Resonant transmission of light through finite chains of subwavelength holes

In this paper we show that the extraordinary optical transmission phenomenon found before in 2D hole arrays is already present in a linear chain of subwavelength holes, which can be considered as the basic geometrical unit showing this property. In order to study this problem we have developed a new theoretical framework, able to analyze the optical properties of finite collections of subwavelength apertures and/or dimples (of any shape and placed in arbitrary positions) drilled in a metallic film.Comment: Accepted for publication in Phys. Rev. Let

Biological synthesis of fluorescent nanoparticles by cadmium and tellurite resistant Antarctic bacteria: exploring novel natural nanofactories

Indexación: Web of ScienceBackground: Fluorescent nanoparticles or quantum dots (QDs) have been intensely studied for basic and applied research due to their unique size-dependent properties. There is an increasing interest in developing ecofriendly methods to synthesize these nanoparticles since they improve biocompatibility and avoid the generation of toxic byproducts. The use of biological systems, particularly prokaryotes, has emerged as a promising alternative. Recent studies indicate that QDs biosynthesis is related to factors such as cellular redox status and antioxidant defenses. Based on this, the mixture of extreme conditions of Antarctica would allow the development of natural QDs producing bacteria. Results: In this study we isolated and characterized cadmium and tellurite resistant Antarctic bacteria capable of synthesizing CdS and CdTe QDs when exposed to these oxidizing heavy metals. A time dependent change in fluorescence emission color, moving from green to red, was determined on bacterial cells exposed to metals. Biosynthesis was observed in cells grown at different temperatures and high metal concentrations. Electron microscopy analysis of treated cells revealed nanometric electron-dense elements and structures resembling membrane vesicles mostly associated to periplasmic space. Purified biosynthesized QDs displayed broad absorption and emission spectra characteristic of biogenic Cd nanoparticles. Conclusions: Our work presents a novel and simple biological approach to produce QDs at room temperature by using heavy metal resistant Antarctic bacteria, highlighting the unique properties of these microorganisms as potent natural producers of nano-scale materials and promising candidates for bioremediation purposes.http://microbialcellfactories.biomedcentral.com/articles/10.1186/s12934-016-0477-

Economic Impact of Quinoa Consumption in the Diet of University Students Case: ESPOCH Agroindustry Career

Quinoa is an ancestral plant, originally cultivated in the Andes. It is a product with exceptional nutritional value and it has been important in the socio-economic evolution of the Andean population. Food is considered a natural, ecological and economic product. Since quinoa has the same amount of protein as meat, it can complement people’s daily food at a very low cost. The objective of this work was to carry out market research to determine the knowledge of university students about the protein value of quinoa in their diet and its purchasing power. The design was semi-experimental and descriptive. The study population was students of the Agroindustry degree of the Faculty of Livestock Sciences of the Higher Polytechnic School of Chimborazo. Data were collected through a questionnaire, which contained ten open and closed questions. 192 people were surveyed. Data were also collected through direct observations in the food laboratory. The results indicated a high level of ignorance of the benefits of quinoa. A lack of knowledge about quinoa can result in smaller economic benefits for those who produce this high protein food, which in most cases are indigenous communities. Keywords: economic, consumption, quinoa, incidence. Resumen El presente trabajo, tiene por objetivo realizar una investigación de mercado, para determinar el conocimiento de los estudiantes universitarios, sobre el valor proteico de la quinua en su alimentación y el poder adquisitivo de la misma. El diseño es de tipo semi experimental y descriptiva. La población en estudio, son estudiantes de la carrera de Agroindustria de la Facultad de Ciencias Pecuarias de la Escuela Superior Politécnica de Chimborazo; para la recolección de datos se utilizó la técnica de la encuesta, apoyado en el cuestionario de la encuesta, como instrumento, la cual contiene diez preguntas abiertas y cerradas, basados en los objetivos de la investigación, se consideró una muestra de 192 personas, con la finalidad de obtener datos importantes que han sido analizados y explicados de forma descriptiva en el proceso, así mismo la observación directa que se realizó en el laboratorio de alimentos, mediante pruebas que se realizaron. La quinua es una planta ancestral, cultivada originariamente en los Andes, producto con excepcional valor nutritivo, e importante evolución socio económica de la población Andina. Alimentariamente es considerado un producto natural, ecológico y económico, ya que tiene la misma cantidad de proteína como la carne, puede complementar el alimento diario de cada persona a un costo muy bajo. Los resultados obtenidos, permitieron identificar el nivel de desconocimiento de los beneficios de la quinua, dando como resultado el mínimo impacto económico en quienes producen este alimento proteico, que, en la mayoría de los casos, son comunidades indígenas que buscan emprender. Palabras clave: economía, consumo, quinua, incidencia

Validation of two complementary oral-health related quality of life indicators (OIDP and OSS 0-10 ) in two qualitatively distinct samples of the Spanish population

<p>Abstract</p> <p>Background</p> <p>Oral health-related quality of life can be assessed positively, by measuring satisfaction with mouth, or negatively, by measuring oral impact on the performance of daily activities. The study objective was to validate two complementary indicators, i.e., the OIDP (Oral Impacts on Daily Performances) and Oral Satisfaction 0–10 Scale (OSS), in two qualitatively different socio-demographic samples of the Spanish adult population, and to analyse the factors affecting both perspectives of well-being.</p> <p>Methods</p> <p>A cross-sectional study was performed, recruiting a Validation Sample from randomly selected Health Centres in Granada (Spain), representing the general population (n = 253), and a Working Sample (n = 561) randomly selected from active Regional Government staff, i.e., representing the more privileged end of the socio-demographic spectrum of this reference population. All participants were examined according to WHO methodology and completed an in-person interview on their oral impacts and oral satisfaction using the OIDP and OSS 0–10 respectively. The reliability and validity of the two indicators were assessed. An alternative method of describing the causes of oral impacts is presented.</p> <p>Results</p> <p>The reliability coefficient (Cronbach's alpha) of the OIDP was above the recommended 0.7 threshold in both Validation and Occupational samples (0.79 and 0.71 respectively). Test-retest analysis confirmed the external reliability of the OSS (Intraclass Correlation Coefficient, 0.89; p < 0.001) Some subjective factors (perceived need for dental treatment, complaints about mouth and intermediate impacts) were strongly associated with both indicators, supporting their construct and criterion validity. The main cause of oral impact was dental pain. Several socio-demographic, behavioural and clinical variables were identified as modulating factors.</p> <p>Conclusion</p> <p>OIDP and OSS are valid and reliable subjective measures of oral impacts and oral satisfaction, respectively, in an adult Spanish population. Exploring simultaneously these issues may provide useful insights into how satisfaction and impact on well-being are constructed.</p

Ratios of sums of two Fibonacci numbers equal to powers of 2

In this paper, we find all solutions to the Diophantine equation $F_n+F_m=2^a(F_r+F_s)$, where $\{F_k\}_{k\ge 0}$ is the Fibonacci sequence. This paper continues and extends a previous work which investigated the powers of 2 which are sums of two Fibonacci numbers