Extraction of polymer stress–strain behavior in the presence of self‐heating by the use of a simple model for the elastic–plastic deformation

Polymer materials are well known to be sensitive to strain rate and temperature. Self‐heating and friction effects also play an important role in the mechanical response of these materials. Numerous constitutive laws and phenomenological models have been developed to take into account these dependencies. This article proposes a simplified phenomenological model based on a mapping technique for the strain rate and temperature dependence. The effects of friction and adiabatic heating are also analyzed in this work. Relatively good results are obtained compared to experimental results for polypropylene and polychlorotrifluoroethylene. A parametric investigation of the effects of the interfacial equivalent stress (between the specimen and the compressive bars) and the fraction of plastic work converted into heat was performed. This parametric study allowed for a good approximation of these two parameters for the two studied polymers. POLYM. ENG. SCI., 55:2474–2481, 2015. © 2015 Society of Plastics Engineers     

Emulsifying and foaming properties of native and chemically modified peptides from the 2S and 12S proteins of rapeseed (Brassica napus L.)

The 2S and 12S proteins of rapeseed were isolated and subsequently hydrolyzed by pepsin or a combination of pepsin plus trypsin. The resulting hydrolysates had a 15% degree of hydrolysis and were purified by gel filtration chromatography in order to obtain homogeneous peptide fractions. Three major fractions, having an average peptide chain length of 7.5–11 amino acids, were recovered. Purified peptide fractions were acylated with butyric anhydride and sulfamidated with p-toluenesulfonyl chloride. The degree of modification was always higher than 90%. Emulsifying and foaming properties of native and chemically modified peptides were studied and compared to those of sodium dodecyl sulfate (SDS) as standard. A peptide fraction from the 15% hydrolysis of the 12S protein exhibited the best foaming properties. After sulfamidation, this peptide fraction showed a foam formation similar to that of SDS. Whereas the attachment of toluene groups generally improved the surface properties, the incorporation of an aliphatic chain of four atoms of carbon was detrimental in most of the cases. On the other hand, none of the native or hydrophobized peptide fractions was able to form a stable emulsion.     

Experimental proof of the existence of mass‐transfer resistance during early stages of ethylene polymerization with silica supported metallocene/MAO catalysts

The size of a silica supported metallocene/MAO (methylaluminoxane) catalyst plays an important role in determining its productivity during ethylene polymerization. From a chemical engineering point of view, this size dependency of catalytic activity of supported metallocenes is mathematically connected with the different levels of mass‐transfer resistance in big and small catalyst particles but no experimental evidence has been provided to date. The results of this systematic experimental study clearly demonstrate that the intraparticle monomer diffusion resistance is high in bigger catalyst particles during initial instants of ethylene polymerization and diminishes with the polymer particle growth. Two different silica supported metallocene/MAO catalysts provided the same results while highlighting the fact that catalyst chemistry should be carefully considered while studying complex chemical engineering problems. © 2017 American Institute of Chemical Engineers AIChE J, 63: 4476–4490, 2017     

Two‐dimensional modeling of an absorbing falling film in its development zone

This work presents the modeling of a vertical falling film expanding or shrinking from the inlet manifold. Considering a stationary approach, the film shape, the flow field and the absorption rate of an ambient gas are computed. For the flow field, one dimensional (1‐D) second‐order weighted integral boundary layer (WIBL) model is shown to accurately reproduce the film deformations. The gas transfer is then solved in a 2‐D predeformed domain to investigate the impact of the film deformations on the gas absorption rate. It is found that a significant mass transfer enhancement, as compared to a flat film, is obtained when the film is expanding due to the concomitant increase of the concentration gradient perpendicular to the interface. On the contrary, a slight hindrance of the mass transfer is observed when the film is shrinking, although it remains in this case very close to the flat film analytical solution. © 2017 American Institute of Chemical Engineers AIChE J, 63: 4370–4378, 2017     

Evaluation of Simple and Inexpensive High-Throughput Methods for Phytic Acid Determination

