Diameter Wall Research Articles

Free convection heat transfer with surface radiation from infrared suppression system and estimation of cooling time

• The thermo-fluid characteristics of the full-scale infrared suppression (IRS) system used in the marine gas turbine as an exhaust system are numerically investigated here. • The combined impact of conduction, convection, and radiation on the cooling of the IRS system is intended to be explored. • Various relevant parameters are taken for the analysis, viz., Rayleigh number (Ra), number of funnels, funnel wall temperature, diameter ratio (DR), funnel overlapping (OL), and emissivity of the surface (ε). • A generalized correlation for Nusselt number is developed, considering surface emissivity and the number of funnels as an independent parameter that can be used for academic and industrial applications. • The novelty of the work lies in finding the heat transfer rate and cooling time of the IRS device with varying numbers of funnels (3 to 6 funnels) subjected to the combined effect of free convection and surface radiation. A numerical study is performed on Infrared Suppression (IRS) system having finite wall thickness to observe the combined effect of free convection and surface radiation. The main focus of this work is to obtain thermo-fluid characteristics of natural convection phenomena from the IRS system due to conjugate heat transfer and surface radiation. In addition, the time required to cool down the hot IRS system to atmospheric temperature is also estimated. For the numerical analysis, different governing equations (Navier-Stokes equation, energy equation, and radiation equation) are solved using the finite volume method (FVM) based solver of ANSYS Fluent v 15. Several pertinent parameters, viz., the number of funnels, Rayleigh number, inner surface temperature, geometric ratio, funnel overlapping, and surface emissivity, are varied to elucidate the heat transfer behavior. It is evident from the research that surface radiation has a significant influent on total heat transfer and should not be ignored. In addition, the total heat transfer rate rises with the number of funnels. Both non-dimensional induced mass flow rate and total heat transfer rate have maximum value for zero overlapping cases. At constant temperature contribution of radiative heat transfer varies from 10 to 38% with the rise in emissivity. The inclusion of radiation with convection lowers the cooling time significantly compared to convection alone.

On the collision of a droplet with a V-shaped wall

The present work experimentally investigates a water droplet impacting a V-shape wall. The effects of eccentricity ratio (0 ≤ b ≤ 14/9), bending angle of the V-shape wall (90o ≤ θ ≤ 180o), Weber number (205.80 ≤ We ≤ 447.92), and droplet diameter (1.3 mm ≤ D ≤ 4.5 mm) are taken into account. In this work, the wrinkles of the lamella not only are observed on the flat wall but also on the V-shaped wall. As We decreases, the wrinkles of the lamella will be seldom observed. As θ increases, the size of the wrinkles decreases, while the number of the wrinkles increases. The secondary spray is observed for the eccentric collision of the droplet against the V-shaped wall. Especially, the secondary spray can be classified into two sub-regimes based on eccentricity ratio: secondary spray-I and secondary spray-II. For the secondary spray-I, the secondary spray and the primary splash form an angle, and the angle decreases against the increment of b. The nondimensional spreading length and height also are studied theoretically.

Mechanical Testing of Artificial Vessels and Tissues for Photoplethysmography Phantoms.

Various studies have looked at the efficiency of artificial vessel and tissue networks in the study of photoplethysmography (PPG) in an effort to better understand the origin of various morphological features present in the signal. Whilst there are all reasonable attempts made to replicate geometrical features such as vessel depth, vessel wall thickness and diameter etc., not many studies have attempted to replicate the mechanical properties such as vessel elasticity and tissue compressibility. This study reports two methods for tissue mechanical testing for the analysis of vessel elasticity and tissue compressibility. A two-part polydimethylsiloxane (PDMS) was used as a base material for both tissue and vessel construction, and the properties altered by changing the curing component ratio. Tissue compression properties were investigated using an industrially calibrated materials testing device using the protocol from the ASTM 0575-91 testing method. Vessel elasticity was investigated using a custom method and apparatus to report vessel diameter and length change simultaneously. Tissue compressive properties proved reasonably easy to replicate through catalyst alteration, however the vessel elasticity properties were found to be higher than expected at all reasonable catalyst ratios. The property of hyper-elasticity was observed in the artificial vessels though, leading to the conclusion that alternative material recipes or construction methods may be needed to correctly replicate the expected mechanical characteristics. Clinical Relevance- The latest generation of health monitoring devices, especially those that are wearable and used widely by individuals wishing to monitor their health daily are becoming smarter and more sophisticated in their functionality. The majority of such devices use photoplethysmography (PPG) as their primary monitoring technique. Being able to replicate the PPG in a phantom allows the continued study and development of devices, and to improve their functionality without the continued need for extensive user-testing.

