Calorimetric investigations on As-Te-Se and Ge-As-Se glasses

Results of calorimetric investigations performed on two groups of glasses, viz. As-Te-Se and Ge-As-Se, are described. The glass transition temperatureT _g and specific heat at constant pressureC _p of these two families of glasses have been determined using a differential scanning calorimeter. The composition dependence of glass transition temperature and variation of heat capacity during transition are discussed.     

A comparative study of short nylon fiber—Natural rubber composites prepared from dry rubber and latex masterbatch

A novel method for the preparation of short nylon fiber–natural rubber composites was developed in which short fibers chopped to approximately 6 mm were incorporated in the latex stage and processed into sheet form. By this method, mixing cycle time was reduced without compromising the fiber dispersion. Fiber breakage during mixing was reduced. The new composites when compounded with a dry bonding system based on hexamethylenetetramine, resorcinol and hydrated silica (HRH) showed improved modulus, tensile strength and abrasion resistance compared to conventional composites. Tear strength, resilience, and compression set were similar to the conventional composites. SEM analysis indicated better interaction between matrix and fibers in the case of latex master batch. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Photoacoustic Thermal Characterization of Porous Rare-Earth Phosphate Ceramics

The laser induced non-destructive photoacoustic technique has been employed to measure the thermal diffusivity of lanthanum phosphate ceramics prepared by the sol–gel route. The thermal diffusivity value was evaluated by knowing the transition frequency between the thermally thin to thermally thick region from the log–log plot of photoacoustic amplitude versus chopping frequency. Analysis of the data was carried out on the basis of the one-dimensional model of Rosencwaig and Gersho. The present investigation reveals that the sintering temperature has great influence on the propagation of heat carriers and hence on the thermal diffusivity value. The results were interpreted in terms of variations in porosity with sintering temperature as well as with changes in grain size.     

Electronic locking devices based on microcontrollers and chaotic maps using Model-Matching Control

In this work a real-time communication system using Arduino® microcontrollers, applied to electronic locking devices, is implemented. Model-Matching Control is used to achieve synchronization between transmitter and receiver Arduino® microcontrollers using only one transmission channel. Model-Matching Control is fed with dynamics from both Arduinos. Transmitter Arduino® is used also to generate in real-time an encrypted chaotic code key based on the Chen map. Receiver Arduino® recover in real-time the chaotic code key that is a binary signal key of an electronic locking device and where wireless communication is made between the two Arduinos using Bluetooth modules. System evaluation in terms of performance, randomness, and time complexity, are shown, as well as experimental results and some discussions are presented.     

Dehydration of aldoximes on rare earth exchanged (La<Superscript>3+</Superscript>, Ce<Superscript>3+</Superscript>, RE<Superscript>3+</Superscript>, Sm<Superscript>3+</Superscript>) Na–Y zeolites: A facile route for the synthesis of nitriles

Rare earth exchanged Na–Y zeolites, H-mordenite, K-10 montmorillonite clay and amorphous silica-alumina were effectively employed for the continuous synthesis of nitriles. Dehydration of benzaldoxime and 4-methoxybenzaldoxime were carried out on these catalysts at 473 K. Benzonitrile (dehydration product) was obtained in near quantitative yield with benzaldoxime whereas; 4-methoxybenzaldoxime produces both Beckmann rearrangement (4-methoxyphenylformamide) as well as dehydration products (4-methoxy benzonitrile) in quantitative yields. The production of benzonitrile was near quantitative under heterogeneous reaction conditions. The optimal protocol allows nitriles to be synthesized in good yields through the dehydration of aldoximes. Time on stream (TOS) studies show decline in the activity of the catalysts due to neutralization of acid sites by the basic reactant and product molecules and water formed during the dehydration of aldoximes.     

Isolation and characterization of cellulose nanowhiskers from Acacia caesia plant

Acacia caesia (L.) Willd (soap bark) fiber is an abundant natural resource, that is rich in cellulose. The study reports the effective utilization of underutilized Acacia caesia fiber for the isolation of nanocellulose whiskers. The nanocellulose whiskers were isolated successfully from Acacia caesia fibers by following alkali, bleaching, and sulfuric acid treatment. The obtained nanocellulose whiskers were carefully investigated for its chemical composition, structure, morphology, crystallinity, and thermal stability. The chemical composition and Fourier transform infrared spectra of nanocellulose whiskers showed the elimination of the non-cellulosic parts present in the raw Acacia caesia fibers. The X-ray diffraction analysis showed an upsurge in the crystallinity of the cellulose fibers after the chemical treatments. The isolation of nanocellulose whiskers from Acacia caesia raw fiber was confirmed by electron microscopy analysis. The thermogravimetric analysis showed remarkably high char residue for the nanocellulose whiskers compared to raw fibers. Based on the properties of nanocellulose whiskers, it can be concluded that the nanocellulose whiskers produced from Acacia caesia raw fibers are potential reinforcing material for developing high-performance green composites.     

Water quality prediction capabilities of WASP model for a tropical lake system

Water quality modelling facilitates our better understanding of the processes taking place in a lake system, and conservation plans to address them. The water quality analysis simulation programme (WASP) was used in this study to predict daily variations in water quality parameters, namely dissolved oxygen, nitrate, phosphate and chlorophyll‐a and biochemical oxygen demand concentrations in a tropical lake system. The lake was divided into eight segments with the respective morphological, environmental and flow details being model inputs. The monthly concentration of each water quality parameter also comprised model input. The model output was daily spatiotemporal variation in these parameters over a period of 476 days. This study also indicated that the occurrence of precipitation plays a major role in defining the water quality of a tropical lake. The heavy precipitation after a long gap, especially during the summer season, results in a large quantity of organic matter entering the lake through drains, thereby increasing the organic matter and phosphate in the water body, and subsequently resulting in high chlorophyll‐a concentrations in the lake. A reduced chlorophyll‐a concentration was observed during the heavy rains. The water quality fluctuations are more pronounced with precipitation, especially where polluted drains enter the lake. An improved water quality can be observed downstream, including increased dissolved oxygen and nitrate concentrations. Improved water quality was observed during the postmonsoon period, with increased salinity and dissolved oxygen concentrations, a finding that confirms generalized and specific conclusions can be achieved with the use of the WASP model.     

Investigations into the molecular-level adhesion characteristics of hydroxyapatite-coated and anodized titanium surfaces using the molecular orbital approach

It has been established that the adhesion of cells on to the surfaces of orthopaedic implants depends on the ability of the surfaces to accommodate protein molecules. Hydroxyapatite coating and anodizing are the most common methods to make TiAl6V4 implants (Ti) more biocompatible. In this paper Spartan 02, a molecular dynamics software, is used to analyze and predict the bonding characteristics of Extra cellular matrix protein sequence arginine-glycine-aspartic acid (RGD) on a Hyrdoxyapatite (HA) coated Ti and an anodized Ti surface based on the property of its constituent atoms, their polarity (net electrostatic charge, Qr), the energies of the molecular orbital E_HOMO (energy of the highest occupied molecular orbital), and E_LUMO (energy of the lowest unoccupied molecular orbital). The results show favourable criterion for formation of bonding between the HOMO orbital of the HA coated and anodized surfaces and LUMO orbital of the glycine strand from the RGD unit. The mechanism of bonding of individual atoms to form primary calcium oxide compounds is likely only in the case of HA coated surfaces . The surface texture of the anodized Ti with inherent porosities appear more responsible for the adsorption of proteins on to them by mechanical interlocking than the formation of any intermediate calcium oxide compounds.