102 research outputs found
Early development and tuning of a global coupled cloud resolving model, and its fast response to increasing CO2
Since the dawn of functioning numerical dynamical atmosphere- and ocean models, their resolution has steadily increased, fed by an exponential growth in computational capabilities. However, because resolution of models is at all times limited by computational power a number of mostly small-scale or micro-scale processes have to be parameterised. Particularly those of atmospheric moist convection and ocean eddies are problematic when scientists seek to interpret output from model experiments. Here we present the first coupled ocean-atmosphere model experiments with sufficient resolution to dispose of moist convection and ocean eddy parameterisations. We describe the early development and discuss the challenges associated with conducting the simulations with a focus on tuning the global mean radiation balance in order to limit drifts. A four-month experiment with quadrupled CO2 is then compared with a ten-member ensemble of low-resolution simulations using MPI-ESM1.2-LR. We find broad similarities of the response, albeit with a more diversified spatial pattern with both stronger and weaker regional warming, as well as a sharpening of precipitation in the inter tropical convergence zone. These early results demonstrate that it is already now possible to learn from such coupled model experiments, even if short by nature
Nuclear envelope structural defects cause chromosomal numerical instability and aneuploidy in ovarian cancer
<p>Abstract</p> <p>Background</p> <p>Despite our substantial understanding of molecular mechanisms and gene mutations involved in cancer, the technical approaches for diagnosis and prognosis of cancer are limited. In routine clinical diagnosis of cancer, the procedure is very basic: nuclear morphology is used as a common assessment of the degree of malignancy, and hence acts as a prognostic and predictive indicator of the disease. Furthermore, though the atypical nuclear morphology of cancer cells is believed to be a consequence of oncogenic signaling, the molecular basis remains unclear. Another common characteristic of human cancer is aneuploidy, but the causes and its role in carcinogenesis are not well established.</p> <p>Methods</p> <p>We investigated the expression of the nuclear envelope proteins lamin A/C in ovarian cancer by immunohistochemistry and studied the consequence of lamin A/C suppression using siRNA in primary human ovarian surface epithelial cells in culture. We used immunofluorescence microscopy to analyze nuclear morphology, flow cytometry to analyze cellular DNA content, and fluorescence <it>in situ </it>hybridization to examine cell ploidy of the lamin A/C-suppressed cells.</p> <p>Results</p> <p>We found that nuclear lamina proteins lamin A/C are often absent (47%) in ovarian cancer cells and tissues. Even in lamin A/C-positive ovarian cancer, the expression is heterogeneous within the population of tumor cells. In most cancer cell lines, a significant fraction of the lamin A/C-negative population was observed to intermix with the lamin A/C-positive cells. Down regulation of lamin A/C in non-cancerous primary ovarian surface epithelial cells led to morphological deformation and development of aneuploidy. The aneuploid cells became growth retarded due to a p53-dependent induction of the cell cycle inhibitor p21.</p> <p>Conclusions</p> <p>We conclude that the loss of nuclear envelope structural proteins, such as lamin A/C, may underlie two of the hallmarks of cancer - aberrations in nuclear morphology and aneuploidy.</p
The climate of a retrograde rotating Earth
To enhance understanding of Earth's climate, numerical experiments are
performed contrasting a retrograde and prograde rotating Earth using the Max
Planck Institute Earth system model. The experiments show that the sense of
rotation has relatively little impact on the globally and zonally averaged
energy budgets but leads to large shifts in continental climates, patterns
of precipitation, and regions of deep water formation.Changes in the zonal asymmetries of the continental climates are expected
given ideas developed more than a hundred years ago. Unexpected was, however,
the switch in the character of the EuropeanâAfrican climate with that of the
Americas, with a drying of the former and a greening of the latter. Also
unexpected was a shift in the storm track activity from the oceans to the
land in the Northern Hemisphere. The different patterns of storms and changes
in the direction of the trades influence fresh water transport, which may
underpin the change of the role of the North Atlantic and the Pacific in
terms of deep water formation, overturning and northward oceanic heat
transport. These changes greatly influence northern hemispheric climate and
atmospheric heat transport by eddies in ways that appear energetically
consistent with a southward shift of the zonally and annually averaged
tropical rain bands. Differences between the zonally averaged energy budget
and the rain band shifts leave the door open, however, for an important role
for stationary eddies in determining the position of tropical rains. Changes
in ocean biogeochemistry largely follow shifts in ocean circulation, but the
emergence of a super oxygen minimum zone in the Indian Ocean is not
expected. The upwelling of phosphate-enriched and nitrate-depleted water
provokes a dominance of cyanobacteria over bulk phytoplankton over vast areas â a phenomenon not observed in the prograde model.What would the climate of Earth look like if it would rotate in the reversed
(retrograde) direction? Which of the characteristic climate patterns in the
ocean, atmosphere, or land that are observed in a present-day climate are the
result of the direction of Earth's rotation? Is, for example, the structure
of the oceanic meridional overturning circulation (MOC) a consequence of the
interplay of basin location and rotation direction? In experiments with the
Max Planck Institute Earth system model (MPI-ESM), we investigate the effects
of a retrograde rotation in all aspects of the climate system.The expected consequences of a retrograde rotation are reversals of the zonal
wind and ocean circulation patterns. These changes are associated with major
shifts in the temperature and precipitation patterns. For example, the
temperature gradient between Europe and eastern Siberia is reversed, and the
Sahara greens, while large parts of the Americas become deserts.
