Ground-based remote sensing of carbon dioxide and methane in the Arctic using Fourier-transform infrared spectrometry

The abundances of the atmospheric greenhouse gases carbon dioxide and methane are monitored across the globe by a network of ground-based solar absorption Fourier-transform infrared spectrometers, the Total Carbon Column Observing Network (TCCON). In this dissertation, the existing measurement time series of both gases, taken at the TCCON site in Ny-A lesund, Spitsbergen, has been augmented in two ways: extension to measurements during the polar night and the usage of middle-infrared spectra. In addition to the near-infrared TCCON measurements, spectra in the middle-infrared are routinely taken in Ny-A lesund. The newly obtained data from these spectra are compared to the standard TCCON retrieval. Additionally, in the high Arctic, measurements of solar absorption spectra are not possible in winter, because the Sun is permanently below the horizon. A new detector for measurements in the near-infrared is introduced and spectra were recorded between 2012 and 2016 to retrieve the column averaged dry-air mole fractions of CO2 and CH4. The lunar measurements were validated and compared to results from various reanalysis model simulations as well as in-situ measurements

Handbook on Industrial Applications of Nanofluids in Energy Sector

The idea of this handbook was to open a call for possible contributions in the field of nanofluids industrial applications in the energy sector among the Nanouptake networ

Dissipationsintegralverfahren für turbulente Grenzschichten

Mit dieser Arbeit liegt eine ausführliche Studie zu den Integralverfahren der Grenzschichttheorie vor. Der Schwerpunkt liegt dabei auf den Dissipationsintegralverfahren. Im Vergleich zu anderen Grenzschichtverfahren bestehen die generellen Vorteile der Integralverfahren in ihrer Robustheit, ihrer hohen Praktikabilität sowie den im Sinne der aufzuwendenden Computerkapazität geringen Kosten. Ein spezieller Vorteil der Dissipationsintegralverfahren ist es zudem, das komplette Schubspannungsprofil der Grenzschicht zu berücksichtigen. Über eine entsprechende Ableitung der Dissipationsintegrale kann die Vorgeschichte der Grenzschicht erfassen werden. Ausgangspunkt der Arbeit ist eine Literaturanalyse, welche aufzeigt, dass Integralverfahren weit verbreitet sind und für vielfältige Typen von Grenzschichten Anwendung finden. Ausgehend von den Navier-Stokes-Gleichungen wird über die Grenzschichtgleichungen die allgemeine Form der Dissipationsintegralgleichungen hergeleitet. Auf der Basis dieser Gleichungen werden Berechnungsalgorithmen für zwei- und dreidimensionale Grenzschichten entworfen und ausführlich diskutiert. Die zur Komplettierung der Berechnungsalgorithmen benötigten Parameterzusammenhänge werden aus expliziten Geschwindigkeitsprofilen hergeleitet. Hierzu werden beruhend auf dem Zweischichtenmodell turbulenter Grenzschichten Geschwindigkeitsprofile turbulenter Grenzschichten diskutiert. Drei Kombinationen von Haupt- und Querströmungsprofil werden für den dreidimensionalen Fall ausgewählt und algorithmisch umgesetzt. Die Algorithmen für zweidimensionale Grenzschichten beruhen auf einem Geschwindigkeitsprofil. Dem Aufbau der Algorithmen schließen sich ausführliche Testrechnungen sowie eine Bewertung der Verfahren an. Es wird festgestellt, dass Dissipationsintegralverfahren für zwei- und dreidimensionale Grenzschichten mit gutem Erfolg angewandt werden können. Vergleiche der Rechenergebnisse für zweidimensionale Grenzschichten zeigen die zumindest Gleichwertigkeit mit Zweigleichungsmodellen an.Calculation and prediction of turbulent boundary layers are among the most challenging tasks of present fluid mechanics. A strong demand exists for robust, easy-to-handle and in terms of computing effort cheap algorithms which can be used for technical applications. From an engineering point of view zonal methods and RANS are the most useful tools for solution of fluid mechanical problems. It is known that zonal methods which use integral approaches for the description of the boundary layer can be used successfully in manifold forms. One way to improve zonal methods further is the Basically three different types of integral algorithms - entrainment, momentum of momentum and dissipation integral method - can be derived from the three-dimensional boundary layer equations. If one compares the usual entrainment integral method with the dissipation integral method it turns out that the latter has the following physical advantages. While the entrainment method considers information about the shear stress distribution only at the outer edge of the boundary layer, the dissipation integral method uses the whole distribution. This work gives an overview over dissipation integral method and extends them to three-dimensional boundary layers. The general integral equations for the three-dimensional case are derived. Using two different sets of mean velocity profiles the hyperbolical character of a dissipation integral method is shown. Apart from the integral momentum balance, the dissipation integral method satisfies a second major balance with the integral balance of mechanical energy. It is found that for a practical calculation the integral momentum equation and the integral energy equation are most useful. Sixteen two-dimensional experimental test cases with none-zero pressure gradients were computed. It was found that the averaged relative deviation between measured and computed values for the skin friction coefficient is about 5 % and about 3 % for the shape parameter. Two three-dimensional fully turbulent boundary layers approaching an obstacle where computed. The agreement between experimental results and the calculation is reasonably good. The calculation allows the prediction of the velocity distributions. Flow angle and flow gradient angle distributions being additional results

