Miracle-dz/UniFAR-FTUs huggingface dataset:
STUDY ON π-π INTERACTION IN HIGH PERFORMANCE LIQUID CHROMATOGRAPHY

In high-performance liquid chromatography, the reversed-phase mode column is used most popularly. In the reversed-phase mode separation, several interactions between the stationary phase and analytes are concerned, i.e., partitioning, adsorption, hydrogen bonding, and π-π interactions. In this paper, a π-π interaction effect on high performance liquid chromatographic separation was studied using some N-substituted aminopropyl modified silyl silica gel stationary phases bearing aromatic moieties in their structures. A series of aromatic polycyclic hydrocarbons, i.e., benzene, naphthalene, phenanthrene, and naphthacene, were retained and separated on those columns in the order of their aromaticities, while no retention was observed by the non-substituted aminopropyl modified silyl silica gel column. These results strongly supported the existence of π-π interactions between N-substituted aminopropyl modified silyl silica gel and the hydrocarbons.
Aqueous rechargeable lithium batteries using NaV6O15 nanoflakes as high performance anodes

Poor cycling performance is still the big challenge for aqueous rechargeable lithium batteries (ARLBs), in which the instability of the anode is considered to be the main issue. In this work, NaV6O15 nanoflakes were synthesized by a two-step approach and a NaV6O15//LiMn2O4 ARLB system with superior cycling performance was constructed. The galvanostatic charge–discharge result demonstrates an initial discharge capacity of 110.7 mA h g−1 (based on anode mass) at 150 mA g−1 and the capacity retention of ca. 90% and 80% at 300 mA g−1 after 100 and 400 cycles, respectively. Such superior cycling performance of ARLBs is mainly due to the intrinsic 3-D tunneled structure of NaV6O15, nanoflake morphology and relatively stable electrode surface, as verified by the X-ray diffraction (XRD), electrochemical impedance spectroscopy (EIS), and scanning electron microscopy (SEM) results of the tested electrodes. Moreover, a simple single-phase reaction mechanism during the lithium ion insertion/extraction process is observed for NaV6O15 by XRD analysis.
Narrow-Spectral-Linewidth Wavelength-Tunable Laser Diode with Si Wire Waveguide Ring Resonators

We fabricated wavelength-tunable laser diodes with Si wire waveguide ring resonators as an external optical cavity. The footprint of the optical cavity including the semiconductor optical amplifier is as small as 2.73×0.89 mm2, which is about 1/5 of those made of silicon oxinitride material. About 44-nm-wavelength tuning operation, which covers the entire L-band of the optical communication wavelength range, was obtained. Furthermore, spectral linewidth narrower than 100 kHz was obtained by optimizing the design of the external optical cavity. The tunable laser diodes with narrow spectral linewidth are suitable as light sources for digital coherent optical transmission systems.
Investigation of Transient Plasma Ignition for a Pulse Detonation Engine

Abstract : Elimination or reduction of auxiliary oxygen use in Pulse Detonation Engines (PDEs) is necessary if the technology is to compete with existing Ramjet systems. This thesis investigated a Transient Plasma Ignition (TPI) system and found that the technology can at least reduce and may be able to completely remove the auxiliary oxygen requirement of current PDE systems. TPI was tested and compared with a traditional capacitive discharge spark plug system in a dynamic flow, ethylene/air mixture combustor. Ignition delay time, Deflagration-to-Detonation transition (DDT) distance and time, detonation wave speed and fire success rate performance were analyzed for various mass flow rates and stoichiometric ratios. A transient plasma dualelectrode concept was also employed and analyzed. Results show that TPI is more effective and reliable than the spark plug ignition with considerable improvements to DDT performance. The TPI dual-electrode concept was proven to be the most effective configuration with average reductions in DDT distance and time of 17% and 41% respectively when compared to the capacitive discharge spark plug system configuration.
Excited molecular terms of the alkali‐rare gas atom pairs

