Showing papers by "Indian Institute of Technology Guwahati published in 2012"

Evidence for an excess of B̄→D( *)τ -ν ̄τ decays

Abstract: Based on the full BaBar data sample, we report improved measurements of the ratios R(D(*)) = B(B -> D(*) Tau Nu)/B(B -> D(*) l Nu), where l is either e or mu. These ratios are sensitive to new physics contributions in the form of a charged Higgs boson. We measure R(D) = 0.440 +- 0.058 +- 0.042 and R(D*) = 0.332 +- 0.024 +- 0.018, which exceed the Standard Model expectations by 2.0 sigma and 2.7 sigma, respectively. Taken together, our results disagree with these expectations at the 3.4 sigma level. This excess cannot be explained by a charged Higgs boson in the type II two-Higgs-doublet model. We also report the observation of the decay B -> D Tau Nu, with a significance of 6.8 sigma.

A New Approach to Practical Active-Secure Two-Party Computation

Abstract: We propose a new approach to practical two-party computation secure against an active adversary. All prior practical protocols were based on Yao's garbled circuits. We use an OT-based approach and get efficiency via OT extension in the random oracle model. To get a practical protocol we introduce a number of novel techniques for relating the outputs and inputs of OTs in a larger construction. We also report on an implementation of this approach, that shows that our protocol is more efficient than any previous one: For big enough circuits, we can evaluate more than 20000 Boolean gates per second. As an example, evaluating one oblivious AES encryption $$\sim 34000$$ gates takes 64i¾?seconds, but when repeating the task 27i¾?times it only takes less than 3i¾?seconds per instance.

Recent developments in mushrooms as anti-cancer therapeutics: a review.

Abstract: From time immemorial, mushrooms have been valued by humankind as a culinary wonder and folk medicine in Oriental practice. The last decade has witnessed the overwhelming interest of western research fraternity in pharmaceutical potential of mushrooms. The chief medicinal uses of mushrooms discovered so far are as anti-oxidant, anti-diabetic, hypocholesterolemic, anti-tumor, anti-cancer, immunomodulatory, anti-allergic, nephroprotective, and anti-microbial agents. The mushrooms credited with success against cancer belong to the genus Phellinus, Pleurotus, Agaricus, Ganoderma, Clitocybe, Antrodia, Trametes, Cordyceps, Xerocomus, Calvatia, Schizophyllum, Flammulina, Suillus, Inonotus, Inocybe, Funlia, Lactarius, Albatrellus, Russula, and Fomes. The anti-cancer compounds play crucial role as reactive oxygen species inducer, mitotic kinase inhibitor, anti-mitotic, angiogenesis inhibitor, topoisomerase inhibitor, leading to apoptosis, and eventually checking cancer proliferation. The present review updates the recent findings on the pharmacologically active compounds, their anti-tumor potential, and underlying mechanism of biological action in order to raise awareness for further investigations to develop cancer therapeutics from mushrooms. The mounting evidences from various research groups across the globe, regarding anti-tumor application of mushroom extracts unarguably make it a fast-track research area worth mass attention.

Silk fibroin in tissue engineering.

Abstract: Tissue engineering (TE) is a multidisciplinary field that aims at the in vitro engineering of tissues and organs by integrating science and technology of cells, materials and biochemical factors. Mimicking the natural extracellular matrix is one of the critical and challenging technological barriers, for which scaffold engineering has become a prime focus of research within the field of TE. Amongst the variety of materials tested, silk fibroin (SF) is increasingly being recognized as a promising material for scaffold fabrication. Ease of processing, excellent biocompatibility, remarkable mechanical properties and tailorable degradability of SF has been explored for fabrication of various articles such as films, porous matrices, hydrogels, nonwoven mats, etc., and has been investigated for use in various TE applications, including bone, tendon, ligament, cartilage, skin, liver, trachea, nerve, cornea, eardrum, dental, bladder, etc. The current review extensively covers the progress made in the SF-based in vitro engineering and regeneration of various human tissues and identifies opportunities for further development of this field.

