Iron (hydr)oxide formation in Andosols under extreme climate conditions.

Redox-driven biogeochemical cycling of iron plays an integral role in the complex process network of ecosystems, such as carbon cycling, the fate of nutrients and greenhouse gas emissions. We investigate Fe-(hydr)oxide (trans)formation pathways from rhyolitic tephra in acidic topsoils of South Patagonian Andosols to evaluate the ecological relevance of terrestrial iron cycling for this sensitive fjord ecosystem. Using bulk geochemical analyses combined with micrometer-scale-measurements on individual soil aggregates and tephra pumice, we document biotic and abiotic pathways of Fe released from the glassy tephra matrix and titanomagnetite phenocrysts. During successive redox cycles that are controlled by frequent hydrological perturbations under hyper-humid climate, (trans)formations of ferrihydrite-organic matter coprecipitates, maghemite and hematite are closely linked to tephra weathering and organic matter turnover. These Fe-(hydr)oxides nucleate after glass dissolution and complexation with organic ligands, through maghemitization or dissolution-(re)crystallization processes from metastable precursors. Ultimately, hematite represents the most thermodynamically stable Fe-(hydr)oxide formed under these conditions and physically accumulates at redox interfaces, whereas the ferrihydrite coprecipitates represent a so far underappreciated terrestrial source of bio-available iron for fjord bioproductivity. The insights into Fe-(hydr)oxide (trans)formation in Andosols have implications for a better understanding of biogeochemical cycling of iron in this unique Patagonian fjord ecosystem.

Redo Transcatheter Aortic Valve Implantation with the ALLEGRA Transcatheter Heart Valve: Insights from Bench Testing.

PURPOSE: Failure of transcatheter heart valves (THV) may potentially be treated with repeat transcatheter aortic valve implantation (redo TAVI). We assessed hydrodynamic performance, stability and pinwheeling utilizing the ALLEGRA (New Valve Technology, Hechingen, Germany) THV, a CE approved and marketed THV in Europe, inside different THVs. METHODS: Redo TAVI was simulated with the 27 mm ALLEGRA THV at three implantation depths (-4 mm, 0 mm and +4 mm) in seven different 'failed' THVs: 26 mm Evolut Pro, 25 mm Lotus, 25 mm JenaValve, 25 mm Portico, 23 mm Sapien 3, 27 mm ALLEGRA and M ACURATE neo. Hydrodynamic evaluation was performed according to International Standards Organization 5840-3:2021. RESULTS: The ALLEGRA THV was stable with acceptable performance (gradient <20 mmHg, effective orifice area >2 cm2, and regurgitant fraction <20%) in all 'failed' THVs except the Evolut Pro at -4 mm implantation depth. In this configuration, the outflow of the ALLEGRA frame was constrained by the Evolut Pro THV and the ALLEGRA leaflets were unable to fully close. Pinwheeling was severe for the ALLEGRA in Evolut Pro. The neo-skirt was higher with taller frame THVs. CONCLUSION: The ALLEGRA THV had favorable hydrodynamic performance, stability and pinwheeling in all redo TAVI samples except the Evolut Pro at low implantation depth with compromised function. The choice of initial THV may have late implications on new THV choice and function.

Impact of Non-Valvular Non-Coronary Concomitant Procedures on Outcomes of Surgical Aortic Valve Replacement in Intermediate Risk Patients.

