198 research outputs found
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The Nili Patea caldera; evolving magma, explosive eruptions and hydrothermal deposits on Mars.
A geological history connecting: Caldera formation, with an ignimbrite or pluton base. Post-caldera dacite flows, resurgent dome, and mafic ring fault volcanism
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Evolving magmas, explosive eruptions and hydrothermal deposits at Nili Patea Caldera, Syrtis Major, Mars
Nili Patera is a 45 km diameter caldera at the centre of the Syrtis Major Planum volcanic province. Nili Patera is unique amongst martian volcanic terrains in that it is now below the surrounding planum and hosts a diverse range of volcanic landforms and mineralogies. Our work addresses the stratigraphic and structural context of the caldera, based on these important, and well-known, initial observations:
• Evidence of effusive and explosive volcanism.
• A compositional diversity from olivine-rich basalts to dacite and feldspathic units.
• Outcrops with spectral features indicative of hydrothermal silica in sinter mounds.
• Asymmetric collapse with a maximum subsidence of 1800 m; dropping the caldera floor below the surrounding volcanic shield.
• A 300 m high resurgent dome in the western caldera floor.
We present a geological map (figure 1) and stratigraphic history of Nili Patera (figure 2) in which these geological findings are put into a nine-part geological history (figure 3). Additionaly, we consider the implications of the caldera’s evolution for the evolution of Syrtis Major Planum and Highland Patera style volcanoes in general
A record of igneous evolution in Elysium, a major martian volcanic province
© 2017 The Author(s). A major knowledge gap exists on how eruptive compositions of a single martian volcanic province change over time. Here we seek to fill that gap by assessing the compositional evolution of Elysium, a major martian volcanic province. A unique geochemical signature overlaps with the southeastern flows of this volcano, which provides the context for this study of variability of martian magmatism. The southeastern lava fields of Elysium Planitia show distinct chemistry in the shallow subsurface (down to several decimeters) relative to the rest of the martian mid-to-low latitudes (average crust) and flows in northwest Elysium. By impact crater counting chronology we estimated the age of the southeastern province to be 0.85 ± 0.08 Ga younger than the northwestern fields. This study of the geochemical and temporal differences between the NW and SE Elysium lava fields is the first to demonstrate compositional variation within a single volcanic province on Mars. We interpret the geochemical and temporal differences between the SE and NW lava fields to be consistent with primary magmatic processes, such as mantle heterogeneity or change in depth of melt formation within the martian mantle due to crustal loading
Astrobiology Survey of a Lava Cave at Lava Beds National Monument by a Rover Carrying a Remote Sensing Instrument Payload
We report here on a survey of a lava tube cave by a rover that is instrumented for astrobiology missions. The NASA Ames testbed rover, CaveR, was deployed in Valentine Cave in Lava Beds National Monument (N. CA, USA) during August of 2018. The rover carried an instrument package consisting of Near Infrared and Visible Spectrometer System (NIRVSS) a point spectrometer operating in 1590-3400 nm range, sensitive to H2O and -OH bearing minerals, pyroxenes, and carbonates (Roush, et al 2018); the bore sighted Drill Operations Camera (DOC), a monochrome imager illuminated by LEDs at 410, 540, 640, 740, 905 and 940 nm; a Realsense depth sensor system for 3D model generation; and a high resolution DSLR stereo camera. The payload was mounted on a tiltable instrument platform attached to the left side of the rover. The rover was driven manually in the cave by field operators, following instructions from a remote science operations team, and simulating a mission concept with science-guided autonomy. A simulated mission took place for 3 days with a team of 3 scientists selecting targets and interpreting data from the payload. To begin the mission, the rover drove along one wall of the cave imaging continuously with the Realsense in 20 m cave segments, three total. At the start of each day, the images from a 20m segment and a panorama stitched from them were provided to the science team to examine. The science team used these data to prioritize specific points along the cave wall for the collection of NIRVSS, DOC, and DSLR data. The objective of the data collection was to identify and study putative biological and mineralogical features in the cave. The data were delivered in xGDS, a customized mapping, planning, and data base management software developed at NASA Ames (Lee, et al 2013). Once the targets for further observations were selected, a plan for collecting the observations (positions in the cave and pointing for each requested observation) was constructed using xGDS and delivered to a rover team to execute the science data collection plan. Acquired data were delivered back to the science team for analysis. Preliminary results from the experiment illustrate the utility of the system (rover plus payload) to study the cave geology and mineralogy and its potential for identifying biomineral features
Evaluation of the high resolution WRF-Chem (v3.4.1) air quality forecast and its comparison with statistical ozone predictions
An integrated modelling system based on the regional online coupled
meteorology–atmospheric chemistry WRF-Chem model configured with two nested
domains with horizontal resolutions of 11.1 and 3.7 km has been applied for
numerical weather prediction and for air quality forecasts in Slovenia. In the
study, an evaluation of the air quality forecasting system has been performed
for summer 2013. In the case of ozone (O3) daily maxima, the first- and
second-day model predictions have been also compared to the operational
statistical O3 forecast and to the persistence. Results of discrete and
categorical evaluations show that the WRF-Chem-based forecasting system is
able to produce reliable forecasts which, depending on monitoring site and
the evaluation measure applied, can outperform the statistical model. For
example, the correlation coefficient shows the highest skill for WRF-Chem
model O3 predictions, confirming the significance of the non-linear
processes taken into account in an online coupled Eulerian model. For some
stations and areas biases were relatively high due to highly complex terrain
and unresolved local meteorological and emission dynamics, which contributed
to somewhat lower WRF-Chem skill obtained in categorical model evaluations.
