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Raman scattering and Fourier-transform infrared (FT-IR) absorption results on confined water are presented. The aim is to characterize different porous materials, studying the vibrational properties of water inserted in their porous structure, and determining the relationship between these two aspects. Confinement has been realized by using a sol–gel silica glass, GelSil, with 26 A diameter pores of huge hydrophilic inner surface, and NaA type zeolites, with 10 A diameter pores in which 27 H2O molecules can be located. The O–H stretching spectral range (2800–3800 cm−1), as a function of temperature and for different water contents, has been explored. From a comparison of the data in these two cases, we put into evidence the structure breaker role of GelSil, as revealed by the slowing down of the collective contribution to the polarized O–H stretching band, indicating that the tetrabonded H2O network is destroyed. On the other side, NaA zeolites will be proofed to play a structure breaker effect on physisorbed water, since the contribution to the O–H stretching band linked to the tetrahedral ice-like arrangement is present even at the lowest hydration conditions.

In the present work we characterized samples of plasters and pictorial layers taken from a fresco in the Acireale Cathedral. The fresco represents the Coronation of Saint Venera, patron saint of this Ionian town. By performing a detailed spectroscopic analysis of the plaster preparation layer by Fourier-transform infrared (FTIR) spectroscopy and x-ray diffraction (XRD), and of the painting layer by FTIR and confocal Raman microspectroscopy, scanning electron microscopy+energy dispersive x-ray spectroscopy, and XRD, we were able to identify the pigments and the binders present. In particular, Raman investigation was crucial to the characterization of the pigments thanks to the high resolution of the confocal apparatus used. It is worth stressing that the simultaneous use of complementary techniques was able to provide more complete information for the conservation of the artifact we studied. (C) 2005 American Institute of Physics.

The aim of the present work is the characterization of decorated pottery samples from Caltagirone (Sicily, Italy), a renowned production centre of this kind of artwork. These fragments were found during archaeological excavations and were attributed to historical periods extremely far in time from each other (from XVIII century b.C. to XVI a.C.). Therefore, we expect that the manufacture techniques result rather different over so long time. The measurements, performed by Fourier Transform-InfraRed (FT-IR) absorbance and micro-Raman scattering, allowed us a non-destructive study of so precious artefacts. Some pigments were identified, various elements of ceramic paste and glazed layer were characterized.

The aim of the present work is the characterization of pottery fragments coming from the town of Caltagirone (Sicily, Italy). The samples belong to very different historical periods, from 18th century B.C. to 16th century A.D., and have finely decorated surfaces. Time-of-flight neutron-diffraction measurements were performed in order to obtain a quantitative identification of the mineralogical composition of the samples. A good determination of the relative weight fractions of the phases was obtained using the Rietveld analysis method. The application of neutron-diffraction technique allowed us to carry out a detailed analysis in a nondestructive way, so intact large fragments were investigated without damaging the precious decoration on the surface.

An investigation was undertaken at St. Agata la Vetere church in Catania, dating back to 333 D.C, in order to obtain essential information for the planned restoration works. In fact, the 1693 earthquake totally destroyed both the church and the adjoining monastery, which when rebuilt changed their original appearance enormously. As a preliminary step, a mineralogic petrographic characterization of the materials was carried out. Optical Microscopy (OM), X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR), Differential Scanning Calorimetry (DSC) and Thermo-Gravimetric (TG) analyses were performed on samples of bricks, plasters and mortars. At the same time, ground penetrating radar (GPR) investigations allowed a series of anomalies in the soils to be discovered which can be attributed to the presence of buried structures under the pavement of the church. Lastly, by collecting and collectively interpreting all the results obtained by in situ drillings and tomographic prospections, it was possible to reproduce the substratum behaviour and to localise areas with electric anomalies confirming the existence of hidden structures.

During recent years, the understanding of the modification of the structural and dynamics of water confined in different environments has been the focus of much interest in scientific research. This topic is in fact of great relevance in a lot of technological areas and, in living systems, essential water related phenomena occur in restricted geometries in cells, and active sites of proteins and membranes, or at their surface. In this paper we report on neutron diffraction results on the microscopic structure of heavy water confined in a fully hydrated sol–gel silica glass (GelSil) as a function of the temperature, in comparison with that of bulk water. Furthermore, at low T , the nucleation of cubic ice superimposed to liquid water, already observed for water within Vycor glasses, is discussed.

