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Areal Density (areal + density)
Selected AbstractsControlling the Morphology of Carbon Nanotube Films by Varying the Areal Density of Catalyst Nanoclusters Using Block-Copolymer Micellar Thin Films,ADVANCED MATERIALS, Issue 17 2006D. Bennett The morphologies of carbon nanotube (CNT) thin films are controlled by varying the areal density of catalytic nanoclusters synthesized from a block-copolymer micellar thin film. The morphologies of the CNT films vary from a tangled and sparse arrangement of individual CNTs, through a transition region with locally bunched and self-aligned CNTs, to a rapid growth of thick vertical CNT films (see figure). [source] Survey of small-scale flame spread test results of modern fabricsFIRE AND MATERIALS, Issue 6 2007Marcelo M. Hirschler Abstract The flammability of apparel worn on a person has one of the highest ratios of fire fatalities per fire, and there are few statutory requirements. A series of evaluations was conducted on the flammability of 50 fabrics (both cellulosic and thermoplastic) using the (now withdrawn) NFPA 701 small-scale test. The fabrics covered a broad range of areal densities (weights) and many were not intended for apparel. A series of conclusions were reached. In particular, it is apparent that the following primary correlation exists between fabric weight and flammability: the heavier the fabric the better it behaves in a fire. Secondarily, however, the type of fabric also strongly affects this conclusion. This paper presents the results of the testing and offers an analysis. Copyright © 2006 John Wiley & Sons, Ltd. [source] A Micellar Approach to Magnetic Ultrahigh-Density Data-Storage Media: Extending the Limits of Current Colloidal Methods,ADVANCED MATERIALS, Issue 3 2007A. Ethirajan An alternative route for producing L10FePt nanoparticles based on the self-organization of diblock copolymers into spherical micelles is presented. It overcomes all of the drawbacks of current colloidal strategies towards densely packed arrays of ferromagnetic FePt nanoparticles while still guaranteeing areal densities exceeding 1,Tbits,inch,2. The figure shows a sketch of the metal-salt-loaded micelles deposited on a substrate: a polystyrene shell (red) covers the poly(2-vinylpyridine) core (blue) forming a nanoreactor loaded with metal salt (yellow). [source] Comparison of the contractile properties, oxidative capacities and fibre type profiles of the voluntary sphincters of continence in the ratJOURNAL OF ANATOMY, Issue 3 2010Maria Buffini Abstract The external urethral sphincter (EUS) and external anal sphincter (EAS) are the principal voluntary striated muscles that sustain continence of urine and faeces. In light of their common embryological origin, shared tonic sphincteric action and synchronized electrical activity in vivo, it was expected that they would exhibit similar physiological and structural properties. However, the findings of this study using paired observations of both sphincters isolated from the rat show clearly that this is not the case. The anal sphincter is much more fatigable than the urethral sphincter. On completion of a fatigue protocol, the amplitude of the last twitch of the EAS had declined to 42 ± 3% of the first twitch, whereas the last twitch of the EUS was almost identical to that of the first (95 ± 3%). Immunocytochemical detection of myosin heavy-chain isoforms showed that this difference was not due to the presence of more slow-twitch oxidative type 1 fibres in the EUS compared with the EAS (areal densities 4 ± 1% and 5 ± 1%, respectively; P = 0.35). In addition, the fatigue difference was not explained by a greater contribution to force production by fast oxidative type 2A fibres in the urethral sphincter. In fact, the anal sphincter contained a higher areal density of type 2A fibres (56 ± 5% vs. 37 ± 4% in the EUS, P = 0.017). The higher oxidative capacity of the EUS, measured histochemically, explained its fatigue resistance. These results were surprising because the fatigue-resistant urethral muscle exhibited faster single-twitch contraction times compared with the anal sphincter (56 ± 0.87 ms vs. 72.5 ± 1.16 ms, P < 0.001). Neither sphincter expressed the type 2X myosin isoform but the fast-twitch isoform type 2B was found exclusively in the EUS (areal density 16 ± 2%). The type 2B fibres of the EUS were small (diameter 19.5 ± 0.4 ,m) in comparison to typical type 2B fibres of other muscles. As a whole the EUS is a more oxidative than glycolytic muscle. In conclusion, analysis of the twitch mechanics and fatigue of two sphincters showed that the EUS contained more fatigue-resistant muscle fibres compared with the