WorldWideScience

Sample records for bound water molecules

  1. On the role of charge transfer in the stabilization of weakly bound complexes involving water and hydrogen sulphide molecules

    International Nuclear Information System (INIS)

    Graphical abstract: A charge-displacement analysis allows to quantitatively assess charge-transfer effects in hydrogen-bonded complexes. Highlights: ► We compare water with hydrogen sulphide both interacting with krypton. ► In both cases the interaction possesses a definite charge transfer component. ► Charge-transfer differs slightly in the two systems and exhibits different stereoselectivity. - Abstract: Integral cross section data for collisions of water and hydrogen sulphide molecules with noble gas atoms, measured with the same apparatus under identical conditions and analyzed by exploiting the same potential model, provided a set of internally consistent potential parameters. Their critical comparison is exploited not only to identify those systems where the intermolecular bond is not simply due to the balancing of size repulsion with dispersion and induction attraction, but also to establish the amount of bond stabilization by charge-transfer effects. Such experimental findings are analyzed through extensive and accurate ab initio calculations, addressed at discovering the relevant differences in the basic features of the potential energy surfaces. In particular, we have analyzed in detail the prototype H2S, H2O–Kr systems and found pronounced differences in the dependence of the interaction nature and energy on the relative orientation of the colliding systems. Using the recently proposed charge-displacement analysis we have been able to quantitatively assess charge-transfer effects, which differ significantly in the two systems and exhibit different stereoselectivity. This casts further light on the specificity of water interactions.

  2. Weakly bound states of polar molecules in bilayers

    CERN Document Server

    Fedorov, D V; Zinner, N T; Jensen, A S

    2011-01-01

    We investigate a system of two polarized molecules in a layered trap. The molecules reside in adjacent layers and interact purely via the dipole-dipole interaction. We determine the properties of the ground state of the system as a function of the dipole moment and polarization angle. A bound state is always present in the system and in the weak binding limit the bound state extends to a very large distance and shows universal behavior.

  3. FTIR Studies of Internal Water Molecules of Bacteriorhodopsin: Structural Analysis of Halide-bound D85S and D212N Mutants in the Schiff Base Region

    Science.gov (United States)

    Shibata, Mikihiro; Kandori, Hideki

    2007-12-01

    Bacteriorhodopsin (BR), a membrane protein found in Halobacterium salinarum, functions as a light-driven proton pump. The Schiff base region has a quadropolar structure with positive charges located at the protonated Schiff base and Arg82, and counterbalancing negative charges located at Asp85 and Asp212 (Figure 1A). It is known that BR lacks a proton-pumping activity if Asp85 or Asp212 is neutralized by mutation. On the other hand, binding of C1- brings different effects for pumping functions in mutants at D85 and D212 position. While C1--bound D85T and D85S pump C1-, photovoltage measurements suggested that C1--bound D212N pumps protons at low pH. In this study, we measured low-temperature FTIR spectra of D85S and D212N containing various halides to compare the halide binding site of both proteins. In the case of D85S, the N-D stretching vibrations of the Schiff base were halide-dependent. This result suggests that the halide is a hydrogen-bond acceptor of the Schiff base, being consistent with the X-ray crystal structure. On the other hand, no halide dependence was observed for vibrational bands of the retinal skeleton and the Schiff base in the D212N mutant. This result suggests that the halide does not form a hydrogen bond with the Schiff base directly, unlike the mutation at D85 position. Halide-dependent water bands in the Schiff base region also differ between D85S and D212N. From these results, halide binding site of both proteins and role of two negative charges in BR will be discussed.

  4. When water molecules meet air

    OpenAIRE

    Hsie, Cho-Shuen; Campen, R. Kramer; Verde, Ana Vila; Bolhuis, Peter; Nienhuys, Han-Kwang; Bonn, Mischa

    2012-01-01

    About 70% of our planet is covered in water. Most of that water exists as water in the bulk – the neighbors of water molecules are other water molecules – and only a small fraction of molecules are at the air-water interface. Despite the small relative abundance of interfacial water, it is of the utmost importance: it governs the chemistry involving the surface of oceans and seawater aerosols, or the small water droplets forming clouds. Reactions at the air-water interface are directly releva...

  5. Bound water in Kevlar 49 fibers

    International Nuclear Information System (INIS)

    From elemental analyses, thermogravimetric-mass spectroscopy studies and re-evaluation of previous water diffusion studies in Kevlar 49 fibers it is concluded that these fibers can contain two types of sorbed moisture. The fibers can absorb up to approx. 6 wt % loosely bound water with an activation energy for outgassing by desorption of 6 kcal/mole. This loosely bound water is a direct result of the presence of Na2SO4 impurities and the perturbations they induce on the packing of the rod-like poly (p-phenylene terephthalamide) macromolecules. Kevlar 49 fibers also inherently contain up to 30 wt % additional water which is tightly bound within the crystal lattice. This water exhibits an activation energy for outgassing by diffusion of approx. 40 kcal/mole and is only evolved from the fiber in significant quantities at t > 3500C over a period of hours

  6. Experimental study of pion capture by hydrogen bound in molecules

    International Nuclear Information System (INIS)

    An experiment was performed at TRIUMF to study the formation of pionic hydrogen atoms and molecules in solids, particularly in groups of organic molecules of slightly different structure in order to help further clarify the problem. The nuclear capture of pions by hydrogen was measured using the charge exchange of stopped pions. The coincident photons emitted by the decaying π0 mesons were detected by TRIUMF's two large NaI spectrometers. Experimental results were obtained for the capture probability of stopped π- mesons in the nuclei of hydrogen atoms, chemically bound in molecules of some simple hydrides, acid anhydrides, and sugar isomers. A possible correlation was found between pion capture in hydrogen and the melting point of sugar isomers. The pion-capture probability in acid anhydrides is fairly well described by a simple atomic-capture model in which the capture probability on the hydrogen dramatically increases as the hydrogen atom is separated from the strongly electronegative C2O3 group. Both effects are consistent with a correlation between pion capture and electron density on hydrogen atoms

  7. Experimental study on pion capture by hydrogen bound in molecules

    International Nuclear Information System (INIS)

    An experiment was performed at TRIUMF to study the formation of pionic hydrogen atoms and molecules in solids, particularly in groups of organic molecules of slightly different structure in order to help further clarify the problem. The nuclear capture of pions by hydrogen was measured using the charge exchange of stopped pions. The coincident photons emitted by the decaying π0 mesons were detected by TRIUMF's two large NaI spectrometers. New experimental results were obtained for the capture probability of stopped π- mesons in the nuclei of hydrogen atoms, chemically bound in molecules of some simple hydrides, acid anhydrides, and sugar isomers. A linear relation was found between pion capture in hydrogen and melting point in sugar isomers. The pion capture probability in acid anhydrides is fairly well described by a simple atomic capture model in which the capture probability on the hydrogen dramatically increases as the hydrogen atom is separated from the strongly electronegative C2O3 group. Both effects are consistent with a correlation between pion capture and electron density on hydrogen atoms. (Author) (38 refs., 4 tabs., 7 figs.)

  8. Water molecules orientation in surface layer

    Science.gov (United States)

    Klingo, V. V.

    2000-08-01

    The water molecules orientation has been investigated theoretically in the water surface layer. The surface molecule orientation is determined by the direction of a molecule dipole moment in relation to outward normal to the water surface. Entropy expressions of the superficial molecules in statistical meaning and from thermodynamical approach to a liquid surface tension have been found. The molecules share directed opposite to the outward normal that is hydrogen protons inside is equal 51.6%. 48.4% water molecules are directed along to surface outward normal that is by oxygen inside. A potential jump at the water surface layer amounts about 0.2 volts.

  9. Positron-molecule interactions: resonant attachment, annihilation, and bound states

    CERN Document Server

    Gribakin, G F; Surko, C M; 10.1103/RevModPhys.82.2557

    2010-01-01

    This article presents an overview of current understanding of the interaction of low-energy positrons with molecules with emphasis on resonances, positron attachment and annihilation. Annihilation rates measured as a function of positron energy reveal the presence of vibrational Feshbach resonances (VFR) for many polyatomic molecules. These resonances lead to strong enhancement of the annihilation rates. They also provide evidence that positrons bind to many molecular species. A quantitative theory of VFR-mediated attachment to small molecules is presented. It is tested successfully for selected molecules (e.g., methyl halides and methanol) where all modes couple to the positron continuum. Combination and overtone resonances are observed and their role is elucidated. In larger molecules, annihilation rates from VFR far exceed those explicable on the basis of single-mode resonances. These enhancements increase rapidly with the number of vibrational degrees of freedom. While the details are as yet unclear, intr...

  10. Bounds on fifth forces from precision measurements on molecules

    CERN Document Server

    Salumbides, E J; Komasa, J; Pachucki, K; Eikema, K S E; Ubachs, W

    2013-01-01

    Highly accurate results from frequency measurements on neutral hydrogen molecules H_2, HD and D_2 as well as the HD^+ ion can be interpreted in terms of constraints on possible fifth-force interactions. Where the hydrogen atom is a probe for yet unknown lepton-hadron interactions, and the helium atom is sensitive for lepton-lepton interactions, molecules open the domain to search for additional long-range hadron-hadron forces. First principles calculations in the framework of quantum electrodynamics have now advanced to the level that hydrogen molecules and hydrogen molecular ions have become calculable systems, making them a search-ground for fifth forces. Following a phenomenological treatment of unknown hadron-hadron interactions written in terms of a Yukawa potential of the form V_5(r)=\\beta exp(-r/\\lambda)/r current precision measurements on hydrogenic molecules yield a constraint \\beta < 1 \\times 10^{-7} eV\\AA for long-range hadron-hadron interactions at typical force ranges commensurate with separat...

  11. Normal-Mode-Analysis–Monitored Energy Minimization Procedure for Generating Small–Molecule Bound Conformations

    OpenAIRE

    Wang, Qi; Pang, Yuan-Ping

    2007-01-01

    The energy minimization of a small molecule alone does not automatically stop at a local minimum of the potential energy surface of the molecule if the minimum is shallow, thus leading to folding of the molecule and consequently hampering the generation of the bound conformation of a guest in the absence of its host. This questions the practicality of virtual screening methods that use conformations at local minima of their potential energy surfaces (local minimum conformations) as potential ...

  12. Electron exchange between dipole-bound anion and polar molecule and dipole-bound anions dimer formation

    International Nuclear Information System (INIS)

    We consider collision between a dipole-bound molecular anion and a neutral polar molecule and show that the excess electron can bind two neutral molecules into a dimer. Using a variational approach similar to the Heitler-London model of H''+2 ion we obtain the energy terms of such a dimer. Their difference determines the cross-section of electron transfer from the anion to the neutral molecule in quasiclassical near-resonant Born-Oppenheimer approximation. We obtain for the cross-section an analytic expression containing the weak (logarythmic) factor depending on the molecular dipole moment, and collision velocity. Our analytic calculations are in a good accordance with the results of a recent experiment.

  13. Normal-mode-analysis-monitored energy minimization procedure for generating small-molecule bound conformations.

    Directory of Open Access Journals (Sweden)

    Qi Wang

    Full Text Available The energy minimization of a small molecule alone does not automatically stop at a local minimum of the potential energy surface of the molecule if the minimum is shallow, thus leading to folding of the molecule and consequently hampering the generation of the bound conformation of a guest in the absence of its host. This questions the practicality of virtual screening methods that use conformations at local minima of their potential energy surfaces (local minimum conformations as potential bound conformations. Here we report a normal-mode-analysis-monitored energy minimization (NEM procedure that generates local minimum conformations as potential bound conformations. Of 22 selected guest-host complex crystal structures with guest structures possessing up to four rotatable bonds, all complexes were reproduced, with guest mass-weighted root mean square deviations of <1.0 A, through docking with the NEM-generated guest local minimum conformations. An analysis of the potential energies of these local minimum conformations showed that 22 (100%, 18 (82%, 16 (73%, and 12 (55% of the 22 guest bound conformations in the crystal structures had conformational strain energies of less than or equal to 3.8, 2.0, 0.6, and 0.0 kcal/mol, respectively. These results suggest that (1 the NEM procedure can generate small-molecule bound conformations, and (2 guests adopt low-strain-energy conformations for complexation, thus supporting the virtual screening methods that use local minimum conformations.

  14. Host-Guest Chemistry in the Gas Phase: Complex Formation of Cucurbit[6]uril with Proton-bound Water Dimer

    Science.gov (United States)

    Noh, Dong Hun; Lee, Shin Jung C.; Lee, Jong Wha; Kim, Hugh I.

    2014-03-01

    The hydration of cucurbit[6]uril (CB[6]) in the gas phase is investigated using electrospray ionization traveling wave ion mobility mass spectrometry (ESI-TWIM-MS). Highly abundant dihydrated and tetrahydrated species of diprotonated CB[6] are found in the ESI-TWIM-MS spectrum. The hydration patterns of the CB[6] ion and the dissociation patterns of the hydrated CB[6] ion indicate that two water molecules are bound to each other, forming a water dimer in the CB[6] complex. Ion mobility studies combined with the structures calculated by density functional theory suggest that the proton-bound water dimer is present as a Zundel-like structure in the CB[6] portal, forming a hydrogen bond network with carbonyl groups of the CB[6]. When a large guest molecule is bound to a CB[6] portal, water molecules cannot bind to the portal. In addition, the strong binding energy of the water dimer blocks the portal, hindering the insertion of the long alkyl chain of the guest molecule into the CB[6] cavity. With small alkali metal cations, such as Li+ and Na+, a single water molecule interacts with the CB[6] portal, forming hydrogen bonds with the carbonyl groups of CB[6]. A highly stable Zundel-like structure of the proton-bound water dimer or a metal-bound water molecule at the CB[6] portal is suggested as an initial hydration process for CB[6], which is only dissolved in aqueous solution with acid or alkali metal ions.

  15. Modelling water molecules inside cyclic peptide nanotubes

    Science.gov (United States)

    Tiangtrong, Prangsai; Thamwattana, Ngamta; Baowan, Duangkamon

    2016-03-01

    Cyclic peptide nanotubes occur during the self-assembly process of cyclic peptides. Due to the ease of synthesis and ability to control the properties of outer surface and inner diameter by manipulating the functional side chains and the number of amino acids, cyclic peptide nanotubes have attracted much interest from many research areas. A potential application of peptide nanotubes is their use as artificial transmembrane channels for transporting ions, biomolecules and waters into cells. Here, we use the Lennard-Jones potential and a continuum approach to study the interaction of a water molecule in a cyclo[(- D-Ala- L-Ala)_4-] peptide nanotube. Assuming that each unit of a nanotube comprises an inner and an outer tube and that a water molecule is made up of a sphere of two hydrogen atoms uniformly distributed over its surface and a single oxygen atom at the centre, we determine analytically the interaction energy of the water molecule and the peptide nanotube. Using this energy, we find that, independent of the number of peptide units, the water molecule will be accepted inside the nanotube. Once inside the nanotube, we show that a water molecule prefers to be off-axis, closer to the surface of the inner nanotube. Furthermore, our study of two water molecules inside the peptide nanotube supports the finding that water molecules form an array of a 1-2-1-2 file inside peptide nanotubes. The theoretical study presented here can facilitate thorough understanding of the behaviour of water molecules inside peptide nanotubes for applications, such as artificial transmembrane channels.

  16. Four-body long-range interactions between ultracold weakly-bound diatomic molecules

    CERN Document Server

    Lepers, Maxence; Luc-Koenig, Eliane; Dulieu, Olivier

    2015-01-01

    Using the multipolar expansion of electrostatic and magnetostatic potential energies, we characterize the long-range interactions between two weakly-bound diatomic molecules, taking as an example the paramagnetic Er$_2$ Feshbach molecules which were produced recently. Since inside each molecule, individual atoms conserve their identity, the intermolecular potential energy can be expanded as the sum of pairwise atomic potential energies. In the case of Er$_2$ Feshbach molecules, we show that the interaction between atomic magnetic dipoles gives rise to the usual $R^{-3}$ term of the multipolar expansion, with $R$ the intermolecular distance, but also to additional terms scaling as $R^{-5}$, $R^{-7}$, and so on. Those terms are due to the interaction between effective molecular multipole moments, and are strongly anisotropic with respect to the orientation of the molecules. Similarly the atomic pairwise van der Waals interaction results in $R^{-6}$, $R^{-8}$, ... terms in the intermolecular potential energy. By...

  17. Bound states in the continuum and spin filter in quantum-dot molecules

    Energy Technology Data Exchange (ETDEWEB)

    Ramos, J.P. [Departamento de Física, Universidad Católica del Norte, Casilla 1280, Antofagasta (Chile); Orellana, P.A., E-mail: pedro.orellana@usm.cl [Departamento de Física, Universidad Técnica Federico Santa María, Vicuña Mackenna 3939, Santiago (Chile)

    2014-12-15

    In this paper we study the formation of bound states in the continuum in a quantum dot molecule coupled to leads and their potential application in spintronics. Based on the combination of bound states in the continuum and Fano effect, we propose a new design of a spin-dependent polarizer. By lifting the spin degeneracy of the carriers in the quantum dots by means of a magnetic field the system can be used as a spin-polarized device. A detailed analysis of the spin-dependent conductance and spin polarization as a function of the applied magnetic field and gate voltages is carried out.

  18. Control of Optical Transitions with Magnetic Fields in Weakly Bound Molecules

    OpenAIRE

    McGuyer, B. H.; McDonald, M.; Iwata, G. Z.; Skomorowski, W.; Moszynski, R.; Zelevinsky, T.

    2015-01-01

    In weakly bound diatomic molecules, energy levels are closely spaced and thus more susceptible to mixing by magnetic fields than in the constituent atoms. We use this effect to control the strengths of forbidden optical transitions in $^{88}$Sr$_2$ over 5 orders of magnitude with modest fields by taking advantage of the intercombination-line threshold. The physics behind this remarkable tunability is accurately explained with both a simple model and quantum chemistry calculations, and suggest...

  19. Modelling proton transfer in water molecule chains

    CERN Document Server

    Korzhimanov, Artem; Shutova, Tatiana; Samuelsson, Goran

    2011-01-01

    The process of protons transport in molecular water chains is of fundamental interest for many biological systems. Although many features of such systems can be analyzed using large-scale computational modeling, other features are better understood in terms of simplified model problems. Here we have tested, analytically and numerically, a model describing the classical proton hopping process in molecular water chains. In order to capture the main features of the proton hopping process in such molecular chains, we use a simplified model for our analysis. In particular, our discrete model describes a 1D chain of water molecules situated in an external protein channel structure, and each water molecule is allowed to oscillate around its equilibrium point in this system, while the protons are allowed to move along the line of neighboring oxygen atoms. The occurrence and properties of nonlinear solitary transport structures, allowing for much faster proton transport, are discussed, and the possible implications of...

  20. Tritium fractionation in anomalous water bound to environmental samples

    International Nuclear Information System (INIS)

    The quantification of the hydrogen isotope effect involved in the physi- and chemisorption of water on to environmental samples provides the possibility for the characterization of their bound water. This is realized by distilling suspensions of samples in tritiated water (HTO/H2O) under near-equilibrium conditions at 5o C and 5 mbar, and measuring the specific tritium activity in fractions of the condensed gas phase in the course of water removal. The tritium fractionation is caused by isotope effects during the evaporation of water as well as during the sorption of water on to the sample matrix. The two isotope effects are separated by comparing the fractionation in the sample-water mixtures with that in pure water. Three typical soils and maize plant seeds are chosen for investigation. The experimental procedure is tested for model substances with well known amounts of bound water, e.g. Na-tartrate-dihydrate and molecular sieve. The investigated examples show a different water sorption capacity from 4 to 60% related to the dry substance. Dehydration kinetics further demonstrate the existence of at least four types of sorbed water with distinct fractionation factors. They are characterized by the specific-activity ratio of sorbed water to free water, which ranges from 0.97 to 1.46. (Author)

  1. Clusters of mobile molecules in supercooled water

    Science.gov (United States)

    Giovambattista, Nicolas; Buldyrev, Sergey V.; Stanley, H. Eugene; Starr, Francis W.

    2005-07-01

    We study the spatially heterogeneous dynamics in water via molecular dynamics simulations using the extended simple point charge potential. We identify clusters formed by mobile molecules and study their properties. We find that these clusters grow in size and become more compact as temperature decreases. We analyze the probability density function of cluster size, and we study the cluster correlation length. We find that clusters appear to be characterized by a fractal dimension consistent with that of lattice animals. We relate the cluster size and correlation length to the configurational entropy, Sconf . We find that these quantities depend weakly on 1/Sconf . In particular, the linearity found between the cluster mass n* and 1/Sconf suggests that n* may be interpreted as the mass of the cooperatively rearranging regions that form the basis of the Adam-Gibbs approach to the dynamics of supercooled liquids. We study the motion of molecules within a cluster, and find that each molecule preferentially follows a neighboring molecule in the same cluster. Based on this finding we hypothesize that stringlike cooperative motion may be a general mechanism for molecular rearrangement of complex, as well as simple liquids. By mapping each equilibrium configuration onto its corresponding local potential energy minimum or inherent structure (IS), we are able to compare the mobile molecule clusters in the equilibrium system with the molecules forming the clusters identified in the transitions between IS. We find that (i) mobile molecule clusters obtained by comparing different system configurations and (ii) clusters obtained by comparing the corresponding IS are completely different for short time scales, but are the same on the longer time scales of diffusive motion.

  2. Scanning a DNA molecule for bound proteins using hybrid magnetic and optical tweezers.

    Directory of Open Access Journals (Sweden)

    Marijn T J van Loenhout

    Full Text Available The functional state of the genome is determined by its interactions with proteins that bind, modify, and move along the DNA. To determine the positions and binding strength of proteins localized on DNA we have developed a combined magnetic and optical tweezers apparatus that allows for both sensitive and label-free detection. A DNA loop, that acts as a scanning probe, is created by looping an optically trapped DNA tether around a DNA molecule that is held with magnetic tweezers. Upon scanning the loop along the λ-DNA molecule, EcoRI proteins were detected with ~17 nm spatial resolution. An offset of 33 ± 5 nm for the detected protein positions was found between back and forwards scans, corresponding to the size of the DNA loop and in agreement with theoretical estimates. At higher applied stretching forces, the scanning loop was able to remove bound proteins from the DNA, showing that the method is in principle also capable of measuring the binding strength of proteins to DNA with a force resolution of 0.1 pN/[Formula: see text]. The use of magnetic tweezers in this assay allows the facile preparation of many single-molecule tethers, which can be scanned one after the other, while it also allows for direct control of the supercoiling state of the DNA molecule, making it uniquely suitable to address the effects of torque on protein-DNA interactions.

  3. Control of Optical Transitions with Magnetic Fields in Weakly Bound Molecules.

    Science.gov (United States)

    McGuyer, B H; McDonald, M; Iwata, G Z; Skomorowski, W; Moszynski, R; Zelevinsky, T

    2015-07-31

    In weakly bound diatomic molecules, energy levels are closely spaced and thus more susceptible to mixing by magnetic fields than in the constituent atoms. We use this effect to control the strengths of forbidden optical transitions in (88)Sr2 over 5 orders of magnitude with modest fields by taking advantage of the intercombination-line threshold. The physics behind this remarkable tunability is accurately explained with both a simple model and quantum chemistry calculations, and suggests new possibilities for molecular clocks. We show how mixed quantization in an optical lattice can simplify molecular spectroscopy. Furthermore, our observation of formerly inaccessible f-parity excited states offers an avenue for improving theoretical models of divalent-atom dimers. PMID:26274416

  4. Structure of bound water and refinement of acid metmyoglobin

    International Nuclear Information System (INIS)

    The structure of myoglobin has been determined by x-ray diffraction for the acidmet, deoxy, and the oxy forms. Neutron diffraction work, done in this laboratory, has demonstrated that hydrogen and deuterium positions can be located. In addition to the localization of H and D, neutron diffraction provides a unique method for studying the water structure because of the strong scattering ability of D2O. The scattering factor of deuterium is nearly twice as large as that of hydrogen, and it increases the visibility of water molecules in Fourier maps, so that in a neutron map a water molecule appears about three times as strong as in an equivalent electron-density map. (DT)

  5. Sequential photochemical and microbial degradation of organic molecules bound to humic acid

    International Nuclear Information System (INIS)

    We studied the effects of photochemical processes on the mineralization by soil microorganisms of [2-14C]glycine bound to soil humic acid. Microbial mineralization of these complexes in the dark increased inversely with the molecular weight of the complex molecules. Sunlight irradiation of glycine-humic acid complexes resulted in loss of absorbance in the UV range and an increase in the amount of 14C-labeled low-molecular-weight photoproducts and the rate and extent of mineralization. More than half of the radioactivity in the low-molecular-weight photoproducts appears to be associated with carboxylic acids. Microbial mineralization of the organic carbon increased with solar flux and was proportional to the loss of A330. Mineralization was proportional to the percentage of the original complex that was converted to low-molecular-weight photoproducts. Only light at wavelengths below 380 nm had an effect on the molecular weight distribution of the products formed from the glycine-humic acid complexes and on the subsequent microbial mineralization. Our results indicate that photochemical processes generate low-molecular-weight, readily biodegradable molecules from high-molecular-weight complexes of glycine with humic acid

  6. Slow neutron scattering by water molecules

    International Nuclear Information System (INIS)

    In this work some new, preliminary formulae for slow neutron scattering cross section calculation by heavy and light water molecules have been done. The idea was to find, from the sum which exists in well known Nelkin model, other cross sections in a more simple analytical form, so that next approximations may be possible. In order to sum a series it was starting from Euler-Mclaurin formula. Some new summation formulae have been derived there, and defined in two theorems. Extensive calculations, especially during the evaluation of residues, have been made at the CDC 3600 computer. validation of derived formulae was done by comparison with the BNL-325 results. Good agreement is shown. (author)

  7. Formation of deeply bound ultracold Sr_2 molecules by photoassociation near the ^1S + ^3P_1 intercombination line

    OpenAIRE

    Skomorowski, Wojciech; Moszynski, Robert; Koch, Christiane P.

    2012-01-01

    We predict feasibility of the photoassociative formation of Sr_2 molecules in arbitrary vibrational levels of the electronic ground state based on state-of-the-art ab initio calculations. Key is the strong spin-orbit interaction between the c^3\\Pi_u, A^1\\Sigma_u^+ and B^1\\Sigma_u^+ states. It creates not only an effective dipole moment allowing free-to-bound transitions near the ^1S + ^3P_1 intercombination line but also facilitates bound-to-bound transitions via resonantly coupled excited st...

  8. Neutron investigations of self-diffusion of water molecules in plasmatic membranes

    International Nuclear Information System (INIS)

    Using of neutron spectroscopy method, we investigated the cisplatin treatment response in cancer cells (Guerin's carcinoma) with relation to antitumor antibiotic effect on self-diffusion of bound water molecules in plasmatic membranes. The drug resistant sample and the sensible one have been used for testing. We found that cisplatin treatment gives rise to: i) useful increasing of self-diffusion coefficient of water molecules (their mobility) both for the drug resistant sample and the sensible one; ii) the mobility of water molecules in the drug resistant (sensible) sample increases due to the collective (single-particle) contribution to self-diffusion coefficient of water molecules that corresponds to increasing (decreasing) of H2O clusterization in cell membranes

  9. Free energy barriers for escape of water molecules from protein hydration layer.

    Science.gov (United States)

    Roy, Susmita; Bagchi, Biman

    2012-03-01

    Free energy barriers separating interfacial water molecules from the hydration layer at the surface of a protein to the bulk are obtained by using the umbrella sampling method of free energy calculation. We consider hydration layer of chicken villin head piece (HP-36) which has been studied extensively by molecular dynamics simulations. The free energy calculations reveal a strong sensitivity to the secondary structure. In particular, we find a region near the junction of first and second helix that contains a cluster of water molecules which are slow in motion, characterized by long residence times (of the order of 100 ps or more) and separated by a large free energy barrier from the bulk water. However, these "slow" water molecules constitute only about 5-10% of the total number of hydration layer water molecules. Nevertheless, they play an important role in stabilizing the protein conformation. Water molecules near the third helix (which is the important helix for biological function) are enthalpically least stable and exhibit the fastest dynamics. Interestingly, barrier height distributions of interfacial water are quite broad for water surrounding all the three helices (and the three coils), with the smallest barriers found for those near the helix-3. For the quasi-bound water molecules near the first and second helices, we use well-known Kramers' theory to estimate the residence time from the free energy surface, by estimating the friction along the reaction coordinate from the diffusion coefficient by using Einstein relation. The agreement found is satisfactory. We discuss the possible biological function of these slow, quasi-bound (but transient) water molecules on the surface. PMID:22288939

  10. WAVE EQUATION MODEL FOR SHIP WAVES IN BOUNDED SHALLOW WATER

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Ships were modelled as moving pressure disturbances on the free surface of a shallow water basin in the present paper.The moving-pressure generating waves were subjected to the reflection of land boundaries and the radiation of open boundaries.This paper proposed and examined a wave equation model (WEM) to solve the shallow water equations with moving surface pressures simulating ship waves in a bounded shallow water region.The Galerkin finite element method was used to solve a second order wave equation for the free surface elevations and the hydrodynamic pressure of the ship bottom simultaneously.Horizontal velocities were obtained from the momentum equations.Numerical solutions of Series 60 CB=0.6 ships moving with the depth Froude number of Fh=0.6, 1.0, 1.3 in a rectangular shallow water harbor were investigated.Three dimensional surface elevation profiles and the depth-averaged horizontal velocities were analysed.The numerical results characterised very well the ship waves in shallow water.Strong boundary reflection waves were found in the case of high depth Froude number (Fh=1.3).Waves generated by the interactions of two ships moving in the same directions and in the opposite directions were also numerically investigated in the present study.

  11. Formation of deeply bound ultracold Sr_2 molecules by photoassociation near the ^1S + ^3P_1 intercombination line

    CERN Document Server

    Skomorowski, Wojciech; Koch, Christiane P

    2012-01-01

    We predict feasibility of the photoassociative formation of Sr_2 molecules in arbitrary vibrational levels of the electronic ground state based on state-of-the-art ab initio calculations. Key is the strong spin-orbit interaction between the c^3\\Pi_u, A^1\\Sigma_u^+ and B^1\\Sigma_u^+ states. It creates not only an effective dipole moment allowing free-to-bound transitions near the ^1S + ^3P_1 intercombination line but also facilitates bound-to-bound transitions via resonantly coupled excited state rovibrational levels to deeply bound rovibrational levels of the ground X^1\\Sigma_g^+ potential, with v" as low as v"=6. The spin-orbit interaction is responsible for both optical pathways. Therefore, those excited state levels that have the largest bound-to-bound transition moments to deeply bound ground state levels also exhibit a sufficient photoassociation probability, comparable to that of the lowest weakly bound excited state level previously observed by Zelevinsky et al. [Phys. Rev. Lett. 96, 203201 (2006)]. Ou...

  12. Reactivity of Metal Ions Bound to Water-Soluble Polymers

    Energy Technology Data Exchange (ETDEWEB)

    Sauer, N.N.; Watkins, J.G.; Lin, M.; Birnbaum, E.R.; Robison, T.W.; Smith, B.F.; Gohdes, J.W.; McDonald, J.G.

    1999-06-29

    The intent of this work is to determine the effectiveness of catalysts covalently bound to polymers and to understand the consequences of supporting the catalysts on catalyst efficiency and selectivity. Rhodium phosphine complexes with functional groups for coupling to polymers were prepared. These catalyst precursors were characterized using standard techniques including IR, NMR, and elemental analysis. Studies on the modified catalysts showed that they were still active hydrogenation catalysts. However, tethering of the catalysts to polyamines gave systems with low hydrogenation activity. Analogous biphasic systems were also explored. Phosphine ligands with a surfactant-like structure have been synthesized and used to prepare catalytically active complexes of palladium. The palladium complexes were utilized in Heck-type coupling reactions (e.g. coupling of iodobenzene and ethyl acrylate to produce ethyl cinnamate) under vigorously stirred biphasic reaction conditions, and were found to offer superior performance over a standard water-soluble palladium catalyst under analogous conditions.

  13. Origin of subdiffusion of water molecules on cell membrane surfaces

    CERN Document Server

    Yamamoto, Eiji; Yasui, Masato; Yasuoka, Kenji

    2014-01-01

    Water molecules play an important role in providing unique environments for biological reactions on cell membranes. It is widely believed that water molecules form bridges that connect lipid molecules and stabilize cell membranes. Using all-atom molecular dynamics simulations, we show that translational and rotational diffusion of water molecules on lipid membrane surfaces exhibit subdiffusion. Moreover, we provide evidence that both divergent mean trapping time (continuous-time random walk) and long-correlated noise (fractional Brownian motion) contribute to this subdiffusion. These results suggest that subdiffusion on cell membranes causes the water retardation, an enhancement of cell membrane stability, and a higher reaction efficiency.

  14. Ficolins and FIBCD1: Soluble and membrane bound pattern recognition molecules with acetyl group selectivity

    DEFF Research Database (Denmark)

    Thomsen, Theresa; Schlosser, Anders; Holmskov, Uffe;

    2011-01-01

    A network of molecules, which recognizes pathogens, work together to establish a quick and efficient immune response to infectious agents. Molecules containing a fibrinogen related domain in invertebrates and vertebrates have been implicated in immune responses against pathogens, and characterized......D-containing molecules, and discusses structural resemblance but also diversity in recognition of acetylated ligands....

  15. Depletion of water molecules during ethanol wet-bonding with etch and rinse dental adhesives

    International Nuclear Information System (INIS)

    The treatment of demineralized dentin with ethanol has been proposed as a way to improve hydrophobic monomer penetration into otherwise water saturated collagen fibrils. The ethanol rinse is expected to preserve the fibrils from collapsing while optimizing resin constituent infiltration for better long term adhesion. The physico-chemical investigations of demineralized dentin confirmed objectively these working hypotheses. Namely, Differential Scanning Calorimetry (DSC) measurements of the melting point of water molecules pointed to the presence of free and bound water states. Unfreezable water was the main type of water remaining following a rinsing step with absolute ethanol. Two different liquid water phases were also observed by Magic Angle Spinning (MAS) solid state Nuclear magnetic Resonance (NMR) spectroscopy. Infrared spectra of ethanol treated specimens illustrated differences with the fully hydrated specimens concerning the polar carbonyl vibrations. Optical microscopy observations as well as scanning electron microscopy showed an improved dentin-adhesive interface with ethanol wet bonding. The results indicate that water can be confined to strongly bound structural molecules when excess water is removed with ethanol prior to adhesive application. This should preserve collagen from hydrolysis upon aging of the hybrid layer. - Highlights: ► Non-freezable water exists in demineralized dentine. ► Free water can be removed by ethanol rinse of the demineralized collagen. ► Ethanol wet bonding leads to a homogeneous hybrid layer free of defects.

  16. Depletion of water molecules during ethanol wet-bonding with etch and rinse dental adhesives

    Energy Technology Data Exchange (ETDEWEB)

    Gregoire, Genevieve, E-mail: gregoire@cict.fr [Department of Biomaterials, Faculty of Odontology, University Toulouse III, 31062, Toulouse (France); Sharrock, Patrick [Medical and Spatial Imaging Laboratory, University Toulouse III, Ave. Pompidou, 81104, Castres (France); Delannee, Mathieu [Department of Biomaterials, Faculty of Odontology, University Toulouse III, 31062, Toulouse (France); Delisle, Marie-Bernadette [Faculty of Medicine, University Toulouse III, 31062, Toulouse (France)

    2013-01-01

    The treatment of demineralized dentin with ethanol has been proposed as a way to improve hydrophobic monomer penetration into otherwise water saturated collagen fibrils. The ethanol rinse is expected to preserve the fibrils from collapsing while optimizing resin constituent infiltration for better long term adhesion. The physico-chemical investigations of demineralized dentin confirmed objectively these working hypotheses. Namely, Differential Scanning Calorimetry (DSC) measurements of the melting point of water molecules pointed to the presence of free and bound water states. Unfreezable water was the main type of water remaining following a rinsing step with absolute ethanol. Two different liquid water phases were also observed by Magic Angle Spinning (MAS) solid state Nuclear magnetic Resonance (NMR) spectroscopy. Infrared spectra of ethanol treated specimens illustrated differences with the fully hydrated specimens concerning the polar carbonyl vibrations. Optical microscopy observations as well as scanning electron microscopy showed an improved dentin-adhesive interface with ethanol wet bonding. The results indicate that water can be confined to strongly bound structural molecules when excess water is removed with ethanol prior to adhesive application. This should preserve collagen from hydrolysis upon aging of the hybrid layer. - Highlights: Black-Right-Pointing-Pointer Non-freezable water exists in demineralized dentine. Black-Right-Pointing-Pointer Free water can be removed by ethanol rinse of the demineralized collagen. Black-Right-Pointing-Pointer Ethanol wet bonding leads to a homogeneous hybrid layer free of defects.

  17. Single-molecule FRET reveals a corkscrew RNA structure for the polymerase-bound influenza virus promoter

    OpenAIRE

    Tomescu, Alexandra I.; Robb, Nicole C.; Hengrung, Narin; Fodor, Ervin; Kapanidis, Achillefs N.

    2014-01-01

    The genome of the influenza virus consists of eight single-stranded segments of RNA with highly conserved 5′ and 3′ termini. These termini associate to form double-stranded structures that act as promoters for viral transcription and replication. Structural information on the polymerase-bound promoter currently does not exist, so to address this we developed a sensitive single-molecule FRET assay that allowed us to measure distances between fluorescent dyes located on the promoter and map its...

  18. Free enthalpies of replacing water molecules in protein binding pockets.

    Science.gov (United States)

    Riniker, Sereina; Barandun, Luzi J; Diederich, François; Krämer, Oliver; Steffen, Andreas; van Gunsteren, Wilfred F

    2012-12-01

    Water molecules in the binding pocket of a protein and their role in ligand binding have increasingly raised interest in recent years. Displacement of such water molecules by ligand atoms can be either favourable or unfavourable for ligand binding depending on the change in free enthalpy. In this study, we investigate the displacement of water molecules by an apolar probe in the binding pocket of two proteins, cyclin-dependent kinase 2 and tRNA-guanine transglycosylase, using the method of enveloping distribution sampling (EDS) to obtain free enthalpy differences. In both cases, a ligand core is placed inside the respective pocket and the remaining water molecules are converted to apolar probes, both individually and in pairs. The free enthalpy difference between a water molecule and a CH(3) group at the same location in the pocket in comparison to their presence in bulk solution calculated from EDS molecular dynamics simulations corresponds to the binding free enthalpy of CH(3) at this location. From the free enthalpy difference and the enthalpy difference, the entropic contribution of the displacement can be obtained too. The overlay of the resulting occupancy volumes of the water molecules with crystal structures of analogous ligands shows qualitative correlation between experimentally measured inhibition constants and the calculated free enthalpy differences. Thus, such an EDS analysis of the water molecules in the binding pocket may give valuable insight for potency optimization in drug design. PMID:23247390

  19. The rotating Morse potential model for diatomic molecules in the tridiagonal J-matrix representation: I. Bound states

    Energy Technology Data Exchange (ETDEWEB)

    Nasser, I [Physics Department, King Fahd University of Petroleum and Minerals, Dhahran 31261 (Saudi Arabia); Abdelmonem, M S [Physics Department, King Fahd University of Petroleum and Minerals, Dhahran 31261 (Saudi Arabia); Bahlouli, H [Physics Department, King Fahd University of Petroleum and Minerals, Dhahran 31261 (Saudi Arabia); Alhaidari, A D [Shura Council, Riyadh 11212 (Saudi Arabia)

    2007-11-14

    This is the first in a series of articles in which we study the rotating Morse potential model for diatomic molecules in the tridiagonal J-matrix representation. Here, we compute the bound-state energy spectrum by diagonalizing the finite-dimensional Hamiltonian matrix of H{sub 2}, LiH, HCl and CO molecules for arbitrary angular momentum. The calculation was performed using the J-matrix basis that supports a tridiagonal matrix representation for the reference Hamiltonian. Our results for these diatomic molecules have been compared with available numerical data satisfactorily. The proposed method is handy, very efficient, and it enhances accuracy by combining analytic power with a convergent and stable numerical technique.

  20. Structure and dynamics of water and lipid molecules in charged anionic DMPG lipid bilayer membranes

    DEFF Research Database (Denmark)

    Rønnest, A. K.; Peters, Günther H.J.; Hansen, Flemming Yssing;

    2016-01-01

    phase with a monovalent counter-ion and in the gel phase with a divalent counter-ion. The diffusion constant of water as a function of its depth in the membrane has been determined from mean-square-displacement calculations. Also, calculated incoherent quasielastic neutron scattering functions have been...... compared to experimental results and used to determine an average diffusion constant for all water molecules in the system. On extrapolating the diffusion constants inferred experimentally to a temperature of 310 K, reasonable agreement with the simulations is obtained. However, the experiments do not have...... the sensitivity to confirm the diffusion of a small component of water bound to the lipids as found in the simulations. In addition, the orientation of the dipole moment of the water molecules has been determined as a function of their depth in the membrane. Previous indirect estimates of the...

  1. Dressed-bound-state molecular strong-field approximation: Application to above-threshold ionization of heteronuclear diatomic molecules

    International Nuclear Information System (INIS)

    The molecular strong-field approximation (MSFA), which includes dressing of the molecular bound state, is introduced and applied to above-threshold ionization of heteronuclear diatomic molecules. Expressions for the laser-induced molecular dipole and polarizability as functions of the laser parameters (intensity and frequency) and molecular parameters [molecular orientation, dipole, and parallel and perpendicular polarizabilities of the highest occupied molecular orbital (HOMO)] are presented. Our previous MSFA theory, which incorporates the rescattering effects, is generalized from homonuclear to heteronuclear diatomic molecules. Angle- and energy-resolved high-order above-threshold ionization spectra of oriented heteronuclear diatomic molecules, exemplified by the carbon monoxide (CO) molecule, exhibit pronounced minima, which can be related to the shape of their HOMO-electron-density distribution. For the CO molecule we have found an analytical condition for the positions of these minima. We have also shown that the effect of the dressing of the HOMO is twofold: (i) the laser-induced Stark shift decreases the ionization yield and (ii) the laser-induced time-dependent dipole and polarizability change the oscillatory structure of the spectra.

  2. Clusterization of water molecules as deduced from statistical mechanical approach

    Science.gov (United States)

    Krasnoholovets, Volodymyr

    2004-12-01

    Using the methods of statistical mechanics we have shown that a homogeneous water network is unstable and spontaneously disintegrates to the nonhomogeneous state (i.e. peculiar clusters), which can be treated as an ordinary state of liquid water. The major peculiarity of the concept is that it separates the paired potential into two independent components—the attractive potential and the repulsive one, which in turn should feature a very different dependence on the distance from the particle (a water molecule in the present case). We choose the interaction potential as a combination of the ionic crystal potential and the vibratory potential associated with the elastic properties of the water system as a whole. The number ℵ of water molecules that enters a cluster is calculated as a function of several parameters, such as the dielectric constant, the mass of a water molecule, the distance between nearest molecules, and the vibrations of nearest molecules in their nodes. The number of H2O molecules that comprise a cluster is estimated as about ℵ ≈ 900, which agrees with the available experimental data.

  3. On the Several Molecules and Nanostructures of Water

    Directory of Open Access Journals (Sweden)

    Cynthia Kolb Whitney

    2012-01-01

    Full Text Available This paper investigates the water molecule from a variety of viewpoints. Water can involve different isotopes of Hydrogen and Oxygen, it can form differently shaped isomer molecules, and, when frozen, it occupies space differently than most other substances do. The tool for conducting the investigation of all this is called ‘Algebraic Chemistry’. This tool is a quantitative model for predicting the energy budget for all sorts of changes between different ionization states of atoms that are involved in chemical reactions and in changes of physical state. The model is based on consistent patterns seen in empirical data about ionization potentials, together with rational scaling laws that can interpolate and extrapolate for situations where no data are available. The results of the investigation of the water molecule include comments, both positive and negative, about technologies involving heavy water, poly water, Brown’s gas, and cold fusion.

  4. Quantum Behavior of Water Molecules Confined to Nanocavities in Gemstones.

    Science.gov (United States)

    Gorshunov, Boris P; Zhukova, Elena S; Torgashev, Victor I; Lebedev, Vladimir V; Shakurov, Gil'man S; Kremer, Reinhard K; Pestrjakov, Efim V; Thomas, Victor G; Fursenko, Dimitry A; Dressel, Martin

    2013-06-20

    When water is confined to nanocavities, its quantum mechanical behavior can be revealed by terahertz spectroscopy. We place H2O molecules in the nanopores of a beryl crystal lattice and observe a rich and highly anisotropic set of absorption lines in the terahertz spectral range. Two bands can be identified, which originate from translational and librational motions of the water molecule isolated within the cage; they correspond to the analogous broad bands in liquid water and ice. In the present case of well-defined and highly symmetric nanocavities, the observed fine structure can be explained by macroscopic tunneling of the H2O molecules within a six-fold potential caused by the interaction of the molecule with the cavity walls. PMID:26283245

  5. Improving the efficiency of branch-and-bound complete-search NMR assignment using the symmetry of molecules and spectra

    International Nuclear Information System (INIS)

    Nuclear magnetic resonance (NMR) assignment of small molecules is presented as a typical example of a combinatorial optimization problem in chemical physics. Three strategies that help improve the efficiency of solution search by the branch and bound method are presented: 1. reduction of the size of the solution space by resort to a condensed structure formula, wherein symmetric nuclei are grouped together; 2. partitioning of the solution space based on symmetry, that becomes the basis for an efficient branching procedure; and 3. a criterion of selection of input restrictions that leads to increased gaps between branches and thus faster pruning of non-viable solutions. Although the examples chosen to illustrate this work focus on small-molecule NMR assignment, the results are generic and might help solving other combinatorial optimization problems

  6. Effects of water molecules on photoluminescence from hierarchical peptide nanotubes and water probing capability.

    Science.gov (United States)

    Wang, Minjie; Xiong, Shijie; Wu, Xinglong; Chu, Paul K

    2011-10-01

    Photoluminescence (PL) spectra reveal that deficiency of water molecules in the channel cores of bioinspired hierarchical diphenylalanine ( L -Phe- L -Phe, FF) peptide nanotubes (PNTs) not only modifies the bandgap of the subnanometer crystalline structure formed by the self-assembly process, but also induces a characteristic ultraviolet PL peak the position of which is linearly proportional to the number of water molecules in the PNTs. Addition or loss of water molecules gives rise to the UV PL redshift or blueshift. Density functional theory calculation also confirms that addition of water molecules to the PNTs causes splitting of the valence-band peak, which corresponds to the shift and splitting of the observed UV PL peak. Water molecules play an important role in the biological properties of FF PNTs and the results demonstrate that the PL spectra can be used to probe the number of water molecules bonded to the FF molecules. PMID:22049551

  7. Theoretical study of impulsive orientation of asymmetric top water molecules

    Science.gov (United States)

    Rangan, Chitra; Senchuk, Andrew

    2008-05-01

    We theoretically study the orientation of a polar, asymmetric top molecule by a terahertz half-cycle pulse. This study is motivated by recent experimental results by C. Herne and P.H. Bucksbaum on the orientation of water molecule using terahertz half-cycle pulses. The half-cycle pulse is modelled as an impulse. The degree of orientation is calculated. Our aim is to characterize the calculated orientation curves in terms of rotational spectroscopy constants.

  8. Single-molecule FRET reveals a corkscrew RNA structure for the polymerase-bound influenza virus promoter.

    Science.gov (United States)

    Tomescu, Alexandra I; Robb, Nicole C; Hengrung, Narin; Fodor, Ervin; Kapanidis, Achillefs N

    2014-08-12

    The influenza virus is a major human and animal pathogen responsible for seasonal epidemics and occasional pandemics. The genome of the influenza A virus comprises eight segments of single-stranded, negative-sense RNA with highly conserved 5' and 3' termini. These termini interact to form a double-stranded promoter structure that is recognized and bound by the viral RNA-dependent RNA polymerase (RNAP); however, no 3D structural information for the influenza polymerase-bound promoter exists. Functional studies have led to the proposal of several 2D models for the secondary structure of the bound promoter, including a corkscrew model in which the 5' and 3' termini form short hairpins. We have taken advantage of an insect-cell system to prepare large amounts of active recombinant influenza virus RNAP, and used this to develop a highly sensitive single-molecule FRET assay to measure distances between fluorescent dyes located on the promoter and map its structure both with and without the polymerase bound. These advances enabled the direct analysis of the influenza promoter structure in complex with the viral RNAP, and provided 3D structural information that is in agreement with the corkscrew model for the influenza virus promoter RNA. Our data provide insights into the mechanisms of promoter binding by the influenza RNAP and have implications for the understanding of the regulatory mechanisms involved in the transcription of viral genes and replication of the viral RNA genome. In addition, the simplicity of this system should translate readily to the study of any virus polymerase-promoter interaction. PMID:25071209

  9. Unprecedentedly rapid transport of single-file rolling water molecules

    Science.gov (United States)

    Qiu, Tong; Huang, Ji-Ping

    2015-10-01

    The realization of rapid and unidirectional single-file water-molecule flow in nanochannels has posed a challenge to date. Here, we report unprecedentedly rapid unidirectional single-file water-molecule flow under a translational terahertz electric field, which is obtained by developing a Debye doublerelaxation theory. In addition, we demonstrate that all the single-file molecules undergo both stable translation and rotation, behaving like high-speed train wheels moving along a railway track. Independent molecular dynamics simulations help to confirm these theoretical results. The mechanism involves the resonant relaxation dynamics of H and O atoms. Further, an experimental demonstration is suggested and discussed. This work has implications for the design of high-efficiency nanochannels or smaller nanomachines in the field of nanotechnology, and the findings also aid in the understanding and control of water flow across biological nanochannels in biology-related research.

  10. Transport behavior of water molecules through two-dimensional nanopores

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, Chongqin; Li, Hui; Meng, Sheng, E-mail: smeng@iphy.ac.cn [Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China)

    2014-11-14

    Water transport through a two-dimensional nanoporous membrane has attracted increasing attention in recent years thanks to great demands in water purification and desalination applications. However, few studies have been reported on the microscopic mechanisms of water transport through structured nanopores, especially at the atomistic scale. Here we investigate the microstructure of water flow through two-dimensional model graphene membrane containing a variety of nanopores of different size by using molecular dynamics simulations. Our results clearly indicate that the continuum flow transits to discrete molecular flow patterns with decreasing pore sizes. While for pores with a diameter ≥15 Å water flux exhibits a linear dependence on the pore area, a nonlinear relationship between water flux and pore area has been identified for smaller pores. We attribute this deviation from linear behavior to the presence of discrete water flow, which is strongly influenced by the water-membrane interaction and hydrogen bonding between water molecules.

  11. 17O nuclear quadrupole coupling constants of water bound to a metal ion: A gadolinium(III) case study

    Science.gov (United States)

    Yazyev, Oleg V.; Helm, Lothar

    2006-08-01

    Rotational correlation times of metal ion aqua complexes can be determined from O17 NMR relaxation rates if the quadrupole coupling constant of the bound water oxygen-17 nucleus is known. The rotational correlation time is an important parameter for the efficiency of Gd3+ complexes as magnetic resonance imaging contrast agents. Using a combination of density functional theory with classical and Car-Parrinello molecular dynamics simulations we performed a computational study of the O17 quadrupole coupling constants in model aqua ions and the [Gd(DOTA)(H2O)]- complex used in clinical diagnostics. For the inner sphere water molecule in the [Gd(DOTA)(H2O)]- complex the determined quadrupole coupling parameter χ√1+η2/3 of 8.7MHz is very similar to that of the liquid water (9.0MHz ). Very close values were also predicted for the the homoleptic aqua ions of Gd3+ and Ca2+. We conclude that the O17 quadrupole coupling parameters of water molecules coordinated to closed shell and lanthanide metal ions are similar to water molecules in the liquid state.

  12. Finite Changes of Bound Water Moisture Content in a Given Volume of Beech Wood

    OpenAIRE

    Richard Hrčka

    2016-01-01

    The undesired wood instabilities are connected with the changes of bound water moisture content. The rates of finite changes of bound water moisture content in a given volume of wood were determined in the frame of the specimen dimensions. The derivation is based on the 1st Fick’s law and diffusion equation solution in three dimensions. The inverse solution of diffusion equation provided the diffusion coefficients in the principal anatomical directions. Beech wood was tested. The nonlinear re...

  13. An Outfit for Improving Potability of Water in Snow-Bound Areas

    OpenAIRE

    Ram Gopal; Ghosh, P K

    1991-01-01

    A water sterilising outfit has been developed for improving potability of water in snow-bound areas by converting snow-melted water into safe drinking water. The outfit(wt.50g) contains a rectangular tin box and two types of tablets-white sterilising tablets and pink thio-mineral tablets-stored in pharmaceutical packings and provides 35 litres of wholesome drinking water as per World Health Organisation and Indian Council of Medical Research standards. The sterilised and mineralised wa...

  14. Two-dimensional crystallography of amphiphilic molecules at the air-water interface

    DEFF Research Database (Denmark)

    Jacquemain, D.; Grayer Wolf, S.; Leveiller, F.; Deutsch, M.; Kjær, K.; Als-Nielsen, J.; Lahav, M.; Leiserowitz, L.

    1992-01-01

    review recent results obtained from them for Langmuir films. The methods have been successfully applied in the elucidation of the structure of crystalline aggregates of amphiphilic molecules such as alcohols, carboxylic acids and their salts, alpha-amino acids, and phospholipids at the water surface. In...... solute species. Examples are given where singly or doubly charged ions bound to the two-dimensional (2D) crystal form either an ordered or diffuse counterionic layer. Finally, the surface diffraction methods provide data on transfer of structural information from 2D clusters to 3D single crystals, which...... had been successfully accomplished by epitaxial-like crystallization both in organic and inorganic crystals....

  15. Precise determination of 6Li cold collision parameters by radio-frequency spectroscopy on weakly bound molecules

    International Nuclear Information System (INIS)

    We employ radio-frequency spectroscopy on weakly bound 6Li2 molecules to precisely determine the molecular binding energies and the energy splittings between molecular states for different magnetic fields. These measurements allow us to extract the interaction parameters of ultracold 6Li atoms based on a multichannel quantum scattering model. We determine the singlet and triplet scattering lengths to be as=45.167(8)a0 and at=-2140(18)a0 (1a0=0.052 917 7 nm), and the positions of the broad Feshbach resonances in the energetically lowest three s-wave scattering channels to be 83.41(15), 69.04(5), and 81.12(10) mT

  16. On the polarity of buckminsterfullerene with a water molecule inside

    NARCIS (Netherlands)

    B. Ensing; F. Costanzo; P.L. Silvestrelli

    2012-01-01

    Since the recent achievement of Kurotobi and Murata to capture a water molecule in a C60 fullerene (Science2011, 333, 613), there has been a debate about the properties of this H2O@C60 complex. In particular, the polarity of the complex, which is thought to be underlying the easy separation of H2O@C

  17. Recrystallization of freezable bound water in aqueous solutions of medium concentration

    Science.gov (United States)

    Lishan, Zhao; Liqing, Pan; Ailing, Ji; Zexian, Cao; Qiang, Wang

    2016-07-01

    For aqueous solutions with freezable bound water, vitrification and recrystallization are mingled, which brings difficulty to application and misleads the interpretation of relevant experiments. Here, we report a quantification scheme for the freezable bound water based on the water-content dependence of glass transition temperature, by which also the concentration range for the solutions that may undergo recrystallization finds a clear definition. Furthermore, we find that depending on the amount of the freezable bound water, different temperature protocols should be devised to achieve a complete recrystallization. Our results may be helpful for understanding the dynamics of supercooled aqueous solutions and for improving their manipulation in various industries. Project supported by the Knowledge Innovation Project of Chinese Academy of Sciences on Water Science Research (Grant No. KJZD-EW-M03) and the National Natural Science Foundation of China (Grant Nos. 11474325 and 11290161).

  18. A tightly bound soil-water scheme within an atmosphere-land-surface model

    Science.gov (United States)

    White, Rachel; Toumi, Ralf

    2012-07-01

    SummaryThe concept of tightly bound water, in which a reservoir of soil water is bound tightly within small soil pores but is still available for evapotranspiration, is parameterised for the first time within the land surface scheme of a fully-coupled regional-scale atmosphere-land surface model. The Weather Research and Forecasting (WRF) regional climate model and the NOAH land surface scheme are selected and a case study is performed on the Olifants River Basin in the Limpopo region of South Africa. Accurate knowledge of water availability in this water-stressed region is of great importance for adaptation and future water policy. Results of a simulation forced by ERA40 re-analysis show that the standard land surface scheme is unable to reproduce the observed runoff despite rainfall and atmospheric conditions similar to observed. This version of the model over-estimates mean annual runoff by 120%. The tightly bound water scheme shows a significant improvement, reducing the bias to 22%. The inclusion of the tightly bound water scheme has little effect on the basin average annual rainfall despite increasing annual evapotranspiration. The tightly bound water physics dampens the response of runoff to precipitation and provides additional de-coupling between precipitation and runoff, increasing the variability in this relationship. Simulations with the WRF model forced with both 1980s and 2040s CCSM3 data show that the tightly bound water scheme significantly reduces runoff in different climates and projects a greater relative future decrease in runoff, from 4% to 10% for the same precipitation decrease of 2.5%. The scheme also affects the projected changes in spatially averaged 100-year return precipitation and runoff with significance at the 0.9 confidence level.

  19. Investigations of the potential functions of weakly bound diatomic molecules and laser-assisted excitive Penning ionization

    International Nuclear Information System (INIS)

    Three variations on the Dunham series expansion function of the potential of a diatomic molecule are compared. The differences among these expansions lie in the choice of the expansion variable, lambda. The functional form of these variables are lambda/sub s/ = l-r/sub e//r for the Simon-Parr-Finlan version, lambda/sub T/ - 1-(r/sub e//r)/sup p/ for that of Thakkar, and lambda/sub H/ = 1-exp(-rho(r/r/sub e/-1) for that of Huffaker. A wide selection of molecular systems are examined. It is found that, for potentials in excess of thirty kcal/mole, the Huffaker expansion provides the best description of the three, extrapolating at large internuclear separation to a value within 10% of the true dissociation energy. For potentials that result from the interaction of excited states, all series expansions show poor behavior away from the equilibrium internuclear separation of the molecule. The series representation of the potentials of weakly bound molecules are examined in more detail. The ground states of BeAr+, HeNe+, NaAr, and Ar2 and the excited states of HeNe+, NaNe, and NaAr are best described by the Thakkar expansion. Finally, the observation of laser-assisted excitive Penning ionization in a flowing afterglow is reported. The reaction Ar(3P2) + Ca + h nu → Ar + Ca+(5p 2P/sub J/) + e- occurs when the photon energy, h nu, is approximately equal to the energy difference between the metastable argon and one of the fine structure levels of the ion's doublet. By monitoring the cascade fluorescence of the above reaction and comparing it to the flourescence from the field-free process Ar(3P2) + Ca → Ar + Ca+(4p 2P/sub J/) + e- a surprisingly large cross section of 6.7 x 103 A2 is estimated

  20. Advanced extraction and lower bounds for removal of pollutants from wastewater by water plants.

    Science.gov (United States)

    Zimmels, Y; Kirzhner, F; Malkovskaja, A

    2007-03-01

    The capacity to reach lower bounds for extraction of pollutants from wastewater by four floating aquatic macrophytes--water hyacinth (Eichhornia crassipes), water lettuce (Pistia stratiotes), salvinia (Salvinia rotundifolia), and water primroses (Ludvigia palustris)--is investigated. It is shown that the following lower bounds can be established for wastewater purification with water hyacinth: biochemical oxygen demand (BOD), 1.3 mg/L; chemical oxygen demand (COD), 11.3 mg/L; total suspended solids (TSS), 0.5 mg/L; turbidity, 0.7 NTU; ammonia, 0.2 mg/L; and phosphorus, 1.4 mg/L. Also, the following lower bounds can be established for wastewater purification with water lettuce: BOD, 1.8 mg/L; COD, 12.5 mg/L; TSS, 0.5 mg/L; turbidity, 0.9 NTU; ammonia, 0.2 mg/L; and phosphorus, 1.6 mg/L. These lower bounds were reached in 11- to 17-day experiments that were performed on diluted wastewater with reduced initial contents of the tested water quality indicators. As expected, water hyacinth exhibited the highest rates and levels of pollutant removal, thereby producing the best lower bounds of the water quality indicators. Given the initially low levels, BOD was further reduced by 86.3%, COD by 66.6%, ammonia by 97.8%, and phosphorus by 65.0% after 11 days of a batch experiment. The capacity of water plants to purify dilute wastewater streams opens new options for their application in the water treatment industry. PMID:17469660

  1. Quantum behaviour of water molecule in gemstone: terahertz fingerprints

    Science.gov (United States)

    Zhukova, Elena S.; Gorshunov, Boris P.; Torgashev, Victor I.; Lebedev, Vladimir V.; Shakurov, Gil'man S.; Kremer, Reinhard K.; Pestrjakov, Efim V.; Thomas, Victor G.; Fursenko, Dimitry A.; Dressel, Martin

    2014-03-01

    We have shown that a weak interaction of a lone H2O molecule with the ''walls'' of nano-sized crystalline cage of gemstone (beryl) results in emergence of a rich set of molecular vibrational states. By analogy with translational and librational bands in liquid water and ice corresponding absorption bands are explained as due to translational (T) and librational (L) movements of the H2O molecule which is hydrogen bonded to the cage walls. In beryl crystal lattice, however, the six-fold symmetry of the cage brings about additional effect of splitting of the T and L bands into fine structure due to tunnelling within the six-well potential relief. The presented results will be of use for analysis of more complicated systems with confined water molecules like H2O chains in carbon nano-tubes, molecular clusters in e.g. zeolites, clays, silica gels and other natural or synthetic frameworks, as well as for interfacial water in biological systems.

  2. Quantum behaviour of water molecule in gemstone: terahertz fingerprints

    International Nuclear Information System (INIS)

    We have shown that a weak interaction of a lone H2O molecule with the ''walls'' of nano-sized crystalline cage of gemstone (beryl) results in emergence of a rich set of molecular vibrational states. By analogy with translational and librational bands in liquid water and ice corresponding absorption bands are explained as due to translational (T) and librational (L) movements of the H2O molecule which is hydrogen bonded to the cage walls. In beryl crystal lattice, however, the six-fold symmetry of the cage brings about additional effect of splitting of the T and L bands into fine structure due to tunnelling within the six-well potential relief. The presented results will be of use for analysis of more complicated systems with confined water molecules like H2O chains in carbon nano-tubes, molecular clusters in e.g. zeolites, clays, silica gels and other natural or synthetic frameworks, as well as for interfacial water in biological systems

  3. Scattering of thermal neutron by the water molecule

    International Nuclear Information System (INIS)

    The calculation of the differenctial cross section for scattering of thermal neutrons by water, taking into account the translational, rotational and vibrational motions of the water molecule, is presented according to Nelkin' model. Some modifications are presented which have been introduced in the original method to improve the results and an application has been made to reactor physics, by calculating the thermal neutron flux in a homogenous medium containing water and absorver. Thirty thermal energy groups have been used to compute the spectra. Within the limits of error, better agreement has been obtained between theory and experiments by using a modified Nelkin kernel consisting of substituting the asymptotic formulae for the rotational and vibrational motions by more exact expressions, similar to the Buttler model for heavy water

  4. Crystallographic characterization of the radixin FERM domain bound to the cytoplasmic tail of adhesion molecule CD44

    Energy Technology Data Exchange (ETDEWEB)

    Mori, Tomoyuki; Kitano, Ken; Terawaki, Shin-ichi; Maesaki, Ryoko; Hakoshima, Toshio, E-mail: hakosima@bs.naist.jp [Structural Biology Laboratory, Nara Institute of Science and Technology, Keihanna Science City, Nara 630-0192 (Japan)

    2007-10-01

    The radixin FERM domain complexed with the CD44 cytoplasmic tail peptide has been crystallized. A diffraction data set from the complex was collected to 2.1 Å. CD44 is an important adhesion molecule that specifically binds hyaluronic acid and regulates cell–cell and cell–matrix interactions. Increasing evidence has indicated that CD44 is assembled in a regulated manner into the membrane–cytoskeletal junction, a process that is mediated by ERM (ezrin/radixin/moesin) proteins. Crystals of a complex between the radixin FERM domain and the C-terminal cytoplasmic region of CD44 have been obtained. The crystal of the radixin FERM domain bound to the CD44 cytoplasmic tail peptide belongs to space group P2{sub 1}2{sub 1}2{sub 1}, with unit-cell parameters a = 62.70, b = 66.18, c = 86.22 Å, and contain one complex in the crystallographic asymmetric unit. An intensity data set was collected to a resolution of 2.1 Å.

