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  • 1
    Electronic Resource
    Electronic Resource
    Relaxation process in deeply supercooled water by Mandelstam-Brillouin scattering (1989)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 93 (1989), S. 942-947 
    Details
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/j100339a077
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  • 2
    Electronic Resource
    Electronic Resource
    Structural changes in potassium oleate microemulsions by ultrasound measurements (1989)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 93 (1989), S. 3251-3255 
    Details
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/j100345a073
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  • 3
    Electronic Resource
    Electronic Resource
    Effect of H-bond active sites on transport properties of poly(ethylene oxide) dissolved in its monomers: Shear viscosity and diffusion coefficient studies (2000)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 112 (2000), S. 5205-5211 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The possibility of dissolving poly(ethylene oxide) [PEO:H–(O–CH2–CH2)n–OH] in its monomeric liquid ethylene glycol [EG:H–(O–CH2–CH2)–OH] represents the only way to verify the complex polymer–monomer interactions, through the OH end groups, resulting in the scaling law R∝Nν. We report viscosity results, in conjunction with photon correlation spectroscopy data, on different molecular weight PEO samples, in a wide range of concentrations, dissolved in EG. In order to distinguish among various interaction mechanisms, we also studied PEO dissolved in EG monomethyl ether [EGmE:CH3–(O–CH2–CH2)–OH] and EG dimethyl ether [EGdE:CH3–(O–CH2–CH2)OCH3], the latter not having in its chemical structure OH hydroxylic groups available to give rise to hydrogen bond interactions. In particular, the quality (good-theta-poor) of the solvents has been analyzed by verifying the well-known Mark–Houwink–Sakurada scaling law and the effects of the polymer–solvent interactions on the coils diffusive properties. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.481075
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  • 4
    Electronic Resource
    Electronic Resource
    Anomalous cryoprotective effectiveness of trehalose: Raman scattering evidences (1999)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 111 (1999), S. 281-287 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Results of Raman scattering measurements performed on aqueous solutions of the homologous disaccharides (trehalose, maltose, and sucrose) are reported. To get some insight into the effects of disaccharides on the hydrogen bond network of water, and to clarify the reasons that make trehalose the most effective in protecting organisms from dehydration and freezing, we investigate the intramolecular OH stretching mode. To carry out this study, two different approaches are employed: namely, a decomposition of the isotropic spectra into an "open" and a "closed" contribution, and a spectral stripping procedure to extract the "collective" contribution from the polarized spectra. Both procedures agree in suggesting that disaccharides promote, with a different strength, a destructuring effect on the tetrahedral H-bond network of pure water. This result makes plausible the hypothesis that disaccharides obstruct the crystallization process reducing the amount of freezable water, namely destroying the network of water compatible with that of ice. What conclusively emerges from this Raman scattering study is that the greater bioprotective action of trehalose on biological structures is to be connected with its greater destructuring effect on the tetrahedral H-bond network of water. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.479288
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  • 5
    Electronic Resource
    Electronic Resource
    Dynamic evidence of chemical and physical traps in H-bonded confined liquids (1998)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 109 (1998), S. 7394-7404 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Rayleigh wing, infrared (IR) absorption, and Raman-scattering measurements are employed to investigate the reorientational and vibrational dynamics of ethylene glycol and its homologous systems, namely ethylene glycol monomethyl ether and ethylene glycol dimethyl ether, in the bulk state and confined into 25 Å pores of a sol-gel porous glass. As far as the Rayleigh wing data are concerned, the quantitative analysis of the different contributions in the spectra shows the clear influence of the physical and chemical confinement on the mobility of the studied liquids. In addition the IR and Raman measurements, performed in the O–H stretching region, allowed to identify the intramolecular, H-bond imposed, sub-band, as well as to connect the various sub-bands to different intermolecular environments originated by the existence of the H-bond potential. The observed dynamics is discussed on the basis of current theories for associated liquids. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.477345
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  • 6
    Electronic Resource
    Electronic Resource
    The puzzle of poly(ethylene oxide) aggregation in water: Experimental findings (1999)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 110 (1999), S. 1801-1806 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Aqueous solutions of poly(ethylene oxide) were investigated using the ultrasonic technique, photon correlation spectroscopy (PCS) and nuclear magnetic resonance (NMR), in a wide range of molecular weight (from ethylene glycol to poly(ethylene oxide) 4 000 000 Da). Ultrasonic data reveal that the mixing process is not ideal and show that the polymer–water interaction strength increases with the polymerization degree. PCS and NMR, on the other hand, furnish a free particle diffusion coefficient which satisfies a unique scaling law from 8000 to 4 000 000 Da and demonstrates the good solvent nature of water. These experimental findings indicate that polymer–polymer aggregation processes are not an inherent property of these systems. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.477888
