Miracle-dz/UniFAR-FTUs huggingface dataset:
Geochemistry of pyrochlore minerals from the Motzfeldt Center, South Greenland: The mineralogy of a syenite-hosted Ta, Nb deposit

Abstract Pyrochlore minerals are common accessory phases in the syenite and nepheline syenite rocks of the Motzfeldt alkaline center, Gardar Province, South Greenland, and are of important economic interest due to their exceptional ability to host various high field strength elements. In this study pyrochlore from two distinct intrusive units within the Motzfeldt Center have been studied. The largely homogeneous syenite and nepheline syenite rocks of the Flinks Dal formation host oscillatory and sector-zoned pyrochlore, which have experienced minor alteration in the presence of high-temperature, dominantly juvenile magmatic fluids. Alteration is characterized by variable decrease in the Na, Ca, and F contents and addition of Sr and K, accompanied by introduction of A and Y site vacancies. Pyrochlore from the more heterogeneous and intensely altered syenite rocks of the Motzfeldt Sø Formation are pervasively altered through interaction with lower temperature evolved hydrothermal fluids. During this phase of alteration cations are preferentially leached from the A and Y sites, accompanied by progressively increasing hydration. In both formations the proportion of B-site cations remains unaltered regardless of the degree of alteration. The alteration encoded in the pyrochlores of the Motzfeldt Center records the different hydrothermal conditions the two formations experienced during the subsolidus, showing how evolution of fluids within one intrusive unit can vary both spatially and temporally.
Nonlinear resonances and vibrational energy flow in model hydrocarbon chains

Intramolecular energy transfer in hydrocarbons is modeled with an anharmonic HC bond coupled to a chain of harmonically coupled carbon atoms. The HC stretch is initially excited to various vibrational states and the flow of energy from the HC bond is observed. It is found that, at sufficiently high excitation, vibrational energy flow is irreversible and occurs on a time scale of roughly 100 fs, independent of chain length. This corresponds very well to experimentally observed spectral bandwidths. By analyzing the motion in a set of natural dynamical modes, it is shown that this energy transfer is due to sequential nonlinear resonances in the chain. Analytic modeling of the mode–mode couplings then provides a simple approximate description of the energy transfer process.
Nonaqueous sol-gel syntheses of microporous manganese oxides

Microporous manganese oxides have been prepared by nonaqueous sol−gel reactions involving tetrabutylammonium (TBA) or tetraethylammonium (TEA) permanganate and methanol in the presence of alkali cation dopants. Layered birnessite-type materials were obtained for Na+ and K+ dopants in a 0.5:1 reactant ratio with manganese. Na−birnessite was isolated in hydrated and dehydrated forms (7 vs 5.6 A interlayer spacing) whereas only the hydrated K−birnessite was observed. Cryptomelane was generated with a K:Mn ratio of 0.25:1. Spinel manganese oxides were formed with Li+ dopants using 0.5:1 and 0.75:1 Li:Mn ratios. The materials were characterized by powder X-ray diffraction (XRD), elemental analyses, Mn oxidation state determination, thermogravimetric analysis, and scanning electron microscopy. Thin films of manganese oxides were prepared by spin coating TEAMnO4-derived sols onto glass slides. Unlike the bulk gel syntheses, only layered birnessite phases were obtained for thin films with Li+, Na+, and K+ dopants.
Water content criterion for relaxation deformation of Nafion based ionic polymer metal composites doped with alkali cations

Water-based ionic polymer–metal composites (IPMCs) exhibit an anode deformation followed by a back-relaxation deformation under a direct current voltage. The latter is strongly related to the water content. This Letter proposes an evaluation method of the critical water content for relaxation deformation. Based on Nafion-IPMC doped with various alkali cations, continuous deformations are measured under a periodic pulse voltage in air. A transformation of the relaxation deformation is found to exist between two successive pulses. The critical water content is confined between the two pulses and evaluated gravimetrically. Removal of no more than 4 wt. % water or 1.4–2 water molecules per cation from the saturated material can completely eliminate the large relaxation deformation in Nafion-IPMC doped with alkali cations.
Distribution of oxygen in marine sediments measured with microelectrodes1

