Thermal Inactivation of Shiga Toxin-Producing \u3ci\u3eEscherichia coli\u3c/i\u3e in Foods

Emerging non-O157 Shiga toxin-producing Escherichia coli (STEC) were recently added to the zero tolerance policy by the USDA-FSIS. Therefore, the precise characterization of their thermal inactivation kinetics in different foods and the effect of stress on thermal inactivation are needed. This research aimed at determining the heat inactivation kinetics of non-O157 and O157 STECs in buffer and model food matrices and the effects of DnaK levels on thermal resistance after acid and heat-shock. Thermal inactivation was carried out in either in 2-ml glass vials or nylon vacuum-sealed bags for buffer and food (spinach, ground-beef, turkey deli-meat, pasta) samples, respectively. Vials or bags were immersed in a re-circulating water bath at various set temperatures for fixed time-intervals. Surviving bacteria were enumerated using Tryptic Soy Agar plates. D-values were calculated using first-order linear and Weibull (for pasta only) models. Total bacterial protein (using Bicinchonic acid assay) and the heat-shock protein (DnaK) concentration were measured (using competitive ELISA) before and after treating overnight-grown cells in Tryptic Soy Broth with either acid- (acetic acid pH 5.5 for 1 h) or heat-shock (46°C for 15 min). All experiments were performed in duplicate and replicated thrice, data were analyzed using SAS (pE. coli O157 and non-O157 in all tested samples, at 56°C D-values ranged from 5.57±0.38 to 15.39±0.14 min; at 58°C D -values ranged from 1.99±0.9 to 7.20±0.55 min and at 60°C D–values ranged from 0.99±0.07 to 2.86±0.22 min. Higher levels of DnaK were detected after sub-lethal injury with heat- or acid-shock that corresponded to enhanced thermal tolerance of all strains, except E. coli O111. D-values in buffer for un-shocked cells ranged from 1.49±0.35 to 2.21±0.17 min, heat-shocked cells from 2.04±0.35 to 2.83±0.35 min and acid-shocked cells from 2.32±0.29 to 4.09±0.29 min. Thus, acid- or heat-shock conditions that might occur during food processing need to be considered during design of thermal inactivation processes and product-formulation to prevent food-borne outbreaks. This study provides insights on the thermal inactivation parameters of O157 and non-O157 STEC in foods that would be beneficial to the food industry

Superconductivity in twisted bismuth bilayers

First-principles calculations for two twisted bismuth bilayers, each with 120 atoms, were studied by means of the electronic density of states and vibrational density of states. Metallic character at the Fermi level was found for the non-rotated sample as well as for each sample rotated 0.5{\deg}, 1.0{\deg}, 1.5{\deg}, 2.0{\deg}, 2.5{\deg}, 3.0{\deg}, 4.0{\deg}, 5.0{\deg}, 6.0{\deg}, 7.0{\deg}, 8.0{\deg} and 10{\deg} with respect to the static bilayer. Assuming that the superconductivity is BCS-type and the invariance of the Cooper pairing potential, we predict a maximum superconducting temperature T_c ~ 1.8 K for a magic angle of 0.5{\deg} degrees between the two bilayers, increasing the superconducting transition temperature from the experimentally measured value of 0.53 mK for the Wyckoff structure of crystalline bismuth.Comment: 12 pages, 6 figure

Communication Architecture for Tracking and Interoperable Services at Hospitals: A Real Deployment Experience

Any new hospital communication architecture has to support existing services, but at the same time new added features should not affect normal tasks. This article deals with issues regarding old and new systems’ interoperability, as well as the effect the human factor has in a deployed architecture. It also presents valuable information, which is a product of a real scenario. Tracking services are also tested in order to monitor and administer several medical resources

Influence of Traction Battery Arrangement on Risk of Thermal Runaway and Loads Suffered by Electric Vehicle Occupant during Side Collision

In the current electric vehicles, the purpose of the traction battery is to store energy. When designing this battery, different parameters are considered to arrange the battery/module/cells in the mechanically and thermally safest configuration. Moreover, the battery layout must produce correct dynamic behavior during collisions. In the present study, different battery configurations plus added energy absorbers were analyzed. To achieve this, an internal combustion vehicle modeled with finite elements was applied as the reference model. The structural behavior of the different battery configurations in the event of a side collision was examined. First, the safest arrangement was established with respect to both cabin intrusion and thermal runaway propagation. Second, the safest arrangement that guarantees the safety of the occupants in the event of a side collision was analyzed using MADYMO. This software includes experimentally validated dummies that allow insight into the stresses experienced by occupants. The results of the analysis showed that battery pack inclusion in the vehicle increases the stiffness of the car floor, resulting in fewer intrusions into the passenger compartment. Therefore, safety of the occupants is increased. However, none of the configurations analyzed showed sufficient safety against thermal runaway. This study contains sufficient contributions to the new body of knowledge, since there is no study that analyzes the safest configuration in terms of battery behavior with respect to intrusion into the passenger compartment and the effect of thermal runaway, together with the fact that this is the safest configuration for occupants after analyzing the injuries they experience in a side collision for the different configurations

Enhanced cohesive zone model to predict delamination behavior of carbon/epoxy laminated curved beams

This paper proposes an enhanced Cohesive Zone Model (CZM) for the prediction of delamination in curved beams of epoxy carbon laminates. This model improves the conventional CZM, taking into account the fiber-bridging phenomenon and the variation of the element size among the thickness in the curved zone. The advantages of the enhanced model are underlined when results obtained from the numerical simulations of a four-point-bending test in compliance with ASTM D6415 standard are compared with the corresponding experimental results. The prediction of the post-failure behavior obtained with this model is closer to that obtained experimentally than with the conventional model

La estabilidad estructural del suelo y turbidez del agua en sistemas agroforestales bajo diferentes niveles de insumo en el cultivo de café (coffea arabica L.), Masatepe, Nicaragua 2015

La estabilidad estructural de suelo y la calidad del agua son factores importantes relacionados a la conservación del suelo y agua en cualquier ecosistema; para tal caso se seleccionaron diferentes sistemas agroforestales en el cultivo de café. (Coffea arabicaL) C.V. PACAS, la plantación de café bajo sombra como Inga laurina + Simarouba glauca (ILSG), Simaruba glauca + Tabebuia rosea (SGTR), Samanea saman + Inga laurina (SSIL), Samanea saman + Tabebuia rosea (SSTR) y a pleno sol y niveles de insumos; Convencional Moderado (MO) Convencional Intensivo (CI), Orgánico Moderado (OI) Orgánico Intensivo (OI), son los tratamientos a evaluar en las tres repeticiones para la extracción de los datos de esta variable se utilizó el método del tamiz húmedo (modelo wetsieving apparatus) las muestras fueron sometidas a dos tiempos de exposición 3 y 5 minutos. El ensayo se realizó en la época seca del 2015 en el Centro Nacional de Estudios de Cooperativismo (CENECOOP) ubicado en Masatepe, Nicaragua. Se realizó un ANDEVA, bajo arreglo bifactorial en parcelas divididas mostro diferencias significativas en estabilidad estructural de suelo a los 5 minutos de exposición y para calidad del agua se empleó el método simple. Los resultado muestran una relación entre materia orgánica vs estabilidad estructural con r =99.45,materia orgánica vs turbidez con r =96.66, la textura vs materia orgánica r= 95.51, Es importante resaltar que el efecto de la materia orgánica tiene un efecto importante en la conservación, mejoramiento de la estabilidad estructural y la calidad del agua en sistemas agroforestales debidamente manejado para la protección del suelo en condiciones de laderas