Effect of debris size on the tribological performance of thermally sprayed coatings

This research aims to assess the effect of the debris particle size on the tribological performance and lubrication regime parameters of a Ni-based alloy coating. This is a key industrial problem, and its resolution can contribute to better machine endurance and proper maintenance. The debris particles are simulated by hard Al2O3 particles of size ranging from nanometers to 45 μm and dispersed in an oil lubricant. The coating studied is NiCrBSi deposited by flame spraying technique followed by the Surface Flame Melting (SFM) process. The counterpart disk sample was fabricated from quenched and tempered F-5220 steel (in line with A681(O1) ASTM). This pair was tested under linear sliding contact. Our results show that the addition of alumina particles contributes to a significant increase in wear, particularly for the largest particles (micrometric size). In the case of micrometric particles, it is possible to observe the formation of higher surface roughness, numerous microgrooves, and plastic flow of NiCrBSi coating perpendicular to the sliding direction, resulting in higher loss of volume. It was found that the actual surface roughness (obtained as a function of the debris particle size) allows better identification and prediction of the lubrication regime for wear processes instead of the traditional approach that uses the initial surface roughness as a parameter

Carboniferous stratigraphie and structure oí the Pisuerga-Carrion unit. NW Spain

[Resumen] La Unidad del Pisuerga-Carri6n (UPC) constituye la parte más externa (Cuenca de antepaís) de la Zona Cantábrica (ZC). Los materiales silúrico-dev6nicos, con facies más profundas que los del resto de la ZC, están circunscritos a unidades alóctonas desenraizadas emplazadas como mantos gravitacionales. El sistema carbonífero se caracteriza por la presencia de series potentes con notables variaciones de facies y potencias. Durante el Carbotírtero inferior es característica la prensencia de facies homogéneas y una baja tasa de sedimentación en un ambiente claramente preorogénico. A partir del Namuriese se inicia la sedimentación sinorogénica, abundan las facies originadas a partir de pendientes submarinas o ligadas a relieves emergidos. La persistencia de las condiciones sinorogénicas desde el Namuriense hasta el Estefaniense A y la relativa proliferación de discordancias son también rasgos peculiares de éste área. En este trabajo se propone un esquema de unidades litoestratigráficas, a las que informalmente se asigna la categoría de «grupo~, separadas por discordancias y/o conglomerados de continuidad lateral limitada. Se considera que estos «grupos~ representan «cuñas clásticas~ relacionadas con el emplazamiento de unidades alóctonas concretas, por lo que se propone también un modelo relacionando grupos litoestratigráficos y unidades alóctonas o mantos. Se establecen los rasgos generales de la estructura de la UPC diferenciando dos tipos de manta> (gravitacionales y enraizados), así como las relaciones entre éstos y las diversas generaciones de pliegues y esquistosidades. Por último se propone un modelo de evolución tectonosedimentaria para la UPC, claramente ligado a la evolución estructural de toda la ZC como una cadena arqueada, en el que se considera que el carácter centrípeto de las vergencias en la ZC origina estructuras en la UPC con vergencias igualmente centrípetas así como cuñas elásticas, genéticamente relacionadas, con depocentros situados en posiciones distintas a través del tiempo.[Abstract] The Pisuerga-Carrion Unit (PCU) forms the most external part (foreland basin) of the Cantabrian Zone (Cl). Siluro-devonian rocks with deeper facies than those of the CZ are limited to alloctonous unit wich have been regarded as gravitational nappes. The main characteristic of Carboniferous system is the presence of thick series with remarkable facies and thickness lateral changes. The outstanding feature of lower Carboniferous is the low rate of sedimentation and the fairly uniform sedimentary facies in a preorigenic environment. The synorogenic sedimentation starts in the Namurian, the most frecuent facies are those originated in submarine slopes or those related to subaerial reliefs. The continous synorogenic conditions from Namurian to the Stephanian A stage and the presence of numerous unconformities and lateral sedimentary changes constitue sorne of the characteristics of this area. In this paper a lithostratigraphic sketch are suggested; alllithostratigraphic units were integrated in higher rank units informally called «groups». These «groups» are separated by conglomerates and /or unconformities of limited lateral extension and would represent clastic wedges generated in the front of the nappes Both clastic wedges and nappes are related in this sketch. The general features of the PCU structure are found and two types of nappes (generated by gliding and /or spreading) are stablished, in this way, severa! Generations of folds and cleavages are related with both types of nappes. Lately a tectonosedimentary evolution model for the PCU which would be directly linked to the structural evolution of the Cl. The centripetal character of the vergences in the Cl produced structures (nappes and related folds) in the PCU that have an equally centripetal vergence and originated a synorogenic clastic wedges with depocenters located, in time, in several positions

Changes in protein synthesis and acid tolerance in Clostridium perfringens type A in response to acid shock

The induction of acid-shock proteins and the degree of acid resistance conferred on Clostridium perfringens by acid shock, and the kinetics of this resistance were determined. A sublethal acid shock at pH 4.5 for 20 min increased the acid tolerance of cells at least fifteenfold. The acquired tolerance was maintained for 3 h after acid treatment. The response of the microorganism to acid shock was also examined by analysis of pulse-labeled proteins. Five acid-shock proteins (molecular weights 120, 84, 58, 45 and 17 kDa) were identified by polyacrylamide gel electrophoresis