Steam reforming of guaiacol and n-hexanol for production of hydrogen: Effects of aromatic and aliphatic structures on properties of the coke

Bio-oil is a renewable and sustainable source for the production of hydrogen via steam reforming, while the hydrocarbons contained in bio-oil have a tendency to polymerize. The aliphatic and phenolic compounds in bio-oil have distinct molecular structures, steam reforming of which should generates the coke of different properties and deserves particular attention. This investigation focuses on understanding the correlation of the benzene ring and aliphatic structures of organics in bio-oil with properties of the coke formed in guaiacol and n-hexanol steam reforming. It was found that coking in n-hexanol reforming was more significant, as the dissociation and adsorption of n-hexanol generates the secondary reaction intermediate CxHy that could not be strongly adsorbed on catalyst surface, which, instead undergo fast cyclization to form the big aromatic ring with π-conjugated structure. Moreover, the coke formed in n-hexanol reforming are more reactive to oxidation, thermally more stable and more hydrophilic than that formed in guaiacol. Furthermore, the coke is mainly catalytic coke with high crystallinity in the form of carbon nanotubes with multiple walls, multiple cavities, thick walls and rough surface in the steam reforming of guaiacol. In n-hexanol reforming, the carbon nanotubes had much thinner wall and larger inner diameter, because of the different reaction intermediates involved on their formation.

The multi-enzymes and probiotics mixture improves the growth performance, digestibility, intestinal health, and immune response of Siberian sturgeon (Acipenser baerii)

Abstract The inclusion of exogenous digestive enzymes and probiotics is well established in the aquafeed industry. The mixture of multi-enzymes and probiotics improves the feed utilization and wellbeing of aquatic animals compared to the individual supplementation. Herein, we evaluated the exogenous multi-enzyme mixture (beta-glucanase, cellulase, alpha-amylase, protease, xylanase, and phytase) at 250 mg/kg and multi-species probiotic (Bacillus subtilis, Lactobacillus acidophilus, L. delbrueckii, L. rhamnosus, L. plantarum, and Pediococcus acidilactici; 1 × 1010 CFU/g for each bacterial strain) at 2 g/kg on the performances of Siberian sturgeon. The final weight, weight gain, SGR, and PER were markedly enhanced while the FCR was reduced in fish fed multi-enzyme and probiotics premix (P<0.05). Multi enzymes and probiotic mixture significantly increased the total body protein content (P˃0.05). Multi enzymes and probiotic mixture also improved the digestibility of crude protein, dry matter, and crude lipids nutrients (P<0.05). The count of goblet cells, microvilli diameter, microvilli length, outer muscle wall diameter, and enterocyte total absorptive surface were markedly increased (P<0.05) by dietary multienzymes and probiotics mixture. The WBCs and neutrophils showed marked improvements (P<0.05). The levels of glucose, triglycerides, blood urea nitrogen, and total bilirubin were markedly higher in fish fed the control than fish fed the multi-enzymes and probiotics mixture (P<0.05). Significantly, Siberian sturgeon-fed dietary multi-enzymes and probiotics had improved lysozyme activity, total immunoglobulin, and total protein in the skin mucus and serum samples (P<0.05). Further, the serum complement C3 and C4 was higher in fish-delivered multi-enzymes and probiotic mixture than in control (P<0.05). In conclusion, dietary probiotics synergistically enhanced the activity of multi-enzymes and resulted in increased feed utilization, nutrient digestibility, and health status of Siberian sturgeon.

