Kurzer Bericht über die sedimentpetrographische Untersuchung zweier Lotkerne der Albatross-Expedition

Ohne Zusammenfassung     

Die Bedeutung der Atmosphärischen Wasserzirkulation für das Klima der Vorzeit

Ohne ZusammenfassungAuf der Heimfahrt von der Jahresversammlung der Geologischen Vereinigung in Köln, auf der das Thema Klima der Vorzeit behandelt wurde, drängte sich mir bei meinen rückschauenden Betrachtungen ein Klimafaktor auf, der bei der Tagung nicht erwähnt worden war und auch sonst wohl kaum in die Diskussion gezogen wurde, der mir aber doch beachtenswert scheint. So sollen die folgenden Zeilen gewissermaßen als nachträgliche Diskussionsbemerkung gewertet werden.     

昔日全球环境变化的自然磁记录

沉积物的岩石磁学参量反映了它在海洋及大陆范围内沉积时的古环境及古气候条件.尽管对这种现象的认识还不彻底,但人们对于那些导致磁性增强或减弱的作用已有了很好的了解.这些作用包括可变的陆源物质沉积通量,铁磁性矿物在原地的有机及无机形成,以及这些矿物成岩过程中的分解.至少在过去的700万年间,在大量的沉积记录中观察到了磁性矿物集合体的周期性出现,这些周期性出现涉及到了标准的米兰柯维奇理论的轨道频率,证实了岩石磁学同过去全球变化间的关系.但是,磁信号的定量解译仍然处在幼年期,并且受到了信号形成过程中复杂的相互作用的干扰.     

XMM–Newton observations of bright ROSAT selected active galactic nuclei with low intrinsic absorption

We present a sample of 21 ROSAT bright active galactic nuclei (AGNs), representing a range of spectral classes, and selected for follow-up snapshot observations with XMM–Newton . The typical exposure was between 5 and 10 ks. The objects were primarily selected on the bases of X-ray brightness and not on hardness ratio; thus the sample cannot be strictly defined as a 'soft'sample. One of the main outcomes from the XMM–Newton observations was that all of the AGN, including 11 type 1.8–2 objects, required low levels of intrinsic absorption  ( N _H≲ 10²¹ cm⁻²)  . The low absorption in type 2 systems is a challenge to account for in the standard orientation-based unification model, and we discuss possible physical and geometrical models which could elucidate the problem. Moreover, there does not appear to be any relation between the strength and shape of the soft excess, and the spectral classification of the AGN in this sample. We further identify a number of AGN which deserve deeper observations or further analysis: for example, the low-ionization nuclear emission regions (LINERs) NGC 5005 and NGC 7331, where optically thin thermal and extended emission is detected, and the narrow-line Seyfert 1 II Zw 177, which shows a broad emission feature at ∼ 5.8 keV.     

Ejection-velocity distributions from impacts into coarse-grained sand

Abstract— Velocities of ejecta from seven impacts of aluminum projectiles into coarse-grained sand have been measured with a laser-based apparatus that produces stroboscopic photographs of individual grains in ballistic flight. Speeds and angles of the majority of the ejecta can then be measured very precisely. There appears to be little effect of impact velocity on the functional relationship between the scaled, radial launch position and either the speed or angle of ejection; the seven experiments covered a range of impact velocities from 0.8 to 1.9 kms^—1. The measured ejection speeds follow power-law distributions, as predicted by dimensional analysis, but the angle of ejection is not constant throughout a given event as predicted. Indeed, the angle of ejection declines gradually with increasing radial distance from the impact point, but there are indications that the angle increases again as the position of the final crater's rim is approached. The exponents determined from scaled crater dimensions and ejection-speed distributions are substantially different. Although this might imply that assumptions used in the dimensional analysis are not valid, it is also possible that the coarse sand, whose component grains were comparable in dimension to the diameter of the impactors, instead presented a target that was more of an inhomogeneous aggregate of large fragments than a uniform, continuous medium.     

