Miracle-dz/UniFAR-FTUs huggingface dataset:
Chemical Recycling, Kinetics, and Thermodynamics of Alkaline Depolymerization of Waste Polyesters

Abstract Depolymerization of waste poly (ethylene terephthalate) and poly (butylene terephthalate) were undertaken in various alkaline solutions at different reaction parameters at 1 atm in a batch operation. Results were evaluated in terms of weight loss of both the waste polyesters as well as products obtained during depolymerization of polyesters. Poly (ethylene terephthalate) (PET) showed more weight loss as compared to that of poly (butylene terephthalate) (PBT) in various potassium hydroxide (KOH) solutions. Methanolic alkaline solution has showed greater reaction effect as compared to those of aqueous as well as ethanolic solutions for both the waste polyesters. Reaction products composed of ethylene glycol (EG)/1,4-butanediol (BD) and terephthalic acid (TPA) that were analyzed and confirmed. Yields of monomeric products (TPA and EG/BD) were almost equal to those of polyester conversion. To accelerate the rate of reaction cyclohexylamine (CHA), tetrahydrofurane (THF), and dimethyl sulfoxide (DMSO) were introduced during depolymerization of polyesters. A kinetic model is developed and experimental data are fitted with it for validity of the model. The model shows good agreement with the experimental data. Thermodynamics are also undertaken to estimate the rate constants, equilibrium constant, Gibbs free energy, enthalpy, and entropy of reaction that is required to transfer laboratory data through the pilot plant for commercialization. Dependence of rate constant on reaction temperature was correlated by Arrhenius plot that was used to determine activation energy and Arrhenius constant.
Reactive Ion Etching of Thin Gold Films

Reactive ion etching of thin gold films using chlorine (Cl 2 ), carbon tetrafluoride (CF 4 ), carbon tetrachloride (CCL 4 ), and a mixture of these gases was investigated. Etch rates were studied by changing the etching gas composition, pressure, and power in a parallel-plate reactive ion etcher. Reactive ion etching of gold using Cl 2 or CCl 4 yields a low etch rate and a carbon residue formation on etched surfaces
Activation of novel copper–carbon catalysts using temperature-programmed mass spectrometry

An entirely new method of preparing metal–carbon catalysts is reported in which the metal is present as small crystallites distributed in a three-dimensional array throughout the bulk of the carbon matrix. The metal particles are linked by a network of pores which exposes virtually all of the metal surface to the gas phase. By virtue of their structure, these new materials exhibit a remarkable resistance to sintering, even near the melting point of the metal. While many catalytically important metals can be incorporated into our materials, this paper concentrates on the structure of one of the copper–carbon systems. These are made by the reduction of a copper(II) cellulose precursor to produce a copper(0) cellulose material, followed by thermal degradation of the cellulose and activation of the resulting carbon to produce the pore network. New techniques, using a temperature-programmed gas-flow micro-reactor linked to an on-line mass spectrometer, are used to investigate the nature of the critical activation process. The resulting pore structure is studied and a mechanism is proposed to explain the catalytic effect of the copper particles on the formation of the pore network. Poisoning experiments demonstrate that access to the active sites is determined by the pore size, thus giving a measure of size selectivity. Using temperature-programmed oxidation with on-line MS it was demonstrated that the pores can be widened in a controlled manner, so reducing any diffusion-induced limitation on reaction rates. This offers the possibility of designing a catalyst with a specified balance between the conflicting requirements for size selectivity and high reaction rates.
Donor-Acceptor Polymers Incorporating Alkylated Dithienylbenzothiadiazole for Bulk Heterojunction Solar Cells: Pronounced Effect of Positioning Alkyl Chains

