bluuebunny/crossref_metadata_2025 huggingface dataset:
NUMERICAL ASPECTS OF NONLINEAR SCHRÖDINGER EQUATIONS IN THE PRESENCE OF CAUSTICS
Authors: CARLES RÉMI , GOSSE LAURENT
Published: September 2007

The aim of this paper is to develop on the asymptotics of some one-dimensional nonlinear Schrödinger equations from both the theoretical and the numerical perspectives, when a caustic is formed. We review rigorous results in the field and give some heuristics in cases where justification is still needed. The scattering operator theory is recalled. Numerical experiments are carried out on the focus point singularity for which several results have been proved rigorously. Furthermore, the scattering operator is numerically studied. Finally, experiments on the cusp caustic are displayed, and similarities with the focus point are discussed. Several shortcomings of spectral time-splitting schemes are investigated.
RAPIDLY VARYING BOUNDARIES IN EQUATIONS WITH NONLINEAR BOUNDARY CONDITIONS: THE CASE OF A LIPSCHITZ DEFORMATION
Authors: ARRIETA JOSÉ M. , BRUSCHI SIMONE M.
Published: September 2007

We analyze the behavior of solutions of nonlinear elliptic equations with nonlinear boundary conditions of type [Formula: see text] when the boundary of the domain varies very rapidly. We show that the limit boundary condition is given by [Formula: see text], where γ(x) is a factor related to the oscillations of the boundary at point x. For the case where we have a Lipschitz deformation of the boundary, γ is a bounded function and we show the convergence of the solutions in H1 and Cα norms and the convergence of the eigenvalues and eigenfunctions of the linearization around the solutions. If, moreover, a solution of the limit problem is hyperbolic, then we show that the perturbed equation has one and only one solution nearby.
NUMERICAL SOLUTION FOR HYPERBOLIC CONSERVATIVE TWO-PHASE FLOW EQUATIONS
Authors: ZEIDAN D. , SLAOUTI A. , ROMENSKI E. , TORO E. F.
Published: September 2007

We outline an approximate solution for the numerical simulation of two-phase fluid flows with a relative velocity between the two phases. A unified two-phase flow model is proposed for the description of the gas–liquid processes which leads to a system of hyperbolic differential equations in a conservative form. A numerical algorithm based on a splitting approach for the numerical solution of the model is proposed. The associated Riemann problem is solved numerically using Godunov methods of centered-type. Results show the importance of the Riemann problem and of centered schemes in the solution of the two-phase flow problems. In particular, it is demonstrated that the Slope Limiter Centered (SLIC) scheme gives a low numerical dissipation at the contact discontinuities, which makes it suitable for simulations of practical two-phase flow processes.
AN EFFICIENT MESH UPDATING TECHNIQUE FOR FLUID–STRUCTURE INTERACTION PROBLEMS
Authors: MOUROUTIS Z. S. , MARKOU G. A. , PAPADRAKAKIS M. , CHARMPIS D. C.
Published: September 2007

The purpose of this paper is to present a robust mesh updating technique combined with an efficient solution algorithm applicable to large-scale fluid–structure interaction problems. We show that a combination of the dimensional torsional spring concept and a preconditioned conjugated gradient type method, for the solution of the "elasticity" problem, provides a powerful tool for this computationally intensive problem.
EXACT SOLUTION FOR BENDING OF AN ELASTIC PLATE CONTAINING A CRACK AND SUBJECTED TO A CONCENTRATED MOMENT
Authors: CHATTOPADHYAY LALITHA , MURTHY S. SRIDHARA , VISWANATH S.
Published: September 2007

The problem of estimating the bending stress distribution in the vicinity of cracks located on a single line in an elastic plate subjected to concentrated moment is examined. Using classical plate theory and integral transform techniques, the general formulae for the bending moment and twisting moment in an elastic plate containing cracks located on a single line are derived. The solution is obtained in detail for the case in which there is a single crack in an infinite plate, and the bending stress intensity factor is determined in a closed form. Two examples are considered to illustrate the present approach.
FLUID SIMULATION USING AN ADAPTIVE SEMI-DISCRETE CENTRAL-UPWIND SCHEME
Authors: CAI L. , ZHOU J. , FENG J.-H. , XIE W.-X.
Published: September 2007

In this paper, we propose an adaptive semi-discrete central-upwind scheme on triangular meshes to approximate the solutions of hyperbolic conservation laws in gas dynamics: a local smoothness indicator is implemented to identify discontinuous solution regions; away from the discontinuities, a simple and computationally economical flux is used; near the discontinuities, an accurate but computationally uneconomical flux is used. Several numerical experiments, Euler equations and Kelvin–Helmholtz instability, are successfully simulated. The numerical results show the desired accuracy, high efficiency and robustness of the adaptive scheme.
MODELING OF SUPERSONIC COMBUSTION USING POINT IMPLICIT FINITE VOLUME METHOD
Authors: DEEPU MUKUNDAN NAIR , GOKHALE SADANAND SADASHIV
Published: September 2007

Numerical modeling of turbulent-reacting flow field in supersonic combustors is presented. When flow field and chemical kinetics with differing time scales need to be solved simultaneously, explicit treatment of all conservation terms with reaction chemistry results in stiff equations and has a tendency to degrade the performance of numerical method. A method of preconditioning, in which the conservation equations in conjunction with chemical source terms alone is treated implicitly. Such a method has the advantage of both explicit and implicit methods. A code was developed using above method and tested successfully for a supersonic combustor configuration.
MANAGING WITHIN DISTRIBUTED INNOVATION NETWORKS
Authors: DOOLEY LAWRENCE , O'SULLIVAN DAVID
Published: September 2007

