Conductance through an array of quantum dots

We propose a simple approach to study the conductance through an array of $N$ interacting quantum dots, weakly coupled to metallic leads. Using a mapping to an effective site which describes the low-lying excitations and a slave-boson representation in the saddle-point approximation, we calculated the conductance through the system. Explicit results are presented for N=1 and N=3: a linear array and an isosceles triangle. For N=1 in the Kondo limit, the results are in very good agreement with previous results obtained with numerical renormalization group (NRG). In the case of the linear trimer for odd $N$, when the parameters are such that electron-hole symmetry is induced, we obtain perfect conductance $G_0=2e^2/h$. The validity of the approach is discussed in detail.Comment: to appear in Phys. Rev.

Genes de virulencia y bacteriocinas en cepas de Enterococcus faecalis aisladas desde diferentes muestras clínicas en la Región del Maule, Chile

Padilla, C (reprint author), Univ Talca, Dept Microbiol, Talca, Chile.The presence of virulence genes (VG) and bacteriocins from different clinical samples was studied in Enterococcus faecalis isolated from urinary tract infections (UTI), bacteremia and endodontitis and was correlated with haemolysin and gelatinase activity. We evaluated the presence of VG by PCR in 150 strains of E. faecalis including cylA, aggA, efaA, eep, gelE, esp, as-48, bac31, entL50 A/B, entA, ent P, entB, enlA and ent1071. Haemolysin and gelatinase activity was studied. gelE and cylA genes expressed hemolysin and gelatinase, respectively. This activity was observed in some strains of bacteremia, UTI and endodontitis. The highest number of VG was detected in bacteremic strains, being aggA and entA genes the most frequent. efaA, esp, entA, entL50A/B were associated with their clinical origin (p <0.05). The most common genetic profile was aggA-eep-enlA-entL50A/B. E. faecalis from UTI, bacteremia and endodontitis presented different gene combinations. Some of the genes studied were related to their clinical origin. The results obtained in this study are similar to those reported in other countries

gtfB and spaP virulence genes in Streptococcus mutans strains and their relationship with the DMFT index

Universidad de Talca, Chile; Vásquez Ibarra, Sonia; Lobos Gilabert, Olga; Padilla Espinoza, CarlosObjetivo: El propósito de este estudio fue determinar la presencia de genes de virulencia en cepas de Streptococcus mutans (S. mutans) aisladas desde saliva de individuos de diferentes edades y asociarlas con el índice COPD y ceod según corresponda. Material y método: A partir de un total de 120 individuos de ambos sexos, se conformaron 4 grupos de 30 personas, que se separaron de acuerdo con los siguientes rangos etarios: 3-5, 6-9, 12-15 y mayores de 18 años. A cada individuo se le determinó el índice COPD y ceod según correspondiera y se realizó recuento salival de S. mutans. La detección de los genes de virulencia: gtfB y spaP se realizó por reacción en cadena de la polimerasa convencional. Resultados: Se estableció una asociación positiva entre el recuento bacteriano e índice COPD y ceod. El 100% de las cepas aisladas evidenciaron la presencia del gen gtfB y el 63,6% presentaron el gen spaP. No hubo evidencia estadísticamente significativa que relacionará un alto recuento bacteriano e índice COPD y ceod con la mayor presencia de genes que codifican factores de virulencia en cepas de S. mutans. Resumen: Aim: The aim of this study was to determine the presence of gtfB and spaP virulence genes in Streptococcus mutans strains isolated from saliva taken from individuals of different ages. Material and method: A total of 120 individuals of both sexes were studied. They were assigned to one of 4 groups, with 30 individuals in each one, according to age; 3-5, 6-9, 12-15, and older than 18 years old. DMFT (decayed, missing, and filled teeth) and DMFT indexes were determined in each participant, depending on his/her age. S. mutans microbial counts were performed. The gtfB and spaP virulence genes were detected using conventional PCR. Results: A positive association was found between microbial count and DMFT and DMFT indexes. All the isolated strains demonstrated the presence of gtfB, and 63.6% of the strains had spaP genes. No association was found between high bacterial counts or DMFT and DMFT indexes with the presence of genes that code for virulence factors in S. mutans strains

Aislamiento de bacterias periodontopáticas desde hemocultivos y ateromas obtenidos de pacientes con aterosclerosis y periodontitis

Carlos Padilla E. Laboratorio de Investigación Microbiológica, Facultad de Ciencias de la Salud, Universidad de Talca. Talca. Chile. Fono: 71-200492. Fax: 71-200439. E mail: [email protected]: Periodontitis is a common oral disease produced by bacterial species that reside in the subgingival plaque. These microorganisms have been associated to atherosclerosis and it is suggested that periodontitis is a cardiovascular risk factor. Aim: To isolate periodontal bacteria from blood and atheroma samples, from patients with atherosclerosis and periodontitis. Material and methods: Twelve patients with periodontitis and a clinical diagnosis of atherosclerosis and 12 patients with periodontitis but without atherosclerosis were studied. Blood samples were obtained immediately before and after scaling and root planing. The samples were incubated in aerobic and anaerobic conditions. One week after scaling, atheromatous plaques were obtained during endarterectomy in the 12 patients with atherosclerosis. These were homogenized and cultured for aerobic and anaerobic bacteria. Microorganisms were identified by means ofPCR. Results: Five patients with and two without atherosclerosis, had bacteremia after scaling and root planing. Bacterial species isolated from blood samples were the same found in periodontic pockets. Four atheromatous plaques of patients with bacteremia yielded positive cultures. The isolated bacteria were the same found in blood samples and periodontal pockets. Conclusions: Bacteremia occurred in seven of 24 patients after scaling and root planing. In four patients, the same species found in periodontic pockets and blood cultures were detected in atherosclerotic plaques obtained one week after the dental procedure

