37,352 research outputs found
Unusual DNA binding modes for metal anticancer complexes
DNA is believed to be the primary target for many metal-based drugs. For example, platinum-based anticancer drugs can form specific lesions on DNA that induce apoptosis. New platinum drugs can be designed that have novel modes of interaction with DNA, such as the trinuclear platinum complex BBR3464. Also it is possible to design inert platinum(IV) pro-drugs which are non-toxic in the dark, but lethal when irradiated with certain wavelengths of light. This gives rise to novel DNA lesions which are not as readily repaired as those induced by cisplatin, and provides the basis for a new type of photoactivated chemotherapy. Finally, newly emerging ruthenium(II) organometallic complexes not only bind to DNA coordinatively, but also by H-bonding and hydrophobic interactions triggered by the introduction of extended arene rings into their versatile structures. Intriguingly osmium (the heavier congener of ruthenium) reacts differently with DNA but can also give rise to highly cytotoxic organometallic complexes
Valley polarization effects on the localization in graphene Landau levels
Effects of disorder and valley polarization in graphene are investigated in
the quantum Hall regime. We find anomalous localization properties for the
lowest Landau level (LL), where disorder can induce wavefunction delocalization
(instead of localization), both for white-noise and gaussian-correlated
disorder. We quantitatively identify the contribution of each sublattice to
wavefunction amplitudes. Following the valley (sublattice) polarization of
states within LLs for increasing disorder we show: (i) valley mixing in the
lowest LL is the main effect behind the observed anomalous localization
properties, (ii) the polarization suppression with increasing disorder depends
on the localization for the white-noise model, while, (iii) the disorder
induces a partial polarization in the higher Landau levels for both disorder
models.Comment: 5 pages, 6 figures, extended version, with 2 new figures adde
Technology adoption and factor proportions in open economies : theory and evidence from the global computer industry
Theories of international trade assume that all countries use similar and exogenous technologies in the production of any good. This paper relaxes this assumption. The marriage of literatures on biased technical change and trade yields a tractable theory, which predicts that differences in factor endowments and intellectual property rights bias technical change toward particular factor intensities, and thus unit factor input requirements can vary across economies. Using data on net exports of a single industry, computers, intellectual property rights and factor endowments for 73 countries during 1980-2000, the paper shows that once technological choices are considered, countries with different factor endowments can become net exporters of the same product.Technology Industry,Economic Theory&Research,ICT Policy and Strategies,E-Business,Labor Policies
Teacher training processes and teachers' competence : A sociological study in the primary school
The paper describes part of a study whose aim was to investigate the relation between
modalities of teacher training and modalities of pedagogic practice implemented in the science classroom. The study is focused on primary school context and analyses the evolution of teachers performance in terms of their acquisition of recognition and realisation rules, i.e.
coding orientation, to specific scientific learning contexts.
Theoretically, the study is based on Bernstein’s theory of pedagogic discourse (1999, 2000)which provided the concepts to characterise the modalities of teacher training and of classroom pedagogic practices and to analyse teachers’ evolution in terms of recognition and realisation rules. The sample was made up of four teachers and their four socially
heterogeneous school classes. An action-research methodology was followed.The results suggest that the teacher training implemented was favourable to the teachers’
professional development and their competence to lead all children to a high level of scientific development. The efficiency of the training process has to be mostly attributed to the strong classification of the researcher-teachers relation and to the strong framing of evaluation criteria, selection and sequence, together with weak framing of hierarchical rules and pacing.Fundação Calouste Gulbenkian, Instituto de Inovação Educacional e Fundação para a Ciência e Tecnologia (FCT)
Generalized uncertainty principle impact onto the black holes information flux and the sparsity of Hawking radiation
We investigate the generalized uncertainty principle (GUP) corrections to the
entropy content and the information flux of black holes, as well as the
corrections to the sparsity of the Hawking radiation at the late stages of
evaporation. We find that due to these quantum gravity motivated corrections,
the entropy flow per particle reduces its value on the approach to the Planck
scale due to a better accuracy in counting the number of microstates. We also
show that the radiation flow is no longer sparse when the mass of a black hole
approaches Planck mass which is not the case for non-GUP calculations.Comment: 6 pages, 2 figures, typos corrected, published in Phys. Rev.
Weak Chaos in large conservative system -- Infinite-range coupled standard maps
We study, through a new perspective, a globally coupled map system that
essentially interpolates between simple discrete-time nonlinear dynamics and
certain long-range many-body Hamiltonian models. In particular, we exhibit
relevant similarities, namely (i) the existence of long-standing
quasistationary states (QSS), and (ii) the emergence of weak chaos in the
thermodynamic limit, between the present model and the Hamiltonian Mean Field
model, a strong candidate for a nonxtensive statistical mechanical approach.Comment: 6 pages, 2 figures. Corrected typos in equation 4. Changed caption in
Fig. 1. Corrected references 2 and 6. Acknowledgements adde
The Weinstein conjecture in the presence of submanifolds having a Legendrian foliation
Helmut Hofer introduced in '93 a novel technique based on holomorphic curves
to prove the Weinstein conjecture. Among the cases where these methods apply
are all contact 3--manifolds with . We modify Hofer's
argument to prove the Weinstein conjecture for some examples of higher
dimensional contact manifolds. In particular, we are able to show that the
connected sum with a real projective space always has a closed contractible
Reeb orbit.Comment: 11 pages, 2 figure
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