Miracle-dz/UniFAR-FTUs huggingface dataset:
Reaction Kinetics and Chemical Equilibrium of Homogeneously and Heterogeneously Catalyzed Acetic Acid Esterification with Methanol and Methyl Acetate Hydrolysis

The reaction kinetics and chemical equilibrium of the reversible esterification of methanol with acetic acid were investigated. This system is of major importance as a model reaction for reactive distillation. The reaction has been catalyzed both homogeneously by acetic acid itself and heterogeneously by an acidic ion-exchange resin (Amberlyst 15). The chemical equilibrium composition was measured for various temperatures and starting compositions of the reactants and products. Kinetic information was obtained at temperatures between 303.15 and 343.15 K at various starting compositions covering concentration ranges from the stoichiometric regime to the dilute regions. Both the esterification and the hydrolysis reaction were investigated to yield a model which is applicable for any starting composition. The homogeneous reaction has been described with a simple power-law model. The use of activities in the kinetic model instead of mole fractions results in a much smaller residual error. To compare pseudohom.
Roles of interstitial Mg in improving thermoelectric properties of Sb-doped Mg2Si0.4Sn0.6 solid solutions

While adding extra Mg is intended to compensate for the Mg loss during the synthesis, it often leads to Mg interstitials in Mg2(Si,Sn) materials and profoundly affects their thermoelectric properties. Herein we studied the electrical conductivity, Seebeck coefficient, and thermal conductivity of Mg2(1 + x)Si0.38Sn0. 6Sb0.02 (0.05 ≤ x ≤ 0.12) as a function of Mg excess between 300 K and 730 K. The presence of interstitial Mg was corroborated by X-ray powder diffraction, X-ray photoelectron spectroscopy, Hall coefficient measurement, and compositional analysis. The electrical properties have been analyzed in the framework of a single parabolic band model to gain more insight on the roles of Mg interstitials. We found that increasing Mg excess content increased the carrier concentration, electronic effective mass, and electrical conductivity, while it decreased the Seebeck coefficient and led to a non-monotonic change in the lattice thermal conductivity. As a result, a maximum ZT ∼ 0.85 was attained at 700 K for Mg excess x = 0.1, a ∼60% enhancement compared to that of the sample x = 0.05. The Mg interstitials thus provide an extra tuning parameter in optimizing the thermoelectric properties of Mg2(Si,Sn)-based materials.
Graphene-based gas sensor: metal decoration effect and application to a flexible device

Roles of metal nanoparticles (NPs) on graphene-based devices were investigated in terms of gas-sensing characteristics of NO2 and NH3, and flexible gas sensing was also realized for future applications. The synergistic combination of metal NPs and graphene modulates the electronic properties of graphene, leading to enhancement of selectivity and sensitivity in gas-sensing characteristics. Introduction of palladium (Pd) NPs on the graphene accumulates hole carriers of graphene, resulting in the gas sensor being sensitized by NH3 gas molecular adsorption. In contrast, aluminum (Al) NPs deplete hole carriers, which dramatically improves NO2 sensitivity. Furthermore, the sensitivity of flexible graphene-based gas sensors was also enhanced via the same approach, even after 104 bending cycles and was maintained after 3 months.
Molecular diffusion in microporous materials : formalisms and mechanisms

In a large variety of microporous materials such as high-surface area catalytic solids, natural or polymer fibers, zeolites, porous sorbents, and other media, the diffusional mass transport of molecules is accompanied by immobilization on internal surface sites. The standard formalisms for diffusion, such as the Fick equation, require modification in order to distinguish between effects of the stochastic diffusion phenomenon (the molecular diffusivity) and consequences related to the immobilization kinetics. This can lead to corrections of several orders of magnitude to the apparent diffusivities derived from non-steady state techniques, such as uptake rate measurements. The modifications to the classical formalisms are relatively simple when the diffusion process is slow compared to the kinetics of ad-/desorption (immobilization). This is the case in many situations and technologies. The results have important implications in zeolite technology, molecular shape-selective catalysis, and many technologies employing microporous substances. Classical considerations of physical chemistry also provide guidance to conditions and systems where interpretation of transport in terms of diffusion coefficients may not be valid.
In‐Stream Nonpoint Source Nutrient Prediction with Land‐Use Proximity and Seasonality

