Bifurcation Angle Research Articles

Evaluating the Temperature Profile in a Branched Tunnel Fire with Various Ramp Slopes: An Experimental Study

ABSTRACT This study conduct a set of small-scale experiments to examine the combined impact of ramp slopes and bifurcation angles on the longitudinal temperature profile beneath the ceiling of a model of branched tunnel. A Liquefied Petroleum Gas (LPG) fire was used to simulated car fires. The range of heat release rates for the experiments was 2.57 kW to 7.70 kW. The experiments also encompassed three bifurcation angles (5° to 15°) and five ramp slopes (0%, 3%, 5%, 7%, and 9%). A simple model was developed to analyze the steady fire-produced ceiling jet in the branched tunnel. It has been found that the longitudinal temperature decay was not affected by the ramp slopes and bifurcation angles. However, the longitudinal temperature decay varied across different tunnel regions due to the dimensions of the tunnel cross section and the branched structure resulting in smoke divergence flow. In addition, the study established a modified model of longitudinal temperature decay based on the experimental results. The results could be used as a point of reference in developing smoke extraction tactics for branched tunnels.

Left main coronary artery morphological phenotypes and its hemodynamic properties.

Atherosclerosis may be linked to morphological defects that lead to variances in coronary artery hemodynamics. Few objective strategies exit at present for generalizing morphological phenotypes of coronary arteries in terms of hemodynamics. We used unsupervised clustering (UC) to classify the morphology of the left main coronary artery (LM) and looked at how hemodynamic distribution differed between phenotypes. In this study, 76 LMs were obtained from 76 patients. After LMs were reconstructed with coronary computed tomography angiography, centerlines were used to extract the geometric characteristics. Unsupervised clustering was carried out using these characteristics to identify distinct morphological phenotypes of LMs. The time-averaged wall shear stress (TAWSS) for each phenotype was investigated by means of computational fluid dynamics (CFD) analysis of the left coronary artery. We identified four clusters (i.e., four phenotypes): Cluster 1 had a shorter stem and thinner branches (n = 26); Cluster 2 had a larger bifurcation angle (n = 10); Cluster 3 had an ostium at an angulation to the coronary sinus and a more curved stem, and thick branches (n = 10); and Cluster 4 had an ostium at an angulation to the coronary sinus and a flatter stem (n = 14). TAWSS features varied widely across phenotypes. Nodes with low TAWSS (L-TAWSS) were typically found around the branching points of the left anterior descending artery (LAD), particularly in Cluster 2. Our findings demonstrated that UC is a powerful technique for morphologically classifying LMs. Different LM phenotypes exhibited distinct hemodynamic characteristics in certain regions. This morphological clustering method could aid in identifying people at high risk for developing coronary atherosclerosis, hence facilitating early intervention.

Partitioning of dense RBC suspensions in single microfluidic bifurcations: role of cell deformability and bifurcation angle

Red blood cells (RBCs) are a key determinant of human physiology and their behaviour becomes extremely heterogeneous as they navigate in narrow, bifurcating vessels in the microvasculature, affecting local haemodynamics. This is due to partitioning in bifurcations which is dependent on the biomechanical properties of RBCs, especially deformability. We examine the effect of deformability on the haematocrit distributions of dense RBC suspensions flowing in a single, asymmetric Y-shaped bifurcation, experimentally. Human RBC suspensions (healthy and artificially hardened) at 20% haematocrit (Ht) were perfused through the microchannels at different flow ratios between the outlet branches, and negligible inertia, and imaged to infer cell distributions. Notable differences in the shape of the haematocrit distributions were observed between healthy and hardened RBCs near the bifurcation apex. These lead to more asymmetric distributions for healthy RBCs in the daughter and outlet branches with cells accumulating near the inner channel walls, exhibiting distinct hematocrit peaks which are sharper for healthy RBCs. Although the hematocrit distributions differed locally, similar partitioning characteristics were observed for both suspensions. Comparisons with RBC distributions measured in a T-shaped bifurcation showed that the bifurcation angle affects the haematocrit characteristics of the healthy RBCs and not the hardened ones. The extent of RBC partitioning was found similar in both geometries and suspensions. The study highlights the differences between local and global characteristics which impact RBC distribution in more complex, multi-bifurcation networks.

