Home  About us  Contact
 

Area Measurements (area + measurement)

Distribution by Scientific Domains
Medical Sciences35%
Chemistry35%

Kinds of Area Measurements

  • surface area measurement
    		•

    Selected Abstracts

    Hybrid ZnAl-LDH/CNTs nanocomposites: Noncovalent assembly and enhanced photodegradation performance

    AICHE JOURNAL, Issue 3 2010
    Hui Wang
    Abstract In this article, we reported a facile and effective strategy for assembling hybrid ZnAl-layered double hydroxide/carbon nanotubes (ZnAl-LDH/CNTs) nanocomposites through noncovalent bonds, for the first time, in the presence of L -cysteine molecules. The materials have been characterized by powder X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS), transmission electron microscopy (TEM), thermogravimetry and differential scanning calorimetry (TG-DSC), X-ray photoelectron spectra (XPS) and specific surface area measurement. The results indicate that L -cysteine as bridging linker plays a key role for enhancing both adhesion and dispersion of LDH nanocrystallites onto the surface of CNTs matrix through the interfacial interaction, and effectively inhibits the in situ growth of LDH crystallites, thus resulting in remarkably reduced LDH crystallite sizes; the Eu(III) fluorescence quenching in intercalated-Eu(III)complex LDH/CNTs nanocomposite can occur because of the interaction between LDH crystallites and CNTs matrix. Furthermore, it is found that as-assembled hybrid LDH/CNTs nanocomposites exhibit excellent performance for photodegradation of methyl orange molecules under UV irradiation, which is closely related to the unique hybrid nanostructure and composition of composites. © 2009 American Institute of Chemical Engineers AIChE J, 2010 [source]

    Quantitative and reliable in vitro method combining scanning electron microscopy and image analysis for the screening of osteotropic modulators

    MICROSCOPY RESEARCH AND TECHNIQUE, Issue 8 2006
    Gaël Grimandi
    Abstract The increased generation and up-regulated activity of bone resorbing cells (osteoclasts) play a part in the impairment of bone remodeling in many bone diseases. Numerous drugs (bisphosphonates, calcitonin, selective estrogen receptor modulators) have been proposed to inhibit this increased osteoclastic activity. In this report, we describe a pit resorption assay quantified by scanning electron microscopy coupled with image analysis. Total rabbit bone cells with large numbers of osteoclasts were cultured on dentin slices. The whole surface of the dentin slice was scanned and both the number of resorption pits and the total resorbed surface area were measured. Resorption pits appeared at 48 h and increased gradually up to 96 h. Despite the observation of a strong correlation between the total resorption area and the number of pits, we suggest that area measurement is the most relevant marker for osteoclastic activity. Osteotropic factors stimulating or inhibiting osteoclastic activity were used to test the variations in resorption activity as measured with our method. This reproducible and sensitive quantitative method is a valuable tool for screening for osteoclastic inhibitors and, more generally, for investigating bone modulators. Microsc. Res. Tech., 2006. © 2006 Wiley-Liss, Inc. [source]

    A novel continuous reactor for catalytic reduction of NOx,fixed bed simulations

    THE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 3 2008
    Terris T. Yang
    Abstract A novel dual-zone fluidized bed reactor was proposed for the continuous adsorption and reduction of NOx from combustion flue gases. The adsorption and reaction behaviour of such a reactor has been simulated in a fixed bed reactor using Fe/ZSM-5 catalyst and propylene reductant with model flue gases. Fe/ZSM-5 exhibited acceptable activity at T,=,350°C and GHSV,=,5000 h,1 when O2 concentration was controlled at levels lower than 1% with a HC to NO molar ratio of about 2:1. XPS and BET surface area measurement revealed the nature of the deactivation of the catalyst. Those performance data demonstrated the feasibility of a continuous dual-zone fluidized bed reactor for catalytic reduction of NOx under lean operating conditions. Un nouveau réacteur à lit fluidisé à double zone est proposé pour l'adsorption et la réduction en continu de NOx à partir de gaz de carneau de combustion. Le comportement d'adsorption et de réaction d'un tel réacteur a été simulé dans un réacteur à lit fixe utilisant un catalyseur Fe/ZSM-5 et un agent réducteur avec des gaz de carneau modèle. Le Fe/ZSM-5 montre une activité acceptable à T,=,350°C et GHSV,=,5000 h,1 lorsque la concentration d'O2 est contrôlée à des niveaux inférieurs à 1% avec un rapport molaire HC,NO d'environ 2:1. La mesure de surface par XPS et BET a permis de caractériser la désactivation du catalyseur. Ces données de performance illustre la faisabilité du réacteur à lit fluidisé à double zone Fe/ZSM-5 pour la réduction catalytique de NOx dans des conditions opératoires pauvres. [source]