4,7-Di(thiophen-2-yl)benzothiadiazole (DTBT) has been used to construct a number of donor−acceptor low band gap polymers for bulk heterojunction (BHJ) photovoltaics with high efficiency numbers. Its strong tendency to π-stack often leads to polymers with low molecular weight and poor solubility, which could potentially be alleviated by anchoring solubilizing chains onto the DTBT unit. A systematic study of the effect of positioning alkyl chains on DTBT on properties of polymers was implemented by investigating a small library of structurally related polymers with identical conjugated backbone. This series of donor−acceptor polymers employed a common donor unit, benzo[2,1-b:3,4-b′]dithiophene (BDT), and modified DTBT as the acceptor unit. Three variations of modified DTBT units were prepared with alkyl side chains at (a) the 5- and 6-positions of 2,1,3-benzothiadiazole (DTsolBT), (b) 3-positions of the flanking thienyl groups (3DTBT), and (c) 4-positions (4DTBT), in addition to the unmodified DTBT. Contrar.
Polystyrene spheres on mica substrates: AFM calibration, tip parameters and scan artefacts

Atomic force microscopy (AFM), in various versions, has had major impact as a surface structural and spectroscopic tool since its invention in 1986. At its present state of development, however, the interpretation of AFM images is limited by the current state of methodologies for calibration over the wide dynamic range of magnification. Also, the parameters of individual tips, as well as the generic characteristics of different kinds of tips, affect both the quality of the images and their interpretation. Finally, the very nature of the tip‐to‐surface interaction will generate artefacts, in addition to those associated with tip shape, which need to be fully understood by the practitioners of force microscopy. This project seeks to address and shed light on some of these issues.
The drying of solids in a modified fluidized bed

When fine and cohesive particles are the subject of study, fluid beds are of concern of due to the formation of channeling. This work presents a study that was carried out on the drying of fine particles, in this case a crystalline organic acid, in a mechanically stirred fluidized bed. The drying kinetics curves were determined by evaluating the influences of initial moisture content and temperature of the drying gas at the entrance of the bed. This study shows the suitability of the stirred fluidized bed for the drying of solids of low-quality fluidization.
Mechanisms of bending of threading dislocations in MOVPE‐grown GaN on (0001) sapphire

In this article, we describe possible mechanisms associated with the bending of threading dislocations (TDs) through 90° in GaN. In-situ ELOG using SiNx masking on a sapphire substrate and in-situ SiNx interlayer (IL) deposition on a GaN pseudo-substrate have been used to reduce the TD density in GaN. The bending of TDs through 90° is essential in order to reduce their numbers in the upper growing layer. The bending of TDs is facilitated by a change in growth mode, i.e. predominantly 2D to 3D and then 3D to 2D. A new mechanism is tentatively proposed which can explain the bending of all types of TDs (edge, screw, and mixed). This new mechanism is based on first, step formation at 3D island side facets when TDs terminate there, following which, depending on the subsequent change in growth mode (3D to 2D) and the direction of the atomic ledge movement, the TDs will bend over. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
Preparation of Free-Standing GaN Substrates from Thick GaN Layers Crystallized by Hydride Vapor Phase Epitaxy on Ammonothermally Grown GaN Seeds

Crystallization of GaN by hydride vapor phase epitaxy (HVPE) on ammonothermally grown GaN seed crystals is described. The initial growth conditions for HVPE are determined and applied for further bulk growth. Smooth GaN layers up to 1.1 mm thick and of excellent crystalline quality, without cracks, and with low dislocation density are obtained. Preparation of the free-standing HVPE-GaN crystal by slicing and structural and optical quality of the resulting wafer are presented.
Ignitable Liquid Classification and Identification Using the Summed-Ion Mass Spectrum

Abstract The mass spectra calculated by summing the intensities of each nominal mass over all chromatographic times, the summed ion spectra, were calculated for a set of 440 commercially available ignitable liquids that had been analyzed by gas chromatography–mass spectrometry. Each ignitable liquid is generally comprised of a mixture of chemicals, and the mixtures may be very complex in some cases, e.g., petroleum distillates, gasoline, etc. The summed ion spectra were evaluated to determine if they contained sufficient information content to allow their use for rapid and accurate identification of the ignitable liquid in a database or library. The summed ion nominal mass spectra were encoded in one bit per channel at 1% transition intensity and a set of 96,580 unique pairwise comparisons were made between spectra, resulting in an average of approximately 50 differing channels per comparison. A subset of 62 summed ion spectra were further compared by a similarity metric and found by cluster analysis to group closely along the ASTM ignitable liquid classification scheme. Receiver operator characteristic analysis of the use of the similarity index in combination with the summed ion spectra was shown to provide 99% probability of correct liquid identification and 95% probability of correct ASTM classification by primary and sub-class. Interlaboratory tests found 95% probability of correct liquid identification and 85% probability of correct ASTM classification at the primary class level. These results demonstrate the use of the summed ion spectrum as a first step in the rapid identification of an ignitable liquid by database or library searching.
Influence of the Interaction of Equivalence Ratio and Mass Flow Fluctuations on Flame Dynamics

