Zirconocene silanolate complexes and their heterogeneous siliceous analogues as catalysts for phenylsilane dehydropolymerization

The efficient catalytic dehydropolymerization of phenylsilane by homogeneous zirconocene bissilanolates ([{(c-C₅H₉)₇Si₈O₁₂O}₂Zr(η⁵-C₅H₅)₂] (1a); [{(c-C₅H₉)₇Si₈O₁₂O}₂Zr(η⁵-C₅H₄Bu)₂] (1b) [{(c-C₅H₉)₇Si₇O₉(OSiMe₃)O₂}Zr(η⁵-C₅H₅)₂] (4); [{(Me₃CO)₃SiO}₂Zr(η⁵-C₅H₅)₂] (5)) and chlorosilanolates ([{(c-C₅H₉)₇Si₈O₁₂O}ZrCl(η⁵-C₅H₄Bu)₂] (2); ([{(c-C₅H₉)₇Si₇O₉O₃}Zr₂Cl(η⁵-C₅H₅)₄] (3a); [{(c-C₅H₉)₇Si₇O₉O₃}Zr₂Cl(η⁵-C₅H₄Bu)₄] (3b)) has been demonstrated. The presence of at least one silanol ligand in the zirconocene moiety was found essential for high catalytic performance. Solid state structure of complex 1a was determined by single crystal X-ray diffraction analysis. A series of nine zirconocene-siliceous catalysts were prepared by grafting of zirconocene moiety onto silica using three general methods: (a) reaction of [(η⁵-C₅H₅)₂ZrCl₂] with silica in the presence of NEt₃; (b) reaction of [(η⁵-C₅H₅)₂ZrMe₂] with silica; (c) reaction of solely [(η⁵-C₅H₅)₂ZrCl₂] with silica. Supported catalysts were characterized by ICP-MS, FT-IR, TGA and selected examples by XPS analysis. Those catalysts prepared by method (a) and (b) were found efficient in the phenylsilane polymerization although a higher Zr/monomer ratio had to be used in comparison with homogeneous analogues. The low concentration of residual silanol groups in supported catalysts was found essential for their high catalytic performance. Advantageous reusability of supported catalysts was demonstrated using SiO₂₍₅₀₀₎/Cp₂ZrCl₂/NEt₃(5.8). The catalytic performance was retained in three consecutive cycles producing polymers with almost identical properties.     

Characterization of Croatian Honeys by Right-Angle Fluorescence Spectroscopy and Chemometrics

The potential of right-angle fluorescence spectroscopy and selected chemical parameters for discrimination of botanical origin of Croatian honey types (n = 55) previously classified by physicochemical and melissopalynological analyses was evaluated. Systematic step-by-step fluorescence analysis included the measurement of complete excitation-emission matrix (EEM) in the range of excitation wavelengths from 260 to 400 nm, and emission wavelengths from 300 to 600 nm, followed by fluorescence intensity measurement at detected peaks of different excitation/emission wavelengths, and emission spectra recordings at selected specific excitation wavelengths of honey solutions in 50 mmol L^?1 phosphate buffer pH 7.0 and methanol. A total of five different sets of emission spectral data for buffer and two for methanolic honey solutions were considered for chemometric analysis of original and normalized emission spectra including principal component analysis and linear discriminant analysis. Additionally, chemical analysis of buffer and methanolic honey solutions included determination of protein, total polyphenol and reactive amino group content. Results showed that right-angle fluorescence spectroscopy of honey solutions has great potential for honey botanical origin discrimination, either by visual comparison of excitation-emission spectra landscapes, or even better, by normalized emission fluorescence spectra recordings at 260 and 280 nm of excitation. Moreover, increased honey discrimination was achieved in conjunction with chemometrics of fluorescence spectras. In addition, two rapid markers/indicators of honey authentication were found. Chestnut honey could be clearly discriminated from the other honey types by simple measurement of fluorescence intensity at 390/470 nm, while sage honeys by measurement of reactive amino group content.     

