Two-dimensional frustrated spin systems in high magnetic fields

We discuss our numerical results on the properties of the S = 1/2 frustrated J1-J2 Heisenberg model on a square lattice as a function of temperature and frustration angle phi = atan(J2/J1) in an applied magnetic field. We cover the full phase diagram of the model in the range -pi <= phi <= pi. The discussion includes the parameter dependence of the saturation field itself, and addresses the instabilities associated with it. We also discuss the magnetocaloric effect of the model and show how it can be used to uniquely determine the effective interaction constants of the compounds which were investigated experimentally.Comment: 4 pages, 5 figures, proceedings of RHMF 200

Plasma cleaning device

High vacuum cleaning of contaminated surfaces such as hydrocarbon containment films can be accomplished by a plasma cleaning device which includes a plasma discharge housing to permit generation of a plasma in an environment having a higher pressure than the surface which is to be cleaned. A ground electrode and a radio frequency electrode partially surround a quartz plasma tube, for the introduction of an ionizable gas. These electrodes ionize the gas and help generate the plasma. This plasma flows through a non-constrictive aperture, through the plasma discharge housing and then on to the contaminated surface

Power laws, Pareto distributions and Zipf's law

When the probability of measuring a particular value of some quantity varies inversely as a power of that value, the quantity is said to follow a power law, also known variously as Zipf's law or the Pareto distribution. Power laws appear widely in physics, biology, earth and planetary sciences, economics and finance, computer science, demography and the social sciences. For instance, the distributions of the sizes of cities, earthquakes, solar flares, moon craters, wars and people's personal fortunes all appear to follow power laws. The origin of power-law behaviour has been a topic of debate in the scientific community for more than a century. Here we review some of the empirical evidence for the existence of power-law forms and the theories proposed to explain them.Comment: 28 pages, 16 figures, minor corrections and additions in this versio

Laboratory demonstration model: Active cleaning technique device

The technique which utilizes exposure to a plasma to remove contaminants from a surface was incorporated into a laboratory model which demonstrates active cleaning by both plasma cleaning and ion sputtering modes of operation. The development phase is reported and includes discussion of the plasma tube configuration, device design, and performance tests. A general description of the active cleaning device is provided which includes information on the main power/plasma discharge sensors, and the power, gas supply, and ion accelerator systems. Development of the active cleaning species at high vacuum conditions is described and results indicate that plasma cleaning occurs in the region of a visible plume which extends from the end of the plasma tube. Recommendations are made for research to determine the plasma cleaning mechanism and the plasma species responsible for the cleaning, as well limitations on the type of contaminants that can be removed

Genetic Diversity and Potential Function of Microbial Symbionts Associated with Newly Discovered Species of Osedax Polychaete Worms

We investigated the genetic diversity of symbiotic bacteria associated with two newly discovered species of Osedax from Monterey Canyon, CA, at 1,017-m (Osedax Monterey Bay sp. 3 "rosy" [Osedax sp. MB3]) and 381-m (Osedax Monterey Bay sp. 4 "yellow collar") depths. Quantitative PCR and clone libraries of 16S rRNA gene sequences identified differences in the compositions and abundances of bacterial phylotypes associated with the newly discovered host species and permitted comparisons between adult Osedax frankpressi and juveniles that had recently colonized whalebones implanted at 2,891 m. The newly discovered Osedax species hosted Oceanospirillales symbionts that are related to Gammaproteobacteria associated with the previously described O. frankpressi and Osedax rubiplumus (S. K. Goffredi, V. J. Orphan, G. W. Rouse, L. Jahnke, T. Embaye, K. Turk, R. Lee, and R. C. Vrijenhoek, Environ. Microbiol. 7:1369-1378, 2005). In addition, Osedax sp. MB3 hosts a diverse and abundant population of additional bacteria dominated by Epsilonproteobacteria. Ultrastructural analysis of symbiont-bearing root tissues verified the enhanced microbial diversity of Osedax sp. MB3. Root tissues from the newly described host species and O. frankpressi all exhibited collagenolytic enzyme activity, which covaried positively with the abundance of symbiont DNA and negatively with mean adult size of the host species. Members of this unusual genus of bone-eating worms may form variable associations with symbiotic bacteria that allow for the observed differences in colonization and success in whale fall environments throughout the world's oceans

