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Turbulent reactive flows laden with droplets appear in various energy systems but are difficult to understand and parametrize. Such flows involve interactions of turbulent fluctuations, phase changes, and chemical reactions that give rise to complex phenomena. To improve our knowledge, we performed direct numerical simulations of a canonical shear flow. It is composed of a hot, quiescent outer layer and a cold, turbulent inner layer that is laden with droplets. Due to the turbulent fluctuations, the droplets form clusters. Due to the high temperatures, the droplets evaporate quickly and flames emerge spontaneously at the interface of the two layers. We observed premixed flames that enclose droplet clusters and diffusion flames that enclose vapor pockets or single droplets. To examine these flame structures in more detail, we varied the droplet size, droplet loading, and shear rate. We found that the droplet size and droplet loading have significant effects, whereas the shear rate has only subtle effects. [ABSTRACT FROM AUTHOR]

This paper examines droplets that cluster and evaporate in reactive turbulence with direct numerical simulations. The flows are statistically homogeneous and isotropic with mass loadings of about 0.1, Stokes numbers of about 1, and Taylor-scale Reynolds numbers of about 40. Our simulation results reveal diffusion and premixed flames. When the mass loading is small or the Stokes number is large, clusters contain few droplets such that diffusion flames surround single droplets. However, when the mass loading is large or the Stokes number is small, clusters contain many droplets such that premixed flames propagate through clusters and diffusion flames surround clusters. [ABSTRACT FROM AUTHOR]

This paper investigates droplets that evaporate and cluster in shear turbulence with direct numerical simulations. The flows are statistically stationary and homogeneous, which reduces the physical complexity and simplifies the statistical analysis. The mass loadings are about 0.1, the Stokes numbers are about 1, and the Taylor-scale Reynolds numbers are about 60. The simulations show that the clusters are anisotropic and inclined toward the flow direction on large scales, but isotropic on small scales. When the mass loading increases, the clusters contain more droplets, but their size remains unchanged, and the droplets in clusters experience higher vapor mass fractions. When the Stokes number increases, the clusters contain fewer droplets and become larger, and the droplets in clusters experience lower vapor mass fractions. When the Reynolds number increases, the clusters contain more, smaller droplets and become smaller, and the inclination angles of the clusters change. [ABSTRACT FROM AUTHOR]

This letter investigates the clustering of particles in isotropic turbulence sustained by linear and spectral forcing. The Stokes numbers range from 0.1 to 100. The time series of particles are analyzed with autocorrelation functions of the particle velocity and local fluid velocity. The spatial distributions of particles are analyzed with probability density functions of Voronoï volumes. These statistics show significant differences between the clustering of particles in linearly and spectrally forced turbulence. [ABSTRACT FROM AUTHOR]

The present paper investigates droplet laden turbulent gas flows with point droplet direct numerical simulations. A novel flow configuration is presented, which allows us to simulate statistically stationary homogeneous isotropic regions of turbulent sprays. This configuration enables a physical analysis with small statistical errors under controllable conditions. The length scales of clusters are analyzed with spectra of the droplet number density and vapor mass fraction fluctuations. The local conditions in clusters and voids are analyzed with probability density functions of the local droplet number density, local vapor mass fraction, and evaporation rate. Effects of the mass loading and Stokes number on the clustering of droplets and the mixing of vapor are characterized, and the compositions of clusters and voids are examined. As the mass loading increases from 2.5% to 12.5%, the fluctuations in the vapor mass fraction and droplet number density increase almost equally at all length scales. Clusters contain more droplets that together release more vapor, but their characteristic size remains unchanged. As the mean Stokes number increases from 1 to 4, the fluctuations in the vapor mass fraction and droplet number density decrease predominantly at small length scales. Clusters contain fewer droplets that together release less vapor, and their characteristic size increases. At a mass loading of 7.5% and a mean Stokes number of 2, clusters contain considerably more droplets and vapor than voids. Droplets located in clusters therefore evaporate more slowly than droplets located in voids. [ABSTRACT FROM AUTHOR]

Due to its superior mechanical properties, castability, machinability and price, the number of applications for high silicon solid solution strenghtened ferritic ductile cast iron is strongly increasing. However, the solid solution strengthening is limited to a maximum of 4.3 wt% silicon. A higher silicon content leads to a decline of UTS, YTS and to a strong decline in elongation at fracture. In order to analyze the fundamental mechanism, Y2 and Y4 standard DI specimens were casted with silicon contents varying between 3.95 and 5.63 wt%. For a comprehensive analysis, all investigations were conducted on specimens manufactured from the same castings. With increasing silicon, the fracture type changes from ductile to brittle, whereas the graphite nodularity, nodule size and nodule count as well as the amount of harmful phases cannot be connected to the observed embrittlement phenomena. Therefore a ductile (3.95 wt% Si) and a brittle specimen (5.36 wt% Si) where investigated via TEM diffraction. It was shown that the amount of B2-ordered phases in the matrix strongly increases with increasing Si-Content. Moreover, reflexes of DO 3 -ordered phases could only be observed in the brittle specimen. Silicon long-range-ordering can be concluded as the main reason for the upper limit of silicon solid solution strengthening in ductile iron grades in accordance to previous findings for silicon steels. The presented study paves the way for mechanistically based new alloy design concepts for high silicon ductile iron. [ABSTRACT FROM AUTHOR]

