An hpr-mesh refinement algorithm for BEM

This paper describes a mesh refinement scheme for boundary element method in which the number of elements, the size of elements, element end locations and the element polynomial order are determined to meet the user specified accuracy. The use of grading function in conjunction with the L₁ norm makes the mesh refinement scheme applicable to a variety of boundary element formulation and applications. The algorithm is stable for smooth, discontinuous, as well as singular density functions. Numerical results for mathematical test functions as well as for elastostatic problems demonstrate the viability and versatility of the algorithm for BEM applications.     

Myocardial stunning in hemodialysis: What is the overall message?

Heart failure and cardiovascular events are common in chronic renal failure. Hemodialysis (HD) causes significant hemodynamic changes and hypotension. New evidence based on intradialytic echocardiography demonstrates transient cardiac dysfunction or stunning in majority of chronic HD patients. Over time, this group may progress to chronic heart failure and appears to predict higher cardiovascular events and mortality. Although the exact etiology is unclear, alterations in HD technique and cardiac medications may reduce this complication. We review the current understanding of acute cardiac stunning during HD and present a systematic management algorithm to optimizing overall outcomes in this high-risk population.     

Role of plasmapheresis in the management of myeloma kidney: a systematic review

Multiple myeloma complicated by acute renal failure is a diagnosis often encountered by the practicing nephrologist. The role of plasmapheresis in such patients has been of interest for decades. Three randomized controlled trials (RCTs) and multiple observational trials have evaluated the potential role of plasmapheresis in the management of this condition. This systematic review presents the results of these trials regarding survival benefits, recovery from dialysis, and improvement in renal function. A comprehensive search revealed 56 articles. Of these, only 8 articles met our inclusion criteria (3 RCTs, 1 correction of results, and 4 observational trials). Two of the 3 RCTs showed no difference in survival benefit. Two of the 3 RCTs showed a greater percentage of patients stopping dialysis in the intervention group; however, these results were not reproduced in the largest trial. All the studies showed an improvement in renal function for patients receiving plasmapheresis; however, only 2 RCTs and 1 retrospective study showed a statistically significant improvement in renal function among patients who received plasmapheresis in comparison with a control group. Our systematic review does not suggest a benefit of plasmapheresis independent of chemotherapy for multiple myeloma patients with acute renal failure in terms of overall survival, recovery from dialysis, or improvement in renal function.     

In0.25Ga0.75As/AlAs-based resonant tunnelingdiodes grown on prepatterned and nonpatterned GaAs (100) substrates

The DC current-voltage characteristics of strained In_0.25 Ga_0.75As/AlAs resonant tunneling diode (RTD) structures grown on GaAs (100) substrates which also include prepatterned mesas are discussed. The observed peak-to-valley current ratios (PVRs) of 4.5 at 300 K and 15 to 77 K with corresponding peak current densities of 11 and 13 kA/cm² are the highest values of PVR to date for this strained system and are the same for the nonpatterned and prepatterned regions     

An algorithm based on the boundary element method for problems in engineering mechanics

The solution to a two-dimensional problem using the boundary element method requires the evaluation of a line integral over the boundary. The integrand ot this line integral is a product of a known Green's function and an unknown function. A large number of Green's functions for two-dimensional problems can be represented by a linear combination of four singular functions. By approximating the unknown function by a linear combination of known polynomials, integrals are generated whose integrand is a product of the polynomiais and one of the four singular functions. To evaluate these integrals analytically, the boundary is approximated by a sum of straight-line segments. Recursive formulae are established which reduce the generality and the complexity of the integrands to simple expressions. Analytical forms for these simple expressions are found and are used for initiating the algorithm.     

Manipulation of gold nanoparticles in liquid environments using scanning force microscopy

Precise and controlled manipulation of individual gold nanoparticles (deposited on a Si/SiO2 surface) in liquid environments using the tip of a scanning force microscope is reported for the first time. Experiments were performed in deionized water and in ethanol as a prototype for an organic solvent. Analysis of the amplitude signal of the cantilever before and during manipulation reveals that the particles are pushed across the surface, similar to the manipulation of nanoparticles in air.     

Postprostatectomy seizures: A case report

A 75-year-old Caucasian male presented with generalized seizures half-hour post-transurethral resection of the prostate surgery. The intra-operative course was complicated by perforation of the posterior wall of the bladder neck during a difficult Foley catheter placement. This resulted in intraperitoneal extravasation of the glycine containing bladder irrigation fluid. An emergent laparotomy was performed, and 3.5-4?L of fluid was drained from the peritoneal cavity. Postoperative course was complicated by two seizures within a short interval. Patient developed profound hyponatremia (Na of 109?mEq/L). However, measured serum osmolality was normal (283?mOsm/kg). The serum osmolality remained relatively stable, indicating that the absorbed glycine and its metabolites remained osmotically active in the intravascular space (until they were dialyzed as mentioned later), making the hyponatremia less pernicious and an unlikely cause of patient's symptoms. The encephalopathy and seizures were ascribed to accumulation of toxic metabolites of glycine, especially ammonia (serum level -1261?mcmol/L). During a complicated postoperative period, patient developed oligo-anuric renal failure, and was started on slow low-efficiency dialysis for 8 hours resulting in rapid lowering of serum ammonia levels and glycine with reversal of encephalopathy including seizures. There was no recurrence of encephalopathy, seizures, or metabolic acidosis. Although rare, glycine toxicity may be life threatening. The pathophysiology, need for early detection and the role of early use of renal replacement therapy in acute glycine toxicity is discussed below.