38 research outputs found
Reviews and syntheses: Heterotrophic fixation of inorganic carbon â significant but invisible flux in environmental carbon cycling
Heterotrophic CO2 fixation is a significant yet underappreciated
CO2 flux in environmental carbon cycling. In contrast to photosynthesis
and chemolithoautotrophy â the main recognized autotrophic CO2
fixation pathways â the importance of heterotrophic CO2 fixation
remains enigmatic. All heterotrophs â from microorganisms to humans â take
up CO2 and incorporate it into their biomass. Depending on the
availability and quality of growth substrates, and drivers such as the
CO2 partial pressure, heterotrophic CO2 fixation contributes at
least 1â%â5â% and in the case of methanotrophs up to 50â% of the carbon
biomass. Assuming a standing stock of global heterotrophic biomass of 47â85âPgâC, we roughly estimate that up to 5âPgâC might be derived from
heterotrophic CO2 fixation, and up to 12âPgâCâyrâ1 originating from
heterotrophic CO2 fixation is funneled into the global annual
heterotrophic production of 34â245âPgâCâyrâ1. These first estimates on
the importance of heterotrophic fixation of inorganic carbon indicate that
this pathway should be incorporated in present and future carbon cycling
budgets.</p
The ANTARES Optical Beacon System
ANTARES is a neutrino telescope being deployed in the Mediterranean Sea. It
consists of a three dimensional array of photomultiplier tubes that can detect
the Cherenkov light induced by charged particles produced in the interactions
of neutrinos with the surrounding medium. High angular resolution can be
achieved, in particular when a muon is produced, provided that the Cherenkov
photons are detected with sufficient timing precision. Considerations of the
intrinsic time uncertainties stemming from the transit time spread in the
photomultiplier tubes and the mechanism of transmission of light in sea water
lead to the conclusion that a relative time accuracy of the order of 0.5 ns is
desirable. Accordingly, different time calibration systems have been developed
for the ANTARES telescope. In this article, a system based on Optical Beacons,
a set of external and well-controlled pulsed light sources located throughout
the detector, is described. This calibration system takes into account the
optical properties of sea water, which is used as the detection volume of the
ANTARES telescope. The design, tests, construction and first results of the two
types of beacons, LED and laser-based, are presented.Comment: 21 pages, 18 figures, submitted to Nucl. Instr. and Meth. Phys. Res.
First results of the Instrumentation Line for the deep-sea ANTARES neutrino telescope
In 2005, the ANTARES Collaboration deployed and operated at a depth of 2500 m a so-called Mini Instrumentation Line equipped with Optical Modules (MILOM) at the ANTARES site. The various data acquired during the continuous operation from April to December 2005 of the MILOM confirm the satisfactory performance of the Optical Modules, their front-end electronics and readout system. as well as the calibration devices of the detector. The in situ measurement of the Optical Module time response yields a resolution better than 0.5 ns. The performance of the acoustic positioning system, which enables the spatial reconstruction of the ANTARES detector with a precision of about 10 cm, is verified. These results demonstrate that with the full ANTARES neutrino telescope the design angular resolution of better than 0.3 degrees can be realistically achieved
The data acquisition system for the ANTARES neutrino telescope
The ANTARES neutrino telescope is being constructed in the Mediterranean Sea.
It consists of a large three-dimensional array of photo-multiplier tubes. The
data acquisition system of the detector takes care of the digitisation of the
photo-multiplier tube signals, data transport, data filtering, and data
storage. The detector is operated using a control program interfaced with all
elements. The design and the implementation of the data acquisition system are
described.Comment: 20 pages, 6 figures, accepted for publication in Nucl. Instrum. Meth.
ANTARES: the first undersea neutrino telescope
The ANTARES Neutrino Telescope was completed in May 2008 and is the first
operational Neutrino Telescope in the Mediterranean Sea. The main purpose of
the detector is to perform neutrino astronomy and the apparatus also offers
facilities for marine and Earth sciences. This paper describes the design, the
construction and the installation of the telescope in the deep sea, offshore
from Toulon in France. An illustration of the detector performance is given
Reviews and syntheses: Heterotrophic fixation of inorganic carbon - Significant but invisible flux in environmental carbon cycling.
Heterotrophic CO2 fixation is a significant yet underappreciated CO2 flux in environmental carbon cycling. In contrast to photosynthesis and chemolithoautotrophy - the main recognized autotrophic CO2 fixation pathways - the importance of heterotrophic CO2 fixation remains enigmatic. All heterotrophs - from microorganisms to humans - take up CO2 and incorporate it into their biomass. Depending on the availability and quality of growth substrates, and drivers such as the CO2 partial pressure, heterotrophic CO2 fixation contributes at least 1%-5% and in the case of methanotrophs up to 50% of the carbon biomass. Assuming a standing stock of global heterotrophic biomass of 47-85PgC, we roughly estimate that up to 5PgC might be derived from heterotrophic CO2 fixation, and up to 12PgCyr-1 originating from heterotrophic CO2 fixation is funneled into the global annual heterotrophic production of 34-245PgCyr-1. These first estimates on the importance of heterotrophic fixation of inorganic carbon indicate that this pathway should be incorporated in present and future carbon cycling budgets