3,772 research outputs found
Report of the SNOMS Project 2006 to 2012, SNOMS SWIRE NOCS Ocean Monitoring System. Part 1: Narrative description
The ocean plays a major role in controlling the concentration of carbon dioxide (CO2) in the atmosphere. Increasing concentrations of CO2 in the atmosphere are a threat to the stability of the earth’s climate. A better understanding of the controlling role of the ocean will improve predictions of likely future changes in climate and the impact of the uptake of CO2 itself on marine eco-systems caused by the associated acidification of the ocean waters. The SNOMS Project (SWIRE NOCS Ocean Monitoring System) is a ground breaking joint research project supported by the Swire Group Trust, the Swire Educational Trust, the China Navigation Company (CNCo) and the Natural Environment Research Council. It collects high quality data on concentrations of CO2 in the surface layer of the ocean. It contributes to the international effort to better quantify (and understand the driving processes controlling) the exchanges of CO2 between the ocean and the atmosphere. In 2006 and 2007 a system that could be used on a commercial ship to provide data over periods of several months with only limited maintenance by the ships crew was designed and assembled by NOCS. The system was fitted to the CNCo ship the MV Pacific Celebes in May 2007. The onboard system was supported by web pages that monitored the progress of the ship and the functioning of the data collection system. To support the flow of data from the ship to the archiving of the data at the Carbon Dioxide Information Analysis Center (CDIAC in the USA) data processing procedures were developed for the quality control and systematic handling of the data. Data from samples of seawater collected by the ships crew and analysed in NOC (730 samples) have been used to confirm the consistency of the data from the automated measurement system on the ship. To examine the data collected between 2007 and 2012 the movements of the ship are divided into 16 voyages. Initially The Celebes traded on a route circum-navigating the globe via the Panama and Suez Canals. In 2009 the route shifted to one between Australia and New Zealand to USA and Canada. Analysis of the data is an on going process. It has demonstrated that the system produces reliable data. Data are capable of improving existing estimates of seasonal variability. The work has improved knowledge of gas exchange processes. Data from the crew-collected-samples are helping improve our ability to estimate alkalinity in different areas. This helps with the study of ocean acidification. Data from the 9 round trips in the Pacific are currently being examined along with data made available by the NOAA-PMEL laboratory forming time series from 2004 to 2012. The data from the Pacific route are of considerable interest. One reason is that the data monitors variations in the fluxes of CO2 associated with the current that flows westwards along the equator. This is one of the major natural sources of CO2 from the ocean into the atmosphere
On the Rotation Period of (90377) Sedna
We present precise, ~1%, r-band relative photometry of the unusual solar
system object (90377) Sedna. Our data consist of 143 data points taken over
eight nights in October 2004 and January 2005. The RMS variability over the
longest contiguous stretch of five nights of data spanning nine days is only
1.3%. This subset of data alone constrain the amplitude of any long-period
variations with period P to be A<1% (P/20 days)^2. Over the course of any given
5-hour segment, the data exhibits significant linear trends not seen in a
comparison star of similar magnitude, and in a few cases these segments show
clear evidence for curvature at the level of a few millimagnitudes per hour^2.
These properties imply that the rotation period of Sedna is O(10 hours), cannot
be 10 days, unless the intrinsic light curve has
significant and comparable power on multiple timescales, which is unlikely. A
sinusoidal fit yields a period of P=(10.273 +/- 0.002) hours and semi-amplitude
of A=(1.1 +/- 0.1)%. There are additional acceptable fits with flanking periods
separated by ~3 minutes, as well as another class of fits with P ~ 18 hours,
although these later fits appear less viable based on visual inspection. Our
results indicate that the period of Sedna is likely consistent with typical
rotation periods of solar system objects, thus obviating the need for a massive
companion to slow its rotation.Comment: 7 pages, 4 figures, 2.5 tables. Final ApJL version, minor changes.
