An alternative derivation of the gravitomagnetic clock effect

The possibility of detecting the gravitomagnetic clock effect using artificial Earth satellites provides the incentive to develop a more intuitive approach to its derivation. We first consider two test electric charges moving on the same circular orbit but in opposite directions in orthogonal electric and magnetic fields and show that the particles take different times in describing a full orbit. The expression for the time difference is completely analogous to that of the general relativistic gravitomagnetic clock effect in the weak-field and slow-motion approximation. The latter is obtained by considering the gravitomagnetic force as a small classical non-central perturbation of the main central Newtonian monopole force. A general expression for the clock effect is given for a spherical orbit with an arbitrary inclination angle. This formula differs from the result of the general relativistic calculations by terms of order c^{-4}.Comment: LaTex2e, 11 pages, 1 figure, IOP macros. Submitted to Classical and Quantum Gravit

The inheritance of the hypersensitivity resistance of European plum (Prunus domestica L.) against the Plum pox virus

In between 2003 and 2009 more than 500 seedlings have been tested for hypersensitivity resistance against the Plum pox virus (PPV), which causes Sharka disease. The seedlings had at least one hypersensitive parent genotype. They were tested for hypersensitivity resistance by double grafting onto PPV infected interstem in the green house. In crossing combinations with two hypersensitive parents the percentage of hypersensitive seedlings was highest. There is also no equal distribution of the genotypes over the individual hypersensitivity classes (HC) in all crossing combinations. The percentage of hypersensitive seedlings strongly depends on the parentage. Furthermore investigations regarding the origin of the hypersensitivity resistance of the cultivar ‘Jojo’, which is a descendant of a crossing combination from ‘Ortenauer’ × ‘Stanley’, were done. It was shown that the cultivar ‘Ortenauer’ is the donor of the hypersensitivity trait.Keywords: Plum pox virus, hypersensitivity, inheritance, Prunus domestica L., resistanc

Phase Transition in a Stochastic Forest Fire Model and Effects of the Definition of Neighbourhood

We present results on a stochastic forest fire model, where the influence of the neighbour trees is treated in a more realistic way than usual and the definition of neighbourhood can be tuned by an additional parameter. This model exhibits a surprisingly sharp phase transition which can be shifted by redefinition of neighbourhood. The results can also be interpreted in terms of disease-spreading and are quite unsettling from the epidemologist's point of view, since variation of one crucial parameter only by a few percent can result in the change from endemic to epidemic behaviour.Comment: 23 pages, 13 figure

On the Possibility of Measuring the Gravitomagnetic Clock Effect in an Earth Space-Based Experiment

In this paper the effect of the post-Newtonian gravitomagnetic force on the mean longitudes $l$ of a pair of counter-rotating Earth artificial satellites following almost identical circular equatorial orbits is investigated. The possibility of measuring it is examined. The observable is the difference of the times required to $l$ in passing from 0 to 2$\pi$ for both senses of motion. Such gravitomagnetic time shift, which is independent of the orbital parameters of the satellites, amounts to 5$\times 10^{-7}$ s for Earth; it is cumulative and should be measured after a sufficiently high number of revolutions. The major limiting factors are the unavoidable imperfect cancellation of the Keplerian periods, which yields a constraint of 10$^{-2}$ cm in knowing the difference between the semimajor axes $a$ of the satellites, and the difference $I$ of the inclinations $i$ of the orbital planes which, for $i\sim 0.01^\circ$, should be less than $0.006^\circ$. A pair of spacecrafts endowed with a sophisticated intersatellite tracking apparatus and drag-free control down to 10$^{-9}$ cm s$^{-2}$ Hz$^{-{1/2}}$ level might allow to meet the stringent requirements posed by such a mission.Comment: LaTex2e, 22 pages, no tables, 1 figure, 38 references. Final version accepted for publication in Classical and Quantum Gravit

Self-consistent modelling of Mercury’s surface composition and exosphere by solar wind sputtering

A Monte-Carlo model of exospheres was extended by treating the solar wind ion induced sputtering process, quantitatively in a self-consistent way starting with the actual release of particles from the mineral surface of Mercury. Mercury is a body without a significant atmosphere, thus, the surface is effected by different processes that are mainly related to the radiation and plasma environment of the Sun and to micrometeorites, which are delivered to Mercury’s surface. In such a case it can be assumed that the composition of Mercury’s thin collisionless atmosphere, the exosphere, is related to the composition of the planetary crustal materials. If so, then inferences regarding the bulk chemistry of the planet can be made from a study of atoms and molecules in the exosphere after they are released from the mineral surface by a variety of release processes. One difficult challenge is the identification of the main source of some elements like H, He, Na or K. Generally it is believed that H and He come primarily from the solar wind, while Na and K originate from volatilized materials partitioned between Mercury’s crust and impacts from meteorites. Besides the before mentioned elements corresponding to spectroscopic observations and experiments with soil analogues, other elements such as O, Na, Mg, Al, Si, P, S, K, Ca, Ti, Cr, Fe, Ni, Zn, OH should also be related with Mercury’s surface soils (Wurz et al., 2010, and references therein). Based on available observational data and literature data we established a global model for the surface mineralogy of Mercury and from that derived the average elemental composition of the surface. Compositional data analysis has been employed for Mercury’s surface minerals recently by (Sprague et al., 2009). In these cases the applied method was based on simple correlation methods, which do not exploit the full potential of the available data. In addition, the closed nature of compositional data, i.e., the assumption that component concentrations have to sum up to 100% in an analysis, bears important implications for the statistical analysis of compositional data, which do not seem to have been sufficiently appreciated until now. To investigate the default of the classical additive analysis method our research group applied recently a more realistic multiplicative method (Aitchison, 1986) based on the Euclidean space geometry of the simplex (see the chapter Elements of simplicial linear algebra and geometry). Our recent results presented in detail in Wurz et al., (2010) for Mercury will be discussed. This model serves as a tool to estimate densities of species in the exosphere depending on the release mechanism and the associated physical parameters quantitatively describing the particle release from the surface

Observation of Fragile-to-Strong Dynamic Crossover in Protein Hydration Water

At low temperatures proteins exist in a glassy state, a state which has no conformational flexibility and shows no biological functions. In a hydrated protein, at and above 220 K, this flexibility is restored and the protein is able to sample more conformational sub-states, thus becomes biologically functional. This 'dynamical' transition of protein is believed to be triggered by its strong coupling with the hydration water, which also shows a similar dynamic transition. Here we demonstrate experimentally that this sudden switch in dynamic behavior of the hydration water on lysozyme occurs precisely at 220 K and can be described as a Fragile-to-Strong dynamic crossover (FSC). At FSC, the structure of hydration water makes a transition from predominantly high-density (more fluid state) to low-density (less fluid state) forms derived from existence of the second critical point at an elevated pressure.Comment: 6 pages (Latex), 4 figures (Postscript

Fuzzy Characterization of Near-Earth-Asteroids

Due to close encounters with the inner planets, Near-Earth-Asteroids (NEAs) can have very chaotic orbits. Because of this chaoticity, a statistical treatment of the dynamical properties of NEAs becomes difficult or even impossible. We propose a new way to classify NEAs by using methods from Fuzzy Logic. We demonstrate how a fuzzy characterization of NEAs can be obtained and how a subsequent analysis can deliver valid and quantitative results concerning the long-term dynamics of NEAs.Comment: 11 pages, presented at the 7th Alexander von Humboldt Colloquium on Celestial Mechanics (2008), accepted for publication in "Celestial Mechanics and Dynamical Astronomy