Statistical investigation on morphology development of gallium nitride in initial growth stage

Morphology of Gallium Nitride (GaN) in initial growth stage was observed with atomic force microscopy (AFM) and scanning electron microscopy (SEM), It was found that the epilayer developed from islands to coalesced film. Statistics based on AFM observation was carried out to investigate the morphology characteristics. It was found that the evolution of height distribution could be used to describe morphology development. Statistics also clearly revealed variation of top-face growth rate among islands. Indium-doping effect on morphology development was also statistically studied. The roughening and smoothing behavior in morphology development was explained. (C) 2002 Elsevier Science B.V. All rights reserved.

Morphology development of ultrathin symmetric diblock copolymer film via solvent vapor treatment

We have followed the time development of the microdomain structure in symmetric diblock copolymer poly(styrene-b-methyl methacrylate), P(S-b-MMA), ultrathin films via PMMA-selective solvent vapor treatment by atomic force microscopy (AFM). After preparation on a substrate preferentially attracting the PMMA block, PS forms a continuous layer at a film's free surface. With subsequent solvent vapor treatment, the film gradually shows a well-ordered hexagonally packed nanocylinders structure. It is shown that only when the film thickness is less than the 1/2L(0) (lamellar repeat spacing), and exposed to PMMA block selective solvent for an appropriate time, can the well-ordered hexagonally packed nanocylinders form. On an extended solvent vapor treatment, a mixed morphology containing nanocylinders and stripes appears, followed by the striped morphologies. When the annealing time is long enough, the film comes back to the flat surface again, however, with PMMA instead of PS dominating the free surface.

Morphology, development and homologies of the perianth and floral nectaries in Croton and Astraea (Euphorbiaceae-Malpighiales)

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Numerical model of solid phase transformations governed by nucleation and growth: microstructure development during isothermal crystallization

A simple numerical model which calculates the kinetics of crystallization involving randomly distributed nucleation and isotropic growth is presented. The model can be applied to different thermal histories and no restrictions are imposed on the time and the temperature dependences of the nucleation and growth rates. We also develop an algorithm which evaluates the corresponding emerging grain-size distribution. The algorithm is easy to implement and particularly flexible, making it possible to simulate several experimental conditions. Its simplicity and minimal computer requirements allow high accuracy for two- and three-dimensional growth simulations. The algorithm is applied to explore the grain morphology development during isothermal treatments for several nucleation regimes. In particular, thermal nucleation, preexisting nuclei, and the combination of both nucleation mechanisms are analyzed. For the first two cases, the universal grain-size distribution is obtained. The high accuracy of the model is stated from its comparison to analytical predictions. Finally, the validity of the Kolmogorov-Johnson-Mehl-Avrami model SSSR, is verified for all the cases studied

Mapping the intriguing transient morphologies and the demixing behavior in PS/PVME blends in the presence of rod-like nanoparticles

The demixing behavior, transient morphologies and mechanism of phase separation in PS/PVME blends were greatly altered in the presence of a very low concentration of rod-like particles (multiwall carbon nanotubes, MWNTs). This phenomenon is due to the specific interaction of one of the phases (PVME) with the anisotropic MWNTs, which creates a heterogeneous environment in the blend. This specific interaction alters the chain dynamics in the interfacial region as against the bulk. A comprehensive analysis using isochronal temperature sweep was performed to understand the demixing temperature in the blends. The evolution of phase morphology as a function of time and temperature was assessed by polarizing optical microscopy (POM), atomic force microscopy (AFM) and scanning electron microscopy (SEM). The addition of MWNTs increased the rheological demixing temperature and the spinodal temperature in almost all the compositions. The intriguing transient morphologies were mapped, which varied from nucleation and growth to coalescence-induced viscoelastic phase separation (C-VPS) in PVME-rich blends, to spinodal decomposition in the near-critical compositions, to transient gel-induced VPS (T-VPS) in the PS-rich compositions. Mapping of the morphology development displayed two types of fracture mechanisms: ductile fracture for near-critical compositions and brittle fracture for off-critical composition. The change in the phase separation mechanism in the presence of MWNTs was due to the variation in dynamic asymmetry brought about by these anisotropic particles. All these observations were correlated by POM, SEM and AFM studies. The length of the cooperatively rearranging region (CRR), as evaluated using modulated differential scanning calorimetry (MDSC) measurements, was found to be composition-independent. The observed variation of effective glass transition of PVME (low T-g component) on blending with PS (high Tg component) and by the addition of MWNTs accounts for the dynamic heterogeneity introduced by MWNTs in the system.

