Fabrication of Cu@Ag core–shell nanoparticles for nonlinear optical applications

We report the preparation of the core–shell structured Cu@Ag nanoparticles by a simple wet chemical route at room temperature. The surface plasmon resonance band at 405 nm is indicative of the formation of Cu@Ag nanoparticles. The powder X-ray diffraction and energy dispersive X-ray analyses were carried out to elucidate the structure and chemical composition respectively. The morphological investigations made by electron microscopes revealed that the particles are spherical in shape with core–shell structures having size of about 50 nm. The X-ray photoelectron spectroscopy was performed to elucidate surface state composition of the core–shell structured nanoparticles based on the binding energies and confirmed the formation of Cu@Ag core–shell nanoparticles. The enhanced non-linear optical response of the Cu@Ag core–shell nanoparticles was demonstrated by z-scan experiment using He–Ne laser. This report provides a simple, economical and practical technology to fabricate Cu@Ag core–shell nanoparticles with enhanced nonlinear optical properties.     

Crystal growth and structure of L-methionine L-methioninium hydrogen maleate—a new NLO material

A new organic nonlinear optical (NLO) crystal from the amino acid family, viz., L-methionine L-methioninium hydrogen maleate (LMMM), has been grown by slow evaporation method from aqueous solution. Bulk crystals were grown using submerged seed solution method. The structure was elucidated using the single crystal x-ray diffraction data. The compound crystallized in the space group P2₁ and the unit cell contains a protonated L-methioninium cation and a zwitterionic methionine residue plus a maleate anion. The backbone conformation angles Ψ¹ and Ψ² are in cis and trans configurations for both the methionine and methioninium residues, respectively. Amino and carboxyl groups of the methioninium and methionine residues are connected through N–H…O hydrogen bonds leading to a ring R₂²(10) motif.     

Performance and Emission characteristics of cotton seed and neem oil biodiesel with CeO2 additives in a single-cylinder diesel engine

Energy utilisation from renewable sources plays a vital role in meeting the demands of a clean environment. Commercialisation of biodiesel is comparatively less than that of other alternative sources due to its suitability and yield. This paper is focused on performance and emission characteristics of neem oil biodiesel and cotton seed oil biodiesel blended with cerium oxide as an additive. The blending proportion was B10, B20, B30, B40 and 100% diesel. The testing was performed in a single-cylinder diesel engine coupled with an exhaust gas analyser. The performance characteristics were obtained in between the brake power with specific fuel consumption and emission characteristics such as carbon monoxide, carbon dioxide and other gases. It was observed that the combination of B20 proportion with CeO₂ blend produces effect results with other blends in specific fuel consumption and reduced emission behaviour.     

Safety of the maternal-infant zidovudine regimen utilized in the Pediatric AIDS Clinical Trial Group 076 Study

OBJECTIVE: To determine the safety of the zidovudine (ZDV) regimen utilized in the Pediatric AIDS Clinical Trial Group (ACTG) 076 study. DESIGN: ACTG 076 was a randomized, double-blind, placebo-controlled trial which demonstrated that a ZDV regimen could prevent mother-to-child HIV-1 transmission. Infants were followed through 18 months of age and women were followed through 6 months postpartum. METHODS: Maternal complications, pregnancy outcomes, growth and development of the uninfected infants, and HIV-1 disease progression in the women were monitored prospectively. RESULTS: Maternal therapy was well tolerated. There was no serious pattern of adverse pregnancy outcomes associated with ZDV use. Amongst the ZDV-exposed infants, the only recognized toxicity was anemia within the first 6 weeks of life; the risk for anemia was not associated with premature delivery, duration of maternal treatment, degree of maternal immunosuppression, or maternal anemia. ZDV treatment was not associated with an increased incidence of newborn structural abnormalities. At 18 months of age, uninfected infants did not differ in growth parameters or immune function. No childhood neoplasias were reported in either group. In the women, at 6 months postpartum, there were no differences in clinical, immunologic, or virologic disease progression. CONCLUSION: There were no identified problems that would alter current recommendations for the routine use of ZDV for the prevention of mother-child HIV-1 transmission.     