Numerous excited molecular terms for the various alkali‐rare gas atom pairs have been determined. The semiempirical potential model of Baylis has been used with some modifications in the calculation of the molecular terms; in particular, a large number of atomic states are included in our calculation, which ensure the stability of the calculated molecular terms. Our results show that coupling among molecular terms is very important and gives rise to structure in the excited potential energy curves. Comparisons between our results and other theoretical and experimental data are made.
Separation of Liquiritin from Glycyrrhizic Acid in Licorice Root Extract by Nanofiltration Membrane

The aim of this work was to study the separation of liquiritin (LQ) from glycyrrhizic acid (GA), in licorice aqueous solutions using nanofiltration (NRT-7450) membrane. The LQ and GA components are the main active ingredients of licorice root extract with various pharmacological effects, The effects of transmembrane pressure, feed temperature, feed pH, and cross-flow velocity on permeate flux and recovery were determined. A lab scale cross-flow set up using flat-sheet configuration membrane was employed for all experiments. SEM micrographs showed the changes in the fouled surface during operating time. The applied transmembrane pressure, feed temperature, feed pH, and cross-flow velocity were varied from 4 to 10 bars, 30 to 40°C, 3 to 9, and 0.8 to 3.1 m s−1 respectively. The obtained recoveries for GA and LQ varied between 0.65 to 1.86% and 16.89 to 41.65%, respectively. The optimum operating conditions for separation LQ from GA in licorice aqueous solutions using NRT-7450 nanofiltration membrane were 1.8 m s−1cross-flow velocity, 8 bars transmembrane pressure, 40°C of feed temperature and pH 7.
Synthesis and Characterization of ZnO, CuO and CuO/ZnO Nanostructures by a Novel Sol-Gel Route under Ultrasonic Conditions

Great interests in metallic oxides have emerged because of the possibility to modify the properties of these materials for different applications such as catalysis or sensors. In this work, CuO, ZnO and CuO-ZnO nanoparticles were prepared by a novel sol-gel route under ultrasonic condition using triethanolamine as an emulsifying surfactant. Fine powders were obtained when the pH of the sols were increased to 13 using NaOH. Particle sizes of the produced oxide materials were in the range of 3-4 nm, 40-50 x 100-150 nm (diameter x length) and 100-200 nm for CuO, ZnO and CuO-ZnO, respectively. The molar ratio of triethanolamine to metal nitrate precursors was set at 2:3. TEM micrographs of these particles were obtained to elucidate the morphology of the nanoparticles. Experimental results show that the band gap energies (Eg) for CuO, ZnO and CuO-ZnO were found to be 2.71, 3.35 and 2.82 eV, respectively.
New Trends in Reforming Technologies: from Hydrogen Industrial Plants to Multifuel Microreformers

Hydrogen production has been a matter of great importance in the last decades, but a renewed interest in its production processes has emerged recently driven by the spectacular advances in fuel cell technology. This review provides a comprehensive overview of the state‐of‐the‐art on reforming technology applicable to the development of small scale reformers. It considers some general aspects on hydrogen production technologies including the current production status, the future needs, and the advantages of decentralized hydrogen production vs its centralized generation in large capacity plants. Conventional and novel technologies are presented together with the new trends in research and development activities.
Modificação das propriedades das fibras de curauá por acetilação

In cementitious composite the vegetable fibers may suffer various degrees of degradation when exposed to alkaline medium. The alkaline degradation of macromolecular components of fibers mainly by lignin solubilization and cellulose defibrillation, compromising the physical and mechanical properties. The resistance of plant fiber to alkali attack can be improved by chemical surface treatments such as acetylation that can reduce the hygroscopic nature of lignocellulosic introducing hydrophobic functional groups in its chemical structure. Thus, the aim of this study was the application of the acetylation treatment at different levels to improve the durability of the fibers.The acetylation treatment in curaua fiber was applied at different temperatures and reaction times, and its efficiency, considering the reduction of hydrophilicity and maintenance of the physical-mechanical performance of fibers was evaluated by water absorption, mechanical resistance, infrared spectroscopy, scanning electron microscopy, thermogravimetric analysis and diffraction of x-rays. When acetylated curaua fibers absorbed up to 55% less water than untreated fibers. In strength, losses were up 52%. The acetylation treatment introduced hydrophobic chemical groups in the composition and changed crystalline character of fibers.
On the Isotopic Chemistry of Carbonates and a Paleotemperature Scale

