Miracle-dz/UniFAR-FTUs huggingface dataset:
Analysis of Mono- and Polycyclic Aromatic Hydrocarbons Using Solid-Phase Microextraction: State-of-the-Art

The contamination of petroleum hydrocarbons, especially mono- and polycyclic aromatic hydrocarbons (MAHs and PAHs), has been discussed for a long time with regard to environmental and health aspects. Solid-phase microextraction (SPME), as a solvent-free sample preparation technique, has been widely used in environmental analysis. This state-of-the-art summarizes current knowledge regarding analysis of MAHs and PAHs using SPME. General aspects of SPME technique are briefly reviewed, including operating principles, methodologies, applications, and possible problems. The methodology of SPME technique in analysis of MAHs and PAHs in gaseous, liquid, and solid matrices is discussed in detail, covering extraction strategy, optimization of experimental parameters, calibration, and validation as well as analytical instruments connected with SPME. The aim of the paper is to give a concise overview together with general guidelines of MAH and PAH analysis using SPME.
Phase Stability and Transformation in Titania Nanoparticles in Aqueous Solutions Dominated by Surface Energy

The surface free energy of small particles in an aqueous solution consists of the electrostatic energy of charged surfaces and the interfacial energy. For nanoparticles in an aqueous solution, the two terms can be modified by solution chemistry and be manipulated to control phase stability and transformation kinetics. Here we show that the phase stability of titania (TiO2) nanoparticles strongly depends on the solution pH. At small sizes, rutile is stabilized relative to anatase in very acidic solutions, whereas in very basic solutions anatase is stabilized relative to rutile and brookite. Rutile is the stable phase at large particle sizes regardless of pH. These results indicate that the activity of potential determining ions (protons or hydroxyl groups) is a factor that can determine the phase stability of nanoparticulate titania in aqueous solutions at pH values far from the point of zero charge of titania. The phase transformation proceeds via a dissolution−precipitation mechanism under hydrothermal c.
An improved Polarflex water model

The three-site polarizable and flexible water potential employing the multistate empirical valence bond (MS–EVB) description for the electronic polarizability [A. E. Lefohn, M. Ovchinnikov, and G. A. Voth, J. Phys. Chem. B 105, 6628 (2001)] has been modified for better reproduction of liquid water properties under ambient conditions. The improvement of the potential model was accomplished by (i) replacing the point charge distribution associated with the atomic interaction sites in the original model with a diffuse Gaussian charge distribution and (ii) reparametrizing the molecular geometry, components of electronic polarizability tensor, the Lennard-Jones parameters, and the widths of the Gaussian charge distribution. Static and dynamic properties, such as the intermolecular interaction energy, radial distribution function, diffusion constant, and dielectric constant, have been used in the model parametrization and the resulting model well reproduces the experimental data. A closely related rigid version.
Characterization of the negative ion fraction in high-density SF6 magnetoplasmas using ion acoustic waves

Most plasmas used in the microelectronics industry are electronegative, i.e., they contain a large number of negative ions. One simple way to characterize the negative-to-positive ion density ratio (n−/n+) in such plasmas is to measure the velocity of ion acoustic waves (IAWs). In this letter, a detailed study of the propagation of IAWs in high-density SF6 magnetoplasmas is given. Results (n−/n+) obtained by way of this technique as functions of different parameters (gas pressure, SF6 content in SF6/Ar mixture, and radial position in the reactor) are compared to those obtained with a more sophisticated technique based on laser photodetachment.
Electrochemical Reduction of Carbon Dioxide in Water: Analysis of Reaction Mechanism on Ruthenium‐Titanium‐Oxide

Mixed ruthenium/titanium oxide electrodes were prepared by thermal decomposition of the halides on titanium sheets. The electrocatalytic activity of the metallic conductive electrodes towards hydrogen evolution and carbon dioxide reduction was investigated in aqueous solutions with rotating-disk electrodes. Current-voltage curves at pH = 4 to 7 show a current-limiting behavior at small overpotentials for hydrogen evolution. In the presence of carbon dioxide, the current efficiency for the CO{sub 2} reduction reaches a maximum under current-limiting conditions for hydrogen ion reduction, before a steep onset of hydrogen evolution takes place due to the reduction of water. In this paper an analysis of the electrode kinetics for the formation of reaction intermediates is given which suggests that the surface recombination of adsorbed hydrogen with CO{sub 2} is the rate-limiting step in the electrochemical reduction of CO{sub 2}.
Novel Electrode Materials for Thin‐Film Ultracapacitors: Comparison of Electrochemical Properties of Sol‐Gel‐Derived and Electrodeposited Manganese Dioxide

