A catalog of mercurian craters that retain their central peak or peak‐ring structure was created to aid target prioritization for the Mercury Imaging X‐ray Spectrometer (MIXS), now on its way to ...Mercury aboard BepiColombo. Preliminary analysis of the MIXS crater catalog suggested a potential spatial correlation between an abnormally high spatial density of peak‐ring basins and a region of Mercury with elevated Mg/Si values (High‐Magnesium Terrane HMT). Robust statistical analysis of previously published crater catalogs confirmed that the spatial correlation exists, with an overall confidence level of 97.7%, specifically between peak‐ring basins and the HMT, delineated by a contour of Mg/Si = mean + 2σ = 0.648. Applying empirical impact cratering scaling laws to the 15 basins intersecting the HMT suggested that all have excavated material from ~13 to 20 km depth. None of the basins excavated mantle material, predicting instead that deep crustal material contains elevated Mg/Si material. However, five of the basins are predicted to have melted underlying mantle material, which might be a contributing factor in the elevated Mg/Si signature. In the absence of resolvable volcanic features associated with the rise of basaltic melts from the mantle, we favor excavation of deep crustal, high Mg/Si material. MIXS‐T is capable of spatially resolving individual features associated with peak‐ring basins and it is proposed that the 15 basins within the HMT are prioritized targets for MIXS, to test the hypothesis of exposed deep‐crustal material.
Plain Language Summary
A catalog of craters that retain a central peak, or peak‐ring structure, was created in order to prioritize targets for the Mercury Imaging X‐ray Spectrometer on the BepiColombo mission. Preliminary analysis of this catalog revealed a potential spatial correlation between a region with an abnormally high spatial density of peak‐ring basins and a region with high Magnesium‐to‐Silicon ratios. Robust statistical analysis of previously published crater catalogs was used to confirm that the spatial correlation exists. Investigation of the depth of excavation for material ejected during impact indicates that the impacts within the main high Mg/Si terrane excavated deep crustal, rather than mantle, material of high Mg/Si ratio. Current X‐ray data do not spatially resolve the basin features to confirm these hypotheses but future observations by the Mercury Imaging X‐ray Spectrometer are capable of doing so.
Key Points
There is a statistically strong spatial correlation between a group of 15 peak‐ring basins on Mercury and the high Mg/Si region
Crater uplift modeling and an absence of associated volcanic landforms, suggest excavation of deep crustal material with high Mg/Si
The High Mg/Si region will be a key target for Mercury Imaging X‐ray Spectrometer‐T on BepiColombo to test the model of deep crustal excavation
Abstract
The goal of this study was to determine if the form of selenium (Se) inorganic (ISe, sodium selenite), organic (OSe, Se-enriched yeast, SEL-PLEX®), or a 1:1 mix of ISe and OSe (MIX) in ...vitamin-mineral mix (Se phenotype) affects metabolic parameters and performance of growing steers grazing endophyte-infected mixed pasture. Predominately-Angus steers (BW = 183.4 ± 32.8 kg) were randomly selected (n = 8) from each of their cow-calf Se phenotypic herds (managed under a typical forage-based, fall-calving, cow-calf production regimen) and assigned to summer-long strip-grazing of a common endophyte-infected mixed pasture (1.27 ppm total ergovaline; 17.5 ha). Steers were fed their respective Se treatment by top-dressing 85 g of a common basal vitamin-mineral mix that contained 3 mg Se/d onto 0.23 kg soyhulls, using in-pasture Calan gates. The PROC MIXED procedure of SAS was used to assess effect of Se phenotype on whole blood Se (ng/mL) and serum prolactin (ng/mL) at d 1, 21, 42, 63, and 84, and caudal arterial area (mm2) at d -7, 42, and 84. After slaughter (d 92 to d 118), the effect of Se phenotype on liver glutathione content (mg/g wet tissue) and glutamine synthetase (GS) activity (nmol·mg-1 wet tissue·min-1) was assessed using the PROC GLM procedure of SAS. Fisher's protected LSD procedure was used to separate treatment means. Blood Se increased (P < 0.01) for all treatments from d 1 to 21 and then plateaued and was greater (P ≤ 0.06) for MIX and OSe steers. Serum prolactin decreased over time (P < 0.01) and was greater (P < 0.05) for MIX and OSe steers. Liver GSH abundance did not differ (P = 0.15) among Se phenotypes, whereas GS activity differed (P ≤ 0.03, MIX > OSe > ISe). ADG (ISe, 0.44 kg/d; OSe, 0.55 kg/d; MIX, 0.48 kg/d) was not affected (P = 0.36) by Se phenotype. Caudal artery area was greater (P < 0.01) on d 42 for all Se phenotypes, but was not affected (P ≥ 0.36) by Se phenotype. These data indicate that consumption of 3 mg Se/d as OSe or MIX forms of Se in vitamin-mineral premixes increase (a) whole blood Se content, an indicator of greater whole-body Se assimilation; (b) serum prolactin, the reduction of which is a hallmark of fescue toxicosis; and (c) hepatic assimilation of acinar ammonia. However, (d) these positive effects on metabolic parameters were not accompanied by increases in peripheral vascular or growth performance.
