Miracle-dz/UniFAR-FTUs huggingface dataset:
The sorption of ammonium chloride vapour in zeolites. Part I. Hydrogen chloride and ammonia

The sorption of anhydrous hydrogen chloride and of ammonia was studied at temperatures in the range 190–320° in molecular sieve zeolites, as part of an investigation of the uptake of ammonium chloride vapour in a similar temperature range.When hydrogen chloride was sorbed in porous crystals it reacted in part with them. In decationated zeolites a small amount of aluminium was released from the aluminosilicate framework. In cation-bearing zeolites there was also considerable exchange of cations by hydrogen. In addition in porous aluminosilicates in which the silica : alumina ratio was less than ca. 5 some lattice breakdown occurred, which was ascribed to attack on Si–O–Al bonds. Because of these reactions isotherms of hydrogen chloride were irreversible.Isotherms of ammonia were reversible except those in H–Y. Chemisorption occurred in H–Y and H–Zeolon, forming the ammonium zeolites. Isosteric heats of sorption and differential entropies of sorbed ammonia showed that Na–Y, H–Zeolon, and K–L were energetically heterogeneous to ammonia. Isotherms in Na–Y and K–L were very well described by the isotherm equation based on a virial equation for sorbed ammonia. The activity coefficient of zeolitic ammonia was examined as a test for isotherm models.
Thermal Diffusion in Polymer Solutions

Thermal diffusion measurements have been made on a series of solutions of polystyrene as follows: (1) Five molecular weights (10 000 to 336 000) in toluene; (2) 136 000 molecular weight in o‐xylene, styrene, ethyl benzene, dioxane, and pyridine; (3) Styrene dimer in toluene and styrene; measurements were also made on some binary monomeric mixtures.The thermodynamic property X∂μ/∂X describes adequately the concentration dependence of the thermal diffusion ratio α. It appears that that portion of the motion of the polystyrene molecule in dilute and somewhat concentrated solutions which is segmental involves 10—13 chain atoms in the moving segment. The results seem consistent with Kauzmann and Eyring's picture for motion of long chain molecules.
Preparation of CuO-Nanoparticle-Modified Electrode and Its Application in the Determination of Rutin

Abstract In this article, highly pure, well-dispersed, 10-nm CuO nanoparticles were obtained by a hydrothermal reduction process, with oxalic acid as precipitator. The CuO nanoparticles were characterized by x-ray powder diffraction, field-emission scanning electron microscopy, and high-resolution transmission electron microscopy. The CuO nanoparticles were modified onto a gold electrode to study the effect on the redox of the rutin. Cyclic voltammetry results show that the CuO nanoparticles were very active for rutin and that the CuO-nanoparticle-modified electrode can even determine rutin in a certain range of concentration from 5.0 × 10−7 to 5.0 × 10−4 mol L−1 by differential pulse voltammertry, which provides a new application for CuO nanoparticles.
Adsorption of alkaline earth transition and heavy metal cations by hydrous oxide gels of iron and aluminum

Freshly precipitated Fe and Al gels (points of zero change at pH 8.1 and 9.4, respectively) strongly specifically adsorb divalent cations from 1M NaNO/sub 3/ solution. Adsorption from a mixed solution of eight divalent cations (each 0.125 x 10/sup -3/ M) in suspensions of freshly precipitated Fe and Al gels (0.093 M with respect to Fe or Al) was measured as a function of pH in 1M NaNO/sub 3/. The selectivity sequence (lower pH = greater selectivity) for the retention of the alkaline earth cations by Fe gel was Ba greater than Ca greater than Sr greater than Mg, but for the Al gel was Mg greater than Ca greater than Sr greater than Ba. The selectivity sequence (Figures in parentheses indicate pH +- 0.2 for 50 percent retention) for the Fe gel was: Pb (3.1) greater than Cu (4.4) greater than Zn (5.4) greater than Ni (5.6) greater than Cd (5.8) greater than Co (6.0) greater than Sr (7.4) greater than Mg (7.8), whereas the sequence for the Al gel was: Cu (4.8) greater than Pb (5.2) greater than Zn (5.6) greater than Ni (6.3) greater than Co (6.5) greater than Cd (6.6) greater than Mg (8.1) greater thanmore » Sr (9.2). Significant adsorption occurred even when the extent of cation hydrolysis was much less than 1 percent, and invariably occurred at a pH lower than that for hydroxide precipitation. Although the adsorption-pH sequences are related to cation hydrolysis and hydroxide precipitation pH values, the relationship is far from perfect, as is evidenced by the different sequences for the two gels. On aging of the Al gel in the presence of alkaline earth cations, the retention of Mg increased, while that of Ca, Sr, and Ba decreased. This result was thought to result from the structural incorporation of some Mg and the exclusion of the other cations. « less
Enhanced Raman Scattering of ZnO Quantum Dots on Silver Colloids

