bluuebunny/crossref_metadata_2025 huggingface dataset:
Assessing population sustainability and response to fishing in terms of aggregation structure for greenlip abalone (Haliotis laevigata) fishery management
Authors: Dowling Natalie A , Hall Stephen J , McGarvey Richard
Published: April 2004

The greenlip abalone (Haliotis laevigata) population in Waterloo Bay, South Australia, has undergone collapse and fishery closure twice since 1978. A rich data set, including survey measures of degree of spatial aggregation, has been gathered over that time and provides a unique opportunity to identify factors accounting for persistence or collapse, an issue that is of significance to abalone fisheries worldwide. Statistical analyses of fishery and survey data were undertaken to infer functional relationships between catch, effort, recruitment, adult density, and extent of aggregation. Catch rates were hyperstable, an observation consistent with the targeting of large aggregations. Statistical analysis of recruitment showed a significant year effect, implying an environmental signal, and suggested that aggregation size impacts fertilization success. Aggregation size grew under closure, suggesting an impact of fishing on this demographic feature. Aggregative behaviour appears to be critical for subpopulation sustainability. Fishery collapse may be triggered by depletion of larger abalone aggregations by heavy fishing, resulting in declines in fertilized egg production. When heavy fishing coincides with unfavourable environmental conditions, recruitment may be insufficient to sustain the subpopulation. If aggregation is similarly critical for other subpopulations, management strategies could be adapted according to the extent of aggregation in each subpopulation.
Using underwater video to directly estimate gear selectivity: the retention probability for walleye (Sander vitreus) in gill nets
Authors: Grant Gerold C , Radomski Paul , Anderson Charles S
Published: April 2004

We developed a new approach for directly quantifying selection parameters for fishing gear using a dual underwater video camera apparatus and employed the method to estimate gill net retention probability for walleye (Sander vitreus). The method allows observation of fish behavior around fishing gear and estimation of the absolute probability of fish encountering, contacting, or being retained by the gear. We demonstrated the applicability of this method by quantifying the probability that walleye were retained in multifilament nylon gill nets after contacting the nets. Walleye with total lengths 2.49 times the perimeter of the mesh were most likely to be retained, and retention probability peaked at 0.60 (95% confidence interval 0.410.90), meaning 40% of walleye that were the ideal size for a given mesh escaped after contacting the net. Our empirically derived retention curve exhibited a steep ascending limb and strong positive skew because of walleye morphology and the tendency for larger walleye to be captured by tangling. Most walleye that avoided capture did not fully enter the mesh or backed out of the mesh after they became temporarily wedged or tangled.
Long-term changes in Baltic herring (Clupea harengus membras) growth in the Gulf of Finland
Authors: Rönkkönen Sanna , Ojaveer Evald , Raid Tiit , Viitasalo Markku
Published: April 2004

We used the longest available weight-at-age (WAA) time series (from 1950 to 1999) for Baltic herring (Clupea harengus membras L.) in the Gulf of Finland to investigate which environmental factors affect Baltic herring growth. The relationships among WAAs, annual weight increments, and growth rates for different herring year classes, water salinity, temperature, zooplankton abundance, and biomass, as well as stock sizes of herring, sprat, and cod, were evaluated. Our results showed that in the Gulf of Finland, herring weight and growth rate correlated positively with salinity, and WAA correlated positively with the abundance of the marine zooplankton species Pseudocalanus minutus elongatus. A density-dependent mechanism was not likely to explain the changes in herring WAA in the Gulf of Finland, because no significant correlation between herring WAAs and herring abundance could be found. Instead, the zooplankton community structure changed during the research period, which supports the theory of bottom-up controlling mechanism. A strong negative correlation between herring weight and sprat biomass may indicate competition for food between these species.
Temperature and hunger mediate sablefish (Anoplopoma fimbria) feeding motivation: implications for stock assessment
Authors: Stoner Allan W , Sturm Erick A
Published: April 2004

Laboratory experiments were conducted to test the hypothesis that temperature (28 °C) and recent feeding history (16 days of food deprivation) influence feeding motivation and attacks on baits by adult sablefish (Anoplo poma fimbria). Activity level after introduction of a bait-related olfactory cue increased with increasing water temperature and food deprivation. Fish at the lowest temperature (2 °C) attacked and consumed fewer squid baits (3371%) than those at higher temperatures (100% at 8 °C). Baits were frequently inspected or handled multiple times before consumption in low temperatures, and time to attack (seconds to >40 min), time to consume, and time to handle baits (220 s) all decreased significantly with increasing temperature, with some temperature × feeding history interactions. The total ration consumed increased (<18% of body weight) with increasing water temperature. The observed variability in activity and feeding motivation in sablefish may have a large impact on the effective area of baited gear but is rarely considered in stock assessment models. In particular, population sizes based upon baited gear surveys may be underestimated in conditions where temperature is low, natural prey density is high, or where other environmental variables reduce feeding motivation.
EXPLORATION OF SPATIAL-TEMPORAL DYNAMIC PHENOMENA IN A 32×32-CELL STORED PROGRAM TWO-LAYER CNN UNIVERSAL MACHINE CHIP PROTOTYPE
Authors: PETRÁS ISTVÁN , REKECZKY CSABA , ROSKA TAMÁS , CARMONA RICARDO , JIMÉNEZ-GARRIDO FRANCISCO , RODRÍGUEZ-VÁZQUEZ ANGEL
Published: April 2004

