Influence of phenoxy addition on the curing kinetics for uncatalyzed and catalyzed cyanate ester resin

The curing behavior of the dicyanate ester of bisphenol‐A (DCBA) modified with poly(hydroxy ether of bisphenol‐A) (phenoxy) is studied by differential scanning calorimetry in dynamic and isothermal tests at temperatures between 120 and 240°C. The addition of phenoxy to DCBA produces an increase in the reaction rate and a decrease in the temperature of maximum reaction rate for the uncatalyzed resin, and also for the system catalyzed with copper (II) acetyl acetonate/nonylphenol. The exothermic heat of curing for the mixtures is also dependent on the phenoxy content. These facts evidence a catalytic effect of phenoxy on the curing of the cyanate ester resin, even though an autocatalytic behavior is observed for all uncatalyzed DCBA/phenoxy mixtures. A simplified mechanistic kinetic model is used to calculate the kinetic parameters. For the uncatalyzed systems, a decrease in the kinetic constant for the initiation reactions, and an increase in the propagation constant are measured when the cyanate content increases. The thermal activation energy for the initiation reaction of the catalyzed systems is lower than that of the uncatalyzed ones, and it depends on the weight fraction of cyanate in the mixture. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Dysregulated Expression of Arterial MicroRNAs and Their Target Gene Networks in Temporal Arteries of Treatment-Naïve Patients with Giant Cell Arteritis

In this study, we explored expression of microRNA (miR), miR-target genes and matrix remodelling molecules in temporal artery biopsies (TABs) from treatment-naïve patients with giant cell arteritis (GCA, n = 41) and integrated these analyses with clinical, laboratory, ultrasound and histological manifestations of GCA. NonGCA patients (n = 4) served as controls. GCA TABs exhibited deregulated expression of several miRs (miR-21-5p, -145-5p, -146a-5p, -146b-5p, -155-5p, 424-3p, -424-5p, -503-5p), putative miR-target genes (YAP1, PELI1, FGF2, VEGFA, KLF4) and matrix remodelling factors (MMP2, MMP9, TIMP1, TIPM2) with key roles in Toll-like receptor signaling, mechanotransduction and extracellular matrix biology. MiR-424-3p, -503-5p, KLF4, PELI1 and YAP1 were identified as new deregulated molecular factors in GCA TABs. Quantities of miR-146a-5p, YAP1, PELI1, FGF2, TIMP2 and MMP9 were particularly high in histologically positive GCA TABs with occluded temporal artery lumen. MiR-424-5p expression in TABs and the presence of facial or carotid arteritis on ultrasound were associated with vision disturbances in GCA patients. Correlative analysis of miR-mRNA quantities demonstrated a highly interrelated expression network of deregulated miRs and mRNAs in temporal arteries and identified KLF4 as a candidate target gene of deregulated miR-21-5p, -146a-5p and -155-5p network in GCA TABs. Meanwhile, arterial miR and mRNA expression did not correlate with constitutive symptoms and signs of GCA, elevated markers of systemic inflammation nor sonographic characteristics of GCA. Our study provides new insights into GCA pathophysiology and uncovers new candidate biomarkers of vision impairment in GCA.     

A new stilbazolium salt with perfectly aligned chromophores for second-order nonlinear optics: 4-N,N-Dimethylamino-4′-N′-methyl-stilbazolium 3-carboxy-4-hydroxybenzenesulfonate

A new organic nonlinear optical crystal 4-N,N-dimethylamino-4′-N′-methyl-stilbazolium 3-carboxy-4-hydroxybenzenesulfonate (DSCHS) has been developed with very promising properties for quadratic nonlinear optical applications. DSCHS single crystals with non-centrosymmetric structure have been obtained from aqueous methanol solution. X-ray crystallographic analysis revealed that the crystal structure of DSCHS is triclinic P1 with the chromophores aligned perfectly parallel, leading to the maximum possible order parameter <cos³θ> = 1 in the crystalline state, which is optimal for electro-optics, THz-wave generation and field detection applications. Kurtz powder test has shown that DSCHS exhibits a very large second-order optical nonlinearity, with a 30 percent higher second-harmonic signal than the well-known organic nonlinear optical crystal 4-N,N-dimethylamino-4′-N′-methyl-stilbazolium tosylate (DAST).     

