Tektites: Origin as melts produced by the impact of small projectiles onto dry targets

The formation of tektites in general and layered tektites in particular seems to require a very special kind of cratering event. Evidence for the formation of pools of melt free of unmelted clasts has not been reported for the well-studied terrestrial craters such as Manicouagan or Ries. It is suggested that large amounts of relict-free melt were produced only when a sizeable fraction of the cratered target consisted of dry, high-porosity materials such as aeolian sediments. Since dry, high-porosity target materials are always confined to the outer 100 to 200 m of the Earth, the fraction of melt produced melt is probably higher in small (radius 50 to 500 m) craters than in large (r greater than 1 km) craters. Another reason to infer that the Southeast Asian tektites were produced in a multitude of small craters is the wide distribution of layered tektites. The file spans at least 1200 km, which would require ballistic ejection at velocities greater than 2 km s(-1) if all melt was generated in a single crater. It seems impossible to devise a scenario that would lead to the deposition of primary melt as a crystal-free pool at a distance of 600 km from the crater

Differentiated meteorites and the components of chondrites

Findings are summarized from research conducted to develop a detailed classification of all kinds of meteorites in an effort to determine the conditions in the solar nebula, the processes that produced chemical fractionations in chondrites and formed chondrules, as well as ascertain the processes that occurred in the parent bodies of differentiated meteorites (which preserve a partial record of the chondritic materials from which they formed). Fractionation patterns within iron meteorite groups are analyzed

Origin of mesosiderites as a natural consequence of planet formation

The mineral composition of mesosiderites is described and a theory of the origin and evolution of these meteorites is presented. It is suggested that the asteroid parent body of the mesosiderites also formed in the inner solar system, perhaps just within the orbit of Mars. As a result of close planetary encounters, some bodies that formed near Earth or Venus were gravitationally perturbed into non-circular orbits; a few such bodies passed through the mesosiderite region at high relative velocities, colliding with and destroying a few of the native asteroids. Olivine-rich silicate mantles shattered into small pieces, but the stronger metal cores remained as large fragments. Much of the debris remained in circular orbits and accreted to the basaltic regoliths of intact native asteroids at low relative velocities. The large core fragments that collided with the crust greatly enriched restricted regions of the surface in metal. These localized regions were the mesosiderite progenitors; they accounted for only about 1% of the surface area of the parent bodies

Exploring the Pathophysiological Concepts of Ebola Virus

The Ebola virus is a member of the filoviridae family. Five distinctive species of ebolavirus have been identified, four of which are known to cause disease in humans (Martines, Ng, Greer, Rollin, and Zaki, 2014). The specific species known to cause disease in humans are Zaire, Sudan, Ivory Coast, and Bundibugyo (Bray & Chertow, 2014). Bah et al. (2015) report that the Zaire ebolavirus (EBOV) was the cause of the most recent West African outbreak and carries the highest human mortality rate among the five known species, with up to 90% of cases being fatal. Ebola is a filamentous, enveloped, single-stranded, negative-sense RNA virus (Martines, et al., 2014). According to Jarrett (2014), just ten Ebola microbes are needed to successfully transmit the virus from human to human, proving it to be highly capable of infectivity. “Outbreaks typically originate with introduction of the virus into humans from a wild animal reservoir, with subsequent human-to-human transmission, often fueled by nosocomial amplification in resource-poor settings” (Bah, et al., 2015, p. 40)

The Effects of Scenic and Environmental Amenities on Agricultural Land Values

Ascribing land value solely to productive capacity does not accurately capture the impact environmental amenities provide on western land prices. Agricultural land prices in Wyoming are estimated using a hedonic price model and Geographic Information Sciences (GIS) data. These GIS measurements include on-parcel wildlife and fish habitat, viewscape attributes and distance to protected federal lands. A feasible generalized least squares (FGLS) approach is used to address both spatial autocorrelation and heteroscedasticity. The estimation is robust and highly significant. Results indicate that amenities as well as productivity are significant in explaining land values for the sample analyzed. Such information is useful for landscape management in the face of amenity threatening parcel fragmentation.Environmental Economics and Policy, Land Economics/Use,

