Finite element modeling and simulation of a robotic finger actuated by Ni-Ti shape memory alloy wires

In this paper, a dynamic model for an artificial finger driven by Shape Memory Alloy (SMA) wires is presented. Due to their high energy density, these alloys permit the realization of highly compact actuation solutions with potential applications in many areas of robotics, ranging from industrial to biomedical ones. Despite many advantages, SMAs exhibit a highly nonlinear and hysteretic behavior which complicates system design, modeling, and control. In case SMA wires are used to activate complex robotic systems, the further kinematic nonlinearities and contact problems make the modeling significantly more challenging. In this paper, we present a finite element model for a finger prototype actuated by a bundle of SMA wires. The commercially available software COMSOL is used to couple the finger structure with the SMA material, described via the Muller-Achenbach-Seelecke model. By means of several experiments, it is demonstrated how the model reproduces the finger response for different control inputs and actuator geometries

Geophysical imaging of the Luhoi geothermal field, Tanzania

The Luhoi prospect is a coastal basin located within Rufiji Trough along the passive continental margin of western Indian Ocean of Tanzania, a sector extending south of the termination of the eastern branch of the African Rift System. The structural pattern is dominated by tectonic features belonging to the WNW-ESE Tagalala Trend and to the NE-SW Selous Trend that have been active until recent times. The thermal manifestations are mostly located along a WNW-ESE direction flowingfollowing the Ruhoi River, in the south-western sector of the focal study area. The Wingoyongo Hill, located in the north-eastern sector of the focal area, forms a morphological high where emissions of H2S and bituminous staining were observed. Here, an old well intersected 800 m of quartz sandstone with minor intercalations of siltstone and claystone (Kipatimu Series, Lower Cretaceous). Magnetotelluric (MT), time-domain electromagnetic (TDEM) and gravimetric geophysical surveys were carried as part of a geoscientific study funded by the Ministry of Foreign Affairs of Iceland through Icelandic International Development Agency (ICEIDA) and the Nordic Development Fund (NDF). The goal of the survey was to advance the state of knowledge of the Luhoi geothermal prospect, in order to elaborate the conceptual model of the field. The survey area extends over a surface of approximately 75 km2, designed to include the Luhoi hot springs and the Wingoyongo fumaroles. The gravimetric data set is composed of 124 measurements collected on a regular grid at a nominal spatial sampling of 800 m, and 16 more to infer the regional field. The residual Bouguer anomaly map shows an elongated gravimetric high trending NE-SW with values up to 3 mGal, surrounded by gravimetric lows up to -2 mGal. Forward and inverse 2D/3D models image an asymmetrical horst like structure trending NE-SW. Both the thermal manifestations and the Wingoyongo Hill are aligned along the NW flank of the horst. Since the Wingoyongo well intersected sandstones for about 800 m, the horst like structure is interpreted as made by the Kipatimu sandstones. The two depressions bordering the horst like structure are filled with lower density materials, likely siltstones, claystones and/or mudstones, with an estimated maximum thickness of 1.1 km. The MT and TDEM data were acquired at 76 locations, with a nominal spatial sampling of 750 m. The static shift effect has been corrected by TDEM/MT phases joint inversion. MT impedances and tippers have been estimated by means of the remote reference technique with robust processing methods coupled with a coherence rejection scheme. Resistivity 3D inversion reveals two conductive anomalies coincident with the low-density sedimentary rocks bordering the horst structure. A clear updoming of resistivity marks the NW flank of the horst and it is interpreted as due to a combined effect of different alteration, lithology and fluid content and to reflect the main upflow of the geothermal system

Three-dimensional geophysical modelling of Kiejo-Mbaka geothermal field, Tanzania

