Simple Exchange Process Research Articles

Activation and Characterization of Algerian Kaolinite, New and Green Catalyst for Synthesis of Polystyrene and Poly(1,3-dioxolane)

In the present work we have explored a new catalyst prepared with Algerian clay and a new method to synthesise polystyrene and poly(1,3-dioxolane). This technique consists of using Algerian modified clay (Kaolinite-H+) as a green catalyst. Kaolinite-H+ is a proton exchanged clay which is prepared through a simple exchange process. Synthesis experiments are performed in bulk. The polymerization of styrene in bulk leads to the yield of 83 % at room temperature with the reaction time of 3 h. Molecular weight of the obtained polystyrene is calculated by 1H NMR and is about 2196 g/mol. Polymerization of (1,3-dioxolane) is carried out at room temperature with the reaction time of 3 h and polymerization yield of 91 %. The calculated molecular weight of the obtained poly(1,3-dioxolane) is about 573 g/mol. The structure of the obtained polymers is confirmed by FT-IR and 1H NMR. The modified clay (Kaolinite-H+) is characterized by FT-IR, XRD and SEM analysis.

A New Green Catalyst for Synthesis of bis-Macromonomers of Polyethylene Glycol (PEG)

A new method to synthesise polyethylene glycol dimethacrylate (PEGDM) with various molecular weights (1000, 3000, 6000 and 8000 g/mol) of polyethylene glycol (PEG) has been developed. This technique consists in using Maghnite-H+ as eco-catalyst to replace еriethylamine, which is toxic. Maghnite-H+ is a proton exchanged montmorillonite clay which is prepared through a simple exchange process. Synthesis experiments are performed in solution using dichloromethane as solvent in the presence of methacrylic anhydride. The effect of reaction time, temperature, amount of catalyst and amount of methacrylic anhydride is studied in order to find the optimal reaction conditions. The synthesis in solution leads to the best yield (98 %) at room temperature for the reaction time of 5 h. The structure of the obtained macromonomers (PEGDM) is confirmed by FTIR, 1H NMR and 13C NMR, where the methacrylate end groups are clearly visible. Thermogravimetric analysis (TGA) is used to study the thermal stability of these obtained macromonomers. The presence of unsaturated end group was confirmed by UV-Visible analysis.

Communication—Highly Efficient Red-Emitting Phosphor Na2SiF6:Mn4+ Prepared in H3PO4 Environment

Red-emitting phosphor Na2SiF6:Mn4+ was synthesized by a simple exchange process in H3PO4. Its crystal structure and morphology were characterized. Na2SiF6:Mn4+ with single phase exhibits intense emission with the strongest peak at ∼ 627 nm. The emission energy from Na2SiF6:Mn4+ is observed to be obviously higher than those from A2SiF6:Mn4+ (A = K, Rb and Cs). This sample also has an excellent thermal quenching behavior. The present red-emitting phosphor was used for the fabrication of white light-emitting diodes and found to show good optical properties with color temperature of 3821 K and color rendering index of 94.4).

A Green Synthesis of Polylimonene Using Maghnite-H+, an Exchanged Montmorillonite Clay, as Eco-Catalyst

A new green polymerization technique to synthesis polylimonene (PLM) is carried out in this work. This technique consists of using Maghnite-H+ as eco-catalyst to replace Friedel-Crafts catalysts which are toxics. Maghnite-H+ is a montmorillonite silicate sheet clay which is prepared through a simple exchange process. Polymerization experiments are performed in bulk and in solution using CH2Cl2 as solvent. Effect of reaction time, temperature and amount of catalyst is studied, in order to find the optimal reaction conditions. The polymerization in solution leads to the best yield (48.5%) at -5°C for a reaction time of 6 h but the bulk polymerization, that is performed at 25°C, remains preferred even if the yield is lower (40.3%) in order to respect the principles of a green chemistry which recommend syntheses under mild conditions, without solvents and at room temperature. The structure of the obtained polymer (PLM) is confirmed by FT-IR and Nuclear Magnetic Resonance of proton (1H-NMR). The glass transition temperature (Tg) of the polylimonene is defined using Differential Scanning Calorimetry (DSC) and is between 113°C and 116°C. The molecular weight of the obtained polymer is determined by Gel Permeation Chromatography (GPC) analysis and is about 1360 g/mol. Copyright © 2019 BCREC Group. All rights reserved

