40Ar-39Ar ages of Dellen,Jänisjärvi,and Sääksjärvi impact craters

Abstract— ⁴⁰Ar-³⁹Ar age measurements were made for three whole rock melt samples produced during impact events which formed the Dellen, Jänisjärvi, and Sääksjärvi craters on the Baltic Shield. An age of 109.6 ± 1.0 Ma was obtained for the Dellen sample based on an age spectrum plateau. The age spectrum shows a small (7%) loss of radiogenic ⁴⁰Ar from low temperature fractions. Ages of 698 ± 22 Ma and 560 ± 12 Ma were obtained from isochrons for the Jänisjärvi and Sääksjärvi samples, respectively. Data obtained by laser degassing support the Sääksjärvi result. The presence of excess ⁴⁰Ar is indicated in lower temperature fractions for both samples and is correlated with K concentrations in the Sääksjärvi sample. Models explaining these results may require a change in the local “atmospheric” Ar isotopic composition as cooling of melt rocks proceeded. However, it cannot be excluded that devitrification and/or alteration changed the Ar budget. A crater production rate on the Baltic Shield based on measured ages of 6 craters is (0.3 ± 0.2) · 10^?14 20-km-and-larger craters per km² per year, in satisfactory agreement with previous estimates.     

Zur dynamischen Äquivalenz der post-NEWTONSCHEN Näherung für die Planetentheorie in der allgemeinen Relativitätstheorie und in der trägheitsfreien Mechanik mit RIEMANNSchem Gravitationspotential

Proof of the dynamical equivalence of the post-NEWTONian approximations for the LAGRANGAIN representations of planetary motions according to GRT and according to our “RIEMANNian dynamics with MACH EINSTEIN doctrine”. Finally, we discuss the equivalence problem for general post-NEWTONian LAGRANGians of the one-body Problem in celestical mechanics.     

Singularitäten in der Allgemeinen Relativitätstheorie

“Regular solutions of EINSTEIN 's equations” mean very different things. In the case of the empty-space equations, R_ik = 0, such solutions must be metrics g_ik(x^l) without additionaly singular “field sources” (EINSTEIN 's “Particle problem”). – However the “phenomenological matter” is defined by the EINSTEIN equations R_ik – 1/2g_ikR =–xT_ik itselves. Therefore if 10 regular functions g_ik(x^l) are given (which the inequalities of LORENTZ -signature fulfil) then these g_ik define 10 functions T_ik(x^l) without singularities. But, the matter-tensor T_ik must fulfil the two inequalities T ≥ 0, T ≥ 1/2 T only and therefore the EINSTEIN -equations with “phenomenological matter” mean the two inequalities R ≥ 0, R ≤ 0 which are incompatible with a permanently regular metric with LORENTZ -signature, generally.     

Wärmetransport und Wärmeerzeugung in einem turbulent bewegten Gas

This paper deals with heat transfer and heat production in a gas being in turbulent motion. Our aim is to derive a general equation for the mean temperature which contains coefficients determined by turbulence. This treatment is restricted to weak, homogeneous and stationary turbulence. Especially the heating by density fluctuations is discussed and compared with heating due to internal friction.     

Agate as an indicator of impact structures: An example from Sääksjärvi,Finland

Abstract— Mineralogical, petrographical and chemical determinations were made for 743 agate (banded variety of chalcedonic quartz) nodules (diameters from 5 mm to 5 cm) formed during postimpact, low-temperature hydrothermal activity as vesicle fillings in the melt rocks of the Sääksjärvi meteorite impact structure (diameter 5 km) in southwest Finland. Other hydrothermal vesicle fillings in the impact melt rocks include chlorite, mordenite, smectite and kaolinite. The agates were classified into two types, whose mineralogical properties and chemical compositions fall within the range of volcanic agates (basaltic and rhyolitic host rocks). The relatively high age (～510 Ma) of the Sääksjärvi impact melt rocks, however, is reflected by the presence of recrystallization textures, which are rare in younger volcanic agates. The Sääksjärvi structure was initially located after following the fortuitous discovery of agate “path-finders” in the glacial overburden. It is recommended that wherever volcanic type agates are found as float in Precambrian shield areas devoid of younger volcanic rocks, the possible presence of impact (or volcanic) craters in the vicinity should be considered.     

