We extend the continuum theory of random intermittent search processes to the case of N independent searchers looking to deliver cargo to a single hidden target located somewhere on a semi-infinite track. Each searcher randomly switches between a stationary state and either a leftward or rightward constant velocity state. We assume that all of the particles start at one end of the track and realize sample trajectories independently generated from the same underlying stochastic process. The hidden target is treated as a partially absorbing trap in which a particle can only detect the target and deliver its cargo if it is stationary and within range of the target; the particle is removed from the system after delivering its cargo. As a further generalization of previous models, we assume that up to n successive particles can find the target and deliver its cargo. Assuming that the rate of target detection scales as 1/N, we show that there exists a well-defined mean-field limit N→∞, in which the stochastic model reduces to a deterministic system of linear reaction-hyperbolic equations for the concentrations of particles in each of the internal states. These equations decouple from the stochastic process associated with filling the target with cargo. The latter can be modeled as a Poisson process in which the time-dependent rate of filling λ(t) depends on the concentration of stationary particles within the target domain. Hence, we refer to the target as a Poisson trap. We analyze the efficiency of filling the Poisson trap with n particles in terms of the waiting time density f_{n}(t). The latter is determined by the integrated Poisson rate μ(t)=∫_{0}^{t}λ(s)ds, which in turn depends on the solution to the reaction-hyperbolic equations. We obtain an approximate solution for the particle concentrations by reducing the system of reaction-hyperbolic equations to a scalar advection-diffusion equation using a quasisteady-state analysis. We compare our analytical results for the mean-field model with Monte Carlo simulations for finite N. We thus determine how the mean first passage time (MFPT) for filling the target depends on N and n.

Objectives. We compared the content/themes and features of intrusive memories versus rumination about such intrusions in a depressed sample. Method. Participants with major depressive disorder (MDD)(N= 38) completed self-report measures about a negative intrusive memory, and rumination in response to their memory. Results. Both rumination and intrusive memories were highly sensory, and associated with similar negative emotions (commonly helplessness and sadness). Preliminary findings suggested that intrusive memories were experienced more frequently during the day, and rumination lasted longer. Participants ruminated about a wide range of themes including the causes of the event in the memory, and the negative impact of the memory (and the recalled event) on their relationships, identity, and the future. Conclusions. The shared features and bidirectional relationship between rumination and intrusive memories suggest that both potentially contribute to prolonged repetitive thinking in depression, and need to be addressed in treatment.

BACKGROUND: Health anxiety is associated with high distress, disability and increased health service utilisation. However, there are relatively few epidemiological studies examining the extent of health anxiety or the associated sociodemographic and health risk factors in the general population. AIMS: To provide epidemiological data on health anxiety in the Australian population. METHOD: Lifetime and current prevalence estimates, associations between comorbid disorders, psychological distress, impairment, disability and mental health service utilisation were generated using the Australian 2007 National Survey of Mental Health and Wellbeing. RESULTS: Health anxiety affects approximately 5.7% of the Australian population across the lifespan and 3.4% met criteria for health anxiety at the time of the interview. Age, employment status, smoking status and comorbid physical conditions were significantly related to health anxiety symptoms. Health anxiety was associated with significantly more distress, impairment, disability and health service utilisation than that found in respondents without health anxiety. CONCLUSIONS: Health anxiety is non-trivial; it affects a significant proportion of the population and further research and clinical investigation of health anxiety is required.

The stochastic mutual repressor model is analysed using perturbation methods. This simple model of a gene circuit consists of two genes and three promotor states. Either of the two protein products can dimerize, forming a repressor molecule that binds to the promotor of the other gene. When the repressor is bound to a promotor, the corresponding gene is not transcribed and no protein is produced. Either one of the promotors can be repressed at any given time or both can be unrepressed, leaving three possible promotor states. This model is analysed in its bistable regime in which the deterministic limit exhibits two stable fixed points and an unstable saddle, and the case of small noise is considered. On small timescales, the stochastic process fluctuates near one of the stable fixed points, and on large timescales, a metastable transition can occur, where fluctuations drive the system past the unstable saddle to the other stable fixed point. To explore how different intrinsic noise sources affect these transitions, fluctuations in protein production and degradation are eliminated, leaving fluctuations in the promotor state as the only source of noise in the system. The process without protein noise is then compared to the process with weak protein noise using perturbation methods and Monte Carlo simulations. It is found that some significant differences in the random process emerge when the intrinsic noise source is removed.

