Time-resolved plasma diagnostic by laser-diode spectroscopy

A tunable diode laser has been used as a light source for line-of-sight absorption and Doppler-shift measurements. We have applied the method to perform plasma diagnostics in a magneto plasma dynamic (MPD) pulsed propulsor device and of an Ar⁺ laser tube plasma. Spectrally resolved argon absorption lineshapes of transitions of neutral and single ionized argon were recorded. A high temporal resolution (a few microseconds) is achieved by fast tuning the laser frequency at a repetition rate greater than 100 kHz. From the recorded spectra, we deduce the dynamics of the neutral components of the plasma in the thruster. We also demonstrate the possibility of direct ion diagnostics by the observation of ionic transitions, using red diode lasers in an Ar⁺-laser commercial tube     

Genotoxicity in primary human peripheral lymphocytes after exposure to radiopacifiers in vitro

Taking into consideration that DNA damage plays an important role in carcinogenesis, the purpose of this study was to evaluate whether some radiopacifiers widely used in clinical practice are able to induce genetic damage in primary human cells in vitro. Human peripheral lymphocytes obtained from 10 healthy volunteers were exposed to barium sulphate (BaSO₄), zirconium oxide (ZnO₂) and bismuth oxide (Bi₂O₃) at final concentrations ranging from 1 to 1000 μg/mL for 1 h at 37 °C. The negative control group was treated with vehicle control (phosphate buffer solution) for 1 h at 37 °C and the positive control group was treated with hydrogen peroxide (at 100 μM) for 5 min on ice. Results were analyzed by the Friedman non-parametric test. The results pointed all compounds tested out did not induce DNA breakage in human peripheral lymphocytes as depicted by the mean tail moment and tail intensity in all concentrations tested. In summary, our results indicate that exposure to these radiopacifiers may not be a factor that increases the level of DNA lesions in human peripheral lymphocytes as detected by single cell gel (comet) assay.     

Synbiotic potential of carrot juice supplemented with Lactobacillus spp. and inulin or fructooligosaccharides

BACKGROUND: The influence of the addition of two probiotic strains, Lactobacillus rhamnosus and Lactobacillus bulgaricus, and the prebiotic components inulin and fructooligosaccharides on carrot juice was investigated in order to evaluate the possibility of producing a functional vegetal beverage. RESULTS: Both bacterial strains were capable of growing in carrot juice, reaching nearly 5 × 10⁹ colony‐forming units after a 48 h fermentation, and the pH was reduced to 3.5–3.7 or below. The viable cell counts of the two lactobacilli in the fermented juice after 4 weeks of storage at 4 °C, demonstrated good survival of the two strains at low pH. Some biochemical characteristics of the fermented juice, such as β‐carotene content and antioxidant activity, were also preserved, indicating that the metabolism of the Lactobacillus spp. did not degrade these nutritional components after 4 weeks of storage at 4 °C. The positive effect was more evident when the juice was inoculated with Lactobacillus rhamnosus. The presence of inulin and fructooligosaccharides did not alter the cell counts or the biochemical characteristics of the fermented juice. CONCLUSION: We propose this as a health juice and functional beverage for vegetarians or consumers who are allergic to dairy products. Copyright © 2008 Society of Chemical Industry     

Preparation of gold nanoparticles on silica substrate by radio frequency sputtering

Radio frequency sputtering of gold on amorphous silica substrates was used for the preparation of Au nanoparticles on SiO2. Deposition experiments were carried out in Ar plasmas under mild conditions (RF power = 5/10 W, total pressure = 0.38 mbar, substrate temperature < or = 210 degrees C), focusing in particular on the effect of sputtering time (5/30 min) and substrate temperature on gold nucleation and coalescence, with the aim of obtaining SiO2-supported Au nanoparticles characterized by precise structural and morphological features. To this aim, several analytical techniques were employed for a thorough characterization of the systems properties, including glancing incidence X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, atomic force microscopy, and UV-Vis absorption spectroscopy. In particular, the evolution of optical spectra, i.e., of the surface plasmon resonance peak, was used as a probe for the structural features and was related to the results obtained by other characterization techniques. Gold nanoclusters (phi approximately 4/10 nm) dispersed uniformly on silica matrices were obtained under soft conditions, with morphology ranging from island to cluster like. The obtained results make possible a careful modulation of substrate coverage and gold nanoparticle size.