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Search Results: 1 - 10 of 208 matches for " Ronei;Hartz "
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Metacommunity Composition of Web-Spiders in a Fragmented Neotropical Forest: Relative Importance of Environmental and Spatial Effects
Ronei Baldissera, Everton N. L. Rodrigues, Sandra M. Hartz
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0048099
Abstract: The distribution of beta diversity is shaped by factors linked to environmental and spatial control. The relative importance of both processes in structuring spider metacommunities has not yet been investigated in the Atlantic Forest. The variance explained by purely environmental, spatially structured environmental, and purely spatial components was compared for a metacommunity of web spiders. The study was carried out in 16 patches of Atlantic Forest in southern Brazil. Field work was done in one landscape mosaic representing a slight gradient of urbanization. Environmental variables encompassed plot- and patch-level measurements and a climatic matrix, while principal coordinates of neighbor matrices (PCNMs) acted as spatial variables. A forward selection procedure was carried out to select environmental and spatial variables influencing web-spider beta diversity. Variation partitioning was used to estimate the contribution of pure environmental and pure spatial effects and their shared influence on beta-diversity patterns, and to estimate the relative importance of selected environmental variables. Three environmental variables (bush density, land use in the surroundings of patches, and shape of patches) and two spatial variables were selected by forward selection procedures. Variation partitioning revealed that 15% of the variation of beta diversity was explained by a combination of environmental and PCNM variables. Most of this variation (12%) corresponded to pure environmental and spatially environmental structure. The data indicated that (1) spatial legacy was not important in explaining the web-spider beta diversity; (2) environmental predictors explained a significant portion of the variation in web-spider composition; (3) one-third of environmental variation was due to a spatial structure that jointly explains variation in species distributions. We were able to detect important factors related to matrix management influencing the web-spider beta-diversity patterns, which are probably linked to historical deforestation events.
Effects of understory structure on the abundance, richness and diversity of Collembola (Arthropoda) in southern Brazil
Ribeiro-Troian, Vera R;Baldissera, Ronei;Hartz, Sandra M;
Neotropical Entomology , 2009, DOI: 10.1590/S1519-566X2009000300007
Abstract: the purpose of this study was to investigate the effects of different landscape structures on the understory collembola community. four different forest physiognomies were compared: pinus spp. plantation, eucalyptus spp. plantation, araucaria angustifolia plantation, and a remaining native araucaria forest. three areas containing two sampling units (25 m x 2 m each) were selected in each forest physiognomy. understory collembola collection was done with a 1 x 1m canvas sheet held horizontally below the vegetation, which was beaten with a 1m long stick, seasonally from september 2003 to august 2004. we evaluated the influence of forest physiognomies on the abundance, richness and diversity of collembola communities. it was also verified if the habitat structure of each physiognomy was associated with the composition of the collembola community. a total number of 4,111 individuals were collected belonging to the families entomobrydae and tomocerida (entomobryomorpha), and sminthuridae (symphypleona), and divided in 12 morphospecies. pinus plantation presented the highest richness, abundance and diversity of collembola and it was associated to diverse understory vegetation. the abundance of entomobrydae and sminthuridae was associated to the presence of bushes, while tomoceridae abundance was associated to the presence of trees. the habitat structure, measured through understory vegetation density and composition, plays an important role on the determination of the structure and composition of the collembola community.
The author replies
Hartz Zulmira
Cadernos de Saúde Pública , 1999,
Measurements of B Hadron Properties at the Tevatron
Mark Hartz
Physics , 2008,
Abstract: Recent measurements of B hadron properties carried out in sqrt(s)=1.96 TeV p/p-bar collisions at the Tevatron are reviewed. Included are measurements of the Bc+ meson lifetime, using J/psi+l+X final states, and the mass, using J/psi+pi final states, a flavor specific measurement of the Bs0 lifetime in Ds+pi+X decays, simultaneous measurements of the Bs0 lifetime and lifetime difference in J/psi+phi decays, the first direct evidence and mass measurements of the Xi_b- baryon, and measurements of the polarization of 1S charmonium. For all measurements, charge conjugate modes are included.
