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Lateral Expansion (lateral + expansion)
Selected AbstractsBioinspired Structural Material Exhibiting Post-Yield Lateral Expansion and Volumetric Energy Dissipation During TensionADVANCED FUNCTIONAL MATERIALS, Issue 18 2010Lifeng Wang Abstract Nature has inspired the design of improved synthetic materials that achieve superior and more efficient mechanical performance. Here microstructures inspired by the inner nacreous layer of seashells are designed and their mechanical properties including stiffness, strength, and energy dissipation are computed using micromechanical analysis. The hierarchical mineral/polymer microstructure can be tailored to achieve not only stiffness and strength, but also lateral plastic expansion during tension providing a volumetric energy dissipation mechanism. [source] Bmp2 is required for migration but not for induction of neural crest cells in the mouseDEVELOPMENTAL DYNAMICS, Issue 9 2007Ana Catarina Correia Abstract Bone morphogenetic protein (BMP) signaling is essential for neural crest development in several vertebrates. Genetic experiments in the mouse have shown that Bmp2 is essential for the genesis of migratory neural crest cells. Using several markers and a transgenic reporter approach, we now show that neural crest cells are induced in Bmp2 null mutant embryos, but that these cells fail to migrate out of the neural tube. The absence of migratory neural crest cells in these mutants is not due to their elimination by cell death. The neuroectoderm of Bmp2,/, embryos fail to close and create abnormal folds both along the anterior,posterior and medio,lateral axes, which are associated with an apparent medio,lateral expansion of the neural tube. Finally, our data suggest that the molecular cascade downstream of BMP signaling in early neural crest development may be different in mouse and avian embryos. Developmental Dynamics 236:2493,2501, 2007. © 2007 Wiley-Liss, Inc. [source] Decadal change in wetland,woodland boundaries during the late 20th century reflects climatic trendsGLOBAL CHANGE BIOLOGY, Issue 8 2010DAVID A. KEITH Abstract Wetlands are important and restricted habitats for dependent biota and play vital roles in landscape function, hydrology and carbon sequestration. They are also likely to be one of the most sensitive components of the terrestrial biosphere to global climate change. An understanding of relationships between wetland persistence and climate is imperative for predicting, mitigating and adapting to the impacts of future climate change on wetland extent and function. We investigated whether mire wetlands had contracted, expanded or remained stable during 1960,2000. We chose a study area encompassing a regional climatic gradient in southeastern Australia, specifically to avoid confounding effects of water extraction on wetland hydrology and extent. We first characterized trends in climate by examining data from local weather stations, which showed a slight increase in precipitation and marked decline in pan evaporation over the relevant period. Remote sensing of vegetation boundaries showed a marked lateral expansion of mires during 1961,1998, and a corresponding contraction of woodland. The spatial patterns in vegetation change were consistent with the regional climatic gradient and showed a weaker co-relationship to fire history. Resource exploitation, wildland fires and autogenic mire development failed to explain the observed expansion of mire vegetation in the absence of climate change. We therefore conclude that the extent of mire wetlands is likely to be sensitive to variation in climatic moisture over decadal time scales. Late 20th-century trends in climatic moisture may be related primarily to reduced irradiance and/or reduced wind speeds. In the 21st century, however, net climatic moisture in this region is projected to decline. As mires are apparently sensitive to hydrological change, we anticipate lateral contraction of mire boundaries in coming decades as projected climatic drying eventuates. This raises concerns about the future hydrological functions, carbon storage capacity and unique biodiversity of these important ecosystems. [source] Radiation dose optimized lateral expansion of the field of view in synchrotron radiation X-ray tomographic microscopyJOURNAL OF SYNCHROTRON RADIATION, Issue 5 2010David Haberthür Volumetric data at micrometer level resolution can be acquired within a few minutes using synchrotron-radiation-based tomographic microscopy. The field of view along the rotation axis of the sample can easily be increased by stacking several tomograms, allowing the investigation of long and thin objects at high resolution. On the contrary, an extension of the field of view in the perpendicular direction is non-trivial. This paper presents an acquisition protocol which increases the field of view of the tomographic dataset perpendicular to its rotation axis. The acquisition protocol can be tuned as a function of the reconstruction quality and scanning time. Since the scanning time is proportional to the radiation dose imparted to the sample, this method can be used to increase