Three-dimensional resistivity tomography of Vulcan's forge, Vulcano Island, southern Italy

International audience9,525 DC resistivity measurements were taken along 9 profiles crossing the volcanic edifice of La Fossa di Vulcano (the forge of God Vulcan in ancient Roman mythology), Vulcano Island (Italy) using a total of 958 electrode locations. This unique data set has been inverted in 3D by minimizing the L2 norm of the data misfit using a Gauss-Newton approach. The true 3D inversion was performed using parallel processing on an unstructured tetrahedral mesh containing 75,549 finite-element nodes and 398,208 elements to accurately model the topography of the volcanic edifice. The 3D tomogram shows a very conductive body (>0.1 S/m) comprised inside the Pietre Cotte crater with conductive volumes that are consistent with the position of temperature and CO2 anomalies at the ground surface. This conductive body is interpreted as the main hydrothermal body. It is overlaid by a resistive and cold cap in the bottom of the crater. The position of the conductive body is consistent with the deformation source responsible for the observed 1990-1996 deflation of the volcano associated with a decrease of hydrothermal activity

The impossibility of effective enforcement mechanisms in collateralized credit markets

We analyze the possibility of the simultaneous presence of three key features in price-taking credit markets: infinity horizon, collateralized credit operations and effective additional enforcement mechanisms, i.e. those implying payments besides the value of the collateral guarantees. We show that these additional mechanisms, instead of strengthening, actually weaken the restrictions that collateral places on borrowing. In fact, when collateral requirements are not large enough in relation to the effectiveness of the additional mechanisms, lenders anticipate total payments exceeding the value of the collateral requirements. Thus, by non-arbitrage, they lend more than the value of these guarantees. In turn, in the absence of other market frictions such as borrowing constraints, agents may indefinitely postpone their debts, implying the collapse of the agent's maximization problem and of such credit markets

INTERNATIONAL NURSING STUDENTS CLINICAL EXPERIENCES: A BASIS FOR STRUCTURAL MANAGEMENT FOR TRANSCULTURAL COMPETENCY

Developing  nurses as global  citizens regardless  of cultural background  becomes imperative for nursing education (Chavez, Bender, Hardie, & Gastaldo, 2010; Mill, Astle, Ogilvie, & Gastaldo, as cited by Asenso, et al, 2012). With a remarkable increase of culturally diverse students entering nursing schools poses a challenge among  academic, clinical staff and significantly to students. In the Philippines, the need to study clinical experiences among international students becomes imperative (Croxon & Maginnis, as cited by Appiah & Wa- Mbaleka, 2014). This inquiry is geared towards international nursing students’ clinical experiences as basis for structural management to guarantee transcultural competency. Quantitative descriptive research design was used. Complete enumeration and purposive random sampling which consist of 25 respondents of the tree sectarian schools, Saint  Louis University, Northern Luzon Adventist College and Manila Adventist Medical Center. A survey questionnaire developed by Appiah and Wa-Mbaleka, (2014) was utilized in data gathering to ascertain the concern of the study. Respondents disagreed that they are culturally competent in terms of academic preparation. Disagreed that they are intercultural competent along culture. Respondents agreed that they experience racial discrimination whether from their patients, classmates, nurses, or doctors due to color. Disagreement was noted on discrimination on country of origin so with the discrimination on tagalong speaking  competency. Disagreed that Filipinos they encounter during clinical are prepared to work with international nursing students. There is no significant difference on transcultural competency along preparation, color, country, language and working with Filipinos in the identified variables gender, year level and race. There are significant differences along preparation in tagalong language proficiency and in terms of culture among personality type. Lastly, there is no significant difference in preparation, culture and clinical challenges with the identified variable race. A structural management   to ensure transcultural competency of international nursing students evolved as a result of the findings of the study. &nbsp

Self-Potential as a Predictor of Seawater Intrusion in Coastal Groundwater Boreholes

This work was supported by the Natural Environment Research Council in the UK, as part of the Science and Solutions for a Changing Planet Doctor Training Partnership, run by the Grantham Institute for Climate Change at Imperial College London. We thank Southern Water for access to the boreholes at Saltdean and Balsdean. We thank Southern Water and Atkins Global for funding the installation of the equipment. We also thank Dr Amadi Ijioma for providing a prototype of the electrodynamic modelling code in MATLAB, which has since been adapted for use in a coastal chalk aquifer. Three anonymous reviewers are thanked for their comments, which greatly helped to improve the manuscript. The data used in this paper are in the tables, figures and cited information. The authors have no conflicts of interest to declare.Peer reviewedPublisher PDFPublisher PD

Hydrogeology of Stromboli volcano, Aeolian Islands (Italy) from the interpretation of resistivity tomograms, self-potential, soil temperature and soil CO2 concentration measurements

International audienceTo gain a better insight of the hydrogeology and the location of the main tectonic faults of Stromboli volcano in Italy, we collected electrical resistivity measurements, soil CO2 concentrations, temperature and self-potential measurements along two profiles. These two profiles started at the village of Ginostra in the southwest part of the island. The first profile (4.8 km in length) ended up at the village of Scari in the north east part of the volcano and the second one (3.5 km in length) at Forgia Vecchia beach, in the eastern part of the island. These data were used to provide insights regarding the position of shallow aquifers and the extension of the hydrothermal system. This large-scale study is complemented by two high-resolution studies, one at the Pizzo area (near the active vents) and one at Rina Grande where flank collapse areas can be observed. The Pizzo corresponds to one of the main degassing structure of the hydrothermal system. The main degassing area is localized along a higher permeability area corresponding to the head of the gliding plane of the Rina Grande sector collapse. We found that the self-potential data reveal the position of an aquifer above the villages of Scari and San Vincenzo. We provide an estimate of the depth of this aquifer from these data. The lateral extension of the hydrothermal system (resistivity ∼15-60 ohm m) is broader than anticipated extending in the direction of the villages of Scari and San Vincenzo (in agreement with temperature data recorded in shallow wells). The lateral extension of the hydrothermal system reaches the lower third of the Rina Grande sector collapse area in the eastern part of the island. The hydrothermal body in this area is blocked by an old collapse boundary. This position of the hydrothermal body is consistent with low values of the magnetization (<2.5 A m−1) from previously published work. The presence of the hydrothermal body below Rina Grande raises questions about the mechanical stability of this flank of the edifice