Enhancement of the Raman signals of ZnO quantum dots on Ag colloids was studied. Unique ZnO/Ag nanostructure materials were obtained by self-assembly of Ag nanocrystals using ZnO nanoparticles as seeds. The morphology and optical properties of ZnO/Ag core/shell particles are dependent on the quality of deposited Ag. The surface plasmon absorption band of Ag shifts toward lower energy due to the interaction between Ag and ZnO quantum dots. The intensities and orders of multiphonon fingerprint Raman lines of ZnO nanocrystals were increased remarkably from the effect of Ag. The efficient quantum dot excitation within the locally enhanced electromagnetic field produced by the silver nanoparticles is evidenced by the observation of the surface plasmon resonance in the enhanced Raman of ZnO nanocrystals.
Design and Manufacture of Polarization-Independent 3D SOI Vertical Optical Coupler

An optical coupler is a key input/output (I/O) device in a photonic integrated circuit (PIC), which plays the role of light-source import and modulated light output. In this research, a vertical optical coupler consisting of a concave mirror and a half-cone edge taper was designed. We optimized the structure of mirror curvature and taper through finite-difference-time-domain (FDTD) and ZEMAX simulation to achieve mode matching between SMF (single-mode fiber) and the optical coupler. The device was fabricated via laser-direct-writing 3D lithography, dry etching and deposition on a 3.5 µm silicon-on-insulator (SOI) platform. The test results show that the overall loss of the coupler and its connected waveguide at 1550 nm was 1.11 dB in transverse-electric (TE) mode and 2.25 dB in transverse-magnetic (TM) mode.
Use of Detergents in the Analysis of Fibrous Feeds. II. A Rapid Method for the Determination of Fiber and Lignin

The capacity of cetyl trimethylammonium bromide to dissolve proteins in acid solution has been utilized in development of a method, called acid-detergent fiber method (ADF), which is not only a fiber determination in itself bnt also the major preparatory step in the determination of lignin. The entire procedure for determining fiber and lignin is considerably more rapid than presently published methods. Compositional studies show ADF to consist chiefly of lignin and polysaccharides. Correlations with the new fiber method and digestibility of 18 forages (r = —0.79) showed it to be somewhat superior to crude fiber (r = —0.73) in estimating nutritive valué. The correla-
The effects of seawater on the dissolution potential of phosphogypsum:cement composites

ABSTRACT Polarized optical microscopy, scanning electron microscopy, and X-ray microprobe analysis were used to investigate the effect of sea water on phosphogypsum (PG):cement composites. Thin surface sections were taken from 85%: 15% PG:cement composites that had been submerged under natural seawater conditions for 1 month and 70%:30% PG:cement composites that had been submerged under natural seawater conditions for 1 year. The optical microscopy results revealed a crystalline layer of carbonates on the surface of the 70%:30% composites, which was absent on the 85%:15% composites. Microprobe analyses indicated that the carbonates, in the form of CaCO3, were formed from Ca2+ and CO32− contained in the seawater, not from the composites. This CaCO3 coating may act as a physical barrier to seawater intrusion into the composites, preventing block degradation. The polarized optical and scanning electron microscopy images of the 85%:15% composites showed surface disruption, which is hypothesized to be caused b.
Biosynthesis of Silver and Gold Nanoparticles Using Huangdan (Camellia sinensis) Leaf Extract

The biosynthesis of nanoparticles is in the limelight of modern nanotechnology. Biogenic Ag and Au nanoparticles were synthesized by a rapid and simple procedure using leaves extract of tea as the reducing agent. The formations of Ag and Au nanoparticles were monitored using the UV-visible spectra as a function of the reaction time and the formation process, which determined that the optimal reaction time of Ag+ and Au3+ ions was 4 and 1 h, respectively. The as-synthesized Ag (53.2 ± 7.1 nm) and Au (31.7 ± 5.2 nm) nanoparticles were characterized by transmission electron microscopy, Fourier transform infrared spectra, and thermogravimetric analysis. The X-ray diffraction spectra showed that the Ag nanoparticle was composed of two nanocrystals, while the Au nanoparticle included one nanocrystal. This rapid biosynthesis approach can be described as a green technology because of no additional chemical reagents as stabilizers or reductants.
Monte Carlo calculation of temperature dependence of the transport properties in compensated GaAs

