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Conversion of Shizochitrium limacinum microalgae to biodiesel by non-catalytic transesterification using various supercritical fluids
No full textBiodiesel was synthesized from Schizochitrium limacinum microalgae with different methylating agents namely, methanol, dimethyl carbonate and methyl acetate. The reactions were conducted at 518-643 K at 20 MPa and methylating agent to algae ratio at 10:1. The reaction time was varied between 10 and 80 min. Conversions of > 90% was observed within 40 min at 543 K for methanol system. However, the conversions were considerably lower for other systems and only 50% was observed with dimethyl carbonate after 30 min at 643 K, and 40% conversion with methyl acetate after 40 min at 643 K. The rate constants were obtained by pseudo-first order kinetic model. Based on the variation of rate constants with temperature, Arrhenius equation was used to determine the activation energy of all the three reaction systems. The reaction rates were the highest and lowest for the reaction with methanol and methyl acetate, respectively
Influence of Au/Pd alloy on an amine functionalised ZnCr LDH-MCM-41 nanocomposite: A visible light sensitive photocatalyst towards one-pot imine synthesis
No full textAchieving photocatalytic organic transformation reactions by using a visible light induced semiconductor-based photocatalyst is promising as a green and sustainable approach. In the present study, Au/Pd bimetallic alloy loaded amine (APTES) functionalised LDH (Layered double hydroxide)-MCM-41 composite was prepared through an in situ co-precipitation followed by a co-reduction method. The structural phases, textural properties, optical behaviour, morphological aspects, chemical states and functional groups of the photocatalysts were thoroughly analysed by powder X-ray diffraction (PXRD), high-resolution transmission electron microscopy (HRTEM), ultraviolet-visible diffuse reflectance (UV-vis DRS), fourier-transform infrared (FTIR) and X-ray photoelectron (XPS) spectroscopies. Moreover, the formation of an alloying structure between Au and Pd was confirmed from PXRD, HRTEM and UV-vis absorption spectra. We investigated one-pot synthesis of imines through photoalkylation of benzyl alcohol with nitrobenzene over Au/Pd bimetal alloy loaded on amine functionalised LDH-MCM-41 composite and it demonstrated imine yield of around 3.1 times (68%) more than the parent LDH (22%). The alloy nanoparticless efficiently harvest light and possess higher photocatalytic activity with respect to single Pd and Au nanoparticles. Due to the alloying structure develops charge heterogeneity on the surface of alloyed nanoparticles and enhances the interaction between metal surface with substrate molecule which promotes the coupling between photo generated benzaldehyde with aniline to form imine. Characterisation such as photoluminescence (PL), time-resolved photoluminescence (TRPL), electrical impedance spectroscopy (EIS) and photocurrent density measurements further proved the superior photoactivity towards imine synthesis. These photocatalytic tandem reactions, therefore, have great potential as an effective pathway for the one-pot organic synthesis and transformation of organics in an environmentally friendly way
Thermodynamically stable octahedral MoS2 in van der Waals hetero-bilayers
No full textReversible switching of the structural ground state of a solid is a fundamental goal in materials engineering, which has not been achieved in atomically thin layers of van der Waals crystals. This is particularly important for the transition metal dichalcogenides, such as molybdenum disulphide (MoS2), where the higher-energy octahedral polymorphs exhibit a wide range of fascinating properties. Here we show that thermodynamically stable octahedral phase of monolayer MoS2 can be achieved in coexistence with the 1H phase, at temperatures below similar to 500 K, by forming a van der Waals hybrid with another layered solid, such as hexagonal boron nitride (hBN) or graphene. Spatial mapping and temperature-dependence of the zone-folded Raman modes reveal that the octahedral phase exists only within the heterostructure region, and exhibits remarkable stability to repeated thermal cycling. A concurrent shift in the out-of-plane A1(g) vibrational mode of MoS2, and near-absence of the octahedral phase in homo-epitaxial structures, suggest likely role of local lattice relaxation due to incommensurability-driven stress fields. Our experiment establishes van der Waals hetero-epitaxy as a new tool for crystal structure engineering in atomic membranes