Online study of the formation of PA6 droplets in PP matrix under shear flow

Breakup process of polyamide 6 (PA6) in polypropylene (PP) matrix under shear flow was online studied by using a Linkam CSS 450 stage equipped with optical microscopy. Both tip streaming and fracture breakup modes of PA6 droplets were observed in this study. It was reported that the droplet would break up by tip streaming model when the radio of the droplet phase viscosity to the matrix phase viscosity (n(r) = n(d)/n(m)) is smaller than 0.1 (Taylor, Proc R Soc London A 1934, 146, 501; Grace, Chem Eng Commun 1982, 14, 225; Bartok and Mason, J Colloid Sci 1959, 14, 13; Rumscheidt and Mason, J Colloid Sci 1961, 16, 238; de Bruijn, Chem Eng Sci 1993, 48, 277). However, the tip streaming model was observed even when the viscosity ratio was much greater than 0.1 (n(r) = 1.9). In this study for the tip streaming mode, small droplets were ruptured from the tip of the mother droplet. On the other hand, the mother droplet was broken into two or more daughter droplets with one or several satellite droplets between them for the fracture mode. It was found that PA6 droplet was much elongated at first, and then broke up via tip streaming or fracture to form daughter droplets or small satellite droplets with the shape of fiber or ellipse.

Toughening PA1010 with a functionalized saturated polyolefin elastomer

Polyamide (PA)1010 is blended with a saturated polyolefin elastomer, ethylene-cu-olefin copolymer (EOCP). To improve the compatibility of PA1010 with EOCP, different grafting rates of EOCP with maleic anhydride (MA) are used. The reaction between PA1010 and EOCP-g-MA during extrusion is verified through an extraction test. Mechanical properties, such as notched Izod impact strength, elongation at break, etc., are examined as a function of grafting rate and weight fraction of elastomer. It was found that in the scale of grafting rate (0.13-0.92 wt %), 0.51 wt % is an extreme point for several mechanical properties. Elastomer domains of PA1010/ EOCP-g-MA blends show a finer and more uniform dispersion in the matrix than that of PA1010/EOCP blends. For the same grafting rate, the average sizes of elastomer particles are almost independent on the contents of elastomer, but for different grafting rates, the particle sizes are decreased with increasing grafting rate. The copolymer formed during extrusion strengthens the interfacial adhesion and acts as an emulsifier to prevent the aggregation of elastomer in the process of blending. (C) 2000 John Wiley & Sons, Inc.

Les végétaux comme éléments du paysage sonore : relations qualitatives entre conditions environnementales, morphologie et organisation dans la production d’ambiances sonores

Le paysage sonore est une forme de perception de notre environnement qui nous permet d’identifier les composantes sonores de notre quotidien. Ce projet de recherche porte sur une thématique particulière, les sons produits par les végétaux et leurs rôles dans les ambiances sonores paysagères. C’est la perspective que nous avons explorée in situ, en comparant les différentes espèces végétales; cette collection d’informations nous permet de proposer une typologie d’ambiances sonores des végétaux. Dans la première partie, des notions rattachées au « monde sonore » telles que l’objet sonore, le paysage sonore et les effets sonores justifient d’établir, dans la méthodologie, une grille d’analyse comportant différentes échelles d’écoute. Une lecture multidisciplinaire propose, d’une part, de réunir de l’information sur le son et les végétaux, la morphologie de ces derniers, l’aménagement au site, les conditions climatiques et, d’autre part, de retrouver ce qui a trait au son dans l’histoire des jardins, dont les jardins sensoriels, thérapeutiques, technologiques, et des sentiers d’interprétation sonore, sous l’angle du son comme projet. De plus, une liste de végétaux recevant les chants et cris de la faune vient introduire la notion de biodiversité sonore. Une enquête sociale de terrain, par la méthode des parcours commentés, et une enquête « experte » ont été réalisées au Jardin botanique de Montréal. Ces deux enquêtes nous ont permis de constituer une grille d’analyse croisée comprenant plusieurs échelles d’écoute : textures, actions sonores, effets sonores... De là, des générateurs d’ambiance (morphologie, organisation, climat) ont été relevés pour déterminer les aspects de récurrences et de différenciations d’un type d’ambiance sonore à l’autre. Des associations se sont formées en fonction de onze types de végétaux, chacun comprenant plusieurs sous-catégories. Celles-ci proposent des ambiances sonores spécifiques, des échelles d’écoute à considérer pour chaque type d’ambiance et l’énumération d’espèces à utiliser. Cette recherche ouvre la voie à un autre type de lecture sonore, par thématique d’ambiance (les sons du végétal dans notre cas), afin d’offrir de nouveaux outils de conception pour les professionnels, en profonde relation avec les perceptions sonores d’usagers sur le terrain et l’agencement spécifique d’un site.

