Miracle-dz/UniFAR-FTUs huggingface dataset:
Prediction of breakthrough curves in packed beds: II. Experimental evidence for axial dispersion and intraparticle effects

The effects of axial fluids dispersion on breakthrough curves in packed beds is considered and formulae are derived for ‘F-factors’, which allow heat transfer coefficients obtained by step testing to be corrected for axial fluids dispersion. A comparison of steady state and unsteady correlations for heat transfer in packed beds suggests that axial dispersion effects are incorporated in certain steady state heat transfer correlaions. Further correction would thus lead to errors in breakthrough curve prediction. Experimental data for breakthrough curves in packed beds of highly conductive and poorly conductive spheres is examined and Biot number correction factor 1 + Bi/5 shown to be valid for Biot numbers up to about 4.
PEMANFAATAN LABORATORIUM VIRTUAL DAN E-REFERENCE DALAM PROSES PEMBELAJARAN DAN PENELITIAN ILMU KIMIA

Teknologi informasi dan komputer telah berkembang sedemikian pesatnya, dan memiliki pengaruh yang luar biasa. Namun, kedua teknologi tersebut masih kurang pemanfaatannya di dunia pendidikan di Indonesia. Me- lalui laboratorium virtual proses pembelajaran menjadi lebih menarik, lebih interaktif, jumlah waktu mengajar dapat dikurangi, kualitas belajar dapat ditingkatkan dan proses belajar mengajar dapat dilakukan di mana saja dan kapan saja. Selain itu, melalui laboratorium virtual, bisa dilakukan penghematan biaya riset, serta riset-riset yang dahulu tidak mungkin dilakukan, karena keterbatasan pengkondisian sistem. Sedangkan E-references bisa digu- nakan bersinergi dalam mengatasi kelemahan laboratori- um virtual yaitu kurangnya kemampuan dalam mengatasi masalah.
Reaction‐diffusion modeling and simulations in positive deep ultraviolet resists

This article examines the effects of acid diffusion in APEX‐E through the quantitative modeling of resist top loss in unexposed samples due to acid diffusion from a top‐to‐top contact bake with an exposed sample. Top‐loss measurements are reported for 90 and 95 °C postexposure bake (PEB) temperatures ranging from 60 to 360 s bake times, resulting in 0.12 and 0.29 μm top loss, respectively, after 360 s PEB times. Results of systematically changing the diffusion constant, the kinetic reaction rates, and the deprotection level for dissolution in a Fickean diffusion model show that this model cannot account for the experimental observations. A better fit of the data and a near linear top‐loss dependence with bake time are obtained with a deprotection dependent diffusion model, suggesting nonlinear diffusion mechanisms are important in modeling lithographic performance in positive deep ultraviolet resists.
IDENTIFICATION AND DETERMINATION OF POLYPHENOLS IN TEA BY LIQUID CHROMATOGRAPHY WITH MULTI-CHANNEL ELECTROCHEMICAL DETECTION

A liquid chromatography method with multi-channel electrochemical detection is reported for the identification and determination of polyphenols in green tea, black tea, and extracted green tea powder. Following a simple aqueous extraction, (−)-epigallocatechin (EGC), (+)-catechin (C), (−)-epicatechin (EC), (−)-epigallocatechin gallate (EGCG), (−)-gallocatechin gallate (GCG), (−)-gallocatechin (GC), (−)-epicatechin gallate (ECG), and (−)-catechin gallate (CG) were successfully separated by reversed phase liquid chromatography within 25 min. The detection limits (S/N=3) of the polyphenols studied were 0.1–1.5 ng/mL at a potential of +900mV. The calibration curve was linear over the range of 1–1000 ng/mL for EGC, C, EC, EGCG, GCG, and GC, 5–1000 ng/mL for ECG and CG. Using this method, the concentration of these eight polyphenols in five different brands of green tea, one brand of black tea, and extracted green tea powder were determined.
1,3,5-triazine-triethylenetetramine polymer: an efficient adsorbent for removal of Cr(VI) ions from aqueous solution

