2,460 research outputs found
Monte Carlo simulation of the classical two-dimensional one component plasma
Monte Carlo simulation, lattice dynamics in the harmonic approximation, and solution of the hypernetted chain equation were used to study the classical two-dimensional one component plasma. The system consists of a single species of charged particles immersed in a uniform neutralizing background. The particles interact via a l/r potential, where r is the two dimensional separation. Equations of state were calculated for both the liquid and solid phases. Results of calculation of the thermodynamic functions and one and two particle correlation functions are presented
Analysis of Barkhausen effect signals in surface-modified magnetic materials using a hysteretic-stochastic model
The effects of microstructural variations with depth on Barkhausen effect (BE) signals in surface-modified ferrous materials have been studied through measurements and simulations based on a hysteretic-stochastic model. The BE signals measured from an unhardened sample show a peak near zero field. In contrast, the BE signals in surface-hardened samples with different case depths exhibit low-amplitude pulses near zero field and a peak at a high reverse field, which are attributed to irreversible magnetization processes in the soft core and the hardened surface layer, respectively. Theoretical analysis showed that the model parameters k and Ο, which describe the domain-wall pinning strength and the range of interaction of a domain wall with pinning sites, respectively, are related to each other as Ο=a Ïâ1/2=b/k via the pinning site density Ï, where a and b are constants. The relationship was used to simulate BE signals of the surface-hardened samples as a sum of signals generated at different depths by taking into account signal attenuation due to eddy current shielding. The simulated results were found to exhibit the general features observed in the experimental results
Chapter 16 Volcanic hazard vulnerability on SĂŁo Miguel Island, Azores
AbstractIn recent years much progress has been made in researching a wide variety of extreme events on SĂŁo Miguel. In addition there are a number of volcano-related risks that impact upon the people of SĂŁo Miguel. Some of these may occur both before and during volcanic emergencies (e.g. earthquakes), whilst others render SĂŁo Miguel dangerous even when its volcanoes are not erupting (e.g. flooding, landslides, tsunamis and health impacts, especially the effects of CO2seepage into dwellings). In this chapter we first define what vulnerability means to the people of SĂŁo Miguel, and relate this to the cultural and economic characteristics of the island. The following aspects of vulnerability are discussed: (a) physical (i.e. housing, settlement and the characteristics of evacuation routes and plans); (b) demographic and economic; and (c) social and cultural and perceptual (i.e. whether people have an accurate cognition of risk). Particular areas of concern relate to housing: the identification of isolated dwellings that would be difficult to evacuate; the vulnerability/resilience of evacuation routes following recent infrastructure improvements; characteristics of the island's transient population; management of livestock under emergency conditions; local leadership roles; and educational outreach.</jats:p
Quantum Dynamics of Solitons in Strongly Interacting Systems on Optical Lattices
Mean-field dynamics of strongly interacting bosons described by hard core
bosons with nearest-neighbor attraction has been shown to support two species
of solitons: one of Gross-Pitaevskii (GP-type) where the condensate fraction
remains dark and a novel non-Gross-Pitaevskii-type (non-GP-type) characterized
by brightening of the condensate fraction. Here we study the effects of quantum
fluctuations on these solitons using the adaptive time-dependent density matrix
renormalization group method, which takes into account the effect of strong
correlations. We use local observables as the density, condensate density and
correlation functions as well as the entanglement entropy to characterize the
stability of the initial states. We find both species of solitons to be stable
under quantum evolution for a finite duration, their tolerance to quantum
fluctuations being enhanced as the width of the soliton increases. We describe
possible experimental realizations in atomic Bose Einstein Condensates,
polarized degenerate Fermi gases, and in systems of polar molecules on optical
lattices
Physical Aggressiveness and Gray Matter Deficits in Ventromedial Prefrontal Cortex
What causes individuals to hurt others? Since the famous case of Phineas Gage, lesions of the ventromedial prefrontal cortex (VMPFC) have been reliably linked to physically aggressive behavior. However, it is unclear whether naturally-occurring deficits in VMPFC, among normal individuals, might have widespread consequences for aggression. Using voxel based morphometry, we regressed gray matter density from the brains of 138 normal female and male adults onto their dispositional levels of physical aggression, verbal aggression, and sex, simultaneously. Physical, but not verbal, aggression was associated with reduced gray matter volume in the VMPFC and to a lesser extent, frontopolar cortex. Participants with less gray matter density in this VMPFC cluster were much more likely to engage in real-world violence. These findings suggest that even granular deficits in normal individualsâ VMPFC gray matter can promote physical aggression
Neural Mechanisms of the Rejection-Aggression Link
Social rejection is a painful event that often increases aggression. However, the neural mechanisms of this rejectionâaggression link remain unclear. A potential clue may be that rejected people often recruit the ventrolateral prefrontal cortexâs (VLPFC) self-regulatory processes to manage the pain of rejection. Using functional MRI, we replicated previous links between rejection and activity in the brainâs mentalizing network, social pain network and VLPFC. VLPFC recruitment during rejection was associated with greater activity in the brainâs reward network (i.e. the ventral striatum) when individuals were given an opportunity to retaliate. This retaliation-related striatal response was associated with greater levels of retaliatory aggression. Dispositionally aggressive individuals exhibited less functional connectivity between the ventral striatum and the right VLPFC during aggression. This connectivity exerted a suppressing effect on dispositionally aggressive individualsâ greater aggressive responses to rejection. These results help explain how the pain of rejection and reward of revenge motivate rejected people to behave aggressively
The Superconducting Condensation Energy and an Antiferromagnetic Exchange Based Pairing Mechanism
For the traditional low T_c superconductors, the superconducting condensation
energy is proportional to the change in energy of the ionic lattice between the
normal and superconducting state, providing a clear link between pairing and
the electron-ion interaction. Here, for the t-J model, we discuss an analogous
relationship between the superconducting condensation energy and the change in
the exchange energy between the normal and superconducting states. We point out
the possibility of measuring this using neutron scattering and note that such a
measurement, while certainly difficult, could provide important evidence for an
exchange interaction-based pairing mechanism.Comment: Replaced with revised versio
Social Rejection Magnifies Impulsive Behavior Among Individuals with Greater Negative Urgency: An Experimental Test of Urgency Theory
Impulsivity is a multifaceted trait with substantial implications for human well-being. One facet of impulsivity is negative urgency, the tendency to act impulsively in response to negative affect. Correlational evidence suggests that negative affect magnifies impulsive behavior among individuals with greater negative urgency, yet causal evidence for this core pillar of urgency theory is lacking. To fill this gap in the literature, participants (N = 363) were randomly assigned to experience social rejection (a situation shown to induce negative affect) or acceptance. Participants then reported their subjective negative affect, completed a behavioral measure of impulsivity, and reported their negative urgency. Among individuals with relatively high and average negative urgency, social rejection increased their impulsive behavior through greater experiences of negative affect. These indirect effects were not observed among individuals relatively low in negative urgency. These findings suggest that negative urgency exists at the nexus of urgent dispositions and situations that elicit negative affect, which offers novel support for urgency theory
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