Geometric Height Research Articles

A successful surgical repair for supravalvular aortic stenosis with a bicuspid valve and malpositioned coronary orifices by partial Brom’s technique: a case report

BackgroundSupravalvular aortic stenosis (SVAS) is a relatively rare form of left ventricular outflow tract obstruction, often accompanied by other cardiac conditions. However, a standard surgical reparative technique has not been established and repairing SVAS remains challenging.Case presentationWe repaired SVAS of a 3-year-old boy accompanied by a bicuspid aortic valve and malpositioned coronary orifices by partial Brom’s technique with two glutaraldehyde-treated autologous pericardial patches, using recent advanced preoperative information, including geometric and effective heights. Echocardiography after the surgery revealed release of SVAS without aortic regurgitation.ConclusionsIn repair for SVAS, it is important not only to release stenosis but also to make a functional aortic valve, using recent advanced preoperative information. In the case of children, repairing the aortic valve by only using autologous tissue having growth potential, is also important.

Properties of sunspot light bridges on a geometric height scale

Context. Investigating light bridges (LBs) helps us comprehend key aspects of sunspots. However, few studies have analyzed the properties of LBs in terms of the geometric height, which is a more realistic perspective given the corrugation of the solar atmosphere. Aims. We aim to shed light on LBs by studying the variation in their physical properties with geometric height. Methods. We used the SICON code to infer the physical quantities in terms of the optical depth and the Wilson depression values of three LBs hosted by a sunspot observed with Hinode/SP in the Fe I 630 nm pair lines. We also used SIR inversions to cross-check the height variation of the field inclination in the LBs. In both output sets, we performed linear interpolation to convert the physical parameters from optical depth into a geometric height scale in each pixel. Results. Depending on their general appearance, we classified each LB as filamentary, grainy, or umbral. They appear as ridges that reach different maximum heights, with the umbral LB being the deepest. While the filamentary LB hosts a plasma inflow from the penumbra, the results for the grainy LB are compatible with an injection of hot plasma through convective cells of reduced field strength. Only a few positions reveal hints suggesting a cusp-like magnetic canopy. Moreover, strong gradients in the magnetic field strength and inclination usually exhibit enhanced electric currents, with the filamentary LB having remarkably strong currents that appear to be related to chromospheric events. Conclusions. The height stratification in filamentary and grainy LBs differ, indicating diverse mechanisms at work. Our results are in general incompatible with a magnetic canopy scenario, and further analysis is needed to confirm whether it exists along the entire LB or only at specific locations. Furthermore, this work assesses the usefulness of the SICON code when determining the height stratification of solar structures.

Comparison of preoperative aortic valve imaging techniques for patients with aortic insufficiency undergoing aortic valve repair surgery

ObjectiveTo report the accuracy of preoperative 4-dimensinal cardiac computed tomography angiogram (CTA), real-time 3-dimensional transesophageal echocardiography (TEE) and intraoperative techniques in aortic valve (AV) measurement and phenotype determination in patients undergoing surgery for aortic insufficiency and/or root aneurysm. MethodsThis is a prospective, observational study of preoperative AV imaging for AV repair surgery. Twenty-two patients were accrued over 12 months. Preoperative TEE and CTA were obtained and measurements provided by dedicated imaging cardiologists. Intraoperative measurements were obtained from the arrested heart and reported by the surgeon before repair. Intraoperative assessment was considered the gold standard of height measurements, with CTA being the standard assessment for commissural orientation. Correlation coefficients were used to describe agreement of measurements. ResultsBaseline characteristics and assessment of phenotype and measurement of commissural orientation, geometric height and commissural heights are reported. TEE (κ = 0.833; P < .01) and CTA (κ = 0.729; P < .01) both agreed with intraoperative assessment of AV phenotype. TEE appeared more accurate than intraoperative measurement at predicting commissural orientation (rs = 0.79; P < .01 vs rs = 0.58; P = .01). CTA and TEE were unlikely to predict and measured shorter than intraoperative geometric height measurement. Measurements of commissural heights by CTA did not agree with and were shorter than intraoperative measurement. ConclusionsTEE and CTA both appear accurate in predicting the AV phenotype identified intraoperatively. CTA and TEE predicted shorter heights than intraoperative measurement.

