255 research outputs found
Theory of agent-based market models with controlled levels of greed and anxiety
We use generating functional analysis to study minority-game type market
models with generalized strategy valuation updates that control the psychology
of agents' actions. The agents' choice between trend following and contrarian
trading, and their vigor in each, depends on the overall state of the market.
Even in `fake history' models, the theory now involves an effective overall bid
process (coupled to the effective agent process) which can exhibit profound
remanence effects and new phase transitions. For some models the bid process
can be solved directly, others require Maxwell-construction type
approximations.Comment: 30 pages, 10 figure
Neutron time-of-flight measurements of charged-particle energy loss in inertial confinement fusion plasmas
Neutron spectra from secondary ^{3}H(d,n)α reactions produced by an implosion of a deuterium-gas capsule at the National Ignition Facility have been measured with order-of-magnitude improvements in statistics and resolution over past experiments. These new data and their sensitivity to the energy loss of fast tritons emitted from thermal ^{2}H(d,p)^{3}H reactions enable the first statistically significant investigation of charged-particle stopping via the emitted neutron spectrum. Radiation-hydrodynamic simulations, constrained to match a number of observables from the implosion, were used to predict the neutron spectra while employing two different energy loss models. This analysis represents the first test of stopping models under inertial confinement fusion conditions, covering plasma temperatures of k_{B}T≈1-4  keV and particle densities of n≈(12-2)×10^{24}  cm^{-3}. Under these conditions, we find significant deviations of our data from a theory employing classical collisions whereas the theory including quantum diffraction agrees with our data
Slowly evolving random graphs II: Adaptive geometry in finite-connectivity Hopfield models
We present an analytically solvable random graph model in which the
connections between the nodes can evolve in time, adiabatically slowly compared
to the dynamics of the nodes. We apply the formalism to finite connectivity
attractor neural network (Hopfield) models and we show that due to the
minimisation of the frustration effects the retrieval region of the phase
diagram can be significantly enlarged. Moreover, the fraction of misaligned
spins is reduced by this effect, and is smaller than in the infinite
connectivity regime. The main cause of this difference is found to be the
non-zero fraction of sites with vanishing local field when the connectivity is
finite.Comment: 17 pages, 8 figure
Toward a Deeper Understanding of the Meaning of Marriage Among Black Men
Black men benefit from healthy, satisfying marriages in domains of physical, psychological, and financial well-being. Yet marriage among Black men has declined and remains elusive for many. One gap in the research concerns the positive meaning that Black men find in their marriages. Prior research has failed to collect in-depth accounts of Black men’s experiences of marriage. The purpose of this qualitative study is to explore the meaning of marriage among 52 Black men, using interview data. Findings highlight four themes in the meaning of marriage—secure emotional support, lifelong commitment, enhanced life success, and secure attachment. Two themes emerged from the data related to important influences on the construction of meaning relative to marriage—faith, and the dynamics of give and take. Responses among the men concerning the change in marriage over time related to transitions in American marriages and a deepened respect for marriage. Implications are discussed
Registration of ‘NH03614 CL’ Wheat
‘NH03614 CL’ (Reg. No. CV-1051, PI 653833) hard red winter wheat (Triticum aestivum L.) was developed cooperatively by the Nebraska Agricultural Experiment Station and the USDA-ARS and released in 2008 by the developing institutions and the South Dakota Agricultural Experiment Station and the Wyoming Agricultural Experiment Station. In addition to researchers at the releasing institutions, USDA-ARS researchers at Manhattan, KS and St. Paul, MN participated in the development of NH03614 CL. NH03614 CL was selected from the cross ‘Wesley’ sib//‘Millennium’ sib/‘Above’ sib that was made in the spring of 1997 to develop new herbicide-tolerant cultivars. NH03614 CL was selected using the bulk breeding method as an F3:4 line (F3–derived line in the F4 generation) in 2001, and in 2003 was assigned experimental line number NH03164. NH03614 CL was released primarily for its herbicide tolerance to imadazolinone compounds which control many previously diffi cult-to-control weeds in wheat production systems, and for its superior adaptation to rainfed wheat production systems in Nebraska, Wyoming, South Dakota, and counties in adjacent states
T–T Neutron Spectrum from Inertial Confinement Implosions