In the present work, we report a spectroscopic analysis of water confined in a powdered zeolite, Na A type, which is able to entrap 27 H2O molecules, by Fourier transform infrared absorption, performed in the OH stretching region, 3000–3800 cm−1. The investigation was carried out as a function of temperature and at different hydration levels. The spectroscopic results were interpreted in the framework of actual theories for associated liquids and on the basis of previously measurements performed in water confined in a different environment, a controlled silica glass (GelSil), by Raman scattering, always in the OH stretching region. The comparison between these two distinct cases of confinement condition unambiguously showed the role of structure maker played by the zeolite for confined water as opposed to the structure breaker character observed in the case of the GelSil matrix.

An incoherent quasi-elastic neutron scattering experiment on pure polymers and on polymeric aqueous solutions is reported. The high resolution of the IRIS spectrometer (7 μeV) allows us to observe the diffusive motion of the pure polymer centre of mass, as well as the confined water motion within the polymer chain. The important role of the polymer—water interaction (H-bond) in the characterization of these liquid systems is also studied and analyzed.

Uncharged star polymers having a porphyrin core and four poly(ethylene glycol)methyl ether (PEGME) arms have been synthesized and investigated (through the study of the structural and dynamical properties) as a function of the molecular mass of the arms, in different thermodynamic conditions. Molecules with short PEGME arms are insoluble in water, whereas in the presence of long PEGME chains, the star polymers are water-soluble; for the intermediate length of the arms, the building up of large rigid monodisperse aggregates, driven by the diffusion limit aggregation mechanism, has been observed by means of static and dynamic light scattering. These aggregated systems, whose sizes are modulated by changing the pH and triggered by the chain flexibility, can be well described in terms of the DLVO interparticle potential in the frame of the colloidal theory.

In this paper, we go deeply into an analysis performed, as a function of T, by means of incoherent inelastic neutron scattering (IINS), of vibrational dynamics of liquid ethylene glycol (EG: HO–CH2CH2–OH) in the bulk state and confined into 26 A interconnected cylindrical pores of a sol-gel porous glass. IINS spectra revealed, as far as the vibrational density of states, Z(ω) is concerned, a different trend in temperature passing from bulk to confined samples. In particular, we observed a thermal stabilization of the disordered longitudinal acoustic mode as a consequence of the interaction between the hydroxyl groups (OH) of the EG molecules and the active silanol groups (Si–OH) on the surface of the porous glass.

In the present work we report a Fourier Transform Infrared (FT-IR) analysis performed on rat encephalon samples in the CHOH vibrational stretching region (2400–3800) cm−1, in order to reveal the presence of a very diffuse commercial benzodiazepine: VALIUM®. The comparison between the spectral features of normal brain and the ones of samples with administrated substance has unambiguously showed that the CH stretching region seems not to suffer from any change for the pharmacological treatment, instead the OH band is strongly modified probably due to the presence of a new spectral contribution characteristic of diazepam molecule.

The understanding of new phenomena arising in confined condensed matter is important for the physics of interfaces and finite systems. This has stimulated intensive research on solids, liquid crystals and liquids confined in different geometries. Experimental techniques and theoretical approaches have shown that a liquid confined to a region that approaches molecular dimension exhibits dynamic and thermodynamic properties strongly changed relatively to the bulk with increasing geometrical confinement. This was interpreted by geometric as well as absorption effects: the first ones are related to the tortuosity of the interconnected channel for diffusion, the second ones take into account the degree of adsorption of molecules on the active inner surface sites. We present a detailed study of the reorientational, vibrational and diffusional dynamics of ethylene glycol (EG: OH–CH2CH2OH), ethylene glycol monomethyl ether (EGmE: CH3–OCH2CH2OH) and ethylene glycol dimethyl ether (EGdE: CH3–OCH2CH2OCH3), in the bulk state and confined in a matrix of sol–gel porous glass with 26 A interconnected cylindrical pores. This investigation has been performed by means of Rayleigh wing (as far as reorientational dynamics is concerned), Raman (as far as vibrational dynamics is concerned) and Incoherent Quasi Elastic Neutron Scattering (as far as diffusional dynamics is concerned). The clear influence of the confinement on the mobility of the studied liquids, with a dramatic frozen-in effect with respect to the bulk state, is evidenced.

