Sample records for eplotr cplotr sepr
-
RNA-Dependent Cysteine Biosynthesis in Bacteria and Archaea
Mukai, Takahito; Crnković, Ana; Umehara, Takuya; ...
2017-05-09
ABSTRACT The diversity of the genetic code systems used by microbes on earth is yet to be elucidated. It is known that certain methanogenic archaea employ an alternative system for cysteine (Cys) biosynthesis and encoding; tRNA Cysis first acylated with phosphoserine (Sep) byO-phosphoseryl-tRNA synthetase (SepRS) and then converted to Cys-tRNA Cysby Sep-tRNA:Cys-tRNA synthase (SepCysS). In this study, we searched all genomic and metagenomic protein sequence data in the Integrated Microbial Genomes (IMG) system and at the NCBI to reveal new clades of SepRS and SepCysS proteins belonging to diverse archaea in the four major groups (DPANN,Euryarchaeota, TACK, and Asgard) andmore » two groups of bacteria (“CandidatusParcubacteria” andChloroflexi). Bacterial SepRS and SepCysS charged bacterial tRNA Cysspecies with cysteinein vitro. Homologs of SepCysE, a scaffold protein facilitating SepRS-SepCysS complex assembly in Euryarchaeota class I methanogens, are found in a few groups of TACK and Asgard archaea, whereas the C-terminally truncated homologs exist fused or genetically coupled with diverse SepCysS species. Investigation of the selenocysteine (Sec)- and pyrrolysine (Pyl)-utilizing traits in SepRS-utilizing archaea and bacteria revealed that the archaea carrying full-length SepCysE employ Sec and that SepRS is often found in Pyl-utilizing archaea andChloroflexibacteria. We further discuss possible contributions of the SepRS-SepCysS system for sulfur assimilation, methanogenesis, and other metabolic processes requiring large amounts of iron-sulfur enzymes or Pyl-containing enzymes.« less
-
RNA-Dependent Cysteine Biosynthesis in Bacteria and Archaea
DOE Office of Scientific and Technical Information (OSTI.GOV)
Mukai, Takahito; Crnković, Ana; Umehara, Takuya
ABSTRACT The diversity of the genetic code systems used by microbes on earth is yet to be elucidated. It is known that certain methanogenic archaea employ an alternative system for cysteine (Cys) biosynthesis and encoding; tRNA Cysis first acylated with phosphoserine (Sep) byO-phosphoseryl-tRNA synthetase (SepRS) and then converted to Cys-tRNA Cysby Sep-tRNA:Cys-tRNA synthase (SepCysS). In this study, we searched all genomic and metagenomic protein sequence data in the Integrated Microbial Genomes (IMG) system and at the NCBI to reveal new clades of SepRS and SepCysS proteins belonging to diverse archaea in the four major groups (DPANN,Euryarchaeota, TACK, and Asgard) andmore » two groups of bacteria (“CandidatusParcubacteria” andChloroflexi). Bacterial SepRS and SepCysS charged bacterial tRNA Cysspecies with cysteinein vitro. Homologs of SepCysE, a scaffold protein facilitating SepRS-SepCysS complex assembly in Euryarchaeota class I methanogens, are found in a few groups of TACK and Asgard archaea, whereas the C-terminally truncated homologs exist fused or genetically coupled with diverse SepCysS species. Investigation of the selenocysteine (Sec)- and pyrrolysine (Pyl)-utilizing traits in SepRS-utilizing archaea and bacteria revealed that the archaea carrying full-length SepCysE employ Sec and that SepRS is often found in Pyl-utilizing archaea andChloroflexibacteria. We further discuss possible contributions of the SepRS-SepCysS system for sulfur assimilation, methanogenesis, and other metabolic processes requiring large amounts of iron-sulfur enzymes or Pyl-containing enzymes.« less
-
NASA Astrophysics Data System (ADS)
Zhang, Haibin; Johnson, Shannon B.; Flores, Vanessa R.; Vrijenhoek, Robert C.
