LBE-cooled tube receiver performance - Design aspects and high-flux operation in a solar furnace

Diese Arbeit untersucht die Eignung von flüssigem Blei-Bismut (Pb-Bi) als Wärmetransport-Medium in zentralen Rohr-Receivern von konzentrierenden solarthermischen Kraftwerken. Dazu werden zwei Ansätze verfolgt: a) auf theoretischer Ebene werden anhand existierender Literatur die Materialeigenschaften von Pb-Bi und existierende Auslegungswerkzeuge für Flüssigmetall-Anwendungen betrachtet und b) anhand eines Praxisbeispiels wird die Auslegung, der Bau, die Inbetriebnahme sowie erste Betriebserfahrung eines Pb-Bi-gekühlten Modellkreislaufs in einem eigens errichteten Solar-Ofen im Technikumsmaßstab erprobt. Der Pb-Bi-gekühlte Solarreceiver dieses Kreislaufs besitzt eine thermische Leistung von 10 kW. Pb-Bi besitzt einige hervorragende und einige ungünstige Stoffeigenschaften für seine Anwendung in Solarreceivern im kommerziellen Groß-Maßstab: eine hohe thermische Leitfähigkeit und eine geringe Viskosität stehen einer durchschnittlichen Wärmekapazität und einer sehr hohen Dichte gegenüber. Diese führen für Pb-Bi im Vergleich mit Alternativ-Wärmetransportmedien Solarsalz und Natrium beim Einsatz in Receiver-Rohren zu den höchsten Entropie-Erzeugungsraten. Pb-Bi ist darüber hinaus teuer. Im Pb-Bi muss eine definierte Sauerstoffkonzentration eingestellt werden, um die Korrosion der Edelstahl-Rohrwerkstoffe zu begrenzen. Dadurch wird allerdings der Bereich der Einsatztemperaturen eingeschränkt: Infolge dessen kann entweder der Vorteil einer geringen Schmelztemperatur von Pb-Bi nicht ausgenutzt werden, oder aber eine Betriebstemperatur oberhalb der Temperaturgrenze von Solarsalz kann nicht erreicht werden. Nach dem aktuellen Stand der Technik dient Solarsalz als Wärmetransportmedium. Die Literaturrecherche dieser Arbeit gibt deutliche Hinweise darauf, dass Fluide mit niedrigen Prandtl-Zahlen und insbesondere Pb-Bi empfindlicher als "konventionelle" Medien auf Randbedingungen mit inhomogener Wärmestromdichteverteilung reagieren. Tatsächlich werden die Rohrströmungen in konventionellen Solarreceivern nur einseitig beheizt. Unter dieser Randbedingung führen klassische Nusselt-Korrelationen, die für homogen beheizte, voll-turbulente Rohrströmung entwickelt wurden, bei Medien geringer Prandtl-Zahl zu einer deutlichen Unterschätzung der Wandtemperatur und damit einhergehend zu einer Unterschätzung der thermischen Spannungen in der Rohrwand. Daher werden alternative Auslegungsmethoden präsentiert. Erste Messungen am Pb-Bi-Kreislauf zeigen tatsächlich äußere Wandtemperaturen der Receiver-Rohre, die höher sind als von klassischen Nusselt-Korrelationen vorhergesagt. Trotz dieses Befundes hat Pb-Bi für seinen Einsatz in einem Modell-System seine Berechtigung, da es im Vergleich zu bspw. Natrium inhärent deutlich sicherer ist und kann für Receiver-Betrieb und die Untersuchung von Phänomenen, die spezifisch für Flüssigmetalle sind, verwendet werden. Diese Arbeit beschreibt die Auslegung der wichtigsten Teile des Pb-Bi-Kreislaufs und die ersten experimentellen Ergebnisse, darunter auch solche bei einer Wärmestromdichte von etwa 4 MW/m$^2$. Zur Messung derart hoher Wärmestromdichten wurde im Rahmen der Arbeit ein passiv-gekühlter Wärmestrom-Scanner entwickelt, dessen Funktion auf einem einzigen Heat-Flux-Mocro-Sensor basiert. Dieser Sensor bewegt sich während des Scannens auf einer Spiral-Bahn durch die Messebene. Dieses Messgerät wurde vor Messbeginn im Solarofen des DLR in Köln für den Betrieb kalibriert

Evidence that breast cancer risk at the 2q35 locus is mediated through IGFBP5 regulation.

