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Mathematical Analysis (mathematical + analysis)
Selected AbstractsMobile-initiated network-executed SIP-based handover in IMS over heterogeneous accessesINTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS, Issue 9-10 2010Wei-Kuo Chiang Abstract The services of next generation networks are envisioned to be potentially capable of seamless mobility in spite of the heterogeneity in underlying access technologies. It is undoubted that to accomplish seamless services across heterogeneous networking environments gets harder in case of simultaneous mobility. In this article, we propose a mobile-initiated network-executed (MINE) session initial protocol (SIP)-based handover mechanism to facilitate simultaneous mobility in IP multimedia subsystem over heterogeneous accesses. The novelty of the proposed approach is that no changes are required to the existing network infrastructure since handover decision is fully made by the mobile host (MH) and handover execution is performed by a new-added application server called mobility server (MS). When the MH decides to initiate a handover and obtains a new IP address, it will send a SIP Publish message to trigger the MS to carry out the handover execution. With the network-executed design of the MINE, the MS can perform third-party registration for security re-association and third-party call control for session re-establishment in parallel. Moreover, the Master,Slave Determination procedures derived from H.245 are used in the MS to handle fairly the racing conditions resulting from simultaneous mobility such that redundant message flows are eliminated. Mathematical analyses present that the MINE can shorten the handover latency and reduce power consumption, as observed from a comparison with the integrated solution of an optimized macro-mobility mechanism and a receiver-side simultaneous mobility approach. Copyright © 2010 John Wiley & Sons, Ltd. [source] Organic Distributions in Dried Alumina Green TapeJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 2 2001Jau-Ho Jean Distributions of organic binder (poly(vinyl butyral) (PVB)) and plasticizer (dibutyl phthalate (DBP)) in alumina green tape dried at different temperatures are studied. More PVB and DBP are observed on the bottom (Mylar side) than on the top surface (air side) of the green tape. Inside the green tape, however, PVB distribution, which remains relatively unchanged with drying temperature in the range of 30°,80°C, increases with distance from the bottom to the top. In contrast, the DBP concentration remains relatively unchanged with the depth of green tape when the drying temperature is <50°C. At 80°C, however, a significant drop in DBP concentration near the top surface of green tape is found. Mathematical analysis using the finite difference method is completed to describe the PVB distribution in alumina green tape, and the results show reasonable agreement with experimental observations. [source] Mathematical analysis of a viscoelastic problem with temperature-dependent coefficients,Part I: Existence and uniquenessMATHEMATICAL METHODS IN THE APPLIED SCIENCES, Issue 13 2007Patricia Barral Abstract The aim of this article is to study the quasistatic evolution of a thermoviscoelastic problem whose behaviour law is of the Maxwell,Norton type with coefficients depending on temperature. In this law, the deformation rate tensor is a superposition of viscoelastic and thermal contributions. The existence and uniqueness of the solution is proved. Copyright © 2007 John Wiley & Sons, Ltd. [source] Mathematical analysis and stability of a chemotaxis model with logistic termMATHEMATICAL METHODS IN THE APPLIED SCIENCES, Issue 16 2004J. Ignacio Tello Abstract In this paper we study a non-linear system of differential equations arising in chemotaxis. The system consists of a PDE that describes the evolution of a population and an ODE which models the concentration of a chemical substance. We study the number of steady states under suitable assumptions, the existence of one global solution to the evolution problem in terms of weak solutions and the stability of the steady states. Copyright © 2004 John Wiley & Sons, Ltd. [source] Mathematical analysis of some new Reynolds-rod elastohydrodynamic modelsMATHEMATICAL METHODS IN THE APPLIED SCIENCES, Issue 15 2001G. Bayada In this paper, some new elastohydrodynamic Reynolds-rod models are posed to obtain the existence of solution (the lubricant pressure and the elastic rod displacement). More precisely, a sign restriction on fluid pressure for cavitation modelling and different unilateral conditions on the rod displacement associated with a rigid structure coating are formulated in terms of coupled variational inequalities. The particular hinged or clamped boundary conditions on the rod displacement require different techniques to prove the existence of solution. Besides nearly linear coupled problems, two