Investigation of air bubble behaviour after gas embolism events induced in a microfluidic network mimicking microvasculature.

Gas embolism is a medical condition that occurs when gas bubbles are present in veins or arteries, decreasing blood flow and potentially reducing oxygen delivery to vital organs, such as the brain. Although usually reported as rare, gas embolism can lead to severe neurological damage or death. However, presently, only limited understanding exists regarding the microscale processes leading to the formation, persistence, movement, and resolution of gas emboli, as modulated by microvasculature geometrical features and blood properties. Because gas embolism is initially a physico-chemical-only process, with biological responses starting later, the opportunity exists to fully study the genesis and evolution of gas emboli using in vitro microfluidic networks mimicking small regions of microvasculature. The microfluidics networks used in this study, which aim to mimic microvasculature geometry, comprise linear channels with T-, or Y-junction air inlets, with 20, 40, and 60 μm widths (arterial or venous), and a 30 μm width honeycombed network (arterial) with three bifurcation angles (30°, 60°, and 90°). Synthetic blood, equivalent to 46% haematocrit concentrations, and water were used to study the modulation of gas embolism-like events by liquid viscosity. Our study shows that (i) longer bubbles with lower velocity occur in narrower channels, e.g., with 20 μm width; (ii) the resistance of air bubbles to the flow increases with the higher haematocrit concentration; and lastly (iii) the propensity of gas embolism-like events in honeycomb architectures increases for more acute, e.g., 30°, bifurcation angles. A dimensionless analysis using Euler, Weber, and capillary numbers demarcated the conditions conducive to gas embolism. This work suggests that in vitro experimentation using microfluidic devices with microvascular tissue-like structures could assist medical guidelines and management in preventing and mitigating the effects of gas embolism.

Quantitative analysis of right coronary artery morphology by digital subtraction angiography

The right coronary artery (RCA) is a major target for interventional and surgical procedures, but its anatomical variations and normal reference values are not well established. This study aimed to establish the normal distribution values of the length, diameter and angle measurements of the RCA. Angiography images of the RCA of 143 patients were analyzed using digital subtraction angiography techniques. The RCA images of each patient were divided into three sections (Proximal RCA, Middle RCA, Distal RCA) and length and diameter measurements were made separately for each section. In addition, the angles formed between the posterior descending artery (PD) and posterior lateral artery (PL) of the RCA and the lengths and diameters of the PD and PL branches were measured separately. The RCA length-diameter measurements were 1.75-4.7 mm for proximal RCA, 4.75-4.2 mm for middle RCA, and 7.45-3.5 mm for distal RCA. The mean values of the angles formed between RCA-PL, PL-PD (bifurcation angle), and RCA-PD were 144.33±19.22˚, 62.67±18.94˚, 151.40±19.33˚, respectively. Our study provides important epidemiological data on the length-diameter-angle values of the RCA. The presented data will be useful in guiding the success and clinical outcomes of the RCA in both interventional and surgical procedures.

PERCOLATION CHARACTERISTICS OF POWER-LAW FLUID IN THE FRACTAL TREE-LIKE BIFURCATION NETWORKS WITH ROUGH SURFACES

In order to study the seepage characteristics of power-law fluids in the fractal tree-like bifurcation networks with rough surfaces based on fractal theory, the shape factor of rough surfaces is treated as the randomly distributed cones. According to the generalized Darcy's law and the constitutive equation of power-law fluids, the fully-developed laminar and incompressible flow of power-law fluids in rough pipelines is explored, and the velocity graduation and flow rate expressions of fluids in rough pipelines are obtained. Then, the fractal model for the permeability of power-law fluid in the tree-like bifurcation network with rough surfaces is proposed, and the total flow rate, total pressure drop, and permeability of power-law fluid in the tree bifurcation network with rough surfaces are derived. The relative increase in pressure and the relative decrease in permeability are also obtained. Finally, the analytical expression for the permeability of power-law fluids is analyzed. It can be seen that the permeability of a rough tree-like bifurcation network is inversely proportional to relative roughness, length ratio, bifurcation angle, etc., and directly proportional to the power-law index and diameter ratio. At the same time, the predicted values of the model are compared with existing models, proving the correctness and rationality of the model.