Flow coefficients v_{n} for n=2, 3, 4, characterizing the anisotropic collective flow in Au+Au collisions at sqrt[s_{NN}]=200  GeV, are measured relative to event planes Ψ_{n}, determined at large rapidity. We report v_{n} as a function of transverse momentum and collision centrality, and study the correlations among the event planes of different order n. The v_{n} are well described by hydrodynamic models which employ a Glauber Monte Carlo initial state geometry with fluctuations, providing additional constraining power on the interplay between initial conditions and the effects of viscosity as the system evolves. This new constraint can serve to improve the precision of the extracted shear viscosity to entropy density ratio η/s.

Back-to-back hadron pair yields in d+Au and p+p collisions at √s(NN)=200 GeV were measured with the PHENIX detector at the Relativistic Heavy Ion Collider. Rapidity separated hadron pairs were detected with the trigger hadron at pseudorapidity |η|<0.35 and the associated hadron at forward rapidity (deuteron direction, 3.0<η<3.8). Pairs were also detected with both hadrons measured at forward rapidity; in this case, the yield of back-to-back hadron pairs in d+Au collisions with small impact parameters is observed to be suppressed by a factor of 10 relative to p+p collisions. The kinematics of these pairs is expected to probe partons in the Au nucleus with a low fraction x of the nucleon momenta, where the gluon densities rise sharply. The observed suppression as a function of nuclear thickness, p(T), and η points to cold nuclear matter effects arising at high parton densities.

We present measurements of J/ψ yields in d+Au collisions at sqrt[s(NN)]=200  GeV recorded by the PHENIX experiment and compare them with yields in p+p collisions at the same energy per nucleon-nucleon collision. The measurements cover a large kinematic range in J/ψ rapidity (-2.2<y<2.4) with high statistical precision and are compared with two theoretical models: one with nuclear shadowing combined with final state breakup and one with coherent gluon saturation effects. In order to remove model dependent systematic uncertainties we also compare the data to a simple geometric model. The forward rapidity data are inconsistent with nuclear modifications that are linear or exponential in the density weighted longitudinal thickness, such as those from the final state breakup of the bound state.

We use the theory of noise-induced phase synchronization to analyze the effects of demographic noise on the synchronization of a metapopulation of predator-prey systems within a fluctuating environment (Moran effect). Treating each local predator-prey population as a stochastic urn model, we derive a Langevin equation for the stochastic dynamics of the metapopulation. Assuming each local population acts as a limit cycle oscillator in the deterministic limit, we use phase reduction and averaging methods to derive the steady-state probability density for pairwise phase differences between oscillators, which is then used to determine the degree of synchronization of the metapopulation.

A stochastic interpretation of spontaneous action potential initiation is developed for the Morris-Lecar equations. Initiation of a spontaneous action potential can be interpreted as the escape from one of the wells of a double well potential, and we develop an asymptotic approximation of the mean exit time using a recently developed quasistationary perturbation method. Using the fact that the activating ionic channel's random openings and closings are fast relative to other processes, we derive an accurate estimate for the mean time to fire an action potential (MFT), which is valid for a below-threshold applied current. Previous studies have found that for above-threshold applied current, where there is only a single stable fixed point, a diffusion approximation can be used. We also explore why different diffusion approximation techniques fail to estimate the MFT.

Two prospective studies have investigated whether the presence, intrusion, and avoidance of negative intrusive memories predict depression, and have reported conflicting findings. We aimed to replicate and extend these investigations by exploring the role of intrusion and avoidance of intrusive memories, as well as memory characteristics, in the prediction of depression prospectively. At Time 1 a mixed sample of community participants (N=85) were interviewed and completed self-report measures of depression, anxiety, and intrusive memory features. At Time 2 (6 months later, N=64) depression and anxiety symptoms were reassessed. Results were partly consistent with hypotheses for the sub-sample of participants who did not receive treatment between the baseline and follow-up assessments. Baseline levels of intrusion and some memory features (uncontrollability, distress, interference, numbness, detachment) predicted follow-up depression, controlling for baseline depression symptoms. Unexpectedly, avoidance of intrusive memories and other features (e.g., here and now quality) did not predict depression. Levels of intrusion and avoidance did not predict anxiety at follow-up. These results provide further evidence that intrusive memories are not simply an epiphenomenon of depression, but predict depression prospectively. Our results suggest that novel, depression-specific theories that emphasise the role of memory disturbances in the maintenance of depression are needed.