Quasi Elastic Research Articles

Diffusive Dynamics of Water in the Presence of Homologous Disaccharides: A Comparative Study by Quasi Elastic Neutron Scattering. IV.

The present paper reports on the study of the disaccharides' dynamics in aqueous solutions and discusses the role of their interaction with water, which seems to be responsible for the protective action on biological membranes and tissues. In particular, using QENS (IRIS at ISIS, RAL, U.K.) we compared the quasielastic spectra from three homologous disaccharides (trehalose, maltose, and sucrose) with a hydration of 20 water molecules per each disaccharide molecule. The isotopic substitution method allowed us to study also the dynamics of water in the presence of the disaccharides. Our results show that trehalose is the most effective in slowing down the water dynamics, inducing a more extensive hydration layer.

Hydration water in macromolecules of biological interest: An incoherent quasi elastic neutron scattering

We report a detailed dynamical study on a hydrated protein, Lysozyme comparing its dynamical features with those obtained in the case of aqueous solutions whose solute is a synthetic polymer, Poly(ethylene glycol), PEG600. The noteworthy feature of this kind of analysis is that it is yet reasonable to apply the same theoretical model to the experimental data, even if the complexity of the solute molecules, in passing from the polymer to the protein, increases dramatically. The experimental measurements performed by Incoherent Quasi Elastic Neutron Scattering technique (IQENS) were carried out by using hydration conditions in H 2O and D 2O in order to clearly evaluate the different contributions of the protein/polymer matrix from that of hydration water. A clear slowing down in the dynamics of the latter with respect to the bulk water is revealed in both the cases.

Fusion barrier and spin distributions in 12C+232Th reaction via quasielastic scattering

Quasielastic (QE) excitation function measurements have been carried out for the ${}^{12}\mathrm{C}{+}^{232}\mathrm{Th}$ fissile system at ${\ensuremath{\theta}}_{\mathrm{lab}}=170\ifmmode^\circ\else\textdegree\fi{}$ in the energy range of ${E}_{\mathrm{lab}}$ = 51--79 MeV. The data has been analyzed to obtain a representation of the fusion barrier distribution, which has been compared with that obtained from fusion-fission excitation function measurements available from literature. The QE data have also been analyzed in the framework of generalized elastic scattering model to obtain the mean-square average compound nuclear spin $(〈{l}^{2}〉)$ values, which has been compared with the prediction of standard fusion model (CCDEF) calculations and also with that obtained from fission fragment angular anisotropy measurements. The results show that the barrier distributions obtained from QE and fission excitation function measurement are consistent with each other. The $〈{l}^{2}〉$ values are also consistent with prediction of CCDEF calculations, but are in disagreement with the experimental $〈{l}^{2}〉$ values obtained from fission fragment anisotropy measurements.

Wave-vector dependence in quasielastic neutron scattering

The wave-vector $(k)$ dependence of the quasielastic (QE) intensity generated by neutrons scattered by particles moving under the action of one-dimensional potentials and weak stochastic forces is investigated in detail. It is shown that, in the low-$k$ limit, the quasielastic intensity due to scatterers subject to symmetric potentials is proportional to ${k}^{4},$ while asymmetric potentials will generally give rise to a ${k}^{2}$ term. Formulas to evaluate the coefficient for an arbitrary term in a $k$ expansion of the cross section are derived. It is also shown that the QE line consists of a superposition of Lorentzians generated by energy relaxation modes. A possible application to the soft-potential model of glasses is indicated.

Dissipative processes in19F +27Al at 5.9 MeV/A

Experimental evidence on the complete dynamics, from quasielastic (QE) to completely dissipated orbiting in the19F+27Al system at 5.9 MeV/A is presented. Comparison with the systematics for much heavier systems speaks in favour of a similar underlying mechanism.

Prenucleation, crystal growth and polymorphism of some proteins

The solubility of the orthorhombic polymorph A of α-amylase was determined at pH = 8 in KSCN, KCl, K 2SO 4 and NaCl solutions and at pH = 7, 8 and 9 in NaCl solutions. The effectiveness of anions in decreasing the solubility of α-amylase at pH = 8 is SO 2− 4>Cl −>SCN −. This order is in agreement with the Hofmeister series. The decrease of pH towards the pI caused the solubility to decrease. Molecular interactions were studied by Quasi Elastic Light Scattering and Small Angle X-ray Scattering. For BPTI in NaCl solutions, the interactions change from repulsive to attractive once NaCl concentration is higher than 1M. For α-amylase (ionic strength 28 mM) interactions are slightly repulsive. However, under both conditions the macromolecules crystallize. The molecular interactions probably explain why the growth rate of BPTI is larger than that of α-amylase.

