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Exploring The Use Of SAR Remote Sensing To Detect Microplastics Pollution In The Oceans
The increase in plastic pollution is advancing micro level pollution and the total weight of microplastics (8 tons and in the North Atlantic as 10.4 x 108 tons. The plastic in marine environment will eventually degrade and it will be promptly colonized by bacteria releasing surfactants. Such surfactants will have the effect of damping the capillary and small gravitational waves on the ocean surface. Since SAR is sensitive to roughness induced by capillary waves, it may be exploited to detect bacterial activities related to plastic pollution.
In this work we used Sentinel-1A and COSMO SkyMed radar images acquired in the Atlantic and Pacific gyres to detect surfactants that may be associated to plastic pollution. We are using SAR, because the damping properties of surfactants produce dark areas in images. Since area of low backscattering in SAR images could also be produced by other oceanographic/meteorological event, we exploited geophysical remote sensing products associated to time and locations synchronised to SAR acquisitions. Among other products we considered sea surface temperature, surface wind, chlorophyll, surface reflectance, turbidity and wave heights. Additionally we made sure that the areas were not within busy shipping routes. The result of the analysis is that, including effects due to colocation errors of SAR and meteorological data, we could identify a large amount of linear slicks in SAR images that were not directly related to apparent meteorological conditions. Such slicks in the gyres have the appearance of oil slicks, however in some areas they are in large amount and they are not connected to large ship traffic. At the moment these slicks seems to only be visible when the wind conditions are moderate (e.g. 6m/s) as it happen for ordinary oil slicks.
Besides the work on radar data, we are making controlled experiments with micro-plastic pollution in sea water, to understand the amount and type of surfactants produced by microbes colonising plastics.
The conclusion of our study is that radar remote sensing has the potential to detect plastic pollution areas under sorter meteorological conditions
Detecting microplastics pollution in world oceans using SAR remote sensing
Plastic pollution in the world’s oceans is estimated to have reached 270.000 tones, or 5.25 trillion pieces. This plastic is now ubiquitous, however due to ocean circulation patterns, it accumulates in the ocean gyres, creating “garbage patches”. This plastic debris is colonized by microorganisms which create unique bio-film ecosystems. Microbial colonization is the first step towards disintegration and degradation of plastic materials: a process that releases metabolic by-products from energy synthesis. These by-products include the release of short-chain and more complex carbon molecules in the form of surfactants, which we hypothesize will affect the fluid dynamic properties of waves (change in viscosity and surface tension) and make them detectable by SAR sensor.
In this study we used Sentinel-1A and COSMO-SkyMed SAR images in selected sites of both the North Pacific and North Atlantic oceans, close to ocean gyres and away from coastal interference. Together with SAR processing we conducted contextual analysis, using ocean geophysical products of the sea surface temperature, surface wind, chlorophyll, wave heights and wave spectrum of the ocean surface. In addition, we started experiments under controlled conditions to test the behaviour of microbes colonizing the two most common pollutants, polyethylene (PE) and polyethylene terephthalate (PET) microplastics. The analysis of SAR images has shown that a combination of surface wind speed and Langmuir cells- ocean circulation pattern is the main controlling factor in creating the distinct appearance of the sea-slicks and microbial bio-films. The preliminary conclusion of our study is that SAR remote sensing may be able to detect plastic pollution in the open oceans and this method can be extended to other areas
Faint high-energy gamma-ray photon emission of GRB 081006A from Fermi observations
Since the launch of the Fermi gamma - ray Space Telescope on June 11, 2008,
the LAT instrument has solidly detected more than 20 GRBs with high energy
photon emission above 100 MeV. Using the matched filter technique, 3 more GRBs
have also shown evidence of correlation with high energy photon emission as
demonstrated by Akerlof et al. In this paper, we present another GRB
unambiguously detected by the matched filter technique, GRB 081006A. This event
is associated with more than 13 high energy photons above 100 MeV. The
likelihood analysis code provided by the Science Support Center (FSSC)
generated an independent verification of this detection by comparison of the
Test Statistics (TS) value with similar calculations for random LAT data
fields. We have performed detailed temporal and spectral analysis of photons
from 8 keV up to 0.8 GeV from the GBM and the LAT. The properties of GRB
081006A can be compared to the other two long duration GRBs detected at similar
significance, GRB 080825C and GRB 090217A. We find that GRB 081006A is more
similar to GRB 080825C with comparable appearances of late high energy photon
emission. As demonstrated previously, there appears to be a surprising dearth
of faint LAT GRBs, with only one additional GRB identified in a sample of 74
GRBs. In this unique period when both and are operational,
there is some urgency to explore this aspect of GRBs as fully as possible.Comment: ApJ, 745, 7
On the evolutionary origin of aging
It is generally believed that the first organisms did not age, and that aging thus evolved at some point in the history of life. When and why this transition occurred is a fundamental question in evolutionary biology. Recent reports of aging in bacteria suggest that aging predates the emergence of eukaryotes and originated in simple unicellular organisms. Here we use simple models to study why such organisms would evolve aging. These models show that the differentiation between an aging parent and a rejuvenated offspring readily evolves as a strategy to cope with damage that accumulates due to vital activities. We use measurements of the age-specific performance of individual bacteria to test the assumptions of the model, and find evidence that they are fulfilled. The mechanism that leads to aging is expected to operate in a wide range of organisms, suggesting that aging evolved early and repeatedly in the history of life. Aging might thus be a more fundamental aspect of cellular organisms than assumed so far
The Allen Telescope Array: The First Widefield, Panchromatic, Snapshot Radio Camera for Radio Astronomy and SETI
The first 42 elements of the Allen Telescope Array (ATA-42) are beginning to
deliver data at the Hat Creek Radio Observatory in Northern California.
