428 research outputs found
In Situ Geochronology on the Mars 2020 Rover with KArLE (Potassium-Argon Laser Experiment)
If extinct and/or extant life is discovered on Mars, knowledge of the chronology of the biosphere will be of paramount importance. KArLE will provide absolute ages of Mars 2020 rocks, which will allow us to understand them in the context of Mars' geologic history, connect them to other landing sites, and compare Martian epochs of habitability with the Earth's history and evolution of life. KArLE significantly enhances the ability of Mars 2020 to meet its science objectives by performing in situ age dating on key lithologies, enabling targeted searches for ancient biosignatures and increasing the chances of identifying evidence for Martian microbial life. The KArLE investigation makes its measurements on a core sample obtained with the rover drill, inserted into a small, mechanically simple chamber, followed by interrogation by laser-induced breakdown spectroscopy (LIBS), mass spectrometry, and optical imaging. The KArLE experiment is flexible enough to accommodate any partner providing these instrument components, a creative approach that extends the ability of the Mars 2020 payload to accomplish an additional highly-desirable science measurement for low cost and risk and minimal extra hardware
Roughness of Crack Interfaces in Two-Dimensional Beam Lattices
The roughness of crack interfaces is reported in quasistatic fracture, using
an elastic network of beams with random breaking thresholds. For strong
disorders we obtain 0.86(3) for the roughness exponent, a result which is very
different from the minimum energy surface exponent, i.e., the value 2/3. A
cross-over to lower values is observed as the disorder is reduced, the exponent
in these cases being strongly dependent on the disorder.Comment: 9 pages, RevTeX, 3 figure
Heterotrophy of oceanic particulate organic matter elevates net ecosystem calcification
Author Posting. Š American Geophysical Union, 2019. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geophysical Research Letters 46(16), (2019): 9851-9860, doi:10.1029/2019GL083726.Coral reef calcification is expected to decline due to climate change stressors such as ocean acidification and warming. Projections of future coral reef health are based on our understanding of the environmental drivers that affect calcification and dissolution. One such driver that may impact coral reef health is heterotrophy of oceanicâsourced particulate organic matter, but its link to calcification has not been directly investigated in the field. In this study, we estimated net ecosystem calcification and oceanic particulate organic carbon (POCoc) uptake across the KÄne'ohe Bay barrier reef in Hawai'i. We show that higher rates of POCoc uptake correspond to greater net ecosystem calcification rates, even under low aragonite saturation states (Ίar). Hence, reductions in offshore productivity may negatively impact coral reefs by decreasing the food supply required to sustain calcification. Alternatively, coral reefs that receive ample inputs of POCoc may maintain higher calcification rates, despite a global decline in Ίar.Data needed for calculations are available in the supporting information. Additional data can be provided upon request directly from the corresponding author or accessed by links provided in the supporting information. The authors declare no competing financial interests. We thank Texas Sea Grant for providing partial funding for this project to A. Kealoha through the GrantsâInâAid of Graduate Research Program. We also thank the NOAA Nancy Foster Scholarship for PhD program funding to A. Kealoha and Texas A&M University for funds awarded to Shamberger that supported this work. This research was also supported by funding from National Science Foundation Grant OCEâ1538628 to RappĂŠ. The Hawaii Institute of Marine Biology (particularly the RappĂŠ Lab and Jason Jones), NOAA's Coral Reef Ecosystem Program, Connie Previti, Serena Smith, and Chris Maupin were instrumental in sample collection and data analysis.2020-02-2
Sea Water Radiocarbon Evolution in the Gulf of Alaska: 2002 Observations
Oceanic uptake and transport of bomb radiocarbon as {sup 14}CO{sub 2} created by atmospheric nuclear weapons testing in the 1950s and 1960s has been a useful diagnostic to determine the carbon transfer between the ocean and atmosphere. In addition, the distribution of radiocarbon in the ocean can be used as a tracer of oceanic circulation. Results obtained from samples collected in the Gulf of Alaska in the summer of 2002 provide a direct comparison with results in the 1970s during GEOSECS and in the early 1990s during WOCE. The open gyre values are 20-40{per_thousand} more negative than those documented in 1991 and 1993 (WOCE) although the general trends as a function of latitude are reproduced. Surface values are still significantly higher than pre-bomb levels ({approx}-105{per_thousand} or lower). In the central gyre, we observe {Delta}{sup 14}C-values that are lower in comparison to GEOSECS (stn 218) and WOCE P16/P17 to a density of {approx}26.8{sigma}t. This observation is consistent with the overall decrease in surface {Delta}{sup 14}C values, and reflects the erosion of the bomb-{sup 14}C transient. We propose that erosion of the bomb-{sup 14}C transient is accomplished by entrainment of low {sup 14}C water via vertical exchange within the Gulf of Alaska and replenishment of surface and sub-thermocline waters with waters derived from the far northwest Pacific