An evaluation of fiber-based damage for assessing the failure of aortic tissue: comparison between healthy and aneurysmal aortas

The decision of surgical intervention for an aortic aneurysm is usually associated with an assessment of risk of its rupture. Global rupture risk assessment parameters like wall diameter and growth of the aneurysm over time often fail at predicting the risk of rupture with accuracy. This paper will investigate the hypothesis that the tissue’s microstructure determines its macroscopic failure. To this aim, two different testing protocols have been implemented. Human ascending thoracic aortic aneurysm (ATAA) tissue samples were subjected to bulge-inflation testing until rupture coupled with multi-photon microscopy (MPM) imaging. Image stacks of the sample were acquired at different pressure levels. Additionally, porcine aorta samples were tested under uniaxial tension until failure and their response was recorded. Prior to mechanical testing, MPM image stacks were acquired at four different zones on the sample. The image stacks acquired at the load free state were used to extract morphological information relating to collagen fibers. Then, an inverse random sampling approach was used to generate pseudomorphological parameters for network reconstruction. A discrete model of the collagen network signifying its stochastic nature was then developed, including both prefailure and post-failure mechanics. The model was able to replicate the mechanical response and failure of the tissue, and demonstrated that fiber-based damage can strongly shape the macroscopic failure response of the tissue. Identified values of collagen fiber failure strain were in the range of 8.8 to 29.3% in the case of aneurysmal samples, and 18.7 to 25.5% in the case of porcine samples. A statistical analysis enabled the characterization of correlation between fiber morphology and tissue failure. The model may serve as a useful tool for predicting macroscale failure of the aortic wall based on the variations in microscale morphology.

Assessment of subclinical left ventricular systolic dysfunction and structural changes in patients with chronic obstructive pulmonary disease.

Patients with chronic obstructive pulmonary disease (COPD) can develop left ventricular (LV) systolic dysfunction and geometric changes due to several reasons. To investigate subclinical LV systolic dysfunction and structural features in patients with COPD, and its correlation with the severity of airway obstruction, identified by GOLD classification. We studied 52 patients with COPD and 29 age and sex-matched controls, without any cardiac disease. In addition to conventional echocardiographic evaluation speckle tracking echocardiography (STE)-based strain imaging were performed to analyse sub-clinical LV systolic dysfunction. Also LV volumes were measured by using three-dimensional real time echocardiography (3DRTE). All patients underwent spirometry. Conventional echocardiographic parameters (LV wall thickness and diameters, LV EF) and LV volume measurements were similar between the groups. LV global longitudinal peak systolic strain (-14.76 ± 2.69% to -20.27 ± 1.41%, P < 0.001) and strain rate (0.75 ± 0.25 1/s to 1.31 ± 0.41 1/s, P < 0.001) were significantly impaired in patients, compared to controls demonstrating sub-clinical ventricular systolic dysfunction. Significant positive correlation was obtained between LV strain/strain rate and spirometry parameters (FEV1, FEV%, FEV1/FVC, PEF%) (r = 0.78/0.68, P < 0.001; r = 0.83/0.70, P < 0.001); r = 0.74/0.55, P < 0.001; r = 0.72/0.65, P < 0.001 respectively). In addition, there was significant negative correlation between LV strain/strain rate and GOLD classification (r = -0.80/ -0.69, P < 0.001 respectively). Subclinical LV systolic dysfunction can occur in COPD patients despite normal EF. STE is a technique that provides additional information for detailed evaluation of subtle changes in LV myocardial contractility, significantly associated with the severity of the disease in COPD patients.

Tracking Early Systolic Motion for Assessing Acute Response to Cardiac Resynchronization Therapy in Real Time.

