Enhanced diffusion and bound exciton interactions of high density implanted bismuth donors in silicon

This study reports the effect of an increasing ion dose on both the electrical activation yield and the characteristic properties of implanted bismuth donors in silicon. A strong dependence of implant fluence is observed on both the yield of bismuth donors and the measured impurity diffusion. This is such that higher ion concentrations result in both a decrease in activation and an enhancement in donor migration through interactions with mobile silicon lattice vacancies and interstitials. Furthermore, the effect of implant fluence on the properties of the Si:Bi donor bound exciton, D0X, is also explored using photoluminescence (PL) measurements. In the highest density sample, centers corresponding to the PL of bismuth D0Xs within both the high density region and the lower concentration diffused tail of the implanted donor profile are identifiable

The composition of the protosolar disk and the formation conditions for comets

Conditions in the protosolar nebula have left their mark in the composition of cometary volatiles, thought to be some of the most pristine material in the solar system. Cometary compositions represent the end point of processing that began in the parent molecular cloud core and continued through the collapse of that core to form the protosun and the solar nebula, and finally during the evolution of the solar nebula itself as the cometary bodies were accreting. Disentangling the effects of the various epochs on the final composition of a comet is complicated. But comets are not the only source of information about the solar nebula. Protostellar disks around young stars similar to the protosun provide a way of investigating the evolution of disks similar to the solar nebula while they are in the process of evolving to form their own solar systems. In this way we can learn about the physical and chemical conditions under which comets formed, and about the types of dynamical processing that shaped the solar system we see today. This paper summarizes some recent contributions to our understanding of both cometary volatiles and the composition, structure and evolution of protostellar disks.Comment: To appear in Space Science Reviews. The final publication is available at Springer via http://dx.doi.org/10.1007/s11214-015-0167-

The long-term Illinois rivers fish population monitoring program 2014

This report presents a summary of those data collected during segment 26(2014-15) of the Long-term Illinois Rivers Fish Population Monitoring Program(LTEF), an annual survey executed by members of the Illinois Natural History Survey with funds administered by the U.S. Fish and Wildlife Service and the Illinois Department of Natural Resources. Sampling for the LTEF program was conducted on: six reaches of the Illinois River Waterway, six segments or pools of the Mississippi River, and navigable portions of the Iroquois and Kankakee Rives. In all segments of the LTEF program, all fish species collected were accurately identified, tallied, measured, and weighed. The catch rates of sportfish species were calculated as the number of individuals collected per hour (CPUEN± standard error). Structural indices [Proportional Size Distribution (PSD) and Relative Weight (Wr)] were also calculated for species of interest to regional managers. Catch rates and species richness varied greatly among all sampling locations and sampling periods. Emerald Shiners and Gizzard Shad comprised the majority of the individuals caught, and Silver Carp and Common Carp accounted for the greatest proportion of the biomass collected in most sampling areas of the survey. The analysis of CPUEN and PSD trends in sportfish populations sampled by the program may indicate inter-annual recruitment patterns in sportfish populations around the state. Both Shovelnose Sturgeon and Blue Catfish were the two species most commonly encountered in the gill net surveys.IDNR Division of Fisheries Project F-101-R, Segment 26unpublishednot peer reviewe

A multi-parametric flow cytometric assay to analyze DNA–protein interactions

Interactions between DNA and transcription factors (TFs) guide cellular function and development, yet the complexities of gene regulation are still far from being understood. Such understanding is limited by a paucity of techniques with which to probe DNA–protein interactions. We have devised magnetic protein immobilization on enhancer DNA (MagPIE), a simple, rapid, multi-parametric assay using flow cytometric immunofluorescence to reveal interactions among TFs, chromatin structure and DNA. In MagPIE, synthesized DNA is bound to magnetic beads, which are then incubated with nuclear lysate, permitting sequence-specific binding by TFs, histones and methylation by native lysate factors that can be optionally inhibited with small molecules. Lysate protein–DNA binding is monitored by flow cytometric immunofluorescence, which allows for accurate comparative measurement of TF-DNA affinity. Combinatorial fluorescent staining allows simultaneous analysis of sequence-specific TF-DNA interaction and chromatin modification. MagPIE provides a simple and robust method to analyze complex epigenetic interactions in vitro

