Miracle-dz/UniFAR-FTUs huggingface dataset:
Source of Photosynthetic Oxygen in Bicarbonate-Stimulated Hill Reaction

The bicarbonate ion can stimulate oxygen evolution fivefold in chloroplasts performing a Hill reaction (oxidation of water to molecular oxygen and reduction ofan artificial oxidant). When bicarbonate containing oxygen-18 is administered, however, the evolved oxygen contains only oxygen-16. Bicarbonate, therefore, cannot be the immediate source ofphotosynthetically evolved oxygen. It is commonly accepted that molecular oxygen evolved during photosynthesis arises from the splitting of H20 molecules and not, as originally postulated by Warburg (1), from the splitting of CO2 molecules. However, the direct evidence to support this belief has been controversial. Experiments using the tracer 180 to reveal the source of 02 can be ambiguous if the normal isotopic exchange between H20 and CO2 is not controlled. Important factors in speeding isotopic exchange are low pH (2) and the presence of the enzyme carbonic anhydrase. Ruben et al. (3), using whole algal cells, could not control these critical internal factors (4). Thus the tracer method, as previously applied, could not allow definite conclusions [see criticisms by Warburg (1)]. Recently, it has become evident (5-7) that the bicarbonate ion, HCO3, does in fact play a critical and direct role in photosystem II activity leading to oxygen evolution. This effect, first discovered by Warburg and Krippahl (8) and offered as proof of Warburg's theory (1), is distinct from the well-known role of CO2 as a terminal electron acceptor in photosynthesis. Removal of HCOR from broken chloroplast fragments can suppress the Hill reaction more than 90 percent (6). To see whether or not HCO3 was acting as the immediate source of 02, as postulated by Warburg and more recently by Metzner (9), we again resorted to tracer methods. The material used was isolated broken chloroplast fragments instead of whole cells. This minimized the problems of low intracellular pH and removed nearly all carbonic anhydrase (10), thus effectively controlling the isotopic exchange reaction between H20 and CO2. In addition, by depieting chloroplasts of HCO3, oxygen evolution was made dependent on an exogenous source of this ion. When labeled bicarbonate, HCI8O3, was resupplied, oxygen evolution 31 OCTOBER 1975 commenced at a high rate. The oxygen given off, however, was unlabeled-that is,
Size Distributions of 0.5 to 20 μm Aerodynamic Diameter Lead-Containing Particles from Aerosol Sampler Walls and Filters

The study presented here investigates the number weighted particle size distributions of aerosols generated in the laboratory from lead oxide and lead sulfide dusts and sampled by Institute of Occupational Medicine (IOM) and closed face cassette (CFC) samplers as determined by scanning electron microscopy (SEM). The wall deposits and filter deposits from each sampler were characterized separately. A Mann-Whitney statistical analysis revealed that differences in the number weighted distributions of particles captured by the filter and the wall were not significant over the size range (up to 20 μm aerodynamic equivalent diameter) present in these laboratory-generated aerosols. Furthermore, for these samples it was not possible to distinguish an absolute difference between the IOM and CFC filter catches. By comparing direct measurements of aerodynamic equivalent diameter (AED) made by an Aerodynamic Particle Sizer (APS) to AEDs calculated from SEM images, empirical shape factors for lead oxide and lead sulfide were determined. To validate this approach APS and SEM measurements of the AED of 2 μm and 6 μm physical diameter monodisperse glass and polystyrene microspheres were made. Using the shape factors of spheres and the known densities of these materials, it was found that the SEM determinations of AED agreed with the APS results. To demonstrate the reliability of the redeposition method of sample preparation, lead sulfide and lead oxide aerosols were briefly sampled by IOM samplers such that sufficient particles were collected for SEM examination directly on the filter but not so many that particles were likely to touch or overlap. Half of each filter was analyzed in the SEM directly; the other half was ultrasonically removed and re-deposited for analysis by SEM. There were no statistically significant differences in their number weighted size distributions, demonstrating that the sample treatment process does not change the size distribution of these particular aerosols.
Predicting the bioavailability of metals and metal complexes: Critical review of the biotic ligand model

