Tunneled Catheter–Associated Atrial Thrombi: Successful Treatment with Chronic Anticoagulation

Tunneled dialysis catheter–associated right atrial thrombus (RAT) is a rarely reported complication. We reviewed hospital records of 10 patients from a teaching hospital dialysis unit, in whom RAT was diagnosed by trans‐esophageal echocardiography (TEE). Patients were treated with chronic anticoagulation (heparin followed by warfarin) and followed over time. The group included 7 women; 6 patients were African American, 3 were Caucasian, and 1 was Hispanic. The average age was 52.1 ± 15.3 years. The most common presenting symptom was poor catheter flow on hemodialysis followed by fever and chills. On average, the patients had had 3.4 ± 2.7 catheter insertions before diagnosis of RAT, and the tunneled dialysis catheter (TC) had been in place for a mean of 91 ± 89.4 days when the thrombi were diagnosed. Trans‐thoracic echocardiography (2‐D echo) was done in 4 patients, but it identified RAT in only 1 patient. The catheter tip was at the junction of the superior vena cava and right atrium (SVC/RA) in most patients. Thrombolysis (unsuccessful) was attempted with urokinase in 3 patients, complicated in 2 patients by hemorrhage. After anticoagulation, 90% of the RAT resolved on repeated TEE. One patient had persistent RAT for 23 weeks and underwent surgical thrombolysis, but died postoperatively. We conclude that RAT is a frequently missed complication of a TC. Positioning the tip of the TC at the SVC/RA junction may not prevent RAT. Trans‐esophageal echocardiography is a more sensitive diagnostic tool than 2‐D echo and should be obtained early. Most patients can be successfully treated with anticoagulation alone. Thrombolytic therapy and surgical thrombolysis have high morbidity and mortality.     

Evaluation of Biodegradation of Pineapple Leaf Fiber Reinforced PVA Composites

Composites of polyvinyl alcohol (PVA) reinforced with different weight percentages of pineapple leaf fibers (PALF) were fabricated and evaluated for biodegradation by soil burial test and plate test. FTIR analysis indicated the existence of a chemical interaction between PVA and PALF. The water uptake study showed that the composites with higher fiber content displayed high tensile strength and brittleness but possessed lower water uptake potential. In the soil burial test, the composites with low matrix to filler ratios exhibited higher rates of degradation as evident by the associated decrease in molecular weights. Plate test performed using Pseudomonas putida showed that the composites were susceptible for degradation by bacteria. The results of this study indicated that PALF-reinforced PVA composites were completely biodegradable and could find potential applications in industries such as agriculture and packaging and safely disposed after use without causing environmental damage.     

Recent developments in the fire retardancy of polymeric materials

The widespread applications of polymeric materials require the use of conventional flame retardants based on halogen and phosphorous compounds to satisfy fire safety regulatory standards. However, these compounds, particularly halogen-based examples, are persistent organic pollutants of global concern and generate corrosive/toxic combustion products. To account for eco-friendliness, ultimate mechanical/physical properties and processing difficulties, the window of options has become too narrow. Although the incorporation of non-toxic nanofillers in polymers shows positive potential towards flame retardancy, many obstacles remain. Moreover, most of the literature on these materials is qualitative, and often points to conflicting/misleading suggestions from the perspectives of short-term and long-term fire exposure tests. Hence, there is a renewed need to fundamentally understand the fire response of such materials, and complement experimental results with theoretical modelling and/or numerical simulation.     

Wear and friction behavior of alloyed gray cast iron with solid lubricants under boundary lubrication

Friction and wear behavior of MoS₂, boric acid, graphite and TiO₂ has been compared under extreme boundary lubrication condition. Boundary lubrication was simulated for the study. Results show that MoS₂ and graphite were 30-50% more effective than other two lubricants. Friction coefficient shows a decreasing trend with increase in sliding speed due to increasing temperature and higher shear force. High friction coefficient values were recorded for all the lubricants (0.2-0.5). This is due to predominating solid interactions during boundary lubrication condition. Boric acid and TiO₂ were not much effective in lubrication.     

Remarks on some aspects of language structure and their relevance to pattern analysis

Some specific aspects of language structure are examined in detail in the context of pattern analysis. In particular, a transformational grammar is constructed for a class of patterns, following the linguistic formulation very closely, by taking a simple example and working it out in detail. Many of the characteristics of the transformational grammars of linguists show up even in this simple example. The need for looking for grammars of different styles and the problem of making meaningful assignment of probabilities to sentences in the context of transformational grammars have also been briefly discussed.