547 research outputs found
How an Unfunded Pension System looks like Defined Benefits but works like Defined Contributions: The German Pension Reform
This paper describes the German pension reform process 1992-2007 with a stress on a remark-able development: the public pay-as-you-go-financed pension system has almost silently moved from a traditional defined benefit system to a system which works in many respects like a defined contribution system. The paper combines economic with political considerations, hopefully offering a few lessons that are useful also for other countries.
Evidences of Positive and Negative Transfer Effects Between Highly Similar Perceptual-Motor Tasks
One hundred twenty male undergraduates, each assigned to one of two groups, performed highly similar perceptual-motor tasks varying in difficulty. The tasks were provided by the Multipoint Two-Hand Coordinator. On Day 2, one-half of the Ss in each group changed tasks while one-half continued on the same task. Evidences of positive and negative transfer effects were found with greater positive transfer from the easier to the more difficult task than in the reverse direction. A striking feature of the study was the persistence of negative transfer effects
Zusammenhang zwischen Mikrohabitatstrukturen, Nahrungsverfügbarkeit und Abundanz von Waldnagern
The impact of microhabitat structures and food availability on the abundance of forest rodent
A New Type of Plasma Wakefield Accelerator Driven by Magnetowaves
We present a new concept for a plasma wakefield accelerator driven by
magnetowaves (MPWA). This concept was originally proposed as a viable mechanism
for the "cosmic accelerator" that would accelerate cosmic particles to ultra
high energies in the astrophysical setting. Unlike the more familiar Plasma
Wakefield Accelerator (PWFA) and the Laser Wakefield Accelerator (LWFA) where
the drivers, the charged-particle beam and the laser, are independently
existing entities, MPWA invokes the high-frequency and high-speed whistler mode
as the driver, which is a medium wave that cannot exist outside of the plasma.
Aside from the difference in drivers, the underlying mechanism that excites the
plasma wakefield via the ponderomotive potential is common. Our computer
simulations show that under appropriate conditions, the plasma wakefield
maintains very high coherence and can sustain high-gradient acceleration over
many plasma wavelengths. We suggest that in addition to its celestial
application, the MPWA concept can also be of terrestrial utility. A
proof-of-principle experiment on MPWA would benefit both terrestrial and
celestial accelerator concepts.Comment: revtex4, 4 pages, 6 figure
Recognition of Clostridium difficile PCR-ribotypes 001, 027 and 126/078 using an extended MALDI-TOF MS system
During the last decade, Clostridium difficile infection (CDI) increased markedly inside as well as outside of hospitals. In association with the occurrence of new hypervirulent C. difficile strains, CDI became more important. Until now typing of C. difficile strains has been enabled by PCR-ribotyping. However, this method is restricted to specialized laboratories combined with high maintenance cost. Therefore, we tested MALDI-TOF mass spectrometry for typing of C. difficile to provide a fast method for surveillance of CDI. Using a standard set of 25 different C. difficile PCR ribotypes a database was made by different mass spectra recorded in the SARAMIS™ software (AnagnosTec, Zossen, Germany). The database was validated with 355 C. difficile strains belonging to 29 different PCR ribotypes collected prospectively from all submitted feces samples in 2009. The most frequent PCR ribotypes were type 001 (70%), 027 (4.8%) and 078/126 (4.7%). All three types were recognized by MALDI-TOF MS. We conclude that an extended MALDI-TOF system was capable to recognize specific markers for ribotypes 001, 027 and 078/126 allowing an effective identification of these strains
Observation of Ultra-high-energy Cosmic Rays with the ANITA Balloon-borne Radio Interferometer
We report the observation of sixteen cosmic ray events of mean energy of 1.5
x 10^{19} eV, via radio pulses originating from the interaction of the cosmic
ray air shower with the Antarctic geomagnetic field, a process known as
geosynchrotron emission. We present the first ultra-wideband, far-field
measurements of the radio spectral density of geosynchrotron emission in the
range from 300-1000 MHz. The emission is 100% linearly polarized in the plane
perpendicular to the projected geomagnetic field. Fourteen of our observed
events are seen to have a phase-inversion due to reflection of the radio beam
off the ice surface, and two additional events are seen directly from above the
horizon.Comment: 5 pages, 5 figures, new figure adde
Search for Point Sources of Ultra-High Energy Cosmic Rays Above 40 EeV Using a Maximum Likelihood Ratio Test
We present the results of a search for cosmic ray point sources at energies
above 40 EeV in the combined data sets recorded by the AGASA and HiRes stereo
experiments. The analysis is based on a maximum likelihood ratio test using the
probability density function for each event rather than requiring an a priori
choice of a fixed angular bin size. No statistically significant clustering of
events consistent with a point source is found.Comment: 7 pages, 7 figures. Accepted for publication in The Astrophysical
Journa
Observations of the Askaryan Effect in Ice
We report on the first observations of the Askaryan effect in ice: coherent
impulsive radio Cherenkov radiation from the charge asymmetry in an
electromagnetic (EM) shower. Such radiation has been observed in silica sand
and rock salt, but this is the first direct observation from an EM shower in
ice. These measurements are important since the majority of experiments to date
that rely on the effect for ultra-high energy neutrino detection are being
performed using ice as the target medium. As part of the complete validation
process for the Antarctic Impulsive Transient Antenna (ANITA) experiment, we
performed an experiment at the Stanford Linear Accelerator Center (SLAC) in
June 2006 using a 7.5 metric ton ice target, yielding results fully consistent
with theoretical expectations.Comment: 4 pages, 5 figures, minor correction
- …