Radiative corrections for (e,e′p) reactions at GeV energies

A general framework for applying radiative corrections to (e,e′p) coincidence reactions at GeV energies is presented, with special emphasis to higher-order bremsstrahlung effects, radiation from the scattered hadron, and the validity of peaking approximations. The sensitivity to the assumptions made in practically applying radiative corrections to (e,e′p) data is extensively discussed. The general framework is tested against experimental data of the 1H(e,e′p) reaction at momentum transfer values larger than 1.0 (GeV/c)^2, where radiative processes become a dominant source of uncertainty. The formulas presented here can easily be modified for any other electron-induced coincidence reaction

Exposing metal and silicate charges to electrical discharges: Did chondrules form by nebular lightning?

In order to investigate the hypothesis that dust aggregates were transformed to meteoritic chondrules by nebular lightning, we exposed silicatic and metallic dust samples to electric discharges with energies of 120 to 500 J in air at pressures between 10 and 10^5 Pa. The target charges consisted of powders of micrometer-sized particles and had dimensions of mm. The dust samples generally fragmented leaving the major fraction thermally unprocessed. A minor part formed sintered aggregates of 50 to 500 micrometer. In a few experiments melt spherules having sizes smaller than 180 micrometer in diameter (and, generally, interior voids) were formed; the highest spherule fraction was obtained with metallic Ni. Our experiments indicate that chondrule formation by electric current or by particle bombardment inside a discharge channel is unlikely.Comment: Accepted by Icaru

Improving the quantification of land cover pressure on stream ecological status at the riparian scale using High Spatial Resolution Imagery

The aim of this paper is to demonstrate the interest of High Spatial Resolution Imagery (HSRI) and the limits of coarse land cover data such as CORINE Land Cover (CLC), for the accurate characterization of land cover structure along river corridors and of its functional links with freshwater ecological status on a large scale. For this purpose, we compared several spatial indicators built from two land cover maps of the Herault river corridor (southern France): one derived from the CLC database, the other derived from HSRI. The HSRI-derived map was obtained using a supervised object-based classification of multi-source remotely-sensed images (SPOT 5 XS-10 m and aerial photography-0.5 m) and presents an overall accuracy of 70 %. The comparison between the two sets of spatial indicators highlights that the HSRI-derived map allows more accuracy in the quantification of land cover pressures near the stream: the spatial structure of the river landscape is finely resolved and the main attributes of riparian vegetation can be quantified in a reliable way. The next challenge will consist in developing an operational methodology using HSRI for large-scale mapping of river corridor land cover,, for spatial indicator computation and for the development of related pressure/impact models, in order to improve the prediction of stream ecological status

Comparison of Reproductive Performance of Crossbred Ewes Bred for Either Fall or Spring Lambing at Two Different Locations: Progress Report

The objective of the current study was to measure the performance of crossbred ewes lambing in the fall compared to similar ewes lambing in the spring at two different locations

Meteorites on Mars observed with the Mars Exploration Rovers

Reduced weathering rates due to the lack of liquid water and significantly greater typical surface ages should result in a higher density of meteorites on the surface of Mars compared to Earth. Several meteorites were identified among the rocks investigated during Opportunity’s traverse across the sandy Meridiani plains. Heat Shield Rock is a IAB iron meteorite and has been officially recognized as ‘‘Meridiani Planum.’’ Barberton is olivine-rich and contains metallic Fe in the form of kamacite, suggesting a meteoritic origin. It is chemically most consistent with a mesosiderite silicate clast. Santa Catarina is a brecciated rock with a chemical and mineralogical composition similar to Barberton. Barberton, Santa Catarina, and cobbles adjacent to Santa Catarina may be part of a strewn field. Spirit observed two probable iron meteorites from its Winter Haven location in the Columbia Hills in Gusev Crater. Chondrites have not been identified to date, which may be a result of their lower strengths and probability to survive impact at current atmospheric pressures. Impact craters directly associated with Heat Shield Rock, Barberton, or Santa Catarina have not been observed, but such craters could have been erased by eolian-driven erosion.Additional co-authors: DW Ming, RV Morris, PA de Souza Jr, SW Squyres, C Weitz, AS Yen, J Zipfel, T Economo