Lower Strain Values Research Articles

Prognostic implications of right and left atrial strain in diabetes mellitus without coronary artery diseases

Abstract Background 2D- speckle-tracking echocardiography (2D-STE) has recently be used to assess subclinical myocardial dysfunction, however its utility in diabetes mellitus (DM) has been specifically focusing on the longitudinal systolic function of the left ventricle (LV). Aim To assess the prognostic relation between left (LA) and right (RA) systolic and diastolic strain parameters with clinical outcome in patients with DM. Methods Of the initial 1721 diabetic patients screened for this study only 502 consecutive patients with DM were eligible and retrospectively enrolled, and 2D-STE strain parameters assessed on the 2D-TTE images. All patients were prospectively followed for development of new outcome/cardiac events which included hospitalization for acute HF, CVS-related death, new onset AF/AFI, stroke, heart transplantation, or need for ventricular assist device implantation. The 2D-STE analysis was used to measure the peak LA (longitudinal, radial and circumferential) and RA (longitudinal) strain. The long-term outcomes were evaluated for all-cause CVS outcomes and recurrent hospitalization. Results For the 502 eligible patients [mean age:58±4; 58 % male sex], 221 reached the combined endpoint. Mean follow-up was 1.1±0.6years. Both LA and RA strain parameters were significantly impaired compared to normal standard references (p<.0001), the RA was more impaired than LA strain parameters. The best performance parameters predictive of CVS (combined outcomes) events were for LA>RA systolic and diastolic strain, global RA systolic and diastolic strain (AUC: 0.74 and 70) and global LA longitudinal systolic and diastolic strain (AUC: 0.86 and 0.77). The strongest association between the degree of atrial myocardial mechanical dysfunction and risk of cardiovascular events was more evident for LA strain (free wall > global strain) and lesser extend to RA strain. More myocardial mechanical strain impairments were demonstrated in those with higher left atrial volume index (LAVI), NYHA ≥II class, significantly impaired diastolic function, lower strain values (LA, LV, RV), and tricuspid annular plane systolic excursion (TAPSE), p<.001). The LA (free wall) strain impairment was the independent predictors of combined outcome (including survival) after multiple adjustments using different models. Conclusion Patients with DM, LA strain parameters are stronger predictors of outcome than RA and other conventional parameters and should be included for regular clinical screening DM patients as these parameters provide a stronger prognostic stratification.

Nonlinear Finite Element Analysis of Bone–Implant Contact in Three Short Dental Implant Models with Varying Osseointegration Percentages

Objectives: Dental implants have become a cornerstone of restorative dentistry, providing a long-lasting method for tooth replacement. The degree of osseointegration has a significant effect on biomechanical stability at the bone–implant contact (BIC), determining the continued efficacy of these implants. However, the exact consequences of changing osseointegration levels on different implant designs, especially in bones with variable densities, are not well known. Methods: This study used 3D finite element analysis (FEA) to look at the biomechanical performance of three short dental implants: BioMet 3iT3, Straumann® Standard Plus Short-Regular Neck (SPS-RN), and Straumann® Standard Plus Short-Wide Neck (SPS-WN). This paper tested the implants at four stages of osseointegration: 25%, 50%, 75%, and 100% in both high-density (bone type III) and low-density (bone type IV) cancellous bone. It also created and examined realistic CAD models under static occlusal loading conditions to assess stress distribution and major strains at the bone–implant contact. Results: The study discovered that as osseointegration increases, von Mises stress and principal strains go down significantly for all implant types. The SPS-WN implant had the lowest strain values, especially for bone with low density. These reductions demonstrate increased mechanical stability as the bone–implant interface becomes more capable of dispersing mechanical stresses, minimizing the potential for localized deformation and bone resorption. Conclusions: The results highlight the importance of achieving optimum osseointegration to reduce mechanical stress and increase the lifespan of dental implants. The SPS-WN type implant performed better in biomechanical tests than the others, especially when bone conditions were not ideal. This makes it a great choice for clinical applications that need long-term implant success.

