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Geometrical
Terms modified by Geometrical Selected AbstractsGEOMETRICAL, THERMAL AND MECHANICAL PROPERTIES OF OLIVE FRUITSJOURNAL OF FOOD PROCESS ENGINEERING, Issue 2 2010MOHAMAD I. AL-WIDYAN ABSTRACT In Mediterranean countries, olive trees play a significant economical role. Knowledge of olive fruits properties is essential for the efficient handling of the product and optimizing oil yield. The lack of such knowledge at the local level triggered this study in an attempt to report the fruit's chemical composition and some major engineering properties. Established procedures were followed in conducting the measurements and calculations on fruit samples. The study examined four major varieties of olive fruits, including Spanish, Black Spanish, improved Nabali and Nabali Baladi for their chemical composition and other properties, including geometrical, thermal and frictional properties. Thermal properties, including thermal conductivity, heat capacity and thermal diffusivity, ranged from 0.41 to 0.47 W/(m·K), 2.35 to 2.39 kJ/(kg·K) and 2.88 × 10,7to 2.779 × 10,7 m2/s, respectively. The geometrical properties of the Spanish and Black Spanish were quite similar except for roundness and sphericity. Similar results were found for improved Nabali and Nabali Baladi. The properties of weight, density and packing coefficient ranged from 2.22 to 8.60 g, 890 to 1,230 kg/m3 and 0.43 to 0.52, respectively. The fruit's static friction coefficient over mild steel, aluminum and softwood surfaces ranged from 0.20 to 0.30, 0.21 to 0.29 and 0.22 to 0.33, respectively. PRACTICAL APPLICATIONS In Jordan and other Mediterranean countries, olive fruits are produced in large quantities every season. They are very widely used as pickled fruits or are processed in mills to extract their oil. Despite the fact that fruit properties are a necessary prerequisite for the efficient handling and processing of fruits, literature search indicated the lack of a comprehensive study of scientific merit that reports on the engineering properties of olive fruits. In addition, it is established that knowledge of the fruit properties leads to optimized handling and processing and results in knowledge-based development of all processes and equipment that deal with the fruits. The practical merit of this study stems from the fact that it reports on the key properties of a major product (olive fruits) that has social, cultural and economical significance throughout a whole region and is expanding throughout the globe. [source] Hip Fractures and the Contribution of Cortical Versus Trabecular Bone to Femoral Neck Strength,JOURNAL OF BONE AND MINERAL RESEARCH, Issue 3 2009Gerold Holzer Abstract Osteoporotic fractures are caused by both cortical thinning and trabecular bone loss. Both are seen to be important for bone fragility. The relative contributions of cortical versus trabecular bone have not been established. The aim of this study was to test the contribution of cortical versus trabecular bone to femoral neck stability in bone strength. In one femur from each pair of 18 human cadaver femurs (5 female; 4 male), trabecular bone was completely removed from the femoral neck, providing one bone with intact and the other without any trabecular structure in the femoral neck. Geometrical, X-ray, and DXA measurements were carried out before biomechanical testing (forces to fracture). Femoral necks were osteotomized, slices were analyzed for cross-sectional area (CSA) and cross-sectional moment of inertia (CSMI), and results were compared with biomechanical testing data. Differences between forces needed to fracture excavated and intact femurs (,F/F mean) was 7.0% on the average (range, 4.6,17.3%). CSA of removed spongiosa did not correlate with difference of fracture load (,F/F mean), nor did BMD. The relative contribution of trabecular versus cortical bone in respect to bone strength in the femoral neck seems to be marginal and seems to explain the subordinate role of trabecular bone and its changes in fracture risk and the effects of treatment options in preventing fractures. [source] Geometrical and Virbrational DFT Studies of HOBr×(H2O)n Clusters (n = 1,4).CHEMINFORM, Issue 52 2003Cristina Maria P. Santos No abstract is available for this article. [source] Geometrical and algebraic approach to central molecular chirality: A chirality index and an Aufbau description of tetrahedral moleculesCHIRALITY, Issue 7 2006Salvatore Capozziello Abstract On the basis of empirical Fischer projections, we develop an algebraic approach to the central molecular chirality of tetrahedral molecules. The elements of such an algebra are obtained from the 24 projections which a single chiral tetrahedron can generate in S and R absolute configurations. They constitute a matrix representation of the O(4) orthogonal group. According to this representation, given a molecule with n chiral centres, it is possible to define an "index of chirality , , {n, p}", where n is the number of stereogenic centres of the molecule and p the number of permutations observed under rotations and superimpositions of the tetrahedral molecule to its mirror image. The chirality index not only assigns the global chirality of a given tetrahedral