2,776 research outputs found
Is the supply of long-term debt independent of the term premia? Evidence from Portugal
An important assumption in the statistical analysis of the financial market effects of the central bankâs large scale asset purchase program is that the "long-term debt stock variables were exogenous to term premia". We test this assumption for a small open economy in a currency union over the period 2000M3 to 2015M10, via the determinants of short- term financing relative to long-term financing. Empirical estimations indicate that the maturity composition of debt does not respond to the level of interest rate or to the term structure. These findings suggest a lower adherence to the cost minimization mandate of debt management. However, we find that volatility and relative market size respectively decrease and increase short-term financing relative to long-term financing, while it decreases with an increase in government indebtedness
SDSSJ143244.91+301435.3 at VLBI: a compact radio galaxy in a narrow-line Seyfert 1
We present VLBI observations, carried out with the European Very Long
Baseline Interferometry Network (EVN), of SDSSJ143244.91+301435.3, a radio-loud
narrow-line Seyfert 1 (RLNLS1) characterized by a steep radio spectrum. The
source, compact at Very Large Array (VLA) resolution, is resolved on the
milliarcsec scale, showing a central region plus two extended structures. The
relatively high brightness temperature of all components (5x10^6-1.3x10^8 K)
supports the hypothesis that the radio emission is non-thermal and likely
produced by a relativistic jet and/or small radio lobes. The observed radio
morphology, the lack of a significant core and the presence of a low frequency
(230 MHz) spectral turnover are reminiscent of the Compact Steep Spectrum
sources (CSS). However, the linear size of the source (~0.5kpc) measured from
the EVN map is lower than the value predicted using the turnover/size relation
valid for CSS sources (~6kpc). This discrepancy can be explained by an
additional component not detected in our observations, accounting for about a
quarter of the total source flux density, combined to projection effects. The
low core-dominance of the source (CD<0.29) confirms that
SDSSJ143244.91+301435.3 is not a blazar, i.e. the relativistic jet is not
pointing towards the observer. This supports the idea that
SDSSJ143244.91+301435.3 may belong to the "parent population" of flat-spectrum
RLNLS1 and favours the hypothesis of a direct link between RLNLS1 and compact,
possibly young, radio galaxies.Comment: 8 pages, 3 figures, accepted for publication in MNRA
Pseudo-science: a meaningful context for assessing nature of science
Although an understanding of nature of science is a core element in scientific literacy, there is considerable evidence that school and university students hold naĂŻve conceptions about it. It is argued that, whilst the failure to learn about nature of science arises from its neglect in formal science education, a major reason is the adherence to the precepts of pseudo-science, a set of beliefs that have wide cultural currency in the general population. University science and non-science students were interviewed about their beliefs in and explanations for âwater dowsingâ, a pseudo-scientific approach to finding groundwater. The demarcation criteria between science and pseudo-science and studentsâ research designs into âwater dowsingâ were also enquired into. The results show that many students believed in the working efficacy of water dowsing and stated pseudo-scientific explanations for it. Furthermore, they were unaware of the demarcation criteria between science and pseudo-science, and designed naĂŻve research studies to enquire into 'water dowsing'
Hemoglobin genotype has minimal influence on the physiological response of juvenile atlantic cod (Gadus morhua) to environmental challenges
Hemoglobin (Hb) polymorphism in cod is associated with temperatureârelated differences in biogeographical distribution, and several authors have suggested that functional characteristics of the various hemoglobin isoforms (HbIs) directly influence phenotypic traits such as growth rate. However, no study has directly examined whether Hb genotype translates into physiological differences at the whole animal level. Thus, we generated a family of juvenile Atlantic cod consisting of all three main Hb genotypes (HbIâ1/1, HbIâ2/2, and HbIâ1/2) by crossing a single pair of heterozygous parents, and we compared their metabolic and cortisol responses to an acute thermal challenge (10°C to their critical thermal maximum [CTM] or 22°C, respectively) and tolerance of graded hypoxia. There were no differences in routine metabolism (at 10°C), maximum metabolic rate, metabolic scope, CTM (overall mean 22.9° ± 0.2°C), or resting and poststress plasma cortisol levels among Hb genotypes. Further, although the HbIâ1/1 fish grew more (by 15%–30% during the first 9 mo) when reared at 10° ± 1°C and had a slightly enhanced hypoxia tolerance at 10°C (e.g., the critical O2 levels for HbIâ1/1, HbIâ2/2, and HbIâ1/2 cod were 35.56% ± 1.24%, and 40.20% ± 1.99% air saturation, respectively), these results are contradictory to expectations based on HbI functional properties. Thus, our findings (1) do not support previous assumptions that growth rate differences among cod Hb genotypes result from a more efficient use of the oxygen supply—that is, reduced standard metabolic rates and/or increased metabolic capacity—and (2) suggest that in juvenile cod, there is no selective advantage to having a particular Hb genotype with regards to the capacity to withstand ecologically relevant environmental challenges.<br /
Systematic Analysis of 22 Microlensing Parallax Candidates
We attempt to identify all microlensing parallax events for which the
parallax fit improves \Delta\chi^2 > 100 relative to a standard microlensing
model. We outline a procedure to identify three types of discrete degeneracies
(including a new one that we dub the ``ecliptic degeneracy'') and find many new
degenerate solutions in 16 previously published and 6 unpublished events. Only
four events have one unique solution and the other 18 events have a total of 44
solutions. Our sample includes three previously identified black-hole (BH)
candidates. We consider the newly discovered degenerate solutions and determine
the relative likelihood that each of these is a BH. We find the lens of event
MACHO-99-BLG-22 is a strong BH candidate (78%), event MACHO-96-BLG-5 is a
marginal BH candidate (37%), and MACHO-98-BLG-6 is a weak BH candidate (2.2%).