This research developed multiple regression models relating land use to in-stream concentrations of total nitrogen (TOTN) and total phosphorus (TOTP) in eight, low-order watersheds on the coastal plain of South Carolina. The study area (4860 km 2 ) included dominant land-use categories of agriculture, forest, urban, and wetland comprising the lower portion of the Lake Marion drainage. Land-use data were obtained from a pre-existing GIS database derived by classification of satellite images. The models partitioned land-use categories according to distance from stream channels using a series of buffer zones around each stream. Effects of point source contributions were removed from observed in-stream concentrations so that nonpoint source effects could be more clearly delineated. All models except two were significant at P 150 m). Land-use change scenarios (converting forest and wetland to agriculture) support the conclusion that management of stream water quality will be most effective with emphasis on riparian and adjacent lands. Seasonal models were generally significant (P < 0.05) and demonstrate that the seasonal profile of stream nutrient concentrations is dependent on the mosaic of land uses in a specific subhasin.
Study of optical properties of (PMMA) doped by methyl red and methyl blue films

The effect of doping by methyl red and methyl blue on the absorption spectra and the optical energy gap of poly (methyl methacrylat) PMMA film have been studied. The optical transmission (T%) in the wavelength range 190-900 nm for films deposited by using solvent casting method were measured. The Absorptance data reveals that the doping affected the absorption edge as a red and blue shift in its values. The films show indirect allowed interband transitions that influenced by the doping. Optical constants; refractive index, extinction coefficient and real and imaginary part of dielectric constant were calculated and correlated with doping.
Bacterial reduction of perchlorate and nitrate in water

A bacterial isolate, strain perc1ace, was shown to reduce the ground water contaminant perchlorate (ClO{sub 4}{sup {minus}}) to levels < 0.005 mg L{sup {minus}1} when grown on acetate under anaerobic conditions. The ability of perc1ace to simultaneously reduce perchlorate and another ground water pollutant, nitrate (NO{sub 3}{sup {minus}}), was examined in batch studies and in a sand packed column under saturated flow conditions. Nitrate removal was monitored using ion chromatography, and perchlorate removal was monitored using a perchlorate specific electrode or ion chromatography, depending on the study. In batch studies, the reduction of 0.089, 0.92, 12.0, and 122 mg L{sup {minus}1} perchlorate was examined in the presence and absence of 62 mg L{sup {minus}1} NO{sub 3}{sup {minus}}. Perchlorate was reduced more rapidly in the absence of NO{sub 3}{sup {minus}} than in its presence. However, both perchlorate and NO{sub 3}{sup {minus}} were reduced by more than 10-fold within 48 h. A sand-packed column inoculated with perc1ace simulated a flow-through biotreatment system for water contaminated with a low level of perchlorate and a much higher level of NO{sub 3}{sup {minus}}. Biotreatment could reduce perchlorate to < 0.005 mg L{sup {minus}1} in a 3 h residence time. The addition of NO{sub 3}{sup {minus}}more » initially decreased the efficiency of perchlorate removal, however within 1 d the biotreatment system had adjusted such that there was complete removal of perchlorate and the reduction of NO{sub 3}{sup {minus}} to < 1 mg L{sup {minus}1}. « less
Modeling Gas-Grain Chemistry with Quantum Chemical Cluster Calculations. I. Heterogeneous Hydrogenation of CO and H2CO on Icy Grain Mantles

