Use of the dart apparatus by the hermaphroditic land snail Polymita muscarum (Lea, 1834).

Many species of pulmonate land snails are equipped with one or more so-called "love darts". Even though the number and shape of these calcareous darts vary considerably between species, dart use has only been investigated in very few species. Here, we redescribe the mating behaviour of Polymita muscarum because previous reports did not include the use of the dart apparatus. Mating in this hermaphroditic land snail can be divided into three stages: courtship, copulation and post-copulatory activity. During courtship, full eversion of the genital atrium is reached, thus exposing the sensitive zone, genital lobes and dart apparatus. We observed that P. muscarum pushes the everted dart apparatus repeatedly onto different parts of the partner's body and does not lose its dart after stabbing. Dissected specimens had a single, slender dart with a round base, a broad corona and a circular cross-section. We propose that the morphology of P. muscarum's dart is consistent with the idea of simple darts needing to be stabbed more often in order to increase the transfer of mucus, which contains a biologically active substance (i.e. allohormone) that enhances the chances of paternity. Besides adding to the growing diversity in the use of love darts in land snails, these findings contribute to the understanding of the evolution of this peculiar reproductive act. © Koninklijke Brill NV 2007

Time delays, choice of energy-momentum variables, and relative locality in doubly special relativity

Doubly special relativity (DSR) theories consider (quantum-gravity motivated) deformations of the symmetries of special relativity compatible with a relativity principle. The existence of time delays for massless particles, one of their proposed phenomenological consequences, is a delicate question since, contrary to what happens with Lorentz invariance violation scenarios, they are not simply determined by the modification in the particle dispersion relation. While some studies of DSR assert the existence of photon time delays, in this paper we generalize a recently proposed model for time delay studies in DSR and show that the existence of photon time delays does not necessarily follow from a DSR scenario, determining in which cases this is so. Moreover, we clarify long-standing questions about the arbitrariness in the choice of the energy-momentum labels and the independence of the time delay on this choice, as well as on the consistency of its calculation with the relative locality paradigm of DSR theories. Finally, we show that the result for time delays is reproduced in models that consider propagation in a noncommutative spacetime

Modification of the mean free path of very high-energy photons due to a relativistic deformed kinematics

Ultra-high-energy physics is about to enter a new era thanks to the impressive results of experiments such as the Large High Altitude Air Shower Observatory, detecting photons of up to 1.4×10^15 eV (PeV scale). These new results could be used to test deviations with respect to special relativity. While this has been already explored within the approach of Lorentz Invariance Violation theories, in this work we consider, for the first time, modifications due to a relativistic deformed kinematics (which appear in Doubly Special Relativity, or DSR, theories). In particular, we study the mean free path of very high-energy photons due to electron-positron pair creation when interacting with low-energy photons of the cosmic microwave background. Depending on the energy scale of the relativistic deformed kinematics, present (or near future) experiments can be sensitive enough to be able to identify deviations from special relativity

Effects of new physics in neutrino propagation

In this work we consider the effects of Lorentz Invariance Violation over the observed flux of very high-energy neutrinos. For that, we study the neutrino propagation in a Modified Dispersion Relation scenario with a superluminal velocity. This makes the neutrino unstable and causes a cut-off in the flux of detected neutrinos. Using simple models, one can approximate the location of the cut-off as functions of the parameters of new physics and the closest source

Correlation functions of the XXZ spin-1/2 Heisenberg chain at the free fermion point from their multiple integral representations

Using multiple integral representations, we derive exact expressions for the correlation functions of the spin-1/2 Heisenberg chain at the free fermion point.Comment: 24 pages, LaTe

Physics of the universe transparency in a deformed kinematics

We present a first study of the possible effects of a relativistic deformation of special relativity in the recent observations of very high-energy gamma rays by the LHAASO experiment, which has opened a new phenomenological window to study deformations in the kinematics of special relativity. Our analysis of the interaction of high-energy photons with the CMB background complements theoretical studies based on Lorentz invariance violation scenarios, while making predictions that would allow one to distinguish between a violation and a deformation of the symmetries of special relativity

Unraveling the sulfate sources of (giant) gypsum crystals using gypsum isotope fractionation factors.

We combine newly determined isotope fractionation factors of gypsum precipitated in the laboratory with the isotopic compositions of natural anhydrite and gypsum to unravel the sulfate sources of the giant selenite crystals in the Naica mine (Chihuahua, Mexico). Gypsum was precipitated in the laboratory from CaSO4-NaCl-H2O solutions across a broad temperature range to establish the isotopic fractionation behavior of the sulfate molecule between the solid and dissolved phase. Oxygen isotopes show a significant fractionation dependence on temperature, with the solid phase more depleted in light isotopes with decreasing temperature. Sulfur isotopes display only a weak but similar dependence on temperature. At high salinity (4.5 M NaCl) no temperature dependence was found for the isotope composition. Based on this fractionation behavior, we attempt to elucidate the origin of the sulfate source(s) responsible for the formation of the (giant) gypsum crystals in the Naica mine. Detailed analysis of the isotopic composition of anhydrite, gypsum, and water samples strongly suggests that different types of anhydrite (of hypogenic and sedimentary origin) were dissolved to form these unique gypsum formations. The homogeneous isotopic composition of most gypsum crystals analyzed reveals an effective hydrodynamic mixing and a slow kinetics of precipitation fed by solutions of calcium sulfate from different anhydrite sources

Burnout and depression among Spanish periodontology practitioners

Objectives: The objective of this study was to determine the prevalence of burnout syndrome and depression symptoms among periodontology practitioners, as well as the relationship with socio-demographic variables and work stress. Study Design: A total of 284 subjects, members of the Spanish Society of Periodontology (SEPA), were selected for this study. The Spanish version of the Maslach Burnout Inventory (MBI) and the Tetradimensional Estructural Questionnaire for Depression (TEC-DE) were sent by post to all participants. Descriptive statistics in addition to mean comparison and chi-square test were used for data analysis. Results: A response rate of 59.85% was obtained. From the total sample, 40% shows high levels of emotional exhaustion, 20% increased depersonalization and 11.20% diminished personal accomplishment. The prevalence of any depression symptom was nearly 16%. Moreover, higher prevalence was found among those practitioners not working a continuous shift and not practicing periodontology on an exclusive basis. Conclusion: Among Spanish periodontology practitioners, a high prevalence of burnout and depression exists

Time resolved particle dynamics in granular convection

We present an experimental study of the movement of individual particles in a layer of vertically shaken granular material. High-speed imaging allows us to investigate the motion of beads within one vibration period. This motion consists mainly of vertical jumps, and a global ordered drift. The analysis of the system movement as a whole reveals that the observed bifurcation in the flight time is not adequately described by the Inelastic Bouncing Ball Model. Near the bifurcation point, friction plays and important role, and the branches of the bifurcation do not diverge as the control parameter is increased. We quantify the friction of the beads against the walls, showing that this interaction is the underlying mechanism responsible for the dynamics of the flow observed near the lateral wall