6,169 research outputs found
GeV Emission from Collisional Magnetized Gamma Ray Bursts
Magnetic fields may play a dominant role in gamma-ray bursts, and recent
observations by the Fermi satellite indicate that GeV radiation, when detected,
arrives delayed by seconds from the onset of the MeV component. Motivated by
this, we discuss a magnetically dominated jet model where both magnetic
dissipation and nuclear collisions are important. We show that, for parameters
typical of the observed bursts, such a model involving a realistic jet
structure can reproduce the general features of the MeV and a separate GeV
radiation component, including the time delay between the two. The model also
predicts a multi-GeV neutrino component.Comment: ApJ(Lett.), in pres
Alarm-Based Prescriptive Process Monitoring
Predictive process monitoring is concerned with the analysis of events
produced during the execution of a process in order to predict the future state
of ongoing cases thereof. Existing techniques in this field are able to
predict, at each step of a case, the likelihood that the case will end up in an
undesired outcome. These techniques, however, do not take into account what
process workers may do with the generated predictions in order to decrease the
likelihood of undesired outcomes. This paper proposes a framework for
prescriptive process monitoring, which extends predictive process monitoring
approaches with the concepts of alarms, interventions, compensations, and
mitigation effects. The framework incorporates a parameterized cost model to
assess the cost-benefit tradeoffs of applying prescriptive process monitoring
in a given setting. The paper also outlines an approach to optimize the
generation of alarms given a dataset and a set of cost model parameters. The
proposed approach is empirically evaluated using a range of real-life event
logs
Anomaly cancellation in M-theory: a critical review
We carefully review the basic examples of anomaly cancellation in M-theory:
the 5-brane anomalies and the anomalies on S^1/Z_2. This involves cancellation
between quantum anomalies and classical inflow from topological terms. To
correctly fix all coefficients and signs, proper attention is paid to issues of
orientation, chirality and the Euclidean continuation. Independent of the
conventions chosen, the Chern-Simons and Green-Schwarz terms must always have
the same sign. The reanalysis of the reduction to the heterotic string on
S^1/Z_2 yields a surprise: a previously neglected factor forces us to slightly
modify the Chern-Simons term, similar to what is needed for cancelling the
normal bundle anomaly of the 5-brane. This modification leads to a local
cancellation of the anomaly, while maintaining the periodicity on S^1.Comment: 35 page
Origin of G Magnetic Fields in the Central Engine of Gamma Ray Bursts
Various authors have suggested that the gamma-ray burst (GRB) central engine
is a rapidly rotating, strongly magnetized, G) compact
object. The strong magnetic field can accelerate and collimate the relativistic
flow and the rotation of the compact object can be the energy source of the
GRB. The major problem in this scenario is the difficulty of finding an
astrophysical mechanism for obtaining such intense fields. Whereas, in
principle, a neutron star could maintain such strong fields, it is difficult to
justify a scenario for their creation. If the compact object is a black hole,
the problem is more difficult since, according to general relativity it has "no
hair" (i.e., no magnetic field). Schuster, Blackett, Pauli, and others have
suggested that a rotating neutral body can create a magnetic field by
non-minimal gravitational-electromagnetic coupling (NMGEC). The
Schuster-Blackett form of NMGEC was obtained from the Mikhail and Wanas's
tetrad theory of gravitation (MW). We call the general theory NMGEC-MW.
