proceed to Glauber multiple scattering theory which lays the foundation for the theoretical treatment of nuclear interactions at high energies. We introduce the concept of Gribov's inelastic shadowing, crucial for the understanding of quantum formation effects. We outline the problems facing Glauber approach at high energies, and discuss how asymptotic freedom of QCD helps to resolve them, introducing the concepts of parton saturation and color glass condensate.

KHARZEEV,D.E.; RAUFEISEN,J.

2002-01-07

355

High energy density interactions for near-earth orbit perturbations  

Science.gov (United States)

Energy requirements for near-Earth object (NEO) threat mitigation are addressed. Due to a large NEO mass range and the possibility of limited available time for orbit change, energy requirements can be large (~petajoules). To quantitatively determine energy requirements for a given momentum change use is made of the momentum coupling coefficient, CM, that depends on the type of energy transfer, energy density, interaction time scale, and target material properties. Inhomogeneous and flawed NEO materials are empirically confronted through experimental methodologies that generate parameters on high energy density mechanical and radiative induced momentum coupling to (primarily) meteorite targets serving as near-Earth asteroid surrogates. Interactants include high speed (> 8 km/s) mechanical projectiles, high intensity (~ GW/cm2) infra-red laser radiation, and (~200 GW/cm2) soft X-ray radiation. Issues exists and are addressed regarding momentum coupling scaling from coupon sized (~mm2) to much larger (~m2) targets. Applications include high energy planetary and astrophysical momentum coupling dynamics.

Remo, John L.; Hammerling, Peter X.

2004-09-01

356

Importance of the donor:fullerene intermolecular arrangement for high-efficiency organic photovoltaics.  

Science.gov (United States)

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 systems. PMID:24932575

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

357

Weak competing interactions control assembly of strongly bonded TCNQ ionic acceptor molecules on silver surfaces  

Science.gov (United States)

The energy scales of interactions that control molecular adsorption and assembly on surfaces can vary by several orders of magnitude, yet the importance of each contributing interaction is not apparent a priori. Tetracyanoquinodimethane (TCNQ) is an archetypal electron acceptor molecule and it is a key component of organic metals. On metal surfaces, this molecule also acts as an electron acceptor, producing negatively charged adsorbates. It is therefore rather intriguing to observe attractive molecular interactions in this system that were reported previously for copper and silver surfaces. Our experiments compared TCNQ adsorption on noble metal surfaces of Ag(100) and Ag(111). In both cases we found net attractive interactions down to the lowest coverage. However, the morphology of the assemblies was strikingly different, with two-dimensional islands on Ag(100) and one-dimensional chains on Ag(111) surfaces. This observation suggests that the registry effect governed by the molecular interaction with the underlying lattice potential is critical in determining the dimensionality of the molecular assembly. Using first-principles density functional calculations with a van der Waals correction scheme, we revealed that the strengths of major interactions (i.e., lattice potential corrugation, intermolecular attraction, and charge-transfer-induced repulsion) are all similar in energy. The van der Waals interactions, in particular, almost double the strength of attractive interactions, making the intermolecular potential comparable in strength to the diffusion potential and promoting self-assembly. However, it is the anisotropy of local intermolecular interactions that is primarily responsible for the difference in the topology of the molecular islands on Ag(100) and Ag(111) surfaces. We anticipate that the intermolecular potential will become more attractive and dominant over the diffusion potential with increasing molecular size, providing new design strategies for the structure and charge transfer within molecular layers.

Park, Changwon; Rojas, Geoffrey A.; Jeon, Seokmin; Kelly, Simon J.; Smith, Sean C.; Sumpter, Bobby G.; Yoon, Mina; Maksymovych, Petro

2014-09-01

358

The role of van der Waals interaction in the tilted binding of amine molecules to the Au(111) surface  

International Nuclear Information System (INIS)

We present the results of ab initio electronic structure calculations for the adsorption characteristics of three amine molecules on Au(111), which show that the inclusion of van der Waals interactions between the isolated molecule and the surface leads in general to good agreement with experimental data on the binding energies. Each molecule, however, adsorbs with a small tilt angle (between -5 and 9°). For the specific case of 1,4-diaminobenzene (BDA) our calculations reproduce the larger tilt angle (close to 24°) measured by photoemission experiments, when intermolecular (van der Waals) interactions (for about 8% coverage) are included. These results point not only to the important contribution of van der Waals interactions to molecule-surface binding energy, but also that of intermolecular interactions, often considered secondary to that between the molecule and the surface, in determining the adsorption geometry and pattern formation. (fast track communication)