An abnormal systolic motion is frequently observed in patients with left bundle branch block (LBBB), and it has been proposed as a predictor of response to cardiac resynchronization therapy (CRT). Our goal was to investigate if this motion can be monitored with miniaturized sensors feasible for clinical use to identify response to CRT in real time. Motion sensors were attached to the septum and the left ventricular (LV) lateral wall of eighteen anesthetized dogs. Recordings were performed during baseline, after induction of LBBB, and during biventricular pacing. The abnormal contraction pattern in LBBB was quantified by the septal flash index (SFI) equal to the early systolic shortening of the LV septal-to-lateral wall diameter divided by the maximum shortening achieved during ejection. In baseline, with normal electrical activation, there was limited early-systolic shortening and SFI was low (9 ± 8%). After induction of LBBB, this shortening and the SFI significantly increased (88 ± 34%, p < 0.001). Subsequently, CRT reduced it approximately back to baseline values (13 ± 13%, p < 0.001 vs. LBBB). The study showed the feasibility of using miniaturized sensors for continuous monitoring of the abnormal systolic motion of the LV in LBBB and how such sensors can be used to assess response to pacing in real time to guide CRT implantation.

Bedside ultrasonography prior to abdominal paracentesis is associated with low complication and high success rate: Experience in a National Health Service District General Hospital in the United Kingdom from 2013 to 2019.

To analyse data from a bedside ultrasound-assisted ascites procedure service in a National Health Service District General Hospital and compare them to results of studies in the medical literature. A retrospective review of audit data collected (January 2013 to December 2019) of the practice of paracentesis in a National Health Service District General hospital. All adult patients referred to the ascites assessment service were included. Bedside ultrasound detected location and volume of ascites, if present. Abdominal wall diameters were determined in order to select the appropriate needle length for procedures. Results and scan images were recorded on a pro-forma. Patients who underwent a procedure were followed up for 7 days, with complications documented. Seven hundred and two scans were performed on 282 patients - 127 (45%) male and 155 (55%) female. In 127 (18%) patients, an intervention was avoided. Five hundred forty-five (78%) patients underwent a procedure: 82 (15%) were diagnostic aspirations and 463 (85%) were therapeutic (large volume) paracentesis. Most scans were performed between 08:00-17:00. Average time from patient assessment to diagnostic aspiration was 4 hours 21 minutes. Complications included three failed procedures (0.6%) and one iatrogenic peritonitis (0.2%), but no bowel perforation, no major haemorrhage or death. It is possible to introduce a bedside ultrasound-assisted ascites procedure service to a National Health Service District General Hospital with a high success and low complication rate.

Estimation of gestational age using ultrasonography in Baluchi sheep.

The aim of this study was to evaluate the correlation between some fetal parameters measured by ultrasonography and fetal age for developing a formula which could be used for estimation of fetal age in Baluchi sheep. Placentome diameter (PD), gestation Sac diameter (GSD), biparietal diameter (BPD), straight crown-rump length (CRL), femural length (FL), occipito-snout diameter (OSD), thoracic diameter (TD) and fetal heart rate (FHR) were measured by transrectal and/or transabdominal ultrasonography. All ewes were synchronized using progesterone sponge for 6 days. On the first day, they received PGF2 and on the last day received 400 IU of equine serum gonadotrophin (eCG). All of the parameters revealed significant correlation by increasing fetal age. Except for PD, for other values linear regression curve was illustrated. BPD (between 36 - 96 days) (R2 = 0.961), CRL (R2 = 0.935), FL (R2 = 0.950), OSD (R2 = 0.981), TD (R2 = 0.975) showed high correlation with fetal age (p < 0.001). Moderate correlation was calculated for FHR (p < 0.001, R2 = 0.883). Low correlations were assessed by measurement of GSD (p = 0.018, R2 = 0.318), BPD (between 96-138 days; p = 0.038, R2 = 0.29) and PD represented the significant non-linear correlation with age (p < 0.001), maximum correlation was assessed by measurement of mean placentome wall diameter. In conclusion, OSD was recommended as the best parameter for estimating of gestational age between days 36 - 109 in Baluchi sheep because of the lowest residuals, the highest correlation coefficient and wide period of availability for imaging in gestation.

