High temperature behavior of Sr-doped layered cobaltites Y(Ba1-xSrx)Co2O5.5: phase stability and structural properties

In this article we present a neutron diffraction in-situ study of the thermal evolution and high-temperature structure of layered cobaltites Y(Ba, Sr)Co2 O5+{\delta}. Neutron thermodiffractograms and magnetic susceptibility measurements are reported in the temperature range 20 K <= T <= 570 K, as well as high resolution neutron diffraction experiments at selected temperatures. Starting from the as-synthesized samples with {\delta} ~ 0.5, we show that the room temperature phases remain stable up to 550 K, where they start loosing oxygen and transform to a vacancy-disordered "112" structure with tetragonal symmetry. Our results also show how the so-called "122" structure can be stabilized at high temperature (around 450 K) in a sample in which the addition of Sr at the Ba site had suppressed its formation. In addition, we present the structural and magnetic properties of the resulting samples with a new oxygen content {\delta} ~ 0.25 in the temperature range 20 K <= T <= 300 K

Gravity Effects on Neutrino Masses in Split Supersymmetry

The mass differences and mixing angles of neutrinos can neither be explained by R-Parity violating split supersymmetry nor by flavor blind quantum gravity alone. It is shown that combining both effects leads, within the allowed parameter range, to good agreement with the experimental results. The atmospheric mass is generated by supersymmetry through mixing between neutrinos and neutralinos, while the solar mass is generated by gravity through flavor blind dimension five operators. Maximal atmospheric mixing forces the tangent squared of the solar angle to be equal to 1/2. The scale of the quantum gravity operator is predicted within a 5% error, implying that the reduced Planck scale should lie around the GUT scale. In this way, the model is very predictive and can be tested at future experiments.Comment: 12 pages, 9 figures; In section 3 we extend our discussion about the definition of flavor basis in order to clarify in which basis the Gravity contributions are flavor blind. In the section 4 we add some words to explain why the Gravity contributions will not affect the charged lepton mass matrix; Finally we also fixed some minor typos regarding units or plot label

Probing phase coexistence and stabilization of the spin-ordered ferrimagnetic state by Calcium addition in the YBa_{1-x}Ca_{x}Co_{2}O_{5.5} layered cobaltites using neutron diffraction

In this article we study the effects of a partial substitution of Ba with the smaller cation Ca in the layered cobaltites YBaCo_2O_{5+\delta} for \delta \approx 0.5. Neutron thermodiffractograms are reported for the compounds YBa_{0.95}Ca_{0.05}Co_2O_{5.5} (x_{Ca}=0.05) and YBa_{0.90}Ca_{0.10}Co_2O_{5.5} (x_{Ca}=0.10) in the temperature range 20 K \leq T \leq 300 K, as well as high resolution neutron diffraction experiments at selected temperatures for the samples x_{Ca}=0.05, x_{Ca}=0.10 and the parent compound x_{Ca}=0. We have found the magnetic properties to be strongly affected by the cationic substitution. Although the "122" perovskite structure seems unaffected by Ca addition, the magnetic arrangements of Co ions are drastically modified: the antiferromagnetic (AFM) long-range order is destroyed, and a ferrimagnetic phase with spin state order is stabilized below T \sim 290 K. For the sample with x_{Ca}=0.05 a fraction of AFM phase coexists with the ferrimagnetic one below T \sim 190 K, whereas for x_{Ca}=0.10 the AFM order is completely lost. The systematic refinement of the whole series has allowed for a better understanding of the observed low-temperature diffraction patterns of the parent compound, YBaCo_2O_{5.5}, which had not yet been clarified. A two-phase scenario is proposed for the x_{Ca}=0 compound which is compatible with the phase coexistence observed in the x_{Ca}=0.05 sample

The Duties of Mercy

If goodness for Kant as seen above comes solely from one’s duty, what then could be the possible motive for “supererogatory acts” (exemplified by the hero or the saint) which go beyond the call of duty? Because “supererogatory acts” involve the transgression of duty, what would be its corresponding motive? This paper will show that it is here in these acts that we may find a place for love, benevolence and kindness, the motives which Kant appears to disqualify as motives for moral action. This will be illustrated by appeal to a famous painting by Caravaggio, “The Seven Works of Mercy”

Neutrino Masses in Split Supersymmetry

We investigate the possibility to generate neutrino masses in the context of Split supersymmetric scenarios where all sfermions are very heavy. All relevant contributions coming from the R-parity violating terms to the neutrino mass matrix up to one-loop level are computed, showing the importance of the Higgs one-loop corrections. We conclude that it is not possible to generate all neutrino masses and mixings in Split SUSY with bilinear R-Parity violating interactions. In the case of Partial Split SUSY the one-loop Higgs contributions are enough to generate the neutrino masses and mixings in agreement with the experiment. In the context of minimal SUSY SU(5) we find new contributions which help us to generate neutrino masses in the case of Split SUSY.Comment: 33 pages, 6 figures, to appear in Physical Review

Substitution site and effects on magnetism in Sr-for-Ca substituted CaBaCo4O7

Under a Creative Commons Attribution (CC BY) license.-- et al.Cationic substitutions in the novel magnetoelectric compound CaBaCo4O7 lead to profound changes in its magnetic and electric behaviors. In this work, we present a structural study of the isovalent substitution Sr-for-Ca in CaBaCo4O7. X-ray diffraction, as well as neutron powder diffraction experiments, are reported for a series of samples Ca1- xSrxBaCo4O7 with 0 ≤ x ≤ 0.10. Special emphasis is given to the identification of the substitution site, as Sr has also been reported to substitute for Ba in this crystal structure. The solubility limit for Sr at the Ca site is shown to be at x ≃ 0.08. The variation of lattice constants with Sr-doping firmly supports the Sr-for-Ca substitution. Rietveld refinements of the Sr-substituted samples are presented, and used as starting point to analyse the local structure around Sr by means of X-ray absorption spectroscopy at the Sr K-edge. Both the near-edge absorption and the extended absorption fine-structure confirm the substitution of Sr for Ca, giving definite support to the proposed nominal formula. In addition, macroscopic magnetization measurements are presented which reveal the striking effects of Sr-substitution over the magnetic landscape of this puzzling compound.This work is part of a research project supported by Agencia Nacional de Promoción Científica y Tecnológica (Argentina), under Grant No. PICT-2011-0752, CONICET under Grant No. PIP 490 2012-2014, and Universidad Nacional de Cuyo. We acknowledge Soleil synchrotron for the beamtime allocation and the MinCyT-Soleil collaboration project for the financial support. We also acknowledge ILL and its staff for the beamtime allocation and technical assistance as well as the MinCyT of Argentina for funding the trip to perform the experiments. G.A. and J.C. thank the CONICET-CSIC program for scientific visits and Grant No. MAT2011-27233-C02-02.Peer Reviewe

The determinants of managerial responses to hotel guests’ reviews: an exploratory study in the city of Milan

The spread of eWOM and travel review websites has profoundly changed the consumer decision-making process along with firms’ strategies. A key topic of discussion, both for academics and practitioners, is the opportunity to reply to online consumers’ reviews. Although some studies have recently investigated the subject, this topic need to be further explored. The purpose of the present study is to investigate the variables that influence hotels’ propensity to reply to guests’ reviews. The results of the research suggest that hotel managers show more propensity to reply to negative guests’ reviews of their native language. Possible motivations and implications are discussed