Abstract Membrane-covered platinum electrodes with a tip diameter of 2-8 pm were used for an amperometric assay of dissolved oxygen in marine sediments. The oxygen profile extended to 3-5mm depth in nonilluminated sediment; even at high light intensities and at low tem- peratures it did not extend below lo-mm depth in a homogeneous sandy sediment. Oxygen profiles recorded during light-dark cycles were used to estimate the rates of oxygen produc- tion and consumption and also to calculate the apparent diffusion coefficient for oxygen in the sediment. Apparently macrofaunal activity, rather than molecular diffusion and water turbulence, was important for the occasional transport of oxygen into deeper layers and thus for the provision of oxidized conditions (positive redox potential) down to 5-10 cm below the sediment surface.
In vivo chemical shift imaging of γ‐aminobutyric acid in the human brain

A gradient‐based multiple quantum filtering method is presented for in vivo chemical shift imaging of γ‐aminobutyric acid (GABA) in the human brain, which provides effective suppression of the overlapping creatine singlet with close to optimal detection efficiency. It is shown by product operator calculations and coherence pathway analysis that under conditions of no B1 and B0 inhomogeneity gradient filtering retains 75% of the two outer resonance lines of the GABA‐4 triplet with no creatine contamination. A variation of the method with 100% retention of the GABA‐4 outer resonance lines but higher sensitivity to B1 inhomogeneity is also discussed. By using a localized version of the sequence with an 8‐cm surface coil for transmission and detection, it was found in phantom experiments at 2.1 T that a 69% signal retention of the two outer resonance lines of the GABA‐4 triplet was achieved relative to a spin echo sequence with inhibition of GABA J modulation. A creatine suppression ratio of 2000:1 was measured. The use of the method for chemical shift imaging of GABA is demonstrated by coronal images obtained from phantoms and from the occipital lobe of a healthy volunteer. Magn Reson Med 41:35‐42, 1999. © 1999 Wiley‐Liss, Inc.
Preparation of monodispersed polymeric microspheres for toner particles by the shirasu Porous Glass membrane emulsification technique

This investigation describes the experiment directed toward the production of monodispersed toner particles by suspension polymerization. That is, relatively monodispersed poly(styrene-co-divinylbenzene) microspheres containing electrifying additives were successfully prepared by suspension polymerization employing the Shirasu Porous Glass (SPG) membrane emulsification technique. The diameter distribution of the dispersed droplets prepared with an SPG membrane module was fairly narrow, compared with that prepared with a conventional mechanical homogenizer. The effect of Sumiplast Blue S as coloring matter and E-81 as charge control agent on the triboelectric discharging properties of prepared polymeric microspheres was studied. The addition of electrifying additives strongly affected the triboelectric discharging property. It was consequently clarified that a small amount of electrifying additives added raised the electrostatic capacity of polymeric microspheres. However, a further addition reduced the triboelectric discharge of polymeric microspheres. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 1107–1113, 1997
Rate constants for the gas‐phase reactions of ozone with unsaturated alcohols, esters, and carbonyls

The kinetics of the gas-phase reaction of ozone with unsaturated alcohols, carbonyls, and esters in air have been investigated at atmospheric pressure, ambient temperature (285–295 K), and in the presence of sufficient cyclohexane to scavenge the hydroxyl radical which forms as a product of the ozone-unsaturated compound reaction. The reaction rate constants, in units of 10−18 cm3 molecule−1 s−1, are 0.26 ± 0.05 for acrolein, 1.07 ± 0.05 for 2-ethyl acrolein, 6.0 ± 0.4 for ethyl vinyl ketone, 4.9 ± 0.4 for 3-buten-1-ol, 14.4 ± 2.0 for allyl alcohol, 105 ± 7 for cis-3-hexen-1-ol, 7.5 ± 0.9 for methyl methacrylate, 2.9 ± 0.3 for vinyl acetate, 4.4 ± 0.3 for methyl crotonate, and 8.1 ± 0.3 for the 1,1-disubstituted alkene 2-ethyl-1-butene. Substituent effects on reactivity are discussed by comparison with alkenes and indicate that the reactivity of unsaturated alcohols is the same as that of alkene structural homologues and that the —C(O)OR, —C(O)R, and —CHO groups decrease the reactivity towards ozone as compared to alkyl groups. Estimates are made of the atmospheric persistence of these unsaturated compounds using the kinetic data obtained in this study as input to structure-reactivity and linear free-energy relationships. © 1993 John Wiley & Sons, Inc.
Electrochemical Reduction of CO at a Copper Electrode