Comprehensive imaging evaluation of the aortic valve and root before aortic root surgery: a study comparing MDCT and TEE

ObjectiveTo investigate the accuracy and consistency of MDCT and TEE in the preoperative assessment of aortic root surgery.MethodsFrom January 2021 to September 2022, 118 patients who underwent aortic root surgery were included in this study. All patients underwent high-quality preoperative MDCT and TEE examinations, and the examination results were independently measured and assessed by two senior radiologists or ultrasound specialists. Bland–Altman analysis and Pearson correlation testing were employed to assess the correlation and consistency between MDCT and TEE. These analyses were then compared with actual intraoperative measurement data.ResultsAmong all the patients, 73 (61.86%) had tricuspid aortic valve (TAV), and 45 (38.14%) had bicuspid aortic valve (BAV). A comparison between the TEE and MDCT measurements showed that for the annulus diameter, the area-derived diameter had the best correlation and agreement. For the sinus of Valsalva diameter, the circumference-derived diameter was optimal. However, for the STJ diameter, the minimum cross-sectional diameter showed the best agreement with TEE. In contrast, measurements of geometric height showed a weaker correlation and agreement.ConclusionContrast-enhanced MDCT can be a valuable tool for perioperative evaluation in aortic root surgery, with good correlation, consistency, and feasibility when compared to TEE. The choice of MDCT measurement methodology, specifically area-derived and circumference-derived diameter, proved to be more accurate than other methods. Further research is required to enhance the understanding of aortic valve repair and associated imaging techniques.

Effects of Incorporating Ionic Crosslinking on 3D Printing of Biomass-Fungi Composite Materials.

Biomass-fungi composite materials primarily consist of biomass particles (sourced from agricultural residues) and a network of fungal hyphae that bind the biomass particles together. These materials have potential applications across diverse industries, such as packaging, furniture, and construction. 3D printing offers a new approach to manufacturing parts using biomass-fungi composite materials, as an alternative to traditional molding-based methods. However, there are challenges in producing parts with desired quality (for example, geometric accuracy after printing and height shrinkage several days after printing) by using 3D printing-based methods. This paper introduces an innovative approach to enhance part quality by incorporating ionic crosslinking into the 3D printing-based methods. While ionic crosslinking has been explored in hydrogel-based bioprinting, its application in biomass-fungi composite materials has not been reported. Using sodium alginate (SA) as the hydrogel and calcium chloride as the crosslinking agent, this paper investigates their effects on quality (geometric accuracy and height shrinkage) of 3D printed samples and physiochemical characteristics (rheological, chemical, and texture properties) of biomass-fungi composite materials. Results show that increasing SA concentration led to significant improvements in both geometric accuracy and height shrinkage of 3D printed samples. Moreover, crosslinking exposure significantly enhanced hardness of the biomass-fungi mixture samples prepared for texture profile analysis, while the inclusion of SA notably improved cohesiveness and springiness of the biomass-fungi mixture samples. Furthermore, Fourier transform infrared spectroscopy confirms the occurrence of ionic crosslinking within 3D printed samples. Results from this study can be used as a reference for developing new biomass-fungi mixtures for 3D printing in the future.

Aortic valve cusp size and shape in dilated trileaflet aortic roots

ObjectivesThe objective of the study was to quantify the differences in cusp size and shape in patients with normal and dilated trileaflet aortic roots and in dilated roots with or without aortic regurgitation. MethodsA retrospective analysis of computed tomography studies in patients with normal and dilated trileaflet aortic roots was performed measuring root and cusp dimensions. Normal root size was defined as sinuses of Valsalva diameter less than 40 mm, dilated as 45 mm or greater. Root measurements normalized to basal ring diameter and cusp measurements normalized to geometric height were analyzed to assess the shape. Additionally, comparison of dilated roots with or without aortic regurgitation was made. ResultsWe analyzed 146 normal and 104 dilated aortic roots and 73 propensity-matched pairs. Dilated roots were larger in all dimensions and had increased ratio between commissural and basal ring diameter (1.58 ± 0.23 vs 1.11 ± 0.10, P < .001). Cusps in dilated roots were larger in all measured dimensions and were elongated with increased normalized cusp insertion length (3.64 ± 0.39 vs 3.26 ± 0.20, P < .001) and normalized free margin length (2.53 ± 0.30 vs 2.16 ± 0.19, P < .001). In patients with dilated root and no cusp prolapse (n = 83), those with moderate or severe aortic regurgitation had larger commissural diameter but similar cusp dimensions compared with those with no or mild aortic regurgitation. ConclusionsThe cusps in dilated roots elongate transversely and to a lesser degree radially. Functional aortic regurgitation is caused by extensive commissural dilatation and not by inadequate cusp adaptation.

