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Fiber/matrix Ratio (matrix + ratio)
Selected AbstractsControlling the properties of single-polymer composites by surface melting of the reinforcing fibers,POLYMERS FOR ADVANCED TECHNOLOGIES, Issue 10-12 2002D. M. Rein Abstract All-thermoplastic single-polymer composites are materials in which both the reinforcing fibrous phase and the matrix between them are made of the same thermoplastic polymer. Excellent bonding is achieved by mutual entanglement macromolecules due to controlled surface melting of the fibers. This results in a uniform structure of a single chemical entity. The physical properties of the consolidated material, such as modulus and coefficient of thermal expansion (CTE), can be controlled by the extent of melting effected in the process, which determines the fiber/matrix ratio. The fabrication technology utilizes oriented polymer fibers in various forms: unidirectional lay-up, woven fabric or chopped fibers/non-woven felt. The key element in the processing scheme is the control of the fibers' melting temperature by hydrostatic pressure. The fibers are heated under high pressure to a temperature that is below their melting point at the high pressure but above the melting temperature at some lower pressure. Reduction of pressure for controlled time results in melting of the fibers, which starts at the fiber surface. This surface melting under controlled pressure followed by crystallization produces the consolidated structure. We illustrate and describe this process using fibers of ultra-high-molecular-weight polyethylene (UHMWPE), showing the effect of the processing conditions on the flexural modulus, fiber/matrix ratio, and CTE in plane and in the thickness direction. These properties are relevant to the use of such composites as substrates for microwave antennae. Copyright © 2003 John Wiley & Sons, Ltd. [source] Menatetrenone (Vitamin K2) and Bone Quality in the Treatment of Postmenopausal OsteoporosisNUTRITION REVIEWS, Issue 12 2006Jun Iwamoto MD Menatetrenone (vitamin K2) reduces the incidence of vertebral fractures but has only modest effects on bone mineral density (BMD) in postmenopausal women with osteoporosis. Combined treatment with bisphosphonates and menatetrenone may be more effective than treatment with bisphosphonates alone in preventing vertebral fractures, despite the lack of an additive effect of menatetrenone on the BMD increase by bisphosphonates. Menatetrenone improves bone architecture in ovariectomized rats, and the mineral/ matrix ratio of the bone in terms of matrix volume and bone strength (without increasing bone mass) in rats with magnesium deficiency. Thus, available evidence supports an effect of menatetrenone on bone quality during osteoporosis treatment [source] Matrix/analyte ratio influencing polymer molecular weight distribution in matrix-assisted laser desorption/ionization time-of-flight mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 9 2009Gitta Schlosser Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) has been used to characterize poly(L-lysine) polymers and unique oligomer peptides, like 10-, 15- and 25-mer [Lys]n oligolysine peptides. Several matrices have been tried in order to find optimal conditions, but only , -cyano-4-hydroxycinnamic acid gave analytically useful spectra. The synthetic oligomers and their mixtures gave good quality spectra, showing protonated and cationized molecules, including doubly charged species. The polymers, analogously, gave a wide distribution of single- and double-cationized peak series. The polymer distributions observed indicate the presence of significant suppression effects. The concentration (matrix/analyte ratio) was found to influence the results significantly; distributions shifting to higher masses when higher polymer concentrations were used. This effect was studied in detail using the synthetic (,monodisperse') oligolysine peptides. It was found that the relative intensities change by over an order of magnitude in the 0.1,10,pmol/µL concentration range (typical for most proteomic analyses). The results indicate that concentration effects need to be considered when MALDI-MS is used for quantitative purposes. Copyright © 2009 John Wiley & Sons, Ltd. [source] Effect of Hormone Replacement Therapy on Bone Quality in Early Postmenopausal WomenJOURNAL OF BONE AND MINERAL RESEARCH, Issue 6 2003Ep Paschalis PhD Abstract HRT is an effective prophylaxis against postmenopausal bone loss. Infrared imaging of paired iliac crest biopsies obtained at baseline and after 2 years of HRT therapy demonstrate an effect on the mineral crystallinity and collagen cross-links that may affect bone quality. Several studies have demonstrated that hormonal replacement therapy (HRT) is an effective prophylaxis against postmenopausal bone loss, although the underlying mechanisms are still debated. Infrared spectroscopy has been used previously for analyzing bone mineral crystallinity and three-dimensional structures of collagen and other proteins. In the present study, the technique of Fourier transform infrared microscopic imaging (FTIRI) was used to investigate the effect of estrogen on bone quality (arbitrarily defined as mineral/matrix ratio, mineral crystallinity/maturity, and relative ratio of collagen cross-links [pyridinoline/deH-DHLNL]) at the ultrastructural level, in mineralized, thin tissue sections from double (before and after administration of HRT regimen; cyclic estrogen and progestogen [norethisterone acetate]) iliac crest biopsy specimens from 10 healthy, early postmenopausal women who were not on any medication with known influence on calcium metabolism. FTIRI allows the analysis of undemineralized thin tissue sections (each image analyzes a 400 × 400 ,m2 area with a spatial resolution of ,6.3 mm). For each bone quality variable considered, the after-treatment data exhibited an increase in the mean value, signifying definite changes in bone properties at the molecular level after HRT treatment. Furthermore, these findings are consistent with suppressed osteoclastic activity. [source] Molecular structural analysis of noncarious cervical sclerotic dentin using Raman spectroscopyJOURNAL OF RAMAN SPECTROSCOPY, Issue 12 2009Changqi Xu Abstract Molecular structure of the sclerotic dentin in noncarious cervical lesions (NCCLs) including both the inorganic phase and organic phase was investigated using Raman spectroscopy. It was found that NCCL sclerotic dentin was hypermineralized with the mineral/matrix ratios 2,3 times higher than those of normal dentin, which was caused by both the increase of mineral content and decrease of organic matrix (collagen) content in the sclerotic dentin. For the inorganic phase, the phosphate band (PO43,, ,1, symmetric stretching vibrational mode) in NCCL sclerotic dentin was shifted from 960 to 963 cm,1, and the width of this band was decreased from 16.4 to 10.4 cm,1, indicating that the degree of mineral crystallinity in NCCL sclerotic dentin was higher than that of normal dentin. In addition, the carbonate content in the mineral of NCCL sclerotic dentin was less than that of normal dentin. As compared to the inorganic phase, the changes within the organic phase were not dramatic. However, the changes in collagen cross-link density along with other spectral changes were still detectable. There was a noteworthy reduction in the ratio of nonreducible to reducible cross-links in the NCCL sclerotic dentin, indicating that cross-link breaks occurred in the collagen matrix of the lesions. Copyright © 2009 John Wiley & Sons, Ltd. [source] | |||||||||||||