Miracle-dz/UniFAR-FTUs huggingface dataset:
Synthesis and characterization of thiophene functionalized polystyrene copolymers and their electrochemical properties

Thiophene functionalized polystyrene samples (TFPS) were synthesized by atom transfer radical polymerization (ATRP) of styrene, followed by Suzuki coupling with 3-thiophene (Th) boronic acid. Conducting graft polymer of TFPS with thiophene was achieved at 1.5 V in tetrabutylammonium tetrafluoroborate/dichloromethane (TBAFB/DM) by electrochemical methods. Spectroelectrochemical analysis of the resulting copolymers [P(TFPS-co-Th)] reflected electronic transitions at 449, 721 and 880 nm, revealing π − π* transition, polaron and bipolaron band formation, respectively. We also successfully established the utilization of dual type complementary colored polymer electrochromic devices using P(TFPS-co-Th)/poly(3,4-ethylenedioxythiophene (PEDOT) in sandwich configuration. The switching ability, stability and optical memory of the electrochromic device were investigated by UV–visible spectrophotometry and cyclic voltammetry. Device switches between brown and blue color with a switching time of 1.3 s were prepared with optical contrast (%ΔT) of 25 %. Copyright © 2005 Society of Chemical Industry
Many chain correlated dynamics in polymer fluids

Starting from the formally exact Liouville equation, we derive a generalized Langevin equation for the simultaneous correlated motion of several molecules in dense melts. Our calculations are based upon phase space kinetic theory and Mori–Zwanzig projection operator techniques. In the overdamped regime, a set of nonlinear coupled equations is found containing cross-interaction contributions to the frequency matrix and to the memory functions. Specializing the problem to the correlated dynamics of polymer melts enables an analytical solution for the nonlinear cross contribution of the frequency matrix. The memory functions are calculated using a generalization of the Schweizer’s single molecule mode-coupling approach. A self-consistent procedure allows a numerical solution of the diffusive dynamics of the chains on the scale of the intermolecular interactions. At long time, depending on the strength of the intermolecular mean-force potential, two different scenarios take place. For weak intermolecular inte.
Investigation of graded index SiOxNy antireflection coating for silicon solar cell manufacturing

An optimization of SiOxNy anti-reflective coatings with graded index layers for silicon solar cells based on the Bruggeman's effective medium approximation is presented. For simulation of reflectance and absorption of graded layer, the experimental optical data of silicon nitride SiNx:H and oxynitride SiOxNy obtained by Low Frequency (440 kHz) Plasma Enhanced Chemical Vapour Deposition (LF-PECVD) were used. We have shown that the graded index oxynitride antireflection coating can reduce the effective reflectance to about 2.5% but the high absorption due to high extinction coefficient compensates this improvement and reduces the short circuit current (Jsc) of the solar cell. The improvement in the Jsc can be obtained for graded SiNxOy layer with smaller value of refractive index of SiNx (n = 2.2). In this case the graded SiOxNy layer is characterized by an abrupt concentration profile and can be considered as a double antireflection coating SiO2/SiNx. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
Effects of soil compaction, seed depth, form of nitrogen fertiliser, fertiliser placement and manganese availability on barley

Investigations on light soils from 1977 to 1981 revealed important effects and interactions of husbandry methods and fertiliser placement on barley growth and yield which were largely due to their effects on Mn availability to the crop. Thus combine-drilling an acidifying fertiliser (but not a non-acidifying fertiliser) with the seed rather than broadcasting it, was very effective in controlling Mn deficiency and increasing yield substantially on Mn deficient sites. Soil compaction was beneficial where the fertiliser was broadcast, primarily because it forced shallow sowing of seed and thus kept the seminal roots near the acidifying fertiliser. Deep sowing of seed greatly reduced yield when fertiliser was broadcast but not when fertiliser was placed near the seed. These effects and interactions explain why poor crops were frequently associated with loose seedbeds, deep sowing and broadcast fertilisers.
Investigation of the electronic and geometric structures of the (110) surfaces of arsenopyrite (FeAsS) and enargite (Cu3AsS4)