With the aim of studying the confinement influence on the molecular mobility of H-bonded systems, high-resolution quasi-elastic neutron scattering data were obtained for ethylene glycol [EG: H(O–CH2–CH2)OH] in the bulk state at T=40°C and confined into 25 A pores of a sol–gel porous glass, at T=−35°C and 40°C. The experimental data are discussed in terms of the α-relaxation dynamics predicted by mode-coupling theory for supercooled liquids. We verified that an Havriliak–Negami profile, that is verified when a distribution of relaxation times is present, represents a good description for the measured QENS translational spectral line shape.

As it is well known, the porous structure of stones can change due to different degradation processes that modify the characteristics of freshly quarried blocks. Their knowledge is fundamental for predicting the behavior of stones and the efficacy of conservative treatments. In this context, neutron radiography is a useful tool not only to visualize the structure of porous materials, but also to evaluate the degree of degradation and surface modifications resulting from weathering processes. Furthermore, since thermal neutrons suffer a strong attenuation by hydrogen, this technique is effective in order to investigate the amount of absorbed water in building materials. In the present work, we report a neutron radiography investigation of limestones cropping out in the South-Eastern Sicily and widely used as building stones in Baroque monuments of the Noto Valley. The analyzed samples have been submitted to cyclic salt crystallization that simulate degradation processes acting in exposed stones of buildings. The obtained results demonstrate the interest of neutron radiography to better understand deterioration processes in limestones and to acquire information useful for restoration projects.

A quantitative analysis of hepatotoxic effects on rat liver, caused by a single administration of carbon tetrachloride (CCl4), and of sequential hepatic regeneration has been performed by the application of biochemical analysis, light microscopy, and Fourier transform infrared (FT-IR) absorption spectroscopy. The joined techniques have allowed to mark the biochemical, structural and dynamical properties (these appear in the O–H vibrational stretching region) of rat liver samples by monitoring the changes versus the time course of injuries. The morphological observations have shown a dramatic increasing of degenerated cellular elements with fatty infiltrations just after 24 h and an initial regeneration already present at 72 h from the CCl4 treatment. As FT-IR measurements are concerned, a vibrational assignment has been made for the observed sub-bands in the analyzed wave number range, by comparing the normal liver spectrum with those in the case of CCl4 administration. In particular, the analysis in the O–H stretching region (3000–3800 cm−1) of intoxicated samples has shown clear changes interpreted on the basis of the structural and biochemical analysis made on the same samples.

A detailed spectroscopic analysis is presented in order to study the reorientational and vibrational dynamics of water and other fundamental H-bonded systems: ethylene glycol (HO−CH2−CH2−OH) and its homologous species, such as ethylene glycol monomethyl ether (CH3O−CH2−CH2−OH) and ethylene glycol dimethyl ether (CH3O−CH2−CH2−OCH3), propylene glycol (HO−CH(CH3)−CH2−OH) and its oligomers, that are confined in a matrix of sol−gel porous glasses with 26 A interconnected cylindrical pores. The use of different spectroscopic techniques, light scattering (Rayleigh wing and Raman scattering), FT-IR absorption, neutron scattering (incoherent quasi elastic and inelastic neutron scattering, IQENS and IINS, respectively) allow the marking of different dynamical parameters, with different probes being used to investigate H-bonded systems. The clear influence of the confinement on the mobility of the studied liquids, with a dramatic frozen-in observed effect respect to the bulk state, is evidenced and compared with li...

The work reports preliminary QENS results on aqueous solutions of trehalose. The employment of H/D substitution allows the separation of the diffusive dynamics of water from that of trehalose. The data analysis shows a slowed down water dynamics in comparison to that of bulk water.

We studied the reorientational and vibrational dynamics of ethylene glycol and its homologous systems, namely ethylene glycol monomethyl ether and ethylene glycol dimethyl ether, having a different number of OH groups per molecule. The above systems were studied in bulk and in confined state within a porous glass matrix with 25 A diameter pores by light scattering (Raman and Rayleigh). By comparing the obtained results the evident influence of the chemical and physical traps on the molecular mobility of the liquids forced to diffuse within the nanopores was shown.

Infrared (IR) absorption measurements are employed to investigate the vibrational spectra of propylene glycol (PG) and its oligomers the poly(propylene glycols) (PPGs) with different molecular weights (425 and 725 Da) in the OH stretching region. The goals are to identify the intramolecular, hydrogen bond imposed, sub-band and to connect the various sub-bands to different intermolecular aggregates originated by the existence of the hydrogen bond potential. The observed experimental data, compared with those of previous IR measurements on other similar polymers, ethylene glycol (EG) and poly(ethylene glycols) (PEGs), confirm the role played by the hydrogen bond in the structure of these liquids, discussed on the basis of current theories for associated systems.

