bluuebunny/crossref_metadata_2025_split huggingface dataset:
Seismicity of the Atlantis Massif detachment fault, 30°N at the Mid‐Atlantic Ridge
Authors: Collins John A. , Smith Deborah K. , McGuire Jeffrey J. 
Published: September 2012

At the oceanic core complex that forms the Atlantis Massif at 30°N on the Mid‐Atlantic Ridge, slip along the detachment fault for the last 1.5–2 Ma has brought lower crust and mantle rocks to the seafloor. Hydroacoustic data collected between 1999 and 2003 suggest that seismicity occurred near the top of the Massif, mostly on the southeastern section, while detected seismicity along the adjacent ridge axis was sparse. In 2005, five short‐period ocean bottom seismographs (OBS) were deployed on and around the Massif as a pilot experiment to help constrain the distribution of seismicity in this region. Analysis of six months of OBS data indicates that, in contrast to the results of the earlier hydroacoustic study, the vast majority of the seismicity is located within the axial valley. During the OBS deployment, and within the array, seismicity was primarily composed of a relatively constant background rate and two large aftershock sequences that included 5 teleseismic events with magnitudes between 4.0 and 4.5. The aftershock sequences were located on the western side of the axial valley adjacent to the Atlantis Massif and close to the ridge‐transform intersection. They follow Omori's law, and constitute more than half of the detected earthquakes. The OBS data also indicate a low but persistent level of seismicity associated with active faulting within the Atlantis Massif in the same region as the hydroacoustically detected seismicity. Within the Massif, the data indicate a north‐south striking normal fault, and a left‐lateral, strike‐slip fault near a prominent, transform‐parallel, north‐facing scarp. Both features could be explained by changes in the stress field at the inside corner associated with weak coupling on the Atlantis transform. Alternatively, the normal faulting within the Massif might indicate deformation of the detachment surface as it rolls over to near horizontal from an initial dip of about 60° beneath the axis, and the strike‐slip events may indicate transform‐parallel movement on adjacent detachment surfaces.
Tracing the Paleo sulfate‐methane transition zones and H2S seepage events in marine sediments: An application of C‐S‐Mo systematics
Authors: Peketi A. , Mazumdar (corresponding author) A. , Joshi R. K. , Patil D. J. , Srinivas P. L. , Dayal A. M. 
Published: September 2012

Microbially mediated anaebic oxidation of methane (AOM) coupled with sulfate consumption within the sulfate methane transition zone (SMTZ) in marine sediments is a widely recorded biogeochemical reaction and has profound influence on the atmospheric CH4budget, marine carbon cycle and composition of sediment pore fluids. Recognizing the paleo‐SMTZs in the marine sediments/rock records can throw light on the variation of paleo‐methane fluxes and occurrences of cold seep (H2S + CH4) events through geologic time. Here, we present results from carbonate carbon, pyrite sulfur and molybdenum analyses for two sediment cores overlying the methane hydrate deposits in the Bay of Bengal. The results show intimate association of isotopically depleted carbonate carbon and enriched pyrite sulfur, constraining the paleo SMTZ within the sediment column. In addition, anomalous enrichments of Mo concentrations indicate hydrogen sulfide seepage events. Here, we propose a geochemical tool using C‐S‐Mo sytematics to decipher the paleo‐SMTZs in marine sediments and rocks.
Liquid‐liquid phase separation in aerosol particles: Dependence on O:C, organic functionalities, and compositional complexity
Authors: Song M. , Marcolli C. , Krieger U. K. , Zuend A. , Peter T. 
Published: September 2012

Atmospheric aerosol particles may undergo liquid‐liquid phase separation (LLPS) when exposed to varying relative humidity. In this study we investigated the occurrence of LLPS for mixtures consisting of up to ten organic compounds, ammonium sulfate, and water in relationship with the organic oxygen‐to‐carbon (O:C) ratio. LLPS always occurred for O:C < 0.56, never occurred for O:C > 0.80, and depended on the specific types and compositions of organic functional groups in the regime 0.56 < O:C < 0.80. In the intermediate regime, mixtures with a high share of aromatic compounds shifted the limit of occurrence of LLPS to lower O:C ratios. The number of mixture components and the spread of the O:C range did not notably influence the conditions for LLPS to occur. Since in ambient aerosols O:C range typically between 0.2 and 1.0, LLPS is expected to be a common feature of tropospheric aerosols.
Multi‐decadal glacier surface lowering in the Antarctic Peninsula
Authors: Kunz Matthias , King Matt A. , Mills Jon P. , Miller Pauline E. , Fox Adrian J. , Vaughan David G. , Marsh Stuart H. 
Published: September 2012

