Non-vanishing Magnetic Flux through the Slightly-charged Kerr Black Hole

In association with the Blanford-Znajek mechanism for rotational energy extraction from Kerr black holes, it is of some interest to explore how much of magnetic flux can actually penetrate the horizon at least in idealized situations. For completely uncharged Kerr hole case, it has been known for some time that the magnetic flux gets entirely expelled when the hole is maximally-rotating. In the mean time, it is known that when the rotating hole is immersed in an originally uniform magnetic field surrounded by an ionized interstellar medium (plasma), which is a more realistic situation, the hole accretes certain amount of electric charge. In the present work, it is demonstrated that as a result of this accretion charge small enough not to disturb the geometry, the magnetic flux through this slightly charged Kerr hole depends not only on the hole's angular momentum but on the hole's charge as well such that it never vanishes for any value of the hole's angular momentum.Comment: 33pages, 1 figure, Revtex, some comments added, typos correcte

Potato cultivar response to seasonal drought patterns

The ability to minimize potato yield and quality losses due to drought can be greatly improved by understanding the relative responses of different cultivars to seasonal variations in water supply. To address this need, we initiated a two year field experiment to determine the responses of the six potato cultivars to different seasonal drought patterns, including 1) full season irrigation at 100% ET, 2) irrigation at 100% ET terminated during late bulking , 3) full season irrigation at 70% ET , 4) irrigation at 70% ET terminated during late bulking , and 5) a gradual reduction in irrigation from 100% ET during tuber initiation through early bulking, to 70% ET during mid-bulking, and 50% ET through late bulking. GemStar Russet and Ranger Russet, two medium-late maturing cultivars, generally produced the highest yields across the range of drought treatments, but both were fairly sensitive to changes in drought severity. Alturas, a late maturing cultivar, produced relatively high yields with full irrigation, but exhibited the greatest sensitivity to increasing drought severity, particularly when severe late-season water deficits were imposed. Yields for the early maturing cultivar Russet Norkotah were relatively low overall, but it was the least sensitive to changes in drought severity, particularly when late season drought was imposed. Russet Burbank produced comparatively high total yields across the range of drought treatments, but U.S. No. 1 yields were substantially reduced by each seasonal drought pattern. However, it was less sensitive to changes in drought severity than GemStar Russet, Ranger Russet and Alturas. Total and U.S. No. 1 yields for Summit Russet were low for each drought treatment and it exhibited intermediate sensitivity to changes in drought severity. GemStar Russet had the highest water use efficiency based on U.S. No. 1 yield

Scintillation of liquid neon from electronic and nuclear recoils

We have measured the time dependence of scintillation light from electronic and nuclear recoils in liquid neon, finding a slow time constant of 15.4+-0.2 us. Pulse shape discrimination is investigated as a means of identifying event type in liquid neon. Finally, the nuclear recoil scintillation efficiency is measured to be 0.26+-0.03 for 387 keV nuclear recoils

Isotope shift calculations for atoms with one valence electron

This work presents a method for the ab initio calculation of isotope shift in atoms and ions with one valence electron above closed shells. As a zero approximation we use relativistic Hartree-Fock and then calculate correlation corrections. The main motivation for developing the method comes from the need to analyse whether different isotope abundances in early universe can contribute to the observed anomalies in quasar absorption spectra. The current best explanation for these anomalies is the assumption that the fine structure constant, alpha, was smaller at early epoch. We test the isotope shift method by comparing the calculated and experimental isotope shift for the alkali and alkali-like atoms Na, MgII, K, CaII and BaII. The agreement is found to be good. We then calculate the isotope shift for some astronomically relevant transitions in SiII and SiIV, MgII, ZnII and GeII.Comment: 11 page

Ab initio Quantum and ab initio Molecular Dynamics of the Dissociative Adsorption of Hydrogen on Pd(100)

The dissociative adsorption of hydrogen on Pd(100) has been studied by ab initio quantum dynamics and ab initio molecular dynamics calculations. Treating all hydrogen degrees of freedom as dynamical coordinates implies a high dimensionality and requires statistical averages over thousands of trajectories. An efficient and accurate treatment of such extensive statistics is achieved in two steps: In a first step we evaluate the ab initio potential energy surface (PES) and determine an analytical representation. Then, in an independent second step dynamical calculations are performed on the analytical representation of the PES. Thus the dissociation dynamics is investigated without any crucial assumption except for the Born-Oppenheimer approximation which is anyhow employed when density-functional theory calculations are performed. The ab initio molecular dynamics is compared to detailed quantum dynamical calculations on exactly the same ab initio PES. The occurence of quantum oscillations in the sticking probability as a function of kinetic energy is addressed. They turn out to be very sensitive to the symmetry of the initial conditions. At low kinetic energies sticking is dominated by the steering effect which is illustrated using classical trajectories. The steering effects depends on the kinetic energy, but not on the mass of the molecules. Zero-point effects lead to strong differences between quantum and classical calculations of the sticking probability. The dependence of the sticking probability on the angle of incidence is analysed; it is found to be in good agreement with experimental data. The results show that the determination of the potential energy surface combined with high-dimensional dynamical calculations, in which all relevant degrees of freedon are taken into account, leads to a detailed understanding of the dissociation dynamics of hydrogen at a transition metal surface.Comment: 15 pages, 9 figures, subm. to Phys. Rev.