EAS. [source] Forensic evaluation of clothing flammabilityFIRE AND MATERIALS, Issue 7 2009M. M. Hirschler Abstract A set of 17 commercial garments were purchased, categorized based on their fabric composition and fire tested. Three fire exposures were used: (a) a simile of the United States regulatory test for apparel fabrics (16CFR1610), (b) a small vertical candle on a small swatch of fabric and (c) a candle applied to a full garment, placed on a mannequin. Comparisons were made between the results of the various tests and of the various fabrics tested. A general correlation was observed whereby increased fabric areal density [weight/unit fabric area] resulted in improved fire performance. Where outliers to this generalization were observed the improved fire performance was due to the superior inherent fire performance of specific fabric types such as silk. Overall, the quantitative behavior with regard to flame spread rate observed after ignition of cellulosic, thermoplastic and blended fabrics was more heavily dependent on fabric areal density than on their chemical composition. Two key conclusions are that very lightweight fabrics constitute a potential danger and that the United States regulatory value, set at 88.3g/m2 (2.6oz/yd2), represents an essentially arbitrary cut-off in this regard. Copyright © 2009 John Wiley & Sons, Ltd. [source] Nanothermometer Using Single Crystal Silver NanospheresADVANCED MATERIALS, Issue 47 2009Yucheng Lan Two-dimensional ex situ nanothermometers are demonstrated using single crystal silver nanospheres. The nanothermometers can record the maximum temperatures experienced by the nanospheres and can be read later with a nanometer-scaled spatial resolution, which is very much desired for the situations where in situ temperature readout is not possible, such as in explosions. The temperature is detected based on the temperature-dependent diameter and areal density of single crystal silver nanospheres formed on carbon films. [source] Controlling the Morphology of Carbon Nanotube Films by Varying the Areal Density of Catalyst Nanoclusters Using Block-Copolymer Micellar Thin Films,ADVANCED MATERIALS, Issue 17 2006D. Bennett The morphologies of carbon nanotube (CNT) thin films are controlled by varying the areal density of catalytic nanoclusters synthesized from a block-copolymer micellar thin film. The morphologies of the CNT films vary from a tangled and sparse arrangement of individual CNTs, through a transition region with locally bunched and self-aligned CNTs, to a rapid growth of thick vertical CNT films (see figure). [source] Ultrahigh-Density Arrays of Ferromagnetic Nanorings on Macroscopic Areas,ADVANCED MATERIALS, Issue 23-24 2004Q. Zhu Arrays of ten billion Co nanorings, with inner diameters of 100,nm, wall widths of 20,nm, and of an ultrahigh areal density of 45,rings,,m,2, are fabricated on a macroscopic area. Magnetometric measurements and micromagnetic simulations reveal two parallel switching processes: a vortex reversal process and a rotating onion process. [source] Comparison of the contractile properties, oxidative capacities and fibre type profiles of the voluntary sphincters of continence in the ratJOURNAL OF ANATOMY, Issue 3 2010Maria Buffini Abstract The external urethral sphincter (EUS) and external anal sphincter (EAS) are the principal voluntary striated muscles that sustain continence of urine and faeces. In light of their common embryological origin, shared tonic sphincteric action and synchronized electrical activity in vivo, it was expected that they would exhibit similar physiological and structural properties. However, the findings of this study using paired observations of both sphincters isolated from the rat show clearly that this is not the case. The anal sphincter is much more fatigable than the urethral sphincter. On completion of a fatigue protocol, the amplitude of the last twitch of the EAS had declined to 42 ± 3% of the first twitch, whereas the last twitch of the EUS was almost identical to that of the first (95 ± 3%). Immunocytochemical detection of myosin heavy-chain isoforms showed that this difference was not due to the presence of more slow-twitch oxidative type 1 fibres in the EUS compared with the EAS (areal densities 4 ± 1% and 5 ± 1%, respectively; P = 0.35). In addition, the fatigue difference was not explained by a greater contribution to force production by fast oxidative type 2A fibres in the urethral sphincter. In fact, the anal sphincter contained a higher areal density of type 2A fibres (56 ± 5% vs. 37 ± 4% in the EUS, P = 0.017). The higher oxidative capacity of the EUS, measured histochemically, explained its fatigue resistance. These results were surprising