On the isomorphism problem for multiplier algebras of Nevanlinna-Pick spaces
Michael Hartz
Mathematics , 2015,
Abstract: We continue the investigation of the isomorphism problem for multiplier algebras of reproducing kernel Hilbert spaces with the complete Nevanlinna-Pick property. In contrast to previous work in this area, we do not study these spaces by identifying them with restrictions of a universal space, namely the Drury-Arveson space. Instead, we work directly with the Hilbert spaces and their reproducing kernels. In particular, we show that two multiplier algebras of Nevanlinna-Pick spaces on the same set are equal if and only if the Hilbert spaces are equal. Most of the article is devoted to the study of a special class of Nevanlinna-Pick spaces on homogeneous varieties. We provide a complete answer to the question of when two multiplier algebras of spaces of this type are algebraically or isometrically isomorphic. This generalizes results of Davidson, Ramsey, Shalit, and the author.
Topological isomorphisms for some universal operator algebras
Michael Hartz
Mathematics , 2012, DOI: 10.1016/j.jfa.2012.08.028
Abstract: Let $I \subset \mathbb C[z_1,...,z_d]$ be a radical homogeneous ideal, and let $\mathcal A_I$ be the norm-closed non-selfadjoint algebra generated by the compressions of the $d$-shift on Drury-Arveson space $H^2_d$ to the co-invariant subspace $H^2_d \ominus I$. Then $\mathcal A_I$ is the universal operator algebra for commuting row contractions subject to the relations in $I$. We ask under which conditions are there topological isomorphisms between two such algebras $\mathcal A_I$ and $\mathcal A_J$? We provide a positive answer to a conjecture of Davidson, Ramsey and Shalit: $\mathcal A_I$ and $\mathcal A_J$ are topologically isomorphic if and only if there is an invertible linear map $A$ on $\mathbb C^d$ which maps the vanishing locus of $J$ isometrically onto the vanishing locus of $I$. Most of the proof is devoted to showing that finite algebraic sums of full Fock spaces over subspaces of $\mathbb C^d$ are closed. This allows us to show that the map $A$ induces a completely bounded isomorphism between $\mathcal A_I$ and $\mathcal A_J$.
Nevanlinna-Pick spaces with hyponormal multiplication operators
Michael Hartz
Mathematics , 2013, DOI: 10.1090/S0002-9939-2015-12373-8
Abstract: We show that the Hardy space on the unit disk is the only non-trivial irreducible reproducing kernel Hilbert space which satisfies the complete Nevanlinna-Pick property and hyponormality of all multiplication operators.
Von Neumann's inequality for commuting weighted shifts
Michael Hartz
Mathematics , 2015,
Abstract: We show that every multivariable contractive weighted shift dilates to a tuple of commuting unitaries, and hence satisfies von Neumann's inequality. This answers a question of Lubin and Shields. We also exhibit a closely related $3$-tuple of commuting contractions, similar to Parrott's example, which does not dilate to a $3$-tuple of commuting unitaries.
Preda??o de sementes ao longo de uma borda de Floresta Ombrófila Mista e pastagem
Baldissera, Ronei;Ganade, Gislene;
Acta Botanica Brasilica , 2005, DOI: 10.1590/S0102-33062005000100016
Abstract: this study aims to evaluate how seed predation of three native tree species (mimosa scabrella bentham, prunus sellowii koehne, and myrsine laetevirens mez.) could be altered along an edge between araucaria forest and pasture at the national forest of s?o francisco de paula, rio grande do sul, brazil. groups of seeds were placed at ten random points in each of the following distances from the forest edge: 0m, 25m, 50m, 100m, and 250m from the edge into the forest, and 5m and 50m from the edge into the pasture. seeds were monitored until total predation or until their time for germination was over. seed predation rates decreased from the edge up to 50m inside the forest in relation to the forest interior and open pasture. m. scabrella and m. laetevirens showed a reduction in seed predation rates in pasture points that were located at the vicinities of the forest. the results indicated a decrease in the activity of seed predators near the forest edge, which could enhance plant community regeneration at the edge, and promote the expansion of the forest towards the adjacent pasture.
A química newtoniana
Mocellin, Ronei Clécio;
Química Nova , 2006, DOI: 10.1590/S0100-40422006000200035
Abstract: the work of newton exerted a profound influence on the development of science. in chemistry this newtonian influence was present in query 31 of newton's optics. however, the incursion of newton's thought into chemistry brought upon the chemists an epistemological question, that of the nature of their discipline. would chemistry be a discipline in its own right, or simply a branch of physics? in this work we present the newtonian program for chemistry, as well as the reaction of traditional chemists to it. we conclude by proposing that lavoisier carried through a synthesis between newtonian methodology and the singularity of traditional chemistry.
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