A Metrology Application of Reverberation Chambers: The Current Probe Calibration

This paper presents how it is possible to characterize a current probe in terms of its transfer impedance inside a reverberation chamber. The probe catches a floating wire placed inside the working volume of the chamber. The current on the wire is calculated from the knowledge of the total measured average field along the wire in the working volume. The current is calculated by representing the field in terms of a summation of random plane waves, where a finite-difference time-domain (FDTD) code is used to compute the current induced by each plane wave along the wire caught by the probe under test. Results for the current distribution along the wire are reported for several frequencies. Finally, the transfer impedance of commercial probes is recovered from the knowledge of the current and compared to the values given by the manufacturers and by an external laboratory     

Bacteriorhodopsin-based Langmuir-Schaefer films for solar energy capture

The photovoltaic (PV) solar cell, converting incident solar radiation directly into electrical energy, today represents the most common power source for the Earth-orbiting spacecraft, and the utilization of organic materials in this context is here explored in comparison with the present state of the art placing emphasis in organic nanotechnology. Poly[3-3'(vinylcarbazole)] (PVK) was synthesized by oxidative polymerization with ferric chloride of N-vinylcarbazole. The resulting polymer was then deposited on solid support by using the Langmuir-Schaefer (LS) technique. The pressure-area isotherm of PVK revealed the possibility of compact monolayer formation at the air-water interface. Different layers of PVK were doped with iodine vapors. The cyclic voltammetry investigation of PVK-doped I/sub 2/ showed a distinctive electrochemical behavior. The photoinduced charge transfer across a donor/acceptor (D/A) hybrid interface provided an effective method to study the PV properties of the composite LS films. The results are compared with other approaches within the biological framework, such as bacteriorhodopsin (BR), and organic nanostructured materials.     

Prevalence of scleroderma spectrum disorders in the general population of Estonia

RATIONALE AND OBJECTIVES: The authors compared the economic effect of stereotactic core needle biopsy (CNB) with that of short-term unilateral surveillance mammography in the management of probably benign breast lesions detected during routine screening mammography. METHODS: Published data with regard to the cost of stereotactic CNB and unilateral mammography were applied to 3,184 patients who underwent surveillance mammography; including 161 patients who underwent biopsy. Costs of immediate tissue diagnosis were compared with costs of surveillance with use of ratios of published reimbursement scales to minimize geographic variations. Sensitivity analyses were applied to this ratio. RESULTS: The cost of managing probably benign breast lesions with surveillance mammography was $3,307,575 less than if all lesions had been managed with CNB. The ratio of the cost of CNB to the cost of surveillance mammography was 8:1. This ratio is more sensitive to the frequency of use of CNB than to reimbursement schedules. CONCLUSION: With similar false-negative rates, CNB is more costly than surveillance and has a negative effect in the management of probably benign breast lesions, unless interval change during surveillance prompts tissue diagnosis.     

Salmonella in surface and drinking water: Occurrence and water-mediated transmission

Salmonella is one of the leading causes of intestinal illness all over the world as well as the etiological agent of more severe systemic diseases such as typhoid and paratyphoid fevers. While water is known to be a common vehicle for the transmission of typhoidal Salmonella serovars, non-typhoidal salmonellae are mainly known as foodborne pathogens. This paper provides a brief review of the last ten years of peer reviewed publications on the prevalence of Salmonella in natural freshwaters and drinking waters, and on the relevance of these sources for Salmonella dissemination. In industrialized countries, Salmonella was rarely reported in water-borne outbreaks despite it being frequently detected in surface waters including recreational waters and waters used for irrigation or as a drinking water source. Consistent contamination with irrigation waters has been shown to be a common route of crop contamination in produces related Salmonella outbreaks. Multiple drug resistant (MDR) Salmonella strains, that represent an increased hazard for human health and that may contribute to the dissemination of drug resistances were also detected in surface water in developed countries. Surface runoff was shown to play a main role as driver of Salmonella load in surface waters. Accordingly, analysis of serovars indicated a mixed human and animal origin of Salmonella contribution to surface waters, emphasizing the role of wild life animals in water contamination. Data relating to Salmonella prevalence in surface and drinking water in developing countries are quite rare. Nevertheless, data on water-borne outbreaks as well as case control studies investigating the risk factors for endemic typhoid fever confirmed the relevance of water as source for the transmission of this disease. In addition epidemiological studies and Salmonella surveys, consistently provided an undeniable evidence of the relevance of MDR Salmonella Typhi strains in water-borne typhoid fever in developing countries.     

Kinetic study on the thermal degradation of heavy oil in presence of SBA-15 containing aluminum and cerium

In research for materials that can be applied in processing heavy oil (petroleum), this work proposes to synthesize mesoporous heterogeneous catalysts, type SBA-15, with the addition of cerium metal and aluminum. These catalysts were characterized by X-ray diffraction, scanning electron micrographs coupled to energy dispersive spectrometry, spectroscopy in the infrared region by Fourier transform, N₂ adsorption and desorption and thermal analysis-thermogravimetry. Thermal tests were performed to evaluate the thermal and catalytic degradation process with a sample of heavy oil (°API = 14). Through the non-isothermal kinetic model of Ozawa Flynn Wall (OFW) some parameters for determining the apparent activation energy of decomposition were obtained. The petroleum with 12% of Ce₅Al₅₀SBA-15 showed a catalytic activity for this material. It has been seen that there was a decrease in the Ea in model free of the order from 89.0 to 104.9 kJ mol^?1 in α = 50% ± 10%, and it was repeated from the first percentage until the last showing performance of Ce₅Al₅₀SBA-15 as a catalyst.