Minimal immersions of closed surfaces in hyperbolic three-manifolds

We study minimal immersions of closed surfaces (of genus $g \ge 2$) in hyperbolic 3-manifolds, with prescribed data $(\sigma, t\alpha)$, where $\sigma$ is a conformal structure on a topological surface $S$, and $\alpha dz^2$ is a holomorphic quadratic differential on the surface $(S,\sigma)$. We show that, for each $t \in (0,\tau_0)$ for some $\tau_0 > 0$, depending only on $(\sigma, \alpha)$, there are at least two minimal immersions of closed surface of prescribed second fundamental form $Re(t\alpha)$ in the conformal structure $\sigma$. Moreover, for $t$ sufficiently large, there exists no such minimal immersion. Asymptotically, as $t \to 0$, the principal curvatures of one minimal immersion tend to zero, while the intrinsic curvatures of the other blow up in magnitude.Comment: 16 page

Lava Volume from Remote Sensing Data: Comparisons with Reverse Petrological Approaches for Two Types of Effusive Eruption

Five effusive eruptions of Piton de la Fournaise (La Réunion) are analyzed to investigate temporal trends of erupted mass and sulfur dioxide (SO2) emissions. Daily SO2 emissions are acquired from three ultraviolet (UV) satellite instruments (the Ozone Monitoring Instrument (OMI), the Ozone Mapping and Profiler Suite (OMPS), and the Tropospheric Monitoring Instrument (TROPOMI)) and an array of ground-based UV spectrometers (Network for Observation of Volcanic and Atmospheric Change (NOVAC)). Time-averaged lava discharge rates (TADRs) are obtained from two automatic satellite-based hot spot detection systems: MIROVA and MODVOLC. Assuming that the lava volumes measured in the field are accurate, the MIROVA system gave the best estimation of erupted volume among the methods investigated. We use a reverse petrological method to constrain pre-eruptive magmatic sulfur contents based on observed SO2 emissions and lava volumes. We also show that a direct petrological approach using SO2 data might be a viable alternative for TADR estimation during cloudy weather that compromises hot spot detection. In several eruptions we observed a terminal increase in TADR and SO2 emissions after initial emission of evolved degassed magma. We ascribe this to input of deeper, volatile-rich magma into the plumbing system towards the end of these eruptions. Furthermore, we find no evidence of volatile excess in the five eruptions studied, which were thus mostly fed by shallow degassed magma

A history of deformation within Pietre Cotte rhyolite flow (Vulcano)

International audienc

Unzipping Dynamics of Long DNAs

The two strands of the DNA double helix can be `unzipped' by application of 15 pN force. We analyze the dynamics of unzipping and rezipping, for the case where the molecule ends are separated and re-approached at constant velocity. For unzipping of 50 kilobase DNAs at less than about 1000 bases per second, thermal equilibrium-based theory applies. However, for higher unzipping velocities, rotational viscous drag creates a buildup of elastic torque to levels above kBT in the dsDNA region, causing the unzipping force to be well above or well below the equilibrium unzipping force during respectively unzipping and rezipping, in accord with recent experimental results of Thomen et al. [Phys. Rev. Lett. 88, 248102 (2002)]. Our analysis includes the effect of sequence on unzipping and rezipping, and the transient delay in buildup of the unzipping force due to the approach to the steady state.Comment: 15 pages Revtex file including 9 figure

Identification of morphological biosignatures in martian analogue field specimens using in situ planetary instrumentation

We have investigated how morphological biosignatures (i.e., features related to life) might be identified with an array of viable instruments within the framework of robotic planetary surface operations at Mars. This is the first time such an integrated lab-based study has been conducted that incorporates space-qualified instrumentation designed for combined in situ imaging, analysis, and geotechnics (sampling). Specimens were selected on the basis of feature morphology, scale, and analogy to Mars rocks. Two types of morphological criteria were considered: potential signatures of extinct life (fossilized microbial filaments) and of extant life (crypto-chasmoendolithic microorganisms). The materials originated from a variety of topical martian analogue localities on Earth, including impact craters, high-latitude deserts, and hydrothermal deposits. Our in situ payload included a stereo camera, microscope, Mössbauer spectrometer, and sampling device (all space-qualified units from Beagle 2), and an array of commercial instruments, including a multi-spectral imager, an X-ray spectrometer (calibrated to the Beagle 2 instrument), a micro-Raman spectrometer, and a bespoke (custom-designed) X-ray diffractometer. All experiments were conducted within the engineering constraints of in situ operations to generate realistic data and address the practical challenges of measurement

Relationship of Weather Types on the Seasonal and Spatial Variability of Rainfall, Runoff, and Sediment Yield in the Western Mediterranean Basin

