Universal aging properties at a disordered critical point

We investigate, analytically near the dimension $d_{uc}=4$ and numerically in $d=3$, the non equilibrium relaxational dynamics of the randomly diluted Ising model at criticality. Using the Exact Renormalization Group Method to one loop, we compute the two times $t,t_w$ correlation function and Fluctuation Dissipation Ratio (FDR) for any Fourier mode of the order parameter, of finite wave vector $q$. In the large time separation limit, the FDR is found to reach a non trivial value $X^{\infty}$ independently of (small) $q$ and coincide with the FDR associated to the the {\it total} magnetization obtained previously. Explicit calculations in real space show that the FDR associated to the {\it local} magnetization converges, in the asymptotic limit, to this same value $X^{\infty}$. Through a Monte Carlo simulation, we compute the autocorrelation function in three dimensions, for different values of the dilution fraction $p$ at $T_c(p)$. Taking properly into account the corrections to scaling, we find, according to the Renormalization Group predictions, that the autocorrelation exponent $\lambda_c$ is independent on $p$. The analysis is complemented by a study of the non equilibrium critical dynamics following a quench from a completely ordered state.Comment: 8 pages, 5 figure

The beginnings of geography teaching and research in the University of Glasgow: the impact of J.W. Gregory

J.W. Gregory arrived in Glasgow from Melbourne in 1904 to take up the post of foundation Professor of Geology in the University of Glasgow. Soon after his arrival in Glasgow he began to push for the setting up of teaching in Geography in Glasgow, which came to pass in 1909 with the appointment of a Lecturer in Geography. This lecturer was based in the Department of Geology in the University's East Quad. Gregory's active promotion of Geography in the University was matched by his extensive writing in the area, in textbooks, journal articles and popular books. His prodigious output across a wide range of subject areas is variably accepted today, with much of his geomorphological work being judged as misguided to varying degrees. His 'social science' publications - in the areas of race, migration, colonisation and economic development of Africa and Australia - espouse a viewpoint that is unacceptable in the twenty-first century. Nonetheless, that viewpoint sits squarely within the social and economic traditions of Gregory's era, and he was clearly a key 'Establishment' figure in natural and social sciences research in the first half of the twentieth century. The establishment of Geography in the University of Glasgow remains enduring testimony of J.W. Gregory's energy, dedication and foresight

Survey of hydrogen production and utilization methods. Volume 1: Executive summary

The use of hydrogen as a synthetic fuel is considered. Processes for the production of hydrogen are described along with the present and future industrial uses of hydrogen as a fuel and as a chemical feedstock. Novel and unconventional hydrogen-production techniques are evaluated, with emphasis placed on thermochemical and electrolytic processes. Potential uses for hydrogen as a fuel in industrial and residential applications are identified and reviewed in the context of anticipated U.S. energy supplies and demands. A detailed plan for the period from 1975 to 1980 prepared for research on and development of hydrogen as an energy carrier is included

MARKETING CHARACTERISTICS ASSOCIATED WITH SEAFOOD COUNTERS IN GROCERY STORES

This study provides a benchmark analysis of seafood counter characteristics corresponding to the peaking of per capita seafood demand in the U.S. Logistic regression results show separate seafood counters are less likely in small stores, in rural stores, and in stores in low or medium income areas. Chain stores and stores with a significant number of non-white customers were more likely to have a seafood counter. Stores in the East South Central region were less likely, and stores in New England more likely, to have a seafood counter. The likelihood that stores will develop seafood counters was related to differences in sales volume, floor space, urban/rural location, income level of clients and regional location. Continuing innovations in marketing technology of seafood counters are likely to provide expanded marketing opportunities in the future.Marketing,

Finite automata for caching in matrix product algorithms

A diagram is introduced for visualizing matrix product states which makes transparent a connection between matrix product factorizations of states and operators, and complex weighted finite state automata. It is then shown how one can proceed in the opposite direction: writing an automaton that ``generates'' an operator gives one an immediate matrix product factorization of it. Matrix product factorizations have the advantage of reducing the cost of computing expectation values by facilitating caching of intermediate calculations. Thus our connection to complex weighted finite state automata yields insight into what allows for efficient caching in matrix product algorithms. Finally, these techniques are generalized to the case of multiple dimensions.Comment: 18 pages, 19 figures, LaTeX; numerous improvements have been made to the manuscript in response to referee feedbac

Predicting the ecological consequences of river management for a riverine cyprinid fish.