2015-11-01
We describe a broad zone of intergradation between genetically differentiated, northern and southern lineages of the hydrothermal vent tubeworm, Tevnia jerichonana. DNA sequences from four genes, nuclear HSP and ATPsα and mitochondrial COI and Cytb were examined in samples from eastern Pacific vent localities between 13°N and 38°S latitude. Allelic frequencies at these loci exhibited concordant latitudinal clines, and genetic differentiation (pairwise ΦST's) increased with geographical distances between sample localities. Though this pattern of differentiation suggested isolation-by-distance (IBD), it appeared to result from hierarchical population structure. Genotypic assignment tests identified two population clusters comprised of samples from the northern East Pacific Rise (NEPR: 9-13°N) and an extension of the Pacific-Antarctic Ridge (PAR: 31-32°S) with a zone of intergradation along the southern East Pacific Rise (SEPR: 7-17°S). The overall degrees of DNA sequence divergence between the NEPR and PAR populations were slight and not indicative of lengthy isolation. Bayesian assignment methods suggested that the SEPR populations constitute intergrades that connect the NEPR and PAR populations. Though it typically is difficult to distinguish between primary and secondary intergradation, our results were consistent with parallel studies of vent-restricted species that suggest a high degree of demographic instability along the superfast-spreading SEPR axis. Frequent local extinctions and immigration from NEPR and PAR refugia probably shaped the observed pattern of intergradation.
-
Hammond, W.C.; Toomey, D.R.
2003-01-01
We use teleseismic P and S delay times and shear wave splitting measurements to constrain isotropic and anisotropic heterogeneity in the mantle beneath the southern East Pacific Rise (SEPR). The data comprise 462 P and S delay times and 18 shear wave splitting observations recorded during the Mantle Electromagnetic and Tomography (MELT) Experiment. We estimate the mantle melt content (F) and temperature (T) variation from the isotropic velocity variation. Our results indicate that the maximum variation in F beneath our array is between zero and ???1.2%, and maximum variation in T is between zero and ???100 K. We favor an explanation having partial contributions from both T and F. We approximate the seismic anisotropy of the upper mantle with hexagonal symmetry, consistent with the assumption of two dimensionality of mantle flow. Our new tomographic technique uses a nonlinear inversion of P and slow S polarization delay times to simultaneously solve for coupled VP and VS heterogeneity throughout the model and for the magnitude of anisotropy within discrete domains. The domain dimensions and the dip of the anisotropy are fixed for each inversion but are varied in a grid search, obtaining the misfit of the models to the body wave delay data and to split times of vertically propagating S waves. The data misfit and the isotropic heterogeneity are sensitive to domain dimensions and dip of anisotropy. In a region centered beneath the SEPR the best average dip of the hexagonal symmetry axis is horizontal or dipping shallowly (<30??) west. Given the resolution of our data, a subaxial region characterized by vertically aligned symmetry axes may exist but is limited to be <80 km deep. We infer that the mantle flow beneath the SEPR is consistent with shallow asthenospheric return flow from the direction of the South Pacific superswell.
-
Brief Psychometric Analysis of the Self-Efficacy Parent Report Scale (SEPRS)
ERIC Educational Resources Information Center
Erford, Bradley T.; Gavin, Kate
2013-01-01
The Self-Efficacy Parent-Report Scale was designed to assess parent perceptions of self-efficacy of their children aged 7 to 17 years. Internal aspects of validity indicated a marginal fit of the data to the unidimensional model. External facets of validity indicated the Self-Efficacy Parent-Report Scale had excellent convergent and discriminant…
-
Liang, Xujun; Guo, Chuling; Liao, Changjun; Liu, Shasha; Wick, Lukas Y; Peng, Dan; Yi, Xiaoyun; Lu, Guining; Yin, Hua; Lin, Zhang; Dang, Zhi
2017-06-01
Surfactant-enhanced remediation (SER) is considered as a promising and efficient remediation approach. This review summarizes and discusses main drivers on the application of SER in removing polycyclic aromatic hydrocarbons (PAHs) from contaminated soil and water. The effect of PAH-PAH interactions on SER efficiency is, for the first time, illustrated in an SER review. Interactions between mixed PAHs could enhance, decrease, or have no impact on surfactants' solubilization power towards PAHs, thus affecting the optimal usage of surfactants for SER. Although SER can transfer PAHs from soil/non-aqueous phase liquids to the aqueous phase, the harmful impact of PAHs still exists. To decrease the level of PAHs in SER solutions, a series of SER-based integrated cleanup technologies have been developed including surfactant-enhanced bioremediation (SEBR), surfactant-enhanced phytoremediation (SEPR) and SER-advanced oxidation processes (SER-AOPs). In this review, the general considerations and corresponding applications of the integrated cleanup technologies are summarized and discussed. Compared with SER-AOPs, SEBR and SEPR need less operation cost, yet require more treatment time. To successfully achieve the field application of surfactant-based technologies, massive production of the cost-effective green surfactants (i.e. biosurfactants) and comprehensive evaluation of the drivers and the global cost of SER-based cleanup technologies need to be performed in the future. Copyright © 2017. Published by Elsevier Ltd.