Elastocaloric, barocaloric and magnetocaloric effects in spin crossover polymer composite films

Giant barocaloric effects were recently reported for spin-crossover materials. The volume change in these materials suggests that the transition can be influenced by uniaxial stress, and give rise to giant elastocaloric properties. However, no measurements of the elastocaloric properties in these compounds have been reported so far. Here, we demonstrated the existence of elastocaloric effects associated with the spin-crossover transition. We dissolved particles of ([Fe(L)2](BF4)2, [L=2,6di(pyrazol-1-yl)pyridine]) into a polymeric matrix. We showed that the application of tensile uniaxial stress to a composite film resulted in a significant elastocaloric effect. The elastocaloric effect in this compound required lower applied stress than for other prototype elastocaloric materials. Additionally, this phenomenon occurred for low values of strain, leading to coefficient of performance of the material being one order of magnitude larger than that of other elastocaloric materials. We believe that spin-crossover materials are a good alternative to be implemented in eco-friendly refrigerators based on elastocaloric effects.

Left atrial function in middle-aged men and women with and without paroxysmal atrial fibrillation: Data from the Akershus Cardiac Examination (ACE) 1950 study.

To assess left atrial (LA) function in individuals with known paroxysmal atrial fibrillation (AF) compared with healthy and nonhealthy individuals without atrial fibrillation. The Akershus Cardiac Examination 1950 Study included 3,706 individuals all born in 1950. LA strain assessment of reservoir (LASr), conduit (LAScd) and contractile (LASct) functions were performed in all participants by investigators blinded to clinical data. Participants with cardiovascular disease, obesity, diabetes, pulmonary or renal disease were defined as nonhealthy, and those without as healthy. Patients with paroxysmal AF were identified through medical history and ECG documentation. LA strain assessment was feasible in 3,229 (87%) of the participants (50% women). The healthy group (n=758) had significantly higher LASr and LAScd than the nonhealthy (n=2,376), but LASct was similar between the groups. Participants with paroxysmal AF had significantly lower values of all strain parameters than the other groups. Multivariable logistic regression showed a significantly reduced probability of having AF per standard deviation increase in LASr and LASct. A nonlinear restricted cubic spline model fitted better with the association of LASr with paroxysmal AF than the linear model, and LA strain values below the population mean associated with an increased probability of having AF, but for values above the population mean no such association was present. Compared to participants without AF, those with known paroxysmal AF had significantly lower values of all LA strain parameters during sinus rhythm. Lower values of LA strain were associated with a significantly increased probability of having AF.

Mild renal dysfunction causes aggravated cardiac damage in type 2 diabetic patients: a comprehensive echocardiography study.

We sought to detect left ventricular (LV) adverse alterations in structure and function in type 2 diabetes mellitus (T2DM) patients with or without mild renal dysfunction (MRD) using comprehensive echocardiography techniques and to explore the independent risk factors for LV remodeling (LVR) and dysfunction in these patients. The study included 82 T2DM patients with normal LV ejection fraction (presence (n = 42)/absence (n = 40) of MRD). Age- and gender-matched controls (n = 40) were also recruited. LV structure and function were evaluated using conventional echocardiography and three-dimensional speckle tracking echocardiography (3DSTE). Global longitudinal strain (GLS), global circumferential strain (GCS), global area strain (GAS), and global radial strain (GRS) were all measured using 3DSTE. Compared with the controls with absolute advantage of LV normal geometry, LVR was more frequently present in the two T2DM groups, with the largest proportion in those with T2DM and MRD (P < 0.001). Fasting plasma glucose (FPG) and MRD were both significant risk factors for LVR in T2DM patients. The detection rates of LV diastolic dysfunction and subclinical systolic dysfunction were significantly higher in the T2DM groups than in the controls (P = 0.000). Moreover, the two case groups also showed significantly lower strain values in multiple directions than the controls (all P < 0.05). FPG was significantly associated with LV diastolic dysfunction, whereas FPG and MRD were both significantly associated with subclinical LV systolic dysfunction in T2DM patients. The combined use of conventional echocardiography and 3DSTE allowed the timely detection of early cardiac damage in T2DM patients with or without MRD.

