57 research outputs found

    Repeating Routines? How transfer and inheritance to corporate spin-offs varies among gestation contexts

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    In economic geography literature the attention for spin‐off entrepreneurship has been steadily growing. Its main driver is that spin-off firms are said to have intrinsic advantages over other start-ups because of their embedded link to a parent company. Through this embedded link spin-off firms have a relatively ââ¬Ëeasyââ¬â¢ access to resources for production which has several interesting implications on both the firm and the regional level. At the firm level, spin-off firms seem to outperform other entrants on at least some aspects of success including employment growth and survival chances. At the regional level, they may play a key role in the development of clusters. Despite the increasing number of studies addressing the effects of spin-off processes, important issues remain unresolved. Most importantly, there is still work to be done in identifying what it is that spin-off entrepreneurs take with them from their previous employer and how this affects their innovative behavior, business strategies and performance; and ultimately their alleged contribution to regional economic development. This has been acknowledged before: ââ¬Åââ¬Â¦ we know little about how conversion [between knowledge and technology commercialization] actually occurs, even though knowledge conversion is at the core of what spin‐offs doââ¬Â¦Ã¢â¬ (Zahra et al., 2007: 570). Based on a review of recent spin-off studies, this paper draws on key inheritance mechanisms in an attempt to develop a new conceptualization of explanations of spin-off effects. Following Koster (2006), initially a distinction will be made between direct resource transfers between parent and spin‐off (providing accommodation or guaranteed turnover) and indirect transfers (spin‐off entrepreneurs capitalizing on previously gained skills). We explore the concept of indirect transfers further in differentiating between personal skills of spin-off entrepreneurs gained while working in the parent organization on the one hand, and the inheritance of specific features of the parental organization, in particular its organizational characteristics and strategies. This closely fits in with the evolutionary economics vocabulary, especially with Nelson and Wintersââ¬â¢ (1982) famous DNA metaphor: the knowledge and routines of firms (their ââ¬ËDNAââ¬â¢) are partially inherited by their spin‐offs (Boschma et al., 2002).

    Design and Characterization of a Magnetic Loop Antenna for Partial Discharge Measurements in Gas Insulated Substations

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    © 2021 IEEE. Personal use of this material is permitted. Permissíon from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertisíng or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.[EN] A recent investigation explored a new measuring concept used in partial discharges (PD) measurements in gas insulated substations (GIS), consisting of a magnetic loop antenna. The sensor¿s frequency response was characterized up to some tens of MHz. This paper proposes an improved version of the sensor with an extended bandwidth (BW) one order of magnitude higher: a resonance, attributed to a common mode current in the mounting hole, is identified and eliminated employing ferrite beads in the feeder cables. Moreover, this publication proposes an electric circuit model that fully covers the transverse electromagnetic mode (TEM) frequency range in GIS. The electric model is compared against experimental measurements using a 1 GHz bandwidth testbench, giving accurate results. Two contributions are achieved in this research: an improved magnetic loop antenna with extended bandwidth and an accurate electric circuit model. This publication paves the way for further research on time resolution and signal postprocessing techniques for magnetic loop antennas in GIS.Mier Escurra, C.; Rodrigo Mor, A.; Vaessen, P. (2021). Design and Characterization of a Magnetic Loop Antenna for Partial Discharge Measurements in Gas Insulated Substations. IEEE Sensors Journal. 21(17):18618-18625. https://doi.org/10.1109/JSEN.2021.3089084S1861818625211

    PEA Electromagnetic Distortion Reduction by Impedance Grounding and Pulsed Voltage Electrode Configurations

