All-oxide ceramic matrix composites (OCMC) based on low cost 3M Nextel™ 610 fabrics

Cost reduction without loss of quality is a key factor during the development of engineering materials. This is particularly true for oxide fibers, which can represent up to 70 % of the real cost of all-oxide ceramic matrix composites (OCMC). Therefore, the objective of this work is to produce and evaluate OCMCs based on novel low-cost Nextel? 610 fiber fabrics with deniers of 3000?20,000. Experiments were divided into fiber and composite characterizations. In general, fiber bundles with higher denier show lower apparent strength; although fiber characteristic strength is very similar for bundles with denier below 4500. Composite characterization showed that certain properties, such as tensile strength, are in accordance to the measured fiber characteristic strength. Other properties like interlaminar shear strength and notch sensitivity did not depend on the type of fabric used. In summary, composites with the new fiber fabrics were successfully produced, showing properties similar to commercially available OCMCs.     

Hollow biomorphic Al<Subscript>2</Subscript>O<Subscript>3</Subscript> fibers produced from sisal

Al₂O₃ fibers with a hollow morphology were produced by Al-vapor infiltration-reaction and subsequent oxidation from pyrolysed fibers of natural sisal. Following pyrolysis, the bio-fiber template was reacted with gaseous Al at 1,400 °C–1,600 °C in vacuum to form Al₄C₃. After an oxidation/sintering process at 1,550 °C, the biomorphic Al₄C₃ fibers were fully converted into Al₂O₃, maintaining the microstructural features of the native sisal. Phase and microstructural characterization during processing were evaluated by high temperature X-ray diffractometry and scanning electron microscopy, respectively. Thermo-analyses were performed in the Al₄C₃ samples in order to estimate the reactions and the weight change during the oxidation step.     

Influence of anionic species on uranium separation from acid mine water using strong base resins

The presence of uranium and other elements in high concentrations in acid mine drainage at Poços de Caldas Uranium Mine (Brazil) is a matter of concern. The acid water pH is around 2.7, the uranium concentration is in the range of 6–14 mg L⁻¹, sulfate concentration near 1400 mg L⁻¹, fluoride 140 mg L⁻¹ and iron 180 mg L⁻¹. In this solution, where sulfate is present in elevated concentrations, uranium is basically in the form of UO₂(SO₄)₃⁴⁻. This study investigated the separation of uranium from the other anions present in the acid water under batch and column mode using ion exchange technique. The pH studied was 2.7 and 3.9. Two strong base anionic resins were tested. The influence of ions, commonly found in acid waters like sulfate and fluoride, on ion exchange process was also assessed. Equilibrium studies were carried out to determine the maximum adsorption capacities of the resins. The resins showed a significant capacity for uranium uptake which varied from 66 to 108 mg g⁻¹ for IRA 910U and 53 to 79 mg g⁻¹ for Dowex A. The results also showed that SO₄²⁻ is the most interfering ion and it had a deleterious effect on the recovery in the pH range studied. Fluoride did not affect uranium removal.     

Evaporative light scattering: a novel detection method for the quantitative analysis of humic-like substances in aerosols

The chemical composition of organic atmospheric aerosols is only poorly understood. Although a significant fraction of organic aerosols consists of humic-like substances (HULIS), only little is known about this class of compound, and accurate quantification remains difficult, partly due to the lack of appropriate standards. Here, evaporative light-scattering detection (ELSD) was applied for the first time to quantify water-soluble HULIS in aerosol particles smaller than 1 microm. This detection method was shown to be suitable for the quantification of compounds with unknown structures and lacking appropriate quantification standards. As compared to organic carbon determination of isolated HULIS, no organic carbon/organic mass (OC/OM) conversion factor needs to be applied with ELSD and therefore eliminates this significant uncertainty factor of the OC/OM method, which is frequently used to quantify HULIS. Solid-phase extraction and size-exclusion chromatography were applied to separate inorganic ions and low molecular weight compounds from HULIS before ELSD quantification. The ELSD itself provides an additional separation step where low volatility HULIS are separated from high volatility, small compounds. Electrospray ionization mass spectrometry was used to identify the molecular weight range of the compounds quantified with ELSD. The most intensive peaks were in the range of m/z 200-500, with some masses upto m/z800. We showed that UV detection using fulvic acid as surrogate quantification standard underestimates the HULIS concentration by a factor of 1.1 to 2.5, which is in agreement with earlier studies. During a 6 week winter 2005-2006 campaign at a suburban site near Zurich, Switzerland, an average of 1.1 microg/m(3) HULIS was found, which is about4-6% of the total particle mass smaller than 1 microm (PM1) and 10-35% of the organic matter in PM1.     

Analysis of volatile components of Petite Arvine wine

Petite Arvine is a white grape variety that grows exclusively in the canton of Valais in Switzerland and is used to produce a typical regional wine. In order to elucidate the nature of the flavour compounds that contribute to the characteristic aroma of this wine, the organic extracts were analysed by gas chromatography and olfactometry. The olfactometrically detected zones were further compared with the odour of extracts of vegetal material. 3-Mercaptohexanol, -ionone and other compounds were identified as main contributors to the characteristic aroma of Petite Arvine wine.     

