MedWorm: Biomedical Engineering

IEEE Signal Processing Society Information

IEEE Transactions on Signal Processing — Thu, 18 Mar 2010 16:53:03 +0100

(Source: IEEE Transactions on Signal Processing)

MedWorm Message: Get the very latest Swine Flu news via the MedWorm Swine Flu RSS news feed - updated hourly from thousands of authoritative health and news sources.

Quality without compromise

IEEE Transactions on Signal Processing — Thu, 18 Mar 2010 16:53:03 +0100

(Source: IEEE Transactions on Signal Processing)

2010 IEEE Workshop on Signal Processing Systems

IEEE Transactions on Signal Processing — Thu, 18 Mar 2010 16:53:03 +0100

(Source: IEEE Transactions on Signal Processing)

Special issue on New Frontier in Rich Transcription

IEEE Transactions on Signal Processing — Thu, 18 Mar 2010 16:53:03 +0100

(Source: IEEE Transactions on Signal Processing)

IEEE Transactions on Signal Processing information for authors

IEEE Transactions on Signal Processing — Thu, 18 Mar 2010 16:53:03 +0100

(Source: IEEE Transactions on Signal Processing)

IEEE Transactions on Signal Processing Edics

IEEE Transactions on Signal Processing — Thu, 18 Mar 2010 16:53:03 +0100

(Source: IEEE Transactions on Signal Processing)

MedWorm Message: Get the very latest Swine Flu news via the MedWorm Swine Flu RSS news feed - updated hourly from thousands of authoritative health and news sources.

Dynamic Spectrum Management With the Competitive Market Model

IEEE Transactions on Signal Processing — Thu, 18 Mar 2010 16:53:03 +0100

Ye [“Competitive Communication Spectrum Economy and Equilibrium,” 2008, working paper] and Lin [“Budget Allocation in a Competitive Communication Spectrum Economy,” EURASIP J. Adv. Signal Process., Article ID: 963717, vol. 2009, p. 12, Sep. 2009] have shown that dynamic spectrum management (DSM) using the market competitive equilibrium (CE), which sets a price for transmission power on each channel, leads to better system performance in terms of the total data transmission rate (by reducing cross talk), than using the Nash equilibrium (NE). But how to achieve such a CE is an open problem. We show that the CE is the solution of a linear complementarity problem (LCP) and can be computed efficiently. We propose a decentralized tâtonnement process for adjusti...

On the Optimal Performance in Asymmetric Gaussian Wireless Sensor Networks With Fading

IEEE Transactions on Signal Processing — Thu, 18 Mar 2010 16:53:03 +0100

We study the estimation of a Gaussian source by a Gaussian wireless sensor network (WSN) where $L$ distributed sensors transmit noisy observations of the source through a fading Gaussian multiple access channel to a fusion center. In a recent work Gastpar, [“Uncoded transmission is exactly optimal for a Simple Gaussian Sensor Network,” IEEE Trans. Inf. Theory, vol. 54, no. 11, pp. 5247–5251, Nov. 2008] showed that for a symmetric Gaussian WSN with no fading, uncoded (analog) transmission achieves the optimal performance theoretically attainable (OPTA). In this correspondence, we consider an asymmetric fading WSN in which the sensors have differing noise and transmission powers. We first present lower and upper bounds on the system's OPTA under random fading. We next fo...

Optimal Linear Fusion for Distributed Detection Via Semidefinite Programming

IEEE Transactions on Signal Processing — Thu, 18 Mar 2010 16:53:03 +0100

The objective is to maximize the probability of detection subject to an upper limit on the probability of false alarm. We propose a more efficient solution that employs a divide-and-conquer strategy to divide the decision optimization problem into two subproblems. Each subproblem is a nonconvex program with a quadratic constraint. Through a judicious reformulation and by employing a special matrix decomposition technique, we show that the two nonconvex subproblems can be solved by semidefinite programs in a globally optimal fashion. Hence, we can obtain the optimal linear fusion rule for the distributed detection problem. Compared with the likelihood-ratio test approach, optimal linear fusion can achieve comparable performance with considerable design flexibility and reduced complexity. (S...

A Two-Step Approach to Power Allocation for OFDM Signals Over Two-Way Amplify-and-Forward Relay

IEEE Transactions on Signal Processing — Thu, 18 Mar 2010 16:53:03 +0100

A two-way relay channel (TWRC) in which two terminals $T_{1}$ and $T_{2}$ exchange orthogonal frequency division multiplexing (OFDM) signals with the help of an amplify-and-forward (AF) relay $T_{3}$ is considered here, and an efficient technique for allocating powers to $N$ parallel tones of OFDM is developed. A sum rate maximization problem is formulated by replacing the individual power constraints of the conventional sum rate maximization problem, which limit the power of each terminal, with the total power constraint limiting the sum of powers of all terminals. The maximization problem with the total power constraint yields a more efficient power allocation policy than the conventional problem with individual power constraints. It is shown that the closed-form solution of the maximiza...

Range-Doppler Imaging via Forward-Backward Sparse Bayesian Learning

IEEE Transactions on Signal Processing — Thu, 18 Mar 2010 16:53:03 +0100

We consider range-Doppler imaging via transmitting a train of probing pulses as in radar and active sonar. We show that range-Doppler imaging can be formulated as a sparse signal recovery problem and that we can use an expectation maximization based sparse Bayesian learning (EM-SBL) algorithm to achieve high resolution imaging. We also reduce the complexity of EM-SBL significantly by using an efficient forward-backward algorithm in the E step of the EM algorithm. (Source: IEEE Transactions on Signal Processing)

MedWorm Message: Get the very latest Swine Flu news via the MedWorm Swine Flu RSS news feed - updated hourly from thousands of authoritative health and news sources.

Performance of Instantaneous Frequency Rate Estimation Using High-Order Phase Function

IEEE Transactions on Signal Processing — Thu, 18 Mar 2010 16:53:03 +0100

The high-order phase function (HPF) is a useful tool to estimate the instantaneous frequency rate (IFR) of a signal with a polynomial phase. In this paper, the asymptotic bias and variance of the IFR estimate using the HPF are derived in closed-forms for the polynomial phase signal with an arbitrary order. The Cramér-Rao bounds (CRBs) for IFR estimation, in both exact and asymptotic forms, are obtained and compared with the asymptotic mean-square error (MSE) of the HPF-based IFR estimator. Simulations are provided to verify our theoretical results. (Source: IEEE Transactions on Signal Processing)

On Entropy Rate for the Complex Domain and Its Application to i.i.d. Sampling

IEEE Transactions on Signal Processing — Thu, 18 Mar 2010 16:53:03 +0100

We derive the entropy rate formula for a complex Gaussian random process by using a widely linear model. The resulting expression is general and applicable to both circular and noncircular Gaussian processes, since any second-order stationary process can be modeled as the output of a widely linear system driven by a circular white noise. Furthermore, we demonstrate application of the derived formula to an order selection problem. We extend a scheme for independent and identically distributed (i.i.d.) sampling to the complex domain to improve the estimation performance of information-theoretic criteria when samples are correlated. We show the effectiveness of the approach for order selection for simulated and actual functional magnetic resonance imaging (fMRI) data that are inherently compl...

Methods for Sparse Signal Recovery Using Kalman Filtering With Embedded Pseudo-Measurement Norms and Quasi-Norms

IEEE Transactions on Signal Processing — Thu, 18 Mar 2010 16:53:03 +0100

We present two simple methods for recovering sparse signals from a series of noisy observations. The theory of compressed sensing (CS) requires solving a convex constrained minimization problem. We propose solving this optimization problem by two algorithms that rely on a Kalman filter (KF) endowed with a pseudo-measurement (PM) equation. Compared to a recently-introduced KF-CS method, which involves the implementation of an auxiliary CS optimization algorithm (e.g., the Dantzig selector), our method can be straightforwardly implemented in a stand-alone manner, as it is exclusively based on the well-known KF formulation. In our first algorithm, the PM equation constrains the $l_{1}$ norm of the estimated state. In this case, the augmented measurement equation becomes linear, so a regular K...

Reducing Front-End Bandwidth May Improve Digital GNSS Receiver Performance

IEEE Transactions on Signal Processing — Thu, 18 Mar 2010 16:53:03 +0100

A novel evaluation of filtering and quantization losses for weak DS-CDMA receivers is presented. Using this method, joint optimization of filter center frequency and bandwidth is conducted for one-, two- and three-bit quantizers. It is demonstrated that a joint loss-analysis of these effects is necessary to optimize front-end design. (Source: IEEE Transactions on Signal Processing)

Least-Squares Design of DFT Filter-Banks Based on Allpass Transformation of Higher Order

IEEE Transactions on Signal Processing — Thu, 18 Mar 2010 16:53:03 +0100

The allpass transformation of higher order is a very general concept to construct a frequency warped analysis–synthesis filter bank (AS FB) with nonuniform time-frequency resolution. In contrast to the more common allpass transformation of first order, the delay elements of the analysis filter bank are substituted by allpass filters of higher order to achieve a more flexible control over its frequency selectivity. Known analytical closed-form designs for the synthesis filter bank can ensure perfect reconstruction (PR), but the synthesis subband filters are not necessarily stable and exhibit no distinctive bandpass characteristic. These problems are addressed by a new least-squares error (LSE) filter bank design. The coefficients of the finite-impulse-response (FIR) synthesis filters...

MedWorm Message: Get the very latest Swine Flu news via the MedWorm Swine Flu RSS news feed - updated hourly from thousands of authoritative health and news sources.

