14 research outputs found
Recommended from our members
Influence of Titanium Diboride Particle Size on Structure and Mechanical Properties of an Al-Mg Alloy
In the present study, aluminum alloys of the Al-Mg system with titanium diboride particles of different size distribution were obtained. The introduction of particles in the alloy was carried out using master alloys obtained through self-propagating high-temperature synthesis (SHS) process. The master alloys consisted of the intermetallic matrix Al-Ti with distributed TiB2 particles. The master alloys with TiB2 particles of different size distribution were introduced in the melt with simultaneous ultrasonic treatment, which allowed the grain refining of the aluminum alloy during subsequent solidification. It was found that the introduction of micro- and nanoparticles TiB2 increased the yield strength, tensile strength, and plasticity of as-cast aluminum alloys. After pass rolling the castings and subsequent annealing, the effect of the presence of particles on the increase of strength properties is much less felt, as compared with the initial alloy. The recrystallization of the structure after pass rolling and annealing was the major contributor to hardening that minimized the effect of dispersion hardening due to the low content of nanosized titanium diboride.Russian Science Foundation; The Research and Researchers for Industry (RRi) under the Thailand Research Fun
Lead Exposure: A Contributing Cause of the Current Breast Cancer Epidemic in Nigerian Women
Breast cancer incidence in Nigerian women has significantly increased during the past three decades in parallel with the rapid industrialization of that country. This suggested that the associated widespread contamination of the soil and of the water supplies by lead (Pb) and other industrial metals was a major contributing cause. Because of its many domestic, industrial, and automotive uses, Pb is of particular concern as it has been shown to promote the development of mammary tumors in murine mammary tumor virus-infected female C3H mice at levels as low of 0.5Â ppm Pb in the drinking water. Lead belongs to the group of selenium-antagonistic elements that interact with selenium (Se), abolishing its anti-carcinogenic effect. Lead on chronic, low-level exposure in addition also accelerates tumor growth rates. Higher levels of Pb were found in blood and head hair samples of newly diagnosed patients with breast cancer, all with infiltrating ductal carcinoma, the most common form of breast cancer in Nigeria, seen at Obafemi Awolowo University, than in cancer-free controls from the same area. Evidence for interactions between Pb and Se was obtained from blood, hair, and tumor biopsy tissue analyses. Furthermore, the Pb levels in hair samples of the patients were directly correlated with the volumes of their tumors, in accord with the tumor growth-promoting effects of Pb. Conversely, Se levels in hair and blood were inversely correlated with the tumor volumes, consistent with the anti-proliferative effects of Se. Several other elements, e.g., Cd, Hg, Cr, Sn, and As, were detected in the scalp hair of the patients and the controls, although at significantly lower levels than those of Pb. However, correlation calculations revealed them also to interact with Se, suggesting that only a fraction of the Se in organs and tissues is actually present in bioactive forms. In metal-exposed subjects, a state of latent Se deficiency may exist, resulting in depressed immune functions and increased cancer susceptibility. Evidence is presented to show that Pb and other metals also interact with iodine, another vitally important essential trace element believed to protect against breast cancer development. Public health programs aiming at lowering the breast cancer risk of Nigerian women thus will have to include effective measures to protect the population from exposures to Pb and other industrial metals that are presently contaminating the environment and the water supplies
Nanoparticles Distribution and Mechanical Properties of Aluminum-Matrix Nano-Composites Treated with External Fields
Nanoparticles distribution and mechanical properties of aluminum-matrix nano-composites treated with external fields
Copyright © 2014 The Minerals, Metals & Materials Society. All rights reserved.Aluminum-matrix nano-composites have been produced after incorporating various hard ceramic nanoparticles (Al2O3, AIN and SiC) and Al2O3 microparticles into liquid metal by mechanical stirring. The mechanical stirring process is optimized to obtain distribution of nanoparticles in entire volume of the liquid. However, locally, nanoparticle clusters have been found. Application of the ultrasound to the slurry containing nanoparticles resulted in significantly improved particle dispersion and reduced nanoparticle clusters density. Nano-composites have been characterized by optical and scanning electron microscopy to see dispersion enhancement. Hardness was measured to study the local mechanical properties of these composites.ExoMet Project, which is co-funded by the European Commission in the 7th Framework Program (contract FP7-NMP3-LA-2012-280421), by the European Space Agency and by the individual partner organizations