bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of Acute and Chronic Treatment with the Sodium Hydrogen Exchanger 1 (NHE‐1) Inhibitor Cariporide on Myocardial Infarct Mass in Rabbits with Hypercholesterolaemia
Authors: Jung Oliver , Albus Udo , Lang Hans‐Jochen , Busch Andreas E. , Linz Wolfgang
Published: July 2004

Abstract: We investigated the cardioprotective effect of acute and chronic sodium hydrogen exchanger 1 (NHE‐1) inhibition with cariporide under pathological conditions in rabbits fed an atherogenic diet (0.25% cholesterol, 3% coconut oil), an experimental model of atherosclerosis. New Zealand White rabbits were fed over 4 weeks with normal diet or with atherogenic diet and randomized in 3 subgroups (n=7 in each group); placebo, acute cariporide (0.3 mg/kg, 10 min. before occlusion of left anterior descending coronary artery and chronic cariporide (4 weeks 0.1% in chow). In the final infarction experiments the animals were subjected to 30 min. of myocardial ischaemia by occlusion of a branch of the left anterior descending coronary artery followed by 2 hr of reperfusion. Infarct mass was evaluated by triphenyl‐tetrazolium chloride staining and the infarct size expressed as a percentage of area at risk. Besides the assessment of aortic endothelium‐dependent function aortic and cardiac vessels were inspected for atherosclerotic lesions. In cholesterol‐fed rabbits, the infarct size was significantly increased when compared with normal diet animals (63±3% versus 41±3%). Acute cariporide treatment reduced the infarct size in normal diet rabbits to 14%±3% (66% decrease, P<0.05) as well as in atherogenic diet rabbits to 22±3% (65% decrease, P<0.05). Chronic treatment with cariporide also reduced the infarct size significantly: normal diet 19±2% (53% decrease, P<0.05), atherogenic diet 32±3% (49% decrease, P<0.05). Total cholesterol serum levels in rabbits with atherogenic diet were significantly higher (15.3±2.7 mmol/l) than those on a standard diet (0.65±0.08 mmol/l). Chronic cariporide treatment significantly attenuated the increase of serum cholesterol (7.9±1.9 mmol/l) and improved the lipoprotein pattern. Although the aortas and heart vessels of hypercholesterolaemic animals were without any histological evidence of atherosclerosis they developed endothelial dysfunction (reduced endothelium‐dependent relaxation by ACh), which was prevented by chronic cariporide treatment. Acute and chronic treatment with the NHE‐1 inhibitor cariporide significantly reduced infarct mass. This effect was associated with improved endothelial function.
Mechanism of spontaneous excitability in human embryonic stem cell derived cardiomyocytes
Authors: Satin Jonathan , Kehat Izhak , Caspi Oren , Huber Irit , Arbel Gil , Itzhaki Ilanit , Magyar Janos , Schroder Elizabeth A. , Perlman Ido , Gepstein Lior
Published: July 2004

Human embryonic stem cell‐derived cardiomyocytes (hES‐CMs) are thought to recapitulate the embryonic development of heart cells. Given the exciting potential of hES‐CMs as replacement tissue in diseased hearts, we investigated the pharmacological sensitivity and ionic current of mid‐stage hES‐CMs (20–35 days post plating). A high‐resolution microelectrode array was used to assess conduction in multicellular preparations of hES‐CMs in spontaneously contracting embryoid bodies (EBs). TTX (10 μm) dramatically slowed conduction velocity from 5.1 to 3.2 cm s−1 while 100 μm TTX caused complete cessation of spontaneous electrical activity in all EBs studied. In contrast, the Ca2+ channel blockers nifedipine or diltiazem (1 μm) had a negligible effect on conduction. These results suggested a prominent Na+ channel current, and therefore we patch‐clamped isolated cells to record Na+ current and action potentials (APs). We found for isolated hES‐CMs a prominent Na+ current (244 ± 42 pA pF−1 at 0 mV; n= 19), and a hyperpolarization‐activated current (HCN), but no inward rectifier K+ current. In cell clusters, 3 μm TTX induced longer AP interpulse intervals and 10 μm TTX caused cessation of spontaneous APs. In contrast nifedipine (Ca2+ channel block) and 2 mm Cs+ (HCN complete block) induced shorter AP interpulse intervals. In single cells, APs stimulated by current pulses had a maximum upstroke velocity (dV/dtmax) of 118 ± 14 V s−1 in control conditions; in contrast, partial block of Na+ current significantly reduced stimulated dV/dtmax (38 ± 15 V s−1). RT‐PCR revealed NaV1.5, CaV1.2, and HCN‐2 expression but we could not detect Kir2.1. We conclude that hES‐CMs at mid‐range development express prominent Na+ current. The absence of background K+ current creates conditions for spontaneous activity that is sensitive to TTX in the same range of partial block of NaV1.5; thus, the NaV1.5 Na+ channel is important for initiating spontaneous excitability in hES‐derived heart cells.
Slow skeletal muscles of the mouse have greater initial efficiency than fast muscles but the same net efficiency
Authors: Barclay C. J. , Weber C. L.
Published: July 2004