359

1,2-Diaryl(3-pyridylethanone Oximes. Intermolecular Hydrogen Bonding Networks Revealed by X-ray Diffraction  

Directory of Open Access Journals (Sweden)

Full Text Available The synthesis of a set of 1-aryl-2-aryl(3-pyridylethanones 1-5 and thecorresponding ketoximes 6-9 is reported. Structural studies of oximes 6, 7 and 9 wereperformed in solution using 1H-NMR and in the solid state by X-ray crystallography,providing evidence of H-bonding networks. The crystal packing was controlled byhomomeric intermolecular oxime···oxime H-bond interactions for 6 and cooperativeoxime···N(pyridyl and CH/π interactions for 7 and 9.

Santiago García-Granda

2008-02-01

360

Cosmography of Interacting Generalized QCD Ghost Dark Energy  

Science.gov (United States)

Exploring the accelerated expansion of the universe, we investigate the generalized ghost dark energy (GGDE) model from the statefinder diagnostic analysis in a flat Friedmann-Robertson-Walker universe. First, we calculate the cosmological evolution and statefinder trajectories for noninteracting case and then extend this work by considering the interaction between dark matter and dark energy components. We show that in the noninteracting case the phantom line cannot be crossed and also the evolutionary trajectories of model in s - r plane cannot be discriminated. It has been shown that the present location of model in s - r plane would be close to observational value for negative values of the model parameter. In the presence of interaction between dark matter and dark energy, the phantom regime is achieved, the accelerated phase of expansion occurs sooner compared with the noninteracting case. The GGDE model is also discussed from the viewpoint of perturbation theory by calculating the adiabatic sound speed of the model. Finally, unlike the noninteracting case, the evolutionary trajectories in s - r plane can be discriminated in the interacting model. Like the noninteracting model, in the interacting case the present location of GGDE model is closer to observational value for negative values of the model parameter.

Malekjani, Mohammad

2013-12-01

 
 
 
 
361

Interactive Energy Planning : towards a sound and effective planning praxis  

DEFF Research Database (Denmark)

Though it is being questioned whether planning theory should be fitted into neat typologies, some have described evolving planning theory as a journey away from ethnocentrism, through the lands of rationalism, pragmatism, socio-ecological idealism, political-economic mobilization, currently anchoring along the shores of the land of communications and collaboration. Whether or not a particular typology is applicable, theory and praxis are establishing standpoints, which strengthens our understanding of the planning complex, and which should inspire improved energy planning methodologies and tools. This paper presents an “Interactive Energy Planning” framework, which is intended to support interactivity in planning, building on important theoretical and experimental advances in planning. In particular, the paper explores the potential significance of allowing a critical perspective on context analysis and problem-orientation to define the course of the planning process, and deploying value-rational planning tools primarily as a platform for interactivity. The focus on interactivity in energy planning will allow contemporary government planners, consultants, researchers, and organizational managers more effectively to address important technical and economic problems.

Blarke, Morten Boje

2006-01-01

362

Interactions of energy and the macroeconomy: 95 years of evidence  

Energy Technology Data Exchange (ETDEWEB)

A series of single equation dynamic regression models are constructed to test the hypotheses that both ''thermodynamic'' and economic efficiency configurations of lagged energy variables are statistically informative about subsequent macroeconomic activity, as represented by changes in real GNP per capita and unemployment rate. The time period tested in most versions of the models is the 1891-1985 period. The ''thermodynamic'' efficiency (t-efficiency) variable counts changes in the use of per capita energy per unit of national output (real GNP per capita). The economic efficiency (e-efficiency) variable is the more traditional price effect variable, in which changes in the real price of energy are tested for their effect on macroeconomic aggregates. The interactive effects of energy price and quantity shifts relative to macroeconomic aggregates are also assessed by use of a ''combined efficiencies'' variable which can also be interpreted as a measure of the difference of changes in energy spending and changes in national output. Of the tested energy variables, the combined energy efficiencies variable is clearly the best and most consistent provider of information about future macroeconomic activity. Macroeconomic activity is found to be much less informative about the energy variables than are the energy variables about macroeconomic activity. Consequently one way tests are conducted in which the informativeness of the combined energy efficiencies variable about subsequent macroeconomic activity is compared to the informativeness of money about subsequent macroeconomic activity. These tests infer that both energy and money are important, but that energy is a more consistent performer and better explainer of variation than money. It is also found that the incremental explanatory power of energy improves when it is included in an equation with money, and similarly, the incremental explanatory power of money improves when it is included in an equation with energy.