Three-dimensional modelling of aortic leaflet coaptation and load-bearing surfaces: in silico design of aortic valve neocuspidizations.

Three-dimensional (3D) modelling of aortic leaflets remains difficult due to insufficient resolution of medical imaging. We aimed to model the coaptation and load-bearing surfaces of the aortic leaflets and adapt this workflow to aid in the design of aortic valve neocuspidizations. Geometric morphometrics, using landmarks and semilandmarks, was applied to the geometric determinants of the aortic leaflets from computed tomography, followed by an isogeometric analysis using Non-Uniform Rational Basis Splines (NURBS). Ten aortic valve models were generated, measuring determinants of leaflet geometry defined as 3D NURBS curves, and leaflet coaptation and load-bearing surfaces were defined as 3D NURBS surfaces. Neocuspidizations were obtained by either shifting the upper central coaptation landmark towards the sinotubular junction or using parametric neo-landmarks placed on a centreline drawn between the centroid of the aortic root base and centroid of a circle circumscribing the 3 upper commissural landmarks. The ratio of the leaflet free margin length to the geometric height was 1.83, whereas the ratio of the commissural coaptation height to the central coaptation height was 1.93. The median coaptation surface was 137 mm2 (IQR 58) and the median load-bearing surface was 203 mm2 (60) per leaflet. Neocuspidization multiplied the central coaptation height by 3.7 and the coaptation surfaces by 1.97 and 1.92 using the native coaptation axis and centroid coaptation axis, respectively. Geometric morphometrics reliably defined the coaptation and load-bearing surfaces of aortic leaflets, enabling an experimental 3D design for the in silico neocuspidization of aortic valves.

The impact of chewing force simulation on stress distribution of implant retained mandibular overdenture with locator attachment system having matrix of PEEK versus nylon insert

The current study investigates the impact of chewing force simulation on stress strain distribution of Mandibular overdentures retained with locator attachment system having matrix of PEEK versus nylon insert. Twenty completely edentulous mandibular digitally printed models were fabricated with beds for two implants, which had been inserted in the estimated canine positions with two grooves mesial and distal at each implant site for the attachment of the strain gauges for each model. Nova loc group NLG with ten implant assisted mandibular complete overdentures were fabricated over ten printed models with nova loc attachments while locator group LG had ten implant assisted mandibular complete overdentures over ten printed models with locator attachments of same retaining force and geometric height. Bilateral vertical load was applied with a universal testing machine and strain induced to the implants was measured around the two implants medially and distally in each group using strain gauges pre &amp; post one year simulated functional aging. Student t test was used for comparing the two types of attachments while paired t test was used for comparison of strain induced to the implants after one year of functional aging, with probability level p &lt; 0.05 is considered statistically significant. Individual statistical analysis of the data revealed increase in the number of measured strains for both attachments which was statistically significant for locator. Comparing the two groups, significant increase for the locator attachment after one year simulated functional aging was detected compared to nova loc. Within the limitations of this study, one year simulated functional aging seems to cause disturbance in the load conveyed to the supporting structures of mandibular implant assisted overdenture retained with locator in contrast to nova loc that showed more resistance to aging process, thus nova loc attachment transmit less stresses than locator attachment to the surrounding implants supporting structures specially after time of service related to its combined materials superior physical properties.