The synthesis of 1,3,5-triazine-triethylenetetramine (TATETA), its characterization by infrared spectroscopy and elemental analysis, and its application for removal of Cr(VI) ions from aqueous solution is reported. The effects of pH, contact time, initial concentration of Cr(VI), sorbent dose, and temperature on adsorption were investigated and optimized by batch adsorption experiments. Adsorption was highest at acidic conditions with an equilibration time of 25 min. The adsorption followed a Langmuir model, with an adsorption capacity of 303 mg g−1, was second order in its kinetics, and exothermic and thus spontaneous.
Synthetic Approaches Towards Quinazolines, Quinazolinones and Quinazolinediones on Solid Phase

Quinazolines are a pharmacologically very attractive class of compounds and have shown activity in various assays. Several successfully launched drugs are based on this scaffold. As a consequence, a more intensive exploitation in drug discovery by solid-phase syntheses of quinazoline libraries has been initiated. A diverse array of combinatorial quinazoline syntheses have been published and an increasing effort is to be expected in the near future to provide more efficient solid phase approaches towards quinazolines, quinazolinones and quinazolinediones. This review summarizes the literature published until January 2004 describing methods for synthesis and modification of these compounds on solid phase.
Determination of selenium in human hair and nail by electrothermal atomic absorption spectrometry

A microwave digestion procedure was used to prepare samples for determination of total Se by electrothermal atomic absorption spectrometry (ETAAS) with palladium modification. Conversion of organoselenium compounds to inorganic selenium was achieved by heating 100 mg hair with 0.5 ml concentrated nitric acid for 1 min and then, after the addition of 0.5 ml hydrogen peroxide (30 vols.), reheating for a further 8 min. The accuracy of the method was confirmed by analysis of certified hair reference materials containing 2.00 and 0.58 µg g–1 Se. The detection limit is 0.02 µg g–1 Se. A variation of the procedure was used to analyse nail samples. Digestion was achieved by heating 100 mg of nail with 1 ml nitric acid for 2 min and, after the addition of 1 ml hydrogen peroxide, for a further 33 (3 × 11) min. The detection limit for this procedure is 0.03 µg g–1 Se. Analysis of hair reference materials and both hair and nail samples by neutron activation analysis and ETAAS showed reasonable agreement between the techniques. The ETAAS procedure is more rapid and convenient. Analysis of 25 hair samples gave a range of 0.31–0.76 µg g–1 Se (mean value 0.52 ± 0.11 µg g–1) and for 27 nail samples a range of 0.17–0.66 µg g–1 Se (mean value 0.46 ± 0.16 µg g–1) was obtained.
Phytoextraction of Cd and Zn with Salix viminalis in field trials

Abstract. Use of high biomass crops such as the willow Salix viminalis to extract metals for soil remediation has been proposed as an alternative to the low biomass‐producing hyperaccumulating plants. High yields compensate for the moderate heavy‐metal concentrations in the shoots of such species. We report the first long‐term trials using Salix viminalis to extract heavy metals from two contaminated soils, one calcareous (5 years) and one acidic (2 years). Total metals extracted by the plants were 170 g Cd ha−1 and 13.4 kg Zn ha−1 from the calcareous soil after 5 years, and 47 g Cd ha−1 and 14.5 kg Zn ha−1 from the acidic soil after 2 years; in the first year outputs were negligible. After 2 years, Salix had performed better on the acidic soil because of larger biomass production and higher metal concentrations in shoots. Addition of elemental sulphur to the soil did not yield any additional benefit in the long term, but application of an Fe chelate improved the biomass production. Cd and Zn concentrations were significantly higher in leaves than stems, highlighting the necessity to collect leaves as well as shoots. On both soils, concentration in shoots decreased with time, indicating a decrease in extraction efficiency.
Midinfrared GaInSb/AlGaInSb quantum well laser diodes operating above 200 K.

