Science.gov

Sample records for additional water molecules

  1. Water: a responsive small molecule.

    PubMed

    Shultz, Mary Jane; Vu, Tuan Hoang; Meyer, Bryce; Bisson, Patrick

    2012-01-17

    Unique among small molecules, water forms a nearly tetrahedral yet flexible hydrogen-bond network. In addition to its flexibility, this network is dynamic: bonds are formed or broken on a picosecond time scale. These unique features make probing the local structure of water challenging. Despite the challenges, there is intense interest in developing a picture of the local water structure due to water's fundamental importance in many fields of chemistry. Understanding changes in the local network structure of water near solutes likely holds the key to unlock problems from analyzing parameters that determine the three dimensional structure of proteins to modeling the fate of volatile materials released into the atmosphere. Pictures of the local structure of water are heavily influenced by what is known about the structure of ice. In hexagonal I(h) ice, the most stable form of solid water under ordinary conditions, water has an equal number of donor and acceptor bonds; a kind of symmetry. This symmetric tetrahedral coordination is only approximately preserved in the liquid. The most obvious manifestation of this altered tetrahedral bonding is the greater density in the liquid compared with the solid. Formation of an interface or addition of solutes further modifies the local bonding in water. Because the O-H stretching frequency is sensitive to the environment, vibrational spectroscopy provides an excellent probe for the hydrogen-bond structure in water. In this Account, we examine both local interactions between water and small solutes and longer range interactions at the aqueous surface. Locally, the results suggest that water is not a symmetric donor or acceptor, but rather has a propensity to act as an acceptor. In interactions with hydrocarbons, action is centered at the water oxygen. For soluble inorganic salts, interaction is greater with the cation than the anion. The vibrational spectrum of the surface of salt solutions is altered compared with that of neat

  2. Enantioselective Michael addition of water.

    PubMed

    Chen, Bi-Shuang; Resch, Verena; Otten, Linda G; Hanefeld, Ulf

    2015-02-09

    The enantioselective Michael addition using water as both nucleophile and solvent has to date proved beyond the ability of synthetic chemists. Herein, the direct, enantioselective Michael addition of water in water to prepare important β-hydroxy carbonyl compounds using whole cells of Rhodococcus strains is described. Good yields and excellent enantioselectivities were achieved with this method. Deuterium labeling studies demonstrate that a Michael hydratase catalyzes the water addition exclusively with anti-stereochemistry.

  3. Enantioselective Michael Addition of Water

    PubMed Central

    Chen, Bi-Shuang; Resch, Verena; Otten, Linda G; Hanefeld, Ulf

    2015-01-01

    The enantioselective Michael addition using water as both nucleophile and solvent has to date proved beyond the ability of synthetic chemists. Herein, the direct, enantioselective Michael addition of water in water to prepare important β-hydroxy carbonyl compounds using whole cells of Rhodococcus strains is described. Good yields and excellent enantioselectivities were achieved with this method. Deuterium labeling studies demonstrate that a Michael hydratase catalyzes the water addition exclusively with anti-stereochemistry. PMID:25529526

  4. Water molecules orientation in surface layer

    NASA Astrophysics Data System (ADS)

    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.

  5. Water based drilling mud additive

    SciTech Connect

    McCrary, J.L.

    1983-12-13

    A water based fluid additive useful in drilling mud used during drilling of an oil or gas well is disclosed, produced by reacting water at temperatures between 210/sup 0/-280/sup 0/ F. with a mixture comprising in percent by weight: gilsonite 25-30%, tannin 7-15%, lignite 25-35%, sulfonating compound 15-25%, water soluble base compound 5-15%, methylene-yielding compound 1-5%, and then removing substantially all of the remaining water to produce a dried product.

  6. Conserved water molecules in bacterial serine hydroxymethyltransferases.

    PubMed

    Milano, Teresa; Di Salvo, Martino Luigi; Angelaccio, Sebastiana; Pascarella, Stefano

    2015-10-01

    Water molecules occurring in the interior of protein structures often are endowed with key structural and functional roles. We report the results of a systematic analysis of conserved water molecules in bacterial serine hydroxymethyltransferases (SHMTs). SHMTs are an important group of pyridoxal-5'-phosphate-dependent enzymes that catalyze the reversible conversion of l-serine and tetrahydropteroylglutamate to glycine and 5,10-methylenetetrahydropteroylglutamate. The approach utilized in this study relies on two programs, ProACT2 and WatCH. The first software is able to categorize water molecules in a protein crystallographic structure as buried, positioned in clefts or at the surface. The other program finds, in a set of superposed homologous proteins, water molecules that occur approximately in equivalent position in each of the considered structures. These groups of molecules are referred to as 'clusters' and represent structurally conserved water molecules. Several conserved clusters of buried or cleft water molecules were found in the set of 11 bacterial SHMTs we took into account for this work. The majority of these clusters were not described previously. Possible structural and functional roles for the conserved water molecules are envisaged. This work provides a map of the conserved water molecules helpful for deciphering SHMT mechanism and for rational design of molecular engineering experiments.

  7. Modelling water molecules inside cyclic peptide nanotubes

    NASA Astrophysics Data System (ADS)

    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.

  8. Classical interaction model for the water molecule.

    PubMed

    Baranyai, András; Bartók, Albert

    2007-05-14

    The authors propose a new classical model for the water molecule. The geometry of the molecule is built on the rigid TIP5P model and has the experimental gas phase dipole moment of water created by four equal point charges. The model preserves its rigidity but the size of the charges increases or decreases following the electric field created by the rest of the molecules. The polarization is expressed by an electric field dependent nonlinear polarization function. The increasing dipole of the molecule slightly increases the size of the water molecule expressed by the oxygen-centered sigma parameter of the Lennard-Jones interaction. After refining the adjustable parameters, the authors performed Monte Carlo simulations to check the ability of the new model in the ice, liquid, and gas phases. They determined the density and internal energy of several ice polymorphs, liquid water, and gaseous water and calculated the heat capacity, the isothermal compressibility, the isobar heat expansion coefficients, and the dielectric constant of ambient water. They also determined the pair-correlation functions of ambient water and calculated the energy of the water dimer. The accuracy of theirs results was satisfactory.

  9. Evidence of water molecules--a statistical evaluation of water molecules based on electron density.

    PubMed

    Nittinger, Eva; Schneider, Nadine; Lange, Gudrun; Rarey, Matthias

    2015-04-27

    Water molecules play important roles in many biological processes, especially when mediating protein-ligand interactions. Dehydration and the hydrophobic effect are of central importance for estimating binding affinities. Due to the specific geometric characteristics of hydrogen bond functions of water molecules, meaning two acceptor and two donor functions in a tetrahedral arrangement, they have to be modeled accurately. Despite many attempts in the past years, accurate prediction of water molecules-structurally as well as energetically-remains a grand challenge. One reason is certainly the lack of experimental data, since energetic contributions of water molecules can only be measured indirectly. However, on the structural side, the electron density clearly shows the positions of stable water molecules. This information has the potential to improve models on water structure and energy in proteins and protein interfaces. On the basis of a high-resolution subset of the Protein Data Bank, we have conducted an extensive statistical analysis of 2.3 million water molecules, discriminating those water molecules that are well resolved and those without much evidence of electron density. In order to perform this classification, we introduce a new measurement of electron density around an individual atom enabling the automatic quantification of experimental support. On the basis of this measurement, we present an analysis of water molecules with a detailed profile of geometric and structural features. This data, which is freely available, can be applied to not only modeling and validation of new water models in structural biology but also in molecular design.

  10. Rotovibrational states of the water molecule on the sun.

    PubMed

    Leite, Bruno S; Bastos, Cristiano C; Pavão, Antonio C

    2016-12-01

    The infrared spectrum of water observed in sunspots is complex and dense, with bands separated by approximately 0.01 cm(-1). For top asymmetrical molecules, there is no theoretical approach that allows for the calculation of rotovibrational energy with such precision. Experimentally derived rotovibracional energy levels of water at high temperatures combined with variational calculations have been used for the band assignments. These energy levels are employed to refine the analysis of a small portion of the infrared absorption spectrum. Such procedure has allowed for the identification of additional 55 bands to the 70 already identified as rotovibrational transitions of the water molecule. Our new assignments, which include pure and cross transitions, offer additional evidence of the existence of water on the sun, but above all they illustrate the complexity of the solar spectrum that involves states with higher levels of rotational excitation. Given the conditions on the sun, more molecules of water would occur in excited electronic states, which include apolar and paramagnetic states, generating intense bands in the spectrum. Since there is an analytical solution for the rotovibrational transitions of linear molecules, we were able to identify 16 bands relative to the excited electronic states (1)B2 and (3)A1 in the sunspot spectrum. Density functional B3LYP/AUG-cc-pVTZ calculations of the electric and magnetic dipole are employed to discuss some consequences of the presence of excited states of water in the dynamics of sunspots and solar magnetic field.

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

    NASA Astrophysics Data System (ADS)

    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.

  12. From single molecules to water networks: Dynamics of water adsorption on Pt(111)

    NASA Astrophysics Data System (ADS)

    Naderian, Maryam; Groß, Axel

    2016-09-01

    The adsorption dynamics of water on Pt(111) was studied using ab initio molecular dynamics simulations based on density functional theory calculations including dispersion corrections. Sticking probabilities were derived as a function of initial kinetic energy and water coverage. In addition, the energy distribution upon adsorption was monitored in order to analyze the energy dissipation process. We find that on the water pre-covered surface the sticking probability is enhanced because of the attractive water-water interaction and the additional effective energy dissipation channels to the adsorbed water molecules. The water structures forming directly after the adsorption on the pre-covered surfaces do not necessarily correspond to energy minimum structures.

  13. Effect of water on overbased sulfonate engine oil additives.

    PubMed

    Tavacoli, J W; Dowding, P J; Steytler, D C; Barnes, D J; Routh, A F

    2008-04-15

    The presence and effect of water on calcium carbonate nanoparticles used in engine additives, stabilized with a sulfonate surfactant, is investigated using small-angle neutron scattering, dynamic light scattering, Fourier transform infrared spectroscopy, and rheometry. These techniques provide complementary data that suggests the formation of a layer of water around the core of the particles ensuring continued colloidal stability yet increasing the dispersion viscosity. Through the use of small-angle neutron scattering, the dimensions of this layer have been quantified to effectively one or two water molecules in thickness. The lack of a significant electrostatic repulsion is evidence that the water layer is insufficient to cause major dissociation of surface ions.

  14. Rotational motion of a single water molecule in a buckyball.

    PubMed

    Farimani, A Barati; Wu, Yanbin; Aluru, N R

    2013-11-07

    Encapsulation of a single water molecule in a buckyball (C60) can provide fundamental insights into the properties of water. Investigation of a single water molecule is feasible through its solitary confinement in C60. In this paper, we performed a detailed study of the properties and dynamics of a single water molecule in a buckyball using DFT and MD simulations. We report on the enhancement of rotational diffusion and entropy of a water molecule in C60, compared to a bulk water molecule. H2O@C60 has zero translational diffusion and terahertz revolution frequency. The harmonic, high amplitude rotation of a single water molecule in C60 is compared to stochastic behavior of bulk water molecules. The combination of large rotational and negligible translational motion of water in C60 creates new opportunities in nanotechnology applications.

  15. Visualizing Water Molecules in Transmembrane Proteins Using Radiolytic Labeling Methods

    SciTech Connect

    Orban, T.; Gupta, S; Palczewski, K; Chance, M

    2010-01-01

    Essential to cells and their organelles, water is both shuttled to where it is needed and trapped within cellular compartments and structures. Moreover, ordered waters within protein structures often colocalize with strategically placed polar or charged groups critical for protein function, yet it is unclear if these ordered water molecules provide structural stabilization, mediate conformational changes in signaling, neutralize charged residues, or carry out a combination of all these functions. Structures of many integral membrane proteins, including G protein-coupled receptors (GPCRs), reveal the presence of ordered water molecules that may act like prosthetic groups in a manner quite unlike bulk water. Identification of 'ordered' waters within a crystalline protein structure requires sufficient occupancy of water to enable its detection in the protein's X-ray diffraction pattern, and thus, the observed waters likely represent a subset of tightly bound functional waters. In this review, we highlight recent studies that suggest the structures of ordered waters within GPCRs are as conserved (and thus as important) as conserved side chains. In addition, methods of radiolysis, coupled to structural mass spectrometry (protein footprinting), reveal dynamic changes in water structure that mediate transmembrane signaling. The idea of water as a prosthetic group mediating chemical reaction dynamics is not new in fields such as catalysis. However, the concept of water as a mediator of conformational dynamics in signaling is just emerging, because of advances in both crystallographic structure determination and new methods of protein footprinting. Although oil and water do not mix, understanding the roles of water is essential to understanding the function of membrane proteins.

  16. Spectroscopy of tryptophan derivatives in supersonic expansions: Addition of solvent molecules

    NASA Astrophysics Data System (ADS)

    Sipior, Jeffrey; Sulkes, Mark

    1988-05-01

    The addition of solvent molecules, primarily water and some alcohols, to isolated tryptophan derivative molecules has been carried out using supersonic free jet techniques. The derivatives studied include 3-indole acetic acid, 3-indole propionic acid, N-acetyltryptophan ethyl ester, tryptamine, and tryptophol. The primary spectroscopic method employed was laser induced fluorescence, with some individual bands also characterized by fluorescence lifetime measurements or dispersed emission spectra. Unlike solvent addition to indoles already studied, these tryptophan derivatives also offer polar addition sites on the 3-indole chain. Addition to these sites, further removed from the electronic transition, produces solvent shifts of the complex origins that are small compared to the red shifts observed in indoles; small blueshifts occur in some instances. Competition between binding at the 3-indole polar group and the indole moiety nitrogen sites is strongly unequal, with the polar 3-indole chain sites favored, especially for larger solvent molecules. In tryptamine, which was studied most extensively, a variety of -OH-bearing solvents were able to collapse the multiple origin bands, due to different conformers, to only one prominent solvent conformer feature. Similar though less pronounced effects were seen in trytophol. Growth of solvent bands was more indiscriminate for the other derivatives studied and was consistent with formation of complexes separately with each bare molecule conformer. The observation of a solvent induced conformation brings up the question of whether tryptophan itself may be ``steered'' predominantly to one conformation by solution interactions and, if so, whether this plays a role in the molecule's fluorescence probe properties.

  17. A transferable classical potential for the water molecule.

    PubMed

    Baranyai, András; Kiss, Péter T

    2010-10-14

    We developed a new model for the water molecule which contains only three Gaussian charges. Using the gas-phase geometry the dipole moment of the molecule matches, the quadrupole moment closely approximates the experimental values. The negative charge is connected by a harmonic spring to its gas-phase position. The polarized state is identified by the equality of the intermolecular electrostatic force and the spring force acting on the negative charge. In each timestep the instantaneous position of the massless negative charge is determined by iteration. Using the technique of Ewald summation, we derived expressions for the potential energy, the forces, and the pressure for Gaussian charges. The only properties to be fitted are the half-width values of the Gaussian charge distributions and the parameters of the nonelectrostatic repulsion-attraction potential. We determined the properties of gas-phase clusters up to six molecules, the internal energy and density of ambient water and hexagonal ice. We calculated the equilibrium density of ice VII as a function of pressure. As an additional test, we calculated the pair-correlation function, the isotherm compressibility, the heat capacity, and the self-diffusion coefficients for ambient water. As far as we know, this is the first classical model of water which is able to estimate both ends of the phase diagram, the high pressure ice VII, and the gas clusters of water with excellent accuracy.

  18. Water molecules in clay minerals: Thermodynamic functions and hydration

    NASA Astrophysics Data System (ADS)

    Gailhanou, Helène; Amouric, Marc; Olives, Juan; Rogez, Jacques; van Miltenburg, J. C.; van der Berg, G. J. K.; de Weireld, G.; Gaucher, E.; Blanc, P.

    2010-05-01

    Thermodynamic functions and adsorption of water molecules are very important properties for clay minerals. Smectite MX-80 and mixed-layer illite-smectite ISCz-1 were selected. They were first carefully characterized (HRTEM with EDX analysis), revealing original results. Then, the thermodynamic properties of water in clay were obtained by (i) comparison of the thermodynamic properties of anhydrous and hydrated minerals, between 0 and 350 K (adiabatic calorimetry, solution isothermal calorimetry), and (ii) water vapor adsorption isotherms, between 300 and 380 K (magnetic suspension thermobalance). Solution isothermal calorimetry is used to determine the enthalpies of formation of the minerals (1 bar and 298 K). Comparison of the results, for the anhydrous and the hydrated minerals, leads to the enthalpies of hydration at 298 K. Adiabatic calorimetry measurements give the heat capacities of the minerals from 5 to 350 K. Entropies, enthalpies of formation and Gibbs free energies of formation, for the anhydrous and the hydrated minerals, and then, entropies of hydration, enthalpies of hydration and Gibbs free energies of hydration, between 0 and 350 K, are finally obtained. Comparison of two close hydration states leads to the entropy, the enthalpy and the Gibbs free energy of the adsorption reaction: H2O free - H2O adsorbed. The Cp(T) curve, for the heat capacity of water in clay - i.e., the difference between the heat capacities of the hydrated and the anhydrous minerals -, shows that water in clay is a glass at low temperature, undergoes one or two continuous glass transitions between 150 and 270 K, and behaves as free liquid water above 273 K. The two glass transitions might correspond to two types of water molecules: (i) first adsorbed water molecules, bound to the interlayer cations of the clay mineral; (ii) last adsorbed water molecules, not bound to the interlayer cations. In addition, water vapor adsorption isotherms are obtained from 298 to 378 K (magnetic

  19. Dissociative Electron Attachment of Water Molecules

    NASA Astrophysics Data System (ADS)

    Belkacem, Ali; Adaniya, Hidehito; Osipov, Timur; Weber, Thorsten; Lee, Sun Y.; Hertlein, Marcus; Rudek, Benedikt

    2008-05-01

    A Coltrims method is developed to measure the kinetic energy and angular distribution of fragment negative ions arising from dissociative electron attachment of molecules. A low energy pulsed electron gun is used in combination with pulsing the extraction plates of the Coltrims spectrometer. This technique is applied to study the negative oxygen anion channel for the three resonances, ^2B1, ^2A1, and ^2B2 resonances of water. The measured kinetic energy of the O- fragment gives a good measure of the two-body channel versus three-body channel for each resonance. The angular distribution of the O- fragments with respect tom the electron beam direction is found reflect well the symmetry of the resonance state. The experimental results are compared to the theoretical predictions.

  20. Water: one molecule, two surfaces, one mistake

    NASA Astrophysics Data System (ADS)

    Vega, Carlos

    2015-05-01

    In order to rigorously evaluate the energy and dipole moment of a certain configuration of molecules, one needs to solve the Schrödinger equation. Repeating this for many different configurations allows one to determine the potential energy surface (PES) and the dipole moment surface (DMS). Since the early days of computer simulation, it has been implicitly accepted that for empirical potentials the charges used to fit the PES should also be used to describe the DMS. This is a mistake. Partial charges are not observable magnitudes. They should be regarded as adjustable fitting parameters. Optimal values used to describe the PES are not necessarily the best to describe the DMS. One could use two fits: one for the PES and the other for the DMS. This is a common practice in the quantum chemistry community, but not used so often by the community performing computer simulations. This idea affects all types of modelling of water (with the exception of ab initio calculations) from coarse-grained to non-polarisable and polarisable models. We anticipate that an area that will benefit dramatically from having both, a good PES and a good DMS, is the modelling of water in the presence of electric fields.

  1. The Large Quadrupole of Water Molecules

    SciTech Connect

    Niu, Shuqiang; Tan, Ming-Liang; Ichiye, Toshhiko

    2011-04-07

    Many quantum mechanical calculations indicate water molecules in the gas and liquid phase have much larger quadrupole moments than any of the common site models of water for computer simulations. Here, comparisons of multipoles from quantum mechanical/molecular mechanical (QM/MM) calculations at the MP2/aug-cc-pVQZ level on a B3LYP/aug-cc-pVQZ level geometry of a waterlike cluster and from various site models show that the increased square planar quadrupole can be attributed to the p-orbital character perpendicular to the molecular plane of the highest occupied molecular orbital as well as a slight shift of negative charge toward the hydrogens. The common site models do not account for the p-orbital type electron density and fitting partial charges of TIP4P- or TIP5P-type models to the QM/MM dipole and quadrupole give unreasonable higher moments. Furthermore, six partial charge sites are necessary to account reasonably for the large quadrupole, and polarizable site models will not remedy the problem unless they account for the p-orbital in the gas phase since the QM calculations show it is present there too. On the other hand, multipole models by definition can use the correct multipoles and the electrostatic potential from the QM/MM multipoles is much closer than that from the site models to the potential from the QM/MM electron density. Finally, Monte Carlo simulations show that increasing the quadrupole in the soft-sticky dipole-quadrupole-octupole multipole model gives radial distribution functions that are in good agreement with experiment

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

    PubMed Central

    Yamamoto, Eiji; Akimoto, Takuma; 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 and aging. 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. PMID:24739933

  3. Structure and dynamics of water molecules confined in triglyceride oils.

    PubMed

    Groot, Carien C M; Velikov, Krassimir P; Bakker, Huib J

    2016-10-26

    Though it is commonly known that a small amount of water can be present in triglyceride oil, a molecular picture of how water molecules organize in the oil phase is lacking. We investigate the hydrogen-bond configuration and dynamics of water in triacetin, tributyrin and trioctanoin using linear infrared and time-resolved two-dimensional infrared (2DIR) spectroscopy of the water hydroxyl stretch vibration. We identify water molecules with a single strong hydrogen bond to the triglyceride, water molecules with two weaker hydrogen bonds to the triglycerides, and water clusters. These species do not interconvert on the 20 ps timescale of the experiment, as evidenced by the absence of cross-peaks in the 2DIR spectrum. The vibrational response of water molecules with a single strong hydrogen bond to the triglyceride depends strongly on the excitation frequency, revealing the presence of different subspecies of singly-bound water molecules that correspond to different hydrogen-bond locations. In contrast, the water molecules with two weaker hydrogen bonds to the triglyceride correspond to a single, specific hydrogen-bond configuration; these molecules likely bridge the carbonyl groups of adjacent triglyceride molecules, which can have considerable influence on liquid triglyceride properties.

  4. Water addition, evaporation and water holding capacity of poultry litter.

    PubMed

    Dunlop, Mark W; Blackall, Patrick J; Stuetz, Richard M

    2015-12-15

    Litter moisture content has been related to ammonia, dust and odour emissions as well as bird health and welfare. Improved understanding of the water holding properties of poultry litter as well as water additions to litter and evaporation from litter will contribute to improved litter moisture management during the meat chicken grow-out. The purpose of this paper is to demonstrate how management and environmental conditions over the course of a grow-out affect the volume of water A) applied to litter, B) able to be stored in litter, and C) evaporated from litter on a daily basis. The same unit of measurement has been used to enable direct comparison-litres of water per square metre of poultry shed floor area, L/m(2), assuming a litter depth of 5cm. An equation was developed to estimate the amount of water added to litter from bird excretion and drinking spillage, which are sources of regular water application to the litter. Using this equation showed that water applied to litter from these sources changes over the course of a grow-out, and can be as much as 3.2L/m(2)/day. Over a 56day grow-out, the total quantity of water added to the litter was estimated to be 104L/m(2). Litter porosity, water holding capacity and water evaporation rates from litter were measured experimentally. Litter porosity decreased and water holding capacity increased over the course of a grow-out due to manure addition. Water evaporation rates at 25°C and 50% relative humidity ranged from 0.5 to 10L/m(2)/day. Evaporation rates increased with litter moisture content and air speed. Maintaining dry litter at the peak of a grow-out is likely to be challenging because evaporation rates from dry litter may be insufficient to remove the quantity of water added to the litter on a daily basis.

  5. Experimental Study of Water Cluster Molecules with Relevance to Mesospheric Clouds

    NASA Astrophysics Data System (ADS)

    Robertson, Scott; Sternovsky, Zoltan; Horanyi, Mihaly

    2000-10-01

    We have begun an experimental investigation of the properties of the water cluster molecules responsible for clouds occurring in the polar mesopause. These clusters disturb the charge balance in the ionosphere by attaching electrons which then creates localized reductions in the electron density. A supersonic nozzle sprays a mixture of water vapor and argon into vacuum and the expansion leads to condensation of clusters with 4 to 11 water molecules. Initial measurements are of the collision cross section of these molecules with neutral gas. The cross sections have a minimum at six waters consistent with the tighter molecular arrangement predicted for this cluster number. Additional measurements are underway for charging processes.

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

    NASA Astrophysics Data System (ADS)

    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.

  7. Quantum Tunneling of Water in Beryl: A New State of the Water Molecule.

    PubMed

    Kolesnikov, Alexander I; Reiter, George F; Choudhury, Narayani; Prisk, Timothy R; Mamontov, Eugene; Podlesnyak, Andrey; Ehlers, George; Seel, Andrew G; Wesolowski, David J; Anovitz, Lawrence M

    2016-04-22

    Using neutron scattering and ab initio simulations, we document the discovery of a new "quantum tunneling state" of the water molecule confined in 5 Å channels in the mineral beryl, characterized by extended proton and electron delocalization. We observed a number of peaks in the inelastic neutron scattering spectra that were uniquely assigned to water quantum tunneling. In addition, the water proton momentum distribution was measured with deep inelastic neutron scattering, which directly revealed coherent delocalization of the protons in the ground state.

  8. Quantum Tunneling of Water in Beryl. A New State of the Water Molecule

    DOE PAGES

    Kolesnikov, Alexander I.; Reiter, George F.; Choudhury, Narayani; ...

    2016-04-22

    When using neutron scattering and ab initio simulations, we document the discovery of a new “quantum tunneling state” of the water molecule confined in 5 Å channels in the mineral beryl, characterized by extended proton and electron delocalization. We observed a number of peaks in the inelastic neutron scattering spectra that were uniquely assigned to water quantum tunneling. Additionally, the water proton momentum distribution was measured with deep inelastic neutron scattering, which directly revealed coherent delocalization of the protons in the ground state.

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

    NASA Astrophysics Data System (ADS)

    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 CH3 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 CH3 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.

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

    PubMed

    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.

  11. Relaxational dynamics of water molecules at protein surface

    NASA Astrophysics Data System (ADS)

    Dellerue, S.; Bellissent-Funel, M.-C.

    2000-08-01

    Relaxational dynamics of water molecules at the surface of a C-phycocyanin protein is studied by high resolution quasi-elastic neutron scattering. The neutron quasi-elastic spectra are well described by the α-relaxation process of mode coupling theory of supercooled liquids. The relaxation times of interfacial water exhibit a power law dependence on the wave vector Q. The average diffusion coefficient is 10 times lower than that of bulk water. This confirms that there is a retardation of water molecules at the protein surface which is in good agreement with the results of water at the surface of hydrophilic model systems.

  12. 21 CFR 173.310 - Boiler water additives.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 3 2011-04-01 2011-04-01 false Boiler water additives. 173.310 Section 173.310... CONSUMPTION Specific Usage Additives § 173.310 Boiler water additives. Boiler water additives may be safely... water. Copolymer contains not more than 0.5 percent by weight of acrylic acid monomer (dry weight...

  13. 21 CFR 173.310 - Boiler water additives.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Boiler water additives. 173.310 Section 173.310... CONSUMPTION Specific Usage Additives § 173.310 Boiler water additives. Boiler water additives may be safely... water. Copolymer contains not more than 0.5 percent by weight of acrylic acid monomer (dry weight...

  14. 21 CFR 173.310 - Boiler water additives.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 3 2013-04-01 2013-04-01 false Boiler water additives. 173.310 Section 173.310... CONSUMPTION Specific Usage Additives § 173.310 Boiler water additives. Boiler water additives may be safely... water. Copolymer contains not more than 0.5 percent by weight of acrylic acid monomer (dry weight...

  15. 21 CFR 173.310 - Boiler water additives.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 3 2012-04-01 2012-04-01 false Boiler water additives. 173.310 Section 173.310... CONSUMPTION Specific Usage Additives § 173.310 Boiler water additives. Boiler water additives may be safely... water. Copolymer contains not more than 0.5 percent by weight of acrylic acid monomer (dry weight...

  16. On the several molecules and nanostructures of water.

    PubMed

    Whitney, Cynthia Kolb

    2012-01-01

    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.

  17. On the Several Molecules and Nanostructures of Water

    PubMed Central

    Whitney, Cynthia Kolb

    2012-01-01

    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. PMID:22312305

  18. Comparison of calculated cross sections for secondary electron emission from a water molecule and clusters of water molecules by protons

    SciTech Connect

    Long, K.A.; Paretzke, H.G. )

    1991-07-15

    Double-differential cross sections for the emission of secondary electrons, as a function of emission angle and energy, from a water molecule, a cluster of water molecules, and liquid water due to proton impact have been calculated using the dielectric response function of the target material and a method which uses an integral formulation of the density-functional theory. From these double-differential cross sections, single-differential and total cross sections, and the energy loss per unit path length, have been calculated by successive integration. The results have been compared to available experimental results and, in the case of single-differential cross sections, also to empirical models. A comparison has been made between the results for the molecule and the central molecule of the cluster in order to obtain insight into how the cross sections might change in the condensed phase, namely in liquid water.

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

    PubMed

    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.

  20. On equilibrium structures of the water molecule

    NASA Astrophysics Data System (ADS)

    Császár, Attila G.; Czakó, Gábor; Furtenbacher, Tibor; Tennyson, Jonathan; Szalay, Viktor; Shirin, Sergei V.; Zobov, Nikolai F.; Polyansky, Oleg L.

    2005-06-01

    Equilibrium structures are fundamental entities in molecular sciences. They can be inferred from experimental data by complicated inverse procedures which often rely on several assumptions, including the Born-Oppenheimer approximation. Theory provides a direct route to equilibrium geometries. A recent high-quality ab initio semiglobal adiabatic potential-energy surface (PES) of the electronic ground state of water, reported by Polyansky et al. [Polyansky et al.Science 299, 539 (2003)] and called CVRQD here, is analyzed in this respect. The equilibrium geometries resulting from this direct route are deemed to be of higher accuracy than those that can be determined by analyzing experimental data. Detailed investigation of the effect of the breakdown of the Born-Oppenheimer approximation suggests that the concept of an isotope-independent equilibrium structure holds to about 3×10-5Å and 0.02° for water. The mass-independent [Born-Oppenheimer (BO)] equilibrium bond length and bond angle on the ground electronic state PES of water is reBO=0.95782Å and θeBO=104.485°, respectively. The related mass-dependent (adiabatic) equilibrium bond length and bond angle of H2O16 is read=0.95785Å and θead=104.500°, respectively, while those of D2O16 are read=0.95783Å and θead=104.490°. Pure ab initio prediction of J =1 and 2 rotational levels on the vibrational ground state by the CVRQD PESs is accurate to better than 0.002cm-1 for all isotopologs of water considered. Elaborate adjustment of the CVRQD PESs to reproduce all observed rovibrational transitions to better than 0.05cm-1 (or the lower ones to better than 0.0035cm-1) does not result in noticeable changes in the adiabatic equilibrium structure parameters. The expectation values of the ground vibrational state rotational constants of the water isotopologs, computed in the Eckart frame using the CVRQD PESs and atomic masses, deviate from the experimentally measured ones only marginally, especially for A0 and B0. The

  1. 21 CFR 173.310 - Boiler water additives.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 3 2014-04-01 2014-04-01 false Boiler water additives. 173.310 Section 173.310... Boiler water additives. Boiler water additives may be safely used in the preparation of steam that will... Total not to exceed 1.5 parts per million in boiler feed water. Copolymer contains not more than...

  2. Adsorption mechanism of water molecule on goethite (010) surface

    NASA Astrophysics Data System (ADS)

    Xiu, Fangyuan; Zhou, Long; Xia, Shuwei; Yu, Liangmin

    2016-12-01

    Goethite widely exists among ocean sediments; it plays an important role in fixing heavy metals and adsorbing organic contaminants. So the understanding of the adsorbing process of water molecule on its surface will be very helpful to further reveal such environmental friendly processes. The configuration, electronic properties and interaction energy of water molecules adsorbed on pnma goethite (010) surface were investigated in detail by using density functional theory on 6-31G (d,p) basis set and projector- augment wave (PAW) method. The mechanism of the interaction between goethite surface and H2O was proposed. Despite the differences in total energy, there are four possible types of water molecule adsorption configurations on goethite (010) surface (Aa, Ab, Ba, Bb), forming coordination bond with surface Fe atom. Results of theoretical modeling indicate that the dissociation process of adsorbed water is an endothermic reaction with high activation energy. The dissociation of adsorbed water molecule is a proton transportation process between water's O atoms and surface. PDOS results indicate that the bonding between H2O and (010) surface is due to the overlapping of water's 2p orbitals and Fe's 3d orbitals. These results clarify the mechanism on how adsorbed water is dissociated on the surface of goethite and potentially provide useful information of the surface chemistry of goethite.

  3. Local order and mobility of water molecules around ambivalent helices.

    PubMed

    Bhattacharjee, Nicholus; Biswas, Parbati

    2011-10-27

    Water on a protein surface plays a key role in determining the structure and dynamics of proteins. Compared to the properties of bulk water, many aspects of the structure and dynamics of the water surrounding the proteins are less understood. It is interesting therefore to explore how the properties of the water within the solvation shell around the peptide molecule depend on its specific secondary structure. In this work we investigate the orientational order and residence times of the water molecules to characterize the structure, energetics, and dynamics of the hydration shell water around ambivalent peptides. Ambivalent sequences are identical sequences which display multiple secondary structures in different proteins. Molecular dynamics simulations of representative proteins containing variable helix, variable nonhelix, and conserved helix are also used to explore the local structure and mobility of water molecules in their vicinity. The results, for the first time, depict a different water distribution pattern around the conserved and variable helices. The water molecules surrounding the helical segments in variable helices are found to possess a less locally ordered structure compared to those around their corresponding nonhelical counterparts and conserved helices. The long conserved helices exhibit extremely high local residence times compared to the helical conformations of the variable helices, whereas the residence times of the nonhelical conformations of the variable helices are comparable to those of the short conserved helices. This differential pattern of the structure and dynamics of water molecules in the vicinity of conserved/variable helices may lend valuable insights for understanding the role of solvent effects in determining sequence ambivalency and help in improving the accuracy of water models used in the simulations of proteins.

  4. Energetics of displacing water molecules from protein binding sites: consequences for ligand optimization.

    PubMed

    Michel, Julien; Tirado-Rives, Julian; Jorgensen, William L

    2009-10-28

    A strategy in drug design is to consider enhancing the affinity of lead molecules with structural modifications that displace water molecules from a protein binding site. Because success of the approach is uncertain, clarification of the associated energetics was sought in cases where similar structural modifications yield qualitatively different outcomes. Specifically, free-energy perturbation calculations were carried out in the context of Monte Carlo statistical mechanics simulations to investigate ligand series that feature displacement of ordered water molecules in the binding sites of scytalone dehydratase, p38-alphaMAP kinase, and EGFR kinase. The change in affinity for a ligand modification is found to correlate with the ease of displacement of the ordered water molecule. However, as in the EGFR example, the binding affinity may diminish if the free-energy increase due to the removal of the bound water molecule is not more than compensated by the additional interactions of the water-displacing moiety. For accurate computation of the effects of ligand modifications, a complete thermodynamic analysis is shown to be needed. It requires identification of the location of water molecules in the protein-ligand interface and evaluation of the free-energy changes associated with their removal and with the introduction of the ligand modification. Direct modification of the ligand in free-energy calculations is likely to trap the ordered molecule and provide misleading guidance for lead optimization.

  5. Autodissociation of doubly charged water molecules

    NASA Astrophysics Data System (ADS)

    Scully, S. W. J.; Wyer, J. A.; Senthil, V.; Shah, M. B.; Montenegro, E. C.

    2006-04-01

    The electron impact dissociative double-ionization cross sections for H2O between 45 and 1500eV have been measured using time of flight mass spectrometry. The energy dependence of the H++OH+ and H++O+ ion pair production cross sections indicate that Auger-like autoionization following a vacancy in the 2a1 molecular orbital is the main double ionization channel at high velocities. In contrast to expectation, these findings show that dissociation through the H2O2+ precursor state is a significant process at high collision energies. Knowledge of this process is vital as it has a direct affect on the production of important molecular species, such as H2 , during water radiolysis. Branching ratios of the various fragments produced following both autoionization and double ionization have also been obtained.

  6. THE FATE OF FLUOROSILICATE DRINKING WATER ADDITIVES

    EPA Science Inventory

    Periodically, the EPA reexamines its information on regulated drinking water contaminants to deterime if further study is required. Fluoride is one such contaminant undergoing review. The chemical literature indicates that some deficiencies exist in our understanding of the spe...

  7. Dynamics of Confined Water Molecules in Aqueous Salt Hydrates

    SciTech Connect

    Werhahn, Jasper C.; Pandelov, S.; Yoo, Soohaeng; Xantheas, Sotiris S.; Iglev, H.

    2011-04-01

    The unusual properties of water are largely dictated by the dynamics of the H bond network. A single water molecule has more H bonding sites than atoms, hence new experimental and theoretical investigations about this peculiar liquid have not ceased to appear. Confinement of water to nanodroplets or small molecular clusters drastically changes many of the liquid’s properties. Such confined water plays a major role in the solvation of macro molecules such as proteins and can even be essential to their properties. Despite the vast results available on bulk and confined water, discussions about the correlation between spectral and structural properties continue to this day. The fast relaxation of the OH stretching vibration in bulk water, and the variance of sample geometries in the experiments on confined water obfuscate definite interpretation of the spectroscopic results in terms of structural parameters. We present first time-resolved investigations on a new model system that is ideally suited to overcome many of the problems faced in spectroscopical investigation of the H bond network of water. Aqueous hydrates of inorganic salts provide water molecules in a crystal grid, that enables unambiguous correlations of spectroscopic and structural features. Furthermore, the confined water clusters are well isolated from each other in the crystal matrix, so different degrees of confinement can be achieved by selection of the appropriate salt.

  8. Roles of water molecules in trapping carbon dioxide molecules inside the interlayer space of graphene oxides.

    PubMed

    Yumura, Takashi; Yamasaki, Ayumi

    2014-05-28

    Density functional theory (DFT) calculations were employed to investigate the energetics of carbon dioxide migration within hydrated or anhydrous graphene oxides (GOs). When anhydrous GO structures contain a carbon dioxide molecule, the carbon dioxide interacts repulsively with the GO layers to increase the interlayer spacing. The repulsive electrostatic interactions are reduced by the insertion of water molecules into CO2-containing GO structures due to the occurrence of attractive water-layer interactions through hydrogen bonding. Consequently, the interlayer spacings in CO2-containing hydrated structures are shortened compared with those in the anhydrous structures. The results indicate that the intercalated water molecules have the ability to connect the GO layers in the presence of carbon dioxide. Furthermore, the DFT calculations indicated that the GO interlayer spacings, which are influenced by the intercalation of water molecules, control carbon dioxide migration within the GO layers. The importance of the interlayer spacings on the migration of carbon dioxide arises from the occurrence of repulsive interactions between CO2 and oxygen-containing groups attached on the graphene sheets. When the GO interlayer spacings are short due to the presence of intercalated water molecules, the repulsive interactions between carbon dioxide and the GO layers are strong enough to prevent CO2 from migrating from its original position. Such repulsive interactions do not occur during the migration of CO2 within anhydrous GO structures because of the relatively longer interlayer spacing. Accordingly, CO2 migrates within anhydrous GO with a less significant barrier, indicating that carbon dioxide molecules are easily released from the GO.

  9. Anisotropic diffusion of water molecules in hydroxyapatite nanopores

    NASA Astrophysics Data System (ADS)

    Prakash, Muthuramalingam; Lemaire, Thibault; Caruel, Matthieu; Lewerenz, Marius; de Leeuw, Nora H.; Di Tommaso, Devis; Naili, Salah

    2017-03-01

    New insights into the dynamical properties of water in hydroxyapatite (HAP) nanopores, a model system for the fluid flow within nanosize spaces inside the collagen-apatite structure of bone, were obtained from molecular dynamics simulations of liquid water confined between two parallel HAP surfaces of different sizes (20 Å ≤ H ≤ 240 Å). Calculations were conducted using a core-shell interatomic potential for HAP together with the extended simple point charge model for water. This force field gives an activation energy for water diffusion within HAP nanopores that is in excellent agreement with available experimental data. The dynamical properties of water within the HAP nanopores were quantified in terms of the second-order water diffusion tensor. Results indicate that water diffuses anisotropically within the HAP nanopores, with the solvent molecules moving parallel to the surface twice as fast as the perpendicular direction. This unusual dynamic behaviour is linked to the strong polarizing effect of calcium ions, and the synergic interactions between the water molecules in the first hydration layer of HAP with the calcium, hydroxyl, and phosphate ions, which facilitates the flow of water molecules in the directions parallel to the HAP surface.

  10. Benchmarking the thermodynamic analysis of water molecules around a model beta sheet.

    PubMed

    Huggins, David J

    2012-06-05

    Water molecules play a vital role in biological and engineered systems by controlling intermolecular interactions in the aqueous phase. Inhomogeneous fluid solvation theory provides a method to quantify solvent thermodynamics from molecular dynamics or Monte Carlo simulations and provides an insight into intermolecular interactions. In this study, simulations of TIP4P-2005 and TIP5P-Ewald water molecules around a model beta sheet are used to investigate the orientational correlations and predicted thermodynamic properties of water molecules at a protein surface. This allows the method to be benchmarked and provides information about the effect of a protein on the thermodynamics of nearby water molecules. The results show that the enthalpy converges with relatively little sampling, but the entropy and thus the free energy require considerably more sampling to converge. The two water models yield a very similar pattern of hydration sites, and these hydration sites have very similar thermodynamic properties, despite notable differences in their orientational preferences. The results also predict that a protein surface affects the free energy of water molecules to a distance of approximately 4.0 Å, which is in line with previous work. In addition, all hydration sites have a favorable free energy with respect to bulk water, but only when the water-water entropy term is included. A new technique for calculating this term is presented and its use is expected to be very important in accurately calculating solvent thermodynamics for quantitative application.

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

    SciTech Connect

    Zhu, Chongqin; Li, Hui; Meng, Sheng

    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.

  12. Solvent additive effects on small molecule crystallization in bulk heterojunction solar cells probed during spin casting.

    PubMed

    Perez, Louis A; Chou, Kang Wei; Love, John A; van der Poll, Thomas S; Smilgies, Detlef-M; Nguyen, Thuc-Quyen; Kramer, Edward J; Amassian, Aram; Bazan, Guillermo C

    2013-11-26

    Solvent additive processing can lead to drastic improvements in the power conversion efficiency (PCE) in solution processable small molecule (SPSM) bulk heterojunction solar cells. In situ grazing incidence wide-angle X-ray scattering is used to investigate the kinetics of crystallite formation during and shortly after spin casting. The additive is shown to have a complex effect on structural evolution invoking polymorphism and enhanced crystalline quality of the donor SPSM.

  13. SPAM: A Simple Approach for Profiling Bound Water Molecules.

    PubMed

    Cui, Guanglei; Swails, Jason M; Manas, Eric S

    2013-12-10

    A method that identifies the hydration shell structure of proteins and estimates the relative free energies of water molecules within that hydration shell is described. The method, which we call "SPAM" (maps spelled in reverse), utilizes explicit solvent molecular dynamics (MD) simulations to capture discrete hydration sites at the water-protein interface and computes a local free energy measure from the distribution of interaction energies between water and the environment at a specific site. SPAM is able to provide a qualitative estimate of the thermodynamic profile of bound water molecules that correlates nicely with well-studied structure-activity relationships and observed binding "hot spots". This is demonstrated in retrospective analyses of HIV1 protease and hen egg white lysozyme, where the effects of water displacement and solvent binding have been studied extensively. The simplicity and effectiveness of SPAM allow for prospective application during the drug discovery process.

  14. Structures of water molecules in carbon nanotubes under electric fields.

    PubMed

    Winarto; Takaiwa, Daisuke; Yamamoto, Eiji; Yasuoka, Kenji

    2015-03-28

    Carbon nanotubes (CNTs) are promising for water transport through membranes and for use as nano-pumps. The development of CNT-based nanofluidic devices, however, requires a better understanding of the properties of water molecules in CNTs because they can be very different from those in the bulk. Using all-atom molecular dynamics simulations, we investigate the effect of axial electric fields on the structure of water molecules in CNTs having diameters ranging from (7,7) to (10,10). The water dipole moments were aligned parallel to the electric field, which increases the density of water inside the CNTs and forms ordered ice-like structures. The electric field induces the transition from liquid to ice nanotubes in a wide range of CNT diameters. Moreover, we found an increase in the lifetime of hydrogen bonds for water structures in the CNTs. Fast librational motion breaks some hydrogen bonds, but the molecular pairs do not separate and the hydrogen bonds reform. Thus, hydrogen bonds maintain the water structure in the CNTs, and the water molecules move collectively, decreasing the axial diffusion coefficient and permeation rate.

  15. Structures of water molecules in carbon nanotubes under electric fields

    NASA Astrophysics Data System (ADS)

    Winarto, Takaiwa, Daisuke; Yamamoto, Eiji; Yasuoka, Kenji

    2015-03-01

    Carbon nanotubes (CNTs) are promising for water transport through membranes and for use as nano-pumps. The development of CNT-based nanofluidic devices, however, requires a better understanding of the properties of water molecules in CNTs because they can be very different from those in the bulk. Using all-atom molecular dynamics simulations, we investigate the effect of axial electric fields on the structure of water molecules in CNTs having diameters ranging from (7,7) to (10,10). The water dipole moments were aligned parallel to the electric field, which increases the density of water inside the CNTs and forms ordered ice-like structures. The electric field induces the transition from liquid to ice nanotubes in a wide range of CNT diameters. Moreover, we found an increase in the lifetime of hydrogen bonds for water structures in the CNTs. Fast librational motion breaks some hydrogen bonds, but the molecular pairs do not separate and the hydrogen bonds reform. Thus, hydrogen bonds maintain the water structure in the CNTs, and the water molecules move collectively, decreasing the axial diffusion coefficient and permeation rate.

  16. Structures of water molecules in carbon nanotubes under electric fields

    SciTech Connect

    Winarto,; Takaiwa, Daisuke; Yamamoto, Eiji; Yasuoka, Kenji

    2015-03-28

    Carbon nanotubes (CNTs) are promising for water transport through membranes and for use as nano-pumps. The development of CNT-based nanofluidic devices, however, requires a better understanding of the properties of water molecules in CNTs because they can be very different from those in the bulk. Using all-atom molecular dynamics simulations, we investigate the effect of axial electric fields on the structure of water molecules in CNTs having diameters ranging from (7,7) to (10,10). The water dipole moments were aligned parallel to the electric field, which increases the density of water inside the CNTs and forms ordered ice-like structures. The electric field induces the transition from liquid to ice nanotubes in a wide range of CNT diameters. Moreover, we found an increase in the lifetime of hydrogen bonds for water structures in the CNTs. Fast librational motion breaks some hydrogen bonds, but the molecular pairs do not separate and the hydrogen bonds reform. Thus, hydrogen bonds maintain the water structure in the CNTs, and the water molecules move collectively, decreasing the axial diffusion coefficient and permeation rate.

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

    PubMed

    Kuffel, Anna; Zielkiewicz, Jan

    2016-02-14

    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.

  18. Non-additivity of molecule-surface van der Waals potentials from force measurements

    PubMed Central

    Wagner, Christian; Fournier, Norman; Ruiz, Victor G.; Li, Chen; Müllen, Klaus; Rohlfing, Michael; Tkatchenko, Alexandre; Temirov, Ruslan; Tautz, F. Stefan

    2014-01-01

    Van der Waals (vdW) forces act ubiquitously in condensed matter. Despite being weak on an atomic level, they substantially influence molecular and biological systems due to their long range and system-size scaling. The difficulty to isolate and measure vdW forces on a single-molecule level causes our present understanding to be strongly theory based. Here we show measurements of the attractive potential between differently sized organic molecules and a metal surface using an atomic force microscope. Our choice of molecules and the large molecule-surface separation cause this attraction to be purely of vdW type. The experiment allows testing the asymptotic vdW force law and its validity range. We find a superlinear growth of the vdW attraction with molecular size, originating from the increased deconfinement of electrons in the molecules. Because such non-additive vdW contributions are not accounted for in most first-principles or empirical calculations, we suggest further development in that direction. PMID:25424490

  19. Reorientional dynamics of water molecules in anionic hydration shells

    PubMed Central

    Laage, Damien; Hynes, James T.

    2007-01-01

    Water molecule rotational dynamics within a chloride anion's first hydration shell are investigated through simulations. In contrast to recent suggestions that the ion's hydration shell is rigid during a water's reorientation, we find a labile hydration sphere, consistent with previous assessments of chloride as a weak structure breaker. The nondiffusive reorientation mechanism found involves a hydrogen-bond partner switch with a large amplitude angular jump and the water's departure from the anion's shell. An analytic extended jump model accounts for the simulation results, as well as available NMR and ultrafast spectroscopic data, and resolves the discrepancy between them. PMID:17581877

  20. 10. Water treatment plant, view to S. 1965 addition is ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    10. Water treatment plant, view to S. 1965 addition is in the foreground - Fort Benton Water Treatment Plant, Filtration Plant, Lots 9-13 of Block 7, Fort Benton Original Townsite at Missouri River, Fort Benton, Chouteau County, MT

  1. Oxidative addition of C--H bonds in organic molecules to transition metal centers

    SciTech Connect

    Bergman, R.G.

    1989-04-01

    Alkanes are among the most chemically inert organic molecules. They are reactive toward a limited range of reagents, such as highly energetic free radicals and strongly electrophilic and oxidizing species. This low reactivity is a consequence of the C--H bond energies in most saturated hydrocarbons. These values range from 90 to 98 kcal/mole for primary and secondary C--H bonds; in methane, the main constituent of natural gas, the C--H bond energy is 104 kcal/mole. This makes methane one of the most common but least reactive organic molecules in nature. This report briefly discusses the search for metal complexes capable of undergoing the C--H oxidative addition process allowing alkane chemistry to be more selective than that available using free radical reagents. 14 refs.

  2. Water and Small-Molecule Permeation of Dormant Bacillus subtilis Spores

    PubMed Central

    Cermak, Nathan; Feijó Delgado, Francisco; Setlow, Barbara; Setlow, Peter

    2015-01-01

    ABSTRACT We use a suspended microchannel resonator to characterize the water and small-molecule permeability of Bacillus subtilis spores based on spores' buoyant mass in different solutions. Consistent with previous results, we found that the spore coat is not a significant barrier to small molecules, and the extent to which small molecules may enter the spore is size dependent. We have developed a method to directly observe the exchange kinetics of intraspore water with deuterium oxide, and we applied this method to wild-type spores and a panel of congenic mutants with deficiencies in the assembly or structure of the coat. Compared to wild-type spores, which exchange in approximately 1 s, several coat mutant spores were found to have relatively high water permeability with exchange times below the ∼200-ms temporal resolution of our assay. In addition, we found that the water permeability of the spore correlates with the ability of spores to germinate with dodecylamine and with the ability of TbCl3 to inhibit germination with l-valine. These results suggest that the structure of the coat may be necessary for maintaining low water permeability. IMPORTANCE Spores of Bacillus species cause food spoilage and disease and are extremely resistant to standard decontamination methods. This hardiness is partly due to spores' extremely low permeability to chemicals, including water. We present a method to directly monitor the uptake of molecules into B. subtilis spores by weighing spores in fluid. The results demonstrate the exchange of core water with subsecond resolution and show a correlation between water permeability and the rate at which small molecules can initiate or inhibit germination in coat-damaged spores. The ability to directly measure the uptake of molecules in the context of spores with known structural or genetic deficiencies is expected to provide insight into the determinants of spores' extreme resistance. PMID:26483518

  3. Variational path integral molecular dynamics study of a water molecule

    NASA Astrophysics Data System (ADS)

    Miura, Shinichi

    2013-08-01

    In the present study, a variational path integral molecular dynamics method developed by the author [Chem. Phys. Lett. 482, 165 (2009)] is applied to a water molecule on the adiabatic potential energy surface. The method numerically generates an exact wavefunction using a trial wavefunction of the target system. It has been shown that even if a poor trial wavefunction is employed, the exact quantum distribution is numerically extracted, demonstrating the robustness of the variational path integral method.

  4. Interaction Of Water Molecules With SiC(001) Surfaces

    SciTech Connect

    Cicero, G; Catellani, A; Galli, G

    2004-08-10

    We have investigated the interaction of water molecules with the polar Si- and C- terminated surfaces of cubic Silicon Carbide by means of ab initio molecular dynamics simulations at finite temperature. Different water coverages were considered, from {1/4} to a complete monolayer. Irrespective of coverage, we find that water dissociates on the silicon terminated surfaces, leading to important changes in both its structural and electronic properties. On the contrary, the carbon terminated surface remains inert when exposed to water. We propose experiments to reveal the ionic and electronic structure of wet Si-terminated surfaces predicted by our calculations, which at full coverage are notably different from those of hydrated Si(001) substrates. Finally, we discuss the implications of our results for SiC surface functionalization.

  5. The role of noninnocent solvent molecules in organocatalyzed asymmetric Michael addition reactions.

    PubMed

    Patil, Mahendra P; Sunoj, Raghavan B

    2008-01-01

    A proline-catalyzed asymmetric Michael addition between ketones and trans-beta-nitrostyrene was studied by using the density-functional theory with mPW1PW91 and B3LYP functionals. Improved insight into the enantio- and diastereoselective formation of gamma-nitroketones/-aldehydes is obtained through transition-state analysis. Consideration of the activation parameters obtained from gas-phase calculations and continuum solvation models failed to reproduce the reported experimental stereoselectivities for the reaction between cyclohexanone and 3-pentanone with trans-beta-nitrostyrene. The correct diastereo- and enantioselectivites were obtained only upon explicit inclusion of solvent molecules in the diastereomeric transition states that pertain to the C--C bond formation. Among the several transition-state models that were examined, the one that exhibits cooperative hydrogen-bonding interactions with two molecules of methanol could explain the correct stereochemical outcome of the Michael reaction. The change in differential stabilization that arises as a result of electrostatic and hydrogen-bonding interactions in the key transition states is identified as the contributing factor toward obtaining the correct diastereomer. This study establishes the importance of including explicit solvent molecules in situations in which the gas-phase and continuum models are inadequate in obtaining meaningful insight regarding experimental stereoselectivities.

  6. Phase Segregation and Dynamics in Strongly Interacting Small Molecule Additive - Block Copolymer Surfactant Complexes

    NASA Astrophysics Data System (ADS)

    Kothari, Rohit; Khalil, Ahmed; Henning Winter, H.; Watkins, James J.

    2012-02-01

    Rheology and Small Angle X-Ray Scattering (SAXS) were used to investigate order to disorder transitions (ODTs) and disorder to order transitions (DOTs) of poly(ethyleneoxide-b-propyleneoxide-b-ethyleneoxide) block copolymer surfactants mixed with hydrogen-bond-donating small molecule additives. A series of additives having a core benzene ring and systematic variation in the number of carboxylic or hydroxyl groups attached to the ring were of particular interest. Ordered cylindrical morphologies, confirmed using SAXS, were obtained only in a certain additive concentration region. ODTs were characterized by sudden changes in the linear viscoelastic properties in low frequency region upon increasing temperature. The locations of ODTs varied widely with hydrogen-bond-donating ability of the functional group and were found to be strongly dependent on the number of functional groups attached to the ring. For a given additive, the temperature at which ODT occur was strong function of the additive loading, whereas the linear viscoelastic properties of the ordered state were little changed upon varying additive concentration in ordered region. The location and dynamics of DOTs upon cooling were comparable to the ODTs upon heating. Studies using these model systems provide insight into the design of well-ordered hybrid materials.

  7. Stereochemistry of enzymatic water addition to C=C bonds.

    PubMed

    Chen, Bi-Shuang; Otten, Linda G; Hanefeld, Ulf

    2015-01-01

    Water addition to carbon-carbon double bonds using hydratases is attracting great interest in biochemistry. Most of the known hydratases are involved in primary metabolism and to a lesser extent in secondary metabolism. New hydratases have recently been added to the toolbox, both from natural sources or artificial metalloenzymes. In order to comprehensively understand how the hydratases are able to catalyse the water addition to carbon-carbon double bonds, this review will highlight the mechanistic and stereochemical studies of the enzymatic water addition to carbon-carbon double bonds, focusing on the syn/anti-addition and stereochemistry of the reaction.

  8. Auger spectrum of a water molecule after single and double core ionization

    NASA Astrophysics Data System (ADS)

    Inhester, Ludger; Burmeister, Carl F.; Groenhof, Gerrit; Grubmueller, Helmut

    2012-06-01

    The high intensity of Free Electron Lasers (FEL) opens up the possibility to perform single-shot molecule scattering experiments. However, even for small molecules radiation damage induced by absorption of intense x-ray radiation is not yet fully understood. To provide insight into this process, we have studied the dynamics of water molecules in single and double core ionized states by means of electronic transition rate calculations and ab initio molecular dynamics (MD) simulations. From MD trajectories photoionization and Auger transition rates were computed based on electronic continuum wavefunctions obtained by explicit integration of the coupled radial Schr"odinger equations. To account for the nuclear dynamics during the core hole lifetime, the calculated electron emission spectra for different molecular geometries were accumulated according to the obtained time-dependent populations. We find that, in contrast to the single core ionized water molecule, the nuclear dynamics for the double core ionized water molecule during the core hole lifetime leaves a clear fingerprint on the electron emission spectra. In addition, the lifetime of the double core ionized water was found to be significantly shorter than half of the single core hole lifetime.

  9. Sticking of Molecules on Nonporous Amorphous Water Ice

    NASA Astrophysics Data System (ADS)

    He, Jiao; Acharyya, Kinsuk; Vidali, Gianfranco

    2016-05-01

    Accurate modeling of physical and chemical processes in the interstellar medium (ISM) requires detailed knowledge of how atoms and molecules 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 H2, D2, N2, O2, CO, CH4, and CO2 on nonporous amorphous solid water. 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 the values of the measured sticking coefficient, we suggest a useful general formula of the sticking coefficient as a function of grain temperature and molecule-surface binding energy. We use this formula in a simulation of ISM gas-grain chemistry to find the effect of sticking on the abundance of key molecules both on grains and in the gas phase.

  10. The spontaneous synchronized dance of pairs of water molecules

    SciTech Connect

    Roncaratti, Luiz F.; Cappelletti, David Pirani, Fernando

    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.

  11. Morphology-Controlled High-Efficiency Small Molecule Organic Solar Cells without Additive Solvent Treatment

    PubMed Central

    Kim, Il Ku; Jo, Jun Hyung; Yun, Jung-Ho

    2016-01-01

    This paper focuses on nano-morphology-controlled small-molecule organic solar cells without solvent treatment for high power-conversion efficiencies (PCEs). The maximum high PCE reaches up to 7.22% with a bulk-heterojunction (BHJ) thickness of 320 nm. This high efficiency was obtained by eliminating solvent additives such as 1,8-diiodooctane (DIO) to find an alternative way to control the domain sizes in the BHJ layer. Furthermore, the generalized transfer matrix method (GTMM) analysis has been applied to confirm the effects of applying a different thickness of BHJs for organic solar cells from 100 to 320 nm, respectively. Finally, the study showed an alternative way to achieve high PCE organic solar cells without additive solvent treatments to control the morphology of the bulk-heterojunction.

  12. Radiation of nitrogen molecules in a dielectric barrier discharge with small additives of chlorine and bromine

    SciTech Connect

    Avtaeva, S. V.; Avdeev, S. M.; Sosnin, E. A.

    2010-08-15

    Spectral and energy characteristics of nitrogen molecule radiation in dielectric barrier discharges in Ar-N{sub 2}, Ar-N{sub 2}-Cl{sub 2}, and Ar-N{sub 2}-Br{sub 2} mixtures were investigated experimentally. Small additives of molecular chlorine or bromine to an Ar-N{sub 2} mixture are found to increase the radiation intensity of the second positive system of nitrogen. The conditions at which the radiation spectrum predominantly consists of vibronic bands of this system are determined. Using a numerical model of plasmachemical processes, it is shown that, at electron temperatures typical of gas discharges (2-4 eV), a minor additive of molecular chlorine to an Ar-N{sub 2} mixture leads to an increase in the concentrations of electrons, positive ions, and metastable argon atoms. In turn, collisional energy transfer from metastable argon atoms to nitrogen molecules results in the excitation of the N{sub 2}(C{sup 3{Pi}}{sub u}) state.

  13. Additivity rule for the calculation of electron scattering from polyatomic molecules

    NASA Astrophysics Data System (ADS)

    Jiang, Yuhai; Sun, Jinfeng; Wan, Lingde

    2000-12-01

    Total cross sections (TCSs) for electron scattering by polyatomic molecules C2F4, C2F6, C3F6, C3F8, C6F6, and C6H6 are calculated in the incident electron energy range 30-3000 eV employing the 100% additivity rule and energy-dependent geometric additivity rule (EGAR) approaches. The EGAR, proposed by Jiang et al. [J. Phys. B 30, 5025 (1997); Phys. Lett. A 237, 53 (1997)], relates to molecular properties and the energy of incident electrons. Two approaches for the TCS of C2F6, C3F8, C6F6, and C6H6 molecules are compared and the EGAR yields better accord with available experimental measurements in the whole energy region. The new results for C2F4 and C3F6 are also presented although no experimental data are available for comparison. The atoms are presented by spherical complex optical potential, which is composed of static, exchange, polarization, and absorption terms.

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

    SciTech Connect

    Loboda, Oleksandr; Ingrosso, Francesca; Ruiz-López, Manuel F.; Millot, Claude; Szalewicz, Krzysztof

    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.

  15. Synthesis and properties of water-soluble asterisk molecules.

    PubMed

    Menger, Fredric M; Azov, Vladimir A

    2002-09-18

    An asterisk is comprised of six semirigid arms projecting from a benzene nucleus. In the case at hand, asterisks were synthesized with one, two, or three aromatic rings (connected by sulfur atoms) in each of the six arms. A phosphomonoester at the termini of each arm solubilized the asterisks in water. The colloidal properties of these amphiphilic molecules were investigated by UV-vis and fluorescence spectroscopy, calorimetry, light scattering, surface tensiometry, and pulse-gradient spin-echo NMR. Solubility, solubilization, metal binding, and micelle "seeding" experiments were also carried out. Chain-conformation and supramolecular assembly into remarkable molecular "scrolls" were investigated by X-ray analysis and electron microscopy, respectively. One of the more interesting properties of the asterisks is that they remain monomeric in water despite having as many as 19 hydrophobic aromatic rings exposed to the water. The reasons for this behavior, and the possibility of exploiting it for constructing enzyme models free from aggregation equilibria, are discussed.

  16. Continuum simulations of water flow past fullerene molecules

    NASA Astrophysics Data System (ADS)

    Popadić, A.; Praprotnik, M.; Koumoutsakos, P.; Walther, J. H.

    2015-09-01

    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 solvers, allowing for investigations into spatiotemporal scales inaccessible to atomistic simulations.

  17. Ionization of water molecules by fast charged projectiles

    SciTech Connect

    Dubois, A.; Carniato, S.; Fainstein, P. D.; Hansen, J. P.

    2011-07-15

    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.

  18. Characterizing Structural Stability of Amyloid Motif Fibrils Mediated by Water Molecules.

    PubMed

    Choi, Hyunsung; Chang, Hyun Joon; Lee, Myeongsang; Na, Sungsoo

    2017-02-04

    In biological systems, structural confinements of amyloid fibrils can be mediated by the role of water molecules. However, the underlying effect of the dynamic behavior of water molecules on structural stabilities of amyloid fibrils is still unclear. By performing molecular dynamics simulations, we investigate the dynamic features and the effect of interior water molecules on conformations and mechanical characteristics of various amyloid fibrils. We find that a specific mechanism induced by the dynamic properties of interior water molecules can affect diffusion of water molecules inside amyloid fibrils, inducing their different structural stabilities. The conformation of amyloid fibrils induced by interior water molecules show the fibrils' different mechanical features. We elucidate the role of confined and movable interior water molecules in structural stabilities of various amyloid fibrils. Our results offer insights not only in further understanding of mechanical features of amyloids as mediated by water molecules, but also in the fine-tuning of the functional abilities of amyloid fibrils for applications.

  19. Toward Additive-Free Small-Molecule Organic Solar Cells: Roles of the Donor Crystallization Pathway and Dynamics.

    PubMed

    Abdelsamie, Maged; Treat, Neil D; Zhao, Kui; McDowell, Caitlin; Burgers, Mark A; Li, Ruipeng; Smilgies, Detlef-M; Stingelin, Natalie; Bazan, Guillermo C; Amassian, Aram

    2015-12-02

    The ease with which small-molecule donors crystallize during solution processing is directly linked to the need for solvent additives. Donor molecules that get trapped in disordered (H1) or liquid crystalline (T1) mesophases require additive processing to promote crystallization, phase separation, and efficient light harvesting. A donor material (X2) that crystallizes directly from solution yields additive-free solar cells with an efficiency of 7.6%.

