981 research outputs found
Optimal Life-Cycle Strategies in the Presence of Interest Rate and Inflation Risk
Defined Contribution Plan
Memetic Multilevel Hypergraph Partitioning
Hypergraph partitioning has a wide range of important applications such as
VLSI design or scientific computing. With focus on solution quality, we develop
the first multilevel memetic algorithm to tackle the problem. Key components of
our contribution are new effective multilevel recombination and mutation
operations that provide a large amount of diversity. We perform a wide range of
experiments on a benchmark set containing instances from application areas such
VLSI, SAT solving, social networks, and scientific computing. Compared to the
state-of-the-art hypergraph partitioning tools hMetis, PaToH, and KaHyPar, our
new algorithm computes the best result on almost all instances
Optimal interdependence between networks for the evolution of cooperation
Recent research has identified interactions between networks as crucial for the outcome of evolutionary
games taking place on them. While the consensus is that interdependence does promote cooperation by
means of organizational complexity and enhanced reciprocity that is out of reach on isolated networks, we
here address the question just how much interdependence there should be. Intuitively, one might assume
the more the better. However, we show that in fact only an intermediate density of sufficiently strong
interactions between networks warrants an optimal resolution of social dilemmas. This is due to an intricate
interplay between the heterogeneity that causes an asymmetric strategy flow because of the additional links
between the networks, and the independent formation of cooperative patterns on each individual network.
Presented results are robust to variations of the strategy updating rule, the topology of interdependent
networks, and the governing social dilemma, thus suggesting a high degree of universality
On the Dynamics of solitons in the nonlinear Schroedinger equation
We study the behavior of the soliton solutions of the equation
i((\partial{\psi})/(\partialt))=-(1/(2m)){\Delta}{\psi}+(1/2)W_{{\epsilon}}'({\psi})+V(x){\psi}
where W_{{\epsilon}}' is a suitable nonlinear term which is singular for
{\epsilon}=0. We use the "strong" nonlinearity to obtain results on existence,
shape, stability and dynamics of the soliton. The main result of this paper
(Theorem 1) shows that for {\epsilon}\to0 the orbit of our soliton approaches
the orbit of a classical particle in a potential V(x).Comment: 29 page
H\"older Continuity of the Integrated Density of States for the Fibonacci Hamiltonian
We prove H\"older continuity of the integrated density of states for the
Fibonacci Hamiltonian for any positive coupling, and obtain the asymptotics of
the H\"older exponents for large and small couplings.Comment: 18 page
Gas-to-particle partitioning of major biogenic oxidation products: a study on freshly formed and aged biogenic SOA
Secondary organic aerosols (SOAs) play a key role in climate change and air
quality. Determining the fundamental parameters that distribute organic
compounds between the phases is essential, as atmospheric lifetime and
impacts change drastically between the gas and particle phase. In this work,
gas-to-particle partitioning of major biogenic oxidation products was
investigated using three different aerosol chemical characterization
techniques. The aerosol collection module, the collection thermal desorption unit, and the
chemical analysis of aerosols online are different aerosol sampling inlets connected to a proton-transfer reaction time-of-flight
mass spectrometer (ACM-PTR-ToF-MS, TD-PTR-ToF-MS, and CHARON-PTR-ToF-MS, respectively, referred to hereafter as
ACM, TD, and CHARON). These techniques
were deployed at the atmosphere simulation chamber SAPHIR to perform
experiments on the SOA formation and aging from different monoterpenes
(β-pinene, limonene) and real plant emissions (Pinus sylvestris L.). The saturation mass
concentration C* and thus the volatility of the individual ions was
determined based on the simultaneous measurement of their signal in the gas and particle phase.A method to identify and exclude ions affected by thermal dissociation
during desorption and ionic dissociation in the ionization chamber of the
proton-transfer reaction mass spectrometer (PTR-MS) was developed and tested for each technique. Narrow volatility
distributions with organic compounds in the semi-volatile (SVOCs – semi-volatile
organic compounds) to
intermediate-volatility (IVOCs – intermediate-volatility organic compounds) regime were found for all systems studied.
