The low Reynolds number turbulent flow and mixing in a confined impinging jet reactor

Turbulent mixing takes an important role in chemical engineering, especially when the chemical reaction is fast compared to the mixing time. In this context a detailed knowledge of the flow field, the distribution of turbulent kinetic energy (TKE) and its dissipation rate is important, as these quantities are used for many mixing models. For this reason we conduct a direct numerical simulation (DNS) of a confined impinging jet reactor (CIJR) at Re = 500 and Sc = 1. The data is compared with particle image velocimetry (PIV) measurements and the basic flow features match between simulation and experiment. The DNS data is analysed and it is shown that the flow is dominated by a stable vortex in the main mixing duct. High intensities of turbulent kinetic energy and dissipation are found in the impingement zone which decrease rapidly towards the exit of the CIJR. In the whole CIJR the turbulence is not in equilibrium. The strong mixing in the impingement zone leads to a rapid development of a monomodal PDF. Due to the special properties of the flow field, a bimodal PDF is generated in cross-sections downstream the impingement zone, that slowly relaxes under relaminarising conditions. The time required for meso-mixing is dominating the overall mixing performance.     

Finite strains at the tip of a crack in a sheet of hyperelastic material: III. General bimaterial case

In this last in a series of three papers, we summarize an asymptotic analysis of the near-tip stress and deformation fields for an interface crack between two sheets of Generalized Neo-Hookean materials. This investigation, which is consistent with the nonlinear elastostatic theory of plane stress, allows for an arbitrary choice, on both sides of the three parameters characterizing this class of hyperelastic materials. The first three terms of the approximation series are obtained, showing the existence of a non-oscillatory and contact-free solution to the interface crack problem. The analytical results are compared with a full-field solution obtained numerically using the finite element method.     

Full-field speckle pattern image correlation with B-Spline deformation function

A full-field speckle pattern image correlation method is presented that will determine directly the complete, two-dimensional deformation field during the image correlation process on digital images obtained using computer vision systems. In this work, a B-Spline function is used to represent the object deformation field throughout the entire image area. This is an improvement over subset-based image correlation methods by implicitly maintaining position and derivative continuity constraints among subsets up to a specified order. The control point variables within the B-Spline deformation function are optimized iteratively with the Levenberg-Marquardt method to achieve minimum disparity between the predicted and actual deformed images. Results have shown that the proposed method is computationally efficient, accurate and robust. The general framework of this method can be applied ton-dimensional image correlation systems that solve for multi-dimension vector fields.     

Order and Pattern Formation in Psychotherapy

In an empirical analysis of the dynamics of psychotherapy processes, concepts and tools from self-organization theory are applied. Our focus is on pattern formation in the therapy system, i.e. the system constituted by the interaction dynamics of therapist and patient. The hypothesis of pattern formation explored is based on data sets of 28 psychotherapy courses (10 behavioral, 3 client-centered, 9 heuristic, 6 schema-oriented; 40 to 90 weekly sessions). Patients' and therapists' therapy session records are analyzed (33 variables addressing various aspects of the therapeutic relationship, of progress within and outside the therapy setting). Multivariate methods are implemented to test the key hypothesis of self-organization theory, namely the reduction of degrees of freedom of a system. Consistent with this hypothesis, a significant reduction of degrees of freedom is found when the initial and final sessions of the therapies are compared. Correspondingly, Landsberg order increased significantly in the course of therapies. Given these findings, the explorative question of how this self-organizing property relates to therapy outcome is investigated. We find a significant positive association with various outcome measures, such as: therapist's and client's evaluations of success (direct change measures), feelings of guilt, anxiety, social potence, depression (pre-post effect sizes), and others. These results suggest that order is related to therapy outcome. In our interpretation, order is a dynamical attribute of the therapeutic alliance to be considered as a promising therapy process variable.     