Electroluminescence from GaInSb/AlGaInSb type I quantum well diode lasers, grown on GaAs, has been investigated as a function of strain in the quantum wells. Lasing was observed, in pulsed operation, up to temperatures of 161, 208, 219, and 202 K for structures containing 0.55%, 0.62%, 0.78%, and 1.1% strain, respectively, with lasing occurring at ∼3.3 μm at 200 K for the 1.1% structure.
Fowler‐Nordheim Tunneling into Thermally Grown SiO2

Electronic conduction in thermally grown SiO2 has been shown to be limited by Fowler‐Nordheim emission, i.e., tunneling of electrons from the vicinity of the electrode Fermi level through the forbidden energy gap into the conduction band of the oxide. Fowler‐Nordheim characteristics have been observed over more than five decades of current for emission from Si, Al, and Mg. If previously measured values of the barrier heights are used, the slopes of the Fowler‐Nordheim characteristics (log J/E2 vs 1/E) imply values of the relative effective mass in the forbidden band of about 0.4. These values take into account corrections for image‐force barrier lowering and for temperature effects. The absolute values of the currents are lower by a factor of five to ten than the theoretically expected values, probably due to trapping effects. The temperature dependence of the current was found to follow the theoretical curve from 80°–420°K. However, an inconsistent relative effective mass of about 0.95 had to be assumed.
Determination of Oxytetracycline with a Gold Electrode Modified by Chitosan-Multiwalled Carbon Nanotube Multilayer Films and Gold Nanoparticles

A molecularly imprinted electrochemical sensor was fabricated based on a gold electrode modified by chitosan-multiwalled carbon nanotube composite (CS-MWCNTs) multilayer films and gold nanoparticles (AuNPs) for convenient and sensitive determination of oxytetracycline (OTC). The multilayer of CS-MWCNTs composites and AuNPs were used to augment electronic transmission and sensitivity. The molecularly imprinted polymers (MIPs) were synthesized using OTC as the template molecule and o-phenylenediamine (OPD) as the functional monomer. They were modified on a gold electrode by electropolymerization. The electrochemical behavior of OTC at the imprinted sensor was characterized by cyclic voltammetry (CV), scanning electron microscopy (SEM), and amperometry. The molecularly imprinted sensor showed high selectivity and excellent stability toward OTC. The linear range was from 3.0 × 10−8 to 8.0 × 10−5 mol/L, with a limit of detection (LOD) of 2.7 × 10−8 mol/L (S/N = 3). The developed sensor showed good recovery in spiked samples analysis.
Chemical Characterization of GPC Fractions of Athabasca Bitumen Asphaltenes Isolated before and after Thermal Treatment

The object of this work was to determine whether new information could be obtained by using gel permeation chromatography (GPC) to fractionate asphaltene samples prior to analysis. In particular, GPC elution profiles, elemental analyses, molecular weights by vapor pressure osmometry (VPO), and boiling point distributions of the asphaltenes isolated from the original Athabasca bitumen feed (Feed) and from its total liquid product (TLP) after visbreaking were compared. The analyses showed that for GPC run using chloroform, fractionation was based on size where elemental analyses and boiling point distributions indicated that the earlier eluting fractions were not aggregates of later eluting fractions. The largest TLP asphaltene species were slightly smaller in size (by GPC and VPO) to those in the Feed asphaltenes; the smallest TLP asphaltene species were smaller than those isolated from the Feed asphaltenes and contained material with an initial boiling point of 340 °C despite both vacuum distillation (524.
Colorimetry Applied to Steam-Treated Biomass and Pellets Made from Western Douglas Fir (Pseudotsuga menziesii L.)

Wood pellets made from sawdust and shavings are white in color and low in ash content. Pellets made from a mix of bark and white wood are darker in color, and bark increases the ash content of pellets. Steam treatment of biomass prior to pelletization improves the durability of pellets. Both wet (steam) and dry thermal (torrefaction) treatments of biomass darken the pellets. The off-color pellets have a lower commercial value than white wood pellets in residential applications. In this research, ground white wood (western Douglas fir, Pseudotsuga menziesii L.) was treated with saturated steam at 200°C and 220°C for 5 and 10 min. The colors of the treated and untreated powders and pellets were evaluated. The Hunter color coordinates L*, a*, and b* were recorded using a Minolta CM-5 spectrophotometer. Compared to untreated samples, the steam-treated samples became darker; the hues shifted from red to green and from blue to yellow. Multi-linear regression models of three color coordinates with elemental composition of carbon and hydrogen were developed. The values of L*, a*, and b* showed good correlation with percentage of carbon, hydrogen, and oxygen of the samples, with R2 values of 0.97, 0.99, and 0.97, respectively. The developed equations can be useful tools for the bioenergy industry for a quick estimation of fuel properties by a simple color measurement.
Simple design but marvelous performances: molecular gels of superior strength and self-healing properties