Applying a bias correction could further improve WRF-Chem model forecasting
skill in these cases
Evaluation of the high resolution WRF-Chem (v3.4.1) air quality forecast and its comparison with statistical ozone predictions
An integrated modelling system based on the regional online coupled
meteorology–atmospheric chemistry WRF-Chem model configured with two nested
domains with horizontal resolutions of 11.1 and 3.7 km has been applied for
numerical weather prediction and for air quality forecasts in Slovenia. In the
study, an evaluation of the air quality forecasting system has been performed
for summer 2013. In the case of ozone (O3) daily maxima, the first- and
second-day model predictions have been also compared to the operational
statistical O3 forecast and to the persistence. Results of discrete and
categorical evaluations show that the WRF-Chem-based forecasting system is
able to produce reliable forecasts which, depending on monitoring site and
the evaluation measure applied, can outperform the statistical model. For
example, the correlation coefficient shows the highest skill for WRF-Chem
model O3 predictions, confirming the significance of the non-linear
processes taken into account in an online coupled Eulerian model. For some
stations and areas biases were relatively high due to highly complex terrain
and unresolved local meteorological and emission dynamics, which contributed
to somewhat lower WRF-Chem skill obtained in categorical model evaluations.
Applying a bias correction could further improve WRF-Chem model forecasting
skill in these cases
The novel lncRNA BlackMamba controls the neoplastic phenotype of ALK- anaplastic large cell lymphoma by regulating the DNA helicase HELLS.
The molecular mechanisms leading to the transformation of anaplastic lymphoma kinase negative (ALK-) anaplastic large cell lymphoma (ALCL) have been only in part elucidated. To identify new culprits which promote and drive ALCL, we performed a total transcriptome sequencing and discovered 1208 previously unknown intergenic long noncoding RNAs (lncRNAs), including 18 lncRNAs preferentially expressed in ALCL. We selected an unknown lncRNA, BlackMamba, with an ALK- ALCL preferential expression, for molecular and functional studies. BlackMamba is a chromatin-associated lncRNA regulated by STAT3 via a canonical transcriptional signaling pathway. Knockdown experiments demonstrated that BlackMamba contributes to the pathogenesis of ALCL regulating cell growth and cell morphology. Mechanistically, BlackMamba interacts with the DNA helicase HELLS controlling its recruitment to the promoter regions of cell-architecture-related genes, fostering their expression. Collectively, these findings provide evidence of a previously unknown tumorigenic role of STAT3 via a lncRNA-DNA helicase axis and reveal an undiscovered role for lncRNA in the maintenance of the neoplastic phenotype of ALK-ALCL
Mitochondria Express α7 Nicotinic Acetylcholine Receptors to Regulate Ca2+ Accumulation and Cytochrome c Release: Study on Isolated Mitochondria
Nicotinic acetylcholine receptors (nAChRs) are ligand-gated ion channels that mediate synaptic transmission in the muscle and autonomic ganglia and regulate transmitter release in the brain. The nAChRs composed of α7 subunits are also expressed in non-excitable cells to regulate cell survival and proliferation. Up to now, functional α7 nAChRs were found exclusively on the cell plasma membrane. Here we show that they are expressed in mitochondria and regulate early pro-apoptotic events like cytochrome c release. The binding of α7-specific antibody with mouse liver mitochondria was revealed by electron microscopy. Outer membranes of mitochondria from the wild-type and β2−/− but not α7−/− mice bound α7 nAChR-specific antibody and toxins: FITC-labeled α-cobratoxin or Alexa 555-labeled α-bungarotoxin. α7 nAChR agonists (1 µM acetylcholine, 10 µM choline or 30 nM PNU-282987) impaired intramitochondrial Ca2+ accumulation and significantly decreased cytochrome