Levels, fingerprint and daily intake of polycyclic aromatic hydrocarbons (PAHs) in bread baked using wood as fuel

Concentrations, fingerprint and daily intake of 16 PAHs in 15 bread samples baked using wood as fuel are examined in this work. Analysis was performed by GC/MS after saponification of the samples and clean up of the extract. The total concentration of the 16 analytes varies from 6 to 230 microg/kg on dry weight (d.w.). The better extraction procedure was estimated by analyzing test-samples and using different extraction methods. Additionally, for every analyzed sample, the extraction yield has been determined by the use of surrogate standards. Extraction yields were never less than 77% and in most cases almost 100%. The profiles of PAHs (percentage) are similar for all the analyzed samples but are different from those reported when other types of fuels are taken in consideration. The daily intake of PAHs was found to range between 1.6 and 68 microg day(-1), while the intake of B[a]P ranges from 0.33 to 8.0 microg day(-1). These results are considerably lower than the slope factor for 14 of the 15 analyzed samples.     

Hazardous impact of toxic metals on tobacco leaves grown in contaminated soil by ultrasonic assisted pseudo-digestion: multivariate study

Tobacco leaves (Nicotiana tabacum L.), agricultural soil and pollute irrigated lake water samples were collected during 2005–2006 and analyzed for Cd and Ni by electrothermal atomic absorption spectrometry (ETAAS). A simple and efficient procedure was investigated for the complete decomposition of tobacco leaves using ultrasonic assisted acid pseudo-digestion method (UPDM). A Plackett–Burman experimental design was used as a multivariate strategy for the evaluation of seven factors/variables at once, while central composite were used to found optimum values of significant variables. The accuracy of the proposed methods was assessed by analyzing certified reference (CRM); Virginia tobacco leaves (CTA-VTL-2). The results being compared with those obtained by conventional wet acid digestion method. The result obtained by optimized method showed good agreement with the certified values and sufficiently high recovery 97.8 and 98.7% for Cd and Ni, respectively. Under optimal conditions, the detection limits (3σ) were evaluated to be 0.019 μg g⁻¹ for Cd and 0.37 μg g⁻¹ for Ni. The proposed method was successfully applied to the determination of Cd and Ni in raw, processed tobacco and different branded cigarettes samples.     

Solid phase extraction of chromium(VI) from aqueous solutions by adsorption of its diphenylcarbazide complex on an Amberlite XAD-4 resin column

A method has been developed for the solid phase extraction of chromium(VI) based on the adsorption of its diphenylcarbazide complex on an Amberlite XAD-4 resin column. The influence of acidity, stability of the column, sample volume, flow rate and interfering ions were studied in detail. The adsorbed complex could be eluted using acetone–sulfuric acid mixture and the concentration of chromium was determined using visible spectrophotometry. A detection limit of 6 μg L⁻¹ could be achieved. A preconcentration factor of 27 could be obtained for 400 mL sample volume. The validity of the method was checked in spiked water samples and electroplating wastewater.     

Removal of mercury species with dithiocarbamate-anchored polymer/organosmectite composites

Mercury is one of the most toxic heavy metals found in solid and liquid waste disposed by chloro-alkali, paint, paper/pulp, battery, pharmaceutical, oil refinery and mining companies. Any form of mercury introduced to nature through any means is converted into a more toxic form such as methylmercury chloride (as produced by aquatic organisms) which usually accumulates in the tissue of fish and birds.

