Probing mSUGRA via the Extreme Universe Space Observatory

An analysis is carried out within mSUGRA of the estimated number of events originating from upward moving ultra-high energy neutralinos that could be detected by the Extreme Universe Space Observatory (EUSO). The analysis exploits a recently proposed technique that differentiates ultra-high energy neutralinos from ultra-high energy neutrinos using their different absorption lengths in the Earth's crust. It is shown that for a significant part of the parameter space, where the neutralino is mostly a Bino and with squark mass $\sim 1$ TeV, EUSO could see ultra-high energy neutralino events with essentially no background. In the energy range 10^9 GeV < E < 10^11 GeV, the unprecedented aperture of EUSO makes the telescope sensitive to neutralino fluxes as low as 1.1 \times 10^{-6} (E/GeV)^{-1.3} GeV^{-1} cm^{-2} yr^{-1} sr^{-1}, at the 95% CL. Such a hard spectrum is characteristic of supermassive particles' $N$-body hadronic decay. The case in which the flux of ultra-high energy neutralinos is produced via decay of metastable heavy particles with uniform distribution throughout the universe is analyzed in detail. The normalization of the ratio of the relics' density to their lifetime has been fixed so that the baryon flux produced in the supermassive particle decays contributes to about 1/3 of the events reported by the AGASA Collaboration below 10^{11} GeV, and hence the associated GeV gamma-ray flux is in complete agreement with EGRET data. For this particular case, EUSO will collect between 4 and 5 neutralino events (with 0.3 of background) in ~ 3 yr of running. NASA's planned mission, the Orbiting Wide-angle Light-collectors (OWL), is also briefly discussed in this context.Comment: Some discussion added, final version to be published in Physical Review

Relic Neutrino Absorption Spectroscopy

Resonant annihilation of extremely high-energy cosmic neutrinos on big-bang relic anti-neutrinos (and vice versa) into Z-bosons leads to sizable absorption dips in the neutrino flux to be observed at Earth. The high-energy edges of these dips are fixed, via the resonance energies, by the neutrino masses alone. Their depths are determined by the cosmic neutrino background density, by the cosmological parameters determining the expansion rate of the universe, and by the large redshift history of the cosmic neutrino sources. We investigate the possibility of determining the existence of the cosmic neutrino background within the next decade from a measurement of these absorption dips in the neutrino flux. As a by-product, we study the prospects to infer the absolute neutrino mass scale. We find that, with the presently planned neutrino detectors (ANITA, Auger, EUSO, OWL, RICE, and SalSA) operating in the relevant energy regime above 10^{21} eV, relic neutrino absorption spectroscopy becomes a realistic possibility. It requires, however, the existence of extremely powerful neutrino sources, which should be opaque to nucleons and high-energy photons to evade present constraints. Furthermore, the neutrino mass spectrum must be quasi-degenerate to optimize the dip, which implies m_{nu} >~ 0.1 eV for the lightest neutrino. With a second generation of neutrino detectors, these demanding requirements can be relaxed considerably.Comment: 19 pages, 26 figures, REVTeX

Unraveling the diverse nature of service quality in a sharing economy: a social exchange theory perspective of Airbnb accommodation

This is an accepted manuscript of an article published by Emerald in International Journal of Contemporary Hospitality Management on 11/09/2017, available online: https://doi.org/10.1108/IJCHM-08-2016-0420 The accepted version of the publication may differ from the final published version.Purpose- This study investigates customers’ perceptions of the service quality facets of Airbnb accommodation using social exchange theory as a suitable conceptual framework to explain aspects of interactivity between guests and hosts. Design/methodology/approach- A self-administered questionnaire consisting of 25 accommodation- specific service quality attributes, structured according to Akbaba’s (2006) measurement scale and based on the service quality hierarchical conceptualization described by Brady and Cronin (2001) and Cronin and Taylor (1992), was distributed to Airbnb international guests visiting Phuket, Thailand. The sample was chosen through a two-stage sampling process and the PLS-SEM technique was used for data analysis. Findings- The results showed that convenience and assurance are critical contributors to the measurement of service quality in remote Airbnb lodgings. The findings further revealed that Airbnb guests are mainly interested in lodgings which have access to certain tourist sights, and in easily accessible information and efficient resolution of problems during their stay. We also found that guests greatly value the convenience and flexibility offered by Airbnb, and that they particularly appreciate the warm hospitality provided by the hosts. Finally, Airbnb guests have very low expectations of the amenities and services available at the lodgings. Research limitations/implications-Airbnb is one of the most well-known examples of hospitality in the sharing economy and results cannot be generalized to similar accommodation providers in sharing economies. Despite the appropriateness of using the measurement tool provided by Akbaba (2006), it is only one option among others for measuring service quality. Practical implications- The current study can assist hosts in gaining better knowledge of guests’ decision making processes and in designing effective marketing strategies by focusing on guests’ requirements in terms of service quality. The effective use of competitive strengths and the prioritization of business resources would potentially enhance guests’ positive experiences at the accommodation and at the destination. Originality/value-Limited numbers of studies have focused on the sharing economy and hospitality and in particular on Airbnb and this is the first study with a focus on service quality issues in terms of Airbnb accommodation

Urban amphibian assemblages as metacommunities

1. Urban ecosystems are expanding throughout the world, and urban ecology is attracting increasing research interest. Some authors have questioned the value of existing ecological theories for understanding the processes and consequences of urbanization.2. In order to assess the applicability of metacommunity theory to urban systems, I evaluated three assumptions that underlie the theory &ndash; the effect of patch area, the effect of patch isolation, and species&ndash;environment relations &ndash; using data on assemblages of pond-breeding amphibians in the Greater Melbourne area of Australia. I also assessed the relative impact of habitat fragmentation, habitat isolation, and changes to habitat quality on these assemblages.3. Poisson regression modelling provided support for an important increase in species richness with patch area (pond size) and a decrease in species richness with increasing patch isolation, as measured by surrounding road cover. Holding all other variables constant, species richness was predicted to be 2&middot;8&ndash;5&middot;5 times higher at the largest pond than at the smallest, while the most isolated pond was predicted to have 12&ndash;19% of the species richness of the least isolated pond. Thus, the data were consistent with the first two assumptions of metacommunity theory evaluated.4. The quality of habitat at a pond was also important, with a predicted 44&ndash;56% decrease in the number of species detected at ponds with a surrounding vertical wall compared with those with a gently sloping bank. This demonstrates that environmental differences between habitat patches were also influencing amphibian assemblages, providing support for the species-sorting and/or mass-effect perspectives of metacommunity theory.5. Without management intervention, urbanization may lead to a reduction in the number of amphibian species persisting in urban ponds, particularly where increasing isolation of ponds by roads and associated infrastructure reduces the probability of re-colonization following local extinction.<br /

Investigations on the characterization of ion implanted hexagonal boron nitride

The effect of ion implantation on hexagonal boron nitride (h-BN) is studied herein. We use boron as an ion of choice to introduce radiation damage into h-BN, at fluences ranging from 1 × 1014–1 × 1016 ions/cm2 and implantation energy ranges from 40 to 160 keV. The thermal dependence is also investigated by varying the annealing temperature from room temperature to 400 °C after implantation. Raman spectroscopy showed Raman active defects one of which is possibly related to the formation of cubic boron nitride nanocrystals (nc-BN) within the implanted range. The relationship of these defect induced Raman active peaks was investigated by varying the implantation parameters. The preliminary Transmission Electron Microscopy (TEM) results also are reported briefly