Free‐volume structure of polyvinylpyrrolidone‐capped glassy As2Se3 nanocomposites prepared by mechanical milling

The method of positron annihilation lifetime (PAL) spectroscopy was first employed to study atomic‐deficient free‐volume structure of nanocomposites prepared by high‐energy mechanical milling of glassy g‐As₂Se₃ in water solution of polyvinylpyrrolidone (PVP). The formalism of x3‐x2‐CDA (coupling decomposition algorithm) describing conversion of bound positron‐electron (positronium Ps) states into positron traps was applied to identify free‐volume elements in pelletized PVP‐capped g‐As₂Se₃ nanocomposite in respect to parent dry‐milled g‐As₂Se₃. Under wet milling, the internanoparticle Ps‐decaying sites in preferential PVP environment were shown to replace free‐volume positron traps in dry‐milled g‐As₂Se₃ with defect‐specific positron lifetime of 0.352 ns, corresponding to diatomic/triatomic vacancies in g‐As‐Se matrix. POLYM. ENG. SCI., 59:2438–2442, 2019. © 2019 Society of Plastics Engineers     

Noise and transport characterisation of tantalum capacitors

A low frequency noise and charge carrier transport mechanisms were investigated on tantalum capacitors made by various producers. The model of Ta–Ta₂O₅–MnO₂ MIS structure was used to give physical interpretation of I–V characteristics in normal and reverse modes. The noise in time and frequency domain was examined and noise sources were identified. We evaluated correlation between leakage current and noise spectral density and discussed corresponding quality and reliability indicators.     

Combined Methylglyoxal Scavenger and Collagen Hydrogel Therapy Prevents Adverse Remodeling and Improves Cardiac Function Post-Myocardial Infarction

Methylglyoxal (MG) is a highly reactive dicarbonyl and the main precursor of advanced glycation end-products (AGEs). After myocardial infarction (MI), MG-derived AGEs accumulate in the heart and contribute to adverse remodeling and loss of cardiac function. In this study, the flavonoid fisetin, a dicarbonyl scavenger, is used to reduce the negative effects of MG in the post-MI heart. A fisetin-loaded collagen type I hydrogel (fisetin-HG) is injected intramyocardially in mice at 3 h post-MI, and compared to fisetin-alone, hydrogel-alone, or saline treatment. Fisetin-HG treatment increases the level of glyoxalase-1 (the main MG-metabolizing enzyme), reduces MG-AGE accumulation, and decreases oxidative stress in the MI heart, which is associated with smaller scar size and improved cardiac function. Treatment with fisetin-HG also promotes neovascularization and increases the number of pro-healing macrophages in the infarct area, while reducing the number of pro-inflammatory macrophages. Taken together, the results demonstrate that the fisetin-collagen hydrogel therapy can reduce the accumulation and negative effects of MG post-MI. This therapy may be a promising approach to limit adverse cardiac remodeling, prevent damage, and preserve function of the infarcted heart.     

Mechanochemical synthesis,structural, magnetic,optical and electrooptical properties of CuFeS2 nanoparticles

The rapid mechanochemical synthesis of nanocrystalline CuFeS₂ particles prepared by high-energy milling for 60?min in a planetary mill from copper, iron and sulphur elements is reported. The CuFeS₂ nanoparticles crystallize in tetragonal structure with mean crystallite size of about 38?±?1?nm determined by XRD analysis. HRTEM study also revealed the presence of nanocrystals with the size of 5–30?nm with the tendency to form agglomerates. The Raman spectrum confirms the chalcopyrite structure. Low temperature magnetic data for CuFeS₂ support the coexistence of antiferromagnetic and paramagnetic spin structure. Moreover, the hysteresis loops taken at temperatures from 5?K to 300?K revealed a presence of very small amount of ferromagnetic phase, which seems to be associated with the non-consumed elemental Fe in as-prepared nanoparticles. The optical band gap of CuFeS₂ nanoparticles has been detected to be 1.05?eV, larger than band gap of the bulk material. The wider gap possibly resulted from the nano-size effect. Photoresponses of CuFeS₂ nanoparticles were confirmed by I-V measurements under dark and light illumination. It was demonstrated that mechanochemical synthesis can be successfully employed in the one step preparation of nanocrystalline CuFeS₂ with good structural, magnetic, optical and electrooptical properties.     

