Characterization of repolarization alternans during ischemia: time-course and spatial analysis

T-wave alternans (TWA) has been linked to increased vulnerability to ventricular fibrillation in different settings including myocardial ischemia. In this study, we propose a methodology for the characterization of TWA induced by transient, regional ischemia. We studied the prevalence, magnitude and spatio-temporal relationship between TWA and ischemia in 95 patients undergoing percutaneous transluminal coronary angioplasty (PTCA). Two electrocardiogram records of each patient, a control recording before PTCA and the PTCA record, were analyzed using a robust, recently proposed method for TWA analysis. The detected episodes were characterized in terms of their time-course, lead distribution and alternans waveform. One third of the patients (33.7%) showed TWA episodes during PTCA. The highest prevalence (51.7%) and amplitude were found in patients with left anterior descendent artery occlusion. The onset of TWA was detected after the first 1-2 min of occlusion, suggesting that some level of ischemia must be attained before TWA arises, while disappearance of TWA following reperfusion was much more rapid. The TWA lead distributions and waveforms showed distinct distributions according to the occluded artery reflecting the regional nature of the TWA phenomenon.     

Effect of dietary crude protein concentration on ruminal nitrogen metabolism in lactating dairy cows

Ten lactating Holstein cows fitted with ruminal cannulas that were part of a larger feeding trial were blocked by days in milk into 2 groups and then randomly assigned to 1 of 2 incomplete 5 × 5 Latin squares. Diets contained [dry matter (DM) basis] 25% alfalfa silage, 25% corn silage, and 50% concentrate. Rolled high-moisture shelled corn was replaced with solvent-extracted soybean meal to increase crude protein (CP) from 13.5% to 15.0, 16.5, 17.9, and 19.4% of DM. Each of the 4 experimental periods lasted 28 d with data and sample collection performed during the last 8 d. Digesta samples were collected from the omasum to quantify the ruminal outflow of different N fractions. Intake of DM was not affected but showed a quadratic trend with maxima of 23.9 kg/d at 16.5% CP. Ruminal outflow of total bacterial nonammonia N (NAN) was not different among diets but a significant linear effect of dietary CP was detected for this variable. Bacterial efficiency (g of total bacterial NAN flow/kg of organic matter truly digested in the rumen) and omasal flows of dietary NAN and total NAN also showed positive linear responses to dietary CP. Total NAN flow increased from 574 g/d at 13.5% CP to 688 g/d at 16.5% CP but did not increase further with the feeding of more CP. Under the conditions of this study, 16.5% of dietary CP appeared to be sufficient for maximal ruminal outflow of total bacterial NAN and total NAN.     

Optimising the inactivation of grape juice spoilage organisms by pulse electric fields

The effect of some pulsed electric field (PEF) processing parameters (electric field strength, pulse frequency and treatment time), on a mixture of microorganisms (Kloeckera apiculata, Saccharomyces cerevisiae, Lactobacillus plantarum, Lactobacillus hilgardii and Gluconobacter oxydans) typically present in grape juice and wine were evaluated. An experimental design based on response surface methodology (RSM) was used and results were also compared with those of a factorially designed experiment. The relationship between the levels of inactivation of microorganisms and the energy applied to the grape juice was analysed. Yeast and bacteria were inactivated by the PEF treatments, with reductions that ranged from 2.24 to 3.94 log units. All PEF parameters affected microbial inactivation. Optimal inactivation of the mixture of spoilage microorganisms was predicted by the RSM models at 35.0 kV cm^− 1 with 303 Hz pulse width for 1 ms. Inactivation was greater for yeasts than for bacteria, as was predicted by the RSM. The maximum efficacy of the PEF treatment for inactivation of microorganisms in grape juice was observed around 1500 MJ L^− 1 for all the microorganisms investigated. The RSM could be used in the fruit juice industry to optimise the inactivation of spoilage microorganisms by PEF.     

Sintering behaviour and mechanical characterisation of Ti64/xTiN composites and bilayer components

Ceramic particle reinforcement can be used to improve the surface properties of Ti6Al4V (Ti64) alloy. Powder metallurgy route is a promising method to fabricate such reinforced Ti64 components. To assess the relevance of this technique, this work investigates the effect generated by the addition of TiN particles in Ti64 powder during free sintering. TiN reinforcement particles were randomly distributed in the Ti64 matrix with three different concentrations in two configurations: completely reinforced and unreinforced–reinforced bilayer. Dilatometry was used to obtain the shrinkage kinetics of samples at 1200, 1300 and 1400°C under inert atmosphere and to investigate the impact of reinforced particles on the sintering behaviour. The microstructure of sintered materials was shown to be lamellar in the unreinforced material and equiaxed in reinforced materials. Finally, the Vickers microhardness measurement showed the huge benefit of adding TiN particles to increase the mechanical strength of the Ti64 alloy.     

