Molecular fluctuations in polyethylene melts. Dependence of the longitudinal and transverse proton relaxation on the chain length

Melts of diverse fractions of linear polyethylene have been investigated by longitudinal and transverse proton relaxation. A three-component model of molecular fluctuations allows to describe the longitudinal relaxation times in the frequency range of our experiments (10⁴ to 10⁸ Hz). The components are ‘anisotropic segment reorientation’, ‘reptation’ and the ‘conformational fluctuation of the surrounding tube’. The molecular weight dependences of the corresponding time parameters are τ_s ～ M⁰, τ_l ～ M¹ and τ_r ～ M³, respectively. These quantities also permit us to explain the molecular weight dependence of the transverse relaxation curves which have been described by the aid of the Anderson-Weiss theory. It is shown that the influence of the molecular weight distribution is not negligible. Rather it is the reason for non-exponential relaxation decays. The free induction decays have been found to decrease essentially faster than the relaxation decays even if the inhomogeneity of the magnet was negligible. As an explanation, internal inhomogeneities caused by microscopic voids have been assumed. An estimate of this effect is given. In addition to the pure fractions we have also studied a mixture of short chains in a matrix of long deuterated chains. It turns out that the fluctuation of the local network depends on both molecular weights and the ratio of mixture.     

Dependence of respiratory time volume and oxygen uptake on the load factor in time

Data on the composition of fatty acids in the visceral, subcutaneous and intra-muscular fat and also of phospholipids in the muscular tissue of freshly frozen reindeer meat (venison) are presented. It is noted that the intra-muscular lipids in the meat of the young stock are richer as concerns the qualitative composition of phospholipids and contain more of the linoleic acid, whereas a reduced nourishing of adult reindeers brings with it a fall in the amount of decitins and an increase in the content of the stearic acid.     

Internal stress of thin silver and gold films and its dependence on gas adsorption

Using the highly sensitive bending beam device described in earlier papers the internal stress versus thickness curves of silver and gold have been measured continuously during metal deposition. The contributions due to momentum transfer and heat transfer have been subtracted from the experimentally determined curves. Using the model for the origin of the internal stress which we have developed previously, the measured dependence of the stress curves on the nature of the substrate, on the evaporation rate for the metal deposition and on gas adsorption by the substrate, as well as by the metal itself, are interpreted in terms of changes in the structure of the metal film.     

Die Anwendung von Prozeßrechnern in der Waschmittelproduktion

The Use of Process Control Computers in the Production of Laundry Detergents Modern laundry detergent production plants require highly sophisticated measuring and controlling systems in order to maintain high and even quality of the products. In addition, the detergent industry is under a very high cost pressure due to market circumstances. It appeared to be efficient to improve the measuring and controlling technology by using process control computers and to come to production methods with lower cost rates. Also, even and safe operation methods are desirable for every production process as well as rapid recognizing and elimination of troubles and early warnings in case of breakdowns. Prerequisites with regard to computer control are a high level of the process equipment and a continuous recording of measuring data, which is very important. The method of operation of the computer control is discussed in general the resulting efficiency is presented. The efficacy can be quantitated with regard to the desired decrease of raw material costs, conservation of energy and saving manpower. The efficiency can not be quantitated with regard to deepening of knowledge of the process, accelerating of the performance of trials, collecting experience for other processes and as prerequisite for a composite system of electronic data processing in the production department.     

Amylose and amylopectin molecular fractions and chain length distribution of amylopectin in 12 varieties of Ghanaian sweet potato (Ipomoea batatas) flours

Sweet potato (Ipomoea batatas) is a commonly cultivated root crop in tropical and subtropical regions, including Ghana. Different varieties of sweet potato have been bred, in order to expand its utilisation within the food and industrial sector. This study analysed flours made from 12 recently developed Ghanaian sweet potato varieties in terms of their amylose and amylopectin molecular fractions and amylopectin chain length distribution. Starch content of the sweet potato flours ranged from 49 to 77 g/100 g dry matter, with 11 of the varieties containing above 60 g/100 g dry matter. An orange-fleshed variety, Apomuden, had the lowest amount of starch (48.9 g/100 g dry matter), while the cream-fleshed variety Histarch had the highest (77.3 g/100 g dry matter). The flours from the 12 sweet potato varieties had intermediate amounts of amylose, within the range 10–30 g/100 g dry matter, and showed typical molecular distribution according to size-exclusion chromatography (SEC). The fine structures of amylopectin, as revealed by anion-exchange chromatography, contained features common for starches of C-type X-ray pattern, but some structural differences were also observed.     

Effects of flavonoids on CYP1 expression in RL95-2 endometrial carcinoma cells

RL95-2 endometrial cancer cells were used to study cytochrome P450-mediated chemopreventative mechanisms of four flavonoids found in foods. To investigate enzymatic CYP1 inhibition, intact cells were induced with benzo(a)pyrene or 2,3,7,8-tetrachlorodibenzo-p-dioxin. Quercetin, kaempferol and myricetin inhibited CYP1 activity dose-dependently with IC₅₀s ranging from 2.2 to 4 μM; while amentoflavone was inactive. Further experiments were designed to determine if flavonoids also interacted with the AhR or caused a decrease in CYP1 protein or mRNA expression. CYP1A1 protein expression was inhibited in cells co-treated with TCDD and quercetin, kaempferol or myricetin compared with TCDD alone, but amentoflavone was ineffective. Relatively higher (∼7-fold) basal levels of CYP1B1 protein were not significantly affected by flavonoid treatments. In general, at the message level significant inhibition of induced CYP1A1 or CYP1B1 was not detected following flavonoid cotreatment. Despite the common inhibitory effects of quercetin, kaempferol, and myricetin on induced CYP1A1-dependent activity and protein expression, the mechanisms of CYP1 inhibition in this cell line are complex and dependent on the CYP gene, AhR inducer and the flavonoid.