Modern lean combustion systems are often prone to combustion instabilities — an interaction of acoustic waves, fluid dynamics and heat release oscillations. Mass flow oscillations are one important part of the feedback loop of combustion instabilities. Therefore, modulated mass flows of fuel or/and combustion air are main objectives in many studies on combustion instabilities and their active control (AIC, Active Instability Control). Flame response and flame transfer matrices are often determined by excitation of combustion air at various frequencies by sirens or loudspeakers. For the purpose of active control modulated secondary fuel is usually injected to the mass flow to dampen heat release fluctuations of the flame in order to de-couple the thermoacoustic feedback loop. This paper demonstrates the influence of modulated mass flows on the flame dynamics in an atmospheric test rig with a natural gas fired swirl burner. In the investigated cases the modulation of combustion air also result in equivalence ratio fluctuations due to choked main fuel injection. This combination has a tremendous effect on the flame dynamics. A model was developed to describe the interaction of equivalence ratio fluctuations and total mass flow oscillations and their influence on combustion instabilities. In experiments these equivalence ratio fluctuations were generated by injecting modulated secondary fuel. The derived model provides a deep insight into the driving mechanisms of combustion instabilities. © 2005 ASME
Stereoselective Bioanalysis of Oxcarbazepine and the Enantiomers of Its Metabolites by High-Performance Liquid Chromatcgraphy

Abstract The simultaneous liquid chromatographic determination of oxcarbazepine and the enantiomers of its metabolites 10,11-dihydro-10-hydroxycarbamazepine and trans-10,11-dihydroxycarbamazepine in spiked human plasma is described. The compounds are subjected to solid phase extraction before chromatography. The separation of the analytes is achieved using chiralcel OD column coupled on line with chiralcel ODH column and a mobile phase consisting of n-hexane-ethanol (70/30, v/v). The compound were detected by ultraviolet absorbance at 220 nm. The limit of quantification for each compound was 5 ng/ml.
Alterações na biomassa e na atividade microbiana da serapilheira e do solo, em decorrência da substituição de cobertura florestal nativa por plantações de eucalipto, em diferentes sítios da Região Sudeste do Brasil

In Brazil, afforestation programs use mainly eucalyptus and it has been frequently questioned due to possible changes in the soil caused by this exotic tree species. The impact of land use changes can vary with climate conditions and soil, and results obtained in a specific area may not be extrapolated to the supra-regional level. Biomass and microbial activity have been suggested as appropriate indicators of soil disturbance caused by management techniques. In this study, these characteristics were used to evaluate changes in forest litter and soil where the native forest was replaced by eucalyptus plantations in four southeastern areas of Brazil. The amounts of forest litter were higher in eucalyptus stands than in the native forest due to the higher C:N ratio of the material. The impact of the conversion of native forest into eucalyptus stands on soil and forest floor properties varied in the site-specific characteristics analyzed. Differences between the contents of microbial biomass C and N in eucalypt and native vegetation were more frequently observed in the soil than in forest litter. Forest litter microbial biomass represented a larger reservoir of C and N than soil microbial biomass, representing a relevant component for C and N cycling in these ecosystems.
Bleeding of Farmed Atlantic Cod: Residual Blood, Color, and Quality Attributes of Pre- and Postrigor Fillets as Affected by Perimortem Stress and Different Bleeding Methods

