Studies of absolute rate coefficients in alternating copolymerization by observation of pre- and after-effects

Expressions are presented for pre- and after-effects in some photo-initiated copolymerizations leading to strongly alternating copolymers. The mechanisms considered include alternation arising from dominant cross-propagation and from homopolymerization of a ternary complex containing both monomers, as well as from a generalized version of the former in which the ternary complex is involved in propagation. Determination of pre- and after-effects by dilatometry is discussed, in particular the necessity of allowing for thermal perturbations during polymerization, which may easily exceed the quantities being measured. A method for making corrections for these perturbations is developed and two ways of plotting experimental data for this purpose are described. In both pre- and after-effects data are plotted in the same diagram to increase the precision. The techniques are applied to the copolymerization of methyl acrylate and styrene, and of methyl methacrylate and styrene, in the presence of the Lewis acid ethylaluminium sesquichloride. Initiation was effected by light with λ=365 nm. The resulting values of k_bak′⁻¹_t(k_ba′k′_t are the velocity coefficients for propagation of a styryl radical with an acrylate type monomer (complexed with the Lewis acid), and for second order termination, respectively) agree satisfactorily with literature values when comparison is possible (i.e. for the system Et₃Al₂Cl₃/MA/St). For this case, combination of the above with literature data on steady-state measurements permits evaluation of the propagation coefficients: k_ba=5.6×10³, k_ab=37.3×10³ mol⁻¹dm³s⁻¹. Progress in the kinetic analysis of these copolymerizations is currently impeded by the shortage of quantitative information about the binary and ternary equilibria involved.     

Concept and Performance of a Non-Azide Propellant for Automotive Airbag Inflators

A university laboratory and three companies have collaborated to develop a non-azide propellant for automotive airbag inflators which is composed of azodicarbonamide(ADCA), potassium perchlorate(KClO₄), and additives such as burning catalyst, binder and others. The new propellant aims at low cost, small size of inflators, featuring low toxicity of not only raw materials of the propellant but also effluent gases, particulates and residues generated on deployment of an airbag. No hygroscopicity and low hazard of the propellant will make manufacturing, transportation, and handling easy. The performances of the propellant were evaluated by strand test, pressure chamber test, 7.5 l tank test, 60 l tank test, and airbag deployment test. The strength of the pellet of the new propellant was evaluated by a small ball drop test.     

Immunoassay based on monoclonal antibodies versus LC-MS: deoxynivalenol in wheat and flour in Southern Brazil

An indirect competitive enzyme-linked immunosorbent assay (ELISA) method using a monoclonal antibody for deoxynivalenol (DON) detection in wheat and flour was standardised and validated (detection limit?=?177.1?μg?kg(-1)) and its performance was compared with LC-MS, quantification limit?=140?μg?kg(-1)). DON recovery ranged from 88.7% to 122.6% for wheat grain and from 70.6% to 139.3% for flour. Among the 38 wheat samples evaluated, DON was detected in 29 samples (76.3%) by ic-ELISA (281.6-12?291.4?μg?kg(-1)) and in 22 samples (57.9%) by LC-MS (155.3-9906.9?μg?kg(-1)). The 0.93 correlation coefficient between ic-ELISA and LC-MS data in 19 positive DON wheat samples demonstrated the reliability and efficiency of ic-ELISA. Results indicated that standardised ic-ELISA was suitable for DON screening in wheat samples and the need for continuous monitoring of mycotoxin levels in foodstuffs.     

Isolation of a Copper‐resistant Sake Yeast Mutant with Improved Flavour Compound Production

The sake (traditional Japanese alcoholic beverage) yeast mutant A1 was previously isolated as a strain resistant to an isoprenoid analog. This strain is used for industrial sake brewing because of its increased production of isoamyl acetate. In this study, a physiological event was identified which was closely related to the elevation of alcohol acetyltransferase (AATase) activity in strain A1. This finding was applied for the isolation of another mutant with an improved capacity for flavour compound production. Strain A1 revealed an additional phenotype showing resistance to Cu²⁺, as seen from its growth and isoamyl acetate production, even in a medium with the copper ion at 6 mM. Mutant strains were successfully isolated with increased isoamyl acetate production capacity from sake yeast strain 2NF on the basis of a Cu²⁺‐resistant phenotype at a high yield. Among them, strain Cu7 was characterized by its ability to produce isoamyl acetate at the highest concentration under condition where isoamyl alcohol (its precursor) was accumulated to the lowest extent. Such a phenotype of strain Cu7 is applicable for the practical production of an alcoholic beverage of excellent quality in terms of flavour.     

