145 research outputs found
A dimensão histórica da ciência presente nas investigações em educação química no brasil (1997-2005)
A investigação refere-se aos diferentes olhares que pesquisadores da área de Química detêm sobre a inserção da abordagem da História da Ciência no processo da Educação Química. O Banco de Dados resultante dos cinco Encontros Nacionais de Pesquisa em Educação em Ciências (1997-2005) revelou-se acervo significativo das produções existentes no Brasil sobre as pesquisas em Educação em Ciências, em especial a Educação Química, traduzindo as tendências temáticas predominantes dessas áreas e os fundamentos teórico-práticos que alicerçam seus diferentes objetivos. As produções analisadas apontam para a renovação da Didática das Ciências, em especial da Ciência Química, sobretudo, à necessidade e importância da contextualização social do ensino de Química no âmbito dos conteúdos, metodologias, organização do processo de ensino-aprendizagem e métodos de avaliação
The suppression of superconductivity in MgCNi3 by Ni-site doping
The effects of partial substitution of Cu and Co for Ni in the intermetallic
perovskite superconductor MgCNi3 are reported. Calculation of the expected
electronic density of states suggests that electron (Cu) and hole (Co) doping
should have different effects. For MgCNi3-xCux, solubility of Cu is limited to
approximately 3% (x = 0.1), and Tc decreases systematically from 7K to 6K. For
MgCNi3-xCox, solubility of Co is much more extensive, but bulk
superconductivity disappears for Co doping of 1% (x = 0.03). No signature of
long range magnetic ordering is observed in the magnetic susceptibility of the
Co doped material.Comment: submitted, Solid State Communication
Mentoring for future female engineers: pilot at the Higher Polytechnic School of Zamora
The gender gap is a problem that affects all areas
and regions in the world. The lack of females depends on
different external and internal factors that make it a complex
problem. In particular, this gap is most pronounced in
engineering. Engineering and technical studies have a shortage
of female vocations and a high dropout rate. In this paper, we
present the pilot peer-mentoring programme, which has been
carried out in the 2020-21 academic year at the University of
Salamanca in the Higher Polytechnic School of Zamora.
Mentoring has been given to first-year female students of
engineering degrees. The implementation of the pilot
programme has provided helpful information for implementing
the mentoring programme from the 2021-22 academic year
Electric field control of multiferroic domains in NiVO imaged by X-ray polarization enhanced topography
The magnetic structure of multiferroic NiVO has been investigated
using non-resonant X-ray magnetic scattering. Incident circularly polarized
X-rays combined with full polarization analysis of the scattered beam is shown
to yield high sensitivity to the components of the cycloidal magnetic order,
including their relative phases. New information on the magnetic structure in
the ferroelectric phase is obtained, where it is found that the magnetic
moments on the "cross-tie" sites are quenched relative to those on the "spine"
sites. This implies that the onset of ferroelectricity is associated mainly
with spine site magnetic order. We also demonstrate that our technique enables
the imaging of multiferroic domains through polarization enhanced topography.
This approach is used to image the domains as the sample is cycled by an
electric field through its hysteresis loop, revealing the gradual switching of
domains without nucleation.Comment: 9 pages, 6 figure
Absence of a structural transition up to 40 Gpa in MgB2 and the relevance of magnesium non-stoichiometry
We report measurements on MgB2 up to ~40GPa. Increasing pressure yields a
monotonous decrease of the lattice parameters and of the c/a ratio, but no
structural transition down to parameters smaller than those of AlB2. The
transition superconducting temperature also decreases with temperature in a
sample dependent way. The results are explained by an increase of the filling
of the 2D pxy bands with pressure, the Mg stoichiometry determining the
starting position of the Fermi level. Our measurements indicate that these hole
bands are the relevant ones for superconductivity.Comment: submitted March 9th 2001, PRB accepte
Direct observation of nm-scale Mg- and B-oxide phases at grain boundaries in MgB2
Here we describe the results of an atomic resolution study of the structure
and composition of both the interior of the grains, and the grain boundaries in
polycrystalline MgB2. We find that there is no oxygen within the bulk of the
grains but significant oxygen enrichment at the grain boundaries. The majority
of grain boundaries contain BOx phases smaller than the coherence length, while
others contain larger areas of MgO sandwiched between BOx layers. Such results
naturally explain the differences in connectivity between the grains observed
by other techniques
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