We present a detailed Raman scattering study performed in liquid water confined in a porous sol-gel glass having 25 A diameter pores. The measurements were carried out in the OH vibrational stretching region, ranging from 2700 cm-1 to 3700 cm-1 . By comparing the bulk water with the confined one, strong modification of the vibrational dynamics of adsorbed water on the inner surface of the glass matrix becomes clear. Furthermore a preliminary analysis of incoherent quasi-elastic neutron scattering data (IQENS) in confined water reveals a strong confinement effect on the water molecules by the host glass that reflects, consequentially, a hindered diffusional dynamics. The experimental results were interpreted following the well known Volino-Dianoux model.

We performed viscosity measurements, at T= 50°C, on poly(ethylene oxide) (H─(O─CH2─CH2)n─OH) at different molecular weight, dissolved in ethylene glycol (H─(O─CH2─CH2)─OH) and in one of its homologous systems, namely ethylene glycol dimethyl ether (CH3─(O─CH2─CH2)─OCH3). The goal is to investigate the effects of the monomer end groups on solute-solvent interactions and, on this basis, to check the auality of these two solvents by using the Mark-Houwink-Sakurada scaling law.

We employed infrared (IR) absorption and Raman scattering to investigate the vibrational dynamics of ethylene glycol (EG) and its homologous systems, EG monomethylether and EG dimethylether, in bulk and confined into 25 A pores of a sol-gel porous glass. The measurements, performed in the O–H stretching region at room temperature, show the main role played by the H-bond in the structural environments of these liquids, discussed on the basis of current theories for associated systems. The goal is to study the intramolecular H-bond imposed band and to assign the various sub-bands in terms of the different aggregates present, clarifying the dynamical response of these associated systems in this very interesting region. Experimental data in the bulk state compared with those in the confined one give a clear indication of the influence of chemical and physical traps present in the glass matrix.

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 2 O and D 2 O 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.

All parameters of a spectrometer, signal detection, and normalization of the recorded Raman signal were controlled by a compatible IBM PC/XT computer which was connected to a Spex Ramalog 5 system. By the use of a motor‐driven polarizer, we are able for each single step time of the instrument, to monitor simultaneously the contributions IVV and IVH of the spectrum. Moreover, the simultaneous normalization of the signal with the intensity of the exciting laser light allows one to avoid the effects of the unwanted laser instability. The program can be requested by electronic mail.

Recently, confinement effects on dynamical properties of liquids inside restricted volumes have been extensively studied, either from a theoretical or technological point of view, thanks to the large possibility of industrial applications (building of optical switches, membrane separation, catalysis). We performed depolarized light scattering measurements on propylene glycol (PG) and its oligomers poly(propylene glycols) (PPG) having different molecular weights ( M w , 425, 725 and 4000 Da), in the bulk state and confined in a silica glass having 25 A pores. Mainly, two relevant effects are responsible for the dynamical response of liquids that diffuse and reorient in a confined geometry: (a) the ‘physical traps’, related to both dead-end groups and the tortuosity of the percolated channels for diffusion; and (b) the ‘chemical traps’, related to the degree of the absorption of molecules on the active surface sites. Hence, by comparing the behaviour of bulk polymers with confined polymers we were able to analyse the confinement influence on the molecular mobility of hydrogen-bonded liquids with different steric hindrance. The experimental results showed a frustration of molecular mobility in the confined samples owing to chemical and physical traps whose main role was highlighted thanks to the opportunity to substitute the active silanol groups (SiOH) in the inner surfaces with the non-active groups in the surfaces (treatment with methanol). In particular, we found that, in the case of low molecular weight samples, the relevant retardation process is connected to the chemical traps while for long chain polymers the physical traps play the main role. Further, the fitting procedure provided a distribution of relaxation times in the bulk systems and in short chain systems when confined in modified glass showing, in particular in the first case, that the distribution of relaxation times increases with polymers weights, occurrence related to a variety of molecular motions triggered by the more or less entangled unites.

