120 research outputs found
Rentabilitätsvergleiche im Umlage- und Kapitaldeckungsverfahren : Konzepte, empirische Ergebnisse, sozialpolitische Konsequenzen
Die demographischen Veränderungen sind Auslöser einer grundsätzlicheren Debatte über Alterssicherungsverfahren, nämlich der Wahl eines effizienten Finanzierungsverfahrens der Altersvorsorge. Im Zentrum der Debatte steht immer wieder der Renditevergleich zwischen dem Umlage- und dem Kapitaldeckungsverfahren. Ihm gilt dieses Papier. Er ist keineswegs so einfach, wie es oft suggeriert wird, da Versicherungs- und Risikoaspekte, vor allem aber das Übergangsproblem berücksichtigt werden müssen. Der vorliegende Beitrag stellt den wirtschaftstheoretischen Hintergrund mit den wichtigsten relevanten Konzepten dar und präsentiert empirische Schätzungen zur heutigen und Simulationsergebnisse zur zukünftigen Entwicklung der relevanten Renditen. Wir schließen mit den sozialpolitischen Konsequenzen für eine reformierte Altersvorsorge
The bimodality of the 10k zCOSMOS-bright galaxies up to z ~ 1: a new statistical and portable classification based on the optical galaxy properties
Our goal is to develop a new and reliable statistical method to classify
galaxies from large surveys. We probe the reliability of the method by
comparing it with a three-dimensional classification cube, using the same set
of spectral, photometric and morphological parameters.We applied two different
methods of classification to a sample of galaxies extracted from the zCOSMOS
redshift survey, in the redshift range 0.5 < z < 1.3. The first method is the
combination of three independent classification schemes, while the second
method exploits an entirely new approach based on statistical analyses like
Principal Component Analysis (PCA) and Unsupervised Fuzzy Partition (UFP)
clustering method. The PCA+UFP method has been applied also to a lower redshift
sample (z < 0.5), exploiting the same set of data but the spectral ones,
replaced by the equivalent width of H. The comparison between the two
methods shows fairly good agreement on the definition on the two main clusters,
the early-type and the late-type galaxies ones. Our PCA-UFP method of
classification is robust, flexible and capable of identifying the two main
populations of galaxies as well as the intermediate population. The
intermediate galaxy population shows many of the properties of the green valley
galaxies, and constitutes a more coherent and homogeneous population. The
fairly large redshift range of the studied sample allows us to behold the
downsizing effect: galaxies with masses of the order of Msun
mainly are found in transition from the late type to the early type group at
, while galaxies with lower masses - of the order of Msun -
are in transition at later epochs; galaxies with Msun did not
begin their transition yet, while galaxies with very large masses ( Msun) mostly completed their transition before .Comment: 16 pages, 14 figures, accepted for publication in A&
A study of patent thickets
Report analysing whether entry of UK enterprises into patenting in a technology area is affected by patent thickets in the technology area
The spatial distribution of the far-infrared emission in NGC 253
We study the far-infrared emission properties of the nearby starburst galaxy
NGC 253 based on IRAS maps and an ISOPHOT map at 180 microns. Based on the
analysis of the light profiles, we have been able to identify three main
structural components: an unresolved nuclear component, an exponential disk,
and a kiloparsec scale bar.In addition, we also found a ring structure at the
end of the bar that is particularly conspicuous at 12 microns. The Spectral
Energy Distribution (SED) of each morphological component has been modeled as
thermal dust emission at different temperatures. The unresolved nuclear
component is dominated by cold dust emission (T ~ 50 K), whereas the disk
emission is dominated by very cold dust (T ~ 16 K) plus a contribution from
cold dust (T ~ 55 K). The bar emission corresponds mainly to cold dust (T ~ 23
K) plus a warm component (T ~ 148 K). We detect an extension of the disk
emission due to very cold dust, which contributes a large fraction (94%) of the
total dust mass of the galaxy. The estimated total dust mass is 8.2 +/- 10^7
Msun.Comment: 20 pages, 9 figures. Accepted in Ap
Percutaneous closure of atrial septal defects leads to normalisation of atrial and ventricular volumes