INTRODUCTION: advanced age and concomitant procedures could increase the risk of perioperative complications during surgical aortic valve replacement (SAVR). We aimed to evaluate results of elderly patients undergoing SAVR and evaluate the impact of concomitant non-valvular, non-coronary procedures on the outcomes. METHODS: A retrospective single-centre study, evaluating 464 elderly patients (mean age = 75.6 ± 4 years) undergoing either isolated-SAVR (I-SAVR = 211) or combined-SAVR (C-SAVR = 253) between 01/2007 and 12/2017. Combined-SAVR involved non-valvular, non-coronary procedures. Study endpoints are postoperative results concerning the VARC-II criteria, valve dysfunction, long-term freedom from redo-AVR and survival. RESULTS: males were 52.8%. Patients had an intermediate risk profile (mean EuroSCORE-II (%) 5.2 ± 5). Postoperative results reported no significant differences in incidence of re-exploration for bleeding (6.6% vs. 6.7%, p = 1.0), stroke (0.9% vs. 0.4%, p = 0.59), dialysis (6.2% vs. 9.5%, p = 0.23) and pacemaker implantation (3.3% vs. 2.8%, p = 0.79) between I-SAVR and C-SAVR groups. Thirty-day (2.4% vs. 7.1% p = 0.03), one-year (5.7% vs. 13.8%, p = 0.003) and overall mortality (24.6% vs. 37.5%, p = 0.002) were lower in the isolated-SAVR group. Re-AVR was indicated in 1.7% of patients due to endocarditis. CONCLUSIONS: SAVR in elderly patients offers good outcomes with increased life quality and rare re-operation for structural valvular deterioration. Mortality rates were significantly higher when SAVR was combined with another "non-valvular, non-coronary" procedure.

Transapical transcatheter mitral valve implantation in patients with degenerated mitral bioprostheses or failed ring annuloplasty.

BACKGROUND: We sought to evaluate the outcomes of transapical transcatheter mitral valve replacement in patients with degenerated mitral bioprostheses or failed mitral ring annuloplasty and high surgical risk for redo mitral valve procedure. METHODS: Between August 2012 and December 2020, 41 consecutive high-risk patients underwent transcatheter mitral 'valve-in-valve' (TM-ViV, n=25) or 'valve-in-ring' (TM-ViR, n=16) implantation at our institution. All procedures were performed in a hybrid operating theater using the SAPIEN XT/3™ or the DIRECT FLOW MEDICAL™ prostheses. Data was collected prospectively according to MVARC criteria. RESULTS: The logistic EuroSCORE-I was 42.3%±20.5% (mean ± SD), the Society of Thoracic Surgeons (STS) score was 11.9%±10.8%, and the STS/ACC-score was 7.6%±4.2%. Transcatheter mitral valve implantations were successful in all patients (100%). Early echocardiographic examinations showed no obstruction of the left ventricular outflow tract (LVOT), no paravalvular leakage, and only trace transvalvular leakage in eight patients. There was no operative mortality; thirty-day mortality was 9.8%. Survival was 72% at one year and 63% at three years. At two-year follow-up, transvalvular mean pressure gradients were 4.6±1.4 mmHg. CONCLUSIONS: Transapical transcatheter mitral valve-in-valve or valve-in-ring implantation represents a true minimally invasive alternative to surgical redo procedures, especially in high-risk patients with failed bioprosthetic mitral valves or annuloplasty and favorable anatomy.

Neosinus and Sinus Flow After Self-Expanding and Balloon-Expandable Transcatheter Aortic Valve Replacement.

OBJECTIVES: The aim of this study was to evaluate flow dynamics in the aortic sinus and the neosinus (NS) after transcatheter heart valve (THV) implantation in valve-in-valve (ViV). BACKGROUND: Leaflet thrombosis may occur on THVs and affect performance and durability. Differences in flow dynamics may affect the risk for leaflet thrombosis. METHODS: Hemodynamic assessment following THV implantation in a surgical aortic valve was performed in a left heart simulator under pulsatile physiological conditions. Assessment was performed using a 23-mm polymeric surgical aortic valve (not diseased) and multiple THV platforms, including self-expanding devices (26-mm Evolut, 23-mm Allegra, small ACURATE neo) and a balloon-expandable device (23-mm SAPIEN 3). Particle image velocimetry was performed to assess flow in the sinus and NS. Sinus and NS washout, shear stress, and velocity were calculated. RESULTS: Sinus and NS washout was fastest and approximately 1 cardiac cycle for each with the Evolut, ACURATE neo, and Allegra compared with the SAPIEN 3, with washout in 2 and 3 cardiac cycles, respectively. The Allegra showed the largest shear stress distribution in the sinus, followed by the SAPIEN 3. In the NS, all 4 valves showed equal likelihoods of occurrence of shear stress <1 Pa, but the Allegra showed the highest likelihoods of occurrence for shear stress >1 Pa. The velocities in the sinus and NS were 0.05, 0.078, 0.080, and 0.075 m/s for Evolut, SAPIEN 3, ACURATE neo, and Allegra ViV, respectively. CONCLUSIONS: Sinus and NS flow dynamics differ substantially among THVs after ViV. Self-expanding supra-annular valves seem to have faster washouts compared with an equivalent-size balloon-expandable THV.