Adventive hydrothermal circulation on Stromboli volcano (Aeolian Islands, Italy) revealed by geophysical and geochemical approaches: Implications for general fluid flow models on volcanoes

International audienceOn March 15th 2007 a paroxysmal explosion occurred at the Stromboli volcano. This event generated a large amount of products, mostly lithic blocks, some of which impacted the ground as far as down to 200 m a.s.l., about 1.5 km far away from the active vents. Two days after the explosion, a new vapour emission was discovered on the north-eastern flank of the volcanic edifice, at 560 m a.s.l., just above the area called "Nel Cannestrà". This new vapour emission was due to a block impact. In order to investigate the block impact area to understand the appearance of the vapour emission, we conducted on May 2008 a multidisciplinary study involving Electrical Resistivity Tomography (ERT), Ground Penetrating Radar (GPR), Self-Potential (SP), CO2 soil diffuse degassing and soil temperature surveys. This complementary data set revealed the presence of an anomalous conductive body, probably related to a shallow hydrothermal level, at about 10-15 m depth, more or less parallel to the topography. It is the first time that such a hydrothermal fluid flow, with a temperature close to the water boiling point (76 °C) has been evidenced at Stromboli at this low elevation on the flank of the edifice. The ERT results suggest a possible link between (1) the main central hydrothermal system of Stromboli, located just above the plumbing system feeding the active vents, with a maximum of subsurface soil temperature close to 90 °C and limited by the NeoStromboli summit crater boundary and (2) the investigated area of Nel Cannestrà, at ~ 500 m a.s.l., a buried eruptive fissure active 9 ka ago. In parallel, SP and CO2 soil diffuse degassing measurements suggest in this sector at slightly lower elevation from the block impact crater a magmatic and hydrothermal fluid rising system along the N41° regional fault. A complementary ERT profile, on May 2009, carried out from the NeoStromboli crater boundary down to the block impact crater displayed a flank fluid flow apparently connected to a deeper system. The concept of shallow hydrothermal level have been compared to similar ERT results recently obtained on Mount Etna and La Fossa cone of Vulcano. This information needs to be taken into account in general fluid flow models on volcanoes. In particular, peripheral thermal waters (as those bordering the north-eastern coast of Stromboli) could be contaminated by hydrothermal and magmatic fluids coming from regional faults but also from the summit

Interpretation of porosity and LWD resistivity from the Nankai accretionary wedge in light of clay physicochemical properties: Evidence for erosion and local overpressuring

International audienceIn this study, we used porosity to assess the compaction state of the Nankai accretionary wedge sediments and any implications for stress and pore pressure. However, hydrous minerals affect porosity measurements, and accounting for them is essential toward defining the interstitial porosity truly representative of the compaction state. The water content of sediments was measured in core samples and estimated from logging data using a resistivity model for shale. We used the cation exchange capacity to correct the porosity data for the amount of water bound to clay minerals and to correct the porosity estimates for the surface conductivity of hydrous minerals. The results indicate that several apparent porosity anomalies are significantly reduced by this correction, implying that they are in part artifacts from hydrous minerals. The correction also improves the fit of porosity estimated from logging-while-drilling (LWD) resistivity data to porosity measured on cores. Low overall porosities at the toe of the accretionary wedge and in the splay fault area are best explained by erosion, and we estimated the quantity of sediments eroded within the splay fault area by comparing porosity-effective stress relationships of the sediments to a reference curve. Additionally, a comparison of LWD data with core data (resistivity and P wave velocity) obtained at Site C0001 landward of the mega-splay fault area, suggested a contribution from the fracture porosity to in situ properties on the formation

Apoptosis of human melanoma cells induced by inhibition of B-RAFV600E involves preferential splicing of bimS

Bim is known to be critical in killing of melanoma cells by inhibition of the RAF/MEK/ERK pathway. However, the potential role of the most potent apoptosis-inducing isoform of Bim, BimS, remains largely unappreciated. Here, we show that inhibition of the mutant B-RAFV600E triggers preferential splicing to produce BimS, which is particularly important in induction of apoptosis in B-RAFV600E melanoma cells. Although the specific B-RAFV600E inhibitor PLX4720 upregulates all three major isoforms of Bim, BimEL, BimL, and BimS, at the protein and mRNA levels in B-RAFV600E melanoma cells, the increase in the ratios of BimS mRNA to BimEL and BimL mRNA indicates that it favours BimS splicing. Consistently, enforced expression of B-RAFV600E in wild-type B-RAF melanoma cells and melanocytes inhibits BimS expression. The splicing factor SRp55 appears necessary for the increase in BimS splicing, as SRp55 is upregulated, and its inhibition by small interfering RNA blocks induction of BimS and apoptosis induced by PLX4720. The PLX4720-induced, SRp55-mediated increase in BimS splicing is also mirrored in freshly isolated B-RAFV600E melanoma cells. These results identify a key mechanism for induction of apoptosis by PLX4720, and are instructive for sensitizing melanoma cells to B-RAFV600E inhibitors