Implementation and validation of a triaxiality dependent cohesive model: experiments and simulations

A recently formulated triaxiality dependent cohesive model for plane strain is implemented and its versatility is tested in simulation of ductile fracture of mild steel at different states of stress. The triaxiality dependent model was implemented as linear displacement formulation based elements whose constitutive behaviour was dependent on the stress-state of the neighbouring continuum element. By comparing the experimental data and predictions of corresponding plane strain simulations, the model parameters are estimated. The model is shown to be effective in reproducing characteristic features of the macroscopic response of both pre-cracked as well as geometries without a preexisting nominal defect. Since the model parameters are held constant for simulations at different stress-states, they are effectively material constants.     

Bioadhesive Ranitidine Hydrochloride for Gastroretention with Controlled Microenvironmental pH

Ranitidine hydrochloride is a H₂ receptor blocker used in the treatment of gastric ulcers. Pharmacological factors, in addition to the dosage regimen, favor development of a sustained-release system for ranitidine especially in the therapeutic condition of erosive esophagitis. This investigation delves into the development of bioadhesive type of gastroretentive formulation (tablets) of ranitidine. The effect of mucoadhesive polymers such as Carbopol, hydroxypropyl methyl cellulose, and dextrose were studied. Mucoadhesion, in vitro drug release profile, water uptake, and swelling of the tablet were evaluated. Alkalizing agents were incorporated in an attempt to maintain an alkaline microenvironment within the tablet and improve the stability of the drug in acidic medium. The stability was evaluated using dye test and degradation studies. The drug release profiles were fit into various kinetic models.     

Application of In Situ Neutron and X-Ray Measurements at High Temperatures in the Development of Co-Re-Based Alloys for Gas Turbines

Co-Re alloy development is prompted by the search for new materials for future gas turbines which can be used at temperatures considerably higher than the current day single crystal Ni-based superalloys. The Co-Re-based alloys have been designed to have very high melting range, and they are meant for application at +373 K (+100 °C) above Ni-superalloys. They are significantly different from the conventional Co-based alloys that are used in static components of today??s gas turbines, and the Co-Re alloys have never been used for structural applications before. The Co-Re-Cr system has complex microstructure with many different phases present. Phase transformations and stabilities of fine strengthening precipitates at high temperatures remain mostly unexplored in the Co-Re alloys, and to develop basic understanding, model ternary and quaternary compositions were studied within the alloy development program. In situ neutron and synchrotron measurements at high temperatures were extensively used for this purpose, and some recent results from the in situ measurements are presented. In particular, the effect of boron doping in Co-Re alloys and the stabilities of the fine TaC precipitates at high temperatures were investigated. A fine dispersion of TaC precipitates strengthens some Co-Re alloys, and their stabilities at the application temperatures are critical. In the beginning, the alloy development strategy is very briefly discussed.     

Distribution of almond polyphenols in blanch water and skins as a function of blanching time and temperature

The distribution of polyphenols in blanched almond skins and blanch water, as a function of time and temperature, was quantified using negative ion electrospray time-of-flight mass spectrometry (ESI TOF MS). Almonds were blanched in 25° (RT) and 100 °C (HW) water for up to 10 min. At 10 min, ∼30% (25°) and 90% (100 °C) of the polyphenols quantified had leached from the skins into the blanch water. Many of the compounds precipitated from the blanch water due to limited water solubility, as evidenced by a logarithmic fit to kinetic data (1st order kinetics). The rate of procyanidin degradation into smaller polymeric units (e.g., catechin and epicatechin) also increased as a function of time and temperature. Finally, hydration in RT water increased the extraction efficiency of phenolics by 25%. This work shows that the blanch water, in particular the 100 °C blanch water, was rich in polyphenols and supports exploration of alternative uses for blanch water.     