From approximately 400 glaciers of the western Antarctic Peninsula, no in situ records of mass balance exist and their recent contribution to sea level is consequently poorly constrained. We seek to address this shortcoming by using surface elevations from USGS and BAS airborne (1948–2005) and ASTER spaceborne (2001–2010) stereo imagery, combined by using a rigorous semi‐automated registration approach, to determine multi‐decadal glacier surface elevation changes in the western Antarctic Peninsula for 12 glaciers. All observed glaciers show near‐frontal surface lowering and an annual mean lowering rate of 0.28 ± 0.03 m/yr at the lower portion of the glaciers during the ∼4 decades following the mid‐1960s, with higher rates for the glaciers in the north‐west parts of the Antarctic Peninsula. Increased lowering of up to 0.6 m/yr can be observed since the 1990s, in close correspondence to increased atmospheric positive degree days. In all cases, surface lowering reduces to zero within 5 km of the glacier front at around 400 m altitude. This lowering may have been at least partially compensated for by increased high‐altitude accumulation.
The vertical and spatial structure of ENSO in the upper troposphere and lower stratosphere from GPS radio occultation measurements
Authors: Scherllin‐Pirscher B. , Deser C. , Ho S.‐P. , Chou C. , Randel W. , Kuo Y.‐H. 
Published: September 2012

The vertical and spatial structure of the atmospheric El Niño‐Southern Oscillation (ENSO) signal is investigated using radio occultation (RO) data from August 2006 to December 2010. Due to their high vertical resolution and global coverage, RO data are well suited to describe the full 3‐dimensional ENSO structure in the troposphere and lower stratosphere. We find that interannual temperature anomalies in the equatorial region show a natural decomposition into zonal‐mean and eddy (deviations from the zonal‐mean) components that are both related to ENSO. Consistent with previous studies, we find that during the warm phase of ENSO, zonal‐mean temperatures increase in the tropical troposphere and decrease in the tropical stratosphere. Maximum warming occurs above 8 km, and the transition between warming and cooling occurs near the tropopause. This zonal‐mean response lags sea surface temperature anomalies in the eastern equatorial Pacific by 3 months. The atmospheric eddy component, in contrast, responds rapidly (within 1 month) to ENSO forcing. This signal features a low‐latitude dipole between the Indian and Pacific Oceans, with off‐equatorial maxima centered around 20° to 30° latitude in both hemispheres. The eddy response pattern attains maximum amplitude in the upper troposphere near 11 km and (with opposite polarity) in a shallow layer near the tropopause at approximately 17 km. The eddy ENSO signal tends to be out‐of‐phase between low and middle latitudes in both the troposphere and lower stratosphere.
Baroclinic adjustment in Drake Passage driven by tropical Pacific forcing
Authors: Close Sally E. , Naveira Garabato Alberto C. 
Published: September 2012

The time series of high‐quality hydrographic measurements of the ACC in Drake Passage is revisited to investigate the extent of baroclinic adjustment in the region on time scales of up to two decades. We find that substantial adjustment of the upper kilometer of northern Drake Passage has occurred on interannual to decadal time scales, driven primarily by tropical Pacific forcing via the poleward propagation of boundary waves. The decadal‐scale signal consists of a marked deepening of isopycnals (by ∼200 m between the early 1990s and the late 2000s), and reflects ENSO‐forced wind‐driven baroclinic changes over an extensive region of the eastern South Pacific.
Tropical daytime lower D‐region dependence on sunspot number
Authors: Thomson Neil R. , Rodger Craig J. , Clilverd Mark A. 
Published: September 2012