-
NASA Astrophysics Data System (ADS)
Fontaine, Fabrice J.; Rabinowicz, M.; Cannat, M.
2017-05-01
We present numerical models to explore possible couplings along the axis of fast-spreading ridges, between hydrothermal convection in the upper crust and magmatic flow in the lower crust. In an end-member category of models corresponding to effective viscosities μM lower than 1013 Pa.s in a melt-rich lower crustal along-axis corridor and permeability k not exceeding ˜10-16 m2 in the upper crust, the hot, melt-rich, gabbroic lower crust convects as a viscous fluid, with convection rolls parallel to the ridge axis. In these models, we show that the magmatic-hydrothermal interface settles at realistic depths for fast ridges, i.e., 1-2 km below seafloor. Convection cells in both horizons are strongly coupled and kilometer-wide hydrothermal upflows/plumes, spaced by 8-10 km, arise on top of the magmatic upflows. Such magmatic-hydrothermal convective couplings may explain the distribution of vent fields along the East (EPR) and South-East Pacific Rise (SEPR). The lower crustal plumes deliver melt locally at the top of the magmatic horizon possibly explaining the observed distribution of melt-rich regions/pockets in the axial melt lenses of EPR and SEPR. Crystallization of this melt provides the necessary latent heat to sustain permanent ˜100 MW vents fields. Our models also contribute to current discussions on how the lower crust forms at fast ridges: they provide a possible mechanism for focused transport of melt-rich crystal mushes from moho level to the axial melt lens where they further crystallize, feed eruptions, and are transported both along and off-axis to produce the lower crust.
-
Dental erosion, prevalence and risk factors among a group of adolescents in Stockholm County.
Skalsky Jarkander, M; Grindefjord, M; Carlstedt, K
2018-02-01
To investigate the prevalence and risk factors of dental erosion (DE) among a group of adolescents in Stockholm County. This cross sectional cohort study was conducted at three clinics of the Public Dental Service in Stockholm County. Fifteen and 17 year old adolescents (1335) who scheduled their regular dental health examination were asked to participate. After drop-outs a sample of 1071 individuals, 547 males and 524 females were enrolled in the study. Presence of erosive wear was diagnosed (yes/no) on marker teeth by trained dentists/dental hygienists and photographs were taken. The adolescents answered a questionnaire regarding oral symptoms, dietary and behavioural factors. Two calibrated specialist dentists performed evaluation of the photographs for severity of DE using a modified version of the Simplified Erosion Partial Recording System (SEPRS). DE was clinically diagnosed in 28.3% of 15 years old and 34.3% of 17 years old. Severe erosive wear (grade 3 and 4 according to SEPRS) was found in 18.3% of the adolescents based upon the intra-oral photographs. DE was more prevalent and severe among males than females. Clinically diagnosed erosive lesions correlated significantly with soft drink consumption (p < 0.001), the use of juice or sport drinks as a thirst quencher after exercise (p = 0.006) and tooth hypersensitivity when eating and drinking (p = 0.012). Furthermore, self-assessed gastric reflux was a factor strongly associated with DE (p < 0.001). The study indicated that DE was common among adolescents in Stockholm County and associated with both internal and external risk factors.
-
NASA Astrophysics Data System (ADS)
McDermott, Jill M.; Ono, Shuhei; Tivey, Margaret K.; Seewald, Jeffrey S.; Shanks, Wayne C.; Solow, Andrew R.
