A Chemical equilibrium model for interfacial activity of crude oil in aqueous alkaline solution: The effects of pH,alkali and salt

A chemical equilibrium model is proposed to describe the effects of acid content, pH and sodium ion concentration on the interfacial activity of crude oil in aqueous alkaline solutions. The model is based on an equilibrium among the dissociation of acids in the crude, the dissociation of the sodium salt containing the active species and the dissociation of water. It is shown that once the pH of the interface reaches the pK_a of the acids, the interfacial tension (IFT) drops steeply and that further addition of sodium ions increases the IFT by shifting the equilibrium to form undissociated soap.     

Wooden window frames with structural sealants: manufacturing improvements and experimental validation of a finite element model

This paper proposes a finite element (FE) model of a novel wooden window frame typology and validates it by experimental tests on window frames and corner joint specimens. The innovation consists of the application of the structural silicone sealant only at the interface between wood and one of the thin glass layers of the double-glazing glass, so achieving a low application depth. This technique reduces the sealant quantity and allows the disassembly and substitution of the glass from the frame in case of breakage. In order to inform the FE model of the whole frame, the dowelled butt corner joint strength is measured by specific experimental tests. The results show a good correlation between the FE model and the experimental results in the range of small frame deformations, which are of interest for the proposed application. In particular, the FE curve overestimates the bottom corner displacement of about 17% at 1000?N load, 7% at 2000?N and less than 5% at higher applied force on the upper corner. The model is then applied to various wooden frame geometries in order to evaluate if the proposed silicone application mode and dowelled corner joints type allow an acceptable stiffness of the frame, and, in particular, low deformations of the bottom corner joint, in order to maintain the wooden frame functionality when subject to external loads. The approach could be useful when assessing optimal sealing application modes, wood-sealant-glass joint geometries, corner joint geometries and window frame geometries to limit the bottom corner joint deformation within the required technical specifications.     

Predicting trends in structural and physical properties of a model polymer with embedded natural fibers: Viability of molecular dynamics studies for a bottom up design

The effects of relatively high- and low-shear processing on the macroscopic and microscopic porosities of a standard packaging polymer—linear low density polyethylene (LLDPE) and its composites with pine flour are studied. The macroscopic porosities, represented by deviations of observed density from the theoretical density, primarily drive the trends in mechanical and solvent uptake properties. The microscopic porosities of the system, however, are independent of the processing method and pine flour concentration. Furthermore, by using molecular dynamics (MD), molecules of LLDPE and pine flour were constructed. The material properties of the molecules, specifically microporosity and elastic moduli, were compared to experiment. A semiempirical modeling approach was used to fit the simulated data to the experimental composite moduli. The model of Halpin and Tsai was found to be the most efficacious for this system, and the benefits of the combined MD-semiempirical modeling for bottom up design are discussed. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48189.     

Extracellular secretion of Escherichia coli alkaline phosphatase with a C-terminal tag by type I secretion system: purification and biochemical characterization

Type I secretion system (TISS) of Gram-negative bacteria permits proteins to be secreted directly from the cytoplasm to the external medium by a single, energy-coupled step. To examine whether this system can be used as an extracellular production system of recombinant proteins, Escherichia coli alkaline phosphatase (AP) was fused to a C-terminal region of Pseudomonas sp. MIS38 lipase (PML) and examined for secretion using the E.coli cells carrying the heterologous TISS. PML is one of the passenger proteins of TISS and contains 12 repetitive sequences and a secretion signal at the C-terminal region. The fusion protein was efficiently secreted to the extracellular medium, while AP was not secreted at all, indicating that the secretion of AP is promoted by a secretion signal of PML. The repetitive sequences were not so important for secretion of the fusion protein, because the secretion level of the fusion protein containing entire repeats ( approximately 10 mg/l culture) was only 2-fold higher than that of the fusion protein without repeats. The fusion protein purified from the culture supernatant existed as a homodimer, like AP, and was indistinguishable from AP in enzymatic properties and stability.     