Multidimensional analysis of single algal cells by integrating microspectroscopy with mass spectrometry

We demonstrate a facile label-free approach for performing multidimensional chemical analysis on individual single-cell organisms by combining optical, fluorescence, and Raman microspectroscopy with matrix-free laser desorption/ionization mass spectrometry (MS). Single unicellular algae are seeded on a bare stainless steel plate and analyzed microspectroscopically. This provides information on the content and distribution of photoactive species, such as β-carotene, as well as chlorophyll and other components of the photosynthetic apparatus. Exactly the same cells are then analyzed by mass spectrometry in the negative ion mode. Phospholipid species are readily ionized by laser desorption/ionization of intact cells, without the need for an auxiliary matrix. This not only facilitates sample preparation but also preserves high spatial resolution and high sensitivity. Using this method, we were able to study the content and arrangement of proplastids and photosystem components, as well as the amounts of various phospholipid species in individual algal cells. The methodology can be used in the fundamental biological studies on these unicellular organisms, which require information on the internal structure as well as the chemical composition of individual cells.     

Polarization-independent tunable spectral slicing filter in Ti:LiNbO3

A two-port polarization-independent tunable spectral slicing filter at the 1530?nm wavelength regime is presented. The design utilizes an asymmetric interferometer with a sparse index grating along its arms. The sparse grating makes it possible to select equally spaced frequency channels from an incident WDM signal and to place nulls between them to coincide with the signal comb frequency. The number of selected channels and nulls between them depends on the number of coupling regions used in the sparse grating. The free spectral range depends on the spacing between the coupling regions. The Z-transform method is used to synthesize the filter and determine the spectral response. The operation of a device with six coupling regions is demonstrated, and good agreement with theoretical predictions is obtained. A 3?dB bandwidth of ～1?nm and thermal tuning over a range of ～13?nm are measured.     

Definition of a short-cut methodology for assessing earthquake-related Na-Tech risk

Na-Tech (Natural and Technological) refers to industrial accidents triggered by natural events such as storms, earthquakes, flooding, and lightning. Herein, a qualitative methodology for the initial assessment of earthquake Na-Tech risk has been developed as a screening tool to identify which situations require a much more expensive Quantitative Risk Analysis (QRA). The proposed methodology, through suitable Key Hazard Indicators (KHIs), identifies the Na-Tech risk level associated with a given situation (i.e., a process plant located in a given territory), using the Analytical Hierarchy Process as a multi-criteria decision tool for the evaluation of such KHIs. The developed methodology was validated by comparing its computational results with QRA results that involved Na-Tech events previously presented in literature.     

Paraquat-loaded alginate/chitosan nanoparticles: preparation, characterization and soil sorption studies

Agrochemicals are amongst the contaminants most widely encountered in surface and subterranean hydrological systems. They comprise a variety of molecules, with properties that confer differing degrees of persistence and mobility in the environment, as well as different toxic, carcinogenic, mutagenic and teratogenic potentials, which can affect non-target organisms including man. In this work, alginate/chitosan nanoparticles were prepared as a carrier system for the herbicide paraquat. The preparation and physico-chemical characterization of the nanoparticles was followed by evaluation of zeta potential, pH, size and polydispersion. The techniques employed included transmission electron microscopy, differential scanning calorimetry and Fourier transform infrared spectroscopy. The formulation presented a size distribution of 635 ± 12 nm, polydispersion of 0.518, zeta potential of -22.8 ± 2.3 mV and association efficiency of 74.2%. There were significant differences between the release profiles of free paraquat and the herbicide associated with the alginate/chitosan nanoparticles. Tests showed that soil sorption of paraquat, either free or associated with the nanoparticles, was dependent on the quantity of organic matter present. The results presented in this work show that association of paraquat with alginate/chitosan nanoparticles alters the release profile of the herbicide, as well as its interaction with the soil, indicating that this system could be an effective means of reducing negative impacts caused by paraquat.     

Silsesquioxane as a new building block material for modified electrodes fabrication and application as neurotransmitters sensors

Nanostructured films comprising a 3-n-propylpyridinium silsesquioxane polymer (designated as SiPy+Cl-) and copper (II) tetrasulfophthalocyanine (CuTsPc) were produced using the Layer-by-Layer technique (LbL). To our knowledge this is the first report on the use of silsesquioxane derivative polymers as building blocks for nanostructured thin films fabrication. Deposition of the multilayers were monitored by UV-Vis spectroscopy revealing the linear increment in the absorbance of the Q-band from CuTsPc at 617 nm with the number of SiPy+Cl-/CuTsPc or CuTsPc/SiPy+Cl-bilayers. FTIR analyses showed that specific interactions between SiPy+Cl- and CuTsPc occurred between SO3- groups of tetrasulfophthalocyanine and the pyridinium groups of the polycation. Morphological studies were carried out using the AFM technique, which showed that the roughness and thickness of the films increase with the number of bilayers. The films displayed electroactivity and were employed to detection of dopamine (DA) and ascorbic acid (AA) using cyclic voltammetry, at concentrations ranging from 1.96 x 10(-4) to 1.31 x 10(-3) molL(-1). The number and the sequence of bilayers deposition influenced the electrochemical response in presence of DA and AA. Using differential pulse technique, films comprising SiPy+/-/CuTsPc were able to distinguish between DA and ascorbic acid (AA), with a potential difference of approximately with 500 mV, in the concentration range of 9.0 x 10(-5) to 2.0 x 10(-4) molL(-1), in pH 3.0.