Eine neue Theorie zur Rotationsumwandlung der n-Paraffine (Kinkentheorie)

Zusammenfassung Die Rotationsumwandlung der n-Paraffine wird als Übergang eines Paraffinkristalls mit 2gl-Kinken als Baufehler in einen Kinkblockkristall theoretisch behandelt. Die dabei mit zwei Methoden diskutierten Näherungen — für kurze und für sehr lange Ketten — liefern Aussagen über Umwandlungstemperatur, Umwandlungswärme und Volumensprung, die den experimentellen Werten entsprechen, die Kettenlängenabhängigkeit annähernd beschreiben und die Konzentrationsabhängigkeit der Umwandlungstemperatur sowie der Umwandlungswärme in Paraffinmischungen richtig wiedergeben.Vorgetragen auf der Jahrestagung der Deutschen Rheologen in Berlin-Dahlem vom 7.–10. Juni 1966.Herrn Prof.H. O. Kneser danken wir für die Förderung dieser Arbeit, der Deutschen Forschungsgemeinschaft für finanzielle Unterstützung.     

Robotic heavy metal anodic stripping voltammetry: ease and efficacy for trace lead and cadmium electroanalysis

A novel strategy for the automation of trace lead (Pb²⁺) and cadmium (Cd²⁺) anodic stripping voltammetry (ASV) is described. This was achieved using an electrode assembly comprising a small standard reference electrode, a Pt wire counter electrode, and an in situ bismuth-plated pencil lead working electrode for ASV in a robotic device adapted for measurements in a 24-well microtiter plate format. The movement of the electrode assembly through individual wells was by computer-controlled micropositioning, and each microtiter plate run included a sequence of electrode pretreatment, water rinsing, and simultaneous Pb²⁺ and Cd²⁺ ASV measurements. Analyte concentrations down to 2 μg/L (Pb²⁺) and 20 μg/L (Cd²⁺) could be measured in drinking and tap water, a wastewater reference material and a soil sample, with an accuracy and standard deviation typical of stripping analysis. This robotic electrochemical strategy offers automated trace metal analysis with simple instrumentation and is suggested as an option for routine use in analytical laboratories such as those providing environmental heavy metal testing services.     

Search of manifolds of nonsymmetric Valley-Ridge inflection points on the potential energy surface of HCN

The potential energy surface (PES) of a chemical reaction contains Valley-Ridge inflection points (VRI) if??an often occurring phenomenon??the reaction path branches. In this paper, we introduce a new direct search method to detect these VRI points. It is based on an inductive execution of Gauss?CNewton steps. For the first time, we were able to find not only singular nonsymmetric VRI points, but also whole VRI manifolds on the PES of HCN.     

Chlorine‐Enhanced Surface Mobility of Au(100)

Motivated by experimental studies of two‐dimensional Ostwald ripening on Au(100) electrodes in chlorine‐containing electrolytes, we have studied diffusion processes using density functional theory. We find that chlorine has a propensity to temporary form AuCl complexes, which diffuse significantly faster than gold adatoms. With and without chlorine, the lowest activation energy is found for the exchange mechanism. Chlorine furthermore reduces the activation energy for the detachment from kink sites. Kinetic Monte Carlo simulations were performed on the basis of extensive density functional theory calculations. The island‐decay rate obtained from these Monte Carlo simulations, as well as the decay rate obtained from the theoretical activation energies and frequency factors when inserted into analytical solutions for Ostwald ripening, are in agreement with experimental island‐decay rates in chlorine‐containing electrolytes.     

Influence of the Metal Ion on the Two‐Photon Absorption Properties of Lanthanide Complexes Including Near‐IR Emitters

The synthesis of tris(2‐thenoyltrifluoroacetonate)lanthanide(III) complexes featuring a diethylaminostyryl‐2,2′‐bipyridine coligand was achieved for lanthanum; the near‐infrared (NIR) emitters neodymium, erbium, and ytterbium; and the transition‐metal yttrium. The photophysical properties were thoroughly studied, and it was demonstrated that the conjugated bipyridine ligand acts as a good antenna for the sensitization of the NIR emitters. The two‐photon absorption (TPA) properties of all five complexes were investigated by using both two‐photon excited fluorescence and the Z‐scan method. We demonstrate that the nature of the rare earth ion has almost no influence on the TPA properties centered on the conjugated bipyridyl ligand. Finally, we show that Yb^III is sensitized by a two‐photon antenna effect, and that Nd^III is mostly sensitized by a one‐photon process involving direct excitation of forbidden f–f transitions.