  20. One-step, low-temperature deposited perovskite solar cell utilizing small molecule additive

    NASA Astrophysics Data System (ADS)

    Chen, Chun-Chao; Hong, Zirou; Li, Gang; Chen, Qi; Zhou, Huanping; Yang, Yang

    2015-01-01

    In the current study, the perovskite absorber (CH3NH3PbI3) is processed via one-step deposition employing the small molecule additive, BmPyPhB, which can be dissolved in dimethylformamide along with precursors. Here, 1,3-Bis[3,5-di(pyridin-3-yl)phenyl]benzene (BmPyPhB) functions as the morphology controller to introduce an intermediate phase during perovskite film growth, which allows well-defined and precrystallized domains formed before the annealing treatment. Furthermore, a chloroform solvent wash procedure is applied afterward to remove BmPyPhB from perovskite without damaging the predetermined morphology. Thus, postannealing as low as 100°C for 5 min can achieve the optimal power conversion efficiency of 8% in a planar-structured inverted solar cell.

  1. Water, UV shielding, and Organic Molecules in the Terrestrial Planet Region of Disks

    NASA Astrophysics Data System (ADS)

    Najita, Joan; Carr, John

    2015-08-01

    Water vapor is abundant in the inner few AU of protoplanetary disks, as shown by the common detection of mid-infrared emission lines of warm water in T Tauri disk atmospheres. Simple organic molecules are also abundant. The properties of the water and organic molecule emission (column densities and abundances) hint at an active disk chemistry and the synthesis of complex organic molecules. Because T Tauri disks have experienced significant grain growth and settling, the water in the disk atmosphere is expected to be a significant UV opacity source. Recent models of disk atmospheres show that the absorption of stellar FUV photons by water and other molecules not only heats the disk atmosphere but also shields the disk midplane from UV radiation. The properties of the molecular layers synthesized in the models are in good agreement with the observed infrared molecular emission from T Tauri stars. In addition to describing these model results, we will present direct observational evidence for the photodissociation of water and its role in shielding T Tauri disks. Detailed study of the mid-infrared OH emission spectrum reveals the signature of a photochemical origin for the OH, i.e., OH production through photodissociation of water by FUV photons at 1150-1400 A, most likely dominated by Lyman alpha. The nearly ubiquitous presence of rotationally hot OH emission in classical T Tauri stars implies that photodissociation of water is common in the terrestrial planet region of the disk. The resulting UV shielding by water could be important in facilitating a rich organic chemistry in the disk midplane.

  2. Single-Molecule FRET Measurements in Additive-Enriched Aqueous Solutions.

    PubMed

    Kempe, Daryan; Cerminara, Michele; Poblete, Simón; Schöne, Antonie; Gabba, Matteo; Fitter, Jörg

    2017-01-03

    The addition of high amounts of chemical denaturants, salts, viscosity enhancers or macro-molecular crowding agents has an impact on the physical properties of buffer solutions. Among others, the (microscopic) viscosity, the refractive index, the dielectric constant, and the ionic strength can be affected. Here, we systematically evaluate the importance of solvent characteristics with respect to single-molecule FRET (smFRET) data. First, we present a confocal based method for the determination of fluorescence quantum yields to facilitate a fast characterization of smFRET-samples at sub-nM-concentrations. As a case study, we analyze smFRET data of structurally rigid, double-stranded DNA-oligonucleotides in aqueous buffer and in buffers with specific amounts of glycerol, guanidine hydrochloride (GdnHCl), and sodium chloride (NaCl) added. We show that the calculation of interdye distances, without taking into account solvent-induced spectral and photophysical changes of the labels, leads to deviations of up to 4 Å from the real interdye distances. Additionally, we demonstrate that electrostatic dye-dye repulsions are negligible for the interdye distance regime considered here (>50 Å). Finally, we use our approach to validate the further compaction of the already unfolded state of phosphoglycerate kinase (PGK) with decreasing denaturant concentrations, a mechanism known as coil-globule transition.

  3. Production of complex organic molecules:H-atom addition versus UV irradiation

    NASA Astrophysics Data System (ADS)

    Chuang, K.-J.; Fedoseev, G.; Qasim, D.; Ioppolo, S.; van Dishoeck, E. F.; Linnartz, H.

    2017-01-01

    Complex organic molecules (COMs) have been identified in different environments in star-forming regions. Laboratory studies show that COMs form in the solid state, on icy grains, typically following a `non-energetic' (atom-addition) or `energetic' (UV photon absorption) trigger. So far, such studies have been largely performed for single processes. Here we present the first work that quantitatively investigates both the relative importance and the cumulative effect of `(non)energetic' processing. We focus on astronomically relevant CO:CH3OH = 4:1 ice analogues exposed to doses relevant for the collapse stage of dense clouds. Hydrogenation experiments result in the formation of methyl formate (MF; HC(O)OCH3), glycolaldehyde (GA; HC(O)CH2OH) and ethylene glycol (EG; H2C(OH)CH2OH) at 14 K. The absolute abundances and the abundance fractions are found to be dependent on the H-atom/CO:CH3OH-molecule ratios and on the overall deposition rate. In the case that ices are exposed to UV photons only, several different COMs are found. Typically, the abundance fractions are 0.2 for MF, 0.3 for GA, and 0.5 for EG as opposed to the values found in pure hydrogenation experiments without UV in which MF is largely absent: 0.0, 0.2-0.6 and 0.8-0.4, respectively. In experiments where both are applied, overall COM abundances drop to about half of those found in the pure UV irradiation experiments, but the composition fractions are very similar. This implies COM ratios can be used as a diagnostic tool to derive the processing history of an ice. Solid-state branching ratios derived here for GA and EG compare well with observations, while the MF case cannot be explained by solid state conditions investigated here.

  4. Molecular multipole moments of water molecules in ice Ih

    NASA Astrophysics Data System (ADS)

    Batista, Enrique R.; Xantheas, Sotiris S.; Jónsson, Hannes

    1998-09-01

    We have used an induction model including dipole, dipole-quadrupole, quadrupole-quadrupole polarizability and first hyperpolarizability as well as fixed octopole and hexadecapole moments to study the electric field in ice. The self-consistent induction calculations gave an average total dipole moment of 3.09 D, a 67% increase over the dipole moment of an isolated water molecule. A previous, more approximate induction model study by Coulson and Eisenberg [Proc. R. Soc. Lond. A 291, 445 (1966)] suggested a significantly smaller average value of 2.6 D. This value has been used extensively in recent years as a reference point in the development of various polarizable interaction potentials for water as well as for assessment of the convergence of water cluster properties to those of bulk. The reason for this difference is not due to approximations made in the computational scheme of Coulson and Eisenberg but rather due to the use of less accurate values for the molecular multipoles in these earlier calculations.

  5. Searching for Water and Other Molecules with JWST

    NASA Astrophysics Data System (ADS)

    Valenti, Jeff

    2015-08-01

    The James Webb Space Telescope (JWST) will be a powerful tool for measuring water and other molecules in transiting exoplanets, warm circumstellar disks, brown dwarfs, and cool stars. In early 2019 the observatory is scheduled to begin science operations near the Sun-Earth L2 Lagrange point. The sunshield will allow the telescope and science instrument module to cool passively to approximately 40 K. The segmented primary mirror has 25 square meters of collecting area, giving the observatory unprecedented sensitivity in the infrared. JWST has four science instruments that cover wavelengths from 0.6 to 28 microns at spectral resolutions up to about R=3000. I will summarize relevant observatory constraints, instrument capabilities, and observing templates. I will illustrate practical issues with examples from the Science Operations Design Reference Mission. Finally, I will discuss the Cycle 1 proposal process, which begins in 2017.

  6. Additives for Water Mist Fire Suppression Systems: A Review

    DTIC Science & Technology

    2012-11-01

    this. Water mist produces no acid gases and therefore can be discharged in a space where persons are present. It consists of small water droplets...investigated include film forming additives for Class B fires (generally fluorinated surfactants), alkali metals salts, transition metal chlorides, sulphates ...et portatif sur les navires militaires continue de croître pour plusieurs raisons. Le brouillard d’eau ne contient pas de gaz acides et, par

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

    SciTech Connect

    Chempath, Shaji; Pratt, Lawrence R

    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.

  8. Cation effects on rotational dynamics of anions and water molecules in alkali (Li+, Na+, K+, Cs+) thiocyanate (SCN-) aqueous solutions.

    PubMed

    Bian, Hongtao; Chen, Hailong; Zhang, Qiang; Li, Jiebo; Wen, Xiewen; Zhuang, Wei; Zheng, Junrong

    2013-07-03

    Waiting time dependent rotational anisotropies of SCN(-) anions and water molecules in alkali thiocyanate (XSCN, X = Li, Na, K, Cs) aqueous solutions at various concentrations were measured with ultrafast infrared spectroscopy. It was found that cations can significantly affect the reorientational motions of both water molecules and SCN(-) anions. The dynamics are slower in a solution with a smaller cation. The reorientational time constants follow the order of Li(+) > Na(+) > K(+) ~/= Cs(+). The changes of rotational time constants of SCN(-) at various concentrations scale almost linearly with the changes of solution viscosity, but those of water molecules do not. In addition, the concentration-dependent amplitudes of dynamical changes are much more significant in the Li(+) and Na(+) solutions than those in the K(+) and Cs(+) solutions. Further investigations on the systems with the ultrafast vibrational energy exchange method and molecular dynamics simulations provide an explanation for the observations: the observed rotational dynamics are the balanced results of ion clustering and cation/anion/water direct interactions. In all the solutions at high concentrations (>5 M), substantial amounts of ions form clusters. The structural inhomogeneity in the solutions leads to distinct rotational dynamics of water and anions. The strong interactions of Li(+) and Na(+) because of their relatively large charge densities with water molecules and SCN(-) anions, in addition to the likely geometric confinements because of ion clustering, substantially slow down the rotations of SCN(-) anions and water molecules inside the ion clusters. The interactions of K(+) and Cs(+) with water or SCN(-) are much weaker. The rotations of water molecules inside ion clusters of K(+) and Cs(+) solutions are not significantly different from those of other water species so that the experimentally observed rotational relaxation dynamics are only slightly affected by the ion concentrations.

  9. Light emission in water-containing cocrystals: the influence of water molecules on the fluorescence properties of a Schiff-base molecule.

    PubMed

    Zhou, Feng; Tan, Pengli; Ma, Yong; Li, Youyong; Li, Najun; Li, Hua; Wang, Lihua; Gu, Hongwei; Xu, Qingfeng; Lu, Jianmei

    2014-01-01

    In the presence or absence of water, a Schiff-base compound, 4-amino-3-(2-(2-hydroxybenzylidene)hydrazinyl)-1H-1,2,4-triazole-5(4H)-thione (HATT), forms different crystalline states (HATT, HATT·2H2O, and a lamellar structure, m-HATT·nH2O), which show different luminescence emission properties. Herein, we investigate the emission of HATT and the role of water molecules. A water molecule, which acts as both a hydrogen-bond acceptor and -donor, enlarges the distance between adjacent HATT molecules and hinders non-radiative decay pathways.

  10. Electron capture by bare ions on water molecules

    NASA Astrophysics Data System (ADS)

    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.

  11. How strongly do hydrogen and water molecules stick to carbon nanomaterials?

    NASA Astrophysics Data System (ADS)

    Al-Hamdani, Yasmine S.; Alfè, Dario; Michaelides, Angelos

    2017-03-01

    The interaction strength of molecular hydrogen and water to carbon nanomaterials is relevant to, among many applications, hydrogen storage, water treatment, and water flow. However, accurate interaction energies for hydrogen and water with carbon nanotubes (CNTs) remain scarce despite the importance of having reliable benchmark data to inform experiments and to validate computational models. Here, benchmark fixed-node diffusion Monte Carlo (DMC) interaction energies are provided for hydrogen and water monomers inside and outside a typical zigzag CNT. The DMC interaction energies provide valuable insight into molecular interactions with CNTs in general and are also expected to be particularly relevant to gas uptake studies on CNTs. In addition, a selection of density functional theory (DFT) exchange-correlation (xc) functionals and force field potentials that ought to be suitable for these systems is compared. An unexpected variation is found in the performance of DFT van der Waals (vdW) models in particular. An analysis of the peculiar discrepancy between different vdW models indicates that medium-range correlation (at circa 3 to 5 Å) plays a key role inside CNTs and is poorly predicted by some vdW models. Using accurate reference information, this work reveals which xc functionals and force fields perform well for molecules interacting with CNTs. The findings will be valuable to future work on these and related systems that involve molecules interacting with low-dimensional systems.

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

    NASA Astrophysics Data System (ADS)

    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

  13. O^- channels of Dissociative Electron Attachment to water and heavy water molecules

    NASA Astrophysics Data System (ADS)

    Adaniya, Hidehito; Rudek, Benedikt; Osipov, Timur; Lee, Sun; Weber, Thorsten; Hertlein, Marcus; Schoeffler, Markus; Prior, Mike; Belkacem, Ali

    2009-05-01

    A COLTRIM technique is modified to measure the kinetic energy and angular distribution of O^- ions arising from dissociative electron attachment to water and heavy water molecules. A low energy pulsed electron, an effusive water target, a pulsed extraction plate are used in combination with the COLTRIMS spectrometer. The spectrometer carries an electrostatic lens system to compensate the effusiveness of the target. This technique is applied to study the O^- channels in the three Feshbach resonances of water and heavy water anion. The measured kinetic energy release will give the energy partitioning among the fragments, and the means to identify the two-body and three-body breakup channels. The angular distribution of the O^- ions with respect to the electron beam is found to reflect well the breakup dynamics of the H2O^- at the dissociation. The experimental results are compared with the theoretical predictions.

  14. Dithienobenzodithiophene-Based Small Molecule Organic Solar Cells with over 7% Efficiency via Additive- and Thermal-Annealing-Free Processing.

    PubMed

    Song, Hyeng Gun; Kim, Yu Jin; Lee, Ji Sang; Kim, Yun-Hi; Park, Chan Eon; Kwon, Soon-Ki

    2016-12-21

    Here we introduce a novel small molecule based on dithienobenzodithiophene and rhodanine, DTBDT-Rho, developed to study the effect of the rhodanine substitutuent on small molecule bulk heterojunction (BHJ) solar cells. DTBDT-Rho possesses distinct crystalline characteristics, sufficient solubility in chlorinated solvents, and broad absorption properties. Therefore, solution-processed BHJ photovoltaic cells made with DTBDT-Rho:PC71BM blends showed an extremely high power conversion efficiency (PCE; 7.10%); notably, this PCE value was obtained without the use of additives or thermal treatments. To our knowledge, the PCE over 7% is a significantly powerful value among rhodanine-based small molecule BHJ solar cells without additives or thermal treatments.

  15. Adsorption of water molecules on selected charged sodium-chloride clusters.

    PubMed

    Bradshaw, James A; Gordon, Sidney L; Leavitt, Andrew J; Whetten, Robert L

    2012-01-12

    The adsorption of water molecules (H(2)O) on sodium chloride cluster cations and anions was studied at 298 K over a mass range of 100-1200 amu using a custom-built laser desorption ionization reactor and mass spectrometer. Under the conditions used, the cations Na(3)Cl(2)(+) and Na(4)Cl(3)(+) bind up to three water molecules, whereas the larger cations, Na(5)Cl(4)(+) to Na(19)Cl(18)(+), formed hydrates with one or two only. The overall trend is a decrease in hydration with increasing cluster size, with an abrupt drop occurring at the closed-shell Na(14)Cl(13)(+). As compared to the cluster cations, the cluster anions showed almost no adsorption. Among smaller clusters, a weak adsorption of one water molecule was observed for the cluster anions Na(6)Cl(7)(-) and Na(7)Cl(8)(-). In the higher mass region, a substantial adsorption of one water molecule was observed for Na(14)Cl(15)(-). Density functional theory (DFT) computations were carried out for the adsorption of one molecule of H(2)O on the cations Na(n)Cl(n-1)(+), for n = 2-8, and the anions Na(n)Cl(n+1)(-), for n = 1-7. For each ion, the structure of the hydrate, the hydration energy, and the standard-state enthalpy, entropy, and Gibbs energy of hydration at 298 K were computed. In addition, it was useful to compute the distortion energy, defined as the electronic energy lost due to weakening of the Na-Cl bonds upon adsorption of H(2)O. The results show that strong adsorption of a H(2)O molecule occurs for the linear cations only at an end Na ion and for the nonlinear cations only at a corner Na ion bonded to two Cl ions. An unexpected result of the theoretical investigation for the anions is that certain low-energy isomers of Na(6)Cl(7)(-) and Na(7)Cl(8)(-) bind H(2)O strongly enough to produce the observed weak adsorption. The possible implications of these results for the initial hydration of extended NaCl surfaces are discussed.

  16. A nano-sized container for specific encapsulation of isolated water molecules.

    PubMed

    Lavendomme, Roy; Marcélis, Lionel; Wouters, Johan; Luhmer, Michel; Jabin, Ivan

    2016-12-01

    A calix[4]arene-based molecular box was synthesized. Its properties were characterized through XRD and extensive NMR studies. This receptor is able to encapsulate specifically two isolated water molecules in both non-protic and protic solvents. This is a consequence of high size, geometric and electronic complementarity between the host and the water molecules.

  17. Key Role of Active-Site Water Molecules in Bacteriorhodopsin Proton-Transfer Reactions

    SciTech Connect

    Bondar, A.N.; Baudry, Jerome Y; Suhai, Sandor; Fischer, S.; Smith, Jeremy C

    2008-10-01

    The functional mechanism of the light-driven proton pump protein bacteriorhodopsin depends on the location of water molecules in the active site at various stages of the photocycle and on their roles in the proton-transfer steps. Here, free energy computations indicate that electrostatic interactions favor the presence of a cytoplasmic-side water molecule hydrogen bonding to the retinal Schiff base in the state preceding proton transfer from the retinal Schiff base to Asp85. However, the nonequilibrium nature of the pumping process means that the probability of occupancy of a water molecule in a given site depends both on the free energies of insertion of the water molecule in this and other sites during the preceding photocycle steps and on the kinetic accessibility of these sites on the time scale of the reaction steps. The presence of the cytoplasmic-side water molecule has a dramatic effect on the mechanism of proton transfer: the proton is channeled on the Thr89 side of the retinal, whereas the transfer on the Asp212 side is hindered. Reaction-path simulations and molecular dynamics simulations indicate that the presence of the cytoplasmic-side water molecule permits a low-energy bacteriorhodopsin conformer in which the water molecule bridges the twisted retinal Schiff base and the proton acceptor Asp85. From this low-energy conformer, proton transfer occurs via a concerted mechanism in which the water molecule participates as an intermediate proton carrier.

  18. Adsorption of Small Molecules at Water--Hexane and Water--Membrane Interfaces

    NASA Astrophysics Data System (ADS)

    Wilson, Michael A.

    1996-03-01

    The interaction of solutes with aqueous interfaces plays a significant role in a variety of physical processes, including general anesthesia and atmospheric chemistry. We present molecular dynamics results for the transfer of several small solutes across water liquid--vapor, water--hexane and water--GMO bilayer membrane interfaces. (A. Pohorille and M. A. Wilson, J. Chem. Phys. (in press, 1995).)^, (A. Pohorille, P. CIeplak, and M. A. Wilson, Chem. Phys. (in press, 1995).) The free energies of transferring small polar molecules across the interface exhibit fairly deep minima while those of nonpolar molecules do not. This is due to a balance between nonelectrostatic contributions --- primarily the work required to create a cavity large enough to accommodate the solute --- and the solute--solvent electrostatic interactions.^1 The surface excess of solute is calculated and compared with experimental results from the Gibbs adsorption isotherm. The interfacial solubilities correlate with measured anesthetic potencies of these compounds, implying that the binding sites for anesthetics are located near the water--membrane interface.

  19. Additive for coal water slurry made from weak slurryability coal

    SciTech Connect

    Zi-xiu Zang; Lin Zhang; Xino-an Fu; Long Jiang

    1993-12-31

    Surface treatment of weak slurryability coal and preparation of highly concentrated coal water slurry (CWS) have been investigated using wettability and rheology measurements. By adding 0.5{approximately}10 wt.% (based on coal) pitch during dry milling coal surface became more hydrophobic and the coal could be easily prepared for CWS which had much lower viscosity compared with CWS of the untreated coal. The reasons of this result is high degree of hydrophobic surface of coal particles made surfactant adsorption easier compared with high degree of hydrophilic surface of coal particles. Another important reason in hydrophobic surface impeded the penetration of water into the inner pores of coal particles which resulted in decreasing swelling ability of coal and enhancing the fluidity of CWS. Four different additives have been investigated including three nonionic ethoxylated surfactants and one mixture of anionic surfactants (sodium humate derivative and naphthalenesulfonic acid-HCHO condensate). Both rheological and thixotropic properties showed that nonionic surfactant G2 was the most efficient additive for preparation of highly concentrated CWS. The results of dynamic experiment illustrated that the slurry had good dynamic stability, in other words, the viscosity of the slurry decreased very slowly at constant stir. The pitch treated coal powders were beneficiated coal had much lower viscosity compared with CWS of the unbeneficiated coal.

  20. Effect of addition of water-soluble chitin on amylose film.

    PubMed

    Suzuki, Shiho; Shimahashi, Katsumasa; Takahara, Junichi; Sunako, Michihiro; Takaha, Takeshi; Ogawa, Kozo; Kitamura, Shinichi

    2005-01-01

    Amylose films blended with chitosan, which were free from additives such as acid, salt, and plasticizer, were prepared by casting mixtures of an aqueous solution of an enzymatically synthesized amylose and that of water-soluble chitin (44.1% deacetylated). The presence of a small amount of chitin (less than 10%) increased significantly the permeability of gases (N2, O2, CO2, C2H4) and improved the mechanical parameters of amylose film; particularly, the elastic modulus and elongation of the blend films were larger than those of amylose or chitin films. No antibacterial activity was observed with either amylose or water-soluble chitin films. But amylose films having a small amount of chitin showed strong antibacterial action, suggesting a morphological change in water-soluble chitin on the film surface by blending with amylose molecule. These facts suggested the presence of a molecular complex of amylose and chitosan.

  1. Competitive Adsorption of Naphthenic Acids and Polyaromatic Molecules at a Toluene-Water Interface.

    PubMed

    Teklebrhan, Robel B; Jian, Cuiying; Choi, Phillip; Xu, Zhenghe; Sjöblom, Johan

    2016-12-22

    The early-stage competitive co-adsorption of interfacially active naphthenic acids (NAs) and polyaromatic (PA) molecules to a toluene-water interface from the bulk toluene phase was studied using molecular dynamics (MD) simulation. The NA molecules studied had the same polar functional group but different cycloaliphatic nonpolar tails, and a perylene bisimide (PBI)-based molecule was used as a representative PA compound. The results from our simulations suggest that the size and structural features of NA molecules greatly influence the interfacial activity of PA molecules and partitioning of NA molecules at the toluene-water interface. At low concentrations of PA (∼2.3 wt %) and NA (∼0.4 wt %) molecules, NA molecules containing large cycloaliphatic rings (e.g., four rings) or with a very long aliphatic tail (e.g., carbon chain length of 14) were observed to impede the migration of PA molecules to the interface, whereas small NA molecules containing two cycloaliphatic rings had little effect on the adsorption of PA molecules at the toluene-water interface. At high NA concentrations, the adsorption of PA molecules (∼5.75-17.25 wt %) was greatly hindered by the presence of small NA molecules (∼1.6-4.8 wt %) due to the solvation of PA nanoaggregates in the bulk. Adsorption mechanisms of PA and NA molecules at toluene-water interfaces were clarified through a detailed analysis on the interactions among different species in the system. The results obtained from this work provide insights into designing appropriate chemical demulsifiers or co-demulsifiers for breaking water-in-oil emulsions of great industrial applications.

  2. Subdivision of phase space for anisotropically interacting water molecules

    NASA Astrophysics Data System (ADS)

    Epifanov, S. Yu.; Vigasin, A. A.

    An efficient numerical algorithm is employed which enables one to perform multidimensional integrations of complicated integrands. Temperature dependence of the second virial coefficient for water is reproduced using the Matsuoka Clementi Yoshimine intermolecular water water potential. Metastable states are shown to occupy significant domain in the water dimer phase space.

  3. Multispectral actinometry of water and water-derivative molecules in moist, inert gas discharge plasmas

    NASA Astrophysics Data System (ADS)

    Bernatskiy, A. V.; Ochkin, V. N.; Kochetov, I. V.

    2016-10-01

    A new version of optical actinometry (OA) is used to determine the concentrations of water molecules and their fragments in hollow cathode discharge plasma in moist inert gases. Use is made of two actinometer particles, namely, the atoms Xe and Ar, for concurrent measurements of the concentrations of the H2O molecule and its fragments O, H, and OH. A self-consistent method is suggested for the determination of particle concentrations with due regard for the quenching of the emitting states. The temporal behavior of particles during discharge glow is studied. Noted are fast variations (lasting from a few to a few tens of s) in the concentrations of all the particles, followed by their stabilization (within a few to a few tens of mins). The scheme of the processes responsible for the observed dynamics of the plasma composition is discussed.

  4. Effects of a single water molecule on the OH + H2O2 reaction.

    PubMed

    Buszek, Robert J; Torrent-Sucarrat, Miquel; Anglada, Josep M; Francisco, Joseph S

    2012-06-21

    The effect of a single water molecule on the reaction between H(2)O(2) and HO has been investigated by employing MP2 and CCSD(T) theoretical approaches in connection with the aug-cc-PVDZ, aug-cc-PVTZ, and aug-cc-PVQZ basis sets and extrapolation to an ∞ basis set. The reaction without water has two elementary reaction paths that differ from each other in the orientation of the hydrogen atom of the hydroxyl radical moiety. Our computed rate constant, at 298 K, is 1.56 × 10(-12) cm(3) molecule(-1) s(-1), in excellent agreement with the suggested value by the NASA/JPL evaluation. The influence of water vapor has been investigated by considering either that H(2)O(2) first forms a complex with water that reacts with hydroxyl radical or that H(2)O(2) reacts with a previously formed H(2)O·OH complex. With the addition of water, the reaction mechanism becomes much more complex, yielding four different reaction paths. Two pathways do not undergo the oxidation reaction but an exchange reaction where there is an interchange between H(2)O(2)·H(2)O and H(2)O·OH complexes. The other two pathways oxidize H(2)O(2), with a computed total rate constant of 4.09 × 10(-12) cm(3) molecule(-1) s(-1) at 298 K, 2.6 times the value of the rate constant of the unassisted reaction. However, the true effect of water vapor requires taking into account the concentration of the prereactive bimolecular complex, namely, H(2)O(2)·H(2)O. With this consideration, water can actually slow down the oxidation of H(2)O(2) by OH between 1840 and 20.5 times in the 240-425 K temperature range. This is an example that demonstrates how water could be a catalyst in an atmospheric reaction in the laboratory but is slow under atmospheric conditions.

  5. Chemical reactions of water molecules on Ru(0001) induced by selective excitation of vibrational modes

    SciTech Connect

    Mugarza, Aitor; Shimizu, Tomoko K.; Ogletree, D. Frank; Salmeron, Miquel

    2009-05-07

    Tunneling electrons in a scanning tunneling microscope were used to excite specific vibrational quantum states of adsorbed water and hydroxyl molecules on a Ru(0 0 0 1) surface. The excited molecules relaxed by transfer of energy to lower energy modes, resulting in diffusion, dissociation, desorption, and surface-tip transfer processes. Diffusion of H{sub 2}O molecules could be induced by excitation of the O-H stretch vibration mode at 445 meV. Isolated molecules required excitation of one single quantum while molecules bonded to a C atom required at least two quanta. Dissociation of single H{sub 2}O molecules into H and OH required electron energies of 1 eV or higher while dissociation of OH required at least 2 eV electrons. In contrast, water molecules forming part of a cluster could be dissociated with electron energies of 0.5 eV.

  6. Additives

    NASA Technical Reports Server (NTRS)

    Smalheer, C. V.

    1973-01-01

    The chemistry of lubricant additives is discussed to show what the additives are chemically and what functions they perform in the lubrication of various kinds of equipment. Current theories regarding the mode of action of lubricant additives are presented. The additive groups discussed include the following: (1) detergents and dispersants, (2) corrosion inhibitors, (3) antioxidants, (4) viscosity index improvers, (5) pour point depressants, and (6) antifouling agents.

  7. Application of inhomogeneous fluid solvation theory to model the distribution and thermodynamics of water molecules around biomolecules.

    PubMed

    Huggins, David J

    2012-11-21

    The structures of biomolecules and the strengths of association between them depend critically on interactions with water molecules. Thus, understanding these interactions is a prerequisite for understanding the structure and function of all biomolecules. Inhomogeneous fluid solvation theory provides a framework to derive thermodynamic properties of individual water molecules from a statistical mechanical analysis. In this work, two biomolecules are analysed to probe the distribution and thermodynamics of surrounding water molecules. The great majority of hydration sites are predicted to contribute favourably to the total free energy with respect to bulk water, though hydration sites close to non-polar regions of the solute do not contribute significantly. Analysis of a biomolecule with a positively and negatively charged functional group predicts that a charged species perturbs the free energy of water molecules to a distance of approximately 6.0 Å. Interestingly, short simulations are found to provide converged predictions if samples are taken with sufficient frequency, a finding that has the potential to significantly reduce the required computational cost of such analysis. In addition, the predicted thermodynamic properties of hydration sites with the potential for direct hydrogen bonding interactions are found to disagree significantly for two different water models. This study provides important information on how inhomogeneous fluid solvation theory can be employed to understand the structures and intermolecular interactions of biomolecules.

  8. Encapsulation and Residency of a Hydrophobic Dye within the Water-Filled Interior of a PAMAM Dendrimer Molecule.

    PubMed

    Koley, Somnath; Ghosh, Subhadip

    2017-03-02

    Tightly confined water within a small droplet behaves differently from bulk water. This notion is obtained on the basis of several reports showing unusual behaviors of water droplet residing at the core of a reverse micelle. In this study, we have shown a well-known hydrophobic dye, coumarin 153 (C153), which prefers to reside at the water-rich region inside the dendrimer molecule. Optical density (OD) measurement at the absorption peak of C153 shows that it is almost insoluble in bulk water but highly soluble in aqueous dendrimer solution. The OD of C153 increases several times in the latter case as compared to that in the former. We found the most interesting observation when we compared the data from fluorescence correlation spectroscopy (FCS) with the fluorescence anisotropy decay of C153 in aqueous dendrimer solution. The FCS measurement reveals a much slower translational diffusion time (τD) of C153 attached to a dendrimer molecule as compared to that of free C153 in bulk water in the absence of dendrimer. The slower τD in the former case is commensurate with the size of the dendrimer molecule. This is possible only when C153 is encapsulated by the dendrimer molecule. In contrast to the FCS study, the fluorescence anisotropy decay of C153 in water remains largely invariant after addition of the dendrimer. This can happen if a bulk-water-like environment at the C153 surroundings is preserved within the C153-dendrimer complex. This supports our institutive expectation that C153 resides within the water-rich peripheral cavities of the dendrimer molecule. A more expected binding of C153 to the hydrophobic core of dendrimer may not be possible here because of an inadequate size of the dendrimer core.

  9. Solvated water molecules and hydrogen-bridged networks in liquid water

    NASA Astrophysics Data System (ADS)

    Corongiu, Giorgina; Clementi, Enrico

    1993-02-01

    We have analyzed the molecular-dynamics (MD) trajectories for the oxygen and hydrogen atoms of liquid water, at six temperatures (from hot, T=361 K, to supercooled water, T=242 K); in the MD simulations the Nieser-Corongiu-Clementi ab initio potential has been used, since it yields reliable x-ray and neutron-diffraction data as well as infrared, Raman, and neutron-scattering spectra. Our analysis leads to two complementary models where we can consider each water as a solvated molecule (placed at the center of a solvation shell) or as a component of a cyclic polymer, a substructure of the hydrogen-bonded network. In the first solvation shell all water molecules are solvated with coordination values in the range 2-8. The most probable solvation number is four, at low temperature, and five at high temperature considering oxygen-oxygen pairs; however, the coordination number is four at all the temperatures if we consider oxygen-hydrogen pairs. The lifetime of the tetra coordinated complexes is the largest one and increases as temperature decreases. The computed population of cyclic polymers is highest for the pentameters in the studied temperature range, the second most probable cyclic structure is for hexamers. The average O-O distances in the liquid are temperature dependent and shorter than those in the gas phase, approaching ice values at low temperature (except for cyclic trimers, for which the O-O distance is nearly temperature independent). As a preliminary result, the lifetime of the polygons is estimated to be around 0.01 ps.

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

    PubMed

    Liu, Zhigang; Wang, Yong; Yedidi, Ravikiran S; Dewdney, Tamaria G; Reiter, Samuel J; Brunzelle, Joseph S; Kovari, Iulia A; Kovari, Ladislau C

    2013-01-18

    The 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. In addition, 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.

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

    SciTech Connect

    Liu, Zhigang; Wang, Yong; Yedidi, Ravikiran S.; Dewdney, Tamaria G.; Reiter, Samuel J.; Brunzelle, Joseph S.; Kovari, Iulia A.; Kovari, Ladislau C.

    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.

  12. Quantifying the entropy of binding for water molecules in protein cavities by computing correlations.

    PubMed

    Huggins, David J

    2015-02-17

    Protein structural analysis demonstrates that water molecules are commonly found in the internal cavities of proteins. Analysis of experimental data on the entropies of inorganic crystals suggests that the entropic cost of transferring such a water molecule to a protein cavity will not typically be greater than 7.0 cal/mol/K per water molecule, corresponding to a contribution of approximately +2.0 kcal/mol to the free energy. In this study, we employ the statistical mechanical method of inhomogeneous fluid solvation theory to quantify the enthalpic and entropic contributions of individual water molecules in 19 protein cavities across five different proteins. We utilize information theory to develop a rigorous estimate of the total two-particle entropy, yielding a complete framework to calculate hydration free energies. We show that predictions from inhomogeneous fluid solvation theory are in excellent agreement with predictions from free energy perturbation (FEP) and that these predictions are consistent with experimental estimates. However, the results suggest that water molecules in protein cavities containing charged residues may be subject to entropy changes that contribute more than +2.0 kcal/mol to the free energy. In all cases, these unfavorable entropy changes are predicted to be dominated by highly favorable enthalpy changes. These findings are relevant to the study of bridging water molecules at protein-protein interfaces as well as in complexes with cognate ligands and small-molecule inhibitors.

  13. Quantifying the Entropy of Binding for Water Molecules in Protein Cavities by Computing Correlations

    PubMed Central

    Huggins, David J.

    2015-01-01

    Protein structural analysis demonstrates that water molecules are commonly found in the internal cavities of proteins. Analysis of experimental data on the entropies of inorganic crystals suggests that the entropic cost of transferring such a water molecule to a protein cavity will not typically be greater than 7.0 cal/mol/K per water molecule, corresponding to a contribution of approximately +2.0 kcal/mol to the free energy. In this study, we employ the statistical mechanical method of inhomogeneous fluid solvation theory to quantify the enthalpic and entropic contributions of individual water molecules in 19 protein cavities across five different proteins. We utilize information theory to develop a rigorous estimate of the total two-particle entropy, yielding a complete framework to calculate hydration free energies. We show that predictions from inhomogeneous fluid solvation theory are in excellent agreement with predictions from free energy perturbation (FEP) and that these predictions are consistent with experimental estimates. However, the results suggest that water molecules in protein cavities containing charged residues may be subject to entropy changes that contribute more than +2.0 kcal/mol to the free energy. In all cases, these unfavorable entropy changes are predicted to be dominated by highly favorable enthalpy changes. These findings are relevant to the study of bridging water molecules at protein-protein interfaces as well as in complexes with cognate ligands and small-molecule inhibitors. PMID:25692597

  14. Benefits of neutral electrolyzed oxidizing water as a drinking water additive for broiler chickens.

    PubMed

    Bügener, E; Kump, A Wilms-Schulze; Casteel, M; Klein, G

    2014-09-01

    In the wake of discussion about the use of drugs in food-producing farms, it seems to be more and more important to search for alternatives and supportive measures to improve health. In this field trial, the influence of electrolyzed oxidizing (EO) water on water quality, drug consumption, mortality, and performance parameters such as BW and feed conversion rate was investigated on 2 broiler farms. At each farm, 3 rearing periods were included in the study. With EO water as the water additive, the total viable cell count and the number of Escherichia coli in drinking water samples were reduced compared with the respective control group. The frequency of treatment days was represented by the number of used daily doses per population and showed lower values in EO-water-treated groups at both farms. Furthermore, the addition of EO water resulted in a lower mortality rate. In terms of analyzed performance parameters, no significant differences were determined. In this study, the use of EO water improved drinking water quality and seemed to reduce the drug use without showing negative effects on performance parameters and mortality rates.

  15. Rapid Recovery of Cyanobacterial Pigments in Desiccated Biological Soil Crusts following Addition of Water

    PubMed Central

    Abed, Raeid M. M.; Polerecky, Lubos; Al-Habsi, Amal; Oetjen, Janina; Strous, Marc; de Beer, Dirk

    2014-01-01

    We examined soil surface colour change to green and hydrotaxis following addition of water to biological soil crusts using pigment extraction, hyperspectral imaging, microsensors and 13C labeling experiments coupled to matrix-assisted laser desorption and ionization time of flight-mass spectrometry (MALD-TOF MS). The topsoil colour turned green in less than 5 minutes following water addition. The concentrations of chlorophyll a (Chl a), scytonemin and echinenon rapidly increased in the top <1 mm layer while in the deeper layer, their concentrations remained low. Hyperspectral imaging showed that, in both wet and dehydrated crusts, cyanobacteria formed a layer at a depth of 0.2–0.4 mm and this layer did not move upward after wetting. 13C labeling experiments and MALDI TOF analysis showed that Chl a was already present in the desiccated crusts and de novo synthesis of this molecule started only after 2 days of wetting due to growth of cyanobacteria. Microsensor measurements showed that photosynthetic activity increased concomitantly with the increase of Chl a, and reached a maximum net rate of 92 µmol m−2 h−1 approximately 2 hours after wetting. We conclude that the colour change of soil crusts to green upon water addition was not due to hydrotaxis but rather to the quick recovery and reassembly of pigments. Cyanobacteria in crusts can maintain their photosynthetic apparatus intact even under prolonged periods of desiccation with the ability to resume their photosynthetic activities within minutes after wetting. PMID:25375172

  16. Rapid recovery of cyanobacterial pigments in desiccated biological soil crusts following addition of water.

    PubMed

    Abed, Raeid M M; Polerecky, Lubos; Al-Habsi, Amal; Oetjen, Janina; Strous, Marc; de Beer, Dirk

    2014-01-01

    We examined soil surface colour change to green and hydrotaxis following addition of water to biological soil crusts using pigment extraction, hyperspectral imaging, microsensors and 13C labeling experiments coupled to matrix-assisted laser desorption and ionization time of flight-mass spectrometry (MALD-TOF MS). The topsoil colour turned green in less than 5 minutes following water addition. The concentrations of chlorophyll a (Chl a), scytonemin and echinenon rapidly increased in the top <1 mm layer while in the deeper layer, their concentrations remained low. Hyperspectral imaging showed that, in both wet and dehydrated crusts, cyanobacteria formed a layer at a depth of 0.2-0.4 mm and this layer did not move upward after wetting. 13C labeling experiments and MALDI TOF analysis showed that Chl a was already present in the desiccated crusts and de novo synthesis of this molecule started only after 2 days of wetting due to growth of cyanobacteria. Microsensor measurements showed that photosynthetic activity increased concomitantly with the increase of Chl a, and reached a maximum net rate of 92 µmol m-2 h-1 approximately 2 hours after wetting. We conclude that the colour change of soil crusts to green upon water addition was not due to hydrotaxis but rather to the quick recovery and reassembly of pigments. Cyanobacteria in crusts can maintain their photosynthetic apparatus intact even under prolonged periods of desiccation with the ability to resume their photosynthetic activities within minutes after wetting.

  17. Relaxation dynamics of surface-adsorbed water molecules in nanoporous silica probed by terahertz spectroscopy

    NASA Astrophysics Data System (ADS)

    Huang, Yu-Ru; Liu, Kao-Hsiang; Mou, Chung-Yuan; Sun, Chi-Kuang

    2015-08-01

    Relaxation dynamics of an exclusively adsorbed water molecule in mesoporous silica MCM-41-S was studied by using terahertz spectroscopy. With the temperature controlled from 0 to 50 °C, we observed strongly frequency- and temperature-dependent dielectric relaxation responses, implying that, unlike ice, surface-adsorbed water molecules retained flourishing picosecond dynamics. Based on the Debye relaxation model, a relaxation time constant was found to increase from 1.77 to 4.83 ps when the water molecule was cooled from 50 to 0 °C. An activation energy of ˜15 kJ/mol, which was in close agreement with a hydrogen-bonding energy, was further extracted from the Arrhenius analysis. Combined with previous molecular dynamics simulations, our results indicate that the reorientation relaxation originated from the "flip-flop" rotation of a three hydrogen-bonded surface-adsorbed water molecule.

  18. Water hyacinth a potential source for value addition: An overview.

    PubMed

    Sindhu, Raveendran; Binod, Parameswaran; Pandey, Ashok; Madhavan, Aravind; Alphonsa, Jose Anju; Vivek, Narisetty; Gnansounou, Edgard; Castro, Eulogio; Faraco, Vincenza

    2017-04-01

    Water hyacinth a fresh water aquatic plant is considered as a noxious weed in many parts of the world since it grows very fast and depletes nutrients and oxygen from water bodies adversely affecting the growth of both plants and animals. Hence conversion of this problematic weed to value added chemicals and fuels helps in the self-sustainability especially for developing countries. The present review discusses the various value added products and fuels which can be produced from water hyacinth, the recent research and developmental activities on the bioconversion of water hyacinth for the production of fuels and value added products as well as its possibilities and challenges in commercialization.

  19. Quasielastic neutron scattering investigation of motion of water molecules in n-propyl alcohol-water mixture.

    PubMed

    Nakada, Masaru; Maruyama, Kenji; Yamamuro, Osamu; Misawa, Masakatsu

    2009-02-21

    The dynamics of water molecules in the n-propyl alcohol-water mixtures is investigated by using quasielastic neutron scattering measurements. The dynamic structure factor S(Q,E) obtained from incoherent scattering of hydrogen atoms of water is fitted with jump diffusion and relaxing cage models. The diffusion constant obtained from the relaxing cage model, which gives better fitting with S(Q,E), shows better agreement to the experimental value than that of jump diffusion model. The dependence of translational relaxation time tau(T)(Q) and stretched exponent beta(T)(Q) on the fraction of hydrophobic hydrating water molecules in the solution is discussed.

  20. Quasielastic neutron scattering investigation of motion of water molecules in n-propyl alcohol-water mixture

    NASA Astrophysics Data System (ADS)

    Nakada, Masaru; Maruyama, Kenji; Yamamuro, Osamu; Misawa, Masakatsu

    2009-02-01

    The dynamics of water molecules in the n-propyl alcohol-water mixtures is investigated by using quasielastic neutron scattering measurements. The dynamic structure factor S(Q,E) obtained from incoherent scattering of hydrogen atoms of water is fitted with jump diffusion and relaxing cage models. The diffusion constant obtained from the relaxing cage model, which gives better fitting with S(Q,E), shows better agreement to the experimental value than that of jump diffusion model. The dependence of translational relaxation time τT(Q) and stretched exponent βT(Q) on the fraction of hydrophobic hydrating water molecules in the solution is discussed.

  1. Clustering of water molecules in ultramicroporous carbon: In-situ small-angle neutron scattering

    SciTech Connect

    Bahadur, Jitendra; Contescu, Cristian I.; Rai, Durgesh K.; Gallego, Nidia C.; Melnichenko, Yuri B.

    2016-10-19

    The adsorption of water is central to most of the applications of microporous carbon as adsorbent material. We report early kinetics of water adsorption in the microporous carbon using in-situ small-angle neutron scattering. It is observed that adsorption of water occurs via cluster formation of molecules. Interestingly, the cluster size remains constant throughout the adsorption process whereas number density of clusters increases with time. The role of surface chemistry of microporous carbon on the early kinetics of adsorption process was also investigated. Lastly, the present study provides direct experimental evidence for cluster assisted adsorption of water molecules in microporous carbon (Do-Do model).

  2. Affinity transformation from hydrophilicity to hydrophobicity of water molecules on the basis of adsorption of water in graphitic nanopores.

    PubMed

    Ohba, Tomonori; Kanoh, Hirofumi; Kaneko, Katsumi

    2004-02-11

    The interaction of water with hydrophobic surfaces is quite important in a variety of chemical and biochemical phenomena. The coexistence of water and oil can be realized by introduction of surfactants. In the case of water vapor adsorption on graphitic nanopores, plenty of water can be adsorbed in graphitic nanopores without surfactants, although the graphitic surface is not hydrophilic. Why are water molecules adsorbed in hydrophobic nanopores remarkably? This work can give an explicit insight to water adsorption in hydrophobic graphite nanopores using experimental and theoretical approaches. Water molecules are associated with each other to form the cluster of 1 nm in size, leading to a significant stabilization of the cluster in the graphitic nanopores. This mechanism can be widely applied to interfacial phenomena relating to coexistence of water and nanostructural materials of hydrophobicity.

  3. The role of water molecules in stereoselectivity of glucose/galactose-binding protein

    NASA Astrophysics Data System (ADS)

    Kim, Minsup; Cho, Art E.

    2016-11-01

    Using molecular dynamics (MD) simulation methods, we attempted to explain the experimental results on ligand specificity of glucose/galactose-binding protein (GGBP) to β-D-glucose and β-D-galactose. For the simulation, a three-dimensional structure of GGBP was prepared, and homology modeling was performed to generate variant structures of GGBP with mutations at Asp14. Then, docking was carried out to find a reasonable β-D-glucose and β-D-galactose binding conformations with GGBP. Subsequent molecular dynamics simulations of β-D-glucose–GGBP and β-D-galactose–GGBP complexes and estimation of the orientation and stability of water molecules at the binding site revealed how water molecules influence ligand specificity. In our simulation, water molecules mediated interactions of β-D-glucose or β-D-galactose with residue 14 of GGBP. In this mechanism, the Phe16Ala mutant leaves both sugar molecules free to move, and the specific role of water molecules were eliminated, while the wild type, Asp14Asn mutant, and Asp14Glu mutant make hydrogen bond interactions with β-D-glucose more favorable. Our results demonstrate that bound water molecules at the binding site of GGBP are related to localized conformational change, contributing to ligand specificity of GGBP for β-D-glucose over β-D-galactose.

  4. Calculations for ion-impact induced ionization and fragmentation of water molecules

    NASA Astrophysics Data System (ADS)

    Kirchner, Tom; Murakami, Mitsuko; Horbatsch, Marko; Jürgen Lüdde, Hans

    2012-10-01

    Charge-state correlated cross sections for single- and multiple-electron removal processes in proton-water-molecule collisions are calculated by using the non-perturbative basis generator method adapted for ion-molecule collisions [1,2]. A fragmentation model is then applied to calculate the yields of H2O^+, OH^+, H^+, and O^+ ions emerging after H2O^q+ formation [3]. A detailed comparison is made with experimental data from three groups covering the energy range from 20--5000 keV. It is found that multiple electron processes with q<=3 play an important role at the lower end of this range and are calculated accurately within an independent particle model. We are currently completing the analogous analysis for He^+-H2O collisions for which the presence of the projectile electron poses some additional challenges. [4pt] [1] H.J. L"udde et al, Phys. Rev. A 80, 060702(R) (2009)[0pt] [2] M. Murakami et al, Phys. Rev. A 85, 052704 (2012)[0pt] [3] M. Murakami et al, Phys. Rev. A 85, 052713 (2012)

  5. Diffusion of small molecules in a chitosan/water gel determined by proton localized NMR spectroscopy.

    PubMed

    García-Aparicio, Carlos; Quijada-Garrido, Isabel; Garrido, Leoncio

    2012-02-15

    Proton localized NMR spectroscopy (MRS) has been applied to study the diffusion of three small molecules, caffeine, theophylline and caprolactam, in chitosan gels with different concentration of water. This technique allows the non-destructive monitorization of diffusant concentration as a function of time and location. Concentration profiles were compared with theoretical curves based on solutions of Fick's diffusion equation for the best fitting, with the appropriate boundary conditions. The measured concentration profiles show a good agreement with the Fickian law. Values of the diffusion coefficients D ranging from 6.1×10(-6) to 3.4×10(-6)cm(2)s(-1) depending on chitosan concentration and type of diffusant molecule were determined. In addition, measurements of diffusion coefficients at equilibrium conditions with proton pulsed field gradient NMR methods supported the observed Fickian behavior and showed values of D in excellent agreement with those determined by proton MRS. All these facts demonstrate that proton MRS is an appropriate method for investigating diffusion process in complex systems, such as polymer gels.

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

    PubMed

    Shinagawa, Tatsuya; Takanabe, Kazuhiro

    2015-06-21

    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.

  7. Incipient ferroelectricity of water molecules confined to nano-channels of beryl

    PubMed Central

    Gorshunov, B. P.; Torgashev, V. I.; Zhukova, E. S.; Thomas, V. G.; Belyanchikov, M. A.; Kadlec, C.; Kadlec, F.; Savinov, M.; Ostapchuk, T.; Petzelt, J.; Prokleška, J.; Tomas, P. V.; Pestrjakov, E. V.; Fursenko, D. A.; Shakurov, G. S.; Prokhorov, A. S.; Gorelik, V. S.; Kadyrov, L. S.; Uskov, V. V.; Kremer, R. K.; Dressel, M.

    2016-01-01

    Water is characterized by large molecular electric dipole moments and strong interactions between molecules; however, hydrogen bonds screen the dipole–dipole coupling and suppress the ferroelectric order. The situation changes drastically when water is confined: in this case ordering of the molecular dipoles has been predicted, but never unambiguously detected experimentally. In the present study we place separate H2O molecules in the structural channels of a beryl single crystal so that they are located far enough to prevent hydrogen bonding, but close enough to keep the dipole–dipole interaction, resulting in incipient ferroelectricity in the water molecular subsystem. We observe a ferroelectric soft mode that causes Curie–Weiss behaviour of the static permittivity, which saturates below 10 K due to quantum fluctuations. The ferroelectricity of water molecules may play a key role in the functioning of biological systems and find applications in fuel and memory cells, light emitters and other nanoscale electronic devices. PMID:27687693

  8. Incipient ferroelectricity of water molecules confined to nano-channels of beryl

    NASA Astrophysics Data System (ADS)

    Gorshunov, B. P.; Torgashev, V. I.; Zhukova, E. S.; Thomas, V. G.; Belyanchikov, M. A.; Kadlec, C.; Kadlec, F.; Savinov, M.; Ostapchuk, T.; Petzelt, J.; Prokleška, J.; Tomas, P. V.; Pestrjakov, E. V.; Fursenko, D. A.; Shakurov, G. S.; Prokhorov, A. S.; Gorelik, V. S.; Kadyrov, L. S.; Uskov, V. V.; Kremer, R. K.; Dressel, M.

    2016-09-01

    Water is characterized by large molecular electric dipole moments and strong interactions between molecules; however, hydrogen bonds screen the dipole-dipole coupling and suppress the ferroelectric order. The situation changes drastically when water is confined: in this case ordering of the molecular dipoles has been predicted, but never unambiguously detected experimentally. In the present study we place separate H2O molecules in the structural channels of a beryl single crystal so that they are located far enough to prevent hydrogen bonding, but close enough to keep the dipole-dipole interaction, resulting in incipient ferroelectricity in the water molecular subsystem. We observe a ferroelectric soft mode that causes Curie-Weiss behaviour of the static permittivity, which saturates below 10 K due to quantum fluctuations. The ferroelectricity of water molecules may play a key role in the functioning of biological systems and find applications in fuel and memory cells, light emitters and other nanoscale electronic devices.

  9. Incipient ferroelectricity of water molecules confined to nano-channels of beryl.

    PubMed

    Gorshunov, B P; Torgashev, V I; Zhukova, E S; Thomas, V G; Belyanchikov, M A; Kadlec, C; Kadlec, F; Savinov, M; Ostapchuk, T; Petzelt, J; Prokleška, J; Tomas, P V; Pestrjakov, E V; Fursenko, D A; Shakurov, G S; Prokhorov, A S; Gorelik, V S; Kadyrov, L S; Uskov, V V; Kremer, R K; Dressel, M

    2016-09-30

    Water is characterized by large molecular electric dipole moments and strong interactions between molecules; however, hydrogen bonds screen the dipole-dipole coupling and suppress the ferroelectric order. The situation changes drastically when water is confined: in this case ordering of the molecular dipoles has been predicted, but never unambiguously detected experimentally. In the present study we place separate H2O molecules in the structural channels of a beryl single crystal so that they are located far enough to prevent hydrogen bonding, but close enough to keep the dipole-dipole interaction, resulting in incipient ferroelectricity in the water molecular subsystem. We observe a ferroelectric soft mode that causes Curie-Weiss behaviour of the static permittivity, which saturates below 10 K due to quantum fluctuations. The ferroelectricity of water molecules may play a key role in the functioning of biological systems and find applications in fuel and memory cells, light emitters and other nanoscale electronic devices.

  10. Auger spectrum of a water molecule after single and double core ionization.

    PubMed

    Inhester, L; Burmeister, C F; Groenhof, G; Grubmüller, H

    2012-04-14

    The high intensity of free electron lasers opens up the possibility to perform single-shot molecule scattering experiments. However, even for small molecules, radiation damage induced by absorption of high intense x-ray radiation is not yet fully understood. One of the striking effects which occurs under intense x-ray illumination is the creation of double core ionized molecules in considerable quantity. To provide insight into this process, we have studied the dynamics of water molecules in single and double core ionized states by means of electronic transition rate calculations and ab initio molecular dynamics (MD) simulations. From the MD trajectories, photoionization and Auger transition rates were computed based on electronic continuum wavefunctions obtained by explicit integration of the coupled radial Schrödinger equations. These rates served to solve the master equations for the populations of the relevant electronic states. To account for the nuclear dynamics during the core hole lifetime, the calculated electron emission spectra for different molecular geometries were incoherently accumulated according to the obtained time-dependent populations, thus neglecting possible interference effects between different decay pathways. We find that, in contrast to the single core ionized water molecule, the nuclear dynamics for the double core ionized water molecule during the core hole lifetime leaves a clear fingerprint in the resulting electron emission spectra. The lifetime of the double core ionized water was found to be significantly shorter than half of the single core hole lifetime.

  11. Auger spectrum of a water molecule after single and double core ionization

    SciTech Connect

    Inhester, L.; Burmeister, C. F.; Groenhof, G.; Grubmueller, H.

    2012-04-14

    The high intensity of free electron lasers opens up the possibility to perform single-shot molecule scattering experiments. However, even for small molecules, radiation damage induced by absorption of high intense x-ray radiation is not yet fully understood. One of the striking effects which occurs under intense x-ray illumination is the creation of double core ionized molecules in considerable quantity. To provide insight into this process, we have studied the dynamics of water molecules in single and double core ionized states by means of electronic transition rate calculations and ab initio molecular dynamics (MD) simulations. From the MD trajectories, photoionization and Auger transition rates were computed based on electronic continuum wavefunctions obtained by explicit integration of the coupled radial Schroedinger equations. These rates served to solve the master equations for the populations of the relevant electronic states. To account for the nuclear dynamics during the core hole lifetime, the calculated electron emission spectra for different molecular geometries were incoherently accumulated according to the obtained time-dependent populations, thus neglecting possible interference effects between different decay pathways. We find that, in contrast to the single core ionized water molecule, the nuclear dynamics for the double core ionized water molecule during the core hole lifetime leaves a clear fingerprint in the resulting electron emission spectra. The lifetime of the double core ionized water was found to be significantly shorter than half of the single core hole lifetime.

  12. Molecular Dynamics Study of Small PNA Molecules in Lipid-Water System

    PubMed Central

    Weroński, Paweł; Jiang, Yi; Rasmussen, Steen

    2007-01-01

    We present the results of molecular dynamics simulations of small peptide nucleic acid (PNA) molecules, synthetic analogs of DNA, at a lipid bilayer in water. At neutral pH, without any salt, and in the NPnγT ensemble, two similar PNA molecules (6-mers) with the same nucleic base sequence and different terminal groups are investigated at the interface between water and a 1-palmitoyl-2-oleoylphosphatidylcholine lipid bilayer. The results of our simulations suggest that at low ionic strength of the solution, both PNA molecules adsorb at the lipid-water interface. In the case where the PNA molecule has charged terminal groups, the main driving force of adsorption is the electrostatic attraction between the charged groups of PNA and the lipid heads. The main driving force of adsorption of the PNA molecule with neutral terminal groups is the hydrophobic interaction of the nonpolar groups. Our simulations suggest that the system free energy change associated with PNA adsorption at the lipid-water interface is on the order of several tens of kT per PNA molecule in both cases. PMID:17307825

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

    PubMed

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

    2014-06-14

    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 ɛ'(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 ɛ'(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.

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

    NASA Astrophysics Data System (ADS)

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

    2014-06-01

    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 ɛ'(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 ɛ'(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.

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

    SciTech Connect

    McDowell, R.S.; Kossiakoff, A.A.

    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.

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

    PubMed

    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.

  17. Water molecules inside protein structure affect binding of monosaccharides with HIV-1 antibody 2G12.

    PubMed

    Ueno-Noto, Kaori; Takano, Keiko

    2016-10-05

    Water molecules inside biomolecules constitute integral parts of their structure and participate in the functions of the proteins. Some of the X-ray crystallographic data are insufficient for analyzing a series of ligand-protein complexes in the same condition. We theoretically investigated antibody binding abilities of saccharide ligands and the effects of the inner water molecules of ligand-antibody complexes. Classical molecular dynamics and quantum chemical simulations using a model with possible water molecules inside the protein were performed with saccharide ligands and Human Immunodeficiency Virus 1 neutralizing antibody 2G12 complexes to estimate how inner water molecules of the protein affect the dynamics of the complexes as well as the ligand-antibody interaction. Our results indicate the fact that d-fructose's strong affinity to the antibody was partly due to the good retentiveness of solvent water molecules of the ligand and its stability of the ligand's conformation and relative position in the active site. © 2016 Wiley Periodicals, Inc.

  18. Electrical-driven transport of endohedral fullerene encapsulating a single water molecule.

    PubMed

    Xu, Baoxing; Chen, Xi

    2013-04-12

    Encapsulating a single water molecule inside an endohedral fullerene provides an opportunity for manipulating the H2O@C60 through the encapsulated polar H2O molecule. Using molecular dynamic simulations, we propose a strategy of electrical-driven transport of H2O@C60 inside a channel, underpinned by the unique behavior of a water molecule free from a hydrogen-bonding environment. When an external electrical field is applied along the channel's axial direction, steady-state transport of H2O@C60 can be reached. The transport direction and rate depend on the applied electrical intensity as well as the polar orientation of the encapsulated H2O molecule.

  19. Molecules, water, and radiant energy: new clues for the origin of life.

    PubMed

    Pollack, Gerald H; Figueroa, Xavier; Zhao, Qing

    2009-03-27

    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 thereby helps explain why life requires water.

  20. Influence of Aromatic Molecules on the Structure and Spectroscopy of Water Clusters

    NASA Astrophysics Data System (ADS)

    Tabor, Daniel P.; Sibert, Edwin; Walsh, Patrick S.; Zwier, Timothy S.

    2016-06-01

    Isomer-specific resonant ion-dip infrared spectra are presented for benzene-(water)_n, 1-2-diphenoxyethane-(water)_n, and tricyclophane-(water)_n clusters. The IR spectra are modeled with a local mode Hamiltonian that was originally formulated for the analysis of benzene-(water)_n clusters with up to seven waters. The model accounts for stretch-bend Fermi coupling, which can complicate the IR spectra in the 3150-3300 cm-1 region. When the water clusters interact with each of the solutes, the hydrogen bond lengths between the water molecules change in a characteristic way, reflecting the strength of the solute-water interaction. These structural effects are also reflected spectroscopically in the shifts of the local mode OH stretch frequencies. When diphenoxyethane is the solute, the water clusters distort more significantly than when bound to benzene. Tricyclophane's structure provides an aromatic-rich binding pocket for the water clusters. The local mode model is used to extract Hamiltonians for individual water molecules. These monomer Hamiltonians divide into groups based on their local H-bonding architecture, allowing for further classification of the wide variety of water environments encountered in this study.

  1. Interaction of water molecules with hexagonal 2D systems. A DFT study

    NASA Astrophysics Data System (ADS)

    Rojas, Ángela; Rey, Rafael

    Over the years water sources have been contaminated with many chemical agents, becoming issues that affect health of the world population. The advances of the nanoscience and nanotechnology in the development new materials constitute an alternative for design molecular filters with great efficiencies and low cost for water treatment and purification. In the nanoscale, the process of filtration or separation of inorganic and organic pollutants from water requires to study interactions of these atoms or molecules with different nano-materials. Specifically, it is necessary to understand the role of these interactions in physical and chemical properties of the nano-materials. In this work, the main interest is to do a theoretical study of interaction between water molecules and 2D graphene-like systems, such as silicene (h-Si) or germanene (h-Ge). Using Density Functional Theory we calculate total energy curves as function of separation between of water molecules and 2D systems. Different spatial configurations of water molecules relative to 2D systems are considered. Structural relaxation effects and changes of electronic charge density also are reported. Universidad Nacional de Colombia.

  2. Femtosecond mid-infrared study of the dynamics of water molecules in water-acetone and water-dimethyl sulfoxide mixtures.

    PubMed

    Lotze, S; Groot, C C M; Vennehaug, C; Bakker, H J

    2015-04-23

    We study the vibrational relaxation dynamics and the reorientation dynamics of HDO molecules in binary water-dimethyl sulfoxide (DMSO) and water-acetone mixtures with polarization-resolved femtosecond mid-infrared spectroscopy. For low solute concentrations we observe a slowing down of the reorientation of part of the water molecules that hydrate the hydrophobic methyl groups of DMSO and acetone. For water-DMSO mixtures the fraction of slowed-down water molecules rises much steeper with solute concentration than for water-acetone mixtures, showing that acetone molecules show significant aggregation already at low concentrations. At high solute concentrations, the vibrational and reorientation dynamics of both water-DMSO and water-acetone mixtures show a clear distinction between the dynamics of water molecules donating hydrogen bonds to other water molecules and the dynamics of water donating a hydrogen bond to the S═O/C═O group of the solute. For water-DMSO mixtures both types of water molecules show a very slow reorientation. The water molecules forming hydrogen bonds to the S═O group reorient with a time constant that decreases from 46 ± 14 ps at XDMSO = 0.33 to 13 ± 2 ps at XDMSO = 0.95. The water molecules forming hydrogen bonds to the C═O group of acetone show a much faster reorientation with a time constant that decreases from 6.1 ± 0.2 ps at Xacet = 0.3 to 2.96 ± 0.05 ps at Xacet = 0.9. The large difference in reorientation time constant of the solute-bound water for DMSO and acetone can be explained from the fact that the hydrogen bond between water and the S═O group of DMSO is much stronger than the hydrogen bond between water and the C═O group of acetone. We attribute the strongly different behavior of water in DMSO-rich and acetone-rich mixtures to their difference in molecular shape.

  3. Molecular mimicry of substrate oxygen atoms by water molecules in the beta-amylase active site.

    PubMed

    Pujadas, G; Palau, J

    2001-08-01

    Soybean beta-amylase (EC 3.2.1.2) has been crystallized both free and complexed with a variety of ligands. Four water molecules in the free-enzyme catalytic cleft form a multihydrogen-bond network with eight strategic residues involved in enzyme-ligand hydrogen bonds. We show here that the positions of these four water molecules are coincident with the positions of four potential oxygen atoms of the ligands within the complex. Some of these waters are displaced from the active site when the ligands bind to the enzyme. How many are displaced depends on the shape of the ligand. This means that when one of the four positions is not occupied by a ligand oxygen atom, the corresponding water remains. We studied the functional/structural role of these four waters and conclude that their presence means that the conformation of the eight side chains is fixed in all situations (free or complexed enzyme) and preserved from unwanted or forbidden conformational changes that could hamper the catalytic mechanism. The water structure at the active pocket of beta-amylase is therefore essential for providing the ligand recognition process with plasticity. It does not affect the protein active-site geometry and preserves the overall hydrogen-bonding network, irrespective of which ligand is bound to the enzyme. We also investigated whether other enzymes showed a similar role for water. Finally, we discuss the potential use of these results for predicting whether water molecules can mimic ligand atoms in the active center.

  4. Effects of water molecules on binding kinetics of peptide receptor on a piezoelectric microcantilever

    NASA Astrophysics Data System (ADS)

    Hui Kim, Sang; Kyoung Yoo, Yong; Chae, Myung-Sic; Yoon Kang, Ji; Song Kim, Tae; Seon Hwang, Kyo; Hoon Lee, Jeong

    2012-12-01

    The use of highly selective reversible peptide receptors is essential for cantilever-based electronic nose systems. Here, we present the effects of water molecules on the binding kinetics of 2,4-dinitrotoluene (DNT) molecules with DNT selective peptide receptors linked with a tri(ethylene glycol)-based (TEG) self-assembled monolayer (SAM) in a gas phase in a piezoelectric microcantilever sensor. We observed 1.5-times faster reaction kinetics in wet conditions compared with dry conditions. In a dissociation step, distinctive differences in the recovery time were observed in wet conditions, which could be attributed to water retention efficiency of TEG-linkers for the conformation of biomolecules.