non-linear rod problems including curvature effects are analysed. Mainly, regularity results and L, estimates for the solution of variational inequalities and fixed-point theorems lead to the existence results for the various coupled models. Copyright © 2001 John Wiley & Sons, Ltd. [source] 2325: Dynamic retinal vessel analysis , how different parameters create the whole pictureACTA OPHTHALMOLOGICA, Issue 2010I LANZL Purpose Dynamic vessel analysis is usually associated with the observation of the reaction of retinal vessels to a defined stimulus. The data which is generated this way may be further analysed with respect to the dynamic unstimulated and stimulated vessel behaviour. Assessment of different parameters may highlight different aspects of the underlying disease. Methods Vessel diameters of retinal vessel segments were assessed by Dynamic Vessel Analyzer (DVA) in healthy volunteers of different age groups and patients with diabetes, glaucoma and systemic hypertension. Mathematical analysis of unstimulated vessels was used to describe vessel wall characteristics. Methods of signal analysis including Fourier Transformation, spectral filtration, auto- and cross correlation were applied to evaluate characteristic oscillations and pulse wave propagation along the vessel. Results Characteristic different vessel behaviour and vessel wall conformation are obtained by dynamic quantitative evaluations from the unstimulated vessels in physiologic aging and disease. Conclusion Dynamic vessel analysis includes information which may lead to further understanding of the vascular status and underlying disease pathology. It is also feasible to assess pulse wave velocities in retinal arterioles und thus clinically characterize the elasticity of the upstream vasculature in health and disease. [source] Mathematical analysis of the cone ERG photopic hill: Clinical applicationsACTA OPHTHALMOLOGICA, Issue 2007P LACHAPELLE Purpose: With brighter stimuli, the photopic ERG b-wave increases to a maximal value and then decreases to a plateau, a feature known as the Photopic Hill (PH). Recently, a mathematical model combining a Gaussian (GF) and a Logistic Growth (LGF) functions was developed to fit the PH (Hamilton et al., Vision Research, in press). We examined if this equation could help us sort out selected retinopathies. Methods: We compared PHs (background: 30 cd.m-2; intensities: -0.8 to 2.84 log cd.sec.m-2) obtained from normals (N=40) and patients (N=20) affected with Congenital Stationary Night Blindness (CSNB), Congenital Postreceptoral Cone Pathway Anomaly (CPCPA) and Retinitis Pigmentosa (RP) with the GL ratio [GL= Gb / (Gb+Vbmax)] were Gb and Vbmax represent the amplitude of the Gaussian and logistic (Vbmax) functions respectively. Results: The normal GL ratio is 0.60 ± 0.08 (mean ± 1SD) compared to ,1.0 in CSNB (almost pure GF) and 0.32±0.08 in CPCP [reduced GF (p<.05) and normal LF (p>.05)] patients. Six of the 8 RP patients had a GL ratio above 0.5 (mean GL= 0.70 ± 0.19) and 2 below (0.28 and 0.41). Of interest, while in some retinopathies, a decline in Gb and Vbmax occurred with disease progression (longitudinal and transversal comparisons), it did not always modify the GL ratio. Conclusions: Human PH can be dissected into two distinct and concomitant phenomena each represented by its own equation. Altghough the retinal origin of the GF and LGF awaits to be confirmed, use of this mathematical approach appears to add valuable information that will further refine the diagnosis of retinal disorders affecting the photopic (cone) pathway. Supported by CIHR and Réseau Vision. [source] Mathematical analysis of vortex sheetsCOMMUNICATIONS ON PURE & APPLIED MATHEMATICS, Issue 8 2006Sijue Wu We consider the motion of the interface separating two domains of the same fluid that moves with different velocities along the tangential direction of the interface. The evolution of the interface (the vortex sheet) is governed by the Birkhoff-Rott (BR) equations. We consider the question of the weakest possible assumptions such that the Birkhoff-Rott equation makes sense. This leads us to introduce chord-arc curves to this problem. We present three results. The first can be stated as the following: Assume that the Birkhoff-Rott equation has a solution in a weak sense and that the vortex strength is bounded away from 0 and ,. Moreover, assume that the solution gives rise to a vortex sheet curve that is chord-arc. Then the curve is automatically smooth, in fact analytic, for fixed time. The second and third results demonstrate that the Birkhoff-Rott equation can be solved if and only if only half the initial data is given. © 2005 Wiley Periodicals, Inc. [source] Adaptive control using multiple models, switching and tuningINTERNATIONAL JOURNAL OF ADAPTIVE CONTROL AND SIGNAL PROCESSING, Issue 2 2003Kumpati S. Narendra Abstract The past decade has witnessed a great deal of interest in both the theory and practice