APEX and ATCA observations of the southern hot core G327.3-0.6 and its environs

There is no generally accepted evolutionary scheme for high mass star formation yet. A simple approach to address this problem is to cover several of the known stages during the formation of massive stars in the same cloud and then investigate their properties trying to construct an evolutionary sequence. Here we present such a project conducted with complementary APEX and ATCA observations. These observations show a compact and bright single hot core in the G327.3-0.6 region on a 0.03 pc scale with a mass of 500 M_⊙ and 0.5–1.5 10⁵ L_⊙. Additionally a clumpy filament is seen in N₂H⁺. Together with cm continuum observations, the data reveal like pearls on a string several stages of massive star formation, with likely the youngest stages hiding in the cold N₂H⁺ cores analysed with a multilevel study of the APEX and ATCA observations.     

Experimental impacts into chondritic targets,part I: Disruption of an L6 chondrite by multiple impacts

Abstract— A fragment of an L6 chondrite (Allan Hills [ALH] 85017,13) with an initial mass (M₀) of 464.1 g was the target in a series of experimental impacts in which the largest remaining fragment (M_R) after each shot was impacted by a 3.18 mm ceramic sphere at a nominal speed of 2 km s^?1. This continued until the mass of the largest remaining piece was less than half the mass of the target presented to that shot (M_S). Two chunks of Bushveldt gabbro with similar initial masses were also impacted under the same conditions until M_R was less than half M₀. The two gabbro targets required a total of 1.51 × 10⁷ and 1.75 × 10⁷ erg g^?1 to attain 0.27 and 0.33 M_R/M₀, respectively; the chondrite, however, was considerably tougher, reaching 0.40 and 0.21 M_R/M₀ only after receiving 2.37 × 10⁷ and 3.10 × 10⁷ erg g^?1, respectively. The combined ejecta and spallation products from the gabbro impacts were coarser than those from the chondrite and in sufficient quantities that the new surface areas exceeded those from the meteorite until the fifth shot in the chondrite series, which was the number of impacts required to disrupt each gabbro target (i.e., M_R/M₀ ≤ 0.5). Unlike the behavior shown in previous regolith‐evolution series, neither gabbro target produced an enhancement in the size fraction reflecting the mean size of the crystals composing the rock (about 3 mm), an effect possibly related to the width of the shock pulse. The original chondrite was so fine‐grained and fractured, and the variance in its grain‐size distribution so large, that effects related to grain size were relegated to the<63 μm fraction. Impacts into ALH 85017 produced abundant, fine‐grained debris, but otherwise the slopes of its size distributions were comparable to those from other experiments involving natural and fabricated terrestrial targets. The characteristic slopes of the chondrite's size distributions, however, were notably more constant over the entire nine‐impact series than those from any of the terrestrial targets, a testament to the control over comminution apparently exerted by pre‐existing fractures and other, microscopic damage in the meteorite. The enhancement in the finer fraction of debris from ALH 85017 indicates that ordinary chondrites in solar orbit would be very efficient contributors to the cosmic‐dust complex. At the same time, the greater resistance to disruption displayed by ordinary chondrites relative to that exhibited by igneous rocks indicates that a selection effect could be operative between the annealed, ordinary‐chondritic breccias and relatively weaker, differentiated meteorites. Preferential survival from their time in the regoliths of their parent bodies through their transit to Earth and passage through the atmosphere suggests that meteorite collections could be biased in favor of the ordinary chondrites.     

Surface features on glass spherules from the Luna 16 sample

Two ellipsoidal spherules approximately 0.5 mm in diameter were studied in detail using a scanning electron microscope. A variety of surface features were observed: vesicles, mounds, dimples, streaks, ridges, grooves, accretion phenomena, and high-speed impact craters. The diameters of 27 glass-lined pits formed by impact on one spherule range from less than 1m to approximately 50m. Intermediate-sized glass-lined pits surrounded by concentric fractures demonstrate the transition between larger craters that have both a pit and a spall zone and generally smaller craters that have only a pit. Assuming all craters showing evidence of impact-related melting or flow are the result of primary impacts, the differential mass spectrum of impacting meteoroids in the range 10^–11 to 10^–10 g is in good agreement with a spectrum based on satellite-borne particle-detecting experiments.