Time course of histopathology of bleomycin-induced pulmonary fibrosis using an intratracheal sprayer in mice.

Idiopathic pulmonary fibrosis (IPF) is a poor prognosis disease that affects approximately 5 million people worldwide, and the detailed mechanisms underlying the pathogenesis of IPF remain unclear. Bleomycin-induced pulmonary fibrosis has been widely used as a representative animal model of IPF that induces fibrosis in lung tissue. The lungs of rodent consist of five lobes and each bronchus enters each lobe of the lung at a different bifurcation angle, path length, and diameter. The method of administration of bleomycin is considered as important thing to establish appropriate animal models. We conducted a time-dependent histopathological study to examine how pulmonary fibrosis develops in each lung lobe when bleomycin was intratracheally sprayed in ICR mice. And we then explored the suitable points for evaluation of anti-fibrotic agents in this model. As a result, we found that homogeneous fibrosis was induced in the 5 lobes of the lungs following initial inflammation. The expression of transforming growth factor (TGF)-β1 and phospho-Smad2 (pSmad2) was observed from Day 1, and their positivity increased until Day 21. In conclusion, we have observed a detailed time course of histological changes in bleomycin-induced pulmonary fibrosis in ICR mice using the aerosolization technique. We found that our protocol can induce a highly homogeneous lesion in the lung and that the most suitable time point to assess anti-fibrotic agents is 14 days after treatment in this model.

Investigation on the Effects of Bifurcation and Trifurcation Angle on Plaque Initiation and Rupture

Investigation on the Effects of Bifurcation and Trifurcation Angle on Plaque Initiation and Rupture

Pore-scale imbibition patterns in layered porous media with fractures

The presence of fractures increases the difficulty of flow mechanisms analysis, and it remains unclear how fractures affect multiphase flow displacement in the layered rock matrix. Herein, a pore-scale imbibition model considering the layered matrix-fracture system is established using the phase-field method, where oil is displaced by a range of fluids with various properties. Two typical flow modes are carefully analyzed, depending on the locations of the fracture and the interfaces between different layers of the matrix: fracture is parallel to the interface (mode I), and it penetrates through the interface (mode II), which are dominated by the co-current imbibition and countercurrent imbibition mechanisms, respectively. Interestingly, the surface tension is found to be negatively correlated with the ultimate oil recovery rate for mode I and plays an opposite effect on that of mode II. For flow mode I, the conditions of lower injection rate, higher viscosity ratio, higher grain diameter ratio, and injection of the invading fluid from the larger pore throat size (positive direction flow) can improve oil recovery. For flow mode II, the fracture bifurcation angle has little effect on the positive direction flow, while it can significantly regulate the phase distribution in the negative direction flow. Based on scaling analysis of relating pore-filling events to displacement modes and the equilibrium relationship between capillary and viscous forces, two theoretical models are derived to predict the imbibition patterns, and the variation of the flow regime under various parameters in the typical layered matrix-fracture models is systematically concluded.

3D printing in microfluidics: experimental optimization of droplet size and generation time through flow focusing, phase, and geometry variation.

Droplet-based microfluidics systems have become widely used in recent years thanks to their advantages, varying from the possibility of handling small fluid volumes to directly synthesizing and encapsulating various living forms for biological-related applications. The effectiveness of such systems mainly depends on the ability to control some of these systems' parameters, such as produced droplet size and formation time, which represents a challenging task. This work reports an experimental study on tuning droplet size and generation time in a flow-focusing geometry fabricated with stereolithography 3D printing by exploring the interplay of phase and geometrical parameters. We produced droplets at different low flow rates of continuous and dispersed phases to assess the effect of each of these phases on the droplets' size and formation time. We observed that smaller droplets were produced for high viscosity oil and water phase, along with high flow rates. In addition, changing the microfluidics channels' width, and morphology of the orifice has shown a similar effect on droplet size, as shown in the case of high-viscosity solutions. The variation of the bifurcation angle shows a noticeable variation in terms of the achieved droplet size and formation time. We further investigated the impact of modifying the width ratio of the continuous and dispersed phases on droplet formation.