Santini, D.J.

1986-01-01

363

Differentiation of energy concepts through speech and gesture in interaction  

Science.gov (United States)

Through microanalysis of speech and gesture in one interaction between learners (in a course on energy for in-service teachers), we observe coherent states of conceptual differentiation of different learners. We observe that the interaction among learners across different states of differentiation is not in itself sufficient to accomplish differentiation; however, the real-time receptivity of the learners to conceptually relevant details in each other's actions suggests that future instruction that focuses explicitly on such actions and their meaning in context may assist differentiation.

Close, Hunter G.; Scherr, Rachel E.

2012-05-15

364

Intermolecular Radical Carbofluorination of Non-activated Alkenes.  

Science.gov (United States)

The Meerwein arylation has recently become an even more powerful tool for the functionalization of alkenes. Besides the attachment of an aryl group, radical reactions of this type allow the introduction of several different heteroatoms and a broad variety of alkenes are meanwhile tolerated as substrates. Closing a long-standing gap of the methodology, this communication describes the first intermolecular Meerwein-type carbofluorination. In metal-free reactions, arylalkyl fluorides were obtained from arylhydrazines and alkenes with Selectfluor acting as oxidant and as radical fluorine source. PMID:25303212

Kindt, Stephanie; Heinrich, Markus R

2014-11-17

365

Intermolecular (OHO) - hydrogen bond formed by a hydroxyquinoline derivative  

International Nuclear Information System (INIS)

1H, 13C, 14N, 15N, 17O and 19F NMR data are presented for HTFMQ and its complexes with DMAN in 2:1 and 1:1 molecular ratios. GIAO-CHF molecular orbital calculations for [1H] and [4H] forms of the free molecule and its anion are also performed. The results show that [4H] form of HTFMQ predominates in acetonitrile solutions. In both complexes with DMAN and HTFMQ forms a semi-anion containing an intermolecular hydrogen bond. (author)

366

Electronic interactions of medium-energy ions in hafnium dioxide  

Science.gov (United States)

In this article, the electronic interaction of medium-energy ions with hafnium dioxide is studied. Stopping cross sections for He ions in the energy range from 30 to 160 keV have been measured in backscattering experiments from thin films of HfO2 on Si using time-of-flight medium-energy ion scattering. The observed energy loss for helium ions is found to be high compared to expectations from earlier results for hydrogen in HfO2, a result which indicates a contribution from energy-loss processes that is different from direct excitation of electron-hole pairs in close collisions. Furthermore, data exhibit a significant deviation from velocity proportionality. A discussion of the results, together with data from studies for H and He in SiO2, show characteristic differences which are traced back to different electronic structures of the target materials and their influence on the charge-exchange channels that are active in the interaction with helium. Charge exchange, in turn, via shifted mean-charge states, will influence the observed ionization along the ion track. The results can furthermore serve as reference values for ion-beam-based depth profiling at medium and low ion energies.

Primetzhofer, D.

2014-03-01

367

Intermolecular repulsive-dispersive potentials explain properties of impurity spectra in soft solids  

International Nuclear Information System (INIS)

Behavior of optical impurity spectra in van der Waals glasses is rationalized with the aid of a two-particle Lennard-Jones model of intermolecular interactions. Simple mathematical manipulations with the 6-12 potential yield inhomogeneous distribution functions (IDFs) of zero phonon lines (ZPLs) at different compressions, and the expressions for wavelength dependent pressure shift coefficients of ZPLs (or holes), local phonon frequencies, and linear and quadratic coupling constants. Experimentally, the ZPL to phonon wing intensity ratios (Huang-Rhys or Debye-Waller factors) are measured for bacteriochlorophyll a in glass-forming triethylamine 5 K. Enhancement of coupling strength with increasing transition wavelength is observed, in qualitative agreement with the model.

