This manuscript deals with the synthesis of new hydrophilic magnetite particles by employing a two-step method: in the first step magnetite particles with hydrophobic shell formed in presence of ...oleic acid–oleylamine complex through a synthesis in mass, without solvent, in a mortar with pestle were obtained; while in the second step the hydrophobic shell was interchanged with an aminosilane monomer. The influence of the Fe2+/Fe3+ molar ratio on the dimension of the particles of high importance for their potential applications was carefully investigated. This paper, also presents an alternative method of synthesis of new core-shell magnetite particles and the complete study of their structure and morphology by FT-IR, XPS, TGA, ESEM and TEM techniques. The rheological properties and magnetization analysis of high importance for magnetic particles were also investigated.
► Magnetite particles are superparamagnetic materials. ► Magnetite has significant role in nanotechnology due to surface properties and applicability in physical and chemical processes. ► We used an ecological method of synthesis, a reaction in mass, without solvent, in a mortar with pestle. ► We prepared hydrophilic magnetite particles, precursors for biomedical applications.
The oxidation reaction of regenerated cellulose fibers mediated by N-hydroxyphthalimide (NHPI) and various cocatalysts at room temperature for different time intervals and various amounts of low ...concentration sodium hypochlorite solution has been investigated to produce oxidized cellulose (OC), a biocompatible and bioresorbable polymer. The results revealed that the nonpersistent phthalimide-N-oxyl (PINO) radical generated in situ from NHPI in both, metallic or metal-free systems, is a powerful agent in this kind of transformation. Moreover, the reaction converts highly selectively C6 primary hydroxyl groups to carboxylic groups under mild reaction conditions and shorter reaction times than previously reported. The amounts of negatively charged groups in OC were determined by means of potentiometric titration. Further characterization of the products were accomplished by using Fourier transform infrared spectroscopy/attenuated total internal reflection spectroscopy (FT-IR/ATR), environmental scanning electron microscopy (ESEM), and X-ray and energy-dispersive X-ray (EDX) spectroscopy. Notably, water retention values of the oxidized fibers increased by 30% in comparison with the original nonoxidized sample, as a result of the introduction of hydrophilic carboxylate groups.
The reaction of 2,6‐diformyl‐4‐methylphenol with 1,3‐bis(3‐aminopropyl)tetramethyldisiloxane in the presence of MnCl2 in a 1:1:2 molar ratio in methanol afforded a dinuclear μ‐chlorido‐bridged ...manganese(II) complex of the macrocyclic 2+2 condensation product (H2L), namely, Mn2Cl2(H2L)(HL)Cl·3H2O (1). The latter afforded a new compound, namely, Mn2Cl2(H2L)2MnCl4·4CH3CN·0.5CHCl3·0.4H2O (2), after recrystallisation from 1:1 CHCl3/CH3CN. The co‐existence of the free and complexed azomethine groups, phenolato donors, μ‐chlorido bridges, and the disiloxane unit were well evidenced by ESI mass spectrometry and FTIR spectroscopy and confirmed by X‐ray crystallography. The magnetic measurements revealed an antiferromagnetic interaction between the two high‐spin (S = 5/2, g = 2) manganese(II) ions through the μ‐chlorido bridging ligands. The electrochemical behaviour of 1 and 2 has been studied, and details of their redox properties are reported. Both compounds act as catalysts or catalyst precursors in the solvent‐free low‐power microwave‐assisted oxidation of selected secondary alcohols, for example, 1‐phenylethanol, cyclohexanol, 2‐ and 3‐octanol, to the corresponding ketones in the absence of solvent. The highest yield of 72 % was achieved for 1‐phenylethanol by using a maximum of 1 % molar ratio of catalyst relative to substrate.
Two μ‐chlorido‐bridged dimanganese(II) complexes with disiloxane‐containing macrocyclic ligands act as catalyst precursors in the solvent‐free low‐power microwave‐assisted oxidation of selected secondary alcohols.
Elastin calcification is a widespread feature of vascular pathology, and circumstantial evidence exists for a correlation between elastin degradation and calcification. We hypothesized that matrix ...metalloproteinase (MMP)-mediated vascular remodeling plays a significant role in elastin calcification.
In the present studies, we determined that short-term periadventitial treatment of the rat abdominal aorta with low concentrations of calcium chloride (CaCl2) induced chronic degeneration and calcification of vascular elastic fibers in the absence of aneurysm formation and inflammatory reactions. Furthermore, the rate of progression of calcification depended on the application method and concentration of CaCl2 applied periarterially. Initial calcium deposits, associated mainly with elastic fibers, were persistently accompanied by elastin degradation, disorganization of aortic extracellular matrix, and moderate levels of vascular cell apoptosis. Application of aluminum ions (known inhibitors of elastin degradation) before the CaCl2-mediated injury significantly reduced elastin calcification and abolished both extracellular matrix degradation and apoptosis. We also found that MMP-knockout mice were resistant to CaCl2-mediated aortic injury and did not develop elastin degeneration and calcification.
Collectively, these data strongly indicate a correlation between MMP-mediated elastin degradation and vascular calcification.
