Showing papers by "Indian Institute of Technology Kharagpur published in 2007"

Interparticle Coupling Effect on the Surface Plasmon Resonance of Gold Nanoparticles: From Theory to Applications

Abstract: 12.2.2. Four-Wave Mixing (FWM) 4849 12.2.3. Dye Aggregation 4850 12.2.4. Optoelectronic Nanodevices 4850 12.3. Sensor 4851 12.3.1. Chemical Sensor 4851 12.3.2. Biological Sensor 4851 12.4. Catalysis 4852 13. Conclusion and Perspectives 4852 14. Abbreviations 4853 15. Acknowledgements 4854 16. References 4854 * Corresponding author E-mail: tpal@chem.iitkgp.ernet.in. † Raidighi College. § Indian Institute of Technology. 4797 Chem. Rev. 2007, 107, 4797−4862

Biodiesel production from jatropha oil (Jatropha curcas) with high free fatty acids: An optimized process

Abstract: Response surface methodology (RSM) based on central composite rotatable design (CCRD) was used to optimize the three important reaction variables—methanol quantity (M), acid concentration (C) and reaction time (T) for reduction of free fatty acid (FFA) content of the oil to around 1% as compared to methanol quantity (M′) and reaction time (T′) and for carrying out transesterification of the pretreated oil. Using RSM, quadratic polynomial equations were obtained for predicting acid value and transesterification. Verification experiments confirmed the validity of both the predicted models. The optimum combination for reducing the FFA of Jatropha curcas oil from 14% to less than 1% was found to be 1.43% v/v H2SO4 acid catalyst, 0.28 v/v methanol-to-oil ratio and 88-min reaction time at a reaction temperature of 60 °C as compared to 0.16 v/v methanol-to-pretreated oil ratio and 24 min of reaction time at a reaction temperature of 60 °C for producing biodiesel. This process gave an average yield of biodiesel more than 99%. The fuel properties of jatropha biodiesel so obtained were found to be comparable to those of diesel and confirming to the American and European standards.

Synthesis and size-selective catalysis by supported gold nanoparticles: Study on heterogeneous and homogeneous catalytic process

Abstract: Core−shell nanocomposites (R−Au) bearing well-defined gold nanoparticles as surface atoms of variable sizes (8−55 nm) have been synthesized exploiting polystyrene-based commercial anion exchangers. Immobilization of gold nanoparticles, prepared by the Frens method, onto the resin beads in the chloride form is possible by the ready exchange of the citrate-capped negatively charged gold particles. The difficulty of nanoparticle loading, avoiding aggregation, has been solved by stepwise operation. Analysis of the gold particles after immobilization and successive elution confirm the unaltered particle morphology while compared to those of the citrate-capped gold particles in colloidal dispersion. It was observed that the rate of the reaction increases with the increase in catalyst loading, which suggests the catalytic behavior of the gold nanoparticles for the reduction of the aromatic nitrocompounds. The rate constant, k, was found to be proportional to the total surface area of the nanoparticles in the sys...

Impact of Network Reconfiguration on Loss Allocation of Radial Distribution Systems

Abstract: This paper presents allocation of power losses to consumers connected to radial distribution networks before and after network reconfiguration in a deregulated environment. Loss allocation is made in a quadratic way and it is based on identifying the real and imaginary parts of current in each branch, and losses are allocated to consumers. The network reconfiguration algorithm is based on the fuzzy multiobjective approach and the max-min principle is adopted for the multiobjective optimization in a fuzzy framework. Multiple objectives are considered for real-power loss reduction in which nodes voltage deviation is kept within a range, and an absolute value of branch currents is not allowed to exceed their rated capacities. At the same time, a radial network structure is maintained with all loads energized. The three objectives considered are modeled with fuzzy sets to evaluate their imprecise nature and one can provide his or her anticipated value of each objective. A 69-node example is considered to demonstrate the effectiveness of the proposed method.

Electrophilicity-based charge transfer descriptor.

Abstract: In line with the charge transfer (ΔNmax = −μ/η) proposed by Parr et al (Parr, R G; Szentpaly, L V; Liu, S J Am Chem Soc 1999, 121, 1922), we propose an electrophilicity-based charge transfer (ECT) descriptor in this paper and validate it through the interaction between a series of chlorophenols and DNA bases Application of ECT can be extended to the interaction of any toxin with the biosystem

Preparation and characterization of polyvinyl alcohol-gelatin hydrogel membranes for biomedical applications.

