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High Voltage Pulsed DBD Effects on the Aerodynamic Performances and on the Shock Buffet
No full textThe applications of surface dielectric barrier discharge plasma actuators, (DBD), have known a considerable interest recently in the field of flow control. In general, such actuators consist of two electrodes separated by an insulation covering the lower electrode entirely, while the upper electrode remains exposed to the flow. This actuator is driven either by a high frequency AC-voltage or by fast rising voltage pulses. In the former case, a sinusoidal voltage of several kilovolts with frequencies of a few hundred to several thousand Hertz is applied to the electrodes. The actuator generates a body force tangentially to the surface which provides a variety of possibilities to manipulate or to create flows. Inside an existing mean flow, the actuator can be used to impart momentum into a boundary layer and to alter the velocity, the turbulence distribution or to control the transition from laminar to turbulent. The amplitude of the force, created by the plasma actuator can be altered by varying the driving voltage. In the case of the fast rising voltage pulse (FRP) driven DBD actuators, pulses with an amplitude of several kilovolts and with a rise/decay time (from 10%-90% max. voltage) of a few nanoseconds are applied. The wall jet’s velocities of these actuators are quite low, and the actuator acts as an equivalent additional energy source. A weak compression wave is generated at the edge of the flow/air-exposed electrode which prevails whatever the flow regime, and seems to be the predominant mechanism of these FRP actuators. A major part of the experimental work up to now using surface dielectric barrier discharge (DBD) actuators was carried out in flow speeds up to 30 m/s, mostly with actuators driven by AC-voltage. The main identified mechanism of successful control with such actuators at such low speeds is the induced ionic wind effect, which can attain velocities limited to a few meters per second, hence influencing mainly only very low speed flows [8]. With increasing flow speed, however, this influence becomes insufficient and the actuator’s control capacity generated by these AC-driven DBD has not yet achieved expectations [2]. Recently, DBD actuators driven by nanosecond pulsed FRP-DBD have been successfully used to reattach leading edge separation in high speed flows [1]. Even though this is not a phenomenon frequently encountered under realistic flight conditions these findings encouraged to investigate possible effects of FRP-DBD on shock buffet, which is a problem pertaining to transonic cruise flight conditions, and is of interest in compressor design. In order to evaluate whether FRP-DBD actuators have beneficial effects on the aerodynamic performance in high subsonic flows and in particular in mitigating shock buffeting phenomena, a series of experimental investigations has been carried out in the CIRA PT-1 transonic wind tunnel. The flow speed was varied between M=0.4 and M=0.85 at angles of attack from -2° to 8° and Reynolds numbers between Re=1.7∙106 and Re=2.5∙106. Tests were performed on a constant wing span model of a BAC 3-11 supercritical airfoil, with 11% of maximum thickness, able to reach shock buffet conditions at Mach numbers in the range (M=0.75-0.88), at low angles of attack (0-5°) and Reynolds number about 2 - 3 million, [3].[4]. During the tests, steady and unsteady pressure measurements were acquired to obtain quantitative measurements. This paper provides a short description of the experimental setup, presents the main results regarding the effect of the plasma presence on the aerodynamic performance and on the shock buffet phenomenon.CRPPGTTLINSP
Stress alleviates reduced expression of cell adhesion molecules (NCAM, L1), and deficits in learning and corticosterone regulation of apolipoprotein E knockout mice