  5. Crystallographic characterization of the radixin FERM domain bound to the cytoplasmic tail of adhesion molecule CD44

    International Nuclear Information System (INIS)

    The radixin FERM domain complexed with the CD44 cytoplasmic tail peptide has been crystallized. A diffraction data set from the complex was collected to 2.1 Å. CD44 is an important adhesion molecule that specifically binds hyaluronic acid and regulates cell–cell and cell–matrix interactions. Increasing evidence has indicated that CD44 is assembled in a regulated manner into the membrane–cytoskeletal junction, a process that is mediated by ERM (ezrin/radixin/moesin) proteins. Crystals of a complex between the radixin FERM domain and the C-terminal cytoplasmic region of CD44 have been obtained. The crystal of the radixin FERM domain bound to the CD44 cytoplasmic tail peptide belongs to space group P212121, with unit-cell parameters a = 62.70, b = 66.18, c = 86.22 Å, and contain one complex in the crystallographic asymmetric unit. An intensity data set was collected to a resolution of 2.1 Å

  6. Investigations of the potential functions of weakly bound diatomic molecules and laser-assisted excitive Penning ionization

    Energy Technology Data Exchange (ETDEWEB)

    Goble, J.H. Jr.

    1982-05-01

    Three variations on the Dunham series expansion function of the potential of a diatomic molecule are compared. The differences among these expansions lie in the choice of the expansion variable, lambda. The functional form of these variables are lambda/sub s/ = l-r/sub e//r for the Simon-Parr-Finlan version, lambda/sub T/ - 1-(r/sub e//r)/sup p/ for that of Thakkar, and lambda/sub H/ = 1-exp(-rho(r/r/sub e/-1) for that of Huffaker. A wide selection of molecular systems are examined. It is found that, for potentials in excess of thirty kcal/mole, the Huffaker expansion provides the best description of the three, extrapolating at large internuclear separation to a value within 10% of the true dissociation energy. For potentials that result from the interaction of excited states, all series expansions show poor behavior away from the equilibrium internuclear separation of the molecule. The series representation of the potentials of weakly bound molecules are examined in more detail. The ground states of BeAr/sup +/, HeNe/sup +/, NaAr, and Ar/sub 2/ and the excited states of HeNe+, NaNe, and NaAr are best described by the Thakkar expansion. Finally, the observation of laser-assisted excitive Penning ionization in a flowing afterglow is reported. The reaction Ar(/sup 3/P/sub 2/) + Ca + h nu ..-->.. Ar + Ca/sup +/(5p /sup 2/P/sub J/) + e/sup -/ occurs when the photon energy, h nu, is approximately equal to the energy difference between the metastable argon and one of the fine structure levels of the ion's doublet. By monitoring the cascade fluorescence of the above reaction and comparing it to the flourescence from the field-free process Ar(/sup 3/P/sub 2/) + Ca ..-->.. Ar + Ca/sup +/(4p /sup 2/P/sub J/) + e/sup -/ a surprisingly large cross section of 6.7 x 10/sup 3/ A/sup 2/ is estimated.

  7. The spontaneous synchronized dance of pairs of water molecules

    International Nuclear Information System (INIS)

    Molecular beam scattering experiments have been performed to study the effect of long-range anisotropic forces on the collision dynamics of two small polar molecules. The main focus of this paper is on water, but also ammonia and hydrogen sulphide molecules have been investigated, and some results will be anticipated. The intermolecular distances mainly probed are of the order of 1 nm and therefore much larger than the molecular dimensions. In particular, we have found that the natural electric field gradient, generated by different spatial orientations of the permanent electric dipoles, is able to promote the transformation of free rotations into coupled pendular states, letting the molecular partners involved in the collision complex swinging to and fro around the field direction. This long-ranged concerted motion manifested itself as large increases of the magnitude of the total integral cross section. The experimental findings and the theoretical treatment developed to shed light on the details of the process suggest that the transformation from free rotations to pendular states depends on the rotational level of both molecules, on the impact parameter, on the relative collision velocity, on the dipole moment product and occurs in the time scale of picoseconds. The consequences of this intriguing phenomenon may be important for the interpretation and, in perspective, for the control of elementary chemical and biological processes, given by polar molecules, ions, and free radicals, occurring in several environments under various conditions

  8. The spontaneous synchronized dance of pairs of water molecules

    Energy Technology Data Exchange (ETDEWEB)

    Roncaratti, Luiz F. [Dipartimento di Chimica, Biologia e Biotecnologie, Università degli Studi di Perugia, 06123 Perugia (Italy); Instituto de Física, Universidade de Brasília, 70910-900 Brasília (Brazil); Cappelletti, David, E-mail: david.cappelletti@unipg.it; Pirani, Fernando [Dipartimento di Chimica, Biologia e Biotecnologie, Università degli Studi di Perugia, 06123 Perugia (Italy)

    2014-03-28

    Molecular beam scattering experiments have been performed to study the effect of long-range anisotropic forces on the collision dynamics of two small polar molecules. The main focus of this paper is on water, but also ammonia and hydrogen sulphide molecules have been investigated, and some results will be anticipated. The intermolecular distances mainly probed are of the order of 1 nm and therefore much larger than the molecular dimensions. In particular, we have found that the natural electric field gradient, generated by different spatial orientations of the permanent electric dipoles, is able to promote the transformation of free rotations into coupled pendular states, letting the molecular partners involved in the collision complex swinging to and fro around the field direction. This long-ranged concerted motion manifested itself as large increases of the magnitude of the total integral cross section. The experimental findings and the theoretical treatment developed to shed light on the details of the process suggest that the transformation from free rotations to pendular states depends on the rotational level of both molecules, on the impact parameter, on the relative collision velocity, on the dipole moment product and occurs in the time scale of picoseconds. The consequences of this intriguing phenomenon may be important for the interpretation and, in perspective, for the control of elementary chemical and biological processes, given by polar molecules, ions, and free radicals, occurring in several environments under various conditions.

  9. Geometry-dependent distributed polarizability models for the water molecule

    International Nuclear Information System (INIS)

    Geometry-dependent distributed polarizability models have been constructed by fits to ab initio calculations at the coupled cluster level of theory with up to noniterative triple excitations in an augmented triple-zeta quality basis set for the water molecule in the field of a point charge. The investigated models include (i) charge-flow polarizabilities between chemically bonded atoms, (ii) isotropic or anisotropic dipolar polarizabilities on oxygen atom or on all atoms, and (iii) combinations of models (i) and (ii). For each model, the polarizability parameters have been optimized to reproduce the induction energy of a water molecule polarized by a point charge successively occupying a grid of points surrounding the molecule. The quality of the models is ascertained by examining their ability to reproduce these induction energies as well as the molecular dipolar and quadrupolar polarizabilities. The geometry dependence of the distributed polarizability models has been explored by changing bond lengths and HOH angle to generate 125 molecular structures (reduced to 75 symmetry-unique ones). For each considered model, the distributed polarizability components have been fitted as a function of the geometry by a Taylor expansion in monomer coordinate displacements up to the sum of powers equal to 4

  10. Geometry-dependent distributed polarizability models for the water molecule

    Energy Technology Data Exchange (ETDEWEB)

    Loboda, Oleksandr; Ingrosso, Francesca; Ruiz-López, Manuel F.; Millot, Claude [Université de Lorraine, SRSMC UMR 7565, Vandoeuvre-les-Nancy F-54506 (France); CNRS, SRSMC UMR 7565, Vandoeuvre-les-Nancy F-54506 (France); Szalewicz, Krzysztof [Department of Physics and Astronomy, University of Delaware, Newark, Delaware 19716 (United States)

    2016-01-21

    Geometry-dependent distributed polarizability models have been constructed by fits to ab initio calculations at the coupled cluster level of theory with up to noniterative triple excitations in an augmented triple-zeta quality basis set for the water molecule in the field of a point charge. The investigated models include (i) charge-flow polarizabilities between chemically bonded atoms, (ii) isotropic or anisotropic dipolar polarizabilities on oxygen atom or on all atoms, and (iii) combinations of models (i) and (ii). For each model, the polarizability parameters have been optimized to reproduce the induction energy of a water molecule polarized by a point charge successively occupying a grid of points surrounding the molecule. The quality of the models is ascertained by examining their ability to reproduce these induction energies as well as the molecular dipolar and quadrupolar polarizabilities. The geometry dependence of the distributed polarizability models has been explored by changing bond lengths and HOH angle to generate 125 molecular structures (reduced to 75 symmetry-unique ones). For each considered model, the distributed polarizability components have been fitted as a function of the geometry by a Taylor expansion in monomer coordinate displacements up to the sum of powers equal to 4.

  11. Structure and dynamics of water and lipid molecules in charged anionic DMPG lipid bilayer membranes

    Science.gov (United States)

    Rønnest, A. K.; Peters, G. H.; Hansen, F. Y.; Taub, H.; Miskowiec, A.

    2016-04-01

    Molecular dynamics simulations have been used to investigate the influence of the valency of counter-ions on the structure of freestanding bilayer membranes of the anionic 1,2-dimyristoyl-sn-glycero-3-phosphoglycerol (DMPG) lipid at 310 K and 1 atm. At this temperature, the membrane is in the fluid phase with a monovalent counter-ion and in the gel phase with a divalent counter-ion. The diffusion constant of water as a function of its depth in the membrane has been determined from mean-square-displacement calculations. Also, calculated incoherent quasielastic neutron scattering functions have been compared to experimental results and used to determine an average diffusion constant for all water molecules in the system. On extrapolating the diffusion constants inferred experimentally to a temperature of 310 K, reasonable agreement with the simulations is obtained. However, the experiments do not have the sensitivity to confirm the diffusion of a small component of water bound to the lipids as found in the simulations. In addition, the orientation of the dipole moment of the water molecules has been determined as a function of their depth in the membrane. Previous indirect estimates of the electrostatic potential within phospholipid membranes imply an enormous electric field of 108-109 V m-1, which is likely to have great significance in controlling the conformation of translocating membrane proteins and in the transfer of ions and molecules across the membrane. We have calculated the membrane potential for DMPG bilayers and found ˜1 V (˜2 ṡ 108 V m-1) when in the fluid phase with a monovalent counter-ion and ˜1.4 V (˜2.8 ṡ 108 V m-1) when in the gel phase with a divalent counter-ion. The number of water molecules for a fully hydrated DMPG membrane has been estimated to be 9.7 molecules per lipid in the gel phase and 17.5 molecules in the fluid phase, considerably smaller than inferred experimentally for 1,2-dimyristoyl-sn-glycero-3-phosphorylcholine (DMPC

  12. Single ionization of water molecules in collisions with bare ions

    Science.gov (United States)

    Mondal, A.; Mandal, C. R.; Purkait, M.

    2016-04-01

    We present the double differential cross sections (DDCSs) for the direct ionization of water molecules by impact of fully stripped helium, carbon and oxygen atoms, respectively. In the present formalism, we have represented the wavefunction in the entrance channel as the product of a plane wave for the projectile and an accurate one-center-molecular wavefunction of the water molecule by Moccia (1964 J. Chem. Phys. 40 2186). In the exit channel, we have expressed the total wavefunction as the product of pair-wise Coulomb wavefunctions among the ejected electron, projectile ion and the residual target ion, respectively. The contributions of DDCSs for five different molecular orbitals of water to the spectrum of angular distributions have been analyzed for several electron emission energies. The present results for DDCSs are compared with existing experimental and theoretical findings. We find an overall good agreement between our calculated results and the experimental findings for electron emission cross sections. In addition, DDCS results for ionization from different orbitals at a few electron emission energies are given in tabular form.

  13. High-harmonic generation in aligned water molecules

    Science.gov (United States)

    Wang, Song; Devin, Julien; Hoffmann, Matthias; Cryan, James; Kaldun, Andreas; Bucksbaum, Philip

    2016-05-01

    In recent years, the use of high harmonic generation (HHG) in aligned molecular vapors has become a powerful tool to study ultrafast dynamics of electronic and nuclear wave packets. In our new experimental setup, we are able to orient H2 O and D2 O molecules using a single cycle terahertz (THz) pulse. Aligning water is especially interesting as the highest occupied molecular orbital (HOMO) of water contains a node in the xz plane of the molecular frame, allowing us to perform HHG from second highest occupied molecular orbital (HOMO-1) only, by setting the polarization of the fundamental laser along the z-axis of the aligned water molecules. We are particularly interested in the HOMO-1 state, as there is fast motion of the H-O-H angle leading to sub-wavelength dynamics. On this poster we present our all-optical alignment setup where HHG and single-cycle THz generation take place in high-vacuum, where measurements with arbitrary polarization angles between the two are possible. In addition, we discuss the effects of the molecular orientation on HHG, including symmetry breaking that could produce even harmonics and isotope effects between H2 O and D2 O due to different vibrational energies. This work was supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Chemical Sciences, Geosciences, and Biosciences Division.

  14. Managing Water Quality under Uncertainty: Application of a New Stochastic Branch and Bound Method

    OpenAIRE

    Lence, B.J.; Ruszczynski, A.

    1996-01-01

    The problem of water quality management under uncertain emission levels, reaction rates and pollutant transport is considered. Various performance measures: reliability, resiliency and vulnerability are taken into account. A general methodology for finding a cost-effective water quality management program is developed. The approach employs a new idea of the stochastic branch and bound method, which combines random estimates of the performance for subsets of decisions with iterative refinement...

  15. Influence of water on the properties of an Au/Mpy/Pd metal/molecule/metal junction

    Directory of Open Access Journals (Sweden)

    Jan Kučera

    2011-07-01

    Full Text Available The geometric and electronic structure of the metal–molecule interface in metal/molecule/metal junctions is of great interest since it affects the functionality of such units in possible nanoelectronic devices. We have investigated the interaction between water and a palladium monolayer of a Au(111/4-mercaptopyridine/Pd junction by means of DFT calculations. A relatively strong bond between water and the palladium monolayer of the Au/Mpy/Pd complex is observed via a one-fold bond between the oxygen atom of the water molecule and a Pd atom. An isolated H2O molecule adsorbs preferentially in a flat-lying geometry on top of a palladium atom that is at the same time also bound to the nitrogen atom of a Mpy molecule of the underlying self-assembled monolayer. The electronic structure of these Pd atoms is considerably modified which is reflected in a reduced local density of states at the Fermi energy. At higher coverages, water can be arranged in a hexagonal ice-like bilayer structure in analogy to water on bulk metal surfaces, but with a much stronger binding which is dominated by O–Pd bonds.

  16. Ionization of water molecules by fast charged projectiles

    International Nuclear Information System (INIS)

    Single-ionization cross sections of water molecules colliding with fast protons are calculated from lowest-order perturbation theory by taking all electrons and molecular orientations consistently into account. Explicit analytical formulas based on the peaking approximation are obtained for differential ionization cross sections with the partial contribution from the various electron orbitals accounted for. The results, which are in very good agreement with total and partial cross sections at high electron and projectile energies, display a strong variation on molecular orientation and molecular orbitals.

  17. Continuum simulations of water flow past fullerene molecules

    DEFF Research Database (Denmark)

    Popadic, A.; Praprotnik, M.; Koumoutsakos, P.;

    2015-01-01

    We present continuum simulations of water flow past fullerene molecules. The governing Navier-Stokes equations are complemented with the Navier slip boundary condition with a slip length that is extracted from related molecular dynamics simulations. We find that several quantities of interest as...... computed by the present model are in good agreement with results from atomistic and atomistic-continuum simulations at a fraction of the cost. We simulate the flow past a single fullerene and an array of fullerenes and demonstrate that such nanoscale flows can be computed efficiently by continuum flow...

  18. Credibility theory based dynamic control bound optimization for reservoir flood limited water level

    Science.gov (United States)

    Jiang, Zhiqiang; Sun, Ping; Ji, Changming; Zhou, Jianzhong

    2015-10-01

    The dynamic control operation of reservoir flood limited water level (FLWL) can solve the contradictions between reservoir flood control and beneficial operation well, and it is an important measure to make sure the security of flood control and realize the flood utilization. The dynamic control bound of FLWL is a fundamental key element for implementing reservoir dynamic control operation. In order to optimize the dynamic control bound of FLWL by considering flood forecasting error, this paper took the forecasting error as a fuzzy variable, and described it with the emerging credibility theory in recent years. By combining the flood forecasting error quantitative model, a credibility-based fuzzy chance constrained model used to optimize the dynamic control bound was proposed in this paper, and fuzzy simulation technology was used to solve the model. The FENGTAN reservoir in China was selected as a case study, and the results show that, compared with the original operation water level, the initial operation water level (IOWL) of FENGTAN reservoir can be raised 4 m, 2 m and 5.5 m respectively in the three division stages of flood season, and without increasing flood control risk. In addition, the rationality and feasibility of the proposed forecasting error quantitative model and credibility-based dynamic control bound optimization model are verified by the calculation results of extreme risk theory.

  19. Bound water at protein-protein interfaces: partners, roles and hydrophobic bubbles as a conserved motif.

    Directory of Open Access Journals (Sweden)

    Mostafa H Ahmed

    Full Text Available BACKGROUND: There is a great interest in understanding and exploiting protein-protein associations as new routes for treating human disease. However, these associations are difficult to structurally characterize or model although the number of X-ray structures for protein-protein complexes is expanding. One feature of these complexes that has received little attention is the role of water molecules in the interfacial region. METHODOLOGY: A data set of 4741 water molecules abstracted from 179 high-resolution (≤ 2.30 Å X-ray crystal structures of protein-protein complexes was analyzed with a suite of modeling tools based on the HINT forcefield and hydrogen-bonding geometry. A metric termed Relevance was used to classify the general roles of the water molecules. RESULTS: The water molecules were found to be involved in: a (bridging interactions with both proteins (21%, b favorable interactions with only one protein (53%, and c no interactions with either protein (26%. This trend is shown to be independent of the crystallographic resolution. Interactions with residue backbones are consistent for all classes and account for 21.5% of all interactions. Interactions with polar residues are significantly more common for the first group and interactions with non-polar residues dominate the last group. Waters interacting with both proteins stabilize on average the proteins' interaction (-0.46 kcal mol(-1, but the overall average contribution of a single water to the protein-protein interaction energy is unfavorable (+0.03 kcal mol(-1. Analysis of the waters without favorable interactions with either protein suggests that this is a conserved phenomenon: 42% of these waters have SASA ≤ 10 Å(2 and are thus largely buried, and 69% of these are within predominantly hydrophobic environments or "hydrophobic bubbles". Such water molecules may have an important biological purpose in mediating protein-protein interactions.

  20. Formation of deeply bound ultracold LiRb molecules via photoassociation near the Li 2S$_{1/2}$ + Rb 5P$_{3/2}$ asymptote

    CERN Document Server

    Lorenz, John; Dutta, Sourav; Chen, Yong P; Elliott, D S

    2014-01-01

    We present spectra of ultracold $^7$Li$^{85}$Rb molecules in their electronic ground state formed by spontaneous decay of weakly bound photoassociated molecules. Beginning with atoms in a dual species magneto-optical trap (MOT), weakly bound molecules are formed in the 4(1) electronic state, which corresponds to the B$^1\\Pi$ state at short range. These molecules spontaneously decay to the electronic ground state and we use resonantly enhanced multiphoton ionization (REMPI) to determine the vibrational population distribution in the electronic ground states after spontaneous emission. Many of the observed lines from the spectra are consistent with transitions from the X$^1\\Sigma^+$ ground electronic state to either the B$^1\\Pi$ or D$^1\\Pi$ electronic states that have been previously observed, with levels possibly as low as X$^1\\Sigma^+$ $(v'' = 2)$ being populated. We do not observe decay to weakly bound vibrational levels of the X$^1\\Sigma^+$ or a$^3\\Sigma^+$ electronic states in the spectra. We also deduce a...

  1. The role of free and bound water in irradiation preservation: Free radical damage as a function of the physical state of water

    Science.gov (United States)

    Wedemeyer, G.A.; Dollar, A.M.

    1964-01-01

    English sole fillets previously equilibrated with aqueous 0.1% cysteine were dehydrated by three methods to moisture levels ranging from 2 to 72%. Model systems using cellulose to replace the fish tissue were also used. The samples were irradiated at 1 Mrad in an air, nitrogen, or oxygen atmosphere. The destruction of −SH groups was measured and related to the amount and physical state of the tissue water. As free water was removed, destruction steadily increased, reaching a maximum at about 20% moisture. Destruction decreased markedly at moisture levels below 10%, and calorimetric measurements confirmed that 10% moisture was about the level of bound water in this species. These data suggest that dehydration favors the reaction of solute molecules with free radicals formed in the free water of muscle cells. At moisture levels greater than about 20%, simple free radical recombination is more likely than reaction with solute molecules, while below 20% moisture the reverse is true. The calculated α values support this conclusion, as do the results from model systems using cellulose.

  2. Sticking of molecules on non-porous amorphous water ice

    CERN Document Server

    He, Jiao; Vidali, Gianfranco

    2016-01-01

    Accurate modeling of physical and chemical processes in the interstellar medium requires detailed knowledge of how atoms and molecule adsorb on dust grains. However, the sticking coefficient, a number between 0 and 1 that measures the first step in the interaction of a particle with a surface, is usually assumed in simulations of ISM environments to be either 0.5 or 1. Here we report on the determination of the sticking coefficient of H$_2$, D$_2$, N$_2$, O$_2$, CO, CH$_4$, and CO$_2$ on non-porous amorphous solid water (np-ASW). The sticking coefficient was measured over a wide range of surface temperatures using a highly collimated molecular beam. We showed that the standard way of measuring the sticking coefficient --- the King-Wells method --- leads to the underestimation of trapping events in which there is incomplete energy accommodation of the molecule on the surface. Surface scattering experiments with the use of a pulsed molecular beam are used instead to measure the sticking coefficient. Based on th...

  3. Mineral and Protein-Bound Water and Latching Action Control Mechanical Behavior at Protein-Mineral Interfaces in Biological Nanocomposites

    Directory of Open Access Journals (Sweden)

    Pijush Ghosh

    2008-01-01

    Full Text Available The nacre structure consists of laminated interlocked mineral platelets separated by nanoscale organic layers. Here, the role of close proximity of mineral to the proteins on mechanical behavior of the protein is investigated through steered molecular dynamics simulations. Our simulations indicate that energy required for unfolding protein in the proximity of mineral aragonite is several times higher than that for isolated protein in the absence of the mineral. Here, we present details of specific mechanisms which result in higher energy for protein unfolding in the proximity of mineral. At the early stage of pulling, peaks in the load-displacement (LD plot at mineral proximity are quantitatively correlated to the interaction energy between atoms involved in the latching phenomenon of amino acid side chain to aragonite surface. Water plays an important role during mineral and protein interaction and water molecules closer to the mineral surface are highly oriented and remain rigidly attached as the protein strand is pulled. Also, the high magnitude of load for a given displacement originates from attractive interactions between the protein, protein-bound water, and mineral. This study provides an insight into mineral-protein interactions that are predominant in biological nanocomposites and also provides guidelines towards design of biomimetic nanocomposites.

  4. Distribution of binding energies of a water molecule in the water liquid-vapor interface

    Energy Technology Data Exchange (ETDEWEB)

    Chempath, Shaji [Los Alamos National Laboratory; Pratt, Lawrence R [TULANE UNIV

    2008-01-01

    Distributions of binding energies of a water molecule in the water liquid-vapor interface are obtained on the basis of molecular simulation with the SPC/E model of water. These binding energies together with the observed interfacial density profile are used to test a minimally conditioned Gaussian quasi-chemical statistical thermodynamic theory. Binding energy distributions for water molecules in that interfacial region clearly exhibit a composite structure. A minimally conditioned Gaussian quasi-chemical model that is accurate for the free energy of bulk liquid water breaks down for water molecules in the liquid-vapor interfacial region. This breakdown is associated with the fact that this minimally conditioned Gaussian model would be inaccurate for the statistical thermodynamics of a dilute gas. Aggressive conditioning greatly improves the performance of that Gaussian quasi-chemical model. The analogy between the Gaussian quasi-chemical model and dielectric models of hydration free energies suggests that naive dielectric models without the conditioning features of quasi-chemical theory will be unreliable for these interfacial problems. Multi-Gaussian models that address the composite nature of the binding energy distributions observed in the interfacial region might provide a mechanism for correcting dielectric models for practical applications.

  5. Dose contribution from organically bound tritum after an acute tritiated water intake

    International Nuclear Information System (INIS)

    To assess the dose contribution from retained organically bound tritium (OBT), we have analyzed urinary excretion data from eight individuals who had an acute intake of tritiated water (HTO). The analysis of the bioassay data showed that the mean body water turnover half-time was 6.3 ± 1.0 d and 8.4 ± 1.9 d for the period of increased water and normal water intake respectively. The long term excretion of tritium was also observed, indicting the tritium incorporation and retention in the organic components of the soft tissues. A mathematical model is proposed to estimate the dose increases from the retained OBT by examining the kinetics of tritium excretion in urine. Based on the kinetics of tritium in urine, the average dose increase from the metabolized OBT was 6.2 ± 1.3% of the HTO dose. The uncertainty in the OBT dose estimates was calculated to be less than 50%

  6. A Simple Three-Parameter Model Potential For Diatomic Systems: From Weakly and Strongly Bound Molecules to Metastable Molecular Ions

    OpenAIRE

    Xie, Rui-Hua; Gong, Jiangbin

    2005-01-01

    Based on a simplest molecular orbital theory of H$_{2}^{+}$, a three-parameter model potential function is proposed to describe ground-state diatomic systems with closed-shell and/or S-type valence-shell constituents over a significantly wide range of internuclear distances. More than 200 weakly and strongly bound diatomics have been studied, including neutral and singly-charged diatomics (e.g., H$_{2}$, Li$_{2}$, LiH, Cd$_{2}$, Na$_{2}^{+}$, and RbH$^{-}$), long-range bound diatomics (e.g., ...

  7. Rapid and accurate prediction and scoring of water molecules in protein binding sites.

    Directory of Open Access Journals (Sweden)

    Gregory A Ross

    Full Text Available Water plays a critical role in ligand-protein interactions. However, it is still challenging to predict accurately not only where water molecules prefer to bind, but also which of those water molecules might be displaceable. The latter is often seen as a route to optimizing affinity of potential drug candidates. Using a protocol we call WaterDock, we show that the freely available AutoDock Vina tool can be used to predict accurately the binding sites of water molecules. WaterDock was validated using data from X-ray crystallography, neutron diffraction and molecular dynamics simulations and correctly predicted 97% of the water molecules in the test set. In addition, we combined data-mining, heuristic and machine learning techniques to develop probabilistic water molecule classifiers. When applied to WaterDock predictions in the Astex Diverse Set of protein ligand complexes, we could identify whether a water molecule was conserved or displaced to an accuracy of 75%. A second model predicted whether water molecules were displaced by polar groups or by non-polar groups to an accuracy of 80%. These results should prove useful for anyone wishing to undertake rational design of new compounds where the displacement of water molecules is being considered as a route to improved affinity.

  8. Disorder of Hydrofluorocarbon Molecules Entrapped in the Water Cages of Structure I Clathrate Hydrate.

    Science.gov (United States)

    Takeya, Satoshi; Udachin, Konstantin A; Moudrakovski, Igor L; Ohmura, Ryo; Ripmeester, John A

    2016-05-23

    Water versus fluorine: Clathrate hydrates encaging hydrofluorocarbons as guests show both isotropic and anisotropic distributions within host water cages, depending on the number of fluorine atoms in the guest molecule; this is caused by changes in intermolecular interactions to host water molecules in the hydrates. PMID:27105807

  9. Electron capture by bare ions on water molecules

    Science.gov (United States)

    Rivarola, Roberto; Montenegro, Pablo; Monti, Juan; Fojón, Omar

    2016-05-01

    Single electron capture from water molecules by impact of bare ions is theoretically investigated at intermediate and high collision energies. This reaction is of fundamental importance to determine the deposition of energy in biological matter irradiated with ion beams (hadrontherapy), dominating other ionizing processes of the target at low-intermediate impact velocities and giving principal contributions to the energetic region where electronic stopping power maximizes. The dynamics of the interaction between the aggregates is described within the one active-electron continuum distorted wave-eikonal initial state theory. The orbitals of the target in the ground state are represented using the approximate self-consistent complete neglect of differential orbitals (SC-CNDO) model. The contribution of different molecular orbitals on the partial cross sections to selected n-principal quantum number projectile states is discriminated as well as the collaboration of these n-states on total cross sections. The latter ones are dominated by capture to n=1 states at high enough energies decreasing their contribution as n increases.

  10. Attachment of Water and Alcohol Molecules onto Water and Alcohol Clusters.

    Science.gov (United States)

    Braud, Isabelle; Boulon, Julien; Zamith, Sébastien; L'Hermite, Jean-Marc

    2015-06-11

    Absolute attachment cross sections of single molecules M (M = water, ethanol, or methanol) onto positively charged mass-selected clusters XnH(+) (X = water, ethanol, or methanol) were measured for cluster sizes ranging from tens to hundreds of molecules and center-of-mass collision energies varying from 0.1 to ∼1 eV. The attachment cross sections, which converge as expected toward geometrical cross sections at large cluster sizes, are systematically and noticeably lower than geometrical cross sections at small sizes. Attachment cross sections depend barely on the nature of the reactants. Homogeneous attachment reactions XnH(+) + X → Xn+1H(+) can be accounted for by a dynamical collisional model, in which the intermolecular interactions between the target cluster and the impinging molecule can be neglected. Dynamical arguments account satisfactorily for size and energy dependences of attachment cross sections and also for their variation from one element to another. It is thus suggested that either the attachment probabilities are likely to be more governed by the capacity of clusters to absorb collision energy rather than by cluster/molecule intermolecular interactions, or it indicates that the strength of these interactions does not differ noticeably among the hydrogen-bonded systems investigated. However, for inhomogeneous reactions of the form XnH(+) + Y → XnYH(+) (X, Y = water, ethanol, methanol), although the global size dependences are qualitatively reproduced, the variations of attachment cross sections with the nature on the impinging molecule are not satisfactorily accounted for within the simple empirical model proposed for homogeneous reactions. PMID:25687764

  11. Enhanced hole injection in a polymer light emitting diode using a small molecule monolayer bound to the anode

    Science.gov (United States)

    Guo, Jing; Koch, Norbert; Bernasek, Steven L.; Schwartz, Jeffrey

    2006-08-01

    A monolayer of quarterthiophene-2-phosphonate (4TP) was chemically bound to the surface of indium tin oxide (ITO) and was then p-doped with the strong acceptor, tetrafluorotetracyanoquinodimethane (F 4-TCNQ). This interface modification strongly reduced the barrier for hole injection compared to unmodified ITO. This doped monolayer surface treatment was also superior to the commonly used anode coating poly(3,4-ethylenedioxythiophene):poly(styrenesulfonic acid) (PEDOT:PPS) at driving voltages above 5.2 V.

  12. Hydration modes of an amphiphilic molecule 2: NMR, FTIR and theoretical study of the interactions in the system water-1,2-dimethoxyethane

    International Nuclear Information System (INIS)

    Graphical abstract: Using NMR spectroscopy, PFG measurements, relaxations and NOESY, as well as FTIR spectroscopy and DFT calculations, 1,2-dimethoxyethane is shown to form a hydrate with five water molecules bound by cooperative hydrogen bonds. Highlights: → Binding of water to DME leads to tgt conformation at all water/DME ratios. → Water is bound to DME in a tight envelope containing at least five water molecules. → The hydration envelope is built up by cooperative O-H...O and O...H-C hydrogen bonds. - Abstract: Using 1H and 13C NMR spectra, PFG NMR self-diffusion measurements, 1H and 13C NMR relaxations and 1H NOESY NMR spectra, FTIR spectra and quantum-chemical DFT and MP2 calculations, the interaction of 1,2-dimethoxyethane (DME) with water (W) was re-examined. It was confirmed that, primarily, one W molecule forms two O...H hydrogen bonds with DME in tgt conformation. At medium and higher W contents, however, larger hydrates of DME are formed, predominantly with five W molecules. The compact structure of the hydrate is warranted by O...H hydrogen bonds, some of them perceptibly tighter than those in the primary hydrate, and by non-classical CH3...O hydrogen bonds.

  13. Synthesis and electrocatalytic water oxidation by electrode-bound helical peptide chromophore-catalyst assemblies.

    Science.gov (United States)

    Ryan, Derek M; Coggins, Michael K; Concepcion, Javier J; Ashford, Dennis L; Fang, Zhen; Alibabaei, Leila; Ma, Da; Meyer, Thomas J; Waters, Marcey L

    2014-08-01

    Artificial photosynthesis based on dye-sensitized photoelectrosynthesis cells requires the assembly of a chromophore and catalyst in close proximity on the surface of a transparent, high band gap oxide semiconductor for integrated light absorption and catalysis. While there are a number of approaches to assemble mixtures of chromophores and catalysts on a surface for use in artificial photosynthesis based on dye-sensitized photoelectrosynthesis cells, the synthesis of discrete surface-bound chromophore-catalyst conjugates is a challenging task with few examples to date. Herein, a versatile synthetic approach and electrochemical characterization of a series of oligoproline-based light-harvesting chromophore-water-oxidation catalyst assemblies is described. This approach combines solid-phase peptide synthesis for systematic variation of the backbone, copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC) as an orthogonal approach to install the chromophore, and assembly of the water-oxidation catalyst in the final step. Importantly, the catalyst was found to be incompatible with the conditions both for amide bond formation and for the CuAAC reaction. The modular nature of the synthesis with late-stage assembly of the catalyst allows for systematic variation in the spatial arrangement of light-harvesting chromophore and water-oxidation catalyst and the role of intrastrand distance on chromophore-catalyst assembly properties. Controlled potential electrolysis experiments verified that the surface-bound assemblies function as water-oxidation electrocatalysts, and electrochemical kinetics data demonstrate that the assemblies exhibit greater than 10-fold rate enhancements compared to the homogeneous catalyst alone. PMID:25046035

  14. Tritium metabolism in cow's milk after administration of tritiated water and of organically bound tritium

    International Nuclear Information System (INIS)

    Tritium was administered as THO and as organically bound tritium (OBT) to lactating cows. Urine and milk samples were collected and analyzed for tritium content. Plateau levels in milk water and in milk fat, lactose and casein were reached in about 20 days after feeding either THO or OBT. Comparison of the specific activity (pCi3H/g H) of the various milk constituents with the specific activity of the body water showed that, after administration of THO, the highest tritium incorporation occurred in lactose (0.58), followed by milk fat (0.36) and casein (0.27). Tritium incorporation in milk dry matter (0.45) is considerably higher than in most tissue components of several mammalian species after continuous ingestion of THO as reported in the literature. After feeding OBT, the highest tritium incorporation occurred in milk fat and to a lesser extent in casein. Tritium levels in lactose were surprisingly low and the reason for this is not clear. They were similar to those in milk water. Tritium levels in milk and urine water showed systematic differences during administration of OBT and after this was stopped. There was more tritium in milk water until the last day of OBT feeding and this situation was reversed after this. (author)

  15. Dynamics of water molecules in the active-site cavity of human cytochromes P450

    DEFF Research Database (Denmark)

    Rydberg, Patrik; Rod, Thomas Holm; Olsen, Lars;

    2007-01-01

    We have studied the dynamics of water molecules in six crystal structures of four human cytochromes P450, 2A6, 2C8, 2C9, and 3A4, with molecular dynamics simulations. In the crystal structures, only a few water molecules are seen and the reported sizes of the active-site cavity vary a lot. In the...

  16. Study of water molecule decomposition in plasma by diode laser spectroscopy and optical actinometry methods

    Science.gov (United States)

    Bernatskiy, A. V.; Lagunov, V. V.; Ochkin, V. N.; Tskhai, S. N.

    2016-07-01

    The methods of diode laser radiation absorption at vibrational–rotational molecule transitions and optical actinometry with measurements of its electron emission spectra are used independently to study water molecule dissociation in glow discharge plasma in a mixture of water vapor and inert gases at reduced pressure. The methods yield close results. The dissociation reaches 98%.

  17. Technique for determining the angular orientation of molecules bound to the surface of an arbitrary planar optical waveguide.

    Science.gov (United States)

    Mendes, Sergio B; Bradshaw, John Thomas; Saavedra, S Scott

    2004-01-01

    A technique to determine the angular orientation of a molecular assembly bound to the surface of a planar optical waveguide of arbitrary structure is described. The approach is based on measuring the absorption dichroic ratio by using the waveguide evanescent fields with orthogonal polarizations (TE, TM) and the same mode order to probe two molecular assemblies, (i) a reference sample composed of an isotropic orientation distribution of dipoles and (ii) a sample of interest. The isotropic sample is used to characterize the waveguide structure, which then allows the orientation parameters of a molecular assembly under investigation to be determined from a measured dichroic ratio. The method developed here is particularly important for applications in gradient-index and multilayer planar waveguide platforms because in those cases the extension of previously reported approaches would require a full experimental characterization of the guiding structure, which would be problematic and may yield inaccurate results. PMID:14714646

  18. Influence of orientation averaging on the anisotropy of thermal neutrons scattering on water molecules

    International Nuclear Information System (INIS)

    Determination of spatial distribution of neutron flux in water, most frequently used moderator in thermal reactors, demands microscopic scattering kernels dependence on cosine of thermal neutrons scattering angle when solving the Boltzmann equation. Since spatial orientation of water molecules influences this dependence it is necessary to perform orientation averaging or rotation-vibrational intermediate scattering function for water molecules. The calculations described in this paper and the obtained results showed that methods of orientation averaging do not influence the anisotropy of thermal neutrons scattering on water molecules, but do influence the inelastic scattering

  19. Monitoring of discharge cleaning for fusion devices by microwave spectroscopy of water molecules

    International Nuclear Information System (INIS)

    The monitoring method of discharge cleaning which was based on microwave spectroscopy was developed in order to apply it to fusion devices and availability of this method was experimentally investigated. Water molecules are one of the major residual molecules in a vacuum vessel, and hence the partial pressure of water is a good index of progress in conditioning. Temporal changes in the partial pressure were measured by using this method during discharge cleaning consequently. Three subjects were studied with a Stark modulated microwave spectrometer, namely, proportionality between the spectrum intensity and the partial pressure, resolving power of the spectrometer for isotopic water molecules and applicability of this method to the measurement of radioactive water molecules. Rotational spectra of the light water H2O (22.235 GHz) and the hydrogen isotopic waters HDO (22.307 GHz) and HTO (16.563 GHz) were observed in several plasma devices for these purposes. (orig.)

  20. A structurally conserved water molecule in Rossmann dinucleotide-binding domains

    OpenAIRE

    Bottoms, Christopher A; Smith, Paul E.; Tanner, John J.

    2002-01-01

    A computational comparison of 102 high-resolution (≤1.90 Å) enzyme-dinucleotide (NAD, NADP, FAD) complexes was performed to investigate the role of solvent in dinucleotide recognition by Rossmann fold domains. The typical binding site contains about 9–12 water molecules, and about 30% of the hydrogen bonds between the protein and the dinucleotide are water mediated. Detailed inspection of the structures reveals a structurally conserved water molecule bridging dinucleotides with the well-known...

  1. Electric-field-dependent empirical potentials for molecules and crystals: a first application to flexible water molecule adsorbed in zeolites

    OpenAIRE

    Cicu, P.; Demontis, Pierfranco; Spanu, Silvano; Suffritti, Giuseppe Baldovino; Tilocca, Antonio

    2000-01-01

    A general method to include electric-field-dependent terms in empirical potential functions representing interatomic interactions is proposed. It is applied to derive an intramolecular potential model for the water molecule able to reproduce the effects of an electric field on its geometry and dynamics: to enlarge the HOH angle, to increase slightly the OH bond lengths, to red-shift the stretching vibrational frequencies, and to blue-shift slightly the bending mode frequency. These effects ha...

  2. Tritiated water uptake kinetics in tissue-free water and organically-bound fractions of tomato plants

    International Nuclear Information System (INIS)

    The kinetics of tritiated water (HTO) vapour uptake into tissue-free water tritium (TFWT) and organically bound tritium (OBT) fractions of tomato, Lycopersicon esculentum Mill., cv Vendor, were investigated under controlled growing conditions. Most uptake data fitted a first-order kinetic model, Ct = C∞ (1-e-kt), where Ct is the tritium concentration at time t, Ca the steady-state concentration and k the uptake rate constant. During atmospheric-HTO exposure with clean-water irrigation in open pots the TFWT k values were 0.024 ± 0.023 h-1 for new foliage, 0.104 ± 0.067 h-1 for old foliage and 0.042 ± to 0.136 h-1 for new green fruit. OBT uptake rate constants were 20 percent less for new foliage and 76 percent less for new green fruit. Under steady-state conditions the ratio of tritium specific activities of TWFT to atmospheric HTO were 0.43 in new foliage, 0.46 in old foliage and 0.19 in green fruit. Within the plant, OBT and TFWT ratios were 0.70 for new foliage, 0.63 for old foliage (maximum) and between 0.72 and 1.92 for green fruit. The greater than unity tritium specific activity ratios in green fruit were not attributed to tritium enrichment but rather to the translocation of foliar OBT to the growing fruit which contained lower specific activity TFWT derived from soil water

  3. Self-induced spontaneous transport of water molecules through a symmetrical nanochannel by ratchetlike mechanism

    CERN Document Server

    Wan, R; Li, J; Bao, J; Hu, J; Fang, H; Wan, Rongzheng; Lu, Hangjun; Li, Jinyuan; Bao, Jingdong; Hu, Jun; Fang, Haiping

    2006-01-01

    Gaining work from thermal fluctuations without external input energy is a dream for scientists but is forbidden by the second law of thermodynamics. Feynman proposed a molecular ratchet toward this direction but there are still theoretical arguments against it. Here, we revisit this classical problem by using molecular dynamics simulation to monitor water molecules confined in a carbon nanotube. A spontaneous directional transportation of water molecules was observed in this symmetrical nanochannel by a ratchetlike mechanism. This is the first ratchetlike system without any asymmetrical structure or external field, while the asymmetric ratchetlike potential solely results from the transported water molecules that form hydrogen-bonded chains among themselves. Importantly, the resulting net water fluxes reached the level of biological channel, suggesting possible adoption by life. This effect is ascribed to the exceptive structure of the water molecule; a minute change in hydrogen-bond strength dramatically aff...

  4. Application of a convergent, composite coupled cluster approach to bound state, adiabatic electron affinities in atoms and small molecules.

    Science.gov (United States)

    Feller, David

    2016-01-01

    Benchmark quality adiabatic electron affinities for a collection of atoms and small molecules were obtained with the Feller-Peterson-Dixon composite coupled cluster theory method. Prior applications of this method demonstrated its ability to accurately predict atomization energies/heats of formation for more than 170 molecules. In the current work, the 1-particle expansion involved very large correlation consistent basis sets, ranging up to aug-cc-pV9Z (aug-cc-pV10Z for H and H2), with the goal of minimizing the residual basis set truncation error that must otherwise be approximated with extrapolation formulas. The n-particle expansion begins with coupled cluster calculations through iterative single and double excitations plus a quasiperturbative treatment of "connected" triple excitations (CCSD(T)) pushed to the complete basis set limit followed by CCSDT, CCSDTQ, or CCSDTQ5 corrections. Due to the small size of the systems examined here, it was possible in many cases to extend the n-particle expansion to the full configuration interaction wave function limit. Additional, smaller corrections associated with core/valence correlation, scalar relativity, anharmonic zero point vibrational energies, and non-adiabatic effects were also included. The overall root mean square (RMS) deviation was 0.005 eV (0.12 kcal/mol). This level of agreement was comparable to what was found with molecular heats of formation. A 95% confidence level corresponds to roughly twice the RMS value or 0.01 eV. While the atomic electron affinities are known experimentally to high accuracy, the molecular values are less certain. This contributes to the difficulty of gauging the accuracy of the theoretical results. A limited number of electron affinities were determined with the explicitly correlated CCSD(T)-F12b method. After extending the VnZ-F12 orbital basis sets with additional diffuse functions, the F12b method was found to accurately reproduce the best F/F(-) value obtained with standard

  5. Application of a convergent, composite coupled cluster approach to bound state, adiabatic electron affinities in atoms and small molecules

    Science.gov (United States)

    Feller, David

    2016-01-01

    Benchmark quality adiabatic electron affinities for a collection of atoms and small molecules were obtained with the Feller-Peterson-Dixon composite coupled cluster theory method. Prior applications of this method demonstrated its ability to accurately predict atomization energies/heats of formation for more than 170 molecules. In the current work, the 1-particle expansion involved very large correlation consistent basis sets, ranging up to aug-cc-pV9Z (aug-cc-pV10Z for H and H2), with the goal of minimizing the residual basis set truncation error that must otherwise be approximated with extrapolation formulas. The n-particle expansion begins with coupled cluster calculations through iterative single and double excitations plus a quasiperturbative treatment of "connected" triple excitations (CCSD(T)) pushed to the complete basis set limit followed by CCSDT, CCSDTQ, or CCSDTQ5 corrections. Due to the small size of the systems examined here, it was possible in many cases to extend the n-particle expansion to the full configuration interaction wave function limit. Additional, smaller corrections associated with core/valence correlation, scalar relativity, anharmonic zero point vibrational energies, and non-adiabatic effects were also included. The overall root mean square (RMS) deviation was 0.005 eV (0.12 kcal/mol). This level of agreement was comparable to what was found with molecular heats of formation. A 95% confidence level corresponds to roughly twice the RMS value or 0.01 eV. While the atomic electron affinities are known experimentally to high accuracy, the molecular values are less certain. This contributes to the difficulty of gauging the accuracy of the theoretical results. A limited number of electron affinities were determined with the explicitly correlated CCSD(T)-F12b method. After extending the VnZ-F12 orbital basis sets with additional diffuse functions, the F12b method was found to accurately reproduce the best F/F- value obtained with standard

  6. Piecewise bounding and Integer Linear Programming for the optimal management of a water pumping and desalination process

    OpenAIRE

    Ngueveu, Sandra Ulrich; Sareni, Bruno; Roboam, Xavier

    2014-01-01

    The problem considered is the optimization of water production for autonomous water pump- ing and desalination units supplied by renewable energy sources, designed to be a viable solution to fresh water scarcity for remote areas. Non-linear gyrators as well as the non-linear efficiency of energy and flow transfers model the mechanical-hydraulic power conversion sys- tems involved. This paper presents a generic formulation and resolution algorithms based on piece-wise bounding and integer line...

  7. Changes in free and bound water in the hippocampus of patients with Alzheimer's disease

    International Nuclear Information System (INIS)

    We measured the T2 relaxation time using dual spin echo MRI, and also the magnetization transfer ratio (MTR) using gradient echo MRI, in the hippocampus of Alzheimer's disease (AD) patients, and compared these factors to those of non-Alzheimer's dementia (non-AD) patients and of control subjects. The degree of medial temporal lobe atrophy in AD patients was similar to that of non-AD patients, although atrophy was more severe in AD and non-AD patients than in the control group. MTRs in the hippocampus were significantly lower in AD patients than in non-AD patients and in the control group. No significant differences in the T2 values of the three groups were found. The change of T2 x (1-MTR/100) in the hippocampus was significantly higher in AD patients than in non-AD patients and the control group and the change of T2 x MTR/100 was significantly lower in AD patients than in non-AD patients and the control group. Significant correlations between MMSE scores and MR parameters were found in AD patients, but not in non-AD patients. These results suggest that a decrease in the MTR in the hippocampus of AD, probably due to a decrease in bound water and an increase in free water, reflects underlying pathological changes which include a loss of neurons and gliosis. (author)

  8. A novel method to measure HLA-DM-susceptibility of peptides bound to MHC class II molecules based on peptide binding competition assay and differential IC(50) determination.

    Science.gov (United States)

    Yin, Liusong; Stern, Lawrence J

    2014-04-01

    HLA-DM (DM) functions as a peptide editor that mediates the exchange of peptides loaded onto MHCII molecules by accelerating peptide dissociation and association kinetics. The relative DM-susceptibility of peptides bound to MHCII molecules correlates with antigen presentation and immunodominance hierarchy, and measurement of DM-susceptibility has been a key effort in this field. Current assays of DM-susceptibility, based on differential peptide dissociation rates measured for individually labeled peptides over a long time base, are difficult and cumbersome. Here, we present a novel method to measure DM-susceptibility based on peptide binding competition assays performed in the presence and absence of DM, reported as a delta-IC(50) (change in 50% inhibition concentration) value. We simulated binding competition reactions of peptides with various intrinsic and DM-catalyzed kinetic parameters and found that under a wide range of conditions the delta-IC(50) value is highly correlated with DM-susceptibility as measured in off-rate assay. We confirmed experimentally that DM-susceptibility measured by delta-IC(50) is comparable to that measured by traditional off-rate assay for peptides with known DM-susceptibility hierarchy. The major advantage of this method is that it allows simple, fast and high throughput measurement of DM-susceptibility for a large set of unlabeled peptides in studies of the mechanism of DM action and for identification of CD4+ T cell epitopes. PMID:24583195

  9. Finite-bias electronic transport of molecules in water solution

    OpenAIRE

    Sanvito, Stefano; RUNGGER, IVAN; Chen, Xihua

    2010-01-01

    The effects of water wetting conditions on the transport properties of molecular nanojunctions are investigated theoretically by using a combination of empirical-potential molecular-dynamics and first-principles electronic-transport calculations. These are at the level of the nonequilibrium Green?s-function method implemented for self-interaction corrected density-functional theory. We find that water effectively produces electrostatic gating to the molecular junction with a gatin...

  10. Roles of water molecules in bacteria and viruses

    Science.gov (United States)

    Cox, C. S.

    1993-02-01

    In addition to water, microbes mainly comprise lipids, carbohydrates, proteins and nucleic acids. Their structure and function singularly and conjointly is affected by water activity. Desiccation leads to dramatic lipid phase changes whereas carbohydrates, proteins and nucleic acids initially suffer spontaneous, reversible low activation energy Maillard reactions forming products that more slowly re-arrange, cross-link etc. to give non-native states. While initial products spontaneously may reverse to native states by raising water activity, later products only do so through energy consumption and enzymatic activity eg. repair. Yet, native states of lipid membranes and associated enzymes are required to generate energy. Consequently, good reserves of high energy compounds (e.g. ATP) and of membrane stabilisers (e.g. trehalose) may be expected to enhance survival following drying and rehydration (e.g. anhydrobiotic organisms).

  11. Bound on the Slope of Steady Water Waves with Favorable Vorticity

    Science.gov (United States)

    Strauss, Walter A.; Wheeler, Miles H.

    2016-07-01

    We consider the angle {θ} of inclination (with respect to the horizontal) of the profile of a steady two dimensional inviscid symmetric periodic or solitary water wave subject to gravity. Although {θ} may surpass 30° for some irrotational waves close to the extreme wave, Amick (Arch Ration Mech Anal 99(2):91-114, 1987) proved that for any irrotational wave the angle must be less than 31.15°. Is the situation similar for periodic or solitary waves that are not irrotational? The extreme Gerstner wave has infinite depth, adverse vorticity and vertical cusps (θ = 90°). Moreover, numerical calculations show that even waves of finite depth can overturn if the vorticity is adverse. In this paper, on the other hand, we prove an upper bound of 45° on {θ} for a large class of waves with favorable vorticity and finite depth. In particular, the vorticity can be any constant with the favorable sign. We also prove a series of general inequalities on the pressure within the fluid, including the fact that any overturning wave must have a pressure sink.

  12. Encapsulation and Characterization of Proton-Bound Amine Homodimers in a Water Soluble, Self-Assembled Supramolecular Host

    Energy Technology Data Exchange (ETDEWEB)

    Pluth, Michael; Fiedler, Dorothea; Mugridge, Jeffrey; Bergman, Robert; Raymond, Kenneth

    2008-10-01

    Cyclic amines can be encapsulated in a water-soluble self-assembled supramolecular host upon protonation. The hydrogen bonding ability of the cyclic amines, as well as the reduced degrees of rotational freedom, allows for the formation of proton-bound homodimers inside of the assembly which are otherwise not observable in aqueous solution. The generality of homodimer formation was explored with small N-alkyl aziridines, azetidines, pyrrolidines and piperidines. Proton-bound homodimer formation is observed for N-alkylaziridines (R = methyl, isopropyl, tert-butyl), N-alkylazetidines (R = isopropyl, tertbutyl), and N-methylpyrrolidine. At high concentration, formation of a proton-bound homotrimer is observed in the case of N-methylaziridine. The homodimers stay intact inside the assembly over a large concentration range, thereby suggesting cooperative encapsulation. Both G3(MP2)B3 and G3B3 calculations of the proton-bound homodimers were used to investigate the enthalpy of the hydrogen bond in the proton-bound homodimers and suggest that the enthalpic gain upon formation of the proton-bound homodimers may drive guest encapsulation.

  13. Dose from organically bound tritium after an acute tritiated water intake in humans

    International Nuclear Information System (INIS)

    We have analyzed the urinary excretion data from eight male workers following an acute intake of tritiated water (HTO) and assessed the dose contribution from organically bound tritium (OBT) in the body. The individuals affected increased their fluid intakes during the first month or more post-exposure, to accelerate the turnover of tritium in the body water for dose mitigation purposes. The volumes of cumulative 24 h urine samples were similar to Reference Man in the latter part of the study (100-300 d post-exposure). The workers' urine samples were analyzed for total tritium up to 300 d post-exposure. The results suggest that a measurement of the tritium activity per unit mass of organic matter in urine can provide an assessment of the specific activity of tritium in the organic fraction of the soft tissue, providing an equilibrium condition exists. A mathematical model is proposed to estimate the dose increase from the retained OBT by examining the kinetics of total tritium excretion in urine. The model accounts for the variable rates of fluid intake. The influence of measurement errors and the limited duration of the study (0-300 d post-exposure) on the OBT dose contribution was assessed through statistical analysis, while the role of direct OBT excretion in urine was estimated by using metabolic models. Based on the time series of tritium concentration in urine, the average dose increase to the workers from the metabolised OBT was calculated as 6.2 ± 1.3% of the HTO dose. 78 refs., 36 tabs., 11 figs

  14. Analytical model for three-dimensional Mercedes-Benz water molecules

    Science.gov (United States)

    Urbic, T.

    2012-06-01

    We developed a statistical model which describes the thermal and volumetric properties of water-like molecules. A molecule is presented as a three-dimensional sphere with four hydrogen-bonding arms. Each water molecule interacts with its neighboring waters through a van der Waals interaction and an orientation-dependent hydrogen-bonding interaction. This model, which is largely analytical, is a variant of a model developed before for a two-dimensional Mercedes-Benz model of water. We explored properties such as molar volume, density, heat capacity, thermal expansion coefficient, and isothermal compressibility as a function of temperature and pressure. We found that the volumetric and thermal properties follow the same trends with temperature as in real water and are in good general agreement with Monte Carlo simulations, including the density anomaly, the minimum in the isothermal compressibility, and the decreased number of hydrogen bonds upon increasing the temperature.

  15. Peculiarities of the Bound Water and Water Ice Seasonal Variations in the Martian Surface Layer of the Regolith.

    Science.gov (United States)

    Kuzmin, R. O.; Zabalueva, E. V.; Evdokimova, N. A.; Christensen, P. H.; Mitrofanov, I. G.; Litvak, M. L.

    2008-09-01

    Introduction: The processes of the hydration/ dehydration of salt minerals within the Martian soil and the condensation/sublimation of water ice (and frost) in the surficial soil layer and on the polar cap surface play great significance in the modern water cycle on Mars and directly affect the redistribution of the water phases and forms in the system "atmosphere/regolith/polar caps" [1, 2, 3, 4, 5]. The processes are reversible in time and their intensity is strongly dependent on such time-variable climatic parameters as atmospheric and surface temperature, atmospheric water vapour content and specific features of atmospheric seasonal circulation [6, 7, 8, 9, 10]. In the work we report the study results of the seasonal variations of the chemically bound water (BW) spectral signature (based on the TES and OMEGA data), estimation and mapping of the winterand spring-time water ice increase within the Martian surface soil (based on the TES and HEND data). Analysis and results: Regional and global mapping of the BW spectral index distribution as function of the seasons was conducted by using of the 6.1 μm emission pick from the TES dataset and the 1.91 μm absorption band from reflectance spectra of the OMEGA data. The study of the seasonal redistribution of the water ice (and frost) within the thin surficial soil layer was conducted based on the TES thermal inertia (TI) data and the HEND neutrons flux mapping data. Bound water mapping: The mapping of the TES 6.1 μm BW index distributions was conducted at the time steps from 30° to 60° of Ls [11]. The mapping results show remarkable changes of the BW index values from one season to other one at notable latitudinal dependence of the index (Fig.1). At that, the higher BW index values are disposed mostly within the peripheral zone near the edge of the perennial and seasonal polar caps (cooler, wetter areas), while the lower BW index values are observed at low latitudes (warmer, drier areas). Between the Nspring (Ls=0

  16. The effect of water treatment on the presence of particle-bound 210Po and 210Pb in groundwater

    International Nuclear Information System (INIS)

    The distribution of 210Po and 210Pb in various particle-size fractions in Finnish groundwater was studied at five private homes. Each site had water treatment equipment comprising either an ion exchange unit or a granular activated carbon filter. Samples of both raw and treated water were filtered using pore sizes ranging from 450 nm to 100 kDa and the activity concentration of 210Po and 210Pb in the filtrate was determined. In untreated groundwater 86% of 210Pb, on average, was found in the large particle fraction (> 450 nm). However, in Fe- and Mn-rich water with a high Fe/Mn ratio and in organic-rich water, the majority of 210Pb was found in either the intermediate particle (100 kDa-450 nm) or small particle (210Pb, 210Po was bound more to the intermediate and small particle fraction. After water treatment, 210Pb was found most frequently in the large particle fraction. The size distribution of particle-bound 210Po was not as clear as that for 210Pb, and in treated water, 210Po was more evenly distributed among fractions. The ion exchange unit removed 210Pb and 210Po bound to the intermediate or small particle fraction, whereas the efficiency of the activated carbon filters in removing 210Pb and 210Po was independent of the particle size. (orig.)

  17. Molecular dynamics simulation studies on some topics of water molecules on hydrophobic surfaces

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Molecular dynamics simulations have been used to study two topics of water molecules on hydrophobic surfaces. Some properties of the nanobubbles with different ingredients and behavior of single water chains in single-walled carbon nanochannels are exploited. Molecular simulations show that the density of the N2 and H2 are quite high, which is critical for the stability of the nanobubbles and may have potential applications, such as hydrogen storage, incorporated with recent experimental method to controllably produce hydrogen nanobubbles. The water molecules inside the nanochannel show an unexpected directed motion with long time period, which is indispensable in the future study of the dynamics of biological channels.

  18. Fast phase transition of water molecules in a defective carbon nanotube under an electric field

    Science.gov (United States)

    Meng, Xianwen; Huang, Jiping

    2016-02-01

    We utilize molecular dynamics simulations to study the effect of an electric field on the permeation of water molecules through a defective single-walled carbon nanotube (DSWCNT). Compared with a perfect single-walled carbon nanotube (PSWCNT), the behaviors of water molecules respond more quickly under the same electric field in a DSWCNT. Wet-dry phase transition of water molecules occurs when the electric field reaches 0.32 V/nm, which is much lower than the case of the PSWCNT. Besides, the critical electric field is affected by the number of defects. These results pave a way for designing fast wet-dry transition devices and provide a new insight into water permeation through a defective nanochannel.

  19. Vibrational states of a water molecule in a nano-cavity of beryl crystal lattice

    International Nuclear Information System (INIS)

    Low-energy excitations of a single water molecule are studied when confined within a nano-size cavity formed by the ionic crystal lattice. Optical spectra are measured of manganese doped beryl single crystal Mn:Be3Al2Si6O18, that contains water molecules individually isolated in 0.51 nm diameter voids within the crystal lattice. Two types of orientation are distinguished: water-I molecules have their dipole moments aligned perpendicular to the c axis and dipole moments of water-II molecules are parallel to the c-axis. The optical conductivity σ(ν) and permittivity ε′(ν) spectra are recorded in terahertz and infrared ranges, at frequencies from several wavenumbers up to ν = 7000 cm−1, at temperatures 5–300 K and for two polarizations, when the electric vector E of the radiation is parallel and perpendicular to the c-axis. Comparative experiments on as-grown and on dehydrated samples allow to identify the spectra of σ(ν) and ε′(ν) caused exclusively by water molecules. In the infrared range, well-known internal modes ν1, ν2, and ν3 of the H2O molecule are observed for both polarizations, indicating the presence of water-I and water-II molecules in the crystal. Spectra recorded below 1000 cm−1 reveal a rich set of highly anisotropic features in the low-energy response of H2O molecule in a crystalline nano-cavity. While for E∥c only two absorption peaks are detected, at ∼90 cm−1 and ∼160 cm−1, several absorption bands are discovered for E⊥c, each consisting of narrower resonances. The bands are assigned to librational (400–500 cm−1) and translational (150–200 cm−1) vibrations of water-I molecule that is weakly coupled to the nano-cavity “walls.” A model is presented that explains the “fine structure” of the bands by a splitting of the energy levels due to quantum tunneling between the minima in a six-well potential relief felt by a molecule within the cavity

  20. Study on the bound water of several high specific surface-area oxides (beryllia, alumina, silica-alumina)

    International Nuclear Information System (INIS)

    This study is concerned with the bound water of several oxides (beryllia, alumina, silica-alumina) at different steps of their dehydration (heating temperatures between 150 and 1100 deg. C). The following techniques have been used simultaneously: Thermal analysis (a new method has been developed), nitrogen adsorption (study of the texture), Diborane hydrolysis (qualitative and quantitative analysis of surface water), Infra-red spectrography (in the absorption range of water), Nuclear magnetic resonance (in the resonance range of protons). Thanks to these different techniques, five kinds of bound water have been observed. Attention is called on the great influence of the thermal treatment conditions on the evolution of the products resulting from the decomposition of alumina α-trihydrate Al(OH)3 and beryllium α-hydroxide, in the course of the dehydration. Moreover, the author emphasizes the peculiar properties of the two kinds of oxides (alumina and beryllia) prepared through a new method of treatment under low pressure and constant speed of decomposition. Such particular features concern mainly texture, bound water, and consequently, also catalytic activity. (author)

  1. Hydroxyl and water molecule orientations in trypsin: Comparison to molecular dynamics structures

    Energy Technology Data Exchange (ETDEWEB)

    McDowell, R.S.; Kossiakoff, A.A. [Genentech, Inc., South San Francisco, CA (United States)

    1994-12-31

    A comparison is presented of experimentally observed hydroxyl and water hydrogens in trypsin determined from neutron density maps with the results of a 140ps molecular dynamics (MD) simulation. Experimental determination of hydrogen and deuterium atom positions in molecules as large as proteins is a unique capability of neutron diffraction. The comparison addresses the degree to which a standard force-field approach can adequately describe the local electrostatic and van der Waals forces that determine the orientations of these hydrogens. Neutron densities, derived from 2.1{Angstrom} D{sub 2}O-H{sub 2}O difference Fourier maps, provide a database of 27 well-ordered hydroxyl hydrogens. Most of the simulated hydroxyl orientations are within a standard deviation of the experimentally-observed positions, including several examples in which both the simulation and the neutron density indicate that a hydroxyl group is shifted from a {open_quote}standard{close_quote} rotamer. For the most highly ordered water molecules, the hydrogen distributions calculated from the trajectory were in good agreement with neutron density; simulated water molecules that displayed multiple hydrogen bonding networks had correspondingly broadened neutron density profiles. This comparison was facilitated by development of a method to construct a pseudo 2{Angstrom} density map based on the hydrogen atom distributions from the simulation. The degree of disorder of internal water molecules is shown to result primarily from the electrostatic environment surrounding that water molecule as opposed to the cavity size available to the molecule. A method is presented for comparing the discrete observations sampled in a dynamics trajectory with the time- averaged data obtained from X-ray or neutron diffraction studies. This method is particularly useful for statically-disordered water molecules, in which the average location assigned from a trajectory may represent a site of relatively low occupancy.