Background: Percutaneous closure of atrial septal defects (ASDs) should potentially reduce right heart volumes by removing left-to-right shunting. Due to ventricular interdependence, this may be associated with impaired left ventricular filling and potentially function. Furthermore, atrial changes post-ASD closure have been poorly understood and may be important for understanding risk of atrial arrhythmia post-ASD closure. Cardiovascular magnetic resonance (CMR) is an accurate and reproducible imaging modality for the assessment of cardiac function and volumes. We assessed cardiac volumes pre- and post-percutaneous ASD closure using CMR. Methods: Consecutive patients (n = 23) underwent CMR pre- and 6 months post-ASD closure. Steady state free precession cine CMR was performed using contiguous slices in both short and long axis views through the ASD. Data was collected for assessment of left and right atrial, ventricular end diastolic volumes (EDV) and end systolic volumes (ESV). Data is presented as mean ± SD, volumes as mL, and paired t-testing performed between groups. Statistical significance was taken as p < 0.05. Results: There was a significant reduction in right ventricular volumes at 6 months post-ASD closure (RVEDV: 208.7 ± 76.7 vs. 140.6 ± 60.4 mL, p < 0.0001) and RVEF was significantly increased (RVEF 35.5 ± 15.5 vs. 42.0 ± 15.2%, p = 0.025). There was a significant increase in the left ventricular volumes (LVEDV 84.8 ± 32.3 vs. 106.3 ± 38.1 mL, p = 0.003 and LVESV 37.4 ± 20.9 vs. 46.8 ± 18.5 mL, p = 0.016). However, there was no significant difference in LVEF and LV mass post-ASD closure. There was a significant reduction in right atrial volumes at 6 months post-ASD closure (pre-closure 110.5 ± 55.7 vs. post-closure 90.7 ± 69.3 mL, p = 0.019). Although there was a trend to a decrease in left atrial volumes post-ASD closure, this was not statistically significant (84.5 ± 34.8 mL to 81.8 ± 44.2 mL, p = NS). Conclusion: ASD closure leads to normalisation of ventricular volumes and also a reduction in right atrial volume. Further follow-up is required to assess how this predicts outcomes such as risk of atrial arrhythmias after such procedures.Karen SL Teo, Benjamin K Dundon, Payman Molaee, Kerry F Williams, Angelo Carbone, Michael A Brown, Matthew I Worthley, Patrick J Disney, Prashanthan Sanders and Stephen G Worthle
The stellar and sub-stellar IMF of simple and composite populations
The current knowledge on the stellar IMF is documented. It appears to become
top-heavy when the star-formation rate density surpasses about 0.1Msun/(yr
pc^3) on a pc scale and it may become increasingly bottom-heavy with increasing
metallicity and in increasingly massive early-type galaxies. It declines quite
steeply below about 0.07Msun with brown dwarfs (BDs) and very low mass stars
having their own IMF. The most massive star of mass mmax formed in an embedded
cluster with stellar mass Mecl correlates strongly with Mecl being a result of
gravitation-driven but resource-limited growth and fragmentation induced
starvation. There is no convincing evidence whatsoever that massive stars do
form in isolation. Various methods of discretising a stellar population are
introduced: optimal sampling leads to a mass distribution that perfectly
represents the exact form of the desired IMF and the mmax-to-Mecl relation,
while random sampling results in statistical variations of the shape of the
IMF. The observed mmax-to-Mecl correlation and the small spread of IMF
power-law indices together suggest that optimally sampling the IMF may be the
more realistic description of star formation than random sampling from a
universal IMF with a constant upper mass limit. Composite populations on galaxy
scales, which are formed from many pc scale star formation events, need to be
described by the integrated galactic IMF. This IGIMF varies systematically from
top-light to top-heavy in dependence of galaxy type and star formation rate,
with dramatic implications for theories of galaxy formation and evolution.Comment: 167 pages, 37 figures, 3 tables, published in Stellar Systems and
Galactic Structure, Vol.5, Springer. This revised version is consistent with
the published version and includes additional references and minor additions
to the text as well as a recomputed Table 1. ISBN 978-90-481-8817-
The 1000 Brightest HIPASS Galaxies: HI Properties
(abridged) We present the HIPASS Bright Galaxy Catalog (BGC) which contains
the 1000 HI-brightest galaxies in the southern sky as obtained from the HI
Parkes All-Sky Survey (HIPASS). The selection of the brightest sources is based
on their HI peak flux density (Speak > 116 mJy) as measured from the spatially
integrated HIPASS spectrum. The derived HI masses range from about 10^7 to 4 x
10^10 Msun. While the BGC (z < 0.03) is complete in Speak, only a subset of
about 500 sources can be considered complete in integrated HI flux density (FHI
> 25 JY km/s). The HIPASS BGC contains a total of 158 new redshifts and yields
no evidence for a population of "free-floating" intergalactic HI clouds without
associated optical counterparts. HIPASS provides a clear view of the local
large-scale structure. The dominant features in the sky distribution of the BGC
are the Supergalactic Plane and the Local Void. In addition, one can clearly
see the Centaurus Wall which connects via the Hydra and Antlia clusters to the
Puppis filament. Some previously hardly noticed galaxy groups stand out quite
