Forms of Limited Practice Under the Medical Practice Act

No abstract available. doi:10.2204/iodp.sd.5.07.2007</a

Petrophysics of Chicxulub Impact Crater's Peak Ring

A new set of physical property measurements was undertaken on 29 peak-ring samples from the IODP-ICDP Expedition 364. Among the studied lithologies, the dominant one recovered in the peak ring consists of shocked granitoid rocks (19 samples). Porosity measurements with two independent methods (triple weight and C-14-PMMA porosity mapping) concur and bring new observations on the intensity and distribution of fracturing and porosity in these shocked target rocks. Characterization of the porous network is taken a step further with two other independent methods (electrical and permeability measurements). Electrical properties such as the cementation exponent (1.59 m < 1.87) and the formation factor (21 F < 103) do not compare with other granites from the published literature; they point at a type of porosity closer to clastic sedimentary rocks than to crystalline rocks. Permeabilities of the granitoid rocks range from 0.1 to 7.1 mD under an effective pressure of similar to 10 MPa. Unlike other fresh to deformed and altered granitoid rocks from the literature compared in this study, this permeability appears to be relatively insensitive to increasing stress (up to similar to 40 MPa), with implications for the nature of the porous network, again, behaving more like cemented clastic rocks than fractured crystalline rocks. Other analyzed lithologies include suevite and impact melt rocks. Relatively low permeability (10(-3) mD) measured in melt-rich facies suggest that, at the matrix scale, these lithologies cutting through more permeable peak-ring granitoid rocks may have been a barrier to fluid flow, with implications for hydrothermal systems.Peer reviewe

Time-lapse cross-hole electrical resistivity tomography (CHERT) for monitoring seawater intrusion dynamics in a Mediterranean aquifer

Surface electrical resistivity tomography (ERT) is a widely used tool to study seawater intrusion (SWI). It is noninvasive and offers a high spatial coverage at a low cost, but its imaging capabilities are strongly affected by decreasing resolution with depth. We conjecture that the use of CHERT (cross-hole ERT) can partly overcome these resolution limitations since the electrodes are placed at depth, which implies that the model resolution does not decrease at the depths of interest. The objective of this study is to test the CHERT for imaging the SWI and monitoring its dynamics at the Argentona site, a well-instrumented field site of a coastal alluvial aquifer located 40¿km NE of Barcelona. To do so, we installed permanent electrodes around boreholes attached to the PVC pipes to perform time-lapse monitoring of the SWI on a transect perpendicular to the coastline. After 2 years of monitoring, we observe variability of SWI at different timescales: (1) natural seasonal variations and aquifer salinization that we attribute to long-term drought and (2) short-term fluctuations due to sea storms or flooding in the nearby stream during heavy rain events. The spatial imaging of bulk electrical conductivity allows us to explain non-monotonic salinity profiles in open boreholes (step-wise profiles really reflect the presence of freshwater at depth). By comparing CHERT results with traditional in situ measurements such as electrical conductivity of water samples and bulk electrical conductivity from induction logs, we conclude that CHERT is a reliable and cost-effective imaging tool for monitoring SWI dynamics.This work was funded by the project CGL2016-77122-C2-1-R/2-R of the Spanish Government. This project also received funding from the European Commission, Horizon 2020 research and innovation programme (Marie Sklodowska-Curie (grant no. 722028)). The author Albert Folch is a Serra Húnter Fellow.Peer ReviewedPostprint (published version

Rochechouart 2017-Drilling Campaign: First Results

No abstract available

Randomness Increases Order in Biological Evolution

n this text, we revisit part of the analysis of anti-entropy in Bailly and Longo (2009} and develop further theoretical reflections. In particular, we analyze how randomness, an essential component of biological variability, is associated to the growth of biological organization, both in ontogenesis and in evolution. This approach, in particular, focuses on the role of global entropy production and provides a tool for a mathematical understanding of some fundamental observations by Gould on the increasing phenotypic complexity along evolution. Lastly, we analyze the situation in terms of theoretical symmetries, in order to further specify the biological meaning of anti-entropy as well as its strong link with randomness

Innovative downhole geophysical methods for high frequency seawater intrusion dynamics monitoring

