The Advanced LIGO gravitational wave detectors are second generation instruments designed and built for the two LIGO observatories in Hanford, WA and Livingston, LA. The two instruments are identical in design, and are specialized versions of a Michelson interferometer with 4 km long arms. As in initial LIGO, Fabry-Perot cavities are used in the arms to increase the interaction time with a gravitational wave, and power recycling is used to increase the effective laser power. Signal recycling has been added in Advanced LIGO to improve the frequency response. In the most sensitive frequency region around 100 Hz, the design strain sensitivity is a factor of 10 better than initial LIGO. In addition, the low frequency end of the sensitivity band is moved from 40 Hz down to 10 Hz. All interferometer components have been replaced with improved technologies to achieve this sensitivity gain. Much better seismic isolation and test mass suspensions are responsible for the gains at lower frequencies. Higher laser power, larger test masses and improved mirror coatings lead to the improved sensitivity at mid-and highfrequencies. Data collecting runs with these new instruments are planned to begin in mid-2015.

Advanced gravitational wave detectors, currently under construction, are expected to directly observe gravitational wave signals of astrophysical origin. The Einstein Telescope (ET), a third-generation gravitational wave detector, has been proposed in order to fully open up the emerging field of gravitational wave astronomy. In this paper we describe sensitivity models for ET and investigate potential limits imposed by fundamental noise sources. A special focus is set on evaluating the frequency band below 10 Hz where a complex

Background and Purpose —In Germany, basic data on stroke morbidity are lacking. If a population-based register in former East Germany is excluded, only routine mortality statistics have thus far provided information on epidemiology of stroke. Therefore, a population-based register of stroke was set up in Southern Germany to determine incidence and case fatality in a defined German population. Methods —The Erlangen Stroke Project (ESPro) is a prospective community-based study among the 101 450 residents of the city of Erlangen, Bavaria, Germany. Standard definitions and overlapping case-finding methods were used to identify all cases of first-ever stroke in all age-groups, occurring in the 2 years of registration (April 1, 1994, to March 31, 1996). All identified cases of first-ever strokes were followed up at 3 and 12 months from onset. Results —During 2 years of registration, 354 first-ever-in-a-lifetime strokes (FELS) were registered. The diagnosis and stroke type were confirmed by CT scan in 95% of cases. Fifty-one percent of all FELS occurred in the age group ≥75 years of age. The crude annual incidence rate was 1.74 per 1000 (1.47 for men and 2.01 for women). After age-adjustment to the European population, the incidence rate was 1.34 per 1000 (1.48 for men and 1.25 for women). The annual crude incidence rate of cerebral infarction was 1.37/1000, intracerebral hemorrhage 0.24/1000, subarachnoid hemorrhage 0.06/1000, and unspecified stroke 0.08/1000. Overall case fatality at 28 days was 19.4%, at 3 months it was 28.5%, and at 1 year 37.3%. Conclusions —The first prospective community-based stroke register including all age groups in Germany revealed incidence rates of stroke similar to those reported from other population-based studies in western industrialized countries, but lower than that observed in former East Germany.