Thin films of manganese dioxide were formed on nickel foils by electrodeposition and by both dip‐coating and drop‐coating with manganese dioxide suspensions (sols) and their subsequent gelation and calcination. The performance of these films as ultracapacitors was studied by cyclic voltammetry in the range 0.0–0.9 V (SCE) and by chronopotentiometry in unbuffered solution. The cyclic voltammograms of ultrathin, dip‐coated sol‐gel‐derived films indicated better capacitive behavior and gave differential specific capacitance values as high as 698 F/g compared to values half to two‐thirds as great for the electrodeposited films. Multilayer drop‐coated sol‐gel films were prepared to attain film thicknesses comparable to the electrodeposited films, and these were found to provide charge‐storage capacity as high as , more than three times greater than that of the electrodeposited films. All films, except electrodeposited films that were not thermally cured, exhibited good cycling stability, losing not much more than 10% of capacity after 1500 cycles. © 2000 The Electrochemical Society. All rights reserved.
Quantification of Coastal New Ultra-Fine Particles Formation from In situ and Chamber Measurements during the BIOFLUX Campaign

Environmental Context. Secondary processes leading to the production of ultra-fine particles by nucle- ation are still poorly understood. A fraction of new particles formed can grow into radiatively active sizes, where they can directly scatter incoming solar radiation and, if partly water soluble, contribute to the cloud condensation nuclei population. New particle formation events have been frequently observed at the Mace Head Atmospheric Research Station (western Ireland), under low tide and sunny conditions, leading to the hypothesis that new particles are formed from iodo-species emitted from macroalgae. Abstract. New particle formation processes were studied during the BIOFLUX campaign in September 2003 and June 2004. The goals were to bring new information on the role of I2 in new particle formation from seaweeds and to quantify the amount of I2 emitted and new particles formed by a given amount of seaweed. These two goals were achieved by using a simulation chamber filled with selected species of seaweeds from the Mace Head area and flushed with particle-free atmospheric air. It was found that total particle concentrations and particles in the 3-3.4 nm size range produced in the chamber are positively correlated with gaseous I2 concentrations emitted by the seaweeds, with a typical source rate of 2800 particles cm −3 ppt −1 (I2) in the 3-3.4 nm size range. In fact, I2 and particle concentrations are also both directly positively correlated with the seaweed mass (64 300 particles cm −3 formed per kg of seaweed, and 24 ppt of I2 per kg of seaweeds) until saturation was reached for a seaweed biomass of 7.5 kg m −2 . From the chamber experiments, the flux of 3-3.4 nm particles was calculated to be 2.5 × 10 10 m −2 s −1 for a seaweed loading of 2.5 kg m −2 (representative of a typical seaweed field density), decreasing to 1 × 10 10 m −2 s −1 for a seaweed loading of 1 kg m −2 . At a seaweed loading of 2.5 kg m −2 , the growth rate of particles produced in the chamber was calculated to be 1.2 nm min −1 . The source rates and growth rates determined from the chamber experiments were used in conjunction with seaweed coverage in and around Mace Head to produce local emission inventories for a meso-scale dispersion model. Comparison of the resulting aerosol size distributions from the model simulations and those observed exhibited good agreement suggesting that the chamber fluxes and growth rates are consistent with those associated with the tidal emission areas in and around Mace Head.
Formation and Characteristics of Cu Colloids from CuO Powder by Laser Irradiation in 2-Propanol

