3,035 research outputs found
An analytic approach to number counts of weak-lensing peak detections
We develop and apply an analytic method to predict peak counts in
weak-lensing surveys. It is based on the theory of Gaussian random fields and
suitable to quantify the level of spurious detections caused by chance
projections of large-scale structures as well as the shape and shot noise
contributed by the background galaxies. We compare our method to peak counts
obtained from numerical ray-tracing simulations and find good agreement at the
expected level. The number of peak detections depends substantially on the
shape and size of the filter applied to the gravitational shear field. Our main
results are that weak-lensing peak counts are dominated by spurious detections
up to signal-to-noise ratios of 3--5 and that most filters yield only a few
detections per square degree above this level, while a filter optimised for
suppressing large-scale structure noise returns up to an order of magnitude
more.Comment: 9 pages, 5 figures, submitted to A&
Weak lensing evidence for a filament between A222/A223
We present a weak lensing analysis and comparison to optical and X-ray maps
of the close pair of massive clusters A222/223. Indications for a filamentary
connection between the clusters are found and discussed.Comment: 6 pages, 1 figure. To appear in Proc. IAU Colloquium 195: Outskirts
of Galaxy Clusters - Intense Life in the Suburbs. Version with higher
resolution available at
http://www.astro.uni-bonn.de/~dietrich/torino_proc.ps.g
The origin of peak-offsets in weak-lensing maps
Centroid positions of peaks identified in weak lensing mass maps often show
offsets with respect to other means of identifying halo centres, like position
of the brightest cluster galaxy or X-ray emission centroid. Here we study the
effect of projected large-scale structure (LSS), smoothing of mass maps, and
shape noise on the weak lensing peak positions. Additionally we compare the
offsets in mass maps to those found in parametric model fits. Using ray-tracing
simulations through the Millennium Run -body simulation, we find that
projected LSS does not alter the weak-lensing peak position within the limits
of our simulations' spatial resolution, which exceeds the typical resolution of
weak lensing maps. We conclude that projected LSS, although a major contaminant
for weak-lensing mass estimates, is not a source of confusion for identifying
halo centres. The typically reported offsets in the literature are caused by a
combination of shape noise and smoothing alone. This is true for centroid
positions derived both from mass maps and model fits.Comment: 6 pages, 4 figures, accepted for publication in MNRAS, significant
additions to v
Leaking method approach to surface transport in the Mediterranean Sea from a numerical ocean model
We use Lagrangian diagnostics (the leaking and the exchange methods) to
characterize surface transport out of and between selected regions in the
Western Mediterranean. Velocity fields are obtained from a numerical model.
Residence times of water of Atlantic origin in the Algerian basin, with a
strong seasonal dependence, are calculated. Exchange rates between these waters
and the ones occupying the northern basin are also evaluated. At surface,
northward transport is dominant, and involves filamental features and eddy
structures that can be identified with the Algerian eddies. The impact on these
results of the presence of small scale turbulent motions is evaluated by adding
Lagrangian diffusion.Comment: 21 pages using the elsart style. Higher resolution figures available
from
http://www.imedea.uib.es/physdept/publications/showpaper_en.php?indice=119
Metabolic engineering of the purine biosynthetic pathway in Corynebacterium glutamicum results in increased intracellular pool sizes of IMP and hypoxanthine
Background: Purine nucleotides exhibit various functions in cellular metabolism. Besides serving as building blocks for nucleic acid synthesis, they participate in signaling pathways and energy metabolism. Further, IMP and GMP represent industrially relevant biotechnological products used as flavor enhancing additives in food industry. Therefore, this work aimed towards the accumulation of IMP applying targeted genetic engineering of Corynebacterium glutamicum.
Results: Blocking of the degrading reactions towards AMP and GMP lead to a 45-fold increased intracellular IMP pool of 22 mumol gCDW-1. Deletion of the pgi gene encoding glucose 6-phosphate isomerase in combination with the deactivated AMP and GMP generating reactions, however, resulted in significantly decreased IMP pools (13 mumol gCDW-1). Targeted metabolite profiling of the purine biosynthetic pathway further revealed a metabolite shift towards the formation of the corresponding nucleobase hypoxanthine (102 mumol gCDW-1) derived from IMP degradation.
