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Search Results: 1 - 10 of 199024 matches for " G. Fernandes "
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On the k-Structure Ratio in Planar and Outerplanar Graphs
Gruia Calinescu,Cristina G. Fernandes
Discrete Mathematics & Theoretical Computer Science , 2008,
Abstract: A planar k-restricted structure is a simple graph whose blocks are planar and each has at most k vertices. Planar k-restricted structures are used by approximation algorithms for Maximum Weight Planar Subgraph, which motivates this work. The planar k-restricted ratio is the infimum, over simple planar graphs H, of the ratio of the number of edges in a maximum k-restricted structure subgraph of H to the number edges of H. We prove that, as k tends to infinity, the planar k-restricted ratio tends to 1/2. The same result holds for the weighted version. Our results are based on analyzing the analogous ratios for outerplanar and weighted outerplanar graphs. Here both ratios tend to 1 as k goes to infinity, and we provide good estimates of the rates of convergence, showing that they differ in the weighted from the unweighted case.
Edge-coloring series-parallel multigraphs
Cristina G. Fernandes,Robin Thomas
Computer Science , 2011,
Abstract: We give a simpler proof of Seymour's Theorem on edge-coloring series-parallel multigraphs and derive a linear-time algorithm to check whether a given series-parallel multigraph can be colored with a given number of colors.
Geodesic stability for memoryless binary long-lived consensus
Cristina G. Fernandes,Maya Stein
Computer Science , 2011,
Abstract: The determination of the stability of the long-lived consensus problem is a fundamental open problem in distributed systems. We concentrate on the memoryless binary case with geodesic paths. We offer a conjecture on the stability in this case, exhibit two classes of colourings which attain this conjectured bound, and improve the known lower bounds for all colourings. We also introduce a related parameter, which measures the stability only for certain geodesics, and for which we also prove lower bounds.
Repetition-free longest common subsequence of random sequences
Marcos Kiwi,Cristina G. Fernandes
Computer Science , 2013,
Abstract: A repetition free Longest Common Subsequence (LCS) of two sequences x and y is an LCS of x and y where each symbol may appear at most once. Let R denote the length of a repetition free LCS of two sequences of n symbols each one chosen randomly, uniformly, and independently over a k-ary alphabet. We study the asymptotic, in n and k, behavior of R and establish that there are three distinct regimes, depending on the relative speed of growth of n and k. For each regime we establish the limiting behavior of R. In fact, we do more, since we actually establish tail bounds for large deviations of R from its limiting behavior. Our study is motivated by the so called exemplar model proposed by Sankoff (1999) and the related similarity measure introduced by Adi et al. (2007). A natural question that arises in this context, which as we show is related to long standing open problems in the area of probabilistic combinatorics, is to understand the asymptotic, in n and k, behavior of parameter R.
Germina??o de aquênios de Baccharis dracunculifolia D.C.(Asteraceae)
Gomes, Vania;Fernandes, G.Wilson;
Acta Botanica Brasilica , 2002, DOI: 10.1590/S0102-33062002000400005
Abstract: we studied the germination of baccharis dracunculifolia (asteraceae), achene, a species that has colonizing traits, which makes it a potential candidate for forest rehabilitation. achenes were collected in 1998 and were germinated at 15o, 20o, 25o and 30oc under continuous light, and darkness conditions with four replicates with 25 achenes in each. we had also collected achenes in 1997, and they were germinated at 20o and 25oc, under the same conditions. the mean germination rate and emergency velocity index (evi) were calculated to answer the following questions: (a) how does the germination behavior of b. dracunculifolia's achenes vary under different temperature and light conditions? (b) is there any relationship between the total number of germinated achenes and the evi? (c) how does achene storage affect the germination rate? achenes that germinated at 15oc both under light and dark conditions and at 20oc under light achieved significantly higher germination rates than achenes that germinated in the other treatments (p < 0.05). achenes of b. dracunculifolia showed a positive relationship between evi and germination rates (y = 0.0802x - 0.0386, r2 = 0.91, p < 0.05). higher evi's were found among achenes that germinated at 15o and 20oc under light and 15oc under dark treatments. storage only affected the germination rates at 20oc under light condition (p < 0.05).