Formaldehyde (H2CO) and methanol (CH3OH) are thought to be produced in the interstellar medium by the successive hydrogenation of carbon monoxide (CO) on grain surfaces. In the gas phase, the steps in which H adds to CO and H2CO possess modest barriers and are too inefficient to account for the observed abundances. Recent laboratory work has confirmed that formaldehyde and methanol are formed when H atoms are deposited on CO ice at 12 K. The present study employs ab initio quantum chemical calculations to investigate the impact of water ice on the sequential hydrogenation of CO. The most favorable pathway is CO → HCO (formyl radical) → H2CO → CH3O (methoxy radical) → CH3OH. There is sufficient reaction energy in the final step to fragment CH3OH into methyl and hydroxyl radicals, which can be hydrogenated to yield methane and water, as observed in the experimental work. The emphasis here was on the two steps with barriers, H + CO and H + H2CO, with both addition and abstraction considered for the latter. Calculations with up to four explicit water molecules were performed, as well as further modeling to incorporate bulk effects. While ice was found to have a nearly negligible impact on H + CO → HCO, it modestly enhances the addition reaction H + H2CO → CH3O and hinders the abstraction reaction H + H2CO → H2 + HCO. The deuterium-substituted reactions D + CO → DCO and D + H2CO → CDH2O were found to be slightly favored over the corresponding H reactions, particularly in the latter case. Overall, the energetics are not favorable: water ice is evidently not a good catalytic substrate for H + CO or H + H2CO addition reactions at very cold temperatures.
Ionic strength effect on extraction of potassium complexed with crown ether 18-crown-6. Preliminary communication

As part of a broad study of the factors which affect extraction of salts of cations, complexed with an uncharged ligand, L, a critical study has been made of the extraction into dichloromethane of K+ complexed with 18-crown ether-6 in the form of picrate (LKPi). In using extraction analysis for the determination of very small concentrations of K+ in the presence of other salts activities of (K+)w and (Pi−)w in the aqueous phase must be written in the expression for Kext(LKPi). The salting out effect on P(L) = [L]0/[L]w can greatly affect the concentration of potassium ions left in the aqueous phase. Selectivity of K+/Na+ in extractions with 18-crown-6 has been determined.The extraction method is very suitable for the determination of traces of potassium in salts of sodium, magnesium, and calcium after calibration with, e.g., potassium chloride in potassium-free salts and also, after proper calibration, in routine analysis of liquids which contain little K+ and a large excess of Na+ (e.g. sea water, blood .
Effects of Powdered Rice Chaff on Growth and Yield of Rice Under Different Soil pH Conditions

Abstract A recent rapid reduction in soil pH has been attributed to fertilizer mismanagement. The decomposition and consequent nutrient release from silicate rich organic material such as powdered rice chaff (Cp) could be affected by such reductions in pH. In the present study, rice plants were grown in either Cp or calcium silicate (Si-Ca) under various soil pH ranging from 5.5 to 7.5. The results show that the pH of soils gradually decreased at different growth stages in the case of pH 6.5 with Cp treatment. On the other hand, pH gradually increased at different growth stages of the rice plants when soil pH was initially 5.5, both with Cp and with calcium silicate. Nitrogen (N) and silicon (Si) contents of the plants decreased gradually with growth stage after the maximum tillering stage. The relationship between Si and N content in the plant at maximum tillering stage showed contradictory results. Si content was higher at pH 6.5 and at pH 5.5 with both Cp and calcium silicate treatments. On the other hand, N content was higher at pH 6.5 and at pH 7.5. Yield and yield components were significantly higher at pH 7.5 with Cp. These results suggest that Cp can be used as an alternative source of inorganic Si fertilizer. The mechanism by which the Cp acts under different pH nutritional conditions is unclear.
In situ synthesis and crystal growth of copper(I) carbonyl trifluoroacetate: a dinuclear [Cu2(O2CCF3)2(CO)2] core structure confirmed

Abstract The solid state structure of the long known but inadequately characterized compound, namely the mixed ligand copper(I) carbonyl trifluoroacetate, [Cu2(O2CCF3)2(CO)2] (1), has been determined by single crystal X-ray crystallography. Instead of the previously assigned tetranuclear core structure, its main building block is now confirmed to be a dinuclear copper(I) unit that is cis-bridged by two trifluoroacetate ligands. The Cu · · · Cu separation within the unit is 3.1382(6) Å. Additionally, each copper center has one terminally bound carbonyl with a Cu–C distance of 1.806(3) Å. In the solid state, 1 displays a 1D chain structure comprised of the [Cu2(μ2-O2CCF3)2(CO)2] units held by axial Cu · · · O interactions at 2.2181(13) Å.
On Nonadiabatic Condensed Phase Combustion