  5. Formation of the prebiotic molecule NH2CHO on astronomical amorphous solid water surfaces: accurate tunneling rate calculations† †Electronic supplementary information (ESI) available: Geometric details, lists of calculated rate constants. See DOI: 10.1039/c6cp05727f Click here for additional data file.

    PubMed Central

    Song, Lei

    2016-01-01

    Investigating how formamide forms in the interstellar medium is a hot topic in astrochemistry, which can contribute to our understanding of the origin of life on Earth. We have constructed a QM/MM model to simulate the hydrogenation of isocyanic acid on amorphous solid water surfaces to form formamide. The binding energy of HNCO on the ASW surface varies significantly between different binding sites, we found values between ∼0 and 100 kJ mol–1. The barrier for the hydrogenation reaction is almost independent of the binding energy, though. We calculated tunneling rate constants of H + HNCO → NH2CO at temperatures down to 103 K combining QM/MM with instanton theory. Tunneling dominates the reaction at such low temperatures. The tunneling reaction is hardly accelerated by the amorphous solid water surface compared to the gas phase for this system, even though the activation energy of the surface reaction is lower than the one of the gas-phase reaction. Both the height and width of the barrier affect the tunneling rate in practice. Strong kinetic isotope effects were observed by comparing to rate constants of D + HNCO → NHDCO. At 103 K we found a KIE of 231 on the surface and 146 in the gas phase. Furthermore, we investigated the gas-phase reaction NH2 + H2CO → NH2CHO + H and found it unlikely to occur at cryogenic temperatures. The data of our tunneling rate constants are expected to significantly influence astrochemical models. PMID:27731439

  6. Migration of additive molecules in a polymer filament obtained by melt spinning: Influence of the fiber processing steps

    SciTech Connect

    Gesta, E.; Skovmand, O.; Espuche, E. Fulchiron, R.

    2015-12-17

    The purpose of this study is to understand the influence of the yarn processing on the migration of additives molecules, especially insecticide, within polyethylene (PE) yarns. Yarns were manufactured in the laboratory focusing on three key-steps (spinning, post-stretching and heat-setting). Influence of each step on yarn properties was investigated using tensile tests, differential scanning calorimetry and wide-angle X-ray diffraction. The post-stretching step was proved to be critical in defining yarn mechanical and structural properties. Although a first orientation of polyethylene crystals was induced during spinning, the optimal orientation was only reached by post-stretching. The results also showed that the heat-setting did not significantly change these properties. The presence of additives crystals at the yarn surface was evidenced by scanning-electron microscopy. These studies performed at each yarn production step allowed a detailed analysis of the additives’ ability to migrate. It is concluded that while post-stretching decreased the migration rate, heat-setting seems to boost this migration.

  7. Characterization of mechanics and cytocompatibility of fibrin-genipin annulus fibrosus sealant with the addition of cell adhesion molecules.

    PubMed

    Guterl, Clare C; Torre, Olivia M; Purmessur, Devina; Dave, Khyati; Likhitpanichkul, Morakot; Hecht, Andrew C; Nicoll, Steven B; Iatridis, James C

    2014-09-01

    There is an unmet clinical need for a biomaterial sealant capable of repairing small annulus fibrosus (AF) defects. Causes of these defects include painful intervertebral disc herniations, microdiscectomy procedures, morbidity associated with needle puncture injury from discography, and future nucleus replacement procedures. This study describes the enhancements of a fibrin gel through genipin crosslinking (FibGen) and the addition of the cell adhesion molecules (CAMs), fibronectin and collagen. The gel's performance as a potential AF sealant is assessed using a series of in vitro tests. FibGen gels with CAMs had equivalent adhesive strength, gene expression, cytomorphology, and cell proliferation as fibrin alone. However, FibGen gels had enhanced material behaviors that were tunable to higher shear stiffness values and approximated human annulus tissue as compared with fibrin alone, were more dimensionally stable, and had a slower in vitro degradation rate. Cytomorphology of human AF cells cultured on FibGen gels exhibited increased elongation compared with fibrin alone, and the addition of CAMs to FibGen did not significantly affect elongation. This FibGen gel offers the promise of being used as a sealant material to repair small AF defects or to be used in combination with other biomaterials as an adhesive for larger defects.

  8. Characterization of Mechanics and Cytocompatibility of Fibrin-Genipin Annulus Fibrosus Sealant with the Addition of Cell Adhesion Molecules

    PubMed Central

    Guterl, Clare C.; Torre, Olivia M.; Purmessur, Devina; Dave, Khyati; Likhitpanichkul, Morakot; Hecht, Andrew C.; Nicoll, Steven B.

    2014-01-01

    There is an unmet clinical need for a biomaterial sealant capable of repairing small annulus fibrosus (AF) defects. Causes of these defects include painful intervertebral disc herniations, microdiscectomy procedures, morbidity associated with needle puncture injury from discography, and future nucleus replacement procedures. This study describes the enhancements of a fibrin gel through genipin crosslinking (FibGen) and the addition of the cell adhesion molecules (CAMs), fibronectin and collagen. The gel's performance as a potential AF sealant is assessed using a series of in vitro tests. FibGen gels with CAMs had equivalent adhesive strength, gene expression, cytomorphology, and cell proliferation as fibrin alone. However, FibGen gels had enhanced material behaviors that were tunable to higher shear stiffness values and approximated human annulus tissue as compared with fibrin alone, were more dimensionally stable, and had a slower in vitro degradation rate. Cytomorphology of human AF cells cultured on FibGen gels exhibited increased elongation compared with fibrin alone, and the addition of CAMs to FibGen did not significantly affect elongation. This FibGen gel offers the promise of being used as a sealant material to repair small AF defects or to be used in combination with other biomaterials as an adhesive for larger defects. PMID:24684314

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

    NASA Astrophysics Data System (ADS)

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

    2016-10-01

    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.

  10. Proton transfer in hydrogen-bonded network of phenol molecules: intracluster formation of water.

    PubMed

    Lengyel, Jozef; Gorejová, Radka; Herman, Zdeněk; Fárník, Michal

    2013-11-07

    Electron ionization and time-of-flight mass spectrometry was used to investigate the phenol clusters (PhOH)n of different size from single molecule to large clusters: in coexpansion with He, the dimers n = 2 are mostly generated; in Ar, large species of n ≥ 10 also occur. Besides [(PhOH)n](+•) cluster ion series, hydrated phenol cluster ions [(PhOH)n·xH2O](+•) with up to x = 3 water molecules and dehydrated phenol clusters [(PhOH)n-H2O](+•) were observed. The hydrated phenol series exhibits minima and maxima that are interpreted as evidence for proton transfer between the hydrogen bonded cluster ions of cyclic structures. The proton transfer leads to a water generation within the clusters, and subsequent elimination of the diphenyl ether molecule(s) from the cluster yields the hydrated phenol cluster ions. Alternatively, a water molecule release yields a series of dehydrated phenols, among which the diphenyl ether ion [PhOPh](+•) (n = 2) constitutes the maximum.

  11. DFTr optimization and DFTr-MD studies of glucose, ten explicit water molecules enclosed by an implicit solvent, COSMO

    Technology Transfer Automated Retrieval System (TEKTRAN)

    DFTr optimization studies are carried out on alpha/beta-glucose surrounded by ten explicit water molecules and the glucose/water super-molecule completely enclosed by an implicit solvation model, COSMO. Twenty one starting configurations of the explicit waters were first optimized empirically with t...

  12. Study of the betulin molecule in a water environment; ab initio and molecular simulation calculations.

    PubMed

    Pospíšil, Miroslav; Kovář, Petr; Vácha, Robert; Svoboda, Michal

    2012-01-01

    Ab initio and molecular simulation methods were used in calculations of the neutral individual betulin molecule, and molecular simulations were used to optimize the betulin molecule immersed in various amounts of water. Individual betulin was optimized in different force fields to find the one exhibiting best agreement with ab initio calculations obtained in the Gaussian03 program. Dihedral torsions of active groups of betulin were determined for both procedures, and related calculated structures were compared successfully. The selected force field was used for subsequent optimization of betulin in a water environment, and a conformational search was performed using quench molecular dynamics. The total energies of betulin and its interactions in water bulk were calculated, and the influence of water on betulin structure was investigated.

  13. Clustering of water molecules in ultramicroporous carbon: In-situ small-angle neutron scattering

    DOE PAGES

    Bahadur, Jitendra; Contescu, Cristian I.; Rai, Durgesh K.; ...

    2016-10-19

    The adsorption of water is central to most of the applications of microporous carbon as adsorbent material. We report early kinetics of water adsorption in the microporous carbon using in-situ small-angle neutron scattering. It is observed that adsorption of water occurs via cluster formation of molecules. Interestingly, the cluster size remains constant throughout the adsorption process whereas number density of clusters increases with time. The role of surface chemistry of microporous carbon on the early kinetics of adsorption process was also investigated. Lastly, the present study provides direct experimental evidence for cluster assisted adsorption of water molecules in microporous carbonmore » (Do-Do model).« less

  14. Molecular Water Lilies: Orienting Single Molecules in a Polymer Film by Solvent Vapor Annealing.

    PubMed

    Würsch, Dominik; Hofmann, Felix J; Eder, Theresa; Aggarwal, A Vikas; Idelson, Alissa; Höger, Sigurd; Lupton, John M; Vogelsang, Jan

    2016-11-17

    The microscopic orientation and position of photoactive molecules is crucial to the operation of optoelectronic devices such as OLEDs and solar cells. Here, we introduce a shape-persistent macrocyclic molecule as an excellent fluorescent probe to simply measure (i) its orientation by rotating the excitation polarization and recording the strength of modulation in photoluminescence (PL) and (ii) its position in a film by analyzing the overall PL brightness at the molecular level. The unique shape, the absorption and the fluorescence properties of this probe yield information on molecular orientation and position. We control orientation and positioning of the probe in a polymer film by solvent vapor annealing (SVA). During the SVA process the molecules accumulate at the polymer/air interface, where they adopt a flat orientation, much like water lilies on the surface of a pond. The results are potentially significant for OLED fabrication and single-molecule spectroscopy (SMS) in general.

  15. Separating Octadecyltrimethoxysilane Hydrolysis and Condensation at the Air/Water Interface through Addition of Methyl Stearate

    PubMed Central

    Britt, David W.; Hlady, Vladimir

    2012-01-01

    The hydrolysis and condensation of octadecyltrimethoxysilane (OTMS) at the air/water interface were monitored through molecular area changes at a constant surface pressure of 10 mN/m. The onset of condensation was delayed through the addition of methyl stearate (SME) acting as an inert filler molecule. In the absence of SME, complete gelation of OTMS required 30 h, during which time OTMS condensation occurred concomitantly with hydrolysis. In the presence of SME, the OTMS monolayer gelation rate increased in proportion to the amount of SME present. A 1:6 OTMS:SME molar ratio resulted in monolayer gelation within 30 min, suggesting completion of monomer hydrolysis prior to condensation. These findings indicate that lability of OTMS to hydrolysis at the air/water interface is governed by steric and conformational constraints at the silicon atom site, with monomeric OTMS being much more reactive than oligomeric OTMS. Fluorescence microscope images demonstrated that the OTMS condensed domain size also decreased with increasing SME concentrations, further implicating SME’s role as an inert filler. PMID:25132807

  16. Vigorous Mold Growth in Soils After Addition of Water-Insoluble Fatty Substances

    PubMed Central

    Krause, Frank P.; Lange, Willy

    1965-01-01

    Various water-insoluble fatty compounds, when added to soil in finely divided form, will support as high-caloric nutrients a visible, vigorous growth of the molds, Fusarium solani Mart., F. diversisporum Sherb., and F. equiseti. n-Paraffins and olefins are most effective, because the effect of additives is reduced to the extent that oxygen atoms are introduced into the molecule. n-Fatty alcohols support growth in soil almost as well as the paraffins; however, growth is reduced when branched-chain compounds are added as nutrients. Compounds that will support mold growth when added to air-dried soil as finely powdered solids will not do so when incorporated at temperatures above their melting point, but will produce dense growth when applied to wet soil in this form. Mold growth is correlated with degradation of fatty matter. The rate of degradation is controlled by the availability of water, oxygen, and the basic inorganic nutrients. Images Fig. 1 Fig. 2 PMID:14325872

  17. An interpretation of the enhancement of the water dipole moment due to the presence of other water molecules.

    PubMed

    Kemp, Daniel D; Gordon, Mark S

    2008-06-05

    The dipole moment of the gas phase water monomer is 1.85 D. When solvated in bulk water, the dipole moment of an individual water molecule is observed to be enhanced to the much larger value of 2.9 +/- 0.6 D. To understand the origin of this dipole moment enhancement, the effective fragment potential (EFP) method is used to solvate an ab initio water molecule to predict the dipole moments for various cluster sizes. The dipole moment as a function of cluster size, nH 2O, is investigated [for n = 6-20 (even n), 26, 32, 41, and 50]. Localized charge distributions are used in conjunction with localized molecular orbitals to interpret the dipole moment enhancement. These calculations suggest that the enhancement of the dipole moment originates from the decrease of the angle between the dipole vectors of the lone pairs on oxygen as the number of hydrogen bonds to that oxygen increases. Thus, the decreased angle, and the consequent increase in water dipole moment, is most likely to occur in environments with a larger number of hydrogen bonds, such as the center of a cluster of water molecules.

  18. In vivo diffusion MRS investigation of non-water molecules in biological tissues.

    PubMed

    Cao, Peng; Wu, Ed X

    2017-03-01

    Diffusion MRS of non-water molecules offers great potential in directly revealing various tissue microstructures and physiology at both cellular and subcellular levels. In brain, (1) H diffusion MRS has been demonstrated as a new tool for probing normal tissue microstructures and their pathological changes. In skeletal muscle, (1) H diffusion MRS could characterize slow and restricted intramyocellular lipid diffusion, providing a sensitive marker for metabolic alterations, while (31) P diffusion MRS can measure ATP and PCr diffusion, which may reflect the capacity of cellular energy transport, complementing the information from frequently used (31) P MRS in muscle. In intervertebral disk, (1) H diffusion MRS can directly monitor extracellular matrix integrity by quantifying the mobility of macromolecules such as proteoglycans and collagens. In tumor tissue, (13) C diffusion MRS could probe intracellular glycolytic metabolism, while (1) H diffusion MRS may separate the spectrally overlapped lactate and lipid resonances. In this review, recent diffusion MRS studies of these biologically relevant non-water molecules under normal and diseased conditions will be presented. Technical considerations for diffusion MRS experiments will be discussed. With advances in MRI hardware and diffusion methodology, diffusion MRS of non-water molecules is expected to provide increasingly valuable and biologically specific information on tissue microstructures and physiology, complementing the traditional diffusion MRI of small and ubiquitous water molecules. Copyright © 2016 John Wiley & Sons, Ltd.

  19. Contribution of water molecules in the spontaneous release of protein by graphene sheets.

    PubMed

    Liang, Li-Jun; Wang, Qi; Wu, Tao; Sun, Tian-Yang; Kang, Yu

    2013-09-16

    Applications of graphene sheets in the fields of biosensors and biomedical devices are limited by the aqueous solubility of graphene. Consequently, understanding the role of water molecules in the aggregation or dispersion of graphene in aqueous solution with a biomolecule is of vital importance to its application. Herein, protein is spontaneously released by the layer-to-layer aggregation of two single-layer graphene sheets due to van der Waals force between the sheets. The properties of water molecules, including density and dynamics, are discussed in detail. The dynamic behavior of aggregation of graphene sheets is triggered by the dynamics of water molecules. To stabilize dispersed graphene sheets in aqueous solution, the density of water molecules between the graphene sheets should be larger than 0.83 g cm(-3), and graphene modified by hydroxyl groups could be a good choice. The stability of a model protein on the graphene sheet is studied to investigate the biological compatibility of graphene sheets. To be a material with good biocompatibility, graphene should be functionalized by hydrophilic groups. The results presented herein could be helpful in the research and application of graphene sheets in the fields of biomaterials, biosensors, and biomedical devices.

  20. Size, separation, structural order, and mass density of molecules packing in water and ice.

    PubMed

    Huang, Yongli; Zhang, Xi; Ma, Zengsheng; Li, Wen; Zhou, Yichun; Zhou, Ji; Zheng, Weitao; Sun, Chang Q

    2013-10-21

    The structural symmetry and molecular separation in water and ice remain uncertain. We present herewith a solution to unifying the density, the structure order and symmetry, the size (H-O length dH), and the separation (d(OO) = d(L) + d(H) or the O:H length d(L)) of molecules packing in water and ice in terms of statistic mean. This solution reconciles: i) the d(L) and the d(H) symmetrization of the O:H-O bond in compressed ice, ii) the d(OO) relaxation of cooling water and ice and, iii) the d(OO) expansion of a dimer and between molecules at water surface. With any one of the d(OO), the density ρ(g·cm⁻³), the d(L), and the d(H), as a known input, one can resolve the rest quantities using this solution that is probing conditions or methods independent. We clarified that: i) liquid water prefers statistically the mono-phase of tetrahedrally-coordinated structure with fluctuation, ii) the low-density phase (supersolid phase as it is strongly polarized with even lower density) exists only in regions consisting molecules with fewer than four neighbors and, iii) repulsion between electron pairs on adjacent oxygen atoms dictates the cooperative relaxation of the segmented O:H-O bond, which is responsible for the performance of water and ice.

  1. Thermodynamics of hydrogen bond patterns in supramolecular assemblies of water molecules.

    PubMed

    Henry, Marc

    2002-07-02

    The PACHA (Partial Atomic Charges and Hardnesses Analysis) formalism is applied to various supramolecular assemblies of water molecules. After a detailed study of all available crystal structures for ice polymorphs, we shown that the hydrogen bond strength is roughly constant below 1 GPa and considerably weakened above that value. New hydrogen bond patterns are proposed for ice IV, V, and VI after (EB) (electrostatic balance) minimization. For other polymorphs, there is an almost perfect coincidence between experimental and predicted hydrogen bond patterns. The evolution of hydrogen bond energy as a function of molecular geometry in water clusters with up to 280 water molecules and in large supramolecular compounds is quantitatively described. Intermolecular hydrogen bonds are found to lie between -9 and -32 kJ mol-1, the stronger interaction occurs within the spherical fully disordered water droplet buried at the heart of Müller's superfullerene keplerate. The weakest one occurs in a chiral molecular snub cube built from six calix[4]resorcinarene and eight water molecules. Intramolecular hydrogen bonds are found in the range -10-100 kJ mol-1 and can thus be considerably stronger than intermolecular bonds. Finally, through the investigation of a clathrate type I compound, it was possible to obtain a deep insight of the host-guest interactions and self-assembly rules of water cages in these materials.

  2. Effect of Periodic Water Addition on Citric Acid Production in Solid State Fermentation

    NASA Astrophysics Data System (ADS)

    Utpat, Shraddha S.; Kinnige, Pallavi T.; Dhamole, Pradip B.

    2013-09-01

    Water addition is one of the methods used to control the moisture loss in solid state fermentation (SSF). However, none of the studies report the timing of water addition and amount of water to be added in SSF. Therefore, this work was undertaken with an objective to evaluate the performance of periodic water addition on citric acid production in SSF. Experiments were conducted at different moistures (50-80 %) and temperatures (30-40 °C) to simulate the conditions in a fermenter. Citric acid production by Aspergillus niger (ATCC 9029) using sugarcane baggase was chosen as a model system. Based on the moisture profile, citric acid and sugar data, a strategy was designed for periodic addition of water. Water addition at 48, 96, 144 and 192 h enhanced the citric acid production by 62 % whereas water addition at 72, 120, and 168 h increased the citric acid production by just 17 %.

  3. 75 FR 41725 - Food Additives Permitted in Feed and Drinking Water of Animals; Ammonium Formate

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-07-19

    ... Additives Permitted in Feed and Drinking Water of Animals; Ammonium Formate AGENCY: Food and Drug... regulations for food additives permitted in feed and drinking water of animals to provide for the safe use of... DRINKING WATER OF ANIMALS 0 1. The authority citation for 21 CFR part 573 continues to read as...

  4. Conserved water molecules in family 1 glycosidases: a DXMS and molecular dynamics study.

    PubMed

    Teze, David; Hendrickx, Johann; Dion, Michel; Tellier, Charles; Woods, Virgil L; Tran, Vinh; Sanejouand, Yves-Henri

    2013-08-27

    By taking advantage of the wealth of structural data available for family 1 glycoside hydrolases, a study of the conservation of internal water molecules found in this ubiquitous family of enzymes was undertaken. Strikingly, seven water molecules are observed in more than 90% of the known structures. To gain insight into their possible function, the water dynamics inside Thermus thermophilus β-glycosidase was probed using deuterium exchange mass spectroscopy, allowing the pinpointing of peptide L117-A125, which exchanges most of its amide hydrogens quickly in spite of the fact that it is for the most part buried in the crystal structure. To help interpret this result, a molecular dynamics simulation was performed whose analysis suggests that two water channels are involved in the process. The longest one (∼16 Å) extends between the protein surface and W120, whose side chain interacts with E164 (the acid-base residue involved in the catalytic mechanism), whereas the other channel allows for the exchange with the bulk of the highly conserved water molecules belonging to the hydration shell of D121, a deeply buried residue. Our simulation also shows that another chain of highly conserved water molecules, going from the protein surface to the bottom of the active site cleft close to the nucleophile residue involved in the catalytic mechanism, is able to exchange with the bulk on the nanosecond time scale. It is tempting to speculate that at least one of these three water channels could be involved in the function of family 1 glycoside hydrolases.

  5. Computing the energy of a water molecule using multideterminants: A simple, efficient algorithm

    SciTech Connect

    Clark, Bryan K.; Morales, Miguel A; Mcminis, Jeremy; Kim, Jeongnim; Scuseria, Gustavo E

    2011-01-01

    Quantum Monte Carlo (QMC) methods such as variational Monte Carlo and fixed node diffusion Monte Carlo depend heavily on the quality of the trial wave function. Although Slater-Jastrow wave functions are the most commonly used variational ansatz in electronic structure, more sophisticated wave functions are critical to ascertaining new physics. One such wave function is the multi-Slater- Jastrow wave function which consists of a Jastrow function multiplied by the sum of Slater deter- minants. In this paper we describe a method for working with these wave functions in QMC codes that is easy to implement, efficient both in computational speed as well as memory, and easily par- allelized. The computational cost scales quadratically with particle number making this scaling no worse than the single determinant case and linear with the total number of excitations. Addition- ally, we implement this method and use it to compute the ground state energy of a water molecule. 2011 American Institute of Physics. [doi:10.1063/1.3665391

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

    SciTech Connect

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

    2013-08-01

    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.

  7. Hydrogen bonding changes of internal water molecules in rhodopsin during metarhodopsin I and metarhodopsin II formation.

    PubMed Central

    Rath, P; Delange, F; Degrip, W J; Rothschild, K J

    1998-01-01

    Rhodopsin is a 7-helix, integral membrane protein found in the rod outer segments, which serves as the light receptor in vision. Light absorption by the retinylidene chromophore of rhodopsin triggers an 11-cis-->all-trans isomerization, followed by a series of protein conformational changes, which culminate in the binding and activation of the G-protein transducin by the metarhodopsin II (Meta II) intermediate. Fourier transform IR difference spectroscopy has been used to investigate the structural changes that water, as well as other OH- and NH-containing groups, undergo during the formation of the metarhodopsin I (Meta I) and Meta II intermediates. Bands associated with the OH stretch modes of water are identified by characteristic downshifts upon substitution of H2(18)O for H2O. Compared with earlier work, several negative bands associated with water molecules in unphotolysed rhodopsin were detected, which shift to lower frequencies upon formation of the Meta I and Meta II intermediates. These data indicate that at least one water molecule undergoes an increase in hydrogen bonding upon formation of the Meta I intermediate, while at least one other increases its hydrogen bonding during Meta II formation. Amino acid residue Asp-83, which undergoes a change in its hydrogen bonding during Meta II formation, does not appear to interact with any of the structurally active water molecules. Several NH and/or OH groups, which are inaccessible to hydrogen/deuterium exchange, also undergo alterations during Meta I and Meta II formation. PMID:9445403

  8. Neuroscience of water molecules: a salute to professor Linus Carl Pauling.

    PubMed

    Nakada, Tsutomu

    2009-04-01

    More than 35 years ago double Nobel laureate Linus Carl Pauling published a powerful model of the molecular mechanism of general anesthesia, generally referred to as the hydrate-microcrystal (aqueous-phase) theory. This hypothesis, based on the molecular behavior of water molecules, did not receive serious attention during Pauling's life time, when scientific tools for examining complex systems such as the brain were still in their infancy. The situation has since drastically changed, and, now, in the twenty first century, many scientific tools are available for examining different types of complex systems. The discovery of aquaporin-4, a subtype of water channel abundantly expressed in glial systems, further highlighted the concept that the dynamics of water molecules in the cerebral cortex play an important role in important physiological brain functions including consciousness and information processing.

  9. Rotational excitation of water by hydrogen molecules: comparison of results from classical and quantum mechanics.

    PubMed

    Faure, Alexandre; Wiesenfeld, Laurent; Wernli, Michael; Valiron, Pierre

    2006-06-07

    Quasiclassical trajectory calculations are carried out for rotational excitation of water by hydrogen molecules. State-to-state rate coefficients are determined at 100 K and are compared to available quantum results. A good agreement between classical and quantum rates is observed for downward transitions, with an average accuracy of classical results better than a factor of 2. It is thus found that the ambiguities described by Faure and Wiesenfeld [J. Chem. Phys. 121, 6771 (2004)] can be solved in the particular case of waterlike asymmetric-top molecules.

  10. Monte Carlo simulation of several biologically relevant molecules and zwitterions in water

    NASA Astrophysics Data System (ADS)

    Patuwo, Michael Y.; Bettens, Ryan P. A.

    2012-02-01

    In this work, we study the hydration free energies of butane, zwitterionic alanine, valine, serine, threonine, and asparagine, and two neuraminidase inhibitors by means of Monte Carlo (MC) simulation. The solute molecule, represented in the form of distributed multipoles and modified 6-12 potential, was varied from a non-interacting 'ghost' molecule to its full potential functions in TIP4P water. Intermediate systems with soft-core solute-solvent interaction potentials are simulated separately and then subjected to Bennett's Acceptance ratio (BAR) for the free energy calculation. Hydration shells surrounding the solute particles were used to assess the quality of potential functions.

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

    PubMed

    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.

  12. Effects of water molecules on tribological behavior and property measurements in nano-indentation processes - a numerical analysis.

    PubMed

    Wang, Yachao; Shi, Jing

    2013-09-17

    Nano/micro-manufacturing under wet condition is an important consideration for various tool-based processes such as indentation, scratching, and machining. The existence of liquids adds complexity to the system, changes the tool/work interfacial condition, and affects material behaviors. For indentation, it may also affect material property measurements. However, little effort has been made to study this challenging issue at nano- or atomistic scale. In this study, we tackle this challenge by investigating nano-indentation processes submerged in water using the molecular dynamics (MD) simulation approach. Compared with dry indentation in which no water molecules are present, the existence of water molecules causes the increase of indentation force in initial penetration, but the decrease of indentation force in full penetration. It also reduces the sticking phenomenon between the work and tool atoms during indenter retraction, such that the indentation geometry can be better retained. Meanwhile, nano-indentation under wet condition exhibits the indentation size effect, while dry nano-indentation exhibits the reverse indentation size effect. The existence of water leads to higher computed hardness values at low indentation loads and a smaller value of Young's modulus. In addition, the friction along the tool/work interface is significantly reduced under wet indentation.

  13. Effects of water molecules on tribological behavior and property measurements in nano-indentation processes - a numerical analysis

    PubMed Central

    2013-01-01

    Nano/micro-manufacturing under wet condition is an important consideration for various tool-based processes such as indentation, scratching, and machining. The existence of liquids adds complexity to the system, changes the tool/work interfacial condition, and affects material behaviors. For indentation, it may also affect material property measurements. However, little effort has been made to study this challenging issue at nano- or atomistic scale. In this study, we tackle this challenge by investigating nano-indentation processes submerged in water using the molecular dynamics (MD) simulation approach. Compared with dry indentation in which no water molecules are present, the existence of water molecules causes the increase of indentation force in initial penetration, but the decrease of indentation force in full penetration. It also reduces the sticking phenomenon between the work and tool atoms during indenter retraction, such that the indentation geometry can be better retained. Meanwhile, nano-indentation under wet condition exhibits the indentation size effect, while dry nano-indentation exhibits the reverse indentation size effect. The existence of water leads to higher computed hardness values at low indentation loads and a smaller value of Young's modulus. In addition, the friction along the tool/work interface is significantly reduced under wet indentation. PMID:24044504

  14. Evaluation of Additives to Eliminate Free Water from Aviation Fuel Light Obscuration Particle Counts

    DTIC Science & Technology

    2015-11-01

    5000 DISTRIBUTION A. Approved for public release: distribution unlimited. Evaluation of Additives to Eliminate Free Water from Aviation Fuel Light...April 2015 4. TITLE AND SUBTITLE Evaluation of Additives to Eliminate Free Water from Aviation Fuel Light Obscuration Particle Counts 5a. CONTRACT...13. SUPPLEMENTARY NOTES 14. ABSTRACT This technical report details the evaluation fuel additives used to eliminate the effects of free water

  15. Structure and dynamics of high- and low-density water molecules in the liquid and supercooled regimes.

    PubMed

    Montes de Oca, Joan Manuel; Rodriguez Fris, J Ariel; Accordino, Sebastián R; Malaspina, David C; Appignanesi, Gustavo A

    2016-12-01

    By combining the local structure index with potential energy minimisations we study the local environment of the water molecules for a couple of water models, TIP5P-Ew and SPC/E, in order to characterise low- and high-density "species". Both models show a similar behaviour within the supercooled regime, with two clearly distinguishable populations of unstructured and structured molecules, the fraction of the latter increasing with supercooling. Additionally, for TIP5P-Ew, we find that the structured component vanishes quickly at the normal liquid regime (above the melting temperature). Thus, while SPC/E provides a fraction of structured molecules similar to that found in X-ray experiments, we show that TIP5P-Ew underestimates such value. Moreover, unlike SPC/E, we demonstrate that TIP5P-Ew does not follow the linear dependence of the logarithm of the structured fraction with inverse temperature, as predicted by the two-order parameter model. Finally, we link structure to dynamics by showing that there exists a strong correlation between structural fluctuation and dynamics in the supercooled state with spatial correlations in both static and dynamic quantities.

  16. INTERSTELLAR ICES AS WITNESSES OF STAR FORMATION: SELECTIVE DEUTERATION OF WATER AND ORGANIC MOLECULES UNVEILED

    SciTech Connect

    Cazaux, S.; Spaans, M.; Caselli, P.

    2011-11-10

    Observations of star-forming environments revealed that the abundances of some deuterated interstellar molecules are markedly larger than the cosmic D/H ratio of 10{sup -5}. Possible reasons for this pointed to grain surface chemistry. However, organic molecules and water, which are both ice constituents, do not enjoy the same deuteration. For example, deuterated formaldehyde is very abundant in comets and star-forming regions, while deuterated water rarely is. In this paper, we explain this selective deuteration by following the formation of ices (using the rate equation method) in translucent clouds, as well as their evolution as the cloud collapses to form a star. Ices start with the deposition of gas-phase CO and O onto dust grains. While reaction of oxygen with atoms (H or D) or molecules (H{sub 2}) yields H{sub 2}O (HDO), CO only reacts with atoms (H and D) to form H{sub 2}CO (HDCO, D{sub 2}CO). As a result, 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. These results reproduce well the deuterium fractionation of formaldehyde observed in comets and star-forming regions and can explain the wide spread of deuterium fractionation of water observed in these environments.

  17. Hydrophobic molecules slow down the hydrogen-bond dynamics of water.

    PubMed

    Bakulin, Artem A; Pshenichnikov, Maxim S; Bakker, Huib J; Petersen, Christian

    2011-03-17

    We study the spectral and orientational dynamics of HDO molecules in solutions of tertiary-butyl-alcohol (TBA), trimethyl-amine-oxide (TMAO), and tetramethylurea (TMU) in isotopically diluted water (HDO:D(2)O and HDO:H(2)O). The spectral dynamics are studied with femtosecond two-dimensional infrared spectroscopy and the orientational dynamics with femtosecond polarization-resolved vibrational pump-probe spectroscopy. We observe a strong slowing down of the spectral diffusion around the central part of the absorption line that increases with increasing solute concentration. At low concentrations, the fraction of water showing slow spectral dynamics is observed to scale with the number of methyl groups, indicating that this effect is due to slow hydrogen-bond dynamics in the hydration shell of the methyl groups of the solute molecules. The slowing down of the vibrational frequency dynamics is strongly correlated with the slowing down of the orientational mobility of the water molecules. This correlation indicates that these effects have a common origin in the effect of hydrophobic molecular groups on the hydrogen-bond dynamics of water.

  18. H^- and D^- channels of Dissociative Electron Attachment to water molecules

    NASA Astrophysics Data System (ADS)

    Adaniya, Hidehito; Rudek, Benedikt; Osipov, Timur; Lee, Sun; Weber, Thorsten; Hertlein, Marcus; Schoeffler, Markus; Prior, Mike; Belkacem, Ali

    2009-05-01

    A COLTRIM technique is modified to measure the kinetic energy and angular distribution of H^- and D^- ions arising from dissociative electron attachment to water and heavy water molecules. A low energy pulsed electron, an effusive water target, a pulsed extraction plate are used in combination with the COLTRIMS spectrometer. The spectrometer carries an electrostatic lens system to compensate the effusiveness of the target. This technique is applied to study the H^- and D^- channels in the three Feshbach resonances of water and heavy water anion. The measured kinetic energy release will give the energy partitioning among the fragments, and the means to identify the two-body and three-body breakup channels. The angular distribution of the H^-(D^-) ions with respect to the electron beam is found to reflect well the breakup dynamics of the H2O^- at the dissociation. The experimental results are compared with the theoretical predictions.

  19. Temperature dependence of local solubility of hydrophobic molecules in the liquid-vapor interface of water.

    PubMed

    Abe, Kiharu; Sumi, Tomonari; Koga, Kenichiro

    2014-11-14

    One important aspect of the hydrophobic effect is that solubility of small, nonpolar molecules in liquid water decreases with increasing temperature. We investigate here how the characteristic temperature dependence in liquid water persists or changes in the vicinity of the liquid-vapor interface. From the molecular dynamics simulation and the test-particle insertion method, the local solubility Σ of methane in the liquid-vapor interface of water as well as Σ of nonpolar solutes in the interface of simple liquids are calculated as a function of the distance z from the interface. We then examine the temperature dependence of Σ under two conditions: variation of Σ at fixed position z and that at fixed local solvent density around the solute molecule. It is found that the temperature dependence of Σ at fixed z depends on the position z and the system, whereas Σ at fixed local density decreases with increasing temperature for all the model solutions at any fixed density between vapor and liquid phases. The monotonic decrease of Σ under the fixed-density condition in the liquid-vapor interface is in accord with what we know for the solubility of nonpolar molecules in bulk liquid water under the fixed-volume condition but it is much robust since the solvent density to be fixed can be anything between the coexisting vapor and liquid phases. A unique feature found in the water interface is that there is a minimum in the local solubility profile Σ(z) on the liquid side of the interface. We find that with decreasing temperature the minimum of Σ grows and at the same time the first peak in the oscillatory density profile of water develops. It is likely that the minimum of Σ is due to the layering structure of the free interface of water.

  20. Local thermodynamics of the water molecules around single- and double-stranded DNA studied by grid inhomogeneous solvation theory

    NASA Astrophysics Data System (ADS)

    Nakano, Miki; Tateishi-Karimata, Hisae; Tanaka, Shigenori; Tama, Florence; Miyashita, Osamu; Nakano, Shu-ichi; Sugimoto, Naoki

    2016-09-01

    Thermodynamic properties of water molecules around single- and double-stranded DNAs (ssDNAs and dsDNAs) with different sequences were investigated using grid inhomogeneous solvation theory. Free energies of water molecules solvating the minor groove of dsDNAs are lower than those near ssDNAs, while water molecules should be released during the formation of dsDNA. Free energies of water molecules around dsDNA are lower than those around ssDNA even in the second and third hydration shells. Our findings will help to clarify the role of water molecules in the formation of dsDNA from ssDNAs, thus facilitating the designs of drugs or nanomaterials using DNA.

  1. Double ionization of single oriented water molecules by electron impact: Second-order Born description

    SciTech Connect

    Dal Cappello, C.; Champion, C.; Kada, I.; Mansouri, A.

    2011-06-15

    The double ionization of isolated water molecules fixed in space is investigated within a theoretical approach based on the second-order Born approximation. Electron angular distributions have been studied for specific kinematical conditions. The three usual mechanisms, the shake-off and the two two-step mechanisms, have been identified. A significant contribution of the two-step mechanism is clearly visible for some particular kinematics.

  2. Effects of water molecules of Ar-Cs MHD disk generator operated with strong MHD interaction

    SciTech Connect

    Ishikawa, M.; Kosugi, A.; Inui, Y.; Kabashima, S.

    1998-07-01

    Effects of water molecule impurity are studied on performance of a disk type MHD generator operated with Ar-Cs weakly ionized plasma. To reveal phenomena for a wide range of operation conditions, time-dependent one-dimensional analyses are carried out, where an up-wind, second order Chakravarthy TVD scheme is applied for the gasdynamics, while a Galerkin FEM is used for the electrodynamics. A simplified model is used for the water molecule impurity, where total effects of nonelastic collision between electrons and water molecules are estimated by the collision loss factor of electrons and also the electron momentum-transfer collision frequency is taken into account. The collision loss factor of electrons and the electron momentum-transfer collision frequency are taken from references, and the loss factor is assumed to be 700 independently of the electron temperature. On the Fuji-1 facilities at Tokyo Institute Technology, Japan, series of experiment A4105 were carried out with the Disk F-4 generator. Ar was heated with the heat-exchanger heated by the natural gas-air combustion and the metal cesium was used as the seeding material, while SCM maintained the magnetic field of 4.7 T at the center of disk and the very strong MHD interaction was realized. The thermal input was about 3 MW, the electrical output was about 500 kW with the enthalpy extraction ratio of about 17%. The numerical analyses have shown that the water molecule enhances the ionization instability at the low voltage loading because of insufficient Joule heating for electrons. The generator performance is degraded and the strong MHD interaction between the unstable plasma and the flow field induces slow and fast moving shock waves, leading to the very complicated flow field. The fast and slow moving shocks collide with each other, merge into a sharp shock moving downward, and then the shock front moves back slightly to maintain the pressure balance, collides again with another weak moving shock, and

  3. Influence of Organic Chemicals on Water Molecule Bridges in Soil Organic Matter of a Sapric Histosol.

    PubMed

    Ondruch, Pavel; Kučerík, Jiri; Steinmetz, Zacharias; Schaumann, Gabriele E

    2017-03-02

    Water molecules in soil organic matter (SOM) can form clusters bridging neighboring molecular segments (water molecule bridges; WaMB). WaMB are hypothesized to enhance physical entrapment of organic chemicals and to control the rigidity of the SOM supramolecular structure. However, the understanding of WaMB dynamics in SOM is still limited. We investigated the relation between WaMB stability and the physicochemical properties of their environment by treating a sapric histosol with various solvents and organic chemicals. Based on predictions from molecular modeling, we hypothesized that the stability of WaMB, measured by differential scanning calorimetry, increases with decreasing ability of a chemical to interact with water molecules of the WaMB. The interaction ability between WaMB and the chemicals was characterized by linear solvation energy relationships. WaMB stability in solvent-treated samples was found to decrease with increasing ability of a solvent to undergo H-donor/acceptor interactions. Spiking with an organic chemical stabilized (naphthalene) or destabilized (phenol) the WaMB. WaMB stability and matrix rigidity were generally reduced strongly and fast when hydrophilic chemicals entered the soil. The physicochemical aging following this destabilization is slow, but leads to a successive WaMB stabilization and matrix stiffening.

  4. WaterLOGSY NMR experiments in conjunction with molecular-dynamics simulations identify immobilized water molecules that bridge peptide mimic MDWNMHAA to anticarbohydrate antibody SYA/J6.

    PubMed

    Szczepina, Monica G; Bleile, Dustin W; Müllegger, Johannes; Lewis, Andrew R; Pinto, B Mario

    2011-10-04

    X-ray crystallographic data of the carbohydrate mimic MDWNMHAA when bound to an anti-Shigella flexneri Y mAb SYA/J6 indicate the immobilization of water molecules, that is, the presence of "bound" waters, in the active site. Water Ligand Observed via Gradient Spectroscopy (WaterLOGSY) was used in conjunction with saturation transfer difference (STD)-NMR spectroscopy to probe the existence of immobilized water molecules in the complex of MDWNMHAA 1 bound to mAb SYA/J6. Molecular dynamics simulations using the ZymeCAD Molecular Dynamics platform were then used to specify the likely locations of these water molecules. Of note, those waters involved in providing complementarity between the peptide and mAb SYA/J6 remained throughout the course of the simulation. Together, the experimental and computational protocols have been used to identify the bound water molecules present in the antibody-peptide complex.

  5. Formation of CO and CO2 Molecules by Ion Irradiation of Water Ice-covered Hydrogenated Carbon Grains

    NASA Astrophysics Data System (ADS)

    Mennella, V.; Palumbo, M. E.; Baratta, G. A.

    2004-11-01

    We present the results of experiments aimed at studying the influence of the type of grain on the chemical composition of the ice mantles during energetic processing under simulated dense medium conditions. Formation of CO and CO2 molecules occurs when hydrogenated carbon grains with a water ice cap are irradiated with 30 keV He+ ions at low temperature. The fraction of carbon in the grains converted to CO and CO2 by ions is at least 0.03 and 0.02, respectively. An estimation of the formation cross section of these molecules by 30 keV He+ ions has been derived from the intensity increase of their infrared stretching bands as a function of the ion fluence. On the basis of the laboratory results, it has been possible to evaluate the contribution of CO and CO2 produced on carbon grain by cosmic rays to the observed column densities of these molecules for dense clouds whose visual extinction is known. The mechanism we have studied does not dominate other CO2 formation processes; however, its contribution is in addition to other processes occurring on ice mantles. The spectral profile and the contribution to the observed column densities make solid CO formed by cosmic-ray irradiation of ice-layered carbon grains a good candidate for the red component of the interstellar CO stretching feature, which is generally attributed to CO mixed in with water ice. As a consequence of the formation of CO and CO2 molecules on carbon grains, a slow chemical erosion of the particles takes place.

  6. Infrared spectroscopy of water clusters co-adsorbed with hydrogen molecules on a sodium chloride film

    NASA Astrophysics Data System (ADS)

    Yamakawa, Koichiro; Fukutani, Katsuyuki

    2016-06-01

    Hydrogen gas containing a trace of water vapor was dosed on a vacuum-evaporated sodium chloride film at 13 K, and water clusters formed on the substrate were investigated by infrared absorption spectroscopy. Absorption bands due to (H2O)n clusters with n = 3-6 and an induced absorption band due to hydrogen were clearly observed. With increasing gas dosage, the intensities of the cluster bands increased linearly while the intensity of the hydrogen band was constant. This suggests that the water clusters were formed in two-dimensional matrices of hydrogen. We found that the water clusters did exist on the surface upon heating even after the hydrogen molecules had desorbed. A further rise of the substrate temperature up to 27 K yielded the formation of larger clusters, (H2O)n with n > 6 . We also discuss the origins of the two bands of the trimer in terms of pseudorotation and a metastable isomer.

  7. Terahertz-dependent evaluation of water content in high-water-cut crude oil using additive-manufactured samplers

    NASA Astrophysics Data System (ADS)

    Guan, LiMei; Zhan, HongLei; Miao, XinYang; Zhu, Jing; Zhao, Kun

    2017-04-01

    The evaluation of water content in crude oil is of significance to petroleum exploration and transportation. Terahertz (THz) waves are sensitive to fluctuations in the dipole moment of water. However, due to the strong absorption of water in the THz range, it is difficult for the THz spectrum to determine high water content with the common sampler. In this research, micron-grade samplers for THz detection were designed and manufactured using additive manufacturing (AM) technology. Oil-water mixtures with water content from 1.8% to 90.6% were measured with the THz-TDS system using sample cells. In addition, a detailed analysis was performed of the relationships among THz parameters such as signal peak, time delay, and refractive index as well as absorption coefficient and high water content (>60%). Results suggest that the combination of THz spectroscopy and AM technique is effective for water content evaluation in crude oil and can be further applied in the petroleum industry.

  8. The interaction of Al atoms with water molecules: A theoretical study.

    PubMed

    Alvarez-Barcia, S; Flores, J R

    2009-11-07

    The interaction of individual Al atoms with water molecules has been studied from the point of view of the energy by means of ab initio and DFT calculations in order to find the pathways for the generation of HAlOH(H(2)O)(n) or AlOH(H(2)O)(n)+H. The potential energy surface of the Al(H(2)O)(n+1) (n=0-3) systems has been explored for local minima and the relevant saddle points. The interaction of Al and several water molecules tends to produce low-lying local minima in which (for n=2-3) Al is "inserted" into relatively compact structures of water molecules, so typically a ring is formed containing an AlOH(2) moiety. Isomerization of such moiety into HAlOH(H(2)O)(n) may take place through saddle points of the "relay" type; however those saddle points lie very close to AlOH(2)(H(2)O)(n-1)+H(2)O, which means that such isomerization process has to compete with a water-elimination process. Larger systems Al(H(2)O)(n+1) (n=4-7) have also been computed by means of a DFT method, as a first step to predict the behavior of isolated Al atoms in even larger clusters or in the bulk. Finally, an effective fragment potential method has been employed to simulate those large clusters together with a polarizable continuum model to take into account the effect of the bulk. Our results suggest that the reaction should take place in inert matrices and in the bulk. We also conclude that HAlOH(H(2)O)(n) and AlOH(H(2)O)(n) could be the intermediates involved in the generation of hydrogen by the interaction of Al atoms with water, so their production would be the critical step of such process.

  9. Reactions of water and C1 molecules on carbide and metal-modified carbide surfaces.

    PubMed

    Wan, Weiming; Tackett, Brian M; Chen, Jingguang G

    2017-02-23

    The formation of carbides can significantly modify the physical and chemical properties of the parent metals. In the current review, we summarize the general trends in the reactions of water and C1 molecules over transition metal carbide (TMC) and metal-modified TMC surfaces and thin films. Although the primary focus of the current review is on the theoretical and experimental studies of reactions of C1 molecules (CO, CO2, CH3OH, etc.), the reactions of water will also be reviewed because water plays an important role in many of the C1 transformation reactions. This review is organized by discussing separately thermal reactions and electrochemical reactions, which provides insights into the application of TMCs in heterogeneous catalysis and electrocatalysis, respectively. In thermal reactions, we discuss the thermal decomposition of water and methanol, as well as the reactions of CO and CO2 over TMC surfaces. In electrochemical reactions, we summarize recent studies in the hydrogen evolution reaction, electrooxidation of methanol and CO, and electroreduction of CO2. Finally, future research opportunities and challenges associated with using TMCs as catalysts and electrocatalysts are also discussed.

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

    SciTech Connect

    Isailovic, Slavica

    2005-01-01

    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.

  11. Effects of water addition on soil arthropods and soil characteristics in a precipitation-limited environment

    NASA Astrophysics Data System (ADS)

    Chikoski, Jennifer M.; Ferguson, Steven H.; Meyer, Lense

    2006-09-01

    We investigated the effect of water addition and season on soil arthropod abundance and soil characteristics (%C, %N, C:N, moisture, pH). The experimental design consisted of 24 groups of five boxes distributed within a small aspen stand in Saskatchewan, Canada. The boxes depressed the soil to create a habitat with suitable microclimate for soil arthropods, and by overturning boxes we counted soil arthropods during weekly surveys from April to September 1999. Soil samples were collected at two-month intervals and water was added once per week to half of the plots. Of the eleven recognizable taxonomic units identified, only mites (Acari) and springtails (Collembola) responded to water addition by increasing abundance, whereas ants decreased in abundance with water addition. During summer, springtail numbers increased with water addition, whereas pH was a stronger determinant of mite abundance. In autumn, springtails were positively correlated with water and negatively correlated with mites, whereas mite abundance was negatively correlated with increasing C:N ratio, positively correlated to water addition, and negatively correlated with springtail abundance. Although both mite and springtail numbers decreased in autumn with a decrease in soil moisture, mites became more abundant than springtails suggesting a predator-prey (mite-springtail) relationship. Water had a significant effect on both springtails and mites in summer and autumn supporting the assertion that prairie soil communities are water limited.

  12. Dangling OH Vibrations of Water Molecules in Aqueous Solutions of Aprotic Polar Compounds Observed in the Near-Infrared Regime.

    PubMed

    Sagawa, Naoya; Shikata, Toshiyuki

    2015-06-25

    Near-infrared (NIR) absorption spectrum measurements over a frequency range from 4000 to 12000 cm(-1) were employed to investigate the effects of the presence of solute compounds to vibrational modes of water molecules in aqueous solutions of some aprotic hydroneutral polar compounds with large dipole moments, such as nitro compounds and nitriles. The obtained NIR spectra for the aqueous solutions were decomposed into three components: free water, solute, and water molecules affected by the presence of solutes. Newly determined NIR spectra of affected water molecules were well-described with at least four absorption modes observed at 7040, 6850, 6450, and 5640 cm(-1) for both the nitro compounds and nitriles. The highest frequency mode at 7040 cm(-1) possessing the strongest intensity was assigned to the first stretching overtone of affected water hydroxy (O-H) groups, which are nonhydrogen bonded to other water molecules and dangling. The second highest frequency mode at 6850 cm(-1) was assigned to the first stretching overtone of affected water O-H groups hydrated to other (free) water molecules. The third mode at 6400 cm(-1) was attributed to a combination mode of the fundamental stretching of O-H and the first overtone of the O-H bending mode of the affected water molecules. The lowest frequency mode at 5640 cm(-1) was assigned to the combination mode of the fundamental O-H stretching mode, the fundamental O-H bending mode, and the hindered rotational (libration) mode of the affected water molecules. Because absorption intensities of the third and lowest frequency modes for water molecules affected by the solutes depended on the sizes of alkyl groups of polar solutes, these two modes possibly result from the contribution of hydrophobic hydration effects.

  13. Identification and characterization of the motion of water molecules in normal and deuterated pyromellitic acid dihydrate

    NASA Astrophysics Data System (ADS)

    Schajor, W.; Haeberlen, U.; Tegenfeldt, T.

    Proton wide-line, multiple-pulse, T1 and T1 ϱ measurements on single crystals of PMADH, and deuteron EFG measurements and bandshape analyses of spectra recorded from deuterated crystals of PMADH are reported. The wide-line and multiple-pulse proton results indicate that the water molecules in PMADH are flipping about their twofold symmetry axes. Both T1 and T1 ϱ were measured as a function of crystal orientation and temperature. Comparison of the experimental data with model calculations for T1 ϱ based on the established flipping motions of the water molecules shows that {1}/{T 1ϱ} is dominated by this process whereas {1}/{T 1} is not. The T1 ϱ data thus enable determination of the rate of the H 2O flips as a function of temperature. EFGs of the water deuterons in deuterated PMADH, measured at low and high temperatures, confirm the occurrence of the flips for D 2O in PMADH. The flips constitute an exchange process for the water deuterons. Bandshape analyses of single-crystal deuteron spectra recorded at temperatures covering the full range of exchange rates allowed determination of the flip rates of the D 2O molecules. The activation energies for the H 2O and D 2O flips are the same, Ea = 10 kcal/mol, within the limits of accuracy of the experiments. The frequency factors in the Arrhenius relation are 8.3 X 10 13 sec -1 (H 2O) and 2.6 X 10 13 sec -1 (D 2O).

  14. Effects of multivalent hexacyanoferrates and their ion pairs on water molecule dynamics measured with terahertz spectroscopy.

    PubMed

    DiTucci, Matthew J; Böhm, Fabian; Schwaab, Gerhard; Williams, Evan R; Havenith, Martina

    2017-02-27

    The valency of aqueous solutes plays a large role in determining the extent of ion-water dynamics, which can greatly influence the chemical and physical properties of solutions. In these experiments, broadband Fourier transform terahertz spectroscopy is used to probe perturbations to the low-frequency dynamics of water molecules by three different multivalent hexacyanoferrate salts. K3Fe(CN)6, K4Fe(CN)6 and Na4Fe(CN)6 were investigated as a function of concentration up to their solubility limits using spectral subtractions and fitting with damped harmonic lineshapes. Regions with subtle nonlinearities in amplitude with respect to solute concentration provide insight into ion-pairing events. The extent of nonlinearity suggests that ion pairs are major constituents in solution for all concentrations measured and is consistent with ion-pairing observed at millimolar concentrations by potentiometric and spectroscopic measurements. A lower estimate for the number of water molecules that are influenced by each ion is obtained from the damped harmonic fits. Values of 19, 28 and 25 water molecules with perturbed dynamics are obtained for KFe(CN)6(2-), KFe(CN)6(3-) and NaFe(CN)6(3-) ion pairs, respectively. These values represent dynamical perturbations into a second solvation shell and are consistent with the long-range structural effects observed in recent aqueous nanodrop spectroscopy experiments. Furthermore, the spectral absorptions for hexacyanoferrates are in agreement with a wide range of solutes studied previously using the developing methodology for interpreting terahertz spectra.

  15. Additional Reserve Recovery Using New Polymer Treatment on High Water Oil Ratio Wells in Alameda Field, Kingman County, Kansas

    SciTech Connect

    James Spillane

    2005-10-01

    The Chemical Flooding process, like a polymer treatment, as a tertiary (enhanced) oil recovery process can be a very good solution based on the condition of this field and its low cost compared to the drilling of new wells. It is an improved water flooding method in which high molecular-weight (macro-size molecules) and water-soluble polymers are added to the injection water to improve the mobility ratio by enhancing the viscosity of the water and by reducing permeability in invaded zones during the process. In other words, it can improve the sweep efficiency by reducing the water mobility. This polymer treatment can be performed on the same active oil producer well rather than on an injector well in the existence of strong water drive in the formation. Some parameters must be considered before any polymer job is performed such as: formation temperature, permeability, oil gravity and viscosity, location and formation thickness of the well, amount of remaining recoverable oil, fluid levels, well productivity, water oil ratio (WOR) and existence of water drive. This improved oil recovery technique has been used widely and has significant potential to extend reservoir life by increasing the oil production and decreasing the water cut. This new technology has the greatest potential in reservoirs that are moderately heterogeneous, contain moderately viscous oils, and have adverse water-oil mobility ratios. For example, many wells in Kansas's Arbuckle formation had similar treatments and we have seen very effective results. In addition, there were previous polymer treatments conducted by Texaco in Alameda Field on a number of wells throughout the Viola-Simpson formation in the early 70's. Most of the treatments proved to be very successful.

  16. Interactions of water, methanol and diethyl ether molecules with the surface of oxidized activated carbon

    NASA Astrophysics Data System (ADS)

    Salame, Issa I.; Bandosz, Teresa J.

    Two samples of oxidized activated carbon of wood origin were used as adsorbents of water, methanol, and diethyl ether. Structural and chemical characteristics of the samples' surfaces were obtained using adsorption of nitrogen and Boehm titration. The adsorption isotherms of water and methanol were measured using a volumetric apparatus whereas the adsorption of diethyl ether was studied by means of inverse gas chromatography at finite concentration. Then the isotherms at three different temperatures were used to calculate the isosteric heats of adsorption. The results showed that the strength of interaction depends on the porosity of the sample and its surface chemistry. The effect of surface chemistry and the presence of oxygenated groups are predominant in the case of water and the least important in the case of diethyl ether. This is the result of the chemical nature of the molecules, their sizes, and the relative strengths of the dispersive interactions in small pores in comparison with hydrogen bonding to surface functional groups.

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

    USGS Publications Warehouse

    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.

  18. Quasiphase Transition in a Single File of Water Molecules Encapsulated in (6,5) Carbon Nanotubes Observed by Temperature-Dependent Photoluminescence Spectroscopy

    NASA Astrophysics Data System (ADS)

    Ma, Xuedan; Cambré, Sofie; Wenseleers, Wim; Doorn, Stephen K.; Htoon, Han

    2017-01-01

    Molecules confined inside single-walled carbon nanotubes (SWCNTs) behave quite differently from their bulk analogues. In this Letter we present temperature-dependent (4.2 K up to room temperature) photoluminescence (PL) spectra of water-filled and empty single-chirality (6,5) SWCNTs. Superimposed on a linear temperature-dependent PL spectral shift of the empty SWCNTs, an additional stepwise PL spectral shift of the water-filled SWCNTs is observed at ˜150 K . With the empty SWCNTs serving as an ideal reference system, we assign this shift to temperature-induced changes occurring in the single-file chain of water molecules encapsulated in the tubes. Our molecular dynamics simulations further support the occurrence of a quasiphase transition of the orientational order of the water dipoles in the single-file chain.

  19. Quasiphase Transition in a Single File of Water Molecules Encapsulated in (6,5) Carbon Nanotubes Observed by Temperature-Dependent Photoluminescence Spectroscopy.

    PubMed

    Ma, Xuedan; Cambré, Sofie; Wenseleers, Wim; Doorn, Stephen K; Htoon, Han

    2017-01-13

    Molecules confined inside single-walled carbon nanotubes (SWCNTs) behave quite differently from their bulk analogues. In this Letter we present temperature-dependent (4.2 K up to room temperature) photoluminescence (PL) spectra of water-filled and empty single-chirality (6,5) SWCNTs. Superimposed on a linear temperature-dependent PL spectral shift of the empty SWCNTs, an additional stepwise PL spectral shift of the water-filled SWCNTs is observed at ∼150  K. With the empty SWCNTs serving as an ideal reference system, we assign this shift to temperature-induced changes occurring in the single-file chain of water molecules encapsulated in the tubes. Our molecular dynamics simulations further support the occurrence of a quasiphase transition of the orientational order of the water dipoles in the single-file chain.

  20. Interfacial water molecules in SH3 interactions: a revised paradigm for polyproline recognition.

    PubMed

    Martin-Garcia, Jose M; Ruiz-Sanz, Javier; Luque, Irene

    2012-03-01

    In spite of its biomedical relevance, polyproline recognition is still not fully understood. The disagreement between the current description of SH3 (Src homology 3) complexes and their thermodynamic behaviour calls for a revision of the SH3-binding paradigm. Recently, Abl-SH3 was demonstrated to recognize its ligands by a dual binding mechanism involving a robust network of water-mediated hydrogen bonds that complements the canonical hydrophobic interactions. The systematic analysis of the SH3 structural database in the present study reveals that this dual binding mode is universal to SH3 domains. Tightly bound buried-interfacial water molecules were found in all SH3 complexes studied mediating the interaction between the peptide ligand and the domain. Moreover, structural waters were also identified in a high percentage of the free SH3 domains. A detailed analysis of the pattern of water-mediated interactions enabled the identification of conserved hydration sites in the polyproline-recognition region and the establishment of relationships between hydration profiles and the sequence of both ligands and SH3 domains. Water-mediated interactions were also systematically observed in WW (protein-protein interaction domain containing two conserved tryptophan residues), UEV (ubiquitin-conjugating enzyme E2 variant) and EVH-1 [Ena/VASP (vasodilator-stimulated phosphoprotein) homology 1] structures. The results of the present study clearly indicate that the current description of proline-rich sequence recognition by protein-protein interaction modules is incomplete and insufficient for a correct understanding of these systems. A new binding paradigm is required that includes interfacial water molecules as relevant elements in polyproline recognition.

  1. Effects of Disaccharide Sugars on Dynamics of Water Molecules: Dynamic Light Scattering and Dielectric Loss Spectroscopy Studies

    NASA Astrophysics Data System (ADS)

    Seo, Jeong-Ah; Kwon, Hyun-Joung; Kim, Hyung Kook; Hwang, Yoon-Hwae

    2008-02-01

    We studied the effects of disaccharide sugars (trehalose, sucrose, and maltose) on the dynamics of water molecules in sugar-water mixtures. We measured the acoustic phonons in sugar-water mixtures with different sugar contents by using a Sandercock Tandem 6-pass Febry-Petor interferometer and found that the Brillouin peak positions shifted to higher frequencies as the sugar concentration increased. We also measured the dielectric loss of hydrogen bonds in water molecules in sugar-water mixtures by using a Network analyzer with different sugar contents. The loss peak position in the dielectric loss spectra moved to lower frequencies as the sugar contents increased. The trehalose-water mixture showed the largest Brillouin peak shift and relaxation time change with increasing sugar content among three disaccharides indicating that the effect of trehalose on the dynamics of water molecules is the strongest. This unique property of trehalose sugar might be the origin of the superior bio-protection ability of trehalose.

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

    NASA Astrophysics Data System (ADS)

    Shepelenko, S. O.; Salnikov, A. S.; Rak, S. V.; Goncharova, E. P.; Ryzhikov, A. B.

    2009-06-01

    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

  3. 35 Years of Marine Natural Product Research in Sweden: Cool Molecules and Models from Cold Waters.

    PubMed

    Bohlin, Lars; Cárdenas, Paco; Backlund, Anders; Göransson, Ulf

    2017-01-01

    Currents efforts in marine biodiscovery have essentially focused on temperate to tropical shallow water organisms. With more than 6000 species of marine plants and animals, the Kosterfjord area has the richest marine biodiversity in Swedish waters, but it remains understudied. The overall objective of our marine pharmacognosy research is to explore and reveal the pharmacological potential of organisms from this poorly explored region. More generally, we wish to understand aspects of structure-activity relationships of chemical interactions in cold-water marine environment (shallow and deep). Our strategy is based on ecologically guided search for compounds through studies of physiology and organism interactions coupled to identification of bioactive molecules guided by especially in vivo assays. The research programme originated in the beginning of the 1980s with a broad screening of Swedish marine organisms using both in vitro and in vivo assays, resulting in isolation and identification of several different bioactive molecules. Two congenerous cyclopeptides, i.e. barettin and 8,9-dihydrobarettin, were isolated from the deep-sea sponge Geodia barretti, and structurally elucidated, guided by their antifouling activity and their affinity to a selection of human serotonin receptors. To optimize the activity a number of analogues of barettin were synthezised and tested for antifouling activity. Within the EU project BlueGenics, two larger homologous peptides, barrettides A and B, were isolated from G. baretti. Also, metabolic fingerprinting combined with sponge systematics was used to further study deep-sea natural product diversity in the genus Geodia. Finally, the chemical property space model 'ChemGPS-NP' has been developed and used in our research group, enabling a more efficient use of obtained compounds and exploration of possible biological activities and targets. Another approach is the broad application of phylogenetic frameworks, which can be used in

  4. The adsorption and dissociation of water molecule on goethite (010) surface: A DFT approach

    NASA Astrophysics Data System (ADS)

    Zhou, Long; Xiu, Fangyuan; Qiu, Meng; Xia, Shuwei; Yu, Liangmin

    2017-01-01

    Using density functional theory (DFT) calculation, we investigate the configuration, stability and electronic properties of fresh cleaved (010) goethite surface (Pnma) and this surface exposed to water monolayer at low, medium and high coverage. Water is predicted to be chemisorbed to the surface, together with the surface reconstruction. The interaction energy of the most stable configuration of both low and medium coverage per water molecule is almost the same (-1.17 eV), while that of high coverage is much lower (less than 1.03 eV). It indicates that highly hydrated surface is less stable. PDOS analysis reveals the adsorption of H2O is due to the formation of Fesbnd O bond, caused by overlapping of Fe's 3d and O's 2p orbitals. Dissociation processes at low and medium water coverage are non-spontaneous; while at high coverage, it can undertake spontaneously both thermodynamically and dynamically. The dissociation paths of all three water coverage are the similar. The proton from one adsorbed water is likely to dissociate to bind to the vicinal surface μ3sbnd O as an intermediate product; the proton belonged to μ3sbnd O transferred to the neighbor surface μ2sbnd O as the dissociative configuration.

  5. Detection of water molecules in inert gas based plasma by the ratios of atomic spectral lines

    NASA Astrophysics Data System (ADS)

    Bernatskiy, A. V.; Ochkin, V. N.

    2017-01-01

    A new approach is considered to detect the water leaks in inert plasma-forming gas present in the reactor chamber. It is made up of the intensity ratio of D α and H α spectral lines in combination with O, Ar and Xe lines intensity. The concentrations of H2O, O, H and D particles have been measured with high sensitivity. At the D2 admixture pressure {{p}{{\\text{D}\\text{2}}}}   =  0.025 mbar, we used the acquisition time of 10 s to measure the rate of water molecules injected from the outside, Γ0  =  1.4 · 10-9 mbar · m3 · s-1, and the incoming water molecules to plasma, Γ  =  5 ·10-11 mbar · m3 · s-1. The scaling proves that at small D2 admixtures (10-4 mbar), the leaks with the rates Γ0  ≈  6 · 10-12 mbar · m3 · s-1 and Γ  ≈  2 · 10-13 mbar · m3 · s-1 can be detected and measured. The difference between Γ0 and Γ values is due to the high degree of H2O dissociation, which can be up to 97-98%.

