The Hazard from Plutonium Dispersal by Nuclear-warhead Accidents

Nuclear weapons are carefully designed to have an extremely low probability of exploding accidentally with an appreciable yield—even if they are involved in a high-speed crash, struck by a bullet or consumed in a fire. The principal concern when nuclear warheads are involved in such accidents is the possible dispersal of plutonium into the environment. In particular, an explosion could disperse a significant fraction of the plutonium in a warhead as particles of respirable size

DU Not a High Priority for Antinuclear Movement

Two years ago, members of anti-nuclear weapons groups began to ask our views about the alarm raised by the International Action Center in its book, Metal of Dishonor, about the use of depleted uranium (DU) penetrators in anti-armor munitions. We were asked whether the hazard was so great that activists should give priority to banning DU. We read Metal of Dishonor and found that, despite the contributions of physicists and radiation-effects analysts, it contained no quantitative risk estimate. We therefore decided to provide the best one we could, using information available in the literature about the health effects of uranium and ionizing radiation. We concluded that, except for soldiers in vehicles when they are struck, or individuals who crawl around inside such vehicles without adequate respiratory protection for extended periods of time later on, the health effects of DU are likely to be very small. The radiation effects would be well below those of natural background radiation and the chemical effects would be well below the thresholds for known toxic effects. Contaminated armored vehicles and pieces of depleted uranium, however, are potential hazards and should be cleaned up or buried—something which was not done in most cases after Desert Storm and is only being done now in Kosovo

D6.1 Market analysis and technology database report

Within the EDEN-ISS project, a lot of technologies were implemented into the Future Expoloration Greenhouse (FEG) for the analogue mission on Antarctica. Most were existing technologies that had been developed within previous “space related” projects and some were derived from existing hightech greenhouse production technology. This document analyses the potential for spin-offs to other applications, particularly of the technologies that were either new or modifications of existing technologies, that is: the E-nose for the microbial detection; the water-cooled LED luminaries for plant lighting; the online, continuous control of the spectrum of the luminaries and the plant health monitoring system. Whereas the potential for application of the modified E-nose is particularly in hospitals and related places, the potential for the other three systems is particularly in high-tech, fresh vegetable production, such as high-tech greenhouses or Vertical Farms. Indeed, given the size of such markets, the potential for each system is certainly high. This document also gives a preview of the improvements/adaptations of each system, which would improve the penetration in the potential market

Microscopic model of critical current noise in Josephson-junction qubits: Subgap resonances and Andreev bound states

We propose a microscopic model of critical current noise in Josephson-junctions based on individual trapping-centers in the tunnel barrier hybridized with electrons in the superconducting leads. We calculate the noise exactly in the limit of no on-site Coulomb repulsion. Our result reveals a noise spectrum that is dramatically different from the usual Lorentzian assumed in simple models. We show that the noise is dominated by sharp subgap resonances associated to the formation of pairs of Andreev bound states, thus providing a possible explanation for the spurious two-level systems (microresonators) observed in Josephson junction qubits [R.W. Simmonds et al., Phys. Rev. Lett. 93, 077003 (2004)]. Another implication of our model is that each trapping-center will contribute a sharp dielectric resonance only in the superconducting phase, providing an effective way to validate our results experimentally. We derive an effective Hamiltonian for a qubit interacting with Andreev bound states, establishing a direct connection between phenomenological models and the microscopic parameters of a Fermionic bath.Comment: 11 pages, 8 figure

The BCS Functional for General Pair Interactions

The Bardeen-Cooper-Schrieffer (BCS) functional has recently received renewed attention as a description of fermionic gases interacting with local pairwise interactions. We present here a rigorous analysis of the BCS functional for general pair interaction potentials. For both zero and positive temperature, we show that the existence of a non-trivial solution of the nonlinear BCS gap equation is equivalent to the existence of a negative eigenvalue of a certain linear operator. From this we conclude the existence of a critical temperature below which the BCS pairing wave function does not vanish identically. For attractive potentials, we prove that the critical temperature is non-zero and exponentially small in the strength of the potential.Comment: Revised Version. To appear in Commun. Math. Phys

