In-situ measurements of gas permeability in fuel cell membranes using a cylindrical microelectrode

A new method to study permeation of gases in proton conducting membranes using a cylindrical microelectrode is presented. The focus of this work was to develop an in-situ method to study transport properties of hydrogen and oxygen close to real fuel cell operating conditions. The gas permeability is strongly affected by the change of water content in the membrane and it is therefore of advantage that, by using this method, measurements can be carried out over a wide range of relative humidities. The numerical method makes it possible to separate the diffusion coefficient and the concentration of dissolved gas in the membrane and also allows kinetic limitations to be taken into account. Chronoamperometric measurements on Nafion® 117 were successfully evaluated numerically. Experiments at temperatures of 25 and 60 °C with respect to oxygen permeation and at 60 °C for hydrogen permeation at relative humidities in the range 30–94% are presented. The reproducibility of data was excellent when measuring with different microelectrodes on the same membrane sample, but differed when measuring on different samples. In general, the permeability increases with increasing temperature and relative humidity.     

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Ohne Zusammenfassung     

Chirurgie der differenzierten Schilddrüsenkarzinome

Die 5-Jahres-überlebensrate von differenzierten Schilddrüsenkarzinomen ist generell sehr gut und betr?gt 80 – 95%. Hierbei bestehen Abh?ngigkeiten zum Alter des Patienten [15], zum prim?ren Tumorstadium, zur histologischen Differenzierung und zum Ausma? der region?ren und Fernmetastasierung [6]. Patienten mit Tumorfreiheit haben ebenfalls eine bessere Prognose gegenüber denen mit einem Resttumor. Dies spricht für ein konsequentes Vorgehen beim Prim?reingriff mit Thyreoidektomie und Entfernung der Lymphknoten des zentralen Kompartments. Stadienadaptiert schlie?t sich eine Radiojodtherapie oder die Kombination mit einer externen Radiatio an. Bei der Reoperation differenzierter Schilddrüsenkarzinome mu? zwischen der individuellen Prognose des Patienten, dem Ziel der Operation und der postoperativen Morbidit?t/Mortalit?t entschieden werden. Aufgrund des hohen Risikos sollten diese Operationen in Zentren durchgeführt werden, so da? postoperative Komplikationen (permanente Recurrensparese/Hypoparathyreoidismus) vertretbar gering gehalten werden k?nnen (Tabelle 11). Dennoch sollte nicht au?er Acht gelassen werden, da? individuell bei differenzierten Schilddrüsenkarzinomen im Stadium pT1 auch ein eingeschr?nkt radikales Vorgehen (Hemithyreoidektomie) ohne Verschlechterung der Prognose m?glich scheint. Strenge Nachuntersuchungsergebnisse und Ergebnisse weiterer klinischer Studien müssen hierzu abgewartet werden.     

Correction of camptodactyly with an external fixator

Camptodactyly is a flexion deformity of the proximal interphalangeal joint. Because of unsatisfactory results, treatment is not recommended for mild deformities, and in severe deformities surgery has been disappointing. A specially designed external fixator providing gradual distraction was used in a severe case. With this mildly aggressive method, an acceptable result was obtained. Received: 5 June 1997/Accepted: 2 February 1998     

Morphological study of neocortical areas in Rett syndrome

Various neocortical areas from four females aged 16–24 years with Rett syndrome (RS) were investigated and compared with brains of therapy-resistant partial epilepsy (TRPE) patients (18–25 years), infantile autism (IA), and control brains (24 and 58 years). The cytoarchitecture of area 10 (frontal), area 21 (temporal), area 4 (primary motor cortex), and area 17 (primary visual cortex) was studied by the combined Klüver-Barrera (luxol fast blue and cresyl violet) standard procedure. Autofluorescence of lipofuscin, immunofluorescence of synaptic vesicle proteins [synaptophysin (p38)] and lectin-stained (Wisteria floribunda agglutinin) perineuronal nets (PNs) were studied in the cortices using dual-channel confocal laser scanning microscopy. The brains of RS females show various types of morphological/cytoarchitectonical abnormalities of single pyramidal neurons in layers II–III, and V–VII of different cortical areas. The abnormalities include mild losses of pyramidal neurons, more pronounced in layers II and III than in layers V and VII, and more evident in frontal and temporal areas than in the visual cortex. Microdysgenesis, including abnormalities due to neuronal migration disorders, was not found in RS, in contrast to the observations in TRPE patients, strongly indicating that RS is not a neuronal migration disorder. Lipofuscin distribution was normal but amounts were lower in RS cases than in control and TRPE brains. PNs were less expressed in cortices of the IA case, but were clearly overexpressed in the motor cortex of RS. Quantitative analysis of p38 showed a decrease in the area occupied by p38 immunoreactivity by 20–40% in RS compared with controls. It is concluded that RS could best be explained by a postnatal synaptogenic developmental deficiency; the basic defect, however, is still completely unknown. Received: 26 February 1996 / Revised, accepted: 11 July 1996     