Business competitiveness and sustainability depends on the effective management of innovation. To be effective, innovation needs to take place within every area of an organisation and by association within organisational networks that include key suppliers, customers and other strategic partners. Distributed innovation management is the process of managing innovation both within and across networks of organisations that have come together to co-design, co-produce and co-service the needs of customers. As innovation collaboration spreads outside the reporting structures of any one organisation, its management faces new challenges that must be addressed if collaboration is to be successful. This paper presents a discussion on the relational capabilities that need to be nurtured if distributed innovation management is to occur. It introduces an integrated framework and tools to support innovation from the individual employees to the distributed network level. Finally, it presents a case study of distributed innovation between a consortium of six organisations within the biotechnology area.
BASIC APPROACHES TO PATENT STRATEGY
Authors: GILARDONI ELENA
Published: September 2007

Patents play a greater role in the economy. The patent strategy is an important tool for creating value and reflects a coordinated effort for developing, managing and using patents to accomplish company's goals. The patent strategy is composed by three dimensions: intent, strategy, and management. The literature considers these elements as independent each others and neglects that some factors could influence them. The study aims at (1) systematising the literature contributions, (2) defining the basic approaches to patent strategy able to suggest a patents strategy policy and establish a relationship among the different patent aspects and (3) studying the dynamics with time.

The study, based on the literature analysis and multiple case studies, identifies five basic approaches to patent strategy. The dynamics in approach to patent strategy and affecting factors have been studied based on a case study.
Mechanisms and Regulation of Epithelial Ca2+ Absorption in Health and Disease
Authors: Suzuki Yoshiro , Landowski Christopher P. , Hediger Matthias A.
Published: September 2007

Ca2+ is essential for numerous physiological functions in our bodies. Therefore, its homeostasis is finely maintained through the coordination of intestinal absorption, renal reabsorption, and bone resorption. The Ca2+-selective epithelial channels TRPV5 and TRPV6 have been identified, and their physiological roles have been revealed: TRPV5 is important in final renal Ca2+ reabsorption, and TRPV6 has a key role in intestinal Ca2+ absorption. The TRPV5 knockout mice exhibit renal leak hypercalciuria and accordingly upregulate their intestinal TRPV6 expression to compensate for their negative Ca2+ balance. In contrast, despite their severe negative Ca2+ balance, TRPV6-null mice do not display any compensatory mechanism, thus resulting in secondary hyperparathyroidism. These results indicate that the genes for TRPV5 and TRPV6 are differentially regulated in human diseases associated with disturbed Ca2+ balance such as hypercalciuria, osteoporosis, and vitamin D–resistant rickets.
Hypoxia-Induced Signaling in the Cardiovascular System
Authors: Simon M. Celeste , Liu Liping , Barnhart Bryan C. , Young Regina M.
Published: September 2007

Low oxygen (O2) levels are a naturally occurring feature of embryonic development, adult physiology, and diseases such as those of the cardiovascular system. Although many responses to O2 deprivation are mediated by hypoxia-inducible factors (HIFs), researchers are finding a growing number of HIF-independent pathways that promote O2 conformance and hypoxia tolerance. Here, we describe HIF-independent responses and how they impact cardiovascular tissue homeostasis.
PPARγ regulates adipose triglyceride lipase in adipocytes in vitro and in vivo
Authors: Kershaw Erin E. , Schupp Michael , Guan Hong-Ping , Gardner Noah P. , Lazar Mitchell A. , Flier Jeffrey S.
Published: September 2007

Peroxisome proliferator-activated receptor-γ (PPARγ) regulates adipocyte genes involved in adipogenesis and lipid metabolism and is the molecular target for thiazolidinedione (TZD) antidiabetic agents. Adipose triglyceride lipase (ATGL) is a recently described triglyceride-specific lipase that is induced during adipogenesis and remains highly expressed in mature adipocytes. This study evaluates the ability of PPARγ to directly regulate ATGL expression in adipocytes in vitro and in vivo. In fully differentiated 3T3-L1 adipocytes, ATGL mRNA and protein are increased by TZD and non-TZD PPARγ agonists in a dose- and time-dependent manner. Rosiglitazone-mediated induction of ATGL mRNA is rapid and is not inhibited by the protein synthesis inhibitor cycloheximide, indicating that intervening protein synthesis is not required for this effect. Rosiglitazone-mediated induction of ATGL mRNA and protein is inhibited by the PPARγ-specific antagonist GW-9662 and is also significantly reduced following siRNA-mediated knockdown of PPARγ, supporting the direct transcriptional regulation of ATGL by PPARγ. In vivo, ATGL mRNA and protein are increased by rosiglitazone treatment in white and brown adipose tissue of mice with and without obesity due to high-fat diet or leptin deficiency. Thus, PPARγ positively regulates ATGL mRNA and protein expression in mature adipocytes in vitro and in adipose tissue in vivo, suggesting a role for ATGL in mediating PPARγ's effects on lipid metabolism.
Amino acids augment muscle protein synthesis in neonatal pigs during acute endotoxemia by stimulating mTOR-dependent translation initiation
Authors: Orellana Renán A. , Jeyapalan Asumthia , Escobar Jeffery , Frank Jason W. , Nguyen Hanh V. , Suryawan Agus , Davis Teresa A.
Published: September 2007