  2. Hydroxyl and water molecule orientations in trypsin: Comparison to molecular dynamics structures

    International Nuclear Information System (INIS)

    A comparison is presented of experimentally observed hydroxyl and water hydrogens in trypsin determined from neutron density maps with the results of a 140ps molecular dynamics (MD) simulation. Experimental determination of hydrogen and deuterium atom positions in molecules as large as proteins is a unique capability of neutron diffraction. The comparison addresses the degree to which a standard force-field approach can adequately describe the local electrostatic and van der Waals forces that determine the orientations of these hydrogens. Neutron densities, derived from 2.1 Angstrom D2O-H2O difference Fourier maps, provide a database of 27 well-ordered hydroxyl hydrogens. Most of the simulated hydroxyl orientations are within a standard deviation of the experimentally-observed positions, including several examples in which both the simulation and the neutron density indicate that a hydroxyl group is shifted from a open-quote standard close-quote rotamer. For the most highly ordered water molecules, the hydrogen distributions calculated from the trajectory were in good agreement with neutron density; simulated water molecules that displayed multiple hydrogen bonding networks had correspondingly broadened neutron density profiles. This comparison was facilitated by development of a method to construct a pseudo 2 Angstrom density map based on the hydrogen atom distributions from the simulation. The degree of disorder of internal water molecules is shown to result primarily from the electrostatic environment surrounding that water molecule as opposed to the cavity size available to the molecule. A method is presented for comparing the discrete observations sampled in a dynamics trajectory with the time- averaged data obtained from X-ray or neutron diffraction studies. This method is particularly useful for statically-disordered water molecules, in which the average location assigned from a trajectory may represent a site of relatively low occupancy

  3. Improving protein-ligand docking with flexible interfacial water molecules using SWRosettaLigand.

    Science.gov (United States)

    Li, Linqing; Xu, Weiwei; Lü, Qiang

    2015-11-01

    Computational protein-ligand docking is of great importance in drug discovery and design. Conformational changes greatly affect the results of protein-ligand docking, especially when water molecules take part in mediating protein ligand interactions or when large conformational changes are observed in the receptor backbone interface. We have developed an improved protocol, SWRosettaLigand, based on the RosettaLigand protocol. This approach incorporates the flexibility of interfacial water molecules and modeling of the interface of the receptor into the original RosettaLigand. In a coarse sampling step, SWRosettaLigand pre-optimizes the initial position of the water molecules, docks the ligand to the receptor with explicit water molecules, and minimizes the predicted structure with water molecules. The receptor backbone interface is treated as a loop and perturbed and refined by kinematic closure, or cyclic coordinate descent algorithm, with the presence of the ligand. In two cross-docking test sets, it was identified that for 8 out of 14, and 16 out of 22, test instances, the top-ranked structures by SWRosettaLigand achieved better accuracy than other protocols. PMID:26515196

  4. Giant pumping of single-file water molecules in a carbon nanotube.

    Science.gov (United States)

    Wang, Y; Zhao, Y J; Huang, J P

    2011-11-17

    Achieving a fast, unidirectional flow of single-file water molecules (UFSWM) across nanochannels is important for membrane-based water purification or seawater desalination. For this purpose, electro-osmosis methods are recognized as a very promising approach and have been extensively discussed in the literature. Utilizing molecular dynamics simulations, here we propose a design for pumping water molecules in a single-walled carbon nanotube in the presence of a linearly gradient electric (GE) field. Such a GE field is inspired by GE fields generated from charged ions located adjacent to biological membrane water nanochannels that can conduct water in and out of cells and can be experimentally achieved by using the charged tip of an atomic force microscope. As a result, the maximum speed of the UFSWM can be 1 or 2 orders of magnitude larger than that in a uniform electric (UE) field. Also, inverse transportation of water molecules does not exist in case of the GE field but can appear for the UE field. Thus, the GE field yields a much more efficient UFSWM than the UE field. The giant pumping ability as revealed is attributed to the nonzero net electrostatic force acting on each water molecule confined in the nanotube. These observations have significance for the design of nanoscale devices for readily achieving controllable UFSWM at high speed. PMID:21977917

  5. An Acetate Bound Cobalt Oxide Catalyst for Water Oxidation: Role of Monovalent Anions and Cations In Lowering Overpotential

    OpenAIRE

    Dey, Subal; Mondal, Biswajit; Dey, Abhishek

    2014-01-01

    Co(II) dissolved in acetate buffer at pH 7 is found to be a good water oxidation catalyst (WOC) showing electrocatalytic water oxidation current significantly greater than Co(II) in phosphate buffer under the same conditions owing to the higher solubility of the former. When electrodeposited on ITO/FTO electrodes it forms acetate bound cobalt(II)oxide based material (Co-Ac-WOC) showing catalytic water oxidation current density of 0.1 mA/cm$^{2}$ at 830 mV and 1 mA/cm$^{2}$ at 1 V in a pH 7 bu...

  6. Bounding the marginal cost of producing potable water including the use of seawater desalinization as a backstop potable water production technology

    Energy Technology Data Exchange (ETDEWEB)

    Dooley, James J.

    2014-04-01

    The analysis presented in this technical report should allow for the creation of high, medium, and low cost potable water prices for GCAM. Seawater reverse osmosis (SWRO) based desalinization should act as a backstop for the cost of producing potable water (i.e., the literature seems clear that SWRO should establish an upper bound for the plant gate cost of producing potable water). Transporting water over significant distances and having to lift water to higher elevations to reach end-users can also have a significant impact on the cost of producing water. The three potable fresh water scenarios describe in this technical report are: low cost water scenario ($0.10/m3); medium water cost scenario ($1.00/m3); and high water cost scenario ($2.50/m3).

  7. Water-mediated influence of a crowded environment on internal vibrations of a protein molecule.

    Science.gov (United States)

    Kuffel, Anna; Zielkiewicz, Jan

    2016-02-01

    The influence of crowding on the protein inner dynamics is examined by putting a single protein molecule close to one or two neighboring protein molecules. The presence of additional molecules influences the amplitudes of protein fluctuations. Also, a weak dynamical coupling of collective velocities of surface atoms of proteins separated by a layer of water is detected. The possible mechanisms of these phenomena are described. The cross-correlation function of the collective velocities of surface atoms of two proteins was decomposed into the Fourier series. The amplitude spectrum displays a peak at low frequencies. Also, the results of principal component analysis suggest that the close presence of an additional protein molecule influences the high-amplitude, low-frequency modes in the most prominent way. This part of the spectrum covers biologically important protein motions. The neighbor-induced changes in the inner dynamics of the protein may be connected with the changes in the velocity power spectrum of interfacial water. The additional protein molecule changes the properties of solvation water and in this way it can influence the dynamics of the second protein. It is suggested that this phenomenon may be described, at first approximation, by a damped oscillator driven by an external random force. This model was successfully applied to conformationally rigid Choristoneura fumiferana antifreeze protein molecules. PMID:26805932

  8. Solvation of a probe molecule by fluid supercooled water in a hydrogel at 200 K.

    Science.gov (United States)

    Santangelo, Maria Grazia; Levantino, Matteo; Cupane, Antonio; Jeschke, Gunnar

    2008-12-11

    By combining electron paramagnetic resonance (EPR) measurements on a nitroxide probe and differential scanning calorimetry (DSC), we demonstrate existence of liquid supercooled water in a silica hydrogel with high hydration level down to temperatures of at least 198 K. Besides the major fraction of liquid supercooled water, a minor fraction crystallizes at about 236 K during cooling and melts at 246 K during heating. The liquid domains are of sufficient size to solvate the nearly spherical paramagnetic probe molecule TEMPO with a diameter of about 6 A. Analysis of EPR spectra provides the rotational correlation time of the probe that is further used to compare the viscosity of the supercooled water with the one of bulk water. In the temperature interval investigated, the supercooled water behaves as a fragile liquid and eventually solidifies at 120 K to a glass that incorporates the probe molecules. PMID:19053683

  9. Water molecule network and active site flexibility of apo protein tyrosine phosphatase 1B

    DEFF Research Database (Denmark)

    Pedersen, A.K.; Peters, Günther H.J.; Møller, K.B.;

    2004-01-01

    Protein tyrosine phosphatase 1B (PTP1B) plays a key role as a negative regulator of insulin and leptin signalling and is therefore considered to be an important molecular target for the treatment of type 2 diabetes and obesity. Detailed structural information about the structure of PTP1B, including...... the conformation and flexibility of active-site residues as well as the water-molecule network, is a key issue in understanding ligand binding and enzyme kinetics and in structure-based drug design. A 1.95 Angstrom apo PTP1B structure has been obtained, showing four highly coordinated water molecules...

  10. Changes in content of free, conjugated and bound polyamines and osmotic adjustment in adaptation of vetiver grass to water deficit.

    Science.gov (United States)

    Zhou, Qiang; Yu, Bingjun

    2010-06-01

    Osmotic adjustment and alteration of polyamines (PAs) have been suggested to play roles in plant adaptation to water deficit/drought stress. In this study, the changes in cell intactness, photosynthesis, compatible solutes and PAs [including putrescine (Put), spermidine (Spd) and spermine (Spm) each in free, conjugated and bound forms] were investigated in leaves of vetiver grass exposed to different intensity of water deficit stress and subsequent rewatering. The results showed that, when vetiver grass was exposed to the moderate (20% and 40% PEG-6000 solutions) and severe (60% PEG solution) water deficit for 6days, the plant injury degree (expressed as the parameters of plant growth, cell membrane integrity, water relations and photosynthesis) increased and contents of free and conjugated Put decreased with the rise of PEG concentration. Under the moderate water deficit, the plants could survive by the reduced osmotic potential (psi(s)), increased free and conjugated Spd and Spm in leaves. After subsequent rewatering, the osmotic balance was re-established, most of the above investigated physiological parameters were fully or partly recovered to the control levels. However, it was not the case for the severely-stressed and rewatering plants. It indicates that, vetiver grass can cope well with the moderate water deficit/drought stress by using the strategies of osmotic adjustment and maintenance of total contents of free, conjugated and bound PAs in leaves. PMID:20363642

  11. Shear-stress-induced structural arrangement of water molecules in nanoscale Couette flow with slipping at wall boundary

    International Nuclear Information System (INIS)

    This study investigated the structuring of water molecules in a nanoscale Couette flow with the upper plate subjected to lateral forces with various magnitudes and water slipping against a metal wall. It was found that when the upper plate is subjected to a force, the water body deforms into a parallelepiped. Water molecules in the channel are then gradually arranged into lattice positions, creating a layered structure. The structural arrangement of water molecules is caused by the water molecules accommodating themselves to the increase in energy under the application of a lateral force on the moving plate. The ordering arrangement of water molecules increases the rotational degree of freedom, allowing the molecules to increase their Coulomb potential energy through polar rotation that accounts for the energy input through the upper plate. With a force continuously applied to the upper plate, the water molecules in contact with the upper plate move forward until slip between the water and upper plate occurs. The relation between the structural arrangement of water molecules, slip at the wall, and the shear force is studied. The relation between the slip and the locking/unlocking of water molecules to metal atoms is also studied

  12. Local lateral environment of the molecules at the surface of DMSO-water mixtures.

    Science.gov (United States)

    Fábián, Balázs; Idrissi, Abdenacer; Marekha, Bogdan; Jedlovszky, Pál

    2016-10-12

    Molecular dynamics simulations of the liquid-vapour interface of dimethyl sulphoxide (DMSO)-water mixtures of 11 different compositions, including two neat systems are performed on the canonical (N, V, T) ensemble at 298 K. The molecules constituting the surface layer of these systems are selected by means of the identification of the truly interfacial molecules (ITIM) method, and their local lateral environment at the liquid surface is investigated by performing Voronoi analysis. The obtained results reveal that both molecules prefer to be in a mixed local environment, consisting of both kinds of molecules, at the liquid surface, and this preference is even stronger here than in the bulk liquid phase. Neat-like patches, in which a molecule is surrounded by like neighbours, are not found. However, vacancies that are surrounded solely by water molecules are observed at the liquid surface. Our results show that strongly hydrogen bonded DMSO·H2O complexes, known to exist in the bulk phase of these mixtures, are absent from the liquid surface. PMID:27506283

  13. Proton-bound dimers of nitrogen heterocyclic molecules: Substituent effects on the structures and binding energies of homodimers of diazine, triazine, and fluoropyridine

    International Nuclear Information System (INIS)

    The bonding energies of proton-bound homodimers BH+B were measured by ion mobility equilibrium studies and calculated at the DFT B3LYP/6-311++G** level, for a series of nitrogen heterocyclic molecules (B) with electron-withdrawing in-ring N and on-ring F substituents. The binding energies (ΔH°dissoc) of the proton-bound dimers (BH+B) vary significantly, from 29.7 to 18.1 kcal/mol, decreasing linearly with decreasing the proton affinity of the monomer (B). This trend differs significantly from the constant binding energies of most homodimers of other organic nitrogen and oxygen bases. The experimentally measured ΔH°dissoc for (1,3-diazine)2H+, i.e., (pyrimidine)2H+ and (3-F-pyridine)2H+ are 22.7 and 23.0 kcal/mol, respectively. The measured ΔH°dissoc for the pyrimidine·+(3-F-pyridine) radical cation dimer (19.2 kcal/mol) is signifcantly lower than that of the proton-bound homodimers of pyrimidine and 3-F-pyridine, reflecting the stronger interaction in the ionic H-bond of the protonated dimers. The calculated binding energies for (1,2-diazine)2H+, (pyridine)2H+, (2-F-pyridine)2H+, (3-F-pyridine)2H+, (2,6-di-F-pyridine)2H+, (4-F-pyridine)2H+, (1,3-diazine)2H+, (1,4-diazine)2H+, (1,3,5-triazine)2H+, and (pentafluoropyridine)2H+ are 29.7, 24.9, 24.8, 23.3, 23.2, 23.0, 22.4, 21.9, 19.3, and 18.1 kcal/mol, respectively. The electron-withdrawing substituents form internal dipoles whose electrostatic interactions contribute to both the decreased proton affinities of (B) and the decreased binding energies of the protonated dimers BH+B. The bonding energies also vary with rotation about the hydrogen bond, and they decrease in rotamers where the internal dipoles of the components are aligned efficiently for inter-ring repulsion. For compounds substituted at the 3 or 4 (meta or para) positions, the lowest energy rotamers are T-shaped with the planes of the two rings rotated by 90° about the hydrogen bond, while the planar rotamers are weakened by repulsion between the

  14. Proton-bound dimers of nitrogen heterocyclic molecules: Substituent effects on the structures and binding energies of homodimers of diazine, triazine, and fluoropyridine

    Energy Technology Data Exchange (ETDEWEB)

    Attah, Isaac K.; Platt, Sean P.; Meot-Ner, Michael; El-Shall, M. S., E-mail: mselshal@vcu.edu [Department of Chemistry, Virginia Commonwealth University, Richmond, Virginia 23284-2006 (United States); Aziz, Saadullah G.; Alyoubi, Abdulrahman O. [Department of Chemistry, Faculty of Science, King Abdulaziz University, Jeddah 21589 (Saudi Arabia)

    2014-03-21

    The bonding energies of proton-bound homodimers BH{sup +}B were measured by ion mobility equilibrium studies and calculated at the DFT B3LYP/6-311++G{sup **} level, for a series of nitrogen heterocyclic molecules (B) with electron-withdrawing in-ring N and on-ring F substituents. The binding energies (ΔH°{sub dissoc}) of the proton-bound dimers (BH{sup +}B) vary significantly, from 29.7 to 18.1 kcal/mol, decreasing linearly with decreasing the proton affinity of the monomer (B). This trend differs significantly from the constant binding energies of most homodimers of other organic nitrogen and oxygen bases. The experimentally measured ΔH°{sub dissoc} for (1,3-diazine){sub 2}H{sup +}, i.e., (pyrimidine){sub 2}H{sup +} and (3-F-pyridine){sub 2}H{sup +} are 22.7 and 23.0 kcal/mol, respectively. The measured ΔH°{sub dissoc} for the pyrimidine{sup ·+}(3-F-pyridine) radical cation dimer (19.2 kcal/mol) is signifcantly lower than that of the proton-bound homodimers of pyrimidine and 3-F-pyridine, reflecting the stronger interaction in the ionic H-bond of the protonated dimers. The calculated binding energies for (1,2-diazine){sub 2}H{sup +}, (pyridine){sub 2}H{sup +}, (2-F-pyridine){sub 2}H{sup +}, (3-F-pyridine){sub 2}H{sup +}, (2,6-di-F-pyridine){sub 2}H{sup +}, (4-F-pyridine){sub 2}H{sup +}, (1,3-diazine){sub 2}H{sup +}, (1,4-diazine){sub 2}H{sup +}, (1,3,5-triazine){sub 2}H{sup +}, and (pentafluoropyridine){sub 2}H{sup +} are 29.7, 24.9, 24.8, 23.3, 23.2, 23.0, 22.4, 21.9, 19.3, and 18.1 kcal/mol, respectively. The electron-withdrawing substituents form internal dipoles whose electrostatic interactions contribute to both the decreased proton affinities of (B) and the decreased binding energies of the protonated dimers BH{sup +}B. The bonding energies also vary with rotation about the hydrogen bond, and they decrease in rotamers where the internal dipoles of the components are aligned efficiently for inter-ring repulsion. For compounds substituted at the 3 or 4

  15. Collision Dynamics and Solvation of Water Molecules in a Liquid Methanol Film

    CERN Document Server

    Thomson, Erik S; Andersson, Patrik U; Marković, Nikola; Pettersson, Jan B C; 10.1021/jz200929y

    2011-01-01

    Environmental molecular beam experiments are used to examine water interactions with liquid methanol films at temperatures from 170 K to 190 K. We find that water molecules with 0.32 eV incident kinetic energy are efficiently trapped by the liquid methanol. The scattering process is characterized by an efficient loss of energy to surface modes with a minor component of the incident beam that is inelastically scattered. Thermal desorption of water molecules has a well characterized Arrhenius form with an activation energy of 0.47{\\pm}0.11 eV and pre-exponential factor of 4.6 {\\times} 10^(15{\\pm}3) s^(-1). We also observe a temperature dependent incorporation of incident water into the methanol layer. The implication for fundamental studies and environmental applications is that even an alcohol as simple as methanol can exhibit complex and temperature dependent surfactant behavior.

  16. Ab Initio Density Functional Theory Investigation of the Interaction between Carbon Nanotubes and Water Molecules during Water Desalination Process

    OpenAIRE

    Loay A. Elalfy; Wael N. Akl; Hassan, Walid M. I.

    2013-01-01

    Density functional theory calculations using B3LYP/3-21G level of theory have been implemented on 6 carbon nanotubes (CNTs) structures (3 zigzag and 3 armchair CNTs) to study the energetics of the reverse osmosis during water desalination process. Calculations of the band gap, interaction energy, highest occupied molecular orbital, lowest unoccupied molecular orbital, electronegativity, hardness, and pressure of the system are discussed. The calculations showed that the water molecule that ex...

  17. Molecules, Water, and Radiant Energy: New Clues for the Origin of Life

    OpenAIRE

    Qing Zhao; POLLACK, GERALD H.; Xavier Figueroa

    2009-01-01

    We here examine the putative first step in the origin of life: the coalescence of dispersed molecules into a more condensed, organized state. Fresh evidence implies that the driving energy for this coalescence may come in a manner more direct than previously thought. The sun’s radiant energy separates charge in water, and this free charge demonstrably induces condensation. This condensation mechanism puts water as a central protagonist in life rather than as an incidental participant, and the...

  18. The dynamics of water molecules in Zn Cl2 aqueous solution

    International Nuclear Information System (INIS)

    The inelastic slow neutron scattering technique was used for the study of dynamics of water molecules in Zn Cl2 aqueous solution at various concentrations, 2 M, 6 M, 12.6 M. A study of molecular motions in pure water and solutions is performed in terms of the frequency spectrum p(ℎω) as a function of solute concentration. A strong concentration dependence of p(ℎω) is observed. (authors)

  19. Vasoactive properties of CORM-3, a novel water-soluble carbon monoxide-releasing molecule

    OpenAIRE

    Foresti, Roberta; Hammad, Jehad; Clark, James E.; Johnson, Tony R.; Mann, Brian E.; Friebe, Andreas; Green, Colin J; Motterlini, Roberto

    2004-01-01

    Carbon monoxide (CO), one of the end products of heme catabolism by heme oxygenase, possesses antihypertensive and vasodilatory characteristics. We have recently discovered that certain transition metal carbonyls are capable of releasing CO in biological fluids and modulate physiological functions via the delivery of CO. Because the initial compounds identified were not water soluble, we have synthesized new CO-releasing molecules that are chemically modified to allow solubility in water. The...

  20. Identification of intrinsic catalytic activity for electrochemical reduction of water molecules to generate hydrogen

    KAUST Repository

    Shinagawa, Tatsuya

    2015-01-01

    Insufficient hydronium ion activities at near-neutral pH and under unbuffered conditions induce diffusion-limited currents for hydrogen evolution, followed by a reaction with water molecules to generate hydrogen at elevated potentials. The observed constant current behaviors at near neutral pH reflect the intrinsic electrocatalytic reactivity of the metal electrodes for water reduction. This journal is © the Owner Societies.

  1. Calculating pure rotational transitions of water molecule with a simple Lanczos method

    Indian Academy of Sciences (India)

    Pranab Sarkar

    2001-04-01

    We have calculated pure rotational transitions of water molecule from a kinetic energy operator (KEO) with the -axis perpendicular to the molecular plane. We have used rotational basis functions which are linear combinations of symmetric top functions so that all matrix elements are real. The calculated spectra agree well with the observed values.

  2. Sliding Mode Control for Pressurized-Water Nuclear Reactors in load following operations with bounded xenon oscillations

    International Nuclear Information System (INIS)

    Highlights: • We present SMC which is a robust nonlinear controller to control the PWR power. • Xenon oscillations are kept bounded within acceptable limits. • The stability analysis has been based on Lyapunov approach. • Simulation results indicate the high performance of this new control. - Abstract: One of the important operations in nuclear power plants is load-following in which imbalance of axial power distribution induces xenon oscillations. These oscillations must be maintained within acceptable limits otherwise the nuclear power plant could become unstable. Therefore, bounded xenon oscillation considered to be a constraint for the load-following operation. In this paper, sliding mode control (SMC) which is a robust nonlinear controller is designed to control the Pressurized-Water Nuclear Reactor (PWR) power for the load-following operation problem that ensures xenon oscillations are kept bounded within acceptable limits. The proposed controller uses constant axial offset (AO) strategy to maintain xenon oscillations to be bounded. The constant AO is a robust state constraint for load-following problem. The reactor core is simulated based on the two-point nuclear reactor model and one delayed neutron group. The stability analysis is given by means Lyapunov approach, thus the control system is guaranteed to be stable within a large range. The employed method is easy to implement in practical applications and moreover, the sliding mode control exhibits the desired dynamic properties during the entire output-tracking process independent of perturbations. Simulation results are presented to demonstrate the effectiveness of the proposed controller in terms of performance, robustness and stability. Results show that the proposed controller for the load-following operation is sufficiently effective so that the xenon oscillations are kept bounded in the considered region

  3. Understanding the role of ions and water molecules in the NaCl dissolution process

    CERN Document Server

    Klimeš, Jiří; Michaelides, Angelos

    2013-01-01

    The dissolution of NaCl in water is one of the most common everyday processes, yet it remains poorly understood at the molecular level. Here we report the results of an extensive density functional theory study in which the initial stages of NaCl dissolution have been examined at low water coverages. Our specific approach is to study how the energetic cost of moving an ion or a pair of ions to a less coordinated site at the surface of various NaCl crystals varies with the number of water molecules adsorbed on the surface. This "microsolvation" approach allows us to study the dependence of the defect energies on the number of water molecules in the cluster and thus to establish when and where dissolution becomes favorable. Moreover, this approach allows us to understand the roles of the individual ions and water molecules in the dissolution process. Consistent with previous work we identify a clear preference for dissolution of Cl ions over Na ions. However, the detailed information obtained here leads to the ...

  4. Polarization induced water molecule dissociation below the first-order electronic-phase transition temperature

    CERN Document Server

    Arulsamy, Andrew Das; Elersic, Kristina; Modic, Martina; Subramani, Uma Shankar

    2011-01-01

    Hydrogen produced from the photocatalytic splitting of water is one of the reliable alternatives to replace the polluting fossil and the radioactive nuclear fuels. Here, we provide unequivocal evidence for the existence of blue- and red-shifting O$-$H covalent bonds within a single water molecule adsorbed on MgO surface as a result of asymmetric displacement polarizabilities. The adsorbed H-O-H on MgO gives rise to one weaker H-O bond, while the other O-H covalent bond from the same adsorbed water molecule compensates this effect with a stronger bond. The weaker bond (nearest to the surface), the interlayer tunneling electrons and the silver substrate are shown to be the causes for the smallest dissociative activation energy on MgO monolayer. The origin that is responsible to initiate the splitting mechanism is proven to be due to the changes in the polarizability of an adsorbed water molecule, which are further supported by the temperature-dependent static dielectric constant measurements for water below the...

  5. Partition Coefficients of Organic Molecules in Squalane and Water/Ethanol Mixtures by Molecular Dynamics Simulations

    DEFF Research Database (Denmark)

    Lundsgaard, Rasmus; Kontogeorgis, Georgios; Economou, Ioannis G.

    2011-01-01

    OPLS-AA (all-atom). The computational cheaper TraPPE-UA force field showed to be more accurate over the whole range of systems compared to the OPLS-AA force field. Moreover, some of the calculations were done with five different water models to investigate the influence of the specific water model on...... the calculations. It was found that the combination of the TraPPE-UA force field and the TIP4p water model gave the best results. Based on the methodology proposed in this article, it is possible to obtain good partition coefficients only knowing the chemical structure of the molecules in the system....... the GROMACS software, by slowly decoupling of firstly the electrostatic and then the Lennard–Jones interactions between molecules in the simulation box. These calculations depend very much on the choice of force field. Two force fields have been tested in this work, the TraPPE-UA (united-atom) and the...

  6. Water-inducing molecular self-assembly of amphiphilic molecules into nanofibers

    International Nuclear Information System (INIS)

    Graphical abstract: TPDP nanofibers with smooth surfaces can be obtained by reprecipitation method using ethanol as good solvent and water as poor solvent. In the self-assembly process, during the water adding to the amphiphilic molecules’ saturated solution, the amphiphilic molecules firstly assembled into needle-like small rods. With an increase in the self-assembled time, a large number of the nanofibers are produced. The assembly behavior was revealed in the course of direct in situ monitoring of its growth with optical microscopy. Highlights: ► 2,3,6,7-Tetramethoxy-9,10-di(4-pyridyl)-9,10-dihydroanthracen (TPDP) was synthesized. ► TPDP nanofibers can be obtained by reprecipitation method. ► The assembly behavior was revealed in situ monitoring with optical microscopy. -- Abstract: We present investigations on the microcosmic self-assembly process of new synthesized amphiphilic TPDP molecules. It can be seen that pure TPDP nanofibers with smooth surfaces can be obtained by reprecipitation method using ethanol as good solvent and water as poor solvent. In the self-assembly process, during the water adding to the amphiphilic molecules’ saturated solution, the amphiphilic molecules firstly assembled into needle-like small rods. With an increase in the self-assembled time, a large number of the nanofibers are produced. The assembly behavior was revealed in the course of direct in situ monitoring of its growth with optical microscopy. Field emission scanning electron microscopy was adopted to characterize the morphologies of the products.

  7. Two-Dimensional Heterodyne-Detected VSFG Spectroscopy of Water Molecules at Charged Interfaces

    Directory of Open Access Journals (Sweden)

    Yamaguchi S.

    2013-03-01

    Full Text Available Two-dimensional heterodyne-detected vibrational sum-frequency generation (2D-HD-VSFG spectroscopy of water at interfaces has been realized for the first time. In the present study, 2D-HD-VSFG spectra were measured at a charged monolayer / isotopically diluted water interface. In contrast to the 2D-IR spectrum of bulk isotopically diluted water, the 2D-HD- VSFG of the charged interface shows a narrower bleach band in the higher frequency region immediately after the photoexcitation. The results clearly show that the dynamics of the water at the charged interface is different from that in the bulk, reflecting the different environment where water molecules are located.

  8. Molecular Dynamics Study of Water Molecules in Interlayer of 14 ^|^Aring; Tobermorite

    KAUST Repository

    Yoon, Seyoon

    2013-01-01

    The molecular structure and dynamics of interlayer water of 14 Å tobermorite are investigated based on molecular dynamics (MD) simulations. Calculated structural parameters of the interlayer water configuration are in good agreement with current knowledge of the refined structure. The MD simulations provide detailed information on the position and mobility of the hydrogen and oxygen of interlayer water, as well as its self-diffusion coefficient, through the interlayer of 14 Å tobermorite. Comparison of the MD simulation results at 100 and 300 K demonstrates that water molecules in the interlayer maintain their structure but change their mobility. The dominant configuration and self-diffusion coefficient of interlayer water are obtained in this study. Copyright © 2013 Japan Concrete Institute.

  9. Anomalous and anisotropic nanoscale diffusion of hydration water molecules in fluid lipid membranes.

    Science.gov (United States)

    Toppozini, Laura; Roosen-Runge, Felix; Bewley, Robert I; Dalgliesh, Robert M; Perring, Toby; Seydel, Tilo; Glyde, Henry R; García Sakai, Victoria; Rheinstädter, Maikel C

    2015-11-14

    We have studied nanoscale diffusion of membrane hydration water in fluid-phase lipid bilayers made of 1,2-dimyristoyl-3-phosphocholine (DMPC) using incoherent quasi-elastic neutron scattering. Dynamics were fit directly in the energy domain using the Fourier transform of a stretched exponential. By using large, 2-dimensional detectors, lateral motions of water molecules and motions perpendicular to the membranes could be studied simultaneously, resulting in 2-dimensional maps of relaxation time, τ, and stretching exponent, β. We present experimental evidence for anomalous (sub-diffusive) and anisotropic diffusion of membrane hydration water molecules over nanometer distances. By combining molecular dynamics and Brownian dynamics simulations, the potential microscopic origins for the anomaly and anisotropy of hydration water were investigated. Bulk water was found to show intrinsic sub-diffusive motion at time scales of several picoseconds, likely related to caging effects. In membrane hydration water, however, the anisotropy of confinement and local dynamical environments leads to an anisotropy of relaxation times and stretched exponents, indicative of anomalous dynamics. PMID:26338138

  10. MM-PBSA Captures Key Role of Intercalating Water Molecules at a Protein−Protein Interface

    OpenAIRE

    Wong, Sergio; Amaro, Rommie E.; McCammon, J. Andrew

    2009-01-01

    The calculation of protein interaction energetics is of fundamental interest, yet accurate quantities are difficult to obtain due to the complex and dynamic nature of protein interfaces. This is further complicated by the presence of water molecules, which can exhibit transient interactions of variable duration and strength with the protein surface. The T-cell receptor (TCR) and its staphylococcal enterotoxin 3 (SEC3) binding partner are well-characterized examples of a protein−protein intera...

  11. [WTP guidance technology: a comparison of payment card, single-bounded and double-bounded dichotomous formats for evaluating non-use values of Sanjiang Plain ecotourism water resources].

    Science.gov (United States)

    Chen, Hong-Guang; Wang, Qiu-Dan; Li, Chen-Yang

    2014-09-01

    Contingent valuation method (CVM) is the most widespread method to assess resources and value of environmental goods and services. The guidance technology of willingness to pay (WTP) is an important means of CVM. Therefore, the study on the WTP guidance technology is an important approach to improve the reliability and validity of CVM. This article conducted comprehensive evaluation on non-use value of eco-tourism water resources in Sanjiang Plain by using payment card, single-bound dichotomous choice and double-bound dichotomous choice. Results showed that the socio-economic attributes were consistent with the willingness to pay in the three formats, and the tender value, age, educational level, annual income and the concern level had significant effect on the willingness to pay, while gender and job did not have significant influence. The WTP value was 112.46 yuan per capita with the payment card, 136.15 with the single-bound dichotomous choice, and 168.74 with the double-bound dichotomous choice. Comprehensive consideration of the nature of the investigation, investigation costs and statistical techniques, the result of double-bound dichotomous choice (47.86 x 10(8) yuan · a(-1)) was best in accordance with the reality, and could be used as non-use value of eco-tourism water resources in Sanjiang Plain. The format of questionnaire was very important to improve its validity, and made a great influence on the WTP. PMID:25757326

  12. Energy expenditure for water molecule ionization by electron impact in weakly ionized plasma

    International Nuclear Information System (INIS)

    The energy balance of the water molecule ionization by a monoenergetic electron beam with the energy of primary electrons in the interval of 15-1000 eV has been calculated. The dependences of the ionization cost on the water ionization degree within the interval from 0 to 0.1 are obtained. The ionization cost is shown to increase with the ionization degree. In particular, for a primary electron energy of 1000 eV, it increases from 25.26 to 52.45 eV in the examined ionization degree interval

  13. WScore: A Flexible and Accurate Treatment of Explicit Water Molecules in Ligand-Receptor Docking.

    Science.gov (United States)

    Murphy, Robert B; Repasky, Matthew P; Greenwood, Jeremy R; Tubert-Brohman, Ivan; Jerome, Steven; Annabhimoju, Ramakrishna; Boyles, Nicholas A; Schmitz, Christopher D; Abel, Robert; Farid, Ramy; Friesner, Richard A

    2016-05-12

    We have developed a new methodology for protein-ligand docking and scoring, WScore, incorporating a flexible description of explicit water molecules. The locations and thermodynamics of the waters are derived from a WaterMap molecular dynamics simulation. The water structure is employed to provide an atomic level description of ligand and protein desolvation. WScore also contains a detailed model for localized ligand and protein strain energy and integrates an MM-GBSA scoring component with these terms to assess delocalized strain of the complex. Ensemble docking is used to take into account induced fit effects on the receptor conformation, and protein reorganization free energies are assigned via fitting to experimental data. The performance of the method is evaluated for pose prediction, rank ordering of self-docked complexes, and enrichment in virtual screening, using a large data set of PDB complexes and compared with the Glide SP and Glide XP models; significant improvements are obtained. PMID:27054459

  14. Formation, Manipulation, and Elasticity Measurement of a Nanometric Column of Water Molecules

    CERN Document Server

    Choe, H; Seo, Y; Lee, K; Kim, G; Cho, Y; Ihm, J; Jhe Won Ho; Jhe, and W.

    2005-01-01

    Nanometer-sized columns of condensed water molecules are created by an atomic-resolution force microscope operated in ambient conditions. Unusual stepwise decrease of the force gradient associated with the thin water bridge in the tip-substrate gap is observed during its stretch, exhibiting regularity in step heights (~0.5 N/m) and plateau lengths (~1 nm). Such "quantized" elasticity is indicative of the atomic-scale stick-slip at the tip-water interface. A thermodynamic-instability-induced rupture of the water meniscus (5-nm long and 2.6-nm wide) is also found. This work opens a high-resolution study of the structure and the interface dynamics of a nanometric aqueous column.

  15. Experimental Evaluation of Proposed Small-Molecule Inhibitors of Water Channel Aquaporin-1.

    Science.gov (United States)

    Esteva-Font, Cristina; Jin, Byung-Ju; Lee, Sujin; Phuan, Puay-Wah; Anderson, Marc O; Verkman, A S

    2016-06-01

    The aquaporin-1 (AQP1) water channel is a potentially important drug target, as AQP1 inhibition is predicted to have therapeutic action in edema, tumor growth, glaucoma, and other conditions. Here, we measured the AQP1 inhibition efficacy of 12 putative small-molecule AQP1 inhibitors reported in six recent studies, and one AQP1 activator. Osmotic water permeability was measured by stopped-flow light scattering in human and rat erythrocytes that natively express AQP1, in hemoglobin-free membrane vesicles from rat and human erythrocytes, and in plasma membrane vesicles isolated from AQP1-transfected Chinese hamster ovary cell cultures. As a positive control, 0.3 mM HgCl2 inhibited AQP1 water permeability by >95%. We found that none of the tested compounds at 50 µM significantly inhibited or increased AQP1 water permeability in these assays. Identification of AQP1 inhibitors remains an important priority. PMID:26993802

  16. An FTIR study on the catalytic effect of water molecules on the reaction of CO successive hydrogenation at 3 K

    International Nuclear Information System (INIS)

    Graphical abstract: This work highlights a selective catalytic action of water molecules on the reaction of CO hydrogenation at 3 K. Research highlights: → [CO/H2O] and [H/H2] are coinjected at 3 K. → H2 molecules condense rapidly at 3 K and screen the reaction mostly at the 1st step. → The observed catalytic effects on CO hydrogenation increase with water concentration. - Abstract: The reaction of successive CO hydrogenation has been performed at 3 K by coinjecting CO molecules and H atoms. The concentration of CO has been progressively reduced and replaced by water molecules to create two different environments where CO and H2O are successively the dominant species in the binary (CO/H2O) mixture. The catalytic effect of water molecules on CO hydrogenation appears clearly since the early times of the experiment and evolves with the formation of the CO/H2/H2O mixed-matrix. The process of CO hydrogenation, initially frozen at the first step of the reaction, is brought to completion through water influence. Water molecules guide the reaction toward the formation of CH3OH and promote different reaction steps depending on water concentration. Water molecules increase the probability of reactive to encounter H atoms either physically, by introducing structural changes in the matrix, or chemically, by raising the number of chemical pathways.

  17. Toward an improved control of the fixed-node error in quantum Monte Carlo: The case of the water molecule

    CERN Document Server

    Caffarel, Michel; Giner, Emmanuel; Scemama, Anthony

    2016-01-01

    All-electron Fixed-node Diffusion Monte Carlo (FN-DMC) calculations for the nonrelativistic ground-state energy of the water molecule at equilibrium geometry are presented. The determinantal part of the trial wavefunction is obtained from a perturbatively selected Configuration Interaction calculation (CIPSI method) including up to about 1.4 million of determinants. Calculations are made using the cc-pCV$n$Z family of basis sets, with $n$=2 to 5. In contrast with most QMC works no re-optimization of the determinantal part in presence of a Jastrow is performed. For the largest cc-pCV5Z basis set the lowest upper bound for the ground-state energy reported so far of -76.43744(18) is obtained. The fixed-node energy is found to decrease regularly as a function of the cardinal number $n$ and the Complete Basis Set limit (CBS) associated with {\\it exact nodes} is easily extracted. The resulting energy of -76.43894(12) -in perfect agreement with the best experimentally derived value- is the most accurate theoretical ...

  18. Single-Molecule Imaging of DNAs with Sticky Ends at Water/Fused Silica Interface

    Energy Technology Data Exchange (ETDEWEB)

    Slavica Isailovic

    2005-12-17

    Total internal reflection fluorescence microscopy (TIRFM) was used to study intermolecular interactions of DNAs with unpaired (sticky) ends of different lengths at water/fused silica interface at the single-molecule level. Evanescent field residence time, linear velocity and adsorption/desorption frequency were measured in a microchannel for individual DNA molecules from T7, Lambda, and PSP3 phages at various pH values. The longest residence times and the highest adsorption/desorption frequencies at the constant flow at pH 5.5 were found for PSP3 DNA, followed by lower values for Lambda DNA, and the lowest values for T7 DNA. Since T7, Lambda, and PSP3 DNA molecules contain none, twelve and nineteen unpaired bases, respectively, it was concluded that the affinity of DNAs for the surface increases with the length of the sticky ends. This confirms that hydrophobic and hydrogen-bonding interactions between sticky ends and fused-silica surface are driving forces for DNA adsorption at the fused-silica surface. Described single-molecule methodology and results therein can be valuable for investigation of interactions in liquid chromatography, as well as for design of DNA hybridization sensors and drug delivery systems.

  19. Are there Helium-like Protonic States of Individual Water Molecules in Liquid H2O?

    CERN Document Server

    Mueller-Herold, Ulrich

    2015-01-01

    Are there indications that individual H2O molecules in liquid water can loose their bent structure, i.e. that the protons give up their rigid angular correlation and behave largely uncorrelated, similar to electrons in the ground-state of helium? In agreement with the two-state picture of liquid water this would allow for the thermal coexistence of tetraedrically coordinated and spherical water molecules in the liquid. In the Hooke-Calogero model of a confined triatomic of XY2-type it is shown that energetically low-lying zero orbital-momentum states, which are bent if unconfined can change to helium-like shape under increasing confinement strength f. For the respective states this occurs at different values for f. It turns out that at f = 2.79 a bent and a helium-like state can thermally coexist. In order to characterize more precisely 'helium-like' angular correlation a maximum entropy estimate for the marginal correlation of electrons in the helium ground state is given. KEY WORDS: Liquid water, molecular ...

  20. Vibrational spectra and molecular dynamics of hydrogen peroxide molecules at quartz/water interfaces

    Science.gov (United States)

    Lv, Ye-qing; Zheng, Shi-li; Wang, Shao-na; Yan, Wen-yi; Zhang, Yi; Du, Hao

    2016-06-01

    The influence of H2O2 on the water vibration at quartz interface was examined using sum-frequency generation (SFG) spectroscopy, and the effect of H2O2 concentration has been systematically studied. Further, the number density and radical distribution of water molecules, H2O2 molecules, and quartz surface silanol groups were calculated using molecular dynamics (MD) simulation to provide molecular level interpretation for the SFG spectra. It is concluded from this study that the hydrogen peroxide molecules prefers to donate H-bonds to the in-plane silanol groups rather than accepting H-bonds from out-of-plane silanol groups, as evidenced by the strengthening of the peak located at 3400 cm-1 assigned to "liquid-like" hydrogen-bonding network. The SFG results have been supported by the MD calculation results, which demonstrate that the relative intensity of the peak located at 3400 cm-1 to that of located at 3200 cm-1 increases monotonously with the increase in the number of hydrogen peroxide in the first hydration shell of silanol.

  1. Biphasic and SAPC Hydroformylation Catalyzed by Rh-phosphines Bound to Water-Soluble Polymers

    DEFF Research Database (Denmark)

    Malmstrøm, Torsten; Andersson, Carlaxel; Hjortkjær, Jes

    1999-01-01

    Coupling of the triphenylphosphine moiety to poly-acrylic acid and poly-ethyleneimine respectively afford the macromolecular ligands PAA-PNH and PEI-PNH. Reaction of the ligands with Rh(CO)2(acac) give water-soluble complexes that are active as catalysts in the hydroformylation ofdifferent olefins...

  2. Ab Initio Density Functional Theory Investigation of the Interaction between Carbon Nanotubes and Water Molecules during Water Desalination Process

    Directory of Open Access Journals (Sweden)

    Loay A. Elalfy

    2013-01-01

    Full Text Available Density functional theory calculations using B3LYP/3-21G level of theory have been implemented on 6 carbon nanotubes (CNTs structures (3 zigzag and 3 armchair CNTs to study the energetics of the reverse osmosis during water desalination process. Calculations of the band gap, interaction energy, highest occupied molecular orbital, lowest unoccupied molecular orbital, electronegativity, hardness, and pressure of the system are discussed. The calculations showed that the water molecule that exists inside the CNT is about 2-3 Å away from its wall. The calculations have proven that the zigzag CNTs are more efficient for reverse osmosis water desalination process than armchair CNTs as the reverse osmosis process requires pressure of approximately 200 MPa for armchair CNTs, which is consistent with the values used in molecular dynamics simulations, while that needed when using zigzag CNTs was in the order of 60 MPa.

  3. Interstellar ices as witnesses of star formation: selective deuteration of water and organic molecules unveiled

    CERN Document Server

    Cazaux, S; Spaans, M

    2011-01-01

    The environments where stars are born contain gas and dust grains covered by icy mantles. As the star forms and heats up its surroundings, the ices evaporate which leads to a very complex chemistry with high abundances of deuterated molecules. While formaldehyde and water are both ice constituents, deuterated formaldehyde is very abundant in comets and star forming regions, while deuterated water rarely is. Here, we explain this selective deuteration by following the formation and evolution of the ices as a cloud collapses to form a star. We show that the deuteration of formaldehyde is sensitive to the gas D/H ratio as the cloud undergoes gravitational collapse, while the deuteration of water strongly depends on the dust temperature at the time of ice formation.

  4. Shape-selective adsorption of aromatic molecules from water by tetramethylammonium-smectite

    Science.gov (United States)

    Lee, J.; Mortland, M.M.; Boyd, S.A.; Chiou, C.T.

    1989-01-01

    The adsorption of aromatic compounds by smectite exchanged with tetramethylammonium (TMA) has been studied. Aromatic compounds adsorbed by TMA-smectite are assumed to adopt a tilted orientation in a face-to-face arrangment with the TMA tetrahedra. The sorptive characteristics of TMA-smectite were influenced strongly by the presence of water. The dry TMA-smectite showed little selectivity in the uptake of benzen, toluene and xylene. In the presence of water, TMA-smectite showed a high degree of selectivity based on molecular size/shape, resulting in high uptake of benzene and progressively lower uptake of larger aromatic molecules. This selectivity appeared to result from the shrinkage of interlamellar cavities by water.

  5. Influence of the water molecules near surface of viral protein on virus activation process

    International Nuclear Information System (INIS)

    The infection of a cell with influenza virus comprises the stages of receptor binding to the cell membrane, endocytosis of virus particle, and fusion of the virus envelope and cell endosome membrane, which is determined by the conformational changes in hemagglutinin, a virus envelope protein, caused by pH decrease within the endosome. The pH value that induces conformation rearrangements of hemagglutinin molecule considerably varies for different influenza virus strains, first and foremost, due to the differences in amino acid structure of the corresponding proteins. The main goal of this study was to construct a model making it possible to assess the critical pH value characterizing the fusogenic activity of influenza virus hemagglutinin from the data on hemagglutinin structure and experimental verification of this model. Under this model, we assume that when the electrostatic force between interacting hemagglutinin molecules in the virus envelop exceeds a certain value, the hemagglutinin HA1 subunits are arranged so that they form a cavity sufficient for penetration of water molecules. This event leads to an irreversible hydration of the inner fragments of hemagglutinin molecule in a trimer and to the completion of conformational changes. The geometry of electrostatic field in hemagglutinin trimer was calculated taking into account the polarization effects near the interface of two dielectrics, aqueous medium and protein macromolecule. The critical pH values for the conformational changes in hemagglutinin were measured by the erythrocyte hemolysis induced by influenza virus particles when decreasing pH. The critical pH value conditionally separating the pH range into the regions with and without the conformational changes was calculated for several influenza virus H1N1 and H3N2 strains based on the data on the amino acid structure of the corresponding hemagglutinin molecules. Comparison of the theoretical and experimental values of critical pH values for

  6. Role of attractive methane-water interactions in the potential of mean force between methane molecules in water

    CERN Document Server

    Asthagiri, D; Pratt, Lawrence R

    2008-01-01

    On the basis of a gaussian quasi-chemical model of hydration, a model of non van der Waals character, we explore the role of attractive methane-water interactions in the hydration of methane and in the potential of mean force between two methane molecules in water. We find that the hydration of methane is dominated by packing and a mean-field energetic contribution. Contributions beyond the mean-field term are unimportant in the hydration phenomena for a hydrophobic solute such as methane. Attractive solute-water interactions make a net repulsive contribution to these pair potentials of mean force. With no conditioning, the observed distributions of binding energies are super-gaussian and can be effectively modeled by a Gumbel (extreme value) distribution. This further supports the view that the characteristic form of the unconditioned distribution in the high-e tail is due to energetic interactions with a small number of molecules. Generalized extreme value distributions also effectively model the results wi...

  7. Intramolecular cyclization of aspartic acid residues assisted by three water molecules: a density functional theory study

    International Nuclear Information System (INIS)

    Aspartic acid (Asp) residues in peptides and proteins (l-Asp) are known to undergo spontaneous nonenzymatic reactions to form l-β-Asp, d-Asp, and d-β-Asp residues. The formation of these abnormal Asp residues in proteins may affect their three-dimensional structures and hence their properties and functions. Indeed, the reactions have been thought to contribute to aging and pathologies. Most of the above reactions of the l-Asp residues proceed via a cyclic succinimide intermediate. In this paper, a novel three-water-assisted mechanism is proposed for cyclization of an Asp residue (forming a gem-diol precursor of the succinimide) by the B3LYP/6-31 + G(d,p) density functional theory calculations carried out for an Asp-containing model compound (Ace−Asp−Nme, where Ace = acetyl and Nme = NHCH3). The three water molecules act as catalysts by mediating ‘long-range’ proton transfers. In the proposed mechanism, the amide group on the C-terminal side of the Asp residue is first converted to the tautomeric iminol form (iminolization). Then, reorientation of a water molecule and a conformational change occur successively, followed by the nucleophilic attack of the iminol nitrogen on the carboxyl carbon of the Asp side chain to form the gem-diol species. A satisfactory agreement was obtained between the calculated and experimental energetics.

  8. Neutral metal-bound water is the base catalyst in liver alcohol dehydrogenase.

    OpenAIRE

    Makinen, M W; Maret, W.; Yim, M B

    1983-01-01

    The catalytic role of the active site metal-water complex in horse liver alcohol dehydrogenase (alcohol:NAD+ oxidoreductase, EC 1.1.1.1) is investigated on the basis of a comparative analysis of the pH dependence of steady-state kinetic parameters of the native and active-site-specific Co2+-reconstituted enzyme and on the basis of assignment of the coordination environment of the Co2+ by electron paramagnetic resonance methods. The pH dependence of the kinetic parameters for the oxidation of ...

  9. Bound on the slope of steady water waves with favorable vorticity

    OpenAIRE

    Strauss, Walter A.; Wheeler, Miles H.

    2015-01-01

    We consider the angle $\\theta$ of inclination (with respect to the horizontal) of the profile of a steady 2D inviscid symmetric periodic or solitary water wave subject to gravity. Although $\\theta$ may surpass 30$^\\circ$ for some irrotational waves close to the extreme wave, Amick [Ami87] proved that for any irrotational wave the angle must be less than 31.15$^\\circ$. Is the situation similar for periodic or solitary waves that are not irrotational? The extreme Gerstner wave has infinite dept...

  10. Continuum Navier-Stokes modelling of water ow past fullerene molecules

    DEFF Research Database (Denmark)

    Walther, J. H.; Popadic, A.; Koumoutsakos, P.;

    We present continuum simulations of water flow past fullerene molecules. The governing Navier-Stokes equations are complemented with the Navier slip boundary condition with a slip length that is extracted from related molecular dynamics simulations. We find that several quantities of interest as...... computed by the present model are in good agreement with results from atomistic and atomistic-continuum simulations at a fraction of the computational cost. We simulate the flow past a single fullerene and an array of fullerenes and demonstrate that such nanoscale flows can be computed efficiently by...

  11. New approximative orientation averaging of the water molecule interacting with the thermal neutron

    International Nuclear Information System (INIS)

    Orientation averaging is performed by exact orientation averaging (EOA→) and four approximate methods (two ell known and two new) and expression for the microscopic scattering kernel of thermal neutrons on water molecules are developed. Two well known approximate orientation averagings are Krieger-Nelkin's (KN) and Kappel-Young;s (KY). The results obtained by one pf the two newly proposed approximate orientation averaging methods agree best with the corresponding results obtained by EOA→. The biggest discrepancies between the EOA→ results and results of the approximate methods are obtained using well known KN approximate orientation averaging. (author)

  12. Two-dimensional interlocked pentagonal bilayer ice: how do water molecules form a hydrogen bonding network?

    Science.gov (United States)

    Zhu, Weiduo; Zhao, Wen-Hui; Wang, Lu; Yin, Di; Jia, Min; Yang, Jinlong; Zeng, Xiao Cheng; Yuan, Lan-Feng

    2016-06-01

    The plethora of ice structures observed both in bulk and under nanoscale confinement reflects the extraordinary ability of water molecules to form diverse forms of hydrogen bonding networks. An ideal hydrogen bonding network of water should satisfy three requirements: (1) four hydrogen bonds connected with every water molecule, (2) nearly linear hydrogen bonds, and (3) tetrahedral configuration for the four hydrogen bonds around an O atom. However, under nanoscale confinement, some of the three requirements have to be unmet, and the selection of the specific requirement(s) leads to different types of hydrogen bonding structures. According to molecular dynamics (MD) simulations for water confined between two smooth hydrophobic walls, we obtain a phase diagram of three two-dimensional (2D) crystalline structures and a bilayer liquid. A new 2D bilayer ice is found and named the interlocked pentagonal bilayer ice (IPBI), because its side view comprises interlocked pentagonal channels. The basic motif in the top view of IPBI is a large hexagon composed of four small pentagons, resembling the top view of a previously reported "coffin" bilayer ice [Johnston, et al., J. Chem. Phys., 2010, 133, 154516]. First-principles optimizations suggest that both bilayer ices are stable. However, there are fundamental differences between the two bilayer structures due to the difference in the selection among the three requirements. The IPBI sacrifices the linearity of hydrogen bonds to retain locally tetrahedral configurations of the hydrogen bonds, whereas the coffin structure does the opposite. The tradeoff between the conditions of an ideal hydrogen bonding network can serve as a generic guidance to understand the rich phase behaviors of nanoconfined water. PMID:27063210

  13. Bounded Earthquakes

    OpenAIRE

    Saric, Dragomir

    2006-01-01

    We give a short proof of the fact that bounded earthquakes of the unit disk induce quasisymmetric maps of the unit circle. By a similar method, we show that symmetric maps are induced by bounded earthquakes with asymptotically trivial measures.

  14. Explicit Consideration of Water Molecules to Study Vibrational Circular DICHROÎSM of Monosaccharide's

    Science.gov (United States)

    Moussi, Sofiane; Ouamerali, Ourida

    2014-06-01

    Carbohydrates have multiples roles in biological systems. It has been found that the glycoside bond is fundamentally important in many aspects of chemistry and biology and forms the basis of carbohydrate chemistry. That means the stereochemical information, namely, glycosidic linkages α or β, gives an significant features of the carbohydrate glycosidation position of the glycosylic acceptor. For these reasons, much effort was made for the synthesis and analysis of the glycoside bond. Vibrational circular dichroism VCD has some advantages over conventional electronic circular dichroism (ECD) due to the applicability to all organic molecules and the reliability of ab initio quantum calculation. However, for a molecule with many chiral centers such as carbohydrates, determination of the absolute configuration tends to be difficult because the information from each stereochemical center is mixed and averaged over the spectrum. In the CH stretching region, only two VCD studies on carbohydrates have been reported and spectra--structure correlation, as determined for the glycoside band, remains to be investigated. T. Taniguchi and collaborators report that methyl glycosides exhibit a characteristic VCD peak, the sign of which solely reflects the C-1 absolute configuration. This work is a theoretical contribution to study the behaviour of VCD spectrum's of the monosaccharides when the water molecules are taken explicitly. This study is focused on six different monosaccharides in theirs absolute configuration R and S. We used the method of density functional theory DFT by means of the B3LYP hybrid functional and 6-31G * basis set.

  15. Correlation between yields of positronium and hydrogen, excited molecules, hydrated electron appearing during water radiolysis

    International Nuclear Information System (INIS)

    Analytic expression for dependences of the yields of positronium (Ps) and radiolytic hydrogen (H2) on concentration of dissolved in water substances (acetone, H2O2, inorganic acids, salts of various metals) under 60Coγ-irradiation were obtained on the basis of assumptions about similarity of the mechanism of Ps and H2 formation - intratrack recombination with participation of nonhydrated electron. Found equations were used for analyzing large amount of experimental results. In majority of cases the dissolved substances effect alike on Ps and H2 yields. Some exceptions are explained in the framework of considered model. It was established that nonhydrated electron represents the direct precursor of not only Ps and radiolytic hydrogen but solvated electron and excited molecules appearing during radiolysis of water and organoaqueous solutions

  16. Conserved hydrogen bonds and water molecules in MDR HIV-1 protease substrate complexes

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Zhigang [Wayne State Univ., Detroit, MI (United States); Case Western Reserve Univ., Cleveland, OH (United States); Harbor Hospital Baltimore, MD (United States); Wang, Yong [Wayne State Univ., Detroit, MI (United States); Yedidi, Ravikiran S. [Wayne State Univ., Detroit, MI (United States); National Institutes of Health, Bethesda, MD (United States); Dewdney, Tamaria G. [Wayne State Univ., Detroit, MI (United States); Reiter, Samuel J. [Wayne State Univ., Detroit, MI (United States); Brunzelle, Joseph S. [Northwestern Univ. Feinberg School of Medicine, Chicago, IL (United States); Kovari, Iulia A. [Wayne State Univ., Detroit, MI (United States); Kovari, Ladislau C. [Wayne State Univ., Detroit, MI (United States)

    2012-12-19

    Success of highly active antiretroviral therapy (HAART) in anti-HIV therapy is severely compromised by the rapidly developing drug resistance. HIV-1 protease inhibitors, part of HAART, are losing their potency and efficacy in inhibiting the target. Multi-drug resistant (MDR) 769 HIV-1 protease (resistant mutations at residues 10, 36, 46, 54, 62, 63, 71, 82, 84, 90) was selected for the present study to understand the binding to its natural substrates. The nine crystal structures of MDR769 HIV-1 protease substrate hepta-peptide complexes were analyzed in order to reveal the conserved structural elements for the purpose of drug design against MDR HIV-1 protease. Our structural studies demonstrated that highly conserved hydrogen bonds between the protease and substrate peptides, together with the conserved crystallographic water molecules, played a crucial role in the substrate recognition, substrate stabilization and protease stabilization. Additionally, the absence of the key flap-ligand bridging water molecule might imply a different catalytic mechanism of MDR769 HIV-1 protease compared to that of wild type (WT) HIV-1 protease.

  17. On the Importance of Water Molecules in the Theoretical Study of Polyphenols Reactivity toward Superoxide Anion

    Directory of Open Access Journals (Sweden)

    Laure Lespade

    2014-01-01

    Full Text Available Numerous studies have shown the benefits of a diet rich in fruits and vegetables. These benefits are partly due to the radical scavenging properties of polyphenols contained in fruits and vegetables since polyphenols can fight against an excess of radicals which goes along inflammation in a certain number of diseases. This pathological state, called oxidative stress, results from the aerobic condition of human organism when OH radical, hydrogen peroxide, superoxide anion, or peroxynitrite is produced in excess. If hydrogen peroxide is easily handled by human defense against radicals, the other radicals can cause damage to biological constituents like lipids, cell membranes, and other biomolecules. This paper is devoted to the theoretical study of the interaction of superoxide anion (O2•- with a very potent radical scavenger, 1,2,4,6,8-pentahydroxynaphthalene. The importance of hydration of superoxide radical for the reactivity is analyzed. Potential energy surfaces (PES are calculated for different number of water molecules around the radical and it is shown that the transition barrier vanishes when complete hydration with six water molecules is explicitly handled. The nature of the reactivity is determined by using the natural bond orbital (NBO analysis.

  18. Tuning dissociation using isoelectronically doped graphene and hexagonal boron nitride: Water and other small molecules

    Science.gov (United States)

    Al-Hamdani, Yasmine S.; Alfè, Dario; von Lilienfeld, O. Anatole; Michaelides, Angelos

    2016-04-01

    Novel uses for 2-dimensional materials like graphene and hexagonal boron nitride (h-BN) are being frequently discovered especially for membrane and catalysis applications. Still however, a great deal remains to be understood about the interaction of environmentally and industrially relevant molecules such as water with these materials. Taking inspiration from advances in hybridising graphene and h-BN, we explore using density functional theory, the dissociation of water, hydrogen, methane, and methanol on graphene, h-BN, and their isoelectronic doped counterparts: BN doped graphene and C doped h-BN. We find that doped surfaces are considerably more reactive than their pristine counterparts and by comparing the reactivity of several small molecules, we develop a general framework for dissociative adsorption. From this a particularly attractive consequence of isoelectronic doping emerges: substrates can be doped to enhance their reactivity specifically towards either polar or non-polar adsorbates. As such, these substrates are potentially viable candidates for selective catalysts and membranes, with the implication that a range of tuneable materials can be designed.

  19. A pilot test of methods for determination of trace metals bound to colloids in surface waters

    Energy Technology Data Exchange (ETDEWEB)

    Nilsson, Kersti (Geosigma AB (Sweden))

    2011-01-15

    Two methods have been tested for the determination of trace metals associated with colloid species in surface waters, using test water from Eckarfjaerden (PFM000070) in Forsmark; 1) fractionation (ultra filtration) using special membrane filters with cut-offs of 1 kD and 5 kD and 2) filtration using a system of standard membrane filters with varying pore sizes connected in series. Both methods were somewhat modified compared to previous methods for colloid determination in groundwater within the site investigations at Forsmark and Laxemar (PLU). The results show that, in general, the largest amounts of metals associated with a colloid phase were recovered in the fraction between 1kD and 5 kD which indicates that the metal ions are associated with low molecular weight organic acids. Similar amounts were recovered on the filters in the filtration experiment. A minor part of the colloidal phase metals was recovered in the fraction larger than 5 kD i.e. metal ions associated with larger organic acids or colloidal size clay minerals. The metals present preferably as colloids in the fractionation experiment were: iron, thorium, cerium, uranium, neodymium, titanium, zirconium and yttrium. The filtering experiment showed larger parts of titanium and aluminum in the colloid phase than the fractionation experiment while the iron and cerium portions were equal and the uranium, yttrium and neodymium portions were lower. The results from the fractionation test showed that the dissolved parts were large for barium, manganese, strontium and rubidium. In the filtration test, uranium, yttrium and rubidium, were also present mainly as dissolved ions. The detection limit for filter analysis of thorium was high, and the part of thorium present as colloids was determined to <50%. Issues and methodological problems: - Severe contamination caused interpretation difficulties for several metal ions, especially chromium, nickel and zinc. - Both methods are time consuming and difficult to

  20. Bioaccumulation of tritiated water in phytoplankton and trophic transfer of organically bound tritium to the blue mussel, Mytilus edulis

    International Nuclear Information System (INIS)

    Large releases of tritium are currently permitted in coastal areas due to assumptions that it rapidly disperses in the water and has a low toxicity due to its low energy emissions. This paper presents a laboratory experiment developed to identify previously untested scenarios where tritium may concentrate or transfer in biota relevant to Baltic coastal communities. Phytoplankton populations of Dunaliella tertiolecta and Nodularia spumigena were exposed at different growth-stages, to tritiated water (HTO; 10 MBq l−1). Tritiated D. tertiolecta was then fed to mussels, Mytilus edulis, regularly over a period of three weeks. Activity concentrations of phytoplankton and various tissues from the mussel were determined. Both phytoplankton species transformed HTO into organically-bound tritium (OBT) in their tissues. D. tertiolecta accumulated significantly more tritium when allowed to grow exponentially in HTO than if it had already reached the stationary growth phase; both treatments accumulated significantly more than the corresponding treatments of N. spumigena. No effect of growth phase on bioaccumulation of tritium was detectable in N. spumigena following exposure. After mussels were given 3 feeds of tritiated D. tertiolecta, significant levels of tritium were detected in the tissues. Incorporation into most mussel tissues appeared to follow a linear relationship with number of tritiated phytoplankton feeds with no equilibrium, highlighting the potential for biomagnification. Different rates of incorporation in species from a similar functional group highlight the difficulties in using a ‘representative’ species for modelling the transfer and impact of tritium. Accumulations of organic tritium into the mussel tissues from tritiated-phytoplankton demonstrate an environmentally relevant transfer pathway of tritium even when water-concentrations are reduced, adding weight to the assertion that organically bound tritium acts as a persistent organic pollutant. The

  1. Single-molecule folding mechanisms of the apo- and Mg2+-bound states of human neuronal calcium sensor-1

    DEFF Research Database (Denmark)

    Naqvi, Mohsin M; Heiðarsson, Pétur Orri; Otazo, Mariela R;

    2015-01-01

    Neuronal calcium sensor-1 (NCS-1) is the primordial member of a family of proteins responsible primarily for sensing changes in neuronal Ca(2+) concentration. NCS-1 is a multispecific protein interacting with a number of binding partners in both calcium-dependent and independent manners, and acting...... transitions were reconstructed through hidden Markov model analysis. Unlike what has been observed with the Ca(2+)-bound state, the presence of Mg(2+) allows both the N- and C-domain to fold through all-or-none transitions with similar refolding rates. In the absence of divalent ions, NCS-1 unfolds and...

  2. A molecular dynamics study of Hras-GTP and GDP complexes: The properties of water molecules around guanine nucleotide

    Science.gov (United States)

    Miyakawa, T.; Morikawa, R.; Takasu, M.; Sugimori, K.; Kawaguchi, K.; Saito, H.; Nagao, H.

    2013-02-01

    We study the structures of Hras-GTP and Hras-GDP complexes in water in order to investigate the mechanism of hydrolysis of GTP in the Hras-GTP complex. Understanding of the mechanism of hydrolysis of GTP in the Hras-GTP complex plays a key role in overcoming the human cancer. We performed molecular dynamics (MD) simulations of Hras-GTP complex and Hras-GDP complex in water using AMBER03 parameters and our calculated parameters around Mg2+. Using the trajectories of the MD simulations, we calculated the radial distribution functions of water molecules around the phosphorus atoms in guanine nucleotide in each complex. We also calculated the radius of the first hydration sphere, the averaged number of water molecules in the first hydration sphere, and the distribution of duration time of water molecules in the first hydration sphere. We also calculated the distribution of water molecules with respect to the angle around the PG in GTP and PB in GDP. It is suggested that the hydrolysis is triggered by water molecules attacking γ-phosphate from the direction rotated 35° to the O1B from the axis defined by PG and O3B.