Hydrogen-bonding in 2-aminobenzoyl-alpha-chymotrypsin formed by acylation of the enzyme with isatoic anhydride: IR and mass spectroscopic studies

The acyl-enzyme formed upon acylation of alpha-chymotrypsin with isatoic anhydride has been characterised by infrared spectroscopy. Acylation at pH 7 to yield the 2-aminobenzoyl-enzyme is rapid (k = 5.57x 10(-2)s(-1)), while deacylation is much slower (k =3.7 x 10(-5)10(-2) (s-). The [1C=O]-labelled form of isatoic anhydride has been synthesised, to allow construction of [72C=O]- minus [13C=O]difference spectra; these highlight the carbonyl absorbance of the ligand and eliminate spectral effects that arise from protein perturbation. The ester carbonyl band of the acyl-enzyme absorbs at a wavenumber of 1695cm(-1) and has been shown by deconvolution analysis to represent a single, well-defined conformation. Model studies of ethyl 2-aminobenzoate in a range of solvents show that its carbonyl group is in a hexane-like environment (that is, very nonpolar). It is proposed that the low wavenumber of the carbonyl absorbance arises from the presence of an internal hydrogen bond between the 2-amino group and the ester carbonyl oxygen; this leads to polarisation of the carbonyl group both in the enzyme and in nonpolar solvents. However, in view of the slow deacylation, it is clear that the acyl group is in a nonproductive conformation, with no interaction with the oxyanion hole, and that deacylation occurs from this form or from a minor, invisible form. The infrared data have been supported by kinetic electrospray mass spectroscopic measurements, which demonstrate that the acyl-enzyme is that previously anticipated, and by molecular modelling of 2-aminobenzoyl-alpha-chymotrypsin. It is concluded from pH-dependence measurements that general base catalysis by the 2-amino group is not involved in deacylation.     

Methods and impact of reducing salt in dyeing cellulose: a case study with CI Direct Blue 90

The addition of large amounts of salt is one of the most important environmental problems in the dyeing of cellulosic fibres with direct or reactive dyes. This study was undertaken to determine an accurate and effective method for measuring the impact of salt on the dyeing process. This method has been applied to the case of CI Direct Blue 90 by utilising real‐time measurements of dye exhaustion for different salt and dye concentrations. Reductions in salt by a factor of 4 were achieved with no effect on the final shade. It is proposed that this method could be used to reduce the amount of salt for many other direct dyes, or to enable the dyer to quantify the trade‐off between time to final exhaustion and salt addition.     

A structural model for gas-solid reactions with a moving boundary-II: The effect of grain size,porosity and temperature on the reaction of porous pellets

A structural model is presented for the non-catalytic reaction between a porous solid and a gas stream. The model incoporates parameters such as solid grain size, porosity, effective pore diffusion coefficient and allows the quantitative assessment of the role played by these in determining the overall reaction rate.The model was found to predict reasonably well the reaction of porous nickel oxide pellets with hydrogen within an intermediate temperature range.In the paper an approximate allowance is made for the effects of sintering and it is suggested that there may exist an optimum combination of grain size, porosity and reaction temperature which would give the fastest overall reaction rate.     

Obtaining a rubber-bitumen asphaltic concrete pavement binder by the thermocatalytic processing of petroleum residues in a mixture with rubber crumb in the presence of zeolites and organo-mineral activators

It has been ascertained that qualitative rubber-bitumen asphaltic concrete pavement binders can be obtained at one stage by the method of the catalytic thermolysis of residual oil in the mixture with rubber crumb of worn-out tires in the presence of synthetic or natural zeolites or pyroshale that adsorb coke besides catalyzing the process. The mineral part of pyroshale and zeolite powder with adsorbed coke and soot forming during the decomposition of rubber are a thin-disperse modifier of paving bitumens. The catalytic thermolysis of residual oil with adding 30–40% of rubber crumb proceeds under comparatively soft conditions (a temperature of 350–375° C, isothermal exposure with a duration of 10–30 min) in the presence of 1–3% of zeolite or pyroshale. The yield of a high-qualitative rubber-bitumen binder with the content of 18–20% of mineral and organic modifiers can reach 50–60 wt % of the used raw material. Rubber crumb is utilized completely. There are no foreign analogs of the suggested technology. An experimental-industrial installation with a capacity of 9000–10000 t of bitumen component/year was created in the city of Kudepsta in the Krasnodar Territory.     

