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Cylindrical Morphology (cylindrical + morphology)
Selected AbstractsPolyhedral serpentine grains in CM chondritesMETEORITICS & PLANETARY SCIENCE, Issue 5 2006Thomas J. ZEGA The structure of these grains is similar to terrestrial polygonal serpentine, but the data show that some have spherical or subspherical, rather than cylindrical morphologies. We therefore propose that the term polyhedral rather than polygonal be used to describe this material. EDS shows that the polyhedral grains are rich in Mg with up to 8 atom% Fe. EELS indicates that 70% of the Fe occurs as Fe3+. Alteration of cronstedtite on the meteorite parent body under relatively oxidizing conditions is one probable pathway by which the polyhedral material formed. The polyhedral grains are the end-member serpentine in a mineralogic alteration sequence for the CM chondrites. [source] Calcite microcrystals in the pineal gland of the human brain: First physical and chemical studiesBIOELECTROMAGNETICS, Issue 7 2002Simon Baconnier Abstract A new form of biomineralization has been studied in the pineal gland of the human brain. It consists of small crystals that are less than 20 ,m in length and that are completely distinct from the often observed mulberry-type hydroxyapatite concretions. A special procedure was developed for isolation of the crystals from the organic matter in the pineal gland. Cubic, hexagonal, and cylindrical morphologies have been identified using scanning electron microscopy. The crystal edges were sharp whereas their surfaces were very rough. Energy dispersive spectroscopy showed that the crystals contained only the elements calcium, carbon, and oxygen. Selected area electron diffraction and near infrared Raman spectroscopy established that the crystals were calcite. With the exception of the otoconia structure of the inner ear, this is the only known nonpathological occurrence of calcite in the human body. The calcite microcrystals are probably responsible for the previously observed second harmonic generation in pineal tissue sections. The complex texture structure of the microcrystals may lead to crystallographic symmetry breaking and possible piezoelectricity, as is the case with otoconia. It is believed that the presence of two different crystalline compounds in the pineal gland is biologically significant, suggesting two entirely different mechanisms of formation and biological functions. Studies directed toward the elucidation of the formation and functions, and possible nonthermal interaction with external electromagnetic fields are currently in progress. Bioelectromagnetics 23:488,495, 2002. © 2002 Wiley-Liss, Inc. [source] Self-Assembled Nanoscale Ring Arrays from a Polystyrene- b -polyferrocenylsilane- b -poly(2-vinylpyridine)Triblock Terpolymer Thin FilmADVANCED MATERIALS, Issue 37 2009Vivian P. Chuang Hollow ring arrays with an outer and inner diameter of 33 and 11,nm, respectively, are formed from a thin film of poly-(styrene- b -ferrocenylethylmethylsilane- b -2-vinyl pyridine) (PS- b -PFS- b -P2VP) triblock terpolymer with a core/shell cylindrical morphology. The PS minority block forms a core surrounded by a PFS shell in a P2VP matrix; the core/shell structure is oriented perpendicularly to the film surface. The PS core and P2VP matrix blocks are partly removed using oxygen reactive ion etching, leaving ring patterns made from oxidized PFS. [source] Microcephalia with mandibular and dental dysplasia in adult Zmpste24-deficient miceJOURNAL OF ANATOMY, Issue 5 2008F. De Carlos Abstract ZMPSTE24 (also called FACE-1) is a zinc-metalloprotease involved in the post-translational processing of prelamin A to mature lamin A, a major component of the nuclear envelope. Mutations in the ZMPSTE24 gene or in that encoding its substrate prelamin A (LMNA) result in a series of human inherited diseases known collectively as laminopathies and showing regional or systemic manifestations (i.e. the Hutchinson,Gilford progeria syndrome). Typically, patients suffering some laminopathies show craniofacial or mandible anomalies, aberrant dentition or facial features characteristic of aged persons. To analyse whether Zmpste24,/, mice reproduce the cranial phenotype observed in humans due to mutations in ZMPSTE24 or LMNA, we conducted a craniometric study based on micro-computer tomography (µCT) images. Furthermore, using simple radiology, µCT, µCT-densitometry and scanning electron microscopy, we analysed the mandible and the teeth from Zmpste24,/, mice. Finally, the structure of the lower incisor was investigated using an H&E technique. The results demonstrate that Zmpste24,/, mice are microcephalic and show mandibular and dental dysplasia affecting only the mandible teeth. In all cases, the lower incisor of mice lacking Zmpste24 was smaller than in control animals, showed cylindrical morphology and a transverse fissure at the incisal edge, and the pulpal cavity was severely reduced. Structurally, the dental layers were normally arranged but cellular layers were disorganized. The inferior molars showed a reduced cusp size. Taken together, these data strongly suggest that Zmpste24,/, mice represent a good model to analyse the craniofacial and teeth malformations characteristic of lamin-related pathologies, and might contribute to a better understanding of the molecular events underlying these diseases. [source] Sphere-to-Rod Transition of Micelles formed by the Semicrystalline Polybutadiene- block -Poly(ethylene oxide) Block Copolymer in a Selective SolventMACROMOLECULAR RAPID COMMUNICATIONS, Issue 5 2010Adriana M. Mihut Abstract We present a morphological study of the micellization of an asymmetric semicrystalline block copolymer, poly(butadiene)- block -poly(ethylene oxide), in the selective solvent n -heptane. The molecular weights of the poly(butadiene) (PB) and poly(ethylene oxide) (PEO) blocks are 26 and 3.5,kg,·,mol,1, respectively. In this solvent, micellization into a liquid PEO-core and a corona of PB-chains takes place at room temperature. Through a thermally controlled crystallization of the PEO core at ,30,°C, spherical micelles with a crystalline PEO core and a PB corona are obtained. However, crystallization at much lower temperatures (,196,°C; liquid nitrogen) leads to the transition from spherical to rod-like micelles. With time these rod-like micelles aggregate and form long needles. Concomitantly, the degree of crystallinity of the PEO-cores of the rod-like micelles increases. The transition from a spherical to a rod-like morphology can be explained by a decrease of solvent power of the solvent n -heptane for the PB-corona chains: n -Heptane becomes a poor solvent at very low temperatures leading to a shrinking of the coronar chains. This favors the transition from spheres to a morphology with a smaller mean curvature, that is, to a cylindrical morphology. [source] | |||||||||||||