  3. The effects of water molecules on the electronic and structural properties of peptide nanotubes.

    Science.gov (United States)

    Andrade-Filho, T; Ferreira, Fabio Furlan; Alves, Wendel Andrade; Rocha, Alexandre Reily

    2013-05-28

    The self-assembly of short amino acid chains appears to be one of the most promising strategies for the fabrication of nanostructures. Their solubility in water and the possibility of chemical modification by targeting the amino or carboxyl terminus give peptide-based nanostructures several advantages over carbon nanotube nanostructures. However, because these systems are synthesized in aqueous solution, a deeper understanding is needed on the effects of water especially with respect to the electronic, structural and transport properties. In this work, the electronic properties of L-diphenylalanine nanotubes (FF-NTs) have been studied using the Self-Consistent Charge Density-Functional-based Tight-Binding method augmented with dispersion interaction. The presence of water molecules in the central hydrophilic channel and their interaction with the nanostructures are addressed. We demonstrate that the presence of water leads to significant changes in the electronic properties of these systems decreasing the band gap which can lead to an increase in the hopping probability and the conductivity. PMID:23588391

  4. Finite-bias electronic transport of molecules in a water solution

    KAUST Repository

    Rungger, Ivan

    2010-06-04

    The effects of water wetting conditions on the transport properties of molecular nanojunctions are investigated theoretically by using a combination of empirical-potential molecular-dynamics and first-principles electronic-transport calculations. These are at the level of the nonequilibrium Green’s-function method implemented for self-interaction corrected density-functional theory. We find that water effectively produces electrostatic gating to the molecular junction with a gating potential determined by the time-averaged water dipole field. Such a field is large for the polar benzene-dithiol molecule, resulting in a transmission spectrum shifted by about 0.6 eV with respect to that of the dry junction. The situation is drastically different for carbon nanotubes (CNTs). In fact, because of their hydrophobic nature the gating is almost negligible so that the average transmission spectrum of wet Au/CNT/Au junctions is essentially the same as that in dry conditions. This suggests that CNTs can be used as molecular interconnects also in water-wet situations, for instance, as tips for scanning tunnel microscopy in solution or in biological sensors.

  5. Ionization of water molecules by ion beams. On the relevance of dynamic screening and the influence of the description of the initial state

    International Nuclear Information System (INIS)

    Single ionization from water molecules by impact of protons, alpha particles and C6+ ions is studied. The post- and prior-versions of the continuum distorted wave-eikonal initial state (CDW-EIS) model within an independent electron approximation are employed to compute double differential cross sections. To avoid the complexity of using numerical molecular continuum states in the cross-section calculations, effective Coulombic continuum wavefunctions are employed. However, this may lead to the appearance of post–prior discrepancies and this fact is examined in detail. Moreover, the influence of the dynamic screening on this behaviour is studied. In addition, the contribution of different molecular orbitals to the angular spectrum is analysed for several ejection electron energies. Finally, the sensitivity of CDW-EIS calculations to the representation of the initial bound molecular orbitals is investigated. (paper)

  6. Magnetic Resonance Imaging of Cartilage Contact and Bound Water in ACL-Deficient and ACL Reconstructed Knees

    Science.gov (United States)

    Baer, Geoffrey Scott; Kaiser, Jarred; Vignos, Michael; Liu, Fang; Smith, Colin Robert; Kijowski, Richard; Thelen, Darryl

    2016-01-01

    Objectives: Osteoarthritis (OA) is common following ACL-reconstructive (ACLR) surgery (6). The cause of early OA is not understood, but theories have focused on osteochondral damage at the time of injury (2) and abnormal joint mechanics following surgical repair (7). In this study, we investigate the inter-relationship of cartilage mechanics and biomarkers of OA in both ACL-deficient (ACLD) and ACLR knees. Our approach employs a novel dynamic MR sequence to measure joint mechanics (3) and the recently developed mcDESPOT to assess regional variations in water bound to proteoglycan (PG) (5). We hypothesize that bound water will be diminished in the cartilage of ACLD knees and, after surgery, will continue to adapt in a manner that reflects altered cartilage loading. This abstract presents initial observations on a cross-section of healthy, ACLD and ACLR knees. Methods: The dominant knees of 8 healthy controls, ACLD knees of 5 patients and ACLR knees of 8 patients were imaged in a 3 T MRI scanner (Table). Controls had no history of pain, injury, or surgery to their knee. Patients had no additional ligament injury and no meniscal damage. ACLD subjects were imaged prior to reconstructive surgery. Femoral and tibial cartilage were segmented from MR images and cartilage thickness was calculated. The mcDESPOT sequence provided a fraction map of water bound to PG (Fpg). Subjects flexed their knee against an inertial load at 0.5 Hz, while a SPGR-VIPR sequence continuously acquired volumetric data. Kinematics were obtained using model tracking of the dynamic images (3). Cartilage was registered to the bone segments for all frames, and contact patterns were characterized by the proximity between surfaces. Spatial representations of tibial cartilage contact, thickness and Fpg were co-registered for each subject. Results: Our initial images suggest lower Fpg values in ACLD knees, primarily on the posterior-lateral tibia. This is also observed in ACLR knees, with additional

  7. Dynamic and Static Water Molecules Complement the TN16 Conformational Heterogeneity inside the Tubulin Cavity.

    Science.gov (United States)

    Majumdar, Sarmistha; Maiti, Satyabrata; Ghosh Dastidar, Shubhra

    2016-01-19

    TN16 is one of the most promising inhibitors of α, β dimer of tubulin that occupies the cavity in the β-subunit located at the dimeric interface, known as the colchicine binding site. The experimentally determined structure of the complex (Protein Data Bank entry 3HKD) presents the conformation and position of the ligand based on the "best fit", keeping the controversy of other significant binding modes open for further investigation. Computation has already revealed that TN16 experiences fluctuations within the binding pocket, but the insight from that previous report was limited by the shorter windows of sampling and by the approximations on the surrounding environment by implicit solvation. This article reports that in most of the cases straightforward MMGBSA calculations of binding energy revealed a gradual loss of stabilization that was inconsistent with the structural observations, and thus, it indicated the lack of consideration of stabilizing factors with appropriate weightage. Consideration of the structurally packed water molecules in the space between the ligand and receptor successfully eliminated such discrepancies between the structure and stability, serving as the "litmus test" of the importance of explicit consideration of such structurally packed water in the calculations. Such consideration has further evidenced a quasi-degenerate character of the different binding modes of TN16 that has rationalized the observed intrinsic fluctuations of TN16 within the pocket, which is likely to be the most critical insight into its entropy-dominated binding. Quantum mechanical calculations have revealed a relay of electron density from TN16 to the protein via a water molecule in a concerted manner. PMID:26666704

  8. Vasoactive properties of CORM-3, a novel water-soluble carbon monoxide-releasing molecule.

    Science.gov (United States)

    Foresti, Roberta; Hammad, Jehad; Clark, James E; Johnson, Tony R; Mann, Brian E; Friebe, Andreas; Green, Colin J; Motterlini, Roberto

    2004-06-01

    1 Carbon monoxide (CO), one of the end products of heme catabolism by heme oxygenase, possesses antihypertensive and vasodilatory characteristics. We have recently discovered that certain transition metal carbonyls are capable of releasing CO in biological fluids and modulate physiological functions via the delivery of CO. Because the initial compounds identified were not water soluble, we have synthesized new CO-releasing molecules that are chemically modified to allow solubility in water. The aim of this study was to assess the vasoactive properties of tricarbonylchloro(glycinato)ruthenium(II) (CORM-3) in vitro and in vivo. 2 CORM-3 produced a concentration-dependent relaxation in vessels precontracted with phenylephrine, exerting significant vasodilatation starting at concentrations of 25-50 microm. Inactive CORM-3, which does not release CO, did not affect vascular tone. 3 Blockers of ATP-dependent potassium channels (glibenclamide) or guanylate cyclase activity (ODQ) considerably reduced CORM-3-dependent relaxation, confirming that potassium channels activation and cGMP partly mediate the vasoactive properties of CO. In fact, increased levels of cGMP were detected in aortas following CORM-3 stimulation. 4 The in vitro and in vivo vasorelaxant activities of CORM-3 were further enhanced in the presence of YC-1, a benzylindazole derivative which is known to sensitize guanylate cyclase to activation by CO. Interestingly, inhibiting nitric oxide production or removing the endothelium significantly decreased vasodilatation by CORM-3, suggesting that factors produced by the endothelium influence CORM-3 vascular activities. 5 These results, together with our previous findings on the cardioprotective functions of CORM-3, indicate that this molecule is an excellent prototype of water-soluble CO carriers for studying the pharmacological and biological features of CO. PMID:15148243

  9. Unintended consequences? Water molecules at biological and crystallographic protein-protein interfaces.

    Science.gov (United States)

    Ahmed, Mostafa H; Habtemariam, Mesay; Safo, Martin K; Scarsdale, J Neel; Spyrakis, Francesca; Cozzini, Pietro; Mozzarelli, Andrea; Kellogg, Glen E

    2013-12-01

    The importance of protein-protein interactions (PPIs) is becoming increasingly appreciated, as these interactions lie at the core of virtually every biological process. Small molecule modulators that target PPIs are under exploration as new therapies. One of the greatest obstacles faced in crystallographically determining the 3D structures of proteins is coaxing the proteins to form "artificial" PPIs that lead to uniform crystals suitable for X-ray diffraction. This work compares interactions formed naturally, i.e., "biological", with those artificially formed under crystallization conditions or "non-biological". In particular, a detailed analysis of water molecules at the interfaces of high-resolution (≤2.30 Å) X-ray crystal structures of protein-protein complexes, where 140 are biological protein-protein complex structures and 112 include non-biological protein-protein interfaces, was carried out using modeling tools based on the HINT forcefield. Surprisingly few and relatively subtle differences were observed between the two types of interfaces: (i) non-biological interfaces are more polar than biological interfaces, yet there is better organized hydrogen bonding at the latter; (ii) biological associations rely more on water-mediated interactions with backbone atoms compared to non-biological associations; (iii) aromatic/planar residues play a larger role in biological associations with respect to water, and (iv) Lys has a particularly large role at non-biological interfaces. A support vector machines (SVMs) classifier using descriptors from this study was devised that was able to correctly classify 84% of the two interface types. PMID:24076743

  10. Isotope engineering - using stable isotopes of the water molecule to solve practical problems

    International Nuclear Information System (INIS)

    This chapter discusses the use of the stable isotope ratios of hydrogen and oxygen (2H/1H and 18O/16O) to address problems related to groundwater as a sustainable resource, and in particular to recharge, delineation of flow systems and quantification of mass-balance relationships (relative amounts of water from various sources) in applied hydrologic investigations. We will attempt to cover many examples from throughout the world. This chapter is written for the hydrologist who needs to solve a problem. We present just enough theory to make this chapter a stand-alone document, followed by several real-world examples of the uses of stable H and O isotope ratios for solving practical hydrologic problems-thus, the title, isotope engineering. Naturally occurring stable isotopes of water have been used extensively in hydrological investigations over the past few decades. The majority of applications have been in the arid to temperate regions of the world, where recharge is often episodic and represents a relatively small fraction of rainfall. Water residence times anywhere between 10 to greater than 1 000 000 years necessitate the use of chemical or isotopic indicators to obtain a view of the entire system through time, rather than a snapshot offered by the present-day piezometric surface. Furthermore, H and O isotopes provide us with information on the water molecules themselves, rather than inferences derived from water-level data and hydraulic conductivities derived from a few pumping tests. We emphasise that the maximum benefit derived from any investigation that uses stable isotope data would be through integration with water-level, chemical and any other relevant data. This will produce more reliable conceptual models of groundwater systems on both local and regional scales. For a relatively small additional investment for comprehensive chemical and isotopic analysis of groundwaters (compared with the cost of installing boreholes), one gains a quantum increase in

  11. Orbiting Water Molecules Dance to Tune Of Galaxy's "Central Engine," Astronomers Say

    Science.gov (United States)

    2000-01-01

    A disk of water molecules orbiting a supermassive black hole at the core of a galaxy 60 million light-years away is "reverberating" in response to variations in the energy output from the galaxy's powerful "central engine" close to the black hole, astronomers say. The team of astronomers used the National Science Foundation's (NSF) Very Large Array (VLA) radio telescope in New Mexico and the 100-meter-diameter radio telescope of the Max Planck Institute for Radio Astronomy at Effelsberg, Germany, to observe the galaxy NGC 1068 in the constellation Cetus. They announced their findings today at the American Astronomical Society's meeting in Atlanta. The water molecules, in a disk some 5 light-years in diameter, are acting as a set of giant cosmic radio-wave amplifiers, called masers. Using energy radiated by the galaxy's "central engine," the molecules strengthen, or brighten, radio emission at a particular frequency as seen from Earth. "We have seen variations in the radio 'brightness' of these cosmic amplifiers that we believe were caused by variations in the energy output of the central engine," said Jack Gallimore, an astronomer at the National Radio Astronomy Observatory (NRAO) in Charlottesville, VA. "This could provide us with a valuable new tool for learning about the central engine itself," he added. Gallimore worked with Stefi Baum of the Space Telescope Science Institute in Baltimore, MD; Christian Henkel of the Max Planck Institute for Radio Astronomy in Bonn, Germany; Ian Glass of the South African Astronomical Observatory; Mark Claussen of the NRAO in Socorro, NM; and Almudena Prieto of the European Southern Observatory in Munich, Germany. "Our observations show that NGC 1068 is the second-known case of a giant disk of water molecules orbiting a supermassive black hole at a galaxy's core," Gallimore said. The first case was the galaxy NGC 4258 (Messier 106), whose disk of radio-amplifying water molecules was measured by the NSF's Very Long Baseline

  12. Anisotropic conductivity tensor imaging in MREIT using directional diffusion rate of water molecules

    International Nuclear Information System (INIS)

    Magnetic resonance electrical impedance tomography (MREIT) is an emerging method to visualize electrical conductivity and/or current density images at low frequencies (below 1 KHz). Injecting currents into an imaging object, one component of the induced magnetic flux density is acquired using an MRI scanner for isotropic conductivity image reconstructions. Diffusion tensor MRI (DT-MRI) measures the intrinsic three-dimensional diffusion property of water molecules within a tissue. It characterizes the anisotropic water transport by the effective diffusion tensor. Combining the DT-MRI and MREIT techniques, we propose a novel direct method for absolute conductivity tensor image reconstructions based on a linear relationship between the water diffusion tensor and the electrical conductivity tensor. We first recover the projected current density, which is the best approximation of the internal current density one can obtain from the measured single component of the induced magnetic flux density. This enables us to estimate a scale factor between the diffusion tensor and the conductivity tensor. Combining these values at all pixels with the acquired diffusion tensor map, we can quantitatively recover the anisotropic conductivity tensor map. From numerical simulations and experimental verifications using a biological tissue phantom, we found that the new method overcomes the limitations of each method and successfully reconstructs both the direction and magnitude of the conductivity tensor for both the anisotropic and isotropic regions. (paper)

  13. Molecular theories and simulation of ions and polar molecules in water

    CERN Document Server

    Hummer, G; García, A; Hummer, Gerhard; Pratt, Lawrence R.; Garcia, Angel E.

    1998-01-01

    Recent developments in molecular theories and simulation of ions and polar molecules in water are reviewed. The hydration of imidazole and imidazolium solutes is used to exemplify the theoretical issues. The treatment of long-ranged electrostatic interactions in simulations is discussed extensively. It is argued that the Ewald approach is an easy way to get correct hydration free energies in the thermodynamic limit from molecular calculations; and that molecular simulations with Ewald interactions and periodic boundary conditions can also be more efficient than many common alternatives. The Ewald treatment permits a conclusive extrapolation to infinite system size. The picture that emerges from testing of simple models is that the most prominent failings of the simplest theories are associated with solvent proton conformations that lead to non-gaussian fluctuations of electrostatic potentials. Thus, the most favorable cases for the second-order perturbation theories are monoatomic positive ions. For polar and...

  14. Cloning of a soluble isoform of the SgIGSF adhesion molecule that binds the extracellular domain of the membrane-bound isoform.

    OpenAIRE

    Koma, Yu-ichiro; Ito, Akihiko; Wakayama, Tomohiko; Watabe, Kenji; OKADA, Morihito; Tsubota, Noriaki; Iseki, Shoichi; Kitamura, Yukihiko

    2004-01-01

    SgIGSF (spermatogenic immunoglobulin superfamily) is a recently identified intercellular adhesion molecule of the immunoglobulin superfamily. In a mast-cell cDNA library, we found a clone that resulted from the retention of intron 7 within the mature SgIGSF message. This clone was predicted to encode a soluble isoform of SgIGSF (sSgIGSF) with 336 amino-acid residues because its open reading frame ended just before the transmembrane domain. We constructed a plasmid expressing sSgIGSF fused to ...

  15. Uncertainties in dose coefficients for intakes of tritiated water and organically bound forms of tritium by members of the public

    International Nuclear Information System (INIS)

    The International Commission on Radiological Protection (ICRP) provides models for the calculation of doses from intakes of radionuclides, including intakes of tritium as tritiated water (HTO) or organically bound tritium (OBT). The ICRP models for HTO and OBT are explained and the assumptions made are examined. The reliability of dose estimates is assessed in terms of uncertainties in central estimates for population groups. The models consider intakes of HTO and OBT by ingestion and inhalation by adults and children and doses to the fetus following intakes by the mother. The analysis includes uncertainties in the absorption of OBT to blood, incorporation of tritium into OBT in body tissues, retention times in tissues, transfer to the fetus and the relative biological effectiveness (RBE) of tritium beta emissions compared with gamma rays. Heterogeneity of dose within tissues and cells is also considered. For intakes as HTO, dose is predominantly due to distribution and retention of HTO in body water and it was concluded that adult doses are reliable to within a factor of 2. For intakes of OBT, the extent of incorporation into OBT in body tissues results in greater uncertainties, with estimates relying on animal data for selected compounds. The analysis indicated that adult doses from OBT can be considered to be known to within a factor of 3. Greater uncertainties in estimated doses for children and for in utero exposures were considered. Central values from the uncertainty analyses of doses for HTO and OBT were greater than the corresponding ICRP dose coefficients by about a factor of 2, mainly due to the inclusion of uncertainties in RBE for tritium. A detailed assessment of doses using appropriate parameters and considering uncertainties would be of particular importance in situations where the dose may approach dose limits or constraints. For exposures to known forms of OBT, specific dose assessments may be required. (author)

  16. Measurements of the number density of water molecules in plasma by using a combined spectral−probe method

    International Nuclear Information System (INIS)

    A novel method for measuring the number density of water molecules in low-temperature plasma is developed. The absolute intensities of rotational lines of the (0,0) band of the OH(A2Σ–X2Π) transition are used. Lines with sufficiently large rotational quantum numbers referring to the so-called “hot” group of molecules produced by electron-impact dissociative excitation of water molecules are chosen for measurements. The excitation rate of a process with a known cross section is determined by measuring the parameters of plasma electrons by means of the probe method. The measured number densities of molecules are compared with those in the initial plasma-forming mixture. The time evolution of the particle densities in plasma is investigated. The problems of the sensitivity and applicability of the absolute spectral method are considered

  17. Measurements of the number density of water molecules in plasma by using a combined spectral−probe method

    Energy Technology Data Exchange (ETDEWEB)

    Bernatskiy, A. V., E-mail: berav@sci.lebedev.ru; Ochkin, V. N., E-mail: ochkin@sci.lebedev.ru [Russian Academy of Sciences, Lebedev Physical Institute (Russian Federation); Afonin, O. N. [Tsentr Information Consulting Company (Russian Federation); Antipenkov, A. B. [ITER Organization (France)

    2015-09-15

    A novel method for measuring the number density of water molecules in low-temperature plasma is developed. The absolute intensities of rotational lines of the (0,0) band of the OH(A{sup 2}Σ–X{sup 2}Π) transition are used. Lines with sufficiently large rotational quantum numbers referring to the so-called “hot” group of molecules produced by electron-impact dissociative excitation of water molecules are chosen for measurements. The excitation rate of a process with a known cross section is determined by measuring the parameters of plasma electrons by means of the probe method. The measured number densities of molecules are compared with those in the initial plasma-forming mixture. The time evolution of the particle densities in plasma is investigated. The problems of the sensitivity and applicability of the absolute spectral method are considered.

  18. Broadband Microwave Spectroscopy as a Tool to Study the Structures of Odorant Molecules and Weakly Bound Complexes in the Gas Phase

    Science.gov (United States)

    Zinn, Sabrina; Betz, Thomas; Medcraft, Chris; Schnell, Melanie

    2015-06-01

    The rotational spectrum of trans-cinnamaldehyde ((2E)-3-phenylprop-2-enal) has been obtained with chirped-pulse microwave spectroscopy in the frequency range of 2 - 8.5 GHz. The odorant molecule is the essential component in cinnamon oil and causes the characteristic smell. In the measured high-resolution spectrum, we were able to assign the rotational spectra of two conformers of trans-cinnamaldehyde as well as all singly 13C-substituted species of the lowest-energy conformer in natural abundance. Two different methods were used to determine the structure from the rotational constants, which will be compared within this contribution. In addition, the current progress of studying ether-alcohol complexes, aiming at an improved understanding of the interplay between hydrogen bonding and dispersion interaction, will be reported. Here, a special focus is placed on the complexes of diphenylether with small aliphatic alcohols.

  19. A proactive role of water molecules in acceptor recognition by protein O-fucosyltransferase 2.

    Science.gov (United States)

    Valero-González, Jessika; Leonhard-Melief, Christina; Lira-Navarrete, Erandi; Jiménez-Osés, Gonzalo; Hernández-Ruiz, Cristina; Pallarés, María Carmen; Yruela, Inmaculada; Vasudevan, Deepika; Lostao, Anabel; Corzana, Francisco; Takeuchi, Hideyuki; Haltiwanger, Robert S; Hurtado-Guerrero, Ramon

    2016-04-01

    Protein O-fucosyltransferase 2 (POFUT2) is an essential enzyme that fucosylates serine and threonine residues of folded thrombospondin type 1 repeats (TSRs). To date, the mechanism by which this enzyme recognizes very dissimilar TSRs has been unclear. By engineering a fusion protein, we report the crystal structure of Caenorhabditis elegans POFUT2 (CePOFUT2) in complex with GDP and human TSR1 that suggests an inverting mechanism for fucose transfer assisted by a catalytic base and shows that nearly half of the TSR1 is embraced by CePOFUT2. A small number of direct interactions and a large network of water molecules maintain the complex. Site-directed mutagenesis demonstrates that POFUT2 fucosylates threonine preferentially over serine and relies on folded TSRs containing the minimal consensus sequence C-X-X-S/T-C. Crystallographic and mutagenesis data, together with atomic-level simulations, uncover a binding mechanism by which POFUT2 promiscuously recognizes the structural fingerprint of poorly homologous TSRs through a dynamic network of water-mediated interactions. PMID:26854667

  20. Activation of a water molecule coordinated to manganese: four study cases

    International Nuclear Information System (INIS)

    The daunting energy consumption of western societies calls for the development of renewable energies. Among them, hydrogen stands as a major candidate. The cleanest way of producing hydrogen is water electro- or photolysis. This reaction is carried out in natural photosynthesis by a manganese-oxo cluster, the functioning of which remains unknown. Insight into this mechanism would greatly help the search for low-cost water splitting catalysts. Our contribution to this field is the understanding of the fundamental processes that govern the activation of water by manganese complexes. This manuscript describes our attempts to generate electrochemically mononuclear manganese(IV) complexes bearing a fully deprotonated water molecule (oxo ligand). We have studied four different cases, which reflect different possible coordination spheres capable of stabilizing such species. In the first chapter, we will give a brief overview of the present energetic challenges faced by western societies. In the second chapter, we will present general considerations about manganese chemistry and a description of the structure and functioning of the water oxidizing enzyme. We will also describe the basic requirements for the splitting of water and present the goals of our work. In the third chapter, we will present the synthesis of a new family of tetradentate ligands, together with the synthesis and full characterization of the corresponding nickel(II) complexes. The first results obtained with the manganese analogue will also be shown. Chapter four presents the formation and the full characterization of a mononuclear manganese(IV)-oxo complex, by electrochemical oxidation of a manganese(II)-aqua complex. We will present different pathways to generate this species and show which intermediates are involved in this 2 e-, 2 H+ reaction. Chapter five describes the formation of a mononuclear manganese(IV) complex, by electrochemical oxidation of a manganese(III)-hydroxo complex. The manganese

  1. Bounding the $\

    CERN Document Server

    Gutiérrez-Rodríguez, A

    2003-01-01

    A bound on the nu /sup tau / magnetic moment is calculated through the reaction e/sup +/e/sup -/ to nu nu gamma at the Z/sub 1/-pole, and in the framework of a left-right symmetric model at LEP energies. We find that the bound is almost independent of the mixing angle phi of the model in the allowed experimental range for this parameter. (31 refs).

  2. Cardioprotective actions by a water-soluble carbon monoxide-releasing molecule.

    Science.gov (United States)

    Clark, James E; Naughton, Patrick; Shurey, Sandra; Green, Colin J; Johnson, Tony R; Mann, Brian E; Foresti, Roberta; Motterlini, Roberto

    2003-07-25

    Carbon monoxide, which is generated in mammals during the degradation of heme by the enzyme heme oxygenase, is an important signaling mediator. Transition metal carbonyls have been recently shown to function as carbon monoxide-releasing molecules (CO-RMs) and to elicit distinct pharmacological activities in biological systems. In the present study, we report that a water-soluble form of CO-RM promotes cardioprotection in vitro and in vivo. Specifically, we found that tricarbonylchloro(glycinato)ruthenium(II) (CORM-3) is stable in water at acidic pH but in physiological buffers rapidly liberates CO in solution. Cardiac cells pretreated with CORM-3 (10 to 50 micromol/L) become more resistant to the damage caused by hypoxia-reoxygenation and oxidative stress. In addition, isolated hearts reperfused in the presence of CORM-3 (10 micromol/L) after an ischemic event displayed a significant recovery in myocardial performance and a marked and significant reduction in cardiac muscle damage and infarct size. The cardioprotective effects mediated by CORM-3 in cardiac cells and isolated hearts were totally abolished by 5-hydroxydecanoic acid, an inhibitor of mitochondrial ATP-dependent potassium channels. Predictably, cardioprotection is lost when CORM-3 is replaced by an inactive form (iCORM-3) that is incapable of liberating CO. Using a model of cardiac allograft rejection in mice, we also found that treatment of recipients with CORM-3 but not iCORM-3 considerably prolonged the survival rate of transplanted hearts. These data corroborate the notion that transition metal carbonyls could be used as carriers to deliver CO and highlight the bioactivity and potential therapeutic features of CO-RMs in the mitigation of cardiac dysfunction. The full text of this article is available online at http://www.circresaha.org. PMID:12842916

  3. About Some Of The Properties Of A Guest Molecule Confined In A Water Network, In Order To Form A Clathrate

    Science.gov (United States)

    Pérez, G. Bravo; Cruz-Torres, A.; Romero-Martínez, A.

    2008-03-01

    At conditions of high pressure and or low temperature, like a sea bottom from even 1 Km deep, hydrates formation may take place. Its presence is facilitated at the water/oil interface inside conducting oil pipelines. Once formed, the hydrates nucleate further to agglomerations, sticking to the inner surface of the tube. This represents a big problem to flow assurance. We present results contributing to a better understanding of the interaction of a guest molecule with a water cage confining it, that give rise to a hydrate formation. The hydrate structure, its formation energy, and the role that the H bond and its cooperative effect in the water network play in the electrostatic dipole moment of the hydrate, are presented. Molecular calculations using the HF/6-311g(d, p), B3LYP/6-311g(d, p), and B3LYP/6-311++g(d,p) methods, have been applied to compare three different hydrates, each one confining one, two CH4 molecules, and a CO2 molecule, requiring respectively n = 14, 35, and 15 water molecules for the confinement.

  4. A role for water molecules in DNA-ligand minor groove recognition

    OpenAIRE

    Nguyen, Binh; Neidle, Stephen; Wilson, W. David

    2009-01-01

    Targeting the minor groove of DNA through binding to a small molecule has long been considered an important molecular-recognition strategy in biology. A wide range of synthetic heterocyclic molecules bind non-covalently in the minor groove of the double helix and are also effective against a number of human and animal diseases. A classic structural concept, the isohelicity principle, has guided much of this work: such heterocyclic molecules require a shape that complements the convex surface ...

  5. Isolation of pregnancy-associated glycoproteins (PAG) from water buffalo (Bubalus bubalis) placenta by use of Vicia villosa bound agarose affinity chromatography

    OpenAIRE

    Beckers, J. F.; Malfatti, A.; V. Barile; Debenedetti, A.; Clerget, E.; K. Klisch; Sousa, N.M.; O. Barbato

    2010-01-01

    The present study describes the isolation and characterisation of new PAG molecules extracted from mid- and late-pregnancy placentas in the water buffalo (Bubalis bubalis). After extraction, acid and ammonium sulphate precipitation and DEAE chromatography water buffalo PAG (wbPAG) were enriched by Vicia villosa agarose (VVA) affininity chromatography. As determined by Western blotting with anti-PAG-sera, apparent molecular masses of immunoreactive bands from VVA peaks ranged from 59.5 to 75.8...

  6. Microassay for measurement of binding of radiolabelled ligands to cell surface molecules

    International Nuclear Information System (INIS)

    An improved technique for measuring the binding of radiolabelled ligands to cell surface molecules has been developed by modification of a procedure using centrifugation through a water-immiscible oil to separate free and cell-bound ligand. It maximises the percentage of ligand bound since cell-bound and free ligand can be separated easily and reproducibly even when very small reaction volumes are used. This permits low levels of ligand radiolabelling and relatively low numbers of cells to be used

  7. Effect of water molecule distribution on the quantitative XRD analysis in the case of Na-montmorillonite exchanged Cu2+

    International Nuclear Information System (INIS)

    Document available in extended abstract form only. Several theoretical models are proposed to describe hydration process for Wyoming-montmorillonite clay exchanged Na+ or Cu2+. They propose some theoretical distribution and disposition for water molecule in the inter-lamellar space in the case of homogeneous and inter-stratified hydration states. For example, Ben Brahim et al. (1983a) studied the interlayer structure (atomic positions of interlayer cations) and associated H2O molecules of Na-saturated montmorillonite and beidellite samples. Moore and Hower (1986) studied ordered structures composed of mono-hydrated and collapsed interlayers in montmorillonite, and Cuadros (1996) estimated the H2O content of smectite as a function of the interlayer cation. Using similar approach, Ferrage et al (2005b) proposed a discreet distribution of water molecule layer in the same z coordinate of the exchangeable cation with inhomogeneous distribution. This heterogeneity was attributed to the surface charge. The main objective of this study is to characterize the structural changes in the theoretical XRD profile, induced by different water molecule distribution, used to simulate experimental XRD patterns in the case of Na-montmorillonite exchanged Cu2+. This problem was achieved by quantitative XRD analysis using an indirect method based on the comparison of the experimental 001 reflections obtained from oriented films patterns with those calculated from structural models. The starting materials were Ca-montmorillonite originated from bentonites of Wyoming (USA). The XRD patterns were obtained by reflection setting with a D8 ADVANCE Bruker installation using Cu-Kα radiation and equipped with solid state detector. Intensities were measured at an interval of 2Θ 0.04 deg. and 40-50 s counting time per step. The diffracted intensity was calculated according to the matrix formalism detailed by Drits and Tchoubar, (1990). The fitting strategies was detailed by Ferrage et al (2005b

  8. High resolution nuclear magnetic resonance studies of the conformation and orientation of melittin bound to a lipid-water interface.

    OpenAIRE

    Brown, L R; Braun, W.; Kumar, A.(State University of New York at Buffalo, Buffalo, USA); Wüthrich, K.

    1982-01-01

    Previously, the size and stoichiometry of mixed micelles of perdeuterated dodecylphosphocholine and melittin were characterized and the 1H NMR spin systems of most amino acid residues of micelle-bound melittin identified. One- and two-dimensional 1H-1H Overhauser experiments have now been used to obtain qualitative information on intramolecular proton-proton distances. These data show that the N-terminal and the C-terminal segments of melittin form two spatially distinct, compact domains; usi...

  9. Radical-Molecule Reaction C3H + H2O on Amorphous Water Ice: A Promising Route for Interstellar Propynal

    Science.gov (United States)

    Xie, Hong-bin; Shao, Chang-bin; Ding, Yi-hong

    2007-11-01

    Intriguing propynal (HCCCHO) has been attracting chemist's attention since 1955. However, to date, no satisfying conclusion concerning its formation mechanism in the interstellar medium (ISM) has been reached, although a variety of gas-reaction models, including ion-molecule, radical-molecule, and molecule-molecule, have been postulated. In this paper, we consider for the first time the gas-grain interaction model that involves heterogeneous reaction at the surface of dust grain or in the icy mantles to account for the propynal's formation. Based on the detailed density functional theory (DFT) and Gaussian-3 potential energy surface studies, we found that although the gaseous process C3H+H2O-->propynal+H must surmount a considerable entrance barrier (around 10 kcal mol-1), amorphous water ice can significantly catalyze the propynal's formation to be barrierless. So, this model should be a more reasonable one for propynal's formation in the low-temperature interstellar space. This result may also represent one rare case of the water-catalyzed reaction associated with a molecular radical in space. Future experimental studies are greatly desired to probe such interesting processes.

  10. Structural Analysis of Iac Repressor Bound to Allosteric Effectors

    Energy Technology Data Exchange (ETDEWEB)

    Daber,R.; Stayrook, S.; Rosenberg, A.; Lewis, M.

    2007-01-01

    The lac operon is a model system for understanding how effector molecules regulate transcription and are necessary for allosteric transitions. The crystal structures of the lac repressor bound to inducer and anti-inducer molecules provide a model for how these small molecules can modulate repressor function. The structures of the apo repressor and the repressor bound to effector molecules are compared in atomic detail. All effectors examined here bind to the repressor in the same location and are anchored to the repressor through hydrogen bonds to several hydroxyl groups of the sugar ring. Inducer molecules form a more extensive hydrogen-bonding network compared to anti-inducers and neutral effector molecules. The structures of these effector molecules suggest that the O6 hydroxyl on the galactoside is essential for establishing a water-mediated hydrogen bonding network that bridges the N-terminal and C-terminal sub-domains. The altered hydrogen bonding can account in part for the different structural conformations of the repressor, and is vital for the allosteric transition.

  11. How water molecules affect the catalytic activity of hydrolases - A XANES study of the local structures of peptide deformylase

    Science.gov (United States)

    Cui, Peixin; Wang, Yu; Chu, Wangsheng; Guo, Xiaoyun; Yang, Feifei; Yu, Meijuan; Zhao, Haifeng; Dong, Yuhui; Xie, Yaning; Gong, Weimin; Wu, Ziyu

    2014-12-01

    Peptide deformylase (PDF) is a prokaryotic enzyme that catalyzes the deformylation of nascent peptides generated during protein synthesis and water molecules play a key role in these hydrolases. Using X-ray absorption near edge spectroscopy (XANES) and ab initio calculations we accurately probe the local atomic environment of the metal ion binding in the active site of PDF at different pH values and with different metal ions. This new approach is an effective way to monitor existing correlations among functions and structural changes. We show for the first time that the enzymatic activity depends on pH values and metal ions via the bond length of the nearest coordinating water (Wat1) to the metal ion. Combining experimental and theoretical data we may claim that PDF exhibits an enhanced enzymatic activity only when the distance of the Wat1 molecule with the metal ion falls in the limited range from 2.15 to 2.55 Å.

  12. Internal water molecules and H-bonding in biological macromolecules: a review of structural features with functional implications.

    OpenAIRE

    Meyer, E.

    1992-01-01

    Conserved structural patterns of internal water molecules and/or H-bond chains were observed and are here correlated in this review, which then describes two functional properties: equilibration of hydrostatic pressure and proton transport. Available evidence in support of these hypotheses is presented, together with suggested experiments to test them. High-resolution crystal structures of a variety of proteins were studied with interactive computer graphics. Conserved H-bonding linkages may ...

  13. Passive water-lipid peptide translocators with conformational switches: From single-molecule probe to cellular assay

    OpenAIRE

    Fernández, Ariel; Crespo, Alejandro; Blau, Axel

    2007-01-01

    Peptide design for unassisted passive water/lipid translocation remains a challenge, notwithstanding its importance for drug delivery. We introduce a design paradigm based on conformational switches operating as passive translocation vehicles. The interfacial behavior of the molecular prototype, probed in single-molecule AFM experiments, reveals a near-barrierless translocation. The associated free-energy agrees with mesoscopic measurements, and the in vitro behavior is quantitatively reprodu...

  14. Effects of water molecules on the chemical stability of MAGeI3 perovskite explored from a theoretical viewpoint.

    Science.gov (United States)

    Sun, Ping-Ping; Chi, Wei-Jie; Li, Ze-Sheng

    2016-09-21

    The stability of perovskite in humid environments is one of the biggest obstacles for its potential applications in light harvesting and electroluminescent displays. Understanding the detailed degradation mechanism of MAGeI3 in moisture is a critical way to explore the practicability of MAGeI3 perovskite. In this study, we report a quantitative and systematic investigation of MAGeI3 degradation processes by exploring the effects of H2O molecules on the structural and electronic properties of the most stable MAGeI3(101) surface under various simulated environmental conditions with different water coverage based on first-principles calculations. The results show that H2O molecules can easily diffuse into the inner side of the perovskite and gradually corrode the structure as the number of H2O molecules increases. As a result of the interactions between perovskite and H2O molecules, a hydrated intermediate will be generated as the first step in the degradation mechanism; the perovskite will further decompose to HI and GeI2. In terms of one MAGeI3 molecule, it will be dissociated completely to GeI2 as a result of hydrolysis reactions with a minimum of 4H2O molecules. In addition, the degradation of the perovskite will also affect the electronic structure, causing a decrease in optical absorption across the visible region of the spectrum and a distinct deformation change in the crystal structure of the material. These findings further illustrate the degradation of the hydrolysis process of MAGeI3 perovskite in humid environments, which should be helpful to inspire experimentalists to take action to prolong the lifetimes of perovskite solar cells to achieve high conversion efficiency in their applications. PMID:27539944

  15. Water-COOH Composite Structure with Enhanced Hydrophobicity Formed by Water Molecules Embedded into Carboxyl-Terminated Self-Assembled Monolayers.

    Science.gov (United States)

    Guo, Pan; Tu, Yusong; Yang, Jinrong; Wang, Chunlei; Sheng, Nan; Fang, Haiping

    2015-10-30

    By combining molecular dynamics simulations and quantum mechanics calculations, we show the formation of a composite structure composed of embedded water molecules and the COOH matrix on carboxyl-terminated self-assembled monolayers (COOH SAMs) with appropriate packing densities. This composite structure with an integrated hydrogen bond network inside reduces the hydrogen bonds with the water above. This explains the seeming contradiction on the stability of the surface water on COOH SAMs observed in experiments. The existence of the composite structure at appropriate packing densities results in the two-step distribution of contact angles of water droplets on COOH SAMs, around 0° and 35°, which compares favorably to the experimental measurements of contact angles collected from forty research articles over the past 25 years. These findings provide a molecular-level understanding of water on surfaces (including surfaces on biomolecules) with hydrophilic functional groups. PMID:26565476

  16. Application of molecular orbital calculation for evaluating binding force of water molecules sorbed on surface of 2:1 type clay mineral

    International Nuclear Information System (INIS)

    We evaluate the bonding force subjecting on the water molecule sorbed on the surface of 2:1 type clay mineral by using semi-empirical molecular orbital calculation, and compare it with the binding forces of solid and liquid phases of water. We can consider that molecular orbital calculation is a useful and helpful tool for characterizing the properties of water molecules present in the clay minerals. (author)

  17. A theoretical model investigation of peptide bond formation involving two water molecules in ribosome supports the two-step and eight membered ring mechanism

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Qiang [School of Chemistry & Chemical Engineering, Shandong University, Jinan 250100 (China); Gao, Jun, E-mail: gaojun@sdu.edu.cn [Agricultural Bioinformatics Key Laboratory of Hubei Province, College of Informatics, Huazhong Agricultural University, Wuhan 430070 (China); School of Chemistry & Chemical Engineering, Shandong University, Jinan 250100 (China); Zhang, Dongju; Liu, Chengbu [School of Chemistry & Chemical Engineering, Shandong University, Jinan 250100 (China)

    2015-04-01

    Highlights: • We theoretical studied peptide bond formation reaction mechanism with two water molecules. • The first water molecule can decrease the reaction barriers by forming hydrogen bonds. • The water molecule mediated three-proton transfer mechanism is the favorable mechanism. • Our calculation supports the two-step and eight membered ring mechanism. - Abstract: The ribosome is the macromolecular machine that catalyzes protein synthesis. The kinetic isotope effect analysis reported by Strobel group supports the two-step mechanism. However, the destination of the proton originating from the nucleophilic amine is uncertain. A computational simulation of different mechanisms including water molecules is carried out using the same reaction model and theoretical level. Formation the tetrahedral intermediate with proton transfer from nucleophilic nitrogen, is the rate-limiting step when two water molecules participate in peptide bond formation. The first water molecule forming hydrogen bonds with O9′ and H15′ in the A site can decrease the reaction barriers. Combined with results of the solvent isotope effects analysis, we conclude that the three-proton transfer mechanism in which water molecule mediate the proton shuttle between amino and carbon oxygen in rate-limiting step is the favorable mechanism. Our results will shield light on a better understand the reaction mechanism of ribosome.

  18. SET7/9 catalytic mutants reveal the role of active site water molecules in lysine multiple methylation.

    Science.gov (United States)

    Del Rizzo, Paul A; Couture, Jean-François; Dirk, Lynnette M A; Strunk, Bethany S; Roiko, Marijo S; Brunzelle, Joseph S; Houtz, Robert L; Trievel, Raymond C

    2010-10-01

    SET domain lysine methyltransferases (KMTs) methylate specific lysine residues in histone and non-histone substrates. These enzymes also display product specificity by catalyzing distinct degrees of methylation of the lysine ε-amino group. To elucidate the molecular mechanism underlying this specificity, we have characterized the Y245A and Y305F mutants of the human KMT SET7/9 (also known as KMT7) that alter its product specificity from a monomethyltransferase to a di- and a trimethyltransferase, respectively. Crystal structures of these mutants in complex with peptides bearing unmodified, mono-, di-, and trimethylated lysines illustrate the roles of active site water molecules in aligning the lysine ε-amino group for methyl transfer with S-adenosylmethionine. Displacement or dissociation of these solvent molecules enlarges the diameter of the active site, accommodating the increasing size of the methylated ε-amino group during successive methyl transfer reactions. Together, these results furnish new insights into the roles of active site water molecules in modulating lysine multiple methylation by SET domain KMTs and provide the first molecular snapshots of the mono-, di-, and trimethyl transfer reactions catalyzed by these enzymes. PMID:20675860

  19. SET7/9 Catalytic Mutants Reveal the Role of Active Site Water Molecules in Lysine Multiple Methylation*

    Science.gov (United States)

    Del Rizzo, Paul A.; Couture, Jean-François; Dirk, Lynnette M. A.; Strunk, Bethany S.; Roiko, Marijo S.; Brunzelle, Joseph S.; Houtz, Robert L.; Trievel, Raymond C.

    2010-01-01

    SET domain lysine methyltransferases (KMTs) methylate specific lysine residues in histone and non-histone substrates. These enzymes also display product specificity by catalyzing distinct degrees of methylation of the lysine ϵ-amino group. To elucidate the molecular mechanism underlying this specificity, we have characterized the Y245A and Y305F mutants of the human KMT SET7/9 (also known as KMT7) that alter its product specificity from a monomethyltransferase to a di- and a trimethyltransferase, respectively. Crystal structures of these mutants in complex with peptides bearing unmodified, mono-, di-, and trimethylated lysines illustrate the roles of active site water molecules in aligning the lysine ϵ-amino group for methyl transfer with S-adenosylmethionine. Displacement or dissociation of these solvent molecules enlarges the diameter of the active site, accommodating the increasing size of the methylated ϵ-amino group during successive methyl transfer reactions. Together, these results furnish new insights into the roles of active site water molecules in modulating lysine multiple methylation by SET domain KMTs and provide the first molecular snapshots of the mono-, di-, and trimethyl transfer reactions catalyzed by these enzymes. PMID:20675860

  20. SET7/9 Catalytic Mutants Reveal the Role of Active Site Water Molecules in Lysine Multiple Methylation

    Energy Technology Data Exchange (ETDEWEB)

    Del Rizzo, Paul A.; Couture, Jean-François; Dirk, Lynnette M.A.; Strunk, Bethany S.; Roiko, Marijo S.; Brunzelle, Joseph S.; Houtz, Robert L.; Trievel, Raymond C. (Michigan); (NWU); (Kentucky)

    2010-11-15

    SET domain lysine methyltransferases (KMTs) methylate specific lysine residues in histone and non-histone substrates. These enzymes also display product specificity by catalyzing distinct degrees of methylation of the lysine {epsilon}-amino group. To elucidate the molecular mechanism underlying this specificity, we have characterized the Y245A and Y305F mutants of the human KMT SET7/9 (also known as KMT7) that alter its product specificity from a monomethyltransferase to a di- and a trimethyltransferase, respectively. Crystal structures of these mutants in complex with peptides bearing unmodified, mono-, di-, and trimethylated lysines illustrate the roles of active site water molecules in aligning the lysine {epsilon}-amino group for methyl transfer with S-adenosylmethionine. Displacement or dissociation of these solvent molecules enlarges the diameter of the active site, accommodating the increasing size of the methylated {epsilon}-amino group during successive methyl transfer reactions. Together, these results furnish new insights into the roles of active site water molecules in modulating lysine multiple methylation by SET domain KMTs and provide the first molecular snapshots of the mono-, di-, and trimethyl transfer reactions catalyzed by these enzymes.

  1. Water adsorption on MnO:ZnO(001) — From single molecules to bilayer coverage

    Science.gov (United States)

    Kanan, Dalal K.; Keith, John A.; Carter, Emily A.

    2013-11-01

    Improving photochemical water oxidation processes on sunlight absorbing materials requires understanding the photoelectrode-solution interface. We use ab initio density functional theory (DFT) + U to investigate the structure and energetics of water adsorbed on MnO:ZnO(001), a potential photoanode material we previously identified as having suitable band gaps and band edge placements for visible light induced water splitting. Our calculations show that there is a preference for molecular adsorption at water coverages of less than half a monolayer (ML). At higher coverages, cooperative water-water interactions facilitate water dissociation at the interface. We find that the work function is very sensitive to water dipole orientation and/or presence of hydroxyls on the surface. The computed phase diagram reveals the surface to be fairly hydrophilic with a preference for the first water ML to be 33% dissociated at 0.75 ML, 50% dissociated at 1 ML, and 50% dissociated at 2 ML water coverage under various conditions away from water-poor conditions.

  2. Serine/threonine phosphatase tapp2cs might be served as an early signal molecule for water stress in wheat

    International Nuclear Information System (INIS)

    Much progress has been made towards understanding the role of serine/threonine phosphatases type 2C (PP2Cs) in abscisic acid (ABA) signaling transduction. However, how the negative regulator, PP2Cs, responds to plant water loss remains unclear. Here, we used a series of relative soil moisture (RSM: 85 percentage (well watered), 65 percentage (moderate stress), 45 percentage (severe stress) potted winter wheat (Triticum aestivum L.) and the detached leaves to detect ABA levels and transcripts of PP2Cs, including PP2C40, PP2C45, PP2C59 and PP2C6 as well as the core downstream signals of ABA, including ABF, SnRK2.4 and SnRK2.5. The results showed that the continual loss of water led to a consistent increase in ABA levels, and that the mRNA expression levels of PP2Cs were dependent on plant water condition. PP2Cs expression could be induced by a slight loss of water, and inhibited under severe loss of water. These results were further confirmed by the transcripts of ABF, SnRK2.4 and SnRK2.5. Furthermore, in slight loss of water, 100 μM exogenous ABA could promote PP2Cs expression; in severe loss of water, it inhibited PP2Cs expression. In conclusion, ABA accumulation is controlled by water condition and the PP2C expression is dependent on plant water condition, suggesting that PP2Cs might be served as an early signal molecule for water stress in wheat. (author)

  3. Density Functional Theory Study of the Complexation of the Uranyl Dication with Anionic Phosphate Ligands with and without Water Molecules

    Energy Technology Data Exchange (ETDEWEB)

    Jackson, Virgil E.; Gutowski, Keith E.; Dixon, David A.

    2013-09-12

    The structures, vibrational frequencies and energetics of anhydrous and hydrated complexes of UO2 2+ with the phosphate anions H2PO4 −, HPO4 2−, and PO4 3− were predicted at the density functional theory (DFT) and MP2 molecular orbital theory levels as isolated gas phase species and in aqueous solution by using self-consistent reaction field (SCRF) calculations with different solvation models. The geometries and vibrational frequencies of the major binding modes for these complexes are compared to experiment where possible and good agreement is found. The uranyl moiety is nonlinear in many of the complexes, and the coordination number (CN) 5 in the equatorial plane is the predominant binding motif. The phosphates are found to bind in both monodentate and bidentate binding modes depending on the charge and the number of water molecules. The SCRF calculations were done with a variety of approaches, and different SCRF approaches were found to be optimal for different reaction types. The acidities of HxPO4 3‑x in HxPO4 3‑x(H2O)4, x = 0−3 complexes were calculated with different SCRF models and compared to experiment. Phosphate anions can displace water molecules from the first solvation shell at the uranyl exothermically. The addition of water molecules can cause the bonding of H2PO4 − and HPO4 2− to change from bidentate to monodentate exothermically while maintaining CN 5. The addition of water can generate monodentate structures capable of cross-linking to other uranyl phosphates to form the types of structures found in the solid state. [UO2(HPO4)(H2O)3] is predicted to be a strong base in the gas phase and in aqueous solution. It is predicted to be a much weaker acid than H3PO4 in the gas phase and in solution.

  4. Subpicosecond energy transfer from a highly intense THz pulse to water: A computational study based on the TIP4P/2005 rigid-water-molecule model

    Science.gov (United States)

    Mishra, Pankaj Kr.; Vendrell, Oriol; Santra, Robin

    2016-03-01

    The dynamics of ultrafast energy transfer to water clusters and to bulk water by a highly intense, subcycle THz pulse of duration ≈150 fs is investigated in the context of force-field molecular dynamics simulations. We focus our attention on the mechanisms by which rotational and translational degrees of freedom of the water monomers gain energy from these subcycle pulses with an electric field amplitude of up to about 0.6 V/Å. It has been recently shown that pulses with these characteristics can be generated in the laboratory [C. Vicario, B. Monoszlai, and C. P. Hauri, Phys. Rev. Lett. 112, 213901 (2014), 10.1103/PhysRevLett.112.213901]. Through their permanent dipole moment, water molecules are acted upon by the electric field and forced off their preferred hydrogen-bond network conformation. This immediately sets them in motion with respect to one another as energy quickly transfers to their relative center of mass displacements. We find that, in the bulk, the operation of these mechanisms is strongly dependent on the initial temperature and density of the system. In low density systems, the equilibration between rotational and translational modes is slow due to the lack of collisions between monomers. As the initial density of the system approaches 1 g/cm3 , equilibration between rotational and translational modes after the pulse becomes more efficient. In turn, low temperatures hinder the direct energy transfer from the pulse to rotational motion owing to the resulting stiffness of the hydrogen bond network. For small clusters of just a few water molecules we find that fragmentation due to the interaction with the pulse is faster than equilibration between rotations and translations, meaning that the latter remain colder than the former after the pulse. In contrast, clusters with more than a few tens of water molecules already display energy gain dynamics similar to water in condensed phases owing to inertial confinement of the internal water molecules by

  5. What governs the fluidic behavior of water near single DNA molecules at the micro/nano scale

    CERN Document Server

    Zhang, Y; Lei, X; Lv, J; Ai, X; Jun, H; Zhang, Yi; Li, Huabing; Lei, Xiaoling; Lv, Junhong; Ai, Xiaobai; Jun, Hu

    2006-01-01

    The fluidic behavior of water at the micro/nano scale is studied by using of single DNA molecules as a model system. Stable curved DNA patterns with spans about one micron were generated by using of water flows, and observed by Atomic Force Microscopy. By rigorously comparing the numerical simulation results with these patterns, it is suggested that the form of the macroscopic hydrodynamic equation still works quantitatively well on the fluid flows at the nanoscale. The molecular effects, however, are still apparent that the effective viscosity of the adjacent water is considerably larger than its bulk value. Our observation is also helpful to understand of the dynamics of biomolecules in solutions from nanoscale to microscale.

  6. Hydrogen bonding of single acetic acid with water molecules in dilute aqueous solutions

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    In separation processes,hydrogen bonding has a very significant effect on the efficiency of isolation of acetic acid (HOAc) from HOAc/H2O mixtures. This intermolecular interaction on aggregates composed of a single HOAc molecule and varying numbers of H2O molecules has been examined by using ab initio molecular dynamics simulations (AIMD) and quantum chemical calculations (QCC). Thermodynamic data in aqueous solution were obtained through the self-consistent reaction field calculations and the polarizable continuum model. The aggregation free energy of the aggregates in gas phase as well as in aqueous system shows that the 6-membered ring is the most favorable structure in both states. The relative stability of the ring structures inferred from the thermodynamic properties of the QCC is consistent with the ring distributions of the AIMD simulation. The study shows that in dilute aqueous solution of HOAc the more favorable molecular interaction is the hydrogen bonding between HOAc and H2O molecules,resulting in the separation of acetic acid from the HOAc/H2O mixtures with more difficulty than usual.

  7. Group-contribution to limiting partial molar isentropic compressions of small amphiphile molecules in water. The temperature effect

    International Nuclear Information System (INIS)

    Highlights: • Limiting partial molar isentropic compressions for small amphiphiles were experimentally determined and compiled. • A simple additive scheme was applied to 31 amphiphiles in order to estimate group contribution values and their uncertainties. • The effect of temperature was studied for temperatures ranging T = (283.15 to 303.15) K. • Few large deviations for molecules not included in the basic set, are tentatively explained. -- Abstract: A simple additive scheme based on a multi-parametric least-squares fitting method is described and employed to estimate group-contributions to limiting partial molar isentropic compressions of small amphiphile molecules in water. To complement high quality literature data for aqueous solutions of aliphatic alcohols, alkoxyalcohols, amines, alkoxyamines, aminoalcohols, amino-acids and dipeptides, new accurate densities and ultrasound speeds have been experimentally determined for several very-dilute aqueous solutions of 2-(isopropylamino)ethanol, 2-butoxyethanol and 2-isobutoxyethanol at 5 K intervals in the temperature range T = (283.15 to 303.15) K. Reliable limiting partial molar isentropic compressions for 31 amphiphiles in water at five fixed temperatures have been used to estimate group-contribution values and their associate uncertainties of the following eleven structural groups: CH3; CH2; CH; N; NH; NH2; CH2COCH2; CH2OH; CHOH; COOH; and CONH, at five different temperatures. The goodness of the fit of reconstituted against experimental values indicates that a consistent set of group-contribution values has been obtained and that their dependence on temperature deserves credit. These values and their sensibility to temperature changes have been analysed in terms of hydration processes in solution. Deviations of predicted from experimental values are found for molecules containing a vicinal diol group and dipeptides showing hindrance or enhancement of H-bond formation. These deviations for molecules not

  8. Water molecules effect on pure Ti passive film structure in methanol solution

    Energy Technology Data Exchange (ETDEWEB)

    Qin, Zhi; Pang, Xiaolu [Corrosion and Protection Center, Key Laboratory for Environmental Fracture (MOE), University of Science and Technology Beijing, Beijing 100083 (China); Qiao, Lijie, E-mail: lqiao@ustb.edu.cn [Corrosion and Protection Center, Key Laboratory for Environmental Fracture (MOE), University of Science and Technology Beijing, Beijing 100083 (China); Khodayari, Mehdi; Volinsky, Alex A. [Department of Mechanical Engineering, University of South Florida, Tampa, FL 33620 (United States)

    2014-06-01

    To understand the role of water on titanium SCC properties in methanol solutions, composition and structure of the passive film were studied using X-ray photoelectron and electrochemical impedance spectroscopies. The passive film consists of the inner compact layer and a porous outer layer. The inner layer thickness is less than 4 nm and decreases with the increasing water content. Water improves the passive film properties, thus changes SCC susceptibility by altering the hydrogen bonding of methanol and reacting with titanium preferentially.

  9. The Relationship Between Bound Water and Carbohydrate Reserves in Association with Cellular Integrity in Fragaria vesca Stored Under Different Conditions

    OpenAIRE

    Blanch, Maria; Sánchez-Ballesta, M. Teresa; Escribano, M. Isabel; Merodio, Carmen

    2015-01-01

    © 2014, The Author(s). It has been recognized that high CO2 concentrations maintain the freshness of strawberries, reducing weight loss and the incidence of decay. Since strawberries have high tolerance threshold to CO2, it is of interest to know what changes occur in cellular water distribution when the threshold is reached or exceeded. Moreover, as strawberries are prone to producing exudate during storage at low temperatures, application of technologies improving water retention is needed....

  10. Approach to calculating upper bounds on maximum individual doses from the use of contaminated well water following a WIPP repository breach

    International Nuclear Information System (INIS)

    As part of the assessment of the potential radiological consequences of the proposed Waste Isolation Pilot Plant (WIPP), this report evaluates the post-closure radiation dose commitments associated with a possible breach event which involves dissolution of the repository by groundwaters and subsequent transport of the nuclear waste through an aquifer to a well assumed to exist at a point 3 miles downstream from the repository. The concentrations of uranium and plutonium isotopes at the well are based on the nuclear waste inventory presently proposed for WIPP and basic assumptions concerning the transport of waste as well as treatment to reduce the salinity of the water. The concentrations of U-233, Pu-239, and Pu-240, all radionuclides originally emplaced as waste in the repository, would exceed current EPA drinking water limits. The concentrations of U-234, U-235, and U-236, all decay products of plutonium isotopes originally emplaced as waste, would be well below current EPA drinking water limits. The 50-year dose commitments from one year of treated drinking water contaminated with U-233 or Pu-239 and Pu-240 were found to be comparable to a one year dose from natural background. The 50-year dose commitments from one year of drinking milk would be no more than about 1/5 the dose obtained from ingestion of treated water. These doses are considered upper bounds because of several very conservative assumptions which are discussed in the report

  11. Approach to calculating upper bounds on maximum individual doses from the use of contaminated well water following a WIPP repository breach. Report EEG-9

    International Nuclear Information System (INIS)

    As part of the assessment of the potential radiological consequences of the proposed Waste Isolation Pilot Plant (WIPP), this report evaluates the post-closure radiation dose commitments associated with a possible breach event which involves dissolution of the repository by groundwaters and subsequent transport of the nuclear waste through an aquifer to a well assumed to exist at a point 3 miles downstream from the repository. The concentrations of uranium and plutonium isotopes at the well are based on the nuclear waste inventory presently proposed for WIPP and basic assumptions concerning the transport of waste as well as treatment to reduce the salinity of the water. The concentrations of U-233, Pu-239, and Pu-240, all radionuclides originally emplaced as waste in the repository, would exceed current EPA drinking water limits. The concentrations of U-234, U-235, and U-236, all decay products of plutonium isotopes originally emplaced as waste, would be well below current EPA drinking water limits. The 50-year dose commitments from one year of drinking treated water contaminated with U-233 or Pu-239 and Pu-240 were found to be comparable to a one-year dose from natural background. The 50-year dose commitments from one year of drinking milk would be no more than about 1/5 the dose obtained from ingestion of treated water. These doses are considered upper bounds because of several very conservative assumptions which are discussed in the report

  12. Water-soluble carbon monoxide-releasing molecules: helping to elucidate the vascular activity of the 'silent killer'.

    Science.gov (United States)

    Chatterjee, Prabal Kumar

    2004-06-01

    Carbon monoxide (CO) is formed during the degradation of haeme by haeme oxygenase (HO). As well as being an important signalling molecule and vasodilator, CO also possesses antihypertensive, anti-inflammatory and antiapoptotic qualities and protects against ischaemic tissue injury. Several approaches have been used to investigate the therapeutic potential of CO, ranging from direct administration of CO gas to the use of prodrugs, which generate CO upon metabolism. A novel approach involves the use of specific CO carriers, which will release measurable, controllable and effective amounts of CO into biological systems. Transitional metal carbonyls based around iron, manganese or ruthenium have recently been developed as CO-releasing molecules (CO-RMs) that, under appropriate conditions, will release CO. Such molecules have been shown to provide cardioprotection in both ex vivo and in vivo experiments. To date, CO-RMs have been largely incompatible with biological systems in that they are only soluble in organic solvents or have to be preactivated either by physical or chemical stimuli. However, the recent development of water-soluble CO-RMs has provided new opportunities to investigate the pharmacological and biological features of CO without such confounding influences. CORM-3, a novel water-soluble CO-RM, has recently been used to confirm the cardioprotective actions of CO. In this issue of British Journal of Pharmacology, Foresti and co-workers report that CORM-3 delivers CO, produces aortic vasodilation ex vivo and reduces blood pressure in vivo via modulation of the same cGMP and potassium channels utilised by endogenous and exogenous CO. These findings suggest that CORM-3 has the potential for use as a modulator of vascular function and hypertension. However, the use of water-soluble CO-RMs raises several questions of their own which will need to be addressed if CO-RMs are to be of future use therapeutically. PMID:15148242

  13. Bounded Rationality

    Directory of Open Access Journals (Sweden)

    Ballester Pla, Coralio

    2012-03-01

    Full Text Available The observation of the actual behavior by economic decision makers in the lab and in the field justifies that bounded rationality has been a generally accepted assumption in many socio-economic models. The goal of this paper is to illustrate the difficulties involved in providing a correct definition of what a rational (or irrational agent is. In this paper we describe two frameworks that employ different approaches for analyzing bounded rationality. The first is a spatial segregation set-up that encompasses two optimization methodologies: backward induction and forward induction. The main result is that, even under the same state of knowledge, rational and non-rational agents may match their actions. The second framework elaborates on the relationship between irrationality and informational restrictions. We use the beauty contest (Nagel, 1995 as a device to explain this relationship.

    La observación del comportamiento de los agentes económicos tanto en el laboratorio como en la vida real justifica que la racionalidad acotada sea un supuesto aceptado en numerosos modelos socio-económicos. El objetivo de este artículo es ilustrar las dificultades que conlleva una correcta definición de qué es un agente racional (irracional. En este artículo se describen dos marcos que emplean diferentes metodologías para analizar la racionalidad acotada. El primero es un modelo de segregación espacial donde se contrastan dos metodologías de optimización: inducción hacia atrás y hacia adelante. El resultado principal es que, incluso con el mismo nivel de conocimiento, tanto agentes racionales como irracionales podrían coincidir en sus acciones. El segundo marco trabaja sobre la relación entre irracionalidad y restricción de información. Se utiliza el juego llamado “beauty contest” (Nagel 1995 como mecanismo para explicar dicha relación.

  14. Possible interstellar formation of glycine from the reaction of CH2=NH, CO and H2O: catalysis by extra water molecules through the hydrogen relay transport.