From dynamic classifier selection to dynamic ensemble selection

In handwritten pattern recognition, the multiple classifier system has been shown to be useful for improving recognition rates. One of the most important tasks in optimizing a multiple classifier system is to select a group of adequate classifiers, known as an Ensemble of Classifiers (EoC), from a pool of classifiers. Static selection schemes select an EoC for all test patterns, and dynamic selection schemes select different classifiers for different test patterns. Nevertheless, it has been shown that traditional dynamic selection performs no better than static selection. We propose four new dynamic selection schemes which explore the properties of the oracle concept. Our results suggest that the proposed schemes, using the majority voting rule for combining classifiers, perform better than the static selection method.     

Leave-One-Out-Training and Leave-One-Out-Testing Hidden Markov Models for a Handwritten Numeral Recognizer: The Implications of a Single Classifier and Multiple Classifications

Hidden Markov models (HMMs) have been shown to be useful in handwritten pattern recognition. However, owing to their fundamental structure, they have little resistance to unexpected noise among observation sequences. In other words, unexpected noise in a sequence might ldquo breakrdquo the normal transmission of states for this sequence, making it unrecognizable to trained models. To resolve this problem, we propose a leave-one-out-training strategy, which will make the models more robust. We also propose a leave-one-out-testing method, which will compensate for some of the negative effects of this noise. The latter is actually an example of a system with a single classifier and multiple classifications. Compared with the 98.00 percent accuracy of the benchmark HMMs, the new system achieves a 98.88 percent accuracy rate on handwritten digits.     

Three-dimensional electrical impedance tomography: a topology optimization approach.

Electrical impedance tomography is a technique to estimate the impedance distribution within a domain, based on measurements on its boundary. In other words, given the mathematical model of the domain, its geometry and boundary conditions, a nonlinear inverse problem of estimating the electric impedance distribution can be solved. Several impedance estimation algorithms have been proposed to solve this problem. In this paper, we present a three-dimensional algorithm, based on the topology optimization method, as an alternative. A sequence of linear programming problems, allowing for constraints, is solved utilizing this method. In each iteration, the finite element method provides the electric potential field within the model of the domain. An electrode model is also proposed (thus, increasing the accuracy of the finite element results). The algorithm is tested using numerically simulated data and also experimental data, and absolute resistivity values are obtained. These results, corresponding to phantoms with two different conductive materials, exhibit relatively well-defined boundaries between them, and show that this is a practical and potentially useful technique to be applied to monitor lung aeration, including the possibility of imaging a pneumothorax.     

Hydrophilic and morphological aspects of films based on quaternary salts of chitosan for edible applications

Aiming to improve the homogeneity of films based on chitosan to be applied as edible coating, we carried out some chemical modifications in the polymeric structure by reductive alkylation and quaternization reactions. The resulting derivatives had different hydrophilic behaviours and cast films were characterized by wetting, swelling and topographic measurements. Concerning wetting, all samples presented similar time dependence with receding water contact angles. The quaternized chitosans were the most hydrophilic derivatives, with lower values of contact angles when compared with the parent sample. These derivatives also exhibited a higher swelling tendency. The analysis shows that the relative amount of absorbed water increases according to the length of moiety added. In general, the cast films of chitosan showed good homogeneity, displaying low roughness and regular distribution over a polar surface. On the other hand, alkyl quaternary salts showed an irregular topography with undulation and mountain‐like formation due probably to agglomeration of polymeric chains. The final film morphology was dependent on the polymer solubility, as observed by microscopic techniques. Copyright © 2010 John Wiley & Sons, Ltd.     

Investigation on crystallinity and optical properties of l-tartaric acid single crystal at dynamic shocked conditions

Journal of Materials Science: Materials in Electronics - In this article, the authors demonstrate the experimental findings of the effect of dynamic shock waves on the crystallographic structural...