bluuebunny/crossref_metadata_2025 huggingface dataset:
Geochemical, Sr and Nd isotopic characteristics and tectonic implications for three stages of igneous rock in the Late Yanshanian (Cretaceous) orogeny, SE China
Authors: Chen Cheng-Hong , Lin Wayne , Lan Ching-Ying , Lee Chi-Yu
Published: July 2007

Late Yanshanian magmatism in SE China includes three stages of thermal event induced by the interaction between the continental margin of Eurasia and the paleo-Pacific plate during the Cretaceous period. Products of syn-orogenic magmatism (130–110 Ma) include high-Al gabbros (HAG), and gneissic tonalite, trondhjemite and granodiorite (TTG), which intruded into the deep basement (18–24 km). Rocks of the post- and an-orogenic magmatism are shallow-level (6–8 km) I-type granitoids (110–99 Ma), and miarolitic A-type granites plus rhyolite-dominate bimodal volcanics (94–81 Ma), respectively. Geochemically, HAG and TTG belong to the medium-K calc-alkaline affinity with high Sr/Y, whereas other granitoids are mainly high-K calc-alkaline to shoshonitic rocks with low Sr/Y. Sr and Nd isotope compositions suggest different sources of HAG and TTG from other rocks. Progressive depletions of Ba, Sr, Eu and P from I- to A-type granites reflect partial melting of felsic granulites from hydrous to dry conditions, whereas high Sr/Y in HAG and TTG are compatible with dehydration melting of amphibolites. Tectonic models which accommodate HAG and TTG may involve thickening of the lithosphere to convert the pre-existing lower-crust basic rocks into amphibolites. It was followed by basaltic underplating which is attributed to delamination of the thickened lithosphere and led to triggering of crust melting under exten
Petrochemical characteristics of felsic veins in mantle xenoliths from Tallante (SE Spain): an insight into activity of silicic melt within the mantle wedge
Authors: Shimizu Yohei , Arai Shoji , Morishita Tomoaki , Yurimoto Hisayoshi , Gervilla Fernando
Published: July 2007

Felsic and related veins within mantle-derived peridotite xenoliths from Tallante, Spain, were examined in order to understand the mantle-wedge processes related to the behaviour of Si-rich melt. The thickest part of the vein has a quartz diorite lithology, and is composed mainly of quartz and plagioclase, with pyroxenes, hydrous mineral, apatite, zircon and rutile present as minor phases. The thinner parts are free of quartz and predominantly composed of plagioclase. Orthopyroxene always intervenes between the internal part (plagioclase ± quartz) and host peridotite, indicating that it is a product of interaction between silica-oversaturated melt and olivine. This indicates that a sufficiently high melt/wall rock ratio enabled the melt to retain its silicaoversaturated character.

The quartz diorite part has adakite-like geochemical signatures, except for negative Ba, Rb Eu and Sr anomalies, and positive Th and U anomalies. These negative anomalies indicate that fractionation of plagioclase and hydrous minerals was achieved between the upper most mantle and the slab melting zone. The shape of the rare-earth element (REE) pattern of clinopyroxene in quartz diorite is strikingly similar to that of clinopyroxene phenocrysts from Aleutian adakites. However, the former has one order higher REE contents than the latter, except for Eu which shows a prominent negative spike. This feature was caused by the precipitation of large amounts of plagioclase and small amounts of clinopyroxene from a fractionated adakitic melt before and during solidification. This adakitic melt was produced by partial melting of a detached and sinking slab beneath the Betic area in the Tertiary.
Source and redox controls on metallogenic variations in intrusion-related ore systems, Tombstone-Tungsten Belt, Yukon Territory, Canada
Authors: Hart Craig J. R. , Mair John L. , Goldfarb Richard J. , Groves David I.
Published: July 2007

The Tombstone, Mayo and Tungsten plutonic suites of granitic intrusions, collectively termed the Tombstone-Tungsten Belt, form three geographically, mineralogically, geochemically and metallogenically distinct plutonic suites. The granites (sensu lato) intruded the ancient North American continental margin of the northern Canadian Cordillera as part of a single magmatic episode in the mid-Cretaceous (96–90 Ma). The Tombstone Suite is alkalic, variably fractionated, slightly oxidised, contains magnetite and titanite, and has primary, but no xenocrystic, zircon. The Mayo Suite is sub-alkalic, metaluminous to weakly peraluminous, fractionated, but with early felsic and late mafic phases, moderately reduced with titanite dominant, and has xenocrystic zircon. The Tungsten Suite is peraluminous, entirely felsic, more highly fractionated, reduced with ilmenite dominant, and has abundant xenocrystic zircon. Each suite has a distinctive petrogenesis. The Tombstone Suite was derived from an enriched, previously depleted lithospheric mantle, the Tungsten Suite is from the continental crust including, but not dominated by, carbonaceous pelitic rocks, and the Mayo Suite is from a similar sedimentary crustal source, but is mixed with a distinct mafic component from an enriched mantle source.