Water diffusion and permeability in unsaturated polyester resin films characterized by measurements performed with a water‐specific permeameter: Analysis of the transient permeation

A water‐specific permeameter was developed to study water diffusion in an unsaturated polyester; these polyesters are often used as high‐barrier materials. Low water enrichment of a dry sweeping gas is measured via the dew point temperature, with two hygrometers, one of which is used because of its fast response and the other because of its accuracy. This high‐performance device is just as suited to pervaporation as to permeation tests and allows the transient and stationary fluxes to be characterized. At first sight, the experimental data seem in good agreement with D = D₀e^γC. However, a more thorough study has shown a time‐dependence of D. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 3380–3395, 1999     

Interaction of fluorocarbon and hydrocarbon hydrophobically co-modified PAA with a nonionic surfactant: rheological properties of polymer solutions in the absence of salt

The interaction of a new hydrocarbon (HC) and fluorocarbon (FC) co-modified poly(acrylic acid), SA-1-FX14-1, with a HC nonionic surfactant, Np7.5, was investigated by rheological measurements. Its solution property was compared with HC or FC modified counterpart. It was found that the incompatibility between HC and FC groups in the micellization process was improved in the solution of SA-1-FX14-1. The terpolymer SA-1-FX14-1 associated with Np7.5 more like SA-2 rather than FX14-2. The latter interacted weakly with the HC surfactant due to the lipophobic tendency of the FC hydrophobe. The random distribution of FC and HC hydrophobes along the polyelectrolyte backbone was confirmed to be responsible for the compromised miscibility of HC and FC hydrophobes demonstrated in the system of SA-1-FX14-1 and Np7.5. Several affecting factors, such as backbone rigidity, polymer concentration, surfactant concentration, and FC modifying degree of the terpolymers, were also taken into account. In terms of hybrid surfactants, this type of hybrid polysoap is promising to serve as novel media improving the miscibility of HC and FC groups just as those hybrid small molecule surfactants have done.     

Amelioration of Al toxicity and P deficiency in acid soils by additions of organic residues: a critical review of the phenomenon and the mechanisms involved

High rates of lime and fertilizer-P are characteristically required to obtain high crop yields on highly weathered acid soils. Much of the agriculture in the southern tropical belt, where acid soils predominate, is carried out by resource-poor, semi-subsistence farmers who are unable to purchase large quantities of lime and fertilizer. There are, however, a number of reports that additions of organic residues to acid soils can reduce Al toxicity (thus lowering the lime requirement) and improve P availability. The literature regarding these effects is sparse and disjointed and an integrated overview of the probable mechanisms responsible and their implications is presented and discussed. During decomposition of organic residues, a wide range of organic compounds are released from the residues and/or are synthesized by the decomposer microflora. The two most important groups in relation to Al toxicity and P availability are soluble humic molecules and low molecular weight aliphatic organic acids. Both these groups of substances can complex with phytotoxic monomeric Al in soil solution thus detoxifying it and they can also be adsorbed to Al and Fe oxide surfaces consequently blocking P adsorption sites. During residue decomposition, there is often a transitory increase in soil pH and this induces a decrease in exchangeable and soil solution Al through their precipitation as insoluble hydroxy-Al compounds. It also confers a greater negative charge on oxide surfaces and thus tends to decrease P adsorption. The increase in pH has been attributed to a number of causes including oxidation of organic acid anions present in decomposing residues, ammonification of residue N, specific adsorption of organic molecules produced during decomposition and reduction reactions induced by anaerobiosis. There are also mechanisms specific to either Al detoxification or improved soil P status. For example, regular applications of organic residues will induce a long-term increase in soil organic matter content. Complexation of Al by the newly-formed organic matter will tend to reduce the concentrations of exchangeable and soluble Al present. As organic residues decompose, P is released and this can become adsorbed to oxide surfaces. This will, in turn, reduce the extent of adsorption of subsequently added P thus increasing P availability. The practical implication of the processes discussed is that organic residues could be used as a strategic tool to reduce the rates of lime and fertilizer P required for optimum crop production on acidic, P-fixing soils. Further research is, therefore, warranted to investigate the use of organic residues in the management of acid soils.     

