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1

Derived Interaction Parameters for the TSAI-WU Tensor Polynomial Theory of Strength for Composite Materials.  

National Technical Information Service (NTIS)

It is shown that the two interactive strength parameters in the Tsai-Wu tensor polynomial strength criterion for fiber composites can be derived in terms of the uniaxial or non-interacting strength parameters if the composite does not fail under practical...

S. J. DeTeresa G. J. Larsen

2001-01-01

2

Consequences of dark matter-dark energy interaction on cosmological parameters derived from type Ia supernova data  

SciTech Connect

Models where the dark matter component of the Universe interacts with the dark energy field have been proposed as a solution to the cosmic coincidence problem, since in the attractor regime both dark energy and dark matter scale in the same way. In these models the mass of the cold dark matter particles is a function of the dark energy field responsible for the present acceleration of the Universe, and different scenarios can be parametrized by how the mass of the cold dark matter particles evolves with time. In this article we study the impact of a constant coupling {delta} between dark energy and dark matter on the determination of a redshift dependent dark energy equation of state w{sub DE}(z) and on the dark matter density today from SNIa data. We derive an analytical expression for the luminosity distance in this case. In particular, we show that the presence of such a coupling increases the tension between the cosmic microwave background data from the analysis of the shift parameter in models with constant w{sub DE} and SNIa data for realistic values of the present dark matter density fraction. Thus, an independent measurement of the present dark matter density can place constraints on models with interacting dark energy.

Amendola, Luca; Campos, Gabriela Camargo; Rosenfeld, Rogerio [INAF/Osservatorio Astronomico di Roma, V. Frascati 33, 00040, Monteporzio Catone (Rome) (Italy); Instituto de Fisica Teorica - UNESP, Rua Pamplona 145, 01405-900, Sao Paulo, SP (Brazil)

2007-04-15

3

Consequences of dark matter-dark energy interaction on cosmological parameters derived from typeIa supernova data  

Microsoft Academic Search

Models where the dark matter component of the Universe interacts with the dark energy field have been proposed as a solution to the cosmic coincidence problem, since in the attractor regime both dark energy and dark matter scale in the same way. In these models the mass of the cold dark matter particles is a function of the dark energy

Luca Amendola; Gabriela Camargo Campos; Rogerio Rosenfeld

2007-01-01

4

Electroweak interaction parameters  

SciTech Connect

The parameters discussed include: the renormalized weak mixing angle, masses and widths of the W plus and minus and of the Z boson, radiative Z and W boson decays. The Higgs-top quark mass connection and the Grand Unification theories are briefly reviewed. It is suggested that a new pseudoscalar particle with a mass near 93 GeV could be produced by gluon-gluon fusion. 28 references. (LEW)

Marciano, W.J.

1984-04-01

5

Derivation of synchronous machine parameters from tests  

Microsoft Academic Search

This paper describes a test procedure for derivation of synchronous machine parameters. The tests can be conducted with ease and without hazard on generators in utility systems. Unlike textbook methods involving short circuit and slip tests which are inconvenient and hazardous, the proposed method involves simple procedures, which can be implemented in normal operation of the machine.

F. P. de Mello; J. R. Ribeiro

1977-01-01

6

Understanding Interactions among Genetic Algorithm Parameters  

Microsoft Academic Search

Genetic algorithms (GAs) are multi-dimensional and stochastic search methods, involving complex in- teractions among their parameters. For last two decades, researchers have been trying to understand the mechanics of GA parameter interactions by using various techniques. The methods include careful 'func- tional' decomposition of parameter interactions, empirical studies, and Markov chain analysis. Although the complex knot of these interactions are

Kalyanmoy Deb; Samir Agrawal

1998-01-01

7

Derivative interactions in de Rham-Gabadadze-Tolley massive gravity  

NASA Astrophysics Data System (ADS)

We investigate the possibility of a new massive gravity theory with derivative interactions as an extension of de Rham-Gabadadze-Tolley massive gravity. We find the most general Lagrangian of derivative interactions using a Riemann tensor whose cutoff energy scale is ?3, which is consistent with de Rham-Gabadadze-Tolley massive gravity. Surprisingly, this infinite number of derivative interactions can be resummed with the same method in de Rham-Gabadadze-Tolley massive gravity, and remaining interactions contain only two parameters. We show that the equations of motion for scalar and tensor modes in the decoupling limit contain fourth derivatives with respect to spacetime, which implies the appearance of ghosts at ?3. We claim that consistent derivative interactions in de Rham-Gabadadze-Tolley massive gravity have a mass scale M, which is much smaller than the Planck mass MPl.

Kimura, Rampei; Yamauchi, Daisuke

2013-10-01

8

Paraglide: Interactive Parameter Space Partitioning for Computer Simulations.  

PubMed

In this paper we introduce ParaGlide, a visualization system designed for interactive exploration of parameter spaces of multi-dimensional simulation models. To get the right parameter configuration, model developers frequently have to go back and forth between setting input parameters and qualitatively judging the outcomes of their model. Current state-of-the-art tools and practices, however, fail to provide a systematic way of exploring these parameter spaces, making informed decisions about parameter configurations a tedious and workload-intensive task. ParaGlide endeavors to overcome this shortcoming by guiding data generation using a region-based user interface for parameter sampling and then dividing the model's input parameter space into partitions that represent distinct output behavior. In particular, we found that parameter space partitioning can help model developers to better understand qualitative differences among possibly high-dimensional model outputs. Further, it provides information on parameter sensitivity and facilitates comparison of models. We developed ParaGlide in close collaboration with experts from three different domains, who all were involved in developing new models for their domain. We first analyzed current practices of six domain experts and derived a set of tasks and design requirements, then engaged in a user-centered design process, and finally conducted three longitudinal in-depth case studies underlining the usefulness of our approach. PMID:23459287

Bergner, Steven; Sedlmair, Michael; Moller, Torsten; Nabi Abdolyousefi, Sareh; Saad, Ahmed

2013-02-28

9

Photon Interaction Parameters for Some Borate Glasses  

NASA Astrophysics Data System (ADS)

Some photon interaction parameters of dosimetric interest such as mass attenuation coefficients, effective atomic number, electron density and KERMA relative to air have been computed in the wide energy range from 1 keV to 100 GeV for some borate glasses viz. barium-lead borate, bismuth-borate, calcium-strontium borate, lead borate and zinc-borate glass. It has been observed that lead borate glass and barium-lead borate glass have maximum values of mass attenuation coefficient, effective atomic number and KERMA relative to air. Hence, these borate glasses are suitable as gamma ray shielding material, packing of radioactive sources etc.

Mann, Nisha; Kaur, Updesh; Singh, Tejbir; Sharma, J. K.; Singh, Parjit S.

2010-11-01

10

Photon Interaction Parameters for Some Borate Glasses  

SciTech Connect

Some photon interaction parameters of dosimetric interest such as mass attenuation coefficients, effective atomic number, electron density and KERMA relative to air have been computed in the wide energy range from 1 keV to 100 GeV for some borate glasses viz. barium-lead borate, bismuth-borate, calcium-strontium borate, lead borate and zinc-borate glass. It has been observed that lead borate glass and barium-lead borate glass have maximum values of mass attenuation coefficient, effective atomic number and KERMA relative to air. Hence, these borate glasses are suitable as gamma ray shielding material, packing of radioactive sources etc.

Mann, Nisha [Department of Applied Sciences, Samalkha Group of Institutions, Samalkha-132 101, Haryana (India); Kaur, Updesh; Singh, Tejbir; Sharma, J. K. [Department of Physics, Maharishi Markandeshwar University, Mullana-133 207, Haryana (India); Singh, Parjit S. [Department of Physics, Punjabi University, Patiala-147 002, Punjab (India)

2010-11-06

11

ATMOSPHERIC INSTABILITY PARAMETERS DERIVED FROM MSG SEVIRI OBSERVATIONS  

Microsoft Academic Search

Within the MSG Global Instability Index (GII) product, information on the static stability and other airmass parameters will be operationally derived and disseminated. The GII product should serve as a nowcasting tool to identify the potential of convection and possibly of severe storms in still preconvective conditions. The applied retrieval method makes use of six MSG SEVIRI thermal bands, and

Marianne König; Stephen Tjemkes; Jochen Kerkmann

12

Determination of some thermodynamic parameters of dissociation of dihydropyrimidine derivatives  

NASA Astrophysics Data System (ADS)

Dissociation constant of dihydropyrimidine derivatives has been determined in dimethyl forma-mide—water (60: 40 v/v) system at different temperatures. The data are discussed in terms of the electron nature of the substituents. Further, some thermodynamics parameters such as enthalpy of solution, Gibbs energy change and entropy of solution have also been evaluated for these systems.

Bhalodia, Rahul; Gajera, Ravi; Baluja, Shipra

2011-08-01

13

On the estimation of interaction parameters in weak measurements  

NASA Astrophysics Data System (ADS)

Since weak measurements are known to produce measurement values that can be much larger than the maximal eigenvalues of the measured observable, it is an interesting question how this enhancement of the measurement signal relates to the sensitivity of quantum measurements as investigated in the field of quantum metrology. In this presentation, it is pointed out that the estimation of a small interaction parameter using weak measurements actually corresponds to standard quantum metrology, where the logarithmic derivatives of the final measurement probabilities are proportional to the corresponding weak values. The analysis of the general weak measurement formalism then shows that extreme weak values do not improve the sensitivity. Instead, all final measurements with real weak values have the same sensitivity as a final measurement of the eigenvalues. This result supports the view that real weak values can be interpreted as precise, zero uncertainty estimates of a quantum observable, despite their deviation from the eigenvalues of the corresponding operator.

Hofmann, Holger F.

2011-10-01

14

Derivation of Pauli-corrected effective intercluster interactions  

NASA Astrophysics Data System (ADS)

In this paper we propose a microscopic method of calculating Pauli-corrected intercluster interactions. The method is based on a microscopic Hamiltonian which contains the influence of the Pauli principle and from which the corresponding intercluster potentials are derived. This method overcomes the difficulties of the inclusion of the Pauli principle in systems of more than two clusters which occur in the resonating group method, orthogonality condition model, projection method, and the fish bone model. Moreover, it allows the investigation of the influence of the microscopic parameters in different systems and the examination of the on- and off-shell behavior of the intercluster forces in a consistent way. NUCLEAR REACTIONS Composite particle interaction, N-cluster theory, nuclear fragments, scattering theory.

Orlowski, M.

1982-10-01

15

Effect of plasma surface interactions on PLT plasma parameters  

SciTech Connect

This paper gives a brief description of the geometry and parameters of the PLT tokamak, reviews some of the last four years' results that are particularly relevant to plasma-boundary interactions, and then concentrates on two specific problems.

Meservey, E.B.; Arunasalam, V.; Barnes, C.

1980-07-01

16

Interactions between specific parameters of cannabis use and verbal memory  

Microsoft Academic Search

Recently, the impact of different parameters of cannabis use, including the age of first use, the average frequency of use, the cumulative lifetime dose, the average dose per occasion, and the duration of regular use upon cognitive functions has been discussed. However, to date no study has systematically investigated the interactions of these parameters with regard to cognitive performance. To

Daniel Wagner; Benjamin Becker; Euphrosyne Gouzoulis-Mayfrank; Jörg Daumann

2010-01-01

17

Galactic spiral structure parameters derived from stellar kinematics  

SciTech Connect

A method is proposed for determining the parameters of galactic spiral structure from an observed stellar velocity field. Both geometrical parameters (the pitch angle i of the spiral arms and the phase chi/sub 0/ of the sun with respect to the spiral density wave) and dynamical parameters (the galactocentric and azimuthal components f/sub R/, f/sub theta/ of systematic stellar motions due to the spiral wave, as well as the potential phi, gravitational force F, surface density ..mu.., and rotational velocity ..cap omega../sub p/ of the spiral pattern) can be established. In addition, the velocity ..cap omega../sub 0/ of galactic rotation and its derivatives ..cap omega../sub 0/', ..cap omega../sub 0/'' can be determined by allowing for the perturbations of the stellar velocity field induced by the spiral structure. The method is applied to a sample of 183 type A, F, G supergiants and a sample of 192 long-period Cepheids. The parameters determined from the two samples are mutually consistent, within the errors. For a two-armed model the Cepheid sample yields i=7/sup 0/.5, chi/sub 0/=150/sup 0/, ..cap omega../sub p/=19.1 +- 3.6 km sec/sup -1/xkpc /sup -1/, f/sub R/ =-5.4 +- 2.3 km/sec, f/sub theta/=12.0 +- 2.3 km/sec, ..mu..=0.71 +- 0.16, phi=-515 +- 111 km/sup 2//sec/sup 2/, F=14.6%, ..cap omega../sub 0/' =-1.78 +- 0.17. These results imply that the sun is located midway between two spiral arms, the Perseus and the Sagittarius; the Orion arm is not part of the fundamental spiral pattern. The rotational velocity of the pattern differs little, if at all, from the galactic rotation in the solar neighborhood, in agreement with earlier calculations by L. S. Marochnik and the authors. The local centroid exhibits motion only from the spiral wave field. The spiral structure represents merely a minor perturbation. in the underlying axisymmetric state of the Galaxy. This determination of the spiral structure geometry (i, chi/sub 0/) from the stellar velocity field is in good accord with the results from optical and 21-cm line data.

Mishurov, Y.N.; Pavlovskaya, E.D.; Suchkov, A.A.

1979-03-01

18

Upscaling water cycle parameters using geomorphometric terrain parameters and topographic indices derived from interferometric DEM  

NASA Astrophysics Data System (ADS)

For assessing a regional water balance in boreal landscapes the extend to which evapo-transpiration is subject to spatial variations needs to be known. Water cycle parameters such as transpiration rates of vegetation are depending on both the vegetation type and hydro-pedologic stand conditions since poor soil drainage respective seasonal soil drought affect water consumption by vegetation. The spatial distribution of the pristine boreal vegetation types can be obtained by SAR or optical remote sensing sensors on a regional scale. Many works have been dealing with this subject in the past and it is widely known how remote sensing can contribute to vegetation mapping. To assess hydro-pedologic stand conditions on a regional scale an alternative method is required. Our approach to resolve this problem is based on the fact that soil water status is essentially a function of topographic properties. For that reason morphometric terrain parameters derived from a Digital Elevation Model (DEM) has been used to indicate regions with homogeneous hydro-pedologic stand conditions, so called "hydropedotopes". To delineate the required hydropedotopes two indicators pertaining to soilwater status and pedo-hydrology were derived from InSAR DEM: (1) The wetness-index and (2) the vertical distance to streams and bottom lines. In a further step the resulting map of hydropedotopes is intersected with a remote sensing derived map of the actual spatial distribution of the boreal vegetation types. This step results in a map which marks out landscape units of homogeneous properties in terms of vegetation type and hydro-pedologic conditions which is the basis for upscaling canopy transpiration measurements. From our approach which uses in addition to conventional remote sensing data the results of an automated digital terrain analysis we expect a substantially enhanced knowledge of the spatial variability of water flux rates conditional on canopy transpiration. The process of our approach at a glance is illustrated.

Etzrodt, N.; Zimmermann, R.; Conrad, O.

2002-01-01

19

Derivation of Delaware Bay tidal parameters from space shuttle photography  

SciTech Connect

The tide-related parameters of the Delaware Bay are derived from space shuttle time-series photographs. The water areas in the bay are measured from interpretation maps of the photographs with a CALCOMP 9100 digitizer and ERDAS Image Processing System. The corresponding tidal levels are calculated using the exposure time annotated on the photographs. From these data, an approximate function relating the water area to the tidal level at a reference point is determined. Based on the function, the water areas of the Delaware Bay at mean high water (MHW) and mean low water (MLW), below 0 m, and for the tidal zone are inferred. With MHW and MLW areas and the mean tidal range, the authors calculate the tidal influx of the Delaware Bay, which is 2.76 x 1O[sup 9] m[sup 3]. Furthermore, the velocity of flood tide at the bay mouth is determined using the tidal flux and an integral of the velocity distribution function at the cross section between Cape Henlopen and Cape May. The result is 132 cm/s, which compares well with the data on tidal current charts.

Zheng, Quanan; Yan, Xiaohai; Klemas, V. (Univ. of Delaware, Newark (United States))

1993-06-01

20

Flory interaction parameter chi for hydrophilic copolymers with water.  

PubMed

In biomedical applications of hydrophilic polymers knowledge is required of the thermodynamic interactions between the candidate biomaterial and biological fluids. Since information on these interactions is not readily available, a new method is proposed here to estimate the copolymer-water Flory interaction parameter, chi, for biomaterials. The method is based on the pairwise thermodynamic interactions of copolymer segments and solvent molecules. It is validated using data for an important biomedical hydrogel, poly(2-hydroxyethyl methacrylate-co-methacrylic acid), in contact with water. PMID:3224127

Mikos, A G; Peppas, N A

1988-09-01

21

Molecular interactions and thermal instability of coal derived liquids  

Microsoft Academic Search

The purpose of the first part of this research was to investigate interactions between the acid\\/neutral and base fractions of coal derived asphaltenes. These interactions are thought to cause high viscosities in coal derived liquids which are obtained from catalytic processes. The asphaltenes were obtained from Synthoil and separated into acid\\/neutral and base fractions. The interactions of model compounds, o-phenylphenol

Galya

1983-01-01

22

Structure of p-shell Nuclei with Interactions Derived from Chiral Effective-Field Theory  

Microsoft Academic Search

Traditional realistic nucleon-nucleon (NN) interactions based on precision fits to 2-body data have not produced high-quality descriptions of light nuclei. Effective-Field theories (EFT) based on chiral-perturbation theory provide a natural scheme to derive inter-nucleon interactions and predict a three-nucleon interaction at next-to-next-to-leading order (N2LO). A key feature of these EFT potentials is a set of parameters; some of which are

W. E. Ormand; V. G. Gueorguiev; P. Navratil; J. P. Vary

2006-01-01

23

Multiple parton-parton interactions in an impact parameter picture  

Microsoft Academic Search

The possibility of having several independent parton-parton interactions in a hadron-hadron collision is studied. A simple framework is developed for the effects of varying impact parameters. The consequences of having several different matter distributions inside the colliding hadrons are explored. Properties studied include multiplicity distributions, minijet rates, average transverse momentum dependence on multiplicity and ET density outside jet cores.

Torbjörn Sjöstrand; Maria van Zijl

1987-01-01

24

Elementary approximate derivations of some retarded Casimir interactions involving one or two dielectric walls  

NASA Astrophysics Data System (ADS)

The original derivation by Lifshitz [Sov. Phys. 2, 73 (1956)] of PDD, the force per unit area between two plane parallel dielectric walls, is extremely complicated; the later derivations are simpler but still difficult. The standard derivation of the interaction VAt D of an atom and a dielectric wall uses the expression for PDD as its starting point. The results are valid for all values of the separation l. For l~?, where the interactions are retarded, we obtain resonably accurate approximate expressions for PDD and for VAt D-and also for VEl D, the retarded interaction of an electron and a dielectric wall-by the elementary procedure of assuming simple forms with one or two open parameters, adjusted to give the known results for retarded interactions which do not include dielectric walls. These include PMM (the force per unit area between two parallel plate metallic walls), VAt M (the atom-metal) interaction, VAt At (the atom-atom interaction), and VEl M (the electron-metal interaction). We also consider the possibility of obtaining an improved estimate of PDD by using known properties of VAt D. The explicit results obtained by Lifshitz for the various interactions are also very complicated. The simple approximate forms of the interactions can be particularly useful for the wall-wall interaction, since PDD is a double integral with a complicated integrand which depends upon two parameters, the zero-frequency dielectric constants of each of the walls.

Spruch, Larry; Tikochinsky, Yoel

1993-12-01

25

Deriving local order parameters from tensor network representations  

Microsoft Academic Search

A large class of quantum phase transitions for quantum lattice systems are characterized by local order parameters. It is shown that local order parameters may be systematically constructed from tensor network representations of quantum many-body ground state wave functions by investigating the reduced density matrices for local areas on an infinite-size lattice. Depending on whether or not the system symmetries

Huan-Qiang Zhou

2008-01-01

26

Parameter Estimation Techniques for Interaction and Redistribution Models of Species Interactions: A Predator-Prey Example.  

National Technical Information Service (NTIS)

The use of parameter estimation techniques for partial differential equations is illustrated using a predator-prey model. These techniques will be general useful for any interaction and redistribution model in ecology, and can even be used to treat spatia...

H. T. Banks P. M. Kareiva K. A. Murphy

1986-01-01

27

Parameter Simulation and Energy Equation Derivation of Port Container Logistics  

Microsoft Academic Search

Movement of port container logistics is similar to fluid, the paper analyzes the sameness and difference between such two movements by means of hydrodynamics, it also defines the concepts and hypothesis of port container logistics simulation. Based on this, the paper derives the energy equation which is suitable for describing the port container movement, and discusses the physical meaning of

Yun Liu; Hongda Shi

2007-01-01

28

Do coinage metal anions interact with substituted benzene derivatives?  

PubMed

The nature of the anion-? interaction has been investigated by carrying out ab initio calculations of the complexes of coinage metal anions (Au(-), Ag(-), and Cu(-)) with different kinds of ?-systems. The binding energies indicate that gold anion has the highest and copper anion has the lowest affinity for interactions with ?-systems. Different aspects of the anion-? interaction in these systems have been investigated, including charge-transfer effects (using the Merz-Kollman method), "atoms-in-molecules" (AIM) topological parameters, and interaction energies (using energy decomposition analysis, EDA). Our results indicated that, for most M(-)···? interactions, the electrostatic term provides the dominant contribution, whereas polarization, charge transfer, and dispersion effects contribute less than 25 % of the interaction. We believe that the present results should lead to a greater understanding of the basis for anion-? interactions of coinage metal anions. PMID:23989771

Aliakbar Tehrani, Zahra; Jamshidi, Zahra; Farhangian, Hossein

2013-08-30

29

Power Saving Optimization for Linear Collider Interaction Region Parameters  

SciTech Connect

Optimization of Interaction Region parameters of a TeV energy scale linear collider has to take into account constraints defined by phenomena such as beam-beam focusing forces, beamstrahlung radiation, and hour-glass effect. With those constraints, achieving a desired luminosity of about 2E34 would require use of e{sup +}e{sup -} beams with about 10 MW average power. Application of the 'travelling focus' regime may allow the required beam power to be reduced by at least a factor of two, helping reduce the cost of the collider, while keeping the beamstrahlung energy loss reasonably low. The technique is illustrated for the 500 GeV CM parameters of the International Linear Collider. This technique may also in principle allow recycling the e{sup +}e{sup -} beams and/or recuperation of their energy.

Seryi, Andrei; /SLAC

2009-10-30

30

Thermodynamically derived relationships between the modified Langmuir isotherm and experimental parameters  

SciTech Connect

The modified Langmuir isotherm parameters and the thermodynamic ion-exchange properties are developed from theoretical considerations leading to the derivation of a relationship between the two. For the binary ion-exchange system, the relationship indicates that a unique set of isotherm parameters can be defined by a minimum set of experimental parameters. Those parameters are the solid-liquid ratio and the initial concentration of the competing solute in the liquid and exchanger phases. In principle, unique sets of isotherm parameters can be predicted for different conditions from a known set of experimentally determined parameters. The effect of experimental parameters (e.g., solid-liquid ratio and competing solute concentration) on isotherm parameters (e.g., linear K{sub d}) have been documented in the literature. Experimental data are used to illustrate the derived relationships.

Polzer, W.L.; Beckman, R.J. [Los Alamos National Lab., NM (US); Rao, M.G. [Howard Univ., Washington, DC (US); Fuentes, H.R. [Univ. of Texas, El Paso (US)

1992-12-31

31

Natural and synthetic G-quadruplex interactive berberine derivatives  

Microsoft Academic Search

The interaction of the natural alkaloid berberine with various G-quadruplex DNA structures and its ability to inhibit telomerase have been examined and compared with those of a synthetic piperidino derivative and the related compound coralyne. The results show that these molecules have selectivity for G-quadruplex compared to duplex DNA, and that their aromatic moieties play a dominant role in quadruplex

Marco Franceschin; Luigi Rossetti; Anna D’Ambrosio; Stefano Schirripa; Armandodoriano Bianco; Giancarlo Ortaggi; Maria Savino; Christoph Schultes; Stephen Neidle

2006-01-01

32

Thermodynamically derived relationships between the modified Langmuir isotherm and experimental parameters  

Microsoft Academic Search

The modified Langmuir isotherm parameters and the thermodynamic ion-exchange properties are developed from theoretical considerations leading to the derivation of a relationship between the two. For the binary ion-exchange system, the relationship indicates that a unique set of isotherm parameters can be defined by a minimum set of experimental parameters. Those parameters are the solid-liquid ratio and the initial concentration

Wilfred L. Polzer; R. J. Beckman; M. G. Rao; H. R. Fuentes

1992-01-01

33

Ultlra-intense laser-matter interactions at extreme parameters  

SciTech Connect

The field of shortpulse lasers has seen rapid growth in the recent years with the three major boundaries of energy, pulse duration and repetition rate being pushed in ever extremer regions. At peak powers, already exceeding 10{sup 22} W/cm{sup 2}, in virtually every experiment in relativistic laser physics, the laser pulse interacts with a more or less extended and heated plasma, due to prepulses and ASE-like pedestals on ps - ns time scales. By developing a new technique for ultrahigh contrast, we were able to initiate the next paradigm shift in relativistic laser-matter interactions, allowing us to interact ultrarelativistic pulses volumetrically with overdense targets. This becomes possible by using target and laser parameters that will turn the target relativistically transparent during the few 10s-100s femtoseconds fo the interaction. Specifically, we interact an ultraintese, ultrahigh contrast pulse with solid density, free standing, nanometer diamond target. This paradigm change towards a volumetric overdense interaction in turn enables new particle acceleration mechanisms for both electrons and ions, as well as forward directed relativistic surface harmonics. We report here on first experiments done on those topics at the 200 TW Trident laser at Los Alamos as well as at the Ti:Sapphire system at MBI. We will compare the experimental data to massive large scale 3D simulations done on the prototype of LANL's new Petafiop supercomputer Roadrunner, which is leading the current top 500 list. Specifically, we developed a shortpulse OPA based pulse cleaning technique. Fielding it at the Trident 200 TW laser at Los Alamos, we were able to improve the pulse contrast by 6 orders of magnitude to better than 2 x 10{sup -12} at less than a ps. This enabled for the first time the interaction of a 100J, 200TW laser pulse with a truly solid target with virtually no expansion before the main pulse - target interaction, making possible the use of very thin targets, The thinnest of these at less than 3nm, i.e. 1/300 of the laser wavelength, are even thinner than the plasma skin depth. This drastically changes the laser-matter interaction physics leading to the emergence of new particle acceleration mechanisms, like Break-Out Afterburner (BOA) Acceleration, driven by a relativistic, kinetic plasma instability or Radiation Pressure Acceleration (RPA), driven by stabilized charge separation. Furthermore, these interactions also produce relativistic high harmonics in forward direction as well as mono-en,ergetic electron pulses which might lend itself as a source for fully coherent Thomson scattering in the mulit-keV regime. In this talk I will present an overview over the laser developments leading to this paradigm change as well as over the theoretical and experimental results following from it. Specifically we were able for the first time to demonstrate BOA acceleration of Carbon ions to up to 0.5 GeV using a laser pulse with {approx}10{sup 20} W/cm{sup 2} intensity and showing the scalability of this mechanism into regimes relevant for Hadron Therapy. We were further able to demonstrate mono-energetic electron break-out from ultrathin targets, as a first step towards a flying mirror.

Hegellich, Bjorn M [Los Alamos National Laboratory

2010-11-24

34

Coseismic stress parameter of three California Earthquakes derived from the stochastic finite fault technique  

Microsoft Academic Search

Stochastic finite fault modeling is used to derive the coseismic stress parameter distribution on the fault surface of three\\u000a well-recorded California earthquakes: M7.0, 1989, Loma Prieta; M7.3, 1992, Landers; and M6.7, 1994, Northridge. Classical waveform inversion techniques are inherently more powerful than stochastic modeling as a\\u000a means of deriving detailed source parameters. However, the application of stochastic methods to the

Karen Assatourians; Gail M. Atkinson

2010-01-01

35

State derivative-free model reference adaptive control of distributed parameter systems  

Microsoft Academic Search

Presents control laws for distributed parameter systems of parabolic and hyperbolic types which on one hand ensure robustness with respect to small dynamic uncertainties and disturbances, and on the other hand permit online plant parameter estimation. The novelty of the algorithms proposed is a) in the construction of a state derivative observer and b) in the inclusion of this observer

Yu. V. Orlov

1998-01-01

36

Molecular interactions and thermal instability of coal derived liquids  

SciTech Connect

The purpose of the first part of this research was to investigate interactions between the acid/neutral and base fractions of coal derived asphaltenes. These interactions are thought to cause high viscosities in coal derived liquids which are obtained from catalytic processes. The asphaltenes were obtained from Synthoil and separated into acid/neutral and base fractions. The interactions of model compounds, o-phenylphenol and quinoline, and the acid/neutral and base fractions with these model compounds were studied by proton nuclear magnetic resonance spectroscopy and solution colorimetry. The results indicate that interactions between the acid/neutral and base fractions of the asphaltenes are partially responsible for high viscosities in these synthetic fuels. The purpose of the second part of this research was to investigate the causes and mechanism of formation of deposits from SRC II naphtha in heat exchangers. Formation of these deposits causes plugging and results in pilot plant shutdowns. A deposit obtained from a hydrogenation reactor was examined, and the deposit precursors were concentrated through distillation and ion exchange chromatography. The results indicate that phenols and alkylated nitrogenous bases are responsible for deposit formation. Phenols react through coupling reactions to give arylethers and water. Alkylated nitrogenous bases react by pyrolysis to produce free radicals which crosslink to produce carbonaceous deposits. These reactons have been followed using thermogravimetric analysis, Fourier transform infrared spectroscopy and gas chromatography in the temperature range of 250-400/sup 0/C.

Galya, L.G.

1983-01-01

37

Determination of NMR interaction parameters from double rotation NMR.  

PubMed

It is shown that the anisotropic NMR parameters for half-integer quadrupolar nuclei can be determined using double rotation (DOR) NMR at a single magnetic field with comparable accuracy to multi-field static and MAS experiments. The (17)O nuclei in isotopically enriched l-alanine and OPPh(3) are used as illustrations. The anisotropic NMR parameters are obtained from spectral simulation of the DOR spinning sideband intensities using a computer program written with the GAMMA spin-simulation libraries. Contributions due to the quadrupolar interaction, chemical shift anisotropy, dipolar coupling and J coupling are included in the simulations. In l-alanine the oxygen chemical shift span is 455 +/- 20 ppm and 350 +/- 20 ppm for the O1 and O2 sites, respectively, and the Euler angles are determined to an accuracy of +/- 5-10 degrees . For cases where effects due to heteronuclear J and dipolar coupling are observed, it is possible to determine the angle between the internuclear vector and the principal axis of the electric field gradient (EFG). Thus, the orientation of the major components of both the EFG and chemical shift tensors (i.e., V(33) and delta(33)) in the molecular frame may be obtained from the relative intensity of the split DOR peaks. For OPPh(3) the principal axis of the (17)O EFG is found to be close to the O-P bond, and the (17)O-(31)P one-bond J coupling ((1)J(OP)=161 +/- 2 Hz) is determined to a much higher accuracy than previously. PMID:17707665

Hung, I; Wong, A; Howes, A P; Anupõld, T; Past, J; Samoson, A; Mo, X; Wu, G; Smith, M E; Brown, S P; Dupree, R

2007-08-03

38

Mass-based hygroscopicity parameter interaction model and measurement of atmospheric aerosol water uptake  

NASA Astrophysics Data System (ADS)

In this study we derive and apply a mass-based hygroscopicity parameter interaction model for efficient description of concentration-dependent water uptake by atmospheric aerosol particles with complex chemical composition. The model approach builds on the single hygroscopicity parameter model of Petters and Kreidenweis (2007). We introduce an observable mass-based hygroscopicity parameter ?m which can be deconvoluted into a dilute hygroscopicity parameter (?m0) and additional self- and cross-interaction parameters describing non-ideal solution behavior and concentration dependencies of single- and multi-component systems. For reference aerosol samples of sodium chloride and ammonium sulfate, the ?m-interaction model (KIM) captures the experimentally observed concentration and humidity dependence of the hygroscopicity parameter and is in good agreement with an accurate reference model based on the Pitzer ion-interaction approach (Aerosol Inorganic Model, AIM). Experimental results for pure organic particles (malonic acid, levoglucosan) and for mixed organic-inorganic particles (malonic acid - ammonium sulfate) are also well reproduced by KIM, taking into account apparent or equilibrium solubilities for stepwise or gradual deliquescence and efflorescence transitions. The mixed organic-inorganic particles as well as atmospheric aerosol samples exhibit three distinctly different regimes of hygroscopicity: (I) a quasi-eutonic deliquescence & efflorescence regime at low-humidity where substances are just partly dissolved and exist also in a non-dissolved phase, (II) a gradual deliquescence & efflorescence regime at intermediate humidity where different solutes undergo gradual dissolution or solidification in the aqueous phase; and (III) a dilute regime at high humidity where the solutes are fully dissolved approaching their dilute hygroscopicity. For atmospheric aerosol samples collected from boreal rural air and from pristine tropical rainforest air (secondary organic aerosol) we present first mass-based measurements of water uptake over a wide range of relative humidity (1-99.4%) obtained with a new filter-based differential hygroscopicity analyzer (FDHA) technique. For these samples the concentration dependence of ?m can be described by a simple KIM model equation based on observable mass growth factors and a total of only six fit parameters summarizing the combined effects of the dilute hygroscopicity parameters, self- and cross-interaction parameters, and solubilities of all involved chemical components. One of the fit parameters represents ?m0 and can be used to predict critical dry diameters for the activation of cloud condensation nuclei (CCN) as a function of water vapor supersaturation according to Köhler theory. For sodium chloride and ammonium sulfate reference particles as well as for pristine rainforest aerosols consisting mostly of secondary organic matter, we obtained good agreement between the KIM predictions and measurement data of CCN activation. The application of KIM and mass-based measurement techniques shall help to bridge gaps in the current understanding of water uptake by atmospheric aerosols: (1) the gap between hygroscopicity parameters determined by hygroscopic growth measurements under sub-saturated conditions and by CCN activation measurements at water vapor supersaturation, and (2) the gap between the results of simplified single parameter models widely used in atmospheric or climate science and the results of complex multi-parameter ion- and molecule-interaction models frequently used in physical chemistry and solution thermodynamics (e.g., AIM, E-AIM, ADDEM, UNIFAC, AIOMFAC).

Mikhailov, E.; Vlasenko, S.; Rose, D.; Pöschl, U.

2013-01-01

39

Molecular interactions and viscosity of coal-derived liquids  

SciTech Connect

The effect of molecular interactions on the viscosity of coal-derived liquids and the influence of various phenol additives on the rate of viscosity increase in the aging process have been studied. IR, NMR, GC, GC/MS, elemental analysis, solvent separation, molecular weight determination, and viscosity measurements have been employed to monitor the nature and strength of hydrogen-bonding and the storage properties of coal-derived liquids. These studies show that the transition from a hydrogen-bonded complex, O-H...N, to proton-transfer complex, O/sup -/...H/sup +/N, is one of the important factors which contributes to the high viscosity of coal-derived liquids. Acid and base fractions separated by ion-exchange resins show a comparable formation constant for the acid-base complex to that from p-cresol + quinoline indicating that phenolic OH and quinoline-type base cause the formation of hydrogen -bonded complexes in coal-derived liquids. Analysis of the solvent-refined coal blends with or without phenol additives show that the less-hindered phenols with a free p-position exhibit greater efficiency in retarding the viscosity increases in the accelerated aging process. The lower molecular weight of unaged and aged toluene-insolubles, obtained from blends with less-hindered phenol additives, suggests that the added phenol disturbs the original hydrogen-bonding equilibria in the blend, thus influencing the aging characteristics of coal-derived liquids.

Young, L.J.S.

1982-01-01

40

Solubility and interaction parameters as references for solution properties II: precipitation and aggregation of asphaltene in organic solvents.  

PubMed

The total combinatory Gibbs free energy was successfully used to model the solubility of two purified asphaltenes in pure and mixed solvents, as well as the precipitation of asphaltenes from mixed solvents. Intrinsic viscosity and aggregate size both sensitively reflected the state of the asphaltenes in homogeneous solution and were used for determining the solubility parameters of the asphaltenes. Phase separation was clearly reflected by a dramatic increase in aggregate size. The interaction parameter was subdivided into enthalpy and entropy contributions. All parameters indicate an extensive association or phase transition when the phase boundary was followed by simultaneously varying the temperature and the solubility parameter of the solvent. However, the interaction parameter is frequently derived in two ways. We show that, depending on the definition, the enthalpy and entropy contributions lead to conflicting results. These were evaluated on thermodynamic grounds. PMID:19019320

Johansson, Bjarne; Friman, Rauno; Hakanpää-Laitinen, Hannele; Rosenholm, Jarl B

2008-10-17

41

Protein interactions with nanoporous sol-gel derived bioactive glasses.  

PubMed

Sol-gel derived bioactive glasses are excellent candidates for bone regenerative implant materials as they bond with bone, stimulate bone growth and degrade in the body. Their interactions with proteins are critical to understanding their performance after implantation. This study focuses on the interactions between fibrinogen and sol-gel glass particles of the 70S30C (70 mol.% SiO(2), 30 mol.% CaO composition). Sol-gel silica and melt-derived Bioglass® were also used for comparison. Fibrinogen penetration into the nanoporous glasses was observed by live tracking the fluorescent-labelled fibrinogen with confocal microscopy. The effect of pore size on protein penetration was investigated. Nanoporous networks with modal pore diameters larger than 6 nm were accessible to fibrinogen. When the modal nanopore diameter was decreased to 2 nm or less, the penetration of fibrinogen was inhibited. The surface properties of the glasses, which can be modulated by media pH, glass composition and final stabilisation temperature in the sol-gel process, have effects on fibrinogen adsorption via long-range Coulombic forces before the adsorption and via short-range interactions such as hydrogen bonding after the adsorption. PMID:21757036

Lin, Sen; Van den Bergh, Wouter; Baker, Simon; Jones, Julian R

2011-06-30

42

Redox interactions of nitric oxide with dopamine and its derivatives.  

PubMed

Nitric oxide (*NO) is a ubiquitous diffusible messenger in the central nervous system. *NO and derived nitrogen species may interact with catecholamines, thus, modifying not only its regulatory actions but also producing oxidants and free radicals that are likely to trigger toxic pathways in the nervous system. Oxidative pathways and chain oxidation reactions triggered by catecholamines may be broken by ascorbate and glutathione, of which there is ample supply in the brain. At the subcellular level, mitochondria and cytosolic dopamine storage vesicles are likely to provide site-specific settings for *NO and catecholamines interactions. Thus, a complex picture emerges in which the steady- state levels of the individual reactants, the rate constants of the reactions involved, the oxygen tension, and the compartmentalization of reactions determine the biological significance of the redox interactions between *NO and dopamine metabolism in the brain. The physiological relevance of *NO-driven chemical modifications of dopamine and its derivatives and the ensuing free radical production are discussed in connection with the neurodegeneration inherent in Parkinson's disease. PMID:15691585

Antunes, Fernando; Nunes, Carla; Laranjinha, João; Cadenas, Enrique

2005-03-15

43

[Parameters of interaction of sodium dodecyl sulfate with human hemoglobin].  

PubMed

It was shown that sodium dodecyl sulfate at concentrations not exceeding the critical micelle concentrations (0-1.9 mM) induced the conversion of oxy- and methemoglobin but not deoxyhemoglobin to hemichrome. The concentration dependences of hemichrome formation were represented as Hill plots, and the parameters of detergent binding were estimated. OxyHb in 20 mM potassium-phosphate buffer, pH 6.8, has two groups of binding sites: the first group is characterized by the Hill constant n1 = 2 and the concentration of half saturation [SDS]50 = 0.8 mM, and the second group is characterized by the Hill constant n2 = 8 and [SDS]50 = 0.9 mM. In the case of metHb one group of binding sites with the Hill constant n = 2 and half saturation concentration [SDS]50 = 0.2 mM was observed. An increase in environmental pH to 7.9 decreased the affinity of Hb for SDS. It is suggested that primary binding sites for SDS in oxyHb coincide with the anion-binding center of the Hb molecule. The interaction of the detergent with these binding sites induced a structural transition of the hemoprotein molecule. As a result of this transition, secondary binding sites were exposed. In a model system (hemin--imidazole in ethanol solution), the enthalpy of the transition of hemin from a high-spin to a low-spin state was estimated to be 47 +/- 7 kJ/mol. PMID:11094702

Zavodnik, I B; Lapshina, E A

44

Stochasticity effects on derivation of physical parameters of unresolved star clusters  

NASA Astrophysics Data System (ADS)

We developed a method for a fast modeling of broad-band UBVRI integrated magnitudes of unresolved star clusters and used it to derive their physical parameters (age, mass, and extinction). The method was applied on M33 galaxy cluster sample and consistency of ages and masses derived from unresolved observations with the values derived from resolved stellar photometry was demonstrated. We found that interstellar extinction causes minor age-extinction degeneracy for the studied sample due to a narrow extinction range in M33.

de Meulenaer, P.; Narbutis, D.; Mineikis, T.; Vansevi?ius, V.

45

Synthesis and interaction of bovine serum albumin with p-hydroxybenzoic acid derivatives.  

PubMed

Three novel p-hydroxybenzoic acid derivatives (HSOP, HSOX, HSCP) were synthesized from p-hydroxybenzoic acid and sulfonamides (sulfamonomethoxine sodium, sulfamethoxazole and sulfachloropyridazine sodium) and characterized by elemental analysis, HNMR and MS. Interactions between derivatives and bovine serum albumin (BSA) were studied by fluorescence quenching spectra, UV-vis absorption spectra and time-resolved fluorescence spectra. Based on fluorescence quenching calculation and Förster's non-radioactive energy transfer theory, the values of the binding constants, basic thermodynamic parameters and binding distances were obtained. Experimental results indicated that the three derivatives had a strong ability to quench fluorescence from BSA and that the binding reactions of the derivatives with BSA were a static quenching process. Thermodynamic parameters showed that binding reactions were spontaneous and exothermic and hydrogen bond and van der Waals force were predominant intermolecular forces between the derivatives and BSA. Synchronous fluorescence spectra suggested that HSOX and HSCP had little effect on the microenvironment and conformation of BSA in the binding reactions but the microenvironments around tyrosine residues were disturbed and polarity around tyrosine residues increased in the presence of HSOP. PMID:22826126

Zhang, Xue-Hong; Liu, Li-Na; Lin, Yi-Jie; Lin, Cui-Wu

2012-07-24

46

Parameter derivation for an acoustic cloak based on scattering theory and realization with tunable metamaterials  

NASA Astrophysics Data System (ADS)

This work derives the set of acoustic parameters of a metamaterial for an ideal cylindrical cloak through scattering theory. A multilayered cloak with homogeneous isotropic materials is introduced to approximate the ideal cloak. An active metamaterial, consisting of active arrays of acoustic cavities separated by piezo-diaphragms, is addressed to achieve the required parameters for each layer of the multilayered cloak. In particular, with the aid of a multi-control strategy that takes into account the coupling between adjacent cells, the effective parameters for the cloak can be accurately realized.

Shen, Huijie; Wen, Jihong; Païdoussis, Michael P.; Yu, Dianlong; Cai, Li; Wen, Xisen

2013-09-01

47

Epistasis interaction of QTL effects as a genetic parameter influencing estimation of the genetic additive effect  

PubMed Central

Epistasis, an additive-by-additive interaction between quantitative trait loci, has been defined as a deviation from the sum of independent effects of individual genes. Epistasis between QTLs assayed in populations segregating for an entire genome has been found at a frequency close to that expected by chance alone. Recently, epistatic effects have been considered by many researchers as important for complex traits. In order to understand the genetic control of complex traits, it is necessary to clarify additive-by-additive interactions among genes. Herein we compare estimates of a parameter connected with the additive gene action calculated on the basis of two models: a model excluding epistasis and a model with additive-by-additive interaction effects. In this paper two data sets were analysed: 1) 150 barley doubled haploid lines derived from the Steptoe × Morex cross, and 2) 145 DH lines of barley obtained from the Harrington × TR306 cross. The results showed that in cases when the effect of epistasis was different from zero, the coefficient of determination was larger for the model with epistasis than for the one excluding epistasis. These results indicate that epistatic interaction plays an important role in controlling the expression of complex traits.

Bocianowski, Jan

2013-01-01

48

Interactions of salicylic acid derivatives with calcite crystals.  

PubMed

Investigation of basic interactions between the active pharmaceutical compounds and calcium carbonates is of great importance because of the possibility to use the carbonates as a mineral carrier in drug delivery systems. In this study the mode and extent of interactions of salicylic acid and its amino acid derivates, chosen as pharmaceutically relevant model compounds, with calcite crystals are described. Therefore, the crystal growth kinetics of well defined rhombohedral calcite seed crystals in the systems containing salicylic acid (SA), 5-amino salicylic acid (5-ASA), N-salicyloil-l-aspartic acid (N-Sal-Asp) or N-salicyloil-l-glutamic acid (N-Sal-Glu), were investigated. The precipitation systems were of relatively low initial supersaturation and of apparently neutral pH. The data on the crystal growth rate reductions in the presence of the applied salicylate molecules were analyzed by means of Cabrera & Vermileya's, and Kubota & Mullin's models of interactions of the dissolved additives and crystal surfaces. The crystal growth kinetic experiments were additionally supported with the appropriate electrokinetic, spectroscopic and adsorption measurements. The Langmuir adsorption constants were determined and they were found to be in a good correlation with values obtained from crystal growth kinetic analyses. The results indicated that salicylate molecules preferentially adsorb along the steps on the growing calcite surfaces. The values of average spacing between the adjacent salicylate adsorption active sites and the average distance between the neighboring adsorbed salicylate molecules were also estimated. PMID:21963207

Ukrainczyk, Marko; Gredi?ak, Matija; Jeri?, Ivanka; Kralj, Damir

2011-09-12

49

Alkane derivative-bacteriorhodopsin interaction: proton transport and protein structure.  

PubMed

The effects of alkane derivatives, 1-alcohols (ROH), aliphatic amine hydrochlorides (RNH(2).HCl) and sodium aliphatic carboxylates (ROONa), on the proton pumping activity of bacteriorhodopsin (bR) in a purple membrane have been examined. Photocurrents in bR in the purple membrane adsorbed onto polyester thin film were recorded before and after exposure to these test substances. The peak photocurrent in bR was reversibly suppressed by each substance. From the dose-response curve, the concentrations required to reduce the peak capacitive current by 50% were determined for each homolog and then the standard free energies per CH(2) for the adsorption of the alkane derivatives to the site of action were estimated: -3.13 kJ mol(-1) for ROH, -3.05 kJ mol(-1) for RNH(3)(+), and -2.95 kJ mol(-1) for ROO(-). The proton pumping activity of bR was mainly suppressed by the hydrophobic interaction with the additive. The relative potencies of the functional groups of the alkane derivatives were almost comparable between 1-octanol (C(8)OH) and octylamine hydrochloride (C(8)NH(3)(+)) and about 10 times less effective for sodium octanoate (C(8)OO(-)) than for others. The addition of C(8)OH or C(8)OO(-) changed the absorption spectra of bR with a maximum at 560 nm to the spectra of the intermediate state with a maximum at 480 nm, while the C(8)NH(3)(+) decreased the intensity of the 560 nm band only with no blue-shift by the 480 nm band. We conclude that the action of the alkane derivatives is nonspecific and directed to all organized purple membrane structures and that the binding sites of the ROH and ROO(-) are different from that of RNH(3)(+). PMID:11438238

Shibata, A; Ikema, H; Ueno, S; Muneyuki, E; Higuti, T

2001-09-01

50

Coseismic stress parameter of three California Earthquakes derived from the stochastic finite fault technique  

NASA Astrophysics Data System (ADS)

Stochastic finite fault modeling is used to derive the coseismic stress parameter distribution on the fault surface of three well-recorded California earthquakes: M7.0, 1989, Loma Prieta; M7.3, 1992, Landers; and M6.7, 1994, Northridge. Classical waveform inversion techniques are inherently more powerful than stochastic modeling as a means of deriving detailed source parameters. However, the application of stochastic methods to the source modeling problem is useful to: (1) explore and calibrate the limitations and boundaries of stochastic modeling, (2) understand its relationship to more deterministically based techniques, and (3) provide a view of the source radiation not available from deterministic modeling. The stress parameter distribution for the M7.0 1989 Loma Prieta earthquake fault shows a concentration of stress in the lower part of the northwest side of the fault and another concentration in the upper southeast side of the fault, with an average stress parameter of 80 bars over the fault surface. The stress parameter distribution for the M7.3 1992 Landers earthquake fault shows a gradual increase of stress starting from the southeast side of the fault, close to the hypocenter, towards the center. The maximum stress occurs in the lower central part of the modeled fault surface. The average stress parameter is 70 bars for the Landers earthquake. The stress parameter distribution of the M6.7 1994 Northridge earthquake shows a concentration at the lower southeast end of the fault surface, extending toward the center of the fault surface and stretching to the northwest end. The average stress parameter is 80 bars for Northridge earthquake. The stress parameter distributions derived in this study by stochastic finite-fault modeling of high-frequency motions show considerable similarity to many of the slip distributions provided by different research groups for the same earthquakes, suggesting that the derivation of stress parameter distribution on a fault surface by the method applied in this study is reliable and closely tied to slip on the fault.

Assatourians, Karen; Atkinson, Gail M.

2010-07-01

51

Interaction of pleuromutilin derivatives with the ribosomal peptidyl transferase center.  

PubMed

Tiamulin is a pleuromutilin antibiotic that is used in veterinary medicine. The recently published crystal structure of a tiamulin-50S ribosomal subunit complex provides detailed information about how this drug targets the peptidyl transferase center of the ribosome. To promote rational design of pleuromutilin-based drugs, the binding of the antibiotic pleuromutilin and three semisynthetic derivatives with different side chain extensions has been investigated using chemical footprinting. The nucleotides A2058, A2059, G2505, and U2506 are affected in all of the footprints, suggesting that the drugs are similarly anchored in the binding pocket by the common tricyclic mutilin core. However, varying effects are observed at U2584 and U2585, indicating that the side chain extensions adopt distinct conformations within the cavity and thereby affect the rRNA conformation differently. An Escherichia coli L3 mutant strain is resistant to tiamulin and pleuromutilin, but not valnemulin, implying that valnemulin is better able to withstand an altered rRNA binding surface around the mutilin core. This is likely due to additional interactions made between the valnemulin side chain extension and the rRNA binding site. The data suggest that pleuromutilin drugs with enhanced antimicrobial activity may be obtained by maximizing the number of interactions between the side chain moiety and the peptidyl transferase cavity. PMID:16569865

Long, Katherine S; Hansen, Lykke H; Jakobsen, Lene; Vester, Birte

2006-04-01

52

Deriving reliable fundamental parameters of pre-main-sequence-rich star clusters affected by differential reddening  

NASA Astrophysics Data System (ADS)

We present an approach that improves the search for reliable astrophysical parameters (e.g. age, mass and distance) of differentially reddened, pre-main-sequence-rich star clusters. It involves simulating conditions related to the early-cluster phases, in particular the differential and foreground reddenings, and internal age spread. Given the loose constraints imposed by these factors, the derivation of parameters based only on photometry may be uncertain, especially for the poorly populated clusters. We consider a wide range of cluster (i) mass and (ii) age, and different values of (iii) distance modulus, (iv) differential and (v) foreground reddenings. Photometric errors and their relation with magnitude are also taken into account. We also investigate how the presence of unresolved binaries affect the derived parameters. For each set of (i)-(v) we build the corresponding model Hess diagram, and compute the root mean squared residual with respect to the observed Hess diagram. The parameters that produce the minimum residuals between model and observed Hess diagrams are searched by exploring the full parameter space of (i)-(v) by means of brute force, which may be time consuming but efficient. Control tests show that an adequate convergence is achieved allowing for solutions with residuals 10 per cent higher than the absolute minimum. Compared to a colour-magnitude diagram containing only single stars, the presence of 100 per cent of unresolved binaries has little effect on cluster age, foreground and differential reddenings; significant differences show up in the cluster mass and distance from the Sun. Our approach proves to be successful in minimizing the subjectiveness when deriving fundamental parameters of young star clusters.

Bonatto, C.; Bica, E.; Lima, E. F.

2012-02-01

53

A derivative-free Landweber iteration for parameter identification in certain elliptic PDEs  

NASA Astrophysics Data System (ADS)

We consider the identification of a parameter in an elliptic equation which—in its weak formulation—can be described by a strictly monotone and Lipschitz continuous operator from knowledge of the physical state. Taking advantage of the special structure, we develop a derivative-free Landweber iteration for solving this nonlinear inverse problem in a stable way. Thereby, the Fréchet differentiability of the parameter-to-output map as well as conditions restricting its nonlinearity are no longer required. As a result, the convergence analysis can be performed using more natural assumptions associated with the solvability of the direct problem, which can also be nonlinear. Numerical experiments are presented.

Kügler, Philipp

2003-12-01

54

An empirically-derived taxonomy of interaction primitives for interactive cartography and geovisualization.  

PubMed

Proposals to establish a 'science of interaction' have been forwarded from Information Visualization and Visual Analytics, as well as Cartography, Geovisualization, and GIScience. This paper reports on two studies to contribute to this call for an interaction science, with the goal of developing a functional taxonomy of interaction primitives for map-based visualization. A semi-structured interview study first was conducted with 21 expert interactive map users to understand the way in which map-based visualizations currently are employed. The interviews were transcribed and coded to identify statements representative of either the task the user wished to accomplish (i.e., objective primitives) or the interactive functionality included in the visualization to achieve this task (i.e., operator primitives). A card sorting study then was conducted with 15 expert interactive map designers to organize these example statements into logical structures based on their experience translating client requests into interaction designs. Example statements were supplemented with primitive definitions in the literature and were separated into two sorting exercises: objectives and operators. The objective sort suggested five objectives that increase in cognitive sophistication (identify, compare, rank, associate, & delineate), but exhibited a large amount of variation across participants due to consideration of broader user goals (procure, predict, & prescribe) and interaction operands (space-alone, attributes-in-space, & space-in-time; elementary & general). The operator sort suggested five enabling operators (import, export, save, edit, & annotate) and twelve work operators (reexpress, arrange, sequence, resymbolize, overlay, pan, zoom, reproject, search, filter, retrieve, & calculate). This taxonomy offers an empirically-derived and ecologically-valid structure to inform future research and design on interaction. PMID:24051802

Roth, Robert E

2013-12-01

55

Calculation of mixture equilibrium binary interaction parameters using closed cup flash point measurements  

Microsoft Academic Search

Proper design and operation of separation processes are highly dependent on phase equilibrium calculations. The common method to treat polar\\/nonpolar systems, and also mixtures of normal compounds where the sizes are significantly different is to use binary interaction parameters. This paper presents a method to calculate mixture binary interaction parameters using closed cup flash point measurements. The measured and literature

M. Noorollahy; A. Zarringhalam Moghadam; A. Ameri Ghasrodashti

2010-01-01

56

Fusion of CSP-derived features and Time-Domain Parameters for mind robotics control  

Microsoft Academic Search

In this paper, fusion of Common Spatial Pattern (CSP) analysis derived features and Time-Domain Parameters (TDP) is investigated for two-class motion imagery classification: left hand movement and right hand movement imagery. This fusion method is aiming at improving the performance of Brain- Computer Interface (BCI) systems in translating human thoughts into command to control certain robots, e.g. rehabilitation robots. In

Shuzhi Sam Ge; Xinyang Li; Yaozhang Pan

2011-01-01

57

Improving evapotranspiration in land surface models by using biophysical parameters derived from MSG\\/SEVIRI satellite  

Microsoft Academic Search

Vegetation parameters derived from the geostationary satellite MSG\\/SEVIRI have been distributed at a daily frequency since 2007 over Europe, Africa and part of South America, through the LSA-SAF facility. We propose here a method to handle two new remote sensing products from LSA-SAF, leaf area index and Fractional Vegetation Cover, noted LAI and FVC respectively, for land surface models at

N. Ghilain; A. Arboleda; G. Sepulcre-Cantò; O. Batelaan; J. Ardö; F. Gellens-Meulenberghs

2011-01-01

58

Determining the parameters of the potential of intermolecular interaction by the Zeno line  

NASA Astrophysics Data System (ADS)

The method of determination of intermolecular interaction potential parameters by the Zeno line is proposed. The intermolecular interaction of ethane, propane, ethylene, and propylene is described using a model of site-site interactions and Karr-Konowalow potential. It is shown that the parameters of intermolecular interaction for this potential can be determined from a small number of experimental data in the single-phase area. It is noted that the final parameters allow us to describe the thermodynamic properties over a broad range of gas and liquid states with precision acceptable for practical use.

Anashkin, I. P.; Klinov, A. V.

