Experimental and Numerical Investigation of Therapeutic Ultrasound Angioplasty

Therapeutic ultrasound angioplasty is an emerging minimally invasive cardiovascular surgical procedure that involves the delivery of ultrasonic displacements to the distal-tip of small diameter wire waveguides. The ultrasonic distal-tip displacements affect atherosclerotic plaque and thrombus by direct contact ablation, pressure wave components and cavitation, in addition to an acoustic streaming event around the distal-tip. This study uses experimental and numerical methods to investigate ultrasonic displacements in wire waveguides and the effect the distal-tip displacements have on the surrounding fluid. An experimental therapeutic ultrasound wire waveguide apparatus is described that delivers displacements to the distal-tip of 1.0 mm and tapered 0.35 mm diameter nickel-titanium (NiTi) waveguides. The operating frequency of the apparatus has been experimentally determined to be 23.5 kHz and for the power settings tested delivers displacements of up to 85 µm peak-to-peak (p-p) to the distal-tip of 1.0 mm diameter waveguides. The apparatus has been shown to directly ablate calcified materials with a stiffer response when compared with atherosclerotic plaques and to generate cavitation and acoustic streaming. A coupled fluid-structure numerical model of the waveguide and fluid surrounding the distal-tip has been developed that predicts the waveguide displacements and stresses along the entire length of the wire waveguide. The structural results of the model have been validated against experimental measurements of the displacements of the waveguide with the inclusion of a constant damping value of 4.5%. The fluid results of the model predict the pressure amplitudes developed in the surrounding fluid and compare closely with values reported in literature. The model predicts the distal-tip displacements required to cause cavitation, a major disruptive event, and has been compared with experimental observations made with the ultrasonic wire waveguide apparatus. The waveguide numerical model will prove a valuable design tool in the further development and improvement of this emerging cardiovascular technology

The Potential of Electrospinning to Enable the Realization of Energy-Autonomous Wearable Sensing Systems

The market for wearable electronic devices is experiencing significant growth and increasing potential for the future. Researchers worldwide are actively working to improve these devices, particularly in developing wearable electronics with balanced functionality and wearability for commercialization. Electrospinning, a technology that creates nano/microfiber-based membranes with high surface area, porosity, and favorable mechanical properties for human in vitro and in vivo applications using a broad range of materials, is proving to be a promising approach. Wearable electronic devices can use mechanical, thermal, evaporative and solar energy harvesting technologies to generate power for future energy needs, providing more options than traditional sources. This review offers a comprehensive analysis of how electrospinning technology can be used in energy-autonomous wearable wireless sensing systems. It provides an overview of the electrospinning technology, fundamental mechanisms, and applications in energy scavenging, human physiological signal sensing, energy storage, and antenna for data transmission. The review discusses combining wearable electronic technology and textile engineering to create superior wearable devices and increase future collaboration opportunities. Additionally, the challenges related to conducting appropriate testing for market-ready products using these devices are also discussed

Pressure Distribution around Spherical Distal Ball-tip in Ultrasound Angioplasty

INTRODUCTION Ultrasound Angioplasty has been shown to be effective in the removal and re-canalising of blockages in arteries (Siegel RJ, 1993). By delivering therapeutic ultrasound to the blockage, via a wire waveguide to a ball-tip, the lesion or thrombus is affected by pressure waves, micro streaming, cavitation and direct contact with the oscillating ball-tip. Most work to date has concentrated on a spherical ball-tip geometry at the distal end of the wire waveguide (Steffen, 1994 and Rosenschein, 1996). Tip displacements usually lie between 10 - 100m (peak-to peak) and ball tip diameters between 1 - 2mm (Atar, 1999 and Yock, 1997). The analytical solution of an oscillating sphere is given in Equation 1 and has previously been used to describe pressures in ultrasound angioplasty (Siegel, 1996). METHODS To simulate the interaction between the ball-tip and surrounding fluid a Finite Element Acoustic Model using fluid-solid interaction and acoustic elements was developed. The displacement and frequency were the input loads on the solid ball tip, while outputs included maximum nodal pressures at points in the acoustic field. From this numerical solution a comparison was performed with the analytical solution to validate the model. DISCUSSION The correspondence between the finite element solution and the analytical solution for an oscillating sphere is shown in Figure 1. This is a plot of the maximum pressures at points axially parallel to the tip at a distance of 1mm. This location is similar to that of the arterial wall, although the presence of the wall is ignored here. Areas of cavitation activity may be identified where the maximum pressure amplitude exceeds ambient fluid pressure. This information may aid in the design of the devices such as desirable ball-tip size, geometry and exposure time. In future work the validated model will be used to solve the pressure distribution around more complex geometries to determine possible advantages in the use of non-spherical ball-tips

Basement membrane properties and their recapitulation in organ-on-chip applications

Drug discovery and toxicology is a complex process that involves considerable basic research and preclinical evaluation. These depend highly on animal testing which often fails to predict human trial outcomes due to species differences. Coupled with ethical concerns around animal testing, this leads to a high demand for improved in vitro cell culture platforms. Current research efforts, in this regard, however, are facing a challenge to provide physiologically relevant in vitro human organ models for a reliable assessment of the physiological responses of the body to drug compounds and toxins. The latest development in in vitro cell culture models, organ-on-chips (OOCs), seek to introduce more realistic models of organ function. Current OOCs often use commercial porous polymeric membranes as a barrier membrane for cell culture which is challenging due to the poor replication of the physiological architectures. Better recapitulation of the native basement membrane (BM) characteristics is desirable for modelling physical (e.g. intestine, skin and lung) and metabolic (e.g. liver) barrier models. In this review, the relevance of the physical and mechanical properties of the membrane to cell and system behaviour is elucidated. Key parameters for replicating the BM are also described. This review provides information for future development of barrier organ models focusing on BM-mimicking substrates as a core structure

