ESC Publications - Cambridge Univesity
Not a member yet
4214 research outputs found
Sort by
Illuminating Earth's Past, Present and Future The Science Plan for the International Ocean Discovery Program 2013 - 2023
No full textPlanning for the International Ocean Discovery Program began in early 2009 with the solicitation of input from the international community on scientific topics that could be addressed by a new ocean drilling program. In September 2009, approximately 600 scientists from 21 nations gathered at the INVEST conference in Bremen, Germany, to discuss and refine a set of scientific questions that require drilling and associated capabilities deep below the ocean floor (go to http://www.marum.de/Page7894.html to download a full copy of the INVEST report). Subsequent to this meeting, a science plan writing team was assembled, consisting of scientific leaders from Integrated Ocean Drilling Program member countries or consortia having expertise in geology, geophysics, geobiology, paleoclimatology, climate modeling, and geochemistry. This writing committee circulated an early draft of the science plan for community review and comment in late 2010. In early 2011, an external panel reviewed a revised draft, and additional comments and discussions contributed to substantive revision as the final document was prepared. This process demonstrates the foundational strength of scientific ocean drilling: the community’s ability to think big, challenge itself, and incorporate diverse ideas through a rigorous process of peer review and prioritization
Evidence for mechanical coupling and strong Indian lower crust beneath southern Tibet
No full textThis study shows that the contrast in tectonic regime between primarily strike-slip faulting in northern Tibet and dominantly normal faulting in southern Tibet requires mechanical coupling between the upper crust of southern Tibet and the underthrusting Indian crust. Such coupling is inconsistent with the presence of active /`channel flow/' beneath southern Tibet, and indicates that the Indian crust retains its strength as it underthrusts the plateau
Recent freshening in the Kara Sea (Siberia) recorded by stable isotopes in Arctic bivalve shells.
No full textOxygen and stable carbon isotope records along the growth direction on shells of the
bivalve species Astarte borealis and Serripes groenlandicus reliably record all important
aspects of the bottom water hydrography in the shallow southeastern Kara Sea, despite
uncertainties about the isotopic range due to sparse sampling and the possibility of growth
rate changes. Changing freshwater supply from the rivers Ob and Yenisei is the main
cause for seasonal temperature and salinity variations near the three sampling locations in
20 to 70 m water depth as suggested by CTD measurements and modeling. Peak winter
salinity of the simulated hydrographic data series and peak winter values in the isotope
records follow negative trends, which indicate a freshening of the bottom water due to an
increasing fraction of river water during the 1990s. This freshening affected the whole
Kara Sea, and coincided with a lowering of regional air pressure gradients, as indicated by
the declining Arctic oscillation index. The resulting weakening of the prevailing
southwesterly winds diminished the inflow of saline Atlantic-derived water from the
Barents Sea through the Kara Strait in the southwest, and, additionally, reduced the export
of river water toward the north and northeast into the Arctic basin. Saline Atlantic-derived
water thus was replaced by freshwater, which was successively accumulated in the
Kara Sea and accordingly imprinted on the stable isotope composition of the bivalve
shells. The 1990s freshening in the Kara Sea thus may be caused by natural variations
rather than being a signal for global change
Ordering and elasticity associated with low-temperature phase transitions in lawsonite.
No full textThe two low-temperature phase transitions of lawsonite have been studied using single-crystal
X-ray diffraction from 86 to 318 K and a single-crystal high-frequency continuous-wave resonance
technique from 323 to 102 K. While recently published data of the variations of strains, birefringence,
and IR line widths are consistent with the (271 K) Cmcm-Pmcn transition being simply tricritical, our
investigation of critical X-ray refl ections and the six diagonal elastic constants of lawsonite reveals,
consistently, a more complex crossover pattern in the temperature range of 205–225 K. Below 205 K
the overall pattern is again in good agreement with a tricritical solution of the Cmcm-Pmcn transition
and a second-order behavior of the (120 K) Pmcn-P21cn transition. The structure determination from
single-crystal X-ray data at 215 K reveals a possible orientational disorder of some of the hydroxyl
groups in the Pmcn phase. From this and a recent strain analysis of deuterated and hydrogenated lawsonite
we conclude that down to 205 K the Cmcm-Pmcn transition is driven by a displacive component,
as observed in strain and birefringence data, plus an order/disorder component or dynamical effects
associated with proton ordering. Below 205 K only the displacive component plays a role, and the (120
K) Pmcn-P21cn transition is driven by a single order parameter. The remarkable elastic softening of
C66 ahead of the Cmcm-Pmcn transition indicates another orthorhombic-monoclinic transition, which
is suppressed on cooling through the low-temperature phase sequence Cmcm-Pmcn-P21cn, but can be
observed on applying pressure to the mineral
Composition-induced structural phase transitions in the (Ba1-xLax)(2)In2O5+x (0 <= x <= 0. 6) system.