In skeletal muscle of adults, sepsis reduces protein synthesis by depressing translation initiation and induces resistance to branched-chain amino acid stimulation. Normal neonates maintain a high basal muscle protein synthesis rate that is sensitive to amino acid stimulation. In the present study, we determined the effect of amino acids on protein synthesis in skeletal muscle and other tissues in septic neonates. Overnight-fasted neonatal pigs were infused with endotoxin (LPS, 0 and 10 μg·kg−1·h−1), whereas glucose and insulin were maintained at fasting levels; amino acids were clamped at fasting or fed levels. In the presence of fasting insulin and amino acids, LPS reduced protein synthesis in longissimus dorsi (LD) and gastrocnemius muscles and increased protein synthesis in the diaphragm, but had no effect in masseter and heart muscles. Increasing amino acids to fed levels accelerated muscle protein synthesis in LD, gastrocnemius, masseter, and diaphragm. LPS stimulated protein synthesis in liver, lung, spleen, pancreas, and kidney in fasted animals. Raising amino acids to fed levels increased protein synthesis in liver of controls, but not LPS-treated animals. The increase in muscle protein synthesis in response to amino acids was associated with increased mTOR, 4E-BP1, and S6K1 phosphorylation and eIF4G-eIF4E association in control and LPS-infused animals. These findings suggest that amino acids stimulate skeletal muscle protein synthesis during acute endotoxemia via mTOR-dependent ribosomal assembly despite reduced basal protein synthesis rates in neonatal pigs. However, provision of amino acids does not further enhance the LPS-induced increase in liver protein synthesis.
Modulation of expression of somatostatin receptor subtypes in Graves’ ophthalmopathy orbits: relevance to novel analogs
Authors: Cozma Irina , Zhang Lei , Uddin James , Lane Carol , Rees Aled , Ludgate Marian
Published: September 2007

Apart from evaluating orbital inflammation in Graves’ ophthalmopathy (GO), somatostatin (SST) analogs have been proposed as a therapy, but recent trials were disappointing. We aimed to measure somatostatin receptor (SSTR) expression in orbital tissues ex vivo and determine whether the new broad-affinity analog SOM230 might be of therapeutic use. Orbital adipose/connective tissues from 29 GO patients and 10 normal individuals were analyzed. Transcripts were quantified using SYBR Green and a light cycler. In vitro models were used to investigate whether thyrotropin receptor activation (as occurs via thyroid stimulating antibodies) or adipogenesis affected SSTR expression in primary preadipocytes and to compare the biological activity of octreotide and SOM230 in their modulation. The expression of SSTR1 was significantly higher in GO patients than normal controls ( P = 0.024). Although differences in the expression of SSTR2 were not significant, 39% of GO samples had levels above the 97th percentile of the controls. SSTR3, -4, and -5 were at or below the limit of detection (LOD). The lymphocyte contribution was minimal, since CD3α transcripts were at the LOD. TSH receptor activation did not modulate SSTR expression. An in vitro model of adipogenesis indicated upregulation of SSTR1 and SSTR2 during differentiation. SOM230 produced significantly greater inhibition of orbital preadipocyte proliferation than octreotide. Ex vivo analysis of orbital tissues reveals upregulation of SSTR1 and -2 in a group of GO patients. Adipogenesis, a process occurring in GO orbits, provides one possible explanation for some of the observed increase.
A noninvasive measure of negative-feedback strength, approximate entropy, unmasks strong diurnal variations in the regularity of LH secretion
Authors: Liu Peter Y. , Iranmanesh Ali , Keenan Daniel M. , Pincus Steven M. , Veldhuis Johannes D.
Published: September 2007

The secretion of anterior-pituitary hormones is subject to negative feedback. Whether negative feedback evolves dynamically over 24 h is not known. Conventional experimental paradigms to test this concept may induce artifacts due to nonphysiological feedback. These limitations might be overcome by a noninvasive methodology to quantify negative feedback continuously over 24 h without disrupting the axis. The present study exploits a recently validated model-free regularity statistic, approximate entropy (ApEn), which monitors feedback changes with high sensitivity and specificity (both >90%; Pincus SM, Hartman ML, Roelfsema F, Thorner MO, Veldhuis JD. Am J Physiol Endocrinol Metab 273: E948–E957, 1999). A time-incremented moving window of ApEn was applied to LH time series obtained by intensive (10-min) blood sampling for four consecutive days (577 successive measurements) in each of eight healthy men. Analyses unveiled marked 24-h variations in ApEn with daily maxima (lowest feedback) at 1100 ± 1.7 h (mean ± SE) and minima (highest feedback) at 0430 ± 1.9 h. The mean difference between maximal and minimal 24-h LH ApEn was 0.348 ± 0.018, which differed by P < 0.001 from all three of randomly shuffled versions of the same LH time series, simulated pulsatile data and assay noise. Analyses artificially limited to 24-h rather than 96-h data yielded reproducibility coefficients of 3.7–9.0% for ApEn maxima and minima. In conclusion, a feedback-sensitive regularity statistic unmasks strong and consistent 24-h rhythmicity of the orderliness of unperturbed pituitary-hormone secretion. These outcomes suggest that ApEn may have general utility in probing dynamic mechanisms mediating feedback in other endocrine systems.
Dynamic regulation of estrogen receptor-α isoform expression in the mouse fallopian tube: mechanistic insight into estrogen-dependent production and secretion of insulin-like growth factors
Authors: Shao Ruijin , Egecioglu Emil , Weijdegård Birgitta , Kopchick John J. , Fernandez-Rodriguez Julia , Andersson Niklas , Billig Håkan
Published: September 2007

