Numerical Modeling of Pulse Wave Propagation in a Stenosed Artery using Two-Way Coupled Fluid Structure Interaction (FSI)

As the heart beats, it creates fluctuation in blood pressure leading to a pulse wave that propagates by displacing the arterial wall. These waves travel through the arterial tree and carry information about the medium that they propagate through as well as information of the geometry of the arterial tree. Pulse wave velocity (PWV) can be used as a non-invasive diagnostic tool to study the functioning of cardiovascular system. A stenosis in an artery can dampen the pulse wave leading to changes in the propagating pulse. Hence, PWV analysis can be performed to detect a stenosed region in arteries. This paper presents a numerical study of pulse wave propagation in a stenosed artery by means of two-way coupled fluid structure interaction (FSI). The computational model was validated by the comparison of the simulated PWV results with theoretical values for a healthy artery. Propagation of the pulse waves in the stenosed artery was compared with healthy case using spatiotemporal maps of wall displacements. The analysis for PWV showed significance differences between the healthy and stenosed arteries including damping of propagating waves and generation of high wall displacements downstream the stenosis caused by flow instabilities. This approach can be used to develop patient-specific models that are capable of predicting PWV signatures associated with stenosis changes. The knowledge gained from these models may increase utility of this approach for managing patients at risk of stenosis occurrence

Linkage Isomers of Tungsten Carbonyl Complexes of Ph₂PCH₂PPhCH₂PPh₂

The linkage isomers (CO)5W[η1-PPh2CH2PPhCH2PPh2], 1, and (CO)5 W[η1-PPh(CH2PPh2)2], 2, have been synthesized from the reaction of (OC)5W(NH2Ph) and Ph2PCH2PPhCH2PPh2. In addition, linkage isomers (CO)5W[μ-PPh2CH2PPhCH2PPh2]-W(CO)5, 3, and (CO)5W{μ-PPh2CH2PPh[W(CO)5] CH2PPh2}, 4, have been prepared. Attempts to obtain (OC)5WPPh2CH2PPh[W(CO)5]CH2PPh2W(CO)5 were unsuccessful, yielding instead (CO)5W[μ-η1,η2-PPh2CH2(PPhCH2PPh2)W(CO)4], 5, and (CO)5W[μ-η1, η2-PPh-(CH2PPh2)]W(CO)4, 8. The isomerization reactions of (CO)5W[η1-PPh2CH2PPhCH2PPh2] and (CO)5 W[η1-PPh(CH2PPh2)2] were monitored independently by 31P{1H} NMR spectroscopy. Equilibrium constants and rate constants, k1 and k-1, for the isomerization were determined at 55°C, 40°C and 25°C. A ΔS# value of -220 eu was found for the isomerization reaction, 2 ⇆ 1, is consistent with an associative 7-coordinate transition state and with a mechanism in which the dangling phosphine ligand interacts with the cis carbonyl groups to facilitate the reaction

Flow characteristics of hydraulically fractured granite rocks under high temperature

Hydraulic fracturing technique, which is widely used to enhance the permeability of tight geological formations, has been employed to stimulate unconventional geothermal systems. However, these reservoirs are accompanied by high in-situ stresses and large geothermal gradients. Therefore, it is important to understand the hydraulic fracturing process and the respective permeability enhancement under extreme temperature and pressure conditions. Therefore, the aim of the present study is to understand the effect of flow performance of hydraulically fractured granite under high temperature and pressure conditions. A series of flow-through experiments were conducted on granite specimens which were hydraulically fractured under 60 MPa confining pressure and two temperature conditions: room temperature and 300 °C. Corresponding influence on rock microstructure was studied using high- resolution CT imaging with the IMBL facility of Australian Synchrotron. Based on the experimental results, it was found that one single fracture is induced at room temperature. However, a perforated zone with multiple inter-crystalline cracks is induced in the wellbore zone under the high-temperature fracturing process. Therefore, the measured permeability was almost one order higher in the sample hydraulically fractured under high temperature up to 20 MPa confining pressure. Further, it was identified that the fracture permeability and the fluid discharge were strongly stressed dependent

Coupled flow and salinity transport modelling and assessment of groundwater availability in the Jaffna Peninsula, Sri Lanka

The development of a groundwater management strategy is essential for the sustainable management of groundwater resources. This study describes the hydrogeology of the two main geological formations, which contain freshwater resources in the Jaffna Peninsula, Sri Lanka. A numerical groundwater flow model was developed as part of the investigation to assist in the analysis of freshwater and saltwater flow for current and changing pumping and recharge conditions. The groundwater flow model MODFLOW, mass transport model MT3DMS, and salinity intrusion model SEAWAT were used to provide additional understanding of the regional flow conditions in the aquifers, including regional movement of the interface separating the freshwater and saltwater flow systems. The calibrated model was used to estimate water balance for the Jaffna Peninsula, assess the potential for seawater intrusion and upcoming, and its impact on low salinity groundwater resources