The impact of K+ content on the structural transformations and morphological changes during the thermal treatment of α-MnO2 nanorods

The effect of heat treatment on the structure and morphology of α-MnO₂ nanorods with different potassium contents was investigated. These nanorods, prepared by ion exchange, were thermally treated at 500, 800, 1000 and 1100 °C, and characterized with X-ray diffraction and electron microscopy. The structure and morphology of the starting sample remained preserved up to 500 °C. The first structural and morphological changes were observed when α-MnO₂ nanorods with different potassium contents were heated at 800 °C. The sample with the highest potassium content decomposed only partially to α-Mn₂O₃, while the decomposition of the α-MnO₂ to α-Mn₂O₃ was complete in the sample with the lowest potassium content. Morphologically, both samples were composed of nanorods and grains. When the temperature was increased to 1000 and 1100 °C, both the structure and morphology changed: the α-MnO₂ nanorods completely decomposed to Mn₃O₄ grains. The acidic media in which the ion exchange took place shortened the α-MnO₂ nanorods.     

A novel user satisfaction prediction model for future network provisioning

The notion of user perception has grown in terms of its importance and complexity. This paper presents results of an experimental study focused on predictive modeling of the relations between the user perception, user satisfaction and objective technical parameters in data communication services. A new model for prediction of user satisfaction was devised using probability theory based on Markov chain. Two experiments were completed for web browsing scenarios. The results of the first experiment have confirmed that previous user experience has significant effect on the user perception of quality and should represent a vital element of future predictive user models. The result of the second experiment is a user satisfaction prediction model, which presents a novel insight and deeper understanding of user perception of quality. This model can significantly improve level of user satisfaction with services in telecommunications systems if implemented within advanced system design, optimization and quality assurance procedures.     

Phase equilibria of vanillins in compressed gases

Solid–liquid phase transitions of vanillin, ethylvanillin, o-vanillin and o-ethylvanillin in compressed hydrocarbons (isobutane and propane), fluorinated hydrocarbons (R23, R134a and R236fa) and sulphur hexafluoride (SF₆) were determined with a modified capillary method in a pressure range between 0.1 and 31.0 MPa. Equilibrium solubilities of vanillins in compressed fluorinated hydrocarbons were determined at temperatures 313.2 and 333.2 K and over a pressure range between 1.1 and 26.0 MPa with a static–analytic method. Experimental solubility data were correlated by a density-based Chrastil model.Results showed that phase equilibria of vanillins in investigated compressed gases are influenced by the type of alchoxy group (methoxy or ethoxy) and the position of OH group (ortho or para), bound to the aromatic ring of solute, as well as the molecular structure of the gas. Three phase SLG curves in p,T-projections mainly exhibited temperature minimums and negative slopes dp/dT, with a maximum melting point depression between 9 and 21 K; all systems with SF₆ exhibited a continuous positive slope dp/dT of approximately 4.5 MPa/K. SLG curves with a temperature maximum at low pressure were observed for systems of o-vanillins with R23. Solubilities of o-vanillins in R23 and R236fa were higher in comparison with p-vanillins, whereas, in the case of R134a, the solubilities were influenced by the alchoxy group bound on aromatic ring: vanillin and o-vanillin with methoxy group are more soluble than vanillins with ethoxy group (ethylvanillin and o-ethylvanillin). The highest solubility of all four vanillins was observed in R236fa.     

Determination of the geographical origin of Slovenian black locust,lime and chestnut honey

The geographical origin of three Slovenian unifloral honey types (black locust, lime and chestnut) was investigated by analysis of some physico-chemical parameters, the elemental content using total reflection X-ray fluorescence spectrometry (TXRF) and the stable carbon and nitrogen isotope ratios using isotope ratio mass spectrometry (IRMS). The results were interpreted by chemometric methods. A total of 122 samples of Slovenian black locust, lime and chestnut honeys were collected from domestic beekeepers all over Slovenia for three years. Slovenia is a small country by area, but paedologically and climatically diverse, therefore offering interesting possibilities for studying geographical influences. The combination of the investigated parameters offers the possibility of distinguishing among samples of specific honey types from the four different Slovenian natural-geographical macroregions, namely the Alpine, Dinaric, Pannonnian and Mediterranean regions. Lime honey samples were 100% correctly classified, while the success rates for black locust and chestnut honeys were slightly lower at 98.2% and 94.6%, respectively.     

