Computational nanoelectronics research and education at nanoHUB.org

The simulation tools and resources available at nanoHUB.org offer significant opportunities for both research and education in computational nanoelectronics. Users can run simulations on existing powerful computational tools rather than developing yet another niche simulator. The worldwide visibility of nanoHUB provides tool authors with an unparalleled venue for publishing their tools. We have deployed a new quantum transport simulator, OMEN, a state-of-the-art research tool, as the engine driving two tools on nanoHUB. The educational resources of nanoHUB are one of the most important aspects of the project, according to user surveys. New collections of tools into unified curricula have found a receptive audience in many university classrooms.     

Optical Spectra of Nickel-Bearing Silicate Gels Prepared by the Geopolymer Technique, with Special Reference to the Low-Temperature Formation of Liebenbergite (Ni2SiO4)

A nickel-bearing silicate gel was prepared from sodium disilicate and nickel nitrate solutions at room temperature. Then, the gel was heat-treated in air up to 800°C at intervals of 200°C. The products were completely amorphous after heating at ≤600°C. However, liebenbergite and cristobalite were identified as products of the crystallization of the gel after heating at 800°C. The polycondensation process of the gel was discussed based on X-ray diffractometry, thermogravimetry-differential thermal analysis, and optical spectroscopy, to clarify the easy crystallization of the gel to liebenbergite and cristobalite. The present technique is very useful for the low-temperature preparation of liebenbergite, which has potential application in the decomposition catalysis of chlorofluorocarbons, in connection with the problem with the ozone layer.     

Natural occurrence of aflatoxin B1 in sorghum grown in different geographical regions of India

BACKGROUND: Sorghum (Sorghum bicolor (L.) Moench) is an important coarse cereal crop grown for grain and fodder in the semi‐arid Tropics, mainly in Asian and African countries. In India sorghum is consumed as human food and poultry feed. Sorghum grain grown in the rainy season (kharif) is becoming severely affected by grain moulds, the major fungi involved being Aspergillus, Fusarium and Curvularia. If the extent of mould is severe, the grain is unsafe for consumption owing to contamination by mycotoxins. RESULTS: This paper presents a multi‐centre study conducted in sorghum to evaluate natural contamination of aflatoxin B₁ in India. A total of 1606 grain sorghum samples were collected during the rainy (kharif) season across 4 years from seven states of India, representing different geographical regions of the country. Aflatoxin B₁ contamination during 2007–08 was the highest (13.1%), followed by samples from the year 2004–05 (2.85%). The samples collected in years 2005–06 and 2006–07 showed contamination below 1%. The number of samples (35) showing aflatoxin B₁ contamination above the safety limit was also highest during 2007–08 as compared to samples from the other years. CONCLUSION: This study, conducted for 4 years, showed that natural contamination of aflatoxin B₁ in sorghum grown in India is within safety limits (20 µg kg^?1) recommended by the Codex Alimentarius Committee and 73% of samples were positive for toxin. However, 0.75% (12) of total samples contained aflatoxin above the safety limit. The overall occurrence of toxin from Madhya Pradesh and Rajasthan was below 5 µg kg^?1. Copyright © 2012 Society of Chemical Industry     

Dynamic surface control for a class of nonlinear systems

A method is proposed for designing controllers with arbitrarily small tracking error for uncertain, mismatched nonlinear systems in the strict feedback form. This method is another "synthetic input technique," similar to backstepping and multiple surface control methods, but with an important addition, /spl tau/-1 low pass filters are included in the design where /spl tau/ is the relative degree of the output to be controlled. It is shown that these low pass filters allow a design where the model is not differentiated, thus ending the complexity arising due to the "explosion of terms" that has made other methods difficult to implement in practice. The backstepping approach, while suffering from the problem of "explosion of terms" guarantees boundedness of tracking errors globally; however, the proposed approach, while being simpler to implement, can only guarantee boundedness of tracking error semiglobally, when the nonlinearities in the system are non-Lipschitz.