of adaptive control using multiple models, switching, and tuning. The general approach was introduced in the early 1990s to cope with large and rapidly varying parameters in control systems. During the following years, detailed mathematical analyses of special classes of systems were carried out. Considerable empirical evidence was also collected to demonstrate the practical viability of the methods proposed. This paper attempts to review critically the stability questions that arise in the study of such systems, describes recent extensions of the approach to non-linear adaptive control, and discuss briefly promising new areas of research, particularly related to the location of models. Copyright © 2003 John Wiley & Sons, Ltd. [source] 1342: Communicating numerical results correctlyACTA OPHTHALMOLOGICA, Issue 2010T KIVELÄ Purpose To highlight some pearls and pitfalls in reporting numerical data related to the eye with special reference to the instructions of the EVER Journal, Acta Ophthalmologica. Methods Personal experience of the author as a writer, reviewer and editorial board member is used to highlight common issues specific for reporting statistics. The rules and the reasoning behind them are explained using abundant real life examples. Results Statistics and mathematical analyses applied should be described in the methods section, but the software used need not be referenced unless it is specific for the test used. The following rules regarding reporting are highly recommended: 1. Report proportions if the number of subjects is smaller than 10; percentages in integers if the number of subjects is less than 100; if the number of subjects is larger, one decimal place can be given but is seldom necessary. 2. Report summary statistics of normally distributed variables as mean with standard deviation; other variables as medium with range. 3. Use parametric and nonparametric statistical tests accordingly. 4. Give exact p-values (e.g. p=0.034); if p-value is less than 0.001, report p<0.001. 5. Give 95% confidence intervals for main findings. 6. Mention the statistical test used with the p-value (e.g. p=0.015, paired t-test) if multiple methods are used. Conclusion Efficient reporting and analysis of data related to the eye is not difficult as long as one is aware of the basic rules. Putting them into action helps to ensure that the conclusions the readers draw from your study are proper. [source] Metric spaces in NMR crystallographyCONCEPTS IN MAGNETIC RESONANCE, Issue 4 2009David M. Grant Abstract The anisotropic character of the chemical shift can be measured by experiments that provide shift tensor values and comparing these experimental components, obtained from microcrystalline powders, with 3D nuclear shielding tensor components, calculated with quantum chemistry, yields structural models of the analyzed molecules. The use of a metric tensor for evaluating the mean squared deviations, d2, between two or more tensors provides a statistical way to verify the molecular structure governing the theoretical shielding components. The sensitivity of the method is comparable with diffraction methods for the heavier organic atoms (i.e., C, O, N, etc.) but considerably better for the positions of H atoms. Thus, the method is especially powerful for H-bond structure, the position of water molecules in biomolecular species, and other proton important structural features, etc. Unfortunately, the traditional Cartesian tensor components appear as reducible metric representations and lack the orthogonality of irreducible icosahedral and irreducible spherical tensors, both of which are also easy to normalize. Metrics give weighting factors that carry important statistical significance in a structure determination. Details of the mathematical analysis are presented and examples given to illustrate the reason nuclear magnetic resonance are rapidly assuming an important synergistic relationship with diffraction methods (X-ray, neutron scattering, and high energy synchrotron irradiation). © 2009 Wiley Periodicals, Inc.Concepts Magn Reson Part A 34A: 217,237, 2009. [source] Dynamic compartmentalization of protein tyrosine phosphatase receptor Q at the proximal end of stereocilia: Implication of myosin VI-based transportCYTOSKELETON, Issue 7 2008Hirofumi Sakaguchi Abstract Hair cell stereocilia are apical membrane protrusions filled with uniformly polarized actin filament bundles. Protein tyrosine phosphatase receptor Q (PTPRQ), a membrane protein with extracellular fibronectin repeats has been shown to localize at the stereocilia base and the apical hair cell surface, and to be essential for stereocilia integrity. We analyzed the distribution of PTPRQ and a possible mechanism for its compartmentalization. Using immunofluorescence we demonstrate that PTPRQ is compartmentalized at the stereocilia base with a decaying gradient from base to apex. This distribution can be explained by a model of transport directed