Monte Carlo calculation has been applied to investigate the temperature and compensation dependence of steady‐state electron transport in n‐type GaAs over a wide range of applied field strengths. It is found that doping compensation has stronger effect on the transport properties at low temperatures than at high temperatures. Compensation‐enhanced impurity scattering is responsible for the reduction not only in low‐field mobilities and peak velocities but also in the negative differential mobilities and the high‐field velocities. The two‐maxima behavior in the velocity‐field characteristics persists at low temperatures through room temperatures for high doping compensation then it starts to diminish at 450 K except for compensation ratio of 0.9. The physical origin of this unique two maxima feature in the velocity‐field relation has been discussed in comparison with other compensated semiconductors.
Soil zinc and pH effects on zinc concentrations of corn plants

Abstract Z1nc (Zn) deficiency of corn (Zea mays L.) has been detected in 20 or more states 1n the United States including Georgia. Since soil pH is a major factor in assessing the availability of soil Zn, this measurement has been included with acid extractable soil Zn in developing calibration Zn soil tests in North Carolina and Virginia. The objectives of this study were to develop a reliable soil test for Zn based on soil pH and Mehlich 1 soil Zn for corn gown on coarse‐textured soils and to compare our soil test values with those recently published from North Carolina where Mehlich 3 was the extractant. The study was conducted 1n 1979 to 1981 on a Tifton loamy sand (Plinthic Paleudult) site which had been used to study the influence of lime rates on micronutrient availability since 1970. Treatments consisted of four soil pH levels ranging from 5.3 to 6.6 and soil Zn levels ranging from 0.5 to 4.9 mg/kg. The Zn levels were established from the previous study where 5.6 kg Zn/ha had been applied annually.
Formulation and Optimization of Alkaline Extracted Ispaghula Husk Microscopic Reservoirs of Isoniazid by Box-Behnken Statistical Design

The main objective of the present work was to formulate and optimize a microparticulate sustained release drug delivery system of isoniazid by using a novel, alkaline extracted ispaghula husk as a polymer. Isoniazid microspheres of alkaline extracted ispaghula husk were prepared by emulsification internal ionic gelation method. Results of preliminary trials indicated that the polymer concentration, cross-linking agent and stirring speed had a noticeable effect on size and surface morphology. A four-factor three-level Box-Behnken design was employed to study the effect of independent variables on dependent variables. The particle size and entrapment efficiency varied from 30.75 to 61.78 µm and 62.27% to 85.80% respectively, depending on the polymer concentration, concentration of cross-linker and stirring speed. Optimized microspheres batch based on point prediction tool of design software exhibited 83.43% drug entrapment and 51.53 µm particle size with 97.80% and 96.37% validity, respectively at the following conditions: sodium alginate (3.55% w/v), alkaline extracted ispaghula husk (3.60% w/v), cross-linker concentration (7.82% w/v), and stirring speed (1200 rpm). The optimized formulation showed controlled drug release for more than 12 hours. The drug release followed Higuchi kinetics via a non-Fickian diffusion.
Improved Method for Determining the Stable-Hydrogen Isotopic Composition (δD) of Complex Organic Materials of Environmental Interest

Despite new and increasing applications in environmental studies, determinations of the stable-hydrogen isotope (δD) composition of complex organic substrates are hampered by laborious preparation techniques and uncontrolled isotopic exchange between labile hydrogen in the sample and ambient water vapor. To date, there has been little agreement in the way laboratories prepare, measure, and correct for uncontrolled hydrogen isotopic exchange in complex organic samples, resulting in incomparable δD results. Previously, nitration and preparative equilibration procedures aimed at controlling exchangeable hydrogen were designed for specific sample types (e.g. cellulose, chitin) but required extensive processing of individual samples. Here we describe a static, high-temperature preparative equilibration technique that provides increased sample throughput and δD measurements that are not compromised by uncontrolled isotopic exchange. By adopting this approach, it will be possible to compare complex organic δD me.
The Sensitivity of Gas Chromatography-Headspace Solid Phase Microextraction in Relationship with Relative Volatility of Volatile Organic Compounds

