Miracle-dz/UniFAR-FTUs huggingface dataset:
Molecular Structure, Bonding, and Jahn−Teller Effect in Gold Chlorides: Quantum Chemical Study of AuCl3, Au2Cl6, AuCl4-, AuCl, and Au2Cl2 and Electron Diffraction Study of Au2Cl6

The molecular geometry of dimeric gold trichloride has been determined by gas-phase electron diffraction and high-level quantum chemical calculations. The molecule has a planar, D2h-symmetry halogen-bridged geometry, with the gold atom in an almost square-planar coordination. The geometrical parameters from electron diffraction (rg and ∠α) are: Au−Clt, 2.236 ± 0.013 A; Au−Clb, 2.355 ± 0.013 A; ∠Clt−Au−Clt, 92.7 ± 2.5°; and ∠Clb−Au−Clb, 86.8 ± 1.8° (t, terminal; b, bridging chlorine). Quantum chemical calculations have also been carried out on the ground-state and transition-state structures of monomeric AuCl3; both have C2v-symmetry structures due to Jahn−Teller distortion. CASSCF calculations show that the triplet D3h-symmetry structure lies ∼29 kcal/mol above the 1A1 symmetry ground state. The Mexican-hat-type potential energy surface of the monomer has three equal minimum-energy positions around the brim of the hat, separated by three transition-state structures, ∼6 kcal/mol higher in energy, at the C.
Equation of state for hard-spheres

A new equation of state is presented for hard-spheres, which can reproduce the exact values of the first seven virial coefficients. These values are in agreement with the molecular dynamic calculations of Alder and Wainwright [J. Chem. Phys. 33, 1439 (1960)]. Comparisons with the existing equations of state show that the new equation possesses superior ability to describe the hard-sphere phase behavior.
Proximate Composition and Phytochemical Constituents Of Aspilia africana (Pers) C. D. Adams and Tithonia diversifolia (Hemsl) A. Gray Stems (Asteraceae)

Proximate composition and phytochemical constituents of stems of A. africana and T. diversifolia (Asteraceae) were investigated. The stems of these species contain anti-oxidant, anticancer, anti-tumor, anti-viral, anti-inflammatory and anti-allergic properties which cures malaria, skin diseases, athlete’s foot, asthma, gonorrhoea and to stop bleeding. The stems of these two species revealed the presence of flavonoids, tannins, saponins and cardiac glycosides. The proximate analysis of the stems of A. africana and T. diversifolia showed the moisture content of 15.7% and 20.6%, total ash of 6.10% and 6.55%, acid insoluble ash of 0.55% and 0.33%, sulphated ash of 18.8% and 14.0%, protein content of 7.87% and 9.62%, fat of 3.68% and 4.21%, fibre of 12.30% and 15.82%, carbohydrate of 75.97% and 70.35%, volatile ether soluble of 7.33% and 1.66%, water soluble of 3.33% and 0.33% and diluted alcohol soluble of 5.33% and 5.66%. The results of this study suggest the popular use of A. africana and T. diversifolia in herbal medicine.
Lead and copper speciation in remote mountain lakes

We determined the chemical speciation of lead and copper in remote mountain and high‐latitude lakes at different times of the year, providing background data for regions in Europe least affected by anthropogenic effects. The lakes are characterized by low ionic strength, clear waters, and oligotrophic conditions; are fed predominantly by atmospheric precipitation; and are ice‐covered during a large part of the year. Lead—and copper‐complexing ligands were determined by cathodic stripping voltammetry with ligand competition using Calcein blue and salicylaldoxime, respectively. Water column averages of the dissolved lead concentrations ranged from 0.2 to 0.9 nmol L−1, with generally lowest levels during the prolonged winter ice cover, whereas dissolved copper concentrations, varying from 1 to 1.7 (±0.1) nmol L−1, showed no significant seasonal variations. The lead speciation was controlled by complexation with ligands at concentrations mostly below 2 nmol L−1, with values for the stability constant (log K’PbL) of 12.5‐13.7; calculated 9PbL ionic lead concentrations (‐log[Pb2+] values) were 11.9‐14.5. Copper complexation was controlled by ligands at concentrations of 12—21 nmol L−1, with values for log K’CuL of 13.5‐14.0 and—log[Cu2+] values of 14.4‐15.1. The concentration of the copper‐binding ligands, but not those for lead, varied seasonally, with about 50% higher concentrations during open water conditions compared to periods of ice cover. The data were consistent with the presence of only one class of ligands for copper and lead. The stability constant of the ligands is similar to that of fulvic acid; however, evidence regarding the actual nature of the ligands is still lacking. The lake data show that (1) competition between calcium and lead causes a reduction in the stability constant of approximately one log‐unit for each order of magnitude of Ca2+, and (2) lead scavenging in the lakes is moderated by complexation.
Temperature Distribution in the Force-Driven Poiseuille Gas Flow by Molecular Dynamics

