7,265 research outputs found
Improving a joint inversion of GRACE, GPS and modelled ocean bottom pressure by using in-situ data.
To investigate the changes in ocean bottom pressure (OBP) and ocean mass Rietbroek et al. (2009) performed a joint least square inversion of weekly GRACE solutions, patterns of large-scale deformation measured by a network of GPS stations and modelled OBP from the Finite Element Sea ice Ocean Model (FESOM). The correlation of this inversion with in-situ OBP ranges between 0.7 and 0.8 in some regions but for example in the tropical Atlantic the correlation is below 0.4. To improve the agreement of the inversion with in-situ data, a part of the in-situ data is included directly into the inversion. The in-situ OBP data was taken from the global OBP data base of Macrander et al. (2010) and averaged to weekly means. Depending on the weight put on the in-situ data, the correlation and regression increases significantly to a value larger than 0.9.
The variance of the system is locally reduced by almost 50% at the locations included into the inversion while the difference of the global ocean mean is on average below 10%. Furthermore the global ocean mean is used to compute a bias term for correcting the global ocean mean obtained by the FESOM model
The dynamical balance, transport and circulation of the Antarctic Circumpolar Current
The physical ingredients of the ACC circulation are reviewed. A picture of thecirculation is sketched by means of recent observations of the WOCE decade. Wepresent and discuss the role of forcing functions (wind stress, surfacebuoyancy flux) in the balance of the (quasi)-zonal flow, the meridionalcirculation and their relation to the ACC transport. Emphasis will be on theinterrelation of the zonal momentum balance and the meridional circulation, theimportance of diapycnal mixing and eddy processes. Finally, new model conceptsare described: a model of the ACC transport dependence on wind stress andbuoyancy flux, based on linear wave theory; and a model of the meridionaloverturning of the Southern Ocean, based on zonally averaged dynamics with eddyparameterization
Ventilation times scales for a subtropical bay from 3-D modelling
[Abstract]: We applied a multi-purpose three-dimensional ocean general circulation model to
compute water renewal time scales for a large coastal embayment situated off the
central eastern coast of Australia (Hervey Bay) that shows features of an inverse estuary.
Water renewal or ventilation time scales are not directly observable but can easily
be diagnosed from numerical simulations. Improved knowledge of these time scales
can assists in evaluating the water quality of coastal environments and can be utilised
in sustainable marine resource management.
The numerical studies are performed with the COupled Hydrodynamical Ecological
model for REgioNal Shelf seas (COHERENS). The model, adopted for Hervey Bay,
provided insight into ventilation pathways, and renewal time scales were found to exhibit
a strong spatial variability. More than 80 % of the coastal embayment was fully
ventilated after about 70-100 days, with the eastern and western shallow coastal regions
ventilated more rapidly than the central, deeper part of the bay.
The concept of a single ’typical’ ventilation timescale characterising this particular
coastal embayment is inadequate and the consideration of spatial variability is clearly
important, hence in a second set of simulations local monitoring boxes and Lagrangian
tracers have been used to focus on this spatial variability. Simple parameters are derived
to estimate local sedimentation, transport processes or places of high/low biological
production
Identification of novel therapeutic targets in the PI3K/AKT/mTOR pathway in hepatocellular carcinoma using targeted next generation sequencing.
