Effect of Processing Variables on the Solution Characteristics of γ-Glycidoxypropyltrimethoxysilane (γ-GPS)

The effects of the hydrolysis and condensation processes on the molecular structure of γ-glycidoxypropyltrimethoxysilane (γ-GPS) in aqueous solutions were investigated using Fourier-transform nuclear magnetic resonance (FT-NMR) spectroscopy and FT-Raman spectroscopy. Hydrolysis was characterized by monitoring the production of methanol and the decrease in concentration of SiOCH₃ groups in 1% solutions of deuterium oxide using proton NMR. The production of methanol and loss of methoxy groups in 25% solutions of γ-GPS in water was characterized using Raman spectroscopy. Hydrolysis was found to be a very rapid process, whose rate could be increased or decreased by altering the pH of the solution. NMR spectroscopy showed that hydrolysis was complete in a 1% γ-GPS solution in deuterium oxide after 34 minutes. Raman spectroscopy also showed hydrolysis to be rapid and complete in a 25% solution of γ-GPS in water after 1 hour. Condensation, on the other hand, took a relatively long time to occur. In the NMR spectra, condensation was observed by the broadening of peaks due to the protons on the carbon atom adjacent to the silicon atom. In the Raman spectra, condensation was characterized by the disappearance of the SiOH band near 725 cm^-1 and the development of an SiOSi band near 600 cm^-1. In addition to the proton NMR, Si-29 NMR was used to characterize the silane in 10% solutions of γ-GPS in water. The Si-29 NMR showed oligomer growth with respect to time. The oligomer growth was correlated with mechanical test results.     

Linking mechanical properties of silanes to their chemical structure: an analytical study of γ-GPS solutions and films

The effects of hydrolysis and condensation processes on the molecular structure of γ-glycidoxypropyltrimethoxysilane (γ-GPS) in aqueous solutions were investigated using Fourier-transform nuclear magnetic resonance (FT-NMR) spectroscopy. Hydrolysis was characterized by monitoring the production of methanol and the decrease in concentration of SiOCH₃ groups in 1% solutions of deuterium oxide using proton NMR. Hydrolysis was found to be a very rapid process, whose rate could be increased or decreased by altering the pH of the solution. NMR spectroscopy showed that hydrolysis was completed in a 1% γ-GPS solution in deuterium oxide after 34 minutes. Condensation, on the other hand, took a relatively long time to occur. In the NMR spectra, condensation was observed by the broadening of peaks due to the protons on the carbon atom adjacent to the silicon atom. In addition to proton NMR, Si-29 NMR was used to characterize the siliane in 10% solutions of γ-GPS in water. The Si-29 NMR showed oligomer growth with respect to time . The oligomer growth was correlated to mechanical test results. Infrared spectroscopy was used to characterized the structure of the γ-GPS as a deposited film on aluminium during drying cycles at elevated temperature. The drying cycles caused increased oligomerization in the silane network and oxidation of the epoxide groups in the film.     

Synthesis of bulk and alumina-supported γ-Mo2N catalysts by a single-step complex decomposition method

A single-step complex decomposition method for the synthesis of bulk and alumina-supported γ-Mo₂N catalysts is described. The complex precursor (HMT)₂(NH₄)₄Mo₇O₂₄·2H₂O (HMT: hexamethylenetetramine) is converted to γ-Mo₂N under a flow of Ar in a temperature range of 823–1023 K. Furthermore, decomposition of the precursor in a NH₃ flow forms γ-Mo₂N in a temperature range of 723–923 K. Compared with direct decomposition of the precursor in Ar, the reaction in NH₃ shows obvious advantages that the nitride forms at a lower temperature. In addition, alumina-supported γ-Mo₂N catalysts with different nitride loadings can be prepared from the alumina-supported complex precursor in the Ar or NH₃ flow. The resultant catalysts exhibit good dibenzothiophene HDS activities, which are similar to the γ-Mo₂N/γ-Al₂O₃ prepared by traditional TPR method. The catalyst prepared by decomposition in an Ar flow exhibits highest activity. It proves that such a single-step complex decomposition method possesses the potential to be a general route for the preparation of molybdenum nitride catalysts.     