Mitral surgical redo versus transapical transcatheter mitral valve implantation.

BACKGROUND: Transcatheter methods have been rapidly evolving to provide an alternative less invasive therapeutic option, mainly because redo patients often present with multiple comorbidities and high operative risk. We sought to evaluate and compare our experience with transapical transcatheter mitral valve replacement (TA-TMVR) to conventional redo mitral valve replacement in patients presenting with degenerated biological mitral valve prostheses or failed valve annuloplasty. METHODS AND MATERIAL: Between March 2012 and November 2020, 74 consecutive high-risk patients underwent surgical redo mitral valve replacement (n = 33) or TA-TMVR (n = 41) at our institution. All patients presented with a history of a surgical mitral valve procedure. All transcatheter procedures were performed using the SAPIEN XT/3™ prostheses. Data collection was prospectively according to MVARC criteria. RESULTS: The mean logistic EuroSCORE-II of the whole cohort was 19.9±16.7%, and the median STS-score was 11.1±12.5%. The mean age in the SMVR group was 63.7±12.8 years and in the TMVR group 73.6±9.7 years. Patients undergoing TA-TMVR presented with significantly higher risk scores. Echocardiography at follow up showed no obstruction of the left ventricular outflow tract, no paravalvular leakage and excellent transvalvular gradients in both groups (3.9±1.2 mmHg and 4.2±0.8 mmHg in the surgical and transcatheter arm respectively). There was no difference in postoperative major adverse events between the groups with no strokes in the whole cohort. Both methods showed similar survival rates at one year and a 30-day mortality of 15.2% and 9.8% in SAVR and TMVR group, respectively. Despite using contrast dye in the transcatheter group, the rate of postoperative acute kidney failure was similar between the groups. CONCLUSION: Despite several contraindications for surgery, we showed the non-inferiority of TA-TMVR compared to conventional surgical redo procedures in high-risk patients. With its excellent hemodynamic and similar survival rate, TA-TMVR offers a feasible alternative to the conventional surgical redo procedure in selected patients.

Expanding Monomers as Anti-Shrinkage Additives.

Commonly, volumetric shrinkage occurs during polymerizations due to the shortening of the equilibrium Van der Waals distance of two molecules to the length of a (significantly shorter) covalent bond. This volumetric shrinkage can have severe influence on the materials' properties. One strategy to overcome this volumetric shrinkage is the use of expanding monomers that show volumetric expansion during polymerization reactions. Such monomers exhibit cyclic or even oligocyclic structural motifs with a correspondingly dense atomic packing. During the ring-opening reaction of such monomers, linear structures with atomic packing of lower density are formed, which results in volumetric expansion or at least reduced volumetric shrinkage. This review provides a concise overview of expanding monomers with a focus on the elucidation of structure-property relationships. Preceded by a brief introduction of measuring techniques for the quantification of volumetric changes, the most prominent classes of expanding monomers will be presented and discussed, namely cycloalkanes and cycloalkenes, oxacycles, benzoxazines, as well as thiocyclic compounds. Spiroorthoesters, spiroorthocarbonates, cyclic carbonates, and benzoxazines are particularly highlighted.

Dielectric Properties of Shrinkage-Free Poly(2-Oxazoline) Networks from Renewable Resources.

