904 resultados para Phloem Mobility


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During the process of facial rehabilitation, the mobility of ocular prostheses must be considered. Whereas some factors depend exclusively on the dentist, such as molding techniques and selection of material for denture construction, regarding ocular rehabilitation, factors, such as type of surgery, whether to adopt implants, and the use of lubricants, deserve special attention owing to their integration and their association with other factors pertaining exclusively to the patient. To establish harmony, and with the intention of aiding the dentist, after a discerning evaluation, the authors of this study report the factors that provide greater or less mobility to ocular prostheses and conceal the prosthesis in a more natural way, thereby contributing toward achieving a favorable aesthetic result in rehabilitations.

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The cambial activity and periodicity of secondary xylem and phloem formation have been less studied in tropical tree species than in temperate ones. This paper describes the relationship between seasonal cambial activity, xylem and phloem development, and phenology in Schizolobium parahyba, a fast growing semideciduous seasonal forest tree from southeastern Brazil. From 2002 to 2003, wood samples were collected periodically and phenology and climate were recorded monthly in the same period. S. parahyba forms annual growth increments in wood, delimited by narrow initial parenchyma bands. The reduction of the cambial activity to a minimum correlates to the dry season and leaf fall. The higher cambial activity correlates to the wet season and the presence of mature leaves. In phloem, a larger conductive region was observed in the wet season, when the trees were in full foliage. The secondary phloem did not exhibit any incremental zone marker; however, we found that the axial parenchyma tends to form irregular bands.

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

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One of the most studied ceramic superconductors for application has been, undoubtedly, Bi2Sr2CaCu2O8+delta. Although being a multiphasic material, it has proved to have great advantages compared to other ceramic systems. Measurements of the elastic energy loss and modulus (anelastic spectroscopy) as a function of temperature call distinguish among different atomic jumps that occur inside the various phases or at different local ordering. In this paper, mechanical loss spectra of Bi2Sr2CaCu2O8+delta bar shaped samples, made by a conventional method, have been measured between 80 and 600 K, using a torsion pendulum operating in frequencies below 50 Hz, for samples annealed in vacuum up to 600 K. Possible relaxation mechanisms are proposed to explain the origin of the mechanical-loss peaks observed 300 and 500 K. (C) 2004 Elsevier B.V. All rights reserved.

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The objective of this work is to present an index which may synthesize a set of indicators of mobility for medium size cities urban centers. Three great areas were selected to compose the mobility index: pedestrians, motor vehicles and cycling. The Sampling Mobility Index is given by the sum of the punctuation the indicators selected and can to result in 700 points, the best result to mobility, and 0 points, the worse to mobility. The result obtained is given by the Sampling Mobility Index equal to 390. This result indicates a critical situation in Assis, as far as mobility is concerned. (c) 2005 Elsevier Ltd. All rights reserved.

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Resin solvation properties affect the efficiency of the coupling reactions in solid-phase peptide synthesis. Here we report a novel approach to evaluate resin solvation properties, making use of spin label electron paramagnetic resonance (EPR) spectroscopy. The aggregating VVLGAAIV and ING sequences were assembled in benzhydrylamine-resin with different amino group contents (up to 2.6 mmol/g) to examine the extent of chain association within the beads. These model peptidyl-resins were first labeled at their N-terminus with the amino acid spin label 2,2,6,6-tetramethylpiperidine-N-oxyl-4-amino-4-carboxylic acid (Toac). Their solvation properties in different solvents were estimated, either by bead swelling measurement or by assessing the dynamics of their polymeric matrixes through the analysis of Toac EPR spectra, and were correlated with the yield of the acylation reaction. In most cases the coupling rate was found to depend on bead swelling. Comparatively, the EPR approach was more effective. Line shape analysis allowed the detection of more than one peptide chain population, which influenced the reaction. The results demonstrated the unique potential of EPR spectroscopy not only for improving the yield of peptide synthesis, even in challenging conditions, but also for other relevant polymer-supported methodologies in chemistry and biology.

