Biological sulfate reduction of a sulfate-rich industrial waste liquor using sulfate reducing bacteria

An industrial waste liquor having high sulfate concentrations was subjected to biological treatment using the sulfate-reducing bacteria (SRB) Desulfovibrio desulfuricans. Toxicity levels of different sulfate, cobalt and nickel concentrations toward growth of the SRB with respect to biological sulfate reduction kinetics was initially established. Optimum sulfate concentration to promote SRB growth amounted to 0.8 - 1 g/L. The strain of D. desulfuricans used in this study initially tolerated up to 4 -5 g/L of sulfate or 50 mg/L of cobalt and nickel, while its tolerance could be further enhanced through adaptation by serial subculturing in the presence of increasing concentrations of sulfate, cobalt and nickel. From the waste liquor, more than 70% of sulfate and 95% of cobalt and nickel could be precipitated as sulfides, using a preadapted strain of D. desulfuricans. Probable mechanisms involving biological sulfide precipitation and metal adsorption onto precipitates and bacterial cells are discussed.

Catalytic Reduction of Graphene Oxide Nanosheets by Glutathione Peroxidase Mimetics Reveals a New Structural Motif in Graphene Oxide

A catalytic reduction of graphene oxide (GO) by glutathione peroxidase (GPx) mimics is reported. This study reveals that GO contains peroxide functionalities, in addition to the epoxy, hydroxyl and carboxylic acid groups that have been identified earlier. It also is shown that GO acts as a peroxide substrate in the GPx-like catalytic activity of organoselenium/tellurium compounds. The reaction of tellurol, generated from the corresponding ditelluride, reduces GO through the glutathione (GSH)-mediated cleavage of the peroxide linkage. The mechanism of GO reduction by the tellurol in the presence of GSH involves the formation of a tellurenic acid and tellurenyl sulfide intermediates. Interestingly, the GPx mimics also catalyze the decarboxylation of the carboxylic acid functionality in GO at ambient conditions. Whereas the selenium/tellurium-mediated catalytic reduction/decarboxylation of GO may find applications in bioremediation processes, this study suggests that the modification of GO by biologically relevant compounds such as redox proteins must be taken into account when using GO for biomedical applications because such modifications can alter the fundamental properties of GO.

In Vivo Genotoxicity Assessment of Titanium Dioxide Nanoparticles by Allium cepa Root Tip Assay at High Exposure Concentrations

The industrial production and commercial applications of titanium dioxide nanoparticles have increased considerably in recent times, which has increased the probability of environmental contamination with these agents and their adverse effects on living systems. This study was designed to assess the genotoxicity potential of TiO2 NPs at high exposure concentrations, its bio-uptake, and the oxidative stress it generated, a recognised cause of genotoxicity. Allium cepa root tips were treated with TiO2 NP dispersions at four different concentrations (12.5, 25, 50, 100 mu g/mL). A dose dependant decrease in the mitotic index (69 to 21) and an increase in the number of distinctive chromosomal aberrations were observed. Optical, fluorescence and confocal laser scanning microscopy revealed chromosomal aberrations, including chromosomal breaks and sticky, multipolar, and laggard chromosomes, and micronucleus formation. The chromosomal aberrations and DNA damage were also validated by the comet assay. The bio-uptake of TiO2 in particulate form was the key cause of reactive oxygen species generation, which in turn was probably the cause of the DNA aberrations and genotoxicity observed in this study.

Synergistic effect of static magnetic field and HA-Fe3O4 magnetic composites on viability of S. aureus and E. coli bacteria