chain, but indicates also a way to predict the same property for new compounds, which can be built up consistently. Chirality 18:462,468, 2006. © 2006 Wiley-Liss, Inc. [source] Contribution to the stability analysis of the dewetted Bridgman growth under microgravity conditionsCRYSTAL RESEARCH AND TECHNOLOGY, Issue 6 2004L. Bizet Abstract Experimental observations show that the gap between the sample and the crucible, commonly obtained after solidification in microgravity, is remarkably stable. With the aim to understand the reason of this stability, the dewetting phenomenon is studied by Lyapunov's method. After a short review of the existing mechanisms leading to dewetting, the open smooth crucible configuration is chosen as the most representative. The analytical stability analysis, taking into account geometrical and thermal effects, performed under some boundary heat transfer approximations, shows that, in most cases, the dewetting process is intrinsically stable. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Mass fractal dimension of soil macropores using computed tomography: from the box-counting to the cube-counting algorithmEUROPEAN JOURNAL OF SOIL SCIENCE, Issue 3 2003J.S. Perret Summary Transport phenomena in porous media depend strongly on three-dimensional pore structures. Macropore networks enable water and solute to move preferentially through the vadose zone. A complete representation of their geometry is important for understanding soil behaviour such as preferential flow. Once we know the geometrical, topological and scaling attributes of preferential flow paths, we can begin computer simulations of water movement in the soil. The box-counting method is used in three dimensions (i.e. cube-counting algorithm) to characterize the mass fractal dimension of macropore networks using X-ray computed tomography (CT) matrices. We developed an algorithm to investigate the mass fractal dimension in three dimensions and to see how it compares with the co-dimensions obtained using the box-counting technique in two dimensions. For that purpose, macropore networks in four large undisturbed soil columns (850 mm × 77 mm diameter) were quantified and visualized, in both two and three dimensions, using X-ray CT. We observed an increasing trend between the fractal dimension and macroporosity for the four columns. Moreover, similar natural logarithm functions were obtained for the four cores by a least squares fit through plots of mass fractal dimension against macroporosity. [source] A wide-band lumped circuit model of the terminal and internal electromagnetic response of coaxially insulated windings mounted on a coreEUROPEAN TRANSACTIONS ON ELECTRICAL POWER, Issue 3 2003P. Holmberg This paper presents a wide-band lumped circuit model of coaxially insulated windings mounted on a core. The polyphase model can be used to simulate the terminal and internal electromagnetic response in DryformerTM, a new oil-free power transformer, and similar electromagnetic power devices. The circuit parameters are based on geometrical and material data. The simulated frequency and transient response of the lumped circuit is compared to measurements on a 20 MVA 140/6.6 kV three-phase transformer of the DryformerTM type. The comparison shows that the model can be used to estimate resonance frequencies and transient overvoltages in the transformer, although the damping is not accurately modelled. The influence of the core is discussed and investigated. [source] String theory: exact solutions, marginal deformations and hyperbolic spacesFORTSCHRITTE DER PHYSIK/PROGRESS OF PHYSICS, Issue 2 2007D. Orlando Abstract This thesis is almost entirely devoted to studying string theory backgrounds characterized by simple geometrical and integrability properties. The archetype of this type of system is given by Wess-Zumino-Witten models, describing string propagation in a group manifold or, equivalently, a class of conformal field theories with current algebras. We study the moduli space of such models by using truly marginal deformations. Particular emphasis is placed on asymmetric deformations that, together with the CFT description, enjoy a very nice spacetime interpretation in terms of the underlying Lie algebra. Then we take a slight detour so to deal with off-shell systems. Using a renormalization-group approach we describe the relaxation towards the symmetrical equilibrium situation. In he final chapter we consider backgrounds with Ramond-Ramond field and in particular we analyze direct products of constant-curvature spaces and find solutions with hyperbolic spaces. [source] Crystal Structure of Garciniaphenone and Evidences on the Relationship between Keto,Enol Tautomerism and ConfigurationHELVETICA CHIMICA ACTA, Issue 7 2008Felipe Abstract Garciniaphenone (=rel- (1R,5R,7R)-3-benzoyl-4-hydroxy-8,8-dimethyl-1,7-bis(3-methylbut-2-en-1-yl)bicyclo[3.3.1]non-3-ene-2,9-dione; 1), a novel natural product, was isolated from a hexane extract of Garcinia brasiliensis fruits. The crystal structure of 1 as well as the selected geometrical and configurational features were compared with those of known related polyprenylated benzophenones. Garciniaphenone is the first representative of polyprenylated benzophenones without a prenyl substituent at