Geography of the asteroid belt

The CSM classification serves as the starting point on the geography of the asteroid belt. Raw data on asteroid types are corrected for observational biases (against dark objects, for instance) to derive the distribution of types throughout the belt. Recent work on family members indicates that dynamical families have a true physical relationship, presumably indicating common origin in the breakup of a parent asteroid

The role of earth-based observations of asteroids during the next decade

Present reconnaissance studies of asteroids shift ground based programs to more specialized, intensive studies of selected individual bodies and special classes. Two powerful techniques--radar and mid-IR spectroscopy--have yet to be widely applied to asteroids; high priority should be given to: (1) search programs with a large Schmidt telescope (especially for Mars- and Earth-approaching bodies); (2) a moderate resolution visible and near-IR spectrophotometric survey of at least half the asteroids; (3) high resolution spectrophotometry and radiometry of unusual objects; (4) radar studies of representative main belt asteroids; and (5) application of the full complement of astrophysical techniques to objects of high scientific interest and to potential space mission targets. The infrared astronomical satellite also has high potential for contributing to asteroid science

Spectrophotometry of planets, asteroids and satellites from the international ultraviolet explorer satellite

A total of 14 8 hour I.U.E. observing sessions resulted in 39 spectra of 11 asteroids and 9 solar type stars as well as 57 spectra at various locations on the disk of Jupiter. The Jupiter observations include a total of 5 center to limb series of spectra at various latitudes and a North South series along the central meridian. In the range from 2000-3000 A, the planet shows a striking decrease in brightness at latitudes greater than about 30 degrees, and exhibits limb brightening at low latitudes and limb darkening at high latitudes. Preliminary results indicate that about 6 km-amagats of clean hydrogen are required above a haze of absorbing aerosols to reproduce the limb brightening observed at 2500 A in the equatorial regions. At higher latitudes, the aerosols extend to even higher levels of the atmosphere. Comparison of the Jovian data with detailed model calculations and the analyses of the asteroid spectra are still in progress with other support

Rainfall as a cause of mechanical damage to Pseudocyphellaria rufovirescens in a New Zealand temperate rainforest

Lichens, like all poikilohydric plants, have a metabolism that is dependent on external moistening from their environment. In the case of green algal lichens high humidities may be sufficient for positive net photosynthesis to occur (Lange et al. 1993a). For these plants water stress is usually taken to mean a lack of water (Kappen 1988; Rundel 1988) but it can also mean an excess of water that leads to depressed CO2 exchange because of increased diffusion resistances at high thallus water contents (Lange & Tenhunen 1981; Kershaw 1985). Rather than this being an unusual occurrence, Lange et al. (19936) found reduced CO2 exchange at thallus supra-saturation to be present over long periods in the temperate rainforest of north-eastern New Zealand

Reduzierung des Phytophthora-Primärbefalls durch eine Kupferbeizung unter den besonderen Bedingungen des Ökologischen Kartoffelanbaus

Im ökologischen Kartoffelanbau stellt der Primärbefall ein großes Problem dar, weil er mit Kupferspritzungen nur schwer zu kontrollieren ist und schnell zum vorzeitigen Ausbruch von Sekundärbefall führen kann. Nach ergiebigen Niederschlägen und hoher Bodenfeuchte kann der Erreger Phytophthora infestans entweder von der latent infizierten Pflanzknolle im Stängel nach oben wachsen oder auf der Oberfläche der Pflanzknolle sporulieren. Unter für den Erreger optimalen Witterungsbedingungen können beide Infektionswege einen Primärbefall am Stängel auslösen

40Ar/39Ar ages of lunar impact glasses: Relationships among Ar diffusivity, chemical composition, shape, and size