Estrogen receptors (ERs) are members of the nuclear receptor superfamily and are involved in regulation of fallopian tube functions (i.e., enhancement of protein secretion, formation of tubal fluid, and regulation of gamete transport). However, the ER subtype-mediated mechanisms underlying these processes have not been completely clarified. Recently, we identified ERβ expression and localization in rat fallopian tubes, suggesting a potential biological function of ERβ related to calcium-dependent ciliated beating. Here we provide for the first time insight into the less studied ERα isoforms, which mediate estrogen-dependent production and secretion of IGFs in vivo. First, Western blot studies revealed that three ERα isoforms were expressed in mouse fallopian tubes. Subsequent immunohistochemical analysis showed that ERα was detected in all cell types, whereas ERβ was mainly localized in ciliated epithelial cells. Second, ERα isoform levels were dramatically downregulated in mouse fallopian tubes by treatment with E2or PPT, an ERα agonist, in a time-dependent manner. Third, the presence of ICI 182,780, an ER antagonist, blocked the E2- or PPT-induced downregulation of tubal ERα isoform expression in mice. However, alteration of ERα immunoreactivity following ICI 182,780 treatment was only detected in epithelial cells of the ampullary region. Fourth, changes in ERα isoform expression were found to be coupled to multiple E2effects on tubal growth, protein synthesis, and secretion in mouse fallopian tube tissues and fluid. In particular, E2exhibited positive regulation of IGF-I and IGF-II protein levels. Finally, using growth hormone receptor (GHR) gene-disrupted mice, we showed that regulation by E2of IGF production was independent of GH-induced GHR signaling in mouse fallopian tubes in vivo. These data, together with previous studies from our laboratory, suggest that the long-term effects of estrogen agonist promote IGF synthesis and secretion in mouse tubal epithelial cells and fallopian tube fluid via stimulation of ERα.
GIP receptor antagonism reverses obesity, insulin resistance, and associated metabolic disturbances induced in mice by prolonged consumption of high-fat diet
Authors: McClean Paula L. , Irwin Nigel , Cassidy Roslyn S. , Holst Jens J. , Gault Victor A. , Flatt Peter R.
Published: September 2007

The gut hormone gastric inhibitory polypeptide (GIP) plays a key role in glucose homeostasis and lipid metabolism. This study investigated the effects of administration of a stable and specific GIP receptor antagonist, (Pro3)GIP, in mice previously fed a high-fat diet for 160 days to induce obesity and related diabetes. Daily intraperitoneal injection of (Pro3)GIP over 50 days significantly decreased body weight compared with saline-treated controls, with a modest increase in locomotor activity but no change of high-fat diet intake. Plasma glucose, glycated hemoglobin, and pancreatic insulin were restored to levels of chow-fed mice, and circulating triglyceride and cholesterol were significantly decreased. (Pro3)GIP treatment also significantly decreased circulating glucagon and corticosterone, but concentrations of GLP-1, GIP, resistin, and adiponectin were unchanged. Adipose tissue mass, adipocyte hypertrophy, and deposition of triglyceride in liver and muscle were significantly decreased. These changes were accompanied by significant improvement of insulin sensitivity, meal tolerance, and normalization of glucose tolerance in (Pro3)GIP-treated high-fat-fed mice. (Pro3)GIP concentrations peaked rapidly and remained elevated 24 h after injection. These data indicate that GIP receptor antagonism using (Pro3)GIP provides an effective means of countering obesity and related diabetes induced by consumption of a high-fat, energy-rich diet.
Identifyingcis-regulatory elements by statistical analysis and phylogenetic footprinting and analyzing their coexistence and related gene ontology
Authors: Shi Wei , Zhou Wanlei , Xu Dakang
Published: September 2007

Discovery of cis-regulatory elements in gene promoters is a highly challenging research issue in computational molecular biology. This paper presents a novel approach to searching putative cis-regulatory elements in human promoters by first finding 8-mer sequences of high statistical significance from gene promoters of humans, mice, and Drosophila melanogaster, respectively, and then identifying the most conserved ones across the three species (phylogenetic footprinting). In this study, a conservation analysis on both closely related species (humans and mice) and distantly related species (humans/mice and Drosophila) is conducted not only to examine more candidates but also to improve the prediction accuracy. We have found 124 putative cis-regulatory elements and grouped these into 20 clusters. The investigation on the coexistence of these clusters in human gene promoters reveals that SP1, EGR, and NRF-1 are the dominant clusters appearing in the combinatorial combination of up to five clusters. Gene Ontology (GO) analysis also shows that many GO categories of transcription factors binding to these cis-regulatory elements match the GO categories of genes whose promoters contain these elements. Compared with previous research, the contribution of this study lies not only in the finding of new cis-regulatory elements, but also in its pioneering exploration on the coexistence of discovered elements and the GO relationship between transcription factors and regulated genes. This exploration verifies the putative cis-regulatory elements that have been found from this study and also gives new insight on the regulation mechanisms of gene expression.
Influence of torpor on cardiac expression of genes involved in the circadian clock and protein turnover in the Siberian hamster (Phodopus sungorus)
Authors: Crawford Fiona I. J. , Hodgkinson Cassandra L. , Ivanova Elena , Logunova Larisa B. , Evans Gary J. , Steinlechner Stephan , Loudon Andrew S. I.
Published: September 2007