High‐throughput/low‐cost/low‐tech methods for phytic acid determination that are sufficiently accurate and reproducible would be of value in plant genetics, crop breeding and in the food and feed industries. Variants of two candidate methods, those described by Vaintraub and Lapteva (Anal Biochem 175:227–24, 1988 ; “VL” methods) and Huang and Lantzsch (J Sci Food Agric 34:1423–1426, 1983 ; “HL” methods), were evaluated. The primary concern with these methods is that, due to interference of matrix constituents including inorganic P, they can overestimate phytic acid and are ineffective at low levels of phytic acid. Twelve seed flours, representing lines of soybean, maize, barley and dry bean, containing a wide range of phytic acid levels, were analyzed by a minimum of eight cooperating laboratories using three variants of the VL method and two variants of the HL method. No method had consistently acceptable (?2.0”) “Horwitz ratios”, a measure of reproducibility, although some treatments approached that. For example, one variant of the VL method when used to assay a soybean flour with a “standard” level of phytic acid had a Horwitz ratio of 2.15. Some variants of the VL method were adequate for analyses of cereal grains regardless of phytic acid level but none accurately measured phytic acid when at low levels in soybean flours. One variant of the HL method in which the 0.2 N HCl extraction media is modified to contain 10% Na₂SO₄, did accurately measure phytic acid levels in both cereal and legume flours regardless of endogenous phytic acid levels or matrix constituents.     

Effects of urban coarse particles inhalation on oxidative and inflammatory parameters in the mouse lung and colon

Background

Air pollution is a recognized aggravating factor for pulmonary diseases and has notably deleterious effects on asthma, bronchitis and pneumonia. Recent studies suggest that air pollution may also cause adverse effects in the gastrointestinal tract. Accumulating experimental evidence shows that immune responses in the pulmonary and intestinal mucosae are closely interrelated, and that gut-lung crosstalk controls pathophysiological processes such as responses to cigarette smoke and influenza virus infection. Our first aim was to collect urban coarse particulate matter (PM) and to characterize them for elemental content, gastric bioaccessibility, and oxidative potential; our second aim was to determine the short-term effects of urban coarse PM inhalation on pulmonary and colonic mucosae in mice, and to test the hypothesis that the well-known antioxidant N-acetyl-L-cysteine (NAC) reverses the effects of PM inhalation.

Results

The collected PM had classical features of urban particles and possessed oxidative potential partly attributable to their metal fraction. Bioaccessibility study confirmed the high solubility of some metals at the gastric level. Male mice were exposed to urban coarse PM in a ventilated inhalation chamber for 15 days at a concentration relevant to episodic elevation peak of air pollution. Coarse PM inhalation induced systemic oxidative stress, recruited immune cells to the lung, and increased cytokine levels in the lung and colon. Concomitant oral administration of NAC reversed all the observed effects relative to the inhalation of coarse PM.

Conclusions

Coarse PM-induced low-grade inflammation in the lung and colon is mediated by oxidative stress and deserves more investigation as potentiating factor for inflammatory diseases.

     

Catalytic olefin polymerisation at short times: Studies using specially adapted reactors

Despite the fact that the very early stages (several tens of seconds) of catalysed olefin polymerisation processes appear negligibly short with respect to the residence time of most industrial reactors, they are critical in terms of catalyst activation, obtaining good particle morphology, and avoiding irreparable problems caused by particle overheating. The different types of reactors that have been used over the course of the past few years are discussed in this feature article. It is shown that despite the difficulties encountered in finding the perfect experimental tool for this purpose, different configurations of stopped flow reactors can be used successfully to explore different aspects of what happens to the catalyst (supported and molecular) during these critical moments of polymerisation. © 2012 Canadian Society for Chemical Engineering     

Design,Synthesis, and Evaluation of WC5 Analogues as Inhibitors of Human Cytomegalovirus Immediate‐Early 2 Protein,a Promising Target for Anti‐HCMV Treatment

Although human cytomegalovirus (HCMV) infection is mostly asymptomatic for immunocompetent individuals, it remains a serious threat for those who are immunocompromised, in whom it is associated with various clinical manifestations. The therapeutic utility of the few available anti‐HCMV drugs is limited by several drawbacks, including cross‐resistance due to their common mechanism of action, i.e., inhibition of viral DNA polymerase. Therefore, compounds that target other essential viral events could overcome this problem. One example of this is the 6‐aminoquinolone WC5 , which acts by directly blocking the transactivation of essential viral Early genes by the Immediate‐Early 2 (IE2) protein. In this study, the quinolone scaffold of the lead compound WC5 was investigated in depth, defining more suitable substituents for each of the scaffold positions explored and identifying novel, potent and nontoxic compounds. Some compounds showed potent anti‐HCMV activity by interfering with IE2‐dependent viral E gene expression. Among them, naphthyridone 1 was also endowed with potent anti‐HIV activity in latently infected cells. Their antiviral profile along with their innovative mechanism of action make these anti‐HCMV quinolones a very promising class of compounds to be exploited for more effective antiviral therapeutic treatment.