Competitive Linear Estimation Under Model Uncertainties

IEEE Transactions on Signal Processing — Thu, 18 Mar 2010 16:53:02 +0100

We investigate a linear estimation problem under model uncertainties using a competitive algorithm framework under mean square error (MSE) criteria. Here, the performance of a linear estimator is defined relative to the performance of the linear minimum MSE estimator tuned to the underlying unknown system model. We then find the linear estimator that minimizes this relative performance measure, i.e., the regret, for the worst possible system model. Two definitions of regret are given: first as a difference of MSEs and second as a ratio of MSEs. We demonstrate that finding the linear estimators that minimize these regret definitions can be cast as a Semidefinite Programming (SDP) problem and provide numerical examples. (Source: IEEE Transactions on Signal Processing)

Estimation of Ambiguity Functions With Limited Spread

IEEE Transactions on Signal Processing — Thu, 18 Mar 2010 16:53:02 +0100

In this correspondence, we propose a class of estimators of the ambiguity function of a discrete-time process using thresholding. To this purpose, the distributional and moment properties of the empirical ambiguity function for a realization of an analytic random process are derived, and the moments for the special cases of stationary, uniformly modulated, and deterministic signals immersed in noise processes are determined. Suitable thresholds are chosen based on the distributional properties of the empirical ambiguity function, and the procedure is tested on simulated data. (Source: IEEE Transactions on Signal Processing)

Generalized Pipelined Tomlinson–Harashima Precoder Design Methodology With Build-In Arbitrary Speed-Up Factors

IEEE Transactions on Signal Processing — Thu, 18 Mar 2010 16:53:02 +0100

In conclusion, for a given design specification, the proposed scheme can provide tradeoffs between hardware complexity and output dynamic range, which leads to a near-optimal solution based on these design criteria. Therefore, the proposed scheme provides more degrees of freedom for the design trade-offs of high-speed pipelining TH precoders with build-in arbitrary speedup factors. (Source: IEEE Transactions on Signal Processing)

A Deflation Procedure for Subspace Decomposition

IEEE Transactions on Signal Processing — Thu, 18 Mar 2010 16:53:02 +0100

A general deflation framework is described for the separation of a desired signal subspace of arbitrary dimensions from noisy multichannel observations. The method simultaneously uses single and multichannel priors to split the desired and undesired subspaces, even for coplanar (intersecting) subspaces. By appropriate use of signal priors, it can even extract signals from degenerate mixtures of signals and noise recorded from a few number of channels in low SNR scenarios, without the reduction of the data dimensions. As a case study, the performance of the proposed method is studied for the problem of extracting fetal cardiac signals from maternal abdominal recordings, over simulated and real data. A second case study deals with the degenerate problem of extracting diaphragmatic electromyo...

Synchronization by Two-Way Message Exchanges: Cramér-Rao Bounds, Approximate Maximum Likelihood, and Offshore Submarine Positioning

IEEE Transactions on Signal Processing — Thu, 18 Mar 2010 16:53:02 +0100

Accurate clock synchronization is vital to many applications of wireless sensor networks (WSNs). The availability of a mathematical tool that at an early design stage can provide insight into the theoretically achievable performance of the clock synchronization may accordingly be valuable in the initial design phase of the network. Therefore, the achievable clock synchronization accuracy is examined in a WSN employing a two-way message exchange model under a Gaussian assumption. The Cramér-Rao bound for the estimation of the clock parameters is derived for four different parameterizations (i.e., different nuisance parameters), reflecting different levels of prior knowledge concerning the system parameters. The results on the Cramér-Rao bound are transformed into a lower bound...

MedWorm Message: Get the very latest Swine Flu news via the MedWorm Swine Flu RSS news feed - updated hourly from thousands of authoritative health and news sources.

Channel Energy Based Estimation of Target Trajectories Using Distributed Sensors With Low Communication Rate

IEEE Transactions on Signal Processing — Thu, 18 Mar 2010 16:53:02 +0100

Sensor localization using channel energy measurements of distributed sensors has been studied in various scenarios. However, it is usually assumed that the target does not move significantly during the time needed to collect and process the data from the sensors. We want to estimate the trajectory of a moving target using a network of distributed sensors that measure only the received signal strength (RSS), sampled and as a function of time, without knowledge of the target amplitude/source level. To reduce the communication load, sensors communicate a reduced data set to the fusion center (FC), generated through local processing. It consists of three characteristic parameters: i) the maximum measured amplitude, corresponding to the closest-point-of-approach (CPA); ii) the corresponding tim...

On Signal-to-Noise Ratio-Assisted Crosstalk Channel Estimation in Downstream DSL Systems

IEEE Transactions on Signal Processing — Thu, 18 Mar 2010 16:53:02 +0100

Downstream (DS) crosstalk channels of digital subscriber line systems can be estimated based on the reported signal-to-noise ratio (SNR). In the case of an already active victim line (VL) impacted by the joining of a new disturber line (DL), sending perturbing signals on the VL and reporting the SNRs allow the estimation of the crosstalk channel from the DL to the VL. This paper generalizes that concept to include full startup, tracking and joining scenarios as well as the impact of different perturbation signal choices. Additionally, the sensitivity of the algorithm to different sources of imperfection is analyzed. Simulation results reveal that starting without precoding, and updating the precoder matrix based on the DS crosstalk channel estimates, the far-end crosstalk-free SNR can be r...

A Linear Fractional Semidefinite Relaxation Approach to Maximum-Likelihood Detection of Higher-Order QAM OSTBC in Unknown Channels

IEEE Transactions on Signal Processing — Thu, 18 Mar 2010 16:53:02 +0100

This paper considers the blind maximum-likelihood (ML) detection problem for orthogonal space–time block codes (OSTBCs) in multiple-input multiple-output flat-fading channels. While the blind ML detection problem for general space-time codes is difficult to solve, it has been shown that for OSTBCs with constant modulus constellations, the blind ML detection problem can be formulated as a discrete quadratic program, and then handled by a powerful convex approximation technique known as semidefinite relaxation (SDR). In this paper, we turn our attention to the case of higher order QAM OSTBCs. Due to the nonconstant modulus nature of higher order QAM signals, the blind ML detection problem turns out to be a discrete Rayleigh quotient maximization problem, and as a result the current SD...

Packet Error Probability of a Transmit Beamforming System With Imperfect Feedback

IEEE Transactions on Signal Processing — Thu, 18 Mar 2010 16:53:02 +0100

Average packet error probability (PEP) is an important error statistic for wireless communication system designers. In this paper, we address the problem of analytically quantifying the effect of channel estimation errors, feedback delay and channel vector quantization on the PEP of transmit beamforming multiple-input-single-output (MISO) systems in a spatially independent slow-fading wireless channel environment. We develop an accurate characterization of estimation errors as well as errors due to feedback delay, and tools relevant for deriving analytical expressions for the PEP. The modeling highlights the distinction between errors that arise due to channel estimation from those that arise due to feedback delay and represents an important departure from past work. Analytical expressions...

Efficient Weighted Sum Rate Maximization With Linear Precoding

IEEE Transactions on Signal Processing — Thu, 18 Mar 2010 16:53:01 +0100

Achieving the boundary of the capacity region in the multiple-input multiple-output (MIMO) broadcast channel requires the use of dirty paper coding (DPC). As practical nearly optimum implementations of DPC are computationally complex, purely linear approaches are often used instead. However, in this case, the problem of maximizing a weighted sum rate constitutes a nonconvex and, in most cases, also a combinatorial optimization problem. In this paper, we present two heuristic nearly optimum algorithms with reduced computational complexity. For this purpose, a lower bound for the weighted sum rate under linear zero-forcing constraints is used. Based on this bound, both greedy algorithms successively allocate data streams to users. In each step, the user is determined that is given an additio...

MedWorm Message: Get the very latest Swine Flu news via the MedWorm Swine Flu RSS news feed - updated hourly from thousands of authoritative health and news sources.

Robust Joint Design of Linear Relay Precoder and Destination Equalizer for Dual-Hop Amplify-and-Forward MIMO Relay Systems

IEEE Transactions on Signal Processing — Thu, 18 Mar 2010 16:53:01 +0100

This paper addresses the problem of robust linear relay precoder and destination equalizer design for a dual-hop amplify-and-forward (AF) multiple-input multiple-output (MIMO) relay system, with Gaussian random channel uncertainties in both hops. By taking the channel uncertainties into account, two robust design algorithms are proposed to minimize the mean-square error (MSE) of the output signal at the destination. One is an iterative algorithm with its convergence proved analytically. The other is an approximated closed-form solution with much lower complexity than the iterative algorithm. Although the closed-form solution involves a minor relaxation for the general case, when the column covariance matrix of the channel estimation error at the second hop is proportional to identity matri...

On the Sensitivity of the MIMO Tomlinson–Harashima Precoder With Respect to Channel Uncertainties

IEEE Transactions on Signal Processing — Thu, 18 Mar 2010 16:53:01 +0100

The multiple-input multiple-output Tomlinson–Harashima (MIMO-TH) precoder is a well-known structure that mitigates interstream interference in flat fading MIMO systems. The MIMO-TH filters are designed by assuming perfect channel state information (CSI) at both the transmitter and the receiver. However, in practice, channel estimates are available instead of the true channels. In this work, we assess the MIMO-TH performance degradation in the cases where the channel estimates are used as if they were the true channels. More specifically, we develop second-order and high-SNR approximations to the excess mean-square error (EMSE) induced by channel uncertainties, uncovering the factors that determine the MIMO-TH performance degradation in practice. Numerical experiments are in agreemen...

Decentralized Dynamic Spectrum Allocation Based on Adaptive Antenna Array Interference Mitigation Diversity

IEEE Transactions on Signal Processing — Thu, 18 Mar 2010 16:53:01 +0100

A new class of decentralized dynamic spectrum allocation (DSA) algorithms that exploit adaptive antenna array interference mitigation (IM) diversity at the receiver, is proposed for interference-limited environments with high level of frequency reuse. The system model consists of base stations (BS) that can optimize uplink frequency allocation to their subscriber stations (SS) to achieve the least impact of IM on the useful signal, assuming no control over band allocation of other BSs sharing the same bands. It is demonstrated that when the number of SSs that share the same frequency approaches the number of antenna elements at a BS, the potential performance gain is most significant for the IM-based DSA compared to the random frequency allocation. A “good neighbor” decentral...

Improved Dual Decomposition Based Optimization for DSL Dynamic Spectrum Management

IEEE Transactions on Signal Processing — Thu, 18 Mar 2010 16:53:01 +0100

Dynamic spectrum management (DSM) has been recognized as a key technology to significantly improve the performance of digital subscriber line (DSL) broadband access networks. The basic concept of DSM is to coordinate transmission over multiple DSL lines so as to mitigate the impact of crosstalk interference amongst them. Many algorithms have been proposed to tackle the nonconvex optimization problems appearing in DSM, many of them relying on a standard subgradient based dual decomposition approach. In practice however, this approach is often found to lead to extremely slow convergence or even no convergence at all, one of the reasons being the very difficult tuning of the stepsize parameters. In this paper we propose a novel improved dual decomposition approach inspired by recent advances ...

Timing Estimation and Resynchronization for Amplify-and-Forward Communication Systems

IEEE Transactions on Signal Processing — Thu, 18 Mar 2010 16:53:01 +0100

This paper proposes a general framework to effectively estimate the unknown timing and channel parameters, as well as design efficient timing resynchronization algorithms for asynchronous amplify-and-forward (AF) cooperative communication systems. In order to obtain reliable timing and channel parameters, a least squares (LS) estimator is proposed for initial estimation and an iterative maximum-likelihood (ML) estimator is derived to refine the LS estimates. Furthermore, a timing and channel uncertainty analysis based on the Cramér–Rao bounds (CRB) is presented to provide insights into the system uncertainties resulted from estimation. Using the parameter estimates and uncertainty information in our analysis, timing resynchronization algorithms that are robust to estimation e...

MedWorm Message: Get the very latest Swine Flu news via the MedWorm Swine Flu RSS news feed - updated hourly from thousands of authoritative health and news sources.