Biodiesel production from renewable feedstocks: Status and opportunities

Abstract: The increased demand for energy, climate change, and energy security concerns has driven the research interest for the development of alternative fuel from plant origin. Biodiesel derived from plant oils, which include edible and non-edible oil have gained interest for the last two decades as alternative for diesel around the world. Among these plant origin oils more than 95% of biodiesel production feedstocks come from edible oils, because they are readily available in many regions. The major advantage of these feedstocks is the properties of biodiesel produced from them are suitable to be used as diesel fuel substitute. But the consequence is the increase demand of the feedstock for food as well as fuel. A sustainable alternative fuel should be derived from renewable non-food biomass sources. The main objective of this review is to give an overview on the synthesis of biodiesel through esterification and transesterification using non-edible oil resources which are available in India, and available processes for synthesis of biodiesel (acid-, base-catalyzed transesterification reactions (homogeneous and heterogeneous), their importance, and which is the commercial process also discussed here.

Arsenic adsorption using copper (II) oxide nanoparticles

Abstract: Arsenic poisoning is a major problem in today's life. To reduce its concentration in drinking water, different metal based compounds were explored as arsenic adsorbents. In the present study, copper (II) oxide nanoparticles were prepared by thermal refluxing technique and used as an adsorbent for arsenic removal from water. Characterization of the adsorbent using TEM, BET, XRD and FTIR implied that the prepared adsorbent was in nano size and had excellent adsorption behavior with surface area of 52.11 m 2 /g. Systematic adsorption experiments were carried out with different process parameters such as contact time, adsorbent mass, pH, temperature and stirring speed and found that copper (II) oxide had very good efficiency towards arsenic adsorption. Thermodynamic parameters and adsorption kinetics were studied in detailed to know the nature and mechanism of adsorption. Results showed that the adsorption process followed pseudo second order kinetic and endothermic behavior. Adsorption equilibrium was studied with Langmuir and Freundlich isotherm models. The adsorption process followed Langmuir isotherm with an adsorption capacity of 1086.2 μg/g. A regeneration study was proposed in order to reuse the adsorbent for better economy of the process. Finally, a process design calculation is reported to know the amount of adsorbent required for efficient removal of arsenic from aqueous medium.

Lime Stabilization of Soils: Reappraisal

Abstract: Lime generally improves the performance of soils. However, some cases reported an adverse effect. To develop an understanding of the underlying mechanisms, a systematic study covering a wide range of plasticity and mineralogy of soils was carried out. Six different soil samples were reconstituted using two extreme types of soils, in other words, a montmorillonite rich expansive soil and a silica-rich non-expansive soil. The influence of lime stabilization on these soils was evaluated through determination of geotechnical properties such as liquid limit, plastic limit, swell, compressive strength, mineralogy, and microstructure. An optimum lime content beyond which the strength improvement decreased was found. This phenomenon is more prominently observed with silica-rich soils that form silica gel. As the silica gel is highly porous, when formed in large scale the strength gain from cementation is substantially countered by the strength loss from gel pores, giving rise to a visible reduction in ove...

Potentials of Exopolysaccharides from Lactic Acid Bacteria

Abstract: Recent research in the area of importance of microbes has revealed the immense industrial potential of exopolysaccharides and their derivative oligosaccharides from lactic acid bacteria. However, due to lack of adequate technological knowledge, the exopolysaccharides have remained largely under exploited. In the present review, the enormous potentials of different types of exopolysaccharides from lactic acid bacteria are described. This also summarizes the recent advances in the applications of exopolysaccharides, certain problems associated with their commercial production and the remedies.

