471 research outputs found
An Integrated Method for Determination of the Oswald Factor in a Multi-Fidelity Design Environment
Aircraft conceptual design often focuses on unconventional
configurations like for example forward
swept wings. Assessing the characteristics
of these configurations usually requires the use
of physic based analysis modules. This is due
to the fact that for unconventional configurations
no sucient database for historic based analysis
modules is available.
Nevertheless, physic based models require a
lot of input data and their computational cost can
be high. Generating input values in a trade study
manually is work-intensive and error-prone.
Conceptual design modules can be used to
generate sucient input data for physic based
models and their results can be re-integrated into
the conceptual design phase. In this study a direct
link between a conceptual design module
and an aerodynamic design module is presented.
Geometric information is generated by the conceptual
design module and the physic based results,
in form of the Oswald factor, are then fed
back.
Apart from the direct link, an equation for determination
of the Oswald factor is derived via a
Symbolic Regression Approach
Experimental Study of Condensation of Water on Polydimethylsiloxane-Coated Copper Surfaces
Modification of surfaces to enable dropwise condensation is a promising
approach for achieving high condensation rates. In this work, we present an
experimental study on condensation of water on copper surfaces coated with an
ultrathin, 5 nm - 10 nm thick polydimethylsiloxane (PDMS) layer. This
hydrophobic coating possesses a very low thermal resistance, which in
combination with copper substrate enables achieving high condensation rates in
heat transfer applications. The PDMS-coated copper substrates have been
fabricated with a newly developed method, which involves turning, sanding,
polishing, oxidation, and polymer coating steps. The measured static contact
angle was 110{\deg}, and a the contact angle hysteresis was 2{\deg}. The
achieved very low hysteresis is advantageous for promoting dropwise
condensation. The surface showed no ageing effects during 100 repetitions of
advancing and receding contact angle (ARCA) measurements. Condensation heat
transfer on uncoated and PDMS-coated copper surfaces surfaces has been studied
experimentally in a saturated water vapor atmosphere at 60{\deg}C. An
enhancement factor for heat flux and heat transfer coefficient of up to 1.6 was
found on PDMS-coated copper surfaces compared to uncoated surfaces, which
decreased to 1.1 on second and third day of condensation operation. Images of
the condensation surface were recorded while conducting condensation
experiments and post processed to evaluate drop departure diameter and
frequency of drop sweeping events. It has been shown that the behavior of the
heat transfer coefficient correlates with the frequency of the sweeping events
AIRCRAFT CONFIGURATION ANALYSIS USING A LOW-FIDELITY, PHYSICS BASED AEROSPACE FRAMEWORK UNDER UNCERTAINTY CONSIDERATIONS
During the early stages of aircraft design, limited
information is available to conduct decisions that
base on the quality of aircraft configurations. In the
present study, information on physical and statistical
models is supplemented by the uncertainty that is
inherent to the applied analysis modules and
propagated through the complete design workflow.
Using this method, the possibility arises to make a
statement on the level of certainty with which one
concept is preferred above another
Airport2030 - Lösungen für den Lufttransport der Zukunft
Im Flightpath 2050, in der Hightech-Strategie der Bundesregierung und der Strategie des Hamburger Luftfahrtclusters werden Ziele für die Effizienz des Lufttransports hinsichtlich Nachhaltigkeit, Komfort, Reisezeit und Intermodalität benannt. Im Verbundprojekt Airport2030 werden am Beispiel des Flughafen Hamburg ausgewählte Technologien und Maßnahmen zu Flughafenanbindung, Terminalbetrieb, Flughafenprozesssteuerung, Flugzeugkonfigurationen und Bodeninfrastrukturen untersucht und bewertet. Es werden hier ein Überblick über das Verbundprojekt gegeben und ausgewählte Ergebnisse der bisherigen Projektlaufzeit vorgestellt. Das Verbundprojekt Airport2030 bildet den Leuchtturm III innerhalb der Spitzencluster-Förderung des Luftfahrtclusters Metropolregion Hamburg durch das Bundesministerium für Bildung und Forschung
Neurocognitive Development of the Resolution of Selective Visuo-Spatial Attention: Functional MRI Evidence From Object Tracking
Our ability to select relevant information from the environment is limited by the resolution of attention – i.e., the minimum size of the region that can be selected. Neural mechanisms that underlie this limit and its development are not yet understood. Functional magnetic resonance imaging (fMRI) was performed during an object tracking task in 7- and 11-year-old children, and in young adults. Object tracking activated canonical fronto-parietal attention systems and motion-sensitive area MT in children as young as 7 years. Object tracking performance improved with age, together with stronger recruitment of parietal attention areas and a shift from low-level to higher-level visual areas. Increasing the required resolution of spatial attention – which was implemented by varying the distance between target and distractors in the object tracking task – led to activation increases in fronto-insular cortex, medial frontal cortex including anterior cingulate cortex (ACC) and supplementary motor area, superior colliculi, and thalamus. This core circuitry for attentional precision was recruited by all age groups, but ACC showed an age-related activation reduction. Our results suggest that age-related improvements in selective visual attention and in the resolution of attention are characterized by an increased use of more functionally specialized brain regions during the course of development
Circulating KRAS G12D but not G12V is associated with survival in metastatic pancreatic ductal adenocarcinoma