In order to explore the analytical performance of Headspace-Solid-phase Microextraction (HS-SPME), the sensitivity of gas chromatography (GC)-Mass Spectrometry (MS) determinations was examined in terms of calibration slopes, that is, response factor values of selected volatile organic compounds (VOC). The HS-SPME was applied to extract two kinds of gaseous VOC analytes, namely group I (methyl ethyl ketone, isobutyl alcohol, methyl isobutyl ketone, and butyl acetate, all having high water solubility) and group II (benzene, toluene, styrene, and xylene, all having moderate water solubility) from water solutions. The results, derived by both external and internal calibration, were then evaluated by considering headspace sample volume and solute volatility. In the case of solutes consisting of group I, sensitivity seems to increase with increasing HS size, although there are no such discernible patterns for group II solutes. The observed relative patterns in extraction efficiency may be accounted for by the differences in intermolecular forces present between the compounds of groups I and II and the possible effects of diffusion kinetics of the VOCs to the SPME fiber or competitive adsorption between different VOCs. As such, sensitivity of HS-SPME is tightly affected by the air-water partitioning properties of the target compounds and the response of SPME to such properties.
Bioactivity of Extractives from Stachytarpheta urticaefolia

The n-hexane and methanol extracts of Stachytarpheta urticaefolia leaves exhibited significant antinociceptive effects (p < 0.01) in acetic acid-induced writhing model at a dose of 250 mg/kg b.w. Two compounds isolated from the plant, ipolamiide (1) and α-spinasterol (2), were also found to be potent inhibitors of acetic acid-induced writhing on mice at 50 mg/kg b.w. (p < 0.01). Abortifacient activity was demonstrated within 20 h of administration of a methanolic leaf extract at 200 mg/kg b.w. The methanolic leaf extract and compounds 1 and 2 were also tested for in vitro antibacterial activities against 18 bacterial strains. The extract showed mean zones of inhibition ranging from 17 to 30 mm at 500 µg/disk, but the compounds demonstrated only mild or no in vitro antibacterial activity even at 400 µg/disk. Finally, in a cytotoxicity study, the n-hexane and methanol extracts of leaves and root bark of the plant and the purified compounds (1, 2) exhibited LC50 values of 5.42, 4.42, 17.15, 5.38, 3.93, and 13.65 µg/ml, respectively, against the brine shrimp nauplii, whereas the positive control, vincristine sulfate, showed an LC50 of 0.583 µg/ml.
SELF-MODELING CURVE RESOLUTION (SMCR): PRINCIPLES, TECHNIQUES, AND APPLICATIONS

ABSTRACT Self-modeling curve resolution (SMCR) comprises a family of chemometric techniques that utilize a certain mathematical decomposition to deconvolve the two-way signals from instrumentally unresolved multi-component mixtures. These techniques are very useful tools for the elucidation of the multi-component phenomena in complex chemical systems. This paper presents a review of basic principle of SMCR and some recent progress in SMCR techniques. One example of application of SMCR in vibrational spectroscopy is also demonstrated.
Ammonia volatilization from soils fertilized with urea and varying rates of urease inhibitor NBPT

Loss of N as ammonia (NH3) from surface-applied urea fertilizer may be high if hydrolysis takes place at the soil surface. The urease inhibitor N-(n-butyl) thiophosphoric triamide (NBPT) may reduce NH3 loss from urea by delaying hydrolysis. Field studies using surface chambers were conducted in 1996 and 1997 to compare the amount of NH3 volatilized from surface applications of granular urea (100 kg N ha–1) treated with varying concentrations of NBPT (0, 0.05, 0.10 and 0.15% NBPT wt/wt). The studies were conducted on two Orthic Black Chernozemic soils, a Stockton fine sandy loam and a Newdale clay loam, in May and again in July to determine the relative influence of soil texture and temperature on NBPT performance at the varying rates. Ammonia losses were measured at various times to 12 d after fertilization (DAF) in 1996 and to 21 DAF in 1997. Total NH3 losses decreased in the order of 0% > 0.05% > 0.15% > 0.10% where use of NBPT reduced total NH3 loss by 28-88% over the entire study duration, and by 82 t.
Photoluminescent Colloidal CdS Nanocrystals with High Quality via Noninjection One-Pot Synthesis in 1-Octadecene