2015-07-01
Multiple sulfur isotopes were measured in metal sulfide deposits, elemental sulfur, and aqueous hydrogen sulfide to constrain sulfur sources and the isotopic systematics of precipitation in seafloor hydrothermal vents. Areas studied include the Eastern Manus Basin and Lau Basin back-arc spreading centers and the unsedimented basalt-hosted Southern East Pacific Rise (SEPR) and sediment-hosted Guaymas Basin mid-ocean ridge spreading centers. Chalcopyrite and dissolved hydrogen sulfide (H2S) δ34S values range from -5.5‰ to +5.6‰ in Manus Basin samples, +2.4‰ to +6.1‰ in Lau Basin samples, and +3.7‰ to +5.7‰ in SEPR samples. Values of δ34S for cubic cubanite and H2S range from -1.4‰ to +4.7‰ in Guaymas Basin samples. Multiple sulfur isotope systematics in fluid-mineral pairs from the SEPR and Lau Basin show that crustal host rock and thermochemical reduction of seawater-derived dissolved sulfate (SO4) are the primary sources of sulfur in mid-ocean ridge and some back-arc systems. At PACMANUS and SuSu Knolls hydrothermal systems in the Eastern Manus Basin, a significant contribution of sulfur is derived from disproportionation of magmatic sulfur dioxide (SO2), while the remaining sulfur is derived from crustal host rocks and SO4 reduction. At the sedimented Guaymas Basin hydrothermal system, sulfur sources include crustal host rock, reduced seawater SO4, and biogenic sulfide. Vent fluid flow through fresher, less-mature sediment supplies an increased quantity of reactant organic compounds that may reduce 34S-enriched SO4, while fluid interaction with more highly-altered sediments results in H2S characterized by a small, but isotopically-significant input of 34S-depleted biogenic sulfides. Near-zero Δ33S values in all samples implicate the abiotic processes of SO4 reduction and leaching of host rock as the major contributors to sulfur content at a high temperature unsedimented mid-ocean ridge and at a back-arc system. Δ33S values indicate that SO2 disproportionation is an additional process that contributes sulfur to a different back-arc system and to acid spring-type hydrothermal fluid circulation. At the sedimented Guaymus Basin, near-zero Δ33S values are also observed, despite negative δ34S values that indicate inputs of biogenic pyrite for some samples. In contrast with previous studies reporting isotope disequilibrium between H2S and chalcopyrite, the δ34S values of chalcopyrite sampled from the inner 1-2 mm of a chimney wall are within ±1‰ of δ34S values for H2S in the paired vent fluid, suggesting equilibrium fluid-mineral sulfur isotope exchange at 300-400 °C. Isotopic equilibrium between hydrothermal fluid H2S and precipitating chalcopyrite implies that sulfur isotopes in the chalcopyrite lining across a chimney wall may accurately record past hydrothermal activity.
-
Genomics approach to the environmental community of microorganisms
NASA Astrophysics Data System (ADS)
Kawarabayasi, Y.; Maruyama, A.
2004-12-01
It was indicated by microscopic observation or comparison of 16S rDNA sequence that many extremophiles were surviving in many hydrothermal environments. But it is generally said that over 99% of total microbes are now uncultivable. Thus, we planned to identify uncultivable microbes through direct sequencing of environmental DNA. At first, shotgun plasmid libraries were directly constructed with the DNA molecules prepared from mixed microbes collected from low-temperature hydrothermal water at RM24 in the Southern East Pacific Rise (S-EPR). It was shown that the sequences of some number of clones indicated the similar feature to the intron in eukaryote or tandem repetitive sequence identified in some human familiar diseases. The results indicated that many microorganisms with eukaryotic feature were dominant in low temperature water of S-EPR. Secondly, shotgun plasmid libraries were constructed from the environmental DNA prepared from Beppu hot springs. The ORFs were easily identified all clones determined entire sequence. Thus it can be said that hot springs is good resources for searching novel genes. At last, the mixed microbes isolated from Suiyo seamount were used for construction of shotgun library. The clones in this library contained the ORFs. From some clones in hot spring and Suiyo sample, aminoacyl-tRNA synthatase, which is generally present in all organisms, was isolated by similarity. The phylogenetic analysis of aminoacyl-tRNA synthetase identified indicated that novel and unidentified microorganisms should be present in hot spring or Suiyo seamount. The novel genes identified from Suiyo seamount were also utilized for expression in E. coli. Some gene products were successfully obtained from the E. coli cells as soluble proteins. Some protein indicated the thermostability up to 70_E#8249;C, meaning that the original host cell of this gene should be stable up to the same temperature. Our work indicates that environmental genomics, including the direct cloning, sequencing of environmental DNA and expression of gene identified, is powerful approach to collect novel uncultivable microbes or novel active genes.