Four nitrobenzoxadiazole (NBD)-containing cholesteryl (Chol) derivatives were prepared, and their gelation behaviors were tested. It was demonstrated that the compounds show a remarkable gelling ability. In particular, a subtle change in the length of the spacers connecting the two structural units of the compounds, which are NBD and Chol, respectively, produced a dramatic change in the gelation ability and the gel properties of the compounds. As for gelation, compound 1 is much more powerful than others, especially in the gelation of methanol-containing organic mixtures. It is to be noted that the gel of 1/pyridine–methanol exhibits superior mechanical strength with a yield stress higher than 6300 Pa at a gelator concentration of 2.5% (w/v), and the value exceeds 23 000 Pa when the gelator concentration reaches 5.0% (w/v), a result never reported before in the field of molecular gels based on low-molecular mass gelators (LMMGs). More importantly, the gel shows a rapid self-healing property as evidenced by the fact that the gel heals up immediately upon cutting, provided the segments from the cutting are squeezed together. No doubt, our findings establish a benchmark for LMMG-based molecular gels in their rheological performances. FTIR, 1H NMR and XRD studies revealed that intermolecular hydrogen bonding and π–π stacking are two of the main driving forces to promote the gelation of the system and the self-assembling of the molecules of the gelator.
A cluster growth route to quantum-confined CdS nanowires

Quantum-confined CdS nanowires with diameters around 4 nm and lengths ranging from 150 to 250 nm were grown for the first time from cadmium bis(diethyldithiocarbamate) [Cd(DDTC)2]2 by removal of the four thione groups with ethylenediamine (en) at 117 °C for 2 min.
Hydrogen storage in different carbon nanostructures

Carbon nanostructures of different kinds have been synthesized by chemical vapor deposition. By modifying the deposition temperature, the catalyst material, and the hydrocarbon, nanofibers with herringbone structure, multi-walled nanotubes with tubular structure, and single-walled nanotubes were deposited. The nanostructures were purified with different treatment methods. The carbon nanostructures were characterized using scanning and transmission electron microscopy. The hydrogen storage capability was investigated for all obtained nanostructures. The measurements show that the storage capacity of hydrogen is very limited in all the carbon nanostructures.
The Application of an Artificial Neural Network (ANN) and a Genetic Programming Neural Network (GPNN) for the Modeling of Experimental Data of Slim Tube Permeability Reduction by Asphaltene Precipitation in Iranian Crude Oil Reservoirs

Abstract The authors introduce a new implementation of the neural network (ANN), genetic programming neural network (GPNN), and neuro-fuzzy (NF) technology in petroleum engineering. An intelligent framework is developed for calculating the amount of permeability reduction by asphaltene precipitation in Iranian crude oil reservoirs over a wide pressure, temperature, and solvent mole fraction range. Theoretical results and practical experience indicate that a feed-forward network can approximate a wide class of function relationships very well. In this work, a conventional feed-forward multilayer ANN, GPNN, and NF approach have been proposed to predict the amount of permeability reduction. The accuracy of the method is evaluated by predicting the amount of permeability reduction of various reservoir fluids not used in the development of the models. One of the ways in modeling such systems is using intelligent techniques, which need information about the systems, so, based on some intelligent learning methods, it can provide a suitable model. Furthermore, the performance of the model is compared with the performance of a simple model for permeability reduction prediction, a new correlation, and experimental data. Results of this comparison show that the proposed GPNN method first and then NF method is superior both in accuracy and generality, over the other models.
Online Flow Injection Preconcentration and Flame Atomic Absorption Spectrometric Determination of Palladium(II) Using Inorganic and Inorganic‐Organic Hybrid Materials–Packed Microcolumns

