292 research outputs found
Clinical and neuropathological study about the neurotization of the suprascapular nerve in obstetric brachial plexus lesions
<p>Abstract</p> <p>Background</p> <p>The lack of recovery of active external rotation of the shoulder is an important problem in children suffering from brachial plexus lesions involving the suprascapular nerve. The accessory nerve neurotization to the suprascapular nerve is a standard procedure, performed to improve shoulder motion in patients with brachial plexus palsy.</p> <p>Methods</p> <p>We operated on 65 patients with obstetric brachial plexus palsy (OBPP), aged 5-35 months (average: 19 months). We assessed the recovery of passive and active external rotation with the arm in abduction and in adduction. We also looked at the influence of the restoration of the muscular balance between the internal and the external rotators on the development of a gleno-humeral joint dysplasia. Intraoperatively, suprascapular nerve samples were taken from 13 patients and were analyzed histologically.</p> <p>Results</p> <p>Most patients (71.5%) showed good recovery of the active external rotation in abduction (60°-90°). Better results were obtained for the external rotation with the arm in abduction compared to adduction, and for patients having only undergone the neurotization procedure compared to patients having had complete plexus reconstruction. The neurotization operation has a positive influence on the glenohumeral joint: 7 patients with clinical signs of dysplasia before the reconstructive operation did not show any sign of dysplasia in the postoperative follow-up.</p> <p>Conclusion</p> <p>The neurotization procedure helps to recover the active external rotation in the shoulder joint and has a good prevention influence on the dysplasia in our sample. The nerve quality measured using histopathology also seems to have a positive impact on the clinical results.</p
Thallium Isotopic Compositions in Hawaiian Lavas: Evidence for Recycled Materials on the Kea Side of the Hawaiian Mantle Plume
Hawaiian volcanoes record 6 Ma of potentially deep mantle chemistry and form two parallel volcanic chains that are geochemically unique, named Loa and Kea. Loa volcanoes erupt lavas with isotopically enriched compositions thought to reflect the presence of recycled material in the deep mantle source of the Hawaiian plume. Variations in stable thallium (Tl) isotopes have been used to trace recycled pelagic ocean sediment from subduction to eruption in arc and intraplate lavas. Previous work attributed heavy Tl isotopic compositions in eight Loa samples to recycled sediments in their source. We reexamined this hypothesis using a large sample set (n = 34) of shield-stage, tholeiitic basalt from 13 Hawaiian volcanoes representing the entire range of isotopically enriched and depleted compositions along the Hawaiian chain. Samples were acid-leached prior to isotopic analysis to remove post-eruption alteration and resulting Δ205Tl values show statistical differences between Loa and Kea volcanoes. Corresponding isotopic data and re-analyzed trace element concentrations suggest that the Δ205Tl values are primary magmatic signatures. Possible co-variations between heavy Δ205Tl and oxygen isotopes in samples from Kea-trend volcanoes could reflect the presence of ancient, recycled pelagic sediment on the Kea side of the Hawaiian plume, which samples the average deep Pacific mantle. As such, the deep mantle source of both Loa and Kea Hawaiian volcanoes may contain recycled materials of different natures and recycling histories, which supports work from both geophysical and geochemical studies suggesting that the Earth's lower mantle is chemically heterogeneous on multiple spatial scales
Radiogenic isotopes in enriched mid-ocean ridge basalts from Explorer Ridge, northeast Pacific Ocean
Extreme gradients in topography related to variations in magma supply are observed on the Southern Explorer Ridge (SER), part of the northern Juan de Fuca ridge system. We report radiogenic isotope (Pb, Sr, Nd, Hf) and geochemical data for twenty-four basalt whole-rock and glass samples collected from the length of the SER and from Explorer Deep, a rift to the north of the SER. Lavas from the SER form a north-south geochemical gradient, dominated by E-MORB at the northern axial high, and range from T-MORB to N-MORB towards the southern deepest part of the ridge. Linear relationships between incompatible element ratios and isotopic ratios in MORB along the ridge are consistent with mixing of magmas beneath the ridge to generate the geographic gradient from E- to N-MORB. The E-MORB have high Sr and Pb, and low Nd and Hf isotopic ratios, typical of enriched mantle that includes a FOZO or HIMU isotopic component. The West Valley and Endeavour segments of the northern Juan de Fuca ridge also include this isotopic component, but the proportion of the FOZO or HIMU component is more extreme in the SER basalts. The FOZO or HIMU component may be garnet-bearing peridotite, or a garnet pyroxenite embedded in peridotite. Recycled garnet pyroxenite better explains the very shallow SER axial high, high Nb/La and La/Sm, and the âenrichedâ isotopic compositions