  6. The Effect of Water Molecules on Mechanical Properties of Bamboo Microfibrils

    NASA Astrophysics Data System (ADS)

    Rahbar, Nima

    Bamboo fibers have higher strength-to-weight ratios than steel and concrete. The unique properties of bamboo fibers come from their natural composite structures that comprise mainly cellulose nanofibrils in a matrix of intertwined hemicellulose and lignin called lignin-carbohydrate complex (LCC). Here, we have utilized atomistic simulations to investigate the mechanical properties and mechanisms of interactions between these materials, in the presence of water molecules. Our results suggest that hemicellulose exhibits better mechanical properties and lignin shows greater tendency to adhere to cellulose nanofibrils. Consequently, the role of hemicellulose found to be enhancing the mechanical properties and lignin found to be providing the strength of bamboo fibers. The abundance of Hbonds in hemicellulose chains is responsible for improving the mechanical behavior of LCC. The strong van der Waals forces between lignin molecules and cellulose nanofibrils is responsible for higher adhesion energy between LCC/cellulose nanofibrils. We also found out that the amorphous regions of cellulose nanofibrils is the weakest interface in bamboo Microfibrils. In presence of water, the elastic modulus of lignin increases at low water content (less than 10 NSF CAREER Grant No. 1261284.

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

    NASA Astrophysics Data System (ADS)

    Takahashi, Ohgi; Kirikoshi, Ryota

    2014-01-01

    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. Comments Received on Proposed Additions to West Virginia's 2014 List of Impaired Waters

    EPA Pesticide Factsheets

    Comments submitted from the public during the public comment period for EPA's partial approval-partial disapproval and proposed additions to West Virginia's 2014 Section 303(d) List of Impaired Waters.

  9. Thermodynamic properties of water molecules in the presence of cosolute depend on DNA structure: a study using grid inhomogeneous solvation theory.

    PubMed

    Nakano, Miki; Tateishi-Karimata, Hisae; Tanaka, Shigenori; Tama, Florence; Miyashita, Osamu; Nakano, Shu-Ichi; Sugimoto, Naoki

    2015-12-02

    In conditions that mimic those of the living cell, where various biomolecules and other components are present, DNA strands can adopt many structures in addition to the canonical B-form duplex. Previous studies in the presence of cosolutes that induce molecular crowding showed that thermal stabilities of DNA structures are associated with the properties of the water molecules around the DNAs. To understand how cosolutes, such as ethylene glycol, affect the thermal stability of DNA structures, we investigated the thermodynamic properties of water molecules around a hairpin duplex and a G-quadruplex using grid inhomogeneous solvation theory (GIST) with or without cosolutes. Our analysis indicated that (i) cosolutes increased the free energy of water molecules around DNA by disrupting water-water interactions, (ii) ethylene glycol more effectively disrupted water-water interactions around Watson-Crick base pairs than those around G-quartets or non-paired bases, (iii) due to the negative electrostatic potential there was a thicker hydration shell around G-quartets than around Watson-Crick-paired bases. Our findings suggest that the thermal stability of the hydration shell around DNAs is one factor that affects the thermal stabilities of DNA structures under the crowding conditions.

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

    NASA Astrophysics Data System (ADS)

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

    2015-11-01

    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 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 continuum flow solvers, allowing for investigations into spatiotemporal scales inaccessible to atomistic simulations.

  11. The effects of metabolite molecules produced by drinking water-isolated bacteria on their single and multispecies biofilms.

    PubMed

    Simões, Lúcia Chaves; Simões, Manuel; Vieira, Maria João

    2011-08-01

    The elucidation of the mechanisms by which diverse species survive and interact in drinking water (DW) biofilm communities may allow the identification of new biofilm control strategies. The purpose of the present study was to investigate the effects of metabolite molecules produced by bacteria isolated from DW on biofilm formation. Six opportunistic bacteria, viz. Acinetobacter calcoaceticus, Burkholderia cepacia, Methylobacterium sp., Mycobacterium mucogenicum, Sphingomonas capsulata and Staphylococcus sp. isolated from a drinking water distribution systems (DWDS) were used to form single and multispecies biofilms in the presence and absence of crude cell-free supernatants produced by the partner bacteria. Biofilms were characterized in terms of mass and metabolic activity. Additionally, several physiological aspects regulating interspecies interactions (sessile growth rates, antimicrobial activity of cell-free supernatants, and production of iron chelators) were studied to identify bacterial species with biocontrol potential in DWDS. Biofilms of Methylobacterium sp. had the highest growth rate and M. mucogenicum biofilms the lowest. Only B. cepacia was able to produce extracellular iron-chelating molecules. A. calcoaceticus, B. cepacia, Methylobacterium sp. and M. mucogenicum biofilms were strongly inhibited by crude cell-free supernatants from the other bacteria. The crude cell-free supernatants of M. mucogenicum and S. capsulata demonstrated a high potential for inhibiting the growth of counterpart biofilms. Multispecies biofilm formation was strongly inhibited in the absence of A. calcoaceticus. Only crude cell-free supernatants produced by B. cepacia and A. calcoaceticus had no inhibitory effects on multispecies biofilm formation, while metabolite molecules of M. mucogenicum showed the most significant biocontrol potential.

  12. THE PERSISTENCE OF MYCOBACTERIUM AVIUM IN A DRINKING WATER SYSTEM AFTER THE ADDITION OF FILTRATION

    EPA Science Inventory

    Drinking water is increasingly recognized as a major source of pathogenic nontuberculous mycobacteria (NTM) associated with human infection. Our goal was to determine if the prevalence of NTM would decrease after the addition of filtration treatment to an unfiltered surface water...

  13. Army Corps of Engineers: Additional Steps Needed for Review and Revision of Water Control Manuals

    DTIC Science & Technology

    2016-07-01

    ARMY CORPS OF ENGINEERS Additional Steps Needed for Review and Revision of Water Control Manuals Report to...Revision of Water Control Manuals What GAO Found According to U.S. Army Corps of Engineers (Corps) officials, the agency conducts ongoing, informal...reviews of selected water control manuals and has revised some of them, but the extent of the reviews and revisions is unclear because they are not

  14. Strongly hydrogen-bonded water molecule present near the retinal chromophore of Leptosphaeria rhodopsin, the bacteriorhodopsin-like proton pump from a eukaryote.

    PubMed

    Sumii, Masayo; Furutani, Yuji; Waschuk, Stephen A; Brown, Leonid S; Kandori, Hideki

    2005-11-22

    Leptosphaeria rhodopsin (LR) is an archaeal-type rhodopsin found in fungi, and is the first light-driven proton-pumping retinal protein from eukaryotes. LR pumps protons in a manner similar to that of bacteriorhodopsin (BR), a light-driven proton pump of haloarchaea. The amino acid sequence of LR is more homologous to that of Neurospora rhodopsin (NR) than BR, whereas NR has no proton-pumping activity. These facts raise the question of how the proton-pumping function is achieved. In this paper, we studied structural changes of LR following the retinal photoisomerization by means of low-temperature Fourier transform infrared (FTIR) spectroscopy, and compared the obtained spectra with those for BR and NR. While the light-induced photoisomerization from the all-trans to 13-cis form was commonly observed among LR, BR, and NR, we found that the structural changes of LR are closer to those of BR than to those of NR in terms of detailed vibrational bands of retinal and protein. The most prominent difference was seen for the water O-D stretching vibrations (measured in D2O). LR exhibits an O-D stretch of water at 2257 cm(-1), indicating the presence of a strongly hydrogen-bonded water molecule. Such strongly hydrogen-bonded water molecules (O-D stretch at <2400 cm(-1)) were observed for BR, but not for NR. Comprehensive studies of BR mutants and archaeal rhodopsins have revealed that strongly hydrogen-bonded water molecules are found only in the proteins exhibiting proton-pumping activity, suggesting that strongly hydrogen-bonded water molecules and transient weakening of their binding are essential for the proton-pumping function of rhodopsins. This observation for LR provided additional experimental evidence of the correlation between strongly hydrogen-bonded water molecules and proton-pumping activity of archaeal rhodopsins.

  15. Standard addition method for the determination of pharmaceutical residues in drinking water by SPE-LC-MS/MS.

    PubMed

    Cimetiere, Nicolas; Soutrel, Isabelle; Lemasle, Marguerite; Laplanche, Alain; Crocq, André

    2013-01-01

    The study of the occurrence and fate of pharmaceutical compounds in drinking or waste water processes has become very popular in recent years. Liquid chromatography with tandem mass spectrometry is a powerful analytical tool often used to determine pharmaceutical residues at trace level in water. However, many steps may disrupt the analytical procedure and bias the results. A list of 27 environmentally relevant molecules, including various therapeutic classes and (cardiovascular, veterinary and human antibiotics, neuroleptics, non-steroidal anti-inflammatory drugs, hormones and other miscellaneous pharmaceutical compounds), was selected. In this work, a method was developed using ultra performance liquid chromatography coupled to tandem mass spectrometry (UPLC-MS/MS) and solid-phase extraction to determine the concentration of the 27 targeted pharmaceutical compounds at the nanogram per litre level. The matrix effect was evaluated from water sampled at different treatment stages. Conventional methods with external calibration and internal standard correction were compared with the standard addition method (SAM). An accurate determination of pharmaceutical compounds in drinking water was obtained by the SAM associated with UPLC-MS/MS. The developed method was used to evaluate the occurrence and fate of pharmaceutical compounds in some drinking water treatment plants in the west of France.

  16. Water makes the difference: rearrangement of water solvation layer triggers non-additivity of functional group contributions in protein-ligand binding.

    PubMed

    Biela, Adam; Betz, Michael; Heine, Andreas; Klebe, Gerhard

    2012-08-01

    The binding of four congeneric peptide-like thermolysin inhibitors has been studied by high-resolution crystal structure analysis and isothermal titration calorimetry. The ligands differ only by a terminal carboxylate and/or methyl group. A surprising non-additivity of functional group contributions for the carboxylate and/or methyl groups is detected. Adding the methyl first and then the carboxylate group results in a small Gibbs free energy increase and minor enthalpy/entropy partitioning for the first modification, whereas the second involves a strong affinity increase combined with large enthalpy/entropy changes. However, first adding the carboxylate and then the methyl group yields reverse effects: the acidic group attachment now causes minor effects, whereas the added methyl group provokes large changes. As all crystal structures show virtually identical binding modes, affinity changes are related to rearrangements of the first solvation layer next to the S(2)' pocket. About 20-25 water molecules are visible next to the studied complexes. The added COO(-) groups perturb the local water network in both carboxylated complexes, and the attached methyl groups provide favorable interaction sites for water molecules. Apart from one example, a contiguously connected water network between protein and ligand functional groups is observed in all complexes. In the complex with the carboxylated ligand, which still lacks the terminal methyl group, the water network is unfavorably ruptured. This results in a surprising thermodynamic signature showing only a minor affinity increase upon COO(-) group attachment. Because the further added methyl group provides a favorable interaction site for water, the network can be reestablished, and a strong affinity increase with a large enthalpy/entropy signature is then detected.

  17. Rain water transport and storage in a model sandy soil with hydrogel particle additives.

    PubMed

    Wei, Y; Durian, D J

    2014-10-01

    We study rain water infiltration and drainage in a dry model sandy soil with superabsorbent hydrogel particle additives by measuring the mass of retained water for non-ponding rainfall using a self-built 3D laboratory set-up. In the pure model sandy soil, the retained water curve measurements indicate that instead of a stable horizontal wetting front that grows downward uniformly, a narrow fingered flow forms under the top layer of water-saturated soil. This rain water channelization phenomenon not only further reduces the available rain water in the plant root zone, but also affects the efficiency of soil additives, such as superabsorbent hydrogel particles. Our studies show that the shape of the retained water curve for a soil packing with hydrogel particle additives strongly depends on the location and the concentration of the hydrogel particles in the model sandy soil. By carefully choosing the particle size and distribution methods, we may use the swollen hydrogel particles to modify the soil pore structure, to clog or extend the water channels in sandy soils, or to build water reservoirs in the plant root zone.

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

    NASA Astrophysics Data System (ADS)

    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.

  19. Toward a mechanistic understanding of the effect of biochar addition on soil water retention

    NASA Astrophysics Data System (ADS)

    Yi, S.; Chang, N.; Guo, M.; Imhoff, P. T.

    2014-12-01

    Biochar (BC) is a carbon-rich product produced by thermal degradation of biomass in an oxygen-free environment, whose application to sediment is said to improve water retention. However, BC produced from different feedstocks and pyrolyzed at different temperatures have distinct properties, which may alter water retention in ways difficult to predict a priori. Our goal is to develop a mechanistic understanding of BC addition on water retention by examining the impact of BC from two feedstocks, poultry litter (PL) and hardwood (HW), on the soil-water retention curves (SWRC) of a uniform sand and a sandy loam (SL). For experiments with sand, BC and sand were sieved to the same particle size (~ 0.547 mm) to minimize effects of BC addition on particle size distribution. Experiments with SL contained the same sieved BC. PL and HW bicohars were added at 2 and 7% (w/w), and water retention was measured from 0 to -4.38 × 106 cm-H2O. Both BCs increased porosities for sand and SL, up to 39 and 13% for sand and SL, respectively, with 7% HW BC addition. The primary cause for these increases was the internal porosity of BC particles. While the matric potential for air-entry was unchanged with BC addition, BC amendment increased water retention for sand and SL in the capillary region (0 to -15,000 cm-H2O) by an average of 26 and 33 % for 7% PL and HW BC in sand, respectively, but only 7 and 14 % for 7% PL and HW BC in SL. The most dramatic influence of BC amendment on water retention occurred in the adsorption region (< -15,000 cm-H2O), where water retention increased by a factor of 11 and 22 for 7% PL and HW BC in sand, respectively, but by 140 and 190 % for 7% PL and HW BC in SL, respectively. The impact of BC on water retention in these sediments is explained primarily by the additional surface area and internal porosity of PL and HW BC particles. van Genuchten (VG) models were fitted to the water retention data. For SL where the impact of BC addition on water retention was

  20. Energy deposition model based on electron scattering cross section data from water molecules

    NASA Astrophysics Data System (ADS)

    Muñoz, A.; Oiler, J. C.; Blanco, F.; Gorfinkiel, J. D.; Limão-Vieira, P.; Maira-Vidal, A.; Borge, M. J. G.; Tengblad, O.; Huerga, C.; Téllez, M.; García, G.

    2008-10-01

    A complete set of electrons scattering cross sections by water molecules over a broad energy range, from the me V to the Me V ranges, is presented in this study. These data have been obtained by combining experiments and calculations and cover most relevant processes, both elastic and inelastic, which can take place in the considered energy range. A new Monte Carlo simulation programme has been developed using as input parameter these cross sectional data as well as experimental energy loss spectra. The simulation procedure has been applied to obtain electron tracks and energy deposition plots in water when irradiated by a Ru-106 plaque as those used for brachyteraphy of ocular tumours. Finally, the low energy electron tracks provided by the present model have been compared with those obtained with other codes available in the literature

  1. Water and complex organic molecules in the warm inner regions of solar-type protostars

    NASA Astrophysics Data System (ADS)

    Coutens, A.; Jørgensen, J. K.; Persson, M. V.; Lykke, J. M.; Taquet, V.; van Dishoeck, E. F.; Vastel, C.; Wampfler, S. F.

    2015-12-01

    Water and complex organic molecules play an important role in the emergence of Life. They have been detected in different types of astrophysical environments (protostars, prestellar cores, outflows, protoplanetary disks, comets, etc). In particular, they show high abundances towards the warm inner regions of protostars, where the icy grain mantles thermally desorb. Can a part of the molecular content observed in these regions be preserved during the star formation process and incorporated into asteroids and comets, that can deliver it to planetary embryos through impacts? By comparison with cometary studies, interferometric observations of solar-type protostars can help to address this important question. We present recent results obtained with the Plateau de Bure interferometer about water deuteration, glycolaldehyde and ethylene glycol towards the low-mass protostar NGC 1333 IRAS2A.

  2. Dynamics and mass accommodation of HCl molecules on sulfuric acid-water surfaces.

    PubMed

    Behr, P; Scharfenort, U; Ataya, K; Zellner, R

    2009-09-28

    A molecular beam technique has been used to study the dynamics and mass accommodation of HCl molecules in collision with sulfuric acid-water surfaces. The experiments were performed by directing a nearly mono-energetic beam of HCl molecules onto a continuously renewed liquid film of 54-76 wt% sulfuric acid at temperatures between 213 K and 243 K. Deuterated sulfuric acid was used to separate sticking but non-reactive collisions from those that involved penetration through the phase boundary followed by dissociation and recombination with D+. The results indicate that the mass accommodation of HCl on sulfuric acid-water surfaces decreases sharply with increasing acidity over the concentration range 54-76 wt%. Using the capillary wave theory of mass accommodation this effect is explained by a change of the surface dynamics. Regarding the temperature dependence it is found that the mass accommodation of HCl increases with increasing temperature and is limited by the bulk phase viscosity and driven by the restoring forces of the surface tension. These findings imply that under atmospheric conditions the uptake of HCl from the gas phase depends crucially on the bulk phase parameters of the sulfuric acid aerosol.

  3. A simple and efficient method to characterize bonded water molecules in aqueous solutions of electrolytes: Application to sodium sulphate decahydrate

    NASA Astrophysics Data System (ADS)

    Fargeot, Carole; Bebon, C.; Colson, D.; Klein, J.-P.; Blandin, A.-F.; Bossoutrot, J.-M.

    2007-09-01

    During a study on crystallization in viscous media, an unexpected relevant theoretical and experimental result about the organization of water molecules in salt solutions has been obtained. Experimental results obtained during measurement of viscosity of saccharose and water solutions demonstrate that the salt dissolved in saccharose solution has the capacity to catch the solvent, namely water, from the solvated substance, here saccharose, which induces a quite large viscosity gap. There is a certain mutual electrolyte-water attraction; it may be pushed on by stronger water-salt than water-saccharose interactions. Determination of the binding of water with the salt in the solution can be done directly from measured viscosity. The number of water molecules withdrawn by Na 2SO 4 in solution is computable from viscosity values. Significance of the results obtained is a relevant demonstration that the 10 water molecules of Na 2SO 4·10H 2O are already organised around the solute before the crystallization. The phenomenon observed here questions theoretical predictions that rely on solvent organization and salt effect in solution. Novelty of this study may thus encourage further experimental work in order to elucidate and test the validity of such investigational method to determine the number of water molecules withdrawn by salt in solution.

  4. Effects of solvent additive on “s-shaped” curves in solution-processed small molecule solar cells

    PubMed Central

    Chou, Shu-Hua; Huang, Ye

    2016-01-01

    A novel molecular chromophore, p-SIDT(FBTThCA8)2, is introduced as an electron-donor material for bulk heterojunction (BHJ) solar cells with broad absorption and near ideal energy levels for the use in combination with common acceptor materials. It is found that films cast from chlorobenzene yield devices with strongly s-shaped current–voltage curves, drastically limiting performance. We find that addition of the common solvent additive diiodooctane, in addition to facilitating crystallization, leads to improved vertical phase separation. This yields much better performing devices, with improved curve shape, demonstrating the importance of morphology control in BHJ devices and improving the understanding of the role of solvent additives. PMID:28144323

  5. Control of unidirectional transport of single-file water molecules through carbon nanotubes in an electric field.

    PubMed

    Su, Jiaye; Guo, Hongxia

    2011-01-25

    The transport of water molecules through nanopores is not only crucial to biological activities but also useful for designing novel nanofluidic devices. Despite considerable effort and progress that has been made, a controllable and unidirectional water flow is still difficult to achieve and the underlying mechanism is far from being understood. In this paper, using molecular dynamics simulations, we systematically investigate the effects of an external electric field on the transport of single-file water molecules through a carbon nanotube (CNT). We find that the orientation of water molecules inside the CNT can be well-tuned by the electric field and is strongly coupled to the water flux. This orientation-induced water flux is energetically due to the asymmetrical water-water interaction along the CNT axis. The wavelike water density profiles are disturbed under strong field strengths. The frequency of flipping for the water dipoles will decrease as the field strength is increased, and the flipping events vanish completely for the relatively large field strengths. Most importantly, a critical field strength E(c) related to the water flux is found. The water flux is increased as E is increased for E ≤ E(c), while it is almost unchanged for E > E(c). Thus, the electric field offers a level of governing for unidirectional water flow, which may have some biological applications and provides a route for designing efficient nanopumps.

  6. The binding energies of one and two water molecules to the first transition-row metal positive ions. II

    NASA Technical Reports Server (NTRS)

    Rosi, Marzio; Bauschlicher, Charles W., Jr.

    1990-01-01

    The present investigation of H2O's binding energy to transition-metal ions proceeds from the D(2h) structure and bends the two water molecules out of plane. The molecule is constrained to have C(2v) symmetry, so that each water molecule and metal ion lies on a plane. The ground states are bent only for Mn(H2O)2(+) and Zn(H2O)2(+), where only 4s4p hybridization is energetically favorable; 4s4p hybridization reduces repulsion.

  7. Nitrogen addition and clonal integration alleviate water stress of dependent ramets of Indocalamus decorus under heterogeneous soil water environment

    PubMed Central

    Guo, Zi-Wu; Hu, Jun-Jing; Chen, Shuang-Lin; Li, Ying-Chun; Yang, Qing-Ping; Cai, Han-Jiang

    2017-01-01

    Water and nitrogen are two of the most important factors for plant growth and development. However, little is known about effects of N on water translocation between connected bamboo ramets. We performed experiment connected Indocalamus decorus ramets in adjacent pots with different soil water contents and three N levels. We determined antioxidase activities, concentration of osmotic adjustment products, O2·−, MDA and photosynthetic pigments, and electrolyte leakage rate in paired unit. When N supply to supporting ramets increased, their electrolyte leakage rates and contents of O2·− and MDA significantly increased, while antioxidase activities and contents of osmotic adjustment products and photosynthetic pigments in connected dependent ramets increased markedly as their electrolyte leakage rates and contents of O2·− and MDA decreased greatly. When N addition to dependent ramets increased, antioxidant enzyme activity and contents of osmotic adjustment products and photosynthetic pigments decreased in both ramets, but electrolyte leakage rates and O2·− and MDA contents increased significantly. Therefore, N addition to either supporting or dependent ramets can improve water integration among I. decorus ramets. N addition to supporting ramets promotes water translocation and alleviates water stress of dependent ramets, but N addition to dependent ramets exacerbates drought stress damage to dependent ramets. PMID:28295023

  8. Nitrogen addition and clonal integration alleviate water stress of dependent ramets of Indocalamus decorus under heterogeneous soil water environment.

    PubMed

    Guo, Zi-Wu; Hu, Jun-Jing; Chen, Shuang-Lin; Li, Ying-Chun; Yang, Qing-Ping; Cai, Han-Jiang

    2017-03-15

    Water and nitrogen are two of the most important factors for plant growth and development. However, little is known about effects of N on water translocation between connected bamboo ramets. We performed experiment connected Indocalamus decorus ramets in adjacent pots with different soil water contents and three N levels. We determined antioxidase activities, concentration of osmotic adjustment products, O2·(-), MDA and photosynthetic pigments, and electrolyte leakage rate in paired unit. When N supply to supporting ramets increased, their electrolyte leakage rates and contents of O2·(-) and MDA significantly increased, while antioxidase activities and contents of osmotic adjustment products and photosynthetic pigments in connected dependent ramets increased markedly as their electrolyte leakage rates and contents of O2·(-) and MDA decreased greatly. When N addition to dependent ramets increased, antioxidant enzyme activity and contents of osmotic adjustment products and photosynthetic pigments decreased in both ramets, but electrolyte leakage rates and O2·(-) and MDA contents increased significantly. Therefore, N addition to either supporting or dependent ramets can improve water integration among I. decorus ramets. N addition to supporting ramets promotes water translocation and alleviates water stress of dependent ramets, but N addition to dependent ramets exacerbates drought stress damage to dependent ramets.

  9. On the reactive uptake of gaseous PAH molecules by micron-sized atmospheric water droplets

    NASA Astrophysics Data System (ADS)

    Raja, S.; Valsaraj, K. T.

    2006-10-01

    A falling droplet reactor was used to study the heterogeneous oxidation of gaseous PAH molecules adsorbed on a 92 μm diameter water droplet by ozone. The dynamic partition constant for the PAH between the droplet and air and the first-order surface rate constant was measured. The increase in uptake with ozone concentration was due to increased mass transfer via surface reaction of co-adsorbed ozone and PAH. The surface rate constant was rationalized through the Langmuir-Hinshelwood mechanism. The rate constant was smaller for phenanthrene than naphthalene. The main reaction products identified in the aqueous phase indicated the peroxidic route for surface reaction of ozone with PAH. The heterogeneous reaction rate of ozone with adsorbed phenanthrene at the air-water interface of a 92-μm droplet was estimated to be 9300 times larger than the homogeneous reaction of ozone with phenanthrene in the gas phase and it was 76 times larger than the homogeneous oxidation by hydroxyl radical in the gas phase. For naphthalene that is more volatile, however, the homogeneous reaction with hydroxyl was more important. Increased organic carbon added to the droplet increased both the partition constant for phenanthrene and surface reaction with ozone. The partition constant for a droplet formed from actual fog water was much larger than for pure distilled water.

  10. [Interactions of DNA bases with individual water molecules. Molecular mechanics and quantum mechanics computation results vs. experimental data].

    PubMed

    Gonzalez, E; Lino, J; Deriabina, A; Herrera, J N F; Poltev, V I

    2013-01-01

    To elucidate details of the DNA-water interactions we performed the calculations and systemaitic search for minima of interaction energy of the systems consisting of one of DNA bases and one or two water molecules. The results of calculations using two force fields of molecular mechanics (MM) and correlated ab initio method MP2/6-31G(d, p) of quantum mechanics (QM) have been compared with one another and with experimental data. The calculations demonstrated a qualitative agreement between geometry characteristics of the most of local energy minima obtained via different methods. The deepest minima revealed by MM and QM methods correspond to water molecule position between two neighbor hydrophilic centers of the base and to the formation by water molecule of hydrogen bonds with them. Nevertheless, the relative depth of some minima and peculiarities of mutual water-base positions in' these minima depend on the method used. The analysis revealed insignificance of some differences in the results of calculations performed via different methods and the importance of other ones for the description of DNA hydration. The calculations via MM methods enable us to reproduce quantitatively all the experimental data on the enthalpies of complex formation of single water molecule with the set of mono-, di-, and trimethylated bases, as well as on water molecule locations near base hydrophilic atoms in the crystals of DNA duplex fragments, while some of these data cannot be rationalized by QM calculations.

  11. Effect of wine addition on microbiological characteristics, volatile molecule profiles and biogenic amine contents in fermented sausages.

    PubMed

    Coloretti, Fabio; Tabanelli, Giulia; Chiavari, Cristiana; Lanciotti, Rosalba; Grazia, Luigi; Gardini, Fausto; Montanari, Chiara

    2014-03-01

    The aim was to evaluate the effect of wine addition during manufacturing of dry fermented sausages, in terms of safety aspects (biogenic amine accumulation), aroma profile and sensory characteristics. Three batches of salami were produced: without wine addition and with 7.5% or 15% (v/w) of white wine. The fermented sausages showed characteristics that can increase product diversification. Some of the sensory features (i.e. increased salty perception) can represent an important strategy because of the trend to reduce salt intake for health reasons. The presence of wine immediately reduced the pH and is a source of ethanol, which can have an inhibitory effect against undesirable microflora. The microbiological results observed regarding Enterobacteriaceae and enterococci were encouraging. The addition of wine did not negatively affect the ripening time or increase the presence of biogenic amines. The samples containing wine showed reduced concentrations of putrescine.

  12. Improvement of organics removal by bio-ceramic filtration of raw water with addition of phosphorus.

    PubMed

    Sang, Junqiang; Zhang, Xihui; Li, Lingzhi; Wang, Zhansheng

    2003-11-01

    The purpose of this study was to investigate the effect of phosphorus addition on biological pretreatment of raw water. Experiments were conducted in pilot-scale bio-ceramic filters with raw water from a reservoir located in Beijing, China. The results demonstrated that phosphorus was the limiting nutrient for bacterial growth in the raw water investigated in this study. The measured values of bacterial regrowth potential (BRP) and biodegradable dissolved organic carbon (BDOC) of the raw water increased by 50-65% and 30-40% with addition of 50 microg of PO4(3-)-PL(-1), respectively. Addition of 25 microg of PO4(3-)-PL(-1) to the influent of bio-ceramic filter enhanced the percent removal of organics by 4.6, 5.7 and 15 percentage points in terms of COD(Mn), TOC and BDOC, respectively. Biomass in terms of phospholipid content increased by 13-22% and oxygen uptake rate (OUR) increased by 35-45%. The ratio of C:P for bacteria growth was 100:1.6 for the raw water used in this study. Since change of phosphorus concentrations can influence the performance of biological pretreatment and the biological stability of drinking water, this study is of substantial significance for waterworks in China. The role of phosphorus in biological processes of drinking water should deserve more attention.

  13. Effects of water molecules on rearrangements of formamide on the kaolinite basal (001) surface.

    PubMed

    Nguyen, Huyen Thi; Nguyen, Minh Tho

    2014-08-28

    The effects of kaolinite mineral surfaces on the unimolecular rearrangements of formamide (FM) were investigated using periodic density functional theory in conjunction with pseudopotential plane-wave approach. Surface hydroxyl groups covering the octahedral surface of kaolinite were found to play the role of catalysts in the transformations of FM. They induce a reduction of 31 kcal/mol on the energy barrier for formation of its isomer aminohydroxymethylene (AHM), which is close to the reduction amount calculated for water-catalyzed reactions. This suggests that the kaolinite octahedral surface exerts a catalytic effect similar to that of the water molecule. As the tetrahedral surface does not contain catalytic surface hydroxyl groups, only water-assisted FM transformation was therefore studied on this surface whose energy barrier amounts to ∼17 kcal/mol. The combined effect of both water and kaolinite on FM rearrangements via triple hydrogen transfer reactions does not significantly lower the energy barriers, as compared to those of double hydrogen transfer reactions. The triple hydrogen transfer energy barriers amount to ∼20 and ∼36 kcal/mol, and the double ones are ∼21 and ∼40 kcal/mol for formation of formimic acid and AHM isomers, respectively. However, the energies of the systems in water-catalyzed channels lie below the available energies of the original reactants, and thus these channels are more favored than the water-free ones. With its multiple functions as both a supporting plate-form and a catalyst for FM reactions, kaolinite can thus be regarded as an important natural catalyst for prebiotic synthesis.

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

    PubMed

    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.

  15. Water solvent effects using continuum and discrete models: The nitromethane molecule, CH3NO2.

    PubMed

    Modesto-Costa, Lucas; Uhl, Elmar; Borges, Itamar

    2015-11-15

    The first three valence transitions of the two nitromethane conformers (CH3NO2) are two dark n → π* transitions and a very intense π → π* transition. In this work, these transitions in gas-phase and solvated in water of both conformers were investigated theoretically. The polarizable continuum model (PCM), two conductor-like screening (COSMO) models, and the discrete sequential quantum mechanics/molecular mechanics (S-QM/MM) method were used to describe the solvation effect on the electronic spectra. Time dependent density functional theory (TDDFT), configuration interaction including all single substitutions and perturbed double excitations (CIS(D)), the symmetry-adapted-cluster CI (SAC-CI), the multistate complete active space second order perturbation theory (CASPT2), and the algebraic-diagrammatic construction (ADC(2)) electronic structure methods were used. Gas-phase CASPT2, SAC-CI, and ADC(2) results are in very good agreement with published experimental and theoretical spectra. Among the continuum models, PCM combined either with CASPT2, SAC-CI, or B3LYP provided good agreement with available experimental data. COSMO combined with ADC(2) described the overall trends of the transition energy shifts. The effect of increasing the number of explicit water molecules in the S-QM/MM approach was discussed and the formation of hydrogen bonds was clearly established. By including explicitly 24 water molecules corresponding to the complete first solvation shell in the S-QM/MM approach, the ADC(2) method gives more accurate results as compared to the TDDFT approach and with similar computational demands. The ADC(2) with S-QM/MM model is, therefore, the best compromise for accurate solvent calculations in a polar environment.

  16. ORGANIC MOLECULES AND WATER IN THE INNER DISKS OF T TAURI STARS

    SciTech Connect

    Carr, John S.; Najita, Joan R. E-mail: najita@noao.edu

    2011-06-01

    We report high signal-to-noise Spitzer Infrared Spectrograph spectra of a sample of 11 classical T Tauri stars. Molecular emission from rotational transitions of H{sub 2}O and OH and rovibrational bands of simple organic molecules (CO{sub 2}, HCN, C{sub 2}H{sub 2}) is common among the sources in the sample. The emission shows a range in both flux and line-to-continuum ratio for each molecule and in the flux ratios of different molecular species. The gas temperatures (200-800 K) and emitting areas we derive are consistent with the emission originating in a warm disk atmosphere in the inner planet formation region at radii <2 AU. The H{sub 2}O emission appears to form under a limited range of excitation conditions, as demonstrated by the similarity in relative strengths of H{sub 2}O features from star to star and the narrow range in derived temperature and column density. Emission from highly excited rotational levels of OH is present in all stars; the OH emission flux increases with the stellar accretion rate, and the OH/H{sub 2}O flux ratio shows a relatively small scatter. We interpret these results as evidence for OH production via FUV photodissociation of H{sub 2}O in the disk surface layers. No obvious explanation is found for the observed range in the relative emission strengths of different organic molecules or in their strength with respect to water. We put forward the possibility that these variations reflect a diversity in organic abundances due to star-to-star differences in the C/O ratio of the inner disk gas. Stars with the largest HCN/H{sub 2}O flux ratios in our sample have the largest disk masses. While larger samples are required to confirm this, we speculate that such a trend could result if higher mass disks are more efficient at planetesimal formation and sequestration of water in the outer disk, leading to enhanced C/O ratios and abundances of organic molecules in the inner disk. A comparison of our derived HCN-to-H{sub 2}O column density ratio

  17. Measurement of water by oven evaporation using a novel oven design. 2. Water in motor oils and motor oil additives.

    PubMed

    Margolis, Sam A; Vaishnav, Kevin; Sieber, John R

    2004-11-01

    The measurement of water in lubricating oils is important because water accelerates the corrosion of metal parts and bearings in motors. Some of the additives added to lubricating oils to improve their performance react with the Karl Fischer reagent (KFR) causing a positive bias in the water measurement. A new oven evaporation technique for measuring water in oils has been developed that is automated, requires less sample handling, is easily calibrated, and is capable of measuring relatively small mass fractions of water (> or =50 mg/kg sample). A series of motor oils was analyzed with the standard KFR, a reagent that detects interfering substances that reduce iodine, and the aldehyde-ketone reagent that does not detect substances that react with methanol and form water. The oil samples were heated to 107 degrees C and then reheated to 160 degrees C. At both temperatures, material was measured by both KFRs, but only zinc dithiophosphate released sulfur compounds that would react with the reagent that detects interfering substances. Mass fractions of between 20 and 70% of the volatile material released at either temperature were measured with the standard KFR but not with the aldehyde-ketone reagent. These results demonstrate that there are a number of sources of positive bias in the measurement of water in motor oils and that the standard KFR cannot be used to measure water in motor oils and motor oil additives. These results also indicate that some of the material reacts with methanol to form water. Finally, these results suggest that some of the material that is volatile at 160 degrees C and not at 107 degrees C may be water that is physically occluded or may be substances that react with diethyleneglycol monomethylether to produce water.

  18. Thermodynamic and Structural Properties of Methanol-Water Solutions Using Non-Additive Interaction Models

    PubMed Central

    Zhong, Yang; Warren, G. Lee; Patel, Sandeep

    2014-01-01

    We study bulk structural and thermodynamic properties of methanol-water solutions via molecular dynamics simulations using novel interaction potentials based on the charge equilibration (fluctuating charge) formalism to explicitly account for molecular polarization at the atomic level. The study uses the TIP4P-FQ potential for water-water interactions, and the CHARMM-based (Chemistry at HARvard Molecular Mechanics) fluctuating charge potential for methanol-methanol and methanol-water interactions. In terms of bulk solution properties, we discuss liquid densities, enthalpies of mixing, dielectric constants, self-diffusion constants, as well as structural properties related to local hydrogen bonding structure as manifested in radial distribution functions and cluster analysis. We further explore the electronic response of water and methanol in the differing local environments established by the interaction of each species predominantly with molecules of the other species. The current force field for the alcohol-water interaction performs reasonably well for most properties, with the greatest deviation from experiment observed for the excess mixing enthalpies, which are predicted to be too favorable. This is qualitatively consistent with the overestimation of the methanol-water gas-phase interaction energy for the lowest-energy conformer (methanol as proton donor). Hydration free energies for methanol in TIP4P-FQ water are predicted to be −5.6±0.2 kcal/mole, in respectable agreement with the experimental value of −5.1 kcal/mole. With respect to solution micro-structure, the present cluster analysis suggests that the micro-scale environment for concentrations where select thermodynamic quantities reach extremal values is described by a bi-percolating network structure. PMID:18074339

  19. Relationship between diffusivity of water molecules inside hydrating tablets and their drug release behavior elucidated by magnetic resonance imaging.

    PubMed

    Kikuchi, Shingo; Onuki, Yoshinori; Kuribayashi, Hideto; Takayama, Kozo

    2012-01-01

    We reported previously that sustained release matrix tablets showed zero-order drug release without being affected by pH change. To understand drug release mechanisms more fully, we monitored the swelling and erosion of hydrating tablets using magnetic resonance imaging (MRI). Three different types of tablets comprised of polyion complex-forming materials and a hydroxypropyl methylcellulose (HPMC) were used. Proton density- and diffusion-weighted images of the hydrating tablets were acquired at intervals. Furthermore, apparent self-diffusion coefficient maps were generated from diffusion-weighted imaging to evaluate the state of hydrating tablets. Our findings indicated that water penetration into polyion complex tablets was faster than that into HPMC matrix tablets. In polyion complex tablets, water molecules were dispersed homogeneously and their diffusivity was relatively high, whereas in HPMC matrix tablets, water molecule movement was tightly restricted within the gel. An optimal tablet formulation determined in a previous study had water molecule penetration and diffusivity properties that appeared intermediate to those of polyion complex and HPMC matrix tablets; water molecules were capable of penetrating throughout the tablets and relatively high diffusivity was similar to that in the polyion complex tablet, whereas like the HPMC matrix tablet, it was well swollen. This study succeeded in characterizing the tablet hydration process. MRI provides profound insight into the state of water molecules in hydrating tablets; thus, it is a useful tool for understanding drug release mechanisms at a molecular level.

  20. Investigations of the Structure and Hydrogen Bonding of Water Molecules at Liquid Surfaces by Vibrational Sum Frequency Spectroscopy

    DTIC Science & Technology

    1998-06-01

    studies conducted for the first time at liquid surfaces are also described. In these studies the intermolecular and intramolecular coupling of vibrational ... modes in the water molecules are diminished. The results of these and above mentioned studies provide valuable information for those interested in developing theoretical descriptions of water at surfaces and interfaces.

  1. Rotations and vibrations of water molecule inside the fullerene cage: infrared study of H2O@C60

    NASA Astrophysics Data System (ADS)

    Room, Toomas; Shugai, A.; Nagel, U.; Mamone, S.; Krachmalnicoff, A.; Whitby, R. J.; Levitt, M. H.; Nishida, T.; Murata, Y.; Lei, Xuegong; Li, Yongjun; Turro, N. J.

    2015-03-01

    Water is the second molecule after hydrogen what has been trapped inside the cage of a C60 molecule by the molucular surgery method. We studied isolated water molecule isotopologs H2O, D2O, and HDO in the solid phase at cryogenic temperatures using IR spectroscopy. The water molecule rotation transitions were observed in the THz and vibration-rotation transitions in the mid-IR range. The slow conversion between para and ortho water allowed us to record the time evolution of spectra and to separate ortho and para absorption lines of water. The similarity of the rotation spectrum of caged water to water in the gas phase indicates that water is free to rotate in the C60 cage even at temperature as low as 3 K. However, spectral lines show a splitting of about 0.5 meV what is not compatible with the icosahedral symmetry of C60. Different models (e.g. crystal field effects in solid C60, C60 cage distortions) will be discussed. This work was supported by institutional research funding IUT23-3 of the Estonian Ministry of Education and Research.

  2. Effects of water and nitrogen addition on species turnover in temperate grasslands in northern China.

    PubMed

    Xu, Zhuwen; Wan, Shiqiang; Ren, Haiyan; Han, Xingguo; Li, Mai-He; Cheng, Weixin; Jiang, Yong

    2012-01-01

    Global nitrogen (N) deposition and climate change have been identified as two of the most important causes of current plant diversity loss. However, temporal patterns of species turnover underlying diversity changes in response to changing precipitation regimes and atmospheric N deposition have received inadequate attention. We carried out a manipulation experiment in a steppe and an old-field in North China from 2005 to 2009, to test the hypothesis that water addition enhances plant species richness through increase in the rate of species gain and decrease in the rate of species loss, while N addition has opposite effects on species changes. Our results showed that water addition increased the rate of species gain in both the steppe and the old field but decreased the rates of species loss and turnover in the old field. In contrast, N addition increased the rates of species loss and turnover in the steppe but decreased the rate of species gain in the old field. The rate of species change was greater in the old field than in the steppe. Water interacted with N to affect species richness and species turnover, indicating that the impacts of N on semi-arid grasslands were largely mediated by water availability. The temporal stability of communities was negatively correlated with rates of species loss and turnover, suggesting that water addition might enhance, but N addition would reduce the compositional stability of grasslands. Experimental results support our initial hypothesis and demonstrate that water and N availabilities differed in the effects on rate of species change in the temperate grasslands, and these effects also depend on grassland types and/or land-use history. Species gain and loss together contribute to the dynamic change of species richness in semi-arid grasslands under future climate change.

  3. Stress corrosion cracking of α-brass in waters with and without additions

    NASA Astrophysics Data System (ADS)

    Parkins, R. N.; Rangel, C. M.; Yu, J.

    1985-09-01

    Slow strain rate stress corrosion tests on a 0.032 pct As brass in SO2 solutions of increasing dilution eventually resulted in tests being carried out in various waters which were also found to promote cracking. A 0.002 pet As brass was also found to be susceptible to cracking in deionized water, but in brackish water or an acidified sulfate solution this brass did not display the stress corrosion cracking observed in these more aggressive solutions by the higher As brass. The addition of arsenite to distilled water or arsenate to deionized water in sufficient amounts effectively inhibited the cracking observed at controlled potentials or open circuit in these waters without the As additions. The results are interpreted as indicative of dezincification being involved in these various environments that promoted cracking, but the extent of the dezincification plays an important role in determining whether or not cracking occurs, those additions leading to rapid and massive dezincification involving redeposition of dissolved Cu not being conducive to cracking.

  4. Impact of orthophosphate addition on biofilm development in drinking water distribution systems.

    PubMed

    Gouider, Mbarka; Bouzid, Jalel; Sayadi, Sami; Montiel, Antoine

    2009-08-15

    The contamination of the water distribution network results from fixed bacteria multiplication (biofilm) on the water pipe walls, followed by their detachment and their transport in the circulating liquid. The presence of biofilms in distribution networks can result in numerous unwanted problems for the user such as microbial contamination of the distributed water and deterioration of the network (bio-corrosion). For old networks, lead-containing plumbings can be a serious cause of worry for the consumer owing to the release of lead ions in the circulating water. Among the solutions considered to reduce the presence of lead in drinking water, the addition of orthophosphates constitutes an interesting alternative. However, the added orthophosphate may cause--even at low doses--additional microbial growth. The main objective of this study was to evaluate the impact of the orthophosphate treatment on the biofilm development in the water supplied by the Joinville-le-Pont water treatment plant (Eau de Paris, France). For this purpose, a laboratory pilot plant was devised and connected to the considered water network. Two quantification methods for monitoring the biofilm formation were used: the enumeration on R2A agar and the determination of proteins. For the biofilm detachment operation, an optimization of the rinsing step was firstly conducted in order to distinguish between free and fixed biomass. The data obtained showed that there was a linear relation between both quantification methods. They also showed that, for the tested water, the bacterial densities were not affected by orthophosphate addition at a treatment rate of 1mg PO(4)(3-)/L.

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

    PubMed

    Kwon, Oh In; Jeong, Woo Chul; Sajib, Saurav Z K; Kim, Hyung Joong; Woo, Eung Je

    2014-06-21

    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.

  6. Adsorption of apolar molecules at the water liquid-vapor interface: A Monte Carlo simulations study of the water-n-octane system

    NASA Astrophysics Data System (ADS)

    Jedlovszky, Pál; Varga, Imre; Gilányi, Tibor

    2003-07-01

    The adsorption of n-octane at the water liquid-vapor interface has been investigated by Monte Carlo computer simulation. For this purpose, simulation of five different water-apolar interfacial systems have been performed, in which the number of n-octane molecules has been varied. The results clearly show that the apolar n-octane molecules are adsorbed from the vapor phase at the interface. The adsorption is driven by the weak attraction due to the dispersion forces acting between the water molecules and the methyl and methylene groups of the octanes. This weak attraction is, however, amplified by the fact that it is added up for the CH2 and CH3 groups belonging to the same molecule. Consistently, the n-octane molecules located closest to the aqueous phase are found to prefer all-trans conformation and parallel alignment with the plane of the interface. On the other hand, entropic effects become more important among the molecules of the outer part of the adsorption layer. Hence, the preferred orientation of these molecules is perpendicular to the interface, as they can be extended toward the less dense region of the apolar phase; and gauche dihedrals appear more frequently here than among the molecules located next to the aqueous phase.

  7. Rate-Enhancing Roles of Water Molecules in Methyltrioxorhenium-Catalyzed Olefin Epoxidation by Hydrogen Peroxide.

    PubMed

    Goldsmith, Bryan R; Hwang, Taeho; Seritan, Stefan; Peters, Baron; Scott, Susannah L

    2015-08-05

    Olefin epoxidation catalyzed by methyltrioxorhenium (MTO, CH3ReO3) is strongly accelerated in the presence of H2O. The participation of H2O in each of the elementary steps of the catalytic cycle, involving the formation of the peroxo complexes (CH3ReO2(η(2)-O2), A, and CH3ReO(η(2)-O2)2(H2O), B), as well as in their subsequent epoxidation of cyclohexene, was examined in aqueous acetonitrile. Experimental measurements demonstrate that the epoxidation steps exhibit only weak [H2O] dependence, attributed by DFT calculations to hydrogen bonding between uncoordinated H2O and a peroxo ligand. The primary cause of the observed H2O acceleration is the strong co-catalytic effect of water on the rates at which A and B are regenerated and consequently on the relative abundances of the three interconverting Re-containing species at steady state. Proton transfer from weakly coordinated H2O2 to the oxo ligands of MTO and A, resulting in peroxo complex formation, is directly mediated by solvent H2O molecules. Computed activation parameters and kinetic isotope effects, in combination with proton-inventory experiments, suggest a proton shuttle involving one or (most favorably) two H2O molecules in the key ligand-exchange steps to form A and B from MTO and A, respectively.

  8. Effects of water and nitrogen addition on ecosystem carbon exchange in a meadow steppe.

    PubMed

    Wang, Yunbo; Jiang, Qi; Yang, Zhiming; Sun, Wei; Wang, Deli

    2015-01-01

    A changing precipitation regime and increasing nitrogen deposition are likely to have profound impacts on arid and semiarid ecosystem C cycling, which is often constrained by the timing and availability of water and nitrogen. However, little is known about the effects of altered precipitation and nitrogen addition on grassland ecosystem C exchange. We conducted a 3-year field experiment to assess the responses of vegetation composition, ecosystem productivity, and ecosystem C exchange to manipulative water and nitrogen addition in a meadow steppe. Nitrogen addition significantly stimulated aboveground biomass and net ecosystem CO2 exchange (NEE), which suggests that nitrogen availability is a primary limiting factor for ecosystem C cycling in the meadow steppe. Water addition had no significant impacts on either ecosystem C exchange or plant biomass, but ecosystem C fluxes showed a strong correlation with early growing season precipitation, rather than whole growing season precipitation, across the 3 experimental years. After we incorporated water addition into the calculation of precipitation regimes, we found that monthly average ecosystem C fluxes correlated more strongly with precipitation frequency than with precipitation amount. These results highlight the importance of precipitation distribution in regulating ecosystem C cycling. Overall, ecosystem C fluxes in the studied ecosystem are highly sensitive to nitrogen deposition, but less sensitive to increased precipitation.

  9. Effects of Water and Nitrogen Addition on Ecosystem Carbon Exchange in a Meadow Steppe

    PubMed Central

    Wang, Yunbo; Jiang, Qi; Yang, Zhiming; Sun, Wei; Wang, Deli

    2015-01-01

    A changing precipitation regime and increasing nitrogen deposition are likely to have profound impacts on arid and semiarid ecosystem C cycling, which is often constrained by the timing and availability of water and nitrogen. However, little is known about the effects of altered precipitation and nitrogen addition on grassland ecosystem C exchange. We conducted a 3-year field experiment to assess the responses of vegetation composition, ecosystem productivity, and ecosystem C exchange to manipulative water and nitrogen addition in a meadow steppe. Nitrogen addition significantly stimulated aboveground biomass and net ecosystem CO2 exchange (NEE), which suggests that nitrogen availability is a primary limiting factor for ecosystem C cycling in the meadow steppe. Water addition had no significant impacts on either ecosystem C exchange or plant biomass, but ecosystem C fluxes showed a strong correlation with early growing season precipitation, rather than whole growing season precipitation, across the 3 experimental years. After we incorporated water addition into the calculation of precipitation regimes, we found that monthly average ecosystem C fluxes correlated more strongly with precipitation frequency than with precipitation amount. These results highlight the importance of precipitation distribution in regulating ecosystem C cycling. Overall, ecosystem C fluxes in the studied ecosystem are highly sensitive to nitrogen deposition, but less sensitive to increased precipitation. PMID:26010888

  10. New approximate orientation averaging of the water molecule interacting with the thermal neutron

    SciTech Connect

    Markovic, M.I.; Minic, D.M.; Rakic, A.D. . Elektrotehnicki Fakultet)

    1992-02-01

    This paper reports that exactly describing the time of thermal neutron collisions with water molecules, orientation averaging is performed by an exact method (EOA{sub k}) and four approximate methods (two well known and two less known). Expressions for the microscopic scattering kernel are developed. The two well-known approximate orientation averaging methods are Krieger-Nelkin (K-N) and Koppel-Young (K-Y). The results obtained by one of the two proposed approximate orientation averaging methods agree best with the corresponding results obtained by EOA{sub k}. The largest discrepancies between the EOA{sub k} results and the results of the approximate methods are obtained using the well-know K-N approximate orientation averaging method.

  11. Three-body neutral dissociations of a multiply excited water molecule around the double ionization potential

    NASA Astrophysics Data System (ADS)

    Odagiri, Takeshi; Nakano, Motoyoshi; Tanabe, Takehiko; Kumagai, Yoshiaki; Suzuki, Isao H.; Kitajima, Masashi; Kouchi, Noriyuki

    2012-11-01

    The cross sections for emission of two fluorescence photons from a pair of excited fragments in photoexcitation of H2O have been measured as a function of the incident photon energy using the photon-photon coincidence technique. The cross section increased in the range 30-45 eV, i.e. in the vicinity of the double ionization potential of H2O. The increase of the cross section was attributed to three-body neutral dissociations of a water molecule via multiply excited states: H2O** → H(2p) + OH** → H(2p) + H(2p) + O(3P). Some multiply excited states of H2O were also found in the cross section curve around 65 eV.

  12. Vibrational-excitation cross sections of water molecules by electron impact

    NASA Technical Reports Server (NTRS)

    Shyn, T. W.; Cho, S. Y.; Cravens, T. E.

    1988-01-01

    A crossed-beam technique was used to measure absolute differential cross sections for the vibrational excitation of water-vapor molecules. The energy and angular range were from 2.2 to 20 eV and from 30 to 150 deg. Vibrational-excitation cross sections were determined for the bending (010) and stretching (100 and 001) modes of the electronic ground state. It is shown that the integral cross sections are generally larger than those of Seng and Linder (1976) by 10-20 percent for both the bending and stretching modes. It is noted that the results obtained are of interest in connection with the theoretical modeling of cometary ionospheres.

  13. Thermochemical properties of the ammonia-water ionized dimer probed by ion-molecule reactions.

    PubMed

    Abdel Azeim, Safwat; van der Rest, Guillaume

    2005-03-24

    The thermochemical properties of some small clusters such as the (H2O)2*+ dimer have already been investigated by both experimental and theoretical methods. The recent method to selectively prepare the ammonia-water ionized dimer [NH3, H2O]*+ (and not its proton transfer isomer [NH4+, OH*]) allowed us to study its chemical reactivity. This study focuses on the charge and proton transfer pathways: Ion-molecule reactions in the cell of an FT-ICR mass spectrometer were carried out with a range of organic compounds. Examination of the reactivity of the [NH3, H2O]*+ ionized dimer versus ionization energy and proton affinity of the neutral reagents shows a threshold in the reactivity in both instances. This leads to a bracketing of thermochemical properties related to the dimer. From these experiments and in agreement with ab initio calculations, the adiabatic recombination energy of the [NH3, H2O]*+ dimer was evaluated at -9.38 +/- 0.04 eV. The proton affinity bracketing required the reevaluation of two reference gas-phase basicity values. The results, in good agreement with the calculation, lead to an evaluation of the proton affinity of the [NH2*, H2O] dimer at 204.4 +/- 0.9 kcal mol(-1). These two experimental values are respectively related to the ionization energy of NH3*+ and to the proton affinity of NH2* by the difference in single water molecule solvation energies of ionized ammonia, of neutral ammonia, and of the NH2* radical.

  14. Single Molecule Lateral Mobility and Membrane Organization in DMPC/Cholesterol Mixtures at the Air-Water Interface

    NASA Astrophysics Data System (ADS)

    Shaikh, Saame; Stillwell, William; Naumann, Christoph

    2002-03-01

    To better understand the lipid heterogeneity of biological membranes, we have studied the lateral mobility and membrane organization of DMPC and cholesterol (Chol) mixtures at the air-water interface using single molecule fluorescence imaging and epifluorescence microscopy. The single molecule imaging technique was used to track the lateral diffusion of single molecules of TRITC-DPPE or cholesteryl Bodipy. In the absence of Chol, mean square displacement histograms obtained from single molecule tracking of TRITC-DPPE show unobstructed diffusion. Including Chol at low levels of Chol (<10 moldiffusion at intermediate levels ( 30 molof Chol (>40 molmacroscopic phase separations. Data obtained from tracking experiments of cholesteryl-Bodipy also show complementary changes in diffusion. Our results indicate that our techniques provide insight into the micro and macro organization of lipid domains at the air-water interface.

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

    NASA Astrophysics Data System (ADS)

    Bernatskiy, A. V.; Ochkin, V. N.; Afonin, O. N.; Antipenkov, A. B.

    2015-09-01

    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 2Σ- X 2П) 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.

  16. Water and a protic ionic liquid acted as refolding additives for chemically denatured enzymes.

    PubMed

    Attri, Pankaj; Venkatesu, P; Kumar, Anil

    2012-10-07

    In this communication, we present the ability of water and a protic ionic liquid, triethyl ammonium phosphate (TEAP) to act as refolding additives for the urea-induced chemical denaturated state of the two enzymes, α-chymotrypsin and succinylated Con A. We show that the enzymatic activity is regained and in certain circumstances enhanced.

  17. Water sorption of CH3- and CF3-Bis-GMA based resins with additives

    PubMed Central

    PRAKKI, Anuradha; CILLI, Renato; VIEIRA, Ian Matos; DUDUMAS, Kristina; PEREIRA, José Carlos

    2012-01-01

    Objectives To evaluate the effect of additives on the water sorption characteristics of Bis-GMA based copolymers and composites containing TEGDMA, CH3Bis-GMA or CF3Bis-GMA. Material and methods Fifteen experimental copolymers and corresponding composites were prepared combining Bis-GMA and TEGDMA, CH3Bis-GMA or CF3Bis-GMA, with aldehyde or diketone (24 and 32 mol%) totaling 30 groups. For composites, barium aluminosilicate glass and pyrogenic silica was added to comonomer mixtures. Photopolymerization was effected by 0.2 wt% each of camphorquinone and N,N-dimethyl-p-toluidine. Specimen densities in dry and water saturated conditions were obtained by Archimedes' method. Water sorption and desorption were evaluated in a desorption-sorption-desorption cycle. Water uptake (%WU), water desorption (%WD), equilibrium solubility (ES; µg/mm3), swelling (f) and volume increase (%V) were calculated using appropriate equations. Results All resins with additives had increased %WU and ES. TEGDMA-containing systems presented higher %WU, %WD, ES, f and %V values, followed by resins based on CH3Bis-GMA and CF3Bis-GMA. Conclusions Aldehyde and diketone led to increases in the water sorption characteristics of experimental resins. PMID:23032211

  18. The development of catalytic nucleophilic additions of terminal alkynes in water.

    PubMed

    Li, Chao-Jun

    2010-04-20

    One of the major research endeavors in synthetic chemistry over the past two decades is the exploration of synthetic methods that work under ambient atmosphere with benign solvents, that maximize atom utilization, and that directly transform natural resources, such as renewable biomass, from their native states into useful chemical products, thus avoiding the need for protecting groups. The nucleophilic addition of terminal alkynes to various unsaturated electrophiles is a classical (textbook) reaction in organic chemistry, allowing the formation of a C-C bond while simultaneously introducing the alkyne functionality. A prerequisite of this classical reaction is the stoichiometric generation of highly reactive metal acetylides. Over the past decade, our laboratory and others have been exploring an alternative, the catalytic and direct nucleophilic addition of terminal alkynes to unsaturated electrophiles in water. We found that various terminal alkynes can react efficiently with a wide range of such electrophiles in water (or organic solvent) in the presence of simple and readily available catalysts, such as copper, silver, gold, iron, palladium, and others. In this Account, we describe the development of these synthetic methods, focusing primarily on results from our laboratory. Our studies include the following: (i) catalytic reaction of terminal alkynes with acid chloride, (ii) catalytic addition of terminal alkynes to aldehydes and ketones, (iii) catalytic addition of alkynes to C=N bonds, and (iv) catalytic conjugate additions. Most importantly, these reactions can tolerate various functional groups and, in many cases, perform better in water than in organic solvents, clearly defying classical reactivities predicated on the relative acidities of water, alcohols, and terminal alkynes. We further discuss multicomponent and enantioselective reactions that were developed. These methods provide an alternative to the traditional requirement of separate steps in

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

    PubMed

    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.

  20. Small molecule, big difference: the role of water in the crystallization of paclitaxel.

    PubMed

    Vella-Zarb, Liana; Baisch, Ulrich; Dinnebier, Robert E

    2013-02-01

    Paclitaxel is an important antineoplastic drug, which is used widely in the treatment of many forms of cancer. The crystal structures of the anhydrous form and the hemihydrate were determined from laboratory X-ray powder diffraction data, whereas the dihydrate was solved from single-crystal synchrotron diffraction data. Intermolecular spaces allow for the inclusion of loosely bound water molecules, which are then lost easily upon heating. All three forms were found to crystallize in the orthorhombic spacegroup P2(1)2(1)2(1), with Z' = 2. The unit cell parameters were found to be a = 9.6530(3) Å, b = 28.1196(8) Å, c = 33.5378(14) Å, and V = 9103.5(5) Å for the anhydrous form (363 K); a = 9.6890(2) Å, b = 28.0760(4) Å, c = 33.6166(8) Å, and V = 9144.7(3) Å(3) for the hemihydrate (333 K); and a = 9.512(6) Å, b = 28.064(16) Å, c = 33.08(2) Å, and V = 8829.0(9) Å(3) for the dihydrate (120 K). Water loss occurs in two steps between 120 K ≤ t ≤ 363 K. The thermal stability of the hydrates and accompanying unit cell changes were observed in situ via temperature-resolved X-ray powder diffraction and thermogravimetric analysis.

  1. A proactive role of water molecules in acceptor recognition by Protein-O-fucosyltransferase 2

    PubMed Central

    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

    2016-01-01

    Protein O-fucosyltransferase 2 (POFUT2) is an essential enzyme that fucosylates serine/threonine residues of folded thrombospondin type 1 repeats (TSRs). To date, the mechanism by which this enzyme recognizes very dissimilar TSRs remained unclear. By engineering of 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 CXX(S/T)C. Crystallographic and mutagenesis data together with atomic-level simulations uncover an unprecedented binding mechanism by which POFUT2 promiscuously recognizes the structural fingerprint of poorly homologous TSRs through a dynamic network of water-mediated interactions. PMID:26854667

  2. Lattice water molecules tuned spin-crossover for an iron(II) complex with thermal hysteresis.

    PubMed

    Luo, Yang-Hui; Yang, Li-Jing; Liu, Qing-Ling; Ling, Yang; Wang, Wei; Sun, Bai-Wang

    2014-11-28

    A new iron(II) complex based on the 4,4'-dimethyl-2,2'-bipyridine ligand [Fe(4,4'-dmbpy)3(ClO4)(SCN)·3H2O (1·3H2O)] has been prepared and characterized. Structural studies and Hirshfeld surface analysis for complex 1·3H2O at three different temperatures (300, 240 and 130 K) are described. The UV-vis absorption spectrum of a water-free sample (1) in methanol solution and magnetic susceptibility measurements for solid-state samples 1·3H2O and 1 revealed that the removal of lattice water molecules from complex 1·3H2O changed the magnetic properties from the low-spin state (1·3H2O) to the complete spin-crossover (1) between 350-220 K with a thermal hysteresis of 7 K, and was accompanied by a colour change from brown to red.

  3. Improvement in properties of coal water slurry by combined use of new additive and ultrasonic irradiation.

    PubMed

    Guo, Zhaobing; Feng, Ruo; Zheng, Youfei; Fu, Xiaoru

    2007-07-01

    Coal water slurry (CWS) was prepared with a newly developed additive from naphthalene oil. The effects of ultrasonic irradiation on coal particle size distribution (PSD), adsorption behavior of additive in coal particles and the characteristics of CWS were investigated. Results showed that ultrasonic irradiation led to a higher proportion of fine coal in CWS and increased the saturated adsorption amount of additive in coal particles. In addition, the rheological behavior and static stability of CWS irradiated by ultrasonic wave were remarkably improved. The changes on viscosity of CWS containing 1% and 2% additive are qualitatively different with the increasing sonication time studied. The reason for the different effect of sonication time on CWS viscosity is presented in this study.

  4. Tuning the Redox Properties of a Nonheme Iron(III)-Peroxo Complex Binding Redox-Inactive Zinc Ions by Water Molecules

    SciTech Connect

    Lee, Yong-Min; Bang, Suhee; Yoon, Heejung; Bae, Seong Hee; Hong, Seungwoo; Cho, Kyung-Bin; Sarangi, Ritimukta; Fukuzumi, Shunichi; Nam, Wonwoo

    2015-06-19

    Here we report redox-inactive metal ions play important roles in tuning chemical properties of metal–oxygen intermediates. We describe the effect of water molecules on the redox properties of a nonheme iron(III)–peroxo complex binding redox-inactive metal ions. The coordination of two water molecules to a Zn2+ ion in (TMC)FeIII-(O2)-Zn(CF3SO3)2 (1-Zn2+) decreases the Lewis acidity of the Zn2+ ion, resulting in the decrease of the one-electron oxidation and reduction potentials of 1-Zn2+. This further changes the reactivities of 1-Zn2+ in oxidation and reduction reactions; no reaction occurred upon addition of an oxidant (e.g., cerium(IV) ammonium nitrate (CAN)) to 1-Zn2+, whereas 1-Zn2+ coordinating two water molecules, (TMC)FeIII-(O2)-Zn(CF3SO3)2-(OH2)2 [1-Zn2+-(OH2)2], releases the O2 unit in the oxidation reaction. In the reduction reactions, 1-Zn2+ was converted to its corresponding iron(IV)–oxo species upon addition of a reductant (e.g., a ferrocene derivative), whereas such a reaction occurred at a much slower rate in the case of 1-Zn2+-(OH2)2. Finally, the present results provide the first biomimetic example showing that water molecules at the active sites of metalloenzymes may participate in tuning the redox properties of metal–oxygen intermediates.

  5. Tuning the Redox Properties of a Nonheme Iron(III)-Peroxo Complex Binding Redox-Inactive Zinc Ions by Water Molecules

    DOE PAGES

    Lee, Yong-Min; Bang, Suhee; Yoon, Heejung; ...

    2015-06-19

    Here we report redox-inactive metal ions play important roles in tuning chemical properties of metal–oxygen intermediates. We describe the effect of water molecules on the redox properties of a nonheme iron(III)–peroxo complex binding redox-inactive metal ions. The coordination of two water molecules to a Zn2+ ion in (TMC)FeIII-(O2)-Zn(CF3SO3)2 (1-Zn2+) decreases the Lewis acidity of the Zn2+ ion, resulting in the decrease of the one-electron oxidation and reduction potentials of 1-Zn2+. This further changes the reactivities of 1-Zn2+ in oxidation and reduction reactions; no reaction occurred upon addition of an oxidant (e.g., cerium(IV) ammonium nitrate (CAN)) to 1-Zn2+, whereas 1-Zn2+ coordinatingmore » two water molecules, (TMC)FeIII-(O2)-Zn(CF3SO3)2-(OH2)2 [1-Zn2+-(OH2)2], releases the O2 unit in the oxidation reaction. In the reduction reactions, 1-Zn2+ was converted to its corresponding iron(IV)–oxo species upon addition of a reductant (e.g., a ferrocene derivative), whereas such a reaction occurred at a much slower rate in the case of 1-Zn2+-(OH2)2. Finally, the present results provide the first biomimetic example showing that water molecules at the active sites of metalloenzymes may participate in tuning the redox properties of metal–oxygen intermediates.« less

  6. New water-soluble metal working fluids additives from phosphonic acid derivatives for aluminum alloy materials.

    PubMed

    Kohara, Ichitaro; Tomoda, Hideyuki; Watanabe, Shoji

    2007-01-01

    Water-soluble metal working fluids are used for processing of aluminum alloy materials. This short paper describes properties of new additives for water-soluble cutting fluids for aluminum alloy materials. Some alkyldiphosphonic acids were prepared with known method. Amine salts of these phosphonic acids showed anti-corrosion property for aluminum alloy materials. However, they have no hard water tolerance. Monoesters of octylphosphonic acid were prepared by the reaction of octylphosphonic acid dichloride with various alcohols in the presence of triethylamine. Amine salts of monoester of octylphosphonic acid with diethyleneglycol monomethyl ether, ethyleneglycol monomethyl ether and triethyleneglycol monomethyl ether showed both of a good anti-corrosion property for aluminum alloy materials and hard water tolerance.