Each suite has a distinctive metallogeny that is related to the source and redox characteristics of the magma. The Tombstone Suite has a Au-Cu-Bi association that is characteristic of most oxidised and alkalic magmas, but also has associated, and enigmatic, U-Th-F mineralisation. The reduced Tungsten Suite intrusions are characterised by world-class tungsten skarn deposits with less significant Cu, Zn, Sn and Mo anomalies. The Mayo Suite intrusions are characteristically gold-enriched, with associated As, Bi, Te and W associations. All suites also have associated, but distal and lower temperature Ag-Pb- and Sb-rich mineral occurrences. Although processes such as fractionation, volatile enrichment and phase separation are ultimately required to produce economic concentrations of ore elements from crystallising magmas, the nature of the source materials and their redox state play an important role in determining which elements are effectively concentrated by magmatic processes
Palaeoproterozoic, rift-related, 13C-rich, lacustrine carbonates, NW Russia. Part II: Global isotope signal recorded in the lacustrine dolostones
Authors: Melezhik V. A. , Fallick A. E. , Kuznetsov A. B.
Published: July 2007

A comprehensive study of the ∼2200-Ma-old Kuetsjärvi Sedimentary Formation (KSF), NW Russia, was undertaken to contribute to our understanding of palaeoenvironments associated with the global perturbation of the carbon cycle between 2330 and 2060 Ma. Closely spaced drill core samples (n=95) were obtained from a 150-m-thick unit deposited in rift-bound fluvial-deltaic and shallow-water lacustrine settings with a short-term invasion of sea water. Apart from a very few de-dolomitised samples, all other carbonate lithologies are represented by Corg-free, S-poor, quartz-rich dolostones, stromatolites and travertines which have high Sr concentrations (51–1069 ppm) and low Mn/Sr ratios (2·9 ± 2·1). The carbonate succession, excluding travertines, shows high δ13C (+7·5 ± 0·6‰, n=95) with a limited variation (+5·8 to +8·9‰). Fluctuating δ18O values (10·8–20·4‰) were overprinted during diagenesis, regional greenschist-grade and later retrograde metamorphism. Several short-term stratigraphic excursions of δ13C were apparently governed by evaporation and CO2 degassing combined with pulses of12C-rich hydrothermal waters precipitating travertines. However, the 13C-rich nature of the dolostones reflects the global isotopic signal, which was modified in a shallow water lacustrine environment by evaporation, enhanced uptake of 12C by cyanobacteria, and pene-contemporaneous oxidation and loss of organic material. The best proxies to δ13C and 87Sr/86 Sr of coeval sea water recorded in the KSF dolostones are likely to be around +5–6‰ and 0·70406, respectively. The study of the KSF has shown that circumspection is necessary when attempting to model the behaviour and evolution of the global C-cycle in Deep Time. Models which purport to explain global oceanic–atmospheric evolution without first adequately accounting for the possibility that many Precambrian carbonate deposits might be non-marine, or at least influenced by non-marine fluids, should be viewed with caution
Revision of the scombroid fishes from the Cenozoic of England
Authors: Monsch Kenneth A.
Published: July 2007

Since 1966, when the last major work on fossil scombroid fishes (Scombroidei, Perciformes) from England appeared, our knowledge of the taxonomy and systematics of Recent scombroids has been thoroughly updated, improved and studied in the context of cladistic methods. In comparison, our knowledge of the fossil taxa has lagged much behind. As part of a revision of all fossil and Recent scombroid fishes, the present paper describes an updated systematic palaeontology of the English fossil taxa. These are a subset of taxa subject to a cladistic analysis of Recent and fossil genera combined, the results of which will appear in future papers. Three new genera are erected, two species transferred to other, already existing, ones and a new species is described (in a new genus). The author follows the opinion that Eothynnus Woodward, 1901 is a carangid. Several individual specimens are re-identified. The systematic affinities of Tamesichthys Casier, 1966, Eocoelopoma Woodward, 1901, Scombramphodon Woodward, 1901, Sphyraenodus Agassiz, 1844, Wetherellus Casier, 1966 and Woodwardella Casier, 1966, and a few new taxa, are here considered unknown. Aglyptorhynchus Casier, 1966 is probably a billfish, and Cylindracanthus Leidy, 1856, is possibly one as well, even though there are serious objections to this.
Protaspid ontogeny of Bolaspidella housensis (Order Ptychopariida, Class Trilobita), and other similar Cambrian protaspides
Authors: Lee Dong-Chan , Chatterton Brian D. E.
Published: July 2007

The protaspid ontogeny of Bolaspidella housensis (Walcott, 1886) is re-described. This species is known from the Marjum Formation (Lower Marjuman Stage) of western Utah, USA. Three protaspid stages are recognised, with the instars discriminated most readily by different spacing between the postero-lateral ends of the fixigena. Protaspides of B. housensis are shown to be similar to those of Glaphyraspis parva, from several Upper Cambrian localities in the USA, and Ptychopariide sp. E from the Upper Cambrian of the Wasatch Mountains in Utah, USA.
The seymouriamorph tetrapod Ariekanerpeton sigalovi from the Lower Permian of Tadzhikistan. Part I: Cranial anatomy and ontogeny
Authors: Klembara Jozef , Ruta Marcello
Published: July 2007