Observed phases and amplitudes of VLF radio signals propagating on (near) tropical all‐sea paths, both short, ∼300 km, and long, ∼10 Mm, are used to find daytime parameter changes for the lowest edge of the (D‐region of the) Earth's ionosphere as the solar cycle advanced from a very low sunspot number of ∼5 up to ∼60, in the period 2009–2011. The VLF phases, relative to GPS 1‐s pulses, and amplitudes were measured ∼100 km from the transmitter, where the direct ground wave is very dominant, ∼300 km from the transmitter, near where the ionospherically reflected waves form a (modal) minimum with the ground wave, and ∼10 Mm away where the lowest order waveguide mode is fully dominant. Most of the signals came from the 19.8 kHz, 1‐MW transmitter, NWC, North West Cape, Australia, propagating ENE, mainly over the sea, to the vicinity of Karratha and Dampier on the NW coast of Australia and then on to Kauai, Hawaii, ∼10.6 Mm from NWC. Observations from the 8.1‐Mm path NPM (21.4 kHz, Hawaii) to Dunedin, NZ, are also used. The sunspot number increase from ∼5 to ∼60 was found to coincide with a decrease in the height,H′, of the midday tropical ionosphere by 0.75 ± 0.25 km (from H′ ≈ 70.5 km to H′ ≈ 69.7 km) while the sharpness, β increased by 0.025 ± 0.01 km−1 (from β ≈ 0.47 km−1 to β ≈ 0.49 km−1) where H′ and βare the traditional height and sharpness parameters used by Wait and by the U.S. Navy in their Earth‐ionosphere VLF radio waveguide programs.
Can a sinking metallic diapir generate a dynamo?
Authors: Monteux Julien , Schaeffer Nathanaël , Amit Hagay , Cardin Philippe 
Published: September 2012

Metallic diapirs may have strongly contributed to core formations during the first million years of planetary evolutions. The aim of this study is to determine whether the dynamics induced by the diapir sinking can drive a dynamo and to characterize the required conditions on the size of the diapir, the mantle viscosity and the planetary latitude at which the diapir sinks. We impose a classical Hadamard flow solution for the motion at the interface between a spherical sinking diapir and a viscous mantle on dynamical simulations that account for rotational and inertial effects in order to model the flow within the diapir. The flows are confined to a velocity layer with a thickness that decreases with increasing rotation rate. These 3D flows are is then used as input for kinematic dynamo simulations to determine the critical magnetic Reynolds number for dynamo onset. Our results demonstrate that the flow pattern inside a diapir sinking into a rotating planet can generate a magnetic field. Large diapirs (R > 10 km) sinking in a mantle with a viscosity ranging from 109 to 1014 Pa.s provide plausible conditions for a dynamo. Equatorial sinking diapirs are confined to a thicker velocity layer and are thus possibly more favorable for dynamo generation than polar sinking diapirs. In addition equatorial sinking diapirs produce stronger saturated magnetic fields. However, for the range of parameters studied here, estimation of the intensity of diapir‐driven magnetic fields suggests that they could not have contributed to the lunar or Martian crustal paleomagnetic fields.
Ion densities and composition of Titan's upper atmosphere derived from the Cassini Ion Neutral Mass Spectrometer: Analysis methods and comparison of measured ion densities to photochemical model simulations
Authors: Mandt Kathleen E. , Gell David A. , Perry Mark , Hunter Waite J. , Crary Frank A. , Young David , Magee Brian A. , Westlake Joseph H. , Cravens Thomas , Kasprzak Wayne , Miller Greg , Wahlund Jan‐Erik , Ågren Karin , Edberg Niklas J. T. , Heays Alan N. , Lewis Brenton R. , Gibson Stephen T. , de la Haye V. , Liang Mao‐Chang 
Published: September 2012

The Cassini Ion Neutral Mass Spectrometer (INMS) has measured both neutral and ion species in Titan's upper atmosphere and ionosphere and the Enceladus plumes. Ion densities derived from INMS measurements are essential data for constraining photochemical models of Titan's ionosphere. The objective of this paper is to present an optimized method for converting raw data measured by INMS to ion densities. To do this, we conduct a detailed analysis of ground and in‐flight calibration to constrain the instrument response to ion energy, the critical parameter on which the calibration is based. Data taken by the Cassini Radio Plasma Wave Science Langmuir Probe and the Cassini Plasma Spectrometer Ion Beam Spectrometer are used as independent measurement constraints in this analysis. Total ion densities derived with this method show good agreement with these data sets in the altitude region (∼1100–1400 km) where ion drift velocities are low and the mass of the ions is within the measurement range of the INMS (1–99 Daltons). Although ion densities calculated by the method presented here differ slightly from those presented in previous INMS publications, we find that the implications for the science presented in previous publications is mostly negligible. We demonstrate the role of the INMS ion densities in constraining photochemical models and find that (1) cross sections having high resolution as a function of wavelength are necessary for calculating the initial photoionization products and (2) there are disagreements between the measured ion densities representative of the initial steps in Titan photochemistry that require further investigation.
Microbial communities in the subglacial waters of the Vatnajökull ice cap, Iceland
Authors: Marteinsson Viggó Thór , Rúnarsson Árni , Stefánsson Andri , Thorsteinsson Thorsteinn , Jóhannesson Tómas , Magnússon Sveinn H , Reynisson Eyjólfur , Einarsson Bergur , Wade Nicole , Morrison Hilary G , Gaidos Eric 
Published: September 2012

