Sutureless/rapid-deployment (SRD) valves for aortic valve replacement (AVR) are new surgical bioprosthetic valves that allow for expedited implantation and facilitate minimally invasive approaches. ...Although clinical trial data are available for SRDs in the United States, how their clinical outcomes compare with traditional stented bioprosthetic (SBP) valves is unknown in a post-approval, commercial setting.
The Society of Thoracic Surgery Adult Cardiac Surgery Database was queried for patients who underwent an AVR. Transcatheter AVR cases were excluded. Thirty-day outcomes were compared between SRD valves (Perceval S LivaNova, Houston, TX and Intuity Elite Edwards Lifesciences, Irvine CA) and SBP valve patients. The SRD and SBP patients were propensity score–matched in a 1:(up to) 3 ratio. Primary outcome was 30-day mortality and secondary outcomes were major comorbidities, paravalvular regurgitation, and predischarge pacemaker implant.
Propensity score matching resulted in 4486 SRD patients and 13,215 SBP patients. The SRD recipients had more permanent pacemakers (11.4% vs 4.9%, P < .001) shorter cross-clamp times (median: 68 vs 86 minutes, P < .001), and fewer full sternotomies (75% vs 77% , P < .024) than SBP but similar 30-day mortality (3.1% vs 3.1%, P = .98) and moderate or greater paravalvular regurgitation (0.2% vs 0.1%, P = .21).
SRD implantation was associated with reduced operative times and smaller incisions. Rates of 30-day mortality, major comorbidities, and perivalvular regurgitation were similar between SRD and SBP patients. Longer follow-up is needed to determine the implications of increased permanent pacemaker implantation rates in SRD patients.
Abstract
As electrification in the automotive industry progresses, the demand is rising for test particles with specific properties. More and more new applications are also being developed, such as ...processes for validating cleaning steps, contamination tracking or determining cleanliness limits. This article describes how test particles can be reproducibly manufactured in all three dimensions by micro milling. In addition, it explains how the dimensional accuracy of these free-form surfaces can be analyzed with computer tomography.
In this study, it was tried to develop a process chain for ceramic injection molding of Al2O3-chopped-fiber reinforced oxide-ceramic-matrix-composite. The feedstocks are compounded at 50 Vol. % ...filling degree of solid (Al2O3 μ-powder (Taimei Chemicals Co. Ltd.) and 3,2 mm chopped fibers (3M)), in which fiber content varies from 0 Vol. % to 100 Vol. %. As binder system, PE + Paraffin Wax + Stearic Acid are used. The ingredients are compounded in a kneader (Brabender) at 125°C and after the viscosity measurement in the high pressure capillary rheometer at 160°C and certain shear rates, the feedstock is injection molded (Battenfeld) at 160°C, which is followed by debinding process, including chemical (in n-Hexane) and thermal steps, and 2h sintering at different temperatures. Flow paths in the machinery parts, rheological properties of binding system, fiber content and the fiber orientation have significant effect on the flow behavior of the feedstock, fiber -orientation, -distribution & -length, which are crucial to understand the properties of end-parts like mechanical reinforcement of the fibers. The fibers in the sintered parts are ca. 200 μm in average length. The fibers in the feedstock show different orientations depending on the part-geometry and the green bodies have different densities depending on sintering temperature, amount of dispersant and fiber orientation.
Industrial use of micro components is determined by the availability of efficient manufacturing techniques. While micro injection moulding of plastic is common practice, metal and ceramic powder ...injection moulding (PIM) still is under development. High-pressure and low-pressure injection moulding methods complement each other ideally, covering the entire spectrum from prototype to large-scale production. With high-pressure PIM, micro gear wheels with diameters <300 μm can be fabricated using LIGA mould inserts. Densities between 97 and 99% of the theoretical values are achieved. Apart from oxide ceramics, metal materials like copper or powder metallurgical steels like 17-4PH or 316L are often applied. Multi-component injection moulding requires less mounting steps and, hence, offers decisive advantages for effective production of interesting material combinations like electrically conductive/insulating or hard/ductile. Studies relating to the fabrication of immobile as well as mobile shaft-wheel components were performed. Other activities focussed on in-mould labelling with foils containing ultra-fine particles to improve surface quality and detail accuracy. Low-pressure injection moulding allows for the manufacture of small series within 1–4 weeks at low cost. However, the process has features which are not compatible with high-pressure PIM. Although use of a low-viscous feedstock is associated with various benefits, low-pressure injection moulding has not met with acceptance in micro moulding.
We describe a multi-purpose platform for the three-dimensional cultivation of tissues. The device is composed of polymer chips featuring a microstructured area of 1-2 cm(2). The chip is constructed ...either as a grid of micro-containers measuring 120-300 x 300 x 300 microm (h x l x w), or as an array of round recesses (300 microm diameter, 300 microm deep). The micro-containers may be separately equipped with addressable 3D-micro-electrodes, which allow for electrical stimulation of excitable cells and on-site measurements of electrochemically accessible parameters. The system is applicable for the cultivation of high cell densities of up to 8 x 10(6) cells and, because of the rectangular grid layout, allows the automated microscopical analysis of cultivated cells. More than 1000 micro-containers enable the parallel analysis of different parameters under superfusion/perfusion conditions. Using different polymer chips in combination with various types of bioreactors we demonstrated the principal suitability of the chip-based bioreactor for tissue culture applications. Primary and established cell lines have been successfully cultivated and analysed for functional properties. When cells were cultured in non-perfused chips, over time a considerable degree of apoptosis could be observed indicating the need for an active perfusion. The system presented here has also been applied for the differentiation analysis of pluripotent embryonic stem cells and may be suitable for the analysis of the stem cell niche.