distinctively in the HI sky distribution. Several new structures are seen for
the first time, not only behind the Milky Way.Comment: AJ, accepted (scheduled for publication in July 2004). Latex, 46
pages. The HIPASS BGC paper, figures, tables, HI spectra and further
infromation are available at
http://www.atnf.csiro.au/research/multibeam/HIPASS-BG
The 3′ Splice Site of Influenza A Segment 7 mRNA Can Exist in Two Conformations: A Pseudoknot and a Hairpin
The 3′ splice site of influenza A segment 7 is used to produce mRNA for the M2 ion-channel protein, which is critical to the formation of viable influenza virions. Native gel analysis, enzymatic/chemical structure probing, and oligonucleotide binding studies of a 63 nt fragment, containing the 3′ splice site, key residues of an SF2/ASF splicing factor binding site, and a polypyrimidine tract, provide evidence for an equilibrium between pseudoknot and hairpin structures. This equilibrium is sensitive to multivalent cations, and can be forced towards the pseudoknot by addition of 5 mM cobalt hexammine. In the two conformations, the splice site and other functional elements exist in very different structural environments. In particular, the splice site is sequestered in the middle of a double helix in the pseudoknot conformation, while in the hairpin it resides in a two-by-two nucleotide internal loop. The results suggest that segment 7 mRNA splicing can be controlled by a conformational switch that exposes or hides the splice site
The 1000 brightest HIPASS galaxies: Newly cataloged galaxies
The H I Parkes All-Sky Survey (HIPASS) is a blind 21 cm survey for extragalactic neutral hydrogen, covering the whole southern sky. The HIPASS Bright Galaxy Catalog (BGC) is a subset of HIPASS and contains the 1000 H I brightest (peak flux density) galaxies. Here we present the 138 HIPASS BGC galaxies that had no redshift measured prior to the Parkes multibeam H I surveys. Of the 138 galaxies, 87 are newly cataloged. Newly cataloged is defined as having no optical ( or infrared) counterpart in the NASA/IPAC Extragalactic Database. Using the Digitized Sky Survey, we identify optical counterparts for almost half of the newly cataloged galaxies, which are typically of irregular or Magellanic morphological type. Several H I sources appear to be associated with compact groups or pairs of galaxies rather than an individual galaxy. The majority ( 57) of the newly cataloged galaxies lie within 10degrees of the Galactic plane and are missing from optical surveys as a result of confusion with stars or dust extinction. This sample also includes newly cataloged galaxies first discovered by Henning et al. in the H I shallow survey of the zone of avoidance. The other 30 newly cataloged galaxies escaped detection because of their low surface brightness or optical compactness. Only one of these, HIPASS J0546-68, has no obvious optical counterpart, as it is obscured by the Large Magellanic Cloud. We find that the newly cataloged galaxies with -b->10degrees are generally lower in H I mass and narrower in velocity width compared with the total HIPASS BGC. In contrast, newly cataloged galaxies behind the Milky Way are found to be statistically similar to the entire HIPASS BGC. In addition to these galaxies, the HIPASS BGC contains four previously unknown H I clouds
Cytogenetic analysis of three species of Pseudacteon (Diptera, Phoridae) parasitoids of the fire ants using standard and molecular techniques
Pseudacteon flies, parasitoids of worker ants, are being intensively studied as potentially effective agents in the biological control of the invasive pest fire ant genus Solenopsis (Hymenoptera: Formicidae). This is the first attempt to describe the karyotype of P. curvatus Borgmeier, P. nocens Borgmeier and P. tricuspis Borgmeier. The three species possess 2n = 6; chromosomes I and II were metacentric in the three species, but chromosome pair III was subtelocentric in P. curvatus and P. tricuspis, and telocentric in P. nocens. All three species possess a C positive band in chromosome II, lack C positive heterochromatin on chromosome I, and are mostly differentiated with respect to chromosome III. P. curvatus and P. tricuspis possess a C positive band, but at different locations, whereas this band is absent in P. nocens. Heterochromatic bands are neither AT nor GC rich as revealed by fluorescent banding. In situ hybridization with an 18S rDNA probe revealed a signal on chromosome II in a similar location to the C positive band in the three species. The apparent lack of morphologically distinct sex chromosomes is consistent with proposals of environmental sex determination in the genus. Small differences detected in chromosome length and morphology suggests that chromosomes have been highly conserved during the evolutionary radiation of Pseudacteon. Possible mechanisms of karyotype evolution in the three species are suggested
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