Petrogenesis and geodynamic significance of the volcanism of the Northern Ethiopian plateau

After the pioneering works of Morgan during the Seventies (Morgan, 1971) a renewed interest on mantle plumes has arisen in the last decades with controversial hypotheses on depths of plume provenance, triggering mechanisms, shape and size of the convective mantle, as well as relationships with hot spots, Large Igneous Province (LIP), and rift volcanism (Ernst & Buchan, 2001; Foulger et al., 2005; Foulger & Jurdy, 2007). In this regard, the Ethiopian-Yemen basaltic plateau represents a very convenient natural laboratory to study Continental Flood Basalts (CFB) and the tectonomagmatic processes that led to the formation of the Red Sea, Gulf of Aden and East African rift system, from Oligocene to Present. This area is centred on the Afar hot spot which appears unequivocally related to a deep plume originating in the lower mantle (Courtillot et al., 2003, Davaille et al., 2005). A multidisciplinary study has been developed on the Ethiopian Oligocene Plateau, integrating field data with detailed sampling of selected basaltic sections, geochemical and petrological results, as well as GIS processing, in order to provide new insights on the mantle plume region from which plateau basalts were generated. The integrated approach includes: 1. Digitalization, georeferentiation and projection in the UTM system WGS-84 Datum of the geological map 1:2.000.000 by Merla et al. (1973), and subsequent creation shapefiles for each geological formations related to the Oligocene CFB and a shapefile containing the UTM coordinates of the studied samples. The topographic values (z) were obtained by NASA Shuttle Radar Tomography Mission (SRTM) rasters. 2. Petrochemical analyses of samples collected along selected plateau sections and petrological classification allowed definition of a zonal arrangement of volcanics with Low-Ti tholeiites in the NW part and High-Ti transitional basalts (and picrites) in the SE sector of the Ethiopian plateau. Calculation of the erupted volumes of each magma-type was carried out. 3. Thermobarometric methods and the Niu & Batiza (1991) empirical model were applied to the various magmatypes in order to constrain their degree of partial melting (F), temperature (T), as well as initial (P ) and final (P ) pressures of melt generation in a mantle upwelling region. Calculations were carried out on selected representative near-primary magmas, i.e. in equilibrium with peridotite mantle sources. Petrogenetic modelling is also used to figure out the plume influenced mantle region from which northern Ethiopia CFB were generated

Investment, replacement and scrapping in a vintage capital model with embodied technological change

This paper analyzes and compares two alternative policies of determining the service life and replacement demand for vintage equipment under embodied technological change. The policies are the infinite-horizon replacement and the transitory replacement ending with scrapping. The corresponding vintage capital models are formulated in the dynamic optimization framework. These two approaches lead to different estimates of the duration of replacements and the impact of technological change on the equipment service life.vintage capital equipment; embodied technological change; service life; replacement; scrapping

Molecular dynamics simulations of reflection and adhesion behavior in Lennard-Jones cluster deposition

We conduct molecular dynamics simulations of the collision of atomic clusters with a weakly-attractive surface. We focus on an intermediate regime, between soft-landing and fragmentation, where the cluster undergoes deformation on impact but remains largely intact, and will either adhere to the surface (and possibly slide), or be reflected. We find that the outcome of the collision is determined by the Weber number, We i.e. the ratio of the kinetic energy to the adhesion energy, with a transition between adhesion and reflection occurring as We passes through unity. We also identify two distinct collision regimes: in one regime the collision is largely elastic and deformation of the cluster is relatively small but in the second regime the deformation is large and the adhesion energy starts to depend on the kinetic energy. If the transition between these two regimes occurs at a similar kinetic energy to that of the transition between reflection and adhesion, then we find that the probability of adhesion for a cluster can be bimodal. In addition we investigate the effects of the angle of incidence on adhesion and reflection. Finally we compare our findings both with recent experimental results and with macroscopic theories of particle collisions.Comment: 18 pages, 13 figure