A pilot study of four-year longitudinal bone changes following anterior cruciate ligament reconstructive surgery using DXA and HR-pQCT

Anterior cruciate ligament reconstructive (ACLR) surgery is an effective and prevalent treatment to restore function following ACL injury. The incidence of post-traumatic osteoarthritis (PTOA) long-term is still a major problem. Longitudinal studies beyond the first year are lacking and no studies have reported high-resolution in vivo bone changes. (1) Determine longitudinal bone changes following surgery in the proximal tibia and distal femur in ACLR and contralateral knees, and (2) determine bone changes at the ACLR tunnel and surrounding region in the injured knee. Participants with acute ACL-injuries (n = 5) had DXA and HR-pQCT imaging at four timepoints: pre-surgery (baseline) and at 2-, 6- and 48-months in the injured and contralateral knees. Areal BMD in peri-articular and epiphyseal regions was evaluated using DXA. Microstructural and vBMD changes of the tibial plateau and femoral condyles and surrounding the ACLR tunnel were determined. Large initial reductions in subchondral density and microstructure within the first year were followed by a period of recovery. Although varying among participants, reduced values in the injured knee remained at 48 months. Substantial adaptations to the surrounding ACLR tunnel bone occurred resulting in a cortex-like thickening and reduced wall diameters at 48 months. Large initial reductions following ACLR surgery followed a similar pattern seen in the first year after injury, indicating the trauma of surgery may reset bone recovery. These longitudinal results are consistent with cross-sectional studies indicating irreversible bone changes following ACLR that may play a role in PTOA initiation and progression. This pilot data suggests that imaging biomarkers are persistent at 48 months, possibly reflecting early PTOA changes.

Anatomical accuracy of the KODEX-EPD novel 3D mapping system of the left atrium during pulmonary vein isolation: a correlation with computer tomography imaging

Abstract Funding Acknowledgements Type of funding sources: None. Background A novel 3D mapping system (KODEX - EPD, EPD Solutions, Best, The Netherlands) enables catheter localization and real-time 3D cardiac mapping. Purpose To evaluate left atrium (LA) anatomical mapping accuracy created by the KODEX-EPD system during pulmonary vein isolation (PVI) compared with gold standard computed tomography (CT) images acquired from the same patients prior to the procedure. Methods In 15 consecutive patients who underwent PVI, 3D mapping of the LA was created on the KODEX-EPD system using the Achieve catheter. Pulmonary vein (PV), posterior wall, and appendage anatomy and diameters, were compared to the CT 3D reconstruction measured on the CARTO 3 system. Measurements were done independently by 2 physicians in each method. Linear correlation and agreement between CT and EPD measurements were assessed by Spearman correlation and Bland-Altman plot. Results Mean LA mapping time was 7.7± 3.6 min. Very high interobserver correlation was found for both EPD and CT measurements (Spearman-r=0.9). High correlation (r=0.75) was found between CT and EPD measurements. Bland-Altman plot method revealed that measurements assessed by EPD were slightly higher than those assessed by CT. Mean difference was 3.5mm, p&amp;lt;0.01. In 2 (13.5%) patients each, disagreement regarding the presence of a left common PV and a right middle accessory vein anatomy was seen. Conclusion The new KODEX-EPD mapping system allows quick and accurate mapping of the LA with high correlation to CT imaging. Some differences in left common and accessory right middle vein anatomy were seen. Central illustration: An example of the anatomy created by the KODEX- EPD system compared with the CT image of the same patient. A standard 4 vein anatomy is demonstrated by both modalities, with early branching of the right inferior pulmonary vein. A: KODEX- EPD pre-CRYO map during atrial fibrillation demonstrating connected pulmonary veins. B: 3D CT image viewed on the CARTO auto-segmentation module. C,D: KODEX- EPD posterior-anterior and PANO images post-CRYO map during sinus rhythm demonstrating pulmonary vein isolation with the same anatomy. E: Spearman correlation demonstrating a high correlation (r 0.75) between CT and KODEX-EPD measurements, p&amp;lt;0.01.

