Terahertz Absorption of Nematic Liquid Crystals

We present the first systematic study of cyanobiphenyls (CBs) and the phenylcyclohexanes in the range between 50 cm^-1 (1.5 THz) and 500 cm^-1 (15 THz). The impact of the alkyl chain length and of variations in the core structure on the spectrum is investigated using liquid crystals from the cyanobiphenyl and phenylcyclohexane families. Our measurements are supported by calculations based on density functional theory. This enables us to shine light on the vibrational dynamics of liquid crystal molecules in the terahertz frequency range.     

Optimizing counter-terror operations: Should one fight fire with “fire” or “water”?

This paper deals dynamically with the question of how recruitment to terror organizations is influenced by counter-terror operations. This is done within an optimal control model, where the key state is the (relative) number of terrorists and the key controls are two types of counter-terror tactics, one (“water”) that does not and one (“fire”) that does provoke recruitment of new terrorists. The model is nonlinear and does not admit analytical solutions, but an efficient numerical implementation of Pontryagin's minimum principle allows for solution with base case parameters and considerable sensitivity analysis. Generally, this model yields two different steady states, one where the terror organization is nearly eradicated and one with a high number of terrorists. Whereas water strategies are used at almost any time, it can be optimal not to use fire strategies if the number of terrorists is below a certain threshold.     

Attentional Capture by an Unannounced Color Singleton Depends on Expectation Discrepancy.

Eight experiments examined the conditions under which a color singleton that is presented for the 1st time without prior announcement captures attention. The main hypothesis is that an unannounced singleton captures attention to the extent that it deviates from expectations. This hypothesis was tested within a visual-search paradigm in which set-size effects were used to infer attentional capture. The results showed that attentional capture by an unannounced color singleton was due to a mismatch with expectations concerning the color of the object and not due to its being a singleton. Thus, the results imply that theories of attention have to consider expectation discrepancy as a determinant of attention shifts. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

On the ferrite-austenite equilibrium in the Fe-Cu system

The thermodynamics of ferrite containing dissolved copper is analyzed theoretically, taking into account the effect of copper on the Curie temperature. By combination with experimental information on the solubility of copper in austenite, this model is used to predict the solubility of copper in ferrite. The result shows good agreement with experimental data but indicates that the data should be extrapolated in a manner different from that which has been previously suggested. The effects of copper and cobalt on the relative stability of the α and γ phases in iron-rich alloys are compared. It is concluded that their difference is mainly caused by the difference in their effects on the Curie temperature of α-iron.     

Interpretation und Modellierung der Temperaturverteilung in einer Sicker- und Grundwassermeßstelle der Braunkohlentagebaukippe Cospuden

The time and depth depending temperature distribution in an isolated expolratory hole in the dump of former open-cast lignite mine Cospuden is analyzed and interpreted. By means of hydrodynamical modeling several model assumptions are tested on following influences: seasons, hydraulic situation, geochemical processes, sampling regime, specific features of drilling, and support of bore hole. Best correspondence between measured temperature distribution and model assumptions is obtained by the following primary processes: seasonal influences of earth's surface and reactive processes in the dump. Then are favored: Slow exothermic reactions with an high extant of reaction heat in the depth of 2 to 6 m, slow strongly exothermic reactions above the piezometric water level in 9 to 13 m depth with a maximum near 11 m, and simultaneously run of fast endothermic and slow weakly exothermic reactions in the zone of saturation of the bore hole. It is tried to assign chemical reactions to these processes.     

Development of Endothelial Cell Networks in 3D Tissues by Combination of Melt Electrospinning Writing with Cell‐Accumulation Technology

A remaining challenge in tissue engineering approaches is the in vitro vascularization of engineered constructs or tissues. Current approaches in engineered vascularized constructs are often limited in the control of initial vascular network geometry, which is crucial to ensure full functionality of these constructs with regard to cell survival, metabolic activity, and potential differentiation ability. Herein, the combination of 3D‐printed poly‐ε‐caprolactone scaffolds via melt electrospinning writing with the cell‐accumulation technique to enable the formation and control of capillary‐like network structures is reported. The cell‐accumulation technique is already proven itself to be a powerful tool in obtaining thick (50 µm) tissues and its main advantage is the rapid production of tissues and its ease of performance. However, the applied combination yields tissue thicknesses that are doubled, which is of outstanding importance for an improved handling of the scaffolds and the generation of clinically relevant sample volumes. Moreover, a correlation of increasing vascular endothelial growth factor secretion to hypoxic conditions with increasing pore sizes and an assessment of the formation of neovascular like structures are included.     

Reduced-order preconditioning for bidomain simulations

Simulations of the bidomain equations involve solving large, sparse, linear systems of the form Ax = b. Being an initial value problems, it is solved at every time step. Therefore, efficient solvers are essential to keep simulations tractable. Iterative solvers, especially the preconditioned conjugate gradient (PCG) method, are attractive since memory demands are minimized compared to direct methods, albeit at the cost of solution speed. However, a proper preconditioner can drastically speed up the solution process by reducing the number of iterations. In this paper, a novel preconditioner for the PCG method based on system order reduction using the Arnoldi method (A-PCG) is proposed. Large order systems, generated during cardiac bidomain simulations employing a finite element method formulation, are solved with the A-PCG method. Its performance is compared with incomplete LU (ILU) preconditioning. Results indicate that the A-PCG estimates an approximate solution considerably faster than the ILU, often within a single iteration. To reduce the computational demands in terms of memory and run time, the use of a cascaded preconditioner was suggested. The A-PCG was applied to quickly obtain an approximate solution, and subsequently a cheap iterative method such as successive overrelaxation (SOR) is applied to further refine the solution to arrive at a desired accuracy. The memory requirements are less than those of direct LU but more than ILU method. The proposed scheme is shown to yield significant speedups when solving time evolving systems.     

Interfacial charges and electric field distribution in organic hetero-layer light-emitting devices

The electric field distribution in organic hetero-layer light-emitting devices based on N,N^′-diphenyl-N,N^′-bis(1-naphtyl)-1,1^′-biphenyl-4,4^′-diamine (NPB) and 8-tris-hydroxyquinoline aluminium (Alq₃) has been investigated under different bias conditions using capacitance–voltage measurements. Although this method yields primarily information on the differential capacitance, the data give clear evidence for the presence of negative interfacial charges with a density of 6.8×10¹¹e cm⁻² at the NPB/Alq₃ interface at large reverse bias. This leads to a jump of the electric field at the interface and a non-uniform field distribution in the hetero-layer device.