HOMOLOGIES OF FLORAL STRUCTURES IN VELLOZIACEAE WITH PARTICULAR REFERENCE TO THE CORONA

New data on floral morphology, development, and vasculature in two Brazilian genera of the monocot family Velloziaceae (Pandanales) are used to explore the homologies of their unusual floral structures, especially the corona of Barbacenia and the corona-like appendages and multiple stamens of some Vellozia species. All Velloziaceae have epigynous flowers. Some species of Vellozia are polyandrous, and stamen number can be variable within species. In Vellozia jolyi, there is a single stamen opposite each sepal and a stamen fascicle (of three secondary stamens) opposite each petal. Each stamen possesses a single vascular bundle, and these are united into a single aggregate bundle in proximal regions of the fascicle. Stamens mature centripetally within each fascicle. The coronal appendages of both genera are closely associated with the stamens, but they share some vasculature with the tepals and develop late in ontogeny. The coronal organs cannot readily be homologized with any of the typical floral organs, but they show partial homology with both tepals and stamens. They are most readily interpreted as a late elaboration of the region between the petals and stamens associated with epigyny and the hypanthium.

Morphologic and morphometric aspects of oenocytes of Apis mellifera queens and workers in different phases of life

Oenocytes of adult workers and queens of Apis mellifera L. were studied in different ages or life stages, by means of morphometric and histologic techniques. In workers, the oenocytes were found in the head, near the mandibles and in the abdomen, immersed in the parietal fat body mainly below the sterna, close to the wax gland. In queens, two populations of oenocytes different in size and localization were found within the parietal and visceral fat body, respectively. The oenocytes of workers and queens show the presence of acid lipids and acid phosphatase. The role of these cells in the castes differences is discussed.

Comportamento de cafeeiros (Coffea arabica L. cv. mundo novo) oriundos de ecossistemas diversos, sob condições uniformes

Estudou-se o desempenho de cafeeiros (Coffea arabica L. cv. Mundo Novo) originários de quatro ecossistemas diferentes (sombra, meia sombra, pleno sol e casa de vegetação), quando submetidos a condições de campo. Realizaram-se avaliações da morfologia, desenvolvimento e produtividade biológica do cafeeiro. Efetuaram-se também determinações da nutrição mineral, infestação de pragas e solarização. O crescimento em altura revelou-se superior nas plantas originárias de casa de vegetação e meia sombra. O número de ramos mostrou-se mais elevado em cafeeiros provenientes de locais mais ensolarados, sendo que plantas originárias de locais mais sombreados apresentaram maior número de folhas por ramo. Nestes três parâmetros notou-se uma tendência de recuperação nas condições de campo em cafeeiros provenientes de sombra. O peso da matéria seca foliar revelou-se mais elevado em plantas oriundas de meia sombra e mais baixo naquelas provenientes de casa de vegetação, sendo que nos dois ocorreu adaptação às condições de campo num período de 75 dias. O peso da matéria seca do caule e das raízes mostrou-se mais alto nos cafeeiros originários de casa de vegetação, sendo que a melhor adaptação às condições uniformes também ocorreu com as plantas oriundas da sombra. Quanto ao aspecto nutricional, determinaram-se teores mais elevados de N foliar em plantas oriundas de pleno sol e níveis mais altos de P e Ca em cafeeiros originários de meia sombra. Esse tratamento promoveu também acúmulo de Zn no cafeeiro. O caule dos cafeeiros mostrou teores de nutrientes inferiores às folhas, exceto o nível mais alto de Zn e os níveis semelhantes de Cu. Plantas originárias de pleno sol apresentaram teores mais elevados de Ca e S. As raízes mostraram níveis de nutrientes superiores ao caule e inferiores às folhas, exceto no caso do Cu, Zn e Mn, que se revelaram mais altos no sistema radicular. O nível de infestação de Perileucoptera coffeclla mostrou-se mais elevado nas plantas provenientes de casa de vegetação, sendo que cafeeiros originários de locais sombreados revelaram-se pouco afetados. A infestação de Coccus viridis revelou-se sempre mais elevada em plantas provenientes de meia sombra. Cafeeiros oriundos de pleno sol e ca sa de vegetação não sofreram solarização, sendo que aqueles provenientes de meia sombra e sombra sofreram danos crescentes nas folhas. Sombreamento afetou o desenvolvimento dos cafeeiros em função de sua intensidade e interação com outros fatores bióticos e abióticos do ecossistema.