This paper describes a full-custom mixed-signal chip that embeds digitally programmable analog parallel processing and distributed image memory on a common silicon substrate. The chip was designed and fabricated in a standard 0.5 μm CMOS technology and contains approximately 500 000 transistors. It consists of 1024 processing units arranged into a 32×32 grid. Each processing element contains two coupled CNN cores, thus, constituting two parallel layers of 32×32 nodes. The functional features of the chip are in accordance with the 2nd Order Complex Cell CNN-UM architecture. It is composed of two CNN layers with programmable inter- and intra-layer connections between cells. Other features are: cellular, spatial-invariant array architecture; randomly selectable memory of instructions; random storage and retrieval of intermediate images. The chip is capable of completing algorithmic image processing tasks controlled by the user-selected stored instructions. The internal analog circuitry is designed to operate with 7-bits equivalent accuracy. The physical implementation of a CNN containing second order cells allows real-time experiments of complex dynamics and active wave phenomena. Such well-known phenomena from the reaction–diffusion equations are traveling waves, autowaves, and spiral-waves. All of these active waves are demonstrated on-chip. Moreover this chip was specifically designed to be suitable for the computation of biologically inspired retina models. These computational experiments have been carried out in a developmental environment designed for testing and programming the analogic (analog-and-logic) programmable array processors.
FLEXIBLY PROGRAMMABLE OPTO-ELECTRONIC ANALOGIC CNN COMPUTER (POAC) IMPLEMENTATION APPLYING AN EFFICIENT, UNCONVENTIONAL OPTICAL CORRELATOR ARCHITECTURE
Authors: TŐKÉS SZABOLCS , ORZÓ LÁSZLÓ , AYOUB AHMED , ROSKA TAMÁS
Published: April 2004

To overcome shortcomings of the currently available optical computer architectures a programmable opto-electronic CNN array computer (POAC) is introduced. It combines the optical correlators' supreme resolution and complexity with the versatility of the single chip adaptive visual CNN-UM sensor and processor arrays. The system is grounded on an unconventional optical correlator architecture, which is a modified joint Fourier transform correlator. This architecture uses the angular coding of the template pixels and applies the template not in the recording phase, but in the reconstruction phase of correlation. Feasibility of this concept has been successfully demonstrated by a breadboard model. It computes correlation in two consecutive steps: First a hologram of the input image is recorded in a dynamic holographic material (we used chemically-modified Bacteriorhodopsin film samples). Next, angularly-coded read-out beams reconstruct the appropriately weighted and shifted replicas of the stored input image. Superposition of these copies produces the correlogram. A programmable adaptive sensor array, a special Visual CNN-UM chip detects the resulting correlogram. So, both the sensing and the required post-processing steps are accomplished in a parallel way. The introduced opto-electronic architecture provides exceptional synergy and good compromise of the applicable technologies and the system performance.
ENHANCED EMULATED DIGITAL CNN-UM (CASTLE) ARITHMETIC CORES
Authors: HIDVÉGI TIMÓT , KERESZTES PÉTER , SZOLGAY PÉTER
Published: April 2004

An emulated digital CNN-UM (CASTLE) architecture was published few years ago.1 Different emulated digital CNN-UM architectures are analyzed in the paper. These new modified architectures are optimized according to the silicon area, operating speed or dissipated power. A reconfigurable arithmetic core will also be shown in the paper, by which solution of the neighborhood size can be changed. An advanced CASTLE with pipe-lining is presented. The operation frequency is increased by using this solution in approximately 10 times.
A BIO-INSPIRED VISUAL FEEDBACK LOCOMOTION CONTROL BASED ON CNN UNIVERSAL MACHINE
Authors: ARENA P. , BASILE A. , BUCOLO M. , FORTUNA L. , VIRZÍ A.
Published: April 2004

In this paper a new framework for bio-inspired robot locomotion control, entirely based on Cellular Neural Networks (CNNs), is introduced. In fact, CNNs are employed both for generating locomotion patterns in a hexapod robot, and for its trajectory control via visual feedback. In the paper the latter problem will be emphasized, being the CNN locomotion generation problem already treated in literature. Feedback signals are images captured by a camera and processed in real time by a CNN used as analog image processor. The actual framework makes use of a traditional PC where a tool for the synchronization of the visual CNN chip and the robot control has been designed. This paper describes the methodology as an important stage for the study, definition and optimization of the overall control methodology. The results obtained reveal true real time capabilities and the PC interface can be easily substituted with a processing board to be integrated with the visual CNN and with the locomotion-devoted CNN, in order to constitute a unified integrated system for real time visual motion control in complex structures.
SPATIO-TEMPORAL DYNAMICS OF BRAIN ELECTRICAL ACTIVITY IN EPILEPSY: ANALYSIS WITH CELLULAR NEURAL NETWORKS (CNNs)
Authors: KUNZ R. , TETZLAFF R.
Published: April 2004