Evidencias de la divergencia entre la visualización y el razonamiento geométrico

El presente estudio tiene por objetivo exponer las principales problemáticas que intervienen en el desarrollo del proceso de enseñanza-aprendizaje asociados a la geometría elemental. Apoyados por la literatura y a través de un cuestionario de tres preguntas; se pondrá en evidencia cómo estudiantes de 8° básico han ido construyendo sus conocimientos geométricos en base a aprendizajes memorísticos y disconexos; lo que presenta un gran obstáculo en el posterior proceso de desarrollo y apropiación de habilidades como la visualización, razonamiento y justificación. Con base en las respuestas obtenidas identificamos que la noción de ciertos elementos principales de la geometría están construidas por apreciaciones visuales más que por características y/o representaciones conceptuales

The Relation between Attitudes toward Functional Foods and Satisfaction with Food-Related Life

Purpose – To assess the effect of attitudes towards functional foods (FF) on university students’ satisfaction with food-related life and to distinguish student typologies, considering that the attitudes towards FF are not homogeneous among consumers. Design/methodology - A survey was applied to 372 university students (mean age=20.4 years, SD=2.4) in southern Chile. The questionnaire included the Attitudes towards Functional Foods (AFF) questionnaire and the Satisfaction with Food-related Life (SWFL) scale, questions about consumption and knowledge about FF and socio-demographic characteristics. Findings – Using Confirmatory Factor Analysis (CFA) and Structural Equation Modelling, it was found that attitudes toward functional foods directly and significantly influence students’ satisfaction with food-related life. A cluster analysis applied to the Z-scores from the factors obtained by the CFA classified three typologies: Positive towards FF (36.3%), moderately positive towards FF (43.0%) and negative towards FF (20.7%). The positive towards FF type had a significantly greater SWFL score than the negative towards FF type. The types differ according to consumption and knowledge about FF. Research limitations/implications – This study was conducted in the context of only one country in South America. Originality/value – This study is the first that assesses the effect of AFF on satisfaction with food-related life in a sample of university students. Fostering positive attitudes towards FF will allow for a growth in the degree of satisfaction with food-related life of university students with features similar to those of the study sample

Evaluation of Teacher Training Needs in Engineering Pedagogy

In European countries, primarily in German-speaking countries, first of all, in Germany (Dresden), the concept of engineering pedagogy (EP) has existed for more than 70 years. In Eastern Europe, particularly in the Russian Federation, the tradition of EP has more than 20 years and shows an extensive network of universities actively participating in IGIP (International Society of Engineering Pedagogy). Several universities offer the IGIP curricula and work on various projects  related to majoring in engineering education and pedagogy in Russian Higher Education Institutions. In Spanish-speaking countries the concept of EP is relatively recent. Particularly, since 2014, the Technical University of Dresden (TU Dresden) works in cooperation with Chilean universities to strengthen engineering pedagogy and education in the university context. This goal was concretized through two cooperation projects “Engineering Didactics at Chilean Universities” (PEDING-Project) and “Strengthening engineering training at Chilean universities through practice partner-ships” (STING-Project), both financially supported by DAAD. The main goal of this paper is to present the results of a survey about teaching needs in engineering pedagogy in a Chilean university. In general, the results showed the high level of interest and motivation that a training course on engineering pedagogy specifically oriented for the academic staff of engineering faculties may have. The project was led by the International Center of Engineering Education (CIEI) at the University of Talca (Chile) under the pedagogical support of the TU Dresden (Germany)

The Caveolin-1 Connection to Cell Death and Survival

Nunez, S (Nunez, S.)[ 1,4 ] 1. Fac Med, CEMC, Lab Comunicac Celulares, Santiago, Chile. 4. Univ Talca, Fac Hlth Sci, Talca, ChileCaveolins are a family of membrane proteins required for the formation of small plasma membrane invaginations called caveolae that are implicated in cellular trafficking processes. In addition to this structural role, these scaffolding proteins modulate numerous intracellular signaling pathways; often via direct interaction with specific binding partners. Caveolin-1 is particularly well-studied in this respect and has been attributed a large variety of functions. Thus, Caveolin-1 also represents the best-characterized isoform of this family with respect to its participation in cancer. Rather strikingly, available evidence indicates that Caveolin-1 belongs to a select group of proteins that function, depending on the cellular settings, both as tumor suppressor and promoter of cellular traits commonly associated with enhanced malignant behavior, such as metastasis and multi-drug resistance. The mechanisms underlying such ambiguity in Caveolin-1 function constitute an area of great interest. Here, we will focus on discussing how Caveolin-1 modulates cell death and survival pathways and how this may contribute to a better understanding of the ambiguous role this protein plays in cancer