368

Intermolecular repulsive-dispersive potentials explain properties of impurity spectra in soft solids  

Energy Technology Data Exchange (ETDEWEB)

Behavior of optical impurity spectra in van der Waals glasses is rationalized with the aid of a two-particle Lennard-Jones model of intermolecular interactions. Simple mathematical manipulations with the 6-12 potential yield inhomogeneous distribution functions (IDFs) of zero phonon lines (ZPLs) at different compressions, and the expressions for wavelength dependent pressure shift coefficients of ZPLs (or holes), local phonon frequencies, and linear and quadratic coupling constants. Experimentally, the ZPL to phonon wing intensity ratios (Huang-Rhys or Debye-Waller factors) are measured for bacteriochlorophyll a in glass-forming triethylamine 5 K. Enhancement of coupling strength with increasing transition wavelength is observed, in qualitative agreement with the model.

Renge, Indrek, E-mail: indrek.renge@ut.e [Institute of Physics, University of Tartu, 142 Riia Street, EE51014 Tartu (Estonia); Raetsep, Margus [Institute of Physics, University of Tartu, 142 Riia Street, EE51014 Tartu (Estonia); Freiberg, Arvi [Institute of Physics, University of Tartu, 142 Riia Street, EE51014 Tartu (Estonia); Institute of Molecular and Cell Biology, University of Tartu, 23 Riia Street, EE51014 Tartu (Estonia)

2011-02-15

369

Dielectric behaviour and intermolecular association between L(+) ascorbic acid and ethanol  

International Nuclear Information System (INIS)

In order to determine the dipole moment of L(+) ascorbic acid and the relation to its structure the experimental variations of permitivities, refractive indices and specific volumes of a series of dilute ethanolic solutions at 25 deg C were examined. The average moment (?) using Buckingham equation was found to be 5,58 D considering the spherical approximation and 7,81 D if the ellipsoidal form factor was considered. The calculated ? value through vectorial addition was 4,98 D. The solute partial molal volume in the studied range was calculated to be 94,73 cm3 instead of the theoretical value of 106,71 cm3. Both discrepancies are attributed to intermolecular solute-solvent interactions. A possible electronic displacement which favours hydrogen bonding with the solvent is postulated. (Author)

370

Photoinduced coupled twisted intramolecular charge transfer and excited-state proton transfer via intermolecular hydrogen bonding: A DFT/TD-DFT study  

Science.gov (United States)

We discuss theoretically the geometric and electronic structure properties of the thiazolidinedione derivative A and its hydrogen-bonded complex in dimethylformamide (DMF) solution in the S0 and S1 states. To gain insight into the photoinduced coupled excited-state proton transfer (ESPT) and twisted intramolecular charge transfer (TICT) associated with intermolecular hydrogen bonding, the potential energy profiles are provided along the Osbnd H bond and the twisted angle. It is predicted that TICT in S1 can facilitate ESPT initiated by intermolecular hydrogen-bond strengthening in the S1 state. The coupling of ESPT and TICT is energetically preferable.

Wang, Dandan; Lü, Rui; Yuan, Minghu; Chen, Junsheng; Feng, Liqiang; Fu, Aiping; Tian, Fenghui; Varandas, António J. C.; Chu, Tianshu

2014-08-01

371

Antineutron and antiproton nuclear interactions at very low energies  

CERN Document Server

Experimental annihilation cross sections of antineutrons and antiprotons at very low energies are compared. Features of Coulomb focusing are observed for $\\bar p$ annihilation on protons. Direct comparisons for heavier targets are not straightforward due to lack of overlap between targets and energies of experimental results for $\\bar p$ and $\\bar n$. Nevertheless, the annihilation cross sections for $\\bar n$ on nuclei cannot be described by an optical potential that fits well all the available data on $\\bar p$ interactions with nuclei. Comparisons made with the help of this potential reveal in the $\\bar n$ data features similar to Coulomb focusing. Direct comparisons between $\\bar n$ and $\\bar p$ annihilations at very low energies would be possible when $\\bar p$ cross sections are measured on the same targets and at the same energies as the available cross sections for $\\bar n$. Such measurements may be possible in the foreseeable future.

Friedman, E

2014-01-01

372

Self-interaction errors in nuclear energy density functionals  

International Nuclear Information System (INIS)

When applied to a single nucleon, nuclear energy density functionals may yield a nonvanishing internal energy thus implying that the nucleon is interacting with itself. It is shown how to avoid this unphysical feature for semilocal phenomenological functionals containing all possible bilinear combinations of local densities and currents up to second order in the derivatives. The method outlined in this Rapid Communication could be easily extended to functionals containing higher-order terms, and could serve as a guide for constraining the time-odd part of the functional.