Spatial and temporal databases that integrate urban tree inventories and soil quality information are needed for modern-day sustainable urban forest management. The objective of this study was to ...demonstrate the usefulness of low-cost and widely-available technology, such as global positioning system (GPS)âenabled cameras to photo-document sites and cloud-based products and services (Google Picasa and Fusion Tables), to aid in developing sustainable street tree management programs. Google Fusion Tables provide a cloud platform to store, share and map urban tree and soil data over time using internet connected computers, tablets or mobile devices. Although indicators of urban soil quality and best methods to assess it are not yet standardized, we demonstrate here promising indicators that are both useful and easy to incorporate into spatial and temporal databases of trees managed in urban environments. By utilizing technology, we demonstrate that site-specific urban soil quality indicators can be used together with readily-available soil rating systems specific to different plant types as a means to better evaluate and manage conditions for optimal street tree growth and health.
This paper describes selection and characterization of the landing site for the Mars 2004 Beagle 2 mission. The site is within Isidis Planitia between 10°–12°N, 266°–274°W, centered at 11.6°N, ...269.5°W. This is at low elevation (−3600 to −3900 m MOLA), is flat (MOLA RMS slope = 0.57°), radar data suggest a smoother surface at decimeter to meter scales than the Pathfinder site and it has a moderate rock abundance (2–17%, mean 11%). In addition to this, Isidis shows evidence for concentration and remobilization of volatiles. In particular, the basin contains conical landforms. We favor models involving the formation of tuff cones during magma‐ice interaction. Structures identified as dykes in MOC images may be remnants of magma conduits. The pattern of bulk thermal inertia in Isidis (higher values of 500 Jm−2s−0.5K−1 around the SW‐S‐E margin decreasing toward the center and north) suggests that an influx of sediment spread from the Noachian areas around the southern half of the basin over the basin floor. The coarse, higher thermal inertia material was deposited closest to the sediment source. The variable state of erosion of the tuff cones suggests that they formed intermittently over a long period of time during Amazonian and possibly Hesperian epochs. Geologically recent resurfacing of Isidis has also occurred by aeolian processes, and this is shown by a deficit in impact craters <120 m diameter. The proportion of rocky material is predicted to be slightly less than the Viking and Pathfinder sites, but there will probably be more duricrust.
Integrin
β
1 is both overexpressed and in an ‘active’ conformation in vulval squamous cell carcinomas (VSCCs) compared to matched normal skin. To investigate the significance of integrin
β
1 ...deregulation we stably knocked-down integrin
β
1 expression in the VSCC cell line A431.
In vitro
analysis revealed that integrin
β
1 is required for cell adhesion, cell spreading and invasion. However, integrin
β
1 is not required for cell growth or activation of FAK and ERK signalling
in vitro
or
in vivo
. Strikingly, while control tumours were able to invade the dermis, integrin
β
1 knockdown tumours were significantly more encapsulated and less invasive.
The Mars Science Laboratory Curiosity rover has encountered both ancient lithified and modern active aeolian dune deposits within Gale crater, providing an opportunity to study how aeolian processes ...have changed during Gale crater's geological history. This study uses data from the Chemistry and Camera (ChemCam) and Chemistry and Mineralogy (CheMin) instrument suites onboard Curiosity to; (1) constrain the diagenetic processes that lithified and altered the ancient aeolian Stimson formation, (2) investigate whether the geochemical signature in the Stimson formation is consistent with the aeolian mafic-felsic mineral sorting trend identified in the modern Bagnold dune fields in Gale crater, and (3) discuss the provenance of the Stimson sediments, comparing it to those identified in the modern dune and ancient river and lake deposits also analyzed along Curiosity's traverse.
