Selected experimental methods for determining droplet parameters from the intensity distribution of scattered light: A review

The present paper summarizes some experimental methods, which have been developed using the results of calculations based on the theory of Gustav Mie. As examples two regions of the scattered light are considered in more detail. The intensity distribution in the forward hemisphere for scattering angles 30 ≤ θ ≤ 60 shows maxima, which can be identified as regular fringes on a screen. The spacing between the fringes is a measure for the droplet size. In the intensity distribution of the backward hemisphere the region of the first rainbow can be found. In the rainbow region a main maximum, subsidiary maxima and a ripple structure can be identified. The angular position of the main maximum is a measure for the refractive index of the droplet. The angular distance between the subsidiary maxima and the angular distance between the ripples both are a function of droplet size. A comparison with other size measurement methods gives information about the sphericity of the droplet. An evaporating droplet shows for instance oscillations of the rainbow position due to morphology dependent resonances. The oscillation frequency is proportional to the evaporation rate.     

Simulation of flow in an exact replica of a diseased human carotid artery

We report on results of ongoing efforts directed towards the development of a computational model for flow in diseased human carotid arteries. Recent visualizations of the flow in an exact replica of an actual diseased artery have revealed the presence of complex, three-dimensional flow structures characterized by multiple recirculation zones and the formation of unstable jets in both the internal and external arteries. Even though the flow conditions at inlet to the artery were kept steady, the experiments showed that the resulting flow downstream of the inlet was unsteady and chaotic. The present computations aim to determine whether such behavior can be captured with a practical finite-volume computational model, and to examine the impact of spatial and temporal resolution on the quality of simulations.     

A comparative study of the steady state and the transient liquid crystal technique for determining the heat transfer coefficients in a bend

For the investigation of internal and external heat transfer thermochromic liquid crystals (TLC's) have become a very commonly used tool. Today, mainly two different experimental methods with TLC's are in use: The steady state TLC method measuring the wall temperature according to a constant heat flux produced by a heater foil and the transient TLC method measuring the time response of the wall temperature due to a sudden change of the fluid temperature. In the present paper the two different measurement techniques are compared for a very complex 3D flow inside a 180°‐turn of a two‐pass cooling system. From theoretical considerations, the general difference in the heat transfer because of the different wall boundary conditions is shown.     

Parametrization of the homogeneous ice nucleation rate for the numerical simulation of multiphase flow

Homogeneous ice nucleation in supercooled water is studied with the classical nucleation theory (CNT). The nucleated ice particles are assumed to possess physical properties of metastable cubic ice. The comparison with literature data on homogeneous ice nucleation rates shows a good agreement between CNT predictions and experimental nucleation rates. The CNT predicted nucleation rate, critical cluster radius, and critical nucleation work are parametrized for use in numerical simulations of the freezing process of supercooled water droplets. (© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Helical Nanographenes Containing an Azulene Unit: Synthesis,Crystal Structures,and Properties

Three unprecedented helical nanographenes ( 1 , 2 , and 3 ) containing an azulene unit are synthesized. The resultant helical structures are unambiguously confirmed by X‐ray crystallographic analysis. The embedded azulene unit in 2 possesses a record‐high twisting degree (16.1°) as a result of the contiguous steric repulsion at the helical inner rim. Structural analysis in combination with theoretical calculations reveals that these helical nanographenes manifest a global aromatic structure, while the inner azulene unit exhibits weak antiaromatic character. Furthermore, UV/Vis‐spectral measurements reveal that superhelicenes 2 and 3 possess narrow energy gaps ( 2 : 1.88 eV; 3 : 2.03 eV), as corroborated by cyclic voltammetry and supported by density functional theory (DFT) calculations. The stable oxidized and reduced states of 2 and 3 are characterized by in‐situ EPR/Vis–NIR spectroelectrochemistry. Our study provides a novel synthetic strategy for helical nanographenes containing azulene units as well as their associated structures and physical properties.     

Selective Separation of Lithium,Magnesium and Calcium using 4-Phosphoryl Pyrazolones as pH-Regulated Receptors

Ensuring continuous and sustainable lithium supply requires the development of highly efficient separation processes such as LLE (liquid-liquid extraction) for both primary sources and certain waste streams. In this work, 4-phosphoryl pyrazolones are used in an efficient pH-controlled stepwise separation of Li⁺ from Ca²⁺, Mg²⁺, Na⁺ and K⁺. The factors affecting LLE process, such as the substitution pattern of the extractant, diluent/water distribution, co-ligand, pH, and speciation of the metal complexes involved, were systematically investigated. The maximum extraction efficiency of Li⁺ at pH 6.0 was 94 % when Mg²⁺ and Ca²⁺ were previously separated at pH<5.0, proving that the separation of these ions is possible by simply modulating the pH of the aqueous phase. Our study points a way to separation of lithium from acid brine or from spent lithium ion battery leaching solutions, which supports the future supply of lithium in a more environmentally friendly and sustainable manner.