A High-Performance Dynamic Controller For an Active Power Decoupler With AC-Side Storage Element
No full textThe instantaneous power in a single-phase system pulsates at double the supply frequency. With the effective use of the storage element, the electrolytic capacitor placed at the dc bus can be replaced by film capacitors, thereby improving the converter lifespan. Active power decoupling (APD) using an extra set of switches aims to attain the same. Recently, a promising APD topology has been reported, offering a lesser number of switches, as well as lesser stress on the switches for a wide range of power factor. However, the control of that converter poses a challenge as it has more number of states than the independent control variables. This paper focuses on the control aspect of the topology. It is shown that controlling two out of three states guarantees the overall system performance at the steady state. Also, ripple power in the dc bus is controlled in a closed-loop fashion so as to handle model uncertainty and thereby improve the steady-state performance. Furthermore, the solution to suppress the harmonic power, reflected on to the dc bus, under polluted grid condition is provided. The simulation and experimental results are presented supporting the analysis and design of the controller structure
Microfluidic In-Flow Decantation Technique Using Stepped Pillar Arrays and Hydraulic Resistance Tuners
No full textSeparating the particles from the liquid component of sample solutions is important for several microfluidic-based sample preparations and/or sample handling techniques, such as plasma separation from whole blood, sheath-free flow focusing, particle enrichment etc. This paper presents a microfluidic in-flow decantation technique that provides the separation of particles from particle-free fluid while in-flow. The design involves the expansion of sample fluid channel in lateral and depth directions, thereby producing a particle-free layer towards the walls of the channel, followed by gradual extraction of this particle-free fluid through a series of tiny openings located towards one-end of the depth-direction. The latter part of this design is quite crucial in the functionality of this decantation technique and is based on the principle called wee-extraction. The design, theory, and simulations were presented to explain the principle-of-operation. To demonstrate the proof-of-principle, the experimental characterization was performed on beads, platelets, and blood samples at various hematocrits (2.5%-45%). The experiments revealed clog-free separation of particle-free fluid for at least an hour of operation of the device and demonstrated purities close to 100% and yields as high as 14%. The avenues to improve the yield are discussed along with several potential applications
Development and characterization of electric field directed preferentially aligned CNT nanocomposites
No full textThe present work demonstrates a novel method to preferentially orient carbon nanotubes (CNTs) in an epoxy matrix using a non-uniform electric field. The alignment method is based on the principle of dielectrophoresis. Aligned CNT/epoxy composites containing 0.01, 0.05 and 0.1 wt. % CNTs, respectively were fabricated using the method. The elastic modulus and hardness of the samples evaluated using nanoindentation technique were observed to increase with increasing CNT loading. The tensile strength of nanocomposite samples containing 0.1 wt. % CNTs increased by approximately 27% due to CNT alignment in epoxy matrix
Heterogeneity of macrolide-lincosamide-streptogramin phenotype & conjugal transfer of erm(B) in Pediococcus pentosaceus
No full textBackground & objectives: Pediococcus pentosaceus has been reported to cause clinical infections while it is being promoted as probiotic in food formulations. Antibiotic resistance (AR) genes in this species are a matter of concern for treating clinical infections. The present study was aimed at understanding the phenotypic resistance of P. pentosaceus to macrolide-lincosamide-streptogramin B (MLSB) antibiotics and the transfer of AR to pathogens. Methods: P. pentosacues isolates (n=15) recovered from fermented foods were screened for phenotypic resistance to MLSB antibiotics using disc diffusion and microbroth dilution methods. Localization and transferability of the identified resistance genes, erm(B) and msr(C) were evaluated through Southern