Nanocasting Synthesis of Ultrafine WO3 Nanoparticles for Gas Sensing Applications

Ultrafine WO3 nanoparticles were synthesized by nanocasting route, using mesoporous SiO2 as a template. BET measurements showed a specific surface area of 700 m 2/gr for synthesized SiO2, while after impregnation and template removal, this area was reduced to 43 m 2/gr for WO3 nanoparticles. HRTEM results showed single crystalline nanoparticles with average particle size of about 5 nm possessing a monoclinic structure, which is the favorite crystal structure for gas sensing applications. Gas sensor was fabricated by deposition of WO3 nanoparticles between electrodes via low frequency AC electrophoretic deposition. Gas sensing measurements showed that this material has a high sensitivity to very low concentrations of NO2 at 250°C and 300°C

Periodic Active Case Finding for TB: When to Look?

OBJECTIVE: To investigate the factors influencing the performance and cost-efficacy of periodic rounds of active case finding (ACF) for TB. METHODS: A mathematical model of TB dynamics and periodic ACF (PACF) in the HIV era, simplified by assuming constant prevalence of latent TB infection, is analyzed for features that control intervention outcome, measured as cases averted and cases found. Explanatory variables include baseline TB incidence, interval between PACF rounds, and different routine and PACF case-detection rates among HIV-infected and uninfected TB cases. FINDINGS: PACF can be cost-saving over a 10 year time frame if the cost-per-round is lower than a threshold proportional to initial incidence and cost-per-case-treated. More cases are averted at higher baseline incidence rates, when more potent PACF strategies are used, intervals between PACF rounds are shorter, and when the ratio of HIV-negative to positive TB cases detected is higher. More costly approaches, e.g. radiographic screening, can be as cost-effective as less costly alternatives if PACF case-detection is higher and/or implementation less frequent. CONCLUSION: Periodic ACF can both improve control and save medium-term health care costs in high TB burden settings. Greater costs of highly effective PACF at frequent (e.g. yearly) intervals may be offset by higher numbers of cases averted in populations with high baseline TB incidence, higher prevalence of HIV-uninfected cases, higher costs per-case-treated, and more effective routine case-detection. Less intensive approaches may still be cost-neutral or cost-saving in populations lacking one or more of these key determinants

Stochastic theory of chromatography. The characteristic function method and the approximation of chromatographic peak shape

NATO ASI serie

MicroRNAs in the Regulation of Melanogenesis

Melanogenesis is the process leading to the synthesis of melanin, the main substance that influences skin color and plays a pivotal role against UV damage. Altered melanogenesis is observed in several pigmentation disorders. Melanogenesis occurs in specialized cells called melanocytes, physically and functionally related by means of autocrine and paracrine interplay to other skin cell types. Several external and internal factors control melanin biosynthesis and operate through different intracellular signaling pathways, which finally leads to the regulation of microphthalmia-associated transcription factor (MITF), the key transcription factor involved in melanogenesis and the expression of the main melanogenic enzymes, including TYR, TYRP-1, and TYRP-2. Epigenetic factors, including microRNAs (miRNAs), are involved in melanogenesis regulation. miRNAs are small, single-stranded, non-coding RNAs, of approximately 22 nucleotides in length, which control cell behavior by regulating gene expression, mainly by binding the 3′ untranslated region (3′-UTR) of target mRNAs. This review collects data on the miRNAs involved in melanogenesis and how these miRNAs can modulate target gene expression. Bringing to light the biological function of miRNAs could lead to a wider understanding of epigenetic melanogenesis regulation and its dysregulation. This knowledge may constitute the basis for developing innovative treatment approaches for pigmentation dysregulation

Fluidic and syringe injection study by peak shape analysis

none5Fluidic and syringe injections with different splitting conditions are compared by using the Edgeworth-Cramer peak shape analysis. Non retained component peaks on capillary and packed columns were considered. Skewness values as low as 0.02, with precision and repeatability of ±0.005, were obtained when using the capillary column with fluidic injection. Extracolumn contributions coming from the injection system were evaluated by using peak skewness under the hypothesis of exponential decay extracolumn factor. The corrected column efficiency values are in good agreement with the theoretically expected van Deemter equation data. A syringe injection system with high split rate can produce, for unretained samples, peak fidelity values greater than 0.8, which are comparable with those observed with the fluidic injection system. Applications in column performance studies are discussed.noneM. Remelli; G. Blo; F. Dondi; M. C. Vidal-Madjar; G. GuiochonRemelli, Maurizio; Blo, Gabriella; Dondi, Francesco; M. C., Vidal Madjar; G., Guiocho

Peak shape analysis and noise evaluation in suppressed ion chromatography for ultra-trace analysis

Numerical analysis was used to study the performance of a suppressed ion chromatographic system with on-line preconcentration for ultra-trace ion determination in ultra-pure power plant waters. Peak-shape analysis by the Edgeworth—Cramér series fitting method was applied in order to check non—linear concentration-dependent effects, so as to evaluate the best experimental practice with regard to the linear calibration range. Noise evaluation by Edgeworth-Cramér fitting residuals and Fourier analysis is discussed in order to establish the detection limits. Results of the checks made for strictly linear conditions and determination of the quantification limits for sodium, chloride and sulphate ions are reported

Colloidal mercury (Hg) distribution in soil samples by sedimentation field flow fractionation coupled to mercury cold vapour generation atomic absorption spectrometry

Dimensional characterisation of potentially toxic elements present in soil is of crucial importance for determining their actual impact on the environment and understanding the role played by colloidal particles in mobilising pollutants. Recently, a number of measurement determinations have been available for this purpose; nevertheless a single technique is often not exhaustive enough to completely determine particle size distribution and element concentration. The present work concerns the investigation of mercury in soil samples collected from a polluted industrial site. The analytical approach here proposed makes use of sedimentation field flow fractionation (SdFFF) instrumentation coupled off-line to a cold vapour generation electrothermal atomic absorption spectroscopic (CV-ETAAS) technique to achieve the complete Hg characterisation in colloidal soil fractions. In the investigated samples the results demonstrated a predominant presence of Hg in the fraction between 400 and 700 nm. The apparent relation between concentration of Hg and organic matter (O.M.) content in the soil samples seems to be not related to Hg sorbtion to soil O.M. but rather to the presence of colloidal mercuric sulphides particles which size is likely to be controlled by the occurrence of dissolved O.M. This research pointed out how relatively high levels of mercury in the original soil samples can become even more alarming if concentrated in the submicronic fraction