Who Has the Responsibility for the Decision

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Extinction and Distance to Anomalous X-ray Pulsars from X-ray Scattering Halos

We analyze the X-ray scattering halos around three Galactic Anomalous X-ray Pulsars (AXPs) in order to constrain the distance and the optical extinction of each source. We obtain surface brightness distributions from EPIC-pn data obtained with XMM-Newton, compare the profiles of different sources, and fit them with a model based on the standard theory of X-ray scattering by dust grains, both for a uniform distribution of dust along the line of sight, and for dust distributions constrained by previous measurements. Somewhat surprisingly, we find that for all three sources, the uniform distribution reproduces the observed surface brightness as well as or better than the distributions that are informed by previous constraints. Nevertheless, the inferred total dust columns are robust, and serve to confirm that previous measurements based on interstellar edges in high-resolution X-ray spectra and on modelling of broad-band X-ray spectra were reliable. Specifically, we find Av ~= 4, 6, and 8 mag for 4U 0142+61, 1E 1048.1-5937, and 1RXS J170849.0-400910, respectively. For 1E 1048.1-5937, this is well in excess of the extinction expected towards a HI bubble along the line of sight, thus casting further doubt on the suggested association with the source.Comment: 8 pages, 6 figure

An affective disorder in zebrafish with mutation of the glucocorticoid receptor

Upon binding of cortisol, the glucocorticoid receptor (GR) regulates the transcription of specific target genes, including those that encode the stress hormones corticotropin-releasing hormone (CRH) and adrenocorticotropic hormone. Dysregulation of the stress axis is a hallmark of major depression in human patients. However, it is still unclear how glucocorticoid signaling is linked to affective disorders. We identified an adult-viable zebrafish mutant in which the negative feedback on the stress response is disrupted, due to abolition of all transcriptional activity of GR. As a consequence, cortisol is elevated, but unable to signal through GR. When placed into an unfamiliar aquarium ('novel tank'), mutant fish become immobile ('freeze'), show reduced exploratory behavior and do not habituate to this stressor upon repeated exposure. Addition of the antidepressant fluoxetine to the holding water and social interactions restore normal behavior, followed by a delayed correction of cortisol levels. Fluoxetine does not affect the overall transcription of CRH, the mineralocorticoid receptor (MR), the serotonin transporter (Serta) or GR itself. Fluoxetine, however, suppresses the stress-induced upregulation of MR and Serta in both wild-type fish and mutants. Our studies show a conserved, protective function of glucocorticoid signaling in the regulation of emotional behavior and reveal novel molecular aspects of how chronic stress impacts vertebrate brain physiology and behavior. Importantly, the zebrafish model opens up the possibility of high-throughput drug screens in search of new classes of antidepressants

Social Science Considerations for Integrating Aviation Technology, Emergency Services, and Human Resilience

Unmanned aerial systems (UAS) have a range of innovative applications within the field of disaster management, underscoring the potential to enhance human security by integrating UAS across phases of disasters. This paper highlights important social science challenges that must be addressed to ensure the effective integration of UAS, the complex team of teams that respond to disasters, and the populations affected by disasters. Expanding upon points of intersection between UAS capabilities and disaster management identified in recent research, UAS uses in disaster management and corresponding psychosocial considerations are discussed. Broadly, these considerations focus on the training and development of the disaster management multiteam system (MTS) as well as the well-being of disaster responders and the populations they serve. Considerations for mitigation (resilient team infrastructure), preparation (education and training), response (an integrated MTS; responder health), and recovery (population resilience) phases of disaster management are discussed to pave the way for future research and application in this area

The proton and electron radiation belts at geosynchronous orbit: Statistics and behavior during high‐speed stream‐driven storms

The outer proton radiation belt (OPRB) and outer electron radiation belt (OERB) at geosynchronous orbit are investigated using a reanalysis of the LANL CPA (Charged Particle Analyzer) 8‐satellite 2‐solar cycle energetic particle data set from 1976 to 1995. Statistics of the OPRB and the OERB are calculated, including local time and solar cycle trends. The number density of the OPRB is about 10 times higher than the OERB, but the 1 MeV proton flux is about 1000 times less than the 1 MeV electron flux because the proton energy spectrum is softer than the electron spectrum. Using a collection of 94 high‐speed stream‐driven storms in 1976–1995, the storm time evolutions of the OPRB and OERB are studied via superposed epoch analysis. The evolution of the OERB shows the familiar sequence (1) prestorm decay of density and flux, (2) early‐storm dropout of density and flux, (3) sudden recovery of density, and (4) steady storm time heating to high fluxes. The evolution of the OPRB shows a sudden enhancement of density and flux early in the storm. The absence of a proton dropout when there is an electron dropout is noted. The sudden recovery of the density of the OERB and the sudden density enhancement of the OPRB are both associated with the occurrence of a substorm during the early stage of the storm when the superdense plasma sheet produces a “strong stretching phase” of the storm. These storm time substorms are seen to inject electrons to 1 MeV and protons to beyond 1 MeV into geosynchronous orbit, directly producing a suddenly enhanced radiation belt population.Key PointsDuring high‐speed stream‐driven storms, the electron and proton radiation belts are directly enhanced by a single substormThe enhancing substorm occurs during the “strong stretching” phase of the storm caused by the superdense plasma sheetProton and electron injection to 1 MeV is seen for these strong stretching phase substormsPeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/133567/1/jgra52702.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/133567/2/jgra52702_am.pd

Remarks on Shannon's Statistical Inference and the Second Law in Quantum Statistical Mechanics

We comment on a formulation of quantum statistical mechanics, which incorporates the statistical inference of Shannon. Our basic idea is to distinguish the dynamical entropy of von Neumann, $H = -k Tr \hat{\rho}\ln\hat{\rho}$, in terms of the density matrix $\hat{\rho}(t)$, and the statistical amount of uncertainty of Shannon, $S= -k \sum_{n}p_{n}\ln p_{n}$, with $p_{n}=$ in the representation where the total energy and particle numbers are diagonal. These quantities satisfy the inequality $S\geq H$. We propose to interprete Shannon's statistical inference as specifying the {\em initial conditions} of the system in terms of $p_{n}$. A definition of macroscopic observables which are characterized by intrinsic time scales is given, and a quantum mechanical condition on the system, which ensures equilibrium, is discussed on the basis of time averaging. An interesting analogy of the change of entroy with the running coupling in renormalization group is noted. A salient feature of our approach is that the distinction between statistical aspects and dynamical aspects of quantum statistical mechanics is very transparent.Comment: 16 pages. Minor refinement in the statements in the previous version. This version has been published in Journal of Phys. Soc. Jpn. 71 (2002) 6

Active particles in periodic lattices

Both natural and artificial small-scale swimmers may often self-propel in environments subject to complex geometrical constraints. While most past theoretical work on low-Reynolds number locomotion addressed idealised geometrical situations, not much is known on the motion of swimmers in heterogeneous environments. As a first theoretical model, we investigate numerically the behaviour of a single spherical micro-swimmer located in an infinite, periodic body-centred cubic lattice consisting of rigid inert spheres of the same size as the swimmer. Running a large number of simulations we uncover the phase diagram of possible trajectories as a function of the strength of the swimming actuation and the packing density of the lattice. We then use hydrodynamic theory to rationalise our computational results and show in particular how the far-field nature of the swimmer (pusher vs. puller) governs even the behaviour at high volume fractions