Hot isostatic pressing as an alternative thermo-mechanical treatment for metallic full-arch implant-supported frameworks obtained by additive and subtractive manufacturing technology: Vertical and horizontal fit, screw removal torque, and stress analysis.

To assess vertical and horizontal fit, screw removal torque, and stress analysis (considered biomechanical aspects) of full-arch implant frameworks manufactured in Ti-6Al-4V through milling, and additive manufacturing Direct Metal Laser Sintering (DMLS) and Electron Beam Melting (EBM), and the effect of the thermo-mechanical treatment Hot Isostatic Pressing (HIP) as a post-treatment after manufacturing. Maxillary full-arch implant frameworks were made by milling, DMLS, and EBM. The biomechanical assessments were screw removal torque, strain-gauge analyses, and vertical and horizontal marginal fits. The vertical fit was assessed by the single-screw test and with all screws tightened. All frameworks were submitted to a standardized HIP cycle (920°C, 1000bar pressure, 2h), and the tests were repeated (α = 0.05). At the initial time, milled frameworks presented higher screw removal torque values, and DMLS and EBM frameworks presented lower levels of strain. Using the single-screw test, milled and DMLS frameworks presented higher vertical fit values, and with all screws tightened and horizontally, higher fit values were found for milled frameworks, followed by DMLS and EBM. After HIP, milling and EBM frameworks presented higher screw removal torque values; the lowest strain values were found for EBM. Using the single-screw test, milled and DMLS frameworks presented higher vertical fit values, and with all screws tightened and horizontally no differences were found. DMLS and EBM full-arch frameworks presented adequate values of screw removal torque, strain, and marginal fit, although the worst values of marginal fit were found for EBM frameworks. The HIP cycle enhanced the screw removal torque of milled and EBM frameworks and reduced the strain values of milled frameworks. The HIP represents a reliable post-treatment for Ti-6Al-4V dental prostheses produced by milling and EBM technologies.

Two-dimensional speckle tracking echocardiography in chemotherapy-induced cardiotoxicity in females with breast cancer

BackgroundCancer and cardiovascular diseases are the main causes of mortality worldwide. Although the incidence of cancer is rising, modern comprehensive management including surgery, chemotherapy, and radiotherapy led to decreased mortality, but also different cardiovascular complications. Conventional EF measurement fails to detect subtle changes in LV function, so a more sensitive tool is needed.MethodsThe study included 101 asymptomatic female patients with newly diagnosed breast cancer who received anthracycline ± trastuzumab-based chemotherapy regimen. A comprehensive echocardiographic examination was performed before receiving the chemotherapy (T0), at 3 months (T1), and at 6 months after (T2). All patients had pre-treatment normal LV EF. Asymptomatic CTRCD is defined as: severe if new LVEF reduction to < 40%, moderate if new LVEF reduction by ≥ 10 percentage points to an LVEF of 40–49% or new LVEF reduction by, 10 percentage points to an LVEF of 40– 49% and either new relative decline in GLS by .15% from baseline or new rise in cardiac biomarkers and mild if LVEF ≥ 50% and new relative decline in GLS by .15% from baseline and/or new rise in cardiac biomarkers. Symptomatic CTRCD is defined as: very severe if HF requiring inotropic support, mechanical circulatory support, or consideration of transplantation, severe if required hospitalization, moderate if required outpatient intensification of diuretic and HF therapy and mild if there are mild HF symptoms and no intensification of therapy required according to the latest ESC cardio oncology guidelines. The Lower reference value set for RV S’ was less than 10cm/s to define RV systolic dysfunction according to ASE guidelines.ResultsCTRCD occurred in 24 patients (25.5%) while RV systolic dysfunction was more common occurring in 37 patients (39.4%). LV GLS at (T1) (cut-off value < -15% with relative 12.5% reduction from the baseline value) was a strong predictor of CTRCD, but combining LV GLS with RV GLS & RV FWLS was the strongest (AUC = 0.947, sensitivity = 91.67%, specificity = 90%).ConclusionChemotherapy induces biventricular changes with more prevalent deterioration in RV values. Low LV & RV strain values at baseline together with reduction of these values after chemotherapy treatment can predict later CTRCD development. Combining LV GLS with RV GLS & FWLS values at (T1) is the strongest predictor of subsequent CTRCD.