While high circulating tumor DNA (ctDNA) levels are associated with poor survival for multiple cancers, variant-specific differences in the association of ctDNA levels and survival have not been examined. Here we investigate KRAS ctDNA (ctKRAS) variant-specific associations with overall and progression-free survival (OS/PFS) in first-line metastatic pancreatic ductal adenocarcinoma (mPDAC) for patients receiving chemoimmunotherapy ("PRINCE", NCT03214250), and an independent cohort receiving standard of care (SOC) chemotherapy. For PRINCE, higher baseline plasma levels are associated with worse OS for ctKRAS G12D (log-rank p = 0.0010) but not G12V (p = 0.7101), even with adjustment for clinical covariates. Early, on-therapy clearance of G12D (p = 0.0002), but not G12V (p = 0.4058), strongly associates with OS for PRINCE. Similar results are obtained for the SOC cohort, and for PFS in both cohorts. These results suggest ctKRAS G12D but not G12V as a promising prognostic biomarker for mPDAC and that G12D clearance could also serve as an early biomarker of response
A highly conserved protein of unknown function in Sinorhizobium meliloti affects sRNA regulation similar to Hfq
The SMc01113/YbeY protein, belonging to the UPF0054 family, is highly conserved in nearly every bacterium. However, the function of these proteins still remains elusive. Our results show that SMc01113/YbeY proteins share structural similarities with the MID domain of the Argonaute (AGO) proteins, and might similarly bind to a small-RNA (sRNA) seed, making a special interaction with the phosphate on the 5′-side of the seed, suggesting they may form a component of the bacterial sRNA pathway. Indeed, eliminating SMc01113/YbeY expression in Sinorhizobium meliloti produces symbiotic and physiological phenotypes strikingly similar to those of the hfq mutant. Hfq, an RNA chaperone, is central to bacterial sRNA-pathway. We evaluated the expression of 13 target genes in the smc01113 and hfq mutants. Further, we predicted the sRNAs that may potentially target these genes, and evaluated the accumulation of nine sRNAs in WT and smc01113 and hfq mutants. Similar to hfq, smc01113 regulates the accumulation of sRNAs as well as the target mRNAs. AGOs are central components of the eukaryotic sRNA machinery and conceptual parallels between the prokaryotic and eukaryotic sRNA pathways have long been drawn. Our study provides the first line of evidence for such conceptual parallels. Furthermore, our investigation gives insights into the sRNA-mediated regulation of stress adaptation in S. meliloti
Regulation of cytoplasmic RNA stability: lessons from drosophila
The process of RNA degradation is a critical level of regulation contributing to the control of gene expression. In the last two decades a number of studies have shown the specific and targeted nature of RNA decay and its importance in maintaining homeostasis. The key players within the pathways of RNA decay are well conserved with their mutation or disruption resulting in distinct phenotypes as well as human disease. Model organisms including Drosophila melanogaster have played a substantial role in elucidating the mechanisms conferring control over RNA stability. A particular advantage of this model organism is that the functions of ribonucleases can be assessed in the context of natural cells within tissues in addition to individual immortalised cells in culture. Drosophila RNA stability research has demonstrated how the cytoplasmic decay machines, such as the exosome, Dis3L2 and Xrn1, are responsible for regulating specific processes including apoptosis, proliferation, wound healing and fertility. The work discussed here has begun to identify specific mRNA transcripts that appear sensitive to specific decay pathways representing mechanisms through which the ribonucleases control mRNA stability. Drosophila research has also contributed to our knowledge of how specific RNAs are targeted to the ribonucleases including AU rich elements, miRNA targeting and 3’ tailing. Increased understanding of these mechanisms is critical to elucidating the control elicited by the cytoplasmic ribonucleases which is relevant to human disease
Clinical and virological characteristics of hospitalised COVID-19 patients in a German tertiary care centre during the first wave of the SARS-CoV-2 pandemic: a prospective observational study
Purpose: Adequate patient allocation is pivotal for optimal resource management in strained healthcare systems, and requires detailed knowledge of clinical and virological disease trajectories. The purpose of this work was to identify risk factors associated with need for invasive mechanical ventilation (IMV), to analyse viral kinetics in patients with and without IMV and to provide a comprehensive description of clinical course.
Methods: A cohort of 168 hospitalised adult COVID-19 patients enrolled in a prospective observational study at a large European tertiary care centre was analysed.
Results: Forty-four per cent (71/161) of patients required invasive mechanical ventilation (IMV). Shorter duration of symptoms before admission (aOR 1.22 per day less, 95% CI 1.10-1.37, p < 0.01) and history of hypertension (aOR 5.55, 95% CI 2.00-16.82, p < 0.01) were associated with need for IMV. Patients on IMV had higher maximal concentrations, slower decline rates, and longer shedding of SARS-CoV-2 than non-IMV patients (33 days, IQR 26-46.75, vs 18 days, IQR 16-46.75, respectively, p < 0.01). Median duration of hospitalisation was 9 days (IQR 6-15.5) for non-IMV and 49.5 days (IQR 36.8-82.5) for IMV patients.
Conclusions: Our results indicate a short duration of symptoms before admission as a risk factor for severe disease that merits further investigation and different viral load kinetics in severely affected patients. Median duration of hospitalisation of IMV patients was longer than described for acute respiratory distress syndrome unrelated to COVID-19
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