Abstract The (110) surfaces of arsenopyrite (FeAsS) and enargite (Cu3AsS4) have been modelled using a Density Functional Theory (DFT) plane-wave pseudopotential method (CASTEP) in order to better understand aspects of the geometric and electronic structures of these minerals, which have important implications for the release of arsenic in acid mine drainage environments. In this study, bulk calculations of these minerals have been conducted to give consistent geometries for surface models and to establish reference states for changes at the surfaces in these models. Surface structure experimental data for enargite were collected using low-energy electron diffraction which confirmed an unreconstructed 1 × 1 (110) lattice, with a and b values of 6.38±0.3 Å and 9.92±0.5 Å, respectively. Surface calculations demonstrate geometric and electronic relaxation of both arsenopyrite and enargite (110) surfaces. Changes in atomic positions, interatomic distances, Mulliken charges and electronic configurations are reported. Enargite has a surface energy of ~0.02 eV/Å2 compared with arsenopyrite which has a surface energy of ~0.11 eV/Å2, indicating that the enargite (110) surface is more energetically stable than that of arsenopyrite. The most stable surfaces are those which relax to restore the surface coordination and partial charge balance. For both minerals this is achieved by the formation of covalent bonds. Arsenic has the most positive Mulliken charge of all the surface atoms and is, therefore, predicted to be the most reactive atom at the arsenopyrite and enargite (110) surfaces. This implies that, according to these calculations, arsenic is most likely to react with oxidative species such as O2 and H2O in environments such as those associated with acid mine drainage, potentially releasing oxides and acids of arsenic into the environment.
Covalently functionalized reduced graphene oxide by organically modified silica: a facile synthesis of electrically conducting black coatings on glass

The fabrication of black and electrically conducting films on glass substrate derived from covalently functionalized reduced graphene oxide (FRGO) has been reported in this work. Graphene oxide (GO) was first prepared following the Hummers method and then functionalized using an organically modified silicon alkoxide, 3-glycidoxypropyltrimethoxysilane (GLYMO) in an ordered fashion. Catalyst (aluminium acetylacetonate) induced selective polymerization of the epoxy groups of GO and GLYMO was found to occur via the formation of ethereal (–C–O–C–) linkages. The formation of such linkages was confirmed by IR, Raman, TGA, X-Ray diffraction and TEM studies. Finally the functionalized graphene oxide (FGO) films were subjected to thermal reduction in an inert (N2) atmosphere to obtain FRGO films. These hard FRGO films are electrically conducting and appeared as black coatings on glass. By varying the loading (20–30 wt%) of GO with the covalently bonded organically modified silica, the sheet resistance values can be tuned in a linear way from 0.8 × 106 to 1.4 × 103 Ω □−1. The uniform current–voltage (I–V) characteristics of the films can be nicely correlated with the sheet resistance values.
Metal catalyst-free low-temperature carbon nanotube growth on SiGe islands

A metal-catalyst-free growth method of carbon nanotubes (CNTs) has been developed using chemical vapor deposition of CNTs on carbon-implanted SiGe islands on Si substrates. From scanning electron microscopy and Raman measurements, the fabricated CNTs are identified as single-walled CNTs with a diameter ranging from 1.2 to 1.6 nm. Essential parts of the substrate preparation after CVD SiGe growth and carbon implant are a chemical oxidization by hydrogen peroxide solution and a heat treatment at 1000 °C prior to CNT growth. We believe that these processes enhance surface decomposition and assist the formation of carbon clusters, which play a role in seeding CNT growth. The growth technique is a practical method of growing metal-free CNTs for a variety of applications, while at the same time opening up the prospect of merging CNT devices into silicon very-large-scale-integration technology.
Greenhouse gases (CO2, CH4 and N2O) in lowland springs within an agricultural impacted watershed (Po River Plain, northern Italy)

In the Po River Plain, nitrogen surplus in permeable soils results in elevated downward nitrogen fluxes, mostly as nitrate. Lowland springs, aligned along interfaces between gravel and sandy soils, recycle part of this nitrogen to the surface and we hypothesised that they may be hot spots of N2O and other greenhouse gases, due to incomplete denitrification in the suboxic environment. In early and late summer 2009, water flow was measured and water samples were collected at the outlet and ∼1 km downstream at 14 springs; physico-chemical parameters [temperature, pH, dissolved inorganic nitrogen (DIN) and dissolved gases (O2, N2O, CH4, CO2)] were analysed. All springs were characterised by elevated nitrate concentrations (154–1411 μ M) and recycled to the surface inorganic nitrogen (∼180 kg N on average). Spring waters were suboxic (40–60% of O2 saturation) and CO2, CH4 and N2O supersaturated (26.6–2399.0, 0.002–1.02 and 0.02–1.02 μ M, respectively). CO2 and N2O underwent a significant degassing process from the supersaturated waters to the atmosphere. Calculated N2O emissions (up to 0.646 g N 2O·m −2·d −1, among the highest reported for aquatic environments) highlight the role of lowland springs as hotspots of N2O. We conclude that lowland springs located in heavily impacted watersheds recycle groundwater nitrate and have an extremely elevated potential as greenhouse gas emitters.
Photocatalytic Degradation of Toluene in Air Using a Fluidized Bed Photoreactor

