Inclusion of non-spherical components of the Pauli blocking operator in (p,p') reactions

We present the first calculations of proton elastic and inelastic scattering in which the Pauli blocking operator contains the leading non-spherical components as well as the usual spherical (angle-averaged) part. We develop a formalism for including the contributions to the effective nucleon-nucleon interaction from the resulting new G-matrix elements that extend the usual two-nucleon spin structure and may not conserve angular momentum. We explore the consequences of parity conservation, time reversal invariance, and nucleon-nucleon antisymmetrization for the new effective interaction. Changes to the calculated cross section and spin observables are small in the energy range from 100 to 200 MeV.Comment: 24 pages, 4 figures, to be published in Physical Review

Gas of self-avoiding loops on the brickwork lattice

An exact calculation of the phase diagram for a loop gas model on the brickwork lattice is presented. The model includes a bending energy. In the dense limit, where all the lattice sites are occupied, a phase transition occuring at an asymmetric Lifshitz tricritical point is observed as the temperature associated with the bending energy is varied. Various critical exponents are calculated. At lower densities, two lines of transitions (in the Ising universality class) are observed, terminated by a tricritical point, where there is a change in the modulation of the correlation function. To each tricritical point an associated disorder line is found.Comment: 19 pages, 6 figures. to appear in J. Phys. A : Math. & Ge

C-Cl Bond Fission, Hcl Elimination, And Secondary Radical Decomposition In The 193 Nm Photodissociation Of Allyl Chloride

The primary photodissociation dynamics of allyl chloride upon excitation at 193 nm is investigated in a crossed laser-molecular beam scattering apparatus. Tunable vacuum ultraviolet (VUV) photoionization of the products provides a unique ability to learn about the secondary reaction products of the nascent photoproducts formed. The data show evidence for four significant primary reaction channels: a previously unidentified low kinetic energy C-Cl bond fission channel producing unstable allyl radicals, an excited state C-Cl bond fission channel producing Cl atoms with high translational energy, an HCl elimination pathway releasing significant energy to product translation to HCl and its momentum-matched mass 40 partner, and an HCl elimination channel producing low kinetic energy HCl products and predominantly unstable mass 40 products. The measured branching of these primary reaction channels of [all C-Cl] : [fast C-Cl] : [slow C-Cl] : [fast HCl] : [slow HCl] : [all HCl] is 1.00: 0.971: 0.029: 0.291: 0.167: 0.458 (where fast refers to the high recoil kinetic energy channels). The high internal energy allyl radicals formed in the slow C-Cl fission pathway of allyl chloride further dissociate/isomerize, as do the unstable mass 40 products formed in the HCl elimination pathways, and these products are investigated. Photoionization efficiency (PIE) curves of the HCl product suggest that a three-centered elimination mechanism contributes significantly to an observed HCl elimination reaction. (C) 2002 American Institute of Physics

Holocene-Neogene volcanism in northeastern Australia: chronology and eruption history

Quaternary and late Neogene volcanism is widespread in northeastern Australia, producing at least 397 eruptions covering more than 20,000 km2, including at least 20 flows over 50 km long. Despite this abundance of young volcanism, before this study numerous eruptions had tentative ages or were undated, and the area requires a comprehensive evaluation of eruption patterns through time. To help address these issues we applied multi-collector ARGUS-V 40Ar/39Ar geochronology to determine the age of four of the younger extensive flows: Undara (160 km long, 189 ± 4/4 ka; 2σ, with full analytical/external uncertainties), Murronga (40 km long, 153 ± 5/5 ka), Toomba (120 km long, 21 ± 3/3 ka), and Kinrara (55 km long, 7 ± 2/2 ka). Verbal traditions of the Gugu Badhun Aboriginal people contain features that may potentially describe the eruption of Kinrara. If the traditions do record this eruption, they would have been passed down for 230 ± 70 generations – a period of time exceeding the earliest written historical records. To further examine north Queensland volcanism through time we compiled a database of 337 ages, including 179 previously unpublished K-Ar and radiocarbon results. The compiled ages demonstrate that volcanic activity has occurred without major time breaks since at least 9 Ma. The greatest frequency of eruptions occurred in the last 2 Ma, with an average recurrence interval of <10–22 ka between eruptions. Activity was at times likely more frequent than these calculations indicate, as the geochronologic dataset is incomplete, with undated eruptions, and intraplate volcanism is often episodic. The duration, frequency, and youthfulness of activity indicate that north Queensland volcanism should be considered as potentially still active, and there are now two confirmed areas of Holocene volcanism in eastern Australia – one at each end of the continent. More broadly, our data provides another example of 40Ar/39Ar geochronology applied to Holocene and latest Pleistocene mafic eruptions, further demonstrating that this method has the ability to examine eruptions and hazards at the youngest volcanoes on Earth