C(5). Notably, the absence of a 5-prenyl substituent has an impact on the molecular geometry. The tautomeric form of 1 in the solid state was readily established by a residual-electronic-density map generated by means of a difference Fourier analysis, and there is an entirely delocalized six-membered chelate ring encompassing the keto,enol moiety. The configuration at C(7) was used to rationalize the nature of the keto,enol tautomeric form within 1. The intermolecular array in the network is maintained by nonclassical intermolecular H-bonds. [source] Accelerating strategies to the numerical simulation of large-scale models for sequential excavationINTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 9 2007M. Noronha Abstract In this paper, a novel combination of well-established numerical procedures is explored in order to accelerate the simulation of sequential excavation. Usually, large-scale models are used to represent these problems. Due to the high number of equations involved, the solver algorithm represents the critical aspect which makes the simulation very time consuming. The mutable nature of the excavation models makes this problem even more pronounced. To accomplish the representation of geometrical and mechanical aspects in an efficient and simple manner, the proposed solution employs the boundary element method with a multiple-region strategy. Together with this representational system, a segmented storage scheme and a time-ordered tracking of the changes form an adequate basis for the usage of fast updating methods instead of frontal solvers. The present development employs the Sherman,Morrison,Woodbury method to speed up the calculation due to sequential changes. The efficiency of the proposed framework is illustrated through the simulation of test examples of 2D and 3D models. Copyright © 2006 John Wiley & Sons, Ltd. [source] Simplified estimation of seismically induced settlementsINTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 8 2003E. Vincens Abstract This paper proposes a predictive expression of settlements for a dry sand deposit overlying a bedrock and subjected to a seismic motion. The proposed formula combines geometrical and mechanical properties of the soil profile with classical characteristics of the input motion. One of the main concepts developed herein consists in regarding the input motion and the dynamical response as samples of random processes; another key concept consists in the common densification curve from Sawicki. The model introduces a parameter k identified by means of an extensive set of accelerograms. The main advantage of the proposed method consists in allowing fast comparisons of earthquake induced settlements for different soil and motion characteristics and therefore quantifying the damage power of a time-history input motion. Copyright © 2003 John Wiley & Sons, Ltd. [source] A dual mortar approach for 3D finite deformation contact with consistent linearizationINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 11 2010Alexander Popp Abstract In this paper, an approach for three-dimensional frictionless contact based on a dual mortar formulation and using a primal,dual active set strategy for direct constraint enforcement is presented. We focus on linear shape functions, but briefly address higher order interpolation as well. The study builds on previous work by the authors for two-dimensional problems. First and foremost, the ideas of a consistently linearized dual mortar scheme and of an interpretation of the active set search as a semi-smooth Newton method are extended to the 3D case. This allows for solving all types of nonlinearities (i.e. geometrical, material and contact) within one single Newton scheme. Owing to the dual Lagrange multiplier approach employed, this advantage is not accompanied by an undesirable increase in system size as the Lagrange multipliers can be condensed from the global system of equations. Moreover, it is pointed out that the presented method does not make use of any regularization of contact constraints. Numerical examples illustrate the efficiency of our method and the high quality of results in 3D finite deformation contact analysis. Copyright © 2010 John Wiley & Sons, Ltd. [source] On the investigation of shell buckling due to random geometrical imperfections implemented using Karhunen,Loève expansionsINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 12 2008K. J. Craig Abstract For the accurate prediction of the collapse behaviour of thin cylindrical shells, it is accepted that geometrical and other imperfections in material properties and loading have to be accounted for in the simulation. There are different methods of incorporating imperfections, depending on the availability of accurate imperfection data. The current paper uses a spectral decomposition of geometrical uncertainty (Karhunen,Loève expansions). To specify the covariance of the required random field, two methods are used. First, available experimentally measured imperfection fields are used as input for a principal component analysis based on pattern recognition literature, thereby reducing the cost of the eigenanalysis. Second, the covariance function is specified analytically and the resulting Friedholm integral equation of