Large emergency-response exercises: qualitative characteristics - a survey

Exercises, drills, or simulations are widely used, by governments, agencies and commercial organizations, to simulate serious incidents and train staff how to respond to them. International cooperation has led to increasingly large-scale exercises, often involving hundreds or even thousands of participants in many locations. The difference between ‘large’ and ‘small’ exercises is more than one of size: (a) Large exercises are more ‘experiential’ and more likely to undermine any model of reality that single organizations may create; (b) they create a ‘play space’ in which organizations and individuals act out their own needs and identifications, and a ritual with strong social implications; (c) group-analytic psychotherapy suggests that the emotions aroused in a large group may be stronger and more difficult to control. Feelings are an unacknowledged major factor in the success or failure of exercises; (d) successful large exercises help improve the nature of trust between individuals and the organizations they represent, changing it from a situational trust to a personal trust; (e) it is more difficult to learn from large exercises or to apply the lessons identified; (f) however, large exercises can help develop organizations and individuals. Exercises (and simulation in general) need to be approached from a broader multidisciplinary direction if their full potential is to be realized

On Hoyle-Narlikar-Wheeler mechanism of vibration energy powered magneto-dipole emission of neutron stars

We revisit the well-known Hoyle-Narlikar-Wheeler proposition that neutron star emerging in the magnetic-flux-conserving process of core-collapse supernova can convert the stored energy of Alfven vibrations into power of magneto-dipole radiation. We show that the necessary requirement for the energy conversion is the decay of internal magnetic field. In this case the loss of vibration energy of the star causes its vibration period, equal to period of pulsating emission, to lengthen at a rate proportional to the rate of magnetic field decay. These prediction of the model of vibration powered neutron star are discussed in juxtaposition with data on pulsating emission of magnetars whose radiative activity is generally associated with the decay of ultra strong magnetic field.Comment: Accepted for publication in Astrophysics & Space Scienc

Phase Transitions of Hard Disks in External Periodic Potentials: A Monte Carlo Study

The nature of freezing and melting transitions for a system of hard disks in a spatially periodic external potential is studied using extensive Monte Carlo simulations. Detailed finite size scaling analysis of various thermodynamic quantities like the order parameter, its cumulants etc. are used to map the phase diagram of the system for various values of the density and the amplitude of the external potential. We find clear indication of a re-entrant liquid phase over a significant region of the parameter space. Our simulations therefore show that the system of hard disks behaves in a fashion similar to charge stabilized colloids which are known to undergo an initial freezing, followed by a re-melting transition as the amplitude of the imposed, modulating field produced by crossed laser beams is steadily increased. Detailed analysis of our data shows several features consistent with a recent dislocation unbinding theory of laser induced melting.Comment: 36 pages, 16 figure

Aspect-ratio dependence of the spin stiffness of a two-dimensional XY model

We calculate the superfluid stiffness of 2D lattice hard-core bosons at half-filling (equivalent to the S=1/2 XY-model) using the squared winding number quantum Monte Carlo estimator. For L_x x L_y lattices with aspect ratio L_x/L_y=R, and L_x,L_y -> infinity, we confirm the recent prediction [N. Prokof'ev and B.V. Svistunov, Phys. Rev. B 61, 11282 (1999)] that the finite-temperature stiffness parameters \rho^W_x and \rho^W_y determined from the winding number differ from each other and from the true superfluid density \rho_s. Formally, \rho^W_y -> \rho_s in the limit in which L_x -> infinity first and then L_y -> infinity. In practice we find that \rho^W_y converges exponentially to \rho_s for R>1. We also confirm that for 3D systems, \rho^W_x = \rho^W_y = \rho^W_z = \rho_s for any R. In addition, we determine the Kosterlitz-Thouless transition temperature to be T_KT/J=0.34303(8) for the 2D model.Comment: 7 pages, 8 figures, 1 table. Minor changes to published versio

The quantum J_{1}-J_{1'}-J_{2} spin-1/2 Heisenberg antiferromagnet: A variational method study

The phase transition of the quantum spin-1/2 frustrated Heisenberg antiferroferromagnet on an anisotropic square lattice is studied by using a variational treatment. The model is described by the Heisenberg Hamiltonian with two antiferromagnetic interactions: nearest-neighbor (NN) with different coupling strengths J_{1} and J_{1'} along x and y directions competing with a next-nearest-neighbor coupling J_{2} (NNN). The ground state phase diagram in the ({\lambda},{\alpha}) space, where {\lambda}=J_{1'}/J_{1} and {\alpha}=J_{2}/J_{1}, is obtained. Depending on the values of {\lambda} and {\alpha}, we obtain three different states: antiferromagnetic (AF), collinear antiferromagnetic (CAF) and quantum paramagnetic (QP). For an intermediate region {\lambda}_{1}<{\lambda}<1 we observe a QP state between the ordered AF and CAF phases, which disappears for {\lambda} above some critical value {\lambda}_{1}. The boundaries between these ordered phases merge at the quantum critical endpoint (QCE). Below this QCE there is again a direct first-order transition between the AF and CAF phases, with a behavior approximately described by the classical line {\alpha}_{c}{\simeq}{\lambda}/2