The laser ablation technique has been employed to prepare Cu colloids from CuO powder in 2-propanol using wavelengths of 1064 and 532 nm. The copper colloids resulting from 1064 nm irradiation were conspicuously stable under aerobic conditions without any protective agent present. In addition to Cu particles, the formation of oxidized product, acetone, from 2-propanol was detected by gas chromatography. The discrepancy in the Cu colloidal formation between 1064 and 532 nm was analyzed on the basis of the absorptive ability of CuO powder, the results of the power dependence, and the measurements of the dose effect. The process of photoinduced coalescence that formed larger spherical particles was found to be wavelength-dependent. The stability of the Cu colloids could be the result of their near-perfect spherical shape and the effect of their larger size.
Inability of the hypernetted chain integral equation to exhibit a spinodal line

The hypernetted chain (HNC) integral equation is solved for a variety of systems including the simple fluid of hard spheres with attractive Yukawa tail, the symmetrical and highly asymmetrical mixtures of charged particles, and the mixtures of hard spheres with positively nonadditive diameters. All these systems exhibit a liquid–gas or fluid–fluid phase separation. We are concerned with the behavior of the HNC solution near the two‐phase region in the phase diagram. In all cases, the HNC equation does not have solutions inside a certain region whose boundary line is not a spinodal line. As the boundary is approached, the isothermal compressibility deduced from the compressibility route does not diverge, but tends to finite values. The isotherms and isochores terminate at the boundary line in square root branch points. This behavior is directly correlated to the existence of multiple HNC solutions. Physical and nonphysical solutions coincide on the boundary line. This universal HNC behavior is compared wit.
Local Structure of Framework Cu(II) in HKUST-1 Metallorganic Framework: Spectroscopic Characterization upon Activation and Interaction with Adsorbates

XRD, UV−Vis, EXAFS, XANES, and Raman techniques have been used to study the removal of water molecules coordinated to the Cu(II) framework atoms of the novel HKUST-1 metal-organic framework. The dehydration process preserves the crystalline nature of the material, just causing a reduction of the cell volume due to the shrinking of the [Cu2C4O8] cage. The removal of adsorbed H2O molecule makes the framework Cu(II) sites available for interaction with other probe molecules. In situ IR spectroscopy has evidenced the formation at liquid nitrogen temperature of labile Cu(II)···CO adducts characterized by a ν(C−O) = 2178 cm-1 and at 15 K of Cu(II)···H2 adducts characterized by a ν(H−H) = 4100 cm-1. To the best of our knowledge, we have observed for the first time a clear signal of Cu(II) carbonyl and dihydrogen complexes formed inside a crystalline microporous hosting matrix. The sinking of the oxygens of the carboxyl units, undergone by the Cu(II) framework ions in the dehydration process, is responsible for.
Structure and Stability of Formates and Carbonates on Monoclinic Zirconia: A Combined Study by Density Functional Theory and Infrared Spectroscopy

The structure and stability of formate and (bi)carbonate species were studied on monoclinic zirconia by theoretical and experimental methods. For the ab initio calculations, the most stable (111) surface containing one dissociatively adsorbed water molecule was used. Infrared spectroscopy measurements were carried out on a commercial catalyst. The calculated vibrational frequencies were in good agreement with species observed by in situ infrared spectroscopy. The most stable structures for both formates and bicarbonates were bidentate formed by an insertion of CO or CO2 to the terminal hydroxyl group. The most stable carbonates were formed on Lewis acid−base pairs by the adsorption of CO2 to the undercoordinated surface sites.
Multimessenger Emission from the Accretion-Induced Collapse of White Dwarfs

We present fully general-relativistic three-dimensional numerical simulations of accretion-induced collapse (AIC) of white dwarfs (WDs). We evolve three different WD models (nonrotating, rotating at 80% and 99% of the Keplerian mass shedding limit) that collapse due to electron capture. For each of these models, we provide a detailed analysis of their gravitational waves (GWs), neutrinos and electromagnetic counterpart and discuss their detectability. Our results suggest that fast rotating AICs could be detectable up to a distance of 8 Mpc with third-generation GW observatories, and up to 1 Mpc with LIGO. AIC progenitors are expected to have large angular momentum due to their accretion history, which is a determining factor for their stronger GW emission compared to core-collapse supernovae (CCSNe). Regarding neutrino emission, we found no significant difference between AICs and CCSNe. In the electromagnetic spectrum, we find that AICs are two orders of magnitude fainter than type Ia supernovae. Our work places AICs as realistic targets for future multimessenger searches with third generation ground-based GW detectors.
Optimization of Ultrasound-Assisted Extraction of Single Cell Oil from Mortierella isabellina