Pachycormid fish fed on octobrachian cephalopods: new evidence from the âSchistes bitumineuxâ (early Toarcian) of southern Luxembourg
A re-examination of the early Toarcian fish fossils preserved in public paleontological collections in Luxembourg revealed 70 specimens of large Toarcian pachycormid fish with an excellent three-dimensional preservation within calcareous nodules. Six of them are associated with octobrachian coleoid gladii in their oesophagus or stomach, an association not previously described from Luxembourg. The pachycormids are ascribed to Pachycormus macropterus (Blainville, 1818) and Saurostomus esocinus Agassiz, 1843 while the octobrachian gladii are ascribed to Teudopsis bollensis Voltz, 1836, Teudopsis sp. indet. and Loligosepiidae indet. The position and orientation of the gladii provide direct evidence of these fishes feeding on coleoids and thus a teuthophagous diet, rather than an accidental joint burial. Together with evidence from coeval deposits in Germany, these findings suggest that teuthophagy was a widespread feeding strategy at the base of the clade that contains the suspension-feeding pachycormid giants of the JurassicâCretaceous
Petrology and Geochemistry of Volcanic Rocks from the South Kauaʻi Swell Volcano, Hawaiʻi: Implications for the Lithology and Composition of the Hawaiian Mantle Plume
The South KauaÊ»i Swell (SKS) volcano was sampled during four JASON dives and three dredge hauls recovering rocks that range from fresh pillow lavas to altered volcanic breccias. Two geochemical groups were identified: shield-stage tholeiites (5·4â3·9 Ma) and rejuvenation-stage alkalic lavas (1·9â0·1 Ma). The young SKS ages and the coeval rejuvenated volcanism along a 400km segment of the Hawaiian Islands (Maui to NiÊ»ihau) are inconsistent with the timing and duration predictions by the flexure and secondary plume melting models for renewed volcanism. The SKS tholeiites are geochemically heterogeneous but similar to lavas from nearby KauaÊ»i, NiÊ»ihau and WaiÊ»anae volcanoes, indicating that their source regions within the Hawaiian mantle plume sampled a well-mixed zone. Most SKS tholeiitic lavas exhibit radiogenic Pb isotope ratios (208Pb*/206Pb*) that are characteristic of Loa compositions (>0·9475), consistent with the volcanoâs location on the west side of the Hawaiian Islands. These results document the existence of the Loa component within the Hawaiian mantle plume prior to 5 Ma. Loa trend volcanoes are thought to have a major pyroxenite component in their source. Calculations of the pyroxenitic component in the parental melts for SKS tholeiites using high-precision olivine analyses and modeling of trace element ratios indicate a large pyroxenite proportion (â„50%), which was predicted by recent numerical models. Rejuvenation-stage lavas were also found to have a significant pyroxenite component based on olivine analyses (40â60%). The abundance of pyroxenite in the source for SKS lavas may be the cause of this volcanoâs extended period of magmatism (>5 Myr). The broad distribution of the Loa component in the northern Hawaiian Island lavas coincides with the start of a dramatic magma flux increase (300%) along the Hawaiian Chain, which may reflect a major structural change in the source of the Hawaiian mantle plume
Liquid-vapor transition of systems with mean field universality class
We have considered a system where the interaction, v(r) = v_IS(r) + xi^2
v_MF(r), is given as a linear combination of two potentials, each of which
being characterized with a well-defined critical behavior: for v_IS(r) we have
chosen the potential of the restricted primitive model which is known to belong
to the Ising 3D (IS) universality class, while for v_MF(r) we have considered a
long-range interaction in the Kac-limit, displaying mean field (MF) behavior.
We study the performance of two theoretical approaches and of computer
simulations in the critical region for this particular system and give a
detailed comparison between theories and simulation of the critical region and
the location of the critical point. Both, theory and simulation give evidence
that the system belongs to the MF universality class for any positive value of
xi and that it shows only non-classical behavior for xi=0. While in this
limiting case theoretical approaches are known to fail, we find good agreement
for the critical properties between the theoretical approaches and the
simulations for xi^2 larger than 0.05.Comment: 9 pages, 11 figures, 3 table
Oceanic mafic magmatism in the Siletz terrane, NW North America: Fragments of an Eocene oceanic plateau?