  7. The Use of Additional GPS Frequencies to Independently Determine Tropospheric Water Vapor Profiles

    NASA Technical Reports Server (NTRS)

    Herman, B.M.; Feng, D.; Flittner, D. E.; Kursinski, E. R.

    2000-01-01

    It is well known that the currently employed L1 and L2 GPS/MET frequencies (1.2 - 1.6) Ghz) do not allow for the separation of water vapor and density (or temperature) from active microwave occultation measurements in regions of the troposphere warmer than 240 K Therefore, additional information must be used, from other types of measurements and weather analyses, to recover water vapor (and temperature) profiles. Thus in data sparse regions, these inferred profiles can be subject to larger errors than would result in data rich regions. The use of properly selected additional GPS frequencies enables a direct, independent measurement of the absorption associated with the water vapor profile, which may then be used in the standard GPS/MET retrievals to obtain a more accurate determination of atmospheric temperature throughout the water vapor layer. This study looks at the use of microwave crosslinks in the region of the 22 Ghz water vapor absorption line for this purpose. An added advantage of using 22 Ghz frequencies is that they are only negligibly affected by the ionosphere in contrast to the large effect at the GPS frequencies. The retrieval algorithm uses both amplitude and phase measurements to obtain profiles of atmospheric pressure, temperature and water water vapor pressure with a vertical resolution of 1 km or better. This technique also provides the cloud liquid water content along the ray path, which is in itself an important element in climate monitoring. Advantages of this method include the ability to make measurements in the presence of clouds and the use of techniques and technology proven through the GPS/MET experiment and several of NASA's planetary exploration missions. Simulations demonstrating this method will be presented for both clear and cloudy sky conditions.

  8. Switching phase separation mode by varying the hydrophobicity of polymer additives in solution-processed semiconducting small-molecule/polymer blends

    NASA Astrophysics Data System (ADS)

    He, Zhengran; Li, Dawen; Hensley, Dale K.; Rondinone, Adam J.; Chen, Jihua

    2013-09-01

    Lateral and vertical phase separations play critical roles in the performance of the next-generation organic and hybrid electronic devices. A method is demonstrated here to switch between lateral and vertical phase separations in semiconducting 6,13-bis(triisopropylsilylethynyl) pentacene (TIPSE pentacene)/polymer blend films by simply varying the alkyl length of the polyacrylate polymer component. The phase separation modes depend on intermolecular interactions between small molecule TIPSE pentancene and polymer additives. The blend film with a dominant vertical phase separation exhibits a significant enhancement in average mobility and performance consistency of organic thin-film transistors.

  9. Oxidative damage to DNA: counterion-assisted addition of water to ionized DNA.

    PubMed

    Barnett, Robert N; Bongiorno, Angelo; Cleveland, Charles L; Joy, Abraham; Landman, Uzi; Schuster, Gary B

    2006-08-23

    Oxidative damage to DNA, implicated in mutagenesis, aging, and cancer, follows electron loss that generates a radical cation that migrates to a guanine, where it may react with water to form 8-oxo-7,8-dihydroguanine (8-OxoG). Molecular dynamics and ab initio quantum simulations on a B-DNA tetradecamer reveal activated reaction pathways that depend on the local counterion arrangement. The lowest activation barrier, 0.73 eV, is found for a reaction that starts from a configuration where a Na(+) resides in the major groove near the N7 atoms of adjacent guanines, and evolves through a transition state where a bond between a water oxygen atom and a carbon atom forms concurrently with displacement of a proton toward a neighboring water molecule. Subsequently, a bonded complex of a hydronium ion and the nearest backbone phosphate group forms. This counterion-assisted proton shuttle mechanism is supported by experiments exploiting selective substitution of backbone phosphates by methylphosphonates.

  10. [A study of brain inner tissue water molecule self-diffusion model based on Monte Carlo simulation].

    PubMed

    Wu, Zhanxiong; Zhu, Shanan; Bin, He

    2010-06-01

    The study of water molecule self-diffusion process is of importance not only for getting anatomical information of brain inner tissue, but also for shedding light on the diffusion process of some medicine in brain tissue. In this paper, we summarized the self-diffusion model of water molecule in brain inner tissue, and calculated the self-diffusion coefficient based on Monte Carlo simulation under different conditions. The comparison between this result and that of Latour model showed that the two self-diffusion coefficients were getting closer when the diffusion time became longer, and that the Latour model was a long time-depended self-diffusion model.

  11. Thermodynamic properties of water in the lattice gas model with consideration of the vibrational motions of molecules

    NASA Astrophysics Data System (ADS)

    Titov, S. V.; Tovbin, Yu. K.

    2016-11-01

    A molecular model developed earlier for a polar fluid within the lattice gas model is supplemented by considering the vibrational motions of molecules using water as an example. A combination of point dipole and Lennard-Jones potentials from SPC parametrization is chosen as the force field model for the molecule. The main thermodynamic properties of liquid water (density, internal energy, and entropy) are studied as functions of temperature. There is qualitative agreement between the calculation results and the experimental data. Ways of refining the molecular theory are discussed.

  12. Hydration of gelatin molecules in glycerol-water solvent and phase diagram of gelatin organogels.

    PubMed

    Sanwlani, Shilpa; Kumar, Pradip; Bohidar, H B

    2011-06-09

    We present a systematic investigation of hydration and gelation of the polypeptide gelatin in water-glycerol mixed solvent (glycerol solutions). Raman spectroscopy results indicated enhancement in water structure in glycerol solutions and the depletion of glycerol density close to hydration sheath of the protein molecule. Gelation concentration (c(g)) was observed to decrease from 1.92 to 1.15% (w/v) while the gelation temperature (T(g)) was observed to increase from 31.4 to 40.7 °C with increase in glycerol concentration. Data on hand established the formation of organogels having interconnected networks, and the universal gelation mechanism could be described through an anomalous percolation model. The viscosity of sol diverged as η ∼ (1 - c(g)/c)(-k) as c(g) was approached from below (c < c(g)), while the elastic storage modulus grew as G' ∼ (c/c(g) - 1)(t) (for c > c(g)). It is important to note that values determined for critical exponents k and t were universal; that is, they did not depend on the microscopic details. The measured values were k = 0.38 ± 0.10 and t = 0.92 ± 0.17 whereas the percolation model predicts k = 0.7-1.3 and t = 1.9. Isothermal frequency sweep studies showed power-law dependence of gel storage modulus (G') and loss modulus (G'') on oscillation frequency ω given as G'(ω) ∼ ω(n') and G''(ω) ∼ ω(n''), and consistent with percolation model prediction it was found that n' ≈ n'' ≈ δ ≈ 0.73 close to gelation concentration. We propose a unique 3D phase diagram for the gelatin organogels. Circular dichroism data revealed that the gelatin molecules retained their biological activity in these solvents. Thus, it is shown that the thermomechanical properties of these organogels could be systematically tuned and customized as per application requirement.

  13. Acidification of East Siberian Arctic Shelf waters through addition of freshwater and terrestrial carbon

    NASA Astrophysics Data System (ADS)

    Semiletov, Igor; Pipko, Irina; Gustafsson, Örjan; Anderson, Leif G.; Sergienko, Valentin; Pugach, Svetlana; Dudarev, Oleg; Charkin, Alexander; Gukov, Alexander; Bröder, Lisa; Andersson, August; Spivak, Eduard; Shakhova, Natalia

    2016-05-01

    Ocean acidification affects marine ecosystems and carbon cycling, and is considered a direct effect of anthropogenic carbon dioxide uptake from the atmosphere. Accumulation of atmospheric CO2 in ocean surface waters is predicted to make the ocean twice as acidic by the end of this century. The Arctic Ocean is particularly sensitive to ocean acidification because more CO2 can dissolve in cold water. Here we present observations of the chemical and physical characteristics of East Siberian Arctic Shelf waters from 1999, 2000-2005, 2008 and 2011, and find extreme aragonite undersaturation that reflects acidity levels in excess of those projected in this region for 2100. Dissolved inorganic carbon isotopic data and Markov chain Monte Carlo simulations of water sources using salinity and δ18O data suggest that the persistent acidification is driven by the degradation of terrestrial organic matter and discharge of Arctic river water with elevated CO2 concentrations, rather than by uptake of atmospheric CO2. We suggest that East Siberian Arctic Shelf waters may become more acidic if thawing permafrost leads to enhanced terrestrial organic carbon inputs and if freshwater additions continue to increase, which may affect their efficiency as a source of CO2.

  14. Vaporization Mechanisms of Water-Insoluble Cs in Ash During Thermal Treatment with Calcium Chloride Addition.

    PubMed

    Jiao, Facun; Iwata, Norie; Kinoshita, Norikazu; Kawaguchi, Masato; Asada, Motoyuki; Honda, Maki; Sueki, Keisuke; Ninomiya, Yoshihiko

    2016-12-20

    The vaporization mechanisms of water-insoluble Cs in raw ash and Cs-doped ash during thermal treatment with CaCl2 addition was systematically examined in a lab-scale electrical heating furnace over a temperature range of 500-1500 °C. The results indicate that the water-insoluble Cs in the ash was associated with aluminosilicate as pollucite. Addition of 10% CaCl2 caused the maximum vaporization ratio of Cs in the raw ash to reach approximately 80% at temperatures higher than 1200 °C, whereas approximately 95% of Cs was vaporized at temperatures higher than 1300 °C when 30% CaCl2 was added. The formation of an intermediate compound, CsCaCl3, through the chemical reaction of Cs with CaCl2 was responsible for Cs vaporization by means of the subsequent decomposition of this intermediate upon the increase in temperature. The indirect chlorination of Cs by the gaseous chlorine released from the decomposition of CaCl2 was insignificant. A high CaCl2 content in the resulting annealed products with 30% CaCl2 addition delayed the decomposition of CsCaCl3 and thus lowered the Cs vaporization ratio compared to that with 10% CaCl2 addition at 900-1250 °C. Thermal treatment with CaCl2 addition is a proposed method to remove Cs from Cs-contaminated incineration ash.

  15. Photodissociation of HBr molecules in clusters: from rare gas clusters to water nanoparticles

    NASA Astrophysics Data System (ADS)

    Fárník, M.; Buck, Udo

    2007-09-01

    Experiments on the photodissociation of molecules in different cluster environments are described and illustrated based on the example of HBr molecules photolysed at 193 nm in various clusters. The photolysis of HBr molecules incorporated in the hydrogen bonded network of (HBr)n clusters exhibits pronounced direct exits of the H-fragments. On the other hand, the H-fragments from HBr molecules bound by much weaker van der Waals forces at the surface of large Arn clusters are trapped efficiently by the cluster cage. These observations are mainly explained by the geometry of the molecule bound to the cluster. The HBr molecules deposited on the large (H2O)n clusters behave quite differently. They undergo acid dissociation and the resulting zwitterionic form is excited by the radiation giving rise to the generation of the hydronium H3O molecule and its subsequent dissociation.

  16. Nano-porous pottery using calcined waste sediment from tap water production as an additive.

    PubMed

    Sangsuk, Supin; Khunthon, Srichalai; Nilpairach, Siriphan

    2010-10-01

    A suspension of sediment from a lagoon in a tap water production plant was collected for this experiment. The suspension was spray dried and calcined at 700 °C for 1 h. After calcining, 30 wt.% of the sediment were mixed with pottery clay. Samples with and without calcined sediment were sintered at 900, 1000 and 1100 °C. The results show that calcined sediment can be used as an additive in pottery clay. The samples with calcined sediment show higher porosity, water absorption and flexural strength, especially for 900 and 1000 °C. At 900 °C, samples with calcined sediment show a porosity of 50% with an average pore size of 68 nm, water absorption of 31% and flexural strength of 12.61 MPa.

  17. State of water molecules and silanol groups in opal minerals: a near infrared spectroscopic study of opals from Slovakia

    NASA Astrophysics Data System (ADS)

    Boboň, Miroslav; Christy, Alfred A.; Kluvanec, Daniel; Illášová, L'udmila

    2011-12-01

    Recently, near infrared spectroscopy in combination with double derivative technique has been effectively used by Christy (Vib Spectrosc 54:42-49, 2010) to study and differentiate between free and hydrogen bonded silanol groups on silica gel surface. The method has given some insight into the type of functionalities, their location in silica gel samples, and the way the water molecules bind onto the silanol groups. The important information in this respect comes from the overtones of the OH groups of water molecules hydrogen-bonded to free silanol groups, and hydrogen-bonded silanol groups absorbing in the region 5,500-5,100 cm-1. Chemically, opal minerals are hydrated silica and the same approach was adapted to study the state of water molecules, silanol functionalities, and their locations in opal samples from Slovakia. Twenty opal samples classified into CT and A classes and one quartz sample were used in this work. The samples were crushed using a hydraulic press and powderized. Each sample was then subjected to evacuation process to remove surface-adsorbed water at 200°C, and the near infrared spectrum of each sample was measured using a Perkin Elmer NTS FT-NIR spectrometer equipped with a transflectance accessory and a DTGS detector. The samples were also heated to 750°C to remove the hydrogen-bonded silanol groups on the surface to reveal their locality. Second derivative profiles of the near infrared reflectance spectra were obtained using the instrument's software and used in the detailed analysis of the samples. The analysis of the near infrared spectra and their second derivative profiles had the aim in finding relationships between the surface chemical structure and the classification of opal samples. The dry opal samples were also tested for their surface adsorption effectivity toward water molecules. The results indicate that the opal samples contain (1) surface-adsorbed water, (2) free and hydrogen-bonded silanol groups on the surface, (3) trapped

  18. The acid-base impact of free water removal from, and addition to, plasma.

    PubMed

    Haskins, Steve C; Hopper, Kate; Rezende, Marlis L

    2006-03-01

    Water, compared with plasma at a pH of 7.4, is a weak acid. The addition of free water to a patient should have an acidifying effect (dilutional acidosis) and the removal of it, an alkalinizing effect (concentrational alkalosis). The specific effects of free water loss or gain in a relatively complex fluid such as plasma has, to the authors' knowledge, not been reported. This information would be useful in the interpretation of the effect of changes in free water in patients. Plasma samples from goats were either evaporated in a tonometer to 80% of baseline volume or hydrated by the addition of distilled water to 120% of baseline volume. The pH and partial pressure of carbon dioxide, sodium, potassium, ionized calcium, chloride, lactate, phosphorous, albumin, and total protein concentrations were measured. Actual base excess (ABE), standard bicarbonate, anion gap, strong ion difference, strong ion gap, unmeasured anions, and the effects of sodium, chloride, phosphate, and albumin changes on ABE were calculated. Most parameters changed 20% in proportion to the magnitude of dehydration or hydration. Bicarbonate concentration, however, increased only 11% in the evaporation trial and decreased only -2% in the dehydration trial. The evaporation trial was associated with a mild, but significant, metabolic alkalotic effect (ABE increased 3.2 mM/L), whereas the hydration trial was associated with a slight, insignificant metabolic acidotic effect (ABE decreased only 0.6 mM/L). The calculated free water ABE effect (change in sodium concentration) was offset by opposite changes in calculated chloride, lactate, phosphate, and albumin ABE effects.

  19. The methods of receiving coal water suspension and its use as the modifying additive in concrete

    NASA Astrophysics Data System (ADS)

    Buyantuyev, S. L.; Urkhanova, L. A.; Lkhasaranov, S. A.; Stebenkova, Y. Y.; Khmelev, A. B.; Kondratenko, A. S.

    2017-01-01

    Results of research of the coal water suspension (CWS) from a cake received in the electrodigit ways in the fluid environment and gas are given in article and also the possibilities of its use as the modifying additive in concrete are considered. Use of a coal cake is perspective as it is a withdrawal of the coal and concentrating enterprises and has extremely low cost. Methods of receiving CWS and possibility of formation of carbon nanomaterials (CNM) are given in their structure. Research and the analysis of a microstructure of a surface of exemplars before electrodigit processing, their element structure, dependence of durability of a cement stone on a look and quantity of an additive of CWS is conducted. For modification of cement the carbon nanomaterials received from the following exemplars of water coal suspensions were used: foams from a cake from a scrubber of the plasma modular reactor, coal water suspension from a cake from electrodigit installation. The product which can find further application for a power engineering as fuel for combustion, and also in structural materials science, in particular, as the modifying additive in concrete allows to receive these methods.

  20. Association of Catechin Molecules in Water: Quantitative Binding Study and Complex Structure Analysis.

    PubMed

    Ujihara, Tomomi; Hayashi, Nobuyuki

    2016-01-22

    Associations between catechin molecules were investigated by (1)H NMR titration experiments. Eight green tea catechins formed self-assembled dimers in water, and gallate-type catechins had a greater tendency to self-associate than non-gallate-type catechins. All eight catechins also associated as 1:1 heterodimer complexes. Investigation of complex formation of epigallocatechin-3-O-gallate (EGCg) and epigallocatechin (EGC) with the other catechins showed that the affinity between EGCg and 2,3-trans-gallate-type catechins was remarkably high, and the binding affinity of EGCg for ECg was also rather strong. In contrast, the non-gallate-type catechin EGC exhibited generally low binding affinity for other catechins. Structural analyses of the complexes by ROESY experiments and density functional theory calculations demonstrated that the higher binding abilities of gallate-type catechins are due to providing multiple intermolecular interactions that remain effective in an aqueous environment, such as aromatic/aromatic or CH/π interactions.

  1. The effect on structural and solvent water molecules of substrate binding to ferric horseradish peroxidase.

    PubMed

    Simpson, Niall; Adamczyk, Katrin; Hithell, Gordon; Shaw, Daniel J; Greetham, Gregory M; Towrie, Michael; Parker, Anthony W; Hunt, Neil T

    2015-01-01

    Ultrafast, multi-dimensional infrared spectroscopy, in the form of 2D-IR and pump-probe measurements, has been employed to investigate the effect of substrate binding on the structural dynamics of the horseradish peroxidase (HRP) enzyme. Using nitric oxide bound to the ferric haem of HRP as a sensitive probe of local dynamics, we report measurements of the frequency fluctuations (spectral diffusion) and vibrational lifetime of the NO stretching mode with benzohydroxamic acid (BHA) located in the substrate-binding position at the periphery of the haem pocket, in both D2O and H2O solvents. The results reveal that, with BHA bound to the enzyme, the local structural dynamics are insensitive to H/D exchange. These results are in stark contrast to those found in studies of the substrate-free enzyme, which demonstrated that the local chemical and dynamic environment of the haem ligand is influenced by water molecules. In light of the large changes in solvent accessibility caused by substrate binding, we discuss the potential for varying roles for the solvent in the haem pocket of HRP at different stages along the reaction coordinate of the enzymatic mechanism.

  2. Two-dimensional description of surface-bounded exospheres with application to the migration of water molecules on the Moon

    NASA Astrophysics Data System (ADS)

    Schorghofer, Norbert

    2015-05-01

    On the Moon, water molecules and other volatiles are thought to migrate along ballistic trajectories. Here, this migration process is described in terms of a two-dimensional partial differential equation for the surface concentration, based on the probability distribution of thermal ballistic hops. A random-walk model, a corresponding diffusion coefficient, and a continuum description are provided. In other words, a surface-bounded exosphere is described purely in terms of quantities on the surface, which can provide computational and conceptual advantages. The derived continuum equation can be used to calculate the steady-state distribution of the surface concentration of volatile water molecules. An analytic steady-state solution is obtained for an equatorial ring; it reveals the width and mass of the pileup of molecules at the morning terminator.

  3. Nitrification in lake sediment with addition of drinking water treatment residuals.

    PubMed

    Wang, Changhui; Liu, Juanfeng; Wang, Zhixin; Pei, Yuansheng

    2014-06-01

    Drinking water treatment residuals (WTRs), non-hazardous by-products generated during potable water production, can effectively reduce the lake internal phosphorus (P) loading and improve water quality in lakes. It stands to reason that special attention regarding the beneficial reuse of WTRs should be given not only to the effectiveness of P pollution control, but also to the effects on the migration and transformation of other nutrients (e.g., nitrogen (N)). In this work, based on laboratory enrichment tests, the effects of WTRs addition on nitrification in lake sediment were investigated using batch tests, fluorescence in situ hybridization, quantitative polymerase chain reaction and phylogenetic analysis techniques. The results indicated that WTRs addition had minor effects on the morphologies of AOB and NOB; however, the addition slightly enhanced the sediment nitrification potential from 12.8 to 13.2 μg-N g(-1)-dry sample h(-1) and also increased the ammonia oxidation bacteria (AOB) and nitrite oxidizing bacteria (NOB) abundances, particularly the AOB abundances (P < 0.05), which increased from 1.11 × 10(8) to 1.31 × 10(8) copies g(-1)-dry sample. Moreover, WTRs addition was beneficial to the enrichment of Nitrosomonas and Nitrosospira multiformis and promoted the emergence of a new Nitrospira cluster, causing the increase in AOB and NOB diversities. Further analysis showed that the variations of nitrification in lake sediment after WTRs addition were primarily due to the decrease of bioavailable P, the introduction of new nitrifiers and the increase of favorable carriers for microorganism attachment in sediments. Overall, these results suggested that WTRs reuse for the control of lake internal P loading would also lead to conditions that are beneficial to nitrification.

  4. The influence of compost addition on the water repellency of brownfield soils

    NASA Astrophysics Data System (ADS)

    Whelan, Amii; Kechavarzi, Cedric; Sakrabani, Ruben; Coulon, Frederic; Simmons, Robert; Wu, Guozhong

    2010-05-01

    Compost application to brownfield sites, which can facilitate the stabilisation and remediation of contaminants whilst providing adequate conditions for plant growth, is seen as an opportunity to divert biodegradable wastes from landfill and put degraded land back into productive use. However, although compost application is thought to improve soil hydraulic functioning, there is a lack of information on the impact of large amounts of compost on soil water repellency. Water repellency in soils is attributed to the accumulation of hydrophobic organic compounds released as root exudates, fungal and microbial by-products and decomposition of organic matter. It has also been shown that brownfield soils contaminated with petroleum-derived organic contaminants can exhibit strong water repellency, preventing the rapid infiltration of water and leading potentially to surface run off and erosion of contaminated soil. However, hydrophobic organic contaminants are known to become sequestrated by partitioning into organic matter or diffusing into nano- and micropores, making them less available over time (ageing). The effect of large amounts of organic matter addition through compost application on the water repellency of soils contaminated with petroleum-derived organic contaminants requires further investigation. We characterised the influence of compost addition on water repellency in the laboratory by measuring the Water Drop Penetration Time (WDPT), sorptivity and water repellency index through infiltration experiments on soil samples amended with two composts made with contrasting feedstocks (green waste and predominantly meat waste). The treatments consisted of a sandy loam, a clay loam and a sandy loam contaminated with diesel fuel and aged for 3 years, which were amended with the two composts at a rate equivalent to 750t/ha. In addition core samples collected from a brownfield site, amended with compost at three different rates (250, 500 and 750t/ha) in 2007, were

  5. Isomerization of HNO to HON in the singlet state assisted by amino acid residues and/or water molecules

    NASA Astrophysics Data System (ADS)

    Shi, Junyou; Li, Ping; Bu, Yuxiang; Wang, Weihua; Mou, Zhaoxia; Song, Rui

    The effects of amino acid residues in the presence or absence of water molecules on the isomerization of the singlet state of HNO/HON have been systematically investigated at the B3LYP/6-311++G** level of theory. The structural characteristics, proton transfer (PT) mechanisms, and the corresponding thermodynamic and kinetic parameters, have been discussed, respectively. All the optimized complexes have been characterized by the ring structures through the intermolecular H-bonds. The origin of the increase in N bond H stretching frequency (blue shifts) occurring in the reactants has also been investigated using the natural bonding orbital (NBO) analyses, which is mainly attributed to the decrease of the electron densities in the antibonding orbital of the N bond H bonds as well as the increase of the polarization of the N bond H bond. All the PTs proceed with the concerted mechanisms since no ionic intermediates have been located during PT processes. At the same time, the cooperative effects of amino acid residues and water molecules on the selected PT processes have been observed, where the PTs assisted solely by the selected residues cannot occur without the participation of the water molecule. Overall, the introductions of one or two water molecules are more favorable for the isomerization of HNO assisted by the amino acid residues.

  6. Suppression of methane/air explosion by ultrafine water mist containing sodium chloride additive.

    PubMed

    Cao, Xingyan; Ren, Jingjie; Zhou, Yihui; Wang, Qiuju; Gao, Xuliang; Bi, Mingshu

    2015-03-21

    The suppression effect of ultrafine mists on methane/air explosions with methane concentrations of 6.5%, 8%, 9.5%, 11%, and 13.5% were experimentally studied in a closed visual vessel. Ultrafine water/NaCl solution mist as well as pure water mist was adopted and the droplet sizes of mists were measured by phase doppler particle analyzer (PDPA). A high speed camera was used to record the flame evolution processes. In contrast to pure water mist, the flame propagation speed, the maximum explosion overpressure (ΔP(max)), and the maximum pressure rising rate ((dP/dt)max) decreased significantly, with the "tulip" flame disappearing and the flame getting brighter. The results show that the suppressing effect on methane explosion by ultrafine water/NaCl solution mist is influenced by the mist amount and methane concentration. With the increase of the mist amount, the pressure, and the flame speed both descended significantly. And when the mist amount reached 74.08 g/m(3) and 37.04 g/m(3), the flames of 6.5% and 13.5% methane explosions can be absolutely suppressed, respectively. All of results indicate that addition of NaCl can improve the suppression effect of ultrafine pure water mist on the methane explosions, and the suppression effect is considered due to the combination effect of physical and chemical inhibitions.

  7. Retardation of crystallization-induced destabilization of PMF-in-water emulsion with emulsifier additives.

    PubMed

    Arima, Satoshi; Ueji, Toshiyuki; Ueno, Satoru; Ogawa, Akihiro; Sato, Kiyotaka

    2007-03-15

    An oil-in-water (O/W) emulsion, in which the oil phase is semi-solid fat, is easily destabilized when stored below the crystallization temperature of the oil phase. Such destabilization, characterized by loss of fluidity at chilled temperature and oil-water separation after re-heating, is caused by inter-droplet bridging of fat crystals protruding out of the emulsion droplets. In the present study, we found that the simultaneous use of additives of highly hydrophobic sucrose oligoester (SOE; P-170) and highly hydrophilic SOE (P-1670) containing palmitic acid moiety remarkably retarded the crystallization-induced destabilization of the O/W emulsion that contains palm-mid-fraction (PMF) as the oil phase. Without the additives, destabilization occurred when the emulsion was cooled from 60 to 0 degrees C and kept at 0 degrees C for 1 day. Microscopic observation revealed that destabilization was caused by coalescence of the oil droplets, which was triggered by the growth of needle-shaped PMF crystals protruding out of the emulsion membranes. However, the addition of P-170 to PMF increased the crystallization temperature of PMF and at the same time retarded the destabilization. Furthermore, the simultaneous addition of P-170 and P-1670 retarded the crystallization-induced destabilization even more. Optical observation, DSC, and synchrotron radiation X-ray diffraction measurements indicated that the P-170 additive enhanced interfacial heterogeneous crystallization to form tiny PMF crystals in the droplets, and that the P-1670 additive retarded morphological change of the PMF crystals into long needle shapes in association with polymorphic transformation from alpha to beta'.

  8. A water soluble additive to suppress respirable dust from concrete-cutting chainsaws: a case study.

    PubMed

    Summers, Michael P; Parmigiani, John P

    2015-01-01

    Respirable dust is of particular concern in the construction industry because it contains crystalline silica. Respirable forms of silica are a severe health threat because they heighten the risk of numerous respirable diseases. Concrete cutting, a common work practice in the construction industry, is a major contributor to dust generation. No studies have been found that focus on the dust suppression of concrete-cutting chainsaws, presumably because, during normal operation water is supplied continuously and copiously to the dust generation points. However, there is a desire to better understand dust creation at low water flow rates. In this case study, a water-soluble surfactant additive was used in the chainsaw's water supply. Cutting was performed on a free-standing concrete wall in a covered outdoor lab with a hand-held, gas-powered, concrete-cutting chainsaw. Air was sampled at the operator's lapel, and around the concrete wall to simulate nearby personnel. Two additive concentrations were tested (2.0% and 0.2%), across a range of fluid flow rates (0.38-3.8 Lpm [0.1-1.0 gpm] at 0.38 Lpm [0.1 gpm] increments). Results indicate that when a lower concentration of additive is used exposure levels increase. However, all exposure levels, once adjusted for 3 hours of continuous cutting in an 8-hour work shift, are below the Occupational Safety and Health Administration (OSHA) permissible exposure limit (PEL) of 5 mg/m(3). Estimates were made using trend lines to predict the fluid flow rates that would cause respirable dust exposure to exceed both the OSHA PEL and the American Conference of Governmental Industrial Hygienists (ACGIH®) threshold limit value (TLV).

  9. Enhancement of nitrate removal at the sediment-water interface by carbon addition plus vertical mixing.

    PubMed

    Chen, Xuechu; He, Shengbing; Zhang, Yueping; Huang, Xiaobo; Huang, Yingying; Chen, Danyue; Huang, Xiaochen; Tang, Jianwu

    2015-10-01

    Wetlands and ponds are frequently used to remove nitrate from effluents or runoffs. However, the efficiency of this approach is limited. Based on the assumption that introducing vertical mixing to water column plus carbon addition would benefit the diffusion across the sediment-water interface, we conducted simulation experiments to identify a method for enhancing nitrate removal. The results suggested that the sediment-water interface has a great potential for nitrate removal, and the potential can be activated after several days of acclimation. Adding additional carbon plus mixing significantly increases the nitrate removal capacity, and the removal of total nitrogen (TN) and nitrate-nitrogen (NO3(-)-N) is well fitted to a first-order reaction model. Adding Hydrilla verticillata debris as a carbon source increased nitrate removal, whereas adding Eichhornia crassipe decreased it. Adding ethanol plus mixing greatly improved the removal performance, with the removal rate of NO3(-)-N and TN reaching 15.0-16.5 g m(-2) d(-1). The feasibility of this enhancement method was further confirmed with a wetland microcosm, and the NO3(-)-N removal rate maintained at 10.0-12.0 g m(-2) d(-1) at a hydraulic loading rate of 0.5 m d(-1).

  10. Poly(ether ester) Ionomers as Water-Soluble Polymers for Material Extrusion Additive Manufacturing Processes.

    PubMed

    Pekkanen, Allison M; Zawaski, Callie; Stevenson, André T; Dickerman, Ross; Whittington, Abby R; Williams, Christopher B; Long, Timothy E

    2017-04-12

    Water-soluble polymers as sacrificial supports for additive manufacturing (AM) facilitate complex features in printed objects. Few water-soluble polymers beyond poly(vinyl alcohol) enable material extrusion AM. In this work, charged poly(ether ester)s with tailored rheological and mechanical properties serve as novel materials for extrusion-based AM at low temperatures. Melt transesterification of poly(ethylene glycol) (PEG, 8k) and dimethyl 5-sulfoisophthalate afforded poly(ether ester)s of sufficient molecular weight to impart mechanical integrity. Quantitative ion exchange provided a library of poly(ether ester)s with varying counterions, including both monovalent and divalent cations. Dynamic mechanical and tensile analysis revealed an insignificant difference in mechanical properties for these polymers below the melting temperature, suggesting an insignificant change in final part properties. Rheological analysis, however, revealed the advantageous effect of divalent countercations (Ca(2+), Mg(2+), and Zn(2+)) in the melt state and exhibited an increase in viscosity of two orders of magnitude. Furthermore, time-temperature superposition identified an elevation in modulus, melt viscosity, and flow activation energy, suggesting intramolecular interactions between polymer chains and a higher apparent molecular weight. In particular, extrusion of poly(PEG8k-co-CaSIP) revealed vast opportunities for extrusion AM of well-defined parts. The unique melt rheological properties highlighted these poly(ether ester) ionomers as ideal candidates for low-temperature material extrusion additive manufacturing of water-soluble parts.

  11. Dendrite-Free Li Deposition Using Trace-Amounts of Water as an Electrolyte Additive

    SciTech Connect

    Qian, Jiangfeng; Xu, Wu; Bhattacharya, Priyanka; Engelhard, Mark H.; Henderson, Wesley A.; Zhang, Yaohui; Zhang, Jiguang

    2015-07-01

    Residual water presents in nonaqueous electrolytes has been widely regarded as a detrimental factor for lithium (Li) batteries. This is because water is highly reactive with the commonly used LiPF6 salt and leads to the formation of HF that corrodes battery materials. In this work, we demonstrate that a controlled trace-amount of water (25-100 ppm) can be an effective electrolyte additive for achieving dendrite-free Li metal deposition in LiPF6-based electrolytes and avoid its detrimental effect at the same time. Detailed analyses reveal that the trace amount of HF formed by the decomposition reaction of LiPF6 with water will be electrochemically reduced during initial Li deposition process to form a uniform and dense LiF-rich SEI layer on the surface of the substrate. This LiF-rich SEI layer leads to a uniform distribution of the electric field on the substrate surface and enables uniform and dendrite-free Li deposition. Meanwhile the detrimental effect of HF is diminished due to the consumption of HF in the LiF formation process. Microscopic analysis reveals that the as-deposited dendrite-free Li films exhibit a self-aligned and highly-compacted Li nanorods structure which is consistent with their charming blue color or known as structure color. These findings clearly demonstrate a novel approach to control the nucleation and grow process of Li metal films using well-controlled trace-amount of water. They also shine the light on the effect of water on other electrodeposition processes.

  12. Molecular interactions of organic molecules at the air/water interface investigated by sum frequency generation vibrational spectroscopy.

    PubMed

    Wang, Wenting; Ye, Shuji

    2017-02-08

    The molecular structure and dynamics of organic molecules at the aqueous interface have attracted a number of investigations owing to their importance and specific nature. However, there are relatively few studies on the direct characterization of the molecular interactions at the air/water interface because they are extremely difficult to measure in experiments. In this study, we use dibutyl ester molecules (R1CO2R2O2CR1) as a model of organic molecules, and investigate their molecular structure and interactions using sum frequency generation vibrational spectroscopy. We demonstrate that the molecular interactions can be estimated by measuring the intensity ratio of the symmetric stretching (ν1) and Fermi resonant bands (2ν2) of methyl groups. Here, dibutyl ester molecules are widely used as plasticizers in polymers to improve the properties of the plastics and polymers. It is found that the orientation angles of the tailed methyl groups at the air/water interface decrease from 34° to 19° when the chain length of R2 increases from 0 to 8. The total intermolecular interactions of the dibutyl ester molecules decrease as the chain length of R2 increases because the van der Waals interactions between the hydrocarbon chains increase, while the hydrogen bond interactions between the carbonyl group and water molecules decrease. Our study demonstrates the stability of ester-based plasticizers in polymers can be well predicted from the intensity ratio of the ν1 and 2ν2 bands of methyl group. Such an intensity ratio can be thus used as an effective vibrational optical ruler for characterizing molecular interactions between plasticizers and polymers.

  13. Inhibition of Ostwald ripening in model beverage emulsions by addition of poorly water soluble triglyceride oils.

    PubMed

    McClements, David Julian; Henson, Lulu; Popplewell, L Michael; Decker, Eric Andrew; Choi, Seung Jun

    2012-01-01

    Beverage emulsions containing flavor oils that have a relatively high water-solubility are unstable to droplet growth due to Ostwald ripening. The aim of this study was to improve the stability of model beverage emulsions to this kind of droplet growth by incorporating poorly water-soluble triglyceride oils. High pressure homogenization was used to prepare a series of 5 wt% oil-in-water emulsions stabilized by modified starch that had different lipid phase compositions (orange oil : corn oil). Emulsions prepared using only orange oil as the lipid phase were highly unstable to droplet growth during storage, which was attributed to Ostwald ripening resulting from the relatively high water-solubility of orange oil. Droplet growth could be effectively inhibited by incorporating ≥ 10% corn oil into the lipid phase prior to homogenization. In addition, creaming was also retarded because the lipid phase density was closer to that of the aqueous phase density. These results illustrate a simple method of improving the physical stability of orange oil emulsions for utilization in the food, beverage, and fragrance industries.

  14. Extraction of Organic Molecules from Terrestrial Material: Quantitative Yields from Heat and Water Extractions

    NASA Technical Reports Server (NTRS)

    Beegle, L. W.; Abbey, W. A.; Tsapin, A. T.; Dragoi, D.; Kanik, I.

    2004-01-01

    In the robotic search for life on Mars, different proposed missions will analyze the chemical and biological signatures of life using different platforms. The analysis of samples via analytical instrumentation on the surface of Mars has thus far only been attempted by the two Viking missions. Robotic arms scooped relogith material into a pyrolysis oven attached to a GC/MS. No trace of organic material was found on any of the two different samples at either of the two different landing sites. This null result puts an upper limit on the amount of organics that might be present in Martian soil/rocks, although the level of detection for each individual molecular species is still debated. Determining the absolute limit of detection for each analytical instrument is essential so that null results can be understood. This includes investigating the trade off of using pyrolysis versus liquid solvent extraction to release organic materials (in terms of extraction efficiencies and the complexity of the sample extraction process.) Extraction of organics from field samples can be accomplished by a variety of methods such utilizing various solvents including HCl, pure water, supercritical fluid and Soxhelt extraction. Utilizing 6N HCl is one of the most commonly used method and frequently utilized for extraction of organics from meteorites but it is probably infeasible for robotic exploration due to difficulty of storage and transport. Extraction utilizing H2O is promising, but it could be less efficient than 6N HCl. Both supercritical fluid and Soxhelt extraction methods require bulky hardware and require complex steps, inappropriate for inclusion on rover spacecraft. This investigation reports the efficiencies of pyrolysis and solvent extraction methods for amino acids for different terrestrial samples. The samples studied here, initially created in aqueous environments, are sedimentary in nature. These particular samples were chosen because they possibly represent one of the

  15. The Formation of Oxygen-Containing Molecules in Liquid Water Environments on the Surface of Titan (Invited)

    NASA Astrophysics Data System (ADS)

    Neish, C.

    2010-12-01

    Saturn’s moon Titan represents a unique locale for studying prebiotic chemistry. Reactions occurring in its thick nitrogen - methane atmosphere produce a wide variety of organic molecules. Observations by the Voyager spacecraft found evidence for six gas-phase hydrocarbons and three nitriles, along with an enveloping haze layer shrouding the surface of the moon (Hanel et al., 1981; Kunde et al., 1981; Maguire et al., 1981). More recently, the INMS instrument on the Cassini spacecraft has found evidence for organic molecules up to its mass limit of 100 Da at altitudes as high as 1200 km (Waite et al., 2005; Vuitton et al. 2007). Laboratory experiments that simulate the reactions occurring in Titan’s atmosphere produce many of the same organic molecules observed by Voyager and Cassini, along with organic precipitates known as tholins. Tholins have the general formula CxHyNz and are spectrally similar to Titan’s haze (Khare et al., 1984). Though interesting from the point of view of organic chemistry, the molecules found in Titan’s atmosphere stop short of addressing questions related to the origins of life. Oxygen - a key element for most known biological molecules - is generally lacking in Titan’s atmosphere. The most abundant oxygenated molecule, CO, is present at only ~50 ppm (de Kok et al., 2007). However, if Titan’s atmospheric organic molecules mix with water found in cryovolcanic lavas or impact melts, they may react to produce oxygen-containing, prebiotic species. In this paper, I will show that reactions between Titan tholins and low temperature aqueous solutions produce a wide variety of oxygen-containing species. These reactions display first-order kinetic behaviour with half-lives between 0.4 to 7 days at 273 K (in water) and between 0.3 and 14 days at 253 K (in 13 wt. % ammonia-water). Tholin hydrolysis is thus very fast compared to the freezing timescales of impact melts and volcanic sites on Titan, which take hundreds to thousands of years

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

    PubMed

    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)]. 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/cm(3), 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 the outer shells. In these cases

  17. Computation of octanol-water partition coefficients by guiding an additive model with knowledge.

    PubMed

    Cheng, Tiejun; Zhao, Yuan; Li, Xun; Lin, Fu; Xu, Yong; Zhang, Xinglong; Li, Yan; Wang, Renxiao; Lai, Luhua

    2007-01-01

    We have developed a new method, i.e., XLOGP3, for logP computation. XLOGP3 predicts the logP value of a query compound by using the known logP value of a reference compound as a starting point. The difference in the logP values of the query compound and the reference compound is then estimated by an additive model. The additive model implemented in XLOGP3 uses a total of 87 atom/group types and two correction factors as descriptors. It is calibrated on a training set of 8199 organic compounds with reliable logP data through a multivariate linear regression analysis. For a given query compound, the compound showing the highest structural similarity in the training set will be selected as the reference compound. Structural similarity is quantified based on topological torsion descriptors. XLOGP3 has been tested along with its predecessor, i.e., XLOGP2, as well as several popular logP methods on two independent test sets: one contains 406 small-molecule drugs approved by the FDA and the other contains 219 oligopeptides. On both test sets, XLOGP3 produces more accurate predictions than most of the other methods with average unsigned errors of 0.24-0.51 units. Compared to conventional additive methods, XLOGP3 does not rely on an extensive classification of fragments and correction factors in order to improve accuracy. It is also able to utilize the ever-increasing experimentally measured logP data more effectively.

  18. Effects of nitrate addition on water column methylmercury in Occoquan Reservoir, Virginia, USA.

    PubMed

    Beutel, Marc W; Duvil, Ricardi; Cubas, Francisco J; Grizzard, Thomas J

    2017-03-01

    Mercury bioaccumulation in aquatic biota poses a widespread threat to human and environmental health. Methylmercury (MeHg), the toxic form of mercury, tends to build up under anaerobic conditions in the profundal zones of lakes. In this study we performed a two-year assessment of spatial and temporal patterns of dissolved oxygen, nitrate, MeHg, manganese (Mn) and iron (Fe) in Occoquan Reservoir, a large run-of-the-river drinking water reservoir in Virginia, USA. A tributary to the reservoir receives input of nitrate-rich tertiary-treated wastewater that enhances the oxidant capacity of bottom water. Multiple lines of evidence supported the hypothesis that the presences of nitrate and/or oxygen in bottom water correlated with low MeHg in bottom water. Bottom water MeHg was significantly lower in a nitrate-rich tributary (annual mean of 0.05 ng/L in both 2012 and 2013) compared to a nitrate-poor tributary (annual mean of 0.58 ng/L in 2012 and 0.21 ng/L in 2013). The presence of nitrate and oxygen in bottom water corresponded with significantly lower bottom water MeHg at an upstream station in the main reservoir (0.05 versus 0.11 ng/L in 2013). In 2012 the reservoir exhibited a longitudinal gradient with nitrate and oxygen decreasing and MeHg and Mn increasing downstream. In both study years, there was a clear threshold of oxygen equivalent (3-5 mg/L), a metric that combines the oxidant capacity of nitrate and oxygen, above which MeHg (<0.05 ng/L), Mn (<0.3 mg/L) and Fe (<0.5 mg/L) were low. Results indicated that the addition of nitrate-rich tertiary-treated wastewater to the bottom of anaerobic reservoirs can reduce MeHg concentrations, and potentially decrease mercury bioaccumulation, while increasing the safe water yield for potable use.

  19. Effects of salt or cosolvent addition on solubility of a hydrophobic solute in water: Relevance to those on thermal stability of a protein

    NASA Astrophysics Data System (ADS)

    Murakami, Shota; Hayashi, Tomohiko; Kinoshita, Masahiro

    2017-02-01

    The solubility of a nonpolar solute in water is changed upon addition of a salt or cosolvent. Hereafter, "solvent" is formed by water molecules for pure water, by water molecules, cations, and anions for water-salt solution, and by water and cosolvent molecules for water-cosolvent solution. Decrease and increase in the solubility, respectively, are ascribed to enhancement and reduction of the hydrophobic effect. Plenty of experimental data are available for the change in solubility of argon or methane arising from the addition. We show that the integral equation theory combined with a rigid-body model, in which the solute and solvent particles are modeled as hard spheres with different diameters, can reproduce the data for the following items: salting out by an alkali halide and salting in by tetramethylammonium bromide, increase in solubility by a monohydric alcohol, and decrease in solubility by sucrose or urea. The orders of cation or anion species in terms of the power of decreasing the solubility can also be reproduced for alkali halides. With the rigid-body model, the analyses are focused on the roles of entropy originating from the translational displacement of solvent particles. It is argued by decomposing the solvation entropy of a nonpolar solute into physically insightful constituents that the solvent crowding in the bulk is a pivotal factor of the hydrophobic effect: When the solvent crowding in the bulk becomes more serious, the effect is strengthened, and when it becomes less serious, the effect is weakened. It is experimentally known that the thermal stability of a protein is also influenced by the salt or cosolvent addition. The additions which decrease and increase the solubility of a nonpolar solute, respectively, usually enhance and lower the thermal stability. This suggests that the enhanced or reduced hydrophobic effect is also a principal factor governing the stability change. However, urea decreases the solubility but lowers the stability

  20. Reaction Kinetics of Water Molecules with Oxygen Vacancies on Rutile TiO2(110)

    SciTech Connect

    Petrik, Nikolay G.; Kimmel, Gregory A.

    2015-09-16

    The formation of bridging hydroxyls (OHb) via reactions of water molecules with oxygen vacancies (VO) on reduced TiO2(110) surfaces is studied using infrared reflection-absorption spectroscopy (IRAS), electron-stimulated desorption (ESD), and photon-stimulated desorption (PSD). Narrow IRAS peaks at 2737 cm-1 and 3711 cm-1 are observed for stretching vibrations of ODb and OHb on TiO2(110), respectively. IRAS measurements with s- and p-polarized light demonstrate that the bridging hydroxyls are oriented normal to the (110) surface. The IR peaks disappear after the sample is exposed to O2 or annealed in the temperature range of 400 – 600 K (correlating with the temperature at which pairs of OHb’s reform water and then desorb), which is consistent with their identification as bridging hydroxyls. We have studied the kinetics of water reacting with the vacancies by monitoring the formation of bridging hydroxyls (using IRAS) as a function of the annealing temperature for a small amount of water initially dosed on the TiO2(110) at low temperature. Separate experiments have also monitored the loss of water molecules (using water ESD) and vacancies (using the CO photooxidation reaction) due to the reactions of water molecules with the vacancies. All three techniques show that the reaction rate becomes appreciable for T > 150 K and that the reactions largely complete for T > 250 K. The temperature-dependent water-VO reaction kinetics are consistent with a Gaussian distribution of activation energies with Ea = 0.545 eV, ΔEa(FWHM) = 0.125 eV, and a “normal” prefactor, v = 1012 s-1. In contrast, a single activation energy with a physically reasonable prefactor does not fit the data well. Our experimental activation energy is close to theoretical estimates for the diffusion of water molecules along the Ti5c rows on the reduced TiO2

  1. Kinetic modeling of the oxidative degradation of additive free PE in bleach disinfected water

    NASA Astrophysics Data System (ADS)

    Mikdam, Aïcha; Colin, Xavier; Billon, Noëlle; Minard, Gaëlle

    2016-05-01

    The chemical interactions between PE and bleach were studied at 60°C in immersion in bleach solutions kept at a free chlorine concentration of 100 ppm and a pH of 5 or 7.2. It was found that the polymer undergoes a severe oxidation from the earliest weeks of exposure, in a superficial layer whose thickness (of about 50-70 µm) is almost independent of the pH value, although the superficial oxidation rate is faster in acidic than in neutral medium. Oxidation leads to the formation and accumulation of a large variety of carbonyl products (mostly ketones and carboxylic acids) and, after a few weeks, to a decrease in the average molar mass due to the large predominance of chain scissions over crosslinking. A scenario was elaborated for explaining such unexpected results. According to this scenario, the non-ionic molecules (Cl2 and ClOH) formed from the disinfectant in the water phase, would migrate deeply into PE and dissociate into highly reactive radicals (Cl• and HO•) in order to initiate a radical chain oxidation. A kinetic model was derived from this scenario for predicting the general trends of the oxidation kinetics and its dependence on environmental factors such as temperature, free chlorine concentration and pH. The validity of this model was successfully checked by comparing the numerical simulations with experimental data.

  2. [Calculation of the amount of free water molecules in aqueous solutions by means of spectral parameters from the terahertz frequency domain taking into account processes of screening].

    PubMed

    Pen'kov, N V; Iashin, V A; Fesenko, E E; Fesenko, E E

    2014-01-01

    In this paper we derive a formula to calculate the amount of free water molecules in solution. Physical values in this formula may be obtained by analyzing the spectra of aqueous solutions in the terahertz frequency range. Formula is derived on the basis of considering water polarization process in electric field. It is shown that without processes of shielding the electric field in the water calculations lead to very high estimation of a share of free water molecule.

  3. Effect of PAC addition on immersed ultrafiltration for the treatment of algal-rich water.

    PubMed

    Zhang, Yan; Tian, Jiayu; Nan, Jun; Gao, ShanShan; Liang, Heng; Wang, Meilian; Li, Guibai

    2011-02-28

    The aim of this study was to evaluate the effect of powdered activated carbon (PAC) addition on the treatment of algal-rich water by immersed ultrafiltration (UF), in terms of permeate quality and membrane fouling. Experiments were performed with a hollow-fiber polyvinyl chloride ultrafiltration membrane at a laboratory scale, 20-25°C and 10 L/(m(2) h) constant permeate flux. UF could achieve an absolute removal of Microcystis aeruginosa cells, but a poor removal of algogenic organic matter (AOM) released into water, contaminants responsible for severe membrane fouling. The addition of 4 g/L PAC to the immersed UF reactor significantly alleviated the development of trans-membrane pressure and enhanced the removal of dissovled organic carbon (by 10.9±1.7%), UV(254) (by 27.1±1.7%), and microcystins (expressed as MC-LR(eq), by 40.8±4.2%). However, PAC had little effect on the rejection of hydrophilic high molecular weight AOM such as carbohydrates and proteins. It was also identified that PAC reduced the concentrations of carbohydrates and proteins in the reactor due to decreased light intensity, as well as the MC-LR(eq) concentration by PAC adsorption.

  4. Additive method for the prediction of protein-peptide binding affinity. Application to the MHC class I molecule HLA-A*0201.

    PubMed

    Doytchinova, Irini A; Blythe, Martin J; Flower, Darren R

    2002-01-01

    A method has been developed for prediction of binding affinities between proteins and peptides. We exemplify the method through its application to binding predictions of peptides with affinity to major histocompatibility complex class I molecule HLA-A*0201. The method is named "additive" because it is based on the assumption that the binding affinity of a peptide could be presented as a sum of the contributions of the amino acids at each position and the interactions between them. The amino acid contributions and the contributions of the interactions between adjacent side chains and every second side chain were derived using a partial least squares (PLS) statistical methodology using a training set of 420 experimental IC50 values. The predictive power of the method was assessed using rigorous cross-validation and using an independent test set of 89 peptides. The mean value of the residuals between the experimental and predicted pIC50 values was 0.508 for this test set. The additive method was implemented in a program for rapid T-cell epitope search. It is universal and can be applied to any peptide-protein interaction where binding data is known.

  5. Degradation of bacterial quorum sensing signaling molecules by the microscopic yeast Trichosporon loubieri isolated from tropical wetland waters.

    PubMed

    Wong, Cheng-Siang; Koh, Chong-Lek; Sam, Choon-Kook; Chen, Jian Woon; Chong, Yee Meng; Yin, Wai-Fong; Chan, Kok-Gan

    2013-09-25

    Proteobacteria produce N-acylhomoserine lactones as signaling molecules, which will bind to their cognate receptor and activate quorum sensing-mediated phenotypes in a population-dependent manner. Although quorum sensing signaling molecules can be degraded by bacteria or fungi, there is no reported work on the degradation of such molecules by basidiomycetous yeast. By using a minimal growth medium containing N-3-oxohexanoylhomoserine lactone as the sole source of carbon, a wetland water sample from Malaysia was enriched for microbial strains that can degrade N-acylhomoserine lactones, and consequently, a basidiomycetous yeast strain WW1C was isolated. Morphological phenotype and molecular analyses confirmed that WW1C was a strain of Trichosporon loubieri. We showed that WW1C degraded AHLs with N-acyl side chains ranging from 4 to 10 carbons in length, with or without oxo group substitutions at the C3 position. Re-lactonisation bioassays revealed that WW1C degraded AHLs via a lactonase activity. To the best of our knowledge, this is the first report of degradation of N-acyl-homoserine lactones and utilization of N-3-oxohexanoylhomoserine as carbon and nitrogen source for growth by basidiomycetous yeast from tropical wetland water; and the degradation of bacterial quorum sensing molecules by an eukaryotic yeast.

  6. Degradation of Bacterial Quorum Sensing Signaling Molecules by the Microscopic Yeast Trichosporon loubieri Isolated from Tropical Wetland Waters

    PubMed Central

    Wong, Cheng-Siang; Koh, Chong-Lek; Sam, Choon-Kook; Chen, Jian Woon; Chong, Yee Meng; Yin, Wai-Fong; Chan, Kok-Gan

    2013-01-01

    Proteobacteria produce N-acylhomoserine lactones as signaling molecules, which will bind to their cognate receptor and activate quorum sensing-mediated phenotypes in a population-dependent manner. Although quorum sensing signaling molecules can be degraded by bacteria or fungi, there is no reported work on the degradation of such molecules by basidiomycetous yeast. By using a minimal growth medium containing N-3-oxohexanoylhomoserine lactone as the sole source of carbon, a wetland water sample from Malaysia was enriched for microbial strains that can degrade N-acylhomoserine lactones, and consequently, a basidiomycetous yeast strain WW1C was isolated. Morphological phenotype and molecular analyses confirmed that WW1C was a strain of Trichosporon loubieri. We showed that WW1C degraded AHLs with N-acyl side chains ranging from 4 to 10 carbons in length, with or without oxo group substitutions at the C3 position. Re-lactonisation bioassays revealed that WW1C degraded AHLs via a lactonase activity. To the best of our knowledge, this is the first report of degradation of N-acyl-homoserine lactones and utilization of N-3-oxohexanoylhomoserine as carbon and nitrogen source for growth by basidiomycetous yeast from tropical wetland water; and the degradation of bacterial quorum sensing molecules by an eukaryotic yeast. PMID:24072030

  7. Estimation of adsorption energy for water molecules on a multi-walled carbon nanotube thin film by measuring electric resistance

    NASA Astrophysics Data System (ADS)

    Kokabu, Takuya; Inoue, Shuhei; Matsumura, Yukihiko

    2016-11-01

    Gas sensors based on carbon nanotube (CNT) films have attracted attention owing to their low power consumption. For further development of these sensors, we need to understand the surface interaction of the films with gas molecules. In our previous research, we investigated the influence of water molecules on the electrical conductance of multi-walled CNT films and explained this phenomenon using a two-layer adsorption model. This work motivated us to measure the adsorption energy of CNT-H2O. In this study, we focused on the first-layer adsorption and investigated the sheet resistance to water vapor pressure at various temperatures using the transmission line method (TLM). The results were fitted to Langmuir adsorption model and the adsorption equilibrium constant was determined. The temperature dependence of the sheet resistance followed a model of fluctuation induced tunneling (FIT), in which the energy barrier at the CNT junction is regarded as the main factor influencing the electrical conductance of the CNT film. The sheet resistance and equilibrium constant decreased as temperature increased. This result was consistent with the adsorption phenomenon. Finally, the adsorption energy was determined to be 0.22-0.31 eV, which is larger than the previously calculated value. It was also reported that the adsorption energy of the gas molecules in the interstitial site between two carbon nanotubes was larger than that on the CNT surface. These results indicate that the CNT junction plays a key role in the detection of gas molecules.

  8. Self-assembly of neuroprotective carbazolium based small molecules at octane/water interface: A simulation investigation

    NASA Astrophysics Data System (ADS)

    Zolghadr, Amin Reza; Heydari Dokoohaki, Maryam

    2016-11-01

    The self-assembly of dibromocarbazole based small molecule (P7C3) and its analogues is studied at the octane/water interface by using molecular dynamics simulations. P7C3 protects newborn neurons from apoptotic cell death and enhances neurogenesis. The bromines on the carbazole appear particularly important, as the derivatives with dichloro and parent carbazole did not appear active at the concentrations tested. We are mainly focused on the question that why is dibromocarbazole derivative an effective neuroprotective drug, but not dichlorocarbazole or parent carbazole? It was found that P7C3 and P7C3-Cl were concentrated in the interfacial region, whereas the parent carbazole derivative were distributed throughout the water phase. The diffusion of P7C3 molecules in the interfacial region are higher than P7C3-Cl. This approach could use by experimentalist to evaluate the permeability of drug candidates prior to their synthesis.

  9. Heat transfer characteristics for some coolant additives used for water cooled engines

    SciTech Connect

    Abou-Ziyan, H.Z.; Helali, A.H.B.

    1996-12-31

    Engine coolants contain certain additives to prevent engine overheating or coolant freezing in cold environments. Coolants, also, contain corrosion and rust inhibitors, among other additives. As most engines are using engine cooling solutions, it is of interest to evaluate the effect of engine coolants on the boiling heat transfer coefficient. This has its direct impact on radiator size and environment. This paper describes the apparatus and the measurement techniques. Also, it presents the obtained boiling heat transfer results at different parameters. Three types of engine coolants and their mixtures in distilled water are evaluated, under sub-cooled and saturated boiling conditions. A profound effect of the presence of additives in the coolant, on heat transfer, was clear since changes of heat transfer for different coolants were likely to occur. The results showed that up to 180% improvement of boiling heat transfer coefficient is experienced with some types of coolants. However, at certain concentrations other coolants provide deterioration or not enhancement in the boiling heat transfer characteristics. This investigation proved that there are limitations, which are to be taken into consideration, for the composition of engine coolants in different environments. In warm climates, ethylene glycol should be kept at the minimum concentration required for dissolving other components, whereas borax is beneficial to the enhancement of the heat transfer characteristics.

  10. Matrix IR spectra and quantum-chemical calculations of the products of small nickel cluster interactions with water molecules

    NASA Astrophysics Data System (ADS)

    Serebrennikov, L. V.; Dalvyatshin, D. I.; Golovkin, A. V.

    2010-12-01

    Reactions of Ni n clusters with water molecules were studied by IR spectroscopy in inert matrices and quantum chemistry methods. The geometric configurations, total energies, and vibrational frequencies of all the possible Ni2(H2O) and Ni3(H2O) isomers were calculated. For both systems, the main minima and transition states were found. Water was shown to dissociate to hydrogen and hydroxyl in the reactions, and, in all the complexes formed, hydrogen is situated in the bridge position on the Ni-Ni bond.

  11. Facile synthesis of SrCO3 nanostructures in methanol/water solution without additives

    PubMed Central

    2012-01-01

    Highly dispersive strontium carbonate (SrCO3) nanostructures with uniform dumbbell, ellipsoid, and rod-like morphologies were synthesized in methanol solution without any additives. These SrCO3 were characterized by X-ray diffraction, field emission scanning electron microscopy, and N2 adsorption-desorption. The results showed that the reaction temperature and the methanol/water ratio had important effects on the morphologies of SrCO3 particles. The dumbbell-like SrCO3 exhibited a Broader-Emmett-Teller surface area of 14.9 m2 g−1 and an average pore size of about 32 nm with narrow pore size distribution. The formation mechanism of the SrCO3 crystal was preliminary presented. PMID:22704526

  12. Polymer Growth Rate in a Wire Chamber with Oxygen,Water, or Alcohol Gas Additives

    SciTech Connect

    Boyarski, Adam; /SLAC

    2008-07-02

    The rate of polymer growth on wires was measured in a wire chamber while the chamber was aged initially with helium-isobutane (80:20) gas, and then with either oxygen, water, or alcohol added to the gas. At the completion of the aging process for each gas mixture, the carbon content on the wires was measured in a SEM/EDX instrument. The same physical wires were used in all the gas mixtures, allowing measurement of polymer build up or polymer depletion by each gas additive. It is found that the rate of polymer growth is not changed by the presence of oxygen, water or alcohol. Conjecture that oxygen reduces breakdown by removing polymer deposits on field wires is negated by these measurements. Instead, it appears that the reduced breakdown is due to lower resistance in the polymer from oxygen ions being transported into the polymer. It is also observed that field wires bombarded by the electrons in the SEM and then placed back into the chamber show an abundance of single electrons being emitted, indicating that electron charge is stored in the polymer layer and that a high electric field is necessary to remove the charge.

  13. [Distribution of Phosphorus Forms in the Overlying Water Under Disturbance with the Addition of Algae].

    PubMed

    Chen, Jun; Li, Yong; Li, Da-peng; Huang, Yong; Zhu, Pei-ying

    2016-04-15

    Distribution of different phosphorus (P) forms in the overlying water and the contribution of different algae to the P disappearance were investigated under disturbance with the addition of algae (Microcystis aeruginosa and Selenastrum capricornutum, respectively). The sediments and overlying water were taken from Meiliang Bay in Taihu Lake. The results showed that the concentrations of total P (TP), dissolved total P (DTP), dissolved inorganic P (DIP) and biavailable P (BAP) decreased with and without disturbance. The uptake of DTP and DIP by Microcystis aeruginosa was better than that of Selenastrum capricornutum under the disturbance, but it was the opposite without the disturbance. The disappearance of P in the overlying water was attributed completely to the physico-chemical adsorption of the suspended solids and the uptake of algae. But the contribution of suspended solids and algae depended on the disturbance. The contribution of Microcystis aeruginosa and Selenastrum capricornutum to DTP and DIP absorption was about 60% without disturbance. However, the value was reduced to 40% (Microcystis aeruginosa) and 25% ( Selenastrum capricornutum) under the disturbance. Under the disturbance and the action of algae, the distribution of sedimentary P forms changed. NH4 Cl-P and Ca-P release and Fe/Al-P increase were observed with and without disturbance. The decrease of NH4 Cl-P and Ca-P and the increase of Fe/Al-P were more obvious with disturbance than without disturbance. Selenastrum capricornutum was favor of the release of Ca-P and the formation of Fe/Al-P.

  14. Long-term nitrogen additions and the intrinsic water-use efficiency of boreal Scots pine.

    NASA Astrophysics Data System (ADS)

    Marshall, John; Wallin, Göran; Linder, Sune; Lundmark, Tomas; Näsholm, Torgny

    2015-04-01

    Nitrogen fertilization nearly always increases productivity in boreal forests, at least in terms of wood production, but it is unclear how. In a mature (80 yrs. old) Scots pine forest in northern Sweden, we tested the extent to which nitrogen fertilization increased intrinsic photosynthetic water-use efficiency. We measured δ13C both discretely, in biweekly phloem sampling, and continuously, by monitoring of bole respiration. The original experiment was designed as a test of eddy covariance methods and is not therefore strictly replicated. Nonetheless, we compared phloem contents among fifteen trees from each plot and stem respiration from four per plot. The treatments included addition of 100 kg N/ha for eight years and a control. Phloem contents have the advantage of integrating over the whole canopy and undergoing complete and rapid turnover. Their disadvantage is that some have observed isotopic drift with transport down the length of the stem, presumably as a result of preferential export and/or reloading. We also measured the isotopic composition of stem respiration from four trees on each plot using a Picarro G1101-I CRDS attached to the vent flow from a continuous gas-exchange system. We detected consistent differences in δ13C between the treatments in phloem contents. Within each treatment, the phloem δ13C was negatively correlated with antecedent temperature (R2= 0.65) and no other measured climate variable. The isotopic composition of stem CO2 efflux will be compared to that of phloem contents. However, when converted to intrinsic water-use efficiency, the increase amounted to only about 4%. This is a small relative to the near doubling in wood production. Although we were able to detect a clear and consistent increase in water-use efficiency with N-fertilization, it constitutes but a minor cause of the observed increase in wood production.

  15. Control of water molecule aggregations in copper 1,4-cyclohexanedicarboxylate coordination polymers containing pyridyl-piperazine type ligands

    NASA Astrophysics Data System (ADS)

    Qiblawi, Sultan H.; LaDuca, Robert L.