Physically Cross-Linked Gels of PVA with Natural Polymers as Matrices for Manuka Honey Release in Wound-Care Applications

Manuka honey is a well-known natural material from New Zealand, considered to have properties beneficial for burn treatment. Gels created from polyvinyl alcohol (PVA) blended with natural polymers are potential burn-care dressings, combining biocompatibility with high fluid uptake. Controlled release of manuka honey from such materials is a possible strategy for improving burn healing. This work aimed to produce polyvinyl alcohol (PVA), PVA⁻sodium carboxymethylcellulose (PVA-CMC), PVA⁻gelatin (PVA-G), and PVA⁻starch (PVA-S) cryogels infused with honey and to characterize these materials physicochemically, morphologically, and thermally, followed by in vitro analysis of swelling capacity, degradation/weight loss, honey delivery kinetics, and possible activity against Staphylococcus aureus. The addition of honey to PVA led to many PVA crystals with defects, while PVA⁻starch⁻honey and PVA⁻sodium carboxymethylcellulose⁻honey (PVA-CMC-H) formed amorphous gels. PVA-CMC presented the highest swelling degree of all. PVA-CMC-H and PVA⁻gelatin⁻honey presented the highest swelling capacities of the honey-laden samples. Weight loss/degradation was significantly higher for samples containing honey. Layers submitted to more freeze⁻thawing cycles were less porous in SEM images. With the honey concentration used, samples did not inhibit S. aureus, but pure manuka honey was bactericidal and dilutions superior to 25% honey were bacteriostatic, indicating the need for higher concentrations to be more effective

Child protection and welfare systems in Ireland: continuities and discontinuities of the present

This chapter provides an overview of the Irish child protection and welfare system, and examines continuities and discontinuities between the past and the present. 2012 is chosen as a pivotal change moment around which to critically examine current developments. This year is chosen due to seminal change events which occurred such as a referendum on the rights of the child and the publication of a report that led to the blueprint for the establishment of an independent Child and Family Agency in Ireland. We chart existing histories of child welfare and comment on significant trends and developments. Against the backdrop of this history, we discuss whether, almost 50 years on, the context, appetite for and investment in change, is to be realised in the biggest structural change to children’s services since the development of Community Care under the Health Act in 1970. In undertaking this analysis, we examine five themes: the establishment of a new Child and Family Agency (Tusla); Signs of Safety adopted as a new national child protection approach; changing trends in child welfare as demonstrated by recent statistics, retention rates for social workers in child protection; and dealing with retrospective child abuse disclosures, institutional abuse and Church-State relations

FTIR analysis and quantification of phenols and flavonoids of five commercially available plants extracts used in wound healing

ABSTRACT Natural products are used in wound healing in order to prevent infection. Propolis is a well known antimicrobial with phenolic compounds and flavonoid content which vary according to the propolis origin. Besides propolis (from both Brazilian and UK sources), pomegranate, dragon's blood and sage are possible antimicrobials to be used in biomaterials. The goal of this work was to analyze the amount of phenols and flavonoid compounds in these natural products, their antioxidant activities and the bonds present by FTIR. The FTIR analysis revealed the presence of active compounds in all drug samples. The phenols quantification showed that Brazilian propolis was rich in phenols compared to the other drugs, followed by pomegranate and UK propolis. UK propolis was the most rich in flavonoids, which is expected on account of its origin. Pomegranate, UK propolis and Dragon's blood presented the highest antioxidant activity. All samples presented antioxidant activity > 82%

Calorie intake and patient outcomes in severe acute kidney injury: Findings from The Randomized Evaluation of Normal vs. Augmented Level of Replacement Therapy (RENAL) study trial

Introduction: Current practice in the delivery of caloric intake (DCI) in patients with severe acute kidney injury (AKI) receiving renal replacement therapy (RRT) is unknown. We aimed to describe calorie administration in patients enrolled in the Randomized Evaluation of Normal vs. Augmented Level of Replacement Therapy (RENAL) study and to assess the association between DCI and clinical outcomes.Methods: We performed a secondary analysis in 1456 patients from the RENAL trial. We measured the dose and evolution of DCI during treatment and analyzed its association with major clinical outcomes using multivariable logistic regression, Cox proportional hazards models, and time adjusted models.Results: Overall, mean DCI during treatment in ICU was low at only 10.9 ± 9 Kcal/kg/day for non-survivors and 11 ± 9 Kcal/kg/day for survivors. Among patients with a lower DCI (below the median) 334 of 729 (45.8%) had died at 90-days after randomization compared with 316 of 727 (43.3%) patients with a higher DCI (above the median) (P = 0.34). On multivariable logistic regression analysis, mean DCI carried an odds ratio of 0.95 (95% confidence interval (CI): 0.91-1.00; P = 0.06) per 100 Kcal increase for 90-day mortality. DCI was not associated with significant differences in renal replacement (RRT) free days, mechanical ventilation free days, ICU free days and hospital free days. These findings remained essentially unaltered after time adjusted analysis and Cox proportional hazards modeling.Conclusions: In the RENAL study, mean DCI was low. Within the limits of such low caloric intake, greater DCI was not associated with improved clinical outcomes. © 2014 Bellomo et al.; licensee BioMed Central Ltd