The Kiejo-Mbaka geothermal field is located close to the eastern margin of the Karonga Rift Basin and is part of the Rungwe volcanic province where the EARS splits up into its Western and Eastern branches in southern Tanzania. The area is characterised by a Precambrian gneiss metamorphic basement complex, outcropping along the NW-trending, SW-dipping Mbaka fault. Geothermal manifestations mainly consist of hot springs, flowing close to the Mbaka fault. An integrated geophysical survey was carried out over the Kiejo-Mbaka geothermal field by TGDC (Tanzania Geothermal Development Company), under the supervision of ELC-Electroconsult (Italy). The campaign included 76 Magnetotelluric (MT) and Transient Electromagnetic (TEM) soundings and 133 gravity measurements; a dense station grid allowed for a detailed geophysical 2D and 3D modelling. Two and 3D gravity modelling indicate that the positive residual Bouguer anomaly can be explained by a high density (3 g/cm3) body, constituting the gneiss basement, elongating NW-SE. NE and SW of it, lower density layers (2.5 g/cm3) are observable; the attitude of their bottoms is compatible with the Mbaka fault direction and the Livingstone fault trend (NNW). We found that 3D MT inversion was the only tool giving a reliable resistivity imaging in the Mbaka prospect. From the final 3D MT model, a very resistive body (>2000 Ohm m) deepening toward SE is visible; this body represent the gneiss basement, and the surfaces delimiting it are associated with the Mbaka fault and the Livingstone fault trend. Three conductive zones (less than 10 Ohm m) have been identified: two of them affect the Mbaka fault footwall, NE of the resistive basement, while another one is located beneath the plain, SE of it. This latter zone shows a thickness of about 1 km. It is apparent that the low-density regions well correspond with the high-conductivity zones imaged by the MT 3D inversion. The integrated geophysical interpretation then leads to two possible geological scenarios: these regions can be constituted by (post-rift) sediments (possibly affected by low-T geothermal alteration) or by intensively fractured and low-T altered basement; however, we stress that the possible geothermal alteration is not necessarily related to the present-day geothermal activity, and caution should be taken in result interpretation

Focused Inversion of Gravimetric and Magnetotelluric Data for Geothermal Investigations

Focused inversion techniques may be applied to geophysical data inversion in order to image complex structures in the subsoil. These algorithms may image complex \u201cblocky\u201d structures giving useful information in geothermal exploration that may be smoothed out by standard inversion algorithms that use stabilizer that penalize sharp transitions. We have tested the modified total variation and the maximum gradient support stabilizers in the inversion of synthetic and field magnetotelluric and gravimetric data. The gravimetric data from the Luhoi geothermal prospect have been used to map the sharp density transition between the sandstone and the overlying claystone layers. The resulting horst structure imaged in 2D and 3D models by the maximum gradient support stabilizer solution allow to trace the main fault system that drives the up-flow of hydrothermal waters. The 1D magnetotelluric \u201cblocky\u201d models with lateral constrain (pseudo-3D) image the lithological contact between the claystone and sandstone far from the horst area and reveal resistivity variations in the claystone layer associated with sand lenses. In the horst area, resistivity models image hydrothermal alteration affecting the sandstone layer

Integrated geophysical imaging of the Aluto-Langano geothermal field (Ethiopia)