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Anelastic spectra (elastic energy absorption as a function of temperature) are reported which provide evidence that excess O in La2CuO4+delta starts forming two different types of defects already at very low concentrations, where no phase separation or changes in the type of O intercalation are believed to occur. The absorption peak with the lowest activation enthalpy, H/k(B) = 5600 K, is visible at lowest values of delta and is attributed to the hopping of single interstitial O2- ions. The second process, with a slightly slower dynamics, appears at higher values of delta and soon becomes preponderant over the former process. The latter process is proposed to be due to stable pairs of O atoms and is put in connection with the formation of partially covalent bonds between interstitial and apical oxygen; such bonds would reduce the doping efficiency of excess O at increasing delta. The geometry of the interstitial O defect is discussed. O 1998 Published by Elsevier B.V. B.V. All rights reserved.

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Since high-temperature superconductors were discovered, several studies have been made on their physical properties, attempting to associate them to the origin of superconductivity. Obviously, the oxygen atoms interstitially dissolved in the matrix have an important role in superconductivity, since they move easily in the lattice. In addition, they contribute to hole creation in the CuO2 planes. Anelastic spectroscopy ( internal friction) measurements are sensitive tools for the study of defects in solids, in particular for oxygen mobility. In this paper, Bi2Sr2CaCu2O8+y samples with several different amounts of interstitial oxygen were analysed by means of anelastic spectroscopy measurements. The measurements were performed by using a torsion pendulum operating at a frequency of about 40 Hz. Complex relaxation structures were observed and attributed to the shift of the oxygen interstitial atoms in BiO chains.

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Anelastic spectroscopy has been performed on a sample of superconducting oxide SmBa2Cu3O7-delta (SBCO) using a torsion pendulum operating with frequency around 10 Hz. A thermally activated relaxation peak is observed near 500 K with the activation enthalpy of 1.55 +/- 0.03 eV and the pre-exponential factor of approximately 10(-15) s, which is attributed to the mobility of non-stoichiometric oxygen by jumps in positions O1 and O5 of the lattice. (c) 2006 Elsevier B.V. All rights reserved.

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Stern anatomy and the development of intraxylary phloem were investigated in six to eight years old Coccinia indica L. (Cucurbitaceae). Secondary growth in the stems was achieved by the normal cambial activity. In the innermost part of the thicker stems, xylem parenchyma and pith cells dedifferentiated into meristematic cells at several points. In some of the wider rays, ray cells dedifferentiate and produce secondary xylem and phloem with different orientations and sometimes a complete bicollateral vascular bundle. The inner cambial segments of the bicollateral vascular bundle (of primary growth) maintained radial arrangement even in the mature stems but in most places the cambia were either inactive or showed very few cell divisions. Concomitant with the obliteration and collapse of inner phloem (of bicollateral vascular bundles), parenchyma cells encircling the phloem became meristematic forming a circular sheath of internal cambia. These internal cambia produce only intraxylary secondary phloem centripetally and do not produce any secondary xylem. In the stem, secondary xylem consisted mainly of axial parenchyma, small strands of thick-walled xylem derivatives, i.e. vessel elements and fibres embedded in parenchymatous ground mass, wide and tall rays along with exceptionally wide vessels characteristic of lianas. In thick stems, the axial parenchyma de-differentiated into meristem, which later re-differentiated into interxylary phloem. Fibre dimorphism and pseudo-vestured pits in the vessels are also reported.