    Corpus callosum and posterior fossa development in monozygotic females: a morphometric MRI study of Turner syndrome

    DEVELOPMENTAL MEDICINE & CHILD NEUROLOGY, Issue 5 2003
    Susannah L Fryer BA
    Previous neuroimaging research in Turner syndrome (TS) has indicated parietal lobe anomalies, while anomalies in other brain loci have been less well-substantiated. This study focused on potential cerebellar abnormalities and possible disruptions of interhemispheric (parietal) callosal connections in individuals with TS. Twenty-seven female children and adolescents with TS (mean age 13 years, SD 4 years 2 months) and 27 age-matched female control individuals (mean age 13 years 2 months, SD 4 years 1 month) underwent MRI. Age range of all participants was 7 to 20 years. Morphometric analyses of midline brain structures were conducted using standardized, reliable methods. When compared with control participants, females with TS showed reduced areas of the genu of the corpus callosum, the pons, and vermis lobules VI,VII, and an increased area of the fourth ventricle. No group difference in intracranial area measurements was observed. The reduced area of the genu in TS may reflect compromised connectivity between inferior parietal regions. Further, cerebellar vermis hypoplasia associated with TS agrees with literature that suggests the posterior fossa as a region prone to structural alterations in the face of early developmental insult. [source]

    Inorganic Analogues of Graphene

    EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 27 2010
    C. N. R. Rao
    Abstract The discovery of graphene has aroused great interest in the properties and phenomena exhibited by two-dimensional inorganic materials, especially when they comprise only a single, two or a few layers. Graphene-like MoS2 and WS2 have been prepared by chemical methods, and the materials have been characterized by electron microscopy, atomic force microscopy (AFM) and other methods. Boron nitride analogues of graphene have been obtained by a simple chemical procedure starting with boric acid and urea and have been characterized by various techniques that include surface area measurements. A new layered material with the composition BCN possessing a few layers and a large surface area discovered recently exhibits a large uptake of CO2. [source]

    Thermal decomposition of tert -butyl peroxide in a gas chromatographic reactor: A comparison of kinetic approaches

    INTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 7 2004
    Peter J. Skrdla
    The thermal decomposition of tert -butyl peroxide is investigated utilizing both the column and the injection port of a commercial gas chromatograph (GC) as chemical reactors. Using the injector liner as the reactor, the chromatographic peak areas of the reactant, measured at various injector temperatures, are used in the determination of the activation energy of the decomposition (Ea). With the column serving as the reactor, both the reactant peak areas and the product peak shapes are similarly utilized for this purpose. Values of Ea obtained using different mathematical treatments for each of the three approaches are found to range from 115 to 164 kJ/mol. Of these methods, the column reactor approach utilizing peak area measurements (referred to as PACR, for "peak area, column reactor") is found to be far superior in terms of its speed, robustness, and its accuracy in determining Ea. The PACR method's effectiveness can be largely attributed to the mathematical treatment that is described in the approach. © 2004 Wiley Periodicals, Inc. Int J Chem Kinet 36: 386,393, 2004 [source]

    A test of two methods of radiographically deriving long bone cross-sectional properties compared to direct sectioning of the diaphysis

