Formation of triphenylmethyl cation during the photolysis of phenylazotriphenyl methane: a laser flash photolysis study

The photolysis of phenylazotriphenyl methane (PAT) in dichloromethane and acetonitrile solution at λ_inc = 347nm and at 23°C results in the formation of triphenyl methyl (trityl) radicals and trityl ions. The quantum yields in dichloromethane solution are Φ(Ph₃C^•) = 0·060 and Φ(Ph₃C⁺) = 0·004. Trityl ions are assumed to be formed by electron transfer between radicals formed by the photodecomposition of PAT. The yield of trityl ions is significantly increased upon irradiation of PAT solutions containing also an onium salt (N-ethoxy-2-methyl pyridinium hexafluorophosphate; (EMP⁺PF₆^-). This is due to the oxidation of trityl radicals by EMP⁺ ions. Trityl ions generated in this way were found to be capable of initiating the cationic polymerization of cyclohexene oxide. © 1998 SCI.     

Determination of polyphenolic constituents and biological activities of bark extracts from different Pinus species

BACKGROUND: The most common commercially available pine bark extract is Pycnogenol^®, a standardised extract of Pinus maritima, which has been reported to have cardiovascular benefits and enhance microcirculation. The present study was conducted to determine the chemical composition of four pine bark extracts, assess their biological activities and to compare the results with Pycnogenol^®. RESULTS: The Pinus species were analysed by LC and LC‐MS; extracts of P. brutia and P. nigra showed higher levels of phenolic constituents compared to P. sylvestris and P. pinea. In particular, P. brutia contained extremely high concentrations of taxifolin (18.5%). The highest radical scavenging activities were attained with P. pinea (88.6%), P. nigra (87.2%) and P. brutia (86.4%) bark extracts. Additionally, anticarcinogenic effects of the extracts and their kinetics were determined in four cell lines including human prostate (PC‐3, DU 145, LNCaP) and breast adenocarcinoma (MCF7) by the MTT assay. Cell viability was reduced to 40% by extracts of P. pinea, and P. sylvestris in PC‐3 cells showing a similar effect like the positive control, CPT‐11. CONCLUSION: Pinus species other than P. maritima definitively possess high biological activities, and therefore present a huge potential to be utilised in the food and the pharmaceutical industries. Copyright © 2009 Society of Chemical Industry     

Thermodynamic analysis and experimental investigation of a unique photoelectrochemical hydrogen production system

In this study, we thermodynamically analyze and experimentally investigate a continuous type hybrid photoelectrochemical H₂ generation reactor. This system enhances solar spectrum use by employing photocatalysis and PV/T. Additionally, by replacing electron donors with electrodes to drive the photocatalysis, the potential of pollutant emissions are minimized. In this study, the present reactor is tested under electrolysis operation during which the present reactor is investigated under three different inlet mass flow rates (0.25, 0.50, and 0.75 g/s) and four different operating temperatures (20, 40, 60, and 80 °C). Some parametric studies are run by varying the environmental temperature between 0 and 40 °C. In addition, the impact of coating the membrane electrode assembly of the reactor with Cu₂O is investigated. The present results show that the highest energy and exergy efficiencies occur at the environmental temperature of 20 °C which is about 60% and 50%, respectively. The Cu₂O coated membrane gives a lot higher current readings, meaning that the coating makes the membrane more conductive and increases H₂ production by permitting ions at a higher rate.     

Lot-splitting approach of a hybrid manufacturing system under CONWIP production control: a mathematical model

This paper discusses the advantages of lot splitting in hybrid manufacturing environments where cellular and functional layouts are combined under Constant Work in Process (CONWIP) production control. The proposed model fills a research gap in the related literature by applying lot splitting and pull production simultaneously. A linear CONWIP control mathematical model that minimises the average flow time is developed in case of lot splitting. The developed model has sequence-dependent set-up times. The demand level, coefficient of variation (CV) impact and set-up time reduction effect on CONWIP production control are also investigated. The model is solved using GAMS21.6 optimisation software; the optimal backlog list, the number and size of sublots are reported. The proposed model is compared with lot production under push control in different settings as well as with two different heuristics from the literature. Experimental results indicate that in all settings, the lot splitting is more advantageous than lot production in terms of average flow time. CV has a greater effect than set-up time reduction on average flow time.     

Advances in Thermal Spray Coatings for Gas Turbines and Energy Generation: A Review

Functional coatings are widely used in energy generation equipment in industries such as renewables, oil and gas, propulsion engines, and gas turbines. Intelligent thermal spray processing is vital in many of these areas for efficient manufacturing. Advanced thermal spray coating applications include thermal management, wear, oxidation, corrosion resistance, sealing systems, vibration and sound absorbance, and component repair. This paper reviews the current status of materials, equipment, processing, and properties’ aspects for key coatings in the energy industry, especially the developments in large-scale gas turbines. In addition to the most recent industrial advances in thermal spray technologies, future technical needs are also highlighted.     