2013-11-01

59

Application of lab derived kinetic biodegradation parameters at the field scale  

NASA Astrophysics Data System (ADS)

Estimating the intrinsic remediation potential of an aquifer typically requires the accurate assessment of the biodegradation kinetics, the level of available electron acceptors and the flow field. Zero- and first-order degradation rates derived at the laboratory scale generally overpredict the rate of biodegradation when applied to the field scale, because limited electron acceptor availability and microbial growth are typically not considered. On the other hand, field estimated zero- and first-order rates are often not suitable to forecast plume development because they may be an oversimplification of the processes at the field scale and ignore several key processes, phenomena and characteristics of the aquifer. This study uses the numerical model BIO3D to link the laboratory and field scale by applying laboratory derived Monod kinetic degradation parameters to simulate a dissolved gasoline field experiment at Canadian Forces Base (CFB) Borden. All additional input parameters were derived from laboratory and field measurements or taken from the literature. The simulated results match the experimental results reasonably well without having to calibrate the model. An extensive sensitivity analysis was performed to estimate the influence of the most uncertain input parameters and to define the key controlling factors at the field scale. It is shown that the most uncertain input parameters have only a minor influence on the simulation results. Furthermore it is shown that the flow field, the amount of electron acceptor (oxygen) available and the Monod kinetic parameters have a significant influence on the simulated results. Under the field conditions modelled and the assumptions made for the simulations, it can be concluded that laboratory derived Monod kinetic parameters can adequately describe field scale degradation processes, if all controlling factors are incorporated in the field scale modelling that are not necessarily observed at the lab scale. In this way, there are no scale relationships to be found that link the laboratory and the field scale, accurately incorporating the additional processes, phenomena and characteristics, such as a) advective and dispersive transport of one or more contaminants, b) advective and dispersive transport and availability of electron acceptors, c) mass transfer limitations and d) spatial heterogeneities, at the larger scale and applying well defined lab scale parameters should accurately describe field scale processes.

Schirmer, M.; Barker, J. F.; Butler, B. J.; Frind, E. O.

2003-04-01

60

Deriving physical parameters of unresolved star clusters. I. Age, mass, and extinction degeneracies  

NASA Astrophysics Data System (ADS)

Context. Stochasticity and physical parameter degeneracy problems complicate the derivation of the parameters (age, mass, and extinction) of unresolved star clusters when using broad-band photometry. Aims: We develop a method to simulate stochasticity and degeneracies and to investigate their influence on the accuracy of derived physical parameters. Then we apply it to star cluster samples of M 31 and M 33 galaxies. Methods: Age, mass, and extinction of observed star clusters are derived by comparing their broad-band UBVRI integrated magnitudes to the magnitudes of a large grid of star cluster models with fixed metallicity Z = 0.008. Masses of stars for a cluster model are randomly sampled from the initial mass function. Models of star clusters from the model grid, which have all of their magnitudes located within 3 observational errors from the magnitudes of the observed cluster, are selected for computing their age, mass, and extinction. Results: In the case of the M 31 galaxy, the extinction range is wide and the age-extinction degeneracy is strong for a fraction of its clusters. Because of a narrower extinction range, the age-extinction degeneracy is weaker for the M 33 clusters. By using artificial cluster sample, we show that age-extinction degeneracy can be reduced significantly if the range of intrinsic extinction within the host galaxy is narrow. Figures 6-8 are available in electronic form at http://www.aanda.org

de Meulenaer, P.; Narbutis, D.; Mineikis, T.; Vansevi?ius, V.

2013-02-01

61

Pitzer Ion Interaction Parameters of Single Aqueous Electrolytes at 25°C  

Microsoft Academic Search

The ion interaction parameters (Pitzer parameters), ß(0), ß(1), and Cf for 52 single 1-1 electrolytes in aqueous solutions have been obtained from experimental data in the literature on the thermodynamic properties at 25°C using Pitzer's equations. Out of these 52 electrolytes investigated, the ion interaction parameters for nine of them have been reported earlier, but those analyses were limited to

Bijan Das

2004-01-01

62

Photon interaction parameters of dosimetric interest in bone.  

PubMed

The effective atomic numbers (Z(eff)) and electron densities (N(el)) of cortical and compact bone have been computed for total and partial photon interactions (photoelectric absorption, coherent scattering, incoherent scattering, pair production in a nuclear field, pair production in an electronic field, and sum of non-coherent scattering) by computing the molecular, atomic, and electronic cross section in the wide energy range of 1 keV-100 GeV using WinXCom. The variations of effective atomic number and electron density with energy are shown graphically for all photon interactions. The effective atomic numbers (ZPEA(eff)) for photon energy absorption are also calculated from mass energy absorption coefficients in the energy range 1 keV-20 MeV. The kerma values of bone relative to air are also computed. Additionally, computed tomography (CT) numbers of bone for photon interaction and energy absorption are also computed. The computed Z(eff) and N(el) may be useful in choosing a substitute composite material in place of bone. The estimated mass energy absorption coefficient may be used to evaluate dose and determine the surviving fraction (S) for bone. The usefulness of computed data in the simulation of tissue substitutes is also discussed. PMID:22850239

Manjunatha, H C; Rudraswamy, B

2012-09-01

63

QSAR analysis for ADA upon interaction with a series of adenine derivatives as inhibitors.  

PubMed

The kinetic parameters of adenosine deaminase such as Km and Ki were determined in the absence and presence of adenine derivatives (R1-R24) in sodium phosphate buffer (50 mM; pH 7.5) solution at 27 degrees C. These kinetic parameters were used for QSAR analysis. As such, we found some theoretical descriptors to which the binding affinity of adenosine deaminase (ADA) towards several adenine nucleosides as inhibitors is correlated. QSAR analysis has revealed that binding affinity of the adenine nucleosides upon interaction with ADA depends on the molecular volume, dipole moment of the molecule, electric charge around the N1 atom, and the highest of positive charge for the related molecules. PMID:15113027

Moosavi-Movahedi, A A; Safarian, S; Hakimelahi, G H; Ataei, G; Ajloo, D; Panjehpour, S; Riahi, S; Mousavi, M F; Mardanyan, S; Soltani, N; Khalafi-Nezhad, A; Sharghi, H; Moghadamnia, H; Saboury, A A

2004-01-01

64

The physical and biological basis of quantitative parameters derived from diffusion MRI  

PubMed Central

Diffusion magnetic resonance imaging is a quantitative imaging technique that measures the underlying molecular diffusion of protons. Diffusion-weighted imaging (DWI) quantifies the apparent diffusion coefficient (ADC) which was first used to detect early ischemic stroke. However this does not take account of the directional dependence of diffusion seen in biological systems (anisotropy). Diffusion tensor imaging (DTI) provides a mathematical model of diffusion anisotropy and is widely used. Parameters, including fractional anisotropy (FA), mean diffusivity (MD), parallel and perpendicular diffusivity can be derived to provide sensitive, but non-specific, measures of altered tissue structure. They are typically assessed in clinical studies by voxel-based or region-of-interest based analyses. The increasing recognition of the limitations of the diffusion tensor model has led to more complex multi-compartment models such as CHARMED, AxCaliber or NODDI being developed to estimate microstructural parameters including axonal diameter, axonal density and fiber orientations. However these are not yet in routine clinical use due to lengthy acquisition times. In this review, I discuss how molecular diffusion may be measured using diffusion MRI, the biological and physical bases for the parameters derived from DWI and DTI, how these are used in clinical studies and the prospect of more complex tissue models providing helpful micro-structural information.

2012-01-01

65

Structural parameters of 11 faint Galactic globular clusters derived with 2MASS  

NASA Astrophysics Data System (ADS)

Context: Structural parameters and the total MV magnitude are important properties for the characterisation of individual globular clusters. With the growth in statistics, especially of the intrinsically faint objects, the collective properties of the Galactic globular cluster system will be better defined, leading to a deeper understanding of the Galaxy formation processes. Aims: We determine the structural parameters of 11 faint Galactic globular clusters that, in most cases, had not been previously studied in this context: IC 1257, Lyngå 7, Terzan 4, Terzan 10, BH 176, ESO 452-SC11, ESO 280-SC08, 2MASS-GC01, 2MASS-GC02, GLIMPSE-C01, and AL 3. They are projected not far from the central region of the Galaxy. Field-star contamination is significant in the colour-magnitude diagrams. Half of the sample has an absorption AV ?7, in some cases reaching AV ?15. Methods: Stellar radial number-density and surface-brightness profiles were built with 2MASS photometry that, for the present clusters, corresponds to giant-branch stars. Field-star decontamination is essential for clusters in dense fields, so an algorithm that we had previously developed for open clusters in rich fields was employed to better define cluster sequences. With decontaminated photometry we also computed the total MV of four such globular clusters, using M 4 as a template. King-like functions were fitted to the radial profiles, from which the core, half-light, half-star count, and tidal radii were derived, together with the concentration parameter. The derived parameters were then compared to equivalent ones available in the literature for other Galactic globular clusters. Results: Compared to massive globular clusters, those in the present sample have smaller tidal and larger core radii for a given Galactocentric distance, which is consistent with rather loose structures. Globular cluster radii derived from number-density and surface-brightness profiles have similar values. The present magnitude estimates are MV ? -4.9 (ESO 280-SC08), MV ? -5.8 (2MASS-GC01), and MV ? -5.6 (2MASS-GC02). We also estimate MV ? -6.1 for GLIMPSE-C01, which is somewhat less luminous than previously given. The density profiles of Tz 4 and 2MASS-GC01 show evidence of post-core collapse clusters. Conclusions: The structural parameters and luminosity of most of the faint globular clusters dealt with in this paper are consistent with those of Palomar-like (low mass and loose structure) globular clusters. This work helps to improve the coverage of the globular cluster parameter space.

Bonatto, C.; Bica, E.

2008-03-01

66

INTERACTION OF CHOLERA TOXIN AND TOXIN DERIVATIVES WITH LYMPHOCYTES  

PubMed Central

The interaction of cholera toxin and a number of toxin derivatives, containing different proportions of light and heavy toxin-composing subunits (L and H), with mouse lymphocytes was studied. Experiments with [125I]toxin showed that a single cell can rapidly, within minutes, bind up to 40,000 molecules of toxin, the association constant was estimated to 7 ± 4 x 108 liters/mol, and binding was found to be very similar at 37°C and 5°C. Immunofluorescence studies revealed that the toxin attachment is located on the cell surface, and that purified L subunit but not H subunit binds to the cells. A natural cholera toxoid, built up by aggregated L subunits, showed almost identical binding properties as toxin to the cells. Pure GM1 ganglioside, the proposed membrane receptor structure for toxin, prevented entirely the cellular binding of both toxin and toxoid. Cholera toxin in concentrations down to approximately 5 x 10–11 mol/liter (corresponding to 10 bound molecules/cell) inhibited thymus cells from being stimulated to DNA synthesis by concanavalin A (con A), and spleen cells from such stimulation by phytohemagglutinin. The GM1 ganglioside but not a series of other pure structurally related gangliosides and neutral glycosphingolipids neutralized this toxin activity. Toxin derivatives which, in similarity with toxin, possessed H as well as L subunits but in other proportions, were potent inhibitors of con A-induced thymocyte stimulation, whereas the natural toxoid (aggregated L subunits), purified toxin L subunit and purified toxin H subunit were up to 300-fold less active on a weight basis. The capacity of cholera proteins to inhibit con A-induced thymocyte stimulation correlated well with their activity in the rabbit intradermal toxicity assay. The inhibitory action of cholera toxin on con A-induced thymocyte stimulation did not depend on decreased cell viability from the toxin treatment, nor was it caused by a reaction between toxin and con A. [125I]con A bound equally well to the cells when toxin was present as when it was absent, which proves that the toxin did not compete for cellular con A receptors. Nor did the toxin seem to disturb the general mobility of membrane receptors or their ability to accumulate in caps. It is concluded that the L type of subunit confers rapid and firm binding of cholera toxin to lymphocyte membranes, probably to GM1 ganglioside receptors. For biologic activity the additional presence of H subunit is important. One manifestation of toxin action on lymphocytes is inhibition of lectin-induced DNA synthesis; probably this effect relates to the ability of cholera toxin to raise the levels of intracellular cyclic 3'5'-adenosine monophosphate.

Holmgren, J.; Lindholm, L.; Lonnroth, I.

1974-01-01

67

Use of a weather buoy to derive improved heat and mass balance parameters for Ruapehu Crater Lake  

NASA Astrophysics Data System (ADS)

Heat and mass balance calculations are important for monitoring volcanoes with heated crater lakes, but for these lakes the critical process of evaporation can be substantially affected by the lake's influence on the air mass above it. Measurements in 2010 using a weather station on a buoy floating in Ruapehu Crater Lake enabled us to derive a relation between wind velocity above the lake and that measured at nearby weather stations, as well as providing direct evidence of the effect of the warm lake on the air above it. This supported the use of evaporation equations that allowed for the changing air conditions as incoming air became warmer and wetter from interaction with the lake, so decreasing the overall evaporation rate.Heat and mass balance calculations using these parameters and equations during the period 2003 to early 2007, as Crater Lake filled before it overflowed, confirm the previously observed high ratio of total heat flow to steam volume.

Hurst, Tony; Christenson, Bruce; Cole-Baker, Jeremy

2012-08-01

68

Quality assessment and derivation of hydrological relevant parameters from Shuttle Radar Topography Mission data  

NASA Astrophysics Data System (ADS)

The aim of the paper is to demonstrate the value of Shuttle Radar Topography Mission (SRTM, X-Band) derived Digital Elevation Model (DEM) Data for hydrological applications. The quality assessment results are compared with other remote sensing derived elevation data, namely a photogrammetrically derived Digital Terrain Model (DTM) of the Thuringian Survey Agency, ERS Tandem Mission data (C-Band) and a high resolution Experimental SAR (E-SAR) DEM. The analysis carried out in three testsites in Thuringia (Biosphere Conservation Area Rhön Mountains, Ilm-Catchment and Zeulenroda Reservoir Area) comprises difference images between several DTMs and DEMs, statistical analysis and quality estimations as well as the derivation of secondary DEM products like slope, aspect, curvature, catchment area, river density, flow direction, flow accumulation, evaporation, transport capacity, etc. These parameters are used as spatial input for distributed hydrological models. Finally the suitability of the SRTM-DEMs for hydrological models (water balance and solute transport models) is assessed on the comparison of simulation results with measured runoff curves.

Hochschild, V.; Wolf, M.

2003-04-01

69

The effects of dust on the derived photometric parameters of disks and bulges in spiral galaxies  

NASA Astrophysics Data System (ADS)

Here we present results on the effects of dust on the derived Sérsic index of disks and bulges. This is part of a larger study (see Pastrav et al. 2012a, Pastrav et al. 2012b) that quantifies the dust effects on all photometric parameters, including scale-lengths, axis-ratios, central surface brightness and effective radii of individual and decomposed (from B/D decomposition) disks and bulges. The effects of dust are derived for both broadband and narrow line (Balmer lines) images. The changes in the derived photometric parameters from their intrinsic values (as seen in the absence of dust) were obtained by fitting simulated images of disks and bulges produced using radiative transfer calculations and the model of Popescu et al. (2011). This study follows on the analysis of Möllenhoff et al. (2006), who quantified the effects of dust on the photometry of old stellar disks seen at low and intermediate inclination. We extend the study to disks at all inclinations and we investigate the changes in the photometry of young stellar disks and bulges. For the individual components, in the majority of cases: 1) the dust lowers the Sérsic index from its intrinsic value; 2) the Sérsic index decreases as the inclination and the B band central face-on dust opacity, ?B f , increase. For the decomposed disks and bulges, dust slightly increases the Sérsic index as compared with the one derived on individual components (e.g. Fig. 1); this effect is stronger for higher values of the inclination, ?B f and B/D.

Pastrav, B. A.; Popescu, C. C.; Tuffs, R. J.; Sansom, A. E.

2013-03-01

70

Morphology analysis of EKG R waves using wavelets with adaptive parameters derived from fuzzy logic  

NASA Astrophysics Data System (ADS)

Understanding of the EKG components P, QRS (R wave), and T is essential in recognizing cardiac disorders and arrhythmias. An estimation method is presented that models the R wave component of the EKG by adaptively computing wavelet parameters using fuzzy logic. The parameters are adaptively adjusted to minimize the difference between the original EKG waveform and the wavelet. The R wave estimate is derived from minimizing the combination of mean squared error (MSE), amplitude difference, spread difference, and shift difference. We show that the MSE in both non-noise and additive noise environment is less using an adaptive wavelet than a static wavelet. Research to date has focused on the R wave component of the EKG signal. Extensions of this method to model P and T waves are discussed.

Caldwell, Max A.; Barrington, William W.; Miles, Richard R.

1996-03-01

71

The effects of dust on the derived photometric parameters of disks and bulges in spiral galaxies  

NASA Astrophysics Data System (ADS)

We present results of a study made to quantify the effects of dust on the derived photometric parameters of disks (old and young stellar disks) and bulges: disk scale-lengths, axis-ratios, central surface-brightness, bulge effective radii, and Sérsic indices. The changes in the derived photometric parameters from their intrinsic values (as would be seen in the absence of dust) were obtained by fitting simulated images of disks and bulges produced using radiative transfer calculations. The simulations were fitted with the GALFIT 3.0.2 data analysis algorithm and the fitted models were the commonly used infinitely thin disks described by exponential, general Sérsic and de Vaucouleurs distributions. We find the young stellar disks to suffer the most severe variation in the photometric parameters due to dust effects. In this context we also present corrections for narrow line (Balmer line) images. Old stellar disks are also significantly affected by dust, in particular when fits are performed with exponential functions. The photometric parameters of bulges are to a lesser extent affected by dust. We also find that the variation of dust corrections with face-on dust opacity and inclination is similar for bulges with different intrinsic stellar emissivities (different Sérsic index), with differences manifesting only close to edge-on orientations of the disk. Dust corrections for bulges are found to be insensitive to the choice of the truncation radius and ellipticity of the bulge. All corrections are listed in the appendices and made available in electronic format. Appendices are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/553/A80

Pastrav, B. A.; Popescu, C. C.; Tuffs, R. J.; Sansom, A. E.

2013-05-01

72

The Interaction between Cytotrophoblasts and Their Derived Tumor Cells  

Microsoft Academic Search

Previous experiments demonstrated that human cytotrophoblasts and cells of the choriocarcinoma cell line JAr interact in vitro. As a result of this interaction there is an increased synthesis of CG and hPL, probably as a result of the increased CG and hPL synthesis by the cytotrophoblasts. In the present investigation we studied this interaction in greater detail and found that

Jacob Rachmilewitz; Ran Goshen; Michael Elkin; Bernard Gonik; Zvi Neaman; Haim Giloh; Brian Strauss; D. Komitowsky; Nathan de Groot; Abraham Hochberg

1995-01-01

73

CRISM-Derived Spectral Scattering Parameters for Surfaces in the Vicinity of Opportunity Mars Rover Traverses  

NASA Astrophysics Data System (ADS)

CRISM (Compact Reconnaissance Imaging Spectrometer for Mars) data were used to retrieve scattering parameters of surfaces traversed by the Opportunity Mars rover, as well as adjacent areas. Our estimates agree with those retrieved by Johnson et al. [2006] using Opportunity's Panoramic Camera data, and we are able to extend estimates of the Hapke single particle scattering albedo and asymmetry parameter (from the one-term Henyey Greenstein single particle phase function) to a greater spectral resolution and spectral range. This analysis allows us to distinguish between surface units that otherwise look relatively uniform spectrally. This work also provides photometric functions essential for converting spectra to a single viewing geometry which will yield more accurate spectral comparisons. Our method involves simultaneously modeling surface and atmospheric contributions, iterating through surface scattering parameters until a Levenberg-Marquardt least squares best fit is achieved. Retrieved single scattering albedos range from 0.42 to 0.57 (0.5663 - 2.2715 micrometers), and retrieved asymmetry parameters range from -0.27 to -0.17 (moderately backscattering). All surfaces become more backscattering with increasing wavelength. Further, the northern and western portions of Victoria crater's ejecta apron are more backscattering than surrounding regions, indicating a change in physical properties. In images taken when the rover traversed this unit, a surface with small ripples and a dense cover of hematitic spherules is apparent, providing agreement with lab experiments by Johnson et al. [2006] showing increased backscattering with the addition of hematitic spherules. The CRISM-derived scattering parameters also show that bedrock-dominated surfaces are less backscattering than soil-covered surfaces.

Shaw, A.; Arvidson, R. E.; Wolff, M. J.; Seelos, F. P.; Wiseman, S. M.; Cull, S.

2011-12-01

74

Better or just different? On the benefits of designing interactive systems in terms of critical parameters  

Microsoft Academic Search

Critical parameters are quantitative measures of perform- ance that may be used to determine the overall ability of a design to serve its purpose. Although critical parameters figure in almost every field of design where there is a de- mand for progressive improvement, they do not appear to figure significantly in the design of interactive systems. As a result, systems

William M. Newman

1997-01-01

75

Photophysical investigations on supramolecular interaction of a C 60 derivative with free-base and metallo-phthalocyanines  

Microsoft Academic Search

The present paper reports the photophysical investigations on non-covalent interaction of a C60-derivative, namely, tert-butyl-(1,2-methanofullerene)-61-carboxylate (1) with H2– (H2–Pc) and Zn–phthalocyanine (Zn–Pc) in toluene medium. Well defined charge transfer (CT) absorption bands have been located in the ground state. Utilizing the CT absorption bands, various consequential physico-chemical parameters like oscillator strength, transition dipole moment, resonance energy, electronic coupling element and

Anamika Ray; Shrabanti Bhattacharya Banerjee; Subrata Chattopadhyay; Sumanta Bhattacharya

2010-01-01

76

A pathwise derivative approach to the computation of parameter sensitivities in discrete stochastic chemical systems  

PubMed Central

Characterizing the sensitivity to infinitesimally small perturbations in parameters is a powerful tool for the analysis, modeling, and design of chemical reaction networks. Sensitivity analysis of networks modeled using stochastic chemical kinetics, in which a probabilistic description is used to characterize the inherent randomness of the system, is commonly performed using Monte Carlo methods. Monte Carlo methods require large numbers of stochastic simulations in order to generate accurate statistics, which is usually computationally demanding or in some cases altogether impractical due to the overwhelming computational cost. In this work, we address this problem by presenting the regularized pathwise derivative method for efficient sensitivity analysis. By considering a regularized sensitivity problem and using the random time change description for Markov processes, we are able to construct a sensitivity estimator based on pathwise differentiation (also known as infinitesimal perturbation analysis) that is valid for many problems in stochastic chemical kinetics. The theoretical justification for the method is discussed, and a numerical algorithm is provided to permit straightforward implementation of the method. We show using numerical examples that the new regularized pathwise derivative method (1) is able to accurately estimate the sensitivities for many realistic problems and path functionals, and (2) in many cases outperforms alternative sensitivity methods, including the Girsanov likelihood ratio estimator and common reaction path finite difference method. In fact, we observe that the variance reduction using the regularized pathwise derivative method can be as large as ten orders of magnitude in certain cases, permitting much more efficient sensitivity analysis than is possible using other methods.

Sheppard, Patrick W.; Rathinam, Muruhan; Khammash, Mustafa

2012-01-01

77

Sensitivity derivatives for advanced CFD algorithm and viscous modeling parameters via automatic differentiation  

SciTech Connect

The computational technique of automatic differentiation (AD) is applied to a complicated computer program to illustrate the simplicity, efficiency, and versatility of AD with complex algorithms for use within a sensitivity analysis. Many algorithmic and physics modeling coefficients appear in computer programs that are routinely set in an ad hoc manner; AD can be used to enhance computer programs with derivative information suitable for guiding formal sensitivity analyses, which allows these coefficient values to be chosen in a rigorous manner to achieve particular program properties such as an improved convergence rate or improved accuracy. In this paper, AD is applied to a three-dimensional thin-layer Navier-Stokes multigrid flow solver to assess the feasibility and computational impact of obtaining exact sensitivity derivatives with respect to algorithmic and physics modeling parameters typical of those needed for sensitivity analyses. Calculations are performed for an ONERA M6 wing in transonic flow with both the Baldwin-Lomax and Johnson-King turbulence models. The wing lift, drag, and pitching moment coefficients are differentiated with respect to two different groups of input parameters. The first group consists of the second- and fourth-order damping coefficients of the computational algorithm, whereas the second group consists of two parameters in the viscous turbulent flow physics modeling. Results obtained via AD are compared for both accuracy and computational efficiency with the results obtained with divided differences (DD). The AD results are accurate, extremely simple to obtain, and show significant computational advantage over those obtained by DD for some cases. 32 refs., 6 figs., 13 tabs.

Green, L.L.; Newman, P.A.; Kaigler, K.J. [NASA Langley Research Center, Hampton, VA (United States)

1996-05-01

78

Improving evapotranspiration in land surface models by using biophysical parameters derived from MSG/SEVIRI satellite  

NASA Astrophysics Data System (ADS)

Vegetation parameters derived from the geostationary satellite MSG/SEVIRI have been distributed at a daily frequency since 2007 over Europe, Africa and part of South America, through the LSA-SAF (http://landsaf.meteo.pt/). We propose here a method to handle two new remote sensing products from LSA-SAF, leaf area index and Fractional Vegetation Cover, noted LAI and FVC respectively, for land surface models at MSG/SEVIRI scale. The developed method relies on an ordinary least-square technique and a land cover map to estimate LAI for each model plant functional types of the model spatial unit. The method is conceived to be applicable for near-real time applications at continental scale. Compared to monthly vegetation parameters from a vegetation database commonly used in numerical weather predictions (ECOCLIMAP-I), the new remote sensing products allows a better monitoring of the spatial and temporal variability of the vegetation, including inter-annual signals, and a decreased uncertainty on LAI to be input into land surface models. We assess the impact of using LSA-SAF vegetation parameters compared to ECOCLIMAP-I in the land surface model H-TESSEL at MSG/SEVIRI spatial scale. Comparison with in-situ observations in Europe and Africa shows that the results on evapotranspiration are mostly improved, and especially in semi-arid climates. At last, the use of LSA-SAF and ECOCLIMAP-I is compared with simulations over a North-South Transect in Western Africa using LSA-SAF radiation forcing derived from remote sensing, and differences are highlighted.

Ghilain, N.; Arboleda, A.; Sepulcre-Cantò, G.; Batelaan, O.; Ardö, J.; Gellens-Meulenberghs, F.

2012-04-01

79

Improving evapotranspiration in land surface models by using biophysical parameters derived from MSG/SEVIRI satellite  

NASA Astrophysics Data System (ADS)

Vegetation parameters derived from the geostationary satellite MSG/SEVIRI have been distributed at a daily frequency since 2007 over Europe, Africa and part of South America, through the LSA-SAF facility. We propose here a method to handle two new remote sensing products from LSA-SAF, leaf area index and Fractional Vegetation Cover, noted LAI and FVC respectively, for land surface models at MSG/SEVIRI scale. The developed method relies on an ordinary least-square technique and a land cover map to estimate LAI for each model plant functional types of the model spatial unit. The method is conceived to be applicable for near-real time applications at continental scale. Compared to monthly vegetation parameters from a vegetation database commonly used in numerical weather predictions (ECOCLIMAP-I), the new remote sensing products allows a better monitoring of the spatial and temporal variability of the vegetation, including inter-annual signals, and a decreased uncertainty on LAI to be input into land surface models. We assess the impact of using LSA-SAF vegetation parameters compared to ECOCLIMAP-I in the land surface model H-TESSEL at MSG/SEVIRI scale. Comparison with in-situ observations in Europe and Africa shows that the results on evapotranspiration are mostly improved, and especially in semi-arid climates. At last, the use of LSA-SAF and ECOCLIMAP-I is compared with simulations over a North-South Transect in Western Africa using LSA-SAF radiation forcing derived from remote sensing, and differences are highlighted.

Ghilain, N.; Arboleda, A.; Sepulcre-Cantò, G.; Batelaan, O.; Ardö, J.; Gellens-Meulenberghs, F.

2011-10-01

80

Derivation of parameters used in Spectrum for eligibility for antiretroviral therapy and survival on antiretroviral therapy  

PubMed Central

Background The Spectrum projection package uses estimates of national HIV incidence, demographic data and other assumptions to describe the consequences of the HIV epidemic in low and middle-income countries. The default parameters used in Spectrum are updated every 2?years as new evidence becomes available to inform the model. This paper reviews the default parameters that define the course of HIV progression among adults and children in Spectrum. Methods For adults, data available from published and grey literature and data from the ART-LINC International epidemiologic Database to Evaluate AIDS (IeDEA) collaboration were combined to estimate survival among those who started antiretroviral therapy (ART). For children, a review of published material on survival on ART and survival on ART and cotrimoxazole was used to derive survival probabilities. Historical data on the distribution of CD4 cell counts and CD4 cell percentages by age among children who were not treated (before treatment was available) were used to progress children from seroconversion to different CD4 cell levels. Results Based on the updated evidence estimated survival among adults aged over 15?years in the first year on ART was 86%, while in subsequent years survival was estimated at 90%. Survival among children during the first year on ART was estimated to be 85% and for subsequent years 93%. Discussion The revised default parameters based on additional data will make Spectrum estimates more accurate than previous rounds of estimates.

Lewden, Charlotte; Brinkhof, Martin W G; Dabis, Francois; Tassie, Jean-Michel; Souteyrand, Yves; Stover, John

2010-01-01

81

On the Dynamics of Dark Energy with Higher Time Derivatives of Hubble Parameter in El-Nabulsi Fractional Action Cosmology  

NASA Astrophysics Data System (ADS)

In this work, we discussed a new dark energy density model which contains one term proportional to the Hubble parameter H squared, one to the first and one to second time derivative of the Hubble parameter H based on El-Nabulsi fractional action cosmology (FAC). Some cosmological parameters, like the Hubble parameter, the Equation of State (EoS) parameter ? DE and the deceleration parameter q have been reconstructed and studied. Finally, through a test made using the squared speed of sound vs2, the proposed reconstruction model results to be classically unstable.

Pasqua, Antonio; Chattopadhyay, Surajit

2013-09-01

82

Precise derivation for the equivalent circuit parameters of a crystal resonator with series capacitor.  

PubMed

An exact formula for the equivalent circuit of a crystal resonator in series with a capacitor is derived. Network analysis is used to obtain an exact formula for the equivalent circuit parameters without applying any approximations. The result is an expansion of that obtained by those who used assumptions regarding high frequency, high quality factor, high capacitance ratio, and so on. Hence, this formula can be used for instances of low quality factor or low capacitance ratio, and even for the actual inductor-capacitor network as long as these devices have the same equivalent circuits. The enhanced accuracy of the new formula extends itself to oscillator frequency calibration, temperature compensation, and electronic frequency control. PMID:22718883

Huang, Xianhe; Liu, Dong; Wang, Yan; Chen, Yan

2012-06-01

83

Deriving an estimate for the Fried parameter in mobile optical transmission scenarios.  

PubMed

Measuring the Fried parameter r(0) (atmospheric optical coherence length) in optical link scenarios is crucial to estimate a receiver's telescope performance or to dimension atmospheric mitigation techniques, such as in adaptive optics. The task of measuring r(0) is aggravated in mobile scenarios, when the receiver itself is prone to mechanical vibrations (e.g., when mounted on a moving platform) or when the receiver telescope has to track a fast-moving signal source, such as, in our case, a laser transmitter on board a satellite or aircraft. We have derived a method for estimating r(0) that avoids the influence of angle-of-arrival errors by only using short-term tilt-removed focal intensity speckle patterns. PMID:21221148

Giggenbach, Dirk

2011-01-10

84

Elastic properties of amorphous Si and derived Debye temperatures and Grueneisen parameters: Model calculation  

SciTech Connect

Calculations, based on the Stillinger-Weber (SW) interatomic-potential model and the method of long waves, are presented for the elastic properties of amorphous Si ({ital a}-Si) and for pressure derivatives of the elastic constants of crystalline Si. Several models of {ital a}-Si, relaxed on the basis of the SW potential, are considered, and the external stresses that are associated with these models are evaluated using the Born-Huang relations. The elastic constants appear to obey the isotropy conditions to within a reasonable accuracy and are also consistent with other predictions based on the SW potential at finite temperature obtained by Kluge and Ray. Estimates of the pressure dependence of the elastic constants, Debye temperature, and Grueeisen parameter for {ital a}-Si are also provided on the basis of these calculations.

Feldman, J.L.; Broughton, J.Q. (Complex Systems Theory Branch, Naval Research Laboratory, Washington, D.C. 20375-5000 (US)); Wooten, F. (Department of Applied Science, University of California at Davis/Livermore, Livermore, California 94550 (US))

1991-01-15

85

Elastic properties of amorphous Si and derived Debye temperatures and Grüneisen parameters: Model calculation  

NASA Astrophysics Data System (ADS)

Calculations, based on the Stillinger-Weber (SW) interatomic-potential model and the method of long waves, are presented for the elastic properties of amorphous Si (a-Si) and for pressure derivatives of the elastic constants of crystalline Si. Several models of a-Si, relaxed on the basis of the SW potential, are considered, and the external stresses that are associated with these models are evaluated using the Born-Huang relations. The elastic constants appear to obey the isotropy conditions to within a reasonable accuracy and are also consistent with other predictions based on the SW potential at finite temperature obtained by Kluge and Ray. Estimates of the pressure dependence of the elastic constants, Debye temperature, and Grüeisen parameter for a-Si are also provided on the basis of these calculations.

Feldman, J. L.; Broughton, J. Q.; Wooten, F.

1991-01-01

86

Sounding-derived parameters associated with tornado occurrence in Poland and Universal Tornadic Index  

NASA Astrophysics Data System (ADS)

This study is mainly devoted to operational meteorology, to improve tornado forecast in Poland and create a Universal Tornadic Index formula. A study is focusing on climatology of sounding-derived parameters associated with tornadoes in Poland and their potential value for tornado forecasting. The data was collected from soundings made in 10 stations in and around Poland which were closely in time and space connected with tornado occurrence. The main aim of the study was to analyze the thermodynamic and kinematic parameters derived from soundings and formulate an index. The information about tornado incidents was taken from media reports and the European Severe Weather Database for the years 1977-2012. Total of 97 tornado cases were divided according to their strength for significant (F2/F3), weak (F0/F1) and unrated cases, and also according to their environmental surface temperature, for warm (> 18 °C) and cold (< 18 °C) tornadoes. As it turned out, depending on the temperature, tornadoes tended to present different environmental conditions for tornadogenesis. In warm cases, the most important factor was instability while for cold cases it was dynamic wind field. It was also proven that significant tornadoes in Poland occur in conditions accompanied by high moisture content, moderate instability and high wind shear conditions. The results of this study were used to create a Universal Tornadic Index designed to forecast activity in warm and cold, and weak and strong tornadic environments. The quality of this index was tested for the period with increased tornado activity in Poland from 2008 to 2010.

Taszarek, M.; Kolendowicz, L.

2013-12-01

87

Sounding-derived parameters associated with large hail and tornadoes in the Netherlands  

NASA Astrophysics Data System (ADS)

A study is presented focusing on the potential value of parameters derived from radiosonde data or data from numerical atmospheric models for the forecasting of severe weather associated with convective storms. Parameters have been derived from soundings in the proximity of large hail, tornadoes (including tornadoes over water: waterspouts) and thunderstorms in the Netherlands. 66,365 radiosonde soundings from six stations in and around the Netherlands between 1 Dec. 1975 to 31 Aug. 2003 were classified as being associated or not associated with these weather phenomena using observational data from voluntary observers, the Dutch National Meteorological Institute (KNMI) and lightning data from the U.K. Met. Office. It was found that instability as measured by the Lifted Index or CAPE and 0-6 km wind shear independently have considerable skill in distinguishing environments of large hail and of non-hail-producing thunderstorms. It was also found that CAPE released below 3 km above ground level is on average high near waterspouts and weak tornadoes that mostly occur with low shear in the lowest 1 km above the Earth's surface. On the other hand, low-level shear is strong in environments of stronger (F1 and F2) tornadoes and increases with increasing F-scale. This is consistent with the notion that stretching of pre-existing vertical vorticity is the most important mechanism for the formation of weak tornadoes while the tilting of vorticity is more important with stronger tornadoes. The presented results may assist forecasters to assess the likelihood of severe hail or tornadoes.

Groenemeijer, P. H.; van Delden, A.

2007-02-01

88

Developing of van der Waals parameters for graphitic carbon-water interaction using ab initio methods  

NASA Astrophysics Data System (ADS)

In this study, graphitic carbon-water van der Waals interaction parameters are developed entirely from first-principle calculation data. First, the Møller-Plesset perturbation theory of the 2nd order (MP2) method is employed to compute the polycyclic aromatic hydrocarbon-water interaction energies. The proper size of basis sets is utilized in the MP2 calculations and the energy component analysis is performed to extrapolate to infinite-sized graphene limit. Then, graphitic carbon-water interaction parameters are developed based on the MP2 results from this work and the ab initio data available in the literature from other methods such as random-phase approximation (RPA), diffusion Monte Carlo (DMC), density functional theory-symmetry-adapted perturbation theory (DFT-SAPT) and couple cluster treatment with single and double excitations and perturbative triples (CCSD(T)). We evaluate the accuracy of the interaction parameters by predicting water contact angle on graphite and compare it with experimental data. The interaction parameters based on RPA, DFT-SAPT and corrected DMC data predict contact angles which agree well with experiments, while the parameters based on MP2 and CCSD(T) data have the tendency to underestimate the contact angle.

Wu, Yanbin; Aluru, Narayana

2013-03-01

89

A pathwise derivative approach to the computation of parameter sensitivities in discrete stochastic chemical systems.  

PubMed

Characterizing the sensitivity to infinitesimally small perturbations in parameters is a powerful tool for the analysis, modeling, and design of chemical reaction networks. Sensitivity analysis of networks modeled using stochastic chemical kinetics, in which a probabilistic description is used to characterize the inherent randomness of the system, is commonly performed using Monte Carlo methods. Monte Carlo methods require large numbers of stochastic simulations in order to generate accurate statistics, which is usually computationally demanding or in some cases altogether impractical due to the overwhelming computational cost. In this work, we address this problem by presenting the regularized pathwise derivative method for efficient sensitivity analysis. By considering a regularized sensitivity problem and using the random time change description for Markov processes, we are able to construct a sensitivity estimator based on pathwise differentiation (also known as infinitesimal perturbation analysis) that is valid for many problems in stochastic chemical kinetics. The theoretical justification for the method is discussed, and a numerical algorithm is provided to permit straightforward implementation of the method. We show using numerical examples that the new regularized pathwise derivative method (1) is able to accurately estimate the sensitivities for many realistic problems and path functionals, and (2) in many cases outperforms alternative sensitivity methods, including the Girsanov likelihood ratio estimator and common reaction path finite difference method. In fact, we observe that the variance reduction using the regularized pathwise derivative method can be as large as ten orders of magnitude in certain cases, permitting much more efficient sensitivity analysis than is possible using other methods. PMID:22280752

Sheppard, Patrick W; Rathinam, Muruhan; Khammash, Mustafa

2012-01-21

90

Reference values for volumetric capnography-derived non-invasive parameters in healthy individuals.  

PubMed

The aim of this study was to determine typical values for non-invasive volumetric capnography (VCap) parameters for healthy volunteers and anesthetized individuals. VCap was obtained by a capnograph connected to the airway opening. We prospectively studied 33 healthy volunteers 32 ± 6 years of age weighing 70 ± 13 kg at a height of 171 ± 11 cm in the supine position. Data from these volunteers were compared with a cohort of similar healthy anesthetized patients ventilated with the following settings: tidal volume (VT) of 6-8 mL/kg, respiratory rate 10-15 bpm, PEEP of 5-6 cmH?O and FiO? of 0.5. Volunteers showed better clearance of CO? compared to anesthetized patients as indicated by (median and interquartile range): (1) an increased elimination of CO? per mL of VT of 0.028 (0.005) in volunteers versus 0.023 (0.003) in anesthetized patients, p < 0.05; (2) a lower normalized slope of phase III of 0.26 (0.17) in volunteers versus 0.39 (0.38) in anesthetized patients, p < 0.05; and (3) a lower Bohr dead space ratio of 0.23 (0.05) in volunteers versus 0.28 (0.05) in anesthetized patients, p < 0.05. This study presents reference values for non-invasive volumetric capnography-derived parameters in healthy individuals. Mechanical ventilation and anesthesia altered these values significantly. PMID:23389294

Tusman, Gerardo; Gogniat, Emiliano; Bohm, Stephan H; Scandurra, Adriana; Suarez-Sipmann, Fernando; Torroba, Agustin; Casella, Federico; Giannasi, Sergio; Roman, Eduardo San

2013-02-07

91

Deriving correlated motions in proteins from X-ray structure refinement by using TLS parameters.  

PubMed

Dynamic information in proteins may provide valuable information for understanding allosteric regulation of protein complexes or long-range effects of the mutations on enzyme activity. Experimental data such as X-ray B-factors or NMR order parameters provide a convenient estimate of atomic fluctuations (or atomic auto-correlated motions) in proteins. However, it is not as straightforward to obtain atomic cross-correlated motions in proteins - one usually resorts to more sophisticated computational methods such as Molecular Dynamics, normal mode analysis or atomic network models. In this report, we show that atomic cross-correlations can be reliably obtained directly from protein structure using X-ray refinement data. We have derived an analytic form of atomic correlated motions in terms of the original TLS parameters used to refine the B-factors of X-ray structures. The correlated maps computed using this equation are well correlated with those of the method based on a mechanical model (the correlation coefficient is 0.75) for a non-homologous dataset comprising 100 structures. We have developed an approach to compute atomic cross-correlations directly from X-ray protein structure. Being in analytic form, it is fast and provides a feasible way to compute correlated motions in proteins in a high throughput way. In addition, avoiding sophisticated computational operations; it provides a quick, reliable way, especially for non-computational biologists, to obtain dynamics information directly from protein structure relevant to its function. PMID:23270923

Liu, Yen-Yi; Shih, Chien-Hua; Hwang, Jenn-Kang; Chen, Chih-Chieh

2012-12-24

92

Interaction of Methylated Adenine Derivatives with the Mercury Electrode.  

National Technical Information Service (NTIS)

Adenine and its methylated derivatives, 1-methyl-6-aminopurine, 3-methyl-6 aminopurine, N-methyl-6-aminopurine, and N,N-dimethyl-6-aminopurine, were studied in alkaline solution by DC, normal pulse and differential pulse polarography and by cyclic voltamm...

E. Palecek J. Osteryoung R. A. Osteryoung

1982-01-01

93

General hybrid projective complete dislocated synchronization with non-derivative and derivative coupling based on parameter identification in several chaotic and hyperchaotic systems  

NASA Astrophysics Data System (ADS)

According to the Lyapunov stability theorem, a new general hybrid projective complete dislocated synchronization scheme with non-derivative and derivative coupling based on parameter identification is proposed under the framework of drive-response systems. Every state variable of the response system equals the summation of the hybrid drive systems in the previous hybrid synchronization. However, every state variable of the drive system equals the summation of the hybrid response systems while evolving with time in our method. Complete synchronization, hybrid dislocated synchronization, projective synchronization, non-derivative and derivative coupling, and parameter identification are included as its special item. The Lorenz chaotic system, Rössler chaotic system, memristor chaotic oscillator system, and hyperchaotic Lü system are discussed to show the effectiveness of the proposed methods.

Sun, Jun-Wei; Shen, Yi; Zhang, Guo-Dong; Wang, Yan-Feng; Cui, Guang-Zhao

2013-04-01

94

Emergent Learning and Interactive Media Artworks: Parameters of Interaction for Novice Groups  

ERIC Educational Resources Information Center

|Emergent learning describes learning that occurs when participants interact and distribute knowledge, where learning is self-directed, and where the learning destination of the participants is largely unpredictable (Williams, Karousou, & Mackness, 2011). These notions of learning arise from the topologies of social networks and can be applied to…

Kawka, Marta; Larkin, Kevin; Danaher, P. A.

2011-01-01

95

How an Agent Can Detect and Use Synchrony Parameter of Its Own Interaction with a Human?  

Microsoft Academic Search

\\u000a Synchrony is claimed by psychology as a crucial parameter of any social interaction: to give to human a feeling of natural\\u000a interaction, a feeling of agency [17], an agent must be able to synchronise with this human on appropriate time [29] [11]\\u000a [15] [16] [27]. In the following experiment, we show that synchrony can be more than a state to

Ken Prepin; Philippe Gaussier

2009-01-01

96

Crystal lattice properties fully determine short-range interaction parameters for alkali and halide ions  

NASA Astrophysics Data System (ADS)

Accurate models of alkali and halide ions in aqueous solution are necessary for computer simulations of a broad variety of systems. Previous efforts to develop ion force fields have generally focused on reproducing experimental measurements of aqueous solution properties such as hydration free energies and ion-water distribution functions. This dependency limits transferability of the resulting parameters because of the variety and known limitations of water models. We present a solvent-independent approach to calibrating ion parameters based exclusively on crystal lattice properties. Our procedure relies on minimization of lattice sums to calculate lattice energies and interionic distances instead of equilibrium ensemble simulations of dense fluids. The gain in computational efficiency enables simultaneous optimization of all parameters for Li+, Na+, K+, Rb+, Cs+, F-, Cl-, Br-, and I- subject to constraints that enforce consistency with periodic table trends. We demonstrate the method by presenting lattice-derived parameters for the primitive model and the Lennard-Jones model with Lorentz-Berthelot mixing rules. The resulting parameters successfully reproduce the lattice properties used to derive them and are free from the influence of any water model. To assess the transferability of the Lennard-Jones parameters to aqueous systems, we used them to estimate hydration free energies and found that the results were in quantitative agreement with experimentally measured values. These lattice-derived parameters are applicable in simulations where coupling of ion parameters to a particular solvent model is undesirable. The simplicity and low computational demands of the calibration procedure make it suitable for parametrization of crystallizable ions in a variety of force fields.

Mao, Albert H.; Pappu, Rohit V.

2012-08-01

97

Crystal lattice properties fully determine short-range interaction parameters for alkali and halide ions.  

PubMed

Accurate models of alkali and halide ions in aqueous solution are necessary for computer simulations of a broad variety of systems. Previous efforts to develop ion force fields have generally focused on reproducing experimental measurements of aqueous solution properties such as hydration free energies and ion-water distribution functions. This dependency limits transferability of the resulting parameters because of the variety and known limitations of water models. We present a solvent-independent approach to calibrating ion parameters based exclusively on crystal lattice properties. Our procedure relies on minimization of lattice sums to calculate lattice energies and interionic distances instead of equilibrium ensemble simulations of dense fluids. The gain in computational efficiency enables simultaneous optimization of all parameters for Li+, Na+, K+, Rb+, Cs+, F-, Cl-, Br-, and I- subject to constraints that enforce consistency with periodic table trends. We demonstrate the method by presenting lattice-derived parameters for the primitive model and the Lennard-Jones model with Lorentz-Berthelot mixing rules. The resulting parameters successfully reproduce the lattice properties used to derive them and are free from the influence of any water model. To assess the transferability of the Lennard-Jones parameters to aqueous systems, we used them to estimate hydration free energies and found that the results were in quantitative agreement with experimentally measured values. These lattice-derived parameters are applicable in simulations where coupling of ion parameters to a particular solvent model is undesirable. The simplicity and low computational demands of the calibration procedure make it suitable for parametrization of crystallizable ions in a variety of force fields. PMID:22897252

Mao, Albert H; Pappu, Rohit V

2012-08-14

98

QuickBird derived vegetation parameters for soil erosion risk assessment in an alpine catchment  

NASA Astrophysics Data System (ADS)

The focus of soil erosion research in the Alps has been in two categories: (i) on-site measurements which are rather small scale point measurements on selected plots often constrained to irrigation experiments or (ii) off-site quantification of sediment delivery at the outlet of the catchment. Results of both categories showed that an intact vegetation cover prevents soil loss. With the recent availability of high-resolution satellites such as IKONOS and QuickBird options for detecting and monitoring of vegetation parameters have increased. The aim of this study is to evaluate the usefulness of QuickBird derived vegetation parameters in soil erosion models by comparison to Cesium-137 (Cs-137) soil erosion estimates. The study site (67km2) is located in the Central Swiss Alps and is dominated by grasslands with strong anthropogenic influences due to farming for centuries. Linear spectral unmixing and supervised classification is applied to produce maps of fractional vegetation cover (FVC) for grasslands and detailed land-cover maps from QuickBird imagery. The maps are used to adapt the C factor, which accounts for land management in the Universal Soil Loss Equation (USLE). Further the data was introduced to the Pan-European Soil Erosion Risk Assessment (PESERA) model. Supervised land-cover classification yielded a total accuracy of 93.3%. Linear spectral unmixing of vegetation abundance showed a significant (at the 0.01 level) correlation to ground truth FVC. Both models yielded higher absolute soil erosion estimates and an improvement of spatial patterns when FVC and a detailed land-cover maps are considered. However, discrepancies between model estimates and Cs-137 erosion estimates remained, especially for the PESERA model. This is leading to the assumption that soil erosion processes not considered in the models, e.g. soil erosion caused by snow gliding, play a decisive role.

Meusburger, Katrin; Konz, Nadine; Schaub, Monika; Alewell, Christine

2010-05-01

99

Thermal and Magnetic Parameters in Solar Flares Derived from GOES X-Ray Light Curves  

NASA Astrophysics Data System (ADS)

The purpose of this study is to reproduce the GOES X-ray (1-8 Å) light curves of the impulsive phase of 20 solar flares and to estimate the thermal and magnetic parameters in flare loops. The expected X-ray light curves are calculated from the values of the coronal field strength and inflow velocity under some assumptions. We used the magnetic reconnection heating model of Shibata and Yokoyama (2002, ApJ, 577, 422), photospheric vector magnetic field data, and a simple 1-D flare loop model. It is found the maximum inflow velocities are ˜ 107cm s-1, and that the maximum magnetic reconnection rates are 0.006-0.9, and further that the characteristic coronal field strengths are 6-100 G. Using the thermal and magnetic parameters derived, we found that geometrically our calculated flare loops are higher than the potential fields that model the postflare loops, and are also higher than the preflare loops containing magnetic free energy that is large enough to provide the thermal energy of a flare. Hence, we conclude that the plasma ? value would be near unity in the flare loops we studied, and the magnetic field lines shrunk during the decay phase. The downward velocities of the field-line shrinkage are estimated to be 106-107cm s-1 except one event. The height of the reconnection point was roughly estimated to be from 1010cm to 4 × 1010cm. We propose a new interpretation of the Neupert effect, and also discuss a temporal relationship between the X-ray flux and the flare loop heating.

Yamamoto, Tetsuya T.; Sakurai, Takashi

2010-06-01

100

DATA BASE ANALYZER AND PARAMETER ESTIMATOR (DBAPE) INTERACTIVE COMPUTER PROGRAM--USER'S MANUAL  

EPA Science Inventory

The Data Base Analyzer and Parameter Estizator (DBAPE) is an interactive computer progran that provides a link between two of EPA's development products--an environmental model and a data base. BAPE was created to encourage and support the use of the RUSTIC model, a newly develop...

101

Volumetric Ion Interaction Parameters for Single-Solute Aqueous Electrolyte Solutions at Various Temperatures  

Microsoft Academic Search

The ion interaction approach developed by Pitzer allows the prediction of thermodynamic characteristics of mixed electrolyte solutions at various temperatures, if the respective parameters for each type of single electrolyte solution are known. Among such thermodynamic characteristics are the volumetric ones (density and apparent molal volumes). A database for the densities and the apparent molal volumes versus concentrations was developed

Boris S. Krumgalz; Rita Pogorelskii; Alex Sokolov; Kenneth S. Pitzer

2000-01-01

102

Predicting the formation and stability of amorphous small molecule binary mixtures from computationally determined Flory-Huggins interaction parameter and phase diagram.  

PubMed

The Flory-Huggins interaction parameter has been shown to be useful in predicting the thermodynamic miscibility of a polymer and a small molecule in a binary mixture. In the present paper, this concept was extended and evaluated to determine whether or not the Flory-Huggins interaction parameter can be applied to small molecule binary mixtures and if this parameter can predict the phase stability of such amorphous binary mixtures. This study was based on the assumption that a thermodynamically miscible binary system is stable and cannot crystallize, and that phase separation is essential before the individual components can crystallize. The stabilization of a binary system is thought to derive from molecular interactions between components in a solid dispersion, which are characterized by the Flory-Huggins interaction parameter. Based on DSC experiments, drug molecules (39) in the present study were classified into three different categories according to their crystallization tendency; i.e., highly crystallizing, moderately crystallizing and noncrystallizing compounds. The Flory-Huggins interaction parameter was systematically calculated for each drug pair. The validity of this approach was empirically verified by hot-stage polarized light microscopy. If both compounds in the pair belonged to the category of highly crystallizing compound, the Flory-Huggins interaction predicted an amorphous or crystalline phase with approximately 88% (23 out of 26) confidence. If one or both compounds of the pair were either moderately crystallizing or noncrystallizing compounds, the binary mixture remained in the amorphous phase during the cooling phase regardless of the interaction parameter. The Flory-Huggins interaction parameter was found to be a reasonably good indicator for predicting the phase stability of small molecule binary mixtures. The method described can enable fast screening of the potential stabilizers needed to produce a stable amorphous binary mixture. PMID:20361760

Pajula, Katja; Taskinen, Markku; Lehto, Vesa-Pekka; Ketolainen, Jarkko; Korhonen, Ossi

2010-06-01

103

Spectroscopic studies on the interaction of cinnamic acid and its hydroxyl derivatives with human serum albumin  

Microsoft Academic Search

Cinnamic acid and its derivatives possess various biological effects in remedy of many diseases. Interaction of cinnamic acid and its hydroxyl derivatives, p-coumaric acid and caffeic acid, with human serum albumin (HSA), and concomitant changes in its conformation were studied using fluorescence and Fourier transform infrared spectroscopic methods. Fluorescence data revealed the presence of one binding site on HSA for

Jiang Min; Xie Meng-Xia; Zheng Dong; Liu Yuan; Li Xiao-Yu; Chen Xing

2004-01-01

104

Two EEG derived parameters for the measurement of the effects caused by propofol on sedation  

Microsoft Academic Search

Two parameters to measure propofol's sedation effect on the EEG signal are presented. One parameter is based on a wavelet multiresolution decomposition that allows spectral analysis on each detail. The other parameter is based on cross spectrum analysis that underlines similar frequency phenomena that appear in two different EEG epochs. Both parameters were compared with the spectral edge that has

N. Ramnirez; G. Lugo; V. Medina

1997-01-01

105

Paracrine Interaction between Adipose-Derived Stromal Cells and Cranial Suture-Derived Mesenchymal Cells  

PubMed Central

Introduction Adipose derived stromal cells (ASCs) are a potential cell source for the successful healing of skeletal defects. In this study we sought to investigate the potential for cranial suture-derived mesenchymal cells (SMCs) to promote the osteogenic differentiation of ASCs. Various reports have previously examined the unique in vitro attributes of SMCs; this study sought to extend those findings. Methods SMCs were isolated from wild-type mice (N=30) from both the fusing posterofrontal (PF) and patent sagittal (SAG) sutures. Cells were placed in transwell inserts with human ASCs (N=5 patients) with osteogenic differentiation medium with or without rNoggin (10-400 ng/ml). Specific gene expression of osteogenic markers and Hedgehog pathway were assayed; standard osteogenic assays (alkaline phosphatase and Alizarin red staining) were performed. All assays were performed in triplicate. Results Both PF and SAG SMCs induced osteogenic differentiation of ASCs (*p<0.05). PF SMCs induced ASC-osteogenesis to a greater degree than SAG SMCs (*p<0.05). This was accompanied by an increase in BMP expression (*p<0.05). Finally, rNoggin mitigated the pro-osteogenic effects of co-culture accompanied by a reduction in Hedgehog signaling (*p<0.05). Conclusions SMCs secrete paracrine factors that induce osteodifferentiation of multipotent stromal cells (hASCs). Cells derived from the fusing PF suture do this to a significantly greater degree than cells from the patent SAG suture. Enhanced BMP and Hedgehog signaling may underlie this paracrine effect.

James, Aaron W.; Levi, Benjamin; Commons, George W.; Glotzbach, Jason; Longaker, Michael T.

2010-01-01

106

Estimating Kinetic and Thermodynamic Parameters from Single Molecule Enzyme-Inhibitor Interactions  

PubMed Central

We report the application of recently developed microscopic models to estimate the apparent kinetic and thermodynamic parameters in a single molecule force spectroscopy study of the carbonic anhydrase enzyme and a complementary sulfonamide inhibitor. The most probable rupture force for the enzyme-inhibitor interaction shows a non-linear dependency on the log-loading rate. Estimates for the kinetic and thermodynamic parameters were obtained by fitting the non-linear dependency to linear cubic potential and cusp potential models and compared to the standard Bell-Evans model. The reliability of the estimated parameters was verified by modeling the experimental rupture force distributions by the theoretically predicted distributions at rupture. We also report that linkers that are attached to the enzyme and inhibitor show appreciable effects on the apparent kinetic and thermodynamic parameters.

Porter-Peden, Laura; Kamper, Sarah G.; Wal, Mark Vander; Blankespoor, Ronald; Sinniah', Kumar

2008-01-01

107

Responses of the second derivative of the finger photoplethysmogram indices and hemodynamic parameters to anesthesia induction.  