Impact of Hemodialysis on Left Ventricular Mass in Patients With Chronic Kidney Disease

Context: Cardiac structural and functional abnormalities are very commonly seen in patients with end-stage renal disease (ESRD). Aim: The aim of this study was to determine the impact of hemodialysis (HD) on left ventricular mass (LVM) over a short period. Settings and Design: This study was a prospective observational study. Subjects and Methods: Twenty-five patients with ESRD, enrolled for HD from January 2018 to December 2019 at tertiary care hospital, were evaluated. All patients underwent two-dimensional echocardiography at the initiation of HD and 3 months later. Statistical Analysis Used: The software used in the analysis was SPSS 22.0 version and Graph Pad Prism 7.0 version. The paired t-test was used to analyze quantitative data. The Chi-square test was used for qualitative data. Data were analyzed by paired t-test. Results: The mean age of the cases was 44.92 ± 13.78 years. The left ventricular end-diastolic diameter in diastole, interventricular septum diameter in diastole, and posterior wall diameter in diastole decreased significantly (3.36 mm, −1.40 mm, and − 1.24 mm, respectively, P = 0.001, S) at the end of 3 months. The LVM and LVM index (LVMI) decreased significantly (−57.25 g and − 32.48 g/m2, respectively, P = 0.001, S) at the end of 3 months. At the end of 3 months, LVMI decreased significantly (148.24 ± 41.26 g/m2 vs. 115.76 ± 34.24 g/m2) which correlates with the increase in hemoglobin (7.62 ± 1.63 gm/dl vs. 8.44 ± 0.81 gm/dl) (P = 0.004, S), with improvement in BP (systolic 141.28 ± 21.70 to 136.32 ± 13.87 &amp; diastolic 86.16 ± 011.40 to 84.40 ± 8.36 mm of Hg) (P = 0.004, S) and with improvement in transferrin saturation (TSAT %) (30.05% ± 13.82% vs. 39.61% ± 14.32%) (P = 0.001, S). Conclusion: In patients with ESRD, cardiac dimensions were higher and LVM was increased at the initiation of HD. We found that LVMI regressed significantly with HD with optimum dry weight.

Multimodal thrombectomy device for treatment of acute deep venous thrombosis

Deep vein thrombosis (DVT) is a potentially deadly medical condition that is costly to treat and impacts thousands of Americans every year. DVT is characterized by the formation of blood clots within the deep venous system of the body. If a DVT dislodges it can lead to venous thromboembolism (VTE) and pulmonary embolism (PE), both of which can lead to significant morbidity or death. Current treatment options for DVT are limited in both effectiveness and safety, in part because the treatment of the DVT cannot be confined to a defined sequestered treatment zone. We therefore developed and tested a novel thrombectomy device that enables the sequesteration of a DVT to a defined treatment zone during fragmentation and evacuation. We observed that, compared to a predicate thrombectomy device, the sequestered approach reduced distal DVT embolization during ex vivo thrombectomy. The sequestered approach also facilitated isovolumetric infusion and suction that enabled clearance of the sequestered treatment zone without significantly impacting vein wall diameter. Results suggest that our novel device using sequestered therapy holds promise for the treatment of high risk large-volume DVTs.

Changes in echocardiographic parameters of the donor's heart before and after heart transplantation and their relationship with post-transplant survival.

BackgroundHeart transplantation is now widely performed in China, but the current entry criteria for heart transplantation donors are simple and lack reliable standards; there are still no studies on the effect of preoperative echocardiographic parameters of heart transplantation donors on the prognosis of the recipient. Therefore, the aim of this study is twofold: (I) to observe the characteristics of changes in echocardiographic parameters of the donor’s heart before and after heart transplantation and (II) to study the relationship between the changes in echocardiographic parameters of the donor’s heart pre- and post-transplant and transplant recipient survival.MethodsA total of 29 patients who underwent orthotopic heart transplant in our hospital from October 2016 to October 2019 were enrolled in this study. All recipients were followed up until April 2020. Echocardiographic data were collected pre-transplantation (donor) and at 1 week and 1 month post-transplant (recipient).ResultsCompared with the pretransplanted donor’s heart, there was an increase in the interventricular septal diameter, left ventricular posterior wall diameter, right atrium diameter and right ventricular diameter, while a decrease was found in the tricuspid annular systolic displacement and tricuspid annular peak systolic velocity at 1 week post-transplant. The survival curve showed that the postoperative survival time in the right atrium/ventricle ≥32 mm group was better than that in the right atrium/ventricle <32 mm group. The survival curve also showed that the postoperative survival time in the right atrium/ventricle enlargement <2 mm group was better than that in the right atrium/ventricle enlargement ≥2 mm group.ConclusionsIn the early post-transplant period, ventricular myocardial thickening, right heart enlargement and a decrease in right heart function were observed in the post-transplanted heart compared to the pretransplanted donor’s heart. Postoperative survival was higher among heart transplant patients who received a heart with right atrium/ventricle ≥32 mm. Postoperative survival was lower among heart transplant patients whose right atrium/ventricle was dilated ≥2 mm at 1 month postoperatively compared with the pretransplanted donor’s heart.