The alkylation of naphthalene over three-dimensional large pore zeolites: The influence of zeolite structure and alkylating agent on the selectivity for dialkylnaphthalenes

In order to elucidate how zeolite structure and alkylating agent play roles in the shape-selective catalysis, the alkylation, i.e., isopropylation, sec-butylation, and tert-butylation, of naphthalene (NP) was examined over three-dimensional twelve-membered (12-MR) zeolites, Y (FAU), Beta (BEA), and CIT-1 (CON), and compared to that of H-mordenite (MOR). The β,β-selectivities (for β,β-dialkylnapthalene (β,β-DAN)) and the 2,6-selctivities (for 2,6-dialkylnaphthalene (2,6-DAN)) among DAN isomers varied with the types of zeolites and alkylating agents. FAU, BEA, and CON gave only low selectivities for 2,6-diisopropylnaphthalene (2,6-DIPN) in the isopropylation, and predominant isomers were bulky and thermodynamically unstable ,β-DIPN (1,3-, 1,6-, and 1,7-DIPN) and ,-DIPN (1,4- and 1,5-DIPN) at lower temperatures, and the formation of the less bulky and thermodynamically stable β,β-DIPN (2,6- and 2,7-DIPN) increased with increasing the temperature: they have quite different features from the shape-selective catalysis over MOR. These results suggest that FAU, BEA, and CON are not shape-selective in the isopropylation, and that the isopropylation is principally controlled kinetically at lower temperatures, and thermodynamically at higher temperatures.

The β,β-selectivities over FAU, BEA, and CON increased with increasing the bulkiness of alkylating agents, and were almost 100% in the tert-butylation. On the other hand, the 2,6-selectivities over these zeolites were much lower than those over MOR at a typically moderate temperature, 250 °C. These results mean that FAU, BEA, and CON have the shape-selective nature to give the less bulky isomers, β,β-DAN, in the sec-butylation and tert-butylation by using bulkier alkylating agents, particularly 2-methyl-2-propene: they can differentiate β,β-DAN from their isomers at the transition states by the steric restriction of zeolite channels. However, the channels of these zeolites are too large for differentiating 2,6- and 2,7-DAN even with 2-methyl-2-propene.     

Acidity of dealuminated β-zeolites via coupled nh3-stepwise temperature programmed desorption (STPD) and FT-IR spectroscopy

Ammonia stepwise temperature programmed desorption (STPD) and FT-IR spectroscopy have been used to study the acidity of dealuminated β-zeolites with Si/Al ratios in the range of 14.5 to 132. A carefully optimized temperature profile starting at 150 °C (in order to exclude physisorbed NH₃) revealed five peaks at about 180 °C, 250 °C, 350 °C, 440 °C, and 540 °C. Our investigations indicate that the first two peaks correspond to Lewis-type acidity of low strength and that the last three peaks correspond to Brønsted-type acidity of increasing strength. A one-to-one relation between the total number of ammonia molecules desorbed in the above temperature range and that of the Al atoms exists. High strength Lewis sites were not observed probably because the extent of dehydroxylation in the above temperature range was minimal. By increasing the level of dealumination, it was found that the relative population of strong Brønsted sites increases in comparison with the weak ones. The present stepwise temperature programmed desorption experiments coupled with FT-IR provide a very accurate tool for the quantitative measurement of the strength of the zeolite acid sites.     

Synthesis and thermal stability of potassium substituted hydroxyapatites and hydroxyapatite/β-tricalciumphosphate mixtures

Hydroxyapatite (HAP) and biphasic ceramics of two different HAP and β-tricalcium phosphate (β-TCP) proportions with substituted potassium were prepared through the aqueous precipitation method. The prepared powders were characterized using XRD, FT-IR and elemental analysis. The results have shown that potassium added during the synthesis was found present in the apatite structure even after calcination at 1300 °C without showing any significant change in the phase behaviour of resultant apatites. The substitution of potassium in the calcium deficient apatites was accompanied by the formation of biphasic mixture of HAP and β-TCP ceramics, upon calcination beyond 700 °C and the resultant mixtures were dependent on the initial Ca/P ratios of the precursors. The calculated cell constant values for potassium substituted apatites have shown contraction in a-axis and irregular changes in the c-axis relative to those of pure HAP prepared under the same experimental conditions.     