Environmental Context. The chemical speciation of trace metals greatly influences their biological effects. Nonetheless, no clear consensus currently exists as to when metal complexes are bioavailable, especially for field conditions. Recently, the USA EPA has incorporated the biotic ligand model (BLM) into their regulatory framework and many other countries are now examining the implications of following suit. This review examines the fundamental basis of the BLM in order to provide the reader with an understanding of its potential uses and limitations. Abstract. The biotic ligand model is a useful construct both for predicting the effects of metals to aquatic biota and for increasing our mechanistic understanding of their interactions with biological surfaces. Since biological effects due to metals are always initiated by metal bioaccumulation, the fundamental processes underlying bio-uptake are examined in this review. The model assumes that the metal of interest, its complexes, and metal bound to sensitive sites on the biological surface are in chemical equilibrium. Therefore, many of the equilibrium constants required for the model have been compiled and their methods of determination evaluated. The underlying equilibrium assumption of the BLM is also examined critically. In an attempt to identify which conditions are appropriate for its application, several documented examples of failures of the BLM are discussed. Finally, the review is concluded by identifying some important future research directions.
The incorporation of arsenic in GaN by metalorganic chemical vapor deposition

We report on the successful incorporation of arsenic (As) in GaN during metalorganic chemical vapor deposition (MOCVD). A characteristic room-temperature luminescence band centered around 2.6 eV (480 nm), similar to the peak position of the As ion-implanted GaN, is found to be related to the As impurity in the MOCVD grown GaN:As films. The arsenic incorporation efficiency as a function of experimental conditions and structure is presented. Temperature- and power-dependent cathodoluminescence measurements have been performed to help establish the nature of the As-related peak.
Modeling biomass gasification system using multistep kinetics under various oxygen–steam conditions

Biomass gasification is an effective method to convert low‐value lingocellulosic biomass into useful gas products. The ability to predict the gas composition is important to process design. In this study, simulations of biomass gasification were carried out for various feedstocks at different operating conditions, and the model results were validated using experimental data. A multistep kinetics model was developed to predict the syngas composition using different biomass feedstocks under various oxygen‐enriched air and steam conditions. The oxygen level in the gasifying agent ranged from 21% (air) to 45% (pure oxygen). Five different biomass materials were used, including pine, maple–oak mixture, seed corn, corn stover, and switchgrass. The fluidized bed gasifier was maintained at 800°C. The present kinetics model was able to predict the concentrations of H2, CO, CO2, H2O, CH4, and N2 in the syngas, and the predicted compositions were in good agreement with the experimental data. The results show that the model was sensitive to the variation in the oxygen level, steam flow rate, and the composition of the biomass material. As the oxygen level increased, the model also predicted the increase in H2, CO, CH4, and the H2/CO ratio. The mechanism on improving the syngas quality was also explained by analyzing the reaction equations. The increase in hydrogen is believed to be due to the use of steam for gasification. The present model can further be integrated into the process simulation model for predicting the performance of a biorefinery to help utilize biomass energy. © 2015 American Institute of Chemical Engineers Environ Prog, 34: 1148–1155, 2015
Changes in ECT and dielectric dissipation factor of insulating oils due to aging in oxygen

It is believed that the aging of insulating oils affects the electrostatic charging tendency (ECT) and dielectric dissipation factor (tan /spl delta/), but there is little hard evidence. We have investigated changes in ECT and tan /spl delta/ of insulating oils aged with oxygen at elevated temperature. We found that ECT and tan /spl delta/ increased with aging time. In some oils aged with a small amount of oxygen, ECT and tan /spl delta/ increased much more than in other oils aged with a large amount of oxygen. In yet other insulating oils, ECT and tan /spl delta/ showed a peak and then declined. Moreover, it was found that aged insulating oil close to the peak in tan /spl delta/ is very unstable. This result suggests that the methods of measurements of tan /spl delta/ of insulating oil prescribed in International Electrotechnical. Commission (IEC) 60247 and Japanese Industrial Standards (JIS) C2101 may be unsatisfactory. The reason is that since in these methods tan /spl delta/ is measured at elevated temperature (IEC 60247, 90/spl deg/C and JIS C2101, 80/spl deg/C), the quality of the insulating oil, especially aged oil, is changed during the measurement, resulting in an incorrect reading.
Analysis of Phase-Transfer-Catalyzed O-Alkylation Reaction Using Fractional Factorial Design Method

