Ambient nitrogen dioxide and distance from a major highway

The primary objective of this pilot study was to measure the variation of ambient nitrogen dioxide (NO(2)) concentration with increasing distance from a major highway in Montréal, Canada, in order to assess the validity of distance from the roadways as a surrogate for exposure to traffic-related air pollution in epidemiologic studies. A total of 31 two-sided Ogawa passive samplers (using triethanolamine-impregnated filters as an absorbent) were installed for 7 days in groups of two or three along an axis perpendicular to a major highway where traffic density exceeds 100000 vehicles/day. Distances ranged from 0 to 1310 m from the highway. Concentrations of NO(2) ranged from 11.9 to 29.3 ppb, and decreased significantly with increasing logarithmic distance from the highway (P<0.0001). Concentrations of NO(2) were also significantly lower upwind than downwind relative to the highway (P=0.0012). These findings indicate that distance from highways may be a valid surrogate for traffic-related air pollution.     

Tetragonal reconstruction and monoclinic variants rearrangement during heat treatment in zirconia

An in situ monoclinic variants selection and rearrangement study on Y₂O₃–ZrO₂ coatings was conducted using electron backscattered diffraction. The sequence growth of variants with the correspondence of (100)_m ∼// (010)_t, [010]_m ∼// [001]_t, and [001]_m ∼// [100]_t (CAB-OR2) was found initially and converted to the 90°-rotated sequence growth with (100)_m ∼// (100)_t, [001]_m ∼// [001]_t, and [010]_m ∼// [010]_t (ABC-OR2) after heat treatment. In another coating, most of the variants first exhibited interleaving growth and changed to typically fourfold growth. This in situ evolution of both variants orientation relationship and arrangement revealed the effects of stress and stress relief on the martensitic transformation. Moreover, the variants selection might be diversified during the cyclic transformation, and the classical phenomenological theory could mainly be proved by the transformation triggered by temperature, instead of external stress. Furthermore, the variants orientation relationship was exactly confirmed by the tetragonal grain reconstructions. In particular, the orientation variation of reconstructed tetragonal grains was also found and could mainly be explained by the behavior of stress relief and dynamic recrystallization.     

Theory and experiments of transport at channel microband electrodes under laminar flows. 1. Steady-state regimes at a single electrode

Integration of microelectrodes in microfluidic devices has attracted significant attention during the past years, in particular for analytical detections performed by direct or indirect electrochemical techniques. In contrast there is a lack of general theoretical treatments of the difficult diffusion-convection problems which are borne by such devices. In this context, we investigated the influence of the confining effect and hydrodynamic conditions on the steady-state amperometric responses monitored at a microband electrode embedded within a microchannel. Several convective-diffusive mass transport regimes were thus identified under laminar flow on the basis of numerical simulations performed as a function of geometrical and hydrodynamic parameters. A rationalization of these results has been proposed by establishing a zone diagram describing all the limiting and intermediate regimes. Concentration profiles generated by the electrode across the microchannel section were also simulated according to the experimental conditions. Their investigation allowed us to evaluate the thickness of the diffusive-convective layer probed by the electrode as well as the distance downstream from which the solution becomes again homogeneous across the whole microchannel section. Experimental checks of the theoretical principles delineated here have validated the present results. Experiments were performed at microband electrodes integrated in microchannels with aqueous solutions of ferrocene methanol under pressure-driven flow.     

High-power, low-divergence, linear array of quasi-diffraction-limited beams supplied by tapered diodes

We describe for the first time to our knowledge the performance for a linear array of tapered laser diodes with both fast- and slow-axis collimation using a microlens for fast-axis collimation and a laser-written phase plate for slow-axis collimation and correction of the residual fast-axis errors from lens aberrations, thermal lensing, astigmatism, pointing errors, and other wavefront distortions. The phase plate leads to M(2) factor reductions of 1.5 for the lensed array following the fast axis and 2.6 for the whole bar following the slow axis.     