Abstract We analyze the effects of melting and volumetric heat losses on the propagation of a reaction front in condensed phase combustion. Considering both homogeneous and heterogeneous models for the reaction rate, we calculate the propagation velocity for steady, planar burning as a function of the parameters in the problem. In particular, we show that this quantity is a multi-valued function of the heat loss parameter. We interpret the critical value of this parameter at which the propagation velocity has a vertical tangent, and which varies with the melting parameter, as an extinction limit beyond which a steady, planar combustion wave cannot sustain itself. We also present a model for nonsteady, nonplanar burning and consider the linear stability of the steady, planar solution. As in the adiabatic case, this basic solution is unstable to pulsating disturbances for sufficiently large values of a modified activation energy parameter. We show, in agreement with experimental results, that the effects of.
Influence of Olive Mill Wastewater (OMW) Spread on Carbon and Nitrogen Dynamics and Biology of an Arid Sandy Soil

Olive mill wastewater (OMW) contains large amounts of organic substances, including phenols, that can have negative environmental consequences when applied to soil. Because of the high concentrations of organic matter and mineral nutrients, OMW holds promise as a fertilizer source for cropping systems. The effects of the addition of 0.5, 1, or 2% OMW to a soil on carbon (C) and nitrogen (N) dynamics and microbiological characteristics of the soil were investigated. Mineral N presented a significant negative correlation with the amount of OMW. The total number of soil bacteria and fungi increased. However, the nitrifying population was sensitive to 2% OMW during the first month. The increase in microbiological activity accelerated the loss of soil organic carbon (SOC). However, the treated soil recovered the SOC, and the total C gains were 2.1, 1.9, and 2.4 g kg−1 for the three doses, whereas the SOC loss was 1.1 g kg−1 for the control.
The structure of asphaltenes in bitumen

ABSTRACT The definition of asphaltenes and some of its chemical properties like polarity and molecular weight is discussed, based on available knowledge. A critical examination of the currently common claim that asphaltenes is dispersed in bitumen in the shape of micelles is made. It is concluded that it is not likely that any micelles exist in bitumen. An alternative model, a thermodynamic solubility model is suggested. As a support for the solubility model, the Hansen solubility parameter is used to describe the solubility properties of bitumen, asphaltenes and maltenes. In the solubility model bitumen is considered to be a mixture of million of different molecules which is kept in solution by its mutual solubility. A continuum of different polarities and molecular weights are necessary for complete stability. The model predicts that if certain fractions are removed from bitumen the stability may be lost resulting in formation of precipitate and phase separations. The usefulness of the model is illustrated by the ability to relate polarity to the elasticity of the bitumen at normal service temperatures (<70°C).
Modeling of Mass Transfer during Osmotic Dehydration of Apple Using an Enhanced Lumped Model

In this study, an improved lumped model has been developed for transient one-dimensional mass transfer inside a solid material during osmotic dehydration using a polynomial approximation method. The proposed model was validated by experimental water loss and solid gain data obtained from osmotic dehydration of infinite slab and infinite cylindrical-shaped samples of apple in sucrose solution. Experiments were conducted at nine combinations of three solution concentrations (30%, 40%, and 50% w/w) and three temperatures (30°C, 40°C, and 50°C). The two-parameter model, developed by Azuara et al., was used to predict water loss and solid gain at equilibrium condition and moisture and sucrose diffusivities were estimated by fitting the experimental moisture loss and solid gain data to the Fick's second law of diffusion. The predicted values of average water loss and solid gain by polynomial approximation method fit approximately well to the experimental data and also to the predicted values by the exact analytical method. The values of mean relative errors for the polynomial approximation method with respect to the experimental data were estimated between 15.0 and 19.1%. Also, the related mean relative errors for exact analytical method were between 4.5 and 8.1%.
Physiological and growth responses of two different salt-sensitive cucumber cultivars to NaCl stress