ABSTRACT The reactions of alcohols and alkyl halides to synthesize di-ether compounds under phase-transfer catalysis conditions were carried out in an alkaline solution/organic solvent two-phase medium. Accordingly, the concentrations of alkyl halide, di-ether compound, active intermediate (QOR), and hydration number of active intermediate (QOR) were measured during these reactions. The fractional factorial design (FFD) method was first employed to study the effects of single factors and the effects of their interactions on the PTC reaction. The following reaction conditions (or factors) were investigated in the present FFD analysis: amount of alkaline salt, temperature, amount of water, amount of catalyst, volume of organic solvent, and agitation speed. A polynomial model and an analysis of variance table (ANOVA) were developed to connect the reaction conditions and the conversion from statistical results. Plots of the partition coefficient of alcohol between organic and aqueous phase, the concentration of active intermediate (QOR), and the hydration number of active intermediate (QOR) were used to elucidate the reasons for interactions between factors.
Potential functions for alkali halide molecules

Repulsion and dispersion parameters for alkali–metal halide diatomic molecules were computed by ionic Rittner and truncated Rittner models with radial dependent repulsion terms. Experimental data on the bond energies, the equilibrium interionic distances, and the spectroscopic frequencies were employed for the purpose. The polarizabilities used were also computed from the experimental dipole moments of alkali–metal halides. The potential parameters obtained were compared with parameters from other sources and checked for consistency. The computed potential parameters of alkali–metal halide monomer molecules were used to predict the energetics and geometries for alkali–metal halide dimer molecules. The predicted values are in good agreement with experiment and other calculations indicating the consistency and reliability of the potential employed. Although the magnitude of repulsive and dispersive energy terms varies with potential functions employed, the difference between the two for a molecule is constant. The repulsive term is more sensitive than the attractive term. The uncertainty in the exponential repulsion results in an inaccurate representation of the attractive contribution. Introduction of the radial‐dependent repulsion term changes the relative magnitudes of repulsive and dispersive parameters and hence the relative contribution to the total potential with monomers. But this has no significant effect on the energetics and geometries of the dimers.
Interdiffusion in the Ta‐W system

Interdiffusion in the Ta‐W system, a continuous body‐centered‐cubic solid solution, has been investigated in the temperature range 1300–2100 °C with single‐phase diffusion couples prepared by chemical vapor deposition. Fine inclusions, presumably oxides or carbides, decorated the couple interfaces and served as Kirkendall markers. The diffusion annealing times ranged from 16 h to 220 days. The resulting concentration profiles were measured with the electron microprobe and analytical electron microscope. The chemical diffusion coefficient was determined by the classical Boltzmann–Matano technique. The intrinsic diffusivities were determined by the technique of Darken. In the composition range 20–80 at. % W, the activation energy Q for chemical diffusion was constant at 130.5±1.5 kcal/mole. The activation energies for the intrinsic diffusion coefficients at the composition of the Kirkendall marker plane, approximately 70 at. % W, were Q(Ta)=132.3±0.5 kcal/mole and Q(W)=122.0±0.5 kcal/mole.
Novel approaches to flexible visible transparent hybrid films for ultraviolet protection

ABSTRACT: Herein, we present an overview of the most recentachievements and innovations regarding the development offlexible visible transparent films for selective ultraviolet (UV)shielding, with focus on those based on hybrid inorganic–or-ganic materials. The main synthetic paths used nowadays toensure a high degree of protection are reviewed. Polymerscontaining organic UV absorbing molecules, hybrid mixturesof polymers and nanoparticles, and the recently introducedseries of structures displaying structural color, are identifiedas the three main types of materials used for this purpose.The use of biocompatible and flexible films to achieve spec-trally selective UV protection can find applications in a widediversity of fields such as photo-treatment of skin diseases,food and beverage packing, and storage of cosmetics. V C 2012Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 50:945–956, 2012 KEYWORDS: flexibility; nanocomposites; nanostructures; nano-particles; optics; photonic crystals; polymer films; polysilox-anes; transparency; UV protection; UV-vis spectroscopyINTRODUCTION
An all-solid-state rechargeable aluminum–air battery with a hydroxide ion-conducting Sb(V)-doped SnP2O7 electrolyte

