Geophysical signature of Målingen,the minor crater of the Lockne–Målingen doublet impact structure

Målingen is the 0.7 km wide minor crater associated to the 10 times larger Lockne crater in the unique Lockne–Målingen doublet. The craters formed at 458 Ma by the impact of a binary asteroid related to the well-known 470 Ma Main Belt breakup event responsible for a large number of Ordovician craters and fossil meteorites. The binary asteroid struck a target sequence including ~500 m of sea water, ~80 m of limestone, ~30 m of dark mud, and a peneplainized Precambrian crystalline basement. Although the Lockne crater has been extensively studied by core drillings and geophysics, little is known about the subsurface morphology of Målingen. We performed magnetic susceptibility and remanence, as well as density, measurements combined with gravity, and magnetic field surveys over the crater and its close vicinity as a base for forward magnetic and gravity modeling. The interior of the crater shows a general magnetic low of 90–100 nT broken by a clustered set of high-amplitude, short wavelength anomalies caused by bodies of mafic rock in the target below the crater and as allogenic blocks in the crater infill. The gravity shows a general −1.4 mgal anomaly over the crater caused by low-density breccia infill and fractured crystalline rocks below the crater floor. The modeling also revealed a slightly asymmetrical shape of the crater that together with the irregular ejecta distribution supports an oblique impact from the east, which is consistent with the direction of impact suggested for the Lockne crater.     

Microscopic evidence of stishovite generated in low‐pressure shock experiments on porous sandstone: Constraints on its genesis

It has been almost exactly half a century since the first synthesis of stishovite in shock experiments on quartz was reported, but its formation conditions during shock is still under debate. Here, we present direct transmission electron microscopic observation of stishovite within material recovered from high‐explosive shock experiments on porous sandstone shocked at 7.5 and 12.5 GPa. Our observations allow for new conclusions on the genesis of stishovite in a close‐to‐nature environment. The formation of stishovite in short‐time shock experiments proves that its crystallization is ultrafast (<1 μs). Crystals were found only embedded in amorphous veins indicating homogeneous nucleation. Crystallization from melt rather than from glass can be concluded from the observation of roundish, defect‐free crystals up to 150 nm in diameter embedded in nondensified glass. The formation of stishovite at 7.5 GPa is in accordance with the phase diagram of silica, if rapid undercooling is present that becomes only possible by the existence of small hot spots in an otherwise cold material, which is supported by transient heat calculation. The absence of coesite at 7.5 GPa suggests kinetic hindrance of its crystallization from melt and, thus, smaller critical cooling rates compared to stishovite where critical cooling rates are estimated to be as large as 10¹¹ K s^?1. While the amorphous veins containing stishovite represent unambiguously hot spots, no associated pressure amplification could be verified within these veins. The rapid liquidus crystallization of stishovite only in hot spots generated in porous material is an alternative formation mechanism to the widely accepted theory of solid–solid transition from quartz to stishovite and might represent the more general mechanism occurring in nature for low shock pressure events.     

Response of the soft coral Heteroxenia fuscescens to ultraviolet radiation regimes as reflected by mycosporine-like amino acid biosynthesis

The variation in mycosporine‐like amino acid (MAA) concentration in the soft coral Heteroxenia fuscescens in relation to changes in ultraviolet radiation (UVR) regimes was investigated at the Gulf of Eilat, northern Red Sea. Solar radiation (300–700 nm) was measured for different depths and seasons. The UVR irradiance was measured to a depth of 25 m on the reef. The mean attenuation coefficient for UV‐B measured in winter was twofold that of the summer value. Separation of H. fuscescens extracts by reverse‐phase isocratic high‐performance liquid chromatography revealed a single MAA compound, palythine (λ_max = 320 nm). Possible seasonal changes in MAAs in colonies of H. fuscescens along a depth gradient were examined on different dates. Palythine concentrations in the colonies were significantly higher in summer than in the other seasons particularly in shallow water. Possible changes in MAA content in colonies of H. fuscescens as a result of UVR protection, were determined by experiments conducted for periods of 1 week, 1 month and 3 months, at a depth of 5 m. In these experiments colonies were removed from the natural substrate and placed underwater, protected from UVR by a PVC filter. Significant differences between UV‐exposed and protected colonies of H. fuscescens were found only in the 3‐month experiment conducted during the summer. These findings demonstrate that UVR is an important environmental factor regulating MAA biosynthesis in the soft coral H. fuscescens.     