Markov Chain Monte Carlo Detectors for Channels With Intersymbol Interference

IEEE Transactions on Signal Processing — Thu, 18 Mar 2010 16:53:01 +0100

In this paper, we propose novel low-complexity soft-in soft-out (SISO) equalizers using the Markov chain Monte Carlo (MCMC) technique. We develop a bitwise MCMC equalizer (b-MCMC) that adopts a Gibbs sampler to update one bit at a time, as well as a group-wise MCMC (g-MCMC) equalizer where multiple symbols are updated simultaneously. The g-MCMC equalizer is shown to outperform both the b-MCMC and the linear minimum mean square error (MMSE) equalizer significantly for channels with severe amplitude distortion. Direct application of MCMC to channel equalization requires sequential processing which leads to long processing delay. We develop a parallel processing algorithm that reduces the processing delay by orders of magnitude. Numerical results show that both the sequential and parallel pro...

An Improved Smoothed Approximation Algorithm for Sparse Representation

IEEE Transactions on Signal Processing — Thu, 18 Mar 2010 16:53:01 +0100

$ell^0$ norm based algorithms have numerous potential applications where a sparse signal is recovered from a small number of measurements. The direct $ell^0$ norm optimization problem is NP-hard. In this paper we work with the the smoothed $ell^0$ (SL0) approximation algorithm for sparse representation. We give an upper bound on the run-time estimation error. This upper bound is tighter than the previously known bound. Subsequently, we develop a reliable stopping criterion. This criterion is helpful in avoiding the problems due to the underlying discontinuities of the $ell^0$ cost function. Furthermore, we propose an alternative optimization strategy, which results in a Newton like algorithm. (Source: IEEE Transactions on Signal Processing)

A Model Reduction Approach for OFDM Channel Estimation Under High Mobility Conditions

IEEE Transactions on Signal Processing — Thu, 18 Mar 2010 16:53:01 +0100

Orthogonal frequency-division multiplexing (OFDM) combines the advantages of high performance and relatively low implementation complexity. However, for reliable coherent detection of the input signal, the OFDM receiver needs accurate channel information. When the channel exhibits fast time variation as it is the case with several recent OFDM-based mobile broadband wireless standards (e.g., WiMAX, LTE, DVB-H), channel estimation at the receiver becomes quite challenging for two main reasons: 1) the receiver needs to perform this estimation more frequently and 2) channel time-variations introduce intercarrier interference among the OFDM subcarriers which can degrade the performance of conventional channel estimation algorithms significantly. In this paper, we propose a new pilot-aided algor...

DOA Estimation of Quasi-Stationary Signals With Less Sensors Than Sources and Unknown Spatial Noise Covariance: A Khatri–Rao Subspace Approach

IEEE Transactions on Signal Processing — Thu, 18 Mar 2010 16:53:01 +0100

In real-world applications such as those for speech and audio, there are signals that are nonstationary but can be modeled as being stationary within local time frames. Such signals are generally called quasi-stationary or locally stationary signals. This paper considers the problem of direction-of-arrival (DOA) estimation of quasi-stationary signals. Specifically, in our problem formulation we assume: i) sensor array of uniform linear structure; ii) mutually uncorrelated wide-sense quasi-stationary source signals; and iii) wide-sense stationary noise process with unknown, possibly nonwhite, spatial covariance. Under the assumptions above and by judiciously examining the structures of local second-order statistics (SOSs), we develop a Khatri–Rao (KR) subspace approach that has two n...

A General Criterion for Analog Tx-Rx Beamforming Under OFDM Transmissions

IEEE Transactions on Signal Processing — Thu, 18 Mar 2010 16:53:00 +0100

In this paper, we study beamforming schemes for a novel MIMO transceiver, which performs adaptive signal combining in the radio-frequency (RF) domain. Assuming perfect channel knowledge at the receiver side, we consider the problem of designing the transmit and receive RF beamformers under orthogonal frequency division multiplexing (OFDM) transmissions. In particular, a general beamforming criterion is proposed, which depends on a single parameter $alpha$. This parameter establishes a tradeoff between the energy of the equivalent SISO channel (after Tx-Rx beamforming) and its spectral flatness. The proposed cost function embraces most reasonable criteria for designing analog Tx-Rx beamformers. Hence, for particular values of $alpha$ the proposed criterion reduces to the minimization of the...

MedWorm Message: Get the very latest Swine Flu news via the MedWorm Swine Flu RSS news feed - updated hourly from thousands of authoritative health and news sources.

Bounded Component Analysis of Linear Mixtures: A Criterion of Minimum Convex Perimeter

IEEE Transactions on Signal Processing — Thu, 18 Mar 2010 16:53:00 +0100

This study presents a blind and geometric technique which pursues the linear decomposition of the observations in bounded component signals. The bounded component analysis of the observations relies on the hypotheses of compactness and Cartesian decomposition of the convex support of the vector of component signals, and in the invertibility of the mixture. Assumptions, which in absence of noise, are able to guarantee the identifiability of the mixture and separability of the components, up to permutation, scaling, and phase ambiguities. Under these conditions, the convex perimeter of the normalized linear combination of the observations is shown to be a global contrast function whose minima correspond with the extraction of bounded components of the observations. Practical extraction and s...

Performing Nonlinear Blind Source Separation With Signal Invariants

IEEE Transactions on Signal Processing — Thu, 18 Mar 2010 16:53:00 +0100

Given a time series of multicomponent measurements $x(t)$, the usual objective of nonlinear blind source separation (BSS) is to find a “source” time series $s(t)$, comprised of statistically independent combinations of the measured components. In this paper, the source time series is required to have a density function in $(s, {mathdot {s}})$-space that is equal to the product of density functions of individual components. This formulation of the BSS problem has a solution that is unique, up to permutations and component-wise transformations. Separability is shown to impose constraints on certain locally invariant (scalar) functions of $x$, which are derived from local higher-order correlations of the data's velocity $ {mathdot {x}}$. The data are separable if and only if the...

Recursive Least Squares Dictionary Learning Algorithm

IEEE Transactions on Signal Processing — Thu, 18 Mar 2010 16:53:00 +0100

We present the recursive least squares dictionary learning algorithm, RLS-DLA, which can be used for learning overcomplete dictionaries for sparse signal representation. Most DLAs presented earlier, for example ILS-DLA and K-SVD, update the dictionary after a batch of training vectors has been processed, usually using the whole set of training vectors as one batch. The training set is used iteratively to gradually improve the dictionary. The approach in RLS-DLA is a continuous update of the dictionary as each training vector is being processed. The core of the algorithm is compact and can be effectively implemented. The algorithm is derived very much along the same path as the recursive least squares (RLS) algorithm for adaptive filtering. Thus, as in RLS, a forgetting factor $lambda$ can ...

A New Approach to Pruning Volterra Models for Power Amplifiers

IEEE Transactions on Signal Processing — Thu, 18 Mar 2010 16:53:00 +0100

The objective of this paper is to present an approach to behavioral modeling that can be applied to predict the nonlinear response of power amplifiers with memory. Starting with the discrete-time, complex-baseband full Volterra model, we define a novel methodology that retains only radial branches that can be implemented with one-dimensional finite impulse response filters. This model is subsequently simplified by selecting a subset of directions using an ad hoc procedure. Both models are evaluated in terms of accuracy in the time and frequency domains and complexity, and are compared with other models described in the literature. The evaluation is conducted using a low-voltage silicon RF driver amplifier and a 5-W PA, which are characterized at different levels with diverse modulation for...

Multirate Filterbank Design: A Relaxed Commutant Lifting Approach

IEEE Transactions on Signal Processing — Thu, 18 Mar 2010 16:53:00 +0100

In this paper, we reformulate the design of the IIR synthesis filters in classical multirate systems as an interpolation problem involving a norm called the ${cal P}_{m}$ norm where $m$ is any positive integer. This interpolation problem can be solved using relaxed commutant lifting techniques in operator theory. The ${cal P}_{m}$ norm is actually a tradeoff in handling energy distortion and error peak distortion. Our development allows the designer to select from a family of filters the one which is best suited for a specific application. The well-known $H^{2}$ and $H^{infty}$ design methods can be viewed as special cases when $m=1$ and $mrightarrowinfty$ respectively. The computation relies mainly on FFT techniques and a finite section of certain Toeplitz matrices. The resulting filters ...

MedWorm Message: Get the very latest Swine Flu news via the MedWorm Swine Flu RSS news feed - updated hourly from thousands of authoritative health and news sources.

Design of Regular Wavelets Using a Three-Step Lifting Scheme

IEEE Transactions on Signal Processing — Thu, 18 Mar 2010 16:53:00 +0100

We propose structural multidimensional multichannel filter banks with desirable numbers of vanishing moments for the analysis and synthesis banks. For a two-channel filter bank, we use a three-step lifting scheme as opposed to the conventional two-step lifting method in order to provide more symmetry between the analysis and synthesis filters. We show that the resulting filters have more regularity, lower frame bounds ratio, and better frequency selectivity. We also extend our design to a general multichannel framework. Three steps of lifting scheme provides us a degree of freedom which we can benefit from toward a more flexible design. (Source: IEEE Transactions on Signal Processing)

Group Lifting Structures for Multirate Filter Banks II: Linear Phase Filter Banks

IEEE Transactions on Signal Processing — Thu, 18 Mar 2010 16:53:00 +0100

The theory of group lifting structures is applied to linear phase lifting factorizations for the two nontrivial classes of two-channel linear phase perfect reconstruction filter banks, the whole- and half-sample symmetric classes. Group lifting structures defined for the reversible and irreversible classes of whole- and half-sample symmetric filter banks are shown to satisfy the hypotheses of the uniqueness theorem for group lifting structures. It follows that linear phase group lifting factorizations of whole- and half-sample symmetric filter banks are therefore independent of the factorization methods used to construct them. These results cover the specification of whole-sample symmetric filter banks in the ISO/IEC JPEG 2000 image coding standard. (Source: IEEE Transactions on Signal Pro...

Group Lifting Structures for Multirate Filter Banks I: Uniqueness of Lifting Factorizations

IEEE Transactions on Signal Processing — Thu, 18 Mar 2010 16:53:00 +0100

Group lifting structures are introduced to provide an algebraic framework for studying lifting factorizations of two-channel perfect reconstruction finite-impulse-response (FIR) filter banks. The lifting factorizations generated by a group lifting structure are characterized by Abelian groups of lower and upper triangular lifting matrices, an Abelian group of unimodular gain scaling matrices, and a set of base filter banks. Examples of group lifting structures are given for linear phase lifting factorizations of the two nontrivial classes of two-channel linear phase FIR filter banks, the whole- and half-sample symmetric classes, including both the reversible and irreversible cases. This covers the lifting specifications for whole-sample symmetric filter banks in Parts 1 and 2 of the ISO/IE...