Effect of ozone treatment on the safety and quality of malting barley

Molds and their mycotoxins are an expensive problem for the malting and brewing industries. Deoxynivalenol (DON) is a mycotoxin that is associated with Fusarium spp. These fungi frequently cause Fusarium head blight in wheat and barley in the midwestern region of the United States; Manitoba, Canada; Europe; and China. Barley growers and malt producers would benefit from a postharvest control method for mold growth and DON production. We evaluated the use of gaseous ozone (O(3)) for preventing Fusarium growth and mycotoxin production while maintaining malt quality characteristics. Micromalting was performed in three replications under standard conditions. Ozone treatment was applied to malting barley during steeping via a submerged gas sparger. Ozone treatment conditions were 26 mg/cm(3) for 120 min after 2 and 6 h of steeping. The effects of gaseous ozone on DON, aerobic plate counts, Fusarium infection, and mold and yeast counts of barley throughout the malting process were measured. Various quality parameters of the malt were measured after kilning. Statistical tools were used to determine the significance of all results. Ozonation of malting barley during steeping did not lead to significant reductions in aerobic plate counts but did lead to a 1.5-log reduction in mold and yeast counts in the final malt. The influence of gaseous ozone on DON concentration was inconclusive because of the low initial concentrations of DON in the barley. Ozone significantly reduced Fusarium infection in germinated barley. Gaseous ozone did not negatively influence any aspect of malt quality and may have subtle beneficial effects on diastatic power and β-glucan concentrations.     

Sensitization of zinc oxide photoanode with an indoline dye

A dye‐sensitized solar cell (DSC) made of nanoporous ZnO film on aluminum‐doped zinc oxide (ZnO/AZO) transparent substrate has higher solar‐to‐electric energy conversion efficiency than a DSC consisting of nanoporous ZnO film deposited on conventional fluorine‐doped tin oxide (ZnO/FTO) transparent substrate. The ZnO/AZO DSC gave an overall conversion efficiency of 7.2% whereas the ZnO/FTO yielded a conversion efficiency of 4.5%. The film‐substrate orientation and higher light harvesting of the nanoporous ZnO film on the AZO after heating in air are mainly attributed to the higher energy conversion efficiency of the ZnO/AZO DSC. Copyright © 2012 John Wiley & Sons, Ltd.     

Er-doped polycrystalline silicon for light emission at λ=1.54 µm

We deposited amorphous silicon films, implanted them with erbium/oxygen, and then recrystallized them with a series of thermal treatments. Recrystallization is necessary to remove implantation damage and optically activate Er/O complexes for light emission at 1.54 μm. Photoluminescence and glancing angle x-ray diffraction were used to characterize the polycrystalline Si:Er. Following 30-minute isochronal anneals and isothermal anneals at 575°C and 600°C, the erbium luminescence intensity was observed to increase in direct relation to the degree of recrystallization during the anneal. Hydrogen passivation of dangling bonds further increased the luminescence intensity to about one half of the intensity found in a comparable single crystal material. The optically active Er is shown to be located within the recrystallized grains, and it exhibits a de-excitation (backtransfer) mechanism similar to that of single crystal Si:Er.     

Bio-functionalization of silicon nitride-based piezo-resistive microcantilevers

Methods of bio-functionalize silicon nitride involve process steps to convert it into an oxynitride via plasma implantation techniques. Such methods can potentially damage microstructures such as cantilevers. In this paper, we report successful bio-functionalization of Hotwire CVD silicon nitride-based piezo-resistive cantilevers without any oxygen plasma treatment. Process to fabricate such structures and to bio-functionalize them is discussed in detail.     

In Depth: Inscribing the Indian Landscape

When India was colonised by the British in the 18th and 19th centuries, it was systematically surveyed and delineated in map form for administrative and political purposes. Here, Anuradha Mathur and Dilip da Cunha urge a new, ‘deeper’ reading of the landscape that fully acknowledges the multiple uses and potential initiations of public spaces. Copyright © 2007 John Wiley & Sons, Ltd.