3,708 research outputs found
Response of deep-water agglutinated foraminifera to dysoxic conditions in the California Borderland basins
Analysis of agglutinated benthic foraminifera from surface samples collected in the San Pedro
and Santa Catalina Basins reveals a predictable relationship between the proportions of morphogroups
with decreasing bottom water oxygen levels and with the TOC content of the surficial sediment.
Living (Rose Bengal stained) foraminiferal faunas from dysaerobic environments display
low diversity and high dominance, suggesting stressed conditions. There is an inverse relationship
between oxygen and the relative abundance of deep infaunal morphogroups.
Samples collected from shallow stations above the oxygen minimum zone are comprised of
epifaunal and shallow infaunal morphotypes. At intermediate depths (~500 m), there is a peak in
the abundance of suspension-feeding and "climbing" forms (watchglass-shaped trochamminids
attached to Rhabdammina). Specimens from intermediate stations display the largest overall size.
Deeper in the San Pedro Basin the living fauna is dominated by a small, flattened, tapered,
species that is interpreted as having a deep infaunal microhabitat. In the dysaerobic environments
off California the greatest degree of faunal change occurs when bottom water dissolved oxygen
values drop from 0.5 ml/l to 0.2 ml/l.
The effect of TOC content on the benthic fauna is demonstrated at two stations from the same
depth in the San Pedro Basin. The station with the higher TOC content (4.2% vs. 2.9%) contains
greater proportions of the small, deep infaunal morphotype. These faunal changes may be
attributed to differences in the depth of the oxygenated zone within the sediment surface layer.
Agglutinated faunas from areas that experience seasonal anoxia are comprised of a large
proportion of opportunistic forms such as Reophax and Psammosphaera. These are the same taxa
that colonised abiotic sediment trays in a recolonisation experiment in the Panama Basin. This
study further demonstrates that agglutinated foraminiferal morphotypes respond in a similar
manner to calcareous benthic foraminifera in dysaerobic environments
A combination of statins and beta-blockers is independently associated with a reduction in the incidence of perioperative mortality and nonfatal myocardial infarction in patients undergoing abdominal aortic aneurysm surgery
Seasonal variation in the interactions between piscivorous fish, planktivorous fish and zooplankton in a shallow eutrophic lake
Herschel PACS and SPIRE spectroscopy of the Photodissociation Regions associated with S 106 and IRAS 23133+6050
Photodissociation regions (PDRs) contain a large fraction of all of the
interstellar matter in galaxies. Classical examples include the boundaries
between ionized regions and molecular clouds in regions of massive star
formation, marking the point where all of the photons energetic enough to
ionize hydrogen have been absorbed. In this paper we determine the physical
properties of the PDRs associated with the star forming regions IRAS 23133+6050
and S 106 and present them in the context of other Galactic PDRs associated
with massive star forming regions. We employ Herschel PACS and SPIRE
spectroscopic observations to construct a full 55-650 {\mu}m spectrum of each
object from which we measure the PDR cooling lines, other fine- structure
lines, CO lines and the total far-infrared flux. These measurements are then
compared to standard PDR models. Subsequently detailed numerical PDR models are
compared to these predictions, yielding additional insights into the dominant
thermal processes in the PDRs and their structures. We find that the PDRs of
each object are very similar, and can be characterized by a two-phase PDR model
with a very dense, highly UV irradiated phase (n 10^6 cm^(-3), G
10^5) interspersed within a lower density, weaker radiation field phase
(n 10^4 cm^(-3), G 10^4). We employed two different numerical
models to investigate the data, firstly we used RADEX models to fit the peak of
the CO ladder, which in conjunction with the properties derived yielded
a temperature of around 300 K. Subsequent numerical modeling with a full PDR
model revealed that the dense phase has a filling factor of around 0.6 in both
objects. The shape of the CO ladder was consistent with these components
with heating dominated by grain photoelectric heating. An extra excitation
component for the highest J lines (J > 20) is required for S 106.Comment: 20 pages, 10 figures, A&A Accepte
Intonation in unaccompanied singing: Accuracy, drift, and a model of reference pitch memory
Copyright 2014 Acoustical Society of America. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the Acoustical Society of America.
The following article appeared in J. Acoust. Soc. Am. 136, 401 (2014) and may be found at http://dx.doi.org/10.1121/1.4881915
Polycyclic Aromatic Hydrocarbon Size Tracers
We examine the dependence of polycyclic aromatic hydrocarbon (PAH) band
intensity ratios as a function of the average number of carbon atoms and assess
their effectiveness as tracers for PAH size, utilising the data, models, and
tools provided by the NASA Ames PAH Infrared Spectroscopic Database. To achieve
this, we used spectra from mixtures of PAHs of different ionisation fractions,
following a size distribution. Our work, congruent with earlier findings, shows
that band ratios that include the 3.3 m PAH band provide the best PAH
size tracers for small-to-intermediate sized PAHs. In addition, we find that
band ratios that include the sum of the 15-20 m PAH features
(I) and the 6.2 or 7.7 m bands also serve as good
tracers for PAH size in the case of small-to-intermediate sized PAHs, for
objects under a similar PAH size distribution as with the presented models. For
different PAH size distributions, the application of a scaling factor to the
I/I ratio can provide estimates for the size of the
small-to-intermediate PAH population within sources. Employment of the
I/I and I/I ratios can be
of particular interest for JWST observations limited only to 5-28
m MIRI(-MRS) coverage.Comment: 8 pages, 5 figures; Accepted for publication in MNRA
Methods for the recovery of nutrients and energy from swine manure. 1. Biogas.
The recovery of nutrients from pig manure (300 l/day discharged by 100 pigs) during digestion for biogas production amounted to 1435 kg N, 350 kg P and 490 kg K per year. When spread on the 15.26 ha of land required to grow the corn and soybean for the pig ration, each hectare would receive 94 kg N, 23 kg P and 32 kg K per year. The energy value of the recovered fertilizer represents 4.4% of the total energy input of the pig production system. (Abstract retrieved from CAB Abstracts by CABI’s permission
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