Localized shock-induced melting of sandstone at low shock pressures (<17.5 GPa): An experimental study

Shock-induced recovery experiments were performed to investigate melt formation in porous sandstones in the low shock pressure regime between 2.5 and 17.5 GPa. The sandstone shocked at 2.5 and 5 GPa is characterized by pore closure, fracturing of quartz (Qtz), and compression and deformation of phyllosilicates; no melting was observed. At higher pressures, five different types of melts were generated around pores and alongside fractures in the sandstone. Melting of kaolinite (Kln), illite (Ill), and muscovite (Ms) starts at 7.5, 12, and 15 GPa, respectively. The larger the amount of water in these minerals (Kln ~14 wt%, Ill ~6–10 wt%, and Ms ~4 wt% H₂O), the higher the shock compressibility and the lower the shock pressure required to induce melting. Vesicles in the almost dry silicate glasses attest to the loss of structural water during the short shock duration of the experiment. The compositions of the phyllosilicate-based glasses are identical to the composition of the parental minerals or their mixtures. Thus, this study has demonstrated that phyllosilicates in shocked sandstone undergo congruent melting during shock loading. In experiments at 10 GPa and higher, iron melt from the driver plate was injected into the phyllosilicate melts. During this process, Fe is partitioned from the metal droplets into the surrounding silicate melts, which induced unmixing of silicate melts with different chemical properties (liquid immiscibility). At pressures between 7.5 and 15 GPa, a pure SiO₂ glass was formed, which is located as short and thin bands within Qtz grains. These bands were shown to contain tiny crystals of experimentally generated stishovite.     

Cryogenically cooled low-noise amplifier for radio-astronomical observations and centimeter-wave deep-space communications systems

We report a design solution for a highly reliable, low-noise and extremely efficient cryogenically cooled transmit/receive unit for a large antenna system meant for radio-astronomical observations and deep-space communications in the X band. We describe our design solution and the results of a series of laboratory and antenna tests carried out in order to investigate the properties of the cryogenically cooled low-noise amplifier developed. The transmit/receive unit designed for deep-space communications (Mars missions, radio observatories located at Lagrangian point L2, etc.) was used in practice for communication with live satellites including “Radioastron” observatory, which moves in a highly elliptical orbit.     

Geology,geochemistry and age of a Cu-Mo-bearing granite at Kabeliai,southern Lithuania

Summary A Cu-Mo-bearing granitoid belonging to the concealed Precambrian crystalline basement of Lithuania has been dated by the U-Pb zircon method and investigated geochemically. chemically. The granitoid is located at Kabeliai in southernmost Lithuania and forms part of a granitoid complex recognized as the Marcinkonys batholith. The Kabeliai granite is composed of quartz, plagioclase, microcline and biotite and shows a granitic to adamellitic peralummous/metaluminous composition with dominantly I-type chemistry. U-Pb dating of zircon yields an age of 1505 ± 11 Ma, which is considered to reflect the crystallization age of the granite.The Kabeliai granite displays several similarities in terms of geological setting, chemistry and age with certain granitoids in northeastern Poland (Mazury complex) and northwestern Belorussia (Mostovsky, Kamensky and Vydgodsky plutons), which are considered rapakivi-like in the literature. It is, however, uncertain whether proper rapakivi granites really exist in these areas as none of these granitoids displays the common characteristics of rapakivi granites (A-type chemistry, wiborgitic textures, associated Sn-Be-Pb-Zn-Cu mineralizations). We speculate that the 1.4-1.5 Ga granites southeast of the Baltic Sea rather might be correlated with granites of comparable age and geochemical character in southwestern Sweden. Another possible alternative is that the granitoids in Lithuania may not be correlated with any part of the Fennoscandian Shield.Zusammenfassung Ein Cu-Mo-führender Granitoid, der zum präkambrischen, kristallinen Grundgebirge Litauens gehört, wurde mittels der U-Pb Methode an Zirkonen datiert und geochemisch untersucht. Der Granit repräsentiert einen Teil des Marcinkonys Batholithes, und tritt in Kabeliai, im südlichsten Litauen auf. Der Kabeliai Granit besteht aus Quarz, Plagioklas, Mikroklin und Biotit und zeigt adamellitische, peraluminöse/metaluminöse Zusammensetzung mit vorwiegend 1-Typ Charakter auf. U-Pb Datierung der Zirkone ergibt ein Alter von 1505 ± 11 Mio Jahren, das als Kristallisationsalter anzusehen ist.In seinem geologischen mit Granitoiden im nordöstlichen Polen (Mazury Komplex) und Grant Ånlichkeiten mit Granitoiden im nordöstlichen Polen (Mazury Komplex) und Grant Ånlichkeiten mit Granitoiden im nordöstlichen Polen (Mazury Komplex) und im nordwestlichen Weißrussland (Mostovsky, Kamensky und Vydgodsky Plutone), die in der Literatur als Rapakivi-ähnlich angesehen werden. Es ist jedoch unischer ob echte Rapakivi-Granite in diesen Regionen existieren. Keiner dieser Granite zeigt nämlich die für Rapakivi-Granite typischen Kennzeichen (A-Typ Chemie, Wiborgit Texturen, assoziierte Sn-Be-Pb-Zn-Cu-Mineralisationen). Wir vermuten, daß die 1.4 1.5 Mia Jahren alten Granite südöstlich der Ostsee eher mit Graniten ähnlichen Alters und von ähnlichem geochemischen Charakter im südwestlichen Schweden zu vergleichen sind. Eine weitere Alternative wäre, daß die Granitoide Litauens mit keinem Granit im Fennoskandischen Schild korreliert werden können.