The primary aim of this study was to investigate performance of dithiocarbamate-anchored polymer/organosmectite composites as sorbents for removal of mercury from aqueous solution. The modified smectite nanocomposites then were reacted with carbondisulfide to incorporate dithiocarbamate functional groups into the nanolayer of the organoclay. These dithiocarbamate-anchored composites were used for the removal of mercury species [Hg(II), CH₃Hg(I) and C₆H₅Hg(I)]. Mercury adsorption was found to be dependent on the solution pH, mercury concentration and the type of mercury species to be adsorbed. The maximum adsorption capacities were equal to 157.3 mg g⁻¹ (782.5 μmol g⁻¹) for Hg(II); 214.6 mg g⁻¹ (993.9 μmol g⁻¹) for CH₃Hg(I); 90.3 mg g⁻¹ (325 μmol g⁻¹) for C₆H₅Hg(I). The competitive adsorption capacities (i.e. adsorption capacities based on solutions containing all three mercuric ions) are 7.7 mg g^−l (38.3 μmol g⁻¹), 9.2 mg g^−l (42.6 μmol g⁻¹) and 12.7 mg g⁻¹ (45.7 μmol g⁻¹) for Hg(II), CH₃Hg(I) and C₆H₅Hg(I), respectively, at 10 ppm initial concentration. The adsorption capacities on molar basis were in order of C₆H₅Hg(I) > CH₃Hg(I) > Hg(II).     

Effect of microarc oxidised layer thickness on plain fatigue and fretting fatigue behaviour of Al–Mg–Si alloy

The objective of this work was to investigate the performance of microarc oxide coatings of two different thicknesses (40 and 100 μm) on Al–Mg–Si alloy samples under plain fatigue and fretting fatigue loadings. Tensile residual stress present in the substrate of 40 μm thick coated samples induced early crack initiation in the substrate and so their plain fatigue lives were shorter than those of untreated specimens. Presence of more pores and tensile surface residual stress in 100 μm thick coated samples caused early crack initiation at the surface leading to their inferior plain fatigue lives compared with 40 μm thick coated samples. While the differences between the lives of coated and uncoated specimens were significant under plain fatigue loading, this was not the case under fretting fatigue loading. This may be attributed to relatively higher surface hardness of coated specimens. The performance of 40 μm thick coated samples was better than that of 100 μm thick coated specimens under both plain fatigue and fretting fatigue loadings.     

Performance characteristics of quaternary silver-based battery systems

The quaternary system of 60AgI---20Ag₂O---16MoO₃---4V₂O₅ (silver vanadium molybdate) has been prepared by melt quenching. The solid formed was powdered and characterized by XRD, IR spectroscopy and EDAX. The electrical conductivity measured was 0.0023 S cm⁻¹ at 1 kHz, 300 K. The electrolyte was used to fabricate several solid-state batteries and the discharge characteristics for the battery system were taken at constant current loads of 1 and 30 μA. The internal resistance of the silver vanadium molybdate battery system was calculated to be about 4.5 kω and the zero current drain (0CV) measured was 0.678 V. Operating time for the 0CV to reach 200 mV for 30 μA was 50 h. The energy density for 30 μA was calculated to be 0.3 W-h kg⁻¹.     

Preparation, characterization, non-isothermal reaction kinetics, thermodynamic properties, and safety performances of high nitrogen compound: hydrazine 3-nitro-1,2,4-triazol-5-one complex

An optimized and validated spectrophotometric method has been developed for the determination of uranyl ion in the presence of other metal ions. The method is based on the chelation of uranyl ion with meloxicam via β-diketone moiety to produce a yellow colored complex, which absorbs maximally at 398 nm. Beer's law is obeyed in the concentration range of 5–60 μg/mL with apparent molar absorptivity and Sandell's sensitivity of 5.02 × 10⁴ L/mol/cm and 0.1 μg/cm²/0.001 absorbance unit, respectively. The method has been successfully applied for the determination of uranyl ion in synthetic mixture and soil samples. Results of analysis were statistically compared with those obtained by Currah's spectrophotometric method showing acceptable recovery and precision.     

Light concentrators for Borexino and CTF

Light concentrators for the solar neutrino experiment Borexino and the Counting Test Facility (CTF) have been developed and constructed. They increase the light yield of these detectors by factors of 2.5 and 8.8, respectively. Technical challenges like long-term stability in various media, high reflectivity and radiopurity have been addressed and the concepts to overcome these difficulties will be described. Gamma spectroscopy measurements of the concentrators show an upper limit of 12 μBq/g for uranium and a value of 120 μBq/g for thorium. Upper limits on other possible contaminations like ²⁶Al are presented. The impact of these results on the performance of Borexino and the CTF are discussed and it is shown that the design goals of both experiments are fulfilled.     