Lunar impact glasses, quenched melts produced during cratering events on the Moon, have the potential to provide not only compositional information about both the local and regional geology of the Moon but also information about the impact flux over time. We present in this paper the results of 73 new 40Ar/39Ar analyses of well-characterized, inclusion-free lunar impact glasses and demonstrate that size, shape, chemical composition, fraction of radiogenic 40Ar retained, and cosmic ray exposure (CRE) ages are important for 40Ar/39Ar investigations of these samples. Specifically, analyses of lunar impact glasses from the Apollo 14, 16, and 17 landing sites indicate that retention of radiogenic 40Ar is a strong function of post-formation thermal history in the lunar regolith, size, and chemical composition. Based on the relationships presented in this paper, lunar impact glasses with compositions and sizes sufficient to have retained 90% of their radiogenic Ar during 750 Ma of cosmic ray exposure at time-integrated temperatures of up to 290 K have been identified and are likely to have yielded reliable 40Ar/39Ar ages of formation. Additionally, ~50% of the identified impact glass spheres have formation ages of <500 Ma, while ~75% of the identified lunar impact glass shards and spheres have ages of formation <2000 Ma. The observed age-frequency distribution of lunar impact glasses may reflect two processes: (i) diminished preservation due to spontaneous shattering with age; and (ii) preservation of a remnant population of impact glasses from the tail end of the terminal lunar bombardment having 40Ar/39Ar ages up to 3800 Ma. A protocol is described for selecting and analyzing lunar impact glasses.Comment: Please contact Zellner ([email protected]) for data tables and other supplemental informatio

Strategien zur Minimierung des Einsatzes kupferhaltiger Fungizide bei der Krautfäulebekämpfung im Ökologischen Kartoffelanbau – ein vom Bundesprogramm Ökologischer Landbau gefördertes Forschungsprojekt

Ziel des Projektes ist es, auf Basis der witterungsbedingten Epidemiebewertung, die Kupferaufwandmengen auf das absolut notwendige Maß zu begrenzen. Dazu werden verschiedene Strategien verfolgt. Zum einen soll durch eine Pflanzgutbeizung mit Kupferpräparaten das Auftreten von Primärbefall reduziert werden, um den Epidemiebeginn und somit auch den Spritzstart nach hinten verlagern zu können. Zum andern werden zur Kontrolle des Sekundärbefalls Applikationsstrategien erarbeitet, bei denen die Kupferaufwandmengen und die Spritzabstände variabel an den Infektionsdruck angepasst werden, um mit möglichst niedrigeren Mengen auszukommen

Prognosegesteuerte Bekämpfungsstrategien im Ökologischen Kartoffelanbau- mögliche Kupfereinsparungspotentiale und Vergleich der Bekämpfungserfolge

Im Rahmen des Forschungsprojektes ÖKOSIMPHYT liegen mittlerweile dreijährige Versuchsergebnisse zur Bekämpfung der Kraut- und Knollenfäule (Phytophthora infestans) im Ökologischen Kartoffelanbau vor, in denen die Anwendung des neuen Prognosesystems ÖKOSIMPHYT im Freiland getestet wurde. Ziel des Projektes ist, durch eine zielgerichtete Applikation den Kupfereinsatz sowohl aus Bekämpfung- als auch aus ökologischer Sicht zu optimieren

Strategien zur Reduzierung der Kupferaufwandmengen im ökologischen Kartoffelanbau – Projekt “ÖKO-SIMPHYT“

Potato late blight (Phytophthora infestans) is still an unsolved problem in organic farming. Up to now the disease can only be controlled by copper fungicides. Our project is aiming to reduce the application of copper-containing fungicides by introduc-tion of the new blight forecasting system “ÖKO-SIMPHYT” based on meteorological parameters. Primary stem infections should be reduced by seed treatment with copper fungicides thus to postpone the beginning of the blight epidemic as well as the start of spraying. To control secondary infections on the foliage, fungicide strategies should be elaborated to achieve best efficacy with reduced amounts of copper. Therefore copper amounts and spraying intervals should be adjusted to the infection pressure. Based on the biological and epidemiological conditions for primary and secondary infections the new developed potato blight forecast system ÖKO-SIMPHYT should be optimized