the second kind is solved using a wavelet-Galerkin approach. Experimentally determined correlation lengths are used as input for the analytical covariance functions. The above procedure enables the generation of imperfection fields for applications where the geometry is slightly modified from the original measured geometry. For example, 100 shells are perturbed with the resulting random fields obtained from both methods, and the results in the form of temporal normal forces during buckling, as simulated using LS-DYNA®, as well as the statistics of a Monte Carlo analysis of the 100 shells in each case are presented. Although numerically determined mean values of the limit load of the current and another numerical study differ from the experimental results due to the omission of imperfections other than geometrical, the coefficients of variation are shown to be in close agreement. Copyright © 2007 John Wiley & Sons, Ltd. [source] Adaptive remeshing in large plastic strain with damageINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 1 2005H. Borouchaki Abstract The analysis of mechanical structures using the finite element method in the framework of large elasto-plastic strain, needs frequent remeshing of the deformed domain during the computation. Indeed, the remeshing is due to the large geometrical distortion of finite elements and the adaptation to the physical behaviour of the solution as the plastic strain or the damage fields. This paper gives the necessary steps to remesh a mechanical structure during large elasto-plastic deformations with damage. An important part of this process concerns the geometrical and physical error estimates. The proposed method is integrated in a computational environment using the ABAQUS/Explicit solver and the BL2D-V2 adaptive mesher. After recalling the formulation of the elasto-plastic problem with damage, four types of applications using the proposed adaptive remeshing are given: orthogonal cutting, side-pressing of an infinite cylinder, blanking and backward extrusion with drilling. Copyright © 2005 John Wiley & Sons, Ltd. [source] Automatic CAD model topology generationINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 8 2006Paresh S. Patel Abstract Computer aided design (CAD) models often need to be processed due to the data translation issues and requirements of the downstream applications like computational field simulation, rapid prototyping, computer graphics, computational manufacturing, and real-time rendering before they can be used. Automatic CAD model processing tools can significantly reduce the amount of time and cost associated with the manual processing. The topology generation algorithm, commonly known as CAD repairing/healing, is presented to detect commonly found geometrical and topological issues like cracks, gaps, overlaps, intersections, T-connections, and no/invalid topology in the model, process them and build correct topological information. The present algorithm is based on the iterative vertex pair contraction and expansion operations called stitching and filling, respectively, to process the model accurately. Moreover, the topology generation algorithm can process manifold as well as non-manifold models, which makes the procedure more general and flexible. In addition, a spatial data structure is used for searching and neighbour finding to process large models efficiently. In this way, the combination of generality, accuracy, and efficiency of this algorithm seems to be a significant improvement over existing techniques. Results are presented showing the effectiveness of the algorithm to process two- and three-dimensional configurations. Copyright © 2006 John Wiley & Sons, Ltd. [source] Optimization of a finned heat sink array based on thermoeconomic analysisINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 5 2007S. Z. Shuja Abstract The design and specification of heat sinks for electronic systems is not easily accomplished through the use of standard thermal design and analysis tools since geometric and boundary conditions are not typically known in advance. A second-law based thermoeconomic optimization procedure is presented for a finned heat sink array. This involves including costs associated with material, and irreversible losses due to heat transfer and pressure drop. The influence of important physical, geometrical and unit cost parameters on the overall finned array are optimized for some typical operating conditions that are representative of electronic cooling applications. The optimized cost results are presented in terms of ReD, ReL, ,P / ,H, and q for a finned system in a graphical form. In addition the methodology of obtaining optimum parameters for a finned heat sink system which will result in minimum operating cost is demonstrated. Copyright © 2006 John Wiley & Sons, Ltd. [source] Parallel transmit and receive technology in high-field magnetic resonance neuroimagingINTERNATIONAL JOURNAL OF IMAGING SYSTEMS AND TECHNOLOGY, Issue 1 2010Andrew G. Webb Abstract The major radiofrequency engineering challenges of high-field MR neuroimaging are as follows: (1) to produce a strong, homogeneous transmit B1 field, while remaining within regulatory guidelines for tissue power deposition and (2) to receive the signal