Do migratory birds need a nap after a long non-stop flight?

After a prolonged period of sleep deprivation, the urge to sleep overrules all other activities. Despite this well-known fact, the occurrence of sleep after naturally occurring sleep deprivation during long non-stop migratory flight in birds has hardly been investigated. The aim of this communication is to stimulate quantitative studies on the requirement for sleep in migrating birds. We present some observations on birds just after landing from a long non-stop flight which indicate that the urge to sleep may take preference over other activities. We ask the question whether sleep deficits should be considered as an important factor shaping the behaviour after long flights and whether the need for sleep compensation during the day might shape the preferred duration of non-stop flights in night migrants

Optimal interpolation of satellite and ground data for irradiance nowcasting at city scales

We use a Bayesian method, optimal interpolation, to improve satellite derived irradiance estimates at city-scales using ground sensor data. Optimal interpolation requires error covariances in the satellite estimates and ground data, which define how information from the sensor locations is distributed across a large area. We describe three methods to choose such covariances, including a covariance parameterization that depends on the relative cloudiness between locations. Results are computed with ground data from 22 sensors over a 75×80 km area centered on Tucson, AZ, using two satellite derived irradiance models. The improvements in standard error metrics for both satellite models indicate that our approach is applicable to additional satellite derived irradiance models. We also show that optimal interpolation can nearly eliminate mean bias error and improve the root mean squared error by 50%

Discovery of photospheric argon in very hot central stars of planetary nebulae and white dwarfs

We report the first discovery of argon in hot evolved stars and white dwarfs. We have identified the ArVII 1063.55A line in some of the hottest known (Teff=95000-110000 K) central stars of planetary nebulae and (pre-) white dwarfs of various spectral type. We determine the argon abundance and compare it to theoretical predictions from stellar evolution theory as well as from diffusion calculations. We analyze high-resolution spectra taken with the Far Ultraviolet Spectroscopic Explorer. We use non-LTE line-blanketed model atmospheres and perform line-formation calculations to compute synthetic argon line profiles. We find a solar argon abundance in the H-rich central star NGC1360 and in the H-deficient PG1159 star PG1424+535. This confirms stellar evolution modeling that predicts that the argon abundance remains almost unaffected by nucleosynthesis. For the DAO-type central star NGC7293 and the hot DA white dwarfs PG0948+534 and REJ1738+669 we find argon abundances that are up to three orders of magnitude smaller than predictions of calculations assuming equilibrium of radiative levitation and gravitational settling. For the hot DO white dwarf PG1034+001 the theoretical overprediction amounts to one dex. Our results confirm predictions from stellar nucleosynthesis calculations for the argon abundance in AGB stars. The argon abundance found in hot white dwarfs, however, is another drastic example that the current state of equilibrium theory for trace elements fails to explain the observations quantitatively.Comment: Accepted for publication in A&

Genitiv på tysk: - en undersøgelse af stil og brug

Jan T. Schlosser and Lasse Holmgren Brunø Genitiv på tysk - en undersøgelse af stil og brug. (The German genitive case an examination of its use and style). The article examines how the genitive case is used in different style registers e.g. internet debates, fiction, officialese and legal texts. The examination utilizes a scale created by the Danish Germanist Peter Jørgensen of the stylistic use of the genitive case. This is supplemented by an examination of the specific genitive construction's syntactic function. This method makes it possible for the article to describe the use of the genitive case in modern German

Genitiv på tysk: - en undersøgelse af stil og brug

Jan T. Schlosser and Lasse Holmgren Brunø Genitiv på tysk - en undersøgelse af stil og brug. (The German genitive case an examination of its use and style). The article examines how the genitive case is used in different style registers e.g. internet debates, fiction, officialese and legal texts. The examination utilizes a scale created by the Danish Germanist Peter Jørgensen of the stylistic use of the genitive case. This is supplemented by an examination of the specific genitive construction's syntactic function. This method makes it possible for the article to describe the use of the genitive case in modern German