83 research outputs found
Signatures of cosmic tau-neutrinos
The importance and signatures of cosmic tau--(anti)neutrinos have been
studied for upward-- and downward--going and hadronic shower
event rates relevant for present and future underground water or ice detectors,
utilizing the unique and reliable ultrasmall-- predictions of the dynamical
(radiative) parton model. The upward--going event rates
calculated just from cosmic fluxes are sizeably
enhanced by taking into account cosmic fluxes
and their associated fluxes as well. The coupled transport
equations for the upward--going flux traversing
the Earth imply an enhancement of the attenuated and regenerated
flux typically around GeV with respect
to the initial cosmic flux. This enhancement turns out to be smaller than
obtained so far, in particular for flatter initial cosmic fluxes behaving like
. Downward--going events and in particular the
background--free and unique hadronic `double bang' and `lollipop' events allow
to test downward--going cosmic fluxes up to
about GeV.Comment: 32 pages, 6 figures; Added reference
How to identify groundwater-caused thermal anomalies in lakes based on multi-temporal satellite data in semi-arid regions
The deduction by conventional means of qualitative and quantitative information about groundwater
discharge into lakes is complicated. Nevertheless, at
least for semi-arid regions with limited surface water availability, this
information is crucial to ensure future water availability for drinking and
irrigation purposes.
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Overcoming this lack of discharge information, we present a satellite-based
multi-temporal sea-surface-temperature (SST) approach. It exploits the
occurrence of thermal anomalies to outline groundwater discharge locations
using the example of the Dead Sea. Based on a set of 19 Landsat Enhanced Thematic Mapper (ETM+) images
6.2 (high gain), recorded between 2000 and 2002, we developed a novel
approach which includes (i) an objective exclusion of surface-runoff-influenced data which would otherwise lead to erroneous results and (ii) a
temporal SST variability analysis based on six statistical measures
amplifying thermal anomalies caused by groundwater.
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After excluding data influenced by surface runoff, we concluded that spatial
anomaly patterns of the standard deviation and range of the SST data series
spatially fit best to in situ observed discharge locations and, hence, are
most suitable for detecting groundwater discharge sites
KiDS+VIKING+GAMA: Halo occupation distributions and correlations of satellite numbers with a new halo model of the galaxy-matter bispectrum for galaxy-galaxy-galaxy lensing
Halo models and halo occupation distributions (HODs) are important tools to
model the galaxy and matter distribution. We present and assess a new method
for constraining the parameters of HODs using the gravitational lensing shear
around galaxy pairs, galaxy-galaxy-galaxy-lensing (G3L). In contrast to
galaxy-galaxy-lensing, G3L is sensitive to correlations between the per-halo
numbers of galaxies from different populations. We use G3L to probe these
correlations and test the default hypothesis that they are negligible. We
derive a halo model for G3L and validate it with realistic mock data from the
Millennium Simulation and a semi-analytic galaxy model. Then, we analyse public
data from the Kilo-Degree Survey (KiDS), the VISTA Infrared Kilo-Degree Galaxy
Survey (VIKING) and data from the Galaxy And Mass Assembly Survey (GAMA) to
infer the HODs of galaxies at in five different stellar mass bins
between and and two colours
(red and blue), as well as correlations between satellite numbers. The analysis
recovers the true HODs in the simulated data within the credibility
range. The inferred HODs vary significantly with colour and stellar mass. There
is also strong evidence () for correlations, increasing with halo
mass, between the numbers of red and blue satellites and galaxies with stellar
masses below $10^{10} \Msun. Possible causes of these correlations are the
selection of similar galaxies in different samples, the survey flux limit, or
physical mechanisms like a fixed ratio between the satellite numbers of
distinct populations. The decorrelation for halos with smaller masses is
probably an effect of shot noise by low-occupancy halos. The inferred HODs can
be used to complement galaxy-galaxy-lensing or galaxy clustering HOD studies or
as input to cosmological analyses and improved mock galaxy catalogues.Comment: 20 pages + Appendix, 14 Figures. Submitted to Astronomy &
Astrophysics. Abstract is abridge
Intrinsic Superconductivity at 25 K in Highly Oriented Pyrolytic Graphite
High resolution magnetoresistance data in highly oriented pyrolytic graphite
thin samples manifest non-homogenous superconductivity with critical
temperature K. These data exhibit: i) hysteretic loops of
resistance versus magnetic field similar to Josephson-coupled grains, ii)
quantum Andreev's resonances and iii) absence of the Schubnikov-de Haas
oscillations. The results indicate that graphite is a system with
non-percolative superconducting domains immersed in a semiconducting-like
matrix. As possible origin of the superconductivity in graphite we discuss
interior-gap superconductivity when two very different electronic masses are
present.Comment: 5 pages, 3 figure
A fitting formula for the non-Gaussian contribution to the lensing power spectrum covariance
Weak gravitational lensing is one of the most promising tools to investigate
the equation-of-state of dark energy. In order to obtain reliable parameter
estimations for current and future experiments, a good theoretical
understanding of dark matter clustering is essential. Of particular interest is
the statistical precision to which weak lensing observables, such as cosmic
shear correlation functions, can be determined. We construct a fitting formula
for the non-Gaussian part of the covariance of the lensing power spectrum. The
Gaussian contribution to the covariance, which is proportional to the lensing
power spectrum squared, and optionally shape noise can be included easily by
adding their contributions. Starting from a canonical estimator for the
dimensionless lensing power spectrum, we model first the covariance in the halo
model approach including all four halo terms for one fiducial cosmology and
then fit two polynomials to the expression found. On large scales, we use a
first-order polynomial in the wave-numbers and dimensionless power spectra that
goes asymptotically towards for , i.e., the result for
the non-Gaussian part of the covariance using tree-level perturbation theory.