High-quality colloidal photoluminescent CdS quantum dots (QDs) were synthesized via a noninjection one-pot approach in noncoordinating solvent 1-octadecene. This synthetic approach uses cadmium acetate dihydrate and elemental sulfur as Cd and S sources, respectively, together with one long-chain fatty acid (CH3−(CH2)n−COOH) as surface ligands and 2,2′-dithiobisbenzothiazole (MBTS) to increase sulfur activity. The CdS QDs were synthesized at elevated temperatures such as 240−300 °C, and the kinetics of nucleation/growth was monitored via the temporal evolution of the optical properties of the growing CdS QDs. Various synthetic parameters were investigated, such as the feed molar ratios of (0.5−8)Cd/1S and (2−64)S/1MBTS, reactant concentrations of 5−80 mmol/Kg, and growth temperature of 220−350 °C. The feed molar ratios of (1−2)Cd/1S and (8−32)S/1MBTS are suggested to be the optimal synthetic window, together with the S feed concentration of 10−20 mmol/Kg and the growth temperature of 240−260 °C. Moreover, .
Determination of Ibuprofen Enantiomers in Human Plasma by Derivatization and High Performance Liquid Chromatography with Fluorescence Detection

Abstract A sensitive and selective reverse phase high performance liquid chromatographic (HPLC) method was developed for the determination of the enantiomers of ibuprofen in human plasma. Ibuprofen and fenoprofen (internal standard, ISTD) are extracted from human plasma by n-butyl chloride, following acidification of plasma. The method is based on the separation of the diasteromers formed on reacting ibuprofen enantiomers and ISTD with S-(-)-1-(1-naphthyl)ethylamine. Separation is achieved by HPLC on an Inertsil ODS-2 column, with a mobile phase composed of water (pH 3.0):ACN (33.5:66.5). Detection is by fluorescence detection with excitation and emission at 280 and 320 nm, respectively. The mean retention times of S-(+)-ibuprofen, R-(-) -ibuprofen, S-fenoprofen and R-fenoprofen (ISTD) are approximately 11.3, 12.3, 7.7 and 8.5 minutes, respectively.
A preliminary study on the effect of mineralization parameters on determination of metals in Viscum album species

An increasing interest in determination of various macro- and microelements in medicinal plants has been observed. The majority of studies are carried out using one mineralization method without any optimization. The present study demonstrates that changes in mineralization parameters can significantly affect the recovery of the elements determined. In the study, the dried plant material was mineralized in 12 ways and iron (Fe), copper (Cu), zinc (Zn), nickel (Ni) and manganese (Mn) levels were determined. The samples were mineralized in the dry or open microwave mode as well as 10 closed microwave modes. The influence of acid amounts, irradiation power and time, addition of hydrogen peroxide and perfluoric acid was examined. All parameters were shown to be critical — good efficiency was observed with larger amounts of acid. The determined content varied significantly in the same sample and were in the ranges (ug g−1): 46–136 (Fe), 1.4–11.8 (Cu), 4.0–11.3 (Ni), 15.4–53.8 (Zn) and 9.5–67.6 (Mn). Increased irradiation resulted in the loss of copper and zinc and better recovery of nickel. The results demonstrate that such determinations should include the mineralization optimization step.
THE ROLE OF BONDED TERMS IN FREE ENERGY SIMULATIONS : 1. THEORETICAL ANALYSIS

The role of the bonded (bond stretching and bond angle) force-field terms in free energy simulations is examined. It is shown that the proper treatment of such terms depends on the choice of the free energy methodology (single or dual topology). Furthermore, while there are no problems in describing changes in bonded terms, care has to be used in creating or destroying them in a molecular dynamics simulation. An approach that avoids the singularity caused by a bond with a zero force constant is outlined. Changes in bond stretching or bond angle terms are shown to give rise to vibrational, Jacobian factor, and potential-of-mean-force-type (pmf) contributions. The meaning of bond stretching and bond angle bending free energy components obtained in single and dual topology simulations and their connection to these three contributions is investigated. Due to the different end states used in single and dual topology simulations, the pmf contribution is projected on different free energy components. In certain .
The discrepancies between theory and experiment in the optical emission of monolayer In(Ga)N quantum wells revisited by transmission electron microscopy

Quantitative high resolution transmission electron microscopy studies of intentionally grown 1InN/nGaN short-period superlattices (SLs) were performed. The structures were found to consist of an InxGa1−xN monolayer with an Indium content of x = 0.33 instead of the intended x = 1. Self-consistent calculations of the band structures of 1In0.33Ga0. 67N/nGaN SLs were carried out, including a semi-empirical correction for the band gaps. The calculated band gap, Eg, as well as its pressure derivative, dEg/dp, are in very good agreement with the measured photoluminescence energy, EPL, and its pressure derivative, dEPL/dp, for a series of 1In0.33Ga0. 67N/nGaN samples with n ranging from 2 to 40. This resolves a discrepancy found earlier between measured and calculated optical emission properties, as those calculations were made with the assumption of a 1InN/nGaN SL composition.