Current river management seeks to resolve a compromise between stakeholder interests, ecosystem services provision and conservation aims, especially in relation to assessment of ecosystem health. While management decisions should be evidenced-based, current population and habitat models fail to incorporate fish behaviour and the interactions between fish and their environment, thus limiting their ability to predict management-relevant, population responses to environmental change. In order to address these weaknesses, an individual-based model is developed and parameterised to predict the distribution and growth of roach (Rutilus rutilus), a common, generalist, freshwater fish; known to be typically dominant in heavily modified rivers. Such a model seeks to build on current management models and practices, with emphasis on improving recruitment of juvenile roach. Virtual forager parameters are derived from foraging experiments, published investigations, models of roach behaviour and bioenergetics. Data collected from field studies in a typical, highly modified, lowland river are used to describe the environment and initial fish population with subsequent data on fish population trends used to validate the IBM, under a pattern-oriented modelling approach; specifically growth rate and habitat distribution patterns. River management practices including the removal of in-stream aquatic macrophytes and regulation of flow regime for flood risk management are predicted as potentially damaging to roach recruitment, subsequent year-class strength and therefore, populations in subsequent years. Recommendations for more sympathetic management schemes are provided. The modelling framework described here can be used to produce robust predictions of roach population patterns in riverine habitats and allows the user to test the impact of environmental change on cyprinid fish, enabling the modelling system to be used to develop proactive, evidence-based management in light of current rates of environmental change

Structural Reorganization of Parallel Actin Bundles by Crosslinking Proteins: Incommensurate States of Twist

We construct a coarse-grained model of parallel actin bundles crosslinked by compact, globular bundling proteins, such as fascin and espin, necessary components of filapodial and mechanosensory bundles. Consistent with structural observations of bundles, we find that the optimal geometry for crosslinking is overtwisted, requiring a coherent structural change of the helical geometry of the filaments. We study the linker-dependent thermodynamic transition of bundled actin filaments from their native state to the overtwisted state and map out the "twist-state'' phase diagram in terms of the availability as well as the flexibility of crosslinker proteins. We predict that the transition from the uncrosslinked to fully-crosslinked state is highly sensitive to linker flexibility: flexible crosslinking smoothly distorts the twist-state of bundled filaments, while rigidly crosslinked bundles undergo a phase transition, rapidly overtwisting filaments over a narrow range of free crosslinker concentrations. Additionally, we predict a rich spectrum of intermediate structures, composed of alternating domains of sparsely-bound (untwisted) and strongly-bound (overtwisted) filaments. This model reveals that subtle differences in crosslinking agents themselves modify not only the detailed structure of parallel actin bundles, but also the thermodynamic pathway by which they form.Comment: Main Text (25 pages, 7 figures) with supporting material (12 pages, 9 figures, 2 tables

Cold, tenuous solar flare: acceleration without heating

We report the observation of an unusual cold, tenuous solar flare, which reveals itself via numerous and prominent non-thermal manifestations, while lacking any noticeable thermal emission signature. RHESSI hard X-rays and 0.1-18 GHz radio data from OVSA and Phoenix-2 show copious electron acceleration (10^35 electrons per second above 10 keV) typical for GOES M-class flares with electrons energies up to 100 keV, but GOES temperatures not exceeding 6.1 MK. The imaging, temporal, and spectral characteristics of the flare have led us to a firm conclusion that the bulk of the microwave continuum emission from this flare was produced directly in the acceleration region. The implications of this finding for the flaring energy release and particle acceleration are discussed.Comment: ApJ Letters accepted; 5 figure