Reorientational dynamics of neat liquid propylene glycol molecules is compared with that of confined molecules in 25 and 75 A pores of a sol-gel porous glass by means of depolarized light-scattering spectroscopy. The experimental spectra, performed as a function of temperature, show unambiguously the slowing down of the collective reorientational processes triggered by the confinement effects. Such results confirm the main role played by the strong dipolar interactions on the dynamics of hydrogen-bonded liquids diffusing within nanoscopic spherical pores.

Incoherent quasi-elastic neutron measurements on polymeric aqueous solutions are reported. Isotopic substitution technique allows to witness the diffusive motion of hydration water which depply differs from that in the bulk. Additional properties are discussed in the framework of current theories.

The vibrational dynamics of a new class of cyclodextrin-based hydrogel is explored in depth here with the aim to clarify the intimate relationship between the structural and functional properties of these innovative polymeric materials. The thorough quantitative analysis of the FTIR-ATR and Raman spectra of the hydrogel obtained by swelling of cross-linked polymers of cyclodextrins with heavy water is performed in the wavenumber range between 1600 and 1800 cm−1 by using best-fitting and deconvolution procedures. The use of D2O instead of H2O allowed us to separately examine in the vibrational spectra of the hydrogel the CO stretching bands assigned to the polymer network and the bending mode of engaged water molecules, giving the possibility to explore the structural changes occurring in the polymer network during the hydration process. The experimental findings were interpreted in the light of a comprehensive model which attempts to understand how physical and covalent cross-links combine to determine the macroscopic properties of the gel, like its water holding capacity and the whole rigidity of the gel network. These results shed light on the complex interplay between physical and chemical interactions which yield the formation and stabilization of the hydrogel network, opening the possibility of a rational design of these innovative soft materials for specific technological applications.

The present work reports the results of viscosity and Photon Correlation Spectroscopy (PCS) measurements performed on polymeric aqueous solutions. The viscosity data show that the transport properties of the H2O molecules in the presence of poly(ethylene glycol) differ greatly from those in the bulk. PCS data, on the other hand, allow us to evaluate the mutual diffusion coefficient and show that in the dilute region the system behaves as a polymer in a good solvent, whereas, at higher concentration indicates a scale behaviour, in agreement with the De Gennes scaling model for semi diluted solutions in a good solvent. An interpretative picture is proposed from these data: starting from pure polymers, and adding water molecules a certain number of these bond by H-bonding to the oxygen atoms of the oxirane groups, each oxygen atom being able to tie two water molecules so that the water-polymer interaction (hydration) plays a major role in the transport properties.

Ultrasonic velocity and density measurements were performed in polymeric aqueous solutions of ethylene glycol (EG) and poly(ethylene glycol) (PEG) as functions of concentration and temperature in the stable liquid region. The non-ideal behaviour of the compressibility allows us to evaluate the hydration number of the polymer as a function of temperature. The experimental data show the presence of an arrangement in which two water molecules are bonded for each oxygen of the oxirane monomeric group.

IQENS (incoherent quasi elastic neutron scattering), Rayleigh wing and Raman measurements on two isomeric alcohols, n -pentanol and 2-methyl-2-butanol, are presented. The presence, in both the isomers, of a “fast” time in the rotational lineshape of IQENS and in the Rayleigh wing rotational component, has been identified as the rotational jump of the methyl group. Furthermore, by a comparison of the extracted “slow” relaxation times, it is possible to evaluate the second rank static Kirkwood correlation factor g 2 for both the alcohols. Finally, analysis of the Raman data provides an interpretation of the spectral features in terms of symmetric OH sub-bands, originated by various intermolecular aggregates.

Incoherent Quasi-Elastic Neutron Scattering, ultrasonic velocity and density measurements on poly(ethylene oxide) aqueous solutions are presented. The neutron analysis indicates the existence of strongly confined water and furnish an estimated value of the confined region size of ~3 A. The behaviour of the excess adiabatic compressibility as a function of concentration and temperature shows the presence of a more compact arrangement in which up to two water molecules for each monomeric unity are allowed.

In the present study we carried out an extensive non-destructive and micro-destructive surface investigation on ancient decorated Sicilian samples of cultural interest, using a combination of different spectroscopic methods. In particular, the elemental composition, obtained by a handheld XRF analyser, acted as a valuable guideline for subsequent targeted sampling actions, thus minimizing the sampling damage. Hence, some questions not answered by XRF measurements (identification of some pigments, preparation layers, etc.) were subsequently resolved using Scanning Electron Microscopy coupled with Energy-Dispersive Spectrometry (SEM-EDS) and Fourier Transform Infrared absorbance spectroscopy (FT-IR). This multi-technique approach allowed us to provide useful information to establish the pigments and the production technique used by the craftsmen.

