Ground-water Levels, Flow, and Specific Conductance in Unconsolidated Aquifers Near Lake Erie, Cleveland to Conneaut, Ohio, September 1984

This report described ground-water levels, flow, and specific conductance in aquifer along the southern shore of Lake Erie from Cleveland to Conneaut, Ohio. The data were collected in September 1984 as part of the U.S Geological Survey\u27s Northeast Glacial Buried Valley Regional Aquifer-System Analysis. The study area is about 60 miles long, extends inland from the lake about 10 miles, and encompasses parts of Cuyahoga, Lake, and Ashtabula Counties. Water levels were measured in 202 existing wells, all of which were completed in the glacial deposits or at the contact with the underlying shale. Specific conductance was measured in 59 of the wells. Results o the survey are presented in table and map form. Unconsolidated material throughout the area consists primarily of till, whereas the bedrock consists of Devonian shale. The till is composed chiefly o silt and clay with some sand and gravel, and is less than 50 feet thick in most areas. Some valleys are filled with as much as 200 feet of glacial till and outwash deposits that are mainly sand and gravel. Ground-water levels in much of the area within 20 feet of the land surface. Contours of ground-water levels resemble a subdued version of those of the land surface, which indicates that ground water generally flows from high areas to low areas following the land-surface gradient. Locally, ground water discharges into streams. Regionally, flow is towards the north-northeast, to Lake Erie. Specific conductance ranged from 160 to 2,900 ?S/cm (microsiemens per centimeter at 25 degrees Celsius) with a median of 540 ?S/cm. Ground water with a specific conductance greater than 650 ?S/cm is localized, with no specific spatial pattern; possible sources of elevated specific conductance are road-deicing salt, leachate from landfills, natural brings associated with oil and gas drilling, and the leakage of saline water from bedrock

The neodymium stable isotope composition of the oceanic crust: Reconciling the mismatch between erupted mid-ocean ridge basalts and lower crustal gabbros

The trace element and isotopic compositions of mid-ocean ridge basalts (MORB) provide an important cornerstone for all studies seeking to understand mantle evolution. Globally there is a significant over-enrichment in the incompatible trace element concentrations of MORB relative to levels which should be generated by fractional crystallization. Thermal and geochemical constraints suggest that MORB require generation in open system magma chambers. However, the petrology of lower oceanic crustal rocks suggests instead that these enrichments maybe formed through reactive porous flow (RPF). Stable isotope compositions are process dependent and therefore provide an excellent mechanism to compare these contrasting models. This study presents the first neodymium (Nd) stable isotope compositions of Indian MORB and well characterized gabbroic rocks from the lower oceanic crust sampled at the Southwest Indian Ridge (Hole 735B). Indian MORB is extremely homogenous with a mean δ146Nd of −0.025 ±0.005‰ which is identical to the composition of Pacific MORB. Despite significant variability in the source composition of MORB globally (i.e. 143Nd/144Nd) their indistinguishable δ146Nd compositions suggests they were homogenized through the same process along the global ridge network. In stark contrast, oceanic gabbros have δ146Nd ranging from −0.026‰ to −0.127‰, doubling the natural variability in Nd stable isotopes observed in terrestrial rocks. Clinopyroxene separates possess variable δ146Nd but are isotopically heavier than the gabbroic whole rocks at the same major element compositions. These large variations in δ146Nd cannot be generated solely by the fractionation or accumulation of clinopyroxene and/or plagioclase. Hole 735B preserves widespread evidence of RPF which could induce kinetic isotopes fractionation during crystal growth. In clinopyroxene kinetic isotope fractionations will only induce ca. 0.02‰ variations therefore several cycles of dissolution and reprecipitation of isotopic signatures at grain boundaries are required to explain the range of δ146Nd observed in the gabbros. Given the large disconnect between the average composition of the lower crust (δ146Nd = −0.076‰) and MORB globally and the evidence of limited melt extraction into the upper crust at Hole 735B it is highly unlikely that the melts involved in RPF contributed in a substantial way to the Nd isotope composition of erupted MORB

Magnetic breakdown in a normal-metal - superconductor proximity sandwich

We study the magnetic response of a clean normal-metal slab of finite thickness in proximity with a bulk superconductor. We determine its free energy and identify two (meta-)stable states, a diamagnetic one where the applied field is effectively screened, and a second state, where the field penetrates the normal-metal layer. We present a complete characterization of the first order transition between the two states which occurs at the breakdown field, including its spinodals, the jump in the magnetization, and the latent heat. The bistable regime terminates at a critical temperature above which the sharp transition is replaced by a continuous cross-over. We compare the theory with experiments on normal-superconducting cylinders.Comment: 7 pages Revtex, 3 Postscript figures, needs psfig.te

Nonlocality in mesoscopic Josephson junctions with strip geometry

We study the current in a clean superconductor-normal-metal-superconductor junction of length d and width w in the presence of an applied magnetic field H. We show that both the geometrical pattern of the current density and the critical current as a function of the total flux in the junction, depend on the ratio of the Josephson vortex distance a_0 and the range r of the nonlocal electrodynamics. In particular, the critical current has the periodicity of the superconducting flux quantum only for r<a_0 and acquires, due to boundary effects, the double (pseudo-) periodicity for strong nonlocality, r>a_0. Comparing our results to recent experiments of Heida et al. [Phys. Rev. B 57, R5618 (1998)] we find good agreement.Comment: 4 pages, 5 figures, to be published in the RC section of Phys. Rev.

The cysteine-rich domain regulates ADAM protease function in vivo

ADAMs are membrane-anchored proteases that regulate cell behavior by proteolytically modifying the cell surface and ECM. Like other membrane-anchored proteases, ADAMs contain candidate “adhesive” domains downstream of their metalloprotease domains. The mechanism by which membrane-anchored cell surface proteases utilize these putative adhesive domains to regulate protease function in vivo is not well understood. We address this important question by analyzing the relative contributions of downstream extracellular domains (disintegrin, cysteine rich, and EGF-like repeat) of the ADAM13 metalloprotease during Xenopus laevis development. When expressed in embryos, ADAM13 induces hyperplasia of the cement gland, whereas ADAM10 does not. Using chimeric constructs, we find that the metalloprotease domain of ADAM10 can substitute for that of ADAM13, but that specificity for cement gland expansion requires a downstream extracellular domain of ADAM13. Analysis of finer resolution chimeras indicates an essential role for the cysteine-rich domain and a supporting role for the disintegrin domain. These and other results reveal that the cysteine-rich domain of ADAM13 cooperates intramolecularly with the ADAM13 metalloprotease domain to regulate its function in vivo. Our findings thus provide the first evidence that a downstream extracellular adhesive domain plays an active role in regulating ADAM protease function in vivo. These findings are likely relevant to other membrane-anchored cell surface proteases