Scratch hardness as a quasi-intrinsic parameter to measure the scratch resistance of polymers

In this work four different polymers (acrylonitrile-butadiene-styrene, high-impact polystyrene, rubber-toughened polybutylene terephthalate, linear low-density polyethylene) were characterized in terms of their bulk (modulus and yield stress) and surface (scratch hardness) mechanical properties. The intrinsic time-dependence of the materials was addressed by performing DMA and compression tests at varying testing speed/frequency, exploiting time-temperature superposition and Eyring’s model to obtain data at strain rates compatible with scratch experiments. The latter were performed by applying different loading histories (constant depth or load) and indenters. Scratch hardness was determined using Pelletier’s model; it was demonstrated that such a parameter provides a reliable and almost intrinsic (i.e. loading history independent) evaluation of scratch resistance, seen as the resistance the material opposes to indenter penetration. The material compressive yield stress (evaluated at the strain rate relevant to scratch phenomena) was found to be the key controlling factor in determining scratch hardness. It can therefore be taken as a measure of the mechanical scratch resistance when evaluating the possible effects of variables such as material composition, crystallinity, physical ageing… Its relation with other aspects of the scratch phenomenon (in particular deformation recovery) was also explored, accounting for the specific deformation regime imposed by the indenter (transitioning from elastic to predominantly plastic)

In vivo analysis of staphylococcus aureus-infected mice reveals differential temporal and spatial expression patterns of fhuD2

Staphylococcus aureus is an opportunistic human pathogen and a major cause of invasive infections such as bacteremia, endocarditis, pneumonia and wound infections. FhuD2 is a staphylococcal lipoprotein involved in the uptake of iron-hydroxymate and is under the control of the iron uptake regulator Fur. The protein is part of an investigational multi-component vaccine formulation that has shown protective efficacy in several murine models of infection. Even though fhuD2 expression was shown to be upregulated in murine kidneys infected with S. aureus, it is unknown whether the bacterium undergoes increased iron deprivation during prolonged infection. Furthermore, different infection niches of S. aureus might provide different environments and iron availability resulting in different fhuD2 expression pattern within different host organs. To address these questions, we characterized the in vitro expression of the fhuD2 gene and confirmed Fur-dependent iron-regulation of its expression. We further investigated its expression in mice infected with a bioluminescent reporter strain of S. aureus expressing the luciferase operon under the control of the fhuD2 promoter. The emission of bioluminescence in different organs was followed over a seven-day time course, as well as quantitative real-time PCR analysis of the RNA transcribed from the endogenous fhuD2 gene. Using this approach, we could show that fhuD2 expression was induced during infection in all organs analyzed and that differences in expression were observed in the temporal expression profiles, and between infected organs. Our data suggest that S. aureus undergoes increased iron deprivation during progression of infection in diverse host organs and accordingly induces dedicated iron acquisition mechanisms. Since FhuD2 plays a central role in providing the pathogen with the required iron, further knowledge of the patterns of fhuD2 expression in vivo during infection is instrumental in better defining the role of this antigen in S. aureus pathogenesis and as a vaccine antigen

Effects of κ-CN Glycosylation on Rennet Coagulation Properties of Milk in Simmental Cattle

Contents of casein fractions are known to affect coagulation properties and cheese yield of milk, but studies on the effects of κ-CN composition on variation of coagulation properties of milk are still very scarce. Effects exerted by κ-CN composition on variation of milk coagulation properties (MCP) were investigated using 2,084 individual milk samples of Simmental cows. Rennet coagulation time (RCT), and curd firmness (A30) were measured using a computerized renneting meter. Milk protein composition and genotypes at CSN2, CSN3 and BLG were obtained by reversed-phase HPLC. The percentage ratios of κ-CN (κCN%), of Glycosylated-κ-CN (G-κCN%), and Unglycosylated-κ-CN (U-κCN%) to total casein were measured. The degree of glycosylation (GD) was measured as the percentage ratio of glycosylated-κ-CN to total κ-CN. A difference of 1.7 min (corresponding to 0.37 SD of the trait) was observed for the average RCT of the two extreme classes of κCN% content. RCT decreased when κCN% and G-κCN% increased, whereas U-κCN% exhibited a slightly unfavourable effect on the onset of the coagulation process. A slight decrease of RCT was also observed for high GD, although this effect was less clear than that of G-κCN%. A favourable effect of κCN%, G-κCN% and GD on A30 was also detected

Modelo de redes neuronales para maximizar la cobertura de camiones en chancadoras para Soc. Minera Cerro Verde S.A.A

