Migration of α-tocopherol from LDPE films to corn oil and its effect on the oxidative stability

The migration of α-tocopherol (α-T) from low density polyethylene (LDPE) films, added with 20 (film A) and 40 mg g^?1 (film B) to corn oil for 12 weeks at 5, 20 and 30 °C was determined. A LDPE film added with no α-T was used as control (film C). Diffusion coefficient (D) values for the film A system were 1.4 × 10^?11, 7.1 × 10^?11 and 30.3 × 10^?11 cm² s^?1 at 5, 20 and 30 °C, respectively. Meanwhile, D values for the film B system were 1.3 × 10^?11, 9.6 × 10^?11 and 51.1 × 10^?11 cm² s^?1 at the same temperatures. The activation energy (E_a) for the diffusion of α-T was 126.5 (film A) and 105.9 kJ mol^?1 (film B). The effect of the migration of α-T on the oxidative stability of corn oil was evaluated by monitoring hexanal content by solid phase micro-extraction (SPME) and gas chromatography. The hexanal content in the oil showed that both films added with α-T resulted suitable to maintain the oxidative stability of the oil for about 16 weeks at 30 °C, compared to 12 weeks for the oil in contact with the film C.     

Formation of mesoglobules in aqueous media from thermo-sensitive poly(ethoxytriethyleneglycol acrylate)

A series of six poly(ethoxytriethyleneglycol acrylate) (PETEGA) homopolymers were synthesized by atom transfer radical polymerization, reversible addition-fragmentation transfer polymerization, and anionic polymerization in order to cover a molecular weight range from 7,000 to 40,000 Da. The polymers exhibited a lower critical solution temperature (LCST) behavior in water, which was observed by the occurrence of a cloud point (CP) at around 35 °C. The transmittance of visible light versus temperature dependence overlapped during the cooling and the heating cycles, showing almost a complete lack of hysteresis. Moreover, instead of the occurrence of an uncontrolled macroscopic phase separation, stable colloidal aggregates (mesoglobules) of narrow distribution in particle size were formed in water at temperatures above the LCST of PETEGA at 1 g L⁻¹ solutions. The dimensions of the mesoglobules ranged from 91 to 235 nm, and particle size was not influenced by the molecular weight of PETEGA. Temperature changes caused considerable variations of the mesoglobules dimensions, which were smaller at higher temperatures. The addition of an anionic surfactant simultaneously increased the CP values by 4–6 °C and lowered the dimensions of the mesoglobules.     

Decision making and set shifting impairments are associated with distinct symptom dimensions in obsessive-compulsive disorder.

Obsessive- compulsive disorder (OCD) is clinically heterogeneous. The authors examined how specific OCD symptom dimensions were related to neuropsychological functions using multiple regression analyses. A total of 39 OCD patients and 40 controls completed the Iowa Gambling Task (IGT; A. Bechara, A. R. Damasio, H. Damasio, & S. W. Anderson, 1994), which is a test of decision making, and the Wisconsin Card Sorting Test (R. K. Heaton, 1981), which is a test of set shifting. OCD patients and controls showed comparable decision making. However, patients with prominent hoarding symptoms showed impaired decision making on the IGT as well as reduced skin conductance responses. OCD patients had poorer set shifting abilities than controls, and symmetry/ordering symptoms were negatively associated with set shifting. These results help explain previous inconsistent findings in neuropsychological research in OCD and support recent neuroimaging data showing dissociable neural mechanisms involved in mediating the different OCD symptom dimensions. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Modeling high-concentration L-band EDFA at high optical powersbased on inversion function

High-concentration erbium-doped fibers used in L-band erbium-doped fiber amplifier (EDFA) are known to experience additional losses due to effects of energy transfer between Er³⁺ ions and possibly quenchers (e.g., homogeneous and clustering-induced up-conversion, quenching, etc.). These interactions between Er³⁺ ions make modeling of inversion dynamics in L-band EDFA more complicated. We present a modeling approach for high-concentration doped fiber based on lumping of all complex phenomena of energy transfer in EDFA into a function of two variables hereafter referred to as the inversion function. The inversion function is evaluated for high optical powers (which constitutes a typical situation for fiber amplifiers) using a cluster expansion and assuming that upconversion is the leading loss mechanism. The modeling results show a close agreement with the measurement data for various input power conditions and inversion levels     

Stochastic approach to the modeling and optimization of thermal spray coating formation

Application of the stochastic process theory is proposed for the modeling and optimization of the thermal spray process (TSP). The advantages of the approach suggested are illustrated by estimation of the“integral” thermal conditions of TSP coating formation, as well as the formation characteristics of the first monolayer coating. Modeling results are in reasonable agreement with bond strength test data for the plasma-, arc-, and flame-spray processes as well as wear resistance data for arc-sprayed steel coatings.