The temperature variation of the fractionation of oxygen in exchange reactions between dissolved carbonate and water and between calcite and water and calculated on theoretical grounds, and checked experimentally. In the course of the experiments it was necessary to investigate several methods of decomposing calcium carbonate to carbon dioxide for mass spectrometer analysis. A method was developed for growing calcium carbonate from solution with the same isotopic composition as the carbonate shells of organisms produced at the same temperature from water of the same isotopic composition, and the results of these experiments at various temperatures are expressed in an equation relating the temperature of formation with the isotopic composition of the calcium carbonate and of the water.
N‐polarity GaN on sapphire substrate grown by MOVPE

N‐polar GaN was grown on (0001) sapphire using two‐step growth technique by MOVPE. In the growth, the key points were the controlling of the density of nuclei in a buffer layer and promoting lateral growth at high temperature. The grown GaN films had mirror‐like smooth surfaces and were proved to have N‐polarity using convergent‐beam electron diffraction and coaxial impact‐collision ion spectroscopy. The FWHM of this GaN in the ω‐scan was also much narrower than the previous reports. The density of threading dislocations was much less than for usual Ga‐polar GaN grown with a GaN or AlN buffer layer by MOVPE and MBE. In PL at room temperature, the strong edge emission was observed as Ga‐polarity. The p‐type conduction in Mg‐doped GaN was also realized by the same methods as for Ga‐polarity. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Collection efficiencies and particle size distributions from sampling cyclones — comparison of recent theories with experimental data

Les efficacites de collection et les distributions de taille des particules obtenues de cyclones d'echantillonnage de type Stairmand sont comparees aux predictions de quatre modeles theoriques, soit les modeles de Leith et Licht (1972), de Dietz (1981), de Mothes et Loffler (1988) et de Li et Wang (1989). On montre que la theorie de Mothes et Loffler, qui considere differentes regions d'ecoulement a l'interieur d'un cyclone, est capable, lorsqu'elle est couplee a une estimation realiste de la diffusivite turbulente des particules, de fournir de bonnes estimations des courbes d'efficacite et des distributions de taille des particules des poussieres au collecteur ou a la sortie du cyclone. L'absence de theories ou de formules empiriques adequates pour estimer la diffusivite turbulente reelle dans des conditions d'ecoulement de cyclone semble le facteur principal qui empeche l'utilisation de la theorie de Mothes et Loffler a des fins de prediction. Les charges elevees de fines et leur agglomeration, lorsqu'il y en a, sont responsables des importants ecarts par rapport aux predictions theoriques
Nature of optical transitions in conjugated oligomers. I. Theoretical characterization of neutral and doped oligo(phenylenevinylene)s

The nature of the main optical transitions taking place in oligo(phenylenevinylene)s is analyzed in both the neutral and oxidized states. Geometry optimizations are first carried out with the Hartree–Fock semiempirical Austin Model 1(AM1) method; on the basis of the resulting geometries, the transition energies and their intensities are determined by means of the Hartree–Fock semiempirical intermediate neglect of differential overlap (INDO) method combined with a single configuration‐interaction (SCI) technique. The major aspect of the results is to show that two subgap absorption peaks are induced by the generation of polarons (radical cations), while a single absorption feature is expected when bipolarons (dications) are formed, in agreement with the experimental absorption spectra of the oligomers; this situation is, however, in marked contrast with that in the polymer. The possible formation of diamagnetic π dimers is also discussed.
Nickel oxide screen printed electrodes for the sensing of hydroxide ions in aqueous solutions

