Fast and Selective Determination of Ochratoxin A in Wines Using an Optimized and Validated Liquid Chromatographic Method

Determination of ochratoxin A (OTA) in wines requires a cleanup step using solid phase extraction (SPE). Immunoaffinity columns are commonly the columns of choice but due to its high cost, other SPE columns have been assayed without optimal results. The present work reports an optimized and validated liquid chromatographic method for a fast and selective quantification of OTA in wines using C₁₈ columns for cleanup. Chromatographic conditions were optimized using a central composite design, establishing the following optimal conditions: acetonitrile/water/acetic acid (59.5:39.5:1.0 v/v/v) as mobile phase, flow rate of 1.2 mL min^?1, and column temperature of 30 °C. With these conditions, OTA had a retention time (~4 min) up to five times lower than those reported earlier. Regarding validation, calibration data (n?=?8) fitted a linear regression model with a determination coefficient (R ²) of 0.9992. Repeatability (relative standard deviation (RSD)) and intermediate precision (RSD) in matrix showed values of 1.3 % (n?=?6) and 0.8 % (n?=?3), respectively. Recoveries at five levels ranged from 87.2 to 118.9 % (mean RSD of 7.4 %). Fifty-three samples from different origins were analyzed, finding only seven samples (13 %) with quantifiable OTA content (0.15–0.26 μg L^?1). According to the levels found, the contribution of wine consumption to OTA daily intake was at least 58 times lower than the current tolerable daily intake. In view of optimization and validation results as well as its applicability to real samples, this method could be considered a good alternative for routine analysis of OTA in wines.     

Reliability analysis using exponentiated Weibull distribution and inverse power law

Today in reliability analysis, the most used distribution to describe the behavior of devices is the Weibull distribution. Nonetheless, the Weibull distribution does not provide an excellent fit to lifetime datasets that exhibit bathtub shaped or upside‐down bathtub shaped (unimodal) failure rates, which are often encountered in the performance of products such as electronic devices (ED). In this paper, a reliability model based on the exponentiated Weibull distribution and the inverse power law model is proposed, this new model provides a better approach to model the performance and fit of the lifetimes of electronic devices. A case study based on the lifetime of a surface‐mounted electrolytic capacitor is presented in this paper. Besides, it was found that the estimation of the proposed model differs from the Weibull classical model and that affects the mean time to failure (MTTF) of the capacitor under analysis.     

Stack-and-Draw Applied to the Engineering of Multi-Material Fibers with Non-Cylindrical Profiles

Here, it is demonstrated that the stack-and-draw approach can be expanded to unusual materials association and profile geometries to generate fiber assemblies with unprecedented functionalities. This approach relies on the stacking of flat oxide glass slides into a preform, which is then thermally elongated into tens-of-meters-long ribbon fibers with preserved cross-section ratio. Fabrication methodology is introduced. In order to illustrate the versatility of the method, a panel of fibers with diverse geometries and functions is exposed, including glass-only exposed-core fibers for chemical sensing and, upon the insertion of metal electrodes, H-shaped multi-cavity structures and compact, glass-metal fiber optical detectors applied to a gas analysis by means of fiber-tip plasma spectroscopy. It is believed this new approach will offer an attractive, straightforward solution for designing innovative, complex multimaterial fiber platforms with enhanced functionalities.     

High-energy neutrons effect on strained and non-strained SOI MuGFETs and planar MOSFETs

A comparative investigation of high-energy neutrons effect on strained and non-strained devices with different geometries is presented. Both single-gate planar and multiple-gate (MuG) silicon-on-insulator (SOI) devices are considered. Device response to the neutron irradiation is assessed through the variations of threshold voltage and transconductance maximum. The difference between strained and non-strained device response to the high-energy neutrons exposure is clearly evidenced. The reasons for such a difference are discussed. Analysis of the experimental results allows for suggesting that strain relaxation is one of the probable causes.     

Shock-Wave Consolidation of Nanostructured Bismuth Telluride Powders

Nanostructured thermoelectric powders can be produced using a variety of techniques. However, it is very challenging to build a bulk material from these nanopowders without losing the nanostructure. In the present work, nanostructured powders of the bismuth telluride alloy system are obtained in kilogram quantities via a gas atomization process. These powders are characterized using a variety of methods including scanning electron microscopy, transition electron microscopy, and x-ray diffraction analysis. Then the powders are consolidated into a dense bulk material using a shock-wave consolidation technique whereby a nanopowder-containing tube is surrounded by explosives and then detonated. The resulting shock wave causes rapid fusing of the powders without the melt and subsequent grain growth of other techniques. We describe the test setup and consolidation results.     

Mapping the "forbidden" transverse-optical phonon in single strained silicon (100) nanowire

The accurate manipulation of strain in silicon nanowires can unveil new fundamental properties and enable novel or enhanced functionalities. To exploit these potentialities, it is essential to overcome major challenges at the fabrication and characterization levels. With this perspective, we have investigated the strain behavior in nanowires fabricated by patterning and etching of 15 nm thick tensile strained silicon (100) membranes. To this end, we have developed a method to excite the "forbidden" transverse-optical (TO) phonons in single tensile strained silicon nanowires using high-resolution polarized Raman spectroscopy. Detecting this phonon is critical for precise analysis of strain in nanoscale systems. The intensity of the measured Raman spectra is analyzed based on three-dimensional field distribution of radial, azimuthal, and linear polarizations focused by a high numerical aperture lens. The effects of sample geometry on the sensitivity of TO measurement are addressed. A significantly higher sensitivity is demonstrated for nanowires as compared to thin layers. In-plane and out-of-plane strain profiles in single nanowires are obtained through the simultaneous probe of local TO and longitudinal-optical (LO) phonons. New insights into strained nanowires mechanical properties are inferred from the measured strain profiles.