Vortex dynamics for two-dimensional XY models

Two-dimensional XY models with resistively shunted junction (RSJ) dynamics and time dependent Ginzburg-Landau (TDGL) dynamics are simulated and it is verified that the vortex response is well described by the Minnhagen phenomenology for both types of dynamics. Evidence is presented supporting that the dynamical critical exponent $z$ in the low-temperature phase is given by the scaling prediction (expressed in terms of the Coulomb gas temperature $T^{CG}$ and the vortex renormalization given by the dielectric constant $\tilde\epsilon$) $z=1/\tilde{\epsilon}T^{CG}-2\geq 2$ both for RSJ and TDGL and that the nonlinear IV exponent a is given by a=z+1 in the low-temperature phase. The results are discussed and compared with the results of other recent papers and the importance of the boundary conditions is emphasized.Comment: 21 pages including 15 figures, final versio

Scaling determination of the nonlinear I-V characteristics for 2D superconducting networks

It is shown from computer simulations that the current-voltage ($I$-$V$) characteristics for the two-dimensional XY model with resistively-shunted Josephson junction dynamics and Monte Carlo dynamics obeys a finite-size scaling form from which the nonlinear $I$-$V$ exponent $a$ can be determined to good precision. This determination supports the conclusion $a=z+1$, where $z$ is the dynamic critical exponent. The results are discussed in the light of the contrary conclusion reached by Tang and Chen [Phys. Rev. B {\bf 67}, 024508 (2003)] and the possibility of a breakdown of scaling suggested by Bormann [Phys. Rev. Lett. {\bf 78}, 4324 (1997)].Comment: 6 pages, to appear in PR

Langevin Simulations of Two Dimensional Vortex Fluctuations: Anomalous Dynamics and a New IVIV-exponent

The dynamics of two dimensional (2D) vortex fluctuations are investigated through simulations of the 2D Coulomb gas model in which vortices are represented by soft disks with logarithmic interactions. The simulations trongly support a recent suggestion that 2D vortex fluctuations obey an intrinsic anomalous dynamics manifested in a long range 1/t-tail in the vortex correlations. A new non-linear IV-exponent a, which is different from the commonly used AHNS exponent, a_AHNS and is given by a = 2a_AHNS - 3, is confirmed by the simulations. The results are discussed in the context of earlier simulations, experiments and a phenomenological description.Comment: Submitted to PRB, RevTeX format, 28 pages and 13 figures, figures in postscript format are available at http://www.tp.umu.se/~holmlund/papers.htm

Phase III study of pasireotide long-acting release in patients with metastatic neuroendocrine tumors and carcinoid symptoms refractory to available somatostatin analogues

In a randomized, double-blind, Phase III study, we compared pasireotide long-acting release (pasireotide LAR) with octreotide long-acting repeatable (octreotide LAR) in managing carcinoid symptoms refractory to first-generation somatostatin analogues. Adults with carcinoid tumors of the digestive tract were randomly assigned (1:1) to receive pasireotide LAR (60 mg) or octreotide LAR (40 mg) every 28 days. Primary outcome was symptom control based on frequency of bowel movements and flushing episodes. Objective tumor response was a secondary outcome. Progression-free survival (PFS) was calculated in a post hoc analysis. Adverse events were recorded. At the time of a planned interim analysis, the data monitoring committee recommended halting the study because of a low predictive probability of showing superiority of pasireotide over octreotide for symptom control (n=43 pasireotide LAR, 20.9%; n=45 octreotide LAR, 26.7%; odds ratio, 0.73; 95% confidence interval [CI], 0.27–1.97; P=0.53). Tumor control rate at month 6 was 62.7% with pasireotide and 46.2% with octreotide (odds ratio, 1.96; 95% CI, 0.89–4.32; P=0.09). Median (95% CI) PFS was 11.8 months (11.0 – not reached) with pasireotide versus 6.8 months (5.6 – not reached) with octreotide (hazard ratio, 0.46; 95% CI, 0.20–0.98; P=0.045). The most frequent drug-related adverse events (pasireotide vs octreotide) included hyperglycemia (28.3% vs 5.3%), fatigue (11.3% vs 3.5%), and nausea (9.4% vs 0%). We conclude that, among patients with carcinoid symptoms refractory to available somatostatin analogues, similar proportions of patients receiving pasireotide LAR or octreotide LAR achieved symptom control at month 6. Pasireotide LAR showed a trend toward higher tumor control rate at month 6, although it was statistically not significant, and was associated with a longer PFS than octreotide LAR

Enhanced stability of the square lattice of a classical bilayer Wigner crystal

The stability and melting transition of a single layer and a bilayer crystal consisting of charged particles interacting through a Coulomb or a screened Coulomb potential is studied using the Monte-Carlo technique. A new melting criterion is formulated which we show to be universal for bilayer as well as for single layer crystals in the case of (screened) Coulomb, Lennard--Jones and 1/r^{12} repulsive inter-particle interactions. The melting temperature for the five different lattice structures of the bilayer Wigner crystal is obtained, and a phase diagram is constructed as a function of the interlayer distance. We found the surprising result that the square lattice has a substantial larger melting temperature as compared to the other lattice structures. This is a consequence of the specific topology of the defects which are created with increasing temperature and which have a larger energy as compared to the defects in e.g. a hexagonal lattice.Comment: Accepted for publication in Physical Review