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 Ni3_3V2_2O8_8 imaged by X-ray polarization enhanced topography

The magnetic structure of multiferroic Ni$_3$V$_2$O$_8$ 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