    INTERNATIONAL JOURNAL OF OSTEOARCHAEOLOGY, Issue 5 2002
    Jay T. Stock
    Abstract Numerous studies have made use of cross-sectional geometry to describe the distribution of cortical bone in long bone diaphyses. Several methods can be used to measure or estimate cross-sectional contours. Direct sectioning (DSM) of the diaphysis is not appropriate in most curatorial contexts, and is commonly substituted with methods based upon bi-planar radiography: a latex cast method (LCM) or an eccentric elliptical method (EEM). Previous studies have demonstrated that the EEM provides accurate estimates of area measurements, while providing less accurate estimates of second moments of area (Biknevicius & Ruff, 1992; Runestad et al., 1993; Lazenby, 1997). The LCM has been commonly employed, as a way to estimate section contours more accurately, yet the validity of this method has not been adequately documented. This study measures the agreement of these methods against DSM of long bone diaphyses using 21 sections of canine tibiae derived from a study of total hip arthroplasty. The accuracy and agreement of these methods is evaluated using reduced major axis regression, paired sample t-tests and tests for agreement (Bland & Altman, 1986). The results illustrate that the LCM provides a reasonable estimate of cross-sectional dimensions, producing cross-sectional properties that are on average within 5% of properties derived from the DSM. The EEM is found to provide adequate estimates of true cross-sectional areas, but poor estimates of second moments of area. The use of the LCM is supported for all cross-sectional properties, but the EEM is only accurate in total area, cortical area and percent cortical area estimates. Copyright © 2002 John Wiley & Sons, Ltd. [source]

    Initial feasibility of a multi-station high resolution three-dimensional dark blood angiography protocol for the assessment of peripheral arterial disease

    JOURNAL OF MAGNETIC RESONANCE IMAGING, Issue 4 2009
    Georgeta Mihai PhD
    Abstract Purpose To evaluate the feasibility of a multi-station three dimensional (3D) T1-weighted turbo spin echo (TSE) dark-blood Sampling Perfection with Application optimized Contrasts using different flip angle Evolution sequence (T1w-SPACE), to assess aorta, iliac, and superficial femoral (SFA) arteries (inflow vessels) by comparing it with a multi-station contrast enhanced MR angiography (CE-MRA) with identical resolution. Materials and Methods A total of 6 volunteers and 14 peripheral arterial disease (PAD) patients were included in the study. Abdominal and thigh T1w-SPACE and lower leg time-resolved MRA (TR-MRA) with low dose contrast were followed by 3-station CE-MRA. Quantitative measurements of lumen area at 17 locations from T1w-SPACE and CE-MRA were obtained. Additionally, vessel wall areas at the same locations were obtained from the T1w-SPACE images. Results Quantitative comparison of lumen areas with T1w-SPACE and CE-MRA revealed strong correlation between the two techniques and strong inter-observer agreement for each of the two imaging methods (r > 0.9; P < 0.001). Localized vessel wall area measurements obtained in PAD patients were significantly greater compared with those obtained in normal volunteers (mean difference 43.75 ± 12.46 mm2; P < 0.001). Stenosis severity obtained from T1w-SPACE localized measurements showed significant arterial area stenosis in PAD patients. Conclusion T1w-SPACE imaging of inflow vessels is feasible, and in addition to CE-MRA has the ability to assess atherosclerotic plaque and vascular remodeling. J. Magn. Reson. Imaging 2009;30:785,793. © 2009 Wiley-Liss, Inc. [source]

    Comparison between three-dimensional volume-selective turbo spin-echo imaging and two-dimensional ultrasound for assessing carotid artery structure and function