A new technique that uses inertial confinement implosions for measuring low-energy nuclear reactions important to nuclear astrophysics is described. Simultaneous measurements of n–D and n–T elastic scattering at 14.1 MeV using deuterium–tritium gas-filled capsules provide a proof of principle for this technique. Measurements have been made of D(d,p)T (dd) and T(t,2n)[superscript 4]He (tt) reaction yields relative to the D(t,n)[superscript]He (dt) reaction yield for deuterium–tritium mixtures with fT/fD between 0.62 and 0.75 and for a wide range of ion temperatures to test our understanding of the implosion processes. Measurements of the shape of the neutron spectrum from the T(t,2n)[superscript 4]He reaction have been made for each of these target configurations.National Laser User’s Facility (Grant NA0000877)United States. Dept. of Energy (Grant DE-FG52-09NA29553)University of Rochester. Fusion Science Center (Rochester Subaward 415023-G, UR Account 5-24431)University of Rochester. Laboratory for Laser Energetics (Grant 412160-001G)Lawrence Livermore National Laboratory (Grants B580243 and DE-AC52-07NA27344
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Ignition Failure Mode Radiochemical Diagnostics Initial Assessment
Radiochemical diagnostic signatures are well known to be effective indicators of nuclear ignition and burn reaction conditions. Nuclear activation is already a reliable technique to measure yield. More comprehensively, though, important quantities such as fuel areal density and ion temperature might be separately and more precisely monitored by a judicious choice of select nuclear reactions. This report details an initial assessment of this approach to diagnosing ignition failures on point-design cryogenic National Ignition Campaign targets. Using newly generated nuclear reaction cross section data for Scandium and Iridium, modest uniform doping of the innermost ablator region provides clearly observable reaction product differences between robust burn and failure for either element. Both equatorial and polar tracer loading yield observable, but indistinguishable, signatures for either choice of element for the preliminary cases studied
Towards a characterization of behavior-disease models
The last decade saw the advent of increasingly realistic epidemic models that
leverage on the availability of highly detailed census and human mobility data.
Data-driven models aim at a granularity down to the level of households or
single individuals. However, relatively little systematic work has been done to
provide coupled behavior-disease models able to close the feedback loop between
behavioral changes triggered in the population by an individual's perception of
the disease spread and the actual disease spread itself. While models lacking
this coupling can be extremely successful in mild epidemics, they obviously
will be of limited use in situations where social disruption or behavioral
alterations are induced in the population by knowledge of the disease. Here we
propose a characterization of a set of prototypical mechanisms for
self-initiated social distancing induced by local and non-local
prevalence-based information available to individuals in the population. We
characterize the effects of these mechanisms in the framework of a
compartmental scheme that enlarges the basic SIR model by considering separate
behavioral classes within the population. The transition of individuals in/out
of behavioral classes is coupled with the spreading of the disease and provides
a rich phase space with multiple epidemic peaks and tipping points. The class
of models presented here can be used in the case of data-driven computational
approaches to analyze scenarios of social adaptation and behavioral change.Comment: 24 pages, 15 figure
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Development of backlighting sources for a Compton radiography diagnostic of Inertial Confinement Fusion targets
We present scaled demonstrations of backlighter sources, emitting Bremsstrahlung x-rays with photon energies above 75 keV, that we will use to record x-ray Compton radiographic snapshots of cold dense DT fuel in inertial confinement fusion implosions at the National Ignition Facility (NIF). In experiments performed at the Titan laser facility at Lawrence Livermore National Laboratory, we measured the source size and the Bremsstrahlung spectrum as a function of laser intensity and pulse length, from solid targets irradiated at 2e17-5e18 W/cm{sup 2} using 2-40 ps pulses. Using Au planar foils we achieved source sizes down to 5.5 {micro}m, and conversion efficiencies of about 1e-3 J/J into x-ray photons with energies in the 75-100 keV spectral range. We can now use these results to design NIF backlighter targets and shielding, and to predict Compton radiography performance as a function of the NIF implosion yield and associated background
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