Separation and quantitation of cholesterol oxides by HPLC with an evaporative light scattering detector in a model system

A method to analyze cholesterol and 10 of its oxidation products, ranging from the weakly polar cholest-4-ene-3,6-dione to moderately polar cholest-5-ene-3β,7α-diol, in a single run is described. The separation was achieved by normal-phase gradient high-performance liquid chromatography with an evaporative light-scattering detector. This universal mass detector does not detect changes in solvent composition; this makes it possible to employ gradients, an essential technique whenever a wide range of compounds with diverse characteristics is to be separated. Standards at concentrations from 0.1–1.0 μg were separated within 37 min on an alumina/silica column with a gradient elution system that contained dichloromethane, acetonitrile, and water.     

Major reduction of malaria morbidity with combined vitamin A and zinc supplementation in young children in Burkina Faso: a randomized double blind trial

Background  

Vitamin A and zinc are crucial for normal immune function, and may play a synergistic role for reducing the risk of infection including malaria caused by Plasmodium falciparum.     

A new approach to artificial and modified proteins: theory-based design, synthesis in a cell-free system and fast testing of structural properties by radiolabels

A novel approach to the creation of artificial and modifiedproteins has been elaborated. The approach includes a sequencedesign based on the molecular theory of protein secondary structureand folding patterns, gene expression in a cell-free systemand testing of structural properties of the synthesized polypeptidesat a nanogram level using radiolabelled chains. The approachhas been applied to a new synthetic protein albebetin whichhas been designed to form a 3-D fold which does not contradictany structural rule but has been never observed up to now innatural proteins. Using size-exclusion chromatography, urea-gradientelectrophoresis and limited proteolysis of a radiolabelled chain,it has been shown that the artificial protein is nearly as compactas natural proteins, cooperatively unfolds at high urea concentrationsand has some structural features of a definite structure consistentwith the designed one. As albebetin has been designed as consistingof two structural repeats, a ‘halfalbebetin’ (oneof these repeats) has also been synthesized and studied. Itwas shown that ‘half-albebetin’ is also compact     

Preparation of networked polymer electrolytes by copolymerization of a methacrylate with an imidazolium salt structure and an ethyleneglycol dimethacrylate in the presence of lithium bis(trifluoromethanesulfonyl)imide

Ionic networked polymers containing ionic liquids were synthesized by radical copolymerization of 1-(2-methacryloyl)ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (Met-IL) and difunctional or trifunctional methacrylate cross-linkers, ethylene glycol dimethacrylate (EGDMA), or trimethylolpropane trimethacrylate (TMPTMA) in the presence of an ionic liquid, 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (EMImTFSI). For comparison, nonionic networked polymers containing the ionic liquid were prepared by radical copolymerization of methyl methacrylate (MMA) with EGDMA in the presence of EMImTFSI. Met-IL/EGDMA/EMImTFSI(50) showed higher ion conductivity and ionic liquid holding ability than the corresponding MMA/EGDMA/EMImTFSI(50), while Met-IL/TMPTMA/EMImTFSI(50) showed lower ionic conductivity with higher holding ability than MMA/EGDMA/EMImTFSI(50).