    JOURNAL OF MAGNETIC RESONANCE IMAGING, Issue 3 2005
    Lindsey A. Crowe PhD
    Abstract Purpose To compare a volume-selective three-dimensional turbo spin echo (TSE) technique with ultrasound (US) for assessing carotid artery wall structure and function. Materials and Methods A three-dimensional volume-selective TSE technique was used to image the carotid artery in 10 healthy subjects and five hypertensive subjects (each of whom were scanned three times while they received different hypertension treatments). Lumen and wall area were measured on MR images. Two-dimensional US measurements of the intima-media thickness (IMT) and lumen diameter were taken in three orientations through a single cross section. The lumen area change over the cardiac cycle was used to determine distension. For validation, a Bland-Altman analysis was used to compare the vessel wall and lumen areas measured by three-dimensional MRI volumes with those obtained by US scans. Results Agreement between the two methods was found. The mean difference in distension between US and MRI was 1.2% (±5.1%). For the wall area measurements, good agreement was shown, but there was a systematic difference due to the visualization of the adventitia by MRI. Both techniques offer an easy way to objectively measure lumen indices. MRI can provide the complete circumference over the length of a vessel, while US is flexible and relatively inexpensive. The application of US is limited, however, when subjects are poorly echogenic. A difference between hypertensive and healthy subjects was found. Conclusion There was a good agreement between MRI and the clinically established two-dimensional US method. The MRI method has the advantage of providing increased vessel coverage, which permits one to assess localized abnormalities without assuming vessel uniformity. J. Magn. Reson. Imaging 2005;21:282,289. © 2005 Wiley-Liss, Inc. [source]

    Synthesis and Characterization of Highly Dispersed Antimony-Doped Stannic Hydroxide Nanoparticles: Effects of the Azeotropic Solvents to Remove Water on the Properties and Microstructures of the Nanoparticles

    JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 4 2007
    Fen Yang
    Highly dispersed antimony (Sb)-doped stannic hydroxide nanoparticles have been successfully prepared using the solution chemistry method. The properties and microstructures of the nanoparticles are investigated in detail by means of infrared, transmission electron microscope, X-ray diffractometer, and Brunauer-Emmett-Teller nitrogen surface area measurements. The results indicate that the properties and microstructures of the nanoparticles strongly depend on the azeotropic solvents used to remove water at the drying stage. Various azeotropic solvents are screened to investigate their effects on the size and dispersivity of dried Sb-doped stannic hydroxide. Three empirical rules are drawn for selecting an effective azeotropic solvent: (1) the solvent molecule should contain at least one atom such as oxygen as the hydrogen (H)-bond acceptor to form H bonds with the surface ,OH (acting as an H-bond donor) of polymer particle; (2) the H-bond acceptor should locate in the middle of the alkane chain rather than on the terminal so that the alkane chain can stretch out and cover more surface area, improving the dispersivity of the dried product; and (3) the solvent should have a higher boiling point (,140°C) to reduce the time of azeotropic distillation for removing water and maintain a lower residual amount of azeotropic agent. Based on the empirical rules, it is discovered that iso-amyl acetate is the most effective azeotropic solvent. [source]

    Low-Temperature Synthesis of Nanocrystalline Yttrium Aluminum Garnet Powder Using Triethanolamine

    JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 10 2003
    Yangqiao Liu
    Nanocrystalline yttrium aluminum garnet (YAG, Y3Al5O12) was synthesized by pyrolysis of complex compounds of aluminum and yttrium with triethanolamine [(HOCH2CH2)3N, (TEA)]. Loose and porous precursor was obtained on complete dehydration of the metal ion,triethanolamine complexes. Pure YAG powder was obtained by calcination of the precursor at 950°C. The precursor was characterized by simultaneous thermogravimetry, differential scanning calorimetry, and mass spectra analyses (TG,DSC,MS). The heat-treated powders were characterized by X-ray diffractometry (XRD), specific surface area measurements, and transmission electron microscopy (TEM). The average crystallite size as determined from X-ray line broadening and transmission electron microscopy studies was ,40 nm. The effects of the calcination temperature and the ratio of triethanolamine to mixed metal ions were also studied. [source]