Justification of design parameters of a two-stage cyclone vortex funnel using computer simulation

It has been established that in mini-feed mills with a productivity of up to 5 t/h, pneumatic transport systems with a cyclone unloader are more promising due to the lower emission of finely dispersed components. However, there are fewer such workshops on the market due to the smaller loading -volume of horizontal mixers on which cyclones are installed compared to vertical mixers that perform the function of cyclone-unloaders, in which emissions of fine dust into the work area are higher, which negatively affects working conditions, health of workers, as well as fire safety of premises. To reduce emissions of fine dust into the exhaust pipe of the cyclone, a technical solution in the form of a two-stage cyclone was proposed. A preliminary experimental test on a laboratory model showed an increase in particle collection by 32% about the serial cyclone-unloader CR under the same initial conditions and in the same standard size. As part of the design of a full-size version of the proposed two-stage cyclone, computer modeling of the separation process was carried out in the FlowSimulation software environment with dimensions close to the commercially produced cyclone BCR-450 to identify the influence of the geometric parameters of the -vortex funnel on the process of separation of fine particles from the transporting air flow with variable geometric dimensions diameter and height of the vortex funnel in the range from 100 to 270 and from 100 to 235 mm, respectively. Preliminary rational geometric parameters of the vortex funnel diameter equal to 180 mm and height equal to 150 mm of the proposed technical solution with a hydraulic resistance coefficient of8.4 are substantiated.

Numerical analysis of a solar air heater with offset transverse ribs placed near the absorber plate

Solar air heater (SAH) is used to convert readily available solar energy into useful thermal energy. Several studies have been conducted with different roughness elements on the absorber plate. However, study with ribs which are placed slightly above the heated plate, termed as offset transverse ribs, are still scant in the literature. Such study would explain the effect of flow between the ribs and the absorber plate on heat transfer augmentation in a SAH. With this objective a 2-D numerical study is performed here by solving steady RANS equations with RNG k−ɛ turbulence model. The effect of offset transverse ribs on heat transfer, pressure drop and thermal enhancement factor (TEF) is investigated. The geometrical parameters, such as, relative gap (α), relative height (β) and relative pitch (λ) are varied in the range of 0.0–0.045, 0.015 to 0.09, and 0.0333 to 0.1, respectively. The performance of SAH is evaluated on the basis of highest enhancement in relative Nusselt number (NuR/Nu) and thermal enhancement factor (TEF). A slight gap between the ribs and the absorber plate (α = 0.0075) is observed to yield better thermal performance than that for the attached ribs (α = 0). The maximum enhancement in NuR/Nu is found to be 1.52 for α = 0.0075. However, increasing the gap (i.e., α) prevents the flow reattachment with the absorber plate. Increase in rib height, on the other hand, is found to be more effective in heat transfer enhancement, but with a price of a significant enhancement in pressure drop. This leads to a reduction in the overall performance of SAH. Increment in pitch distance, however, reduces the enhancement in both Nusselt number and friction factor. By considering these three parameters, the highest TEF is found to be 1.042 for α=0.0075, β=0.030, and λ=0.0333 at Re equal to 13000. Finally, correlations for NuR and fR are derived as a function of the parameters investigated for helping the design of SAHs.

Four-Dimensional Aircraft Trajectory Prediction Based on Generative Deep Learning

Aircraft four-dimensional (4D) trajectory prediction (TP) is among the critical techniques of current existing automation systems in air traffic management (ATM), which is also the basis of future airspace operation models. This paper proposes a 4D TP method based on a conditional tabular generative adversarial network (CTGAN). The model is trained and tested using historical 4D trajectory data from the Hong Kong region. It is then compared with the most extensively researched conditional generative adversarial network (CGAN) and LSTM methods in the field of TP. The results show that Jensen–Shannon (JS) divergence, maximum mean discrepancy (MMD), and mean Euclidean distance (MED) of the model evaluation metrics for the selected route are 0.0539, 0.0150, and 0.0085, respectively. This confirms that the model for predicting 4D trajectory can accurately learn complex airspace’s trajectory distribution characteristics. Compared with the CTGAN algorithms shown in previous studies, the enhanced CTGAN approach developed in our research can reduce around 10% running time and 20% MED. Compared to CGAN, it results in an 81.55% reduction in MED. Compared to LSTM, when predicting with a 10-minute time span, the average mean absolute error for parameters latitude (Lat), longitude (Lon), geometric height (GH), and ground speed (GS) decreases by 7.76, 84.48, 81.98, and 36.51%, respectively.

