Optical absorption of divalent metal tungstates: Correlation between the band-gap energy and the cation ionic radius

We have carried out optical-absorption and reflectance measurements at room temperature in single crystals of AWO4 tungstates (A = Ba, Ca, Cd, Cu, Pb, Sr, and Zn). From the experimental results their band-gap energy has been determined to be 5.26 eV (BaWO4), 5.08 eV (SrWO4), 4.94 eV (CaWO4), 4.15 eV (CdWO4), 3.9-4.4 eV (ZnWO4), 3.8-4.2 eV (PbWO4), and 2.3 eV (CuWO4). The results are discussed in terms of the electronic structure of the studied tungstates. It has been found that those compounds where only the s electron states of the A2+ cation hybridize with the O 2p and W 5d states (e.g BaWO4) have larger band-gap energies than those where also p, d, and f states of the A2+ cation contribute to the top of the valence band and the bottom of the conduction band (e.g. PbWO4). The results are of importance in view of the large discrepancies existent in prevoiusly published data.Comment: 16 pages, 3 figures, 1 tabl

Synchronization of the Frenet-Serret linear system with a chaotic nonlinear system by feedback of states

A synchronization procedure of the generalized type in the sense of Rulkov et al [Phys. Rev. E 51, 980 (1995)] is used to impose a nonlinear Malasoma chaotic motion on the Frenet-Serret system of vectors in the differential geometry of space curves. This could have applications to the mesoscopic motion of biological filamentsComment: 12 pages, 7 figures, accepted at Int. J. Theor. Phy

LICOR-Liquid Columns' Resonances

The aim of the experiment LICOR was the investigation of the axial resonances oi cylindrical liquid columns supported by equal circular coaxiaJ disks. In preparation ot the D-2 experiment a •heoreiical model has been developed, which exactly describes the small amplitude oscillations of finite cylindrical columns between coaxial circular disks. In addition, in terrestrial experiments the resonance frequencies of small liquid columns with up to 5 mm in diameter have been determined and investigations with density-matched liquids (silicon oil in a waierlmethanol mixture) have been performed. For the D-2 experiment LICOR the front disk and the rear disk lor use in the AFPM have been constructed and equipped with pressure sensors and the necessary electronics. The pressure exerted by the oscillating liquid column on trie supporting disks vsas as low as 10 Pa. Since the data downlink of the Materials Research Laboratory was just one signal oer second and channel, it was necessary to determine amplitude and phase of the pressure already in the LICOR disks. The D-2 experiment has been successfully performed. It has fully confirmed the theoretical models and remarkably supplements the experiments on small liquid columns and on density-matched columns

Supervised physical activity during pregnancy improves fetal cardiac response

Objetivo: Valorar la influencia de un programa de ejercicio físico durante la gestación en la adaptación de la frecuencia cardiaca fetal (FCF). Se espera encontrar una mejor adaptación de la FCF especialmente en cuanto a recuperaciones más rápidas. Método: 45 gestantes participantes en un ensayo clínico aleatorizado sin complicaciones ni contraindicaciones para el ejercicio fueron estudiadas durante el tercer trimestre de embarazo. Se midieron las siguientes variables: FCF en reposo, FCF post-ejercicio y tiempo de recuperación de la FCF a los niveles de reposo. Resultados: La FCF en reposo fue similar en ambos grupos. La FCF post-ejercicio fue significativamente mayor en el grupo control (GC) que en el grupo ejercicio (GE) en ambas pruebas, al 40% GE=138,5±6,4GE vs 141±7,5 GC (p=0,001), al 60% 141,6±10,8 GE vs 150,3±16,8GC. Lo mismo ocurre en los tiempos de recuperación, al 40% 78,2±95,7GE vs 328,4±315,2GC (p=0,001), al 60% 193,3±257,8 GE vs 542,6±482,9GC (p=0,003). Conclusión: El ejercicio físico desarrollado durante el embarazo tiene como consecuencia una mejor adaptación de la FCF post-ejercicio, así como recuperaciones más rápidas.Objective: To assess the influence of a physical activity program during pregnancy on the adaptation of the fetal heart rate (FHR). Greater adaptations and faster recovery are expected to find. Methods: 45 pregnant women included in a randomized control trial, all with uncomplicated pregnancies for exercise were studied in their third trimester of pregnancy. Rest FHR, post-exercise FHR and recovery time were assessed. Results: Rest FHR was similar in both groups. Post-exercise FHR were significantly higher in control group (CG) than in exercise group (EG) in both test, 40% 138,5±6,4EG vs 141±7,5CG (p=0,001), 60% 141,6±10,8EG vs 150,3±16,8CG. The same was found in recovery time, 40% 78,2±95,7EG vs 328,4±315,2CG (p=0,001), al 60% 193,3±257,8EG vs 542,6±482,9CG (p=0,003)

La enseñanza de las ciencias en algunas instituciones educativas del estado de jalisco

El objeto de investigación en este estudio es el diagnóstico de las prácticas y los saberes científicos de los agentes educativos, docentes y estudiantes, desde el nivel de educación preescolar hasta la educación superior tecnológica. La perspectiva es desde el marco de la cultura y el significado en uso. La investigación que se expone es descriptiva, de tipo diagnóstica, con un enfoque cualitativo. El método utilizado es la entrevista en grupos focales, con la intención de recuperar los significados referidos a la enseñanza, el aprendizaje y los saberes de las ciencias naturales y las matemáticas de los profesores del estado de Jalisco en México. Los reusltados dan pauta para conocer los significados cientìficos que cotidianamente utilizan los docentes y que se convierten en el referente desde donde enseñan las ciencias y las matemáticas