Histological comparison of the dorsal ordinary muscles of wild and full‐cycle cultured Pacific bluefin tuna (Thunnus orientalis)

The histological properties of the cephalad parts of the dorsal ordinary muscles (CD‐OMs) of wild (body weight 33.3 ± 0.9 kg, n = 3) and full‐cycle cultured (body weights 13.1 ± 2.6 (FC 1), 20.2 ± 1.0 (FC 2) and 28.5 ± 3.6 (FC 3) kg, n = 3 respectively) Pacific bluefin tuna were investigated. The CD‐OMs of FC 1–3 tuna showed low moisture content (P < 0.05) and high fat content (about six times more, P < 0.05) in comparison with wild fish. A large quantity of adipose tissue was observed in the wide spaces between muscle fibres in the CD‐OMs of FC 1‐3 tuna. The muscle fibre diameter of the CD‐OM of FC 3 tuna was significantly lower than that of wild fish (P < 0.05). Myofibrils in the CD‐OM of wild tuna were surrounded by a developed sarcoplasmic reticulum and mitochondria; however, there were many glycogen granules among the myofibrils and a large quantity of fat in the CD‐OM of full‐cycle cultured fish. In particular, the glycogen content of the CD‐OM of FC 3 tuna was significantly higher (about 50 times) than that of wild fish. These results indicate that feeding and exercise conditions affect the histological structure and metabolism of the bluefin tuna muscle. Copyright © 2006 Society of Chemical Industry     

Effects of sinoaortic denervation on Fos expression in the brain evoked by hypertension and hypotension in conscious rabbits

We have previously shown [Li and Dampney (1994) Neuroscience 61, 613-634] that periods of sustained hypertension and hypotension each induces a distinctive and reproducible pattern of neuronal expression of Fos (a marker of neuronal activation) in specific regions of the brainstem and forebrain of conscious rabbits. The aim of this study was to determine the contribution of afferent inputs from arterial baroreceptors to the activation of neurons in these various brain regions that is caused by a sustained change in arterial pressure. Experiments were carried out on rabbits in which the carotid sinus and aortic depressor nerves were cut in a preliminary operation. Following a recovery period of seven to 10 days, a moderate hypertension or hypotension (increase or decrease in arterial pressure of 20-30 mmHg) was induced in conscious barodenervated rabbits for 60 min by the continuous infusion of phenylephrine or sodium nitroprusside, respectively. In control experiments, barodenervated rabbits were subjected to the identical procedures except that they were infused with the vehicle solution alone. Compared with the effects seen in barointact rabbits, [Li and Dampney (1994) Neuroscience 61, 613-634] the number of neurons that expressed Fos in response to hypertension was reduced by approximately 90% in the nucleus of the solitary tract and in the caudal and intermediate parts of the ventrolateral medulla. In supramedullary regions, baroreceptor denervation resulted in a reduction of approximately 60% in hypertension-induced Fos expression in the central nucleus of the amygdala and in the bed nucleus of the stria terminalis, but no significant reduction in the parabrachial complex in the pons. Following hypotension, the number of neurons that expressed Fos in barodenervated rabbits, compared with barointact rabbits, [Li and Dampney (1994) Neuroscience 61, 613-634] was reduced by approximately 90% in the nucleus of the solitary tract, area postrema, and caudal, intermediate and rostral parts of the ventrolateral medulla. Baroreceptor denervation also resulted in a similar large reduction in hypotension-induced Fos expression in many supramedullary regions (locus coeruleus, midbrain periaqueductal grey, hypothalamic paraventricular nucleus, and in the central nucleus of the amygdala and the bed nucleus of the stria terminalis in the basal forebrain). In the supraoptic nucleus, hypotension-induced Fos expression in barodenervated rabbits was reduced by 75% compared to barointact animals, but was still significantly greater than in control animals. There was also a high level of Fos expression, much greater than in control animals, in the circumventricular organs surrounding the third ventricle (subfornical organ and organum vasculosum lamina terminalis). The results indicate that in conscious rabbits the activation of neurons that occurs in several discrete regions at all levels of the brain following a sustained change in arterial pressure is largely dependent upon inputs from arterial baroreceptors, with the exception of neurons in the circumventricular organs surrounding the third ventricle that are activated by sustained hypotension. The latter group of neurons are known to project to vasopressin-secreting neurons in the supraoptic nucleus, and may therefore via this pathway trigger the hypotension-induced release of vasopressin that occurs in the absence of baroreceptor inputs.