Comparison of the Kinetic Parameters of Escherichia coli 0157:H7, Listeria monocytogenes and Salmonella typhimurium Derived from the Baranyi and Huang Models in a Chemically Defined Minimal Medium

Microbial growth can be characterized by parameters such as lag time, growth rate, and maximum population density at any specific point of time. Mathematical models that predict microbial growth of foodborne pathogens are increasingly used in the food industry as a viable alternative to traditional methods of microbial enumeration. The Baranyi model has been widely used as the primary model of choice by many authors because of its performance and accuracy. The most recently developed Huang model has been less implemented and few comparisons between the Baranyi and Huang models have been made when modeling pathogenic growth. For this research, pure cultures of E.coli O157:H7 ATCC 43895, Salmonella Typhimurium ATCC 14028 and Listeria monocytogenes V7 (serotype 1/2a) strains were sub-cultured overnight in Brain-Heart Infusion broth at 37 °C for 24 h. Bacteria were grown in a chemically defined media and sampled periodically at regular time intervals to estimate microbial growth. Three repetitions for the growth experiments were conducted. Kinetic parameters of both models from the growth curves were obtained using the USDA Integrated Pathogen Modeling Program. An analysis of variance was performed to determine whether there were any significant differences among means of parameter estimates at a 95.0% confidence level. Additionally, statistic indicators were used to validate the performance of the models based on the bias factor and the accuracy factor. Predictions made by the Baranyi and Huang models for each treatment were evaluated using the Acceptable Prediction Zone, Akaike’s Information Criterion, the Mean Square Error, and the Root Mean Square Error. Graphically, pathogenic growth as a function of time was well described by both models. Bacteria grew faster at 10 mM of glucose compared to a higher (15 mM) or lower (5 mM) nutrient concentration. Both models performed well as indicated by the MSE, RMSE, and AIC. The Baranyi model consistently estimated longer lag phases and higher growth rates than the Huang model. These results provide an insight into modeling growth of pathogens as a function of time and nutrient concentration and may help to choose between the Baranyi or Huang models when determining the best-fitting model

Green Security Plugin for Pervasive Computing using the HADAS toolkit

Energy is a critical resource in pervasive computing devices. However, information about energy consumption is not directly accessible through software development environments, making it difficult to reuse the knowledge provided by existing energy-consumption experimental studies. To address this limitation, this paper presents a solution to enrich Android Studio with energy consumption information. We have developed a Green Security Plugin that provides energy-aware information to developers that make use of Android Security API. This plugin has been developed taking advantage of the functionalities provided by the HADAS toolkit. HADAS is a repository of energy consuming concerns in which researchers can store the energy measures obtained during their experimental studies and developers can perform a sustainability analysis to make green design/implementation decisions.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tec

Study of the lateral pass width for conventional and ultrasonic vibrations-assisted ball burnishing on Ti-6Al-4V specimens

Ball burnishing is a technological finishing process based on plastic deformation of the objective surface by means of a hard ball gliding over it. Along with its easiness of application, possible on the same machine where machining was performed [1], burnishing is a comprehensive process able to achieve surface roughness improvements, and compressive residual stresses up to deep layers of the material [2]. Burnishing results have proved to be depending of a proper selection of parameters, which must be correctly controlled during the process. That is the case of burnishing force or the number of passes [3]. Among these parameters, the lateral pass width has proved to be influential on the surface roughness results, due to the behavior that most materials show when being plastically deformed. In effect, the applied force makes the material to flow to the borders of the burnishing imprint, giving way to a pile-up effect. This paper deals with indentation experiments on Ti-6Al-4V to deepen in the burnishing process of this material. Single burnishing imprints are geometrically characterized combining different levels of force, number of passes, and comparing the conventional process with that assisted with vibrations. An optimal lateral pass width is thus determined, and technological recommendations are made for future applications of the process.Peer ReviewedPostprint (author's final draft

