Journals
2011 EN
Wasyl Wasylkiwskyj · Shahram Shiri
Deep shadowing of a normally incident plane wave by an opaque circular disk is partially negated by the formation of a region of strong intensity surrounding the axis passing normally through the disk center. This local intensity enhancement, historically referred to as the Poisson Spot (also known as the Spot of Arago), has been the principal source of difficulties in applications where a significant reduction of the incident intensity is essential. In particular, the NASA Terrestrial Planet Finder's (TPF) mission requires suppression of direct starlight by at least 10 orders of magnitude over the entire visible spectral range. One technique that has been proposed for blocking the direct starlight is to use a rotationally symmetric disk with petallike segments along its boundary. We find that, even though such configurations could, indeed, theoretically provide the desired intensity reduction, they would require unreasonably small radii of curvature at the petals' tips (in the range of micrometers). When the radii of curvature are increased to 3 mm, the intensity reduction drops to a modest 5 to 6 orders of magnitude. Given that for the NASA's TPF mission the proposed occulter radius would be on the order of 25 m, even the 3 mm radius of curvature would be too small for any practical implementation. Further increases of the radius of curvature result in progressively poorer intensity suppression. As an alternative solution we propose an apodized circular disk. We show that with an optimized apodization function, intensity reductions of at least 10 orders of magnitude can be achieved over the entire visible spectral range. Numerical results are presented for parameters appropriate to the NASA TPF mission.
Journals
2011 EN
Maria-Guglielmina Pelizzo · Alain Jody Corso · Paola Zuppella
+3 more
In this work we present results of an new experiment related to low energy protons bombardments on nano-structured optical coatings. Multilayer structures protected by different capping layers have been fabricated and exposed to low energy protons (1 keV). The experimental parameters have been selected considering the potential application of the coatings to solar mission instrumentation. Future solar missions will investigate the Sun from very close distances and optical components are constantly exposed to low energy ion particles irradiation. The experiment was repeated fixing the proton flux while varying the total dose accumulated. Results show that physical processes occurred at the uppermost interfaces can strongly damage the structure.
Journals
2011 EN
Frédéric Mélin · Giuseppe Zibordi · JeanFrançois Berthon
+5 more
The uncertainties associated with MERIS remote sensing reflectance (RRS) data derived from the SeaWiFS Data Analysis System (SeaDAS) are assessed with field observations. In agreement with the strategy applied for other sensors, a vicarious calibration is conducted using in situ data from the Marine Optical BuoY offshore Hawaii, and leads to vicarious adjustment factors departing from 1 by 0.2% to 1.6%. The three field data sets used for validation have been collected at fixed stations in the northern Adriatic Sea and the Baltic Sea, and in a variety of European waters in the Baltic, Black, Mediterranean and North Seas. Excluding Baltic waters, the mean absolute relative difference |ψ| between satellite and field data is 10-14% for the spectral interval 490-560 nm, 16-18% at 443 nm, and 24-26% at 413 nm. In the Baltic Sea, the |ψ| values are much higher for the blue bands characterized by low RRS amplitudes, but similar or lower at 560 and 665 nm. For the three validation sets, the root-mean-square differences decrease from approximately 0.0013 sr-1 at 413 nm to 0.0002 sr-1 at 665 nm, and are found similar or lower than those obtained for SeaWiFS or MODIS-Aqua. As derived from SeaDAS, the RRS records associated with these three missions thus provide a multi-mission data stream of consistent accuracy.
Journals
2011 EN
R Myers
The mission of the Encyclopedia of DNA Elements (ENCODE) Project is to enable the scientific and medical communities to interpret the human genome sequence and apply it to understand human biology and improve health. The ENCODE Consortium is integrating multiple technologies and approaches in a collective effort to discover and define the functional elements encoded in the human genome, including genes, transcripts, and transcriptional regulatory regions, together with their attendant chromatin states and DNA methylation patterns. In the process, standards to ensure high-quality data have been implemented, and novel algorithms have been developed to facilitate analysis. Data and derived results are made available through a freely accessible database. Here we provide an overview of the project and the resources it is generating and illustrate the application of ENCODE data to interpret the human genome.
Public Library of Science
Journals
2011 EN
Yukiko Nariai · Saki Hayashi · Satoru Morita
+5 more
Periodical cicadas ( Magicicada spp.) in the USA are divided into three species groups (-decim, -cassini, -decula) of similar but distinct morphology and behavior. Each group contains at least one species with a 17-year life cycle and one with a 13-year cycle; each species is most closely related to one with the other cycle. One explanation for the apparent polyphyly of 13- and 17-year life cycles is that populations switch between the two cycles. Using a numerical model, we test the general feasibility of life cycle switching by the introduction of alleles for one cycle into populations of the other cycle. Our results suggest that fitness reductions at low population densities of mating individuals (the Allee effect) could play a role in life cycle switching. In our model, if the 13-year cycle is genetically dominant, a 17-year cycle population will switch to a 13-year cycle given the introduction of a few 13-year cycle alleles under a moderate Allee effect. We also show that under a weak Allee effect, different year-classes (“broods”) with 17-year life cycles can be generated. Remarkably, the outcomes of our models depend only on the dominance relationships of the cycle alleles, irrespective of any fitness advantages.
