Numerical analysis of coronary artery bypass grafts: An over view

Arterial bypass grafts tend to fail after some years due to the development of intimal thickening (restenosis). Non-uniform hemodynamics following a bypass operation contributes to restenosis and bypass failure can occur due to the focal development of anastomotic intimal hyperplasia. Additionally, surgical injury aggravated by compliance mismatch between the graft and artery has been suggested as an initiating factor for progress of wall thickening along the suture line Vascular grafts that are small in diameter tend to occlude rapidly. Computational fluid dynamics (CFD) methods have been effectively used to simulate the physical and geometrical parameters characterizing the hemodynamics of various arteries and bypass configurations. The effects of such changes on the pressure and flow characteristics as well as the wall shear stress during a cardiac cycle can be simulated. Recently, utilization of fluid and structure interactions have been used to determine fluid flow parameters and structure forces including stress and strains relationships under steady and transient conditions. In parallel to this, experimental diagnostics techniques such as Laser Doppler Anemometry, Particle Image Velocimetry, Doppler Guide wire and Magnetic Resonance Imaging have been used to provide essential information and to validate the numerical results. Moreover, clinical imaging techniques such as magnetic resonance or computed tomography have assisted considerably in gaining a detailed patient-specific picture of the blood flow and structure dynamics. This paper gives a review of recent numerical investigations of various configurations of coronary artery bypass grafts (CABG). In addition, the paper ends with a summary of the findings and the future directions.     

Determination of density distribution in ferrous powder compacts using ultrasonic tomography.

Laser-induced ultrasonic bulk wave tomography is used for density variation determination of powder metal compacts. A laser beam is used to excite ultrasonic energy, and the signals passing through the specimen are received by an air-coupled transducer. The density variations of powder metal compacts can be determined directly by the cross-sectional tomographic images of slowness obtained by using a filtered, backprojection algorithm based on measured time of flights. Interpolations with respect to sample and projection angles are used to generate the input data required for displaying a well-balanced, reconstructed image to reduce the aliasing distortions caused by insufficient input data. Results of presintered cylindrical ferrous powdered samples show that this novel approach makes the reconstruction process more cost effective than the very tedious, time-consuming, and inaccurate metallographic methods, thus making it a potentially powerful tool for studying manufacturing processes through significant parameters to obtain a more uniform density distribution.     

Classifying and detecting anomalies in hybrid knowledge-based systems

The increasing need for hybrid Knowledge-Based Systems (KBS) that accommodate more complex applications has led to the need for new verification concerns that are more specific to the hybrid representation using objects and rule-based inference. Traditionally, verification of expert systems has focused solely on rule-based inference systems. Hybrid KBSs present additional verification problems not found in traditional rule-based systems. This paper is an investigation into the anomalies that may be present in a hybrid representation that warrant detection for the verification of the KBS. Many anomalies are due to the interaction of the component parts of the hybrid KBS. For example, subsumption anomalies arise due to an interaction between inheritance of objects and rule-based inference. In this paper, we extend the context of subsumption anomalies and introduce additional types of anomalies that may be present in the KBS. The goal of this research is to make hybrid KBSs more reliable by detecting such anomalies.     

Overt and Relational Aggression and Perceived Popularity: Developmental Differences in Concurrent and Prospective Relations.

Relations of overt and relational aggression with perceived popularity among children and early adolescents were examined in 2 studies (Ns = 607 and 1,049). Among older youths, positive concurrent relations found between overt aggression and perceived popularity became nonsignificant when relational aggression was controlled, whereas positive associations found between relational aggression and perceived popularity held when overt aggression was controlled. Aggression and perceived popularity were not positively related for the younger participants. The 2nd study also examined the temporal ordering of these relations over 6 months. For older girls, positive relations between relational aggression and perceived popularity were bidirectional. For older boys, relational aggression did not predict increased perceived popularity, but perceived popularity predicted increased relational aggression. Implications for intervention are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Knowing and Not Knowing About Trauma: Implications for Therapy.

Levels of awareness for trauma and their consequences for research, treatment, and prevention within professional psychology and society are considered. When people must endure chronically traumatic environments, it may be adaptive to isolate from awareness information that would produce cognitive dissonance and threaten necessary relationships. Unawareness may also facilitate functioning in environments that invalidate the prevalence and impact of trauma. In addition, characteristics of the posttraumatic environment can promote or impede individuals' awareness of trauma and their psychological functioning. Though often initially adaptive, unawareness for trauma is linked to intergenerational transmission of trauma and its effects and may preclude public and professional attention to trauma treatment and prevention. Understanding the processes through which individuals become unaware or aware of traumatic experience is therefore essential to conducting effective psychotherapy with trauma survivors. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Evaluation of four blood pump geometries: the optical tracer technique

Artificial blood pump assistance of the failing human heart can allow it to recover. Analysis of blood pump fluid flow is a useful tool for design development and thrombosis minimization. The aim of this study was to investigate fluid flow, particularly ventricular clearance rate and stagnation areas, in four different blood pump geometries and to determine the best design. The blood pumps consisted of a polyurethane ventricle, and combinations of inlet/outlet pipe angles and compression plate shapes. A video camera recorded the motion of fluid labelled with an optical tracer (Methyl Blue histological dye). A novel processing method was developed to produce colour maps of tracer concentration, experimentally calibrated. An overall picture of fluid flow in each pump geometry was generated by considering clearance curves, tracer concentration maps and inflow jet animations. Overall and local mixing coefficients are calculated for each pump. The best geometry featured straight inlet/outlet pipes and a domed compression plate. This optical tracer technique has proven convenient, economical, sensitive to low concentrations of tracer and provides instantaneous pictures of tracer distribution in a ventricle.     

Access to Pediatric Neurologists - Will Telemedicine Close the Gap?

Many times both physicians and patients take for granted that they are qualified to treat certain ages and certain conditions. Neurological conditions are diagnosed and treated by neurologists, pediatric neurologists, and neurosurgeons. What is the difference and why does it matter? It is a balancing act of risk and benefit and the physician’s obligation to know her/his limitations. Telemedicine may play a key role in enabling a greater access to pediatric neurologists. If telemedicine becomes more available, then access even in more remote areas without child neurologists may be possible. As this article discusses, there may be certain limitations to using telemedicine, which is distinguishable from telehealth, in relation to pediatric neurology. This article examines the type of neurological physician that is the most appropriate; the availability of and access to pediatric neurologists; and the applicability of telemedicine to the diagnosis and treatment of pediatric neurological conditions.     

Accelerating protein release from microparticles for regenerative medicine applications

There is a need to control the spatio-temporal release kinetics of growth factors in order to mitigate current usage of high doses. A novel delivery system, capable of providing both structural support and controlled release kinetics, has been developed from PLGA microparticles. The inclusion of a hydrophilic PLGA–PEG–PLGA triblock copolymer altered release kinetics such that they were decoupled from polymer degradation. A quasi zero order release profile over four weeks was produced using 10% w/w PLGA–PEG–PLGA with 50:50 PLGA whereas complete and sustained release was achieved over ten days using 30% w/w PLGA–PEG–PLGA with 85:15 PLGA and over four days using 30% w/w PLGA–PEG–PLGA with 50:50 PLGA. These three formulations are promising candidates for delivery of growth factors such as BMP-2, PDGF and VEGF. Release profiles were also modified by mixing microparticles of two different formulations providing another route, not previously reported, for controlling release kinetics. This system provides customisable, localised and controlled delivery with adjustable release profiles, which will improve the efficacy and safety of recombinant growth factor delivery.