In the course of this study, the dielectric and physicochemical properties of poly(2-oxazoline) (POx) networks from renewable resources were compared with those of fossil-based polyamide 12 (PA 12) networks. POx was synthesized by the energy-efficient, microwave-assisted copolymerization of 2-oxazoline monomers, which were derived from fatty acids of coconut and castor oil. For the preparation of composites, aluminum nitride nanoparticles n-AlN and microparticles µ-AlN as well as hexagonal boron nitride BN submicroparticles were used. Additionally, 0, 15, or 30 wt.% of a spiroorthoester (SOE) were added as an expanding monomer aiming to reduce the formation of shrinkage-related defects. For the crosslinking of the polymers and the SOE as well as the double ring-opening reaction of the SOE, a thermally triggered dual-cure system was developed. The fully-cured blends and composites containing SOEs exhibited lower densities than their fully-cured SOE-free analogues, which was indicative of a lower extent of shrinkage (or even volumetric expansion) during the curing reaction, which is referred to as relative expansion RE. The RE amounted to values in the range of 0.46 to 2.48 for PA 12-based samples and 1.39 to 7.50 vol.% for POx-based samples. At 40 Hz, the "green" POx networks show low loss factors, which are competitive to those of the fossil-based PA 12.

An in vitro comparison of flow dynamics of the Magna Ease and the Trifecta prostheses.

Objectives: We aimed to compare the in vitro flow dynamics of the Perimount Magna Ease™ (PME) and the Trifecta™ (TF) bioprostheses.Material and methods: A new flow chamber was designed to compare the flow patterns of the PME (Edwards Lifesciences, Irvine, CA, USA) and the TF (SJM, St. Paul, MN, USA) aortic valve prostheses. This new channel offered the possibility of 2D-particle-image-velocimetry (2D-PIV) to completely evaluate the flow field downstream from the aortic valve to the middle of the aortic arch. Maximum average velocities, vorticity, shear strength, maximum orifice diameters and jet flow diameters were analyzed. Valve sizes of 21, 23 and 25 mm were evaluated.Results: Average velocity values, shear strength and vorticities were smaller in the flow field of the TF (maximum average velocity: 0.81 ± 0.03m/s, PME 23 mm vs. 0.7 ± 0.02m/s TF 23 mm, P < .001) under pulsatile flow conditions (70 Hz, 70 mL stroke volume). The evaluation of the upper orifice area revealed bigger maximum diameters during the peak flow phase for the TF, but more leaflet-flutter.Conclusions: Our flow chamber allowed a precise and highly sensitive characterization and comparison of complex fluid dynamics of different aortic valve prostheses. Both the Trifecta™ and the Perimount Magna Ease™ showed a good performance on a high level.

A wearable EIT system for detection of muscular activity in the extremities.

Electrical Impedance Tomography (EIT) is a method for measuring physiological states and processes that can be used as an imaging method for muscular activities. In addition to the medical evaluation of the EIT data of the lung, this technology can be used to make a statement about muscular activity in the extremities. This paper presents a developed, mobile EIT system that can be used with an electrode bracelet on the arm. In a rst study, the EIT data for different hand gestures were evaluated.

Transit time flow measurement and high frequency ultrasound epicardial imaging to guide coronary artery bypass surgery.

BACKGROUND: Transit-time flow measurement (TTFM) should be routinely used in CABG surgery to verify graft function. Most recently, a 2D high-frequency-ultrasound (HF-US) epicardial imaging probe has been released (MiraQ™, Medistim, Oslo, Norway), which allows to evaluate the cannulation/clamping site of the aorta morphologically and to evaluate the completed anastomosis. We aimed to evaluate the use of TTFM and HF-US on surgical strategy during CABG surgery. METHODS: A total of 65 consecutive patients undergoing CABG surgery were evaluated. The target vessels, the clamping/cannulation site and the anastomosis were evaluated by HF-US. TTFM was performed on all grafts and the mean flow (mL/min) and pulsatility indices (PI) were recorded. Troponin-I levels (ng/L) were obtained within the first 4 postoperative days. RESULTS: A total of 3.3±0.9 grafts were performed, with 98.5% LIMA use and a sequential graft was performed in 55.4%. The mean PI and flow (mL/min) were 2.3±2.7 and 70.8±50.6 for the right coronary artery system, 2.4±2.2 and 82.0±47.6 for the circumflex system, and 2.1±1.2 and 78.0±35.0 for the LAD system, respectively. Postoperative troponin-I levels showed a maximum on postoperative day 1. A surgical strategy change, based on imaging, was done in 15%. Moreover, we observed a correlation of PI and flow with maximum postoperative troponin-I levels. CONCLUSIONS: The present study evaluated the combination of TTFM and HF-US in CABG surgery. Epicardial scanning was helpful to evaluate the potential opening site of the vessel, to evaluate the completed anastomosis or to evaluate the clamping or cannulation site. Troponin-I levels were directly correlated to mean graft flow and PI levels.