Sutureless/rapid-deployment (SRD) valves for aortic valve replacement (AVR) are new surgical bioprosthetic valves that allow for expedited implantation and facilitate minimally invasive approaches. ...Although clinical trial data are available for SRDs in the United States, how their clinical outcomes compare with traditional stented bioprosthetic (SBP) valves is unknown in a post-approval, commercial setting.
The Society of Thoracic Surgery Adult Cardiac Surgery Database was queried for patients who underwent an AVR. Transcatheter AVR cases were excluded. Thirty-day outcomes were compared between SRD valves (Perceval S LivaNova, Houston, TX and Intuity Elite Edwards Lifesciences, Irvine CA) and SBP valve patients. The SRD and SBP patients were propensity score-matched in a 1:(up to) 3 ratio. Primary outcome was 30-day mortality and secondary outcomes were major comorbidities, paravalvular regurgitation, and predischarge pacemaker implant.
Propensity score matching resulted in 4486 SRD patients and 13,215 SBP patients. The SRD recipients had more permanent pacemakers (11.4% vs 4.9%, P < .001) shorter cross-clamp times (median: 68 vs 86 minutes, P < .001), and fewer full sternotomies (75% vs 77% , P < .024) than SBP but similar 30-day mortality (3.1% vs 3.1%, P = .98) and moderate or greater paravalvular regurgitation (0.2% vs 0.1%, P = .21).
SRD implantation was associated with reduced operative times and smaller incisions. Rates of 30-day mortality, major comorbidities, and perivalvular regurgitation were similar between SRD and SBP patients. Longer follow-up is needed to determine the implications of increased permanent pacemaker implantation rates in SRD patients.
Replication processes offer a number of considerable advantages for the production of micro components. This is not limited to the high economic efficiency achieved by numerous multiplications of ...master structures. Furthermore, micro devices can be produced of nearly every kind of material by one or a sequence of replication steps. In this contribution, five important processes of micro replication will be described, reflecting the wide variety from rapid prototyping over small and medium series to mass production. For future development, three main trends can be observed: the steady further miniaturization of shaping capability, the efforts to increase economic efficiency mainly by reducing cycle times and enlarging work areas, and the different approaches to combine shaping and joining procedures thus obtaining a minimum of process steps.
In this paper, a new LIGA related process chain, named MSG process German acronym for multicomponent injection molding (MS) and electroplating (G) is presented as a promising production cycle for the ...replication of micro-testing samples. Structures manufactured by the LIGA process but also e.g. micro-milled structures can be reproduced. The focus of this work was two fold: First, the accuracy of different replicated structures was investigated, and second, the influence of the surface quality on mechanical performance of electrodeposited nanocrystalline materials was tested. Therefore, micro samples were manufactured by the use of different methods resulting in a variation of the measured surface quality. The surface of LIGA and micro-milled samples can be accurately replicated using this process. Furthermore, it can be shown which dimensional variations within the process occur and how this is influenced by the surface of the original structure. Finally, preliminary mechanical tests are presented which show the successful application of the MSG process.
Spacing patterns of adult Proechimys semispinosus (Central American spiny rat) within five island populations in central Panamá were determined by live‐trapping over a one‐year period. Home ranges ...were described by minimum convex polygons for each individual that had a sufficient number of captures to allow accurate description. Home‐range size was calculated as the area of an individual's polygon. The total area of overlap of each individual's home range with every other consexual's home range was also calculated. Mean home‐range size and overlap were compared among islands and between sexes with two‐way analysis of variance and were related to mean density of adult males and females and island size with linear regression analysis. Home‐range size and overlap were also compared while controlling for density using analysis of covariance.
Home‐range size varied between the sexes but not among islands, with males generally having larger home ranges than females. Home‐range size showed a negative relationship to density, and the difference in home‐range size between the sexes prevailed even after controlling for density. Home‐range overlap varied among islands but not between the sexes. There was no linear relationship between overlap and density, although individuals within two low‐density populations had nearly exclusive home ranges. The high degree of overlap among home ranges within some populations suggests that P. semispinosus do not maintain large exclusive territories. Such territories may be economically indefensible because of the spatial and temporal distribution of resources (i.e. primarily falling fruit). Although theory predicts that spatially patchy and poorly renewable resources promote territoriality, resources in tropical forests of the study area may be randomly or too patchily distributed or ephemeral to permit maintenance of territories that span a large portion of an animal's home range. More detailed study is necessary to reveal finer‐scale patterns of territoriality (e.g. defence of burrows or concentrations of fallen fruit).
Increasing demand for ever-smaller devices presents challenges for materials science. German researchers are looking at the possibilities of micro powder injection moulding, and how to match the ...process to the needs of large-scale industrial production…
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