The aim of this study was to determine whether the net efficiency of mammalian muscles depends on muscle fibre type. Experiments were performed in vitro (35°C) using bundles of muscle fibres from the slow‐twitch soleus and fast‐twitch extensor digitorum longus (EDL) muscles of the mouse. The contraction protocol consisted of 10 brief contractions, with a cyclic length change in each contraction cycle. Work output and heat production were measured and enthalpy output (work + heat) was used as the index of energy expenditure. Initial efficiency was defined as the ratio of work output to enthalpy output during the first 1 s of activity. Net efficiency was defined as the ratio of the total work produced in all the contractions to the total, suprabasal enthalpy produced in response to the contraction series, i.e. net efficiency incorporates both initial and recovery metabolism. Initial efficiency was greater in soleus (30 ± 1%; n= 6) than EDL (23 ± 1%; n= 6) but there was no difference in net efficiency between the two muscles (12.6 ± 0.7% for soleus and 11.7 ± 0.5% for EDL). Therefore, more recovery heat was produced per unit of initial energy expenditure in soleus than EDL. The calculated efficiency of oxidative phosphorylation was lower in soleus than EDL. The difference in recovery metabolism between soleus and EDL is unlikely to be due to effects of changes in intracellular pH on the enthalpy change associated with PCr hydrolysis. It is suggested that the functionally important specialization of slow‐twitch muscle is its low rate of energy use rather than high efficiency.
A novel physiological mechanism of glycine‐induced immunomodulation: Na+‐coupled amino acid transporter currents in cultured brain macrophages
Authors: Schilling Tom , Eder Claudia
Published: July 2004

Glycine is known to modulate immune cell responses. However, the physiological mechanisms underlying inhibitory effects of glycine on macrophages are not well understood. Here we show that glycine is capable of inducing inward currents in brain macrophages (microglia). In contrast to glycine, the glycine receptor agonist taurine failed to elicit currents. Glycine‐evoked currents of brain macrophages were unaffected by strychnine, Cl−‐free extracellular solution, N‐[3‐(4′‐fluorophenyl)‐3‐(4′‐phenylphenoxy)propyl])sarcosine (NFPS) and amoxapine, but were abolished upon omission of extracellular Na+. Furthermore, glycine caused increases in the intracellular Na+ concentration and pronounced membrane depolarization. Glycine‐evoked depolarization was Na+ dependent and occurred independently of the intracellular Cl− concentration. Similarly to glycine, glutamine and α‐(methylamino)isobutyric acid (MeAIB) elicited inward currents in brain macrophages. In the presence of either glutamine or MeAIB, glycine‐induced currents were inhibited. It is concluded that neither functional glycine receptors nor glycine transporters are expressed in brain macrophages. We suggest that glycine mediates its effects by activation of system A Na+‐coupled neutral amino acid transporters.
Mimicking Surface Plasmons with Structured Surfaces
Authors: Pendry J. B. , Martín-Moreno L. , Garcia-Vidal F. J.
Published: July 2004

Metals such as silver support surface plasmons: electromagnetic surface excitations localized near the surface that originate from the free electrons of the metal. Surface modes are also observed on highly conducting surfaces perforated by holes. We establish a close connection between the two, showing that electromagnetic waves in both materials are governed by an effective permittivity of the same plasma form. The size and spacing of holes can readily be controlled on all relevant length scales, which allows the creation of designer surface plasmons with almost arbitrary dispersion in frequency and in space, opening new vistas in surface plasmon optics.
A Compound from Smoke That Promotes Seed Germination
Authors: Flematti Gavin R. , Ghisalberti Emilio L. , Dixon Kingsley W. , Trengove Robert D.
Published: July 2004

Exposure of seeds to aerosol smoke or crude smoke extracts stimulates the germination of a number of fire-dependent and fire-independent plant species. We now report the identity of a germination-promoting compound present in plant- and cellulose-derived smoke. The structure of this compound, deduced from spectroscopic analysis and confirmed by synthesis, was shown to be that of the butenolide 3-methyl-2
H
-furo[2,3-
c
]pyran-2-one (
1
). Here we show that
1
promotes germination of a number of plant species at a level similar to that observed with plant-derived smoke water.
Latitudinal and vertical distributions of particle-associated dimethylsulfoniopropionate (DMSP) lyase activity in the western North Atlantic Ocean
Authors: Harada Hyakubun , Rouse Mary-Anne , Sunda William , Kiene Ronald P
Published: July 2004

Dimethylsulfoniopropionate (DMSP) lyase enzymes cleave phytoplankton-derived DMSP into dimethylsulfide (DMS) and acrylate. We measured particle-associated (>0.7 µm) DMSP lyase activity (DLA) in diverse waters from the Gulf of Maine to the Sargasso Sea. DLA fell within a relatively narrow range (0.635.4 nmol DMS·L1·min1), with no significant geographic trend. DLA was, however, generally highest near the surface and decreased with depth within the euphotic zone. When normalized to chlorophyll a (Chl a), DLA was significantly higher in oligotrophic surface waters of the Sargasso Sea (DLA:Chl a = 3353 nmol DMS·min1·µg Chl a1) compared with more productive Gulf of Maine waters (DLA:Chl a = 0.57.9 nmol DMS·min1·µg Chl a1). In optically clear waters of the Sargasso Sea, DLA:Chl a was generally highest near the surface and decreased with depth, following a similar trend to that of the photoprotective pigment diadinoxanthin. When ammonium and phosphate were added to oligotrophic water from the Sargasso Sea, Chl a increased exponentially, whereas DLA:Chl a decreased by 83%. Our results suggest that Chl a specific DLA is highest when plankton are exposed to high solar radiation and low nutrients, consistent with the idea that DMSP lyases may be involved in oxidative stress protection.
Possible impacts of zooplankton grazing on dimethylsulfide production in the Antarctic Ocean
Authors: Kasamatsu Nobue , Kawaguchi So , Watanabe Shuichi , Odate Tsuneo , Fukuchi Mitsuo
Published: July 2004