How metal ions affect amyloid formation: Cu2+- and Zn2+-sensitive peptides

The common feature of proteins involved in many neurodegenerative diseases is their ability to adopt at least two different stable conformations. The conformational transition that shifts the equilibrium from the functional, mostly partially alpha-helical structure, to the beta-sheet rich amyloid can be triggered by numerous factors, such as mutations in the primary structure or changes in the environment. We present a set of model peptides that, without changes in their primary structure, react in a predictable fashion in the presence of transition metal ions by adopting different conformations and aggregate morphologies. These de novo designed peptides strictly follow the characteristic heptad repeat of the alpha-helical coiled-coil structural motif. Furthermore, domains that favor beta-sheet formation have been incorporated to make the system prone to amyloid formation. As a third feature, histidine residues create sensitivity towards the presence of transition metal ions. CD spectroscopy, ThT fluorescence experiments, and transmission electron microscopy were used to characterize peptide conformation and aggregate morphology in the presence of Cu2+ and Zn2+. Furthermore, the binding geometry within peptide-Cu2+ complexes was characterized by electron paramagnetic resonance spectroscopy.     

Development of a ligation-based impedimetric DNA sensor for single-nucleotide polymorphism associated with metabolic syndrome

Single-nucleotide polymorphism (SNP) detection is becoming important in molecular diagnostics, clinical assay, and novel drug development. Electrochemical methods are well suited for the DNA diagnostics system. Since electrochemical reactions directly emit an electronic signal, expensive signal transduction equipment is not required. We describe the development of a novel DNA sensor that utilizes impedance spectroscopy and DNA ligation reaction on a gold electrode. Impedance spectroscopy enables label-free detection and is nondestructive and useful in equivalent circuit models for interpretation on an electrode surface, whereas from the ligation reaction, the specificity is derived by the allele-specific oligonucleotide of the capture probe on immobilized gold electrode. In other words, DNA diagnostics system using the combination of impedance spectroscopy and ligation reaction is simple, rapid, and allele specific. In this report, we have described a ligation-based impedimetric DNA sensor and the analysis of Trp64Arg polymorphism in the beta3-adrenergic receptor gene (ADRβ3).     

Lipid components of flax,perilla, and chia seeds

Composition of fatty acids, tocopherols, sterols, and TAGs in the lipids of flax, perilla, and chia seeds were investigated where lipid content was at 45, 40, and 35%, respectively. α‐Linolenic acid (ALA) dominated among fatty acids in all oils and accounted for 58.2, 60.9, and 59.8% in flax, perilla, and chia, correspondingly in these three oils trilinolenin was the main TAG found at 19.7, 22.6, and 21.3%. Triunsaturated TAGs accounted for 77.9, 77.5, and 74.5% of the total amounts in flax, perilla, and chia oils. Contents of tocopherol were at 747 in flax, 734 in perilla, and 446 mg/kg in chia seed lipids. γ‐Tocopherol was the dominating isomer contributing 72.7% in flax, 94.3% in perilla, and 94.4% in chia to the total amount of tocopherols. Flaxseed lipids contained 25.6% of plastochromanol‐8, derivative of γ‐tocotrienol with longer side chain; perilla and chia oils contained only 1.4% of it. Phytosterols were present at 4072, 4606, and 4132 mg/kg in those seeds, respectively. Among sterols, β‐sitosterol dominated and was found at 35.6, 73.3, and 49.8% of the total amounts of sterols in flax, perilla, and chia seed lipids. All of the investigated oilseeds have an excellent nutritional quality and can be a potential source of nutraceutical fats which can enrich diet in linolenic acid and other functional components.     

Catalytic activity of zeolites for synthesis reaction of methylenedianiline from aniline and formaldehyde

The catalytic activities of Y-, β-, and ZSM-5-zeolites for methylenedianiline (MDA) synthesis from the condensation reaction of aniline and formaldehyde have been investigated. Among β-zeolites with various Al concentrations (Si/Al ratios from 10 to 120 mol mol⁻¹), β-zeolite with Si/Al ratio of 13.6 mol mol⁻¹ shows the best catalytic performance in MDA synthesis. Y-zeolite exhibited lower catalytic activity than β-zeolites under the identical reaction conditions, however, exhibited the higher selectivity to 4,4′-MDA. Furthermore, it revealed that aniline/formaldehyde and catalyst/formaldehyde ratio, and reaction temperature also influenced on the MDA yield and isomers distribution.     

