Interactive simulation and visualization of massless, massed, and evaporating particles

Most software packages available for particle tracing focus on visualizing steady or unsteady vector fields by using massless particle trajectories. For many applications, however, the use of massed and evaporating particles would provide a model of physical processes that could be used in product testing or design. In this article we describe the TrackPack toolkit, which provides an integrated interface for computing massless, massed, and evaporating particle trajectories in steady flow. In all cases, we assume a noncoupled model and compute particle trajectories through an existing vector field by numerically integrating with forward Euler, fourth-order Runge-Kutta, or an analytic streamline calculation. The TrackPack software effort was motivated by an industrial application to model pollution control systems in industrial boilers. We briefly describe the project and the visualization environment, and we demonstrate the necessity for massed, evaporating models in the application.     

Psoriatic arthritis in children

Juvenile psoriatic arthritis has been accepted as a disease entity. Arthritis and psoriasis occur in the same individual more often than would be expected by pure coincidence and appear in about 2% to 4% of children with chronic arthritis. A genetic background becomes obvious with a family history of psoriasis in half of the patients, but no consistent HLA associations have been detected. A joint pattern with asymmetric arthritis of big and small joints and a high rate of dactylitis is typical for the disease. However, juvenile psoriatic arthritis presents in subsets that are similar to the subgroups of juvenile chronic arthritis but occurs with different frequencies. Oligoarticular courses dominate in psoriatic patients, and systemic manifestations are extremely rare. For children with symmetric polyarthritis who are at risk to develop severe disabling disease, early aggressive therapy should be considered.     

The determination of the second and third virial coefficients frompVT-X data of binary systems

The compressibility factor of multicomponent systems can be obtained in terms of virial coefficients of the pure components and their binary mixtures. This paper concerns a method with which, for that purpose, the second and third virial coefficients for these binaries have been determined from experimental data. From useful data, second and third virial coefficients are obtained as a quadratic function of the temperature. The density domain for which these results are applicable is discussed. When ample data are available, results for a sample mixture can be obtained in a straightforward manner. Nevertheless, it is shown that under much less favorable conditions—sometimes even when pure-component data are lacking—fairly good results can still be obtained. In that case, the choice for an appropriate combining rule has to be considered carefully. Finally, the involvement of ternary mixture data, both obtained experimentally and predicted by the equation, is considered.Paper presented at the Tenth Symposium on Thermophysical Properties, June 20–23, 1988, Gaithersburg, Maryland, U.S.A.     

Comment on “Digital signature with (t, n) shared verificationbased on discrete logarithms”

For the original article see ibid., vol. 29, no. 24, p. 2094-95 (1993). The digital signature scheme with (r, n) shared verification proposed by Harn in the aforementioned article can be easily forged universally, as shown by Lee and Chang (see ibid., vol. 31, no. 3, p. 176-7, 1995). In the reply of Harn (see ibid., vol. 31, no. 3, p. 177, 1995), two different solutions to overcome this attack were presented. The commenters discuss the first solution and show that the second solution (and related ones) are flawed, because with a simple attack one can forge this scheme and related ones universally. Finally, they propose a simple solution to countermeasure all attacks     

Peroxidative and glutathione status in uterus and placenta after normal and pathological pregnancy

The content and amount of the allergologic diagnostic measures differs more and more in comparison to the causal treatment and consulting of the patient during care. The tasks of quality assurance may include the development of criteria for evaluated diagnostic measures and the resulting treatment concepts with respect to an interdisciplinary approach. The cooperation with patient groups should be integrated in such a concept. The basic allergologic care, the interaction with allergologic centers, the supervision and coordination with facilities of in-patient care have to be newly defined in the frame of a structural discussion.     

Galvanic Transformation Dynamics in Heterostructured Nanoparticles

Corrosion is a significant problem for the stability of structural metals and potentially for functional nanomaterials in operating environments. When two metals with different electrochemical potentials form a junction, galvanic corrosion occurs, resulting in the sacrificial dissolution of the metal with a higher oxidation potential (lower electrode potential). Here, it is shown that bimetallic hetero-nanostructures composed of phase-segregated metals undergo galvanic corrosion in aqueous environments. Such selective etching of the sacrificial metal in heterojunction particles leads to the formation of unusual and kinetically stabilized half-spheroid particles. By using a fluid cell and in situ scanning transmission electron microscopy, a two-stage corrosion process can be observed where the Cu experiences a fractal breakdown before the Ag corrodes due to the lack of a protective oxide layer. However, when treated with a mild Ar plasma, the stability of these structures against corrosion is enhanced due to the conversion of the amorphous native oxide to a denser, thin layer of CuO on the Cu surface. Taken together, this work highlights the importance of considering the effects of galvanic corrosion on the stability of multicomponent nanoparticles, and it shows how mass transport in a nanoscale system is influenced by redox processes.     

Efficient wave propagation simulation on quadtree meshes using SBFEM with reduced modal basis

We apply a combination of the transient scaled boundary finite element method (SBFEM) and quadtree‐based discretization to model dynamic problems at high frequencies. We demonstrate that the current formulation of the SBFEM for dynamics tends to require more degrees of freedom than a corresponding spectral element discretization when dealing with smooth problems on regular domains. Thus, we improve the efficiency of the SBFEM by proposing a novel approach to reduce the number of auxiliary variables for transient analyses. Based on this improved SBFEM, we present a modified meshing procedure, which creates a quadtree mesh purely based on the geometry and allows arbitrary sizes and orders of elements, as well as an arbitrary number of different materials. The discretization of each subdomain is created automatically based on material parameters and the highest frequency of interest. The transition between regions of different properties is straightforward when using the SBFEM. The proposed approach is applied to image‐based analysis with a particular focus on geological models. Copyright © 2016 John Wiley & Sons, Ltd.     

Macroscopic simulation and experimental measurement of melt pool characteristics in selective electron beam melting of Ti-6Al-4V

Selective electron beam melting of Ti-6Al-4V is a promising additive manufacturing process to produce complex parts layer-by-layer additively. The quality and dimensional accuracy of the produced parts depend on various process parameters and their interactions. In the present contribution, the lifetime, width and depth of the pools of molten powder material are analyzed for different beam powers, scan speeds and line energies in experiments and simulations. In the experiments, thin-walled structures are built with an ARCAM AB A2 selective electron beam melting machine and for the simulations a thermal finite element simulation tool is used, which is developed by the authors to simulate the temperature distribution in the selective electron beam melting process. The experimental and numerical results are compared and a good agreement is observed. The lifetime of the melt pool increases linearly with the line energy, whereby the melt pool dimensions show a nonlinear relation with the line energy.     

Tailored Systemic Therapy for Colorectal Cancer Liver Metastases

Liver metastases are the most common site of metastatic spread in colorectal cancer. Current treatment approaches involve effective systemic therapies in combination with surgical and/or interventional strategies. Multimodal strategies greatly improved clinical outcomes of patients with metastatic colorectal cancer over the last decades. Identification of predictive and prognostic biomarkers helped to comprehensively refine individual targeted treatment approaches and resulted in median overall survival rates of 30 months or longer. Current guidelines, thus, recommend treatment selection according to patients’ performance status, tumor localization and stage as well as the tumor’s molecular and genetic status. Here, we outline the latest developments in molecular decision-making for patients with upfront resectable, potentially or initially unresectable and non/never-resectable colorectal cancer liver metastases.