MultiSig: a new high-precision approach to the analysis of complex biomolecular systems
MultiSig is a newly developed mode of analysis of sedimentation equilibrium (SE) experiments in the analytical ultracentrifuge, having the capability of taking advantage of the remarkable precision (~0.1 % of signal) of the principal optical (fringe) system employed, thus supplanting existing methods of analysis through reducing the ânoiseâ level of certain important parameter estimates by up to orders of magnitude. Long-known limitations of the SE method, arising from lack of knowledge of the true fringe number in fringe optics and from the use of unstable numerical algorithms such as numerical differentiation, have been transcended. An approach to data analysis, akin to âspatial filteringâ, has been developed, and shown by both simulation and practical application to be a powerful aid to the precision with which near-monodisperse systems can be analysed, potentially yielding information on protein-solvent interaction. For oligo- and poly-disperse systems the information returned includes precise average mass distributions over both cell radial and concentration ranges and mass-frequency histograms at fixed radial positions. The application of MultiSig analysis to various complex heterogenous systems and potentially multiply-interacting carbohydrate oligomers is described
Barrett's esophagus: prevalenceâincidence and etiologyâorigins
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/86957/1/j.1749-6632.2011.06042.x.pd
From Radio to X-ray: Flares on the dMe Flare Star EV Lacertae
We present the results of a campaign to observe flares on the M dwarf flare
star EV Lacertae over the course of two days in 2001 September, utilizing a
combination of radio continuum, optical photometric and spectroscopic,
ultraviolet spectroscopic, and X-ray spectroscopic observations, to
characterize the multi-wavelength nature of flares from this active, single
late-type star. We find flares in every wavelength region in which we observed.
In the multi-wavelength context, the start of the intense radio flare is
coincident with an impulsive optical U-band flare, to within one minute, and
yet there is no signature of an X-ray response. There are other intervals of
time where optical flaring and UV flaring is occurring, but these cannot be
related to the contemporaneous X-ray flaring: the time-integrated luminosities
do not match the instantaneous X-ray flare luminosity, as one would expect for
the Neupert effect. We investigate the probability of chance occurrences of
flares from disparate wavelength regions producing temporal coincidences, but
find that not all the flare associations can be explained by a superposition of
flares due to a high flaring rate. We caution against making causal
associations of multi-wavelength flares based solely on temporal correlations
for high flaring rate stars like EV Lac.Comment: 52 pages, 13 figures, accepted for publication in the Astrophysical
Journa
IL-17 Expression in the Time Course of Acute Anti-Thy1 Glomerulonephritis
Background Interleukin-17 (IL-17) is a new pro-inflammatory cytokine involved
in immune response and inflammatory disease. The main source of IL-17 is a
subset of CD4+ T-helper cells, but is also secreted by non-immune cells. The
present study analyzes expression of IL-17 in the time course of acute anti-
thy1 glomerulonephritis and the role of IL-17 as a potential link between
inflammation and fibrosis. Methods Anti-thy1 glomerulonephritis was induced
into male Wistar rats by OX-7 antibody injection. After that, samples were
taken on days 1, 5, 10 (matrix expansion phase), 15 and 20 (resolution phase).
PBS-injected animals served as controls. Proteinuria and histological matrixes
score served as the main markers for disease severity. In in vitro
experiments, NRK-52E cells were used. For cytokine expressions, mRNA and
protein levels were analyzed by utilizing RT-PCR, in situ hybridization and
immunofluorescence. Results Highest IL-17 mRNA-expression (6.50-fold vs. con;
p<0.05) was found on day 5 after induction of anti-thy1 glomerulonephritis
along the maximum levels of proteinuria (113 Âą 13 mg/d; p<0.001), histological
glomerular-matrix accumulation (82%; p<0.001) and TGF-β1 (2.2-fold; p<0.05),
IL-6 mRNA expression (36-fold; p<0.05). IL-17 protein expression co-localized
with the endothelial cell marker PECAM in immunofluorescence. In NRK-52E
cells, co-administration of TGF-β1 and IL-6 synergistically up-regulated IL-17
mRNA 4986-fold (p<0.001). Conclusions The pro-inflammatory cytokine IL-17 is
up-regulated in endothelial cells during the time course of acute anti-thy1
glomerulonephritis. In vitro, NRK-52E cells secrete IL-17 under pro-fibrotic
and pro-inflammatory conditions
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