2,465 research outputs found
Studies of Quaternary Depositional Systems of the Coastal Plain and Inner Continental Shelf along the Georgia Bight: South Carolina and Georgia, U.S.A.
The Quaternary stratigraphy of the continental shelf offshore of South Carolina consists of stratigraphic units deposited in coastal plain, shallow marine, and shelfal environments bound by composite erosional surfaces that developed in response to numerous glacioeustatic cycles and overprinted by regional uplift. These units are commonly distributed laterally rather than stacked vertically, a function of the long-term, low shelf gradient and the resulting lack of accommodation. This study integrates high-resolution geological and geophysical data sets acquired offshore and onshore with existing data onshore into a comprehensive conceptual model describing the Quaternary geologic evolution of the coastal plain and continental shelf within a study area of approximately 8,000 km2. We use seismic facies and core analysis to define stratigraphic units associated with transgressive, regressive, and lowstand systems offshore. Regressive systems include progradational wave- and river-dominated deltaic and shoreface deposits. Lowstand systems consist of a complex network of paleo-incisions produced by regional, Piedmont-draining fluvial systems and smaller coastal-plain rivers. Transgressive systems include paleochannel-fill successions dominated by mud-rich, tidally-influenced backbarrier deposits, cuspate and linear shelf sand ridges; and transgressive sand sheets and shoals. The low-accommodation setting of the continental shelf influences the stratigraphic record in several key ways: 1) the geometry of progradational coastal lithosomes; 2) the development of composite allogenic erosional surfaces; 3) the deposition of widespread, thin transgressive sand sheets; and 4) the restriction of thicker transgressive deposits to paleo-incisions. In this setting, the use of a hierarchical bounding surface scheme is preferable to the more common sequence stratigraphic or allostratigraphic conventions for several reasons: 1) major erosional bounding surfaces are commonly amalgamated; 2) lower-order surfaces capture internal variability which is key to the genetic interpretation of stratigraphic units; and 3) stratal stacking patterns typically used to define a sequence stratigraphic framework are rare
Embodied Computational Evolution: Feedback Between Development and Evolution in Simulated Biorobots
Given that selection removes genetic variance from evolving populations, thereby reducing exploration opportunities, it is important to find mechanisms that create genetic variation without the disruption of adapted genes and genomes caused by random mutation. Just such an alternative is offered by random epigenetic error, a developmental process that acts on materials and parts expressed by the genome. In this system of embodied computational evolution, simulated within a physics engine, epigenetic error was instantiated in an explicit genotype-to-phenotype map as transcription error at the initiation of gene expression. The hypothesis was that transcription error would create genetic variance by shielding genes from the direct impact of selection, creating, in the process, masquerading genomes. To test this hypothesis, populations of simulated embodied biorobots and their developmental systems were evolved under steady directional selection as equivalent rates of random mutation and random transcriptional error were covaried systematically in an 11 × 11 fully factorial experimental design. In each of the 121 different experimental conditions (unique combinations of mutation and transcription error), the same set of 10 randomly created replicate populations of 60 individuals were evolved. Selection for the improved locomotor behavior of individuals led to increased mean fitness of populations over 100 generations at nearly all levels and combinations of mutation and transcription error. When the effects of both types of error were partitioned statistically, increasing transcription error was shown to increase the final genetic variance of populations, incurring a fitness cost but acting on variance independently and differently from genetic mutation. Thus, random epigenetic errors in development feed back through selection of individuals with masquerading genomes to the population’s genetic variance over generational time. Random developmental processes offer an additional mechanism for exploration by increasing genetic variation in the face of steady, directional selection
Thank You to Our 2018 Peer Reviewers
AbstractThe editorial and scientific publishing process relies on the sustained work of volunteer reviewers, and evaluating the inter‐disciplinary and broad interest papers published in Geochemistry, Geophysics, Geosystems can be a particular challenge. As editors and associated editors, we are therefore hugely appreciative of the efforts of our reviewers, and would like to thank and acknowledge them in this editorial. G‐Cubed published 271 manuscripts in 2018, and for this we were able to rely on the efforts of 873 dedicated reviewers. A big thank you from the G‐Cubed team
SDSS J092455.87+021924.9: an Interesting Gravitationally Lensed Quasar from the Sloan Digital Sky Survey
We report the discovery of a new gravitationally lensed quasar from the Sloan
Digital Sky Survey, SDSS J092455.87+021924.9 (SDSS J0924+0219). This object was
selected from among known SDSS quasars by an algorithm that was designed to
select another known SDSS lensed quasar (SDSS 1226-0006A,B). Five separate
components, three of which are unresolved, are identified in photometric
follow-up observations obtained with the Magellan Consortium's 6.5m Walter
Baade telescope at Las Campanas Observatory. Two of the unresolved components
(designated A and B) are confirmed to be quasars with z=1.524; the velocity
difference is less than 100 km sec^{-1} according to spectra taken with the W.
M. Keck Observatory's Keck II telescope on Mauna Kea. A third stellar
component, designated C, has the colors of a quasar with redshift similar to
components A and B. The maximum separation of the point sources is 1.78". The
other two sources, designated G and D, are resolved. Component G appears to be
the best candidate for the lensing galaxy. Although component D is near the
expected position of the fourth lensed component in a four image lens system,
its properties are not consistent with being the image of a quasar at z~1.5.