toward the stereocilia base, which counteracts diffusion of the molecules. By mathematical analysis, we show that this counter transport is consistent with the minus end-directed movement of myosin VI along the stereocilia actin filaments. Myosin VI is localized at the stereocilia base, and exogenously expressed myosin VI and PTPRQ colocalize in the perinuclear endosomes in COS-7 cells. In myosin VI-deficient mice, PTPRQ is distributed along the entire stereocilia. PTPRQ-deficient mice show a pattern of stereocilia disruption that is similar to that reported in myosin VI-deficient mice, where the predominant features are loss of tapered base, and fusion of adjacent stereocilia. Thin section and freeze-etching electron microscopy showed that localization of PTPRQ coincides with the presence of a dense cell surface coat. Our results suggest that PTPRQ and myosin VI form a complex that dynamically maintains the organization of the cell surface coat at the stereocilia base and helps maintain the structure of the overall stereocilia bundle. Cell Motil. Cytoskeleton 2008. Published 2008 Wiley-Liss, Inc. [source] Solution of the linear diffusion equation for modelling erosion processes with a time varying diffusion coefficientEARTH SURFACE PROCESSES AND LANDFORMS, Issue 10 2008Georgios Aim. Abstract In the present paper the differential equation of the temporal development of a landform (mountain) with a time dependent diffusion coefficient is solved. It is shown that the shape and dimensions of the landform at time t are independent of the specific variation of the diffusion coefficient with time; they only depend on the mean value of the diffusion coefficient in the time interval where the erosion process takes place. Studying the behaviour of the solution of the differential equation in the wave number domain, it is concluded that Fourier analysis may help in estimating, in quantitative terms, the initial dimensions, the age or, alternatively, the value of the diffusion coefficient of the landform. The theoretical predictions are tested on a hill of the southern part of the Ural mountainous region, in order to show how the results of the mathematical analysis can be used in describing, in quantitative terms, the morphological development of landforms due to erosion processes. Copyright © 2007 John Wiley & Sons, Ltd. [source] A stability criterion inherent in laws governing alluvial channel flowEARTH SURFACE PROCESSES AND LANDFORMS, Issue 9 2002He Qing Huang Abstract The stability criterion of maximum flow efficiency (MFE) has previously been found inherent in typical alluvial channel flow relationships, and this study investigates the general nature of this criterion using a wider range of flow resistance and bedload transport formulae. For straight alluvial channels, in which the effect of sediment sorting is insignificant, our detailed mathematical analysis demonstrates that a flow efficiency factor , occurs generally as the ratio of sediment (bedload) discharge Qs to stream power , (,QS) in the form of . When , is maximized (i.e. Qs is maximized or , is minimized), maximally efficient straight channel geometries derived from most flow resistance and bedload transport formulae are found compatible with observed bankfull hydraulic geometry relations. This study provides support for the use of the criteria of MFE, maximum sediment transporting capacity and minimum stream power for understanding the operation of alluvial rivers, and also addresses limitations to the direct application of its findings. Copyright © 2002 John Wiley & Sons, Ltd. [source] Multi-linearity algorithm for wall slip in two-dimensional gap flowINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 12 2007G. J. Ma Abstract Wall slip has been observed in a micro/nanometer gap during the past few years. It is difficult to make a mathematical analysis for the hydrodynamics of the fluid flowing in a gap with wall slip because the fluid velocity at the liquid,solid interface is not known a priori. This difficulty is met especially in a two-dimensional slip flow due to the non-linearity of the slip control equation. In the present paper we developed a multi-linearity method to approach the non-linear control equation of the two-dimensional slip gap flow. We used an amended polygon to approximate the circle yield (slip) boundary of surface shear stress. The numerical solution does not need an iterative process and can simultaneously give rise to fluid pressure distribution, wall slip velocity and surface shear stress. We analysed the squeeze film flow between two parallel discs and the hydrodynamics of a finite slider gap with wall slip. Our numerical solutions show that wall slip is first developed in the large pressure gradient zone, where a high surface shear stress is easily generated, and then the slip zone is enlarged with the increase in the shear rate. Wall slip dramatically affects generation of the hydrodynamic