The role of zooplankton grazing on dimethylsulfide (DMS) and dissolved dimethylsulfoniopropionate (DMSPd) production was investigated in the Antarctic Ocean in January and February 2002. Dominant herbivorous macrozooplankton of this region, the Antarctic krill Euphausia superba and the tunicate Salpa thompsoni, were used in shipboard incubation experiments. The concentration of DMSPd + DMS increased in the water during incubation with krill. The production rate was 2.96 ± 2.78 nmol DMSPd + DMS·krill1·h1 (mean ± SD). In addition, the DMSPd + DMS production rate was linearly related to the ingestion rate of krill (r2 = 0.664, p ≤ 0.01). Addition of salps to natural surface water, however, did not change the DMSPd + DMS concentrations. During the experiments, both animals fed on phytoplankton cells. The fecal pellets of krill contained broken phytoplankton cells, whereas those of salps contained unbroken cells. These results suggest that sloppy feeding by krill is a more likely mechanism for producing DMS and DMSPd than the direct ingestion of phytoplankton cells by salps. The decrease of DMS concentrations in the upper 200 m of the water column from January to February may be explained, in part, by changes in the composition of the macrozooplankton community.
Sulphur isotopic composition of aerosols over the western North Atlantic Ocean
Authors: Wadleigh Moire A
Published: July 2004

During spring (1998) and fall (1999) cruises of the Northern Oceans Dimethylsulphide (DMS) Emissions Model programme (NODEM II and III), size-segregated atmospheric aerosol samples were collected above the western North Atlantic Ocean. The soluble portion of the aerosols was analyzed for concentrations of sulphate, sodium, nitrate, and methane sulphonic acid (MSA). Sulphur isotopic compositions were measured on total soluble sulphur. The stable isotope data conform to a mixing model involving contributions from biogenic, anthropogenic, and sea salt sulphur sources. Biogenic sulphur fractions calculated using stable isotopic compositions range from 0.00 to 0.64 of the total sulphate, higher than most previously reported values. %MSA/NSS (non-sea-salt) SO42 ranges from 0 to 94. The data suggest that sulphates of clearly biogenic origin (MSA) are formed in areas where surface-ocean DMS concentrations are high. These sulphates contribute to aerosol mass in particles up to 3 µm in diameter. This seems to occur by condensation onto existing aerosols. Stable isotope data indicate that these existing aerosols can be of either biogenic or anthropogenic origin depending on the size fraction and geographic location. Stable isotope data also reveal other areas where sulphate aerosols of biogenic origin are produced, not associated with MSA.
Carbon monoxide poisoning associated with blasting operations close to underground enclosed spaces. Part 2. Special working procedures to minimize CO migration
Authors: Martel Richard , Trépanier Luc , Lavigne Marc-André , Lévesque Benoît , Sanfaçon Guy , Brousseau Patrick , Auger Pierre
Published: July 2004

Carbon monoxide (CO) produced by blasting operations in civil engineering works in residential environments can migrate fair distances in the surrounding fractured bedrock and underground infrastructures in the blast area and can then infiltrate enclosed spaces. Poisoning of workers and people in general exposed to an emission of CO produced by explosives has occurred many times. Special working procedures must be developed to minimize the risk of poisoning. Three different procedures were tested in the field where the geologic conditions (slate confined with more than 0.5 m of clayey till) were favourable for CO migration. The first procedure tested aimed to minimize CO production and migration by changing the usual explosive type and the sequence of blasting, excavating and embanking the debris, and installing vents in the surrounding rock. This method did not have a significant effect on CO migration. The second method aimed to mitigate the CO produced by excavating the overburden before drilling, placing blast mats, excavating the broken rock after each blast, and changing the sequence of blasting. This procedure was efficient and safe. The third method consisted of pumping the interstitial air in the broken rock with a vacuum truck immediately after each blast. This method was a good alternative but requires monitoring of the exhaust air and was not as efficient and reliable as the excavation method.Key words: carbon monoxide, blasting, poisoning, enclosed spaces, remediation, house.
The influence of temperature on earth pressure cell readings
Authors: Daigle Lyne , Zhao Jack Q
Published: July 2004

Vibrating-wire earth pressure cells are often used to measure soil pressure in fills and embankments or contact pressure between soil and buried structures. Instrumentation companies provide each cell with a formula to calculate pressure based on frequency and temperature readings. This paper presents the calibration work that was carried out on a series of 76 mm diameter cells and four 228 mm diameter cells with temperatures ranging from 10 to +30 °C with and without the effect of applied pressure. Based on this work and additional data from two field sites, it was found that temperature calibration factors given on the calibration sheet specific to each cell largely underestimated the temperature effect. It was also found that the correction factors were dependent not only on temperature, but also on the pressure applied to the cell. The temperature calibration factor, which is given as a linear correction on the calibration datasheet, becomes parabolic as a pressure is applied on the cell. Based on the findings, recommendations are provided for minimizing the temperature effect on pressure cell readings and improving the accuracy of the temperature calibration factor.Key words: earth pressure cells, soil pressure, temperature calibration, instrumentation.
STORAGE CAPACITY OF EXTREMELY DILUTED HOPFIELD MODEL
Authors: AKCAN BURCU , GÜNDÜÇ YİĞİT
Published: July 2004

