The translucent concrete (TC) as a building envelope can offset some lighting energy that is consumed within a room in an office. It is constructed from concrete panels which are functionalized by embedding optical fibers during the manufacturing phase to transmit sunlight. From preliminary results, a volumetric fiber ratio of 6% used in the TC panel leads to savings in lighting energy by around 50%. The utility of panels is enhanced if it reduces the heating and cooling requirements of the office room. The sunlight channeled by optical fibers can contribute in heating of room during winter but in summer months, it leads to spike in cooling loads. Also, daylight reduces heat dissipation from lighting installations and positively impacts cooling loads. The conduction through walls allows heat to be removed from the room during morning but transmits heat from ambient environment into the room later in the afternoon and evening. The presented research combines thermal and lighting analyses to search for an optimal fiber volumetric ratio for TC panels that would result in energy savings. The TC panels can cut down energy expenditure by 18% for a fiber volumetric ratio of 5.6% which renders the fabrication process to be practical.
The last decade has witnessed a heightened interest in making buildings more sustainable, which has been fueled largely by the increase in energy costs and advancements in manufacturing technology. Lighting consumes a substantial amount of this energy, making it necessary to look for alternative technology that depends more on natural lighting. This study investigated a novel building envelope material that consists of optical fibers embedded in concrete. The fibers are used to channel solar radiation into the building to reduce the dependence on artificial lighting especially during peak time. This paper presents a geometrical ray-tracing algorithm to simulate light transmission properties of the proposed translucent concrete panel. It was concluded that a tilt angle of 30°for the panel transmits the maximum amount of light among all the tilt angles considered. Using this tilt angle, the rate at which sunlight radiation is absorbed by the panel was calculated, and a preliminary study was conducted to estimate the solar heat gain coefficient of the panel for possible use in place of a glazing material by the construction industry.
The use of endovascular treatment in the thoracic aorta has revolutionized the clinical approach for treating Stanford type B aortic dissection. The endograft procedure is a minimally invasive alternative to traditional surgery for the management of complicated type-B patients. The endograft is first deployed to exclude the proximal entry tear to redirect blood flow toward the true lumen and then a stent graft is used to push the intimal flap against the false lumen (FL) wall such that the aorta is reconstituted by sealing the FL. Although endovascular treatment has reduced the mortality rate in patients compared to those undergoing surgical repair, more than 30% of patients who were initially successfully treated require a new endovascular or surgical intervention in the aortic segments distal to the endograft. One reason for failure of the repair is persistent FL perfusion from distal entry tears. This creates a patent FL channel which can be associated with FL growth. Thus, it is necessary to develop stents that can promote full re-apposition of the flap leading to complete closure of the FL. In the current study, we determine the radial pressures required to re-appose the mid and distal ends of a dissected porcine thoracic aorta using a balloon catheter under static inflation pressure. The same analysis is simulated using finite element analysis (FEA) models by incorporating the hyperelastic properties of porcine aortic tissues. It is shown that the FEA models capture the change in the radial pressures required to re-appose the intimal flap as a function of pressure. The predictions from the simulation models match closely the results from the bench experiments. The use of validated computational models can support development of better stents by calculating the proper radial pressures required for complete re-apposition of the intimal flap.
Aortic dissection (AD) involves tearing of the medial layer, creating a blood-filled channel called false lumen (FL). To treat dissections, clinicians are using endovascular therapy using stent grafts to seal the FL. This procedure has been successful in reducing mortality but has failed in completely re-attaching the torn intimal layer. The use of computational analysis can predict the radial forces needed to devise stents that can treat ADs. To quantify the hyperelastic material behavior for therapy development, we harvested FL wall, true lumen (TL) wall, and intimal flap from the middle and distal part of five dissected aortas. Planar biaxial testing using multiple stretch protocols were conducted on tissue samples to quantify their deformation behavior. A novel non-linear regression model was used to fit data against Holzapfel–Gasser–Ogden hyperelastic strain energy function. The fitting analysis correlated the behavior of the FL and TL walls and the intimal flap to the stiffness observed during tensile loading. It was hypothesized that there is a variability in the stresses generated during loading among tissue specimens derived from different regions of the dissected aorta and hence, one should use region-specific material models when simulating type-B AD. From the data on material behavior analysis, the variability in the tissue specimens harvested from pigs was tabulated using stress and coefficient of variation (CV). The material response curves also compared the changes in compliance observed in the FL wall, TL wall, and intimal flap for middle and distal regions of the dissection. It was observed that for small stretch ratios, all the tissue specimens behaved isotropically with overlapping stress–stretch curves in both circumferential and axial directions. As the stretch ratios increased, we observed that most tissue specimens displayed different structural behaviors in axial and circumferential directions. This observation was very apparent in tissue specimens from mid FL region, less apparent in mid TL, distal FL, and distal flap tissues and least noticeable in tissue specimens harvested from mid flap. Lastly, using mixed model ANOVAS, it was concluded that there were significant differences between mid and distal regions along axial direction which were absent in the circumferential direction.
Cardiac allograft vasculopathy (CAV) is one of the most common long-term complications in patients following heart transplantation. Because of its irreversible nature, early detection is essential to impact progression. Thus, imaging techniques play a crucial role in the diagnosis and subsequent treatment. Major advancements in imaging and analysis are required to overcome the limitations of current techniques. Coronary angiography which is the standard method, presents low sensitivity in detection, especially at an early stage. Intravascular ultrasonography is a more reliable alternative but is limited to the epicardial vessels. Novel non-invasive techniques, such as stress echocardiography and nuclear imaging, have been introduced but not without limitations. Here, we review various imaging methods and associated analyses to improve diagnostic predictions. We discuss recent advances in the diagnosis of coronary artery disease and their potential translation in the diagnosis of CAV. Additionally, we present potential biomarkers that have been identified for CAV. Finally, we provide a discussion on microvessels with novel anticoagulant properties that are mostly identified in patients with severe CAV.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.