Photoelectrochemical imaging of metal-scale decohesion on titanium thermally oxidised in oxygen

Important compressive stress developed in TiO₂ films thermally grown on pure titanium in oxygen is known to induce scale decohesion at the metal-oxide interface. If such a phenomenon is identified in the literature to play a key role on life time of many materials used at high temperatures, no data at the microscopic level can be found at this time. In the present work using photoelectrochemical microscopy, new information in the form of two specific images ICI (interface cohesion image) and SQI (structural quality image) could be obtained. Such images revealed the level of scale decohesion induced by growth stress as well as the structural quality of the oxide layer.     

Design,processing, and characterization of an optical core-bioactive clad phosphate fiber for biomedical applications

The aim of this study was to fabricate a bioactive optical fiber able to monitor “in situ” its reaction with the body through changes in its optical properties. Core and cladding preforms were prepared with the composition (97.25*(0.50P₂O₅-0.40SrO-0.10Na₂O)-2.5ZnO-0.25Er₂O₃) and (98.25*(0.50P₂O₅-0.40SrO-0.10Na₂O)-1.75ZnO) (in mol%), respectively, and successfully drawn into a multimode core/clad optical fiber. Optical and near-Infrared images assessed the proper light guiding properties of the fiber. The fibers favor the precipitation of a Ca-P reactive layer at its surface concomitant with a reduction in the fiber diameter, when immersed in SBF, often assigned as a sign of bioactivity. It is clearly shown here that the bio-response of the fiber upon immersion in SBF can be tracked from the decrease in the intensity of the Er³⁺ ions emission at 1.5 µm. This confirms that the newly developed optical fiber, which combines good optical properties with a suitable bioactive behavior, is a promising platform for the development of novel biomedical devices for biophotonic and photomedical applications. Finally, the successful splicing of the newly developed fiber with commercial optical fibers was an evidence of the possibility to integrate the newly developed phosphate fiber within existing components used in the field of biomedicine.     

Eyeblink conditioning leads to fewer synapses in the rabbit cerebellar cortex.

Eyeblink conditioning involves the pairing of a conditioned stimulus (tone) to an aversive unconditioned stimulus (air puff). Although the circuitry that underlies this form of learning is well defined, synaptic changes in these structures have not been fully investigated. This experiment examined synaptic structural plasticity in the cerebellar cortex, a structure that has been found to modulate the acquisition and timing of the conditioned response. Long-term depression of Purkinje cells (PCs) in the cerebellar cortex has been proposed as a mechanism for releasing inhibition of the interpositus nuclei, a structure critical for the formation of the CR. Adult albino rabbits were randomly allocated to either a paired, unpaired, or exposure-only condition. The results showed a significant decrease in the number of excitatory synapses in the outer layer of the cerebellar cortex in the conditioned rabbits compared with controls. This finding suggests that a reduction in the number of excitatory synapses may contribute to the lasting depression of PC activity that is associated with eyeblink conditioning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Using aerosol light absorption measurements for the quantitative determination of wood burning and traffic emission contributions to particulate matter

A source apportionment study was performed for particulate matter in the small village of Roveredo, Switzerland, where more than 70% of the households use wood burning for heating purposes. A two-lane trans-Alpine highway passes through the village and contributes to the total aerosol burden in the area. The village is located in a steep Alpine valley characterized by strong and persistent temperature inversions during winter, especially from December to February. During two winter and one early spring campaigns, a seven-wavelength aethalometer, high volume (HIVOL) samplers, an Aerodyne quadrupole aerosol mass spectrometer (AMS), an optical particle counter (OPC), and a Sunset Laboratory OCEC analyzer were deployed to study the contribution of wood burning and traffic aerosols to particulate matter. A linear regression model of the carbonaceous particulate mass in the submicrometer size range CM(PM1) as a function of aerosol light absorption properties measured by the aethalometer is introduced to estimate the particulate mass from wood burning and traffic (PM(wb), PM(traffic)). This model was calibrated with analyses from the 14C method using HIVOL filter measurements. These results indicate that light absorption exponents of 1.1 for traffic and 1.8-1.9 for wood burning calculated from the light absorption at 470 and 950 nanometers should be used to obtain agreement of the two methods regarding the relative wood burning and traffic emission contributions to CM(PM1) and also to black carbon. The resulting PM(wb) and PM(traffic) values explain 86% of the variance of the CM(PM1) and contribute, on average, 88 and 12% to CM(PM1), respectively. The black carbon is estimated to be 51% due to wood burning and 49% due to traffic emissions. The average organic carbon/total carbon (OC/TC) values were estimated to be 0.52 for traffic and 0.88 for wood burning particulate emissions.     

