Investigation of the suitability of high-power LEDs for the use as radiation source for PTB’s gonioreflectometer

The application areas in which light-emitting diodes (LEDs) are used as radiation sources are growing steadily. Main reasons are their long lifetime, efficiency and the available high radiation power. Also, the increase of accessible spectral ranges through the use and production of new semiconductor compounds make them attractive for many applications. Due to these advantages of LEDs, the suitability as (supplementary) radiation sources for the existing robot-based gonioreflectometer at PTB was investigated

An insight into the present capabilities of national metrology institutes for measuring sparkle

Large effect pigments, due to their strongly specular reflectance, produce a special visual texture known as sparkle. The use of these pigments in many industries (automotive, cosmetic, paper, architecture...) makes the control of this visual texture necessary. A measurement scale has to be developed, so that traceability can be provided by national metrology institutes (NMI) or designated institutes. Some of them (PTB, METAS, CMI and CSIC) have tested their existing capabilities to measure sparkle, and their results are presented. Two possible sources of systematic errors have been identified: inadequate illumination and collection full-angles, and inadequate size of the virtual aperture used to assess the luminous flux reflected on the effect pigments. The measurement scale of sparkle used in this comparison is thoroughly presented. This comparison will allow the methodology to measure sparkle to be improved.This article was written within the EMPIR 16NRM08 Project “Bidirectional reflectance definition” (BiRD). The EMPIR is jointly funded by the EMPIR participating countries within EURAMET and the European Union. The EMPIR is jointly funded by the EMPIR participating countries within EURAMET and the European Union. Part of the authors (Instituto de Óptica “Daza de Valdés”) are also grateful to Comunidad de Madrid for funding the project S2018/NMT-4326-SINFOTON2-C

Experimental Determination of the Uncertainty of the Absorption Coefficient of Crystalline Silicon

Based on a combined analysis of spectroscopic ellipsometry, reflectance and transmittance measurements as well as spectrally resolved luminescence measurements and spectral responsivity measurements, we present data of the coefficient of band-to-band absorption of crystalline silicon at 295 K in the wavelength range 250 - 1450 nm. A systematic measurement uncertainty analysis according to the "Guide to the Expression of Uncertainty in Measurements" (GUM) is carried out for each method, showing that the relative uncertainty of the absorption coefficient data so determined is of the order of 0.3% at 300 nm, 1% at 900 nm, 10% at 1200 nm and 180% at 1450 nm. The data are consolidated by comparison of measurements carried out independently at different institutions. The uncertainty of solar cell energy conversion predictions by means of simulations due to the uncertainty of the absorption coefficient data is shown to be of the order of 0.1% relative.Deutsche Bundesstiftung UmweltState of Lower Saxon

Preliminary measurement scales for sparkle and graininess

Large effect pigments, widely used in various fields of industrial applications, produce characteristic visual textures known as sparkle and graininess, which need to be quantified by objective or subjective methods. The development of preliminary measurement scales for sparkle and graininess, whose recommendation is now under discussion in the International Commission on Illumination (CIE), is described in this article. These scales are absolute, linear and traceable to standards of optical radiation metrology. The main purpose of this article is to justify the convenience of adopting these preliminary measurements scales, showing clear evidence that they correlate well with subjective evaluations. Before standardization, these scales need to be validated with more experimental data, including different specimens and experimental systems from other research groups.This article was written within the EMPIR 16NRM08 Project “Bidirectional reflectance definitions” (BiRD). The EMPIR is jointly funded by the EMPIR participating countries within EURAMET and the European Union. Part of the authors (E. Perales and F.M. Martínez-Verdú) are also grateful to Ministerio de Ciencia, Innovación y Universidades for project RTI2018-096000-B-I00

Further development of an LED-based radiation source for goniometric spectral radiance factor measurements

In previous work, the suitability of LEDs as a radiation source for the gonioreflectometer was investigated. An LED-Sphere Radiator (LED-SR) was constructed and its essential properties were described [1]. Based on these investigations, the further development of the LED-SR is presented here. Significant improvements such as a specially developed high-power LED board and active temperature control have been made. Due to the great influence of the reflecting insert on the radiation characteristics of the sphere, its optical and mechanical properties have also been optimized. Investigations with respect to these modifications and their effects are explained. The achieved improvements and the performance of the LED-SR are evaluated in comparison to measurements with the typically used halogen sphere radiator (Halogen-SR). It can be shown that with the new radiator more accurate results can be obtained in the observed spectral range in a shorter measurement time