Photoelectrochemical and physical properties of tungsten trioxide films obtained by aerosol pyrolysis

Aerosol pyrolysis (AP) was used for preparing semiconducting films of tungsten trioxide using peroxotungstic acid as a precursor. The films were characterized by SEM, XRD, and by their photoelectrochemical response. Porous, polycrystalline (monoclinic) films of thickness up to 3 μm were prepared. An incident photon to current efficiency (IPCE) of 0.55 at 365 nm was obtained for films of 1 μm thickness on conducting F:SnO₂/glass substrates under depletion conditions, in junctions with aqueous electrolytes. The spectral (photocurrent) response extended into the visible region (up to 470 nm) which is of importance for solar applications like photocatalysis.     

Effect of hydrogen radical on growth of μc-Si in hetero-structured SiCx alloy films

The changes of the crystallinity of μc-Si phase are studied in samples deposited with hydrogen dilution ratio, H₂/SiH₄, from 9.0 to 19.0 by hot-wire CVD (Cat-CVD). In the samples deposited at filament temperature, T_f, of 1850 °C, the crystalline fraction and the crystallite size of μc-Si phase increased with increasing the H₂/SiH₄. The carbon content, C/(Si+C), was almost constant. In the XRD patterns, the intensity of Si(1 1 1) peak decreased and that of Si(2 2 0) peak increased with increasing the H₂/SiH₄. In the samples deposited at T_f of 2100 °C with H₂/SiH₄ over 11.4, the μc-Si phase was not formed and the C/(Si+C) increased. The growth mechanism of μc-Si in hetero-structured SiC_x alloy films is discussed.     

RuO2–TiO2 mixed oxides prepared from the hydrolysis of the metal alkoxides

The hydrolysis of ruthenium alkoxide/titanium tetraethoxide mixtures to gels and powders containing 30–40 mol% Ru was investigated. Basic or neutral conditions led to powders consisting of 2–10 nm diameter crystalline RuO₂ nanoparticles embedded in a matrix of crystalline (anatase) and amorphous TiO₂. Acid hydrolysis conditions gave gels containing smaller, amorphous RuO₂ nanoparticles (1–3 nm). In all samples the RuO₂ nanoparticles tended to clump into aggregates up to 0.5 μm across. Acid or neutral hydrolysis of ruthenium ethoxide gave samples which displayed lower surface Ru:Ti ratios as measured by XPS compared to the bulk (XRF), and also contained more low-valent Ru (as measured by XRF), probably due to incomplete hydrolysis of the precursors. These samples also contained more Ru metal after calcination (XRD). Calcination (450 °C) was accompanied by Ru-promoted combustion of organic material and led to crystalline (anatase) TiO₂ and Ti_xRu_1−xO₂ solid solution (rutile phase).     

Semi-solid processing of ultrahigh-carbon steel castings

Semi-solid processing using cooling plate technique was developed to produce a high quality ultrahigh-carbon steel (UHCS) components. Microstructure and mechanical properties were investigated as a function of fraction of solid. The microstructure of UHCS was improved using semi-solid processing. A unique homogenized microstructure comprised of fine particles grain size (200–100 μm) was obtained which totally differs from that obtained by ordinary UHCS casting (520 μm particle grain size). Tensile strength of as-cast and heat treated semi-solid processed UHCS is relatively high compared with ordinary one. Both the tensile strength and elongation closely connect with the particle grain size and cementite network changed with fraction of solid. Increasing fraction of solid increases hardness values, which is attributed to the fine and homogenous structure by semi-solid processing.     