The effect of bifurcation angulation on flow characteristics and hemodynamic indicators in an idealized left coronary artery

Atherosclerosis is a pathological condition characterized by inflammation in the main arteries, which serves as the primary factor for the development of cardiovascular disease. This condition represents the prevailing medical and surgical issue. Clinically, consequences of this condition might include stroke, coronary artery and heart disease, or peripheral vascular disease. In this study, the hemodynamic effect of three different angulations is numerically analyzed on left coronary artery and constant degree of stenosis (DoS) which equals to 50 % is implemented on each branch of three models to create stenotic arteries. The idealized left main coronary artery (LM) is modeled with its primary branches, namely left anterior descending (LAD) and left circumflex (LCx). The bifurcation angulations between LAD and LCx are considered 30°, 75° and 120°. All numerical analyses are carried out in transient regime, blood is considered as a non-Newtonian fluid and the Carreau viscosity model is selected to describe the viscosity variation of blood. The outcomes of all numerical analyses revealed that the blood flow across the branches is closely related to bifurcation angle. Recirculation is vital in the post-stenotic regions of LAD and LCx, and velocity enhances its breadth. WSS is highest in the stenosis and carina regions. OSI values are greater in the post-stenotic LAD and LCx regions where recirculation and plaque development are more likely. Helical flow appears in the post-stenotic region of the LM when velocity is lowest and in the stenotic area when velocity is highest.

Middle cerebral artery bifurcation aneurysms are associated with patient age, sex, bifurcation angle, and vascular diameters

To investigate the relationship of the middle cerebral artery (MCA) bifurcation aneurysms with patients’ age and sex, vascular angles at the bifurcation, and diameters of the M1 and two M2 arteries, patients with and without MCA aneurysms were retrospectively enrolled. The lateral angles, MCA bifurcation angle and arterial diameter were measured and analyzed. Totally, 121 (19.0%) patients with and 517 (81.0%) without MCA aneurysms were enrolled. Most (n = 88 or 72.7%) aneurysms were present in the age range of 40–70 years, and significantly (P = 0.01) more women than men had the bifurcation aneurysms. The MCA bifurcation angle was significantly greater (149.2° ± 32.6° vs. 107.2° ± 26.3°; P < 0.0001) while both the smaller and larger lateral (M1/M2) angles were significantly smaller in patients with than without aneurysms (82.0° ± 23.7° vs. 109.1° ± 22.7° with P < 0.001 for the smaller and 123.2° ± 25.2° vs. 139.5° ± 16.9° with P < 0.001 for the larger lateral angle). 109 (90.1%) bifurcation aneurysms deviated towards the smaller lateral angle, and 103 (85.1%) aneurysms deviated towards the thinner M2 branch. The maximal aneurysm diameter ranged 1.6–13.8 (mean 5.4 ± 2.4) mm and was significantly (P < 0.05) positively correlated with the diameter of both M2 arterial branches (R = 0.57 and P = 0.01 for the smaller M2, and R = 0.69 and P = 0.002 for the larger M2) or the MCA bifurcation angle. A significant (P < 0.0001) negative correlation was detected between age and the smaller lateral angle but a significant (P < 0.0001) positive correlation between age and the MCA bifurcation angle in patients without MCA bifurcation aneurysms or in the total patients. MCA bifurcation angle was the only significant (P = 0.0001, odds ratio 2.7, 95% confidence interval 1.6–3.8) independent risk factor for MCA bifurcation aneurysm presence, with the bifurcation angle threshold of 124.1° and an area under the ROC curve of 0.86. In conclusion, significantly more MCA bifurcation aneurysms are present in older patients, females, and patients with a wider MCA bifurcation angle, and deviate towards the smaller lateral angle and the thinner M2 segment. MCA bifurcation angle is the only independent risk factor for presence of MCA bifurcation aneurysms with the threshold of 124.1°.