Conclusions: The purine biosynthetic pathway is strongly interconnected with various parts of the central metabolism and therefore tightly controlled. However, deleting degrading reactions from IMP to AMP and GMP significantly increased intracellular IMP levels. Due to the complexity of this pathway further degradation from IMP to the corresponding nucleobase drastically increased suggesting additional targets for future strain optimization
Ion Selectivity and Competition in Channelrhodopsins
AbstractChannelrhodopsins are light-gated ion channels of green algae. They are widely used for the analysis of neuronal networks using light in the emerging field of optogenetics. Under steady-state light conditions, the two open states, O1 and O2, mediate the photocurrents with different ion conductance and selectivity. To understand the conducting process as well as its optogenetic applications, it is important to study ion binding and transport of this promiscuous cation channel. Here, we present an enzyme kinetic algorithm that allowed us to calculate the ion composition of the initial and steady-state photocurrents for multication media. The approach is based on current-voltage relations determined for the individual ions H+, Na+, Ca2+, and Mg2+. We identify and quantify the widely different competition of the ions in wild-type channelrhodopsin-2 and two high-performing channelrhodopsin variants CatCh+ and C1V1. Both variants show enhanced Ca2+ conductance, but only CatCh+ displays high steady-state Ca2+ currents at neutral pH due to reduced H+ competition and low inactivation. We demonstrate that for optogenetic applications, one should always take into account that the variable equilibria of the two open states depend on light intensity, voltage, and the ionic composition of the medium
GaBoDS: The Garching-Bonn Deep Survey VIII. Lyman-break galaxies in the ESO Deep Public Survey
Aims. The clustering properties of a large sample of U-dropouts are
investigated and compared to very precise results for B-dropouts from other
studies to identify a possible evolution from z=4 to z=3. Methods. A population
of ~8800 candidates for star-forming galaxies at z=3 is selected via the
well-known Lyman-break technique from a large optical multicolour survey (the
ESO Deep Public Survey). The selection efficiency, contamination rate, and
redshift distribution of this population are investigated by means of extensive
simulations. Photometric redshifts are estimated for every Lyman-break galaxy
(LBG) candidate from its UBVRI photometry yielding an empirical redshift
distribution. The measured angular correlation function is deprojected and the
resulting spatial correlation lengths and slopes of the correlation function of
different subsamples are compared to previous studies. Results. By fitting a
simple power law to the correlation function we do not see an evolution in the
correlation length and the slope from other studies at z=4 to our study at z=3.
In particular, the dependence of the slope on UV-luminosity similar to that
recently detected for a sample of B-dropouts is confirmed also for our
U-dropouts. For the first time number statistics for U-dropouts are sufficient
to clearly detect a departure from a pure power law on small scales down to ~2"
reported by other groups for B-dropouts.Comment: 10 pages, 11 figures, accepted by A&A, full resolution version
available at http://www.astro.uni-bonn.de/~hendrik/5880.pd
What Is Important When We Evaluate Movies? Insights from Computational Analysis of Online Reviews
The question of what is important when we evaluate movies is crucial for understanding how lay audiences experience and evaluate entertainment products such as films. In line with this, subjective movie evaluation criteria (SMEC) have been conceptualized as mental representations of important attitudes toward specific film features. Based on exploratory and confirmatory factor analyses of self-report data from online surveys, previous research has found and validated eight dimensions. Given the large-scale evaluative information that is available in online usersâ comments in movie databases, it seems likely that what online users write about movies may enrich our knowledge about SMEC. As a first fully exploratory attempt, drawing on an open-source dataset including movie reviews from IMDb, we estimated a correlated topic model to explore the underlying topics of those reviews. In 35,136 online movie reviews, the most prevalent topics tapped into three major categoriesâHedonism, Actorsâ Performance, and Narrativeâand indicated what reviewers mostly wrote about. Although a qualitative analysis of the reviews revealed that users mention certain SMEC, results of the topic model covered only two SMEC: Story Innovation and Light-heartedness. Implications for SMEC and entertainment research are discussed
Inklusion in der Sozialen Arbeit: Darstellung am Beispiel von alt gewordenen Menschen mit geistiger Behinderung
Am Beispiel der Personengruppe alt gewordener Menschen mit geistiger Behinderung wird untersucht, wie unter den erschwerenden Bedingungen von Behinderung und Alter dennoch Inklusion als sozialer Prozess stattfindet.
Zur Operationalisierung systemtheoretischer Aussagen bedient sich die Studie des von Otto Neurath begrĂŒndeten Konzeptes der Lebenslagen.
Das vom Verfasser als Rebekka-Effekt bezeichnete PhÀnomen der Konstruktion von "Voralterung" wird als ein deutlicher Hinweis gewertet, dass auch unter problematischen Voraussetzungen das generalisierte Inklusionsgebot moderner Gesellschaften wirksam wird
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