No full textCell adhesion molecules (CAMs) involved in synaptic changes underlying learning and memory processes, are implicated in the effect of stress on behavioural performance. The present study was designed to test the hypothesis that (i) expression of CAMs is apolipoprotein E- (apoE) genotype dependent and (ii) repeated exposure to stress modulates the synthesis of CAMs in an apoE-genotype dependent manner. Using ELISA we tested this hypothesis and measured expression of NCAM and L1 in different brain regions of naive and stressed apolipoprotein E-knockout (apoE0/0) and C57Bl6 (wild-type) mice. Naive apoE0/0 mice had elevated basal morning corticosterone and ACTH concentrations and decreased expression of NCAM and L1 compared to wild-type mice. Repeated exposure of mice to rats, as the common stressor, alleviated the reduction in expression of CAMs in apoE0/0 mice; seven days after the last rat exposure, expression of NCAM was increased in frontal brain and hippocampus whereas expression of L1 was increased in hippocampus and cerebellum. Rat stress attenuated the elevation of basal morning corticosterone concentration in apoE0/0 mice towards concentrations detected in wild-type mice. Moreover, rat stress improved learning and memory of apoE0/0 mice in the water maze. In conclusion, repeated exposure to stress eliminated apoE-genotype-related differences in expression of CAMs. Under these same conditions the differences in cognitive performance and corticosterone concentrations were abolished between wild type and apoE0/0 mice.LGCAuthor address: Division of Medical Pharmacology, LACDR and Leiden University Medical Center, Leiden University, PO Box 9503, 2300 RA Leiden, The Netherlands
Das Verhalten von Gebäuden mit Stahlbetontragwänden während des Erdbebens Centro-Sur in Chile am 27.2.2010 (On the behaviour of RC wall buildings during the Centro-Sur earthquake in Chile on February 27, 2010)
No full textEES
The reconstruction theorem in Besov spaces
No full textThe theory of regularity structures [9] sets up an abstract framework of modelled distributions generalising the usual Holder functions and allowing one to give a meaning to several ill-posed stochastic PDEs. A key result in that theory is the so-called reconstruction theorem: it defines a continuous linear operator that maps spaces of modelled distributions into the usual space of distributions. In the present paper, we extend the scope of this theorem to analogues to the whole class of Besov spaces B-p,q(gamma) with non-integer regularity indices. We then show that these spaces behave very much like their classical counterparts by obtaining the corresponding embedding theorems and Schauder-type estimates. (C) 2017 Elsevier Inc. All rights reserved.PROPD
TGR5 signalling promotes mitochondrial fission and beige remodelling of white adipose tissue
No full textUPSCHOONJAN
Accurate mapping of chromatic dispersion distribution along optical fibres with spatial resolution below 100 m
No full textTHEVESCI-STI-L
Boosting the Sensitivity of Ligand-Protein Screening by NMR of Long-Lived States
No full textA new NMR method for the study of ligand protein interactions exploits the unusual lifetimes of long-lived states (LLSs). The new method provides better contrast between bound and free ligands and requires a protein-ligand ratio ca. 25 times lower than for established T-1 rho methods, thus saving on costly proteins. The new LLS method was applied to the screening of inhibitors of urokinase-type plasminogen activator (uPA), which is a prototypical target of cancer research. With only 10 mu M protein, a dissociation constant (K-D) of 180 +/- 20 nM was determined for the strong ligand (inhibitor) UK-18, which can be compared with K-D = 157 +/- 39 nM determined by the established surface plasmon resonance method.LRMBLPP
Assessment of simplified 2D grain growth models from numerical experiments based on a level set framework
No full textIn this paper, the results of a 2D full field grain growth model are compared with several 2D mean field grain growth models (Burke and Turbull model and Hillert/Abbruzzese model), using simplified assumptions of isotropic grain boundary energy and mobility, and under the absence of precipitates. The full field model is based on a finite element formulation combined with a level set framework, used to describe the granular structure, and model grain boundary motion through a diffusion formulation. The initial digital microstructures are created using a coupled "Voronoï-Laguerre/dense sphere packing" algorithm, which allows to obey different types of initial grain size distributions, in the considered 2D context. The results show that only the Hillert/Abbruzzese model accurately describes grain growth kinetics for all considered grain size distributions. The validity of the Burke and Turnbull model is, on the contrary, restricted to specific distributions. © 2014 Elsevier Inc. All rights reserved.LMT