733 research outputs found
Up to No Good? Recent Critics and Critiques of NGOs
This chapter examines the various criticisms of NGOs and calls attention to both the validity of these criticisms as well as contradictions and inconsistencies. Critics of NGOs can be found across the political spectrum, ranging from rightists who object to NGOs in principle to leftists who criticize NGOs for their failures to advance a progressive agenda or for deferring to government preferences. Despite their ideological differences and ultimate objectives, however, critics are remarkably similar in terms of many of their main complaints about NGOs. During the course of the 1990s and early 2000s, a clearly defined set of critiques of NGOs have appeared focusing on: (1) their performance and actual effectiveness, (2) accountability issues, (3) issues of autonomy, (4) commercialization, and (5) ideological and/or political interpretations of their rising influence. Now appearing with increasing regularity and frequency in the academic literature, the policy world, and the popular press, these critiques have been directed towards not only NGOs working in the area of conflict resolution (the main subject of this book), but to all NGOs: advocacy NGOs, service NGOs, and NGOs working in various issues areas. In order to provide both a comprehensive and a refined examination of the debate, this chapter will present the major criticisms of NGOs in general, while distinguishing critiques as they apply to various types of NGOs
Building Networks from the Outside In: Japanese NGOs and the Kyoto Climate Change Conference
This chapter looks at changing patterns of Japanese environmental NGOs active in the international sphere and argues that in the early 1990s changes in the international realm provided activists new opportunities and frameworks that allowed them to overcome steep domestic organizational barriers and participate in new activities focused on global environmental issues. Building upon recent work done by sociologists and political scientists, it outlines how international opportunity, transational diffusion, and international socialization of state actors have encouraged the growth of NGOs and new forms of social action
Correlation energy and spin polarization in the 2D electron gas
The ground state energy of the two--dimensional uniform electron gas has been
calculated with fixed--node diffusion Monte Carlo, including backflow
correlations, for a wide range of electron densities as a function of spin
polarization. We give a simple analytic representation of the correlation
energy which fits the density and polarization dependence of the simulation
data and includes several known high- and low-density limits. This
parametrization provides a reliable local spin density energy functional for
two-dimensional systems and an estimate for the spin susceptibility. Within the
proposed model for the correlation energy, a weakly first--order polarization
transition occurs shortly before Wigner crystallization as the density is
lowered.Comment: Minor typos corrected, see erratum: Phys. Rev. Lett. 91, 109902(E)
(2003
Neutrinos and Cosmic Rays Observed by IceCube
The core mission of the IceCube Neutrino observatory is to study the origin
and propagation of cosmic rays. IceCube, with its surface component IceTop,
observes multiple signatures to accomplish this mission. Most important are the
astrophysical neutrinos that are produced in interactions of cosmic rays, close
to their sources and in interstellar space. IceCube is the first instrument
that measures the properties of this astrophysical neutrino flux, and
constrains its origin. In addition, the spectrum, composition and anisotropy of
the local cosmic-ray flux are obtained from measurements of atmospheric muons
and showers. Here we provide an overview of recent findings from the analysis
of IceCube data, and their implications on our understanding of cosmic rays.Comment: Review article, to appear in Advances in Space Research, special
issue "Origins of Cosmic Rays
Search for astrophysical sources of neutrinos using cascade events in IceCube
The IceCube neutrino observatory has established the existence of a flux of
high-energy astrophysical neutrinos inconsistent with the expectation from
atmospheric backgrounds at a significance greater than . This flux has
been observed in analyses of both track events from muon neutrino interactions
and cascade events from interactions of all neutrino flavors. Searches for
astrophysical neutrino sources have focused on track events due to the
significantly better angular resolution of track reconstructions. To date, no
such sources have been confirmed. Here we present the first search for
astrophysical neutrino sources using cascades interacting in IceCube with
deposited energies as small as 1 TeV. No significant clustering was observed in
a selection of 263 cascades collected from May 2010 to May 2012. We show that
compared to the classic approach using tracks, this statistically-independent
search offers improved sensitivity to sources in the southern sky, especially
if the emission is spatially extended or follows a soft energy spectrum. This
enhancement is due to the low background from atmospheric neutrinos forming
cascade events and the additional veto of atmospheric neutrinos at declinations
.Comment: 14 pages, 9 figures, 1 tabl
The IceCube Neutrino Observatory: Instrumentation and Online Systems
The IceCube Neutrino Observatory is a cubic-kilometer-scale high-energy
neutrino detector built into the ice at the South Pole. Construction of
IceCube, the largest neutrino detector built to date, was completed in 2011 and
enabled the discovery of high-energy astrophysical neutrinos. We describe here
the design, production, and calibration of the IceCube digital optical module