The lens of event OGLE-2003-BLG-84 may be a Jupiter-mass free-floating planet
candidate based on a weak 3 sigma detection of finite-source effects. We find
that event MACHO-179-A is a brown dwarf candidate within ~100 pc of the Sun,
mostly due to its very small projected Einstein radius, \tilde r_E = 0.23+-0.05
AU. As expected, these microlensing parallax events are biased toward lenses
that are heavier and closer than average. These events were examined for
xallarap (or binary-source motion), which can mimic parallax. We find that 23%
of these events are strongly affected by xallarap.Comment: 69 Pages, 10 Figures, 24 Tables, Submitted to Ap
The direct role of enzyme hydrolysis on ammonium regeneration rates in estuarine sediments
Benthic ammonium (NH4 +) regeneration in coastal marine sediments has a fundamental role in nitrogen (N) cycling and N supply to primary producers. Nitrogen regeneration involves benthic microbial mineralization of organic-N, which, in turn, depends on protein hydrolysis. These processes were examined in Aransas Bay (Texas, USA) sediments by monitoring NH4 + evolution as a function of enzyme activity in controlled sediment slurries. Casein and tannic acid were added to evaluate the direct role of aminopeptidase on NH4 + production and the effects of a polyphenolic enzyme inhibitor, respectively. Casein additions increased the NH4 + concentration from 19 ± 0.3 to 737 ± 150 ΌM in 120 h, a final concentration 4.3-fold higher than that of control samples and 2.9-fold higher than that of samples with casein and tannic added together. Lower NH4 + concentration in samples with tannic acid indicated that inhibiting aminopeptidase activity reduced NH4 + production rates. The concentration of the regenerated NH4 + related directly to aminopeptidase activity in controls (r = 0.86, p \u3c 0.01), casein-enriched (r = 0.89, p \u3c 0.01), and casein plus polyphenol treatments (r = 0.71, p \u3c 0.01) over the first 72 h. The results demonstrate the importance of aminopeptidase in regenerating NH4 + in sediments and provide insights about mechanisms of enzyme hydrolysis and NH4 + fluxes in estuarine sediments
Coarse-grained description of a passive scalar
The issue of the parameterization of small-scale dynamics is addressed in the
context of passive-scalar turbulence. The basic idea of our strategy is to
identify dynamical equations for the coarse-grained scalar dynamics starting
from closed equations for two-point statistical indicators. With the aim of
performing a fully-analytical study, the Kraichnan advection model is
considered. The white-in-time character of the latter model indeed leads to
closed equations for the equal-time scalar correlation functions. The classical
closure problem however still arises if a standard filtering procedure is
applied to those equations in the spirit of the large-eddy-simulation strategy.
We show both how to perform exact closures and how to identify the
corresponding coarse-grained scalar evolution.Comment: 22 pages; submitted to Journal of Turbulenc
An efficient and general approach for implementing thermodynamic phase equilibria information in geophysical and geodynamic studies
We present a flexible, general, and efficient approach for implementing thermodynamic phase equilibria information (in the form of sets of physical parameters) into geophysical and geodynamic studies. The approach is based on Tensor Rank Decomposition methods, which transform the original multidimensional discrete information into a separated representation that contains significantly fewer terms, thus drastically reducing the amount of information to be stored in memory during a numerical simulation or geophysical inversion. Accordingly, the amount and resolution of the thermodynamic information that can be used in a simulation or inversion increases substantially. In addition, the method is independent of the actual software used to obtain the primary thermodynamic information, and therefore, it can be used in conjunction with any thermodynamic modeling program and/or database. Also, the errors associated with the decomposition procedure are readily controlled by the user, depending on her/his actual needs (e.g., preliminary runs versus full resolution runs). We illustrate the benefits, generality, and applicability of our approach with several examples of practical interest for both geodynamic modeling and geophysical inversion/modeling. Our results demonstrate that the proposed method is a competitive and attractive candidate for implementing thermodynamic constraints into a broad range of geophysical and geodynamic studies. MATLAB implementations of the method and examples are provided as supporting information and can be downloaded from the journal's website.Peer ReviewedPostprint (author's final draft
The VLA Survey of the Chandra Deep Field South. IV. Source Population
We present a detailed analysis of 256 radio sources from our deep (flux
density limit of 42 microJy at the field centre at 1.4 GHz) Chandra Deep Field
South 1.4 and 5 GHz VLA survey. The radio population is studied by using a
wealth of multi-wavelength information in the radio, optical, and X-ray bands.
The availability of redshifts for ~ 80% of the sources in our complete sample
allows us to derive reliable luminosity estimates for the majority of the
objects. X-ray data, including upper limits, for all our sources turn out to be
a key factor in establishing the nature of faint radio sources. Due to the
faint optical levels probed by this study, we have uncovered a population of
distant Active Galactic Nuclei (AGN) systematically missing from many previous
studies of sub-millijansky radio source identifications. We find that, while
the well-known flattening of the radio number counts below 1 mJy is mostly due
to star forming galaxies, these sources and AGN make up an approximately equal
fraction of the sub-millijansky sky, contrary to some previous results. The AGN
include radio galaxies, mostly of the low-power, Fanaroff-Riley I type, and a
significant radio-quiet component, which amounts to approximately one fifth of
the total sample. The ratio of radio to optical luminosity depends more on
radio luminosity, rather than being due to optical absorption.Comment: 13 pages, 8 figures, accepted for publication in the Astrophysical
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