The thermal behavior of the force-driven compressible Poiseuille gas flow is studied by molecular dynamics (MD) simulation method. This type of flow situation occurs in the cooling system of MEMS/NEMS devices and hence the properties of Poiseuille gas flow become significant, especially the thermal behavior. The peculiar behavior of the force-driven Poiseuille gas flow, local minimum at the center in the temperature profile, is investigated in detail. Emphasis is placed on variations of the temperature distribution for different Knudsen numbers. Previously, the central temperature minimum and other flow peculiarities have been described by a non-classical non-Fourier theory based on nonlinear coupled constitutive relations. The main goal of this study is to investigate the thermal behavior of the force-driven Poiseuille gas flow using molecular dynamics simulations and to compare the results with that of non- classical non-Fourier theory. The MD results in general show agreement with the data from the non-classical hydrodynamic theory, which confirms the validity of MD method in analyzing the micro/nano gas flows including thermal behaviors.
Original Article Potassium Hydrogen Sulphate - A New Ionic Strength Adjustor for Determination of Nitrate in Potable Waters and Denitration Plant Effluents using Ion Selective Electrode

An Ion Selective Electrode (ISE) method using potassium hydrogen sulphate (KHSO4) as a new ionic strength adjustor (ISA) is described for the rapid determination of nitrate in potable waters and in the denitration plant effluents. Effluent samples containing ammonium nitrate (in the concentration range of 0.1-150 g L -1 ), generated during the denitration plant operations and potable water samples from Anantpur district were analyzed by this method. Nitrate could be quantified in the range of 5-1000 mgL -1 with a detection limit of 1.5 mgL -1 . The calibration slope was found to be 54.3±1.1 mV/decade concentration of nitrate. In the case of potable water samples, the interferences from bicarbonate, nitrite, carbonate, sulphate and phosphate were found to be insignificant. Chloride concentration greater than 100 mgL -1 notably affected the nitrate measurement. A column separation step was employed for chloride removal prior to the analysis. Standard addition method applied to samples showed > 95 % recovery. The relative standard deviation (RSD) was found to be between 4-6% (for n = 6). The results obtained by this method showed good agreement with those obtained by ion chromatography technique (R 2 = 0.99). The analysis throughput using ion selective electrode (ISE) was 20 samples per hour.
Vacancy short-range order in substoichiometric transition metal carbides and nitrides with the NaCl structure. II. Numerical calculation of vacancy arrangement

Using Babinet's theorem and certain results of the theory of short-range order originally developed for Cu3Au alloys it is shown that the diffuse scattering intensity in the electron diffraction patterns of the substoichiometric transition metal carbides is related to a short-range order of carbon vacancies. Numerical values for the short-range order parameters can be obtained by integrating over the total diffuse intensity within one repetitive unit in reciprocal space. To perform such calculations on VC0.75 an analytical function was identified which describes the shape of the diffuse intensity curves in reciprocal space. Making the simplifying assumption that the value of the diffuse intensity is 1 on the diffuse intensity curve and 0 everywhere else numerical values for the vacancy short-range order in VC0.75 were obtained. The results, represented as average numbers of vacancies in different coordination shells around a vacancy, agree with the general principles of vacancy arrangement found in ordered transition metal carbides and nitrides.
Aerosol characteristics at a continental urban station in southern India