EBSD analysis of a Ti-IF steel subjected to hot torsion in the ferritic region

The effect of grain size on the warm deformation behaviour of a titanium stabilized interstitial free steel was investigated using hot torsion. Tests were performed at temperatures between 765 °C and 850 °C at strain rates between 0.003 s⁻¹ and 1 s⁻¹ for samples with grain sizes of 25 μm, 75 μm and 150 μm. The structures were observed using EBSD analysis and are consistent with those expected for materials dominated by dynamic recovery. Some evidence was found for small amounts of thermally induced migration of pre-existing boundary (bulging) and for the generation of new segments of high angle boundaries by continuous dynamic recrystallization. The early onset of a steady-state flow stress in the finer grained samples is attributed to one or a combination of thermally induced boundary migration and enhanced rates of recovery near subgrain (and grain) boundaries.     

Speciation determination of chromium(III) and (VI) using preconcentration cloud point extraction with flame atomic absorption spectrometry (FAAS)

bis-[2-Hydroxy-1-naphthaldehyde] thiourea was synthesized and preconcentration cloud point extraction (CPE) for speciation determination of chromium(III) and (VI) in various environmental samples with flame atomic absorption spectrometry (FAAS) has been developed. Chromium(III) complexes with bis-[2-hydroxynaphthaldehyde] thiourea is subsequently entrapped in the surfactant micelles. After complexation of chromium(III) with reagent, the analyte was quantitatively extracted to the surfactant-rich phase in the non-ionic surfactant Triton X-100 after centrifugation. The effect of pH, concentration of chelating agent, surfactant, equilibration temperature and time on CPE was studied. The relative standard deviation was 2.13% and the limits of detection were around 0.18 μg L⁻¹.     

Ion formation by high velocity impacts on porous metal targets

In impact ionization studies the target normally consists of a metal surface of compact solid density. In the present experiments, we investigate the use of a layer of a highly porous structure of nanometre-sized grains, sometimes also called “metal black”, as an alternative target. In our comparative experiments, spherical iron particles (0.1<d_p<1.5 μm) were shot with velocities 2–30 km/s onto both a compact solid silver plate and a silver metal black layer of about 7 μm thickness (grain size 20–40 nm, mean density ≈1 g/cm³), deposited on a compact solid gold plate. Impact generated ions were analysed by means of time-of-flight mass spectrometry. The results reveal important advantages of the porous black layer, such as better mass resolution and a larger amount of ions from the impacting particle. Therefore metal blacks may be very suitable targets for the purposes of identification and characterisation of the impacting particle's composition. An attempt is made to give a physical explanation of the results in the frame of existing empirical ionization models. The study is part of a programme to improve devices for in-situ analysis of fast moving cosmic dust particles.     

Cryogenic and elevated temperature hypervelocity impact facility

The hypervelocity impact facility at Space Research Institute (SRI), Auburn University has recently completed a facility upgrade that permits the impact testing of space materials within the cryogenic and elevated temperature range. Sample temperatures within the range of 40–450 K have been achieved for polymer films. These wide temperature range capabilities add to the facilities current testing experience with impact initiated plasma discharge testing for solar cell arrays. The facility utilizes a plasma drag gun to accelerate a variety simulated micrometeorite materials in the 50–150 μm range to velocities between 5 and 12 km/s. For each test 5–50 particles impact the surface of the target sample within an impact area of approximately 15 cm in diameter. The test chamber can accommodate samples up to a meter wide for ambient and heated tests, and 48 cm for cryogenic samples. The gun and test chambers are evacuated by He cryopumps and dry roughing pumps to produce a clean, oil free environment. Utilizing a streak camera and PMT detection system, the correspondence between individual particle size, speed and impact site can be determined. Standard post-analysis yields: micrographs of each impact site, dimensions of the pertinent impact characteristics, individual particle velocity and size estimates.     

Preparation of Sm-doped ceria (SDC) nanowires and tubes by gas–liquid co-precipitation at room temperature

Sm-doped cerium dioxide (SDC) with fcc structure was formed using a gas–liquid chemical co-precipitation process at room temperature. Morphology and structure of the as-prepared samples were characterized using TG, XRD, TEM, HRTEM and SAED techniques. Under our specific experimental conditions, two kinds of 1D nano-structures SDC have been mainly obtained. SDC nanowires are 0.3–1.2 μm in lengths and 5–20 nm in diameters. SDC nanotubes have outer diameters in 10–40 nm with lengths up to 2 μm. The as-prepared SDC shows very strong UV absorption ability and the maximum absorption peak redshifts compared with that of SDC nanoparticles.     