with the maximum signal-to-noise and the greatest flexibility in terms of utilizing the benefits of parallel imaging. Borrowing from developments in electromagnetic hyperthermia, the first challenge has been met by the use of transmit arrays, in which the input power to each element of the array can be varied in terms of magnitude and phase. Optimization of these parameters, as well as the form of the applied RF pulse, leads to very homogeneous B1 fields throughout the brain. The design of large receive arrays, using impedance-mismatched preamplifiers and geometrical overlap for interelement isolation, has resulted in significant sensitivity improvements as well as large acceleration factors in parallel imaging. © 2010 Wiley Periodicals, Inc. Int J Imaging Syst Technol, 20, 2,13, 2010 [source] Numerical modelling of anisotropy and eddy current effects in ferromagnetic laminations using a co-energy formulationINTERNATIONAL JOURNAL OF NUMERICAL MODELLING: ELECTRONIC NETWORKS, DEVICES AND FIELDS, Issue 5 2001L. R. Dupré Abstract The paper deals with a numerical model for the evaluation of electromagnetic fields in one steel lamination under the influence of a rotating magnetic flux, taking into account anisotropy effects. For this purpose a detailed material model, described by a differential permeability tensor, is included in the macroscopic electromagnetic field calculations in one lamination. Here, by geometrical and physical considerations, the governing Maxwell equations are reduced to a system of parabolic PDEs for the components of the magnetic field vector, under appropriate boundary and initial conditions. We present a suitable numerical approximation based upon a finite element,finite difference method, which properly takes into account the material characteristics. The study leads to a more realistic numerical modelling of the electromagnetic phenomena inside electric and magnetic conducting laminations due to anisotropy effects. Numerical results are compared with those from simplified analytical formulae. Copyright © 2001 John Wiley & Sons, Ltd. [source] The effect of nucleus implant parameters on the compressive mechanics of the lumbar intervertebral disc: A finite element studyJOURNAL OF BIOMEDICAL MATERIALS RESEARCH, Issue 2 2009Abhijeet Joshi Abstract A simplified finite element model of the human lumbar intervertebral disc was utilized for understanding nucleus pulposus implant mechanics. The model was used to assess the effect of nucleus implant parameter variations on the resulting compressive biomechanics of the lumbar anterior column unit. The effects of nucleus implant material (modulus and Poisson's ratio) and geometrical (height and diameter) parameters on the mechanical behavior of the disc were investigated. The model predicted that variations in implant modulus contribute less to the compressive disc mechanics compared to the implant geometrical parameters, for the ranges examined. It was concluded that some threshold exists for the nucleus implant modulus, below which little variations in load,displacement behavior were shown. Compressive biomechanics were highly affected by implant volume (under-filling the nucleus cavity, line-to-line fit, or over-filling the nucleus cavity) with a greater restoration of compressive mechanics observed with the over-filled implant design. This work indicated the effect of nucleus implant parameter variations on the compressive mechanics of the human lumbar intervertebral disc and importance of the "fit and fill" effect of the nuclear cavity in the restoration of the human intervertebral disc mechanics in compression. These findings may have clinical significance for nucleus implant design. © 2009 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2009 [source] GEOMETRICAL, THERMAL AND MECHANICAL PROPERTIES OF OLIVE FRUITSJOURNAL OF FOOD PROCESS ENGINEERING, Issue 2 2010MOHAMAD I. AL-WIDYAN ABSTRACT In Mediterranean countries, olive trees play a significant economical role. Knowledge of olive fruits properties is essential for the efficient handling of the product and optimizing oil yield. The lack of such knowledge at the local level triggered this study in an attempt to report the fruit's chemical composition and some major engineering properties. Established procedures were followed in conducting the measurements and calculations on fruit samples. The study examined four major varieties of olive fruits, including Spanish, Black Spanish, improved Nabali and Nabali Baladi for their chemical composition and other properties, including geometrical, thermal and frictional properties. Thermal properties, including thermal conductivity, heat capacity and thermal diffusivity, ranged from 0.41 to 0.47 W/(m·K), 2.35 to 2.39 kJ/(kg·K) and 2.88 × 10,7to 2.779 × 10,7 m2/s, respectively. The geometrical properties of the Spanish and Black Spanish were quite similar except for roundness and sphericity. Similar results were found for improved Nabali and Nabali Baladi. The properties of weight, density and packing coefficient ranged from 2.22 to 8.60 g, 890 to 1,230 kg/m3 and 0.43 to 0.52, respectively. The fruit's static friction coefficient over mild steel, aluminum and softwood surfaces ranged from 0.20 to 0.30, 0.21 to 0.29 and 0.22 to 0.33, respectively. PRACTICAL