The main objectives of the study were to (a) assess the effect of perimortem stress on blood drainage, (b) compare the efficiency of gill cutting and direct gutting as bleeding methods, and (c) compare pre- and postrigor filleting strategies for presence of residual blood in Atlantic cod fillets. Anesthetized cod had significantly higher drainage of blood compared to stressed fish. Nevertheless, the visual assessments of residual blood were not affected by stress or bleeding method. Some minor, but significant, differences between pre- and postrigor fillets were found. Stressed fish were initially less light in color than those unstressed, but after ice storage there was no noticeable difference. However, initially, the largest difference in fillet color was due to different bleeding methods. Fillets cut from fish subjected to gill cutting were lighter and less red in color than those bled by direct gutting. After 7 and 21 days of storage, the color differences observed in fresh and salted fillets, respectively, were mainly due to the different rigor status when they were filleted, indicating that fillets cut postrigor were superior to fillets cut prerigor. Prerigor filleting resulted in lower water holding capacity after ice storage in anesthetized, direct gutted cod.
A Kinetic Analysis of the Reaction Catalysed by (Hydroxymethyl)bilane Synthase

(Hydroxymethyl)bilane synthase (HMBS) catalyses the conversion of porphobilinogen (2) into the (hydroxymethyl)bilane derivative 3, a linear tetrapyrrolic intermediate in the biosynthesis of haem, chlorophyll, and related pigments. The conversion involves the sequential formation of four intermediate covalent enzyme-substrate complexes, before the product is released. We analysed the pre-steady-state kinetics of the formation of the complexes, taking advantage of their remarkable chemical stability allowing chromatographic separation. The experimental approach involved the generation of the complexes while HMBS was immobilised on an anion-exchange column. A solution being 0.2 Km in substrate was pumped through the column during a time interval which was varied to sample the pre-steady-state period. Then, the enzyme and enzyme-substrate complexes were eluted and their proportions evaluated. A computer simulation of the pre-steady-state time course, in combination with a χ2 fitting to the experimental data, allowed the specificity constants kcat/Km for the individual steps of the process to be derived. By repeating the analysis with variants of HMBS in which specific amino acids were replaced by others, we demonstrated that it is possible to trace the consequences of amino-acid replacements down to the individual steps of the reaction sequence. Since the positions of the amino acids concerned in the three-dimensional structure were known, detailed structure-function relationships become evident in this way.
Negative ion–molecule reactions of ozone and their implications on the thermochemistry of O3−

An in‐line double mass spectrometer has been employed to determine reaction rate coefficients and excitation functions for several types of negative ion reactions involving ozone. The interactions studied include electron transfer reactions, such as, M−+O3→M+O3− (where M−=O−, OH−, F−, Cl−, Br−, I−, S−, SH−, Cl−2, C2H−, NO2−, and CO3−) and particle transfer reactions, such as MO−+O2→M+O3− (where MO−=O2−, NO2−, NO3−, CO3−). Translational energy thresholds have been determined for those reactions which are endothermic by applying exact Doppler corrections for the thermal motion of the neutral as well as corrections for the translational energy distribution of the projecticle ions. These experiments place a lower limit of 2.26+0.04−0.06 eV on the electron affinity of ozone. This value is in excellent agreement with the value computed from the bond dissociation energy of O3− in its most stable configuration, D00(O−–O2) =1.80 eV, as deduced from measurements of the translational energy thresholds for the collis.
Use of Raw and Acid-Treated MnO2 as Catalysts for Oxidation of Dyes in Water: A Case Study with Aqueous Methylene Blue