Spectral Aerosol Optical Depth (AOD), Black Carbon (BC) mass concentration and Suspended Particulate Matter (SPM) measurements were made at an urban continental location, Bangalore (13°N, 77.6°E), in southern India. These results show that AODs reach a maximum during April (∼0.5) and minimum during December (∼0.2) at 500 nm. BC and SPM showed variations of 0.6-4.2 μg m³ and 120-195 μg m³, respectively. The Angstrom wavelength exponent (α) was ∼1.0 during the dry season (December? April), which, in conjunction with the high optical depth, indicates significant anthropogenic influence. Boundary layer dynamics plays an important role in the redistribution of aerosols at the surface. The seasonal variations in AOD, BC and SPM have an association with monsoon rainfall. The similarity in the seasonal characteristics of AOD, BC and SPM shows that the location is mostly characterised by anthropogenic activities during the dry periods (December? April).
DESIGNING STARCH-BASED NANOSPHERES TO MAKE HYDROGELS WITH HIGH MECHANICAL STRENGTH

A robust method to prepare hydrogels with high mechanical strength is presented. Core/shell nanospheres with derivatizable allyl groups in the shell were first prepared. Starch-based nanospheres were used as crosslinker to prepare polyacrylamide hydrogels. The starch-based nanospheres were bridged by acrylamide to form crosslink points in the hydrogel network. They possess an extremely high mechanical strength. The results show that starch-based nanosphere hydrogels can sustain strengths of 10.34 MPa, which is 60 times greater than for a normal hydrogel. The mechanical properties of SNH can be tailored by varying the content of SN. This approach offered a new way of making functional hydrogel with biodegradable component as a substitute for tissue.
Synthesis and Properties Measurement of Pour Point Depressant

The amidation grafted copolymers derived from styrene-maleic anhydride copolymer were prepared and characterized by FTIR. Their intrinsic viscosity and crystal morphology were measured. The prepared polymers were investigated as pour point depressants (PPD) and flow improvers for waxy crude oil, and it was found that the depression effect of PPD modified by mixture amines was more effective than single amine, and the maximum depression was obtained by the sample that modified by mixture amines from 13 °C to 4 °C (ΔPP = 9 °C, at 3 000 ppm). The effect of the PPD modified by mixture amines on the flow properties of waxy crude oil was investigated. The result show that the viscosity decreased from 1 223 mPa.s to 81.3 mPa.s at 13 °C and 3 000 ppm. In addition, the crystal morphology have also been improved for the same sample and conditions.
A single-crystal neutron diffraction study of the temperature dependence of hydrogen-atom disorder in benzoic acid dimers

Hydrogen-atom transfer across the hydrogen bonds of benzoic acid dimers has been studied previously by spectroscopic and X-ray methods, but no high-resolution neutron single crystal structures have ever been reported. The system is of interest because the hydrogen-atom dynamics change from classical Arrhenius behaviour to phonon-assisted quantum tunnelling as a function of decreasing temperature. Here we present a series of neutron single-crystal structure refinements at five temperatures ranging from 175 K, where Arrhenius behaviour holds, down to 20 K, where translational tunnelling is dominant. The refinements yield accurate atomic coordinates, thermal parameters and site occupancy factors for all atoms, and show that conversion of the B dimer configuration to the lower energy A dimer configuration in the range 175 to 50 K is primarily enthalpy driven, in good agreement with spectroscopic data. Site occupancies for the hydrogen-bonded hydrogen atom at 20 K do not fit the trend in occupancies observed at the four higher temperatures, and a further series of structure refinements at temperatures below 50 K is planned to investigate this.
Synthesis and characterization of two classes of hyperstar polymers bearing hyperbranched cores grafted with linear arms

New hyperstar polymers (HSP) consisting of two different hyperbranched (hb) aromatic/aliphatic cores grafted with linear polymer arms were successfully synthesized. The hb cores were based on either hb poly(vinylbenzylchloride) synthesized by SCVP-ATRP or hb polyester from a polycondensation reaction. For the core-first approach, the hb cores have been modified to hb macroinitiators initiating either the cationic ring-opening polymerization of oxazolines (Oxa) or the atom transfer radical polymerization of alkylmethacrylates. For potential use as reactive binders in epoxy coatings the HSPs were equipped with a defined amount of OH-groups during arm growth via controlled block-copolymerization with nonfunctionalized and OH-functionalized monomers, either an oxazoline (OH)Oxa (2-[1-(hydroxymethyl)ethyl]-oxazoline) or a methacrylate HEMA (2-hydroxyethyl methacrylate). The amount of OH-groups could be well adjusted in this way. The hyperstars were comprehensively characterized with respect to chemical structure and molecule dimension. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 000: 000–000, 2012
Efectos de los surfactantes en la biorremediación de suelos contaminados con hidrocarburos

