Insights into plant water uptake from xylem‐water isotope measurements in two tropical catchments with contrasting moisture conditions

Water transpired by trees has long been assumed to be sourced from the same subsurface water stocks that contribute to groundwater recharge and streamflow. However, recent investigations using dual water stable isotopes have shown an apparent ecohydrological separation between tree‐transpired water and stream water. Here we present evidence for such ecohydrological separation in two tropical environments in Puerto Rico where precipitation seasonality is relatively low and where precipitation is positively correlated with primary productivity. We determined the stable isotope signature of xylem water of 30 mahogany (Swietenia spp.) trees sampled during two periods with contrasting moisture status. Our results suggest that the separation between transpiration water and groundwater recharge/streamflow water might be related less to the temporal phasing of hydrologic inputs and primary productivity, and more to the fundamental processes that drive evaporative isotopic enrichment of residual soil water within the soil matrix. The lack of an evaporative signature of both groundwater and streams in the study area suggests that these water balance components have a water source that is transported quickly to deeper subsurface storage compared to waters that trees use. A Bayesian mixing model used to partition source water proportions of xylem water showed that groundwater contribution was greater for valley‐bottom, riparian trees than for ridge‐top trees. Groundwater contribution was also greater at the xeric site than at the mesic–hydric site. These model results (1) underline the utility of a simple linear mixing model, implemented in a Bayesian inference framework, in quantifying source water contributions at sites with contrasting physiographic characteristics, and (2) highlight the informed judgement that should be made in interpreting mixing model results, of import particularly in surveying groundwater use patterns by vegetation from regional to global scales. Copyright © 2016 John Wiley & Sons, Ltd.     

AstroGrid-D: Grid technology for astronomical science

We present status and results of AstroGrid-D, a joint effort of astrophysicists and computer scientists to employ grid technology for scientific applications. AstroGrid-D provides access to a network of distributed machines with a set of commands as well as software interfaces. It allows simple use of computer and storage facilities and to schedule or monitor compute tasks and data management. It is based on the Globus Toolkit middleware (GT4).Chapter 1 describes the context which led to the demand for advanced software solutions in Astrophysics, and we state the goals of the project.We then present characteristic astrophysical applications that have been implemented on AstroGrid-D in chapter 2. We describe simulations of different complexity, compute-intensive calculations running on multiple sites (Section 2.1), and advanced applications for specific scientific purposes (Section 2.2), such as a connection to robotic telescopes (Section 2.2.3). We can show from these examples how grid execution improves e.g. the scientific workflow.Chapter 3 explains the software tools and services that we adapted or newly developed. Section 3.1 is focused on the administrative aspects of the infrastructure, to manage users and monitor activity. Section 3.2 characterises the central components of our architecture: The AstroGrid-D information service to collect and store metadata, a file management system, the data management system, and a job manager for automatic submission of compute tasks.We summarise the successfully established infrastructure in chapter 4, concluding with our future plans to establish AstroGrid-D as a platform of modern e-Astronomy.     

X-ray Spectromicroscopy of Mineral Intergrowths in the Santa Catharina Meteorite

This work describes the application of microfocus X-ray absorption spectroscopy (XAS) and X-ray photo-emission electron microscopy (XPEEM) to the study of the complex mineralogical intergrowths within the Santa Catharina meteorite. The Santa Catharina meteorite of this study (BM52283 from the meteorite collection of the Natural History Museum, London, UK) primarily comprises a taenite bulk host phase (Fe:Ni ratio = 70.9 ± 0.8%:29.1 ± 0.8%) with a set of oxide-bearing cloudy zone textured regions (Fe:Ni:O ratio = 40.4 ± 0.3%:49.0 ± 0.7%:10.6 ± 0.8% at the core and Fe:Ni:O ratio = 34.4 ± 1.5%:42.7 ± 0.6%:22.9 ± 1.8% towards the rims) and numerous schreibersite (Fe:Ni:P ratio = 38.6 ± 1.6%:38.4 ± 0.9%:23.0 ± 0.5%) inclusions. Between the schreibersite and the taenite are rims up to 50 μm across of Ni-rich kamacite (Fe:Ni ratio = 93.4 ± 0.4%:6.6 ± 0.5%). No chemical zoning or spatial variations in the Fe and Ni speciation was observed within either the schreibersite or the kamacite phases. The oxide-bearing cloudy zone textured regions mostly comprise metallic Fe–Ni alloy, predominantly tetrataenite. Within the oxide phases, the Fe is predominantly, but not entirely, tetrahedrally co-ordinated Fe³⁺ and the Ni is octahedrally co-ordinated Ni²⁺. Structural analysis supports the suggestion that non-stoichiometric Fe₂NiO₄ trevorite is the oxide phase. The trevorite:tetrataenite ratio increases at the edges of the oxide-bearing cloudy zone textured regions indicating increased oxidation at the edges of these zones. The spatial resolution of the XPEEM achieved was between 110 and 150 nm, which precluded the study of either the previously reported ∼ 10 nm precipitates of tetrataenite within the bulk taenite or any antitaenite.     