Fried-Breadstick sign: A novel marker for healthy vasculature in magnetic resonance angiography

The Fried-Breadstick sign is characterized as a continuous signal loss at the center of the intracranial internal carotid artery (ICA) on time-of-flight magnetic resonance angiography (TOF-MRA). In this study, we present a novel imaging marker on TOF-MRA and investigate its potential association with ICA-middle cerebral artery (ICA-MCA) atherosclerosis and ischemic stroke. Vessel wall magnetic resonance imaging data were obtained from patients with recent clinical stroke or asymptomatic patients with suspected middle cerebral artery (MCA) atherosclerosis, covering the period from January 2007 to August 2015. We conducted a comparative analysis of ICA stenosis, MCA atherosclerosis and stenosis degree, and the terminal ICA bifurcation angle between ICA-MCAs with and without the Fried-Breadstick sign, involving a total of 1,005 ICA-MCAs from 553 patients. The Fried-Breadstick sign exhibited a higher prevalence in non-to-mild stenotic ICAs (57.5% vs. 9.8% in severely stenotic ICA, P &lt; 0.001) and plaque-free MCAs (53.2% vs. 26.6% in MCAs with plaque, P &lt; 0.001). Factors independently associated with the presence of the Fried-Breadstick sign included MCA stenosis degree (odds ratio [OR]: 0.85/10% increase, 95% confidence interval [CI]: 0.80 &amp;ndash; 0.90), ICA stenosis (compared to non-to-mild stenosis, moderate stenosis: OR: 0.39, 95% CI: 0.28 &amp;ndash; 0.54, severe stenosis: OR: 0.10, 95% CI: 0.06 &amp;ndash; 0.17), and terminal ICA bifurcation angle (OR: 0.86/10&amp;deg; increase, 95% CI: 0.79 &amp;ndash; 0.93). In atherosclerotic MCAs without luminal narrowing, the Fried-Breadstick sign was also less frequently observed than in plaque-free MCAs (34.6% vs. 53.2%, P = 0.012). In conclusion, the presence of the Fried-Breadstick sign is associated with healthier ICA-MCAs devoid of stenosis or plaque. The Fried-Breadstick sign may signify healthy ICA-MCA hemodynamics, serving as a potential screening tool for intracranial atherosclerosis without incurring additional cost or risk.

Versatile Ultrasound-Compatible Microfluidic Platform for In Vitro Microvasculature Flow Research and Imaging Optimization.

Ultrasound localization microscopy (ULM) enables the creation of super-resolved images and velocity maps by localizing and tracking microbubble contrast agents through a vascular network over thousands of frames of ultrafast plane wave images. However, a significant challenge lies in developing ultrasound-compatible microvasculature phantoms to investigate microbubble flow and distribution in controlled environments. In this study, we introduce a new class of gelatin-based microfluidic-inspired phantoms uniquely tailored for ULM studies. These devices allow for the creation of complex and reproducible microvascular networks featuring channel diameters as small as 100 μm. Our experiments focused on microbubble behavior under ULM conditions within bifurcating and converging vessel phantoms. We evaluated the impact of bifurcation angles (25, 45, and 55°) and flow rates (0.01, 0.02, and 0.03 mL/min) on the acquisition time of branching channels. Additionally, we explored the saturation time effect of narrow channels branching off larger ones. Significantly longer acquisition times were observed for the narrow vessels, with an average increase of 72% when a 100 μm channel branched off from a 300 μm channel and an average increase of 90% for a 200 μm channel branching off from a 500 μm channel. The robustness of our fabrication method is demonstrated through the creation of two trifurcating microfluidic phantoms, including one that converges back into a single channel, a configuration that cannot be achieved through traditional methods. This new class of ULM phantoms serves as a versatile platform for noninvasively studying complex flow patterns using ultrasound imaging, unlocking new possibilities for in vitro microvasculature research and imaging optimization.