A Procedure to Adapt Filter Banks to Finite-Length Signals

IEEE Transactions on Signal Processing — Thu, 18 Mar 2010 16:53:00 +0100

In this paper, we consider the problem of processing finite-length signals by means of critically sampled or oversampled filter banks. Based on a polyphase matrix factorization of the filter bank, we propose a realization adaptation that does not make any assumption about the signal values outside the support of the input signal, contrary to what is done, for instance, when using zero padding, periodic repetition or extension by symmetry. The proposed procedure has several advantages. In particular, we show that it preserves the perfect reconstruction and the general properties of the filter bank. (Source: IEEE Transactions on Signal Processing)

Efficient NLMS and RLS Algorithms for Perfect and Imperfect Periodic Sequences

IEEE Transactions on Signal Processing — Thu, 18 Mar 2010 16:53:00 +0100

The paper discusses computationally efficient NLMS and RLS algorithms for perfect and imperfect periodic excitation sequences. The most interesting aspect of these algorithms is that they are exact LMS and RLS algorithms suitable for identification and tracking of every linear system and they require a real-time computational effort of just a multiplication, an addition and a subtraction per sample time. Moreover, the algorithms have convergence and tracking properties that can be better than or comparable with the NLMS algorithm for white noise input. The transient and steady state behavior of the algorithms and their tracking properties are also studied in the paper. (Source: IEEE Transactions on Signal Processing)

MedWorm Message: Get the very latest Swine Flu news via the MedWorm Swine Flu RSS news feed - updated hourly from thousands of authoritative health and news sources.

A PNLMS Algorithm With Individual Activation Factors

IEEE Transactions on Signal Processing — Thu, 18 Mar 2010 16:53:00 +0100

This paper presents a proportionate normalized least-mean-square (PNLMS) algorithm using individual activation factors for each adaptive filter coefficient, instead of a global activation factor as in the standard PNLMS algorithm. The proposed individual activation factors, determined in terms of the corresponding adaptive filter coefficients, are recursively updated. This approach leads to a better distribution of the adaptation energy over the filter coefficients than the standard PNLMS does. Thereby, for impulse responses exhibiting high sparseness, the proposed algorithm achieves faster convergence, outperforming both the PNLMS and improved PNLMS (IPNLMS) algorithms. (Source: IEEE Transactions on Signal Processing)

A Sparse-Interpolated Scheme for Implementing Adaptive Volterra Filters

IEEE Transactions on Signal Processing — Thu, 18 Mar 2010 16:53:00 +0100

In most practical applications, the major drawback for using adaptive Volterra filters is the large number of coefficients to cope with. Several research works discussing strategies to reduce the computational burden of these structures have been presented in the open literature. For such, a common approach has been the use of some type of sparseness in Volterra filter kernels. In this work, a sparse-interpolated approach, with the interpolation having the purpose of recreating (in an approximate way) the elements disregarded for obtaining sparse kernels, is presented and discussed. Thus, for the adaptive sparse-interpolated Volterra filter, coefficient update expressions considering both least-mean-square (LMS) and normalized LMS (NLMS) algorithms are derived by using a constrained approa...

Computationally Efficient Sparse Bayesian Learning via Belief Propagation

IEEE Transactions on Signal Processing — Thu, 18 Mar 2010 16:53:00 +0100

We present a belief propagation (BP)-based sparse Bayesian learning (SBL) algorithm, referred to as the BP-SBL, to recover sparse transform coefficients in large scale compressed sensing problems. BP-SBL is based on a widely used hierarchical Bayesian model, which is turned into a factor graph so that BP can be applied to achieve computational efficiency. We prove that the messages in BP are Gaussian probability density functions and therefore, we only need to update their means and variances when we update the messages. The computational complexity of BP-SBL is proportional to the number of transform coefficients, allowing the algorithms to deal with large scale compressed sensing problems efficiently. Numerical examples are provided to demonstrate the effectiveness of BP-SBL. (Source: IE...

An Efficient Approach for Two-Dimensional Parameter Estimation of a Single-Tone

IEEE Transactions on Signal Processing — Thu, 18 Mar 2010 16:53:00 +0100

In this paper, parameter estimation of a two-dimensional (2-D) single damped real/complex tone in the presence of additive white Gaussian noise is addressed. By utilizing the rank-one property of the 2-D noise-free data matrix, the damping factor and frequency for each dimension are estimated in a separable manner from the principal left and right singular vectors according to an iterative weighted least squares procedure. The remaining parameters are then obtained straightforwardly using standard least squares. The biases as well as variances of the damping factor and frequency estimates are also derived, which show that they are approximately unbiased and their performance achieves Cramér–Rao lower bound (CRLB) at sufficiently large signal-to-noise ratio (SNR) and/or data s...

The Estimation of the Fourth-Order Cumulant for Dependent Data: Consistency and Asymptotic Normality

IEEE Transactions on Signal Processing — Thu, 18 Mar 2010 16:52:59 +0100

Let ${X_{i}}$ be a stationary dependent random process with finite eight-order moments. For broad classes of processes ($rho$-mixing and strongly mixing), we obtain the convergence in probability, with sharp rates, of the estimate of the fourth-order cumulant from $n$ observations ${{X_{i}}}_{i=1}^{n}$ . We also establish the asymptotic distribution of the estimation error. The asymptotic expression of the variance is explicitly specified. (Source: IEEE Transactions on Signal Processing)

MedWorm Message: Get the very latest Swine Flu news via the MedWorm Swine Flu RSS news feed - updated hourly from thousands of authoritative health and news sources.

Refining Decisions After Losing Data: The Unlucky Broker Problem

IEEE Transactions on Signal Processing — Thu, 18 Mar 2010 16:52:59 +0100

Consider a standard statistical hypothesis test, leading to a binary decision made by exploiting a certain dataset. Suppose that, later, part of the data is lost, and we want to refine the test by exploiting both the surviving data and the previous decision. What is the best one can do? Such a question, here referred to as the unlucky broker problem, can be addressed by very standard tools from detection theory, but the solution gives intriguing insights and is by no means obvious. We provide the general form of the optimal detectors and discuss in depth their modus operandi, ranging from simple likelihood ratio tests to more complex behaviors. Limiting cases, where either the surviving data or the initial decision is almost useless, are also discussed. (Source: IEEE Transactions on Signal...

On the Invariance, Coincidence, and Statistical Equivalence of the GLRT, Rao Test, and Wald Test

IEEE Transactions on Signal Processing — Thu, 18 Mar 2010 16:52:59 +0100

Three common techniques to discriminate between alternatives in a binary hypothesis testing problem are: the generalized likelihood ratio test (GLRT), the Rao test, and the Wald test. In this paper, we investigate some characteristics of the corresponding decision statistics and provide their expressions for some problems of particular interest in statistical signal processing. First of all, we focus on the invariance of the Rao and Wald tests with respect to transformations leaving the testing problem unaltered. Then, we introduce necessary and sufficient conditions in order for their decision statistics to coincide with twice the logarithm of the GLRT statistic. Finally, we present some detection problems, usually encountered in practical signal processing applications, where the decisio...

Robust Filtering for a Class of Nonlinear Networked Systems With Multiple Stochastic Communication Delays and Packet Dropouts

IEEE Transactions on Signal Processing — Thu, 18 Mar 2010 16:52:59 +0100

In this paper, the robust $H_{infty}$ filtering problem is studied for a class of uncertain nonlinear networked systems with both multiple stochastic time-varying communication delays and multiple packet dropouts. A sequence of random variables, all of which are mutually independent but obey Bernoulli distribution, are introduced to account for the randomly occurred communication delays. The packet dropout phenomenon occurs in a random way and the occurrence probability for each sensor is governed by an individual random variable satisfying a certain probabilistic distribution in the interval [0 1]. The discrete-time system under consideration is also subject to parameter uncertainties, state-dependent stochastic disturbances and sector-bounded nonlinearities. We aim to design a linear ful...

IEEE Transactions on Signal Processing publication information

IEEE Transactions on Signal Processing — Thu, 18 Mar 2010 16:52:59 +0100

(Source: IEEE Transactions on Signal Processing)

IEEE Transactions on Signal Processing — Thu, 18 Mar 2010 16:52:59 +0100

(Source: IEEE Transactions on Signal Processing)

MedWorm Message: Get the very latest Swine Flu news via the MedWorm Swine Flu RSS news feed - updated hourly from thousands of authoritative health and news sources.

Comparative Finite Element Analysis of the Debonding Process in Different Concepts of Cemented Hip Implants.

Annals of Biomedical Engineering — Tue, 16 Mar 2010 00:00:00 +0100

Authors: Pérez MA, Palacios J Damage accumulation in the cement mantle and debonding of the bone-cement interface are basic events that contribute to the long-term failure of cemented hip reconstructions. In this work, a numerical study with these two process coupled is presented. Previously uniform bone-cement interface mechanical properties were only considered. In this work, a new approach assuming nonuniform and random bone-cement interface mechanical properties was applied to investigate its effect on cement degradation. This methodology was also applied to simulate and compare the degradation process of the cement and bone-cement interface in three different concepts of design: Exeter, Charnley, and ABG II stems. Nonuniform and random mechanical properties of the bone-cement...

Combined Method for Reduction of High Frequency Interferences in Surface Electroenterogram (EEnG).

Annals of Biomedical Engineering — Tue, 16 Mar 2010 00:00:00 +0100

Authors: Ye-Lin Y, Garcia-Casado J, Prats-Boluda G, Martinez-de-Juan JL Surface electroenterogram (EEnG) recording is a novel technique for monitoring intestinal motility non-invasively. However, surface EEnG recordings are contaminated by cardiac activity, the respiratory artefact, movement artefacts and other types of interference. The goal of this work is to remove electrocardiogram (ECG) interference and movement artefacts from surface EEnG by means of a combined method of empirical mode decomposition and independent component analysis. For this purpose, 11 recording sessions were conducted on animal models. In order to quantify the effectiveness of the proposed method, several parameters were calculated from each session: signal-to-ECG interference ratio (S/I), energy over 2 Hz (E...

Second Harmonic Generation Imaging and Fourier Transform Spectral Analysis Reveal Damage in Fatigue-Loaded Tendons.

Annals of Biomedical Engineering — Tue, 16 Mar 2010 00:00:00 +0100

This study established an objective 3D imaging and analysis method for tendon microstructure, which characterizes directionality and anisotropy of the tendon microstructure and quantitative measures of damage that will advance investigations of the microstructural basis of degradation that precedes overuse injuries. PMID: 20232150 [PubMed - as supplied by publisher] (Source: Annals of Biomedical Engineering)

Carotid Atheroma Rupture Observed In Vivo and FSI-Predicted Stress Distribution Based on Pre-rupture Imaging.