The ancient Stimson dune deposits that stratigraphically overlie the Gale fluvio-lacustrine units were analyzed in two locations; the Emerson and the Naukluft plateaus. ChemCam data show that the Stimson formation has subtle variations in MgO, Al2O3, Na2O, and K2O between the two localities. An agglomerative cluster analysis of the constrained Stimson dataset reveals five clusters, four of which relate to different proportions of mafic and felsic minerals analyzed by ChemCam. In general, the cluster analysis shows that the Emerson plateau has a greater proportion of mafic minerals and fewer coarse, felsic grains relative to the Naukluft plateau. This variation in mafic and felsic minerals between localities suggests a southwest to northeast net sediment transport direction due to aeolian mineral sorting dynamics preferentially transporting mafic minerals that are easier to saltate than the elongate, often coarser, felsic minerals. This derived transport direction for the Stimson formation supports that determined by sedimentological evidence and is opposite to that previously determined for the active Bagnold dunes inferring a change in the wind regime with time. An opposite sediment transport direction between the ancient and modern dunes in Gale crater further supports geochemical and mineralogical evidence that suggests different basaltic source regions. Compositionally, the bulk Stimson formation is most similar to the subalkaline basalt source region that is inferred to be the dominant sediment source of the fluvio-lacustrine Bradbury group. This is likely the result of the Stimson formation and basaltic Bradbury group sediments sharing a similar local basaltic source region such as the rim and walls of Gale crater.
•A ChemCam geochemical study of the ancient aeolian Stimson formation in Gale crater•The geochemical effect of mineral sorting in the ancient dunes has been preserved.•The Stimson dunes were transported SW-NE, opposite to the modern Bagnold dunes.•A subalkaline basaltic source region is suggested for the Stimson formation.
•Ca-siderite comprises between trace amounts and 4% of Lafayette sections.•Electron Microscopy and synchrotron analysis shows variable carbonate dissolution.•Ferric-(hydr)oxide nanoparticles are ...present on saponite and corroded siderite.•Serpentine-berthierine is re-described as odinite, a ferric low-temperature mineral.•Dissolution of carbonate can lead to methane on Mars via a Sabatier type reaction.
New mineralogical studies of Lafayette reveal that it contains a notably variable abundance of martian carbonate. Four percent was identified in mesostasis (3.2%) and olivine-hosted (0.8%) fractures in one polished section, but only 0.2% of both textural types in another. The Lafayette carbonates are Mg0.0-2.0Cc13.2-38.6Sd17.7-81.9Rh3.1-42.9. They have undergone variable but extensive amounts of dissolution and replacement as the nakhlite secondary fluid evolved, associated with the precipitation of ferric saponite in olivine fractures and a serpentine-like phyllosilicate in the mesostasis. The mesostasis carbonate has undergone the highest degree of corrosion and replacement. TEM analysis has shown the presence of Fe-(hydr)oxide (likely ferrihydrite) nanoparticles on olivine-hosted carbonates which can be linked to the cessation of more extensive carbonate dissolution at those sites. The mesostasis serpentine-like mineral has been described here on the basis of WDS and EDX analyses, HRTEM and Fe-K XANES, as odinite, a ferric, 0.7 nm d001-spacings phyllosilicate mineral with a characteristic 1:1 serpentine-like structure. The carbonate dissolution stage and then formation of Fe-(hydr)oxide nanoparticles occurred under circumneutral-alkaline conditions (7) < pH < 10. This range of pH is also where the general dissolution mechanism switched from a proton-promoted, to a water hydrolysis reaction associated with a reduction in the dissolution rates. As dissolution rates were reduced and the fluid had cooled to ≤50 °C, the precipitation of the ferric saponite and odinite, a phyllosilicate associated with temperatures of ∼25 °C, dominated over the carbonate dissolution. The extensive dissolution of such crustal carbonate across the upper martian crust, producing bicarbonate and carbon dioxide, and the coupled formation of ferric phyllosilicates, would lead to the formation of CH4 in substantial amounts via a Fischer-Tropsch type reaction. The results of our study illustrate a process to explain the relatively low abundance of detected carbonate on Mars and a likely source for some of the methane on Mars.