Infections after transcatheter versus surgical aortic valve replacement: mid-term results of 200 consecutive patients.

BACKGROUND: Transcatheter aortic valve implantation (TAVI) is the standard therapy for high-risk patients with aortic stenosis (AS). TAVI-outcomes are widely investigated in comparison to surgical aortic valve replacement (SAVR), but less is known about infectious complications after TAVI. We aimed to compare early and mid-term infectious outcomes of patients undergoing TAVI or SAVR. METHODS: The present study is a prospective single-centre study including 200 consecutive patients between 06/2014-03/2015 undergoing TAVI (either transfemoral or transapical and transaortic, n=47+53=100) or SAVR (either isolated or concomitant with CABG, n=52+48=100). The mean age and log. EuroSCORE were significantly different between both groups (81±6 versus 69±11 years, P<0.001 and 23.1%±13.8% versus 8.7%±9.5%, P<0.001). Primary endpoints included wound healing disorders, respiratory and urinary tract infections and incidence of endocarditis or sepsis within hospital stay. Secondary endpoints included infectious parameters, infectious related rehospitalisation and 2-year mortality. RESULTS: Primary endpoints showed no difference in overall TAVI- versus SAVR-groups regarding respiratory- (14% versus 19%, P=0.45), urinary-tract (7% versus 4%, P=0.54) infections, sepsis (5% versus 6%, P=1.0), endocarditis (0% versus 1%, P=1.0) or 30-day mortality (10% versus 4%, P=0.09), except for wound disorders, which were significantly lower in the TAVI-group (1% versus 8%, P=0.035), respectively. Secondary endpoints reported no difference regarding infectious related rehospitalisation (4% versus 4%, P=1.0), but significantly higher 2-year mortality (28% versus 16%, P=0.048) in the TAVI-group. CONCLUSIONS: So far, little has been studied about infectious complications after TAVI. This study reports no difference between the overall TAVI and SAVR groups regarding infectious complications. However, SAVR group show more wound healing disorders but less mortality than TAVI group.

The Fluid Dynamical Performance of the Carpentier-Edwards PERIMOUNT Magna Ease Prosthesis.

The aim of the present in vitro study was the evaluation of the fluid dynamical performance of the Carpentier-Edwards PERIMOUNT Magna Ease depending on the prosthetic size (21, 23, and 25 mm) and the cardiac output (3.6-6.4 L/min). A self-constructed flow channel in combination with particle image velocimetry (PIV) enabled precise results with high reproducibility, focus on maximal and local peek velocities, strain, and velocity gradients. These flow parameters allow insights into the generation of forces that act on blood cells and the aortic wall. The results showed that the 21 and 23 mm valves have a quite similar performance. Maximal velocities were 3.03 ± 0.1 and 2.87 ± 0.13 m/s; maximal strain Exx , 913.81 ± 173.25 and 896.15 ± 88.16 1/s; maximal velocity gradient Eyx , 1203.14 ± 221.84 1/s and 1200.81 ± 61.83 1/s. The 25 mm size revealed significantly lower values: maximal velocity, 2.47 ± 0.15 m/s; maximal strain Exx , 592.98 ± 155.80 1/s; maximal velocity gradient Eyx , 823.71 ± 38.64 1/s. In summary, the 25 mm Magna Ease was able to create a wider, more homogenous flow with lower peak velocities especially for higher flow rates. Despite the wider flow, the velocity values close to the aortic walls did not exceed the level of the smaller valves.