The photocatalytic degradation of toluene in air was carried out on particles of TiO2 in a photocatalytic reactor that had been developed to study the treatment of organic pollutants in a gaseous phase. Hypothetically, the fluidized bed technology of this reactor could make it possible to increase the mass transfer coefficients in comparison with those of conventional photoreactors. The photocatalytic particles used were prepared by mixing TiO2 (Degussa P25) and starch in a methanol solution. The XRD and SEM results of these aggregates confirm the titanium dioxide (Degussa P25) characteristics, such as the presence of anatase on the particle surface and spongy and wrinkled morphology. Toluene concentrations varied from 0.9 to 199 ppmv, and all the experiments were carried out with a flow rate of 300 NL/h. Toluene conversions from 77% to 100% were obtained in the range studied. In this work, the regeneration processes of deactivated TiO2 photocatalysts have been investigated using FT-IR and GC/MS techniques. Benzoic acid, benzaldehyde, and benzyl alcohol were the three major intermediate products identified.
Passivation and depassivation of silicon dangling bonds at the Si/SiO2 interface by atomic hydrogen

Atomic hydrogen is found to simultaneously passivate and depassivate silicon dangling bonds at the Si(111)/SiO2 interface at room temperature via the reactions Pb+H0→PbH and PbH+H0→Pb+H2. The passivation reaction occurs more efficiently keeping the steady‐state Pb density at a low value of only 3–6×1011 cm−2 during atomic hydrogen exposure. This low Pb density can only account for a small fraction of the total number of interface states produced by atomic hydrogen.
Transient pulsed analysis on GaN HEMTs at cryogenic temperatures

A pulsed measurement of AlGaN/GaN high electron mobility transistors (HEMTs) current-voltage (I-V) output characteristics from 100 to 300 K temperatures has been systematically investigated, and a significant kink is clearly observed, which is more severe at cryogenic temperatures. By comparing the pulsed and dc I-V curves, the kink effect is more significant in the pulsed mode evaluation, which indicates a time constant related mechanism involved in the carrier transport. Moreover, a weak impact ionization by monitoring the gate current in the on-state of device has also been observed, and it is more significant at cryogenic temperatures.
Simultaneous and Rapid Microwave Synthesis of Polyacrylamide−Metal Sulfide (Ag2S, Cu2S, HgS) Nanocomposites

Polyacrylamide−metal sulfide (Ag2S, Cu2S, HgS) nanocomposites with metal sulfide nanoparticles homogeneously dispersed in the polyacrylamide (PAM) matrix have been successfully synthesized using corresponding metal salt, sulfur powder, and acrylamide monomer (AM) in ethylene glycol (EG) by microwave heating. This method is based on the simultaneous formation of metal sulfide nanoparticles and polymerization of the AM, leading to a homogeneous distribution of metal sulfide nanoparticles in PAM matrix without aggregation. EG acts simultaneously as a solvent, a microwave absorber, and a reductant; thus no additional reductant is needed. Another advantage is that no initiator for AM polymerization and no surfactant for the stabilization of these metal sulfide nanoparticles are necessary. The products are characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared (FT-IR), ultraviolet visible (UV−vis) absorption spectra, photoluminescence (PL), thermograv.
Metal-free doped carbon materials as electrocatalysts for the oxygen reduction reaction