We investigate here the possible origin of the intense magnetic fields G in GRBs by NMGEC-MW. Whereas these fields are difficult to
explain astrophysically, we find that they are easily explained by NMGEC-MW. It
not only explains the origin of the G fields when the
compact object is a neutron star, but also when it is a black hole.Comment: 9 pages, accepted for publication in JCA
Climate change and sugarcane expansion increase Hantavirus infection risk
Hantavirus Cardiopulmonary Syndrome (HCPS) is a disease caused by Hantavirus, which is highly virulent for humans. High temperatures and conversion of native vegetation to agriculture, particularly sugarcane cultivation can alter abundance of rodent generalist species that serve as the principal reservoir host for HCPS, but our understanding of the compound effects of land use and climate on HCPS incidence remains limited, particularly in tropical regions. Here we rely on a Bayesian model to fill this research gap and to predict the effects of sugarcane expansion and expected changes in temperature on Hantavirus infection risk in the state of São Paulo, Brazil. The sugarcane expansion scenario was based on historical data between 2000 and 2010 combined with an agro-environment zoning guideline for the sugar and ethanol industry. Future evolution of temperature anomalies was derived using 32 general circulation models from scenarios RCP4.5 and RCP8.5 (Representative greenhouse gases Concentration Pathways adopted by IPCC). Currently, the state of São Paulo has an average Hantavirus risk of 1.3%, with 6% of the 645 municipalities of the state being classified as high risk (HCPS risk ≥ 5%). Our results indicate that sugarcane expansion alone will increase average HCPS risk to 1.5%, placing 20% more people at HCPS risk. Temperature anomalies alone increase HCPS risk even more (1.6% for RCP4.5 and 1.7%, for RCP8.5), and place 31% and 34% more people at risk. Combined sugarcane and temperature increases led to the same predictions as scenarios that only included temperature. Our results demonstrate that climate change effects are likely to be more severe than those from sugarcane expansion. Forecasting disease is critical for the timely and efficient planning of operational control programs that can address the expected effects of sugarcane expansion and climate change on HCPS infection risk. The predicted spatial location of HCPS infection risks obtained here can be used to prioritize management actions and develop educational campaigns
Adsorption of Multi-block and Random Copolymer on a Solid Surface: Critical Behavior and Phase Diagram
The adsorption of a single multi-block -copolymer on a solid planar
substrate is investigated by means of computer simulations and scaling
analysis. It is shown that the problem can be mapped onto an effective
homopolymer adsorption problem. In particular we discuss how the critical
adsorption energy and the fraction of adsorbed monomers depend on the block
length of sticking monomers , and on the total length of the polymer
chains. Also the adsorption of the random copolymers is considered and found to
be well described within the framework of the annealed approximation. For a
better test of our theoretical prediction, two different Monte Carlo (MC)
simulation methods were employed: a) off-lattice dynamic bead-spring model,
based on the standard Metropolis algorithm (MA), and b) coarse-grained lattice
model using the Pruned-enriched Rosenbluth method (PERM) which enables tests
for very long chains. The findings of both methods are fully consistent and in
good agreement with theoretical predictions.Comment: 27 pages, 12 figure
Navigating pluralism: understanding perceptions of the ecosystem services concept
Being open to multiple interpretations allows the ecosystem services concept to operate as a boundary object, facilitating communication and cooperation between different user groups. Yet there is a risk the resultant pluralism limits the capacity of ecosystem services assessments to directly inform decision and policy making, and that the concept could be used to support environmentally or socially harmful activities. Here, we report results from a large mixed methods survey conducted among academics, policymakers and practitioners working in the field of ecosystem services across Europe. We use these results to explore the trade-off that exists between the role of ecosystem services as a boundary object and the needs of policy and decision makers of more standardisation. We conclude this can be done by working towards the standardisation of ecosystem service assessments within specific jurisdictions, whilst maintaining forums for debate, collaboration, and critical reflection within the broader ecosystem services community. We also aim to deduce guiding principles to ensure the ecosystem services concept is not used to support detrimental activities. The consideration of shared and cultural values, the expansion of inter- and transdisciplinary work and the integration of the concept of sustainability are identified as valuable guiding principles to this end.</p
Lattice-gas model for alkali-metal fullerides: face-centered-cubic structure
A lattice-gas model is suggested for describing the ordering phenomena in
alkali-metal fullerides of face-centered-cubic structure assuming the electric
charge of alkali ions residing in either octahedral or tetrahedral interstitial
sites is completely screened by the first-neighbor C_60 molecules. This
approximation allows us to derive an effective ion-ion interaction. The van der
Waals interaction between the ion and C_60 molecule is characterized by
introducing an additional energy at the tetrahedral sites. This model is
investigated by using a three-sublattice mean-field approximation and a simple
cluster-variation method. The analysis shows a large variety of phase diagrams
when changing the site energy parameter.Comment: 10 twocolumn pages (REVTEX) including 12 PS figure
Extending WS-Agreement to Support Automated Conformity Check on Transport and Logistics Service Agreements
Checking whether the agreed service quality attributes are fulfilled or maintained during the service life-cycle is a very important task for SLA (Service Level Agreement) enforcement. in this paper, we leverage conformance checking techniques developed for computational services to automate the conformity checking of transport & logistics services. Our solution extends the WS-Agreement metamodel to support the definition of frame and specific SLAs. With this extension, we define a new validation operation for the conformity check of transport & logistics SLAs based on CSPs solvers. The key contribution of our work is that, as far as we know, it is the first definition of an automated conformity check solution for long term agreements in the transport & logistics domain. Nonetheless, other domains in which similar SLAs are defined can also benefit from our solution
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