In this contribution a new procedure is proposed for the analysis of the spatio-temporal dynamics of brain electrical activity in epilepsy. Recent investigations1–3 have clarified that changes of estimates of the effective correlation dimension D2(k,m) from successive data segments allow a characterization of the epileptogenic process. These results provide important information for diagnostical purposes and enable a prediction of seizures in many cases. It will be shown that an accurate approximation of [Formula: see text] can be obtained by Cellular Neural Networks (CNNs),4,5 which form a unified paradigm. Moreover, the type of CNN presented here is optimized with respect to future implementations as VLSI realizations.6
SUDDEN GLOBAL SPATIAL-TEMPORAL CHANGE DETECTION AND ITS APPLICATIONS
Authors: BÁLYA DAVID
Published: April 2004

We are watching the news on TV: the change of the background tells us when a new story begins. A glance at the clock and we can clearly see what time it is. These are special spatial-temporal episodes caused by ballistic eye movements and sudden optical changes. In this paper we give a useful definition for generalized sudden global change events, present its main properties and give an algorithm to recognize them in any video-flow. The proposed algorithm is implemented on a standard Cellular Nonlinear Network Universal Machine (CNN-UM). The processing time of the detection is roughly one millisecond on the ACE4k CNN-UM chip in the Aladdin environment. Therefore it can serve as a common function in any online, real-time spatial-temporal algorithm. The sudden global change event can be used to define the instant when the time-dependent part of that algorithm, e.g., homotopy, has to be initialized. The first steps of the multimedia processing, such as searching for key frames — for compression, browsing or indexing — can be helped by the proposed algorithm as a robust video shot change detection method.
A FEM-BASED QUASI-STATIC NEURO-MODEL FOR ACOUSTIC NOISE IN SWITCH RELUCTANCE MOTORS
Authors: LUCAS C. , SHAHMIRZADI D. , BAHRAMI M. NIKKHAH , GHAFOORIFARD H.
Published: April 2004

Elimination of stator oscillations in electromotors is among the least studied, but important problems that can influence the electric performance, mechanical wear and tear and acoustical noise. In this paper, we focus on a switch reluctance motor (SRM) designed and prototyped for eventual production in Iran. The stator oscillation problems due to radial forces in SRMs have been reported as more acute as compared to similar motors. Due to the complicated mechanical and electrical structure of SRMs, obtaining any analytical model for its acoustical noise is quite impossible. This necessitates using numerical and experimental methods for obtaining an approximating model for acoustical noise. Since, off line simulation can be carried out, finite element (FE) analysis can be utilized so as to generate enough data for identifying a valid model. In this paper, we introduce a neuro-model with excitation current (amp) and position of stator (degree) as inputs and acoustical noise (db) as output. We performed two subsequent FE analysis using ANSYS package. Our first magnetic analysis is aimed at getting magnetic forces on the body of the stator and rotor, by exerting excitation current. In the second acoustical analysis, we give the magnetic forces, resulting from previous corresponding analysis, to the model and get the acoustical noise. We consider the acoustical behavior of the motor, in its inside and outside spaces, separately. Our approach is quasi-static, since we performed some FEM static analyses for approximating the dynamic behavior of the motor. Some simulation results of a acoustic noise in a designed SR motor, using our proposed model, is also given.
ON SOME APPROXIMATIONS FOR NONSTATIONARY PROBLEM OF THE ACOUSTICAL PULSE SCATTERING BY A RANDOM MEDIUM
Authors: GULIN OLEG E. , YAROSHCHUK IGOR O.
Published: April 2004

Statistical boundary value problem of a scattering of sound pulses incident on the randomly fluctuating layered medium is considered on the basis of an exact wave formulation in the spatial-time domain. To solve this problem we developed an analytical-numerical approach in earlier papers, and results of a statistical simulation were presented both for various durations of the incident pulses and for various thickness of a random medium layer. Analysis for the statistical moments, correlation functions and power spectral densities of the backscattered wave field has been carried out. Comparison with the results of this problem approximate asymptotical analysis, previously carried out by the other authors, finds out the number of differences. In this paper we examine both the results of an exact statistical simulation and the approximate analytical ones and propose, as a generalization, some quite simple approximations to describe statistical moments of the backscattered field in the region of nonstationarity. Studying the problem considered is of a fundamental interest for theoretical acoustics as well as its outcomes can be applied to interpret the data on the ocean water and bottom sediments probing with the time pulse.
VALIDITY OF ONE-WAY MODELS IN THE WEAK RANGE DEPENDENCE LIMIT
Authors: ZHU JIANXIN , LU YA YAN
Published: April 2004

Numerical solutions of the Helmholtz equation and the one-way Helmholtz equation are compared in the weak range dependence limit, where the overall range distance is increased while the range dependence is weakened. It is observed that the difference between the solutions of these two equations persists in this limit. The one-way Helmholtz equation involves a square root operator and it can be further approximated by various one-way models used in underwater acoustics. An operator marching method based on the Dirichlet-to-Neumann map and a local orthogonal transform is used to solve the Helmholtz equation.
ASYMPTOTIC BEHAVIOR OF SOLUTIONS OF THE HELMHOLTZ EQUATION CONCENTRATED NEAR THE AXIS OF A DEEP-WATER WAVEGUIDE IN A RANGE-INDEPENDENT MEDIUM
Authors: GRIGORIEVA NATALIE S. , FRIDMAN GREGORY M.
Published: April 2004