Composites formed by glass fibers and PS‐modified epoxy matrix. Influence of the glass fibers surface on the morphologies and mechanical properties of the interphases generated

In this work, the influence of the nature of the reinforcement surface on the interfacial morphologies developed in E‐glass fibers/polystyrene (PS)‐modified epoxy composites has been studied. Different surface modifications of the fibers were considered. In a complementary way, morphological analysis and nanoindentation measurements were carried out using atomic force microscopy to subsequently correlate the interfacial structure with the morphologies observed. In every composite, reaction‐induced phase separation happened with a morphology composed of PS‐rich domains immersed in an epoxy‐rich phase. However, depending on the surface modification of the glass fibers, different distributions of PS‐rich domains at the interfaces were obtained. The results were interpreted in terms of a gradual phase separation process because of stoichiometric gradients from the glass fibers surface to the matrix bulk caused by specific segregation of one of the components of the reactive epoxy mixture to the fibers occurs. It was concluded that specific and controlled reinforcement modification allows obtaining tailored interfaces formed by a polymer blend and a reinforcement in which the morphology can be previously selected. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers     

Technetium-99m dimercaptosuccinic acid and ifosfamide tubular dysfunction in children with cancer

Quantitative 99mTc-dimercaptosuccinic acid (99mTc-DMSA) renal scintigraphy was used to asses ifosfamide-induced changes in renal function in 11 children who received chemotherapy for various malignancies. Serial measurements of absolute 99mTc-DMSA renal uptake, calculated on conjugated views, were performed during and after chemotherapy. Data of 37 studies obtained before and at different cumulative dose levels of ifosfamide were analysed in relation to clinical and biochemical parameters. A highly significant relationship between 99mTc-DMSA uptake and cumulative ifosfamide dose was found (P < 0.001). The most frequently observed abnormal pattern on scintigraphic images was decreased kidney uptake together with increased accumulation in bladder. 99mTc-DMSA uptake was more consistent than beta 2-microglobulin values in urine and more sensitive than quantitative hyperaminoaciduria and tubular resorption of phosphate for the detection of ifosfamide-induced tubular dysfunction. 99mTc-DMSA uptake was decreased in both patients with and patients without clinical toxicity. Persistently reduced 99mTc-DMSA uptake was observed in four patients during follow-up; in one of them, who was asymptomatic after ifosfamide therapy, sudden onset of Fanconi syndrome was observed when he was retreated with carboplatin 1 year later. It is concluded that 99mTc-DMSA renal scintigraphy is a suitable method to assess progressive ifosfamide-induced tubular injury whereas scintigraphic imaging is helpful for interpreting renal uptake changes. The test is able to detect subclinical injury and may potentially predict high risk at retreatment.     

Registration of Anatomical Images Using Paths of Diffeomorphisms Parameterized with Stationary Vector Field Flows

Computational Anatomy aims for the study of variability in anatomical structures from images. Variability is encoded by the spatial transformations existing between anatomical images and a template selected as reference. In the absence of a more justified model for inter-subject variability, transformations are considered to belong to a convenient family of diffeomorphisms which provides a suitable mathematical setting for the analysis of anatomical variability. One of the proposed paradigms for diffeomorphic registration is the Large Deformation Diffeomorphic Metric Mapping (LDDMM). In this framework, transformations are characterized as end points of paths parameterized by time-varying flows of vector fields defined on the tangent space of a Riemannian manifold of diffeomorphisms and computed from the solution of the non-stationary transport equation associated to these flows. With this characterization, optimization in LDDMM is performed on the space of non-stationary vector field flows resulting into a time and memory consuming algorithm. Recently, an alternative characterization of paths of diffeomorphisms based on constant-time flows of vector fields has been proposed in the literature. With this parameterization, diffeomorphisms constitute solutions of stationary ODEs. In this article, the stationary parameterization is included for diffeomorphic registration in the LDDMM framework. We formulate the variational problem related to this registration scenario and derive the associated Euler-Lagrange equations. Moreover, the performance of the non-stationary vs the stationary parameterizations in real and simulated 3D-MRI brain datasets is evaluated. Compared to the non-stationary parameterization, our proposal provides similar results in terms of image matching and local differences between the diffeomorphic transformations while drastically reducing memory and time requirements.     

KMoS-RE: knowledge management on a strategy to requirements engineering

This paper introduces the KMoS-RE Strategy, a novel requirements engineering strategy to Informal Structured Domains. Requirements engineering aims to elicit, analyze, evaluate, consolidate, and manage the requirements of a software system. The complexity of this process depends on the application domain. In Informal Structured Domains, not all concepts and their relations are formally defined, most of the problems do not have algorithms to obtain solutions, and the domain specialists use large amounts of tacit knowledge to solve problems. These characteristics generate ambiguous, inappropriate, and incomplete requirements. It could generate an inadequate software solution, or it could be the cause of increasing the project development time. Therefore, it is important to use an appropriate requirements engineering strategy to minimize these problems. The objective of this study is to present the Knowledge Management on a Strategy to Requirements Engineering (KMoS-RE Strategy): a novel requirements engineering strategy oriented to the transformation and transference of knowledge, and with the aim to minimize the percentage of ambiguous, incomplete, and inappropriate requirements. The functionality and utility of the strategy is explained through its application to a real case study. The case study shows that using the KMoS-RE Strategy helps to internalize the domain knowledge, to clarify the solution idea, to reduce the ignorance of symmetry, to structure the domain knowledge, and to detect and correct wrong beliefs about the domain. All of these are performed in the early stage of the project development.