Redescription of the cranial anatomy of Ariekanerpeton sigalovi (Seymouriamorpha: Discosauriscidae; Lower Permian, Tadzhikistan) highlights new diagnostic features which permit a new skull reconstruction and revised diagnosis. The largest Ariekanerpeton specimens differ from like-sized Discosauriscus, a second member of Discosauriscidae, in showing: oblique anterior margin of tabular ornamented surface; acute, elongate posterolateral corner of supratemporal; postorbital ventrolateral ramus with small anteroventral process and forming oblique suture with jugal dorsomedial ramus; jugal posterior ramus tapering rearward, forming subhorizontal suture with quadratojugal; weak ventral sculpture lateral to pterygoid articular recess; parasphenoid subrhomboidal, with lightly sculptured anterior wedge-like process; more densely arranged denticle rows on top of low radiating ridges on pterygoid palatal ramus. Gill filaments occur in specimens with skull lengths of up to 30 mm. Detailed examination of ontogenetic changes in Ariekanerpeton and comparisons with other seymouriamorphs are presented.
The seymouriamorph tetrapod Ariekanerpeton sigalovi from the Lower Permian of Tadzhikistan. Part II: Postcranial anatomy and relationships
Authors: Klembara Jozef , Ruta Marcello
Published: July 2007

The postcranial skeleton of Ariekanerpeton sigalovi (Seymouriamorpha: Discosauriscidae; Lower Permian, Tadzhikistan) differs from that of like-sized Discosauriscus specimens in showing: wider interclavicle anterior plate with smaller, rhomboidal sculptured field on its ventral surface not reaching plate posteromedial margins; broader interclavicle plate-stem junction; slightly narrower interclavicle posterior stem; anteroposteriorly narrower clavicle ventral plate with convex posterior margin; shorter, more robust humerus; four phalanges on fourth manus digit (five phalanges in Discosauriscus); ilium more elongate dorsoventrally with anteroposteriorly narrower neck; posterior process of iliac blade oriented distinctly posterodorsally rather than horizontally; more gracile atlantal rib; broadened distal end of second presacral rib. A revised cladistic analysis of the best known seymouriamorph species retrieves Ariekanerpeton either as sister group to both species of Discosauriscus, or to D. austriacus only.
Tooth histology patterns in early tetrapods and the presence of ‘dark dentine’
Authors: Warren Anne , Turner Susan
Published: July 2007

The presence of a petaloid pattern (previously known as ‘dark dentine’) in cross sections of teeth of the embolomere Pholiderpeton attheyi has been used as a synapomorphy of the embolomeres or of the embolomeres plus the stem tetrapod, Crassigyrinus scoticus. Among the taxa studied, dentine that appears dark results from closely packed dentine tubules and can be found in any part of a tooth section in which such crowding occurs. The petaloid pattern is restricted to tooth sections of a particular diameter, and is obliterated in larger sections of teeth that show complex folding. Petaloid dentine has been found in all tetrapod teeth with plicidentine that were sectioned in this study, whether from stem tetrapods, the Embolomeri, Temnospondyli, or Stereospondyli, and has been recognised in some sarcopterygian fish, an extant actinopterygian fish, ichthyosaurs, and Varanus. The presence of petaloid dentine is neither a synapomorphy of the tetrapod node nor of any node within tetrapods
Cranial morphology and ontogeny of the Permo-Carboniferous temnospondyl Archegosaurus decheni Goldfuss, 1847 from the Saar–Nahe Basin, Germany
Authors: Witzmann Florian
Published: July 2007

Morphology and ontogenetic changes in the skull and hyobranchium of the Permo-Carboniferous temnospondyl Archegosaurus decheni from the Saar–Nahe Basin (SW Germany) are described in detail, based on 181 skulls ranging from 18 to 279 mm in length. Three-dimensional skull reconstructions including the palate of different growth stages are provided. The extremely elongate choanae and up to four median symphyseal teeth are unique to A. decheni. Among neurocranial elements, the exoccipital is well ossified and forms the paroccipital process as in stereospondyls. The shaft of the stapes which projects into the squamosal embayment grows with positive allometry and possesses a distinct lateral process. The basibranchial is well ossified in adults and exhibits a complex, spoon-like morphology. Small larvae were euryphagous and used non-directed suction and jaw prehension during prey capture. Larger larvae and adults were mainly ichthyophagous, as is indicated by the increasingly elongated snout, differentiation of marginal teeth, and nutrition remains. After a prolonged larval period, juvenile and adult A. decheni remained in the aquatic habitat, as suggested by the presence of lateral line sulci, the ‘aquatic type’ of septomaxilla and choana, and the absence of a nasolacrimal duct.
A new Late Cambrian pentastomid and a review of the relationships of this parasitic group
Authors: Waloszek Dieter , Repetski John E. , Maas Andreas
Published: July 2007