Presence of Amorphous Carbon Nanoparticles in Food Caramels

Abstract: We report the finding of the presence of carbon nanoparticles (CNPs) in different carbohydrate based food caramels, viz. bread, jaggery, sugar caramel, corn flakes and biscuits, where the preparation involves heating of the starting material. The CNPs were amorphous in nature; the particles were spherical having sizes in the range of 4-30 nm, depending upon the source of extraction. The results also indicated that particles formed at higher temperature were smaller than those formed at lower temperature. Excitation tuneable photoluminescence was observed for all the samples with quantum yield (QY) 1.2, 0.55 and 0.63%, for CNPs from bread, jaggery and sugar caramels respectively. The present discovery suggests potential usefulness of CNPs for various biological applications, as the sources of extraction are regular food items, some of which have been consumed by humans for centuries, and thus they can be considered as safe.

Implementation of Vehicle to Grid Infrastructure Using Fuzzy Logic Controller

Abstract: With high penetration of electric vehicles (EVs), stability of the electric grid becomes a challenging task. A greater penetration level would demand a proper coordination amongst the various EVs as they charge or discharge to the grid. Coordination here refers to controlling the charging and discharging patterns of different EVs depending on their individual battery states and the present grid condition. Therefore, a good coordination between EVs is required for making the grid stable. With high penetration of EVs, the vehicle to grid (V2G) concept can be explored where excess energy of the battery can be supplied back to the grid in controlled fashion. Discharging EVs' battery energy to the grid in coordination can make V2G utilization as distributed energy storage. Charging EVs in coordination can flatten the voltage profile of a distribution node. In this work, a typical distribution system of a city is modeled to demonstrate V2G capabilities such as meeting peak demand and voltage sag reduction. The simulation of the distribution system with V2G capabilities are tested using fuzzy logic controller (FLC). Two controllers have been developed, namely the charging station controller and the V2G controller. Together they decide the proper energy flow between the EVs and the grid. Energy discharge to the grid from EVs or energy required for charging EVs is controlled and tested for the real time scenario.

Measurement of γγ *→π0 transition form factor at Belle

Abstract: We report a measurement of the process gamma gamma* -> pi(0) with a 759 fb(-1) data sample recorded with the Belle detector at the KEKB asymmetric-energy e(+)e(-) collider. The pion transition form factor, F(Q(2)), is measured for the kinematical region 4 GeV2 <= Q(2) <= 40 GeV2, where -Q(2) is the invariant-mass squared of a virtual photon. The measured values of Q(2)vertical bar F(Q(2))vertical bar agree well with the previous measurements below Q(2) similar or equal to 9 GeV2 but do not exhibit the rapid growth in the higher Q(2) region seen in another recent measurement, which exceeds the asymptotic QCD expectation by as much as 50%.

The current trends and future perspectives of prebiotics research: a review

Abstract: Prebiotics are non-digestible food ingredients that stimulate the growth of bifidogenic and lactic acid bacteria in the gastro-intestinal tract. Typically, the prebiotics consist of dietary fibers and oligosaccharides. Prebiotics exert a plethora of health-promoting effects, owing to which multi million food and pharma industries have been established. Prebiotics are being implicated in starter culture formulation, gut health maintenance, colitis prevention, cancer inhibition, immunopotentiaton, cholesterol removal, reduction of cardiovascular disease, prevention of obesity and constipation, bacteriocin production, use in fishery, poultry, pig, cattle feed and pet food. Looking at the ever-increasing demand of prebiotics, in this review, recent trends in prebiotic production from new novel sources, from food industrial wastes, prebiotic supplementation in food, commercially available prebiotic agents, prebiotic production by various techniques and future perspectives has been discussed. The critical insight into this hot research area aims to stimulate further ponderance.

Measurement of branching fractions and rate asymmetries in the rare decays B -> K((*))l(+)l(-)

Abstract: In a sample of 471×10^6 BB events collected with the BABAR detector at the PEP-II e^+e^- collider we study the rare decays B→K^(*)l^+l^-, where l^+l^- is either e^+e^- or μ^+μ^-. We report results on partial branching fractions and isospin asymmetries in seven bins of dilepton mass-squared. We further present CP and lepton-flavor asymmetries for dilepton masses below and above the J/ψ resonance. We find no evidence for CP or lepton-flavor violation. The partial branching fractions and isospin asymmetries are consistent with the Standard Model predictions and with results from other experiments.