To derive the integral representation for the axial wave describing the interference of near-axial waves in an arbitrary deep-water waveguide in a range-independent medium in long-range acoustic propagation in the ocean, it is necessary to construct the solutions of the homogeneous Helmholtz equation concentrated near the waveguide axis in a narrow strip having a width of order ω-1/2, where ω is a cyclic frequency. In a range-independent (separable) case the desired solutions coincide with the principal term of the uniform asymptotic expansion as ω→∞ of normal modes when a mode number is a value of order of unity. In this paper, the solutions of the homogeneous Helmholtz equation concentrated near the waveguide axis in a range-independent ocean and which decrease exponentially outside a strip containing the axis are constructed in the form admitting generalization to the case of a range-dependent medium. The solutions are represented as the product of exponentials and parabolic cylinder functions whose arguments are infinite series in powers of ω-1/2. Coefficients of these series are found from a recurrent system of partial differential equations up to terms allowing to get a residual (difference between the left-hand side of the Helmholtz equation and zero) of order ω-1/2. Numerical results are obtained for medium parameters corresponding to the Munk canonical sound-speed profile.
A LOCAL ORTHOGONAL TRANSFORM FOR ACOUSTIC WAVEGUIDES WITH AN INTERNAL INTERFACE
Authors: LU YA YAN , ZHU JIANXIN
Published: April 2004

A numerical method is developed for solving the two-dimensional Helmholtz equation in a two layer region bounded by a flat top, a flat bottom and a curved interface. A local orthogonal transform is used to flatten the curved interface of the waveguide. The one-way reformulation based on the Dirichlet-to-Neumann (DtN) map is then used to reduce the boundary value problem to an initial value problem. Numerical implementation of the resulting operator Riccati equation uses a large range step method for discretizing the range variable and a truncated local eigenfunction expansion for approximating the operators. This method is particularly useful for solving long range wave propagation problems in slowly varying waveguides.
SIMULATION OF WAVES IN PORO-VISCOELASTIC ROCKS SATURATED BY IMMISCIBLE FLUIDS: NUMERICAL EVIDENCE OF A SECOND SLOW WAVE
Authors: SANTOS JUAN ENRIQUE , RAVAZZOLI CLAUDIA LEONOR , GAUZELLINO PATRICIA MERCEDES , CARCIONE JOSE M. , CAVALLINI FABIO
Published: April 2004

We present an iterative algorithm formulated in the space-frequency domain to simulate the propagation of waves in a bounded poro-viscoelastic rock saturated by a two-phase fluid. The Biot-type model takes into account capillary forces and viscous and mass coupling coefficients between the fluid phases under variable saturation and pore fluid pressure conditions. The model predicts the existence of three compressional waves or Type-I, Type-II and Type-III waves and one shear or S-wave. The Type-III mode is a new mode not present in the classical Biot theory for single-phase fluids. Our differential and numerical models are stated in the space-frequency domain instead of the classical integrodifferential formulation in the space-time domain. For each temporal frequency, this formulation leads to a Helmholtz-type boundary value problem which is then solved independently of the other frequency problems, and the time-domain solution is obtained by an approximate inverse Fourier transform. The numerical procedure, which is first-order correct in the spatial discretization, is an iterative nonoverlapping domain decomposition method that employs an absorbing boundary condition in order to minimize spurious reflections from the artificial boundaries. The numerical experiments showing the propagation of waves in a sample of Nivelsteiner sandstone indicate that under certain conditions the Type-III wave can be observed at ultrasonic frequencies.
Preemptive Strategies for the Assessment and Management of Financial System Risk Levels: An Application to Japan with Implications for Emerging Economies
Authors: Barnhill Theodore M. , Papapanagiotou Panagiotis , Souto Marcos Rietti
Published: April 2004

We estimate the current potential default cost of the large amount of bad loans in the Japanese banking system to fail to range from 30 trillion yen to 45 trillion yen or higher. For many banks this would deplete at least 50% of their capital. However, it would also fix the loss and avoid potentially larger losses if weak credits continue to be supported. Using a simulation methodology, we also find that the assumed level of credit risk, equity investment, bank operating expenses, bank net interest margin, and the assumed future financial environments interact to determine future bank risk levels. If the negative financial and real estate market conditions of the recent past persist over the next three years, it is very likely that the major Japanese banks will suffer further large losses and exhaust their already low levels of capital. Alternatively, a return to a more positive economic and financial environment would moderate the risks and the cost of resolving the current problems. Nevertheless, under both scenarios, the risk of further bank failures appears to be substantial and additional large capital infusions will likely be needed to avoid losses by depositors. The implications of this analysis for emerging economies, center on the management and regulation of financial institutions in countries where financial market regulatory structures are in a state of change and asset price bubbles also occur.
Crisis, Contagion, and East Asian Stock Markets
Authors: Yang Tracy , Lim Jamus Jerome
Published: April 2004

Following the 1997 financial crisis in East Asia, the issue of contagion has resurfaced. Contagion has most often been associated with high frequency events; hence, it has been measured on stock market returns, interest rates, the exchange rate, or linear combinations of them. This paper tests for evidence of contagion between selected East Asian stock markets, thereby exploring the importance of the linkages between stock markets as a transmission channel during the crisis.
STABILITY ANALYSIS OF NONLINEAR INTERCONNECTED SYSTEMS VIA T–S FUZZY MODELS
Authors: CHIANG WEI-LING , CHEN CHENG-WU , HSIAO FENG-HSIAG
Published: April 2004