In vitro antioxidant and antiproliferative activity of three rosemary (Rosmarinus officinalis L.) extract formulations

Antioxidant and antiproliferative activities of three rosemary extract formulations (VivOX 20, VivOX 40 and Inolens 50) with different contents of carnosic acid, carnosol and methylcarnosol were tested in vitro. Electron spin resonance measurements revealed that Inolens 50 extract that contained highest amount of carnosic acid was the most potent scavenger of hydroxyl (concentration of extract where 50% of its maximal scavenging activity is observed, that is, EC₅₀, 109.54 μg mL^?1), superoxide anion (EC₅₀ = 7.94 μg mL^?1) and 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH) (EC₅₀ = 27.4 μg mL^?1)‐free radicals. Comparison of the radar charts of standard antioxidants and rosemary extracts showed similarity between antioxidant characteristics of Inolens 50 and chlorogenic and caffeic acids. Tested rosemary extracts exhibited significant (P ≤ 0.01) antiproliferative effect in cervix epitheloid carcinoma (HeLa), breast adenocarcinoma (MCF7) and colon adenocarcinoma (HT‐29) cell lines. In both MCF7 and HeLa cell lines, the extracts yielded very low IC₅₀ values (concentration of extract needed to inhibit cell growth by 50%), the most pronounced being for Inolens 50 in MCF7 (IC₅₀ = 9.95 μg mL^?1) and VivOX 20 in HeLa cell line (IC₅₀ = 10.02 μg mL^?1). The obtained results may provide support for the use of tested rosemary extracts as nutraceuticals and phytopharmaceuticals.     

LC-DAD-ESI/MS analysis of flavonoids and abscisic acid with chemometric approach for the classification of Slovenian honey

The flavonoid profiles of seven types of Slovenian honey were analysed. The flavonoids are phenolic compounds that have health-related properties, and their presence in honey is attributed to the plants visited by the bees. The flavonoids were extracted from honey samples by solid-phase extraction and analysed by liquid chromatography, with diode array detection and electrospray ionisation mass spectrometry (LC-DAD-ESI/MS). The honey samples had similar, but quantitatively different, flavonoid profiles. The flavonoids myricetin, luteolin, quercetin, naringenin, apigenin, kaempferol, pinocembrin, chrysin and galangin were identified using reference standards, while pinobanksin was tentatively identified through its retention time, m/z, UV spectrum and MS/MS data. Two non-phenolic compounds were also identified; cis–trans-abscisic acid and, tentatively, trans–trans-abscisic acid. The analysis did not show any specific compounds to use as markers for determination of the botanical origins of these different types of Slovenian honey. Further analyses of more honey samples with additional standards are needed to identify such potential markers, although linear discriminant analysis correctly classified 85% of these honey samples according to their botanical origins.     

The cholesterol content of eggs produced by the Slovenian autochthonous Styrian hen

The cholesterol content of eggs produced by the Slovenian autochthonous Styrian hen in comparison with eggs of the Isa Brown, reared in two different rearing systems, was determined. Eggs were collected four times during the year. The cholesterol content was determined by the enzymatic-spectrophotometric method. The influence of genotype, in two different rearing systems, on the cholesterol content in eggs was studied. The cholesterol content determined in eggs from cages was 13.1 ± 0.43 mg g⁻¹ yolk of the Styrian hens as compared to 11.4 ± 0.49 mg g⁻¹ yolk of Isa Brown hens. The cholesterol content determined in free range eggs was 13.6 ± 0.22 mg g⁻¹ yolk of the Styrian hen and 11.8 ± 0.30 mg g⁻¹ yolk of Isa Brown.