    Science.gov (United States)

    Nhlabatsi, Zanele P; Bhasi, Priya; Sitha, Sanyasi

    2016-01-01

    "How the fundamental life elements are created in the interstellar medium (ISM)?" is one of the intriguing questions related to the genesis of life. Using computational calculations, we have discussed the reaction of CH2=NH, CO and H2O for the formation of glycine, the simplest life element. This reaction proceeds through a concerted mechanism with reasonably large barriers for the cases with one and two water molecules as reactants. For the two water case we found that the extra water molecule exhibits some catalytic role through the hydrogen transport relay effect and the barrier height is reduced substantially compared to the case with one water molecule. These two cases can be treated as ideal cases for the hot-core formation of the interstellar glycine. With an increasing number of water molecules as the reactants, we found that when the numbers of water molecules are three or more than three, the barrier height reduced so drastically that the transition states were more stable than the reactants. Such a situation gives a clear indication that with excess water molecules as the reactants, this reaction will be feasible even under the low temperature conditions existing in the cold interstellar clouds and the exothermic nature of the reaction will be the driving force. PMID:26616741

  15. Bibliography of electron and photon cross sections with atoms and molecules published in the 20th century. Water vapour

    International Nuclear Information System (INIS)

    Bibliographies of original and review reports of experiments or theories of electron and photon cross sections and also electron swarm data are presented for atomic or molecular species with specified targets. These works covered 17 atoms and 51 molecules. The present bibliography is only for water vapour (H2O, D2O and HDO). About 1200 papers were compiled. A comprehensive author index is included. The bibliography covers the period 1915 through 2000 for H2O. Finally, author's comments for electron collision cross sections and photodissociation processes of H2O are given. (author)

  16. Partial oxidation of step-bound water leads to anomalous pH effects on metal electrode step-edges.

    Science.gov (United States)

    Schwarz, Kathleen; Xu, Bingjun; Yan, Yushan; Sundararaman, Ravishankar

    2016-06-28

    The design of better heterogeneous catalysts for applications such as fuel cells and electrolyzers requires a mechanistic understanding of electrocatalytic reactions and the dependence of their activity on operating conditions such as pH. A satisfactory explanation for the unexpected pH dependence of electrochemical properties of platinum surfaces has so far remained elusive, with previous explanations resorting to complex co-adsorption of multiple species and resulting in limited predictive power. This knowledge gap suggests that the fundamental properties of these catalysts are not yet understood, limiting systematic improvement. Here, we analyze the change in charge and free energies upon adsorption using density-functional theory (DFT) to establish that water adsorbs on platinum step edges across a wide voltage range, including the double-layer region, with a loss of approximately 0.2 electrons upon adsorption. We show how this as-yet unreported change in net surface charge due to this water explains the anomalous pH variations of the hydrogen underpotential deposition (Hupd) and the potentials of zero total charge (PZTC) observed in published experimental data. This partial oxidation of water is not limited to platinum metal step edges, and we report the charge of the water on metal step edges of commonly used catalytic metals, including copper, silver, iridium, and palladium, illustrating that this partial oxidation of water broadly influences the reactivity of metal electrodes. PMID:27250359

  17. Understanding the role of ions and water molecules in the NaCl dissolution process

    OpenAIRE

    Klimeš, J.; Bowler, D. R.; Michaelides, A.

    2013-01-01

    The dissolution of NaCl in water is one of the most common everyday processes, yet it remains poorly understood at the molecular level. Here we report the results of an extensive density functional theory study in which the initial stages of NaCl dissolution have been examined at low water coverages. Our specific approach is to study how the energetic cost of moving an ion or a pair of ions to a less coordinated site at the surface of various NaCl crystals varies with the number of water mole...

  18. Incorporation of tritiated water (HTO) and organically bound tritium (OBT) into phospholipids and gangliosides of rat brain

    International Nuclear Information System (INIS)

    Three generations of rats were long-term exposed to HTO in drinking water at activity of 37.0 kBq/ml or to food containing OBT at activity of 48.1 kBq/g. The rats consumed tritiated water and tritiated food ad libitum. In the experiment the F1 and F2 generation of rats were exposed continuously from conception to the 21-st or 120-th day of age and rats of F3 generation during 22 days of their intrauterine life. It was found that the amount of tritium incorporated into the major rat brain phospholipids and gangliosides after administration of tritiated food was higher than after administration of tritiated water. Tritium activity in all studied phospholipids and gangliosides was the highest in 21-day-old rats exposed during both-pregnancy and lactation. (author)

  19. Prototropic tautomerism of 4-Methyl 1,2,4-Triazole-3-Thione molecule in solvent water medium: DFT and Car-Parrinello molecular dynamics study

    Science.gov (United States)

    Dutta, Bipan; De, Rina; Chowdhury, Joydeep

    2015-12-01

    The ground state prototropic tautomerism of 4-Methyl 1,2,4-Triazole-3-Thione molecule in solvent water medium has been investigated with the aid of DFT and Car-Parrinello molecular dynamics (CPMD) simulation studies. The CPMD simulations envisage the possibility of proton transfer reactions of the molecule through the solvent water medium. Probable proton transfer pathways have been predicted from the DFT calculations which are substantiated by the natural bond orbital analyses. The evolution and breaking of the concerned bonds of the molecule for different proton transfer reaction pathways are also estimated.

  20. Partial oxidation of Step-Bound Water Leads to Anomalous pH Effects on Metal Electrode Step-Edges

    CERN Document Server

    Schwarz, Kathleen; Yan, Yushan; Sundararaman, Ravishankar

    2016-01-01

    The design of better heterogeneous catalysts for applications such as fuel cells and electrolyzers requires a mechanistic understanding of electrocatalytic reactions and the dependence of their activity on operating conditions such as pH. A satisfactory explanation for the unexpected pH dependence of electrochemical properties of platinum surfaces has so far remained elusive, with previous explanations resorting to complex co-adsorption of multiple species and resulting in limited predictive power. This knowledge gap suggests that the fundamental properties of these catalysts are not yet understood, limiting systematic improvement. Here, we analyze the change in charge and free energies upon adsorption using density-functional theory (DFT) to establish that water adsorbs on platinum step edges across a wide voltage range, including the double-layer region, with a loss of approximately 0.2 electrons upon adsorption. We show how the change in net surface charge due to this water explains the anomalous pH variat...

  1. Effect of anodizing voltage on the sorption of water molecules on porous alumina

    Energy Technology Data Exchange (ETDEWEB)

    Vrublevsky, I., E-mail: vrublevsky@bsuir.edu.by [Belarusian State University of Informatics and Radioelectronics, Department of Micro and Nanoelectronics, 220013 Minsk (Belarus); Chernyakova, K. [Belarusian State University of Informatics and Radioelectronics, Department of Micro and Nanoelectronics, 220013 Minsk (Belarus); Bund, A.; Ispas, A.; Schmidt, U. [Fachgebiet Elektrochemie und Galvanotechnik, Technische Universitaet Ilmenau, 98693 Ilmenau (Germany)

    2012-05-01

    The amount of water adsorbed on different centers on the surface of oxalic acid alumina films is a function of the anodizing voltage. It is decreased with increasing the anodizing voltage from 20 up to 50 V, came up to maximum value at 20-30 V and slightly increased at voltages above 50 V. Water adsorption by oxide films formed at voltages below 50 V can be due to the negative surface charge that is present on the alumina surface. The negative surface charge disappears in the films formed at voltages higher than 50 V, and thus, the water is adsorbed on aluminum ions in a tetrahedral and octahedral environment. The correlation between anodizing conditions of aluminum in oxalic acid and the structure and composition of anodic alumina was established by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM), thermogravimetric and differential thermal analyses (TG/DTA).

  2. Effect of anodizing voltage on the sorption of water molecules on porous alumina

    International Nuclear Information System (INIS)

    The amount of water adsorbed on different centers on the surface of oxalic acid alumina films is a function of the anodizing voltage. It is decreased with increasing the anodizing voltage from 20 up to 50 V, came up to maximum value at 20-30 V and slightly increased at voltages above 50 V. Water adsorption by oxide films formed at voltages below 50 V can be due to the negative surface charge that is present on the alumina surface. The negative surface charge disappears in the films formed at voltages higher than 50 V, and thus, the water is adsorbed on aluminum ions in a tetrahedral and octahedral environment. The correlation between anodizing conditions of aluminum in oxalic acid and the structure and composition of anodic alumina was established by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM), thermogravimetric and differential thermal analyses (TG/DTA).

  3. Calculation of the free energy profile of the transfer of small molecules through water/organic interface by the potential of mean force method

    International Nuclear Information System (INIS)

    Transport phenomena of organic molecules and ions are of considerable interest, since they play a vital role in metabolic processes as well as in the functioning of the nervous system. In particular, the transport of such molecules through lipid membranes and water/organic phase boundaries is the subject of extensive experimental and theoretical research. In our present work, the free energy profiles of the transfer from water to dichloroethane (DCE) of a simple a rodanide (SCN-) ion and of a cocaine molecule were obtained from complex potential of mean force calculations. The calculations were performed obeying the following algorithm. As the first step Steered Molecular Dynamics (SMD) simulations were carried out for each system, using the interfacial molecules of the DCE/water interface, the coordinates of which were preliminarily determined by the novel Identification of the Truly Interfacial Molecules (ITIM) method, as reference group. A number of configurations with the SCN- ion or the cocaine molecule at different positions were then extracted from the obtained trajectory. PMF calculations using the constraint force algorithm were performed on each of these systems to give the potential of mean force, which, after integration, yields the free energy profile characteristic of the transfer through the water/organic phase boundary. It is easily understood that this method is applicable for calculating the free energy of small molecules through lipid membranes as well. (authors)

  4. Mercedes–Benz water molecules near hydrophobic wall: Integral equation theories vs Monte Carlo simulations

    Science.gov (United States)

    Urbic, T.; Holovko, M. F.

    2011-01-01

    Associative version of Henderson-Abraham-Barker theory is applied for the study of Mercedes–Benz model of water near hydrophobic surface. We calculated density profiles and adsorption coefficients using Percus-Yevick and soft mean spherical associative approximations. The results are compared with Monte Carlo simulation data. It is shown that at higher temperatures both approximations satisfactory reproduce the simulation data. For lower temperatures, soft mean spherical approximation gives good agreement at low and at high densities while in at mid range densities, the prediction is only qualitative. The formation of a depletion layer between water and hydrophobic surface was also demonstrated and studied. PMID:21992334

  5. Mercedes-Benz water molecules near hydrophobic wall: Integral equation theories vs Monte Carlo simulations

    Science.gov (United States)

    Urbic, T.; Holovko, M. F.

    2011-10-01

    Associative version of Henderson-Abraham-Barker theory is applied for the study of Mercedes-Benz model of water near hydrophobic surface. We calculated density profiles and adsorption coefficients using Percus-Yevick and soft mean spherical associative approximations. The results are compared with Monte Carlo simulation data. It is shown that at higher temperatures both approximations satisfactory reproduce the simulation data. For lower temperatures, soft mean spherical approximation gives good agreement at low and at high densities while in at mid range densities, the prediction is only qualitative. The formation of a depletion layer between water and hydrophobic surface was also demonstrated and studied.

  6. The added value of a water footprint approach: Micro- and macroeconomic analysis of cotton production, processing and export in water bound Uzbekistan

    Science.gov (United States)

    Rudenko, I.; Bekchanov, M.; Djanibekov, U.; Lamers, J. P. A.

    2013-11-01

    Since independence from the former Soviet Union in 1991, Uzbekistan is challenged to consolidate its efforts and identify and introduce suitable agricultural policies to ease the threat of advancing land, water and ecosystem deterioration. On the one hand, irrigated cotton production provides income, food and energy sources for a large part of the rural households, which accounts for about 70% of the total population. On the other hand, this sector is considered a major driver of the on-going environmental degradation. Due to this dual nature, an integrated approach is needed that allows the analyses of the cotton sector at different stages and, consequently, deriving comprehensive options for action. The findings of the economic based value chain analysis and ecologically-oriented water footprint analysis on regional level were complemented with the findings of an input-output model on national level. This combination gave an added value for better-informed decision-making to reach land, water and ecosystem sustainability, compared to the individual results of each approach. The synergy of approaches pointed at various options for actions, such as to (i) promote the shift of water use from the high water consuming agricultural sector to a less water consuming cotton processing sector, (ii) increase overall water use efficiency by expanding the highly water productive industrial sectors and concurrently decreasing sectors with inefficient water use, and (iii) reduce agricultural water use by improving irrigation and conveyance efficiencies. The findings showed that increasing water use efficiency, manufacturing products with higher value added and raising water users' awareness of the real value of water are essential for providing water security in Uzbekistan.

  7. Structural and atoms-in-molecules analysis of hydrogen-bond network around nitroxides in liquid water

    Science.gov (United States)

    Houriez, Céline; Masella, Michel; Ferré, Nicolas

    2010-09-01

    In this study, we investigated the hydrogen-bond network patterns involving the NO moieties of five small nitroxides in liquid water by analyzing nanosecond scale molecular dynamics trajectories. To this end, we implemented two types of hydrogen-bond definitions, based on electronic structure, using Bader's atoms-in-molecules analysis and based on geometric criteria. In each definition framework, the nitroxide/water hydrogen-bond networks appear very variable from a nitroxide to another. Moreover, each definition clearly leads to a different picture of nitroxide hydration. For instance, the electronic structure-based definition predicts a number of hydrogen bonds around the nitroxide NO moiety usually larger than geometric structure-based ones. One particularly interesting result is that the strength of a nitroxide/water hydrogen bond does not depend on its linearity, leading us to question the relevance of geometric definition based on angular cutoffs to study this type of hydrogen bond. Moreover, none of the hydrogen-bond definitions we consider in the present study is able to quantitatively correlate the strength of nitroxide/water hydrogen-bond networks with the aqueous nitroxide spin properties. This clearly exhibits that the hydrogen-bonding concept is not reliable enough to draw quantitative conclusions concerning such properties.

  8. Dynamics of low-energy electrons in liquid water with consideration of Coulomb interaction with positively charged water molecules induced by electron collision

    International Nuclear Information System (INIS)

    Highlights: • Dynamical calculations of electrons in water were performed. • Effect of Coulomb interaction between charged particles was investigated. • About 20% of the ionized electrons were returned to the ions within 100 fs. - Abstract: To explain the electron energy relaxation process in water, we performed dynamical calculations of electrons in water using a simulation code developed in this study to calculate mean diffusion distances and mean energies of incident and secondary electrons released by the impact of the incident electron, as well as spatial probability-distribution of the secondary electrons. In addition to the following molecular processes of water: ionization: electronic, vibrational, and rotational excitation by electron impact; dissociative electron attachment; and elastic electron scattering, which were basic parameters used by Monte Carlo simulation, we newly took into account Coulomb interactions between electrons and positively ionized water molecules to calculate classical electron trajectories. We found that the Coulomb interactions enhance the number of collisions for the vibrational and rotational excitation processes at the incident 500 eV electron energy. The secondary electrons diffuse to an average of 3 nm from their original position, resulting much different spatial probability-distribution of those electrons in comparison to those previously reported. We also found that approximately 20% of the secondary electrons were returned to the parent ions within 100 fs. By the electron re-capturing to either bonding or antibionding orbital, the molecules might be converted to some electronic excitation states. We suggest that the spatial probability-distribution of electrons, taken into account the re-capturing process, should be essential for detailed analysis of following chemical process arising in nanometer scales, such as biomolecular damage caused by radiation

  9. Isolation of pregnancy-associated glycoproteins (PAG from water buffalo (Bubalus bubalis placenta by use of Vicia villosa bound agarose affinity chromatography

    Directory of Open Access Journals (Sweden)

    J.F. Beckers

    2010-02-01

    Full Text Available The present study describes the isolation and characterisation of new PAG molecules extracted from mid- and late-pregnancy placentas in the water buffalo (Bubalis bubalis. After extraction, acid and ammonium sulphate precipitation and DEAE chromatography water buffalo PAG (wbPAG were enriched by Vicia villosa agarose (VVA affininity chromatography. As determined by Western blotting with anti-PAG-sera, apparent molecular masses of immunoreactive bands from VVA peaks ranged from 59.5 to 75.8 kDa and from 57.8 to 80.9 kDa in the mid- and late- pregnancy placenta respectively. Aminoterminal microsequencing of proteins allowed the identification of three distinct wbPAG sequences wich have ben deposed in the SwissProt database: RGSXLTIHPLRNIRDFFYUG (Acc. n. P85048, RGSXLTILPLRNIID (P85049 and RGSXLTHLPLRNI (P85050. Their comparison to those previously identified revealed that two of them were new since they have not been described yet. Our results confirm the suitability of VVA chromatography in enrichment of multiple PAG molecules expressed in buffalo placenta. Productions of specific antisera can be very useful in immonoistochemical and immunocyitochemical studies of PAG expression in fetomaternal interfaces. Purified native PAG are also required for development on specific immoassays (RIA/ELISA currently used for pregnancy diagnosis and physiological investigation in farm animal.

  10. Reverse self-assemblies based on amphiphilic polyphosphazenes for encapsulation of water-soluble molecules

    International Nuclear Information System (INIS)

    A novel series of amphiphilic polyphosphazenes (PNIPAm/AA-PPP) containing hydrophilic oligo-(N-isopropylacrylamide) (oligo-NIPAm) and various hydrophobic aliphatic amines as co-substitutes was synthesized via a two-step substitution reaction. The extraction and solubilization of water-soluble substances such as fluorescein sodium and trypan blue from an aqueous phase into the chloroform phase were supposed to result from the formation of polyphosphazene reverse self-assemblies in the organic phase. A field emission scanning electronic microscope was adopted to characterize the morphology of reverse assemblies in chloroform. Additionally, a significant improvement of encapsulation and release profiles of water-soluble substances was found for poly(lactic-co-glycolic acid) (PLGA) microparticles in the presence of amphiphilic copolymers, which was associated with the chemical structure of copolymers as well as the content of copolymer in the microparticles

  11. Reverse self-assemblies based on amphiphilic polyphosphazenes for encapsulation of water-soluble molecules

    Energy Technology Data Exchange (ETDEWEB)

    Qiu Liyan [College of Pharmaceutical Sciences, Zhejiang University, Hangzhou 310058 (China); Zhang Jianxiang [College of Pharmaceutical Sciences, Zhejiang University, Hangzhou 310058 (China); Yan Meiqiu [College of Pharmaceutical Sciences, Zhejiang University, Hangzhou 310058 (China); Jin Yi [College of Pharmaceutical Sciences, Zhejiang University, Hangzhou 310058 (China); Zhu Kangjie [Institute of Polymer Science, Zhejiang University, Hangzhou 310027 (China)

    2007-11-28

    A novel series of amphiphilic polyphosphazenes (PNIPAm/AA-PPP) containing hydrophilic oligo-(N-isopropylacrylamide) (oligo-NIPAm) and various hydrophobic aliphatic amines as co-substitutes was synthesized via a two-step substitution reaction. The extraction and solubilization of water-soluble substances such as fluorescein sodium and trypan blue from an aqueous phase into the chloroform phase were supposed to result from the formation of polyphosphazene reverse self-assemblies in the organic phase. A field emission scanning electronic microscope was adopted to characterize the morphology of reverse assemblies in chloroform. Additionally, a significant improvement of encapsulation and release profiles of water-soluble substances was found for poly(lactic-co-glycolic acid) (PLGA) microparticles in the presence of amphiphilic copolymers, which was associated with the chemical structure of copolymers as well as the content of copolymer in the microparticles.

  12. Binding Energy of Molecules on Water Ice: Laboratory Measurements and Modeling

    CERN Document Server

    He, Jiao; Vidali, Gianfranco

    2016-01-01

    We measured the binding energy of N$_2$, CO, O$_2$, CH$_4$, and CO$_2$ on non-porous (compact) amorphous solid water (np-ASW), of N$_2$ and CO on porous amorphous solid water (p-ASW), and of NH$_3$ on crystalline water ice. We were able to measure binding energies down to a fraction of 1\\% of a layer, thus making these measurements more appropriate for astrochemistry than the existing values. We found that CO$_2$ forms clusters on np-ASW surface even at very low coverages. The binding energies of N$_2$, CO, O$_2$, and CH$_4$ decrease with coverage in the submonolayer regime. Their values at the low coverage limit are much higher than what is commonly used in gas-grain models. An empirical formula was used to describe the coverage dependence of the binding energies. We used the newly determined binding energy distributions in a simulation of gas-grain chemistry for cold cloud and hot core models. We found that owing to the higher value of desorption energy in the sub-monlayer regime a fraction of all these ice...

  13. Proposed photosynthesis method for producing hydrogen from dissociated water molecules using incident near-infrared light.

    Science.gov (United States)

    Li, Xingxing; Li, Zhenyu; Yang, Jinlong

    2014-01-10

    Highly efficient solar energy utilization is very desirable in photocatalytic water splitting. However, until now, the infrared part of the solar spectrum, which constitutes almost half of the solar energy, has not been used, resulting in significant loss in the efficiency of solar energy utilization. Here, we propose a new mechanism for water splitting in which near-infrared light can be used to produce hydrogen. This ability is a result of the unique electronic structure of the photocatalyst, in which the valence band and conduction band are distributed on two opposite surfaces with a large electrostatic potential difference produced by the intrinsic dipole of the photocatalyst. This surface potential difference, acting as an auxiliary booster for photoexcited electrons, can effectively reduce the photocatalyst's band gap required for water splitting in the infrared region. Our electronic structure and optical property calculations on a surface-functionalized hexagonal boron-nitride bilayer confirm the existence of such photocatalysts and verify the reaction mechanism. PMID:24483934

  14. Photo-electrochemical Oxidation of Organic C1 Molecules over WO3 Films in Aqueous Electrolyte: Competition Between Water Oxidation and C1 Oxidation.

    Science.gov (United States)

    Reichert, Robert; Zambrzycki, Christian; Jusys, Zenonas; Behm, R Jürgen

    2015-11-01

    To better understand organic-molecule-assisted photo-electrochemical water splitting, photo-electrochemistry and on-line mass spectrometry measurements are used to investigate the photo-electrochemical oxidation of the C1 molecules methanol, formaldehyde, and formic acid over WO3 film anodes in aqueous solution and its competition with O2 evolution from water oxidation O2 (+) and CO2 (+) ion currents show that water oxidation is strongly suppressed by the organic species. Photo-electro-oxidation of formic acid is dominated by formation of CO2 , whereas incomplete oxidation of formaldehyde and methanol prevails, with the selectivity for CO2 formation increasing with increasing potential and light intensity. The mechanistic implications for the photo-electro-oxidation of the organic molecules and its competition with water oxidation, which could be derived from this novel approach, are discussed. PMID:26382643

  15. Binding Energy of Molecules on Water Ice: Laboratory Measurements and Modeling

    Science.gov (United States)

    He, Jiao; Acharyya, Kinsuk; Vidali, Gianfranco

    2016-07-01

    We measured the binding energy of N2, CO, O2, CH4, and CO2 on non-porous (compact) amorphous solid water (np-ASW), of N2 and CO on porous ASW, and of NH3 on crystalline water ice. We were able to measure binding energies down to a fraction of 1% of a layer, thus making these measurements more appropriate for astrochemistry than the existing values. We found that CO2 forms clusters on the np-ASW surface even at very low coverages. The binding energies of N2, CO, O2, and CH4 decrease with coverage in the submonolayer regime. Their values at the low coverage limit are much higher than what is commonly used in gas-grain models. An empirical formula was used to describe the coverage dependence of the binding energies. We used the newly determined binding energy distributions in a simulation of gas-grain chemistry for cold cloud and hot-core models. We found that owing to the higher value of binding energy in the submonolayer regime, a fraction of all these ices remains for much longer and up to higher temperatures on the grain surface compared to the single value energies currently used in the astrochemical models.

  16. Anion emission from water molecules colliding with positive ions: Identification of binary and many-body processes

    CERN Document Server

    Chesnel, J -Y; Lattouf, E; Tanis, J A; Huber, B A; Bene, E; Kovács, S T S; Herczku, P; Méry, A; Poully, J -C; Rangama, J; Sulik, B

    2015-01-01

    It is shown that negative ions are ejected from gas-phase water molecules when bombarded with positive ions at keV energies typical of solar-wind velocities. This finding is relevant for studies of planetary and cometary atmospheres, as well as for radiolysis and radiobiology. Emission of both H- and heavier (O- and OH-) anions, with a larger yield for H-, was observed in 6.6-keV 16O+ + H2O collisions. The ex-perimental setup allowed separate identification of anions formed in collisions with many-body dynamics from those created in hard, binary collisions. Most of the ani-ons are emitted with low kinetic energy due to many-body processes. Model calcu-lations show that both nucleus-nucleus interactions and electronic excitations con-tribute to the observed large anion emission yield.

  17. CO2 and C2H2 in cold nanodroplets of oxygenated organic molecules and water

    Science.gov (United States)

    Devlin, J. Paul; Balcı, F. Mine; Maşlakcı, Zafer; Uras-Aytemiz, Nevin

    2014-11-01

    Recent demonstrations of subsecond and microsecond timescales for formation of clathrate hydrate nanocrystals hint at future methods of control of environmental and industrial gases such as CO2 and methane. Combined results from cold-chamber and supersonic-nozzle [A. S. Bhabhe, "Experimental study of condensation and freezing in a supersonic nozzle," Ph.D. thesis (Ohio State University, 2012), Chap. 7] experiments indicate extremely rapid encagement of components of all-vapor pre-mixtures. The extreme rates are derived from (a) the all-vapor premixing of the gas-hydrate components and (b) catalytic activity of certain oxygenated organic large-cage guests. Premixing presents no obvious barrier to large-scale conditions of formation. Further, from sequential efforts of the groups of Trout and Buch, a credible defect-based model of the catalysis mechanism exists for guidance. Since the catalyst-generated defects are both mobile and abundant, it is often unnecessary for a high percentage of the cages to be occupied by a molecular catalyst. Droplets represent the liquid phase that bridges the premixed vapor and clathrate hydrate phases but few data exist for the droplets themselves. Here we describe a focused computational and FTIR spectroscopic effort to characterize the aerosol droplets of the all-vapor cold-chamber methodology. Computational data for CO2 and C2H2, hetero-dimerized with each of the organic catalysts and water, closely match spectroscopic redshift patterns in both magnitude and direction. Though vibrational frequency shifts are an order of magnitude greater for the acetylene stretch mode, both CO2 and C2H2 experience redshift values that increase from that for an 80% water-methanol solvent through the solvent series to approximately doubled values for tetrahydrofuran and trimethylene oxide (TMO) droplets. The TMO solvent properties extend to a 50 mol.% solution of CO2, more than an order of magnitude greater than for the water-methanol solvent mixture

  18. Back to the roots: photodynamic inactivation of bacteria based on water-soluble curcumin bound to polyvinylpyrrolidone as a photosensitizer.

    Science.gov (United States)

    Winter, Sandra; Tortik, Nicole; Kubin, Andreas; Krammer, Barbara; Plaetzer, Kristjan

    2013-10-01

    Photodynamic inactivation (PDI), the light-induced and photosensitizer-mediated overproduction of reactive oxygen species in microorganisms, represents a convincing approach to treat infections with (multi-resistant) pathogens. Due to its favourable photoactive properties combined with excellent biocompatibility, curcumin derived from the roots of turmeric (Curcuma longa) has been identified as an advantageous photosensitizer for PDI. To overcome the poor water solubility and the rapid decay of the natural substance at physiological pH, we examined the applicability of polyvinylpyrrolidone curcumin (PVP-C) in an acidified aqueous solution (solubility of PVP-C up to 2.7 mM) for photoinactivation of Gram(+) and Gram(-) bacteria. Five micromolar PVP-C incubated for 5 minutes and illuminated using a blue light LED array (435 ± 10 nm, 33.8 J cm(-2)) resulted in a >6 log10 reduction of the number of viable Staphylococcus aureus. At this concentration, longer incubation periods result in a lower phototoxicity, most likely due to degeneration of curcumin. Upon an increase of the PVP-C concentration to 50 μM (incubation for 15 or 25 min) a complete eradication of Staphylococcus aureus can be achieved. As expected for a non-cationic photosensitizer, cell wall permeabilization with CaCl2 prior to addition of 50 μM PVP-C for 15 min is necessary to induce a drop in the count of the Gram(-) Escherichia coli for more than 3 log10. As both constituents of the formulation, curcumin (E number E100) and polyvinylpyrrolidone (E1201), have been approved as food additives, a PDI based on PCP-C might allow for a very sparing clinical application (e.g. for disinfection of wounds) or even for employment in aseptic production of foodstuffs. PMID:23828307

  19. Bond-selective fragmentation of water molecules with intense, ultrafast, carrier envelope phase stabilized laser pulses

    CERN Document Server

    Mathur, D; Dharmadhikari, J A; Dharmadhikari, A K

    2013-01-01

    Carrier envelope phase (CEP) stabilized pulses of intense 800 nm light of 5 fs duration are used to probe the dissociation dynamics of dications of isotopically-substituted water, HOD. HOD$^{2+}$ dissociates into either H$^+$ + OD$^+$ or D$^+$ + OH$^+$. The branching ratio for these two channels is CEP-dependent; the OD$^+$/OH$^+$ ratio (relative to that measured with CEP-unstabilized pulses) varies from 150% to over 300% at different CEP values, opening prospects of isotope-dependent control over molecular bond breakage. The kinetic energy released as HOD$^{2+}$ Coulomb explodes is also CEP-dependent. Formidable theoretical challenges are identified for proper insights into the overall dynamics which involve non-adiabatic field ionization from HOD to HOD$^+$ and, thence, to HOD$^{2+}$ via electron rescattering.

  20. Bidirectional water fluxes and specificity for small hydrophilic molecules in aquaporins 0-5

    DEFF Research Database (Denmark)

    Meinild, A K; Klærke, Dan Arne; Zeuthen, T

    1998-01-01

    for the osmotic water permeability (L p) were obtained in swelling as in shrinkage experiments demonstrating, for the first time, that aquaporins are bidirectional. The reflection coefficients (¿) of urea, glycerol, acetamide, and formamide at 23¿°C were: AQP0: 1, 1, 0.8, 0.6; AQP1: 1, 0.8, 1, 1; AQP2: 1, 0.8, 1......The dimensions of the aqueous pore in aquaporins (AQP) 0, 1, 2, 3, 4, and 5 expressed in Xenopus laevisoocytes were probed by comparing the ability of various solutes to generate osmotic flow. By improved techniques, volume flows were determined from initial rates of changes. Identical values...... and increased ¿glyc to 1 and ¿form to 0.6. We conclude that the pore of the various aquaporins are structurally different and that a simple steric model is insufficient to explain solute-pore interactions....

  1. Ubiquitous water-soluble molecules in aquatic plant exudates determine specific insect attraction.

    Directory of Open Access Journals (Sweden)

    Julien Sérandour

    Full Text Available Plants produce semio-chemicals that directly influence insect attraction and/or repulsion. Generally, this attraction is closely associated with herbivory and has been studied mainly under atmospheric conditions. On the other hand, the relationship between aquatic plants and insects has been little studied. To determine whether the roots of aquatic macrophytes release attractive chemical mixtures into the water, we studied the behaviour of mosquito larvae using olfactory experiments with root exudates. After testing the attraction on Culex and Aedes mosquito larvae, we chose to work with Coquillettidia species, which have a complex behaviour in nature and need to be attached to plant roots in order to obtain oxygen. This relationship is non-destructive and can be described as commensal behaviour. Commonly found compounds seemed to be involved in insect attraction since root exudates from different plants were all attractive. Moreover, chemical analysis allowed us to identify a certain number of commonly found, highly water-soluble, low-molecular-weight compounds, several of which (glycerol, uracil, thymine, uridine, thymidine were able to induce attraction when tested individually but at concentrations substantially higher than those found in nature. However, our principal findings demonstrated that these compounds appeared to act synergistically, since a mixture of these five compounds attracted larvae at natural concentrations (0.7 nM glycerol, <0.5 nM uracil, 0.6 nM thymine, 2.8 nM uridine, 86 nM thymidine, much lower than those found for each compound tested individually. These results provide strong evidence that a mixture of polyols (glycerol, pyrimidines (uracil, thymine, and nucleosides (uridine, thymidine functions as an efficient attractive signal in nature for Coquillettidia larvae. We therefore show for the first time, that such commonly found compounds may play an important role in plant-insect relationships in aquatic eco-systems.

  2. Complex bounds for multimodal maps: bounded combinatorics

    OpenAIRE

    Smania, Daniel

    2000-01-01

    We proved the so called complex bounds for multimodal, infinitely renormalizable analytic maps with bounded combinatorics: deep renormalizations have polynomial-like extensions with definite modulus. The complex bounds is the first step to extend the renormalization theory of unimodal maps to multimodal maps.

  3. Systemic structural modular generalization of the crystallography of bound water applied to study the mechanisms of processes in biosystems at the atomic and molecular level

    International Nuclear Information System (INIS)

    The main reasons of the modern scientific revolution, one of the consequences of which are nanotechnologies and the development of interdisciplinary overall natural science (which can build potentially possible atomic structures and study the mechanisms of the processes occurring in them), are considered. The unifying role of crystallography in the accumulation of interdisciplinary knowledge is demonstrated. This generalization of crystallography requires the introduction of a new concept: a module which reflects the universal condition for stability of all real and potential and equilibrium and nonequilibrium structures of matter (their connectivity). A modular generalization of crystallography covers all forms of solids, including the structure of bound water (a system-forming matrix for the self-organization and morphogenesis of hierarchical biosystems which determines the metric selection of all other structural components of these systems). A dynamic model of the water surface layer, which serves as a matrix in the formation of Langmuir monolayers and plays a key role in the occurrence of life on the Earth, is developed.

  4. Dynamics of water around the complex structures formed between the KH domains of far upstream element binding protein and single-stranded DNA molecules

    International Nuclear Information System (INIS)

    Single-stranded DNA (ss-DNA) binding proteins specifically bind to the single-stranded regions of the DNA and protect it from premature annealing, thereby stabilizing the DNA structure. We have carried out atomistic molecular dynamics simulations of the aqueous solutions of two DNA binding K homology (KH) domains (KH3 and KH4) of the far upstream element binding protein complexed with two short ss-DNA segments. Attempts have been made to explore the influence of the formation of such complex structures on the microscopic dynamics and hydrogen bond properties of the interfacial water molecules. It is found that the water molecules involved in bridging the ss-DNA segments and the protein domains form a highly constrained thin layer with extremely retarded mobility. These water molecules play important roles in freezing the conformational oscillations of the ss-DNA oligomers and thereby forming rigid complex structures. Further, it is demonstrated that the effect of complexation on the slow long-time relaxations of hydrogen bonds at the interface is correlated with hindered motions of the surrounding water molecules. Importantly, it is observed that the highly restricted motions of the water molecules bridging the protein and the DNA components in the complexed forms originate from more frequent hydrogen bond reformations

  5. Water and oxygen induced degradation of small molecule organic solar cells

    DEFF Research Database (Denmark)

    Hermenau, Martin; Riede, Moritz; Leo, Karl;

    2011-01-01

    ,4′-diamine p-doped with C60F36 (MeO-TPD:C60F36), which acted as hole transporting layer. Indium-tin-oxide (ITO) and aluminum served as hole and electron collecting electrode, respectively. Time-of-flight secondary ion mass spectrometry (TOF-SIMS) and X-ray photoelectron spectroscopy (XPS) in conjunction...... by the donor material zinc-phthalocyanine (ZnPc) and the acceptor material Buckminsterfullerene (C60) followed by 30 nm C60 for additional absorption. The active layers are sandwiched between 6 nm 4,7-diphenyl-1,10-phenanthroline (Bphen) and 30 nm N,N′-diphenyl-N,N′-bis(3-methylphenyl)-[1,1′-biphenyl]-4...... of aluminum oxide at the BPhen/Al interface, and diffusion of water into the ZnPc:C60 layer where ZnPc becomes oxidized. Finally, diffusion from the electrodes was found to have no or a negligible effect on the device lifetime....

  6. Mitigation of organically bound sulphate from water treatment plants at Bruce NGS and impact on steam generator secondary side chemistry control

    International Nuclear Information System (INIS)

    Bruce Power is the source of more than 20 per cent of Ontario's electricity and currently operates six reactor units at the Bruce Nuclear Generating Station A (two units) and B (four units) stations located on Lake Huron. This paper discusses the challenges faced and operating experience (OPEX) gained in meeting WANO 1.0 chemistry performance objectives for steam generator secondary side chemistry control, particularly with control of steam generator sulphates. A detailed sampling and analysis program conducted as part of this study concluded that a major contributor to steam generator (SG) elevated sulphates is Organically Bound Sulphate (OBS) in Water Treatment Plants (WTP) effluent. The Bruce A and B WTPs consist of clarification with downstream sand and carbon filtration for Lake Water pre-treatment, which are followed by conventional Ion Exchange (IX) demineralization. Samples taken from various locations in the process stream were analyzed for a variety of parameters including both organic bound and inorganic forms of sulphate. The results are inconclusive with respect to finding the definitive source of OBS. This is primarily due to the condition that the OBS in the samples, which are in relatively low levels, are masked during chemical analysis by the considerably higher inorganic sulphate background. Additionally, it was also determined that on-line Total Organic Carbon (TOC) levels at different WTP locations did not always correlate well with OBS levels in the effluent, such that TOC could not be effectively used as a control parameter to improve OBS performance of the WTP operation. Improvement efforts at both plants focused on a number of areas including optimization of clarifier operation, replacement of IX resins, addition of downstream mobile polishing trailers, testing of new resins and adsorbents, pilot-scale testing with a Reverse Osmosis (RO) rig, review of resin regeneration and backwashing practices, and operating procedure improvements

  7. The effect of excitation and preparation pulses on nonslice selective 2D UTE bicomponent analysis of bound and free water in cortical bone at 3T

    International Nuclear Information System (INIS)

    Purpose: The purpose of this study was to investigate the effect of excitation, fat saturation, long T2 saturation, and adiabatic inversion pulses on ultrashort echo time (UTE) imaging with bicomponent analysis of bound and free water in cortical bone for potential applications in osteoporosis. Methods: Six bovine cortical bones and six human tibial midshaft samples were harvested for this study. Each bone sample was imaged with eight sequences using 2D UTE imaging at 3T with half and hard excitation pulses, without and with fat saturation, long T2 saturation, and adiabatic inversion recovery (IR) preparation pulses. Single- and bicomponent signal models were utilized to calculate the T2*s and/or relative fractions of short and long T2*s. Results: For all bone samples UTE T2* signal decay showed bicomponent behavior. A higher short T2* fraction was observed on UTE images with hard pulse excitation compared with half pulse excitation (75.6% vs 68.8% in bovine bone, 79.9% vs 73.2% in human bone). Fat saturation pulses slightly reduced the short T2* fraction relative to regular UTE sequences (5.0% and 2.0% reduction, respectively, with half and hard excitation pulses for bovine bone, 6.3% and 8.2% reduction, respectively, with half and hard excitation pulses for human bone). Long T2 saturation pulses significantly reduced the long T2* fraction relative to regular UTE sequence (18.9% and 17.2% reduction, respectively, with half and hard excitation pulses for bovine bone, 26.4% and 27.7% reduction, respectively, with half and hard excitation pulses for human bone). With IR-UTE preparation the long T2* components were significantly reduced relative to regular UTE sequence (75.3% and 66.4% reduction, respectively, with half and hard excitation pulses for bovine bone, 87.7% and 90.3% reduction, respectively, with half and hard excitation pulses for human bone). Conclusions: Bound and free water T2*s and relative fractions can be assessed using UTE bicomponent analysis

  8. The effect of excitation and preparation pulses on nonslice selective 2D UTE bicomponent analysis of bound and free water in cortical bone at 3T

    Energy Technology Data Exchange (ETDEWEB)

    Li, Shihong [Department of Radiology, University of California, San Diego, California 92103-8226 (United States); Department of Radiology, Hua Dong Hospital, Fudan University, Shanghai 200040 (China); Yancheng Medical College, Jiangsu (China); The First People' s Hospital of Yancheng City, Jiangsu 224005 (China); Chang, Eric Y.; Chung, Christine B. [VA San Diego Healthcare System, San Diego, California 92161 and Department of Radiology, University of California, San Diego, California 92103-8226 (United States); Bae, Won C.; Du, Jiang, E-mail: jiangdu@ucsd.edu [Department of Radiology, University of California, San Diego, California 92103-8226 (United States); Hua, Yanqing [Department of Radiology, Hua Dong Hospital, Fudan University, Shanghai 200040 (China); Zhou, Yi [The First People' s Hospital of Yancheng City, Jiangsu 224005 (China)

    2014-02-15

    Purpose: The purpose of this study was to investigate the effect of excitation, fat saturation, long T2 saturation, and adiabatic inversion pulses on ultrashort echo time (UTE) imaging with bicomponent analysis of bound and free water in cortical bone for potential applications in osteoporosis. Methods: Six bovine cortical bones and six human tibial midshaft samples were harvested for this study. Each bone sample was imaged with eight sequences using 2D UTE imaging at 3T with half and hard excitation pulses, without and with fat saturation, long T2 saturation, and adiabatic inversion recovery (IR) preparation pulses. Single- and bicomponent signal models were utilized to calculate the T2{sup *}s and/or relative fractions of short and long T2{sup *}s. Results: For all bone samples UTE T2{sup *} signal decay showed bicomponent behavior. A higher short T2{sup *} fraction was observed on UTE images with hard pulse excitation compared with half pulse excitation (75.6% vs 68.8% in bovine bone, 79.9% vs 73.2% in human bone). Fat saturation pulses slightly reduced the short T2{sup *} fraction relative to regular UTE sequences (5.0% and 2.0% reduction, respectively, with half and hard excitation pulses for bovine bone, 6.3% and 8.2% reduction, respectively, with half and hard excitation pulses for human bone). Long T2 saturation pulses significantly reduced the long T2{sup *} fraction relative to regular UTE sequence (18.9% and 17.2% reduction, respectively, with half and hard excitation pulses for bovine bone, 26.4% and 27.7% reduction, respectively, with half and hard excitation pulses for human bone). With IR-UTE preparation the long T2{sup *} components were significantly reduced relative to regular UTE sequence (75.3% and 66.4% reduction, respectively, with half and hard excitation pulses for bovine bone, 87.7% and 90.3% reduction, respectively, with half and hard excitation pulses for human bone). Conclusions: Bound and free water T2{sup *}s and relative fractions can

  9. Specific Na+ and K+ Cation Effects on the Interfacial Water Molecules at the Air/Aqueous Salt Solution Interfaces Probed with Non-resonant Second Harmonic Generation (SHG)

    OpenAIRE

    Bian, Hong-tao; Feng, Ran-Ran; Guo, Yuan; Wang, Hong-fei

    2008-01-01

    Here we report the polarization dependent non-resonant second harmonic generation (SHG) measurement of the interfacial water molecules at the aqueous solution of the following salts: NaF, NaCl, NaBr, KF, KCl, and KBr. Through quantitative polarization analysis of the SHG data,the orientational parameter D value and the relative surface density of the interfacial water molecules at these aqueous solution surfaces were determined. From these results we found that addition of each of the six sal...

  10. Chemical interaction of water molecules with framework Al in acid zeolites: a periodic ab initio study on H-clinoptilolite.

    Science.gov (United States)

    Valdiviés-Cruz, Karell; Lam, Anabel; Zicovich-Wilson, Claudio M

    2015-09-28

    Periodic quantum-chemistry methods as implemented in the CRYSTAL14 code were considered to analyse the interaction of acid clinoptilolite with water. Initially adsorbed molecules hydrolyse the Al-O bonds, giving rise to defective dealuminated materials. A suitable and representative periodic model of the partially disordered hydrated H-zeolite is the primitive cell (18 T sites) of a decahydrated trialuminated structure of HEU topology. The water distribution inside the material cavities was initially investigated. The model considered for further dealumination was the most stable one from those generated through a combined force field Monte Carlo and ab initio optimization strategy. Optimizations and energy estimations were made at the hybrid DFT level of theory (PBE0 functional) with an atomic basis set of VDZP quality. The energetics of the different pathways involved in the dealumination process was addressed by considering the Gibbs free energy with thermal and zero-point corrections through phonon analysis. It arises that hydrated models exhibit protonated water clusters stabilized by different kinds of H-bonds. The first Al extraction is slightly more energetically favourable from T3 than T2 sites, but at the same time the latter is more probable owing to its larger Al population. However, concerning the second dealumination step, it is more favourable removing the Al atom from both remaining sites after a starting abstraction from T2 rather than T3. These facts determine that the most probable overall pathways go through a first Al removal from T2. The agreement with experimental results is discussed. PMID:26299763

  11. Construction of diverse supramolecular assemblies of dimetal subunits differing in coordinated water molecules via strong hydrogen bonding interactions: Synthesis, crystal structures and spectroscopic properties

    Indian Academy of Sciences (India)

    Sadhika Khullar; Sanjay K Mandal

    2014-09-01

    Three new supramolecular assemblies (constructed through strong hydrogen bonding) of [Co2(bpta)2(adc)(H2O)4](ClO4)2.2H2O (1), [Cu2(bpta)2(fum)(H2O)2](ClO4)2 (2) and [Cu2(bpta)2(tdc)(H2O) (ClO4)](ClO4).3H2O (3), which are synthesised by one pot self-assembly of the metal salt, bpta ligand and the corresponding dicarboxylate under the same reaction conditions, are reported (where adc = acetylene dicarboxylate, fum = fumarate, tdc = 2,5-thiophenedicarboxylate and bpta = N,N'-bis(2-pyridylmethyl)-tertbutylamine). These compounds have varying degrees of coordinatedwater molecules per dimetal subunits (four for 1, two for 2 and one for 3, respectively). Furthermore, the orientation of the coordinated water molecules in 1 and 2, with respect to the mono (carboxylato)-bridged dimetal subunit, is different (cis and trans, respectively). On the other hand, there is a coordinated perchlorate ion in 3 making the two metal centers inequivalent. Unlike 1 and 3, there are no lattice water molecules in 2. This difference in the dimetal subunit in 1-3 and the presence or absence of the lattice water molecules are the keys to forming the diverse supramolecular assemblies. In 1 and 3, the involvement of lattice water molecules in the construction of such assemblies is distinctly different. In case of 2, the formation of supramolecular assembly depends on the coordinated water molecule (trans to each other) and thus a ladder shaped supramolecular assembly is the result. The strength of hydrogen bonding observed in the networks of 1-3 is indicated in the O…O distances (2.596 Å to 3.160 Å) and the OH…O angles 124° to 176°. All are characterised by elemental analysis, FTIR spectroscopy and single crystal X-ray diffraction studies.

  12. A new model for exchange of deuterium in oxide ceramics for protium in light water molecule at room temperature

    International Nuclear Information System (INIS)

    For exchange of deuterium (D) in oxide ceramics for protium (H) in light water molecule at room temperature is proposed the one way diffusion model: absorption of proton and adsorption of OH- due to dissociation of H2O at the surface, diffusion of proton, release of deuteron in trapping site due to local molecular recombination with proton and the subsequent trapping of another proton into the vacant trapping site. The one way diffusion model has been formulated in form of the mass balance equations for free proton and both proton and deuteron trapped in trapping sites which include the rate constants of chemical reactions for proton described above. The solutions of the concentrations of deuterons retained and protons uptaken in the specimen have been fitted to the experimental data and the rate constants of the chemical reactions relevant to the D-H exchange have been determined. The rate constants of the chemical reactions are discussed. Moreover, potential applications of the one way diffusion model are discussed. (author)

  13. Circuit lower bounds in bounded arithmetics

    Czech Academy of Sciences Publication Activity Database

    Pich, Ján

    2015-01-01

    Roč. 166, č. 1 (2015), s. 29-45. ISSN 0168-0072 R&D Projects: GA AV ČR IAA100190902 Keywords : bounded arithmetic * circuit lower bounds Subject RIV: BA - General Mathematics Impact factor: 0.548, year: 2014 http://www.sciencedirect.com/science/article/pii/S0168007214000888

  14. Effects of protonation state of Asp181 and position of active site water molecules on the conformation of PTP1B.

    Science.gov (United States)

    Ozcan, Ahmet; Olmez, Elif Ozkirimli; Alakent, Burak

    2013-05-01

    In protein tyrosine phosphatase 1B (PTP1B), the flexible WPD loop adopts a closed conformation (WPDclosed ) in the active state of PTP1B, bringing the catalytic Asp181 close to the active site pocket, while WPD loop is in an open conformation (WPDopen ) in the inactive state. Previous studies showed that Asp181 may be protonated at physiological pH, and ordered water molecules exist in the active site. In the current study, molecular dynamics simulations are employed at different Asp181 protonation states and initial positions of active site water molecules, and compared with the existing crystallographic data of PTP1B. In WPDclosed conformation, the active site is found to maintain its conformation only in the protonated state of Asp181 in both free and liganded states, while Asp181 is likely to be deprotonated in WPDopen conformation. When the active site water molecule network that is a part of the free WPDclosed crystal structure is disrupted, intermediate WPD loop conformations, similar to that in the PTPRR crystal structure, are sampled in the MD simulations. In liganded PTP1B, one active site water molecule is found to be important for facilitating the orientation of Cys215 and the phosphate ion, thus may play a role in the reaction. In conclusion, conformational stability of WPD loop, and possibly catalytic activity of PTP1B, is significantly affected by the protonation state of Asp181 and position of active site water molecules, showing that these aspects should be taken into consideration both in MD simulations and inhibitor design. PMID:23239271

  15. Microassay for measurement of binding of radiolabelled ligands to cell surface molecules.

    Science.gov (United States)

    Woof, J M; Burton, D R

    1988-07-22

    An improved technique for measuring the binding of radiolabelled ligands to cell surface molecules has been developed by modification of a procedure using centrifugation through a water-immiscible oil to separate free and cell-bound ligand. It maximises the percentage of ligand bound since cell-bound and free ligand can be separated easily and reproducibly even when very small reaction volumes are used. This permits low levels of ligand radiolabelling and relatively low numbers of cells to be used. PMID:2840465

  16. A Causal Entropy Bound

    CERN Document Server

    Brustein, Ram

    2000-01-01

    The identification of a causal-connection scale motivates us to propose a new covariant bound on entropy within a generic space-like region. This "causal entropy bound", scaling as the square root of EV, and thus lying around the geometric mean of Bekenstein's S/ER and holographic S/A bounds, is checked in various "critical" situations. In the case of limited gravity, Bekenstein's bound is the strongest while naive holography is the weakest. In the case of strong gravity, our bound and Bousso's holographic bound are stronger than Bekenstein's, while naive holography is too tight, and hence typically wrong.

  17. L-Alanyl-L-alanine in the zwitterionic state: structures determined in the presence of explicit water molecules and with continuum models using density functional theory

    International Nuclear Information System (INIS)

    The structures and relative energies for L-alanyl-L-alanine (LALA) in the presence of explicit water molecules have been determined by using the density functional theory (DFT) Becke3-Lee-Yang-Parr functional and the 6-31G* basis set (B3LYP/6-31G*). In aqueous solution the dominant state of LALA is the zwitterionic form, while its neutral form is dominant in vacuo. Attempts to locate or determine a gas-phase zwitterionic species failed. That is, on the B3LYP/6-31G* potential energy surface, there is no barrier to proton transfer from the positively charged ammonium group to the negatively charged carboxylate group, or from the ammonium group to the adjacent carbonyl oxygen and from the amide nitrogen to the carboxylate group. To stabilize the zwitterion, we modelled the system by adding explicit water molecules and by placing the zwitterion within a sphere surrounded by a medium with a dielectric constant of 78.5, that is, within the Onsager continuum model, where the recommended cavity radius is obtained from a solute volume calculation. The zwitterionic species is only stable in the presence of water at the B3LYP/6-31G* level. This makes it imperative to include water molecules to model the zwitterionic species of LALA, peptides and amino acids at the B3LYP/6-31G* level. Finally, the zwitterionic structure stabilized by explicit water molecules has also been modelled within the Onsager theory. Here the Onsager model represents the effects due to the bulk water and the explicit water molecules stand for the effect due to direct H-bonding between the zwitterion and the solvent, that is, the first solvation shell. We used molecular dynamics simulations utilizing the CHARMm force field to produce structural input for the subsequent quantum-mechanical simulations. The structures determined using various methods to model the LALA zwitterionic form in aqueous solution were compared. We were able to find additional stable structures for LALA by adding water molecules and

  18. Snapshot of the equilibrium dynamics of a drug bound to HIV-1 reverse transcriptase

    OpenAIRE

    Kuroda, Daniel G.; Bauman, Joseph D.; Challa, J. Reddy; Patel, Disha; Troxler, Thomas; Das, Kalyan; Arnold, Eddy; Hochstrasser, Robin M.

    2013-01-01

    The anti-AIDS drug rilpivirine undergoes conformational changes to bind HIV-1 reverse transcriptase and retain potency against drug-resistance mutations. Our discovery that water molecules play an essential role in the drug binding is reported. Femtosecond experiments and theory expose molecular level dynamics of rilpivirine bound to HIV-1 reverse transcriptase. The two nitrile substituents (-CN), one on each arm of the drug, have vibrational spectra consistent with their protein environments...

  19. Clusters containing open-shell molecules. III. Quantum five-dimensional/two-surface bound-state calculations on ArnOH van der Waals clusters (X2Π, n=4 to 12).

    OpenAIRE

    Xu, M Z; Bačić, Z.; Hutson, J. M.

    2002-01-01

    This paper presents a theoretical study of the bound states of the open-shell OH radical in its ground electronic state(X2Π) interacting with n Ar atoms, for n from 4 to 12. After freezing the geometry of the Arn cage or subunit at the equilibrium structure (preceding paper), we carry out nonadiabatic five-dimensional quantum dynamics calculations on two coupled potential energy surfaces, using an extension of the method previously applied to closed-shell ArnHFclusters [J. Chem. Phys. 103, 18...

  20. Photoinduced conversion of carbon dioxide and water molecules to methanol on the surface of molybdenum oxide MoO x ( x < 2)

    Science.gov (United States)

    Silaev, I. V.; Khubezhov, S. A.; Ramonova, A. G.; Grigorkina, G. S.; Kaloeva, A. G.; Demeev, Z. S.; Bliev, A. P.; Sekiba, D.; Ogura, S.; Fukutani, K.; Magkoev, T. T.

    2016-03-01

    X-ray and UV photoelectron spectroscopic data are used to demonstrate that, when pulsed laser light with a photon energy of 6.4 eV acts on the surface of nonstoichiometric molybdenum oxide MoO x ( x < 2), methanol is effectively formed from adsorbed molecules of carbon dioxide and water. The processes in which CO2 and H2O molecules are adsorbed on substrate surface defects and their bonds are activated, enhanced under the effect of photons, should be regarded as the key factors.

  1. Scattering by bound nucleons

    International Nuclear Information System (INIS)

    Scattering of a particle by bound nucleons is discussed. Effects of nucleons that are bound in a nucleus are taken as a structure function. The way how to calculate the structure function is given. (author)

  2. The accommodation coefficient of water molecules on ice-cirrus cloud studies at the AIDA simulation chamber

    Directory of Open Access Journals (Sweden)

    J. Skrotzki

    2012-09-01

    Full Text Available Cirrus clouds and their impact on the Earth's radiative budget are subjects of current research. The processes governing the growth of cirrus ice particles are central to the radiative properties of cirrus clouds. At temperatures relevant to cirrus clouds, the growth of ice crystals smaller than a few microns in size is strongly influenced by the accommodation coefficient of water molecules on ice, αice, making this parameter relevant for cirrus cloud modeling. However, the experimentally determined magnitude of αice for cirrus temperatures is afflicted with uncertainties of almost three orders of magnitude and values for αice derived from cirrus cloud data lack significance so far. This has motivated dedicated experiments at the cloud chamber AIDA (Aerosol Interactions and Dynamics in the Atmosphere to determine αice in the cirrus-relevant temperature interval between 190 K and 235 K under realistic cirrus ice particle growth conditions. The experimental data sets have been evaluated independently with two model approaches: the first relying on the newly developed model SIGMA (Simple Ice Growth Model for determining Alpha, the second one on an established model, ACPIM (Aerosol-Cloud-Precipitation Interaction Model. Within both approaches, a careful uncertainty analysis of the obtained αice values has been carried out for each AIDA experiment. The results show no significant dependence of αice on temperature between 190 K and 235 K. In addition, we find no evidence for a dependence of αice on ice particle size or on water vapor supersaturation for ice particles smaller than 20 μm and supersaturations of up to 70%. The temperature averaged and combined result from both models is αice=0.6−0.4+0.4 which implies that αice may only exert a minor impact on cirrus clouds and their characteristics when compared to the

  3. The accommodation coefficient of water molecules on ice – cirrus cloud studies at the AIDA simulation chamber

    Directory of Open Access Journals (Sweden)

    J. Skrotzki

    2013-04-01

    Full Text Available Cirrus clouds and their impact on the Earth's radiative budget are subjects of current research. The processes governing the growth of cirrus ice particles are central to the radiative properties of cirrus clouds. At temperatures relevant to cirrus clouds, the growth of ice crystals smaller than a few microns in size is strongly influenced by the accommodation coefficient of water molecules on ice, αice, making this parameter relevant for cirrus cloud modeling. However, the experimentally determined magnitude of αice for cirrus temperatures is afflicted with uncertainties of almost three orders of magnitude, and values for αice derived from cirrus cloud data lack significance so far. This has motivated dedicated experiments at the cloud chamber AIDA (Aerosol Interactions and Dynamics in the Atmosphere to determine αice in the cirrus-relevant temperature interval between 190 K and 235 K under realistic cirrus ice particle growth conditions. The experimental data sets have been evaluated independently with two model approaches: the first relying on the newly developed model SIGMA (Simple Ice Growth Model for determining Alpha, the second one on an established model, ACPIM (Aerosol-Cloud-Precipitation Interaction Model. Within both approaches a careful uncertainty analysis of the obtained αice values has been carried out for each AIDA experiment. The results show no significant dependence of αice on temperature between 190 K and 235 K. In addition, we find no evidence for a dependence of αice on ice particle size or on water vapor supersaturation for ice particles smaller than 20 μm and supersaturations of up to 70%. The temperature-averaged and combined result from both models is αice = 0.7−0.5+0.3, which implies that αice may only exert a minor impact on cirrus clouds and their characteristics when compared to the assumption of αice =1. Impact on prior calculations of cirrus cloud properties, e.g., in climate models, with

  4. Inorganics in Organics: Tracking down the Intrinsic Equilibriums between Organic Molecules and Trace Elements in Oceanic Waters

    Science.gov (United States)

    Lechtenfeld, O. J.; Koch, B. P.; Kattner, G.

    2010-12-01

    Recent developments in analytical instrumentation enable to describe biogeochemical processes in oceanic waters on a molecular level. This is the prerequisite to integrate biological and geochemical parameters and to develop chemical cycles on a global perspective. The state-of-the-art Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) applications for dissolved organic matter (DOM) focus mainly on carbon, hydrogen, oxygen and nitrogen isotopes. Implementation of sulfur and especially phosphorus in the molecular formula assignment has been questionable because of ambiguous calculated elemental formulas. On the other hand, many compounds bearing these elements are well known to occur in the dissolved state as part of the permanent recycling processes (e.g. phospholipids, phosphonates) but analytics of dissolved organic phosphorus (DOP) and sulfur (DOS) are often hampered by the large inorganic P and S pools. Even less is known about complexation characteristics of the DOM moieties. Although electrochemical methods provide some information about trace metal speciation, the high amount of organic molecules and its insufficient description as chemical functional classes prevent the assignment of trace metals to ligand classes. Nevertheless, it is undoubtful that a varying but extensive amount of transition metals is bond in form of organic complexes. Hyphenation of reversed phase high performance liquid chromatography (RP-HPLC) with high resolution inductively coupled plasma mass spectrometry (HR-ICP-MS) is a valuable tool to study these metal-organic interactions in a qualitative and quantitative approach. We established a desolvation method that allows direct transfer of high organic solvent loads into the plasma. Thus, in combination with internal standardization and external calibration, the investigation of a broad polarity scale was possible. This approach overcomes previous restrictions to non-organic solvent separation techniques like size

  5. Coulomb bound states of strongly interacting photons

    CERN Document Server

    Maghrebi, M F; Bienias, P; Choi, S; Martin, I; Firstenberg, O; Lukin, M D; Büchler, H P; Gorshkov, A V

    2015-01-01

    We show that two photons coupled to Rydberg states via electromagnetically induced transparency can interact via an effective Coulomb potential. This interaction gives rise to a continuum of two-body bound states. Within the continuum, metastable bound states are distinguished in analogy with quasi-bound states tunneling through a potential barrier. We find multiple branches of metastable bound states whose energy spectrum is governed by the Coulomb potential, thus obtaining a photonic analogue of the hydrogen atom. Under certain conditions, the wavefunction resembles that of a diatomic molecule in which the two polaritons are separated by a finite "bond length." These states propagate with a negative group velocity in the medium, allowing for a simple preparation and detection scheme, before they slowly decay to pairs of bound Rydberg atoms.

  6. Variance bounding Markov chains

    OpenAIRE

    Roberts, Gareth O.; Jeffrey S. Rosenthal

    2008-01-01

    We introduce a new property of Markov chains, called variance bounding. We prove that, for reversible chains at least, variance bounding is weaker than, but closely related to, geometric ergodicity. Furthermore, variance bounding is equivalent to the existence of usual central limit theorems for all L2 functionals. Also, variance bounding (unlike geometric ergodicity) is preserved under the Peskun order. We close with some applications to Metropolis–Hastings algorithms.

  7. Bound states and the Bekenstein bound

    CERN Document Server

    Bousso, R

    2004-01-01

    We explore the validity of the generalized Bekenstein bound, S <= pi M a. We define the entropy S as the logarithm of the number of states which have energy eigenvalue below M and are localized to a flat space region of width a. If boundary conditions that localize field modes are imposed by fiat, then the bound encounters well-known difficulties with negative Casimir energy and large species number, as well as novel problems arising only in the generalized form. In realistic systems, however, finite-size effects contribute additional energy. We study two different models for estimating such contributions. Our analysis suggests that the bound is both valid and nontrivial if interactions are properly included, so that the entropy S counts the bound states of interacting fields.

  8. Water exchange at a hydrated platinum electrode is rare and collective

    CERN Document Server

    Limmer, David T; Madden, Paul A; Chandler, David

    2015-01-01

    We use molecular dynamics simulations to study the exchange kinetics of water molecules at a model metal electrode surface -- exchange between water molecules in the bulk liquid and water molecules bound to the metal. This process is a rare event, with a mean residence time of a bound water of about 40 ns for the model we consider. With analysis borrowed from the techniques of rare-event sampling, we show how this exchange or desorption is controlled by (1) reorganization of the hydrogen bond network within the adlayer of bound water molecules, and by (2) interfacial density fluctuations of the bulk liquid adjacent to the adlayer. We define collective coordinates that describe the desorption mechanism. Spatial and temporal correlations associated with a single event extend over nanometers and tens of picoseconds.

  9. Suppressing the fragmentation of fragile molecules in helium nanodroplets by co-embedding with water: Possible role of the electric dipole moment

    CERN Document Server

    Ren, Yanfei

    2007-01-01

    When fragile molecules such as glycine, polyglicine, alkanes, and alkanethiols are embedded in liquid helium nanodroplets, electron-impact ionization of the beam leads to fragmentation which is as extensive as that of isolated gas-phase molecules. However, it turns out that if a few molecules of water are co-embedded with the peptide and alkane chains, their fragmentation is drastically reduced or completely eliminated. On the other hand, the fragmentation of alkanethiols remains unaffected. On the basis of these observations, it is proposed that the fragmentation "buffering" effect may correlate with the magnitude of the impurity's electric dipole moment, which steers the migration of the ionizing He^+ hole in the droplet.

  10. An FTIR study on the catalytic effect of water molecules on the reaction of CO successive hydrogenation at 3 and 10K

    Science.gov (United States)

    Pirim, C.; Krim, L.

    2011-05-01

    The ubiquitous presence of water and the relative high abundance of H2, H and CO molecules in the interstellar medium motivated numerous studies on their potential interaction. The reaction of successive hydrogenation of CO is of large interest in astrochemistry because of its implication in the formation of formaldehyde and methanol in interstellar grains and in comets. The catalytic effect of water on the successive hydrogenation of CO has been investigated by two methods. The first is the hydrogenation of a CO/H2O surface. The second is a co-injection of (CO/H2O) mixtures and H atoms. Both methods have been performed at 3 and 10 K. When the hydrogenation of a CO surface is performed at 3 K, no products are observed. In fact, the presence of solid hydrogen screens the hydrogenation process. However, when performed at 10 K, the experiment shows that water molecules increase the concentration of the H2CO and CH3OH species. At 3 and 10K, [(CO/H2O)+H] co-depositions confirm a subtantial impact on by-products formation. We show that water molecules increase the probability of reactive to encounter H atoms either physically, or chemically, by raising the number of chemical pathways. A coordinated theoretical study of the possible chemical pathways is currently under way.