Catalytic wet oxidation has become one of the best options for mineralization of dyes in water. In this work, mineralization of methylene blue in water was tried by using raw and acid-treated (0.50, 0.75, and 1.00 N H2SO4) MnO2 as oxidation catalysts. Fourier transform infrared, scanning electron microscopy, surface area and cation exchange capacity measurements were used to characterize the catalysts. The acid-treated materials showed large increases in surface area while changes in other surface characteristics were moderate in nature. The oxidative destruction of the dye was possible at near room temperature and the process was optimized with respect to interaction time, dye concentration, catalyst loading, pH of the medium, and temperature. The dye (1.0 mg/L) was oxidized to the extents of 88.5%, 96.5%, 96.8%, and 97.7% with corresponding chemical oxygen demand (COD) reduction of 64.7%, 86.4%, 87.2%, and 88.2% by raw MnO2, 0.50, 0.75, and 1.00 N acid-treated MnO2(catalyst loading 2.5 g/L), respectively. The reduction in COD indicated oxidation of the dye to simpler organic compounds achieving mineralization to a large extent. The oxidation followed first-order kinetics and the catalysts could be used up to six repeated runs without much change in activity. Analysis of the intermediate products of oxidation helped in proposing the potential pathways for oxidative conversion of methylene blue.
State Estimation of a Linear System on a Network subject to Sporadic Measurements and Time-Delays

Author(s): Guarro, Marcello Daniele | Advisor(s): Sanfelice, Ricardo G. | Abstract: This paper proposes a hybrid observer for state estimation over a network. The network provides delayed measurements of the output of the plant at time instants that are not necessarily periodic and are accompanied by timestamps provided by a clock that synchronizes with the clock of the observer in finite time. The proposed observer, along with the plant and communication network, are modeled by a hybrid dynamical system that has two timers, a logic variable, and two memory states to capture the mechanisms involved in the events associated with sampling and arrival of information, as well as the logic in the estimation algorithm. The hybrid model also includes a generic clock synchronization scheme to cope with a mismatch between the clocks at the plant and the observer. Convergence properties of the estimation error of the system are shown analytically and supported by numerical examples.
Immobilization of Antibodies on a Photoactive Self-Assembled Monolayer on Gold

This paper presents a strategy for immobilizing biomolecules on a photoactivable surface. A self-assembled monolayer is prepared by adsorbing an ω-functionalized dialkyl disulfide on gold. Functional groups of this monolayer are converted in two steps into a benzophenone derivative with an overall yield of 50 ± 10%. Several independent techniques (ellipsometry, X-ray photoelectron spectroscopy, scanning electron microscopy, atomic force microscopy, radiolabel assay, and autoradiography) characterize the reaction and photoimmobilization of antibodies on this surface. The photoimmobilized antibodies cover the surface as a homogeneous and dense monolayer that could not be disrupted by vigorous washing with the detergent Tween 20. Immunoassays demonstrated specific recognition of the immobilized immunoglobulins as measured by their complexation with alkaline phosphatase-linked antibodies. The method of photoimmobilization used here leads to a homogeneous single layer of IgGs, in which the proteins maximize th.
On The Impact of the Ideal Gas Assumption to High-Pressure Combustion Phenomena in Engines

The effect of the ideal gas law assumption on auto-ignition and NOx-formation in a rapid compression machine is studied. For both processes the simulations are compared to a reference simulation using a Redlich-Kwong equation-of-state based on the critical properties of all constituents. Auto-ignition is studied for several n-heptane/air mixtures and the results show that the ideal gas assumption can impose large deviations. However, only marginal differences (< 7%) appear if the pressure history is used. A simplified theory is presented that explains these observations. For the case of NOx-formation similar observations can be made. Large deviations from the full simulation occur for the case of a prescribed pressure and volume history (≈ 100%). This, however, is mainly due to the fact that in engine like applications NOx concentrations never reach their equilibrium value. Equilibrium values only differ by a maximum of 20%.
Bubble Formation at an Orifice in Surfactant Solutions under Constant-Flow Conditions

Bubble formation in surfactant solutions is frequently encountered in systems of practical importance but has seldom been investigated systematically. In this work a simple modified two-stage spherical model, by which the dynamic surface tension at the bubble surface plays a role, was developed for bubble formation under constant-flow conditions. Equilibrium and dynamic surface tension data and the values of bubble volume at detachment were obtained experimentally for aqueous solutions of sodium dodecyl sulfate and Triton X-100. The predicted results are shown to agree well with experimental ones, especially for concentrations less than the critical micelle concentration. This implies that the surface relaxation phenomenon is important for bubble formation in surfactant solutions. For accurate prediction of bubble formation in surfactant solutions, dynamic surface tension rather than equilibrium data should be taken into consideration.