This paper is concerned with the stability problem of nonlinear interconnected systems. Each of them consists of a few interconnected subsystems which are approximated by Takagi–Sugeno (T–S) type fuzzy models. In terms of Lyapunov's direct method, a stability criterion is derived to guarantee the asymptotic stability of interconnected systems. It is shown that the stability analysis problems of nonlinear interconnected systems can be reduced to linear matrix inequality (LMI) problems via suitable Lyapunov functions and T–S fuzzy techniques. Finally, numerical examples with simulations are given to demonstrate the validity of the proposed approach.
COMPARISON OF SYSTEMS BASED ON EVOLUTIONARY SEARCH AND SIMULATED ANNEALING TO SOLVE THE VRPTW PROBLEM
Authors: ARBELAITZ OLATZ , RODRIGUEZ CLEMENTE
Published: April 2004

This paper presents the design and analysis of several systems to solve Vehicle Routing Problems with Time Windows (VRPTW) limiting the search to a small number of solutions explored. All of them combine a metaheuristic technique with a route building heuristic. Simulated Annealing, different evolutionary approaches and hybrid methods have been tried. Preliminary results for each of the strategies are presented in the paper, where the combination created by some iterations of the best evolutionary approach and some iterations of SA stands out. A more exhaustive analysis of the three methods behaving better is also presented confirming the previous results. The different strategies have been implemented and tested on a series of the well-known Solomon's benchmark problems of size up to 100 customers. One of the described systems combined with a local optimization part that tries to optimize parts of a solution is being used as part of a real oil distribution system, obtaining very satisfactory results for the company.
Induction of colitis in cftr−/− mice results in bile duct injury
Authors: Blanco Paola G. , Zaman Munir M. , Junaidi Omer , Sheth Sunil , Yantiss Rhonda K. , Nasser Imad A. , Freedman Steven D.
Published: April 2004

It is unknown why some patients with inflammatory bowel disease develop primary sclerosing cholangitis. We have recently shown that patients with primary sclerosing cholangitis have an increased prevalence of mutations in the gene responsible for cystic fibrosis (CFTR) compared with individuals with inflammatory bowel disease alone. Our aim was to examine whether induction of colitis by oral dextran leads to bile duct injury in mice heterozygous or homozygous for mutations in CFTR. The effect of oral administration of docosahexaenoic acid to correct a fatty acid imbalance associated with cystic fibrosis was also examined to determine whether this would prevent bile duct inflammation. Wild-type mice and mice heterozygous and homozygous for CFTR mutations were given dextran orally for 14 days to induce colitis. Bile duct injury was quantitated by blinded histological scoring and measurement of serum alkaline phosphatase activity. The effect of pretreatment with docosahexaenoic acid for 7 days was examined. Treatment of mice with 100 mg dextran/day for 9 days followed by 85 mg/day for 5 days resulted in a significant increase in bile duct injury as determined by histological scoring in homozygous cystic fibrosis mice compared with wild-type mice ( P = 0.005). The bile duct injury seen in cystic fibrosis mice was reflected in a threefold increase in serum alkaline phosphatase ( P = 0.0006). Pretreatment with oral docosahexaenoic acid decreased both histological evidence of bile duct injury and serum alkaline phosphatase levels. In the setting of colitis, loss of CFTR function leads to bile duct injury.
Interaural Level Difference Processing in the Lateral Superior Olive and the Inferior Colliculus
Authors: Park Thomas J. , Klug Achim , Holinstat Michael , Grothe Benedikt
Published: April 2004

Interaural level differences (ILDs) provide salient cues for localizing high-frequency sounds in space, and populations of neurons that are sensitive to ILDs are found at almost every synaptic level from brain stem to cortex. These cells are predominantly excited by stimulation of one ear and predominantly inhibited by stimulation of the other ear, such that the magnitude of their response is determined in large part by the intensities at the 2 ears. However, in many cases ILD sensitivity is also influenced by overall intensity, which challenges the idea of unambiguous ILD coding. We investigated whether ambiguity is reduced from one synaptic level to another for 2 centers in the so-called ILD processing pathway. We recorded from single cells in the free-tailed bat lateral superior olive (LSO), the first station where ILDs are coded, and the central nucleus of the inferior colliculus (ICC), which receives a strong projection from the LSO, as well as convergent projections from many other auditory centers. We assessed effects of overall intensity by comparing ILD functions generated with different fixed intensities to the excitatory ear. LSO cells were characterized by functions that shifted in a systematic manner with increasing intensity to the excitatory ear. In contrast, significantly more ICC cells had functions that were stable across overall sound intensity, indicating that hierarchical transformations increase stability. Furthermore, a population analysis based on proportion of active cells indicated that stability in the ICC was greatly enhanced when overall population activity was considered.
Auditory Thalamus Bursts in Anesthetized and Non-Anesthetized States: Contribution to Functional Properties
Authors: Massaux A. , Dutrieux G. , Cotillon-Williams N. , Manunta Y. , Edeline J.-M.
Published: April 2004