The phase in which a microemulsion is of water in oil type, as shown by S.A.N.S. data, can be considered as a colloidal suspension. The pair potential presents a repulsive hard-core plus a Yukawa tail representing the attractive interaction1) V(r) = VA(r) + VR(r). This potential form, similar to that used in the DLVO (Derjaguin, Landau, Verwey and Overbeek)2 theory for colloids, shows two minima with a barrier and gives origin to interesting phenomena such as a phase transition with an upper cloud point temperature and a percolation-like transition 1,3 that suggest aggregation processes can be present in our system. Furthermore, the packing fraction of the droplets, keeping constant their sizes, can be easily changed1, giving rise to a very dense liquid. From a microscopic point of view, the motion of the individual droplet is constrained by the interaction among its neighbours. At normal densities, the probability of an entrapment of the particle, in a cage formed by its nearest neighbours, is low and the particle can diffuse over large distances. For high concentrations (very high packing) the diffusional motion of the particle is dominated by a continuous and, for long time trapping into structural cages, translational motion is possible only if a hole is opened in these cages (for high dense systems the probability of a hole to be opened is very small). This latter process, which corresponds to a slowing-down in the density correlation function, is the configurational or structural arrest, well described by mode-mode coupling theories4 on glassy state. The glass-transition can be studied by dynamic light scattering as a function of the microemulsion concentration; in particular we measure the dynamic structure factor S(k,τ) proportional to the autocorrelation function of the scattered field g1(k,τ). Its initial slope is the mean linewidth (Γ) of spatial fluctuations of wavevector k. Care measurements5 of this latter quantity have shown in the system AOT-water-decane the slowing-down of the density-density correlation function supporting the idea of large clustering effects among the spherical droplets in agreement with structural models of simple glasses generated by the assembly of hard spheres. Different theories6, in particular the well-known free volume theory, indicate that glass transition is a cooperative phenomenon where all particles are involved; in particular several models invoke the presence of clusters. Molecular Dynamics7 experiments in densely packed hard spheres give evidence that large clusters can arise spontaneously. Therefore, we have several suggestions that at high concentrations large clusters can originate from the droplets aggregation and light scattering (elastic and quasi elastic) experiments can give a direct way of studying the system, particularly in the region where it presents a glass transition verifying if ordered structures are present, and of measuring their dimensions and the kinetics of the aggregation. Also in an indirect way viscosity measurements can give information about such a process; in particular as shown in the final part of this work the data of this quantity as function of temperature and of volume fraction o present a well pronounced peak that in the frame of the current theories can be ascribed to an aggregation process.

We report measurements of the viscosity in a very packed AOT microemulsion as a function of the volume fraction o at different temperatures. The data are analyzsed considering the system as colloidal. In such terms, we consider two contributions to the viscosity: one is directly connected to the repulsive interaction potential, while the second one to the attractive interactions that contribute indirectly, through the formation of aggregates among the spherical droplets constituent the microemulsion.

We study the dynamics of hydration water in the protein lysozyme in the temperature range 180 KT360 K using Fourier-transform-infrared and nuclear magnetic resonance NMR spectroscopies. By analyzing the thermal evolution of spectra of the OH-stretching vibration modes and the NMR self-diffusion DS and spin-lattice relaxation time T1, we demonstrate the existence of two dynamical transitions in the protein hydration water. Below the first transition, at about 220 K, the hydration water displays an unambiguous fragile-to-strong dynamic crossover, resulting in the loss of the protein conformational flexibility. Above the second transition, at about 346 K, where the protein unfolds, the dynamics of the hydration water appears to be dominated by the non-hydrogen-bonded fraction of water molecules. © 2007 American Institute of Physics. DOI: 10.1063/1.2757171

EXAFS spectra of amorphous bulk selenium and Se80Te20 alloy have been analysed in the temperature range of the glass transition region (−15 to 37°C). α-Se shows an unexpected behaviour because the modulated part of the X absorption increases with the temperature, irrespectively of the action of the EXAFS Debye-Waller factor from which one expects an opposite behaviour. Analogous features do not appear in the Se80Te20 alloy, probably because of the role played by the intramolecular covalent Se−Te bond strength, weaker than the corresponding Se−Se. In the absence of suitable models for the temperature dependence of the microscopic processes occurring in glasses nearTg, a tentative explanation is proposed in terms of the temperature dependence of the backscattering amplitude functionF(k).