Supramolecular Peptide Amphiphile Vesicles through Host–Guest Complexation

Abstract: Single-tail peptide amphiphiles, have been explored as a new class of biomaterials in many fields including nanotechnology and tissue engineering. A typical peptide amphiphile molecule is linked through a covalent amide bond between a hydrophilic peptide sequence and a hydrophobic lipid of variable length. In an aqueous environment, these peptide amphiphiles undergo self-assembly into structures such as vesicles, both spherical and cylindrical micelles or nanotubes, and have been successfully applied in the biomedical sciences for biomaterial conjugation and as bioactive scaffolds for tissue engineering. Although covalent attachment of two components to form peptide amphiphiles has been extremely successful, the synthetic versatility and the ability to respond to external triggers remains limited. A supramolecular approach to form the peptide amphiphile by connecting two building blocks through a non-covalent interaction would represent a major advance, especially in designing stimuliresponsive systems capable of being targeted by specific triggers. Cucurbit[n]urils (CB[n]) are a family of macrocyclic hosts known to form inclusion complexes with selectivity and high binding affinity in aqueous media. One of the larger macrocycles in this family, CB[8], can be used as a “molecular handcuff” to join two molecules together in a non-covalent fashion, and has been applied to form biomaterials such as polymer–protein conjugation and protein dimerization. Additionally, CB[n] hosts have found great utility in “switch on/switch off” fluorescence assays by supramolecular complexation with various fluorescent guests. Pyrene and its derivatives have been widely used as fluorescence probes in a large number of complex systems, on account of their high fluorescence quantum yields, long excited state lifetimes and the ability to form excimers. Herein, we utilize a functional pyrene bearing an imidazolium group both as a fluorescence sensor and as a guest for CB[8] and linked it to a simple peptide sequence (1). Pyrene-functionalized peptide 1 is able to form the supramolecular peptide amphiphile complex 3 with viologen lipid 2 through CB[8] conjugation, as shown in Figure 1a. During the

Fabrication of antibacterial silver nanoparticle—sodium alginate–chitosan composite films

Abstract: A new and simple ecofriendly method for the synthesis of silver nanoparticles (Ag NPs) using a natural biopolymer, sodium alginate as both reducing and stabilizing agent is reported. The synthesized NPs were characterized using UV-Vis spectroscopy, transmission electron microscopy (TEM) and selected area electron diffraction pattern (SAED). The alginate capped NPs (Alg–Ag NPs) were found to be antibacterial. The Alg–Ag NPs were blended with varying amounts of chitosan to form polyelectrolyte complex that was cast into stable films. The films were characterized by field emission scanning electron microscopy (FESEM), optical microscopy, Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). The water uptake and mechanical properties of the films were also studied. The blended film demonstrated excellent antibacterial activity against both Gram negative and Gram positive bacteria with more activity against Gram positive bacteria. Thus, the developed films have a potential to be used for various antibacterial applications in biotechnology and biomedical fields.

The role of hydrogen bonding in excited state intramolecular charge transfer.

Abstract: Intramolecular charge transfer (ICT) that occurs upon photoexcitation of molecules is a vital process in nature and it has ample applications in chemistry and biology. The ICT process of the excited molecules is affected by several environmental factors including polarity, viscosity and hydrogen bonding. The effect of polarity and viscosity on the ICT processes is well understood. But, despite the fact that hydrogen bonding significantly influences the ICT process, the specific role of hydrogen bonding in the formation and stabilization of the ICT state is not unambiguously established. Some literature reports predicted that the hydrogen bonding of the solvent with a donor promotes the formation of a twisted intramolecular charge transfer (TICT) state. Some other reports stated that it inhibits the formation of the TICT state. Alternatively, it was proposed that the hydrogen bonding of the solvent with an acceptor favors the TICT state. It is also observed that a dynamic equilibrium is established between the free and the hydrogen bonded ICT states. This perspective focuses on the specific role played by hydrogen bonding of the solvent with the donor and the acceptor, and by proton transfer in the ICT process. The utility of such influence in molecular recognition and anion sensing is discussed with a few recent literature examples in the end.