APPLICATIONS In Jordan and other Mediterranean countries, olive fruits are produced in large quantities every season. They are very widely used as pickled fruits or are processed in mills to extract their oil. Despite the fact that fruit properties are a necessary prerequisite for the efficient handling and processing of fruits, literature search indicated the lack of a comprehensive study of scientific merit that reports on the engineering properties of olive fruits. In addition, it is established that knowledge of the fruit properties leads to optimized handling and processing and results in knowledge-based development of all processes and equipment that deal with the fruits. The practical merit of this study stems from the fact that it reports on the key properties of a major product (olive fruits) that has social, cultural and economical significance throughout a whole region and is expanding throughout the globe. [source] Hydrogen bonds assisted by ,-electron delocalization , the influence of external intermolecular interactions on dimer of formic acidJOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 7-8 2008awomir J. Grabowski Abstract MP2 and DFT calculations with the use of 6-311++G(d,p) basis set were carried out to study formic acid dimer as well as this species interacting with additional Lewis acids such as HF, Li+ and Na+. These Lewis acids were positioned near carbonyl or hydroxyl oxygen atoms and their influence on geometrical and other parameters of formic acid dimer was analysed. Additionally the ,quantum theory of atoms in molecules' (QTAIM) was applied as well as the ,natural bond orbitals' (NBO) method. Numerous correlations between geometrical, QTAIM and energetic parameters were found. It was found that ,-electron delocalization is not always connected with the enhancement of H-bond strength. Copyright © 2008 John Wiley & Sons, Ltd. [source] Nanocarbon materials: probing the curvature and topology effects using phonon spectraJOURNAL OF RAMAN SPECTROSCOPY, Issue 9 2009Sanju Gupta Abstract Much has been learned from the use of resonance Raman spectroscopy and high-resolution transmission electron microscopy techniques about the micro-/nanoscopic structure of various nanostructured carbons. However, they still possess some features that are not entirely understood particularly in terms of topological characteristics, which go beyond making a distinction with just the geometrical structure at nanoscale. To effectively utilize the potential of these materials for technological needs, understanding both the geometrical and topological structure and perhaps relating these attributes to physical (optical/electronic, lattice vibrational) properties become indispensable. Here, we make an attempt to describe the differences between various nanostructures and provide geometrical and topological property assessment semiquantitatively by monitoring the phonon spectra using resonance Raman spectroscopy thereby also capturing the electronic spectra. We elucidate the notion of global topology and curvature for a range of technologically important nanoscale carbons including tubular (single-, double- and multiwalled nanotubes, peapod), spherical (hypo- and hyperfullerenes, onion-like carbon) and complex (nanocones, nanohorns, nanodisks and nanorings) geometries. To demonstrate the proof-of-concept, we determined the variation in the prominent Raman bands of the respective materials, represented as D, G and D* (the overtone of D) bands, as a possible topological or curvature trend due to their sensitivity toward structural modification. The latter arises from local topological defects such as pentagons giving rise to curved nanocarbons. In this study, we provide systematics of their variation with respect to their geometric forms and compare with highly oriented pyrolytic graphite and monolayer graphene since the nanocarbons discussed are their derivatives. Once established, this knowledge will provide a powerful machinery to understand newer nanocarbons and indeed point to an unprecedented emergent paradigm of global topology/curvature , property , functionality relationship. We emphasize that these concepts are applicable to other topologically distinct nanomaterials, which include boron-nitride (BN) nanotubes and nanotori, helical gold nanotubes and Möbius conjugated organics. Copyright © 2009 John Wiley & Sons, Ltd. [source] Separation of structural, geometrical and optical isomers of epoxycarotenoids using triacontyl-bonded stationary phasesJOURNAL OF SEPARATION SCIENCE, JSS, Issue 11 2009Antonio J. Meléndez-Martínez Abstract The efficiency of C30 stationary phases in the separation of carotenes and diverse hydroxycarotenoids has been the subject of several studies. However, little is known concerning their ability to resolve epoxycarotenoids isomers, whose study is of great importance due to the functions they serve and the information they can reveal concerning the processing of foods. We have concluded that C30 columns provide an excellent separation of structural, geometrical and optical isomers of epoxycarotenoids and that the presence of 5,8-epoxide groups leads to a better shape recognition, to the extent that over 10 geometrical,optical isomers of 5,8-epoxycarotenoids