5,094 research outputs found
Models of Saturn's Interior Constructed with Accelerated Concentric Maclaurin Spheroid Method
The Cassini spacecraft's Grand Finale orbits provided a unique opportunity to
probe Saturn's gravity field and interior structure. Doppler measurements
yielded unexpectedly large values for the gravity harmonics J_6, J_8, and J_10
that cannot be matched with planetary interior models that assume uniform
rotation. Instead we present a suite of models that assume the planet's
interior rotates on cylinders, which allows us to match all the observed even
gravity harmonics. For every interior model, the gravity field is calculated
self-consistently with high precision using the Concentric Maclaurin Spheroid
(CMS) method. We present an acceleration technique for this method, which
drastically reduces the computational cost, allows us to efficiently optimize
model parameters, map out allowed parameter regions with Monte Carlo sampling,
and increases the precision of the calculated J_2n gravity harmonics to match
the error bars of the observations, which would be difficult without
acceleration. Based on our models, Saturn is predicted to have a dense central
core of 15-18 Earth masses and an additional 1.5-5 Earth masses of heavy
elements in the envelope. Finally, we vary the rotation period in the planet's
deep interior and determine the resulting oblateness, which we compare with the
value from radio occultation measurements by the Voyager spacecraft. We predict
a rotation period of 10:33:34 h +- 55s, which is in agreement with recent
estimates derived from ring seismology.Comment: 12 color figures, 5 tables, Astrophysical Journal, in press (2019
The CRESST Dark Matter Search
We present first competitive results on WIMP dark matter using the
phonon-light-detection technique. A particularly strong limit for WIMPs with
coherent scattering results from selecting a region of the phonon-light plane
corresponding to tungsten recoils. The observed count rate in the neutron band
is compatible with the rate expected from neutron background. CRESST is
presently being upgraded with a 66 channel SQUID readout system, a neutron
shield and a muon veto system. This results in a significant improvement in
sensitivity.Comment: 6 pages, 3 figures, to be published in the proceedings of the 5th
International Workshop on the Identification and Detection of Dark Matter IDM
2004, Edinburgh, Sept. 2004, World Scientifi
Decreased depth distribution of Fucus vesiculosus (Phaeophyceae) in the Western Baltic: effects of light deficiency and epibionts on growth and photosynthesis
For many coastal areas of the world, a decrease in abundance and depth penetration of perennial macroalgae and seagrasses has been documented and attributed to eutrophication. A surplus of nutrients impairs perennial seaweeds in at least two ways: increased phytoplankton densities reduce the depth penetration of light and in addition filamentous seaweeds and microalgae growing epiphytically shade their perennial hosts. A reduction of depth limit and total abundance has also been observed for the brown seaweed Fucus vesiculosus at many sites in the Baltic Sea. However, in most cases the mechanistic reason for the loss of Fucus has been deduced from observations rather than from experimental evidence. Here, we present results of a two-factorial (water depth/light supply and epibionts) experiment that was run in the Kiel Fjord, western Baltic, from August to October 2005. Performance of F. vesiculosus was recorded by growth and chlorophyll measurements, PI-curves and in situ measurements of the photosynthetic activity as the relative rate of electron transport (rETR). rETR and growth decreased with water depth. Chlorophyll a concentrations increased with reduced light intensities, but this apparently could not compensate for the light deficiency. Epibionts enhanced the negative effect of reduced light conditions on growth. According to these findings we estimated the physiological depth limit of F. vesiculosus in the Kiel Fjord to lie between 4 and 6 m water depth
Semiquantitative interpretation of anticardiolipin and antiβ2glycoprotein I antibodies measured with various analytical platforms: communication from the ISTH SSC subcommittee on Lupus Anticoagulant/Antiphospholipid antibodies
Background
Antiβ2glycoprotein I (aβ2GPI) and anticardiolipin (aCL) IgG/IgM show differences in positive/negative agreement and titers between solid phase platforms. Method specific semiquantitative categorization of titers could improve and harmonize the interpretation across platforms.
Aim
To evaluate the traditionally 40/80 units thresholds used for aCL and aβ2GPI for categorization into moderate/high positivity with different analytical systems, and to compare with alternative thresholds.
Material and methods
aCL and aβ2GPI thresholds were calculated for two automated systems (chemiluminescent immunoassay (CLIA) and multiplex flow immunoassay (MFI)) by ROC-curve analysis on 1108 patient samples, including patients with and without APS, and confirmed on a second population (n=279). Alternatively, regression analysis on diluted standard material was applied to identify thresholds. Thresholds were compared to 40/80 threshold measured by an enzyme linked immunosorbent assay (ELISA). Additionally, likelihood ratios (LR) were calculated.