373

Interaction of Compliance and Voluntary Renewable Energy Markets  

Energy Technology Data Exchange (ETDEWEB)

In recent years, both compliance and voluntary markets have emerged to help support the development of renewable energy resources. Both of these markets are growing rapidly and today about half of U.S. states have RPS policies in place, with a number of these policies adopted in the last several years. In addition, many states have recently increased the stringency of their RPS policies. This paper examines key market interaction issues between compliance and voluntary renewable energy markets. It provides an overview of both the compliance and voluntary markets, addressing each market's history, purpose, size, scope, and benefits while addressing issues, including double counting.

Bird, L.; Lokey, E.

2007-10-01

374

Distributed energy resources in grid interactive AC microgrids  

DEFF Research Database (Denmark)

Increased penetration of distributed energy resources (DER) and large-scale deployment of renewable energy sources are challenging the entire architecture of traditional power system. Microgrid, featuring higher flexibility and reliability, becomes an attractive candidate for the configuration of future electrical power system. This paper gives an overview of DER units in the grid interactive ac microgrid. The options in structures and control methods of power electronics interfaced DER units are described. Instantaneous load sharing strategies among DER units in the islanded microgrid operations are discussed pointing out the importance of closed loop system output impedance for the power electronics interfaced DER units.

Wang, Xiongfei; Guerrero, Josep

2010-01-01

375

Nucleon-nucleon tensor interaction and the triton binding energy  

International Nuclear Information System (INIS)

We have investigated a sensitivity of short range behavior of the nucleon-nucleon tensor interaction on the 3S1-3D1 mixing parameter and the triton binding energy. It is found that, by varying the short range behavior of a tensor component to repulsive from attractive, we can get an additional triton binding energy of about 0.7 MeV. At the same time, the mixing parameter becomes too small to be acceptable. For a proposed potential to be really ''realistic,'' the mixing parameter should carefully be fitted to experimental values

376

Nucleon-nucleon tensor interaction and the triton binding energy  

Science.gov (United States)

We have investigated a sensitivity of short range behavior of the nucleon-nucleon tensor interaction on the 3S1-3D1 mixing parameter and the triton binding energy. It is found that, by varying the short range behavior of a tensor component to repulsive from attractive, we can get an additional triton binding energy of about 0.7 MeV. At the same time, the mixing parameter becomes too small to be acceptable. For a proposed potential to be really ``realistic,'' the mixing parameter should carefully be fitted to experimental values.

Ishikawa, S.; Sasakawa, T.

1987-11-01

377

A phenomenological analysis of antiproton interactions at low energies  

CERN Document Server

We present an optical potential analysis of the antiproton-protoninteractions at low energies. Our optical potential is purely phenomenological,and has been parametrized on data recently obtained by the Obelix Collaborationat momenta below 180 MeV/c. It reasonably fits annihilation and elastic databelow 600 MeV/c, and allows us for an evaluation of the elastic cross sectionand rho-parameter down to zero kinetic energy. Moreover we show that themechanism that depresses antiproton-nucleus annihilation cross sections at lowenergies is present in antiproton-proton interactions too.

Bianconi, A; Bussa, M P; Lodi-Rizzini, E; Venturelli, L; Zenoni, A

2000-01-01

378

Analytic energy gradients for constrained DFT-configuration interaction  

Science.gov (United States)

The constrained density functional theory-configuration interaction (CDFT-CI) method has previously been used to calculate ground-state energies and barrier heights, and to describe electronic excited states, in particular conical intersections. However, the method has been limited to evaluating the electronic energy at just a single nuclear configuration, with the gradient of the energy being available only via finite difference. In this paper, we present analytic gradients of the CDFT-CI energy with respect to nuclear coordinates, which gives the potential for accurate geometry optimization and molecular dynamics on both the ground and excited electronic states, a realm which is currently quite challenging for electronic structure theory. We report the performance of CDFT-CI geometry optimization for representative reaction transition states as well as molecules in an excited state. The overall accuracy of CDFT-CI for computing barrier heights is essentially unchanged whether the energies are evaluated at geometries obtained from quadratic configuration-interaction singles and doubles (QCISD) or CDFT-CI, indicating that CDFT-CI produces very good reaction transition states. These results open up tantalizing possibilities for future work on excited states.

