Synthesis of trimethylene carbonate/ϵ‐caprolactone copolymers initiated with zinc alkoxide: influence of copolymer chain microstructure on thermal and mechanical properties

Ethylzinc(II ) ethoxide is a highly active and efficient initiator for the bulk polymerization of 1,3‐trimethylene carbonate and its copolymerization with ? ‐caprolactone. This initiator allows one to obtain (co)polymers with high molar masses in quite a short time. Significant difference in co‐monomer reactivity and relatively low participation of intermolecular transesterification processes lead to the obtained copolymers being characterized by a gradient chain microstructure. In ¹³C NMR spectra, in all regions, we observed the presence of triads which were distinctly represented by four peaks for the carbonyl signal. Mechanical tests showed that copolymers containing 70% and more of ? ‐caprolactone presented a relatively high Young's modulus and a very high maximum elongation factor; therefore these materials are promising in many biomedical applications. Due to the high reaction rate, we also made an attempt at copolymerization using reactive extrusion which gave promising results. © 2017 Society of Chemical Industry     

A comparative study on selective properties of Kraft lignin–natural rubber composites containing different plasticizers

Effect of plasticizer type on the kraft lignin–natural rubber composite microstructure and selected properties was determined. The composites were prepared with addition of a commonly used naphthenic oil plasticizer to study the decomposition product of polyurethane (glycerolysate) and its characteristics. Kraft lignin powder was incorporated into the natural rubber matrix in amounts of 10 and 40 parts per 100 parts of natural rubber (phr). The reference samples were prepared without any lignin present. The chemical interaction between the filler particles and natural rubber macromolecules was analyzed by Fourier transform infrared spectroscopy (FTIR) and the adhesion was characterized by scanning electron microscopy (SEM). The results of the adhesion measurements confirmed poor distribution of lignin particles into the natural rubber matrix with increasing filler content. Optimal lignin content in the composites was 10 phr in the case of both plasticizers. Moreover, the results of FTIR verified the formation of non-covalent bonds and the need for modification of the filler to enhance the reinforcing effect in the natural rubber matrix. Dynamic mechanical analysis (DMA) and mechanical measurements proved that the specimen containing 10 phr of lignin with the use of glycerolysate as plasticizer displayed the highest mechanical performance. It was demonstrated that glycerolysate and naphthenic oil as plasticizing agents showed similar effect on the thermal properties of the prepared composites. Also, the measured mechanical properties, such as tensile strength, hardness, resilience, and abrasiveness confirmed these findings.     

电弧炉粉尘球团直接还原的热传导模型

对电弧炉炼钢粉尘加上还原剂碳混合制粒成的球团还原过程的热传导行为进行了研究,根据实验推导了球团导热模型的结构参数,并试图建立热传导模型。     

Thermochemistry, lattice energetics and stability of hexahalogenohafnates

The enthalpies of thermal dissociation (Δ_dH) and formation (Δ_fH) found in the literature as well as the crystal lattice energies (E_c) of inorganic and organic hexahalogenohafnates (M^I₂(or M^{II)HfX2−₆}; M^I and M^II denote monovalent and divalent cations respectively and X denotes a halogen) are reviewed and discussed. The enthalpies of formation of the salts were evaluated using the above-mentioned Δ_dH values and known enthalpies of formation of products of decomposition. Combination of the enthalpies of formation of hexahalogenohafnates thus obtained or those of the literature with the literature values of the enthalpy of formation of cations and theoretically determined enthalpies of formation of HfX²⁻₆ (or electrostatic lattice energies of the salts) afforded lattice energies of the salts (or enthalpies of formation of gaseous HfX²⁻₆). Values of Δ_fH were also assessed taking theoretically obtained electrostatic lattice energies of the salts and enthalpies of formation of HfX²⁻₆ and literature or theoretically determined values of the enthalpy of formation of gaseous cations. The independent sets of crystal lattice energies and thermochemical radii for HfX²⁻₆ were obtained following the Kapustinskii—Yatsimirskii approach. Combination of the latter method with the thermochemical cycle afforded information on the influence of the dimensions of ions on the thermodynamic stability of hexahalogenohafnates with respect to dissociation and oxidation processes. The thermochemical quantities of experimental and theoretical origin correlate with each other reasonably well, thus increasing their reliability.     

A modified creep model of epoxy adhesive at ambient temperature

The paper presents the results of experimental investigations of the creep behavior of epoxy adhesive-hardened samples. The determined creep characteristics for an assumed range of tensile stresses show that the rheological effects in the examined adhesive have already occurred very distinctly at room temperature, for a relatively short time; moreover, the examined adhesive is a nonlinear viscoelastic medium and does not obey the Boltzmann's superposition principle. The obtained results of experimental investigations were subjected to detailed analysis and mathematical treatments. As a result of these actions, the so-called modified Burgers model has been finally developed for the studied adhesive with a constant modulus of elasticity for the non-relaxing part (describing the instant elastic strain) and variables, dependent on the tensile stress, the parameter values for its relaxing part (describing non-linearly viscoelastic properties of this adhesive). The creep deformations calculated for this model have demonstrated a very good consistency with the results of experimental investigations over the assumed range of stresses and the duration time of measurements.     

