Effects of Landscape Structure on Plants Species Richness in Small Grassland Remnants in Two Different Landscapes

There is an increasing interest in using the landscape as the operational scale in many ecological studies. Current species richness in the landscape may be explained by past land use, and habitats may harbour species favoured by an environment that no longer exists. In this study we have included both a landscape scale and a temporal scale. The objective was to explain species pattern and the effect of isolation, habitat size and surrounding land use, and past land use change, on small grassland remnants in rural landscapes

Land Use History and the Build-Up and Decline of Species Richness in Scandinavian Semi-Natural Grasslands

Scandinavian semi-natural grasslands have an exceptionally high small-scale species richness. In the past, these grasslands covered extensive areas but they have declined drastically during the last century. How species richness of semi-natural grasslands was built up during history, and how species respond to land use change, are discussed. The agricultural expansion from the late Iron Age was associated with increasing grassland extent and spatial predictability, resulting in accumulation of species at small spatial scales. Although few species directly depend on management, the specific composition of these grasslands is a product of haymaking and grazing. Grassland fragmentation initially has small effects on species richness, due to slow extinction of many species. Species loss in grasslands is, however, expected in the coming decades. Restoration efforts may fail due to slow colonization. Effects of landscape configuration may be overlooked, if land use history is not considered, since present-day species richness largely reflects landscape history

Josephson Effect between Condensates with Different Internal Structures

A general formula for Josephson current in a wide class of hybrid junctions between different internal structures is derived on the basis of the Andreev picture. The formula extends existing formulae and also enables us to analyze novel B-phase/A-phase/B-phase (BAB) junctions in superfluid helium three systems, which are accessible to experiments. It is predicted that BAB junctions will exhibit two types of current-phase relations associated with different internal symmetries. A ``pseudo-magnetic interface effect'' inherent in the system is also revealed.Comment: 4 pages, 2 figure

Mass Segregation in the Globular Cluster Palomar 5 and its Tidal Tails

We present the stellar main sequence luminosity function (LF) of the disrupted, low-mass, low-concentration globular cluster Palomar 5 and its well-defined tidal tails, which emanate from the cluster as a result of its tidal interaction with the Milky Way. The results of our deep (B ~ 24.5) wide-field photometry unequivocally indicate that preferentially fainter stars were removed from the cluster so that the LF of the cluster's main body exhibits a significant degree of flattening compared to other globular clusters. There is clear evidence of mass segregation, which is reflected in a radial variation of the LFs. The LF of the tidal tails is distinctly enhanced with faint, low-mass stars. Pal 5 exhibits a binary main sequence, and we estimate a photometric binary frequency of roughly 10%. Also the binaries show evidence of mass segregation with more massive binary systems being more strongly concentrated toward the cluster center.Comment: 14 pages, 12 figures, accepted for publication in the Astronomical Journa

The Palomar Testbed Interferometer Calibrator Catalog

The Palomar Testbed Interferometer (PTI) archive of observations between 1998 and 2005 is examined for objects appropriate for calibration of optical long-baseline interferometer observations - stars that are predictably point-like and single. Approximately 1,400 nights of data on 1,800 objects were examined for this investigation. We compare those observations to an intensively studied object that is a suitable calibrator, HD217014, and statistically compare each candidate calibrator to that object by computing both a Mahalanobis distance and a Principal Component Analysis. Our hypothesis is that the frequency distribution of visibility data associated with calibrator stars differs from non-calibrator stars such as binary stars. Spectroscopic binaries resolved by PTI, objects known to be unsuitable for calibrator use, are similarly tested to establish detection limits of this approach. From this investigation, we find more than 350 observed stars suitable for use as calibrators (with an additional $\approx 140$ being rejected), corresponding to $\gtrsim 95$ sky coverage for PTI. This approach is noteworthy in that it rigorously establishes calibration sources through a traceable, empirical methodology, leveraging the predictions of spectral energy distribution modeling but also verifying it with the rich body of PTI's on-sky observations.Comment: 100 pages, 7 figures, 7 tables; to appear in the May 2008ApJS, v176n

Quantum Dissipative Effects and Neutrinos : current constraints and future perspectives

We establish the most stringent experimental constraints coming from recent terrestrial neutrino experiments on quantum mechanical decoherence effects in neutrino systems. Taking a completely phenomenological approach, we probe vacuum oscillations plus quantum decoherence between two neutrino species in the channels $\nu_\mu \to \nu_\tau$, $\nu_\mu \to \nu_e$ and $\nu_e \to \nu_\tau$, admitting that the quantum decoherence parameter $\gamma$ is related to the neutrino energy $E_\nu$ as : $\gamma=\gamma_0 (E_\nu/\text{GeV})^{n}$, with $n=-1,0,1$ and 2. Our bounds are valid for a neutrino mass squared difference compatible with the atmospheric, the solar and, in many cases, the LSND scale. We also qualitatively discuss the perspectives of the future long baseline neutrino experiments to further probe quantum dissipation.Comment: 26 pages, 8 encapsulated postscript figure

