1,282 research outputs found
Numerical methods for the simulation of an aggregation-driven droplet size distribution
A droplet size distribution in a turbulent flow field is considered and modeled by means of a population balance system. This paper studies different numerical methods for the 4D population balance equation and their impact on an output of interest, the time-space-averaged droplet size distribution at the outlet which is known from experiments. These methods include different interpolations of the experimental data at the inlet, various discretizations in time and space, and different schemes for computing the aggregation integrals. It will be shown that notable changes in the output of interest might occur. In addition, the efficiency of the studied methods is discussed
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Numerical methods for the simulation of an aggregation-driven droplet size distribution
A droplet size distribution in a turbulent flow field is considered and
modeled by means of a population balance system. This paper studies different
numerical methods for the 4D population balance equation and their impact on
an output of interest, the time-space-averaged droplet size distribution at
the outlet which is known from experiments. These methods include different
interpolations of the experimental data at the inlet, various discretizations
in time and space, and different schemes for computing the aggregation
integrals. It will be shown that notable changes in the output of interest
might occur. In addition, the efficiency of the studied methods is discussed
Numerical simulations and measurements of a droplet size distribution in a turbulent vortex street
A turbulent vortex street in an air flow interacting with a disperse droplet population is investigated in a wind tunnel.
Non-intrusive measurement techniques are
used to obtain data for the air velocity and the droplet velocity. The process is modeled
with a population balance system consisting of the incompressible Navier--Stokes equations
and a population balance equation for the droplet size distribution. Numerical simulations
are performed that rely
on a variational multiscale method for turbulent flows, a direct discretization of the
differential operator of the population balance equation, and a modern technique for the
evaluation of the coalescence integrals. After having calibrated two unknown model parameters,
a very good agreement of the experimental and numerical results can be observed.
Eine turbulente Wirbelstra\ss e in einer Luftstr\"omung mit einer dispergierten Tr\"opfchenpopulation
wird in einem Windkanal untersucht. Nichtintrusive Messtechniken werden verwendet, um Daten bez\"uglich
der Luft-- und Tr\"opfchengeschwindigkeiten zu gewinnen. Der zu Grunde liegende Prozess wird mit
einem Populationsbilanzsystem modelliert, welches aus den inkompressiblen Navier--Stokes--Gleichungen
und einer Populationsbilanzgleichung f\"ur die Tr\"opfchenverteilungsdichte besteht. Numerische Simulationen
werden durchgef\"uhrt, welche ein variationelle Mehrskalenmethode f\"ur turbulente Str\"omungen,
eine direkte Diskretisierung des Differentialoperators der Populationsbilanzgleichung und ein
modernes Verfahren zur Berechnung der Koaleszensintegrale verwenden. Nachdem zwei unbekannte
Modellparameter kalibriert worden sind, kann eine sehr gute Ãœbereinstimmung der experimentellen
und numerischen Ergebnisse beobachtet werden
Suppression of electrical breakdown phenomena in liquid TriMethyl Bismuth based ionization detectors
Organometallic liquids provide good properties for ionization detectors.
TriMethyl Bismuth (TMBi) has been proposed as a detector medium with charge and
Cherenkov photon readout for Positron Emission Tomography. In this work, we
present studies for the handling of TMBi at different electric fields and under
different environmental conditions to find applicable configurations for the
suppression of electrical breakdowns in TMBi at room temperature. A simple
glass cell with two electrodes filled with TMBi was constructed and tested
under different operation conditions. Working at the vapour pressure of TMBi at
room temperature of about 40 mbar and electric fields of up to 20 kV/cm in
presence of a small oxygen contamination we found the formation of a discharge
channel in the liquid and a steady increase in the current. Further reduction
of pressure by pumping caused the TMBi to boil and a spontaneous combustion.