because the fatigue-resistant urethral muscle exhibited faster single-twitch contraction times compared with the anal sphincter (56 ± 0.87 ms vs. 72.5 ± 1.16 ms, P < 0.001). Neither sphincter expressed the type 2X myosin isoform but the fast-twitch isoform type 2B was found exclusively in the EUS (areal density 16 ± 2%). The type 2B fibres of the EUS were small (diameter 19.5 ± 0.4 ,m) in comparison to typical type 2B fibres of other muscles. As a whole the EUS is a more oxidative than glycolytic muscle. In conclusion, analysis of the twitch mechanics and fatigue of two sphincters showed that the EUS contained more fatigue-resistant muscle fibres compared with the EAS. [source] Exercise When Young Provides Lifelong Benefits to Bone Structure and Strength,JOURNAL OF BONE AND MINERAL RESEARCH, Issue 2 2007Stuart J Warden PT Abstract Short-term exercise in growing rodents provided lifelong benefits to bone structure, strength, and fatigue resistance. Consequently, exercise when young may reduce the risk for fractures later in life, and the old exercise adage of "use it or lose it" may not be entirely applicable to the skeleton. Introduction: The growing skeleton is most responsive to exercise, but low-trauma fractures predominantly occur in adults. This disparity has raised the question of whether exercised-induced skeletal changes during growth persist into adulthood where they may have antifracture benefits. This study investigated whether brief exercise during growth results in lifelong changes in bone quantity, structure, quality, and mechanical properties. Materials and Methods: Right forearms of 5-week-old Sprague-Dawley rats were exercised 3 days/week for 7 weeks using the forearm axial compression loading model. Left forearms were internal controls and not exercised. Bone quantity (mineral content and areal density) and structure (cortical area and minimum second moment of area [IMIN]) were assessed before and after exercise and during detraining (restriction to home cage activity). Ulnas were removed after 92 weeks of detraining (at 2 years of age) and assessed for bone quality (mineralization) and mechanical properties (ultimate force and fatigue life). Results: Exercise induced consistent bone quantity and structural adaptation. The largest effect was on IMIN, which was 25.4% (95% CI, 15.6,35.3%) greater in exercised ulnas compared with nonexercised ulnas. Bone quantity differences did not persist with detraining, whereas all of the absolute difference in bone structure between exercised and nonexercised ulnas was maintained. After detraining, exercised ulnas had 23.7% (95% CI, 13.0,34.3%) greater ultimate force, indicating enhanced bone strength. However, exercised ulnas also had lower postyield displacement (,26.4%; 95% CI, ,43.6% to ,9.1%), indicating increased brittleness. This resulted from greater mineralization (0.56%; 95% CI, 0.12,1.00%), but did not influence fatigue life, which was 10-fold greater in exercised ulnas. Conclusions: These data indicate that exercise when young can have lifelong benefits on bone structure and strength, and potentially, fracture risk. They suggest that the old exercise adage of "use it or lose it" may not be entirely applicable to the skeleton and that individuals undergoing skeletal growth should be encouraged to perform impact exercise. [source] Towards ideal hexagonal self-ordering of TiO2 nanotubesPHYSICA STATUS SOLIDI - RAPID RESEARCH LETTERS, Issue 5 2007Jan M. Macak Abstract The present work reports on key factors that influence the degree of order in anodic TiO2 nanotube layers. We show that the anodization voltage and the Ti purity are of crucial importance for the ideality of self-organization within the nanotube layers and that repeated anodization can significantly improve hexagonal ordering. Optimizing each factor significantly reduces the variation in the average pore diameter and strongly reduces the areal density of polygon ordering/packing errors. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Distribution and Quantity of Contractile Tissue in Postnatal Development of Rat Alveolar InterstitiumTHE ANATOMICAL RECORD : ADVANCES IN INTEGRATIVE ANATOMY AND EVOLUTIONARY BIOLOGY, Issue 1 2008Renée Dickie Abstract Alpha,smooth muscle actin (,-SMA) -expressing cells are important participants in lung remodeling, during both normal postnatal ontogeny and after injury. Developmental dysregulation of these contractile cells contributes to bronchopulmonary dysplasia in newborns, and aberrant recapitulation in adults of the normal ontogeny of these cells has been speculated to underlie disease and repair in mature lungs. The significance of airway smooth muscle has been widely investigated, but