Numerical Simulations of Solid Circulation Characteristics in an Internally Circulating Elevated Fluidized Bed

A twin‐chamber internally circulating elevated fluidized bed (EFB) with one chamber elevated higher than the other within a single vessel is simulated using a two‐fluid model. Two EFB configurations termed as reaction chamber (RC)‐elevated and heat exchange chamber (HEC)‐elevated is evaluated. The effect of chamber elevation, variation of superficial velocities, and interchanging the two chambers are investigated and the results are quantified in terms of solid flux G_s. By increasing the RC gas velocity U_R at constant HEC velocity U_H, G_s is increased in both EFBs while an opposite behavior is observed by increasing U_H at constant U_R. Variation of the chamber elevation as well as interchanging the chambers also affects the performance of the two EFBs.     

Extension of the kinetic theory of granular flow to include dense quasi-static stresses

Fluidized bed technology has diverse industrial applications ranging from the gasification of coal in the power industry to chemical reactions for the plastic industry. Due to their complex chaotic non-linear behaviour understanding the hydrodynamic behaviour in fluidized beds is often limited to pressure drop measurements and a mass balance of the system. Computational fluid dynamics has the capability to model multiphase flows and can assist in understanding gas-solid fluidized beds by modeling their hydrodynamics. The multiphase Eulerian-Eulerian gas-solid model, extended and validated here improves on the kinetic theory of granular flow by including a closure term for the quasi-static stress associated with the long term particle contact at high solid concentrations. Similar quasi-static models have been widely applied to slow granular flow such as chute flow, flow down an incline plane and geophysical flow. However combining the kinetic theory of granular flow and the quasi-static stress model for the application of fluidized beds is limited. The objective of the present paper is to compare two quasi-static stress models to the experimental fluidized bed data of Bouillard et al. [4]. A quasi-static granular flow model (QSGF) initially developed by Gray and Stiles [18] is compared to the commonly used Srivastava and Sundaresan [37]. Both models show good agreement with the experimental bubble diameter and averaged porosity profiles. However only the QSGF model shows a distinct asymmetry in the bubble shape which was documented by Bouillard et al. [4].     

Empfehlungen des Arbeitskreises 6.1 “Geotechnik der Deponiebauwerke” der Deutschen Gesellschaft für Geotechnik e. V. (DGGT)

Der Arbeitskreis “Geotechnik der Deponiebauwerke” hat in 5 Themengruppen bisher 76 Empfehlungen zur Planung, zum Bau und zur Qualitätsüberwachung von Abfalldeponien veröffentlicht. Der diesjährige Bericht zu den Arbeitsergebnissen stellt den Bezug zwischen der im Juli in Kraft getretenen Verordnung zur Vereinfachung des Deponierechts und den GDA‐Empfehlungen her. Recommendations of the DGGT Committee “Geotechnics of Landfill Structures”. The Technical Committee “Geotechnics of Landfill Structures” of the German Geotechnical Society published up to now 76 recommendations (GDA‐Geotechnical Landfill Recommendations) structured in 5 main issues. This report on the recent results of the working group delivers the link between the requirements of the new German Directive on the Landfilling of Waste and the detailed technical standard described in the GDA‐Recommendations.     

Molecular biology and congenital hand anomalies: from molecules and mutations to man

Potassium channels have been implicated in central roles in activity-dependent neural plasticity. The giant fiber escape pathway of Drosophila has been established as a model for analyzing habituation and its modification by memory mutations in an identified circuit. Several genes in Drosophila encoding K+ channel subunits have been characterized, permitting examination of the contributions of specific channel subunits to simple conditioning in an identified circuit that is amenable to genetic analysis. Our results show that mutations altering each of four K+ channel subunits (Sh, slo, eag, and Hk) have distinct effects on habituation at least as strong as those of dunce and rutabaga, memory mutants with defective cAMP metabolism (). Habituation, spontaneous recovery, and dishabituation of the electrically stimulated long-latency giant fiber pathway response were shown in each mutant type. Mutations of Sh (voltage-gated) and slo (Ca2+-gated) subunits enhanced and slowed habituation, respectively. However, mutations of eag and Hk subunits, which confer K+-current modulation, had even more extreme phenotypes, again enhancing and slowing habituation, respectively. In double mutants, Sh mutations moderated the strong phenotypes of eag and Hk, suggesting that their modulatory functions are best expressed in the presence of intact Sh subunits. Nonactivity-dependent responses (refractory period and latency) at two stages of the circuit were altered only in some mutants and do not account for modifications of habituation. Furthermore, failures of the long-latency response during habituation, which normally occur in labile connections in the brain, could be induced in the thoracic circuit stage in Hk mutants. Our work indicates that different K+ channel subunits play distinct roles in activity-dependent neural plasticity and thus can be incorporated along with second messenger "memory" loci to enrich the genetic analysis of learning and memory.     

Runtime analysis of a binary particle swarm optimizer

We investigate the runtime of a binary Particle Swarm Optimizer (PSO) for optimizing pseudo-Boolean functions f:{0,1}ⁿ→R. The binary PSO maintains a swarm of particles searching for good solutions. Each particle consists of a current position from {0,1}ⁿ, its own best position and a velocity vector used in a probabilistic process to update its current position. The velocities for a particle are then updated in the direction of its own best position and the position of the best particle in the swarm.We present a lower bound for the time needed to optimize any pseudo-Boolean function with a unique optimum. To prove upper bounds we transfer a fitness-level argument that is well-established for evolutionary algorithms (EAs) to PSO. This method is applied to estimate the expected runtime for the class of unimodal functions. A simple variant of the binary PSO is considered in more detail for the test function OneMax, showing that there the binary PSO is competitive to EAs. An additional experimental comparison reveals further insights.     

A systematic review on the use of quantitative imaging to detect cancer therapy adverse effects in normal-appearing brain tissue

Cancer therapy for both central nervous system (CNS) and non-CNS tumors has been previously associated with transient and long-term cognitive deterioration, commonly referred to as ‘chemo fog’. This therapy-related damage to otherwise normal-appearing brain tissue is reported using post-mortem neuropathological analysis. Although the literature on monitoring therapy effects on structural magnetic resonance imaging (MRI) is well established, such macroscopic structural changes appear relatively late and irreversible. Early quantitative MRI biomarkers of therapy-induced damage would potentially permit taking these treatment side effects into account, paving the way towards a more personalized treatment planning.

This systematic review (PROSPERO number 224196) provides an overview of quantitative tomographic imaging methods, potentially identifying the adverse side effects of cancer therapy in normal-appearing brain tissue. Seventy studies were obtained from the MEDLINE and Web of Science databases. Studies reporting changes in normal-appearing brain tissue using MRI, PET, or SPECT quantitative biomarkers, related to radio-, chemo-, immuno-, or hormone therapy for any kind of solid, cystic, or liquid tumor were included. The main findings of the reviewed studies were summarized, providing also the risk of bias of each study assessed using a modified QUADAS-2 tool. For each imaging method, this review provides the methodological background, and the benefits and shortcomings of each method from the imaging perspective. Finally, a set of recommendations is proposed to support future research.