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Biodiesel is among the prospective renewable energy due to its superior properties as fuel such as environment friendly, non-toxic, biodegradable, resulting low pollutant emission, having high energy value and high cetane number, as well as can be readily applied in diesel machine. Biodiesel is also among the priority in the Indonesian national blue print on new and renewable energy development 2005-2025. Currently, Biodiesel is commonly produced through alkaline-catalyzed transesterification of vegetable oil which is conducted in conventional batch reactor. However, this process shows several drawbacks for instance the low reaction conversion. To overcome this challenge, process intensification of biodiesel production using ultrasound-enhanced transesterification process in batch reactor was employed in this work. The feedstock used for biodiesel synthesis in this work was kapok (Ceiba pentandra L.) seed oil. The oil contains gum and high free fatty acid (FFA) as much as 8.89%. Therefore, prior to the transesterification reaction, two steps of pretreatment processes i.e. degumming process for gum removal and esterification for reducing the FFA content until it reaches the value below 2%. The main transesterification reaction was then performed by using ultrasound enhanced batch reactor which was operated at the frequency of 20 Hz and temperature of 60℃ in the presence of KOH catalyst. The reaction time was fixed 60 minutes. On the other hand, the molar ratio of methanol to oil was varied at 1:4, 1:5 and 1:6, and the catalyst concentration was studied at 0.5, 1, and 1.5% w cat/w oil. It was found that highest yield was obtained at the reaction conducted using 0.5% catalyst and the molar ratio of 1.6 with the reaction conversion of 99.82%. This result was higher than the yield resulted by the conventional process performed at the similar condition which revealed the yield of 90%. Biodiesel produced using ultrasound-enhanced reactor fulfilled the SNI standard of properties in term of viscosity and density. [ABSTRACT FROM AUTHOR]

In order to fully assess contrast-enhanced acoustic bioeffects in diagnostic and therapeutic ultrasound, the mechanical properties of microbubbles need to be taken into account. In the present study, direct measurements of the microbubble stiffness were performed using atomic force microscopy by applying nanoscale compressions (up to 25 nN/s) on size-isolated, phospholipid-coated microbubbles (diameters between 4-6 and 6-8 μm). The stiffness was found to lie between 4 and 22 mN/m and to decrease exponentially with microbubble size within the diameter range investigated. No cantilever spring constant effect was noted on the measured stiffness. The Young's modulus of the size-isolated microbubbles used in our study ranged between 0.4 and 2 MPa. Microstructures on the surface of the microbubbles were found to influence the overall microbubble elasticity. Our results indicated that more detailed theoretical models are needed to account for the size-dependent microbubble mechanical properties in order to accurately predict their acoustic behavior. The findings provided useful insights to control cavitation-induced drug and gene delivery and could be used as part of the framework in studies on the shear stresses induced on the blood vessel walls by the oscillating microbubbles. [ABSTRACT FROM AUTHOR]

The aim of this work was to evaluate Shear Wave Elastography (SWE) as a tool to visualize HIFU lesions in an acute in-vivo setting. Extracorporeal HIFU sonications of liver were performed on 14 rabbits in 19 consecutive, adjacent pulses, with in situ energies between 75 J and 228 J. A set of images of the sonicated area was acquired prior and post HIFU ablation: 2 orthogonal SWE images (transverse and sagittal) and contrast enhanced CT scan. SWE images were acquired with theAixplorer® device (SuperSonic Imagine, Aix, France). Prior to the treatment, the liver elasticity appeared homogeneous, with a elasticity comprised between 5 and 11 kPa. The lesion extents were manually segmented on post-treatment SWE images and their areas A(SWE)T (transverse) and A(SWE)S (sagittal) were computed. On 3D CT the lesions were segmented as a hypo intense (devascularized) region on 3D CT images, and considered as "ground truth". The transverse and sagittal planes passing by their centers of mass were extracted. The lesion areas were computed for each plane, respectively A(CT)T and A(CT)S. The ratios A(CT)T/A(SWE)T and A(CT)S/A(SWE)S were computed for all the 14 cases. SWE appear to underestimate the lesion extent in the sagittal orientation with respect to CT images, while a good matching is obtained in the transverse orientation. [ABSTRACT FROM AUTHOR]

Reliable instigation of cavitation in-vivo during ultrasound therapy is notoriously difficult. Lowering the peak rarefractional pressure required to initiate cavitation (the cavitation threshold) has been previously addressed using ultrasound contrast agents in the form of encapsulated stabilized micron scale bubbles. These agents lack stability and are generally too large to extravasate into tumours and other target tissues. Solid nanoparticles are proposed as novel cavitation nucleation agents, which overcome these limitations. Such agents are manufactured to achieve high surface roughness and hydrophobicity, facilitating air entrapment upon drying, thus harboring an abundance of cavitation nucleation sites. These nanoparticulate nucleating agents have been found to lower the cavitation threshold significantly in aqueous biological media, enabling reproducible cavitation activity during repeated exposure to therapeutic ultrasound. This paper investigates the engineering of core-shell nanoparticles and examines their ability to initiate inertial cavitation in the context of ultrasound-enhanced localized drug delivery for cancer. Core-shell nanoparticles have been found to decrease the peak focal pressure where the probability of cavitation is greater than 0.5, by factors of five- to ten-fold, dependent on particle size, total surface area and surface morphology. [ABSTRACT FROM AUTHOR]

The aim of this paper is to introduce a novel approach to quantify liver arterial perfusion. In this study, the contrast-enhanced ultrasound modality is used to investigate liver diseases. The results show the pertinence of this approach in liver carcinoma. The method is based on perfusion estimation, in a regional basis and characterized by a fully-automated tracking of lesion in images sequences based on image statistics. This approach proceeds in two steps in a new framework, a first PDE algorithm and a second segmentation step by competitive clustering. [ABSTRACT FROM PUBLISHER]

A high-intensity focused ultrasound (HIFU) treatment that employs microbubbles to provide enhanced heating has been investigated in order to develop a less invasive and more rapid tumor therapy. Previous studies by the authors have demonstrated that ultrasound propagation is disturbed when microbubbles are in front of the focus. In the present study, we develop a method for obtaining enhanced heating using microbubbles just at the focus, thus avoiding heating on the transducer side. In this method, microbubbles are destroyed in front of the focal position of the HIFU (on the transducer side) by emitting a burst wave prior to the ultrasound waves used for heating the focal position. The burst wave is emitted to destroy the microbubbles. As the non-exposed time increases, the heating region moves from the transducer side to the focus because microbubbles in front of the focus are destroyed, allowing the ultrasound to effectively propagate around the target position. Using a medical ultrasound scanner, microbubble destruction and wave propagation can be visualized from the distribution of the microbubbles. Experimental results suggest that the microbubble distribution and the heating position in the developed HIFU system can be controlled. [ABSTRACT FROM AUTHOR]