An inter-comparison of black-carbon-related instruments in a laboratory study of biomass burning aerosol

Black carbon (BC)-containing particles are the most strongly light absorbing aerosols in the atmosphere. Measurements of BC are challenging because of its semi-empirical definition based on physical properties and not chemical structure, the complex and continuously changing morphology of the corresponding particles, and the effects of other particulate components on its absorption. In this study, we compare six available commercial continuous instruments measuring BC using biomass burning aerosol. The comparison involves a Soot Particle Aerosol Mass Spectrometer (SP-AMS), a Single-Particle Soot Photometer (SP2), an aethalometer, a Multiangle Absorption Photometer (MAAP), and a blue and a green photoacoustic extinctiometer (PAX). An SP-AMS collection efficiency equal to 0.35 was measured for this aerosol system. The corrected SP-AMS BC mass measurements agreed within 6% with the SP2 refractory BC mass values. Two regimes of behavior were identified for the optical instruments corresponding to high and low organic/BC ratio. The mass absorption cross-sections (MAC) measured varied from 26% to two times the instrument default values depending on the instrument and the regime. The presence of high organic aerosol concentration in this system can lead to overestimation of the BC mass by the optical instruments by as much as a factor of 2.7. In general, the discrepancy among the BC measurements increased as the organic carbon content of the BC-containing particles increased.

© 2018 American Association for Aerosol Research     

Modulating the physical properties of sunflower oil and sorbitan monopalmitate‐based organogels

The present study deals with the modulation of the sunflower oil (SO) and sorbitan monopalmitate (SM) organogels using water. The gels were prepared by heating either SO–SM mixture or SO–SM–water mixture at 60°C and subsequently cooling the mixture to room temperature. The gels were characterized by microscopy (light and electron), Fourier transform infrared (FTIR) spectroscopy, X‐ray diffraction (XRD), differential thermal analysis, rheometry, pH, dc impedance, hemocompatibility, and antimicrobial studies. The gels without water (G) were found to be pale yellow in color while gels containing water (GW) were white in color. Both types of gels were thermoreversible in nature. The microscopic analysis revealed that clusters of rod‐shaped tubules were responsible in the formation of network. GW also showed the presence of water droplets encapsulated within the networked structure. FTIR studies indicated the presence of intermolecular hydrogen bonding, responsible for gel formation. Gel‐to‐sol transition temperatures (T_gs) of the GW gels were higher than G gels, which might be accounted to the higher crystallinity of the GW gels. XRD studies confirmed the higher crystallinity of the GW gels. The gels showed pseudoplastic flow behavior and were hemocompatible in nature. Ciprofloxacin‐loaded gels showed good anti‐microbial properties against Bacillus subtilis. Based on the preliminary results, the developed gels may be used as delivery vehicles for various bioactive agents. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Structural,Dielectric,and Magnetic Studies on Electrospun Magnesium Ferrite-Polyvinylidene Fluoride Core–Shell Composite Fibers

The sub-micron(of the order of 150 nm) thick core–shell composite fibers of magnesium ferrite-polyvinylidene fluoride are prepared by electrospinning.The loading of magnesium ferrite is varied from 1 to 10 wt%.The study results by X-ray diffraction,scanning electron microscope,and infra-red spectroscopy indicate the formation of core–shell structure and an enhancement in the amount of b-phase compared to a-phase in the polyvinylidene fluoride.The particle size of the magnesium ferrite in the fiber is evaluated to be 30 nm.The low frequency dielectric studies indicate that the addition of the magnesium ferrite increases the polarization resulting in the increase in the dielectric constant but decreases the dielectric loss.The magnetization measurements indicate an increased value of coercivity compared to bulk due to the nano-size of the magnesium ferrite.The microwave absorption at the ferromagnetic resonance increases with the increase in the concentration of magnesium ferrite.The resonance field is found to vary with the loading of MFO.     

Electromigration in Sn-Bi Modified with Polyhedral Oligomeric Silsesquioxane

Electromigration (EM) behavior of eutectic Sn-Bi modified with cage-type polyhedral oligomeric silsesquioxane (POSS) trisilanol was investigated. A direct current (DC) was applied to solder joints newly designed for uniform current distribution throughout the joint. For this study, a current density of 10⁴ A/cm² was applied at 25°C and 50°C. The evolution of surface and interior microstructure due to current stressing was observed periodically using optical and scanning electron microscopy. The results revealed that the EM behavior was retarded significantly in solder joints with the addition of POSS trisilanol. Different from eutectic Sn-Bi solder joints, no continuous hillocks formed at the anode side and no cracks occurred at the cathode side in solder joints modified with POSS trisilanol even after 336 h of current stressing at 25°C. In addition, the accumulation of Bi/Sn phases at regions near the anode/cathode was also effectively limited. Joints stressed at 50°C also exhibited similar behavior. It is postulated that POSS trisilanol near the phase boundary provided significant restriction to the mass transport due to DC current stressing.     

Laser micromachining for biomedical applications

Laser micromachining is becoming a common method for fabrication of microstructured medical devices. Developments in pulsed laser technology have made it possible to achieve precision machining of sub-micrometer features with minimal damage to the surrounding material. Several aspects of laser micromachining, including machining methods, types of lasers used in micromachining, and laser-material interaction, are discussed in this article. Biomedical applications of laser micromachining are also reviewed. The ablation behavior of silicon was examined as a function of laser energy, aperture, and repetition rate. In vitro studies showed that microscale grooves on silicon substrates may be used to orient human aortic vascular smooth muscle cells. We anticipate that the use of laser micromachining for modifying medical and dental devices will become more significant over the coming years.     