Interestingly, the Intertropical Convergence Zone (ITCZ) shifts southward and
the modeled double ITCZ in the Pacific changes to a single ITCZ, a result of
zonal asymmetries in the structure of the tropical circulation.One of the most prominent non-trivial effects of a retrograde rotation is a
collapse of the Atlantic MOC, while a strong overturning cell emerges in the
Pacific. This clearly shows that the position of the MOC is not controlled by
the sizes of the basins or by mountain chains splitting the continents in
unequal runoff basins but by the location of the basins relative to the
dominant wind directions. As a consequence of the changes in the ocean
circulation, a super oxygen minimum zone develops in the Indian Ocean
leading to upwelling of phosphate-enriched and nitrate-depleted water. These
conditions provoke a dominance of cyanobacteria over bulk phytoplankton over
vast areas, a phenomenon not observed in the prograde model.</p
BerĂŒcksichtigung von Wandrauhigkeit in einem RANS-basierten CFD-Verfahren fĂŒr Turbomaschinenströmungen
Appropriate Turbulence Modelling for Turbomachinery Flows
The simulation quality of numerical flow simulations depends on the choice of physical modelling as well as an appropriate numerical treatment. In this study, a standard two-equation turbulence model has been extended for compressible, rotational flow as it occurs in turbomachinery and subsequently applied to different turbomachinery relevant flows of various complexity. Additionally, a number of different numerical schemes has been employed to evaluate their impact on the solution
Modifications of a Two-Equation Turbulence Model for Turbomachinery Fluid Flows
An improvement of simulation quality of turbomachinery fluid flows has been achieved in upgrading the original k-w turbulence model by Wilcox. The modifications cover fixes for anomalous turbulent energy production and alterations to include the effects of compressibility and rotation. Furthermore, a block-local transition model which is based on experimental correlations has been implemented. Finally, the performance of modifications presented is demonstrated on turbomachinery flows which are relevant to applications in industrial aero design
New structure and function in plant K+ channels: KCO1, an outward rectifier with a steep Ca2+ dependency.
Potassium (K+) channels mediating important physiological functions are characterized by a common pore-forming (P) domain. We report the cloning and functional analysis of the first higher plant outward rectifying K+ channel (KCO1) from Arabidopsis thaliana. KCO1 belongs to a new class of 'two-pore' K+ channels recently described in human and yeast. KCO1 has four putative transmembrane segments and tandem calcium-binding EF-hand motifs. Heterologous expression of KCO1 in baculovirus-infected insect (Spodoptera frugiperda) cells resulted in outwardly rectifying, K+-selective currents elicited by depolarizing voltage pulses in whole-cell measurements. Activation of KCO1 was strongly dependent on the presence of nanomolar concentrations of cytosolic free Ca2+ [Ca2+]cyt. No K+ currents were detected when [Ca2+]cyt was adjusted to <150 nM. However, KCO1 strongly activated at increasing [Ca2+]cyt, with a saturating activity observed at approximately 300 nM [Ca2+]cyt. KCO1 single channel analysis on excised membrane patches, resulting in a single channel conductance of 64 pS, confirmed outward rectification as well as Ca2+-dependent activation. These data suggest a direct link between calcium-mediated signaling processes and K+ ion transport in higher plants. The identification of KCO1 as the first plant K+ outward channel opens a new field of structure-function studies in plant ion channels
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