Electron-phonon interaction for adiabatic anharmonic phonons

A model with Holstein-like electron-phonon coupling is studied in the limit of adiabatic phonons. The phonon distribution is anharmonic with two degenerate maxima. This model can be related to fermions in a correlated binary alloy and describes microscopic phase separation. We discuss the weak and strong electron-phonon coupling limit and present a qualitative phase diagram. In terms of the phononic displacements it consists of a homogeneous, an alternating, and a disordered phase. There is a first order phase transition between the homogeneous and the alternating phase, and second order phase transition between the alternating and the disordered phase. The opening of a gap inside the disordered phase is treated by a dynamical mean-field theory.Comment: 11 pages, 3 figures, revised and published versio

The z>4 Quasar Population Observed by Chandra and XMM-Newton

The current status of our Chandra and XMM-Newton project on high-redshift (z>4) quasars is briefly reviewed. We report the main results obtained in the last few years for the detected quasars, along with a few (~10%) intriguing cases where no detection has been obtained with Chandra snapshot observations.Comment: 4 pages, to appear in the proceedings of 'Multiwavelength AGN surveys' (Cozumel, December 8-12 2003), ed. R. Maiolino and R. Mujic

New records of Neelipleona for the Iranian springtail fauna (Collembola)

Three new species of Collembola belonging to genus Megalothorax Willem, 1900 (new genus for Iran) are recorded for the fauna of Iran. M. willemi Schneider & D´Haese, 2013 and M. perspicillum Schneider & D´Haese, 2013 have recently described and known from Belgium and France respectively. In this survey they were collected from Mazandaran province in northern Iran and are first record for the Middle East (and the second record in the world). Also M. incertus Börner, 1903 is recorded for the first time from Iran. The specimens were found in the soil, litter and dead wood from four localities in Caspian Hyrcanian Mixed Forests

Creativity in Citizen Cyberscience

An interview study was conducted to explore volunteers’ experiences of creativity in citizen cyberscience. Participants were recruited from 4 projects: GeoTag-X, Virtual Atom Smasher, Synthetic Biology, and Extreme Citizen Science. Ninety-six interviews were conducted in total: 86 with volunteers (citizen scientists) and 10 with professional scientists. The resulting thematic analysis revealed that volunteers are involved in a range of creative activities, such as discussing ideas, suggesting improvements, gamification, artwork, creative writing, and outreach activities. We conclude that the majority of creative products are community-related. Creativity in citizen cyberscience is a collective process: volunteers create within a project and a community, both for themselves and for others

NLTE spectroscopic analysis of the 3^3He anomaly in subluminous B-type stars

Several B-type main-sequence stars show chemical peculiarities. A particularly striking class are the $^3$He stars, which exhibit a remarkable enrichment of $^3$He with respect to $^4$He. This isotopic anomaly has also been found in blue horizontal branch (BHB) and subdwarf B (sdB) stars, which are helium-core burning stars of the extreme horizontal branch. Using a hybrid local/non-local thermodynamic equilibrium (LTE/NLTE) approach for B-type stars, we analyzed high-quality spectra of two known $^3$He BHBs and nine known $^3$He sdBs to determine their isotopic helium abundances and $^4$He/$^3$He abundance ratios. We redetermined their atmospheric parameters and analyzed selected neutral helium lines, including $\lambda$4922 $\mathring{A}$ and $\lambda$6678 $\mathring{A}$, which are very sensitive to $^4$He/$^3$He. Most of the $^3$He sdBs cluster in a narrow temperature strip between 26000 K and 30000 K and are helium deficient in accordance with previous LTE analyses. BD+48$^\circ$ 2721 is reclassified as a BHB star because of its low temperature ($T_{\mathrm{eff}}=$ 20700 K). Whereas $^4$He is almost absent ($^4$He/$^3$He$<$ 0.25) in most of the known $^3$He stars, other sample stars show abundance ratios up to $^4$He/$^3$He$=$2.51. A search for $^3$He stars in the ESO SPY survey led to the discovery of two new $^3$He sdB stars (HE 0929-0424 and HE 1047-0436). The observed helium line profiles of all BHBs and of three sdBs are not matched by chemically homogeneous atmospheres, but hint at vertical helium stratification. This phenomenon has been seen in other peculiar B-type stars, but is found for the first time for sdBs. We estimate helium to increase from the outer to the inner atmosphere by factors ranging from 1.4 (SB 290) up to 8.0 (BD+48$^\circ$ 2721).Comment: 19 pages, 79 figures submitted to Astronomy&Astrophysic

Motivations, Learning and Creativity in Online Citizen Sceince Charlene Jennett, Laure Kloetzer, Daniel Schneider, Ioanna Iacovides, Anna L. Cox, Margaret Gold, Brian Fuchs, Alexandra Eveleigh, Kathleen Mathieu, Zoya Ajani and Yasmin Talsi

Online citizen science projects have demonstrated their usefulness for research, however little is known about the potential benefits for volunteers. We conducted 39 interviews (28 volunteers, 11 researchers) to gain a greater understanding of volunteers' motivations, learning and creativity (MLC). In our MLC model we explain that participating and progressing in a project community provides volunteers with many indirect opportunities for learning and creativity. The more aspects that volunteers are involved in, the more likely they are to sustain their participation in the project. These results have implications for the design and management of online citizen science projects. It is important to provide users with tools to communicate in order to supporting social learning, community building and sharing.This article is licensed under the terms of the Creative Commons Attribution - NonCommercial - NoDerivativeWorks 4.0 License. The article attached is the publisher's pdf

Physics Results from the AMANDA Neutrino Detector

In the winter season of 2000, the AMANDA (Antarctic Muon And Neutrino Detector Array) detector was completed to its final state. We report on major physics results obtained from the AMANDA-B10 detector, as well as initial results of the full AMANDA-II detector