18F-Labeled aromatic amino acids exhibit great potential for diagnostic applications using positron emission tomography. However, the introduction of 18F into aromatic compounds remains challenging, and novel fluorination methods facilitating easy access to 18F-labeled arenes are highly sought after. In recent years, novel metal-mediated fluorination methods have been reported and transferred into radiochemistry. Based on Cu-mediated radiofluorination, a two-step synthesis of no-carrier-added (n.c.a.) 6-[18F]fluoro- l-tryptophan was developed. 6-[18F]Fluoro- l-tryptophan was synthesized with an overall radochemical yield of 16 ± 4% within 110 min and a specific activity of 280 GBq µmol-1. The radiochemical purity was more than 99 %. The developed method allowed access to radiofluorinated tryptophan derivatives in high radiochemical yields and opens new ways to provide radiofluorinated amino acids. Furthermore, the reaction conditions were optimized to facilitate automation. [ABSTRACT FROM AUTHOR]

Several 18 F-labeled aromatic amino acids have been developed primarily for tumor imaging with positron-emission-tomography (PET). Also, 18 F-labeled tryptophan derivatives were synthesized by electrophilic 18 F-fluorination or by introducing a [ 18 F]fluoroalkyl group. Here, a 3-step method for a nucleophilic radiosynthesis of 4-[ 18 F]fluoro- l -tryptophan was developed. A carbonyl activated precursor containing a chiral amino acid building block was radiofluorinated by isotopic exchange, followed by removal of the activating formyl group by reductive decarbonylation and subsequent cleavage of the building block under acidic conditions. The title compound was obtained within 100 min with a radiochemical yield of about 13%, a molar activity of >70 MBq/mmol and an enantiomeric excess of >99%. [ABSTRACT FROM AUTHOR]

Focuses on the considerations made by the U.S. government on international fusion power project. Expansion on the research and development (R&D) tax credit in Great Britain; Production of neutrons by powerful accelerator to probe the structure of proteins; Persuasion of firms to shift R&D operations to the island through the proposed rebates.

Highlights the convention for scientists and policy-makers to discuss global bioethics. Expansion of bioethics education and training; Discussion of the commercial use of biotechnology; Proposal to strengthen ethical restrictions on embryo research.

A 34 year old woman, who had suffered from hypertension for 16 years, presented with systolic blood pressure up to 220 mm Hg and diastolic blood pressure up to 120 mm Hg, accompanied by headaches, dizziness, and paraesthesia in both arms. Auscultation revealed an aortic systolic murmur with radiation to the back. Doppler echocardiography showed a pressure gradient of 66 mm Hg in the descending part of the aorta. The suspicion of congenital postductal aortic coarctation was confirmed by transoesophageal echocardiography. Because of the impression of a complex structure of the stenosis, magnetic resonance imaging and dynamic three dimensional computed tomographic angiography were performed preoperatively where a siphon-like 75 % stenosis with pre- and poststenotic dilation of the aorta were clearly shown. Because of the complex structure of the stenosis, surgery instead of balloon dilatation was recommended. Intraoperatively, the minimal lumen diameter in the stenotic region was 3 mm. A resection of the aorta was performed with an interposition of a Vascutek prosthesis. The patient recovered uneventfully and has no residual hypertension.

The article presents the production and investigation of a bio-inspired metal–metal-composite inspired by the pomelo peel. The pomelo fruit is able to withstand a fall externally undamaged, even from heights of over 10 m most likely due to the hierarchical structuring of its foamy peel, which represents a complex composite structure. Especially the foam’s struts, which are cells from the biological point of view, consisting of liquid-filled cores and shells (cell walls) with relatively high strength, give point to a technical adaptation. With the objective to make use of the pomelo’s ability to absorb impact energy, the design of a pomelo strut is abstracted and transferred to aluminium/aluminium–silicon-alloy (A356) composite tensile specimens. Testing results show that the properties of the individual materials can successfully be combined. After fracture of the outer high strength, but less ductile A356-shell, the applied stress can still be absorbed by deformation of the inner highly ductile pure aluminium. As a result, the ductility of a bio-inspired composite is significantly higher compared with an A356 tensile specimen. By varying the mould and casting temperatures, the relationship between the production parameters and the quality of the composite is shown. A reduced mould and casting temperature lowers the dendrite arm spacing in the A356 outer shell of the composite material thus leading to an increased tensile strength. The detected metal bond between the two materials is mainly influenced by the interaction between the casting and the mould temperature. [ABSTRACT FROM AUTHOR]

Lamb-shift polarimeters are used to measure the nuclear polarization of protons and deuterons at energies of a few keV. In combination with an ionizer, the polarization of hydrogen and deuterium atoms was determined after taking into account the loss of polarization during the ionization process. The present work shows that the nuclear polarization of hydrogen or deuterium molecules can be measured as well, by ionizing the molecules and injecting the H2+ (or D2+) ions into the Lamb-shift polarimeter. [ABSTRACT FROM AUTHOR]

Examines the association between intravenous erythromycin and ventricular tachycardia with Q-T prolongation. Reference to the case of a woman admitted to the hospital with fever, pneumonia and severe respiratory distress; Factors contributing to erythromycin toxicity; Avoidance of erythromycin injection to minimize the danger of toxic plasma concentrations.