Oregano: properties, composition and biological activity

The oregano spice includes various plant species. The most common are the genus Origanum, native of Europe, and the Lippia, native of Mexico. Among the species of Origanum. their most important components are the limonene, gamma-cariofilene, rho-cymenene, canfor, linalol, alpha-pinene, carvacrol and thymol. In the genus Lippia, the same compounds can be found. The oregano composition depends on the specie, climate, altitude, time of recollection and the stage of growth. Some of the properties of this plant's extracts are being currently studied due to the growing interest for substituting synthetic additives commonly found in foods. Oregano has a good antioxidant capacity and also presents antimicrobial activity against pathogenic microorganisms like Salmonella typhimurium, Escherichia coli, Staphylococcus aureus, Staphylococcus epidermidis, among others. These are all characteristics of interest for the food industry because they may enhance the safety and stability of foods. There are also some reports regarding the antimutagenic and anticarcinogenic effect of oregano; representing an alternative for the potential treatment and/or prevention of certain chronic ailments, like cancer.     

Iodine content of cattle milk from mountain and coast from Perú

With the objective to establish the cause-effect relationship between a geological area and the iodine content in cattle milk, and to estimate the contribution of milk consumption to the dietary iodine intake, the iodine content in cattle milk from the sierra and the coastal regions of Perú was determined. Milk samples were collected of cows from the three main productive zones of Perú, 62 in Cajamarca, 42 in Arequipa, both in the sierra, and 27 in Lima at the coast. The measurement of iodine was made by the method of Zak, based on the Sandell- Kolthoff reaction. The median values obtained were 24 microg/L in Cajamarca, 34 microg/L in Arequipa, and 170 microg/L in Lima. The median value in the sierra, 26 microg/L, was significantly lower than the one found in the coast. Moreover, while in the former 81% of individual values were below 50 microg/L, in the latter, on the contrary, 77% were above 80 microg/L. These results confirm that the iodine content in cattle milk is related to ecological factors. At the same time, they demonstrate that the iodine content in milk from the sierra is six times lower than in milk from the coast, and also that its consumption does not contribute significantly to satisfy the human physiological requirements of iodine in that zone.     

Photocurable shape-memory polyether-polythioether/graphene nanocomposites and the study of their thermal conductivity

Herein a method is described to prepare photocurable thermally-conductive shape memory epoxy/ graphene composites. By photopolymerizing the epoxy resin diglycidyl ether of bisphenol A with an allyl-functionalized ditertiary amine as the curing agent, jointly with a multifunctional thiol, a crosslinked polyether-polythioether co-network was obtained. The presence of a soft domain like the flexible polythioethers enable the co-network to display shape memory properties. By varying the polyether to polythioether ratio it was possible to modulate the shape memory characteristics of the composite. The effect of the concentration of graphene nanoplatelets (GNP) in the composite was also investigated. Shape memory performances revealed excellent values of shape recovery and shape fixity with maximums of 98 and 99% respectively. The temporary- shaped composites with higher concentration of polythioethers and GNP regained their permanent shapes in 2–3 s when heated above the programming temperature. The thermal conductivity in the composites reached 0.39 W/m°K for the composite with 15% w/w of GNP. The presence of the polythioethers in the co-network enhanced the toughness of the composite as revealed by the impact resistance analysis.     

An energy consistent frictional dissipating algorithm for particle contact problems

An energy frictional dissipating algorithm (EFDA) for time integration of Coulomb frictional impact‐contact problems is presented. With the use of the penalty method, and in the context of a conserving framework, linear and angular momenta are conserved, and energy is consistently dissipated. Previously published formulations were stable, forcing the energy dissipation to be monotonic to prevent unstable energy growth. The shortcoming of many was that they were not able to reproduce the real kinematics and dissipation of physical processes, provided by analytical formulations and experiments. EFDA formulates a conserving framework on the basis of a physical energy dissipation estimator. This framework uses an enhanced penalty contact model based on a spring and a dashpot, enforcing physical frictional energy dissipation, controlling gap vibrations, and modifying the velocities and contact forces during each time step. The result is that the dissipated energy, kinematics, and contact forces are consistent with the expected physical behavior. Energy frictional dissipating algorithm has been applied to four rigid‐body frictional problems using the discrete element method. The first problem is the analysis of a disk moving on a flat rough surface; the second problem analyzes the kinematics and energy dissipation of elliptical particle impacts. Numerical solutions are compared with analytical ones in both problems. The motion and impact of two disks moving on a semicircular surface are studied in the third problem. Finally, the fourth problem simulates the collapse of a two‐dimensional granular column, which is compared with the experimental results. Copyright © 2012 John Wiley & Sons, Ltd.     