Rainfall is the key factor to understand soil erosion processes, mechanisms, and rates. Most research was conducted to determine rainfall characteristics and their relationship with soil erosion (erosivity) but there is little information about how atmospheric patterns control soil losses, and this is important to enable sustainable environmental planning and risk prevention. We investigated the temporal and spatial variability of the relationships of rainfall, runoff, and sediment yield with atmospheric patterns (weather types, WTs) in the western Mediterranean basin. For this purpose, we analyzed a large database of rainfall events collected between 1985 and 2015 in 46 experimental plots and catchments with the aim to: (i) evaluate seasonal differences in the contribution of rainfall, runoff, and sediment yield produced by the WTs; and (ii) to analyze the seasonal efficiency of the different WTs (relation frequency and magnitude) related to rainfall, runoff, and sediment yield. The results indicate two different temporal patterns: the first weather type exhibits (during the cold period: autumn and winter) westerly flows that produce the highest rainfall, runoff, and sediment yield values throughout the territory; the second weather type exhibits easterly flows that predominate during the warm period (spring and summer) and it is located on the Mediterranean coast of the Iberian Peninsula. However, the cyclonic situations present high frequency throughout the whole year with a large influence extended around the western Mediterranean basin. Contrary, the anticyclonic situations, despite of its high frequency, do not contribute significantly to the total rainfall, runoff, and sediment (showing the lowest efficiency) because of atmospheric stability that currently characterize this atmospheric pattern. Our approach helps to better understand the relationship of WTs on the seasonal and spatial variability of rainfall, runoff and sediment yield with a regional scale based on the large dataset and number of soil erosion experimental stations.Spanish Government (Ministry of Economy and Competitiveness, MINECO) and FEDER Projects: CGL2014 52135-C3-3-R, ESP2017-89463-C3-3-R, CGL2014-59946-R, CGL2015-65569-R, CGL2015-64284-C2-2-R, CGL2015-64284-C2-1-R, CGL2016-78075-P, GL2008-02879/BTE, LEDDRA 243857, RECARE-FP7, CGL2017-83866-C3-1-R, and PCIN-2017-061/AEI. Dhais Peña-Angulo received a “Juan de la Cierva” postdoctoral contract (FJCI-2017-33652 Spanish Ministry of Economy and Competitiveness, MEC). Ana Lucia acknowledge the "Brigitte-Schlieben-Lange-Programm". The “Geoenvironmental Processes and Global Change” (E02_17R) was financed by the Aragón Government and the European Social Fund. José Andrés López-Tarazón acknowledges the Secretariat for Universities and Research of the Department of the Economy and Knowledge of the Autonomous Government of Catalonia for supporting the Consolidated Research Group 2014 SGR 645 (RIUS- Fluvial Dynamics Research Group). Artemi Cerdà thank the funding of the OCDE TAD/CRP JA00088807. José Martínez-Fernandez acknowledges the project Unidad de Excelencia CLU-2018-04 co-funded by FEDER and Castilla y León Government. Ane Zabaleta is supported by the Hydro-Environmental Processes consolidated research group (IT1029-16, Basque Government). This paper has the benefit of the Lab and Field Data Pool created within the framework of the COST action CONNECTEUR (ES1306)

Globular cluster luminosity function as distance indicator

Globular clusters are among the first objects used to establish the distance scale of the Universe. In the 1970-ies it has been recognized that the differential magnitude distribution of old globular clusters is very similar in different galaxies presenting a peak at M_V ~ -7.5. This peak magnitude of the so-called Globular Cluster Luminosity Function has been then established as a secondary distance indicator. The intrinsic accuracy of the method has been estimated to be of the order of ~0.2 mag, competitive with other distance determination methods. Lately the study of the Globular Cluster Systems has been used more as a tool for galaxy formation and evolution, and less so for distance determinations. Nevertheless, the collection of homogeneous and large datasets with the ACS on board HST presented new insights on the usefulness of the Globular Cluster Luminosity Function as distance indicator. I discuss here recent results based on observational and theoretical studies, which show that this distance indicator depends on complex physics of the cluster formation and dynamical evolution, and thus can have dependencies on Hubble type, environment and dynamical history of the host galaxy. While the corrections are often relatively small, they can amount to important systematic differences that make the Globular Cluster Luminosity Function a less accurate distance indicator with respect to some other standard candles.Comment: Accepted for publication in Astrophysics and Space Science. Review paper based on the invited talk at the conference "The Fundamental Cosmic Distance Scale: State of the Art and Gaia Perspective", Naples, May 2011. (13 pages, 8 figures