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OBJECTIVES Our goal was to evaluate whether four-dimensional (4D) flow magnetic resonance imaging (MRI) can predict the growth rate of dilatation of the ascending aorta (AA) in patients with a tricuspid, normally functioning aortic valve. METHODS In this prospective clinical study, aortic 4D flow MRI was performed at the Kuopio University Hospital on 30 patients diagnosed with AA dilatation (maximum diameter >40 mm) between August 2017 and July 2020. The MRI was repeated after a 1-year follow-up, with AA dimensions and 4D flow parameters analysed retrospectively at both time points. The standard error of measurement was used to assess the statistical significance of the growth rate of AA dilatation. Flow displacement (FD) was transformed to a class-scaled parameter using FD ≥5% as a threshold. RESULTS Statistically significant growth [median 2.1 mm (1.5–2.2 mm); P = 0.03] was detected in 6 male patients (20%); the AA diameter remained unchanged [0.2 mm (−0.3 to 0.9 mm)] in 24 patients (80%). An increased FD at the baseline was associated with significant growth during the 1-year follow-up in the proximal AA. An association was detected between decreased total wall shear stress and significant aortic growth in the inner curve of the sinotubular junction [529 mPa (449–664 mPa) vs 775 mPa (609–944 mPa); P = 0.03] and the anterior side of the proximal aortic arch [356 mPa (305–367 mPa) vs 493 mPa (390–586 mPa); P CONCLUSIONS FD and decreased wall shear stress seem to be associated with significant growth of AA dilatation at the 1-year follow-up. Thus, 4D flow MRI might be useful in assessing risk for AA diameter growth in patients with a tricuspid aortic valve.

To explore the risk factors, growth rate and outcomes of ascending aortic (AA) dilatation in patients scheduled for imaging follow-up.This retrospective study included 143 patients who were followed-up with thoracic aortic CT-angiography. AA diameters were measured from aortic root (sinus Valsalva) and mid-AA at the baseline and after long-term follow-up. Risk factors and clinical outcomes were collected from medical records. The standard error of measurement (SEM) method was used to assess the statistical significance of the growth rate of AA dilatation.The patients' mean age was 64.0 ± 10.0 years (males n = 115, 80.4%). The mean imaging follow-up time was 3.4 ± 1.6 years and 5.7 ± 1.7 years in the clinical follow-up. According to the SEM method, 37.8% of the patients (n = 54) experienced significant AA growth; 18.9% (n = 27) in the aortic root (0.5 ± 0.7 mm/year), and 24.5% (n = 35) in the mid-AA (0.4 ± 0.5 mm/year). None of the patients experienced aortic rupture or dissection or died due to aortic reasons during the follow-up. Eighteen patients (12.6%) underwent elective surgical AA reconstruction and 10 patients (7.0%) died due to some other reason. Male gender was the only factor to associate with significant accelerated growth (p = 0.047). However, antihypertensive medication did seem to be a protective factor (p = 0.01).Less than half of the patients followed due to AA dilatation displayed significant AA growth during the long-term follow-up. In addition, the growth rate per year was small. None of the patients experienced any aortic catastrophes indicating that the prognosis of patients participating in regular imaging follow-up is good.

Background The heart’s position determined as the heart–aorta angle (HAA) has been demonstrated to associate with ascending aortic (AA) dilatation. Visceral adipose tissue (VAT) and aortic elongation may shift the heart to the steeper position. Purpose To investigate whether VAT and aortic length influence the HAA. Material and Methods We examined 346 consecutive patients (58.4% men; mean age = 67.0 ± 14.1 years) who underwent aortic computed tomography angiography (CTA). HAA was measured as the angle between the long axis of the heart and AA midline. The amount of VAT was measured at the level of middle L4 vertebra from a single axial CT slice. Aortic length was measured by combining four anatomical segments in different CTA images. The amount of VAT and aortic length were determined as mild with values in the lowest quartile and as excessive with values in the other three quartiles. Results A total of 191 patients (55.2%) had no history of aortic diseases, 134 (38.7%) displayed AA dilatation, 8 (2.3%) had abdominal aortic aneurysm (AAA), and 13 (3.8%) had both AA dilatation and AAA. There was a strong nonlinear regression between smaller HAA and VAT/height, and HAA and aortic length/height. Median HAA was 124.2° (interquartile range 119.0°–130.8°) in patients with a mild amount of VAT versus 120.5° (interquartile range 115.4°–124.7°) in patients with excessive VAT ( P Conclusion An excessive amount of VAT and aortic elongation led to a steeper heart position. These aspects may possess clinical value when evaluating aortic diseases in obese patients.

The addition of zinc oxide (ZnO) to sulfur (S-) vulcanized rubbers is known to accelerate the cross-linking kinetics and to increase the heterogeneity of the cross-link density. However, the spatial distribution of cross-links is hardly known and the mechanism of the activity of ZnO is disputed. We therefore investigated S-vulcanized butadiene-styrene rubber comprising ZnO particles. The samples were fractured and then investigated employing the nano-mechanical mapping mode (NM) of scanning force microscopy (SFM), supported by scanning electron microscopy (SEM). We find that rubber around the ZnO particles exhibits a higher Young's modulus in a shell with a width up to about 200 nm. Furthermore, the extension and retraction curves on these shells exhibit a smaller hysteresis than on the rubber further away from the ZnO particles. We attribute the higher Young's modulus and the smaller hysteresis to a higher cross-link density in rubber surrounding the ZnO particles and we discuss a mechanism of the activity of ZnO in rubbers which can explain this.

