Test of structural models for the (4 4) phase formed by oxygen adsorption on the Pt3Sn(1 1 1) surface

Exposure of the Pt3Sn(1 1 1) surface to oxygen at a pressure in the 10-6 mbar range at 800 K leads to the formation of a chemisorbed phase with a (4 × 4) periodicity. In previous works we investigated the structure of the (4 × 4) phase by means of scanning tunneling microscopy (STM) and XPD. STM images show that the (4 × 4) periodicity results from an array of protrusions and holes. XPD data suggest that oxygen adsorption induces the reconstruction of the substrate with the formation of a Sn-O overlayer. In the present work, several structural models compatible with the STM and XPD results were tested by tensor LEED analysis. The best agreement with the experimental I-V curves was obtained for a model similar to that proposed to interpret the STM images of the Ag(1 1 1)(4 × 4)-O phase. According to this structure, the protrusions observed in STM would correspond to tin atoms occupying on-top positions

Preventable infectious diseases using vaccination in developmental age in the Province of Frosinone, Italy

Introduction. A study has been made of the behaviour of preventable infectious diseases by means of vaccination in the developmental age, reported between 1995 and 2003, in the area of Frosinone and Province, Italy. Results. Analysis of the distribution of the 185 cases of hepatitis B notified, demonstrates that the mean age has increased from 26.5 to 41.1 years. Notifications of invasive diseases due to haemophilus influenzae type b (Hib) refer exclusively to 13 cases of meningitis. As far as concerns pertussis, 119 cases have been reported (median age 4.0 years, mode 1.0). Overall 850 cases of measles were reported (median age 7.0 years, mode 5.0), the highest number being recorded in 1997 (349 cases: median age 7.0 years, mode 5.0) and 2002 (199 cases: median age 8.0 years, mode 8.0). Rubella occurred in 411 cases (median age 12.0 years, mode 11.0), with 53.3% involving females. As far as concerns mumps, the last peak of the epidemic occurred in 2001 (median age 7.0 years, mode 6.0) with 137 cases. Discussion and conclusion. Results emerging from the study demonstrate a reduction in time in the number of notifications for almost all the diseases under consideration. The distribution of the cases of rubella in fertile females, in 2002, stresses the need to promote campaigns in order to recuperate still-susceptible women of childbearing age. The cases of hepatitis B, pertussis and meningitis due to Hib confirm the high rate of protection resulting from vaccination. The incidence rates of measles, mumps, rubella and pertussis when compared with those of the paediatric sentinel surveillance system (SPES) clearly demonstrate not only that these are underestimated but also reveal controversial findings with respect to data provided by Infectious Diseases Italian Surveillance System (SIMI)

Are measles, mumps and rubella a public health issue in young adults? Results from a seroprevalence survey in university students in Italy

Aims: A survey was conducted amongst university students to assess their level of susceptibility to and knowledge about measles, mumps and rubella (MMR) and their prevention, and to find factors associated to their seropositivity for MMR viruses. Subjects, and methods: A cross-sectional study was conducted involving 961 students from the University of Cassino (Italy). The enzyme immunoassay method was used to assess seropositivity for MMR, while knowledge and previous vaccination information were acquired through a self-administered questionnaire. Results: The prevalence of IgG antibodies was 93.2% for measles, 91.4% for mumps and 81.3% for rubella. The susceptibility for measles was higher in the 21–25 and over 31 age groups. The seroprevalence profile of mumps was similar to that of measles, while the level of immunity to rubella was very low in students aged under 20 years (76.7%) and 21–25 years (81.2%). Only 111 students said they had been vaccinated against measles, 46 against mumps and 103 against rubella. Most students demonstrated poor knowledge concerning MMR and were not practicing preventive behaviours. Conclusions: The susceptibility was particularly high for rubella. Concerted efforts are needed to educate young adults about the benefits of vaccination and to raise their level of consciousness so as to motivate them to request vaccination

Optimised atmospheric pressure CVD of monoclinic VO2 thin films with picosecond phase transition

Monoclinic vanadium oxide (VO2) thin films with low roughness values were deposited and optimised by atmospheric pressure chemical vapour deposition using vanadium tetrachloride (VCl4) and water (H2O). Smooth VO2 films with good transmittance properties were successfully produced on fluorine doped tin oxide/borosilicate substrates. Systematic investigations confirmed that the quality (including phase) of films being produced strongly depended on substrate, deposition time, temperature, and precursor ratio within the process. Optical characterisation using ellipsometry revealed a strong thermochromic response of the films with a large change in the dielectric function, while time-resolved pump-probe transmission showed the picosecond nature of the phase transition

Chemical Composition and Micro Morphology of Golden Laminae in the Wall Painting “La Maestà” by Simone Martini: A Study by Optical Microscopy, XRD, FESEM-EDS and ToF-SIMS

The chemical characterization of gilding decorations in works of art is fundamental in order to elucidate the techniques and materials used by the artists. In the present work we investigated by a combination of bulk and surface sensitive methods the composition and micro stratigraphy of the gilding laminae in the wall painting of the 14th century “La Maestà”, the masterpiece of Simone Martini. The aim of this study was to determine the composition of the gilding leaves and of the adhesive organic materials used to glue the metallic decorations to the wall painting. Due to the altered state of the samples we could not univocally identify the nature of the adhesive materials. Time of flight secondary ion mass spectrometry measurements showed that the gilding layers consisted of a gold leaf which was laid either directly on a preparation layer or on a tin lamina. The high sensitivity of ToF-SIMS and its spatial resolution allowed us to find traces of silver in the gold leaves and in the tin laminae which were not revealed by energy dispersive X-ray analysis

Effect of Citrate on the Size and the Magnetic Properties of Primary Fe3O4 Nanoparticles and Their Aggregates

The size, size distribution and magnetic properties of magnetite nanoparticles (NPs) prepared by co-precipitation without citrate, in the presence of citrate and citrate adsorbed post-synthesis were studied by X-ray Diffraction (XRD), Dynamic Light Scattering (DLS), Electron Paramagnetic Resonance (EPR) and magnetization measurements. The aim of this investigation was to clarify the effect of citrate ions on the size and magnetic properties of magnetite NPs. The size of the primary NPs, as determined by analysing the width of diffraction peaks using various methods, was ca. 10 nm for bare magnetite NPs and with citrate adsorbed post-synthesis, whereas it was around 5 nm for the NPs co-precipitated in the presence of citrate. DLS measurements show that the three types of NPs form aggregates (100–200 nm in diameter) but the dispersions of the citrate-coated NPs are more stable against sedimentation than those of bare NPs. The sizes and size distributions determined by XRD are in good agreement with those of the magnetic domains obtained by fitting of the magnetization vs. magnetic field intensity curves. Magnetization vs. magnetic field intensity curves show that the three kinds of sample are superparamagnetic