pressure. Copyright © 2006 John Wiley & Sons, Ltd. [source] A new dual mortar method for curved interfaces: 2D elasticityINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 6 2005B. Flemisch Abstract Dual mortar method formulations have shown to be a very effective and efficient way for interfacing (e.g. tying, contacting) dissimilar meshes. On the other hand, we have recently found that they can sometimes perform quite poorly when applied to curved surfaces in some solid mechanics applications. A new modified two-dimensional dual mortar method for piecewise linear finite elements is developed that overcomes this deficiency and is demonstrated on a model problem. Furthermore, mathematical analysis is provided to demonstrate the optimal convergence and stability of the new method. Copyright © 2005 John Wiley & Sons, Ltd. [source] Quadratic programming algorithm for wall slip and free boundary pressure conditionINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 2 2006C. W. Wu Abstract Wall slip is often observed in a highly sheared fluid film in a solid gap. This makes a difficulty in mathematical analysis for the hydrodynamic effect because fluid velocity at the liquid,solid interfaces is not known a priori. If the gap has a convergent,divergent wedge, a free boundary pressure condition, i.e. Reynolds pressure boundary condition, is usually used in the outlet zone in numerical solution. This paper, based on finite element method and parametric quadratic programming technique, gives a numerical solution technique for a coupled boundary non-linearity of wall slip and free boundary pressure condition. It is found that the numerical error decreases with the number of elements in a negative power law having an index larger than 2. Our method does not need an iterative process and can simultaneously gives rise to fluid film pressure distribution, wall slip velocity and surface shear stress. Wall slip always decreases the hydrodynamic pressure. Large wall slip even causes a null hydrodynamic pressure in a pure sliding solid gap. Copyright © 2005 John Wiley & Sons, Ltd. [source] MLCC: A new hash-chained mechanism for multicast source authenticationINTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS, Issue 9 2009H. Eltaief Abstract Asymmetric cryptography has been widely used to generate a digital signature for message authentication. However, such a strategy cannot be used for packet authentication. Neither the source nor the receiver will be capable of handling the computational cost of asymmetric cryptography. For unicast communication, the solution adopted is based on symmetric cryptography. Solutions based on symmetric cryptography do not scale for multicast communication. Several solutions have been reported to authenticate multicast streams, with the possibility of packet losses. Proposed solutions are based on the concept of signature amortization, where a single signature is amortized on several packets. In this paper we present a new mechanism for multicast data source authentication based on signature amortization. Multi-layers connected chains divides the packet stream into a multi-layer structure, where each layer is a two-dimensional matrix. The hash of a packet is included into a forward chain of packets within the same layer as well as a downward chain of packets across multiple layers. The values of the key parameters that influence the mechanism efficiency as well as its performance are selected following a mathematical analysis. Comparisons of performance results with the well-known efficient multi-chained stream signature scheme as well as a recently reported scheme multiple connected chains model show that the proposed mechanism achieves a stronger resistance to packet losses with low overhead and high authentication probability. Copyright © 2008 John Wiley & Sons, Ltd. [source] Mathematical framework towards the analysis of a generic traffic markerINTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS, Issue 4 2007Nasser-Eddine Rikli Abstract DiffServ architecture has been widely adopted for the provision of QoS over the Internet. This makes the full understanding of its operation imperative. We believe that only mathematical analysis may have the power of such goal. As the heart of a DiffServ router is the token bucket algorithm, a generic one, with two-colours marking, is to be considered here. A mathematical framework will be first developed for its analysis. Then, assuming an input traffic with Poisson arrivals and Exponential packet lengths, and a memoryless token bucket system, the two types of generated streams will be statistically characterized through their distributions and averages. This analysis will be carried out for two types of buckets, one with infinite size and a second with finite size. It will be shown how the derived equations will allow the prediction of the output traffic streams for given bucket and input traffic stream parameters. The paper