476 research outputs found
Research data management : policy and course development at the University of Twente, The Netherlands : poster
Charge carrier density collapse in La_0.67Ca_0.33MnO_3 and La_0.67Sr_0.33MnO_3 epitaxial thin films
We measured the temperature dependence of the linear high field Hall
resistivity of La_0.67Ca_0.33MnO_3 (T_C=232K) and La_0.67Sr_0.33MnO_3
(T_C=345K) thin films in the temperature range from 4K up to 360K in magnetic
fields up to 20T. At low temperatures we find a charge carrier density of 1.3
and 1.4 holes per unit cell for the Ca- and Sr-doped compound, respectively. In
this temperature range electron-magnon scattering contributes to the
longitudinal resistivity. At the ferromagnetic transition temperature T_C a
dramatic drop in the number of current carriers down to 0.6 holes per unit
cell, accompanied by an increase in unit cell volume, is observed. Corrections
of the Hall data due to a non saturated magnetic state will lead a more
pronounced charge carrier density collapse.Comment: 5 pages, 5 EPS figures, submitted to Eur. Phys. J.
ESCAPE: A generic tool for enhanced scientific communication
General scope
In order to enhance communication of research results as part of a network of actors in a particular field one wants to
· relate relevant objects (documents, persons, institutions, projects, ... on the basis of content and describe/annotate these relations
· communicate and present these aggregated objects for various target groups, not only scientists but also policy makers, journalists, companies, and the general public
· enhance this communication by commenting and tagging related objects
The tool
ESCAPE is a tool in which users can aggregate digital objects stored at any location and describe, annotate, comment and tag the relations between these objects. The system not only allows formal relations (like bibliographic metadata) but especially "content relations" concerning topics, reviews, comments, discussions, applications, etc
ESCAPE: A generic tool for enhanced scientific communication
General scope
In order to enhance communication of research results as part of a network of actors in a particular field one wants to
· relate relevant objects (documents, persons, institutions, projects, ... on the basis of content and describe/annotate these relations
· communicate and present these aggregated objects for various target groups, not only scientists but also policy makers, journalists, companies, and the general public
· enhance this communication by commenting and tagging related objects
The tool
ESCAPE is a tool in which users can aggregate digital objects stored at any location and describe, annotate, comment and tag the relations between these objects. The system not only allows formal relations (like bibliographic metadata) but especially "content relations" concerning topics, reviews, comments, discussions, applications, etc
Water, werk en waterwerken : de ontwikkeling van irrigatietechnologie in het stroomgebied van de Segura, Zuidoost - Spanje
This book deals with irrigation technology, with special reference to the social process of its construction, use and adaptation. The aim is to bring (back) designing of irrigation technology closer to the practice of farming. Besides, this book tries to contribute in a specific way to the general notion that technology development is related to social, political and economic changes. It is based on empirical research carried out in irrigated agricultural areas in the lower Segura River basin in South East Spain. One of the main conclusions is that the possibility to adapt the irrigation system to the specific requirements of the agricultural production process, is an important condition to successful irrigation development. Based on knowledge of the existing variety of the agricultural production process, the irrigation engineer should subordinate his or her own frame of reference to that of the future users of the irrigation system
Disorder-induced melting of the charge order in thin films of Pr0.5Ca0.5MnO3
We have studied the magnetic-field-induced melting of the charge order in
thin films of Pr0.5Ca0.5MnO3 (PCMO) films on SrTiO3 (STO) by X-ray diffraction,
magnetization and transport measurement. At small thickness (25 nm) the films
are under tensile strain and the low-temperature melting fields are of the
order of 20 T or more, comparable to the bulk value. With increasing film
thickness the strain relaxes, which leads to a strong decrease of the melting
fields. For a film of 150 nm, with in-plane and out-of-plane lattice parameters
closer to the bulk value, the melting field has reduced to 4 T at 50 K, with a
strong increase in the hysteretic behavior and also an increasing fraction of
ferromagnetic material. Strain relaxation by growth on a template of
YBa2Cu3O(7-delta) or by post-annealing yields similar results with an even
stronger reduction of the melting field. Apparently, strained films behave
bulk-like. Relaxation leads to increasing suppression of the CO state,
presumably due to atomic scale disorder produced by the relaxation process.Comment: 7 pages, 4 fig
Extensive infrared spectroscopic study of CuO: signatures of strong spin-phonon interaction and structural distortion
Optical properties of single-crystal monoclinic CuO in the range 70 - 6000
\cm were studied at temperatures from 7 to 300 K. Normal reflection spectra
were obtained from the (001) and (010) crystal faces thus giving for the first
time separate data for the and phonon modes excited in the
purely transverse way (TO modes). Mode parameters, including polarizations of
the modes not determined by the crystal symmetry, were extracted by the
dispersion analysis of reflectivity curves as a function of temperature.
Spectra of all the components of the optical conductivity tensor were obtained
using the Kramers-Kronig method recently extended to the case of the
low-symmetry crystals. The number of strong phonon modes is in agreement with
the factor-group analysis for the crystal structure, currently accepted for the
CuO. However, several "extra" modes of minor intensity are detected. Comparison
of frequencies of "extra" modes with the available phonon dispersion curves
points to possible "diagonal" doubling of the unit cell \{{\bf a}, {\bf b},
{\bf c}\} \{{\bf a}+{\bf c}, {\bf b}, {\bf a}-{\bf c}\} and formation of
the superlattice. The previously reported softening of the mode
( 400 \cm) with cooling at is found to be 10 % for the TO
mode. The mode is very broad at high temperatures and strongly narrows in the
AFM phase. We attribute this effect to strong resonance coupling of this mode
to optical or acoustic bi-magnons and reconstruction of the magnetic
excitations spectrum at the N\'eel point. A significant anisotropy of
is observed: it was found to be 5.9 along the {\bf b}-axis,
6.2 along the {[}101{]} chains and 7.8 the {[}10{]} chains. The
"transverse" effective charge is value is about 2 electrons.Comment: 23 pages, 14 figures, REVTeX, submitted to PR
DARIS : a low-frequency distributed aperture array for radio astronomy in space
The frequency band below 30 MHz is one of the last unexplored bands in radio astronomy. This band is well suited for studying the early cosmos at high hydrogen redshifts, the so-called dark ages, extragalactic surveys, (extra) solar planetary bursts, and high energy particle physics. In addition, space research such as space weather tomography, are also areas of scientific interest. \ud
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Due to ionospheric scintillation (below 30MHz) and its opaqueness (below 15MHz), earth-bound radio astronomy observations in these bands are either severely limited in sensitivity and spatial resolution or entirely impossible. A radio telescope in space obviously would not be hampered by the Earth's ionosphere. In the past, several (limited) studies have been conducted to explore possibilities for such an array in space. These studies considered aperture synthesis arrays in space, at the back-side of the Moon, or a satellite constellation operating in a coherent mode. \u
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