Raman spectroscopic study of water in the poly(ethylene glycol) hydration shell

Raman scattering spectra of polymeric aqueous solutions of poly(ethylene glycol) vs. concentration and temperature are presented. We show that the shape of the OH band can be reproduced by a suitable superposition of the spectra of bulk and hydration water. The relative amount of the two contributions changes with concentration and temperature, furnishing information on the number of water molecules bonded to the polymer chain. The results show that, when water concentration increases, water molecules saturate the two lone pairs of each oxygen atom of the polymer in agreement with previous adiabatic compressibility and Incoherent Quasi Elastic Neutron Scattering measurements.

Interaction between an Anionic Polysaccharide and an Oppositely Charged Surfactant. Quasi Elastic Light Scattering, Size Exclusion Chromatography, and Capillary Electrophoresis Study of the Sodium Hyaluronate/Tetradecyltrimethylammonium Bromide/Sodium Chloride/Water System

The interaction between the anionic polysaccharide sodium hyaluronate (NaHy) and the positively charged surfactant tetradecyltrimethylammonium bromide (TTAB) in water leads to phase separation if an insufficient amount of salt (NaCl in this study) is added. With increasing TTAB concentration a pronounced interaction remains even under single-phase conditions. This is experimentally supported by a lowered relative viscosity, a decreased electrophoretic mobility as determined by high performance capillary electrophoresis (HPCE) approaching zero mobility at infinite TTAB concentrations, and changes in hydrodynamic size as well as an increased relative scattered intensity as determined by quasi elastic light scattering (QELS). The extent of this interaction is controlled mainly by the ionic strength of the solution and by the concentration of surfactant. The data obtained are reasonably explained by the model developed in interaction studies of a positively charged polymer with a negatively charged surfactant.

Dynamic scattering of ternary polymer mixtures in solutions: The χF interaction parameter and the single chain diffusion coefficient DS

AbstractThis work discusses the dynamic scattering properties of ternary polymer mixtures in solution and emphasizes on how can be extracted the value of the single chain diffusion coefficient DS and that of the interaction parameter χF when using Quasi Elastic Light Scattering (QELS) in any good solvent. This is the direct consequence of considerable efforts made during the past decade, in the understanding of dynamic properties of multicomponent systems from both theoretical and experimental points of view.

Quasi Elastic Light Scattering Study on Solutions of Linear Flexible Polyelectrolytes at Low Ionic Strengths

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTQuasi Elastic Light Scattering Study on Solutions of Linear Flexible Polyelectrolytes at Low Ionic StrengthsRoy G. Smits, Maxim E. Kuil, and Michel MandelCite this: Macromolecules 1994, 27, 20, 5599–5608Publication Date (Print):September 1, 1994Publication History Published online1 May 2002Published inissue 1 September 1994https://doi.org/10.1021/ma00098a013RIGHTS & PERMISSIONSArticle Views125Altmetric-Citations34LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (1 MB) Get e-Alerts Get e-Alerts

Vibrational and diffusional behaviour of H2O molecules encaged in reversed micellar aggregates

Measurements performed by means of Small Angle Neutron Scattering (SANS), Incoherent Quasi Elastic Neutron Scattering (IQENS) and Fourier Transform Infrared (FTIR) techniques on reversed water-in-oil micelles are presented and analysed. This ternary system, constituted by water/surfactant Me+n(AOT)n/oil forms droplets whose shapes and sizes have been determined by SANS. Moreover a strong confinement effect for the H2O molecules, whose dynamical properties reflect themselves on the O-H stretching band (FTIR) and on the low frequency diffusive motions (IQENS), is revealed.

Study of inelastic magnetic excitations in Na 3Cr 2(PO 4) 3 by neutron scattering

The quasielastic (QES) and the inelastic scattering (INS) observed in the neutron scattering spectra of polycrystalline Na 3Cr 2P 3O 12 (noted NaCr) from 0.8 to 673 K is due to spin fluctuations. The QES of NaCr and NaFe were analyzed within de Gennes' (DG) theory in a previous article. The present work is devoted to the INS of NaCr, it was measured from 0.8 to 673 K, at the time of flight IN6, IN5 and D7 (polarized neutrons) spectrometers at ILL. The Q dependence of the frequency maximum, of the half-width and of the amplitude of the INS have been investigated and discussed in the light of different models and theories such as the zero-field splitting (ZFS), the exchange coupled Cr 3+ dimers (ECCD) model and Lovesey and Meserve's (LM) theory. Although qualitative agreement can be obtained with the ECCD model, the LM model is more suitable for reproducing the experimental data. In particular the QES and the INS are treated simultaneously. For the last two models the average Jvalue ( ca 0.35 meV) which must be introduced is much larger than the value which was derived using the DG theory from the QES study of NaCr (0.083 meV), but of the same order as that found for NaFe in its paramagnetic phase (0.35 meV), this value being close to those found from low temperature measurements of magnon energies in NaFe and associated to the nearest Fe-Fe exchange couplings (0.2 meV), as if only these couplings were responsible for the paramagnetic fluctuations. For NaCr the situation is different since it is not possible to obtain consistent J values when one treats the QES and INS separately. Thus it remains difficult, both from a chemical point of view and with the J values reported above, to explain why for NaCr the INS persists to 673 K while for its Fe isomorph it disappears above 47 K. In any case the fact that NaCr does not order cannot be attributed to a small J value and must be found in the structural disorder associated to the Na + ions and to the presence of magnetic frustrations.

