Reactions between Strontium-Substituted Lanthanum Manganite and Yttria-Stabilized Zirconia: II, Diffusion Couples

Formation of secondary phases and diffusion of cations in diffusion couples of yttria-stabilized zirconia and lanthanum manganite substituted with 0 to 60 mol% strontium have been studied by scanning electron microscopy and energy dispersive X-ray spectroscopy. Only the primary phases were observed after 120 h at 1200°C, while formation of secondary phases was identified already after 1 h heat treatment at 1350°C. The phase composition of the reaction layer altered from La₂Zr₂O₇ to SrZrO₃ at increasing Sr content in La _x Sr_{1- x} MnO₃. The thickness of the reaction layer was increasing with heat treatment time. In diffusion couples of La_0.4Sr_0.6MnO₃ formation of manganese oxide was observed in the perovskite layer after 1 h heat treatment at 1350°C, while isolated grains of SrZrO₃ relatively deep inside the zirconia were observed after longer heat treatment time. Diffusion of Mn into zirconia was observed preferenced along grain boundaries in the early stage of the interface reaction.     

A simple method for endoscopic placement of a nasojejunal feeding tube

The aim of this paper is to describe a simple, nonsurgical method for endoscopic placement of a nasojejunal feeding tube. A stylet inserted in the tube facilitates nasogastric intubation. A thread on the tip of the tube is grasped with a biopsy forceps inserted through an endoscope, and the tube can be placed in the distal part of the duodenum under direct endoscopic inspection. By means of a guide wire the tube can be pushed further to the desired position in the upper part of the jejunum. The endoscope can now be removed while pressure is exerted on the stylet, thus preventing the tube from dislocating. By this method, oral-nasal transfer of the tube is avoided, the tube is placed in the upper jejunum under direct endoscopic inspection, and the stylet inserted in the tube facilitates intubation and prevents it from dislocating when the endoscope is withdrawn.     

Compressive Creep Performance of SrFeO3

Compressive creep performance of strontium-deficient and strontium-excess SrFeO_3-δ materials has been investigated in the temperature range 800°–1000°C and in the stress range 2.5–25 MPa. The absolute densities of the strontium-deficient and strontium-excess materials are 4.99 and 5.25 g/cm³, respectively, which corresponds to porosities of ∼2% and 5%, respectively. Both materials contain secondary phases because of the cation nonstoichiometry. The creep rate is faster for the strontium-deficient material than the strontium-excess material. The stress exponent is approximately unity, and the activation energy is 260± 30 kJ/mol for both materials. The results can be explained by a cation diffusion mechanism. The present findings are discussed in relation to previous sintering data and the possible application of these materials as oxygen-permeable membranes.     

512-Mb PROM with a three-dimensional array of diode/antifuse memory cells

A 512-Mb one-time-programmable memory is described, which uses a transistorless two-terminal memory cell containing an antifuse and a diode. Cells are fabricated in polycrystalline silicon, stacked vertically in eight layers above a 0.25-/spl mu/m CMOS substrate. One-time programming is performed by applying a high voltage across the cell terminals, which ruptures the antifuse and permanently encodes a logic 0. Unruptured antifuses encode a logic 1. Cells are arranged in 8-Mb tiles, 1 K rows by 1 K columns by 8 bits high. The die contains 72 such tiles: 64 tiles for data and eight tiles for error-correcting code bits. Wordline and bitline decoders, bias circuits, and sense amplifiers are built in the CMOS substrate directly beneath the memory tiles, improving die efficiency. The device supports a generic standard NAND flash interface and operates from a single 3.3-V supply.     

