SU(5) Gravitating Monopoles

Spherically symmetric solutions of the SU(5) Einstein-Yang-Mills-Higgs system are constructed using the harmonic map ansatz \cite{IS}. This way the problem reduces to solving a set of ordinary differential equations for the appropriate profile functions.Comment: 12 pages, 3 Figure

Astroglial-axonal interactions during early stages of myelination in mixed cultures using in vitro and ex vivo imaging techniques

<b>Background</b><p></p> Myelination is a very complex process that requires the cross talk between various neural cell types. Previously, using cytosolic or membrane associated GFP tagged neurospheres, we followed the interaction of oligodendrocytes with axons using time-lapse imaging in vitro and ex vivo and demonstrated dynamic changes in cell morphology. In this study we focus on GFP tagged astrocytes differentiated from neurospheres and their interactions with axons.<p></p> <b>Results</b><p></p> We show the close interaction of astrocyte processes with axons and with oligodendrocytes in mixed mouse spinal cord cultures with formation of membrane blebs as previously seen for oligodendrocytes in the same cultures. When GFP-tagged neurospheres were transplanted into the spinal cord of the dysmyelinated shiverer mouse, confirmation of dynamic changes in cell morphology was provided and a prevalence for astrocyte differentiation compared with oligodendroglial differentiation around the injection site. Furthermore, we were able to image GFP tagged neural cells in vivo after transplantation and the cells exhibited similar membrane changes as cells visualised in vitro and ex vivo.<p></p> <b>Conclusion</b><p></p> These data show that astrocytes exhibit dynamic cell process movement and changes in their membrane topography as they interact with axons and oligodendrocytes during the process of myelination, with the first demonstration of bleb formation in astrocytes

Design and simulation of an actively controlled building unit

[EN] Conflagrations often lead to catastrophic phenomena in several countries across the globe during the summer period. Such phenomena advocate for multidisciplinary research activities including on- and off-site investigations of data-collection and evaluation as well as event-based virtual scenarios and action solutions respectively. In this framework, a temporary building unit is proposed to host single researchers in remote environments. The unit consists of a lightweight structure that can be easily erected and actively controlled. The unit is supported on four diagonals anchored to the ground and it has a circular horizontal and an elliptical vertical section. The core consists of a glass-fiber polymer (GFRP) cone base at its lower level, vertically positioned GFRP bending-active strips and a GFRP cone at its upper level. The cones are vertically connected through tendons that are activated by linear motion actuators. The structure consists of a double layer gridshell of GFRP bending-active rods and a semitransparent ETFE membrane with embedded thin-film CIGS photovoltaics. Sensors on the membrane transfer continuously the external wind pressure to a control system for the adjustment of the spatial shape of the unit through the tendons. The paper displays the design of the unit in its components, and emphasizes on its adaptivity features with regard to the structural deformability in parametric associative design logic. The methodology followed serves as a basis for further iterative analyses with regard to the form optimization of the structural elements, the system’s load-deformation and dynamic behavior.Ioannidou, P.; Kontovourkis, O.; Phocas, MC. (2023). Design and simulation of an actively controlled building unit. Editorial Universitat Politècnica de València. 250-259. https://doi.org/10.4995/VIBRArch2022.2022.1513025025

(Why) Do Central Banks Care About Their Profits?

We document that central banks are significantly more likely to report slightly positive profits than slightly negative profits. The discontinuity in the profit distribution is (i) more pronounced amid greater political or public pressure, the public’s receptiveness to more extreme political views, and agency frictions arising from governor career concerns, but absent when no such factors are present, and (ii) correlated with more lenient monetary policy inputs and greater inflation. These findings indicate that profitability concerns, while absent from standard theoretical models of central banking, are both present and effective in practice, and inform a theoretical debate about monetary stability and the effectiveness and riskiness of non-traditional central banking