Fabrication of Amphiphilic Nanoparticles via Mixed Homopolymer Brushes and NMR Characterization of Surface Phase Separation

“Patchy particles”, where the surface is anisotropically patterned through variation in the surface composition, can assemble into different colloidal crystal structures as well as act as interface stabilizers, heterogeneous reaction catalysts, and targeted drug delivery agents. Patchy nanoparticles (NPs) can be formed by adsorbing two chemically different polymer chains that will spontaneously phase separate. Although there is growing interest in polymer-based patchy nanoparticles, the majority of the studies have been theoretical rather than experimental due to difficulties in preparing significant quantities of nanoparticles with controlled polymer ratios. Likewise, characterization of the phase separation on the nanoparticle surface is challenging. Here we simultaneously overcome the synthesis and characterization hurdles by developing a facile, versatile protocol to produce sufficient quantities of patchy NPs for quantitative solid-state NMR measurements of the patch fractions, degree of phase separation, and morphology. Monodisperse 3.5 nm ZrO2 nanocrystals with polystyrene (PS) and poly(ethylene oxide) (PEO) ligands, covering the entire possible composition range, were reproducibly prepared through a simple exchange process. This approach has the advantage of well-defined polymer molecular weights and NP sizes, allowing experimental validation of theoretical predictions for nanophase separation in NPs with mixed homopolymer brushes. Upon exposure to a nonselective solvent, the nanoparticles assemble into different morphologies, namely micelles and vesicles, as a function of the PEO:PS ratios.

Design and Numerical Analysis of a Novel Counter-Rotating Self-Adaptable Wave Energy Converter Based on CFD Technology

The lack of an efficient and reliable power supply is currently one of the bottlenecks restricting the practical application of unmanned ocean detectors. Wave energy is the most widely distributed ocean energy, with the obvious advantages of high energy density and predictability. In this paper, a novel wave energy converter (WEC) for power supply of low-power unmanned ocean detectors is proposed, which is a small-scale counter-rotating self-adaptive point absorber-type WEC. The double-layer counter-rotating absorbers can achieve the torque balance of the whole device. Besides, the self-adaptation of the blade to the water flow can maintain a unidirectional continuous rotation of the single-layer absorber. The WEC has several advantages, including small occupied space, simple exchange process and convenient modular integration. It is expected to meet the power demand of low-power ocean detectors. Through modeling and CFD analysis, it was found that the power and efficiency characteristics of WEC are greatly influenced by the relative flow velocity, the blade angle of the absorber and the interaction between the upper and lower absorbers. A physical prototype of the WEC was made and some related experiments were conducted to verify the feasibility of WEC working principle and the reliability of CFD analysis.

Two-dimensional second-order quadrupolar exchange powder spectra for nuclei with half-integer spins. Calculations and an experimental example using oxygen NMR

Two-dimensional chemical exchange spectra are determined for powders containing half-integer quadrupolar nuclei that evolve under the second-order quadrupolar interaction. For simple exchange processes it is shown that the calculated exchange patterns depend sensitively on the jump angles, the tensor parameters, and the rotation axes characterizing the geometry of the underlying molecular motion. The inclusion of other interactions is discussed. To demonstrate the feasibility of the experimental method a two-dimensional second-order quadrupolar exchange spectrum was recorded for a clathrate hydrate using oxygen NMR. Simulations based on a motional model involving a six-site jump capture the essential features of the experimental results.