  11. Changes in the hydrogen-bonding strength of internal water molecules and cysteine residues in the conductive state of channelrhodopsin-1

    Science.gov (United States)

    Lórenz-Fonfría, Víctor A.; Muders, Vera; Schlesinger, Ramona; Heberle, Joachim

    2014-12-01

    Water plays an essential role in the structure and function of proteins, particularly in the less understood class of membrane proteins. As the first of its kind, channelrhodopsin is a light-gated cation channel and paved the way for the new and vibrant field of optogenetics, where nerve cells are activated by light. Still, the molecular mechanism of channelrhodopsin is not understood. Here, we applied time-resolved FT-IR difference spectroscopy to channelrhodopsin-1 from Chlamydomonas augustae. It is shown that the (conductive) P2380 intermediate decays with τ ≈ 40 ms and 200 ms after pulsed excitation. The vibrational changes between the closed and the conductive states were analyzed in the X-H stretching region (X = O, S, N), comprising vibrational changes of water molecules, sulfhydryl groups of cysteine side chains and changes of the amide A of the protein backbone. The O-H stretching vibrations of "dangling" water molecules were detected in two different states of the protein using H218O exchange. Uncoupling experiments with a 1:1 mixture of H2O:D2O provided the natural uncoupled frequencies of the four O-H (and O-D) stretches of these water molecules, each with a very weakly hydrogen-bonded O-H group (3639 and 3628 cm-1) and with the other O-H group medium (3440 cm-1) to moderately strongly (3300 cm-1) hydrogen-bonded. Changes in amide A and thiol vibrations report on global and local changes, respectively, associated with the formation of the conductive state. Future studies will aim at assigning the respective cysteine group(s) and at localizing the "dangling" water molecules within the protein, providing a better understanding of their functional relevance in CaChR1.

  12. Ultracold polar molecules near quantum degeneracy

    OpenAIRE

    Ospelkaus, S.; Ni, K.-K.; de Miranda, M. H. G.; Neyenhuis, B.; Wang, D; Kotochigova, S.; Julienne, P. S.; Jin, D. S.; J. Ye

    2008-01-01

    We report the creation and characterization of a near quantum-degenerate gas of polar $^{40}$K-$^{87}$Rb molecules in their absolute rovibrational ground state. Starting from weakly bound heteronuclear KRb Feshbach molecules, we implement precise control of the molecular electronic, vibrational, and rotational degrees of freedom with phase-coherent laser fields. In particular, we coherently transfer these weakly bound molecules across a 125 THz frequency gap in a single step into the absolute...

  13. A Causal Entropy Bound

    OpenAIRE

    Brustein, R; Veneziano, G

    1999-01-01

    The identification of a causal-connection scale motivates us to propose a new covariant bound on entropy within a generic space-like region. This "causal entropy bound", scaling as the square root of EV, and thus lying around the geometric mean of Bekenstein's S/ER and holographic S/A bounds, is checked in various "critical" situations. In the case of limited gravity, Bekenstein's bound is the strongest while naive holography is the weakest. In the case of strong gravity, our bound and Bousso...

  14. A matrix lower bound

    Energy Technology Data Exchange (ETDEWEB)

    Grcar, Joseph F.

    2002-02-04

    A matrix lower bound is defined that generalizes ideas apparently due to S. Banach and J. von Neumann. The matrix lower bound has a natural interpretation in functional analysis, and it satisfies many of the properties that von Neumann stated for it in a restricted case. Applications for the matrix lower bound are demonstrated in several areas. In linear algebra, the matrix lower bound of a full rank matrix equals the distance to the set of rank-deficient matrices. In numerical analysis, the ratio of the matrix norm to the matrix lower bound is a condition number for all consistent systems of linear equations. In optimization theory, the matrix lower bound suggests an identity for a class of min-max problems. In real analysis, a recursive construction that depends on the matrix lower bound shows that the level sets of continuously differential functions lie asymptotically near those of their tangents.

  15. Sorption Characteristics of Mixed Molecules of Glutaraldehyde from Water on Mesoporous Acid-Amine Modified Low-Cost Activated Carbon: Mechanism, Isotherm, and Kinetics

    OpenAIRE

    2015-01-01

    The environmental discharge of inefficiently treated waste solutions of the strong biocide glutaraldehyde (GA) from hospitals has potential toxic impact on aquatic organisms. The adsorption characteristics of mixed polarized monomeric and polymeric molecules of GA from water on mesoporous acid-amine modified low-cost activated carbon (AC) were investigated. It was found that the adsorption strongly depended on pH and surface chemistry. In acidic pH, the adsorption mechanism was elaborated to ...

  16. Detection of dynamic water molecules in a microcrystalline sample of the SH3 domain of {alpha}-spectrin by MAS solid-state NMR

    Energy Technology Data Exchange (ETDEWEB)

    Chevelkov, Veniamin [Forschungsinstitut fuer Molekulare Pharmakologie (FMP) (Germany); Faelber, Katja [Max-Delbrueck-Centrum fuer Molekulare Medizin (Germany); Diehl, Anne [Forschungsinstitut fuer Molekulare Pharmakologie (FMP) (Germany); Heinemann, Udo [Max-Delbrueck-Centrum fuer Molekulare Medizin (Germany); Oschkinat, Hartmut; Reif, Bernd [Forschungsinstitut fuer Molekulare Pharmakologie (FMP) (Germany)], E-mail: reif@fmp-berlin.de

    2005-04-15

    Water molecules are a major determinant of protein stability and are important for understanding protein-protein interactions. We present two experiments which allow to measure first the effective T{sub 2} decay rate of individual amide proton, and second the magnetization build-up rates for a selective transfer from H{sub 2}O to H{sup N} using spin diffusion as a mixing element. The experiments are demonstrated for a uniformly {sup 2}H, {sup 15}N labeled sample of a microcrystalline SH3 domain in which exchangeable deuterons were back-substituted with protons. In order to evaluate the NMR experimental data, as X-ray structure of the protein was determined using the same crystallization protocol as for the solid-state NMR sample. The NMR experimental data are correlated with the dipolar couplings calculated from H{sub 2}O-H{sup N} distances which were extracted from the X-ray structure of the protein. We find that the H{sup N}T{sub 2} decay rates and H{sub 2}O-H{sup N} build-up rates are sensitive to distance and dynamics of the detected water molecules with respect to the protein. We show that qualitative information about localization and dynamics of internal water molecules can be obtained in the solid-state by interpretation of the spin dynamics of a reporter amide proton.

  17. Physical Uncertainty Bounds (PUB)

    Energy Technology Data Exchange (ETDEWEB)

    Vaughan, Diane Elizabeth [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Preston, Dean L. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2015-03-19

    This paper introduces and motivates the need for a new methodology for determining upper bounds on the uncertainties in simulations of engineered systems due to limited fidelity in the composite continuum-level physics models needed to simulate the systems. We show that traditional uncertainty quantification methods provide, at best, a lower bound on this uncertainty. We propose to obtain bounds on the simulation uncertainties by first determining bounds on the physical quantities or processes relevant to system performance. By bounding these physics processes, as opposed to carrying out statistical analyses of the parameter sets of specific physics models or simply switching out the available physics models, one can obtain upper bounds on the uncertainties in simulated quantities of interest.

  18. Energy transfer in complexes of water-soluble quantum dots and chlorin e6 molecules in different environments

    Directory of Open Access Journals (Sweden)

    Irina V. Martynenko

    2013-12-01

    Full Text Available The photoexcitation energy transfer is found and investigated in complexes of CdSe/ZnS cationic quantum dots and chlorin e6 molecules formed by covalent bonding and electrostatic interaction in aqueous solution and in porous track membranes. The quantum dots and chlorin e6 molecules form stable complexes that exhibit Förster resonance energy transfer (FRET from quantum dots to chlorin e6 regardless of complex formation conditions. Competitive channels of photoexcitation energy dissipation in the complexes, which hamper the FRET process, were found and discussed.

  19. Asymptotic Entropy Bounds

    CERN Document Server

    Bousso, Raphael

    2016-01-01

    We show that known entropy bounds constrain the information carried off by radiation to null infinity. We consider distant, planar null hypersurfaces in asymptotically flat spacetime. Their focussing and area loss can be computed perturbatively on a Minkowski background, yielding entropy bounds in terms of the energy flux of the outgoing radiation. In the asymptotic limit, we obtain boundary versions of the Quantum Null Energy Condition, of the Generalized Second Law, and of the Quantum Bousso Bound.

  20. Bound soliton fiber laser

    OpenAIRE

    Tang, D. Y.; B. Zhao; Shen, D. Y.; Lu, C.

    2009-01-01

    Experimental study on the soliton dynamics of a passively mode locked fiber ring laser firstly revealed a state of bound soliton operation in the laser, where two solitons bind together tightly with fixed pulse separation. We further report on the properties of the bound-soliton emission of the laser. In particular, we demonstrate both experimentally and numerically that, like the single pulse soliton operation of the laser, the bound soliton emission is another intrinsic feature of the laser.

  1. KETERKAITAN BERBAGAI KONSEP INTERAKSI AIR DALAM PRODUK PANGAN [Interrelation on Water Interaction Concepts in Foods]--Komunikasi Singkat

    Directory of Open Access Journals (Sweden)

    Dede R. Adawiyah

    2012-06-01

    Full Text Available The idea of water interaction with chemicals in the food dry matter or solid was inspired from gas interaction with surface active chemicals, almost a hundred years ago, such as association of gases with active carbon. However, until now the mechanisms and consequences of water molecule associated with chemicals in food solid is still in debate among the food scientists. The concept of water interaction or association with chemicals in the food solid or dry matter was initially introduced as water activity (aw, then in the terminology of “Bound Water”. Water activity concept was further developed by Labuza in 1960s. The concept or idea of glass transition temperature (Tg from Polymers Science discipline was applied to foods in decade of 1980 by Slade & Levine, who denied or negated the earlier concepts of bound water and water activity. In glass transition concept of food products, water functions as a plasticizer related to the textural properties and safety of the products. Knowledge of structure and behaviours of water molecule is required to understand how water interacts or associates with chemicals in food solid. The unique nature of water molecule is a tetrahedral structure with 4 polar angles, which behaves strongly binding or being bound by polar or ionic chemicals in food solid. A number of physicochemical forces act how water molecules interact in complex ways with chemicals in food solid, and the interaction among water molecules in foods. Both types of water interaction lead to the consept of three fractions of bound water as well as to the varities of food characteristics, including preservability and food qualities, either appraisable or unacceptable by consummers. Relationship analyses among various parameter data of associated water in foods such as aw, Me, Tg, and enriched by NMR data, specific weight and specific heat of bound water, indicated that among the different concepts of water interaction in foods were

  2. Temporal and spatial variability of stable isotopes of the water molecule in the Ebro River basin, Spain

    OpenAIRE

    Négrel, Philippe; Petelet Giraud, Emmanuelle; Millot, Romain

    2014-01-01

    International audience Variations in the stable-isotope O and H composition in a catchment's water balance are mainly caused by natural variations in the isotopic composition of rainfall, through the mixing with pre-existing waters and the influence of evaporation. Stable isotopes of water can be considered as conservative and as not being affected by exchanges with soil or rock. Stable isotopes were analysed in the surface waters along the course of the Ebro River, in main tributaries of ...

  3. Coulomb Bound States of Strongly Interacting Photons

    Science.gov (United States)

    Maghrebi, M. F.; Gullans, M. J.; Bienias, P.; Choi, S.; Martin, I.; Firstenberg, O.; Lukin, M. D.; Büchler, H. P.; Gorshkov, A. V.

    2015-09-01

    We show that two photons coupled to Rydberg states via electromagnetically induced transparency can interact via an effective Coulomb potential. This interaction gives rise to a continuum of two-body bound states. Within the continuum, metastable bound states are distinguished in analogy with quasibound states tunneling through a potential barrier. We find multiple branches of metastable bound states whose energy spectrum is governed by the Coulomb potential, thus obtaining a photonic analogue of the hydrogen atom. Under certain conditions, the wave function resembles that of a diatomic molecule in which the two polaritons are separated by a finite "bond length." These states propagate with a negative group velocity in the medium, allowing for a simple preparation and detection scheme, before they slowly decay to pairs of bound Rydberg atoms.

  4. A combined prediction strategy increases identification of peptides bound with high affinity and stability to porcine MHC class I molecules SLA-1*04:01, SLA-2*04:01, and SLA-3*04:01

    DEFF Research Database (Denmark)

    Pedersen, Lasse Eggers; Rasmussen, Michael; Harndahl, Mikkel;

    2016-01-01

    constitute an attractive protocol to select target peptides from the vast pool of viral proteome peptides. We have earlier reported the peptide binding motif of the porcine MHC-I molecules SLA-1*04:01 and SLA-2*04:01, identified by an ELISA affinity-based positional scanning combinatorial peptide library...... (PSCPL) approach. Here, we report the peptide binding motif of SLA-3*04:01 and combine two prediction methods and analysis of both peptide binding affinity and stability of peptide-MHC complexes to improve rational peptide selection. Using a peptide prediction strategy combining PSCPL binding matrices...... and in silico prediction algorithms (NetMHCpan), peptide ligands from a repository of 8900 peptides were predicted for binding to SLA-1*04:01, SLA-2*04:01, and SLA-3*04:01 and validated by affinity and stability assays. From the pool of predicted peptides for SLA-1*04:01, SLA-2*04:01, and SLA-3...

  5. Specific Na+ and K+ Cation Effects on the Interfacial Water Molecules at the Air/Aqueous Salt Solution Interfaces Probed with Non-resonant Second Harmonic Generation (SHG)

    CERN Document Server

    Bian, Hong-tao; Guo, Yuan; Wang, Hong-fei

    2008-01-01

    Here we report the polarization dependent non-resonant second harmonic generation (SHG) measurement of the interfacial water molecules at the aqueous solution of the following salts: NaF, NaCl, NaBr, KF, KCl, and KBr. Through quantitative polarization analysis of the SHG data,the orientational parameter D value and the relative surface density of the interfacial water molecules at these aqueous solution surfaces were determined. From these results we found that addition of each of the six salts caused increase of the thickness of the interfacial water layer at the surfaces to a certain extent. Noticeably, both the cations and the anions contributed to the changes, and the abilities to increase the thickness of the interfacial water layer were in the following order: KBr > NaBr > KCl > NaCl ~ NaF > KF. Since these changes can not be factorized into individual anion and cation contributions, there are possible ion pairing or association effects, especially for the NaF case. We also found that the orientational ...

  6. Active-Site Hydration and Water Diffusion in Cytochrome P450cam: A Highly Dynamic Process

    Energy Technology Data Exchange (ETDEWEB)

    Miao, Yinglong [ORNL; Baudry, Jerome Y [ORNL

    2011-01-01

    Long-timescale molecular dynamics simulations (300 ns) are performed on both the apo- (i.e., camphor-free) and camphor-bound cytochrome P450cam (CYP101). Water diffusion into and out of the protein active site is observed without biased sampling methods. During the course of the molecular dynamics simulation, an average of 6.4 water molecules is observed in the camphor-binding site of the apo form, compared to zero water molecules in the binding site of the substrate-bound form, in agreement with the number of water molecules observed in crystal structures of the same species. However, as many as 12 water molecules can be present at a given time in the camphor-binding region of the active site in the case of apo-P450cam, revealing a highly dynamic process for hydration of the protein active site, with water molecules exchanging rapidly with the bulk solvent. Water molecules are also found to exchange locations frequently inside the active site, preferentially clustering in regions surrounding the water molecules observed in the crystal structure. Potential-of-mean-force calculations identify thermodynamically favored trans-protein pathways for the diffusion of water molecules between the protein active site and the bulk solvent. Binding of camphor in the active site modifies the free-energy landscape of P450cam channels toward favoring the diffusion of water molecules out of the protein active site.

  7. Bounded Gaussian process regression

    DEFF Research Database (Denmark)

    Jensen, Bjørn Sand; Nielsen, Jens Brehm; Larsen, Jan

    2013-01-01

    We extend the Gaussian process (GP) framework for bounded regression by introducing two bounded likelihood functions that model the noise on the dependent variable explicitly. This is fundamentally different from the implicit noise assumption in the previously suggested warped GP framework. We...

  8. Graviton Mass Bounds

    CERN Document Server

    de Rham, Claudia; Tolley, Andrew J; Zhou, Shuang-Yong

    2016-01-01

    Recently, aLIGO has announced the first direct detections of gravitational waves, a direct manifestation of the propagating degrees of freedom of gravity. The detected signals GW150914 and GW151226 have been used to examine the basic properties of these gravitational degrees of freedom, particularly setting an upper bound on their mass. It is timely to review what the mass of these gravitational degrees of freedom means from the theoretical point of view, particularly taking into account the recent developments in constructing consistent massive gravity theories. Apart from the GW150914 mass bound, a few other observational bounds have been established from the effects of the Yukawa potential, modified dispersion relation and fifth force that are all induced when the fundamental gravitational degrees of freedom are massive. We review these different mass bounds and examine how they stand in the wake of recent theoretical developments and how they compare to the bound from GW150914.

  9. Van der Waals interactions in a monosolvated chiral fluorinated molecule: R2PI vibroelectronic spectra of ( R)-1-phenyl-2,2,2-trifluoroethanol clustered with water

    Science.gov (United States)

    Giardini, A.; Rondino, F.; Cattenacci, G.; Paladini, A.; Piccirillo, S.; Satta, M.; Speranza, M.

    2007-02-01

    One colour mass selected resonant two photon ionization R2PI spectra of supersonically expanded ( R)-1-phenyl-2,2,2-trifluoroethanol ( FER) and its complex with water are reported. The excitation spectra are analyzed and discussed on the basis of theoretical predictions at the B3LYP/6-31G ∗∗ level of theory. In the most stable conformer of FER, the OH group establishes an intramolecular hydrogen bond with one of the fluorine atoms of CF 3. In the FER/water complex the formation of a structure in which the water molecule acts as proton acceptor from the OH group and proton donor to the fluorine atom of the CF 3 group is found.

  10. Electron capture by polar molecules and cluster in magnetic field

    International Nuclear Information System (INIS)

    Impact of external magnetic field on formation of a bound electron state with neutral molecular complex, consisting of polar molecules, is considered. It is shown that in case of one polar molecule with dipole moment anti ρ, positioned in the magnetic field, the electron forms the bound state therewith, if anti ρ equals to 0.318D. The polar theory of bound states in magnetic fields is developed for a cluster of polar molecules with the summarized of polar molecules with the summarized dipole moment equal to zero. The electron and cluster bound states are considered. The spectrum of such states is obtained

  11. Dual reorientation relaxation routes of water molecules in oxyanion’s hydration shell: A molecular geometry perspective

    Energy Technology Data Exchange (ETDEWEB)

    Xie, Wen Jun; Yang, Yi Isaac; Gao, Yi Qin, E-mail: gaoyq@pku.edu.cn [Institute of Theoretical and Computational Chemistry, College of Chemistry and Molecular Engineering and Biodynamic Optical Imaging Center, Peking University, Beijing 100871 (China)

    2015-12-14

    In this study, we examine how complex ions such as oxyanions influence the dynamic properties of water and whether differences exist between simple halide anions and oxyanions. Nitrate anion is taken as an example to investigate the hydration properties of oxyanions. Reorientation relaxation of its hydration water can occur through two different routes: water can either break its hydrogen bond with the nitrate to form one with another water or switch between two oxygen atoms of the same nitrate. The latter molecular mechanism increases the residence time of oxyanion’s hydration water and thus nitrate anion slows down the translational motion of neighbouring water. But it is also a “structure breaker” in that it accelerates the reorientation relaxation of hydration water. Such a result illustrates that differences do exist between the hydration of oxyanions and simple halide anions as a result of different molecular geometries. Furthermore, the rotation of the nitrate solute is coupled with the hydrogen bond rearrangement of its hydration water. The nitrate anion can either tilt along the axis perpendicularly to the plane or rotate in the plane. We find that the two reorientation relaxation routes of the hydration water lead to different relaxation dynamics in each of the two above movements of the nitrate solute. The current study suggests that molecular geometry could play an important role in solute hydration and dynamics.

  12. Dual reorientation relaxation routes of water molecules in oxyanion’s hydration shell: A molecular geometry perspective

    International Nuclear Information System (INIS)

    In this study, we examine how complex ions such as oxyanions influence the dynamic properties of water and whether differences exist between simple halide anions and oxyanions. Nitrate anion is taken as an example to investigate the hydration properties of oxyanions. Reorientation relaxation of its hydration water can occur through two different routes: water can either break its hydrogen bond with the nitrate to form one with another water or switch between two oxygen atoms of the same nitrate. The latter molecular mechanism increases the residence time of oxyanion’s hydration water and thus nitrate anion slows down the translational motion of neighbouring water. But it is also a “structure breaker” in that it accelerates the reorientation relaxation of hydration water. Such a result illustrates that differences do exist between the hydration of oxyanions and simple halide anions as a result of different molecular geometries. Furthermore, the rotation of the nitrate solute is coupled with the hydrogen bond rearrangement of its hydration water. The nitrate anion can either tilt along the axis perpendicularly to the plane or rotate in the plane. We find that the two reorientation relaxation routes of the hydration water lead to different relaxation dynamics in each of the two above movements of the nitrate solute. The current study suggests that molecular geometry could play an important role in solute hydration and dynamics

  13. Hydrophobic Porous Material Adsorbs Small Organic Molecules

    Science.gov (United States)

    Sharma, Pramod K.; Hickey, Gregory S.

    1994-01-01

    Composite molecular-sieve material has pore structure designed specifically for preferential adsorption of organic molecules for sizes ranging from 3 to 6 angstrom. Design based on principle that contaminant molecules become strongly bound to surface of adsorbent when size of contaminant molecules is nearly same as that of pores in adsorbent. Material used to remove small organic contaminant molecules from vacuum systems or from enclosed gaseous environments like closed-loop life-support systems.

  14. Deeply bound pionic atom

    International Nuclear Information System (INIS)

    The standard method of pionic atom formation does not produce deeply bound pionic atoms. A study is made on the properties of deeply bound pionic atom states by using the standard pion-nucleus optical potential. Another study is made to estimate the cross sections of the formation of ls pionic atom states by various methods. The pion-nucleus optical potential is determined by weakly bound pionic atom states and pion nucleus scattering. Although this potential may not be valid for deeply bound pionic atoms, it should provide some hint on binding energies and level widths of deeply bound states. The width of the ls state comes out to be 0.3 MeV and is well separated from the rest. The charge dependence of the ls state is investigated. The binding energies and the widths increase linearly with Z azbove a Z of 30. The report then discusses various methods to populate deeply bound pionic atoms. In particular, 'pion exchange' reactions are proposed. (n, pπ) reaction is discussed first. The cross section is calculated by assuming the in- and out-going nucleons on-shell and the produced pion in (n1) pionic atom states. Then, (n, dπ-) cross sections are estimated. (p, 2Heπ-) reaction would have cross sections similar to the cross section of (n, dπ-) reaction. In conclusion, it seems best to do (n, p) experiment on heavy nuclei for deeply bound pionic atom. (Nogami, K.)

  15. Water-dispersible nanoparticles via interdigitation of sodium dodecylsulphate molecules in octadecylamine-capped gold nanoparticles at a liquid-liquid interface

    Indian Academy of Sciences (India)

    Anita Swami; Amol Jadhav; Ashavani Kumar; Suguna D Adyanthaya; Murali Sastry

    2003-10-01

    This paper describes the formation of water-dispersible gold nanoparticles capped with a bilayer of sodium dodecylsulphate (SDS) and octadecylamine (ODA) molecules. Vigorous shaking of a biphasic mixture consisting of ODA-capped gold nanoparticles in chloroform and SDS in water results in the rapid phase transfer of ODA-capped gold nanoparticles from the organic to the aqueous phase, the latter acquiring a pink, foam-like appearance in the process. Drying of the coloured aqueous phase results in the formation of a highly stable, reddish powder of gold nanoparticles that may be readily redispersed in water. The water-dispersible gold nanoparticles have been investigated by UV-Vis spectroscopy, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and Fourier transform infrared spectroscopy (FTIR). These studies indicate the presence of interdigitated bilayers consisting of an ODA primary monolayer directly coordinated to the gold nanoparticle surface and a secondary monolayer of SDS, this secondary monolayer providing sufficient hydrophilicity to facilitate gold nanoparticle transfer into water and rendering them water-dispersible.

  16. Generalized Sphere Packing Bound

    OpenAIRE

    Fazeli, Arman; Vardy, Alexander; Yaakobi, Eitan

    2014-01-01

    Kulkarni and Kiyavash recently introduced a new method to establish upper bounds on the size of deletion-correcting codes. This method is based upon tools from hypergraph theory. The deletion channel is represented by a hypergraph whose edges are the deletion balls (or spheres), so that a deletion-correcting code becomes a matching in this hypergraph. Consequently, a bound on the size of such a code can be obtained from bounds on the matching number of a hypergraph. Classical results in hyper...

  17. Photoisomerisable molecules

    OpenAIRE

    Peris Fajarnes, Eduardo Víctor; Mata Martínez, José Antonio; Márquez Linares, Francisco Manuel; Sabater Picot, María José

    2005-01-01

    [EN] The invention relates to a molecule comprising at least one carbon-carbon double bond which is substituted by at least one cyclopentadienyl-metal-cyclopentadienyl complex, having the cis/trans isomerisation property, in a reversible manner in response to the absorption of light. Preferably, the rest of the molecule comprises a dendrimer of any generation, advantageously of the polypropylenimine octaamine type. The inventive molecule can be used as a molecular switch and in various differ...

  18. IN-SITU MAGIC ANGLE SPINNING NMR INVESTIGATIONS ON CATALYTIC CONVERSION OF BIOGENIC MOLECULES IN THE PRESENCE OF AQUEOUS WATER

    Energy Technology Data Exchange (ETDEWEB)

    Hu, Mary Y.; Feng, Ju; Camaioni, Donald M.; Turcu, Romulus VF; Peden, Charles HF; Lercher, Johannes A.; Hu, Jian Z.

    2012-09-01

    The catalyzed conversion of biomass to hydrocarbon energy carriers requires a cascade of reactions that deconstruct and reduce the polymeric, highly oxofunctionalized biomass material. While lignin is the most intractable component of lignocellulose, its conversion to useful products is key in this catalytic chemistry, because the carbon in lignin is the most reduced one in lignocellulose. This chemistry faces steep challenges, as most of the reactions have to be performed in an aqueous environment under conditions that are highly corrosive towards catalysts. The anticipated scale of the transformations demands that the complex catalysts involved be highly efficient, stable, regenerable, and economically viable catalysts. Currently, none of the known heterogeneous solid catalysts meets these requirements. In order to develop new catalysts satisfying these requirements, a fundamental understanding of the active centers, reaction intermediates and reaction dynamics/kinetics associated with the multi-step conversion of biomass/biomass components, or biomass related polar molecules, i.e., the precursor molecules to fuels, on multifunctional catalytic surfaces is critically needed.

  19. Deeply bound pionic states

    International Nuclear Information System (INIS)

    We discuss the structure and formation of deeply bound π- states in heavy nuclei, which are expected to be narrow due to the repulsive π--nucleus interaction. Possible experiments to produce those states are described. (author)

  20. Exotic helium molecules

    International Nuclear Information System (INIS)

    We study the photo-association of an ultracold cloud of magnetically trapped helium atoms: pairs of colliding atoms interact with one or two laser fields to produce a purely long range 4He2(23S1-23P0) molecule, or a 4He2(23S1-23S1) long range molecule. Light shifts in one photon photo-association spectra are measured and studied as a function of the laser polarization and intensity, and the vibrational state of the excited molecule. They result from the light-induced coupling between the excited molecule, and bound and scattering states of the interaction between two metastable atoms. Their analysis leads to the determination of the scattering length a = (7.2 ± 0.6) ruling collisions between spin polarized atoms. The two photon photo-association spectra show evidence of the production of polarized, long-range 4He2(23S1-23S1) molecules. They are said to be exotic as they are made of two metastable atoms, each one carrying a enough energy to ionize the other. The corresponding lineshapes are calculated and decomposed in sums and products of Breit-Wigner and Fano profiles associated to one and two photon processes. The experimental spectra are fit, and an intrinsic lifetime τ = (1.4 ± 0.3) μs is deduced. It is checked whether this lifetime could be limited by spin-dipole induced Penning autoionization. This interpretation requires that there is a quasi-bound state close to the dissociation threshold in the singlet interaction potential between metastable helium atoms for the theory to match the experiment. (author)

  1. Iridium-mediated Bond Activation and Water Oxidation as an Exemplary Case of CARISMA, A European Network for the Development of Catalytic Routines for Small Molecule Activation.

    Science.gov (United States)

    Licini, Giulia; Albrecht, Martin

    2015-01-01

    CARISMA is a currently running COST Action that pools leading European experts in computational and experimental chemistry to foster synergies for developing new catalytic processes for the transformation of abundant small molecules such as water, carbon dioxide, or ammonia into high-value chemicals and energy-relevant products. CARISMA promotes new collaborations, exchange of knowledge and skills, frontier training to young as well as established researchers, and a platform for the advancement of theoretical and experimental research in an iterative process, comprised of expertise in various connate domains including synthesis, catalysis, spectroscopy, kinetics, and computational chemistry. These interactions stimulate the discovery of new and efficient catalytic processes, illustrated in the second part of this contribution with the collaborative development of powerful iridium-based complexes for bond activation and water oxidation catalysis. PMID:26507475

  2. Self-assembly of a Co(II) dimer through H-bonding of water molecules to a 3D open-framework structure

    Indian Academy of Sciences (India)

    Sujit K Ghosh; Parimal K Bharadwaj

    2005-01-01

    Reaction of pyridine-2,4,6-tricarboxylic acid (ptcH3) with Co(NO3)2.6H2O in presence of 4,4'-bipyridine (4,4'-bpy) in water at room temperature results in the formation of {[Co2(ptcH)2(4,4'-bpy)(H2O)4].2H2O}, (1). The solid-state structure reveals that the compound is a dimeric Co(II) complex assembled to a 3D architecture via an intricate intra- and inter-molecular hydrogen-bonding interactions involving water molecules and carboxylate oxygens of the ligand ptcH2-. Crystal data: monoclinic, space group 21/, = 11.441(5) Å, = 20.212(2) Å, = 7.020(5) Å, = 103.77(5)°, = 1576.7(1) Å3, = 2, 1 = 0.0363, 2 = 0.0856, = 1.000.

  3. Study on the bound water of several high specific surface-area oxides (beryllia, alumina, silica-alumina); Etude de l'eau de constitution de plusieurs oxydes a grande surface specifique (glucine, alumine, silice-alumine)

    Energy Technology Data Exchange (ETDEWEB)

    Rouquerol, J. [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1964-11-01

    This study is concerned with the bound water of several oxides (beryllia, alumina, silica-alumina) at different steps of their dehydration (heating temperatures between 150 and 1100 deg. C). The following techniques have been used simultaneously: Thermal analysis (a new method has been developed), nitrogen adsorption (study of the texture), Diborane hydrolysis (qualitative and quantitative analysis of surface water), Infra-red spectrography (in the absorption range of water), Nuclear magnetic resonance (in the resonance range of protons). Thanks to these different techniques, five kinds of bound water have been observed. Attention is called on the great influence of the thermal treatment conditions on the evolution of the products resulting from the decomposition of alumina {alpha}-trihydrate Al(OH){sub 3} and beryllium {alpha}-hydroxide, in the course of the dehydration. Moreover, the author emphasizes the peculiar properties of the two kinds of oxides (alumina and beryllia) prepared through a new method of treatment under low pressure and constant speed of decomposition. Such particular features concern mainly texture, bound water, and consequently, also catalytic activity. (author) [French] Ce travail porte sur l'eau de constitution de plusieurs oxydes (glucine, alumine, silice-alumine) aux differents degres de leur deshydratation (temperatures de traitement comprises entre 150 et 1100 deg. C). Cette etude met simultanement en oeuvre: l'analyse thermique (proposition d'une nouvelle methode), l'adsorption d'azote (etude de texture), l'hydrolyse du diborane (analyse qualitative et quantitative de l'eau de surface), la spectrographie infra-rouge (dans le domaine d'absorption de l'eau), la resonance magnetique nucleaire (dans le domaine de resonance des protons). A l'aide de ces differentes techniques, cinq formes d'eau de constitution ont ete observees. L'attention est attiree sur la tres grande influence

  4. Just three water molecules can trigger the undesired nonenzymatic reactions of aspartic acid residues: new insight from a quantum-chemical study

    International Nuclear Information System (INIS)

    Aspartic acid (Asp) residues in peptides and proteins (L-Asp) can undergo spontaneous, nonenzymatic reactions under physiological conditions by which abnormal L-β-Asp, D-Asp, and/or D-β-Asp residues are formed. These altered Asp residues may affect the three-dimensional structures of the peptides and proteins and hence their properties and functions. In fact, the altered Asp residues are relevant to age-related diseases such as cataract and Alzheimer's disease. Most of the above reactions of the L-Asp residue proceed via a cyclic succinimide intermediate. In this paper, I propose a detailed mechanism of cyclization of an Asp residue (forming a precursor of the succinimide) by the B3LYP/6-31+G(d,p) density functional theory calculations carried out for a small Asp-containing model compound complexed with three water molecules which act as general acid-base catalysts in proton transfers. In the proposed mechanism, the amide group on the C-terminal side of the Asp residue is first converted to the tautomeric iminol form. Then, successive reorientation of a water molecule and conformational change occur followed by the nucleophilic attack of the iminol nitrogen atom on the carboxyl carbon atom of the Asp side chain to form a five-membered ring. A satisfactory agreement was obtained between the calculated and experimental energetics

  5. Organically bound tritium, OBT: Its true constitution

    International Nuclear Information System (INIS)

    Tritium which is analytically determined to be non exchangeable bound in tissue solids is assumed to be bound to carbon. Furthermore, it is followed, the biochemical Powys's by photosynthesis or enzymatic transfer reactions are retarded by the kinetic isotope effect leading to discrimination of tritium in biomolecules. Contradictory, the logistic growth analysis of plants discloses a larger intrinsic growth rate of OBT than of OBH resulting in tritium accumulation in biomolecules. Exchange experiments providing fractionation factors of 1.4 and 2 confirm this accumulation. In summary, a larger part of the so called OBT is not carbon bound but consists of tritium positioned in hydrogen bridges of biopolymers which have been occupied during formation of the molecules and which became later inacessible for exchange (so called buried hydrogens). Furthermore, there are experimental results indicating even rapid exchange during the 'in vivo'-state but inhibited in the 'in vitro'-state which is commonly given in biosamples prepared for analysis. (author)

  6. Lectures on Bound states

    CERN Document Server

    Hoyer, Paul

    2016-01-01

    Even a first approximation of bound states requires contributions of all powers in the coupling. This means that the concept of "lowest order bound state" needs to be defined. In these lectures I discuss the "Born" (no loop, lowest order in $\\hbar$) approximation. Born level states are bound by gauge fields which satisfy the classical field equations. As a check of the method, Positronium states of any momentum are determined as eigenstates of the QED Hamiltonian, quantized at equal time. Analogously, states bound by a strong external field $A^\\mu(\\xv)$ are found as eigenstates of the Dirac Hamiltonian. Their Fock states have dynamically created $e^+e^-$ pairs, whose distribution is determined by the Dirac wave function. The linear potential of $D=1+1$ dimensions confines electrons but repels positrons. As a result, the mass spectrum is continuous and the wave functions have features of both bound states and plane waves. The classical solutions of Gauss' law are explored for hadrons in QCD. A non-vanishing bo...

  7. Bounding species distribution models

    Institute of Scientific and Technical Information of China (English)

    Thomas J. STOHLGREN; Catherine S. JARNEVICH; Wayne E. ESAIAS; Jeffrey T. MORISETTE

    2011-01-01

    Species distribution models are increasing in popularity for mapping suitable habitat for species of management concern.Many investigators now recognize that extrapolations of these models with geographic information systems (GIS) might be sensitive to the environmental bounds of the data used in their development,yet there is no recommended best practice for “clamping” model extrapolations.We relied on two commonly used modeling approaches:classification and regression tree (CART) and maximum entropy (Maxent) models,and we tested a simple alteration of the model extrapolations,bounding extrapolations to the maximum and minimum values of primary environmental predictors,to provide a more realistic map of suitable habitat of hybridized Africanized honey bees in the southwestern United States.Findings suggest that multiple models of bounding,and the most conservative bounding of species distribution models,like those presented here,should probably replace the unbounded or loosely bounded techniques currently used [Current Zoology 57 (5):642-647,2011].

  8. Production and characterization of protonated molecular clusters containing a given number of water molecules with the DIAM set-up

    International Nuclear Information System (INIS)

    nano-scale characterization of irradiation in bio-molecular systems requires observation of novel features which are now achievable with the recent technical progress. This work is a central part in the development of DIAM which is a new experimental set-up devoted to irradiation of bio-molecular clusters at the Institut de Physique Nucleaire de Lyon. The development of the cluster source and of a double focusing mass spectrometer leads to the production of intense beams of mass selected protonated molecular clusters. Combined with this mass selected cluster beams an innovative detection technique is demonstrated in collision induced dissociation experiments. The results contribute to the knowledge of the stability and the structure of the small protonated water clusters and mixed clusters of water and pyridine. (author)

  9. Validation of EMP bounds

    Energy Technology Data Exchange (ETDEWEB)

    Warne, L.K.; Merewether, K.O.; Chen, K.C.; Jorgenson, R.E.; Morris, M.E.; Solberg, J.E.; Lewis, J.G. [Sandia National Labs., Albuquerque, NM (United States); Derr, W. [Derr Enterprises, Albuquerque, NM (United States)

    1996-07-01

    Test data on canonical weapon-like fixtures are used to validate previously developed analytical bounding results. The test fixtures were constructed to simulate (but be slightly worse than) weapon ports of entry but have known geometries (and electrical points of contact). The exterior of the test fixtures exhibited exterior resonant enhancement of the incident fields at the ports of entry with magnitudes equal to those of weapon geometries. The interior consisted of loaded transmission lines adjusted to maximize received energy or voltage but incorporating practical weapon geometrical constraints. New analytical results are also presented for bounding the energies associated with multiple bolt joints and for bounding the exterior resonant enhancement of the exciting fields.

  10. Information, Utility & Bounded Rationality

    CERN Document Server

    Ortega, Pedro A

    2011-01-01

    Perfectly rational decision-makers maximize expected utility, but crucially ignore the resource costs incurred when determining optimal actions. Here we employ an axiomatic framework for bounded rational decision-making based on a thermodynamic interpretation of resource costs as information costs. This leads to a variational "free utility" principle akin to thermodynamical free energy that trades off utility and information costs. We show that bounded optimal control solutions can be derived from this variational principle, which leads in general to stochastic policies. Furthermore, we show that risk-sensitive and robust (minimax) control schemes fall out naturally from this framework if the environment is considered as a bounded rational and perfectly rational opponent, respectively. When resource costs are ignored, the maximum expected utility principle is recovered.

  11. Enumerating molecules.

    Energy Technology Data Exchange (ETDEWEB)

    Visco, Donald Patrick, Jr. (, . Tennessee Technological University, Cookeville, TN); Faulon, Jean-Loup Michel; Roe, Diana C.

    2004-04-01

    This report is a comprehensive review of the field of molecular enumeration from early isomer counting theories to evolutionary algorithms that design molecules in silico. The core of the review is a detail account on how molecules are counted, enumerated, and sampled. The practical applications of molecular enumeration are also reviewed for chemical information, structure elucidation, molecular design, and combinatorial library design purposes. This review is to appear as a chapter in Reviews in Computational Chemistry volume 21 edited by Kenny B. Lipkowitz.

  12. New measurements of the sticking coefficient and binding energy of molecules on non-porous amorphous solid water in the submonolayer regime

    Science.gov (United States)

    He, Jiao; Acharyya, Kinsuk; Emtiaz, S. M.; Vidali, Gianfranco

    2016-06-01

    Sticking and adsorption of molecules on dust grains are two important processes in gas-grain interactions. We accurately measured both the sticking coefficient and the binding energy of several key molecules on the surface of amorphous solid water as a function of coverage.A time-resolved scattering technique was used to measure sticking coefficient of H2, D2, N2, O2, CO, CH4, and CO2 on non-porous amorphous solid water (np-ASW) in the low coverage limit over a wide range of surface temperatures. We found that the time-resolved scattering technique is advantageous over the conventional King-Wells method that underestimates the sticking coefficient. Based on the measured values we suggest a useful general formula of the sticking coefficient as a function of grain temperature and molecule-surface binding energy.We measured the binding energy of N2, CO, O2, CH4, and CO2 on np-ASW, and of N2 and CO on porous amorphous solid water (p-ASW). We were able to measure binding energies down to a fraction of 1% of a layer, thus making these measurements more appropriate for astrochemistry than the existing values. We found that CO2 forms clusters on np-ASW surface even at very low coverage; this may help in explaining the segregation of CO2 in ices. The binding energies of N2, CO, O2, and CH4 on np-ASW decrease with coverage in the submonolayer regime. Their values in the low coverage limit are much higher than what is commonly used in gas-grain models. An empirical formula was used to describe the coverage dependence of the binding energies. We used the newly determined binding energy distributions in a simulation of gas-grain chemistry for cold dense clouds and hot core models. We found that owing to the higher value of desorption energy in the sub-monlayer regime a fraction of all these ices stays much longer and to higher temperature on the grain surface compared to the case using single value energies as currently done in astrochemical models.This work was supported in

  13. A comparative study of thermo-sensitive hydrogels with water-insoluble paclitaxel in molecule, nanocrystal and microcrystal dispersions

    Science.gov (United States)

    Lin, Zhiqiang; Mei, Dong; Chen, Meiwan; Wang, Yitao; Chen, Xianhui; Wang, Zhaoyang; He, Bing; Zhang, Hua; Wang, Xueqing; Dai, Wenbing; Yin, Yuxin; Zhang, Qiang

    2015-09-01

    In situ thermo-sensitive hydrogels have attracted increasing attention for alternative cancer therapies due to their long-term and effective drug levels at local sites. Besides synthesizing new thermo-sensitive polymers, we can also fabricate this delivery system by combining a hydrogel with a thermo-response and drug in a different dispersion state, such as drug nanocrystals. However, the impact of the drug dispersion state or dimension on the quality of such a local injectable system is still unknown. So, here we developed and compared three types of F127 hydrogel systems with either paclitaxel or the near infra-red probe DiR in molecules (MOs), nanocrystals (NCs) and microcrystals (MCs), respectively. With 120 nm rod-shape nanocrystals, the NCs-Gel achieved a high drug loading, moderate drug release rate and gel erosion in vitro and in vivo, medium intratumoral drug residue but the best anti-tumor efficacy in 4T1 tumor bearing BALB/c mice. With the free drug solubilized in 20 nm micelles of the gel, the MOs-Gel system demonstrated the least drug loading and the fastest drug release and gel erosion, leading to the least intratumoral residue as well as the lowest anti-tumor effect. Finally, when dispersed in micron-grade rod-shape drug crystals, the MCs-Gel exhibited a high drug loading but poor stability, precipitating in vitro and in vivo, the highest intratumoral residue but the least drug release, resulting in moderate tumor inhibition. In conclusion, this study clarifies the effect of the drug dispersion state and scale on the behavior of a thermo-sensitive hydrogel, indicating the advantage of the NCs-Gel system, and it provides a basis for the future design of the local delivery of hydrophobic anti-cancer agents.

  14. Bounded variation and around

    CERN Document Server

    Appell, Jürgen; Merentes Díaz, Nelson José

    2013-01-01

    This monographis a self-contained exposition of the definition and properties of functionsof bounded variation and their various generalizations; the analytical properties of nonlinear composition operators in spaces of such functions; applications to Fourier analysis, nonlinear integral equations, and boundary value problems. The book is written for non-specialists. Every chapter closes with a list of exercises and open problems.

  15. Sorption Characteristics of Mixed Molecules of Glutaraldehyde from Water on Mesoporous Acid-Amine Modified Low-Cost Activated Carbon: Mechanism, Isotherm, and Kinetics

    Directory of Open Access Journals (Sweden)

    Mukosha Lloyd

    2015-01-01

    Full Text Available The environmental discharge of inefficiently treated waste solutions of the strong biocide glutaraldehyde (GA from hospitals has potential toxic impact on aquatic organisms. The adsorption characteristics of mixed polarized monomeric and polymeric molecules of GA from water on mesoporous acid-amine modified low-cost activated carbon (AC were investigated. It was found that the adsorption strongly depended on pH and surface chemistry. In acidic pH, the adsorption mechanism was elaborated to involve chemical sorption of mainly hydroxyl GA monomeric molecules on acidic surface groups, while in alkaline pH, the adsorption was elaborated to involve both chemical and physical sorption of GA polymeric forms having mixed functional groups (aldehyde, carboxyl, and hydroxyl on acidic and amine surface groups. The optimum pH of adsorption was about 12 with significant contribution by cooperative adsorption, elucidated in terms of hydrogen bonding and aldol condensation. Freundlich and Dubinin-Radushkevich models were fitted to isotherm data. The adsorption kinetics was dependent on initial concentration and temperature and described by the Elovich model. The adsorption was endothermic, while the intraparticle diffusion model suggested significant contribution by film diffusion. The developed low-cost AC could be used to supplement the GA alkaline deactivation process for efficient removal of residual GA aquatic toxicity.

  16. Tar removal from biosyngas in the biomass gasification process. (Liquid + liquid) equilibrium {water + solvent (paraxylene and methyl hexadecanoate) + model molecules of tar (benzene, toluene, phenol)}

    International Nuclear Information System (INIS)

    Highlights: ► (Liquid + liquid) equilibria at atmospheric pressure. ► Solubility of benzene (or toluene or phenol) in paraxylene at (303 to 343) K. ► Solubility of benzene (or toluene or phenol) in methyl palmitate or methyl hexadecanoate at (303 to 343) K. ► Correlation of LLE using NRTL model. - Abstract: Tar is generated in the process by the condensation of the gas resulting from biomass gasification. The objective of this work is a contribution to the database on thermodynamic quantity which will be useful at the operation of tar removal from aqueous medium. With this aim, (liquid + liquid) equilibrium of {water + solvent (paraxylene and methyl hexadecanoate) + model molecules of tar (benzene, toluene, phenol)} was studied at temperatures (303.2, 323.2, and 343.2) K. The data obtained were correlated with the non-random two-liquid (NRTL) model.

  17. Molecular properties by Quantum Monte Carlo: an investigation on the role of the wave function ansatz and the basis set in the water molecule

    CERN Document Server

    Zen, Andrea; Sorella, Sandro; Guidoni, Leonardo

    2013-01-01

    Quantum Monte Carlo methods are accurate and promising many body techniques for electronic structure calculations which, in the last years, are encountering a growing interest thanks to their favorable scaling with the system size and their efficient parallelization, particularly suited for the modern high performance computing facilities. The ansatz of the wave function and its variational flexibility are crucial points for both the accurate description of molecular properties and the capabilities of the method to tackle large systems. In this paper, we extensively analyze, using different variational ansatzes, several properties of the water molecule, namely: the total energy, the dipole and quadrupole momenta, the ionization and atomization energies, the equilibrium configuration, and the harmonic and fundamental frequencies of vibration. The investigation mainly focuses on variational Monte Carlo calculations, although several lattice regularized diffusion Monte Carlo calculations are also reported. Throu...

  18. Annual Variations in Water Storage and Precipitation in the Amazon Basin: Bounding Sink Terms in the Terrestrial Hydrological Balance using GRACE Satellite Gravity Data

    Science.gov (United States)

    Crowley, John W.; Mitrovica, Jerry X.; Bailey, Richard C.; Tamisiea, Mark E.; Davis, James L.

    2007-01-01

    We combine satellite gravity data from the Gravity Recovery and Climate Experiment (GRACE) and precipitation measurements from the National Oceanic and Atmospheric Administration (NOAA) Climate Prediction Center's (CPC) Merged Analysis of Precipitation (CMAP) and the Tropical Rainfall Measuring Mission (TRMM), over the period from mid-2002 to mid-2006, to investigate the relative importance of sink (runoff and evaporation) and source (precipitation) terms in the hydrological balance of the Amazon Basin. When linear and quadratic terms are removed, the time series of land water storage variations estimated from GRACE exhibits a dominant annual signal of 250 mm peak-to-peak, which is equivalent to a water volume change of approximately 1800 cubic kilometers. A comparison of this trend with accumulated (i.e., integrated) precipitation shows excellent agreement and no evidence of basin saturation. The agreement indicates that the net runoff and evaporation contributes significantly less than precipitation to the annual hydrological mass balance. Indeed, raw residuals between the detrended water storage and precipitation anomalies range from plus or minus 40 mm. This range is consistent with streamflow measurements from the region, although the latter are characterized by a stronger annual signal than ow residuals, suggesting that runoff and evaporation may act to partially cancel each other.

  19. Annual variations in water storage and precipitation in the Amazon Basin. Bounding sink terms in the terrestrial hydrological balance using GRACE satellite gravity data

    Science.gov (United States)

    Crowley, John W.; Mitrovica, Jerry X.; Bailey, Richard C.; Tamisiea, Mark E.; Davis, James L.

    2008-01-01

    We combine satellite gravity data from the gravity recovery and climate experiment (GRACE) and precipitation measurements from the National Oceanic and Atmospheric Administration (NOAA) Climate Prediction Center’s (CPC) Merged Analysis of Precipitation (CMAP) and the Tropical Rainfall Measuring Mission (TRMM), over the period from mid-2002 to mid-2006, to investigate the relative importance of sink (runoff and evaporation) and source (precipitation) terms in the hydrological balance of the Amazon Basin. When linear and quadratic terms are removed, the time-series of land water storage variations estimated from GRACE exhibits a dominant annual signal of 250 mm peak-to-peak, which is equivalent to a water volume change of ~1,800 km3. A comparison of this trend with accumulated (i.e., integrated) precipitation shows excellent agreement and no evidence of basin saturation. The agreement indicates that the net runoff and evaporation contributes significantly less than precipitation to the annual hydrological mass balance. Indeed, raw residuals between the de-trended water storage and precipitation anomalies range from ±40 mm. This range is consistent with stream-flow measurements from the region, although the latter are characterized by a stronger annual signal than our residuals, suggesting that runoff and evaporation may act to partially cancel each other.

  20. Wide-amplitude rovibrational bound states in polyatomic molecules[Molecular quantum dynamics; rovibrational; bound states; polyatomic molecules; CCP6

    Energy Technology Data Exchange (ETDEWEB)

    Kozin, Igor N.; Law, Mark M.; Connor, Jonathan N.L. (eds.)

    2002-07-01

    The objective of the Workshop was to bring together the leading specialists in the fields of rovibrational quantum calculation and experimental spectroscopy to share ideas and expertise on the challenging problems faced in dealing with wide-amplitude molecular motion. The results of work in this field have not only resolved difficult problems in the interpretation of high-resolution molecular spectra but have also allowed the determination of accurate potential energy surfaces (PESs) by fitting to such data. Conversely the most rigorous tests of ab initio PESs depend on being able to calculate accurate spectroscopic transitions based on the potentials for comparison with experimental data.

  1. Asynchronous Bounded Expected Delay Networks

    OpenAIRE

    Bakhshi, Rena; Endrullis, Jörg; Fokkink, Wan; Pang, Jun

    2010-01-01

    The commonly used asynchronous bounded delay (ABD) network models assume a fixed bound on message delay. We propose a probabilistic network model, called asynchronous bounded expected delay (ABE) model. Instead of a strict bound, the ABE model requires only a bound on the expected message delay. While the conditions of ABD networks restrict the set of possible executions, in ABE networks all asynchronous executions are possible, but executions with extremely long delays are less probable. In ...

  2. On Entropy Bounds and Holography

    CERN Document Server

    Halyo, Edi

    2009-01-01

    We show that the holographic entropy bound for gravitational systems and the Bekenstein entropy bound for nongravitational systems are holographically related. Using the AdS/CFT correspondence, we find that the Bekenstein bound on the boundary is obtained from the holographic bound in the bulk by minimizing the boundary energy with respect the AdS radius or the cosmological constant. This relation may also ameliorate some problems associated with the Bekenstein bound.

  3. Atoms, Molecules, and Compounds

    CERN Document Server

    Manning, Phillip

    2007-01-01

    Explores the atoms that govern chemical processes. This book shows how the interactions between simple substances such as salt and water are crucial to life on Earth and how those interactions are predestined by the atoms that make up the molecules.

  4. Stability of small exotic molecules

    International Nuclear Information System (INIS)

    Complete text of publication follows. Three and four unit-charge particles with different masses may form bound states depending on the mass ratios. The aim of this work is to find out how many particles of unit charges can be put together to form bound states. We explore the possibility of the formation of stable N = 5,6...-particle systems of unit charges. We use a variational approach, in which the trial function is constructed out of generalised Gaussians whose parameters are determined by stochastic sampling. For few-body bound states this method has been shown to produce accurate results. First we made calculations for the five-body system (m+, m-, m+, m-, M+) with 0 ≤ σ ≤ ∞, where σ = m/M. We found that the binding energy of the system is larger than the nearest threshold for 0 ≤ σ ≤ 1.81, so the system in this region of mass ratio is bound. In the case of the system (m+, m-, m-, M+, M+) we cannot find a bound state for σ = 0. For 1 ≤ σ ≤ ∞, however, the system is bound. By decreasing σ from σ = 1, the binding energy is reduced, and around σ = 0.4 the system dissociates into (m-, m-, M+, M+) plus m+. Some six-body systems are under study, and cases have been found both for the existence and non-existence of bound states. From this study we can learn, e.g. that an H2 molecule cannot bind a positron and the positronium molecule can bind a proton, but it cannot bind an electron, unless we make the extra electron non-identical with the others. By comparing systems formed by identical and non-identical particles, we can point out the role of the Pauli principle in reducing the binding energy. (author)

  5. Bounded Tamper Resilience

    DEFF Research Database (Denmark)

    Damgård, Ivan Bjerre; Faust, Sebastian; Mukherjee, Pratyay; Venturi, Daniele

    Related key attacks (RKAs) are powerful cryptanalytic attacks where an adversary can change the secret key and observe the effect of such changes at the output. The state of the art in RKA security protects against an a-priori unbounded number of certain algebraic induced key relations, e...... bounded tamper and leakage resilient CCA secure public key cryptosystem based on the DDH assumption. We first define a weaker CPA-like security notion that we can instantiate based on DDH, and then we give a general compiler that yields CCA-security with tamper and leakage resilience. This requires a...... public tamper-proof common reference string. Finally, we explain how to boost bounded tampering and leakage resilience (as in 1. and 2. above) to continuous tampering and leakage resilience, in the so-called floppy model where each user has a personal hardware token (containing leak- and tamper...

  6. Deeply bound $\\Xi$ tribaryon

    CERN Document Server

    Garcilazo, H

    2016-01-01

    We have used realistic local interactions based on the recent update of the strangeness $-2$ Nijmegen ESC08c potential to calculate the bound state problem of the $\\Xi NN$ system in the $(I)J^P=(\\frac{1}{2})\\frac{3}{2}^+$ state. We found that this system presents a deeply bound state lying $13.5$ MeV below the $\\Xi d$ threshold. Since in lowest order, pure S$-$wave configuration, this system can not decay into the open $\\Lambda\\Lambda N$ channel, its decay width is expected to be very small. We have also recalculated the $(I)J^P=(\\frac{3}{2})\\frac{1}{2}^+$ state and we have compared with results of quark-model based potentials.

  7. Petawatt laser absorption bounded

    CERN Document Server

    Levy, Matthew C; Tabak, Max; Libby, Stephen B; Baring, Matthew G

    2014-01-01

    The interaction of petawatt ($10^{15}\\ \\mathrm{W}$) lasers with solid matter forms the basis for advanced scientific applications such as table-top particle accelerators, ultrafast imaging systems and laser fusion. Key metrics for these applications relate to absorption, yet conditions in this regime are so nonlinear that it is often impossible to know the fraction of absorbed light $f$, and even the range of $f$ is unknown. Here using a relativistic Rankine-Hugoniot-like analysis, we show for the first time that $f$ exhibits a theoretical maximum and minimum. These bounds constrain nonlinear absorption mechanisms across the petawatt regime, forbidding high absorption values at low laser power and low absorption values at high laser power. For applications needing to circumvent the absorption bounds, these results will accelerate a shift from solid targets, towards structured and multilayer targets, and lead the development of new materials.

  8. Towards Secure Distance Bounding

    OpenAIRE

    Boureanu, Ioana; Mitrokotsa, Aikaterini; Vaudenay, Serge

    2013-01-01

    Relay attacks (and, more generally, man-in-the-middle attacks) are a serious threat against many access control and payment schemes. In this work, we present distance-bounding protocols, how these can deter relay attacks, and the security models formalizing these protocols. We show several pitfalls making existing protocols insecure (or at least, vulnerable, in some cases). Then, we introduce the SKI protocol which enjoys resistance to all popular attack-models and features provable security....

  9. Maps of Bounded Rationality

    OpenAIRE

    Kahneman, Daniel

    2002-01-01

    The work cited by the Nobel committee was done jointly with the late Amos Tversky (1937-1996) during a long and unusually close collaboration. Together, we explored the psychology of intuitive beliefs and choices and examined their bounded rationality. This essay presents a current perspective on the three major topics of our joint work: heuristics of judgment, risky choice, and framing effects. In all three domains we studied intuitions - thoughts and preferences that come to mind quickly an...

  10. Bounded Active Perception

    OpenAIRE

    KETENCI, Uktu Gorkem; Bremond, Roland; Auberlet, Jean Michel; GRISLIN, Emmanuelle

    2010-01-01

    There are two kinds of perception : active and passive. This paper is an attempt to take advantage of active perception to improve the agent's perception of relevant information. Through the data filtering capacity, active perception is a useful tool for modeling human-like bounded perception. Using such filters, either the agent or the environment take an active role. We determine several unsolved issues in active perception and do several proposals to implement our concept on the active per...

  11. Bounded Discrete Walks

    OpenAIRE

    Banderier, Cyril; Nicodeme, Pierre

    2010-01-01

    This article tackles the enumeration and asymptotics of directed lattice paths (that are isomorphic to unidimensional paths) of bounded height (walks below one wall, or between two walls, for \\emphany finite set of jumps). Thus, for any lattice paths, we give the generating functions of bridges (``discrete'' Brownian bridges) and reflected bridges (``discrete'' reflected Brownian bridges) of a given height. It is a new success of the ``kernel method'' that the generating functions of such wal...

  12. Dynamic scanning probe microscopy of adsorbed molecules on graphite

    OpenAIRE

    Berdunov, N.; Pollard, A J; Beton, P. H.

    2008-01-01

    We have used a combined dynamic scanning tunneling and atomic force microscope to study the organisation of weakly bound adsorbed molecules on a graphite substrate. Specifically we have acquired images of islands of the perylene derivative molecules. These weakly bound molecules may be imaged in dynamic STM, in which the probe is oscillated above the surface. We show that molecular resolution may be readily attained and that a similar mode of imaging may be realised using conventional STM arr...

  13. Reflecting Magnon Bound States

    CERN Document Server

    Ahn, C; Rey, S J

    2008-01-01

    In N=4 super Yang-Mills spin chain, we compute reflection amplitudes of magnon bound-state off giant graviton. We first compute the reflection amplitude off Y=0 brane boundary and compare it with the scattering amplitude between two magnon bound-states in the bulk. We find that analytic structure of the two amplitudes are intimately related each other: the boundary reflection amplitude is a square-root of the bulk scattering amplitude. Using such relation as a guide and taking known results at weak and strong coupling limits as inputs, we find the reflection amplitude of an elementary magnon off Z=0 giant graviton boundary. The reflection phase factor is shown to solve crossing and unitarity relations. We then compute the reflection amplitude of magnon bound-state off the Z=0 brane boundary and observe that its analytic structures are again intimately related to the bulk scattering and the Y=0 boundary reflection amplitudes. We also take dyonic giant magnon limit of these reflection amplitudes and confirm tha...

  14. The nature of nonfreezing water in carbohydrate polymers.

    Science.gov (United States)

    Kocherbitov, Vitaly

    2016-10-01

    In an aqueous environment, carbohydrate polymers are surrounded by hydration shells consisting of water molecules that are sometimes called "bound". When polymer solutions are subjected to low temperatures, a part of water turns into ice, another part remains in the biopolymer phase and is called "nonfreezing water". Thermodynamic analysis of water freezing shows that the amount of non-freezing water does not reflect the amount of bound water, neither can it be used as a measure of strength of polymer-water interactions. Upon deep cooling, crystallization of water should desiccate polymers more than is observed in experiment. The reason for existence of non-freezing water is an interplay between the crystallization of water and the glass transition in biopolymers that prevents dehydration. PMID:27312645

  15. Photonic Molecule Lasers Revisited

    Science.gov (United States)

    Gagnon, Denis; Dumont, Joey; Déziel, Jean-Luc; Dubé, Louis J.

    2014-05-01

    Photonic molecules (PMs) formed by coupling two or more optical resonators are ideal candidates for the fabrication of integrated microlasers, photonic molecule lasers. Whereas most calculations on PM lasers have been based on cold-cavity (passive) modes, i.e. quasi-bound states, a recently formulated steady-state ab initio laser theory (SALT) offers the possibility to take into account the spectral properties of the underlying gain transition, its position and linewidth, as well as incorporating an arbitrary pump profile. We will combine two theoretical approaches to characterize the lasing properties of PM lasers: for two-dimensional systems, the generalized Lorenz-Mie theory will obtain the resonant modes of the coupled molecules in an active medium described by SALT. Not only is then the theoretical description more complete, the use of an active medium provides additional parameters to control, engineer and harness the lasing properties of PM lasers for ultra-low threshold and directional single-mode emission. We will extend our recent study and present new results for a number of promising geometries. The authors acknowledge financial support from NSERC (Canada) and the CERC in Photonic Innovations of Y. Messaddeq.

  16. Anion binding by biotin[6]uril in water

    DEFF Research Database (Denmark)

    Lisbjerg, Micke; Nielsen, Bjarne Enrico; Milhøj, Birgitte Olai; Sauer, Stephan P. A.; Pittelkow, Michael

    2015-01-01

    In this contribution we show that the newly discovered 6 + 6 biotin-formaldehyde macrocycle Biotin[6]uril binds a variety of anionic guest molecules in water. We discuss how and why the anions are bound based on data obtained using NMR spectroscopy, mass spectrometry, isothermal titration...... calorimetry (ITC), computational calculations and single crystal X-ray crystallography....

  17. Anion binding by biotin[6]uril in water

    DEFF Research Database (Denmark)

    Lisbjerg, Micke; Nielsen, Bjarne Enrico; Milhøj, Birgitte Olai;

    2015-01-01

    In this contribution we show that the newly discovered 6 + 6 biotin-formaldehyde macrocycle Biotin[6]uril binds a variety of anionic guest molecules in water. We discuss how and why the anions are bound based on data obtained using NMR spectroscopy, mass spectrometry, isothermal titration...

  18. A bound on chaos

    CERN Document Server

    Maldacena, Juan; Stanford, Douglas

    2015-01-01

    We conjecture a sharp bound on the rate of growth of chaos in thermal quantum systems with a large number of degrees of freedom. Chaos can be diagnosed using an out-of-time-order correlation function closely related to the commutator of operators separated in time. We conjecture that the influence of chaos on this correlator can develop no faster than exponentially, with Lyapunov exponent $\\lambda_L \\le 2 \\pi k_B T/\\hbar$. We give a precise mathematical argument, based on plausible physical assumptions, establishing this conjecture.

  19. Regularity of Bound States

    DEFF Research Database (Denmark)

    Faupin, Jeremy; Møller, Jacob Schach; Skibsted, Erik

    2011-01-01

    We study regularity of bound states pertaining to embedded eigenvalues of a self-adjoint operator H, with respect to an auxiliary operator A that is conjugate to H in the sense of Mourre. We work within the framework of singular Mourre theory which enables us to deal with confined massless Pauli......–Fierz models, our primary example, and many-body AC-Stark Hamiltonians. In the simpler context of regular Mourre theory, our results boil down to an improvement of results obtained recently in [8, 9]....

  20. Understanding water: Molecular dynamics simulations of solubilized and crystallized myoglobin

    Energy Technology Data Exchange (ETDEWEB)

    Wei Gu; Garcia, A.E.; Schoenborn, B.P. [Los Alamos National Laboratory, NM (United States)

    1994-12-31

    Molecular dynamics simulations were performed on CO myoglobin to evaluate the stability of the bound water molecules as determined in a neutron diffraction analysis. The myoglobin structure derived from the neutron analysis provided the starting coordinate set used in the simulations. The simulations show that only a few water molecules are tightly bound to protein atoms, while most solvent molecules are labile, breaking and reforming hydrogen bonds. Comparison between myoglobin in solution and in a single crystal highlighted some of the packing effects on the solvent structure and shows that water solvent plays an indispensable role in protein dynamics and structural stability. The described observations explain some of the differences in the experimental results of protein hydration as observed in NMR, neutron and X-ray diffraction studies.

  1. Tight Bernoulli tail probability bounds

    OpenAIRE

    Dzindzalieta, Dainius

    2014-01-01

    The purpose of the dissertation is to prove universal tight bounds for deviation from the mean probability inequalities for functions of random variables. Universal bounds shows that they are uniform with respect to some class of distributions and quantity of variables and other parameters. The bounds are called tight, if we can construct a sequence of random variables, such that the upper bounds are achieved. Such inequalities are useful for example in insurance mathematics, for constructing...

