Influence of residual solvent on physical and chemical properties of amorphous glassy polymer films

One of the most important areas of current research is the study of the influence of the prehistory of samples of amorphous glassy polymers on their physical and chemical properties. The study of structural changes by high temperature IR spectroscopy compared with of quantum chemical calculations allows for an understanding of the mechanism and nature of such processes. The changes in the structure of the polymer chain depending on the type of solvent used in the formation of the films are demonstrated using the examples of several different classes of polymers. In turn, the impact of such changes in the structure on the physical and chemical properties of the polymer films is demonstrated. © 2013 Society of Chemical Industry     

Femtosecond laser modification of an array of vertically aligned carbon nanotubes intercalated with Fe phase nanoparticles

Femtosecond lasers (FSL) are playing an increasingly important role in materials research, characterization, and modification. Due to an extremely short pulse width, interactions of FSL irradiation with solid surfaces attract special interest, and a number of unusual phenomena resulted in the formation of new materials are expected. Here, we report on a new nanostructure observed after the interaction of FSL irradiation with arrays of vertically aligned carbon nanotubes (CNTs) intercalated with iron phase catalyst nanoparticles. It was revealed that the FSL laser ablation transforms the topmost layer of CNT array into iron phase nanospheres (40 to 680 nm in diameter) located at the tip of the CNT bundles of conical shape. Besides, the smaller nanospheres (10 to 30 nm in diameter) are found to be beaded at the sides of these bundles. Some of the larger nanospheres are encapsulated into carbon shells, which sometime are found to contain CNTs. The mechanism of creation of such nanostructures is proposed.     

Identification of purple dye from molluscs on an excavated textile by non-destructive analytical techniques

The inherent sensitivity of textile fibres to the aggressive process of burial accounts for the rarity and poor condition of excavated textile finds retrieved. However, the information contained within these finds is important and yielding it contributes to the longevity of the finds. Therefore, the application of non-destructive methods of investigation for the extraction of the data present is imperative. This paper presents the results of dye analysis performed on the excavated textile find HTR-73 from the Kerameikos cemetery in Athens. The Kerameikos textile find is from the 5th century BC, and has been preserved in association with copper. The techniques applied were Scanning Electron Microscopy (SEM), Energy Dispersive X-Ray (EDX) analysis, Cathodoluminescence and micro Raman. For the first time Cathodoluminescence from an indigoid compound is reported. Comparison of the analysis results on samples from the find with the contemporary reference samples lead to the identification of purple dye as a dibromoindigo compound with the origin from molluscs of Murex trunculus species. The application of non-destructive analytical methods of investigation was successful in analysing dyes on excavated textiles.     

Magnetic behavior of nickel–bismuth ferrite synthesized by a combined sol–gel/thermal method

The bulk NiFe_2?xBi_xO₄ ferrites with various Bi³⁺ concentration (x=0, 0.1, 0.15) were synthesized via sol–gel procedure, starting from nickel, bismuth and iron nitrate powders, followed by the conventional thermal treatment. The structural and magnetic properties of the as-prepared ferrites were studied by means of X-ray diffraction, alternating gradient force magnetometry and Faraday balance. The anisotropy constant was determined by the law of approach to saturation (LAS) model. An increasing Bi³⁺ concentration in NiFe_2?xBi_xO₄ leads to a decrease in the saturation magnetization, Néel temperature and the anisotropy constant of the material.     

Two-variable periodic perturbation of kinetic oscillations

Using one of the generic models (CO oxidation on Pt with surface-oxide formation) predicting kinetic oscillations in heterogeneous catalytic reactions, we show that the efficiency of two-variable periodic perturbations with respect to converting natural period-1 oscillations to period-l oscillations at the forcing frequency is remarkably sensitive to the kind of perturbations used. Counter-phase perturbations are much more effective compared to in-phase perturbations. The physics underlying these findings is suggestive of their applicability to many other models and/or real systems exhibiting kinetic oscillations.     

Electromagnetic properties of aluminosilicate‐filled polymer composites of poly(vinyl alcohol)–poly(vinyl pyrrolidone)

Nanocomposites of aluminocilicate are of growing interest not only because they offer exceptional reinforcement at very low filler concentrations, but also because of their electromagnetic properties and natural origin. Aluminosilicate‐filled biodegradable composites of poly(vinyl alcohol) (PVA) and poly(vinyl pyrrolidone) (PVP) were prepared by a conventional solvent casting technique using glass plates as the casting surfaces. The aluminosilicate used in this study is a multicomponent natural clay material. Its average particle size is 23–24 nm. The dielectric and magnetic properties of composite materials of PVA‐PVP and aluminosilicate were investigated in wide frequency ranges from 1 MHz to 1 GHz. The complex permittivity spectra (ε* = ε′ – jε″) had a relaxation type frequency dispersion with an ill‐defined broad resonance line width of the dielectric losses (ε″). The magnetic properties of composites are very low and are independent of the filler concentration. The new nanobiocomposites are brick red in color and weakly ferromagnetic in nature. POLYM. COMPOS., 26:739–744, 2005. © 2005 Society of Plastics Engineers     