Identification of extra neutral gauge bosons at the International Linear Collider

Heavy neutral gauge bosons, Z's, are predicted by many theoretical schemes of physics beyond the Standard Model, and intensive searches for their signatures will be performed at present and future high energy colliders. It is quite possible that Z's are heavy enough to lie beyond the discovery reach expected at the CERN Large Hadron Collider LHC, in which case only indirect signatures of Z' exchanges may occur at future colliders, through deviations of the measured cross sections from the Standard Model predictions. We here discuss in this context the foreseeable sensitivity to Z's of fermion-pair production cross sections at an e^+e^- linear collider, especially as regards the potential of distinguishing different Z' models once such deviations are observed. Specifically, we assess the discovery and identification reaches on Z' gauge bosons pertinent to the E_6, LR, ALR and SSM classes of models, that should be attained at the planned International Linear Collider (ILC). With the high experimental accuracies expected at the ILC, the discovery and the identification reaches on the Z' models under consideration could be increased substantially. In particular, the identification among the different models could be achieved for values of Z' masses in the discovery (but beyond the identification) reach of the LHC. An important role in enhancing such reaches is played by the electron (and possibly the positron) longitudinally polarized beams. Also, although the purely leptonic processes are experimentally cleaner, the measurements of c- and b-quark pair production cross sections are found to carry important, and complementary, information on these searches.Comment: 21 page

Localized instabilities of the Wigner equation as a model for the emergence of Rogue Waves

In this paper, we model Rogue Waves as localized instabilities emerging from homogeneous and stationary background wavefields, under NLS dynamics. This is achieved in two steps: given any background Fourier spectrum P(k), we use the Wigner transform and Penrose’s method to recover spatially periodic unstable modes, which we call unstable Penrose modes. These can be seen as generalized Benjamin–Feir modes, and their parameters are obtained by resolving the Penrose condition, a system of nonlinear equations involving P(k). Moreover, we show how the superposition of unstable Penrose modes can result in the appearance of localized unstable modes. By interpreting the appearance of an unstable mode localized in an area not larger than a reference wavelength λ0 as the emergence of a Rogue Wave, a criterion for the emergence of Rogue Waves is formulated. Our methodology is applied to δ spectra, where the standard Benjamin–Feir instability is recovered, and to more general spectra. In that context, we present a scheme for the numerical resolution of the Penrose condition and estimate the sharpest possible localization of unstable modes. Keywords: Rogue Waves; Wigner equation; Nonlinear Schrodinger equation; Penrose modes; Penrose conditio

Momentum asymmetries as CP violating observables

Three body decays can exhibit CP violation that arises from interfering diagrams with different orderings of the final state particles. We construct several momentum asymmetry observables that are accessible in a hadron collider environment where some of the final state particles are not reconstructed and not all the kinematic information can be extracted. We discuss the complications that arise from the different possible production mechanisms of the decaying particle. Examples involving heavy neutralino decays in supersymmetric theories and heavy Majorana neutrino decays in Type-I seesaw models are examined.Comment: 20 pages, 9 figures. Clarifying comments and one reference added, matches published versio

Initial oak regeneration responses to experimental warming along microclimatic and macroclimatic gradients

Quercus spp. are one of the most important tree genera in temperate deciduous forests in terms of biodiversity, economic and cultural perspectives. However, natural regeneration of oaks, depending on specific environmental conditions, is still not sufficiently understood. Oak regeneration dynamics are impacted by climate change, but these climate impacts will depend on local forest management and light and temperature conditions. Here, we studied germination, survival and seedling performance (i.e. aboveground biomass, height, root collar diameter and specific leaf area) of four oak species (Q. cerris, Q. ilex, Q. robur and Q. petraea). Acorns were sown across a wide latitudinal gradient, from Italy to Sweden, and across several microclimatic gradients located within and beyond the species' natural ranges. Microclimatic gradients were applied in terms of forest structure, distance to the forest edge and experimental warming. We found strong interactions between species and latitude, as well as between microclimate and latitude or species. The species thus reacted differently to local and regional changes in light and temperature ; in southern regions the temperate Q. robur and Q. petraea performed best in plots with a complex structure, whereas the Mediterranean Q. ilex and Q. cerris performed better in simply structured forests with a reduced microclimatic buffering capacity. The experimental warming treatment only enhanced height and aboveground biomass of Mediterranean species. Our results show that local microclimatic gradients play a key role in the initial stages of oak regeneration; however, one needs to consider the species-specific responses to forest structure and the macroclimatic context