Purification of β-galactosidase from recombinant Pichia pastoris using aqueous two-phase separation technique

In the current investigation, aqueous two-phase methodology with polyethylene glycol (PEG) 6000/phosphate salt has been used for single-step purification of β-galactosidase from recombinant Pichia pastoris. Optimized parameters with 12% (w/w) salt concentration, 25% (w/w) polymer concentration, 0.6 (mg/ml) protein load and 0.1 M ionic concentration resulted in a maximum of 4.7 purification fold with a 97% yield. The enzyme kinetic study of purified protein revealed V_m and K_m of 97.087 (U/mg), 0.027(U/mg), 0.07 (U/mg) and 0.7 (mM), 11.13 (mM), 10.73 (mM) with O-nitrophenyl-β-D-galactopyranoside, lactose and milk substrate, respectively.     

Thermodynamic evaluation of hydrazine assisted glycerol reforming for syngas production and coke inhibition

Thermodynamic investigation of glycerol reforming has been performed to study hydrogen production, carbon dioxide evolution and coke formation. Gibb's free energy direct minimization procedure was used to calculate the concentration of different components at equilibrium. The analysis was performed at temperatures from 300K to 1000K under unit atmospheric pressure. A comparative study on steam reforming of glycerol (SRG) and glycerol reforming reaction with hydrazine has been conducted in the presence of hydrazine that act as a suitable reducing agent. Incorporation of hydrazine into glycerol reforming system helped in minimizing coke formation, maximizing hydrogen and syn-gas production. A complete conversion of glycerol with coke free products, along with reduced level of carbon dioxide and maximum hydrogen generation was obtained when glycerol steam reforming process (S/G = 1) was combined with higher moles of hydrazine. Reformation at higher temperatures could enhance the hydrogen production and decrease carbon generation due to methanation reaction and hence optimum results were accomplished at 1000K and atmospheric pressure.     

Software design pattern mining using classification-based techniques

Design patterns are often used in the development of object-oriented software. It offers reusable abstract information that is helpful in solving recurring design problems. Detecting design patterns is beneficial to the comprehension and maintenance of object-oriented software systems. Several pattern detection techniques based on static analysis often encounter problems when detecting design patterns for identical structures of patterns. In this study, we attempt to detect software design patterns by using software metrics and classification-based techniques. Our study is conducted in two phases: creation of metrics-oriented dataset and detection of software design patterns. The datasets are prepared by using software metrics for the learning of classifiers. Then, pattern detection is performed by using classification-based techniques. To evaluate the proposed method, experiments are conducted using three open source software programs, JHotDraw, QuickUML, and JUnit, and the results are analyzed.     

Studies on sorption of some geomaterials for fluoride removal from aqueous solutions

In the present study the defluoridation capacities of some of the naturally occurring materials like low and high iron containing lateritic ores, overburden from chromite mines of Orissa Mining Corporation (OMC) and Tata Steel have been estimated. The various experimental parameters studied for fluoride sorption from aqueous solutions were: time, pH, initial fluoride concentration, sorbent dose and temperature. The three geomaterials, namely chromite overburden from Orissa Mining Corporation, both low and high iron containing lateritic ores sorbed fluoride effectively. The sorption kinetics for these samples was found to follow first order rate expression and the experimental equilibrium sorption data fitted reasonably well to both Langmuir and Freundlich models. The negative values of ΔG° suggest the sorption of fluoride onto three samples to be spontaneous and the exothermic nature of sorption is confirmed by the −ΔH° values. The negative ΔS° values for these sorbents point towards decreased randomness at the solid/solution interface. The sorption studies were also carried out at natural pH conditions for fluoride removal from ground water samples and the fluoride level could be reduced from 10.25 to <1.0 mg L⁻¹ by multistage adsorption process using OMC and NH samples.     

Nanospheres and nanorods structured Fe2O3 and Fe2−xGaxO3 photocatalysts for visible-light mediated (λ ≥ 420 nm) H2S decomposition and H2 generation

This article reports our investigation on H₂ generation from visible light (λ ≥ 420 nm) photodecomposition of H₂S by nanomaterial catalysts, α-Fe₂O₃ and its chemically modified Fe_2−xGa_xO₃ (Ga substitution at x = 0.6, FeGaO₃-I and x = 1.0, FeGaO₃-II). Simple template-free hydrothermal technique was employed to synthesize the three photocatalysts. XRD study reveals rhombohedral nanocrystalline structure and FESEM shows nanospheres morphology for Fe₂O₃ and nanosticks/nanorods for both FeGaO₃-I, and FeGaO₃-II. In H₂ generation, Fe₂O₃ and FeGaO₃-II perform moderate and almost same activities in the fresh and used conditions (quantum yield, QY = 6.0–6.8% at 550 nm). Contrarily, fresh FeGaO₃-I exhibits a greater activity (11.2% QY) and the activity is further enhanced (QY = 15.3%) on regeneration and reuse. The intricacy, as resolved by XRD and FESEM, appears to take place through morphology transformation. The present work, thus, successfully demonstrates H₂ generation from H₂S by nanostructured photocatalysts involving morphology dependent activity enhancement.