contractile elements within the pulmonary parenchyma, although also of structural and functional consequence in developing and mature lungs, are relatively unstudied and little quantitative information exists. Here, we quantify the areal density of ,-SMA expression in lung parenchyma and assess changes in its spatiotemporal distribution through postnatal ontogeny. Using an antibody against ,-SMA, we immunofluorescently labeled contractile elements in lung sections from a postnatal growth series of rats. Images were segmented using thresholded pixel intensity. Alpha-SMA areal density in the alveolar interstitium was calculated by dividing the area of ,-SMA,positive staining by the tissue area. The areal density of ,-SMA in 2-day neonates was 3.7%, almost doubled, to 7.2% by 21 days, and decreased to 3% in adults. Neonates had large, elongate concentrations of ,-SMA, and ,-SMA localized both at septal tips and within the interstitium. In adults, individual areas of ,-SMA expression were smaller and more round, and located predominately in alveolar ducts, at alveolar ends and bends. The results are consistent with increasing ,-SMA expression during the period of peak myofibroblast activity, corresponding to the phase of rapid alveolarization in the developing lung. Anat Rec, 291:83,93, 2007. © 2007 Wiley-Liss, Inc. [source] Purification,chemical structure,electrical property relationship in gold nanoparticle liquids,APPLIED ORGANOMETALLIC CHEMISTRY, Issue 8 2010Robert I. MacCuspie Abstract Macroscopic assemblies of nanoparticles with fluid like characteristics, i.e. nanoparticle liquids (NPLs), are a new class of materials that exhibit unique properties compared with dispersions of nanoparticles in a molecularly distinct matrix phase. By focusing on reaction ratios, techniques to maximize concentration of reactants and quantification of chemical content during washing steps, a high degree of control over the purity of NPLs was maintained while allowing for easy scalability in batch sizes and synthesis throughput. A range of tertiary amines and quaternary ammoniums were used to successfully synthesize Au NPLs from a range of Au nanoparticles with nominal diameters from 6 to 20 nm and initially stabilized with either citrate or dodecanethiol. Stable Au NPLs after purification exhibited a sub-equivalence ratio of canopy to ligand molecules within the corona. This small canopy density most likely arose from the incommensurate areal density of anionic charge within the ligand shell relative to the larger size of the cationic canopy molecule, resulting in a population of cation,anion pairs too weakly bound to be retained in the initial assembly of the canopy post-purification. Finally, increasing either the volume fraction or molecular weight of the canopy was found to increase exponentially the electrical resistance of the bulk NPLs. Removal of excess canopy molecules created a conductive Au NPL that improved hot-current switching durability by at least two orders of magnitude beyond prior reports. Published in 2010 by John Wiley & Sons, Ltd. [source] Decreased spinal and femoral neck volumetric bone mineral density (BMD) in men with primary osteoporosis and their first-degree male relatives: familial effect on BMD in menCLINICAL ENDOCRINOLOGY, Issue 1 2007Bircan Erbas Summary Objective, Low bone mass may be caused by a reduction in the amount of bone or density of bone or both. The purpose of this study was to examine differences in bone volume and volumetric bone mineral density (vBMD) in men with primary osteoporosis and their first-degree male relatives (FDMR). Design, We used dual-energy X-ray absorptiometry (DXA) to measure areal density, then calculated bone volume and volumetric density in 121 men with primary osteoporosis, 73 FDMR and 66 normal men. We used regression methods adjusting for age, height and weight to determine deficits in bone volume and vBMD at the spine and femoral neck between men with spinal fractures due to primary osteoporosis, FDMR and normal men. Results, Men with osteoporosis had a tendency to smaller bone volume in the spine and femoral neck (P = 0·08 and P = 0·09, respectively) and lower volumetric bone density at the spine (by about 50%) and femoral neck (by about 30%) compared with healthy controls (P < 0·0001). FDMR had no deficit in bone volume but did have lower volumetric density at the spine (by 10·2%) compared with healthy controls (P < 0·0001). Conclusions, A deficit in bone mineral accrual may underlie the pathogenesis of primary osteoporosis in men, resulting in low vBMD. This is likely to be determined by genetic factors, although shared common environmental factors may also be important. [source] | |||||||||||||