Over the last 10 years, high-frequency bursts of action potentials have been the subject of intense researches to understand their potential role in information encoding. Based on recordings from auditory thalamus neurons ( n = 302) collected during anesthesia (pentobarbital, urethan, or ketamine/xylazine), waking (W), and slow-wave sleep (SWS), we investigated how bursts participate to frequency tuning, intensity-function, response latency (and latency variability), and stimulus detectability. Although present in all experimental conditions, bursts never dominated the cells mode of discharge: the highest proportion was found during ketamine/xylazine anesthesia (22%), the lowest during waking (4.5%). In all experimental conditions, bursts preferentially occurred at or around the cells best frequency (BF), thus increasing the frequency selectivity. This effect was observed at both the intensities producing the highest and the lowest evoked responses. Testing the intensity-functions indicated that for most of the cells, there was no systematic relationship between burst proportion and responses strength. Under several conditions (W, SWS, and urethan), when cells exhibited bursts >20%, the variability of their response latency was reduced in burst mode compared with single-spike mode. During W, this effect was accompanied by a reduction of the response latency. Finally, a receiver operating characteristic analysis indicated no particular relation between bursts and stimulus detectability. Compared with single-spike mode, which is present for broader frequency ranges, the prominence of bursts at the BF should contribute to filter information reaching the targets of medial geniculate cells at both cortical and subcortical levels.
Influence of low frequency electric fields on anti- and pro-coagulability of the vascular endothelium: new insights into high-voltage electrical injury
Authors: Pallua Norbert , Lichtenegger Franziska , Hafemann Bernd , Silny Jiri , Ulrich Dietmar
Published: April 2004

After high-voltage electric injury, patients often show tissue necrosis and thrombosis of blood vessels even remote from entry and exit site of electrical current. In this study, plasma levels of TAT, F1+2, PAI-1, and t-PA were determined in vivo in three patients with high-voltage injury for 96 hours after trauma. In order to analyse a possible effect on haemostasis related to endothelial cell damage, protein S, TF, ET-1, PGI2, NO, t-PA, and PAI-1 were determined for 72 hours in vitro in cell culture supernatant of HUVECs that had been exposed to 1, 10, 30, and 50 electric field periods of 50 Hz with field strength of 60 V/cm and duration of 20 ms. Furthermore, expression of thrombomodulin was immunohistochemically analysed. Clotting activation could be observed in our patients by increased levels of F1+2 and TAT between 12 and 72 hours after injury, whereas fibrinolysis was disturbed due to high PAI-1. One patient presented thrombosis of vessels by day 3. In vitro, PAI-1 increased significantly (p<0.05) in medium of cells with an application of 30 and 50 periods between 2 and 48 hours. Between 4 and 72 hours, the concentration of t-PA was significantly lower (p<0.05) in the medium of HUVECs exposed to 10, 30, and 50 periods, whereas there was a significant increase (p<0.05) in the concentration of TF in the cell groups with an application of 30 and 50 periods. 24, 48, and 72 hours after injury, there was just weak or no staining for thrombomodulin in HUVECs with an application of 30 and 50 periods. The disturbed balance between clotting system and fibrinolysis seen in vitro after electric injury might explain the clinical observation of a progressive thrombosis of blood vessels after electric injury leading to tissue loss.
Effect of recombinant factor VIIa on melagatran-induced inhibition of thrombin generation and platelet activation in healthy volunteers
Authors: Levi Marcel , Sarich Troy , Boström Stig , Eriksson Ulf , Eriksson-Lepkowska Maria , Svensson Mia , Weitz Jeffrey , Elg Margareta , Wåhlander Karin , Wolzt Michael
Published: April 2004

The objectives were to investigate whether activation of the extrinsic coagulation cascade by recombinant factor VIIa (rFVIIa) reverses the inhibition of thrombin generation and platelet activation by melagatran, the active form of the oral direct thrombin inhibitor ximelagatran. In a single-blind, randomized, parallel-group study, volunteers (20 per group) received a 5-hour intravenous (iv) infusion to achieve steadystate melagatran plasma concentrations of approximately 0.5 µmol/L, with a single iv bolus of rFVIIa (90 µg/kg) or placebo at 60 minutes. Prothrombin fragment 1+2, thrombin-antithrombin complex, fibrinopeptide A, β-thromboglobulin, and thrombin-activatable fibrinolysis inhibitor were quantified for venous and shed blood. Activated partial thromboplastin time (APTT), prothrombin time (PT), endogenous thrombin potential, thrombus precursor protein (TpP), and plasmin-α2-antiplasmin complex concentrations were determined in venous blood. Shed blood volume was measured. Melagatran reduced markers of thrombin generation and platelet activation in shed blood and prolonged APTT. rFVIIa increased FVIIa activity, PT, and TpP in venous blood. All other parameters were unaffected. In conclusion, rFVIIa did not reverse the anticoagulant effects of high constant concentrations of melagatran. However, the potential value of higher, continuous or repeated doses of rFVIIa or its use with lower melagatran concentrations has not been excluded.
Strong correlation between the prevalence of cerebral infarction and the presence of anti-cardiolipin/β2-glycoprotein I and anti-phosphatidylserine/prothrombin antibodies
Authors: Kuratsune Hirohiko , Suehisa Etsuji , Kitani Teruo , Iwatani Yoshinori , Kanakura Yuzuru , Nojima Junzo
Published: April 2004

