490 research outputs found
MONETARY POLICY, INVESTMENT DYNAMICS, AND THE INTERTEMPORAL APPROACH TO THE CURRENT ACCOUNT
This paper applies the intertemporal approach to the current account to the case of monetary shocks. A two-country dynamic general equilibrium model with predetermined wages is proposed as a means to bridge the gap between Mundell-Fleming and modern intertemporal models. Early versions of Mundell-Fleming implied that a monetary expansion must necessarily improve the current account; the alternative result became a possibility in more contemporary versions when intertemporal features were introduced into the asset market. The present model suggests that when intertemporal features are also introduced into the other markets of the economy, the model''s prediction is transformed yet further. A calibrated version of the model suggests a beggar-thy-neighbor improvement in the current account becomes unlikely for reasonable parameter values.
Collaborative research: particulate organic carbon in the air and snow at Summit, Greenland
Issued as final reportNational Science Foundation (U.S.
Towards a Community Framework for Agent-Based Modelling
Agent-based modelling has become an increasingly important tool for scholars studying social and social-ecological systems, but there are no community standards on describing, implementing, testing and teaching these tools. This paper reports on the establishment of the Open Agent-Based Modelling Consortium, www.openabm.org, a community effort to foster the agent-based modelling development, communication, and dissemination for research, practice and education.Replication, Documentation Protocol, Software Development, Standardization, Test Beds, Education, Primitives
Water, O2 and Ice in Molecular Clouds
We model the temperature and chemical structure of molecular clouds as a
function of depth into the cloud, assuming a cloud of constant density n
illuminated by an external FUV (6 eV < E < 13.6 eV) flux G_0 (scaling factor in
multiples of the local interstellar field). Extending previous
photodissociation region models, we include the freezing of species, simple
grain surface chemistry, and desorption (including FUV photodesorption) of
ices. We also treat the opaque cloud interior with time-dependent chemistry.
Here, under certain conditions, gas phase elemental oxygen freezes out as water
ice and the elemental C/O abundance ratio can exceed unity, leading to complex
carbon chemistry. Gas phase H2O and O2 peak in abundance at intermediate depth
into the cloud, roughly A_V~3-8 from the surface, the depth proportional to
ln(G_0/n). Closer to the surface, molecules are photodissociated. Deeper into
the cloud, molecules freeze to grain surfaces. At intermediate depths
photodissociation rates are attenuated by dust extinction, but photodesorption
prevents total freezeout. For G_0 < 500, abundances of H2O and O2 peak at
values ~10^(-7), producing columns ~10^(15) per cm^2, independent of G_0 and n.
The peak abundances depend primarily on the product of the photodesorption
yield of water ice and the grain surface area per H nucleus. At higher values
of G_0, thermal desorption of O atoms from grains enhances the gas phase H2O
peak abundance and column slightly, whereas the gas phase O2 peak abundance
rises to ~10^(-5) and the column to ~2x10^(16) per cm^2. We present simple
analytic equations for the abundances as a function of depth which clarify the
dependence on parameters. The models are applied to observations of H2O, O2,
and water ice in a number of sources, including B68, NGC 2024, and Rho Oph.Comment: 70 pages including 17 figure
Critical realism: a philosophical framework for the study of gender and mental health
This paper explores gender and mental health with particular reference to the emerging philosophical field of critical realism. This philosophy suggests a shared ontology and epistemology for the natural and social sciences. Until recently, most of the debate surrounding gender and mental health has been guided either implicitly or explicitly within a positivist or constructivist philosophy. With this in mind, key areas of critical realism are explored in relation to gender and mental health, and contrasted with the positions of positivism and constructivism. It is
argued that critical realism offers an alternative philosophical framework for the exploration of gender issues within mental health care
Spitzer spectral line mapping of supernova remnants: I. Basic data and principal component analysis
We report the results of spectroscopic mapping observations carried out
toward small (1 x 1 arcmin) regions within the supernova remnants W44, W28,
IC443, and 3C391 using the Infrared Spectrograph of the Spitzer Space
Telescope. These observations, covering the 5.2 - 37 micron spectral region,
have led to the detection of a total of 15 fine structure transitions of Ne+,
Ne++, Si+, P+, S, S++, Cl+, Fe+, and Fe++; the S(0) - S(7) pure rotational
lines of molecular hydrogen; and the R(3) and R(4) transitions of hydrogen
deuteride. In addition to these 25 spectral lines, the 6.2, 7.7, 8.6, 11.3 and
12.6 micron PAH emission bands were also observed. Most of the detected line
transitions have proven strong enough to map in several sources, providing a
comprehensive picture of the relative distribution of the various line
emissions observable in the Spitzer/IRS bandpass. A principal component
analysis of the spectral line maps reveals that the observed emission lines
fall into five distinct groups, each of which may exhibit a distinct spatial
distribution: (1) lines of S and H2 (J > 2); (2) the H2 S(0) line; (3) lines of
ions with appearance potentials less than 13.6 eV; (4) lines of ions with
appearance potentials greater than 13.6 eV, not including S++; (5) lines of
S++. Lines of group (1) likely originate in molecular material subject to a
slow, nondissociative shock that is driven by the overpressure within the
supernova remnant, and lines in groups (3) - (5) are associated primarily with
dissociative shock fronts with a range of (larger) shock velocities. The H2
S(0) line shows a low-density diffuse emission component, and - in some sources
- a shock-excited component.Comment: 43 pages, including 21 figures. Accepted for publication in Ap
Distribution of Water Vapor in Molecular Clouds
We report the results of a large-area study of water vapor along the Orion
Molecular Cloud ridge, the purpose of which was to determine the
depth-dependent distribution of gas-phase water in dense molecular clouds. We
find that the water vapor measured toward 77 spatial positions along the
face-on Orion ridge, excluding positions surrounding the outflow associated
with BN/KL and IRc2, display integrated intensities that correlate strongly
with known cloud surface tracers such as CN, C2H, 13CO J =5-4, and HCN, and
less well with the volume tracer N2H+. Moreover, at total column densities
corresponding to Av < 15 mag., the ratio of H2O to C18O integrated intensities
shows a clear rise approaching the cloud surface. We show that this behavior
cannot be accounted for by either optical depth or excitation effects, but
suggests that gas-phase water abundances fall at large Av. These results are
important as they affect measures of the true water-vapor abundance in
molecular clouds by highlighting the limitations of comparing measured water
vapor column densities with such traditional cloud tracers as 13CO or C18O.
These results also support cloud models that incorporate freeze-out of
molecules as a critical component in determining the depth-dependent abundance
of water vapor
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