Two views of Hawaiian plume structure Hofmann, Albrecht W.; Farnetani, Cinzia G.
Geochemistry, geophysics, geosystems : G3,
December 2013, Letnik:
14, Številka:
12
Journal Article
Recenzirano
Odprti dostop
Fundamentally contradictory interpretations of the isotopic compositions of Hawaiian basalts persist, even among authors who agree that the Hawaiian hotspot is caused by a deep‐mantle plume. One view ...holds that the regional isotopic pattern of the volcanoes reflects large‐scale heterogeneities in the basal thermal boundary layer of the mantle. These are drawn into the rising plume conduit, where they are vertically stretched and ultimately sampled by volcanoes. The alternative view is that the plume resembles a “uniformly heterogeneous plum pudding,” with fertile plums of pyroxenite and/or enriched peridotite scattered in a matrix of more refractory peridotite. In a rising plume, the plums melt before the matrix, and the final melt composition is controlled significantly by the bulk melt fraction. Here we show that the uniformly heterogeneous plum pudding model is inconsistent with several geochemical observations: (1) the relative melt fractions inferred from La/Yb ratios in shield‐stage basalts of the two parallel (Kea‐ and Loa‐) volcanic chains, (2) the systematic Pb‐isotopic differences between the chains, and the absence of such differences between shield and postshield phases, (3) the systematic shift to uniformly depleted Nd‐isotopic compositions during rejuvenated volcanism. We extend our previous numerical simulation to the low melt production rates calculated far downstream (200–400 km) from shield volcanism. Part of these melts, feeding rejuvenated volcanism, are formed at pressures of ∼5 GPa in the previously unmelted underside of the plume, from material that originally constituted the uppermost part of the thermal boundary layer at the base of the mantle.
Key Points
Small-scale heterogeneities do not explain geochemical structure Hawaiian plume
Rejuvenated volcanism is derived from the fertile underside of the plume
Its source comes from the upper portion of the thermal boundary layer
Summary
The increasing incidence of invasive fungal diseases (IFD), most of all invasive aspergillosis (IA) in immunocompromised patients emphasises the need to improve the diagnostic tools for ...detection of fungal pathogens. We investigated the diagnostic performance of a multifungal DNA‐microarray detecting 15 different fungi Aspergillus, Candida, Fusarium, Mucor, Rhizopus, Scedosporium and Trichosporon species (spp.) in addition to an Aspergillus specific polymerase chain reaction (PCR) assay. Biopsies, bronchoalveolar lavage and peripheral blood samples of 133 immunocompromised patients (pts) were investigated by a multifungal DNA‐microarray as well as a nested Aspergillus specific PCR assay. Patients had proven (n = 18), probable (n = 29), possible (n = 48) and no IFD (n = 38) and were mostly under antifungal therapy at the time of sampling. The results were compared to culture, histopathology, imaging and serology, respectively. For the non‐Aspergillus IFD the microarray analysis yielded in all samples a sensitivity of 64% and a specificity of 80%. Best results for the detection of all IFD were achieved by combining DNA‐microarray and Aspergillus specific PCR in biopsy samples (sensitivity 79%; specificity 71%). The molecular assays in combination identify genomic DNA of fungal pathogens and may improve identification of causative pathogens of IFD and help overcoming the diagnostic uncertainty of culture and/or histopathology findings, even during antifungal therapy.
Amount of Recycled Crust in Sources of Mantle-Derived Melts Sobolev, Alexander V; Hofmann, Albrecht W; Kuzmin, Dmitry V ...
Science (American Association for the Advancement of Science),
04/2007, Letnik:
316, Številka:
5823
Journal Article
Recenzirano
Plate tectonic processes introduce basaltic crust (as eclogite) into the peridotitic mantle. The proportions of these two sources in mantle melts are poorly understood. Silica-rich melts formed from ...eclogite react with peridotite, converting it to olivine-free pyroxenite. Partial melts of this hybrid pyroxenite are higher in nickel and silicon but poorer in manganese, calcium, and magnesium than melts of peridotite. Olivine phenocrysts' compositions record these differences and were used to quantify the contributions of pyroxenite-derived melts in mid-ocean ridge basalts (10 to 30%), ocean island and continental basalts (many >60%), and komatiites (20 to 30%). These results imply involvement of 2 to 20% (up to 28%) of recycled crust in mantle melting.