GWAS have identified a breast cancer susceptibility locus on 2q35. Here we report the fine mapping of this locus using data from 101,943 subjects from 50 case-control studies. We genotype 276 SNPs using the 'iCOGS' genotyping array and impute genotypes for a further 1,284 using 1000 Genomes Project data. All but two, strongly correlated SNPs (rs4442975 G/T and rs6721996 G/A) are excluded as candidate causal variants at odds against >100:1. The best functional candidate, rs4442975, is associated with oestrogen receptor positive (ER+) disease with an odds ratio (OR) in Europeans of 0.85 (95% confidence interval=0.84-0.87; P=1.7 × 10(-43)) per t-allele. This SNP flanks a transcriptional enhancer that physically interacts with the promoter of IGFBP5 (encoding insulin-like growth factor-binding protein 5) and displays allele-specific gene expression, FOXA1 binding and chromatin looping. Evidence suggests that the g-allele confers increased breast cancer susceptibility through relative downregulation of IGFBP5, a gene with known roles in breast cell biology

Can user testing of a clinical trial patient information sheet make it fit-for-purpose? - a randomized controlled trial

Background: The participant information sheet (PIS) provided to potential trial participants is a critical part of the process of valid consent. However, there is long-standing concern that these lengthy and complex documents are not fit-for-purpose. This has been supported recently through the application of a performance-based approach to testing and improving readability called user testing. This method is now widely used to improve patient medicine leaflets - determining whether people can find and understand key facts. This study applied for the first time a controlled design to determine whether a PIS developed through user testing had improved readability over the original, using a sheet from a UK trial in acute myeloid leukemia (AML16). Methods: In the first phase the performance of the original PIS was tested on people in the target group for the trial. There were three rounds of testing including 50 people in total - with the information revised according to its performance after each of the first 2 rounds. In the second phase, the revised PIS was compared with the original in a parallel groups randomised controlled trial (RCT) A total of 123 participants were recruited and randomly allocated to read one version of the PIS to find and show understanding of 21 key facts. Results: The first, developmental phase produced a revised PIS significantly altered in its wording and layout. In the second, trial phase 66% of participants who read the revised PIS were able to show understanding of all aspects of the trial, compared with 15% of those reading the original version (Odds Ratio 11.2; Chi-square = 31.5 p < .001). When asked to state a preference, 87.1% participants chose the revised PIS (Sign test p < .001). Conclusions: The original PIS for the AML16 trial may not have enabled valid consent. Combining performance-based user testing with expertise in writing for patients and information design led to a significantly improved and preferred information sheet. User testing is an efficient method for indicating strengths and weaknesses in trial information, and Research Ethics Committees and Institutional Review Boards should consider requesting such testing, to ensure that PIS are fit-for-purpose

Extension and stress during continental breakup: seismic anisotropy of the crust in Northern Afar

Studies that attempt to simulate continental rifting and subsequent breakup require detailed knowledge of crustal stresses, however observational constraints from continental rifts are lacking. In addition, a knowledge of the stress field around active volcanoes can be used to detect sub-surface changes to the volcanic system. Here we use shear wave splitting to measure the seismic anisotropy of the crust in Northern Afar, a region of active, magma-rich continental breakup. We combine shear wave splitting tomography with modelling of gravitational and magmatic induced stresses to propose a model for crustal stress and strain across the rift. Results show that at the Ethiopian Plateau, seismic anisotropy is consistently oriented N–S. Seismic anisotropy within the rift is generally oriented NNW–SSE, with the exception of regions north and south of the Danakil Depression where seismic anisotropy is rift-perpendicular. These results suggest that the crust at the rift axis is characterized by rift-aligned structures and melt inclusions, consistent with a focusing of tectonic extension at the rift axis. In contrast, we show that at regions within the rift where extension rate is minimal the seismic anisotropy is best explained by the gravitationally induced stress field originating from variations in crustal thickness. Seismic anisotropy away from the rift is controlled by a combination of inherited crustal structures and gravitationally induced extension whereas at the Dabbahu region we show that the stress field changes orientation in response to magmatic intrusions. Our proposed model provides a benchmark of crustal stress in Northern Afar which will aid the monitoring of volcanic hazard. In addition we show that gravitational forces play a key role in measurements of seismic anisotropy, and must be considered in future studies. We demonstrate that during the final stages of continental rifting the stress field at the rift axis is primarily controlled by tectonic extension, but that gravitational forces and magmatic intrusions can play a key role in the orientation of the stress field

Parent-of-origin-specific allelic associations among 106 genomic loci for age at menarche.