Inhibition of polyphenoloxidase activity by mixtures of heated cysteine derivatives with carbonyl compounds

It had previously been shown that soluble Maillard reaction products (MRP) made from thiol compounds and glucose or fructose contained powerful inhibitors of various fruit and vegetable polyphenoloxidase (PPO) activity. In MRP from cysteine and glucose, the amount of hydroxymethylfurfural (HMF) formed increased with the increase in glucose concentration (0-1 M), particularly under acidic (pH 2) conditions. Using model mixtures containing a preheated cysteine-derived compound and a carbonyl component, especially HMF, furfural and benzaldehyde, we showed that the neoformed compounds produced exhibited a stronger inhibitory potency toward PPO activity of eggplant, apple, and mushroom than former MRP. Optimal reaction conditions for the formation of inhibitory compounds when HMF reacted with preheated cysteine were investigated. It was found that a reactants molar ratio of 1:1 and a reaction time exceeding 1 h were the most efficient reaction conditions to generate inhibitory compounds. The stability of the newly formed products, evaluated during storage, showed that their inhibitory potency was globally kept at 4, 21, and 37 degrees C for 72 h but was unstable when stored at -20 degrees C and lost when exposed to UV radiations for 24 h.     

A patch antenna design for application in a phased-array head and neck hyperthermia applicator

In this paper, we describe a specifically designed patch antenna that can be used as the basis antenna element of a clinical phased-array head and neck hyperthermia applicator. Using electromagnetic simulations we optimized the dimensions of a probe-fed patch antenna design for operation at 433 MHz. By several optimization steps we could converge to a theoretical reflection of -38 dB and a bandwidth (-15 dB) of 20 MHz (4.6%). Theoretically, the electrical performance of the antenna was satisfactory over a temperature range of 15 degrees C-35 degrees C, and stable for patient-antenna distances to as low as 4 cm. In an experimental cylindrical setup using six elements of the final patch design, we measured the impedance characteristics of the antenna 1) to establish its performance in the applicator and 2) to validate the simulations. For this experimental setup we simulated and measured comparable values: -21 dB reflection at 433 MHz and a bandwidth of 18.5 MHz. On the basis of this study, we anticipate good central interference of the fields of multiple antennas and conclude that this patch antenna design is very suitable for the clinical antenna array. In future research we will verify the electrical performance in a prototype applicator.     

Steady-state asymmetric nanospray dual ion source for accurate mass determination within a chromatographic separation

Here we report the design, implementation, and initial use of an asymmetric steady-state continuous dual-nanospray ion source. This new source design consists of two independently controlled and continuously operating nanospray interfaces with funnel shaped counter electrodes. A steady-state ion mixing region combines the ions from the two sources into a single ion beam in the intermediate region after ion extraction from the nanospray sources but before the bulk of the pressure gradient of the vacuum interface. With this design we have achieved robust mixing of ions with no loss of duty cycle and remarkable ionization characteristics that appear entirely noncompetitive and potentially beneficial. This allows continuous introduction of internal mass calibration ions during a liquid chromatography-mass spectrometric analysis. This in turn allows for recalibration of individual spectra yielding sub part per million mass accuracy throughout the run. The steady-state approach presented here has several advantages over previous approaches. Since neither the voltage nor positions of the sprayers are changed, the nanospray has greater spray stability. The ions produced by the analyte sprayer are continuously sampled, as opposed to time-sharing which necessitates that the analyte ion stream be interrupted for some part of the duty cycle. There are no moving parts, no rapid changes to high voltages requiring additional control electronics, and no need for completely separate vacuum interfaces and the associated complexity. The sprayers are independently controlled and do not exhibit competition or mutual ionization suppression. This novel source has been implemented with a Bruker Apex II 9.4 T FTICR with a modified Apollo electrospray ion source as part of a nanoflow liquid chromatography-Fourier transform ion cyclotron resonance mass spectrometry analysis platform. Because of the low cost of implementation, the new source could potentially be applied to other forms of mass spectrometry, such as electrospray ionization-time-of-flight (ESI-TOF), which can benefit from internal mass calibration.     

High performance grinding of zirconium oxide (ZrO2) using hybrid bond diamond tools

Hybrid bond (metal–ceramic) diamond tools are proposed for grinding zirconium oxide used in medical implants. Compared to conventional grinding tools, material removal rates and tool life time are drastically increased without deterioration in mechanical properties of the workpiece. This is achieved within a selected process window in combination with an elaborate oil cooling system, where material removal is mainly occurring within the ductile cutting mode. Self-sharpening effect of the tool can be observed and the dressability of the tool further improves the grinding performance.