Understanding genetic aberrations in cancer leads to discovery of new targets for cancer therapies. The genomic landscape of hepatocellular carcinoma (HCC) has not been fully described. Therefore, patients with refractory advanced/metastatic HCC referred for experimental therapies, who had adequate tumor tissue available, had targeted next generation sequencing (NGS) of their tumor samples using the Illumina HiSeq 2000 platform (Foundation One, Foundation Medicine, MA) and their treatment outcomes were analyzed. In total, NGS was obtained for 14 patients (median number of prior therapies, 1) with advanced/metastatic HCC. Of these 14 patients, 10 (71%) were men, 4 (29%) women, 6 (43%) had hepatitis B or C-related HCC. NGS revealed at least 1 molecular abnormality in 12 patients (range 0-8, median 2). Detected molecular aberrations led to putative activation of the PI3K/AKT/mTOR pathway (n=3 [mTOR, PIK3CA, NF1]), Wnt pathway (n=6 [CTNNA1, CTNNB1]), MAPK pathway (n=2 [MAP2K1, NRAS]), and aberrant DNA repair mechanisms, cell cycle control and apoptosis (n=18 [ATM, ATR, BAP1, CCND1, CDKN2A, CDK4, FGF3, FGF4, FGF19, MCL1, MDM2, RB1, TP53]). Of the 3 patients with molecular aberrations putatively activating the PI3K/AKT/mTOR pathway, 2 received therapies including a mTOR inhibitor and all demonstrated therapeutic benefit ranging from a partial response to minor shrinkage per RECIST (-30%, -15%; respectively). In conclusion, genomic alterations are common in advanced HCC. Refractory patients with alterations putatively activating the PI3K/AKT/mTOR pathway demonstrated early signals of clinical activity when treated with therapies targeting mTOR
Coherent Patterning of Matter Waves with Subwavelength Localization
We propose the Subwavelength Localization via Adiabatic Passage (SLAP)
technique to coherently achieve state-selective patterning of matter waves well
beyond the diffraction limit. The SLAP technique consists in coupling two
partially overlapping and spatially structured laser fields to three internal
levels of the matter wave yielding state-selective localization at those
positions where the adiabatic passage process does not occur. We show that by
means of this technique matter wave localization down to the single nanometer
scale can be achieved. We analyze in detail the potential implementation of the
SLAP technique for nano-lithography with an atomic beam of metastable Ne* and
for coherent patterning of a two-component 87Rb Bose-Einstein condensate.Comment: 6 pages, 5 figure
Magnetoelectric effects in an organo-metallic quantum magnet
We observe a bilinear magnetic field-induced electric polarization of 50 in single crystals of NiCl-4SC(NH) (DTN). DTN forms a
tetragonal structure that breaks inversion symmetry, with the highly polar
thiourea molecules all tilted in the same direction along the c-axis.
Application of a magnetic field between 2 and 12 T induces canted
antiferromagnetism of the Ni spins and the resulting magnetization closely
tracks the electric polarization. We speculate that the Ni magnetic forces
acting on the soft organic lattice can create significant distortions and
modify the angles of the thiourea molecules, thereby creating a magnetoelectric
effect. This is an example of how magnetoelectric effects can be constructed in
organo-metallic single crystals by combining magnetic ions with electrically
polar organic elements.Comment: 3 pages, 3 figure
Perturbation expansion for the diluted two-dimensional XY model
We study the quasi-long-range ordered phase of a 2D XY model with quenched
site-dilution using the spin-wave approximation and expansion in the parameter
which characterizes the deviation from completely homogeneous dilution. The
results, obtained by keeping the terms up to the third order in the expansion,
show good accordance with Monte Carlo data in a wide range of dilution
concentrations far enough from the percolation threshold. We discuss different
types of expansion.Comment: 8 pages, 1 eps figure, style file include
A Structured Approach to Scenario Generation for the Design of Crew Expert Tool
It is often difficult to identify the ways in which
innovative systems can be used to support the crews on
long duration space missions over the coming decades.
This paper presents a structured approach towards
scenario generation for crew autonomous operations
during these future missions. The proposed approach
will help to systematically generate scenarios that help
define the design requirements for mission related
equipment. A crew expert tool is used to illustrate our
approach. This system is intended to help
crewmembers identify and then resolve complex system
failures in situations where it may not be possible to call
upon immediate technical assistance from ground
support staff. Our approach to scenario design helps to
identify ways in which such an application may support
crew tasks during the initial development of the
application
Human Mission to Mars: Designing a Crew Expert Tool for a Safety Critical Environment
On a mission to other planets, the crew would come
across situations and challenges that have not been
foreseen even by experienced engineers, designers,
scientists and previous explorers. This paper considers
existing problem solving approaches that can help
structure the development of ‘troubleshooting support
tools’ for autonomous crews during long-duration
missions. It also considers the suitability of these
problem solving techniques for crew autonomous
operations
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