Translumbar placement of inferior vena caval catheters: a solution for challenging hemodialysis access

Access to the central venous circulation for hemodialysis has traditionally been achieved via the subclavian or jugular venous routes. With ongoing improvements in medical management, many hemodialysis recipients develop exhaustion of these routes and require alternative means of central venous access. Inferior vena caval (IVC) catheters have been placed with a percutaneous translumbar approach to allow central venous access for chemotherapy, harvesting of stem cells, and total parenteral nutrition. Translumbar placement of IVC catheters has become accepted by some as a useful and reliable alternative in patients who require long-term hemodialysis but have exhausted traditional access sites. IVC catheters have been placed in patients with IVC filters, and IVC filters have been placed in patients with IVC catheters. Complications include those associated with central venous catheters, for example, sepsis, fibrin sheaths, and thrombosis. A complication specific to placement of IVC hemodialysis catheters is migration of the catheter into the subcutaneous soft tissues, retroperitoneum, or iliac veins. Translumbar placement of IVC catheters is performed only in patients considered to have few or no other medical options and is not intended as a primary means of central venous access.     

A methodical assessment of integrative model-based E-course development

A number of course content development models are being prescribed. How effective are these models? Does course content, developed using these models, lead to improved learning? Empirical evaluation is perhaps the only way one can hope to get reliable answers to such questions. This paper describes a methodical assessment process consisting of unique experimental efforts undertaken for evaluation of one such model. After briefly introducing the new systematized courseware development model used, the paper describes the development of an e-course on Introduction to Internet Technology and its evaluation. The evaluation does indicate a significant difference in the knowledge level attained by students learning from online lessons created using the specific development model.     

Effect of hydrogen on four-point bend

U-notched, four-point bend tests of 1090 steel were performed in the presence or absence of precharged hydrogen. Failure occurred in a mode II manner under mixed mode I–II loading, with cracking preceded by plastic instability in the form of surface rumpling and shear localization. The critical strain for surface instability was less in compression than in tension and was reduced by hydrogen, markedly in the tension case and weakly in the compression case. The results are discussed in terms of models for plastic instability and for hydrogen degradation.     

Intermediate Voltage Microscopy

Examining the advantages and limitations of electron microscopy at inter-mediate voltages (greater than ≈100 kV but less than 500 kV), this article emphasizes aspects of microscopy that cannot be performed using ≈100 kV instruments as well as applications that previously required instruments operating at greater than 500 kV. Based on early results, intermediate voltage microscopy appears to be achieving theoretical predictions. In the area of analytical microscopy, however, further research is necessary to explore its full potential. Nevertheless, these new classes of microscopes have enabled high resolution imaging and microanalysis with the same instrument.     

Microstructural study of a high-strength stress-corrosion resistant 7075 aluminium alloy

A heat-treatment procedure providing for enhanced stress-corrosion cracking resistance without any sacrifice of yield strength in 7075 aluminium alloy is investigated using transmission electron microscopy. It is suggested that the heat treatment (known as retrogression and re-ageing) provides for large grain-boundary precipitates and coherent matrix precipitates. The latter provides for the high strength levels while the grainboundary precipitates provide for enhanced stress-corrosion cracking resistance. A hydrogen embrittlement mechanism of stress-corrosion cracking is assigned to this alloy system.