双螺杆挤出机连续生产

在日常生产中 ,绝大多数的橡胶聚合物最大的缺点是它们都呈胶包状 ,这导致了造粒过程的额外支出 ,而且在加工不同胶料时 ,缺乏多数连续混炼系统所需的灵活性。正是由于原材料费用过高 ,1975～ 1980年间聚合物生产商才未能够把新开发的粉末橡胶在橡胶工业中推广开来。塑料工业中双螺杆挤出机和分批投料技术的发展 ,为橡胶混炼胶连续生产开启了希望之门。图 1所示即为一种带有多个重力计量加料口的连续混炼挤出机。除可以分批投料以外 ,这种双螺杆挤出机的螺杆和机筒内壳还采用了积木式设计 (见图2 ) ,从而使这种挤出机的加工部分能够轻松地适…     

Alcoholysis of waste fats with 2‐ethyl‐1‐hexanol using Candida antarctica lipase A in large‐scale tests

Commercial native lipase A from Candida antarctica was used to produce alkyl esters through the alcoholysis of (waste) fats with 2‐ethyl‐1‐hexanol. The process was carried out in batch stirred tank reactors (from 100 mL up to 3000 L). The content of alkyl esters in reaction mixtures was determined by gradient HPLC using an evaporative light scattering detector and the reaction progress was controlled by determining the ratio of the palmitic acid ester peak area to the oleic acid ester peak area in HPLC chromatograms. The results show that alcoholysis is the favoured reaction in presence of excess water and water‐insoluble alcohols in comparison with hydrolysis (fatty acid content <5%). The optimum amount of water for the alcoholysis was found to be 80–100% of the amount of fat. In the presence of low quantities of water both alcoholysis and hydrolysis are slow. Conversion rate increases with increasing temperature to 65–70 °C. Based on these results a large‐scale test to produce 3000 L of alkyl ester (to be used as lubricant coolant) was carried out. The experiments have proved that alcoholysis is completed after about 7–10 h depending on temperature.     

Fatty fish intake,n‐3 fatty acids and self‐rated health in middle‐aged adults

Background – Since n‐3 fatty acids, abundant in fatty fish, may improve health, we raised the question whether self‐reported intake frequency of fatty fish (FF) might be related to the percentage of n‐3 fatty acids in serum phospholipids (PL‐n‐3), and also to self‐rated health (H). Design – The study followed a cross‐sectional design. Methods – In the cross‐sectional Oslo Health Study, PL‐n‐3 were determined in 121 middle‐aged ethnic Norwegians and 102 immigrants from the Indian subcontinent and correlated with FF and H. Logistic regression was used to study the relationship between PL‐n‐3 and H (dichotomized, i.e. Poor vs. Good health). Results – FF correlated positively with PL20:5n‐3 (PL‐EPA, r = 0.467, p <0.001) and PL22:6n‐3 (PL‐DHA, r = 0.499, p <0.001), and negatively with PL20:4n‐6 (PL‐AA, r = –0.350, p = 0.001). H was positively associated with PL‐EPA (r = 0.321, p <0.001) and PL‐DHA (r = 0.275; p <0.001), but negatively with PL‐AA (r = –0.220, p = 0.001). The odds ratio for reporting Poor vs. Good health was significantly higher in subjects with low levels of PL‐EPA (OR = 1.49; 95% confidence interval = 1.17–1.89, p = 0.001), persisting after adjusting for sex, physical activity, ethnicity and length of education. Conclusion – The intake frequency of fatty fish is related to n‐3 fatty acids in the serum phospholipids, and to self‐rated health.     

Quantitative relationships between microstructure and effective transport properties based on virtual materials testing

The microstructure influence on conductive transport processes is described in terms of volume fraction ε, tortuosity τ, and constrictivity β. Virtual microstructures with different parameter constellations are produced using methods from stochastic geometry. Effective conductivities are obtained from solving the diffusion equation in a finite element model. In this way, a large database is generated which is used to test expressions describing different micro–macro relationships such as Archie's law, tortuosity, and constrictivity equations. It turns out that the constrictivity equation has the highest accuracy indicating that all three parameters are necessary to capture the microstructure influence correctly. The predictive capability of the constrictivity equation is improved by introducing modifications of it and using error‐minimization, which leads to the following expression: with intrinsic conductivity . The equation is important for future studies in, for example, batteries, fuel cells, and for transport processes in porous materials. © 2014 American Institute of Chemical Engineers AIChE J, 60: 1983–1999, 2014     

Substituenteneffekte in den 13C-NMR-Spektren von diastereomeren Chalkondihalogeniden. VI. Konfigurationsbestimmung von Chalkonrhodanhydrinen mittels lösungsmittelinduzierter Signalverschiebung in den 13C-NMR-Spektren

Substituent Effects in ¹³C-N.M.R. Spectra of Diastereomeric Chalcone Dihalogenides. VI. Assignment of Configuration on Chalcone Rhodanohydrins by Solvent Induced Shift of Signals in ¹³C-N.M.R. Spectra The erythro configuration of chalcone rhodanohydrins 1 was determined by comparison of solvent dependent shifts of C-α and C-β signals of 1 and both the erythro and threo isomeres of chalcone chlorohydrins 2 as standard in ¹³C n.m.r. spectra.     

Control of Directed Cell Migration after Tubular Cell Injury by Nucleotide Signaling

Acute kidney injury (AKI) is a common complication of severe human diseases, resulting in increased morbidity and mortality as well as unfavorable long-term outcomes. Although the mammalian kidney is endowed with an amazing capacity to recover from AKI, little progress has been made in recent decades to facilitate recovery from AKI. To elucidate the early repair mechanisms after AKI, we employed the zebrafish pronephros injury model. Since damaged cells release large amounts of ATP and ATP-degradation products to signal apoptosis or necrosis to neighboring cells, we examined how depletion of purinergic and adenosine receptors impacts the directed cell migration that ensues immediately after a laser-induced tubular injury. We found that depletion of the zebrafish adenosine receptors adora1a, adora1b, adora2aa, and adora2ab significantly affected the repair process. Similar results were obtained after depletion of the purinergic p2ry2 receptor, which is highly expressed during zebrafish pronephros development. Released ATP is finally metabolized to inosine by adenosine deaminase. Depletion of zebrafish adenosine deaminases ada and ada2b interfered with the repair process; furthermore, combinations of ada and ada2b, or ada2a and ada2b displayed synergistic effects at low concentrations, supporting the involvement of inosine signaling in the repair process after a tubular injury. Our findings suggest that nucleotide-dependent signaling controls immediate migratory responses after tubular injury.     

Steroide. LXX [1]. Stereoselektive Epoxidation von 14,15-ungesättigten Östratrien-3-methylethern. Zum syn-dirigierenden Effekt von Urethanen

Steroides. LXX. Stereoselective Epoxidation of 14,15-Unsaturated Estratriene-3-methyl Ethers. On the syn-Directive Effect of Urethanes The stereochemistry of the epoxidation of 14,15-unsaturated estratriene-3-methyl ethers with peroxyacids is examined. The influence of different 17-substituents and of the solvent on the stereoselectivity is discussed. Whereas on epoxidation of 17β-esters and 17β-ethers mainly 14α, 15α-epoxides are formed (up to 89%), the 17β-urethane derivatives yield the 14β, 15β-epoxides up to 87% by a syn-directive effect.