  2. Bounded Rationality in Transposition Processes

    DEFF Research Database (Denmark)

    Vollaard, Hans; Martinsen, Dorte Sindbjerg

    2014-01-01

    concerns the organisation and financing of national healthcare systems. This article applies the perspective of bounded rationality to explain (irregularities in) the timely and correct transposition of EU directives. The cognitive and organisational constraints long posited by the bounded rationality...... bounded rationality is apparent in the transposition processes in these relatively well-organised countries, future transposition studies should devote greater consideration to the bounded rationality perspective....

  3. Novel Bounds on Marginal Probabilities

    OpenAIRE

    Mooij, Joris M.; Kappen, Hilbert J

    2008-01-01

    We derive two related novel bounds on single-variable marginal probability distributions in factor graphs with discrete variables. The first method propagates bounds over a subtree of the factor graph rooted in the variable, and the second method propagates bounds over the self-avoiding walk tree starting at the variable. By construction, both methods not only bound the exact marginal probability distribution of a variable, but also its approximate Belief Propagation marginal (``belief''). Th...

  4. Separable subgroups have bounded packing

    CERN Document Server

    Yang, Wen-yuan

    2010-01-01

    In this note, we prove that separable subgroups have bounded packing in ambient groups. The notion bounded packing was introduced by Hruska-Wise \\cite{HrWi} and in particular, our result confirms a conjecture in \\cite{HrWi} which states each subgroup of a virtually polycyclic group has the bounded packing property.

  5. On bound entanglement assisted distillation

    OpenAIRE

    Vedral, V.

    1999-01-01

    We investigate asymptotic distillation of entanglement in the presence of an unlimited amount of bound entanglement for bi-partite systems. We show that the distillability is still bounded by the relative entropy of entanglement. This offers a strong support to the fact that bound entanglement does not improve distillation of entanglement.

  6. Work function variation of MoS2 atomic layers grown with chemical vapor deposition: The effects of thickness and the adsorption of water/oxygen molecules

    International Nuclear Information System (INIS)

    The electrical properties of two-dimensional atomic sheets exhibit remarkable dependences on layer thickness and surface chemistry. Here, we investigated the variation of the work function properties of MoS2 films prepared with chemical vapor deposition (CVD) on SiO2 substrates with the number of film layers. Wafer-scale CVD MoS2 films with 2, 4, and 12 layers were fabricated on SiO2, and their properties were evaluated by using Raman and photoluminescence spectroscopies. In accordance with our X-ray photoelectron spectroscopy results, our Kelvin probe force microscopy investigation found that the surface potential of the MoS2 films increases by ∼0.15 eV when the number of layers is increased from 2 to 12. Photoemission spectroscopy (PES) with in-situ annealing under ultra high vacuum conditions was used to directly demonstrate that this work function shift is associated with the screening effects of oxygen or water molecules adsorbed on the film surface. After annealing, it was found with PES that the surface potential decreases by ∼0.2 eV upon the removal of the adsorbed layers, which confirms that adsorbed species have a role in the variation in the work function

  7. Work function variation of MoS{sub 2} atomic layers grown with chemical vapor deposition: The effects of thickness and the adsorption of water/oxygen molecules

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Jong Hun; Kim, Jae Hyeon; Park, Jeong Young, E-mail: peterlee@skku.edu, E-mail: jeongypark@kaist.ac.kr [Center for Nanomaterials and Chemical Reactions, Institute for Basic Science (IBS), Daejeon 305–701 (Korea, Republic of); Graduate School of EEWS, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 305–701 (Korea, Republic of); Lee, Jinhwan [School of Mechanical Engineering, Sungkyunkwan University, Suwon 440-746 (Korea, Republic of); Hwang, C. C. [Beamline Research Division, Pohang Accelerator Laboratory (PAL), Pohang University of Science and Technology (POSTECH), Pohang 790-784 (Korea, Republic of); Lee, Changgu, E-mail: peterlee@skku.edu, E-mail: jeongypark@kaist.ac.kr [School of Mechanical Engineering, Sungkyunkwan University, Suwon 440-746 (Korea, Republic of); SKKU Advanced Institute of Nanotechnology (SAINT) and Center for Human Interface Nano Technology (HINT), Sungkyunkwan University, Suwon 440-746 (Korea, Republic of)

    2015-06-22

    The electrical properties of two-dimensional atomic sheets exhibit remarkable dependences on layer thickness and surface chemistry. Here, we investigated the variation of the work function properties of MoS{sub 2} films prepared with chemical vapor deposition (CVD) on SiO{sub 2} substrates with the number of film layers. Wafer-scale CVD MoS{sub 2} films with 2, 4, and 12 layers were fabricated on SiO{sub 2}, and their properties were evaluated by using Raman and photoluminescence spectroscopies. In accordance with our X-ray photoelectron spectroscopy results, our Kelvin probe force microscopy investigation found that the surface potential of the MoS{sub 2} films increases by ∼0.15 eV when the number of layers is increased from 2 to 12. Photoemission spectroscopy (PES) with in-situ annealing under ultra high vacuum conditions was used to directly demonstrate that this work function shift is associated with the screening effects of oxygen or water molecules adsorbed on the film surface. After annealing, it was found with PES that the surface potential decreases by ∼0.2 eV upon the removal of the adsorbed layers, which confirms that adsorbed species have a role in the variation in the work function.

  8. Pharmacological modulation of histone demethylase activity by a small molecule isolated from subcritical water extracts of Sasa senanensis leaves prolongs the lifespan of Drosophila melanogaster

    Directory of Open Access Journals (Sweden)

    Nakagawa-Yagi Yuzo

    2012-07-01

    Full Text Available Abstract Background Extracts of Sasa senanensis Rehder are used in traditional Japanese medicine; however, little is known about the underlying mechanisms of their potential health benefits. Methods S. senanensis leaves were extracted with subcritical water. An active small-molecule was isolated using reversed-phase high-performance liquid chromatography (HPLC, and identified as 3,4-dihydroxybenzaldehyde (protocatechuic aldehyde or PA. The effects of PA on the activity of histone demethylase, the Drosophila melanogaster lifespan and gene expression in Drosophila S2 cells were investigated. Results PA inhibited the activity of Jumonji domain-containing protein 2A (JMJD2A histone demethylase in a dose-dependent manner with a half-maximal inhibitory concentration (IC50 of 11.6 μM. However, there was no effect on lysine-specific demethylase 1 (LSD1, histone deacetylase 1 (HDAC1 or HDAC8. PA significantly extended the lifespan of female, but not male, Drosophila. In Drosophila S2 cells, the eukaryotic translation initiation factor 4E binding protein (4E-BP was up-regulated by PA exposure. Conclusions Our findings provide insight into the possible relationship between the pharmacological modulation of histone demethylation and lifespan extension by PA; they might also be important in the development of alternative therapies for age-related disorders.

  9. Density functional theory, natural bond orbital and quantum theory of atoms in molecule analyses on the hydrogen bonding interactions in tryptophan-water complexes

    Indian Academy of Sciences (India)

    Xiqian Niu; Zhengguo Huang; Lingling Ma; Tingting Shen; Lingfei Guo

    2013-07-01

    The tryptophan-water (Trp-H2O) complexes formed by hydrogen bonding interactions were investigated at the B97XD/6-311++G(d,p) level. Five Trp-H2O complexes possessing various types of hydrogen bonds (H-bonds) were characterized by geometries, energies, vibrational frequencies. The nature of the H-bonds were characterized by the natural bond orbital (NBO) and the quantum theory of atoms in molecule (QTAIM) analyses as well. The intramolecular H-bond formed between the amino and carboxyl oxygen atom of tryptophan was retained in most of the complexes, and the cooperativity between the intra and intermolecular H-bonds exist in some complexes. The intramolecular H-bond and some intermolecular H-bonds are strong and have partial covalent character. The H-bonds formed between carboxyl and oxygen/nitrogen atoms are stronger than other H-bonds. The H-bonds involving methylene of tryptophan as H-donor are weak H-bonds. For all complexes,ele and ex makes major contributions to the total interaction energy (MP2), while disp is the smallest component of the interaction energy. Both hydrogen bonding interaction and structural deformation play important roles in the relative stabilities of the complexes. Regardless of strong H-bonds, the stabilities of some complexes are weakened by the serious structural deformations.

  10. Universal quantum dot-based sandwich-like immunoassay strategy for rapid and ultrasensitive detection of small molecules using portable and reusable optofluidic nano-biosensing platform.

    Science.gov (United States)

    Zhou, Liping; Zhu, Anna; Lou, Xuening; Song, Dan; Yang, Rong; Shi, Hanchang; Long, Feng

    2016-01-28

    A universal sandwich-like immunoassay strategy based on quantum-dots immunoprobe (QD-labeled anti-mouse IgG antibody) was developed for rapid and ultrasensitive detection of small molecules. A portable and reusable optofluidic nano-biosensing platform was applied to investigate the sandwich-like immunoassay mechanism and format of small molecules, as well as the binding kinetics between QD immunoprobe and anti-small molecule antibody. A two-step immunoassay method that involves pre-incubation mixture of different concentration of small molecule and anti-small molecule antibody, and subsequent introduction of QD immunoprobe into the optofluidic cell was conducted for small molecule determination. Compared with the one-step immunoassay method, the two-step immunoassay method can obtain higher fluorescence signal and higher sensitivity index, thus improving the nano-biosensing performance. Based on the proposed strategy, two mode targets, namely, microcystin-LR (MC-LR) and Bisphenol A (BPA) were tested with high sensitivity, rapidity, and ease of use. A higher concentration of small molecules in the sample led to less anti-small molecule antibody bound with antigen-carrier protein conjugate immobilized onto the sensor surface, and less QD immunoprobes bound with anti-small molecule antibody. This phenomenon lowered the fluorescence signal detected by nano-biosensing platform. Under optimal operating conditions, MC-LR and BPA exhibited a limit of detection of 0.003 and 0.04 μg/L, respectively. The LODs were better than those of the indirect competitive immunoassay method for small molecules via Cy5.5-labeled anti-small molecule antibody. The proposed QD-based sandwich-like immunoassay strategy was evaluated in spiked water samples, and showed good recovery, precision and accuracy without complicated sample pretreatments. All these results demonstrate that the new detection strategy could be readily applied to the other trace small molecules in real water samples

  11. Strongly Bounded Partial Sums

    Directory of Open Access Journals (Sweden)

    Charles Swartz

    2014-06-01

    Full Text Available If λ is a scalar sequence space, a series P Zj in a topological vector space Z is λ multiplier convergent in Z if the series P ∞J =1 tj Zj converges in Z for every t = {tj} ∈ λ-If λ satisfies appropriate conditions, a series in a locally convex space X which is λ multiplier convergent in the weak topology is λ multiplier convergent in the original topology ofthe space (the Orlicz-Pettis Theorem but may fail to be λ multiplier convergent in the strong topology of the space. However, we show under apprpriate conditions on the multiplier space λ that the series will have strongly bounded partial sums.

  12. Photoassociative production of ultracold heteronuclear ytterbium molecules

    Energy Technology Data Exchange (ETDEWEB)

    Borkowski, Mateusz; Ciurylo, Roman [Instytut Fizyki, Uniwersytet Mikolaja Kopernika, ul. Grudziadzka 5/7, PL-87-100 Torun (Poland); Julienne, Paul S. [Joint Quantum Institute, National Institute of Standards and Technology and the University of Maryland, 100 Bureau Drive, Stop 8423, Gaithersburg, Maryland 20899-8423 (United States); Yamazaki, Rekishu; Takahashi, Yoshiro [Department of Physics, Graduate School of Science, Kyoto University, Kyoto 606-8502 (Japan); CREST, JST, 4-1-8 Honcho Kawaguchi, Saitama 332-0012 (Japan); Hara, Hideaki; Taie, Shintaro; Sugawa, Seiji; Takasu, Yosuke [Department of Physics, Graduate School of Science, Kyoto University, Kyoto 606-8502 (Japan); Enomoto, Katsunari [Department of Physics, University of Toyama, Toyama 930-8555 (Japan)

    2011-09-15

    We report observations of photoassociation (PA) spectra near the intercombination line in isotopic mixtures of ultracold ytterbium gases. Several heteronuclear bound states have been found for the excited {sup 170}Yb{sup 174}Yb and {sup 174}Yb{sup 176}Yb molecules. We develop a single-channel mass-scaled interaction model for the excited state molecule which well reproduces the measured bound state energies. This is an important step toward optical control of interactions in mixtures of ultracold ytterbium gases using heteronuclear optical Feshbach resonances. The model developed is applicable in collisions of other similar systems, such as cadmium and mercury.

  13. The free jet microwave spectrum of 2-phenylethylamine-water.

    Science.gov (United States)

    Melandri, Sonia; Maris, Assimo; Giuliano, Barbara M; Favero, Laura B; Caminati, Walther

    2010-09-21

    We observed the rotational spectrum of the 1:1 molecular adduct between 2-phenylethylamine and water (normal and H(2)(18)O species) by free jet absorption microwave spectroscopy in the frequency region 60-78 GHz. The dominant spectrum belongs to the structure where the PEA moiety is in the most stable gauche conformation and the water molecule is hydrogen bound to the nitrogen lone pair. The orientation of the water molecule is such that the oxygen atom is almost equidistant (ca. 2.5 A) from the closest methylenic and aromatic hydrogen atoms. PMID:20601990

  14. Watching single molecules dance

    Science.gov (United States)

    Mehta, Amit Dinesh

    Molecular motors convert chemical energy, from ATP hydrolysis or ion flow, into mechanical motion. A variety of increasingly precise mechanical probes have been developed to monitor and perturb these motors at the single molecule level. Several outstanding questions can be best approached at the single molecule level. These include: how far does a motor progress per energy quanta consumed? how does its reaction cycle respond to load? how many productive catalytic cycles can it undergo per diffusional encounter with its track? and what is the mechanical stiffness of a single molecule connection? A dual beam optical trap, in conjunction with in vitro ensemble motility assays, has been used to characterize two members of the myosin superfamily: muscle myosin II and chick brain myosin V. Both move the helical polymer actin, but myosin II acts in large ensembles to drive muscle contraction or cytokinesis, while myosin V acts in small numbers to transport vesicles. An optical trapping apparatus was rendered sufficiently precise to identify a myosin working stroke with 1nm or so, barring systematic errors such as those perhaps due to random protein orientations. This and other light microscopic motility assays were used to characterize myosin V: unlike myosin II this vesicle transport protein moves through many increments of travel while remaining strongly bound to a single actin filament. The step size, stall force, and travel distance of myosin V reveal a remarkably efficient motor capable of moving along a helical track for over a micrometer without significantly spiraling around it. Such properties are fully consistent with the putative role of an organelle transport motor, present in small numbers to maintain movement over long ranges relative to cellular size scales. The contrast between myosin II and myosin V resembles that between a human running on the moon and one walking on earth, where the former allows for faster motion when in larger ensembles but for less

  15. Tapping mode AFM study on the surface dynamics of a single glucose oxidase molecule on a Au(1 1 1) surface in water with implication for a surface-induced unfolding pathway

    International Nuclear Information System (INIS)

    We have investigated a surface-induced unfolding dynamics of a single glucose oxidase (GO) molecule on Au(1 1 1) in air-saturated water, using tapping mode atomic force microscopy (TMAFM). We followed the unfolding process by measuring the maximum height of a well-isolated GO molecule on a terrace near a step-edge of the surface as a function of contact time. We find three linear portions with two intersections in a power-law fit to the selected values of the observed heights. The kinetic TMAFM result implies that there exist at least two distinct dynamic regimes in the unfolding

  16. Osmotic and motional properties of intracellular water as influenced by osmotic swelling and shrinkage of Xenopus oocytes.

    Science.gov (United States)

    Cameron, I L; Merta, P; Fullerton, G D

    1990-03-01

    Experiments were done on fully grown Xenopus oocytes to determine the extent and the properties of cellular water of hydration. The studies involved the osmotic shrinking and swelling of the oocytes under known osmotic pressure as well as proton NMR spectral, titration, and free induction decay analyses. Studies were done both on whole oocytes and on subcellular fractions. The results show that little if any of the oocyte water in situ has the motional or osmotic properties expected of pure "bulk" water. Four distinct water of hydration compartments were found and defined on the basis of distinct hydrogen bounding mechanisms. Some of the water in yolk platelets was found not to be in fast exchange with other water compartments. Osmotic shrinkage of oocytes caused an adaptive decrease in the bound water of hydration compartments. This osmotically induced decrease is attributed to decreased surface area available for the hydrogen bounding of water molecules on cellular proteins. PMID:2312616

  17. Generating substrate bound functional chemokine gradients in vitro

    DEFF Research Database (Denmark)

    Hjortø, Gertrud Malene; Hansen, Morten; Larsen, Niels Bent;

    2009-01-01

    transmembrane molecule extending its chemokine domain into the vascular lumen. Substrate bound in vitro gradients may thus closely resemble in vivo conditions. Direct mCP of sensitive proteins like fractalkine may cause partial protein denaturation and will not ensure correct orientation of the biologically...... active part of the molecules. Here, indirect mCP of a capture antibody recognizing a molecular tag on the target protein is successfully used to pattern tagged fractalkine in microscale gradient patterns. Fractalkine functions as an adhesion molecule for leukocytes. Cells expressing the fractalkine...

  18. Quantum Effects at Low Energy Atom-Molecule Interface

    OpenAIRE

    Deb, B.; Rakshit, A.; Hazra, J.; Chakraborty, D.

    2013-01-01

    Quantum interference effects in inter-conversion between cold atoms and diatomic molecules are analysed. Within the framework of Fano's theory, continuum-bound anisotropic dressed state formalism of atom-molecule quantum dynamics is presented. This formalism is applicable in photo- and magneto-associative strong-coupling regimes. The significance of Fano effect in ultracold atom-molecule transitions is discussed. Quantum effects at low energy atom-molecule interface are important for explorin...

  19. Bounded cascade clouds: albedo and effective thickness

    OpenAIRE

    Cahalan, R. F.

    2002-01-01

    If climate models produced clouds having liquid water amounts close to those observed, they would compute a mean albedo that is often much too large, due to the treatment of clouds as plane-parallel. An approximate lower-bound for this "plane-parallel albedo bias" may be obtained from a fractal model having a range of optical thicknesses similar to those observed in marine stratocumulus, since they are more nearly plane-parallel than most other cloud types. We review ...

  20. Bounding approaches to system identification

    CERN Document Server

    Norton, John; Piet-Lahanier, Hélène; Walter, Éric

    1996-01-01

    In response to the growing interest in bounding error approaches, the editors of this volume offer the first collection of papers to describe advances in techniques and applications of bounding of the parameters, or state variables, of uncertain dynamical systems. Contributors explore the application of the bounding approach as an alternative to the probabilistic analysis of such systems, relating its importance to robust control-system design.

  1. Organically bound tritium, OBT: Its true constitution

    International Nuclear Information System (INIS)

    Full text: Tritium, which is analytically determined to be non-exchangeable bound in tissue solids, is assumed to be bound to carbon. Furthermore, it follows that the biochemical passways by photosynthesis or enzymatic transfer reactions are retarded by the kinetic isotope effect leading to discrimination of tritium in biomolecules. In contrast, the logistic growth analysis of plants discloses a larger intrinsic growth rate of OBT than of OBH, resulting in tritium accumulation in biomolecules. Exchange experiments providing fractionation factors of 1.4 and 2 confirm this accumulation. In summary a larger part of the so called OBT is not carbon bound but consists of tritium positioned in hydrogen bridges of biopolymers which have been occupied during formation of the molecules and which became later inaccessible for exchange (so called buried hydrogens). Furthermore, there are experimental results indicating even rapid exchange during the in vivo state but inhibited in the in vitro state, which is commonly given in bio samples prepared for analysis. (author)

  2. Observation of pendular butterfly Rydberg molecules

    CERN Document Server

    Niederprüm, Thomas; Eichert, Tanita; Lippe, Carsten; Pérez-Ríos, Jesús; Greene, Chris H; Ott, Herwig

    2016-01-01

    Obtaining full control over the internal and external quantum states of molecules is the central goal of ultracold chemistry and allows for the study of coherent molecular dynamics, collisions and tests of fundamental laws of physics. When the molecules additionally have a permanent electric dipole moment, the study of dipolar quantum gases and spin-systems with long-range interactions as well as applications in quantum information processing are possible. Rydberg molecules constitute a class of exotic molecules, which are bound by the interaction between the Rydberg electron and the ground state atom. They exhibit extreme bond lengths of hundreds of Bohr radii and giant permanent dipole moments in the kilo-Debye range. A special type with exceptional properties are the so-called butterfly molecules, whose electron density resembles the shape of a butterfly. Here, we report on the photoassociation of butterfly Rydberg molecules and their orientation in a weak electric field. Starting from a Bose-Einstein cond...

  3. Exotic helium molecules; Molecules exotiques d'helium

    Energy Technology Data Exchange (ETDEWEB)

    Portier, M

    2007-12-15

    We study the photo-association of an ultracold cloud of magnetically trapped helium atoms: pairs of colliding atoms interact with one or two laser fields to produce a purely long range {sup 4}He{sub 2}(2{sup 3}S{sub 1}-2{sup 3}P{sub 0}) molecule, or a {sup 4}He{sub 2}(2{sup 3}S{sub 1}-2{sup 3}S{sub 1}) long range molecule. Light shifts in one photon photo-association spectra are measured and studied as a function of the laser polarization and intensity, and the vibrational state of the excited molecule. They result from the light-induced coupling between the excited molecule, and bound and scattering states of the interaction between two metastable atoms. Their analysis leads to the determination of the scattering length a = (7.2 {+-} 0.6) ruling collisions between spin polarized atoms. The two photon photo-association spectra show evidence of the production of polarized, long-range {sup 4}He{sub 2}(2{sup 3}S{sub 1}-2{sup 3}S{sub 1}) molecules. They are said to be exotic as they are made of two metastable atoms, each one carrying a enough energy to ionize the other. The corresponding lineshapes are calculated and decomposed in sums and products of Breit-Wigner and Fano profiles associated to one and two photon processes. The experimental spectra are fit, and an intrinsic lifetime {tau} = (1.4 {+-} 0.3) {mu}s is deduced. It is checked whether this lifetime could be limited by spin-dipole induced Penning autoionization. This interpretation requires that there is a quasi-bound state close to the dissociation threshold in the singlet interaction potential between metastable helium atoms for the theory to match the experiment. (author)

  4. Ultrafast vibrational dynamics of water confined in phospholipid reverse micelles

    Directory of Open Access Journals (Sweden)

    Elsaesser T.

    2013-03-01

    Full Text Available We study the ultrafast dynamics of OH stretching and bending vibrations of water inside dioleoylphosphatidylcholine (DOPC reverse micelles in a wide range of hydration. A strong hydration level dependence for the spectral diffusion rates is found and explained by the distinctly different environment for single water molecules bound to the anionic phosphate group. We show that the energy relaxation pathway of the OH stretching vibration at low hydration level involves the OH bending.

  5. Size exclusion and anion exchange high performance liquid chromatography for characterizing metals bound to marine dissolved organic matter

    Energy Technology Data Exchange (ETDEWEB)

    Garcia-Otero, Natalia; Bermejo-Barrera, Pilar [Department of Analytical Chemistry, Nutrition and Bromatology, Faculty of Chemistry, University of Santiago de Compostela, Avenida das Ciencias, s/n, 15782 Santiago de Compostela (Spain); Moreda-Pineiro, Antonio, E-mail: antonio.moreda@usc.es [Department of Analytical Chemistry, Nutrition and Bromatology, Faculty of Chemistry, University of Santiago de Compostela, Avenida das Ciencias, s/n, 15782 Santiago de Compostela (Spain)

    2013-01-14

    Highlights: Black-Right-Pointing-Pointer Fractionation methods for assessing metals bound to marine DOM were developed. Black-Right-Pointing-Pointer SEC and AEC with UV detection and hyphenated with inductively coupled plasma-mass spectrometry were used. Black-Right-Pointing-Pointer SEC-UV showed marine DOM of molecular weights from 16 to 1 kDa. Black-Right-Pointing-Pointer Cobalt, manganese, strontium and zinc are bound to marine DOM. - Abstract: Size exclusion chromatography (SEC) followed by anion exchange chromatography (AEC) hyphenated with inductively coupled plasma-mass spectrometry (ICP-MS) was applied for fractionating metals bound to marine dissolved organic matter (DOM). Surface seawater samples (100 L) were subjected to tangential flow ultrafiltration (10,000 Da cut off) for isolating and pre-concentrating dissolved large molecules. The isolated fraction (retentate) consisted of 1 L, which was further freeze-dried and re-dissolved to 250 mL with ultrapure water. After HI Trap desalting of the re-dissolved retentate, SEC with UV detection showed marine DOM ranging from 6.5 kDa (lower than the permeable volume of the SEC column) to 16 kDa. A further characterization of this fraction by AEC with UV detection revealed the existence of four groups of macromolecules exhibiting retention times of 2.3, 2.8, 4.5 and 14.0 min. AEC hyphenated with ICP-MS showed the presence of strontium and zinc in the first AE fraction isolated from the SEC fraction; while manganese was found to be bound to the second AE fraction. Cobalt was found to be bound to molecules comprising the third AE fraction.

  6. Characteristics and Performance of Novel Water-Absorbent Slow Release Nitrogen Fertilizers

    Institute of Scientific and Technical Information of China (English)

    HE Xu-sheng; LIAO Zong-wen; HUANG Pei-zhao; DUAN Ji-xian; GE Ren-shan; LI Hong-bo; GENG Zeng-chao

    2007-01-01

    In this article, a research on the characteristics and performance of water-absorbent slow release nitrogen fertilizer (WASRNF)using infrared spectroscopy (IR), scanning electronic microscopy (SEM), differential scanning calorimetry (DSC), and thermogravimetry analysis (TGA), was present. The results indicate that the water absorbency and nitrogen analysis of WASRNF is 103 g g-1 and 30%, respectively, and WASRNF exhibits approximately neutral pH and very low salt index.WASRNF is a copolymer of nitrogen fertilizer and super absorbent polymer (SAP) monomers which is formed through hydrogen bond interaction, and the molecule contains hydrophilic groups, which is responsible for the absorption and water retention capacity of the molecule. WASRNF is a gel that exhibits the ability to swell, but does not dissolve in water.WASRNF shows non-homogenous nature as a whole, but in local zone it is homogenous, the copolymer molecule shows chain network that is the physical structure responsible for absorption and retention of water in WASRNF. The water retained in WASRNF exists as free and nonfreezing bound and freezing bound water states, with the free and the nonfreezing water accounting for more than 95% of water retained in WASRNF, and the nonfreezing bound water for less than 5%. WASRNF functions in delaying the release of nitrogen from it, thereby serving a novel slow release nitrogenous fertilizer.

  7. Bounds for Asian basket options

    Science.gov (United States)

    Deelstra, Griselda; Diallo, Ibrahima; Vanmaele, Michèle

    2008-09-01

    In this paper we propose pricing bounds for European-style discrete arithmetic Asian basket options in a Black and Scholes framework. We start from methods used for basket options and Asian options. First, we use the general approach for deriving upper and lower bounds for stop-loss premia of sums of non-independent random variables as in Kaas et al. [Upper and lower bounds for sums of random variables, Insurance Math. Econom. 27 (2000) 151-168] or Dhaene et al. [The concept of comonotonicity in actuarial science and finance: theory, Insurance Math. Econom. 31(1) (2002) 3-33]. We generalize the methods in Deelstra et al. [Pricing of arithmetic basket options by conditioning, Insurance Math. Econom. 34 (2004) 55-57] and Vanmaele et al. [Bounds for the price of discrete sampled arithmetic Asian options, J. Comput. Appl. Math. 185(1) (2006) 51-90]. Afterwards we show how to derive an analytical closed-form expression for a lower bound in the non-comonotonic case. Finally, we derive upper bounds for Asian basket options by applying techniques as in Thompson [Fast narrow bounds on the value of Asian options, Working Paper, University of Cambridge, 1999] and Lord [Partially exact and bounded approximations for arithmetic Asian options, J. Comput. Finance 10 (2) (2006) 1-52]. Numerical results are included and on the basis of our numerical tests, we explain which method we recommend depending on moneyness and time-to-maturity.

  8. A Lower Bound on Concurrence

    Institute of Scientific and Technical Information of China (English)

    LIU Li-Guo; TIAN Cheng-Lin; CHEN Ping-Xing; YUAN Nai-Chang

    2009-01-01

    We derive an analytical lower bound on the concurrence for bipartite quantum systems with an improved computable cross norm or realignment criterion and an improved positive partial transpose criterion respectively.Furthermore we demonstrate that our bound is better than that obtained from the local uncertainty relations criterion with optimal local orthogonal observables which is known as one of the best estimations of concurrence.

  9. Keto-Enol Tautomerizations Catalyzed by Water and Carboxylic Acids

    Science.gov (United States)

    da Silva, G.

    2009-12-01

    The ability of weakly-bound complexes to influence the kinetics of gas phase reactions, particularly in atmospheric chemistry, has long been speculated. This study uses quantum chemistry and statistical reaction rate theory to identify that bound water molecules can significantly reduce barriers to intramolecular hydrogen shift reactions, via a double-hydrogen-shift mechanism. The bound water molecule directly participates in the hydrogen shift reaction, exchanging a H atom with its counterpart. For the vinyl alcohol to acetaldehyde keto-enol tautomerization this mechanism cuts the reaction barrier approximately in half, reducing it by over 30 kcal mol-1. In contrast, while a non-participatory ‘bystander’ water molecule also reduces the hydrogen shift barrier, it is only by around 3 kcal/mol. When a carboxylic acid replaces water in the double-hydrogen-shift mechanism the barrier to keto-enol tautomerization is decimated, reduced to less than 6 kcal/mol (around 15 kcal/mol in the reverse direction). This results from reduced strain in the hydrogen shift transition state, and achieves enol lifetimes in the troposphere that become short on relevant timescales. Rapid enol to ketone isomerizations are currently required to explain the oxidation products of isoprene. The wider significance of rapid hydrogen shift reactions in atmospherically relevant molecules and radicals is also explored.

  10. Regulation Mechanism of Interlayer Water in Bio-nano Assembly of a \\b{eta}-sheets Protein on Graphene

    CERN Document Server

    Lv, Wenping; Zhang, Hongyan; Li, Xin; Niu, Huan; Liu, Shengju; Xu, Dongsheng; Wu, Ren'an

    2014-01-01

    Understanding bio-nano interfaces is essential for the design of bionanomaterials and biomedical devices. Here, we explore a bio-nano interface of a \\b{eta}-sheets protein on graphene in water by molecular dynamics simulations. We prove that the CH...{\\pi} attraction driving the assembly of \\b{eta}-sheets on graphene is impaired by the interface-confined water molecules. The observed assembly hindering by the interlayer water can be slacked owing to a transversal motion of protein in searching for appropriate adsorption pathways on graphene with the whittled intermolecular-coupling of interlayer water. The distinct dissipation and clustering behaviors of the retentive and diffusive interlayer water unveil the weak coupling among water molecules inside the interface. The hydrogen bonding between protein-bound and unbound interlayer water molecules demonstrates an atomic-level modulation of water towards the attraction between protein and graphene. The regulating of interlay water gives a deep insight to unders...

  11. Flow enhancement of water flow through silica slit pores with graphene-coated walls

    DEFF Research Database (Denmark)

    Walther, J. H.; Popadic, A.; Koumoutsakos, P.; Praprotnik, M.

    We present continuum simulations of water flow past fullerene molecules. The governing Navier-Stokes equations are complemented with the Navier slip bound-ary condition with a slip length that is extracted from related molecular dynamics simulations. We find that several quantities of interest as...

  12. Adsorption of Organic Molecules on Kaolinite from the Exchange-Hole Dipole Moment Dispersion Model.

    Science.gov (United States)

    Johnson, Erin R; Otero-de-la-Roza, Alberto

    2012-12-11

    Intermolecular interactions between organic molecules and clay minerals are important in a wide range of chemical applications, ranging from oil-sands petroleum extraction to environmental chemistry and catalysis. The binding energies between each of benzene, n-hexane, pyridine, 2-propanol, and water and the kaolinite surface are calculated using density functional theory with the exchange-hole dipole moment dispersion model. The dominant noncovalent interactions are found to be hydrogen bonding for pyridine, 2-propanol, and water, OH-π interactions for benzene, and CH-O interactions for n-hexane. All molecules considered are more strongly bound to the hydrophilic alumina face, rather than the hydrophobic siloxane face, of kaolinte. PMID:26593201

  13. Evidence that the corneocyte has a chemically bound lipid envelope.

    Science.gov (United States)

    Swartzendruber, D C; Wertz, P W; Madison, K C; Downing, D T

    1987-06-01

    The stratum corneum of mammalian epidermis contains a mixture of ceramides, free fatty acids, cholesterol, and cholesteryl sulfate, amounting to 14% of the dry weight of the tissue, that can be removed by exhaustive extraction with chloroform/methanol. Subsequent mild alkaline hydrolysis liberates additional lipid, consisting almost exclusively of C30-C34 omega-hydroxyacids in amide linkage with sphingosine, equal to 2% of the tissue mass. In the present study, transmission electron microscopy was used to demonstrate that the initial extraction removes the intercellular lamellae that constitute the epidermal water barrier but leaves the lucent band that has been termed the corneocyte plasma membrane. The subsequent alkaline hydrolysis and lipid extraction remove the lucent band, which must therefore contain the omega-hydroxyacylsphingosines. From the results of in situ derivatization of these lipids and the construction of molecular models, it is inferred that the bound lipids exist in ester linkage with protein on the surface of the corneocyte envelope. The tightly packed hydroxyacylsphingosine molecules thus form a lipid envelope for each corneocyte. PMID:3585054

  14. Combining Alphas via Bounded Regression

    Directory of Open Access Journals (Sweden)

    Zura Kakushadze

    2015-11-01

    Full Text Available We give an explicit algorithm and source code for combining alpha streams via bounded regression. In practical applications, typically, there is insufficient history to compute a sample covariance matrix (SCM for a large number of alphas. To compute alpha allocation weights, one then resorts to (weighted regression over SCM principal components. Regression often produces alpha weights with insufficient diversification and/or skewed distribution against, e.g., turnover. This can be rectified by imposing bounds on alpha weights within the regression procedure. Bounded regression can also be applied to stock and other asset portfolio construction. We discuss illustrative examples.

  15. Bounded Model Checking of CTL

    Institute of Scientific and Technical Information of China (English)

    Zhi-Hong Tao; Cong-Hua Zhou; Zhong Chen; Li-Fu Wang

    2007-01-01

    Bounded Model Checking has been recently introduced as an efficient verification method for reactive systems.This technique reduces model checking of linear temporal logic to propositional satisfiability.In this paper we first present how quantified Boolean decision procedures can replace BDDs.We introduce a bounded model checking procedure for temporal logic CTL* which reduces model checking to the satisfiability of quantified Boolean formulas.Our new technique avoids the space blow up of BDDs, and extends the concept of bounded model checking.

  16. Water

    Science.gov (United States)

    ... www.girlshealth.gov/ Home Nutrition Nutrition basics Water Water Did you know that water makes up more ... to drink more water Other drinks How much water do you need? top Water is very important, ...

  17. Bound states in string nets

    CERN Document Server

    Schulz, M D; Vidal, J

    2016-01-01

    We discuss the emergence of bound states in the low-energy spectrum of the string-net Hamiltonian in the presence of a string tension. In the ladder geometry, we show that a single bound state arises either for a finite tension or in the zero-tension limit depending on the theory considered. In the latter case, we perturbatively compute the binding energy as a function of the total quantum dimension. We also address this issue in the honeycomb lattice where the number of bound states in the topological phase depends on the total quantum dimension. Finally, the internal structure of these bound states is analyzed in the zero-tension limit.

  18. Curvature bounds for configuration spaces

    OpenAIRE

    Erbar, Matthias; Huesmann, Martin

    2014-01-01

    We show that the configuration space over a manifold M inherits many curvature properties of the manifold. For instance, we show that a lower Ricci curvature bound on M implies for the configuration space a lower Ricci curvature bound in the sense of Lott-Sturm-Villani, the Bochner inequality, gradient estimates and Wasserstein contraction. Moreover, we show that the heat flow on the configuration space, or the infinite independent particle process, can be identified as the gradient flow of t...

  19. Entropy bounds for uncollapsed matter

    Energy Technology Data Exchange (ETDEWEB)

    Abreu, Gabriel; Visser, Matt, E-mail: Gabriel.Abreu@msor.vuw.ac.nz, E-mail: Matt.Visser@msor.vuw.ac.nz [School of Mathematics, Statistics and Operation Research Victoria University of Wellington Wellington (New Zealand)

    2011-09-22

    In any static spacetime the quasilocal Tolman mass contained within a volume can be reduced to a Gauss-like surface integral involving the flux of a suitably defined generalized surface gravity. By introducing some basic thermodynamics, and invoking the Unruh effect, one can then develop elementary bounds on the quasilocal entropy that are very similar in spirit to the holographic bound, and closely related to entanglement entropy.

  20. Finite Domain Bounds Consistency Revisited

    OpenAIRE

    Choi, Chiu Wo; Harvey, Warwick; Lee, Jimmy Ho-Man; Stuckey, Peter J.

    2004-01-01

    A widely adopted approach to solving constraint satisfaction problems combines systematic tree search with constraint propagation for pruning the search space. Constraint propagation is performed by propagators implementing a certain notion of consistency. Bounds consistency is the method of choice for building propagators for arithmetic constraints and several global constraints in the finite integer domain. However, there has been some confusion in the definition of bounds consistency. In t...

  1. Microcanonical distribution for one-electron triatomic molecules

    CERN Document Server

    Lazarou, C; Emmanouilidou, A

    2015-01-01

    We formulate a microcanonical distribution for an arbitrary one-electron triatomic molecule. This distribution can be used to describe the initial state in strongly-driven two-electron triatomic molecules. Namely, in many semiclassical models that describe ionization of two-electron molecules driven by intense infrared laser fields in the tunneling regime initially one electron tunnels while the other electron is bound. The microcanonical distribution presented in this work can be used to describe the initial state of this bound electron.

  2. Optical Production of Stable Ultracold $^{88}$Sr$_2$ Molecules

    CERN Document Server

    Reinaudi, G; McDonald, M; Kotochigova, S; Zelevinsky, T

    2012-01-01

    We have produced large samples of ultracold $^{88}$Sr$_2$ molecules in the electronic ground state in an optical lattice. The molecules are bound by 0.05 cm$^{-1}$ and are stable for several milliseconds. The fast, all-optical method of molecule creation via intercombination line photoassociation relies on a near-unity Franck-Condon factor. The detection uses a weakly bound vibrational level corresponding to a very large dimer. This is the first of two steps needed to create Sr$_2$ in the absolute ground quantum state. Lattice-trapped Sr$_2$ is of interest to frequency metrology and ultracold chemistry.

  3. Optical Production of Stable Ultracold $^{88}$Sr$_2$ Molecules

    OpenAIRE

    Reinaudi, G.; Osborn, C. B.; McDonald, M.; Kotochigova, S.; Zelevinsky, T.

    2012-01-01

    We have produced large samples of ultracold $^{88}$Sr$_2$ molecules in the electronic ground state in an optical lattice. The molecules are bound by 0.05 cm$^{-1}$ and are stable for several milliseconds. The fast, all-optical method of molecule creation via intercombination line photoassociation relies on a near-unity Franck-Condon factor. The detection uses a weakly bound vibrational level corresponding to a very large dimer. This is the first of two steps needed to create Sr$_2$ in the abs...

  4. Reversible Photomechanical Switching of Individual Engineered Molecules at a Surface

    OpenAIRE

    Comstock, Matthew J.; Levy, Niv; Kirakosian, Armen; Cho, Jongweon; Lauterwasser, Frank; Harvey, Jessica H.; Strubbe, David A; Frechet, Jean M. J.; Trauner, Dirk; Louie, Steven G.; Crommie, Michael F.

    2006-01-01

    We have observed reversible light-induced mechanical switching for a single organic molecule bound to a metal surface. Scanning tunneling microscopy (STM) was used to image the features of an individual azobenzene molecule on Au(111) before and after reversibly cycling its mechanical structure between trans and cis states using light. Azobenzene molecules were engineered to increase their surface photomechanical activity by attaching varying numbers of tert-butyl (TB) ligands ("legs") to the ...

  5. Small molecule annotation for the Protein Data Bank

    OpenAIRE

    Sen, Sanchayita; Young, Jasmine; Berrisford, John M.; Chen, Minyu; Conroy, Matthew J.; Dutta, Shuchismita; Di Costanzo, Luigi; Gao, Guanghua; Ghosh, Sutapa; Hudson, Brian P.; Igarashi, Reiko; Kengaku, Yumiko; Liang, Yuhe; Peisach, Ezra; Persikova, Irina

    2014-01-01

    The Protein Data Bank (PDB) is the single global repository for three-dimensional structures of biological macromolecules and their complexes, and its more than 100 000 structures contain more than 20 000 distinct ligands or small molecules bound to proteins and nucleic acids. Information about these small molecules and their interactions with proteins and nucleic acids is crucial for our understanding of biochemical processes and vital for structure-based drug design. Small molecules present...

  6. On a Generalization of Kingman's Bounds

    OpenAIRE

    Liu, Zhen; Nain, Philippe; Towsley, Don

    1994-01-01

    In this paper we develop a framework for computing upper and lower bounds of an exponential form for a class of single server queueing systems with non-renewal inputs. These bounds generalize Kingman's bounds for queues with renewal inputs.

  7. Heavy Meson Molecules in Effective Field Theory

    OpenAIRE

    AlFiky, Mohammad T.; Gabbiani, Fabrizio; Petrov, Alexey A.

    2006-01-01

    We consider the implications from the possibility that the recently observed state X(3872) is a meson-antimeson molecule. We write an effective Lagrangian consistent with the heavy-quark and chiral symmetries needed to describe X(3872). We explore the consequences of the assumption that X(3872) is a molecular bound state of D^{*0} and anti-D^0 mesons for the existence of bound states in the D^0-anti-D^0 and D^{*0}-anti-D^{*0}.

  8. 高密度CO2处理虾仁营养组成和水分子状态的变化规律%Changes in nutritious component and water molecule of peeled shrimp during dense phase carbon dioxide treatment

    Institute of Scientific and Technical Information of China (English)

    陈亚励; 屈小娟; 刘书成; 吉宏武; 郝记明; 黄万有; 郭明慧

    2014-01-01

    and small molecular compounds containing nitrogen (e.g. free amino acids) were carried out with CO2 in the unloading process. While using the untreated peeled shrimp, the contents of myofibrillar and sarcoplasmic protein decreased significantly (P<0.05) and the content of insoluble protein increased significantly (P<0.05) with exposure to time, temperature, and pressure when DPCD was increasing. The reason for that was myofibrillar and sarcoplasmic protein were denatured and transformed to insoluble protein by DPCD. The results of low field nuclear magnetic resonance (LF-NMR) showed that peeled shrimp contained four kinds of water molecules with different mobility. With exposure to time, temperature, and pressure when DPCD was increasing, the degree of freedom of bound water increased while the degree of freedom of immobilized water and free water decreased. Nonetheless, the content of bound water and free water increased significantly (P<0.05) while the content of immobilized water decreased significantly (P<0.05), when the peeled shrimp was treated for 30 min at 15 MPa and 55℃ of DPCD. Microorganism and PPO from Litopenaeus vannamei were inactivated, but the content of moisture, crude protein, crude fat, and ash decreased by 7%、3%、25%, and 11%, respectively. Sarcoplasmic and myofibrillar protein were denatured, and the free water ratio increased significantly (P<0.05). The research results will provide a reference for the application of DPCD in shrimp processing.%为了探讨高密度CO2(dense phase carbon dioxide,DPCD)处理对虾仁肌肉品质的影响,以未处理的新鲜虾仁为对照,研究了DPCD处理过程中虾仁营养组成和水分子状态的变化规律。结果表明:在温度35~55℃和压力5~25 MPa的条件下处理10~50 min,与未处理虾仁相比,虾仁的水分、粗蛋白、粗脂肪和灰分含量均显著下降(P<0.05),尤其是脂肪含量下降幅度最大;随着DPCD处理强度增加,虾仁肌

  9. Improved Range Searching Lower Bounds

    DEFF Research Database (Denmark)

    Larsen, Kasper Green; Nguyen, Huy L.

    2012-01-01

    range reporting problem. In approximate simplex range reporting, points that lie within a distance of ε ⋅ Diam(s) from the border of a query simplex s, are free to be included or excluded from the output, where ε ≥ 0 is an input parameter to the range searching problem. We prove our lower bounds......Table of Contents -------------------------------------------------------------------------------- In this paper we present a number of improved lower bounds for range searching in the pointer machine and the group model. In the pointer machine, we prove lower bounds for the approximate simplex...... by constructing a hard input set and query set, and then invoking Chazelle and Rosenberg's [CGTA'96] general theorem on the complexity of navigation in the pointer machine. For the group model, we show that input sets and query sets that are hard for range reporting in the pointer machine (i.e. by Chazelle...

  10. Simulation bounds for system availability

    International Nuclear Information System (INIS)

    System availability is a dominant factor in the practicality of nuclear power electrical generating plants. A proposed model for obtaining either lower bounds or interval estimates on availability uses observed data on ''n'' failure-to-repair cycles of the system to estimate the parameters in the time-to-failure and time-to-repair models. These estimates are then used in simulating failure/repair cycles of the system. The availability estimate is obtained for each of 5000 samples of ''n'' failure/repair cycles to form a distribution of estimates. Specific percentile points of those simulated distributions are selected as lower simulation bounds or simulation interval bounds for the system availability. The method is illustrated with operational data from two nuclear plants for which an exponential time-to-failure and a lognormal time-to-repair are assumed

  11. BENZO[A]PYRENE AND BENZO[C]PHENANTHRENE: THE EFFECT OF STRUCTURE ON THE BINDING OF WATER MOLECULES TO THE DIOL EPOXIDES

    Science.gov (United States)

    ABSTRACTThe interaction with water of the diol epoxides (DEs) of both a planar and a non-planar PAH have been examined using molecular dynamics. To determine probable water locations around the DE for later use in the study of DE protonation, molecular dynamics simulations u...

  12. Application of MRIL-WD (Magnetic Resonance Imaging Logging While Drilling) for irreducible water saturation, total reservoir, free-fluid, bound-fluid porosity measurements and its value for the petrophysical analysis of RT/RM data from the Shah Deniz well

    Science.gov (United States)

    Amirov, Elnur

    2016-04-01

    Sperry-Sun (Sperry Drilling Services) is the leader in MWD/LWD reliability, has developed the industry's first LWD NMR/MRIL-WD (nuclear magnetic resonance) tool. The MRIL-WD (magnetic resonance imaging logging-while-drilling) service directly measures the T1 component of hydrogen in subsurface rock units while drilling to obtain total reservoir porosity and to dissect the observed total porosity into its respective components of free fluid and bound fluid porosity. These T1 data are used to secure accurate total, free-fluid, capillary-bound water, and clay-bound water porosity of the reservoir sections which can be drilled in the several Runs. Over the last decade, results from Magnetic Resonance Imaging logs (NMR) have added significant value to petrophysical analysis and understanding by providing total, free-fluid and bound-fluid porosities, combined with fluid typing capabilities. With MRIL-WD very valuable Real-Time or Recorded Memory data/information is now available during or shortly after the drilling operation (formation properties measurement can be taken right after a drill bit penetration), while trip in and trip out as well. A key point in utilizing MRIL in an LWD environment is motion-tolerant measurements. Recent MRIL-WD logging runs from the Shah Deniz wells located in the Khazarian-Caspian Sea of the Azerbaijan Republic helped to delineate and assess hydrocarbon bearing zones. Acquired results demonstrate how MRIL data can be acquired while-drilling and provide reliable/high quality measurements. Magnetic Resonance Imaging logs at some developments wells have become a cornerstone in formation evaluation and petrophysical understanding. By providing total, free-fluid, and bound-fluid porosities together with fluid typing, MRIL results have significantly added to the assessment of reservoirs. In order to reduce NPT (Non-Productive Time) and save the rig operations time, there is always the desire to obtain logging results as soon as possible

  13. Refining Castelnuovo-Halphen bounds

    CERN Document Server

    Di Gennaro, Vincenzo

    2011-01-01

    Fix integers $r,d,s,\\pi$ with $r\\geq 4$, $d\\gg s$, $r-1\\leq s \\leq 2r-4$, and $\\pi\\geq 0$. Refining classical results for the genus of a projective curve, we exhibit a sharp upper bound for the arithmetic genus $p_a(C)$ of an integral projective curve $C\\subset {\\mathbb{P}^r}$ of degree $d$, assuming that $C$ is not contained in any surface of degree $ \\pi$. Next we discuss other types of bound for $p_a(C)$, involving conditions on the entire Hilbert polynomial of the integral surfaces on which $C$ may lie.

  14. Space-bounded communication complexity

    DEFF Research Database (Denmark)

    Brody, Joshua Eric; Chen, Shiteng; Papakonstantinou, Periklis A.;

    2013-01-01

    In the past thirty years, Communication Complexity has emerged as a foundational tool to proving lower bounds in many areas of computer science. Its power comes from its generality, but this generality comes at a price---no superlinear communication lower bound is possible, since a player may...... communicate his entire input. However, what if the players are limited in their ability to recall parts of their interaction? We introduce memory models for 2-party communication complexity. Our general model is as follows: two computationally unrestricted players, Alice and Bob, each have s(n) bits of memory...

  15. Bounding solutions of Pfaff equations

    OpenAIRE

    Esteves, E.; Kleiman, S

    2003-01-01

    Let \\omega be a Pfaff system of differential forms on a projective space. Let S be its singular locus, and Y a solution of \\omega=0. We prove Y\\cap S is of codimension at most 1 in Y, just as Jouanolou suspected; he proved this result assuming \\omega is completely integrable, and asked if the integrability is, in fact, needed. Furthermore, we prove a lower bound on the Castelnuovo--Mumford regularity of Y\\cap S. As in two related articles, we derive upper bounds on numerical invariants of Y, ...

  16. Bound orbits and gravitational theory

    OpenAIRE

    Dadhich, Naresh; Ghosh, Sushant G.(School of Mathematical Sciences, University of KwaZulu-Natal, Westville, 4000, Durban, South Africa); Jhingan, Sanjay

    2013-01-01

    It can be easily shown that bound orbits around a static source can exist only in 4 dimension and in none else for any long range force. This is so not only for Maxwell's electromagnetic and Newton's gravity but also for Einstein's gravitation theory. In contrast to Maxwell's electrodynamics and Newton's gravity, GR has a natural higher dimensional generalization in Lovelock gravity which remarkably admits bound orbits around a static black hole in all even d=2N+2 dimensions where $N$ is degr...

  17. Resonance reactions and enhancement of weak interactions in collisions of cold molecules

    OpenAIRE

    Flambaum, V. V.; Ginges, J. S. M.

    2006-01-01

    With the creation of ultracold atoms and molecules, a new type of chemistry - "resonance" chemistry - emerges: chemical reactions can occur when the energy of colliding atoms and molecules matches a bound state of the combined molecule (Feshbach resonance). This chemistry is rather similar to reactions that take place in nuclei at low energies. In this paper we suggest some problems for future experimental and theoretical work related to the resonance chemistry of ultracold molecules. Molecul...

  18. Ultracold polar molecules near quantum degeneracy.

    Science.gov (United States)

    Ospelkaus, S; Ni, K K; de Miranda, M H G; Neyenhuis, B; Wang, D; Kotochigova, S; Julienne, P S; Jin, D S; Ye, J

    2009-01-01

    We report the creation and characterization of a near quantum-degenerate gas of polar 40K-87Rb molecules in their absolute rovibrational ground state. Starting from weakly bound heteronuclear KRb Feshbach molecules, we implement precise control of the molecular electronic, vibrational, and rotational degrees of freedom with phase-coherent laser fields. In particular, we coherently transfer these weakly bound molecules across a 125 THz frequency gap in a single step into the absolute rovibrational ground state of the electronic ground potential. Phase coherence between lasers involved in the transfer process is ensured by referencing the lasers to two single components of a phase-stabilized optical frequency comb. Using these methods, we prepare a dense gas of 4 x 10(4) polar molecules at a temperature below 400 nK. This fermionic molecular ensemble is close to quantum degeneracy and can be characterized by a degeneracy parameter of T/T(F) = 3. We have measured the molecular polarizability in an optical dipole trap where the trap lifetime gives clues to interesting decay mechanisms. Given the large measured dipole moment of the KRb molecules of 0.5 Debye, the study of quantum degenerate molecular gases interacting via strong dipolar interactions is now within experimental reach. PACS numbers: 37.10.Mn, 37.10.Pq. PMID:20151553

  19. Long-lived dipolar molecules and Feshbach molecules in a 3D optical lattice

    CERN Document Server

    Chotia, Amodsen; Moses, Steven A; Yan, Bo; Covey, Jacob P; Foss-Feig, Michael; Rey, Ana Maria; Jin, Deborah S; Ye, Jun

    2011-01-01

    We have realized long-lived ground-state polar molecules in a 3D optical lattice, with a lifetime of up to 25 s, which is limited only by off-resonant scattering of the trapping light. Starting from a 2D optical lattice, we observe that the lifetime increases dramatically as a small lattice potential is added along the tube-shaped lattice traps. The 3D optical lattice also dramatically increases the lifetime for weakly bound Feshbach molecules. For a pure gas of Feshbach molecules, we observe a lifetime of >20 s in a 3D optical lattice; this represents a 100-fold improvement over previous results. This lifetime is also limited by off-resonant scattering, the rate of which is related to the size of the Feshbach molecule. Individually trapped Feshbach molecules in the 3D lattice can be converted to pairs of K and Rb atoms and back with nearly 100% efficiency.

  20. Spin Labeling ESR Investigation of Covalently Bound Residues in Soil

    Science.gov (United States)

    Aleksandrova, Olga; Steinhoff, Heinz-Juergen; Klasmeier, Joerg; Schulz, Marcus; Matthies, Michael

    2013-04-01

    Organic xenobiotic chemicals, such as pesticides, biocides and veterinary pharmaceuticals, interact with soil, which results in the simultaneous formations of metabolites, mineralization products, and bound or non-extractable residues (NER). Substances or metabolites with reactive functional groups, such as aniline or phenol, have a tendency to give a larger proportion of NER. Despite numerous studies on NER, the majority of their chemical structures is still unknown. Reversible sequestration and irreversible formation of NER were also observed for veterinary antibiotic pharmaceuticals, after their application to soil with and without manure. For this purpose, we hypothesized a key role of specific functional groups of soil contaminants, via which contaminants are covalently bound to soil constituents, and advance a method of spin labeling ESR investigation of reaction products using a membrane method. Spin labels (SL) represent chemically stable paramagnetic molecules used as molecular labels and molecular probes for testing the covalent binding, structural properties, and molecular mobility of different physical, chemical, and biological systems. In the case of covalent binding of SL, their ESR spectra become broadened. We used stable nitroxide radicals (NR) as SL. These radicals modeled organic chemical contaminants and differed only in one functional group. The paramagnetic SL 4-Amino Tempo (4-amino-2,2,6,6-tetramethyl-1-piperidinylox) differed from Tempo (2,2,6,6-Tetramethylpiperidinooxy) in a substituent at the para-position of the piperidine ring, whereas Aniline Tempo (1-Piperidinyloxy, 2,2,6,-tetramethyl, 6-Aniline) differed from Tempo in an Aniline substituting one CH3 functional group. Before experimental analysis, we tested temporal changes in the concentration of both NR incubated with soil and found that the life-times of them in soil exceeded 3 days. We contaminated and labeled soil samples with NR, adding to soil the aqueous solution, which already

  1. The relationship between the formation of clusters containing tetrahedral molecules and the dynamic and thermodynamic anomalies of cooled TIP4P/2005 water

    Science.gov (United States)

    Van Sang, Le

    2016-07-01

    Molecular dynamics simulations have been used to cool the simple liquid TPI4P/2005 water at 350 K to 100 K. We find that structural changes of the system cause dynamic and thermodynamic anomalies. A strong increase in the number of tetrahedral oxygen atoms and combinations of these atoms lead to water's a phase transition from a simple liquid form into a supercooled one or ice at T I = 200 K. In the initial stage, small patches containing tetrahedral oxygen atoms connect together to yield large clusters. The rapid drop in the number of clusters and the speedy growth in the size of the largest cluster lead to water's exhibiting anomalously dynamic behaviors at temperatures around 279 K. Our results also show that water is very stable in its supercooled or ice state, exhibiting no change in the mean squared displacement, light oscillation in the number of the clusters and in the size of the largest cluster.

  2. Bound states of 'dressed' particles

    International Nuclear Information System (INIS)

    A new approach to the problem of bound states in relativistic quantum field theories is suggested. It uses the creation - destruction operators of 'dresses' particles which have been granted by Faddeev's (1963) 'dressing' formalism. Peculiarities of the proposed approach as compared to the known ones are discussed. 8 refs. (author)

  3. Bounded Densities and Their Derivatives

    DEFF Research Database (Denmark)

    Kozine, Igor; Krymsky, V.

    2009-01-01

    This paper describes how one can compute interval-valued statistical measures given limited information about the underlying distribution. The particular focus is on a bounded derivative of a probability density function and its combination with other available statistical evidence for computing...

  4. Semiclassical bounds in magnetic bottles

    Czech Academy of Sciences Publication Activity Database

    Barseghyan, Diana; Exner, Pavel; Kovařík, H.; Weidl, T.

    2016-01-01

    Roč. 28, č. 1 (2016), s. 1650002. ISSN 0129-055X R&D Projects: GA ČR(CZ) GA14-06818S Institutional support: RVO:61389005 Keywords : magnetic Laplacian * discrete spectrum * eigenvalue bounds Subject RIV: BE - Theoretical Physics Impact factor: 1.329, year: 2014

  5. Unconditional lower bounds against advice

    NARCIS (Netherlands)

    H. Buhrman; L. Fortnow; R. Santhanam

    2009-01-01

    We show several unconditional lower bounds for exponential time classes against polynomial time classes with advice, including: (1) For any constant c, NEXP not in P^{NP[n^c]} (2) For any constant c, MAEXP not in MA/n^c (3) BPEXP not in BPP/n^{o(1)}. It was previously unknown even whether NEXP in NP

  6. Bounded Fixed-Point Iteration

    DEFF Research Database (Denmark)

    Nielson, Hanne Riis; Nielson, Flemming

    1992-01-01

    In the context of abstract interpretation the authors study the number of times a functional needs to be unfolded in order to give the least fixed point. For the cases of total or monotone functions they obtain an exponential bound and in the case of strict and additive (or distributive) functions...

  7. Market Access through Bound Tariffs

    DEFF Research Database (Denmark)

    Sala, Davide; Schröder, Philipp J.H.; Yalcin, Erdal

    WTO negotiations deal predominantly with bound - besides applied - tariff rates. But, how can reductions in tariffs ceilings, i.e. tariff rates that no exporter may ever actually be confronted with, generate market access? The answer to this question relates to the effects of tariff bindings on t...

  8. Market access through bound tariffs

    DEFF Research Database (Denmark)

    Sala, Davide; Schröder, Philipp J.H.; Yalcin, Erdal

    2010-01-01

    WTO negotiations deal predominantly with bound - besides applied - tariff rates. But, how can reductions in tariffs ceilings, i.e. tariff rates that no exporter may ever actually be confronted with, generate market access? The answer to this question relates to the effects of tariff bindings on t...

  9. Improved Bounds for Geometric Permutations

    CERN Document Server

    Rubin, Natan; Sharir, Micha

    2010-01-01

    We show that the number of geometric permutations of an arbitrary collection of $n$ pairwise disjoint convex sets in $\\mathbb{R}^d$, for $d\\geq 3$, is $O(n^{2d-3}\\log n)$, improving Wenger's 20 years old bound of $O(n^{2d-2})$.

  10. Photoassociative Excitation Spectroscopy of Excimer Molecules

    Science.gov (United States)

    Jones, Ronald Blake

    Laser excitation spectroscopy of transitions having dissociative ground states was explored as a tool for the study of excimer molecules. Since the repulsive nature of the ground state constrains collision pairs to large internuclear transitions, bound >=ts free excitation spectra contain more structure than the bound to free fluorescence spectra for the same molecules, therefore containing more information about the potential surfaces. Unique properties of the photoassociative excitation spectroscopy technique are described which allow the dependence of the dipole transition moment on the internuclear separation (mu (R)) to be extracted in a very direct manner. Excitation spectra are presented for the B >=ts X transitions of KrF and XeI for the wavelength (lambda) interval 206 nm KrI are given. This work required the development of a tunable VUV source, which is described.

  11. Diphenylalanine self assembly: novel ion mobility methods showing the essential role of water.

    Science.gov (United States)

    Do, Thanh D; Bowers, Michael T

    2015-04-21

    The mechanism and driving forces behind the formation of diphenylalanine (FF) nanotubes have attracted much attention in the past decades. The hollow structure of the nanotubes suggests a role for water during the self-assembly process. Here, we use novel ion-mobility mass spectrometry methods to probe the early oligomers formed by diphenylalanine peptides. Interestingly, water-bound oligomers are observed in nano-electrospray ionization (ESI) mass spectra in the absence of bulk solvent. In addition, ligated water clusters transit the ion mobility cell but (often) dissociate before detection. These water molecules are shown to be essential for the formation of diphenylalanine oligomers larger than the dimer. The ligated water molecules exist in the solvent free environment either as neutral water or as protonated water clusters, depending on the composition of solvent from which they are sprayed. Water adduction helps stabilize conformers that are otherwise energetically unstable ultimately leading to the assembly of FF nanotubes. PMID:25785477

  12. Universal Entropy Bound for Rotating Systems

    OpenAIRE

    Hod, Shahar

    1999-01-01

    We conjecture a universal upper bound to the entropy of a rotating system. The entropy bound follows from application of the generalized second law of thermodynamics to an idealized gedanken experiment in which an entropy-bearing rotating system falls into a black hole. This bound is stronger than the Bekenstein entropy bound for non-rotating systems.

  13. Tritiated Water Interaction with Stainless Steel

    Energy Technology Data Exchange (ETDEWEB)

    Glen R. Longhurst

    2007-05-01

    Experiments conducted to study tritium permeation of stainless steel at ambient and elevated temperatures revealed that HT converts relatively quickly to HTO. Further, the HTO partial pressure contributes essentially equally with elemental tritium gas in driving permeation through the stainless steel. Such permeation appears to be due to dissociation of the water molecule on the hot stainless steel surface. There is an equilibrium concentration of HTO vapor above adsorbed gas on the walls of the experimental apparatus evident from freezing transients. The uptake process of tritium from the carrier gas involves both surface adsorption and isotopic exchange with surface bound water.

  14. Mesoscopic Simulation of Aggregates in Surfactant/Oil/Water Systems

    Institute of Scientific and Technical Information of China (English)

    苑世领; 蔡政亭; 徐桂英

    2003-01-01

    The aggregates in sodium dedecylsulphate(SDS)/dimethylbenzene/water systems have been investigated using dissipative particles dynamic(DPD) simulation method.Through analyzing three-dimensional structures of aggregates,three simulated results are found.One is the phase separation,which is clearly observed by water density and the aggregates in the simulated cell;another is the water morphology in reverse micelle,which can be found through the isodensity slice of water including bound water,trapped water and bulky water;the third is about the water/oil interface,i.e.,ionic surfactant molecules,SDS,prefer to exist in the interface between water and oil phase at the low concentraion.

  15. Heavy Exotic Molecules with Charm and Bottom

    CERN Document Server

    Liu, Yizhuang

    2016-01-01

    We revisit the formation of pion-mediated heavy-light exotic molecules with both charm and bottom and their chiral partners under the general strictures of both heavy-quark and chiral symmetry. The chiral exotic partners with good parity formed using the $(0^+, 1^+)$ multiplet are about twice more bound than their primary exotic partners formed using the $(0^-,1^-)$ multiplet. The chiral couplings across the multiplets $(0^\\pm, 1^\\pm)$ cause the chiral exotic partners to unbind, and the primary exotic molecules to be about twice more bound, for $J\\leq 1$. Our multi-channel coupling results show that only the charm isosinglet exotic molecules with $J^{PC}=1^{++}$ binds, which we identify as the reported neutral $X(3872)$. Also, the bottom isotriplet exotic with $J^{PC}=1^{+-}$ binds, which we identify as a mixture of the reported charged exotics $Z^+_b(10610)$ and $Z^+_b(10650)$. The bound isosinglet with $J^{PC}=1^{++}$ is suggested as a possible neutral $X_b(10532)$ not yet reported.