Flow affects the structural and mechanical properties of the fibrin network in plasma clots

The fibrin network is one of the main components of thrombi. Altered fibrin network properties are known to influence the development and progression of thrombotic disorders, at least partly through effects on the mechanical stability of fibrin. Most studies investigating the role of fibrin in thrombus properties prepare clots under static conditions, missing the influence of blood flow which is present in vivo. In this study, plasma clots in the presence and absence of flow were prepared inside a Chandler loop. Recitrated plasma from healthy donors were spun at 0 and 30 RPM. The clot structure was characterized using scanning electron microscopy and confocal microscopy and correlated with the stiffness measured by unconfined compression testing. We quantified fibrin fiber density, pore size, and fiber thickness and bulk stiffness at low and high strain values. Clots formed under flow had thinner fibrin fibers, smaller pores, and a denser fibrin network with higher stiffness values compared to clots formed in absence of flow. Our findings indicate that fluid flow is an essential factor to consider when developing physiologically relevant in vitro thrombus models used in researching thrombectomy outcomes or risk of embolization.Graphical

Analysis of Myocardial Left Ventricular Deformation During the Third Trimester of Healthy Pregnancy

Background: Pregnancy, a distinctive physiologic state, that associated with multiple changes in the several body systems. One of the affected systems is cardiovascular system , with volume overload being one of the typical adaptation encountered during pregnancy, with chronic volume overload being one of the characteristic changes experienced during pregnancy. However, the effect of these changes on left ventricular myocardial contractile function has not been fully illustrated. Aim: To assess the maternal cardiac function during the third trimester of healthy pregnancy using Speckle Tracking echocardiography. Patient and Methods: This cross sectional study was carried out in Al-Furat teaching hospital in the time period from 1st of April 2022 to 30 of May 2023. A total of 150 women were studied, they were classified into two groups: 75 pregnant women with normal singleton pregnancy at their third trimester served as study group and 75 non pregnant women served as control group. Clinical evaluation, anthropometric assessments, and two-dimensional M-mode and Doppler echocardiography as well as Speckle Tracking echocardiographic study had been done for each one of them to assess the left ventricular systolic function. Results: The two groups showed significant difference in accordance with weight , height &amp; BMI. Global longitudinal strain (GLS) was significantly different between the study groups . Its Average value was decrease to -20.3 compared with -25.3 in control group. Besides, apical long-axis , three-, and four-chamber strain showed significant changes as well. With lowest strain value was the apical long-axes -18.96 in comparison with the control. Conclusion: Left ventricular global longitudinal strain (GLS) shows significant reduction during the third trimester of healthy pregnancy ,this reduction in LV thickening is one of the cardiac adaptation throughout the pregnancy.

