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- Suomalainen, S., et al.
(författare)
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Semiconductor saturable absorbers with recovery time controlled by lattice mismatch and band-gap engineering
- 2008
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Ingår i: Materials Science & Engineering. - : Elsevier BV. - 0921-5107 .- 1873-4944. ; 147:2-3, s. 156-160
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Tidskriftsartikel (refereegranskat)abstract
- The recovery time of absorption in semiconductor quantum-well structures is one of the key parameters that determines the performance of pulsed lasers mode-locked or Q-switched by semiconductor saturable absorbers. In this paper we discuss new methods to control the recovery time of absorption. The first method is based on controlling the crystalline quality of the absorbing material and thus the density of non-radiative recombination centers that are responsible for the fast recovery of the absorption. With this technique, we were able to fabricate semiconductor saturable absorber mirrors (SESAMs) with recovery times of about 4.5 ps at 1 mu m and 40 ps at 1.55 mu m. Another approach that we propose and demonstrate in this paper is based on band-gap engineering that enables short recovery times to be achieved through fast relaxation of excited photocarriers via intraband scattering. A 24 ps carrier decay time was achieved by placing deep quantum-wells next to the shallow quantum-wells responsible for the nonlinear absorption. We demonstrated that the recovery time can be changed by modifying the thickness of the deep and shallow quantum-wells.
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- Draxler, K., et al.
(författare)
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International comparison of current transformer calibration systems up to 10 kA at 50 Hz frequency
- 2016
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Ingår i: 2016 Conference on Precision Electromagnetic Measurements (CPEM 2016). - 9781467391344
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Konferensbidrag (refereegranskat)abstract
- Current transformers (CTs) are precision devices that scale high currents down to values that can be easily handled by measurement equipment. To support CT applications in revenue metering, a comparison on AC current transformer calibration systems was performed among 15 European national metrology institutes using a precision CT as the travelling device. The first comparison results for the transformation ratios (4, 5, 6, 8, 10) kA/5 A of the travelling CT at nominal burden of 5 VA and 15 VA indicate good agreement between the participating laboratories. The main differences are found for phase displacement, at least partly caused by the instability of the traveling standard.
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- Lehtonen, J. M., et al.
(författare)
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Diagnostic value of serum biomarkersFGF21andGDF15compared to muscle sample in mitochondrial disease
- 2021
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Ingår i: Journal of Inherited Metabolic Disease. - : Wiley. - 0141-8955 .- 1573-2665. ; 44:2, s. 469-480
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this study was to compare the value of serum biomarkers, fibroblast growth factor 21 (FGF21) and growth differentiation factor 15 (GDF15), with histological analysis of muscle in the diagnosis of mitochondrial disease. We collected 194 serum samples from patients with a suspected or known mitochondrial disease. Biomarkers were analyzed blinded using enzyme-labeled immunosorbent assay. Clinical data were collected using a structured questionnaire. Only 39% of patients with genetically verified mitochondrial disease had mitochondrial pathology in their muscle histology. In contrast, biomarkers were elevated in 62% of patients with genetically verified mitochondrial disease. Those with both biomarkers elevated had a muscle manifesting disorder and a defect affecting mitochondrial DNA expression. If at least one of the biomarkers was induced and the patient had a myopathic disease, a mitochondrial DNA expression disease was the cause with 94% probability. Among patients with biomarker analysis and muscle biopsy taken <12 months apart, a mitochondrial disorder would have been identified in 70% with analysis of FGF21 and GDF15 compared to 50% of patients whom could have been identified with muscle biopsy alone. Muscle findings were nondiagnostic in 72% (children) and 45% (adults). Induction of FGF21 and GDF15 suggest a mitochondrial etiology as an underlying cause of a muscle manifesting disease. Normal biomarker values do not, however, rule out a mitochondrial disorder, especially if the disease does not manifest in muscle. We suggest that FGF21 and GDF15 together should be first-line diagnostic investigations in mitochondrial disease complementing muscle biopsy.
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