Pentastomida, tongue worms, are a taxon of about 130 species of parasites, living exclusively in the respiratory tracts of vertebrates. Three-dimensionally preserved Upper Cambrian larvae already demonstrate a high degree of adaptation to parasitism, striking morphological conservatism, and a high diversification by the Late Cambrian, thereby suggesting a likewise diversified host group. Not least due to their highly modified morphology, the systematic affinities of pentastomids remain controversial. The two major alternatives place the group as either close to branchiuran crustaceans or as stem-lineage derivatives of the Euarthropoda. To this set of Cambrian fossil representatives of the pentastomids we can add a new form from Lower Ordovician boundary beds from Sweden, most likely reworked from Upper Cambrian horizons. Based on this new species, named Aengapentastomum andresi gen. et sp. nov., and the available information about fossil and Recent pentastomids, we review the diverging ideas on the systematic position of this fully parasitic taxon.
The structure of the sarcopterygian Onychodus jandemarrai n. sp. from Gogo, Western Australia: with a functional interpretation of the skeleton
Authors: Andrews Mahala , Long John , Ahlberg Per , Barwick Richard , Campbell Ken
Published: July 2007

A description of the head, mandible, pectoral girdle, humerus, medial fins and their supports, and the dissociated vertebral column has been prepared for Onychodus jandemarrai n. sp. from the Gogo Formation (Frasnian) of Western Australia. This is the most completely known species of the genus. The feature influencing most of the head morphology is the retractable parasymphysial tusk whorls. Their presence has caused a reorganisation of the braincase, palate (including the loss of the vomers), and lateral displacement of the nasal capsules. The extensive mandibular articulation is in cartilage, and the mandibular symphysis is weak. This makes for a kinetic skull. There is a single submandibular on each side. The vertebral column is poorly ossified, consisting of intercentra which have no ventral contact, and pleurocentra. The neural arches have no longitudinal ligament, have unequal sides, and asymmetrical placing of the dorsal and ventral nerve root foramina. Each arch has an anterior surface that often attaches to the next anterior arch. The caudal fin is almost diphycercal; all the medial fins have strong support structures. An attempt is made to discuss the functional morphology of many features of the skeleton.
Hybodont sharks from the Middle Jurassic of the Inner Hebrides, Scotland
Authors: Rees Jan , Underwood Charlie J.
Published: July 2007

Non-marine Bathonian (Middle Jurassic) strata on the Isles of Eigg and Skye in Scotland have yielded fossil remains of eight hybodont shark taxa. Faunas from several horizons within the Lealt Shale and Valtos Formation on the Isle of Eigg include six species: Hybodus grossiconus, Hybodus sp. 1, Hybodus sp. 2, Lissodus leiodus, L. leiopleurus and Parvodus pattersoni. Large collections of teeth of L. leiodus and L. leiopleurus enable a better understanding of the dentitional patterns of the two species and their differential diagnosis. Surface-collecting from exposures of the Kilmalaug Formation on the Isle of Skye yielded hybodont teeth of two taxa: Hybodus sp. 3 and Acrodus caledonicus sp. nov. The occurrence of Acrodus in the Bathonian of Scotland is one of the youngest known occurrences of this genus, and the only non-marine record in the European Jurassic. Collectively, the hybodont assemblages from the Scottish Bathonian provide evidence that non-marine faunas of the group were specifically diverse in the Middle Jurassic.
Skeletal development of the temnospondyl Acanthostomatops vorax from the Lower Permian Döhlen Basin of Saxony
Authors: Witzmann Florian , Schoch Rainer R.
Published: July 2007

The development of the skeleton of the small temnospondyl Acanthostomatops vorax is described, based on 32 specimens from the Lower Rotliegend of Niederhäslich in Saxony. Both individually and ontogenetically, the skull table, length of gape, and dentition of the parasphenoid are broadly variable. The stapes has a short and straight shaft and a well-defined two-headed proximal region. Small specimens have three or four pairs of ossified ceratobranchials in the gill region, while the adult hyobranchium is composed of four pairs of hypobranchials and probably some additional elements. The postcranium is characterised by a stout and well-ossified humerus that is already large in small larvae, a minute rectangular interclavicle, a robust but short femur, a relatively short trunk with 21–22 presacrals and a moderate tail with 28 vertebrae. In adults, the trunk skeleton became proportionally shorter and the femur smaller with respect to skull length. Metamorphosis is best indicated by the disappearance of the larval gill skeleton, which was probably resorbed, while the structure of the limbs and axial skeleton as well as the absence of lateral line sulci suggest a terrestrial existence for adults.
The Sub-Boreal/Boreal ammonite succession at the Oxfordian/Kimmeridgian boundary at Flodigarry, Staffin Bay (Isle of Skye), Scotland
Authors: Matyja Bronisław A. , Wierzbowski Andrzej , Wright John K.
Published: July 2007