Nevertheless, the identical redshifts of components A and B and the presence of
component C strongly suggest that this object is a gravitational lens. Our
observations support the idea that a foreground object reddens the fourth
lensed component and that another unmodeled effect (such as micro- or
milli-lensing) demagnificates it, but we cannot rule out the possibility that
SDSS0924+0219 is an example of the relatively rare class of ``three component''
lens systems.Comment: 24 pages, 6 figures, accepted by A
Tuning of Human Modulation Filters Is Carrier-Frequency Dependent
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GPR35 promotes glycolysis, proliferation, and oncogenic signaling by engaging with the sodium potassium pump.
The sodium potassium pump (Na/K-ATPase) ensures the electrochemical gradient of a cell through an energy-dependent process that consumes about one-third of regenerated ATP. We report that the G protein-coupled receptor GPR35 interacted with the α chain of Na/K-ATPase and promotes its ion transport and Src signaling activity in a ligand-independent manner. Deletion of Gpr35 increased baseline Ca2+ to maximal levels and reduced Src activation and overall metabolic activity in macrophages and intestinal epithelial cells (IECs). In contrast, a common T108M polymorphism in GPR35 was hypermorphic and had the opposite effects to Gpr35 deletion on Src activation and metabolic activity. The T108M polymorphism is associated with ulcerative colitis and primary sclerosing cholangitis, inflammatory diseases with a high cancer risk. GPR35 promoted homeostatic IEC turnover, whereas Gpr35 deletion or inhibition by a selective pepducin prevented inflammation-associated and spontaneous intestinal tumorigenesis in mice. Thus, GPR35 acts as a central signaling and metabolic pacesetter, which reveals an unexpected role of Na/K-ATPase in macrophage and IEC biology.European Research Council Consolidator Grant n° 648889 to A.K.
Scientia Fellowship (FP7-PEOPLE-2013-COFUND) grant agreement n° 609020 to G.S.
Addenbrooke’s Charitable Trust (ACT 25/16A) to J.E.E.
UniNA and Compagnia Di San Paolo ‘STAR program for young researchers’ fellowship to E.P
The word as a unit of meaning. The role of context in words meaning
A unit of meaning is a word plus all those words within its contextual context that are needed to disambiguate this word to make it monosemous. A lot of research were made to study the influence of the context. They testify that there is usually in each word a hard core of relatively stable meaning and can be modified by the context within certain limits
The Sloan Digital Sky Survey Quasar Catalog IV. Fifth Data Release
We present the fourth edition of the Sloan Digital Sky Survey (SDSS) Quasar
Catalog. The catalog contains 77,429 objects; this is an increase of over
30,000 entries since the previous edition. The catalog consists of the objects
in the SDSS Fifth Data Release that have luminosities larger than M_i = -22.0
(in a cosmology with H_0 = 70 km/s/Mpc, Omega_M = 0.3, and Omega_Lambda = 0.7)
have at least one emission line with FWHM larger than 1000 km/s, or have
interesting/complex absorption features, are fainter than i=15.0, and have
highly reliable redshifts. The area covered by the catalog is 5740 sq. deg. The
quasar redshifts range from 0.08 to 5.41, with a median value of 1.48; the
catalog includes 891 quasars at redshifts greater than four, of which 36 are at
redshifts greater than five. Approximately half of the catalog quasars have i <
19; nearly all have i < 21. For each object the catalog presents positions
accurate to better than 0.2 arcsec. rms per coordinate, five-band (ugriz)
CCD-based photometry with typical accuracy of 0.03 mag, and information on the
morphology and selection method. The catalog also contains basic radio,
near-infrared, and X-ray emission properties of the quasars, when available,
from other large-area surveys. The calibrated digital spectra cover the
wavelength region 3800--9200A at a spectral resolution of ~2000. The spectra
can be retrieved from the public database using the information provided in the
catalog. The average SDSS colors of quasars as a function of redshift, derived
from the catalog entries, are presented in tabular form. Approximately 96% of
the objects in the catalog were discovered by the SDSS.Comment: 37 pages, Accepted for publication in A
The First Hour of Extra-galactic Data of the Sloan Digital Sky Survey Spectroscopic Commissioning: The Coma Cluster
On 26 May 1999, one of the Sloan Digital Sky Survey (SDSS) fiber-fed
spectrographs saw astronomical first light. This was followed by the first
spectroscopic commissioning run during the dark period of June 1999. We present
here the first hour of extra-galactic spectroscopy taken during these early
commissioning stages: an observation of the Coma cluster of galaxies. Our data
samples the Southern part of this cluster, out to a radius of 1.5degrees and
thus fully covers the NGC 4839 group. We outline in this paper the main
characteristics of the SDSS spectroscopic systems and provide redshifts and
spectral classifications for 196 Coma galaxies, of which 45 redshifts are new.
For the 151 galaxies in common with the literature, we find excellent agreement
between our redshift determinations and the published values. As part of our
analysis, we have investigated four different spectral classification
algorithms: spectral line strengths, a principal component decomposition, a
wavelet analysis and the fitting of spectral synthesis models to the data. We
find that a significant fraction (25%) of our observed Coma galaxies show signs
of recent star-formation activity and that the velocity dispersion of these
active galaxies (emission-line and post-starburst galaxies) is 30% larger than
the absorption-line galaxies. We also find no active galaxies within the
central (projected) 200 h-1 Kpc of the cluster. The spatial distribution of our
Coma active galaxies is consistent with that found at higher redshift for the
CNOC1 cluster survey. Beyond the core region, the fraction of bright active
galaxies appears to rise slowly out to the virial radius and are randomly
distributed within the cluster with no apparent correlation with the potential
merger of the NGC 4839 group. [ABRIDGED]Comment: Accepted in AJ, 65 pages, 20 figures, 5 table
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