Actualmente, durante los procesos de refrigerio y cambio de turno en las operaciones de la mina, se presentan retrasos en los equipos de acarreo, provocando una caída en el suministro de mineral en los chancadores a menos del 82% en promedio en una hora regular. Por ello, desarrollé un modelo de redes neuronales de aprendizaje profundo por refuerzo tipo Q-learning que asegura al menos el 90% del suministro de mineral, para lo cual generé un entorno de simulación análogo al entorno real, con datos obtenidos del análisis de la situación actual, permitiéndome probar a los agentes, en este caso los camiones, en diferentes escenarios considerando como acciones la selección de los equipos de carga y como recompensa el tiempo de ciclo, el tiempo de cola en los destinos y el tipo de material cargado, con estos resultados, entrené una red neuronal profunda, con la cual verifiqué que la solución propuesta asegura una cobertura de camiones en la trituradora superior al 90% durante las horas de refrigerio y cambios de turno, con tiempos de ejecución promedio menores a un milisegundo

Recensioni

- Donatella Della Porta, L’intervista qualitativa, Roma-Bari, Laterza, 2010, pp. 160 di Manlio Chiarot;- Valentina Grion, Narrare di sé. L’identità professionale dell’insegnante in servizio: riflessioni e proposte, Milano, Guerini, 2011, pp. 203 di Emma Gasperi;- Giorgio Chiosso, Alfabeti d’Italia. La lotta contro l’ignoranza nell’Italia unita, Torino, SEI, 2011, pp. 320 di Fabio Targhetta

Recensioni

- Mirella Chiaranda (a cura di), Storia comparata dell’educazione.Problemi ed esperienze tra Otto e Novecento, Milano, FrancoAngeli, 2010, pp. 315 di Margherita Cestaro;- Paola Milani, Marco Ius, Sotto un cielo di stelle. Educazione, bambini e resilienza, Milano, Raffaello Cortina, 2010, pp. 320 di Elena Pegoraro;- Sergio Tramma, Pedagogia della comunità. Criticità e prospettive educative, Milano, FrancoAngeli, 2009, pp. 125 di Manlio Chiarot

Mejora del proceso de reclutamiento y selección de personal para incrementar la productividad de producción de palta en una agroindustria

En la tesis titulada Mejora del proceso de reclutamiento y selección de personal para incrementar la productividad de producción de palta en una agroindustria, tuvo por objetivo general a mejorar los procesos de reclutamiento y selección de personal para incrementar la productividad en las operaciones de empaque de palta en una empresa agroindustrial, Trujillo 2022. Con metodología es del tipo aplicado, de diseño pre-experimental y transversal. La población fue todo el personal que trabaja en una campaña de producción de palta; muestreo probabilístico a conveniencia, y en este caso la muestra coincide con la población. En los resultados la producción diaria se encontró en 5.4 cajas/HH y el valor estándar de la productividad requerido por la empresa es de 6.5 cajas por hora hombre, la eficiencia física es del 83%. Luego de la aplicación de la mejora al proceso de reclutamiento y selección se logró un incremento de la productividad de 5.4 cajas/HH a 7.0 cajas/HH; y un indicador de merma reducido del 4.1% al 1.05%; y en cuanto a los productos observados se redujo del 0.90% al 0.51%. El valor del beneficio económico de la propuesta de mejora que asciende a una ganancia de S/ 28,292.0 por campaña de producción de palt

Effects of κ-CN Glycosylation on Rennet Coagulation Properties of Milk in Simmental Cattle

Contents of casein fractions are known to affect coagulation properties and cheese yield of milk, but studies on the effects of κ-CN composition on variation of coagulation properties of milk are still very scarce. Effects exerted by κ-CN composition on variation of milk coagulation properties (MCP) were investigated using 2,084 individual milk samples of Simmental cows. Rennet coagulation time (RCT), and curd firmness (A30) were measured using a computerized renneting meter. Milk protein composition and genotypes at CSN2, CSN3 and BLG were obtained by reversed-phase HPLC. The percentage ratios of κ-CN (κCN%), of Glycosylated-κ-CN (G-κCN%), and Unglycosylated-κ-CN (U-κCN%) to total casein were measured. The degree of glycosylation (GD) was measured as the percentage ratio of glycosylated-κ-CN to total κ-CN. A difference of 1.7 min (corresponding to 0.37 SD of the trait) was observed for the average RCT of the two extreme classes of κCN% content. RCT decreased when κCN% and G-κCN% increased, whereas U-κCN% exhibited a slightly unfavourable effect on the onset of the coagulation process. A slight decrease of RCT was also observed for high GD, although this effect was less clear than that of G-κCN%. A favourable effect of κCN%, G-κCN% and GD on A30 was also detected