In addressing the issue of prosthetic infection, this work demonstrated the synergistic effect of the application of static magnetic field (SMF) and ferrimagnetic substrate properties on the bactericidal property in vitro. This aspect was studied using hydroxyapatite (HA)-xFe(3)O(4) (x=10, 20, and 40 wt.%) substrates, which have different saturation magnetization properties. During bacteria culture experiments, 100 mT SMF was applied to growth medium (with HA-xFe(3)O(4) substrate) in vitro for 30, 120, and 240 min. A combination of MTT assay, membrane rupture assays, live/dead assay, and fluorescence microscopic analysis showed that the bactericidal effect of SMF increases with the exposure duration as well as increasing Fe3O4 content in biomaterial substrates. Importantly, the synergistic bactericidal effect was found to be independent of bacterial cell type, as similar qualitative trend is measured with both gram negative Escherichia coli (E. coli) and gram positive Staphylococcus aureus (S. aureus) strains. The reduction in E. coli viability was 83% higher on HA-40 Wt % Fe3O4 composite after 4 h exposure to SMF as compared to nonexposed control. Interestingly, any statistically significant difference in ROS was not observed in bacterial growth medium after magnetic field exposure, indicating the absence of ROS enhancement due to magnetic field. Overall, this study illustrates significant role being played by magnetic substrate compositions towards bactericidal property than by magnetic field exposure alone. (c) 2013 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 102B: 524-532, 2014.

Few-Layer Borocarbonitride Nanosheets: Platinum-Free Catalyst for the Oxygen Reduction Reaction

The present study demonstrates the use of few-layer borocarbonitride nanosheets synthesized by a simple method as non-platinum cathode catalysts for the oxygen reduction reaction (ORR) in alkaline medium. Composition-dependent ORR activity is observed and the best performance was found when the composition was carbon-rich. Mechanistic aspects reveal that ORR follows the 4e(-) pathway with kinetic parameters comparable to those of the commercial Pt/C catalyst. Excellent methanol tolerance is observed with the BCN nanosheets unlike with Pt/C.

Rhythmic egg-laying behaviour in virgin females of fruit flies Drosophila melanogaster

Fruit fly Drosophila melanogaster females display rhythmic egg-laying under 12: 12 h light/dark (LD) cycles which persists with near 24 h periodicity under constant darkness (DD). We have shown previously that persistence of this rhythm does not require the neurons expressing pigment dispersing factor (PDF), thought to be the canonical circadian pacemakers, and proposed that it could be controlled by peripheral clocks or regulated/triggered by the act of mating. We assayed egg-laying behaviour of wild-type Canton S (CS) females under LD, DD and constant light (LL) conditions in three different physiological states; as virgins, as females allowed to mate with males for 1 day and as females allowed to mate for the entire duration of the assay. Here, we report the presence of a circadian rhythm in egg-laying in virgin D. melanogaster females. We also found that egg-laying behaviour of 70 and 90% females from all the three male presence/absence protocols follows circadian rhythmicity under DD and LL, with periods ranging between 18 and 30 h. The egg-laying rhythm of all virgin females synchronized to LD cycles with a peak occurring soon after lights-off. The rhythm in virgins was remarkably robust with maximum number of eggs deposited immediately after lights-off in contrast to mated females which show higher egg-laying during the day. These results suggest that the egg-laying rhythm of D. melanogaster is endogenously driven and is neither regulated nor triggered by the act of mating; instead, the presence of males results in reduction in entrainment to LD cycles.

Facile hydrothermal synthesis of carbon nanoparticles and possible application as white light phosphors and catalysts for the reduction of nitrophenol

We report a simple hydrothermal synthesis of highly reproducible carbon nanoparticles in a size range between 2 and 7 nmfroma single precursor sucrose without either surface passivating agents or acids and bases. The carbon nanoparticles can be used as white light phosphors, especially for ultraviolet light emitting diodes and metal-free catalyst for the reduction of nitrophenol.

Lattice Reduction Aided Detection in Large-MIMO Systems

Lattice reduction (LR) aided detection algorithms are known to achieve the same diversity order as that of maximum-likelihood (ML) detection at low complexity. However, they suffer SNR loss compared to ML performance. The SNR loss is mainly due to imperfect orthogonalization and imperfect nearest neighbor quantization. In this paper, we propose an improved LR-aided (ILR) detection algorithm, where we specifically target to reduce the effects of both imperfect orthogonalization and imperfect nearest neighbor quantization. The proposed ILR detection algorithm is shown to achieve near-ML performance in large-MIMO systems and outperform other LR-aided detection algorithms in the literature. Specifically, the SNR loss incurred by the proposed ILR algorithm compared to ML performance is just 0.1 dB for 4-QAM and < 0.5 dB for 16-QAM in 16 x 16 V-BLAST MIMO system. This performance is superior compared to those of other LR-aided detection algorithms, whose SNR losses are in the 2 dB to 9 dB range.

