Image registration and atlas-based segmentation of cardiac outflow velocity profiles

Cardiovascular disease is the leading cause of death worldwide and for this reason computer-based diagnosis of cardiac diseases is a very important task. In this article, a method for segmentation of aortic outflow velocity profiles from cardiac Doppler ultrasound images is presented. The proposed method is based on the statistical image atlas derived from ultrasound images of healthy volunteers. The ultrasound image segmentation is done by registration of the input image to the atlas, followed by a propagation of the segmentation result from the atlas onto the input image. In the registration process, the normalized mutual information is used as an image similarity measure, while optimization is performed using a multiresolution gradient ascent method. The registration method is evaluated using an in-silico phantom, real data from 30 volunteers, and an inverse consistency test. The segmentation method is evaluated using 59 images from healthy volunteers and 89 images from patients, and using cardiac parameters extracted from the segmented image. Experimental validation is conducted using a set of healthy volunteers and patients and has shown excellent results. Cardiac parameter segmentation evaluation showed that the variability of the automated segmentation relative to the manual is comparable to the intra-observer variability. The proposed method is useful for computer aided diagnosis and extraction of cardiac parameters.     

Static and dynamic 3D facial expression recognition: A comprehensive survey

Automatic facial expression recognition constitutes an active research field due to the latest advances in computing technology that make the user's experience a clear priority. The majority of work conducted in this area involves 2D imagery, despite the problems this presents due to inherent pose and illumination variations. In order to deal with these problems, 3D and 4D (dynamic 3D) recordings are increasingly used in expression analysis research. In this paper we survey the recent advances in 3D and 4D facial expression recognition. We discuss developments in 3D facial data acquisition and tracking, and present currently available 3D/4D face databases suitable for 3D/4D facial expressions analysis as well as the existing facial expression recognition systems that exploit either 3D or 4D data in detail. Finally, challenges that have to be addressed if 3D facial expression recognition systems are to become a part of future applications are extensively discussed.     

Software quality improvement: a model based on managing factors impacting software quality

Software quality is recognized as being very significant for achieving competitiveness in the software industry, so improvements in this area are gaining increasing importance. Software quality improvements can only be achieved by managing all of the factors that influence it. However, in a real business system, there are a great number of factors impacting software quality, while the processes are stochastic and resources are limited, so economic data should also be taken into consideration. This paper uses a Markov chain and proposes a systematic framework for modelling the stochastic processes of a quality management system and selection of the optimum set of factors impacting software quality. A methodology is presented for managing the factors that affect software quality with an illustrative hypothetical example for convenience of application of the proposed methodology.     

An optimization approach to adaptive Kalman filtering

In this paper, an optimization-based adaptive Kalman filtering method is proposed. The method produces an estimate of the process noise covariance matrix Q by solving an optimization problem over a short window of data. The algorithm recovers the observations h(x) from a system without a priori knowledge of system dynamics. Potential applications include target tracking using a network of nonlinear sensors, servoing, mapping, and localization. The algorithm is demonstrated in simulations on a tracking example for a target with coupled and nonlinear kinematics. Simulations indicate superiority over a standard MMAE algorithm for a large class of systems.     

SAS and R functions to compute pseudo-values for censored data regression

Recently, in a series of papers, a method based on pseudo-values has been proposed for direct regression modeling of the survival function, the restricted mean and cumulative incidence function with right censored data. The models, once the pseudo-values have been computed, can be fit using standard generalized estimating equation software. Here we present SAS macros and R functions to compute these pseudo-values. We illustrate the use of these routines and show how to obtain regression estimates for a study of bone marrow transplant patients.     

Relative survival analysis in R

Relative survival techniques are used to compare the survival experience in a study cohort with the one expected should they follow the background population mortality rates. The techniques are especially useful when the cause-specific death information is not accurate or not available since they provide a measure of excess mortality in a group of patients with a certain disease. There are several approaches to modeling relative survival, but there is no widely used statistical package that would incorporate the relevant techniques. The existing software was mostly written by the authors of different methods, in different computer languages and with different requirements for the data input, which makes it almost impossible for a user to choose between available models. We describe our R package relsurv that provides functions for easy and flexible fitting of several relative survival regression models.     

Local and Global Lyapunov Exponents of Blood Flow

The Lyapunov exponents are calculated from numerically simulated and measured time series. The existing algorithms for the estimation of Lyapunov spectra have free parameters. Hence, their influence is analysed on various chaotic and quasi-periodic simulated signals. Furthermore, the exponents of a blood flow signal, measured on a healthy subject, are calculated over a wide range of parameter values. For the embedding dimension d 10, two typical spectra are observed for both the global and the local Lyapunov exponents. There are either 4 paired and 1 zero, or 5 paired exponents. At least one exponent equals zero within the calculation error.     

Lipase-catalyzed esterification of citronellol with lauric acid in supercritical carbon dioxide/co-solvent media

Direct esterification of citronellol and lauric acid catalyzed by immobilized lipase B from Candida antarctica was performed in supercritical carbon dioxide with different organic solvents and ionic liquids serving as co-solvents. The highest concentration of citronellol laurate after 1 h of reaction performance (3.95 mmol/g substrates) was obtained in SC CO₂ with ethyl methylketone serving as a co-solvent. The optimal temperature and pressure for citronellol laurate synthesis in SC CO₂/EMK medium was determined to be 60 °C and 10 MPa.     

The effect of electrolyte flow rate and temperature on corrosion and protection of Al–2.5 Mg alloy by (+)-catechin

The effects of flow rate and temperature on the corrosion behaviour of the Al–2.5 Mg alloy in a 3% NaCl solution and the inhibiting efficiency of (+)-catechin on the corrosion of the same alloy have been examined. Measurements were carried out in a flow-through cell, at different flow rates (v ₁ = 0.0029 m s⁻¹, v ₂ = 0.0059 m s⁻¹ and v ₃ = 0.0118 m s⁻¹) and temperatures (20, 30, 40 °C). Electrochemical parameters for the Al–2.5 Mg alloy were determined by polarisation techniques and electrochemical impedance spectroscopy (EIS). Increased flow rate and temperature cause a stronger corrosion attack on the alloy. The addition of (+)-catechin inhibited corrosion at all temperatures and flow rates. The inhibitor efficiency decreased with increase in flow rate and temperature.     

Dissolution of pastes in lead-acid battery recycling plants

The dissolution of the active materials of lead-acid batteries in fluoboric electrolyte has been studied. The use of redox couples such as Ti³⁺/Ti⁴⁺ is proposed for an efficient and quick dissolution of lead and lead dioxide mixtures. For PbO₂ and Pb electrodeposited on platinum electrodes the rate of dissolution in HBF₄ (200 g dm⁻³) containing Ti ions (0.3m) corresponds to a current density of 400 A cm⁻² and 160 A cm⁻², respectively. Dissolved oxygen has a marked influence on lead dissolution acting as an oxidizer of Ti³⁺ to Ti⁴⁺. It has also been shown that the Fe²⁺/Fe³⁺ couple can be used, although with lower benefits. For industrial applications, a concentration of Ti ions of about 0.051m and the use of a counter-current electrolyte flow in the electrolysis cell can advantageously accomplish the leaching process of pastes and slimes in a batteries recycling plant.