Distribution of periodic points of polynomial diffeomorphisms of C^2

This paper deals with the dynamics of a simple family of holomorphic diffeomorphisms of \C^2: the polynomial automorphisms. This family of maps has been studied by a number of authors. We refer to [BLS] for a general introduction to this class of dynamical systems. An interesting object from the point of view of potential theory is the equilibrium measure $\mu$ of the set $K$ of points with bounded orbits. In [BLS] $\mu$ is also characterized dynamically as the unique measure of maximal entropy. Thus $\mu$ is also an equilibrium measure from the point of view of the thermodynamical formalism. In the present paper we give another dynamical interpretation of $\mu$ as the limit distribution of the periodic points of $f$

Rhythms of Locomotion Expressed by Limulus polyphemus, the American Horseshoe Crab: II. Relationship to Circadian Rhythms of Visual Sensitivity

In the laboratory, horseshoe crabs express a circadian rhythm of visual sensitivity as well as daily and circatidal rhythms of locomotion. The major goal of this investigation was to determine whether the circadian clock underlying changes in visual sensitivity also modulates locomotion. To address this question, we developed a method for simultaneously recording changes in visual sensitivity and locomotion. Although every animal (24) expressed consistent circadian rhythms of visual sensitivity, rhythms of locomotion were more variable: 44% expressed a tidal rhythm, 28% were most active at night, and the rest lacked statistically significant rhythms. When exposed to artificial tides, 8 of 16 animals expressed circatidal rhythms of locomotion that continued after tidal cycles were stopped. However, rhythms of visual sensitivity remained stable and showed no tendency to be influenced by the imposed tides or locomotor activity. These results indicate that horseshoe crabs possess at least two biological clocks: one circadian clock primarily used for modulating visual sensitivity, and one or more clocks that control patterns of locomotion. This arrangement allows horseshoe crabs to see quite well while mating during both daytime and nighttime high tides

Nonparametric Bayesian grouping methods for spatial time-series data

We describe an approach for identifying groups of dynamically similar locations in spatial time-series data based on a simple Markov transition model. We give maximum-likelihood, empirical Bayes, and fully Bayesian formulations of the model, and describe exhaustive, greedy, and MCMC-based inference methods. The approach has been employed successfully in several studies to reveal meaningful relationships between environmental patterns and disease dynamics.Comment: 11 pages, no figure

Synthetic Studies in the Tetracycline Field

Abstract Not Provided

Use of personal child health records in the UK: findings from the millennium cohort study.

OBJECTIVES: The personal child health record (PCHR) is a record of a child's growth, development, and uptake of preventive health services, designed to enhance communication between parents and health professionals. We examined its use throughout the United Kingdom with respect to recording children's weight and measures of social disadvantage and infant health. DESIGN: Cross sectional survey within a cohort study. SETTING: UK. PARTICIPANTS: Mothers of 18,503 children born between 2000 and 2002, living in the UK at 9 months of age. MAIN OUTCOME MEASURES: Proportion of mothers able to produce their child's PCHR; proportion of PCHRs consulted containing record of child's last weight; effective use of the PCHR (defined as production, consultation, and child's last weight recorded). RESULTS: In all, 16,917 (93%) mothers produced their child's PCHR and 15,138 (85%) mothers showed effective use of their child's PCHR. Last weight was recorded in 97% of PCHRs consulted. Effective use was less in children previously admitted to hospital, and, in association with factors reflecting social disadvantage, including residence in disadvantaged communities, young maternal age, large family size (four or more children; incidence rate ratio 0.87; 95% confidence interval 0.83 to 0.91), and lone parent status (0.88; 0.86 to 0.91). CONCLUSIONS: Use of the PCHR is lower by women living in disadvantaged circumstances, but overall the record is retained and used by a high proportion of all mothers throughout the UK in their child's first year of life. PCHR use is endorsed in the National Service Framework for Children and has potential benefits which extend beyond the direct care of individual children

Matrix Big Brunch

Following the holographic description of linear dilaton null Cosmologies with a Big Bang in terms of Matrix String Theory put forward by Craps, Sethi and Verlinde, we propose an extended background describing a Universe including both Big Bang and Big Crunch singularities. This belongs to a class of exact string backgrounds and is perturbative in the string coupling far away from the singularities, both of which can be resolved using Matrix String Theory. We provide a simple theory capable of describing the complete evolution of this closed Universe.Comment: 15 pages, no figures. References adde

Geochemical Endmembers preserved in Gale Crater: A tale of two mudstones and their compositional differences according to ChemCam

Gale crater contains two fine-grained mudstone sedimentary units: The Sheepbed mudstone member, and the Murray formation mud-stones. These mudstones formed as part of an ancient fluviolacustrine system. The NASA Curiosity rover has analysed these mudstone units using the Chemistry and Camera (ChemCam), Alpha Particle X-ray Spectrometer (APXS) and Chemistry and Mineralogy (CheMin) onboard instrument suites. Subsequent mineralogical analyses have uncovered a wide geochemical and mineralogical diversity across and within these two mudstone formations. This study aims to determine the principal cause (alteration or source region) of this geochemical variation through a statistical analysis of the ChemCam dataset up to sol 1482, including the lower to middle Murray formation

Adding flavour to twistor strings

Twistor string theory is known to describe a wide variety of field theories at tree-level and has proved extremely useful in making substantial progress in perturbative gauge theory. We explore the twistor dual description of a class of N=2 UV-finite super-Yang-Mills theories with fundamental flavour by adding 'flavour' branes to the topological B-model on super-twistor space and comment on the appearance of these objects. Evidence for the correspondence is provided by matching amplitudes on both sides.Comment: 6 pages; contribution to the proceedings for the European Physical Society conference on High Energy Physics in Manchester, 19-25 July 2007. v3: Typos correcte