On the other hand, for small scales we employ a second-order polynomial in the
dimensionless power spectra for the fit. We obtain a fitting formula for the
non-Gaussian contribution of the convergence power spectrum covariance that is
accurate to 10% for the off-diagonal elements, and to 5% for the diagonal
elements, in the range and can be used for
single source redshifts in WMAP5-like cosmologies.Comment: 23 pages, 15 figures, submitted to A&
A SEPT1-based scaffold is required for Golgi integrity and function
Compartmentalization of membrane transport and signaling processes is of pivotal importance to eukaryotic cell function. While plasma membrane compartmentalization and dynamics are well known to depend on the scaffolding function of septin GTPases, the roles of septins at intracellular membranes have remained largely elusive. Here, we show that the structural and functional integrity of the Golgi depends on its association with a septin 1 (SEPT1)-based scaffold, which promotes local microtubule nucleation and positioning of the Golgi. SEPT1 function depends on the Golgi matrix protein GM130 (also known as GOLGA2) and on centrosomal proteins, including CEP170 and components of γ-tubulin ring complex (γ-Turc), to facilitate the perinuclear concentration of Golgi membranes. Accordingly, SEPT1 depletion triggers a massive fragmentation of the Golgi ribbon, thereby compromising anterograde membrane traffic at the level of the Golgi
New perspectives on interdisciplinary earth science at the Dead Sea: The DESERVE project
The Dead Sea region has faced substantial environmental challenges in recent decades, including water resource scarcity, ~ 1 m annual decreases in the water level, sinkhole development, ascending-brine freshwater pollution, and seismic disturbance risks. Natural processes are significantly affected by human interference as well as by climate change and tectonic developments over the long term. To get a deep understanding of processes and their interactions, innovative scientific approaches that integrate disciplinary research and education are required. The research project DESERVE (Helmholtz Virtual Institute Dead Sea Research Venue) addresses these challenges in an interdisciplinary approach that includes geophysics, hydrology, and meteorology. The project is implemented by a consortium of scientific institutions in neighboring countries of the Dead Sea (Israel, Jordan, Palestine Territories) and participating German Helmholtz Centres (KIT, GFZ, UFZ). A new monitoring network of meteorological, hydrological, and seismic/geodynamic stations has been established, and extensive field research and numerical simulations have been undertaken. For the first time, innovative measurement and modeling techniques have been applied to the extreme conditions of the Dead Sea and its surroundings. The preliminary results show the potential of these methods. First time ever performed eddy covariance measurements give insight into the governing factors of Dead Sea evaporation. High-resolution bathymetric investigations reveal a strong correlation between submarine springs and neo-tectonic patterns. Based on detailed studies of stratigraphy and borehole information, the extension of the subsurface drainage basin of the Dead Sea is now reliably estimated. Originality has been achieved in monitoring flash floods in an arid basin at its outlet and simultaneously in tributaries, supplemented by spatio-temporal rainfall data. Low-altitude, high resolution photogrammetry, allied to satellite image analysis and to geophysical surveys (e.g. shear-wave reflections) has enabled a more detailed characterization of sinkhole morphology and temporal development and the possible subsurface controls thereon. All the above listed efforts and scientific results take place with the interdisciplinary education of young scientists. They are invited to attend joint thematic workshops and winter schools as well as to participate in field experiments
Microbial and Chemical Characterization of Underwater Fresh Water Springs in the Dead Sea
Due to its extreme salinity and high Mg concentration the Dead Sea is characterized by a very low density of cells most of which are Archaea. We discovered several underwater fresh to brackish water springs in the Dead Sea harboring dense microbial communities. We provide the first characterization of these communities, discuss their possible origin, hydrochemical environment, energetic resources and the putative biogeochemical pathways they are mediating. Pyrosequencing of the 16S rRNA gene and community fingerprinting methods showed that the spring community originates from the Dead Sea sediments and not from the aquifer. Furthermore, it suggested that there is a dense Archaeal community in the shoreline pore water of the lake. Sequences of bacterial sulfate reducers, nitrifiers iron oxidizers and iron reducers were identified as well. Analysis of white and green biofilms suggested that sulfide oxidation through chemolitotrophy and phototrophy is highly significant. Hyperspectral analysis showed a tight association between abundant green sulfur bacteria and cyanobacteria in the green biofilms. Together, our findings show that the Dead Sea floor harbors diverse microbial communities, part of which is not known from other hypersaline environments. Analysis of the water’s chemistry shows evidence of microbial activity along the path and suggests that the springs supply nitrogen, phosphorus and organic matter to the microbial communities in the Dead Sea. The underwater springs are a newly recognized water source for the Dead Sea. Their input of microorganisms and nutrients needs to be considered in the assessment of possible impact of dilution events of the lake surface waters, such as those that will occur in the future due to the intended establishment of the Red Sea−Dead Sea water conduit
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