Improving cluster recovery with feature rescaling factors

The data preprocessing stage is crucial in clustering. Features may describe entities using different scales. To rectify this, one usually applies feature normalisation aiming at rescaling features so that none of them overpowers the others in the objective function of the selected clustering algorithm. In this paper, we argue that the rescaling procedure should not treat all features identically. Instead, it should favour the features that are more meaningful for clustering. With this in mind, we introduce a feature rescaling method that takes into account the within-cluster degree of relevance of each feature. Our comprehensive simulation study, carried out on real and synthetic data, with and without noise features, clearly demonstrates that clustering methods that use the proposed data normalization strategy clearly outperform those that use traditional data normalization

The Noncommutative Harmonic Oscillator based in Simplectic Representation of Galilei Group

In this work we study symplectic unitary representations for the Galilei group. As a consequence the Schr\"odinger equation is derived in phase space. The formalism is based on the non-commutative structure of the star-product, and using the group theory approach as a guide a physical consistent theory in phase space is constructed. The state is described by a quasi-probability amplitude that is in association with the Wigner function. The 3D harmonic oscillator and the noncommutative oscillator are studied in phase space as an application, and the Wigner function associated to both cases are determined.Comment: 7 pages,no figure

New remarks on the linear constraint self-dual boson and Wess-Zumino terms

In this work we prove in a precise way that the soldering formalism can be applied to the Srivastava chiral boson (SCB), in contradiction with some results appearing in the literature. We have promoted a canonical transformation that shows directly that the SCB is composed of two Floreanini-Jackiw's particles with the same chirality which spectrum is a vacuum-like one. As another conflictive result we have proved that a Wess-Zumino term used in the literature consists of the scalar field, once again denying the assertion that the WZ term adds a new degree of freedom to the SCB theory in order to modify the physics of the system.Comment: 6 pages, Revtex. Final version to appear in Physical Review

Composição mineral de folhas e exportação de nutrientes pelos frutos de mangueira, em cultivo irrigado, no Rio Grande do Norte.

O objetivo de determinar a composição mineral das folhas e dos frutos da mangueira, cv. Tommy Atkins, sob cultivo irrigado em três diferentes classes de solo, foram coletadas folhas em quatro fases fenológicas da cultura: vegetativa, pré-floração, floração e maturação, e frutos maduros, em plantios existentes nas zonas fisiográficas homogêneas do Litoral Oriental, Litoral Norte e Mossoroense do Rio Grande do Norte. Pelos resultados das análises químicas, verificou-se que houve diferenças nas concentrações de macro e micronutrientes das folhas entre os plantios. Os níveis de macronutrientes declinaram com a evolução das fases fenológicas da planta, notadamente os de nitrogênio e potássio. Exceto para o potássio, as mais altas concentrações foram registradas nas folhas das plantas cultivadas em solo Neossolo, enquanto as menores concentrações, nas cultivadas em Latossolo. As concentrações dos micronutrientes nas folhas variaram entre os plantios, notadamente para o cobre e manganês. Nos frutos coletados na época da maturação houve variação na composição mineral entre os plantios, sendo que os macronutrientes presentes em maiores quantidades foram o potássio e o cálcio. Quanto aos micronutrientes, os maiores níveis obtidos foram de ferro e de cobre, seguidos do zinco e do manganês. O peso médio de frutos variou entre 377g e 496 g, com uma produção média de 130 a 240 frutos por planta.bitstream/CPATSA/36387/1/OPB1413.pd

A self-organized model for cell-differentiation based on variations of molecular decay rates

Systemic properties of living cells are the result of molecular dynamics governed by so-called genetic regulatory networks (GRN). These networks capture all possible features of cells and are responsible for the immense levels of adaptation characteristic to living systems. At any point in time only small subsets of these networks are active. Any active subset of the GRN leads to the expression of particular sets of molecules (expression modes). The subsets of active networks change over time, leading to the observed complex dynamics of expression patterns. Understanding of this dynamics becomes increasingly important in systems biology and medicine. While the importance of transcription rates and catalytic interactions has been widely recognized in modeling genetic regulatory systems, the understanding of the role of degradation of biochemical agents (mRNA, protein) in regulatory dynamics remains limited. Recent experimental data suggests that there exists a functional relation between mRNA and protein decay rates and expression modes. In this paper we propose a model for the dynamics of successions of sequences of active subnetworks of the GRN. The model is able to reproduce key characteristics of molecular dynamics, including homeostasis, multi-stability, periodic dynamics, alternating activity, differentiability, and self-organized critical dynamics. Moreover the model allows to naturally understand the mechanism behind the relation between decay rates and expression modes. The model explains recent experimental observations that decay-rates (or turnovers) vary between differentiated tissue-classes at a general systemic level and highlights the role of intracellular decay rate control mechanisms in cell differentiation.Comment: 16 pages, 5 figure