hybridization and in vitro conjugation methods. Results: Four different phenotypes; sensitive (S) (n=5), macrolide (M) (n=7), lincosamide (L) (n=2) and constitutive (cMLS(B)) (n=1) were observed among the 15 P. pentosaceus isolates. High-level resistance (>256 mu g/ml) to MLSB was observed with one cMLS(B) phenotypic isolate IB6-2A. Intermediate resistance (8-16 mu g/ml) to macrolides and lincosamides was observed among M and L phenotype isolates, respectively. Cultures with S phenotype were susceptible to all other antibiotics but showed unusual minimum inhibitory concentration (MIC) values of 8-16 mu g/ml for azithromycin. Southern hybridization studies revealed that resistance genes localized on the plasmids could be conjugally transferred to Enterococcus faecalis JH2-2. Interpretation & conclusions: The study provides insights into the emerging novel resistance patterns in P. pentosaceus and their ability to disseminate AR. Monitoring their resistance phenotypes before use of MLS antibiotics can help in successful treatment of Pediococcal infections in humans
Pullout Behavior of Geocell-Reinforced Vertical Plate Anchors under Lateral Loading
No full textVertical plate anchors are being widely used in the construction of earth retaining structures. In the present study, experimental and numerical investigations were carried out to develop an understanding of the behavior of geocell-reinforced vertical plate anchors in sand. The parameters studied include anchor embedment depth, strength of geocell reinforcement, and geocell-soil interface friction angle. It was observed that geocell reinforcement can significantly enhance the anchor capacity, both at shallow and deeper embedment. The unreinforced anchor, at an embedment depth of about seven times its height, tended to reach a critical stage beyond which the load-carrying capacity did not increase much. However, with geocell reinforcement, this limitation was overcome and the pullout capacity continued to increase further. Moreover, a shallow anchor with geocell reinforcement could perform better than the unreinforced anchor placed deeper. The central portion of the geocell mattress close to the anchor plate actively sustains the loading, and the end portions serve in a secondary manner to mobilize passive resistance from the surrounding soil. For better performance improvement, the geocell-soil stiffness ratio should be in the range of 5-30. With increases of the geocell-soil interface friction angle beyond 1.8 times the soil friction angle, further increases in performance improvement tend to be negligible
A theoretical analysis of the structure and properties of B26H30 isomers. Consequences to the laser and semiconductor doping capabilities of large borane clusters
No full textDecaborane(14), nido-B10H14, is the major commercially available molecular building block in boron cluster chemistry. The condensation of two such {nido-B-10} blocks gives the known isomers of B18H22 - a molecule used in the fabrication of p-type semiconductors and capable of blue laser emission. Here, we computationally determine the structures and thermodynamic stabilities of 20 possible B26H30 regioisomers constructed from the fusion of three {nido-B-10} blocks with the three subclusters conjoined by two-boron atom shared edges. In addition, density functional theory, time-dependent (TD)-DFT and multiconfigurational CASPT2 methods have been used to model and investigate the physical and photophysical properties of the three most stable of these isomers. Our findings predict these isomers to be potentially useful materials for the semiconductor industry, as high boron-content doping agents, and in the fabrication of new optical materials
Epitaxial growth of 3C-SiC (111) on Si via laser CVD carbonization
No full textA qualitative and quantitative study was performed on the carbonization temperature (T-C) and carbonization time (t(C)) with respect to the microstructure and growth rate (R-g) of a 3C-SiC epitaxial layer on Si (111) substrates by carbonization via laser chemical vapor deposition (LCVD). The results showed that the density and size of the voids depended strongly on T-C. The voids were sealed, and thin films were formed continuously and uniformly after a carbonization time of 6 min at T-C = 1200 degrees C. R-g was also dependent on T-C, and increased from 0.43 to 1.35 mu m center dot h(-1) with increases in T-C from 1000 to 1200 degrees C. These deposition rates are 10 to 100 times greater than those of observed for conventional CVD methods