Entropy-driven optimization of radiative Jeffrey tetrahybrid nanofluid flow through a stenosed bifurcated artery with Hall effects

Atherosclerosis, which causes the artery walls to thicken, the lumen to narrow, and the wall to thin in some places, is characterized by plaque accumulation in the arteries. These blood flow modifications can cause aneurysms and heart attacks if left unattended. Most of the arteries in the cardiovascular system are branched; therefore, a parent artery (main artery) with two daughter arteries (branched arteries) is considered in the present analysis. To examine the impact of various nanoparticle combinations on blood flow, four distinct nanoparticles, namely, gold (Au), graphene oxide (GO), copper (Cu), and tantalum (Ta), were injected into the blood to generate Au–GO–Cu–Ta/blood tetrahybrid nanofluid. In arteries with small diameters, blood behavior is regarded as non-Newtonian; therefore, blood behavior is governed by Jeffrey fluid in the present analysis. It has been investigated how Hall effects, Joule heating, radiation, and viscous dissipation affect blood flow through an artery that has an overlapping stenosis in the branches and a bell-shaped stenosis in the main artery. The approximation of mild stenosis is utilized to simplify and non-dimensionalize the governing equations. The Crank–Nicolson finite-difference scheme is used in MATLAB to solve the resulting equations. The results for velocity, temperature, wall shear stress, flow rate, and heat transfer rate are represented graphically. Furthermore, the entropy optimization has been performed for the specified problem. Enhancement in velocity with half of the bifurcation angle (η) can be observed from the velocity contours. The velocity of the tetrahybrid nanofluid increases with an increase in Jeffrey fluid parameter (λ1*) and shape parameter of the nanoparticles (n) as well. Introducing nanoparticles into the bloodstream can improve targeted drug delivery, allowing for more precise treatment at the cellular level. In addition, the tunable properties of nanoparticles offer possibilities for enhanced therapeutic and diagnostic treatments in a variety of medical disorders.

Computed tomography-based imaging biomarker identifies coal workers’ pneumoconiosis

Rationale: The increase in the incidence and the diagnostic limitations of pneumoconiosis have emerged as a public health concern. This study aimed to conduct a computed tomography (CT)- based quantitative analysis to understand differences in imaging results of pneumoconiosis according to disease severity.Methods: According to the International Labor Organization (ILO) guidelines, coal workers’ pneumoconiosis (CWP) are classified into five categories. CT images were obtained only at full inspiration and were quantitatively evaluated for airway structural variables such as bifurcation angle (θ), hydraulic diameter (Dh), wall thickness (WT), and circularity (Cr). Parenchymal functional variables include abnormal regions (emphysema, ground–glass opacities, consolidation, semi consolidation, and fibrosis) and blood vessel volume. Through the propensity score matching method, the confounding effects were decreased.Results: Category 4 demonstrated a reduced θ in TriLUL, a thicker airway wall in both the Trachea and Bronint compared to Category 0, and a decreased Cr in Bronint. Category 4 presented with higher abnormal regions except for ground–glass opacity and a narrower pulmonary blood vessel volume. A negative correlation was found between abnormal areas with lower Hounsfield units (HU) than the normal lung and the ratio of forced expiratory volume in 1 s/forced vital capacity, with narrowed pulmonary blood vessel volume which is positively correlated with abnormal areas with upper HU than the normal lung.Conclusion: This study provided valuable insight into pneumoconiosis progression through a comparison of quantitative CT images based on severity. Furthermore, as there has been paucity of studies on the pulmonary blood vessel volume of the CWP, in this study, a correlation between reduced pulmonary blood vessel volume and regions with low HU values holds significant importance.

Morphology and variability of the facial nerve trunk depending on the branching pattern, gender, anthropometric type and side of the head in Moldovan population.