The Siberian hamster exhibits the key winter adaptive strategy of daily torpor, during which metabolism and heart rate are slowed for a few hours and body temperature declines by up to 20°C, allowing substantial energetic savings. Previous studies of hibernators in which temperature drops by >30°C for many days to weeks have revealed decreased transcription and translation during hypometabolism and identified several key physiological pathways involved. Here we used a cDNA microarray to define cardiac transcript changes over the course of a daily torpor bout and return to normothermia, and we show that, in common with hibernators, a relatively small proportion of the transcriptome (<5%) exhibited altered expression over a torpor bout. Pathways exhibiting significantly altered gene expression included transcriptional regulation, RNA stability and translational control, globin regulation, and cardiomyocyte function. Remarkably, gene representatives of the entire ubiquitylation pathway were significantly altered over the torpor bout, implying a key role for cardiac protein turnover and translation during a low-temperature torpor bout. The circadian clock maintained rhythmic transcription during torpor. Quantitative PCR profiling of heart, liver, and lung and in situ hybridization studies of clock genes in the hypothalamic circadian clock in the suprachiasmatic nucleus revealed that many circadian regulated transcripts exhibited synchronous alteration in expression during arousal. Our data highlight the potential importance of genes involved in protein turnover as part of the adaptive strategy of low-temperature torpor in a seasonal mammal.
ACTN3 (R577X) genotype is associated with fiber type distribution
Authors: Vincent Barbara , De Bock Katrien , Ramaekers Monique , Van den Eede Els , Van Leemputte Marc , Hespel Peter , Thomis Martine A.
Published: September 2007

α-Actinin-3 is a Z-disc structural protein found only in type II muscle fibers. The X allele of the R577X polymorphism in the ACTN3 gene results in a premature stop codon and α-actinin-3 deficiency in XX homozygotes. Associations between the R577X polymorphism and the muscle-power performance of elite athletes have been described earlier. About 45% of the fiber type proportions are determined by genetic factors. The ACTN3 variant could be one of the contributing genes in the heritability of fiber type distribution through its interaction with calcineurin. The aim of this study was to quantify the association between the polymorphism and muscle fiber type distribution and fast-velocity knee extension strength. Ninety healthy young men (18–29 y) were genotyped for ACTN3 R577X. Knee extensor strength was measured isometrically (45°) and at different dynamic velocities (100–300°/s) on a programmable dynamometer. Twenty-two XX and twenty-two RR subjects underwent a biopsy of the right vastus lateralis muscle. Fiber type composition was determined by immunohistochemistry. Homozygotes for the R allele show significantly higher relative dynamic quadriceps torques at 300°/s, compared with XX carriers ( P < 0.05). Fiber type characteristics differed significantly between the two genotype groups. The percentage surface and number of type IIx fibers were greater in the RR than the XX genotype group ( P < 0.05), and α-actinin-3 protein content is systematically higher in type IIx compared with type IIa fibers (staining intensity ratio IIx to IIa = 1.17). This study shows that the mechanism, by which the ACTN3 polymorphism has its effect on muscle power, might rely on a control function of fiber type proportions.
Approximation Technics for an Unsteady Dynamic Koiter Shell
Authors: Aouadi Saloua Mani
Published: September 2007

We propose a mixed formulation in dynamical elasticity of shells which allows a locking-free finite element approximation in particular cases of Koiter shells.
Quadratic Stabilization of LPV System by an LTI Controller Based on ILMI Algorithm
Authors: Xie Wei
Published: September 2007

A linear time-invariant (LTI) output feedback controller is designed for a linear parameter-varying (LPV) control system to achieve quadratic stability. The LPV system includes immeasurable dependent parameters that are assumed to vary in a polytopic space. To solve this control problem, a heuristic algorithm is proposed in the form of an iterative linear matrix inequality (ILMI) formulation. Furthermore, an effective method of setting an initial value of the ILMI algorithm is also proposed to increase the probability of getting an admissible solution for the controller design problem.
Enhanced Detection of Visual-Evoked Potentials in Brain-Computer Interface Using Genetic Algorithm and Cyclostationary Analysis
Authors: Gupta Cota Navin , Palaniappan Ramaswamy
Published: September 2007

We propose a novel framework to reduce background electroencephalogram (EEG) artifacts from multitrial visual-evoked potentials (VEPs) signals for use in brain-computer interface (BCI) design. An algorithm based on cyclostationary (CS) analysis is introduced to locate the suitable frequency ranges that contain the stimulus-related VEP components. CS technique does not require VEP recordings to be phase locked and exploits the intertrial similarities of the VEP components in the frequency domain. The obtained cyclic frequency spectrum enables detection of VEP frequency band. Next, bandpass or lowpass filtering is performed to reduce the EEG artifacts using these identified frequency ranges. This is followed by overlapping band EEG artifact reduction using genetic algorithm and independent component analysis (G-ICA) which uses mutual information (MI) criterion to separate EEG artifacts from VEP. The CS and GA methods need to be applied only to the training data; for the test data, the knowledge of the cyclic frequency bands and unmixing matrix would be sufficient for enhanced VEP detection. Hence, the framework could be used for online VEP detection. This framework was tested with various datasets and it showed satisfactory results with very few trials. Since the framework is general, it could be applied to the enhancement of evoked potential signals for any application.
Delay-Dependent Asymptotic Stability of Cohen-Grossberg Models with Multiple Time-Varying Delays
Authors: Liao Xiaofeng , Guo Songtao
Published: September 2007