Despite significant differences in the aerosol collection and desorption
methods of the proton-transfer-reaction (PTR)-based techniques, a comparison of the C* values obtained
with different techniques was found to be in good agreement (within 1 order
of magnitude) with deviations explained by the different operating
conditions of the PTR-MS.The C* of the identified organic compounds were mapped onto the
two-dimensional volatility basis set (2D-VBS), and results showed a decrease in C* with increasing oxidation state. For all experiments conducted in
this study, identified partitioning organic compounds accounted for
20–30 % of the total organic mass measured from an aerosol mass spectrometer (AMS). Further
comparison between observations and theoretical calculations was performed
for species found in our experiments that were also identified in previous
publications. Theoretical calculations based on the molecular structure of
the compounds showed, within the uncertainties ranges, good agreement with
the experimental C* for most SVOCs, while IVOCs deviated by up to a factor of
300. These latter differences are discussed in relation to two main
processes affecting these systems: (i) possible interferences by thermal and
ionic fragmentation of higher molecular-weight compounds, produced by
accretion and oligomerization reactions, that fragment in the m∕z range
detected by the PTR-MS and (ii) kinetic influences in the distribution
between the gas and particle phase with gas-phase condensation, diffusion in
the particle phase, and irreversible uptake.</p
Linking larval transport and fisheries demographic models to study the influence of environmental variability and larval behavior on juvenile recruitment to oyster populations
Abstract Annual variations in freshwater flow and wind may influence the dispersal of oyster larvae (by affecting circulation patterns) and the survival of adults (by influencing salinity-dependent disease mortality) in Chesapeake Bay, a region whose oyster fishery has greatly declined. These observations suggest that environmental variability has important implications for rehabilitation efforts that involve enhancing native oyster broodstock. We tested this hypothesis for the eastern oyster Crassostrea virginica by linking larval transport and fisheries demographic models. Physical conditions in both models were based on five years with differing wind and freshwater flow patterns (1995)(1996)(1997)(1998)(1999). The larval transport model predicted spatial settlement patterns by using a particle tracking model parameterized with larval behaviors discerned in preliminary analysis of ongoing laboratory studies. The demographic model incorporated estimates of stockrecruitment relationships, growth, natural mortality, disease mortality, fishing mortality, and the effect of extreme events such as freshets. A validation analysis of the linked models compared predictions of juvenile oyster settlement success with field observations from 1995 to1999. Larval transport model results indicated that settlement success of C. virginica larvae was influenced by freshwater flow conditions, with larval settlement higher in low freshwater flow years. The validation analysis indicated that including spawning stock abundance and mortality estimates in the linked larvaltransport-demographic model may have improved predictions of juvenile recruitment. Our linked model could be used to assess risks associated with introducing a new species and guide oyster management activities such as locating brood stock sanctuaries and managing harvest in response to climate variability
Connectivity of the Primate Superior Colliculus Mapped by Concurrent Microstimulation and Event-Related fMRI
Background: Neuroanatomical studies investigating the connectivity of brain areas have heretofore employed procedures in which chemical or viral tracers are injected into an area of interest, and connected areas are subsequently identified using histological techniques. Such experiments require the sacrifice of the animals and do not allow for subsequent electrophysiological studies in the same subjects, rendering a direct investigation of the functional properties of anatomically identified areas impossible. Methodology/Principal Findings: Here, we used a combination of microstimulation and fMRI in an anesthetized monkey preparation to study the connectivity of the superior colliculus (SC). Microstimulation of the SC resulted in changes in the blood oxygenation level-dependent (BOLD) signals in the SC and in several cortical and subcortical areas consistent with the known connectivity of the SC in primates. Conclusions/Significance: These findings demonstrates that the concurrent use of microstimulation and fMRI can be used to identify brain networks for further electrophysiological or fMRI investigation
Overconfidence in Labor Markets
This chapter reviews how worker overconfidence affects labor markets. Evidence from psychology and economics shows that in many situations, most people tend to overestimate their absolute skills, overplace themselves relative to others, and overestimate the precision of their knowledge. The chapter starts by reviewing evidence for overconfidence and for how
overconfidence affects economic choices. Next, it reviews economic explanations for overconfidence. After that, it discusses research on the impact of worker overconfidence on labor markets where wages are determined by bargaining between workers and firms. Here, three key questions are addressed. First, how does worker overconfidence affect effort provision
for a fixed compensation scheme? Second, how should firms design compensation schemes when workers are overconfident? In particular, will a compensation scheme offered to an overconfident worker have higher-or lower-powered incentives than that offered to a worker with accurate self-perception? Third, can worker overconfidence lead to a Pareto improvement? The chapter continues by reviewing research on the impact of worker overconfidence on labor markets where workers can move between firms and where neither firms nor workers have discretion over wage setting. The chapter concludes with a summary of its main findings and a discussion of avenues for future research
Maintenance of cooperation in a public goods game: A new decision-making criterion with incomplete information
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