Quantitative neuroanatomy for connectomics in Drosophila

Neuronal circuit mapping using electron microscopy demands laborious proofreading or reconciliation of multiple independent reconstructions. Here, we describe new methods to apply quantitative arbor and network context to iteratively proofread and reconstruct circuits and create anatomically enriched wiring diagrams. We measured the morphological underpinnings of connectivity in new and existing reconstructions of Drosophila sensorimotor (larva) and visual (adult) systems. Synaptic inputs were preferentially located on numerous small, microtubule-free 'twigs' which branch off a single microtubule-containing 'backbone'. Omission of individual twigs accounted for 96% of errors. However, the synapses of highly connected neurons were distributed across multiple twigs. Thus, the robustness of a strong connection to detailed twig anatomy was associated with robustness to reconstruction error. By comparing iterative reconstruction to the consensus of multiple reconstructions, we show that our method overcomes the need for redundant effort through the discovery and application of relationships between cellular neuroanatomy and synaptic connectivity.Publisher PDFPeer reviewe

Renormalization Group Approach to Low Temperature Properties of a Non-Fermi Liquid Metal

We expand upon on an earlier renormalization group analysis of a non-Fermi liquid fixed point that plausibly govers the two dimensional electron liquid in a magnetic field near filling fraction $\nu=1/2$. We give a more complete description of our somewhat unorthodox renormalization group transformation by relating both our field-theoretic approach to a direct mode elimination and our anisotropic scaling to the general problem of incorporating curvature of the Fermi surface. We derive physical consequences of the fixed point by showing how they follow from renormalization group equations for finite-size scaling, where the size may be set by the temperature or by the frequency of interest. In order fully to exploit this approach, it is necessary to take into account composite operators, including in some cases dangerous ``irrelevant'' operators. We devote special attention to gauge invariance, both as a formal requirement and in its positive role providing Ward identities constraining the renormalization of composite operators. We emphasize that new considerations arise in describing properties of the physical electrons (as opposed to the quasiparticles.) We propose an experiment which, if feasible, will allow the most characteristic feature of our results, that isComment: 42 pages, 5 figures upon request, uses Phyzzx, IASSNS-HEP 94/6

Retrograde semaphorin-plexin signalling drives homeostatic synaptic plasticity.

Homeostatic signalling systems ensure stable but flexible neural activity and animal behaviour. Presynaptic homeostatic plasticity is a conserved form of neuronal homeostatic signalling that is observed in organisms ranging from Drosophila to human. Defining the underlying molecular mechanisms of neuronal homeostatic signalling will be essential in order to establish clear connections to the causes and progression of neurological disease. During neural development, semaphorin-plexin signalling instructs axon guidance and neuronal morphogenesis. However, semaphorins and plexins are also expressed in the adult brain. Here we show that semaphorin 2b (Sema2b) is a target-derived signal that acts upon presynaptic plexin B (PlexB) receptors to mediate the retrograde, homeostatic control of presynaptic neurotransmitter release at the neuromuscular junction in Drosophila. Further, we show that Sema2b-PlexB signalling regulates presynaptic homeostatic plasticity through the cytoplasmic protein Mical and the oxoreductase-dependent control of presynaptic actin. We propose that semaphorin-plexin signalling is an essential platform for the stabilization of synaptic transmission throughout the developing and mature nervous system. These findings may be relevant to the aetiology and treatment of diverse neurological and psychiatric diseases that are characterized by altered or inappropriate neural function and behaviour

Incommensurate ground state of double-layer quantum Hall systems

Double-layer quantum Hall systems possess interlayer phase coherence at sufficiently small layer separations, even without interlayer tunneling. When interlayer tunneling is present, application of a sufficiently strong in-plane magnetic field $B_\parallel > B_c$ drives a commensurate-incommensurate (CI) transition to an incommensurate soliton-lattice (SL) state. We calculate the Hartree-Fock ground-state energy of the SL state for all values of $B_\parallel$ within a gradient approximation, and use it to obtain the anisotropic SL stiffness, the Kosterlitz-Thouless melting temperature for the SL, and the SL magnetization. The in-plane differential magnetic susceptibility diverges as $(B_\parallel - B_c)^{-1}$ when the CI transition is approached from the SL state.Comment: 12 pages, 7 figures, to be published in Physical Review