the field of view of tomographic microscopy instruments while optimizing the radiation dose for radiation-sensitive samples and keeping the quality of the tomographic dataset on the required level. This approach, dubbed wide-field synchrotron radiation tomographic microscopy, can increase the lateral field of view up to five times. The method has been successfully applied for the three-dimensional imaging of entire rat lung acini with a diameter of 4.1,mm at a voxel size of 1.48,µm. [source] MECHANICAL PROPERTIES OF UNPRESSED SEMI-HARD CHEESES BY UNIAXIAL COMPRESSIONJOURNAL OF TEXTURE STUDIES, Issue 2 2000BRIGITTE WEINRICHTER ABSTRACT Different lots of Tilsit cheeses, which are characterized by their open structure caused by pressing under their own weight during manufacture, were subjected to uniaxial compression, a quasi-standard for the evaluation of mechanical properties of hard and semi-hard cheeses. Additionally, video films showing the behaviour of the specimens during compression were analysed. For standard Tilsit with a fat content of 35% in dry matter, the cheese mass proved to be highly anisotropic with respect to stress response and lateral expansion expressed as apparent Poisson number. Specimens cut perpendicular to the flat side of the cheese wheels, which had lentil-shaped eyes with their major axis parallel to the compression plates, showed significantly higher stresses and lower Poisson numbers than specimens sampled parallel to the flat side of the cheese wheels. Therefore, stress values calculated on the basis of actual specimen diameter were different from those calculated by assuming constant specimen's volume. However, for samples with a fat content of approx. 60% in dry matter no differences caused by compression direction were observed. [source] Validation of plant functional types across two contrasting landscapesJOURNAL OF VEGETATION SCIENCE, Issue 2 2002Michael Kleyer Disturbance; Fertility; Logistic regression; Trait; Urban landscape Abstract. The validation of plant functional type models across contrasting landscapes is seen as a step towards the claim that plant functional types should recur regionally or even globally. I sampled the vegetation of an urban landscape on a range of sites representing gradients of resource supply and disturbance intensity. A group of plants with similar attributes was considered a ,functional type', if the species significantly co-occurred in a certain segment of the gradient plane of resource supply and disturbance intensity. Vegetative and regeneration traits were considered. A similar study was performed in a nearby agricultural landscape (Kleyer 1999). The logistic regression models from the urban landscape were applied to the data set of the agricultural landscape and vice versa. Although the overall environment of the two landscapes was very different, recurrent patterns of several functional types were found. At high fertility and high disturbance levels, annual species predominated with a persistent seed bank, high seed output, and short vertical expansion. When disturbances changed from below-ground to above-ground, the sexual regeneration mode was replaced by the vegetative mode, while vertical expansion remained low. At medium disturbance intensities, the vertical expansion and vegetative regeneration increased with fertility, while the seed bank remained mostly transient to short-term persistent and lateral expansion and sexual regeneration was intermediate. At low disturbances and low resource supplies, seed bank longevity, and vertical and lateral expansion tended to be long. Diversity of groups of plants with similar attributes was highest at intermediate disturbance levels and low fertility. These results correspond with Grime's humped-back model and Connell's intermediate disturbance hypothesis. [source] Morphological, Biochemical and Molecular Characterization of Herpetomonas samuelpessoai camargoi n. subsp., a Trypanosomatid Isolated from the Flower of the Squash Cucurbita moschataTHE JOURNAL OF EUKARYOTIC MICROBIOLOGY, Issue 1 2001JOAO E. FIORINI ABSTRACT. We report the morphological, biochemical and molecular characteristics of a trypanosomatid isolated from the flower of Cucurbita moschata. Although the trypanosomatid was isolated from a plant, the lack of recognition of Phytomonas-spccific molecular markers based on spliced-leader and ribosomal genes as well as by monoclonal antibodies specific for Phytomonas argues against assigning it to this genus. Because the isolate displayed typical opisthomastigote forms in culture, it is assigned to the genus Herpetomonas. Analysis of randomly amplified polymorphic DNA (RAPD) patterns and characterization of ribosomal SSU and ITS markers suggest that it is more closely related to H. samuelpessoai than to any other species. However, the presence of spined flagellates in culture (displaying lateral expansions of the plasma membrane originating near the flagellar pocket) and isolate-specific RAPD fingerprints argue strongly that the trypanosomatid belongs to a new subspecies, for which the name Herpetomonas samuelpessoai camargoi n. subsp. is proposed. [source] | |||||||||||||