Carbon materials such as graphite, graphene, carbon nanotubes and ordered mesoporous carbon have attracted a lot of attention for their use in fuel cells, due to beneficial properties like high conductivity, high mechanical and chemical stability and, for the latter, high surface area. Doping these materials with nitrogen or, less commonly, other elements alters their (electronic) properties, making them particularly suitable for application as electrocatalysts for the oxygen reduction reaction (ORR) in a fuel cell. This paper reviews the synthesis methods employed for the doping of these different types of carbon materials with various elements and the characterization techniques used to investigate their physicochemical properties such as degree of graphitization, dopant content, dopant configuration and surface area. Furthermore, their application as electrocatalysts for the oxygen reduction in a fuel cell is reviewed. Finally, the possible mechanisms for the ORR on N-doped carbon materials are critically discussed and compared to the mechanisms of commercial Pt/C electrocatalysts.
Separation of the Jacobsens catalyst in the enantioselective epoxidation of cis-ethyl cinnamate under homogeneous conditions

In this work, we report on a new methodology for the recovery and reutilization of the Jacobsen’s catalyst in the enantioselective epoxidation of cis-ethyl * Autor de correspondencia: teléfono + 57 + 4 + 219 66 07, fax: + 57 + 4 + 219 66 09, correo electrónico: jacubil@gmail.com (J. Cubillos). Rev. Fac. Ing. Univ. Antioquia N. ° 47. pp. -1 . Marzo, 200
A novel tool for the local anodic oxidation of graphite

A novel probe for partial local anodic oxidation is presented, which allows bulging regions to be grown on the graphite surface. Based on the scanning probe microscopy observations, it was concluded that the bulging regions consist of graphite oxide. The partial oxidation occurs in two stages, which are related to the formation of C–O bonds on the graphite surface and the adsorbed water intercalation of the oxidized graphite. The bulging regions have low conductivity, therefore their formation is a promising method to be used in the production of nanoelectronic devices.
Control of periodic defect arrays of 8CB (4′-n-octyl-4-cyano-biphenyl) liquid crystals by multi-directional rubbing

In this study, we introduce a simple multi-directional rubbing method to generate various periodic patterns of toric focal conic domains (TFCDs), a typical smectic (Sm) LC defect by using the commonly used Sm LC materials, 4′-n-octyl-4-cyano-biphenyl (8CB). We have successfully obtained a variety of spatially arranged TFCD arrays such as parallelogrammic, hexagonal and square arrays by changing the rubbing angle (Ω) between two different rubbing directions. Our experimental results demonstrate that frustration and distortion of nematic LC molecules at the intersections act as effective seeds to help positioning of TFCDs. Furthermore, the existence of nematic–Smectic A (SmA) phase transition is quite important in controlling the arrangement of TFCDs as the alignment of the nematic director strongly influences the arrangement of TFCDs formed in the SmA phase.
Development of methane-releasing permeation devices for intraruminal use

For the past decade, methane production rate of grazing ruminants has been estimated by a tracer based technique in which the tracer (sulphur hexafluoride; SF6) is released by a permeation device in the rumen and the ratio of methane and SF6 in expired gas is determined (Johnston et al. 1994). While the method has been extensively used, the physical attributes of SF6 gas (density and solubility) differ from those of methane so SF6 is not an ideal tracer for enteric methane studies. These differences, together with SF6 being a potent greenhouse gas, indicate that use of an isotopic form of methane in place of SF6 would be advantageous for field studies. 14C and 3H labelled methane has been used for studies in housed animals (Murray et al. 1976) and stable isotopes (13C, 2H) could potentially be used in the field. Methane has a low boiling point and a high vapour pressure, relative to SF6, so the constant release of SF6 from permeation devices cannot be presumed to occur for methane. Two brass permeation tubes (internal volume 2.7 ml) with TeflonTM permeation membranes (125 μm, 7 mm diameter) at each end were constructed. With the lower membrane installed, each tube was cooled in liquid nitrogen and approximately 1500 ml of methane gas injected over a period of 4 minutes. Methane that liquefied in the tubes was then trapped by fitting and tightening the upper membrane. Both membranes were repeatedly tightened on removal from liquid nitrogen.Tubes were incubated at 39°C and change in weight of the tubes was measured for 24 days (Figure 1). The daily release rate of methane was not constant as had been found for SF6 permeation tubes (Lassey et al. 2001), but declined at 2.3% to 2.6% of the initial rate of methane release each day. The rate of decline was strongly linear (r2 = 0.9 – 0.94) which suggests that the release rate while the permeation tube was in the rumen could be adequately predicted from a preliminary (gravimetric) calibration period, with the standard error of the regression coefficient being less than 3% of the mean slope.
Developmental Lead Exposure Impairs Anxiolytic-Like Effects of Diazepam and 8-OH-DPAT in Male Wistar Rats