The storage capacity of the extremely diluted Hopfield Model is studied by using Monte Carlo techniques. In this work, instead of diluting the synapses according to a given distribution, the dilution of the synapses is obtained systematically by retaining only the synapses with dominant contributions. It is observed that by using the prescribed dilution method the critical storage capacity of the system increases with decreasing number of synapses per neuron reaching almost the value obtained from mean-field calculations. It is also shown that the increase of the storage capacity of the diluted system depends on the storage capacity of the fully connected Hopfield Model and the fraction of the diluted synapses.
ENTROPIC LATTICE BOLTZMANN SIMULATION OF THE FLOW PAST SQUARE CYLINDER
Authors: ANSUMALI SANTOSH , CHIKATAMARLA SHYAM SUNDER , FROUZAKIS CHRISTOS EMMANOUIL , BOULOUCHOS KONSTANTINOS
Published: July 2004

Minimal Boltzmann kinetic models, such as lattice Boltzmann, are often used as an alternative to the discretization of the Navier–Stokes equations for hydrodynamic simulations. Recently, it was argued that modeling sub-grid scale phenomena at the kinetic level might provide an efficient tool for large scale simulations. Indeed, a particular variant of this approach, known as the entropic lattice Boltzmann method (ELBM), has shown that an efficient coarse-grained simulation of decaying turbulence is possible using these approaches. The present work investigates the efficiency of the entropic lattice Boltzmann in describing flows of engineering interest. In order to do so, we have chosen the flow past a square cylinder, which is a simple model of such flows. We will show that ELBM can quantitatively capture the variation of vortex shedding frequency as a function of Reynolds number in the low as well as the high Reynolds number regime, without any need for explicit sub-grid scale modeling. This extends the previous studies for this set-up, where experimental behavior ranging from Re ~O(10) to Re ≤1000 was predicted by a single simulation algorithm.1–5
FIELD ALGEBRA, TOPOLOGICAL GAUGE CLASSES AND VACUUM STRUCTURE IN TWO-DIMENSIONAL GAUGE THEORIES WITH FERMIONIC QUARTIC-SELF INTERACTION
Authors: BELVEDERE L. V.
Published: July 2004

We analyze the field algebra, the unitary operators implementing local gauge transformations, the existence of inequivalent gauge classes and the vacuum structure of QED2 generalized to include Thirring-type interactions.
DISCRETE QUANTUM MODES OF THE DIRAC FIELD IN AdSd+1 BACKGROUNDS
Authors: COTĂESCU ION I.
Published: July 2004

It is shown that the free Dirac equation in spherically symmetric static backgrounds of any dimensions can be put in a simple form using a special version of Cartesian gauge in Cartesian coordinates. This is manifestly covariant under the transformations of the isometry group so that the generalized spherical coordinates can be separated in terms of angular spinors like in the flat case, obtaining a pair of radial equations. In this approach the equation of the Dirac free field in AdS d+1 backgrounds is analytically solved obtaining the formula of the energy levels and the corresponding normalized eigenspinors.
QED IN STRONG EXTERNAL FIELD: CALCULATION OF NONLINEAR EFFECTS BY MEANS OF THE PROPER TIME METHOD
Authors: ANDREEV A. A. , LABZOVSKY G. L. , YU. M. PISMAK  , MARKOV V. N.
Published: July 2004

Modern lasers are unable yet to cause electron–positron pair production in vacuum, however it is possible to notice considerable influence of vacuum polarization on radiation that propagates in such medium. In our work we present nonlocal theory of interaction of intensive laser radiation with electron–positron vacuum. We refuse from Heisenberg–Euler approximation and it permits us to calculate nonzero response of vacuum even for a plane wave. We show how to use the "proper time" method for calculation of corrections to the Maxwell equations. These equations are solved for the case of plane wave and their solutions are investigated.
RAPIDITY SPECTRA OF THE PARTICLE-SECONDARIES AND A COMBINATIONAL APPROACH
Authors: DE BHASKAR , BHATTACHARYYA S.
Published: July 2004

We would try, in the present work, to understand the nature of the rapidity spectra of the major categories of the secondaries produced in NN, NA and AB collisions at high energies from the viewpoint of a combinational approach, called chosen combination of models (CCM), proposed very recently by the same authors. Despite several difficulties pertaining to the availability of reliable data and the large ranges of uncertainties of measurements in many cases in the reported data, we have reproduced here the measured behavior of the data-sets with a modest degree of success.
NONLINEAR DYNAMICAL SYSTEM IDENTIFICATION FROM UNCERTAIN AND INDIRECT MEASUREMENTS
Authors: VOSS HENNING U. , TIMMER JENS , KURTHS JÜRGEN
Published: July 2004

We review the problem of estimating parameters and unobserved trajectory components from noisy time series measurements of continuous nonlinear dynamical systems. It is first shown that in parameter estimation techniques that do not take the measurement errors explicitly into account, like regression approaches, noisy measurements can produce inaccurate parameter estimates. Another problem is that for chaotic systems the cost functions that have to be minimized to estimate states and parameters are so complex that common optimization routines may fail. We show that the inclusion of information about the time-continuous nature of the underlying trajectories can improve parameter estimation considerably. Two approaches, which take into account both the errors-in-variables problem and the problem of complex cost functions, are described in detail: shooting approaches and recursive estimation techniques. Both are demonstrated on numerical examples.
BIAS REDUCTION FOR TIME SERIES MODELS BASED ON SUPPORT VECTOR REGRESSION
Authors: HORNSTEIN ALEXANDER , PARLITZ ULRICH
Published: July 2004