Routine – Kontingenz – Reflexivität: Warum Praxistheorien nicht ohne ein Konzept der Subjektivierung auskommen

Die Engführung von Praktiken auf die routinehafte Reproduktion des Sozialen ist, so unsere Ausgangsthese, das Konstrukt einer „Theaterperspektive“ (Bourdieu) auf soziales Geschehen, mit dem der Anspruch der Praxistheorien, eine Soziologie jenseits von Strukturalismus und Handlungstheorie zu formulieren, nicht eingelöst wird. Denn „Struktur“ und „Handeln“ sind nicht gleichzeitig und in gleicher Weise zu beobachten: Strukturen können ausschließlich im Nachhinein identifiziert werden. Gegenwärtiges Geschehen gehört hingegen zu einer kontingenten, im Werden begriffenen Wirklichkeit, in der Ereignisse und Erfahrungen auftauchen, deren Möglichkeit nicht in den rekonstruierten Strukturen enthalten war und die sich deshalb auch nicht im Rekurs auf diese Muster erklären lässt. Entsprechend koexistieren in der praxistheoretischen Debatte zwei analytisch zu unterscheidende Sichtweisen: Während Akteure in der einen Perspektive auf bloße Vollzugsorgane sie „rekrutierender“ Praktiken reduziert werden, denen lediglich die Funktion zukommt, Praktiken routinehaft am Laufen zu halten, neigt die andere Perspektive dazu, ein präpraktisches Subjekt vorauszusetzen, um die Vollzugsoffenheit der Praxis überhaupt denken zu können. Zur Überwindung dieser Polarisierung ist es nötig, die Ausformung sozialer Ordnungen und ihrer „Akteure“ als einen ko-konstitutiven Verweisungszusammenhang zu begreifen.Da es sich bei Praxiskonzeptionen um Beobachtungskonstrukte handelt, bleiben Praxisverständnis und Beobachterperspektive wechselseitig aufeinander verwiesen. Im Anschluss daran schlagen wir eine Methode systematischer Perspektivwechsel vor, um sowohl die Strukturierungen des Handelns und der „Einstellungen“ der Agierenden als auch die kontingente (interaktive) Entfaltung von Praxis durch sich darin selbst bildende „Handlungssubjekte“ in den Blick zu bringen. So sollen Konzepte praktischer Teilnahmebefähigung ausgelotet werden, um zu zeigen, dass „Akteure“ erst in ihrer Teilnahme an Praktiken zu Trägern von Fähigkeiten werden und sich zu solchen machen. Es wird deutlich, dass der Status als kompetentes Teilnehmersubjekt von Akten der Anerkennung abhängig ist, in die je spezifische normative Erwartungen eingefaltet sind. Um ihre von Spannungen und Widersprüchen gekennzeichnete Ambivalenz zwischen Aktivität und Passivität, Anpassung und Eigensinn, Routine und Reflexivität in den Blick zu bekommen, beobachten wir diese Vorgänge als Prozesse der Subjektivierung und Selbst-Bildung

Numerical analysis of performance uncertainty of heat exchangers operated with nanofluids

In this paper, we analyse the performance of two types of heat exchangers with nanofluid as the working fluid in turbulent flow regime ( 4, 000–180, 000). Based on the experimental uncertainty of the thermophysical properties of the nanofluids, we use the Stochastic Collocation Method in combination with a deterministic simulation programme to estimate the expected value and variance of the targeted engineering results. We find that the uncertainty in the thermal conductivity of the nanofluid has the largest impact on the uncertainty in the heat exchanger performance, while the uncertainty in the density can be neglected. The uncertainties in the Nusselt number, friction factor and several figures of merit are smaller than the change in these performance estimators due to a change in nanoparticle concentration. Predictions for heat exchanger performance agree much better with experimental data when used with empirical heat transfer correlations developed specifically for nanofluids than with the general Gnielinski correlation developed for pure fluids. We also perform a correlation analysis of the relationships between heat exchanger performance enhancement and pressure drop to show that they are strongly correlated. We find that the relationship between the concentration of nanoparticles and the Nusselt number is statistically insignificant. The relationship is significant, indicating the importance of flow conditions. The correlation between nanoparticle concentration and friction factor is significant and strong. This result suggests that the optimisation of the thermal-hydrodynamic behaviour should be sought in a parameter other than the nanoparticle volume fraction