PubMed

The finger photoplethysmogram (PTG) is a non-invasive method for pulse-wave analysis. The second derivative wave of the PTG (SDPTG) enables evaluation of atherosclerosis and cardiovascular aging. Responses of SDPTG indices and hemodynamic parameters to anesthesia induction are unknown. A total of 42 patients aged ?40 years, who may have had atherosclerotic change, and who underwent elective oral surgery, were analyzed. Patients were divided into sevoflurane (S group; N=22) and sevoflurane with remifentanil (R group; N=20) groups. Systolic and diastolic blood pressure (SBP, DBP), heart rate (HR) and SDPTG were measured at four time points: before induction, after loss of consciousness, after tracheal intubation and 30?min after induction. At postintubation, b/a was elevated (that is, large arterial stiffness was increased), and d/a was reduced (that is, peripheral vascular resistance was increased) in the S group compared with the R group. SBP, DBP and HR were increased in the S group compared with those in the R group. In the S group, preanesthetic b/a and the aging index (AGI) were positively correlated with SBP at immediate postintubation, and preanesthetic d/a was negatively correlated with SBP and DBP at immediate postintubation. It is suggested that usage of remifentanil, a potent ?-opioid analgesic, with sevoflurane anesthesia prevented an increase in blood pressure and HR in response to laryngoscopy and tracheal intubation, which was accompanied by suppression of both elevation of b/a and the AGI and reduction of d/a. SDPTG indices are useful for predicting hypertension during induction of sevoflurane anesthesia, regardless of a history of hypertension or hypertensive factors. PMID:21937996

Kohjitani, Atsushi; Miyata, Masaaki; Iwase, Yoko; Sugiyama, Kazuna

2011-09-22

108

Seven-year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Power Spectra and WMAP-derived Parameters  

NASA Astrophysics Data System (ADS)

The WMAP mission has produced sky maps from seven years of observations at L2. We present the angular power spectra derived from the seven-year maps and discuss the cosmological conclusions that can be inferred from WMAP data alone. With the seven-year data, the temperature (TT) spectrum measurement has a signal-to-noise ratio per multipole that exceeds unity for l < 919; and in band powers of width ?l = 10, the signal-to-noise ratio exceeds unity up to l = 1060. The third acoustic peak in the TT spectrum is now well measured by WMAP. In the context of a flat ?CDM model, this improvement allows us to place tighter constraints on the matter density from WMAP data alone, ? m h 2 = 0.1334+0.0056 -0.0055, and on the epoch of matter-radiation equality, z eq = 3196+134 -133. The temperature-polarization (TE) spectrum is detected in the seven-year data with a significance of 20?, compared to 13? with the five-year data. We now detect the second dip in the TE spectrum near l ~ 450 with high confidence. The TB and EB spectra remain consistent with zero, thus demonstrating low systematic errors and foreground residuals in the data. The low-l EE spectrum, a measure of the optical depth due to reionization, is detected at 5.5? significance when averaged over l = 2-7: l(l + 1)C EE l /(2?) = 0.074+0.034 -0.025 ?K2 (68% CL). We now detect the high-l, 24 <= l <= 800, EE spectrum at over 8?. The BB spectrum, an important probe of gravitational waves from inflation, remains consistent with zero; when averaged over l = 2-7, l(l + 1)C BB l /(2?) < 0.055 ?K2 (95% CL). The upper limit on tensor modes from polarization data alone is a factor of two lower with the seven-year data than it was using the five-year data. The data remain consistent with the simple ?CDM model: the best-fit TT spectrum has an effective ?2 of 1227 for 1170 degrees of freedom, with a probability to exceed of 9.6%. The allowable volume in the six-dimensional space of ?CDM parameters has been reduced by a factor of 1.5 relative to the five-year volume, while the ?CDM model that allows for tensor modes and a running scalar spectral index has a factor of three lower volume when fit to the seven-year data. We test the parameter recovery process for bias and find that the scalar spectral index, ns , is biased high, but only by 0.09?, while the remaining parameters are biased by <0.15?. The improvement in the third peak measurement leads to tighter lower limits from WMAP on the number of relativistic degrees of freedom (e.g., neutrinos) in the early universe: N eff>2.7(95%CL). Also, using WMAP data alone, the primordial helium mass fraction is found to be Y He = 0.28+0.14 -0.15, and with data from higher-resolution cosmic microwave background experiments included, we now establish the existence of pre-stellar helium at >3?. These new WMAP measurements provide important tests of big bang cosmology. WMAP is the result of a partnership between Princeton University and NASA's Goddard Space Flight Center. Scientific guidance is provided by the WMAP Science Team.

Larson, D.; Dunkley, J.; Hinshaw, G.; Komatsu, E.; Nolta, M. R.; Bennett, C. L.; Gold, B.; Halpern, M.; Hill, R. S.; Jarosik, N.; Kogut, A.; Limon, M.; Meyer, S. S.; Odegard, N.; Page, L.; Smith, K. M.; Spergel, D. N.; Tucker, G. S.; Weiland, J. L.; Wollack, E.; Wright, E. L.

2011-02-01

109

Size-density scaling in protists and the links between consumer-resource interaction parameters.  

PubMed

Recent work indicates that the interaction between body-size-dependent demographic processes can generate macroecological patterns such as the scaling of population density with body size. In this study, we evaluate this possibility for grazing protists and also test whether demographic parameters in these models are correlated after controlling for body size. We compiled data on the body-size dependence of consumer-resource interactions and population density for heterotrophic protists grazing algae in laboratory studies. We then used nested dynamic models to predict both the height and slope of the scaling relationship between population density and body size for these protists. We also controlled for consumer size and assessed links between model parameters. Finally, we used the models and the parameter estimates to assess the individual- and population-level dependence of resource use on body-size and prey-size selection. The predicted size-density scaling for all models matched closely to the observed scaling, and the simplest model was sufficient to predict the pattern. Variation around the mean size-density scaling relationship may be generated by variation in prey productivity and area of capture, but residuals are relatively insensitive to variation in prey size selection. After controlling for body size, many consumer-resource interaction parameters were correlated, and a positive correlation between residual prey size selection and conversion efficiency neutralizes the apparent fitness advantage of taking large prey. Our results indicate that widespread community-level patterns can be explained with simple population models that apply consistently across a range of sizes. They also indicate that the parameter space governing the dynamics and the steady states in these systems is structured such that some parts of the parameter space are unlikely to represent real systems. Finally, predator-prey size ratios represent a kind of conundrum, because they are widely observed but apparently have little influence on population size and fitness, at least at this level of organization. PMID:22803630

Delong, John P; Vasseur, David A; Meiri, Shai

2012-07-16

110

Estimation of the solubility parameters of model plant surfaces and agrochemicals: a valuable tool for understanding plant surface interactions  

PubMed Central

Background Most aerial plant parts are covered with a hydrophobic lipid-rich cuticle, which is the interface between the plant organs and the surrounding environment. Plant surfaces may have a high degree of hydrophobicity because of the combined effects of surface chemistry and roughness. The physical and chemical complexity of the plant cuticle limits the development of models that explain its internal structure and interactions with surface-applied agrochemicals. In this article we introduce a thermodynamic method for estimating the solubilities of model plant surface constituents and relating them to the effects of agrochemicals. Results Following the van Krevelen and Hoftyzer method, we calculated the solubility parameters of three model plant species and eight compounds that differ in hydrophobicity and polarity. In addition, intact tissues were examined by scanning electron microscopy and the surface free energy, polarity, solubility parameter and work of adhesion of each were calculated from contact angle measurements of three liquids with different polarities. By comparing the affinities between plant surface constituents and agrochemicals derived from (a) theoretical calculations and (b) contact angle measurements we were able to distinguish the physical effect of surface roughness from the effect of the chemical nature of the epicuticular waxes. A solubility parameter model for plant surfaces is proposed on the basis of an increasing gradient from the cuticular surface towards the underlying cell wall. Conclusions The procedure enabled us to predict the interactions among agrochemicals, plant surfaces, and cuticular and cell wall components, and promises to be a useful tool for improving our understanding of biological surface interactions.

2012-01-01

111

Derivation of site-specific relationships between hydraulic parameters and p-wave velocities based on hydraulic and seismic tomography  

NASA Astrophysics Data System (ADS)

In this study, hydraulic and seismic tomographic measurements were used to derive a site-specific relationship between the geophysical parameter p-wave velocity and the hydraulic parameters, diffusivity and specific storage. Our field study includes diffusivity tomograms derived from hydraulic travel time tomography, specific storage tomograms, derived from hydraulic attenuation tomography, and p-wave velocity tomograms, derived from seismic tomography. The tomographic inversion was performed in all three cases with the Simultaneous Iterative Reconstruction Technique algorithm, using a ray tracing technique with curved trajectories. The experimental set up was designed such that the p-wave velocity tomogram overlaps the hydraulic tomograms by half. The experiments were performed at a well-characterized sand and gravel aquifer, located in the Leine River valley near Göttingen, Germany. Access to the shallow subsurface was provided by direct-push technology. The high spatial resolution of hydraulic and seismic tomography was exploited to derive representative site-specific relationships between the hydraulic and geophysical parameters, based on the area where geophysical and hydraulic tests were performed. The transformation of the p-wave velocities into hydraulic properties was undertaken using a k-means cluster analysis. Results demonstrate that the combination of hydraulic and geophysical tomographic data is a promising approach to improve hydrogeophysical site characterization.

Brauchler, R.; Doetsch, J.; Dietrich, P.; Sauter, M.

2012-03-01

112

Derivation of site-specific relationships between hydraulic parameters and p-wave velocities based on hydraulic and seismic tomography  

SciTech Connect

In this study, hydraulic and seismic tomographic measurements were used to derive a site-specific relationship between the geophysical parameter p-wave velocity and the hydraulic parameters, diffusivity and specific storage. Our field study includes diffusivity tomograms derived from hydraulic travel time tomography, specific storage tomograms, derived from hydraulic attenuation tomography, and p-wave velocity tomograms, derived from seismic tomography. The tomographic inversion was performed in all three cases with the SIRT (Simultaneous Iterative Reconstruction Technique) algorithm, using a ray tracing technique with curved trajectories. The experimental set-up was designed such that the p-wave velocity tomogram overlaps the hydraulic tomograms by half. The experiments were performed at a wellcharacterized sand and gravel aquifer, located in the Leine River valley near Göttingen, Germany. Access to the shallow subsurface was provided by direct-push technology. The high spatial resolution of hydraulic and seismic tomography was exploited to derive representative site-specific relationships between the hydraulic and geophysical parameters, based on the area where geophysical and hydraulic tests were performed. The transformation of the p-wave velocities into hydraulic properties was undertaken using a k-means cluster analysis. Results demonstrate that the combination of hydraulic and geophysical tomographic data is a promising approach to improve hydrogeophysical site characterization.

Brauchler, R.; Doetsch, J.; Dietrich, P.; Sauter, M.

2012-01-10

113

Simple model for deriving sdg interacting boson model Hamiltonians: 150Nd example  

NASA Astrophysics Data System (ADS)

A simple and yet useful model for deriving sdg interacting boson model (IBM) Hamiltonians is to assume that single-boson energies derive from identical particle (pp and nn) interactions and proton, neutron single-particle energies, and that the two-body matrix elements for bosons derive from pn interaction, with an IBM-2 to IBM-1 projection of the resulting p-n sdg IBM Hamiltonian. The applicability of this model in generating sdg IBM Hamiltonians is demonstrated, using a single-j-shell Otsuka-Arima-Iachello mapping of the quadrupole and hexadecupole operators in proton and neutron spaces separately and constructing a quadrupole-quadrupole plus hexadecupole-hexadecupole Hamiltonian in the analysis of the spectra, B(E2)'s, and E4 strength distribution in the example of 150Nd.

Devi, Y. D.; Kota, V. K. B.

1993-07-01

114

Simple model for deriving [ital sdg] interacting boson model Hamiltonians: [sup 150]Nd example  

SciTech Connect

A simple and yet useful model for deriving [ital sdg] interacting boson model (IBM) Hamiltonians is to assume that single-boson energies derive from identical particle ([ital pp] and [ital nn]) interactions and proton, neutron single-particle energies, and that the two-body matrix elements for bosons derive from [ital pn] interaction, with an IBM-2 to IBM-1 projection of the resulting [ital p]-[ital n] [ital sdg] IBM Hamiltonian. The applicability of this model in generating [ital sdg] IBM Hamiltonians is demonstrated, using a single-[ital j]-shell Otsuka-Arima-Iachello mapping of the quadrupole and hexadecupole operators in proton and neutron spaces separately and constructing a quadrupole-quadrupole plus hexadecupole-hexadecupole Hamiltonian in the analysis of the spectra, [ital B]([ital E]2)'s, and [ital E]4 strength distribution in the example of [sup 150]Nd.

Devi, Y.D.; Kota, V.K.B. (Physical Research Laboratory, Ahmedabad 380 009 (India))

1993-07-01

115

Structural parameters of 11 faint Galactic globular clusters derived with 2MASS  

Microsoft Academic Search

Context: Structural parameters and the total MV magnitude are important properties for the characterisation of individual globular clusters. With the growth in statistics, especially of the intrinsically faint objects, the collective properties of the Galactic globular cluster system will be better defined, leading to a deeper understanding of the Galaxy formation processes. Aims: We determine the structural parameters of 11

C. Bonatto; E. Bica

2008-01-01

116

Applications using estimates of forest parameters derived from satellite and forest inventory data  

Microsoft Academic Search

From the combination of optical satellite data, digital map data, and forest inventory plot data, continuous estimates have been made for several forest parameters (wood volume, age, and biomass). Five different project areas within Sweden are presented which have utilized these estimates for a range of applications. The method for estimating the forest parameters was a ‘k-nearest neighbor (kNN)’ algorithm,

Heather Reese; Mats Nilsson; Per Sandström; Håkan Olsson

2002-01-01

117

Reconstructed historical land cover and biophysical parameters for studies of land-atmosphere interactions within the eastern United States  

USGS Publications Warehouse

Over the past 350 years, the eastern half of the United States experienced extensive land cover changes. These began with land clearing in the 1600s, continued with widespread deforestation, wetland drainage, and intensive land use by 1920, and then evolved to the present-day landscape of forest regrowth, intensive agriculture, urban expansion, and landscape fragmentation. Such changes alter biophysical properties that are key determinants of land-atmosphere interactions (water, energy, and carbon exchanges). To understand the potential implications of these land use transformations, we developed and analyzed 20-km land cover and biophysical parameter data sets for the eastern United States at 1650, 1850, 1920, and 1992 time slices. Our approach combined potential vegetation, county-level census data, soils data, resource statistics, a Landsat-derived land cover classification, and published historical information on land cover and land use. We reconstructed land use intensity maps for each time slice and characterized the land cover condition. We combined these land use data with a mutually consistent set of biophysical parameter classes, to characterize the historical diversity and distribution of land surface properties. Time series maps of land surface albedo, leaf area index, a deciduousness index, canopy height, surface roughness, and potential saturated soils in 1650, 1850, 1920, and 1992 illustrate the profound effects of land use change on biophysical properties of the land surface. Although much of the eastern forest has returned, the average biophysical parameters for recent landscapes remain markedly different from those of earlier periods. Understanding the consequences of these historical changes will require land-atmosphere interactions modeling experiments.

Steyaert, L. T.; Knox, R. G.

2008-01-01

118

Weak Interactions Govern the Viscosity of Concentrated Antibody Solutions: High-Throughput Analysis Using the Diffusion Interaction Parameter  

PubMed Central

Weak protein-protein interactions are thought to modulate the viscoelastic properties of concentrated antibody solutions. Predicting the viscoelastic behavior of concentrated antibodies from their dilute solution behavior is of significant interest and remains a challenge. Here, we show that the diffusion interaction parameter (kD), a component of the osmotic second virial coefficient (B2) that is amenable to high-throughput measurement in dilute solutions, correlates well with the viscosity of concentrated monoclonal antibody (mAb) solutions. We measured the kD of 29 different mAbs (IgG1 and IgG4) in four different solvent conditions (low and high ion normality) and found a linear dependence between kD and the exponential coefficient that describes the viscosity concentration profiles (|R| ? 0.9). Through experimentally measured effective charge measurements, under low ion normality where the electroviscous effect can dominate, we show that the mAb solution viscosity is poorly correlated with the mAb net charge (|R| ? 0.6). With this large data set, our results provide compelling evidence in support of weak intermolecular interactions, in contrast to the notion that the electroviscous effect is important in governing the viscoelastic behavior of concentrated mAb solutions. Our approach is particularly applicable as a screening tool for selecting mAbs with desirable viscosity properties early during lead candidate selection.

Connolly, Brian D.; Petry, Chris; Yadav, Sandeep; Demeule, Barthelemy; Ciaccio, Natalie; Moore, Jamie M.R.; Shire, Steven J.; Gokarn, Yatin R.

2012-01-01

119

The two-parameter Poisson-Dirichlet distribution derived from a stable subordinator  

Microsoft Academic Search

The two-parameter Poisson-Dirichlet distribution, denoted\\u000a$\\\\mathsf{PD}(\\\\alpha, \\\\theta)$ is a probability distribution on the set of\\u000adecreasing positive sequences with sum 1. The usual Poisson-Dirichlet\\u000adistribution with a single parameter $\\\\theta$, introduced by Kingman, is\\u000a$\\\\mathsf{PD}(0, \\\\theta)$. Known properties of $\\\\mathsf{PD}(0, \\\\theta)$,\\u000aincluding the Markov chain description due to Vershik, Shmidt and Ignatov, are\\u000ageneralized to the two-parameter case. The size-biased

Jim Pitman; Marc Yor

1997-01-01

120

Evaluation of two models for human topoisomerase I interaction with dsDNA and camptothecin derivatives.  

PubMed

Human topoisomerase I (Top1) relaxes supercoiled DNA during cell division. Camptothecin stabilizes Top1/dsDNA covalent complexes which ultimately results in cell death, and this makes Top1 an anti-cancer target. There are two current models for how camptothecin and derivatives bind to Top1/dsDNA covalent complexes (Staker, et al., 2002, Proc Natl Acad Sci USA 99: 15387-15392; and Laco, et al., 2004, Bioorg Med Chem 12: 5225-5235). The interaction energies between bound camptothecin, and derivatives, and Top1/dsDNA in the two models were calculated. The published structure-activity-relationships for camptothecin and derivatives correlated with the interaction energies for camptothecin and derivatives in the Laco et al. model, however, this was not the case for several camptothecin derivatives in the Stacker et al. model. By defining the binding orientation of camptothecin and derivatives in the Top1/dsDNA active-site these results allow for the rational design of potentially more efficacious camptothecin derivatives. PMID:21912628

Laco, Gary S

2011-08-30

121

Negative protein-protein interaction datasets derived from large-scale two-hybrid experiments.  

PubMed

Negative protein-protein interaction datasets are needed for training and evaluation of interaction prediction methods, as well as validation of high-throughput interaction discovery experiments. In large-scale two-hybrid assays, the direct interaction of a large number of protein pairs is systematically probed. We present a simple method to harness two-hybrid data to obtain negative protein-protein interaction datasets, which we validated using other available experimental data. The method identifies interactions that were likely tested but not observed in a two-hybrid screen. For each negative interaction, a confidence score is defined as the shortest-path length between the two proteins in the interaction network derived from the two-hybrid experiment. We show that these high-quality negative datasets are particularly important when a specific biological context is considered, such as in the study of protein interaction specificity. We also illustrate the use of a negative dataset in the evaluation of the InterPreTS interaction prediction method. PMID:22884951

Trabuco, Leonardo G; Betts, Matthew J; Russell, Robert B

2012-08-04

122

Physicochemical study on interactions between T-2 and HT-2 toxin derivatives and cyclodextrins  

Technology Transfer Automated Retrieval System (TEKTRAN)

Physicochemical interactions occurring between fluorescent anthracene derivatives of T-2 and HT-2 toxins and different cyclodextrins (CDs) were investigated in aqueous solutions by means of UV-Vis absorption, fluorescence emission, and Dynamic Light Scattering. Binding constant values and physicoche...

123

INTERACTION OF A WATER SOLUBLE FULLERENE DERIVATIVE WITH REACTIVE OXYGEN SPECIES AND MODEL ENZYMATIC SYSTEMS  

Microsoft Academic Search

Fullerenes are a new class of compounds with potential uses in biology and medicine but little is known about their interaction with biological systems. Fullerenes were reported to be pro- or anti-oxidants depending on their structure or on experimental conditions. This work presents the effects of dendrofullerene, a water soluble derivative of C60, on model biological systems from both perspectives.

Sarah Foley; Anthony D. M. Curtis; Andreas Hirsch; Michael Brettreich; André Pelegrin; Patrick Seta; Christian Larroque

2002-01-01

124

Analyzing different parameters of steered molecular dynamics for small membrane interacting molecules.  

PubMed

The aim of this report is two-fold: First, to show the applicability of the Steered Molecular Dynamics (SMD) methodology for analyzing non-specific interactions governing the membrane affinity process of small biological molecules. Second, to point out a correlation between the system response and certain combinations of the SMD parameters (spring-elastic-constant and pulling-group). For these purposes, a simplified membrane model was used, modeled as a non-polar region limited by two polar aqueous media in a continuous dielectric representation. Polarization-induced effects at both interfaces were taken into account by the "electrostatic images" method. To perform SMD simulations a harmonic external force, representing a spring acting on a selected atom, forces the molecule to "break" its interaction with the surrounding environment by extracting it out of the membrane. With this approach, small molecules and peptides, with known affinity for the membrane environment, were studied: the zwitterionic tryptophan residue and a pentapeptide AcWLKLL. The SMD parameters, spring-elastic-constant and pulling-group, were varied and combined in order to analyze the systems responses in each case. It was observed that, the spring stiffness was crucial to reveal specific events that occur during the molecule behavior; hence, it was directly responsible for the sensitivity of this methodology. The pulling-group selected highly influenced on the reaction pathway, a fact that it was not observed with other parameters; consequently, force profiles are like the "fingerprints" of these induced pathways. The potential profile for the tryptophan was recovered from the SMD simulations being in good agreement with that estimated by an approximation method. With this rather simple model approach, SMD methodology has proven to be suitable for revealing the main interactions that govern the membrane affinity processes of small molecules and peptides. PMID:16002307

Lorenzo, Alicia C; Bisch, Paulo M

2005-09-01

125

Tight correlations between forest parameters and backscattering coefficient derived by the L-band airborne SAR (PiSAR)  

Microsoft Academic Search

We examined relationship between forest parameters and ?0 derived by airborne multi-polarization SAR (PiSAR). PiSAR observations and field measurements were simultaneously performed on November 2002 and August 2003. One data set was taken from stands with pure pine (Picea glehnii Masters) forest. More than 70% of the trees in biomass are Picea glehnii Masters in the data set with same

Manabu Watanabe; Masanobu Shimada; Ake Rosenqvist; Shakil Ahmad Romshoo; Kazuo Ohta; Takeo Tadono; Masayuki Matsuoka; Ryoichi Furuta

2004-01-01

126

Microscopic calculation of interacting boson model parameters by potential-energy surface mapping  

SciTech Connect

A coherent state technique is used to generate an interacting boson model (IBM) Hamiltonian energy surface which is adjusted to match a mean-field energy surface. This technique allows the calculation of IBM Hamiltonian parameters, prediction of properties of low-lying collective states, as well as the generation of probability distributions of various shapes in the ground state of transitional nuclei, the last two of which are of astrophysical interest. The results for krypton, molybdenum, palladium, cadmium, gadolinium, dysprosium, and erbium nuclei are compared with experiment.

Bentley, I. [Department of Physics, University of Notre Dame, Notre Dame, Indiana 46556 (United States); Frauendorf, S. [Department of Physics, University of Notre Dame, Notre Dame, Indiana 46556 (United States); ISP, Forschungszentrum Dresden-Rossendorf, Dresden (Germany)

2011-06-15

127

Derivative Discontinuity in the Strong-Interaction Limit of Density-Functional Theory  

NASA Astrophysics Data System (ADS)

We generalize the exact strong-interaction limit of the exchange-correlation energy of Kohn-Sham density functional theory to open systems with fluctuating particle numbers. When used in the self-consistent Kohn-Sham procedure on strongly interacting systems, this functional yields exact features crucial for important applications such as quantum transport. In particular, the steplike structure of the highest-occupied Kohn-Sham eigenvalue is very well captured, with accurate quantitative agreement with exact many-body chemical potentials. While it can be shown that a sharp derivative discontinuity is present only in the infinitely strongly correlated limit, at finite correlation regimes we observe a slightly smoothened discontinuity, with qualitative and quantitative features that improve with increasing correlation. From the fundamental point of view, our results obtain the derivative discontinuity without making the assumptions used in its standard derivation, offering independent support for its existence.

Mirtschink, André; Seidl, Michael; Gori-Giorgi, Paola

2013-09-01

128

Derivation of Quality Parameters for Terrain Models: Examples from Seafloor and Landscape Mapping  

Microsoft Academic Search

Random measurement errors in digital terrain models are im- portant to their quality. The present paper describes an untypical use of variograms to compute this kind of measurement errors. After subtract- ing a low frequency drift from depth\\/height measurements, a variogram analysis of the residuals is used to derive the random measurement errors of the observations. Numerical experiments on lasercanning

Jan T. Bjørke; Stein Nilsen

129

Modeling dispersion of dry powders for inhalation. The concepts of total fines, cohesive energy and interaction parameters.  

PubMed

A range of carrier based dry powder formulations consisting of micronized drug, carrier lactose and, in some formulations, lactose fines were produced and tested for dispersibility, i.e. fine particle fraction (FPF). Two different drugs were used, budesonide (BUD) and beclomethasone dipropionate (BDP). A model based on the total amount of fines (TF) and the cohesive energy (CE) of the formulation is proposed, where TF is the sum of added drug, lactose fines and the fines inherent to the carrier. The expression for CE is derived from regular solutions theory and allows calculation of interparticle interaction parameters. The model was able to describe experimental data well, such as the decrease in FPF when the proportion of drug is increased at a constant TF level and the non-linear effects seen when a cohesive drug is added to carrier. BDP and BUD were found to be 5.3 times and 1.8 times more cohesive than lactose fines respectively. The model hence provides a link between the macroscopic behavior of a dry powder formulation and the interaction between the different species at the particulate level. PMID:22349053

Thalberg, Kyrre; Berg, Elna; Fransson, Magnus

2012-02-14

130

On the derivation of passive 3D material parameters from 1D stress-strain data of hydrostats.  

PubMed

The present paper offers a novel equivalent-pressure approach to the derivation of isotropic passive muscle parameters from 1D stress-strain data sets. The approach aims specifically at the identification of material parameters in hydrostats, in which case the equivalent-force approach that is common for skeletal muscle generates suboptimal results. Instead, an equivalent-pressure hypothesis is formulated which provides more adequate boundary conditions for the concluding curve-fitting procedure. The choice of an appropriate constitutive description is decisive for the quality of the deduced parameter sets. Here, a Yeoh material law is chosen for the model of a squid tentacle. Parameters derived by both, equivalent-force and equivalent-pressure algorithms, are compared, illustrating the applicability limits of either. They are implemented in a finite element model of the tentacle. A prey-capture strike is simulated and compared to data from literature. The hydrostat-specific interpretation of the equivalent-pressure hypothesis is shown to match the reference very well. PMID:21696743

Winkel, Benjamin; Schleichardt, Axel

2011-06-22

131

Derivation of the n'th order uncertainty analysis for normally distributed parameters  

Microsoft Academic Search

An n'th order uncertainty analysis methodology for problems involving generally correlated but normally distributed parameters is presented. All terms required to apply this uncertainty analysis methodology are expressed analytically in terms of the customary covariance matrices and in terms of up to the n'th order sensitivities.

Ronen

1985-01-01

132

Identificacao de Parametros DA Deriva de Sensores Inercials (Identification of Parameters Derived from Inertial Sensors).  

National Technical Information Service (NTIS)

The modeling and parameter estimation of drift in inertial sensors is discussed. The model includes constant drift, ramp effects, white noise (short-term random drift), and random walk (long-term random drift). The estimation is based on two different pro...

G. Gandelman

1990-01-01

133

New Methods to Derive the Optical and Beam Parameters in Transport Channels  

Microsoft Academic Search

The standard approach to compute the optical parameters and the beam emittance in a transport channel is based on the analysis of the profiles measured by three monitors. This requires the independent measurement of the dispersion function at the monitor locations and the knowledge of the value of the beam's momentum spread. In this paper different approaches based on the

Gianluigi Arduini; Massimo Giovannozzi; K Hanke; Django Manglunki; M Martini

2000-01-01

134

Binary Fluids with Long Range Segregating Interaction. I: Derivation of Kinetic and Hydrodynamic Equations  

Microsoft Academic Search

We study the evolution of a two component fluid consisting of “blue” and “red” particles which interact via strong short range (hard core) and weak long range pair potentials. At low temperatures the equilibrium state of the system is one in which there are two coexisting phases. Under suitable choices of space-time scalings and system parameters we first obtain (formally)

S. Bastea; R. Esposito; J. L. Lebowitz; R. Marra

2000-01-01

135

Processing parameters affecting the properties of sol-gel-derived modified lead titanate thin films  

SciTech Connect

Calcium modified lead titanate thin films have been prepared by spin-coating of aquo-diol solutions on platinized silicon substrates. The influence of the chemical processing parameters and of the heating rates on the crystallization of the films is studied. Different ferroelectric properties are measured in films prepared under different conditions. These differences are related to the crystalline phases and structural characteristics developed in the films during their preparation.

Calzada, M.L.; Mendiola, J.; Carmona, F.; Ramos, P.; Sirera, R. [C.S.I.C., Madrid (Spain). Inst. Ciencia de Materials

1996-04-01

136

How useful are Green-Ampt parameters derived from small rainfall simulation plots for modelling runoff at different plot lengths?  

NASA Astrophysics Data System (ADS)

Rainfall simulation on small field plots is an invaluable method to derive effective field parameters for infiltration models such as Green-Ampt. Plot scales of ca. 1m² integrate much of the micro-scale variability and processes, which ring-infiltrometers or soil core measurements cannot capture. However, these parameters have to be used with caution on larger scales, because processes such as run-on infiltration can be considerable. The Green-Ampt parameters suction across the wetting front (psi) and effective hydraulic conductivity (Ke) were estimated from rainfall simulations on two ridged fields in Togo, West Africa. Additionally, rainfall events were recorded, and on plots of 1m width and lengths of 1, 4 and 16m, total runoff volume and sediment concentration were measured. The storm runoff hydrographs of the plots were modelled with Chu's Green-Ampt variable rainfall intensity infiltration model, using the field-average parameters derived from the simulations. Potential effects of runoff lag time were assumed negligible. Calculated total runoff volumes were compared to measured runoff volumes. For the 1m plots, runoff was underestimated, as patches of seal in the furrows produced runoff already at rainfall intensities much lower than the average infiltration capacity. For the longer plots, no run-on infiltration or other scale dependent processes were assumed, so the relative error due to scale effects was proportional to the average difference or runoff depth. In contrast to the 1m plots, runoff was overestimated by a factor of 1.2 and 2 for the 4m and 16m plots, respectively. It appears that the application of the Green-Ampt effective hydraulic conductivity derived from rainfall simulations faces two main problems, which are their dependence on one single rainfall intensity and scale-effects by run-on infiltration. Errors necessarily propagate into the scale dependency of erosion and sediment transport, as these processes are directly dependent on runoff characteristics such as stream power and shear stress.

Langhans, Christoph; Engels, Lien; Tegenbos, Lize; Govers, Gerard; Diels, Jan

2010-05-01

137

Novel interactions of fluorinated nucleotide derivatives targeting orotidine-5?-monophosphate decarboxylase  

PubMed Central

Fluorinated nucleosides and nucleotides are of considerable interest to medicinal chemists due to their antiviral, anticancer, and other biological activities. However, their direct interactions at target binding sites are not well understood. A new class of 2?-deoxy-2?-fluoro-C6-substituted uridine and UMP derivatives were synthesized and evaluated as inhibitors of orotidine-5?-monophosphate decarboxylase (ODCase). These compounds were synthesized from the key intermediate, fully-protected 2?-deoxy-2?-fluorouridine. Among the synthesized compounds, 2?-deoxy-2?-fluoro-6-iodo-UMP covalently inhibited human ODCase with a second-order rate constant of 0.62 ± 0.02 M?1sec?1. Interestingly, the 6-cyano-2?-fluoro derivative covalently interacted with ODCase defying the conventional thinking, where its ribosyl derivative undergoes transformation into BMP by ODCase. This confirms that the 2?-fluoro moiety influences the chemistry at the C6 position of the nucleotides, thus interactions in the active site of ODCase. Molecular interactions of the 2?-fluorinated nucleotides are compared to those with the 3?-fluorinated nucleotides bound to the corresponding target enzyme, and the carbohydrate moieties were shown to bind in different conformations.

Lewis, Melissa; Avina, Maria Elena Meza; Wei, Lianhu; Crandall, Ian E.; Bello, Angelica Mara; Poduch, Ewa; Liu, Yan; Paige, Christopher J.; Kain, Kevin C.; Pai, Emil F.; Kotra, Lakshmi P.

2011-01-01

138

Novel Peptide-Mediated Interactions Derived from High-Resolution 3-Dimensional Structures  

PubMed Central

Many biological responses to intra- and extracellular stimuli are regulated through complex networks of transient protein interactions where a globular domain in one protein recognizes a linear peptide from another, creating a relatively small contact interface. These peptide stretches are often found in unstructured regions of proteins, and contain a consensus motif complementary to the interaction surface displayed by their binding partners. While most current methods for the de novo discovery of such motifs exploit their tendency to occur in disordered regions, our work here focuses on another observation: upon binding to their partner domain, motifs adopt a well-defined structure. Indeed, through the analysis of all peptide-mediated interactions of known high-resolution three-dimensional (3D) structure, we found that the structure of the peptide may be as characteristic as the consensus motif, and help identify target peptides even though they do not match the established patterns. Our analyses of the structural features of known motifs reveal that they tend to have a particular stretched and elongated structure, unlike most other peptides of the same length. Accordingly, we have implemented a strategy based on a Support Vector Machine that uses this features, along with other structure-encoded information about binding interfaces, to search the set of protein interactions of known 3D structure and to identify unnoticed peptide-mediated interactions among them. We have also derived consensus patterns for these interactions, whenever enough information was available, and compared our results with established linear motif patterns and their binding domains. Finally, to cross-validate our identification strategy, we scanned interactome networks from four model organisms with our newly derived patterns to see if any of them occurred more often than expected. Indeed, we found significant over-representations for 64 domain-motif interactions, 46 of which had not been described before, involving over 6,000 interactions in total for which we could suggest the molecular details determining the binding.

Stein, Amelie; Aloy, Patrick

2010-01-01

139

The Meaning of the Climate Sensitivity Parameter (and how not to derive it)  

NASA Astrophysics Data System (ADS)

The climate sensitivity represents the change in temperature per unit radiative forcing. That simple statement covers several important details. For example, should we use surface temperature or higher altitude temperatures to define the change in temperature? Answering questions like this clarifies what is meant by a feedback and what is meant by an adjusted forcing. Regressions of outgoing radiation against temperature have been used to diagnose the climate sensitivity parameters. Some robust results are possible but there have also been a couple of papers that obtained erroneously low climate sensitivities. Understanding what climate sensitivity means illuminates an error in a paper widely cited by climate denialists’ web blogs.

Murphy, D. M.

2010-12-01

140

Determination of the parameters of a Skyrme type effective interaction using the simulated annealing approach  

SciTech Connect

We implement for the first time the simulated annealing method to the problem of searching for the global minimum in the hypersurface of the {chi}{sup 2} function, which depends on the values of the parameters of a Skyrme-type effective nucleon-nucleon interaction. We undertake a realistic case of fitting the values of the Skyrme parameters to an extensive set of experimental data on the ground-state properties of many nuclei, ranging from normal to exotic ones. The set of experimental data used in our fitting procedure includes the radii for the valence 1d{sub 5/2} and 1f{sub 7/2} neutron orbits in the {sup 17}O and {sup 41}Ca nuclei, respectively, and the breathing-mode energies for several nuclei, in addition to the typically used data on binding energy, charge radii, and spin-orbit splitting. We also include in the fit the critical density {rho}{sub cr} and further constrain the values of the Skyrme parameters by requiring that (i) the quantity P=3{rho}(dS/d{rho}), directly related to the slope of the symmetry energy S, must be positive for densities up to 3{rho}{sub 0}; (ii) the enhancement factor {kappa}, associated with the isovector giant dipole resonance, should lie in the range of 0.1-0.5; and (iii) the Landau parameter G{sub 0}{sup '} is positive at {rho}={rho}{sub 0}. We provide simple but consistent schemes to account for the center-of-mass corrections to the binding energy and charge radii.

Agrawal, B.K.; Shlomo, S.; Au, V. Kim [Cyclotron Institute, Texas A and M University, College Station, Texas 77843 (United States)

2005-07-01

141

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

NASA Astrophysics Data System (ADS)

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

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

2013-08-01

142

Interactions of curcumin and its derivatives with nucleic acids and their implications.  

PubMed

Curcumin (diferuloylmethane) is a yellow polyphenol found in the rhizome of the annual herb turmeric (Curcuma longa) belonging to the family Zingiberaceae. Its interaction with a huge number of molecular targets like cytokines, growth factors, transcription factors, receptors, pro-inflammatory enzymes, protein kinases and adhesion molecules has been studied extensively. Interaction of curcumin with nucleic acids has been the focus of extensive research in recent years. Curcumin is observed to be genotoxic and antigenotoxic agent in time and concentration dependent manner. Curcumin and its derivatives either alone or as metal complexes have been reported to bind directly to DNA. The interactions are mainly as DNA minor groove binding or as DNA intercalating agents. The similarity in the shape of curcumin to DNA minor groove binding drugs is the motivation for exploring its binding to DNA minor grooves. Thus curcumin is a "double edged sword": having therapeutic potential as a minor groove binder but at the same time it may cause DNA damage in the cell at high concentration. The purpose of this review is to summarize the current information related to interaction of curcumin metal complexes and its derivatives with nucleic acids and the implication such interaction can have on therapeutics. PMID:23095000

Kumar, Anil; Bora, Utpal

2013-02-01

143

Snow parameters derived from microwave measurements during the BOREAS winter field campaign  

NASA Astrophysics Data System (ADS)

Passive microwave data have been used to infer the snow-covered area and snow water equivalent (SWE) over forested areas, but the accuracy of these retrieved snow parameters cannot be easily validated for heterogeneous vegetated regions. The Boreal Ecosystem-Atmosphere Study Winter Field Campaign provided the opportunity to study the effect of boreal forests on snow parameter retrieval in detail. Microwave radiometers (18, 37, and 92 GHz) were flown on board the Canadian National Aeronautical Establishment's Twin Otter. Flight lines covered both the southern study area near Prince Albert and the northern study area near Thompson, Canada. During the 1994 winter campaign, extensive ground-based snow cover information, including depth, density, and grain size, was collected along most of the flight lines, jointly by U.S. and Canadian investigators. Satellite data collected by the special sensor microwave imager are also used for comparison. Preliminary results reconfirmed the relationship between microwave brightness temperature and SWE. However, the effect of forest cover observed by the aircraft sensors is different from that of the satellite observations. This is probably due to the difference in footprint averaging. There were also several flight lines flown over Candle Lake and Waskesiu Lake to assess lake ice signatures. Preliminary results show the thickness of the lake ice may be inferred from the airborne microwave observations. The microwave signature relationship between lake ice and snow matches the results from radiative transfer calculations.

Chang, A. T. C.; Foster, J. L.; Hall, D. K.; Goodison, B. E.; Walker, A. E.; Metcalfe, J. R.; Harby, A.

1997-12-01

144

Complex order parameter phase-field models derived from structural phase-field-crystal models  

NASA Astrophysics Data System (ADS)

The phase-field-crystal (PFC) modeling paradigm is rapidly emerging as the model of choice when investigating materials phenomena with atomistic scale effects over diffusive time scales. Recent variants of the PFC model, so-called structural PFC (XPFC) models introduced by Greenwood , have further increased the capability of the method by allowing for easy access to various structural transformations in pure materials [Greenwood, Provatas, and Rottler, Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.105.045702 105, 045702 (2010)] and binary alloys [Greenwood, Ofori-Opoku, Rottler, and Provatas, Phys. Rev. BPRBMDO1098-012110.1103/PhysRevB.84.064104 84, 064104 (2011)]. We present an amplitude expansion of these XPFC models, leading to a mesoscale complex order parameter, i.e., phase-field, model for two-dimensional square-triangular structures. Amplitude models retain the salient atomic scale features of the underlying PFC models, while resolving microstructures on mesoscales as traditional phase-field models. The applicability and capability of these complex-order parameter models is demonstrated with simulations of peritectic solidification and grain growth exhibiting the emergence of secondary phase structures.

Ofori-Opoku, Nana; Stolle, Jonathan; Huang, Zhi-Feng; Provatas, Nikolas

2013-09-01

145

Brain-derived neurotrophic factor and androgen interactions in spinal neuromuscular systems.  

PubMed

Neurotrophic factors and steroid hormones interact to regulate a variety of neuronal processes such as neurite outgrowth, differentiation, and neuroprotection. The coexpression of steroid hormone and neurotrophin receptor mRNAs and proteins, as well as their reciprocal regulation provides the necessary substrates for such interactions to occur. This review will focus on androgen brain-derived neurotrophic factor (BDNF) interactions in the spinal cord, describing androgen regulation of BDNF in neuromuscular systems following castration, androgen manipulation, and injury. Androgens interact with BDNF during development to regulate normally-occurring motoneuron death, and in adulthood, androgen-BDNF interactions are involved in the maintenance of several features of neuromuscular systems. Androgens regulate BDNF and trkB expression in spinal motoneurons. Androgens also regulate BDNF levels in the target musculature, and androgenic action at the muscle regulates BDNF levels in motoneurons. These interactions have important implications for the maintenance of motoneuron morphology. Finally, androgens interact with BDNF after injury, influencing soma size, dendritic morphology, and axon regeneration. Together, these findings provide further insight into the development and maintenance of neuromuscular systems and have implications for the neurotherapeutic/neuroprotective roles of androgens and trophic factors in the treatment of motoneuron disease and recovery from injury. PMID:23103213

Verhovshek, T; Rudolph, L M; Sengelaub, D R

2012-10-24

146

A quantitative uncertainty assessment of eruptive parameters derived from tephra deposits: the example of two large eruptions of Cotopaxi volcano, Ecuador  

Microsoft Academic Search

Physical parameters of explosive eruptions are typically derived from tephra deposits. However, the characterization of a\\u000a given eruption relies strongly on the quality of the dataset used, the strategy chosen to obtain and process field data and\\u000a the particular model considered to derive eruptive parameters. As a result, eruptive parameters are typically affected by\\u000a a certain level of uncertainty and

Sébastien Biass; Costanza Bonadonna

2011-01-01

147

Synthesis of fluorescent derivatives of praziquantel: cell-imaging and interaction with Schistosoma japonicum cercariae.  

PubMed

Schistosomiasis is one of the most burdensome of the neglected tropical diseases. Praziquantel is a recommended drug for treatment against all forms of schistosomiasis. To investigate the interaction between praziquantel and Schistosoma japonicum cercariae, two praziquantel derivatives (PZQ-2 and PZQ-3) and one praziquantel fluorescent derivative (PZQ-5) have been synthesized and characterized using nuclear magnetic resonance spectroscopy (NMR) and MS spectra. The cytotoxicity of PZQ-2, PZQ-3 and PZQ-5 was measured by performing the methyl thiazolyl tetrazolium (MTT) assay. The cell viability for them shows that the three compounds exhibit low cytotoxicity to HeLa cells. Cell imaging experiments demonstrate that PZQ-5 is biocompatible and cell-permeable, which indicates that PZQ-5 is suitable for studying their interaction. Confocal fluorescence microscopy revealed that PZQ-5 is mainly located at the cercarial tegument, which leads to the death of cercariae with the increase in time. PMID:23925274

Xie, Yunzhi; Li, Yibao; Wu, Yongquan; Liu, Chunhua; Li, Xiaokang; Li, Xun; Fan, Xiaolin

2013-09-28

148

Macrophage-derived SPARC bridges tumor cell-extracellular matrix interactions toward metastasis.  

PubMed

Other than genetic imprinting and epithelial to mesenchymal transition, cancer cells need interaction with the nearby stroma toward metastasis. Secreted protein acidic and rich in cysteine (SPARC) is a matricellular protein known to regulate extracellular matrix (ECM) deposition and cell-ECM interaction. Gene expression profiles associate SPARC to malignant progression. Using reciprocal bone marrow chimeras between SPARC knockout and wild-type mice, we show that SPARC produced by inflammatory cells is necessary for spontaneous, but not experimental, i.v. metastasis. Macrophage-derived SPARC induces cancer cell migration and enhances their migration to other ECM proteins at least through alpha(v)beta(5) integrin. Indeed, RNA interference knockdown of beta(5) integrin expression reduces cell migration in vitro and metastasis in vivo. Together these results show that macrophage-derived SPARC takes part in metastasis, acting at the step of integrin-mediated migration of invasive cells. PMID:18974151

Sangaletti, Sabina; Di Carlo, Emma; Gariboldi, Silvia; Miotti, Silvia; Cappetti, Barbara; Parenza, Mariella; Rumio, Cristiano; Brekken, Rolf A; Chiodoni, Claudia; Colombo, Mario P

2008-11-01

149

Spontaneous and reversible interaction of vanadium(V) oxyanions with amine derivatives  

SciTech Connect

The interaction between vanadate and tri- or tetradentate ethanolamine derivatives has been studied by using /sup 51/V NMR spectroscopy. The reactions occur spontaneously in aqueous solutions, at ambient temperatures and in the physiological pH range. In addition to one amine group and one hydroxyl group, the ethanolamine derivative should contain a third and/or fourth functionality that is an alcohol, a carboxylic acid, a phosphonium acid, or an amine. The reactions are highly dependent on pH, concentrations of monomeric vanadate, amine. The stability constants for the complexes are minimum orders of magnitude greater than those found for vanadate derivatives of corresponding ether derivatives, and the high stability is associated with the central nitrogen. Only one vanadium complex is formed in substantial amounts in the reaction of ethanolamine derivatives with vanadate, and that complex is mononuclear in vanadium. Several of the ethanolamine derivatives that form complexes are commonly used buffers in biological and biomedical studies in vitro. 22 refs., 10 figs., 7 tabs.

Crans, D.C.; Shin, P.K.

1988-05-18

150

Interactions between indazole derivative and magnesium cations – NMR investigations and theoretical calculations  

NASA Astrophysics Data System (ADS)

The paper describes a new NMR approach for the determination of interaction sites between a heterocyclic ligand, like indazole, and magnesium ions. The method is based on the comparison of chemical shifts of indazole derivative before and after complexation with magnesium salt and is supported by DFT (B3LYP/6-31G(d,p) level of theory, solvent model PCM, IGLO-II basis set) theoretical calculations.

Kujawski, Jacek; Doskocz, Marek; Popielarska, Hanna; Myka, Anna; Drabi?ska, Beata; Kruk, Joanna; Bernard, Marek K.

2013-09-01

151

Study of DNA interactions with cyclic chalcone derivatives by spectroscopic techniques  

NASA Astrophysics Data System (ADS)

A series of chalcone derivatives ( 1- 4) were studied. The interaction between these ligands and calf thymus DNA was studied with UV-vis spectrophotometry, fluorescence and circular dichroism spectroscopy. The binding constants K were estimated at 0.5-4.6 × 10 5 M -1. All these measurements indicated that the compounds behave as effective DNA-intercalating agents. Electrophoretic separation proved that ligands inhibited topoisomerase I at a concentration of 60 ?M.

Štefanišinová, M.; Tome?ková, V.; Kožurková, M.; Ostró, A.; Mareková, M.

2011-10-01

152

The efficient evaluation of configuration interaction analytic energy second derivatives: Application to hydrogen thioperoxide, HSOH  

Microsoft Academic Search

We present an efficient reformulation of the analytic configuration interaction (CI) energy second derivative. Specifically, the Z-vector method of Handy and Schaefer is used to avoid solving the second order coupled perturbed Hartree–Fock (CPHF) equations. We have incorporated translational–rotational invariance into the new method. We present a more efficient method for the evaluation of the Y matrix contribution. The procedure

Timothy J. Lee; Nicholas C. Handy; Julia E. Rice; Andrew C. Scheiner; Henry F. Schaefer

1986-01-01

153

The efficient evaluation of configuration interaction analytic energy second derivatives: Application to hydrogen thioperoxide, HSOH  

Microsoft Academic Search

We present an efficient reformulation of the analytic configuration interaction (CI) energy second derivative. Specifically, the Z-vector method of Handy and Schaefer is used to avoid solving the second order coupled perturbed Hartree--Fock (CPHF) equations. We have incorporated translational--rotational invariance into the new method. We present a more efficient method for the evaluation of the Y matrix contribution. The procedure

Timothy J. Lee; Nicholas C. Handy; Julia E. Rice; Andrew C. Scheiner; Henry F. Schaefer III

1986-01-01

154

Hoiamide D, a marine cyanobacteria-derived inhibitor of p53/MDM2 interaction  

PubMed Central

Bioassay-guided fractionation of two cyanobacterial extracts from Papua New Guinea has yielded hoiamide D in both its carboxylic acid and conjugate base forms. Hoiamide D is a polyketide synthase (PKS)/non-ribosomal peptide synthetase (NRPS)-derived natural product that features two consecutive thiazolines and a thiazole, as well as a modified isoleucine residue. Hoiamide D displayed inhibitory activity against p53/MDM2 interaction (EC50= 4.5 ?M), an attractive target for anticancer drug development.

Malloy, Karla L.; Choi, Hyukjae; Fiorilla, Catherine; Valeriote, Fred A.; Matainaho, Teatulohi; Gerwick, William H.

2011-01-01

155

Development of the smooth orthogonal decomposition method to derive the modal parameters of vehicle suspension system  

NASA Astrophysics Data System (ADS)

In this paper, the smooth orthogonal decomposition (SOD) method is developed to the light damped systems in which the inputs are time shifted functions of one or more random processes. An example of such practical cases is the vehicle suspension system in which the random inputs due to the road roughness applied to the rear wheels are the shifted functions of the same random inputs on the front wheels with a time lag depending on the vehicle wheelbase as well as its velocity. The developed SOD method is applied to determine the natural frequencies and mode shapes of a certain vehicle suspension system and the results are compared with the true values obtained by the structural eigenvalue problem. The consistency of the results indicates that the SOD method can be applied with a high degree of accuracy to calculate the modal parameters of vibrating systems in which the system inputs are shifted functions of one or more random processes.

Rezaee, Mousa; Shaterian-Alghalandis, Vahid; Banan-Nojavani, Ali

2013-04-01

156

Gravity wave parameters derived from traveling ionospheric disturbances observations in the auroral zone  

SciTech Connect

Large-scale wavelike fluctuations of ion velocity, as measured by the European incoherent scatter radar along the geomagnetic field line, have been attributed to gravity wave effects. The height-dependent parameters of the causative gravity waves are calculated, taking into account the neutral horizontal wind and the electric field. The results are compared with the solutions of a dissipative dispersion relation. Much better agreement is achieved for the imaginary part of the vertical wave vector than for its real part. The calculated wave damping is greater than that given by theory. The possible reasons for this are discussed. It is suggested that E x B drift of the ions and vertical neutral winds, which are characteristic features of the auroral zone ionosphere, may contribute to the observed discrepancies. 40 refs.

Natorf, L.; Schlegel, K.; Wernik, A.W. (Max-Planck-Inst. fuer Aeronomie, Katlenburg-Lindau (Germany) Space Research Centre, Warsaw (Poland))

1992-12-01

157

ESTIMATES OF GENETIC PARAMETERS AND AN EVALUATION OF GENOTYPE X ENVIRONMENT INTERACTION FOR WEANING WEIGHT IN NELLORE CATTLE  

Technology Transfer Automated Retrieval System (TEKTRAN)

Records of 105,645 Nellore calves born from 1977 to 1994 in eight different regions of Brazil were used to estimate genetic parameters for weaning weight (kg). The objective of this study was to estimate genetic and environmental parameters and evaluate genotype x environment interaction for weaning...

158

??, ?? and ?? potentials derived from the SU quark-model baryon baryon interaction  

NASA Astrophysics Data System (ADS)

We calculate ??, ?? and ?? potentials from the nuclear-matter G-matrices of the SU quark-model baryon baryon interaction. The ?-cluster wave function is assumed to be a simple harmonic-oscillator shell-model wave function. A new method is proposed to derive the direct and knock-on terms of the interaction Born kernel from the hyperon nucleon G-matrices, with explicit treatments of the nonlocality and the center-of-mass motion between the hyperon and ?. We find that the SU quark-model baryon baryon interactions, FSS and fss2, yield a reasonable bound-state energy for 5?He, from -3.18 to -3.62MeV, in spite of the fact that they give relatively large depths for the ? single-particle potentials, 46 48 MeV, in symmetric nuclear matter. An equivalent local potential derived from the Wigner transform of the nonlocal ?? kernel shows a strong energy dependence for the incident ?-particle, indicating the importance of the strangeness-exchange process in the original hyperon nucleon interaction. For the ?? and ?? potentials, we only discuss the zero-momentum Wigner transform of the interaction kernels, since these interactions turn out to be repulsive when the two isospin contributions for the ?N and ?N interactions are added up. These components show a strong isospin dependence: they are attractive in the isospin I=1/2 (??) and I=0 (??) components and repulsive in I=3/2 (??) and I=1 (??) components, which indicate that ? and ? potentials could be attractive in some particular systems such as the well-known 4?He system.

Fujiwara, Y.; Kohno, M.; Suzuki, Y.

2007-03-01

159

New Microscopic Derivation of the Interacting Boson Model and Its Applications to Exotic Nuclei  

SciTech Connect

We present a new scheme to determine the Hamiltonian of the Interacting Boson Model (IBM) microscopically, which starts from the mean-field model with Skyrme-type interactions. Surface deformations and the effects of the nuclear force are simulated in terms of bosons. By comparing Potential Energy Surface (PES) of the mean-field model with that of the IBM, the parameters of the IBM Hamiltonian can be obtained. By this method, quantum shape/phase transitions and critical-point symmetries can be reproduced. Systematic calculations on Xe and Ru isotopes shall be newly presented, which partly contain the predicted energy levels.

Nomura, K.; Shimizu, N. [Department of Physics, University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan); Otsuka, T. [Department of Physics, University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan); RIKEN Nishina center, Hirosawa, Wako-shi, 351-0198 Saitama (Japan); National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, MI (United States)

2009-08-26

160

Experimental investigation of 3-D MHD flows at high Hartmann number and interaction parameters  

SciTech Connect

Experimental investigations of 3-D MHD flows in uniform thin conducting wall ducts of circular and square cross section, conducted at Argonne National Laboratory's ALEX facility, are reported. The three-dimensional nature of the flow arises from the spacial variation of the applied transverse magnetic field. Measurements were performed at several Hartmann numbers, M, and interaction parameters, N, with the peak value for M exceeding 6 /times/ 10/sup 3/ and the peak value for N exceeding 10/sup 5/. Typical results and their comparison to numerical analysis reported in a companion paper are given, as is a brief description of the ALEX facility and the experimental methods employed. Ongoing activities and plans for future experiments are also discussed. 6 refs., 3 figs.

Picologlou, B.F.; Reed, C.B.

1988-01-01

161

Lattice-parameter determination from the interaction of short femtosecond laser pulses with crystalline solids.  

PubMed

A novel method for determining the lattice parameter in a crystalline solid from the harmonic emission spectra reflected in laser-solid layers interactions is proposed. Radiated emission at high-order harmonic numbers is observed from thin crystalline layers illuminated by short femtosecond elliptically polarized laser light. The radiation mechanism presented here accounts for optical emission effects when free electrons in the material, ionized by the action of an applied external radiation field, are driven to large oscillation amplitudes and harmonics are generated by the electronic response to the periodic lattice potential. Perturbations in the electron motion inside the material due to the ion cores give rise to harmonic emission. In this work, the condition for radiation--the resonance condition--is found analytically through an exact expression for the electron displacement. The analytic prediction is supported by results obtained by solving numerically the electromagnetic force equations for electrons moving in the lattice potential. PMID:11752760

Ondarza-Rovira, R

2001-12-20

162

Experimental determination of the third derivative of G. I. Enthalpic interaction  

NASA Astrophysics Data System (ADS)

The solute (i)-solute interaction in terms of enthalpy, Hi-iE=N(?2HE/?ni2)=(1-xi)(?2HE/?ni?xi), the third derivative of G, was experimentally determined using a Thermal Activity Monitor isothermal titration calorimeter for aqueous solutions of 2-butoxyethanol (BE) and 1-propanol (1P). This was done using both calorimetric reference and sample vessels actively. We simultaneously titrate small and exactly equal amounts of solute i (=BE or 1P) into both cells which contain the binary mixtures at an average mole fraction, xi, which differs by a small amount ?xi. The appropriate amount of titrant ?ni was chosen so that the quotient (?HE/?ni) can be approximated as (?HE/?ni), and so that the scatter of the results is reasonable. ?HE is the thermal response from an individual cell on titration, and we measure directly the difference in the thermal response between the two cells, ?(?HE). The resulting quotient, ?(?HE)/?ni/?xi, can be approximated as (?2HE/?ni?xi) and hence provides a direct experimental avenue for the enthalpy interaction function. We varied the value of ?xi to seek its appropriate size. Since HE contains the first derivative of G with respect to T, the result is the third derivative quantity. Thus we present here a third derivative quantity directly determined experimentally for the first time.

Westh, Peter; Inaba, Akira; Koga, Yoshikata

2008-12-01

163

Ab initio DFT study of bisphosphonate derivatives as a drug for inhibition of cancer: NMR and NQR parameters.  