CO2 is electrochemically reduced to CH4, C2H4, and alcohols in aqueous electrolytes at Cu electrode with high current density. CO2 is initially reduced to adsorbed CO and further to hydrocarbons and alcohols. This paper describes macroscopic electrolytic reduction of CO at a Cu electrode in various electrolyte solutions in order to reveal the unique properties of Cu electrode in comparison with Fe and Ni electrodes. The reaction products from the Cu electrode are CH4, C2H4, C2H5OH, n-C3H7OH, CH3CHO, and C2H5CHO. Neither C2H6 nor CH3OH is produced. CH4 is favorably produced in aqueous KHCO3 of high concentrations (e.g. 0.3 mol dm-3), whereas C2H4 and C2H5OH are produced in dilute KHCO3 solutions (0.03 mol dm-3). Such product selectivity is derived from the electrogenerated OH- in the cathodic reaction, as is the case in the CO2 reduction. The partial current densities of CH4, C2H4, and C2H5OH are correlated with the electrode potential. Tafel relationships hold for C2H4 and C2H5OH irrespective of pH. The p.
Preparation and characterization of electrospun polyurethane–polypyrrole nanofibers and films

Polyurethane (PU)–polypyrrole (PPy) composite films and nanofibers were successfully prepared for the purpose of combining the properties of PU and PPy. Pyrrole (Py) monomer was polymerized and dispersed uniformly throughout the PU matrix by means of oxidative polymerization with cerium(IV) [ceric ammonium nitrate Ce(IV)] in dimethylformamide. Films and nanofibers were prepared with this solution. The effects of the PPy content on the thermal, mechanical, dielectric, and morphological properties of the composites were investigated with differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), Fourier transform infrared (FTIR)–attenuated total reflection (ATR) spectroscopy, dielectric spectrometry, and scanning electron microscopy. The Young's modulus and glass-transition temperatures of the composites exhibited an increasing trend with increases in the initially added amount of Py. The electrical conductivities of the composite films and nanofibers increased. The crystallinity of the composites were followed with DSC, the mechanical properties were followed with DMA, and the spectroscopic results were followed with FTIR–ATR spectroscopy. In the composite films, a new absorption band located at about 1650 cm−1 appeared, and its intensity improved with the addition of Py. The studied composites show potential for promising applications in advanced electronic devices. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012
Bioremediation Potential of Cr(VI)-Contaminated Soil Using Indigenous Microorganisms

Amendment of Cr(VI)-contaminated soil (approx. 200 mg/kg) with various treatments resulted in greater CO2 evolution and Cr(VI) reduction with organic amendments relative to controls receiving no organics, indicating bacterial reduction of Cr(VI) under anaerobic conditions. Isolation of Cr(VI)-reducing, indigenous bacteria, representative of the dominant soil population, further indicated Cr(VI) reduction by indigenous bacteria. Although desorption of Cr(VI) was evident with some treatments, its reduction was not affected.
Discovery and Evaluation of a Functional Ternary Polymer Blend for Bone Repair: Translation from a Microarray to a Clinical Model

Skeletal tissue regeneration is often required following trauma, where substantial bone or cartilage loss may be encountered and is a significant driver for the development of biomaterials with a defined 3D structural network. Solvent blending is a process that avoids complications associated with conventional thermal or mechanical polymer blending or synthesis, opening up large areas of chemical and physical space, while potentially simplifying regulatory pathways towards in vivo application. Here ternary mixtures of natural and synthetic polymers were solvent blended and evaluated as potential bone tissue engineering matrices for osteoregeneration by the assessment of growth and differentiation of STRO‐1+ skeletal stem cells. Several of the blend materials were found to be excellent supports for human bone marrow‐derived STRO‐1+ skeletal cells and fetal skeletal cells, with the optimized blend exhibiting in vivo osteogenic potential, suggesting that these polymer blends could act as suitable matrices for bioengineering of hard tissues.
Computational methods to study Ca2+-triggered secretion at the cellular level