Titanium promoted reduction of imines with Grignards, silanes, and zinc: identification of a new mechanism with silanes

Aldimines react with reducing agents, such as Grignards, phenylsilane or zinc in the presence of titanium(IV) isopropoxide to form amines and reductively coupled imines (diamines). Using deuterium labeled reagents, the mechanism of reduction to form amines is described. Reducing agents, such as the Grignard and zinc result in the formation of low valent titanium (LVT), which in turn reduces the imine. On the other hand, phenylsilane reacts by a distinctly different mechanism and where a hydrogen atom from silicon is directly transferred to the titanium coordinated imine. (c) 2014 Elsevier Ltd. All rights reserved.

Effect of size reduction on magnetic ordering in Bi0.2Sr0.8MnO3

We present a comparative study of the temperature dependent magnetic properties and electron paramagnetic resonance parameters of nano and bulk samples of Bi0.2Sr0.8MnO3 (BSMO). Bulk BSMO is known to have a high T-N similar to 260K and robust charge ordering (T-CO similar to 360 K). We confirm that the bulk sample shows an antiferromagnetic transition around similar to 260K and a spin-glass transition similar to 40 K. For the nano sample, we see a clear ferromagnetic transition at around similar to 120 K. We conclude that spin glass state, which is present due to the co-existence of antiferromagnetic and ferromagnetic states in the bulk sample, is suppressed in the nano sample and ferromagnetism is induced instead. (C) 2014 AIP Publishing LLC.

Rad51-Rad52 Mediated Maintenance of Centromeric Chromatin in Candida albicans

Specification of the centromere location in most eukaryotes is not solely dependent on the DNA sequence. However, the non-genetic determinants of centromere identity are not clearly defined. While multiple mechanisms, individually or in concert, may specify centromeres epigenetically, most studies in this area are focused on a universal factor, a centromere-specific histone H3 variant CENP-A, often considered as the epigenetic determinant of centromere identity. In spite of variable timing of its loading at centromeres across species, a replication coupled early S phase deposition of CENP-A is found in most yeast centromeres. Centromeres are the earliest replicating chromosomal regions in a pathogenic budding yeast Candida albicans. Using a 2-dimensional agarose gel electrophoresis assay, we identify replication origins (ORI7-LI and ORI7-RI) proximal to an early replicating centromere (CEN7) in C. albicans. We show that the replication forks stall at CEN7 in a kinetochore dependent manner and fork stalling is reduced in the absence of the homologous recombination (HR) proteins Rad51 and Rad52. Deletion of ORI7-RI causes a significant reduction in the stalled fork signal and an increased loss rate of the altered chromosome 7. The HR proteins, Rad51 and Rad52, have been shown to play a role in fork restart. Confocal microscopy shows declustered kinetochores in rad51 and rad52 mutants, which are evidence of kinetochore disintegrity. CENP-A(CaCse4) levels at centromeres, as determined by chromatin immunoprecipitation (ChIP) experiments, are reduced in absence of Rad51/Rad52 resulting in disruption of the kinetochore structure. Moreover, western blot analysis reveals that delocalized CENP-A molecules in HR mutants degrade in a similar fashion as in other kinetochore mutants described before. Finally, co-immunoprecipitation assays indicate that Rad51 and Rad52 physically interact with CENP-A(CaCse4) in vivo. Thus, the HR proteins Rad51 and Rad52 epigenetically maintain centromere functioning by regulating CENP-A(CaCse4) levels at the programmed stall sites of early replicating centromeres.