Eine neue Methode zur Bestimmung der statistischen Zählverluste bei Photonenzählern

A simple method for the determination of statistical pulse losses of photon counting photometer in dependence on the pulse intensity was deveoloped. The slowly decereasin brightness of the clear sky in the dusk serves a light source. With the help of neutral filter one gets two different pulse rates for two intensities. From a series of such measurements with different intensities one can derive the correction in dependence on pulse density in form of a power sequence.     

Eine einfache Methode zur Bestimmung und Berücksichtigung der Zählverluste bei Photonenzählern

The statistical puls loss by the use of a photon counting photometer can be corrected on the base of the equation n = Ne^−Nι. A simple method is given for determination of the parameter ι which can be realized on each photometer.     

Über schnelle Änderungen der magnetischen Feldstärke von Sonnenflecken

The results from hourly measurements of the magnetic field strengths of several main spots in three selected spot groups within the years 1968/69 are given in graphs. The values of the field strength used in the graphs are mean values out of three spectrograms taken immediately one after another. The mean error of a mean value is ±85 Gauss. Besides a general tendency in the daily course of the field strength the graphs are showing rapid variations up to 500 Gauss within a few hours. In contrast to these variations which are probably real, the frequent short time variations indicated cannot be regarded as certain. In addition to the observations of the field strength the development of the spot groups is described, and informations on the flare-activity are given.     

Paleomagnetism and petrophysics of the Jänisjärvi impact structure,Russian Karelia

Abstract— Paleomagnetic, rock magnetic, and petrophysical results are presented for impactites and target rocks from the Lake Jänisjärvi impact structure, Russian Karelia. The impactites (tagamites, suevites, and lithic breccias) are characterized by increased porosity and magnetization, which is in agreement with observations performed at other impact structures. Thermomagnetic, hysteresis, and scanning electron microscope (SEM) analysis document the presence of primary multidomain titanomagnetite with additional secondary titanomaghemite and ilmenohematite. The characteristic impact‐related remanent magnetization (ChRM) direction (D = 101.5°, I = 73.1°, α₉₅ = 6.2°) yields a pole (Lat. = 45.0°N, Long. = 76.9°E, dp = 9.9°, dm = 11.0°). Additionally, the same component is observed as an overprint on some rocks located in the vicinity of the structure, which provides proofs of its primary origin. An attempt was made to determine the ancient geomagnetic field intensity. Seven reliable results were obtained, yielding an ancient intensity of 68.7 ± 7.6 μT (corresponding to VDM of 10.3 ± 1.1 times 10²² Am²). The intensity, however, appears to be biased toward high values mainly because of the concave shape of the Arai diagrams. The new paleomagnetic data and published isotopic ages for the structure are in disagreement. According to well‐defined paleomagnetic data, two possible ages for magnetization of Jänisjärvi rocks exist: 1) Late Sveconorwegian age (900–850 Myr) or 2) Late Cambrian age (?500 Myr). However, published isotopic ages are 718 ± 5 Myr (K‐Ar) and 698 ± 22 Myr (³⁹Ar‐⁴⁰Ar), but such isotopic dating methods are often ambiguous for the impactites.     

Über periodische Bahnen im eingeschränkten Dreikörperproblem und in der Nähe der Kommensurabilitäten vom Typus (k + 1)/k

The authors, collaborating during the winter 1966/67, performed numerical investigations on form and character of periodic solutions of the restricted problem of three bodies in the Sun–Jupiter-System and in the neighbourhood of the resonances of the (k + 1)/k type. The principal part of these computations which were achieved using a fast IBM-computer refers to the cases 2/1 (Hecuba-gap) and 3/2 (Hilda-group). The results gave new insight into the genealogy of periodic orbits in the regions which do not contain solutions of Poincaré's first genre. Moreover, L. Carpenter tried to develop an analytical theory (here not explicitely described) which leads to convergent trigonometric series for the coordinates of periodic orbits with restricted eccentricities, using the method of general perturbations in rectangular coordinates recently published by P. Musen and himself.     