Broadening even more the internal marketing concept

PurposeBased on the reasoning that work means more than just material rewards, the purpose of this paper is to propose the broadening of internal marketing concept (IMC) role through incorporation of happiness in the workplace (HWP) construct.Design/methodology/approachA conceptual approach is outlined.FindingsThis paper provides a theoretical foundation and conceptual framework – based on internal marketing (IM) variables – explaining how goals related to HWP could be achieved.Practical implicationsGiven that happiness in life is a goal that everyone pursues, and HWP is one of its dimensions, it is suggested that firms could employ it as a strategy to maintain and motivate their best assets (i.e. their employees). It also suggests that work is far beyond a simple exchange process between employers and employees. Thus, given the nature and meaning of work for human beings, it should be treated as a channel whereby people could improve their self‐esteem and could fulfill themselves through their tasks on the job and feel happy.Originality/valueRegarding IMC managerial approach and features, it is sustained that it could more aptly address the issue of HWP. To some degree, the desire of HWP brings about the need of changing the current management mindset that puts people on a secondary role.

Isotopic labelling of pharmaceutical agents by a simple exchange process

Isotopic labelling of pharmaceutical agents by a simple exchange process

Preferential uptake of lipids by mycoplasma membranes from human plasma low-density lipoproteins.

The binding and transfer of low-density lipoprotein (LDL) constituents to mycoplasma membranes were examined. Mycoplasma capricolum was found to bind more 125I-labeled LDL than Acholeplasma laidlawii. Free and esterified cholesterol uptake was 3-4 times higher in M. capricolum than in A. laidlawii. Cholesterol transfer to the membranes of both organisms far exceeded the amounts of cholesterol expected according to LDL protein found associated with the membranes. Trypsin digestion of the membranes prior to incubation with LDL decreased the binding of LDL and the transfer of free cholesterol to M. capricolum membranes but did not affect these processes with A. laidlawii membranes. These findings suggest the existence of protease-sensitive receptors on M. capricolum cell surface responsible for tighter contact with LDL. Analysis of LDL after incubation with large amounts of M. capricolum membranes revealed a loss of 60% of the lipoprotein-free cholesterol, 25.9% of the esterified cholesterol, and 20.7% of phospholipids without appreciable loss of protein. Rate zonal ultracentrifugation showed that the LDL separated as a single symmetrical peak, denser than the control. Electron microscopy showed that the lipoprotein particles retained their spherical shape but became about 10% smaller in diameter. These observations lead us to conclude that both free and esterified cholesterols are transferable from LDL to the membranes by a simple exchange process which does not involve prolonged contact or fusion of the particle with the membrane and does not result in degradation of the lipoprotein particle. We propose that similar mechanisms of free and esterified cholesterol transfer may also operate in vivo and contribute to the process of cholesterol exit from the plasma.

Studies on the Interaction between Mercury(II) Chloride and Copper(I) Halides in Solid State

Abstract Kinetics and mechanism of HgCl2–CuI and HgCl2–CuBr reactions were studied in solid state. It has been demonstrated that HgCl2 reaches CuI by surface migration and the reaction proceeds through counter diffusion of Cu+ and Hg2+. Both the reactions follow the parabolic rate law and the activation energies are 77.11±3.84 and 51.08±1.29 kJ/mol. While the former is a complex multi-stage reaction, the latter is a simple exchange process.