Age at menarche is a marker of timing of puberty in females. It varies widely between individuals, is a heritable trait and is associated with risks for obesity, type 2 diabetes, cardiovascular disease, breast cancer and all-cause mortality. Studies of rare human disorders of puberty and animal models point to a complex hypothalamic-pituitary-hormonal regulation, but the mechanisms that determine pubertal timing and underlie its links to disease risk remain unclear. Here, using genome-wide and custom-genotyping arrays in up to 182,416 women of European descent from 57 studies, we found robust evidence (P < 5 × 10(-8)) for 123 signals at 106 genomic loci associated with age at menarche. Many loci were associated with other pubertal traits in both sexes, and there was substantial overlap with genes implicated in body mass index and various diseases, including rare disorders of puberty. Menarche signals were enriched in imprinted regions, with three loci (DLK1-WDR25, MKRN3-MAGEL2 and KCNK9) demonstrating parent-of-origin-specific associations concordant with known parental expression patterns. Pathway analyses implicated nuclear hormone receptors, particularly retinoic acid and γ-aminobutyric acid-B2 receptor signalling, among novel mechanisms that regulate pubertal timing in humans. Our findings suggest a genetic architecture involving at least hundreds of common variants in the coordinated timing of the pubertal transition

The new CCSDS standard for low-complexity lossless and near-lossless multispectral and hyperspectral image compression

This paper describes the emerging Issue 2 of the CCSDS-123.0-B standard for low-complexity compression of multispectral and hyperspectral imagery, focusing on its new features and capabilities. Most significantly, this new issue incorporates a closed-loop quantization scheme to provide near-lossless compression capability while still supporting lossless compression, and introduces a new entropy coding option that provides better compression of low-entropy data

The new CCSDS standard for low-complexity lossless and near-lossless multispectral and hyperspectral image compression

This paper describes the emerging Issue 2 of the CCSDS-123.0-B standard for low-complexity compression of multispectral and hyperspectral imagery, focusing on its new features and capabilities. Most significantly, this new issue incorporates a closed-loop quantization scheme to provide near-lossless compression capability while still supporting lossless compression, and introduces a new entropy coding option that provides better compression of low-entropy data

Assessing interactions between the associations of common genetic susceptibility variants, reproductive history and body mass index with breast cancer risk in the breast cancer association consortium: a combined case-control study.

INTRODUCTION: Several common breast cancer genetic susceptibility variants have recently been identified. We aimed to determine how these variants combine with a subset of other known risk factors to influence breast cancer risk in white women of European ancestry using case-control studies participating in the Breast Cancer Association Consortium. METHODS: We evaluated two-way interactions between each of age at menarche, ever having had a live birth, number of live births, age at first birth and body mass index (BMI) and each of 12 single nucleotide polymorphisms (SNPs) (10q26-rs2981582 (FGFR2), 8q24-rs13281615, 11p15-rs3817198 (LSP1), 5q11-rs889312 (MAP3K1), 16q12-rs3803662 (TOX3), 2q35-rs13387042, 5p12-rs10941679 (MRPS30), 17q23-rs6504950 (COX11), 3p24-rs4973768 (SLC4A7), CASP8-rs17468277, TGFB1-rs1982073 and ESR1-rs3020314). Interactions were tested for by fitting logistic regression models including per-allele and linear trend main effects for SNPs and risk factors, respectively, and single-parameter interaction terms for linear departure from independent multiplicative effects. RESULTS: These analyses were applied to data for up to 26,349 invasive breast cancer cases and up to 32,208 controls from 21 case-control studies. No statistical evidence of interaction was observed beyond that expected by chance. Analyses were repeated using data from 11 population-based studies, and results were very similar. CONCLUSIONS: The relative risks for breast cancer associated with the common susceptibility variants identified to date do not appear to vary across women with different reproductive histories or body mass index (BMI). The assumption of multiplicative combined effects for these established genetic and other risk factors in risk prediction models appears justified.RIGHTS : This article is licensed under the BioMed Central licence at http://www.biomedcentral.com/about/license which is similar to the 'Creative Commons Attribution Licence'. In brief you may : copy, distribute, and display the work; make derivative works; or make commercial use of the work - under the following conditions: the original author must be given credit; for any reuse or distribution, it must be made clear to others what the license terms of this work are