Dynamics of Mars Trojans

In this paper we explore the dynamical stability of the Mars Trojan region applying mainly Laskar's Frequency Map Analysis. This method yields the chaotic diffusion rate of orbits and allows to determine the most stable regions. It also gives the frequencies which are responsible for the instability of orbits. The most stable regions are found for inclinations between about 15° and 30°. For inclinations smaller than 15°, we confirm, by applying a synthetic secular theory, that the secular resonances ν₃, ν₄, ν₁₃, ν₁₄ rapidly excite asteroid orbits within a few Myrs, or even faster. The asteroids are removed from the Trojan region after a close encounter with Mars. For large inclinations, the secular resonance ν₅ clears a small region around 30° while the Kozai resonance rapidly removes bodies for inclinations larger than 35°. The dynamical lifetimes of the three L5 Trojans, (5261) Eureka, 1998 VF31, 2001 DH47, and the only L4 Trojan 1999 UJ7 are determined by numerically integrating clouds of corresponding clones over the age of the Solar System. All four Trojans reside in the most stable region with smallest diffusion coefficients. Their dynamical half-lifetime is of the order of the age of the Solar System. The Yarkovsky force has little effect on the known Trojans but for bodies smaller than about 1-5 m the drag is strong enough to destabilize Trojans on a timescale shorter than 4.5 Gyr.     

Benkovac Stone (Eocene,Croatia): a deep-sea Plattenkalk?

In contrast to Solnhofen-type conservation Lagerstätten, the platy limestones of the Benkovac Stone of the Eocene of Croatia contains a variety of trace fossils. They belong to the Nereites ichnofacies, characterized by a suite of highly specialized ichnogenera, turbiditic preservation, and distinctive pre-event versus post-event communities. In siliciclastic rocks, this ichnofacies stands for turbiditic deep-sea sediments. Also unusual is the lack of body fossils. The only exceptions are occasional plant debris and Bencovacina concentrica. n. gen., n. sp., which is affiliated with xenophyophorian Foraminifera. These giant protozoans survive on present deep-sea bottoms, but they were also common on the shallow-marine biomats in Ediacaran times. These findings contradict the current shallow-marine interpretation, which is based on the regional geologic setting and sedimentary structures typical for tempestites. Thus, the Benkovac Stone would be an ideal place to test the reliability of ichnological versus sedimentological depth criteria in an entirely calcareous sequence.     

Automatic Detection and Classification of Coronal Holes and Filaments Based on EUV and Magnetogram Observations of the Solar Disk

