6,653 research outputs found
Supply-side peacekeeping: theories and new evidence from a panel data analysis
Why do nations with heterogeneous economies, geographic positions and institutions agree to dispatch their troops to remote conflict areas? This paper explores the domestic and international determinants of countries' contribution to peacekeeping operations from 1999 to 2009. Individual nations make their decision about where, when and how to send their military personnel as well as the justifications on which they base their involvement in sovereign states. Moral imperative for peacekeeping may be universally accepted but a country decision to participate is also based on self-interest combined to the geo-strategic dimension and finally constrained by political and technical considerations. Empirical results suggest that at the domestic level technical forces, such as the sustainability of multiple missions and military capabilities, all play a role. At the international level peacekeeping contributions are driven by the security threat that a conflict poses and the number of displaced people
The segregation of starless and protostellar clumps in the Hi-GAL l=224deg region
Stars form in dense, dusty structures, which are embedded in larger clumps of
molecular clouds often showing a clear filamentary structure on large scales (>
1pc). One of the best-studied regions in the Hi-GAL survey can be observed
toward the l=224deg field. Here, a filamentary region has been studied and it
has been found that protostellar clumps are mostly located along the main
filament, whereas starless clumps are detected off this filament and are
instead found on secondary, less prominent filaments. We want to investigate
this segregation effect and how it may affect the clumps properties. We mapped
the 12CO(1-0) line and its main three isotopologues toward the two most
prominent filaments observed toward the l=224deg field using the Mopra radio
telescope, in order to set observational constraints on the dynamics of these
structures and the associated starless and protostellar clumps. Compared to the
starless clumps, the protostellar clumps are more luminous, more turbulent and
lie in regions where the filamentary ambient gas shows larger linewidths. We
see evidence of gas flowing along the main filament, but we do not find any
signs of accretion flow from the filament onto the Hi-GAL clumps. We analyze
the radial column density profile of the filaments and their gravitational
stability. The more massive and highly fragmented main filament appears to be
thermally supercritical and gravitationally bound, assuming that all of the
non-thermal motion is contributing thermal-like support, suggesting a later
stage of evolution compared to the secondary filament. The status and
evolutionary phase of the Hi-GAL clumps would then appear to correlate with
that of the host filament.Comment: Accepted for publication on "Astronomy and Astrophysics
Identification and Characterization of Phytoplankton in Barnegat Bay, New Jersey
Barnegat Bay is a marine estuary that encompasses 670-square miles of the eastern coast of New Jersey. The bay serves as a home to thousands of species of plants, animals, and microorganisms. During the summer months, the population of the bay increases from 576,000 to over 1.5 million residents. In 2011, the Barnegat Bay Partnership reported that environmental conditions of the bay are declining due to increased pollutants from nutrient fertilizers and runoff. Increased nitrogen levels have led to eutrophication and proliferation of phytoplankton algal blooms. Harmful algal blooms (HABs) cause a decrease in dissolved oxygen levels in the water as well as the release of harmful toxins that affect organisms inhabiting the bay, including humans.
To research and develop methods to prevent HABs from occurring, 16 Barnegat Bay sites ranging from the northern to southern regions of the bay were studied in order identify species of cyanobacteria, such as Synechococcus and Prochlorococcus, and other phytoplankton such as diatoms and dinoflagellates. Polymerase chain reaction (PCR), microscopy, and flow cytometry were utilized to generate profiles of each site. Collectively, the utilization of the three methods detected phytoplankton species such as Synechococcus, Prochlorococcus, and Cylindrotheca fusiformis. Viral plaque assays using viral lysate from each site detected the presence of cyanophage as a natural control for phytoplankton populations
Task oriented nonlinear control laws for telerobotic assembly operations
The goal of this research is to achieve very intelligent telerobotic controllers which are capable of receiving high-level commands from the human operator and implementing them in an adaptive manner in the object/task/manipulator workspace. Initiatives by the authors at Integrated Systems, Inc. to identify and develop the key technologies necessary to create such a flexible, highly programmable, telerobotic controller are presented. The focus of the discussion is on the modeling of insertion tasks in three dimensions and nonlinear implicit force feedback control laws which incorporate tool/workspace constraints. Preliminary experiments with dual arm beam assembly in 2-D are presented
Not a galaxy: IRAS 04186+5143, a new young stellar cluster in the outer Galaxy
We report the discovery of a new young stellar cluster in the outer Galaxy
located at the position of an IRAS PSC source that has been previously
mis-identified as an external galaxy. The cluster is seen in our near-infrared
imaging towards IRAS 04186+5143 and in archive Spitzer images confirming the
young stellar nature of the sources detected. There is also evidence of
sub-clustering seen in the spatial distributions of young stars and of gas and
dust.
Near- and mid-infrared photometry indicates that the stars exhibit colours
compatible with reddening by interstellar and circumstellar dust and are likely
to be low- and intermediate-mass YSOs with a large proportion of Class I YSOs.