Caracterización socio productiva y ambiental en las comunidades de Santo Domingo de Bull Bull y San Agustín de Bull Bull, en el II semestre 2015

Este trabajo se elaboró en base a información recopilada referente a las características sociales productivas y ambientales en las comunidades de Santo Domingo de Bull Bull y San Agustín de Bull Bull las cuales forman parte de las 149 comunidades que conforman el municipio El Tuma La Dalia. Estas poseen climas entre los 20 y 22 grados centígrados. Contribuyendo esto a la estabilidad de su nivel de producción predominando el desarrollo de cultivos del rubro agrícola, y actividades pecuarias a menor escala, de esta manera generando ingresos económicos para el sustento de las familias productoras. Es por ello que esta investigación se centró en estudiar la caracterización socio productiva y ambiental de las comunidades antes mencionadas, enfatizándose en los procesos de producción, así como también en el impacto que representan las actividades agrícolas y pecuarias en el desarrollo social y productivo desde el desgaste de los recursos naturales, como la contaminación de las fuentes de agua y el deterioro de los suelos. De igual forma las incidencias sociales que presentan estas comunidades, siendo una de ellas: la falta de acceso a la educación, la falta de accesibilidad de centros de salud, y el mal estado de las viviendas. También se describieron las actividades que afectan negativamente al medio ambiente, las cuales son, el aumento de las áreas de producción, el lavado de coralios. Lográndose finalmente desarrollar la aplicación del instrumento, la cual permitió conocer más de cerca las problemáticas mencionadas y describir a profundidad en el desarrollo de este estudi

Relaxation and Linear Programs on a Hybrid Control Model

Some optimality results for hybrid control problems are presented. The hybrid model under study consists of two subdynamics, one of a standard type governed by an ordinary differential equation, and the other of a special type having a discrete evolution. We focus on the case when the interaction between the subdynamics takes place only when the state of the system reaches a given fixed region of the state space. The controller is able to apply two controls, each applied to one of the two subdynamics, whereas the state follows a composite evolution, of continuous type and discrete type. By the relaxation technique, we prove the existence of a pair of controls that minimizes an incurred (discounted) cost. We conclude the analysis by introducing an auxiliary infinite-dimensional linear program to show the equivalence between the initial control problem and its associated relaxed counterpart

Small-scale forward smouldering experiments for remediation of coal tar in inert media

This paper presents a series of experiments conducted to assess the potential of smouldering combustion as a novel technology for remediation of contaminated land by water-immiscible organic compounds. The results from a detailed study of the conditions under which a smouldering reaction propagates in sand embedded with coal tar are presented. The objective of the study is to provide further understanding of the governing mechanisms of smouldering combustion of liquids in porous media. A small-scale apparatus consisting of a 100 mm in diameter quartz cylinder arranged in an upward configuration was used for the experiments. Thermocouple measurements and visible digital imaging served to track and characterize the ignition and propagation of the smouldering reaction. These two diagnostics are combined here to provide valuable information on the development of the reaction front. Post-treatment analyses of the sand were used to assess the amount of coal tar remaining in the soil. Experiments explored a range of inlet airflows and fuel concentrations. The smouldering ignition of coal tar was achieved for all the conditions presented here and self-sustained propagation was established after the igniter was turned off. It was found that the combustion is oxygen limited and peak temperatures in the range 800-1080 °C were observed. The peak temperature increased with the airflow at the lower range of flows but decreased with airflow at the higher range of flows. Higher airflows were found to produce faster propagation. Higher fuel concentrations were found to produce higher peak temperatures and slower propagation. The measured mass removal of coal tar was above 99% for sand obtained from the core and 98% for sand in the periphery of the apparatus

Comparison of thermal performance of 3D printer liquefiers through finite element models

