Model experiments mimicking the human intestinal transit and metabolism of D-galacturonic acid and amidated pectin

In order to study the human intestinal transit and metabolism of D-galacturonic acid and amidated pectin a number of model experiments were carried out. Both substrates were incubated under aerobic conditions at 37 degrees C using saliva (2 min) and simulated gastric juice (4 h). Under anaerobic conditions the substrates were incubated at 37 degrees C using human ileostomy and colostomy fluids, each obtained from three different donors, for 10 and for 24 h, respectively. D-Galacturonic acid, SCFA (acetic acid, propionic acid, and butyric acid), as well as methanol were analyzed photometrically after carbazole reaction, GC-flame ionization detection (GC-FID), and headspace solid-phase microextraction GC/MS (HS-SPME-GC/MS), respectively. D-Galacturonic acid and amidated pectin were found to be stable during incubations with saliva and simulated gastric juice, whereas both substrates underwent degradation in the course of human ileostomy and colostomy fluid incubations. D-Galacturonic acid was practically completely decomposed within 10 h and SCFA, with acetic acid as the major representative, were formed up to 98% of the incubated substrate in colostomy effluent. The amidated pectin was only degraded in part, revealing stable amounts of 22-35% and 3-17% in ileostomy (after 10 h) and colostomy fluid (after 24 h), respectively. SCFA were generated up to 59% of the applied amidated pectin. In parallel, 19-60% and 52-67% of the available methyl ester groups were cleaved in the course of incubations with ileostomy and colostomy fluids, respectively. The results demonstrate for the first time that D-galacturonic acid and amidated pectin are stable in human saliva and simulated gastric juice. The degradation of both compounds during incubation with ileostomy effluent is highlighted, providing evidence for a considerable metabolic potential of the small intestine.     

High-throughput characterization of Pt supported on thin film oxide material libraries applied in the oxygen reduction reaction

Thin film metal oxide material libraries were prepared by sputter deposition of nanoscale Ti/Nb precursor multilayers followed by ex situ oxidation. The metal composition was varied from 6 at.% Nb to 27 at.% Nb. Additionally, thin wedge-type layers of Pt with a nominal thickness gradient from 0 to 5 nm were sputter-deposited on top of the oxides. The materials libraries were characterized with respect to metallic film composition, oxide thickness, phases, electrical conductivity, Pt thickness, and electrochemical activity for the oxygen reduction reaction (ORR). Electrochemical investigations were carried out by cyclic voltammetry using an automated scanning droplet cell. For a nominal Pt thickness >1 nm, no significant dependence of the ORR activity on the Pt thickness or the substrate composition was observed. However, below that critical thickness, a strong decrease of the surface-normalized activity in terms of reduction currents and potentials was observed. For such thin Pt layers, the conductivity of the substrate seems to have a substantial impact on the catalytic activity. Results from X-ray photoelectron spectroscopy (XPS) measurements suggest that the critical Pt thickness coincides with the transition from a continuous Pt film into isolated particles at decreasing nominal Pt thickness. In the case of isolated Pt particles, the activity of Pt decisively depends on its ability to exchange electrons with the oxide layer, and hence, a dependence on the substrate conductivity is rationalized.     

Effect of long-time postweld heat treatments on the mechanical properties of a carbon-manganese pressure vessel steel

Postweld heat treatment is a common practice among building codes for welded steel structures and equipment to reduce the high as-welded residual stress level, improve the fracture toughness, and increase the critical size of acceptable defects. There are many discrepancies among international building codes for storage spheres, pressure vessels, and welded structure components about parameters such as duration and temperature for postweld heat treatments. Furthermore, the codes frequently omit the top number of thermal cycles, which the structure may support to maintain the mechanical properties and toughness in an acceptable level, keeping the physical integrity of the equipment. The present work analyzes the effect of duration of the postweld heat treatments on the mechanical properties and fracture toughness of a carbon-manganese steel of specification ASTM A-516 G 70, which frequently is used to build spheres and pressure vessels in the petrochemical industry. The regions corresponding to the base metal (BM) and heat-affected zone (HAZ) were studied. Through the results obtained from the tensile tests, hardness measurements, Charpy V-notch impact and crack-tip opening displacement (CTOD) testing, and microstructural characterization, it is concluded that the mechanical properties and fracture toughness were reduced by increasing the time of the postweld heat treatment. The degradation of the original properties of the steel is attributed to the changes that occurred in the microstructure. With the welding procedure used, it was verified that the fracture resistance of the HAZ was higher than that of the BM.     

Quantification of the total amount of artemisinin in leaf samples by thin layer chromatography

Artemisinin is a natural molecule highly active against malaria. At present, the extraction of this molecule from the leaves of Artemisia annua L. remains the only viable method to produce cheaply large quantities of artemisinin. Agronomic research on this plant species aims to improve agricultural yields, to decrease production costs and to ensure a steady global supply of artemisinin. These research activities require an easy, rapid, low cost, and reliable analytical technique to quantify the artemisinin content in the leaves. Thin layer chromatography (TLC) methods to quantify this molecule have already been published. However, this method does not allow the quantification of the total artemisinin content in the leaves. In order to validate the TLC method, results obtained with this method were related to results for the same samples obtained by accelerated solvent extraction and high pressure liquid chromatography with an evaporative light scattering detector (ASE-HPLC-ELSD). Using the Nernst partition law, a corrective factor of 1.21 is suggested to enable information about the true total amount of artemisinin in leaf samples to be obtained within a range of 0.25 to 3%. In conclusion, this study proposes for the first time a corrective factor in order to quantify the total artemisinin content of A. annua leaves with TLC.     

Diagnostic localization of insulinoma. Experiences with 25 patients with solitary tumors

A 71-year old man presented with partial rupture progressing to complete rupture of the left ventricular anterior papillary muscle after acute anterolateral myocardial infarction. The progressive rupture was demonstrated by transthoracic and transesophageal echocardiography. Transthoracic echocardiography showed exaggerated systolic prolapse of the anterior mitral leaflet with grade III mitral regurgitation and partial disruption of the anterolateral papillary muscle, but transesophageal echocardiography during surgery disclosed the progression of the partial rupture to complete rupture. The flail anterior mitral leaflet with severe mitral regurgitation and the head of the ruptured papillary muscle into the left atrium in systole were confirmed. The patient was treated by coronary artery bypass grafting and mitral valve prosthesis using a St. Jude Medical valve with good outcome.