Kaduk, Benjamin; Tsuchimochi, Takashi; Van Voorhis, Troy

2014-05-01

379

Analytic energy gradients for constrained DFT-configuration interaction  

International Nuclear Information System (INIS)

The constrained density functional theory-configuration interaction (CDFT-CI) method has previously been used to calculate ground-state energies and barrier heights, and to describe electronic excited states, in particular conical intersections. However, the method has been limited to evaluating the electronic energy at just a single nuclear configuration, with the gradient of the energy being available only via finite difference. In this paper, we present analytic gradients of the CDFT-CI energy with respect to nuclear coordinates, which gives the potential for accurate geometry optimization and molecular dynamics on both the ground and excited electronic states, a realm which is currently quite challenging for electronic structure theory. We report the performance of CDFT-CI geometry optimization for representative reaction transition states as well as molecules in an excited state. The overall accuracy of CDFT-CI for computing barrier heights is essentially unchanged whether the energies are evaluated at geometries obtained from quadratic configuration-interaction singles and doubles (QCISD) or CDFT-CI, indicating that CDFT-CI produces very good reaction transition states. These results open up tantalizing possibilities for future work on excited states

380

Low-Energy Interaction of Anti-Kaons  

International Nuclear Information System (INIS)

A usr the physics of strong interaction has the dynamics driven by chiral symmetry breaking in low-energy QCD. High precision measurements of the antikaon interaction with nucleons and nuclei - like SIDDHARTA at LNF/Italy and E17 at J-PARC/Japan - open the way to study the low energy regime of strong interaction involving strangeness. Especially interesting are nuclear systems (KNCs, kaonic nuclear clusters) involving strangeness and bound by the strong force. At present this topic is in lively discussion and the search for KNCs is conducted in new experiments (e.g. FOPI at GSI, AMADEUS at LNF, E15 at J-PARC). An international scientific network (LEANNIS) in Hadron physics 2 of the European Framework Program FP7 will bring together experimentalists and theorists for joint work on the antikaon interaction with nucleons and nuclei. This talk will give an overview on open problems and will present research activities in this challenging field. The progress in precision spectroscopy of kaonic atoms will be discussed in detail.

 
 
 
 
381

Neutral current neutrino-nucleus interactions at intermediate energies  

Science.gov (United States)

We have extended our model for charged current neutrino-nucleus interactions developed in Phys. Rev. C 73, 065502 (2006) to neutral current reactions. For the elementary neutrino-nucleon interaction, we take into account quasielastic scattering, ? excitation, and the excitation of the resonances in the second resonance region. Our model for the neutrino-nucleus collisions includes in-medium effects such as Fermi motion, Pauli blocking, nuclear binding, and final-state interactions. They are implemented by means of the Giessen Boltzmann-Uehling-Uhlenbeck (GiBUU) coupled-channel transport model. This allows us to study exclusive channels, namely pion production and nucleon knockout. We find that final-state interactions modify considerably the distributions through rescattering, charge-exchange, and absorption. Side-feeding induced by charge-exchange scattering is important in both cases. In the case of pions, there is a strong absorption associated with the in-medium pionless decay modes of the ?, while nucleon knockout exhibits a considerable enhancement of low-energy nucleons because of rescattering. At neutrino energies above 1 GeV, we also obtain that the contribution to nucleon knockout from ? excitation is comparable to that from quasielastic scattering.

Leitner, T.; Alvarez-Ruso, L.; Mosel, U.

2006-12-01

382

Buckyplates and buckybowls: examining the effects of curvature on ?-? interactions.  

Science.gov (United States)

?-? interactions are integral to many areas of chemistry, biochemistry, and materials science. Here we use electronic structure theory to analyze how ?-? interactions change as the ?-systems are curved in model complexes based on coronene and corannulene dimers. Curvature redistributes electronic charge in the ?-cloud and creates a dipole moment in these systems, leading to enhanced intermolecular electrostatic interactions in the concave-convex (nested) geometries that are the focus of this work. Curvature of both monomers also has a geometric effect on the interaction by decreasing the average C-C distance between monomers and by increasing the magnitude of both favorable London dispersion interactions and unfavorable exchange-repulsion interactions. Overall, increasing curvature in nested ?-? interactions leads to more favorable interaction energies regardless of the native state of the monomers, except at short distances where the most highly curved systems are less favorable as exchange repulsion terms begin to dominate the interaction. PMID:23137341

Kennedy, Matthew R; Burns, Lori A; Sherrill, C David

2012-12-01

383

Interacting quintessence dark energy models in Lyra manifold  

CERN Document Server

In this paper, we consider two-component dark energy models in Lyra manifold. The first component is assumed as a quintessence field while the second model may be a viscous polytropic gas, a viscous Van der Waals gas or a viscous modified Chaplygin gas. We also consider the possibility of interaction between components. By using numerical analysis, we study some cosmological parameters of the models and compare them with observational data.

