Employing pre-stress to generate finite cloaks for antiplane elastic waves

It is shown that nonlinear elastic pre-stress of neo-Hookean hyperelastic materials can be used as a mechanism to generate finite cloaks and thus render objects near-invisible to incoming antiplane elastic waves. This approach appears to negate the requirement for special cloaking metamaterials with inhomogeneous and anisotropic material properties in this case. These properties are induced naturally by virtue of the pre-stress. This appears to provide a mechanism for broadband cloaking since dispersive effects due to metamaterial microstructure will not arise.Comment: 4 pages, 2 figure

Neutral hydrogen gas, past and future star-formation in galaxies in and around the 'Sausage' merging galaxy cluster

CIZA J2242.8+5301 ($z = 0.188$, nicknamed 'Sausage') is an extremely massive ($M_{200}\sim 2.0 \times 10^{15}M_\odot$ ), merging cluster with shock waves towards its outskirts, which was found to host numerous emission-line galaxies. We performed extremely deep Westerbork Synthesis Radio Telescope HI observations of the 'Sausage' cluster to investigate the effect of the merger and the shocks on the gas reservoirs fuelling present and future star formation (SF) in cluster members. By using spectral stacking, we find that the emission-line galaxies in the 'Sausage' cluster have, on average, as much HI gas as field galaxies (when accounting for the fact cluster galaxies are more massive than the field galaxies), contrary to previous studies. Since the cluster galaxies are more massive than the field spirals, they may have been able to retain their gas during the cluster merger. The large HI reservoirs are expected to be consumed within $\sim0.75-1.0$ Gyr by the vigorous SF and AGN activity and/or driven out by the out-flows we observe. We find that the star-formation rate in a large fraction of H$\alpha$ emission-line cluster galaxies correlates well with the radio broad band emission, tracing supernova remnant emission. This suggests that the cluster galaxies, all located in post-shock regions, may have been undergoing sustained SFR for at least 100 Myr. This fully supports the interpretation proposed by Stroe et al. (2015) and Sobral et al. (2015) that gas-rich cluster galaxies have been triggered to form stars by the passage of the shock.Comment: Accepted to MNRAS, 14 pages, 9 figures, 7 table

The Brightening of Re50N: Accretion Event or Dust Clearing?

The luminous Class I protostar HBC 494, embedded in the Orion A cloud, is associated with a pair of reflection nebulae, Re50 and Re50N, which appeared sometime between 1955 and 1979. We have found that a dramatic brightening of Re50N has taken place sometime between 2006 and 2014. This could result if the embedded source is undergoing a FUor eruption. However, the near-infrared spectrum shows a featureless very red continuum, in contrast to the strong CO bandhead absorption displayed by FUors. Such heavy veiling, and the high luminosity of the protostar, is indicative of strong accretion but seemingly not in the manner of typical FUors. We favor the alternative explanation that the major brightening of Re50N and the simultaneous fading of Re50 is caused by curtains of obscuring material that cast patterns of illumination and shadows across the surface of the molecular cloud. This is likely occurring as an outflow cavity surrounding the embedded protostar breaks through to the surface of the molecular cloud. Several Herbig-Haro objects are found in the region.Comment: 8 pages, accepted by Ap

Molecular crosstalk between apoptosis, necroptosis, and survival signaling

Our current knowledge of the molecular mechanisms regulating the signaling pathways leading to cell survival, cell death, and inflammation has shed light on the tight mutual interplays between these processes. Moreover, the fact that both apoptosis and necrosis can be molecularly controlled has greatly increased our interest in the roles that these types of cell death play in the control of general processes such as development, homeostasis, and inflammation. In this review, we provide a brief update on the different cell death modalities and describe in more detail the intracellular crosstalk between survival, apoptotic, necroptotic, and inflammatory pathways that are activated downstream of death receptors. An important concept is that the different cell death processes modulate each other by mutual inhibitory mechanisms, serve as alternative back-up death routes in the case of a defect in the first-line cell death response, and are controlled by multiple feedback loops. We conclude by discussing future perspectives and challenges in the field of cell death and inflammation research

Artificially engineered capacitors for discrete high-frequency electronic circuitry

The concept of the artificially engineered capacitor (AEC) is presented as a 3D printable 3D capacitive component for the use in discrete RF/microwave electronic circuitry. The intention of the AEC concept is a highly customizable 3D printable component whose capacitance value is stable over a wider frequency band when compared to commercial alternatives. AECs can be viewed as impedance structures with predominantly capacitive characteristics. Both series and shunt AEC configurations are considered with simulation and measurement data along with equivalent circuit models. The tolerance of the equivalent capacitance over frequency is focused upon in this paper. Within the 40 % tolerance band from the nominal value an improvement of 26 % and 197 % frequency band was achieved for the series and shunt variants respectively when compared to a commercial alternative. Further simulations show that with finer 3D printing resolutions, this frequency stable bandwidth can be further increased. Finally, an example design application of a halfwavelength microstrip resonator is presented in which the AECs’ Q factor is measured, and the its equivalent circuits are implemented and validated via simulations and measurements.</div

Meta-atom loaded patch antenna

© 2018 Institution of Engineering and Technology. All rights reserved. The design of a meta-atom/metamaterial assisted patch antenna is presented. By utilizing strategically placed meta-atom in the patch antenna design miniaturization benefits can be gained with minimal impact to the total efficiency and the fractional bandwidth

Equivalent circuit analysis for 3D metamaterials with fringing field correction factor

© 2017 Institution of Engineering and Technology. All rights reserved. This paper presents a fringing field correction factor for circuit modelling techniques of metasurfaces and metamaterials. The theory is then applied to periodic three dimensional metamaterial meta-atoms. Equivalent circuits have been validated using CST Microwave Studio

A crystal plasticity study of the micromechanics of interfaces in TiAl

Submicron resolution deformation mapping techniques implemented into both micro and macro mechanical testing have recently provided measurements of the deformation of titanium aluminide at the microstructural scale. Experimental observations indicate that damage in such alloy strongly depends on the way shear localization associated with slip bands or twins is accommodated at the interface between colonies. Here, crystal plasticity finite element analysis has been carried out to simulate the relevant micromechanics. It is shown that it is possible to capture the deformation patterns observed at colony boundaries, therefore providing trustworthy predictions of the associated stress field. Different conditions are explored for which a given imposed deformation can be achieved with minimum stress concentration. The implications for microstructure engineering aimed to delay the nucleation of damage in such alloy are discussed