Simulating coronal condensation dynamics in 3D

We present numerical simulations in 3D settings where coronal rain phenomena take place in a magnetic configuration of a quadrupolar arcade system. Our simulation is a magnetohydrodynamic simulation including anisotropic thermal conduction, optically thin radiative losses, and parametrised heating as main thermodynamical features to construct a realistic arcade configuration from chromospheric to coronal heights. The plasma evaporation from chromospheric and transition region heights eventually causes localised runaway condensation events and we witness the formation of plasma blobs due to thermal instability, that evolve dynamically in the heated arcade part and move gradually downwards due to interchange type dynamics. Unlike earlier 2.5D simulations, in this case there is no large scale prominence formation observed, but a continuous coronal rain develops which shows clear indications of Rayleigh-Taylor or interchange instability, that causes the denser plasma located above the transition region to fall down, as the system moves towards a more stable state. Linear stability analysis is used in the non-linear regime for gaining insight and giving a prediction of the system's evolution. After the plasma blobs descend through interchange, they follow the magnetic field topology more closely in the lower coronal regions, where they are guided by the magnetic dips.Comment: 47 pages, 59 figure

The Space Environment and Atmospheric Joule Heating of the Habitable Zone Exoplanet TOI700-d

We investigate the space environment conditions near the Earth-size planet TOI~700~d using a set of numerical models for the stellar corona and wind, the planetary magnetosphere, and the planetary ionosphere. We drive our simulations using a scaled-down stellar input and a scaled-up solar input in order to obtain two independent solutions. We find that for the particular parameters used in our study, the stellar wind conditions near the planet are not very extreme -- slightly stronger than that near the Earth in terms of the stellar wind ram pressure and the intensity of the interplanetary magnetic field. Thus, the space environment near TOI700-d may not be extremely harmful to the planetary atmosphere, assuming the planet resembles the Earth. Nevertheless, we stress that the stellar input parameters and the actual planetary parameters are unconstrained, and different parameters may result in a much greater effect on the atmosphere of TOI700-d. Finally, we compare our results to solar wind measurements in the solar system and stress that modest stellar wind conditions may not guarantee atmospheric retention of exoplanets.Comment: accepted to Ap

Fabrication and modeling of a continuous-flow microfluidic device for on-chip DNA amplification

This paper was presented at the 3rd Micro and Nano Flows Conference (MNF2011), which was held at the Makedonia Palace Hotel, Thessaloniki in Greece. The conference was organised by Brunel University and supported by the Italian Union of Thermofluiddynamics, Aristotle University of Thessaloniki, University of Thessaly, IPEM, the Process Intensification Network, the Institution of Mechanical Engineers, the Heat Transfer Society, HEXAG - the Heat Exchange Action Group, and the Energy Institute.The fabrication process and heat transfer computations for a continuous flow microfluidic device for DNA amplification by polymerase chain reaction (PCR) are described. The building blocks are thin polymeric materials aiming at a low cost and low power consumption device. The fabrication is performed by standard pattern transfer techniques (lithography and etching) used for microelectronics fabrication. The DNA sample flows in a meander shaped microchannel formed on a 100μm thick polyimide (PI) layer through three temperature regions defined by the integrated resistive heaters. The heat transfer computations are performed in a unit cell of the device. They show that, for the fabricated device, the variation of the temperature inside the channel zones where each step (denaturation, annealing, or extension) of PCR occur is less than 1.3K. This variation increases when the thickness of the PI layer increases. The computations also show that similar Silicon-based devices lead to lower temperature difference between the heaters and the DNA sample compared to the polymer-based fabricated device. However, the power consumption is estimated much greater for Silicon-based devices.This work was co-financed by Hellenic Funds and by the European Regional Development Fund (ERDF) under the Hellenic National Strategic Reference Framework (NSRF) 2007-2013, according to Contract no. MICRO2-45 of the Project “Microelectronic Components for Lab-on-chip molecular analysis instruments for genetic and environmental applications” within the Programme "Hellenic Technology Clusters in Microelectronics – Phase-2 Aid Measure"

Stellar energetic particles in the magnetically turbulent habitable zones of TRAPPIST-1-like planetary systems

Planets in close proximity to their parent star, such as those in the habitable zones around M dwarfs, could be subject to particularly high doses of particle radiation. We have carried out test-particle simulations of ~GeV protons to investigate the propagation of energetic particles accelerated by flares or travelling shock waves within the stellar wind and magnetic field of a TRAPPIST-1-like system. Turbulence was simulated with small-scale magnetostatic perturbations with an isotropic power spectrum. We find that only a few percent of particles injected within half a stellar radius from the stellar surface escape, and that the escaping fraction increases strongly with increasing injection radius. Escaping particles are increasingly deflected and focused by the ambient spiralling magnetic field as the superimposed turbulence amplitude is increased. In our TRAPPIST-1-like simulations, regardless of the angular region of injection, particles are strongly focused onto two caps within the fast wind regions and centered on the equatorial planetary orbital plane. Based on a scaling relation between far-UV emission and energetic protons for solar flares applied to M dwarfs, the innermost putative habitable planet, TRAPPIST-1e, is bombarded by a proton flux up to 6 orders of magnitude larger than experienced by the present-day Earth. We note two mechanisms that could strongly limit EP fluxes from active stars: EPs from flares are contained by the stellar magnetic field; and potential CMEs that might generate EPs at larger distances also fail to escape.Comment: 17 pages, 12 figures, ApJ in pres

Temperature-modulated solution-based synthesis of copper oxide nanostructures for glucose sensing

Glucose sensors are widely applied in society as an effective way to diagnose and control diabetes by monitoring the blood glucose level. With advantages in stability and efficiency in glucose detection, non-enzymatic glucose sensors are gradually replacing their enzymatic counterparts and copper(ii) oxide (CuO) is a leading material. However, previous work extensively shows that even if the synthesis of CuO nanostructures is performed under nominally similar conditions, entirely different nanostructured products are obtained, resulting in varying physical and chemical properties of the final product, thereby leading to a differing performance in glucose detection. This work investigates the temperature dependence of a wet chemical precipitation synthesis for CuO nanostructures with the resulting samples showing selectivity for glucose in electrochemical tests. X-ray diffraction (XRD), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS) demonstrate that all products are predominantly CuO, with some contribution from Cu(OH)2 and other surface species varying across synthesis temperatures. The most important change with increasing synthesis temperature is that the overall nanostructure size changes and the morphology shifts from nanoneedles to nanoparticles between 65 and 70 °C. This work helps to understand the critical relationship between synthesis temperature and final nanostructure and can explain the seemingly random nanostructures observed in the literature. The variations are key to controlling sensor performance and ultimately offering further development in copper oxide-based glucose sensors