Flow injection preconcentration system using a new functionalized resin for determination of cadmium and nickel in tobacco samples

A solid-phase extraction method combined with flow injection (FI) on-line flame atomic absorption spectrometry (FAAS) for the determination of cadmium and nickel in tobacco samples is presented. The 2-aminothiophenol functionalized Amberlite XAD-4 (AT-XAD) resin was synthesized by covalent coupling of the ligand with the copolymer through a methylene group. A minicolumn packed with AT-XAD was connected into the automated on-line preconcentration system. Elution of metal ions from minicolumn can be made with 0.50 mol L⁻¹ hydrochloric acid solution. With a consumption of 21.0 mL of sample solution, detection limits (3 s) of 0.3 (Cd) and 0.8 μg L⁻¹ (Ni) were achieved at a sample throughput of 18 h⁻¹. Enrichment factors (EF) of 99 (cadmium) and 43 (nickel) were obtained compared with the slope of the linear portion of the calibration curves before and after preconcentration. The contents of Cd and Ni in a certified reference material (NIST 1570a, spinach leaves) determined by the present method was in good agreement with the certified value. The developed procedure was also successfully applied to the determination of Cd and Ni in local tobacco samples.     

Microstructural and mechanical properties evolution of magnesium AZ61 alloy processed through a combination of extrusion and thermomechanical processes

In this work, the microstructures and tensile properties of a commercial magnesium alloy “AZ61” processed by a combination of hot extrusion and thermomechanical processing (TMP) were investigated. The TMP was consisting of two or three hot rolling steps with large reductions per pass, thus allowing significant grain refinement. The microstructural evolution has been studied by means of optical and scanning electron microscopes, as well as X-ray diffraction analysis. The as-cast material is extruded in the form of a cylinder with initial diameter of 250 mm to a final diameter of 110 mm (80% reduction in cross-sectional area). Then hot rolling regimes were performed at 300 °C with different percentage of strain per pass. Tensile and hardness tests were performed in the samples (as-cast, extruded, and rolled) at room temperature in order to evaluate the mechanical properties of the material. The results of experiments demonstrated that fine grain size might be achieved in magnesium alloy AZ61 by using a two-step processing route involving an initial extrusion step followed by thermomechanical processing with large reduction in thickness per pass. This two-step process, designed to achieve average grain sizes of 10–20 μm.     

Sintering behavior and microwave dielectric properties of Bi3(Nb1−xTax)O7 solid solutions

Solid solutions of Bi₃(Nb_1−xTa_x)O₇ (x = 0.0, 0.3, 0.7, 1) were synthesized using solid state reaction method and their microwave dielectric properties were first reported. Pure phase of fluorite-type could be obtained after calcined at 700 °C (2 h)⁻¹ between 0 ≤ x ≤ 1 and Bi₃(Nb_1−xTa_x)O₇ ceramics could be well densified below 990 °C. As x increased from 0.0 to 1.0, saturated density of Bi₃(Nb_1−xTa_x)O₇ ceramics increased from 8.2 to 9.1 g cm⁻³, microwave permittivity decreased from 95 to 65 while Q_f values increasing from 230 to 560 GHz. Substitution of Ta for Nb modified temperature coefficient of resonant frequency τ_f from −113 ppm °C⁻¹ of Bi₃NbO₇ to −70 ppm °C⁻¹ of Bi₃TaO₇. Microwave permittivity, Q_f values and τ_f values were found to correlate strongly with the structure parameters of fluorite solid solutions and the correlation between them was discussed in detail. Considering the low densified temperature and good microwave dielectric proprieties, solid solutions of Bi₃(Nb_1−xTa_x)O₇ ceramics could be a good candidate for low temperature co-fired ceramics application.