Knowledge concerning variability of the facial nerve trunk (FNT) direction after its exit through the stylomastoid foramen is of a great clinical significance for maxillofacial surgeons, otorhinolaryngologists, oncologists, specialists in plastic and aesthetic surgery. The aim of our study was to establish the variation of the FNT direction and its peculiarities depending on the branching pattern, gender, anthropometric type and side of the head. The direction of the FNT and its branching pattern were studied on 75 dissected hemifaces of adult formalised cadavers (59 male/ /16 female), and the morphometry of the FNT length, width and bifurcation angle was carried out. Seven branching patterns of the facial nerve were established: type I - 18.7%, type II - 14.7%, type III - 20%, type IV - 14.6%, type V - 5.3%, type VI - 18.7%, and type NI - 8% (bizarre types). The FNT had a descending direction in 73.3% of cases; ascending FNT - 9.3% (including 5.3% of very short diffuse branching trunks and 1.3% of arch-shaped FNT); horizontal FNT - 10.7%; number variants - 6.7%. The male/female ratio of the descending FNT was 69.5%/87.4%; ascending - 10.2%/6.3%; horizontal - 11.9%/6.3%; number variants - 8.4% (only in male). The right/left ratio of the descending FNT was 62.9%/82.5%; ascending - 11.4%/7.5%; horizontal - 11.4%/10%; number variants - 14.3% (only on the right side). The ratio of the descending FNT in mesocephalic type (MCT)/brachycephalic type (BCT)/dolichocephalic type (DCT) was respectively 70.6%/100%/66.7%; ascending - 12.1%/0%/0%; horizontal - 12.1/0%/11.1%. Numerical variants in MCT - 5.2%, in DCT - 22.2%. The mean number of FNT in MCT/BCT/DCT was respectively 1.07/1.0/1.22. Three main directions are characteristic of the FNT: the descending, ascending and horizontal ones, which vary depending on the branching pattern, gender, shape and side of the head.

CT-based comparison of porcine, ovine, and human pulmonary arterial morphometry

To facilitate pre-clinical animal and in-silico clinical trials for implantable pulmonary artery pressure sensors, understanding the respective species pulmonary arteries (PA) anatomy is important. Thus, morphological parameters describing PA of pigs and sheep, which are common animal models, were compared with humans. Retrospective computed tomography data of 41 domestic pigs (82.6 ± 18.8 kg), 14 sheep (49.1 ± 6.9 kg), and 49 patients (76.8 ± 18.2 kg) were used for reconstruction of the subject-specific PA anatomy. 3D surface geometries including main, left, and right PA as well as LPA and RPA side branches were manually reconstructed. Then, specific geometric parameters (length, diameters, taper, bifurcation angle, curvature, and cross-section enlargement) affecting device implantation and post-interventional device effect and efficacy were automatically calculated. For both animal models, significant differences to the human anatomy for most geometric parameters were found, even though the respective parameters’ distributions also featured relevant overlap. Out of the two animal models, sheep seem to be better suitable for a preclinical study when considering only PA morphology. Reconstructed geometries are provided as open data for future studies. These findings support planning of preclinical studies and will help to evaluate the results of animal trials.

Impact of donor hepatic duct bifurcation location and angle on posttransplant biliary complications in recipients following living donor liver transplantation

Impact of donor hepatic duct bifurcation location and angle on posttransplant biliary complications in recipients following living donor liver transplantation

Evaluating the smoke back-layering length and critical velocity in branched tunnel fire with sloped mainline: An experimental study

The branched tunnel with inclined mainline is increasingly common to link ground and underground transportation network. The smoke movement characteristics and critical velocity in branched tunnel with uphill mainline are still unclear. This work investigated the smoke back-layering length and critical velocity in branched tunnel with inclined upstream and horizontal downstream via model-scale (1/20) experiments. The mainline slope varied from 1% to 7%, and three bifurcation angles of 10°, 20° and 30° were considered. Results show that the increasing of the uphill mainline slope promotes the shorter backflow distance in inclined mainline that requires smaller wind speed to control smoke return. The smoke back-layering length monotonically ascends with the heat release rate, but the effect of bifurcation angle is fluctuant. The critical velocity is higher for greater heat release rate. The logarithmic function can well express the relationship between Q*/V*3 and L/Hc that the correction factor of bifurcation angle is used to modify the expression. A new model of critical velocity is characterized by considering the mainline slope and bifurcation angle. The proposed model for critical velocity shows good agreement with experimental results, which can apply to horizontal branched tunnel and branched tunnel with uphill mainline.