Bioremediation process in soil contaminated with hydrocarbons, carried out with surfactants, is conditioned by physiological capabilities of microorganisms, chemical structure of hydrocarbon, surfactant type and environmental factors of soil. Applying surfactants in bioremediation may act by increasing the bioavailability of oil by the parallel action of the contaminant desorption and solubilization, allowing mass transfer and biodegradation. However it can produce or cause an inhibition and / or toxicity. The aim of this review is to describe the effects of surfactants in the bioremediation process giving emphasis to the effects that influence the bioavailability and finally to discuss factors causing inhibition or toxicity.
Characterization of membranes prepared from PVDF/PAN blends and their modification with hydrolysis

In this study, the melt-spinning and stretching processes were used to prepare polyvinylidene fluoride (PVDF)/polyacrylonitrile (PAN) blend hollow-fiber membranes. These blend membranes have a higher tensile strength than those prepared via the wet phase inversion method. The influence of stretching temperature and draw ratios on the membrane microstructure, pure water flux, and porosity of the membranes was studied. The draw ratio and the stretching temperature can greatly affect the morphology and the permeation performance of the membranes. The Fourier transform infrared spectra demonstrate the differences in the PVDF/PAN blend membranes before and after hydrolysis. The water flux of the hydrolyzed PVDF/PAN blend membranes is sensitive to pH value and salt ionic strength. The effects of different salt ions on the permeability of the hydrolyzed membranes were also investigated.
Influence of growth temperature, working gas ratio, and buffer layer in ZnO films grown on (001) Si substrates by using rf-sputtering

We report on an extensive research result about the relationship between the growth parameters of growth temperature, working gas ratio, and Low-temperature (LT) ZnO buffer and the physical properties of surface properties, structural properties, and optical properties in the ZnO films grown on (001) Si substrates by rf-sputtering. In the substrate temperature range of room temperature (RT) - 500 °C, a higher temperature is found to lengthen the surface migration lengths of Zn and O atoms and to promote their surface reaction. In the O2/Ar+O2 ratio range of 0–80%, a higher O2/Ar+O2 ratio is found to suppress the generation of nonradiative recombination centers due to the nonstoichiometric point defects such as O vacancies and Zn interstitials. The buffer layers deposited at RT are found to be partially crystallized by annealing at a high temperature and to be able to serve as seeds for the following ZnO film growth. As a result, the ZnO films fabricated at a substrate temperature of 500 °C and an O2/Ar+O2 ratio of 80% with a LT-ZnO buffer annealed under an O2 ambient of 10 mTorr have the highest crystalline quality.
Influence of the temperature‐dependent dielectric constant on the H/D isotope effects on the NMR chemical shifts and the hydrogen bond geometry of the collidine–HF complex in CDF3/CDClF2 solution