Supra- and Infra-Renal Aortic Neck Diameter Increase after Endovascular Repair of a Ruptured Abdominal Aortic Aneurysm.

Hypovolemia-induced hypotension may lead to an aortic diameter decrease in patients with a ruptured abdominal aortic aneurysm (rAAA). This study investigates the changes in supra- and infra-renal aortic neck diameters before and after endovascular aortic aneurysm repair (EVAR) for rAAA and the possible association with endograft apposition. A retrospective cohort study was conducted including 74 patients treated between 2010 and 2019 in two large European vascular centers. Outer-to-outer wall diameters were measured at +40, +10, 0, −10, and −20 mm relative to the lowest renal artery baseline on the last pre- and first post-EVAR computed tomography angiography (CTA) scan in a vascular workstation. Endograft apposition was determined on the first post-EVAR CTA scan. The post-operative diameter was significantly (p < 0.001) larger than the preoperative diameter at all aortic levels. The aortic diameter at +40 mm (supra-renal) and −10 mm (infra-renal) increased by 6.2 ± 7.3% and 12.6 ± 9.8%, respectively. The aortic diameter at +40 mm increased significantly more in patients with low preoperative systolic blood pressure (<90 mmHg; p = 0.005). A shorter apposition length was associated with a higher aortic diameter increase (R = −0.255; p = 0.032). Hypovolemic-induced hypotension results in a significant decrease in the aortic diameter in patients with an rAAA, which should be taken into account when oversizing the endograft.

Anatomical accuracy of the KODEX-EPD novel 3D mapping system of the left atrium during pulmonary vein isolation: A correlation with computer tomography imaging.

BackgroundA novel 3D mapping system (KODEX‐EPD, EPD Solutions) enables catheter localization and real‐time 3D cardiac mapping.ObjectiveTo evaluate left atrium (LA) anatomical mapping accuracy created by the KODEX‐EPD system during pulmonary vein isolation (PVI) compared with gold standard computed tomography (CT) images acquired from the same patients before the procedure.MethodsIn 15 consecutive patients who underwent PVI, 3D mapping of the LA was created on the KODEX‐EPD system using the Achieve catheter. Pulmonary vein (PV), posterior wall, and appendage anatomy and diameters, were compared to the CT 3D reconstruction measured on the CARTO 3 system. Measurements were done independently by two physicians in each method. Linear correlation and agreement between CT and EPD measurements were assessed by Spearman correlation and Bland‐Altman plot.ResultsMean LA mapping time was 7.7 ± 3.6 min. Very high interobserver correlation was found for both EPD and CT measurements (Spearman r = .9). High correlation (r = .75) was found between CT and EPD measurements. Bland‐Altman plot method revealed that measurements assessed by EPD were slightly higher than those assessed by CT. Mean difference was 3.5 mm, p < .01. In 2 (13.5%) patients each, disagreement regarding the presence of a left common PV and a right middle accessory vein anatomy was seen.ConclusionThe new KODEX‐EPD mapping system allows quick and accurate mapping of the LA with high correlation to CT imaging. Some differences in left common and accessory right middle vein anatomy were seen.