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Geologie, Geochemie und Alter des Cu-Mo führenden granites von Kabeliai, südliches Litauen

     

Patterns of tourist destination-choice and travel behaviour among members of the urban and rural Arab community of Israel: A comparative study of Haifa and Ibilin

The destination-choice and travel behaviour of urban Arab-Israelis from Haifa, and rural Arab-Israelis from the village of Ibillin, are compared. The study examines the role of tradition, socio-economic background and geographical location of residence, in designing the two communities' destination-choice and travel behaviour. The results show that while socio-economic characteristics and life in a city or in a village do not differentiate between the two communities, religious affiliation does play a major role in determining the destination-choice and tourist behaviour of the two sub-communities. It was also found that the predominant factors that shape Arab-Israelis' tourist behaviour are the familiarity factors and that social rather than personal constraints play a major role in deciding which tourist destination is chosen. Policy oriented conclusions are presented in the light of these findings.     

WORK-PLACE UTILITIES AND COMMUTING PATTERNS: ARE THEY CLASS OR PLACE DIFFERENTIATED?*

The work-place utilities and commuting patterns of the employed in Haifa's (Israel) metropolitan field are analyzed using the value-stretch methodology. Statistical test scores reveal class and place (location) variations in the perceived utilities of employed, especially in their commuting patterns (flows). A meaningful commuting pattern analysis should incorporate socioeconomic and demographic elements along with the spatial distribution of job opportunities. Some analytical and policy implications of employment strategies for a postindustrial metropolis are evaluated.     

Group-Differentiated Perceptions of Social Impacts Related to Tourism Development

Perceived social impacts of tourism development on local residents in peripheral destinations are examined in the case of the resort city of Eilat (Israel) by utilizing a value-stretch methodology. Analysis shows that local's perceptions are group differentiated. The less locals are affiliated with tourist occupations, the less affluent they are, and the less their sense of peripherality, the more they are affected by the social consequences of tourism development. Policy implications for tourism development in such peripheral settings are suggested.     

Impact of a non-Gaussian density field on Sunyaev–Zeldovich observables

The main statistical properties of the Sunyaev–Zeldovich (S–Z) effect – the power spectrum, cluster number counts and angular correlation function – are calculated and compared within the framework of two density fields which differ in their predictions of the cluster mass function at high redshifts. We do so for the usual Press & Schechter mass function, which is derived on the basis of a Gaussian density fluctuation field, and for a mass function based on a  χ²  distributed density field. These three S–Z observables are found to be very significantly dependent on the choice of the mass function. The different predictions of the Gaussian and non-Gaussian density fields are probed in detail by investigating the behaviour of the three S–Z observables in terms of cluster mass and redshift. The formation time distribution of clusters is also demonstrated to be sensitive to the underlying mass function. A semiquantitative assessment is given of its impact on the concentration parameter and the temperature of intracluster gas.