Ammonia and CO lines were detected, with the CO emission well centred near
the position of the richest part of the cluster. The velocity of the CO and
NH lines indicates that the gas is Galactic and located at a distance of
about 5.5 kpc, in the outer Galaxy.
Herschel data of this region characterise the dust environment of this
molecular cloud core where the young cluster is embedded. We derive masses,
luminosities and temperatures of the molecular clumps where the young stars
reside and discuss their evolutionary stages.Comment: 14 pages, 15 figure
Kualitas Spermatozoa Tikus Wistar (Rattus Norvegicus) Setelah Pemaparan Obat Nyamuk Elektrik Berbahan Aktif Transflutrin
: Transflutrin (C15H12CL2F4O2) is an active substance, a derivative of pyrethroid compounds found in electric mosquito repellent. Previous studies showed that group of pyrethroid insecticides can play a role in causing histological changes in testes, decreased testicular weight and reducing diameter of seminiferous tubules. The purpose of this study was to determine the quality of wistar male sperm that are exposed to electric mosquito repellent with transflutrin as active ingredients. This study is experimental with completely randomized design, conducted for 52 days by using eight wistar which consists of two wistar as controls P0, 3 wistar with exposure to electric insect repellent for 8 hours/day (P1), and 3 other wistar for 12 hours/day (P2). The results of this study, the concentration of spermatozoa in the treatment group P1 and P2 respectively at 54.17 x 106 spermatozoa/ml and 45.5 x 106 spermatozoa / ml, in the control group P0 of 59.25 x 106 spermatozoa/ml. Abnormal sperm motility in P1 and P2 is 40% and 35%, at P0 is 45%. Morphologically normal spermatozoa in P1 and P2 is 49% and 78%. It can be concluded that exposure to electric mosquito repellent with transflutrin as active ingredients causes a decrease in sperm quality
Case history : a magnetic and GPR prospection on a Roman rural villa in western Piedmont (Italy )
To explore an archaeological site in western Piedmont we proceed to a multimethod survey using fast methods and taking
also into account the information achievable after a 2D or 3D data processing and/or rendering.
This choice restricted the methodologies to magnetic and GPR prospecting. The non contact
resistance imaging, in our opinion, still gives too smeared results even if indicative of resistivity
anomalies. We selected the magnetic prospecting because of the remarkable size of some of
the walls actually excavated even if, as we explain in the geological context, the probability of
collecting a significant amount of noise was high
On Filippov solutions of discontinuous DAEs of index 1
We study discontinuous differential-algebraic equations (DDAEs) with a co-dimension 1 discontinuity manifold Σ. Our main objectives are to give sufficient conditions that allow to extend the DAE along Σ and, when this is possible, to define sliding motion (the sliding DAE) on Σ, extending Filippov construction to this DAE case. Our approach is to consider discontinuous ODEs associated to the DDAE and apply Filippov theory to the discontinuous ODEs, defining sliding/crossing solutions of the DDAE to be those inherited by the sliding/crossing solutions of the associated discontinuous ODEs. We will see that, in general, the sliding DAE on Σ is not defined unambiguously. When possible, we will consider in greater details two different methods based on Filippov's methodology to arrive at the sliding DAE. We will call these the direct approach and the Singular Perturbation Approach and we will explore advantages and disadvantages of each of them. We illustrate our development with numerical examples
On the shape of the mass-function of dense clumps in the Hi-GAL fields. II. Using Bayesian inference to study the clump mass function
Context. Stars form in dense, dusty clumps of molecular clouds, but little is
known about their origin, their evolution and their detailed physical
properties. In particular, the relationship between the mass distribution of
these clumps (also known as the "clump mass function", or CMF) and the stellar
initial mass function (IMF), is still poorly understood. Aims. In order to
better understand how the CMF evolve toward the IMF, and to discern the "true"
shape of the CMF, large samples of bona-fide pre- and proto-stellar clumps are
required. Two such datasets obtained from the Herschel infrared GALactic Plane
Survey (Hi-GAL) have been described in paper I. Robust statistical methods are
needed in order to infer the parameters describing the models used to fit the
CMF, and to compare the competing models themselves. Methods. In this paper we
apply Bayesian inference to the analysis of the CMF of the two regions
discussed in Paper I. First, we determine the Bayesian posterior probability
distribution for each of the fitted parameters. Then, we carry out a
quantitative comparison of the models used to fit the CMF. Results. We have
compared the results from several methods implementing Bayesian inference, and
we have also analyzed the impact of the choice of priors and the influence of
various constraints on the statistical conclusions for the preferred values of
the parameters. We find that both parameter estimation and model comparison
depend on the choice of parameter priors. Conclusions. Our results confirm our
earlier conclusion that the CMFs of the two Hi-GAL regions studied here have
very similar shapes but different mass scales. Furthermore, the lognormal model
appears to better describe the CMF measured in the two Hi-GAL regions studied
here. However, this preliminary conclusion is dependent on the choice of
parameters priors.Comment: Submitted for publication to A&A on November 12, 2013. This paper
contains 11 pages and 7 figure
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