The critical earthquake concept applied to mine rockbursts with time-to-failure analysis

We report new tests of the critical earthquake concepts performed on rockbursts in deep South African mines. We extend the concept of an optimal time and space correlation region and test it on the eight main shocks of our catalog provided by ISSI. In a first test, we use the simplest signature of criticality in terms of a power law time-to-failure formula. Notwithstanding the fact that the search for the optimal correlation size is performed with this simple power law, we find evidence both for accelerated seismicity and for the presence of logperiodic behavior with a prefered scaling factor close to 2. We then propose a new algorithm based on a space and time smoothing procedure, which is also intended to account for the finite range and time mechanical interactions between events. This new algorithm provides a much more robust and efficient construction of the optimal correlation region, which allows us the use of the logperiodic formula directly in the search process. In this preliminary work, we have only tested the new algorithm on the largest event on the catalog. The result is of remarkable good quality with a dramatic improvement in accuracy and robustness. This confirms the potential importance of logperiodic signals. Our study opens the road for an efficient implemention of a systematic testing procedure of real-time predictions.Comment: 22 pages, 32 figure

Particle physics models of inflation

Inflation models are compared with observation on the assumption that the curvature perturbation is generated from the vacuum fluctuation of the inflaton field. The focus is on single-field models with canonical kinetic terms, classified as small- medium- and large-field according to the variation of the inflaton field while cosmological scales leave the horizon. Small-field models are constructed according to the usual paradigm for beyond Standard Model physicsComment: Based on a talk given at the 22nd IAP Colloquium, ``Inflation +25'', Paris, June 2006 Curve omitted from final Figur

Red Queen Coevolution on Fitness Landscapes

Species do not merely evolve, they also coevolve with other organisms. Coevolution is a major force driving interacting species to continuously evolve ex- ploring their fitness landscapes. Coevolution involves the coupling of species fit- ness landscapes, linking species genetic changes with their inter-specific ecological interactions. Here we first introduce the Red Queen hypothesis of evolution com- menting on some theoretical aspects and empirical evidences. As an introduction to the fitness landscape concept, we review key issues on evolution on simple and rugged fitness landscapes. Then we present key modeling examples of coevolution on different fitness landscapes at different scales, from RNA viruses to complex ecosystems and macroevolution.Comment: 40 pages, 12 figures. To appear in "Recent Advances in the Theory and Application of Fitness Landscapes" (H. Richter and A. Engelbrecht, eds.). Springer Series in Emergence, Complexity, and Computation, 201

Professional closure by proxy: the impact of changing educational requirements on class mobility for a cohort of Big 8 partners

Closure events impacting on class mobility may include mechanisms initiated by bodies other than the professional body. The research examines if the introduction of full-time study requirements at universities for aspiring accountants effectively introduced a closure mechanism in the accounting profession. Data was derived from an Oral History study of partners in large firms. The younger partners (born after the Second World War) completed full-time degree study at university, but did not provide evidence of class mobility into the profession. The older cohort, born between 1928 and 1946, completed part-time studies only, few completed a degree, and, in contrast to the younger cohort, shows a perceptible upward movement from lower socio-economic classes into the professional class. This suggests that changing the preferred educational routes for new accountants entering the large chartered accounting (CA) firms compromised the "stepping stone" function of accounting as a portal into the professional class

Origins of the Ambient Solar Wind: Implications for Space Weather

The Sun's outer atmosphere is heated to temperatures of millions of degrees, and solar plasma flows out into interplanetary space at supersonic speeds. This paper reviews our current understanding of these interrelated problems: coronal heating and the acceleration of the ambient solar wind. We also discuss where the community stands in its ability to forecast how variations in the solar wind (i.e., fast and slow wind streams) impact the Earth. Although the last few decades have seen significant progress in observations and modeling, we still do not have a complete understanding of the relevant physical processes, nor do we have a quantitatively precise census of which coronal structures contribute to specific types of solar wind. Fast streams are known to be connected to the central regions of large coronal holes. Slow streams, however, appear to come from a wide range of sources, including streamers, pseudostreamers, coronal loops, active regions, and coronal hole boundaries. Complicating our understanding even more is the fact that processes such as turbulence, stream-stream interactions, and Coulomb collisions can make it difficult to unambiguously map a parcel measured at 1 AU back down to its coronal source. We also review recent progress -- in theoretical modeling, observational data analysis, and forecasting techniques that sit at the interface between data and theory -- that gives us hope that the above problems are indeed solvable.Comment: Accepted for publication in Space Science Reviews. Special issue connected with a 2016 ISSI workshop on "The Scientific Foundations of Space Weather." 44 pages, 9 figure