Nickel oxide bulk modified screen printed electrodes are developed for the first time and explored towards the electroanalytical sensing of hydroxide ions and shown to be analytically useful. The nickel oxide screen printed sensor allows the detection of hydroxide ions over the low micro-molar to milli-molar range with a detection limit of 23 µM. The sensor is simplified over existing analytical methodologies and given its disposable and economical nature holds promise for the sensing of hydroxide ions and consequently the measurement of pH in aqueous solutions.
On the Relation between the Semiclassical Initial Value Representation and an Exact Quantum Expansion in Time-Dependent Coherent States †

The Herman-Kluk (HK) or coherent state initial value representation (IVR) of semiclassical (SC) theory expresses a time-evolving wave function as a sum (integral) over the initial conditions of classically evolved coherent states (aka minimum uncertainty wave packets). An exact expansion of the wave function can also be made in terms of these same coherent states, thinking of them simply as a (time-dependent) basis set. This paper shows the precise set of approximations that are necessary to degenerate the exact expansion into the SC-IVR result. As a byproduct, we also obtain a generalization of the HK "prefactor".
Semiconductor clusters in the sol-gel process: quantized aggregation, gelation, and crystal growth in concentrated zinc oxide colloids

A new synthesis of ZnO wurtzite clusters (crystallite sizes 3-6 nm) is presented. This novel approach, employing ultrasound, allows one to produce relatively highly concentrated 0.1 M Q-ZnO colloids within a few minutes. These colloids remains in a dispersed state for weeks. They can be further concentrated into stable syruplike liquids (molarities of ∼1 M). Under the externe concentration conditions (10 M Q-ZnO colloids) employed, ZnO alcogels are formed, and self-induced crystal growth occurs in the alcogels (sizes ranging between 1 and 5 mm)
Removal of BPA and NPnEOs from Secondary Effluents of Municipal WWTPs by Means of Ozonation

Removal potential of many EDCs by conventional WWTPs is recognized. Nevertheless, in order to reach very low concentrations, further treatment (e.g., chemical oxidation) might be required. In this work, two estrogen-like substances were considered: nonylphenol (NP) (and its parent compounds) and bisphenol A (BPA). The experimental work was conducted at Verona (Northern Italy) WWTP (370,000 p.e.): the effluent was submitted to ozonation in a pilot scale plant. Beside chemical and microbiological analyses, estrogenic activity measurements were also carried out by means of breast cancer MCF-7 cells transfected with the luminescence luciferase gene. Economic feasibility of tertiary ozonation is finally discussed.
Assessing a Kerbside Recycling Scheme: A Quantitative and Willingness to Pay Case Study

Abstract This paper reports on the results of a contingent valuation survey of a kerbside recycling scheme in the village of Hethersett, South Norfolk, U.K. A “dichotomous choice” (DC) willingness-to-pay question was applied, the setting of the bid levels being determined from a pilot sample of respondents presented with an open-ended question. The study was unique in that, as the scheme was already operational, the respondents had a high level of information about the good that they were valuing, thus minimising many of the common problems facing contingent valuation studies. The survey was undertaken in conjunction with a recycling survey, allowing responses to be related to the use that people were making of the recycling scheme. It was found that socio-economic factors were important in determining whether or not people said they would pay for the scheme, but that, once they had accepted the payment principle, their response to the DC bid level depended mainly upon its magnitude, and, to a lesser extent, on the amount of recycling that they were already undertaking before the scheme's implementation.
Structural Criteria for the Rational Design of Selective Ligands:Extension of the MM3 Force Field to Aliphatic Ether Complexes of the Alkali and Alkaline Earth Cations