Working Group Reports

Final report of the five Working Group (WG) meetings have been held in the frame of Nanouptake during the whole duration of the Actio

Extracellular Vesicle Associated miRNAs Regulate Signaling Pathways Involved in COVID-19 Pneumonia and the Progression to Severe Acute Respiratory Corona Virus-2 Syndrome

Background: Extracellular vesicles (EVs) are mediators of cell-to-cell communication in inflammatory lung diseases. They function as carriers for miRNAs which regulate mRNA transcripts and signaling pathways after uptake into recipient cells. We investigated whether miRNAs associated with circulating EVs regulate immunologic processes in COVID-19. Methods: We prospectively studied 20 symptomatic patients with COVID-19 pneumonia, 20 mechanically ventilated patients with severe COVID-19 (severe acute respiratory corona virus-2 syndrome, ARDS) and 20 healthy controls. EVs were isolated by precipitation, total RNA was extracted, profiled by small RNA sequencing and evaluated by differential gene expression analysis (DGE). Differentially regulated miRNAs between groups were bioinformatically analyzed, mRNA target transcripts identified and signaling networks constructed, thereby comparing COVID-19 pneumonia to the healthy state and pneumonia to severe COVID-19 ARDS. Results: DGE revealed 43 significantly and differentially expressed miRNAs (25 downregulated) in COVID-19 pneumonia when compared to controls, and 20 miRNAs (15 downregulated) in COVID-19 ARDS patients in comparison to those with COVID-19 pneumonia. Network analysis for comparison of COVID-19 pneumonia to healthy controls showed upregulated miR-3168 (log2FC=2.28, padjusted<0.001), among others, targeting interleukin-6 (IL6) (25.1, 15.2 - 88.2 pg/ml in COVID-19 pneumonia) and OR52N2, an olfactory smell receptor in the nasal epithelium. In contrast, miR-3168 was significantly downregulated in COVID-19 ARDS (log2FC=-2.13, padjusted=0.003) and targeted interleukin-8 (CXCL8) in a completely activated network. Toll-like receptor 4 (TLR4) was inhibited in COVID-19 pneumonia by miR-146a-5p and upregulated in ARDS by let-7e-5p. Conclusion: EV-derived miRNAs might have important regulative functions in the pathophysiology of COVID-19: CXCL8 regulates neutrophil recruitment into the lung causing epithelial damage whereas activated TLR4, to which SARS-CoV-2 spike protein binds strongly, increases cell surface ACE2 expression and destroys type II alveolar cells that secrete pulmonary surfactants; both resulting in pulmonary-capillary leakage and ARDS. These miRNAs may serve as biomarkers or as possible therapeutic targets

CH4_4 Fluxes Derived from Assimilation of TROPOMI XCH4_4 in CarbonTracker Europe-CH4_4: Evaluation of Seasonality and Spatial Distribution in the Northern High Latitudes

Recent advances in satellite observations of methane provide increased opportunities for inverse modeling. However, challenges exist in the satellite observation optimization and retrievals for high latitudes. In this study, we examine possibilities and challenges in the use of the total column averaged dry-air mole fractions of methane (XCH$_4$) data over land from the TROPOspheric Monitoring Instrument (TROPOMI) on board the Sentinel 5 Precursor satellite in the estimation of CH4 fluxes using the CarbonTracker Europe-CH$_4$ (CTE-CH$_4$) atmospheric inverse model. We carry out simulations assimilating two retrieval products: Netherlands Institute for Space Research’s (SRON) operational and University of Bremen’s Weighting Function Modified Differential Optical Absorption Spectroscopy (WFM-DOAS). For comparison, we also carry out a simulation assimilating the ground-based surface data. Our results show smaller regional emissions in the TROPOMI inversions compared to the prior and surface inversion, although they are roughly within the range of the previous studies. The wetland emissions in summer and anthropogenic emissions in spring are lesser. The inversion results based on the two satellite datasets show many similarities in terms of spatial distribution and time series but also clear differences, especially in Canada, where CH$_4$ emission maximum is later, when the SRON’s operational data are assimilated. The TROPOMI inversions show higher CH$_4$ emissions from oil and gas production and coal mining from Russia and Kazakhstan. The location of hotspots in the TROPOMI inversions did not change compared to the prior, but all inversions indicated spatially more homogeneous high wetland emissions in northern Fennoscandia. In addition, we find that the regional monthly wetland emissions in the TROPOMI inversions do not correlate with the anthropogenic emissions as strongly as those in the surface inversion. The uncertainty estimates in the TROPOMI inversions are more homogeneous in space, and the regional uncertainties are comparable to the surface inversion. This indicates the potential of the TROPOMI data to better separately estimate wetland and anthropogenic emissions, as well as constrain spatial distributions. This study emphasizes the importance of quantifying and taking into account the model and retrieval uncertainties in regional levels in order to improve and derive more robust emission estimates