-
Jang, Sook-Jin; Park, Eunji; Lee, Won-Kyung; Johnson, Shannon B; Vrijenhoek, Robert C; Won, Yong-Jin
2016-10-28
The Equator and Easter Microplate regions of the eastern Pacific Ocean exhibit geomorphological and hydrological features that create barriers to dispersal for a number of animals associated with deep-sea hydrothermal vent habitats. This study examined effects of these boundaries on geographical subdivision of the vent polychaete Alvinella pompejana. DNA sequences from one mitochondrial and eleven nuclear genes were examined in samples collected from ten vent localities that comprise the species' known range from 23°N latitude on the East Pacific Rise to 38°S latitude on the Pacific Antarctic Ridge. Multi-locus genotypes inferred from these sequences clustered the individual worms into three metapopulation segments - the northern East Pacific Rise (NEPR), southern East Pacific Rise (SEPR), and northeastern Pacific Antarctic Ridge (PAR) - separated by the Equator and Easter Microplate boundaries. Genetic diversity estimators were negatively correlated with tectonic spreading rates. Application of the isolation-with-migration (IMa2) model provided information about divergence times and demographic parameters. The PAR and NEPR metapopulation segments were estimated to have split roughly 4.20 million years ago (Mya) (2.42-33.42 Mya, 95 % highest posterior density, (HPD)), followed by splitting of the SEPR and NEPR segments about 0.79 Mya (0.07-6.67 Mya, 95 % HPD). Estimates of gene flow between the neighboring regions were mostly low (2 Nm < 1). Estimates of effective population size decreased with southern latitudes: NEPR > SEPR > PAR. Highly effective dispersal capabilities allow A. pompejana to overcome the temporal instability and intermittent distribution of active hydrothermal vents in the eastern Pacific Ocean. Consequently, the species exhibits very high levels of genetic diversity compared with many co-distributed vent annelids and mollusks. Nonetheless, its levels of genetic diversity in partially isolated populations are inversely correlated with tectonic spreading rates. As for many other vent taxa, this pioneering colonizer is similarly affected by local rates of habitat turnover and by major dispersal filters associated with the Equator and the Easter Microplate region.
-
Evaluation of microbial community in hydrothermal field by direct DNA sequencing
NASA Astrophysics Data System (ADS)
Kawarabayasi, Y.; Maruyama, A.
2002-12-01
Many extremophiles have been discovered from terrestrial and marine hydrothermal fields. Some thermophiles can grow beyond 90°C in culture, while direct microscopic analysis occasionally indicates that microbes may survive in much hotter hydrothermal fluids. However, it is very difficult to isolate and cultivate such microbes from the environments, i.e., over 99% of total microbes remains undiscovered. Based on experiences of entire microbial genome analysis (Y.K.) and microbial community analysis (A.M.), we started to find out unique microbes/genes in hydrothermal fields through direct sequencing of environmental DNA fragments. At first, shotgun plasmid libraries were directly constructed with the DNA molecules prepared from mixed microbes collected by an in situ filtration system from low-temperature fluids at RM24 in the Southern East Pacific Rise (S-EPR). A gene amplification (PCR) technique was not used for preventing mutation in the process. The nucleotide sequences of 285 clones indicated that no sequence had identical data in public databases. Among 27 clones determined entire sequences, no ORF was identified on 14 clones like intron in Eukaryote. On four clones, tetra-nucleotide-long multiple tandem repetitive sequences were identified. This type of sequence was identified in some familiar disease in human. The result indicates that living/dead materials with eukaryotic features may exist in this low temperature field. Secondly, shotgun plasmid libraries were constructed from the environmental DNA prepared from Beppu hot springs. In randomly-selected 143 clones used for sequencing, no known sequence was identified. Unlike the clones in S-EPR library, clear ORFs were identified on all nine clones determined the entire sequence. It was found that one clone, H4052, contained the complete Aspartyl-tRNA synthetase. Phylogenetic analysis using amino acid sequences of this gene indicated that this gene was separated from other Euryarchaea before the differentiation of species. Thus, some novel archaeal species are expected to be in this field. The present direct cloning and sequencing technique is now opening a window to the new world in hydrothermal microbial community analysis.
-
NASA Astrophysics Data System (ADS)
Hayman, Nicholas W.; Karson, Jeffrey A.