PubMed

DFT computations were carried out to characterize the (17)Oand (2)H electric field gradient, EFG, in various bisphosphonate derivatives. The computations were performed at the B3LYP level with 6-311++G (d,P) standard basis set. Calculated EFG tensors were used to determine the (17)O and (2)H nuclear quadrupole coupling constant, ? and asymmetry parameter, ?. For better understanding of the bonding and electronic structure of bisphosphonates, isotropic and anisotropic NMR chemical shieldings were calculated for the (13)C, (17)O and (31)P nuclei using GIAO method for the optimized structure of intermediate bisphosphonates at B3LYP level of theory using 6-311++G (d, p) basis set. The results showed that various substituents have a strong effect on the nuclear quadrupole resonance (NQR) parameters (?, ?) of (17)O in contrast with (2)H NQR parameters. The NMR and NQR parameters were studied in order to find the correlation between electronic structure and the activity of the desired bisphosphonates. In addition, the effect of substitutions on the bisphosphonates polarity was investigated. Molecular polarity was determined via the DFT calculated dipole moment vectors and the results showed that substitution of bromine atom on the ring would increase the activity of bisphosphonates. PMID:21633790

Aghabozorg, Hussein; Sohrabi, Beheshteh; Mashkouri, Sara; Aghabozorg, Hamid Reza

2011-06-02

164

Urban Heat Island Modeling in Conjunction with Satellite-Derived Surface/Soil Parameters.  

NASA Astrophysics Data System (ADS)

Although it has been studied for over 160 years, the urban heat island (UHI) effect is still not completely understood, yet it is increasingly important. The main purpose of this work is to improve UHI modeling by using AVHRR (Advanced Very High Resolution Radiometer) satellite data to retrieve the surface parameters (albedo, as well as soil thermal and moisture properties). In this study, a hydrostatic three-dimensional mesoscale model was used to perform the numerical modeling. The Carlson technique was applied to retrieve the thermal inertia and moisture availability using the thermal AVHRR channels 4 and 5. The net urban effect was determined as the difference between urban and nonurban simulations, in which urban parameters were replaced by rural parameters.Two winter days were each used for two numerical simulations: a control and an urban-to-rural replacement run. Moisture availability values on the less windy day showed generally a south to north gradient downwind of the city and urban values less than rural values (the urban dry island day). Moisture availability was higher on the windy day, with uniform values in the rural and urban areas (uniform soil moisture day). The only exceptions were variations in the rural hills north of the city and the low rural values under the polluted urban plume downwind of the city.While thermal inertia values showed no urban-rural differences on the uniform soil moisture day, they exhibited larger values over Atlanta than in surrounding rural area on the (less moist) dry island day. Two puzzling facts exist in the data: 1) lack of a north-south thermal inertia gradient on the dry soil day to correspond to its above-mentioned moisture availability gradient and 2) rural thermal inertia values do not change between both days in spite of their large difference in soil moisture. The observed lack of corresponding urban change is expected, as its thermal inertia values depend more on urban building materials than on moisture of soil.In both cases both the 2-m and surface skin UHIs showed positive values at night and negative values (an urban cool island, UCI) during the day. The larger nighttime 2-m UHI was on the dry day (0.8° vs 0.6°C), while the larger daytime 2-m UCI was on the moist soil day (0.3° vs 0.5°C). Note that the surface differences were almost always greater than the 2-m differences.These day-night differences imply a rural thermal inertia lower than its urban values on both days, which is in conflict with the observations on the wet uniform soil moisture day. On the uniform thermal inertia day (wet day), both the UHI and UCI amplitudes should be less than on the other day, but this is not the case. A possible explanation for both of these conflicts is the improper influence of the urban plume on this day on lowering the thermal inertia and moisture availability values used in the replacement urban simulation.

Hafner, Jan; Kidder, Stanley Q.

1999-04-01

165

Interaction of process parameters in the laser deposition of YBa2Cu3O7 films  

NASA Astrophysics Data System (ADS)

The electrical and morphological properties of YBa2Cu3O7 films grown on SrTiO3(100) substrates in a laser deposition process using a pulsed KrF excimer laser are investigated. For the first time, a quantitative order of importance of the relevant deposition parameters and their interactions that determine the quality of such films can be given. This is achieved by using statistical methods such as analysis of variance and multiple regression analysis for the design and evaluation of the experiments. The films prepared under optimum conditions grow c-axis oriented with low outgrowth densities and reveal transition temperatures Tc?89 K, resistivities ?(100 K)<=60 ?? cm, and resistance ratios R(300 K)/R(100 K)?3. The surface of the targets used for the deposition turned out to be crucial. Fresh targets yield significantly better electrical properties with a much lower spread of the data. Thus, a region in the process parameter space of YBa2Cu3O7 film deposition has been identified where electrical and morphological properties are at optimum, simultaneously. This is prerequisite for the preparation of multilayer devices.

Heinsohn, J.-K.; Reimer, D.; Richter, A.; Subke, K.-O.; Schilling, M.

1998-04-01

166

Simultaneous determination of the interaction parameter and topological scaling features of polymers in dilute solutions  

NASA Astrophysics Data System (ADS)

The RPA equation using the Debye polymer chain scattering function has been widely used to model polymer blends of linear chains in the melt where it is safe to assume a Gaussian conformation. When chains display more complicated topologies or when chains are in dilute solution Gaussian scaling no longer applies. In some cases the Zimm double extrapolation has been used to determine the second virial coefficient and the interaction parameter under the assumption that the deviation of chain scaling from a random walk is acceptable in the low qRg region such as when light scattering is used. If it is of interest to explicitly determine the nature of chain scaling, related to topology or solvent quality, as well as to quantify the thermodynamic interaction, such as in studies of cyclic and branched chains, networks, or polymers in good solvents, there is no analytically valid scattering model for data analysis. We propose the coupling of the unified scattering function with the RPA equation to analytically model these effects. Nevertheless, some issues remain to be resolved with star polymers in particular, such as scattering from highly branched high molecular weight symmetric stars in good solvents where it appears that the Daoud-Cotton model may be appropriate but a colloidal scattering model may be more appropriate.

Rai, Durgesh; Beaucage, Gregory; Kedar, Ratkanthwar; Hadjichristidis, Nikos; Kunlun, Hong; Uhrig, David; Tsou, Andy

2013-03-01

167

Kinetic parameters for thermal decomposition of supramolecular polymers derived from diclofenac-meglumine supramolecular adducts.  

PubMed

Meglumine is an aminocarbohydrate able to form supramolecular adducts with organic acids. The recognition is based on hydrogen bonds and the structures resulting from the complexation have high solubility in water. This property has been exploited by the pharmaceutical industry in the improvement of existing drugs, and the successful example of this approach involves the poorly soluble non-steroidal anti-inflammatory drugs (NSAIDs). Investigation of the thermal behavior of adduct obtained from meglumine and the NSAID diclofenac revealed that a polymer-like material is formed from the self-assembly of diclofenac-meglumine adducts in the melt. This polymer showed a high molecular weight around 2.0×10(5)kDa. The kinetic parameters for the thermal decomposition step of the polymer were determined by the Capela-Ribeiro non-linear isoconversional method. From data for the TG curves in nitrogen atmosphere and heating rates of 5, 10, 15 and 20°Cmin(-1), the E(?) and B(?) terms could be determined, and consequently the pre-exponential factor, A(?), as well as the kinetic model, g(?). PMID:22561058

Cassimiro, Douglas L; Ferreira, Leonardo M B; Capela, Jorge M V; Crespi, Marisa S; Ribeiro, Clóvis A

2012-04-24

168

Hemorheological changes and characteristic parameters derived from whole blood viscometry in chronic heroin addicts.  

PubMed

A group of 15 chronic opioid addicts (DA) with mean age 26.5+/-7.3 years was studied by means of a rotational Contraves Low Shear 30 viscometer and the results have been compared with a control group of 19 healthy subjects. It was found that the mean whole blood viscosity values of the investigated group of heroin abusers (n=15) were elevated compared to that of healthy persons (n=19) over the whole shear rate range and fell by more than ten orders of magnitude (Savov et al., 2006). The present investigation uses the coefficients of the models of Ostwald-de-Walle (power law) and Herschel-Bulkley law, which describe whole blood flow curves (tau-gamma) within the shear rates range from 10(-2) to 10(2) s(-1) and itself incorporate whole blood viscosity data in the entire shear rate range. A significant difference in the mean yield shear stress tau(0) values of the drug abusers' group compared to the controls was found. A strong positive linear correlation was determined between the parameters of RBC aggregation in the group of heroin addicts confirming our previous results (Ivanov and Antonova, 2005; Savov, Zvetkova et al., 2007; Savov, Antonova et al., 2007) for intensive RBC and platelet aggregation and morphological changes in DA group. PMID:18503110

Antonova, N; Zvetkova, E; Ivanov, I; Savov, Y

2008-01-01

169

Testosterone and brain-derived neurotrophic factor interactions in the avian song control system.  

PubMed

Interaction between steroid sex hormones and brain-derived neurotrophic factor (BDNF) is a common feature of vertebrate brain organization. The avian song control system provides an excellent model for studying such interactions in neural circuits that regulate song, a learned sensorimotor behavior that is often sexually dimorphic and restricted to reproductive contexts. Testosterone (T) and its steroid metabolites interact with BDNF during development of the song system and in adult plasticity, including the addition of newborn neurons to the pallial nucleus HVC and seasonal changes in structure and function of these circuits. T and BDNF interact locally within HVC to influence cell proliferation and survival. This interaction may also occur transsynpatically; T increases the synthesis of BDNF in HVC, and BDNF protein is then released on to postsynaptic cells in the robust nucleus of the arcopallium (RA) where it has trophic effects. The interaction between sex steroids and BDNF is an example of molecular exploitation, with the evolutionarily ancient steroid-receptor complex having been captured by the more recently evolved BDNF. The functional linkage of sex steroids to BDNF may be of adaptive value in regulating the trophic effects of the neurotrophin in sexually dimorphic and reproductively relevant contexts. PMID:23123886

Brenowitz, E A

2012-10-30

170

Structural evolution in Pt isotopes with the interacting boson model Hamiltonian derived from the Gogny energy density functional  

SciTech Connect

Spectroscopic calculations are carried out for the description of the shape/phase transition in Pt nuclei in terms of the interacting boson model (IBM) Hamiltonian derived from (constrained) Hartree-Fock-Bogoliubov (HFB) calculations with the finite range and density-dependent Gogny-D1S energy density functional. Assuming that the many-nucleon driven dynamics of nuclear surface deformation can be simulated by effective bosonic degrees of freedom, the Gogny-D1S potential energy surface (PES) with quadrupole degrees of freedom is mapped onto the corresponding PES of the IBM. By using this mapping procedure, the parameters of the IBM Hamiltonian, relevant to the low-lying quadrupole collective states, are derived as functions of the number of valence nucleons. Merits of both Gogny-HFB and IBM approaches are utilized so that the spectra and the wave functions in the laboratory system are calculated precisely. The experimental low-lying spectra of both ground-state and sideband levels are well reproduced. From the systematics of the calculated spectra and the reduced E2 transition probabilities B(E2), the prolate-to-oblate shape/phase transition is shown to take place quite smoothly as a function of neutron number N in the considered Pt isotopic chain, for which the {gamma} softness plays an essential role. All of these spectroscopic observables behave consistently with the relevant PES and the derived parameters of the IBM Hamiltonian as functions of N. Spectroscopic predictions are also made for those nuclei that do not have enough experimental E2 data.

Nomura, K. [Department of Physics, University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan); Otsuka, T. [Department of Physics, University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan); Center for Nuclear Study, University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan); National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, Michigan 48824 (United States); Rodriguez-Guzman, R.; Sarriguren, P. [Instituto de Estructura de la Materia, CSIC, Serrano 123, E-28006 Madrid (Spain); Robledo, L. M. [Departamento de Fisica Teorica, Universidad Autonoma de Madrid, E-28049 Madrid (Spain)

2011-01-15

171

Modified parameter sets of M3Y-type semi-realistic nucleon-nucleon interactions for nuclear structure studies  

SciTech Connect

New parameter sets of Michigan three-range Yukawa-type semirealistic nucleon-nucleon interaction are obtained by taking into account the whole contribution of the interaction to the pairing. The interactions are applicable to nuclear structure studies via mean-field calculations and their extensions. Implementing self-consistent mean-field calculations for the spherical nuclei, the author confirms that the results do not change significantly from previous results, in which the parameters were determined by partly discarding the influence of the density-dependent repulsion on the pairing.

Nakada, H. [Department of Physics, Graduate School of Science, Chiba University, Yayoi-cho 1-33, Inage, Chiba 263-8522 (Japan)

2010-02-15

172

Numerical Studies of Small Repeating Earthquakes and Their Source Parameters Using Laboratory-derived Friction Laws  

NASA Astrophysics Data System (ADS)

Small repeating earthquakes have short recurrence times and known locations, and hence they present a rare predictable opportunity for detailed observation and insights into earthquake physics. That has been exploited in the San Andreas Fault Observatory at Depth (SAFOD) drilling project. It is important to establish realistic models for their occurrence, to provide a framework for proper interpretation of SAFOD data and other studies. One of the intriguing observation about repeating earthquakes is the scaling of their repeat time T and seismic moment M0 as T\\propto M00.17 (Nadeau and Johnson, 1998). The scaling is abnormal compared to T\\propto M01/3, the typical scaling that results from a simple conceptual model of circular ruptures with stress drop independent of the seismic moment and slip proportional to the repeat time. Several explanations for the discrepancy in scaling have been proposed, including high stress drop (Nadeau and Johnson, 1998), shading asperity (Sammis and Rice, 2001), and aseismic slip (Beeler et al., 2001). Our studies show that a model based on Dieterich-Ruina rate and state friction laws reproduces the observed abnormal scaling. In our 3D model, a small patch with rate-weakening friction is surrounded by a much larger region with rate-strengthening friction. Our simulations use the 3D methodology of Liu and Lapusta (AGU, 2006) that fully resolves all aspects of seismic and aseismic behavior of the fault. For a set of laboratory-based friction parameters, we can reproduce the observed scaling simply by varying the size of the rate-weakening patch. When the patch size is smaller than the nucleation size implied by the underlying rate and state formulation, the patch has fully aseismic slip. For larger patch sizes, small repeating events start to occur, with slip rates of order of 1 m/s and sharp stress drops. The events are accompanied by significant aseismic slip on the patch, providing a physical explanation for the idea of Beeler et al. (2001). Our recent and current work pursues several directions. We have studied properties of individual small events and found that their static stress drop, averaged over the zone of seismic slip, is in the typical range, although the stress drop is quite heterogeneous in space. We will use our simulations to investigate how well the average value of stress drop on the interface corresponds to the one determined from near-field seismograms. We have found a trade-off between values of frictional parameters and plate loading rate in determining the repeat time and moment of seismic events, and we will report on our current efforts to quantify it. Simulations in 2D models, needed to study a wider range of formulations, produce the same scaling, although individual small earthquakes have much larger moment and repeat time in 2D than in 3D. Our preliminary simulations with Ruina-Dieterich version of rate and state friction have results qualitatively similar to those with Dieterich-Ruina formulation. We are also exploring models that combine rate and state friction with dynamic weakening in the form of flash heating.

Chen, T.; Lapusta, N.

2007-12-01

173

Deriving the Physical Parameters of a Solar Ejection with an Isotropic Magnetohydrodynamic Evolutionary Model  

NASA Astrophysics Data System (ADS)

The time-space evolution of a ~50° wide coronal mass ejection (CME) on 2007 May 21 is followed remotely with the Solar Terrestrial Relations Observatory heliospheric imager HI-1, and measured in situ near Venus by the MESSENGER and Venus-Express spacecraft. The paper compares the observations of the CME structure with a simple, analytical magnetohydrodynamic force-free solution. It corresponds to a self-similar evolution, which gives a consistent picture of the main spatial-temporal features for both remote and in situ observations. Our main findings are (1) the self-similar evolution allows us to map the CME bright front into about 1/3 of the whole interplanetary counterpart of the coronal mass ejection (ICME, i.e., corresponding to the in situ observed passage of the plasma and magnetic field structure), in good quantitative agreement with the imaging measurements, (2) the cavity following the CME front maps into the rest of the ICME structure, 80% or more of which is consistent with a force free, cylindrically shaped flux rope, and (3) time and space conditions constrain the translational speed of the FR center to 301 km s-1, and the expansion speed of the FR core to 26 km s-1. A careful determination of the ICME cross-section and volume allows us to calculate the mass of the CME bright region (4.3 ± 1.1 1014 g) from the in situ measurements of the proton number density, which we assume to be uniform inside the bright region, of excellent agreement with the value estimated from the SECCHI HI-1 observations for the same structure. We provide model estimates for several global parameters including FR helicity (~2 × 1026 Weber2).

Berdichevsky, Daniel B.; Stenborg, Guillermo; Vourlidas, Angelos

2011-11-01

174

Spatial Prediction of Soil Classes by Using Soil Weathering Parameters Derived from vis-NIR Spectroscopy  

NASA Astrophysics Data System (ADS)

There is consensus in the scientific community about the great need of spatial soil information. Conventional mapping methods are time consuming and involve high costs. Digital soil mapping has emerged as an area in which the soil mapping is optimized by the application of mathematical and statistical approaches, as well as the application of expert knowledge in pedology. In this sense, the objective of the study was to develop a methodology for the spatial prediction of soil classes by using soil spectroscopy methodologies related with fieldwork, spectral data from satellite image and terrain attributes in simultaneous. The studied area is located in São Paulo State, and comprised an area of 473 ha, which was covered by a regular grid (100 x 100 m). In each grid node was collected soil samples at two depths (layers A and B). There were extracted 206 samples from transect sections and submitted to soil analysis (clay, Al2O3, Fe2O3, SiO2 TiO2, and weathering index). The first analog soil class map (ASC-N) contains only soil information regarding from orders to subgroups of the USDA Soil Taxonomy System. The second (ASC-H) map contains some additional information related to some soil attributes like color, ferric levels and base sum. For the elaboration of the digital soil maps the data was divided into three groups: i) Predicted soil attributes of the layer B (related to the soil weathering) which were obtained by using a local soil spectral library; ii) Spectral bands data extracted from a Landsat image; and iii) Terrain parameters. This information was summarized by a principal component analysis (PCA) in each group. Digital soil maps were generated by supervised classification using a maximum likelihood method. The trainee information for this classification was extracted from five toposequences based on the analog soil class maps. The spectral models of weathering soil attributes shown a high predictive performance with low error (R2 0.71 to 0.90). The spatial prediction of these attributes also showed a high performance (validations with R2> 0.78). These models allowed to increase spatial resolution of soil weathering information. On the other hand, the comparison between the analog and digital soil maps showed a global accuracy of 69% for the ASC-N map and 62% in the ASC-H map, with kappa indices of 0.52 and 0.45 respectively.

Ramirez-Lopez, Leonardo; Alexandre Dematte, Jose

2010-05-01

175

Evaluation of morphometric parameters of drainage networks derived from topographic maps and DEM in point of floods  

NASA Astrophysics Data System (ADS)

An evaluation of morphometric parameters of two drainage networks derived from different sources was done to determine the influence of sub-basins to flooding on the main channel in the Havran River basin (Bal?kesir-Turkey). Drainage networks for the sub-basins were derived from both topographic maps scaled 1:25.000 and a 10-m resolution digital elevation model (DEM) using geographic information systems (GIS). Blue lines, representing fluvial channels on the topographic maps were accepted as a drainage network, which does not depict all exterior links in the basin. The second drainage network was extracted from the DEM using minimum accumulation area threshold to include all exterior links. Morphometric parameters were applied to the two types of drainage networks at sub-basin levels. These parameters were used to assess the influence of the sub-basins on the main channel with respect to flooding. The results show that the drainage network of sub-basin 4—where a dam was constructed on its outlet to mitigate potential floods—has a lower influence morphometrically to produce probable floods on the main channel than that of sub-basins 1, 3, and 5. The construction of the dam will help reduce flooding on the main channel from sub-basin 4 but it will not prevent potential flooding from sub-basin 1, 3 and 5, which join the main channel downstream of sub-basin 4. Therefore, flood mitigation efforts should be considered in order to protect the settlement and agricultural lands on the floodplain downstream of the dam. In order to increase our understanding of flood hazards, and to determine appropriate mitigation solutions, drainage morphometry research should be included as an essential component to hydrologic studies.

Ozdemir, Hasan; Bird, Deanne

2009-02-01

176

Tables of Parameters for the Three Parameter Log Normal Probability Distribution.  

National Technical Information Service (NTIS)

This report is intended to present a single package to aid the practitioner who desires to use the three parameter log normal probability distribution. Theoretical derivations are presented which aid in identifying parameter interactions. Two methods of s...

C. L. Bates D. P. Lettenmaier S. J. Burges

1974-01-01

177

Multipolar Interaction Derived from d--f Hybridization in Pr-Based Filled Skutterudite Compounds  

NASA Astrophysics Data System (ADS)

The conduction bands of the skutterudite compounds are composed of p orbitals of the pnictogen cages and d orbitals of the transition metal ions. In this paper, we address the effect of hybridization between the d bands and localized 4f states in relation with ordering and fluctuation of multipole moments in Pr-based filled skutterudites. First, we study the properties of a non-degenerate d band around the zone center in the framework of a tight-binding band model. Introducing a realistic form of the d--f hybridization, we show that the ag band can be hybridized only with the ?8 orbitals of f electrons. Then, we derive d--f multipolar interactions from the hybridization in the localized limit of f electrons in which the basis states are restricted to the singlet--triplet crystal field states. It is found that the quadrupolar interaction of the Oxy-type becomes predominant in the case of the singlet ground state, whereas the triplet ground state apparently favors the magnetic interaction. The relationship with experimental results in the Pr skutterudites, especially in PrOs4Sb12 and PrFe4As12, is discussed in view of the nature of quadrupolar and magnetic interactions. It is shown that the complex non-collinear magnetic structure of Fe ions observed in the latter material is reproduced well by the effective d--f interaction.

Shiina, Ryousuke

2012-02-01

178

Studies on the interaction mechanism of aminopyrene derivatives with human tumor-related DNA.  

PubMed

Polycyclic aromatic hydrocarbons derivatives (PAHs) have been confirmed to be carcinogenic, teratogenic and mutagenic, and have the potential to cause human malignant diseases. In this work, interactions of two selected amino-PAHs (aminopyrene derivatives) and human tumor-related DNA were evaluated using spectroscopic and polyacrylamide gel electrophoresis (PAGE) methods. Spectroscopic results demonstrated that there were remarkable interactions between PAHs and the targeted DNA with the order of the binding ability as 1-AP>1-PBA. The binding constants of 1-AP with the targeted DNA were at the level of about 10(6) L/mol, while that of 1-PBA only to about 10(3) L/mol. 1-AP with a short side-chain acted mainly as an intercalator, and its interactions with DNA were strengthened with electrostatic forces. As for 1-PBA with a flexible long side-chain, the intercalation mode was dominated with an auxiliary role of Van der Wals forces and hydrogen bonds. Besides, the binding abilities of amino-PAHs to p53 DNA seemed stronger than that for C-myc DNA. PAGE results showed that the binding of amino-PAHs could further change the conformation of DNA sequences from the duplex to the antiparallel G-quadruplex. PMID:23608671

Li, Li; Lu, Jia; Zhou, Wenshu; Li, Huihui; Yang, Xiaodi

2013-04-04

179

Cytotoxic and DNA-topoisomerase effects of lapachol amine derivatives and interactions with DNA.  

PubMed

The cytotoxic activity of amino (3a-e), aza-1-antraquinone (4a-e) lapachol derivatives against Ehrlich carcinoma and human K562 leukemia cells was investigated. Cell viability was determined using MTT assay, after 48 (Ehrlich) or 96 h (K562) of culture, and vincristine (for K562 leukemia) and quercetin (for Ehrlich carcinoma) were used as positive controls. The results showed dose-dependent growth-inhibiting activities and that the amino derivatives were active against the assayed cells, whereas the 4a-e derivatives were not. The allylamine derivative 3a was the most active against Ehrlich carcinoma, with IC50 = 16.94 +/- 1.25 microM, and against K562 leukemia, with IC50 = 14.11 +/- 1.39 microM. The analogous lawsone derivative, 5a, was also active against Ehrlich carcinoma (IC50 = 23.89 +/- 2.3 microM), although the 5d and 5e derivatives showed lower activity. The interaction between 3a-d and calf thymus DNA was investigated by fluorimetric titration and the results showed a hyperchromic effect indicating binding to DNA as presented of ethidium bromide, used as positive control. The inhibitory action on DNA-topoisomerase II-a was also evaluated by a relaxation assay of supercoiled DNA plasmid, and the etoposide (200 microM) was used as positive control. Significant inhibitory activities were observed for 3a-d at 200 microM and a partial inhibitory action was observed for lapachol and methoxylapachol. PMID:17713652

Esteves-Souza, A; Figueiredo, D V; Esteves, A; Câmara, C A; Vargas, M D; Pinto, A C; Echevarria, A

2007-07-31

180

Intramolecular interactions of N-(3,5-di- tert-butyl-2-hydroxyphenyl)acetamide derivatives  

NASA Astrophysics Data System (ADS)

IR-Fourier spectroscopy methods are adopted to the study of intramolecular interactions occurring in CCl4 solutions of antivirally active derivatives of N-(3,5-di- tert-butyl-2-hydroxyphenyl)acetamide. Analysis of IR spectra has shown that intramolecular H-bonds O-H···O=C and N-H···O=C are formed in solutions of these compounds. The O-H···O=C and N-H···O=C bond strengths and the direction of the equilibrium shift between the two types of conformers depend on the type of carbonyl group substituent. An intramolecular O-H···O=C H-bond is characteristic of highly active derivatives of N-(3,5-di- tert-butyl-2-hydroxyphenyl)acetamide.

Belkov, M. V.; Harbachova, A. N.; Ksendzova, G. A.; Polozov, G. I.; Skornyakov, I. V.; Sorokin, V. L.; Tolstorozhev, G. B.; Shadyro, O. I.

2010-03-01

181

Lumpy - an interactive Lumped Parameter Modeling code based on MS Access and MS Excel.  

NASA Astrophysics Data System (ADS)

Several tracers for dating groundwater (18O/2H, 3H, CFCs, SF6, 85Kr) need lumped parameter modeling (LPM) to convert measured values into numbers with unit time. Other tracers (T/3He, 39Ar, 14C, 81Kr) allow the computation of apparent ages with a mathematical formula using radioactive decay without defining the age mixture that any groundwater sample represents. Also interpretation of the latter profits significantly from LPM tools that allow forward modeling of input time series to measurable output values assuming different age distributions and mixtures in the sample. This talk presents a Lumped Parameter Modeling code, Lumpy, combining up to two LPMs in parallel. The code is standalone and freeware. It is based on MS Access and Access Basic (AB) and allows using any number of measurements for both input time series and output measurements, with any, not necessarily constant, time resolution. Several tracers, also comprising very different timescales like e.g. the combination of 18O, CFCs and 14C, can be modeled, displayed and fitted simultaneously. Lumpy allows for each of the two parallel models the choice of the following age distributions: Exponential Piston flow Model (EPM), Linear Piston flow Model (LPM), Dispersion Model (DM), Piston flow Model (PM) and Gamma Model (GM). Concerning input functions, Lumpy allows delaying (passage through the unsaturated zone) shifting by a constant value (converting 18O data from a GNIP station to a different altitude), multiplying by a constant value (geochemical reduction of initial 14C) and the definition of a constant input value prior to the input time series (pre-bomb tritium). Lumpy also allows underground tracer production (4He or 39Ar) and the computation of a daughter product (tritiugenic 3He) as well as partial loss of the daughter product (partial re-equilibration of 3He). These additional parameters and the input functions can be defined independently for the two sub-LPMs to represent two different recharge areas. For a user defined choice of up to five parameters (mean residence times and dispersion parameters of the two sub-LPM plus the mixing ratios of the two models) the best fit can be determined. Fits can be assessed using different methods for the Goodness Of Fit. Input and output data are send to MS Excel for interactive display of modeling result and comparison with measurements. Excel only serves as data display; computations are performed in AB throughout. Lumpy allows display of time series and any combination of tracer vs. tracer plot. In the latter, the possible output data space assessable by the input variables can be displayed, to check if any of the model combinations under consideration is able to explain the measured data. Comparison and fit to measurements is possible after each of the two sub-models and after mixing these two. The talk will demonstrate the usefulness of this approach with examples from the Croatian Karst (Babinka 2007), the Fischa tracer test (Stolp et al., 2010) and the 30 years monthly tritium time series of the Danube (Aggarwal et al., 2010).

Suckow, A.

2012-04-01

182

Antimicrobial Activity and Bacterial-Membrane Interaction of Ovine-Derived Cathelicidins  

PubMed Central

Three ovine-derived cathelicidins, SMAP29, OaBac5mini, and OaBac7.5mini, were compared with respect to their antibacterial activities and interactions with membranes. SMAP29 was confirmed to be ?-helical, broad spectrum, and able to disrupt both the outer and the cytoplasmic membranes at relatively low concentrations. In contrast, the two proline- and arginine-rich OaBac peptides had more-modest antibacterial activities, reduced levels of lipopolysaccharide binding, and a lesser ability to depolarize the cytoplasmic membrane, consistent with a cytoplasmic target.

Anderson, Rachel C.; Hancock, Robert E. W.; Yu, Pak-Lam

2004-01-01

183

Interaction of Salmonella Typhimurium with Dendritic Cells Derived from Pluripotent Embryonic Stem Cells  

PubMed Central

Using an in vitro differentiation protocol we isolated cells with the properties of dendritic cells (DCs) from immunologically refractive pluripotent murine embryonic stem cells (ESCs). These ES-derived dendritic cells (ESDCs) expressed cytokines and were able to present antigen to a T cell line. Infection of ESDCs with Salmonella Typhimurium stimulated the expression of immune cell markers and thousands of murine genes, many associated with the immune response. Consequently, this system provides a novel in vitro model, amenable to genetic modification, for monitoring host/pathogen interactions.

Rossi, Raffaella; Hale, Christine; Goulding, David; Andrews, Robert; Abdellah, Zarah; Fairchild, Paul J.; Dougan, Gordon

2012-01-01

184

Tritium plasma experiment: parameters and potentials for fusion plasma-wall interaction studies.  

PubMed

The tritium plasma experiment (TPE) is a unique facility devoted to experiments on the behavior of deuterium/tritium in toxic (e.g., beryllium) and radioactive materials for fusion plasma-wall interaction studies. A Langmuir probe was added to the system to characterize the plasma conditions in TPE. With this new diagnostic, we found the achievable electron temperature ranged from 5.0 to 10.0 eV, the electron density varied from 5.0 × 10(16) to 2.5 × 10(18) m(-3), and the ion flux density varied between 5.0 × 10(20) to 2.5 × 10(22) m(-2) s(-1) along the centerline of the plasma. A comparison of these plasma parameters with the conditions expected for the plasma facing components (PFCs) in ITER shows that TPE is capable of achieving most (?800 m(2) of 850 m(2) total PFCs area) of the expected ion flux density and electron density conditions. PMID:21895244

Shimada, Masashi; Kolasinski, Robert D; Sharpe, J Phillip; Causey, Rion A

2011-08-01

185

Tritium Plasma Experiment (TPE) - parameters and potentials for fusion plasma-wall interaction studies  

SciTech Connect

The Tritium plasma experiment (TPE) is a unique facility devoted to experiments on the behavior of deuterium/tritium in toxic (e.g. beryllium) and radioactive materials for fusion plasma-wall interaction (PWI) studies. A Langmuir probe was added to the system to characterize the plasma conditions in TPE. With this new diagnostic, we found the achievable electron temperature ranged from 5.0 to 10.0 eV, the electron density varied from 5.0 x 10{sup 16} to 2.5 x 10{sup 18} m{sup -3}, and the ion flux density varied between 5.0 x 10{sup 20} to 2.5 x 10{sup 22} m{sup -2}s{sup -1} along the centerline of the plasma. A comparison of these plasma parameters with the conditions expected for the plasma facing components (PFCs) in ITER shows that TPE is capable of achieving most (approximately 800 m{sup 2} of 850 m{sup 2} total PFCs area) of the expected ion flux density and electron density conditions.

Masashi Shimada; Robert D. Kolasinski; J. Phillip Sharpe; Rion A. Causey

2011-08-01

186

Tritium plasma experiment: Parameters and potentials for fusion plasma-wall interaction studies  

SciTech Connect

The tritium plasma experiment (TPE) is a unique facility devoted to experiments on the behavior of deuterium/tritium in toxic (e.g., beryllium) and radioactive materials for fusion plasma-wall interaction studies. A Langmuir probe was added to the system to characterize the plasma conditions in TPE. With this new diagnostic, we found the achievable electron temperature ranged from 5.0 to 10.0 eV, the electron density varied from 5.0 x 10{sup 16} to 2.5 x 10{sup 18} m{sup -3}, and the ion flux density varied between 5.0 x 10{sup 20} to 2.5 x 10{sup 22} m{sup -2} s{sup -1} along the centerline of the plasma. A comparison of these plasma parameters with the conditions expected for the plasma facing components (PFCs) in ITER shows that TPE is capable of achieving most ({approx}800 m{sup 2} of 850 m{sup 2} total PFCs area) of the expected ion flux density and electron density conditions.

Shimada, Masashi; Sharpe, J. Phillip [Fusion Safety Program, Idaho National Laboratory, Idaho Falls, Idaho 83415 (United States); Kolasinski, Robert D.; Causey, Rion A. [Hydrogen and Metallurgical Science Department, Sandia National Laboratories, Livermore, California 94551 (United States)

2011-08-15

187

Vascular Morphogenesis of Adipose-Derived Stem Cells is Mediated by Heterotypic Cell-Cell Interactions  

PubMed Central

Adipose-derived stromal/stem cells (ASCs) are a promising cell source for vascular-based approaches to clinical therapeutics, as they have been shown to give rise to both endothelial and perivascular cells. While it is well known that ASCs can present a heterogeneous phenotypic profile, spontaneous interactions among these subpopulations that result in the formation of complex tissue structures have not been rigorously demonstrated. Our study reports the novel finding that ASCs grown in monolayers in the presence of angiogenic cues are capable of self-assembling into complex, three-dimensional vascular structures. This phenomenon is only apparent when the ASCs are seeded at a high density (20,000 cells/cm2) and occur through orchestrated interactions among three distinct subpopulations: CD31-positive cells (CD31+), ?-smooth muscle actin-positive cells (?SMA+), and cells that are unstained for both these markers (CD31?/?SMA?). Investigations into the kinetics of the process revealed that endothelial vessel-like structures initially arose from individual CD31+ cells through proliferation and their interactions with CD31?/?SMA? cells. During this period, ?SMA+ cells proliferated and appeared to migrate toward the vessel structures, eventually engaging in cell-cell contact with them after 1 week. By 2 weeks, the lumen-containing CD31+ vessels grew greater than a millimeter in length, were lined with vascular basement membrane proteins, and were encased within a dense, three-dimensional cluster of ?SMA+ and CD31?/?SMA? cells. The recruitment of ?SMA+ cells was largely due to platelet-derived growth factor (PDGF) signaling, as the inhibition of PDGF receptors substantially reduced ?SMA+ cell growth and vessel coverage. Additionally, we found that while hypoxia increased endothelial gene expression and vessel width, it also inhibited the growth of the ?SMA+ population. Together, these findings underscore the potential use of ASCs in forming mature vessels in vitro as well as the need for a further understanding of the heterotypic interactions among ASC subpopulations.

Hutton, Daphne L.; Logsdon, Elizabeth A.; Moore, Erika M.; Gabhann, Feilim Mac; Gimble, Jeffrey M.

2012-01-01

188

Photoisomerization of cyanine derivatives in 1-butyl-3-methylimidazolium hexafluorophosphate and aqueous glycerol: Influence of specific interactions  

SciTech Connect

Photoisomerization of two cyanine derivatives, 3,3{sup '}-diethyloxadicarbocyanine iodide (DODCI) and merocyanine 540 (MC 540), has been investigated in an ionic liquid, 1-butyl-3-methylimidazolium hexafluorophosphate and aqueous glycerol (93 wt % glycerol +7 wt % water) by measuring fluorescence lifetimes and quantum yields. The aim of this work is to understand how the rates of photoisomerization of DODCI and MC 540 are influenced by specific solute-solvent interactions besides the viscosity of the medium. For DODCI, it has been observed that the nonradiative rate constants, which represent the rates of photoisomerization, are almost identical in the ionic liquid and aqueous glycerol at given temperature, indicating that viscosity is the sole parameter that governs the rate of photoisomerization. In contrast, the photoisomerization rate constants of MC 540 have been found to be a factor of 2 higher in aqueous glycerol compared to the ionic liquid. The observed behavior is due to the zwitterionic character of MC 540, a consequence of which, the twisted state gets stabilized by the solute-solvent hydrogen bonding interactions in aqueous glycerol, thus lowering the barrier for isomerization.

Mali, K. S.; Dutt, G. B.; Mukherjee, T. [Radiation and Photochemistry Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400 085 (India)

2008-03-28

189

Inclusion interactions and molecular microcapsule of Salvia sclarea L. essential oil with ?-cyclodextrin derivatives  

Microsoft Academic Search

The inclusion interactions of ?-cyclodextrin (?-CD), heptakis (2,6-di-methyl)-?-CD (DM-?-CD), mono[2-O-(2-hydroxyethyl)]-?-CD (2-HE-?-CD), and mono[2-O-(2-hydro-xypropyl)]-?-CD (2-HP-?-CD) with Salvia sclarea L. essential oil (SEO) were investigated by spectrofluorimetry, and the various factors affecting the inclusion process were\\u000a examined in detail. At the same time, the formation constants at different temperatures and the thermodynamic parameters (?H, ?S and ?G) were calculated. The molecular microcapsule

Xiang-Nan Tian; Zi-Tao Jiang; Rong Li

2008-01-01

190

Mean-Field Derivation of the Interacting Boson Model Hamiltonian and Exotic Nuclei  

SciTech Connect

A novel way of determining the Hamiltonian of the interacting boson model (IBM) is proposed. Based on the fact that the potential energy surface of the mean-field model, e.g., the Skyrme model, can be simulated by that of the IBM, parameters of the IBM Hamiltonian are obtained. By this method, the multifermion dynamics of surface deformation can be mapped, in a good approximation, onto a boson system. The validity of this process is examined for Sm and Ba isotopes, and an application is presented to an unexplored territory of the nuclear chart, namely, the right lower corner of {sup 208}Pb.

Nomura, Kosuke; Shimizu, Noritaka [Department of Physics, University of Tokyo, Hongo, Bunkyo-ku, Tokyo, 113-0033 (Japan); Otsuka, Takaharu [Department of Physics, University of Tokyo, Hongo, Bunkyo-ku, Tokyo, 113-0033 (Japan); Center for Nuclear Study, University of Tokyo, Hongo, Bunkyo-ku Tokyo, 113-0033 (Japan); RIKEN, Hirosawa, Wako-shi, Saitama 351-0198 (Japan); National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, 48824 Michigan (United States)

2008-10-03

191

Comparison of dual-echo DSC-MRI- and DCE-MRI-derived contrast agent kinetic parameters  

PubMed Central

The application of dynamic susceptibility contrast (DSC) MRI methods to assess brain tumors is often confounded by the extravasation of contrast agent (CA). Disruption of the blood–brain barrier allows CA to leak out of the vasculature leading to additional T1, T2 and T2? relaxation effects in the extravascular space, thereby affecting the signal intensity time course in a complex manner. The goal of this study is to validate a dual-echo DSC-MRI approach that separates and quantifies the T1 and T2? contributions to the acquired signal and enables the estimation of the volume transfer constant, Ktrans, and the volume fraction of the extravascular extracellular space, ?e. To test the validity of this approach, DSC-MRI- and dynamic contrast enhanced (DCE) MRI-derived Ktrans and ?e estimates were spatially compared in both 9L and C6 rat brain tumor models. A high degree of correlation (concordance correlation coefficients >0.83, Pearson's r>0.84) and agreement was found between the DSC-MRI- and DCE-MRI-derived measurements. These results indicate that dual-echo DSC-MRI can be used to simultaneously extract reliable DCE-MRI kinetic parameters in brain tumors in addition to conventional blood volume and blood flow metrics.

Quarles, C. Chad; Gore, John C.; Xu, Lei; Yankeelov, Thomas E.

2012-01-01

192

Derivation and solution of a time-dependent, nonlinear, Schrodinger-like equation for the superconductivity order parameter  

SciTech Connect

A time-dependent, nonlinear, Schrodinger-like equation for the superconductivity order parameter is derived from the Gor'kov equations. Three types of traveling wave solutions of the equation are discussed. The phases and amplitudes of these solutions propagate at different speeds. The first type of solution has an amplitude that propagates as a soliton and it is suggested that this solution might correspond to the recently observed propagating collective modes of the order parameter. The amplitude of the second type of solution propagates as a periodic disturbance in space and time. It is suggested that this type of solution might explain the recently observed multiple values of the superconductor energy gap as well as the spatially inhomogenous superconducting state. The third type of solution, which is of a more general character, might provide some insight into non-periodic, inhomogeneous states occuring in superconductors. It is also proposed that quasiparticle injection and microwave irradiation might generate soliton-like disturbances in superconductors.

Esrick, M.A.

1981-01-01

193

Interaction between chitosan and uranyl ions. Role of physical and physicochemical parameters on the kinetics of sorption  

SciTech Connect

This work corresponds to the first part of our studies on the interactions between chitosan particles dispersed in water and uranyl ions. The measurements were obtained by ICP, and we considered the role of various physical and physicochemical parameters related to chitosan. We showed that the crystallinity, the particle dimensions, and the swelling in water of chitosan are parameters which are connected together and govern the kinetic laws of metal diffusion and sorption. The molecular mobility of the polymer chains is then essential parameter. 31 refs., 5 figs., 3 tabs.

Piron, E. [Universite Claude Bernard, Villeurbanne (France)]|[COGEMA, Velizy-Villacoublay (France); Accominotti, M. [Hopital Edouard Heriot, Lyon (France); Domard, A. [Universite Claude Bernard, Villeurbanne (France)

1997-03-19

194

Using Electronic Properties of Adamantane Derivatives to Analyze their Ion Channel Interactions: Implications for Alzheimer's Disease  

NASA Astrophysics Data System (ADS)

The derivatives of adamantane, which is a cage-like diamondoid structure, can be used as pharmaceuticals for the treatment of various diseases and disorders such as Alzheimer's disease. These drugs interact with ion channels, and they act by electronically and physically hindering the ion transport. The electronic properties of each compound influence the location and level of ion channel hindrance, and the specific use of each compound depends on the functional groups that are attached to the adamantane base chain. Computational analysis and molecular simulations of these different derivatives and the ion channels can provide useful insight into the effect that the functional groups have on the properties of the compounds. Using this information, conclusions can be made about the pharmaceutical mechanisms, as well as how to improve them or create new beneficial compounds. Focusing on the electronic properties, such as the dipole moments of the derivatives and amino acids in the ion channels, can provide more efficient predictions of how these drugs work and how they can be enhanced.

Bonacum, Jason

2013-03-01

195

CONTROL OF LASER RADIATION PARAMETERS: Tunable acousto-optic filters with the multiple interaction of light and sound  

NASA Astrophysics Data System (ADS)

Optical multipass schemes of the interaction of light and sound, which are promising for filtration of optical beams based on tunable acousto-optic filters, are studied. The features of operation of acousto-optic filters in the rejection and transmission regimes are considered. It is proved theoretically and confirmed experimentally that the use of multiple interaction improves the spectral and energy parameters of acousto-optic devices. The collinear and transverse geometry of acousto-optic interaction in cells based on a paratellurite crystal is studied in the double-pass, three-pass, and multipass diffraction regimes.

Voloshinov, V. B.; Magdich, L. N.; Knyazev, G. A.

2005-11-01

196

A methodology for determining interactions in probabilistic safety assessment models by varying one parameter at a time.  

PubMed

In risk analysis problems, the decision-making process is supported by the utilization of quantitative models. Assessing the relevance of interactions is an essential information in the interpretation of model results. By such knowledge, analysts and decisionmakers are able to understand whether risk is apportioned by individual factor contributions or by their joint action. However, models are oftentimes large, requiring a high number of input parameters, and complex, with individual model runs being time consuming. Computational complexity leads analysts to utilize one-parameter-at-a-time sensitivity methods, which prevent one from assessing interactions. In this work, we illustrate a methodology to quantify interactions in probabilistic safety assessment (PSA) models by varying one parameter at a time. The method is based on a property of the functional ANOVA decomposition of a finite change that allows to exactly determine the relevance of factors when considered individually or together with their interactions with all other factors. A set of test cases illustrates the technique. We apply the methodology to the analysis of the core damage frequency of the large loss of coolant accident of a nuclear reactor. Numerical results reveal the nonadditive model structure, allow to quantify the relevance of interactions, and to identify the direction of change (increase or decrease in risk) implied by individual factor variations and by their cooperation. PMID:20199656

Borgonovo, Emanuele

2010-02-25

197

Probing deep into the interaction of a fluorescent chalcone derivative and bovine serum albumin (BSA): an experimental and computational study.  

PubMed

In the present manuscript, a novel fluorescent chalcone derivative is synthesized and its photophysical properties are fully characterized. The designed fluorophore is applied as a probe to study protein-dye interactions with bovine serum albumin. Circular dichroism gave interesting results on the thermodynamics of the interaction. NMR spectroscopy, especially relaxation measurements, revealed the atoms in the chalcone derivative that interacts with the protein upon binding. Molecular docking calculations indicate that the most favourable binding sites are near the two tryptophan residues. Furthermore, ab initio and DFT calculations offer insights into the reactivity and physicochemical properties of this novel fluorophore. PMID:23680860

Alvim, Haline G O; Fagg, Emma L; de Oliveira, Aline L; de Oliveira, Heibbe C B; Freitas, Sonia M; Xavier, Mary-Ann E; Soares, Thereza A; Gomes, Alexandre F; Gozzo, Fabio C; Silva, Wender A; Neto, Brenno A D

2013-05-16

198

Structural Determinates for Apolipoprotein E-Derived Peptide Interaction with the ?7 Nicotinic Acetylcholine Receptor  

PubMed Central

Neuronal nicotinic acetylcholine receptor (nAChR) signaling has been implicated in a variety of normal central nervous system (CNS) functions as well as an array of neuropathologies. Previous studies have demonstrated both neurotoxic and neuroprotective actions of peptides derived from apolipoprotein E (apoE). It has been discovered that apoE-derived peptides inhibit native and recombinant ?7-containing nAChRs, indicating a direct interaction between apoE peptides and nAChRs. To probe the structure/function interaction between ?7 nAChRs and the apoE peptide apoE141-148, experiments were conducted in Xenopus laevis oocytes expressing wild-type and mutated nAChRs. Mutation of Trp55 to alanine blocks apoE peptide-induced inhibition of acetylcholine (ACh)-mediated ?7 nAChR responses. Additional mutations at Trp55 suggest that hydrophobic interactions between the receptor and apoE141-148 are essential for inhibition of ?7 nAChR function. A mutated apoE peptide also demonstrated decreased inhibition at ?7-W55A nAChRs as well as activity-dependent inhibition of both wild-type ?7 nAChRs and ?7-W55A receptors. Finally, a three-dimensional model of the ?7 nAChR was developed based on the recently refined Torpedo marmorata nACh receptor. A structural model is proposed for the binding of apoE141-148 to the ?7 nAChR where the peptide binds at the interface between two subunits, near the ACh binding site. Similar to the functional data, the computational docking suggests the importance of hydrophobic interactions between the ?7 nAChR and the apoE peptide for inhibition of receptor function. The current data suggest a mode for apoE peptide binding that directly blocks ?7 nAChR activity and consequently may disrupt nAChR signaling.

Gay, Elaine A.; Bienstock, Rachelle J.; Lamb, Patricia W.; Yakel, Jerrel L.

2009-01-01

199

Polarizable simulations with second order interaction model (POSSIM) force field: developing parameters for protein side-chain analogues.  

PubMed

A previously introduced polarizable simulations with second-order interaction model (POSSIM) force field has been extended to include parameters for small molecules serving as models for peptide and protein side-chains. Parameters have been fitted to permit reproducing many-body energies, gas-phase dimerization energies, and geometries and liquid-phase heats of vaporization and densities. Quantum mechanical and experimental data have been used as the target for the fitting. The POSSIM framework combines accuracy of a polarizable force field and computational efficiency of the second-order approximation of the full-scale induced point dipole polarization formalism. The resulting parameters can be used for simulations of the parameterized molecules themselves or their analogues. In addition to this, these force field parameters are currently being used in further development of the POSSIM fast polarizable force field for proteins. PMID:23420678

Li, Xinbi; Ponomarev, Sergei Y; Sa, Qina; Sigalovsky, Daniel L; Kaminski, George A

2013-02-19

200

Prediction of drug-polymer miscibility through the use of solubility parameter based Flory-Huggins interaction parameter and the experimental validation: PEG as model polymer.  

PubMed

Important consideration for developing physically stable solid dispersion is miscibility of drug in carrier matrix. It is possible to predict thermodynamics of binary system through free energy calculations based on Flory-Huggins interaction parameter (?(dp)). In present study, PEG 6000 as model polymer and dataset comprising commonly used drugs/excipients was selected. The three-dimensional solubility parameter based on group contribution method was utilized for systemic calculation of ?(dp) of the polymer with each compound in data set. On the basis of the values of ?(dp), it was possible to categorize all the compounds into three distinct categories, Types I and II: compounds predicted to be miscible and immiscible respectively with the polymer in all proportions and Type III: compounds expected to exhibit composition dependent miscibility behavior. The Bagley plot showed that majority of points for Type I fall in a region, which can approximately be delimited by a circle. Experimental verification through thermal analysis revealed that though it was possible to predict correctly miscibility behavior of Type II class compounds, distinction between Types I and III was less evident. Hence, solubility parameter based ?(dp) may be used as an initial tool for fast screening of immiscible combination of polymer and drug. PMID:23649486

Thakral, Seema; Thakral, Naveen K

2013-05-06

201

Glionitrin A, an antibiotic-antitumor metabolite derived from competitive interaction between abandoned mine microbes  

SciTech Connect

The nutrient conditions present in abandoned coal mine drainages create an extreme environment where defensive and offensive microbial interactions could be critical for survival and fitness. Coculture of a mine drainage-derived Sphingomonas bacterial strain, KMK-001, and a mine drainage-derived Aspergillus fumigatus fungal strain, KMC-901, resulted in isolation of a new diketopiperazine disulfide, glionitrin A (1). Compound 1 was not detected in monoculture broths of KMK-001 or KMC-901. The structure of 1, a (3S,10aS) diketopiperazine disulfide containing a nitro aromatic ring, was based on analysis of MS, NMR, and circular dichroism spectra and confirmed by X-ray crystal data. Glionitrin A displayed significant antibiotic activity against a series of microbes including methicillin-resistant Staphylococcus aureus. An in vitro MTT cytotoxicity assay revealed that 1 had potent submicromolar cytotoxic activity against four human cancer cell lines: HCT-116, A549, AGS, and DU145. The results provide further evidence that microbial coculture can produce novel biologically relevant molecules.

Park, H.B.; Kown, H.C.; Lee, C.H.; Yang, H.O. [Korean Institute of Science & Technology KIST, Kangnung (Republic of Korea)

2009-02-15

202

Polymer-Drug Interactions in Tyrosine-Derived Triblock Copolymer Nanospheres: a Computational Modeling Approach  

PubMed Central

A combination of Molecular Dynamics (MD) simulations and docking calculations was employed to model and predict polymer-drug interactions in self-assembled nanoparticles consisting of ABA-type triblock copolymers, where A-blocks are poly(ethylene glycol) units and B-blocks are low molecular weight tyrosine-derived polyarylates. This new computational approach was tested on three representative model compounds: nutraceutical curcumin, anti-cancer drug paclitaxel and pre-hormone vitamin D3. Based on this methodology, the calculated binding energies of polymer-drug complexes can be correlated with maximum drug loading determined experimentally. Furthermore, the modeling results provide an enhanced understanding of polymer-drug interactions, revealing subtle structural features that can significantly affect the effectiveness of drug loading (as demonstrated for a fourth tested compound, anticancer drug camptothecin). The present study suggests that computational calculations of polymer-drug pairs hold the potential of becoming a powerful prescreening tool in the process of discovery, development and optimization of new drug delivery systems, reducing both the time and the cost of the process.

Costache, Aurora D.; Sheihet, Larisa; Zaveri, Krishna; Knight, Doyle D.; Kohn, Joachim

2009-01-01

203

Fermi Surface, Fermi Velocity, and Electron--Phonon Interaction Parameter in Nb.  

National Technical Information Service (NTIS)

A Korringa--Kohn--Rostoker band structure formalism was used to fit extremal areas and effective masses obtained from de Haas--van Alphen measurements by using the appropriate cubic scattering phase shifts and their energy derivatives as disposable parame...

D. H. Dye D. P. Karim J. B. Ketterson G. W. Crabtree

1977-01-01

204

CJX1, an amlodipine derivative, interacts with ATPase of human P-glycoprotein.  

PubMed

Our aim has been to elucidate the possible mechanism of CJX1, an amlodipine derivative, in the modulation of P-gp function by determining its effect on P-gp ATPase activity. Basal P-gp ATPase activity was increased by CJX1 with half-maximal activity concentration (Km) of 8.6+/-1.4 microM. Kinetic analysis indicated a non-competitive inhibition of Verapamil (Ver)-stimulated P-gp ATPase activity by CJX1 and competitive inhibition of CJX1-stimulated P-gp ATPase activity by tetrandrine (Tet). The effect of CsA on CJX1-stimulated and Ver-stimulated P-gp ATPase activity was non-competitive and competitive inhibition, respectively. These findings implying that CJX1 and Tet can bind P-gp either on overlapping sites or distinct but interacting sites, while CJX1 and Ver as well as CsA can bind P-gp on separated sites in K562/DOX cells. Furthermore, the combined effect of CJX1 and Ver has been evaluated isobolographically in numerous fixed-ratio combinations of 1:1, 1:2, 1:4, 1:8, 1:10 in K562/DOX cells. The results show that mixtures of both drugs at these fixed-ratios exerted synergistic interactions, indicating that when the two reverses that bind P-gp on separated sites are combined, each can contribute to the overall interaction with P-gp, leading to the greater effect than that by either agent alone. PMID:19589390

Ji, Bian-Sheng; He, Ling

2009-07-07

205

Heritability of model-derived parameters of beta cell secretion during intravenous and oral glucose tolerance tests: a study of twins  

Microsoft Academic Search

Aims\\/hypothesis  The genetic architecture of model-derived parameters of beta cell function has never been assessed. Therefore, we estimated heritability (h2) for model-derived phenotypes of insulin secretion in twins.Methods  Thirty-three monozygotic (MZ) and 23 dizygotic (DZ) twin pairs from the Finnish Twin Cohort Study underwent an OGTT (plasma glucose\\/C-peptide at 0, 30, 60, 90 and 120 min). A subset of the twin pairs (21

M. Lehtovirta; J. Kaprio; L. Groop; M. Trombetta; R. C. Bonadonna

2005-01-01

206

Entropy and superfluid critical parameters of a strongly interacting Fermi gas  

NASA Astrophysics Data System (ADS)

Strongly interacting Fermi gases provide a paradigm for studying strong interactions in nature. Strong interactions play a central role in the physics of a wide range of exotic systems, including high temperature superconductors, neutron stars, quark-gluon plasmas, and even a particular class of black holes. In an ultracold degenerate 6Li Fermi gas, interactions between the atoms in the two lowest hyperfine states can be widely tuned by a magnetic-field-dependent collisional resonance. At the resonance, the strongly interacting Fermi gas has an infinite s-wave scattering length and a negligible potential range, which ensures that the behavior of the gas is independent of the microscopic details of the interparticle interactions. In this limit, a strongly interacting Fermi gas is known as the unitary Fermi gas. The unitary Fermi gas emerges as one of the most fascinating problems in current many-body physics. It not only exhibits universal thermodynamic properties in common with a variety of strongly interacting systems, but also shows ideal hydrodynamic behavior. In this dissertation, I present the first model-independent thermodynamic study of a strongly interacting degenerate Fermi gas. The measurements determine the entropy and energy. The entropy versus energy data has been adopted by several theoretical groups as a benchmark to test current strong-coupling many-body theories, which reveals universal thermodynamics in unitary Fermi gases. My measurements show a transition in the energy-entropy behavior at Sc/kB = 2.2 +/- 0.1 corresponding to the energy Ec/EF = 0.83 +/- 0.02, where Sc and Ec are the critical entropy and energy per particle respectively, k B is Boltzmann constant, and EF is the Fermi energy of a trapped gas. This behavior change of entropy is interpreted as a thermodynamic signature of a superfluid transition in a strongly interacting Fermi gas. By parametrization of energy-entropy data, the temperature is extracted by T = ?E/?S, where E and S are the energy and entropy of a strongly interacting Fermi gas. I find that the critical temperature is about T/TF = 0.21 +/- 0.01, which agrees extremely well with very recent theoretical predictions. I also present an investigation of viscosity from the hydrodynamics of a strongly interacting Fermi gas. First, the study of the hydrodynamic expansion of a rotating strongly interacting Fermi gas reveals nearly prefect irrotational flow arising in both the superfluid and the normal fluid regime. Second, by modeling the damping data of the breathing mode, I present an estimation of the upper bound of viscosity in a strongly interacting Fermi gas. Using the entropy data, this study provides the first experimental estimate of the ratio of the viscosity eta to the entropy density s in strongly interacting Fermi systems. Recently the lower bound of eta/s is conjectured by using a string theory method, which shows eta/ s ? h/(4pikB). Our experimental estimate indicates that this quantity in strongly interacting Fermi gases approaches the lower bound limit. Finally, I describe the technical details of building a new all-optical cooling and trapping apparatus in our lab for the purpose of the above research as well as our studies on optimizing the evaporative cooling of a unitary Fermi gas in an optical trap.

Luo, Le

207

Interactive Initialization of Heat Flux Parameters for Numerical Models Using Satellite Temperature Measurements.  