This paper describes extensive new collections of ammonites made bed-by-bed across the Oxfordian/Kimmeridgian boundary sequence in the Flodigarry sections at Staffin Bay on the Isle of Skye. The ammonites belong to the Sub-Boreal family Aulacostephanidae and the Boreal family Cardioceratidae, enabling recognition of both the current standard Sub-Boreal and Boreal ammonite zonations. In consequence, it is possible to make a close correlation of these two zonal schemes through the interval studied in Skye. The research has provided new palaeontological data at levels of precision that justify the proposal of the section at Staffin as the site of a potential Global Boundary Stratotype Section and Point (GSSP) for the Oxfordian/Kimmeridgian boundary.

The traditional Oxfordian/Kimmeridgian boundary placed at the Pseudocordata/Baylei zonal boundary of the Sub-Boreal zonal scheme corresponds precisely to the Rosenkrantzi/Bauhini zonal boundary of the Boreal zonal scheme. This level is characterised by the appearance of the first Pictonia (Pictonia flodigarriensis sp. nov.) together with first Prorasenia, replacing an older assemblage of Ringsteadia–Microbiplices (Sub-Boreal). It is also characterised by the first occurrence of small-sized Amoeboceras (Plasmatites) spp., as well as large Amoeboceras schulginae Mesezhnikov (Boreal). An alternative level that may be considered as a potential GSSP is the boundary between the Bauhini Zone and the Kitchini Zone of the Boreal zonal scheme, characterised by first occurrence of Amoeboceras (Amoebites) of the A. bayi group. This level corresponds to the Planula/Galar subzonal boundary of the Sub-Mediterranean zonal scheme, and lies close to the currently accepted Oxfordian/Kimmeridgian boundary in the Sub-Mediterranean Province.
Mechanism of emplacement and crystallisation history of the northern margin and centre of the Galway Granite, western Ireland
Authors: Leake Bernard Elgey
Published: July 2007

The main phase (∼400 Ma) emplacement of the central and northern part of the reversely zoned Galway Granite was incremental by progressive northward marginal dyke injection and stoping of the 470–467 Ma Connemara metagabbro-gneiss country rock. The space was provided by the synchronous ESE-opening, along the strike of the country rocks, of extensional fractures generated successively northward by a releasing bend in the sinistrally moving Skird Rocks Fault or an equivalent Galway Bay Fault. This fault is a prolongation of the Antrim–Galway (a splay off the Highland Boundary Fault) and Southern Upland Faults. The ESE-strike of the spalled-off rocks controlled the resultant ESE-elongated shape of the batholith. The magma pulses (∼5–30 m in thickness) were progressively more fractionated towards the northern margin so that the coarse Porphyritic (or Megacrystic) Granite (GP; technically granodiorite) in the centre was followed outwards by finer grained, drier and more siliceous granite, until the movements opening the fractures ceased and the magma became too viscous to intrude. ‘Out-of-sequence’ pulses of more basic diorite-granodiorite (including the Mingling–Mixing Zone) and late main phase, more acid, coarse but Aphyric Granite, into the centre of the batholith, complicated the outward fractionation scheme. The outward expansion, caused by the intrusions into the centre, caused a foliation and flattening of cognate xenoliths within the partly crystallised northern marginal granite and in the Mingling–Mixing Zone to the south.

Late phase (∼380 Ma) central intrusions of the newly-discovered aphyric Shannapheasteen Finegrained Granite (technically granodiorite), the Knock, the Lurgan and the Costello Murvey Granites, all more siliceous and less dense than the GP, were emplaced by pushing up the already solid and jointed GP along marginal faults. This concentration of lighter granites plus compression shown in thrusting, caused overall fault uplift of the Central Block of the Galway batholith so that the originally deepest part of the GP is exposed where there is the most late phase granite. Chemical analyses show the main and late phase magmas, including late dykes, were very similar, with repetition of the same fractionation except that the late phase magmas were drier and more quickly cooled, giving finer grained rocks.
A sauropod dinosaur tooth from the Middle Jurassic of Skye, Scotland
Authors: Barrett Paul M.
Published: July 2007

A sauropod dinosaur tooth has been recovered from the Kilmaluag Formation (Middle Jurassic: late Bathonian) of Strathaird, Isle of Skye, Western Scotland. It represents the first dinosaur tooth to be described from Scotland. The combination of character states present indicates that it cannot be referred to either Cetiosaurus or Cardiodon and that it may pertain to a basal eusauropod or a basal titanosauriform. A diversity of sauropods was present in the UK in the Middle Jurassic and these faunas have the potential to illuminate many aspects of sauropod evolutionary history.
A review of Silvanerpeton miripedes, a stem amniote from the Lower Carboniferous of East Kirkton, West Lothian, Scotland
Authors: Ruta Marcello , Clack Jennifer A.
Published: July 2007