Enhancement of the Insulation Properties of Poly(2-oxazoline)-co-Polyester Networks by the Addition of Nanofillers.

Copoly(2-nonyl-2-oxazoline)-stat-poly(2-dec-9'enyl-2-oxazoline)s can be crosslinked by the thiol-ene reaction with glycol dimercaptoacetate. The copoly(2-oxazoline)-stat-copolyester is tested as dielectric for high-voltage applications, either as unfilled resin or as composite with nanoscaled fillers of silica, alumina, and hexagonal boron nitride. During AC voltage tests, all materials have an average breakdown strength of 45-50 kV mm-1 . For DC voltage tests, samples with SiO2 (hBN) have an average breakdown strength of ≈100 (80) kV mm-1 , while the unfilled copoly(2-oxazoline) has an average breakdown strength of ≈60 kV mm-1 . Permittivity measurements at 20 °C and 50 Hz reveal that all nanocomposites are dielectrics (D = 0.06-0.08), while the unfilled copoly(2-oxazoline)s has a high loss factor of D = 8.43. This phenomenon can be retraced to the phase separation in the crosslinked copolymer, the M-OH functionality of silica and alumina particles, and models of polymer-particle interactions such as the Tanaka model, revealing that the nanofillers reduce the interfacial and dipolar polarizability.

Heat Dissipation in Epoxy/Amine-Based Gradient Composites with Alumina Particles: A Critical Evaluation of Thermal Conductivity Measurements.

For the design of the next generation of microelectronic packages, thermal management is one of the key aspects and must be met by the development of polymers with enhanced thermal conductivity. While all polymer classes show a very low thermal conductivity, this shortcoming can be compensated for by the addition of fillers, yielding polymer-based composite materials with high thermal conductivity. The inorganic fillers, however, are often available only in submicron- and micron-scaled dimensions and, consequently, can sediment during the curing reaction of the polymer matrix. In this study, an epoxy/amine resin was filled with nano- and submicron-scaled alumina particles, yielding a gradient composite. It was found that the thermal conductivity according to laser flash analysis of a sliced specimen ranged from 0.25 to 0.45 W·m-1·K-1 at room temperature. If the thermal conductivity of an uncut specimen was measured with a guarded heat flow meter, the 'averaged' thermal conductivity was measured to be only 0.25 W·m-1·K-1. Finite element analysis revealed that the heat dissipation through a gradient composite was of intermediate speed in comparison with homogeneous composites exhibiting a non-gradient thermal conductivity of 0.25 and 0.45 W·m-1·K-1.

Impact of Liver Indicators on Clinical Outcome in Patients Undergoing Transcatheter Aortic Valve Implantation.

BACKGROUND: Liver dysfunction increases death and morbidity after cardiac operations. There are currently no data evaluating liver function in patients undergoing transcatheter aortic valve replacement (TAVR). We aimed therefore to evaluate our TAVR results in regard to liver function. METHODS: A total of 640 consecutive TAVR patients were evaluated. Of those, 11 patients presented with chronic liver disease before TAVR. The Model for End-Stage Liver Disease score was used to measure liver function in these patients. The primary study end point was 30-day mortality in patients presenting with liver dysfunction. Secondary study end point was liver enzymes after TAVR. RESULTS: The mean Model for End-Stage Liver Disease score in patients with chronic liver disease was 16.8 ± 6.2 (median, 18; range, 7 to 26). The 30-day mortality was 9.1% (57 of 629) in patients presenting without liver disease and 9.1% (1 of 11) in patients with liver disease (p = 1.00). Patients with chronic liver disease showed significantly higher preoperative levels of γ-glutamyl transpeptidase (p < 0.001). After TAVR, we observed a significant increase in alanine aminotransferase on postoperative day 3 compared with preoperative values (p < 0.001), accompanied by a decrease in albumin (p < 0.001). CONCLUSIONS: Liver cirrhosis per se is not considered as a contraindication for cardiac operations. In the present study, we did not observe a higher 30-day mortality rate in liver cirrhotic patients undergoing TAVR, suggesting TAVR as a feasible alternative with acceptable outcomes in patients with chronic liver disease. Moreover, the present study is the first to evaluate liver variables in patients undergoing TAVR.