The effects of developmental lead (Pb 2+ ) exposure on the anxiolytic-like effect of diazepam (5.0 mg/kg IP) and 8-OH-DPAT (0.3 mg/kg IP) were studied. Wistar dams were exposed to 250 ppm lead acetate in drinking water during pregnancy. Control rats were derived from dams that consumed tap water, and had no exposure to Pb 2+ afterwards. Male offspring were tested at the age of 12 weeks. We studied the anxiolytic-like effect of diazepam and 8-OH-DPAT in an elevated plus maze device and the Vogel conflict test. Diazepam in doses of 5.0 mg/kg IP significantly increased the percentage of time spent on open arms in control rats being without effect in Pb 2+ -exposed animals. 8-OH-DPAT 0.3 mg/kg IP increased the percentage of time spent on open arms in both experimental groups (control and Pb 2+ ), but the anxiolytic-like effect was much more pronounced in Pb 2+ -intoxicated animals. The benzodiazepine anxiolytic diazepam produced a significant effect in the Vogel conflict test in control rats. A 5.0 mg/kg dose of those drugs caused a significant increase in the number of electric shocks rats received. In the ontogenetically Pb 2+ -exposed rats diazepam also augmented the number of shocks accepted, but this effect was much less pronounced than in control animals. Conversely, 8-OH-DPAT at doses of 0.3 mg/kg IP was without effect in both tested groups as far as the anticonflict effect is concerned. The results of the present report demonstrated that exposure to Pb 2+ during pregnancy induced hypersensitivity to 5-HT1A agonist mediated anxiolytic-like effect but attenuated that of benzodiazepine (diazepam).
A long‐term study of anaerobic dechlorination of PCB congeners by sediment microorganisms: Pathways and mass balance

Reductive dechlorination of PCBs by Hudson River sediment microorganisms was investigated using individual congeners, 2,3,4,2[prime],4[prime],5[prime]-, 2,4,5,2[prime],4[prime],5[prime]-, 2,3,4,5,6-, 2,4,2[prime],4[prime]-, and 3,4,3[prime],4[prime]-chlorobiphenyls (CBPs) in long-term studies lasting 15 to 20 months. The dechlorination of 2,3,4,2[prime],4[prime],5[prime]-CBP yielded 2,4,5,2[prime],4[prime]-, 2,4,2[prime],4[prime]-, 2,4,2[prime],5[prime]-, and 2,4,2[prime],5[prime]-, and 2,4,2[prime]-CBPs; notably absent was 2,2[prime]-CBP. Yet, the total molar concentration of all congeners decreased with time and at 15 months accounted for only 25% of the initial concentration of the parent compound. 2,3,4,5,6-CBP produced 2,3,5,6-, 2,4,6-, and 2,6-CBPs. At 15 months the sum of all congeners accounted for only about 50% of the initial amount of the parent congener. On the other hand, 2,4,5,2[prime],4[prime],5[prime]-CBP yielded six daughter products, including 2,2[prime]-CBP, and did not show any decrease in total molar concentration even at 20 months. 2,4,2[prime],4[prime]-CBP did not show any change at 15 months. These results indicate that anaerobic PCB biotransformation may include mechanisms other than dechlorination and that the mechanisms are congener dependent. Biphenyl was detected with 3,4,3[prime],4[prime]-CBP, indicating complete dechlorination; however, it accounted for <10% of the total molar loss. [sup 14]C-labeled tracer of this congener showed that all radioactivity was in the hexane fraction, suggesting that transformation products were hydrophobic.
Electrohydrodynamic Particle Aggregation on an Electrode Driven by an Alternating Electric Field Normal to It

An approximate model for the velocity due to electrohydrodynamic flow of electrolyte in the vicinity of a dielectric sphere near an electrode is described. The model considers the interaction of a lateral electric field, caused by the presence of the sphere, with free charge produced in the diffusion layer near an electrode when alternating current is passed through it. An equation based on the model predicts that adjacent dielectric particles aggregate or separate depending on the relative magnitude of the individual ionic conductivities and the frequency of oscillation in the case of a binary electrolyte. If the anion reacts and its conductance exceeds the cation conductance, the particles repel each other; the particles aggregate if the reverse is true. The equation also predicts that separation or aggregation depends on frequency of oscillation of the current. The model accounts for observed effects of frequency and particle size found in the literature. Finally, a dimensionless group that places a co.