Enhanced antiproliferative and apoptotic response of HT-29 adenocarcinoma cells to combination of photoactivated hypericin and farnesyltransferase inhibitor manumycin A

Several photodynamically-active substances and farnesyltransferase inhibitors are currently being investigated as promising anticancer drugs. In this study, the combined effect of hypericin (the photodynamically-active pigment from Hypericum perforatum) and selective farnesyltransferase inhibitor manumycin (manumycin A; the selective farnesyltransferase inhibitor from Streptomyces parvulus) on HT-29 adenocarcinoma cells was examined. We found that the combination treatment of cells with photoactivated hypericin and manumycin resulted in enhanced antiproliferative and apoptotic response compared to the effect of single treatments. This was associated with increased suppression of clonogenic growth, S phase cell cycle arrest, elevated caspase-3/7 activity and time-dependent total cleavage of procaspase-3 and lamin B, cleavage of p21Bax into p18Bax and massive PARP cleavage. Moreover, we found that the apoptosis-inducing factor is implicated in signaling events triggered by photoactivated hypericin. Our results showed the relocalization of apoptosis-inducing factor (AIF) to the nuclei after hypericin treatment. In addition, we discovered that not only manumycin but also photoactivated hypericin induced the reduction of total Ras protein level. Manumycin decreased the amount of farnesylated Ras, and the combination treatment decreased the amount of both farnesylated and non-farnesylated Ras protein more dramatically. The present findings indicate that the inhibition of Ras processing may be the determining factor for enhancing the antiproliferative and apoptotic effects of combination treatment on HT-29 cells.     

Dependence of carbon dioxide sorption on the petrographic composition of bituminous coals from the Czech part of the Upper Silesian Basin, Czech Republic

The effect of the rank and of the maceral composition of bituminous coal on carbon dioxide sorption capacity was studied on the basis of samples from two coal mines (Darkov, ?SM) from the Czech part of the Upper Silesian Basin. The samples from the two mines cover a small but very significant section of coalification within the transition zone between high-volatile bituminous A coal and medium-volatile bituminous coal, where porosity and sorption properties pass through their minima. The coal porous system was characterized by the micropore volume evaluated using the sorption isotherm of carbon dioxide and the volumes of meso-, macro- and coarse pores were determined by high-pressure mercury porosimetry. The micropore fraction in the coal porous system ranged between 53% and 75%. It was particularly high in coals with high vitrinite content, namely collotelinite, and also in coals with high inertinite content. The carbon dioxide sorption capacity was determined from the carbon dioxide sorption isotherms measured using a gravimetric sorption analyzer at 298 K until a relative pressure of 0.015 p/p_s, and was interpreted by characteristic parameters of the Dubinin and Langmuir equations. It was found that the adsorbed amount of CO₂ in the ?SM coal increases with the content of vitrinite and collotelinite, whereas no increase or only a slight increase was observed for the Darkov coal. The tendency of adsorption capacity to depend on maceral composition, and also to some extent on coalification, observed for the ?SM coal, may be related to higher microporosity due to the coalification process or oxidative processes leading to the formation of pseudovitrinite.     

The Efficacy of the Quorum Sensing Inhibitor FS8 and Tigecycline in Preventing Prosthesis Biofilm in an Animal Model of Staphylococcal Infection

We investigated the efficacy of tigecycline and FS8, alone or combined, in preventing prosthesis biofilm in a rat model of staphylococcal vascular graft infection. Graft infections were established in the back subcutaneous tissue of adult male Wistar rats by implantation of Dacron prostheses followed by topical inoculation with 2 × 10⁷ colony-forming units of Staphylococcus aureus, strain Smith diffuse. The study included a control group, a contaminated group that did not receive any antibiotic prophylaxis, and three contaminated groups that received: (i) intraperitoneal tigecycline, (ii) FS8-soaked graft, and (iii) tigecycline plus FS8-soaked graft, respectively. Each group included 15 animals. The infection burden was evaluated by using sonication and quantitative agar culture. Moreover, an in vitro binding-study was performed to quantify the how much FS8 was coated to the surface of the prosthesis. Tigecycline, combined with FS8, against the adherent bacteria showed MICs (2.00 mg/L) and MBCs (4.00 mg/L) four-fold lower with respect to tigecycline alone in in vitro studies. The rat groups treated with tigecycline showed the lowest bacterial numbers (4.4 × 10⁴ ± 1.2 × 10⁴ CFU/mL). The FS8-treated group showed a good activity and significant differences compared to control group with bacterial numbers of 6.8 × 10⁴ ± 2.0 × 10⁴ CFU/mL. A stronger inhibition of bacterial growth was observed in rats treated with a combined FS8 and tigecycline therapy than in those that were singly treated with bacterial numbers of 10¹ CFU/mL graft. In conclusion, the ability to affect biofilm formation as well, its property to be an antibiotic enhancer suggests FS8 as alternative or additional agent to use in conjunction with conventional antimicrobial for prevention of staphylococcal biofilm related infection.     

Outage analysis of selection diversity over Rayleigh fading channels with multiple co-channel interferers

In this paper an approach to the performance analysis of signal-to-interference (SIR) based selection combining (SC) operating over the Rayleigh fading channels experiencing an arbitrary number of multiple, Rayleigh co-channel interferers is presented. We have presented a general analysis of multibranch SC where each branch experiences an arbitrary number of multiple equal power co-channel interferers. Useful closed form expressions are derived for the probability density function (PDF) and cumulative distribution function (CDF) at the output of the combiner. Also an outage analysis is performed in order to show the effects of the number of multiple interferers, diversity order and input SIR unbalance to the system performances.     