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    [EN] Space charges are one of the main challenges facing the constantly increasing use of extruded high voltage direct current (HVDC) cables. The Pulsed Electro-Acoustic (PEA) method is one of the most common procedures for space charge measurements of insulation. One issue with the PEA method is distortion due to the crosstalk between the applied voltage pulse and the acoustic sensor. This work analyzed two factors involved in the reduction in this distortion: the influence of the exposed semiconductor distance between the injection electrodes and PEA test cell, and the influence of adding a reactance at the grounding circuit of the PEA test cell. The interaction of these two factors with the distortion was analyzed through a series of experimental testing. Moreover, the performance regarding distortion after applying a developed coaxial injection was compared with the standard non-coaxial injection configuration. It was observed that these two factors had a direct impact on distortion and can be utilized for the reduction in distortion arising from the crosstalk of the applied pulsed voltage. The results can be utilized for the consideration of practical aspects during the construction of a PEA test setup for the measurement of full-size HVDC cables.This research was funded by Delt University of Technology.Mier Escurra, G.; Rodrigo Mor, A.; Castro, LC.; Vaessen, P. (2021). PEA Electromagnetic Distortion Reduction by Impedance Grounding and Pulsed Voltage Electrode Configurations. Sensors. 21(17):1-12. https://doi.org/10.3390/s21175837S112211

    The Control Stage of a Modular Multilevel Converter-based Arbitrary Wave shape Generator for Dielectric Testing of High Voltage Grid Assets

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    A Modular Multilevel Converter (MMC)-based Arbitrary Wave shape Generator (AWG) for High Voltage (HV) testing faces challenges in the control hardware to generate kHz-range high-frequency waveforms. Real Time Simulators (RTS) provide a simple way to implement the control of the MMC-based AWG in the FPGA. One of the commercially available RTS named Typhoon HIL is found to satisfy the small simulation step requirement such as minimum of 200 ns for generating kHz-range high-frequency waveforms. The performance of Typhoon HIL device is demonstrated with a scaled-down prototype of MMC-based AWG where sinusoidal and other arbitrary waveforms are generated up to 5kHz with a THD less than 5 %

    Implementation of Active Damping Control Methodology on Modular Multilevel Converter(MMC)-Based Arbitrary Wave Shape Generator Used for High Voltage Testing

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    In order to damp the resonance in the MMC-based Arbitrary Wave shape Generator (AWG) used for high voltage testing, an active damping control methodology is proposed in this paper instead of the passive damping with an arm resistor. It is vital to ensure the system’s stability when such an active damping closed loop control is implemented. Consequently, optimal parameters of a PI controller are designed by analyzing the stability margins of the involved transfer function using Bode-Plots. The performance of the designed active damping control methodology and the PI controller have been demonstrated with a 50 Hz sinusoidal waveform and arbitrary waveforms such as triangular, trapezoidal, and complex waveforms in MATLAB-Simulink. These results proves that the output voltage can track the reference without any reasonable error and does not contain any resonant frequency. Additionally, the Total Harmonic Distortion (THD) of the sinusoidal waveform and other arbitrary waveforms is less than 1% with the Phase Shift Carrier (PSC) modulation technique

    Survival and cellular heterogeneity of epithelium in cultured mouse and rat precision-cut intestinal slices

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    Precision-cut intestinal slices (PCIS) are used to study intestinal (patho)physiology, drug efficacy, toxicity, transport and metabolism ex vivo. One of the factors that limit the use of PCIS is a relatively short life-span. Moreover, culture-induced changes in cellular composition of PCIS remain largely uncharacterized. In this study, we demonstrated the epithelial cell heterogeneity in mouse and rat PCIS and its alterations during culture. In addition, we evaluated whether the presence of niche growth factors impacts the survival of PCIS epithelial cells. We showed that freshly prepared PCIS retained the main epithelial cell types, namely absorptive enterocytes, goblet cells, enteroendocrine cells, stem cells, transit-amplifying cells and Paneth cells. Once placed in culture, PCIS displayed progressive epithelial damage, and loss of these epithelial cell types. Cells comprising the intestinal stem cell niche were especially sensitive to the damage, and the addition of niche growth factors beneficially affected the survival of stem cells and transit-amplifying cells in PCIS during culture. In conclusion, this study provides new insights into the dynamic changes in cellular composition of epithelium in cultured PCIS, paving the way to future toxicological and pharmacological studies in an informed and reliable ex vivo setting

    A genome-wide search for linkage-disequilibrium with type 1 diabetes in a recent genetically isolated population from the Netherlands