2009-02-01
The escarpments that bound the Pito Deep Rift (northeastern Easter microplate) expose in situ upper oceanic crust that was accreted ˜3 Ma ago at the superfast spreading (˜142 mm/a, full rate) southeast Pacific Rise (SEPR). Samples and images of these escarpments were taken during transects utilizing the human-occupied vehicle Alvin and remotely operated vehicle Jason II. The dive areas were mapped with a "deformation intensity scale" revealing that the sheeted dike complex and the base of the lavas contain approximately meter-wide fault zones surrounded by fractured "damage zones." Fault zones are spaced several hundred meters apart, in places offset the base of the lavas, separate areas with differently oriented dikes, and are locally crosscut by (younger) dikes. Fault rocks are rich in interstitial amphibole, matrix and vein chlorite, prominent veins of quartz, and accessory grains of sulfides, oxides, and sphene. These phases form the fine-grained matrix materials for cataclasites and cements for breccias where they completely surround angular to subangular clasts of variably altered and deformed basalt. Bulk rock geochemical compositions of the fault rocks are largely governed by the abundance of quartz veins. When compositions are normalized to compensate for the excess silica, the fault rocks exhibit evidence for additional geochemical changes via hydrothermal alteration, including the loss of mobile elements and gain of some trace metals and magnesium. Microstructures and compositions suggest that the fault rocks developed over multiple increments of deformation and hydrothermal fluid flow in the subaxial environment of the SEPR; faults related to the opening of the Pito Deep Rift can be distinguished by their orientation and fault rock microstructure. Some subaxial deformation increments were likely linked with violent discharge events associated with fluid pressure fluctuations and mineral sealing within the fault zones. Other increments were linked with the influx of relatively fresh seawater. The spacing of the faults is consistent with fault localization occurring every 7000 to 14,000 years, with long-term slip rates of <3 mm/a. Once spread from the ridge axis, the faults were probably not active, and damage zones likely played a more significant role in axial flank and off-axis crustal permeability.
-
Lithographic performance of recent DUV photoresists
NASA Astrophysics Data System (ADS)
Streefkerk, Bob; van Ingen Schenau, Koen; Buijk, Corine
1998-06-01
Commercially available photoresists from the major photoresist vendors are investigated using a PAS 5500/300 wafer stepper, a 31.1 mm diameter field size high throughput wafer stepper with variable NA capability up to 0.63. The critical dimension (CD) investigated is 0.25 micrometers and lower for dense and isolated lines and 0.25 micrometers for dense contact holes. The photoresist process performance is quantified by measuring exposure-defocus windows for a specific resolution using a CD SEM. Photoresists that are comparable with or better than APEX-E with RTC top coat, which is the current base line process for lines and spaces imaging performance, are Clariant AZ-DX1300 and Shin Etsu SEPR-4103PB50. Most recent photoresists have much improved delay performance when compared to APEX without top coat. Improvement, when an organic BARC is applied, depends on the actual photoresist characteristics. The optimal photoresist found for 0.25 micrometers contact holes is TOK DP015 C. This process operates at optimal conditions.
-
Nanoparticulate, sub-micron and micron sized particles emanating from hydrothermal vents
NASA Astrophysics Data System (ADS)
Luther, G. W., III; Gartman, A.; Findlay, A.; Yucel, M.; Chan, C. S. Y.
2015-12-01
Recent data from Geotraces cruises over the MAR and SEPR indicate dissolved and particulate Fe enrichment in waters 1000 and 4000 km from their vent sources, respectively. Deep-sea hydrothermal vents and the waters in the reactive mixing zone above vent orifices have been suggested to be an important source of fine material that can pass through normal filters (0.2 and 0.4 μm). In this work, nanoparticles are defined operationally as that which can pass through a 0.2 μm filter. We investigated two vent sites (Lau Basin and the MAR). Chimneys from both vent sites have fluids that can be sulfide rich or metal rich. We also present chemical and physical chemical data (SEM-EDS, TEM, XRD, EELS) showing some of the materials found in these (nano)particulate phases including pyrite, metal sulfides, silicate and aluminosilicate material. Enrichment of Mg and K in the latter suggest that reverse weathering may occur in the waters within 1-2 meters of the vent orifice where vent waters mix with cold oxygenated bottom waters.
-
NASA Astrophysics Data System (ADS)
Rubin, K. H.; Smith, M. C.; Sinton, J. M.; Sacks, L. F.; Bergmanis, E.