Dynamical behavior of a class of Cohen-Grossberg models with multiple time-varying delays is studied in detail. Sufficient delay-dependent criteria to ensure local and global asymptotic stabilities of the equilibrium of this network are derived by constructing suitable Lyapunov functionals. The obtained conditions are shown to be less conservative and restrictive than those reported in the known literature. Some numerical examples are included to demonstrate our results.
On Localα-Times IntegratedC-Semigroups
Authors: Li Yuan-Chuan , Shaw Sen-Yen
Published: September 2007

This paper presents several characterizations of a localα-times integratedC-semigroup{T(t);0≤t<τ}by means of functional equation, subgenerator, and well-posedness of an associated abstract Cauchy problem. We also discuss properties concerning the nondegeneracy ofT(⋅), the injectivity ofC, the closability of subgenerators, the commutativity ofT(⋅), and extension of solutions of the associated abstract Cauchy problem.
Frequency‐Division Multiplexing for Electrical Impedance Tomography in Biomedical Applications
Authors: Granot Yair , Ivorra Antoni , Rubinsky Boris
Published: September 2007

Electrical impedance tomography (EIT) produces an image of the electrical impedance distribution of
tissues in the body, using electrodes that are placed on the periphery of the imaged area. These
electrodes inject currents and measure voltages and from these data, the impedance can be
computed. Traditional EIT systems usually inject current patterns in a serial manner which means
that the impedance is computed from data collected at slightly different times. It is usually also a time‐consuming process. In this paper, we propose a method for collecting data concurrently from all of the current patterns in biomedical applications of EIT. This is achieved by injecting current through all of
the current injecting electrodes simultaneously, and measuring all of the resulting voltages at once.
The signals from various current injecting electrodes are separated by injecting different frequencies
through each electrode. This is called frequency‐division multiplexing (FDM). At the voltage
measurement electrodes, the voltage related to each current injecting electrode is isolated by using
Fourier decomposition. In biomedical applications, using different frequencies has important
implications due to dispersions as the tissue′s electrical properties change with
frequency. Another significant issue arises when we are recording data in a dynamic environment
where the properties change very fast. This method allows simultaneous measurements of all the
current patterns, which may be important in applications where the tissue changes occur in the same
time scale as the measurement. We discuss the FDM EIT method from the biomedical point of view
and show results obtained with a simple experimental system.
Strong Convergence Theorems for a Finite Family of Nonexpansive Mappings
Authors: Shang Meijuan , Su Yongfu , Qin Xiaolong
Published: September 2007

We modified the classic Mann iterative process to have strong convergence theorem for a finite family of nonexpansive mappings in the framework of Hilbert spaces. Our results improve and extend the results announced by many others.
Self-Paced (Asynchronous) BCI Control of a Wheelchair in Virtual Environments: A Case Study with a Tetraplegic
Authors: Leeb Robert , Friedman Doron , Müller-Putz Gernot R. , Scherer Reinhold , Slater Mel , Pfurtscheller Gert
Published: September 2007

The aim of the present study was to demonstrate for the first time that brain waves can be used by a tetraplegic to control movements of his wheelchair in virtual reality (VR). In this case study, the spinal cord injured (SCI) subject was able to generate bursts of beta oscillations in the electroencephalogram (EEG) by imagination of movements of his paralyzed feet. These beta oscillations were used for a self-paced (asynchronous) brain-computer interface (BCI) control based on a single bipolar EEG recording. The subject was placed inside a virtual street populated with avatars. The task was to “go” from avatar to avatar towards the end of the street, but to stop at each avatar and talk to them. In average, the participant was able to successfully perform this asynchronous experiment with a performance of 90%, single runs up to 100%.
Traumatic Anterior Cerebral Artery Aneurysm following Blunt Craniofacial Trauma
Authors: Yang Tao-Chieh , Lo Yang-Lan , Huang Yin-Chen , Yang Shun-Tai
Published: September 2007

Background: Traumatic aneurysms of the anterior cerebral artery (ACA) were retrospectively reviewed in an effort to identify patients at high risk of ACA aneurysm. Methods: Blunt craniofacial trauma patients featuring vascular injuries over the region of the ACA were studied. Results: Six patients featuring eight ACA aneurysms were diagnosed between June 1992 and December 2005, inclusively. Seven aneurysms were located at nonbranched sites and one was located over the right ACA-anterior communicating artery junction. One patient died immediately of massive intracranial lobar hemorrhage (ICH). The other 5 patients experienced rebleeding during a period of from 1 to 29 days. Brain computed tomography revealed subarachnoid hemorrhage (SAH) in 1 of these 6 patients, ICH over the medial frontal area or cingulated gyrus in 4 patients, intraventricular hemorrhage (IVH) in 3 patients, and an interhemispheric subdural hematoma (SDH) in 2 patients. Conclusion: Delayed-onset deterioration of neurological deficit is the most common clinical presentation of traumatic ACA aneurysms. Midline hemorrhage such as medial frontal hemorrhage or cingulate gyrus hemorrhage, and the presence of an interhemispheric SDH associated with SAH and IVH subsequent to blunt craniofacial trauma should be further evaluated, as they pre-sent a high risk of traumatic ACA aneurysms to patients.
Malpighi and the Discovery of Capillaries
Authors: Pearce J.M.S.
Published: September 2007