In this paper, ultrasound-assisted extraction of single cell oil (SCO) from Mortierella isabellina (MI) was investigated using mathematical statistics, such as Plackett–Burman (PB) design, steepest ascent (SA) design, and Box–Behnken (BB) design. The results from response surface methodology (RSM) indicated the hydrochloric acid concentration, ultrasound time, ultrasound temperature, and extraction time are the most significant parameters. The optimum extraction conditions were as follows: ultrasound power 300 W, ultrasound time 12.20 min, ultrasound temperature 53.42°c, hydrochloric acid 30 mmol in each gram of wet fungal mycelia, extraction time 19.45 min, extraction solvent (CH3Cl-CH3OH) ratio 2:1. Under the conditions, the extraction rate of SCO from MI was up to 90.63 ± 1.35%, and the yield of SCO was 109.88 ± 0.02 mg/g (P < 0.05) that was 1.23-fold and 1.35-fold the yield of acid-heating method and ultrasound method, respectively.
Role of electrostatic interactions in determining the crystal structures of polar organic molecules. A distributed multipole study

The effect of using a realistic model for the electrostatic forces on the calculated structures of molecular crystals is explored by using atomic multipoles derived from an SCF 6-31G** wave function. This was tested on a wide ranging database of 40 rigid organic molecules containing C, H, N, and O atoms, including nucleic acid bases, nonlinear optic materials, azabenzenes, nitrobenzenes, and simpler molecules. The distributed multipole electrostatic model, plus an empirical repulsion-dispersion potential, was able to successfully reproduce the lattice vectors and available heats of sublimation of the experimental room temperature structure in almost all cases. Scaling the electrostatic energy to allow for the effect of electron correlation on the molecular charge density generally improved the lattice energies and the calculated structures to a lesser extent. However, omitting the anisotropic multipole moments usually gave very poor, sometimes qualitatively wrong structures, emphasizing the sensitivity of.
Synthesis of Novel Quinone–Amino Acid Hybrids via Cross‐Enyne Metathesis and Diels–Alder Reaction as Key Steps

A "Building Block Approach" for the synthesis of various quinone-amino acid hybrids through ethylene cross-enyne metathesis and Diels-Alder reaction as key steps is described. A library of comformationally constrained quinone-based phenylalanine derivatives and dicarba analogs of cystine have been generated starting from a common precursor using Grubbs' catalysts. This methodology has also been extended for the synthesis of fullerene-based dicarba analogs of cystine.
Different iron‐manganese relationships in two flax cultivars

Abstract Manganese content of flax (Linum usitatissimum L.) is greatly affected by Fe supply. Two flax cultivars, Clark and Culbert, were grown on a Calciaquoll under greenhouse conditions to compare their responses to FeEDDHA. Although the Mn concentrations of both Clark and Culbert were greatly reduced by FeEDDHA, the performance of the two cultivars varied as follows: (i) Culbert accumulated less Mn in tops, especially leaves, than did Clark, but the relative differences between cultivars were larger in the presence of the chelate; (ii) Culbert accumulated more Fe than Clark, particularly in young plants at low soil temperatures; (iii) necrotic spots were present on lower leaves of Culbert, but not of Clark, containing high levels of Mn in the absence of the chelate; (iv) a decrease in soil temperature appreciably lowered Mn concentrations in Clark but not in Culbert; and (v) FeEDDHA reduced Mn concentration of Culbert, but not of Clark, to such an extent that an apparent Mn deficiency was induced in C.
Interaction between tissue-type plasminogen activator and ligands grafted onto hydrogel

Tissue-type plasminogen activator (t-PA) has shown significant effects on the treatment of common thrombosis. In this work, molecular dynamics simulations are used in protein–ligand interaction analysis to investigate the affinity of ligands for affinity chromatography. A hydrogel matrix grafted with amine (positively charged), carboxyl (negatively charged) and hydroxyl (neutral) ligands separately is designed, and its adsorption–desorption dynamics are studied in detail. The residues on the surface of t-PA, on which the S1 pocket is located, could be more easily adsorbed by charged ligands grafted onto the hydrogel matrix than neutral ligands. The findings offer new insights into the affinity of various ligands for t-PA, and could be of potential use in t-PA purification.
Non‐Markovian activated rate processes: Comparison of current theories with numerical simulation data