Parametric study on the crushing performance of a polyurethane foam-filled CFRP/Al composite sandwich structure

Composite structures have drawn growing attention for their outstanding characteristics benefiting from the combination of multi materials. This paper aims to investigate the crushing performance of a hybrid system involving an outer thin-walled tube made of carbon fibre-reinforced plastic (CFRP), a medial polyurethane (PU) foam and an inner thin-walled tube made of aluminium alloy (Al). The elastoplastic model of Al, the continuous damage model of CFRP and the compressible foam model of PU were established with assistance of universal material tests. The finite element model of the composite structure, namely CFRP-PU-Al, was validated by the experimental study. Based upon the reliable numerical modelling, the parametric study was carried out for exploring the effects of the wall thickness, diameter and ply orientation of the outer CFRP tube, namely CFRP-O, on the crushing behaviours of the composite structure. It was found that increasing the diameter or wall thickness of CFRP-O was helpful to increase the mean crushing force and energy absorption of CFRP-PU-Al, however, the overall specific energy absorption of the composite sandwich structure was limited by the characteristics of constitutive materials. Compared with the diameter, the wall thickness had a higher impact on the energy absorption characteristics, and increasing the diameter may decrease the specific energy absorption due to the increase of the overall structural mass. In terms of the ply orientation, the composite structure with stacking sequence of [0°/45°]3 possessed higher mean crushing force and energy absorption than the structure with stacking sequence of [0°/90°]3 under axial compression in this study.

Engineering in-plane mechanics of electrospun polyurethane scaffolds for cardiovascular tissue applications

Effective cardiovascular tissue surrogates require high control of scaffold structural and mechanical features to match native tissue properties, which are dependent on tissue-specific mechanics, function heterogenicity, and morphology. Bridging scaffold processing variables with native tissue properties is recognized as a priority for advancing biomechanical performance of biomedical materials and, when translated to the clinical practice, their efficacy. Accordingly, this study selected electrospinning on a rotating cylindrical target as an apparatus of broad application and mapped the relationship between key processing variables and scaffold mechanics and structure. This information was combined with mechanical anisotropy ranges of interest for the three main categories of tissue surrogated in cardiovascular tissue engineering: heart valve leaflets, ventricle wall, and large diameter blood vessels. Specifically, three processing variables have been considered: the rotational velocity and the rastering velocity of the mandrel and the dry (single nozzle – polymer only) vs wet (double nozzle – polymer plus phosphate buffer saline solution) fabrication configuration. While the dry configuration is generally utilized to obtain micro-fiber based polymeric mats, the wet fabrication is representative of processing conditions utilized to incorporate cells, growth factors, or micro-particles within the fibrous scaffold matrix. Dry and wet processed electrospun mats were fabricated with tangential and rastering velocities within the 0.3–9.0 m/s and 0.16–8 cm/s range respectively. Biaxial mechanics, fiber network, and pore micro-architectures were measured for each combination of velocities and for each fabrication modality (dry and wet). Results allowed identification of the precise combination of rotational and rastering velocities, for both dry and wet conditions, that is able to recapitulate the native cardiovascular tissue anisotropy ratio. By adopting a simple and broadly utilized electrospinning layout, this study is meant to provide a repeatable and easy to access methodology to improve biomimicry of the in plane-mechanics of heart valve leaflets, ventricular wall, and large diameter blood vessels.

Effects of the geometrical shapes on buckling of conical shells under external pressure

The purpose of this study is to investigate the effects of geometrical shapes on the buckling of conical shells under uniform external pressure. A curved conical shell, straight conical shell, and equivalent cylindrical shell were respectively designed with constant mass. Two curved conical shells, two straight conical shells and two cylindrical shells made of 201 austenitic stainless steel were fabricated and tested. Measurements were made to the wall thickness, diameter, axial length, and geometry of each shell and the material properties of the corresponding sheets. The conical shells were destroyed by slow pressure, resulting in good repeatability. According to measured results, the buckling of the tested shells was further studied numerically. The results reveal that the load-carrying capacity of the conical shell was significantly improved when the meridional shape was in the form of a circular arc.