Effect of Interfacial Polarization and Water Absorption on the Dielectric Properties of Epoxy-Nanocomposites.

Five types of nanofillers, namely, silica, surface-silylated silica, alumina, surface-silylated alumina, and boron nitride, were tested in this study. Nanocomposites composed of an epoxy/amine resin and one of the five types of nanoparticles were tested as dielectrics with a focus on (i) the surface functionalization of the nanoparticles and (ii) the water absorption by the materials. The dispersability of the nanoparticles in the resin correlated with the composition (OH content) of their surfaces. The interfacial polarization of the thoroughly dried samples was found to increase at lowered frequencies and increased temperatures. The ß relaxation, unlike the interfacial polarization, was not significantly increased at elevated temperatures (below the glass-transition temperature). Upon the absorption of water under ambient conditions, the interfacial polarization increased significantly, and the insulating properties decreased or even deteriorated. This effect was most pronounced in the nanocomposite containing silica, and occurred as well in the nanocomposites containing silylated silica or non-functionalized alumina. The alternating current (AC) breakdown strength of all specimens was in the range of 30 to 35 kV·mm-1. In direct current (DC) breakdown tests, the epoxy resin exhibited the lowest strength of 110 kV·mm-1; the nanocomposite containing surface-silylated alumina had a strength of 170 kV·mm-1. In summary, water absorption had the most relevant impact on the dielectric properties of nanocomposites containing nanoparticles, the surfaces of which interacted with the water molecules. Nanocomposites containing silylated alumina particles or boron nitride showed the best dielectric properties in this study.

Radical-Induced Hydrosilylation Reactions for the Functionalization of Two-Dimensional Hydride Terminated Silicon Nanosheets.

Herein we present the functionalization of freestanding silicon nanosheets (SiNSs) by radical-induced hydrosilylation reactions. An efficient hydrosilylation of Si-H terminated SiNSs can be achieved by thermal initiation or the addition of diazonium salts with a variety of alkene or alkyne derivatives. The radical-induced hydrosilylation is applicable for a wide variety of substrates with different functionalities, improving the stability and dispersibility of the functional SiNSs in organic solvents and potentially opening up new fields of application for these hybrid materials.

The investigation of systolic and diastolic leaflet kinematics of bioprostheses with a new in-vitro test method.

OBJECTIVES: We aimed to investigate leaflet kinematics of bioprostheses with a novel high-speed imaging method. MATERIAL AND METHODS: High-speed-imaging (1000 Hz) was used to evaluate leaflet kinematics of the Carpentier-Edwards Perimount Magna (PM) and Magna Ease (PME) aortic bioprostheses. Both prostheses (diameter 23 mm) were placed inside a model aorta under pulsatile flow conditions. Frequencies (F) and different stroke volumes (S) were simulated. Maximum aortic valve area (AVA), total ejection time (TET), rapid valve opening time (RVOT) and rapid valve closing time (RVCT) as well as opening (OS) and closing (CS) speeds were evaluated. RESULTS: Both bioprostheses showed different results dependent on flow conditions. The test setup was capable of identifying small AVA-differences between both valves (235 vs. 202 mm², F60/S60; 272 vs. 207 mm²; F70/S80), as well as differences in OS and CS (2.36 vs. 1.62 mm²/ms; 2.97 vs. 2.44 mm²/ms, F80/S60). TET was comparable (638 vs. 645 ms F60/S60; 341 vs. 343 ms, F90/S60), while results for RVOT and RVCT were equal, and dependent on frequency and stroke volume. CONCLUSIONS: The novel evaluation method is sensitive to detect differences between valves, although differences were found to be small. PM has a larger visible AVA associated with higher opening and closing speeds in contrast to PME.