will be then complemented by conclusions and suggestions. Copyright © 2006 John Wiley & Sons, Ltd. [source] Achieving performance enhancement in IEEE 802.11 WLANs by using the DIDD backoff mechanismINTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS, Issue 1 2007P. Chatzimisios Abstract Wireless local area networks (WLANs) based on the IEEE 802.11 standards have been widely implemented mainly because of their easy deployment and low cost. The IEEE 802.11 collision avoidance procedures utilize the binary exponential backoff (BEB) scheme that reduces the collision probability by doubling the contention window after a packet collision. In this paper, we propose an easy-to-implement and effective contention window-resetting scheme, called double increment double decrement (DIDD), in order to enhance the performance of IEEE 802.11 WLANs. DIDD is simple, fully compatible with IEEE 802.11 and does not require any estimation of the number of contending wireless stations. We develop an alternative mathematical analysis for the proposed DIDD scheme that is based on elementary conditional probability arguments rather than bi-dimensional Markov chains that have been extensively utilized in the literature. We carry out a detailed performance study and we identify the improvement of DIDD comparing to the legacy BEB for both basic access and request-to-send/clear-to-send (RTS/CTS) medium access mechanisms. Copyright © 2006 John Wiley & Sons, Ltd. [source] Performance analysis of the IEEE 802.11 MAC protocol for wireless LANsINTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS, Issue 6 2005P. Chatzimisios Abstract Wireless local area networks (WLANs) are extremely popular being almost everywhere including business, office and home deployments. The IEEE 802.11 protocol is the dominating standard for WLANs. The essential medium access control (MAC) mechanism of 802.11 is called distributed co-ordination function (DCF). This paper provides a simple and accurate analysis using Markov chain modelling to compute IEEE 802.11 DCF performance, in the absence of hidden stations and transmission errors. This mathematical analysis calculates in addition to the throughput efficiency, the average packet delay, the packet drop probability and the average time to drop a packet for both basic access and RTS/CTS medium access schemes. The derived analysis, which takes into account packet retry limits, is validated by comparison with OPNET simulation results. We demonstrate that a Markov chain model presented in the literature, which also calculates throughput and packet delay by introducing an additional transition state to the Markov chain model, does not appear to model IEEE 802.11 correctly, leading to ambiguous conclusions for its performance. We also carry out an extensive and detailed study on the influence on performance of the initial contention window size (CW), maximum CW size and data rate. Performance results are presented to identify the dependence on the backoff procedure parameters and to give insights on the issues affecting IEEE 802.11 DCF performance. Copyright © 2005 John Wiley & Sons, Ltd. [source] Logical approaches to deontic reasoning: From basic questions to dynamic solutionsINTERNATIONAL JOURNAL OF INTELLIGENT SYSTEMS, Issue 10 2008Philippe Balbiani The development of deontic logic has opened new possibilities for the mathematical analysis of norms. This article tackles the description of large families of deontic systems that attempt to formalize such-and-such idea of juridical notions like obligation. It also introduces a modal logic based on actions for studying deontic reasoning within the context of a dynamic logic. © 2008 Wiley Periodicals, Inc. [source] Fractal and Fourier analysis of the hepatic sinusoidal network in normal and cirrhotic rat liverJOURNAL OF ANATOMY, Issue 2 2005Eugenio Gaudio Abstract The organization of the hepatic microvascular network has been widely studied in recent years, especially with regard to cirrhosis. This research has enabled us to recognize the distinctive vascular patterns in the cirrhotic liver, compared with the normal liver, which may explain the cause of liver dysfunction and failure. The aim of this study was to compare normal and cirrhotic rat livers by means of a quantitative mathematical approach based on fractal and Fourier analyses performed on photomicrographs and therefore on discriminant analysis. Vascular corrosion casts of livers belonging to the following three experimental groups were studied by scanning electron microscopy: normal rats, CCl4 -induced cirrhotic rats and cirrhotic rats after ligation of the bile duct. Photomicrographs were taken at a standard magnification; these images were used for the mathematical analysis. Our experimental design found that use of these different analyses reaches an efficiency of over 94%. Our analyses demonstrated a higher complexity of the normal hepatic sinusoidal network in comparison with the