Eliminating the oxygen contamination led the TMBi under the same condition to
only decompose. When operating the setup under an argon atmosphere of 1 bar we
did not observe breakdowns of the electrical potential up to field strengths of
20 kV/cm. Still, in presence of a small oxygen contamination fluctuating
currents in the nA range were observed, but no decomposition or combustion. We
conclude from our experiments that TMBi at room temperature in a pure argon
atmosphere of 1 bar remains stable against electrical breakdown at least up to
electric field strengths of 20 kV/cm, presumably because the formation of
gaseous TMBi was prevented.Comment: 14 page, 8 figure
Towards a personalised approach in exercise-based cardiovascular rehabilitation: How can translational research help?: A ‘call to action’ from the Section on Secondary Prevention and Cardiac Rehabilitation of the European Association of Preventive Cardiology
The benefit of regular physical activity and exercise training for the prevention of cardiovascular and metabolic diseases is undisputed. Many molecular mechanisms mediating exercise effects have been deciphered. Personalised exercise prescription can help patients in achieving their individual greatest benefit from an exercise-based cardiovascular rehabilitation programme. Yet, we still struggle to provide truly personalised exercise prescriptions to our patients. In this position paper, we address novel basic and translational research concepts that can help us understand the principles underlying the inter-individual differences in the response to exercise, and identify early on who would most likely benefit from which exercise intervention. This includes hereditary, non-hereditary and sex-specific concepts. Recent insights have helped us to take on a more holistic view, integrating exercise-mediated molecular mechanisms with those influenced by metabolism and immunity. Unfortunately, while the outline is recognisable, many details are still lacking to turn the understanding of a concept into a roadmap ready to be used in clinical routine. This position paper therefore also investigates perspectives on how the advent of ‘big data’ and the use of animal models could help unravel interindividual responses to exercise parameters and thus influence hypothesis-building for translational research in exercisebased cardiovascular rehabilitation
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Monitoring the thermally induced transition from sp3-hybridized into sp2-hybridized carbons
The preparation of carbons for technical applications is typically based on a treatment of a precursor, which is transformed into the carbon phase with the desired structural properties. During such treatment the material passes through several different structural stages, for example, starting from precursor molecules via an amorphous phase into crystalline-like phases. While the structure of non-graphitic and graphitic carbon has been well studied, the transformation stages from molecular to amorphous and non-graphitic carbon are still not fully understood. Disordered carbon often contains a mixture of sp3-, sp2-and sp1-hybridized bonds, whose analysis is difficult to interpret. We systematically address this issue by studying the transformation of purely sp3-hybridized carbons, that is, nanodiamond and adamantane, into sp2-hybridized non-graphitic and graphitic carbon. The precursor materials are thermally treated at different temperatures and the transformation stages are monitored. We employ Raman spectroscopy, WAXS and TEM to characterize the structural changes. We correlate the intensities and positions of the Raman bands with the lateral crystallite size La estimated by WAXS analysis. The behavior of the D and G Raman bands characteristic for sp2-type material formed by transforming the sp3-hybridized precursors into non-graphitic and graphitic carbon agrees well with that observed using sp2-structured precursors
Identifying Activated T Cells in Reconstituted RAG Deficient Mice Using Retrovirally Transduced Pax5 Deficient Pro-B Cells
Various methods have been used to identify activated T cells such as binding of MHC tetramers and expression of cell surface markers in addition to cytokine-based assays. In contrast to these published methods, we here describe a strategy to identify T cells that respond to any antigen and track the fate of these activated T cells. We constructed a retroviral double-reporter construct with enhanced green fluorescence protein (EGFP) and a far-red fluorescent protein from Heteractis crispa (HcRed). LTR-driven EGFP expression was used to enrich and identify transduced cells, while HcRed expression is driven by the CD40Ligand (CD40L) promoter, which is inducible and enables the identification and cell fate tracing of T cells that have responded to infection/inflammation. Pax5 deficient pro-B cells that can give rise to different hematopoietic cells like T cells, were retrovirally transduced with this double-reporter cassette and were used to reconstitute the T cell pool in RAG1 deifcient mice that lack T and B cells. By using flow cytometry and histology, we identified activated T cells that had developed from Pax5 deficient pro-B cells and responded to infection with the bacterial pathogen Listeria monocytogenes. Microscopic examination of organ sections allowed visual identification of HcRed-expressing cells. To further characterize the immune response to a given stimuli, this strategy can be easily adapted to identify other cells of the hematopoietic system that respond to infection/inflammation. This can be achieved by using an inducible reporter, choosing the appropriate promoter, and reconstituting mice lacking cells of interest by injecting gene-modified Pax5 deficient pro-B cells
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