Cerebral infarction is the most common arterial thromboembolic complication in the anti-phospholipid antibodies (aPL) syndrome. In an effort to clarify the roles of aPL in the pathogenesis of cerebral infarction in patients with SLE, we examined the levels of anti-cardiolipin/β2-glycoprotein I antibodies (antiCL/β2-GPI) and anti-phosphatidylserine/prothrombin antibodies (anti-PS/PT) in addition to lupus anticoagulant (LA) activity in 126 patients with SLE (35 with cerebral infarction and 91 without thrombosis). Both anti-CL/β2-GPI and antiPS/PT strongly correlated with the presence of LA activity. The prevalence of cerebral infarction was obviously higher in the patients who had both anti-CL/β2-GPI and anti-PS/PT (76.5% [26/34 cases], p<0.0001) than in the other patients having antiCL/β2-GPI or anti-PS/PT alone or neither of them (9.8% [9/92 cases]). Furthermore, we studied the in vitro effects of antiCL/β2-GPI and/or anti-PS/PT on the enhancement of platelet activation induced by stimulation with a low concentration of adenosine diphosphate (ADP). The purified IgG containing both anti-CL/β2-GPI and anti-PS/PT caused significant enhancement of platelet activation caused by ADP. However, the purified IgG containing either anti-CL/β2-GPI or anti-PS/PT had no enhancing effects on it. Furthermore, platelet activation was generated by the mixture of anti-CL/β2-GPI-IgG and anti-PS/PT-IgG prepared from individual patients, but not by each fraction alone. These results indicate that anti-CL/β2-GPI and antiPS/PT may cooperate to promote platelet activation, which may contribute to the risk of cerebral infarction in patients with SLE.
Interaction of platelets with liposomes containing dodecapeptide sequence from fibrinogen
Authors: Toma Chikaho , Nishiya Takako
Published: April 2004

Liposomes with a covalently bound synthetic peptide containing the dodecapeptide sequence HHLGGAKQAGDV, the putative platelet interaction site at γ400-411 of fibrinogen (dodecapeptide-liposomes), were prepared. These liposomes enhanced platelet aggregation and specifically adhered to platelets activated on the collagen surface. Dodecapeptide-liposomes released encapsulated materials upon interacting with platelets activated on the collagen surface.The rate of content release was dependent on the peptide surface density, indicating that the interaction between the dodecapeptide-liposomes and platelets activated on the collagen surface induces clustering of the surfacecoupled ligands at the binding site on the receptor matrix to facilitate release of the internal contents through the liposome membranes. The level of lipid mixing between the dodecapeptide-liposomes and platelets activated on the collagen surface was relatively low, however it was increased in liposome preparations containing octa-arginine, the (R)8GDV sequence, while content release was maintained at the same level as that of the dodecapeptide-liposomes. The level of content release and lipid mixing for liposome preparations containing the RGD sequence as a ligand (RGD-liposomes) upon interacting with platelets activated on the collagen surface was extremely low. Both the level of the content release and lipid mixing, however, were enhanced in liposome preparations containing octa-arginine, the (R)8RGD sequence. Dodecapeptide-liposomes and RGD-liposomes were not internalized by activated platelets. On the other hand, liposomes containing (R)8PPQ, (R)8RGD, or (R)8GDV were internalized by activated platelets, and the extent of internalization was inversely related to ligand affinity to the target.
Association after linkage analysis indicates that homozygosity for the 46C→T polymorphism in the F12 gene is a genetic risk factor for venous thrombosis
Authors: Tirado Isabel , Mateo José , Oliver Artur , Souto Juan , Santamaria Amparo , Felices Rosa , Borrell Montserrat , Fontcuberta Jordi , Soria José
Published: April 2004

In a family-based study called GAIT (Genetic Analysis of Idiopathic Thrombophilia) that included a genome-wide scan we demonstrated that a polymorphism (46C→T) in the F12 locus jointly influences variability of plasma (Factor XII) FXII levels and susceptibility to thrombotic disease. It then became germane to determine the prevalence of the 46C→T polymorphism and its relative risk of thrombotic disease. We followed up evidence for genetic linkage with a case-control study, including 250 unrelated consecutive Spanish patients suffering from venous thrombotic disease and 250 Spanish subjects matched for sex and age as a controls. We measured FXII levels and genotyped the 46C→T polymorphism, as well as a number of classical risk factors for thrombotic disease. We confirmed that individuals with different genotypes for this polymorphism showed significant differences in their FXII levels. Most importantly, the mutated T allele in the homozygous state (genotype T/T) was associated with an increased risk of thrombosis (adjusted OR of 4.82; 95% CI 1.5-15.6), suggesting that the polymorphism itself is an independent risk factor for venous thromboembolism. This study confirms that the 46C→T polymorphism is a genetic risk factor for venous thrombosis in the Spanish population. In addition, our results confirm that a genome-wide scan coupled with a classical case-control association study is an extremely valuable approach to identify DNA variants that affect complex diseases.
The role of platelets and recombinant factor VIIa on thrombin generation, platelet activation and clot formation
Authors: Chakroun Tahar , Depasse François , Arzoglou Pantelis , Samama Meyer , Elalamy Ismail , Gerotziafas Grigoris
Published: April 2004

