Magnetic resonance imaging allows a noninvasive assessment of myelination during normal brain maturation as well as the detection of genetically determined and acquired diseases that affect the synthesis and maintenance of myelin. If this high sensitivity of magnetic resonance imaging for white matter changes is completed by adequate clinical and biochemical information, a unique diagnostic tool is available to gain new insights in the formation of myelin and pathogenesis of myelin disorders. 相似文献
Molecularly imprinted polymer-magnetic iron oxide composite materials which exhibit recognition properties and can be withdrawn from solution by application of a magnetic field were prepared for the first time. Magnetic iron oxide was incorporated using a suspension polymerisation methodology with a perfluorocarbon liquid as the dispersing phase for the preparation of methacrylic acid-1,1,1-trimethylolpropane trimethacrylate copolymer beads molecularly imprinted with the beta-blocker (S)-propranolol. The resulting superparamagnetic imprinted polymer beads were capable of binding [3H]-(S)-propranolol more strongly than a non-imprinted, otherwise identical, polymer. In a competitive radioligand binding assay using a magnet to separate polymer from solution, (R)-propranolol and (R,S)-metoprolol exhibited cross-reactivities of 19 and 0.7%, respectively, compared with (S)-propranolol. 相似文献
The aim of this study was to reproduce the delayed (secondary) cerebral energy failure previously described in birth-asphyxiated newborn infants and to investigate relationships between primary insult severity and the extent of the delayed energy failure. Phosphorus (31P) magnetic resonance spectroscopy (MRS) at 7 T was used to study the brains of 12 newborn piglets during an acute, reversible, cerebral hypoxic-ischemic episode which continued until nucleotide triphosphates (NTP) were depleted. After reperfusion and reoxygenation, spectroscopy was continued for 48 h. High-energy metabolite concentrations returned to near normal levels after the insult, but later they fell as delayed energy failure developed. The time integral of NTP depletion in the primary insult correlated strongly with the minimum [phosphocreatine (PCr)]/[inorganic orthophosphate (Pi)] observed 24–48 h after the insult. (Linear regression analysis gave slope –8.04 h–1; ordinate intercept=1.23;r=0.92;P<0.0001.) This model is currently being used to investigate the therapeutic potential of various cerebroprotective strategies including hypothermia. 相似文献
The application of cryogenics in manufacturing has previously received significant attention in supporting manufacturing processes. This paper explores the continued application of cryogenic manufacturing for producing personalised products. This paper presents the novel concept of cryogenic CNC machining of elastomers and the development of a process control system for cryogenic CNC machining. The control process is illustrated alongside material dependent machining data and example soft elastomer machined parts. An enhancement to the process is also detailed within a closed loop thermally monitored cryogenic CNC machining facility. 相似文献
In this study a thorough analysis of physical and fine structure of hemp fibre bundles, namely surface topography, diameter,
cellulose content and crystallinity index, have been presented. The fibre bundles have been alkalised and physical and mechanical
properties analysed. Alkalisation was found to change the surface topography of fibre bundles and the diameter decreased with
increased concentration of caustic soda. Cellulose content increase slightly at lower NaOH concentrations and decrease at
higher NaOH concentrations. The crystallinity index decrease with increase in caustic soda concentration up to 0.24% NaOH
beyond which, it decreases with increase in NaOH concentration. It was also found that the tensile strength and stiffness
increases with increase in the concentration of NaOH up to a limit. Tensile strength and Young’s modulus increase with decrease
in cellulose content, while crystalline cellulose decreases slightly but with improved crystalline packing order resulting
in increased mechanical properties. Similar observations are elucidated by the crystallinity index. Alkalised hemp fibre bundles
were found to exhibit a similar specific stiffness to steel, E-glass and Kevlar 29 fibres. The results also show that crystallinity
index obtained following alkalisation has a reverse correlation to the mechanical properties. Stiffer alkalised hemp fibre
bundles are suitable candidates as reinforcements to replace synthetic fibres. The improvement in mechanical properties of
alkali treated hemp fibre bundles confirms their use as reinforcement materials. 相似文献
In spite of great advancements in multimedia data storage and communication technologies, compression of medical data remains challenging. This paper presents a novel compression method for the compression of medical images. The proposed method uses Ripplet transform to represent singularities along arbitrarily shaped curves and Set Partitioning in Hierarchical Trees encoder to encode the significant coefficients. The main objective of the proposed method is to provide high quality compressed images by representing images at different scales and directions and to achieve high compression ratio. Experimental results obtained on a set of medical images demonstrate that besides providing multiresolution and high directionality, the proposed method attains high Peak Signal to Noise Ratio and significant compression ratio as compared with conventional and state-of-art compression methods. 相似文献
The non-centrosymmetric space group organic nonlinear optical single crystal of 4-chloro-2-nitroaniline (4Cl2NA) was developed by slow evaporation method at 40 °C. Grown 4Cl2NA was monoclinic structure with Pc space group which was recognized by single-crystal XRD analysis. An intermolecular contact of 4Cl2NA was visually analysed by Hirshfeld surface analysis. Active functional groups and their respective vibrations were identified by FTIR and FT-Raman spectral analysis. Optical properties were evaluated by UV–Visible spectral analysis. Thermal TG/DTA thermogram analysis and mechanical Vickers hardness analysis revealed that the synthesis material was thermally stable up to 115 °C and mechanical work hardness coefficient (n?=?2.98) confirmed the grown crystal was soft material. Laser beam-irradiated LDT analysis expressed the laser utility limitation of the 4Cl2NA crystal. The NLO second harmonic generation efficiency was tested by Kurtz Perry powder method.