The detailed characterization of salt water intrusion is a key to understand both submarine groundwater discharge and manage often intensively exploited groundwater resources in coastal areas. With the objective to study the response of a coastal aquifer to a series of boundary conditions, a new experimental site has been developed through a clastic aquifer located north of Barcelona (Spain). This hectometer scale site is located 50 m from the seashore and equipped with 17 nearby shallow holes, with depths ranging from 15 to 28 m. In order to study not only the sedimentary structure but also the response of the aquifer to a set of natural boundary conditions, downhole geophysical measurements have been deployed over the past 3 years in an innovative manner, either in a time-lapse or stationary manner. The downhole measurements are complicated by the unconsolidated nature of the sediment, obliging to perform all measurements through PVC. Also, the granitic nature of the sediment prevents clays identification from a direct use of gamma ray profiles. For this, constituting minerals (quartz, albite, feldspar, microcline, illite) were identified from X-ray diffraction on cores, and spectral gamma logs used to determine the illite fractions from Th/K ratios. In time lapse, high frequency electrical resistivity induction measurements show that preferential flow paths through the aquifer can be identified in a fast and reliable manner. Also, changes in depth of the fresh to salt water interface (FSWI) are precisely described, either in response to marine tides, or to a short but intense mediterranean rain event. Changes on the order of than 1.70 m are obtain in less than a day of heavy rain. Overnight as well as seasonal changes such as months of dryness are also illustrated due to the variability of pore fluid salinity and temperature, even over short periods of time such as tens of minutes. In stationary mode, the spectral natural gamma sensor located in front of the FSWI fluctuation zones records changes in front of all radioactive peaks (from K, Tl, Bi, but also Ra with Rn) during intense rain events such as that of October 18-19, 2017. This places constraints on Ra and Rn production rate during such an event, leading to trace fresh water outpour into the sea.Peer reviewe

Hydrodynamics and hydrogeochemical changes in the mixing zone of a coastal aquifer during a heavy rain event

The coastal aquifers are the place where meet fresh water and seawater. This confluence between both of them is called mixing zone which is in equilibrium due to the different density of the two masses and where various biogeochemical reactions takes place. We know that this equilibrium can be canceled during an important recharge event. Within the aquifer, such events displace the mixing zone over a short time period. This study is aims at the identification and description at high frequency of spatial and temporal response of the mixing zone and its impact on geochemical processes during one such fast water inflow event. We choose the experimental site of Argentona as the place of this study. Located in the northeast of Spain this site is subjected to a Mediterranean climate characterized by heavy rainfall amount recorded during Fall and early Spring period, concentrated during a few hours. Furthermore, this site is located on an alluvial aquifer, equipped with 16 shallow boreholes over a 100 m scale (Fig.1). The geological cross section presented in Fig.2 shows that the aquifer is multilayered and we suspect an effect of a clay/silt layer located at around 12 m.This work was funded by the projects CGL2013-48869-C2-1 y CGL2013-48869-C2-2-R of the Spanish Government. We would like to thank SIMMAR (Serveis Integrals de Manteniment del Maresme) and the Consell Comarcal del Maresme in the construction of the research site.Peer reviewe

Sublethal Doses of Anthrax Lethal Toxin on the Suppression of Macrophage Phagocytosis

BACKGROUND: Lethal toxin (LT), the major virulence factor produced by Bacillus anthracis, has been shown to suppress the immune system, which is beneficial to the establishment of B. anthracis infections. It has been suggested that the suppression of MEK/MAPK signaling pathways of leukocytes contributes to LT-mediated immunosuppressive effects. However, the involvement of MAPK independent pathways has not been clearly elucidated; nor has the crucial role played by LT in the early stages of infection. Determining whether LT exerts any pathological effects before being enriched to an MEK inhibitory level is an important next step in the furtherance of this field. METHODOLOGY/PRINCIPAL FINDINGS: Using a cell culture model, we determined that low doses of LT inhibited phagocytosis of macrophages, without influencing MAPK pathways. Consistent low doses of LT significantly suppressed bacterial clearance and enhanced the mortality of mice with bacteremia, without suppressing the MEK1 of splenic and peripheral blood mononuclear cells. CONCLUSION/SIGNIFICANCE: These results suggest that LT suppresses the phagocytes in a dose range lower than that required to suppress MEK1 in the early stages of infection