Search results for " Chemical Engineering"
showing 10 items of 2965 documents
Influence of Surface-Related Phenomena on Mechanism, Selectivity, and Conversion of TiO2 -Induced Photocatalytic Reactions
2018
Heterogeneous photocatalysis is the result of an inextricable connection of several factors differently contributing to the overall process. Photon absorption is the “sine qua non” condition for the reaction to occur. In fact, photons can be considered as immaterial reactants, and all of the phenomena related to the interaction of light–matter play a prominent role. However, other factors contribute in a concerted way to address the reaction, so that the relative contribution of each of them is often difficult to evaluate. In this framework, the present paper highlights some aspects of the interaction of TiO 2 surface-adsorbate species that could be underestimated and their influence on the…
Substrate Selectivity of Coumarin Derivatives by Human CYP1 Enzymes: In Vitro Enzyme Kinetics and In Silico Modeling
2021
Of the three enzymes in the human cytochrome P450 family 1, CYP1A2 is an important enzyme mediating metabolism of xenobiotics including drugs in the liver, while CYP1A1 and CYP1B1 are expressed in extrahepatic tissues. Currently used CYP substrates, such as 7-ethoxycoumarin and 7-ethoxyresorufin, are oxidized by all individual CYP1 forms. The main aim of this study was to find profluorescent coumarin substrates that are more selective for the individual CYP1 forms. Eleven 3-phenylcoumarin derivatives were synthetized, their enzyme kinetic parameters were determined, and their interactions in the active sites of CYP1 enzymes were analyzed by docking and molecular dynamic simulations. All cou…
Enhancement of Hydrolysis through the Formation of Mixed Heterometal Species: Al3+/CH3Sn3+ Mixtures
2013
ABSTRACT: The hydrolysis of mixed-metal cations (Al3+/CH3Sn3+) was studied in aqueous solutions of NaNO3, at I = 1.00 ± 0.05 mol·dm−3 and T = 298.15 K, by potentiometric technique. Several hydrolytic mixed species are formed in this mixed system, namely, Alp(CH3Sn)q(OH)r with (p, q, r) = (1, 1, 4), (1, 1, 5), (1, 1, 6), (2, 1, 4), (1, 2, 5), (1, 4, 11), (1, 3, 8), and (7, 6, 32). The stability of these species, expressed by the equilibrium: pAl3+ + qCH3Sn3+ + rOH− = Alp(CH3Sn)q(OH)r 3(p+q)−r, βpqr OH, can be modeled by the empirical relationship: log βpqr OH = −3.34 + 2.67p + 9.23(q + r). By using the equilibrium constant Xpqr relative to the formation reaction: pAl(p+q)(OH)r + q(CH3Sn)(p+q…
Microwave-Assisted Esterification of Tall Oil Fatty Acids with Methanol Using Lignin-Based Solid Catalyst
2016
During alkaline pulping significant amounts of lignin, carbohydrates (mostly hemicelluloses), and extractives (tall oil soap and turpentine) are removed from wood feedstock. In this study, the catalytic esterification of fatty acids in tall oil with methanol to produce fatty acid methyl esters under microwave irradiation was performed at 100 °C for 10–60 min. A novel heterogeneous acid catalyst tested for this purpose was synthesized from the hardwood alkali lignin that was precipitated by acidification from the black liquor from soda-AQ pulping. The comparative reaction data were obtained by using other solid catalysts, Amberlyst 15, and p-toluenesulfonic acid. The results showed the highe…
Normal pressures and frictional tractions on shallow conical hopper walls after concentric filling: Predictions and experiments
2013
Author's version of an article in the journal: Chemical Engineering Science. Also available from the publisher at: http://dx.doi.org/10.1016/j.ces.2012.11.028 A silo with a shallow hopper is designed to achieve the required silo capacity when the headroom available is limited, provided that the issue of segregation of stored particulate solids is not a problem. Several analytical models have been proposed to try to predict the design loads for such shallow silo hoppers to guarantee their structural integrity. In this study, a novel finite element analysis has been conducted to explore the development of pressures and tractions on the wall of a full scale shallow hopper when it is filled wit…
Comparison of feature importance measures as explanations for classification models
2021
AbstractExplainable artificial intelligence is an emerging research direction helping the user or developer of machine learning models understand why models behave the way they do. The most popular explanation technique is feature importance. However, there are several different approaches how feature importances are being measured, most notably global and local. In this study we compare different feature importance measures using both linear (logistic regression with L1 penalization) and non-linear (random forest) methods and local interpretable model-agnostic explanations on top of them. These methods are applied to two datasets from the medical domain, the openly available breast cancer …
Influence of organic material and sample parameters on the surface potential in Kelvin probe measurements
2019
Financial support provided by ERDF 1.1.1.1 activity project Nr. 1.1.1.1/16/A/046 “Application assessment of novel organic materials by prototyping of photonic devices” as well as Scientific Research Project for Students and Young Researchers Nr. SJZ2016/20 realized at the Institute of Solid State Physics, University of Latvia is greatly acknowledged.
Physical properties of aerosol particles measured from a bubbling fluidized bed boiler
2015
Abstract Increased use of biomass and waste fuels, and the consequent corrosion problem have led to an increased need to study and monitor the combustion processes. This study presents an extensive physical characterization of aerosol particles measured from a bubbling fluidized bed boiler with different fuel mixtures and optional ferric sulfate feeding. The fuel mixtures included bark, sludge, peat and solid recovered fuel. Previously, the characterization of the particles analyzed from a fluidized bed reactor has mainly focused on chemical off-line analysis of collected impactor samples, large coarse mode particles or laboratory-scale reactors. In this study, the focus is in the particle …
Bio-orthogonal Red and Far-Red Fluorogenic Probes for Wash-Free Live-Cell and Super-resolution Microscopy
2021
Small-molecule fluorophores enable the observation of biomolecules in their native context with fluorescence microscopy. Specific labeling via bio-orthogonal tetrazine chemistry combines minimal label size with rapid labeling kinetics. At the same time, fluorogenic tetrazine–dye conjugates exhibit efficient quenching of dyes prior to target binding. However, live-cell compatible long-wavelength fluorophores with strong fluorogenicity have been difficult to realize. Here, we report close proximity tetrazine–dye conjugates with minimal distance between tetrazine and the fluorophore. Two synthetic routes give access to a series of cell-permeable and -impermeable dyes including highly fluorogen…
Biodiesel via in situ wet microalgae biotransformation: Zwitter-type ionic liquid supported extraction and transesterification
2017
The production of biodiesel derived from microalgae is among the most forthcoming technologies that provide an ecologic alternative to fossil fuels. Herein, a method was developed that enables the direct extraction and conversion of algal oil to biodiesel without prior isolation. The reaction occurs in aqueous media catalyzed by immobilized Candida antarctica lipase B (Novozyme 435). Zwitter-type ionic liquids were used as cocatalyst to improve the selectivity and reactivity of the enzyme. In a model reaction with sunflower oil, 64% biodiesel was obtained. Applying this method to a slurry of whole-cell Chlorella zof ingiensis in water resulted in 74.8% of lipid extraction, with 27.7% biotra…