A new method for the automated detection of coronal holes and filaments on the solar disk is presented. The starting point is coronal images taken by the Extreme Ultraviolet Telescope on the Solar and Heliospheric Observatory (SOHO/EIT) in the Fe ix/x 171 Å, Fe xii 195 Å, and He ii 304 Å extreme ultraviolet (EUV) lines and the corresponding full-disk magnetograms from the Michelson Doppler Imager (SOHO/MDI) from different phases of the solar cycle. The images are processed to enhance their contrast and to enable the automatic detection of the two candidate features, which are visually indistinguishable in these images. Comparisons are made with existing databases, such as the He i 10830 Å NSO/Kitt Peak coronal-hole maps and the Solar Feature Catalog (SFC) from the European Grid of Solar Observations (EGSO), to discriminate between the two features. By mapping the features onto the corresponding magnetograms, distinct magnetic signatures are then derived. Coronal holes are found to have a skewed distribution of magnetic-field intensities, with values often reaching 100?–?200 gauss, and a relative magnetic-flux imbalance. Filaments, in contrast, have a symmetric distribution of field intensity values around zero, have smaller magnetic-field intensity than coronal holes, and lie along a magnetic-field reversal line. The identification of candidate features from the processed images and the determination of their distinct magnetic signatures are then combined to achieve the automated detection of coronal holes and filaments from EUV images of the solar disk. Application of this technique to all three wavelengths does not yield identical results. Furthermore, the best agreement among all three wavelengths and NSO/Kitt Peak coronal-hole maps occurs during the declining phase of solar activity. The He ii data mostly fail to yield the location of filaments at solar minimum and provide only a subset at the declining phase or peak of the solar cycle. However, the Fe ix/x 171 Å and Fe xii 195 Å data yield a larger number of filaments than the Hα data of the SFC.     

Partial fusion of basic granulites at 5 to 15 kbar: implications for the origin of TTG magmas

Partial fusion experiments with basic granulites (S6, S37) believed to represent the lower crust beneath the Eifel region (Germany) were performed at pressures from 5 to 15 kbar. Water-undersaturated experiments were carried out in the presence of 1 wt% H₂O plus 2.44 or 0.81 wt% CO₂ equivalent to mole fractions of H₂O/(H₂O + CO₂) of 0.5 and 0.75, respectively, of the volatile components added. At temperatures from 850 to 1100 °C the weight proportions of melt range from 7 to 30 %. Melt compositions change from trondhjemitic over tonalitic to dioritic with increasing degree of partial melting. Crystalline residua are plagioclase/pyroxene dominated at 5 kbar to garnet/pyroxene dominated at 15␣kbar. Dehydration melting was studied in granulite S35 similar in composition to S6. The magmatic precursors of the granulite xenoliths used in this study had geochemical characteristics of cumulate gabbro (metagabbro S37) and evolved melts (metabasalts S6, S35), respectively. Melts from granulite S37 match the major element compositions of natural trondhjemites and tonalites. At 5 kbar, their Al₂O₃ is relatively low, similar to tonalites from ophiolites. At 15 kbar, Al₂O₃ in the melts is high due to the near absence of plagioclase in the crystalline residua. The Al₂O₃ concentrations in 15 kbar melts from S6 (˜20 wt%) are higher than in natural tonalites. Depth constraints on the formation of tonalitic magmas in the continental crust are provided by REE (rare earth element) patterns of the synthetic melts calculated from the known REE abundances in metagabbro S37 and metabasalt S6 assuming batch melting and using partition coefficients from the literature. The REE patterns of tonalites from active continental margins and Archean trondhjemite-tonalite-granodiorite␣associations low in REE with La_N (chondrite normalised) from 10 to 30 and Yb_N from 1 to 2 are reproduced at pressures of 10 and 12.5 kbar from metagabbro S37 which displays a slightly L(light)REE enriched pattern with La_N = 8 and Yb_N = 3. Natural tonalites with La_N from 30 to 100 require a source richer in REE than granulite S37. At 15 kbar, H(heavy)REE_N in melts from granulite S37 are depressed below the level observed in natural tonalites due to the high proportion of garnet (>30 wt%) in the residue. Melts from metabasalt S6 (enriched in REE with La_N = 38 and Yb_N = 16) do not match the REE characteristics of natural tonalites under any conditions. Received: 1 July 1994 / Accepted: 11 September 1996     

Observations of the performance of buildings during the 1985 Mexico earthquake,and structural design implications

Summary The high amplification of the 1985 Mexico City earthquake is explained by the large number of strong and nearly continuous cycles of 2 s period motion lasting for more than 30 s. The type of damage caused by the earthquake—particularly to engineered multi-storey buildings of high flexibility is described, and methods of adding damping and stiffness elements to reduce and resist earthquake demand forces are discussed.