    Effect of black blood MR image quality on vessel wall segmentation

    MAGNETIC RESONANCE IN MEDICINE, Issue 2 2001
    Jonathan B. Thomas
    Abstract Black blood MRI has become a popular technique for measuring arterial wall area as an indicator of plaque size. Computer-assisted techniques for segmenting vessel boundaries have been developed to increase measurement precision. In this study, the carotid arteries of four normal subjects were imaged at seven different fields of view (FOVs), keeping all other imaging parameters fixed, to determine whether spatial resolution could be increased at the expense of image quality without sacrificing precision. Wall areas were measured via computer-assisted segmentation of the vessel boundaries performed repeatedly by two operators. Analysis of variance (ANOVA) demonstrated that the variability of wall area measurements was below 1.5 mm2 for in-plane spatial resolutions between 0.22 mm and 0.37 mm. An inverse relationship between operator variability and the signal difference-to-noise ratio (SDNR) demonstrated that semi-automatic segmentation of the wall boundaries was robust for SDNR >3, defining a criterion above which subjective image quality can be degraded without an appreciable loss of information content. Our study also suggested that spatial resolutions higher than 0.3 mm may be required to quantify normal wall areas to within 10% accuracy, but that the reduced SNR associated with the higher resolution may be tolerated by semi-automated wall segmentation without an appreciable loss of precision. Magn Reson Med 46:299,304, 2001. © 2001 Wiley-Liss, Inc. [source]

    A quantitative analysis of the Eutherian orbit: correlations with masticatory apparatus

    BIOLOGICAL REVIEWS, Issue 1 2008
    Philip G. Cox
    Abstract The mammalian orbit, or eye-socket, is a highly plastic region of the skull. It comprises between seven and nine bones, all of which vary widely in their contribution to this region among the different mammalian orders and families. It is hypothesised that the structure of the mammalian orbit is principally influenced by the forces generated by the jaw-closing musculature. In order to quantify the orbit, fourteen linear, angular and area measurements were taken from 84 species of placental mammals using a Microscribe-3D digitiser. The results were then analysed using principal components analysis. The results of the multivariate analysis on untransformed data showed a clear division of the mammalian taxa into temporalis-dominant forms and masseter-dominant forms. This correlation between orbital structure and masticatory musculature was reinforced by results from the size-corrected data, which showed a separation of the taxa into the three specialised feeding types proposed by Turnbull (1970): i.e. ,carnivore-shear', ,ungulate-grinding' and ,rodent-gnawing'. Moreover, within the rodents there was a clear distinction between species in which the masseter is highly developed and those in which the temporalis has more prominence. These results were reinforced by analysis of variance which showed significant differences in the relative orbital areas of certain bones between temporalis-dominant and masseter-dominant taxa. Subsequent cluster analysis suggested that most of the variables could be grouped into three assemblages: those associated with the length of the rostrum; those associated with the width of the skull; and those associated with the relative size of the orbit and the shape of the face. However, the relative area of the palatine bone showed weak correlations with the other variables and did not fit into any group. Overall the relative area of the palatine was most closely correlated with feeding type, and this measure that appeared to be most strongly associated with the arrangement of the masticatory musculature. These results give a strong indication that, although orbital structure is in part determined by the relative size and orientation of the orbits, the forces generated by the muscles of mastication also have a large effect. [source]

    Some remarks on characterization and application of stationary phases for RP-HPLC determination of biologically important compounds

    BIOMEDICAL CHROMATOGRAPHY, Issue 1 2006
    Sylwia Kowalska
    Abstract Biologically active compounds such as vitamins, steroids, nucleosides, peptides and proteins play a very important role in coordinating living organism functions. Determination of those substances is indispensable in pathogenesis. Their complex structure and physico-chemical properties cause many analytical problems. Chromatography is the most common technique used in pharmaceutical and biomedical analysis. The interaction between analyte and stationary phase plays a major role in the separation process. The structure of the packing has a significant influence on the results of the separation process. Various types of spectroscopic techniques, such as nuclear magnetic resonance spectroscopy, infrared spectroscopy, fluorescence spectroscopy and photoacoustic spectroscopy can be useful tools for the characterization of packings. Surface area measurements, elemental analysis, thermal analysis and microcalorimetric measurements are also helpful in this field. Part of the paper contains a description of chromatographic tests used for the determination of column properties. The description of the possibilities of surface characterization is not complete, but is focused on the most popular techniques and practical chromatographic tests. All the presented methods made possible the design and quality control of a new generation stationary phases, which are the future of high-performance liquid chromatography. Copyright © 2005 John Wiley & Sons, Ltd. [source]