Abstract: The purpose of this research was to design and develop hydrogels by esterification of polyvinyl alcohol (PVA) with gelatin. The membranes were characterized by Fourier Transform Infrared (FTIR) spectroscopy, x-ray diffraction (XRD), and differential scanning calorimetry. The viscosity of the esterified product (as solution) was compared with the mixture of PVA and gelatin of the same composition. The mechanical properties of the hydrogels were characterized by tensile tests. Swelling behavior and hemocompatibility of the membrane were also evaluated. The diffusion coefficient of salicylic acid (SA), when the receptor compartment contained Ringer's solution, through the membrane was determined. SA was used as a model drug. FTIR spectra of the membranes indicated complete esterification of the free carboxylic groups of gelatin. XRD studies indicated that the crystallinity of the membranes was mainly due to gelatin. The comparison of viscosity indicated an increase in segment density within the molecular coil. The membrane had sufficient strength and water-holding capacity. Hemocompatibility suggested that the hydrogel could be tried as wound dressing and as an implantable drug delivery system. The diffusion coefficient of SA through the membrane was found to be 1.32×10−5 cm2/s. The experimental results indicated that the hydrogel could be tried for various biomedical applications.

The Prospect of Purple Non-Sulfur (PNS) Photosynthetic Bacteria for Hydrogen Production: The Present State of the Art

Abstract: Hydrogen is the fuel for the future, mainly due to its recyclability and nonpolluting nature. Biological hydrogen production processes are operated at ambient temperature and atmospheric pressures, thus are less energy intensive and more environmentally friendly as compared to thermochemical and electrochemical processes. Biohydrogen processes can be broadly classified as: photofermentation and dark fermentation. Two enzymes namely, nitrogenase and hydrogenase play an important role in biohydrogen production. Photofermentation by Purple Non-Sulfur bacteria (PNS) is a major field of research through which the overall yield for biological hydrogen production can be improved significantly by optimization of growth conditions and immobilization of active cells. The purpose of this paper is to review various processes of biohydrogen production using PNS bacteria along with several current developments. However, suitable process parameters such as carbon and nitrogen ratio, illumination intensity, bioreactor configuration and inoculum age may lead to higher yields of hydrogen generation using PNS bacteria.

Synthesis of Normal and Inverted Gold−Silver Core−Shell Architectures in β-Cyclodextrin and Their Applications in SERS

Abstract: Beta-cyclodextrin (β-CD) in alkaline solution has been observed to produce mono- and bimetallic nanoparticles of silver and gold and to provide in-house stability to both types of particles. Thus, the weak reducing capability of the β-CD molecule (oxidation occurs at +1.33 V vs Ag/AgCl) and its unique kinetic control over the evolution of both normal and inverted core−shell bimetallic architectures have been established. The structure and composition of the bimetallic particles were characterized by UV−visible spectroscopy, transmission electron microscopy, high-resolution transmission electron microscopy, electron dispersive spectroscopy, and X-ray photoelectron spectroscopy. Bimetallic core−shell particles containing silver shells have been shown to provide an elegant SERS-active substrate compared to the corresponding monometallic nanoparticles, and therefore, they highlight the importance of electronic ligand effects on the enhancement of the Raman signals of molecular probes on nanostructured metallic surfaces.

Synthesis of flower-like gold nanoparticles and their electrocatalytic activity towards the oxidation of methanol and the reduction of oxygen.

Abstract: This article describes the synthesis of branched flower-like gold (Au) nanocrystals and their electrocatalytic activity toward the oxidation of methanol and the reduction of oxygen. Gold nanoflowers (GNFs) were obtained by a one-pot synthesis using N-2-hydroxyethylpiperazine-N-2-ethanesulphonic acid (HEPES) as a reducing/stabilizing agent. The GNFs have been characterized by UV−visible spectroscopy, transmission electron microscopy (TEM), X-ray diffraction (XRD), and electrochemical measurements. The UV−visible spectra show two bands corresponding to the transverse and longitudinal surface plasmon (SP) absorption at 532 and 720 nm, respectively, for the colloidal GNFs. The GNFs were self-assembled on a sol−gel-derived silicate network, which was preassembled on a polycrystalline Au electrode and used for electrocatalytic applications. The GNFs retain their morphology on the silicate network; the UV−visible diffuse reflectance spectra (DRS) of GNFs on the silicate network show longitudinal and transverse b...