    2014-01-01

    A series of layered divalent copper coordination polymers containing 1,4-cyclohexanedicarboxylate and long-spanning pyridyl-piperazine type ligands exhibits greatly different co-crystallized water molecule aggregations depending on the specific ligands used. Both [Cu(t-14cdc)(4-bpmp)]n (1, t-14cdc = trans-1,4-cyclohexanedicarboxylate, 4-bpmp = bis(4-pyridylmethyl)piperazine) and {[Cu(t-14cdc)(4-bpfp)(H2O)2]·6H2O}n (2, 4-bpfp = bis(4-pyridylformyl)piperazine) possess 2D (4,4) coordination polymer grids. However 1 lacks any co-crystallized water and has pinched grid apertures, while 2 manifests infinite water tapes with T6(2)4(2) classification and rectangular grid apertures. {[Cu2(c-14cdc)2(4-bpmp)]·2H2O}n (3, c-14cdc = cis-1,4-cyclohexanedicarboxylate) has [Cu2(c-14cdc)]2 ribbons with paddlewheel dimeric units linked into 2D slabs by 4-bpmp tethers, along with isolated water molecule pairs. In contrast, {[Cu2(c-14cdc)2(4-bpfp)]·10H2O}n (4) shows a very similar underlying coordination polymer topology but entrains unique decameric water molecule clusters. The minor product {[Cu2(c-14cdcH)2(t-1,4-cdc)(4-bpfp)2(H2O)2]·2H2O}n (5) was isolated along with 4; this compound underwent some in situ cis to trans cyclohexane-dicarboxylate ligand isomerization and exhibits a ladder polymer motif.

  16. Segmentation and additive approach: A reliable technique to study noncovalent interactions of large molecules at the surface of single-wall carbon nanotubes.

    PubMed

    Torres, Ana M; Scheiner, Steve; Roy, Ajit K; Garay-Tapia, Andrés M; Bustamante, John; Kar, Tapas

    2016-08-05

    This investigation explores a new protocol, named Segmentation and Additive approach (SAA), to study exohedral noncovalent functionalization of single-walled carbon nanotubes with large molecules, such as polymers and biomolecules, by segmenting the entire system into smaller units to reduce computational cost. A key criterion of the segmentation process is the preservation of the molecular structure responsible for stabilization of the entire system in smaller segments. Noncovalent interaction of linoleic acid (LA, C18 H32 O2 ), a fatty acid, at the surface of a (10,0) zigzag nanotube is considered for test purposes. Three smaller segmented models have been created from the full (10,0)-LA system and interaction energies were calculated for these models and compared with the full system at different levels of theory, namely ωB97XD, LDA. The success of this SAA is confirmed as the sum of the interaction energies is in very good agreement with the total interaction energy. Besides reducing computational cost, another merit of SAA is an estimation of the contributions from different sections of the large system to the total interaction energy which can be studied in-depth using a higher level of theory to estimate several properties of each segment. On the negative side, bulk properties, such as HOMO-LUMO (highest occupied molecular orbital - lowest occupied molecular orbital) gap, of the entire system cannot be estimated by adding results from segment models. © 2016 Wiley Periodicals, Inc.

  17. Excitation of water molecules by electron impact with formation of OH-radicals in the A2Σ+ state

    NASA Astrophysics Data System (ADS)

    Khodorkovskii, M. A.; Murashov, S. V.; Artamonova, T. O.; Rakcheeva, L. P.; Beliaeva, A. A.; Shakhmin, A. L.; Michael, D.; Timofeev, N. A.; Mel'nikov, A. S.; Shevkunov, I. A.; Zissis, G.

    2009-11-01

    The excitation cross-sections of the OH-radical band A2Σ+ → X2 (v' = 0 → v'' = 0, v' = 1 → v'' = 1) were measured. OH-radicals were formed during dissociation of water molecules by electron impact in the conditions of crossing of supersonic molecular and electron beams in the energy range 10-120 eV. Measurements were conducted at temperatures of 50, 80 and 200 K. It was shown that the excitation function had a sharp maximum in the region of low energies (at 16 eV) and an extended plateau up to 120 eV. It is proved that there are two channels of molecule dissociation with formation OH (A2Σ+) through excitation of either the triplet b3A1 or the singlet B1A1 states of H2O molecules. The form of the excitation function essentially depends on the temperature of water vapours in the beam. With the decrease of the water molecule temperature the height of the plateau in the region 30-120 eV decreases in comparison with that of the peak at 16 eV. The absolute value of the excitation cross-section of the OH band at the temperature 50 K has been measured. It is equal to (1.6 ± 0.5) × 10-18 cm2 in the maximum at 16 eV. The ratio of cross-sections of bands 1-1 and 0-0 weakly depends on the energy of the exciting electron in the range 12-120 eV and is equal to 0.28 ± 0.05. The appearance threshold is equal to (9.1 ± 0.5) eV.

  18. Effects of water soaking and/or sodium polystyrene sulfonate addition on potassium content of foods.

    PubMed

    Picq, Christian; Asplanato, Marion; Bernillon, Noémie; Fabre, Claudie; Roubeix, Mathilde; Ricort, Jean-Marc

    2014-09-01

    In this study, we determined, by atomic absorption spectrophotometry, the potassium amount leached by soaking or boiling foods identified by children suffering from chronic renal failure as "pleasure food" and that they cannot eat because of their low-potassium diet, and evaluated whether addition of sodium polystyrene sulfonate resin (i.e. Kayexalate®) during soaking or boiling modulated potassium loss. A significant amount of potassium content was removed by soaking (16% for chocolate and potato, 26% for apple, 37% for tomato and 41% for banana) or boiling in a large amount of water (73% for potato). Although Kayexalate® efficiently dose-dependently removed potassium from drinks (by 48% to 73%), resin addition during soaking or boiling did not eliminate more potassium from solid foods. Our results therefore provide useful information for dietitians who elaborate menus for people on potassium-restricted diets and would give an interesting alternative to the systematic elimination of all potassium-rich foods from their diet.

  19. Effects of Additives, Photodegradation, and Water-tree Degradation on the Photoluminescence in Polyethylene and Polypropylene

    NASA Astrophysics Data System (ADS)

    Ito, Toshihide; Fuse, Norikazu; Ohki, Yoshimichi

    Photoluminescence (PL) spectra induced by irradiation of ultraviolet photons are compared among low-density polyethylene (LDPE), crosslinked polyethylene (XLPE), and polypropylene (PP). Three PL bands appear around 4.2, 3.6, and 3.1 eV in LDPE and XLPE, while similar three PL bands are observed at similar energies in PP. The PL spectra and their decay profiles are independent of the presence of additives and are also independent of whether the samples were crosslinked or not. These results indicate that neither the additives nor the crosslinking has any significant effects on the respective three PLs in PE and PP. When the sample was pre-irradiated by the ultraviolet photons under different atmospheres (air, O2, and vacuum), all the PL intensities decrease with the progress of the pre-irradiation regardless of whether the sample is PE or PP. Therefore, all the PLs are considered to result from impurities. In all the pre-irradiated samples, a new PL band appears at 2.9 eV, of which intensity is stronger when the oxygen partial pressure during the pre-irradiation was lower. This PL is considered to be due to photo-induced conjugated double bonds. It has also been confirmed that water-tree degradation in LDPE or in XLPE does not contribute to PL.

  20. The effect of quantity and timing of brine addition on water binding and textural characteristics of cooked beef rolls.

    PubMed

    Pietrasik, Z; Shand, P J

    2003-10-01

    The combined influence of quantity and timing of water/sodium chloride/phosphate addition on quality characteristics of beef rolls processed with 25 or 50% brine level was investigated. Properties of beef rolls were determined by measuring hydration and textural characteristics. The higher level of brine addition (50%) had detrimental effects on product water binding and textural characteristics. Late addition of brine/water during tumbling (i.e. during the last hour) resulted in rolls which were less hard, chewy and elastic, and had poorer water holding properties. Addition of brine in two parts favourably affected hydration properties and thermal stability, yielding lower cooking loss and purge and higher WHC, irrespective of level of brine addition. It also increased hardness and chewiness and improved springiness, cohesiveness and bind of cooked beef rolls.

  1. [Dynamics of Irreversible Evaporation of a Water-Protein Droplet and a Problem of Structural and Dynamical Experiments with Single Molecules].

    PubMed

    Shaitan, K V; Armeev, G A; Shaytan, A K

    2016-01-01

    We discuss the effect of isothermal and adiabatic evaporation of water on the state of a water-protein droplet. The discussed problem is of current importance due to development of techniques to perform single molecule experiments using free electron lasers. In such structure-dynamic experiments the delivery of a sample into the X-ray beam is performed using the microdroplet injector. The time between the injection and delivery is in the order of microseconds. In this paper we developed a specialized variant of all-atom molecular dynamics simulations for the study of irreversible isothermal evaporation of the droplet. Using in silico experiments we determined the parameters of isothermal evaporation of the water-protein droplet with the sodium and chloride ions in the concentration range of 0.3 M at different temperatures. The energy of irreversible evaporation determined from in silico experiments at the initial stages of evaporation virtually coincides with the specific heat of evaporation for water. For the kinetics of irreversible adiabatic evaporation an exact analytical solution was obtained in the limit of high thermal conductivity of the droplet (or up to the droplet size of -100 Å). This analytical solution incorporates parameters that are determined using in silico. experiments on isothermal droplet evaporation. We show that the kinetics of adiabatic evaporation and cooling of the droplet scales with the droplet size. Our estimates of the water-protemi droplet. freezing rate in the adiabatic regime in a vacuum chamber show that additional techniques for stabilizing the temperature inside the droplet should be used in order to study the conformational transitions of the protein in single molecules. Isothermal and quasi-isothermal conditions are most suitable for studying the conformational transitions upon object functioning. However, in this case it is necessary to take into account the effects of dehydration and rapid increase of ionic strength in an

  2. Role of Interfacial Water Molecules in Proline-rich Ligand Recognition by the Src Homology 3 Domain of Abl*

    PubMed Central

    Palencia, Andres; Camara-Artigas, Ana; Pisabarro, M. Teresa; Martinez, Jose C.; Luque, Irene

    2010-01-01

    The interaction of Abl-Src homology 3 domain (SH3) with the high affinity peptide p41 is the most notable example of the inconsistency existing between the currently accepted description of SH3 complexes and their binding thermodynamic signature. We had previously hypothesized that the presence of interfacial water molecules is partially responsible for this thermodynamic behavior. We present here a thermodynamic, structural, and molecular dynamics simulation study of the interaction of p41 with Abl-SH3 and a set of mutants designed to alter the water-mediated interaction network. Our results provide a detailed description of the dynamic properties of the interfacial water molecules and a molecular interpretation of the thermodynamic effects elicited by the mutations in terms of the modulation of the water-mediated hydrogen bond network. In the light of these results, a new dual binding mechanism is proposed that provides a better description of proline-rich ligand recognition by Abl-SH3 and that has important implications for rational design. PMID:19906645

  3. Synthesis of CO and CO2 Molecules by UV Irradiation of Water Ice-covered Hydrogenated Carbon Grains

    NASA Astrophysics Data System (ADS)

    Mennella, V.; Baratta, G. A.; Palumbo, M. E.; Bergin, E. A.

    2006-06-01

    We present the results of UV irradiation with Lyα photons of carbon grains with a water ice cap at 11 K. Formation of CO and CO2 molecules takes place during irradiation. An estimation of the formation cross section of these molecules by Lyα photons has been obtained from the intensity increase of their infrared stretching bands as a function of the photon fluence. The fraction of carbon in the grains converted to CO and CO2 by UV photons is 0.06 and 0.05, respectively. The spectral profile of the CO stretching feature and that of the CO2 bending mode indicate a polar environment for these molecules. On the basis of the present laboratory results and those obtained in previous work on ion irradiation of similar samples, it has been possible to estimate the contribution of polar CO and CO2 produced on carbon grains by energetic processing to the observed column densities of these molecules for dense clouds whose visual extinction is known. A significant amount of polar CO and CO2 is produced through the mechanism we have studied. Furthermore, we have found that the laboratory profile of the bending band of CO2 produced on carbon grains is compatible with that observed toward the field star Elias 16.

  4. Relationships between membrane water molecules and Patman equilibration kinetics at temperatures far above the phosphatidylcholine melting point.

    PubMed

    Vaughn, Alexandra R; Bell, Thomas A; Gibbons, Elizabeth; Askew, Caitlin; Franchino, Hannabeth; Hirsche, Kelsey; Kemsley, Linea; Melchor, Stephanie; Moulton, Emma; Schwab, Morgan; Nelson, Jennifer; Bell, John D

    2015-04-01

    The naphthalene-based fluorescent probes Patman and Laurdan detect bilayer polarity at the level of the phospholipid glycerol backbone. This polarity increases with temperature in the liquid-crystalline phase of phosphatidylcholines and was observed even 90°C above the melting temperature. This study explores mechanisms associated with this phenomenon. Measurements of probe anisotropy and experiments conducted at 1M NaCl or KCl (to reduce water permittivity) revealed that this effect represents interactions of water molecules with the probes without proportional increases in probe mobility. Furthermore, comparison of emission spectra to Monte Carlo simulations indicated that the increased polarity represents elevation in probe access to water molecules rather than increased mobility of relevant bilayer waters. Equilibration of these probes with the membrane involves at least two steps which were distinguished by the membrane microenvironment reported by the probe. The difference in those microenvironments also changed with temperature in the liquid-crystalline phase in that the equilibrium state was less polar than the initial environment detected by Patman at temperatures near the melting point, more polar at higher temperatures, and again less polar as temperature was raised further. Laurdan also displayed this level of complexity during equilibration, although the relationship to temperature differed quantitatively from that experienced by Patman. This kinetic approach provides a novel way to study in molecular detail basic principles of what happens to the membrane environment around an individual amphipathic molecule as it penetrates the bilayer. Moreover, it provides evidence of unexpected and interesting membrane behaviors far from the phase transition.

  5. Solvent isotope effects on the kinetics of nucleophilic addition of water to a. beta. -nitrostyrene

    SciTech Connect

    Crowell, T.I.

    1983-09-23

    The hydrolysis rate of 3,4-(methylenedioxy)-..beta..-nitrostyrene (S) has been measured in H/sub 2/O and in 99% D/sub 2/O buffer solutions from pH -0.9 to 10.6. The kinetic solvent isotope effect (KSIE), k(H/sub 2/O)/k(D/sub 2/O), is 6.2 at pH 2.5, where k is independent of pH in both solvents and attains a higher value, approximately 22, at about pH 6.2. The isotope effects k/sub i/(H/sub 2/O)/k/sub i/(D/sub 2/O) on the rate constants for the individual steps of the mechanism have been determined and their contributions to the overall KSIE evaluated. Accordingly, the KSIE on the pH-rate plateau at pH 1-4 can be separated into two factors: 5.0 for K/sub 12/, the ionization constant of S as a pseudo-base in water; and 1.4 for k/sub 3//sup H/, the rate constant for rate-controlling protonation of the resulting anion by H/sub 3/O/sup +/. At pH 6.2, the higher KSIE (7.6) on k/sub 3//sup H/sub 2/O/ becomes important while the uncatalyzed addition of water to the double bond is partly rate controlling. The rate at the midpoint of a proton-inventory plot (49.5% D/sub 2/O) shows a negative deviation from linearity of 18%. 2 figures, 2 tables.

  6. Charge-specific size-dependent separation of water-soluble organic molecules by fluorinated nanoporous networks

    NASA Astrophysics Data System (ADS)

    Byun, Jeehye; Patel, Hasmukh A.; Thirion, Damien; Yavuz, Cafer T.

    2016-11-01

    Molecular architecture in nanoscale spaces can lead to selective chemical interactions and separation of species with similar sizes and functionality. Substrate specific sorbent chemistry is well known through highly crystalline ordered structures such as zeolites, metal organic frameworks and widely available nanoporous carbons. Size and charge-dependent separation of aqueous molecular contaminants, on the contrary, have not been adequately developed. Here we report a charge-specific size-dependent separation of water-soluble molecules through an ultra-microporous polymeric network that features fluorines as the predominant surface functional groups. Treatment of similarly sized organic molecules with and without charges shows that fluorine interacts with charges favourably. Control experiments using similarly constructed frameworks with or without fluorines verify the fluorine-cation interactions. Lack of a σ-hole for fluorine atoms is suggested to be responsible for this distinct property, and future applications of this discovery, such as desalination and mixed matrix membranes, may be expected to follow.

  7. ADDITIONAL STRESS AND FRACTURE MECHANICS ANALYSES OF PRESSURIZED WATER REACTOR PRESSURE VESSEL NOZZLES

    SciTech Connect

    Walter, Matthew; Yin, Shengjun; Stevens, Gary; Sommerville, Daniel; Palm, Nathan; Heinecke, Carol

    2012-01-01

    In past years, the authors have undertaken various studies of nozzles in both boiling water reactors (BWRs) and pressurized water reactors (PWRs) located in the reactor pressure vessel (RPV) adjacent to the core beltline region. Those studies described stress and fracture mechanics analyses performed to assess various RPV nozzle geometries, which were selected based on their proximity to the core beltline region, i.e., those nozzle configurations that are located close enough to the core region such that they may receive sufficient fluence prior to end-of-life (EOL) to require evaluation of embrittlement as part of the RPV analyses associated with pressure-temperature (P-T) limits. In this paper, additional stress and fracture analyses are summarized that were performed for additional PWR nozzles with the following objectives: To expand the population of PWR nozzle configurations evaluated, which was limited in the previous work to just two nozzles (one inlet and one outlet nozzle). To model and understand differences in stress results obtained for an internal pressure load case using a two-dimensional (2-D) axi-symmetric finite element model (FEM) vs. a three-dimensional (3-D) FEM for these PWR nozzles. In particular, the ovalization (stress concentration) effect of two intersecting cylinders, which is typical of RPV nozzle configurations, was investigated. To investigate the applicability of previously recommended linear elastic fracture mechanics (LEFM) hand solutions for calculating the Mode I stress intensity factor for a postulated nozzle corner crack for pressure loading for these PWR nozzles. These analyses were performed to further expand earlier work completed to support potential revision and refinement of Title 10 to the U.S. Code of Federal Regulations (CFR), Part 50, Appendix G, Fracture Toughness Requirements, and are intended to supplement similar evaluation of nozzles presented at the 2008, 2009, and 2011 Pressure Vessels and Piping (PVP

  8. Fermentation Quality of Ensiled Water Hyacinth (Eichhornia crassipes) as Affected by Additives.

    PubMed

    Tham, Ho Thanh; Van Man, Ngo; Pauly, Thomas

    2013-02-01

    A lab-scale ensiling study was carried out to investigate the fermentation quality of water hyacinth (WH) supplemented with molasses, rice bran, as an absorbent, and an inoculant in the form of fermented vegetable juice and their combinations. After wilting the water hyacinths for 7 h to a dry matter (DM) content of 240 to 250 g/kg, the following treatments were applied: i) Control (C), WH only; ii) WH with sugarcane molasses at 40 g/kg WH (CM); iii) WH inoculated with fermented vegetable juice at 10 ml/kg WH (CI); iv) CM and CI (CMI) combined; v) WH with 150 g rice bran/kg WH (CA); vi) CA and CI combined (CAI); vii) CA and CM combined (CAM); and viii) CA, CM and CI combined (CAMI). After application of additives, the differently treated forages were mixed and ensiled in triplicates in 1,500-ml polyethylene jars. After ensiling for 3 d, pH values in all treatments, except C and CI, had decreased to approximately 4.0 and remained low till 14 d. After 56 d, pH had increased between 0.4 to 0.9 pH-units compared to those at 14 d. The ammonia nitrogen (NH3-N) concentration ranged from an acceptable level in treatment CM (8 g/kg N) to a high NH3-N value in treatment CMI (16 g/kg N). Lactic acid formation was higher in CI than in all other treatments. Butyric acid contents, which indicate badly fermented silages, were low in all silages (<2 g/kg DM). There were two-way interactions (p-values from <0.001 to 0.045) for almost all fermentation end-products and pH, except for the molasses×inoculant interaction on NH3-N (p = 0.26). Significant 3-way interactions were found on all observed variables except for weight losses of silages. It is concluded that conserving wilted WH as silage for ruminants may be improved by the addition of molasses or rice bran.

  9. Fermentation Quality of Ensiled Water Hyacinth (Eichhornia crassipes) as Affected by Additives

    PubMed Central

    Tham, Ho Thanh; Van Man, Ngo; Pauly, Thomas

    2013-01-01

    A lab-scale ensiling study was carried out to investigate the fermentation quality of water hyacinth (WH) supplemented with molasses, rice bran, as an absorbent, and an inoculant in the form of fermented vegetable juice and their combinations. After wilting the water hyacinths for 7 h to a dry matter (DM) content of 240 to 250 g/kg, the following treatments were applied: i) Control (C), WH only; ii) WH with sugarcane molasses at 40 g/kg WH (CM); iii) WH inoculated with fermented vegetable juice at 10 ml/kg WH (CI); iv) CM and CI (CMI) combined; v) WH with 150 g rice bran/kg WH (CA); vi) CA and CI combined (CAI); vii) CA and CM combined (CAM); and viii) CA, CM and CI combined (CAMI). After application of additives, the differently treated forages were mixed and ensiled in triplicates in 1,500-ml polyethylene jars. After ensiling for 3 d, pH values in all treatments, except C and CI, had decreased to approximately 4.0 and remained low till 14 d. After 56 d, pH had increased between 0.4 to 0.9 pH-units compared to those at 14 d. The ammonia nitrogen (NH3-N) concentration ranged from an acceptable level in treatment CM (8 g/kg N) to a high NH3-N value in treatment CMI (16 g/kg N). Lactic acid formation was higher in CI than in all other treatments. Butyric acid contents, which indicate badly fermented silages, were low in all silages (<2 g/kg DM). There were two-way interactions (p-values from <0.001 to 0.045) for almost all fermentation end-products and pH, except for the molasses×inoculant interaction on NH3-N (p = 0.26). Significant 3-way interactions were found on all observed variables except for weight losses of silages. It is concluded that conserving wilted WH as silage for ruminants may be improved by the addition of molasses or rice bran. PMID:25049776

  10. Performance Characterization of the Free Molecule Micro-Resistojet Utilizing Water Propellant (Preprint)

    DTIC Science & Technology

    2007-05-24

    missions are currently being conceived as a result of the development of micro - and nano - technologies. The general agreement in the spacecraft...Article 3. DATES COVERED (From - To) 4. TITLE AND SUBTITLE 5a. CONTRACT NUMBER Performance Characterization of the Free Molecule Micro -Resistojet...Submitted for publication in the Journal of Spacecraft and Rockets. 14. ABSTRACT Advances in micro -technology manufacturing and capability have led

  11. EPA Proposes Additional Water Line Connections for Groundwater Contamination at Tinkham Garage Superfund Site in Londonderry, NH

    EPA Pesticide Factsheets

    The U.S. EPA in consultation with NHDES, is proposing additional connections to an existing water line for residents whose wells have been found to have contamination and whom live northeast section of the Tinkham Garage Superfund Site (Site).

  12. Soy Protein Isolate As Fluid Loss Additive in Bentonite-Water-Based Drilling Fluids.

    PubMed

    Li, Mei-Chun; Wu, Qinglin; Song, Kunlin; Lee, Sunyoung; Jin, Chunde; Ren, Suxia; Lei, Tingzhou

    2015-11-11

    Wellbore instability and formation collapse caused by lost circulation are vital issues during well excavation in the oil industry. This study reports the novel utilization of soy protein isolate (SPI) as fluid loss additive in bentonite-water based drilling fluids (BT-WDFs) and describes how its particle size and concentration influence on the filtration property of SPI/BT-WDFs. It was found that high pressure homogenization (HPH)-treated SPI had superior filtration property over that of native SPI due to the improved ability for the plugging pore throat. HPH treatment also caused a significant change in the surface characteristic of SPI, leading to a considerable surface interaction with BT in aqueous solution. The concentration of SPI had a significant impact on the dispersion state of SPI/BT mixtures in aquesous solution. At low SPI concentrations, strong aggregations were created, resulting in the formation of thick, loose, high-porosity and high-permeability filter cakes and high fluid loss. At high SPI concentrations, intercatlated/exfoliated structures were generated, resulting in the formation of thin, compact, low-porosity and low-permeability filter cakes and low fluid loss. The SPI/BT-WDFs exhibited superior filtration property than pure BT-WDFs at the same solid concentraion, demonstrating the potential utilization of SPI as an effective, renewable, and biodegradable fluid loss reducer in well excavation applications.

  13. Slug tests in wells screened across the water table: some additional considerations.

    PubMed

    Butler, J J

    2014-01-01

    The majority of slug tests done at sites of shallow groundwater contamination are performed in wells screened across the water table and are affected by mechanisms beyond those considered in the standard slug-test models. These additional mechanisms give rise to a number of practical issues that are yet to be fully resolved; four of these are addressed here. The wells in which slug tests are performed were rarely installed for that purpose, so the well design can result in problematic (small signal to noise ratio) test data. The suitability of a particular well design should thus always be assessed prior to field testing. In slug tests of short duration, it can be difficult to identify which portion of the test represents filter-pack drainage and which represents formation response; application of a mass balance can help confirm that test phases have been correctly identified. A key parameter required for all slug test models is the casing radius. However, in this setting, the effective casing radius (borehole radius corrected for filter-pack porosity), not the nominal well radius, is required; this effective radius is best estimated directly from test data. Finally, although conventional slug-test models do not consider filter-pack drainage, these models will yield reasonable hydraulic conductivity estimates when applied to the formation-response phase of a test from an appropriately developed well.

  14. An aspartate and a water molecule mediate efficient acid-base catalysis in a tailored antibody pocket.

    PubMed

    Debler, Erik W; Müller, Roger; Hilvert, Donald; Wilson, Ian A

    2009-11-03

    Design of catalysts featuring multiple functional groups is a desirable, yet formidable goal. Antibody 13G5, which accelerates the cleavage of unactivated benzisoxazoles, is one of few artificial enzymes that harness an acid and a base to achieve efficient proton transfer. X-ray structures of the Fab-hapten complexes of wild-type 13G5 and active-site variants now afford detailed insights into its mechanism. The parent antibody preorganizes Asp(H35) and Glu(L34) to abstract a proton from substrate and to orient a water molecule for leaving group stabilization, respectively. Remodeling the environment of the hydrogen bond donor with a compensatory network of ordered waters, as seen in the Glu(L34) to alanine mutant, leads to an impressive 10(9)-fold rate acceleration over the nonenzymatic reaction with acetate, illustrating the utility of buried water molecules in bifunctional catalysis. Generalization of these design principles may aid in creation of catalysts for other important chemical transformations.

  15. Binding site identification and role of permanent water molecule of PIM-3 kinase: A molecular dynamics study.

    PubMed

    Ul-Haq, Zaheer; Gul, Sana; Usmani, Saman; Wadood, Abdul; Khan, Waqasuddin

    2015-11-01

    The kinome is a protein kinase complement of the human genome, categorized as serine/threonine and tyrosine kinases. These kinases catalyze phosphorylation reaction by using ATP as phosphoryl donor. Proviral Integration Site for Moloney Murine Leukemia Virus (PIM) kinase encodes serine/threonine protein kinases that recognized as proto-oncogene, responsible for rapid growth of cancerous cells. It is implicated in cell survival and function via cell cycle progression and its metabolism. PIM-3, sub-member of PIM kinases is a proto-oncogene, its overexpression inhibits apoptosis, and results in progression of hepatocellular carcinoma. PIM-3 is considered as a promising drug target but attempts to develop its specific inhibitors is slowed down due to the lack of 3D structure by any experimental technique. In silico techniques generally facilitate scientist to explore hidden structural features in order to improve drug discovery. In the present study, homology modeling, molecular docking and MD simulation techniques were utilized to explore the structure and dynamics of PIM-3 kinase. Induction of water molecules during molecular docking simulation explored differences in the hinge region between PIM-1 and PIM-3 kinases that may be responsible for specificity. Furthermore, role of water molecules in the active site was also explored via radial distribution function (RDF) after a 10 ns molecular dynamics (MD) simulations. Generated RDF plots exhibited the importance of water for inhibitor binding through their bridging capability that links the ligand with binding site residues.

  16. An aspartate and a water molecule mediate efficient acid-base catalysis in a tailored antibody pocket

    SciTech Connect

    Debler, Erik W.; Müller, Roger; Hilvert, Donald; Wilson, Ian A.

    2009-12-01

    Design of catalysts featuring multiple functional groups is a desirable, yet formidable goal. Antibody 13G5, which accelerates the cleavage of unactivated benzisoxazoles, is one of few artificial enzymes that harness an acid and a base to achieve efficient proton transfer. X-ray structures of the Fab-hapten complexes of wild-type 13G5 and active-site variants now afford detailed insights into its mechanism. The parent antibody preorganizes Asp{sup H35} and Glu{sup L34} to abstract a proton from substrate and to orient a water molecule for leaving group stabilization, respectively. Remodeling the environment of the hydrogen bond donor with a compensatory network of ordered waters, as seen in the Glu{sup L34} to alanine mutant, leads to an impressive 10{sup 9}-fold rate acceleration over the nonenzymatic reaction with acetate, illustrating the utility of buried water molecules in bifunctional catalysis. Generalization of these design principles may aid in creation of catalysts for other important chemical transformations.

  17. Preparations and properties of anti-corrosion additives of water-soluble metal working fluids for aluminum alloy materials.

    PubMed

    Watanabe, Shoji

    2008-01-01

    This short review describes various types of anti-corrosion additives of water-soluble metal working fluids for aluminum alloy materials. It is concerned with synthetic additives classified according to their functional groups; silicone compounds, carboxylic acids and dibasic acids, esters, Diels-Alder adducts, various polymers, nitrogen compounds, phosphoric esters, phosphonic acids, and others. Testing methods for water-soluble metal working fluids for aluminum alloy materials are described for a practical application in a laboratory.

  18. 78 FR 56695 - Proposed Listing of Additional Waters To Be Included on Indiana's 2010 List of Impaired Waters...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-09-13

    ... EPA's proposed decision identifying water quality limited segments and associated pollutants in Indiana to be listed pursuant to the Clean Water Act Section 303(d)(2), and requests public comment. For... Under the Clean Water Act AGENCY: Environmental Protection Agency (EPA). ACTION: Reopening of...

  19. 78 FR 35929 - Proposed Listing of Additional Waters To Be Included on Indiana's 2010 List of Impaired Waters...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-06-14

    ... decision identifying water quality limited segments and associated pollutants in Indiana to be listed... pollution controls are not stringent enough to attain or maintain state water quality standards and for... certain water quality limited segments and associated pollutants (Table 1 in Appendix A1 of EPA's...

  20. THE COMBINED CARCINOGENIC RISK FOR EXPOSURE TO MIXTURES OF DRINKING WATER DISINFECTION BY-PRODUCTS MAY BE LESS THAN ADDITIVE

    EPA Science Inventory

    The Combined Carcinogenic Risk for Exposure to Mixtures of Drinking Water Disinfection By-Products May be Less Than Additive

    Risk assessment methods for chemical mixtures in drinking water are not well defined. Current default risk assessments for chemical mixtures assume...

  1. [Effects of nitrogen and water addition on soil bacterial diversity and community structure in temperate grasslands in northern China].

    PubMed

    Yang, Shan; Li, Xiao-bing; Wang, Ru-zhen; Cai, Jiang-ping; Xu, Zhu-wen; Zhang, Yu-ge; Li, Hui; Jiang, Yong

    2015-03-01

    In this study, we measured the responses of soil bacterial diversity and community structure to nitrogen (N) and water addition in the typical temperate grassland in northern China. Results showed that N addition significantly reduced microbial biomass carbon (MBC) and microbial biomass nitrogen (MBN) under regular precipitation treatment. Similar declined trends of MBC and MBN caused by N addition were also found under increased precipitation condition. Nevertheless, water addition alleviated the inhibition by N addition. N addition exerted no significant effects. on bacterial α-diversity indices, including richness, Shannon diversity and evenness index under regular precipitation condition. Precipitation increment tended to increase bacterial α-diversity, and the diversity indices of each N gradient under regular precipitation were much lower than that of the corresponding N addition rate under increased precipitation. Correlation analysis showed that soil moisture, nitrate (NO3(-)-N) and ammonium (NH4+-N) were significantly negatively correlated with bacterial evenness index, and MBC and MBN had a significant positive correlation with bacterial richness and evenness. Non-metric multidimensional scaling (NMDS) ordination illustrated that the bacterial communities were significantly separated by N addition rates, under both water ambient and water addition treatments. Redundancy analysis (RDA) revealed that soil MBC, MBN, pH and NH4+-N were the key environmental factors for shaping bacterial communities.

  2. Computational study of the interaction of indole-like molecules with water and hydrogen sulfide

    NASA Astrophysics Data System (ADS)

    Cabaleiro-Lago, Enrique M.; Rodríguez-Otero, Jesús; Peña-Gallego, Ángeles

    2011-10-01

    The characteristics of the interaction between water and hydrogen sulfide with indole and a series of analogs obtained by substituting the NH group of indole by different heteroatoms have been studied by means of ab initio calculations. In all cases, minima were found corresponding to structures where water and hydrogen sulfide interact by means of X-H...π contacts. The interaction energies for all these π complexes are quite similar, spanning from -13.5 to -18.8 kJ/mol, and exhibiting the stability sequence NH > CH2 ≈ PH > Se ≈ S > O, for both water and hydrogen sulfide. Though interaction energies are similar, hydrogen sulfide complexes are slightly favored over their water counterparts when interacting with the π cloud. σ-Type complexes were also considered for the systems studied, but only in the case of water complexes this kind of complexes is relevant. Only for complexes formed by water and indole, a significantly more stable σ-type complex was found with an interaction energy amounting to -23.6 kJ/mol. Oxygen and phosphorous derivatives also form σ-type complexes of similar stability as that observed for π ones. Despite the similar interaction energies exhibited by complexes with water and hydrogen sulfide, the nature of the interaction is very different. For π complexes with water the main contributions to the interaction energy are electrostatic and dispersive contributing with similar amounts, though slightly more from electrostatics. On the contrary, in hydrogen sulfide complexes dispersion is by far the main stabilizing contribution. For the σ-type complexes, the interaction is clearly dominated by the electrostatic contribution, especially in the indole-water complex.

  3. DFT studies of carbohydrate solvation: II. MD-DFTr of a super-molecule complex of glucose, explicit waters, and an implicit solvent (COSMO)

    Technology Transfer Automated Retrieval System (TEKTRAN)

    MD-DFTr studies are carried out on the super-molecule solvated complexes of glucose described in paper I. Included were ten explicit water molecules and an implicit solvation model, COSMO, superimposed upon the complex. Starting configurations were taken from DFTr optimized complexes resulting from ...

  4. On the connection between the Koppel-Young and the Nelkin Models for thermal neutron scattering in water molecules

    SciTech Connect

    Markovic, M.I.

    1982-10-01

    A critical analysis of the Koppel-Young model is presented and compared with Nelkin's model and their equivalence is asserted. It is shown that the only distinction between the two models is in the orientational averaging of the rotational-vibrational intermedial scattering function. Based on total cross sections, the Krieger-Nelkin orientation averaging has been confirmed to give excellent agreement with the Koppel-Young orientation averaging. However, significant quasi-periodical differences are observed when calculating differential cross sections. As a result of these insights, a new unified model is proposed for microdynamics of water molecules.

  5. Product distributions and rate constants for ion-molecule reactions in water, hydrogen sulfide, ammonia, and methane

    NASA Technical Reports Server (NTRS)

    Huntress, W. T., Jr.; Pinizzotto, R. F., Jr.

    1973-01-01

    The thermal energy, bimolecular ion-molecule reactions occurring in gaseous water, hydrogen sulfide, ammonia, and methane have been identified and their rate constants determined using ion cyclotron resonance methods. Absolute rate constants were determined for the disappearance of the primary ions by using the trapped ion method, and product distributions were determined for these reactions by using the cyclotron ejection method. Previous measurements are reviewed and compared with the results using the present methods. The relative rate constants for hydrogen-atom abstraction, proton transfer, and charge transfer are also determined for reactions of the parent ions.

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

    NASA Astrophysics Data System (ADS)

    Wang, Qiang; Gao, Jun; Zhang, Dongju; Liu, Chengbu

    2015-04-01

    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.

  7. Litter Decomposition in a Semiarid Dune Grassland: Neutral Effect of Water Supply and Inhibitory Effect of Nitrogen Addition

    PubMed Central

    Li, Yulin; Ning, Zhiying; Cui, Duo; Mao, Wei; Bi, Jingdong; Zhao, Xueyong

    2016-01-01

    Background The decomposition of plant material in arid ecosystems is considered to be substantially controlled by water and N availability. The responses of litter decomposition to external N and water, however, remain controversial, and the interactive effects of supplementary N and water also have been largely unexamined. Methodology/Principal Findings A 3.5-year field experiment with supplementary nitrogen and water was conducted to assess the effects of N and water addition on mass loss and nitrogen release in leaves and fine roots of three dominant plant species (i.e., Artemisia halondendron, Setaria viridis, and Phragmites australis) with contrasting substrate chemistry (e.g. N concentration, lignin content in this study) in a desertified dune grassland of Inner Mongolia, China. The treatments included N addition, water addition, combination of N and water, and an untreated control. The decomposition rate in both leaves and roots was related to the initial litter N and lignin concentrations of the three species. However, litter quality did not explain the slower mass loss in roots than in leaves in the present study, and thus warrant further research. Nitrogen addition, either alone or in combination with water, significantly inhibited dry mass loss and N release in the leaves and roots of the three species, whereas water input had little effect on the decomposition of leaf litter and fine roots, suggesting that there was no interactive effect of supplementary N and water on litter decomposition in this system. Furthermore, our results clearly indicate that the inhibitory effects of external N on dry mass loss and nitrogen release are relatively strong in high-lignin litter compared with low-lignin litter. Conclusion/Significance These findings suggest that increasing precipitation hardly facilitates ecosystem carbon turnover but atmospheric N deposition can enhance carbon sequestration and nitrogen retention in desertified dune grasslands of northern China

  8. GYY4137, a novel water-soluble, H2S-releasing molecule.

    PubMed

    Rose, Peter; Dymock, Brian W; Moore, Philip K

    2015-01-01

    Hydrogen sulfide (H2S) is now recognized as the so called "third gasotransmitter" taking its place alongside nitric oxide and carbon monoxide. In recent years, H2S has been reported to exhibit a diverse range of pharmacological effects in biological systems. Much of this evidence is derived from a combination of conventional pharmacological and genetic approaches coupled with the use of chemical compounds such as sodium hydrosulfide, a rapid H2S releasing donor. Developments in the design of new drug entities which attempt to take into account physicochemical properties, targeting to specific cellular organelles, triggering of H2S release upon specific chemical reactions in the cell, and controlling the release of H2S over extended periods of time have been described. For most of these molecules, little or no work has been conducted to determine their biological activity or possible therapeutic effects. It is therefore not clear whether such molecules have therapeutic potential which highlights the need for further in vivo studies. One exception to the general rule is GYY4137 (morpholin-4-ium 4-methoxyphenyl(morpholino) phosphinodithioate), a slow releasing H2S donor, which has been evaluated for activity in a range of pharmacological models both in vitro and in vivo. GYY4137 was first reported to release H2S and exhibit vasodilator activity over 5 years ago and, to date, GYY4137 is becoming increasingly employed as a pharmacological "tool" to explore the biological functions of H2S.

  9. THE CARCINOGENIC RESPONSE TO A MIXTURE OF DRINKING WATER DISINFECTION BY-PRODUCTS (DBP) WAS LESS THAN ADDITIVE

    EPA Science Inventory

    THE CARCINOGENIC RESPONSE TO A MIXTURE OF DRINKING WATER DISINFECTION BY -PRODUCTS (DBP) W AS LESS THAN ADDITIVE.

    Current default risk assessments for chemical mixtures assume additivity of carcinogenic effects but this may under or over represent the actual biological res...

  10. Expanding the scope of Lewis acid catalysis in water: remarkable ligand acceleration of aqueous ytterbium triflate catalyzed Michael addition reactions.

    PubMed

    Ding, Rui; Katebzadeh, Kambiz; Roman, Lisa; Bergquist, Karl-Erik; Lindström, Ulf M

    2006-01-06

    [reaction: see text] Significant rate acceleration of metal-catalyzed Michael addition reactions in water was observed upon addition of small, dibasic ligands. Ytterbium triflate and TMEDA was the most effective combination leading to a nearly 20-fold faster reaction than in the absence of ligand.

  11. Addition of chlorine during water purification reduces iodine content of drinking water and contributes to iodine deficiency.

    PubMed

    Samson, L; Czegeny, I; Mezosi, E; Erdei, A; Bodor, M; Cseke, B; Burman, K D; Nagy, E V

    2012-01-01

    Drinking water is the major natural source of iodine in many European countries. In the present study, we examined possible sites of iodine loss during the usual water purification process.Water samples from 6 sites during the technological process were taken and analyzed for iodine content. Under laboratory circumstances, prepared iodine in water solution has been used as a model to test the effect of the presence of chlorine. Samples from the purification sites revealed that in the presence of chlorine there is a progressive loss of iodine from the water. In the chlorine concentrations employed in the purification process, 24-h chlorine exposure eliminated more than 50% of iodine when the initial iodine concentration was 250 μg/l or less. Iodine was completely eliminated if the starting concentration was 16 μg/l.We conclude that chlorine used during water purification may be a major contributor to iodine deficiency in European communities.

  12. Water soluble graphene as electrolyte additive in magnesium-air battery system

    NASA Astrophysics Data System (ADS)

    Saminathan, K.; Mayilvel Dinesh, M.; Selvam, M.; Srither, S. R.; Rajendran, V.; Kaler, Karan V. I. S.

    2015-02-01

    Magnesium-air (Mg-air) batteries are an important energy source used to power electronic equipment and automobiles. Metal-air batteries give more energy density due to surplus air involved in reduction reaction at air cathode. In this study, the scope of improvements in the efficiency of Metal-air batteries is investigated through addition of water soluble graphene (WSG) as inhibitor in NaCl electrolyte. The discharge performance, corrosion behaviour and electrochemical impedance are studied for (i) the conventional Mg-air battery using 3.5% NaCl and (ii) Mg-air battery with WSG-based 3.5% NaCl electrolyte. X-ray diffraction analysis for WSG is carried out and it shows the crystalline nature of WSG by an intense sharp peak at 26.3°. Scanning electron microscope study is also performed and shows the flake-like structure of WSG denoted by thin layers of carbon. The immersion of WSG in 3.5% NaCl electrolyte increased the current density from 13.24 to 19.33 mA cm-2. Meanwhile, the WSG-based Mg-air battery was found to hold specific discharge capacity of 1030.71 mAh g-1, which was higher than that obtained in 3.5% NaCl electrolyte (i.e., 822.85 mAh g-1). The WSG-based Mg-air battery shows good self-discharge capacity and higher electrochemical activity during discharge.

  13. Nutrient and water addition effects on day- and night-time conductance and transpiration in a C3 desert annual.

    PubMed

    Ludwig, Fulco; Jewitt, Rebecca A; Donovan, Lisa A

    2006-06-01

    Recent research has shown that many C3 plant species have significant stomatal opening and transpire water at night even in desert habitats. Day-time stomatal regulation is expected to maximize carbon gain and prevent runaway cavitation, but little is known about the effect of soil resource availability on night-time stomatal conductance (g) and transpiration (E). Water (low and high) and nutrients (low and high) were applied factorially during the growing season to naturally occurring seedlings of the annual Helianthus anomalus. Plant height and biomass were greatest in the treatment where both water and nutrients were added, confirming resource limitations in this habitat. Plants from all treatments showed significant night-time g (approximately 0.07 mol m(-2) s(-1)) and E (approximately 1.5 mol m(-2) s(-1)). In July, water and nutrient additions had few effects on day- or night-time gas exchange. In August, however, plants in the nutrient addition treatments had lower day-time photosynthesis, g and E, paralleled by lower night-time g and E. Lower predawn water potentials and higher integrated photosynthetic water-use efficiency suggests that the nutrient addition indirectly induced a mild water stress. Thus, soil resources can affect night-time g and E in a manner parallel to day-time, although additional factors may also be involved.

  14. The key role of meteorites in the formation of relevant prebiotic molecules in a formamide/water environment

    PubMed Central

    Rotelli, Luca; Trigo-Rodríguez, Josep M.; Moyano-Cambero, Carles E.; Carota, Eleonora; Botta, Lorenzo; Di Mauro, Ernesto; Saladino, Raffaele

    2016-01-01

    We show that carbonaceous chondrite meteorites actively and selectively catalyze the formation of relevant prebiotic molecules from formamide in aqueous media. Specific catalytic behaviours are observed, depending on the origin and composition of the chondrites and on the type of water present in the system (activity: thermal > seawater > pure). We report the one-pot synthesis of all the natural nucleobases, of aminoacids and of eight carboxylic acids (forming, from pyruvic acid to citric acid, a continuous series encompassing a large part of the extant Krebs cycle). These data shape a general prebiotic scenario consisting of carbonaceous meteorites acting as catalysts and of a volcanic-like environment providing heat, thermal waters and formamide. This scenario also applies to the other solar system locations that experienced rich delivery of carbonaceous materials, and whose physical-chemical conditions could have allowed chemical evolution. PMID:27958316

  15. The key role of meteorites in the formation of relevant prebiotic molecules in a formamide/water environment

    NASA Astrophysics Data System (ADS)

    Rotelli, Luca; Trigo-Rodríguez, Josep M.; Moyano-Cambero, Carles E.; Carota, Eleonora; Botta, Lorenzo; di Mauro, Ernesto; Saladino, Raffaele

    2016-12-01

    We show that carbonaceous chondrite meteorites actively and selectively catalyze the formation of relevant prebiotic molecules from formamide in aqueous media. Specific catalytic behaviours are observed, depending on the origin and composition of the chondrites and on the type of water present in the system (activity: thermal > seawater > pure). We report the one-pot synthesis of all the natural nucleobases, of aminoacids and of eight carboxylic acids (forming, from pyruvic acid to citric acid, a continuous series encompassing a large part of the extant Krebs cycle). These data shape a general prebiotic scenario consisting of carbonaceous meteorites acting as catalysts and of a volcanic-like environment providing heat, thermal waters and formamide. This scenario also applies to the other solar system locations that experienced rich delivery of carbonaceous materials, and whose physical-chemical conditions could have allowed chemical evolution.

  16. Premelted liquid water in frozen soils and its interaction with bio-molecules

    NASA Astrophysics Data System (ADS)

    Hansen-Goos, H.; Wettlaufer, J. S.

    2011-12-01

    While liquid water in bulk is unstable on the surface of Mars, there is a possibility for the persistence of thin films of liquid water in the Martian regolith as a result of interfacial forces between the interstitial ice and the soil grains even below the bulk melting temperature. This is referred to as premelting. We present a calculation of the liquid fraction of frozen soils which takes into account premelting in combination with the effect of ionic impurities and the curvature induced freezing point depression (Gibbs-Thomson effect). We introduce a revised density functional theory which accurately treats a simple model for confined liquid water. We use the theory to study how biological matter (antifreeze proteins in particular) inside a narrow liquid cavity in ice interacts with the surrounding ice-water interface. Because in this case the interface is concave and hence the Gibbs-Thomson effect is antagonistic to the liquid phase, the protein-ice interaction is responsible for the persistence of liquid water.

  17. Use of additives to enhance the removal of phenols from water treated with horseradish and hydrogen peroxide.

    PubMed

    Tonegawa, Masami; Dec, Jerzy; Bollag, Jean-Marc

    2003-01-01

    Use of additives, such as polyethylene glycol (PEG), selected surfactants, chitosan gel, or activated carbon, has been shown to enhance enzymatic treatment of water polluted with organic compounds. In this study, additives were used to facilitate the removal of 2,4-dichlorophenol (2,4-DCP) from water using minced horseradish (Armoracia rusticana P. Gaertn. et al.) as a carrier of peroxidase activity. The specific objectives of the study were to (i) enhance the pollutant removal activity of minced horseradish by the addition of PEG and other additives (e.g., Tween 20, Triton X-100, and rhamnolipid); (ii) eliminate colored reaction products by the addition of chitosan; and (iii) eliminate color by amending treated water with activated carbon. The disappearance of 2,4-DCP in horseradish-treated water samples amended with PEG or various surfactants (75-90%) was greatly increased over that observed in nonamended samples (29%). The effect of PEG depended on its average molecular weight. As indicated by visible spectrophotometry, enclosing horseradish pieces between two sealed chitosan films completely eliminated colored reaction products; however, the decolorization was accompanied by a reduction in 2,4-DCP removal (from 95 to 60%). On the other hand, commercially available activated carbon completely removed colored reaction products from the treated water without reducing the removal efficiency. Based on the results obtained, it can be concluded that the use of additives may considerably improve the quality of wastewater treated by plant materials.

  18. Proposed Photosynthesis Method for Producing Hydrogen from Dissociated Water Molecules Using Incident Near-Infrared Light

    NASA Astrophysics Data System (ADS)

    Li, Xingxing; Li, Zhenyu; Yang, Jinlong

    2014-01-01

    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.

  19. What interactions can distort the orientational distribution of interfacial water molecules as probed by second harmonic and sum frequency generation?

    PubMed

    de Beer, Alex G F; Roke, Sylvie

    2016-07-28

    Aqueous interfaces are omnipresent in nature. Nonlinear optical methods such as second harmonic and sum frequency generation (SHG/SFG) are valuable techniques to access molecular level information from these interfaces. In the interpretation of SHG and SFG data for both scattering and reflection mode experiments, the relation between the second-order hyperpolarizability tensor β(2), a molecular property, and the surface second-order susceptibility χ(2), a surface averaged property, plays a central role. To correctly describe the molecular details of the interface, it needs to be determined how molecules are oriented, and what the influence is of interfacial electrostatic fields and H-bonding on the orientational distribution. Here, we revisit the relations between β(2) and χ(2) and show, by means of a Boltzmann average, that significant energy differences are needed to generate measurable changes in the molecular orientational distribution at the interface. In practice, H-bonding and surface pressure such as applied in a Langmuir trough can be strong enough to alter the shape of the orientational distribution function of water. In contrast, electrostatic fields, such as those present in the Stern layer, will not have a significant impact on the shape of the orientational distribution function of water molecules.

  20. Ligand uptake in Mycobacterium tuberculosis truncated hemoglobins is controlled by both internal tunnels and active site water molecules

    PubMed Central

    Davidge, Kelly S; Singh, Sandip; Bowman, Lesley AH; Tinajero-Trejo, Mariana; Carballal, Sebastián; Radi, Rafael; Poole, Robert K; Dikshit, Kanak; Estrin, Dario A; Marti, Marcelo A; Boechi, Leonardo

    2015-01-01

    Mycobacterium tuberculosis, the causative agent of human tuberculosis, has two proteins belonging to the truncated hemoglobin (trHb) family. Mt-trHbN presents well-defined internal hydrophobic tunnels that allow O 2 and •NO to migrate easily from the solvent to the active site, whereas Mt-trHbO possesses tunnels that are partially blocked by a few bulky residues, particularly a tryptophan at position G8. Differential ligand migration rates allow Mt-trHbN to detoxify •NO, a crucial step for pathogen survival once under attack by the immune system, much more efficiently than Mt-trHbO. In order to investigate the differences between these proteins, we performed experimental kinetic measurements, •NO decomposition, as well as molecular dynamics simulations of the wild type Mt-trHbN and two mutants, VG8F and VG8W. These mutations introduce modifications in both tunnel topologies and affect the incoming ligand capacity to displace retained water molecules at the active site. We found that a single mutation allows Mt-trHbN to acquire ligand migration rates comparable to those observed for Mt-trHbO, confirming that ligand migration is regulated by the internal tunnel architecture as well as by water molecules stabilized in the active site. PMID:26478812

  1. A strategy for the incorporation of water molecules present in a ligand binding site into a three-dimensional quantitative structure--activity relationship analysis.

    PubMed

    Pastor, M; Cruciani, G; Watson, K A

    1997-12-05

    Water present in a ligand binding site of a protein has been recognized to play a major role in ligand-protein interactions. To date, rational drug design techniques do not usually incorporate the effect of these water molecules into the design strategy. This work represents a new strategy for including water molecules into a three-dimensional quantitative structure-activity relationship analysis using a set of glucose analogue inhibitors of glycogen phosphorylase (GP). In this series, the structures of the ligand-enzyme complexes have been solved by X-ray crystallography, and the positions of the ligands and the water molecules at the ligand binding site are known. For the structure-activity analysis, some water molecules adjacent to the ligands were included into an assembly which encompasses both the inhibitor and the water involved in the ligand-enzyme interaction. The mobility of some water molecules at the ligand binding site of GP gives rise to differences in the ligand-water assembly which have been accounted for using a simulation study involving force-field energy calculations. The assembly of ligand plus water was used in a GRID/GOLPE analysis, and the models obtained compare favorably with equivalent models when water was excluded. Both models were analyzed in detail and compared with the crystallographic structures of the ligand-enzyme complexes in order to evaluate their ability to reproduce the experimental observations. The results demonstrate that incorporation of water molecules into the analysis improves the predictive ability of the models and makes them easier to interpret. The information obtained from interpretation of the models is in good agreement with the conclusions derived from the structural analysis of the complexes and offers valuable insights into new characteristics of the ligands which may be exploited for the design of more potent inhibitors.

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

    NASA Astrophysics Data System (ADS)

    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.

  3. Investigating Arsenic Contents in Surface and Drinking Water by Voltammetry and the Method of Standard Additions

    ERIC Educational Resources Information Center

    Cheng, Anran; Tyne, Rebecca; Kwok, Yu Ting; Rees, Louis; Craig, Lorraine; Lapinee, Chaipat; D'Arcy, Mitch; Weiss, Dominik J.; Salau¨n, Pascal

    2016-01-01

    Testing water samples for arsenic contamination has become an important water quality issue worldwide. Arsenic usually occurs in very small concentrations, and a sensitive analytical method is needed. We present here a 1-day laboratory module developed to introduce Earth Sciences and/or Chemistry student undergraduates to key aspects of this…

  4. 76 FR 7106 - Food Additives Permitted in Feed and Drinking Water of Animals; Formic Acid

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-02-09

    ... Drinking Water of Animals; Formic Acid AGENCY: Food and Drug Administration, HHS. ACTION: Final rule... in feed and drinking water of animals to provide for the safe use of formic acid as an acidifying... safe use of formic acid as an acidifying agent at levels not to exceed 1.2 percent in swine feed....

  5. Structure and energetics of model amphiphilic molecules at the water liquid-vapor interface - A molecular dynamics study

    NASA Technical Reports Server (NTRS)

    Pohorille, Andrew; Benjamin, Ilan

    1993-01-01

    A molecular dynamics study of adsorption of p-n-pentylphenol at infinite dilution at the water liquid-vapor interface is reported. The calculated free energy of adsorption is -8.8 +/- 0.7 kcal/mol, in good agreement with the experimental value of -7.3 kcal/mol. The transition between the interfacial region and the bulk solution is sharp and well-defined by energetic, conformational, and orientational criteria. At the water surface, the phenol head group is mostly immersed in aqueous solvent. The most frequent orientation of the hydrocarbon tail is parallel to the interface, due to dispersion interactions with the water surface. This arrangement of the phenol ring and the alkyl chain requires that the chain exhibits a kink. As the polar head group is being moved into the solvent, the chain length increases and the tail becomes increasingly aligned toward the surface normal, such that the nonpolar part of the molecule exposed to water is minimized. The same effect was achieved when phenol was replaced by a more polar head group, phenolate.

  6. Effect of water quality improvement on the remediation of river sediment due to the addition of calcium nitrate.

    PubMed

    Liu, Xiaoning; Tao, Yi; Zhou, Kuiyu; Zhang, Qiqi; Chen, Guangyao; Zhang, Xihui

    2017-01-01

    In situ sediment remediation technique is commonly used to control the release of pollutants from sediment. Addition of calcium nitrate to sediment has been applied to control the release of phosphorus from sediments. In this study, laboratory experiments were conducted to investigate the effect of water quality improvement on the remediation of river sediment with the addition of calcium nitrate. The results demonstrated that the redox-potential of sediments increased from -282mV to -130mV after 28days of calcium nitrate treatment. The acid volatile sulphide in the sediments significantly decreased (by 54.9% to 57.1%), whereas the total organic carbon decreased by 9.7% to 10.2%. However, the difference between these and water quality improvement was not significant. Due to the addition of calcium nitrate, low phosphate concentration in the water column and interstitial phosphate in the sediment were observed, indicating that the calcium nitrate was beneficial to controlling the release of phosphorus from river sediment. The decrease in phosphorus release could be attributed to the fixation of iron-phosphorus and calcium-phosphorus due to the addition of calcium nitrate. The addition of calcium nitrate to sediment caused the oxidation of sulphide to sulphate, hence resulting in high nitrate and sulphate concentrations in the water column, and high interstitial nitrate and sulphate concentrations in the sediment. The results also showed that only the water quality improvement had a significant effect on the interstitial nitrate and sulphate concentrations in the sediment.

  7. Addition of nucleophiles on cyanoacetylene N≡CCH=CH-X (X = NH2, OH, SH, …). Synthesis and Physico-chemical Properties of Potential Prebiotic Compounds or Interstellar Molecules.

    NASA Astrophysics Data System (ADS)

    Guillemin, Jean-Claude

    Among the molecules detected to date in the interstellar medium (ISM), cyanopolyynes constitute a rich and important subset. These robust compounds exhibit special properties with respect to their reactivity and kinetic stability, and some have been found in other astrochemical environments, such as comets or in lab simulations of planetary atmospheres.[1] These systems are supposed to be good starting materials for the formation of new, more complex, astrochemical species, or amino acids on primitive Earth. The formal addition of water, hydrogen sulfur or ammonia on cyanoacetylene (H-C≡C-C≡N) gives the corresponding heterosubstitued acrylonitriles. We have extensively investigated the study of such adducts. With water, the formed cyanovinylalcohol (NC-CH=CH-OH) is in a tautomeric equilibrium with the kinetically more stable cyanoacetaldehyde (NC-CH2 CH(=O)). Isolation of these compounds in pure form is challenging but the gas phase infrared spectrum has been recorded. Reaction of ammonia with cyanoacetylene gives aminoacrylonitrile (H2 N-CH=CH-CN), a stable enamine; microwave and infrared spectra were obtained.[2] Similarly the MW spectrum of 3-mercapto-2-propenenitrile (HS-CH=CH-CN) has been recorded.[3] Attempts to detect both species in the ISM have been performed. A combined experimental and theoretical study on the gas-phase basicity and acidity of a series of cyanovinyl derivatives is also presented.[4] We will demonstrate that many particular physicochemical properties are associated to these simple adducts of cyanoacetylene, compounds often proposed as prebiotic molecules or components of the ISM. 1] S. W. Fow, K. Dose, Molecular Evolution and the Origin of Life, Marcel Dekker, Stateplace- New York, metricconverterProductID1977. A1977. A. Coustenis, T. Encrenaz, B. BJzard, B. Bjoraker, G. Graner, G. Dang-Nhu, E. AriJ, Icarus 1993, 102, 240 - 269. [2] Benidar, A. ; Guillemin, J.-C. ; M—, O. ; Y‡-ez, M. J. Phys. Chem. A. 2005, 109, 4705-4712. E

  8. Addition of a Magnetite Layer onto a Polysulfone Water Treatment Membrane to Enhance Virus Removal

    NASA Astrophysics Data System (ADS)

    Raciny, Isabel

    The applicability of low-pressure membranes systems in distributed (point of use) water treatment is hindered by, among other things, their inability to remove potentially harmful viruses and ions via size exclusion. According to the USEPA and the Safe Drinking Water Act, drinking water treatment processes must be designed for 4-log virus removal. Batch experiments using magnetite nanoparticle (nano-Fe3O4) suspensions and water filtration experiments with Polysulfone (PSf) membranes coated with nano-Fe3O 4 were conducted to assess the removal of a model virus (bacteriophage MS2). The membranes were coated via a simple filtration protocol. Unmodified membranes were a poor adsorbent for MS2 bacteriophage with less than 0.5-log removal, whereas membranes coated with magnetite nanoparticles exhibited a removal efficiency exceeding 99.99% (4-log). Thus, a cartridge of PSf membranes coated with nano-Fe3O4 particles could be used to remove viruses from water. Such membranes showed negligible iron leaching into the filtrate, thus obviating concern about colored water. Further research is needed to reduce the loss of water flux caused by coating.

  9. Addition of a magnetite layer onto a polysulfone water treatment membrane to enhance virus removal.

    PubMed

    Raciny, I; Zodrow, K R; Li, D; Li, Q; Alvarez, P J J

    2011-01-01

    The applicability of low-pressure membranes systems in distributed (point of use) water treatment is hindered by, among other things, their inability to remove potentially harmful viruses and ions via size exclusion. According to the USEPA and the Safe Drinking Water Act, drinking water treatment processes must be designed for 4-log virus removal. Batch experiments using magnetite nanoparticle (nano-Fe3O4) suspensions and water filtration experiments with polysulfone membranes coated with nano-Fe3O4 were conducted to assess the removal of a model virus (bacteriophage MS2). The membranes were coated via a simple filtration protocol. Unmodified membranes were a poor adsorbent for MS2 bacteriophage with less than 0.5-log removal, whereas membranes coated with magnetite nanoparticles exhibited a removal efficiency exceeding 99.99% (4-log). Thus, a cartridge of PSf membranes coated with nano-Fe3O4 particles could be used to remove viruses from water. Such membranes showed negligible iron leaching into the filtrate, thus obviating concern about coloured water. Further research is needed to reduce the loss of water flux caused by coating.

  10. Dissociative electron attachment to water molecule: Experimental study of the dissociation dynamics

    NASA Astrophysics Data System (ADS)

    Adaniya, H.; Rudek, B.; Osipov, T.; Weber, T.; Lee, S.; Hertlein, M.; Schoeffler, M.; Prior, M.; Belkacem, A.

    2009-11-01

    The dynamics of the dissociative electron attachment(DEA)to water(H2O, D2O)via three resonances, 2B1, 2A1, 2B2, are investigated using the modified Coltrims spectrometer. The angular dependence of the negative ion shows unique distribution in each resonance indicating the three resonances involve different dissociation dynamics. The energy distribution among the fragments shows considerable amount of three body break.

  11. Organic Molecules and Water in the Inner Disks of T Tauri Stars

    DTIC Science & Technology

    2011-05-11

    water emission properties in the full Spitzer spectrum (but see Section 4.2.2). By focusing on this wavelength region we can also optimize the...cores and comets are from references given in the text . (A color version of this figure is available in the online journal.) error bars corresponds to...because comets are made of icy material that was originally present in the Jupiter– Saturn region and in the outer solar nebula (the Kuiper Belt) during

  12. Phase transition study of confined water molecules inside carbon nanotubes: hierarchical multiscale method from molecular dynamics simulation to ab initio calculation.

    PubMed

    Javadian, Soheila; Taghavi, Fariba; Yari, Faramarz; Hashemianzadeh, Seyed Majid

    2012-09-01

    In this study, the mechanism of the temperature-dependent phase transition of confined water inside a (9,9) single-walled carbon nanotube (SWCNT) was studied using the hierarchical multi-scale modeling techniques of molecular dynamics (MD) and density functional theory (DFT). The MD calculations verify the formation of hexagonal ice nanotubes at the phase transition temperature T(c)=275K by a sharp change in the location of the oxygen atoms inside the SWCNT. Natural bond orbital (NBO) analysis provides evidence of considerable intermolecular charge transfer during the phase transition and verifies that the ice nanotube contains two different forms of hydrogen bonding due to confinement. Nuclear quadrupole resonance (NQR) and nuclear magnetic resonance (NMR) analyses were used to demonstrate the fundamental influence of intermolecular hydrogen bonding interactions on the formation and electronic structure of ice nanotubes. In addition, the NQR analysis revealed that the rearrangement of nano-confined water molecules during the phase transition could be detected directly by the orientation of ¹⁷O atom EFG tensor components related to the molecular frame axes. The effects of nanoscale confinements in ice nanotubes and water clusters were analyzed by experimentally observable NMR and NQR parameters. These findings showed a close relationship between the phase behavior and orientation of the electronic structure in nanoscale structures and demonstrate the usefulness of NBO and NQR parameters for detecting phase transition phenomena in nanoscale confining environments.

  13. Highly efficient "on water" catalyst-free nucleophilic addition reactions using difluoroenoxysilanes: dramatic fluorine effects.

    PubMed

    Yu, Jin-Sheng; Liu, Yun-Lin; Tang, Jing; Wang, Xin; Zhou, Jian

    2014-09-01

    A remarkable fluorine effect on "on water" reactions is reported. The CF⋅⋅⋅HO interactions between suitably fluorinated nucleophiles and the hydrogen-bond network at the phase boundary of oil droplets enable the formation of a unique microstructure to facilitate on water catalyst-free reactions, which are difficult to realize using nonfluorinated substrates. Accordingly, a highly efficient on water, catalyst-free reaction of difluoroenoxysilanes with aldehydes, activated ketones, and isatylidene malononitriles was developed, thus leading to the highly efficient synthesis of a variety of α,α-difluoro-β-hydroxy ketones and quaternary oxindoles.

  14. Ordering of protein and water molecules at their interfaces with chitin nano-crystals.

    PubMed

    Valverde Serrano, Clara; Leemreize, Hanna; Bar-On, Benny; Barth, Friedrich G; Fratzl, Peter; Zolotoyabko, Emil; Politi, Yael

    2016-02-01

    Synchrotron X-ray diffraction was applied to study the structure of biogenic α-chitin crystals composing the tendon of the spider Cupiennius salei. Measurements were carried out on pristine chitin crystals stabilized by proteins and water, as well as after their deproteinization and dehydration. We found substantial shifts (up to Δq/q=9% in the wave vector in q-space) in the (020) diffraction peak position between intact and purified chitin samples. However, chitin lattice parameters extracted from the set of reflections (hkl), which did not contain the (020)-reflection, showed no systematic variation between the pristine and the processed samples. The observed shifts in the (020) peak position are discussed in terms of the ordering-induced modulation of the protein and water electron density near the surface of the ultra-thin chitin fibrils due to strong protein/chitin and water/chitin interactions. The extracted modulation periods can be used as a quantitative parameter characterizing the interaction length.