Previously described and new specimens of the anthracosaur Silvanerpeton miripedes from the Scottish Viséan of East Kirkton yield important new data which allow us to provide a more complete reconstruction of the skull roof, palate, braincase and lower jaw. A stout sacral rib and an incompletely ossified tarsus with a subquadrangular intermedium are also recorded for the first time. A remarkably well preserved humerus in extensor view shows similarities with humeri of immature specimens of the embolomere Proterogyrinus. A new cladistic analysis, built from combining characters used in two recent matrices, places Silvanerpeton in a basal position relative to embolomeres and more derived stem amniotes. Data from Silvanerpeton inform character polarity near the base of the amniote total group. We discuss some morphofunctional implications of character changes at the root of total group amniotes, acquisition of terrestrial habits, and patterns of early disparity in this clade.
Timing of acid weathering on Mars: A kinetic‐thermodynamic assessment
Authors: Zolotov Mikhail Y. , Mironenko Mikhail V.
Published: July 2007

Weathering of olivine basalt by H2SO4‐HCl aqueous solutions at the conditions of early Mars was investigated through numerical modeling in a system open with respect to CO2and O2only. The model includes dissolution rates of primary and secondary minerals and oxidation rate of aqueous Fe2+, as well as chemical equilibration among solutes, dissolved gases, and precipitates. The results reveal fast dissolution of Fe‐Mg minerals at low pH, followed by preferential dissolution of plagioclase at higher pH. Correspondingly, solutions evolve from acidic, Mg‐Ca‐Fe2+‐Fe3+‐Al3+compositions toward Na‐rich alkaline fluids. The period over which neutralization and mineral precipitation may occur is shorter at higher initial pH, lower water to rock ratios, and larger mineral surface areas. Early stages of weathering are characterized by the formation of amorphous silica, goethite, and kaolinite, while zeolites and carbonates form considerably later at higher pH, where silica dissolves. Slow oxidation of Fe2+causes precipitation of ferrous phyllosilicates. Comparison with Martian observations indicate that amorphous silica, Fe3+oxyhydroxides, and Mg‐, Ca‐, and Fe‐sulfates could have formed during multiple short‐term episodes of acid weathering that were terminated by freezing and/or evaporation. Throughout history, impact generation of oxidants (e.g., O2, SO3, NO2) caused formation of strong acids and incremental Fe2+oxidation, the processes that are not efficient during O2‐deficient periods of volcanic degassing. Although impact‐generated acid rainfalls could have caused intense weathering and erosion in Noachian time, dilution of acids and a prolonged existence of surface solutions favored local neutralization of solution, and formation, transport and deposition of clays.
Modeling englacial radar attenuation at Siple Dome, West Antarctica, using ice chemistry and temperature data
Authors: MacGregor Joseph A. , Winebrenner Dale P. , Conway Howard , Matsuoka Kenichi , Mayewski Paul A. , Clow Gary D.
Published: July 2007

The radar reflectivity of an ice‐sheet bed is a primary measurement for discriminating between thawed and frozen beds. Uncertainty in englacial radar attenuation and its spatial variation introduces corresponding uncertainty in estimates of basal reflectivity. Radar attenuation is proportional to ice conductivity, which depends on the concentrations of acid and sea‐salt chloride and the temperature of the ice. We synthesize published conductivity measurements to specify an ice‐conductivity model and find that some of the dielectric properties of ice at radar frequencies are not yet well constrained. Using depth profiles of ice‐core chemistry and borehole temperature and an average of the experimental values for the dielectric properties, we calculate an attenuation rate profile for Siple Dome, West Antarctica. The depth‐averaged modeled attenuation rate at Siple Dome (20.0 ± 5.7 dB km−1) is somewhat lower than the value derived from radar profiles (25.3 ± 1.1 dB km−1). Pending more experimental data on the dielectric properties of ice, we can match the modeled and radar‐derived attenuation rates by an adjustment to the value for the pure ice conductivity that is within the range of reported values. Alternatively, using the pure ice dielectric properties derived from the most extensive single data set, the modeled depth‐averaged attenuation rate is 24.0 ± 2.2 dB km−1. This work shows how to calculate englacial radar attenuation using ice chemistry and temperature data and establishes a basis for mapping spatial variations in radar attenuation across an ice sheet.
Perturbative treatment of scalar-relativistic effects in coupled-cluster calculations of equilibrium geometries and harmonic vibrational frequencies using analytic second-derivative techniques
Authors: Michauk Christine , Gauss Jürgen
Published: July 2007