Full light curve data in tex
Biogeochemical variations at the Porcupine Abyssal Plain sustained Observatory in the northeast Atlantic Ocean, from weekly to inter-annual timescales
We present high-resolution autonomous measurements of carbon dioxide partial pressure p(CO2) taken in situ at the Porcupine Abyssal Plain sustained Observatory (PAP-SO) in the northeast Atlantic (49° N, 16.5° W; water depth of 4850 m) for the period 2010–2012. Measurements of p(CO2) made at 30 m depth on a sensor frame are compared with other autonomous biogeochemical measurements at that depth (including chlorophyll a fluorescence and nitrate concentration data) to analyse weekly to seasonal controls on p(CO2) flux in the inter-gyre region of the North Atlantic. Comparisons are also made with in situ regional time series data from a ship of opportunity and mixed layer depth (MLD) measurements from profiling Argo floats. There is a persistent under-saturation of CO2 in surface waters throughout the year which gives rise to a perennial CO2 sink. Comparison with an earlier data set collected at the site (2003–2005) confirms seasonal and inter-annual changes in surface seawater chemistry. There is year-to-year variability in the timing of deep winter mixing and the intensity of the spring bloom.The 2010–2012 period shows an overall increase in p(CO2) values when compared to the 2003–2005 period as would be expected from increases due to anthropogenic CO2 emissions. The surface temperature, wind speed and MLD measurements are similar for both periods of time. Future work should incorporate daily CO2 flux measurements made using CO2 sensors at 1 m depth and the in situ wind speed data now available from the UK Met Office Buoy
Normal frames and the validity of the equivalence principle. III. The case along smooth maps with separable points of self-intersection
The equivalence principle is treated on a mathematically rigorous base on
sufficiently general subsets of a differentiable manifold. This is carried out
using the basis of derivations of the tensor algebra over that manifold.
Necessary and/or sufficient conditions of existence, uniqueness, and
holonomicity of these bases in which the components of the derivations of the
tensor algebra over it vanish on these subsets, are studied. The linear
connections are considered in this context. It is shown that the equivalence
principle is identically valid at any point, and along any path, in every
gravitational theory based on linear connections. On higher dimensional
submanifolds it may be valid only in certain exceptional cases.Comment: 15 standard LaTeX 2e (11pt, A4) pages. The package amsfonts is
require
External-environmental and internal-health early-life predictors of adolescent development
External-environmental and internal-health early-life predictors of adolescent development
Authors' preprin
Normal frames and the validity of the equivalence principle
We investigate the validity of the equivalence principle along paths in
gravitational theories based on derivations of the tensor algebra over a
differentiable manifold. We prove the existence of local bases, called normal,
in which the components of the derivations vanish along arbitrary paths. All
such bases are explicitly described. The holonomicity of the normal bases is
considered. The results obtained are applied to the important case of linear
connections and their relationship with the equivalence principle is described.
In particular, any gravitational theory based on tensor derivations which obeys
the equivalence principle along all paths, must be based on a linear
connection.Comment: 14 pages, LaTeX 2e, the package amsfonts is neede
An R- and I-Band Photometric Variability Survey of the Cygnus OB2 Association
We present a catalog of photometrically variable stars discovered within two
21'.3 X 21'.3 fields centered on the Cygnus OB2 association. There have
hitherto been no deep optical variability studies of Cyg OB2 despite it being
replete with early-type massive stars, perhaps due to the high and variable
extinction (up to A_V ~ 20) that permeates much of the region. Here we provide
results of the first variability study with this combination of spatial
coverage (~ 0.5 deg) and photometric depth (R ~ 21 mag). We find 121 stars to
be variable in both R- and I-band, 116 of them newly discovered. Of the 121
variables, we identify 27 eclipsing binaries (EBs) and eclipsing binary
candidates, 20 potential Herbig Ae/Be stars, and 52 pulsating variables.
Confirming both the status and the cluster membership of the Herbig Ae/Be stars
would address the uncertainty regarding the age and star formation history of
Cyg OB2. We match our catalog to known variables and binaries in the region,
2MASS near-IR (NIR) data, and Chandra X-ray observations to find counterparts
to new variables in other wavelengths.Comment: 34 pages, 12 figures, submitted to Ap
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