Open source 3D printers have experienced an intense expansion during the last years, mainly because of their accessibility and the vast availability of information thanks to user communities. This fact presents researchers with a perfect context for hardware innovation, by improving the overall printing process, also in terms of durability of the printing machine. A 3D printer liquefier must transmit heat to the thermoplastic material in order to extrude it, reaching temperatures above 200 degrees for some materials like ABS on the tip of the nozzle. The design of the heating process must comply with keeping the balance between proper heating of the material and controlling the temperature along the extruding body, so that the printer itself is not harmed for overtemperature. On the other hand, the design must guarantee that the melting front is located in an intermediate point between the nozzle tip and the entrance of the raw material, to minimize pressure drops in the system, and so decreasing the demanding energy to the feeding motors. An alternative design of the heating system, Twist3D, is proposed in this paper.Peer ReviewedPostprint (published version

In What Ways do Formal and Informal Mentoring Experiences Influence New Administrators’ Leadership Practices

This qualitative study examined the ways formal and informal mentoring influences leadership practices in traditional urban schools. The PSEL standards anchored the leadership practices. Ten vice-principals and nine principals with less than 3 years of experience in their roles were interviewed. They included administrators promoted from within the district and those promoted externally. This study addressed the following overarching research questions: In what way(s) does mentoring influence new administrators’ leadership practices in traditional urban schools? Five subquestions supplemented this question: (a) In what way(s) does formal mentoring influence administrator leadership practices? (b) In what way(s) does informal mentoring influence administrator leadership practices? (c) How do these experiences vary from principal and vice-principal? (d) How do these experiences vary from those administrators promoted within the district and those external to the district? and (e) How do new administrators in traditional urban schools believe that mentoring and other supports can be improved? Findings from this study noted that mentoring influenced administrators’ leadership practices in all of the 10 PSEL standards. However, mentoring influenced leadership practices in PSEL 4 Curriculum, PSEL 6 Staff Capacity, PSEL 8 Family Engagement, PSEL 9 Operations, and PSEL 10 School Improvement the most. The data showed that formal mentoring influenced PSEL 9 Operations and PSEL 10 School Improvement the most, while informal mentoring influenced leadership practices the most in PSEL 4 Curriculum and PSEL 6 Staff Capacity. The data also revealed that peer group meetings added a significant value to the administrators’ formal mentoring experience and helped improve their leadership practices. Another theme that emerged was that most vice-principals and principals reported their supervisors as their informal mentors and described their relationship with their mentors with positivity. Finally, mentoring influenced the leadership practices of administrators promoted from within the district and those hired externally differently. The findings provide valuable insights into different stakeholders, including new administrators, mentors, district leaders, and policymakers, on how mentoring and other supports help new administrators address their jobs’ challenges and complexities. This study opens the opportunity for future research in a few areas. First, it is important to explore the influence mentoring has on new administrator job performance, not just leadership practices. Second, it is necessary to expand the research to explore the ways peer group meetings add value to the vice-principal’s experience and improve their leadership practices. Third, additional research should be conducted to explore the relationship between new administrators and their supervisors’ role in their growth and development. Fourth, further research should be done between mentor pairing and the effectiveness of mentoring on the development of new administrators. Fifth, continue to expand on this study’s findings of the influence mentoring has on administrators who are promoted from within the district and those promoted externally. Finally, this study focused on the ways mentoring influences leadership practices, but further studies should be done to determine how mentoring influences administrator performance

El autoconcepto en hombres y mujeres mexicanos

The aim of the present research is to know the characteristics of the self-concept, which prevail in Mexican men and women of different ages. It was used the self-concept questionnaire (Valdez-Medina, 1994), with validity for Mexican samples, and the study was carried out with a sample of 600 subjects distributed in six groups, according to their ages and sex. The result shows that Mexican women, except those with a college level, still see themselves as sentimental, affectionate, warm, romantic, and not as smart as men. These characteristics, besides clearly showing the sensibility, tenderness, love and peace Mexican women have, denote some socially worthwhile features in Mexican culture. Mexican women are seen as expressive, while, on the other hand, men are seen as instrumental