(DOM), the cable systems, computing hardware, and our methodology for drilling
and deployment. We also describe the online triggering and data filtering
systems that select candidate neutrino and cosmic ray events for analysis. Due
to a rigorous pre-deployment protocol, 98.4% of the DOMs in the deep ice are
operating and collecting data. IceCube routinely achieves a detector uptime of
99% by emphasizing software stability and monitoring. Detector operations have
been stable since construction was completed, and the detector is expected to
operate at least until the end of the next decade.Comment: 83 pages, 50 figures; updated with minor changes from journal review
and proofin
The contribution of Fermi-2LAC blazars to the diffuse TeV-PeV neutrino flux
The recent discovery of a diffuse cosmic neutrino flux extending up to PeV
energies raises the question of which astrophysical sources generate this
signal. One class of extragalactic sources which may produce such high-energy
neutrinos are blazars. We present a likelihood analysis searching for
cumulative neutrino emission from blazars in the 2nd Fermi-LAT AGN catalogue
(2LAC) using an IceCube neutrino dataset 2009-12 which was optimised for the
detection of individual sources. In contrast to previous searches with IceCube,
the populations investigated contain up to hundreds of sources, the largest one
being the entire blazar sample in the 2LAC catalogue. No significant excess is
observed and upper limits for the cumulative flux from these populations are
obtained. These constrain the maximum contribution of the 2LAC blazars to the
observed astrophysical neutrino flux to be or less between around 10
TeV and 2 PeV, assuming equipartition of flavours at Earth and a single
power-law spectrum with a spectral index of . We can still exclude that
the 2LAC blazars (and sub-populations) emit more than of the observed
neutrinos up to a spectral index as hard as in the same energy range.
Our result takes into account that the neutrino source count distribution is
unknown, and it does not assume strict proportionality of the neutrino flux to
the measured 2LAC -ray signal for each source. Additionally, we
constrain recent models for neutrino emission by blazars.Comment: 18 pages, 22 figure
Lowering IceCube’s energy threshold for point source searches in the southern sky
Observation of a point source of astrophysical neutrinos would be a "smoking gun" signature of a cosmic-ray accelerator. While IceCube has recently discovered a diffuse flux of astrophysical neutrinos, no localized point source has been observed. Previous IceCube searches for point sources in the southern sky were restricted by either an energy threshold above a few hundred TeV or poor neutrino angular resolution. Here we present a search for southern sky point sources with greatly improved sensitivities to neutrinos with energies below 100 TeV. By selecting charged-current nu(mu) interacting inside the detector, we reduce the atmospheric background while retaining efficiency for astrophysical neutrino-induced events reconstructed with sub-degree angular resolution. The new event sample covers three years of detector data and leads to a factor of 10 improvement in sensitivity to point sources emitting below 100 TeV in the southern sky. No statistically significant evidence of point sources was found, and upper limits are set on neutrino emission from individual sources. A posteriori analysis of the highest-energy (similar to 100 TeV) starting event in the sample found that this event alone represents a 2.8 sigma deviation from the hypothesis that the data consists only of atmospheric background
All-sky search for time-integrated neutrino emission from astrophysical sources with 7 years of IceCube data
Since the recent detection of an astrophysical flux of high energy neutrinos,
the question of its origin has not yet fully been answered. Much of what is
known about this flux comes from a small event sample of high neutrino purity,
good energy resolution, but large angular uncertainties. In searches for
point-like sources, on the other hand, the best performance is given by using
large statistics and good angular reconstructions. Track-like muon events
produced in neutrino interactions satisfy these requirements. We present here
the results of searches for point-like sources with neutrinos using data
acquired by the IceCube detector over seven years from 2008--2015. The
discovery potential of the analysis in the northern sky is now significantly
below , on average
lower than the sensitivity of the previously published analysis of four
years exposure. No significant clustering of neutrinos above background
expectation was observed, and implications for prominent neutrino source
candidates are discussed.Comment: 19 pages, 17 figures, 3 tables; ; submitted to The Astrophysical
Journa
A Search for Neutrino Emission from Fast Radio Bursts with Six Years of IceCube Data
We present a search for coincidence between IceCube TeV neutrinos and fast
radio bursts (FRBs). During the search period from 2010 May 31 to 2016 May 12,
a total of 29 FRBs with 13 unique locations have been detected in the whole
sky. An unbinned maximum likelihood method was used to search for spatial and
temporal coincidence between neutrinos and FRBs in expanding time windows, in
both the northern and southern hemispheres. No significant correlation was
found in six years of IceCube data. Therefore, we set upper limits on neutrino
fluence emitted by FRBs as a function of time window duration. We set the most
stringent limit obtained to date on neutrino fluence from FRBs with an
energy spectrum assumed, which is 0.0021 GeV cm per burst for emission
timescales up to \textasciitilde10 seconds from the northern hemisphere
stacking search.Comment: 15 pages, 9 figure
- …