National Technical Information Service (NTIS)

Progress made in HCMM research, including testing the interactive minicomputer system and preparation of a paper on the analysis of regional scale soil moisture patterns, is summarized. An exhibit on remote sensing including a videotape display of HCMM im...

T. N. Carlson

1982-01-01

208

Baseline tissue Doppler imaging-derived echocardiographic parameters and left ventricle reverse remodelling following cardiac resynchronization therapy introduction  

PubMed Central

Introduction The aim of the study was to assess the relation of baseline mechanical dyssynchrony with the left ventricular end-systolic volume (LVESV) decrease following cardiac resynchronization (CRT) therapy introduction. Material and methods Sixty consecutive patients (aged 66.3 ± 8.7 years; 57 men) with chronic heart failure (71.7% of ischaemic and 28.3% of non-ischaemic origin) and current indications for CRT were assessed before and 3 months after biventricular heart stimulator implantation. Longitudinal movements of twelve segments of the left ventricle (LV) (6 basal and 6 midlevel) and two segments of the right ventricle (RV) were analysed using tissue Doppler imaging (TDI) techniques with time from onset of Q wave in ECG to peak systolic velocity in colour-coded TDI (TTDI), time to peak strain (Tstrain) and time to peak strain rate (Tstrain rate). Minimal and maximal time differences within LV and between LV and RV walls were calculated. Results In the study group LVEF and 6-min walk test distance increased, while NYHA class, NT-proBNP level, left ventricular end-diastolic volume and LVESV decreased. Significant correlations between the magnitude of LVESV reduction with maximal time differences between Tstrain of 12 LV segments (r=0.34, p = 0.017) and time differences between TTDI basal LV-RV segments (r = –0.29, p=0.041) were found. Conclusions Only a few TDI-derived parameters such as maximal time differences between Tstrain of 12 LV segments and TTDI difference of LV-RV basal segments can be useful to predict the magnitude of left ventricle reverse remodelling after CRT introduction.

Wilinski, Jerzy; Czarnecka, Danuta; Wojciechowska, Wiktoria; Kloch-Badelek, Malgorzata; Jastrzebski, Marek; Bacior, Bogumila; Sondej, Tomasz; Kusiak, Aleksander

2011-01-01

209

Effect of sucrose on molecular and interaction parameters of sodium caseinate in aqueous solution: relationship to protein gelation  

Microsoft Academic Search

The effect of sucrose on molecular and interaction parameters of sodium caseinate in aqueous medium has been investigated using static and dynamic multi-angle laser light scattering over a wide range of sucrose concentration (from 10 to 78 w\\/v%) and pH values (from 7.0 to 3.5). Measurements have been made of the molar mass, the radius of gyration, the hydrodynamic radius,

Larisa E Belyakova; Anna S Antipova; Maria G Semenova; Eric Dickinson; Lara Matia Merino; Elena N Tsapkina

2003-01-01

210

Simulations of anionic lipid membranes: development of interaction-specific ion parameters and validation using NMR data.  

PubMed

Overbinding of ions to lipid head groups is a potentially serious artifact in simulations of charged lipid bilayers. In this study, the Lennard-Jones radii in the CHARMM force field for interactions of Na(+) and lipid oxygen atoms of carboxyl, phosphate, and ester groups were revised to match osmotic pressure data on sodium acetate and electrophoresis data on palmitoyloleoyl phosphatidylcholine (POPC) vesicles. The new parameters were then validated by successfully reproducing previously published experimental NMR deuterium order parameters for dimyristoyl phosphatidylglycerol (DMPG) and newly obtained values for palmitoyloleoyl phosphatidylserine (POPS). Although the increases in Lennard-Jones diameters are only 0.02-0.12 Å, they are sufficient to reduce Na+ binding, and thereby increase surface areas per lipid by 5-10% compared with the unmodified parameters. PMID:23924441

Venable, Richard M; Luo, Yun; Gawrisch, Klaus; Roux, Benoît; Pastor, Richard W

2013-08-22

211

Effect of formulation parameters and drug-polymer interactions on drug release from starch acetate matrix tablets.  

PubMed

The aim of this study was to determine, whether interactions between a drug and hydrophobic polymer matrix are present, and if so, how they affect the drug release. In addition, the most important formulation parameters, for example porosity or structure of the tablet, which have the greatest impact on drug release, were defined. Six different drug compounds, that is allopurinol, acyclovir, metronidazole, paracetamol, salicylamide and theophylline, were used in different formulations with hydrophobic starch acetate (DS 2.7) as a matrix forming polymer. Results indicate that the formulation parameters describing directly or indirectly the structure of the matrix, such as porosity, compaction force and the particle size fraction of the filler-binder, have the strongest impact on drug release. The contribution of drug property based variables is not as high as formulation parameters, but they cannot be overlooked. The contribution of water solubility and dissolution rate of the compound are obvious, but there are other significant parameters, which describe the hydrophobic and hydrophilic regions of the molecule, that also affect the drug release. This can be seen especially with the salicylamide: compound which appears to have a strong and sufficiently high hydrophobic region that interacts with starch acetate and impairs the drug release. PMID:19177516

Pajander, Jari; Korhonen, Ossi; Laamanen, Maria; Ryynänen, Eeva-Leena; Grimsey, Ian; van Veen, Bert; Ketolainen, Jarkko

2009-10-01

212

Diurnal Variability of Regional Cloud and Clear-Sky Radiative Parameters Derived from GOES Data. Part III: November 1978 Radiative Parameters  

Microsoft Academic Search

The diurnal variability of the radiation emitted and reflected from the earth-atmosphere is investigated at the regional scale using November 1978 GOES-East visible and infrared data and GOES-derived cloud information. Narrowband GOES data are converted to broadband radiances using spectral calibration functions determined empirically from colocated Nimbus-7 ERB and GOES-East measurements over ocean, land and cloud surfaces. Shortwave radiances are

Patrick Minnis; Edwin F. Harrison

1984-01-01

213

Interstellar Gas Flow Parameters Derived from Interstellar Boundary Explorer-Lo Observations in 2009 and 2010: Analytical Analysis  

NASA Astrophysics Data System (ADS)

Neutral atom imaging of the interstellar gas flow in the inner heliosphere provides the most detailed information on physical conditions of the surrounding interstellar medium (ISM) and its interaction with the heliosphere. The Interstellar Boundary Explorer (IBEX) measured neutral H, He, O, and Ne for three years. We compare the He and combined O+Ne flow distributions for two interstellar flow passages in 2009 and 2010 with an analytical calculation, which is simplified because the IBEX orientation provides observations at almost exactly the perihelion of the gas trajectories. This method allows separate determination of the key ISM parameters: inflow speed, longitude, and latitude, as well as temperature. A combined optimization, as in complementary approaches, is thus not necessary. Based on the observed peak position and width in longitude and latitude, inflow speed, latitude, and temperature are found as a function of inflow longitude. The latter is then constrained by the variation of the observed flow latitude as a function of observer longitude and by the ratio of the widths of the distribution in longitude and latitude. Identical results are found for 2009 and 2010: an He flow vector somewhat outside previous determinations (?ISM? = 79fdg0+3fdg0(-3fdg5), ? ISM? = -4fdg9 ± 0fdg2, V ISM? = 23.5 + 3.0(-2.0) km s-1, T He = 5000-8200 K), suggesting a larger inflow longitude and lower speed. The O+Ne temperature range, T O+Ne = 5300-9000 K, is found to be close to the upper range for He and consistent with an isothermal medium for all species within current uncertainties.

Möbius, E.; Bochsler, P.; Bzowski, M.; Heirtzler, D.; Kubiak, M. A.; Kucharek, H.; Lee, M. A.; Leonard, T.; Schwadron, N. A.; Wu, X.; Fuselier, S. A.; Crew, G.; McComas, D. J.; Petersen, L.; Saul, L.; Valovcin, D.; Vanderspek, R.; Wurz, P.

2012-02-01

214

Study on the Inclusion Interactions of ??Cyclodextrin and Its Derivative with Clomipramine by Spectroscopy and Its Analytic Application  

Microsoft Academic Search

The inclusion interactions of ??cyclodextrin (??CD) and its derivative, namely hydroxypropyl???cyclodextrin (HP???CD) with clomipramine (CLOM) have been investigated. The guest molecule was clomipramine and inclusion complexes were characterized by UV, H NMR, C NMR, and 2D NMR spectroscopy. The main factors affecting the inclusion interaction were discussed in detail. The inclusion complexation behaviour of cyclodextrins with clomipramine was studied in

Wieslawa Misiuk; Magdalena Zalewska

2008-01-01

215

A global wave parameter database for wave-current-turbulence interaction studies  

Microsoft Academic Search

Ocean surface mixing and drift are functions of the surface Stokes drift, Uss, volume Stokes transport TS, a wave breaking height scale Hswg, and the flux of energy from waves to ocean turbulent kinetic energyoc. Here we describe a global database of these parameters, estimated from a well-validated numerical wave model, that covers the years 2003 to 2007. Compared to

Nicolas Rascle; Fabrice Ardhuin; Pierre Queffeulou; Denis Croize-Fillon

216

FOCUS: An Interactive Crystal Electric Field Parameter Fitting Package Using Neutron Scattering Data.  

National Technical Information Service (NTIS)

The aim of FOCUS is to provide an easy-to-use program fitting package for crystal electric field parameter determination of rare earth containing materials. In general, neutron spectra of crystal electric field excitations are too complex to be run by bat...

P. Fabi

1995-01-01

217

Synthesis and interaction studies of benzimidazole derivative with human serum albumin  

NASA Astrophysics Data System (ADS)

A benzimidazole derivative, 1-(2-picolyl)-3-(2-picolyl) benzimidazole iodide (PPB), was synthesized. Fourier transform infrared spectroscopy (FT-IR), UV-visible, three-dimensional (3D) fluorescence, synchronous fluorescence (SF) and fluorescence spectroscopic methods were used to determine the PPB binding mode and the effects of PPB on protein stability and secondary structure. Fluorescence results revealed the presence of static type of quenching mechanism in the binding of PPB to human serum albumin (HSA). The binding constants between PPB and HSA were obtained according to Scatchard equation. The number of binding sites, the binding constants and the thermodynamic parameters were measured. The results showed a spontaneous binding of PPB to HSA through hydrogen bonds and van der Waals forces. In addition, the distance between PPB and the Trp 214 was estimated via employing the Förster's non-radiative energy transfer theory, and was found to be 3.49 nm, which indicated that PPB can bind to HSA with high probability. Site marker competitive experiments indicated that the binding of PPB to HSA primarily took place in subdomain IIA.

Liu, Jianming; Yue, Yuanyuan; Liu, Muwen; Zhang, Ningfei; Zhuo, Kelei

2011-11-01

218

Synthesis and interaction studies of benzimidazole derivative with human serum albumin.  

PubMed

A benzimidazole derivative, 1-(2-picolyl)-3-(2-picolyl) benzimidazole iodide (PPB), was synthesized. Fourier transform infrared spectroscopy (FT-IR), UV-visible, three-dimensional (3D) fluorescence, synchronous fluorescence (SF) and fluorescence spectroscopic methods were used to determine the PPB binding mode and the effects of PPB on protein stability and secondary structure. Fluorescence results revealed the presence of static type of quenching mechanism in the binding of PPB to human serum albumin (HSA). The binding constants between PPB and HSA were obtained according to Scatchard equation. The number of binding sites, the binding constants and the thermodynamic parameters were measured. The results showed a spontaneous binding of PPB to HSA through hydrogen bonds and van der Waals forces. In addition, the distance between PPB and the Trp 214 was estimated via employing the Förster's non-radiative energy transfer theory, and was found to be 3.49 nm, which indicated that PPB can bind to HSA with high probability. Site marker competitive experiments indicated that the binding of PPB to HSA primarily took place in subdomain IIA. PMID:21820945

Liu, Jianming; Yue, Yuanyuan; Liu, Muwen; Zhang, Ningfei; Zhuo, Kelei

2011-07-23

219

Lens Epithelium-derived Growth Factor/p75 Interacts with the Transposase-derived DDE Domain of PogZ*S?  

PubMed Central

Lens epithelium-derived growth factor/p75 (LEDGF/p75) is a prominent cellular interaction partner of human immunodeficiency virus-1 (HIV-1) integrase, tethering the preintegration complex to the host chromosome. In light of the development of LEDGF/p75-integrase interaction inhibitors, it is essential to understand the cell biology of LEDGF/p75. We identified pogZ as new cellular interaction partner of LEDGF/p75. Analogous to lentiviral integrase, pogZ, a domesticated transposase, carries a DDE domain, the major determinant for LEDGF/p75 interaction. Using different in vitro and in vivo approaches, we corroborated the interaction between the C terminus of LEDGF/p75 and the DDE domain of pogZ, revealing an overlap in the binding of pogZ and HIV-1 integrase. Competition experiments showed that integrase is efficient in displacing pogZ from LEDGF/p75. Moreover, pogZ does not seem to play a role as a restriction factor of HIV. The finding that LEDGF/p75 is capable of interacting with a DDE domain protein that is not a lentiviral integrase points to a profound role of LEDGF/p75 in DDE domain protein function.

Bartholomeeusen, Koen; Christ, Frauke; Hendrix, Jelle; Rain, Jean-Christophe; Emiliani, Stephane; Benarous, Richard; Debyser, Zeger; Gijsbers, Rik; De Rijck, Jan

2009-01-01

220

Solar Wind, Interplanetary Magnetic Field, and Geodipole Tilt Control of Central Plasma Sheet Parameters and Magnetotail Geometry as Derived From Geotail's LEP and MGF Data  

Microsoft Academic Search

Simple analytical models have been derived for the first time, describing the 2-D distribution (along and across the Earth's magnetotail) of the central plasma sheet (CPS) ion temperature, density, and pressure, as functions of the incoming solar wind and IMF parameters, in the range of distances between 10 and 50 RE. Another result of this effort is a new quantitative

N. A. Tsyganenko

2002-01-01

221

Hydrophobic folding units derived from dissimilar monomer structures and their interactions.  

PubMed Central

We have designed an automated procedure to cut a protein into compact hydrophobic folding units. The hydrophobic units are large enough to contain tertiary non-local interactions, reflecting potential nucleation sites during protein folding. The quality of a hydrophobic folding unit is evaluated by four criteria. The first two correspond to visual characterization of a structural domain, namely, compactness and extent of isolation. We use the definition of Zehfus and Rose (Zehfus MH, Rose GD, 1986, Biochemistry 25:35-340) to calculate the compactness of a cut protein unit. The isolation of a unit is based on the solvent accessible surface area (ASA) originally buried in the interior and exposed to the solvent after cutting. The third quantity is the hydrophobicity, equivalent to the fraction of the buried non-polar ASA with respect to the total non-polar ASA. The last criterion in the evaluation of a folding unit is the number of segments it includes. To conform with the rationale of obtaining hydrophobic units, which may relate to early folding events, the hydrophobic interactions are implicitly and explicitly applied in their generation and assessment. We follow Holm and Sander (Holm L, Sander C, 1994, Proteins 19:256-268) to reduce the multiple cutting-point problem to a one-dimensional search for all reasonable trial cuts. However, as here we focus on the hydrophobic cores, the contact matrix used to obtain the first non-trivial eigenvector contains only hydrophobic contracts, rather than all, hydrophobic and hydrophilic, interactions. This dataset of hydrophobic folding units, derived from structurally dissimilar single chain monomers, is particularly useful for investigations of the mechanism of protein folding. For cases where there are kinetic data, the one or more hydrophobic folding units generated for a protein correlate with the two or with the three-state folding process observed. We carry out extensive amino acid sequence order independent structural comparisons to generate a structurally non-redundant set of hydrophobic folding units for fold recognition and for statistical purposes.

Tsai, C. J.; Nussinov, R.

1997-01-01

222

Enterocyte microvillus-derived vesicles detoxify bacterial products and regulate epithelial-microbial interactions.  

PubMed

The continuous monolayer of intestinal epithelial cells (IECs) lining the gut lumen functions as the site of nutrient absorption and as a physical barrier to prevent the translocation of microbes and associated toxic compounds into the peripheral vasculature. IECs also express host defense proteins such as intestinal alkaline phosphatase (IAP), which detoxify bacterial products and prevent intestinal inflammation. Our laboratory recently showed that IAP is enriched on vesicles that are released from the tips of IEC microvilli and accumulate in the intestinal lumen. Here, we show that these native "lumenal vesicles" (LVs) (1) contain catalytically active IAP that can dephosphorylate lipopolysaccharide (LPS), (2) cluster on the surface of native lumenal bacteria, (3) prevent the adherence of enteropathogenic E. coli (EPEC) to epithelial monolayers, and (4) limit bacterial population growth. We also find that IECs upregulate LV production in response to EPEC and other Gram-negative pathogens. Together, these results suggest that microvillar vesicle shedding represents a novel mechanism for distributing host defense machinery into the intestinal lumen and that microvillus-derived LVs modulate epithelial-microbial interactions. PMID:22386311

Shifrin, David A; McConnell, Russell E; Nambiar, Rajalakshmi; Higginbotham, James N; Coffey, Robert J; Tyska, Matthew J

2012-03-01

223

Enterocyte microvillus-derived vesicles detoxify bacterial products and regulate epithelial-microbial interactions  

PubMed Central

SUMMARY The continuous monolayer of intestinal epithelial cells (IECs) lining the gut lumen functions as the site of nutrient absorption and as a physical barrier to prevent the translocation of microbes and associated toxic compounds into the peripheral vasculature [1]. IECs also express host defense proteins such as intestinal alkaline phosphatase (IAP), which detoxify bacterial products and prevent intestinal inflammation [2-5]. Our laboratory recently showed that IAP is enriched on vesicles that are released from the tips of IEC microvilli and accumulate in the intestinal lumen [6, 7]. Here, we show that these native ‘lumenal vesicles’ (LVs): (i) contain catalytically active IAP that can dephosphorylate lipopolysaccharide (LPS), (ii) cluster on the surface of native lumenal bacteria, (iii) prevent the adherence of enteropathogenic E. coli (EPEC) to epithelial monolayers, and (iv) limit bacterial population growth. We also find that IECs upregulate LV production in response to EPEC and other Gram-negative pathogens. Together, these results suggest that microvillar vesicle shedding represents a novel mechanism for distributing host defense machinery into the intestinal lumen, and that microvillus-derived LVs modulate epithelial-microbial interactions.

Shifrin, David A.; McConnell, Russell E.; Nambiar, Rajalakshmi; Higginbotham, James N.; Coffey, Robert J.; Tyska, Matthew J.

2012-01-01

224

Interactions of a platinum-modified perylene derivative with the human telomeric G-quadruplex.  

PubMed

The interactions of a newly synthesized platinum-modified perylene derivative, compound 7 ([{Pt(dien)}(2)(?-4-S,S')](NO(3))(4) (dien = diethylenetriamine, 4 = N,N'-bis(1-(2-aminoethyl)-1,3-dimethylthiourea)-3,4,9,10-perylenetetracarboxylic acid diimide), with the human telomeric repeat were studied using various model oligo(deoxy)ribonucleotides to mimic the polymorphic nature of the telomeric G-quadruplex. UV/visible spectroscopy, CD spectropolarimetry, electrospray mass spectrometry (ES-MS), and isothermal titration calorimetry (ITC) were used to demonstrate that compound 7 selectively recognizes the antiparallel form of the unimolecular telomeric G-quadruplex formed by the sequence d(TTAGGG)(4) (dG-24), to which it binds with a 2:1 stoichiometry and nanomolar affinity. Compared with telomeric DNA, the first binding event of compound 7 in titrations with the RNA quadruplex formed by r(UUAGGG)(4) (rG-24) is 1 order of magnitude weaker. Compound 7 does not induce the antiparallel G-quadruplex RNA, which invariably exists in a parallel form and dimerizes in solution. On the basis of the cumulative experimental data, two distinct mechanisms are proposed for the recognition of G-quadruplex DNA and RNA by compound 7. Potential biomedical and biochemical applications of the platinum-perylene technology are discussed. PMID:21999566

Rao, Lu; Dworkin, Joshua D; Nell, William E; Bierbach, Ulrich

2011-10-28

225

Interactions of a Platinum-Modified Perylene Derivative with the Human Telomeric G-Quadruplex  

PubMed Central

The interactions of a newly synthesized platinum-modified perylene derivative, compound 7 ([{Pt(dien)}2(?-4-S,S')](NO3)4 (dien = diethylenetriamine, 4 = N,N'-bis(1-(2-aminoethyl)-1,3-dimethylthiourea)-3,4,9,10-perylenetetracarboxylic acid diimide), with the human telomeric repeat were studied using various model oligo(deoxy)ribonucleotides to mimic the polymorphic nature of the telomeric G-quadruplex. UV/visible spectroscopy, CD spectropolarimetry, electrospray mass spectrometry (ES-MS), and isothermal titration calorimetry (ITC) were used to demonstrate that compound 7 selectively recognizes the antiparallel form of the unimolecular telomeric G-quadruplex formed by the sequence d(TTAGGG)4 (dG-24), to which it binds with a 2:1 stoichiometry and nanomolar affinity. Compared with telomeric DNA, the first binding event of compound 7 in titrations with the RNA quadruplex formed by r(UUAGGG)4 (rG-24) is an order of magnitude weaker. Compound 7 does not induce the antiparallel G-quadruplex RNA, which invariably exists in a parallel form and dimerizes in solution. Based on the cumulative experimental data, two distinct mechanisms are proposed for the recognition of G-quadruplex DNA and RNA by compound 7. Potential biomedical and biochemical applications of the platinum–perylene technology are discussed.

Rao, Lu; Dworkin, Joshua D.; Nell, William E.; Bierbach, Ulrich

2012-01-01

226

Estimation of flotation kinetic parameters by considering interactions of the operating variables  

Microsoft Academic Search

In this study, the classical first-order kinetic model was combined with a properly built statistical model based on a factorial experimental design, in order to accurately predict the rougher flotation efficiency for various flotation conditions. A three-level, three-factor experimental design was used to develop a statistical model to predict each of the kinetic model parameters as a function of the

E. C. Çilek

2004-01-01

227

New Limits on Fundamental Weak-Interaction Parameters from Superallowed ? Decay  

Microsoft Academic Search

A new critical survey of all world data on superallowed beta decays provides\\u000ademanding tests of, and tight constraints on, the weak interaction. In\\u000aconfirmation of the conserved vector current (CVC) hypothesis, the vector\\u000acoupling coupling constant is demonstrated to be constant to better than 3\\u000aparts in 10^4, and any induced scalar current is limited to fs \\\\leq 0.0013

J. C. Hardy; I. S. Towner

2005-01-01

228

New PAH derivatives functionalized by cyclic nitrone framework: synthetic design, anti-proliferative activity and interaction with DNA.  

PubMed

Novel approach to functionalized polycyclic aromatic hydrocarbons (PAHs) is presented. Incorporation of cyclic nitrone framework into the structure of PAHs was studied with respect to their anti-proliferative activities and interaction with double stranded DNA. Theoretical docking studies and UV titration methods were used for preliminary evaluation of binding of new PAH derivatives to DNA structure. PMID:23352483

Buchlovi?, Marian; K?íž, Zden?k; Hofr, Ctirad; Potá?ek, Milan

2013-01-11

229

Interactions between hematological derivatives and dipalmitoyl phosphatidyl choline: implications for adult respiratory distress syndrome.  

PubMed

Blood and its components flood the alveoli in adult respiratory distress syndrome (ARDS) and may be responsible for the inhibition of lung surfactant in this syndrome. We have evaluated the surface properties of dipalmitoyl phosphatidylcholine (DPPC) monolayers-the main component of lung surfactant, in the presence of blood and its components. Experiments were performed using a Langmuir-Blodgett trough at physiological temperature (37 degrees C), pH 7.0 and using 0.9% saline as the sub-phase. Whole blood (WB), membranes obtained from whole blood cells (Mem), lysed blood (LB), homogenized blood clot (CLOT), serum (SER), platelet rich plasma (PRP), platelet poor plasma (PPP) and individual plasma proteins (albumin, fibrinogen) were added to the sub-phase in the equivalent proportion of 10 parts of DPPC per million parts (w/v) of hematological inhibitor. Cell membranes were found to be the most inhibitory agent for DPPC surface activity as evidenced by an increase in the minimum surface tension (from 0.818 +/- 0.219 to 7.373 +/- 0.854 mN/m) and percentage area change required to reduce the surface tension from 30 to 10 mN/m (from 21.24 +/- 0.99 to 66.83 +/- 4.44). The inhibitory potential of pure plasma proteins differed from those of more complex blood derivatives like platelet rich plasma and serum. Whole blood and platelet poor plasma were non-inhibitory, but serum, platelet rich plasma and clot significantly increased the minimum surface tension of DPPC to 6.819 +/- 0.925, 6.625 +/- 2.261 and 6.060 +/- 0.640 mN/m, respectively. These results were statistically significant with one-way analysis of variance and Newman-Keul's test (P < 0.05). The present study suggests that, not only the presence of the individual blood component(s) in the lung alveoli but also their interactions decide their inhibitory capability. Pure plasma proteins are not representative of the inhibitory effects of blood derivatives like serum, platelet rich plasma and blood cell membranes which would be more relevant for inhibitory models of ARDS. PMID:15261079

Banerjee, Rachana R

2004-03-15

230

Kinetic model framework for aerosol and cloud surface chemistry and gas-particle interactions: Part 1 - general equations, parameters, and terminology  

NASA Astrophysics Data System (ADS)

Aerosols and clouds play central roles in atmospheric chemistry and physics, climate, air pollution, and public health. The mechanistic understanding and predictability of aerosol and cloud properties, interactions, transformations, and effects are, however, still very limited. This is due not only to the limited availability of measurement data, but also to the limited applicability and compatibility of model formalisms used for the analysis, interpretation, and description of heterogeneous and multiphase processes. To support the investigation and elucidation of atmospheric aerosol and cloud surface chemistry and gas-particle interactions, we present a comprehensive kinetic model framework with consistent and unambiguous terminology and universally applicable rate equations and parameters. It allows to describe mass transport and chemical reactions at the gas-particle interface and to link aerosol and cloud surface processes with gas phase and particle bulk processes in systems with multiple chemical components and competing physicochemical processes. The key elements and essential aspects of the presented framework are: a simple and descriptive double-layer surface model (sorption layer and quasi-static layer); straightforward flux-based mass balance and rate equations; clear separation of mass transport and chemical reactions; well-defined rate parameters (uptake and accommodation coefficients, reaction and transport rate coefficients); clear distinction between gas phase, gas-surface, and surface-bulk transport (gas phase diffusion correction, surface and bulk accommodation); clear distinction between gas-surface, surface layer, and surface-bulk reactions (Langmuir-Hinshelwood and Eley-Rideal mechanisms); mechanistic description of concentration and time dependencies; flexible inclusion/omission of chemical species and physicochemical processes; flexible convolution/deconvolution of species and processes; and full compatibility with traditional resistor model formulations. Exemplary practical applications and model calculations illustrating the relevance of the above aspects will be presented in a companion paper (Ammann and Pöschl, 2005). We expect that the presented model framework will serve as a useful tool and basis for experimental and theoretical studies investigating and describing atmospheric aerosol and cloud surface chemistry and gas-particle interactions. In particular, it is meant to support the planning and design of laboratory experiments for the elucidation and determination of kinetic parameters; the establishment, evaluation, and quality assurance of comprehensive and self-consistent collections of rate parameters; and the development of detailed master mechanisms for process models and the derivation of simplified but yet realistic parameterizations for atmospheric and climate models.

Pöschl, U.; Rudich, Y.; Ammann, M.

2005-04-01

231

Interaction water-polyethyleneglycols: Determination of hydration parameters from hydrodynamic data  

NASA Astrophysics Data System (ADS)

Densities, viscosities and refractive indexes of diluted aqueous solutions of polyethylene glycols (Mw=200-6000) are determined at 25 °C. The non-linear increase of viscosity B and C coefficients with the number of ethylenoxide (EO) units are discussed. The solvation (hydration) becomes dominant when the number of ethylenoxide group increases. The hydration parameter, ?, the specific increment of density, dds/dc, and of refractive index, dnD/dc, for the various PEGs are the consequence of dimension and of conformation that assumes the polymer. .

Donato, Ines D.; Agozzino, Pasquale; Perzia, Patrizia

2000-04-01

232

Effect of mode interaction on spectroscopic parameters of molecular vibrations with combination frequencies  

NASA Astrophysics Data System (ADS)

An equation has been obtained for excited vibrations with combination frequencies by modifying the equation for the normal vibrations of the molecules, using the direct product operation and its properties for the eigenvalues and eigenvectors of the cofactor matrices within matrix perturbation theory. From the solution of the equation, the elements of the vibrational mode tensor are determined, for which formulas are written (in terms of projectors of the matrix of the dynamic coefficients) that take into account their changes for excited vibrations. Using these formulas makes it possible to study the effect of perturbations on the change in the intramolecular and spectroscopic parameters of combination vibrations of the molecules.

Gavva, S. P.

2006-07-01

233

Numerical simulations of the atmospheric and land conditions over the Jinta oasis in northwestern China with satellite-derived land surface parameters  

Microsoft Academic Search

Mesoscale meteorological modeling is an important tool to help understand the energy budget of the oasis, while some of its initial field data are rough limited to describe the atmosphere and land conditions over a small oasis. Local factors including land surface parameters and their interaction with the atmosphere play a dominant role in the local circulation. Therefore, in this

Xianhong Meng; Shihua Lü; Tangtang Zhang; Jüxin Guo; Yanhong Gao; Yan Bao; Lijuan Wen; Siqiong Luo; Yuanpu Liu

2009-01-01

234

Study of parameters important to soil-structure interaction in seismic analyses of nuclear power plants  

SciTech Connect

The development of state-of-the-art techniques for analyzing the effects of soil-structure interaction (SSI) on structures during earthquakes is outlined. Emphasis is placed on methods to account for energy dissipation as a result of both wave propagation away from the structure's foundation and hysteretic soil response. Solution techniques are grouped into two major types: substructure methods, which break the problem into a series of steps; and direct methods, which analyze the soil-structure model in one step. In addition to theoretical and historical development of SSI methodology, case studies are presented illustrating the application of these solution techniques. 94 references.

Nelson, T.A.

1983-12-01

235

Frequency-Dependent Selection and the Maintenance of Genetic Variation: Exploring the Parameter Space of the Multiallelic Pairwise Interaction Model  

PubMed Central

When individuals' fitnesses depend on the genetic composition of the population in which they are found, selection is then frequency dependent. Frequency-dependent selection (FDS) is often invoked as a heuristic explanation for the maintenance of large numbers of alleles at a locus. The pairwise interaction model is a general model of FDS via intraspecific competition at the genotypic level. Here we use a parameter-space approach to investigate the full potential for the maintenance of multiallelic equilibria under the pairwise interaction model. We find that FDS maintains full polymorphism more often than classic constant-selection models and produces more skewed equilibrium allele frequencies. Fitness sets with some degree of rare advantage maintained full polymorphism most often, but a wide variety of nonobvious fitness patterns were also found to have positive potential for polymorphism. An example is put forth suggesting possible explanations for multiallelic polymorphisms maintained despite positive FDS on individual alleles.

Trotter, Meredith V.; Spencer, Hamish G.

2007-01-01

236

Electronic properties of two interacting electrons in a quantum pseudodot under magnetic field: Perturbation theory and two parameters variational procedure  

NASA Astrophysics Data System (ADS)

In this paper, we have studied the ground state energy and wave function of a system of two interacting electrons in a two-dimensional (2D) quantum pseudodot under the influence of an external magnetic field. For this purpose, we have employed two different methods. First, we have used the perturbation theory and obtained analytic ground state energy of the system. Second, we have applied the variational procedure and considered a trial wave function with one and two variational parameters. We have found that against to a 2D quantum dot with parabolic potential, the results obtained from that first-order perturbation method is lower than the results with variational method.

Khordad, R.

2013-10-01

237

General characteristics ofbar pp interactions at low energies in terms of principal axis and impact parameter variables  

NASA Astrophysics Data System (ADS)

The reaction configuration in momentum and position space has been investigated in detail from exclusive final states inbar pp interactions at centre of mass energies 2.01 and 2.96 GeV. In momentum space one finds a tendency towards a planar configuration at low multiplicities. In position space, one sees the average impact parameter decreasing with increasing multiplicity. At large multiplicities, events become more phase-space like i.e., more central whereas at lower multiplicities the effect of p t damping can be seen.

Banerjee, S.; Ganguli, S. N.; Gurtu, A.; Malhotra, P. K.; Raghavan, R.; Sudhakar, K.

1982-03-01

238

Interaction of carbon nanoparticles to serum albumin: elucidation of the extent of perturbation of serum albumin conformations and thermodynamical parameters.  

PubMed

Carbon nanoparticles continuously generated from industries and vehicles due to incomplete combustion of fuels is one of the potent causes of air pollution. The exposure of this polluted air with carbon nanoparticles, introduced into the bloodstream of animals in the course of respiration, motivated us to study their interaction with plasma proteins, bovine serum albumin and human serum albumin. Carbon nanoparticles with very small size and high purity were synthesized by dehydration of d-glucose using concentrated sulphuric acid as dehydrating agent. These were characterized by transmission electron microscopy, atomic force microscopy, X-ray diffraction, Raman spectroscopy, FTIR spectroscopy and UV-visible spectroscopy. Carbon nanoparticles-protein interactions were studied by fluorescence spectroscopy, circular dichroism spectroscopy and isothermal titration calorimetry. The fluorescence quenching constants and thermodynamic parameters such as enthalpy change (?H°), entropy change (?S°) and free energy change (?G°) were calculated, which indicated a strong static quenching and primary electrostatic interaction between the carbon nanoparticles and blood proteins. Circular dichroism spectra provided the information about the secondary structure alteration of the proteins in presence of carbon nanoparticles. These findings have shed light towards an understanding of the interactions between carbon nanoparticles and serum proteins which may clarify the potential risks and undesirable health effects of carbon nanoparticles, as well as the related cellular trafficking and systemic translocation. PMID:23385204

Mandal, Samir; Hossain, Maidul; Devi, P Sujatha; Kumar, Gopinatha Suresh; Chaudhuri, Keya

2013-01-14

239

Mass spectrometric determination of ternary interaction parameters of liquid Cu-In-Sn alloy  

NASA Astrophysics Data System (ADS)

The vaporisation of a liquid Cu-In-Sn system has been investigated between 1273 and 1473 K using Knudsen effusion mass spectrometry (KEMS) and the data obtained fitted to a Redlich-Kister sub-regular solution model. We examined 23 different compositions at four fixed indium concentrations: xIn = 0.20, 0.25, 0.29, 0.30 and 0.40 and evaluate the thermodynamic activities of all three components, not by applying the standard KEMS pressure calibration procedure, but from the measured ion intensity ratios of Cu+ to Sn+ using a recently published mathematical regression technique. The intermediate data obtained directly from the regression technique are the Redlich-Kister ternary L-parameters that are, as a function of temperature, as follows: L0 D (-59473 +/- 7057) + (726.8 +/- 42.3)[middle dot]T - (89.0 +/- 5.1)[middle dot]T[middle dot]ln(T); L1 = (156840 +/- 5.2E - 9) - (80 +/- 3.3E - 11)[middle dot]T - (5.57E - 11 +/- 4E - 12)[middle dot]T[middle dot]ln(T); L2 = (-137168 +/- 8819) + (592.4 +/- 52.9)[middle dot]T - (70.6 +/- 6.4)[middle dot]T[middle dot]ln(T). By using these values together with binary parameters taken from the literature, we were able to calculate several other thermodynamic functions of mixing. In particular, the partial heat of mixing of indium and its activity, which we evaluated and compared with the measured values along the Cu/Sn = 1 isopleths. We obtained a good agreement between the calculated and measured values for partial heats while in the case of activity a good agreement between the two data sets is limited to a lower mole fraction of indium.

Popovic, A.; Bencze, L.

2006-11-01

240

Disentangling fluxes of energy and matter in plasma-surface interactions: Effect of process parameters  

SciTech Connect

The possibility to discriminate between the relative importance of the fluxes of energy and matter in plasma-surface interaction is demonstrated by the energy flux measurements in low-temperature plasmas ignited by the radio frequency discharge (power and pressure ranges 50-250 W and 8-11.5 Pa) in Ar, Ar+H{sub 2}, and Ar+H{sub 2}+CH{sub 4} gas mixtures typically used in nanoscale synthesis and processing of silicon- and carbon-based nanostructures. It is shown that by varying the gas composition and pressure, the discharge power, and the surface bias one can effectively control the surface temperature and the matter supply rates. The experimental findings are explained in terms of the plasma-specific reactions in the plasma bulk and on the surface.

Wolter, M. [Institute of Experimental and Applied Physics, University of Kiel, D-24098 Kiel (Germany); Plasma Nanoscience Centre Australia (PNCA), CSIRO Materials Science and Engineering, Lindfield, New South Wales 2070 (Australia); Levchenko, I.; Ostrikov, K. [Plasma Nanoscience Centre Australia (PNCA), CSIRO Materials Science and Engineering, Lindfield, New South Wales 2070 (Australia); Plasma Nanoscience, School of Physics, University of Sydney, Sydney, New South Wales 2006 (Australia); Kersten, H. [Institute of Experimental and Applied Physics, University of Kiel, D-24098 Kiel (Germany); Kumar, S. [Plasma Nanoscience Centre Australia (PNCA), CSIRO Materials Science and Engineering, Lindfield, New South Wales 2070 (Australia); Nanotechnology and Integrated BioEngineering Centre, University of Ulster at Jordanstown, Newtownabbey, Northern Ireland BT37 0QB (United Kingdom)

2010-09-15

241

EFFECTS OF GIS DERIVED SPATIAL PARAMETERS AT VARIOUS RESOLUTIONS ON WATERSHED ANALYSIS AND AGNPS POLLUTION MODEL OUTPUT  

Technology Transfer Automated Retrieval System (TEKTRAN)

Researchers often generate digital geospatial data layers at various resolutions, and resample or aggregate to different raster pixel sizes to support environmental models at particular scales. Current efforts revolve around quantifying the significance that automatically generated spatial paramete...

242

Enthalpies of interaction between cellobiose and the derivatives of cellulose in aqueous solutions  

NASA Astrophysics Data System (ADS)

The enthalpy of interaction between cellobiose and sodium carboxymethyl cellulose, methyl cellulose, and 2-hydroxyethyl cellulose in water is determined. The exothermal nature of the interaction between cellulose and cellulose ethers is established. The strongest intermolecular interaction is found between cellobiose and 2-hydroxyethyl cellulose. The results are discussed in the context of the polysaccharide molecular structure.

Radugin, M. V.; Lebedeva, T. N.; Prusov, A. N.; Zakharov, A. G.

2011-10-01

243

Parameter identification method for a polycrystalline viscoplastic selfconsistent model based on analytical derivatives of the direct model equations  

Microsoft Academic Search

An inverse method for automatic identification of the parameters involved in a polycrystalline viscoplastic selfconsistent (VPSC) model is presented. The parameters of the constitutive viscoplastic law at the single-crystal level, i.e. the critical resolved shear stresses (CRSS) of slip and twinning and the micro-hardening coefficients, can be identified using experimental data at the polycrystal level, i.e. stress-strain curves and deformation-induced

J. W. Signorelli; R. E. Logé; Y. B. Chastel; R. A. Lebensohn

2000-01-01

244

Pulse radiolysis studies of the interaction of tea polyphenol derivatives with oxidizing OH adduct of thymine  

NASA Astrophysics Data System (ADS)

The electron transfer reactions between oxidizing OH adduct of thymine with tea polyphenol derivatives has been investigated by pulse radiolysis. The tea polyphenol derivatives are identified as good antioxidants for reduction of oxidizing OH adducts of thymine. From buildup kinetic analysis of radical phenoxyl product, the rate constants for reactions of the N3 radical with tea polyphenol derivatives have been determined to be (8-9) × 109 dm3/mol s, while the rate constants of electron transfer from tea polyphenol derivatives to oxidizing OH adducts of thymine was obtained to be around 109 dm3/mol s.

Jiang, Yue; Li, Hu-Cheng; Yao, Si-De; Zuo, Zhi-Hua; Wang, Zai-Lan; Zhang, Jia-Shan; Lin, Nian-Yun

1996-09-01

245

Nonlinearity parameters of polymers  

NASA Astrophysics Data System (ADS)

Three types of acoustic nonlinearity parameters for solids are discussed. The results of measurements of these parameters for three polymers - polymethyl methacrylate, Polystyrene, and polysulfone - are presented. A new technique was developed, using piezoelectric transducers directly bonded to the specimens, which allows the measurements of fundamental and second harmonics generated in the solids, and thereby the determination of nonlinearity parameter beta(sub 3), which is the ratio of a linear combination of second- and third-elastic coefficients to the second-order elastic coefficient. The second nonlinearity parameter, B/A can be determined from the temperature and pressure derivatives of the sound velocity. Its exact relationship for the case of solids was derived. The results from the two techniques are shown to be consistent. The pressure derivative of the sound velocity is also related to the Grueneisen parameter, which can be used to describe the anharmonicity of interactions in polymer molecules, especially of interchain vibrations. The interchain specific heat for these polymers is then calculated from the Grueneisen parameters; and the characterization of polymers by using these thermoacoustic parameters is discussed.

Wu, Meng-Chou

246

Spectral singularities, biorthonormal systems and a two-parameter family of complex point interactions  

NASA Astrophysics Data System (ADS)

A curious feature of complex scattering potentials v(x) is the appearance of spectral singularities. We offer a quantitative description of spectral singularities that identifies them with an obstruction to the existence of a complete biorthonormal system consisting of the eigenfunctions of the Hamiltonian operator, i.e., -\\frac{d^2}{dx^2}+v(x) , and its adjoint. We establish the equivalence of this description with the mathematicians' definition of spectral singularities for the potential v(x) = z-?(x + a) + z+?(x - a), where z± and a are respectively complex and real parameters and ?(x) is the Dirac delta function. We offer a through analysis of the spectral properties of this potential and determine the regions in the space of the coupling constants z± where it admits bound states and spectral singularities. In particular, we find an explicit bound on the size of certain regions in which the Hamiltonian is quasi-Hermitian and examine the consequences of imposing {\\cal P}{\\cal T} -symmetry.

Mostafazadeh, Ali; Mehri-Dehnavi, Hossein

2009-03-01

247

Interactions between glycine derivatives and mineral surfaces: Implications for the origins of life on planetary surfaces  

NASA Astrophysics Data System (ADS)

Various mechanisms could have delivered amino acids to the prebiotic Earth (Miller and Orgel 1974). The polymerization of amino acids may have been important for the origin of life, as peptides may have been components for the first self-replicating systems (Kauffman 1971; Yao et al 1998). Though amino acid concentrations in the primitive oceans were likely too dilute for significant oligomerization to occur (Cleaves et al 2009), mineral surface adsorption may have concentrated these biomolecules (Bernal 1951; Lambert 2008). Few studies have examined the catalytic effects of mineral surfaces on aqueous peptide oligomerization or degradation. As unactivated amino acid polymerization is thermodynamically unfavorable and kinetically slow in aqueous solution, we studied the reverse reaction of polymer degradation to measure potential mineral catalysis. Glycine (G) derivatives glycylglycine (GG), diketopiperazine (DKP), and glycylglycylglycine (GGG) were reacted with different minerals (calcite, hematite, montmorillonite, rutile, amorphous silica, and pyrite) in the presence of 0.05 M pH 8.1 KHCO3 buffer and 0.1 M NaCl as background electrolyte. Experiments were performed by reacting the aqueous amino acid derivative-mineral mixtures in a thermostatted oven (modified to accommodate a mechanical rotator) at 25°, 50° or 70°C. Samples were removed after 30, 60, 90, and 140 hours. Samples were then analyzed using high performance liquid chromatography to quantify the products. Besides mineral catalysis, it was determined that degradation of GGG proceeds principally via a GGG ? DKP + G mechanism, rather than via GGG ? GG + G. Below 70°C kinetics were generally too sluggish to detect catalytic activity over reasonable laboratory time-scales at this pH. At 70°C, pyrite was the only mineral with detectible catalytic effects on the degradation of GGG. GGG degraded ~ 1.5 - 4 x faster in the presence of pyrite than in control reactions, depending on the ratio of solution to mineral surface area. Catalysis was found to be saturable, suggesting the presence of discrete catalytic sites on the mineral surface. These and other results will be presented and discussed. References Bernal, J. D. (1951) The Physical Basis of Life (Routledge, London). Cleaves, H.J., Aubrey, A.D., Bada, J.L. (2009) An evaluation of the critical parameters for abiotic peptide synthesis in submarine hydrothermal systems. Origins of Life Evol Biosph. 39:109-26. Kauffman, S.A. (1971) Cellular homeostasis, epigenesis and replication in randomly aggregated macromolecular systems. Cybernetics and Systems: An International Journal 1: 71 - 96. Lambert, J. (2008) Adsorption and polymerization of amino acids on mineral surfaces: A review. Origins of Life Evol. Biosph. 38: 211-42. Miller, S.L. and Orgel, L.E. (1974) The Origins of Life on the Earth, Prentice Hall (Englewood Cliffs, NJ) Yao, Y., Ghosh, I., Zutshi, R., Chmielewski, J. (1998) Selective amplification by auto- and cross-catalysis in a replicating peptide system. Nature 396, 447 - 450.

Marshall-Bowman, K. J.; Cleaves, H. J.; Sverjensky, D. A.; Hazen, R. M.

2009-12-01

248

Determination of the Jones matrix of an LC cell and derivation of the physical parameters of the LC molecules  

NASA Astrophysics Data System (ADS)

The wavelength-dependent Jones matrix representation of a twisted-nematic liquid crystal (TN-LC) cell contains four independent parameters. The absolute values of these parameters and two mutual sign relationships can be determined from comparatively simple transmission measurements of the TN-LC cells sandwiched between two rotatable polarizers. The physical parameters of the cell (twist angle ?, director orientation ?, birefringence ?) can be retrieved if the Jones matrix is known for more than one wavelength. We have measured the Jones matrices of the TN-LC cells of a translucent Sony LCX-016 microdisplay for six wavelengths ranging from 488nm to 1064nm and determined the physical parameters of the cell. We have also measured the Jones matrices for one wavelength for a number of applied voltages. These experimental results show that it is not sufficiently exact to calculate the Jones matrix from the known physical parameters of the cell assuming a voltage-dependent birefringence only. We attribute the deviations from the theoretical model to edge effects which are not taken into account. The direct experimental determination of the Jones matrix components is therefore preferable and permits a more accurate simulation of the TN-LC microdisplay in experimental configurations involving other polarization-dependent optical components.

Hermerschmidt, Andreas; Quiram, Stephanie; Kallmeyer, Frank; Eichler, Hans Joachim

2007-05-01

249

Evaluation of Interactive Visualization on Mobile Computing Platforms for Selection of Deep Brain Stimulation Parameters  

PubMed Central

In recent years there has been significant growth in the use of patient-specific models to predict the effects of neuromodulation therapies such as deep brain stimulation (DBS). However, translating these models from a research environment to the everyday clinical workflow has been a challenge, primarily due to the complexity of the models and the expertise required in specialized visualization software. In this paper, we deploy the interactive visualization system ImageVis3D Mobile, which has been designed for mobile computing devices such as the iPhone or iPad, in an evaluation environment to visualize models of Parkinson’s disease patients who received DBS therapy. Selection of DBS settings is a significant clinical challenge that requires repeated revisions to achieve optimal therapeutic response, and is often performed without any visual representation of the stimulation system in the patient. We used ImageVis3D Mobile to provide models to movement disorders clinicians and asked them to use the software to determine: 1) which of the four DBS electrode contacts they would select for therapy; and 2) what stimulation settings they would choose. We compared the stimulation protocol chosen from the software versus the stimulation protocol that was chosen via clinical practice (independently of the study). Lastly, we compared the amount of time required to reach these settings using the software versus the time required through standard practice. We found that the stimulation settings chosen using ImageVis3D Mobile were similar to those used in standard of care, but were selected in drastically less time. We show how our visualization system, available directly at the point of care on a device familiar to the clinician, can be used to guide clinical decision making for selection of DBS settings. In our view, the positive impact of the system could also translate to areas other than DBS.

Butson, Christopher R.; Tamm, Georg; Jain, Sanket; Fogal, Thomas; Kruger, Jens

2012-01-01

250

Interaction of amphiphilic derivatives of chitosan with DPPC (1,2-dipalmitoyl-sn-glycero-3-phosphocholine)  

Microsoft Academic Search

The interaction of chitosan and its N-dodecyl and poly(ethylene glycol) derivatives with 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) vesicles was studied\\u000a to evaluate the influence of molecular architecture of the polymers on the liposomes. The study was carried out in aqueous\\u000a solution using differential scanning microcalorimetry (DSC) and dynamic light scattering. The interaction of these polymers\\u000a with DPPC vesicles altered the gel–liquid crystalline phase

Vera Aparecida de Oliveira Tiera; Françoise M. Winnik; Márcio José Tiera

2010-01-01

251

Effect of Olive?Derived Organic Amendments on Lead, Zinc, and Biochemical Parameters of an Artificially Contaminated Soil  

Microsoft Academic Search

An incubation experiment was conducted to ascertain the effects of three olive?derived organic amendments (fresh, compost, and vermicompost olive cake) on the soluble and diethylenetriamine pentaacetic acid (DTPA)–extractable lead (Pb) and zinc (Zn) and on different enzymatic activities in an artificially contaminated calcareous soil. Application of the compost and vermicompost, which increased amounts of humic acids in soil, initially stimulated

R. Nogales; E. Benítez

2007-01-01

252

The interaction of hematoporphyrin derivative, light, and ionizing radiation in a rat glioma model.  

PubMed

The effects of hematoporphyrin derivative, light, and cobalt 60 (60Co) irradiation were studied in a rat glioma model using an in vivo and an in vitro clonogenic assay. There was no effect on tumor growth by visible light or by a single dose of 60Co irradiation at 4 Gy or 8 Gy, whereas 16 Gy inhibited tumor growth to 40% versus the control. Hematoporphyrin derivative alone slightly stimulated growth (P less than 0.1). Light in the presence of 10 mg hematoporphyrin derivative/kg inhibited tumor growth to 32%. 60Co irradiation in the presence of hematoporphyrin derivative produced a significant tumor growth inhibition (P less than 0.02). This growth inhibition was directly related to the concentration of hematoporphyrin derivative. The addition of 60Co to light in the presence of hematoporphyrin derivative produced a greater growth inhibition than light or 60Co irradiation alone. This effect was most pronounced when light was applied 30 minutes before 60Co irradiation. Our experiments in a subcutaneous rat glioma model suggest a radiosensitizing effect of hematoporphyrin derivative. Furthermore, the photodynamic inactivation is enhanced by the addition of 60Co irradiation. These findings may be of importance in planning new treatment modalities in malignant brain tumors. PMID:3943032

Kostron, H; Swartz, M R; Miller, D C; Martuza, R L

1986-03-01

253

Interaction of hematoporphyrin derivative, light, and ionizing radiation in a rat glioma model  

SciTech Connect

The effects of hematoporphyrin derivative, light, and cobalt 60 (/sup 60/Co) irradiation were studied in a rat glioma model using an in vivo and an in vitro clonogenic assay. There was no effect on tumor growth by visible light or by a single dose of /sup 60/Co irradiation at 4 Gy or 8 Gy, whereas 16 Gy inhibited tumor growth to 40% versus the control. Hematoporphyrin derivative alone slightly stimulated growth (P less than 0.1). Light in the presence of 10 mg hematoporphyrin derivative/kg inhibited tumor growth to 32%. /sup 60/Co irradiation in the presence of hematoporphyrin derivative produced a significant tumor growth inhibition (P less than 0.02). This growth inhibition was directly related to the concentration of hematoporphyrin derivative. The addition of /sup 60/Co to light in the presence of hematoporphyrin derivative produced a greater growth inhibition than light or /sup 60/Co irradiation alone. This effect was most pronounced when light was applied 30 minutes before /sup 60/Co irradiation. Our experiments in a subcutaneous rat glioma model suggest a radiosensitizing effect of hematoporphyrin derivative. Furthermore, the photodynamic inactivation is enhanced by the addition of /sup 60/Co irradiation. These findings may be of importance in planning new treatment modalities in malignant brain tumors.

Kostron, H.; Swartz, M.R.; Miller, D.C.; Martuza, R.L.

1986-03-01

254

Land cover conversion and degradation analyses through coupled soil-plant biophysical parameters derived from hyperspectral EO1 Hyperion  

Microsoft Academic Search

Land degradation in semiarid areas results from various factors, including climate variations and human activity, and can lead to desertification. The process of degradation results in simultaneous and complex variations of many interrelated soil and vegetation biophysical parameters, rendering it difficult to develop simple and robust remote sensing mapping and monitoring approaches. In this study, we tested the use of

Alfredo R. Huete; Tomoaki Miura; Xiang Gao

2003-01-01

255

A statistical analysis of sounding derived indices and parameters for extreme and non-extreme thunderstorm events over Cyprus  

NASA Astrophysics Data System (ADS)

The main purpose of this study is to provide a simple statistical analysis of several stability indices and parameters for extreme and non-extreme thunderstorm events during the period 1997 to 2001 in Cyprus. For this study, radiosonde data from Athalassa station (35°1´ N, 33°4´ E) were analyzed during the aforementioned period. The stability indices and parameters set under study are the K index, the Total Totals (TT) index, the Convective Available Potential Energy related parameters such as Convective Available Potential Energy (CAPE), Downdraft CAPE (DCAPE) and the Convective Inhibition (CIN), the Vorticity Generator Parameter (VGP), the Bulk Richardson Number (BRN), the BRN Shear and the Storm Relative Helicity (SRH). An event is categorized as extreme, if primarily, CAPE was non zero and secondary, if values of both the K and the TotalTotals (TT) indices exceeded 26.9 and 50, respectively. The cases with positive CAPE but lower values of the other indices, were identified as non-extreme. By calculating the median, the lower and upper limits, as well as the lower and upper quartiles of the values of these indices, the main characteristics of their distribution were determined.

Savvidou, K.; Orphanou, A.; Charalambous, D.; Lingis, P.; Michaelides, S.

2010-06-01

256

Corrosion inhibitors part V: QSAR of benzimidazole and 2-substituted derivatives as corrosion inhibitors by using the quantum chemical parameters  

Microsoft Academic Search

Quantum chemical SCF calculations of some parameters of benzimidazoles were correlated with their inhibition efficiency in case of steel in aqueous acidic medium. Geometric structures, total negative charge on the molecule (TNC), highest occupied molecular orbital (EHOMO), lowest unoccupied molecular orbital (ELUMO), dipole moment (?) and linear solvation energy terms, molecular volume (Vi) and dipolar-polarization (?*) were correlated to corrosion

El Sayed H. El Ashry; Ahmed El Nemr; Samy A. Essawy; Safaa Ragab

2008-01-01

257

IMPROVEMENT OF A SURFACE ENERGY BALANCE MODEL BY THE USE OF MSG-SEVIRI DERIVED VEGETATION PARAMETERS  

Microsoft Academic Search

In the framework of the EUMETSAT Land Surface Analysis (LSA) - Satellite Application Facility (SAF), models have been developed to retrieve from the MSG SEVIRI imager, surface variables like albedo, short- and long-wave radiation fluxes and vegetation parameters (Leaf Area Index, LAI, and Fraction of Vegetation Cover, FVC). An energy balance model is also being elaborated to produce actual evapotranspiration

Nicolas Ghilain; Alirio Arboleda; Françoise Gellens-Meulenberghs

258

On the Interaction Between System and Task Parameters Through Continuous Manual Control Interaktion von System- und Aufgabenparametern bei Kontinuierlicher Manueller Regflung.  

National Technical Information Service (NTIS)

Experiments in pursuit tracking with a first order system were conducted. Tracking performance, depending on the forcing function bandwidth, the system parameters control gain and control spring resistance as well as their interactive influence, was inves...

G. Rothbauer

1979-01-01

259

Glycosaminoglycans in human retinoblastoma cells: Heparan sulfate, a modulator of the pigment epithelium-derived factor-receptor interactions  

Microsoft Academic Search

BACKGROUND: Pigment epithelium-derived factor (PEDF) has binding affinity for cell-surface receptors in retinoblastoma cells and for glycosaminoglycans. We investigated the effects of glycosaminoglycans on PEDF-receptor interactions. RESULTS: 125I-PEDF formed complexes with protease-resistant components of medium conditioned by human retinoblastoma Y-79 cells. Using specific glycosaminoglycan degrading enzymes in spectrophotometric assays and PEDF-affinity chromatography, we detected heparin and heparan sulfate-like glycosaminoglycans in

Elena M Alberdi; John E Weldon; S Patricia Becerra

2003-01-01

260

Interaction between a plant-derived smoke extract, light and phytohormones on the germination of light-sensitive lettuce seeds  

Microsoft Academic Search

Plant-derived smoke extracts mimics the effect of red light on germination in light-sensitive lettuce seeds and partially overcomes the inhibitory effect of far-red light. Interaction between a smoke extract and gibberellins, cytokinins, abscisic acid and ethephon was investigated. Smoke acted synergistically with GA3 and increased the sensitivity of the lettuce seeds to ABA. It seems likely that smoke affects membrane

J. Staden; A. K. Jäger; A. Strydom

1995-01-01

261

A simple procedure for morphometric analysis of processes and growth cones of neurons in culture using parameters derived from the contour and convex hull of the object.  