The Siletz terrane, a predominantly mafic accreted oceanic terrane, is located in the Cascadia Forearc region of Oregon, Washington and Vancouver Island. The terrane represents a late Paleocene â Eocene large igneous province that consists of pillow lavas, massive flows and intrusive sheets. Previously it has been proposed that the Siletz terrane represents either an accreted oceanic plateau, hotspot island chain, backarc basin, island arc, or a sequence of slab window volcanics. A province-wide geochemical reassessment of the terrane, including new high precision Sr-Pb-Nd-Hf isotope, has been used to assess the validity of the proposed tectonomagmatic models for the Siletz terrane. The trace element data show little evidence of crustal contamination, or an arc signature, and the samples have rare earth element (REE) patterns that are flat to light REE enriched. These features are similar to other oceanic plateaus such as the Ontong Java and the Caribbean. Initial isotope ratios range from 206Pb/204 Pb: 18.751 to 19.668, 207Pb/204Pb: 15.507â15.661, 207Pb/204Pb: 38.294â39.2128, 176Hf/177Hf: 0.28300â0.28316 (ΔHf: 9.0 to 14.5), 143Nd/144Nd: 0.51282â0.51299 (ΔNd: 5.0 to 8.1) and 87Sr/86Sr: 0.70302â0.70380. These data are consistent with a mantle source of the Siletz terrane that appears to have been heterogeneous and slightly enriched. The enriched signature has characteristics of both EM2 and HIMU components and this, combined with a calculated mantle potential temperature well above ambient mantle, indicates derivation of the Siletz magmatism from a mantle plume, possibly the Yellowstone Hotspot. We therefore conclude that the Siletz terrane represents an accreted oceanic plateau
Submarine radial vents on Mauna Loa Volcano, Hawai'i
A 2002 multibeam sonar survey of Mauna Loa's western flank revealed ten submarine radial vents and three submarine lava flows. Only one submarine radial vent was known previously. The ages of these vents are constrained by eyewitness accounts, geologic relationships, Mn-Fe coatings, and geochemical stratigraphy; they range from 128 years B.P. to possibly 47 ka. Eight of the radial vents produced degassed lavas despite eruption in water depths sufficient to inhibit sulfur degassing. These vents formed truncated cones and short lava flows. Two vents produced undegassed lavas that created ''irregular'' cones and longer lava flows. Compositionally and isotopically, the submarine radial vent lavas are typical of Mauna Loa lavas, except two cones that erupted alkalic lavas. He-Sr isotopes for the radial vent lavas follow Mauna Loa's evolutionary trend. The compositional and isotopic heterogeneity of these lavas indicates most had distinct parental magmas. Bathymetry and acoustic backscatter results, along with photography and sampling during four JASON2 dives, are used to produce a detailed geologic map to evaluate Mauna Loa's submarine geologic history. The new map shows that the 1877 submarine eruption was much larger than previously thought, resulting in a 10% increase for recent volcanism. Furthermore, although alkalic lavas were found at two radial vents, there is no systematic increase in alkalinity among these or other Mauna Loa lavas as expected for a dying volcano. These results refute an interpretation that Mauna Loa's volcanism is waning. The submarine radial vents and flows cover 29 km 2 of seafloor and comprise a total volume of âŒ2 Ă 10 9 m3 of lava, reinforcing the idea that submarine lava eruptions are important in the growth of oceanic island volcanoes even after they emerged above sea level
Tracing molybdenum attenuation in mining environments using molybdenum stable isotopes
Molybdenum contamination is a concern in mining regions worldwide. Better understanding of processes controlling Mo mobility in mine wastes is critical for assessing potential impacts and developing water-quality management strategies associated to this element. Here, we used Mo stable isotope (ÎŽ98/95Mo) analyses to investigate geochemical controls on Mo mobility within a tailings management facility (TMF) featuring oxic and anoxic environments. These isotopic analyses were integrated with X-ray absorption spectroscopy, X-ray diffraction, Raman spectroscopy, transmission electron microscopy, and aqueous chemical data. Dissolved Mo concentrations were inversely correlated with ÎŽ98/95Mo values such that enrichment of heavy Mo isotopes in solution reflected attenuation processes. Inner-sphere complexation of Mo(VI) with ferrihydrite was the primary driver of Mo removal and was accompanied by a circa 1 â° isotope fractionation. Limited Mo attenuation and isotope fractionation was observed in Fe(II)- and Mo-rich anoxic TMF seepage, while attenuation and isotope fractionation were greatest during discharge and oxidation of this seepage after discharge into a pond where Fe-(oxyhydr)oxide precipitation promoted Mo sorption. Overall, this study highlights the role of sorption onto Fe-(oxyhydr)oxides in attenuating Mo in oxic environments, a process which can be traced by Mo isotope analyses
- âŠ