This paper provides an overview of the
rover's exploration at Vera Rubin ridge (VRR) and summarizes the science results. VRR is a distinct geomorphic feature on lower Aeolis Mons (informally known as ...Mount Sharp) that was identified in orbital data based on its distinct texture, topographic expression, and association with a hematite spectral signature.
conducted extensive remote sensing observations, acquired data on dozens of contact science targets, and drilled three outcrop samples from the ridge, as well as one outcrop sample immediately below the ridge. Our observations indicate that strata composing VRR were deposited in a predominantly lacustrine setting and are part of the Murray formation. The rocks within the ridge are chemically in family with underlying Murray formation strata. Red hematite is dispersed throughout much of the VRR bedrock, and this is the source of the orbital spectral detection. Gray hematite is also present in isolated, gray-colored patches concentrated toward the upper elevations of VRR, and these gray patches also contain small, dark Fe-rich nodules. We propose that VRR formed when diagenetic event(s) preferentially hardened rocks, which were subsequently eroded into a ridge by wind. Diagenesis also led to enhanced crystallization and/or cementation that deepened the ferric-related spectral absorptions on the ridge, which helped make them readily distinguishable from orbit. Results add to existing evidence of protracted aqueous environments at Gale crater and give new insight into how diagenesis shaped Mars' rock record.
The Yellowknife Bay formation represents a ~5 m thick stratigraphic section of lithified fluvial and lacustrine sediments analyzed by the Curiosity rover in Gale crater, Mars. Previous works have ...mainly focused on the mudstones that were drilled by the rover at two locations. The present study focuses on the sedimentary rocks stratigraphically above the mudstones by studying their chemical variations in parallel with rock textures. Results show that differences in composition correlate with textures and both manifest subtle but significant variations through the stratigraphic column. Though the chemistry of the sediments does not vary much in the lower part of the stratigraphy, the variations in alkali elements indicate variations in the source material and/or physical sorting, as shown by the identification of alkali feldspars. The sandstones contain similar relative proportions of hydrogen to the mudstones below, suggesting the presence of hydrous minerals that may have contributed to their cementation. Slight variations in magnesium correlate with changes in textures suggesting that diagenesis through cementation and dissolution modified the initial rock composition and texture simultaneously. The upper part of the stratigraphy (~1 m thick) displays rocks with different compositions suggesting a strong change in the depositional system. The presence of float rocks with similar compositions found along the rover traverse suggests that some of these outcrops extend further away in the nearby hummocky plains.
Key Points
Fluvial sandstones analyzed by ChemCam display subtle chemical variations
Combined analysis of chemistry and texture highlights the role of diagenesis
Distinct chemistry in upper layers suggests distinct setting and/or source
Increased treatment options and longer survival for lung cancer have generated increased interest in patient preferences. Previous studies of patient preferences in lung cancer have not fully ...explored preference heterogeneity. We demonstrate a method to explore preference heterogeneity in the willingness of patients with lung cancer and caregivers to trade progression-free survival (PFS) with side effects.
Patients and caregivers attending a national lung cancer meeting completed a discrete-choice experiment (DCE) designed through a collaboration with patients. Participants answered 13 choice tasks described across PFS, short-term side effects, and four long-term side effects. Side effects were coded as a one-level change in severity (none-mild, mild-moderate, or moderate-severe). A mixed logit model in willingness-to-pay space estimated preference heterogeneity in acceptable tradeoffs (time equivalents) between PFS and side effects. The study was reported following quality indicators from the United States Food and Drug Administration's patient preference guidance.
A total of 87 patients and 24 caregivers participated in the DCE. Participants would trade 3.7 month PFS (95% CI (CI): 3.3-4.1) for less severe functional long-term treatment side effects, 2.3 months for less severe physical long-term effects (CI: 1.9-2.8) and cognitive long-term effects (CI: 1.8-2.8), 0.9 months (CI: 0.4-1.4) for less severe emotional long-term effects, and 1.8 months (CI: 1.4-2.3) for less severe short-term side effects. Most participants (90%) would accept treatment with more severe functional long-term effects for 8.4 additional month PFS.
Participants would trade PFS for changes in short-term side effects and long-term side effects, although preference heterogeneity existed. Lung cancer treatments that offer less PFS but also less severe side effects might be acceptable to some patients.
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