Summary
We characterized the early dynamics of hepatitis B virus (HBV) quasispecies evolution during the first weeks of antiviral therapy with low‐to‐moderate genetic barrier antiviral drugs and ...associated these data with antiviral response patterns. Fifteen chronic hepatitis B patients (men, 10; mean age, 34; HBeAg positive, 6) who received lamivudine or telbivudine for at least 52 weeks were included. HBV DNA was extracted from serum, and a 910‐bp fragment covering domains A–F of the reverse transcriptase region was amplified, cloned and sequenced. Parameters of quasispecies heterogeneity, genetic diversity and complexity were calculated and were correlated with complete virologic response, defined as undetectable HBV DNA at week 52. Nine patients achieved complete virologic response during the observational period. While baseline HBV DNA levels and HBeAg status were associated with virologic response, baseline quasispecies complexity and diversity of responders showed no significant difference to those of nonresponders (P > 0.05). However, at week 4, quasispecies complexity of nonresponders was significantly higher compared with that of responders on the nucleotide level (P = 0.01) and the aa level (P = 0.04). The number of synonymous substitutions per synonymous site dropped significantly in responders at week 4 (P = 0.04), while there was no difference in nonresponders. The HBV quasispecies complexity at the early stage of antiviral therapy (week 4) with the low‐to‐moderate genetic barrier nucleoside analogs lamivudine or telbivudine was associated with subsequent virologic response. Further studies are needed to confirm HBV quasispecies evolution as additional predictive marker for beneficial treatment outcome.
Long-wavelength, InP-based, vertical-cavity surface-emitting lasers with buried tunnel junction (LW-BTJ-VCSELs) and VCSEL arrays are presented. Emitting at the telecommunications wavelengths around ...1.3 and 1.55 mum, these devices show high modulation bandwidth in excess of 10 GHz over a wide temperature range. Small-signal equivalent circuits for the parasitic and intrinsic response are given. Various data-transmission experiments are performed with data rates up to 12.5 Gb/s over different fiber channels. 1-D LW-BTJ-VCSEL arrays can be used in wavelength-division multiplexing systems for high bandwidth per fiber channel. 2-D high-speed arrays with 64 individually addressable channels are presented that are particularly suited for optical ultrabroadband interconnects. Furthermore, large-scale arrays are investigated for high-power applications. In a detailed investigation, we derive scaling rules considering the influence of aperture, array size, and pitch on laser power. At room temperature, optical output powers in the watt regime have been realized at 1.55 mum. Divergence angles are as low as 13deg-17deg full-width at half-maximum. Wall plug efficiencies in excess of 20% over a wide current range and high-temperature operation up to 80degC are obtained.
Polymyalgia rheumatica is the second most frequent inflammatory rheumatic disease in people aged over 50 years, after rheumatoid arthritis. It is characterized by pain and morning stiffness in the ...region of the shoulders, hip girdle and neck. It can be associated with giant cell arteritis (CGA). Treatment with glucocorticoids is indispensable. The duration of treatment varies and often exceeds 1 year. The additive administration of methotrexate is an option for saving glucocorticoids. The biologicals tocilizumab or secukinumab are very promising alternatives. The course of treatment should be closely monitored for inflammation parameters, glucocorticoid side effects, pain, visual acuity, depression, activities of daily living and especially related to functions of the upper extremities. The geriatric assessment plays an important role in the management of this condition.
Myelodysplastic syndromes (MDS) with del(5q) are considered to have a benign course of the disease. In order to address the issue of the propensity of those patients to progress to acute myeloid ...leukemia (AML), data on 381 untreated patients with MDS and del(5q) characterized by low or intermediate I International Prognostic Scoring System (IPSS) risk score were collected from nine centers and registries. Median survival of the entire group was 74 months. Transfusion-dependent patients had a median survival of 44 months vs 97 months for transfusion-independent patients (P<0.0001). Transfusion need at diagnosis was the most important patient characteristic for survival. Of the 381 patients, 48 (12.6%) progressed to AML. The cumulative progression rate calculated using the Kaplan-Meier method was 4.9% at 2 years and 17.6% at 5 years. Factors associated with the risk of AML transformation were high-risk World Health Organization adapted Prognostic Scoring System (WPSS) score, marrow blast count >5% and red-cell transfusion dependency at diagnosis. In conclusion, patients with MDS and del(5q) are facing a considerable risk of AML transformation. More detailed cytogenetic and molecular studies may help to identify the patients at risk of progression.
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