275 research outputs found
Supersymmetry and a rationale for small CP violating phases
We analyse the CP problem in the context of a supersymmetric extension of the
standard model with universal strength of Yukawa couplings. A salient feature
of these models is that the CP phases are constrained to be very small by the
hierarchy of the quark masses, and the pattern of CKM mixing angles. This leads
to a small amount of CP violation from the usual KM mechanism and a significant
contribution from supersymmetry is required. Due to the large generation mixing
in some of the supersymmetric interactions, the electric dipole moments impose
severe constraints on the parameter space, forcing the trilinear couplings to
be factorizable in matrix form. We find that the LL mass insertions give the
dominant gluino contribution to saturate epsilon_K. The chargino contributions
to epsilon'/epsilon are significant and can accommodate the experimental
results. In this framework, the standard model gives a negligible contribution
to the CP asymmetry in B-meson decay, a_{J/\psi K_s}. However, due to
supersymmetric contributions to B_d-\bar{B}_d mixing, the recent large value of
a_{J/\psi K_s} can be accommodated.Comment: 30 pages, 5 figures. Version to appear in Nucl. Phys.
Characterization of the volatile fraction emitted by phloems of four pinus species by solid-phase microextraction and gas chromatography–mass spectrometry
Pine forests constitute some of the most important renewable resources supplying timber, paper and chemical industries, among other functions. Characterization of the volatiles emitted by different Pinus species has proven to be an important tool to decode the process of host tree selection by herbivore insects, some of which cause serious economic damage to pines. Variations in the relative composition of the bouquet of semiochemicals are responsible for the outcome of different biological processes, such as mate finding, egg-laying site recognition and host selection. The volatiles present in phloem samples of four pine species, P. halepensis, P. sylvestris, P. pinaster and P. pinea, were identified and characterized with the aim of finding possible host-plant attractants for native pests, such as the bark beetle Tomicus piniperda. The volatile compounds emitted by phloem samples of pines were extracted by headspace solid-phase micro extraction, using a 2 cm 50/30 mm divinylbenzene/carboxen/polydimethylsiloxane table flex solid-phase microextraction fiber and its contents analyzed by high-resolution gas chromatography, using flame ionization and a non polar and chiral column phases. The components of the volatile fraction emitted by the phloem samples were identified by mass spectrometry using time-of-flight and quadrupole mass analyzers. The estimated relative composition was used to perform a discriminant analysis among pine species, by means of cluster and principal component analysis. It can be concluded that it is possible to discriminate pine species based on the monoterpenes emissions of phloem samples
Influência da qualidade dos materiais de reprodução na reflorestação com sobreiro
O sobreiro ocupa em Portugal cerca de 721000 ha o que corresponde a 21,5 % da área fl orestal nacional e 33% da área
mundial (APCOR, 2005). A sua distribuição no território nacional traduz não só a sua adaptação a determinadas
condições edafo-climaticas, mas tem sido condicionada por várias circunstancias, como o arroteamento, o fogo, o
abuso do pastoreio, a exploração agrícola intensiva e as plantações fl orestais que contrariaram ou favoreceram a sua
existência nesses locais (Natividade, 1950). A distribuição desta espécie é particularmente signifi cativa em zonas
onde têm ocorrido acontecimentos climáticos graves e onde os níveis de desertifi cação humana são críticos.
A fi leira da cortiça salienta-se por Portugal ocupar o primeiro lugar entre os países produtores, transformadores e
exportadores de cortiça, correspondendo-lhe mais de metade da produção mundial desta matéria-prima. O nosso
País é a origem de aproximadamente 60% das transacções de cortiça a nível mundial, valor que sobe para 80%
quando nos referimos a transacções de produtos transformados. A nível nacional, o valor das exportações de cortiça
representam aproximadamente 0,7% do PIB, 2,24% das exportações e correspondem a mais de 33% do conjunto das
exportações de produtos fl orestais (APCOR, 2005). Para além da importância económica do sector corticeiro a nível
nacional, o aumento da consciência e do interesse da sociedade nas questões ambientais, faz com que o montado de
sobro seja reconhecido cada vez mais como um espaço fl orestal, de elevada biodiversidade, paisagísticamente único,
que potencia micro-economias locais baseadas numa agricultura e pastorícia extensivas, interessante para outras
actividades como o turismo rural e a caça.
O sobreiro tem sido a espécie fl orestal que mais tem benefi ciado dos meios fi nanceiros disponibilizados aos proprietários
fl orestais para a refl orestação no âmbito da aplicação das medidas de reforma da Política Agrícola Comum
da UE, na arborização das terras agrícolas. Contudo, têm-se registado com frequência elevadas taxas de insucesso
na arborização sendo a qualidade dos materiais florestais de reprodução (MFR) apontada como uma das causas.
Neste trabalho abordaremos a a qualidade dos materiais de reprodução, considerando-a do ponto de vista genético
e fisiológicoN/
Fermion Masses and Mixing in Intersecting Branes Scenarios
We study the structure of Yukawa couplings in intersecting D6-branes wrapping
a factorizable 6-torus compact space T^6. Models with MSSM-like spectrum are
analyzed and found to fail in predicting the quark mass spectrum because of the
way in which the family structure for the left-handed, right-handed quarks and,
eventually, the Higgses is `factorized' among the different tori. In order to
circumvent this, we present a model with three supersymmetric Higgs doublets
which satisfies the anomaly cancellation condition in a more natural way than
the previous models, where quarks were not treated universally regarding their
branes assignments, or some particular branes were singled out being invariant
under orientifold projection. In our model, the family structures for the left,
right quarks, left leptons and the Higgses arise from one of the tori and can
naturally lead to universal strength Yukawa couplings which accommodate the
quark mass hierarchy and the mixing angles.Comment: 21 pages, latex, matches the Phys. Rev. D versio
An updated overview of the neurophysiological and psychosocial dimensions of fibromyalgia: A call for an integrative model
Research into the neurobiological and psychosocial mechanisms involved in fibromyalgia (FM) has progressed remarkably in recent years. Despite this, currents accounts of FM fail to capture the complex, dynamic and mutual crosstalk between neurophysiological and psychosocial domains. We conducted a comprehensive review of the existing literature in order to synthesise current knowledge on FM, explore and highlight multi-level links and pathways among different systems and build bridges between existing approaches. An extensive panel of international experts in neurophysiology and psychosocial aspects of FM discussed the collected evidence and progressively refined and conceptualized its interpretation. Fibromyalgia is a complex condition resulting from the dynamic interplay between multiple systems and processes. We provided an updated overview of the most relevant observations in FM to date as well as the potential pathways by which they exert they are related and exert their mutual influence, to produce the manifestations commonly associated with FM. This review constituted the first step towards and supported the development of a much needed model capable of integrating the main factors implicated in FM into a single, unified model that may prove valuable in understanding and managing FM
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