Thermal and Mechanical Properties of Polymeric Films Based on PLA / PBAT and Corn Starch and Babassu Mesocarp Starch by Flat Extrusion for Packaging

The influence of different amounts (1, 3 and 5%) of commercial corn starch and of babassu mesocarp starch on a (polylactic acid)/poly (butylene co-terephthalate adipate) (PLA/PBAT) based blend obtained by flat extrusion was ascertained. The thermal and mechanical properties were determined and the results obtained are independent of the type of starch employed but are dependent on its concentration, the nucleating effect of the different starches and on the mobility of the polymer chains that make up the blend. Thermogravimetric analysis indicated the presence of two defined stages of mass loss for all films under investigation. Tensile testing shows that films containing starch had similar behavior to that of PLA in the PLA/PBAT blend, presenting high values of tensile strength, elastic modulus and tensile strength and low values of strain at break. The results suggest that babassu mesocarp starch is viable alternatives to the production of packaging films.

A comparative study to evaluate microstrain of low-profile attachment associated with and without bar connection in implant assisted mandibular overdenture (in vitro study)

BackgroundThe aim of this study was to compare the microstrain transmitted to peri-implant tissues of implant-assisted mandibular overdentures using two different low-profile attachment designs; OT- Equator attachment with and without bar attachment.Materials and methodsA completely edentulous epoxy resin mandibular model was used, in which two parallel dental implants were inserted at the canine region bilaterally and one in the middle. Sixteen identical complete edentulous mandibular overdentures were fabricated following conventional, standardized techniques and were divided equally between two groups according to the design and placement of the OT-Equator. Group A implants were kept solitary with an OT-Equator attachment, while group B implants were kept splinted with a bar associated with two mini-OT-Equator attachments in between. Sixteen identical mandibular complete overdentures were constructed, to which attachments were picked up. The difference in stress distribution was measured using strain gauges and compared between the two studied groups. A vertical load of 100 N using the universal testing machine was applied unilaterally on the left mesial fossae of the mandibular first molar and bilaterally on the bar attached to the mandibular premolar molar region of the overdentures. Statistical analysis was conducted using IBM SPSS version 28. Normality was checked by using the Shapiro-Wilk test and normality plots. The Mann-Whitney U test was then used to analogize the groups.ResultsThere was a statistically significant difference between groups A and B upon application of vertical unilateral and bilateral loadings of 100 N, with mean microstrain values of P 0.05. Group A (OT-Equator attachment) showed lower strain values than Group B (OT-Equator bar attachment) upon application of vertical, unilateral, and bilateral loadings of 100 N.ConclusionsImplant-assisted mandibular overdenture with a solitary attachment is associated with lower microstrain values around the implants after application of unilateral and bilateral vertical loadings of 100 N.

Pengaruh Penambahan Filler Al2O3 dan TiO2 pada Resin Polyester terhadap Sifat Fisik dan Mekanik

Polyester composites have been developed to have high strength and light density, but the fracture occurs due to very little plastic deformation or low strain values, pre-failure detection is difficult in these composites due to the rapid propagation of cracks in the composite system. To increase the strength and delay failure, the addition of filler in the form of Al2O3 and TiO2 particles is carried out. The use of particles as fillers in polymer composite materials is increasingly being developed. In this study, Al2O3 and TiO2 particles (0%, 2%, 4%, 6%, 8%, 10% vol.) were added in polyester matrix BQIN EX 157. by casting method; the liquid homogeneous mixture was carefully poured into a simple mould to be air dried. The composites were cut to serve as specimens for density test, mechanical tests such as tensile and compressive tests. The results showed a density of 1.23 g/cm3, a maximum strength of 47 MPa for 2% additional Al2O3 filler, (tensile, decreasing ̴11%) and 120 MPa (compressive) for a maximum of 2% additional Al2O3 (compressive, decreasing ̴3%) with TiO2 filler. The decrease in strength was caused by uneven particle dispersion, voids and agglomeration that occurred during the casting process.