Do Community-Level Models Account for the Effects of Biotic Interactions? A Comparison of Community-Level and Species Distribution Modeling of Rocky Mountain Conifers

Community-level models (CLMs) aim to improve species distribution modeling (SDM) methods by attempting to explicitly incorporate the influences of interacting species. However, the ability of CLMs to appropriately account for biotic interactions is unclear. We applied CLM and SDM methods to predict the distributions of three dominant conifer tree species in the U.S. Rocky Mountains and compared CLM and SDM predictive accuracy as well as the ability of each approach to accurately reproduce species co-occurrence patterns. We specifically evaluated the performance of two statistical algorithms, MARS and CForest, within both CLM and SDM frameworks. Across all species, differences in SDM and CLM predictive accuracy were slight and can be attributed to differences in model structure rather than accounting for the effects of biotic interactions. In addition, CLMs generally over-predicted species cooccurrence, while SDMs under-predicted cooccurrence. Our results demonstrate no real improvement in the ability of CLMs to account for biotic interactions relative to SDMs. We conclude that alternative modeling approaches are needed in order to accurately account for the effects of biotic interactions on species distributions

Generalized Hurst exponent and multifractal function of original and translated texts mapped into frequency and length time series

A nonlinear dynamics approach can be used in order to quantify complexity in written texts. As a first step, a one-dimensional system is examined : two written texts by one author (Lewis Carroll) are considered, together with one translation, into an artificial language, i.e. Esperanto are mapped into time series. Their corresponding shuffled versions are used for obtaining a "base line". Two different one-dimensional time series are used here: (i) one based on word lengths (LTS), (ii) the other on word frequencies (FTS). It is shown that the generalized Hurst exponent $h(q)$ and the derived $f(\alpha)$ curves of the original and translated texts show marked differences. The original "texts" are far from giving a parabolic $f(\alpha)$ function, - in contrast to the shuffled texts. Moreover, the Esperanto text has more extreme values. This suggests cascade model-like, with multiscale time asymmetric features as finally written texts. A discussion of the difference and complementarity of mapping into a LTS or FTS is presented. The FTS $f(\alpha)$ curves are more opened than the LTS onesComment: preprint for PRE; 2 columns; 10 pages; 6 (multifigures); 3 Tables; 70 reference

Light Element Synthesis in High Entropy Relativistic Flows Associated with Gamma Ray Bursts

We calculate and discuss the light element freeze-out nucleosynthesis in high entropy winds and fireballs for broad ranges of entropy-per-baryon, dynamic timescales characterizing relativistic expansion, and neutron-to-proton ratios. With conditions characteristic of Gamma Ray Bursts (GRBs) we find that deuterium production can be prodigious, with final abundance values 2H/H approximately 2%, depending on the fireball isospin, late time dynamics, and the effects of neutron decoupling- induced high energy non-thermal nuclear reactions. This implies that there potentially could be detectable local enhancements in the deuterium abundance associated with GRB events.Comment: 14 pages 3 figure

Thermodynamic cost of reversible computing

Since reversible computing requires preservation of all information throughout the entire computational process, this implies that all errors that appear as a result of the interaction of the information-carrying system with uncontrolled degrees of freedom must be corrected. But this can only be done at the expense of an increase in the entropy of the environment corresponding to the dissipation, in the form of heat, of the ``noisy'' part of the system's energy. This paper gives an expression of that energy in terms of the effective noise temperature, and analyzes the relationship between the energy dissipation rate and the rate of computation. Finally, a generalized Clausius principle based on the concept of effective temperature is presented.Comment: 5 pages; added two paragraphs and fixed a number of typo