Low molecular weight ϵ-caprolactone-pcoumaric acid copolymers as potential biomaterials for skin regeneration applications

ϵ-caprolactone-p-coumaric acid copolymers at different mole ratios (ϵ-caprolactone:p-coumaric acid 1:0, 10:1, 8:1, 6:1, 4:1, and 2:1) were synthesized by melt-polycondensation and using 4-dodecylbenzene sulfonic acid as catalyst. Chemical analysis by NMR and GPC showed that copolyesters were formed with decreasing molecular weight as p-coumaric acid content was increased. Physical characteristics, such as thermal and mechanical properties, as well as water uptake and water permeability, depended on the mole fraction of pcoumaric acid. The p-coumarate repetitive units increased the antioxidant capacity of the copolymers, showing antibacterial activity against the common pathogen Escherichia coli. In addition, all the synthesized copolyesters, except the one with the highest concentration of the phenolic acid, were cytocompatible and hemocompatible, thus becoming potentially useful for skin regeneration applications

The significance of «Peña Prieta» stock in the magmatism of the «Pisuerga-Carrion» unit (Cantabrian Zone, N of Spain)

[Resumen] Se describe en este trabajo el stock intrusivo de Peña Prieta, el mayor y más complejo, estructural y petrológicamente, del conjunto de rocas ígneas emplazadas en la UPC (Zona Cantábrica) durante una etapa de actividad ígnea tardihercínica de naturaleza calcoalcalina. Asimismo se sugiere una hip6tesis general para justificar el desarrollo de este magmatismo postectónico en la parte más externa de una cordillera de plegamiento y un emplazamiento en condiciones permitidas, con ciertas afinidades con modelos de emplazamiento por subsidencia de caldera, para el stock considerado.[Abstract] The Peña Prieta intrusive stock is described in this paper. It is the largest intrusive body belonging to the set of igneous rocks emplaced in the PCU (Cantabrian Zone) during a calc-alkaline late hercynian magmatic stage. It is also the most complex on the basis of its structural and petrological features. A general hypothesis is suggested to justify the occurence of this postectonic magmatism in the most external part (foreland basin) of the folded belt. We also propose a model of emplacement for this stock, under permisive conditions, which shows sorne resemblances with the cauldron subsidence model

Depositional style and tectonostratigraphic evolution of El Bierzo Tertiary sub-basin (Pyrenean orogen, NW Spain)

El Bierzo Tertiary sub-basin (Oligocene-Miocene, NW Spain) is a small remnant of the western Duero Basin, a nonmarine broken foreland basin developed in front of the Cantabrian Mountains (Pyrenean orogen). The alluvial infill of El Bierzo Tertiary sub-basin consists of a coarsening-upward succession from fluvial (Toral Formation) to alluvial-fan deposits (Las Médulas Formation) and reflects the uplift of the Cantabrian Mountains, in the north, and then of the related Galaico-Leoneses Mountains, in the south. These alluvial deposits show signs of having been laid down mainly by catastrophic flows (flood-dominated systems) and consist of three main depositional elements, namely, flood-plain fines, and lobe and channel conglomerates and sandstones. The vertical stacking patterns of these deposits and their relationships to the Alpine structures permit to unravel the tectonosedimentary evolution of the basin. The alluvial-plain element is the main constituent of a wide unconfined alluvial plain (Toral Formation) during the early stages of basin evolution, whereas the channel and lobe elements form a set of relatively small, laterally confined alluvial fans (Las Médulas Formation) fed first from the north and then from the south. Las Médulas deposits form two superposed units, the lower unit, cut by the Alpine thrusts, shows a progradational character, and the upper unit, which postdates most of the thrusts but not the youngest ones, displays a composite retrogradational trend. This organisation reflects the interplay between thrust emplacement and alluvial-fan sedimentation and suggests that maximum progradation took place during the climax of Alpine deformation

Secadero solar forzado para productos agricolas

Se propone un secadero solar forzado, formado por un colector solar y una cámara de secado donde se coloca el producto. El colector construido tiene una cobertura de policarbonato de 7.5 m2 . Las paredes de la cámara construida con placas de cemento autoclavadas, tiene una cubierta de policarbonato y una puerta de ingreso en la parte posterior. En el interior se colocan bandejas apiladas donde se coloca el producto. El aire de secado fluye a través del producto por circulación forzada impulsado por medio de dos ventiladores de 0,45 kW, colocados debajo de las bandejas. Para el primer ensayo se eligió papa cortada en bastones. El contenido de humedad de las papas se redujo al 20 % durante 2 días de secado. Se analizan los resultados experimentales durante el tiempo de secadoFil: García, V.. Universidad Nacional de Catamarca; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Salta. Instituto de Investigaciones en Energía no Convencional; ArgentinaFil: Iriarte, Adolfo Antonio. Universidad Nacional de Catamarca; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Salta. Instituto de Investigaciones en Energía no Convencional; ArgentinaFil: Justinovich, S.. Universidad Nacional de Catamarca; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Salta. Instituto de Investigaciones en Energía no Convencional; ArgentinaFil: Angel, L.. Universidad Nacional de Catamarca; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Salta. Instituto de Investigaciones en Energía no Convencional; ArgentinaFil: Heredia, T.. Universidad Nacional de Catamarca; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Salta. Instituto de Investigaciones en Energía no Convencional; Argentin