No full textComposition-induced structural phase changes across the high temperature, fast oxide ion conducting (Ba1xLax)2In2O5+x,
0pxp0.6, system have been carefully analysed using hard mode infrared (IR) powder absorption spectroscopy, X-ray powder
diffraction and electron diffraction. An orthorhombic brownmillerite to three-dimensionally disordered cubic perovskite phase
transition in this system is signalled by a drastic change in slope of both wavenumber and average line widths of IR spectra as a
function of composition. Some evidence is found for the existence of an intermediate tetragonal phase (previously reported to exist
from electron diffraction data) around x 0:2: The new spectroscopic data have been used to compare microscopic and
macroscopic strain parameters arising from variation in composition. The strain and spectroscopic data are consistent with firstorder
character for the tetragonal-orthorhombic transition, while the cubic-tetragonal transition could be continuous.
Differences between the variation with composition of spectral parameters and of macroscopic strain parameters are consistent with
a substantial order/disorder component for the transitions. There is also evidence for precursor effects within the cubic structure
before symmetry is broken
Simple Grid Access using the Business Process Execution Language
No full textScientists require means of exploiting large numbers of grid resources in a fully integrated manner
through the definition of computational processes specifying the sequence of tasks and services they
require. The deployment of such processes, however, can prove difficult in networked environments,
due to the presence of firewalls, software requirements and platform incompatibility. Using the Business
Process Execution Language (BPEL) standard, we propose here an architecture that builds on a
delegation model by which scientist may rely on middle-tier services to orchestrate subsets of the
processes on their behalf. We define a set of inter-related workflows that correspond to basic patterns
observed on the eMinerals minigrid. These will enable scientists to incorporate job submission and
monitoring, data storage and transfer management, and automated metadata harvesting in a single
unified process, which they may control from their desktops using the Simple Grid Access tool
Chlorine degassing during the lava dome-building eruption of Mount St Helens, USA, 2004-2005
No full textRemote measurements of volcanic gases from the Mount St. Helens lava dome were carried out using Open-Path Fourier-Transform Infrared spectroscopy on August 31, 2005. Measurements were performed at a site ~1 km from the lava dome, which was used as a source of IR radiation. On average, during the period of measurement, the volcanic gas contained 99 mol percent H2O, 0.78 percent CO2, 0.095 percent HCl, 0.085 percent SO2, 0.027 percent HF, 4.8×10-4 percent CO, and 2.5×10-4 percent COS close to the active vent. The fluxes of these species, constrained by synchronous measurements of SO2 flux, were 7,200 t/d H2O, 140 t/d CO2, 22 t/d SO2, 14 t/d HCl, 2.0 t/d HF, 54 kg/d CO, and 59 kg/d COS, ±20 percent. Observations of H2O/Cl in the vapor and melt are compared to models of closed- and open-system degassing and to models where a closed system dominates to depths as shallow as ~1 km, and gases are then allowed to escape through a permeable bubble network. Although several features are consistent with this model—for example, (1) H2O/Cl in the gases emitted from stagnant parts of the lava dome, (2) the concentration of Cl in the matrix glass of erupted dacite, and (3) the glass H2O/Cl—the gases emitted from the active part of the lava dome have much higher H2O/Cl than expected. These higher H2O/Cl levels result from a combination of two factors (1) the addition of substantial amounts of ground water or glacier-derived H2O to the gases at shallow depths, such that only ~10 mol percent of the measured H2O is magmatic, and (or) (2) some Cl present as alkali chloride (NaCl and KCl) in the gas phase. The mean molar Cl/S is similar to gases measured at other silicic subduction-zone volcanoes during effusive activity; this may be due to the influence of Cl in the vapor on S solubility in the melt, which produces a solubility maximum for S at vapor Cl/
Identifying and quantifying actinide radiation damage in ZrSiO4 minerals and ceramics with nuclear magnetic resonance
No full textThis paper discusses how high-resolution solid-state nuclear magnetic resonance (NMR) can be used to characterize and quantify radiation damage in natural minerals and ceramic nuclear waste forms that contain actinides. The scientific goal is to identify the nature of the amorphous component of the radiation damaged material through similar approaches to those where NMR has been used to study glasses and amorphous materials. NMR also allows the amount of amorphous material to be quantified as an atomic number fraction of the total. This is in contrast to traditional methods that express the damaged amorphous component as volume fractions of the total. Very old mineral samples of ZrSiO4 (zircon) containing 238U and 232Th with varying alpha radiation doses can be used to provide samples with differing levels of radiation damage. Radiation damage due to the emission of an alpha particle by an actinide nucleus is believed to occur through two distinct processes. The alpha particle itself (4.5 ? 5.5 MeV), will mainly cause ionizations during its flight through a material, it is also thought to cause a few hundred atomic displacements (Frenkel defects) as it is stopped by collision with atomic nuclei. The recoil of the heavy actinide nucleus (70-100 keV) is believed to cause the majority of the localized structural damage (amorphization) as it creates a cascade of collisions with surrounding ions. The extent and nature of this ''displacement cascade'' is the subject of extensive modeling by both ballistic and increasingly molecular dynamics methods. There is a profound need for experimental data to distinguish between these models