In the past few years a new learning method called Support Vector Machines (SVMs) has enjoyed increasing popularity. Based on statistical learning theory it shows very good generalization abilities. Though SVMs are mainly used for classification tasks, they are also applicable to regression problems and thus to modeling the dynamics of a time series. However when regression techniques are used to build dynamical models caution is advisable if the data are noisy. Due to correlations between data points, estimates of model parameters deviate systematically from the true values. An approach is presented to reduce such bias in SVM parameters.
NONPARAMETRIC MODELING AND SPATIOTEMPORAL DYNAMICAL SYSTEMS
Authors: ABEL MARKUS
Published: July 2004

This article describes how to use statistical data analysis to obtain models directly from data. The focus is put on finding nonlinearities within a generalized additive model. These models are found by means of backfitting or more general algorithms, like the alternating conditional expectation value one. The method is illustrated by numerically generated data. As an application, the example of vortex ripple dynamics, a highly complex fluid-granular system, is treated.
NONPARAMETRIC DETECTION OF DEPENDENCES IN STOCHASTIC POINT PROCESSES
Authors: KAISER ANDREAS , SCHREIBER THOMAS
Published: July 2004

A new, parameter-free approach based on information theoretical tools is presented which allows the detection of dependences in the dynamics between two point processes. The crucial point is the definition of sequences of inter-event intervals between the events of two stochastic point processes where these sequences are ordered to only one common time index. This is an enhancement of the concept of event intervals of a single point process and makes the analysis of the process dynamics of more than one point processes possible. An application of this method is also illustrated using a model consisting of two synaptically coupled Hindmarsh–Rose neurons.
OPTIMAL NONLINEAR MODELS FROM EMPIRICAL TIME SERIES: AN APPLICATION TO CLIMATE
Authors: GUTIÉRREZ RAFAEL M.
Published: July 2004

In this work we propose a method that exploits the feedback between empirical and theoretical knowledge of a complex macroscopic system in order to build a nonlinear model. We apply the method to the monthly earth's mean surface temperature time series. The problems of contamination and stationarity are considered noting the importance of observation and modeling scales. We construct a dynamical system of ordinary differential equations where the vector field relating the relevant degrees of freedom and their variations in time is expressed in terms of a polynomial base orthonormal to the measure associated to the time series under study. The optimal size of the model and the values of its parameters are estimated with the principle of minimum description length and the Adams–Molton predictor–corrector method. This procedure is self-consistent because it does not use any external parameter or assumption. We then present a first approach to find the closest chaotic dynamical system corresponding to the earth's mean surface temperature and compare it with scale consistent theoretical or phenomenological models of the lower atmosphere. This comparison allows us to obtain an explicit functional form of the heat capacity of the earth's surface as a function of the earth's mean surface temperature.
NONPARAMETRIC STATISTICAL MODELING OF SPATIOTEMPORAL DYNAMICS BASED ON RECORDED DATA
Authors: MANDELJ SIMON , GRABEC IGOR , GOVEKAR EDVARD
Published: July 2004

Experimental analysis of spatially extended processes is based on measured data of characteristic dynamic variables in space and time. The basic aim of the analysis is to extract a field evolution law from data thus recorded. We present a nonparametric statistical modeling of field evolution, following a state space reconstruction technique. For this purpose a novel state reconstruction is proposed that properly describes chaotic field evolution on short- as well as statistically on long-term basis. From the reconstructed state vectors, deterministic and random parts of field evolution are then approximated by employing a conditional average estimator. The performance of such statistical modeling is demonstrated by predicting simulated stochastic fields, and experimental fields generated by cutting and welding manufacturing processes. The results presented indicate that the proposed method of modeling can be successfully utilized for experimental characterization of different stochastic processes.
MODELING THE NONLINEAR DYNAMICS OF CELLULAR SIGNAL TRANSDUCTION
Authors: TIMMER J. , MÜLLER T. G. , SWAMEYE I. , SANDRA O. , KLINGMÜLLER U.
Published: July 2004

During the past decades the components involved in cellular signal transduction from membrane receptors to gene activation in the nucleus have been studied in detail. Based on the qualitative biochemical knowledge, signalling pathways are drawn as static graphical schemes. However, the dynamics and control of information processing through signalling cascades is not understood. Here we show that based on time resolved measurements it is possible to quantitatively model the nonlinear dynamics of signal transduction. To select an appropriate model we performed parameter estimation by maximum likelihood and statistical testing. We apply this approach to the JAK-STAT signalling pathway that was believed to represent a feed-forward cascade. We show by comparison of different models that this hypothesis is insufficient to explain the experimental data and suggest a new model including a delayed feedback.
MODELING THERMAL DISPLACEMENTS IN MODULAR TOOL SYSTEMS
Authors: WESSEL NIELS , AßMUS JÖRG , SCHWARZ UDO , KURTHS JÜRGEN , WEIDERMANN FRANK , KONVICKA JAN , NESTMANN STEFFEN , NEUGEBAUER RAIMUND
Published: July 2004

There is an important interest in compensating thermally induced errors of modular tool systems to improve the manufacturing accuracy. In this paper, we test the hypothesis whether we can predict such thermal displacements by using a nonlinear regression analysis, namely the alternating conditional expectation algorithm (ACE [Breiman & Friedman, 1985]), reliably. The data analyzed were generated by two different finite element spindle models of modular tool systems. As the main result, we find that the ACE-algorithm is a powerful tool to model the relation between temperatures and displacements. The maximal correlation is larger than 0.999 in both cases, which demonstrates the suitability of the ACE algorithm. Furthermore, preconditions for the applicability of this approach, such as the length and the support of measured data sets, are studied. Hence, this approach seems to be promising for the application to real modular tool systems.
ON THE LIMITS OF SPECTRAL METHODS FOR FREQUENCY ESTIMATION
Authors: ROSSBERG A. G.
Published: July 2004

