Surface Microstructure Changes Induced by Ion Beam Irradiation

As a study result of irradiation-induced damage, various mathematical models have been developed to explain the phenomenon of irradiation-induced surface sputtering, these models are currently used in technological fields as diverse as materials characterization and in thin film deposition used in the manufacture of electronic or medical components. However, the phenomenon is not fully understood due to its high complexity, this work has the goal to present experimental evidence of the changes induced in the surface of hypereutectic alloy Ni-22% at Si promoted by the nickel ion beam irradiation, the surface changes induced will be explained in terms of the Sigmund theory of surface sputtering

Weeds Forage Potential for Ruminant Feeding: Chemical Composition and Kinetics of Rumen Degradation

Systems of ruminant production in the Andean highlands of Ecuador are dominated by monoculture grasses, where producers do not allow association with other plants such as weeds. These systems have small areas of land and the peasants would be wasting feed resources (association) with high nutritional content and secondary compounds that may be beneficial for feeding ruminants improving the nutritional value of grassland. In this context, Castelán et al. (2003) mention that the use of weeds in ruminant nutrition by small producers in temperate areas of Mexico, it becomes the main natural forage resource for livestock to feed round the year, as there great availability. For farmers with limited financial resources this practice is very common, because it represents feeding efficiency with low production costs, because they use non-conventional feed resources. Weed species such as Sicyos deppei G., Jaltomata procumbens (Cav.), Drymaria laxiflora Benth y Lopezia racemosa Cav. contain high levels of ruminal fermentation and high crude protein content, as well as low levels of fiber (Castelán et al., 2003). Under this background, the objective of this research is to determine the chemical composition and in situ ruminal degradation of weeds with forage potential that exist in the grasslands of the Andean highlands of Ecuador

Electrocatalytic urea mineralization in aqueous alkaline medium using NiIIcyclam-modified nanoparticulate TiO2 anodes and its relationship with the simultaneous electrogeneration of H2 on Pt counterelectrodes

NiIIcyclam-modified nanoparticulate TiO2-coated ITO electrodes (ITO/TiO2//NiIIcyclam) were prepared by electropolymerization of NiIIcyclam monomers to TiO2-coated ITO electrodes (ITO/TiO2) to improve electrocatalytic urea CO(NH2)2 oxidation in alkaline aqueous solutions. A high value adding secondary effect was the collection of electrons at Pt cathodes, to simultaneously generate H2 from water reduction. NiIIcyclam-modified ITO electrodes (ITO//NiIIcyclam) were also prepared by electropolymerization of NiIIcyclam monomers to bare ITO electrodes (ITO) for comparison purposes. In the presence of the TiO2 nanoparticles, the urea mineralization on NiIIcyclam coatings was doubled (23.95% – organic carbon removal at 120 min of electrolysis) compared to those without TiO2 nanoparticles (13.02% – organic carbon removal at 120 min of electrolysis). In agreement, the faradaic efficiency for H2 generation at the Pt cathode, electrically connected to an anode having TiO2 nanoparticles (0.99 at 120 min of electrolysis), was also twice as effective than that observed when the same Pt cathode was electrically connected to an anode without TiO2 nanoparticles (0.46 at 120 min of electrolysis). The experimental results indicated that the poisoning of NiII centers (which is caused by an excessive production of CO intermediates during the urea oxidation on both NiIIcyclam-modified anodes) was strongly inhibited in the presence of the nanoparticulate TiO2|NiIIcyclam junction. A final comparison between our results and those reported in selected publications revealed that the NiIIcyclam-modified nanoparticulate TiO2-coated ITO anodes here developed, constitutes a promising electrocatalytic system for performing direct urea mineralization at a relative short electrolysis time. Furthermore, the combination of the following phenomena: (a) effective charge separation on the semiconducting ITO|nanoparticulate TiO2 junctions, (b) remarkable capabilities of the nanoporous TiO2 films for tuning the load of OH� anions demanded by the urea oxidation and, (c) outstanding capabilities of the TiO2 nanoparticles for capturing CO intermediates (at Ti3+ donor sites), successfully promoted the enhancement of the electron external transport to Pt cathodes, and consequently improved the faradaic efficiency associated to the cathodic generation of H2

Intermediate band formation in a δ-doped like QW superlattices of GaAs/AlxGa1−xAs for solar cell design

It is reported a numerical computation of the local density of states for a δ-doped like QW superlattices of AlxGa1−xAs, as a possible heterostructure that, being integrated into a solar cell device design, can provide an intermediate band of allowed states to assist the absorption of photons with lower energies than that of the energy gap of the solar-cell constituent materials. This work was performed using the nearest neighbors tight-binding model including spin. The confining potential caused by the ionized donor impurities in δ-doped impurities seeding that was obtained analytically within the lines of the Thomas-Fermi approximation was reproduced here by the Al concentration x variation. This potential is considered as an external perturbation in the tight-binding methodology and it is included in the diagonal terms of the tight-binding Hamiltonian. Special attention is paid to the width of the intermediate band caused by the change in the considered aluminium concentration x, the inter-well distance between δ-doped like QW wells and the number of them in the superlattice. In general we can conclude that this kind of superlattices can be suitable for intermediate band formation for possible intermediate-band solar cell design

Homogeneous and Stratified Liquid-Liquid Flow Effect of a Viscosity Reducer: I. Comparison in parallel plates for heavy crude

Production of heavy crude oil in Mexico, and worldwide, is increasing which has led to the application of different methods to reduce viscosity or to enhance transport through stratified flow to continue using the existing infrastructures. In this context, injecting a viscosity improver that does not mix completely with the crude, establishes a liquid-liquid stratified flow. On the basis of a parallel plates model, comparing the increase of flow that occurs in the one-phase case which assumes a complete mixture between the crude and the viscosity improver against another stratified liquid-liquid (no mixing between the oil and compared improver); it was found that in both cases there is a flow increase for the same pressure drop with a maximum for the case in which the flow improver is between the plates and the crude

A comparison of human and mouse protein corona profiles of functionalized SiO2 nanocarriers

<p>Proteomic evaluation of the protein corona formed on SiO2 nanoparticles with human and mouse plasma.</p

Inflammatory response in human alveolar epithelial cells after TiO NPs or ZnO NPs exposure: Inhibition of surfactant protein A expression as an indicator for loss of lung function.

The increasing use of metal oxide nanoparticles (MONPs) as TiO2 NPs or ZnO NPs has led to environmental release and human exposure. The respiratory system, effects on lamellar bodies and surfactant protein A (SP-A) of pneumocytes, can be importantly affected. Exposure of human alveolar epithelial cells (A549) induced differential responses; a higher persistence of TiO2 in cell surface and uptake (measured by Atomic Force Microscopy) and sustained inflammatory response (by means of TNF-α, IL-10, and IL-6 release) and ROS generation were observed, whereas ZnO showed a modest response and low numbers in cell surface. A reduction in SP-A levels at 24 h of exposure to TiO2 NPs (concentration-dependent) or ZnO NPs (the higher concentration) was also observed, reversed by blocking the inflammatory response (by the inhibition of IL-6). Loss of SP-A represents a relevant target of MONPs-induced inflammatory response that could contribute to cellular damage and loss of lung function