Biobutanol: science, engineering, and economics

Abstract: SUMMARY Among several liquid alternative fuels, biobutanol has shown great promise because of its very similar properties to gasoline. This review provides an overview of research activities in acetone–butanol–ethanol (ABE) fermentation over the past two and a half decades. We have addressed seven important facets of ABE fermentation, viz. biochemistry, microbial cultures, alternative substrates, solvent recovery, fermentation mode and reactor designs, mathematical modeling, and economics. Development of mutant strains having higher yield, selectivity and tolerance to inhibition, and search for cheap alternative substrates for fermentation are most important thrust areas in biobutanol production. New and efficient processes have been developed for in situ removal and recovery of the ABE solvents. Several rigorous kinetic and physiological models for fermentation have been formulated, which form useful tool for optimization of the process. These research activities have been reviewed in this paper. Finally, we have summarized studies on the economic viability of large-scale ABE fermentation processes employing various process designs, substrates, and microbial cultures. With the use of new strains, inexpensive substrates, and superior reactor designs, economic potential of ABE fermentation has been found to be highly attractive. Research efforts in science, engineering, and economics of ABE fermentation have brought biobutanol close to commercialization as liquid alternate fuel. Copyright © 2011 John Wiley & Sons, Ltd.

Hierarchically Grown Urchinlike CdS@ZnO and CdS@Al2O3 Heteroarrays for Efficient Visible-Light-Driven Photocatalytic Hydrogen Generation

Abstract: Nanourchin-shaped narrow-band-gap semiconductor photocatalysts with high surface area combined with good crystallinity result in effective photocatalysis. In this work, the impregnating growth of 1D CdS nanowires onto Al2O3 and ZnO templates as cores generates novel urchinlike morphology of CdS@oxide photocatalysts. The CdS@Al2O3 and CdS@ZnO nanourchins explicitly show a major role in enhanced hydrogen generation with apparent quantum yields (AQY) of 11% and 15%, respectively. Mechanistically, the template-based CdS can influence the photocatalytic activity in two ways: (i) direct well-dispersed growth of CdS onto the oxide core, leading to a high surface area for enhanced light absorption, and (ii) charge transfer from the conduction band of highly crystalline CdS to that of the oxide, which facilitate efficient charge separation for hydrogen production. Following these two mechanisms, a simple, low-cost, and environmentally friendly hydrothermal strategy is employed to synthesize novel nanourchin-shaped...

Observation of Time-Reversal Violation in the B-0 Meson System

Abstract: Although CP violation in the B meson system has been well established by the B factories, there has been no direct observation of time-reversal violation. The decays of entangled neutral B mesons into definite flavor states (B^0 or B^0), and J/ψK_L^0 or cc K_S^0 final states (referred to as B_+ or B_-), allow comparisons between the probabilities of four pairs of T-conjugated transitions, for example, B^0→B_- and B_-→B^0, as a function of the time difference between the two B decays. Using 468×10^6 BB pairs produced in Υ(4S) decays collected by the BABAR detector at SLAC, we measure T-violating parameters in the time evolution of neutral B mesons, yielding ΔS_T^+=-1.37±0.14(stat)±0.06(syst) and ΔS_T^-=1.17±0.18(stat)±0.11(syst). These nonzero results represent the first direct observation of T violation through the exchange of initial and final states in transitions that can only be connected by a T-symmetry transformation.