Isotopic exchange of cyclic ethers with deuterium over metal catalysts

The exchange reaction between deuterium and cyclic ethers (oxolane and α-methyl derivatives) has been investigated using rhodium and palladium catalysts. The first hydrogen undergoing exchange has been found to be located on a β-carbon. This fact, and the poisoning of the exchange of cyclopentane in the presence of ether, suggest that the O atom participates in the exchange mechanism of ethers. It appears, however, that the oxygen-metal bonding occurs only during this simple exchange process; simultaneous adsorption of oxygen and a vicinal carbon causes hydrogenolysis of the OC bond. In each case multiple exchange is important. In the oxolane molecule two sets of exchangeable hydrogens are distinguished according to their reactivities, as could be expected by analogy with cycloalkanes. However, this distinction is not so clear in the exchange patterns of substituted oxolanes, since intermediate maxima are observed in these cases. It is suggested that the conformational properties of the substituted rings cause a constraint in the formation of 3,4-diadsorbed oxolanes. Thus, multiple exchange, based on α,β-process, and epimerization via the “roll-over” mechanism occur preferentially in certain parts of the molecules.

Infinite order radiative corrections and renormalization

By means of the Ward identity and the correlation expansion derived earlier, we calculate virtual radiative corrections to an infinite order. Partial factorization of the correlation effects, as in the simple exchange processes, makes infinite summation possible. Furthermore, because the Ward identity is satisfied order by order and because we are able to carry out the infinite order summation and obtain a closed form, renormalization turns out to be very simple and transparent. Here the calculations are performed for a scalar: ϕ 2: φ model, but are easily generalized to other similar models. We also indicate why this rearrangement of the ordinary perturbation expansion is suitable for strong coupling theories, ordinary local field theories as well as dual models.

In Vitro incorporation of [ 3H] methyl choline into phosphatidyl choline of rat liver subcellular fractions

Incubation of a rat liver total homogenate with radioactive choline and subsequent isolation of subcellular fractions, at different times, showed similar patterns of labeling. Incubation of microsomes, mitochondria and purified nuclei isolated from rat liver, showed that all fractions were able to incorporate the precursor into phosphatidyl choline. The specific activity was higher in mitochondria and increased in all cases with added supernatant. The addition of microsomes to mitochondria diminished the incorporation of label. Contamination of mitochondria by microsomes, was negligible as shown by undetectable amounts of cytochrome P 450, while NADPH 2 cytochrome c reductase showed a 10% contamination. A certain amount of radioactivity was incorporated in the absence of ATP and oxidizable substrates due to the presence of substrates and cofactors in the fraction and/or the supernatant. Labeled fractions reincubated with unlabeled choline, showed no loss of radioactivity, proving that incorporation was not due to simple exchange processes. It is concluded that although rat liver mitochondria can acquire part of their own provision of phosphatidyl choline by transference from microsomes, all organelles and specially mitochondria, can independently synthesize this phospholipid.

Study of the K ∗O Λ and K ∗OΣ O final states from π−p interactions at 3.9 GeV/ c

A study of π − p → K ∗Λ and π − p → K ∗Σ° at 3.9 GeV/c indicates that the main features of both reactions can be interpreted in terms of simple exchange processes, the first involving both natural and unnatural exchange, the second showing evidence for natural parity exchange only.

The effect of partial replacements of membrane cholesterol by other steroids on the osmotic fragility and glycerol permeability of erythrocytes

1. 1. (A) Sonicated dispersions of lecithins were incubated with aliquots of washed human erythrocytes, leading to the removal of part of the cholesterol complement, eventually followed by lysis. (B) Sonicated dispersions of lecithin and cholesterol with one of a range of other steroids were prepared and incubated with aliquots of washed human erythrocytes. By a simple exchange process, the steroid composition of the erythrocytes were modified. 2. 2. (A) The osmotic fragility of erythrocytes was considerably increased after removal of part of the cholesterol complement with pure lecithin dispersions. (B) The osmotic fragilities of the modified erythrocytes were measured, and it was found that relatively small differences were detectable in view of the substantial replacement of part of the cholesterol with one of the other steroids. 3. 3. Significant differences in the glycerol permeabilities of the modified human and pig erythrocytes were demonstrated. In the presence of 3-ketosteroids, the rates of penetration of glycerol were significantly higher than those containing 3β-hydroxy steroids. Cholesterol-depleted erythrocytes also exhibited considerably increased glycerol permeability.