Abstract
Subglacial lakes beneath the Vatnajökull ice cap in Iceland host endemic communities of microorganisms adapted to cold, dark and nutrient-poor waters, but the mechanisms by which these microbes disseminate under the ice and colonize these lakes are unknown. We present new data on this subglacial microbiome generated from samples of two subglacial lakes, a subglacial flood and a lake that was formerly subglacial but now partly exposed to the atmosphere. These data include parallel 16S rRNA gene amplicon libraries constructed using novel primers that span the v3–v5 and v4–v6 hypervariable regions. Archaea were not detected in either subglacial lake, and the communities are dominated by only five bacterial taxa. Our paired libraries are highly concordant for the most abundant taxa, but estimates of diversity (abundance-based coverage estimator) in the v4–v6 libraries are 3–8 times higher than in corresponding v3–v5 libraries. The dominant taxa are closely related to cultivated anaerobes and microaerobes, and may occupy unique metabolic niches in a chemoautolithotrophic ecosystem. The populations of the major taxa in the subglacial lakes are indistinguishable (&gt;99% sequence identity), despite separation by 6 km and an ice divide; one taxon is ubiquitous in our Vatnajökull samples. We propose that the glacial bed is connected through an aquifer in the underlying permeable basalt, and these subglacial lakes are colonized from a deeper, subterranean microbiome.
The yeast vacuolar ABC transporter Ybt1p regulates membrane fusion through Ca2+ transport modulation
Authors: Sasser Terry L. , Padolina Mark , Fratti Rutilio A. 
Published: September 2012

Ybt1p is a class C ABC transporter (ATP-binding cassette transporter) that is localized to the vacuole of Saccharomyces cerevisiae. Although Ybt1p was originally identified as a bile acid transporter, it has also been found to function in other capacities, including the translocation of phosphatidylcholine to the vacuole lumen, and the regulation of Ca2+ homoeostasis. In the present study we found that deletion of YBT1 enhanced in vitro homotypic vacuole fusion by up to 50% relative to wild-type vacuoles. The increased vacuole fusion was not due to aberrant protein sorting of SNAREs (soluble N-ethylmaleimide-sensitive factor-attachment protein receptors) or recruitment of factors from the cytosol such as Ypt7p and the HOPS (homotypic fusion and vacuole protein sorting) tethering complex. In addition, ybt1Δ vacuoles displayed no observable differences in the formation of SNARE complexes, interactions between SNAREs and HOPS, or formation of vertex microdomains. However, the absence of Ybt1p caused significant changes in Ca2+ transport during fusion. One difference was the prolonged Ca2+ influx exhibited by ybt1Δ vacuoles at the start of the fusion reaction. We also observed a striking delay in SNARE-dependent Ca2+ efflux. As vacuole fusion can be inhibited by high Ca2+ concentrations, we suggest that the delayed efflux in ybt1Δ vacuoles leads to the enhanced SNARE function.
MpaA is a murein-tripeptide-specific zinc carboxypeptidase that functions as part of a catabolic pathway for peptidoglycan-derived peptides in γ-proteobacteria
Authors: Maqbool Abbas , Hervé Mireille , Mengin-Lecreulx Dominique , Wilkinson Anthony J. , Thomas Gavin H. 
Published: September 2012