The Aluto-Langano geothermal system is located in the central part of the Main Ethiopian Rift, one of the world\u2019s most tectonically active areas, where continental rifting has been occurring since several Ma and has yielded widespread volcanism and enhanced geothermal gradient. The geothermal system is associated to the Mt Aluto Volcanic Complex, located along the eastern margin of the rift and related to the Wonji Fault Belt, constituted by Quaternary NNE-SSW en-echelon faults. These structures are younger than the NE-SW border faults of the central Main Ethiopian Rift and were originated by a stress field oblique to the rift direction. This peculiar tectonism yielded local intense rock fracturing that may favour the development of geothermal reservoirs. In this paper, we present the results of an integrated geophysical survey carried out in 2015 over an area of about 200 km2 covering the Mt Aluto Volcanic Complex. The geophysical campaign included 162 coincident magnetotelluric and time domain electromagnetic soundings, and 207 gravity stations, partially located in the sedimentary plain surrounding the volcanic complex. Three-dimensional inversion of the full MT static-corrected tensor and geomagnetic tipper was performed in the 338-0.001 Hz band. Gravity data processing comprised digital enhancement of the residual Bouguer anomaly and 2D-3D inverse modelling. The geophysical results were compared to direct observations of stratigraphy, rock alteration and temperature available from the several deep wells drilled in the area. The magnetotelluric results imaged a low-resistivity layer which appears well correlated with the mixed alteration layer found in the wells and can be interpreted as a low-temperature clay cap. The clay-cap bottom depth is well corresponds to a change of thermal gradient. The clay cap is discontinuous, and in the central area of the volcanic complex is characterised by a dome-shape structure likely related to isotherm rising. The propilitic alteration layer, pinpointed as the 80-Ohm-m isosurface, shows two dome-shape highs. The first is NNE-trending, and may be interpreted as an upflow zone along a fault of the Wonji belt. Two productive wells are located along the borders of this area, as well as the alignements of fumaroles and altered grounds. The second is linked to a wide resistive area, located at shallow depth, where no clay cap was detected. It could be interpreted as a fossil high-temperature alteration zone reaching shallow depths, and it is associated to several fumaroles. Modeling of 2D/3D gravity data shows that the anomalies are due to shallow density variations likely related to lithology. The deep lateral variations due to structural lineaments inferred from well stratigraphy have no detectable signature. However, the trend analysis performed on the residual Bouguer anomaly (via horizontal and tilt derivative computations), allowed to identify five lineaments. Three of them exhibit NNE-SSW strike, corresponding to the Wonji Fault Belt Trend, whereas two have NNW-SSE strike, corresponding to the Red Sea Rift trend, which in this area is of minor evidence. The signature of shallow structures is then indicative of major regional structures. One of the lineaments marks the presence of a major fumarolic zone

Multidisciplinary exploration of the Tendaho Graben geothermal fields

The NW-SE trending Tendaho Graben is the major extensional feature of the Afar, Ethiopia. Rifting and volcanic activity within the graben occurred mostly between 1.8 and 0.6 Ma, but extended to at least 0.2 Ma. Very recent (0.22\u2013 0.03 Ma) activity is focused along the southern part of the younger and active Manda Hararo Rift, which is included in the north-western part of the graben. Extension gave rise to about 1600 m of vertical displacement (verified by drilling) of the basaltic Afar Stratoid sequence, over a crust with a mean thickness of about 23 km. The infill of graben, overlying the Stratoids, consists of volcanic and sedimentary deposits that have been drilled by six exploratory wells. Within the graben, two main geothermal fields have been explored by intensive geological, geochemical and geo- physical surveys over an area that approximately covers a square sector of 40x40 km. Both new and existing data sets have been integrated. The Dubti-Ayrobera system is located along the central axis of the graben. Available data, acquired in the last three decades, comprise more than two thousands gravity and magnetic stations, 229 magnetotelluric stations and structural-geological and geochemical observations. The Alalobeda system is located along the SW flank of the graben, at about 25 km from the Dubti-Ayrobera system and has been very recently stud- ied by means of gravimetric (300 stations), magnetotelluric and TDEM (140 stations) geological and geochemical surveys. The new residual magnetic anomaly map has been used to map the younger normal polarity basalt distribution and infer the location of the unknown main rift axis. The bedrock surface resulting by the 3D inversion of the new residual Bouguer anomaly enlightens the main normal faults hindered by sediments and the secondary structures represented by horsts and grabens. The three-dimensional resistivity models allow mapping the sedimentary infill of the graben, fracture zones in the Afar Stradoids bedrock and the dome-shape structure of the clay cap layer. The 2D and 3D gravimetric, magnetic and resistivity models have been integrated with the structural, geological and geochemical outcomings in order to get an updated conceptual model of the geothermal systems