Hydroxyethyl starch does not improve pancreas preservation with HTK

The effect of hydroxyethyl starch on pancreas preservation with cardioplegic histidine-tryptophan-ketoglutarate solution (HTK) was investigated. The study was performed using an in vitro reperfusion system of the porcine pancreas. During organ preservation pancreatic weight, arterial pressure, volume flow, and washout of amylase and lactate were quantified. Addition of hydroxyethyl starch did not affect arteriovenous volume flow or washout of amylase and lactate during protective perfusion after pancreas preparation. However, hydroxyethyl starch in HTK prevented an increase in pancreatic weight at the end of the protective perfusion (102.2 ± 4.55% vs 127.8 ± 4.62% in controls; p < 0.005) and after 24 h cold ischemia (72.9 ± 3.91 % vs. 83.5 ± 3.49 % in controls; p < 0.05). Hydroxyethyl starch did not affect postischemic organ quality assessed during reperfusion in a perfusion chamber by pancreatic vascular resistance, amylase and lactate release, insulin secretion, and oxygen consumption. We conclude that hydroxyethyl starch does not bring about any further improvement in immediate postischemic organ quality assessed in an in vitro reperfusion system.

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Hydroxyäthylstärke bringt keine verbesserung der pankreaskonservierung mit HTK-Lösung

Zusammenfassung Der Effekt von Hydroxyäthylstärke auf die Pankreaskonservierung mit der kardioplegischen Histidin-Tryptophan-Ketoglutarat-Lösung (HTK) wurde untersucht. Die Studie wurde an einem Reperfusionssystem des in vitro perfundierten Pankreas vom Schwein durchgeführt. Während der Organprotektion wurden das Pankreasgewicht, der arterielle Perfusionsdruck, die Volumenstromstärke sowie Amylase und Laktat im Perfusat bestimmt. Der Zusatz von Hydroxyäthylstärke bewirkte keine Änderung der Volumenstromstärke oder der Amylase- und Laktatauswaschung aus dem Organ während der Protektion. Allerdings konnte eine Zunahme des Organgewichts am Ende der protektiven Perfusion (102,2 ± 4,55% vs. 127,8 ± 4,62%in Kontrollen; p < 0,005) und nach 24 h kalter Ischamie (72,9 ± 3,91 vs. 83,5 ± 3,49% in Kontrollen; p < 0,05) durch Hydroxyathylstärke in der HTK-Lösung verhindert werden. Hydroxyäthylstärke hatte keinen Einfluß auf die postischämische Organqualität, die während der Reperfusion in einer Perfusionskammer anhand von Gefäßwiderstand, Amylase- und Laktatfreisetzung, Insulinsekretion und Sauerstoffverbrauch abgeschätzt wurde. Wir schließen daraus, daß Hydroxyäthylstärke die sofort nach einer Ischämie in einem In-vitro-Reperfusionssystem bestimmte Pankreasfunktion nicht weiter verbessert.

     

Bone mineral density in patients with prostatic cancer treated with orchidectomy and with estrogens

Bone mineral density (BMD) and bone mineral content (BMC) were measured in the femoral neck area, trochanteric area and Wards triangle, and in the distal radius of the left forearm before and after 1 year of endocrine treatment in 27 patients with prostatic cancer. Eleven of the patients were treated with orchidectomy and 16 with combined oral and intramuscular estrogens. The patients were free from metastases during the entire observation period. In the orchidectomized patients, BMD and BMC of the distal radius decreased significantly following treatment, whereas no changes were observed in the estrogen-treated patients. These preliminary results demonstrate that estrogens may protect bone in male subjects also and may merit further investigations on larger groups of patients.