Public Library of Science
Journals
2011 EN
Nader Rifai · James C. Boyd · Thomas M Annesley
Clinical Chemistry is pleased to announce the launching of a new initiative, called the “ Clinical Chemistry Trainee Council,” that will provide educational materials to trainees in clinical chemistry and laboratory medicine. This program combines the Journal's commitment to education and its mission to disseminate information to laboratory scientists throughout the world.In the past 3 years, considerable efforts have been exerted by the editors of Clinical Chemistry to build a solid educational program; the publication of Reviews, Mini-Reviews, Perspectives, Clinical Case Studies, Q&A articles, and the Clinical Chemistry Guide to Scientific Writing are examples of this commitment. Through our Reaching Out to the World program, articles from the Journal have been translated into 15 languages: The 143 articles translated into Chinese reach more than 210 000 laboratory scientists in …
American Association for Clinical Chemistry
Journals
2011 EN
Alan Grossman · Áine O’Brien
This article foregrounds the methodological and curatorial concerns of a cross-sectoral public media programme titled the ‘Forum on Migration and Communication’ (FOMACS), which produces film, photographic, digital storytelling, print media and radio stories on the topic of migration into Ireland. Framing two key FOMACS projects using animation and digital storytelling with young children and asylum seekers, this article centrally engages with an ongoing problematic situated across the nexus between participatory media, the ‘politics of voice’, and the politics or ethics of listening. FOMACS’ deployment of participatory research methods – aimed at prising open a space for collaborative media production, facilitating the articulation of diverse immigrant and non-immigrant ‘voices’ – instantiates the problematic notion of ‘giving voice’, a practice associated with media advocacy and community development projects. This article addresses the question of how to negotiate a working dialectic between a ‘politics of voice’ and ‘political listening’, specifically within the field of participatory media production and in the context of challenges posed by the FOMACS mission, which aims to engage diverse audiences by creating a continuum between production, dissemination and reception, together with impact on public policy through the advocacy work of its migration NGO partners.
Resource
2011 EN
for the GRIPS collaboration,
www.grips-mission.eu J. Greiner · for the GRIPS collaboration,
www.grips-mission.eu G. Kanbach · for the GRIPS collaboration,
www.grips-mission.eu K. Mannheim
We describe the potential of GRIPS, a future MeV mission. The Gamma-RayImaging, Polarimetry and Spectroscopy ("GRIPS") concept combines a Compton andpair telescope, and will be a very sensitive polarimeter. GRIPS would perform acontinuously scanning all-sky survey from 200 keV to 80 MeV achieving asensitivity which is better by a factor of 40 compared to the previous missionsin this energy range.
Resource
2011 EN
O. Tibolla · K. Mannheim · A. Paravac
+2 more
GRIPS is planned to be the next great satellite-born survey mission lead byEurope; it will look into the cosmos with unprecedented accuracy in severalbands of the EM spectrum (infrared, X-rays, MeV gamma-rays); in particular ingamma-rays, GRIPS will be able to bridge the so-called MeV gap and to answerseveral questions brought forth by GeV-TeV gamma-ray observations. We willdiscuss here several connections to GeV-TeV gamma-ray astrophysics, focussingin particular to show how GRIPS will be crucial in revealing the origin ofcosmic rays.
Journals
2011 EN
İlknur Keçik · Belgin Aydın
The aim of this article is to describe the model developed for the teaching practice component of the pre-service Distance English Language Teacher Training Program (DELTT) at Anadolu University, Eski s ehir, Turkey. The steps taken to improve the model over a six-year period will be explained and the recent developments in the teaching practice area of the current program will be discussed in the light of recent research on learning and personal development. Lessons learned and the steps taken during this developmental process will be explored and recommendations for other programs concerned with the teaching practice component will be made. Introduction Preparing high-quality teachers is the ultimate aim of teacher education programs (Bransford, Darling-Hammond & LePage, 2005; Darling-Hammond, 2010; Feiman-Nemser & Buchman, 1997), These programs have the responsibility of educating future teachers who will directly affect the future of a nation. Such programs should be able to help its trainees to prepare well-organized lesson plans, to adapt a flexible attitude while applying those plans, to reflect on their lessons and to think about the strengths and weaknesses of their lessons. Considering the fact that student teachers have varying degrees of success in adapting to the challenges of a real classroom while they are all provided with the same knowledge during their formal education, we can conclude that knowledge does not lead to good practice all the time and learning is an ongoing process (Fairbanks, Duffy, Faircloth, He, Levin, Rohr & Stein, 2010). As a result, the most important aim of teacher education programs should be to give their trainees the perspective that they should feel themselves responsible and willing for learning from every opportunity throughout their lives. Student teachers working in these programs should also serve as models of this mission in their own practices. Teaching practice that builds a bridge between university and schools and helps future teachers to apply what they learn at the university is the most important component of teacher education programs (Broadbent, 1998; Hazzan & Lapidot; 2004; Smith & Lev-Ari, 2005; Stanulis R Tanruther, 1994). Although most teaching practices support school-university partnerships, many of them demonstrate problems related to organizing and monitoring teaching practice. Most of them have been criticized for not establishing an equal relationship between school teachers (practitioners) and university supervisors (academics). As Valencia, Martin, Place & Grossman (2009) argue, one of the reasons for the above mentioned disorganization problem is that most of the school-based teacher educators are not usually provided with the kind of preparation and support they need in guiding the student teachers. However, as indicated by Zeihner (2010), an equal and more dialectical relationship between the academic and the practitioner is necessary for building a bridge between