Abstract The effect of NaCl stress on the growth, membrane permeability, anti-oxidant enzyme activities and ion content of cucumber seedlings was investigated. Two cultivars (Jinchun No. 2, a relatively salt-sensitive cultivar, and Zaoduojia, a relatively salt-tolerant cultivar) of cucumber were used. Shoot and root dry weights, plant height, stem diameter, leaf area and leaf number of both cultivars decreased when NaCl concentrations increased. The decreases in shoot and root dry weights and leaf area were more significant in Jinchun No. 2 than in Zaoduojia. Meanwhile, the salt injury index, the membrane permeability, malondialdehyde (MDA) contents, superoxide dismutase (SOD) and peroxidase (POD) activities of both cultivars increased significantly with salt stress, and the increases in the salt injury index and MDA were higher in Jinchun No. 2 than in Zaoduojia, whereas the increase in POD activity was lower in Jinchun No. 2 than in Zaoduojia. Free proline content of Zaoduojia increased markedly with increasing concentrations of NaCl, whereas the content of Jinchun No. 2 was unaffected by salt stress. In addition, the contents of Na+ in the leaf, stem and root of both cultivars increased significantly, whereas the contents of K+ decreased significantly, resulting in an increase in the Na+/K+ ratio when NaCl concentrations increased. These results suggest that Zaoduojia exhibits a better protection mechanism against oxidative damage and lipid peroxidation by maintaining higher proline content and POD activity than the salt-sensitive Jinchun No. 2 cultivar.
Synthesis of mesoporous and tetragonal zirconia with inherited morphology from metal–organic frameworks

Controlled synthesis of porous metal oxides with desired morphology has been motivating scientists to explore and develop new preparation methodologies. Among them, thermal decomposition of metal–organic frameworks (MOFs) has been employed for the fabrication of several metal oxides. In this work, this strategy is employed to prepare mesoporous and tetragonal zirconia (t-ZrO2) from a metal–organic framework (UiO-66), acting as both a morphological template and a zirconium source. This process avoids the use and removal of an extra template as well as the addition of stabilizers for t-ZrO2. After thermal decomposition at 500 °C, t-ZrO2 inherited an octahedral morphology from the pristine precursor and possessed small nanoparticles with an average size of 3.1 nm. The derived t-ZrO2 had a large surface area of 174 m2 g−1 and a pore diameter of 5–8 nm. The formation mechanism of t-ZrO2 was also discussed. This simple and potentially universal strategy can be used to fabricate porous metal oxides with desired shape for many applications.
Scions influence apparent transpiration efficiency of Vitis vinifera (cv. Shiraz) rather than rootstocks

Carbon isotope discrimination (D) is used to determine differences in apparent transpiration efficiency amongst genotypes of many C3 plant species. In this present study the possible influence of certain commercially-available rootstocks on apparent transpiration efficiency in grapevines was investigated. Variation in was studied for Shiraz and each of six rootstock varieties when grown either (1) on their own roots, (2) with Shiraz grafted as a scion onto different rootstocks (conventional graft) or (3) with rootstock varieties grafted onto Shiraz roots (reciprocal graft). When grown on own roots or as a reciprocal graft, there was significant variation in D. In contrast, there was no significant variation in D for Shiraz (as a scion variety) when grafted onto different rootstock varieties (conventional graft). These results imply a predominance by the scion genotype in determining variation in the leaf-level physiological characteristics that determine apparent transpiration efficiency under well-watered (and non-saline) conditions.
Single‐fibre surface‐enhanced Raman sensors with angled tips

Single-fibre surface-enhanced Raman sensors were prepared by depositing rough metal films at the tips of optical fibres. Different deposition techniques such as slow evaporation of metal island films and vacuum deposition of metal films over nanoparticles or on pre-roughened surfaces were applied and compared. The superposition of surface Raman spectra from the tips with Raman spectra of the fibre core made maximum enhancements necessary for the construction of long fibre sensors. The enhancement was improved significantly by altering the tip geometry. Angled polishing has enhanced the SERS intensity by up to a factor of 6. The intensity increases monotonically with increase in the angle, reaching its maximum value at the largest prepared angle of 40°. Copyright © 2000 John Wiley & Sons, Ltd.