cirrhotic network. In particular, the morphological changes were more marked in the animals with bile duct-ligation cirrhosis compared with animals with CCl4 -induced cirrhosis. The present findings based on fractal and Fourier analysis could increase our understanding of the pathophysiological alterations of the liver, and may have a diagnostic value in future clinical research. [source] Dyeability improvement of polyester pretreated with some alkoxidesJOURNAL OF APPLIED POLYMER SCIENCE, Issue 1 2008A. Bendak Abstract The influence of some alkoxides in alcoholic media, having various dielectric constants, on the physical and mechanical properties was thoroughly studied in a previous work to attain silk-like polyester fibers. In this investigation, the dyeability behavior of this silk-like polyester is tried. Both immersion and padding techniques are applied in the treatment. The dyeability of the pretreated polyester fabric with disperse dyes shows some progressive improvements with lowering the dyeing temperature and/or decreasing the time of dyeing attained. Ethoxide is found to be more effective in enhancing the dyeability of polyester fabric than either methoxide or propoxide. Dyeing of the pretreated polyester fabric at the boil without using carriers or conducting high temperature/high pressure dyeing is also possible. Washing and crocking fastness are relatively enhanced. Physicochemical investigations of the dyeing process and a mathematical analysis for evenness are given. A decrease in the half dyeing time and an increase in the rate of dyeing of the pretreated polyester as compared with the untreated one are noticed. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] The stable isotope ketoisocaproic acid breath test as a measure of hepatic decarboxylation capacity: a quantitative analysis in normal subjects after oral and intravenous administrationLIVER INTERNATIONAL, Issue 9 2009Heiner K. Berthold Abstract Background and aims: There is no generally accepted kinetic evaluation method for the stable isotope [13C]ketoisocaproic acid (KIC) breath test. Differences found in the results between women and men are contradictory. Methods: Oral and intravenous breath tests using 1 mg/kg stable isotope-labelled KIC were performed in healthy male and female volunteers. A power exponential function was fitted to the mass spectrometric data of breath 13CO2 enrichment, allowing mathematical analysis of time-to-peak-excretion, half-excretion time, percent label recovery and parameters describing the shape of the curve. Body composition was determined using bioelectrical impedance analysis. Results: After oral administration, total label recovery after 3 h was about 22% and was not different between men (n=7) and women (n=8). The time to maximal label excretion was 0.67 ± 0.12 h in men and 0.9 ± 0.32 h in women (P=0.028) and the excretion curve showed an initially slower rise in women compared with men. Adjusting for lean body mass or body water abrogated the sex differences. Total label recovery after intravenous administration was about 9%, suggesting that the substrate was rapidly catabolized in the muscle compartment after intravenous administration. Conclusions: The modified power exponential function described allows standardized estimates of the KIC breath test results. When corrected for body composition, there are no differences in breath test results between men and women. The comparison between oral and intravenous results provides robust evidence that the KIC breath test measures predominantly hepatic and not muscle decarboxylation and is thus a highly specific liver function test. [source] Reducing oblique flow effects in interleaved EPI with a centric reordering techniqueMAGNETIC RESONANCE IN MEDICINE, Issue 4 2001Gabriele Beck Abstract Segmented interleaved echo planar imaging offers a fast and efficient approach to magnetic resonance angiography. Unfortunately, this technique is particularly sensitive to oblique flow in the imaging plane. In this work, a mathematical analysis of oblique flow effects for several types of k -space coverage is presented. The conventional linear acquisition scheme, an alternating centric and a nonalternating centric encoding scheme are compared with respect to their flow properties. It is shown both by simulations and imaging experiments that artifacts from oblique in-plane flow are effectively reduced by both centric reordered phase-encoding schemes. The nonalternating centric acquisition scheme is preferred to the alternating centric scheme due to the smoother phase error transition in k -space in the presence of obliquely-angled flow. Magn Reson Med 45:623,629, 2001. © 2001 Wiley-Liss, Inc. [source] Semigroup approach for identification of the unknown diffusion coefficient in a quasi-linear parabolic equationMATHEMATICAL METHODS IN THE APPLIED SCIENCES, Issue 11 2007Ali Demir Abstract This article presents a semigroup approach for the mathematical