Investigations on growth, XRD, strain, FTIR, UV–Vis NIR, photoluminescence, SHG, and Z-scan analyses of L-cysteine picrate single crystal for NLO and optical limiting applications

Organic single crystal of L-cysteine picrate (LCP), an efficient NLO material for frequency conversion, optoelectronic, and optical limiting applications has been grown within 20 days by Slow Evaporation Solution Technique (SEST). PXRD analysis shows that the LCP is subjected to the noncentrosymmetric space group of P21 with a monoclinic crystal system. The very low strain value depicts that the level and dislocations of the defect in the lattice of LCP crystal are very low. The various functional group assignments were investigated by using Fourier-Transform Infrared (FTIR) spectrum analysis with the range of 4000–400 cm−1. The optical analysis (UV–Visible) confirmed that the crystal has a lower cut-off wavelength of 250 nm and very low absorption in the entire visible region. Photoluminescence (PL) spectrum analysis confirmed that the material exhibits blue emission and is suitable for LED device fabrication. The SHG efficiency for LCP crystal is established to be 1.7 times higher than KDP material. Z-scan measurement determined the LCP exhibits two-photon absorption-induced optical limiting action with a nonlinear absorption coefficient of 0.70 × 10−10 m/W and onset limiting threshold of 2.36 × 1012 W/m2 which indicates that it can be used in making laser protection gadgets.

Effect of strain on electronic properties of tri-layer MoS2/h-BN/graphene van der Waals heterostructures

The two-dimensional materials have grabbed the attention of researchers because of their high functionality and widely controllable properties. Due to the dimensionality reduction, the external factors have a significant influence on their properties. The density functional theory calculations have been performed on the heterostructures of single-layer graphene (G), boron nitride (BN) and molybdenum disulfide (MoS2) to investigate the alteration in their electronic properties. Our calculations predict that electronic properties such as bandgap, work function, Schottky barrier height and tunnelling barrier probability can be modulated by applying mechanical strain. The application of strain resulted in a band gap opening of about 1 eV in trilayer heterostructures. At low values of strain, heterostructures maintained a low resistance ohmic contact. At −9% strain, the p-to-n-type transition of Schottky contact was observed indicating the flow of electrons from semiconductor to metal. The MoS2 monolayer was found to be more electron deficient and exhibited a greater charge accumulation. MoS2/BN/G heterostructure can be used for the fabrication of capacitive devices. Whereas BN/G/MoS2 and BN/MoS2/G heterostructures can act as potential candidates for trilayer Schottky devices due to the presence of low-barrier metal-semiconductor junction.

Freeze-Thaw resistance and mechanical properties of UHPC reinforced with a lower amount of hybrid fibers

Sustainable development is becoming critical in many industrial fields, including building materials. The rapid development of the construction industry in Kazakhstan requires construction materials having high-quality, low maintenance, and good durability. The main durability issue of construction material associated with Kazakhstan’s severe climate is the volume change of water in concrete caused by the freezing and thawing (F-T) cycles, which threatens the material’s strength and microstructure. Therefore, ultra-high-performance concrete (UHPC), a relatively new material with high compressive and tensile strength and improved microstructural properties, is suggested. Nevertheless, a limited number of researches have been done regarding the F-T resistance of UHPC. This research focuses on the effect of combining two types of fibers (steel and polypropylene (PP) fibers) on the compressive, flexural, and direct tensile strength and F-T resistance of UHPC. Test results indicated higher dosages of PP fiber in UHPC increased strength before exposure to F-T cycles. Adding PP fiber to UHPC led to more prolonged strains for each UHPC mixture. However, adding more steel fibers was beneficial for UHPC exposed to F-T cycles. Although mixtures with high steel fiber dosage presented a more brittle type of failure and lower strain values than mixtures with higher PP fiber dosage, the compressive, flexural, and tensile strength of UHPC mixtures containing higher steel fiber dosages increased after 90F-T cycles. Relative dynamic modulus of elasticity (RDME), which is a common indicator of F-T resistance of concrete, tends to increase for all tested mixtures, with the highest values belonging to ones with higher steel fiber dosage. Hence, it is suggested that UHPC with higher steel fiber dosage is more beneficial in terms of the F-T resistance of UHPC.