Insect galls from Serra de S?o José (Tiradentes, MG, Brazil)
Maia, V. C.;Fernandes, G. W.;
Brazilian Journal of Biology , 2004, DOI: 10.1590/S1519-69842004000300007
Abstract: one hundred thirty-seven morphotypes of insect galls were found on 73 plant species (47 genera and 30 families) in serra de s?o josé, in tiradentes, mg, brazil. fabaceae, myrtaceae, asteraceae, and melastomataceae were the plant families that supported most of the galls (49.6% of the total). galls were mostly found on leaves and stems (66.4% and 25.5%, respectively). galls were induced by diptera, lepidoptera, coleoptera, hemiptera (sternorrhyncha), hymenoptera, and thysanoptera. the majority of them (73.7%) were induced by gall midges (cecidomyiidae: diptera). besides the gall inducers, other insects found associated with the galls were parasitoids (hymenoptera), inquilines (coleoptera, lepidoptera, diptera, and hemiptera), and predators (diptera).
Twenty years of research on cholesteric lyotropic liquid crystals at the Chemistry Institute of the University of S?o Paulo
Alcantara, M. R.;Fernandes Jr., E. G.;
Brazilian Journal of Physics , 2002, DOI: 10.1590/S0103-97332002000300009
Abstract: in this paper we present a review of twenty years of research on cholesteric liquid crystals at the chemistry institute of the university of s?o paulo. the results on the interaction forces, responsible for the maintenance of the helical structure, are a function of the chemical variability obtained in these systems. the last results obtained using rheological techniques are presented, and research in this field was undertaken in order to understand the cholesterization process when different systems and inductors are involved.
On the Thermodynamics of Ionized Gases
Xavier, Christine Fernandes;Kremer, G. M.;
Brazilian Journal of Physics , 1997, DOI: 10.1590/S0103-97331997000400017
Abstract: the transport coefficients of a completely ionized gas are determined from an extended thermodynamic theory of mixtures of ideal gases in the presence of external electromagnetic fieds. the onsager relations for the transport coefficients in the presence of external magnetic flux density are also discussed.
INGUINAL RINGS: MORPHOMETRIC STUDY ON BRAZILIAN MALE NEWBORNS
Fernandes,G. J. M.; Prates,J. C.;
Revista chilena de anatomía , 1997, DOI: 10.4067/S0716-98681997000200012
Abstract: although of most importance for pediatricians and pediatric surgeons, the inguinal region of male newborns has never been steadily studied in a morphometric view. our investigation was performed in order to measure the diameters of the inguinal rings (internal and external) and to determine their exact relative position. we used 30 fixed bodies of brazilian male newborns, chosen randomly, from the laboratories of anatomy of the faculty of medical sciences of santos and unifesp - epm. the dissection of the inguinal region was carried out in a classical way and the diameters of the inguinal rings were taken and their relative position observed. our data confirmed that exact superposition of inguinal rings is quite rare in male newborns, the majority of them having a wellformed inguinal canal at birth. the diameters of both inguinal rings show no significant differences in size (one to another) nor in comparison to both sides of the body
Insect herbivores associated with Baccharis dracunculifolia (Asteraceae): responses of gall-forming and free-feeding insects to latitudinal variation
Fagundes,Marcílio; Wilson Fernandes,G;
Revista de Biología Tropical , 2011,
Abstract: the spatial heterogeneity hypothesis has been invoked to explain the increase in species diversity from the poles to the tropics: the tropics may be more diverse because they contain more habitats and microhabitats. in this paper, the spatial heterogeneity hypothesis prediction was tested by evaluating the variation in richness of two guilds of insect herbivores (gall-formers and free-feeders) associated with baccharis dracunculifolia (asteraceae) along a latitudinal variation in brazil. the seventeen populations of b. dracunculifolia selected for insect herbivores sampling were within structurally similar habitats, along the n-s distributional limit of the host plant, near the brazilian sea coast. thirty shrubs were surveyed in each host plant population. a total of 8 201 galls and 864 free-feeding insect herbivores belonging to 28 families and 88 species were sampled. the majority of the insects found on b. dracunculifolia were restricted to a specific site rather than having ageographic distribution mirroring that of the host plant. species richness of free-feeding insects was not affected by latitudinal variation corroborating the spatial heterogeneity hypothesis. species richness of gall-forming insects was positively correlated with latitude, probably because galling insect associated with baccharris genus radiated in southern brazil. other diversity indices and evenness estimated for both gall-forming and free feeding insect herbivores, did not change with latitude, suggesting a general structure for different assemblages of herbivores associated with the host plant b. dracunculifolia. thus it is probable that, insect fauna sample in each site resulted of large scale events, as speciation, migration and coevolution, while at local level, the population of these insects is regulated by ecological forces which operate in the system. rev. biol. trop. 59 (3): 1419-1432. epub 2011 september 01.
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