analysis of the inverse coefficient problems of identifying the unknown coefficient k(u(x,t)) in the quasi-linear parabolic equation ut(x,t)=(k(u(x,t))ux(x,t))x, with Dirichlet boundary conditions u(0,t)=,0, u(1,t)=,1. The main purpose of this paper is to investigate the distinguishability of the input,output mappings ,[,]:,, ,C1[0,T], ,[,]:,,,C1[0,T] via semigroup theory. In this paper, it is shown that if the null space of the semigroup T(t) consists of only zero function, then the input,output mappings ,[,] and ,[,] have the distinguishability property. It is also shown that the types of the boundary conditions and the region on which the problem is defined play an important role in the distinguishability property of these mappings. Moreover, under the light of measured output data (boundary observations) f(t):=k(u(0,t))ux(0,t) or/and h(t):=k(u(1,t))ux(1,t), the values k(,0) and k(,1) of the unknown diffusion coefficient k(u(x,t)) at (x,t)=(0,0) and (x,t)=(1,0), respectively, can be determined explicitly. In addition to these, the values ku(,0) and ku(,1) of the unknown coefficient k(u(x,t)) at (x,t)=(0,0) and (x,t)=(1,0), respectively, are also determined via the input data. Furthermore, it is shown that measured output dataf(t) and h(t) can be determined analytically by an integral representation. Hence the input,output mappings ,[,]:,,, C1[0,T], ,[,]:,,,C1[0,T] are given explicitly in terms of the semigroup. Copyright © 2007 John Wiley & Sons, Ltd. [source] The Milne problem for the linear Fokker,Planck operator with a force termMATHEMATICAL METHODS IN THE APPLIED SCIENCES, Issue 5 2003Brigitte Lucquin-Desreux Abstract This paper deals with the mathematical analysis of the linear stationary Fokker,Planck equation in a half-space (also called ,Milne' problem), in presence of an external electrostatic force field. We prove existence, uniqueness and asymptotic properties of the solution. Copyright © 2003 John Wiley & Sons, Ltd. [source] The pathophysiology of tremorMUSCLE AND NERVE, Issue 6 2001Günther Deuschl MD Abstract Tremor is defined as rhythmic oscillatory activity of body parts. Four physiological basic mechanisms for such oscillatory activity have been described: mechanical oscillations; oscillations based on reflexes; oscillations due to central neuronal pacemakers; and oscillations because of disturbed feedforward or feedback loops. New methodological approaches with animal models, positron emission tomography, and mathematical analysis of electromyographic and electroencephalographic signals have provided new insights into the mechanisms underlying specific forms of tremor. Physiological tremor is due to mechanical and central components. Psychogenic tremor is considered to depend on a clonus mechanism and is thus believed to be mediated by reflex mechanisms. Symptomatic palatal tremor is most likely due to rhythmic activity of the inferior olive, and there is much evidence that essential tremor is also generated within the olivocerebellar circuits. Orthostatic tremor is likely to originate in hitherto unidentified brainstem nuclei. Rest tremor of Parkinson's disease is probably generated in the basal ganglia loop, and dystonic tremor may also originate within the basal ganglia. Cerebellar tremor is at least in part caused by a disturbance of the cerebellar feedforward control of voluntary movements, and Holmes' tremor is due to the combination of the mechanisms producing parkinsonian and cerebellar tremor. Neuropathic tremor is believed to be caused by abnormally functioning reflex pathways and a wide variety of causes underlies toxic and drug-induced tremors. The understanding of the pathophysiology of tremor has made significant progress but many hypotheses are not yet based on sufficient data. Modern neurology needs to develop and test such hypotheses, because this is the only way to develop rational medical and surgical therapies. © 2001 John Wiley & Sons, Inc. Muscle Nerve 24: 716,735, 2001 [source] A Matter of Trust: From Social Preferences to the Strategic Adherence to Social NormsNEGOTIATION AND CONFLICT MANAGEMENT RESEARCH, Issue 1 2008Joachim I. Krueger Abstract In a mathematical analysis of the trust game, we show that utility-maximizing trustees should establish equal payoffs or return nothing depending on the strength of their social preferences (benevolence and inequality aversion). Trustors may invest any amount depending on their social preferences and their expectations regarding the trustees' preferences. For both types of player, empirical distributions of transfers are rather flat, however, and players' morality, but not their rationality, is judged in proportion to the money transferred. This pattern of findings suggests that people are primarily motivated by self-interest, and that they adhere to relevant social norms inasmuch as they can enhance their self-image or reputation as a moral person. 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