Fluctuation suppression in microgels by polymer electrolytes.

Structural details of thermoresponsive, cationically poly(N-iso-propylacrylamide-co-methacrylamido propyl trimethyl ammonium chloride) microgels and the influence of the anionic electrolyte polystyrene sulfonate (PSS) on the internal structure and dynamics of the cationic microgels have been studied with a combination of small angle neutron scattering (SANS) and neutron spin echo (NSE) spectroscopy. While SANS can yield information on the overall size of the particles and on the typical correlation length inside the particles, studying the segmental polymer dynamics with NSE gives access to more internal details, which only appear due to their effect on the polymer motion. The segmental dynamics of the microgels studied in this paper is to a large extent suppressed by the PSS additive. Possible scenarios of the influence of the polyanions on the microgel structure and dynamics are discussed.

Simultaneous measurement of the microscopic dynamics and the mesoscopic displacement field in soft systems by speckle imaging.

The constituents of soft matter systems such as colloidal suspensions, emulsions, polymers, and biological tissues undergo microscopic random motion, due to thermal energy. They may also experience drift motion correlated over mesoscopic or macroscopic length scales, e.g. in response to an internal or applied stress or during flow. We present a new method for measuring simultaneously both the microscopic motion and the mesoscopic or macroscopic drift. The method is based on the analysis of spatio-temporal cross-correlation functions of speckle patterns taken in an imaging configuration. The method is tested on a translating Brownian suspension and a sheared colloidal glass.

SANS study of polymer-linked droplets.

We report experimental results obtained from SANS on microemulsion droplets connected by a telechelic polymer. Thanks to its ability to anchor droplets through its short stickers, the addition of this polymer leads to the formation of transient aggregates. Measurements were performed on samples at low surfactant content in such a way that the droplets appear to be isolated with a separation distance longer than the end-to-end distance of the polymer. The locally spherical structure of the micelles is unchanged in size upon polymer addition whereas the large rise in scattered intensity at low Q is due to the induced effective attractive interaction between droplets. The fitting model that we propose allows a quantitative description of the bridging effect.

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.

"Side" effects of HAART: decreasing and changing occupational exposure to HIV-infected patients.

To investigate percutaneous exposures to HIV in the highly active antiretroviral therapy (HAART) era, we performed an analysis of all percutaneous exposures reported from January 1994 to December 1998 in 18 Italian acute-care hospitals. Frequency and rate per 100 prevalent AIDS cases of HIV exposures decreased by 40% (from 4.3% to 2.6%, and from 1.0% to 0.6%, respectively; p<0.001), which were mainly those related to the insertion/manipulation of peripheral vascular access devices (from 7.2% to 4.8%; p=0.05). We conclude that the benefits of HAART have changed the complexity of care required and therefore, the number and type of procedures performed on HIV patients that place the HCW at risk of injury.

[Prevalence of anti-LAV/HTLV III antibodies in groups at risk of infection and in donors blood in the province of Catania]. / Prevalenza di anticorpi anti-LAV/HTLV III in gruppi a rischio di infezione e in donatori di sangue nella provincia di Catania.

The prevalence of anti-LAV/HTLV III antibodies in serum samples of individuals at high risk for AIDS and of healthy individuals living in the province of Catania is reported. Serum samples were collected over the period 1983-86 from 220 drug addicts adults, 339 from multitransfused thalassemia patients, 71 from hemophiliacs, 22 from subjects of the hospital staff who had had contacts with positive subjects, 9 from family contacts of positive multitransfused thalassemics and 7270 from blood donors. Prevalence of antibodies among drug addicts was 14% and a positive subject was found as early as 1983. This result suggested that LAV/HTLV III was already present in Catania at that year. Among the thalassemics and the hemophiliacs the prevalence was 2.3% and 21% respectively. No positive subject was found among hospital staff nor among family contacts of positive thalassemic subjects. Three positive cases have been found among the blood donors and even though these are drug addicts, it is important to underline the necessity of a regular screening of the blood units to prevent LAV/HTLV III diffusion.

[Bone marrow T-lymphocyte subpopulations in patients with multiple myeloma]. / Studio delle sottopopolazioni T-linfocitarie nel midollo osseo di soggetti con mieloma multiplo.

The bone marrow quantitative distribution of the two main T-lymphocyte subsets, recognizable by the "high" and "low-affinity" E-rosette forming cell technique, according to West, was evaluated in ten untreated myeloma patients and twelve normal controls. It was observed, within a normal total T-lymphoid cell count, a significant predominance of the T-lymphocyte subset with "low-affinity" characteristics. An inverse correlation, with statistical significance, between the monoclonal malignant B-component and "low-affinity" T-cell percentage was also seen in all cases. It was suggested, therefore, that such an imbalance between "high" and "low-affinity" T-subsets, with the latter predominating, could play a role in the regulation of the monoclonal B-component growth rate.