Interstitial cell network volume is reduced in the terminal bowel of ageing mice

Ageing is associated with impaired neuromuscular function of the terminal gastrointestinal (GI) tract, which can result in chronic constipation, faecal impaction and incontinence. Interstitial cells of cajal (ICC) play an important role in regulation of intestinal smooth muscle contraction. However, changes in ICC volume with age in the terminal GI tract (the anal canal including the anal sphincter region and rectum)have not been studied. Here, the distribution, morphology and network volume of ICC in the terminal GI tract of 3‐to 4‐month‐old and 26‐to 28‐month‐old C57BL/6mice were investigated. ICC were identified by immunofluorescence labelling of wholemount preparations with an antibody against c‐Kit. ICC network volume was measured by software‐based 3D volume rendering of confocal Z stacks. A significant reduction in ICC network volume per unit volume of muscle was measured in aged animals. No age‐associated change in ICC morphology was detected. The thickness of the circular muscle layer of the anal sphincter region and rectum increased with age, while that in the distal colon decreased. These results suggest that ageing is associated with a reduction in the network volume of ICC in the terminal GI tract, which may influence the normal function of these regions

Challenges in Applying the DCF Method for Investment Property Valuation in Sri Lanka: Insights from a Delphi Study

This study aimed to identify the challenges of implementing the Discounted Cash Flow (DCF) valuation method for investment properties in Sri Lanka. Through a mixed methodological approach involving the Delphi technique and structured interviews, insights were gathered from industry valuation experts via two Delphi rounds. The study's key findings were derived from the consensus reached among these experts, focusing on data- and valuer-bound factors. One of the primary challenges identified in the Sri Lankan context is the lack of training, which significantly hinders the knowledge and understanding required for implementing the DCF method effectively. Other significant hurdles included obtaining relevant data and accurately determining the discount rate. Imperfections in available data, the absence of a centralized digital data system, and challenges associated with increasing cash flows and market uncertainties also hindered the adoption of the DCF method in Sri Lanka. This study contributes to the existing DCF literature and provides valuable insights for practitioners and future researchers in the field of property valuation in Sri Lanka

Enforcing Information Flow Security Properties in Cyber-Physical Systems: A Generalized Framework Based on Compensation

This paper presents a general theory of event compensation as an information flow security enforcement mechanism for Cyber-Physical Systems (CPSs). The fundamental research problem being investigated is that externally observable events in modern CPSs have the propensity to divulge sensitive settings to adversaries, resulting in a confidentiality violation. This is a less studied yet emerging concern in modern system security. A viable method to mitigate such violations is to use information flow security based enforcement mechanisms since access control based security models cannot impose restrictions on information propagation. Further, the disjoint nature of security analysis is not appropriate for systems with highly integrated physical and cyber infrastructures. The proposed compensation based security framework is foundational work that unifies cyber and physical aspects of security through the shared semantics of information flow. A DC circuit example is presented to demonstrate this concept

Towards portable muography with small-area, gas-tight glass Resistive Plate Chambers

Imaging techniques that use atmospheric muons, collectively named under the neologism "muography", have seen a tremendous growth in recent times, mainly due to their diverse range of applications. The most well-known ones include but are not limited to: volcanology, archaeology, civil engineering, nuclear reactor monitoring, nuclear waste characterization, underground mapping, etc. These methods are based on the attenuation or deviation of muons to image large and/or dense objects where conventional techniques cannot work or their use becomes challenging. In this context, we have constructed a muography telescope based on "mini glass-RPC planes" following a design similar to the glass-RPC detectors developed by the CALICE Collaboration and used by the TOMUVOL experiment in the context of volcano radiography, but with smaller active area (16 $\times$ 16 cm$^{2}$). The compact size makes it an attractive choice with respect to other detectors previously employed for imaging on similar scales. An important innovation in this design is that the detectors are sealed. This makes the detector more portable and solves the usual safety and logistic issues for gas detectors operated underground and/or inside small rooms. This paper provides an overview on our guiding principles, the detector development and our operational experiences. Drawing on the lessons learnt from the first prototype, we also discuss our future direction for an improved second prototype, focusing primarily on a recently adopted serigraphy technique for the resistive coating of the glass plates.Comment: 8 pages, 7 figures, XV Workshop on Resistive Plate Chambers and Related Detectors (RPC2020