An algorithm is presented which generates pairs of oscillatory random time series which have identical periodograms but differ in the number of oscillations. This result indicates the intrinsic limitations of spectral methods when it comes to the task of measuring frequencies. Other examples, one from medicine and one from bifurcation theory, are given, which also exhibit these limitations of spectral methods. For two methods of spectral estimation it is verified that the particular way end points are treated, which is specific to each method, is, for long enough time series, not relevant for the main result.
INVARIANT SNAKES AND INITIALIZATION OF DEFORMABLE MODELS
Authors: GIRALDI GILSON A. , OLIVEIRA ANTONIO A. F.
Published: July 2004

Parametric snake models are deformable models very useful for boundary extraction and tracking. Despite their abilities, the non-invariance of the internal energy under affine transformations and the non-convexity of the model energy are known limitations for most of these methods. The former has been addressed in the context of active shape models. The latter can be addressed through Dual contour approaches as well as an automatic procedure to initialize the model closer to the desired boundary. In this paper we first analyze the effects of reparameterization for invariant snake models through the Lie Group Theory. In the second part of this work, we present our Dual-T-Snakes model and a methodology based on the T-Snakes framework to initialize deformable models. In the experimental results we explore and combine these techniques for segmentation of medical images.
AUTOMATIC 3D PROSTATE SURFACE DETECTION FROM TRUS WITH LEVEL SETS
Authors: SHAO FAN , LING KECK VOON , NG WAN SING
Published: July 2004

Prostate boundary detection from ultrasound images plays an important role in prostate disease diagnoses and treatments. However, due to the low contrast, speckle noise and shadowing in ultrasound images, this still remains a difficult task. Currently, prostate boundary detection is performed manually, which is arduous and heavily user dependent. A possible solution is to improve the efficiency by automating the boundary detection process with minimal manual involvement. This paper presents a new approach based on the level set method to automatically detect the prostate surface from 3D transrectal ultrasound images. The user interaction in the initialization procedure is relieved by automatically putting the centroid of the initial zero level sets close to the image center. Region information, instead of the image gradient, is integrated into the level set method to remedy the "boundary leaking" problem caused by gaps or weak boundaries. Moreover, to increase the accuracy and robustness, knowledge-based features, such as expected shape (kidney-like) and ultrasound appearance of the prostate (looking from within the gland, the intensities are transitions from dark to light), are also incorporated into the model. The proposed method is applied to eight 3D TRUS images and the results have shown its effectiveness.
TEXTURE SEGMENTATION BY STATISTICAL DEFORMABLE MODELS
Authors: PUJOL ORIOL , RADEVA PETIA
Published: July 2004

Deformable models have received much popularity due to their ability to include high-level knowledge on the application domain into low-level image processing. Still, most proposed active contour models do not sufficiently profit from the application information and they are too generalized, leading to non-optimal final results of segmentation, tracking or 3D reconstruction processes. In this paper we propose a new deformable model defined in a statistical framework to segment objects of natural scenes. We perform a supervised learning of local appearance of the textured objects and construct a feature space using a set of co-occurrence matrix measures. Linear Discriminant Analysis allows us to obtain an optimal reduced feature space where a mixture model is applied to construct a likelihood map. Instead of using a heuristic potential field, our active model is deformed on a regularized version of the likelihood map in order to segment objects characterized by the same texture pattern. Different tests on synthetic images, natural scene and medical images show the advantages of our statistic deformable model.
PROBABILISTIC BOUNDARY-BASED CONTOUR TRACKING WITH SNAKES IN NATURAL CLUTTERED VIDEO SEQUENCES
Authors: TSECHPENAKIS GABRIEL , TSAPATSOULIS NICOLAS , KOLLIAS STEFANOS
Published: July 2004

Moving object detection and tracking in video sequences is a task that emerges in various research fields of video processing, including video analysis and understanding, object-based coding and many related applications, such as content-based retrieval, remote surveillance and object recognition. This work revisits one of the most popular deformable templates for shape modeling and object tracking, the Snakes, and proposes a modified snake model and a probabilistic utilization of it for object tracking. Special attention has been drawn to complex natural (indoor and outdoor) sequences, where temporal clutter, abrupt motion and external lighting changes are crucial for the accuracy of the results, also focusing on the ability of the proposed approach to handle specific HCI problems, such as face and facial feature tracking. A variety of image sequences are used to illustrate the method's capability, providing theoretical explanation as well as experimental verification in specific tracking problems.
FACE AND FACIAL FEATURE TRACKING USING DEFORMABLE MODELS
Authors: DORNAIKA F. , AHLBERG J.
Published: July 2004

In this paper, we address the 3D tracking of pose and animation of the human face in monocular image sequences using deformable 3D models. The main contributions of this paper are as follows. First, we show how the robustness and stability of the Active Appearance Algorithm can be improved through the inclusion of a simple motion compensation based on feature correspondence. Second, we develop a new method able to adapt a deformable 3D model to a face in the input image. Central to this method is the decoupling of global head movements and local non-rigid deformations/animations. This decoupling is achieved by, first, estimating the global (rigid) motion using robust statistics and a statistical model for face texture, and then, adapting the 3D model to possible local animations using the concept of the Active Appearance Algorithm. This proposed method constitutes a significant step towards reliable model-based face trackers since the strengths of complementary tracking methodologies are combined.

