Foliar and twigs lesions of sweet orange caused by citrus leprosis

O objetivo deste trabalho foi apresentar a descrição anatômica dos tecidos lesionados pelo Citrus leprosis virus do tipo citoplasmático (CiLV-C), em ramos e folhas de laranjeira-doce (Citrus sinensis (L.) Osbeck) 'Pêra', e fornecer dados para a compreensão das interações entre o vírus e a planta hospedeira. Tecidos que apresentavam lesões foram seccionados em micrótomo rotativo (5–7 µm de espessura) e, posteriormente, as lâminas foram coradas e montadas em resina sintética. Nas análises realizadas no microscópio eletrônico de varredura, as amostras, depois de fixadas, foram imersas em glicerina 30% e, em seguida, criofraturadas, desidratadas em série etílica, secadas ao ponto crítico de CO2, e cobertas com uma delgada camada de ouro. As lesões foliares se iniciaram como pontuações necróticas, envolvidas por halos cloróticos que limitam o crescimento da lesão. Nos ramos, ocorreram dois tipos de lesões com fendas. Na região da fenda, houve intensa hiperplasia do parênquima cortical e floemático, que promoveu a obliteração das células condutoras do floema. A formação de ductos gomosos traumáticos nas lesões caulinares foi descrita. As alterações verificadas no floema podem explicar porque o vírus torna-se não-sistêmico.The objective of this work was to present the anatomical description of tissues lesioned by Citrus leprosis virus cytoplasmatic type (CiLV-C), in leaves and twigs of 'Pêra' sweet orange (Citrus sinensis (L.) Osbeck) providing new data to understand the interactions between the virus and the plant host, in Brazil. Leprosis lesions were cut on a rotary microtome (5–7 µm thick), stained and mounted in synthetic resin. For scanning electron microscope analysis, fixed tissues were immersed in glycerin 30% and criofractured, dehydrated in a graded ethylic series, critical point drying and coated with gold. Foliar lesions began as necrotic points surrounded by a yellow halo that inhibited the lesion expansion. The twigs presented two different lesions: depressed ones and pustules with ruptures. There was hyperplasia of the cortical and phloematic parenchyma cells causing the obliteration of phloematic vessels. These histological alterations of the phloem tissue could explain why the virus does not become systemic even occasionally infecting phloem parenchyma cells. The development of gummosis traumatic ducts in twig lesions was described here

ANDES: Evaluating Mapping Strategies with Synthetic Programs

This paper presents the ANDES performance evaluation tool. ANDES is based on the synthetic execution of parallel programs and it is used for the evaluation of mapping strategies. The Meganode, a distributed memory parallel computer, is considered as our target architecture. ANDES takes into account a benchmark of quantitative models of parallel algorithms and a set of mapping strategies (greedy and iterative algorithms are used). We show how this tool allows an extensive comparison of mapping strategies by using the benchmark, the mapping strategies and different cost functions. 1 Introduction Distributed memory multiprocessors (DMM) are the current trend of high-performance parallel computers. They represent a good balance between cost and performance, mainly because of the connection of several commercial, general and relatively cheap microprocessors. A distributed memory multiprocessor is a computer composed of autonomous processors connected by a high speed communication network...

Distributed Generation of Suffix Arrays: a Quicksort-Based Approach

An algorithm for the distributed computation of suffix arrays for large texts is presented. The parallelism model is that of a set of sequential tasks which execute in parallel and exchange messages between each other. The underlying architecture is that of a highbandwidth network of processors. In such a network, a remote memory access has a transfer time similar to the transfer time of magnetic disks (with no seek cost) which allows to use the aggregate memory distributed over the various processors as a giant cache for disks. Our algorithm takes advantage of this architectural feature to implement a quicksort-based distributed sorting procedure for building the suffix array. We show that such algorithm has computation complexity given by O(r log(n=r)+n=r log r log n) in the worst case and O(n=r log n) on average and communication complexity given by O(n=r log 2 r) in the worst case and O(n=r log r) on average, where n is the text size and r is the number of processors. This is ..