c release stimulated with either 90 µM CaCl2 or 0.5 mM H2O2. α7-specific antagonist methyllicaconitine (50 nM) did not affect Ca2+ accumulation in mitochondria but attenuated the effects of agonists on cytochrome c release. Inhibitor of voltage-dependent anion channel (VDAC) 4,4′-diisothio-cyano-2,2′-stilbene disulfonic acid (0.5 µM) decreased cytochrome c release stimulated with apoptogens similarly to α7 nAChR agonists, and VDAC was co-captured with the α7 nAChR from mitochondria outer membrane preparation in both direct and reverse sandwich ELISA. It is concluded that α7 nAChRs are expressed in mitochondria outer membrane to regulate the VDAC-mediated Ca2+ transport and mitochondrial permeability transition
The alpha 7 nicotinic receptor agonist PHA-543613 hydrochloride inhibits <i>Porphyromonas gingivalis</i>-induced expression of interleukin-8 by oral keratinocytes
Objective:
The alpha 7 nicotinic receptor (α7nAChR) is expressed by oral keratinocytes. α7nAChR activation mediates anti-inflammatory responses. The objective of this study was to determine if α7nAChR activation inhibited pathogen-induced interleukin-8 (IL-8) expression by oral keratinocytes.<p></p>
Materials and methods:
Periodontal tissue expression of α7nAChR was determined by real-time PCR. OKF6/TERT-2 oral keratinocytes were exposed to <i>Porphyromonas gingivalis</i> in the presence and absence of a α7nAChR agonist (PHA-543613 hydrochloride) alone or after pre-exposure to a specific α7nAChR antagonist (α-bungarotoxin). Interleukin-8 (IL-8) expression was measured by ELISA and real-time PCR. Phosphorylation of the NF-κB p65 subunit was determined using an NF-κB p65 profiler assay and STAT-3 activation by STAT-3 in-cell ELISA. The release of ACh from oral keratinocytes in response to <i>P. gingivalis</i> lipopolysaccharide was determined using a GeneBLAzer M3 CHO-K1-blacell reporter assay.<p></p>
Results:
Expression of α7nAChR mRNA was elevated in diseased periodontal tissue. PHA-543613 hydrochloride inhibited <i>P. Gingivalis</i>-induced expression of IL-8 at the transcriptional level. This effect was abolished when cells were pre-exposed to a specific α7nAChR antagonist, α-bungarotoxin. PHA-543613 hydrochloride downregulated NF-κB signalling through reduced phosphorylation of the NF-κB p65-subunit. In addition, PHA-543613 hydrochloride promoted STAT-3 signalling by maintenance of phosphorylation. Furthermore, oral keratinocytes upregulated ACh release in response to <i>P. Gingivalis</i> lipopolysaccharide.<p></p>
Conclusion:
These data suggest that α7nAChR plays a role in regulating the innate immune responses of oral keratinocytes.<p></p>
Silencing and Nuclear Repositioning of the λ5 Gene Locus at the Pre-B Cell Stage Requires Aiolos and OBF-1
The chromatin regulator Aiolos and the transcriptional coactivator OBF-1 have been implicated in regulating aspects of B cell maturation and activation. Mice lacking either of these factors have a largely normal early B cell development. However, when both factors are eliminated simultaneously a block is uncovered at the transition between pre-B and immature B cells, indicating that these proteins exert a critical function in developing B lymphocytes. In mice deficient for Aiolos and OBF-1, the numbers of immature B cells are reduced, small pre-BII cells are increased and a significant impairment in immunoglobulin light chain DNA rearrangement is observed. We identified genes whose expression is deregulated in the pre-B cell compartment of these mice. In particular, we found that components of the pre-BCR, such as the surrogate light chain genes λ5 and VpreB, fail to be efficiently silenced in double-mutant mice. Strikingly, developmentally regulated nuclear repositioning of the λ5 gene is impaired in pre-B cells lacking OBF-1 and Aiolos. These studies uncover a novel role for OBF-1 and Aiolos in controlling the transcription and nuclear organization of genes involved in pre-BCR function
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