Experiments evaluating the effectiveness of the methods are reported. Adaptation and tracking examples demonstrate the feasibility and robustness of the developed methods.
PHYSICAL MODEL FOR LOW FREQUENCY NOISE IN AVALANCHE BREAKDOWN OF PN JUNCTIONS
Authors: MARINOV O. , JAMAL DEEN M.
Published: July 2004

A physically-based transient model for low frequency noise of both microplasma and impact ionization in PN diodes is discussed and implemented in the SPICE simulator. The simulation indicates that the model correctly describes the non-monotonic behavior of both the DC and the noise characteristics of diode at the onset of avalanche breakdown. The model is based on a new microplasma switching theory, and the results of simulation confirm the findings of this theory. The microplasma switching threshold is the condition of equality of free- to space charge concentration in the depletion layer. The microplasma turn-on is initialized by the charge generation due to few recombination centers in the microplasma region at high avalanche multiplication due to impact ionization. The microplasma on-current is approximately twice the threshold current and the on-current sustains until the low, but larger than 1, avalanche multiplication compensates for the carrier diffusion from microplasma region into the depletion layer. When the multiplication becomes lower than the diffusion, the microplasma switches off.
LOW FREQUENCY NOISE IN SUB-0.1μmSiGepMOSFETs, CHARACTERISATION AND MODELING
Authors: ROMANJEK KRUNOSLAV , GHIBAUDO GÉRARD , ERNST THOMAS , CHROBOCZEK JAN A.
Published: July 2004

Drain current-gate voltage, I d ( V g ) characteristics and the power spectral density, PSD , of I d fluctuations were obtained on SiGe channel pMOSFETs and on their Si homologues, for I d intensities varied from deep sub-threshold to strong inversion values. Devices with 2.2nm thick SiO 2 gates and channel lengths 50 nm <L<10μm were used. In heterostructures, the SiGe layers were 20nm thick and buried under 2nm of Si . The data were simulated, assuming a parallel current flow in the interface and the SiGe channels, with associated noise sources. The transport parameters, extracted from I d ( V g ) characteristics, served for calculating the PSD ( I d ) functions. The latter required adjusting the interface trap density and a parameter α c , accounting for the effect of the interface charge fluctua-tions on the hole mobility fluctuations, significant at high levels of trap filling i.e. high I d . We found that the PSD in the SiGe devices was up to 10 times lower than in the Si controls at sufficiently high I d . The simulation, accounting for the data, required a significant lowering of α c for the SiGe channel. That implies that the LFN reduction in SiGe MOSFETs results from a weaker interaction of the SiGe holes with the interface charges. The sub-0.1μm channel devices show a similar noise lowering, in spite of the hole mobility degradation.
ANALYSIS OF LOW FREQUENCY DRAIN CURRENT NOISE IN AlGaN/GaN HEMTS ON Si SUBSTRATE
Authors: MALBERT NATHALIE , LABAT NATHALIE , CURUTCHET ARNAUD , TOUBOUL ANDRE , GAQUIÈRE CHRISTOPHE , MINKO AUXENS
Published: July 2004

This paper deals with the analysis of the low frequency drain current noise in gallium nitride FET on silicon substrate. The drain current noise is compared for devices with gate length of 1.5μm and 3.5μm. We discuss two types of noise mechanisms both used as a diagnostic tool: generation-recombination noise and 1/f noise. Measurements in saturation regime have revealed a g-r noise mechanism correlated with the activation of discrete traps. The analysis of the normalized drain current spectral density vs. the normalized gate voltage Vgn=(Vg-Vt)/|Vt| has been studied. In particular, we have pointed out that the evolution of the 1/f noise level strongly depends on the evolution of the gate leakage current. On the basis of the 1/f normalized noise, i.e. the αH/N parameter, GaN HEMT on silicon have demonstrated as low LF noise as GaAs based transistors.
Nitric oxide donor induces temporal and dose-dependent reduction of gene expression in human endothelial cells
Authors: Braam Branko , de Roos Remmert , Dijk Adele , Boer Peter , Post Jan Andries , Kemmeren Patrick P. C. W. , Holstege Frank C. P. , Bluysen Hans A. R. , Koomans Hein A.
Published: July 2004

The present study tested the hypothesis that acute increases in nitric oxide (NO) exert substantial influences on gene transcription in endothelial cells (ECs) via guanylyl cyclase (GC). Human umbilical veins ECs (HUVECs) were exposed to 0.1, 1, and 10 mM of sodium nitroprusside (SNP) for 4 h and to 1 mM SNP or 250 μM of ( Z)-1[ N-(2-aminoethyl)- N-(2-ammonioethyl)amino]diazen-1-ium-1,2-diolate (DETA-NONOate) for 2, 4, 8, and 24 h. Also, cells were exposed to DETA-NONOate in the presence and absence of the GC inhibitor 1 H-[1,2,4]oxadiazolo-[4,3- a]quinoxalin-1-one (ODQ; 10 μM) for 4 h. RNA was isolated, reverse transcribed, Cy3 and Cy5 labeled, and analyzed using cDNA microarrays. Increasing doses of SNP predominantly depressed gene expression in HUVECs. Gene function was related to growth, adhesion, and cell structure. DETA-NONOate evoked a wave of expression changes (maximum at 4 h), with a remarkable downregulation of the transcription factors MSX1, RELB, and Egr-1. Both SNP- and DETA-NONOate-induced gene expression had faded after 24 h, despite continued elevation of cGMP in the medium. Coadministration of ODQ decreased many, but not all, of the transcriptional responses to DETA-NONOate. NO pronouncedly depressed EC gene expression, in particular of transcription factors. The observation that many, but not all, transcriptional changes induced by NO could be inhibited by inhibition of GC indicates the presence of GC-independent NO actions on gene expression. Thus EC gene expression responds to NO; however, the transcriptional response fades during prolonged exposure. This could allow the EC to respond to increased shear, without vigorous changes in gene expression.
Opening of mitochondrial KATPchannels enhances cardioprotection through the modulation of mitochondrial matrix volume, calcium accumulation, and respiration
Authors: Rousou Anthony J. , Ericsson Maria , Federman Micheline , Levitsky Sidney , McCully James D.
Published: July 2004