Validation of the oxygen radical absorbance capacity (ORAC) parameter as a new index of quality and stability of virgin olive oil

The induction period (IP), determined using accelerated methods such as the Rancimat test, is a parameter that has been used to predict the shelf life of virgin olive oil. The oxygen radical absorbance capacity (ORAC) has recently been proposed as a quality index of virgin olive oil because it measures the efficiency of phenolic compounds in the protection against peroxyl radicals. This study aims to investigate relationships between the ORAC and IP values and proposes ORAC as a new parameter of virgin olive oil stability. The concentrations of phenolics, o-diphenols, tocopherol, β-carotene, lutein, and ORAC and IP values were determined in 33 virgin olive oils. Regression analyses showed that both ORAC and IP values correlate with total phenols and o-diphenols with highly significant indices, whereas the correlations of both ORAC and IP with tocopherols, β-carotene, and lutein were not significant. The ORAC values correlate with the IP values with low but significant indices (R=0.42; P<0.02). The results confirm the key role of phenolic compounds in accounting for the shelf life of virgin olive oil and suggest that the ORAC parameter may be used as a new index of quality and stability.     

Supercritical CO2 extraction of biological active compounds from loquat seed

Amygdalin and β-sitosterol from roasted powder and ground unroasted loquat seed were extracted using supercritical CO₂. Loquat seed is the waste of loquat fruit (Eribotrya japonica), that called biwa in Japan. Loquat seed contains some active compounds, such as amygdalin, sterol and β-sitosterol. Amygdalin is used for medical purposes, mainly as drug in cancer. β-Sitosterol is found in health supplement for various physical ailments. In this work, extraction was conducted at pressure of 20, 30 and 45 MPa, temperature of 40, 60 and 80 °C, and CO₂ flow rate of 3 ml/min for 180 min. Roasted powder and ground unroasted loquat seeds were used as materials. Component in extract was analyzed by HPLC carried out on 5C18-MS column at 27 °C for amygdalin, and 35 °C for β-sitosterol using acetonitrile:water (85:15 v/v) as mobile phase. Based on results, a change in temperature and pressure affected the yield of total extract, amygdalin and β-sitosterol recovery. For comparison between extract from roasted powder and ground unroasted loquat seed, total extract and β-sitosterol recovery from roasted powder loquat seed were higher than that from unroasted one. On the other hand, amygdalin recovery from ground unroasted seed was much higher than that from roasted powder. The optimum condition of extract from roasted powder and ground unroasted loquat seed and amygdalin recovery were obtained at 80 °C and 20 MPa.     

Cathodic Delamination of an Epoxy/Polyamide Coating from Steel

X-ray photoelectron spectroscopy (XPS) has been used to determine the mechanism responsible for debonding of an epoxy/polyamide coating from steel during cathodic delamination in 3.5% aqueous NaCl solutions. Coating failure always occurred near the interface between the coating and the oxide. The nitrogen content of the free surface of the prepared coatings was about 10%. However, the nitrogen content of the free surface dropped to only 5% after exposure to 1 N NaOH for four weeks and that of the coating failure surface after cathodic delamination was only about 2%, implying that the failure involved degradation of the polyamide curing agent by hydroxide ions formed at the steel surface by reduction of oxygen. That conclusion was supported by results obtained from curve fitting of C(1s) and O(1s) spectra. The intensity of components in the C(1s) spectra due to C—N and C≡O bonds in amide functional groups decreased significantly after coatings were exposed to NaOH or subjected to cathodic delamination. Small amounts of organic materials characteristic of the coating were observed on the substrate failure surface, perhaps indicating that the failure was cohesive within the coating but very close to the interface or that some products from degradation of the curing agent precipitated on the substrate. Use of silane coupling agents to retard cathodic delamination was also investigated. Coupling agents were added directly to the coating or applied to the substrate as a primer before application of the coating. Significant reduction in the rate of cathodic delamination was seen only when the silane coupling agent was applied to the substrate and cured at elevated temperatures before the epoxy/polyamide coating was applied.     

