Macro- and microdefinitions of fragility of hydrogen-bonded glass-forming liquids.

In the present paper, the nature of the fragility of liquids with a developed H-bond network is investigated. It is shown that the effective activation energy of the shear viscosity eta and the fragility parameter defined as m=d log eta/d(Tg/T)|t=t+g are immediately connected with the average number nH(T) of the H-bond per molecule. The consistency of the macroscopic (m) and the microscopic [M=d(u(2)(0)/2)>loc)/d(Tg/T)|T=T+8, where 2>loc=2>anharm - 2>harm] definitions of the fragility is established.

Tetrahedral order in homologous disaccharide-water mixtures.

The present work aims at evidencing the "kosmotrope" nature of trehalose through the analysis of inelastic neutron scattering measurements on trehalose and sucrose water solutions at different temperatures. Neutron spectra were collected by using the spectrometer MARI at the ISIS pulsed neutron source of the Rutherford Appleton Laboratory (Chilton, UK). To study the structural modifications induced on the tetrahedral hydrogen-bond network of water by homologous disaccharides, as a first step, the vibrational properties of pure water at different temperatures have been investigated. In particular, the temperature behavior of the intramolecular OH stretching mode has been analyzed. Successively, the vibrational properties for pure water have been compared with those of the sugar water solutions focusing the attention on the tetrahedral network-forming tendency. Finally, the obtained findings have been compared with previous Raman scattering evidences, and the results interpreted in the frame of recent molecular dynamics simulation works.

Fragility by elastic incoherent neutron scattering.

The present work furnishes an operative definition for the fragility degree by using elastic incoherent neutron scattering (EINS). Such a definition is based on the relation between viscosity, a macroscopic quantity, and the atomic mean-square displacement, which refers to a nanoscopic property. This procedure has been used to analyze a set of glass-forming systems and it allows to obtain a linear dependence of the fragility parameter M, obtained by EINS, on the fragility parameter m, obtained by viscosity measurements.

Mean-square displacement relationship in bioprotectant systems by elastic neutron scattering.

Neutron intensity elastic scans on trehalose, maltose, and sucrose/H(2)O mixtures as a function of concentration, temperature, and exchanged wave vector are presented. The experimental findings show a crossover in molecular fluctuations between harmonic and anharmonic dynamical regimes. A new operative definition for the degree of fragility of glass-forming systems is furnished by using explicitly the connection between viscosity and mean-square displacement. The procedure is tested for the investigated mixtures and for a set of glass-forming systems. In this frame, the stronger character of trehalose/H(2)O mixture indicates a better attitude in respect to maltose and sucrose/H(2)O mixtures to encapsulate biostructures in a more rigid matrix.

Nature of self-diffusion and viscosity in supercooled liquid water

The nature of the simplest transport processes in water, namely, self-diffusion and shear viscosity, is analyzed on the basis of a version of the microinhomogeneous structure model. The study predicts the existence of locally ordered groups of molecules, taking into account considerations of acoustic properties, light scattering, and computer simulation findings. In particular, it is shown that the anomalous properties of water in supercooled states are mainly connected with the existence of quasiordered regions, which we call clusters. Furthermore, the spatial sizes and evolution times of the crystal-like clusters, as well as the temperature dependence of their fraction volume, are established. Special invariants of the characteristic parameters of molecular motion are pointed out. Finally, it is shown that the self-diffusion in supercooled water is caused by the processes of formation and destruction of crystal-like clusters, while the processes of internal partial reconstruction give the main contribution to the shear viscosity coefficient.

Experimental study of the hydration properties of homologous disaccharides.

To get some insight into the hydration mechanisms of homologousdisaccharides, we report measurements on trehalose, maltose, and sucroseaqueous solutions. The interest on these systems is mainly due to theextraordinary properties of disaccharides and especially of trehalose, themost effective bio-protector against freezing and dehydration. To carry outthis study we have investigated the volumetric properties of the threedisaccharide solutions, by performing density and ultrasonic velocitymeasurements at different concentration and temperature values. Whatemerges from these studies is that trehalose shows, in comparison withmaltose and sucrose, the greatest structural sensitivity to temperaturechanges and the smallest values of the partial molar volume in all theinvestigated temperature range, this circumstance being indicative of a morepacked conformational arrangement.

The proposal of the Italian Committee on Occupational Cardiology.

This paper describes a protocol of assessing specific working fitness of post-myocardial infarction patients proposed by the Italian Committee on Occupational Cardiology. After cardiovascular (cross-sectional echocardiography, Holter monitoring and maximal symptom-limited ergometric test) and psychological evaluation (CBA-2.0), two ambulatory ECGs were used during work to confirm the first judgement of specific work fitness expressed by occupational specialists. The preliminary results obtained in 106 uncomplicated male patients (mean age 49 +/- 8 years) show that: (i) return to work (89.6%) at 117 +/- 51 days after the acute event is mainly related to socio-occupational variables rather than to cardiovascular status; (ii) the results of the ambulatory monitoring usually confirm the first judgment of specific work fitness; (iii) heart rate responses recorded during work are unrelated to the judgment of fitness; and (iv) the repeatability of the results observed during the two ambulatory ECGs at work is good.

Human relations as a coronary risk factor.

Psychological variables are significant in the evolution of coronary heart disease (CHD). Two types of personality have been identified as constituting coronary risk: Type 1 which is hypercompetitive and anxious, and Type 2 which is overscrupulous and guilt prone. Both these behavioural types are formed during infancy, and are thought to be neurotic. In rehabilitation it is therefore necessary to take into consideration the psychological as well as the physiological aspects, and so the evaluation of the patient's suitability for return to work, should be, at least in part, psychosomatic. The approach used by the Cardiac Rehabilitation Centre of Udine seems to point towards a successful strategy. The aim of the strategy is to improve the chances of secondary prevention, to correct risk factors on a long-term basis, and to arrive at safe and reliable criteria for return to work.