An analytic scheme for the computation of scalar-relativistic corrections to nuclear forces is presented. Relativistic corrections are included via a perturbative treatment involving the mass-velocity and the one-electron and two-electron Darwin terms. Such a scheme requires mixed second derivatives of the nonrelativistic energy with respect to the relativistic perturbation and the nuclear coordinates and can be implemented using available second-derivative techniques. Our implementation for Hartree-Fock self-consistent field, second-order Møller-Plesset perturbation theory, as well as the coupled-cluster level is used to investigate the relativistic effects on the geometrical parameters and harmonic vibrational frequencies for a set of molecules containing light elements (HX, X=F, Cl, Br; H2X, X=O, S; HXY, X=O, S and Y=F, Cl, Br). The focus of our calculations is the basis-set dependence of the corresponding relativistic effects, additivity of electron correlation and relativistic effects, and the importance of core correlation on relativistic effects.
Surface structures and electronic states of silicon nanotubes stabilized by oxygen atoms
Authors: Zhao Mingwen , Zhang R. Q. , Xia Yueyuan
Published: July 2007

The geometric and electronic structures of silicon nanotubes stabilized by incorporating oxygen atoms were studied using first-principles calculations within density functional theory. The predicted tubes present one-dimensional characters stacked with n-side silicon polygons connected by oxygen atoms. The stable configurations considered in this work include the tubes with varied facet number of the silicon polygons (n) from n=4 to 28 and of different surface structures. The configurations with n=5, 12, 15, 18, and 21 were found energetically extremely favorable. All the tubes are narrow-band-gap semiconductors with the band gap varying between 0.17 and 0.84eV, dependent on the surface structure of the tubes. This study provides an interesting route to stabilize silicon nanotubes and tune their electronic properties.
Theoretical investigation on o-, m-, and p-chlorotoluene photodissociations at 193 and 266nm
Authors: Tian Yan-Cong , Liu Ya-Jun , Fang Wei-Hai
Published: July 2007

Photodissociations of the o-, m-, and p-chlorotoluene at 193 and 266nm were investigated by ab initio calculations with and without spin-orbit interaction. The experimentally observed photodissociation channels were clearly assigned by multistate second order multiconfigurational perturbation theory (MS-CASPT2) calculated potential energy curves. The dissociation products with spin-orbit-coupled states of Cl*(P1∕22) and Cl(P3∕22) were identified by MS-CASPT2 in conjunction with spin-orbit interaction through complete active space state interaction (MS-CASPT2/CASSI-SO) calculations. The effects of methyl rotation and substituent on the photodissociation mechanism were discussed in detail.
Collective solvent flows around a protein investigated by molecular dynamics simulation
Authors: Umezawa Koji , Higo Junichi , Shimotakahara Sakurako , Shindo Heisaburo
Published: July 2007

Translational motions of water molecules in various systems equilibrated at room temperature are thought to be diffusive and nondirectional. We performed molecular dynamics simulations of a protein system and showed that the water molecules collectively move around the protein. The motions of two water molecules, which were about 12Å away from each other, are correlated to each other. Such collective motions of water can be regarded as flows around the protein, and the flows exhibited various coherent patterns: fair currents, vortices, and divergent flows. The patterns were highly fluctuating: a set of patterns changed to a different set of patterns within a time scale of 10ps. Thus, the water motions observed in a scale of length smaller than 12Å and a time scale shorter than 10ps were nondiffusive, and the motions above these scales were diffusive, where the flows disappeared. The flows near the protein surface had an orientational propensity to be highly parallel to the protein surface, and this propensity gradually vanished with an increment of distance from the protein surface. The divergent patterns of flows, which frequently emerge during the fluctuations of flows, may temporarily cause solvent drying in the vicinity of solutes. The current simulation is supportive of a molecular interaction mechanism that the fluctuations of hydration structure induce attractive interactions between solutes.
Quartz crystal microbalance based on torsional piezoelectric resonators
Authors: Bücking W. , Du B. , Turshatov A. , König A. M. , Reviakine I. , Bode B. , Johannsmann D.
Published: July 2007

A quartz crystal microbalance (QCM) is described, which is based on a torsional resonator, rather than a conventional thickness-shear resonator. Typical applications are measurements of film thickness in the coating industry and monitoring of biofouling. The torsional QCM is about a factor of 100 less sensitive than the conventional QCM. On the other hand, it can probe film thicknesses in the range of hundreds of microns, which is impossible with the conventional QCM due to viscoelastic artifacts. Data acquisition and data analysis proceed in analogy to the conventional QCM. An indicator of the material’s softness can be extracted from the bandwidth of the resonance. Within the small-load approximation, the frequency shift is independent of whether the sample is applied to the face or to the side of the cylinder. Details of the geometry matter if the viscoelastic properties of the sample are of interest.
Elucidation of homojunction formation in CuInS2 with impedance spectroscopy
Authors: Loef Ruben , Schoonman Joop , Goossens Albert
Published: July 2007

