Capsule-based ultrasound-mediated targeted gastrointestinal drug delivery

Diseases which are prevalent in the gastrointestinal (GI) tract, such as Crohn's disease, are a topic of increasing concern because diagnosis and specific treatment are difficult and may be ineffective. New techniques are therefore sought after and this paper describes a proof-of-concept tethered capsule for targeted drug delivery (TDD) in the GI tract. The capsule consists of a camera, illumination, a drug delivery channel and an ultrasound (US) transducer. The transducer is described in detail, including a comparison of different piezoceramic materials that has been carried out. It was found that PZ54 (Ferroperm Piezoceramics, Kvistgaard, Denmark) was the most suitable material for our application. When driven at 4 Vpp, the outer diameter 5 mm PZ54 transducer operates at a frequency f = 4.05 MHz providing an acoustic pressure, Pac = 125 kPa, with a beam diameter, BD = 0.75 mm at the focus. Pressures in the range 50 - 300 kPa have been previously reported as suitable for sonoporation, a process vital in many TDD applications, so this is a promising result. Basic functional testing of the capsule was performed by supplying glass microbubbles (MBs) through the drug delivery channel into the US focus, monitored via the onboard camera. It was found that the acoustic radiation forces have a clear influence on the MBs, significantly changing their direction at the US focus. This suggests that drugs may be targeted to specific tissue in the GI tract by the new capsule. The results translate into a capsule configuration with the potential to be clinically and biologically useful

Numerical simulation of turbulent pipe flow with elbow bend: comparison between RANS and LES

Primary and secondary flow in 90-degree pipe elbow with curvature radius ratio of Rc/D=2 and Reynolds Number = 60,000 is investigated using CFD to evaluate relative performance between RANS (standard k-ε and RSM) and LES turbulence approaches. The present numerical results are compared against both experimental data (Sudo et al., 1998)and numerical simulations(Kim et al., 2014). In previous publications, RANS and LES have been investigated separately for different flow regimes (based on different Reynolds numbers and curvature radius ratios). The current work aims to make direct comparison between the two different turbulence approaches against validation data and preliminary results are presented in the figure below. The results indicate that RSM predicts the flow regime sufficiently accurate and is less computationally expensive than LES. The computed flow field variables will be coupled to ANSYS Mechanical to model the structural response of the pipe and subsequently the induced vibration

CFD-FEA Based Model to Predict Leak-Points in a 90-Degree Pipe Elbow

The aim of this paper is to numerically investigate Vibration-Based Leak Detection (VBLD) method in pipeline systems based on Fluid-Structure Interaction (FSI) analysis to predict leakages. In previous investigations, laboratory tests were widely used to study the VBLD technique in small-diameter water loop system pipes. The current project uses Ansys Workbench to extend these findings by integrating Computational Fluid Dynamics (CFD) with Finite Element Analysis (FEA). The study outlines a numerical method for VBLD to identify leakages in a 90-degree pipe elbow by predicting variations in vibration signals, with applications in the oil and gas industry. Firstly, changes in fluid behaviour (centrifugal force, pressure drop, secondary flow, and frictional force) experienced in the internal pipe wall resulting from a probable leakage (modelled as an additional outlet) are determined using CFD. Subsequently, the CFD results are coupled with FEA to model structural responses of the pipe walls subjected to different forces. This in turn allows the variations in vibration signals to be measured. The numerical approach presented in this paper based on FSI and incorporating the VBLD method provides a practical and convenient early detection tool that can complement physical vibration monitoring equipment in the field

Effects of curvature radius ratio of 90-degree pipe elbow on FIV signal

Investigation on Flow Induced Vibration (FIV) in pipes is relatively new. Previous publications focused on characterizing the influences of geometric and material properties of a straight pipe. The current study investigates the influence of the curvature radius ratio in a90-degreepipe elbow for ratios (Rc/D = 1.5, 2, 2.5, 3 and 3.5). Reynolds Stress Model (RSM) is coupled with a finite element structural model to simulate the fluid-structure interaction (FSI) using one-way coupling. The RSM turbulence model and FSI model are validated against published experimental and numerical results[1][2][3]. Preliminary results presented in the figure below indicate that vibration signal increases as the curvature ratio decreases in a quadratic manner. This functional relationship can be used as a design tool, and with further application in improving non-intrusive flow measurement techniques

A hydraulically driven colonoscope

BACKGROUND: Conventional colonoscopy requires a high degree of operator skill and is often painful for the patient. We present a preliminary feasibility study of an alternative approach where a self-propelled colonoscope is hydraulically driven through the colon. METHODS: A hydraulic colonoscope which could be controlled manually or automatically was developed and assessed in a test bed modelled on the anatomy of the human colon. A conventional colonoscope was used by an experienced colonoscopist in the same test bed for comparison. Pressures and forces on the colon were measured during the test. RESULTS: The hydraulic colonoscope was able to successfully advance through the test bed in a comparable time to the conventional colonoscope. The hydraulic colonoscope reduces measured loads on artificial mesenteries, but increases intraluminal pressure compared to the colonoscope. Both manual and automatically controlled modes were able to successfully advance the hydraulic colonoscope through the colon. However, the automatic controller mode required lower pressures than manual control, but took longer to reach the caecum. CONCLUSIONS: The hydraulic colonoscope appears to be a viable device for further development as forces and pressures observed during use are comparable to those used in current clinical practice

HelexKids:a word frequency database for Greek and Cypriot primary school children

In this article, we introduce HelexKids, an online written-word database for Greek-speaking children in primary education (Grades 1 to 6). The database is organized on a grade-by-grade basis, and on a cumulative basis by combining Grade 1 with Grades 2 to 6. It provides values for Zipf, frequency per million, dispersion, estimated word frequency per million, standard word frequency, contextual diversity, orthographic Levenshtein distance, and lemma frequency. These values are derived from 116 textbooks used in primary education in Greece and Cyprus, producing a total of 68,692 different word types. HelexKids was developed to assist researchers in studying language development, educators in selecting age-appropriate items for teaching, as well as writers and authors of educational books for Greek/Cypriot children. The database is open access and can be searched online at www.helexkids.org

Prediction of periodic centerline porosity and pulse marks by CFD and experimentation for continuously cast copper

For 8 mm OFCu rod, the formation of pulse mark defects on the exterior of the rod and periodic macroporosity (&gt; 1 mm diameter pores) occurring internally along the centerline of the castings have been observed and noted to limit the maximum attainable withdrawal rates (~ 4 m/s). Conversely, the same casting defects have been witnessed for slower rates; therefore, investigations were performed to investigate how the casting motions (withdrawal, dwell, and pushback) formed these defects and could be prevented. Characterization of the physical properties of the cast rods by tensile testing and analysis by optical and computed tomography (CT) imaging revealed correlations to the outer pitch length marks on the rods and confirmed relationships to casting motions and pitch lengths evaluated from metallurgical equations. Computational fluid dynamic modeling using Ansys Fluent v.R1 was applied to quantify the localized formation and dissipation of periodic hotspots internally within the die for the different motions. A mechanism leading to periodic porosity was identified, which was irrespective of the average casting withdrawal rates and enabled prediction of the location, frequency, and magnitude of the macroporosity defect.<br/