Moving mountains: reevaluating the elevations of Colorado mountain summits using modern geodetic techniques

One of the most challenging environments for accurate geoid models is in high, rugged mountain areas. Orthometric heights derived from GNSS and a geoid model can easily have errors at the decimeter level. To investigate the effect of geoid model variability on the elevations of peaks in high, rugged mountain areas, this paper is focused on the “Fourteeners” of Colorado, USA (a group of about 60 peaks that are above 14,000 feet = 4267.2 m). Airborne LiDAR data are used to determine geometric (ellipsoidal) heights, which first requires removing a hybrid geoid model, as the LiDAR data is originally provided as orthometric heights. We quantify a significant improvement when using these derived ellipsoidal heights compared with the original orthometric heights: from ± 0.074 to ± 0.054 m (RMSE), an improvement of 28%. Next, a mean geoid model is determined with a relative accuracy of ± 0.06 to 0.08 m and used as a “stand in” realization of the future, official geopotential datum of the USA, NAPGD2022. Using the LiDAR ellipsoidal heights and geoid model, elevations (and uncertainties) for each of the Fourteener summits are determined and found to be, on average, 1.6 m lower than currently published values. This is a much larger change than the 0.5 m decrease expected from the new datum shift alone. The bulk of the difference is due to the original treatments of the vertical angle, triangulation data. A reanalysis of 32 of the 60 peaks shows that the historic data were indeed too high by about 1.0 m or more. Ultimately, no peak falls below the 14,000-foot level nor are any peaks elevated above this level.

Virtual Reality Computed Tomography Evaluation - Anatomy and Clinical Implications for Valve-Sparing Aortic Root Replacement.

Three-dimensional aortic root evaluation using virtual reality (VR) techniques for valve-sparing aortic root replacement (VSARR) preparation has not yet been implemented, so we demonstrated VR computed tomography (VR-CT) and assessed its utility for VSARR.Methods and Results: We enrolled 72 patients who underwent multidetector CT before elective VSARR for annuloaortic ectasia with tricuspid aortic valve. The geometries of their aortic roots were measured with a VR-CT workstation. The mean values of geometric height (GH), free margin length (FML), and commissural height (CH) were 17.2±2.4 mm, 36.0±5.2 mm, and 24.0±4.3 mm, respectively. The right coronary/noncoronary CH was significantly greater than the left coronary/right coronary and left coronary/noncoronary CH. The left coronary cusp had the shortest FML, intercommissural distances (ICD), and smallest central angle. Although the right coronary cusp had the largest values for FML, ICD, and central angle, the right coronary cusp had the lowest GH and EH. The VR-CT measurements strongly correlated with intraoperative alternatives, especially with mean GH (R2=0.75) and left coronary/noncoronary CH (R2=0.79). Furthermore, mean GH was observed to be significantly different among the selected graft size groups; therefore, the preoperative mean GH could play a significant role in graft sizing. VR-CT evaluation allows a thorough understanding of aortic root anatomy, which could facilitate VSAAR.

OPTIMAL PROFILE FOR A FIN OF CONSTANT CROSS SECTION WITH MODELATION OF THE THERMOPHYSICAL PROPERTIES

The dependence of the temperature and composition on thermal conductivity of steel, and its influence in the optimal profile for a fin of constant cross section to be used in air cooled condenser is presented. In Air Cooled Condensers (ACC), air is used as refrigerant, which forces the need for fins to improve the heat transfer process leading to appreciable increments in the costs of the installation. Therefore, developing better fins profile will allow optimizing the operation, maximizing the heat transfer and minimizing the manufacturing cost of the fins. To this objective, in the present paper, three geometric parameters, thickness, height and surface of heat transfer of the fin, this parameters influence directly the optimal obtained profile for conditions of maximum heat flux and optimal Biot number. The study was accomplished for fins of constant cross section. In a future work, fins of variable cross sections will be considered.