  16. Continuous adsorption and biotransformation of micropollutants by granular activated carbon-bound laccase in a packed-bed enzyme reactor.

    Science.gov (United States)

    Nguyen, Luong N; Hai, Faisal I; Dosseto, Anthony; Richardson, Christopher; Price, William E; Nghiem, Long D

    2016-06-01

    Laccase was immobilized on granular activated carbon (GAC) and the resulting GAC-bound laccase was used to degrade four micropollutants in a packed-bed column. Compared to the free enzyme, the immobilized laccase showed high residual activities over a broad range of pH and temperature. The GAC-bound laccase efficiently removed four micropollutants, namely, sulfamethoxazole, carbamazepine, diclofenac and bisphenol A, commonly detected in raw wastewater and wastewater-impacted water sources. Mass balance analysis showed that these micropollutants were enzymatically degraded following adsorption onto GAC. Higher degradation efficiency of micropollutants by the immobilized compared to free laccase was possibly due to better electron transfer between laccase and substrate molecules once they have adsorbed onto the GAC surface. Results here highlight the complementary effects of adsorption and enzymatic degradation on micropollutant removal by GAC-bound laccase. Indeed laccase-immobilized GAC outperformed regular GAC during continuous operation of packed-bed columns over two months (a throughput of 12,000 bed volumes). PMID:26803903

  17. Physics with loosely bound nuclei

    Indian Academy of Sciences (India)

    Chhanda Samanta

    2001-08-01

    The essential aspect of contemporary physics is to understand properties of nucleonic matter that constitutes the world around us. Over the years research in nuclear physics has provided strong guidance in understanding the basic principles of nuclear interactions. But, the scenario of nuclear physics changed drastically as the new generation of accelerators started providing more and more rare isotopes, which are away from the line of stability. These weakly bound nuclei are found to exhibit new forms of nuclear matter and unprecedented exotic behaviour. The low breakup thresholds of these rare nuclei are posing new challenges to both theory and experiments. Fortunately, nature has provided a few loosely bound stable nuclei that have been studied thoroughly for decades. Attempts are being made to find a consistent picture for the unstable nuclei starting from their stable counterparts. Some significant differences in the structure and reaction mechanisms are found.

  18. Concentration Bounds for Stochastic Approximations

    CERN Document Server

    Frikha, Noufel

    2012-01-01

    We obtain non asymptotic concentration bounds for two kinds of stochastic approximations. We first consider the deviations between the expectation of a given function of the Euler scheme of some diffusion process at a fixed deterministic time and its empirical mean obtained by the Monte-Carlo procedure. We then give some estimates concerning the deviation between the value at a given time-step of a stochastic approximation algorithm and its target. Under suitable assumptions both concentration bounds turn out to be Gaussian. The key tool consists in exploiting accurately the concentration properties of the increments of the schemes. For the first case, as opposed to the previous work of Lemaire and Menozzi (EJP, 2010), we do not have any systematic bias in our estimates. Also, no specific non-degeneracy conditions are assumed.

  19. Quantum effects at low-energy atom–molecule interface

    Indian Academy of Sciences (India)

    B Deb; A Rakshit; J Hazra; D Chakraborty

    2013-01-01

    The effects of quantum interference in inter-conversion between cold atoms and diatomic molecules are analysed in this study. Within the framework of Fano’s theory, continuum bound anisotropic dressed state formalism of atom–molecule quantum dynamics is presented. This formalism is applicable in photo- and magneto-associative strong-coupling regimes. The significance of Fano effect in ultracold atom–molecule transitions is discussed. Quantum effects at low-energy atom–molecule interface are important for exploring coherent phenomena in hitherto unexplored parameter regimes.

  20. Quantum Effects at Low Energy Atom-Molecule Interface

    CERN Document Server

    Deb, B; Hazra, J; Chakraborty, D

    2013-01-01

    Quantum interference effects in inter-conversion between cold atoms and diatomic molecules are analysed. Within the framework of Fano's theory, continuum-bound anisotropic dressed state formalism of atom-molecule quantum dynamics is presented. This formalism is applicable in photo- and magneto-associative strong-coupling regimes. The significance of Fano effect in ultracold atom-molecule transitions is discussed. Quantum effects at low energy atom-molecule interface are important for exploring coherent phenomena in hither-to unexplored parameter regimes.

  1. Bound anionic states of adenine

    OpenAIRE

    Harańczyk, Maciej; Gutowski, Maciej; Li, Xiang; Bowen, Kit H.

    2007-01-01

    Anionic states of nucleic acid bases are involved in DNA damage by low-energy electrons and in charge transfer through DNA. Previous gas phase studies of free, unsolvated nucleic acid base parent anions probed only dipole-bound states, which are not present in condensed phase environments, but did not observe valence anionic states, which for purine bases are thought to be adiabatically unbound. Contrary to this expectation, we have demonstrated that some thus far ignored tautomers of adenine...

  2. The bound mu+ mu- system

    OpenAIRE

    Jentschura, U.; Soff, G.; Ivanov, V.; Karshenboim, S.

    1997-01-01

    We consider the hyperfine structure, the atomic spectrum and the decay channels of the bound mu+ mu- system (dimuonium). The annihilation lifetimes of low-lying atomic states of the system lie in the nanosecond range range. The decay rates could be measured by detection of the decay products (high energy photons or electron-positron pairs). The hyperfine structure splitting of the dimuonic system and its decay rate are influenced by electronic vacuum polarization effects in the far time-like ...

  3. Provably Bounded-Optimal Agents

    OpenAIRE

    Russell, S J; Subramanian, D.

    1995-01-01

    Since its inception, artificial intelligence has relied upon a theoretical foundation centered around perfect rationality as the desired property of intelligent systems. We argue, as others have done, that this foundation is inadequate because it imposes fundamentally unsatisfiable requirements. As a result, there has arisen a wide gap between theory and practice in AI, hindering progress in the field. We propose instead a property called bounded optimality. Roughly speaking, an agent is boun...

  4. 78 FR 18326 - Agency Information Collection Activities; Comment Request; Upward Bound and Upward Bound Math...

    Science.gov (United States)

    2013-03-26

    ... Agency Information Collection Activities; Comment Request; Upward Bound and Upward Bound Math Science... Upward Bound Math Science Annual Performance Report. OMB Control Number: 1840-NEW. Type of Review: New... under the regular Upward Bound (UB) and Upward Bound Math and Science (UBMS) Programs. The Department...

  5. IM-CRDS for the analysis of matrix-bound water isotopes: a streamlined (and updated) tool for ecohydrologists to probe small-scale variability in plants Yasuhara, S. (syasuhara@picarro.com)1,Carter, J.A. (jcarter@picarro.com)1, Dennis, K.J. (kdennis@picarro.com)1 1Picarro Inc., 3105 Patrick Henry Drive, Santa Clara, CA 95054

    Science.gov (United States)

    Yasuhara, S.

    2013-12-01

    The ability to measure the isotopic composition of matrix-bound water is valuable to many facets of earth and environmental sciences. For example, ecohydrologists use stable isotopes of oxygen and hydrogen in plant and soil water, in combination with measurements of atmospheric water vapor, surface water and precipitation, to estimate budgets of evapotranspiration. Likewise, water isotopes of oceanic water, brines and other waters with high total dissolved solids (TDS, e.g., juices) are relevant to studying large-scale oceanic circulation, small-scale mixing, groundwater contamination, the balance of evaporation to precipitation, and the provenance of food. Conventionally matrix-bound water has been extracted using cryogenic distillation, whereby water is distilled from the material in question (e.g., a leaf sample) by heating under vacuum and collecting the resultant water vapor using liquid nitrogen. The water can then be analyzed for its stable isotopic composition by a variety of methods, including isotope ratio mass spectrometry and laser techniques, such as Cavity Ring-Down Spectroscopy (CRDS). Here we present recent improvements in an alternative, and stream-lined, solution for integrated sample extraction and isotopic measurement using a Picarro Induction Module (IM) coupled to commercially-available CRDS analyzer from Picarro. This technique is also valuable for waters with high TDS, which can have detrimental effects on flash vaporization process, typically used for the introduction of water to Picarro CRDS water isotope analyzers. The IM works by inductively heating a sample held within a metal sample holder in a glass vial flushed with dry air. Tested samples include leaves, stems, twigs, calibration water, juices, and salt water. The heating process evolves water vapor which is then swept through the system at approximately 150 standard cubic centimeters per minute. The evolved water vapor passes through an activated charcoal cartridge for removal of

  6. The Cost of Bounded Curvature

    CERN Document Server

    Kim, Hyo-Sil

    2011-01-01

    We study the motion-planning problem for a car-like robot whose turning radius is bounded from below by one and which is allowed to move in the forward direction only (Dubins car). For two robot configurations $\\sigma, \\sigma'$, let $\\ell(\\sigma, \\sigma')$ be the shortest bounded-curvature path from $\\sigma$ to $\\sigma'$. For $d \\geq 0$, let $\\ell(d)$ be the supremum of $\\ell(\\sigma, \\sigma')$, over all pairs $(\\sigma, \\sigma')$ that are at Euclidean distance $d$. We study the function $\\dub(d) = \\ell(d) - d$, which expresses the difference between the bounded-curvature path length and the Euclidean distance of its endpoints. We show that $\\dub(d)$ decreases monotonically from $\\dub(0) = 7\\pi/3$ to $\\dub(\\ds) = 2\\pi$, and is constant for $d \\geq \\ds$. Here $\\ds \\approx 1.5874$. We describe pairs of configurations that exhibit the worst-case of $\\dub(d)$ for every distance $d$.

  7. CD molecules 2005: human cell differentiation molecules

    Czech Academy of Sciences Publication Activity Database

    Zola, H.; Swart, B.; Nicholson, I.; Aasted, B.; Bensussan, A.; Boumsell, L.; Buckley, C.; Clark, G.; Drbal, Karel; Engel, P.; Hart, D.; Hořejší, Václav; Isacke, C.; Macardle, P.; Malavasi, F.; Mason, D.; Olive, D.; Saalmüller, A.; Schlossman, S.F.; Schwartz-Albiez, R.; Simmons, P.; Tedder, T.F.; Uguccioni, M.; Warren, H.

    2005-01-01

    Roč. 106, č. 9 (2005), s. 3123-3126. ISSN 0006-4971 Institutional research plan: CEZ:AV0Z5052915 Keywords : CD molecules * leukocyte antigen Subject RIV: EC - Immunology Impact factor: 10.131, year: 2005

  8. Dipole Correlation of the Electronic Structures of theConformations of Water Molecule Evolving Through theNormal Modes of Vibrations Between Angular (C2v to Linear(D∝h Shapes

    Directory of Open Access Journals (Sweden)

    Arindam Chakraborty

    2006-03-01

    Full Text Available In order to settle the issue of equivalence or non-equivalence of the two lone pairsof electrons on oxygen atom in water molecule, a quantum chemical study of the dipolecorrelation of the electronic structure of the molecule as a function of conformationsgenerated following the normal modes of vibrations between the two extremeconformations, C2v (∠HOH at 90o and D∝h (∠HOH at 180o, including the equilibrium one,has been performed. The study invokes quantum mechanical partitioning of moleculardipoles into bond moment and lone pair moment and localization of delocalized canonicalmolecular orbitals, CMO’s into localized molecular orbitals, LMO’s. An earlier suggestion,on the basis of photoelectron spectroscopy, that one lone pair is in p-type and the other is ins-type orbital of O atom of water molecule at its equilibrium shape, and also the qualitative“Squirrel Ears” structure are brought under serious scrutiny. A large number ofconformations are generated and the charge density matrix, dipole moment of eachconformation is computed in terms of the generated canonical molecular orbitals, CMO’sand then Sinanoğlu’s localization method is invoked to localize the CMO’s of eachconformation and the quantum mechanical hybridizations of all the bonds and lone pairs onO center are evaluated in terms of the localized molecular orbitals. Computed datademonstrate that the electronic structures i.e. two bond pairs and two lone pairs and itshybridization status of all conformations of water molecule are straightforward in terms ofthe LMO’s. It is further revealed that the pattern of orbital hybridization changescontinuously as a function of evolution of molecular shape. The close analysis of thegenerated LMO’s reveals that one lone pair is accommodated in a pure p orbital and anotherlone pair is in a hybrid

  9. Vibrational dynamics of thiocyanate and selenocyanate bound to horse heart myoglobin

    Science.gov (United States)

    Maj, Michał; Oh, Younjun; Park, Kwanghee; Lee, Jooyong; Kwak, Kyung-Won; Cho, Minhaeng

    2014-06-01

    The structure and vibrational dynamics of SCN- and SeCN-bound myoglobin have been investigated using polarization-controlled IR pump-probe measurements and quantum chemistry calculations. The complexes are found to be in low and high spin states, with the dominant contribution from the latter. In addition, the Mb:SCN high spin complex exhibits a doublet feature in the thiocyanate stretch IR absorption spectra, indicating two distinct molecular conformations around the heme pocket. The binding mode of the high spin complexes was assigned to occur through the nitrogen atom, contrary to the binding through the sulfur atom that was observed in myoglobin derived from Aplysia Limacina. The vibrational energy relaxation process has been found to occur substantially faster than those of free SCN- and SeCN- ions and neutral SCN- and SeCN-derivatized molecules reported previously. This supports the N-bound configurations of MbNCS and MbNCSe, because S- and Se-bound configurations are expected to have significantly long lifetimes due to the insulation effect by heavy bridge atom like S and Se in such IR probes. Nonetheless, even though their lifetimes are much shorter than those of corresponding free ions in water, the vibrational lifetimes determined for MbNCS and MbNCSe are still fairly long compared to those of azide and cyanide myoglobin systems studied before. Thus, thiocyanate and selenocyanate can be good local probes of local electrostatic environment in the heme pocket. The globin dependence on binding mode and vibrational dynamics is also discussed.

  10. Vibrational dynamics of thiocyanate and selenocyanate bound to horse heart myoglobin

    Energy Technology Data Exchange (ETDEWEB)

    Maj, Michał; Oh, Younjun; Park, Kwanghee; Lee, Jooyong; Cho, Minhaeng, E-mail: mcho@korea.ac.kr [Department of Chemistry, Korea University, Seoul 136-713 (Korea, Republic of); Kwak, Kyung-Won [Department of Chemistry, Chung-Ang University, Seoul 156-756, SouthKorea (Korea, Republic of)

    2014-06-21

    The structure and vibrational dynamics of SCN- and SeCN-bound myoglobin have been investigated using polarization-controlled IR pump-probe measurements and quantum chemistry calculations. The complexes are found to be in low and high spin states, with the dominant contribution from the latter. In addition, the Mb:SCN high spin complex exhibits a doublet feature in the thiocyanate stretch IR absorption spectra, indicating two distinct molecular conformations around the heme pocket. The binding mode of the high spin complexes was assigned to occur through the nitrogen atom, contrary to the binding through the sulfur atom that was observed in myoglobin derived from Aplysia Limacina. The vibrational energy relaxation process has been found to occur substantially faster than those of free SCN{sup −} and SeCN{sup −} ions and neutral SCN- and SeCN-derivatized molecules reported previously. This supports the N-bound configurations of MbNCS and MbNCSe, because S- and Se-bound configurations are expected to have significantly long lifetimes due to the insulation effect by heavy bridge atom like S and Se in such IR probes. Nonetheless, even though their lifetimes are much shorter than those of corresponding free ions in water, the vibrational lifetimes determined for MbNCS and MbNCSe are still fairly long compared to those of azide and cyanide myoglobin systems studied before. Thus, thiocyanate and selenocyanate can be good local probes of local electrostatic environment in the heme pocket. The globin dependence on binding mode and vibrational dynamics is also discussed.

  11. Valence-bound and diffuse-bound anions of 5-azauracil.

    Science.gov (United States)

    Corzo, H H; Dolgounitcheva, O; Zakrzewski, V G; Ortiz, J V

    2014-08-28

    Structures, isomerization energies, and electron binding energies of 5-azauracil and its anions have been calculated ab initio with perturbative, coupled-cluster, and electron-propagator methods. Tautomeric structures, including those produced by proton transfer to a CH group, have been considered. Dyson orbitals and pole strengths from electron-propagator calculations validated a simple, molecular-orbital picture of anion formation. In one case, an electron may enter a delocalized π orbital, yielding a valence-bound (VB) anion with a puckered ring structure. The corresponding electron affinity is 0.27 eV; the vertical electron detachment energy (VEDE) of this anion 1.05 eV. An electron also may enter a molecular orbital that lies outside the nuclear framework, resulting in a diffuse-bound (DB) anion. In the latter case, the electron affinity is 0.06 eV and the VEDE of the DB anion is 0.09 eV. Another VB isomer that is only 0.02 eV more stable than the neutral molecule has a VEDE of 2.0 eV. PMID:25102270

  12. Crystal Structure of Phosphatidylglycerophosphatase (PGPase), a Putative Membrane-Bound Lipid Phosphatase, Reveals a Novel Binuclear Metal Binding Site and Two Proton Wires

    Energy Technology Data Exchange (ETDEWEB)

    Kumaran,D.; Bonnano, J.; Burley, S.; Swaminathan, S.

    2006-01-01

    Phosphatidylglycerophosphatase (PGPase), an enzyme involved in lipid metabolism, catalyzes formation of phosphatidylglycerol from phosphatidylglycerophosphate. Phosphatidylglycerol is a multifunctional phospholipid, found in the biological membranes of many organisms. Here, we report the crystal structure of Listeria monocytogenes PGPase at 1.8 Angstroms resolution. PGPase, an all-helical molecule, forms a homotetramer. Each protomer contains an independent active site with two metal ions, Ca{sup 2+} and Mg{sup 2+}, forming a hetero-binuclear center located in a hydrophilic cavity near the surface of the molecule. The binuclear center, conserved ligands, metal-bound water molecules, and an Asp-His dyad form the active site. The catalytic mechanism of this enzyme is likely to proceed via binuclear metal activated nucleophilic water. The binuclear metal-binding active-site environment of this structure should provide insights into substrate binding and metal-dependent catalysis. A long channel with inter-linked linear water chains, termed 'proton wires', is observed at the tetramer interface. Comparison of similar water chain structures in photosynthetic reaction centers (RCs), Cytochrome f, gramicidin, and bacteriorhodopsin, suggests that PGPase may conduct protons via proton wires.

  13. Occurrence of organically bound tritium in the Mohelno lake system

    Czech Academy of Sciences Publication Activity Database

    Kořínková, Tereza; Světlík, Ivo; Fejgl, Michal; Povinec, P. P.; Šimek, Pavel; Tomášková, Lenka

    2016-01-01

    Roč. 307, č. 3 (2016), s. 2295-2299. ISSN 0236-5731. [10th International Conference on Methods and Applications of Radioanalytical Chemistry (MARC). Kailua Kona, 12.04.2015-17.04.2015] Institutional support: RVO:61389005 Keywords : Mohelno reservoir * Dukovany nuclear power plant * Tissue free water tritium * Non-exchangeable organically bound tritium Subject RIV: DJ - Water Pollution ; Quality Impact factor: 1.034, year: 2014

  14. Causal Entropy Bound for a Spacelike Region

    Science.gov (United States)

    Brustein, R.; Veneziano, G.

    2000-06-01

    The identification of a causal-connection scale motivates us to propose a new covariant bound on entropy within a generic spacelike region. This ``causal entropy bound,'' scaling as EV, and thus lying around the geometric mean of Bekenstein's S/ER and holographic S/A bounds, is checked in various ``critical'' situations. In the case of limited gravity, Bekenstein's bound is the strongest while naive holography is the weakest. In the case of strong gravity, our bound and Bousso's holographic bound are stronger than Bekenstein's, while naive holography is too tight, and hence typically wrong.

  15. Occurrence of organically bound tritium in the Mohelno lake system

    International Nuclear Information System (INIS)

    This study was focused on the 3Hactivitylevels in the unique 'tritium valley' around the Mohelno reservoir, which receives outlet cooling waters from the Dukovany nuclear power plant. Tritium activity levels above the background reference value were found in water from the reservoir and from the effluent part of the Jihlava water, in air moisture and in plant tissues tissue free water tritium(TFWT), and nonexchangeable organically bound tritium (NE-OBT). These zones were discernible that had noticeably different TFWT and NE-OBT values: (1) littoral zones, (2) slopes above the reservoir, (3) plateaus above the reservoir/river. (author)

  16. Optical production of stable ultracold (88)Sr(2) molecules.

    Science.gov (United States)

    Reinaudi, G; Osborn, C B; McDonald, M; Kotochigova, S; Zelevinsky, T

    2012-09-14

    We have produced large samples of stable ultracold (88)Sr(2) molecules in the electronic ground state in an optical lattice. The fast, all-optical method of molecule creation involves a near-intercombination-line photoassociation pulse followed by spontaneous emission with a near-unity Franck-Condon factor. The detection uses excitation to a weakly bound electronically excited vibrational level corresponding to a very large dimer and yields a high-Q molecular vibronic resonance. This is the first of two steps needed to create deeply bound (88)Sr(2) for frequency metrology and ultracold chemistry. PMID:23005643

  17. Volume Stability of Bitumen Bound Building Blocks

    Directory of Open Access Journals (Sweden)

    Thanaya I.N.A.

    2010-01-01

    Full Text Available This paper covers results of laboratory investigations on the volume stability of masonry units incorporating waste materials bound with bitumen (Bitublocks, due to moisture adsorption, thermal exposure and vacuum saturation. The materials used were steel slag, crushed glass, coal fly ash, and 50 pen bitumen. The samples were produced in hot mix method, compacted, then exposed to moist and temperature. It was found that moisture adsorption from the environment caused the Bitublock to expand. The samples with less intense curing regime experienced lower expansion and became stable faster, and vice versa. Under thermal condition (at 70°C, the samples with less intense curing regime underwent higher expansion, and vice versa. They were also highly reversible. Their volume stability was found unique under water exposure. The expansion on first vacuum saturation cycle was irreversible, then largely reversible on the following cycles.

  18. Single-molecule studies using magnetic traps.

    Science.gov (United States)

    Lionnet, Timothée; Allemand, Jean-François; Revyakin, Andrey; Strick, Terence R; Saleh, Omar A; Bensimon, David; Croquette, Vincent

    2012-01-01

    In recent years, techniques have been developed to study and manipulate single molecules of DNA and other biopolymers. In one such technique, the magnetic trap, a single DNA molecule is bound at one end to a glass surface and at the other to a magnetic microbead. Small magnets, whose position and rotation can be controlled, pull on and rotate the microbead. This provides a simple method to stretch and twist the molecule. The system allows one to apply and measure forces ranging from 10(-3) to >100 pN. In contrast to other techniques, the force measurement is absolute and does not require calibration of the sensor. In this article, we describe the principle of the magnetic trap, as well as its use in the measurement of the elastic properties of DNA and the study of DNA-protein interactions. PMID:22194259

  19. Influence of Adsorbed Water on the Oxygen Evolution Reaction on Oxides

    DEFF Research Database (Denmark)

    Siahrostami, Samira; Vojvodic, Aleksandra

    2015-01-01

    We study the interface between adsorbed water and stoichiometric, defect-free (110) rutile oxide surfaces of TiO2, RuO2, and IrO2 in order to understand how water influences the stabilities of the intermediates of the oxygen evolution reaction (OER). In our model the water is treated as explicitly...... molecules binding to bridging oxygens. The third chain interacts weakly and predominantly with the H2O molecules of the second layer, resembling bulk water. We find that the stability of the water layer close to the oxide surface is almost the same as the one found on flat metal surfaces, such as the Pt(111...... adsorbed H2O molecules, which are found to form two-dimensional water chains (layers) on all investigated oxide surfaces. The first chain formed by the most strongly bound H2O molecules is adsorbed on the 5-fold coordinated surface metal atoms. The second chain is composed of less strongly bound H2O...

  20. Water vapour self-continuum and water dimers: 1. Analysis of recent work

    International Nuclear Information System (INIS)

    Recent laboratory observations and advances in theoretical quantum chemistry allow a reappraisal of the fundamental mechanisms that determine the water vapour self-continuum absorption throughout the infrared and millimetre wave spectral regions. By starting from a framework that partitions bimolecular interactions between water molecules into free-pair states, true bound and quasi-bound dimers, we present a critical review of recent observations, continuum models and theoretical predictions. In the near-infrared bands of the water monomer, we propose that spectral features in recent laboratory-derived self-continuum can be well explained as being due to a combination of true bound and quasi-bound dimers, when the spectrum of quasi-bound dimers is approximated as being double the broadened spectrum of the water monomer. Such a representation can explain both the wavenumber variation and the temperature dependence. Recent observations of the self-continuum absorption in the windows between these near-infrared bands indicate that widely used continuum models can underestimate the true strength by around an order of magnitude. An existing far-wing model does not appear able to explain the discrepancy, and although a dimer explanation is possible, currently available observations do not allow a compelling case to be made. In the 8-12 μm window, recent observations indicate that the modern continuum models either do not properly represent the temperature dependence, the wavelength variation, or both. The temperature dependence is suggestive of a transition from the dominance of true bound dimers at lower temperatures to quasi-bound dimers at higher temperatures. In the mid- and far-infrared spectral region, recent theoretical calculations indicate that true bound dimers may explain at least between 20% and 40% of the observed self-continuum. The possibility that quasi-bound dimers could cause an additional contribution of the same size is discussed. Most recent

  1. Two applications of the thermogram of the alcohol/water binary system with compositions of cryobiological interests.

    Science.gov (United States)

    Weng, Lindong; Li, Weizhong; Zuo, Jianguo

    2011-06-01

    Quantitative analyses of the bound water content in the alcohol aqueous solution and its osmotic behavior should be cryobiologically significant. This paper has presented two applications of the thermogram of the alcohol/water system recorded by differential scanning calorimeter (DSC). Both applications are: (1) generating the quantitative relationship between the bound water content and the solution composition; (2) calculating the osmotic virial coefficients for alcohols. Five alcohols including methanol, ethanol, ethylene glycol, propylene glycol and glycerol are investigated. In the present study, partial binary phase diagrams of these five alcohol solutions are determined in the first place. The bound water contents in these solutions are quantitatively evaluated by three criteria afterwards. In the end, the osmotic virial coefficients for these alcohols are calculated according to the osmotic virial equation. It is turned out that the bound water fraction out of the total water content increases with a rising molality. The ability of the solute to restrict water molecules can be weakened when the solution becomes more concentrated. The results also indicate that propylene glycol should be the strongest "water-blocker" while methanol the weakest one. These findings can deepen our understanding of the cryoprotective properties of the alcohols from the perspectives of their roles in binding free water and promoting the osmotic efflux of cell water. PMID:21458437

  2. Monotonicity of the quantum linear programming bound

    OpenAIRE

    Eric M. Rains

    1998-01-01

    The most powerful technique known at present for bounding the size of quantum codes of prescribed minimum distance is the quantum linear programming bound. Unlike the classical linear programming bound, it is not immediately obvious that if the quantum linear programming constraints are satisfiable for dimension K, that the constraints can be satisfied for all lower dimensions. We show that the quantum linear programming bound is indeed monotonic in this sense, and give an explicitly monotoni...

  3. Synchrotron X-ray footprinting as a method to visualize water in proteins.

    Science.gov (United States)

    Gupta, Sayan; Feng, Jun; Chan, Leanne Jade G; Petzold, Christopher J; Ralston, Corie Y

    2016-09-01

    The vast majority of biomolecular processes are controlled or facilitated by water interactions. In enzymes, regulatory proteins, membrane-bound receptors and ion-channels, water bound to functionally important residues creates hydrogen-bonding networks that underlie the mechanism of action of the macromolecule. High-resolution X-ray structures are often difficult to obtain with many of these classes of proteins because sample conditions, such as the necessity of detergents, often impede crystallization. Other biophysical techniques such as neutron scattering, nuclear magnetic resonance and Fourier transform infrared spectroscopy are useful for studying internal water, though each has its own advantages and drawbacks, and often a hybrid approach is required to address important biological problems associated with protein-water interactions. One major area requiring more investigation is the study of bound water molecules which reside in cavities and channels and which are often involved in both the structural and functional aspects of receptor, transporter and ion channel proteins. In recent years, significant progress has been made in synchrotron-based radiolytic labeling and mass spectroscopy techniques for both the identification of bound waters and for characterizing the role of water in protein conformational changes at a high degree of spatial and temporal resolution. Here the latest developments and future capabilities of this method for investigating water-protein interactions and its synergy with other synchrotron-based methods are discussed. PMID:27577756

  4. Analytic description of dipole-bound anion photodetachment

    International Nuclear Information System (INIS)

    An analytical model for a dipole-bound anion (DBA) is proposed based on the exactly solvable three-dimensional Schroedinger equation for the excess electron bound by dipole potential of the parent neutral molecule (NM) in the Born-Oppenheimer approximation. The model gives reasonable analytical approximation for the dependence of the DBA binding energy on the NM dipole moment previously found numerically by many authors. The cross section of one-photon photodetachment of DBA is calculated in explicit analytical form. In the limit of high photon frequency, ω, the calculated cross-section displays ∼ω-2 behavior, which agrees perfectly with the experimental data [Bailey et al., J. Chem. Phys 104, 6976 (1996)]. At the threshold, the cross section demonstrates Gailitis-Damburg oscillations. Numerical dependence is provided for the maximal value of the cross section as a function of the NM dipole moment and the binding energy of the excess electron

  5. Quantum and classical dynamics of water dissociation on Ni(111): A test of the site-averaging model in dissociative chemisorption of polyatomic molecules

    International Nuclear Information System (INIS)

    Recently, we reported the first highly accurate nine-dimensional global potential energy surface (PES) for water interacting with a rigid Ni(111) surface, built on a large number of density functional theory points [B. Jiang and H. Guo, Phys. Rev. Lett. 114, 166101 (2015)]. Here, we investigate site-specific reaction probabilities on this PES using a quasi-seven-dimensional quantum dynamical model. It is shown that the site-specific reactivity is largely controlled by the topography of the PES instead of the barrier height alone, underscoring the importance of multidimensional dynamics. In addition, the full-dimensional dissociation probability is estimated by averaging fixed-site reaction probabilities with appropriate weights. To validate this model and gain insights into the dynamics, additional quasi-classical trajectory calculations in both full and reduced dimensions have also been performed and important dynamical factors such as the steering effect are discussed

  6. Quantum and classical dynamics of water dissociation on Ni(111): A test of the site-averaging model in dissociative chemisorption of polyatomic molecules

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, Bin [Department of Chemistry and Chemical Biology, University of New Mexico, Albuquerque, New Mexico 87131 (United States); Department of Chemical Physics, University of Science and Technology of China, Hefei 230026 (China); Guo, Hua, E-mail: hguo@unm.edu [Department of Chemistry and Chemical Biology, University of New Mexico, Albuquerque, New Mexico 87131 (United States)

    2015-10-28

    Recently, we reported the first highly accurate nine-dimensional global potential energy surface (PES) for water interacting with a rigid Ni(111) surface, built on a large number of density functional theory points [B. Jiang and H. Guo, Phys. Rev. Lett. 114, 166101 (2015)]. Here, we investigate site-specific reaction probabilities on this PES using a quasi-seven-dimensional quantum dynamical model. It is shown that the site-specific reactivity is largely controlled by the topography of the PES instead of the barrier height alone, underscoring the importance of multidimensional dynamics. In addition, the full-dimensional dissociation probability is estimated by averaging fixed-site reaction probabilities with appropriate weights. To validate this model and gain insights into the dynamics, additional quasi-classical trajectory calculations in both full and reduced dimensions have also been performed and important dynamical factors such as the steering effect are discussed.

  7. Formation of Ultracold Molecules

    Energy Technology Data Exchange (ETDEWEB)

    Cote, Robin [Univ. of Connecticut, Storrs, CT (United States)

    2016-01-28

    Advances in our ability to slow down and cool atoms and molecules to ultracold temperatures have paved the way to a revolution in basic research on molecules. Ultracold molecules are sensitive of very weak interactions, even when separated by large distances, which allow studies of the effect of those interactions on the behavior of molecules. In this program, we have explored ways to form ultracold molecules starting from pairs of atoms that have already reached the ultracold regime. We devised methods that enhance the efficiency of ultracold molecule production, for example by tuning external magnetic fields and using appropriate laser excitations. We also investigates the properties of those ultracold molecules, especially their de-excitation into stable molecules. We studied the possibility of creating new classes of ultra-long range molecules, named macrodimers, thousand times more extended than regular molecules. Again, such objects are possible because ultra low temperatures prevent their breakup by collision. Finally, we carried out calculations on how chemical reactions are affected and modified at ultracold temperatures. Normally, reactions become less effective as the temperature decreases, but at ultracold temperatures, they can become very effective. We studied this counter-intuitive behavior for benchmark chemical reactions involving molecular hydrogen.

  8. Bound entangled states invariant under Ux

    Institute of Scientific and Technical Information of China (English)

    Wang Zhen; Wang Zhi-Xi

    2008-01-01

    This paper obtains an entangled condition for isotropic-like states by using an atomic map. It constructs a class of bound entangled states from the entangled condition and shows that the partial transposition of the state from the constructed bound entangled class is an edge bound entangled state by using range criterion.

  9. Bounded rationality and heterogeneous expectations in macroeconomics

    NARCIS (Netherlands)

    D. Massaro

    2012-01-01

    This thesis studies the effect of individual bounded rationality on aggregate macroeconomic dynamics. Boundedly rational agents are specified as using simple heuristics in their decision making. An important aspect of the type of bounded rationality described in this thesis is that the population of

  10. Upper Bounds on Numerical Approximation Errors

    DEFF Research Database (Denmark)

    Raahauge, Peter

    2004-01-01

    This paper suggests a method for determining rigorous upper bounds on approximationerrors of numerical solutions to infinite horizon dynamic programming models.Bounds are provided for approximations of the value function and the policyfunction as well as the derivatives of the value function. The...... approximations of a standard (strictly concave)growth model.KEYWORDS: Numerical approximation errors, Bellman contractions, Error bounds...

  11. K(6S-4P) stimulated emission excited by bound-bound transitions of NaK

    International Nuclear Information System (INIS)

    The stimulated fluorescence emission in potassium atom excited by hybrid transitions involving heteronuclear molecules has been studied by a wavelength tunable pump laser. The emission lines are identified as 691.1 nm and 693.9 nm (6S-4P1/2,3/2) transitions. The stimulated character is confirmed by measurements of threshold, exponential increase and high intensity as well as temporal and polarization properties. The origin of the stimulated emission are both Four Wave Parametric Emission and Amplified Spontaneous Emission, with the first one dominant as indicated by intensity and temporal measurements. The main excitation mechanism is shown to be bound-bound NaK (X-B) transitions. This is confirmed by the absence of signal in pure potassium vapour, coincidence of excitation lines with NaK (X-B) bound-bound transitions in the excitation and absorption spectra. The fluorescence spectra have been also identified as NaK (B-X). The process observed proceeds via hybrid resonances. The measured exponential gain factor of the signal is γEp-6.6. Using this process the rate of energy transfer NaK(B) → K(4P), K7s = 8.8x10-9 cm3s-1 and K5d 1.6x10-10 cm3s-1 has been estimated. (author)

  12. Water

    International Nuclear Information System (INIS)

    An up-date overview of the situation of the Austrian waters is given by analyzing the status of the water quality (groundwater, surface waters) and water protection measures. Maps containing information of nitrate and atrazine in groundwaters (analyses at monitoring stations), nitrate contents and biological water quality of running waters are included. Finally, pollutants (nitrate, orthophosphate, ammonium, nitrite, atrazine etc.) trends in annual mean values and median values for the whole country for the years 1992-1999 are presented in tables. Figs. 5. (nevyjel)

  13. Atoms as Qed bound atoms

    International Nuclear Information System (INIS)

    The relevance of Quantum Electrodynamics (Qed) in contemporary atomic structure theory is reviewed. Recent experimental advances allow both the production of heavy ions of high charge as well as the measurement of atomic properties with a precision never achieved before. The description of heavy atoms with few electrons via the successive incorporation of one, two, etcetera photons in a rigorous manner and within the bound state Furry representation of Qed is technically feasible. For many-electron atoms the many-body (correlation) effects are very important and it is practically impossible to evaluate all the relevant Feynman diagrams to the required accuracy. Thus, it is necessary to develop a theoretical scheme in which the radiative and nonradiative effects are taken into account in an effective way making emphasis in electronic correlation. Preserving gauge invariance, and avoiding both continuum dissolution and variational collapse are basic problems that must be solved when using effective potential methods and finite-basis representations of them. In this context, we shall discuss advances and problems in the description of atoms as Qed bound states. (Author)

  14. Application of MRIL-WD (Magnetic Resonance Imaging Logging While Drilling) for irreducible water saturation, total reservoir, free-fluid, bound-fluid porosity measurements and its value for the petrophysical analysis of RT/RM data from the Shah Deniz well

    Science.gov (United States)

    Amirov, Elnur

    2016-04-01

    Sperry-Sun (Sperry Drilling Services) is the leader in MWD/LWD reliability, has developed the industry's first LWD NMR/MRIL-WD (nuclear magnetic resonance) tool. The MRIL-WD (magnetic resonance imaging logging-while-drilling) service directly measures the T1 component of hydrogen in subsurface rock units while drilling to obtain total reservoir porosity and to dissect the observed total porosity into its respective components of free fluid and bound fluid porosity. These T1 data are used to secure accurate total, free-fluid, capillary-bound water, and clay-bound water porosity of the reservoir sections which can be drilled in the several Runs. Over the last decade, results from Magnetic Resonance Imaging logs (NMR) have added significant value to petrophysical analysis and understanding by providing total, free-fluid and bound-fluid porosities, combined with fluid typing capabilities. With MRIL-WD very valuable Real-Time or Recorded Memory data/information is now available during or shortly after the drilling operation (formation properties measurement can be taken right after a drill bit penetration), while trip in and trip out as well. A key point in utilizing MRIL in an LWD environment is motion-tolerant measurements. Recent MRIL-WD logging runs from the Shah Deniz wells located in the Khazarian-Caspian Sea of the Azerbaijan Republic helped to delineate and assess hydrocarbon bearing zones. Acquired results demonstrate how MRIL data can be acquired while-drilling and provide reliable/high quality measurements. Magnetic Resonance Imaging logs at some developments wells have become a cornerstone in formation evaluation and petrophysical understanding. By providing total, free-fluid, and bound-fluid porosities together with fluid typing, MRIL results have significantly added to the assessment of reservoirs. In order to reduce NPT (Non-Productive Time) and save the rig operations time, there is always the desire to obtain logging results as soon as possible

  15. Ultracold molecules from ultracold atoms: a case study with the KRb molecule

    OpenAIRE

    Julienne, Paul S.

    2008-01-01

    Ultracold collisions of cold atoms or molecules make the bound states of the collision complex formed from the two colliding species accessible for control and manipulation of the cold species or the complex. Such resonances are best treated by a resonant scattering theory, which in the ultracold domain can take advantage of the properties of the long-range potential and the methods of multichannel quantum defect theory. Coupled channels calculations on the threshold scattering states and bou...

  16. Relevance of the ICRP biokinetic model for dietary organically bound tritium

    International Nuclear Information System (INIS)

    Ingested dietary tritium can participate in metabolic processes, and become synthesized into organically bound tritium in the tissues and organs. The distribution and retention of the organically bound tritium throughout the body are much different than tritium in the body water. The International Commission on Radiological Protection (ICRP) Publication 56 (1989) has a biokinetic model to calculate dose from the ingestion of organically bound dietary tritium. The model predicts that the dose from the ingestion of organically bound dietary tritium is about 2.3 times higher than from the ingestion of the same activity of tritiated water. Under steady-state conditions, the calculated dose rate (using the first principle approach) from the ingestion of dietary organically bound tritium can be twice that from the ingestion of tritiated water. For an adult, the upper-bound dose estimate for the ingestion of dietary organically bound tritium is estimated to be close to 2.3 times higher than that of tritiated water. Therefore, given the uncertainty in the dose calculation with respect to the actual relevant dose, the ICRP biokinetic model for organically bound tritium is sufficient for dosimetry for adults. (author)

  17. Bounded generalized Harish-Chandra modules

    OpenAIRE

    Penkov, Ivan; Serganova, Vera

    2007-01-01

    Let $\\gg$ be a complex reductive Lie algebra and $\\kk\\subset\\gg$ be any reductive in $\\gg$ subalgebra. We call a $(\\gg,\\kk)$-module $M$ bounded if the $\\kk$-multiplicities of $M$ are uniformly bounded. In this paper we initiate a general study of simple bounded $(\\gg,\\kk)$-modules. We prove a strong necessary condition for a subalgebra $\\kk$ to be bounded (Corollary \\ref{cor1.6}), i.e. to admit an infinite-dimensional simple bounded $(\\gg,\\kk)$-module, and then establish a sufficient conditio...

  18. Higgs mass bounds from the functional RG

    International Nuclear Information System (INIS)

    We investigate a Top-Yukawa toy model to study Higgs mass bounds in the framework of the functional renormalization group (RG). Starting the calculations with a quartic ultraviolet (UV) potential we get a finite range of values for the Higgs mass in the infrared for a given cutoff. The bounds appear in a natural way as a consequence of the RG flow. The lower mass bound is approached for a vanishing UV quartic coupling. Furthermore, we study the influence of higher-dimensional operators on the lower Higgs mass bound. We find that even seemingly RG irrelevant interactions can take a substantial influence on the lower bound for the Higgs mass.

  19. Trapping molecules on chips

    CERN Document Server

    Santambrogio, Gabriele

    2015-01-01

    In the last years, it was demonstrated that neutral molecules can be loaded on a microchip directly from a supersonic beam. The molecules are confined in microscopic traps that can be moved smoothly over the surface of the chip. Once the molecules are trapped, they can be decelerated to a standstill, for instance, or pumped into selected quantum states by laser light or microwaves. Molecules are detected on the chip by time-resolved spatial imaging, which allows for the study of the distribution in the phase space of the molecular ensemble.

  20. Soluble HLA-G Molecules Are Increased during Acute Leukemia, Especially in Subtypes Affecting Monocytic and Lymphoid Lineages1

    OpenAIRE

    Gros, Frédéric; Sebti, Yasmine; de Guibert, Sophie; Branger, Bernard; Bernard, Marc; Fauchet, Renée; Amiot, Laurence

    2006-01-01

    Human leukocyte antigen G (HLA-G) molecules corresponding to nonclassic class I genes of the major histocompatibility complex exhibit immunomodulatory properties. They are either membrane-bound or solubly expressed during certain tumoral malignancies. Soluble human leukocyte antigen G (sHLA-G) molecules seem more frequently expressed than membrane-bound isoforms during hematologic malignancies, such as lymphoproliferative disorders. Assay of these molecules by enzyme-linked immunosorbent assa...

  1. Mechanisms of the vasorelaxing effects of CORM-3, a water-soluble carbon monoxide-releasing molecule: interactions with eNOS.

    Science.gov (United States)

    Alshehri, Ali; Bourguignon, Marie-Pierre; Clavreul, Nicolas; Badier-Commander, Cécile; Gosgnach, Willy; Simonet, Serge; Vayssettes-Courchay, Christine; Cordi, Alex; Fabiani, Jean-Noël; Verbeuren, Tony J; Félétou, Michel

    2013-03-01

    The purpose of the present work was to elucidate the mechanisms underlying the endothelium-dependent and endothelium-independent components of the vascular relaxation induced by a water-soluble and ruthenium-based carbon monoxide (CO)-releasing agent, tricarbonylchloro(glycinato)ruthenium(II) (CORM-3). Changes in isometric tension and cyclic guanosine monophosphate (cGMP) production were measured in isolated aortic rings from normotensive Wistar-Kyoto rats. Nitric oxide (NO) generation was assessed in cultured human umbilical vein endothelial cells (HUVEC) by electron spin resonance. In rat aortic rings, CORM-3, but not the inactivated compound, iCORM, induced relaxations. In rings with but not in those without endothelium relaxations were partially inhibited by L-nitro-arginine (L-NA), 1H-(1,2,4)-oxadiazolo(4,2-a)quinoxalin-1-one (ODQ), or hydroxocobalamin, inhibitors of NO-synthase, soluble guanylyl cyclase, and scavenger of NO, respectively. In rings with and without endothelium, deoxyhemoglobin abolished the relaxations. A combination of potassium channel blockers (barium, glibenclamide, and iberiotoxin) blunted the relaxation in rings without endothelium. CORM-3 produced an endothelium-dependent generation of cGMP that was inhibited by L-NA. CORM-3, but not iCORM, inhibited the endothelium-dependent relaxation to acetylcholine without affecting the response to sodium nitroprusside. In HUVEC, CORM-3 produced a concentration-dependent release of NO. Therefore, CORM-3-induced relaxations involve the soluble guanylyl cyclase-independent activation of smooth muscle potassium channels. Additionally, CO can produce concomitantly activation and inhibition of NO synthase, the former being responsible for the endothelium- and cGMP-dependent effect of CORM-3, the latter for the inhibition of acetylcholine-induced endothelium-dependent relaxations. PMID:23296254

  2. Capacity Bounds for Parallel Optical Wireless Channels

    KAUST Repository

    Chaaban, Anas

    2016-01-01

    A system consisting of parallel optical wireless channels with a total average intensity constraint is studied. Capacity upper and lower bounds for this system are derived. Under perfect channel-state information at the transmitter (CSIT), the bounds have to be optimized with respect to the power allocation over the parallel channels. The optimization of the lower bound is non-convex, however, the KKT conditions can be used to find a list of possible solutions one of which is optimal. The optimal solution can then be found by an exhaustive search algorithm, which is computationally expensive. To overcome this, we propose low-complexity power allocation algorithms which are nearly optimal. The optimized capacity lower bound nearly coincides with the capacity at high SNR. Without CSIT, our capacity bounds lead to upper and lower bounds on the outage probability. The outage probability bounds meet at high SNR. The system with average and peak intensity constraints is also discussed.

  3. Information bounds for Gaussian copulas

    CERN Document Server

    Hoff, Peter D; Wellner, Jon A

    2011-01-01

    Often of primary interest in the analysis of multivariate data are the copula parameters describing the dependence among the variables, rather than the univariate marginal distributions. Since the ranks of a multivariate dataset are invariant to changes in the univariate marginal distributions, rank-based procedures are natural candidates as semiparametric estimators of copula parameters. Asymptotic information bounds for such estimators can be obtained from an asymptotic analysis of the rank likelihood, i.e. the probability of the multivariate ranks. In this article, we obtain limiting normal distributions of the rank likelihood for Gaussian copula models. Our results cover models with structured correlation matrices, such as exchangeable, autoregressive and circular correlation, as well as unstructured correlation matrices. For all Gaussian copula models, the limiting distribution of the rank likelihood ratio is shown to be equal to that of a parametric likelihood ratio for an appropriately chosen multivari...

  4. Spectral computations for bounded operators

    CERN Document Server

    Ahues, Mario; Limaye, Balmohan

    2001-01-01

    Exact eigenvalues, eigenvectors, and principal vectors of operators with infinite dimensional ranges can rarely be found. Therefore, one must approximate such operators by finite rank operators, then solve the original eigenvalue problem approximately. Serving as both an outstanding text for graduate students and as a source of current results for research scientists, Spectral Computations for Bounded Operators addresses the issue of solving eigenvalue problems for operators on infinite dimensional spaces. From a review of classical spectral theory through concrete approximation techniques to finite dimensional situations that can be implemented on a computer, this volume illustrates the marriage of pure and applied mathematics. It contains a variety of recent developments, including a new type of approximation that encompasses a variety of approximation methods but is simple to verify in practice. It also suggests a new stopping criterion for the QR Method and outlines advances in both the iterative refineme...

  5. Antibaryon-nucleus bound states

    CERN Document Server

    Hrtánková, J

    2014-01-01

    We calculated antibaryon ($\\bar{B}$ = $\\bar{p}$, $\\bar{\\Lambda}$, $\\bar{\\Sigma}$, $\\bar{\\Xi}$) bound states in selected nuclei within the relativistic mean-field (RMF) model. The G-parity motivated $\\bar{B}$-meson coupling constants were scaled to yield corresponding potentials consistent with available experimental data. Large polarization of the nuclear core caused by $\\bar{B}$ was confirmed. The $\\bar{p}$ annihilation in the nuclear medium was incorporated by including a phenomenological imaginary part of the optical potential. The calculations using a complex $\\bar{p}$-nucleus potential were performed fully self-consistently. The $\\bar{p}$ widths significantly decrease when the phase space reduction is considered for $\\bar{p}$ annihilation products, but they still remain sizeable for potentials consistent with $\\bar{p}$-atom data.

  6. Towards Bounded Infeasible Code Detection

    CERN Document Server

    Christ, Jürgen; Schäf, Martin

    2012-01-01

    A first step towards more reliable software is to execute each statement and each control-flow path in a method once. In this paper, we present a formal method to automatically compute test cases for this purpose based on the idea of a bounded infeasible code detection. The method first unwinds all loops in a program finitely often and then encodes all feasible executions of the loop-free programs in a logical formula. Helper variables are introduced such that a theorem prover can reconstruct the control-flow path of a feasible execution from a satisfying valuation of this formula. Based on this formula, we present one algorithm that computes a feasible path cover and one algorithm that computes a feasible statement cover. We show that the algorithms are complete for loop-free programs and that they can be implemented efficiently. We further provide a sound algorithm to compute procedure summaries which makes the method scalable to larger programs.

  7. Performance Bounds of Quaternion Estimators.

    Science.gov (United States)

    Xia, Yili; Jahanchahi, Cyrus; Nitta, Tohru; Mandic, Danilo P

    2015-12-01

    The quaternion widely linear (WL) estimator has been recently introduced for optimal second-order modeling of the generality of quaternion data, both second-order circular (proper) and second-order noncircular (improper). Experimental evidence exists of its performance advantage over the conventional strictly linear (SL) as well as the semi-WL (SWL) estimators for improper data. However, rigorous theoretical and practical performance bounds are still missing in the literature, yet this is crucial for the development of quaternion valued learning systems for 3-D and 4-D data. To this end, based on the orthogonality principle, we introduce a rigorous closed-form solution to quantify the degree of performance benefits, in terms of the mean square error, obtained when using the WL models. The cases when the optimal WL estimation can simplify into the SWL or the SL estimation are also discussed. PMID:25643416

  8. Nuclear magnetic resonance relaxometry as a spectroscopic probe of the coordination sphere of a paramagnetic metal bound to a humic acid mixture

    International Nuclear Information System (INIS)

    Protons on water molecules are strongly affected by paramagnetic ions. Since the acid-base properties of water facilitate rapid proton exchange, a single proton nuclear magnetic resonance (NMR) signal is seen in aqueous solutions of paramagnetic ions. Proton relaxation times are significantly affected by paramagnetic species and the readily detectable single signal serves as a powerful amplifier of the information contained concerning the protons in the paramagnetic environment. Where water molecules coordinated to free paramagnetic ions and to metal complexes of ligands that form non-labile (on the NMR time scale) complexes, the effects on water in the two environments can be distinguished. This can provide information on the nature of the ligand binding sites. The example of Cu2+ bound to the Laurentian humic acid mixture reported here using convenient low field NMR relaxometers shows that the information can enrich our understanding of complexation and speciation in the presence of complex mixture ligands characteristic of natural water systems. In this case, the data underline the role of aggregation and conformation in defining the complexation sites

  9. Dimers, Effective Interactions, and Pauli Blocking Effects in a Bilayer of Cold Fermionic Polar Molecules

    OpenAIRE

    Zinner, N. T.; Armstrong, J. R.; Volosniev, A G; Fedorov, D.V.; Jensen, A. S.

    2011-01-01

    We consider a bilayer setup with two parallel planes of cold fermionic polar molecules when the dipole moments are oriented perpendicular to the planes. The binding energy of two-body states with one polar molecule in each layer is determined and compared to various analytic approximation schemes in both coordinate- and momentum-space. The effective interaction of two bound dimers is obtained by integrating out the internal dimer bound state wave function and its robustness under analytical a...

  10. How to make big molecules fly out of liquid water: applications, features and physics of laser assisted liquid phase dispersion mass spectrometry.

    Science.gov (United States)

    Charvat, Ales; Abel, Bernd

    2007-07-14

    Applications, features, and mechanistic details of laser assisted liquid phase dispersion mass spectrometry are highlighted and discussed. It has been used in the past to directly isolate charged molecular aggregates from the liquid phase and to determine their molecular weight employing sensitive time-of-flight mass spectrometry. The liquid matrix in this MALDI (matrix assisted laser desorption and ionization) type approach consists of a 10 microm diameter free liquid filament in vacuum (or a free droplet) which is excited with a focused infrared laser pulse tuned to match the absorption frequency of the OH-stretch vibration of bulk water near 2.8 microm. Due to these features we will refer to the approach as free liquid matrix assisted laser dispersion of ions or ionic aggregates (IR-FL-MALDI), although also LILBID ("laser induced liquid beam (bead) desorption and ionization") has been proposed early as a descriptive acronym for the technique and may be used alternatively. Low-charge-state macromolecular adducts are isolated in the gas phase from solution via a yet poorly characterized mechanism which sensitively depends upon the laser intensity and wavelength, and after the gentle liquid-to-vacuum transfer the aggregates are analyzed via time-of-flight (TOF) mass spectrometry (MS). Possible mechanisms for the isolation and charging of biomolecules directly from liquid solution are discussed in the present contribution. Recent technical advances such as minimizing the sample consumption, strategies for high throughput mass spectrometry, and coupling of liquid beam MS with HPLC will be highlighted as well. An interesting feature of IR-FL-MALDI is what we call the linear response, i.e., a surprising linearity of the gas phase mass signal on the solution concentration over many orders of magnitude for a large number of biomolecular systems as well as ions. Due to these features the approach may be regarded as a true solution probing spectroscopy, which enables

  11. Conduction mechanisms and stability of single molecule nanoparticle/molecule/nanoparticle junctions

    International Nuclear Information System (INIS)

    Nanoparticle/molecule/nanoparticle dimer assemblies have been successfully trapped by dielectrophoresis across nanogap electrodes, enabling temperature dependent charge transport measurements through an oligomeric phenylene ethynylene molecule, and transition from direct tunnelling to Fowler-Nordheim tunnelling is observed at ∼1.5 V. Samples formed by dielectrophoresis show better contact stability than those formed by receding meniscus. The junction shows stable operation over several weeks in a vacuum, but current increases with time upon exposure to air, possibly due to the adsorbed water molecules near the molecule/gold nanoparticle contacts

  12. Ultracold Long-Range Rydberg Molecules with Complex Multichannel Spectra.

    Science.gov (United States)

    Eiles, Matthew T; Greene, Chris H

    2015-11-01

    A generalized class of ultralong-range Rydberg molecules is predicted which consist of a multichannel Rydberg atom whose outermost electron creates a chemical bond with a distant ground state atom. Such multichannel Rydberg molecules exhibit favorable properties for laser excitation, because states exist where the quantum defect varies strongly with the principal quantum number. The resulting occurrence of near degeneracies with states of high orbital angular momentum promotes the admixture of low l into the high l deeply bound "trilobite" molecule states, thereby circumventing the usual difficulty posed by electric dipole selection rules. Such states also can exhibit multiscale binding possibilities that could present novel options for quantum manipulation. PMID:26588378

  13. Rotational structures of long-range diatomic molecules

    OpenAIRE

    Gao, Bo

    2004-01-01

    We present a systematic understanding of the rotational structure of a long-range (vibrationally highly-excited) diatomic molecule. For example, we show that depending on a quantum defect, the least-bound vibrational state of a diatomic molecule with $-C_n/r^n$ ($n>2$) asymptotic interaction can have only 1, 2, and up to a maximum of $n-2$ rotational states. A classification scheme of diatomic molecules is proposed, in which each class has a distinctive rotational structure and corresponds to...

  14. Kinetics, in silico docking, molecular dynamics, and MM-GBSA binding studies on prototype indirubins, KT5720, and staurosporine as phosphorylase kinase ATP-binding site inhibitors: the role of water molecules examined.

    Science.gov (United States)

    Hayes, Joseph M; Skamnaki, Vicky T; Archontis, Georgios; Lamprakis, Christos; Sarrou, Josephine; Bischler, Nicolas; Skaltsounis, Alexios-Leandros; Zographos, Spyros E; Oikonomakos, Nikos G

    2011-03-01

    With an aim toward glycogenolysis control in Type 2 diabetes, we have investigated via kinetic experiments and computation the potential of indirubin (IC₅₀ > 50 μM), indirubin-3'-oxime (IC₅₀ = 144 nM), KT5720 (K(i) = 18.4 nM) and staurosporine (K(i) = 0.37 nM) as phosphorylase kinase (PhKγtrnc) ATP-binding site inhibitors, with the latter two revealed as potent inhibitors in the low nM range. Because of lack of structural information, we have exploited information from homologous kinase complexes to direct in silico calculations (docking, molecular dynamics, and MMGBSA) to predict the binding characteristics of the four ligands. All inhibitors are predicted to bind in the same active site area as the ATP adenine ring, with binding dominated by hinge region hydrogen bonds to Asp104:O and Met106:O (all four ligands) and also Met106:NH (for the indirubins). The PhKγtrnc-staurosporine complex has the greatest number of receptor-ligand hydrogen bonds, while for the indirubin-3'-oxime and KT5720 complexes there is an important network of interchanging water molecules bridging inhibitor-enzyme contacts. The MM-GBSA results revealed the source of staurosporine's low nM potency to be favorable electrostatic interactions, while KT5720 has strong van der Waals contributions. KT5720 interacts with the greatest number of protein residues either by direct or 1-water bridged hydrogen bond interactions, and the potential for more selective PhK inhibition based on a KT5720 analogue has been established. Including receptor flexibility in Schrödinger induced-fit docking calculations in most cases correctly predicted the binding modes as compared with the molecular dynamics structures; the algorithm was less effective when there were key structural waters bridging receptor-ligand contacts. PMID:21287607

  15. Accurate reproduction of 161 small-molecule complex crystal structures using the EUDOC program: expanding the use of EUDOC to supramolecular chemistry.

    Directory of Open Access Journals (Sweden)

    Qi Wang

    Full Text Available EUDOC is a docking program that has successfully predicted small-molecule-bound protein complexes and identified drug leads from chemical databases. To expand the application of the EUDOC program to supramolecular chemistry, we tested its ability to reproduce crystal structures of small-molecule complexes. Of 161 selected crystal structures of small-molecule guest-host complexes, EUDOC reproduced all these crystal structures with guest structure mass-weighted root mean square deviations (mwRMSDs of <1.0 A relative to the corresponding crystal structures. In addition, the average interaction energy of these 161 guest-host complexes (-50.1 kcal/mol was found to be nearly half of that of 153 previously tested small-molecule-bound protein complexes (-108.5 kcal/mol, according to the interaction energies calculated by EUDOC. 31 of the 161 complexes could not be reproduced with mwRMSDs of <1.0 A if neighboring hosts in the crystal structure of a guest-host complex were not included as part of the multimeric host system, whereas two of the 161 complexes could not be reproduced with mwRMSDs of <1.0 A if water molecules were excluded from the host system. These results demonstrate the significant influence of crystal packing on small molecule complexation and suggest that EUDOC is able to predict small-molecule complexes and that it is useful for the design of new materials, molecular sensors, and multimeric inhibitors of protein-protein interactions.

  16. Control of the Selectivity of the Aquaporin Water Channel Family by Global Orientational Tuning

    Science.gov (United States)

    Tajkhorshid, Emad; Nollert, Peter; Jensen, Morten Ø.; Miercke, Larry J. W.; O'Connell, Joseph; Stroud, Robert M.; Schulten, Klaus

    2002-04-01

    Aquaporins are transmembrane channels found in cell membranes of all life forms. We examine their apparently paradoxical property, facilitation of efficient permeation of water while excluding protons, which is of critical importance to preserving the electrochemical potential across the cell membrane. We have determined the structure of the Escherichia coli aquaglyceroporin GlpF with bound water, in native (2.7 angstroms) and in W48F/F200T mutant (2.1 angstroms) forms, and carried out 12-nanosecond molecular dynamics simulations that define the spatial and temporal probability distribution and orientation of a single file of seven to nine water molecules inside the channel. Two conserved asparagines force a central water molecule to serve strictly as a hydrogen bond donor to its neighboring water molecules. Assisted by the electrostatic potential generated by two half-membrane spanning loops, this dictates opposite orientations of water molecules in the two halves of the channel, and thus prevents the formation of a ``proton wire,'' while permitting rapid water diffusion. Both simulations and observations revealed a more regular distribution of channel water and an increased water permeability for the W48F/F200T mutant.

  17. A New and Simple Approach to Determine the Abundance of Hydrogen Molecules on Interstellar Ice Mantles

    CERN Document Server

    Hincelin, Ugo; Herbst, Eric

    2014-01-01

    Water is usually the main component of ice mantles, which cover the cores of dust grains in cold portions of dense interstellar clouds. When molecular hydrogen is adsorbed onto an icy mantle through physisorption, a common assumption in gas-grain rate equation models is to use an adsorption energy for molecular hydrogen on a pure water substrate. However, at high density and low temperature, when H2 is efficiently adsorbed onto the mantle, its surface abundance can be strongly overestimated if this assumption is still used. Unfortunately, the more detailed microscopic Monte Carlo treatment cannot be used to study the abundance of H2 in ice mantles if a full gas-grain network is utilized. We present a numerical method adapted for rate-equation models that takes into account the possibility that an H2 molecule can, while diffusing on the surface, find itself bound to another hydrogen molecule, with a far weaker bond than the H2-water bond, which can lead to more efficient desorption. We label the ensuing desorp...

  18. Instanton bound states in ABJM theory

    Energy Technology Data Exchange (ETDEWEB)

    Hatsuda, Yasuyuki [DESY Hamburg (Germany). Theory Group; Tokyo Institute of Technology (Japan). Dept. of Physics; Moriyama, Sanefumi [Nagoya Univ. (Japan). Kobayashi Maskawa Inst. and Graduate School of Mathematics; Okuyama, Kazumi [Shinshu Univ., Matsumoto, Nagano (Japan). Dept. of Physics

    2013-06-15

    The partition function of the ABJM theory receives non-perturbative corrections due to instanton effects. We study these non-perturbative corrections, including bound states of worldsheet instantons and membrane instantons, in the Fermi-gas approach. We require that the total non-perturbative correction should be always finite for arbitrary Chern-Simons level. This finiteness is realized quite non-trivially because each bound state contribution naively diverges at some levels. The poles of each contribution should be canceled out in total. We use this pole cancellation mechanism to find unknown bound state corrections from known ones. We conjecture a general expression of the bound state contribution. Summing up all the bound state contributions, we find that the effect of bound states is simply incorporated into the worldsheet instanton correction by a redefinition of the chemical potential in the Fermi-gas system. Analytic expressions of the 3- and 4-membrane instanton corrections are also proposed.

  19. Thermodynamic law from the entanglement entropy bound

    Science.gov (United States)

    Park, Chanyong

    2016-04-01

    From black hole thermodynamics, the Bekenstein bound has been proposed as a universal thermal entropy bound. It has been further generalized to an entanglement entropy bound which is valid even in a quantum system. In a quantumly entangled system, the non-negativity of the relative entropy leads to the entanglement entropy bound. When the entanglement entropy bound is saturated, a quantum system satisfies the thermodynamicslike law with an appropriately defined entanglement temperature. We show that the saturation of the entanglement entropy bound accounts for a universal feature of the entanglement temperature proportional to the inverse of the system size. In addition, we show that the deformed modular Hamiltonian under a global quench also satisfies the generalized entanglement entropy boundary after introducing a new quantity called the entanglement chemical potential.

  20. Nuclear magnetic relaxation studies on polyelectrolytes with water

    International Nuclear Information System (INIS)

    Studies on the longitudinal and transverse relaxation times (T1 and T2) of 1H and 23Na in water-polyelectrolytes systems were carried out. The polyelectrolyte samples used were sodium polystyrene sulfonate, sodium lignosulfonate and sodium cellulose sulfate. The water content (Wc's) of the samples was varied from 0 to 2.0 (grams of water per gram of polyelectrolyte). A minimum value for 1HT1 values of water in the system was observed at a temperature ranging from -25 to -40 degree C. The temperature where the 1HT1 minimum value was observed depended on Wc, corresponding to the crystallization of water in each system. From 1HT1 two groups of water molecules (bound and free water) are considered to exist in water-polyelectrolyte systems. The calculated τc values of bound water increased with decreasing temperature from the order of 10-7 sec to 10-6 sec. The observed 23Na in the water-polyelectrolyte systems relaxed with a single T1. 23NaT2 values showed that the relaxation process was separated into two fractions