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The critical transmural pressure (Ptm) is defined as the transmural pressure of the airway at the site where and when flow is limited during a forced expiration. According to the presented theory, the maximal expiratory flow (Vmax) can be calculated from the relation between Ptm and the corresponding cross-sectional area of the airway (A). By means of a pitot-static tube, Ptm-A curves were constructed for several locations in the elastic airway of a mechanical model. From these curves local Vmax was calculated at different values of Ptm and compared with actual flow, i.e. measured Vmax for the entire airway. In the downstream part of the airway, the actual flow equalled calculated Vmax at most Ptm values. The site of flow limitation, being the most upstream point where actual flow equals calculated local Vmax could therefore be located. Theory and experiments showed positive as well as negative Ptm not influenced by change in upstream or downstream resistance. Flow limitation could therefore be initiated at distending as well as compressing pressures across the wall of the airway. V was regarded as a function of Ptm and the elastic recoil pressure of the lung (Pel). Measured and calculated iso-Pel, Ptm-V curves agreed well with one major exception: when Ptm less than Ptm measured curves were distorted due to a concomitant downstrean compression of the collapsible airway. 相似文献
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Holger Weiß Georg Teutsch Peter Fritz Birgit Daus Andreas Dahmke Peter Grathwohl Ralf Trabitzsch Bernd Feist Ralf Ruske Olaf Böhme Mario Schirmer 《Grundwasser》2001,6(3):113-122
The SAFIRA-project (remediation research in regionally contaminated aquifers) focuses on innovative in situ remediation technologies to treat complex groundwater contamination. For this purpose, a model site located in Bitterfeld, Germany, was selected. The site is heavily contaminated with aliphatic and aromatic chlorinated hydrocarbons. The goal of the project is to develop, test and optimize new technologies of reactive barriers under controlled in situ conditions in a pilot plant. In order to create the necessary basis for this model project, the hydrogeological and hydrogeochemical conditions at the selected field site were investigated and various technologies for the design of the in situ pilot plant were examinated. Small-scale laboratory studies and tests in a mobile test unit (scale 1 m) were carried out in order to test the technologies prior to their application in the field. The technologies now tested in the reactive columns at the pilot plant include physico-chemical, microbial and combined techniques. 相似文献
86.
Dipl.-Geol. A. Musolff Dipl.-Hydrol. S. Leschik Dr. F. Reinstorf Dr. G. Strauch Prof. Dr. habil. M. Schirmer Dr. M. Möder 《Grundwasser》2007,12(3):217-231
Xenobiotics are increasingly being considered as ecotoxicologically relevant for the aquatic environment and human health. Their behaviour and the effects on the environment have not yet been comprehensively investigated and, therefore, are currently the subject of the project WASSER Leipzig initiated by the UFZ. The results of this article are based on groundwater and surface water analyses of a watershed within the town of Leipzig. Here the industrial chemicals bisphenol-A and t-nonylphenol, the polycyclic fragrances galaxolide and tonalide, the antiepileptic drug carbamacepine and caffeine where investigated. Xenobiotics showed ubiquitous occurrence in the rivers, which were contaminated from treated and untreated sewage, as well as in groundwater, contaminated by leaky sewers. Mean concentrations up to several hundred ng/l were found in the rivers, while groundwater concentrations, except for bisphenol-A, tended to be lower. Applying the statistical factor analysis on the hydrochemical measurements, a differentiation of the xenobiotics with regard to their hydrochemical behaviour in groundwater was performed. 相似文献
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用液氨代替烧碱作钛液水解晶种的中和剂,所得TiO2产品的白度、着色力好,且经济效益好。介绍了液氨中和剂用量的计算和TiO2晶种的制法。讨论了影响产品质量的因素。 相似文献
89.
采用氧化后再氧化的实验方法,通过对 Si3 N4 陶瓷材料氧化行为的研究和氧化动力学的分析,讨论了 Si3 N4 陶瓷材料的氧化机理。结果表明, Si3 N4 陶瓷材料的氧化行为表现为氧化增量随时间的变化服从抛物线规律:(Δ W )2 = Kp t 。提出了氧在氧化层中的向内扩散是 Si3 N4 氧化过程中的控制步骤;并认为烧结添加剂或杂质等对 Si3 N4 陶瓷材料氧化速度的影响,是通过改变氧化层的组成、结构,使氧在氧化层中的扩散速度发生变化而产生的。 相似文献
90.
The method of hierarchical imprinting was used for the first time in order to synthesize polymers with a high affinity for
nisin. The concept of this approach is demonstrated by filling the pores of silica particles, which contain immobilized peptidic
templates, with a mixture of monomers/initiator, followed by polymerization and subsequent dissolution of the silica template.
This method leaves imprinted polymers with binding sites located at the surface that are capable of recognizing larger molecules
with the same immobilized epitope. The results of the high-performance liquid chromatography analyses illustrate that the
highest retention factors and imprinting factors of nisin on nisin C-terminal analogously imprinted polymers could be obtained
with acetonitrile/water mixtures containing more than 80% water. Furthermore, nisin was strongly retained on polymers that
were imprinted with a longer amino acid sequence because of better sterical accessibility of the binding sites for the C terminus
of nisin. The retention of nisin (k = 21.65) under aqueous elution conditions results from selective ionic interactions and hydrophobic interactions. Furthermore,
the polymers exhibited selectivity for the template Lys-Ala and the structurally related dipeptide Ala-Lys. The results of
the present work show that these hierarchically imprinted polymers could be used for the chromatographic separation of the
polypeptide nisin in aqueous solutions. 相似文献