We calculate the barrier crossing rate constants for a Brownian particle in a double well potential experiencing a non‐Markovian friction kernel using a full stochastic simulation. We compare the simulation results with recently proposed interpolation formulas which are based on the Grote–Hynes theory and the energy diffusion mechanism. We find that such formulas can fail by orders of magnitude in a physically interesting regime. Slow activation in an effective dynamic double well potential is probably responsible for the deviations observed.
Structural transformation of an alumina-supported MnO2–CuO oxidation catalyst by hydrothermal impact of sub- and supercritical water

The structural transformation of a MnO2–CuO-containing catalyst supported on X-ray amorphous Al2O3 used in oxidative conversion of ethyl acetate in water under sub-critical (p = 200 bar, T = 633 K) and supercritical reaction conditions (p = 240 bar, T = 673 K) has been studied by X-ray diffractometry (XRD), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). TEM investigations revealed very small primary crystallites of the parent sample (ca. 5–20 nm), in contrast to a catalyst specimen exposed to supercritical water for ca. 100–200 hours which exhibited large micron-sized crystallites. This crystallisation process is accompanied by a drastic decline in the catalyst BET surface area. XRD studies support this observation: the basic material is nearly X-ray amorphous whereas the used catalyst shows several crystalline phases (e.g. Mn2O3, Al2O3, AlO(OH)). The patterns of spent catalysts taken from the reactor after different running times also gave evidence for the existence of mixed manganese copper oxides. Furthermore, XRD analysis of the used catalysts revealed a reduction of the basic MnO2 to Mn3O4 and Mn2O3; this was also clearly proven by XPS analysis. Hydrolysis runs at supercritical water oxidation conditions showed that ethyl acetate is only hydrolysed into ethanol and acetic acid but, in contrast to these non-catalysed runs, the further oxidation of the hydrolysis products to carbon dioxide and water occurs in the presence of the oxidation catalyst. It may be stated that during time-on-stream up to ca. 200 h neither activity nor selectivity was found to significantly change, apart from the found structural alterations.
Isolation, Characterization, and Conformational Characteristics of p-tert-Butylcalix[9−20]arenes1

p-tert-Butylcalix[n]arenes in which n = 9−20 (designated as “large” calixarenes) have been isolated from both the base-induced and the acid-catalyzed condensation of p-tert-butylphenol and formaldehyde. The acid-catalyzed process, previously thought to form linear oligomers as the major or even exclusive products, has been optimized to produce calixarenes in almost quantitative yield, providing a better source of these “large” calixarenes than the base-induced process. Central to the discovery of the calix[9−20]arenes and the optimization of the acid-catalyzed condensation was the development of an HPLC assay that allows baseline resolution of the 17 cyclic oligomers as well as their linear counterparts. Using this assay for guidance, procedures for the obtention of ponderable amounts of p-tert-butylcalix[7−20]arenes from the acid-catalyzed process have been developed. Data are adduced that bear on possible mechanistic pathways for calixarene formation under these conditions. A study measuring the amount .
GENERALIZED CORRESPONDING STATES CORRELATIONS FOR THE VISCOSITY AND THERMAL CONDUCTIVITY OF AQUEOUS ELECTROLYTE SOLUTIONS

Corresponding slates correlations have been developed for the viscosity and thermal conductivity of aqueous electrolyte solutions for a wide range of temperatures, pressures, and concentrations. For viscosity, the Vogel-Tamann-Fulcher equation has been generalized using the corresponding states theory, and extended to include pressure effects. Twenty six aqueous electrolyte solutions, including both monovalent and multivalent electrolytes, have been studied and a generalized correlation has been developed for viscosity, with four system dependent parameters. For thermal conductivity, a similar corresponding states based correlation has been developed. Twenty three aqueous electrolyte solutions were studied for thermal conductivity and a generalized equation was obtained that requires only two System dependent parameters. With both correlations, the maximum error is usually within 10% of the experimental values, with the average errors being much less. Additional systems can also be included in both correl.