QENS and NMR Investigation of Molecular DIF Fusion in the Nematic Phase of EBBA

Abstract In this paper we present a combined Quasi Elastic Neutron Scattering and 13C magnetic relaxation study of the molecular dynamics in the nematic phase of EBBA. Attention has been focused on the relatively rigid biphenylic core of the molecule. In both cases a global model dependent fit of the obtained data has been performed. We were able to separate the rotational and translational contributions to QENS. The translational broadening displays an anomalous behavior in the high Q region which has been discussed against different diffusional mechanisms. The values of the rotational diffusion around the long molecular axis has been extracted as a function of temperature and compared to those measured with 13C magnetic relaxation of the orthophenylic carbons. Finally, the flexibility of the considered molecular fragment has been taken into account in interpreting the 13C relaxation data.

The 20Ne+ 159Tb reaction studied with the KX-ray method at 15 [formula omitted

Employing the KX-ray method, in which coincidences are measured between projectile-like fragments (PLF) and the characteristic KX rays from the target-like fragments (TLF), partial cross sections dσ-(Z PLF , Z TLF )/ dΩ PLF were obtained for the 20Ne+ 159Tb reaction at E lab = 294 MeV for both the quasi-elastic (QE) and the deep-inelastic (DI) components. By in addition measuring triple coincidences with charged particles at back angles the results could be corrected for charged particle evaporation from the TLF. Primary PLF cross sections were reconstructed for both components and the corresponding probabilities for sequential charged particle decay of the fragments were deduced. The very different behaviour of the QE and DI components will be discussed. As in a previous study of the 14N+ 159Tb reaction large cross sections are observed for channels in which only nucleons and α-particles are emitted. Statistical model calculations were performed to deduce the excitation energy distribution of the primary PLF's. Comparison with other methods to reconstruct primary cross sections are made. The predictions of several models are evaluated.

Extensive Measurements on Soot Particles in Laminar Premixed Flames by Quasi Elastic Light Scattering Spectroscopy

Abstract The data obtained by Quasi-Elastic Light-Scattering Spectroscopy on twenty five alkane-oxygen sooting flames are presented. This optical method, based on the interaction between particles and their surrounding, allows the granulometric study of the soot aerosol evolution accounting for the specific aerosol regime existing in the considered flame. Diffusion Broadening and/or Photon Correlation Spectroscopy adapted to a Brownian aerosol in a flowing high temperature medium are used for the simultaneous measurements of soot diameter and number density or diameter and polydispersity. The data reduction method employed permits easy analysis including the transit time and the polydispersity aspects of the scatterers. Soot coagulation growth rates are also determined for these flames.

Quasi-elastic reaction cross sections and the merging instability

Considering a broad diversity of experimental heavy-ion data we suggest a physical separation between quasi-elastic (QE) and deep-inelastic (DI) processes. Methods for the determination of QE cross sections are described, and 48 values are compiled. The separation is proposed to be related to an instability, and a formula for the prediction of QE cross sections is derived. The formula is applicable to reactions with nuclei as light as nitrogen and as heavy as uranium at impact energies just sufficient to pass the interaction barrier up to three times the barrier. The ratio of experimental to model calculated data gives a weighted average of 0.99 ± 0.03 with a weighted mean deviation of ± 17%.

Viscosity Measurements by Quasi Elastic Light Scattering in p-Azoxyanisol

Viscosity Measurements by Quasi Elastic Light Scattering in <i>p</i>-Azoxyanisol

Composite Model and High Energy Quasi Elastic Scattering

u u ~~~ d~U ii () (a) Z~r--g U~~d d (b) u ~~~ d~U ii () (a) Z~r--g U~~d d (b) Fig. L a) and b) correspond to the exchange and annihilation of quark respectively. These are refered to as X- and H-type respectively.2) We formulate the above mechanisms fol­ lowing the multiple scattering theory.4) The amplitude of X-type in the c.m. sys­ tem is given in the form

Discussion of the Quasi Elastic Scattering of Neutrons in Incoherent Liquids

Abstract A critical discussion of the quasi-elastic scattering of neutrons by incoherent (hydrogenous) liquids is presented. Using the line shape expression a comparative discussion of several phenomenological models has been undertaken. Extension of the Singwi-Sjolander zero phonon expression, for the jump-diffusion model, so as to include the one phonon expression has also been given. For a delayed diffusion model a complete treatment of S(K, ω) is presented. Along the lines of the macroscopic diffusion cooling, a microscopic diffusion cooling effect in fluids is speculated. He is thankful to Jack Chernick, Head of Theoretical Reactor Physics Division, Brookhaven National Laboratory, for extending the hospitality of his group where this manuscript was finally completed. The author is grateful to Dr. G. Vineyard for discussing the finalised manuscript and valuable comments.