  15. Depth profiles of hydrogen bound water molecule types and their relation to lipid and protein interaction in the human stratum corneum in vivo.

    PubMed

    Choe, ChunSik; Lademann, Jürgen; Darvin, Maxim E

    2016-11-21

    Confocal Raman microscopy has been used to measure depth-dependent profiles of human SC in vivo in the high wavenumber (HWN) region. In order to keep the linearity of HWN region boundaries and to not remove an informative signal from Raman spectra, a new baseline subtraction procedure has been introduced. After baseline subtraction, the HWN spectrum was deconvoluted using 10 Gaussian functions with individual chemical meanings. The results show that the hydrogen bound water molecule types contributed differently to the water diffusion process in the SC. The most concentrated double donor-double acceptor (DDAA) and single donor-single acceptor (DA) water molecule types in the SC represent more than 90% of the SC's water and mostly contribute to the water flux in the skin. Single donor-double acceptor (DAA) and weakly-bound water molecule types represent less than 10% of the SC's water content. The most tightly hydrogen bound water molecule type, DAA, reaches its maximum concentration near the skin surface and does not take part in the water diffusion process via the SC. The results show that the hydrogen bonding state of water (DA/DDAA water molecule type ratio) reaches its maximum at the depth of approx. 30% of the SC thickness, which correlates well with the maximum lateral packing order of intercellular lipids (ICL) and the natural moisturizing factor (NMF), and does not coincide with the folding/unfolding state of keratin. The NMF's contribution to the bonding of water in the SC is supposed to dominate over that of ICL.

  16. Additivity of water sorption, alpha-relaxations and crystallization inhibition in lactose-maltodextrin systems.

    PubMed

    Potes, Naritchaya; Kerry, Joseph P; Roos, Yrjö H

    2012-08-01

    Water sorption of lactose-maltodextrin (MD) systems, structural relaxations and lactose crystallization were studied. Accurate water sorption data for non-crystalline lactose previously not available over a wide range of water activity, aw (<0.76aw) were derived from lactose-MD systems data. Structural relaxations and crystallization of lactose in lactose-maltodextrin (MD) systems were strongly affected by water and MD. At high MD contents, inhibition of crystallization was significant. Inhibition with a high dextrose equivalent (DE) MD was more pronounced possibly because of molecular number and size effects. At 0.55-0.76aw, inhibition increased with increasing MD content. At aw>0.66, the rate of lactose crystallization decreased at increasing MD contents. Different MDs with similar Tg in lactose-MD systems showed different crystallization inhibition effects. The results of the present study showed that the DE in selection of MD for applications has important effects on component crystallization characteristics.

  17. Synthesis of DHA/EPA-rich phosphatidylcholine by immobilized phospholipase A1: effect of water addition and vacuum condition.

    PubMed

    Li, Daoming; Qin, Xiaoli; Wang, Weifei; Li, Zhigang; Yang, Bo; Wang, Yonghua

    2016-08-01

    DHA/EPA-rich phosphatidylcholine (PC) was successfully synthesized by immobilized phospholipase A1 (PLA1)-catalyzed transesterification of PC and DHA/EPA-rich ethyl esters in a solvent-free system. Effects of reaction temperature, water addition and substrate mass ratio on the incorporation of DHA/EPA were evaluated using response surface methods (RSM). Water addition had most significant effect on the incorporation. Reaction temperature and substrate mass ratio, however, had no significant effect on the incorporation. The maximal incorporation was 19.09 % (24 h) under the following conditions: temperature 55.7 °C, water addition 1.1 wt % and substrate mass ratio (ethyl esters/PC) 6.8:1. Furthermore, effects of water addition (from 0 to 1.25 wt %) on DHA/EPA incorporation and the composition of products were further investigated. The immobilized PLA1 was more active when water addition was above 0.5 wt %. By monitoring the reaction processes with different water addition, a possible reaction scheme was proposed for transesterification of PC with DHA/EPA-rich ethyl esters. In summary, PC and sn2-lysophosphatidylocholine (LPC) were predominant in the mixtures at early stages of reaction, whereas sn1-LPC and glycerophosphocholine (GPC) predominant at later stages. The vacuum employed after 24 h significantly increased the incorporation of DHA/EPA and the composition of PC, and the highest incorporation (30.31 %) of DHA/EPA was obtained at 72 h and the yield of PC was 47.2 %.

  18. Orientation and structure-building role of the water molecules bound at the contact surface of the dihydrofolate reductase-methotrexate complex

    NASA Astrophysics Data System (ADS)

    Nagy, P.

    1988-04-01

    Orientation of ten water molecules bound strongly at the contact surface of the dihydrofolate reductase-methotrexate enzyme-inhibitor complex was determined theoretically. To optimize the orientation of the water molecules, a recent method based on a simple electrostatic model was applied. The electrostatic complementarity in the binary complex was investigated using the lock-and-key model, considering the effect of the water molecules as well. The strongly bound water molecules improve the electrostatic fit in the pteridine region of methotrexate. Their role in the benzoic amide and γ-glutamate region is to decrease the internal energy by creating water bridges among remote polar sites making it possible to form H-bonds. Some modifications in the inhibitor structure were proposed for achieving greater inhibitor potency. The presumably enhanced effect is ascribed to the free energy gain in repelling the water molecules from the contact surface to the bulk of the solvent, and, in other cases, to internal energy decreases due to better electrostatic fit in the enzyme-inhibitor complex.

  19. Optimizing electrostatic field calculations with the Adaptive Poisson-Boltzmann Solver to predict electric fields at protein-protein interfaces II: explicit near-probe and hydrogen-bonding water molecules.

    PubMed

    Ritchie, Andrew W; Webb, Lauren J

    2014-07-17

    We have examined the effects of including explicit, near-probe solvent molecules in a continuum electrostatics strategy using the linear Poisson-Boltzmann equation with the Adaptive Poisson-Boltzmann Solver (APBS) to calculate electric fields at the midpoint of a nitrile bond both at the surface of a monomeric protein and when docked at a protein-protein interface. Results were compared to experimental vibrational absorption energy measurements of the nitrile oscillator. We examined three methods for selecting explicit water molecules: (1) all water molecules within 5 Å of the nitrile nitrogen; (2) the water molecule closest to the nitrile nitrogen; and (3) any single water molecule hydrogen-bonding to the nitrile. The correlation between absolute field strengths with experimental absorption energies were calculated and it was observed that method 1 was only an improvement for the monomer calculations, while methods 2 and 3 were not significantly different from the purely implicit solvent calculations for all protein systems examined. Upon taking the difference in calculated electrostatic fields and comparing to the difference in absorption frequencies, we typically observed an increase in experimental correlation for all methods, with method 1 showing the largest gain, likely due to the improved absolute monomer correlations using that method. These results suggest that, unlike with quantum mechanical methods, when calculating absolute fields using entirely classical models, implicit solvent is typically sufficient and additional work to identify hydrogen-bonding or nearest waters does not significantly impact the results. Although we observed that a sphere of solvent near the field of interest improved results for relative field calculations, it should not be consider a panacea for all situations.

  20. Layered Double Hydroxide Nanoplatelets with Excellent Tribological Properties under High Contact Pressure as Water-Based Lubricant Additives

    NASA Astrophysics Data System (ADS)

    Wang, Hongdong; Liu, Yuhong; Chen, Zhe; Wu, Bibo; Xu, Sailong; Luo, Jianbin

    2016-03-01

    High efficient and sustainable utilization of water-based lubricant is essential for saving energy. In this paper, a kind of layered double hydroxide (LDH) nanoplatelets is synthesized and well dispersed in water due to the surface modification with oleylamine. The excellent tribological properties of the oleylamine-modified Ni-Al LDH (NiAl-LDH/OAm) nanoplatelets as water-based lubricant additives are evaluated by the tribological tests in an aqueous environment. The modified LDH nanoplatelets are found to not only reduce the friction but also enhance the wear resistance, compared with the water-based cutting fluid and lubricants containing other particle additives. By adding 0.5 wt% LDH nanoplatelets, under 1.5 GPa initial contact pressure, the friction coefficient, scar diameter, depth and width of the wear track dramatically decrease by 83.1%, 43.2%, 88.5% and 59.5%, respectively. It is considered that the sufficiently small size and the excellent dispersion of NiAl-LDH/OAm nanoplatelets in water are the key factors, so as to make them enter the contact area, form a lubricating film and prevent direct collision of asperity peaks. Our investigations demonstrate that the LDH nanoplatelet as a water-based lubricant additive has a great potential value in industrial application.

  1. Layered Double Hydroxide Nanoplatelets with Excellent Tribological Properties under High Contact Pressure as Water-Based Lubricant Additives

    PubMed Central

    Wang, Hongdong; Liu, Yuhong; Chen, Zhe; Wu, Bibo; Xu, Sailong; Luo, Jianbin

    2016-01-01

    High efficient and sustainable utilization of water-based lubricant is essential for saving energy. In this paper, a kind of layered double hydroxide (LDH) nanoplatelets is synthesized and well dispersed in water due to the surface modification with oleylamine. The excellent tribological properties of the oleylamine-modified Ni-Al LDH (NiAl-LDH/OAm) nanoplatelets as water-based lubricant additives are evaluated by the tribological tests in an aqueous environment. The modified LDH nanoplatelets are found to not only reduce the friction but also enhance the wear resistance, compared with the water-based cutting fluid and lubricants containing other particle additives. By adding 0.5 wt% LDH nanoplatelets, under 1.5 GPa initial contact pressure, the friction coefficient, scar diameter, depth and width of the wear track dramatically decrease by 83.1%, 43.2%, 88.5% and 59.5%, respectively. It is considered that the sufficiently small size and the excellent dispersion of NiAl-LDH/OAm nanoplatelets in water are the key factors, so as to make them enter the contact area, form a lubricating film and prevent direct collision of asperity peaks. Our investigations demonstrate that the LDH nanoplatelet as a water-based lubricant additive has a great potential value in industrial application. PMID:26951794

  2. Water reuse: >90% water yield in MBR/RO through concentrate recycling and CO2 addition as scaling control.

    PubMed

    Joss, Adriano; Baenninger, Claudia; Foa, Paolo; Koepke, Stephan; Krauss, Martin; McArdell, Christa S; Rottermann, Karin; Wei, Yuansong; Zapata, Ana; Siegrist, Hansruedi

    2011-11-15

    Over 1.5 years continuous piloting of a municipal wastewater plant upgraded with a double membrane system (ca. 0.6 m(3) d(-1) of product water produced) have demonstrated the feasibility of achieving high water quality with a water yield of 90% by combining a membrane bioreactor (MBR) with a submerged ultrafiltration membrane followed by a reverse osmosis membrane (RO). The novelty of the proposed treatment scheme consists of the appropriate conditioning of MBR effluent prior to the RO and in recycling the RO concentrates back to the biological unit. All the 15 pharmaceuticals measured in the influent municipal sewage were retained below 100 ng L(-1), a proposed quality parameter, and mostly below detection limits of 10 ng L(-1). The mass balance of the micropollutants shows that these are either degraded or discharged with the excess concentrate, while only minor quantities were found in the excess sludge. The micropollutant load in the concentrate can be significantly reduced by ozonation. A low treated water salinity (<10 mM inorganic salts; 280 ± 70 μS cm(-1)) also confirms that the resulting product has a high water quality. Solids precipitation and inorganic scaling are effectively mitigated by lowering the pH in the RO feed water with CO(2) conditioning, while the concentrate from the RO is recycled to the biological unit where CO(2) is stripped by aeration. This causes precipitation to occur in the bioreactor bulk, where it is much less of a process issue. SiO(2) is the sole exception. Equilibrium modeling of precipitation reactions confirms the effectiveness of this scaling-mitigation approach for CaCO(3) precipitation, calcium phosphate and sulfate minerals.

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

    NASA Astrophysics Data System (ADS)

    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.

  4. Passive nutrient addition for the biodegradation of ethylene glycol in storm water.

    PubMed

    Safferman, Steven I; Azar, Roger A; Sigler, Stephanie

    2002-01-01

    This laboratory proof-of-concept research examined the feasibility of adding solid, slow-release macronutrients to a biofilm reactor system to achieve the effective biodegradation of a predominately organic polluted storm water. The target scenario was treating ethylene glycol in storm water, representing the runoff of airport deicing and anti-icing fluids. However, the results can also be generalized for any water polluted with a predominately carbonaceous material. The use of a solid, slow-release nutrient source, compared to amending with a soluble solution in proportion to influent flow, would be ideal for storm water applications and other specialized wastewater flows when maintenance requirements and operational support must be minimized. Several commercially available fertilizers were preliminarily examined to determine which had the best potential to provide the required amount of nutrients. A time-released, polymer-coated granular fertilizer was ultimately selected. Based on laboratory studies, it was found that this fertilizer could provide a controllable source of macronutrients that enabled treatment to a similar degree as if the macronutrients had been dissolved in the influent. The only major operational problem was reduced nutrient delivery from the fertilizer after it became coated with a thick biofilm. However, the inherent intermittent nature of storm water production resulting in wet/dry cycles may minimize the development of a thick biofilm.

  5. Atmospheric transport and deposition, an additional input pathway for triazine herbicides to surface waters

    SciTech Connect

    Muir, D.C.G.; Rawn, D.F.

    1996-10-01

    Although surface runoff from treated fields is regarded as the major route of entry of triazine herbicides to surface waters, other pathways such as deposition via precipitation, gas absorption and dryfall may also be important. Triazine herbicides have been detected in precipitation but there has been only a very limited amount of work on gas phase and aerosols. To examine the importance of atmospheric inputs concentrations of atrazine, cyanazine and terbuthylazine in gas phase/aerosols, precipitation, and surface waters were determined (along with other herbicides) using selected ion GC-MS. Atrazine was detected at low ng/L concentrations in surface waters (<0.04-5.3 ng/L) and precipitation (0.1-53 ng/L), and at 0.02-0.1 ng/m{sup 3} in air. Cyanazine and terbuthylazine were detected in air and infrequently in water. Highest atrazine concentrations in air were found during June each year on both gas phase and particles. Concentrations of atrazine in surface waters at both locations increased during June, even in the absence of precipitation or overland flow, presumably due to inputs from dryfall and to gas areas and boreal forest lakes due to transport and deposition. Ecological risk assessment of triazines, especially for pristine aquatic environments should include consideration of this atmospheric pathway.

  6. Water as probe molecule for midgap states in nanocrystalline strontium titanate by conventional and synchronous luminescence spectroscopy under ambient conditions

    NASA Astrophysics Data System (ADS)

    Taylor, Sean; Samokhvalov, Alexander

    2017-03-01

    Alkaline earth metal titanates are broad bandgap semiconductors with applications in electronic devices, as catalysts, photocatalysts, sorbents, and sensors. Strontium titanate SrTiO3 is of interest in electronic devices, sensors, in the photocatalytic hydrogen generation, as catalyst and sorbent. Both photocatalysis and operation of electronic devices rely upon the pathways of relaxation of excited charge in the semiconductor, including relaxation through the midgap states. We report characterization of nanocrystalline SrTiO3 at room temperature by "conventional" vs. synchronous luminescence spectroscopy and complementary methods. We determined energies of radiative transitions in the visible range through the two midgap states in the nanocrystalline SrTiO3. Further, adsorption and desorption of vapor of water as "probe molecule" for midgap states in the nanocrystalline SrTiO3 was studied, for the first time, by luminescence spectroscopy under ambient conditions. Emission of visible light from the nanocrystalline SrTiO3 is significantly increased upon desorption of water and decreased (quenched) upon adsorption of water vapor, due to interactions with the surface midgap states.

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

    PubMed

    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.

  8. Charge-specific size-dependent separation of water-soluble organic molecules by fluorinated nanoporous networks

    PubMed Central

    Byun, Jeehye; Patel, Hasmukh A.; Thirion, Damien; Yavuz, Cafer T.

    2016-01-01

    Molecular architecture in nanoscale spaces can lead to selective chemical interactions and separation of species with similar sizes and functionality. Substrate specific sorbent chemistry is well known through highly crystalline ordered structures such as zeolites, metal organic frameworks and widely available nanoporous carbons. Size and charge-dependent separation of aqueous molecular contaminants, on the contrary, have not been adequately developed. Here we report a charge-specific size-dependent separation of water-soluble molecules through an ultra-microporous polymeric network that features fluorines as the predominant surface functional groups. Treatment of similarly sized organic molecules with and without charges shows that fluorine interacts with charges favourably. Control experiments using similarly constructed frameworks with or without fluorines verify the fluorine-cation interactions. Lack of a σ-hole for fluorine atoms is suggested to be responsible for this distinct property, and future applications of this discovery, such as desalination and mixed matrix membranes, may be expected to follow. PMID:27830697

  9. Nutrient additions by waterfowl to lakes and reservoirs: predicting their effects on productivity and water quality

    USGS Publications Warehouse

    Manny, Bruce A.; Johnson, W.C.; Wetzel, R.G.

    1994-01-01

    Lakes and reservoirs provide water for human needs and habitat for aquatic birds. Managers of such waters may ask whether nutrients added by waterfowl degrade water quality. For lakes and reservoirs where primary productivity is limited by phosphorus (P), we developed a procedure that integrates annual P loads from waterfowl and other external sources, applies a nutrient load-response model, and determines whether waterfowl that used the lake or reservoir degraded water quality. Annual P loading by waterfowl can be derived from a figure in this report, using the days per year that each kind spent on any lake or reservoir. In our example, over 6500 Canada geese (Branta canadensis) and 4200 ducks (mostly mallards, Anas platyrhynchos) added 4462 kg of carbon (C), 280 kg of nitrogen (N), and 88 kg of P y-1 to Wintergreen Lake in southwestern Michigan, mostly during their migration. These amounts were 69% of all C, 27% of all N, and 70% of all P that entered the lake from external sources. Loads from all external sources totaled 840 mg P m-2 y-1. Application of a nutrient load-response model to this concentration, the hydraulic load (0.25 m y-1), and the water residence time (9.7 y) of Wintergreen Lake yielded an average annual concentration of total P in the lake of 818 mg m-3 that classified the lake as hypertrophic. This trophic classification agreed with independent measures of primary productivity, chlorophyll-a, total P, total N, and Secchi disk transparency made in Wintergreen Lake. Our procedure showed that waterfowl caused low water quality in Wintergreen Lake.

  10. The influence of polyvinylacetate additive in water on turbulent velocity field and drag reduction

    NASA Astrophysics Data System (ADS)

    Lodes, A.; Macho, V.

    1989-06-01

    The effect of polymer concentration on drag reduction was studied experimentally with diluted water solutions of polyvinylacetate in a 2.4 cm I. D. pipe. The instantaneous local velocities of the velocity fields were measured by a one-channel differential laser-Doppler anemometer DISA Mark II, with forward scattering. Concentrations of water-polyvinylacetate over the range from 10 to 2,000 ppm were used. The drag reduction coefficient is proportional to the concentration and hydrolysis degree of the saponificated polyvinylacetate (PVAC) employed. A mechanical degradation in the turbulent shear flow was not observed.

  11. Incorporation of metabolically stable ketones into a small molecule probe to increase potency and water solubility.

    PubMed

    Larraufie, Marie-Helene; Yang, Wan Seok; Jiang, Elise; Thomas, Ajit G; Slusher, Barbara S; Stockwell, Brent R

    2015-11-01

    Introducing a reactive carbonyl to a scaffold that does not otherwise have an electrophilic functionality to create a reversible covalent inhibitor is a potentially useful strategy for enhancing compound potency. However, aldehydes are metabolically unstable, which precludes the use of this strategy for compounds to be tested in animal models or in human clinical studies. To overcome this limitation, we designed ketone-based functionalities capable of forming reversible covalent adducts, while displaying high metabolic stability, and imparting improved water solubility to their pendant scaffold. We tested this strategy on the ferroptosis inducer and experimental therapeutic erastin, and observed substantial increases in compound potency. In particular, a new carbonyl erastin analog, termed IKE, displayed improved potency, solubility and metabolic stability, thus representing an ideal candidate for future in vivo cancer therapeutic applications.

  12. Three-body breakup in dissociative electron attachment to the water molecule

    SciTech Connect

    Haxton, Daniel J.; Rescigno, Thomas N.; McCurdy, C. William

    2008-08-28

    We report the results of {\\em ab initio} calculations on dissociative electron attachment (DEA) to water that demonstrate the importance of including three-body breakup in the dissociation dynamics. While three-body breakup is ubiquitous in the analogous process of dissociative recombination, its importance in low-energy dissociative electron attachment to a polyatomic target has not previously been quantified. Our calculations, along with our earlier studies of DEA into two-body channels, indicate that three-body breakup is a major component of the observed O- cross section. The local complex potential model provides a generally accurate picture of the experimentallyobserved features in this system, reproducing some quantitatively, others qualitatively, and one not at all.

  13. Unified Effect of Hydrophobic Hydration on the Dynamics and the Structure of Water Molecules in Lower Alcohol Aqueous Solutions

    NASA Astrophysics Data System (ADS)

    Nakada, Masaru; Maruyama, Kenji; Yamamuro, Osamu; Kikuchi, Tatsuya; Misawa, Masakatsu

    2011-04-01

    After the analysis of the quasi-elastic neutron scattering (QENS) spectra of lower alcoholic aqueous solutions, we found that the parameter α, which is the number fraction of hydrophobic hydrating water molecules, has an important role in describing the dynamics and other properties of these solutions. The diffusion coefficient D was obtained from QENS spectra using the relaxing cage model, and D was found to have the same linear relation against α for ethyl alcohol, n-propyl alcohol, i-propyl alcohol, and t-butyl alcohol (with a small deviation) aqueous solutions. The excess molar volume and average hydration number of these solutions could also be expressed with common parameters, which are independent of the alcohol species.

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

    NASA Astrophysics Data System (ADS)

    Chakraborty, Kaushik; Bandyopadhyay, Sanjoy

    2015-07-01

    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.

  15. Crystal Structure of Fatty Acid Amide Hydrolase Bound to the Carbamate Inhibitor URB597: Discovery of a Deacylating Water Molecule and Insight into Enzyme Inactivation

    SciTech Connect

    Mileni, Mauro; Kamtekar, Satwik; Wood, David C.; Benson, Timothy E.; Cravatt, Benjamin F.; Stevens, Raymond C.

    2010-08-12

    The endocannabinoid system regulates a wide range of physiological processes including pain, inflammation, and cognitive/emotional states. URB597 is one of the best characterized covalent inhibitors of the endocannabinoid-degrading enzyme fatty acid amide hydrolase (FAAH). Here, we report the structure of the FAAH-URB597 complex at 2.3 {angstrom} resolution. The structure provides insights into mechanistic details of enzyme inactivation and experimental evidence of a previously uncharacterized active site water molecule that likely is involved in substrate deacylation. This water molecule is part of an extensive hydrogen-bonding network and is coordinated indirectly to residues lining the cytosolic port of the enzyme. In order to corroborate our hypothesis concerning the role of this water molecule in FAAH's catalytic mechanism, we determined the structure of FAAH conjugated to a urea-based inhibitor, PF-3845, to a higher resolution (2.4 {angstrom}) than previously reported. The higher-resolution structure confirms the presence of the water molecule in a virtually identical location in the active site. Examination of the structures of serine hydrolases that are non-homologous to FAAH, such as elastase, trypsin, or chymotrypsin, shows a similarly positioned hydrolytic water molecule and suggests a functional convergence between the amidase signature enzymes and serine proteases.

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

    PubMed

    Chakraborty, Kaushik; Bandyopadhyay, Sanjoy

    2015-07-28

    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.

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

    SciTech Connect

    Chakraborty, Kaushik; Bandyopadhyay, Sanjoy

    2015-07-28

    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.

  18. X-ray multiphoton ionization dynamics of a water molecule irradiated by an x-ray free-electron laser pulse

    NASA Astrophysics Data System (ADS)

    Inhester, Ludger; Hanasaki, Kota; Hao, Yajiang; Son, Sang-Kil; Santra, Robin

    2016-08-01

    We present a theoretical investigation of x-ray multiphoton ionization dynamics of polyatomic molecules, based on the rate equation model and molecular electronic structure calculations. An efficient numerical procedure is developed to calculate photoionization cross sections, Auger rates, and fluorescence rates for all possible electronic multiple-hole configurations of molecules. We investigate the charge-state distribution of a water molecule after interaction with an intense x-ray pulse and discuss its dependence on the fluence and the pulse duration of the x-ray beam. Our results demonstrate that a water molecule exposed to an intense x-ray pulse is more ionized than what would be expected within the independent-atom picture.

  19. Addition of a worm leachate as source of humic substances in the drinking water of broiler chickens.

    PubMed

    Gomez-Rosales, S; de L Angeles, M

    2015-02-01

    The objective of this research was to evaluate the growth performance, the apparent ileal digestibility of nitrogen and energy, the retention of nutrients and the apparent metabolizable energy corrected to zero nitrogen retention (AMEn) in broiler chickens supplemented with increasing doses of a worm leachate (WL) as a source of humic substances (HS) in the drinking water. In Exp. 1, 140 male broilers were penned individually and assigned to four WL levels (0%, 10%, 20%, and 30%) mixed in the drinking water from 21 to 49 days of age. Water was offered in plastic bottles tied to the cage. In Exp. 2, 600 male broilers from 21 to 49 days of age housed in floor pens were assigned to three levels of WL (0%, 10%, and 20%) mixed in the drinking water. The WL was mixed with tap water in plastic containers connected by plastic tubing to bell drinkers. The results of both experiments were subjected to analysis of variance and polynomial contrasts. In Exp. 1, the daily water consumption was similar among treatments but the consumption of humic, fulvic, and total humic acids increased linearly (p<0.01) as the WL increased in the drinking water. The feed conversion (p<0.01) and the ileal digestibility of energy, the excretion of dry matter and energy, the retention of dry matter, ash and nitrogen and the AMEn showed quadratic responses (p<0.05) relative to the WL levels in drinking water. In Exp. 2, the increasing level of WL in the drinking water had quadratic effects on the final body weight, daily weight gain and feed conversion ratio (p<0.05). The addition of WL as a source of HS in the drinking water had beneficial effects on the growth performance, ileal digestibility of energy, the retention of nutrients as well on the AMEn in broiler chickens; the best results were observed when the WL was mixed at levels of 20% to 30% in the drinking water.

  20. Effect of addition of coconut water (Cocos nucifera) to the freezing media on post-thaw viability of boar sperm.

    PubMed

    Bottini-Luzardo, María; Centurión-Castro, Fernando; Alfaro-Gamboa, Militza; Aké-López, Ricardo; Herrera-Camacho, José

    2013-01-01

    The aims of this experiment were to evaluate the addition of coconut water in natura to the freezing media, compare the effect of deionized water vs filtered water of coconut over the post-thaw seminal characteristics, and evaluate the effect of the deionized water and in natura coconut water on the seminal characteristics of boar sperm at different post-thaw times. Thirty-four ejaculates were used divided in three aliquots which received one of the following treatments (T): T1, LEY (bidistilled water, lactose, and egg yolk) and LEYGO (LEY + glycerol and Orvus ET paste); T2, LEY(A) (coconut deionized water, lactose, and egg yolk)-LEYGO(A); and T3, LEY(B) (in natura coconut water, lactose, and egg yolk)-LEYGO(B). Samples of boar semen were frozen according to the Westendorf method, thawed at 38°C, and evaluated at three incubation times (0, 30, and 60 min). Seminal characteristics assessed were motility (Mot), acrosomal integrity (AInt), membrane integrity (MInt), and mitochondrial activity (MAct). T1 showed a higher percentage of viable sperm than T3 (Mot 36.5 vs 5.4 %, AInt 61.8 vs 41.2 %, MInt 50.4 vs 41.3 %, and MAct 56.9 vs 50.5 %). T2 kept a higher percentage of viable sperm at all incubation times. In natura coconut water showed a detrimental effect over the viability of the frozen-thawed boar semen. Deionized coconut water improved the boar semen viability post-thaw, outperforming results of in natura coconut water.

  1. Corrosion and Heat Transfer Characteristics of Water Dispersed with Carboxylate Additives and Multi Walled Carbon Nano Tubes

    NASA Astrophysics Data System (ADS)

    Moorthy, Chellapilla V. K. N. S. N.; Srinivas, Vadapalli

    2016-10-01

    This paper summarizes a recent work on anti-corrosive properties and enhanced heat transfer properties of carboxylated water based nanofluids. Water mixed with sebacic acid as carboxylate additive found to be resistant to corrosion and suitable for automotive environment. The carboxylated water is dispersed with very low mass concentration of carbon nano tubes at 0.025, 0.05 and 0.1 %. The stability of nanofluids in terms of zeta potential is found to be good with carboxylated water compared to normal water. The heat transfer performance of nanofluids is carried out on an air cooled heat exchanger similar to an automotive radiator with incoming air velocities across radiator at 5, 10 and 15 m/s. The flow Reynolds number of water is in the range of 2500-6000 indicating developing flow regime. The corrosion resistance of nanofluids is found to be good indicating its suitability to automotive environment. There is a slight increase in viscosity and marginal decrease in the specific heat of nanofluids with addition of carboxylate as well as CNTs. Significant improvement is observed in the thermal conductivity of nanofluids dispersed with CNTs. During heat transfer experimentation, the inside heat transfer coefficient and overall heat transfer coefficient has also improved markedly. It is also found that the velocity of air and flow rate of coolant plays an important role in enhancement of the heat transfer coefficient and overall heat transfer coefficient.

  2. Additive Effect on Soybean Peroxidase-Catalyzed Removal of Anilines from Water

    PubMed Central

    Mazloum, Samar; Al-Ansari, Mohammed Mousa; Taylor, Keith; Bewtra, Jatinder K.; Biswas, Niharendu

    2016-01-01

    Abstract Soybean peroxidase has been shown to be effective in removal of aromatic compounds from wastewater, while the use of additives effectively reduces enzyme concentration requirement, hence overall treatment cost. Enzymatic treatment, an oxidative polymerization, was successful in removal of over 95% of both aniline and o-anisidine. The originality of this study lies in the findings that the additives, sodium dodecyl sulfate (SDS), sodium dodecylbenzenesulfonate (SDBS), Triton X-100, and sodium dodecanoate (SDOD), reduced enzyme concentration requirement, while polyethylene glycol (PEG, average molar mass of 3350 g/mol) had no effect on the required enzyme concentration. In addition, the presence of SDS also enhanced treatment by improving precipitation and color removal. These results are enabling advancement of soybean peroxidase-catalyzed treatment of anilines found in wastewaters as a new sustainable method. PMID:26989345

  3. Testing the Addition of Topographic Features for Field Scale Infiltration Excess Water Quality Modeling in SWAT

    NASA Astrophysics Data System (ADS)

    Collick, A.; Easton, Z. M.; Kleinman, P. J. A.; Sommerlot, A.; White, M. J.; Harmel, D.; Fuka, D.

    2014-12-01

    Watershed planners and managers need reliable tools that can capture the spatial and temporal complexity of agricultural landscapes, and water quality models are increasingly relied upon to represent P loss from agricultural watersheds. While a significant amount of modeling work has attempted to incorporate factors controlling P loss (e.g. representing solubility, manure types, timing and application type), these models still typically require significant calibration and are thus difficult to apply meaningfully in areas without copious data with which to calibrate. This is partially because these models were never really intended as field scale tools, while we are trying to use them to define different hydrologic pathways, area weighted potential energy (slopes and saturated conductivities), and the resulting lag time of P in different transport states. The movement of water within the landscape as surface (or near-surface) storm runoff and interflow is driven by gravity, topography, contributing area and soil and landuse characteristics, which play roles in concentrating water flows. Soil surveys have played a key role in the development of pedology and spatially derived pedon soil maps have become valuable datasets for natural resource management. Unfortunately, the soil surveys, commonly available at ~1:20,000 scale, are not designed to provide the high-resolution models of the soil continuum required in field scale environmental modeling applications and site specific crop and water quality management. The goal of this project is to test a methodology designed initially for representing saturation excess hydrology in the SWAT model to incorporate topographic attributes, and resulting spatially explicit soil morphology, that are missing from standard SWAT model initializations.

  4. Understanding the site selectivity in small-sized neutral and charged Al(n) (4 ≤ N ≤ 7) clusters using density functional theory based reactivity descriptors: a validation study on water molecule adsorption.

    PubMed

    Das, Susanta; Pal, Sourav; Krishnamurty, Sailaja

    2013-09-12

    Aluminum clusters are now technologically important due to their high catalytic activity. Our present study on the small-sized aluminum clusters applies density functional theory (DFT)-based reactivity descriptors to identify potential sites for adsorption and eventual chemical reaction. Depending on symmetry, susceptibility of various type of reactive sites within a cluster toward an impending electrophilic and/or nucleophilic attack is predicted using the reactivity descriptors. In addition, the study devises general rules as to how the size, shape, and charge of the cluster influences the number of available sites for an electrophilic and/or nucleophilic attack. The predictions by reactivity descriptors are validated by performing an explicit adsorption of water molecule on Al clusters with four atoms. The adsorption studies demonstrate that the most stable water-cluster complex is obtained when the molecule is adsorbed through an oxygen atom on the site with the highest relative electrophilicity.

  5. Additive Effects on Si3n4 Oxidation/Volatilization in Water Vapor

    NASA Technical Reports Server (NTRS)

    Opila, Elizabeth J.; Robinson, R. Craig; Fox, Dennis S.; Wenglarz, Richard A.; Ferber, Mattison K.

    2002-01-01

    Two commercially available additive-containing silicon nitride materials were exposed in four environments which range in severity from dry oxygen at 1 atm pressure, and low gas velocity to an actual turbine engine. Oxidation and volatilization kinetics were monitored at temperatures ranging from 1066 to 1400 C. The main purpose of this paper is to examine the surface oxide morphology resulting from the exposures. It was found that the material surface was enriched in rare earth silicate phases in combustion environments when compared to the oxides formed on materials exposed in dry oxygen. However, the in situ formation of rare earth disilicate phases offered little additional protection from the volatilization of silica observed in combustion environments. It was concluded that externally applied environmental barrier coatings are needed to protect additive-containing silicon nitride materials from volatilization reactions in combustion environments. Introduction Si3N4 is proposed for use as components, such as vanes, in turbine applications. Tens of thousands of hours of life are needed for both land-based turbines and aeropropulsion applications. Additive-containing SisN4 materials are

  6. Interactions between organic additives and active powders in water-based lithium iron phosphate electrode slurries

    NASA Astrophysics Data System (ADS)

    Li, Chia-Chen; Lin, Yu-Sheng

    2012-12-01

    The interactions of organic additives with active powders are investigated and are found to have great influence on the determination of the mixing process for preparing electrode slurries with good dispersion and electrochemical properties of lithium iron phosphate (LiFePO4) electrodes. Based on the analyses of zeta potential, sedimentation, and rheology, it is shown that LiFePO4 prefers to interact with styrene-butadiene rubber (SBR) relative to other organic additives such as sodium carboxymethyl cellulose (SCMC), and thus shows preferential adsorption by SBR, whereas SBR has much lower efficiency than SCMC in dispersing LiFePO4. Therefore, for SCMC to interact with and disperse LiFePO4 before the interaction of LiFePO4 with SBR, it is suggested to mix SCMC with LiFePO4 prior to the addition of SBR during the slurry preparation process. For the electrode prepared via the suggested process, i.e., the sequenced adding process in which SCMC is mixed with active powders prior to the addition of SBR, a much better electrochemical performance is obtained than that of the one prepared via the process referred as the simultaneous adding process, in which mixing of SCMC and SBR with active powders in simultaneous.

  7. Chill water additive controls transfer of Salmonella and Campylobacter by improved chlorine efficacy

    Technology Transfer Automated Retrieval System (TEKTRAN)

    In earlier work, we showed that a proprietary additive (T-128) maintains chlorine activity in the presence of organic material such as broiler parts. T-128 improves the efficacy of chlorine to control transfer of Campylobacter and Salmonella from inoculated wings to un-inoculated wings during immer...

  8. 78 FR 42692 - Food Additives Permitted in Feed and Drinking Water of Animals; Ammonium Formate

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-07-17

    ..., Center for Veterinary Medicine (HFV-6), Food and Drug Administration, 7519 Standish Pl., Rockville, MD... Veterinary Medicine, 21 CFR part 573 is amended as follows: PART 573--FOOD ADDITIVES PERMITTED IN FEED AND...: July 11, 2013. Bernadette Dunham, Director, Center for Veterinary Medicine. BILLING CODE 4160-01-P...

  9. The rates of exchange of water molecules from Al(III)-methylmalonate complexes: The effect of chelate ring size

    SciTech Connect

    Casey, W.H.; Phillips, B.L.; Nordin, J.P.; Sullivan, D.J.

    1998-08-01

    Rate coefficients are reported for exchange of hydration waters in the inner-coordination-sphere of Al(III)-methylmalonate complexes with bulk solution as determined via {sup 17}O-NMR. Surprisingly, water molecules in the thermodynamically less-stable complexes containing six-membered chelates are much more labile than those in five-membered oxalate-A(III) complexes. The surprising trend in reactivity is attributable either to differences in the Lewis basicities of oxygens in bidentate oxalate and methylmalonate ligands, or to rapid dissociation/reassociation of one of the acetate groups to the metal center. These results identify a useful case where trends in the apparent labilities of dissolved and presumed surface complexes deviate sharply. This deviation could be usefully exploited to probe surfaces if ligand-promoted dissolution rates could be compared at conditions where inner-sphere and outer-sphere chelate complexes could be distinguished spectroscopically. The authors expect inner-sphere oxalate to have a smaller labilizing effect than malonate or methylmalonate. A contrary result would indicate structural dissimilarity between complexes on the surface and in solution, or perhaps steric hindrance.

  10. Significant Change in Marine Plankton Structure and Carbon Production After the Addition of River Water in a Mesocosm Experiment.

    PubMed

    Fouilland, E; Trottet, A; Alves-de-Souza, C; Bonnet, D; Bouvier, T; Bouvy, M; Boyer, S; Guillou, L; Hatey, E; Jing, H; Leboulanger, C; Le Floc'h, E; Liu, H; Mas, S; Mostajir, B; Nouguier, J; Pecqueur, D; Rochelle-Newall, E; Roques, C; Salles, C; Tournoud, M-G; Vasseur, C; Vidussi, F

    2017-03-16

    Rivers are known to be major contributors to eutrophication in marine coastal waters, but little is known on the short-term impact of freshwater surges on the structure and functioning of the marine plankton community. The effect of adding river water, reducing the salinity by 15 and 30%, on an autumn plankton community in a Mediterranean coastal lagoon (Thau Lagoon, France) was determined during a 6-day mesocosm experiment. Adding river water brought not only nutrients but also chlorophyceans that did not survive in the brackish mesocosm waters. The addition of water led to initial increases (days 1-2) in bacterial production as well as increases in the abundances of bacterioplankton and picoeukaryotes. After day 3, the increases were more significant for diatoms and dinoflagellates that were already present in the Thau Lagoon water (mainly Pseudo-nitzschia spp. group delicatissima and Prorocentrum triestinum) and other larger organisms (tintinnids, rotifers). At the same time, the abundances of bacterioplankton, cyanobacteria, and picoeukaryote fell, some nutrients (NH4(+), SiO4(3-)) returned to pre-input levels, and the plankton structure moved from a trophic food web based on secondary production to the accumulation of primary producers in the mesocosms with added river water. Our results also show that, after freshwater inputs, there is rapid emergence of plankton species that are potentially harmful to living organisms. This suggests that flash flood events may lead to sanitary issues, other than pathogens, in exploited marine areas.

  11. Effect of water addition on selective consumption (sorting) of dry diets by dairy cattle.

    PubMed

    Leonardi, C; Giannico, F; Armentano, L E

    2005-03-01

    The objective of this study was to determine whether adding water to a dry diet would reduce sorting and improve cow performance. Eighteen multiparous lactating Holstein cows were used in a cross-over design with 21-d periods. Treatments had the same dietary composition and differed only by adding water (WET) or not (DRY). Diets consisted of 10% alfalfa silage, 30% hay (approximately 80% grass and 20% alfalfa), and 60% concentrate [dry matter (DM) basis]. Dietary DM was 80.8% for DRY and 64.4% for WET. Both diets contained 16.9% crude protein and 24.3% neutral detergent fiber. Particle size was determined using the Wisconsin Particle Size Separator on the as-fed diets. The separator has five square-hole screens (Y(1) to Y(5)) with diagonal openings of 26.9 mm for Y(1), 18 mm for Y(2), 8.98 mm for Y(3), 5.61 mm for Y(4), and 1.65 mm for Y(5), and one pan. Sorting was calculated on a 60 degrees C DM basis (60DM). Predicted intake of Y(i) was calculated as the product of 60DM intake (60DMI) and the 60DM fraction of Y(i) in the total mixed ration for that screen. For DRY and WET, actual 60DMI by screen expressed as a percentage of predicted intake was 61.4% vs. 75.2% for Y(1), 83.8% vs. 98.6% for Y(2), 85.6% vs. 90.8% for Y(3), 95.2% vs. 96.0% for Y(4), 100.1% vs. 101.9% for Y(5), and 105.9% vs. 102.9% for pan, respectively. Adding water did not affect total DM intake (28.3 kg/d) or milk production (41.3 kg/d). Neutral detergent fiber intake was 6.42 kg/d for WET and 6.15 kg/d for DRY. Milk fat percentage tended to be higher (3.41% vs. 3.31%) when cows consumed WET vs. DRY. No differences in ruminal pH, NH(3), and volatile fatty acids were observed. Cows sorted against long particles in favor of shorter particles on both diets. Adding water to dry diets reduced sorting and tended to increase neutral detergent fiber intake and milk fat percentage.

  12. Effects of Proposed Additional Ground-Water Withdrawals from the Mississippi River Valley Alluvial Aquifer on Water Levels in Lonoke County, Arkansas

    USGS Publications Warehouse

    Czarnecki, John B.

    2006-01-01

    The Grand Prairie Water Users Association, located in Lonoke County, Arkansas, plans to increase ground-water withdrawals from the Mississippi River Valley alluvial aquifer from their current (2005) rate of about 400 gallons per minute to 1,400 gallons per minute (2,016,000 gallons per day). The effect of pumping from a proposed well was simulated using a digital model of ground-water flow. The proposed additional withdrawals were added to an existing pumping cell specified in the model, with increased pumping beginning in 2005, and specified to pump at a total combined rate of 2,016,000 gallons per day for a period of 46 years. In addition, pumping from wells owned by Cabot Water Works, located about 2 miles from the proposed pumping, was added to the model beginning in 2001 and continuing through to the end of 2049. Simulated pumping causes a cone of depression to occur in the alluvial aquifer with a maximum decline in water level of about 8.5 feet in 46 years in the model cell of the proposed well compared to 1998 withdrawals. However, three new dry model cells occur south of the withdrawal well after 46 years. This total water-level decline takes into account the cumulative effect of all wells pumping in the vicinity, although the specified pumping rate from all other model cells in 2005 is less than for actual conditions in 2005. After 46 years with the additional pumping, the water-level altitude in the pumped model cell was about 177.4 feet, which is 41.7 feet higher than 135.7 feet, the altitude corresponding to half of the original saturated thickness of the alluvial aquifer (a metric used to determine if the aquifer should be designated as a Critical Ground-Water Area (Arkansas Natural Resources Commission, 2006)).

  13. A first screening and risk assessment of pharmaceuticals and additives in personal care products in waste water, sludge, recipient water and sediment from Faroe Islands, Iceland and Greenland.

    PubMed

    Huber, Sandra; Remberger, Mikael; Kaj, Lennart; Schlabach, Martin; Jörundsdóttir, Hrönn Ó; Vester, Jette; Arnórsson, Mímir; Mortensen, Inge; Schwartson, Richard; Dam, Maria

    2016-08-15

    A screening of a broad range of pharmaceuticals and additives in personal care products (PPCPs) in sub-arctic locations of the Faroe Islands (FO), Iceland (IS) and Greenland (GL) was conducted. In total 36 pharmaceuticals including some metabolites, and seven additives in personal care products were investigated in influent and effluent waters as well as sludge of waste water treatment plants (WWTPs) and in water and sediment of recipients. Concentrations and distribution patterns for PPCPs discharged via sewage lines (SLs) to the marine environment were assessed. Of the 36 pharmaceuticals or metabolites analysed 33 were found close to or above the limit of detection (LOD) in all or a part of the samples. All of the seven investigated additives in personal care products were detected above the LOD. Some of the analysed PPCPs occurred in every or almost every sample. Among these were diclofenac, ibuprofen, lidocaine, naproxen, metformin, citalopram, venlafaxine, amiloride, furosemide, metoprolol, sodium dodecyl sulphate (SDS) and cetrimonium salt (ATAC-C16). Additionally, the study encompasses ecotoxicological risk assessment of 2/3 of the analysed PPCPs in recipient and diluted effluent waters. For candesartan only a small margin to levels with inacceptable risks was observed in diluted effluent waters at two locations (FO). Chronical risks for aquatic organisms staying and/or living around WWTP effluent pipe-outlets were indicated for 17β-estradiol and estriol in the three countries. Additives in PCPs were found to pose the largest risk to the aquatic environment. The surfactants CAPB and ATAC-C16 were found in concentrations resulting in risk factors up to 375 for CAPB and 165 for ATAC-C16 in recipients for diluted effluents from Iggia, Nuuk (GL) and Torshavn (FO) respectively. These results demonstrates a potentially high ecological risk stemming from discharge of surfactants as used in household and industrial detergents as well as additives in personal care

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

    PubMed

    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.

  15. Methemoglobinemia attributable to nitrite contamination of potable water through boiler fluid additives--New Jersey, 1992 and 1996.

    PubMed

    1997-03-07

    Nitrite and nitrate ions are naturally occurring forms of nitrogen that can be present in ground and surface water and can be used as a food preservative because they inhibit the growth of Clostridium botulinum. Exposure to excessive levels of nitrite or nitrate may result in the acute syndrome of methemoglobinemia (MetHb), in which nitrite binds to hemoglobin. This report summarizes the findings of investigations of two incidents in which unintentional exposure to high doses of nitrite occurred through drinking potable water contaminated with additives to boiler conditioning fluids.

  16. Dihydrogen phosphate-water tape and layers vs dihydrogen phosphate layers tuned by hydrophobic isomeric pyridine-diamine functionalized molecules

    NASA Astrophysics Data System (ADS)

    Huang, Jing; Liu, Tong-Peng; Huo, Li-Hua; Deng, Zhao-Peng; Gao, Shan

    2017-01-01

    Assembly of six isomeric pyridine-diamine-based molecules, N,N‧-bis(pyridin-4-ylmethyl)ethane-1,2-diamine (M1), N,N‧-bis(pyridin-3-ylmethyl)ethane-1,2-diamine (M2), N,N‧-bis(pyridin-2-ylmethyl)ethane-1,2-diamine (M3), N,N‧-bis(pyridin-4-ylmethyl)propane-1,3-diamine (M4), N,N‧-bis(pyridin-3-ylmethyl)propane-1,2-diamine (M5), and N,N‧-bis(pyridin-2-ylmethyl)propane-1,3-diamine (M6), with phosphoric acid (H3PO4) in different ratio (1:2 and 1:4), leads to the formation of nine salts, H2M12+·2H2PO4-·4H2O (1), H2M22+·2H2PO4-·2H2O (2), H2M32+·2H2PO4-·2H2O (3), H4M14+·4H2PO4- (4), H4M24+·4H2PO4- (5), H4M34+·4H2PO4- (6), H2M42+·2H2PO4-·3H2O (7), 2H2M52+·4H2PO4-·2H3PO4 (8), and H2M62+·2H2PO4- (9), which have been characterized by elemental analysis, IR, TG, PL, powder and single-crystal X-ray diffraction. Structural analyses indicate that hydrogen-bonding patterns of H2PO4- anions, conformation of protonated cations can effectively influence the supramolecular architectures through diverse non-covalent interactions. Hydrous salts 1-3 and 7 present 2D and 3D host-guest supramolecular networks, in which the connection of H2PO4- anions and water molecules generates diverse tape and layer motifs. H2PO4- anions in anhydrous salts 4-6 interconnect with each other through hydrogen bonds to form two types of layers, which are joined by discrete H4M4+ cations into 3D inorganic-organic hybrid supramolecular networks. Salts 8-9 also present 2D and 3D host-guest supramolecular networks where the interconnection of H2PO4- anions and its combination with H3PO4 molecules leads to diverse layers. Luminescent analyses indicate that salts 1-9 exhibit violet and blue emission maximum in the range of 390-467 nm at room temperature.

  17. Combined quantum mechanics/molecular mechanics (QM/MM) simulations for protein-ligand complexes: free energies of binding of water molecules in influenza neuraminidase.

    PubMed

    Woods, Christopher J; Shaw, Katherine E; Mulholland, Adrian J

    2015-01-22

    The applicability of combined quantum mechanics/molecular mechanics (QM/MM) methods for the calculation of absolute binding free energies of conserved water molecules in protein/ligand complexes is demonstrated. Here, we apply QM/MM Monte Carlo simulations to investigate binding of water molecules to influenza neuraminidase. We investigate five different complexes, including those with the drugs oseltamivir and peramivir. We investigate water molecules in two different environments, one more hydrophobic and one hydrophilic. We calculate the free-energy change for perturbation of a QM to MM representation of the bound water molecule. The calculations are performed at the BLYP/aVDZ (QM) and TIP4P (MM) levels of theory, which we have previously demonstrated to be consistent with one another for QM/MM modeling. The results show that the QM to MM perturbation is significant in both environments (greater than 1 kcal mol(-1)) and larger in the more hydrophilic site. Comparison with the same perturbation in bulk water shows that this makes a contribution to binding. The results quantify how electronic polarization differences in different environments affect binding affinity and also demonstrate that extensive, converged QM/MM free-energy simulations, with good levels of QM theory, are now practical for protein/ligand complexes.

  18. Microwave-assisted synthesis of water-soluble, fluorescent gold nanoclusters capped with small organic molecules and a revealing fluorescence and X-ray absorption study

    NASA Astrophysics Data System (ADS)

    Helmbrecht, C.; Lützenkirchen-Hecht, D.; Frank, W.

    2015-03-01

    Colourless solutions of blue light-emitting, water-soluble gold nanoclusters (AuNC) were synthesized from gold colloids under microwave irradiation using small organic molecules as ligands. Stabilized by 1,3,5-triaza-7-phosphaadamantane (TPA) or l-glutamine (GLU), fluorescence quantum yields up to 5% were obtained. AuNC are considered to be very promising for biological labelling, optoelectronic devices and light-emitting materials but the structure-property relationships have still not been fully clarified. To expand the knowledge about the AuNC apart from their fluorescent properties they were studied by X-ray absorption spectroscopy elucidating the oxidation state of the nanoclusters' gold atoms. Based on curve fitting of the XANES spectra in comparison to several gold references, optically transparent fluorescent AuNC are predicted to be ligand-stabilized Au5+ species. Additionally, their near edge structure compared with analogous results of polynuclear clusters known from the literature discloses an increasing intensity of the feature close to the absorption edge with decreasing cluster size. As a result, a linear relationship between the cluster size and the X-ray absorption coefficient can be established for the first time.Colourless solutions of blue light-emitting, water-soluble gold nanoclusters (AuNC) were synthesized from gold colloids under microwave irradiation using small organic molecules as ligands. Stabilized by 1,3,5-triaza-7-phosphaadamantane (TPA) or l-glutamine (GLU), fluorescence quantum yields up to 5% were obtained. AuNC are considered to be very promising for biological labelling, optoelectronic devices and light-emitting materials but the structure-property relationships have still not been fully clarified. To expand the knowledge about the AuNC apart from their fluorescent properties they were studied by X-ray absorption spectroscopy elucidating the oxidation state of the nanoclusters' gold atoms. Based on curve fitting of the XANES

  19. THE USE OF DI WATER TO MITIGATE DUSTING FOR ADDITION OF DWPF FRIT TO THE SLURRY MIX EVAPORATOR

    SciTech Connect

    Hansen, E.

    2010-07-21

    The Defense Waste Processing Facility (DPWF) presently is in the process to determine means to reduce water utilization in the Slurry Mix Evaporator (SME) process, thus reducing effluent and processing times. The frit slurry addition system mixes the dry frit with water, yielding approximately a 50 weight percent slurry containing frit and the other fraction water. This slurry is discharged into the SME and excess water is removed via boiling. To reduce this water load to the SME, DWPF has proposed using a pneumatic system in conveying the frit to the SME, in essence a dry delivery system. The problem associated with utilizing a dry delivery system with the existing frit is the generation of dust when discharged into the SME. The use of water has been shown to be effective in the mining industry as well in the DOE complex to mitigate dusting. The method employed by SRNL to determine the quantity of water to mitigate dusting in dry powders was effective, between a lab and bench scale tests. In those tests, it was shown that as high as five weight percent (wt%) of water addition was required to mitigate dust from batches of glass forming minerals used by the Waste Treatment Plant at Hanford, Washington. The same method used to determine the quantity of water to mitigate dusting was used in this task to determine the quantity of water to mitigate this dusting using as-received frit. The ability for water to mitigate dusting is due to its adhesive properties as shown in Figure 1-1. Wetting the frit particles allows for the smaller frit particles (including dust) to adhere to the larger frit particles or to agglomerate into large particles. Fluids other than water can also be used, but their adhesive properties are different than water and the quantity required to mitigate dusting is different, as was observed in reference 1. Excessive water, a few weight percentages greater than that required to mitigate dusting can cause the resulting material not to flow. The primary

  20. A Novel Lipase as Aquafeed Additive for Warm-Water Aquaculture

    PubMed Central

    Yang, Yalin; Huang, Lu; Zhou, Zhigang

    2015-01-01

    A novel Acinetobacter lipase gene lipG1was cloned from DNA extracted from intestinal sample of common carp (Cyprinus carpio), and expressed in E. coli BL21. The encoded protein was 406 amino acids in length. Phylogenetic analysis indicated that LipG1 and its relatives comprised a novel group of true lipases produced by Gram-negative bacteria. LipG1 showed maximal activity at 40℃ and pH 8.0 when pNP decanoate (C10) was used as the substrate, and remained high activity between 20℃ and 35℃. Activity of the lipase was promoted by Ca2+ and Mg2+, and inhibited by Zn2+ and Cu2+. Moreover, LipG1 is stable with proteases, most commercial detergents and organic solvents. Substrate specificity test indicated that LipG1can hydrolyse pNP esters with acyl chain length from C2 to C16, with preference for medium-chain pNP esters (C8, C10). Lastly, LipG1was evaluated as an aquafeed additive for juvenile common carp (Cyprinus carpio). Results showed that supplementation of LipG1significantly improved the gut and heptaopancreas lipase activity of fish fed with palm oil diet. Consistently, improved feed conversion ratio and growth performance were recorded in the LipG1 feeding group, to levels comparable to the group of fish fed with soybean oil diet. Collectively, LipG1 exhibited good potential as an aquafeed additive enzyme, and deserves further characterization as the representative of a novel group of lipases. PMID:26147311

  1. A Novel Lipase as Aquafeed Additive for Warm-Water Aquaculture.

    PubMed

    Ran, Chao; He, Suxu; Yang, Yalin; Huang, Lu; Zhou, Zhigang

    2015-01-01

    A novel Acinetobacter lipase gene lipG1 was cloned from DNA extracted from intestinal sample of common carp (Cyprinus carpio), and expressed in E. coli BL21. The encoded protein was 406 amino acids in length. Phylogenetic analysis indicated that LipG1 and its relatives comprised a novel group of true lipases produced by Gram-negative bacteria. LipG1 showed maximal activity at 40℃ and pH 8.0 when pNP decanoate (C10) was used as the substrate, and remained high activity between 20℃ and 35℃. Activity of the lipase was promoted by Ca2+ and Mg2+, and inhibited by Zn2+ and Cu2+. Moreover, LipG1 is stable with proteases, most commercial detergents and organic solvents. Substrate specificity test indicated that LipG1 can hydrolyse pNP esters with acyl chain length from C2 to C16, with preference for medium-chain pNP esters (C8, C10). Lastly, LipG1 was evaluated as an aquafeed additive for juvenile common carp (Cyprinus carpio). Results showed that supplementation of LipG1 significantly improved the gut and heptaopancreas lipase activity of fish fed with palm oil diet. Consistently, improved feed conversion ratio and growth performance were recorded in the LipG1 feeding group, to levels comparable to the group of fish fed with soybean oil diet. Collectively, LipG1 exhibited good potential as an aquafeed additive enzyme, and deserves further characterization as the representative of a novel group of lipases.

  2. Enhancing water repellence and mechanical properties of gelatin films by tannin addition.

    PubMed

    Peña, Cristina; de la Caba, Koro; Eceiza, Arantxa; Ruseckaite, Roxana; Mondragon, Iñaki

    2010-09-01

    In order to reduce pollution caused by traditional non-biodegradable plastic films, renewable raw materials from plants and wastes of meat industries have been employed in this work. A hydrolysable chestnut-tree tannin was used for gelatin modification. Films of gelatin and gelatin-tannin were obtained by casting at room conditions. Transition temperatures of both gelatin and gelatin-tannin systems were determined by differential scanning calorimetry (DSC). Glass transition temperatures of modified gelatin occurred at higher temperatures than for neat gelatin. Enthalpy and temperature of helix-coil transition decreased when tannin content increased due to variations in the helical structure of gelatin as a consequence of tannin presence in agreement with X-ray analysis. Mechanical and thermal behaviour varied as a function of the content of tannin, showing optimum values for films modified with 10 wt% tannin. The transparency of films was maintained after modification with tannin. Solubility and swelling tests of the films revealed that the presence of tannin reduced the water affinity of gelatin.

  3. Highly enantioselective Michael addition of cyclohexanone to nitroolefins catalyzed by pyrrolidine-based bifunctional benzoylthiourea in water.

    PubMed

    Wang, Zhen-Yu; Ban, Shu-Rong; Yang, Meng-Chen; Li, Qing-Shan

    2016-11-01

    Organocatalysis and aqueous reactions are identified as the focus of the greening of chemistry. Combining these two strategies effectively remains an interesting challenge in organic synthesis. Herein, we used pyrrolidine-based benzoylthiourea 1c to catalyze the asymmetric Michael addition of cyclohexanone to various nitroolefins in water to afford the corresponding compounds in moderate to good yields, and with excellent diastereoselectivities (up to >99:1 dr) and enantioselectivities (up to 99% ee).

  4. A new Gaussian MCTDH program : implementation and validation on the levels of the water and glycine molecules

    PubMed Central

    Skouteris, D.; Barone, V.

    2015-01-01

    We report the main features of a new general implementation of the Gaussian Multi-Configuration Time-Dependent Hartree (G-MCTDH) model. The code allows effective computations of time-dependent phenomena, including calculation of vibronic spectra (in one or more electronic states), relative state populations etc. Moreover, by expressing the Dirac-Frenkel variational principle in terms of an effective Hamiltonian we are able to provide a new reliable estimate of the representation error. After validating the code on simple one-dimensional systems, we analyze the harmonic and anharmonic vibrational spectra of water and glycine showing that reliable and converged energy levels can be obtained with reasonable computing resources. The data obtained on water and glycine are compared with results of previous calculations using the vibrational second-order perturbation theory (VPT2) method. Additional features and perspectives are also shortly discussed. PMID:24985615

  5. Phase behavior and hydrated solid structure in lysophospholipid/long-chain alcohol/water system and effect of cholesterol addition.

    PubMed

    Konno, Yoshikazu; Naito, Noboru; Yoshimura, Akio; Aramaki, Kenji

    2010-01-01

    Phase behavior in lysophospholipid/long-chain alcohol/water system at 80°C was investigated using hexanol and oleyl alcohol as the long-chain alcohol. Similarly to hydrophilic surfactant, a micellar phase in a lysophospholipid/water system transitioned to a lamellar liquid-crystalline phase by the addition of long-chain alcohol. In the oleyl alcohol system the lamellar liquid-crystalline phase was observed in wider region compared to the hexanol system. The effect of cholesterol addition on the phase behavior was also studied. The region of liquid-crystalline phase and (reverse micellar + liquid-crystalline + water) phase shifted towards higher lysophospholipid concentrations. The structure of hydrated solid as well as the transition between lamellar liquid-crystalline phase and hydrated solid was analyzed by X-ray scattering measurement and differential scanning calorimetry measurement. It was revealed that the hydrated solid was α-type crystals with lamellar structure. The hydrated solid (gel)-liquid crystal transition temperature gradually decreased with increasing oleyl alcohol concentration and the decrement was enhanced by the addition of cholesterol.

  6. Tracking all-vapor instant gas-hydrate formation and guest molecule populations: A possible probe for molecules trapped in water nanodroplets

    NASA Astrophysics Data System (ADS)

    Uras-Aytemiz, Nevin; Cwiklik, Lukasz; Paul Devlin, J.

    2012-11-01

    Quantitative Fourier-transform infrared spectra for low-temperature (160-200 K) aerosols of clathrate-hydrate nanoparticles that contain large-cage catalysts and small-cage nonpolar guests have been extended to a broad range of vapor compositions and sampling conditions. The data better reveal the stages by which room-temperature vapor mixtures, when cooled below ˜220 K, instantly generate aerosols with particles composed exclusively of the corresponding clathrate hydrates. In particular the quantitative data help relate the nature of the hydrates that form to the composition of the aqueous nanodroplets of the first stages of the rapid transition from the all-vapor mixture. The overall transition from an all-vapor mixture to "gas"-hydrate nanocrystals is a multistage one that has been characterized as homogeneous nucleation and growth of solution nanodroplets (˜240 K) followed by nucleation and growth of the gas-hydrate particles (˜220 K); all occurring within a subsecond that follows pulsing of the warm vapor into a sampling cold chamber. This may serve well as a general description of the instantaneous generation of the gas-hydrate aerosols, but closer consideration of the nature of the sampling method, in context with recent computation-based insights to (a) gas-hydrate nucleation stages/rates and (b) the lifetimes of trapped small nonpolar molecules in cold aqueous nanodroplets, suggests a more complex multistage transition. The simulated lifetimes and extensive new quantitative infrared data significantly broaden the knowledge base in which the instantaneous transition from vapor to crystalline hydrate particles is viewed. The apparent need for a high occupancy of large-cage catalytic guest molecules currently limits the practical value of the all-vapor method. Only through greater clarity in the molecular-level description of the transition will the ultimate limits be defined.

  7. Moisture effects in low-slope roofs: Drying rates after water addition with various vapor retarders

    SciTech Connect

    Pedersen, C.R.; Petrie, T.W.; Courville, G.E.; Desjarlais, A.O.; Childs, P.W.; Wilkes, K.E.

    1992-10-01

    Tests have been conducted in the Large Scale Climate Simulator (LSCS) of the US. Building Envelope Research Center at the Oak Ridge National Laboratory (ORNL) to investigate downward drying rates of various unvented, low-slope roof systems. A secondary objective was to study heat flow patterns so as to understand how to control latent heat effects on impermeable heat flux transducers. Nine test sections were tested simultaneously. The sections had a p deck above fibrous-glass insulation and were examples of cold-deck systems. These five sections had various vapor retarder systems on a gypsum board ceiling below the insulation. The other four sections had a lightweight insulating concrete deck below expanded polystyrene insulation and the same vapor retarder systems, and were examples of warm-deck systems. The cold-deck systems had materials that were relatively permeable to water vapor, while the materials in the warm-deck systems were less permeable. All test sections were topped by an impermeable roofing membrane. The test sections were instrumented with thermocouples between all layers and with small heat flux transducers at the bottom and top of the fibrous-glass insulation and in the middle of the expanded polystyrene insulation. Two different kinds of moisture probes were used to qualitatively monitor the movement of the moisture. The heat flux measurements showed that heat conduction dominates the system using impermeable insulation materials, with only a slight increase due to increased thermal conductivity of wet expanded polystyrene. There was significant transfer of latent heat in the test sections with permeable insulation, causing the peak heat fluxes to increase by as much as a factor of two. With temperatures imposed that are typical of summer days, latent heat transfer associated with condensation and evaporation of moisture in the test sections was measured to be as important as the heat transfer by conduction.

  8. Impact of mass addition on extreme water level statistics during storms along the coast of the Mediterranean Sea

    NASA Astrophysics Data System (ADS)

    Lionello, Piero; Conte, Dario; Marzo, Luigi; Scarascia, Luca

    2015-04-01

    In the Mediterranean Sea there are two contrasting factors affecting the maximum level that water will reach during a storm in the next decades: the increase of mean sea level and the decrease of storminess. Future reduction of storminess, which is associated with a decreased intensity of the Mediterranean branch on the north hemisphere storm track, will determine a reduction of maxima of wind wave height and storm surge levels. Changes of mean sea level are produced by regional steric effects and by net mass addition. While it is possible to compute the steric effects with regional models, mass addition is ultimately the consequence of a remote cause: the melting of Greenland and Antarctica ice caps. This study considers four indicators of extreme water levels, which, ranked in order of increasing values: the average of the 10 largest annual maxima (wlind10), the largest annual maximum (wlind1), the 5 (rv5) and 50 (rv50) year return level. The analysis is based on a coordinated set of wave and storm surge simulation forced by inputs provided by regional climate model simulations that were carried out in the CIRCE EU-fp7 and cover the period 1951-2050. Accounting for all affecting factors but the mass addition, in about 60% of the Mediterranean coast reduced storminess and steric expansion will compensate each other and produce no significant change of maximum water level statistics. The remaining 40% of the coastline is almost equally divided between significant positive and negative changes. However, if a supplementary sea level increase, representing the effect of water mass addition, is added, the fraction of the coast with significant positive/negative changes increase/decrease quickly. If mass addition would contribute 10cm, there will be no significant negative changes and for any indicator. With a 20cm addition the increase would be significant for wlind10, wlind1, rv5 along more than 75% of the Mediterranean coastline. With a 35cm addition the increase

  9. Changes in the structure and function of microbial communities in drinking water treatment bioreactors upon addition of phosphorus.