Khurshudyan, M; Myrzakulov, R; Pasqua, A; Farahani, H

2014-01-01

384

Two-particle binding energy of interacting Bose gases  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The pole of the two-particle T-matrix including the influence of the surrounding medium is analyzed for an interacting Bose gas. The phase diagram of the Bose -Einstein condensation (BEC) depending on the temperature, density, scattering length, and momentum is derived from this pole. The critical momentum for the occurrence of superfluidity is obtained in this way. As a new observation a two- particle binding energy is reported intimately connected with the occurrence of th...

Ma?nnel, K. Morawetz M.; Schreiber, M.; Lipavsky?, P.

2007-01-01

385

On the nuclear interaction. Potential, binding energy and fusion reaction  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The nuclear interaction is responsible for keeping neutrons and protons joined in an atomic nucleus. Phenomenological nuclear potentials, fitted to experimental data, allow one to know about the nuclear behaviour with more or less success where quantum mechanics is hard to be used. A nuclear potential is suggested and an expression for the potential energy of two nuclear entities, either nuclei or nucleons, is developed. In order to estimate parameters in this expression, so...

Casinos, I.

2008-01-01

386

Interacting Quintessence Dark Energy Models in Lyra Manifold  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In this paper, we consider two-component dark energy models in Lyra manifold. The first component is assumed as a quintessence field while the second model may be a viscous polytropic gas, a viscous Van der Waals gas or a viscous modified Chaplygin gas. We also consider the possibility of interaction between components. By using numerical analysis, we study some cosmological parameters of the models and compare them with observational data.

Farahani, H. Department Of Physics; Khurshudyan, M.; Sadeghi, J.; Myrzakulov, R.; Pasqua, Antonio

2014-01-01

387

Energy-dependent interactions in few-body systems  

International Nuclear Information System (INIS)

Energy-dependent interactions in few-body systems are discussed. A class of multichannel few-body scattering models which are characterized by the simultaneous presence of and communication between two different types of channels. First, usual two- and three-particle scattering channels (external ones), hamiltonians for which have ordinary spectral properties. Second, the internal channels, hamiltonians for which have only a point spectrum. Faddeev equations for external and internal channels are discussed

388

Energy dependence of the 16O - 208Pb effective interaction  

International Nuclear Information System (INIS)

The Coulomb-nuclear interference in the excitation probability of the 2.615 MeV (3-) state of 208Pb by 16O at ?CM 172 deg for bombarding energies between 57 MeV and 79 MeV has been studied. The data are described by an effective interaction which has a behaviour similar to that expected from the dispersion relation connecting the real and imaginary parts of the generalized optical potential

389

Energy dependence of the 16O-208Pb effective interaction  

International Nuclear Information System (INIS)

The Coulomb-nuclear interference in the excitation probability of the 2.615 MeV(3-) state of 208Pb by 16O at ?CM = 1720 for bombarding energies 57 MeV ? Elab ? 79 MeV has been studied. The data are described by an effective interaction which has a behaviour similar to that expected from the dispersion relation connecting the real and imaginary parts of the generalized optical potential. (orig.)

390

Post-Planck constraints on interacting vacuum energy  

Science.gov (United States)

We present improved constraints on an interacting vacuum model using updated astronomical observations including the first data release from Planck. We consider a model with one dimensionless parameter, ?, describing the interaction between dark matter and vacuum energy (with fixed equation of state w=-1). The background dynamics correspond to a generalized Chaplygin gas cosmology, but the perturbations have a zero sound speed. The tension between the value of the Hubble constant, H0, determined by Planck data plus WMAP polarization (Planck +WP) and that determined by the Hubble Space Telescope (HST) can be alleviated by energy transfer from dark matter to vacuum (?>0). A positive ? increases the allowed values of H0 due to parameter degeneracy within the model using only cosmic microwave background data. Combining with additional data sets of including supernova type Ia (SN Ia) and baryon acoustic oscillation (BAO), we can significantly tighten the bounds on ?. Redshift-space distortions (RSD), which constrain the linear growth of structure, provide the tightest constraints on vacuum interaction when combined with Planck+WP, and prefer energy transfer from vacuum to dark matter (?combined data sets of Planck +WP+Union2.1+BAO+RSD, we obtain the constraint on ? to be -0.0830, but not both at the same time.

