Prognostication of system-state in lead-free electronics equipment under cyclic and steady-state thermo-mechanical loads

In this paper, a mathematical approach for interrogation of system-state under cyclic thermo-mechanical stresses has been developed for three-different lead-free solder alloy systems. Data have been collected for leading indicators-of-failure for alloy systems including, Sn1Ag0.5Cu, Sn3Ag0.5Cu, Sn4Ag0.5Cu second-level interconnects under the application of cyclic thermo-mechanical loads. Methodology presented resides in the pre-failure space of the system in which no macro-indicators such as cracks or delamination exist. Systems subjected to thermo-mechanical damage have been interrogated for system state and the computed damage state correlated with known imposed damage. The approach involves the use of condition monitoring devices which can be interrogated for damage proxies at finite time-intervals. Interrogation techniques are based on non-linear least-squares methods. Various techniques including the Levenberg–Marquardt Algorithm have been investigated. The system’s residual life is computed based on residual-life computation algorithms. Detection of system-state significantly prior to catastrophic failure can significantly impact the reliability and availability of electronic systems. Requirements for system availability for ultra-high reliability electronic systems are driving the need for advanced heath monitoring techniques for early detection of onset of damage. Traditional health monitoring methodologies have relied on reactive methods of failure detection often providing little on no insight into the remaining useful life of the system.     

Volkmann's ischemic contracture: An unusual complication of arterio‐venous fistula

Native arterio‐venous fistulae (AVF) are vascular access of first choice for chronic hemodialysis. However, AVF are also associated with many adverse events like: primary or secondary failure, infection, lymphedema, stenosis, thrombosis, and ischemia of distal extremities. The most common ischemia related complications of AVF are: ischemic neuropathy and steal syndrome with its consequences like pain and peripheral necrosis. Ischemic muscle contracture is a rare complication of AVF. Herein, we are reporting a case of Volkmann's ischemic contracture developing after creation of brachiocephalic AVF.     

Filament Nucleation Tunes Mechanical Memory in Active Polymer Networks

Incorporating growth into contemporary material functionality presents a grand challenge in materials design. The F‐actin cytoskeleton is an active polymer network that serves as the mechanical scaffolding for eukaryotic cells, growing and remodeling in order to determine changes in cell shape. Nucleated from the membrane, filaments polymerize and grow into a dense network whose dynamics of assembly and disassembly, or “turnover,” coordinates both fluidity and rigidity. Here, the extent of F‐actin nucleation is varied from a membrane surface in a biomimetic model of the cytoskeleton constructed from purified protein. It is found that nucleation of F‐actin mediates the accumulation and dissipation of polymerization‐induced F‐actin bending energy. At high and low nucleation, bending energies are low and easily relaxed yielding an isotropic material. However, at an intermediate critical nucleation, stresses are not relaxed by turnover and the internal energy accumulates 100‐fold. In this case, high filament curvatures template further assembly of F‐actin, driving the formation and stabilization of vortex‐like topological defects. Thus, nucleation coordinates mechanical and chemical timescales to encode shape memory into active materials.     

Slow release of ciprofloxacin from double potential drug delivery system

Psyllium polysaccharide is a bulk laxative and has been used for the treatment of constipation which is responsible for the diverticulitis. Ciprofloxacin is an antibiotic used for the microorganism infested in the diverticula. Hence, the functionalization of psyllium with polyvinyl alcohol (PVA) and poly(acrylamide) [poly(AAm)] will develop the drug delivery system (DDS) with potential for dual action for the treatment of diverticulitis, that is, by treating the constipation due to laxative action of psyllium and release of ciprofloxacin from DDS in controlled manner. The optimum conditions for the synthesis of hydrogels have been obtained as 42.21 × 10⁻² mol/L of AAm, 3% (w/v) of PVA, 32.43 × 10⁻³ mol/L of N,N′-methylenebisacrylamide (NN-MBA), 17.53 × 10⁻³ mol/L ammonium persulfate, and 1 g of psyllium. The characterization of the hydrogels has been carried out by SEMs, EDAX, FTIR, and swelling studies. Swelling and drug release studies have also been carried out to determine the mechanism of swelling of hydrogels and drug release from the drug loaded hydrogels. The release of the drug from the hydrogels occurred through Fickian diffusion mechanism in pH 2.2 and pH 7.4 buffer.     

Extraction and Characterization of Lignocellulosic Fibers from Girardinia Bullosa (Steudel) Wedd. (Ethiopian Kusha Plant)

ABSTRACT

Currently, eco-friendly products have been given great attention as the world is being polluted severely by non-biodegradable products and by-products. Different textile products have their own share in affecting the environment. This research is focused on exploring alternative bast fiber products to support the supply chain and to assess the possibility of using this fiber as a substitute to already available bast fibers. Kusha fiber was extracted and optimized from Ethiopian kusha plant stem – Girardinia bullosa (Steudel) wedd. – using caustic soda solution by varying the concentration, temperature, and time using design expert 6.0.10, quadratic model software. Tensile property, chemical composition, X-ray diffractometer (XRD), Fourier-transform-infrared spectroscopy (FTIR), fiber morphology, and thermogravimetric analysis (TGA) of the fiber were determined. Fiber characterization showed its tensile strength, and the cellulose content was equivalent to or even better than other bast fibers. Morphology of the fiber was similar to that of typical cotton with visible lumen and a slightly flat surface. Therefore, this new extracted fiber has a great potential to be used for different applications such as fiber-reinforced composites, textile furnishing, apparel, and nanocellulose extraction.