The prospective kindergarten and elementary school teachers’ understanding of the ratio concept

Este artigo centra-se na compreensão que futuros educadores e professores dos primeiros anos de escolaridade evidenciam do conceito de razão. No estudo participaram 81 estudantes do 2º ano da Licenciatura em Educação Básica, de uma universidade portuguesa, aos quais foi aplicado um questionário, incidindo em quatro dimensões: significado de razão; usos do conceito de razão; representação simbólica de razão; e representações para explicação do conceito de razão. Em termos de resultados, as maiores frequências foram obtidas para a: ideia de razão como comparação/relação entre grandezas; crença em que o conceito de razão pode ser usado em contextos diversificados; crença em que pode ser representado através de operações envolvendo letras, números ou apenas os sinais das operações, quando é pedida a sua representação simbólica, e através de diagramas e representações gráficas, quando é solicitada a descrição da sua explicação. Estes resultados revelam fragilidades no conhecimento matemático dos estudantes, sobretudo no que se refere à definição do conceito de razão e às suas representações.This paper focuses on the prospective kindergarten and elementary school teachers’ understanding of the ratio concept. Eighty-one undergraduates preparing to become kindergarten and primary school teachers, in a Portuguese university, participated in the study. They answered to a questionnaire aiming at evaluating their understanding of the ratio concept based on four dimensions: meaning of ratio; use of the ratio concept; symbolic representations of ratio; and representations for explaining the ratio concept. As far as results are concerned, the highest frequencies were obtained for: the idea of ratio as a comparison/relationship between two magnitudes; the belief that this concept is used in several contexts; the belief that it can be represented through operations with letters, figures or operation signals, as in symbolic representations; and through diagrams and graphical representations, as in representations for explaining the ratio concept. The results show weaknesses in prospective teachers’ mathematical knowledge of ratio, namely with regard to its definition and representations.Este trabalho contou com o apoio de Fundos Nacionais através da FCT – Fundação para a Ciência e a Tecnologia no âmbito do projecto PEst-OE/CED/UI1661/2014 do CIEd-UM.info:eu-repo/semantics/publishedVersio

Effects of interactions between the constituents of chitosan-edible films on their physical properties

The main objective of this work was to evaluate the effect of chitosan and plasticizer concentrations and oil presence on the physical and mechanical properties of edible films. The effect of the film constituents and their in-between interactions were studied through the evaluation of permeability, opacity and mechanical properties. The effects of the studied variables (concentrations of chitosan, plasticizer and oil) were analysed according to a 2 3 factorial design. Pareto charts were used to identify the most significant factors in the studied properties (water vapour, oxygen and carbon dioxide permeability; opacity; tensile strength; elongation at break and Young's modulus). When addressing the influence of the interactions between the films' constituents on the properties above, results show that chitosan and plasticizer concentrations are the most significant factors affecting most of the studied properties, while oil incorporation has shown to be of a great importance in the particular case of transport properties (gas permeability), essentially due to its hydrophobicity. Water vapour permeability values (ranging from 1. 62 × 10 -11 to 4. 24 × 10 -11 g m -1 s -1 Pa -1) were half of those reported for cellophane films. Also the mechanical properties (tensile strength values from 0. 43 to 13. 72 MPa and elongation-at-break values from 58. 62% to 166. 70%) were in the range of those reported for LDPE and HDPE. Based on these results, we recommend the use of 1. 5% (w/w) chitosan concentration to produce films, where the oil and plasticizer proportions will have to be adjusted in a case-by-case basis according to the use intended for the material. This work provides a useful guide to the formulation of chitosan-based film-forming solutions for food packaging applications.The author MA Cerqueira is a recipient of a fellowship from Fundacao para a Ciencia e Tecnologia (FCT, SFRH/BD/23897/2005) and BWS Souza is a recipient of a fellowship from the Coordenacao Aperfeicoamento de Pessoal de Nivel Superior, Brazil (Capes, Brazil)