Investigation and modeling of the structure of texting language

Abstract: Language usage over computer mediated discourses, such as chats, emails and SMS texts, significantly differs from the standard form of the language and is referred to as texting language (TL). The presence of intentional misspellings significantly decrease the accuracy of existing spell checking techniques for TL words. In this work, we formally investigate the nature and type of compressions used in SMS texts, and develop a Hidden Markov Model based word-model for TL. The model parameters have been estimated through standard machine learning techniques from a word-aligned SMS and standard English parallel corpus. The accuracy of the model in correcting TL words is 57.7%, which is almost a threefold improvement over the performance of Aspell. The use of simple bigram language model results in a 35% reduction of the relative word level error rates.

A genetic algorithms based multi-objective neural net applied to noisy blast furnace data

Abstract: A genetic algorithms based multi-objective optimization technique was utilized in the training process of a feed forward neural network, using noisy data from an industrial iron blast furnace. The number of nodes in the hidden layer, the architecture of the lower part of the network, as well as the weights used in them were kept as variables, and a Pareto front was effectively constructed by minimizing the training error along with the network size. A predator-prey algorithm efficiently performed the optimization task and several important trends were observed.

Drought Forecasting Using a Hybrid Stochastic and Neural Network Model

Abstract: Treating the occurrence and severity of droughts as random, a hybrid model, combining a linear stochastic model and a nonlinear artificial neural network (ANN) model, is developed for drought forecasting. The hybrid model combines the advantages of both stochastic and ANN models. Using the Standardized Precipitation Index series, the hybrid model as well as the individual stochastic and ANN models were applied to forecast droughts in the Kansabati River basin in India, and their performances were compared. The hybrid model was found to forecast droughts with greater accuracy.

Congestion Management Using Multiobjective Particle Swarm Optimization

Abstract: This paper presents an effective method of congestion management in power systems. Congestions or overloads in transmission network are alleviated by generation rescheduling and/or load shedding of participating generators and loads. The two conflicting objectives 1) alleviation of overload and 2) minimization of cost of operation are optimized to provide pareto-optimal solutions. A multiobjective particle swarm optimization (MOPSO) method is used to solve this complex nonlinear optimization problem. A realistic frequency and voltage dependent load flow method which considers the voltage and frequency dependence of loads and generator regulation characteristics is used to solve this problem. The proposed algorithm is tested on IEEE 30-bus system, IEEE 118-bus system, and Northern Region Electricity Board, India (NREB) 390-bus system with smooth as well as nonsmooth cost functions due to valve point loading effect.

Characteristics of Horseshoe Vortex in Developing Scour Holes at Piers

Abstract: The outcome of an experimental study on the turbulent horseshoe vortex flow within the developing (intermediate stages and equilibrium) scour holes at cylindrical piers measured by an acoustic Doppler velocimeter (ADV) are presented. Since the primary objective was to analyze the evolution of the turbulent flow characteristics of a horseshoe vortex within a developing scour hole, the flow zone downstream of the pier was beyond the scope of the investigation. Experiments were conducted for the approaching flow having undisturbed flow depth (=0.25 m) greater than twice the pier diameter and the depth-averaged approaching flow velocity (=0.357 m/s) about 95% of the critical velocity of the uniform bed sand that had a median diameter of 0.81 mm. The flow measurements by the ADV were taken within the intermediate (having depths of 0.25, 0.5, and 0.75 times the equilibrium scour depth) and equilibrium scour holes (frozen by spraying glue) at a circular pier of diameter 0.12 m. In order to have a comparative study, the ADV measurements within an equilibrium scour hole at a square pier (side facing the approaching flow) of sides equaling the diameter of the circular pier were also taken. The contours of the time-averaged velocities, turbulence intensities, and Reynolds stresses at different azimuthal planes (0, 45, and 90°) are presented. Vector plots of the flow field at azimuthal planes reveal the evolution of the characteristics of the horseshoe vortex flow associated with a downflow from intermediate stages to equilibrium condition of scour holes. The bed-shear stresses are determined from the Reynolds stress distributions. The flow characteristics of the horseshoe vortex are discussed from the point of view of the similarity with the velocity and turbulence characteristic scales. The imperative observation is that the flow and turbulence intensities in the horseshoe vortex flow in a developing scour hole are reasonably similar.

Stability, reactivity, and aromaticity of compounds of a multivalent superatom.

Abstract: In this article, we analyze the stability, reactivity, and possible aromatic behavior of two recently reported clusters (Reveles, J. U.; Khanna, S. N.; Roach, P. J.; Castleman, A. W., Jr. Proc. Natl. Acad. Sci. 2006, 103, 18405), viz., Al(7)C(-) and Al(7)O(-) in the light of the principles of the maximum hardness and minimum electrophilicity as well as the nucleus-independent chemical shift values. Stability of these clusters in the context of addition/removal of an electron or an Al atom is now clearly understood.