An anhydrous hydroxide ion conductor, Sn0.92Sb0. 08P2O7, can function as an electrolyte for aluminum–air batteries, where aluminum is oxidized to an aluminate species during discharge, and the aluminate species is reduced to aluminum by charging the cell. This battery generated an open-circuit voltage of ca. 1.6 V with a discharge capacity of ca. 800 mA h g−1electrode.
Synthesis of chiral ruthenium and cobalt (meso-2-amidophenyl)porphyrins and their catalytic activity in cyclopropanation reactions

The preparation of two chiral porphyrin ligands 7 and 9 and of their ruthenium and cobalt complexes is reported. These new complexes have been used as catalysts in cyclopropanation reactions. Both 7-Ru and 9-Ru complexes showed a catalytic activity in the enantiomeric cyclopropanation of α-methylstyrene by ethyldiazoacetate whereas amination of ethylbenzene by arylazide in the presence of 7-Ru or 9-Ru did not stop at the corresponding benzylamine stage but instead afforded the corresponding benzylimine.
Platinum and palladium ions adsorption at the trace amounts by radiation crosslinked carboxymethylchitin and carboxymethylchitosan hydrogels

Adsorption of palladium and platinum ions at the trace amounts onto radiation crosslinked carboxymethylchitin (CMCht) and carboxymethylchitosan (CMChts) has been investigated. Maximum adsorption capacities for palladium were 2.679 and 1.053 mg/g dry gel, whereas for platinum they were 2.513 and 1.155 mg/dry gel for CMCht and CMChts, respectively. Retention capacity values for palladium were 0.45 and 0.06; for platinum 0.25 and 0.11 mEquiv. /g for CMCht and CMChts, correspondingly. It has been shown that adsorption of Pd and Pt ions onto both hydrogels were dependent on the chloric and nitric ions concentration. Desorption experiments in HCl and HNO3 solutions proved that adsorption is governed by chelating mechanism rather than ion-exchange one. SEM-EDX spectroscopy showed that palladium and platinum ions were homogeneously distributed in all sections of hydrogel matrix. DSC experiments demonstrated decreasing in the decomposition temperature of polymers after inclusion of palladium and platinum ions, suggesting that metals are causing lowering of stability in polymer structural integrity. 2007 Wiley Periodicals, Inc.
Gas Transport in Proton Exchange Membranes for use in Fuel Cell Applications

The objectives of this research were to study the gas transport properties of proton exchange membranes (PEM), namely disulfonated poly(arylene ether sulfone) (BPSH-35), post sulfonated diels-alder poly(phenylene) (SDAPP), and poly(perfluoro sulfonic acid) (Nafion). The O2 gas permeabilities were found to be lower in BPSH and SDAPP as compared to poly(perfluoro sulfonic acid) because of difference in Tg (TgBSPH= 250 oC, TgSDAPP= 330 oC versus TgNafion=150 oC). Higher Tg polymers have a more rigid, inflexible polymer segments causing a reduction in gas permeability. In comparison to SDAPP, BPSH has a lower O2 gas permeability because of the bulky side groups in the SDAPP backbone. O2 sorption measurements were carried out both under non-humidified and humidified conditions as a function of relative humidity and temperature at a normal PEM operating pressure of 1 atm. Under non-humidified conditions, BPSH, SDAPP, and Nafion 112 exhibited Henry’s Law sorption, consistent with dilute dissolution of O2 into the polymer matrix. The enthalpies of sorption were calculated to determine the interaction of O2 with each membrane. The sorption enthalpies in BPSH and SDAPP increased with increasing pressure indicating the formation of more O2-O2 interactions. The enthalpies in Nafion 112 were relatively constant with increasing pressure. In the presence of moisture, the sorption behavior changed from Henry’s Law to Type IV sorption behavior, which is common in hydrophilic polymers. The SDAPP membrane was found to have the highest percent wet O2 mass uptake because of a higher number of sulfonic acid groups interacting with the water/O2 system. Finally the O2 sorption for various porous catalyst powders, consisting of platinum supported on carbon was measured in the non-humidified and humidified state. The catalysts were found to have Knudsen diffusion in the non-humidified state with 20 wt% Pt-C having the largest O2 sorption. In the humidified state, the highest O2 mass uptake was achieved with 40 wt% Pt-C. These results are explained in terms of the trade-off between catalyst dispersion and catalyst size. Furthermore, O2 sorption measurements were utilized for membrane electrode assemblies containing 40 wt% Pt-C and hot pressed at 210 oC for BPSH-35 (25 and 80K) and Nafion 112 membranes. The same sorption behavior occurred in the MEAs as in the neat membrane, but at a lower capacity. This is because the electrode introduces a more tortuous path to the gas molecules permeating across the membrane.
Synthetic Jet Fuel Production by Combined Propene Oligomerization and Aromatic Alkylation over Solid Phosphoric Acid