Annals of Biomedical Engineering — Tue, 16 Mar 2010 00:00:00 +0100

Authors: Leach JR, Rayz VL, Soares B, Wintermark M, Mofrad MR, Saloner D Atherosclerosis at the carotid bifurcation is a major risk factor for stroke. As mechanical forces may impact lesion stability, finite element studies have been conducted on models of diseased vessels to elucidate the effects of lesion characteristics on the stresses within plaque materials. It is hoped that patient-specific biomechanical analyses may serve clinically to assess the rupture potential for any particular lesion, allowing better stratification of patients into the most appropriate treatments. Due to a sparsity of in vivo plaque rupture data, the relationship between various mechanical descriptors such as stresses or strains and rupture vulnerability is incompletely known, and the patient-specific util...

Temporal Effects of Mechanical Loading on Deformation-Induced Damage in Skeletal Muscle Tissue.

Annals of Biomedical Engineering — Tue, 16 Mar 2010 00:00:00 +0100

Authors: Loerakker S, Stekelenburg A, Strijkers GJ, Rijpkema JJ, Baaijens FP, Bader DL, Nicolay K, Oomens CW Mechanical loading of soft tissues covering bony prominences can cause skeletal muscle damage, ultimately resulting in a severe pressure ulcer termed deep tissue injury. Recently, by means of an experimental-numerical approach, it was shown that local tissue deformations cause tissue damage once a deformation threshold is exceeded. In the present study, the effects of load exposure time and intermittent load relief on the development of deformation-induced muscle damage were investigated. The data showed that a 2 h loading period caused more damage than 10 min loading. Intermittent load reliefs of 2 min during a 2 h loading period had minimal effect on the evolution of skeletal ...

MedWorm Message: Get the very latest Swine Flu news via the MedWorm Swine Flu RSS news feed - updated hourly from thousands of authoritative health and news sources.

Numerical Modeling of Hemodynamics with Pulsatile Impeller Pump Support.

Annals of Biomedical Engineering — Tue, 16 Mar 2010 00:00:00 +0100

Authors: Shi Y, Lawford PV, Hose DR There is significant interest in the development and application of variable speed impeller-pump type ventricular assist devices designed to generate pulsatile blood flow. However, no study has so far been carried out to investigate the systemic cardiovascular response to various aspects of pump motion. In this article, a numerical model is constructed for the simulation of the cardiovascular response in the heart failure condition under representative cases of pulsatile impeller pump support. The native cardiovascular model is based on a previously validated model, and the impeller pump is modeled by directly fitting the pressure-flow curves that describe the pump characteristics. The model developed is applied to study circulatory dynamics under di...

Medical Engineering and Physics — Mon, 15 Mar 2010 17:02:19 +0100

(Source: Medical Engineering and Physics)

Special Issue on Wheelchair Transportation Safety – Introduction

Medical Engineering and Physics — Mon, 15 Mar 2010 17:02:18 +0100

Full integration of wheelchair users into our communities and societies is key to maximizing their potential to live productive and fulfilling lives. Transportation plays an important role in meeting this goal. Many wheelchair users travel seated in their wheelchairs and do so using a variety of transport modes; these include private vehicles, fixed-route transit vehicles and demand-responsive vehicles. Wheelchair users travel as both wheelchair-seated drivers and passengers. Safe transportation for these individuals is dependent upon a structurally sound wheelchair, securement of the wheelchair to the vehicle, and use of an appropriately positioned crashworthy occupant restraint system. Moreover, the transportation process, which includes boarding and alighting from the vehicle requires t...

Editorial Board

Medical Engineering and Physics — Mon, 15 Mar 2010 17:02:18 +0100

(Source: Medical Engineering and Physics)

Development and in-vitro characterization of an implantable flow sensing transducer for hydrocephalus.

Biomedical Microdevices — Sat, 13 Mar 2010 00:00:00 +0100

Authors: Bork T, Hogg A, Lempen M, Müller D, Joss D, Bardyn T, Büchler P, Keppner H, Braun S, Tardy Y, Burger J An implantable transducer for monitoring the flow of Cerebrospinal fluid (CSF) for the treatment of hydrocephalus has been developed which is based on measuring the heat dissipation of a local thermal source. The transducer uses passive telemetry at 13.56 MHz for power supply and read out of the measured flow rate. The in vitro performance of the transducer has been characterized using artificial Cerebrospinal Fluid (CSF) with increased protein concentration and artificial CSF with 10% fresh blood. After fresh blood was added to the artificial CSF a reduction of flow rate has been observed in case that the sensitive surface of the flow sensor is close to the sedimen...

MedWorm Message: Get the very latest Swine Flu news via the MedWorm Swine Flu RSS news feed - updated hourly from thousands of authoritative health and news sources.

Mechanobiological prediction of proximal femoral deformities in children with cerebral palsy.

Computer Methods in Biomechanics and Biomedical Engineering — Fri, 12 Mar 2010 00:00:00 +0100

In this study, the mechanobiological principles were implemented on a 3D finite element (FE) model of the proximal femur in order to predict changes in morphology over time in healthy and CP children. This model relies on the assumption that cyclic octahedral shear stress promotes growth and cyclic hydrostatic compressive stress inhibits growth. Growth was simulated over 16 iterations, representing approximately 5 months of growth. The FE model predicts an increase in the femoral anteversion and coxa valga for CP loading conditions when compared with healthy ones. Understanding the role of loading in skeletal morphogenesis may help prevent bone deformities and improve function in children with gait abnormalities. PMID: 20229379 [PubMed - as supplied by publisher] (Source: Computer Meth...

DT-MRI Based Computation of Collagen Fiber Deformation in Human Articular Cartilage: A Feasibility Study.

Annals of Biomedical Engineering — Fri, 12 Mar 2010 00:00:00 +0100

Authors: Pierce DM, Trobin W, Raya JG, Trattnig S, Bischof H, Glaser C, Holzapfel GA Accurate techniques for simulating the deformation of soft biological tissues are an increasingly valuable tool in many areas of biomechanical analysis and medical image computing. To model the complex morphology and response of articular cartilage, a hyperviscoelastic (dispersed) fiber-reinforced constitutive model is employed to complete two specimen-specific finite element (FE) simulations of an indentation experiment, with and without considering fiber dispersion. Ultra-high field Diffusion Tensor Magnetic Resonance Imaging (17.6 T DT-MRI) is performed on a specimen of human articular cartilage before and after indentation to approximately 20% compression. Based on this DT-MRI data, we detail a nov...

Are We Studying What Matters? Health Priorities and NIH-Funded Biomedical Engineering Research.

Annals of Biomedical Engineering — Fri, 12 Mar 2010 00:00:00 +0100

Authors: Rubin JB, Paltiel AD, Saltzman WM With the founding of the National Institute of Biomedical Imaging and Bioengineering (NIBIB) in 1999, the National Institutes of Health (NIH) made explicit its dedication to expanding research in biomedical engineering. Ten years later, we sought to examine how closely federal funding for biomedical engineering aligns with U.S. health priorities. Using a publicly accessible database of research projects funded by the NIH in 2008, we identified 641 grants focused on biomedical engineering, 48% of which targeted specific diseases. Overall, we found that these disease-specific NIH-funded biomedical engineering research projects align with national health priorities, as quantified by three commonly utilized measures of disease burden: cause of dea...

Development and characterization of a FIA system for selective assay of L: -ascorbic acid in food samples.

Bioprocess and Biosystems Engineering — Fri, 12 Mar 2010 00:00:00 +0100

Authors: Vig A, Igloi A, Adanyi N, Gyemant G, Csutoras C, Kiss A An amperometric detector and an enzymatic reaction were combined for the measurement of L: -ascorbic acid. The enzyme cell (containing immobilized ascorbate oxidase) was connected to a flow injection analyzer (FIA) system with a glassy carbon electrode as an amperometric detector. During optimization and measurements two sample injectors were used, one before and one after the enzyme cell, thus eliminating the background interferences. Subtraction of the signal area given in the presence of enzyme from the one given in the absence of enzyme was applied for measuring analyte concentrations and calibration at 400 mV. Analysis capacity of system is 25 samples/hour. The relative standard deviation (RSD) was below 5% (5 times ...

Strategies for utilisation of food-processing wastes to produce lipases in solid-state cultures of Rhizopus oryzae.

Bioprocess and Biosystems Engineering — Fri, 12 Mar 2010 00:00:00 +0100

Authors: López E, Deive FJ, Longo MA, Sanromán MA The aim of the present study was to investigate the feasibility of several food-processing wastes as support substrate for lipolytic enzymes production by the fungus Rhizopus oryzae under solid-state conditions. Different experiments were conducted to select the variables that allow obtaining high levels of lipolytic enzyme activity. In particular, the use of inert and non-inert solid materials and lipidic and surfactant compounds was evaluated. It was observed that the addition of Triton X-100 together with barley bran involved lipolytic production values tenfold higher than the cultures exclusively grown on an inert support. In addition, from preliminary thermoinactivation kinetics studies, it was concluded that the strategy...

MedWorm Message: Get the very latest Swine Flu news via the MedWorm Swine Flu RSS news feed - updated hourly from thousands of authoritative health and news sources.

Finite element analysis of idealised unit cell cancellous structure based on morphological indices of cancellous bone

Medical and Biological Engineering and Computing — Thu, 11 Mar 2010 18:26:30 +0100

In this study, two idealised architectures were developed based on morphological indices of cancellous bone: the tetrakaidecahedral and the prismatic. The two architectures were further subdivided into two types of microstructure, the first consists of struts only and the second consists of a combination of plates and struts. The microstructures were transformed into finite element models and displacement boundary condition was applied to all four idealised cancellous models with periodic boundary conditions. Eight unit cells extracted from the actual cancellous bone obtained from micro-computed tomography were also analysed with the same boundary conditions. Young’s modulus values were calculated and comparison was made between the idealised and real cancellous structures. Results...

Electrocardiogram Signals to Assess Zebrafih Heart Regeneration: Implication of Long QT Intervals.

Annals of Biomedical Engineering — Thu, 11 Mar 2010 00:00:00 +0100

Authors: Yu F, Li R, Parks E, Takabe W, Hsiai TK Zebrafish is an emerging model system for cardiac conduction and regeneration. Zebrafish heart regenerates after 20% ventricular resection within 60 days. Whether cardiac conduction phenotype correlated with cardiomyocyte regeneration remained undefined. Longitudinal monitoring of the adult zebrafish heart (n = 12) was performed in terms of atrial contraction (PR intervals), ventricular depolarization (QRS complex) and repolarization (heart rated corrected QTc interval). Baseline electrocardiogram (ECG) signals were recorded one day prior to resection and twice per week over 59 days. Immunostaining for gap junctions with anti-Connexin-43 antibody was compared between the sham (n = 5) and ventricular resection at 60 days post-resection (d...