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    Type 1 diabetes has a substantial genetic component, with consistent evidence for a susceptibility locus in the HLA-DR/DQ region (chromosome 6p) and the insulin gene region (chromosome 11p). Genome scans have identified >18 other genomic regions that may harbor putative type 1 diabetes genes. However, evidence for most regions varies in different data sets. Given the genetic heterogeneity of type 1 diabetes, studies in homogeneous genetically isolated populations may be more successful in mapping susceptibility loci than in complex outbred populations. We describe a genome-wide search in a recently Dutch isolated population. We identified 43 patients that could be traced back to a common ancestor within 15 generations and performed a genome-wide scan using a combined linkage- and association-based approach. In addition to the HLA locus, evidence for type 1 diabetes loci was observed on chromosome 8q24 (marker D8S1128) and on chromosome 17q24 (marker D17S2059). Both the 8q and 17q localization are supported by allele-sharing at adjacent markers in affected individuals. Statistical evidence for a conserved ancestral haplotype was found for chromosome 8q24

    Risk factors for intensive care admission in children with severe acute asthma in the Netherlands:a prospective multicentre study

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    Rationale: Severe acute asthma (SAA) can be fatal, but is often preventable. We previously observed in a retrospective cohort study, a three-fold increase in SAA paediatric intensive care (PICU) admissions between 2003 and 2013 in the Netherlands, with a significant increase during those years of numbers of children without treatment of inhaled corticosteroids (ICS). Objectives: To determine whether steroid-naïve children are at higher risk of PICU admission among those hospitalised for SAA. Furthermore, we included the secondary risk factors tobacco smoke exposure, allergic sensitisation, previous admissions and viral infections. Methods: A prospective, nationwide multicentre study of children with SAA (2-18 years) admitted to all Dutch PICUs and four general wards between 2016 and 2018. Potential risk factors for PICU admission were assessed using logistic regression analyses. Measurements and main results: 110 PICU and 111 general ward patients were included. The proportion of steroid-naïve children did not differ significantly between PICU and ward patients. PICU children were significantly older and more exposed to tobacco smoke, with symptoms >1 week prior to admission. Viral susceptibility was not a significant risk factor for PICU admission. Conclusions: Children with SAA admitted to a PICU were comparable to those admitted to a general ward with respect to ICS treatment prior to admission. Preventable risk factors for PICU admission were >7 days of symptoms without adjustment of therapy and exposure to tobacco smoke. Physicians who treat children with asthma must be aware of these risk factors

    The Role of Body Mass Index, Insulin, and Adiponectin in the Relation Between Fat Distribution and Bone Mineral Density

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    Despite the positive association between body mass index (BMI) and bone mineral density (BMD) and content (BMC), the role of fat distribution in BMD/BMC remains unclear. We examined relationships between BMD/BMC and various measurements of fat distribution and studied the role of BMI, insulin, and adiponectin in these relations. Using a cross-sectional investigation of 2631 participants from the Erasmus Rucphen Family study, we studied associations between BMD (using dual-energy X-ray absorptiometry (DXA]) at the hip, lumbar spine, total body (BMD and BMC), and fat distribution by the waist-to-hip ratio (WHR), waist-to-thigh ratio (WTR), and DXA-based trunk-to-leg fat ratio and android-to-gynoid fat ratio. Analyses were stratified by gender and median age (48.0 years in women and 49.2 years in men) and were performed with and without adjustment for BMI, fasting insulin, and adiponectin. Using linear regression (adjusting for age, height, smoking, and use of alcohol), most relationships between fat distribution and BMD and BMC were positive, except for WTR. After BMI adjustment, most correlations were negative except for trunk-to-leg fat ratio in both genders. No consistent influence of age or menopausal status was found. Insulin and adiponectin levels did not explain either positive or negative associations. In conclusion, positive associations between android fat distribution and BMD/BMC are explained by higher BMI but not by higher insulin and/or lower adiponectin levels. Inverse associations after adjustment for BMI suggest that android fat deposition as measured by the WHR, WTR, and DXA-based android-to-gynoid fat ratio is not beneficial and possibly even deleterious for bone
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