MORPHOLOGIC AND MORPHOMETRIC ASPECTS OF ENOCYTES OF APIS-MELLIFERA QUEENS AND WORKERS IN DIFFERENT PHASES OF LIFE

Oenocytes of adult workers and queens of Apis mellifera L. were studied in different ages or life stages, by means of morphometric and histologic techniques. In workers, the oenocytes were found in the head, near the mandibles and in the abdomen, immersed in the parietal fat body mainly below the sterna, close to the wax glands. In queens, two populations of oenocytes different in size and localization were found within the parietal and visceral fat body, respectively. The oenocytes of workers and queens show the presence of acid lipids and acid phosphatase. The role of these cells in the castes differences is discussed.

Homologies of floral structures in velloziaceae with particular reference to the corona

New data on floral morphology, development, and vasculature in two Brazilian genera of the monocot family Velloziaceae (Pandanales) are used to explore the homologies of their unusual floral structures, especially the corona of Barbacenia and the corona-like appendages and multiple stamens of some Vellozia species. All Velloziaceae have epigynous flowers. Some species of Vellozia are polyandrous, and stamen number can be variable within species. In Vellozia jolyi, there is a single stamen opposite each sepal and a stamen fascicle (of three secondary stamens) opposite each petal. Each stamen possesses a single vascular bundle, and these are united into a single aggregate bundle in proximal regions of the fascicle. Stamens mature centripetally within each fascicle. The coronal appendages of both genera are closely associated with the stamens, but they share some vasculature with the tepals and develop late in ontogeny. The coronal organs cannot readily be homologized with any of the typical floral organs, but they show partial homology with both tepals and stamens. They are most readily interpreted as a late elaboration of the region between the petals and stamens associated with epigyny and the hypanthium. © 2010 by The University of Chicago. All rights reserved.

Effect of human TGF-beta on the gene expression profile of Schistosoma mansoni adult worms

Schistosoma mansoni is responsible for schistosomiasis, a parasitic disease that affects 200 million people worldwide. Molecular mechanisms of host-parasite interaction are complex and involve a crosstalk between host signals and parasite receptors. TGF-beta signaling pathway has been shown to play an important role in S. mansoni development and embryogenesis. In particular human (h) TGF-beta has been shown to bind to a S. mansoni receptor, transduce a signal that regulates the expression of a schistosome target gene. Here we describe 381 parasite genes whose expression levels are affected by in vitro treatment with hTGF-beta. Among these differentially expressed genes we highlight genes related to morphology, development and cell cycle that could be players of cytokine effects on the parasite. We confirm by qPCR the expression changes detected with microarrays for 5 out of 7 selected genes. We also highlight a set of non-coding RNAs transcribed from the same loci of protein-coding genes that are differentially expressed upon hTCF-beta treatment. These datasets offer potential targets to be explored in order to understand the molecular mechanisms behind the possible role of hTGF-beta effects on parasite biology. (C) 2012 Elsevier B.V. All rights reserved.