Secretion is a widespread and fundamental physiological process that is tightly controlled by intracellular Ca 2+ . Here, we present computational methods to study the functional dynamics of cellular secretion. We propose two computational schemes in order to reproduce the Ca 2+ dynamics and exocytosis associated to different spatiotemporal scales: a microscopic scheme, suitable for fast spatiotemporal processes and a whole-cell scheme, suitable for slower (larger) scales. Some results showing the dynamic behaviour of two specific cell types are included in order to show the interest of a computational approach to gain insight about the molecular aspects of secretion, as well as to make theoretical predictions.
Microporous polypropylene sheets

Biaxial stretching of polypropylene sheets containing filler results in microporous polypropylene sheets, which are soft and dry to the touch. Their pore size and porosity are controllable by adjusting the filler content, particle size of filler, and stretching degree. The microporous sheets show some interesting properties: controllability of gas permeation, permeability for aqueous vapor but not for liquid water, laminatability with some cloth or film, etc. The microporous sheets are used practically in various ways
Quantitative determination of E. coli, and fecal coliforms in water using a chromogenic medium

Abstract A new medium, Chromocult Coliform® Agar (CC agar) developed by E. Merck AG (Darmstadt, Germany) was compared with the Standard Methods, membrane filtration fecal coliform (mFC) medium for fecal coliform detection and enumeration. In the CC agar, non‐E. coli, fecal coliforms (Klebsiella, Enterobacter, and Citrobacter,), (KEC) were identified by the production of a salmon to red colour from p‐galactosidase (LAC) cleavage of the substrate Salmon‐GAL, while E. coli, colonies were detected by the blue colour, produced by the cleavage of X‐glucuronide by β‐ glucuronidase (GUS). Statistically, there was no significant differences between fecal coliform counts obtained with the two media (CC agar and mFC agar) and two incubation procedures (2h‐37°C plus 22h‐44.5°, and 44.5°C) as determined by variance analysis. In our study K coli, represented, on average 70.5–92.5% of the fecal coliform population. A high incidence of false negative KEC (19.5%) and E. coli, (29.6%) colonies was detected at 44.5°C. Two K.
Adsorption of a polyelectrolyte chain to a charged surface

The criteria for the adsorption of a polyelectrolyte chain in a salt solution on a uniformly charged planar membrane are derived using mean field arguments. Explicit formulas are obtained to describe the adsorption characteristics for varying surface charge density, charge on the polymer, Debye screening length κ−1, chain length L, and temperature T. The adsorption can be tuned using any one of these parameters. When T is the tuning variable, for example, the chain is adsorbed at T<Tc, where Tc is proportional to κ−3L−1 and κ−11/5L−1/5 in the weak and strong Coulombic screening limits, respectively. The thickness of the adsorbed layer is derived to vary linearly with κ−1 ln(Tc /T) for T<Tc.
Recent Advances in Ring-Opening Polymerization of Lactones and Related Compounds

Abstract Polyesters are currently synthesized by a step-growth mechanism from a mixture of a diol and a diacid (or a diacid derivative), or from a hydroxy-acid when available. Ring-opening polymerization (ROP) of lactones and related compounds is an alternative method for the synthesis of aliphatic polyesters. Comparison of these two mechanisms is clearly in favor of the polyaddition process. The drawbacks of polycondensation are well known:high temperatures and long reaction times are required to produce high-molecular-weight chains. Even though conversion of the hydroxyl and acid group is close to completion, any departure from the reaction stoichiometry has a very detrimental effect on the chain length.
Enhanced Electrokinetic Remediation of Heavy Metals in Glacial Till Soils Using Different Electrolyte Solutions