Previously, we have shown that the pharmacological opening of the mitochondrial ATP-sensitive K channels with diazoxide (DZX) enhances the cardioprotection afforded by magnesium-supplemented potassium (K/Mg) cardioplegia. To determine the mechanisms involved in the cardioprotection afforded by K/Mg + DZX cardioplegia, rabbit hearts ( n = 24) were subjected to isolated Langendorff perfusion. Control hearts were perfused for 75 min. Global ischemia (GI) hearts were subjected to 30 min of equilibrium, 30 min of GI, and 15 min of reperfusion. K/Mg and K/Mg + DZX cardioplegia hearts received either K/Mg or K/Mg + DZX for 5 min before GI and reperfusion. Tissue was harvested for mitochondrial isolation and transmission electron microscopy (TEM). Mitochondrial structure, area, matrix volume, free calcium, and oxygen consumption were determined. TEM demonstrated that GI mitochondria were damaged and that K/Mg and K/Mg + DZX preserved mitochondrial structure. TEM and light scattering demonstrated separately that mitochondrial matrix and cristae area and matrix volume were significantly increased after GI and reperfusion with GI > K/Mg + DZX > K/Mg hearts ( P < 0.05 vs. control). Mitochondrial free calcium was significantly increased in GI and K/Mg hearts. K/Mg + DZX significantly decreased mitochondrial free calcium accumulation ( P < 0.05 vs. GI and K/Mg). State 3 oxygen consumption and respiratory control index in malate (complex I substrate)- and succinate (complex II substrate)-energized mitochondria were significantly decreased ( P < 0.05 vs. control) in the GI and K/Mg + DZX groups. These data indicate that the enhanced cardioprotection afforded by K/Mg + DZX cardioplegia occurs through the preservation of mitochondrial structure and the significant decrease in mitochondrial free calcium accumulation and mitochondrial state 3 oxygen consumption.
Adenylyl cyclase type VI corrects cardiac sarcoplasmic reticulum calcium uptake defects in cardiomyopathy
Authors: Tang Tong , Gao Mei Hua , Roth David M. , Guo Tracy , Hammond H. Kirk
Published: July 2004

Calcium malfunction plays a central role in heart failure. Here, we provide evidence that adenylyl cyclase type VI restores sarco(endo)plasmic reticulum 2a (SERCA2a) affinity for calcium and maximum velocity of cardiac calcium uptake by sarcoplasmic reticulum in murine dilated cardiomyopathy. Restoration of normal SERCA2a affinity for calcium is associated not only with decreased phospholamban protein expression but also with increased phospholamban phosphorylation by PKA activation. The ratio of phosphorylated ryanodine receptor 2 (RyR2) to RyR2 protein was increased, but the amount of phosphorylated RyR2 was unaffected. These data provide a possible mechanism by which adenylyl cyclase type VI (in contrast to other signaling elements associated with increased cAMP generation) has a salutary effect in the failing heart.
The impact of aging and habitual physical activity on static respiratory work at rest and during exercise
Authors: Chaunchaiyakul Rungchai , Groeller Herb , Clarke John R. , Taylor Nigel A. S.
Published: July 2004

We investigated the effects of aging on the elastic properties of lung tissue and the chest wall, simultaneously quantifying the contribution of each component to static inspiratory muscle work in resting and exercising adults. We further evaluated the interaction of aging and habitual physical activity on respiratory mechanics. Static lung volumes and elastic properties of the lung and chest wall (pressure-volume relaxation maneuvers) in 29 chronically sedentary and 29 habitually active subjects, grouped by age, were investigated: young (Y, 20–30 years), middle-aged (M, 40–50 years), and older (O, >60 years). Using static pressure-volume data, we computed the elastic work of breathing (joules per liter, J·l−1), including inspiratory muscle work, over resting and exercising tidal volume excursions. Elastic work of the lung (Y = 0.79 ± 0.05; M = 0.47 ± 0.05; O = 0.43 ± 0.05 J·l−1) and chest wall (Y = −0.49 ± 0.06; M = −0.12 ± 0.07; O = 0.04 ± 0.05 J·l−1 ) changed significantly with age ( P < 0.05). With aging, a parallel displacement of the chest wall pressure-volume curve resulted in a shift from energy being stored primarily during expiration to energy storage during inspiration, and driving expiration, both at rest and during exercise. Although deviating significantly from young adults, this did not significantly elevate static inspiratory muscle work but resulted in a redistribution of the tissues on which this work was performed and the phase of the respiratory cycle in which it occurred. Nevertheless, static inspiratory muscle work remained similar across age groups, at rest and during exercise, and habitual physical activity failed to influence these changes.