Analysis of mixed-mode fracture in concrete using interface elements and a cohesive crack model

The paper presents a model, based on nonlinear fracture mechanics, for analysing crack propagation in quasi-brittle materials, such as concrete. The work is limited to two-dimensions, and therefore, the fracture modes of interest are mode I (pure tension) and mode II (pure shear). The constitutive model has been implemented in the context of the finite element method using interface elements. The fracture is simulated through a discrete crack represented by the interface with a cohesive crack stress-separation relation derived from the model, which is based on a fracture criterion, together with a flow rule and a softening law. The model is used for simulating results from an experimental study on beams with centric and eccentric notches of high and normal strength concretes, and explaining other test results available in the literature.     

Effects of high molybdenum intake on 1,2-dimethylhydrazine-induced intestinal tumors in rats

Wistar male rats, 3 months of age were given ad-libitum a nutritionally adequate diet and demineralized drinking water. The Molybdenum (Mo) and Tungsten (W) were provided in the drinking water at 200 ppm concentration. Intestinal tumors were induced by 1,2-dimethylhydrazine (DMH) given subcutaneously as 16 weekly doses at 20 mg/kg body weight. Mo in the form of (NH₄)₆ Mo₇O₂₄ 4H₂O or W in the form of (Na₂ WO₄) were provided in the drinking water two months before the first DMH treatment and were continued during 4 months more until the last DMH treatment. Three months after the last carcinogen injection, all animals were sacrificed and examined for intestinal tumors. The number, size and location of the tumors were recorded and the pathology was examined. The addition of Mo to the drinking water induced an increase of hepatic Mo content. At the end of the second month, the hepatic content of Mo was 5.61 ppm, compared with control and W groups (2.18 and 0.96 ppm, respectively). A significantly lower incidence of tumors was observed in the Mo group (47), compared with the control group given DMH alone (105) and W group (113). On the other hand, the Mo group showed a significant decrease in the numbers of multiple tumors per rat.     

Compositional Analysis of Oil Samples Implicated in the Spanish Toxic Oil Syndrome

A selected group of 195 oils from the Spanish “Toxic Oil” Syndrome (TOS) epidemic including 29 high-probability “case” and 64 “control” oils were examined to investigate the relationship between oil composition and the risk of TOS. As indicated by fatty acid and sterol patterns, the presence of rapeseed oil was significantly more prevalent in the case than in the control oils, but fatty acid anilides were the most useful markers of case-related samples. Anilides were detected in 62% of case oils and at lower concentrations in 23% of the control samples. The ratios of individual anilides were quite constant in these oils and most consistent with their formation in the original (undiluted) rapeseed oil.     

MODELING THE INACTIVATION KINETICS OF ESCHERICHIA COLI O157:H7 DURING THE STORAGE UNDER REFRIGERATION OF APPLE JUICE TREATED BY PULSED ELECTRIC FIELDS

The aim was to describe the inactivation kinetics of Escherichia coli O157:H7 suspended in apple juice after pulsed electric fields (PEF) and a subsequent storage under refrigeration. Escherichia coli O157:H7 showed a great PEF resistance in apple juice, when survivors were evaluated immediately after PEF. However, PEF-treated cells exhibited a great sensitivity to a subsequent holding in apple juice for 3 days. For instance, although a PEF treatment of 80 pulses at 35.0 kV/cm inactivated less than 0.5 log₁₀ cell cycles, the maintenance of the samples up to 3 days at 4C caused an inactivation of 5.0 log₁₀ cycles. An equation based on the Weibullian-like distribution accurately described the kinetics of cell inactivation.

PRACTICAL APPLICATIONS

The storage time influences the pulsed electric fields (PEF) inactivation of Escherichia coli O157:H7 cells suspended in apple juice. The potential of Weibullian-like distributions to describe survival curves with deviations in their linearity has allowed us to obtain an equation that accurately describes the complete PEF survival profile of E. coli in apple juice, when survivors were evaluated immediately after PEF and also after a subsequent storage under refrigeration. These results underline the possibility of applying PEF to pasteurize acidic foods by taking into account the postprocessing effect of the acidity of the product.     

A method to simulate the optical image from far-field scattering numerical data and its application to the total internal reflection microscopy of metallic nanowires

Computational electrodynamics modelling plays an important role in understanding and designing new photonic devices. The results offered by these simulations are usually close-range field distributions or angular power emission plots. We describe a procedure to compute the optical microscopy image from simulated far-field scattering data using three-dimensional discrete Fourier transforms that can be used when the simulation software package do not include proper far-field to optical imaging projection routines. The method is demonstrated comparing simulated images with real images of nanowires obtained with a total internal reflection microscope.     

Ready to migrate? Reading cellular signs of migration in an epithelial to mesenchymal transition model

The epithelial to mesenchymal transition (EMT) is a cellular program that drives de-differentiation of cells in both physiological and pathological processes. One of the characteristics of cells describing an EMT is the (re)acquisition of a motility capacity that allows them to migrate through the original tissue as well as to other sites in the organism. The molecular mechanisms that control the EMT are rapidly emerging and here we add to the idea that the adaptation required for cells to commit to the EMT includes adjustments of the translation machinery and metabolic pathways to cope with a high demand of extracellular components.     

Bioconversion of Shellfish Chitin Waste: Waste Pretreatment, Enzyme Production, Process Design, and Economic Analysis

Study of pretreatment of shrimp processing waste for a chitin bioconversion scheme to produce yeast single-cell protein established conditions for size reduction, deproteination, and demineralization. Enzymatic hydrolysis of pretreated chitin waste achieved 80% conversion in 24 hr. Optimum temperature and pH were determined for maximum chitinase production in submerged culture, using pretreated chitin waste as substrate. An integrated process scheme for conversion of shrimp shell chitin waste to yeast single-cell protein based on these and previous results was designed and analyzed economically, giving a negative after-tax cash flow of $0.06 per kg of wet waste.