Improved numerical approach for electrical modeling of biological cell clusters

Medical and Biological Engineering and Computing — Wed, 10 Mar 2010 15:55:50 +0100

This article presents an efficient numerical approach to simulate the process of polarization and ion conduction in membranes of biological cells subjected to intense electric fields. The proposed method uses Coulomb’s law to calculate the electric field on the surface of the cell membrane and the continuity equation for calculating the difference in electric potential between the faces of the membrane. The behavior of the membrane conductance is described by a model of electroporation proposed in literature. This method provides results that agree well with the analytical model of polarization of an isolated cell suspended in electrolytic solution and also provides results for the conductance of the membrane during electroporation of cells in concentrated suspensions that agree wi...

Enhancing the deceleration capacity index of heart rate by modified-phase-rectified signal averaging

Medical and Biological Engineering and Computing — Wed, 10 Mar 2010 15:55:49 +0100

Abstract Deceleration capacity (DC) of heart rate is a novel indicator of autonomic nervous system (ANS) activity. In this paper, we proposed a modified DC index based on improved phase-rectified signal averaging (PRSA) algorithm. Sinusoidal analysis is applied to elucidate the rationality of the improved PRSA. Then the validity of the modified DC is verified by the databases of chronic heart failure (CHF) patients and control group. Both the conventional and modified DCs are significantly lower in CHF patients than that in the control group (2.12 ± 2.98 vs. 6.34 ± 1.92 ms, P < 0.0001 and 5.45 ± 2.48 vs. 10.64 ± 1.76 ms, P < 0.0001, respectively). And the modified DC provides higher accuracy in d...

A method to determine in vivo, specific airway compliance, in humans

Medical and Biological Engineering and Computing — Wed, 10 Mar 2010 15:26:44 +0100

In conclusion, our 3D surface is a useful tool to measure and quantify in vivo specific airway compliance in humans. Content Type Journal ArticleCategory Short CommunicationDOI 10.1007/s11517-010-0576-3Authors Vanessa J. Kelly, Monash University Department of Medicine, Nursing and Health Sciences Clayton VIC AustraliaNathan J. Brown, Co-operative Research Centre for Asthma and Airways Glebe NSW AustraliaGregory G. King, Co-operative Research Centre for Asthma and Airways Glebe NSW AustraliaBruce R. Thompson, Monash University Department of Medicine, Nursing and Health Sciences Clayton VIC Australia Journal Medical and Biological Engineering and ComputingOnline ISSN 1741-0444Print ISSN 0140-0118 (Source: Medical and Biological Engineering and Computing)

MedWorm Message: Get the very latest Swine Flu news via the MedWorm Swine Flu RSS news feed - updated hourly from thousands of authoritative health and news sources.

New feature extraction approach for epileptic EEG signal detection using time-frequency distributions

Medical and Biological Engineering and Computing — Wed, 10 Mar 2010 15:26:42 +0100

Abstract This paper describes a new method to identify seizures in electroencephalogram (EEG) signals using feature extraction in time–frequency distributions (TFDs). Particularly, the method extracts features from the Smoothed Pseudo Wigner-Ville distribution using tracks estimated from the McAulay-Quatieri sinusoidal model. The proposed features are the length, frequency, and energy of the principal track. We evaluate the proposed scheme using several datasets and we compute sensitivity, specificity, F-score, receiver operating characteristics (ROC) curve, and percentile bootstrap confidence to conclude that the proposed scheme generalizes well and is a suitable approach for automatic seizure detection at a moderate cost, also opening the possibility of formulating new...

Role of Molecular Level Interfacial Forces in Hard Biomaterial Mechanics: A Review.

Annals of Biomedical Engineering — Wed, 10 Mar 2010 00:00:00 +0100

Authors: Dubey DK, Tomar V Biological materials have evolved over millions of years and are often found as complex composites with superior properties compared to their relatively weak original constituents. Hard biomaterials such as nacre, bone, and dentin have intrigued researchers for decades for their high stiffness and toughness, multifunctionality, and self-healing capabilities. Challenges lie in identifying nature's mechanisms behind imparting such properties and her pathways in fabricating these composites. The route frequently acquired by nature is embedding submicron- or nano-sized mineral particles in protein matrix in a well-organized hierarchical arrangement. The key here is the formation of large amount of precisely and carefully designed organic-inorganic interfaces and ...

Enhancement of hexavalent chromium reduction and electricity production from a biocathode microbial fuel cell.

Bioprocess and Biosystems Engineering — Wed, 10 Mar 2010 00:00:00 +0100

This study is a beneficial attempt to improve the efficiency of biocathode MFCs and provide a good candidate of bioremediation process for Cr (VI)-contaminated sites. PMID: 20217142 [PubMed - as supplied by publisher] (Source: Bioprocess and Biosystems Engineering)

Automated measurement and statistical modelling of elastic laminae in arteries.

Computer Methods in Biomechanics and Biomedical Engineering — Tue, 09 Mar 2010 00:00:00 +0100

Authors: Xu H, Hu JJ, Humphrey JD, Liu JC Structural features of elastic laminae within arteries can provide vital information for both the mechanobiology and the biomechanics of the wall. In this paper, we propose, test and illustrate a new computer-based scheme for automated analysis of regional distributions of elastic laminae thickness, inter-lamellar distances and fragmentation furcation points (FPs) from standard histological images. Our scheme eliminates potential artefacts produced by tissue cutting, automatically aligns tissue according to physiologic orientations and performs cross-sectional measurements along radial directions. A statistical randomised complete block design and F test were used to assess the potential (non)-uniformity of lamellar thicknesses and separations ...

Electrical Impedance of Stainless Steel Needle Electrodes.

Annals of Biomedical Engineering — Tue, 09 Mar 2010 00:00:00 +0100

We present experimental findings regarding variability and stability of the electrical impedance properties of medical grade stainless steel needle electrodes in vitro. Monopolar impedance spectra (1 Hz to 1 MHz) were measured and scanning electron microscope images were obtained for five needle types with active electrode area from 0.28 to 0.7 mm(2). A saline tank (0.9% NaCl) was used as tissue model. Measurements were done before and after electrolytic treatment with anodic and cathodic DC currents of 1 muA. With active electrode areas below 1 mm(2), high influence from electrode polarization impedance (EPI) was expected at low frequencies (LF). For higher frequencies (HF) the EPI decreases and the impedance of the surrounding tissue is more pronounced. The hypothesis tested was that the...

MedWorm Message: Get the very latest Swine Flu news via the MedWorm Swine Flu RSS news feed - updated hourly from thousands of authoritative health and news sources.

A Clinically Applicable Model to Estimate the Opposing Muscle Groups Contributions to Isometric and Dynamic Tasks.

Annals of Biomedical Engineering — Tue, 09 Mar 2010 00:00:00 +0100

This article presents an EMG-to-moment optimization model suitable for clinical studies to estimate the contribution of agonist and antagonist muscle groups to the net ankle joint moment during dynamic and isometric tasks. The proposed EMG-to-moment model took into account realistic muscle properties such as the electromechanical delay, and a force-length-velocity relationship with subject-specific muscle anthropometric data. Subjects performed isometric ankle plantar-flexion (fixed-end contraction) and dynamic tasks (heel-raise) in two positions, seated and upright. Two models were compared: the proposed EMG-to-moment model calibrated on eight dynamic and isometric tasks (Model 8-tasks) and on two dynamic tasks (Model 2-tasks), and a published reference model. First, each model was calibr...

Tensile Strain as a Regulator of Mesenchymal Stem Cell Osteogenesis.

Annals of Biomedical Engineering — Tue, 09 Mar 2010 00:00:00 +0100

This study investigates strain-induced differentiation and proliferation of MSCs, and investigates the cellular mechanisms of mechanotransduction. MSCs were seeded onto a collagen-coated silicone substrate and exposed to cyclic tensile mechanical strain of 2.5% at 0.17 Hz for 1-14 days. To examine mechanotransduction, cells were strained in the presence of the stretch-activated cation channel (SACC) blocker, gadolinium chloride (GdCl(3)); the extracellular regulated kinase (ERK) inhibitor, U0126; the p38 inhibitor, SB203580; and the phosphatidylinosito1 3-kinase (PI3-kinase) inhibitor, LY294002. Following exposure to strain, the osteogenic markers Cbfalpha1, collagen type I, osteocalcin, and BMP2 were temporally expressed. Exposure to strain in the presence of GdCl(3) (10 muM) reduced the ...

Measurement of single-cell adhesion strength using a microfluidic assay.

Biomedical Microdevices — Tue, 09 Mar 2010 00:00:00 +0100

Authors: Christ KV, Williamson KB, Masters KS, Turner KT Despite the importance of cell adhesion in numerous physiological, pathological, and biomaterial-related responses, our understanding of adhesion strength at the cell-substrate interface and its relationship to cell function remains incomplete. One reason for this deficit is a lack of accessible experimental approaches that quantify adhesion strength at the single-cell level and facilitate large numbers of tests. The current work describes the design, fabrication, and use of a microfluidic-based method for single-cell adhesion strength measurements. By applying a monotonically increasing flow rate in a microfluidic channel in combination with video microscopy, the adhesion strength of individual NIH3T3 fibroblasts cultured for 24...

Motion artifact cancellation in NIR spectroscopy using discrete Kalman filtering

BioMedical Engineering OnLine — Tue, 09 Mar 2010 00:00:00 +0100

Conclusions: This paper presented a novel approach based on Kalman filtering for motion artifact removal in NIR recordings. The proposed approach provides a suitable solution to the motion artifact removal problem in NIR studies by combining the advantages of the existing adaptive and Wiener filtering methods in one algorithm which allows efficient real time application with no requirement on additional sensor measurements. (Source: BioMedical Engineering OnLine)

Factors that affect mass transport from drug eluting stents into the artery wall

BioMedical Engineering OnLine — Tue, 09 Mar 2010 00:00:00 +0100

Coronary artery disease can be treated by implanting a stent into the blocked region of an artery, thus enabling blood perfusion to distal vessels. Minimally invasive procedures of this nature often result in damage to the arterial tissue culminating in the re-blocking of the vessel. In an effort to alleviate this phenomenon, known as restenosis, drug eluting stents were developed. They are similar in composition to a bare metal stent but encompass a coating with therapeutic agents designed to reduce the overly aggressive healing response that contributes to restenosis. There are many variables that can influence the effectiveness of these therapeutic drugs being transported from the stent coating to and within the artery wall, many of which have been analysed and documented by researchers...

MedWorm Message: Get the very latest Swine Flu news via the MedWorm Swine Flu RSS news feed - updated hourly from thousands of authoritative health and news sources.