Empirische Atmosphärenmodelle zur Erklärung des Lichtwechsels magnetischer Sterne

Empirical model atmospheres on the basis of MIHALAS models were investigated. If the temperature of the outer layers in a spot is higher than in the surrounding normal atmosphere and lower than in the deeper layers, many characteristics of the observed amplitude-wavelength relation of magnetic stars can be explained.     

MAXWELLs Äthertheorien

The present paper is devoted to MAXWELL 's most peculiar finding of his celebrated theory of electrodynamics. We explain carefully the essential ideas of MAXWELL 's works from 1855 and 1861/62 in a modern style of reasoning and the nomenclature used nowadays. Quotations refer to ”︁The Scientific Papers of J. C. MAXWELL ” (1890).     

Über die Möglichkeit,die Temperaturverteilung in Sonnenflecken durch einen anisotropen Wärmetransport zu erklären

Numerical solutions of a heat conduction problem in an anisotropic medium are used for a discussion of the possibility to explain the temperature distribution in sunspots and their environment. The anisotropy is assumed being due to the strong magnetic field in sunspots and the region below. This magnetic field forces the convection to take an anisotropic structure (two-dimensional turbulence) and thus the region gets anisotropic conduction properties, on the average. The discussion shows that the observed temperature profiles can be explained in case the depth of the region of anisotropy is about as large as the diameter of the spot or larger.     

On the ultracompact nature of 4U 1822−000

We report the discovery of a periodic modulation in the optical lightcurve of the candidate ultracompact X-ray binary 4U 1822−000. Using time-resolved optical photometry taken with the William Herschel Telescope we find evidence for a sinusoidal modulation with a semi-amplitude of 8 per cent and a period of 191 min, which is most likely close to the true orbital period of the binary. Using the van Paradijs & McClintock relation for the absolute magnitude and the distance modulus allowing for interstellar reddening, we estimate the distance to 4U 1822−000 to be 6.3 kpc. The long orbital period casts severe doubts on the ultracompact nature of 4U 1822−000.     

Über die Kontinuitätsmethode zur Auffindung periodischer Lösungen

POINCARÉ's conditions for the existence of periodic solutions of systems of differential equations are simplified by use of transformations of coordinates.     

Shock metamorphic features in quartz grains from the Saarijärvi and Söderfjärden impact structures,Finland

Shock metamorphic features at the Saarijärvi (D > 2 km) and Söderfjärden (D = 6.5 km) structures in Finland have so far only been studied tentatively, although both are considered to be proven impact structures. This work presents the first detailed universal stage study of planar deformation features (PDFs), feather feature lamellae (FFL), and planar fractures (PFs) in quartz grains from a polymict impact breccia dike from Söderfjärden, and from sedimentary crater‐fill rocks from Saarijärvi. Planar microstructures, particularly PDFs, are very rare and poorly developed or preserved in Saarijärvi, whereas in Söderfjärden they are much more common and well defined. Miller–Bravais indices of the planar microstructures in both Saarijärvi and Söderfjärden are indicative of relatively low‐shock pressure but high shear conditions, only compatible with an impact origin for these structures. Although a Proterozoic age for Saarijärvi cannot be ruled out, the observations of shock features throughout the sedimentary crater‐fill sequence and a brecciated sedimentary dike below the crater floor are more consistent with a Lower Cambrian (or younger) impact age.     

Zur Metallhäufigkeit in ω Centauri

Radiation pressure during the high-luminosity collapse phase of cluster evolution may, under certain circumstances, lead to the ejection of interstellar grains. For the most luminous clusters such ejection might produce significant depletion of heavy elements. It is suggested that the metal abundance dispersion that has recently been detected among the giant stars in ω Centauri (which is the brightest known galactic globular cluster) might be accounted for by such radiation pressure induced heavy element depletion.     

The Widmanstätten pattern

A table is provided to determine the angles within the Widmanstätten pattern as a function of orientation of the slice, and methods are provided to solve the inverse problem, namely to determine the orientation of the slice from measurements of the Widmanstätten pattern.