PubMed

Morphometric estimation of neuronal processes is currently laborious and time-consuming, since the individual processes (axons and dendrites) have to be traced manually. In order to facilitate the measurement of cellular processes, we have tested a series of parameters derived from the contour and the convex hull of an object and estimated to which extent they reflect process length and number. The parameters included the area, perimeter and form factor of the object and convex hull, their ratios as well as object length, breadth, width, length/width and spreading index. Some new parameters derived from the contour and convex hull of the object, were also computed: process index (the number of areas contained within the convex hull outside the object contour), process domain (the total area contained within the convex hull outside the object contour), their ratio and the square root of the process domain (SR process domain). In total, 18 parameters were estimated. Populations of motoneurons, growth cones of cerebellar granule cells and N2a neuroblastoma cells were utilized due to their diversity in morphological features. The processes of each object were drawn by hand to establish the actual length and number. Total process length per object correlated strongly with object perimeter, process domain and SR process domain. The number of processes per object correlated well with perimeter ratio, process index and form factor, whereas object length, convex hull perimeter and spreading index correlated acceptably with the average process length. Using these parameters for the evaluation of neurite outgrowth in developing of hippocampal neurons in vitro, variables such as object perimeter, process domain and SR process domain were found to be very well suited for estimation of the total length of neurites. We conclude that based on the contour and convex hull of an object it is possible to calculate a series of parameters which may substitute direct measurements of process length. PMID:9531460

Kawa, A; Stahlhut, M; Berezin, A; Bock, E; Berezin, V

1998-01-31

262

Self-Assembly of Pyridine-Modified Lipoic Acid Derivatives on Gold and Their Interaction with Thyroxine (T4)  

PubMed Central

Pyridyl derivatives of lipoic acid were prepared as ligands for the study of the interaction with thyroxine (T4). Thin self-assembled films of the ligands were prepared in 70% ethanol on gold and their interaction with T4 was studied by titration experiments in an aqueous buffer solution using Surface Plasmon Resonance (SPR). The thickness and refractive index of the ligand layers were calculated from SPR spectra recorded in two media, also allowing for surface coverage and the density of the layers to be estimated. Two ligands, a 4-pyridyl and a bis(2-hydroxyethyl) derivative of lipoic acid, were selected to investigate the feasibility for producing molecularly imprinted self-assembled layers on gold for T4. The methodology was to co-assemble T4 and the ligand onto the gold surface, elute the T4 from the layer under alkaline conditions, and study the rebinding of T4 to the layer. Multiple elution/rebinding cycles were conducted in different buffer solutions, and rebinding of T4 could be observed, with a moderate binding affinity that depended greatly on the solvent used. More optimal binding was observed in HBS buffer, and the affinity of the interaction could be slightly increased when the 4-pyridyl and bis(2-hydroxy-ethyl) derivatives of lipoic acid were combined in the imprinted layer.

Albers, Willem M.; Milani, Roberto; Tappura, Kirsi; Munter, Tony; Resnati, Giuseppe; Metrangolo, Pierangelo

2013-01-01

263

Macrophage-Derived SPARC Bridges Tumor Cell-Extracellular Matrix Interactions toward Metastasis  

Microsoft Academic Search

Other than genetic imprinting and epithelial to mesenchymal transition, cancer cells need interaction with the nearby stroma toward metastasis. Secreted protein acidic and rich in cysteine (SPARC) is a matricellular protein known to regulate extracellular matrix (ECM) deposition and cell-ECM interaction. Gene expression profiles associate SPARC to malignant progression. Using reciprocal bone marrow chime- ras between SPARC knockout and wild-type

Sabina Sangaletti; Emma Di Carlo; Silvia Gariboldi; Barbara Cappetti; Mariella Parenza; Cristiano Rumio; Rolf A. Brekken; Claudia Chiodoni

2008-01-01

264

Analysis of Anthrax and Plague Biowarfare Vaccine Interactions with Human Monocyte-Derived Dendritic Cells1  

Microsoft Academic Search

The anti-biowarfare anthrax and plague vaccines require repeated dosing to achieve adequate protection. To test the hypothesis that this limited immunogenicity results from the nature of vaccine interactions with the host innate immune system, we inves- tigated molecular and cellular interactions between vaccines, dendritic cells (DCs), and T cells and explored the potential for adjuvants (pertussis) to boost induction of

Anna Skowera; Esther C. de Jong; Joost H. N. Schuitemaker; Jennifer S. Allen; Simon C. Wessely; Gareth Griffiths; Martien Kapsenberg; Mark Peakman

265

Pharmacokinetic Drug Interactions of Morphine, Codeine, and Their Derivatives: Theory and Clinical Reality, Part I  

Microsoft Academic Search

Pharmacokinetic drug-drug interactions with morphine, hydromorphone, and oxymorphone are reviewed in this column. Morphine is a naturally occurring opiate that is metabolized chiefly through glucuronidation by uridine diphosphate glucuronosyl transferase (UGT) enzymes in the liver. These enzymes produce an active analgesic metabolite and a potentially toxic metabolite. In vivo drug-drug interaction studies with morphine are few, but they do suggest

SCOTT C. ARMSTRONG; KELLY L. COZZA

2003-01-01

266

Monte Carlo and experimental derivation of TG43 dosimetric parameters for CSM-type Cs137 sources  

Microsoft Academic Search

In this study, complete dosimetric datasets for the CSM2 and CSM3 Cs-137 sources were obtained using the Monte Carlo GEANT4 code. The application of this calculation method was experimentally validated with thermoluminescent dosimetry (TLD). Functions and parameters following the TG43 formalism are presented: the dose rate constant, the radial dose functional, and the anisotropy function. In addition, to aid the

J. Perez-Calatayud; D. Granero; E. Casal; F. Ballester; V. Puchades

2005-01-01

267

Evaluation of intensity and energy interaction parameters for the complexation of Pr(III) with selected nucleoside and nucleotide through absorption spectral studies  

NASA Astrophysics Data System (ADS)

The interactions of Pr(III) with nucleosides and nucleotides have been studied in different organic solvents employing absorption difference and comparative absorption spectrophotometry. The magnitudes of the variations in both energy and intensity interaction parameters were used to explore the degree of outer and inner sphere co-ordination, incidence of covalency and the extent of metal 4f-orbital involvement in chemical bonding. Various electronic spectral parameters like Slater-Condon (Fk), Racah (Ek), Lande parameter (?4f), Nephelauxatic ratio (?), bonding (b1/2), percentage covalency (?) and intensity parameters like oscillator strength (P) and Judd Ofelt electronic dipole intensity parameter (T?, ? = 2, 4, 6) have been evaluated. The variation of these evaluated parameters were employed to interpret the nature of binding of Pr(III) with different ligands i.e. Adenosine/ATP in presence and absence of Ca2+.

Bendangsenla, N.; Moaienla, T.; David Singh, Th.; Sumitra, Ch.; Rajmuhon Singh, N.; Indira Devi, M.

2013-02-01

268

Evaluation of intensity and energy interaction parameters for the complexation of Pr(III) with selected nucleoside and nucleotide through absorption spectral studies.  

PubMed

The interactions of Pr(III) with nucleosides and nucleotides have been studied in different organic solvents employing absorption difference and comparative absorption spectrophotometry. The magnitudes of the variations in both energy and intensity interaction parameters were used to explore the degree of outer and inner sphere co-ordination, incidence of covalency and the extent of metal 4f-orbital involvement in chemical bonding. Various electronic spectral parameters like Slater-Condon (F(k)), Racah (E(k)), Lande parameter (?(4f)), Nephelauxatic ratio (?), bonding (b(1/2)), percentage covalency (?) and intensity parameters like oscillator strength (P) and Judd Ofelt electronic dipole intensity parameter (T(?), ?=2,4,6) have been evaluated. The variation of these evaluated parameters were employed to interpret the nature of binding of Pr(III) with different ligands i.e. Adenosine/ATP in presence and absence of Ca(2+). PMID:23257345

Bendangsenla, N; Moaienla, T; David Singh, Th; Sumitra, Ch; Rajmuhon Singh, N; Indira Devi, M

2012-11-16

269

A cancer derived mutation in the Retinoblastoma gene with a distinct defect for LXCXE dependent interactions  

Microsoft Academic Search

BACKGROUND: The interaction between viral oncoproteins such as Simian virus 40 TAg, adenovirus E1A, and human papilloma virus E7, and the retinoblastoma protein (pRB) occurs through a well characterized peptide sequence, LXCXE, on the viral protein and a well conserved groove in the pocket domain of pRB. Cellular proteins, such as histone deacetylases, also use this mechanism to interact with

Shauna A Henley; Sarah M Francis; Jordan Demone; Peter Ainsworth; Frederick A Dick

2010-01-01

270

Relationship between lipophilicities of 1,4-dihydropyridine derivatives and pharmacokinetic interaction strengths with grapefruit juice.  

PubMed

It is well known fact that the strengths of drug interactions with grapefruit juice (GFJ) differ greatly depending on the 1,4-dihydropyridine calcium channel antagonist (DHP) used. However, there are no available data on the relationship between interactions with GFJ and its physicochemical attributes. Therefore we endeavored to study the correlation between calculated logP values, indicating lipophilicity, from chemical structures of DHPs as well as water diffusion, molecular volume, molecular polarization, molecular density, refractive index, topologic polar surface area, and calculated molar refractivity. Thirteen forms of DHP, amlodipine, azelnidipine, benidipine, cilnidipine, efonidipine, felodipine, manidipine, nicardipine, nifedipine, nimodipine, nisoldipine, nitrendipine, and pranidipine were analyzed due to clinical trials performed with GFJ and these agents. The pharmacokinetic interaction strengths were defined in common logarithmic values of increasing ratios of area under the plasma concentration-time curve (AUC) with GFJ intake compared with controls. Physicochemical properties including three categories of predicted logP values were calculated from the structures of DHPs and their estimated relationship with the interactions. As a result, the logP values indicated significant positive correlations with the interaction strengths. This finding suggests that lipophilicity is an important factor in the strengths of pharmacokinetic interactions of DHPs with GFJ intake. PMID:18176062

Uesawa, Yoshihiro; Mohri, Kiminori

2008-01-01

271

The relationship between "BET" and "free volume"-derived parameters for water vapor absorption into amorphous solids.  

PubMed

Water vapor absorption isotherms for amorphous solids with the same chemical composition but differing in molecular weight (i.e., PVP-90, PVP-30, and PVP-12), and for glucose, trehalose, and two molecular weight grades of dextran were obtained at 30 degrees C and analyzed using the Brunauer-Emmett-Teller (BET) equation to obtain the parameters, W(m) and C(B). Similar analyses were carried out for the same molecule (e.g., glucose or fructose) at -10 and 40 degrees C. Within each chemical group, W(m), the apparent BET-like parameter that is generally referred to as the "monolayer-limit of absorption", changed very little. In contrast, C(B), a measure of the free energy of absorption, significantly increased with increasing molecular weight or decreasing temperature, leading to a shift from a Type III to a Type II isotherm. The shift in isotherm shape correlates directly with the glass transition temperature, T(g), of the dry sample relative to the operating temperature, T (i.e., Type III when T > T(g) and Type II when T < T(g). These results are shown to be consistent with the combined Flory-Huggins solution model and Vrentas structural relaxation model; wherein Type II isotherm behavior, observed for T < T(g), reflects nonideal volumetric contributions to the overall free energy of absorption due to plasticization by water, as described by Vrentas, whereas Type III behavior only reflects the Flory-Huggins solution model. These volumetric free energy changes within each chemical group are shown to be correlated to the values of the "BET" parameter C(B). PMID:10906730

Zhang, J; Zografi, G

2000-08-01

272

Polarizable Simulations with Second order Interaction Model (POSSIM) force field: Developing parameters for alanine peptides and protein backbone  

PubMed Central

A previously introduced POSSIM (POlarizable Simulations with Second order Interaction Model) force field has been extended to include parameters for alanine peptides and protein backbones. New features were introduced into the fitting protocol, as compared to the previous generation of the polarizable force field for proteins. A reduced amount of quantum mechanical data was employed in fitting the electrostatic parameters. Transferability of the electrostatics between our recently developed NMA model and the protein backbone was confirmed. Binding energy and geometry for complexes of alanine dipeptide with a water molecule were estimated and found in a good agreement with high-level quantum mechanical results (for example, the intermolecular distances agreeing within ca. 0.06Å). Following the previously devised procedure, we calculated average errors in alanine di- and tetra-peptide conformational energies and backbone angles and found the agreement to be adequate (for example, the alanine tetrapeptide extended-globular conformational energy gap was calculated to be 3.09 kcal/mol quantim mechanically and 3.14 kcal/mol with the POSSIM force field). However, we have now also included simulation of a simple alpha-helix in both gas-phase and water as the ultimate test of the backbone conformational behavior. The resulting alanine and protein backbone force field is currently being employed in further development of the POSSIM fast polarizable force field for proteins.

Ponomarev, Sergei Y.; Kaminski, George A.

2011-01-01

273

Derivation of Structure Parameters of Temperature and Humidity in the Convective Boundary Layer from Large-Eddy Simulations and Implications for the Interpretation of Scintillometer Observations  

NASA Astrophysics Data System (ADS)

We derive the turbulent structure parameters of temperature CT^2 and humidity C_q^2 from high-resolution large-eddy simulations (LES) of a homogeneously-heated convective boundary layer. Boundary conditions and model forcing were derived from measurements at Cabauw in The Netherlands. Three different methods to obtain the structure-parameters from LES are investigated. The shape of the vertical structure-parameter profiles from all three methods compare well with former experimental and LES results. Depending on the method, deviations in the magnitude up to a factor of two are found and traced back to the effects of discretization and numerical dissipation of the advection scheme. Furthermore, we validate the LES data with airborne and large-aperture scintillometer (LAS) measurements at Cabauw. Virtual path measurements are used to study the variability of CT^2 in the mixed layer and surface layer and its implications for airborne and LAS measurements. A high variability of CT^2 along a given horizontal path in the LES data is associated with plumes (high values) and downdrafts (low values). The path average of CT^2 varies rapidly in time due to the limited path length. The LES results suggest that measured path averages require sufficient temporal averaging and an adequate ratio of path length to height above the ground for the LAS in order to approach the domain average of CT^2.

Maronga, Björn; Moene, Arnold F.; van Dinther, Daniëlle; Raasch, Siegfried; Bosveld, Fred C.; Gioli, Beniamino

2013-07-01

274

Problems in the Derivations of the Renormalization Group Equation for the Low Momentum Nucleon Interactions  

NASA Astrophysics Data System (ADS)

We carefully examine one of the derivations of the renormalization group equation (RGE) for the so-called V_{low k} potential, given by Bogner et al. [nucl-th/0111042]. The derivation, based on the completeness relation of the model space, must be modified if there are bound states. It is however shown that the RGE is unchanged if the bound state wavefunctions in the reduced theory are required to have the same low-momentum components as those in the original theory. Several aspects of the V_{low k} approach are also discussed.

Harada, K.

2008-10-01

275

Comparison of topside equatorial parameters derived from DMSP, Jicamarca, and Another Model of the Ionosphere (SAMI2)  

NASA Astrophysics Data System (ADS)

Comparison is made of topside equatorial parameters obtained from DMSP satellites with those measured from Jicamarca radar and those calculated from Another Model of the Ionosphere (SAMI2). To determine acceptable limits for this volume, knowledge of the spatial and temporal gradients in the parameters must be defined. Those can be obtained independently from each data source and are dependent on local time and season. Having described the spatial gradients, a comparison of the ionospheric variables can be made. The present study focuses on simultaneous ground-based and satellite data obtained for June 2002. Data for days 11, 12, and 13 are compared in this study. Satellite data are obtained from the DMSP satellites F13 (0600-1800 LT) and F15 (0900-2100 LT), respectively. Ground-based data are obtained from the Jicamarca radar. These are then compared with numerical computations performed by the SAMI2 model for the same period. Good agreement between observation and model is achieved for the total ion concentration during daytime and nighttime, while the ion and electron temperatures agree well at night. The light ion fraction is usually <20% from all three sources except during sunrise where the light ion content can be higher. Accounting for the variables H+ and He+ concentrations in the topside appears to be the major factor affecting the different data sources.

Venkatraman, Sarita; Heelis, R. A.; Hysell, D. L.

2005-01-01

276

Parameter identification method for a polycrystalline viscoplastic selfconsistent model based on analytical derivatives of the direct model equations  

NASA Astrophysics Data System (ADS)

An inverse method for automatic identification of the parameters involved in a polycrystalline viscoplastic selfconsistent (VPSC) model is presented. The parameters of the constitutive viscoplastic law at the single-crystal level, i.e. the critical resolved shear stresses (CRSS) of slip and twinning and the micro-hardening coefficients, can be identified using experimental data at the polycrystal level, i.e. stress-strain curves and deformation-induced textures. The minimization problem is solved by means of a Gauss-Newton scheme and the sensitivity matrix is evaluated by analytical differentiation of the direct model equations. As a particular case, the optimization procedure for the Taylor full constraints (FC) formulation is also presented. The convergence and stability of the identification scheme are analysed using several validation tests for different deformation paths imposed to a polycrystal of hexagonal structure. As an example of application of this inverse method, the relative CRSS of the active deformation systems of a Zircaloy-4 sheet are identified, based on several textures measured for different reductions and rolling directions.

Signorelli, J. W.; Logé, R. E.; Chastel, Y. B.; Lebensohn, R. A.

2000-03-01

277

Screening of the most relevant parameters for method development in ultra-high performance hydrophilic interaction chromatography.  

PubMed

The goal of the present work was to provide some guidelines for method development in hydrophilic interaction chromatography (HILIC). For this purpose, a training set of 82 representative pharmaceutical compounds possessing diverse polarity and including acidic, basic and neutral properties was analyzed. All these drugs were injected on five short HILIC columns packed with sub-2?m particles and dedicated for UHPLC (ultra-high performance liquid chromatography) operation. Four different pH conditions ranging from pH 3 to 6 were tested at two ionic strengths (10 and 50mmol/L) and finally, the reference organic modifier in HILIC, namely acetonitrile was modified with small amounts of methanol or isopropanol. From these experiments and using multivariate data analysis, it is clear that the stationary phase was the most relevant parameters for tuning selectivity in HILIC, since the types of interactions (i.e. dipole-dipole, hydrogen bonding and ion exchange) with analytes strongly vary between columns. Among the selected phases, the diol phase was the less interesting one, in terms of selectivity and peak shape. The zwitterionic phase was attractive, as it allowed a better retention of acidic compounds. Finally, the bare silica phase was the most versatile HILIC column packed with sub-2?m particles in terms of retention, peak shape and selectivity. Mobile phase pH was the other important parameter to achieve an appropriate selectivity and retention, even if it remains always difficult to assess precisely the mobile phase pH, analyte pKa and silanols pKa, when working with more 70% acetonitrile. Finally, buffer ionic strength and organic modifier nature could be considered as secondary parameters for HILIC method development. In conclusion, screening four different columns packed with sub-2?m particles at two mobile phase pH, using a fast gradient seems to be a good generic approach for initial HILIC method development. The total time for such a screening was estimated at ?1h, including reequilibration. PMID:23411147

Periat, Aurélie; Debrus, Benjamin; Rudaz, Serge; Guillarme, Davy

2013-01-16

278

The interaction of PVP complexes of gossypol and its derivatives with an artificial membrane lipid matrix.  

PubMed

In this paper, we present the results of a study on the membrane-active properties of gossypol, its derivatives and their polyvinylpyrrolidone complexes as assessed by differential scanning calorimetry and by the fluorescent probe method. The latter revealed the change in polarization of the incident radiation caused by the action of the polyphenol on the artificial membrane lipid matrix. PMID:19936629

Ionov, Maksim; Tukfatullina, Ilnora; Salakhutdinov, Bakhtiyar; Baram, Nina; Bryszewska, Maria; Aripov, Takhir

2009-11-20

279

Interactions of Jet Fuels with Nitrile O-Rings: Petroleum-Derived versus Synthetic Fuels  

SciTech Connect

A transition from petroleum-derived jet fuels to blends with Fischer-Tropsch (F-T) fuels, and ultimately fully synthetic hydro-isomerized F-T fuels has raised concern about the fate of plasticizers in nitrile-butadiene rubber o-rings that are contacted by the fuels as this transition occurs. The partitioning of plasticizers and fuel molecules between nitrile o-rings and petroleum-derived, synthetic, and additized-synthetic jet fuels has been measured. Thermal desorption of o-rings soaked in the various jet fuels followed by gas chromatographic analysis with a mass spectrometric detector showed many of the plasticizer and stabilizer compounds were removed from the o-rings regardless of the contact fuel. Fuel molecules were observed to migrate into the o-rings for the petroleum-derived fuel as did both the fuel and additive for a synthetic F-T jet fuel additized with benzyl alcohol, but less for the unadditized synthetic fuel. The specific compounds or classes of compounds involved in the partitioning were identified and a semiquantitative comparison of relative partitioning of the compounds of interest was made. The results provide another step forward in improving the confidence level of using additized, fuIly synthetic jet fuel in the place of petroleum-derived fueL

Gormley, R.J.; Link, D.D.; Baltrus, J.P.; Zandhuis, P.H.

2008-01-01

280

Interactions of Jet Fuels with Nitrile O-Rings: Petroleum-Derived versus Synthetic Fuels  

SciTech Connect

A transition from petroleum~derived jet fuels to blends with Fischer-Tropsch (F~T) fuels, and ultimately fully synthetic hydro-isomerized F-T fuels has raised concern about the fate of plasticizers in nitrile-butadiene rubber a-rings that are contacted by the fuels as this transition occurs. The partitioning of plasticizers and fuel molecules between nitrile a-rings and petroleum-derived, synthetic, and additized-synthetic jet fuels has been measured. Thermal desorption of o-rings soaked in the various jet fuels followed by gas chromatographic analysis with a mass spectrometric detector showed many of the plasticizer and stabilizer compounds were removed from the o-rings regardless of the contact fuel. Fuel molecules were observed to migrate into the o-rings for the petroleum-derived fuel as did both the fuel and additive for a synthetic F-T jet fuel additized with benzyl alcohol, but less for the unadditized synthetic fuel. The specific compounds or classes of compounds involved in the partitioning were identified and a semiquantitative comparison of relative partitioning of the compounds of interest was made. The results provide another step forward in improving the confidence level of using additized, fully synthetic jet fuel in the place of petroleum-derived fuel.

Gormley, R.J.; Link, D.D.; Baltrus, J.P.; Zandhuis, P.H.

2009-01-01

281

OPACOS: OVRO POST-AGB CO (1-0) EMISSION SURVEY. I. DATA AND DERIVED NEBULAR PARAMETERS  

SciTech Connect

We have performed interferometric observations of the {sup 12}CO (J = 1-0) emission in a sample of 27 objects spanning different evolutionary stages from the late asymptotic giant branch (late-AGB), through the post-AGB (pAGB) phase, and to the planetary nebula (PN) stage, but dominated by pAGB objects and young PNs ({>=}81%). In this paper (the first in a series) we present our maps and main nebular properties derived for the whole sample. Observations were performed with the Caltech Millimeter Array at the Owens Valley Radio Observatory. The angular resolution obtained in our survey ranges between 2.''3 and 10.''7. The {sup 13}CO and C{sup 18}O (J = 1-0) transitions as well as the 2.6 mm continuum emission have also been observed in several objects. The detection statistics in the {sup 12}CO, {sup 13}CO, C{sup 18}O transitions and 2.6 mm continuum are 89%, 83%, 0%, and 37%, respectively. We report first detections of {sup 12}CO (J = 1-0) emission in 13 targets and confirm emission from several previous marginal detections. The molecular envelope probed by {sup 12}CO (J = 1-0) emission is extended for 18 (out of 24) sources; envelope asymmetries and/or velocity gradients are found in most extended objects. Our data have been used to derive accurate target coordinates and systemic velocities and to characterize the envelope size, morphology, and kinematics. We also provide an estimate of the total molecular mass and the fraction of it contained in fast flows, lower limits to the linear momentum and to the isotopic {sup 12}C/{sup 13}C ratio, as well as the AGB mass-loss rate and timescale for sources with extended CO emission.

Sanchez Contreras, C. [Centro de Astrobiologia, INTA-CSIC, E-28691 Villanueva de la Canada, Madrid (Spain); Sahai, R. [Jet Propulsion Laboratory, MS 183-900, California Institute of Technology, Pasadena, CA 91109 (United States)

2012-11-15

282

O glycosylation of an Sp1-derived peptide blocks known Sp1 protein interactions.  

PubMed Central

The O-linked N-acetylglucosamine (O-GlcNAc) modification of proteins is dynamic and abundant in the nucleus and cytosol. Several transcription factors, including Sp1, have been shown to contain this modification; however, the functional role of O-GlcNAc in these proteins has not been determined. In this paper we describe the use of the previously characterized glutamine-rich transactivation domain of Sp1 (B-c) as a model to investigate the role of O-GlcNAc in Sp1's transcriptionally relevant protein-to-protein interactions with the TATA-binding-protein-associated factor (TAF110) and holo-Sp1. When the model Sp1 peptide was overexpressed in primate cells, this 97-amino-acid domain of Sp1 was found to contain a dominant O-GlcNAc residue at high stoichiometry, which allowed the mapping and mutagenesis of this glycosylation site. In vitro interaction studies between this segment of Sp1 and Drosophila TAF110 or holo-Sp1 indicate that the O-GlcNAc modification functions to inhibit the largely hydrophobic interactions between these proteins. In HeLa cells, the mutation at the mapped glycosylation site was permissive for transcriptional activation. We propose the hypothesis that the removal of O-GlcNAc from an interaction domain can be a signal for protein association. O-GlcNAc may thereby prevent untimely and ectopic interactions.

Roos, M D; Su, K; Baker, J R; Kudlow, J E

1997-01-01

283

Interaction of Earthquakes and Aseismic Slip: Insights From 3D Fault Models Governed by Lab-Derived Friction Laws  

NASA Astrophysics Data System (ADS)

Recent improvements in availability and quality of seismic and geodetic data have revealed complex interactions of seismic and aseismic slip. This rich information, interpreted through modeling, can help us understand mechanics and physics of faults. Our simulation approach (Lapusta and Liu, 2008) produces spontaneous long-term fault slip and the resulting stress redistribution with full inclusion of inertial effects during simulated earthquakes in the context of a 3D fault model. The approach incorporates laboratory- derived rate and state friction laws, involves slow, tectonic-like loading, resolves all stages of seismic and aseismic slip, and results in realistic rupture speeds, slip velocities, and stress drops. We use the simulations to study two phenomena that arise due to interaction of seismic and aseismic slip: (i) supershear transition in 3D models due to rheological boundaries and (ii) mechanics of small repeating earthquakes. In our simulations, aseismic slip in creeping regions concentrates stress at rheological boundaries and promotes supershear transition during dynamic events (Liu and Lapusta, 2008). Transition of earthquakes from subshear to supershear speeds has important implications for strong ground motion and fault properties. Simulations of supershear transition are typically done in models of single events on linear slip- weakening faults. We simulate long-term seismic and aseismic slip on a strike-slip fault with a rectangular velocity-weakening (VW) region surrounded by velocity-strengthening (VS) regions. Existence of shallow and deeper VS regions is supported by lab friction studies as well as observations of interseismic creep, postseismic slip, limits on the depth extent of seismicity, and clustering of small events. In our simulations, steady slip throughout the interseismic period in the VS areas concentrates stress next to rheological boundaries and promotes faster rupture speeds and local supershear propagation of dynamic events. Under a range of conditions, this local behavior causes the entire rupture to become supershear. Our modeling of small repeating earthquakes reproduces several observational constraints, including their nontrivial scaling of seismic moment with the recurrence time (Chen and Lapusta, 2008). In our 3D model, a small circular patch with velocity-weakening friction is surrounded by a much larger velocity-strengthening region. When the patch size is smaller than the nucleation size implied by the underlying rate and state formulation, all slip on the patch is aseismic. For larger patch sizes, small repeating events occur, with slip rates of the order of 1 m/s and sharp stress drops; however, the patch also experiences significant aseismic slip. By varying the patch radius, we are able to produce repeating earthquakes that (i) reproduce the observed scaling T? M01/6 of the repeat time T and seismic moment M0 and (ii) have source dimensions and stress drops typical for earthquakes of comparable sizes and similar to recent inversions for Parkfield repeaters. Remarkably, the scaling T? M01/6 is independent of the variation, within a factor of 4, of rate and state parameters a and b. The scaling is also reproduced in a model with a rectangular velocity-weakening patch and with quasi-dynamic approach.

Lapusta, N.; Liu, Y.; Chen, T.

2008-12-01

284

Derivation of analytical expressions for the network dislocation density, change in lattice parameter, and for the recrystallized grain size in nuclear fuels  

NASA Astrophysics Data System (ADS)

At relatively high burn-up, both UO2 and U 10Mo nuclear fuels undergo irradiation-induced recrystallization wherein grains of micron size transform to grains of submicron size. Previously, expressions have been derived for the initiation, and for the progression of recrystallization as a function of fission density, fission rate, fuel temperature, and as-fabricated grain size. Here, analytical expressions are derived for the network dislocation density, change in lattice parameter, and the size of the recrystallized grains. The basic premise of the theory presented in this work is that irradiation-induced recrystallization is driven by the behavior of interstitial loops. It is demonstrated that these phenomena can be simulated in both UO2 and in U xMo with the same theory, albeit with various property differences. Results of the calculations are compared with available data.

Rest, J.

2006-02-01

285

Direct Interaction between Scaffolding Proteins RACK1 and 14-3-3? Regulates Brain-derived Neurotrophic Factor (BDNF) Transcription*  

PubMed Central

RACK1 is a scaffolding protein that spatially and temporally regulates numerous signaling cascades. We previously found that activation of the cAMP signaling pathway induces the translocation of RACK1 to the nucleus. We further showed that nuclear RACK1 is required to promote the transcription of the brain-derived neurotrophic factor (BDNF). Here, we set out to elucidate the mechanism underlying cAMP-dependent RACK1 nuclear translocation and BDNF transcription. We identified the scaffolding protein 14-3-3? as a direct binding partner of RACK1. Moreover, we found that 14-3-3? was necessary for the cAMP-dependent translocation of RACK1 to the nucleus. We further observed that the disruption of RACK1/14-3-3? interaction with a peptide derived from the RACK1/14-3-3? binding site or shRNA-mediated 14-3-3? knockdown inhibited cAMP induction of BDNF transcription. Together, these data reveal that the function of nuclear RACK1 is mediated through its interaction with 14-3-3?. As RACK1 and 14-3-3? are two multifunctional scaffolding proteins that coordinate a wide variety of signaling events, their interaction is likely to regulate other essential cellular functions.

Neasta, Jeremie; Kiely, Patrick A.; He, Dao-Yao; Adams, David R.; O'Connor, Rosemary; Ron, Dorit

2012-01-01

286

Ab initio calculation of the effective on-site Coulomb interaction parameters for half-metallic magnets  

NASA Astrophysics Data System (ADS)

Correlation effects play an important role in the electronic structure of half-metallic (HM) magnets. In particular, they give rise to nonquasiparticle states above (or below) the Fermi energy at finite temperatures that reduce the spin polarization and, as a consequence, the efficiency of spintronics devices. Employing the constrained random-phase approximation (cRPA) within the full-potential linearized augmented-plane-wave (FLAPW) method using maximally localized Wannier functions, we calculate the strength of the effective on-site Coulomb interaction (Hubbard U and Hund exchange J) between localized electrons in different classes of HM magnets considering: (i) sp-electron ferromagnets in rock-salt structure, (ii) zinc-blende 3d binary ferromagnets, as well as (iii) ferromagnetic and ferrimagnetic semi- and full-Heusler compounds. For HM sp-electron ferromagnets, the calculated Hubbard U parameters are between 2.7 and 3.9 eV, while for transition-metal-based HM compounds, they lie between 1.7 and 3.8 eV, being smallest for MnAs (Mn-3d orbitals) and largest for Cr2CoGa (Co-3d orbitals). For the HM full-Heusler compounds, the Hubbard U parameters are comparable to the ones in elementary 3d transition metals, while for semi-Heusler compounds, they are slightly smaller. We show that the increase of the Hubbard U with structural complexity, i.e., from MnAs to Cr2CoGa, stems from the screening of the p electrons of the nonmagnetic sp atoms. The p-electron screening turns out to be more efficient for MnAs than for Cr2CoGa. The calculated Hubbard U parameters for CrAs, NiMnSb, and Co2MnSi are about two times smaller than previous estimates based on the constrained local-density approximation (cLDA) method. Furthermore, the width of the correlated d or p bands of the studied compounds is usually smaller than the calculated Hubbard U parameters. Thus these HM magnets should be classified as weakly correlated materials.

?a??o?lu, Ersoy; Galanakis, Iosif; Friedrich, Christoph; Blügel, Stefan

2013-10-01

287

Derivative expansion for the boundary interaction terms in the Casimir effect: Generalized {delta} potentials  

SciTech Connect

We calculate the Casimir energy for scalar fields in interaction with finite-width mirrors, described by nonlocal interaction terms. These terms, which include quantum effects due to the matter fields inside the mirrors, are approximated by means of a local expansion procedure. As a result of this expansion, an effective theory for the vacuum field emerges, which can be written in terms of generalized {delta} potentials. We compute explicitly the Casimir energy for these potentials and show that, for some particular cases, it is possible to reinterpret them as imposing imperfect Dirichlet boundary conditions.

Fosco, C. D. [Centro Atomico Bariloche and Instituto Balseiro, Comision Nacional de Energia Atomica, R8402AGP Bariloche (Argentina); Lombardo, F. C.; Mazzitelli, F. D. [Departamento de Fisica Juan Jose Giambiagi, FCEyN UBA, Facultad de Ciencias Exactas y Naturales, Ciudad Universitaria, Pabellon I, 1428 Buenos Aires (Argentina)

2009-10-15

288

Derivatives of any order of the hypergeometric function pFq(a1, ..., ap; b1, ..., bq; z) with respect to the parameters ai and bi  

NASA Astrophysics Data System (ADS)

The derivatives of any order of the general hypergeometric function pFq(a1, ..., ap; b1, ..., bq; z) with respect to the parameters ai or bi are expressed, in compact form, in terms of generalizations of multivariable Kampé de Fériet functions. To achieve this, use is made of Babister's solution to non-homogeneous differential equations for pFq(a1, ..., ap; b1, ..., bq; z). An application to Hahn polynomials, which are 3F2 functions, is given as an illustration.

Ancarani, L. U.; Gasaneo, G.

2010-02-01

289

Interactions between L-arginine/L-arginine derivatives and lysozyme and implications to their inhibition effects on protein aggregation.  

PubMed

L-arginine (Arg), L-homoarginine (HArg), L-arginine ethylester (ArgEE) and L-arginine methylester (ArgME) were found effective in inhibiting protein aggregation, but the molecular mechanisms are not clear. Herein, stopped-flow fluorescence spectroscopy, isothermal titration calorimetry and mass spectroscopy were utilized to investigate the folding kinetics of lysozyme and the interactions of the additives with lysozyme. It was found that the interactions of ArgME and ArgEE with lysozyme were similar to that of guanidine hydrochloride, and were much stronger than those of Arg and HArg. The binding forces were all mainly hydrogen bonding and cation-? interaction from the guanidinium group, but their differences in molecular states led to the significantly different binding strengths. The additives formed molecular clusters in an increasing order of ArgEE, ArgME, HArg and Arg. Arg and HArg mainly formed annular clusters with head-to-tail bonding, while ArgME and ArgEE formed linear clusters with guanidinium groups stacking. The interactions between the additives and lysozyme were positively related to the monomer contents. That is, the monomers were the primary species that participated in the direct interactions due to their intact guanidinium groups and small sizes, while the clusters performed as barriers to crowd out the protein-protein interactions for aggregation. Thus, it is concluded that the effects of Arg and its derivatives on protein aggregation stemed from the direct interactions by the monomers and the crowding effects by the clusters. Interplay of the two effects led to the differences in their inhibition effects on protein aggregation. © 2013 American Institute of Chemical Engineers Biotechnol. Prog., 2013. PMID:23737098

Gao, Ming-Tao; Dong, Xiao-Yan; Sun, Yan

2013-06-01

290

Investigation on interaction and sonodynamic damage of fluorescein derivants to bovine serum albumin (BSA) under ultrasonic irradiation  

NASA Astrophysics Data System (ADS)

The fluorescein derivants (Fluorescein: (2-(6-Hydroxy-3-oxo-(3H)-xanthen-9-yl) benzoic acid), Fluorescein-DA: (Bis [N,N-bis (carboxymethyl) aminomethyl] fluorescein) and Fluorescein-DAsbnd Fe(III): (Bis [N,N-bis (carboxymethyl) aminomethyl] fluoresceinsbnd Ferrous(III)) with a tricyclic plane structure were used to study the interaction and sonodynamic damage to bovine serum albumin (BSA) under ultrasonic irradiation through fluorospectrometry and UV-vis spectrophotometry. Besides, because of the existence of Fe(III) ion in Fluorescein-DAsbnd Fe(III), under ultrasonic irradiation the sonocatalytic activity in the damage of BSA molecules was also found. Three-dimensional fluorescence spectra and three-dimensional fluorescence contour profile spectra were mentioned to determine the fluorescence quenching and the conformation change of BSA in the absence and presence of these fluorescein derivants. As judged from the experimental results, the fluorescence quenching of BSA in aqueous solution caused by these fluorescein derivants were all attributed to static quenching process. The damage degree and mode were related to some factors such as ultrasonic irradiation time, fluorescein derivant concentration and ionic strength. Finally, several quenchers were used to determine the amount and kind of generated reactive oxygen species (ROS) during sonodynamic and sonocatalytic reaction processes. It suggests that these fluorescein derivants induce protein damage via various ROS, at least, including singlet oxygen (1O2) and hydroxyl radicals (rad OH). Perhaps, this paper may offer some important subjects for broadening the application of these fluorescein derivants in sonodynamic therapy (SDT) and sonocatalytic therapy (SCT) technologies for tumor treatment.

Zou, Mingming; Zhang, Lei; Wang, Jun; Wang, Qi; Gao, Jingqun; Fan, Ping

2013-06-01

291

Investigation on interaction and sonodynamic damage of fluorescein derivants to bovine serum albumin (BSA) under ultrasonic irradiation.  

PubMed

The fluorescein derivants (Fluorescein: (2-(6-Hydroxy-3-oxo-(3H)-xanthen-9-yl) benzoic acid), Fluorescein-DA: (Bis [N,N-bis (carboxymethyl) aminomethyl] fluorescein) and Fluorescein-DA-Fe(III): (Bis [N,N-bis (carboxymethyl) aminomethyl] fluorescein-Ferrous(III)) with a tricyclic plane structure were used to study the interaction and sonodynamic damage to bovine serum albumin (BSA) under ultrasonic irradiation through fluorospectrometry and UV-vis spectrophotometry. Besides, because of the existence of Fe(III) ion in Fluorescein-DA-Fe(III), under ultrasonic irradiation the sonocatalytic activity in the damage of BSA molecules was also found. Three-dimensional fluorescence spectra and three-dimensional fluorescence contour profile spectra were mentioned to determine the fluorescence quenching and the conformation change of BSA in the absence and presence of these fluorescein derivants. As judged from the experimental results, the fluorescence quenching of BSA in aqueous solution caused by these fluorescein derivants were all attributed to static quenching process. The damage degree and mode were related to some factors such as ultrasonic irradiation time, fluorescein derivant concentration and ionic strength. Finally, several quenchers were used to determine the amount and kind of generated reactive oxygen species (ROS) during sonodynamic and sonocatalytic reaction processes. It suggests that these fluorescein derivants induce protein damage via various ROS, at least, including singlet oxygen ((1)O2) and hydroxyl radicals (OH). Perhaps, this paper may offer some important subjects for broadening the application of these fluorescein derivants in sonodynamic therapy (SDT) and sonocatalytic therapy (SCT) technologies for tumor treatment. PMID:23583854

Zou, Mingming; Zhang, Lei; Wang, Jun; Wang, Qi; Gao, Jingqun; Fan, Ping

2013-03-25

292

Kinetic model framework for aerosol and cloud surface chemistry and gas-particle interactions - Part 1: General equations, parameters, and terminology  

NASA Astrophysics Data System (ADS)

Aerosols and clouds play central roles in atmospheric chemistry and physics, climate, air pollution, and public health. The mechanistic understanding and predictability of aerosol and cloud properties, interactions, transformations, and effects are, however, still very limited. This is due not only to the limited availability of measurement data, but also to the limited applicability and compatibility of model formalisms used for the analysis, interpretation, and description of heterogeneous and multiphase processes. To support the investigation and elucidation of atmospheric aerosol and cloud surface chemistry and gas-particle interactions, we present a comprehensive kinetic model framework with consistent and unambiguous terminology and universally applicable rate equations and parameters. It enables a detailed description of mass transport and chemical reactions at the gas-particle interface, and it allows linking aerosol and cloud surface processes with gas phase and particle bulk processes in systems with multiple chemical components and competing physicochemical processes. The key elements and essential aspects of the presented framework are: a simple and descriptive double-layer surface model (sorption layer and quasi-static layer); straightforward flux-based mass balance and rate equations; clear separation of mass transport and chemical reactions; well-defined and consistent rate parameters (uptake and accommodation coefficients, reaction and transport rate coefficients); clear distinction between gas phase, gas-surface, and surface-bulk transport (gas phase diffusion, surface and bulk accommodation); clear distinction between gas-surface, surface layer, and surface-bulk reactions (Langmuir-Hinshelwood and Eley-Rideal mechanisms); mechanistic description of concentration and time dependences (transient and steady-state conditions); flexible addition of unlimited numbers of chemical species and physicochemical processes; optional aggregation or resolution of intermediate species, sequential processes, and surface layers; and full compatibility with traditional resistor model formulations. The outlined double-layer surface concept and formalisms represent a minimum of model complexity required for a consistent description of the non-linear concentration and time dependences observed in experimental studies of atmospheric multiphase processes (competitive co-adsorption and surface saturation effects, etc.). Exemplary practical applications and model calculations illustrating the relevance of the above aspects are presented in a companion paper (Ammann and Pöschl, 2007). We expect that the presented model framework will serve as a useful tool and basis for experimental and theoretical studies investigating and describing atmospheric aerosol and cloud surface chemistry and gas-particle interactions. It shall help to end the "Babylonian confusion" that seems to inhibit scientific progress in the understanding of heterogeneous chemical reactions and other multiphase processes in aerosols and clouds. In particular, it shall support the planning and design of laboratory experiments for the elucidation and determination of fundamental kinetic parameters; the establishment, evaluation, and quality assurance of comprehensive and self-consistent collections of rate parameters; and the development of detailed master mechanisms for process models and derivation of simplified but yet realistic parameterizations for atmospheric and climate models.

Pöschl, U.; Rudich, Y.; Ammann, M.

2007-12-01

293

Optimization of Parameters for a More Efficient Use of Adipose-Derived Stem Cells in Regenerative Medicine Therapies  

PubMed Central

Adipose tissue-derived stem cells (ASCs) association to fat in autologous lipotransfer is promising for a more effective soft tissue reconstruction, and optimization of protocols to isolate ASCs from lipoaspirate fat is much needed. We demonstrated that an increase in adipocyte differentiation is dependent on the number of ASCs. In a sample of 10 donors, we found a higher concentration of nucleated cells in the lower abdomen compared to flank (P = 0.015). In a sample of 6 donors we did not find differences in the cell yield obtained by manual or pump-assisted aspiration (P = 0.56). We suggest that the increase in the number of ASCs in the reinjected fat may enhance the efficiency of newly formed adipose tissue and that the anatomical region from which to harvest fat tissue needs to be considered to optimize the number of ASCs in the harvested tissue. Finally, pump-assisted aspiration can be used without any significant harm to the viability of cells.

Aguena, Meire; Dalto Fanganiello, Roberto; Tissiani, Luiz Alexandre Lorico; Ishiy, Felipe Augusto Andre; Atique, Rodrigo; Alonso, Nivaldo; Passos-Bueno, Maria Rita

2012-01-01

294

Thermodynamics of Solution, Interaction with Calf Thymus DNA and Anticancer Activity of Phenylhydrazone Derivatives  

Microsoft Academic Search

The solubilities in water (W) and in 3 mol?L?1 aqueous acetonitrile at 298.15 K of thiophene-2-, furan-2- and pyrrole-2-carboxaldehyde phenylhydrazone along with their\\u000a nitro and 2,4-dinitro derivatives, referred to as PCT, PCF, PCP, NPCT, NPCF, NPCP, DPCT, DPCF and DPCP, respectively, are\\u000a reported. The standard Gibbs energy of transfer from W to solvent mixtures () was estimated for each solute. The

Ysaías J. Alvarado; Joanna Baricelli; José Caldera-Luzardo; Néstor Cubillán; Gladys Ferrer-Amado; Yovani Marrero-Ponce; Victoria Mancilla; Miguel A. Rocafull; José Ojeda-Andara; Luz E. Thomas; Joan Vera-Villalobos; Miguel Morales-Toyo

2011-01-01

295

CJX1, an amlodipine derivative, interacts with ATPase of human P-glycoprotein  

Microsoft Academic Search

Our aim has been to elucidate the possible mechanism of CJX1, an amlodipine derivative, in the modulation of P-gp function by determining its effect on P-gp ATPase activity. Basal P-gp ATPase activity was increased by CJX1 with half-maximal activity concentration (Km) of 8.6±1.4?M. Kinetic analysis indicated a non-competitive inhibition of Verapamil (Ver)-stimulated P-gp ATPase activity by CJX1 and competitive inhibition

Bian-Sheng Ji; Ling He

2009-01-01

296

Solid Phase Synthesis and Application of Labeled Peptide Derivatives: Probes of Receptor-Opioid Peptide Interactions  

Microsoft Academic Search

Solid phase synthetic methodology has been developed in our laboratory to incorporate an affinity label (a reactive functionality\\u000a such as isothiocyanate or bromoacetamide) into peptides (Leelasvatanakij and Aldrich J Peptide Res 56, 80, 2000), and we have\\u000a used this synthetic strategy to prepare affinity label derivatives of a variety of opioid peptides. To date side reactions\\u000a have been detected only

Jane V. Aldrich; Vivek Kumar; Bhaswati Dattachowdhury; Angela M. Peck; Xin Wang; Thomas F. Murray

2008-01-01

297

Interaction of lipophilic VIP derivatives with recombinant VIP 1\\/PACAP and VIP 2\\/PACAP receptors  

Microsoft Academic Search

Stearyl vasoactive intestinal polypeptide has been reported to be a VIP (vasoactive intestinal polypeptide) receptor agonist of high potency with an original bioavailability and action. We synthesized three fatty acyl derivatives, myristyl-, palmityl- and stearyl-[Nle17]VIP, and tested their capacity to recognize recombinant rat- and human VIP1- and VIP2\\/PACAP (pituitary adenylate cyclase-activating polypeptide) receptors and to stimulate adenylate cyclase activity. The

Philippe Gourlet; Jean Rathé; Philippe De Neef; Johnny Cnudde; Marie-Claire Vandermeers-Piret; Magali Waelbroeck; Patrick Robberecht

1998-01-01

298

Relation between Coda-Q and stress loaded to an elastic body. -parameters of material conditions derived by stochastic measurement-  

NASA Astrophysics Data System (ADS)

Seismic coda is formed by superposed signals caused by scatterers. When heterogeneous condition is changed due to crustal deformations, coda-Q should vary reflecting the physical state if the materials. When the spatial scale of scatters in a medium becomes comparable with or smaller then the wavelength of seismic waves traveling through, it becomes very difficult to analyze the coda-wave quantitatively in terms of the location of scatterers, scattering mechanisms, etc. For inhomogeneous medium, it is natural to deal with stochastic methodologies to interpret seismic data. In this regard coda-Q has been frequently used as a stochastic measure of the medium in which seismic waves propagate. Since objectives of recent structural surveys include spatiotemporal or time-lapse variation of physical properties of underground medium, we propose a new geophysical monitoring method using the stochastic parameters if these parameters reflect changes of physical state of the medium. Several observed examples are reported that the relationship between the coda-Q and the number of earthquakes (e.g., Aki,2004). Aki (2004) said that the interrelation between the coda-Q and the number of earthquakes might be a key to understand the change in the state of crustal stress field. Here, we hypothesize that the change of the coda- Q reflects that of the stress magnitude and direction and try to focus on the relationship between the coda-Q and loaded stress which could cause earthquakes. The purpose of this study is to relate this relationship to non-stochastic quantity of the underground physical state, i.e., the stress to test our hypothesis. We employ two methods to achieve our objectives. One is Finite Difference Method (FDM), and the other is Boundary Integral Equation Method (BIEM). FDM is superior in the calculation of large field and saving calculation time. BIEM is superior in the free shape of boundaries. These two methods are applied to a numerical model of elastic body including inhomogeneities. First, we analyze the effects of velocity anisotropy on coda-Q using FDM. The velocity anisotropy caused by the stress loaded to the elastic model is included. The analysis reveals that the behavior of coda-Q depends on the magnitude of loaded stress and coda-Q decreases as stress is loaded. The gradient of the decrement varies according to the direction of the stress. Second, we analyze the effects of the behavior of cracks as the shape of cracks changes depending on the magnitude and the orientation of loaded stress on coda-Q. We found that the coda-Q varies with stress in terms of the behavior of cracks. When cracks are closed by applied stress, coda-Q increases. Because the spatial orientation of each crack depends on the stress history, the behavior of coda-Q also varies according to the orientation of principal stress. In conclusion, we propose that the loaded stress could be estimated (e.g. the orientation of stress and relative magnitude of stress) if we precisely obtain the change of Coda-Q varying with loaded stresses. It means that non-stochastic physical-state properties could be obtained from coda-wave and will lead to more clear deterministic model essential for engineering application of wave theories.

Okamoto, K.; Mikada, H.; Goto, T.; Takekawa, J.

2010-12-01

299

Kinetic rate laws derived from order parameter theory IV: Kinetics of Al,Si disordering in Na-feldspars  

NASA Astrophysics Data System (ADS)

The kinetic rate laws of Al-Si disordering under dry conditions ( T = 1353K, 1253 K, 1223 K, 1183 K) and in the presence of water (p = 1 kbar, T = 1023 K, 1073 K, 1103 K) were studied both experimentally and theoretically. A gradual change of the degree of order was found under dry conditions. For intermediate degrees of order broad distributions of the order parameter Q od occur. The variations of Q od are correlated with structural modulations as observed in the transmission electron microscope. The time evolution of the mean value of Q od can be well described by the rate law: 269_2004_Article_BF00202240_TeX2GIFE1.gif {dQ_{od} }/{dt} = - ? /{RT}exp sumlimits_{i = 1}^n {X_i^2 } left[ {{ - (G_a^0 + \\varepsilon (? Q_{od} )^2 )}/{RT}} right]{dG}/{dQ_{od }} with the excess Gibbs energy G and G {a/0}= 433.8 kJ/mol, ?= -27.4 kJ/mol, ? = 1.687 · 1014 h -1. Under wet conditions, two processes were found which occur simultaneously. Firstly, some material renucleated with the equilibrium degree of order. Secondly, the bulk of the material transformed following the same rate law as under dry conditions but with the reduced activation energy G {a/0}= 332.0 kJ/mol and ? = -43.0 kJ/ mol, ? = 1.047 · 1013 h-1. The applicability of the kinetic theory is discussed and some ideas for the analysis of geological observations are evolved.

Wruck, Bernd; Salje, Ekhard K. H.; Graeme-Barber, Ann

1991-05-01

300

nd Scattering Observables Derived from the Quark-Model Baryon-Baryon Interaction  

NASA Astrophysics Data System (ADS)

We solve the nd scattering in the Faddeev formalism, employing the NN sector of the quark-model baryon-baryon interaction fss2. The energy-dependence of the NN interaction, inherent to the (3q)-(3q) resonating-group formulation, is eliminated by the standard off-shell transformation utilizing the 1/N factor, where N is the normalization kernel for the (3q)-(3q) system. This procedure yields an extra nonlocality, whose effect is very important to reproduce all the scattering observables below En<=65 MeV. The different off-shell properties from the standard meson-exchange potentials, related to the non-locality of the quark-exchange kernel, yields appreciable effects to the differential cross sections and polarization observables of the nd elastic scattering, which are usually attributed to the specific properties of three-body forces.

Fujiwara, Y.; Fukukawa, K.

2010-05-01

301

Novel surface-based methodologies for investigating GH11 xylanase-lignin derivative interactions.  

PubMed

The recalcitrance of lignocellulose to bioprocessing represents the core problem and remains the limiting factor in creating an economy based on lignocellulosic ethanol production. Lignin is responsible for unproductive interactions with enzymes, and understanding how lignin impairs the susceptibility of biomass to enzymatic hydrolysis represents a significant aim in optimising the biological deconstruction of lignocellulose. The objective of this study was to develop methodologies based on surface plasmon resonance (SPR), which provide novel insights into the interactions between xylanase (Tx-xyn11) and phenolic compounds or lignin oligomers. In a first approach, Tx-xyn11 was fixed onto sensor surfaces, and phenolic molecules were applied in the liquid phase. The results demonstrated weak affinity and over-stoichiometric binding, as several phenolic molecules bound to each xylanase molecule. This approach, requiring the use of soluble molecules in the liquid phase, is not applicable to insoluble lignin oligomers, such as the dehydrogenation polymer (DHP). An alternative approach was developed in which a lignin oligomer was fixed onto a sensor surface. Due to their hydrophobic properties, the preparation of stable lignin layers on the sensor surfaces represented a considerable challenge. Among the various chemical and physico-chemical approaches assayed, two approaches (physisorption via the Langmuir-Blodgett technique onto self-assembled monolayer (SAM)-modified gold and covalent coupling to a carboxylated dextran matrix) led to stable lignin layers, which allowed the study of its interactions with Tx-xyn11 in the liquid phase. Our results indicated the presence of weak and non-specific interactions between Tx-xyn11 and DHP. PMID:24071685

Zeder-Lutz, G; Renau-Ferrer, S; Aguié-Béghin, V; Rakotoarivonina, H; Chabbert, B; Altschuh, D; Rémond, C

2013-10-15

302

Interactions between hypoxia and sewage-derived contaminants on gene expression in fish embryos  

Microsoft Academic Search

Fish embryos were used to evaluate the interaction among common environmental and chemical stressors found in urban coastal environments, namely hypoxia, aryl hydrocarbon receptor (AhR) agonists, and estrogenic compounds. At the molecular level, the systems responding to these stressors share common response factors, and evidence exists for cross-talk between them. Biomarkers of exposure to these stressors, cytochrome P4501a (Cyp1a), estrogen

A. McElroy; C. Clarke; T. Duffy; B. Cheng; J. Gondek; M. Fast; K. Cooper; L. White

303

Interaction of Mycobacterium avium with Human Monocyte-Derived Dendritic Cells  

Microsoft Academic Search

The mechanism by which mycobacteria elicit class I-restricted T-cell responses remains undefined because these organisms have been shown to reside exclusively within membrane-bound vesicles in macrophages (Mf), their primary host cells. We studied the interaction of M. avium with dendritic cells (DC) because they are the most potent antigen-presenting cells and are abundant at M. avium infection sites. We observed

NAHID MOHAGHEGHPOUR; ANNIKA VAN VOLLENHOVEN; JOSEPH GOODMAN; LUIZ E. BERMUDEZ

2000-01-01

304

Antithrombotic treatment (argatroban vs. heparin) in coronary angioplasty in angina pectoris: effects on inflammatory, hemostatic, and endothelium-derived parameters.  

PubMed

To evaluate the suitability of two anticoagulants (heparin vs. argatroban) as adjunctive drugs during and after elective conventional percutaneous transluminal coronary angioplasty, we compared the changes in inflammatory, hemostatic, and endothelium-derived markers in groups of patients with stable angina treated with the two drugs during percutaneous transluminal coronary angioplasty. Twenty-seven patients were randomly allocated to either group 1 (15 patients who received an empiric dose of heparin and aspirin as anticoagulant), or group 2 (12 patients who received an alternative regimen of argatroban and aspirin). Both drugs were administered as a bolus followed by continuous infusion for 96 hours during and after percutaneous transluminal coronary angioplasty. There were no differences in the inflammatory response induced by percutaneous transluminal coronary angioplasty in both groups, but the fibrinogen concentration significantly decreased during percutaneous transluminal coronary angioplasty in group 2. Decreased platelet counts and increased mean platelet volume were observed during percutaneous transluminal coronary angioplasty in both groups. The levels of prothrombin fragment 1+2 and thrombin antithrombin III complex increased markedly during percutaneous transluminal coronary angioplasty. Group 2 showed a more rapid return to the baseline levels of these two markers than group 1. Secondary fibrinolysis was evidenced by a steep increase of D-dimer after percutaneous transluminal coronary angioplasty in both groups. In contrast to the significant decrease in antithrombin activities during percutaneous transluminal coronary angioplasty in group 1, no marked change in these markers was found in group 2. Although the levels of von Willebrand factor and plasminogen activator inhibitor-1 showed essentially the same changes in both groups during and after percutaneous transluminal coronary angioplasty, more markedly increased levels of tissue type plasminogen activator and type plasminogen activator-plasminogen activator inhibitor-1 complex after percutaneous transluminal coronary angioplasty were found in group 1 than in group 2. While neither drug had any effect on the percutaneous transluminal coronary angioplasty-induced inflammatory response, argatroban may more effectively inhibit the generated thrombin and prevent antithrombin consumption during and after percutaneous transluminal coronary angioplasty. PMID:10822073

Suzuki, S; Matsuo, T; Kobayashi, H; Matsuo, M; Shimamo, C; Koide, M; Sakamoto, S

2000-05-15

305

Image-Based Quantification of Benzoporphyrin Derivative Uptake, Localization, and Photobleaching in 3D Tumor Models, for Optimization of PDT Parameters  

PubMed Central

Photodynamic therapy (PDT) is a light-based treatment modality in which wavelength specific activation of a photosensitizer (PS) generates cytotoxic response in the irradiated region. PDT response is critically dependent on several parameters including light dose, PS dose, uptake time, fluence rate, and the mode of light delivery. While the systematic optimization of these treatment parameters can be complex, it also provides multiple avenues for enhancement of PDT efficacy under diverse treatment conditions, provided that a rational framework is established to quantify the impact of parameter selection upon treatment response. Here we present a theranostic technique, combining the inherent ability of the PS to serve simultaneously as a therapeutic and imaging agent, with the use of image-based treatment assessment in three dimensional (3D) in vitro tumor models, to comprise a platform to evaluate the impact of PDT parameters on treatment outcomes. We use this approach to visualize and quantify the uptake, localization, and photobleaching of the PS benzoporphyrin derivative monoacid ring-A (BPD) in a range of treatment conditions with varying uptake times as well as continuous and fractionated light delivery regimens in 3D cultures of AsPC-1 and PANC-1 cells. Informed by photobleaching patterns and correlation with cytotoxic response, asymmetric fractionated light delivery at 4 hours BPD uptake was found to be the most effective regimen assessed. Quantification of the spatial profile of cell killing within multicellular nodules revealed that these conditions also achieve the highest depth of cytotoxicity along the radial axis of 3D nodules. The framework introduced here provides a means for systematic assessment of PDT treatment parameters in biologically relevant 3D tumor models with potential for broader application to other systems.