Review on thermal energy storage with phase change: materials, heat transfer analysis and applicationsEngineering

Elsevier Updates: Engineering — Mon, 08 Mar 2010 00:00:00 +0100

This article, published in Applied Thermal Engineering, Volume 23, Issue 3, February 2003, Pages 251-283, was one of the Top 25 most downloaded Engineering articles between October and December 2009. (Source: Elsevier Updates: Engineering)

Review on thermal energy storage with phase change: materials, heat transfer analysis and applicationsEngineering

Elsevier Updates: Engineering — Mon, 08 Mar 2010 00:00:00 +0100

Current Application of Micro/Nano-Interfaces to Stimulate and Analyze Cellular Responses.

Annals of Biomedical Engineering — Sat, 06 Mar 2010 00:00:00 +0100

Authors: Cho YK, Shin H, Lee SK, Kim T Microfabrication technologies have a high potential for novel approaches to access living cells at a cellular or even at a molecular level. In the course of reviewing and discussing the current application of microinterface systems including nanointerfaces to stimulate and analyze cellular responses with subcellular resolution, this article focuses on interfaces based on microfluidics, nanoparticles, and scanning electrochemical microscopy (SECM). Micro/nanointerface systems provide a novel, attractive means for cell study because they are capable of regulating and monitoring cellular signals simultaneously and repeatedly, leading us to an enhanced understanding and interpretation of cellular responses. Therefore, it is hoped that the integrated m...

Modeling of Active Transmembrane Transport in a Mixture Theory Framework.

Annals of Biomedical Engineering — Sat, 06 Mar 2010 00:00:00 +0100

This study formulates governing equations for active transport across semi-permeable membranes within the framework of the theory of mixtures. In mixture theory, which models the interactions of any number of fluid and solid constituents, a supply term appears in the conservation of linear momentum to describe momentum exchanges among the constituents. In past applications, this momentum supply was used to model frictional interactions only, thereby describing passive transport processes. In this study, it is shown that active transport processes, which impart momentum to solutes or solvent, may also be incorporated in this term. By projecting the equation of conservation of linear momentum along the normal to the membrane, a jump condition is formulated for the mechano-electrochemical pot...

Finite Element Investigation of Stentless Pericardial Aortic Valves: Relevance of Leaflet Geometry.

Annals of Biomedical Engineering — Sat, 06 Mar 2010 00:00:00 +0100

Authors: Xiong FL, Goetz WA, Chong CK, Chua YL, Pfeifer S, Wintermantel E, Yeo JH Recent developments in aortic valve replacement include the truly stentless pericardial bioprostheses with single point attached commissures (SPAC) implantation technique. The leaflet geometry available for the SPAC valves can either be a simple tubular or a complex three-dimensional structure molded using specially designed molds. Our main objective was to compare these two leaflet designs, the tubular vs. the molded, by dynamic finite element simulation. Time-varying physiological pressure loadings over a full cardiac cycle were simulated using ABAQUS. Dynamic leaflet behavior, leaflet coaptation parameters, and stress distribution were compared. The maximum effective valve orifice area during systole i...

MedWorm Message: Get the very latest Swine Flu news via the MedWorm Swine Flu RSS news feed - updated hourly from thousands of authoritative health and news sources.

Hydrogel cell patterning incorporating photocaged RGDS peptides.

Biomedical Microdevices — Sat, 06 Mar 2010 00:00:00 +0100

In this report, we discuss the chemical synthesis and photoactive properties of the caged peptides as well as the subsequent binding of these peptides to our hydrogel base. We further demonstrate the ability of this modified hydrogel material to pattern fibroblast cells on the micron scale using near-UV light exposure through a patterned photomask to selectively switch areas of the hydrogel surface from cell non-adhesive to cell adhesive. The cells are found to adhere and proliferate along the developed line patterns for at least 2.5 days, demonstrating significantly enhanced pattern longevity in comparison with previously reported studies. PMID: 20213214 [PubMed - as supplied by publisher] (Source: Biomedical Microdevices)

Droplet-based microsystem for multi-step bioreactions.

Biomedical Microdevices — Sat, 06 Mar 2010 00:00:00 +0100

Authors: Wang F, Burns MA A droplet-based microfluidic platform was used to perform on-chip droplet generation, merging and mixing for applications in multi-step reactions and assays. Submicroliter-sized droplets can be produced separately from three identical droplet-generation channels and merged together in a single chamber. Three different mixing strategies were used for mixing the merged droplet. For pure diffusion, the reagents were mixed in approximately 10 min. Using flow around the stationary droplet to induce circulatory flow within the droplet, the mixing time was decreased to approximately one minute. The shortest mixing time (10 s) was obtained with bidirectional droplet motion between the chamber and channel, and optimization could result in a total time of less than 1 s....

Fast and continuous plasma extraction from whole human blood based on expanding cell-free layer devices.

Biomedical Microdevices — Sat, 06 Mar 2010 00:00:00 +0100

Authors: Sollier E, Cubizolles M, Fouillet Y, Achard JL This paper presents promising microfluidic devices designed for continuous and passive extraction of plasma from whole human blood. These designs are based on red cells lateral migration and the resulting cell-free layer locally expanded by geometric singularities such as an enlargement of the channel or a cavity adjacent to the channel. After an explanation of flow patterns, different tests are described that confirm the advantages of both proposed singularities, providing a 1.5 and 2X increase in extraction yield compared to a reference device, for 1:20 diluted blood at 100 microL/min. Devices have also been successively optimized, with extraction yields up to 17.8%, and biologically validated for plasma extraction, with no prot...

Evaluation of the Potential Clinical Application of Low-Intensity Ultrasound Stimulation for Preventing Osteoporotic Bone Fracture.

Annals of Biomedical Engineering — Fri, 05 Mar 2010 00:00:00 +0100

In conclusion, LIUS may potentially prove very effective clinically for preventing osteoporotic bone fractures. PMID: 20204699 [PubMed - as supplied by publisher] (Source: Annals of Biomedical Engineering)

Binary Segmentation Masks Can Improve Intrasubject Registration Accuracy of Bone Structures in CT Images.

Annals of Biomedical Engineering — Fri, 05 Mar 2010 00:00:00 +0100

Authors: Museyko O, Eisa F, Hess A, Schett G, Kalender WA, Engelke K Registration of bone structures is a common problem in medical research as well as in clinical applications. Intrasubject rigid 3D monomodality registration of segmented bone structures of CT images and multimodality registration of muMR and segmented muCT bone images were performed with the multiresolution intensity-based technique implemented in ITK. The registration results for binary volumes of interest (VOI) masks and for segmented gray value VOIs were compared. To determine the registration quality, in the monomodality case the sum of squared difference, the sum of absolute differences, and the normalized symmetric difference of binary masks and in the multimodality case Mattes mutual information were applied. T...

MedWorm Message: Get the very latest Swine Flu news via the MedWorm Swine Flu RSS news feed - updated hourly from thousands of authoritative health and news sources.

Simplified Pulse Reactor for Real-Time Long-Term In Vitro Testing of Biological Heart Valves.

Annals of Biomedical Engineering — Fri, 05 Mar 2010 00:00:00 +0100

The objective of this work was development of an easy to handle real-time pulse reactor for evaluation of biological and tissue engineered heart valves under different pressures and long-term conditions. The pulse reactor was made of medical grade materials for placement in a 37 degrees C incubator. Heart valves were mounted in a housing disc moving horizontally in culture medium within a cylindrical culture reservoir. The microprocessor-controlled system was driven by pressure resulting in a cardiac-like cycle enabling competent opening and closing of the leaflets with adjustable pulse rates and pressures between 0.25 to 2 Hz and up to 180/80 mmHg, respectively. A custom-made imaging system with an integrated high-speed camera and image processing software allow calculation of effective o...

Studies on substrate utilisation in L: -valine-producing Corynebacterium glutamicum strains deficient in pyruvate dehydrogenase complex.

Bioprocess and Biosystems Engineering — Fri, 05 Mar 2010 00:00:00 +0100

Authors: Bartek T, Rudolf C, Kerßen U, Klein B, Blombach B, Lang S, Eikmanns BJ, Oldiges M The pyruvate dehydrogenase complex was deleted to increase precursor availability in Corynebacterium glutamicum strains overproducing L: -valine. The resulting auxotrophy is treated by adding acetate in addition glucose for growth, resulting in the puzzling fact of gluconeogenic growth with strongly reduced glucose uptake in the presence of acetate in the medium. This result was proven by intracellular metabolite analysis and labelling experiments. To increase productivity, the SugR protein involved in negative regulation of the phosphotransferase system, was inactivated, resulting in enhanced consumption of glucose. However, the surplus in substrate uptake was not converted to L: -valine; i...

Effect of redox potential regulation on succinic acid production by Actinobacillus succinogenes.

Bioprocess and Biosystems Engineering — Thu, 04 Mar 2010 00:00:00 +0100

Authors: Li J, Jiang M, Chen KQ, Ye Q, Shang LA, Wei P, Ying HJ, Chang HN The effects of redox potential used as a control parameter on the process of succinic acid production in batch cultures of Actinobacillus succinogenes NJ113 have been investigated. In batch fermentation, cell growth and metabolite distribution were changed with redox potential levels in the range of -100 to -450 mV. From the results, the ORP level of -350 mV was preferable, which resulted in high succinic acid yield (1.28 mol mol(-1)), high succinic acid productivity (1.18 g L(-1) h(-1)) and high mole ratio of succinic acid to acetic acid (2.02). The mechanism of redox potential regulation was discussed by metabolic flux analysis and the ratio of NADH/NAD(+). We expected that redox potential can be used as a valu...

Jaw motor plasticity in health and disease.

Computer Methods in Biomechanics and Biomedical Engineering — Wed, 03 Mar 2010 00:00:00 +0100

Authors: Peck CC, Wirianski A, Murray GM The human jaw's structure-function relationships are complex. A recent example of this complexity is the lateral pterygoid muscle which we now consider as a single unit made up of functional regions with activity in each dependent on the biomechanical demands of the task. We have also characterised the effects on the jaw motor system of pain or exercise, as examples of how the jaw motor system adapts. Synchronised jaw tracking and electromyographic acquisition systems were used to study the effects on jaw muscle activity of experimentally induced masseter muscle pain or resistance exercises during goal-directed tasks. With both interventions, subjects were able to perform the same movement with different muscle co-activation strategies. In futur...

A procedure for estimating the relevant forces in the human knee using a four-bar mechanism.

Computer Methods in Biomechanics and Biomedical Engineering — Wed, 03 Mar 2010 00:00:00 +0100

Authors: Farhat N, Mata V, Rosa D, Fayos J Knee injuries, especially those that affect the cruciate and lateral ligaments, are one of the most serious and frequent pathologies that affect the lower human extremity. Hence, the aim of this study is to develop a dynamic model for the lower extremity capable of estimating forces, forces in the cruciate and collateral ligaments and those normal to the articular cartilage, generated in the knee. The proposed model considers a four-bar mechanism in the knee, a spherical joint in the pelvis and a revolute one in the ankle. The four-bar mechanism is obtained by a synthesis process. The dynamic model includes the inertial properties of the femur, tibia, patella and the foot, the ground reaction force and the most important muscles in the knee. M...

