Anatomical data fusion for quantitative reconstruction inmyocardial tomoscintigraphy using a spline model of the thorax organs

The authors present the fusion of anatomical data as a method for improving the reconstruction in single photon emission computed tomography (SPECT). Anatomical data is used to deduce a parameterized model of organs in a reconstructed slice using spline curves. This model allows the authors to define the imaging process, i.e., the direct problem, more adequately, and furthermore to restrict the reconstruction to the emitting zones. Instead of the usual square pixels, the authors use a new kind of discretization pixel, which fits to the contour in the region of interest. In the reconstruction phase, the authors estimate the activity in the emitting zones and also the optimum parameters of their model. Concentrating on the left ventricular (LV) wall activity, the simulation and phantom results show an accurate estimation of both the myocardial shape and the radioactive emission     

Technological and environmental behavior of sewage sludge ash (SSA) in cement-based materials

Sewage sludge ash (SSA) is a waste material obtained from the incineration of wastewater sludge. The physical, chemical and mineralogical characteristics of SSA, and the evaluation of its use in cement-based materials, are presented in this paper. Results show that SSA is composed of irregular grains having a high specific surface area and thus leading to a significantly high water demand. A fraction of the ash is rapidly soluble (sulfates, aluminum and silica) and can create new-formed products in presence of lime. SSA induces short delays of cement hydration, probably due to both minor elements of the ash and dilution effect. Compressive strengths of mortars containing 25% and 50% of SSA are always lower than those of reference mortars but it is shown that SSA has a long-term positive effect which might be related to a slight pozzolanic activity. The amount of elements leached from SSA mortars is slightly higher than from the reference mortar without residue but it remains of the same order of magnitude. An extensive literature review was performed in order to compare the residue used in this study with others included in the same category. This analysis highlighted the principal characteristics that must be taken into account to use SSA correctly in cement-based materials.     

Characteristics of industrial and laboratory meat and bone meal ashes and their potential applications

This paper reports the characterization of four meat and bone meal (MBM) ashes obtained from specific incineration (laboratory) and from co-incineration (industrial process). Three out of the four MBM ashes were mainly composed of calcium phosphates (hydroxyapatite and whitlockite). Their compositions (major and trace) were in the range for natural phosphate rocks. Trace element contents, including heavy metals, were below 0.6% and industrial ashes contained much more heavy metals than laboratory ash. The amounts of leached elements were low, especially for laboratory ash. According to the European classification of waste to be landfilled, the laboratory ash can be classified as an inert waste. Two industrial ashes are mostly inert. Only one ash is highly leachable and needs a stabilization treatment to be classified at least in the category of hazardous waste. It seems, from these results, that possibilities other than landfilling could be considered to give economic value to these ashes.     

Experimental study of the viscoelastic properties of green poplar wood during maturation

During the radial growth of trees, internal stresses are created because of wood-cell maturation. Biomechanical models can compute these stresses, but they are currently limited by a lack of knowledge about the viscoelastic behavior of green wood. The aim of the present paper is to study the viscoelastic behavior of green wood and to obtain measurements of viscoelastic parameters. In order to accomplish this, the effect of internal maturation stresses on the studied samples was first eliminated by studying viscoelastic phenomena. Creep tests were then performed on small slats of wood using a cantilever bending test. It is shown that green wood viscoelastic behavior can be modeled with Burgers’ model. The corresponding parameters are estimated with respect to the wood-cells age. No significant difference between tension wood and normal wood is revealed, but it appears that green wood tends to lose its viscoelastic behavior with maturation.     

Morphological responses and molecular modifications in tomato plants after mechanical stimulation

Study of the growth responses of Lycopersicon esculentum (Mill. cv. VFN8) to mechanical stimulation applied to a single young internode showed a rapid and sharp decrease in stem elongation and an inhibition of elongation of several internodes, indicative of information transmission in the plant. A new tomato cDNA partial clone encoding calmodulin was isolated and used to study the time course of the gene induction in response to the rubbing treatment. Northern blot analysis showed a maximum accumulation of calmodulin mRNA 2 h after mechanical stimulation, not only in the rubbed internode, but also in upper and lower internodes and in young leaves. Treatment of the plant with calcium and EGTA showed the involvement of calcium and, in particular, intracellular calcium in calmodulin gene expression and cellular response.     

A new test method to assess the bacterial deterioration of cementitious materials

The biodegradation of cement-based matrices by agro-industrial effluents is a very complex phenomenon. In this work, a test was developed – the Build-Mat Bio-test (BMB test) – to examine the degradation mechanisms caused by microbial activity on any type of building material. The main objective of this device was to analyze and distinguish between the effects caused by the bacteria and those caused by their metabolites in the deterioration. In this study, the BMB test was used to evaluate the impact on cementitious matrices of the bacterium Escherichia coli, found in liquid manure. The mechanisms and kinetics of deterioration resulting from exposure to the bacterial culture or to the metabolites were compared with those obtained with synthetic organic acids alone. It was notably observed that the bacterial suspension caused more intense deterioration and higher alteration kinetics as compared to the medium without microorganisms and to the synthetic acid solution.     

Longitudinal Creep Behaviour of a SiC/Ti-6242 Composite in a Vacuum Atmosphere

This study deals with the longitudinal creep behaviour of a unidirectionally reinforced SM1140+/Ti-6242 composite at 500C in a vacuum atmosphere. The monitoring of acoustic emission and microstructural observations show that filament fracture develops during the creep test. This damage results from the stress relaxation in the matrix, which increases the axial stress in the filament. Time till the creep rupture can be predicted with a model describing the filament damage accumulation.