Polarized Mandelstam-Brillouin scattering data in bulk supercooled water are presented. The hypersonic velocity and absorption are measured as a function of the scattering angle {theta} at temperatures ranging from +20 to {minus}27.4{degree}C. The experimental results indicate the existence of a relaxation process in the gigahertz region. The authors discuss the observed dispersion in the frame of the relaxation theory for moderately supercooled liquids. The obtained relaxation times and relaxation strengths are interpreted in terms of man-body effects involved to explain the behavior of supercooled water.

We report measurements on the aggregation processes in a colloidal solution of polystyrene particles performed by elastic (intensity) and quasielastic light scattering. In order to observe the different kinetics of aggregation of the system, reversible flocculation, and the slow and the fast irreversible coagulation, the experiment was made varying the concentration of a simple electrolyte (NaCl) in the 0.01--3 mol/liter range. Intensity data give direct information that aggregated clusters are built with fractal structure and different kinetics; in the slow regime the aggregation process is reaction limited, whereas in the raft regime we have a diffusion-limited cluster-cluster aggregation. Dynamical data, showing well-defined scaling behavior in the measured mean linewidth, confirm such a picture and give a rough estimate of the cluster dimension. Experimental results are consistent with the Derjaguin-Landau-Verwey-Overbeek theory on colloidal stability [Derjaguin and Landau, Acta Phys. Chim. Debricina 14, 633 (1941); Verwey and Overbeek, Theory of the Stability of Lyophobic Colloids (Elsevier, Amsterdam, 1948)].

Measurements of photon correlation spectroscopy (P.C.S.) are performed on vitreous ZnCl2 above the glass transition. The results show a correlation function that decays with a single relaxation time ζ. This latter exhibits a time dependence typical of many physical quantities in glassy systems above Tg. A tentative interpretation of the data in the framework of current theories is given.

By means of a light scattering experiment as a function of scattered wavevector, we have directly studied the aggregation properties of polystyrene particles in water solutions. For different ionic strength the system shows different kinetics with different fractal dimensions. At high strengths a fast aggregation kinetics with a fractal dimension D = 1.75 (diffusion limited aggregation) is obtained, whereas at low strengths the system evidences a slow kinetics D = 2.1 (reaction limited aggregation).

The hydrodynamic triplet in the spectrum of light scattered from liquid H2O has been investigated over the range -25·5 to 49·0°C. These measurements allow the first precise determination of the Landau-Placzek ratio (LPR) in the supercooled region. The data can be explained only by taking into account both an explicit temperature dependence of the refractive index as well as the effect of a relaxation process. The analysis furnishes the temperature dependence of the density and temperature derivatives of the dielectric constant. An evolution of the relaxing contribution to the thermal expansion coefficient is also obtained.

EXAFS Rayleigh wing and Raman-scattering data in SbCl3/H2O mixture are presented. The measurements, carried out at the PULS facility on the ClK-edge and on theL I, II, III-edges as a function of temperature, allow us to define the local order around the absorber. In particular, clear evidence exists that intramolecular Sb−Cl and intermolecular Sb...Cl distances and coordination, similar to the ones existing in pure SbCl3, are present. The data analysis reveals also that the water molecules are linked to the chlorine, giving rise to a cross-link between the antimony trichloride chains. The light scattering response confirms these structural hypotheses, indicating that the primitiveC 3v symmetry of the SbCl3 molecule is lowered by the water presence. Evidence also exists that new vibrational bands are originated by the chlorine-water bonds. Finally we detected a phononlike contribution, in the low-frequency region, that gives an effective Raman vibrational density of states.

Elastic and quasielastic light-scattering measurements were made on di-2-ethylhexylsufosuccinate microemulsions as a function of the droplet concentration. Dynamical-measurement data show at high concentrations a ${k}^{3}$ dependence typical of systems with large structural order; moreover, in agreement with previous data, they confirm that the system undergoes a structural transition similar to the glass transition. Intensity data show the presence of large cluster aggregates with a fractal structure in the concentration region where the system presents a structural arrest, which is typical of dense-packing liquid. The fractal dimension D=2.1\ifmmode\pm\else\textpm\fi{}0.05 gives an indication that the aggregation process is reaction limited.