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Notes: Abstract Recently reported measurements on a plasma betatronM II were continued and under certain conditions bremsstrahlung produced by relativistic electrons was observed associated with conduction currents of some 100 A. But also early beam disruption occured. The time τgg of disruption of the stream has been measured as a function of gas pressure and acceleration field strength. Most of the electrons were lost during an early stage of the acceleration process but also beam loss was observed over a long period of the acceleration time. The expected increase of the circulating runaway current due to improved parameters was not found.

Notes: Zusammenfassung 1. Die wirbelartigen Figuren der Spermienschwänze in den Tubuli contorti des Rattenhodens können nicht als Folge einer Wirbelbildung des Hodensekretes verstanden werden; lediglich die Ausrichtung der Spermienschwänze nebenhodenwärts ist durch das langsame Strömen des Sekretes gegeben. 2. Für das von Rolshoven postulierte Strömungsgefälle konnte kein Beweis erbracht werden. Insbesondere konnte kein Anhaltspunkt dafür gefunden werden, daß die Sekretströmung im Tubulus contortus die Folge eines allgemeinen Strömungsgefälles vom Kreislauf aus sein könnte. Die von Rolshoven entwickelte Vorstellung vom Zustandekommen der Figuren vom Kreislauf aus wird somit abgelehnt. 3. Eine der wesentlichsten Voraussetzungen für das Auftreten der Figuren ist in dem Verhältnis von Spermienlänge zum freien Lumen zu sehen. Tiere mit langen Spermien (Ratte, Meerschweinchen, Maus usw.) zeigen solche Figuren, die dadurch bedingt sind, daß die lichte Weite des Tubuluslumens kleiner ist als die Schwanzlänge der Spermien. 4. Beim Menschen können wegen der Weite des Tubuluslumens einerseits und der Kleinheit der Spermien andererseits wirbelartige Figuren nicht auftreten.

Notes: Abstract When the University of Bonn lidar on the Esrange (68°N, 21°E), Sweden, was switched on in the evening of July 18, 1998, a geometrically and optically thin cloud layer was present near 14 km altitude or 400 K potential temperature, where it persisted for two hours. The tropopause altitude was 4 km below the cloud altitude. The cloud particles depolarized the lidar returns, thus must they have been aspherical and hence solid. Atmospheric temperatures near 230 K were approximately 40 K too high to support ice particles at stratospheric water vapour pressures of a few ppmv. The isentropic back trajectory on 400 K showed the air parcels to have stayed clear of active major rocket launch sites. The air parcels at 400 K had travelled from the Aleutians across Canada and the Atlantic Ocean arriving above central Europe and then turned northward to pass over above the lidar station. Parcels at levels at ±25 K from 400 K had come from the pole and joined the 400 K trajectory path above eastern Canada. Apparently the cloud existed in a filament of air with an origin different from those filaments both above and below. Possibly the 400 K level air parcels had carried soot particles from forest wild fires in northern Canada or volcanic ash from the eruption of the Korovin Volcano in the Aleutian Islands.

Notes: Abstract Polar stratospheric clouds (PSCs) are often observed in the Kiruna region in northern Sweden, east of the Scandinavian mountain range, during wintertime. PSC occurrence can be detected by ground-based optical instruments. Most of these require clear tropospheric weather. By applying the zenith-sky colour index technique, which works under most weather conditions, the data availability can be extended. The observations suggest that PSC events, especially of type II (water PSCs) may indeed more common than predicted by synoptic models, which is expected because of the frequent presence of mountain-induced leewaves. However, it will be of importance to increase the density of independent observations.

Notes: Abstract We report on the development and current capabilities of the ALOMAR Rayleigh/Mie/Raman lidar. This instrument is one of the core instruments of the international ALOMAR facility, located near Andenes in Norway at 69°N and 16°E. The major task of the instrument is to perform advanced studies of the Arctic middle atmosphere over altitudes between about 15 to 90 km on a climatological basis. These studies address questions about the thermal structure of the Arctic middle atmosphere, the dynamical processes acting therein, and of aerosols in the form of stratospheric background aerosol, polar stratospheric clouds, noctilucent clouds, and injected aerosols of volcanic or anthropogenic origin. Furthermore, the lidar is meant to work together with other remote sensing instruments, both ground- and satellite-based, and with balloon- and rocket-borne instruments performing in situ observations. The instrument is basically a twin lidar, using two independent power lasers and two tiltable receiving telescopes. The power lasers are Nd:YAG lasers emitting at wavelengths 1064, 532, and 355 nm and producing 30 pulses per second each. The power lasers are highly stabilized in both their wavelengths and the directions of their laser beams. The laser beams are emitted into the atmosphere fully coaxial with the line-of-sight of the receiving telescopes. The latter use primary mirrors of 1.8 m diameter and are tiltable within 30° off zenith. Their fields-of-view have 180 μrad angular diameter. Spectral separation, filtering, and detection of the received photons are made on an optical bench which carries, among a multitude of other optical components, three double Fabry-Perot interferometers (two for 532 and one for 355 nm) and one single Fabry-Perot interferometer (for 1064 nm). A number of separate detector channels also allow registration of photons which are produced by rotational-vibrational and rotational Raman scatter on N2 and N2+O2 molecules, respectively. Currently, up to 36 detector channels simultaneously record the photons collected by the telescopes. The internal and external instrument operations are automated so that this very complex instrument can be operated by a single engineer. Currently the lidar is heavily used for measurements of temperature profiles, of cloud particle properties such as their altitude, particle densities and size distributions, and of stratospheric winds. Due to its very effective spectral and spatial filtering, the lidar has unique capabilities to work in full sunlight. Under these conditions it can measure temperatures up to 65 km altitude and determine particle size distributions of overhead noctilucent clouds. Due to its very high mechanical and optical stability, it can also employed efficiently under marginal weather conditions when data on the middle atmosphere can be collected only through small breaks in the tropospheric cloud layers.