Shape memory behavior of high strength NiTiHfPd polycrystalline alloys

Systematic characterization of the shape memory properties of a quaternary Ni_45.3–Ti_29.7–Hf₂₀–Pd₅ (at.%) polycrystalline alloy was performed in compression after selected aging treatments. Precipitation characteristics were revealed by transmission electron microscopy. The effects of aging temperature and time on transformation temperatures, recoverable and residual strains, and temperature and stress hystereses were determined by differential scanning calorimetry, constant-load thermal cycling experiments and isothermal strain cycling (superelasticity) tests. The crystal structure and lattice parameters of the transforming phases were determined from X-ray diffraction analysis. It was revealed that precipitation hardening significantly improved the shape memory properties of the NiTiHfPd alloy. Under optimum aging conditions, shape memory strains of up to 4% under 1 GPa were possible, and superelasticity experiments resulted in full strain recovery without any plastic deformation, even at stress levels as high as 2 GPa. The NiTiHfPd polycrystalline alloy exhibited very high damping capacity/absorbed energy (30–34 J cm^?3) and work output (30–35 J cm^?3), which were attributed to the ability to operate at high stress levels without significant plastic deformation and to a high mechanical hysteresis (>900 MPa) at temperatures ranging from 20 °C to 80 °C.     

Obtaining Butter Oil Triacylglycerols Free from β-Carotene and α-Tocopherol via Activated Carbon Adsorption and Alumina-Column Chromatography Treatments

It is difficult to remove β-carotene from oils with alumina-column chromatography, because β-carotene is even less-polar than triacylglycerols (TAGs) are. The objective of this study was to obtain butter oil TAGs free from β-carotene and antioxidants via sequential treatments with activated carbon (AC) adsorption and alumina column chromatography. The AC used was prepared from waste apricots. The effects of AC dosages, temperatures and time courses on β-carotene adsorption were studied. The Langmuir and Freundlich isotherms were used to describe the adsorption of β-carotene onto AC, and it was found to be more consistent with the Freundlich isotherm with a higher R ² value (0.9784). Adsorption kinetics of β-carotene was analyzed by pseudo-first order and pseudo-second order models. The pseudo-second order model was found to explain the kinetics of β-carotene adsorption more effectively (R ² = 0.9882). The highest β-carotene reduction was achieved (from 31.9 to 1.84 mg/kg) at an AC dosage of 10 wt%, temperature of 50 °C, and adsorption time of 240 min. A considerable amount of α-tocopherol was also adsorbed during the AC treatment. Remaining portions of α-tocopherol were completely removed with alumina adsorption chromatography. The method described may be used for purification of vegetable oil TAGs, which will be used as model compounds in model oxidation studies.     

Thermal oxidative degradation kinetics and thermal properties of poly(ethylene terephthalate) modified with poly(lactic acid)

The thermal oxidative degradation kinetics of poly(ethylene terephthalate) (PET) copolymers modified with poly(lactic acid) (PLA) were investigated with thermogravimetric analyzer (TGA). The thermal properties of the modified products were also determined by differential scanning calorimeter (DSC) technique. Waste PET (P100) obtained from postconsumer water bottles was modified with a low‐molecular‐weight PLA. The PET/PLA weight ratio was 90/10 (P90) and 50/50 (P50) in the modified samples. The thermal oxidative degradation kinetics of the modified samples was compared with those of PET (P100). The segmented block and/or random copolymer structure of the modified samples formed by a transesterification reaction between the PLA and PET units in solution and the length of the aliphatic and aromatic blocks were found to have a great effect on the degradation behavior. On the basis of the results of the degradation kinetics determined by Kissinger method, the degradation rate of the samples decreased in the order of P50 > P90 > P100, depending on the amount of PLA in the copolymer structure. However, the degradation activation energies (E_A) of the samples decreased in the order of P100 > P90 > P50. It was concluded that the degradation rate and mechanism were affected significantly by the incorporation of PLA into the copolymer structure. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Estimation of strength and deformation properties of Quaternary caliche deposits

The aim of this study was to develop and evaluate statistical models for predicting the uniaxial compressive strength (UCS) and average Young’s modulus (E _av) for caliches, using some index and physical properties. The caliche samples, from Adana, southern Turkey, were of low strength and difficult to sample. X-ray diffraction and microscopy were undertaken and the following physical parameters established: unit weight, apparent porosity, Schmidt rebound number, Shore hardness, P-wave velocity, slake durability, point load, uniaxial compressive strength and average Young’s modulus. Simple and linear regression variable selection analyses were performed. The best relationships were obtained for UCS with P-wave velocity and unit weight and for average Young’s modulus with P-wave velocity, porosity and slake durability. Empirical equations are proposed, although it is emphasised that these may only be applicable for caliche of a similar geological character.      

Synthesis and characterization of polyimide/hexagonal boron nitride composite

Polyimide (PI)/hexagonal boron nitride (h‐BN) composites were produced via the thermal imidization procedure from solution mixtures of a polyamicacid, which is prepared from 3,3′,4,4′‐benzophenonetetracarboxylic dianhydride and 3,3′‐diaminodiphenyl sulfone (DADPS) in N‐methyl‐2‐pyrrolidone (NMP), and alkoxysilane functionalized h‐BN. The structure, thermostability, thermal behavior, and surface properties of the resulting materials were characterized by means of Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), scanning electron microscopy (SEM). The thermal characteristics of PI/h‐BN films were better than the pure PIs. The physical and mechanical properties of the films were evaluated by various techniques such as contact angle, chemical resistance, and tensile tests. The flame retardancy of the composite materials was also examined by the limiting oxygen index (LOI). The experiments showed that the LOI values of PIs increased from 32 to 43 for the materials containing hexagonal boron nitride. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012