The murein peptide amidase MpaA is a cytoplasmic enzyme that processes peptides derived from the turnover of murein. We have purified the enzyme from Escherichia coli and demonstrated that it efficiently hydrolyses the γ-D-glutamyl-diaminopimelic acid bond in the murein tripeptide (L-Ala-γ-D-Glu-meso-Dap), with Km and kcat values of 0.41±0.05 mM and 38.3±10 s−1. However, it is unable to act on the murein tetrapeptide (L-Ala-γ-D-Glu-meso-Dap-D-Ala). E. coli MpaA is a homodimer containing one bound zinc ion per chain, as judged by mass spectrometric analysis and size-exclusion chromatography. To investigate the structure of MpaA we solved the crystal structure of the orthologous protein from Vibrio harveyi to 2.17 Å (1Å=0.1 nm). Vh_MpaA, which has identical enzymatic and biophysical properties to the E. coli enzyme, has high structural similarity to eukaryotic zinc carboxypeptidases. The structure confirms that MpaA is a dimeric zinc metalloprotein. Comparison of the structure of MpaA with those of other carboxypeptidases reveals additional structure that partially occludes the substrate-binding groove, perhaps explaining the narrower substrate specificity of the enzyme compared with other zinc carboxypeptidases. In γ-proteobacteria mpaA is often located adjacent to mppA which encodes a periplasmic transporter protein previously shown to bind murein tripeptide. We demonstrate that MppA can also bind murein tetrapeptide with high affinity. The genetic coupling of these genes and their related biochemical functions suggest that MpaA amidase and MppA transporter form part of a catabolic pathway for utilization of murein-derived peptides that operates in γ-proteobacteria in addition to the established murein recycling pathways.
Factors affecting levels of urinary albumin excretion in the general population of Spain: the Di@bet.es study
Authors: Gutiérrez-Repiso Carolina , Rojo-Martínez Gemma , Soriguer Federico , García-Fuentes Eduardo , Vendrell Joan , Vázquez José A. , Valdés Sergio , Urrutia Inés , Serrano-Rios Manuel , Pascual-Manich Gemma , Ortega Emilio , Mora-Peces Inmaculada , Menéndez Edelmiro , Martínez-Larrad M. Teresa , López-Alba Alfonso , Gutiérrez Galder , Gomis Ramón , Goday Albert , Girbés Juan , Gaztambide Sonia , Franch Josep , Delgado Elías , Catalá Miguel , Castell Conxa , Castaño Luis , Casamitjana Roser , Carmena Rafael , Calle-Pascual Alfonso , Bordiú Elena , Bosch-Comas Anna 
Published: September 2012

The present study was undertaken to examine the prevalence of urinary ACR (albumin/creatinine ratio) &gt;30 mg/g and the associated clinical and environmental factors in a representative sample of the population of Spain. Di@bet.es study is a national, cross-sectional population-based survey conducted in 2009–2010. Clinical, metabolic, socio-demographic, anthropometric data and information about lifestyle habit were collected. Those subjects without KDM (known diabetes mellitus) were given an OGTT (oral glucose tolerance test). Albumin and creatinine were measured in a urinary sample and ACR was calculated. The population prevalence of ACR &gt;30 mg/g was 7.65% (adjusted for sex and age). The prevalence of ACR &gt;30 mg/g increased with age (P&lt;0.001). Subjects with carbohydrate metabolism disorders had a greater prevalence of ACR &gt;30 mg/g but after being adjusted for age, sex and hypertension, was significant only in those subjects with UKDM (unknown diabetes mellitus) {OR (odd ratio), 2.07 [95% CI (confidence interval), 1.38–3.09]; P&lt;0.001] and KDM [OR, 3.55 (95% CI, 2.63–4.80); P&lt;0.001]. Prevalence of ACR &gt;30 mg/g was associated with hypertension [OR, 1.48 (95% CI, 1.12–1.95); P=0.001], HOMA-IR (homoeostasis model assessment of insulin resistance) [OR, 1.47 (95% CI, 1.13–1.92); P≤0.01], metabolic syndrome [OR, 2.17 (95% CI, 1.72–2.72); P&lt;0.001], smoking [OR, 1.40 (95% CI, 1.06–1.83); P≤0.05], physical activity [OR, 0.68 (95% CI, 0.54–0.88); P≤0.01] and consumption of fish [OR, 0.38 (95% CI, 0.18–0.78); P≤0.01]. This is the first study that reports the prevalence of ACR &gt;30 mg/g in the Spanish population. The association between clinical variables and other potentially modifiable environmental variables contribute jointly, and sometimes interactively, to the explanation of prevalence of ACR &gt;30 mg/g. Many of these risk factors are susceptible to intervention.