Scientists and engineers are actively exploiting all of the flexibility
designed into this innovative instrument for simultaneously conducting surveys
of the astrophysical sky and conducting searches for distant technological
civilizations. This paper summarizes the design elements of the ATA, the cost
savings made possible by the use of COTS components, and the cost/performance
trades that eventually enabled this first snapshot radio camera. The
fundamental scientific program of this new telescope is varied and exciting;
some of the first astronomical results will be discussed.Comment: Special Issue of Proceedings of the IEEE: "Advances in Radio
Telescopes", Baars,J. Thompson,R., D'Addario, L., eds, 2009, in pres
The Allen Telescope Array Pi GHz Sky Survey I. Survey Description and Static Catalog Results for the Bootes Field
The Pi GHz Sky Survey (PiGSS) is a key project of the Allen Telescope Array.
PiGSS is a 3.1 GHz survey of radio continuum emission in the extragalactic sky
with an emphasis on synoptic observations that measure the static and
time-variable properties of the sky. During the 2.5-year campaign, PiGSS will
twice observe ~250,000 radio sources in the 10,000 deg^2 region of the sky with
b > 30 deg to an rms sensitivity of ~1 mJy. Additionally, sub-regions of the
sky will be observed multiple times to characterize variability on time scales
of days to years. We present here observations of a 10 deg^2 region in the
Bootes constellation overlapping the NOAO Deep Wide Field Survey field. The
PiGSS image was constructed from 75 daily observations distributed over a
4-month period and has an rms flux density between 200 and 250 microJy. This
represents a deeper image by a factor of 4 to 8 than we will achieve over the
entire 10,000 deg^2. We provide flux densities, source sizes, and spectral
indices for the 425 sources detected in the image. We identify ~100$ new flat
spectrum radio sources; we project that when completed PiGSS will identify 10^4
flat spectrum sources. We identify one source that is a possible transient
radio source. This survey provides new limits on faint radio transients and
variables with characteristic durations of months.Comment: Accepted for publication in ApJ; revision submitted with extraneous
figure remove
The Allen Telescope Array Pi GHz Sky Survey I. Survey Description and Static Catalog Results for the Bootes Field
The Pi GHz Sky Survey (PiGSS) is a key project of the Allen Telescope Array.
PiGSS is a 3.1 GHz survey of radio continuum emission in the extragalactic sky
with an emphasis on synoptic observations that measure the static and
time-variable properties of the sky. During the 2.5-year campaign, PiGSS will
twice observe ~250,000 radio sources in the 10,000 deg^2 region of the sky with
b > 30 deg to an rms sensitivity of ~1 mJy. Additionally, sub-regions of the
sky will be observed multiple times to characterize variability on time scales
of days to years. We present here observations of a 10 deg^2 region in the
Bootes constellation overlapping the NOAO Deep Wide Field Survey field. The
PiGSS image was constructed from 75 daily observations distributed over a
4-month period and has an rms flux density between 200 and 250 microJy. This
represents a deeper image by a factor of 4 to 8 than we will achieve over the
entire 10,000 deg^2. We provide flux densities, source sizes, and spectral
indices for the 425 sources detected in the image. We identify ~100$ new flat
spectrum radio sources; we project that when completed PiGSS will identify 10^4
flat spectrum sources. We identify one source that is a possible transient
radio source. This survey provides new limits on faint radio transients and
variables with characteristic durations of months.Comment: Accepted for publication in ApJ; revision submitted with extraneous
figure remove
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