Glidden, Michael D.; Celli, Jonathan P.; Massodi, Iqbal; Rizvi, Imran; Pogue, Brian W.; Hasan, Tayyaba

2012-01-01

306

CE study of neuroprotective humanin peptide and its derivatives: interactions with phosphate, sulphate, alkylsulphonates and sulphated-beta-CD.  

PubMed

Humanin (HN), Met-Ala-Pro-Arg-Gly-Phe-Ser-Cys-Leu-Leu-Leu-Leu-Thr-Ser-Glu-IIe-Asp-Leu-Pro-Val-Lys-Arg-Arg-Ala, recently discovered in the human brain, is an important neuroprotective peptide. Some derivatives of HN show even higher biological activity, for example [G-14]-HN, where Ser at position 14 is replaced with Gly. As structurally related HN peptide derivatives have similar chemical properties, their separation by CE is difficult. In this work, the electrophoretic behaviour of HN derivatives including [G-14]-HN, a tryptophan HN derivative [W-14]-HN, several other HN derivatives and HN fragments was studied. While phosphate buffer was used as the general BGE, the effects of the buffer concentration and various additives were examined, including sulphate, heptane sulphonate, 2-morpholinoethanesulphonic acid N-[tris(hydroxymethyl)methyl]-2-aminoethane sulphonic acid (TES), sulphated-beta-CD and beta-CD. Separation efficiency of 200,000 theoretical plates was achieved in a BGE of 80 mM phosphate at pH 2.5 where seven out of nine major peaks were partially separated. By investigating the influence of concentration of the interrogated ions on peptides migration, the association between positively charged protonated sites of peptides and various anions was proved. Especially a strong interaction with phosphate, sulphate and sulphonate groups was established. Conditional stability constant of the [Pep(z+), (H(2)PO(4)(-))(n)](z - n) ion associate (n = 1) for [G-14]-HN equals to log K approximately 1.78. PMID:18203257

Havel, Josef; Li, Rong; Macka, Mirek

2008-02-01

307

Synthesis and antimitotic and tubulin interaction profiles of novel pinacol derivatives of podophyllotoxins.  

PubMed

Several pinacol derivatives of podophyllotoxins bearing different side chains and functions at C-7 were synthesized through reductive cross-coupling of podophyllotoxone and several aldehydes and ketones. While possessing a hydroxylated chain at C-7, the compounds retained their respective hydroxyl group with either the 7? (podo) or 7? (epipodo) configuration. Along with pinacols, some C-7 alkylidene and C-7 alkyl derivatives were also prepared. Cytotoxicities against neoplastic cells followed by cell cycle arrest and cellular microtubule disruption were evaluated and mechanistically characterized through tubulin polymerization inhibition and assays of binding to the colchicine site. Compounds of the epipodopinacol (7?-OH) series behaved similarly to podophyllotoxin in all the assays and proved to be the most potent inhibitors. Significantly, 7?-isopropyl-7-deoxypodophyllotoxin (20), without any hydroxyl function, appeared as a promising lead compound for a novel type of tubulin polymerization inhibitors. Experimental results were in overall agreement with modeling and docking studies performed on representative compounds of each series. PMID:22607205

Abad, Andrés; López-Pérez, José L; del Olmo, Esther; García-Fernández, Luis F; Francesch, Andrés; Trigili, Chiara; Barasoain, Isabel; Andreu, José M; Díaz, J Fernando; San Feliciano, Arturo

2012-07-23

308

Interaction of lipophilic VIP derivatives with recombinant VIP1/PACAP and VIP2/PACAP receptors.  

PubMed

Stearyl vasoactive intestinal polypeptide has been reported to be a VIP (vasoactive intestinal polypeptide) receptor agonist of high potency with an original bioavailability and action. We synthesized three fatty acyl derivatives, myristyl-, palmityl- and stearyl-[Nle17]VIP, and tested their capacity to recognize recombinant rat- and human VIP1- and VIP2/PACAP (pituitary adenylate cyclase-activating polypeptide) receptors and to stimulate adenylate cyclase activity. The three lipophilic analogues bound with high affinity (from 0.5 to 20 nM) to both receptor subtypes but did not distinguish between them. In preparations expressing a high density of human VIP1/PACAP receptors, the three lipophilic analogues had the same efficacy as VIP and [Nle17]VIP. In preparations expressing the rat receptors, stearyl-[Nle17]VIP had a lower efficacy than the other peptides tested. In preparations expressing a low level of VIP1/PACAP receptors and in those expressing VIP2/PACAP receptors, all analogues behaved like partial agonists. The lowest efficacy was observed for stearyl-[Nle17]VIP on the VIP2/PACAP receptor subclass. Based on our results, a complex pattern of in vivo biological effects of the lipophilic VIP derivatives should be expected: these compounds might behave as full agonists, partial agonists, or antagonists of the VIP response, depending on the number and the subtype of receptor expressed. PMID:9726637

Gourlet, P; Rathé, J; De Neef, P; Cnudde, J; Vandermeers-Piret, M C; Waelbroeck, M; Robberecht, P

1998-07-31

309

Synergistic interaction of NaCl and Cd on growth and photosynthetic parameters in soybean genotypes differing in salinity tolerance*  

PubMed Central

The effects of salinity (50 mmol/L NaCl) and Cd (1 ?mol/L CdCl2) as sole and combined on growth and photosynthetic parameters were studied using two soybean genotypes, Huachun 18 and NGB. The concentrations of Cd2+, Zn2+, Ca2+, Mg2+, K+ and Na+ were also determined in seeds and pods. Huachun 18 suffered a more serious decrease than NGB in net photosynthetic rate (P n) in the treatments of salinity stress alone and combined stress (NaCl+Cd), showing that it is relatively sensitive to salinity. The decrease in P n caused by salt stress in Huachun 18 was mainly due to the reduced total chlorophyll content and photosynthetic efficiency (the ratio of variable fluorescence to maximal fluorescence, F v/F m), whereas the decease in NGB was mainly related to reduced stomatal conductance (G s). The combined stress of both Na and Cd did not induce further decrease in photosynthesis and fluorescence in the two genotypes relative to salt or Cd stress alone. Greater change in the pod concentrations of Zn2+, Ca2+, Mg2+, K+ and Na+ was detected under salt stress for Huachun 18 than for NGB. The results suggested that the interactive effect of NaCl-Cd on growth and nutrient uptake differs between the two soybean genotypes.

Wei, Kang; Shamsi, Imran Haider; Zhang, Guo-ping

2007-01-01

310

Synergistic interaction of NaCl and Cd on growth and photosynthetic parameters in soybean genotypes differing in salinity tolerance.  

PubMed

The effects of salinity (50 mmol/L NaCl) and Cd (1 micromol/L CdCl(2)) as sole and combined on growth and photosynthetic parameters were studied using two soybean genotypes, Huachun 18 and NGB. The concentrations of Cd(2+), Zn(2+), Ca(2+), Mg(2+), K(+) and Na(+) were also determined in seeds and pods. Huachun 18 suffered a more serious decrease than NGB in net photosynthetic rate (P(n)) in the treatments of salinity stress alone and combined stress (NaCl+Cd), showing that it is relatively sensitive to salinity. The decrease in P(n) caused by salt stress in Huachun 18 was mainly due to the reduced total chlorophyll content and photosynthetic efficiency (the ratio of variable fluorescence to maximal fluorescence, F(v)/F(m)), whereas the decease in NGB was mainly related to reduced stomatal conductance (G(s)). The combined stress of both Na and Cd did not induce further decrease in photosynthesis and fluorescence in the two genotypes relative to salt or Cd stress alone. Greater change in the pod concentrations of Zn(2+), Ca(2+), Mg(2+), K(+) and Na(+) was detected under salt stress for Huachun 18 than for NGB. The results suggested that the interactive effect of NaCl-Cd on growth and nutrient uptake differs between the two soybean genotypes. PMID:17444602

Wei, Kang; Shamsi, Imran Haider; Zhang, Guo-ping

2007-04-01

311

Diffusion and Sedimentation Interaction Parameters for Measuring the Second Virial Coefficient and Their Utility as Predictors of Protein Aggregation  

PubMed Central

The concentration-dependence of the diffusion and sedimentation coefficients (kD and ks, respectively) of a protein can be used to determine the second virial coefficient (B2), a parameter valuable in predicting protein-protein interactions. Accurate measurement of B2 under physiologically and pharmaceutically relevant conditions, however, requires independent measurement of kD and ks via orthogonal techniques. We demonstrate this by utilizing sedimentation velocity (SV) and dynamic light scattering (DLS) to analyze solutions of hen-egg white lysozyme (HEWL) and a monoclonal antibody (mAb1) in different salt solutions. The accuracy of the SV-DLS method was established by comparing measured and literature B2 values for HEWL. In contrast to the assumptions necessary for determining kD and ks via SV alone, kD and ks were of comparable magnitudes, and solution conditions were noted for both HEWL and mAb1 under which 1), kD and ks assumed opposite signs; and 2), kD ? ks. Further, we demonstrate the utility of kD and ks as qualitative predictors of protein aggregation through agitation and accelerated stability studies. Aggregation of mAb1 correlated well with B2, kD, and ks, thus establishing the potential for kD to serve as a high-throughput predictor of protein aggregation.

Saluja, Atul; Fesinmeyer, R. Matthew; Hogan, Sabine; Brems, David N.; Gokarn, Yatin R.

2010-01-01

312

Agouti-related protein (83-132) is a competitive antagonist at the human melanocortin-4 receptor: no evidence for differential interactions with pro-opiomelanocortin-derived ligands  

Microsoft Academic Search

Interactions between pro-opiomelanocortin (POMC)- derived peptides, agouti-related protein (AGRP) and the melanocortin-4 receptor (MC4-R) are central to energy homeostasis. In this study we have undertaken compre- hensive pharmacological analysis of these interactions using a CHOK1 cell line stably transfected with human MC4-R. Our main objectives were (1) to compare the relative affinities and potencies of POMC-derived pep- tides endogenously secreted

L E Pritchard; D Armstrong; N Davies; R L Oliver; C A Schmitz; J C Brennand; G F Wilkinson

2004-01-01

313

Lateral interaction energy derived from Frumkin isotherm for c(2 x 2) Br/Ag(100)  

SciTech Connect

The structure of the bromide adlayer on Ag(100) and the adsorption isotherm have been determined by using in situ surface x-ray scattering techniques and chronocoulometry. Bromide adsorbed on Ag(100) forms a fourfold-hollow-site lattice gas and the adsorption saturates at 1/2 monolayer in a c(2 x 2) structure. The Frumkin isotherm has been employed to fit the experimentally obtained isotherm. Using the experimentally determined electrosorption valency, the lateral interaction energy of 220 meV/atom at full coverage is obtained.

Wang, J.X.; Ocko, B.M. [Brookhaven National Lab., Upton, NY (United States); Wandlowski, T. [Univ. of Ulm (Germany). Dept. of Electrochemistry

1997-10-01

314

Robustness of quantitative compressive sensing MRI: The effect of random undersampling patterns on derived parameters for DCE- and DSC-MRI  

PubMed Central

Compressive sensing (CS) in Cartesian magnetic resonance imaging (MRI) involves random partial Fourier acquisitions. The random nature of these acquisitions can lead to variance in reconstruction errors. In quantitative MRI, variance in the reconstructed images translates to an uncertainty in the derived quantitative maps. We show that for a spatially regularized 2×-accelerated human breast CS DCE-MRI acquisition with a 1922 matrix size, the coefficients of variation (CoVs) in voxel-level parameters due to the random acquisition are 1.1%, 0.96%, and 1.5% for the tissue parameters Ktrans, ve, and vp, with an average error in the mean of ?2.5%, ?2.0%, and ?3.7%, respectively. Only 5% of the acquisition schemes had a systematic underestimation larger than than 4.2%, 3.7%, and 6.1%, respectively. For a 2×-accelerated rat brain CS DSC-MRI study with a 642 matrix size, the CoVs due to the random acquisition were 19%, 9.5%, and 15% for the cerebral blood flow and blood volume and mean transit time, respectively, and the average errors in the tumor mean were 9.2%, 0.49%, and ?7.0%, respectively. Across 11 000 different CS reconstructions, we saw no outliers in the distribution of parameters, suggesting that, despite the random undersampling schemes, CS accelerated quantitative MRI may have a predictable level of performance.

Smith, David. S.; Li, Xia; Gambrell, James V.; Arlinghaus, Lori R.; Quarles, C. Chad; Yankeelov, Thomas E.; Welch, E. Brian

2012-01-01

315

Evaluation of relationship between preoperative bone density values derived from cone beam computed tomography and implant stability parameters: a clinical study.  

PubMed

OBJECTIVES: The aim of this study was to explore the efficacy of bone density value derived from cone beam computed tomography (CBCT) by evaluating its correlation with implant stability parameters including insertion torque value (ITV) and radiofrequency analysis in relation to different clinical variables including location, gender, age, bone quality, and implant diameter. MATERIAL AND METHODS: A total of 65 implants were placed in 17 patients. The bone densities of implant recipient sites were preoperatively recorded using CBCT. Bone quality was subjectively assessed, which depends on the stiffness of the jawbone according to the Lekholm and Zarb index during drilling procedure. The maximum ITV of each implant was recorded using a digital torque meter during implant placement. Resonance frequency measurements were taken using an Osstell(®) Mentor immediately after implant placement. Data were analyzed statistically. RESULTS: The mean bone density, insertion torque, and implant stability quotient values of all implants were 556 ± 80, 37.4 ± 3.3 Ncm, and 73.8 ± 7.2, respectively. Statistically significant correlations were found between bone density values from CBCT and implant stability parameters in relation to all variables. CONCLUSION: Bone density assessment using CBCT is an efficient method and significantly correlated with implant stability parameters and Lekholm and Zarb index. Thus, it is possible to predict initial implant stability and possibility of immediate or early loading using CBCT scans prior to implant placement. PMID:23772811

Salimov, Fariz; Tatli, Ufuk; Kürkçü, Mehmet; Ako?lan, Mücahide; Oztunç, Haluk; Kurto?lu, Cem

2013-06-17

316

Predicting forest structural parameters using the image texture derived from WorldView-2 multispectral imagery in a dryland forest, Israel  

NASA Astrophysics Data System (ADS)

Estimation of forest structural parameters by field-based data collection methods is both expensive and time consuming. Satellite remote sensing is a low-cost alternative in modeling and mapping structural parameters in large forest areas. The current study investigates the potential of using WordView-2 multispectral satellite imagery for predicting forest structural parameters in a dryland plantation forest in Israel. The relationships between image texture features and the several structural parameters such as Number of Trees (NT), Basal Area (BA), Stem Volume (SV), Clark-Evans Index (CEI), Diameter Differentiation Index (DDI), Contagion Index (CI), Gini Coefficient (GC), and Standard Deviation of Diameters at Breast Heights (SDDBH) were examined using correlation analyses. These variables were obtained from 30 m × 30 m square-shaped plots. The Standard Deviation of Gray Levels (SDGL) as a first order texture feature and the second order texture variables based on Gray Level Co-occurrence Matrix (GLCM) were calculated for the pixels that corresponds to field plots. The results of the correlation analysis indicate that the forest structural parameters are significantly correlated with the image texture features. The highest correlation coefficients were calculated for the relationships between the SDDBH and the contrast of red band (r = 0.75, p < 0.01), the BA and the entropy of blue band (r = 0.73, p < 0.01), and the GC and the contrast of blue band (r = 0.71, p < 0.01). Each forest structural parameter was modeled as a function of texture measures derived from the satellite image using stepwise multi linear regression analyses. The determination coefficient (R2) and root mean square error (RMSE) values of the best fitting models, respectively, are 0.38 and 109.56 ha-1 for the NT; 0.54 and 1.79 m2 ha-1 for the BA; 0.42 and 27.18 m3 ha-1 for the SV; 0.23 and 0.16 for the CEI; 0.32 and 0.05 for the DDI; 0.25 and 0.06 for the CI; 0.50 and 0.05 for the GC; and 0.67 and 0.70 for the SDDBH. The leave-one-out cross-validation technique was applied for validation of the best-fitted models (R2 > 0.50). In conclusion, cross-validated statistics confirmed that the structural parameters including the BA, SDDBH, and GC can be predicted and mapped with a reasonable accuracy using the texture features extracted from the spectral bands of WorldView-2 image.

Ozdemir, Ibrahim; Karnieli, Arnon

2011-10-01

317

Microwave spectroscopic studies of molecular recognition: Analysis of diastereomeric interactions between ethanol and oxirane derivatives  

NASA Astrophysics Data System (ADS)

High resolution microwave spectroscopy complimented by ab initio calculations has been used to elucidate the diastereomeric interactions in a set of small model complexes. Ethanol, a transient chiral alcohol, was combined with oxirane (achiral), methyl-oxiraneootnotetextmark[1] (1 stereocenter) and trans-2,3-dimethyloxirane (2 stereocenters) to form hydrogen-bonded 1:1 complexes. The rotational constants of two conformers of ethanoloxirane, six conformers of ethanolmethyl-oxirane and three conformers of ethanoltrans-2,3-dimethyloxirane have been determined and the relative stability order of the conformers has been established. The dependence of the observed intensity on pressure, nozzle temperature and different carrier gases has been investigated for the case of ethanoltrans-2,3-dimethyloxirane to give a first insight into the kinetical and thermodynamical influence on the formation of different conformers. The step-by-step methyl addition to oxirane helps to unravel the diastereomeric interactions at play via analysis of the subtle energy differences between each set of conformers, allowing for a detailed understanding of molecular recognition in this benchmark system.ootnotetextmark[1]Nicole Borho, Yunjie Xu, Angew. Chem., 2006, (VIP paper, Published Online: 17 Nov 2006, DOI: 10.1002/anie.200603809).

Borho, Nicole; Xu, Yunjie

2007-06-01

318

Semi-Empirical Effective Interactions for Inelastic Scattering Derived from the Reid Potential  

NASA Astrophysics Data System (ADS)

An effective local interaction suitable for inelastic scattering is constructed from the Reid soft - core potential. We proceed in two stages: We first calculated a set of relative two - body matrix elements in a variational approach using the Reid soft-core potential folded with two-body correlation functions. In the second stage we constructed a potential for inelastic scattering by fitting the matrix elements to a sum of Yukawa central, tensor and spin-orbit terms to the set of relative two - body matrix elements obtained in the first stage by a least squares fitting procedure. The ranges of the new potential were selected to ensure the OPEP tails in the relevant channels as well as the short - range part of the interaction. It is found that the results of our variational techniques are very similar to the G - matrix calculations of Bertsch and co - workers in the singlet - even, triplet - even, tensor - even and spin-orbit odd channels thus putting our calculations of two - body matrix elements of nuclear forces in these channels on a sound footing. However, there exist major differences in the singlet - odd, triplet - odd, tensor - odd and spin - orbit even channels which casts some doubt on our understanding of nuclear forces in these channels.

Fiase, J. O.; Sharma, L. K.; Winkoun, D. P.; Hosaka, A.

2001-09-01

319

Statistically Derived Amino Acid Pair Potentials: Applications to Protein Folding and Protein-Protein Interactions  

NASA Astrophysics Data System (ADS)

A new approach to generation of tertiary conformations for a protein of given primary sequence is reviewed. Amino acid pair potentials are derived based on the hypothesis that the observed pair correlation function for a given pair of amino acids is distributed according to a Boltzmann probability distribution. Tests of this idea have been reported by Wilson and Doniach for folding of a small protein and by Sippl and collaborators for discriminating a correctly folded protein from a set of artificially misfolded models. Preliminary tests are reported on the use of this approach for the antibody-antigen docking problem and for exploration of conformation space of a polypeptide loop using a Langevin dynamics approach.

Doniach, S.

1991-10-01

320

Study on the interaction of amino phosphine ester derivatives with DNA by spectroscopy, modeling and calorimetry  

NASA Astrophysics Data System (ADS)

The binding properties of amino phosphate ester derivatives, compound 1 and 2 with calf thymus DNA (CT-DNA) were investigated by UV spectra, fluorescence spectra, molecular modeling and isothermal titration calorimetry (ITC). The intrinsic binding constants Kb of compound 1 and 2 with CT-DNA were determined by fluorescence spectroscopy and ITC, respectively. The results indicated that the two compounds bind to CT-DNA with different binding affinity, which is in the order of compound 1 > compound 2. At the same time, fluorescence spectra suggested that the mechanism of the binding of the two compounds to CT-DNA is a static enhancing type. According to the ethidium bromide displacement experiments, UV spectra, molecular modeling and ITC studies, it can be concluded that compound 1 and 2 are intercalators that can slide into the G-C rich region of CT-DNA. Furthermore, ITC data showed that compound/DNA binding is enthalpy controlled.

Lu, Yan; Wang, Gongke; Tang, Wen; Hao, Xiaoxiao; Xu, Meihua; Li, Xiang

2011-11-01

321

Hedgehog-mediated paracrine interaction between hepatic stellate cells and marrow-derived mesenchymal stem cells  

SciTech Connect

During liver injury, bone marrow-derived mesenchymal stem cells (MSCs) can migrate and differentiate into hepatocytes. Hepatic stellate cell (SC) activation is a pivotal event in the development of liver fibrosis. Therefore, we hypothesized that SCs may play an important role in regulating MSC proliferation and differentiation through the paracrine signaling pathway. We demonstrate that MSCs and SCs both express hedgehog (Hh) pathway components, including its ligands, receptors, and target genes. Transwell co-cultures of SCs and MSCs showed that the SCs produced sonic hedgehog (Shh), which enhanced the proliferation and differentiation of MSCs. These findings demonstrate that SCs indirectly modulate the activity of MSCs in vitro via the Hh pathway, and provide a plausible explanation for the mechanisms of transplanted MSCs in the treatment of liver fibrosis.

Lin Nan [Division of Hepatology, Third Hospital of Sun Yat-Sen University, Tianhe Road 600, Guangzhou City 510630, Guangdong Province (China)], E-mail: linnancn@gmail.com; Tang Zhaofeng; Deng Meihai; Zhong Yuesi; Lin Jizong [Division of Hepatology, Third Hospital of Sun Yat-Sen University, Tianhe Road 600, Guangzhou City 510630, Guangdong Province (China); Yang Xuhui; Xiang Peng [Center for Stem Cell Biology and Tissue Engineering, Sun Yat-Sen University, Guangzhou City, Guangdong Province (China); Xu Ruiyun [Division of Hepatology, Third Hospital of Sun Yat-Sen University, Tianhe Road 600, Guangzhou City 510630, Guangdong Province (China)

2008-07-18

322

Secretion Modification Region-Derived Peptide Disrupts HIV-1 Nef's Interaction with Mortalin and Blocks Virus and Nef Exosome Release  

PubMed Central

Nef is secreted from infected cells in exosomes and is found in abundance in the sera of HIV-infected individuals. Secreted exosomal Nef (exNef) induces apoptosis in uninfected CD4+ T cells and may be a key component of HIV pathogenesis. The exosomal pathway has been implicated in HIV-1 virus release, suggesting a possible link between these two viral processes. However, the underlying mechanisms and cellular components of exNef secretion have not been elucidated. We have previously described a Nef motif, the secretion modification region (SMR; amino acids 66 to 70), that is required for exNef secretion. In silico modeling data suggest that this motif can form a putative binding pocket. We hypothesized that the Nef SMR binds a cellular protein involved in protein trafficking and that inhibition of this interaction would abrogate exNef secretion. By using tandem mass spectrometry and coimmunoprecipitation with a novel SMR-based peptide (SMRwt) that blocks exNef secretion and HIV-1 virus release, we identified mortalin as an SMR-specific cellular protein. A second set of coimmunoprecipitation experiments with full-length Nef confirmed that mortalin interacts with Nef via Nef's SMR motif and that this interaction is disrupted by the SMRwt peptide. Overexpression and microRNA knockdown of mortalin revealed a positive correlation between exNef secretion levels and mortalin protein expression. Using antibody inhibition we demonstrated that the Nef/mortalin interaction is necessary for exNef secretion. Taken together, this work constitutes a significant step in understanding the underlying mechanism of exNef secretion, identifies a novel host-pathogen interaction, and introduces an HIV-derived peptide with antiviral properties.

Shelton, Martin N.; Huang, Ming-Bo; Ali, Syed A.; Powell, Michael D.

2012-01-01

323

Interactions between hypoxia and sewage-derived contaminants on gene expression in fish embryos.  

PubMed

Fish embryos were used to evaluate the interaction among common environmental and chemical stressors found in urban coastal environments, namely hypoxia, aryl hydrocarbon receptor (AhR) agonists, and estrogenic compounds. At the molecular level, the systems responding to these stressors share common response factors, and evidence exists for cross-talk between them. Biomarkers of exposure to these stressors, cytochrome P4501a (Cyp1a), estrogen receptor alpha (ER?), brain cytochrome P450 aromatase (Cyp19a2 or AromB), and hypoxia inducible factor 1 alpha (Hif-1?) mRNA expression were examined using qRT-PCR simultaneously in embryos of two well studied species, the Atlantic killifish, Fundulus heteroclitus, and the zebrafish Danio rerio. Embryos of both species were exposed to the model Cyp1a inducer ?-naphthoflavone (BNF) or 17-? estradiol (E2) under either normoxic or hypoxic (5% oxygen atmosphere) conditions and harvested prior to hatch at 9 days post fertilization (dpf) for the killifish, and 48h post fertilization (hpf) for the zebrafish. BNF significantly induced Cyp1a expression in embryos of both species with killifish embryos being more responsive (700-fold>control) than zebrafish embryos (7-100-fold>control). AromB was also significantly influenced by treatment, but to a lesser extent, with mean expression levels increased by less than two-fold over control values in response to E2, and in one case upregulated by BNF. ER? and Hif-1? were constitutively expressed in embryos of both species, but expression was unaffected by exposure to either BNF or E2. Hypoxic conditions downregulated AromB expression strongly in killifish but not in zebrafish embryos. The impact of hypoxia on expression of other genes in either species was inconsistent, although an interactive effect between hypoxia and BNF on several of the genes evaluated was observed. These data are the first to examine expression patterns of these important environmental response genes together in embryos of two important model fish species. The results support the use of Cyp1a expression as a biomarker of AhR agonists in fish embryos, and indicate that AromB may be more responsive than ER? to estrogenic chemicals at this stage in development. Hif-1? expression was not found to be a good biomarker of hypoxic exposure in either killifish or zebrafish embryos. The interaction observed between BNF and co-exposure to hypoxia warrants further investigation. Finally killifish embryos are generally more sensitive than zebrafish embryos at this stage of development supporting their use in environmental assessments. PMID:22104699

A McElroy; Clark, Carissa; Duffy, T; Cheng, B; Gondek, J; Fast, M; Cooper, K; White, L

2011-11-03

324

Tensor Interaction Limit Derived From the ?-?-?¯ Correlation in Trapped Li8 Ions  

NASA Astrophysics Data System (ADS)

A measurement of the ?-?-?¯ angular correlation in the Gamow-Teller decay Li8?Be*8+?¯+?, Be*8??+? has been performed using ions confined in a linear Paul trap surrounded by silicon detectors. The energy difference spectrum of the ? particles emitted along and opposite the direction of the ? particle is consistent with the standard model prediction and places a limit of 3.1% (95.5% confidence level) on any tensor contribution to the decay. From this result, the amplitude of any tensor component CT relative to that of the dominant axial-vector component CA of the electroweak interaction is limited to |CT/CA|<0.18 (95.5% confidence level). This experimental approach is facilitated by several favorable features of the Li8 ? decay and has different systematic effects than the previous ?-?¯ correlation results for a pure Gamow-Teller transition obtained from studying He6 ? decay.

Li, G.; Segel, R.; Scielzo, N. D.; Bertone, P. F.; Buchinger, F.; Caldwell, S.; Chaudhuri, A.; Clark, J. A.; Crawford, J. E.; Deibel, C. M.; Fallis, J.; Gulick, S.; Gwinner, G.; Lascar, D.; Levand, A. F.; Pedretti, M.; Savard, G.; Sharma, K. S.; Sternberg, M. G.; Sun, T.; Van Schelt, J.; Yee, R. M.; Zabransky, B. J.

2013-03-01

325

Nucleon-Deuteron Breakup Differential Cross Sections Derived from the Quark-Model NN Interaction  

NASA Astrophysics Data System (ADS)

The nd and pd breakup differential cross sections for E N ? 65 MeV are examined using the energy-independent quark-model nucleon-nucleon interaction fss2. The Coulomb effect is incorporated by the sharp cut-off Coulomb force, acting between quarks, without the phase-shift renormalization for the breakup amplitudes. Our model yields the results very similar to the meson-exchange potentials, including disagreement for some specific kinematical configurations. This includes the notorious space star anomaly of the nd and pd scattering at E N = 13 MeV. The KVI data for the breakup differential cross sections of E d = 130 MeV dp scattering are reasonably reproduced by taking the Coulomb cut-off radius ? = 16 fm.

Fujiwara, Y.; Fukukawa, K.

2013-03-01

326

Interaction of nickel-based SOFC anodes with trace contaminants from coal-derived synthesis gas  

NASA Astrophysics Data System (ADS)

New and efficient methods of producing electrical energy from natural resources have become an important topic for researchers. Integrated gasification and fuel cell (IGFC) systems offer a fuel-flexible, high-efficiency method of energy generation. Specifically, in coal gasification processes, coal can be changed into a high-quality gaseous fuel suitable for feeding solid oxide fuel cells (SOFCs). However, trace species found in coal synthesis gas (syngas) may have a deleterious effect on the performance of nickel-based SOFC anodes. Generally, the cost of removing these species down to parts per million (ppm) levels is high. The purpose of this research is to determine the highest amount of contaminant that results in a low rate (˜1% per 1000 h) of cell performance degradation, allowing the SOFC to produce usable power for 40,000 hours. The cell performance degradation rate was determined for benzene, naphthalene, and mercury-doped syngas based on species concentration. Experimental data are fitted with degradation models to predict cell lifetime behavior. From these results, the minimum coal syngas cleanup required for these trace materials is determined. It is found that for a final cell voltage of 0.6 V, naphthalene and benzene must be cleaned to 360 ppm and less than 150 ppm, respectively. No additional cleaning is required for mercury beyond established environmental standards. Additionally, a detailed attack and recovery mechanism is proposed for the hydrocarbon species and their interaction with the fuel cell. This mechanism is proposed by considering the type of degradation models predicted and how carbon would interact with the Ni-YSZ anode to justify those models. The mechanism postulates that carbon is diffusing into the nickel structure, creating a metal solution. Once the nickel is saturated, the carbon begins to deposit on the nickel surface, reducing the electrode active area. The formation of metal solutions and the deposition of carbon results in reduced cell productivity.

Hackett, Gregory Allen

327

New insights into calicheamicin-DNA interactions derived from a model nucleosome system.  

PubMed

Using the Xenopus borealis 5S RNA gene, we have identified several new features of the interaction of calicheamicin (CAL), an enediyne antitumor agent, with nucleosomal and naked DNA targets. CAL-mediated DNA damage was generally reduced by incorporation of the DNA into a nucleosome. However, in one instance, the frequency of DNA damage was enhanced in the nucleosome compared to naked DNA. This increase in CAL damage may result from bending-induced changes in the target site, while the association of histone proteins with DNA in the nucleosome may generally reduce the affinity of CAL for its targets by imposing dynamic constraints on the DNA, by altering target structure, or by steric hindrance. One implication of these observations is that new structural features created by incorporation of DNA into chromatin may produce 'hot spots' for CAL-mediated DNA damage not apparent in naked DNA studies. In a second set of experiments, the orientation of CAL at damage sites in naked 5S rDNA was determined. The results suggest that minor groove width per se is not a major determinant of CAL target selection. Our studies support the generality of an oligopurine recognition element, with the additional requirement that the purine tract is interrupted at the 3'-end by a pyrimidine(s). To account for these observations, we propose a model in which CAL recognizes the unique structural and dynamic features associated with the 3'-end of an oligopurine tract. Finally, we conclude that the dyad axis of pseudosymmetry of the 5S rRNA gene nucleosome cannot be determined with any degree of certainty. This places significant limitations on the interpretation of results from the study of drug-DNA interactions with reconstituted nucleosomes. PMID:7582951

Yu, L; Salzberg, A A; Dedon, P C

1995-06-01

328

Interactions of selected indole derivatives with phospholipase A?: in silico and in vitro analysis.  

PubMed

Phospholipase A2 (PLA?) is one of the key enzymes involved in the formation of inflammatory mediators. Inhibition of PLA? is considered to be one of the efficient methods to control inflammation. In silico docking studies of 160 selected indole derivatives performed against porcine pancreatic PLA? (ppsPLA2) suggested that, CID2324681, CID8617 (indolebutyric acid or IBA), CID22097771 and CID802 (indoleacetic acid or IAA) exhibited highest binding energies. In silico analysis was carried out to predict some of the ADME properties. The binding potential of these compounds with human non pancreatic secretory PLA? (hnpsPLA?) was determined using molecular docking studies. In order to corroborate the in silico results, enzyme kinetics and isothermal titration calorimetric analysis of the two selected compounds, IAA and IBA were performed against ppsPLA?. From the analysis, it was concluded that IAA and IBA can act as competitive inhibitors to the enzyme and may be used as anti inflammatory agents. PMID:23315198

Dileep, Kalarickal Vijayan; Remya, Chandran; Tintu, Ignatius; Haridas, Madathilkovilakathu; Sadasivan, Chittalakkottu

2013-01-13

329

Combining intracellular selection with protein-fragment complementation to derive A? interacting peptides  

PubMed Central

Aggregation of the ?-amyloid (A?) peptide into toxic oligomers is considered the primary event in the pathogenesis of Alzheimer's disease. Previously generated peptides and mimetics designed to bind to amyloid fibrils have encountered problems in solubility, protease susceptibility and the population of small soluble toxic oligomers. We present a new method that opens the possibility of deriving new amyloid inhibitors. The intracellular protein-fragment complementation assay (PCA) approach uses a semi-rational design approach to generate peptides capable of binding to A?. Peptide libraries are based on A? regions responsible for instigating amyloidosis, with screening and selection occurring entirely inside Escherichia coli. Successfully selected peptides must therefore bind A? and recombine an essential enzyme while permitting bacterial cell survival. No assumptions are made regarding the mechanism of action for selected binders. Biophysical characterisation demonstrates that binding induces a noticeable reduction in amyloid. Therefore, this amyloid-PCA approach may offer a new pathway for the design of effective inhibitors against the formation of amyloid in general.

Acerra, Nicola; Kad, Neil M.; Mason, Jody M.

2013-01-01

330

Food plant derived disease tolerance and resistance in a natural butterfly-plant-parasite interactions.  

PubMed

Organisms can protect themselves against parasite-induced fitness costs through resistance or tolerance. Resistance includes mechanisms that prevent infection or limit parasite growth while tolerance alleviates the fitness costs from parasitism without limiting infection. Although tolerance and resistance affect host-parasite coevolution in fundamentally different ways, tolerance has often been ignored in animal-parasite systems. Where it has been studied, tolerance has been assumed to be a genetic mechanism, unaffected by the host environment. Here we studied the effects of host ecology on tolerance and resistance to infection by rearing monarch butterflies on 12 different species of milkweed food plants and infecting them with a naturally occurring protozoan parasite. Our results show that monarch butterflies experience different levels of tolerance to parasitism depending on the species of milkweed that they feed on, with some species providing over twofold greater tolerance than other milkweed species. Resistance was also affected by milkweed species, but there was no relationship between milkweed-conferred resistance and tolerance. Chemical analysis suggests that infected monarchs obtain highest fitness when reared on milkweeds with an intermediate concentration, diversity, and polarity of toxic secondary plant chemicals known as cardenolides. Our results demonstrate that environmental factors-such as interacting species in ecological food webs-are important drivers of disease tolerance. PMID:23106703

Sternberg, Eleanore D; Lefèvre, Thierry; Li, James; de Castillejo, Carlos Lopez Fernandez; Li, Hui; Hunter, Mark D; de Roode, Jacobus C

2012-06-27

331

Interactions between rod-like cellulose nanocrystals and xylan derivatives: A light scattering study  

NASA Astrophysics Data System (ADS)

Interactions between rod-like cellulose nanocrystals and 2-hydroxypropyl-trimethylammonium (HPMA) xylan were investigated by polarized (DLS) and depolarized dynamic light scattering (DDLS). Cellulose nanocrystals were prepared by the controlled hydrolysis of black spruce pulp. Binary rod-like cellulose nanocrystal/water and ternary HPMA xylan/rod-like cellulose nanocrystal/water systems with different concentrations of cellulose nanocrystals were probed. Translational and rotational diffusion coefficients of cellulose nanocrystals in water are (4.8 ± 0.4) x 10-8 cm^2s-1 and (526 ± 20) s-1, respectively, and calculated lengths and diameters for nanocrystals are comparable to those of cellulose whiskers from cotton. At high cellulose nanocrystal concentrations, DDLS studies in ternary systems provide translational and rotational diffusion coefficients. However, at low cellulose nanocrystal concentrations, DDLS studies of ternary systems do not yield rotational diffusion coefficients. This behavior is attributed to bridging between polymer chains that causes non-linear deviation on standard decay rate (?) versus scattering vector magnitude (q^2) plots.

Sim, Jae Hyun; Schwikal, Katrin; Heinze, Thomas; Dong, Shuping; Roman, Maren; Esker, Alan

2009-03-01

332

The CXC Chemokine Receptor 4 Ligands Ubiquitin and Stromal Cell-derived Factor-1? Function through Distinct Receptor Interactions*  

PubMed Central

Recently, we identified extracellular ubiquitin as an endogenous CXC chemokine receptor (CXCR) 4 agonist. However, the receptor selectivity and molecular basis of the CXCR4 agonist activity of ubiquitin are unknown, and functional consequences of CXCR4 activation with ubiquitin are poorly defined. Here, we provide evidence that ubiquitin and the cognate CXCR4 ligand stromal cell-derived factor (SDF)-1? do not share CXCR7 as a receptor. We further demonstrate that ubiquitin does not utilize the typical two-site binding mechanism of chemokine-receptor interactions, in which the receptor N terminus is important for ligand binding. CXCR4 activation with ubiquitin and SDF-1? lead to similar G?i-responses and to a comparable magnitude of phosphorylation of ERK-1/2, p90 ribosomal S6 kinase-l and Akt, although phosphorylations occur more transiently after activation with ubiquitin. Despite the similarity of signal transduction events after activation of CXCR4 with both ligands, ubiquitin possesses weaker chemotactic activity than SDF-l? in cell migration assays and does not interfere with productive entry of HIV-1 into P4.R5 multinuclear activation of galactosidase indicator cells. Unlike SDF-1?, ubiquitin lacks interactions with an N-terminal CXCR4 peptide in NMR spectroscopy experiments. Binding and signaling studies in the presence of antibodies against the N terminus and extracellular loops 2/3 of CXCR4 confirm that the ubiquitin CXCR4 interaction is independent of the N-terminal receptor domain, whereas blockade of extracellular loops 2/3 prevents receptor binding and activation. Our findings define ubiquitin as a CXCR4 agonist, which does not interfere with productive cellular entry of HIV-1, and provide new mechanistic insights into interactions between CXCR4 and its natural ligands.

Saini, Vikas; Staren, Daniel M.; Ziarek, Joshua J.; Nashaat, Zayd N.; Campbell, Edward M.; Volkman, Brian F.; Marchese, Adriano; Majetschak, Matthias

2011-01-01

333

Interactions of oxime reactivators with diethylphosphoryl adducts of human acetylcholinesterase and its mutant derivatives.  

PubMed

Diethylphosphoryl conjugates of human acetylcholinesterase (AChE) and selected mutants, carrying amino acid replacements at the active center and at the peripheral anionic site, were subjected to reactivation with the monopyridinium oxime 2-hydroxy-iminomethyl-1-methylpyridinium chloride and the bispyridinium oximes 1,3-bis(4'-hydroxyiminomethyl-1'-pyridinium),propane dibromide (TMB-4) and 1-(2'-hydroxyiminomethyl-1'-pyridinium)-3-(4"-carbamoyl-1"-pyridinium)-2 - oxapropane dichloride (HI-6). The kinetic profiles for all of the reactivation reactions indicate single populations of reactivatable species. Replacement of Trp86, the anionic subsite in the active center, lowered the affinity of the free enzyme toward all three reactivators, but in the corresponding diethylphosphoryl conjugate, only affinity toward TMB-4 was affected. Replacement of other constituents of the hydrophobic subsite (Tyr337, Phe338) had no major effect on either affinity to the free enzymes or rates of reactivation. Substitution of residues of the acyl pocket (Phe295, Phe297) lowered the affinities toward reactivators except for the 20-fold increase in affinity of F295A toward HI-6. Replacement of the acidic residues in the active center (Glu202, Glu450) affected mainly the rates of nucleophilic displacement of the phosphoryl moiety. The effect of substituting residues constituting the peripheral anionic site at the rim of the active site gorge (Tyr72, Asp74, Trp286) was particularly puzzling because for 2-hydroxy-iminomethyl-1-methylpyridinium chloride and HI-6, mainly the nucleophilic reaction rate constants were affected, whereas for TMB-4, the affinities of the phosphorylated enzymes were significantly reduced. The fact that perturbations of the functional architecture of HuAChE active center can account for only some of the observed effects on the reactivation rates suggests that the binding modes of oxime to the phosphorylated and nonphosphorylated enzymes are considerably different and/or that interactions of the reactivators with the phosphoryl moieties play a dominant role in the reactivation process. PMID:8794905

Grosfeld, H; Barak, D; Ordentlich, A; Velan, B; Shafferman, A

1996-09-01

334

Derivation of Orbital Parameters of Very Low-Mass Companions in Double Stars from Radial Velocities and Observations of Space-Astrometry Missions like HIPPARCOS, DIVA and GAIA  

NASA Astrophysics Data System (ADS)

Radial velocity measurements are a well known high-precision method to obtain the orbits of extrasolar planets or brown dwarfs. However, this method is not able to determine the inclination which could be derived from astrometry. The astrometric effects of those objects are very minute, wherefore the interest of astronomers in astrometric techniques was very poor. This situation changes fundamentally since space astrometry observations are available. HIPPARCOS demonstrated the power of space astrometry and the extremely high accuracy of the DIVA, and especially the GAIA observations allows one to detect Jupiter- and Earth-like objects. The optimal estimation of the parameters of the orbit of extrasolar planets or brown dwarfs is a combination of radial velocity measurements and space astrometry observations. Here it is possible to overcome problems which are inherent in both observation methods, so space astrometry complements radial velocity observations and vice versa. This paper gives a method for the parameter estimation using both tools of measurements and shows the limits of this procedure. In addition an error assessment gives the capability of the combination of radial velocity observations and space astrometry.

Bernstein, H.-H.

335

Tables and graphs of electron-interaction cross sections from 10 eV to 100 GeV derived from the LLNL Evaluated Electron Data Library (EEDL), Z = 1--100  

SciTech Connect

Energy-dependent evaluated electron interaction cross sections and related parameters are presented for elements H through Fm (Z = 1 to 100). Data are given over the energy range from 10 eV to 100 GeV. Cross sections and average energy deposits are presented in tabulated and graphic form. In addition, ionization cross sections and average energy deposits for each shell are presented in graphic form. This information is derived from the Livermore Evaluated Electron Data Library (EEDL) as of July, 1991.

Perkins, S.T.; Cullen, D.E. (Lawrence Livermore National Lab., CA (United States)); Seltzer, S.M. (National Inst. of Standards and Technology (NML), Gaithersburg, MD (United States). Center for Radiation Research)

1991-11-12

336

A SNAP-Tagged Derivative of HIV-1--A Versatile Tool to Study Virus-Cell Interactions  

PubMed Central

Fluorescently labeled human immunodeficiency virus (HIV) derivatives, combined with the use of advanced fluorescence microscopy techniques, allow the direct visualization of dynamic events and individual steps in the viral life cycle. HIV proteins tagged with fluorescent proteins (FPs) have been successfully used for live-cell imaging analyses of HIV-cell interactions. However, FPs display limitations with respect to their physicochemical properties, and their maturation kinetics. Furthermore, several independent FP-tagged constructs have to be cloned and characterized in order to obtain spectral variations suitable for multi-color imaging setups. In contrast, the so-called SNAP-tag represents a genetically encoded non-fluorescent tag which mediates specific covalent coupling to fluorescent substrate molecules in a self-labeling reaction. Fusion of the SNAP-tag to the protein of interest allows specific labeling of the fusion protein with a variety of synthetic dyes, thereby offering enhanced flexibility for fluorescence imaging approaches. Here we describe the construction and characterization of the HIV derivative HIVSNAP, which carries the SNAP-tag as an additional domain within the viral structural polyprotein Gag. Introduction of the tag close to the C-terminus of the matrix domain of Gag did not interfere with particle assembly, release or proteolytic virus maturation. The modified virions were infectious and could be propagated in tissue culture, albeit with reduced replication capacity. Insertion of the SNAP domain within Gag allowed specific staining of the viral polyprotein in the context of virus producing cells using a SNAP reactive dye as well as the visualization of individual virions and viral budding sites by stochastic optical reconstruction microscopy. Thus, HIVSNAP represents a versatile tool which expands the possibilities for the analysis of HIV-cell interactions using live cell imaging and sub-diffraction fluorescence microscopy.

Eckhardt, Manon; Anders, Maria; Muranyi, Walter; Heilemann, Mike; Krijnse-Locker, Jacomine; Muller, Barbara

2011-01-01

337

Interaction of artemisinin and its derivatives with human serum albumin studied using spectroscopies and molecular modeling methods.  

PubMed

The interactions of artemisinins including artemisinin, dihydroartemisinin, artemether and artesunate with human serum albumin (HSA) were studied by fluorescence spectroscopy, UV-Vis absorption spectroscopy, synchronous fluorescence, three-dimensional fluorescence, circular dichroism (CD) and molecular modeling. Results obtained from analysis of fluorescence spectrum and fluorescence intensity indicated that the artemisinins had a strong ability to quench the intrinsic fluorescence of HSA through a static quenching procedure. Furthermore, the association constants K a and the corresponding thermodynamic parameters ?H, ?G and ?S at various temperatures were also calculated. Based on the mechanism of Förster's non-radiative energy transfer theory, the distance between the acceptors and HSA were found. In addition, alteration of the secondary structure of HSA in the presence of the artemisinins was tested by CD spectroscopy. Molecular modeling revealed that the artemisinins were bounded in the large hydrophobic cavity of the site I of HSA. PMID:23645089

Chen, Rongrong; Jiang, Hua; Pu, Hanlin

2013-05-06

338

Interactions of histatin 5 and histatin 5-derived peptides with liposome membranes: surface effects, translocation and permeabilization.  

PubMed Central

A number of cationic antimicrobial peptides, among which are histatin 5 and the derived peptides dhvar4 and dhvar5, enter their target cells and interact with internal organelles. There still are questions about the mechanisms by which antimicrobial peptides translocate across the membrane. We used a liposome model to study membrane binding, translocation and membrane-perturbing capacities of histatin 5, dhvar4 and dhvar5. Despite the differences in amphipathic characters of these peptides, they bound equally well to liposomes, whereas their membrane activities differed remarkably: dhvar4 translocated at the fastest rate, followed by dhvar5, whereas the histatin 5 translocation rate was much lower. The same pattern was seen for the extent of calcein release: highest with dhvar4, less with dhvar5 and almost none with histatin 5. The translocation and disruptive actions of dhvar5 did not seem to be coupled, because translocation occurred on a much longer timescale than calcein release, which ended within a few minutes. We conclude that peptide translocation can occur through peptide-phospholipid interactions, and that this is a possible mechanism by which antimicrobial peptides enter cells. However, the translocation rate was much lower in this model membrane system than that seen in yeast cells. Thus it is likely that, at least for some peptides, additional features promoting the translocation across biological membranes are involved as well.

Den Hertog, Alice L; Wong Fong Sang, Harro W; Kraayenhof, Ruud; Bolscher, Jan G M; Van't Hof, Wim; Veerman, Enno C I; Nieuw Amerongen, Arie V

2004-01-01

339

Brain-derived neurotrophic factor as a model system for examining gene by environment interactions across development.  

PubMed

There has been a dramatic rise in gene x environment studies of human behavior over the past decade that have moved the field beyond simple nature versus nurture debates. These studies offer promise in accounting for more variability in behavioral and biological phenotypes than studies that focus on genetic or experiential factors alone. They also provide clues into mechanisms of modifying genetic risk or resilience in neurodevelopmental disorders. Yet, it is rare that these studies consider how these interactions change over the course of development. In this paper, we describe research that focuses on the impact of a polymorphism in a brain-derived neurotrophic factor (BDNF) gene, known to be involved in learning and development. Specifically we present findings that assess the effects of genotypic and environmental loadings on neuroanatomic and behavioral phenotypes across development. The findings illustrate the use of a genetic mouse model that mimics the human polymorphism, to constrain the interpretation of gene-environment interactions across development in humans. PMID:19358879

Casey, B J; Glatt, C E; Tottenham, N; Soliman, F; Bath, K; Amso, D; Altemus, M; Pattwell, S; Jones, R; Levita, L; McEwen, B; Magariños, A M; Gunnar, M; Thomas, K M; Mezey, J; Clark, A G; Hempstead, B L; Lee, F S

2009-04-07

340

Fourier transform infrared spectroscopic and theoretical study of water interactions with glycine and its N-methylated derivatives  

NASA Astrophysics Data System (ADS)

In this study we attempt to explain the molecular aspects of amino acids' hydration. Glycine and its N-methylated derivatives: N-methylglycine, N,N-dimethylglycine, and N,N,N-trimethylglycine were used as model solutes in aqueous solution, applying FT-IR spectroscopy as the experimental method. The quantitative version of the difference spectra method enabled us to obtain the solute-affected HDO spectra as probes of influenced water. The spectral results were confronted with density functional theory calculated structures of small hydration complexes of the solutes using the polarizable continuum model. It appears that the hydration of amino acids in the zwitterionic form can be understood allowing a synchronized fluctuation of hydrogen bonding between the solute and the water molecules. This effect is caused by a noncooperative interaction of water molecules with electrophilic groups of amino acid and by intramolecular hydrogen bond, allowing proton transfer from the carboxylic to the amine group, accomplishing by the chain of two to four water molecules. As a result, an instantaneous water-induced asymmetry of the carboxylate and the amino group of amino acid molecule is observed and recorded as HDO band splitting. Water molecules interacting with the carboxylate group give component bands at 2543 +/- 11 and 2467 +/- 15 cm-1, whereas water molecules interacting with protons of the amine group give rise to the bands at 2611 +/- 15 and 2413 +/- 12 cm-1. These hydration effects have not been recognized before and there are reasons to expect their validity for other amino acids.

Panuszko, Aneta; ?miechowski, Maciej; Stangret, Janusz

2011-03-01

341

Molecular modeling and QSAR analysis of the interaction of flavone derivatives with the benzodiazepine binding site of the GABA(A) receptor complex.  

PubMed

A large number of structurally different classes of ligands, many of them sharing the main characteristics of the benzodiazepine (BDZ) nucleus, are active in the modulation of anxiety, sedation, convulsion, myorelaxation, hypnotic and amnesic states in mammals. These compounds have high affinity for the benzodiazepine binding site (BDZ-bs) of the GABA(A) receptor complex. Since 1989 onwards our laboratories established that some natural flavonoids were ligands for the BDZ-bs which exhibit medium to high affinity in vitro and anxiolytic activity in vivo. Further research resulted in the production of synthetic flavonoid derivatives with increased biochemical and pharmacological activities. The currently accepted receptor/pharmacophore model of the BDZ-bs (Zhang, W.; Koeler, K. F.; Zhang, P.; Cook, J. M. Drug Des. Dev. 1995, 12, 193) accounts for the general requirements that should be met by this receptor for ligand recognition. In this paper we present a model pharmacophore which defines the characteristics for a ligand to be able to interact and bind to a flavone site, in the GABA(A) receptor. closely related to the BDZ-bs. A model of a flavone binding site has already been described (Dekermendjian, K.; Kahnberg, P.; Witt, M. R.; Sterner, O.; Nielsen, M.; Liljerfors, T. J. Med. Chem. 1999, 42, 4343). However, this alternative model is based only on graphic superposition techniques using as template a non-BDZ agonist. In this investigation all the natural and synthetic flavonoids found to be ligands for the BDZ-bs have been compared with the classical BDZ diazepam. A QSAR regression analysis of the parameters that describe the interaction demonstrates the relevance of the electronic effects for the ligand binding, and shows that they are associated with the negatively charged oxygen atom of the carbonyl group of the flavonoids and with the nature of the substituent in position 3'. PMID:11249125

Marder, M; Estiú, G; Blanch, L B; Viola, H; Wasowski, C; Medina, J H; Paladini, A C

2001-02-01

342

The Energy Dependence of the Fragmentation Parameters and Interaction Mean Free Paths in Nuclear Emulsion for Heavy Cosmic Ray Nuclei.  

National Technical Information Service (NTIS)

It is generally assumed that the fragmentation parameters and absorption mean free paths used in extrapolating the charge spectrum of cosmic ray nuclei to the top of the atmosphere are independent of energy. However recent results suggest that these quant...

T. E. Cleghorn

1967-01-01

343

On the role of the functional group in determining the strength of hydrophobic interactions in aqueous solutions of ?-amino acid derivatives  

Microsoft Academic Search

Calorimetric measurements were carried out at 25°C on binary aqueous solutions containing N-acetyl derivatives of the following a-amino acids: glycine, alanine, valine, leucine, norleucine, aspartic acid, glutamic acid, phenylalanine, methionine, asparagine, glutamine, cysteine, histidine, serine. The N-acetyl derivative of the a-amino acid proline was also studied. The results obtained have been used to calculate the pairwise enthalpic interaction coefficients and

Giuseppina Castronuovo; Vittorio Elia; Filomena Velleca

1996-01-01

344

Chirality Effect on Flory-Huggins Interaction Parameters in Polylactide-b-Poly(ethylene-co-1-butene)-b-Polylactide Triblock Copolymers  

NASA Astrophysics Data System (ADS)

In this work, a set of well-defined polylactide-b-poly(ethylene-co-1-butene)-b-polylactide (PLA-PEB-PLA) triblock copolymers were synthesized by controlled ring-opening polymerization of corresponding lactide monomers (L-lactide and racemic mixture of D- and L-lactides) using Sn(Oct)2 as the catalyst. The volume fractions of PLA in the triblock copolymers were adjusted by tuning its molecular weight. The mesophase morphology and phase transitions in these triblock copolymers were studied by temperature-dependent small-angle X-ray scattering (SAXS). The Flory-Huggins interaction parameter ? between EB and lactide as a function of temperature were estimated from the order-disorder transition temperature (TODT) using the mean-field critical (?N)c values. The effects of PLA chirality on both Flory-Huggins interaction parameter and segmental lengths were investigated.

Cao, Weiqiang; Zhu, Lei; Rong, Lixia; Hsiao, Benjamin S.

