Analysis of New Nitinol Ingot Qualities

New ingot qualities, processed by optimized vacuum arc remelting (VAR), optimized vacuum induction melting followed by VAR and VAR followed by electron beam remelting, were compared with standard quality. Finished components as well as diamond-shaped samples representing a typical dimension of self-expanding stents were produced using Nitinol tubing drawn from the new ingot qualities. Metallographic longitudinal sections were prepared and analyzed to determine inclusion size and distributions of the various ingot qualities. Radial force and uniaxial tensile tests were used to determine the mechanical properties of fully processed material and tubing, respectively. Transformation temperatures of tubing as delivered from supplier and processed stents were measured by differential scanning calorimetry and deformation-and-free-recovery testing. Finally, fatigue tests were performed on diamond-shaped samples to evaluate the strain-life characteristics of the new ingot qualities. Results of this study are compared to ADMEDES historical data from standard Nitinol materials to gain an assessment of the new improved ingot qualities with regard to the production of Nitinol vascular implants. The latest developments in Nitinol ingot quality are highlighted and the results of the comparison from technical point of view are shown.     

Frequency and phase estimation in time series with quasi periodic components

In this article, we consider frequency and phase estimation in a noisy oscillation with potentially non‐constant phase increments resulting from an underlying non‐constant frequency. A maximum periodogram method on segments is used to estimate the time‐varying frequency and a subsequent least squares approach to estimate the phase. A key problem addressed in this article is the question how to set up a meaningful concept of asymptotic statistics for this model. This problem is solved by a special infill asymptotics concept. We use this concept to prove consistency and asymptotic normality of the estimates. Furthermore, the phase estimate is compared to the Hilbert transform in a simulation.     

Is Upregulation of Aquaporin 4-M1 Isoform Responsible for the Loss of Typical Orthogonal Arrays of Particles in Astrocytomas?

The astrocytic endfoot membranes of the healthy blood-brain barrier—contacting the capillary—are covered with a large number of the water channel aquaporin 4 (AQP4). They form orthogonal arrays of particles (OAPs), which consist of AQP4 isoform M1 and M23. Under pathologic conditions, AQP4 is distributed over the whole cell and no or only small OAPs are found. From cell culture experiments, it is known that cells transfected only with AQP4-M1 do not form OAPs or only small ones. We hypothesized that in astrocytomas the situation may be comparable to the in vitro experiments expecting an upregulation of AQP4-M1. Quantitative Real-time PCR (qRT-PCR) of different graded astrocytomas revealed an upregulation of both isoforms AQP4 M1 and M23 in all astrocytomas investigated. In freeze fracture replicas of low-grade malignancy astrocytomas, more OAPs than in high-grade malignancy astrocytomas were found. In vitro, cultured glioma cells did not express AQP4, whereas healthy astrocytes revealed a slight upregulation of both isoforms and only a few OAPs in freeze fracture analysis. Taken together, we found a correlation between the decrease of OAPs and increasing grade of malignancy of astrocytomas but this was not consistent with an upregulation of AQP4-M1 in relation to AQP4 M23.     

AI and robotics in the European restaurant sector: Assessing potentials for process innovation in a high-contact service industry

Electronic Markets - The restaurant technology market is rapidly evolving and is transforming the restaurant business as a significant sector of tourism and hospitality. Enabled by artificial...     

From competitive advantage to social welfare

Electronic Markets -     

Development and operation of Digital Twins for technical systems and services

Digital Twins are new solution elements to enable ongoing digital monitoring and active functional improvement of interconnected products, devices and machines. In addition, benefits of horizontal and vertical integration in manufacturing are targeted by the introduction of Digital Twins. Using the test environment of smart factory cells, this paper investigates methodological, technological, operative, and business aspects of developing and operating Digital Twins. The following Digital Twin dimensions are considered in scientific and application oriented analysis: (1) integration breadth, (2) connectivity modes, (3) update frequency, (4) CPS intelligence, (5) simulation capabilities, (6) digital model richness, (7) human interaction, and (8) product lifecycle. From this, design elements for the development of Digital Twins are derived and presented.