VSI: the VLTI spectro-imager

The VLTI Spectro Imager (VSI) was proposed as a second-generation instrument of the Very Large Telescope Interferometer providing the ESO community with spectrally-resolved, near-infrared images at angular resolutions down to 1.1 milliarcsecond and spectral resolutions up to R=12000. Targets as faint as K=13 will be imaged without requiring a brighter nearby reference object. The unique combination of high-dynamic-range imaging at high angular resolution and high spectral resolution enables a scientific program which serves a broad user community and at the same time provides the opportunity for breakthroughs in many areas of astrophysic including: probing the initial conditions for planet formation in the AU-scale environments of young stars; imaging convective cells and other phenomena on the surfaces of stars; mapping the chemical and physical environments of evolved stars, stellar remnants, and stellar winds; and disentangling the central regions of active galactic nuclei and supermassive black holes. VSI will provide these new capabilities using technologies which have been extensively tested in the past and VSI requires little in terms of new infrastructure on the VLTI. At the same time, VSI will be able to make maximum use of new infrastructure as it becomes available; for example, by combining 4, 6 and eventually 8 telescopes, enabling rapid imaging through the measurement of up to 28 visibilities in every wavelength channel within a few minutes. The current studies are focused on a 4-telescope version with an upgrade to a 6-telescope one. The instrument contains its own fringe tracker and tip-tilt control in order to reduce the constraints on the VLTI infrastructure and maximize the scientific return.Comment: 12 pages, to be published in Proc. SPIE conference 7013 "Optical and Infrared Interferometry", Schoeller, Danchi, and Delplancke, F. (eds.). See also http://vsi.obs.ujf-grenoble.f

Comportamento, adaptabilidade e estabilidade de híbridos de milho no Nordeste brasileiro no ano agrícola de 2004.

Em ensaios de campo com delineamento em blocos ao acaso, com três repetições foram avaliados 45 híbridos de milho em 21 ambientes do Nordeste brasileiro no ano agrícola de 2004, visando conhecer a adaptabilidade e a estabilidade desses materiais para fins de recomendação. Detectaram-se, nas análises de variância conjuntas, diferenças entre os ambientes e os híbridos e comportamento diferenciado desses híbridos em face das oscilações ambientais, quanto aos caracteres alturas de planta e de inserção da primeira espiga, estande de colheita, número de espigas colhidas e peso de grãos. Os híbridos diferiram entre si, quanto a adaptabilidade e a estabilidade de produção, destacando-se os Pionner 30 F 90 e DAS 8420 com melhor adaptação nos ambientes favoráveis. Os híbridos que associaram melhor adaptação a estimativas de b1 semelhantes à unidade evidenciaram adaptabilidade ampla, tornando-se de importância relevante para a agricultura regional.bitstream/item/34047/1/Ok.bp-09.pd

Comportamento, adaptabilidade e estabilidade de cultivares de milho no Nordeste brasileiro no ano agrícola de 2004.

Foram avaliadas 16 variedades e 24 híbridos de milho em 17 ambientes do Nordeste brasileiro, no ano agrícola de 2004, em blocos ao acaso, com três repetições, visando conhecer a adaptabilidade e a estabilidade desses materiais para fins de recomendação. Os híbridos mostraram melhor adaptação que as variedades, destacando-se, entre eles, os AG 7000, BRS 1010, AG 7575, DKB 350, DKB 466, dentre outros, por revelarem adaptabilidade ampla, consubstanciando-se em excelentes opções para os diferentes sistemas de produção prevalecentes na região. As variedades AL Piratininga, Sertanejo, AL Alvorada, Asa Branca, SHS 3031, AL 30 e AL Ipiranga mostraram também adaptabilidade ampla, considerando-se a média das variedades, tornando-se alternativas importantes para os diferentes sistemas de produção executadas na região, especialmente, aqueles sistemas praticados pelos pequenos e médios produtores rurais.bitstream/item/33986/1/bp-08.pd

Milli-arcsecond astrophysics with VSI, the VLTI spectro-imager in the ELT era

Nowadays, compact sources like surfaces of nearby stars, circumstellar environments of stars from early stages to the most evolved ones and surroundings of active galactic nuclei can be investigated at milli-arcsecond scales only with the VLT in its interferometric mode. We propose a spectro-imager, named VSI (VLTI spectro-imager), which is capable to probe these sources both over spatial and spectral scales in the near-infrared domain. This instrument will provide information complementary to what is obtained at the same time with ALMA at different wavelengths and the extreme large telescopes.Comment: 8 pages. To be published in the proceedings of the ESO workshop "Science with the VLT in the ELT Era", held in Garching (Germany) on 8-12 October 2007, A. Moorwood edito