Reduced dynamics of Ward solitons

The moduli space of static finite energy solutions to Ward's integrable chiral model is the space $M_N$ of based rational maps from \CP^1 to itself with degree $N$. The Lagrangian of Ward's model gives rise to a K\"ahler metric and a magnetic vector potential on this space. However, the magnetic field strength vanishes, and the approximate non--relativistic solutions to Ward's model correspond to a geodesic motion on $M_N$. These solutions can be compared with exact solutions which describe non--scattering or scattering solitons.Comment: Final version, to appear in Nonlinearit

Radon measurements along active faults in the Langadas Basin, northern Greece

A network of three radon stations has been established in the Langadas Basin, northern Greece for radon monitoring by various techniques in earthquake prediction studies. Specially made devices with plastic tubes including Alpha Tracketch Detectors (ATD) were installed for registering alpha particles from radon and radon decay products exhaled from the ground, every 2 weeks, by using LR-115, type II, non-strippable Kodak films, starting from December 1996. Simultaneous measurements started using Lucas cells alpha spectrometer for instantaneous radon measurements in soil gas, before and after setting ATDs at the radon stations. Continuous monitoring of radon gas exhaling from the ground started from the middle of August 1999 by using silicon diode detectors, which simultaneously register meteorological parameters, such as rainfall, temperature and barometric pressure. The obtained data were studied together with the data of seismic events, such as the magnitude, <i>M_L</i>, of earthquakes that occurred at the Langadas Basin during the period of measurements, as registered by the Laboratory of Geophysics, Aristotle University of Thessaloniki, in order to find out any association between them

Deep stratosphere-to-troposphere transport (STT) over SE Europe: a complex case study captured by enhanced ⁷Be concentrations at the surface of a low topography region

International audienceIn this study we present a complex case study of a Stratosphere-to-Troposphere Transport (STT) event down to the surface of a low topography region in Northern Greece, during the second fortnight of March 2000. During this event our surface station at Livadi (23°15 E/40°32 N, 850 m a.s.l.), was influenced by very different synoptic systems developing over Eastern Europe, N. America and the N. Atlantic, the last one evolving to a cut-off low over France/Spain. This is the first study, to our knowledge, that presents a down to the surface STT event in the eastern Mediterranean. The intrusion is primarily captured with the use of the cosmogenic radionuclide 7Be, which increased to 9.07 mBq m-3 and 9.37 mBq m-3 on 30 and 31 March 2000, respectively. A 7Be concentration of around 8 mBq m-3 recorded during parallel measurements at Thessaloniki (20 m a.s.l.) gives strong evidence that air of stratospheric origins has even gone down to sea level. A rapid increase of 10?15 ppb is also observed in the surface ozone concentration on 31 March 2000. The relative increase of both tracers is consistent with a volume fraction of stratospheric air at the surface of about 5%, but the substantial increase in 7Be flags more clearly the event. Trajectory analyses, in conjunction with the evolution of the synoptic situation described by potential vorticity maps, are used for the exact identification of the different intrusions and the attribution of each intruding parcel of stratospheric air to a certain filament of high PV. Finally, the persistency of the stratospheric layers in the troposphere is another interesting point of this case study. The vast majority of the trajectories spent 7?10 days in the troposphere before reaching the surface at Livadi station

Eco-friendly location of small hydropower

We address the problem of locating small hydropower dams in an environmentally friendly manner. We propose the use of a multi-objective optimization model to maximize total hydropower production, while limiting negative impacts on river connectivity. Critically, we consider the so called “backwater effects” that dams have on power generation at nearby upstream sites via changes in water surface profiles. We further account for the likelihood that migratory fish and other aquatic species can successfully pass hydropower dams and other artificial/natural barriers and how this is influenced by backwater effects. Although naturally represented in nonlinear form, we manage through a series of linearization steps to formulate a mixed integer linear programing model. We illustrate the utility of our proposed framework using a case study from England and Wales. Interestingly, we show that for England and Wales, a region heavily impacted by a large number of existing river barriers, that installation of small hydropower dams fitted with even moderately effective fish passes can, in fact, create a win-win situation that results in increased hydropower and improved river connectivity