Proteomic analysis of porcine oocytes during in vitro maturation reveals essential role for the ubiquitin C-terminal hydrolase-L1

In this study, we performed proteomic analysis of porcine oocytes during in vitro maturation. Comparison of oocytes at the initial and final stages of meiotic division characterized candidate proteins that were differentially synthesized during in vitro maturation. While the biosynthesis of many of these proteins was significantly decreased, we found four proteins with increased biosynthetic rate, which are supposed to play an essential role in meiosis. Among them, the ubiquitin C-terminal hydrolase-L1 (UCH-L1) was identified by mass spectrometry. To study the regulatory role of UCH-L1 in the process of meiosis in pig model, we used a specific inhibitor of this enzyme, marked C30, belonging to the class of isatin O-acyl oximes. When germinal vesicle (GV) stage cumulus-enclosed oocytes were treated with C30, GV breakdown was inhibited after 28 h of culture, and most of the oocytes were arrested at the first meiosis after 44 h. The block of metaphase I-anaphase transition was not completely reversible. In addition, the inhibition of UCH-L1 resulted in elevated histone H1 kinase activity, corresponding to cyclin-dependent kinase(CDK1)-cyclin B1 complex, and a low level of monoubiquitin. These results supported the hypothesis that UCH-L1 might play a role in metaphase I-anaphase transition by regulating ubiquitin-dependent proteasome mechanisms. In summary, a proteomic approach coupled with protein verification study revealed an essential role of UCH-L1 in the completion of the first meiosis and its transition to anaphase.     

Differencing sea bass (Dicentrarchus labrax) fillets frozen in different conditions by impedance measurements

The potential of electrical impedance was investigated to differentiate thawed sea bass fillets (Dicentrarchus labrax) previously subjected to different freezing conditions. The HP 4284A Precise LCR meter was used to measure impedance magnitude (|Z|) and phase (?) at 27 frequencies from 0.1 to 1000 kHz. A needle‐type multi electrode array was tested as a probe for impedance measurements. The study showed that fast and non‐invasive control method based on measurement of ? on thawed fillets could assess the freezing conditions of white fish at higher frequencies of measurements (500–1000 kHz). The advantages of ? when compared with |Z| include its independence on temperature, on puncture depth of the probe and on duration of storage prior to freezing. Usage of a needle‐type multi electrode array reduced the effect of muscle tissue anisotropy; however, even at 1 MHz, the differences in electrical measurements varied around 10–11% depending on muscle fibre direction.     

Thermal study on the copolymers of phthalonitrile and phenylnitrile‐functional benzoxazines

Ortho‐, meta‐, and para‐phenylnitrile–functional benzoxazines are polymerized at different compositions with phthalonitrile‐functional monomers providing copolybenzoxazines of high thermal stability and easy processability. The most positive effect on these properties is obtained on copolymerizing phthalonitrile‐ and ortho‐phenylnitrile–functional benzoxazines. Thermal decomposition of these polybenzoxazines is studied by thermogravimetry (TGA). It is demonstrated that only 30 mol % of phthalonitrile‐functional benzoxazine added to the ortho‐phenylnitrile–substituted monomer improves char yield significantly from 59 to 77 wt %, which is the value of neat phthalonitrile‐based polybenzoxazine. Glass transition temperature (T_g) also dramatically increases from 180°C for neat ortho‐phenylnitrile polymer to 294°C for the copolymer with 30 mol % of phthalonitrile‐functional monomer. Additionally, the high melt viscosity of phthalonitrile‐functional benzoxazines is dramatically decreased upon blending with phenylnitrile‐functional monomer. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 2937–2949, 1999