Material Optimization for Structural Strength of Hexacopter Landing Skid Using Finite Element Method

Hexacopter is a type of UAV that has six propellers with a load of 15 kg or about 147 N in this study. Then, to support the landing of the hexacopter and to support it while being on the ground, landing skid is needed. The landing skid is designed using 3D printing from selected materials to find out which material is best used for the landing skid, including PLA, PETG, and ABS. 3D-printing supports the production of lightweight and high-strength parts. This research method uses finite element to compare several materials and uses SolidWorks to simulate static load and drop test by landing skid. The results show that PETG material is the best material with the highest safety factor in the static load and has the lowest strain value in the drop test.

Low-cycle fatigue behavior of differently matched welded joints of quenched and tempered steel

The appropriate matching of base and filler material is a complex task, where yield strength matching is the most general aspect. As the strength properties of structural steels have significantly improved in the past decades, the matching problem has become more relevant today. The mismatch phenomenon significantly affects the behavior of welded joints under dynamic and cyclic loading. Among cyclic loading, low-cycle fatigue (LCF) often occurs in welded steel constructions; furthermore, the LCF resistance of these advanced steels and their welded joints is limitedly known. In this paper, welding experiments are presented for the analysis of the LCF behavior of differently matched butt-welded joints made from two grades of quenched and tempered (Q + T) high-strength steels. For S690QL steel, matched and overmatched consumables were applied, while for S960QL steel, matched and undermatched filler materials were used. Material tests were performed to determine the mechanical properties of the different welded joints. In both examined steel grades, the welded joints tolerated a smaller number of cycles until failure than the base materials. In the case of S690QL, the LCF resistance of the matched welded joints was higher than the overmatched filler material. At S960QL in the higher strain amplitude range, the number of cycles to failure was higher at the same total and plastic strain amplitudes when undermatched filler material was used; however, an opposite ratio can be observed at lower strain values, compared to the matching filler material.

Left atrial function after thoracoscopic left atrial appendage exclusion as standalone and as combined with epicardial atrial fibrillation ablation: echocardiographic findings at one- year follow up

Abstract Funding Acknowledgements Type of funding sources: None. Introduction Left atrial appendage (LAA) is the most common source of thrombi in patients with atrial fibrillation (AF). The Totally Thoracoscopic (TT)-LAA exclusion with epicardial clip is an effective procedure, however the effects on left atrial (LA) function remain unknown. Purpose The aim of this study was to assess the impact of TT-LAA exclusion on the LA function in patients undergoing to standalone TT-LAA exclusion and patients received combined procedure, namely: TT-LAA exclusion and Thoracoscopic Epicardial Ablation (TEA). Methods 39 AF Patients underwent to TT-LAA exclusion with the clip. Indication to standalone TT-LAA exclusion was: high risk for ischemic stroke or contraindication to long-term anticoagulant therapy. All patients were screened preoperatively with 3D CT scan, transthoracic and trans-esophageal echocardiography. Intraoperative clip positioning and LAA exclusion were guided by trans-esophageal echo. To evaluate LA function, standard transthoracic echocardiography and 2D strain of LA were performed before surgery, at discharge (3-4 days after the procedure), at 3-month and at 1 year. Routine blood tests and BNP levels were also measured. Results The study enrolled 39 consecutive patients, 25 underwent to standalone TT-LAA exclusion (mean age 78.6 ± 5.7 years, 79% males), and 14 LAA exclusion during TEA (mean age 64.5 ± 8.2 years, 82% males). The mean CHA2DS2-VASc and HASBLED scores were 3.5 and 2.1 respectively. Baseline characteristics are summarized in Figure 1. There were no major complications during the procedure. At median follow-up of 13 months, 1 non cardiovascular death, 1 ischemic stroke and 4 cardiovascular hospitalizations occurred. At 2D strain of LA, the reservoir function decreased significantly after clip implantation and recovered at 3-months follow-up; at 1 year it remained stable. Furthermore, NT-proBNP increased significantly after LAA exclusion with a return to baseline after 3 months. Changes in E/A occurred at predischarge and did not persist at follow up. Echocardiographic findings are summarized in Figure 2. Patients with indication to TEA and LAA exclusion presented a lower LA volume and a lower strain value. Conclusion The main findings of this study can be summarized as follows: 1) The amputation of LAA is a safe procedure at long term follow up. 2) LAA amputation with the clip is associated with acute elevation of BNP levels the days after the procedure with return to baseline at 3 months and one year. 3) LAA amputation impairs the LA reservoir function after the procedure, with recovery after 3 months and remains preserved at one-year. This occurs either when LA strain is measured in sinus rhythm or in AF. 4) LAA exclusion results in a change in E/A that does not persist at three months follow-up and at 1 year. 5) Patients with indication to epicardial AF ablation and LAA exclusion present a lower LA volume with a lower strain value than patients undergoing standalone TT-LAA exclusion.