A Shell of Thermal X-ray Emission Associated with the Young Crab-like Remnant 3C58

Deep X-ray imaging spectroscopy of the bright pulsar wind nebula 3C58 confirms the existence of an embedded thermal X-ray shell surrounding the pulsar PSR J0205+6449. Radially resolved spectra obtained with the XMM-Newton telescope are well-characterized by a power-law model with the addition of a soft thermal emission component in varying proportions. These fits reproduce the well-studied increase in the spectral index with radius attributed to synchrotron burn-off of high energy electrons. Most interestingly, a radially resolved thermal component is shown to map out a shell-like structure ~6' in diameter. The presence of a strong emission line corresponding to the Ne IX He-like transition requires an overabundance of ~3 x [Ne/Ne(sun)] in the Raymond-Smith plasma model. The best-fit temperature kT ~ 0.23 keV is essentially independent of radius for the derived column density of N_H = (4.2 +/- 0.1)E21 per cm squared. Our result suggests that thermal shells can be obscured in the early evolution of a supernova remnant by non-thermal pulsar wind nebulae emission; the luminosity of the 3C58 shell is more than an order of magnitude below the upper limit on a similar shell in the Crab Nebula. We find the shell centroid to be offset from the pulsar location. If this neutron star has a velocity similar to that of the Crab pulsar, we derive an age of 3700 yr and a velocity vector aligned with the long axis of the PWN. The shell parameters and pulsar offset add to the accumulating evidence that 3C58 is not the remnant of the supernova of CE 1181.Comment: 7 pages, 8 figures, 2 tables, Latex emulateapj style. To appear in the Astrophysical Journa

A short response-time atomic source for trapped ion experiments

Ion traps are often loaded from atomic beams produced by resistively heated ovens. We demonstrate an atomic oven which has been designed for fast control of the atomic flux density and reproducible construction. We study the limiting time constants of the system and, in tests with $^{40}\textrm{Ca}$, show we can reach the desired level of flux in 12s, with no overshoot. Our results indicate that it may be possible to achieve an even faster response by applying an appropriate one-off heat treatment to the oven before it is used.Comment: 5 pages, 7 figure

Pace of life, predators and parasites: predator-induced life-history evolution in Trinidadian guppies predicts decrease in parasite tolerance

A common evolutionary response to predation pressure is increased investment in reproduction, ultimately resulting in a fast life history. Theory and comparative studies suggest that short-lived organisms invest less in defence against parasites than those that are longer lived (the pace of life hypothesis). Combining these tenets of evolutionary theory leads to the specific, untested prediction that within species, populations experiencing higher predation pressure invest less in defence against parasites. The Trinidadian guppy, Poecilia reticulata, presents an excellent opportunity to test this prediction: guppy populations in lower courses of rivers experience higher predation pressure, and as a consequence have evolved faster life histories, than those in upper courses. Data from a large-scale field survey showed that fish infected with Gyrodactylus parasites were of a lower body condition (quantified using the scaled mass index) than uninfected fish, but only in lower course populations. Although the evidence we present is correlational, it suggests that upper course guppies sustain lower fitness costs of infection, i.e. are more tolerant, than lower course guppies. The data are therefore consistent with the pace of life hypothesis of parasite defence allocation, and suggest that life-history traits mediate the indirect effect of predators on the parasites of their prey

Ludii -- The Ludemic General Game System

While current General Game Playing (GGP) systems facilitate useful research in Artificial Intelligence (AI) for game-playing, they are often somewhat specialised and computationally inefficient. In this paper, we describe the "ludemic" general game system Ludii, which has the potential to provide an efficient tool for AI researchers as well as game designers, historians, educators and practitioners in related fields. Ludii defines games as structures of ludemes -- high-level, easily understandable game concepts -- which allows for concise and human-understandable game descriptions. We formally describe Ludii and outline its main benefits: generality, extensibility, understandability and efficiency. Experimentally, Ludii outperforms one of the most efficient Game Description Language (GDL) reasoners, based on a propositional network, in all games available in the Tiltyard GGP repository. Moreover, Ludii is also competitive in terms of performance with the more recently proposed Regular Boardgames (RBG) system, and has various advantages in qualitative aspects such as generality.Comment: Accepted at ECAI 202

Architectural/Environmental Handbook for Extraterrestrial Design

Handbook on environmental and space utilization criteria for design of extraterrestrial manned spacecraft and shelter