SELECTIVE ALDEHYDE REDUCTION IN KETOALDEHYDES WITH NaBH4-Na2CO3-H2O AT ROOM TEMPERATURES

A variety of aliphatic and aromatic ketoaldehydes were reduced to the corresponding ketoalcohols with a mixture of sodium borohydride (1.2 equivalents) and sodium carbonate (sixfold molar excess) in water. Reactions were performed at room temperatures over (typically) 2 h, and yields of isolated products generally ranged from 70% to 85%. A biscarbonate-borane complex, (BH3)(2)CO2](2-) 2Na(+), possibly formed from the reagent mixture, is likely the active reductant. The moderated reactivity of this acylborane species would explain the chemoselectivity observed in the reactions. The readily available reagents and the mild aqueous conditions make for ease of operation and environmental compatibility, and make a useful addition to available methodology.

The morphology dependent electrocatalytic activity of Ir nanostructures towards oxygen reduction

Iridium nanostructures with different morphologies are synthesized by a simple, environmentally friendly approach in aqueous media under mild conditions. The morphology dependent electrocatalytic activity of Ir nanochains and nanoparticles towards oxygen reduction reaction (ORR) has been demonstrated in both acidic and alkaline media. Comparative electrochemical studies reveal that nanochains exhibit significantly enhanced ORR activities in both acidic and alkaline media as compared with nanoparticles, as a result of the continuous structure of interconnected particles. The mechanism of oxygen reduction on Ir nanostructures predominantly follows a four-electron pathway in alkaline and acidic solutions. Excellent stability and good selectivity towards methanol tolerance are reported.

Sensitivity of simulated climate to latitudinal distribution of solar insolation reduction in solar radiation management

Solar radiation management (SRM) geoengineering has been proposed as a potential option to counteract climate change. We perform a set of idealized geoengineering simulations using Community Atmosphere Model version 3.1 developed at the National Center for Atmospheric Research to investigate the global hydrological implications of varying the latitudinal distribution of solar insolation reduction in SRM methods. To reduce the solar insolation we have prescribed sulfate aerosols in the stratosphere. The radiative forcing in the geoengineering simulations is the net forcing from a doubling of CO2 and the prescribed stratospheric aerosols. We find that for a fixed total mass of sulfate aerosols (12.6 Mt of SO4), relative to a uniform distribution which nearly offsets changes in global mean temperature from a doubling of CO2, global mean radiative forcing is larger when aerosol concentration is maximum at the poles leading to a warmer global mean climate and consequently an intensified hydrological cycle. Opposite changes are simulated when aerosol concentration is maximized in the tropics. We obtain a range of 1 K in global mean temperature and 3% in precipitation changes by varying the distribution pattern in our simulations: this range is about 50% of the climate change from a doubling of CO2. Hence, our study demonstrates that a range of global mean climate states, determined by the global mean radiative forcing, are possible for a fixed total amount of aerosols but with differing latitudinal distribution. However, it is important to note that this is an idealized study and thus not all important realistic climate processes are modeled.

Controlling air solubility to maintain `'Cassie'' state for sustained drag reduction

`'Cassie'' state of wetting can be established by trapping air pockets on the crevices of textured hydrophobic surfaces, leading to significant drag reduction. However, this drag reduction cannot be sustained due to gradual dissolution of trapped air into water. In this paper, we explore the possibility of sustaining the underwater Cassie state of wetting in a microchannel by controlling the solubility of air in water; the solubility being changed by controlling the local absolute pressure near the surface. We show that using this method, we can in fact make the water locally supersaturated with air thus encouraging the growth of trapped air pockets on the surface. In this case, the water acts as a pumping medium, delivering air to the crevices of the hydrophobic surface in the microchannel, where the presence of air pockets is most beneficial from the drag reduction perspective. In our experiments, the air trapped on a textured surface is visualized using total internal reflection based technique, at different local absolute pressures with the pressure drop (or drag) also being simultaneously measured. We find that, by controlling the pressure and hence the solubility close to the surface, we can either shrink or grow the trapped air bubbles, uniformly over a large surface area. The experiments show that, by precisely controlling the pressure and hence the solubility we can sustain the `'Cassie state'' over extended periods of time. This method thus provides a means of getting sustained drag reduction from a textured hydrophobic surface in channel flows. (C) 2014 Elsevier B.V. All rights reserved.