Exploiting CMOS reverse interconnect scaling in multigigahertzamplifier and oscillator design

The increasing number of interconnect layers that are needed in a CMOS process to meet the routing and power requirements of large digital circuits also yield significant advantages for analog applications. The reverse thickness scaling of the top metal layer can be exploited in the design of low-loss transmission lines. Coplanar transmission lines in the top metal layers take advantage of a low metal resistance and a large separation from the heavily doped silicon substrate. They are therefore fully compatible with current and future CMOS process technologies. To investigate the feasibility of extending CMOS designs beyond 10 GHz, a wide range of coplanar transmission lines are characterized. The effect of the substrate resistivity on coplanar wave propagation is explained. After achieving a record loss of 0.3 dB/mm at 50 GHz, coplanar lines are used in the design of distributed amplifiers and oscillators. They are the first to achieve higher than 10 GHz operating frequencies in a conventional CMOS technology     

Microstructure and the influence of spontaneous strain in LaCoO3, La0.8Sr0.2CoO3 and La0.8Ca0.2CoO3

Transmission Electron Microscopy has been conducted on rhombohedral perovskite oxides with composition LaCoO₃, La_0.8Sr_0.2CoO₃, and La_0.8Ca_0.2CoO₃. Thin foils prepared within the first weeks of sintering showed macroscopic strain and a very high defect density, which included fault-related superlattice structures. Samples prepared several months after sintering, showed no significant macroscopic strain and the main defect was found to be domains due to reflection twinning in the pseudo-cube plane. The behaviour is likely to be related to accomodation of spontaneous strain arising upon cooling of the material from the sintering temperature. The presence of twin domains illustrates the lowering of lattice symmetry as compared to the ideal cubic perovskite structure, and is relevant for explaining recent observations of ferroelastic behaviour of these materials.     

Treatment of Helicobacter pylori infection

The article presents information gained from a survey among Norwegian hospitals in March 1997 concerning their treatment of infections with Helicobacter pylori. Altogether 52 hospitals answered the questionnaire. A combination of proton pump inhibitors, metronidazole and clarithromycin was used by 59% as first choice and urea quick test (94%) and urea breath test (42%) as the primary diagnostic procedures, whereas serology was in little use (17%). Besides ordinary ulcer disease, indications for treatment were: ulcer induced by non-steroid anti-inflammatory drugs (79%), gastrooesophageal reflux (37%), non-ulcer dyspepsia (14%) and cancer prophylaxis (14%). The gastro group at the Department of Pharmacotherapeutics at the University of Oslo invited specialists from all health regions to discuss indications for treatment of H pylori, the diagnosis and the role of general practitioners. The extensive use of clarithromycin might be doubtful due to development of resistance. Indications for treatment of H pylori other than ulcer disease and mucosa associated lymphoid tissue lymphoma are still uncertain. Uncritical use of serological tests in primary care should be discouraged. At present there is no uniform strategy for the diagnosis and treatment of H pylori infection, and a coordinated strategy between general practitioners and specialists is needed.     

Detailed analysis of edge effects in SIMOX-MOS transistors

A comprehensive investigation of edge effects in LOCOS-isolated silicon-on-insulator devices is made by combining the measurements of the static characteristics, charge pumping, and noise. Even when a substrate bias is used to mask the conduction on the island edges, the high-frequency edge effects are still detectable. Appropriate models are proposed to separate the edge contribution from those of the front and back interfaces. It is found that the defect density on the edges is inhomogeneous, increasing vertically from the top to the bottom of the film and laterally from the middle to the end of the channel. Slow traps are identified at the back interface, close to the source/drain junctions     

Nozzle extraction geometry of a liquid metal atomizer optimized bycomputer simulation of electric fields

Experimental measurements are compared with results obtained using a dedicated computer program for finite element modeling of electric fields in the vicinity of a liquid metal atomizer nozzle/tip. Good agreement between the experiment and the computer model has been achieved for two different nozzle geometries (Taylor cone and rounded tip), while paying particular attention to accuracy of the numerical solution near the tip (for equipotentials as well as derived values of field strength). In addition, the potential distribution has been calculated for several different positions of extractor voltage observed for each case. Finally, the assessment of suitability of the computer technique for qualitative consideration of the atomization process itself is presented