Results
Threshold levels of 40/80 units show poor agreement between ELISA and automated platforms for classification into low/moderate/high positivity, especially for aCL/aβ2GPI IgG. Agreement for semiquantitative interpretation of aPL IgG between ELISA and CLIA/MFI improves with alternative thresholds. LR for aPL IgG increase for thrombotic and obstetric APS based on 40/80 thresholds for ELISA and adapted thresholds for the other systems, but not for IgM.
Conclusion
Use of 40/80 units as medium/high thresholds is acceptable for aCL/aβ2GPI IgG ELISA, but not for CLIA and MFI. Alternative semiquantitative thresholds for non-ELISA platforms can be determined by a clinical approach or by using monoclonal antibodies. Semiquantitative reporting of aPL IgM has less impact on increasing probability for APS
Finite population size effects in quasispecies models with single-peak fitness landscape
We consider finite population size effects for Crow-Kimura and Eigen quasispecies
models with single-peak fitness landscape. We formulate accurately the iteration procedure for
the finite population models, then derive the Hamilton-Jacobi equation (HJE) to describe the
dynamic of the probability distribution. The steady-state solution of HJE gives the variance of
the mean fitness. Our results are useful for understanding the population sizes of viruses in which
the infinite population models can give reliable results for biological evolution problems
Effects of epibiosis on consumer-prey interactions
In many benthic communities predators play a crucial role in the population dynamics of their prey. Surface characteristics of the prey are important for recognition and handling by the predator. Because the establishment of an epibiotic assemblage on the surface of a basibiont species creates a new interface between the epibiotized organism and its environment, we hypothesised that epibiosis should have an impact on consumer-prey interactions. In separate investigations, we assessed how epibionts on macroalgae affected the susceptibility of the latter to herbivory by the urchin Arbacia punctulata and how epibionts on the blue mussel Mytilus edulis affected its susceptibility to predation by the shore crab Carcinus maenas.
Some epibionts strongly affected consumer feeding behavior. When epibionts were more attractive than their host, consumer pressure increased. When epibionts were less attractive than their host or when they were repellent, consumer pressure decreased. In systems that are controlled from the top-down, epibiosis can strongly influence community dynamics. For the Carcinus/Mytilus system that we studied, the insitu distribution of epibionts on mussels reflected the epibiosis-determined preferences of the predator. Both direct and indirect effects are involved in determining these epibiont-prey-consumer interactions
Saturn's Interior After the Cassini Grand Finale
We present a review of Saturn's interior structure and thermal evolution,
with a particular focus on work in the past 5 years. Data from the Cassini
mission, including a precise determination of the gravity field from the Grand
Finale orbits, and the still ongoing identification of ring wave features in
Saturn's C-ring tied to seismic modes in the planet, have led to dramatic
advances in our understanding of Saturn's structure. Models that match the
gravity field suggest that differential rotation, as seen in the visible
atmosphere, extends down to at least a depth of 10,000 km (1/6 the
planet's radius). At greater depths, a variety of different investigations all
now point to a deep Saturn rotation rate of 10 hours and 33 minutes. There is
very compelling evidence for a central heavy element concentration (``core''),
that in most recent models is 12-20 Earth masses. Ring seismology strongly
suggests that the core is not entirely compact, but is dilute (mixed in with
the overlying H/He), and has a substantial radial extent, perhaps out to around
one-half of the planet's radius. A wide range of thermal evolution scenarios
can match the planet's current luminosity, with progress on better quantifying
the helium rain scenario hampered by Saturn's poorly known atmospheric helium
abundance. We discuss the relevance of magnetic field data on understanding the
planet's current interior structure. We point towards additional future work
that combines seismology and gravity within a framework that includes
differential rotation, and the utility of a Saturn entry probe.Comment: Invited review. Accepted for publication in "Saturn: The Grand
Finale", K. H. Baines et al., eds., Cambridge University Press. All-new
follow-up to previous 2016 (pre-Grand Finale) review chapter here:
arXiv:1609.0632
On the superconductivity in the system with preformed pairs
We discuss the phenomenology of the superconductivity resulting from the bose
condensation of the preformed pairs coexisting with unpaired fermions. We show
that this transition is more mean field like than usual bose condensation, i.e.
it is characterized by a relatively small value of the Ginzburg parameter. We
consider the Hall effect in the vortex flow regime and in the fluctuational
regime above and show that in this situation it is much less than in the
transition driven entirely by bose condesation but much larger than in a usual
superconductivity. We analyse the available Hall data and conclude that this
phenomenology describes reasonably well the data in the underdoped materials of
family but is not an appropriate description of optimally doped
materials or underdoped .Comment: Latex/Revtex file, 2 Postscript figures, 10 page
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