The oligomerization of propene, as well as the alkylation of benzene and toluene with propene, was evaluated at 160−240 °C, 3.8 MPa, and aromatic to olefin ratios of 1:6 to 6:1 using solid phosphoric acid (SPA) as a catalyst. It was found that steric effects were more important than electronic effects in determining alkylation rate and selectivity. Monoalkylation was favored even at the lowest aromatic to olefin ratio, and the isomer distribution of dialkylated aromatics remained constant irrespective of the conversion or operating conditions. No transalkylation or alkylbenzene isomerization activity was observed. It was shown that olefin oligomerization and aromatic alkylation could be combined in a single SPA catalyzed reaction system to produce a synthetic jet fuel that meets Jet A-1 specifications.
Potencial de culturas de cobertura em acumular carbono e nitrogênio no solo no plantio direto e a melhoria da qualidade ambiental

Soil is an important component of the ecosystem. Its management affects air and water quality. Nowadays, the soil potential to sequester carbon and, therefore, mitigate global warming, is an emergent subject. The main goals of this research were: (a) to evaluate the potential of cover crops (black oat, blue lupine (priori to oat + vetch), velvet bean and jack bean) used in corn production systems to increase soil organic carbon (OC) and total nitrogen (TN) content in a sandy-loam typic Paleudalf, in comparison with traditional farm system (fallow/corn) and a native grass field; and (b) to assess soil potential for acting as a sink of atmospheric CO2 under a no-tillage system. To establish this experiment, all treatments, except for native pasture, were conventionally tilled with plow plus disk for soil fertilization and liming. This soil disturbance caused an expressive decrease of soil OC and TN contents as compared to native vegetation, in the first four years. From the fourth to the eighth year, the cropping systems in no-tillage recovered the OC and TN contents in soil, this effect being highest in corn + velvet bean. At the eighth year, the soil under the corn+velvet bean system had 5.42 Mg ha-1 of C and 1.27 Mg ha-1 of N more than the fallow/corn system, in the 0 to 20 cm soil layer. It was estimated that corn+velvet bean, in the eight year, acted as a sink of 15.5 Mg ha-1 of CO2, while the treatment fallow/corn had a net emission of 4.32 Mg ha-1 of CO2. The use of conservation cropping systems in substitution to traditional fallow/corn systems used by farmers was an efficient tool to store soil organic matter and increase agricultural carbon sequestration and, therefore, mitigate the greenhouse effect.
Flow and heat transfer to modified second grade fluid over a non-linear stretching sheet

The objective of the present work is to analyze the two-dimensional boundary layer flow and heat transfer of a modified second grade fluid over a non-linear stretching sheet of constant surface temperature. The modelled momentum and energy equations are deduced to a system of ordinary differential equations by employing suitable transformations in boundary layer region and integrated numerically by fourth and fifth order Runge-Kutta Fehlberg method. Additionally, the analytic solutions of the governing problem are presented for some special cases. The secured results make it clear that the power-law index reduces both the momentum and thermal boundary layers. While the incremented values of the generalized second grade parameter leads to an increase in the momentum boundary layer and a decrease in the thermal boundary layer. To see the validity of the present results we have made a comparison with the previously published results as a special case with an outstanding compatibility.