AICAR Protects Vascular Endothelial Cells from Oxidative Injury Induced by the Long-Term Palmitate Excess

Hyperlipidemia manifested by high blood levels of free fatty acids (FFA) and lipoprotein triglycerides is critical for the progression of type 2 diabetes (T2D) and its cardiovascular complications via vascular endothelial dysfunction. However, attempts to assess high FFA effects in endothelial culture often result in early cell apoptosis that poorly recapitulates a much slower pace of vascular deterioration in vivo and does not provide for the longer-term studies of endothelial lipotoxicity in vitro. Here, we report that palmitate (PA), a typical FFA, does not impair, by itself, endothelial barrier and insulin signaling in human umbilical vein endothelial cells (HUVEC), but increases NO release, reactive oxygen species (ROS) generation, and protein labeling by malondialdehyde (MDA) hallmarking oxidative stress and increased lipid peroxidation. This PA-induced stress eventually resulted in the loss of cell viability coincident with loss of insulin signaling. Supplementation with 5-aminoimidazole-4-carboxamide-riboside (AICAR) increased endothelial AMP-activated protein kinase (AMPK) activity, supported insulin signaling, and prevented the PA-induced increases in NO, ROS, and MDA, thus allowing to maintain HUVEC viability and barrier, and providing the means to study the long-term effects of high FFA levels in endothelial cultures. An upgraded cell-based model reproduces FFA-induced insulin resistance by demonstrating decreased NO production by vascular endothelium.     

Interferon-β Activity Is Affected by S100B Protein

Interferon-β (IFN-β) is a pleiotropic cytokine secreted in response to various pathological conditions and is clinically used for therapy of multiple sclerosis. Its application for treatment of cancer, infections and pulmonary diseases is limited by incomplete understanding of regulatory mechanisms of its functioning. Recently, we reported that IFN-β activity is affected by interactions with S100A1, S100A4, S100A6, and S100P proteins, which are members of the S100 protein family of multifunctional Ca²⁺-binding proteins possessing cytokine-like activities (Int J Mol Sci. 2020;21(24):9473). Here we show that IFN-β interacts with one more representative of the S100 protein family, the S100B protein, involved in numerous oncological and neurological diseases. The use of chemical crosslinking, intrinsic fluorescence, and surface plasmon resonance spectroscopy revealed IFN-β binding to Ca²⁺-loaded dimeric and monomeric forms of the S100B protein. Calcium depletion blocks the S100B–IFN-β interaction. S100B monomerization increases its affinity to IFN-β by 2.7 orders of magnitude (equilibrium dissociation constant of the complex reaches 47 pM). Crystal violet assay demonstrated that combined application of IFN-β and S100B (5–25 nM) eliminates their inhibitory effects on MCF-7 cell viability. Bioinformatics analysis showed that the direct modulation of IFN-β activity by the S100B protein described here could be relevant to progression of multiple oncological and neurological diseases.     

Ferritinophagy and α-Synuclein: Pharmacological Targeting of Autophagy to Restore Iron Regulation in Parkinson’s Disease

A major hallmark of Parkinson’s disease (PD) is the fatal destruction of dopaminergic neurons within the substantia nigra pars compacta. This event is preceded by the formation of Lewy bodies, which are cytoplasmic inclusions composed of α-synuclein protein aggregates. A triad contribution of α-synuclein aggregation, iron accumulation, and mitochondrial dysfunction plague nigral neurons, yet the events underlying iron accumulation are poorly understood. Elevated intracellular iron concentrations up-regulate ferritin expression, an iron storage protein that provides cytoprotection against redox stress. The lysosomal degradation pathway, autophagy, can release iron from ferritin stores to facilitate its trafficking in a process termed ferritinophagy. Aggregated α-synuclein inhibits SNARE protein complexes and destabilizes microtubules to halt vesicular trafficking systems, including that of autophagy effectively. The scope of this review is to describe the physiological and pathological relationship between iron regulation and α-synuclein, providing a detailed understanding of iron metabolism within nigral neurons. The underlying mechanisms of autophagy and ferritinophagy are explored in the context of PD, identifying potential therapeutic targets for future investigation.     

Kinetics of Multi‐Step Redox Processes by Time‐Resolved In Situ X‐ray Diffraction

The kinetics of redox reactions of iron oxide in oxygen carrier 50Fe₂O₃/MgAl₂O₄ are examined using different time‐resolved techniques. Reduction kinetics are studied by H₂ temperature‐programmed reduction (H₂‐TPR) monitored by time‐resolved in situ XRD. In contrast to conventional TPR, in situ XRD distinguishes the three‐stage reduction of Fe₂O₃ → Fe₃O₄ → FeO → Fe. It also shows that the oxidation of Fe → Fe₃O₄ by CO₂ has no intermediate crystalline phases, explaining why its kinetics can easily be investigated by conventional CO₂ temperature‐programmed oxidation (CO₂‐TPO). A shrinking core model which takes into account solid state diffusion allows describing the experimental data.