Subcellular Localization of Acyl-CoA: Lysophosphatidylethanolamine Acyltransferases (LPEATs) and the Effects of Knocking-Out and Overexpression of Their Genes on Autophagy Markers Level and Life Span of A. thaliana

Arabidopsis thaliana possesses two acyl-CoA:lysophosphatidylethanolamine acyltransferases, LPEAT1 and LPEAT2, which are encoded by At1g80950 and At2g45670 genes, respectively. Both single lpeat2 mutant and double lpeat1 lpeat2 mutant plants exhibit a variety of conspicuous phenotypes, including dwarfed growth. Confocal microscopic analysis of tobacco suspension-cultured cells transiently transformed with green fluorescent protein-tagged versions of LPEAT1 or LPEAT2 revealed that LPEAT1 is localized to the endoplasmic reticulum (ER), whereas LPEAT2 is localized to both Golgi and late endosomes. Considering that the primary product of the reaction catalyzed by LPEATs is phosphatidylethanolamine, which is known to be covalently conjugated with autophagy-related protein ATG8 during a key step of the formation of autophagosomes, we investigated the requirements for LPEATs to engage in autophagic activity in Arabidopsis. Knocking out of either or both LPEAT genes led to enhanced accumulation of the autophagic adaptor protein NBR1 and decreased levels of both ATG8a mRNA and total ATG8 protein. Moreover, we detected significantly fewer membrane objects in the vacuoles of lpeat1 lpeat2 double mutant mesophyll cells than in vacuoles of control plants. However, contrary to what has been reported on autophagy deficient plants, the lpeat mutants displayed a prolonged life span compared to wild type, including delayed senescence.     

Interfacial reactions of Sn–Zn–Ag–Cu alloy on soldered Al/Cu and Al/Al joints

This work shows the effect on the soldering process of the addition of Ag and Cu to Sn–Zn alloys. Soldering of Al/Cu and Al/Al joints was performed for a time of 3?min, at a temperature of 250°C, with the use of flux. Aging was carried out at 170°C for Al/Cu and Al/Al joints for 1 and 10 days. During the aging process, intermetallic layers grew at the interface of the Al/Cu joint at the Cu substrate. Intermetallic layers were not observed during wetting of Al/Al joints. On the contrary, dissolution of the Al substrate and migration of Al-rich particles into the bulk of the solder were observed. The experiment was designed to demonstrate the effect of Ag and Cu addition on the dissolution of Al substrate during the soldering and aging processes. In the solder alloys, small precipitates of AgZn₃ and Cu₅Zn₈ were observed.     

Potential of Telomerase in Age-Related Macular Degeneration—Involvement of Senescence,DNA Damage Response and Autophagy and a Key Role of PGC-1α

Age-related macular degeneration (AMD), the main cause of vision loss in the elderly, is associated with oxidation in the retina cells promoting telomere attrition. Activation of telomerase was reported to improve macular functions in AMD patients. The catalytic subunit of human telomerase (hTERT) may directly interact with proteins important for senescence, DNA damage response, and autophagy, which are impaired in AMD. hTERT interaction with mTORC1 (mTOR (mechanistic target of rapamycin) complex 1) and PINK1 (PTEN-induced kinase 1) activates macroautophagy and mitophagy, respectively, and removes cellular debris accumulated over AMD progression. Ectopic expression of telomerase in retinal pigment epithelium (RPE) cells lengthened telomeres, reduced senescence, and extended their lifespan. These effects provide evidence for the potential of telomerase in AMD therapy. Peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α) may be involved in AMD pathogenesis through decreasing oxidative stress and senescence, regulation of vascular endothelial growth factor (VEGF), and improving autophagy. PGC-1α and TERT form an inhibitory positive feedback loop. In conclusion, telomerase activation and its ectopic expression in RPE cells, as well as controlled clinical trials on the effects of telomerase activation in AMD patients, are justified and should be assisted by PGC-1α modulators to increase the therapeutic potential of telomerase in AMD.     

Kynurenine Pathway of Tryptophan Metabolism in Migraine and Functional Gastrointestinal Disorders

Migraine, the leading cause of disability in the population aged below 50, is associated with functional gastrointestinal (GI) disorders (FGIDs) such as functional nausea, cyclic vomiting syndrome, and irritable bowel syndrome (IBS). Conversely, changes in intestinal GI transit may cause diarrhea or constipation and are a component of the autonomic symptoms associated with pre- and post-dorsal phases of migraine attack. These mutual relationships provoke a question on a common trigger in migraine and FGIDs. The kynurenine (l-kyn) pathway (KP) is the major route for l-tryptophan (l-Trp) metabolism and transforms l-Trp into several neuroactive compounds. Changes in KP were reported in both migraine and FGIDs. Migraine was largely untreatable, but several drugs approved lately by the FDA, including monoclonal antibodies for calcitonin gene-related peptide (CGRP) and its receptor, create a hope for a breakthrough in migraine treatment. Derivatives of l-kyn were efficient in pain relief with a mechanism including CGRP inhibition. KP products are important ligands to the aryl hydrocarbon receptor (AhR), whose activation is implicated in the pathogenesis of GI and migraine. Toll-like receptors (TLRs) may play a role in migraine and IBS pathogeneses, and KP metabolites detected downstream of TLR activation may be an IBS marker. The TLR4 signaling was observed in initiating and maintaining migraine-like behavior through myeloid differentiation primary response gene 88 (MyD88) in the mouse. The aim of this review is to justify the view that KP modulation may provide common triggers for migraine and FGIDs with the involvement of TLR, AhR, and MyD88 activation.