11 research outputs found
Can induced gravity isotropize Bianchi I, V, or IX Universes?
We analyze if Bianchi I, V, and IX models in the Induced Gravity (IG) theory
can evolve to a Friedmann--Roberson--Walker (FRW) expansion due to the
non--minimal coupling of gravity and the scalar field. The analytical results
that we found for the Brans-Dicke (BD) theory are now applied to the IG theory
which has ( being the square ratio of the Higgs to
Planck mass) in a cosmological era in which the IG--potential is not
significant. We find that the isotropization mechanism crucially depends on the
value of . Its smallness also permits inflationary solutions. For the
Bianch V model inflation due to the Higgs potential takes place afterwads, and
subsequently the spontaneous symmetry breaking (SSB) ends with an effective FRW
evolution. The ordinary tests of successful cosmology are well satisfied.Comment: 24 pages, 5 figures, to be published in Phys. Rev. D1
Late Winter Biogeochemical Conditions Under Sea Ice in the Canadian High Arctic
With the Arctic summer sea-ice extent in decline, questions are arising as to how changes in sea-ice dynamics might affect biogeochemical cycling and phenomena such as carbon dioxide (CO2) uptake and ocean acidification. Recent field research in these areas has concentrated on biogeochemical and CO2 measurements during spring, summer or autumn, but there are few data for the winter or winterâspring transition, particularly in the High Arctic. Here, we present carbon and nutrient data within and under sea ice measured during the Catlin Arctic Survey, over 40 days in March and April 2010, off Ellef Ringnes Island (78° 43.11âČ N, 104° 47.44âČ W) in the Canadian High Arctic. Results show relatively low surface water (1â10 m) nitrate (<1.3 ”M) and total inorganic carbon concentrations (mean±SD=2015±5.83 ”mol kgâ1), total alkalinity (mean±SD=2134±11.09 ”mol kgâ1) and under-ice pCO2sw (mean±SD=286±17 ”atm). These surprisingly low wintertime carbon and nutrient conditions suggest that the outer Canadian Arctic Archipelago region is nitrate-limited on account of sluggish mixing among the multi-year ice regions of the High Arctic, which could temper the potential of widespread under-ice and open-water phytoplankton blooms later in the season
Giardia intestinalis and nutritional status in children participating in the complementary nutrition program, Antioquia, Colombia, May to October 2006
Seasonal changes in POC export flux in the Chukchi Sea and implications for water column-benthic coupling in Arctic shelves
As part of the 2002 Shelf-Basin Interactions (SBI) process study, measurements of the seasonal variation in the export flux of particulate organic carbon (POC) are reported for the upper waters of the Chukchi Sea. POC fluxes were quantified by determination of 234Th/238U disequilibrium and POC/234Th ratios in large View the MathML source aggregates collected using in situ pumps. Samples were collected at 35 stations on two cruises, one in predominantly ice-coved conditions during the spring (May 6âJune 15) and the other in predominantly open water during the summer (July 17âAugust 26). Enhanced particle export was observed in the shelf and slope waters, particularly within Barrow Canyon, and there was a marked increase in particle export at all stations during the summer (JulyâAugust) relative to the spring (MayâJune). 234Th-derived POC fluxes exhibit significant seasonal and spatial variability, averaging View the MathML sourceView the MathML source in the spring and increasing ?4-fold in the summer to an average value of View the MathML sourceView the MathML source. The fraction of primary production exported from the upper waters increases from ?15% in the spring to ?32% in the summer. By comparison, DOC accumulation associated with net community production represented ?6% of primary production View the MathML source. The majority of shelf and slope stations indicate a close agreement between POC export and benthic C respiration in the spring, whereas there is an imbalance between POC export and benthic respiration in the summer. The implication is that up to ?20% of summer production View the MathML source may be seasonally exported off-shelf in this productive shelf/slope region of the Arctic Ocean
Spring phytoplankton onset after the ice break-up and sea-ice signature (Adélie Land, East Antarctica)
The phytoplankton onset following the spring ice break-up in Adélie Land, East Antarctica, was studied along a short transect, from 400 m off the continent to 5 km offshore, during the austral summer of 2002. Eight days after the ice break-up, some large colonial and solitary diatom cells, known to be associated with land-fast ice and present in downward fluxes, were unable to adapt in ice-free waters, while some other solitary and short-colony forming taxa (e.g., Fragilariopsis curta, F. cylindrus) did develop. Pelagic species were becoming more abundant offshore, replacing the typical sympagic (ice-associated) taxa. Archaeomonad cysts, usually associated with sea ice, were recorded in the surface waters nearshore. Rough weather restricted the data set, but we were able to confirm that some microalgae may be reliable sea-ice indicators and that seeding by sea ice only concerns a few taxa in this coastal area of East Antarctica. Keywords: Ice break-up; phytoplankton; sea-ice signature; East Antarctica (Published: 10 January 2011) Citation: Polar Research 2011, 30, 5910, doi: 10.3402/polar.v30i0.591
Spatial and temporal variability of ice algal production in a 3D iceâocean model of the Hudson Bay, Hudson Strait and Foxe Basin system
Common Neural Mechanisms of Palatable Food Intake and Drug Abuse: Knowledge Obtained with Animal Models
The BigBOSS Experiment
BigBOSS is a Stage IV ground-based dark energy experiment to study baryon
acoustic oscillations (BAO) and the growth of structure with a wide-area galaxy
and quasar redshift survey over 14,000 square degrees. It has been
conditionally accepted by NOAO in response to a call for major new
instrumentation and a high-impact science program for the 4-m Mayall telescope
at Kitt Peak. The BigBOSS instrument is a robotically-actuated, fiber-fed
spectrograph capable of taking 5000 simultaneous spectra over a wavelength
range from 340 nm to 1060 nm, with a resolution R = 3000-4800.
Using data from imaging surveys that are already underway, spectroscopic
targets are selected that trace the underlying dark matter distribution. In
particular, targets include luminous red galaxies (LRGs) up to z = 1.0,
extending the BOSS LRG survey in both redshift and survey area. To probe the
universe out to even higher redshift, BigBOSS will target bright [OII] emission
line galaxies (ELGs) up to z = 1.7. In total, 20 million galaxy redshifts are
obtained to measure the BAO feature, trace the matter power spectrum at smaller
scales, and detect redshift space distortions. BigBOSS will provide additional
constraints on early dark energy and on the curvature of the universe by
measuring the Ly-alpha forest in the spectra of over 600,000 2.2 < z < 3.5
quasars.
BigBOSS galaxy BAO measurements combined with an analysis of the broadband
power, including the Ly-alpha forest in BigBOSS quasar spectra, achieves a FOM
of 395 with Planck plus Stage III priors. This FOM is based on conservative
assumptions for the analysis of broad band power (kmax = 0.15), and could grow
to over 600 if current work allows us to push the analysis to higher wave
numbers (kmax = 0.3). BigBOSS will also place constraints on theories of
modified gravity and inflation, and will measure the sum of neutrino masses to
0.024 eV accuracy.Comment: This report is based on the BigBOSS proposal submission to NOAO in
October 2010, and reflects the project status at that time with minor update