Leonardo da Vinci clearly observed and described capillaries. Using the microscope, Marcello Malpighi examined the brain and major organs to demonstrate their finer anatomical features. This led to his discovery in 1661, of capillaries that proved fundamental to our understanding of the vascular system in the brain and cord. He hypothesized that capillaries were the connection between arteries and veins that allowed blood to flow back to the heart in the circulation of the blood, as first asserted by William Harvey.
Mild Cognitive Impairment in General Practice: Age-Specific Prevalence and Correlate Results from the German Study on Ageing, Cognition and Dementia in Primary Care Patients (AgeCoDe)
Authors: Luck Tobias , Riedel-Heller Steffi G. , Kaduszkiewicz Hanna , Bickel Horst , Jessen Frank , Pentzek Michael , Wiese Birgitt , Koelsch Heike , van den Bussche Hendrik , Abholz Heinz-Harald , Moesch Edelgard , Gorfer Sandra , Angermeyer Matthias C. , Maier Wolfgang , Weyerer Siegfried
Published: September 2007

Background: Although mild cognitive impairment (MCI) represents a high-risk factor for developing dementia, little is known about the prevalence of MCI among patients of general practitioners (GPs). Aims: Estimation of age-specific prevalence for original and modified concepts of MCI and their association with sociodemographic, medical and genetic (apoE Ε4 genotype) factors among patients of GPs. Methods: A GP practice sample of 3,327 individuals aged 75+ was assessed by structured clinical interviews. Results: Prevalence was 15.4% (95% CI = 14.1–16.6) for original and 25.2% (95% CI = 23.7–26.7) for modified MCI. Rates increased significantly with older age. Positive associations were found for apoE Ε4 allele, vascular diseases and depressive symptoms. Conclusion: MCI is frequent in elderly patients of GPs. GPs have a key position in secondary prevention and care of incipient cognitive deterioration up to the diagnosis of dementia.
Plasma Mineral Content in Type-2 Diabetic Patients and Their Association with the Metabolic Syndrome
Authors: Aguilar M.V. , Saavedra P. , Arrieta F.J. , Mateos C.J. , González M.J. , Meseguer I. , Martínez-Para M.C.
Published: September 2007

Background: Metabolic syndrome is a clinical disorder that is becoming more prevalent in Spain. The syndrome encompasses a set of metabolic disorders such as type-2 diabetes mellitus, hypertension, dyslipidemia, and obesity, which may be associated with variations in serum levels and poor delivery of certain mineral elements. Methods: This study attempted to ascertain whether metabolic syndrome might be linked to alterations in serum levels of the mineral elements magnesium, copper, zinc, chromium, and nickel in a population of 92 diabetic subjects, some suffering from certain conditions associated with the metabolic syndrome, and 72 control subjects (Hospital Príncipe de Asturias, Alcalá de Henares, Spain). Results: The results indicated that as a group the alterations implicated in metabolic syndrome were indeed associated with variations in blood levels of the mineral elements considered, though statistically significant differences were recorded only in the case of copper. Still, trends in mineral levels for each of the separate components contributing to the syndrome tended to increase. Conclusion: Metabolic complications appear to be associated with alterations in the levels of some minerals, especially copper.
Decision Making for Solitary Vestibular Schwannoma and Contralateral Meniere’s Disease
Authors: Dispenza Francesco , De Stefano Alessandro , Flanagan Sean , Romano Guglielmo , Sanna Mario
Published: September 2007

The existence of dual inner ear pathology such as unilateral Meniere’s disease (MD) with a contralateral vestibular schwannoma (VS) is very rare, but provides the otologist with a significant management dilemma. In this study, we present 5 cases of unilateral disabling MD with a contralateral VS in the better hearing ear. Conservative management of the VS is mandated unless there are impending complications, with management directed toward controlling the vertigo attributed to MD. If and when the VS requires intervention, or the hearing in that ear deteriorates to unserviceable levels, cochlear implant of the ear affected by MD prior to addressing the VS provides optimal management.
Prevalence of Stroke in an Urban, Mixed-Income Community in Lagos, Nigeria
Authors: Danesi Mustapha , Okubadejo Njideka , Ojini Frank
Published: September 2007

Background: The burden of cerebrovascular disease in developing countries is projected to be on the rise. However, data on the current epidemiology of stroke in Africa are sparse. Methods: Using a 3-staged method, we conducted a door-to-door study of stroke in an urban, mixed-income community in Lagos, Nigeria. We used a modification of the WHO protocol in the first stage, a stroke-specific questionnaire in the second stage and neurological examination of all persons screening positive for stroke in the third stage. We also examined an equal number of stroke-negative persons. Results: Overall, the crude prevalence rate of stroke in urban Nigeria was 1.14/1,000 (males: 1.51; females: 0.69). The age-adjusted prevalence rates per 1,000 (adjusted to the USA population 2000) in mid-decade strata showed a trend of increasing prevalence with advancing age as follows: 35–44 years = 0.009, 45–54 years = 0.33, 55–64 years = 0.71, 65–74 years = 0.98, 75–84 years = 2.04 and >85 years = 0.74. Conclusions: Stroke prevalence rates in urban Nigeria are lower than those in most developed countries. The lower rates may be related to lower incidence and higher stroke mortality in developing countries.
Clusters of Cognitive and Behavioral Disorders Clearly Distinguish Primary Progressive Aphasia from Frontal Lobe Dementia, and Alzheimer’s Disease
Authors: Marra C. , Quaranta D. , Zinno M. , Misciagna S. , Bizzarro A. , Masullo C. , Daniele A. , Gainotti G.
Published: September 2007

