Mechanistic study of Sn(Oct)2‐catalyzed ε‐caprolactone polymerization using Sn(Oct)2/BF3 dual catalyst

A novel method was used to investigate the mechanism of Sn(Oct)₂‐catalyzed ε‐caprolactone polymerization by using Sn(Oct)₂/BF₃ dual catalyst. The bulk polymerization was conducted at 110 and 130°C with different Sn(Oct)₂/BF₃ ratios. The polymerization kinetics was followed using gel permeation chromatography, and the molecular structures of the low‐molecular weight polymers were examined using ¹H‐nuclear magnetic resonance (NMR). A polymerization induction period was observed in polymerizations containing the Sn(Oct)₂ catalyst, but it was not observed in the system containing only BF₃. After the induction period, BF₃ and Sn(Oct)₂ initiated the polymerization separately. For Sn(Oct)₂ catalyst with no purposely added alcohol, the actual initiation species is a tin hydroxide species formed in situ by the reaction of Sn(Oct)₂ and adventitious water. For BF₃ catalyst, the active species is the protonic acid formed by the reaction of BF₃ with the adventitious water. When mixed, the Sn(Oct)₂ reacts with the adventitious water faster than the BF₃, preventing the BF₃ catalyzing any polymerizations during the induction period. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Volatile organic compound concentrations and emission rates in new manufactured and site-built houses

Concentrations of 54 volatile organic compounds (VOCs) and ventilation rates were measured in four new manufactured houses over 2-9.5 months following installation and in seven new site-built houses 1-2 months after completion. The houses were in four projects located in hot-humid and mixed-humid climates. They were finished and operational, but unoccupied. Ventilation rates ranged from 0.14-0.78 h-1. Several of the site-built houses had ventilation rates below the ASHRAE recommended value. In both manufactured and site-built houses, the predominant airborne compounds were alpha-pinene, formaldehyde, hexanal, and acetic acid. Formaldehyde concentrations were below or near 50 ppb with a geometric mean value for all houses of 40 ppb. Similarities in the types of VOCs and in VOC concentrations indicated that indoor air quality in the houses was impacted by the same or similar sources. Major identified sources included plywood flooring, latex paint and sheet vinyl flooring. One site-built house was operated at ventilation rates of 0.14 and 0.32 h-1. VOC emission rates calculated at the two conditions agreed within +/- 10% for the most volatile compounds. Generally, the ratios of emission rates at the low and high ventilation rates decreased with decreasing compound volatility. Changes in VOC emission rates in the manufactured houses over 2-9.5 months after installation varied by compound. Only several compounds showed a consistent decrease in emission rate over this period.     

2D-LC analysis of BRP 3 erythropoietin N-glycosylation using anion exchange fractionation and hydrophilic interaction UPLC reveals long poly-N-acetyl lactosamine extensions

Post-translational modifications, in particular glycosylation, represent critical structural attributes that govern both the pharmacodynamic and pharmacokinetic properties of therapeutic glycoproteins. To guarantee safety and efficacy of recombinant therapeutics, characterization of glycosylation present is a regulatory requirement. In the current paper, we applied a multidimensional strategy comprising a shallow anion exchange gradient in the first dimension, followed by analysis using the recently introduced 1.7 μm HILIC phase in the second dimension for the comprehensive separation of complex N-glycans present on the European Biological Reference Preparation (BRP) 3 erythropoietin standard. Tetra-antennary glycans with multiple sialic acids and poly-N-acetyl lactosamine extensions were the most abundant oligosaccharides present on the molecule. Site-specific glycan analysis was performed to examine microheterogeneity. Tetra-antennary glycans with up to four sialic acids and up to five poly-N-acetyl lactosamine extensions were observed at asparagine 24 and 83, while biantennary glycans were the major structures at asparagine 38. The combined AEC x UPLC HILIC allows for the rapid and comprehensive analysis of complex N-glycosylation present on therapeutic glycoproteins, such as BRP3 erythropoietin.     

A comparison of flavonoids,carotenoids and vitamin C in commercial organic and conventional marinara pasta sauce

BACKGROUND: Characterising the levels of key phytochemicals in foods commonly consumed in the Western diet is critical for database development, estimating intake and assessing the potential health benefits associated with the consumption of these products. This paper describes a market‐basket evaluation of the key flavonoids, carotenoids and vitamin C in commercial organic (five brands) and conventional (five brands) marinara pasta sauces. RESULTS: Levels of ascorbic acid ranged from undetected up to 6.87 mg per 100 g fresh weight. The levels of total vitamin C in six of the ten samples were significantly lower than the amount listed on the Nutrition Facts Panel (P < 0.001 or P < 0.01). The contents of total vitamin C, flavonoids and lycopene were not statistically different between organic and conventional samples. Conventional pasta sauces demonstrated a significantly higher level of all‐trans‐β‐carotene (P < 0.05). CONCLUSION: This suggests that any beneficial differences in levels of flavonoids, carotenoids and vitamin C gained through cultivation practices are not measurable at the consumer level in processed tomato products. Additionally, the results point to a large disparity between the actual vitamin C content of these products and the content listed on the Nutrition Facts Panel. Copyright © 2007 Society of Chemical Industry     

Modeling the deformation of thermoformable random fiber reinforcements during preform manufacture

Liquid molding processes have been identified by the automotive and aerospace industries as having potential for structural and semistructural applications. Of the several obstacles to their more widespread use, the major drawback is the lack of an automated and reliable technology for producing reinforcement preforms. Current preform technology is usually based on the forming of continuous fiber mats or fabrics between matched molds. This can result in defects within the fiber structure including wrinkling, thinning, and, in extreme cases, tearing. To understand and eliminate these defects, it is necessary to develop a simulation of the preforming process. This paper is aimed at developing a mathematical model of the deformation of thermoformable continuous filament random mat. The analysis presented is based on plasticity theory, suitably modified to describe the behavior of fiber reinforcements. This is demonstrated for the stretch-forming of reinforcement using arbitrary axisymmetric punch and die profiles. Experimental work is included to demonstrate the effect of varying a range of process parameters, including rate of forming, reinforcement temperature, and stack thickness. The Validity of the model is demonstrated for a number of punch geometries.