Quantum dynamics of a vibrational mode of a membrane within an optical cavity

Optomechanical systems are a promising candidate for the implementation of quantum interfaces for storing and redistributing quantum information. Here we focus on the case of a high-finesse optical cavity with a thin vibrating semitransparent membrane in the middle. We show that robust and stationary optomechanical entanglement could be achieved in the system, even in the presence of nonnegligible optical absorption in the membrane. We also present some preliminary experimental data showing radiation-pressure induced optical bistability.Comment: 6 pages, 2 figures. Work presented at the conference QCMC 2010 held on 19-23 July 2010 at the University of Queensland, Brisbane, Australi

Quantum dynamics of a high-finesse optical cavity coupled with a thin semi-transparent membrane

We study the quantum dynamics of the cavity optomechanical system formed by a Fabry-Perot cavity with a thin vibrating membrane at its center. We first derive the general multimode Hamiltonian describing the radiation pressure interaction between the cavity modes and the vibrational modes of the membrane. We then restrict the analysis to the standard case of a single cavity mode interacting with a single mechanical resonator and we determine to what extent optical absorption by the membrane hinder reaching a quantum regime for the cavity-membrane system. We show that membrane absorption does not pose serious limitations and that one can simultaneously achieve ground state cooling of a vibrational mode of the membrane and stationary optomechanical entanglement with state-of-the-art apparatuses.Comment: 14 pages, 7 figure

Optomechanically induced transparency in membrane-in-the-middle setup at room temperature

We demonstrate the analogue of electromagnetically induced transparency in a room temperature cavity optomechanics setup formed by a thin semitransparent membrane within a Fabry-P\'erot cavity. Due to destructive interference, a weak probe field is completely reflected by the cavity when the pump beam is resonant with the motional red sideband of the cavity. Under this condition we infer a significant slowing down of light of hundreds of microseconds, which is easily tuned by shifting the membrane along the cavity axis. We also observe the associated phenomenon of electromagnetically induced amplification which occurs due to constructive interference when the pump is resonant with the blue sideband.Comment: 5 pages, 4 figure

Optimal Equipment Replacement and Scrapping Under Improving Technology

The rational replacement management of hi-tech equipment is an important problem of technology management. This paper analyzes and compares two alternative policies for determining the service life and replacement demand of industrial equipment under improving technology. These policies lead to different estimates of the impact of new technology on the replacement policies and equipment service life

Structural transitions in a NiTi alloy: a multistage loading-unload cycle

NiTi shape memory alloys (SMAs) are increasingly used in many engineering and medical applications, because they combine special functional properties, such as shape memory effect and pseudoelasticity, with good mechanical strength and biocompatibility. However, the microstructural changes associated with these functional properties are not yet completely known. In this work a NiTi pseudo-elastic alloy was investigated by means of X-ray diffraction in order to assess micro-structural transformations under mechanical uniaxial deformation. The structure after complete shape recovery have been compared with initial state

Optomechanical sideband cooling of a thin membrane within a cavity

We present an experimental study of dynamical back-action cooling of the fundamental vibrational mode of a thin semitransparent membrane placed within a high-finesse optical cavity. We study how the radiation pressure interaction modifies the mechanical response of the vibrational mode, and the experimental results are in agreement with a Langevin equation description of the coupled dynamics. The experiments are carried out in the resolved sideband regime, and we have observed cooling by a factor 350 We have also observed the mechanical frequency shift associated with the quadratic term in the expansion of the cavity mode frequency versus the effective membrane position, which is typically negligible in other cavity optomechanical devices.Comment: 15 pages, 7 figure

Ergodicity breaking in strong and network-forming glassy system

The temperature dependence of the non-ergodicity factor of vitreous GeO$_2$, $f_{q}(T)$, as deduced from elastic and quasi-elastic neutron scattering experiments, is analyzed. The data are collected in a wide range of temperatures from the glassy phase, up to the glass transition temperature, and well above into the undercooled liquid state. Notwithstanding the investigated system is classified as prototype of strong glass, it is found that the temperature- and the $q$-behavior of $f_{q}(T)$ follow some of the predictions of Mode Coupling Theory. The experimental data support the hypothesis of the existence of an ergodic to non-ergodic transition occurring also in network forming glassy systems