The Potts Fully Frustrated model: Thermodynamics, percolation and dynamics in 2 dimensions

We consider a Potts model diluted by fully frustrated Ising spins. The model corresponds to a fully frustrated Potts model with variables having an integer absolute value and a sign. This model presents precursor phenomena of a glass transition in the high-temperature region. We show that the onset of these phenomena can be related to a thermodynamic transition. Furthermore this transition can be mapped onto a percolation transition. We numerically study the phase diagram in 2 dimensions (2D) for this model with frustration and {\em without} disorder and we compare it to the phase diagram of $i)$ the model with frustration {\em and} disorder and of $ii)$ the ferromagnetic model. Introducing a parameter that connects the three models, we generalize the exact expression of the ferromagnetic Potts transition temperature in 2D to the other cases. Finally, we estimate the dynamic critical exponents related to the Potts order parameter and to the energy.Comment: 10 pages, 10 figures, new result

The PHENIX Experiment at RHIC

The physics emphases of the PHENIX collaboration and the design and current status of the PHENIX detector are discussed. The plan of the collaboration for making the most effective use of the available luminosity in the first years of RHIC operation is also presented.Comment: 5 pages, 1 figure. Further details of the PHENIX physics program available at http://www.rhic.bnl.gov/phenix

Sloan digital sky survey multicolor observations of GRB 010222

The discovery of an optical counterpart to GRB 010222 (detected by BeppoSAX) was announced 4.4 hr after the burst by Henden. The Sloan Digital Sky Survey's 0.5 m photometric telescope (PT) and 2.5 m survey telescope were used to observe the afterglow of GRB 010222 starting 4.8 hr after the gamma-ray burst. The 0.5 m PT observed the afterglow in five 300 s g*-band exposures over the course of half an hour, measuring a temporal decay rate in this short period of Fv ∝ t-1±0.5. The 2.5 m camera imaged the counterpart nearly simultaneously in five filters (u*, g*, r*, i*, z*), with r* = 18.74 ± 0.02 at 12:10 UT. These multicolor observations, corrected for reddening and the afterglow's temporal decay, are well-fitted by the power law Fv ∝ v-0.90±0.03 with the exception of the u*-band UV flux which is 20% below this slope. We examine possible interpretations of this spectral shape, including source extinction in a star-forming region

University-industry relationships and open innovation: Towards a research agenda

Accepted versio

Relaxed Stratification: A New Approach to Practical Complete Predicate Refinement

Abstract. In counterexample-guided abstraction refinement, a predi-cate refinement scheme is said to be complete for a given theory if it is guaranteed to eventually find predicates sufficient to prove the given property, when such exist. However, existing complete methods require deciding if a proof of the counterexample’s spuriousness exists in some fi-nite language of predicates. Such an exact finite-language-restricted pred-icate search is quite hard for many theories used in practice and incurs a heavy overhead. In this paper, we address the issue by showing that the language restriction can be relaxed so that the refinement process is restricted to infer proofs from some finite language Lbase ∪ Lext but is only required to return a proof when the counterexample’s spurious-ness can be proved in Lbase. Then, we show how a proof-based refine-ment algorithm can be made to satisfy the relaxed requirement and be complete by restricting only the theory-level reasoning in SMT to emit Lbase-restricted partial interpolants (while such an approach has been proposed previously, we show for the first time that it can be done for languages that are not closed under conjunctions and disjunctions). We also present a technique that uses a property of counterexample patterns to further improve the efficiency of the refinement algorithm while still satisfying the requirement. We have experimented with a prototype im-plementation of the new refinement algorithm, and show that it is able to achieve complete refinement with only a small overhead.

Mineral investigations in the Northumberland trough : part 5, The Kirkbean area, south-west Scotland

Exploration for carbonate-hosted base-metal mineralisation on the North Solway coastal belt was undertaken in 1992-93 as part of a broader scale MRP investigation of a 70 km strike length of Lower Carboniferous rocks at the northern margin of the Solway-Northumberland Basin. The project area was selected partly on the basis of its similarities with the tectonosedimentary environment of the Lower Dinantian central Irish basin which hosts several major stratabound lead-zinc deposits, and the presence of geochemical base-metal anomalies coincident with basin margin structures. Two of the most important criteria for the formation of major SEDEX Irish-style deposits, the presence of major syn-depositional basin margin faults and_ a geothermal system over a zone of high heat flow in the crust (Andrew, 1993), are recognised in the north Solway area. The presence of mafic lavas and possible associated mineralising hydrothermal activity are considered to further increase the economic potential of the area

Estimating dinosaur maximum running speeds using evolutionary robotics

Maximum running speed is an important locomotor parameter for many animals—predators as well as prey—and is thus of interest to palaeobiologists wishing to reconstruct the behavioural ecology of extinct species. A variety of approaches have been tried in the past including anatomical comparisons, bone scaling and strength, safety factors and ground reaction force analyses. However, these approaches are all indirect and an alternative approach is to create a musculoskeletal model of the animal and see how fast it can run. The major advantage of this approach is that all assumptions about the animal's morphology and physiology are directly addressed, whereas the exact same assumptions are hidden in the indirect approaches. In this paper, we present simple musculoskeletal models of three extant and five extinct bipedal species. The models predict top speed in the extant species with reasonably good agreement with accepted values, so we conclude that the values presented for the five extinct species are reasonable predictions given the modelling assumptions made. Improved musculoskeletal models and better estimates of soft tissue parameters will produce more accurate values. Limited sensitivity analysis is performed on key muscle parameters but there is considerable scope for extending this in the future