In the present study we assessed the effect of platelet counts and rFVIIa on thrombin generation, platelet activation and clot formation after tissue factor pathway activation in human plasma aiming to investigate the mechanism by which rFVIIa induces haemostasis in patients with severe thrombocytopenia. Plasma samples with platelet counts from 5 ×109/l to 150 ×109/l were spiked with rFVIIa (1 µg/ml) or buffer. Clotting was initiated in the presence of diluted thromboplastin. Thrombin generation was assessed using the Thrombogram-Thrombinoscope™ assay. The kinetics of platelet activation was assessed using flow cytometry to measure the expression the Pselectin on platelet membrane of washed platelets suspended in defibrinated homologous PPP. Thromboelastography was used to evaluate the effect of platelets and rFVIIa on the kinetics of clot formation and clot’s firmness. In the presence of low platelet counts the endogenous thrombin potential (ETP) and the maximum concentration of generated thrombin (Cmax) were reduced by 60%-70%.The lag-time of thrombin generation and the time required to reach the Cmax (Tmax) were prolonged, the velocity of platelet activation was decreased and thrombus formation was delayed. Recombinant FVIIa accelerated thrombin generation and platelet activation but it did not significantly modify ETP or Cmax. Recombinant FVIIa enhanced platelet activation in a TF and thrombin dependent manner since its effect on the studied parameters was abolished when TF was omitted or when hirudin was added into the experimental system respectively. Recombinant FVIIa normalized the velocity of clot formation but it did not modify clot firmness, which depended mainly on platelets’ count. In conclusion, in experimental conditions simulating severe thrombocytopenia rFVIIa in the presence of low amounts of TF, accelerates thrombin generation, without increasing the maximum amount of generated thrombin, thus leading in enhanced platelet activation and rapid clot formation.
Erythrocyte sodium/lithium countertransport is associated with thrombotic and fibrinolytic factors in 58-year-old men
Authors: Bokemark Lena , Fagerberg Björn , Herlitz Hans
Published: April 2004

The metabolic syndrome, in which insulin resistance is the core feature, is associated both with dysregulation of thrombosis/ fibrinolysis and erythrocyte sodium/lithium countertransport (SLC).To investigate this further we designed a cross-sectional study to examine whether factors involved in coagulationand fibrinolysis systems were associated with SLC independently of insulin resistance in 93 58-year-old men. SLC was in univariate analysis positively correlated with PAI-1 activity (r = 0.35, p <0.01), tPA antigen (r = 0.38, p <0.01), von Willebrand factor (r = 0.25, p <0.05), protein S (r = 0.26, p <0.05), and C (r = 0.30, p <0.01), and negatively associated with tPA activity(r = −0.28, p <0.01). Since these correlations could be influenced by the components of the metabolic syndrome itself, a separate analysis with adjustment for glucose infusion rate (GIR), plasma insulin, body fat, sagittal diameter of the abdomen (SD) and log serum triglyceride concentration (TG) was conducted. Then SLC was associated with tPA antigen independent of GIR, plasma insulin, body fat, SD and TG. SLC was also associated with protein C independent of GIR, insulin, body fat and SD but not TG. In conclusion, we found a relationship between SLC and the fibrinolytic system that was not related to the metabolic syndrome.
Human α-defensins neutralize fibrinolytic activity exerted by staphylokinase
Authors: Tarkowski Andrej , Bokarewa Maria
Published: April 2004

Defensins, cationic peptides with bacteriolytic properties, are abundantly found at inflammation sites and in human coronary vessels. Vascular occlusive diseases, such as myocardial infarction, pulmonary embolism, and peripheral arterial occlusion are presently treated by thrombolytic intervention using staphylokinase, a plasminogen activator of bacterial origin. In this study we assessed a possible interaction between defensins and staphylokinase, both molecules being present in an acutely ill patient. Using an ELISA-based system, we found that staphylokinase and defensins displayed a strong and dose-dependent binding. In contrast, urokinase, another plasminogen activator of endogenous origin, displayed only minimal binding to defensins. Next, we proved that interaction between staphylokinase and defensins led to fuctional consequences resulting in a significant decrease (p<0.002) of plasminogen activation capacity upon complex formation. In contrast, urokinase retained most of its activity even in 10-fold molar excess of defensins. Finally, we found that staphylokinase-triggered lysis of fibrin was efficiently inhibited in the presence of defensins. To assess structural requirements for staphylokinase/defensin interaction, six staphylokinase mutant variants were studied. Inactivation pattern of the tested staphylokinase variants suggested a direct binding of defensins to serine protease-like domain of staphylokinase. In conclusion, we show complex formation between staphylokinase and α-defensins resulting in a significant reduction of fibrinolytic activity. This finding may have clinical implications, since fibrinolytic effects of staphylokinase may be downregulated at the site of vascular occlusion.
In proven deep vein thrombosis, a low positive D-Dimer score is a strong negative predictor for associated malignancy
Authors: Jones Sue , Day Jane , Hoggarth Catherine , Rege Kanchan
Published: April 2004

D-Dimer measurements are being increasingly used for negative prediction of deep vein thrombosis (DVT). At our institution, clinical score, D-Dimer assay, plethysmography and, if necessary, Doppler ultrasound are used to secure the diagnosis. We collected the data from 100 consecutive patients proven to have DVT. We examined their medical case notes at diagnosis for concurrent clinical conditions and one year later to look for documented evidence of malignancy. Twenty-two of the 66 patients with D-Dimers greater than 1000 ng/ml were diagnosed with a cancer compared with only 2 of the 34 patients with a presenting D-Dimer score of less than 1000 ng/ml. We propose that a D-Dimer score of less than 1000 ng/ml in proven DVT is a strong negative predictor for malignancy (p = 0.0025).