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  • 7
    Electronic Resource
    Electronic Resource
    Hydration and transport properties of aqueous solutions of α-α-trehalose (1998)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 109 (1998), S. 1170-1174 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We report measurements of the sound velocity diffusivity and viscosity of aqueous solutions of α-α-trehalose at temperatures between 20 and 85 °C for volume fractions from 0.041 to 0.705. The ultrasonic data show that the mixing process is not ideal and that the trehalose-water interaction strength, because of the saturation of H-bond sites, decreases with increasing concentration. Photon correlation spectroscopy reveals marked changes in the effective diffusion coefficient in the dilute region over a limited temperature range. These measurements, interpreted in conjunction with viscosity data on the basis of a model by Mooney and Padova, quantify the hydration properties of α-α-trehalose. The dependence on volume fraction and the sensitivity to temperature changes characterize the "fragility" of this disaccharide-water system. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.476662
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  • 8
    Electronic Resource
    Electronic Resource
    Experimental simulation of macromolecules in trehalose aqueous solutions: A photon correlation spectroscopy study (1999)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 111 (1999), S. 9086-9092 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The protective effect of trehalose on biological membranes against freezing or dehydration has been the subject of many studies aimed to understand the reasons why some lower organisms, under stress conditions, synthesize trehalose. In this work we report the results of a study on Poly(Ethylene Oxide)/trehalose/water mixtures performed by Photon Correlation Spectroscopy. The chemical structure of the polymer, simpler than that of proteins and its helical conformation in water, constitute a useful starting point for understanding the more complex protein/trehalose/water interactions. In order to distinguish the different dynamics, trehalose and PEO have been studied separately in water, at different concentration and temperature values; then the ternary PEO/trehalose/water system has been investigated at different sugar amounts. The obtained findings support the "water-replacement" hypothesis, indicating that a direct polymer–trehalose interaction occurs. Furthermore, trehalose is shown to affect the swelling properties of the polymer with temperature, stabilizing its conformation. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.480250
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  • 9
    Electronic Resource
    Electronic Resource
    Role of the H bond and cooperative effects in normal and supercooled water studied by anisotropic low frequency light scattering (1986)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 84 (1986), S. 4731-4738 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Depolarized Rayleigh and low frequency Raman scattering data in bulk supercooled water are presented. The measurements, performed from the normal region down to −26.95 °C for the first time, allow a quantitative data analysis and reveal the existence of a fine structure of the central contribution. We have identified a "fast'' and "slow'' contribution whose intensities show an opposite behavior as a function of temperature. Such a behavior is understood as a decay of local order due to the H bond. The spectral density function, as derived from the depolarized Raman data, shows the presence of acoustical and intermolecular optical contributions characteristic of many structured disordered materials. A critical comparison with molecular dynamics (MD) and neutron scattering results is also presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.450007
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  • 10
    Electronic Resource
    Electronic Resource
    SANS Studies of Octyl-β-glucoside and Glycine Micellar Solutions (1997)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 30 (1997), S. 761-764 
    Details
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: Small-angle neutron scattering (SANS) experiments were performed on micellar solutions of octyl-β-glucoside (OBG) in water and on solutions of OBG + glycine in water. A detailed analysis of the results obtained for different concentrations (from 0.026 to 1 M) of glycine and OBG shows that: (i) the structure of the micelles of OBG is always ellipsoidal with the long axis increasing as the concentration of OBG increases from the critical micellar concentration (c.m.c. = 0.022 M) to 1 M; (ii) there is a tendency to form aggregates at concentrations of OBG smaller than 0.5 M; (iii) steric repulsive interactions are clearly seen for concentrations above 0.6 M. The virial coefficient is evaluated as a function of the concentration in OBG. The negative values at low concentration reveal the presence of attractive interactions, while at high concentration the repulsive steric interaction dominates. At high concentration of OBG, the spectra with or without glycine are the same. The analysis shows that glycine remains in water and that its presence does not affect the structure of the micelles.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0021889897001817
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