2009-03-01

345

UNIQUAC interaction parameters for molecules with ?OH group on adjacent carbon atoms in aqueous solution determined by molecular mechanics—glycols, glycerol and glucose  

Microsoft Academic Search

UNIQUAC interaction parameters have been determined, using molecular mechanics calculations, for 1,2-ethanediol, 1,2-propanediol, glycerol and glucose with water in aqueous solution. Conformational space for individual pairs of molecules was explored using a stochastic method, the Boltzmann Jump Procedure (BJP).The predicted vapor-liquid equilibrium (VLE) data for the water1,2-ethanediol system are in excellent agreement with the experimental values and good results were

Svava Ósk Jónsdóttir; Roger A Klein

1997-01-01

346

TransCAIP: A Live 3D TV System Using a Camera Array and an Integral Photography Display with Interactive Control of Viewing Parameters  

Microsoft Academic Search

The system described in this paper provides a real-time 3D visual experience by using an array of 64 video cameras and an integral photography display with 60 viewing directions. The live 3D scene in front of the camera array is reproduced by the full-color, full-parallax autostereoscopic display with interactive control of viewing parameters. The main technical challenge is fast and

Yuichi Taguchi; Takafumi Koike; Keita Takahashi; Takeshi Naemura

2009-01-01

347

New potential antitumoral fluorescent tetracyclic thieno[3,2-b]pyridine derivatives: interaction with DNA and nanosized liposomes  

PubMed Central

Fluorescence properties of two new potential antitumoral tetracyclic thieno[3,2-b]pyridine derivatives were studied in solution and in liposomes of DPPC (dipalmitoyl phosphatidylcholine), egg lecithin (phosphatidylcholine from egg yolk; Egg-PC) and DODAB (dioctadecyldimethylammonium bromide). Compound 1, pyrido[2',3':3,2]thieno[4,5-d]pyrido[1,2-a]pyrimidin-6-one, exhibits reasonably high fluorescence quantum yields in all solvents studied (0.20 ? ?F ? 0.30), while for compound 2, 3-[(p-methoxyphenyl)ethynyl]pyrido[2',3':3,2]thieno[4,5-d]pyrido[1,2-a]pyrimidin-6-one, the values are much lower (0.01 ? ?F ? 0.05). The interaction of these compounds with salmon sperm DNA was studied using spectroscopic methods, allowing the determination of intrinsic binding constants, Ki = (8.7 ± 0.9) × 103 M-1 for compound 1 and Ki = (5.9 ± 0.6) × 103 M-1 for 2, and binding site sizes of n = 11 ± 3 and n = 7 ± 2 base pairs, respectively. Compound 2 is the most intercalative compound in salmon sperm DNA (35%), while for compound 1 only 11% of the molecules are intercalated. Studies of incorporation of both compounds in liposomes of DPPC, Egg-PC and DODAB revealed that compound 2 is mainly located in the hydrophobic region of the lipid bilayer, while compound 1 prefers a hydrated and fluid environment.

2011-01-01

348

Interaction between invariant NKT cells and myeloid-derived suppressor cells in cancer patients: evidence and therapeutic opportunities.  

PubMed

Despite advances in therapeutic strategies, the ability of cancer cells to evade destruction remains a significant obstacle to the development of effective anticancer treatment. In recent years a subset of immune cells, myeloid-derived suppressor cells (MDSCs), has been shown to play a key role in evasion of the patient's immune system by tumor cells. A number of different tumor types are associated with increased numbers of circulating MDSCs in cancer patients, suppressing the immune response and permitting continued tumor cell proliferation. Invariant NKT (iNKT) cells have recently been defined as a unique subset of immune cells that are able to act as a link between the innate and adaptive arms of the immune system. iNKT cells have the ability to carry out immune surveillance of tumor cells and control proliferation of malignant cells. Recently, we presented evidence that iNKT cells are able to interact with and decrease the numbers of circulating MDSCs in melanoma patients. This review discusses the evidence for MDSCs in tumor progression and the implication that iNKT cells could be developed as a potent therapeutic strategy. PMID:22735803

Mussai, Francis; De Santo, Carmela; Cerundolo, Vincenzo

2012-07-01

349

Hepatoma-derived Growth Factor-related Protein-3 Interacts with Microtubules and Promotes Neurite Outgrowth in Mouse Cortical Neurons  

PubMed Central

Hepatoma-derived growth factor-related proteins (HRP) comprise a family of 6 members, which the biological functions are still largely unclear. Here we show that during embryogenesis HRP-3 is strongly expressed in the developing nervous system. At early stages of development HRP-3 is located in the cytoplasm and neurites of cortical neurons. Upon maturation HRP-3 relocalizes continuously to the nuclei and in the majority of neurons of adult mice it is located exclusively in the nucleus. This redistribution from neurites to nuclei is also found in embryonic cortical neurons maturing in cell culture. We show that HRP-3 is necessary for proper neurite outgrowth in primary cortical neurons. To identify possible mechanisms of how HRP-3 modulate neuritogenesis we isolated HRP-3 interaction partners and demonstrate that it binds tubulin through the N-terminal so called HATH region, which is strongly conserved among members of the HRP family. It promotes tubulin polymerization, stabilizes and bundles microtubules. This activity depends on the extranuclear localization of HRP-3. HRP-3 thus could play an important role during neuronal development by its modulation of the neuronal cytoskeleton.

El-Tahir, Heba M.; Abouzied, Mekky M.; Gallitzendoerfer, Rainer; Gieselmann, Volkmar; Franken, Sebastian

2009-01-01

350

Do Most Planetary Nebulae Derive from Binary Interactions? The Binary Fraction of Central Stars of Planetary Nebula  

NASA Astrophysics Data System (ADS)

During the past 20 years, the idea that non-spherical planetary nebulae, comprising 80% of the total population, might need a binary or planetary interaction to be shaped, was discussed by various authors. It is now generally agreed that the varied morphologies of planetary nebulae cannot currently be explained by rotation and magnetic fields in single giant stars. Observationally, more binary central stars of planetary nebula have been discovered, opening new possibilities to understand the connections between binarity and morphology. So far, 45 binary central stars of planetary nebulae have been detected, most being close systems detected via flux variability. In order to determine the actual PN binary fraction, one needs a method that can detect wider binaries. We present here early results from a survey of high precision I-band and near infrared photometry of planetary nebula central stars aimed at detecting binaries with any separation. Eventually our survey will sample most of the 2-kpc volume limited sample of Frew (2008). At that time we expect that the binary fraction will reveal whether PN derive primarily from binaries or whether the current scenario, whereby single stars somehow, can generate non spherical planetary nebulae, is more in line with observation.

De Marco, Orsola; Douchin, D.; Passy, J. C.; Jacoby, G. H.; Frew, D. J.; Hillwig, T.

2012-01-01

351

Solar Wind, Interplanetary Magnetic Field, and Geodipole Tilt Control of Central Plasma Sheet Parameters and Magnetotail Geometry as Derived From Geotail's LEP and MGF Data.  

NASA Astrophysics Data System (ADS)

Simple analytical models have been derived for the first time, describing the 2-D distribution (along and across the Earth's magnetotail) of the central plasma sheet (CPS) ion temperature, density, and pressure, as functions of the incoming solar wind and IMF parameters, in the range of distances between 10 and 50 RE. Another result of this effort is a new quantitative model, representing as a~function of the dipole tilt angle the shape of the cross-tail current sheet and its response to varying solar wind and IMF conditions. The models are based on a~large set of data of the Low-Energy Particle (LEP) and Magnetic Field (MGF) instruments, taken by Geotail spacecraft in 1994-1998 and used in the form of 1-min average values of the CPS parameters and magnetic field components. The concurrent solar wind and IMF data were provided by Wind and IMP~8 spacecraft. The overall quality of the modeling was characterized by the correlation coefficient (c.c.) R between the observed and predicted values of a parameter. The CPS ion density N, controlled mostly by the solar wind proton density and by the northward IMF component, is the most unstable characteristic of the CPS, yielding the lowest c.c., RN=0.57. The CPS temperature T, controlled mainly by the solar wind speed V and the IMF Bz, yielded a higher c.c., RT=0.71. The CPS ion pressure P was found to be most effectively controlled by the solar wind ram pressure Psw and by an IMF-related parameter composed of the perpendicular IMF component Bperpendicular to and the sine of half clock angle ? /2. In a striking contrast with N and T, the model pressure P revealed a~very high c.c. with the data, RP=0.95, manifesting approximate force balance in the CPS due to its confinement by the external tail lobe magnetic field. The modeling revealed very little dawn-dusk asymmetry of the CPS beyond 10 RE, consistent with the observed symmetry of the tail lobe magnetic field. The plasma ion density N is the lowest at midnight and grows towards the tail's flanks. Larger/smaller solar wind ion densities and northward/southward IMF Bz result in larger/smaller N in the CPS. In contrast to the density N, the temperature T peaks at the midnight meridian and falls off towards the CPS flanks (so that the dawn-dusk variation of their product, the CPS pressure, is much smaller). Faster/slower solar wind and southward/northward IMF Bz result in a~hotter/cooler CPS. The CPS ion pressure P is nearly constant across the midtail (20-50RE); at closer distances the isobars gradually bend and approximately follow the contours of constant geomagnetic field in the equatorial plane. For northward IMF conditions combined with a~slow solar wind, this transition occurs at much larger distances, reflecting a weaker tail current and hence more dipole-like magnetic field. Geodipole tilt and solar wind effects on the shape of the cross-tail current sheet have been modeled in the range of distances 10-50 RE, using the magnetic field data from the entire near-tail phase of the Geotail operation.

Tsyganenko, N. A.

2002-12-01

352

Evolution of air–sea interaction parameters during the temperature front passage: The measurements on an oceanographic platform  

Microsoft Academic Search

The paper presents the results of the experiment CAPMOS'05 performed on an offshore oceanographic platform in the Black Sea in June 2005. Measurements on the platform were carried during June 2–20 round a clock. A set of meteorological and oceanographic parameters was measured: water and air temperature and water salinity at several levels, sea current vectors at various depths, turbulence

I. A. Repina; A. M. Chukharev; Y. N. Goryachkin; N. Y. Komarova; M. N. Pospelov

2009-01-01

353

Studies on Platelet-Derived Growth Factor Beta-Receptor and Hepatocyte Growth Factor Receptor c-met in Paracrine Interactions in Human Breast Cancer.  

National Technical Information Service (NTIS)

The overall aim of our project is to identify paracrine and autocrine mechanisms that regulate stromal-tumor cell interactions in breast cancer. We have shown that platelet-derived growth factor (PDGF) Beta-receptors, which are high affinity receptors for...

B. E. Elliott

1996-01-01

354

Studies on Platelet-Derived Growth Factor Beta-Receptor and Hepatocyte Growth Factor Receptor c-met in Paracrine Interactions in Human Breast Cancer.  

National Technical Information Service (NTIS)

Platelet-derived growth factor (pDGF) and hepatocyte growth factor (HGF) are key regulators of breast stromal- epithelial interactions. We examined the expression of PDGF 13-receptor, HGF receptor/Met and the corresponding ligands in primary human breast ...

B. E. Elliot

1995-01-01

355

Antagonistic Interactions between Stress Factors during the Growth of Microorganisms under Conditions Simulating the Parameters of Their Natural Ecotopes  

Microsoft Academic Search

Two stress factors, hypoxia (microaerobic conditions) and a high salt concentration, if applied simultaneously to aerobic microorganisms, display an antagonistic mode of interaction. As a result, the NaCl level that is usually optimal for moderate halophiles (5–6 %) becomes optimal for the growth of weak halophiles (Rhodococcus erythropolis and Shewanella sp. CN32); the halotolerant yeast Yarrowia lypolytica acquires halophilic properties

V. G. Arzumanyan; N. A. Voronina; O. V. Geidebrekht; O. V. Shelemekh; V. K. Plakunov; S. S. Belyaev

2002-01-01

356

Fructose metabolizing enzymes in the rat liver and metabolic parameters: Interactions between dietary copper, type of carbohydrates, and gender  

Microsoft Academic Search

This study was conducted to determine the effects of nutrient interactions between dietary carbohydrates and copper levels on fructose-metabolizing hepatic enzymes in male and female rats. Male and female rats were fed diets for 5 weeks that were either adequate or deficient in copper that contained either starch or fructose. Rats of both sexes fed fructose as compared with those

Moshe J. Werman; Sam J. Bhathena

1995-01-01

357

The effect of different background separation methods on gravity wave parameters in the upper troposphere and lower stratosphere region derived from GPS radio occultation data  

NASA Astrophysics Data System (ADS)

When vertical temperature profiles are used for the detection of gravity wave (GW) parameters a separation between a GW induced fluctuation and the background temperature field has to be performed. According the linear theory of GWs the measured temperature profile is expanded into a background temperature and a perturbation. The background is assumed to be steady, the fluctuations are much smaller than the background and the fluctuations should not affect the background. Usually, the fluctuations are addressed to GWs, but this depends strongly on the measuring method (observational filter) and the background separation approach. One possibility to separate GWs from the measurement is the application of band-pass filter associated to different vertical wavelengths to the measured temperature profiles. But, this analysis technique introduces an artificial enhancement of wave activity at the tropopause, mainly in the tropics, depending on the ability of the used filter to reproduce the tropopause kink. One possible method to solve this problem in the tropopause region is the separation of the profile into a tropospheric and a stratospheric part and the application of the filter for each region. A more appropriate approach is the double filtering method previously introduced. Alternatively to vertical detrending, a temperature background can be separated by horizontal detrending. For it temperature climatologies based on a sufficient temporal and spatial data density and averaging intervals must be present. In this study we demonstrate and discuss global GW temperature variances, and vertical wavelengths and amplitudes retrieved from GPS radio occultation (RO) data from COSMIC (2009 and 2010) between 10 and 40 km based on the different vertical and horizontal detrending approaches. The RO technique uses GPS radio signals received aboard low orbiting satellites for atmospheric limb sounding. Atmospheric temperature profiles are derived with high vertical resolution. The GPS RO technique is sensitive to GWs with small ratios of vertical to horizontal wavelengths.

Schmidt, Torsten; Wickert, Jens; De la Torre, Alejandro; Alexander, Peter; Faber, Antonia; Llamedo, Pablo; Heise, Stefan

2012-07-01

358

Investigation and correlation of physical stability, dissolution behaviour and interaction parameter of amorphous solid dispersions of telmisartan: a drug development perspective.  

PubMed

The aim of this study was to investigate if amorphous solid dispersions of telmisartan, prepared in presence of different polymers, exhibit different structural and thermodynamic characteristics and whether these differences can be correlated to their physical stability (time to crystallisation) and dissolution behaviour. Amorphous samples were prepared by melt quenching. The resulting amorphous materials were characterised using X-ray diffraction, Raman spectroscopy and differential scanning calorimetry. All freshly prepared samples were completely X-ray amorphous (with a halo being the only feature in the diffractograms). The shape of the halos in the diffractograms varied suggesting structural variations in the near order of the molecules between the different amorphous solid dispersions (ASDs). Principal component analysis of the Raman spectra of the various ASD revealed that the samples clustered in the scores plot, again suggesting structural differences due to the presence of different drug-polymer interaction. The ranking of the samples with respect to physical stability and interaction parameter was: ASD of telmisartan:eudragit>ASD of telmisartan:soluplus>ASD of telmisartan:HPMC>ASD of telmisartan:PVP>amorphous telmisartan. The interaction parameter, calculated by using the Flory Huggins theory, showed a good correlation with the experimentally determined stability whereas a weak correlation was found with dissolution behaviour of different ASD. This study showed that correlation of physical stability and dissolution behaviour with calculated interaction parameter is possible for the same amorphous systems prepared by using different polymers. This could aid in selecting the most appropriate polymer for the development of optimised formulations containing amorphous drugs. It can be concluded that ASD prepared by using different polymers have different structural and thermal properties. These differences affect the physical stability and dissolution profiles of the amorphous solids. Thus, choosing the right polymer for preparing ASD is critical for producing materials with desired dissolution profiles and enhanced stability. PMID:23684913

Dukeck, R; Sieger, P; Karmwar, P

2013-05-16

359

The effects and interactions of fabrication parameters on the properties of selective laser sintered hydroxyapatite polyamide composite biomaterials  

Microsoft Academic Search

Purpose – Hydroxyapatite-polymer composite materials are being researched for the development of low-load bearing implants because of their bioactive and osteoconductive properties, while avoiding modulus mismatch found in homogenous materials. For the direct production of hydroxyapatite-polymer composite implants, selective laser sintering (SLS) has been used and various parameters and their effects on the physical properties (micro and macro morphologies) have

M. M. Savalani; L. Hao; P. M. Dickens; Y. Zhang; K. E. Tanner; R. A. Harris

2012-01-01

360

Eight salts constructed from 4-phenylthiazol-2-amine and carboxylic acid derivatives through combination of strong hydrogen bonding and weak noncovalent interactions  

NASA Astrophysics Data System (ADS)

Eight crystalline organic salts derived from 4-phenylthiazol-2-amine and carboxylic acid derivatives (2-chloronicotinic acid, 3-hydroxy-2-naphthoic acid, p-nitrobenzoic acid, 2-hydroxy-5-(phenyldiazenyl)benzoic acid, 5-nitrosalicylic acid, 5-sulfosalicylic acid, oxalic acid, and L-malic acid) were prepared and characterized by X-ray diffraction analysis, IR, mp, and elemental analysis. In all of the salts except 6, 7, and 8, the 4-phenylthiazol-2-amine and carboxylic acid components are held together by two fused heterosynthons: a R22(7) heterosynthon and a R22(8) heterosynthon. All supramolecular architectures of the organic salts 1–8 involve extensive NH⋯O hydrogen bonds as well as other noncovalent interactions. The role of weak and strong noncovalent interactions in the crystal packing is ascertained. The salts displayed 2D/3D framework structure under these weak interactions.

Jin, Shouwen; Zhu, Qiaowang; Wei, ShuaiShuai; Wang, Daqi

2013-10-01

361

The electrooptical parameters of suspensions of Escherichia coli XL1 cells interacting with helper phage M13K07  

Microsoft Academic Search

The electrophysical properties of Escherichia coli XL-1 cells interacting with helper phage M13K07 were studied as a function of the phage-to-cell ratio and the contact time. The electro-optical signal of bacterial cells changed considerably as soon as 10 min after the onset of their incubation with phage particles, presumably due to phage adsorption on the cell surface. The maximum changes

V. D. Bunin; O. V. Ignatov; O. I. Guliy; I. S. Zaitseva; D. O’Neil; D. Ivnitskii

2005-01-01

362

Methane?hydrocarbon interaction parameters correlation for the Peng-Robinson and the t-mPR equation of state  

Microsoft Academic Search

Generalized expressions for the interaction coefficients (kij) of CH4hydrocarbon binary systems are presented for a modified and translated Peng-Robinson equation of state (t-mPR). The correlations involve the acentric factor of the heavier hydrocarbon and cover the CH4n-alkane systems up to n-C44 plus isomers and cycloalkanes. Typical errors in bubble point pressure predictions are below 5%, similar to those obtained by

Aris Kordas; Kostis Magoulas; Sofia Stamataki; Dimitrios Tassios

1995-01-01

363

Theoretical study on the interaction of pyrrolopyrimidine derivatives as LIMK2 inhibitors: insight into structure-based inhibitor design.  

PubMed

LIM kinases (LIMKs), downstream of Rho-associated protein kinases (ROCKs) and p21-activated protein kinases (PAKs), are shown to be promising targets for the treatment of cancers. In this study, the inhibition mechanism of 41 pyrrolopyrimidine derivatives as LIMK2 inhibitors was explored through a series of theoretical approaches. First, a model of LIMK2 was generated through molecular homology modeling, and the studied inhibitors were docked into the binding active site of LIMK2 by the docking protocol, taking into consideration the flexibility of the protein. The binding poses predicted by molecular docking for 17 selected inhibitors with different bioactivities complexed with LIMK2 underwent molecular dynamics (MD) simulations, and the binding free energies for the complexes were predicted by using the molecular mechanics/generalized born surface area (MM/GBSA) method. The predicted binding free energies correlated well with the experimental bioactivities (r(2) = 0.63 or 0.62). Next, the free energy decomposition analysis was utilized to highlight the following key structural features related to biological activity: (1) the important H-bond between Ile408 and pyrrolopyrimidine, (2) the H-bonds between the inhibitors and Asp469 and Gly471 which maintain the stability of the DFG-out conformation, and (3) the hydrophobic interactions between the inhibitors and several key residues (Leu337, Phe342, Ala345, Val358, Lys360, Leu389, Ile408, Leu458 and Leu472). Finally, a variety of LIMK2 inhibitors with a pyrrolopyrimidine scaffold were designed, some of which showed improved potency according to the predictions. Our studies suggest that the use of molecular docking with MD simulations and free energy calculations could be a powerful tool for understanding the binding mechanism of LIMK2 inhibitors and for the design of more potent LIMK2 inhibitors. PMID:23881296

Shen, Mingyun; Zhou, Shunye; Li, Youyong; Li, Dan; Hou, Tingjun

2013-08-27

364

Interaction of inflammatory and anti-inflammatory responses in microglia by Staphylococcus aureus-derived lipoteichoic acid.  

PubMed

We investigated the interaction between proinflammatory and inflammatory responses caused by Staphylococcus aureus-derived lipoteichoic acid (LTA) in primary cultured microglial cells and BV-2 microglia. LTA induced inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) protein levels increase in a concentration- and time-dependent manner. Meanwhile, LTA also increased nitric oxide (NO) and PGE2 production in microglia. Administration of TLR2 antagonist effectively inhibited LTA-induced NO, iNOS, and COX-2 expression. Moreover, treatment of cells with LTA caused a time-dependent activation of ERK, p38, JNK, as well as AKT. We also found that LTA-induced iNOS and COX-2 up-regulation were attenuated by p38, JNK, and PI3-kinase inhibitors. On the other hand, LTA-enhanced HO-1 expression was attenuated by p38 and PI3-kinase inhibitors. Treatment of cells with NF-?B and AP-1 inhibitors antagonized LTA-induced iNOS and COX-2 expression. However, only NF-?B inhibitors reduced LTA-induced HO-1 expression in microglia. Furthermore, stimulation of cells with LTA also activated I?B? phosphorylation, p65 phosphorylation at Ser?³?, and c-Jun phosphorylation. Moreover, LTA-induced increases of ?B-DNA and AP-1-DNA binding activity were inhibited by p38, JNK, and PI3-kinase inhibitors. HO-1 activator CoPP IX dramatically reversed LTA-induced iNOS expression. Our results provided mechanisms linking LTA and inflammation/anti-inflammation, and indicated that LTA plays a regulatory role in microglia activation. PMID:23500011

Huang, Bor-Ren; Tsai, Cheng-Fang; Lin, Hsiao-Yun; Tseng, Wen-Pei; Huang, Shiang-Suo; Wu, Chi-Rei; Lin, Chingju; Yeh, Wei-Lan; Lu, Dah-Yuu

2013-03-14

365

Relationships among vegetation properties related to their interactions with atmosphere from the analysis of satellite derived data  

NASA Astrophysics Data System (ADS)

Vegetation is an important element to understand the complex interrelationship between atmosphere and land surface. In this study, we analyze Normalized Difference Vegetation Index (NDVI), Leaf Area Index (LAI), and Vegetation Water Content (VegWC). These variables selected in this study are closely related to vegetation water status with surface temperature (Ts) as a key factor of the interaction between vegetation and atmosphere. These satellite derived data sets are from Moderate Resolution Imaging Spectroradiometer (MODIS) data for NDVI, LAI, and Ts, and Advanced Microwave Scanning Radiometer (AMSR) for VegWC. Three different regions, each of which is climatically unique, are selected in North America for this study: North American Monsoon System region (NAMS), South Great Plain (SGP), and Tifton, Georgia. The relationship between NDVI and Ts (known as TvX relationship) which has been studied in many previous works is identified and validated from a weather forecasting model (WRF). The sensitivity of the TvX relationship to land surface roughness is analyzed to quantify the TvX relationship, and the limits of the relationship between NDVI, LAI, and VegWC are presented. A new variable, Normalized Vegetation Water Content (NVegWC) from the ratio of VegWC and LAI, and NDVI show significant relationship especially in relatively arid regions such as NAMS region. In order to investigate the local variation of the relationships between the variables in the three study regions, the land cover classification map is analyzed, and it is identified that different environments related to water status influence the physiological properties of vegetation.

Hong, S.; Lakshmi, V.; Small, E. E.; Njoku, E. G.; Chen, F.

2005-12-01

366

Structure of Ca2+ -Bound S100A4 and Its Interaction With Peptides Derived from Nonmuscle Myosin-IIA  

SciTech Connect

S100A4, also known as mts1, is a member of the S100 family of Ca2+-binding proteins that is directly involved in tumor invasion and metastasis via interactions with specific protein targets, including nonmuscle myosin-IIA (MIIA). Human S100A4 binds two Ca2+ ions with the typical EF-hand exhibiting an affinity that is nearly 1 order of magnitude tighter than that of the pseudo-EF-hand. To examine how Ca2+ modifies the overall organization and structure of the protein, we determined the 1.7 Angstroms crystal structure of the human Ca2+-S100A4. Ca2+ binding induces a large reorientation of helix 3 in the typical EF-hand. This reorganization exposes a hydrophobic cleft that is comprised of residues from the hinge region, helix 3, and helix 4, which afford specific target recognition and binding. The Ca2+-dependent conformational change is required for S100A4 to bind peptide sequences derived from the C-terminal portion of the MIIA rod with submicromolar affinity. In addition, the level of binding of Ca2+ to both EF-hands increases by 1 order of magnitude in the presence of MIIA. NMR spectroscopy studies demonstrate that following titration with a MIIA peptide, the largest chemical shift perturbations and exchange broadening effects occur for residues in the hydrophobic pocket of Ca2+-S100A4. Most of these residues are not exposed in apo-S100A4 and explain the Ca2+ dependence of formation of the S100A4-MIIA complex. These studies provide the foundation for understanding S100A4 target recognition and may support the development of reagents that interfere with S100A4 function.

Malashkevich,V.; Varney, K.; Garrett, S.; Wilder, P.; Knight, D.; Charpentier, T.; Ramagopal, U.; Almo, S.; Weber, D.; Bresnick, A.

2008-01-01

367

Roles of Capsule and Lipopolysaccharide O Antigen in Interactions of Human Monocyte-Derived Dendritic Cells and Klebsiella pneumoniae?  

PubMed Central

In humans, Klebsiella pneumoniae is a saprophytic bacterium of the nasopharyngeal and intestinal mucosae that is also frequently responsible for severe nosocomial infections. Two major factors of virulence, capsular polysaccharide (CPS) and lipopolysaccharide (LPS) O antigen, are involved in mucosal colonization and the development of infections. These bacterial surface structures are likely to play major roles in interactions with the mucosal immune system, which are orchestrated by a network of surveillance based on dendritic cells (DCs). To determine the roles of K. pneumoniae CPS and LPS in the DC response, we investigated the response of immature human monocyte-derived DCs to bacterial challenge with a wild-type strain and its isogenic mutants deficient in CPS or LPS O-antigen production. As observed by flow cytometry and confocal laser microscopy, the rate of phagocytosis was inversely proportional to the amount of CPS on the bacterial cell surface, with LPS playing little or no role. The K. pneumoniae wild-type strain induced DC maturation with upregulation of CD83, CD86, and TLR4 and downregulation of CD14 and DC-SIGN. With CPS mutants, we observed a greater decrease in DC-SIGN, suggesting a superior maturation of DCs. In addition, incubation of DCs with CPS mutants, and to a lesser extent with LPS mutants, resulted in significantly higher Th1 cytokine production. Combined, our findings suggest that K. pneumoniae CPS, by hampering bacterial binding and internalization, induces a defective immunological host response, including maturation of DCs and pro-Th1 cytokine production, whereas the LPS O antigen seems to be involved essentially in DC activation.

Evrard, B.; Balestrino, D.; Dosgilbert, A.; Bouya-Gachancard, J.-L. J.; Charbonnel, N.; Forestier, C.; Tridon, A.

2010-01-01

368

Interaction  

NSDL National Science Digital Library

Set values for the initial position, velocity, and mass of the two particles, and click on the button "Initialize Animation" to play the animation using your specified values. Note, if m or v are too large, the particles may actually pass through one another which will seem a little strange. Note: the interaction between the particles is a "non-contact" interaction, much like the electrostatic force on two charges. Mathematically, it is actually a Hooke's law interaction.

Christian, Wolfgang; Belloni, Mario

2008-02-19

369

Effective medium super-cell approximation for interacting disordered systems: an alternative real-space derivation of generalized dynamical cluster approximation  

NASA Astrophysics Data System (ADS)

We develop a generalized real-space effective medium super-cell approximation (EMSCA) method to treat the electronic states of interacting disordered systems. This method is general and allows randomness both in the on-site energies and in the hopping integrals. For a non-interacting disordered system, in the special case of randomness in the on-site energies, this method is equivalent to the non-local coherent potential approximation (NLCPA) derived previously. Also, for an interacting system the EMSCA method leads to the real-space derivation of the generalized dynamical cluster approximation (DCA) for a general lattice structure. We found that the original DCA and the NLCPA are two simple cases of this technique, so the EMSCA is equivalent to the generalized DCA where there is included interaction and randomness in the on-site energies and in the hopping integrals. All of the equations of this formalism are derived by using the effective medium theory in real space.

Moradian, Rostam

2006-01-01

370

Pulse radiolysis studies of the interaction of hydroxy-cinnamic acid derivatives with oxidizing OH adducts of pyrimidine  

NASA Astrophysics Data System (ADS)

The electron transfer reactions between oxidizing OH adducts of pyrimidine with hydroxy-cinnamic acid derivatives have been investigated by pulse radiolysis. The hydroxy-cinnamic acid derivatives identified as good antioxidant for reduction of oxidizing OH adducts of pyrimidine via electron transfer reactions. From buildup kinetic analysis of radical product, the rate constants for reactions of N?3 radical with hydroxy-cinnamic acid derivatives have been determined to be (8-11) × 109 dm3 mol-1 s-1, while the rate constant of electron transfer from hydroxy-cinnamic acid derivatives to oxidizing OH adducts of cytosine or thymine were obtained to be 109 dm3 mol-1 s-1.

Wang, Wenfeng; Luo, Jian; Yao, Side; Lian, Zhirui; Zuo, Zhihua; Zhang, Jiashan; Lin, Nianyun

1995-07-01

371

Interaction of rat lung SSAO with the novel 1-N-substituted thiocarbamoyl-3-substituted phenyl-5-(2-pyrolyl)-2-pyrazoline derivatives  

Microsoft Academic Search

Summary  Interactions of twelve new synthesized 1-N-substituted thiocarbamoyl-3-substituted phenyl-5-pyrolyl-2-pyrazoline derivatives\\u000a with rat lung semicarbazide-sensitive amine oxidase (SSAO) were assessed. Pyrazoline derivatives were synthesized according\\u000a to previous methods and SSAO was purified from the crude microsomal fractions of rat lung.\\u000a \\u000a Three compounds (3e, 3f, 3k) with a p-methoxy group at the phenyl ring inhibited rat lung SSAO non-competitively and irreversibly, and showed

S. Yabanoglu; G. Ucar; N. Gokhan; U. Salgin; A. Yesilada; A. A. Bilgin

2007-01-01

372

Reoptimized interaction parameters for the peptide-backbone model compound N-methylacetamide in the GROMOS force field: influence on the folding properties of two beta-peptides in methanol.  

PubMed

Considering N-methylacetamide (NMA) as a model compound, new interaction parameters are developed for the amide function in the GROMOS force field that are compatible with the recently derived 53A6(OXY) parameter set for oxygen-containing chemical functions. The resulting set, referred to as 53A6(OXY+A) , represents an improvement over earlier GROMOS force-field versions in the context of the pure-liquid properties of NMA, including the density, heat of vaporization, dielectric permittivity, self-diffusion constant and viscosity, as well as in terms of the Gibbs hydration free energy of this molecule. Assuming that NMA represents an adequate model compound for the backbone of peptides, 53A6(OXY+A) may be expected to also provide an improved description of polypeptide chains. As an initial test, simulations are reported for two ?-peptides characterized by very different folding properties in methanol. For these systems, earlier force-field versions provided good agreement with experimental NMR data, and the test shows that the improved description achieved in the context of NMA is not accompanied by any deterioration in the representation of the conformational properties of these peptides. PMID:22648867

Horta, Bruno A C; Lin, Zhixiong; Huang, Wei; Riniker, Sereina; van Gunsteren, Wilfred F; Hünenberger, Philippe H

2012-05-30

373

Head-to-tail and back-to-back dimerization of an open-cage fullerene derivative through ?-? interaction-based self-assembly.  

PubMed

Open-cage fullerene derivative 2, C(59)(O)(4)(NAr)(2) (Ar = p-tBuC(6)H(4)), was prepared from 1, C(60)(O)(4)(OH)(2)(NAr)(2), through processes involving decarbonylation and elimination of the two hydroxyl groups. The phenyl groups in compound 2 act as chelating ligands for the fullerene cage and induce partial dimerization of 2 in solution. The single crystal X-ray structure of 2 shows strong intradimer ?-? interactions and also weaker interdimer CH-? and ?-? interactions. PMID:22831400

Liu, Shuming; Zhang, Qianyan; Yu, Yuming; Gan, Liangbing

2012-07-25

374

Interaction between cellular voltage-sensitive conductance and network parameters in a model of neocortex can generate epileptiform bursting.  

SciTech Connect

We examined the effects of both intrinsic neuronal membrane properties and network parameters on oscillatory activity in a model of neocortex. A scalable network model with six different cell types was built with the pGENESIS neural simulator. The neocortical network consisted of two types of pyramidal cells and four types of inhibitory interneurons. All cell types contained both fast sodium and delayed rectifier potassium channels for generation of action potentials. A subset of the pyramidal neurons contained an additional slow inactivating (persistent) sodium current (NaP). The neurons with the NaP current showed spontaneous bursting activity in the absence of external stimulation. The model also included a routine to calculate a simulated electroencephalogram (EEG) trace from the population activity. This revealed emergent network behavior which ranged from desynchronized activity to different types of seizure-like bursting patterns. At settings with weaker excitatory network effects, the propensity to generate seizure-like behavior increased. Strong excitatory network connectivity destroyed oscillatory behavior, whereas weak connectivity enhanced the relative importance of the spontaneously bursting cells. Our findings are in contradiction with the general opinion that strong excitatory synaptic and/or insufficient inhibition effects are associated with seizure initiation, but are in agreement with previously reported behavior in neocortex.

van Drongelen, W.; Lee, H. C.; Koch, H.; Elsen, F.; Carroll, M. S.; Hereld, M.; Stevens, R. L.; Mathematics and Computer Science; Univ. of Chicago

2004-01-01

375

Monitoring of Interaction-Point Parameters Using the 3-Dimensional Luminosity Distribution Measured at PEP-II  

SciTech Connect

The 3-D luminosity distribution at the IP of the SLAC B-Factory is monitored using e{sup +}e{sup -} {yields} e{sup +}e{sup -}, {mu}{sup +}{mu}{sup -} events reconstructed online in the BABAR detector. The transverse centroid and spatial orientation of the luminosity ellipsoid reliably monitor IP orbit drifts. The longitudinal centroid is sensitive to small variations in the average relative RF phase of the beams and provides a detailed measurement of the phase transient along the bunch train. The longitudinal luminosity distribution depends on the e{sup +,-} overlap bunch length and the vertical IP {beta}-functions. Relative variations in horizontal luminous size are detectable at the micron level. In addition to continuous on-line monitoring of all the parameters above, we performed detailed studies of their variation along the bunch train to investigate a temporary luminosity degradation. We also compare {beta}*{sub y} measurements, collected over a year of high-luminosity operation, with HER and LER lattice functions measured by resonant transverse excitation. Our bunch-length measurements are consistent with those obtained by other methods and provide direct evidence for bunch-length modulation.

Viaud, B.F.; /Montreal U.; Kozanecki, W.; /DAPNIA, Saclay; O'Grady, C.; Thompson, J.; Weaver, M.; /SLAC

2006-07-28

376

A non-homogeneous dynamic Bayesian network with sequentially coupled interaction parameters for applications in systems and synthetic biology.  

PubMed

An important and challenging problem in systems biology is the inference of gene regulatory networks from short non-stationary time series of transcriptional profiles. A popular approach that has been widely applied to this end is based on dynamic Bayesian networks (DBNs), although traditional homogeneous DBNs fail to model the non-stationarity and time-varying nature of the gene regulatory processes. Various authors have therefore recently proposed combining DBNs with multiple changepoint processes to obtain time varying dynamic Bayesian networks (TV-DBNs). However, TV-DBNs are not without problems. Gene expression time series are typically short, which leaves the model over-flexible, leading to over-fitting or inflated inference uncertainty. In the present paper, we introduce a Bayesian regularization scheme that addresses this difficulty. Our approach is based on the rationale that changes in gene regulatory processes appear gradually during an organism's life cycle or in response to a changing environment, and we have integrated this notion in the prior distribution of the TV-DBN parameters. We have extensively tested our regularized TV-DBN model on synthetic data, in which we have simulated short non-homogeneous time series produced from a system subject to gradual change. We have then applied our method to real-world gene expression time series, measured during the life cycle of Drosophila melanogaster, under artificially generated constant light condition in Arabidopsis thaliana, and from a synthetically designed strain of Saccharomyces cerevisiae exposed to a changing environment. PMID:22850067

Grzegorczyk, Marco; Husmeier, Dirk

2012-07-12

377

Interaction of fission products and SiC in TRISO fuel particles: a limiting HTGR design parameter  

SciTech Connect

The fuel particle system for the steam cycle cogeneration HTGR being developed in the US consists of 20% enriched UC/sub 0/./sub 3/O/sub 1/./sub 7/ and ThO/sub 2/ kernels with TRISO coatings. The reaction of fission products with the SiC coating is the limiting thermochemical coating failure mechanism affecting performance. The attack of the SiC by palladium (Pd) is considered the controlling reaction with systems of either oxide or carbide fuels. The lanthanides, such as cerium, neodymium, and praseodymium, also attack SiC in carbide fuel particles. In reactor design, the time-temperature relationships at local points in the core are used to calculate the depth of SiC-Pd reaction. The depth of penetration into the SiC during service varies with core power density, power distribution, outlet gas temperature, and fuel residence time. These parameters are adjusted in specifying the core design to avoid SiC coating failure.

Stansfield, O.M.; Homan, F.J.; Simon, W.A.; Turner, R.F.

1983-09-01

378

Change in the rate of phosphorescence decay caused by the intramolecular vibronic-spin-orbit interactions in fluorene derivatives with N, O, P, S, and Se heteroatoms  

SciTech Connect

The vibrations and vibronic structure in the phosphorescence spectrum of the fluorene derivative containing phosphorus are interpreted. Based on the fine-structure phosphorescence spectra of fluorene derivatives containing N, O, P, S, and Se heteroatoms, contributions of the spin-orbit (SO) and vibronic-spin-orbit (VSO) interactions to the rate of phosphorescence decay are separated. It is established that, as the nuclear charge and the spin-orbit coupling constant {zeta}{sub M} of the heteroatom increase, the SO component of the rate of phosphorescence decay does not change, whereas the VSO component increases faster than {zeta}{sub M}{sup 2}. These effects are explained based on the symmetry of the functions of molecular orbitals (MOs) and the operator entering matrix elements of spin-orbit interactions. 18 refs., 2 figs., 5 tabs.

Gastilovich, E.A.; Klimenko, V.G.; Ni, B.V. [Karpov Institute of Physical Chemistry, Moscow (Russian Federation)

1995-05-01

379

Monte-Carlo Analysis of the Composition Dependence of the Flory-Huggins Interaction Parameter in PE-dPE Blends  

NASA Astrophysics Data System (ADS)

Experimental SANS research displays a significant concentration dependence of the Flory-Huggins (?) interaction parameter in isotopic polymer blends. At the extremes of the deuterated polymer concentration (?D< 0.2, ?D > 0.8), ? is shown to exhibit a greater than fourfold increase over its value at ?D = 0.5. However, despite numerous attempts to theoretically describe the nature of this phenomenon, consensus is still lacking regarding the mechanisms at work in this system. This study uses free-space, spatially discretized Monte Carlo simulations to investigate the ? composition dependence of PE-dPE blends. Initial simulations are run on simple Lennard-Jones fluids to display the capability of the simulation method to track local concentration and energy across the discretized space as well as to investigate the concentration dependence of the radial distribution function, g(r), and structure factor, S(k). After which, MC simulations are performed on the PE-dPE system with varying ?D. Both local and average system energies are tracked in addition to g(r) and S(k). The Flory-Huggins interaction parameter is then calculated using the Random Phase Approximation.

Russell, Travis; Edwards, Brian; Khomami, Bamin

2012-02-01

380

Platelet-derived growth factor and transforming growth factor-? in invertebrate immune and neuroendocrine interactions: another sign of conservation in evolution  

Microsoft Academic Search

Growth factor-like molecules have been found in various invertebrate species. In particular, we have reported the presence of platelet-derived growth factor (PDGF)-AB and transforming growth factor-? (TGF-?)1 immunoreactive molecules in molluscs, insects and annelids. Moreover, PDGF-AB and TGF-?1 affect the main immune functions, such as phagocytosis, chemotaxis and cell motility. Changes in cell shape are induced via interactions of growth

Enzo Ottaviani; Antonella Franchini; Dimitris Kletsas

2001-01-01

381

Hyperglycemia regulates thioredoxin-ROS activity through induction of thioredoxin-interacting protein (TXNIP) in metastatic breast cancer-derived cells MDA-MB-231  

Microsoft Academic Search

BACKGROUND: We studied the RNA expression of the genes in response to glucose from 5 mM (condition of normoglycemia) to 20 mM (condition of hyperglycemia\\/diabetes) by microarray analysis in breast cancer derived cell line MDA-MB-231. We identified the thioredoxin-interacting protein (TXNIP), whose RNA level increased as a gene product particularly sensitive to the variation of the level of glucose in

Francesco Turturro; Ellen Friday; Tomas Welbourne

2007-01-01

382

Induction of Mammary Differentiation by Mammary-derived Growth Inhibitor related Gene That Interacts with an v-3 Fatty Acid on Growth Inhibition of Breast Cancer Cells1  

Microsoft Academic Search

We previously identified and characterized a novel tumor growth inhibitor and a fatty acid-binding protein in human mammary gland and named it the mammary-derived growth inhibitor-related gene (MRG). Here, the effects of MRG on mammary gland differentiation and its interaction with v-3 polyunsaturated fatty acids (v-3 PUFAs) on growth inhibition were investigated. MRG protein expression was associated with human mammary

Mingsheng Wang; Yiliang E. Liu; Jian Ni; Banu Aygun; Itzhak D. Goldberg; Y. Eric Shi

2000-01-01

383

Influence of functionalization on interaction and drug release from ?,?-polyaspartylhydrazide derivatives to a biomembrane model: evaluation by differential scanning calorimetry technique  

Microsoft Academic Search

A comparative study on the ability of various polymers to interact with a biomembrane model was carried out by differential scanning calorimetry (DSC). The investigated samples were a water soluble polymer, the ?,?-polyaspartylhydrazide (PAHy) and its derivatives containing polyethylene glycol (PEG2000) (sample PAHy–PEG2000), or hexadecylamine (C16) (sample PAHy–C16) or both compounds (sample PAHy–PEG2000–C16). Some samples are able to arrange themselves

Francesco Castelli; Chiara Messina; Elisa Martinetti; Mariano Licciardi; Emanuela Fabiola Craparo; Giovanna Pitarresi

2004-01-01

384

D77, one benzoic acid derivative, functions as a novel anti-HIV-1 inhibitor targeting the interaction between integrase and cellular LEDGF\\/p75  

Microsoft Academic Search

Integration of viral-DNA into host chromosome mediated by the viral protein HIV-1 integrase (IN) is an essential step in the HIV-1 life cycle. In this process, Lens epithelium-derived growth factor (LEDGF\\/p75) is discovered to function as a cellular co-factor for integration. Since LEDGF\\/p75 plays an important role in HIV integration, disruption of the LEDGF\\/p75 interaction with IN has provided a

Li Du; Yaxue Zhao; Jing Chen; Liumeng Yang; Yongtang Zheng; Yun Tang; Xu Shen; Hualiang Jiang

2008-01-01

385

Dynamic interactions between T cells and dendritic cells and their derived cytokines\\/chemokines in the rheumatoid synovium  

Microsoft Academic Search

This review focuses on the contributions made by interactions between dendritic cells (DCs) and T cells, and by local production of cytokines and chemokines to the pathogenesis of rheumatoid arthritis (RA) synovitis. DCs are efficient professional antigen-presenting cells, which are critical for the development of innate and adaptative immune responses through interactions with T cells. Cytokines from DCs play a

Pierre Miossec

2008-01-01

386

Calculation of Lateral-Directional Stability Derivatives for Wing-Body Combinations with and Without Jet-Interaction Effects.  

National Technical Information Service (NTIS)

A theoretical method is presented for predicting the lateral-directional stability derivatives of wing-body combinations with or without the blowing jet effect. The fuselage effect is accounted for by the axial distribution of vortex multiplets. Compariso...

C. E. Lan

1977-01-01

387

Effect of nonlinear optical three-wave interaction on the lasing parameters of a dual-wavelength vertical-external-cavity surface-emitting laser  

NASA Astrophysics Data System (ADS)

The influence of nonlinear optical interaction in a semiconductor dual-wavelength vertical-external-cavity surface-emitting laser on the main parameters of dual-wavelength radiation and lasing in the long-wavelength part of the mid-IR range, obtained in this laser as a result of nonlinear wave mixing, is investigated. An increase in the pump power leads to saturation of the short-wavelength lasing intensity and to a more rapid rise in the long-wavelength lasing intensity in comparison with the linear increase in lasing intensity in these regions in the absence of nonlinear interaction. Under the conditions of nonlinear interaction, the carrier concentration in the active layers is not stabilised near the lasing threshold but changes with an increase in the pump intensity and provides the corresponding gain in the laser active region, thus maintaining steadystate lasing. Some ways for modifying the laser active region in order to obtain the most efficient lasing in the mid-IR range are proposed.

Morozov, M. Yu; Morozov, Yu A.; Krasnikova, I. V.

2013-09-01

388

Reconciliation of essential process parameters for an enhanced predictability of Arctic stratospheric ozone loss and its climate interactions  

NASA Astrophysics Data System (ADS)

Significant reductions in stratospheric ozone occur inside the polar vortices each spring when chlorine radicals produced by heterogeneous reactions on cold particle surfaces in winter destroy ozone mainly in two catalytic cycles, the ClO dimer cycle and the ClO/BrO cycle. Chlorofluorocarbons (CFCs), which are responsible for most of the chlorine currently present in the stratosphere, have been banned by the Montreal Protocol and its amendments, and the ozone layer is predicted to recover to 1980 levels within the next few decades. During the same period, however, climate change is expected to alter the temperature, circulation patterns and chemical composition in the stratosphere, and possible geo-engineering ventures to mitigate climate change may lead to additional changes. To realistically predict the response of the ozone layer to such influences requires the correct representation of all relevant processes. The European project RECONCILE has comprehensively addressed remaining questions in the context of polar ozone depletion, with the objective to quantify the rates of some of the most relevant, yet still uncertain physical and chemical processes. To this end RECONCILE used a broad approach of laboratory experiments, two field missions in the Arctic winter 2009/10 employing the high altitude research aircraft M55-Geophysica and an extensive match ozone sonde campaign, as well as microphysical and chemical transport modelling and data assimilation. Some of the main outcomes of RECONCILE are as follows: (1) vortex meteorology: the 2009/10 Arctic winter was unusually cold at stratospheric levels during the six-week period from mid-December 2009 until the end of January 2010, with reduced transport and mixing across the polar vortex edge; polar vortex stability and how it is influenced by dynamic processes in the troposphere has led to unprecedented, synoptic-scale stratospheric regions with temperatures below the frost point; in these regions stratospheric ice clouds have been observed, extending over >106km2 during more than 3 weeks. (2) Particle microphysics: heterogeneous nucleation of nitric acid trihydrate (NAT) particles in the absence of ice has been unambiguously demonstrated; conversely, the synoptic scale ice clouds also appear to nucleate heterogeneously; a variety of possible heterogeneous nuclei has been characterised by chemical analysis of the non-volatile fraction of the background aerosol; substantial formation of solid particles and denitrification via their sedimentation has been observed and model parameterizations have been improved. (3) Chemistry: strong evidence has been found for significant chlorine activation not only on polar stratospheric clouds (PSCs) but also on cold binary aerosol; laboratory experiments and field data on the ClOOCl photolysis rate and other kinetic parameters have been shown to be consistent with an adequate degree of certainty; no evidence has been found that would support the existence of yet unknown chemical mechanisms making a significant contribution to polar ozone loss. (4) Global modelling: results from process studies have been implemented in a prognostic chemistry climate model (CCM); simulations with improved parameterisations of processes relevant for polar ozone depletion are evaluated against satellite data and other long term records using data assimilation and detrended fluctuation analysis. Finally, measurements and process studies within RECONCILE were also applied to the winter 2010/11, when special meteorological conditions led to the highest chemical ozone loss ever observed in the Arctic. In addition to quantifying the 2010/11 ozone loss and to understand its causes including possible connections to climate change, its impacts were addressed, such as changes in surface ultraviolet (UV) radiation in the densely populated northern mid-latitudes.

von Hobe, M.; Bekki, S.; Borrmann, S.; Cairo, F.; D'Amato, F.; Di Donfrancesco, G.; Dörnbrack, A.; Ebersoldt, A.; Ebert, M.; Emde, C.; Engel, I.; Ern, M.; Frey, W.; Griessbach, S.; Grooß, J.-U.; Gulde, T.; Günther, G.; Hösen, E.; Hoffmann, L.; Homonnai, V.; Hoyle, C. R.; Isaksen, I. S. A.; Jackson, D. R.; Jánosi, I. M.; Kandler, K.; Kalicinsky, C.; Keil, A.; Khaykin, S. M.; Khosrawi, F.; Kivi, R.; Kuttippurath, J.; Laube, J. C.; Lefèvre, F.; Lehmann, R.; Ludmann, S.; Luo, B. P.; Marchand, M.; Meyer, J.; Mitev, V.; Molleker, S.; Müller, R.; Oelhaf, H.; Olschewski, F.; Orsolini, Y.; Peter, T.; Pfeilsticker, K.; Piesch, C.; Pitts, M. C.; Poole, L. R.; Pope, F. D.; Ravegnani, F.; Rex, M.; Riese, M.; Röckmann, T.; Rognerud, B.; Roiger, A.; Rolf, C.; Santee, M. L.; Scheibe, M.; Schiller, C.; Schlager, H.; Siciliani de Cumis, M.; Sitnikov, N.; Søvde, O. A.; Spang, R.; Spelten, N.; Stordal, F.; Sumi?ska-Ebersoldt, O.; Viciani, S.; Volk, C. M.; vom Scheidt, M.; Ulanovski, A.; von der Gathen, P.; Walker, K.; Wegner, T.; Weigel, R.; Weinbuch, S.; Wetzel, G.; Wienhold, F. G.; Wintel, J.; Wohltmann, I.; Woiwode, W.; Young, I. A. K.; Yushkov, V.; Zobrist, B.; Stroh, F.

2012-11-01

389

Global mapping of vegetation parameters from POLDER multiangular measurements for studies of surface-atmosphere interactions: A pragmatic method and its validation  

NASA Astrophysics Data System (ADS)

This paper presents a pragmatic method to produce global maps of vegetation parameters, which offer essential data for weather forecast and climate modeling. The crucial variables are leaf area index (LAI), fractional vegetation cover (FVC), and fraction of absorbed photosynthetically active radiation (fAPAR). The approach relies on the use of spectral and directional vegetation indices simulated by a bidirectional reflectance model and calibrated against sets of satellite data. The model belongs to the kernel-driven category, and the coefficients obtained, as the result of linear inversion, are the basis of the proposed method. The strategy presented relies upon the existence of suitable angular measurements to derive each biophysical parameter. An application is shown with the global POLDER/ADEOS-I database. Special attention is given here to the future production of LAI and fAPAR since the albedo is a product already disseminated by the POLDER production center. Terrestrial ecosystems show a high level of aggregation and, in practice, only effective LAI can be measured. Therefore a correction factor, namely the clumping index, must be applied to help resolve the scaling issue. Clumping corrections are performed biome by biome, using empirical equations where it appears that LAI assessments for boreal and tropical forests would otherwise be significantly inaccurate. However, the effect of clumping will be less on FVC and fAPAR. The relevance of the proposed method is demonstrated through a comparison of POLDER-derived LAI values with a varied set of ground LAI measurements, including their coherence with the corresponding fAPAR.

Roujean, Jean-Louis; Lacaze, Roselyne

2002-06-01

390

Geographic whistler distributions as a function of the dispersion parameter and the ionosphere configuration derived from the RNF experiment onboard DEMETER  

NASA Astrophysics Data System (ADS)

Whistlers are electromagnetic impulses generated during lightning and propagating across the ionospheric and magnetospheric plasmas in the ELF VLF frequency range Their typical signature in the frequency time domain is characterized by the dispersion parameter which is related to the plasma parameters encountered during the propagation The RNF experiment onboard DEMETER allows for the first time a continuous survey of these phenomena It consists of a neural network system dedicated to automatic identification and classification of the whistlers encountered by the satellite From ELF-VLF electric field measurements each whistler is identified and characterized onboard DEMETER by the RNF experiment Using the data provided by the neural network it is then possible to obtain the geographic whistler distributions at the altitude of the satellite for different ranges of dispersion parameters and for both night time and day time conditions The results are presented and discussed

Pinçon, J.-L.

391

Analysis of sub-micron parameters derived from multi-altitude and multi-spectral AOD measurements acquired during the 2009 PAM-ARCMIP airborne campaign  

NASA Astrophysics Data System (ADS)

A series of Arctic sunphotometry flights were analyzed in terms of their multi-altitude, sub-micron (fine mode) information content. A spectral deconvolution algorithm (SDA) and a fine mode curvature algorithm (FMC) were applied to extract fine mode and coarse mode optical depth as well as the effective radius of the fine mode as a function of altitude. The fine mode optical depth was differentiated as a function of altitude to retrieve vertical profiles of fine mode extinction coefficient. These optical results were compared with volumetric altitude profiles of fine mode particle size distribution acquired by a UHSAS (Ultra High Sensitivity Aerosol Spectrometer).The results showed that layer-averaged extinction cross sections derived from the ratio of fine mode optical depth to integrated UHSAS number density were significantly larger than extinction cross sections derived from the application of Mie theory to the UHSAS particle size distributions. Vertical profiles of extinction coefficients derived from altitude derivatives of the fine mode optical depth profiles showed some correlation with the UHSAS extinction coefficients. Profiles of the fine mode effective radius retrieved from the sunphotometry data were generally of similar magnitude to columnar averages of the UHSAS radii but no significant trend with altitude could be detected. An example was given of a high altitude smoke plume whose presence eliminated any hope of correlating the volumetric sampling information with the sunphotometer profiles. This is simply a statement of the obvious; that the atmospheric state must be stable in order to make such comparisons.

Saha, Auromeet; O'Neill, Norman T.; Stone, Robert S.; Liu, Peter S.; Herber, Andreas B.

2012-06-01

392

Diurnal Variability of Regional Cloud and Clear-Sky Radiative Parameters Derived from GOES Data. Part II: November 1978 Cloud Distributions  

Microsoft Academic Search

Regional (250 × 250 km2) diurnal cloud variability is examined using mean hourly cloud amounts derived from November 1978 GOES-East visible and infrared data with a hybrid bispectral threshold technique. A wide variety of diurnal variations in cloud cover is presented. A morning maximum in low cloudiness is found over much of the eastern Pacific. Many regions in the western

Patrick Minnis; Edwin F. Harrison

1984-01-01

393

Influence of host plant-derived and abiotic environmental parameters on the composition of the diazotroph assemblage associated with roots of Juncus roemerianus  

Microsoft Academic Search

Environmental factors governing the distributions of plant root-associated bacteria are poorly understood. Most plant species occurring in salt marsh estuaries are restricted to very specific habitats within the marsh and plant-derived and abiotic environmental features covary. We examined diazotrophic bacteria inhabiting the rhizoplanes of different populations of the black needlerush, Juncus roemerianus, growing in two different habitats, in order to

Jeannine R. LaRocque; Peter W. Bergholz; Christopher E. Bagwell; Charles R. Lovell

2004-01-01

394

Interaction of indole and tryptophan derivatives with sodium dodecyl sulfate micelles measured with ultraviolet absorption and fluorescence quenching  

Microsoft Academic Search

The distribution of indole and tryptophan derivatives between sodium dodecyl sulfate (SDS) micellar and aqueous phases was analyzed using conventional methods of ultraviolet (UV) absorption spectroscopy and measurement of fluorescence quenching by succinimide. On the assumption of a simple pseudo-phase equilibrium between both phases the distribution coefficient was easily obtained by the measurement of the ratioRpv of the absorbance intensity

Takeyoshi Imamura; Katsutoshi Konishi

1995-01-01

395

Gene, pathway and network frameworks to identify epistatic interactions of single nucleotide polymorphisms derived from GWAS data  

PubMed Central

Background Interactions among genomic loci (also known as epistasis) have been suggested as one of the potential sources of missing heritability in single locus analysis of genome-wide association studies (GWAS). The computational burden of searching for interactions is compounded by the extremely low threshold for identifying significant p-values due to multiple hypothesis testing corrections. Utilizing prior biological knowledge to restrict the set of candidate SNP pairs to be tested can alleviate this problem, but systematic studies that investigate the relative merits of integrating different biological frameworks and GWAS data have not been conducted. Results We developed four biologically based frameworks to identify pairwise interactions among candidate SNP pairs as follows: (1) for each human protein-coding gene, a set of SNPs associated with that gene was constructed providing a gene-based interaction model, (2) for each known biological pathway, a set of SNPs associated with the genes in the pathway was constructed providing a pathway-based interaction model, (3) a set of SNPs associated with genes in a disease-related subnetwork provides a network-based interaction model, and (4) a framework is based on the function of SNPs. The last approach uses expression SNPs (eSNPs or eQTLs), which are SNPs or loci that have defined effects on the abundance of transcripts of other genes. We constructed pairs of eSNPs and SNPs located in the target genes whose expression is regulated by eSNPs. For all four frameworks the SNP sets were exhaustively tested for pairwise interactions within the sets using a traditional logistic regression model after excluding genes that were previously identified to associate with the trait. Using previously published GWAS data for type 2 diabetes (T2D) and the biologically based pair-wise interaction modeling, we identify twelve genes not seen in the previous single locus analysis. Co