INFLUENCE OF A RETICULATED MATRIX OVER THE DIELECTRIC RESPONSE OF E

Viciosa, M.T.a; Nunes, A.b; Almeida, P.L.c,d; Godinho, M.H.d; Dionísio, M.b

a_{CQFM/IN, IST, Universidade Técnica de Lisboa, Avda. Rovisco Pais, 1049-001 Lisboa,}

Portugal

b_{Requimte/CQFB, Depto. de Química, FCT, Universidade Nova de Lisboa, 2829-516}

Caparica, Portugal

c_{ISEL, Inst Super Engn Lisboa, ACF-DEEA, 1959-007 Lisbon, Portugal}

d_{CENIMAT/I3N, FCT, Universidade Nova de Lisboa, 2829-516 Caparica, Portugal}

Fonte: Proceedings of the ILCEC2011

Conferência: 6th International Liquid Crystal Elastomer Conference (ILCEC2011), Lisboa, Portugal, 2011

Tipo de Documento: Proceeding Paper

Resumo: The deposition of a liquid crystal as it can be the nematic misture E7 over a polymer film of hydroxypropylcellulose (HPC) has revealed good properties for electro-optical devices. In this work we investigated the influence of a cross-linked HPC matrix, obtained by adding 7% w/w of 1,4 diisocianatobutane as crosslinking agent (BDI), over the molecular motions detected in bulk E7. In a previous work we carried out the study of the molecular dynamics of bulk E7 by using

Dielectric Relaxation Spectroscopy (DRS). It was found that bulk E7 is a glass former with a Tg around -60 ºC.

Dielectric loss spectra has been collected of the unaligned HPC-BDI/E7 composite on cooling from 20 to -120 ºC. Figure 1 illustrates the spectra collected at -30 ºC of the composite and bulk E7, including the deconvolution in three relaxation processes. The dominant relaxation mode observed is due to rotational fluctuations of the molecule around its short axis being associated mainly with the component of the dipolar

moment parallel to the applied electric field; by effect of the crosslinked matrix, the intensity decreases and the maximum of the dielectric spectrum (fmax) shifts to higher frequencies.

Concerning the relaxation mode located at higher frequencies, that corresponds to the superposition of different tumbling motions around the molecular long axis, it is noticeable the increase of intensity when the E7 is over the polymeric matrix. This process is mostly related to the dipolar component perpendicular to the

applied electrical field. On the other side, the relaxation process detected at low

frequencies becomes better defined when E7 is over the cross-linked matrix.
The variation of relative weight of each individual contribution to the overall spectrum in

the composite relative to bulk E7 indicates a change in the preferential orientation of E7 when it is in contact with an HPC based subtract, as confirmed by the higher tension required to produce full alignment relative to a non-crosslinked HPC/E7 matrix.

INTRODUÇÃO À FÍSICA ESTATÍSTICA Casquilho, J.P.a; Teixeira, P.I.C.b,c

a_{Departamento de Física and CENIMAT/I3N, Faculdade de Ciências e Tecnologia,}

Universidade Nova de Lisboa, Caparica, P-2829-516 Caparica, Portugal

b_{ISEL, Inst Super Engn Lisboa, P-1959-007 Lisbon, Portugal}

c_{Univ Lisbon, Ctr Fis Teor & Computac, P-1649-003 Lisbon, Portugal}

Fonte: Introdução à Física Estatística, 428 páginas, 2011 ISBN: 978-972-8469-99-3

Editor: IST Press

Tipo de Documento: Livro Área Científica: Física Estatística

Resumo: O programa do curso está organizado segundo uma divisão da matéria em cinco partes, correspondendo ao Passeio Aleatório (um capítulo), à Termodinâmica Estatística (dois capítulos), ao Gás Ideal (dois capítulos), ao estudo de sistemas não ideais (dois capítulos), a um breve estudo de transições de fase e fenómenos críticos (um capítulo), e uma introdução ao estudo dos processos irreversíveis (um capítulo). O primeiro capítulo destina-se a fornecer uma introdução aos métodos estatísticos em Física e aos métodos de simulação numérica de Monte Carlo. O segundo e o terceiro capítulos constituem o núcleo do curso, na medida em que aí é desenvolvido o formalismo da Física Estatística e é feita a conexão com a Termodinâmica. O quarto e o quinto capítulos são dedicados a aplicações da teoria ao gás ideal. A matéria respeitante a sistemas não ideais é dada nos dois capítulos seguintes. No oitavo capítulo, recapitulam-se alguns dos resultados antes obtidos para transições de fase em sistemas não ideais (ferromagnetes e cristais líquidos), colocando-os no contexto mais geral dos fenómenos críticos (expoentes e leis de escala). No nono capítulo, para abordar o assunto dos processos irreversíveis em Física Estatística, escolhem-se os temas da difusão e do movimento Browniano que, aliás, estão relacionados.

LEPTONIC MIXING, FAMILY SYMMETRIES, AND NEUTRINO

PHENOMENOLOGY

Varzielas, I.D.a,b,c; Felipe, R.G.b,d_{; Serôdio, H.}b

a_{Inst Super Tecn, Dept Fis, P-1049001 Lisbon, Portugal}

b_{Inst Super Tecn, Ctr Fis Teor Particulas, P-1049001 Lisbon, Portugal} c_{Tech Univ Dortmund, Fak Phys, D-44221 Dortmund, Germany}

d_{ISEL, Inst Super Engn Lisboa, P-1959-007 Lisbon, Portugal}

Fonte: Physical Review D, Volume 83, Issue 3, Article Number 033007, Feb 28 2011 ISSN: 1550-7998

DOI: 10.1103/PhysRevD.83.033007 Editor: Amer Physical Soc

Tipo de Documento: Article

Área Científica: Astronomy & Astrophysics; Physics

Resumo: Tribimaximal leptonic mixing is a mass-independent mixing scheme consistent with the present solar and atmospheric neutrino data. By conveniently decomposing the effective neutrino mass matrix associated to it, we derive generic predictions in terms of the parameters governing the neutrino masses. We extend this phenomenological analysis to other mass- independent mixing schemes which are related to the tribimaximal form by a unitary transformation. We classify models that produce tribimaximal leptonic mixing through the group structure of their family symmetries in order to point out that there is often a direct connection between the group structure and the phenomenological analysis. The type of seesaw mechanism responsible for neutrino masses plays a role here, as it restricts the choices of family representations and affects the viability of leptogenesis. We also present a recipe to generalize a given tribimaximal model to an associated model with a different mass- independent mixing scheme, which preserves the connection between the group structure and phenomenology as in the original model. This procedure is explicitly illustrated by constructing toy models with the transpose tribimaximal, bimaximal, golden ratio, and hexagonal leptonic mixing patterns.

LIGHT CHARGED HIGGS BOSONS AT THE LHC IN TWO-HIGGS-DOUBLET