Wang, Yuting; Wands, David; Zhao, Gong-Bo; Xu, Lixin

2014-07-01

391

Revisiting the interacting model of new agegraphic dark energy  

Science.gov (United States)

In this paper, a new version of the interacting model of new agegraphic dark energy (INADE) is proposed and analyzed in detail. The interaction between dark energy and dark matter is reconsidered. The interaction term Q = bH 0 ? {de/ ? } ? {dm/1-? } is adopted, which abandons the Hubble expansion rate H and involves both ? de and ? dm. Moreover, the new initial condition for the agegraphic dark energy is used, which solves the problem of accommodating baryon matter and radiation in the model. The solution of the model can be given using an iterative algorithm. A concrete example for the calculation of the model is given. Furthermore, the model is constrained by using the combined Planck data (Planck+BAO+SNIa+H 0) and the combined WMAP-9 data (WMAP+BAO+SNIa+H 0). Three typical cases are considered: (A) Q = bH 0 ? de, (B) Q = bH 0 ?? de ? dm, and (C) Q = bH 0 ? dm, which correspond to ? = 1, 1/2, and 0, respectively. The departures of the models from the ?CDM model are measured by the ?BIC and ?AIC values. It is shown that the INADE model is better than the NADE model in the fit, and the INADE(A) model is the best in fitting data among the three cases.

Zhang, JingFei; Zhao, LiAng; Zhang, Xin

2014-01-01

392

Revisiting the interacting model of new agegraphic dark energy  

CERN Document Server

In this paper, a new version of the interacting model of new agegraphic dark energy (INADE) is proposed and analyzed in detail. The interaction between dark energy and dark matter is reconsidered. The interaction term $Q=bH_0\\rho_{\\rm de}^\\alpha\\rho_{\\rm dm}^{1-\\alpha}$ is adopted, which abandons the Hubble expansion rate $H$ and involves both $\\rho_{\\rm de}$ and $\\rho_{\\rm dm}$. Moreover, the new initial condition for the agegraphic dark energy is used, which solves the problem of accommodating baryon matter and radiation in the model. The solution of the model can be given using an iterative algorithm. A concrete example for the calculation of the model is given. Furthermore, the model is constrained by using the combined Planck data (Planck+BAO+SNIa+$H_0$) and the combined WMAP-9 data (WMAP+BAO+SNIa+$H_0$). Three typical cases are considered: (A) $Q=bH_0\\rho_{\\rm de}$, (B) $Q=bH_0\\sqrt{\\rho_{\\rm de}\\rho_{\\rm dm}}$, and (C) $Q=bH_0\\rho_{\\rm dm}$, which correspond to $\\alpha=1$, 1/2, and 0, respectively. The...

Zhang, Jing-Fei; Zhang, Xin

2014-01-01

393

Investigation of dark matter-dark energy interaction cosmological model  

CERN Document Server

In this paper, we test the dark matter-dark energy interacting cosmological model with a dynamic equation of state $w_{DE}(z)=w_{0}+w_{1}z/(1+z)$, using type Ia supernovae (SNe Ia), Hubble parameter data, baryonic acoustic oscillation (BAO) measurements, and the cosmic microwave background (CMB) observation. This interacting cosmological model has not been studied before. The best-fitted parameters with $1 \\sigma$ uncertainties are $\\delta=-0.022 \\pm 0.006$, $\\Omega_{DM}^{0}=0.213 \\pm 0.008$, $w_0 =-1.210 \\pm 0.033$ and $w_1=0.872 \\pm 0.072$ with $\\chi^2_{min}/dof = 0.990$. At the $1 \\sigma$ confidence level, we find $\\delta<0$, which means that the energy transfer prefers from dark matter to dark energy. We also find that the SNe Ia are in tension with the combination of CMB, BAO and Hubble parameter data. The evolution of $\\rho_{DM}/\\rho_{DE}$ indicates that this interacting model is a good approach to solve the coincidence problem, because the $\\rho_{DE}$ decrease with