Background/Aims: Frontal lobe dementia (FLD) and primary nonfluent progressive aphasia (PnPA) are two forms of frontotemporal lobe degeneration. The relationship between these conditions remains unclear. Our study aimed to better define the behavioral and cognitive clusters characterizing PnPA patients. Methods: We cognitively and behaviorally evaluated three groups of newly diagnosed patients affected by Alzheimer’s disease (AD, n = 20), FLD (n = 22) and PnPA (n = 10), in order to assess the cognitive-behavioral pattern of PnPA, compared to both FLD and AD. Results: We found, as expected, worse performances in episodic memory in AD, of both the verbal fluency and naming tasks in PnPA, while FLD mainly showed behavioral disorders associated with an unremarkable deficit in the executive tasks. PnPA was not characterized by any significant behavioral disorders. Factor analysis-extracted three main factors (‘mnesic’, ‘behavioral’ and ‘linguistic’) clearly correlated to each group. A discriminant analysis based on the extracted factors correctly classified 84.6% of all patients. Conclusion: The evidence of a characteristics cognitive profile, without any significant behavioral changes, highlights that PnPA is different from other forms of frontotemporal lobe degeneration regarding both the cognitive and behavioral patterns; thus, it should be considered independently in further studies.
Protective Effect of Viscoelastics against Retina Lipid Peroxidation
Authors: Miranda M. , Bosch-Morell F. , Belda J.I. , García-Manzanares M.D. , Barcia J. , Alió J.L. , Romero F.J.
Published: September 2007

Viscoelastics or ophthalmic viscosurgical devices are routinely used during anterior segment surgery and also in posterior segment surgery. Studies of the harmful effects of phacoemulsification on corneal endothelial cells suggest that much of this damage is mediated by free radicals. In this study, we compare the possible effects against lipid peroxidation in the retina of three different viscoelastic substances: Viscoat, Healon and Visiol. Herein we demonstrate for the first time that viscoelastics are effective to protect the retina against lipid peroxidation, as can be seen by the slight increase of malondialdehyde in the homogenates incubated with viscoelastic exposed to light and to a temperature of 37°C when compared with the control homogenates.
Effects of Tear Substitutes on Conjunctival Epithelium of Mice
Authors: Aragona Pasquale , Micali Antonio , Paladino Grazia , Ferreri Felicia , Puzzolo Domenico
Published: September 2007

Aim: The effects of the administration of three tear substitutes on normal conjunctival epithelium of the mouse, with particular regard to goblet cells, were studied. Methods: Three-month-old Swiss CD 1 mice were divided into four groups of 7 animals each. Group 1 was untreated (control). The other animals were treated with the instillation of 5 drops/day for 10 days as follows: group 2, 0.2% sodium hyaluronate (SH); group 3, 0.5% hydroxypropylmethylcellulose (HPMC); group 4, 0.9% NaCl. The entire conjunctiva was processed for light and electron microscopy. A morphometric study was performed to evaluate: the number and size of goblet cells and the number, size and optical density of mucin granules. Furthermore, Alcian blue/periodic acid-Schiff (AB/PAS) staining for goblet cells was carried out. Results: The SH-treated group showed that the area and number of goblet cells were similar to the untreated group; the mucin granules were reduced in number and optical density but increased in size. The HPMC-treated group showed a reduced area of goblet cells with reduced optical density of mucin granules. The saline-treated group showed that goblet cells were reduced in area and number; mucin granules showed a reduction in number and optical density and an increased size. The AB/PAS stain showed that each treatment was able to induce a treatment-specific modification of the staining characteristics of goblet cells. Conclusion: Our results strongly suggest that tear substitutes can induce treatment-specific modifications of the conjunctival epithelium with particular regard to goblet cell structure and ultrastructure.
Multifocal Electroretinogram Responses of the Clinically Normal Retinal Areas in Diabetes
Authors: Kim Sang Jin , Song Su-Jeong , Yu Hyeong Gon
Published: September 2007

Aims: To investigate the degree of implicit time delay in aretinopathic hexagons according to the grading of diabetic retinopathy and factors that affect the mfERG responses of aretinopathic areas. Methods: MfERG was recorded using the RETIscan system (Roland consult, Brandenbrug, Germany) in 40 eyes of 20 nondiabetic controls, 32 eyes of 16 diabetic patients without retinopathy, and 96 eyes of 48 diabetic patients with nonproliferative diabetic retinopathy (NPDR). Hexagons are divided into retinopathic and aretinopathic hexagons, which were selected using fundus photographs and fluorescence angiography. Relative amplitude and implicit time delay were compared between patient groups and controls. Results: The mean implicit time delay in aretinopathic hexagons was significantly different between each subject group and correlated with the retinopathy severity of the whole retina, as well as in retinopathic hexagons. In all three NPDR groups, implicit time was significantly more delayed in retinopathic hexagons compared to aretinopathic hexagons. Relative amplitude was significantly decreased only in the severe NPDR group in both retinopathic and aretinopathic hexagons. The duration of diabetes and glycemic control status did not correlate with the local mfERG responses. Conclusions: Local mfERG showed considerable implicit time delays in clinically normal retinal areas that correlated significantly with the severity of diabetic retinopathy of the whole retina.