Mesoporous Zn2SnO4 for efficient sensing of ethylene glycol vapor

Within this study, mesoporous Zn2SnO4 nanostructures have been prepared by a facile and eco-friendly hydrothermal method. Through X-ray diffraction analysis, a polycrystalline zinc tin oxide structure is recognized with a cubic inverse spinel phase crystal structure. By Field emission scanning electron microscopy method, various morphologies based on the hydrothermal time ranging from the cubic-like morphology, irregular hexagonal plates, and large quantity of microspheres to the truncated octahedron have been observed. By the aid of Energy dispersive X-ray spectroscopy and Fourier transform infrared spectroscopy analyses, the atomic ratio and characteristic vibration peaks of Zn2SnO4 have been evaluated. By the help of Brunauer–Emmett–Teller analysis, specific surface area, mean pore diameter, and total pore volume were measured. The nanostructured Zn2SnO4 prepared in 36 h hydrothermal treatment (as a selected sample) showed a higher BET specific surface area (9.10 m2/g) and total pore volume (0.078 cm3/g) than the other samples. The gas-sensing performance of the samples was investigated towards different vapors. The optimum operating temperature (270 °C), transient response, response/recovery times, and long-term stability (eight months) of the samples have been evaluated. For the selected sample, appreciable sensing response (92.92 toward 100 ppm ethylene glycol), the ultra-fast response time (1 s), excellent selectivity (about 6–23 times more than other tested vapors) and excellent long-term stability (the response decay of about 10% after eight months) has been perceived which makes it a promising gas sensor. It seems that the selected sample has shown relatively better performance for two reasons: Firstly, high crystalline quality (largest crystallite size and lowest strain value) which can affect the combination or separation of adsorbed oxygen species on the surface of the material. Secondly, the higher specific surface area and the relatively larger total pore volume can lead to more gas adsorption sites leading to further narrowing of the depletion layer and resulting in a high and very fast response.

Temperature dependent constitutive plastic flow behaviour of titanium alloy Ti6Al4V

Abstract The constitutive relationship between stress and strain for titanium alloy Ti6Al4V has been investigated using tensile tests at four different temperatures that is room temperature, 200 °C, 400 °C, and 550 °C. Detail observations on the variation of nature of flow curves in the work hardening regime have been reported at different test temperatures. At room temperature and 550 °C, the flow curves are found to be linear in nature and follow the Hollomon relationship. The flow curves at 200 and 400 °C exhibit non-linear nature and demonstrate Ludwigson relationship. The various constant parameters of above relationships influence the overall strength and ductility of the alloy at different temperatures. The alloy shows presence of premature plastic instability or inflection points in the early period of flow curves and displays a fast decrease in work hardening rate at room temperature and 550 °C, which in turn results in lower values of strain to fracture.