The Weissella and Periweissella genera: up-to-date taxonomy, ecology, safety, biotechnological, and probiotic potential

Bacteria belonging to the genera Weissella and Periweissella are lactic acid bacteria, which emerged in the last decades for their probiotic and biotechnological potential. In 2015, an article reviewing the scientific literature till that date on the taxonomy, ecology, and biotechnological potential of the Weissella genus was published. Since then, the number of studies on this genus has increased enormously, several novel species have been discovered, the taxonomy of the genus underwent changes and new insights into the safety, and biotechnological and probiotic potential of weissellas and periweissellas could be gained. Here, we provide an updated overview (from 2015 until today) of the taxonomy, ecology, safety, biotechnological, and probiotic potential of these lactic acid bacteria

A HGF/cMET Autocrine Loop Is Operative in Multiple Myeloma Bone Marrow Endothelial Cells and May Represent a Novel Therapeutic Target

Purpose: The aim of this study was to investigate the angiogenic role of the hepatocyte growth factor (HGF)/cMET pathway and its inhibition in bone marrow endothelial cells (EC) from patients with multiple myeloma versus from patients with monoclonal gammopathy of undetermined significance (MGUS) or benign anemia (control group). Experimental Design: The HGF/cMET pathway was evaluated in ECs from patients with multiple myeloma (multiple myeloma ECs) at diagnosis, at relapse after bortezomib- or lenalidomide-based therapies, or on refractory phase to these drugs; in ECs from patients with MGUS (MGECs); and in those patients from the control group. The effects of a selective cMET tyrosine kinase inhibitor (SU11274) on multiple myeloma ECs' angiogenic activities were studied in vitro and in vivo. Results: Multiple myeloma ECs express more HGF, cMET, and activated cMET (phospho (p)-cMET) at both RNAand protein levels versus MGECs and control ECs. Multiple myeloma ECs are able to maintain the HGF/cMET pathway activation in absence of external stimulation, whereas treatment with anti-HGF and anti-cMET neutralizing antibodies (Ab) is able to inhibit cMET activation. The cMET pathway regulates several multiple myeloma EC activities, including chemotaxis, motility, adhesion, spreading, and whole angiogenesis. Its inhibition by SU11274 impairs these activities in a statistically significant fashion when combined with bortezomib or lenalidomide, both in vitro and in vivo. Conclusions: An autocrine HGF/cMET loop sustains multiple myeloma angiogenesis and represents an appealing new target to potentiate the antiangiogenic management of patients with multiple myeloma

Smooth magnetotelluric impedance estimation by optimization

In urban and industrialised areas, magnetotelluric (MT) recordings often contain a significant amount of highpower near-field noise which, constituting non-Gaussian noise for most of the recording length, may lead to the failure of the common transfer functions (TF) estimation methods. The most evident consequence of this is the appearance of sharp points in the TF curves versus frequency, deteriorating their inherent smoothness. The TF’s smoothness is in fact one of the main criteria adopted by MT practitioners to evaluate the data quality and effectiveness of the estimation procedure; when not reached by the estimation, it may be a-posteriori introduced by splines or filtering procedures, but these approaches lack physical soundness. We propose a new heuristic algorithm aimed at obtaining the maximum TF versus frequency smoothness, through an optimization scheme rejecting EM events in frequency-domain. The algorithm searches for frequency-dependent power thresholds to be applied to the events, rejecting those making the TF sharp. The TF’s smoothness is the objective function to be minimized, and the model space is constituted by the infinite set of threshold vectors for each analysed frequency. After the process, the Ordinaly Least Squares (OLS) residual distribution is much closer to a Rayleigh one, allowing for an unbiased estimation. We applied the procedure both to synthetic and real MT data. Measured data has been collected for a geothermal exploration project in the East Africa Rift, where strong coherent noise affected the recordings. The combination of the technique with the remote-reference technique effectively reduced the bias due to the artificial signal. The physical consistency of the resulting TF has been tested by dispersion relationships