MedWorm Message: Get the very latest Swine Flu news via the MedWorm Swine Flu RSS news feed - updated hourly from thousands of authoritative health and news sources.

Electrically Active Bioceramics: A Review of Interfacial Responses.

Annals of Biomedical Engineering — Wed, 03 Mar 2010 00:00:00 +0100

Authors: Baxter FR, Bowen CR, Turner IG, Dent AC Electrical potentials in mechanically loaded bone have been implicated as signals in the bone remodeling cycle. Recently, interest has grown in exploiting this phenomenon to develop electrically active ceramics for implantation in hard tissue which may induce improved biological responses. Both polarized hydroxyapatite (HA), whose surface charge is not dependent on loading, and piezoelectric ceramics, which produce electrical potentials under stress, have been studied in order to determine the possible benefits of using electrically active bioceramics as implant materials. The polarization of HA has a positive influence on interfacial responses to the ceramic. In vivo studies of polarized HA have shown polarized samples to induce improve...

New Editor-in-Chief for Soil Dynamic and Earthquake EngineeringEngineering

Elsevier Updates: Engineering — Tue, 02 Mar 2010 00:00:00 +0100

Ahmed Elgamal has been appointed joint Editor-in-Chief of Soil Dynamics and Earthquake Engineering, alongside Prof Dimitri Beskos and Mustafa Erdik. (Source: Elsevier Updates: Engineering)

Award for Editor of Journal of Constructional Steel ResearchEngineering

Elsevier Updates: Engineering — Tue, 02 Mar 2010 00:00:00 +0100

Reidar Bjorhovde, Editor of the Journal of Constructional Steel Research is the 2010 winner of the Lynn S. Beedle Award of the the Structural Stability Research Council (SSRC). (Source: Elsevier Updates: Engineering)

Computational Hemodynamic Analysis in Congenital Heart Disease: Simulation of the Norwood Procedure.

Annals of Biomedical Engineering — Tue, 02 Mar 2010 00:00:00 +0100

In this study, computational fluid dynamics (CFD) was used to estimate the performance of first stage HLHS surgery, the Norwood operation. An image data transfer system was developed to convert clinical images into three-dimensional geometry. To confirm software applicability, a validation process was carried out to eliminate any influence of numerical procedures. The velocities derived from echocardiography measurements were used as boundary conditions, and pressure waves measured by a cardiac catheter simultaneous with an electrocardiogram (ECG) were employed to validate the results of CFD simulation. Calculated results were congruent with the in vivo measurement results. The blood flow circulations were successfully simulated and the distribution of blood flow in each vessel was estimat...

March Editorial.

Annals of Biomedical Engineering — Tue, 02 Mar 2010 00:00:00 +0100

Authors: PMID: 20195759 [PubMed - as supplied by publisher] (Source: Annals of Biomedical Engineering)

MedWorm Message: Get the very latest Swine Flu news via the MedWorm Swine Flu RSS news feed - updated hourly from thousands of authoritative health and news sources.

A Stretching Device for High-Resolution Live-Cell Imaging.

Annals of Biomedical Engineering — Tue, 02 Mar 2010 00:00:00 +0100

We describe a novel stretch device optimized for high-resolution live-cell imaging. The unit assembles onto standard inverted microscopes and applies constant magnitude or cyclic stretch at physiological magnitudes to cultured cells on elastic membranes. Interchangeable modular indenters enable delivery of equibiaxial and uniaxial stretch profiles. Strain analysis performed by tracking fluorescent microspheres adhered onto the substrate demonstrated reproducible application of stretch profiles. In endothelial cells transiently expressing enhanced green fluorescent protein (EGFP)-vimentin and paxillin-DsRed2 and subjected to constant magnitude equibiaxial stretch, the two-dimensional strain tensor demonstrated efficient transmission through the extracellular matrix and focal adhesions. Decr...

Evaluating Anisotropic Properties in the Porcine Temporomandibular Joint Disc Using Nanoindentation.

Annals of Biomedical Engineering — Tue, 02 Mar 2010 00:00:00 +0100

The objective of this study was to determine the viscoelastic properties present within the intermediate zone of the porcine temporomandibular joint (TMJ) disc using nanoindentation. A 50-mum conospherical indenter tip using a displacement-controlled ramp function with a 600 nm/s loading and unloading rate, a 3000-nm peak displacement with a holding period of 30 s was used to indent the samples. Experimental load-relaxation tests were performed on the TMJ disc to determine the response in three different directions; the mediolateral, anteroposterior, and articular surface directions. The experimental data were analyzed using a generalized Maxwell model to obtain values for short- and long-time relaxation modulus and of material time constants. The short time relaxation modulus E ( I ) valu...

Microfluidic devices for characterizing the agonist of formyl peptide receptor in RBL-FPR cells.

Biomedical Microdevices — Tue, 02 Mar 2010 00:00:00 +0100

Authors: Ye N, Wang MW, Qin J, Lin B The human formyl peptide receptor (FPR) plays an important role in inflammation and immunity. Finding of specific agonists and antagonists of FPR may provide potential therapeutic agents for FPR related disorders. The binding of agonist by FPR induces a cascade of G protein-mediated signaling events leading to neutrophil chemotaxis, intracellualr calcium mobilization, FPR ligand uptake and so on. This work proposed a microfluidic-based method to characterize FPR-related cellular events in response to small peptides, N-formyl-Met-Leu-Phe (fMLF), in rat basophilic leukemia cell line RBL-2H3 expressing human FPR (RBL-FPR). The results showed that fMLF triggered chemotaxis, calcium mobilization and FPR ligand uptake in RBL-FPR cells, indicating the pote...

Multiphysics modeling of responsive characteristics of ionic-strength-sensitive hydrogel.

Biomedical Microdevices — Tue, 02 Mar 2010 00:00:00 +0100

Authors: Li H, Lai F A multiphysics model is developed in this paper for simulation of the volume transition mechanism of the smart hydrogel in response to the changes in the ionic strength of bathing solution as an important measure of the ionic concentration of that solution, which is termed the multi-effect-coupling ionic-strength-stimulus (MECis) model. In the present works, the ionic strength is treated as a main stimulus and incorporated into both the ionic convection-diffusion system in the Nernst-Planck flux and the fixed charge density equation characterized by Langmuir isotherm theory. Due to the diffusion and convection, the osmotic pressure is produced by the difference in the ionic concentration between the interior hydrogel and exterior solution, which drives the swelling...

New Editor-in-Chief for Soil Dynamic and Earthquake EngineeringEngineering

Elsevier Updates: Engineering — Tue, 02 Mar 2010 00:00:00 +0100

Ahmed Elgamal has been appointed joint Editor-in-Chief of Soil Dynamics and Earthquake Engineering, alongside Prof Dimitri Beskos and Mustafa Erdik. (Source: Elsevier Updates: Engineering)

MedWorm Message: Get the very latest Swine Flu news via the MedWorm Swine Flu RSS news feed - updated hourly from thousands of authoritative health and news sources.

Award for Editor of Journal of Constructional Steel ResearchEngineering

Elsevier Updates: Engineering — Tue, 02 Mar 2010 00:00:00 +0100

Channel-Aware Decision Fusion With Unknown Local Sensor Detection Probability

IEEE Transactions on Signal Processing — Mon, 01 Mar 2010 00:00:00 +0100

Existing channel-aware decision fusion schemes assume that the local detection probability is known at the fusion center (FC). However, this paradigm ignores the possibility of unknown sensor alarm responses to the occurrence of events. Accordingly, this correspondence examines the binary decision fusion problem under the assumption that the local detection probability is unknown. Treating the communication links between the nodes and the FC as binary symmetric channels and assuming that the sensor nodes transmit simple one-bit reports to the FC, the global fusion rule is formulated initially in terms of the generalized likelihood ratio test (GLRT). Adopting the assumption of a high SNR regime, an approximate maximum likelihood (ML) estimate is derived for the unknown parameter required to...

Resolution Enhancement in Learners for Superresolution Source Separation

IEEE Transactions on Signal Processing — Mon, 01 Mar 2010 00:00:00 +0100

Many source separation algorithms fail to deliver robust performance when applied to signals recorded using high-density sensor arrays where the distance between sensor elements is much less than the wavelength of the signals. This can be attributed to limited dynamic range (determined by analog-to-digital conversion) of the sensor which is insufficient to overcome the artifacts due to large cross-channel redundancy, nonhomogeneous mixing, and high-dimensionality of the signal space. This paper proposes a novel framework that overcomes these limitations by integrating statistical learning directly with the signal measurement (analog-to-digital) process which enables high fidelity separation of linear instantaneous mixtures. At the core of the proposed approach is a min-max optimization of ...

Convolution on the -Sphere With Application to PDF Modeling

IEEE Transactions on Signal Processing — Mon, 01 Mar 2010 00:00:00 +0100

In this paper, we derive an explicit form of the convolution theorem for functions on an n -sphere. Our motivation comes from the design of a probability density estimator for n -dimensional random vectors. We propose a probability density function (pdf) estimation method that uses the derived convolution result on Sn. Random samples are mapped onto the n -sphere and estimation is performed in the new domain by convolving the samples with the smoothing kernel density. The convolution is carried out in the spectral domain. Samples are mapped between the n-sphere and the n-dimensional Euclidean space by the generalized stereographic projection. We apply the proposed model to several synthetic and real-world data sets and discuss the results. (Source: IEEE Transactions on Signal Processing)

Robust Estimation of a Random Parameter in a Gaussian Linear Model With Joint Eigenvalue and Elementwise Covariance Uncertainties

IEEE Transactions on Signal Processing — Mon, 01 Mar 2010 00:00:00 +0100

We consider the estimation of a Gaussian random vector ${mmb x}$ observed through a linear transformation ${mmb H}$ and corrupted by additive Gaussian noise with a known covariance matrix, where the covariance matrix of ${mmb x}$ is known to lie in a given region of uncertainty that is described using bounds on the eigenvalues and on the elements of the covariance matrix. Recently, two criteria for minimax estimation called difference regret (DR) and ratio regret (RR) were proposed and their closed form solutions were presented assuming that the eigenvalues of the covariance matrix of ${mmb x}$ are known to lie in a given region of uncertainty, and assuming that the matrices ${mmb H}^{T}{mmb C}_{mmb w}^{-{bf 1}}{mmb H}$ and ${mmb C}_{mmb x}$ are jointly diagonalizable, where ${mmb C}_{mmb ...

MedWorm Message: Get the very latest Swine Flu news via the MedWorm Swine Flu RSS news feed - updated hourly from thousands of authoritative health and news sources.

IEEE Transactions on Medical Imaging information for authors