Das Jahr des Lichtes

PTB-Mitteilungen. Band 125 (2015), Heft 4. ISSN 0030-834X1.: Stefan Kück und Armin Sperling: Einführung in die Metrologie des Lichtes. doi: 10.7795/310.20150401 http://dx.doi.org/10.7795/310.20150401 2.: Armin Sperling: Die Candela als Maßeinheit des Lichtes. doi: 10.7795/310.20150402 http://dx.doi.org/10.7795/310.20150402 3.: Detlef Lindner und Stefan Winter: Rückführung in der Photometrie - die Realisierung und Rückführung der Candela . doi: 10.7795/310.20150403 http://dx.doi.org/10.7795/310.20150403 4.: Matthias Lindemann: Kurze Geschichte der Goniophotometrie in der PTB. doi: 10.7795/310.20150404 http://dx.doi.org/10.7795/310.20150404 5.: Thorsten Gerloff: Metrologie für moderne Lichtquellen: LEDs und OLEDs. doi: 10.7795/310.20150405 http://dx.doi.org/10.7795/310.20150405 6.: Egbert Buhr, Alfred Schirmacher und Andreas Höpe: Effektpigmente: Eine Herausforderung für die optische Messtechnik. doi: 10.7795/310.20150406 http://dx.doi.org/10.7795/310.20150406 7.: Impressum

Serum Response Factor (SRF) Drives the Transcriptional Upregulation of the MDM4 Oncogene in HCC.

Different molecular mechanisms support the overexpression of the mouse double minute homolog 4 (MDM4), a functional p53 inhibitor, in human hepatocellular carcinoma (HCC). However, the transcription factors (TFs) leading to its transcriptional upregulation remain unknown. Following promoter and gene expression analyses, putative TFs were investigated using gene-specific siRNAs, cDNAs, luciferase reporter assays, chromatin immunoprecipitation, and XI-011 drug treatment in vitro. Additionally, MDM4 expression was investigated in SRF-VP16iHep transgenic mice. We observed a copy-number-independent upregulation of MDM4 in human HCCs. Serum response factor (SRF), ELK1 and ELK4 were identified as TFs activating MDM4 transcription. While SRF was constitutively detected in TF complexes at the MDM4 promoter, presence of ELK1 and ELK4 was cell-type dependent. Furthermore, MDM4 was upregulated in SRF-VP16-driven murine liver tumors. The pharmacological inhibitor XI-011 exhibited anti-MDM4 activity by downregulating the TFs driving MDM4 transcription, which decreased HCC cell viability and increased apoptosis. In conclusion, SRF drives transcriptional MDM4 upregulation in HCC, acting in concert with either ELK1 or ELK4. The transcriptional regulation of MDM4 may be a promising target for precision oncology of human HCC, as XI-011 treatment exerts anti-MDM4 activity independent from the MDM4 copy number and the p53 status

Serum Response Factor (SRF) Drives the Transcriptional Upregulation of the MDM4 Oncogene in HCC

Different molecular mechanisms support the overexpression of the mouse double minute homolog 4 (MDM4), a functional p53 inhibitor, in human hepatocellular carcinoma (HCC). However, the transcription factors (TFs) leading to its transcriptional upregulation remain unknown. Following promoter and gene expression analyses, putative TFs were investigated using gene-specific siRNAs, cDNAs, luciferase reporter assays, chromatin immunoprecipitation, and XI-011 drug treatment in vitro. Additionally, MDM4 expression was investigated in SRF-VP16iHep transgenic mice. We observed a copy-number-independent upregulation of MDM4 in human HCCs. Serum response factor (SRF), ELK1 and ELK4 were identified as TFs activating MDM4 transcription. While SRF was constitutively detected in TF complexes at the MDM4 promoter, presence of ELK1 and ELK4 was cell-type dependent. Furthermore, MDM4 was upregulated in SRF-VP16-driven murine liver tumors. The pharmacological inhibitor XI-011 exhibited anti-MDM4 activity by downregulating the TFs driving MDM4 transcription, which decreased HCC cell viability and increased apoptosis. In conclusion, SRF drives transcriptional MDM4 upregulation in HCC, acting in concert with either ELK1 or ELK4. The transcriptional regulation of MDM4 may be a promising target for precision oncology of human HCC, as XI-011 treatment exerts anti-MDM4 activity independent from the MDM4 copy number and the p53 status