2001-12-01
Quantification of the absolute ages and geochemistry of individual seafloor lava flows provides important constraints on the magmatic processes responsible for building the oceanic crust. Here we present new 238U-230Th-226Ra-210Pb radioactive disequilibrium age constraints (decadal to millennial time scale) for 3 mid-ocean ridge lava flows at 17° 26'S on the East Pacific Rise (EPR): Aldo-Kihi, Rehu-Marka, and a neighboring unnamed flow. Our continuing study using high-resolution surveys and manned-submersible sampling (NAUDUR, 1993, and STOWA, 1991, expeditions) has previously shown that Aldo-Kihi is compositionally variable, is probably one of the youngest axial lavas in the 17° -19° S region, and was most likely erupted from a series of fissures extending >18 km along the ridge axis (Sinton et al., JGR, in revision). Rehu Marka has a more trace element enriched and evolved composition. The strongest age constraints in our U-series data set are from the 210Pb-226Ra (half-life = 22.3 yrs) and 226Ra-230Th (half life = 1600 yrs) systems. 210Pb-226Ra disequilibrium (as 5-7% Pb deficits) is common in lavas from our S-EPR study area and slightly lower than disequilibria we have measured in lavas erupted in 1991 and 1992 at 9° 50'N EPR. Although we are still developing our understanding of how this disequilibrium arises in MORB (e.g., how the radioactive "clock" is set for this isotope pair) a number of features of our preliminary data support the idea that these lavas are very young and that geologically observed contact relationships in the field separate the products of chronologically distinguishable eruptions. Also, the extent of 226Ra-210Pb disequilibrium in 3 Aldo-Kihi samples compared to that observed at 9° 50'N indicates that the Aldo-Kihi lava probably erupted within the last 10-20 yrs, and the higher but still <1 (210Pb/226Ra) activity ratio in a lava sampled near to but outside the boundaries of Aldo-Kihi indicates it is slightly older, but probably only by a decade or so. Although the older lava's major element composition is very similar to Aldo-Kihi, it has distinct U-Th-Ra chemistry, indicating it is from a different parental magma. Finally, the compositionally very distinct Rehu Marka flow just to the north has no 226Ra-210Pb disequilibrium, indicating it is likely older than the maximum resolvable age with this method (100-120 years). An age estimate (about 750 yrs) of the latter can be made from its 226Ra excess. Together, these preliminary age constraints provide insight into eruption recurrence rates and the processes that allow for preservation of compositional variability within proximally located (in space and time) lava flows along this magmatically robust segment of the EPR.
-
A new scaling for divertor detachment
NASA Astrophysics Data System (ADS)
Goldston, R. J.; Reinke, M. L.; Schwartz, J. A.
2017-05-01
The ITER design, and future reactor designs, depend on divertor ‘detachment,’ whether partial, pronounced or complete, to limit heat flux to plasma-facing components and to limit surface erosion due to sputtering. It would be valuable to have a measure of the difficulty of achieving detachment as a function of machine parameters, such as input power, magnetic field, major radius, etc. Frequently the parallel heat flux, estimated typically as proportional to P sep/R or P sep B/R, is used as a proxy for this difficulty. Here we argue that impurity cooling is dependent on the upstream density, which itself must be limited by a Greenwald-like scaling. Taking this into account self-consistently, we find the impurity fraction required for detachment scales dominantly as power divided by poloidal magnetic field. The absence of any explicit scaling with machine size is concerning, as P sep surely must increase greatly for an economic fusion system, while increases in the poloidal field strength are limited by coil technology and plasma physics. This result should be challenged by comparison with 2D divertor codes and with measurements on existing experiments. Nonetheless, it suggests that higher magnetic field, stronger shaping, double-null operation, ‘advanced’ divertor configurations, as well as alternate means to handle heat flux such as metallic liquid and/or vapor targets merit greater attention.
-
Magosch, P; Habermeyer, P; Lichtenberg, S; Tauber, M; Gohlke, F; Mauch, F; Boehm, D; Loew, M; Zeifang, F; Pötzl, W
2017-12-01
Anatomic shoulder arthroplasty in osteoarthritis with biconcave glenoid wear results in decreased functional results and a higher rate of early glenoid loosening. The aim of the data analysis of the German shoulder arthroplasty register was to clarify whether reverse shoulder arthroplasty can provide better functional results and a lower complication rate than anatomic arthroplasty in osteoarthritis with biconcave glenoid wear. The analysis included 1052 completely documented primary implanted arthroplasties with a minimum follow-up of 2 years. In 119 cases, a B2-type glenoid was present. Out of these cases, 86 were treated with an anatomic shoulder arthroplasty, and in 33 cases a reverse shoulder arthroplasty was implanted. The mean follow-up was 47.6 months. The Constant score with its subcategories, as well as the active range of movement improved significantly after anatomic and after reverse shoulder arthroplasty. We observed no difference in functional results between both types of arthroplasty; however, reverse arthroplasty showed a significant higher revision rate (21.2%) (3% glenoid loosening, 6% prosthetic instability) than anatomic shoulder arthroplasty (12.8%) (11.6% glenoid loosening, 1.2% prosthetic instability), whereas anatomic shoulder arthroplasty showed a higher rate of glenoid loosening. Functional and radiographic results of both types of arthroplasty are comparable with the results reported in the literature, although our analysis represents results from an implant registry (data pertaining to medical care quality).