We present Atacama Large Millimeter/submillimeter Array and Multi-Unit Spectroscopic Explorer observations of the brightest cluster galaxy in Abell 2597, a nearby (z = 0.0821) cool core cluster of ...galaxies. The data map the kinematics of a three billion solar mass filamentary nebula that spans the innermost 30 kpc of the galaxy's core. Its warm ionized and cold molecular components are both cospatial and comoving, consistent with the hypothesis that the optical nebula traces the warm envelopes of many cold molecular clouds that drift in the velocity field of the hot X-ray atmosphere. The clouds are not in dynamical equilibrium, and instead show evidence for inflow toward the central supermassive black hole, outflow along the jets it launches, and uplift by the buoyant hot bubbles those jets inflate. The entire scenario is therefore consistent with a galaxy-spanning "fountain," wherein cold gas clouds drain into the black hole accretion reservoir, powering jets and bubbles that uplift a cooling plume of low-entropy multiphase gas, which may stimulate additional cooling and accretion as part of a self-regulating feedback loop. All velocities are below the escape speed from the galaxy, and so these clouds should rain back toward the galaxy center from which they came, keeping the fountain long lived. The data are consistent with major predictions of chaotic cold accretion, precipitation, and stimulated feedback models, and may trace processes fundamental to galaxy evolution at effectively all mass scales.
This paper aims to provide an up-to-date, realistic picture of the Romanian coal sector based on four interconnected perspectives: geological, economical, energy, and strategical. It reviews the ...latest data, evaluations, and reassessments regarding the potential of current resources and reserves, geological and petrographic aspects, current status of the coal mining industry, resource management, and analyzes the present national strategies in this field. This review provides some perspectives towards key aspects of the Romanian coal sector and builds a foundation for a more in-depth analysis and strategical development of the Romanian coal mining and management.
•The investigation of coal resources and reserves in Romania•The geological and economic perspectives of coal resources and reserves in Romania•The importance of coal in the Romanian energy mix
The synthesis, characterization and photochemical properties of a new polyurethane cationomer (PUC–AN) with anthracene chromophore groups attached on the quaternary ammonium units is reported and ...compared to those of a model compound (AN) carrying the same moiety. PUC–AN synthesis implied the quaternization reaction with 9-chloromethylanthracene of the tertiary amine of one precursor polymer based on poly(tetramethylene oxide) diol of 2000 average molecular weight, tolylene-2,4-diisocyanate (as 2,4- and 2,6-TDI, 80:20 v/v isomers mixture),
N-methyldiethanol amine and terephthalaldehyd-bis(3-hydroxymethylphenylimine) in a molar ratio of 1:3:1:1. The fluorescence spectra of the anthracene structure indicates that the synthesized compounds present different shifts in solution and in the solid state, their photochemical behavior being influenced by monomer and excimer emission. The photophysical investigations revealed that such structures can function as fluorescent chemosensors for transitional metals, showing a fluorescence quenching in the presence of different metal ions (
UO
2
2
+
, Fe
3+, Cu
2+). The quenching mechanisms for PUC–AN and the corresponding model compound (AN) are assigned to electron transfer and/or energy transfer processes of Dexter type.
Two aromatic polyimides and the corresponding poly(amic acid)s, with oxadiazole and
para/meta
phenoxyphenylene rings in the backbone, were synthesized and the structure — thermal properties ...correlation was followed by dynamic mechanical analysis. Concerning the poly(amic acid)s, the glass transition domain was emphasized only for the compound with
meta
-oriented rings because the process of imidization takes place with increasing temperature. A multiplex experiment was performed to calculate the activation energy of the transition localized under 200°C. Consecutive heating-cooling-heating cycles were accomplished. All phenomena are discussed by cross-examination of the storage modulus (
E′
), loss modulus (
E
″) and loss factor tanδ variation with temperature.
Lubricants based on ionic liquid (IL) modified poly(dimethylsiloxane–alkylene oxide) graft co-polymers (GC) were synthesised by condensation of hydroxyalkyl groups linked to GC chains and to IL ...moieties. The tribological performances of neat and IL-modified co-polymers were investigated in reciprocating steel–steel and in rotating steel–PTFE contacts at 30 and 100°C. A clear dependence of friction and wear on temperature was observed for both neat and IL-modified co-polymers. Generally, friction decreased at higher temperature, especially pronounced for neat co-polymers. Neat as well as IL-modified co-polymers tend to increase wear at elevated temperature. At 30°C, the IL-modified co-polymers exhibited significantly improved anti-wear properties when compared to neat co-polymers with bis(trifluoromethylsulfonyl)amide anion being the crucial moiety involved in tribochemical reactions.
•Novel polymeric lubricants composed of ionic liquids (IL).•Fundamental investigations of IL-modified copolymers behaviour in comparison with their respective precursors.•Synthesis issues, in particular structure confirmation.•Viscometrical data, thermal-oxidative stability and corrosiveness.•Tribological investigations in steel–polymer and steel–steel contact.
The article reviews the thermodynamic aspects of ultrahigh molecular weight polymers in dilute solutions. The investigation of these compounds is much more complicated as compared to the study of ...usual length polymer–solvent systems. The restrictions applying to the establishment of concentration regimes, short range interactions (theta condition, unperturbed dimensions, chain flexibility, the transition from theta to collapsed regime), and long range interactions (excluded volume effect by intermolecular and intramolecular interactions, conformational characteristics and conformational transitions phenomena) are discussed. Systematic studies, based on the coupling of different experimental techniques, are described for the elucidation of diverse theoretical and experimental contributions.
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