Out-of-plane behavior of U-shaped unreinforced masonry structures

The out-of-plane behavior of masonry walls is an important aspect of their response, particularly in seismic regions. While previous studies have examined various geometries and materials, there exists a dearth of research on U-shaped walls, specifically with diverse geometric configurations. Moreover, the influence of axial load on out-of-plane behavior remains largely unexplored, limiting practical applications. This study aims to bridge these gaps by comprehensively investigating the out-of-plane behavior of U-shaped walls, focusing on the quantification of variable parameters encompassing geometry and axial load. A three-dimensional finite element model using the macro-modeling approach is used to analyze the structural response of U-shaped masonry walls under out-of-plane loading. The accuracy of the numerical modeling approach has been validated by available experimental test results to demonstrate the effectiveness of the modeling approach in predicting the out-of-plane behavior of U-shaped masonry structures. Subsequently, a series of parametric studies delves into the impacts of distinct geometrical attributes, including thickness, height, and span size, shedding light on the behavior of these walls across diverse geometric configurations. The results indicate that the capacity of the wall at the connection between out-of-plane and cross walls significantly influences the overall behavior and the failure mode. It was found that axial load substantially increases the strength of walls, in order of 1.5–3 times, and the positive effect of axial load was more significant than the secondary effects in most cases, though the significance of secondary effect drastically increases by increasing the height. It is shown that walls with longer span have much better behavior in the presence of axial load. Based on the results, for each specific geometrical parameter, a linear function can be considered for relation between strength and axial load. These findings can provide useful insights for the design and analysis of U-shaped masonry structures, particularly in seismic regions where out-of-plane behavior is a critical factor in their performance.

Florida sleeve procedure for type II aortic regurgitation with aortic root enlargement: a case report.

Florida sleeve procedure is an operative technique for aortic root reconstruction that offers advantages such as reduced bleeding risk, shorter operation time, and improved formation of the atrioventricular junction (AVJ) and sinotubular junction (STJ). In our department, we perform a Florida sleeve procedure for aortic regurgitation (AR) associated with aortic root enlargement of less than 40 mm in diameter of the Valsalva sinus. Here, we present a case of severe type II AR with aortic root enlargement where we successfully performed Florida sleeve procedure and augmented it with autologous pericardium. A 62-year-old male patient was referred for cardiovascular surgery after a transthoracic echocardiogram indicated left ventricular enlargement and severe AR. Preoperative multidetector computed tomography (MDCT) revealed AVJ of 28.2 mm, Valsalva sinus of 38.4 mm, STJ of 36.1 mm, and ascending aorta of 40.1 mm, indicating enlargement from the aortic root to ascending aorta. Preoperative transesophageal echocardiography (TEE) revealed that the main cause of AR was suspected to be the right coronary cusp prolapse (RCC). Intraoperative findings showed that the tricuspid aortic valve had no limitation of motion, but the RCC was subjected to central bending and prolapsed. The leaflet bend was thickened and shortened causing AR (type II). The geometric height (gH) of RCC was short at 14 mm, while the other valve cusps were 20 mm. An augmentation of RCC was performed using autologous pericardium, followed by a Florida sleeve procedure performed using 26-mm Gelweave Valsalva™ grafts. The gH of RCC after augmentation was 23 mm, and the effective height was adjusted to 10 mm by central plication, showing no AR by TEE. Postoperative MDCT revealed AVJ of 22.2 mm, Valsalva sinus of 30.9 mm, and STJ of 21.9 mm. Therefore, the Florida sleeve procedure provided a reduction that preserved the geometry of the aortic root, including AVJ and STJ, as intended. Florida sleeve procedure is a reliable and simple method for ensuring uniform aortic root geometry. A favorable outcome was obtained using the Florida sleeve procedure and augmentation with autologous pericardium in a patient with type II AR and aortic root enlargement.

Systematic adjustment of root dimensions to cusp size in aortic valve repair: a computer simulation.

Aortic valve repair requires the creation of a normal geometry of cusps and aortic root. Of the different dimensions, geometric cusp height is the most difficult to change while annular and sinotubular dimensions can be easily modified. The objective of this study was to investigate, by computer simulation, ideal combinations of annular and sinotubular junction size for a given geometric height. Based on a literature review of anatomical data, a computational biomechanics model was generated for a tricuspid aortic valve. We aimed to determine the ideal relationships for the root dimensions, keeping geometric height constant and creating different combinations of the annular and sinotubular junction dimensions. Using this model, 125 virtual anatomies were created, with 25 different combinations of annulus and sinotubular junction. Effective height, coaptation height and mechanical cusp stress were calculated with the valves in closed configuration. Generally, within the analysed range of geometric heights, changes to the annular diameter yielded a stronger impact than sinotubular junction diameter changes for optimal valve configuration. The best results were obtained with the sinotubular junction being 2-4 mm larger than the annulus, leading to higher effective height, normal coaptation height and lower stress. Within the range tested, stenosis did not occur due to annular reduction. In tricuspid aortic valves, the geometric height can be used to predict ideal post-repair annular and sinotubular junction dimensions for optimal valve configuration. Such an ideal configuration is associated with reduced cusp stress.