Bacterial Kinetics of Sulfur Oxidizing Bacteria and Their Biodeterioration Rates of Concrete Sewer Pipe Samples

The importance of bacteria in catalyzing microbially induced concrete corrosion was evaluated. Experiments were conducted to determine the optimum pH and growth kinetics of four selected bacterial strains (Thiobacillus neapolitanus C2, Thiobacillus thioparus H1, Acidithiobacillus thiooxidans, and Acidiphilium cryptum LHET2). Combinations of these strains were inoculated into flasks containing ～ 42?g concrete blocks half-submerged in 600 mL of synthetic wastewater with hydrogen sulfide in the headspace air. Controls not inoculated with bacteria lost 0–3 mg/g concrete over 227 days; in the aqueous phase the minimum pH was 6–6.7 and 19–23 mg of calcium/g concrete was released. Systems inoculated with two species of neutrophilic sulfur oxidizing microorganisms (SOM) lost 8 mg/g concrete; in the aqueous phase the minimum pH was 4.5 and 25 mg of calcium/g concrete was released. The concrete samples incubated with neutrophilic and acidophilic SOM and an acidophilic heterotroph experienced the greatest deterioration, with a total mass loss of 13 mg/g concrete, minimum aqueous pH of 3.0, 28 mg calcium/g concrete released, and 47 mg sulfate/g concrete produced.     

Fatigue design of wire-wound pressure vessels using ASME-API 579 procedure

The wire winding of high pressure vessels is a technique usually applied to introduce initial compressive stresses in the inner core of the vessel, with the aim to improve the fatigue life under cyclic pressure conditions. In this work, the procedure followed to calculate the number of design cycles is presented, using the fracture mechanics approach and the structural integrity concepts. In particular, the API 579-1/ASME FFS-1 procedure has been used to analyse the structural integrity of the vessel through the crack propagation stage. Starting from a postulated internal semi-elliptical crack the number of design cycles is determined, the flaw aspect ratio is updated and the structural integrity of the cracked vessel is evaluated using the Failure Assessment Diagram (FAD). Different propagation laws, which take into account for negative stress intensity ratio factors R = K_min/K_max < 0, are reviewed, because of their high influence on the fatigue life of wire-wound vessels. In addition, this paper presents a number of useful expressions to calculate the stress intensity factor (SIF) for internal semi-elliptical cracks in wire-wound pressure vessels, in order to carry out the numerical integration of the number of cycles, updating the flaw aspect ratio, during the fatigue crack growth.     

Development of engineered cementitious composites with limestone powder and blast furnace slag

Nowadays limestone powder and blast furnace slag (BFS) are widely used in concrete as blended materials in cement. The replacement of Portland cement by limestone powder and BFS can lower the cost and enhance the greenness of concrete, since the production of these two materials needs less energy and causes less CO₂ emission than Portland cement. Moreover, the use of limestone powder and BFS improves the properties of fresh and hardened concrete, such as workability and durability. Engineered cementitious composites (ECC) is a class of ultra ductile fiber reinforced cementitious composites, characterized by high ductility, tight crack width control and relatively low fiber content. The limestone powder and BFS are used to produce ECC in this research. The mix proportion is designed experimentally by adjusting the amount of limestone powder and BFS, accompanied by four-point bending test and uniaxial tensile test. This study results in an ECC mix proportion with the Portland cement content as low as 15% of powder by weight. This mixture, at 28 days, exhibits a high tensile strain capacity of 3.3%, a tight crack width of 57 μm and a moderate compressive strength of 38 MPa. In order to promote a wide use of ECC, it was tried to simplify the mixing of ECC with only two matrix materials, i.e. BFS cement and limestone powder, instead of three matrix materials. By replacing Portland cement and BFS in the aforementioned ECC mixture with BFS cement, the ECC with BFS cement and limestone powder exhibits a tensile strain capacity of 3.1%, a crack width of 76 μm and a compressive strength of 40 MPa after 28 days of curing.