    PubMed

    Li, Xu; Upadhyaya, Giridhar; Yuen, Wangki; Brown, Jess; Morgenroth, Eberhard; Raskin, Lutgarde

    2010-11-01

    Phosphorus was added as a nutrient to bench-scale and pilot-scale biologically active carbon (BAC) reactors operated for perchlorate and nitrate removal from contaminated groundwater. The two bioreactors responded similarly to phosphorus addition in terms of microbial community function (i.e., reactor performance), while drastically different responses in microbial community structure were detected. Improvement in reactor performance with respect to perchlorate and nitrate removal started within a few days after phosphorus addition for both reactors. Microbial community structures were evaluated using molecular techniques targeting 16S rRNA genes. Clone library results showed that the relative abundance of perchlorate-reducing bacteria (PRB) Dechloromonas and Azospira in the bench-scale reactor increased from 15.2% and 0.6% to 54.2% and 11.7% after phosphorus addition, respectively. Real-time quantitative PCR (qPCR) experiments revealed that these increases started within a few days after phosphorus addition. In contrast, after phosphorus addition, the relative abundance of Dechloromonas in the pilot-scale reactor decreased from 7.1 to 0.6%, while Zoogloea increased from 17.9 to 52.0%. The results of this study demonstrated that similar operating conditions for bench-scale and pilot-scale reactors resulted in similar contaminant removal performances, despite dramatically different responses from microbial communities. These findings suggest that it is important to evaluate the microbial community compositions inside bioreactors used for drinking water treatment, as they determine the microbial composition in the effluent and impact downstream treatment requirements for drinking water production. This information could be particularly relevant to drinking water safety, if pathogens or disinfectant-resistant bacteria are detected in the bioreactors.

  10. Insights into the mechanism of the reaction between tetrachloro-p-benzoquinone and hydrogen peroxide and their implications in the catalytic role of water molecules in producing the hydroxyl radial.

    PubMed

    Li, Ping; Wang, Weihua; Sun, Qiao; Li, Zhen; Du, Aijun; Bi, Siwei; Zhao, Yan

    2013-08-26

    Detailed mechanisms for the formation of hydroxyl or alkoxyl radicals in the reactions between tetrachloro-p-benzoquinone (TCBQ) and organic hydroperoxides are crucial for better understanding the potential carcinogenicity of polyhalogenated quinones. Herein, the mechanism of the reaction between TCBQ and H2O2 has been systematically investigated at the B3LYP/6-311++G** level of theory in the presence of different numbers of water molecules. We report that the whole reaction can easily take place with the assistance of explicit water molecules. Namely, an initial intermediate is formed first. After that, a nucleophilic attack of H2O2 onto TCBQ occurs, which results in the formation of a second intermediate that contains an OOH group. Subsequently, this second intermediate decomposes homolytically through cleavage of the O-O bond to produce a hydroxyl radical. Energy analyses suggest that the nucleophilic attack is the rate-determining step in the whole reaction. The participation of explicit water molecules promotes the reaction significantly, which can be used to explain the experimental phenomena. In addition, the effects of F, Br, and CH3 substituents on this reaction have also been studied.

  11. Maximizing T2-exchange in Dy3+DOTA-(amide)X chelates: Fine-tuning the water molecule exchange rate for enhanced T2 contrast in MRI

    PubMed Central

    Soesbe, Todd C.; Ratnakar, S. James; Milne, Mark; Zhang, Shanrong; Do, Quyen N.; Kovacs, Zoltan; Sherry, A. Dean

    2014-01-01

    Purpose The water molecule exchange rates in a series of DyDOTA-(amide)X chelates were fine-tuned to maximize the effects of T2-exchange line broadening and improve T2 contrast. Methods Four DyDOTA-(amide)X chelates having a variable number of glycinate side-arms were prepared and characterized as T2-exchange agents. The non-exchanging DyTETA chelate was also used to measure the bulk water T2 reduction due solely to T2*. The total transverse relaxivity (r2tot) at 22, 37, and 52 °C for each chelate was measured in vitro at 9.4 T (400 MHz) by fitting plots of total T2−1 versus concentration. The water molecule exchange rates for each complex were measured by fitting 17O line-width versus temperature data taken at 9.4 T (54.3 MHz). Results The measured transverse relaxivities due to water molecule exchange (r2ex) and bound water lifetimes (τM) were in excellent agreement with Swift-Connick theory, with DyDOTA-(gly)3 giving the largest r2ex = 11.8 s−1 mM−1 at 37 °C. Conclusion By fine-tuning the water molecule exchange rate at 37 °C, the transverse relaxivity has been increased by 2 to 30 times compared to previously studied Dy3+-based chelates. Polymerization or dendrimerization of the optimal chelate could yield a highly sensitive, molecule-sized T2 contrast agent for improved molecular imaging applications. PMID:24390729

  12. Interactions of carbon nanotubes with the nitromethane-water mixture governing selective adsorption of energetic molecules from aqueous solution.

    PubMed

    Liu, Yingzhe; Lai, Weipeng; Yu, Tao; Kang, Ying; Ge, Zhongxue

    2015-03-14

    The structure and dynamics of the nitromethane-water (NM-WT) binary mixture surrounding single walled carbon nanotubes (SWNTs) have been investigated by molecular dynamics simulations. The simulation trajectories show that the NM molecules can be selectively adsorbed both outside the surface and inside the cavity of SWNTs mainly dominated by van der Waals attractions because SWNTs have a higher binding affinity for NM than WT. The binding energies of SWNTs with NM and WT obtained from electronic structure calculations at the M06-2X/6-31+G* level are 15.31 and 5.51 kcal mol(-1), respectively. Compared with the SWNT exterior, the selective adsorption of NM is preferentially occurred in the SWNT interior due to the hydrophobic interactions and the dipole-dipole interactions, which induces the decrease of the hydrogen-bond number of NM with WT and ordered structures of NM with preferred intermolecular orientation in the SWNT cavity. Furthermore, the selective adsorption dynamics of NM from the aqueous solution is regardless of the chirality and radius of SWNTs. The SWNT radius plays a negligible role in the mass density distributions of NM outside the SWNTs, while the mass density of NM in the SWNT interior decreases gradually as the SWNT radius increases. The structural arrangements and intermolecular orientations of NM in the SWNT cavity are greatly dependent on the SWNT radius due to the size effect.

  13. Adsorption of insulin peptide on charged single-walled carbon nanotubes: significant role of ordered water molecules.

    PubMed

    Shen, Jia-Wei; Wu, Tao; Wang, Qi; Kang, Yu; Chen, Xin

    2009-06-02

    Ordered hydration shells: The more ordered hydration shells outside the charged CNT surfaces prevent more compact adsorption of the peptide in the charged CNT systems [picture: see text], but peptide binding strengths on the charged CNT surfaces are stronger due to the electrostatic interaction.Studies of adsorption dynamics and stability for peptides/proteins on single-walled carbon nanotubes (SWNTs) are of great importance for a better understanding of the properties and nature of nanotube-based biosystems. Herein, the dynamics and mechanism of the adsorption of the insulin chain B peptide on different charged SWNTs are investigated by explicit solvent molecular dynamics simulations. The results show that all types of surfaces effectively attract the model peptide. Water molecules play a significant role in peptide adsorption on the surfaces of charged carbon nanotubes (CNTs). Compared to peptide adsorption on neutral CNT surfaces, the more ordered hydration shells outside the tube prevent more compact adsorption of the peptide in charged CNT systems. This shield effect leads to a smaller conformational change and van der Waals interaction between the peptide and surfaces, but peptide binding strengths on charged CNT surfaces are stronger than those on the neutral CNT surface due to the strong electrostatic interaction. The result of these simulations implies the possibility of improving the binding strength of peptides/proteins on CNT surfaces, as well as keeping the integrity of the peptide/protein conformation in peptide/protein-CNT complexes by charging the CNTs.

  14. Improved Estimation of Protein-Ligand Binding Free Energy by Using the Ligand-Entropy and Mobility of Water Molecules

    PubMed Central

    Fukunishi, Yoshifumi; Nakamura, Haruki

    2013-01-01

    We previously developed the direct interaction approximation (DIA) method to estimate the protein-ligand binding free energy (ΔG). The DIA method estimates the ΔG value based on the direct van der Waals and electrostatic interaction energies between the protein and the ligand. In the current study, the effect of the entropy of the ligand was introduced with protein dynamic properties by molecular dynamics simulations, and the interaction between each residue of the protein and the ligand was also weighted considering the hydration of each residue. The molecular dynamics simulation of the apo target protein gave the hydration effect of each residue, under the assumption that the residues, which strongly bind the water molecules, are important in the protein-ligand binding. These two effects improved the reliability of the DIA method. In fact, the parameters used in the DIA became independent of the target protein. The averaged error of ΔG estimation was 1.3 kcal/mol and the correlation coefficient between the experimental ΔG value and the calculated ΔG value was 0.75. PMID:24276169

  15. A comparison of additional treatment processes to limit particle accumulation and microbial growth during drinking water distribution.

    PubMed

    Liu, G; Lut, M C; Verberk, J Q J C; Van Dijk, J C

    2013-05-15

    Water quality changes, particle accumulation and microbial growth occurring in pilot-scale water distribution systems fed with normally treated and additional treated groundwater were monitored over a period of almost one year. The treatment processes were ranked in the following order: nanofiltration (NF) > (better than) ultrafiltration (UF) > ion exchange (IEX) for limiting particle accumulation. A different order was found for limiting overall microbial growth: NF > IEX > UF. There were strong correlations between particle load and particle accumulation, and between nutrient load and microbial growth. It was concluded that particle accumulation can be controlled by reducing the particle load in water treatment plants; and the microbial growth can be better controlled by limiting organic nutrients rather than removing biomass in water treatment plants. The major focus of this study was on microbial growth. The results demonstrated that growth occurred in all types of treated water, including the phases of bulk water, biofilm and loose deposits. Considering the growth in different phases, similar growth in bulk water was observed for all treatments; NF strongly reduced growth both in loose deposits and in biofilm; UF promoted growth in biofilm, while strongly limiting growth in loose deposits. IEX had good efficiency in between UF and NF, limiting both growths in loose deposits and in biofilm. Significant growth was found in loose deposits, suggesting that loose deposit biomass should be taken into account for growth evaluation and/or prediction. Strong correlations were found between microbial growth and pressure drop in a membrane fouling simulator which proved that a membrane fouling simulator can be a fast growth predictor (within a week). Different results obtained by adenosine triphosphate and flow cytometry cell counts revealed that ATP can accurately describe both suspended and particle-associated biomass, and flow cytometry files of TCC measurements needs

  16. Effect of two-stage coagulant addition on coagulation-ultrafiltration process for treatment of humic-rich water.

    PubMed

    Liu, Ting; Chen, Zhong-lin; Yu, Wen-zheng; Shen, Ji-min; Gregory, John

    2011-08-01

    A novel two-stage coagulant addition strategy applied in a coagulation-ultrafiltration (UF) process for treatment of humic-rich water at neutral pH was investigated in this study. When aluminum sulfate (alum) doses were set at a ratio of 3:1 added during rapid mix stage and half way through flocculation stage, the integrated process of two-stage alum addition achieved almost the same organic matter removal as that of conventional one-stage alum addition at the same overall dose. Whereas membrane fouling could be effectively mitigated by the two-stage addition exhibited by trans-membrane pressure (TMP) developments. The TMP developments were found to be primarily attributed to external fouling on membrane surface, which was closely associated with floc characteristics. The results of jar tests indicated that the average size of flocs formed in two-stage addition mode roughly reached one half larger than that in one-stage addition mode, which implied a beneficial effect on membrane fouling reduction. Moreover, the flocs with more irregular structure and lower effective density resulted from the two-stage alum addition, which caused higher porosity of cake layer formed by such flocs on membrane surface. Microscopic observations of membrane surface demonstrated that internal fouling in membrane pores could be also remarkably limited by two-stage alum addition. It is likely that the freshly formed hydroxide precipitates were distinct in surface characteristics from the aged precipitates due to formation of more active groups or adsorption of more labile aluminum species. Consequently, the flocs could further connect and aggregate to contribute to preferable properties for filtration performance of the coagulation-UF process. As a simple and efficient approach, two-stage coagulant addition strategy could have great practical significance in coagulation-membrane processes.

  17. Heterogeneous versus homogeneous copper(II) catalysis in enantioselective conjugate-addition reactions of boron in water.

    PubMed

    Kitanosono, Taku; Xu, Pengyu; Kobayashi, Shū

    2014-01-01

    We have developed Cu(II)-catalyzed enantioselective conjugate-addition reactions of boron to α,β-unsaturated carbonyl compounds and α,β,γ,δ-unsaturated carbonyl compounds in water. In contrast to the previously reported Cu(I) catalysis that required organic solvents, chiral Cu(II) catalysis was found to proceed efficiently in water. Three catalyst systems have been exploited: cat. 1: Cu(OH)2 with chiral ligand L1; cat. 2: Cu(OH)2 and acetic acid with ligand L1; and cat. 3: Cu(OAc)2 with ligand L1. Whereas cat. 1 is a heterogeneous system, cat. 2 and cat. 3 are homogeneous systems. We tested 27 α,β-unsaturated carbonyl compounds and an α,β-unsaturated nitrile compound, including acyclic and cyclic α,β-unsaturated ketones, acyclic and cyclic β,β-disubstituted enones, acyclic and cyclic α,β-unsaturated esters (including their β,β-disubstituted forms), and acyclic α,β-unsaturated amides (including their β,β-disubstituted forms). We found that cat. 2 and cat. 3 showed high yields and enantioselectivities for almost all substrates. Notably, no catalysts that can tolerate all of these substrates with high yields and high enantioselectivities have been reported for the conjugate addition of boron. Heterogeneous cat. 1 also gave high yields and enantioselectivities with some substrates and also gave the highest TOF (43,200 h(-1) ) for an asymmetric conjugate-addition reaction of boron. In addition, the catalyst systems were also applicable to the conjugate addition of boron to α,β,γ,δ-unsaturated carbonyl compounds, although such reactions have previously been very limited in the literature, even in organic solvents. 1,4-Addition products were obtained in high yields and enantioselectivities in the reactions of acyclic α,β,γ,δ-unsaturated carbonyl compounds with diboron 2 by using cat. 1, cat. 2, or cat. 3. On the other hand, in the reactions of cyclic α,β,γ,δ-unsaturated carbonyl compounds with compound 2, whereas 1,4-addition products

  18. Crystallization of a complex between human CDK6 and a virus-encoded cyclin is critically dependent on the addition of small charged organic molecules

    SciTech Connect

    Schulze-Gahmne, Ursula; Kim, Sung-Hou

    2001-07-06

    Human CDK6 plays an important role in controlling entry into the eucaryotic cell cycle. An activated complex of human CDK6 with a viral cyclin from herpesvirus saimiri was purified to homogeneity and crystallized using polyethylene glycol 3350 as precipitant. Crystallization was critically dependent on a narrow range of Ca Acetate concentration and the presence of Sulfo-betaine 201 as additive. Crystals belong to the hexagonal space group P6122 or P6522 with unit cell parameters a = b = 70.14 Angstrom, c = 448.77 Angstrom, g = 120 degrees and diffract X-rays to at least 3.1 Angstrom resolution.

  19. Odour and flavour thresholds of gasoline additives (MTBE, ETBE and TAME) and their occurrence in Dutch drinking water collection areas.

    PubMed

    van Wezel, Annemarie; Puijker, Leo; Vink, Cees; Versteegh, Ans; de Voogt, Pim

    2009-07-01

    The use of ETBE (ethyl-tert-butylether) as gasoline additive has recently grown rapidly. Contamination of aquatic systems is well documented for MTBE (methyl-tert-butylether), but less for other gasoline additives. Due to their mobility they may easily reach drinking water collection areas. Odour and flavour thresholds of MTBE are known to be low, but for ETBE and TAME (methyl-tert-amylether) hardly information is available. The objective here is to determine these thresholds for MTBE, ETBE and TAME, and relate these to concentrations monitored in thousands of samples from Dutch drinking water collection areas. For ETBE odour and flavour thresholds are low with 1-2microgL(-1), for MTBE and TAME they range from 7 to 16microg L(-1). In most groundwater collection areas MTBE concentrations are below 0.1microg L(-1). In phreatic groundwaters in sandy soils not covered by a protective soil layer, occasionally MTBE occurs at higher concentrations. For surface water collection areas a minority of the locations is free of MTBE. For river bank and dune infiltrates, at a few locations the odour and flavour threshold is exceeded. For ETBE fewer monitoring data are available. ETBE was found in 2 out of 37 groundwater collection areas, in concentrations below 1microgL(-1). In the surface water collection areas monitored ETBE was found in concentrations near to the odour and flavour thresholds. The low odour and flavour thresholds combined with the high mobility and persistence of these compounds, their high production volumes and their increased use may yield problems with future production of drinking water.

  20. Environmental swap energy and role of configurational entropy in transfer of small molecules from water into alkanes

    NASA Astrophysics Data System (ADS)

    Smejtek, Pavel; Word, Robert C.

    2004-01-01

    We studied the effect of segmented solvent molecules on the free energy of transfer of small molecules from water into alkanes (hexane, heptane, octane, decane, dodecane, tetradecane, and hexadecane). For these alkanes we measured partition coefficients of benzene, 3-methylindole (3MI), 2,3,4,6-tetrachlorophenol (TeCP), and 2,4,6-tribromophenol (TriBP) at 3, 11, 20, 3, and 47 °C. For 3MI, TeCP, and TriBP the dependence of free energy of transfer on length of alkane chains was found to be very different from that for benzene. In contrast to benzene, the energy of transfer for 3MI, TeCP, and TriBP was independent of the number of carbons in alkanes. To interpret data, we used the classic Flory-Huggins (FH) theory of concentrated polymer solutions for the alkane phase. For benzene, the measured dependence of energy of transfer on the number of carbons in alkanes agreed well with predictions based on FH model in which the size of alkane segments was obtained from the ratio of molar volumes of alkanes and the solute. We show that for benzene, the energy of transfer can be divided into two components, one called environmental swap energy (ESE), and one representing the contribution of configurational entropy of alkane chains. For 3MI, TeCP, and TriBP the contribution of configurational entropy was not measurable even though the magnitude of the effect predicted from the FH model for short chain alkanes was as much as 20 times greater than experimental uncertainties. From the temperature dependence of ESE we obtained enthalpy and entropy of transfer for benzene, 3MI, TeCP, and TriBP. Experimental results are discussed in terms of a thermodynamic cycle considering creation of cavity, insertion of solute, and activation of solute-medium attractive interactions. Our results suggest that correcting experimental free energy of transfer by Flory-Huggins configurational entropy term is not generally appropriate and cannot be applied indiscriminately.

  1. Amino group combined P/Ge and P/Sn Lewis pairs: synthesis and dipolar addition reactions to alkyne and aldehyde molecules.

    PubMed

    Yu, Ying; Li, Jiancheng; Liu, Weiping; Ye, Qingsong; Zhu, Hongping

    2016-04-14

    Amino group combined P/Ge-based frustrated Lewis pairs (FLPs) Ph2PN(R)GeCl3 (R = 2,6-iPr2C6H3 (1), 2,4,6-Me3C6H2 (2), and C6H11 (3)) and Ph2PN(2,6-iPr2C6H3)GeMe3 (4) as well as P/Sn-based FLP Ph2PN(2,6-iPr2C6H3)SnMe3 (5) were prepared and utilized for reactions with alkyne and aldehyde molecules. Compounds 1-3 each reacted with MeO2CC[triple bond, length as m-dash]CCO2Me to give zwitterionic cyclic vinyls [Ph2PN(R)GeCl3](MeO2CC[double bond, length as m-dash]CCO2Me) (6-8) and compound 1 reacted with HC[triple bond, length as m-dash]CCO2Me to give the similar compound [Ph2PN(2,4,6-Me3C6H2)GeCl3](HC[double bond, length as m-dash]CCO2Me) (9). Compound 4 reacted with RC[triple bond, length as m-dash]CCO2Me to afford acyclic vinyls 2,6-iPr2C6H3N[double bond, length as m-dash]P(Ph2)C(R)[double bond, length as m-dash]C(CO2Me)GeMe3 (R = CO2Me (10), H (11)) and 5 reacted with MeO2CC[triple bond, length as m-dash]CCO2Me to give 2,6-iPr2C6H3N[double bond, length as m-dash]P(Ph2)C(CO2Me)[double bond, length as m-dash]C(CO2Me)SnMe3 (12). The reactions of 1 with CH3CH2CHO and 1,4-(CHO)2C6H4 were also investigated and yielded novel zwitterionic OCPNGe five-heteroatom cycles [Ph2PN(2,6-iPr2C6H3)GeCl3][CH(CH2CH3)O] (13) and [Ph2PN(2,6-iPr2C6H3)GeCl3][p-(OCH)C6H4CHO][Cl3GeN(2,6-iPr2C6H3)PPh2] (14). Compounds 1-14 were characterized by NMR ((1)H, (13)C, and (31)P) and CHN elemental analysis, of which 1, 7, and 10-14 were further studied by X-ray crystallography. The reactions of 4 (or 5) with RC[triple bond, length as m-dash]CCO2Me to produce 10-12 present a novel way of obtaining the germyl (or stannyl) and iminophosphoranyl co-substituted vinyls.

  2. Decrease of droplet size of the reverse microemulsion 1-butyl-3-methylimidazolium tetrafluoroborate/Triton X-100/cyclohexane by addition of water.

    PubMed

    Gao, Yanan; Hilfert, Liane; Voigt, Andreas; Sundmacher, Kai

    2008-03-27

    In the present contribution, results concerning the role of small amounts of water in the 1-butyl-3-methylimidazolium tetrafluoroborate (bmimBF4)-in-cyclohexane ionic liquid (IL) reverse microemulsions are reported. Dynamic light scattering (DLS) revealed that the size of microemulsion droplets decreased remarkably with increasing water content although water is often used as a polar component to swell reverse microemulsions. It was thus deduced that the number of microemulsion droplets was increased which was confirmed by conductivity measurements. The states of dissolved water were investigated by Fourier transform IR (FTIR) spectroscopic analysis showing that water molecules mainly act as bound water. 1H NMR along with two-dimensional rotating frame nuclear Overhauser effect (NOE) experiments (ROESY) further revealed that water molecules were mainly located in the periphery of the polar core of the microemulsion droplets and behave like a chock being inserted in the palisade layer of the droplet. This increased the curvature of the surfactant film at the IL/cyclohexane interface and thus led to the decrease of the microemulsion droplet size. The order of surfactant molecules arranged in the interface film was increased and thus induced a loss of entropy. Isothermal titration calorimetry (ITC) indicated that an enthalpy increase compensates for the loss of entropy during the process of microstructural transition.

  3. Addition of hydrogen peroxide for the simultaneous control of bromate and odor during advanced drinking water treatment using ozone.

    PubMed

    Wang, Yongjing; Yu, Jianwei; Zhang, Dong; Yang, Min

    2014-03-01

    Complete removal of the characteristic septic/swampy odor from Huangpu River source water could only be achieved under an ozone dose as high as 4.0 mg/L in an ozone-biological activated carbon (O3-BAC) process, which would lead to the production of high concentrations of carcinogenic bromate due to the high bromide content. This study investigated the possibility of simultaneous control of bromate and the septic/swampy odor by adding H2O2 prior to the O3-BAC process for the treatment of Huangpu River water. H2O2 addition could reduce the bromate concentration effectively at an H2O2/O3 (g/g) ratio of 0.5 or higher. At the same time, the septic/swampy odor removal was enhanced by the addition of H2O2, although optimization of the H2O2/O3 ratio was required for each ozone dose. At an ozone dose of 2.0 mg/L, the odor was removed completely at an H2O2/O3 ratio of 0.5. The results indicated that H2O2 application at a suitable dose could enhance the removal of the septic/swampy odor while suppressing the formation of bromate during ozonation of Huangpu River source water.

  4. Free energy profiles for penetration of methane and water molecules into spherical sodium dodecyl sulfate micelles obtained using the thermodynamic integration method combined with molecular dynamics calculations

    NASA Astrophysics Data System (ADS)

    Fujimoto, K.; Yoshii, N.; Okazaki, S.

    2012-01-01

    The free energy profiles, ΔG(r), for penetration of methane and water molecules into sodium dodecyl sulfate (SDS) micelles have been calculated as a function of distance r from the SDS micelle to the methane and water molecules, using the thermodynamic integration method combined with molecular dynamics calculations. The calculations showed that methane is about 6-12 kJ mol-1 more stable in the SDS micelle than in the water phase, and no ΔG(r) barrier is observed in the vicinity of the sulfate ions of the SDS micelle, implying that methane is easily drawn into the SDS micelle. Based on analysis of the contributions from hydrophobic groups, sulfate ions, sodium ions, and solvent water to ΔG(r), it is clear that methane in the SDS micelle is about 25 kJ mol-1 more stable than it is in the water phase because of the contribution from the solvent water itself. This can be understood by the hydrophobic effect. In contrast, methane is destabilized by 5-15 kJ mol-1 by the contribution from the hydrophobic groups of the SDS micelle because of the repulsive interactions between the methane and the crowded hydrophobic groups of the SDS. The large stabilizing effect of the solvent water is higher than the repulsion by the hydrophobic groups, driving methane to become solubilized into the SDS micelle. A good correlation was found between the distribution of cavities and the distribution of methane molecules in the micelle. The methane may move about in the SDS micelle by diffusing between cavities. In contrast, with respect to the water, ΔG(r) has a large positive value of 24-35 kJ mol-1, so water is not stabilized in the micelle. Analysis showed that the contributions change in complex ways as a function of r and cancel each other out. Reference calculations of the mean forces on a penetrating water molecule into a dodecane droplet clearly showed the same free energy behavior. The common feature is that water is less stable in the hydrophobic core than in the water phase

  5. Water properties and structure of pork sausages as affected by high-pressure processing and addition of carrot fibre.

    PubMed

    Møller, Sandie M; Grossi, Alberto; Christensen, Mette; Orlien, Vibeke; Søltoft-Jensen, Jakob; Straadt, Ida K; Thybo, Anette K; Bertram, Hanne C

    2011-04-01

    The effects of high-pressure processing (HPP) and addition of carrot fibre on pork sausages have been studied using NMR T₂ relaxometry and measurements of water-binding capacity (WBC) by centrifugation. Significant effects of temperature (raw, 40, 50, or 60 °C), holding time (1s, 3, 6, or 9 min), and addition of carrot fibre on the distribution and mobility of water were found. However, the effect of carrot fibre could not be explained by structural changes in the sausages when examined by confocal laser scanning microscopy (CLSM). Correlations between T₂ relaxation measurements and WBC determined by centrifugation revealed that T₂ relaxation times were able to explain more than 90% of the variation in WBC for both non-pressure and pressure-treated sausages. However, only 49% of the variation was explained for pressure-treated sausages with carrot fibre, indicating that combining addition of fibre and high pressure treatment causes non-coherent changes in T₂ NMR relaxation times.

  6. Reduction of the native microflora on alfalfa sprouts during propagation by addition of antimicrobial compounds to the irrigation water.

    PubMed

    Fett, William F

    2002-01-30

    Alfalfa and other types of sprouts are known to harbor large populations of native microorganisms. As some of these microbes may be causes of reduced shelf life of the product (plant pathogens and other spoilage organisms) and sprouts may, on occasion, harbor bacteria pathogenic towards humans, the addition of antimicrobial compounds to the irrigation water may be warranted. In this study, we tested the efficacy of several antimicrobial compounds for reducing the native microbial populations on alfalfa sprouts during propagation. These compounds included H2O2, peroxyacetic acid+hydrogen peroxide (Tsunami 100), acidified NaClO2, NaClO2 (Aquatize), EDTA, Na3PO4 and NaOCl. When added to the irrigation water at vanous concentrations, none of the antimicrobial compounds reduced the levels of any class of native microflora by more than 1 log10 without evidence of phytotoxicity.

  7. Synthesis of binder-like molecules covalently linked to silicon nanoparticles and application as anode material for lithium-ion batteries without the use of electrolyte additives

    NASA Astrophysics Data System (ADS)

    Assresahegn, Birhanu Desalegn; Bélanger, Daniel

    2017-03-01

    A chemically modified silicon anode is prepared for application as anode in lithium-ion batteries by covalent attachment of polyacrylic acid to enable self-adhesion between the active material particles. The polyacrylic acid polymer is formed by atom transfer radical polymerization using 1-(bromoethyl)benzene initiator groups initially bonded to a hydrogenated silicon surface. The grafting of 1-(bromoethyl)benzene and polyacrylic acid is confirmed by various material characterization techniques. The electrochemical performance of the silicon anodes is also evaluated by galvanostatic cycling. The chemically modified composite silicon anode (with active material loading of 0.9-1 mg cm-2) showed a significantly improved performance in terms of: gravimetric capacitance (more than 2000 mAh g-1) after 300 cycles and 80% capacity retention with an average 99.6% Coulombic efficiency at a current density of 0.34 A g-1. However, the unmodified electrode cycled 75 times in the same conditions only retains 46% of its initial capacity with an average 95.1% Coulombic efficiency. The new composite Si electrode performs better at high charge/discharge rate and allows the use of larger proportion of the active material by reducing the amount of binder. It is noteworthy that these composite silicon electrodes are tested without the use of expensive electrolyte additives.

  8. Effect of water treatment additives on lime softening residual trace chemical composition--implications for disposal and reuse.

    PubMed

    Cheng, Weizhi; Roessler, Justin; Blaisi, Nawaf I; Townsend, Timothy G

    2014-12-01

    Drinking water treatment residues (WTR) offer potential benefits when recycled through land application. The current guidance in Florida, US allows for unrestricted land application of lime softening WTR; alum and ferric WTR require additional evaluation of total and leachable concentrations of select trace metals prior to land application. In some cases a mixed WTR is produced when lime softening is accompanied by the addition of a coagulant or other treatment chemical; applicability of the current guidance is unclear. The objective of this research was to characterize the total and leachable chemical content of WTR from Florida facilities that utilize multiple treatment chemicals. Lime and mixed lime WTR samples were collected from 18 water treatment facilities in Florida. Total and leachable concentrations of the WTR were measured. To assess the potential for disposal of mixed WTR as clean fill below the water table, leaching tests were conducted at multiple liquid to solid ratios and under reducing conditions. The results were compared to risk-based soil and groundwater contamination thresholds. Total metal concentrations of WTR were found to be below Florida soil contaminant thresholds with Fe found in the highest abundance at a concentration of 3600 mg/kg-dry. Aluminum was the only element that exceeded the Florida groundwater contaminant thresholds using SPLP (95% UCL = 0.23 mg/L; risk threshold = 0.2 mg/L). Tests under reducing conditions showed elevated concentrations of Fe and Mn, ranging from 1 to 3 orders of magnitude higher than SPLP leachates. Mixed lime WTR concentrations (total and leachable) were lower than the ferric and alum WTR concentrations, supporting that mixed WTR are appropriately represented as lime WTR. Testing of WTR under reducing conditions demonstrated the potential for release of certain trace metals (Fe, Al, Mn) above applicable regulatory thresholds; additional evaluation is needed to assess management options where

  9. Effects of protein flexibility and active site water molecules on the prediction of sites of metabolism for cytochrome P450 2C19 substrates.

    PubMed

    Li, Junhao; Cai, Jinya; Su, Haixia; Du, Hanwen; Zhang, Juan; Ding, Shihui; Liu, Guixia; Tang, Yun; Li, Weihua

    2016-03-01

    Structure-based prediction of sites of metabolism (SOMs) mediated by cytochrome P450s (CYPs) is of great interest in drug discovery and development. However, protein flexibility and active site water molecules remain a challenge for accurate SOM prediction. CYP2C19 is one of the major drug-metabolizing enzymes and has attracted considerable attention because of its polymorphism and capability of metabolizing ∼7% clinically used drugs. In this study, we systematically evaluated the effects of protein flexibility and active site water molecules on SOM prediction for CYP2C19 substrates. Multiple conformational sampling techniques including GOLD flexible residues sampling, molecular dynamics (MD) and tCONCOORD side-chain sampling were adopted for assessing the influence of protein flexibility on SOM prediction. The prediction accuracy could be significantly improved when protein flexibility was considered using the tCONCOORD sampling method, which indicated that the side-chain conformation was important for accurate prediction. However, the inclusion of the crystallographic or MD-derived water molecule(s) does not necessarily improve the prediction accuracy. Finally, a combination of docking results with SMARTCyp was found to be able to increase the SOM prediction accuracy.

  10. The Accommodation Coefficient of Water Molecules on Ice: Results from Cirrus Cloud Experiments at the Aerosol Chamber AIDA

    NASA Astrophysics Data System (ADS)

    Skrotzki, J.; Connolly, P.; Niemand, M.; Saathoff, H.; Moehler, O.; Ebert, V.; Leisner, T.

    2010-12-01

    Cirrus clouds are pure ice clouds in the upper troposphere or lower stratosphere. One of the parameters governing the growth of ice crystals in these clouds is the accommodation coefficient of water molecules on ice. However, its magnitude is still uncertain to a large degree, since experimental results vary from below 0.01 up to unity depending on the design of the experiment and the examined ice growth process [1]. For the specific case of ice crystal growth in cirrus clouds, no previous experimental studies regarding the accommodation coefficient exist. Therefore, dedicated experiments were carried out at the cloud simulation chamber AIDA [2], examining the ice crystal growth for deposition nucleation in the temperature range from -75 °C to -40 °C. These experiments were evaluated with two different models, a simple one, which just incorporates kinetic and diffusive theory of ice crystal growth, and the more advanced and extended aerosol-cloud-precipitation interaction model (ACPIM) [3]. The outcome of these two models is compared to absolute in-situ humidity data measured within AIDA using extractive as well as open path diode laser hygrometers (TDLAS) [4]. For every experiment, this is done by varying the value of the accommodation coefficient within each model, in order to get best agreement with experimental data. The values obtained for the accommodation coefficient at different temperatures are presented and the overall uncertainties as well as the consistency between the two different models are discussed. [1] D. R. Heynes, N. J. Tro, and S. M. George, J. Phys. Chem. 1992, 96, 8502-8509 (1992) [2] O. Möhler et al., Atmos. Chem. Phys. 3, 211-223 (2003) [3] P. J. Connolly et al., Atmos. Chem. Phys. 9, 2805-2824 (2009) [4] D. W. Fahey et al., AquaVIT White Paper, avail. at https://aquavit.icg.kfa-juelich.de/AquaVit/AquaVitWiki

  11. PbnI4n+2(2n+2)- ribbons (n = 3, 5) as dimensional reductions of 2D perovskite layers in cystamine cation based hybrids, also incorporating iodine molecules or reversible guest water molecules.

    PubMed

    Louvain, Nicolas; Bi, Wenhua; Mercier, Nicolas; Buzaré, Jean-Yves; Legein, Christophe; Corbel, Gwenaël

    2007-03-07

    Pb(n)I(4n+2)((2n+2)-) (n = 3, 5) ribbons, which can be regarded as dimensional reductions of 2D perovskite layers, are stabilized by diprotonated cystamine cations in (NH(3)(CH(2))(2)SS(CH(2))(2)NH(3))(4)Pb(3)I(14),I(2) (1) and (NH(3)(CH(2))(2)SS(CH(2))(2)NH(3))(6)Pb(5)I(22).4H(2)O (2). Both 1 and 2 have interesting structural characteristics; it is unprecedented that the ribbons are linked via I(2) molecules incorporated in the lattice of 1, while tetrameric water clusters are trapped in the structure of 2. 2 undergoes a (reversible) water desorption process at 310 K leading to (NH(3)(CH(2))(2)SS(CH(2))(2)NH(3))(6)Pb(5)I(22).2H(2)O (3). The electrical behavior of 2 and 3 has been investigated in the ranges 293-310 K and 310-358 K respectively. Above 310 K, the electronic contribution remains constant while the ionic transference number tends towards unity showing almost pure ionic transport at 360 K (6 x 10(-7) S cm(-1) at 330 K) originating probably from the migration of protons through the hydrogen bonds connecting the water molecules to the cystamine counter cations.

  12. The effects of leachate recirculation with supplemental water addition on methane production and waste decomposition in a simulated tropical landfill.

    PubMed

    Sanphoti, N; Towprayoon, S; Chaiprasert, P; Nopharatana, A

    2006-10-01

    In order to increase methane production efficiency, leachate recirculation is applied in landfills to increase moisture content and circulate organic matter back into the landfill cell. In the case of tropical landfills, where high temperature and evaporation occurs, leachate recirculation may not be enough to maintain the moisture content, therefore supplemental water addition into the cell is an option that could help stabilize moisture levels as well as stimulate biological activity. The objectives of this study were to determine the effects of leachate recirculation and supplemental water addition on municipal solid waste decomposition and methane production in three anaerobic digestion reactors. Anaerobic digestion with leachate recirculation and supplemental water addition showed the highest performance in terms of cumulative methane production and the stabilization period time required. It produced an accumulated methane production of 54.87 l/kg dry weight of MSW at an average rate of 0.58 l/kg dry weight/d and reached the stabilization phase on day 180. The leachate recirculation reactor provided 17.04 l/kg dry weight at a rate of 0.14l/kg dry weight/d and reached the stabilization phase on day 290. The control reactor provided 9.02 l/kg dry weight at a rate of 0.10 l/kg dry weight/d, and reached the stabilization phase on day 270. Increasing the organic loading rate (OLR) after the waste had reached the stabilization phase made it possible to increase the methane content of the gas, the methane production rate, and the COD removal. Comparison of the reactors' efficiencies at maximum OLR (5 kgCOD/m(3)/d) in terms of the methane production rate showed that the reactor using leachate recirculation with supplemental water addition still gave the highest performance (1.56 l/kg dry weight/d), whereas the leachate recirculation reactor and the control reactor provided 0.69 l/kg dry weight/d and 0.43 l/kg dry weight/d, respectively. However, when considering

  13. A plan for directional dark matter sensitivity in high-pressure xenon detectors through the addition of wavelength shifting gaseous molecules

    NASA Astrophysics Data System (ADS)

    Gehman, V. M.; Goldschmidt, A.; Nygren, D.; Oliveira, C. A. B.; Renner, J.

    2013-10-01

    Xenon is an especially attractive candidate for both direct WIMP and 0νββ decay searches. Although the current trend has exploited the liquid phase, the gas phase xenon offers remarkable performance advantages for: energy resolution, topology visualization, and discrimination between electron and nuclear recoils. The NEXT-100 experiment, now under construction in the Canfranc Underground Laboratory, Spain, will operate at ~ 15 bars with 100 kg of 136Xe for the 0νββ decay search. We will describe recent results with small prototypes, indicating that NEXT-100 can provide about 0.5% FWHM energy resolution at the decay's Q value (2457.83 keV), as well as rejection of γ-rays with topological cuts. However, sensitivity goals for WIMP dark matter and 0νββ decay searches indicate the probable need for ton-scale active masses. NEXT-100 provides the springboard to reach this scale with xenon gas. We describe a scenario for performing both searches in a single, high-pressure, ton-scale xenon gas detector, without significant compromise to either. In addition, even in a single ton-scale, high-pressure xenon gas TPC, an intrinsic sensitivity to the nuclear recoil direction may exist. This plausibly offers an advance of more than two orders of magnitude relative to current low-pressure TPC concepts. We argue that, in an era of deepening fiscal austerity, such a dual-purpose detector may be possible at acceptable cost, within the time frame of interest, and deserves our collective attention.

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

    NASA Astrophysics Data System (ADS)

    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

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

    PubMed

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

    2014-11-01

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

  16. Hydrogen production from water decomposition by redox of Fe 2O 3 modified with single- or double-metal additives

    NASA Astrophysics Data System (ADS)

    Liu, Xiaojie; Wang, Hui

    2010-05-01

    Iron oxide modified with single- or double-metal additives (Cr, Ni, Zr, Ag, Mo, Mo-Cr, Mo-Ni, Mo-Zr and Mo-Ag), which can store and supply pure hydrogen by reduction of iron oxide with hydrogen and subsequent oxidation of reduced iron oxide with steam (Fe 3O 4 (initial Fe 2O 3)+4H 2↔3Fe+4H 2O), were prepared by impregnation. Effects of various metal additives in the samples on hydrogen production were investigated by the above-repeated redox. All the samples with Mo additive exhibited a better redox performance than those without Mo, and the Mo-Zr additive in iron oxide was the best effective one enhancing hydrogen production from water decomposition. For Fe 2O 3-Mo-Zr, the average H 2 production temperature could be significantly decreased to 276 °C, the average H 2 formation rate could be increased to 360.9-461.1 μmol min -1 Fe-g -1 at operating temperature of 300 °C and the average storage capacity was up to 4.73 wt% in four cycles, an amount close to the IEA target.

  17. DNA-Accelerated Copper Catalysis of Friedel-Crafts Conjugate Addition/Enantioselective Protonation Reactions in Water.

    PubMed

    García-Fernández, Almudena; Megens, Rik P; Villarino, Lara; Roelfes, Gerard

    2016-12-21

    DNA-induced rate acceleration has been identified as one of the key elements for the success of the DNA-based catalysis concept. Here we report on a novel DNA-based catalytic Friedel-Crafts conjugate addition/enantioselective protonation reaction in water, which represents the first example of a reaction that critically depends on the >700- to 990-fold rate acceleration caused by the presence of a DNA scaffold. The DNA-induced rate acceleration observed is the highest reported due to the environment presented by a biomolecular scaffold for any hybrid catalyst, to date. Based on a combination of kinetics and binding studies, it is proposed that the rate acceleration is in part due to the DNA acting as a pseudophase, analogous to micelles, in which all reaction components are concentrated, resulting in a high effective molarity. The involvement of additional second coordination sphere interactions is suggested by the enantioselectivity of the product. The results presented here show convincingly that the DNA-based catalysis concept, thanks to the DNA-accelerating effect, can be an effective approach to achieving a chemically challenging reaction in water.

  18. Optimal Control of Shock Tube Flow via Water Addition with Application to Ignition Overpressure Mitigation in Launch Vehicles

    NASA Astrophysics Data System (ADS)

    Moshman, Nathan

    2009-11-01

    Ignition Overpressure (IOP) in launch vehicles occurs at the start of ignition when a steep rise in pressure propagates outward from the rocket nozzle. It is crucial to minimize the overpressure so as to decrease risk of damage to the rocket body. Currently, CFD studies exist on this situation but there are no optimization studies of the water addition as a means to suppress the IOP. The proposed dissertation will use a numerical method to compute an approximate solution for an optimal control problem constrained by the one-dimensional Euler PDEs of fluid dynamics as well as volume fraction conservation. A model for inter-phase transport of mass momentum and energy and fluid interface quantities will be given. The control will be water addition from external nozzles. The adjoint system of equations will be derived and discretized. Necessary optimal conditions will be derived. An SQP method will solve an optimal situation. Predictions will be validated against shock tube experiments at the NPS rocket lab.

  19. [Effects of biochar addition into soils in semiarid land on water infiltration under the condition of the same bulk density].

    PubMed

    Qi, Rui-Peng; Zhang, Lei; Yan, Yong-Hao; Wen, Man; Zheng, Ji-Yong

    2014-08-01

    Making clear the effects of biochar addition on soil water infiltration process can provide the scientific basis for the evaluation of the influence of biochar application on soil hydrology in semi-arid region. In this paper, through the soil column simulation method in laboratory, the effects of biochar of three sizes (1-2 mm, 0.25-1 mm and ≤ 0.25 mm) at 4 doses (10, 50, 100 and 150 g x kg(-1)) on the cumulative infiltration, the permeability and the stable infiltration rate of two different soils (anthrosol and aeolian sandy soil) were studied. The results showed that the infiltration capacity of the anthrosol was obviously increased compared to the control, however, the one in the aeolian sandy soil was decreased due to the biochar addition. At 100 minutes after infiltration starting, the averaged cumulative infiltration was increased by 25.1% in the anthrosol with comparison to the control. Contrarily, the averaged cumulative infiltration was decreased by 11.1% in the aeolian sandy soil at 15 minutes after infiltration starting. When the dose was the same, biochar with different particle sizes improved the infiltration for the anthrosol, but for the different dose treatments, the particle size of biochar which showed the greatest improvement was different. As for the aeolian sandy soil, the infiltration increased at the dose of 10 g x kg(-1) after the addition of biochar with different particle sizes, while decreased at the higher dose of 50, 100 and 150 g x kg(-1). The cumulative infiltration of the aeolian sandy soil was decreased with the increase in addition amount of biochar with the same particle size, while it was not so for the anthrosol. The determination coefficient fitted by the Philip infiltration model ranged from 0.965 to 0.999, suggesting this model was suitable for the simulation of soil water infiltration process after biochar application. Statistical analysis of main effects showed that the biochar particle size, the biochar addition amount

  20. DNA origami based Au–Ag-core–shell nanoparticle dimers with single-molecule SERS sensitivity† †Electronic supplementary information (ESI) available: Additional information about materials and methods, designs of DNA origami templates, height profiles, additional SERS spectra, assignment of DNA bands, SEM images, additional AFM images, FDTD simulations, additional reference spectra for Cy3 and detailed description of EF estimation, simulated absorption and scattering spectra. See DOI: 10.1039/c5nr08674d Click here for additional data file.

    PubMed Central

    Prinz, J.; Heck, C.; Ellerik, L.; Merk, V.

    2016-01-01

    DNA origami nanostructures are a versatile tool to arrange metal nanostructures and other chemical entities with nanometer precision. In this way gold nanoparticle dimers with defined distance can be constructed, which can be exploited as novel substrates for surface enhanced Raman scattering (SERS). We have optimized the size, composition and arrangement of Au/Ag nanoparticles to create intense SERS hot spots, with Raman enhancement up to 1010, which is sufficient to detect single molecules by Raman scattering. This is demonstrated using single dye molecules (TAMRA and Cy3) placed into the center of the nanoparticle dimers. In conjunction with the DNA origami nanostructures novel SERS substrates are created, which can in the future be applied to the SERS analysis of more complex biomolecular targets, whose position and conformation within the SERS hot spot can be precisely controlled. PMID:26892770

  1. A hot water extract of Curcuma longa inhibits adhesion molecule protein expression and monocyte adhesion to TNF-α-stimulated human endothelial cells.

    PubMed

    Kawasaki, Kengo; Muroyama, Koutarou; Yamamoto, Norio; Murosaki, Shinji

    2015-01-01

    The recruitment of arterial leukocytes to endothelial cells is an important step in the progression of various inflammatory diseases. Therefore, its modulation is thought to be a prospective target for the prevention or treatment of such diseases. Adhesion molecules on endothelial cells are induced by proinflammatory cytokines, including tumor necrosis factor-α (TNF-α), and contribute to the recruitment of leukocytes. In the present study, we investigated the effect of hot water extract of Curcuma longa (WEC) on the protein expression of adhesion molecules, monocyte adhesion induced by TNF-α in human umbilical vascular endothelial cells (HUVECs). Treatment of HUVECs with WEC significantly suppressed both TNF-α-induced protein expression of adhesion molecules and monocyte adhesion. WEC also suppressed phosphorylation and degradation of nuclear factor of kappa light polypeptide gene enhancer in B-cells inhibitor, alpha (IκBα) induced by TNF-α in HUVECs, suggesting that WEC inhibits the NF-κB signaling pathway.

  2. Additions of nutrients and major ions by the atmosphere and tributaries to nearshore waters of northwestern Lake Huron

    USGS Publications Warehouse

    Manny, Bruce A.; Owens, R.W.

    1983-01-01

    Nutrient additions by the atmosphere and six tributaries to nearshore waters of northwestern Lake Huron were measured at weekly intervals from August 1975 to July 1976. The atmosphere contributed 43% of the nitrogen (N) and 10% of the phosphorus (P) that was added during the year. The 1975–76 atmospheric loading rate of total N to this area (11 kg/ha/yr) was one of the highest found to date in the United States. N was conserved more efficiently than P in the tributary drainage basins. Of the N and P that fell annually on the watersheds under study, 2 to 37% of the N and 31 to 84% of the P was carried with runoff to the lake. From a basin where ditching and clear-cutting occurred, water, P, silica (SiO2), N, and sodium were lost at higher rates than from five other basins. Most of the N in bulk atmospheric samples (23%) and tributary waters (56%) was dissolved organic N, a form of N not often measured.

  3. Effect of treatment with probiotics as water additives on tilapia (Oreochromis niloticus) growth performance and immune response.

    PubMed

    Zhou, Xuxia; Tian, Ziqiang; Wang, Yanbo; Li, Weifen

    2010-09-01

    A feeding trial was conducted for 40 days to delineate the effect of treatment with probiotics as water additives on tilapia (Oreochromis niloticus) growth performance and immune response. About 360 juveniles were randomly distributed into four treatment groups, each with three replicates. Different probiotics (T-1, Bacillus subtilis B10; T-2, Bacillus coagulans B16; T-3, Rhodopseudomonas palustris G06) were added to the water of tanks at final concentration of 1 x 10(7) cfu ml(-1) every 2 days, with no probiotic added to control tanks. At the end of the feeding trial, fish treated with B. coagulans B16 (T-2) and R. palustris G06 (T-3) had significantly (P < 0.05) higher final weight, daily weight gain, and specific growth rate compared with those treated with B. subtilis B10 (T-1) and those without probiotics (control). The highest (P < 0.05) content of total serum protein was found in T-2 compared with that in T-1, T-3, and the control. However, albumin concentration and albumin/globulin ratio were not affected by the probiotics treatments. Compared with the control, probiotic supplementation remarkably improved activities of superoxide dismutase and catalase (P < 0.05). T-2 fish exhibited higher average myeloperoxidase activity than the control, T-1, and T-3 groups. Regarding serum lysozyme content in tilapia, assays showed no difference (P > 0.05) among the treatment groups. Furthermore, probiotics treatments remarkably increased respiratory burst activity compared with control, with T-2 showing higher values than T-1 and T-3. This indicated that treatment with probiotics, B. coagulans B16 and R. palustris G06, as water additives could be used to enhance immune and health status, thereby improving growth performance of O. niloticus.

  4. Effect of Salt Additives to Water on the Severity of Vapor Explosions and on the Collapse of Vapor Film

    NASA Astrophysics Data System (ADS)

    Arai, Takahiro; Furuya, Masahiro

    We proposed ultra rapid solidification and atomization technique, CANOPUS (Cooling and Atomizing based on NOble Process Utilizing Steam explosion), using small-scale vapor explosions to make an amorphous metal. The CANOPUS method is suitable for rapid cooling and atomization process, which utilizing sustainable small-scale vapor explosions. In order to apply the CANOPUS method to a high melting point metal, it is necessary to make a small-scale vapor explosion occur at a high temperature of the molten metal. Small-scale experiment is conducted to develop the vapor explosion promotor in which spontaneous vapor explosion can occur at a high temperature of a molten metal. Spontaneous vapor explosion do not occur when water at 80°C is used as a coolant. However, spontaneous vapor explosion occurs when water at 80°C with salt additives is used as a coolant. Specifically, lithium chloride solution generates spontaneous vapor explosions at the highest temperature of the molten tin in the experiment. In order to clarify the triggering mechanism of the spontaneous vapor explosion when the promotor is used as a coolant, a high-temperature solid stainless steel sphere is immersed into a coolant. The interfacial temperature of the stainless steel sphere is measured, and the behavior of a vapor film around the stainless steel sphere is observed with a digital video camera. As a result, salt additives resulted in an increase of quench temperature in all salt solutions. The quenching curves of each coolant indicate that the salt additives improve the film boiling heat transfer. The improvement of the film boiling heat transfer causes an unstable formation of the vapor film and a rise of the quench temperature. It is clarified that the salt additives to water promotes a vapor film collapse. Comparing two experiments, the quench temperature of each solution is in close agreement with the upper limit of the molten tin temperature that causes spontaneous vapor explosion. This

  5. The effects of nutrient additions on particulate and dissolved primary production in surface waters of three Mediterranean eddies

    NASA Astrophysics Data System (ADS)

    Lagaria, A.; Psarra, S.; Lefèvre, D.; van Wambeke, F.; Courties, C.; Pujo-Pay, M.; Oriol, L.; Tanaka, T.; Christaki, U.

    2010-12-01

    The effects of additions of nitrogen (+N), phosphorus (+P), alone and in combination, were assessed during three microcosm experiments performed with surface waters of three anticyclonic eddies, located in the Western, Central and Eastern Mediterranean. We examined the effects of nutrient additions on rates of dissolved and particulate primary production and on metabolic rates of the osmotrophic community (phytoplankton and heterotrophic prokaryotes). The experiments were performed in June/July 2008 during the BOUM (Biogeochemistry from the Oligotrophic to the Ultra-oligotrophic Mediterranean) cruise. In all three experiments, particulate primary production was significantly stimulated by the additions of nitrogen (+N, +NP) while no effect was observed with the addition of phosphorus alone. Percent extracellular release (PER) showed an inverse relation with total primary production (PPtotal), displaying the lowest values (4-8%) in the +NP treatment. Among the three treatments, the +NP had the strongest effect on the community metabolic rates leading to positive net community production values (NCP>0). These changes of NCP were mainly due to enhanced gross community production (GCP) rather than lower respiration rates (CR). In +NP treatments autotrophic production (whether expressed as GCP or PPtotal) was high enough to fulfil the carbon requirements of the heterotrophic prokaryotes, with phytoplankton and heterotrophic prokaryote production positively correlated. Addition of nitrogen alone (+N) had a smaller effect on community production, resulting in metabolically balanced systems (NCP≍0). Finally, heterotrophic conditions persisted in the +P treatment at the central and eastern stations, and gross production was not sufficient to supply bacterial carbon demand, evidence of a decoupling of phytoplankton production and consumption by heterotrophic prokaryotes.

  6. The mobility of single-file water molecules is governed by the number of H-bonds they may form with channel-lining residues

    PubMed Central

    Horner, Andreas; Zocher, Florian; Preiner, Johannes; Ollinger, Nicole; Siligan, Christine; Akimov, Sergey A.; Pohl, Peter

    2015-01-01

    Channel geometry governs the unitary osmotic water channel permeability, pf, according to classical hydrodynamics. Yet, pf varies by several orders of magnitude for membrane channels with a constriction zone that is one water molecule in width and four to eight molecules in length. We show that both the pf of those channels and the diffusion coefficient of the single-file waters within them are determined by the number NH of residues in the channel wall that may form a hydrogen bond with the single-file waters. The logarithmic dependence of water diffusivity on NH is in line with the multiplicity of binding options at higher NH densities. We obtained high-precision pf values by (i) having measured the abundance of the reconstituted aquaporins in the vesicular membrane via fluorescence correlation spectroscopy and via high-speed atomic force microscopy, and (ii) having acquired the vesicular water efflux from scattered light intensities via our new adaptation of the Rayleigh-Gans-Debye equation. PMID:26167541

  7. Enhancement of critical heat flux in subcooled flow boiling of water by use of a volatile additive

    SciTech Connect

    Pabisz, R.A. Jr.; Bergles, A.E.

    1996-12-31

    The present investigation considers the effect of a 1-pentanol additive in water on the critical heat flux (CHF) and pressure drop in forced subcooled boiling. A small quantity of 1-pentanol was added to distilled water with the objective of getting an approximate 2% by weight mixture, which had been found to give superior performance in previous studies of pool and flow boiling. Experiments were performed using stainless steel tubes with internal diameters of 4.4 and 6.1 mm. Tests were conducted with mass fluxes of 4,400 kg/m{sup 2}s, exit pressures of 9 bar, length-to-diameter ratios of 25, and exit subcoolings from 65 to 90 C. Test sections were heated directly by DC power, and critical heat flux data were inferred from test-section burnout. The alcohol concentration was periodically checked by draining off a sample and performing a Proton Nuclear Magnetic Resonance scan on the mixture. At high subcoolings, the mixture exhibited an increase in the critical heat flux over that of pure water. However at low subcoolings there is a decrease in the critical heat flux. The increases in critical heat flux noted with the 1-pentanol mixture in this experiment were not as large as would be expected from saturated pool boiling results published by Van Stralen (1959). Pressure drop data for both the mixture and the pure water also were recorded. The 1-pentanol mixture, in general, exhibited larger pressure drops for the same conditions. Subcooled flow boiling has a wide array of commercial cooling applications, including blades in gas turbines, high power laser optics, plasma-facing components in fusion reactors, supercomputers, etc.

  8. New functional form of the dependence of rotational and centrifugal distortional parameters of the water molecule on the bending vibration v2

    NASA Astrophysics Data System (ADS)

    Starikov, V. I.; Tyuterev, Vl. G.

    1982-10-01

    A regularity is found for the anomalous behavior of the rotational and centrifugal distortion parameters of the water molecule in the bending states (0 v20). This regularity is described by simple nonpolynomial formulae which are used to calculate Watson's parameters A, Δ K, Δ KJ, δK, HK, HKJ, hK, LK, LKKJ, and lK for the states (010), (020), (030), and (040). The calculated v2 behavior of these parameters is in agreement with the experimental one.

  9. Transitional liquid crystalline phases between the hexagonal and lamellar phases in ternary cesium N-tetradecanoate-water-additive mixtures

    SciTech Connect

    Blackburn, J.C.; Kilpatrick, P.K. )

    1993-04-01

    The effects of added salt (CsOH, CsCl), long-chain carboxylic acid, and long-chain alcohol on the lyotropic liquid crystalline phase behavior in the cesium n-tetradecanoate (CsTD)-water system is reported. The transitional region between the hexagonal (H) and lamellar (L) phases was the compositional range of focus. Three transitional phases were observed: (i) the ribbon (R) phase, a biaxial phase consisting of cylinders of ellipsoidal cross section; (ii) the viscous isotropic (VI) phase, an isotropic phase thought to consist of interconnected rods on an Ia3d lattice; and (iii) the intermediate (Int) phase, a uniaxial anisotropic phase thought to consist of interconnected rods on a planar lattice. The effect of the additives was to decrease the interfacial curvature of the surfactant head group layer by varying head group repulsion and by varying the surfactant tail volume relative to the surfactant head group area. These changes resulted in formation of transitional phases seeming to possess curvature between that of the cylindrical H phase and the planar L phase. The ionic repulsion between carboxylate head groups was reduced by the addition of CsOH or CsCl, and resulted in destabilization of the VI phase and the formation of the anisotropic Int phase. With the addition of cosurfactants, n-tetradecanoic acid (TDA) and 1-tetradecanol (TDOH), no Int phase was observed. With 7 wt% added TDA the R phase was stabilized up to temperatures of 336 K, above the 330 K temperature limit in the binary CsTD-D[sub 2]O system. In all four systems, sufficient additive (5-10 wt%) resulted in a transition to the L phase, which was stable over a large portion of the compositional range. In order of apparently decreasing mean curvature, the phase sequence is: hexagonal, ribbon, viscous isotropic, intermediate, and lamellar.

  10. Is the mobility of the pore walls and water molecules in the selectivity filter of KcsA channel functionally important?

    PubMed

    Kraszewski, Sebastian; Yesylevskyy, Semen O; Boiteux, Céline; Ramseyer, Christophe; Kharkyanen, Valery N

    2008-04-28

    We performed in-depth analysis of the forces which act on the K(+) ions in the selectivity filter of the KcsA channel in order to estimate the relative importance of static and dynamic influence of the filter wall and water molecules on ion permeation and selectivity. The forces were computed using the trajectories of all-atom molecular dynamics simulations. It is shown that the dynamics of the selectivity filter contributes about 3% to the net force acting on the ions and can be neglected in the studies focused on the macroscopic properties of the channel, such as the current. Among the filter atoms, only the pore-forming carbonyl groups can be considered as dynamic in the studies of microscopic events of conduction, while the dynamic effects from all other atoms are negligible. We also show that the dynamics of the water molecules in the filter can not be neglected. The fluctuating forces from the water molecules can be as strong as net forces from the pore walls and can effectively drive the ions through the local energy barriers in the filter.

  11. The advantage of polymer addition to a non-ionic oil in water microemulsion for the dermal delivery of progesterone.

    PubMed

    Biruss, Babette; Valenta, Claudia

    2008-02-12

    The influence of progesterone on the physicochemical behaviour of the o/w microemulsion consisting of the non-ionic surfactant polyoxyethylene-10-dodecyl ether, tributyrin and water was investigated. Thereby no significant influence could be detected in terms of droplet size, zeta potential, conductivity and pH by progesterone. However the chemical stability of progesterone was insufficient during the storage of 6 months. Therefore, two different polymeric agents, named silicon dioxide and polymeric emulsifier, were added to the progesterone containing microemulsions. These polymers increased the chemical stability of progesterone significantly. Moreover the polymeric additives improved the skin permeation 1.24- and 1.63-fold and decreased the skin retention in relation to the pure microemulsion. The polymer-stabilized progesterone microemulsions are interesting vehicles for skin application of progesterone.

  12. Influence of Anthropogenic Nutrient Additions on Greenhouse Gas Production Rates at Water-soil Interfaces in an Urban Dominated Estuary

    NASA Astrophysics Data System (ADS)

    Brigham, B. A.; O'Mullan, G. D.; Bird, J. A.

    2014-12-01

    The tidal Hudson River Estuary (HRE) receives significant inputs of readily dissolvable carbon (C) and nitrogen (N) from incomplete wastewater treatment and sewer overflow during storm events associated with NYC and other urban centers. Nutrient deposition may alter C utilization in the estuarine water column, associated sediments and surrounding wetlands. In these anaerobic systems, we hypothesize that microbial activity is limited by the availability of easily-degradable C (not electron acceptors), which acts as a co-metabolite and provides energy for organic matter decomposition. Sporadic transport of highly C enriched storm derived runoff may substantially enhance greenhouse gas (GHG) production rates through the utilization of stored C pools. To test our hypothesis carbon dioxide (CO2) and methane (CH4) process rates (1) were evaluated from soil cores removed from three distinct HRE wetland sites (Saw Mill Creek, Piermont, and Iona Island Marsh(s)) across a salinity gradient and incubated under varying nutrient treatments. Further, CO2 and CH4 surface water effluxes (2) were quantified from multiple river cruises spanning two years at varying distance from nutrient sources associated with NYC. Incubation experiments from wetland soil core experiments demonstrated that readily degradable C but not inorganic N additions stimulated GHG production (200 - 350 ug C g-1 of dry soil day-1) threefold compared to negative controls. The HRE was found to be both a CO2 and CH4 source under all conditions. The greatest GHG efflux (300 - 3000 nmoles C m-2 day-1) was quantified in mid-channel, tributary, and near shore sites in close proximity to NYC which following precipitation events demonstrated 2-20X increased GHG efflux. These results demonstrate that anthropogenic C additions associated with dense urban centers have the potential to enhance anaerobic microbial degradation of organic matter and subsequent GHG production.

  13. Model assessment of additional contamination of water bodies as a result of wildfires in the Chernobyl exclusion zone.

    PubMed

    Bondar, Yu I; Navumau, A D; Nikitin, A N; Brown, J; Dowdall, M

    2014-12-01

    Forest fires and wild fires are recognized as a possible cause of resuspension and redistribution of radioactive substances when occurring on lands contaminated with such materials, and as such are a matter of concern within the regions of Belarus and the Ukraine which were contaminated by the Chernobyl accident in 1986. Modelling the effects of such fires on radioactive contaminants is a complex matter given the number of variables involved. In this paper, a probabilistic model was developed using empirical data drawn from the Polessie State Radiation-Ecological Reserve (PSRER), Belarus, and the Maximum Entropy Method. Using the model, it was possible to derive estimates of the contribution of fire events to overall variability in the levels of (137)Cs and (239,240)Pu in ground air as well as estimates of the deposition of these radionuclides to specific water bodies within the contaminated areas of Belarus. Results indicate that fire events are potentially significant redistributors of radioactive contaminants within the study area and may result in additional contamination being introduced to water bodies.

  14. Effects of organic and inorganic additives on flotation recovery of washed cells of Saccharomyces cerevisiae resuspended in water.

    PubMed

    DeSousa, Sandro Rogério; Laluce, Cecilia; Jafelicci, Miguel

    2006-03-01

    Separation of microbial cells by flotation recovery is usually carried out in industrial reactors or wastewater treatment systems, which contain a complex mixture of microbial nutrients and excretion products. In the present study, the separation of yeast cells by flotation recovery was carried out using a simple flotation recovery systems containing washed yeast cells resuspended in water in order to elucidate the effects of additives (defined amounts of organic and inorganic acids, ethanol, surfactants and sodium chloride) on the cellular interactions at interfaces (cell/aqueous phase and cell/air bubble). When sodium chloride, organic acids (notably propionic, succinic and acetic acids) and organic surfactants (sodium dodecyl sulphate (SDS), cetyltrimethylammonium bromi