have been separated. Additionally, it was observed that these carotenoids elute later than their 5,6-epoxide counterparts, albeit the latter have a longer chromophore. [source] NEXAFS multiple scattering calculations of KO2JOURNAL OF SYNCHROTRON RADIATION, Issue 2 2001M. Pedio Since many years the oxidation of alkali metals has being attracted much interest due to the catalytic properties of metal promoters and the simple electronic structure of alkali atoms. The alkali-oxides phase diagram indicates that the interaction of oxygen with alkali metals can lead to the formation of different atomic O2- ions and molecular O2 - and O22- ions. Potassium superoxide has been prepared in situ and high resolution O k-edge absorption NEXAFS spectra have been measured at the VUV beam-line at ELETTRA facility. The experimental data have been analyzed by multiple scattering approach deriving many geometrical and electronic details. In particular, we have found that the growth material structure is of the KO2 type with an O-O distance of about 1.35Å and that the transition involving single , molecular empty state of the superoxide O2 - anion has a fine structure. Multiple Scattering self consistent calculation indicates that the bond between oxygen anion and K atom is totally ionic and that the fine structure is essentially due to solid state effects. [source] INFLUENCE OF UNIAXIAL COMPRESSION RATE ON RHEOLOGICAL PARAMETERS AND SENSORY TEXTURE PREDICTION OF COOKED POTATOESJOURNAL OF TEXTURE STUDIES, Issue 1 2000ANETTE KISTRUP THYBO ABSTRACT The effect of uniaxial compression rate (20,1000 mm/min) on the parameters: Stress (,ftrue), strain (,fHencky) and work to fracture (Wf), modulus of deformability (Ed), maximum slope before fracture (Emax) and work during 75% compression (Wtotal) was investigated for ten potato varieties. Multivariate data analysis was used to study the correlation between and within the sensory and nonsensory measurements by Principal Component Analysis (PCA) which showed ,ftrue, Emax, Wf, and Wtotal to explain the same type of information in the data, and ,fHencky versus Ed another type of information in the data. The deformation rate had a large effect on ,fHencky. Nine sensory texture attributes covering the mechanical, geometrical and moistness attributes were evaluated. Relationships between uniaxial compression data at various deformation rates and the sensory texture attributes were studied by Partial Least Squares Regression (PLSR). A minor effect of deformation rate on the correlation with the sensory texture properties was obtained. Mechanical properties were predicted to a higher extent than the geometrical attributes and moistness. The prediction of the mechanical, geometrical and moistness attributes increased largely by using uniaxial compression supplemented by chemical measures such as dry matter and pectin methylesterase, but here no relevant effect of deformation rate was obtained. [source] Integrated catchment management in semiarid environments in the context of the European Water Framework DirectiveLAND DEGRADATION AND DEVELOPMENT, Issue 4 2006J. B. Thornes Abstract Two recent developments draw attention to the need for integrated catchment management. First is the European Union's (EU) Water Framework Directive (WFD), which insists on an integrated catchment management plan for each European river basin within the next 15 years. Second is the current trend for river restoration; practitioners have concluded that this can only be achieved through a thorough appreciation of the integrated character of catchments. This paper addresses the question as to whether it makes sense to apply the WFD methodology across the range of European catchments and, in particular, what special provisions need to be made for dry Mediterranean catchments. The Southern European rivers are episodic. They yield high and coarse sediment loads and some are still used as waste repositories. They interact intermittently with groundwater. Reference conditions, both geometrical and water quality, require different measures and observations from those of the temperate and Arctic régime rivers that dominate much of the rest of the EU. These properties are identified and discussed with reference to nested subcatchments of the River Segura in the Province of Murcia, Spain. New research in the Nogalte sub-basin demonstrates a possible ,reference site' for this environment. Copyright © 2006 John Wiley & Sons, Ltd. [source] The Role of the Extracellular Matrix in Tissue Distribution of Macromolecules in Normal and Pathological Tissues: Potential Therapeutic ConsequencesMICROCIRCULATION, Issue 4 2008Helge Wiig ABSTRACT The interstitial space is a dynamic microenvironment that consists of interstitial fluid and structural molecules of the extracellular matrix, such as glycosaminoglycans (hyaluronan and proteoglycans) and collagen. Macromolecules can distribute in the interstitium only in those spaces unoccupied by structural components, a phenomenon called interstitial exclusion. The exclusion phenomenon has direct consequences for plasma volume regulation. Early studies have assigned a major role to collagen as an excluding agent that accounts for the sterical (geometrical) exclusion. More recently, it has been