Effect of selenium on lipid alternations in pigment-forming yeasts

The work deals with lipid modifications of pigment-forming yeasts Rhodotorula and Sporobolomyces growing under presence of selenium. This metal in the medium significantly prolonged lag-phase of all cultures and enlarged yeast cells. Total, neutral, and membrane yeast lipids (phosphatidylcholine, phosphatidylethanolamine, phosphatidylserine, and phosphatidylinositol) consisted of predominantly palmitic, palmitoleic, stearic, oleic, linoleic, and linolenic acids. Selenium activated fatty acid unsaturation mainly in phosphatidylcholine due to elevated levels of linoleic and linolenic acids. Because biosynthesis of C18 unsaturated fatty acids in Rhodotorula and Sporobolomyces species may be associated with phosphatidylcholine moieties, selenium might be involved to the induction of membranebound fatty acid Δ¹² and Δ¹⁵ desaturases in red yeasts. Oppositely, neutral lipids (primarily triacylglycerols) did not show such intensive changes in fatty acid composition as their polar counterparts. These observations could be applied for preparation of selenized red yeasts containing carotenoid pigments with enhanced accumulation of linoleic and linolenic acids.     

High-Area Ti/Pt Electrodes for the Electrochemically Catalyzed Transesterification of Soybean Oil with Methanol

Biodiesel fuel is a renewable energy source normally produced in industry by using an alkaline homogeneous catalyst to promote the transesterification of oil and methanol to fatty acid methyl ester (FAME). Undesirable side reactions occur when poorly refined oils are used, leading to serious problems of product separation and low FAME yield. Therefore, about 85% of the cost of biodiesel is determined by the cost of the feedstock. Here, we describe the development of high-area Pt films deposited on Ti substrates for the electrolytic synthesis of biodiesel from soybean oil containing water, without the addition of catalyst. The higher both the calcination temperature and the number of layers deposited on the Ti surface, the higher the electrochemically active area of Pt exposed to surface. Conversion into esters in electrolysis is proportional to the increase in the superficial area of the Ti/Pt electrodes. Thus, it is possible to synthesize biodiesel using electrodes containing very low amounts of Pt (<0.441 mg cm^?2), an important parameter in the industrial production of biodiesel.     

Influence of thermomechanical treatment on the hardening mechanisms and structural changes of a cast Cu–6.6 wt.%Ag alloy

Investigations were carried out on the cast samples of Cu–6.6 wt.%Ag alloy, as well as pure copper samples, for the sake of comparison. Cast samples of copper and alloy were subjected to the same thermomechanical treatment. The thermomechanical treatment included the homogenized annealing, prefinal cold rolling, solution annealing, final cold rolling with a final reduction of 20%, 40% and 60% as well as the isochronal and isothermal annealing up to the recrystallization temperature. Influence of thermomechanical treatment on the hardening mechanisms and structural changes of cast Cu–6.6 wt.%Ag alloy has been investigated for the hardness and electrical conductivity measurements as well as optical microscopy. The study has shown that the anneal hardening effect appeared on the cast Cu–6.6 wt.%Ag alloy in the temperature range of 160–400 °C and was followed by an increase in the hardness and electrical conductivity.     

Current Concepts on Genetic Aspects of Mitochondrial Dysfunction in Amyotrophic Lateral Sclerosis

Amyotrophic Lateral Sclerosis (ALS), neurodegenerative motor neuron disorder is characterized as multisystem disease with important contribution of genetic factors. The etiopahogenesis of ALS is not fully elucidate, but the dominant theory at present relates to RNA processing, as well as protein aggregation and miss-folding, oxidative stress, glutamate excitotoxicity, inflammation and epigenetic dysregulation. Additionally, as mitochondria plays a leading role in cellular homeostasis maintenance, a rising amount of evidence indicates mitochondrial dysfunction as a substantial contributor to disease onset and progression. The aim of this review is to summarize most relevant findings that link genetic factors in ALS pathogenesis with different mechanisms with mitochondrial involvement (respiratory chain, OXPHOS control, calcium buffering, axonal transport, inflammation, mitophagy, etc.). We highlight the importance of a widening perspective for better understanding overlapping pathophysiological pathways in ALS and neurodegeneration in general. Finally, current and potentially novel therapies, especially gene specific therapies, targeting mitochondrial dysfunction are discussed briefly.