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V. S. PATIL (Department of Botany, Faculty of Science, The Maharaja Sayajirao University of Baroda, Vadodara-390002 India), K. S. RAO (BRD School of Bioscieces, S. P. University, Vallabh Vidyanagar, India), and K. S. RAJPUT (Department of Botany, Faculty of Science, The Maharaja Sayajirao University of Baroda, Vadodara-390002 India). Development of intraxylary phloem and internal cambium in Ipomoea hederifolia (Convolvulaceae). J. Torrey Bot. Soc. 136: 423-432. 2009-In Ipomoea hederifolia L. (Convolvulaceae), internal/intraxylary phloem originated as isolated strands from the procambially derived cells after the formation of protoxylem and protophloem. Bands of internal phloem were apparent in the sixth internode after the development of metacambium. In the relatively thick stems several small arcs/segments of internal cambium ensues from the parenchyma cells between the protoxylem and internal protophloem. Though all the segments were active, some of them (two of them located opposite to each other) were relatively more active. Bidirectional differentiation of these segments gave rise to secondary xylem centrifugally and secondary phloem centripetally, resulting inverted vascular bundles. Rest of the internal cambium segments were unidirectional and formed only secondary phloem centripetally. Like external vascular cambium, the internal cambium was non-storied. Structurally, secondary xylem and phloem was composed of axial and radial system in which rays were mostly uni- to biseriate. Secondary xylem produced by the internal cambium was more or less similar to the xylem formed by the external successive cambia. Secondary phloem produced by the internal cambium was composed of sieve tubes, companion cells, axial and ray parenchyma cells. Simple sieve plates of internal phloem were mostly arranged on transverse end walls in contrast to compound and obliquely placed sieve plates of external phloem formed by the successive cambia.

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Time-of-flight measurements were carried out in orthorhombic sulfur for various fields, ranging from -2 to -20 kV/cm. No dependence of the mobility with the electric field was found but the current, normalized by the initial current, showed an electric field dependence at small times, decaying faster for larger electric field. After the failure of the usual models in explaining the resultsincluding the assumption of depth-dependent density of trapsa model assuming an extra mobility channel near the surface provided a reasonable set of parameters independent of the electric field. The measurements were carried out at 8.5, 29, 53, 68, and 79°C. © 1988 The American Physical Society.

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Vesicles prepared with synthetic amphiphiles (dioctadecyldimethylammonium bromide and chloride, dihexadecyl phosphate and its sodium salt) were obtained by sonication, ethanol injections, and chloroform injections. The hydrodynamic diameter of vesicles (Dh), estimated from the diffusivity measured by quasielastic light scattering, ranged from 230 to 3000 Å. The electrophoretic mobility (Um) was measured by free-flow electrophoresis. The zeta potential (ζ) and the degree of counterion dissociation (α) of the vesicles were calculated from Um and conductivity data, α decreased with increasing Dh of the vesicles, probably due to the decreasing headgroup area and the increasing counterion association needed to relax the surface electrostatic potential. The electrophoretic mobility was also calculated (Uc) according to an impenetrable, nonconducting sphere model with a spherically symmetric charge distribution approximation. Within the limits of the experimental error(s) of the (different) methods employed and the assumptions made in the calculations, the fact that the Um/Uc ratio ranged from 1.3 to 7.5 was considered to be a good agreement between the calculated and the experimental values. © 1990 American Chemical Society.

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The authors studied the utility of the physical test of laryngeal movement in swallowing disorders of the oropharyngeal region. Measurement and palpation of the larynx during deglutition were performed in the neck of 14 dysphagic patients and in two normal control groups. The normal groups were used to establish the pattern of the movement and the normal values of laryngeal elevation. Control elevation ranged from 1.80 to 2.50 cm. In eight patients laryngeal motion was defective and presented values ranging from zero to 1.50 cm. Palpation during laryngeal movement also revealed unexpected anomalous displacement such as lateral shifting and lowering of the larynx. In six patients with defective laryngeal motion, pharyngeal and upper esophageal sphincter function were also impaired. Direct measurement and palpation of laryngeal mobility during deglutition is a noninvasive method that can be used to evaluate dysphagia and the risk for aspiration. Also, it allows physical assessment of the evolution of the disorder.