-
Basin-scale transport of hydrothermal dissolved metals across the South Pacific Ocean.
Resing, Joseph A; Sedwick, Peter N; German, Christopher R; Jenkins, William J; Moffett, James W; Sohst, Bettina M; Tagliabue, Alessandro
2015-07-09
Hydrothermal venting along mid-ocean ridges exerts an important control on the chemical composition of sea water by serving as a major source or sink for a number of trace elements in the ocean. Of these, iron has received considerable attention because of its role as an essential and often limiting nutrient for primary production in regions of the ocean that are of critical importance for the global carbon cycle. It has been thought that most of the dissolved iron discharged by hydrothermal vents is lost from solution close to ridge-axis sources and is thus of limited importance for ocean biogeochemistry. This long-standing view is challenged by recent studies which suggest that stabilization of hydrothermal dissolved iron may facilitate its long-range oceanic transport. Such transport has been subsequently inferred from spatially limited oceanographic observations. Here we report data from the US GEOTRACES Eastern Pacific Zonal Transect (EPZT) that demonstrate lateral transport of hydrothermal dissolved iron, manganese, and aluminium from the southern East Pacific Rise (SEPR) several thousand kilometres westward across the South Pacific Ocean. Dissolved iron exhibits nearly conservative (that is, no loss from solution during transport and mixing) behaviour in this hydrothermal plume, implying a greater longevity in the deep ocean than previously assumed. Based on our observations, we estimate a global hydrothermal dissolved iron input of three to four gigamoles per year to the ocean interior, which is more than fourfold higher than previous estimates. Complementary simulations with a global-scale ocean biogeochemical model suggest that the observed transport of hydrothermal dissolved iron requires some means of physicochemical stabilization and indicate that hydrothermally derived iron sustains a large fraction of Southern Ocean export production.
-
NASA Astrophysics Data System (ADS)
Poulton, Simon W.; Canfield, Donald E.
2006-12-01
We present a detailed study of the co-diagenesis of Fe and P in hydrothermal plume fallout sediments from ˜19°S on the southern East Pacific Rise. Three distal sediment cores from 340-1130 km from the ridge crest, collected during DSDP Leg 92, were analysed for solid phase Fe and P associations using sequential chemical extraction techniques. The sediments at all sites are enriched in hydrothermal Fe (oxyhydr)oxides, but during diagenesis a large proportion of the primary ferrihydrite precipitates are transformed to the more stable mineral form of goethite and to a lesser extent to clay minerals, resulting in the release to solution of scavenged P. However, a significant proportion of this P is retained within the sediment, by incorporation into secondary goethite, by precipitation as authigenic apatite, and by readsorption to Fe (oxyhydr)oxides. Molar P/Fe ratios for these sediments are significantly lower than those measured in plume particles from more northern localities along the southern East Pacific Rise, and show a distinct downcore decrease to a depth of ˜12 m. Molar P/Fe ratios are then relatively constant to a depth of ˜35 m. The Fe and P speciation data indicate that diagenetic modification of the sediments is largely complete by a depth of 2.5 m, and thus depth trends in molar P/Fe ratios can not solely be explained by losses of P from the sediment by diffusion to the overlying water column during early diagenesis. Instead, these sediments are likely recording changes in dissolved P concentrations off the SEPR, possibly as a result of redistribution of nutrients in response to changes in oceanic circulation over the last 10 million years. Furthermore, the relatively low molar P/Fe ratios observed throughout these sediments are not necessarily solely due to losses of scavenged P by diffusion to the overlying water column during diagenesis, but may also reflect post-depositional oxidation of pyrite originating from the volatile-rich vents of the southern East Pacific Rise. This study suggests that the molar P/Fe ratio of oxic Fe-rich sediments may serve as a proxy of relative changes in paleoseawater phosphate concentrations, particularly if Fe sulfide minerals are not an important component during transport and deposition.