Structural requirements for strain-free metal ion complexation by an aliphatic ether group are investigated through the use of both ab initio molecular orbital and molecular mechanics calculations. Hartree-Fock calculations on simple models, M-O(Me)[sub 2] and M-O(Me)(Et), reveal a preference for trigonal planar geometry when aliphatic ether oxygens are coordinated to alkali and alkaline earth cations. This preference is found to be strongest in small, high-valent cations and weakest in large, low-valent cations. Results from the Hartree-Fock calculations are used to extend the MM3 force field for calculation on aliphatic ether complexes with the alkali (Li to Cs) and alkaline earth (Mg to Ba) cations. The resulting molecular model (i) reproduces the experimental crystal structures of 51 different complexes of multidentate ethers with alkali and alkaline earth cations, (ii) explains experimental trends in the structure of five-membered chelate rings of aliphatic ethers, (iii) reveals a fundamental difference between the metal ion size selectivity of five-membered chelate rings of ethers versus that of amines, and (iv) rationalizes trends in the stability of four potassium complexes with the diasteriomers of dicyclohexyl-18-crown-6. 40 refs., 9 figs., 5 tabs.
Capillary Electrochromatography with Predetermined Selectivity Obtained through Molecular Imprinting

This article presents a novel approach to capillary electrochromatography by which predetermined selectivity is achieved. A simple and quick method for the in situ preparation of monolithic molecularly imprinted flow-through polymers inside fused silica capillaries is described. The superporous structure of the polymers permits rapid solvent and electrolyte exchange, as well as easy regeneration of the capillaries by hydrodynamic pumping. Chiral stationary phases were prepared by molecular imprinting of the β-adrenergic antagonists propranolol and metoprolol. The separation systems were operational within 3 h of the start of capillary preparation. Chiral separations with baseline resolution could be carried out in less than 120 s.
The wave vector dependence of diffusion coefficients in photon correlation spectroscopy of protein solutions

The mutual diffusion coefficient Dm was measured by means of photon correlation spectroscopy (PCS) for bovine serum albumin (BSA) at pH 4.7 and ionic strength I≃0.12 M. The BSA concentrations ranged from 1.00 to 10.7 g/dl and the magnitude of the scattering wave vector K varied from 3.21×104 to 3.51×105 cm−1. It was found that Dm=D0[1−(0.0166±0.0009)C], where D0=(5.92±0.04)×10−7 cm2/s corrected to water at 20 °C and the C measured in units of g/dl. The quantity Cn/K3, where Cn is the concentration in number of solute particles per cm3, ranged from 2 to 27 000, but this had no influence on the measured values of Dm. This work does not support the idea that the small size of K−1 or the small number of molecules contained in the volume K−3 affects the magnitudes of diffusion coefficients determined by PCS for proteins at moderate ionic strengths.
Novel perovskite–spinel composite approach to enhance the magnetization of LaFeO3

In the present work, the perovkite–spinel interface effect on the bulk magnetic behavior of lanthanum ferrite (LaFeO3) based composite systems is under investigation in view of the enhancement of the magnetization of LaFeO3. By using LaFeO3 as the perovskite phase and NiFe2O4 as the spinel phase with the compositions x = 0, 20, 30, 40 and 100 wt%, a composite system is developed by mechanical mixing. The structures are confirmed using X-ray diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FTIR). Physical interaction at the interface of the LaFeO3 and NiFe2O4 phases is realized by XRD peak broadening and shifting. The M–T and M–H curves are closely monitored to investigate the perovskite–spinel interface effect on the bulk magnetic behavior of the composites. Significant enhancement in the magnetization of the perovskite–spinel composite phase with a 60% LaFeO3–40% NiFe2O4 composition over individual phases is detected. The composition effect up to 60 : 40 of LaFeO3–NiFe2O4 is considered to preserve the dominance of the LaFeO3 phase. The spin coupling mechanism across the interface is speculated for the enhancement of the magnetization in the composite. Mossbauer spectroscopic investigation confirms the co-existence of magnetization in the composites.
Understanding the reasons that hinder mobile e-book use of university mathematics students

This study determined the issues related to usage of mathematics mobile e-book and how these issues affected the learning process of the participants. The study used qualitative case study design. Eight postgraduate Mathematics students from Abstract Algebra research group from a local public university in Malaysia were interviewed and observed. The data were analysed in terms of content analysis and descriptive analysis. The findings showed that, utilitarian, affective and cognitive reasons affected the learning activities of the participants negatively. It is concluded that, this study contributed in terms of expanding readers understanding on the reasons that demotivates the usage of mobile e-books and how it's dampen the learning process of the participants.