Simulation-based design of bicuspidization of the aortic valve

ObjectiveSevere congenital aortic valve pathology in the growing patient remains a challenging clinical scenario. Bicuspidization of the diseased aortic valve has proven to be a promising repair technique with acceptable durability. However, most understanding of the procedure is empirical and retrospective. This work seeks to design the optimal gross morphology associated with surgical bicuspidization with simulations based on the hypothesis that modifications to the free edge length cause or relieve stenosis. MethodsModel bicuspid valves were constructed with varying free edge lengths and gross morphology. Fluid-structure interaction simulations were conducted in a single patient-specific model geometry. The models were evaluated for primary targets of stenosis and regurgitation. Secondary targets were assessed and included qualitative hemodynamics, geometric height, effective height, orifice area, and billow. ResultsStenosis decreased with increasing free edge length and was pronounced with free edge length less than or equal to 1.3 times the annular diameter d. With free edge length 1.5d or greater, no stenosis occurred. All models were free of regurgitation. Substantial billow occurred with free edge length 1.7d or greater. ConclusionsFree edge length 1.5d or greater was required to avoid aortic stenosis in simulations. Cases with free edge length 1.7d or greater showed excessive billow and other changes in gross morphology. Cases with free edge length 1.5d to 1.6d have a total free edge length approximately equal to the annular circumference and appeared optimal. These effects should be studied in vitro and in animal studies.

Approximation of extracted features enabling 3D design tuning for reproducing the mechanical behaviour of biological soft tissues.

This article describes a new method, inspired by machine learning, to mimic the mechanical behaviour of target biological soft tissues with 3D printed materials. The principle is to optimise the structure of a 3D printed composite consisting of a geometrically tunable fibre embedded in a soft matrix. Physiological features are extracted from experimental stress-strain curves of several biological soft tissues. Then, using a cubic Bézier curve as the composite inner fibre, we optimised its geometric parameters, amplitude and height, to generate a specimen that exhibits a stress-strain curve in accordance with the extracted features of tensile tests. From this first phase, we created a database of specimen geometries that can be used to reproduce a wide variety of biological soft tissues. We applied this process to two soft tissues with very different behaviours: the mandibular periosteum and the calvarial periosteum. The results show that our method can successfully reproduce the mechanical behaviour of these tissues. This highlights the versatility of this approach and demonstrates that it can be extended to mimic various biological soft tissues.

A comparative performance analysis of thermoelectric generators with a novel leg geometries

Thermoelectric (TE) devices utilize the Seebeck effect to produce electricity from waste heat. The optimization of TE leg geometry and its structure has lately drawn more attention to improving TE power generators. This study uses the finite element method to examine thermoelectric generators' thermal reliability and performance (TEGs) for novel TE leg designs. New leg shapes, such as a cross-vertical and butterfly, are introduced and contrasted with the squared (conventional) leg and other leg shapes, such as trapezoidal, cross-horizontal, I-shaped, X-shaped, and Y-shaped. The design of the main geometric parameters, including structure, height, volume, and surface area of the thermoelectric leg, is discussed in detail. As the TE leg has a larger heated surface area, the results demonstrate that the cross-vertical and butterfly legs perform 39.2% and 30.4%, respectively, higher than the squared (conventional) shape. However, the square-shaped leg shows the least thermal stress compared to other designs, especially at high thermal gradients. For low-temperature gradients (Th < 100 °C), the new TE leg designs of the cross-vertical and butterfly structures exhibit thermal stresses below the yield stress of bismuth telluride, indicating that their use is suitable for upcoming low-temperature gradient thermoelectric system applications.