shown that the contribution of negatively charged glycosaminoglycans might also be significant, resulting in an additional electrostatical exclusion effect. This charge effect may be of importance for drug uptake and suggests that either the glycosaminoglycans or the net charge of macromolecular substances to be delivered may be targeted to increase the available volume and uptake of macromolecular therapeutic agents in tumor tissue. Here, we provide an overview of the structural components of the interstitium and discuss the importance the sterical and electrostatical components have on the dynamics of transcapillary fluid exchange. [source] Coupling between dissimilar rectangular dielectric waveguidesMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 2 2003H. Cory Abstract The coupling between two identically excited, dissimilar rectangular dielectric waveguides, whose axes are parallel, is studied as a function of frequency and of the geometrical and the electrical properties of the structure. It is found that, for a given permittivity ratio, the power transfer between the guides is maximal, but not complete, at some particular frequency. It is also found that, for a given frequency, the power transfer between the guides is complete for the appropriate combination of permittivity and size of the guides, thus the same propagation coefficient is achieved for both. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 38: 136,139, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10996 [source] Standardized T2* map of normal human heart in vivo to correct T2* segmental artefactsNMR IN BIOMEDICINE, Issue 6 2007Vincenzo Positano Abstract A segmental, multislice, multi-echo T2* MRI approach could be useful in heart iron-overloaded patients to account for heterogeneous iron distribution, demonstrated by histological studies. However, segmental T2* assessment in heart can be affected by the presence of geometrical and susceptibility artefacts, which can act on different segments in different ways. The aim of this study was to assess T2* value distribution in the left ventricle and to develop a correction procedure to compensate for artefactual variations in segmental analysis. MRI was performed in four groups of 22 subjects each: healthy subjects (I), controls (II) (thalassemia intermedia patients without iron overload), thalassemia major patients with mild (III) and heavy (IV) iron overload. Three short-axis views (basal, median, and apical) of the left ventricle were obtained and analyzed using custom-written, previously validated software. The myocardium was automatically segmented into a 16-segment standardized heart model, and the mean T2* value for each segment was calculated. Punctual distribution of T2* over the myocardium was assessed, and T2* inhomogeneity maps for the three slices were obtained. In group I, no significant variation in the mean T2* among slices was found. T2* showed a characteristic circumferential variation in all three slices. The effect of susceptibility differences induced by cardiac veins was evident, together with low-scale variations induced by geometrical artefacts. Using the mean segmental deviations as correction factors, an artefact correction map was developed and used to normalize segmental data. The correction procedure was validated on group II. Group IV showed no significant presence of segmental artefacts, confirming the hypothesis that susceptibility artefacts are additive in nature and become negligible for high levels of iron overload. Group III showed a greater variability with respect to normal subjects. The correction map failed to compensate for these variations if both additive and percentage-based corrections were applied. This may reinforce the hypothesis that true inhomogeneity in iron deposition exists. Copyright © 2007 John Wiley & Sons, Ltd. [source] Sparse matrix element topology with application to AMG(e) and preconditioning,NUMERICAL LINEAR ALGEBRA WITH APPLICATIONS, Issue 6-7 2002Panayot S. Vassilevski Abstract This paper defines topology relations of elements treated as overlapping lists of nodes. In particular, the element topology makes use of element faces, element vertices and boundary faces which coincide with the actual (geometrical) faces, vertices and boundary faces in the case of true finite elements. The element topology is used in an agglomeration algorithm to produce agglomerated elements (a non-overlapping partition of the original elements) and their topology is then constructed, thus allowing for recursion. The main part of the algorithms is based on operations on Boolean sparse matrices and the implementation of the algorithms can utilize any available (parallel) sparse matrix format. Applications of the sparse matrix element topology to AMGe (algebraic multigrid for finite element problems), including elementwise constructions of coarse non-linear finite element operators are outlined. An algorithm to generate a block nested dissection ordering of the nodes for generally unstructured finite element meshes is given as well. The coarsening of the element topology is illustrated on a number of fine-grid unstructured triangular meshes. Published in 2002 by John Wiley & Sons, Ltd. [source] | ||||||||||||||||||||||||||||||||||||||||