Abstract Various inorganic and inorganic‐organic hybrid materials–packed columns, including commercially available C18 bonded silica gel and alumina columns, were tested for the on‐line preconcentration of palladium(II) and subsequent determination by flame atomic absorption spectrometry (AAS). Several thioligands were investigated for complexing palladium(II) and subsequent sorption, elution, and determination by flame atomic absorption spectrometer. Among them, diethyl ammonium dithiocarbamate was found to give the highest enrichment factor for a given concentration of palladium(II) under optimized conditions. After testing the accuracy of the developed method by analyzing certified reference material (SARM 7), it was applied for the analysis of street and domestic fan blade dust samples.
First polarization-engineered compressively strained AlInGaN barrier enhancement-mode MISHFET

One current focus of research is the realization of GaN-based enhancement-mode devices. A novel approach for the realization of enhancement-mode behaviour is the utilization of polarization matching between the barrier and the GaN buffer. Yet, the utilization of a quaternary barrier combining polarization engineering together with a large conduction band offset has not been demonstrated so far. Here, epitaxially grown, compressively strained AlInGaN is applied as a nearly polarization-matched barrier layer on GaN resulting in enhancement-mode operation. The insulated-gate devices are fabricated gate-first with Al2O3 as gate dielectric. Passivated metal insulator semiconductor heterostructure field effect transistors yielded threshold voltages (Vth) of up to +1 V. The devices withstand negative and positive gate-biased stress and a positive Vth is maintained even after long-time negative bias stress.
Fabrication of Dual-Barrier Planar Structure Diamond Schottky Diodes by Rapid Thermal Annealing

Fabrication of dual-barrier planar (DBP) structure diamond Schottky barrier diodes (SBDs) with only Ni Schottky contact was carried out by rapid thermal annealing. Ni/Au narrow stripes were first patterned on <inline-formula> <tex-math notation="LaTeX">$\text{p}^{-}$ </tex-math></inline-formula> layer and annealed at 550 °C to decrease Schottky barrier height and form low barrier contact. Then, Ni/Au Schottky electrodes were deposited on the window area between stripes to serve as high barrier contact. Ti/Pt/Au ohmic contact was formed on the back side of <inline-formula> <tex-math notation="LaTeX">$\text{p}^{+}$ </tex-math></inline-formula> diamond substrate. The fabricated DBP structure SBDs exhibit low forward voltage drops compared with single high barrier diode, and reverse leakage current densities of two to three orders of magnitude smaller than that of single low barrier diode. The influence of stripes area proportion on device properties was investigated and the barrier height can be adjusted by changing dual-barrier ratio. This new device structure displays a small power dissipation of 0.54 W/cm<sup>2</sup>, which is a promising technology for high power diamond diodes.
Determination of VOC in aqueous samples by the combination of headspace (HS) and solid-phase microextraction (SPME)

The application of solid phase microextraction (SPME) is generally conducted by directly immersing the fiber into the liquid sample or by exposing the fiber in the head space (HS). The extraction temperature, the time of incubation, and application of stirring are often designated to be the most important parameters for achieving the best extraction efficiencies of HS-SPME analysis. In this study, relative importance of these three analytical parameters involved in the HS-SPME method is evaluated using a polydimethylsiloxane/carboxen (PDMS/CAR) fiber. To optimize its operation conditions the competing relationships between different parameters were investigated by comparing the extraction efficiency based on the combination of three parameters and two contracting conditions: (1) heating the sample at 30 vs. 50 C, (2) exposing samples at two durations of 10 vs. 30 min, and (3) application of stirring vs. no stirring. According to our analysis among 8 combination types of HS-SPME method, an extraction condition termed as S50-30 condition ((1) 1200 rpm stirring, (2) exposure temp, and (3) 30 min exposure duration) showed maximum recovery rate of 45.5~68.5% relative to an arbitrary reference of direct GC injection. According to this study, the employment of stirring is the most crucial factor to improve extraction efficiency in the application of HS-SPME.