Macro-scale surface patterns are often used with tool and working surfaces to improve gripping, sliding or other working abilities. Polyacetal (POM) samples possessing micron-scale surface structures were examined to determine effects of micro-scale patterning on the sliding friction and wear rate of POM surfaces. The micro-patterned samples were manufactured via injection molding and their friction/wear behaviors were compared to those of identically micro-patterned polypropylene (PP) surfaces. Polymer surfaces were slid against polished steel using a reciprocating pin-on-disk type measuring system. The wear and friction properties of the patterned polymers were studied as functions of surface pressure, induced by loads and pattern densities applied. For both materials, the wear rate was found to diminish with increasing surface pressure and the wear mechanism to resemble extrusion, producing flake-like particles. Dynamic friction levels were found to correlate with surface pressure, the micro-pattern having a distinct effect on friction with low loads. Both POM and PP were found to possess a friction minimum in the surface pressure range of 0.5–1.0 MPa, which is attainable by adjusting either the used load or the density of micro-patterns.

Polypropylene/viscose fiber (PP/VF) composite with a surface pattern consisting of periodic, micro-scale cylindrical pillars were manufactured and the effect of fiber loading and micro-patterning on the friction and wear properties of the composites was studied. The micro-patterned viscose fiber composite surfaces were prepared via melt compounding and injection molding. SEM studies showed that the fiber dispersion within the micro-bumps was influenced by the fiber loading and high aspect ratio (300–1200) of viscose fibers. With higher fiber loadings the fiber content of the micro-bumps was prominently higher than with lower fiber loadings of the composites. The wear and friction behavior of the patterned composite series were evaluated by sliding the fabricated surfaces against rough and smooth steel surfaces with a pin-on-disc type tribometer. It was noted especially in the case of a smooth counter surface that while both high fiber content and sparse micro-bump coverage individually decreased the sliding friction, their synergetic effect produced a dramatic drop in friction coefficient.

Considerable attention is currently being devoted less to the question of whether it is possible to produce superhydrophobic polymer surfaces than to just how robust they can be made. The present study demonstrates a new route for improving the mechanical durability of water-repellent structured surfaces. The key idea is the protection of fragile fine-scale surface topographies against wear by larger scale sacrificial micropillars. A variety of surface patterns was manufactured on polypropylene using a microstructuring technique and injection molding. The surfaces subjected to mechanical pressure and abrasive wear were characterized by water contact and sliding angle measurements as well as by scanning electron microscopy and roughness analysis based on optical profilometry. The superhydrophobic polypropylene surfaces with protective structures were found to maintain their wetting properties in mechanical compression up to 20 MPa and in abrasive wear tests up to 120 kPa. For durable properties, the optimal surface density of the protective pillars was found to be about 15%. The present approach to the production of water-repellent polymer surfaces provides the advantages of mass production and mechanical robustness with practical applications of structurally functionalized surfaces.

The influence of well-defined periodic micro-scale pillars on the friction and wear behavior of polypropylene (PP) surfaces was examined in dry sliding against roughened steel surfaces. The steel surfaces were linearly ground, allowing monitoring of the difference in friction when samples passed over the grooves and ridges of the steel surface in perpendicular and parallel directions. Micro-scale patterns with different surface coverage (SC) on the PP surface were produced by preparation of micro-depressions on aluminum foil and subsequent use of the foils as mold inserts in injection molding. The effects of the patterning on friction and wear of the PP surface were evaluated as a function of surface coverage of the micro-pillar features. The friction behavior in sliding of the patterned PP against steel surfaces was affected by the micro patterns. The coefficient of friction (COF) was slightly lower for the less densely patterned surfaces than the unpatterned PP. The COF increased with further SC. Patterning reduced the noise of the COF curves of the micro-patterned surfaces. Wear of the PP surface was strongly affected by the percentage of surface covered by the micro bumps. Scanning electron microscopy studies of the contact surfaces revealed that the transfer layer between PP and the steel surface evolved at different rates for perpendicular and parallel passing direction.

Particle growth and fragmentation of solid Ziegler–Natta-type catalysts prepared via emulsion technique were studied in propylene polymerization. Before polymerizations the catalyst particles were activated with triethyl aluminum (TEA) and cyclohexyl methyl dimethoxy silane (CMMS). Polymerizations were carried out in gas-phase in a micro-reactor system that allows the particle growth to be observed with a microscope. Several polymerizations were done under a propylene pressure of 2 bar and with polymerization times from 20 s to 2 h. Fragmentation morphology of the catalyst particles and cross-sections of the particles after polymerization were studied by scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS). Fragmentation morphology of the catalysts prepared via emulsion technique was compared with the fragmentation morphology of a conventional MgCl2-supported Ziegler–Natta-type catalyst, which could be described by the multigrain model. Polymer growth appeared to occur throughout the emulsion-based catalyst particle right from the start of the polymerization, even though the surface area and porosity of the catalyst were low. The surface of the catalyst particles broke up at the beginning of the polymerization, and catalyst fragments appeared on the surface as plates between which the polymer was growing.