Farmers' management of rice varietal diversity in the mid-hills of Nepal: implications for on-farm conservation and crop improvement

Season-long monitoring of on-farm rice (Oryza sativa, L.) plots in Nepal explored farmers' decision-making process on the deployment of varieties to agroecosystems, application of production inputs to varieties, agronomic practices and relationship between economic return and area planted per variety. Farmers deploy varieties [landraces (LRs) and modern varieties (MVs)] to agroecosystems based on their understanding of characteristics of varieties and agroecosystems, and the interaction between them. In marginal growing conditions, LRs can compete with MVs. Within an agroecosystem, economic return and area planted to varieties have positive relationship, but this is not so between agroecosystems. LRs are very diverse on agronomic and economic traits; therefore, they cannot be rejected a priori as inferior materials without proper evaluation. LRs have to be evaluated for useful traits and utilized in breeding programmes to generate farmer-preferred materials for marginal environments and for their conservation on-farm

"A Decentralized Operations Concept for the European Payloads on the International Space Station"

The European Module Columbus of the International Space Station (ISS) is planned to be launched 2004. For its exploitation phase as well as for the early utilisation of the Space Station starting from 2003 onwards the operations procedures are now being defined in detail and the implementation of specific infrastructure has started. A decentralised operations concept will allow the investigators to perform their experiments using the telescience technique of remote experiment operations whenever feasible. User Support and Operation Centres (USOCs) will act as Facility Responsible Centres (FRC) performing the operations for multi user experiment facilities. The Columbus Control Centre (COL-CC) will perform the Columbus system operations, co-ordinate the European payload operations and provide the European Communications network. This paper gives an overview on the operations concepts and the tasks and set up of the involved sites

Dispersal of transgenes through maize seed systems in Mexico.

ObjectivesCurrent models of transgene dispersal focus on gene flow via pollen while neglecting seed, a vital vehicle for gene flow in centers of crop origin and diversity. We analyze the dispersal of maize transgenes via seeds in Mexico, the crop's cradle.MethodsWe use immunoassays (ELISA) to screen for the activity of recombinant proteins in a nationwide sample of farmer seed stocks. We estimate critical parameters of seed population dynamics using household survey data and combine these estimates with analytical results to examine presumed sources and mechanisms of dispersal.ResultsRecombinant proteins Cry1Ab/Ac and CP4/EPSPS were found in 3.1% and 1.8% of samples, respectively. They are most abundant in southeast Mexico but also present in the west-central region. Diffusion of seed and grain imported from the United States might explain the frequency and distribution of transgenes in west-central Mexico but not in the southeast.ConclusionsUnderstanding the potential for transgene survival and dispersal should help design methods to regulate the diffusion of germplasm into local seed stocks. Further research is needed on the interactions between formal and informal seed systems and grain markets in centers of crop origin and diversification

LIN-42, the Caenorhabditis elegans PERIOD homolog, Negatively Regulates MicroRNA Transcription

During C. elegans development, microRNAs (miRNAs) function as molecular switches that define temporal gene expression and cell lineage patterns in a dosage-dependent manner. It is critical, therefore, that the expression of miRNAs be tightly regulated so that target mRNA expression is properly controlled. The molecular mechanisms that function to optimize or control miRNA levels during development are unknown. Here we find that mutations in lin-42, the C. elegans homolog of the circadian-related period gene, suppress multiple dosage-dependent miRNA phenotypes including those involved in developmental timing and neuronal cell fate determination. Analysis of mature miRNA levels in lin-42 mutants indicates that lin-42 functions to attenuate miRNA expression. Through the analysis of transcriptional reporters, we show that the upstream cis-acting regulatory regions of several miRNA genes are sufficient to promote highly dynamic transcription that is coupled to the molting cycles of post-embryonic development. Immunoprecipitation of LIN-42 complexes indicates that LIN-42 binds the putative cis-regulatory regions of both non-coding and protein-coding genes and likely plays a role in regulating their transcription. Consistent with this hypothesis, analysis of miRNA transcriptional reporters in lin-42 mutants indicates that lin-42 regulates miRNA transcription. Surprisingly, strong loss-of-function mutations in lin-42 do not abolish the oscillatory expression patterns of lin-4 and let-7 transcription but lead to increased expression of these genes. We propose that lin-42 functions to negatively regulate the transcriptional output of multiple miRNAs and mRNAs and therefore coordinates the expression levels of genes that dictate temporal cell fate with other regulatory programs that promote rhythmic gene expression

Problem based learning case in a control undergraduate subject

Brescia, 4-6 Nov., 2015Student motivation is a relevant subject in many engineering areas including control and related subjects such as instrumentation. The classic approach to teaching has revealed itself a major obstacle for today’s students characterized by a being users of advanced technology in their daily life. Theoretical classes and even old laboratory experiments are of no appeal to them. In this paper a case study of the application of Problem Based Learning ideas is presented. The students are faced with a design problem in which they build a temperature control from basics components. The experience took place at the Engineering College of the University of Seville. The results shown are drawn from a three-year study and are compared with other undergraduate subjects