Microstructure of the coating and mechanical properties of galvanized chromium-rich martensitic steel

Protecting the modern high-strength steels against corrosion is a challenge because the coating technology must be compatible with forming and must preserve the mechanical performances. Batch galvanizing after hot stamping could provide a simple solution to this complex problem. A commercial high-strength martensitic steel containing 13 wt.% Cr, 0.35 wt.% Si, 0.3 wt.% Mn and 0.15 wt.% carbon has been galvanized with a commercial zinc alloy. Galvanizing produces a ~ 15 μm thick coating that is bright, continuous and metallurgically bonded. The intermetallic layer is made of ? crystals, which forms an open 3-dimensional structure. Tin, nickel and aluminium are found able to moderate the Sandelin effect. Comparison with other steels galvanized the same way indicates that chromium slows down the kinetics of the metallurgical reaction. Chromium distributes both in the ? and η phases, and follows a diffusion-like profile in the coating. The nickel from the alloy concentrates in the Fe-Zn intermetallic compound. Aluminium segregates at the surface and interface. It also provides a gettering effect that fixes silicon in sub-micron particles dispersed in the ? and η phases. Tensile experiments and fatigue tests demonstrate that the mechanical performances of the martensitic steel are preserved after coating. Comparison with similar experiments performed on a TRIP800 steel indicates that using galvanized martensitic steel is best worth in static applications.     

Fast domain wall motion in magnetic comb structures

Modern fabrication technology has enabled the study of submicron ferromagnetic strips with a particularly simple domain structure, allowing single, well-defined domain walls to be isolated and characterized. However, these domain walls have complex field-driven dynamics. The wall velocity initially increases with field, but above a certain threshold the domain wall abruptly slows down, accompanied by periodic transformations of the domain wall structure. This behaviour is potentially detrimental to the speed and proper functioning of proposed domain-wall-based devices, and although methods for suppression of the breakdown have been demonstrated in simulations, a convincing experimental demonstration is lacking. Here, we show experimentally that a series of cross-shaped traps acts to prevent transformations of the domain wall structure and increase the domain wall velocity by a factor of four compared to the maximum velocity on a plain strip. Our results suggest a route to faster and more reliable domain wall devices for memory, logic and sensing.     

Polarization-independent thermooptic phase shifters in silicon-oxynitride waveguides

The effective refractive index of dielectric waveguides can be tuned using the thermooptic effect. In general, the tuning efficiency is polarization-dependent owing to temperature-induced stress in the layers, which causes polarization-dependent loss in optical devices. These stress issues are analyzed and tested for a high-index-contrast waveguide structure based on a silicon-oxynitride core. Experimental results are in agreement with simulations. The relative difference in tuning efficiency for transverse electric and transverse magnetic polarized light can be tuned from -3% to +3% by appropriate waveguide technology control. The optimized thermooptic phase shifters show tuning efficiency differences below 0.25%, which are reproducible from wafer to wafer.     

Application of alumina supported gold-based catalysts in total oxidation of CO and light hydrocarbons mixture

Gold nanoparticles supported on alumina have been produced using the anionic exchange method and ammonia washing procedure. The catalysts are tested in the reaction of total oxidation of a mixture of light hydrocarbons and carbon monoxide in order to study the possibility of application in the reduction of cold start emissions. The obtained results are promising according to the temperature range observed for the oxidation of unsaturated hydrocarbons. The results obtained for acetylene confirms the difference of oxidation of this hydrocarbon over gold catalysts. An ageing procedure has been employed. This procedure does not affect the comportment of the catalysts versus hydrocarbon oxidation.