The influence of solvent polarity on the properties of hydrogen‐bonded 1 : 1 complexes of 2,4,6‐trimethylpyridine‐15N with HF and DF, labeled below as FHN and FDN, has been studied by multinuclear magnetic resonance spectroscopy in the slow hydrogen bond exchange regime reached below 190 K. Mixtures of CDF3/CDClF2 were employed as solvent, which is liquid down to 90 K. In order to evaluate their polarity, the static dielectric constants εo of the CHF3, CHClF2 and of the binary 1 : 1 mixture were measured from 160 K down to 90 K. A strong increase of εo from 14 at 190 K to 38 at 103 K is observed for the mixtures used in the NMR measurements. Upon cooling, i.e. increase of the dielectric constant, the NMR spectra indicate a gradual transformation of an asymmetric molecular complex FH···N to a quasi‐symmetric complex Fδ−···H···Nδ+ and eventually to a more or less zwitterionic species F−···H N+. These changes are not only manifested in the scalar couplings J(1H,19F) and J(1H,15N) but also lead to characteristic primary and secondary H/D isotope effects on the chemical shifts of the hydrogen bonded nuclei. Whereas the primary isotope chemical shift effect pΔ(D/H) ≡ δ(F2HN) − δ(F1HN) = −0.2 ppm is negative at 190 K and in agreement with an asymmetric hydrogen bond in the molecular complex, it changes its sign when the temperature is lowered, goes through a maximum of +0.27 ppm at εo ≈ 22 and finally decreases again. The positive value of pΔ(D/H) is in agreement with D more confined to the hydrogen bond center compared with H, which constitutes a fingerprint of a quasi‐symmetric hydrogen bond involving a single well potential for the proton motion. The quasi‐symmetric complex is further characterized by the following NMR parameters, J(1H,19F) = 30 Hz, J(1H,15N) = −50 Hz, J(19F,15N) = −96 Hz, δ(F1HN) = 20.0 ppm, δ(19FHN) = −114.2 ppm, δ(FH15N) = −63.5 ppm, and the one‐bond H/D‐isotope effects δ(F2HN) − δ(F1HN) = +0.27 ppm, δ(19FDN) − δ(19FHN) = 1.4 ppm and δ(FD15N) − δ(FH15N) = −3.4 ppm. Copyright © 2001 John Wiley & Sons, Ltd.
Science-based management of forest soil disturbance

The challenge for all agencies managing public or private forest lands is to develop resource management policy and procedures based on the best available information. Science-based resource management occurs through an adaptive management process that includes three types of monitoring: implementation (compliance), effectiveness, and validation (research). Continued research, and the establishment of new trials is required to support soil conservation efforts and to investigate new concerns, such as climate change, bio-fuel harvest, and changing practices. Cooperative scientific networks and other collaborations are required to secure benefits from a common approach to soil disturbance management and reporting under various provincial/state, national and international sustainability protocols such as the Montreal Process. The technical session on Forest Soil Disturbances at the 2006 Annual Meeting of the Canadian Society of Soil Science in Banff, Alberta, is one step in collaboration, and brought togethe.
Modifications induced in soil physico-chemical parameters by experimental fires at different intensities

Field studies on the effects of heating soil are rare. Studies in which the temperature was varied and measured are even rarer. To cover this lack of knowledge, we conducted some experimental fires in which the fuel was controlled to obtain different fire intensities. Induced temperatures were measured by k-type thermocouples placed at various soil depths. These induced temperatures were highly variable at the soil surface, whereas below 2.5-cm depth, the temperature rise was negligible. Modifications of various soil physico-chemical parameters caused by fire were related to increasing temperatures at the soil surface. The passage of fire promoted the aggregation of clay particles into sand-sized particles, which become even more resistant to the disrupting action of water. The soil pH decreased at temperatures up to 395°C, followed by a clear increase at higher temperatures; however, both the cation exchange capacity and the organic matter content decreased continuously with increasing soil temperature. Total nitrogen content remained surprisingly constant as the soil surface temperature increased, whereas ammonium nitrogen peaked at 184°C. The organic phosphorus decreased continuously, and the available fractions increased. These results are in agreement with the results of our previous research on the effects of the artificial heating on soil properties and confirm that the processes occurring in soil are related to the temperature reached during the fire. The ashes, at least immediately after fire, do not affect these processes.
Organic–inorganic hybrid poly(silsesquioxane) monoliths with controlled macro- and mesopores

Siloxane-based organic–inorganic hybrid monoliths with well-defined macropores and/or mesopores have been synthesized by a sol–gel process, accompanied by polymerization-induced phase separation. Using aklyltrialkoxysilanes and alkylene-bridged alkoxysilanes, two different categories of organosiloxane networks have been characterized in view of macroporosity (based on phase separation) and mesoporosity (supramolecularly templated by surfactants). While the alkyl-terminated poly(siloxane) networks exhibit substantial surface hydrophobicity accompanied by mechanical flexibility, the alkylene-bridged networks behave much more similarly to those prepared from tetraalkoxysilanes with regard to surface hydrophilicity, mechanical rigidness and mesopore-forming ability. The supramolecular templating of mesopores embedded in the gel skeletons (which comprise well-defined macroporous networks) has proven to give a wide variety of hierarchically-designed macro–mesoporous hybrid materials.