Previous electrokinetic remediation studies involving the geochemical characterization of heavy metals in high acid buffering soils, such as glacial till soil, revealed significant hexavalent chromium migration towards the anode. The migration of cationic contami- nants, such as nickel and cadmium, towards the cathode was insignificant due to their precipitation under the high pH conditions that result when the soil has a high acid buffering capacity. Therefore the present laboratory study was undertaken to investigate the performance of different electrolyte ~or purging! solutions, which were introduced to either dissolve the metal precipitates and/or form soluble metal complexes. Tests were conducted on a glacial till soil that was spiked with Cr~VI! ,N i~II! , and Cd~II! in concentrations of 1,000, 500, and 250 mg/kg, respectively, under the application of a 1.0 VDC/cm voltage gradient. The electrolyte solutions tested were 0.1M EDTA ~ethylenediaminetetraacetic acid! , 1.0M acetic acid, 1.0M citric acid, 0.1M NaCl/0.1M EDTA, and 0.05M sulfuric acid/0.5 M sulfuric acid. The results showed that 46 - 82% of the Cr~VI! was removed from the soil, depending on the purging solution used. The highest removal of Ni~II! and Cd~II! was 48 and 26%, respectively, and this removal was achieved using 1.0M acetic acid. Although cationic contaminant removal was low, the use of 0.1M NaCl as an anode purging solution and 0.1M EDTA as a cathode purging solution resulted in significant contaminant migration towards the soil regions adjacent to the electrodes. Compared to low buffering capacity soils, such as kaolin, the removal of heavy metals from the glacial till soil was low, and this was attributed to the more complex composition of glacial till. Overall, this study showed that the selection of the purging solutions for the enhanced removal of heavy metals from soils should be primarily based upon the contaminant characteristics and the soil composition.
Thermodynamics of Extraction of Copper(II) from Aqueous Solutions by Chelation in Supercritical Carbon Dioxide

The primary goal of this research was to investigate the feasibility of removing heavy metals from wastewater by chelation in supercritical carbon dioxide. Copper was used as the model contaminant. Extraction efficiency was determined as a function of temperature, pressure, initial moles of chelating agent, and initial moles of copper in a 300-cm3 autoclave. Results indicated that 60% removal of copper can be achieved in a single equilibrium stage with an initial copper concentration of 100 ppm and hexafluoroacetylacetone (HFA), present in excess, as the chelating agent. Experimental extraction efficiencies ranged from 14 to 60% and increased with increasing initial chelate concentration and CO2 density and with decreasing initial copper concentration. A thermodynamic model based on combined reaction and phase equilibria was developed for the prediction of extraction efficiencies. Five aqueous-phase reactions and four phase equilibrium relations were considered in the development of the model. Equilibrium.
Structure and Water Relations of Melanoidins Investigated by Thermal, Rheological, and Microscopic Analysis

Water soluble melanoidins (WSM) from a glucose-glycine model system were obtained and separated into high (HMW) and low (LMW) molecular weight fractions. Adsorption isotherm and GAB and BET fitting parameters of WSM were determined. Physical and structural properties were investigated through thermal and rheological analysis. The LMW fraction exhibited thermal properties similar to that of oligosaccharides and the HMW fraction was compatible with a complex and large molecular size biopolymer structure, while both exhibited gel like properties. Intrinsic viscosity values were consistent with spherical hydrodynamic volumes.
Lignin and its effects on litter decomposition in forest ecosystems

Lignin is a major component of plant litter. In this review, we found lignin comprises a complex class of organic compounds whose concentration differs greatly both between and within plant species. There are many analytical methods for detecting the composition and structure of lignins. As lignins are enormously complex compounds, chemical assay is difficult and different methods vary with the results. Lignin plays a significant role in the carbon cycle, sequestering atmospheric carbon into the living tissues of woody perennial vegetation. It has also great effects on nitrogen dynamics of forest ecosystems as well as other ecological processes. Lignin is one of the most slowly decomposing components of dead vegetation, contributing a major fraction of the material that becomes humus as it decomposes. Lignin is highly correlated with decomposition of litter. Thus, there is evidence that the lignin concentration is a more influential factor than the other chemical concentrations, in determining the rate of leaf litter decomposition of different forest ecosystems. Although a great number of researchers have addressed lignin's role in litter decomposition, still there are many aspects of lignin biogeochemistry that are not known. This lack of information hinders complete amalgam of lignin effects on litter decomposition processes and dynamics of nutrient cycling.