Oxidative stability during storage of structured lipids produced from fish oil and caprylic acid

Structured lipids produced by enzymatic or chemical methods for different applications have been receiving considerable attention. The oxidative stability of a randomized structured lipid (RFO), produced by chemical interesterification from fish oil (FO) and tricaprylin, and a specific structured lipid (SFO), produced by enzymatic interesterification from the same oil and caprylic acid, was compared with the stability of FO. Oils were stored at 2°C for 11 wk followed by storage at 20°C for 6 wk. In addition, the antioxidative effect of adding the metal chelators EDTA or citric acid to SFO was investigated. FO contained the largest amount of PUFA and RFO the lowest. However, SFO had a higher PV initially and during storage at 2°C, whereas the PV of FO was highest during storage at 20°C. The level of volatile oxidation products was highest in SFO during the entire storage period, and off-flavors were more pronounced in SFO. The lower oxidative stability of SFO was probably related to the initially lower quality (regarding oxidation products), which is apparently a result of the long production procedure required. Addition of metal chelators did not reduce the oxidation of the SFO.     

Profile of Bioactive Compounds in Avocado Pulp Oil: Influence of the Drying Processes and Extraction Methods

The influence of different procedures of pulp drying and oil extraction methods on the concentrations of α-tocopherol, squalene and several phytosterols in avocado oil was evaluated. Pulp portions of Fortune variety avocados were dried either by lyophilization or under circulating air at 40 or 70 °C. For lyophilization and for each air drying temperature, the oil was obtained either by cold pressing or with Soxhlet extraction using petroleum ether. The dehydrated pulp (73 % of the pulp weight) yielded 25–33 % oil by cold pressing, and 45–57 % oil by Soxhlet extraction. Infrared spectroscopy and gas chromatography with FID and mass spectrometry detection were used to analyze the oils. α-Tocopherol, squalene, cycloartenol acetate, β-sitosterol, campesterol and stigmasterol were present in all the oil samples. In comparison to lyophilization, hot air drying resulted in smaller concentrations of α-tocopherol, squalene and β-sitosterol, and larger relative concentrations of campesterol and cycloartenol acetate. On the other hand, extraction by cold pressing produced a smaller amount of oil, with greater concentrations of α-tocopherol and squalene, and lower contents of campesterol and cycloartenol acetate, than Soxhlet extraction. Thus, the oil yield was maximal with lyophilization and Soxhlet extraction, but lyophilization and cold pressing produced oils which had greater concentrations of antioxidants and other bioactive compounds.     

Hydrodesulfurization activity of CoMo and NiMo supported on Al2O3–TiO2 for some model compounds and gas oils

Catalytic activities of Al₂O₃–TiO₂ supporting CoMo and NiMo sulfides (CoMoS and NiMoS) catalysts were examined in the transalkylation of isopropylbenzene and hydrogenation of naphthalene as well as the hydrodesulfurization (HDS) of model sulfur compounds, conventional gas oil (GO), and light cycle oil (LCO). Al₂O₃–TiO₂ supporting catalysts exhibited higher activities for these reactions except for the HDS of the gas oil than a reference Al₂O₃ supporting catalyst, indicating the correlation of these activities. Generally, more content of TiO₂ promoted the activities. Inferior activity of the catalyst for HDS of the gas oil is ascribed to its inferior activity for HDS of dibenzothiophene (DBT) in gas oil as well as in model solvent decane, while the refractory 4,6-dimethyldibenzothiophene (4,6-DMDBT) in gas oil as well as in decane was more desulfurized on the catalyst. Characteristic features of Al₂O₃–TiO₂ catalyst are discussed based on the paper results.     

Formation of β-modification of isotactic polypropylene in its late stage of crystallization

In the late stage of the crystallization of isotactic polypropylene (IPP), melt inclusions are encapsulated by the crystallized phase. The contraction caused by the proceeding crystallization within the inclusion leads to a reduced pressure accompanied by the appearance of vacuum bubbles. In the surface layer of the melt surrounding the vacuum bubbles, the polymer chains are subjected to extension during the development of bubbles, which leads to the formation of -row nuclei. As has been observed during the shear-induced crystallization of IPP, the row-nuclei formed in situ can also induce the growth of the β-phase in this case. It was demonstrated that a possible reason for the — β transition on the surface of growing -spherulites is the local mechanical stress caused by the contraction. Based on experimental results, suggestions are made for the origin of the strongly birefringent phase observed by Duval et al. during the crystallization of blends of IPP and IPP grafted with maleic anhydride.