Visible light assisted photocatalytic hydrogen generation and organic dye degradation by CdS–metal oxide hybrids in presence of graphene oxide

Abstract: Single step hydrothermal synthesis of CdS/Oxide (Oxide = ZnO, Al2O3) was demonstrated and examines their photocatalytic activity in presence of graphene oxide (GO). CdS/Al2O3/GO and CdS/ZnO/GO both exhibits enhanced photocatalytic activity for hydrogen generation with apparent quantum yields (AQY) of 14% and 30% respectively. Moreover, CdS/Oxide/GO displayed efficient photodegradation of an organic dye; ∼90% for CdS/Al2O3/GO and ∼99% for CdS/ZnO/GO within 60 min of time interval. Superior photocatalytic properties are attributed to the enhanced surface area and effective separation of photoinduced charge carriers due to the presence of GO. The present study highlights the potential application of graphene based materials in the field of energy conversion and environment remediation.

Hierarchical 3D NiO–CdS heteroarchitecture for efficient visible light photocatalytic hydrogen generation

Abstract: A novel hierarchical three dimensional (3D) NiO–CdS heteroarchitecture was successfully synthesized by a facile single pot hydrothermal route and characterized by powder X-ray diffractogram, UV-Vis spectroscopy, BET, FE-SEM and TEM FE-SEM and TEM analyses revealed the formation of the hierarchical 3D structure of the as-prepared NiO–CdS The purity and crystalline phase of the individual component in 3D NiO–CdS were determined by a powder X-ray diffractogram The hierarchical 3D NiO–CdS exhibited enhanced photocatalytic activity for hydrogen generation by water reduction with an AQY value of 6% In 3D NiO–CdS, the high hydrogen production rate in comparison to 1D CdS NWs (AQY 2%) is mainly attributed to the enhanced specific surface area and facile charge transfer from the conduction band of highly crystalline CdS to the conduction band of NiO, which reduces the recombination rate of reductive electrons and oxidative holes for efficient hydrogen production

Iodine-stabilized Cu nanoparticle chitosan composite for antibacterial applications.

Abstract: We report herein the synthesis of a new composite consisting of Cu nanoparticles (NPs) and chitosan (CS), which has been found to be stable in the presence of molecular iodine and has also high antimicrobial activities. The composite could be obtained when aqueous CuSO4 was treated with hydrazine in the presence of CS. The spherical Cu NPs present in the composite were of average diameters 8±4 nm. The NPs were unstable in atmospheric conditions leading to the formation of oxides of Cu. On the other hand, when molecular iodine was added to the medium following synthesis the NPs were rather stable. Studies of antibacterial property were carried out on Gram-negative green fluorescent expressing Escherichia coli bacteria & Gram-positive Bacillus cereus bacteria. The minimum inhibitory concentration (MIC) of the iodinated composite on Escherichia coli was found to be 130.8 μg/mL, which contained 21.5 μg/mL Cu NPs. This determined value of MIC for Cu NPs was much lower than those reported in the literature. Zet...

Organocatalytic C–H activation reactions

Abstract: Organocatalytic C-H activation reactions have recently been developed besides the traditional metal-catalysed C-H activation reactions. The recent non-asymmetric and asymmetric C-H activation reactions mediated by organocatalysts are discussed in this review.

First observation of the P-wave spin-singlet bottomonium states h b(1P) and h b(2P)

Abstract: We report the first observations of the spin-singlet bottomonium states h(b)(1P) and h(b)(2P). The states are produced in the reaction e(+)e(-) --> h(b)(nP)pi(+)pi(-) using a 121.4 fb(-1) data sample collected at energies near the Y(5S) resonance with the Belle detector at the KEKB asymmetric-energy e(+)e(-) collider. We determine M[h(b)(1P)] = (9898.2(-1.0-1.1)(+1.1+1.0)) MeV/c(2) and M[h(b)(2P)] = (10 259.8 +/- 0.6(-1.0)(+1.4)) MeV/c(2), which correspond to P-wave hyperfine splittings Delta M-HF = (+1.7 +/- 1.5) and (+0.5(-1.2)(+1.6)) MeV/c(2), respectively. The significances of the h(b)(1P) and h(b)(2P) are 5.5 sigma and 11.2 sigma, respectively. We find that the production of the h(b)(1P) and h(b)(2P) is not suppressed relative to the production of the Y(1S), Y(2S), and Y(3S).