Type transformation in CuInSe2 and CuInS2 solar cells is an important issue with far reaching consequences. In the present study, the presence of a p-n homojunction inside CuInS2 in a TiO2∕CuInS2 device is revealed with a detailed impedance spectroscopy and capacitance study. A n-type CuInS2 film with a thickness of 40nm is found at the TiO2 (n-type)/CuInS2 (p-type) interface. The effective donor density of this n-type film is 2×1017cm−3 at 400K and is higher than the effective acceptor density in the remaining p-type CuInS2, being 4×1016cm−3 at 400K. Both densities decrease upon increasing the temperature. This is explained by the activation of a CuIn″ acceptor state in n-type CuInS2 and a thermally activated hole trap in p-type CuInS2.
Comment on “Ultrathin low-temperature SiGe buffer for the growth of high quality Ge epilayer on Si(100) by ultrahigh vacuum chemical vapor deposition” [Appl. Phys. Lett. 90, 092108 (2007)]
Authors: Bolkhovityanov Yu. B.
Published: July 2007

An absence of shift in X-ray diffraction peaks between fully strained and relaxed GeSi buffers is inconsistent with elasticity theory and demands an explanation.
Large ferroelectric polarization in antiferromagnetic BiFe0.5Cr0.5O3 epitaxial films
Authors: Kim Dae Ho , Lee Ho Nyung , Biegalski Michael D. , Christen Hans M.
Published: July 2007

Multiferroic BiFe0.5Cr0.5O3 solid solution epitaxial films were grown by pulsed laser deposition on SrTiO3 (001) substrates with SrRuO3 bottom electrodes. Formation of the metastable composition in the form of high-quality epitaxial films was made possible by a sequential deposition of 0.1 unit cell amounts of BiFeO3 and BiCrO3. The random distribution of Fe and Cr cation results in a linear response of magnetization with varying magnetic field, consistent with a dominant antiferromagnetic order. Polarization measurements at 77.3K reveal ferroelectric hysteresis with a remanent polarization as high as 60±1μC∕cm2 along the pseudocubic [001] direction.
Sequential thermal treatments of SiC in NO and O2: Atomic transport and electrical characteristics
Authors: Soares G. V. , Baumvol I. J. R. , Hold L. , Kong F. , Han J. , Dimitrijev S. , Radtke C. , Stedile F. C.
Published: July 2007

Sequential thermal oxidations and oxynitridations of SiC were performed using O218 and NO. The resulting films were characterized by x-ray photoelectron spectroscopy, ion beam analyses, and capacitance-voltage measurements. The best electrical characteristics were obtained from films directly grown in NO. A subsequent oxidation in O2 degraded the interface due to negative flatband-voltage shift, removal of N, and formation of C compounds, while a further annealing in NO brought the flatband shift in the C-V curves to rather moderate figures. This shift is related to competitive processes taking place during dielectric film formation which are discussed.
Enhanced extraction efficiency of Y2O3:Eu3+ thin-film phosphors coated with hexagonally close-packed polystyrene nanosphere monolayers
Authors: Lee Young Kwang , Oh Jeong Rok , Do Young Rag
Published: July 2007

A hexagonally close-packed, two-dimensional (2D) polystyrene (PS) nanosphere photonic crystal (PC) monolayer was built on a sol-gel derived Y2O3:Eu3+ thin film in an attempt to improve the efficiency of light extraction from the phosphor side of the Y2O3:Eu3+ thin film. The effects of crystallinity and particle size of the 2D PS nanosphere/air PC layer on the extraction efficiencies of the Y2O3:Eu3+ thin-film phosphors were investigated. The integrated photoluminescence extraction was improved by a factor of over 3.7 compared to that of a conventional Y2O3:Eu3+ thin film, by adding a 2D PS monolayer array of 580nm sized nanospheres with high crystallinity.
Micromachined cascade virtual impactor with a flow rate distributor for wide range airborne particle classification
Authors: Kim Yong-Ho , Maeng Jwa-Young , Park Dongho , Jung Il-Hyun , Hwang Jungho , Kim Yong-Jun
Published: July 2007

This letter reports a module for airborne particle classification, which consists of a micromachined three-stage virtual impactor for classifying airborne particles according to their size and a flow rate distributor for supplying the required flow rate to the virtual impactor. Dioctyl sebacate particles, 100–600nm in diameter, and carbon particles, 0.6–10μm in diameter, were used for particle classification. The collection efficiency and cutoff diameter were examined. The measured cutoff diameters of the first, second, and third stages were 135nm, 1.9μm, and 4.8μm, respectively.
Optimal roughness for minimal adhesion
Authors: Liu D.-L. , Martin J. , Burnham N. A.
Published: July 2007

Roughness has a significant affect on adhesion. The authors used a single-asperity model to describe a smooth tip in contact with a rough surface and predicted that an optimal size of asperity yields a minimum of adhesion. Experimentally, adhesive forces on silicon wafers with varying roughness were measured using atomic-force-microscopy cantilevers with varying tip radii. It was found that minima do exist, and for all tip radii, the adhesion falls significantly for roughness greater than 1–2nm and drops at higher roughness for larger tips. This work should help minimize stiction in microelectromechanical systems and progress the understanding of nanoscale-contact mechanics.
Widespread occurrence of multiple herbicide resistance in Western Australian annual ryegrass (Lolium rigidum) populations
Authors: Owen Mechelle J. , Walsh Michael J. , Llewellyn Rick S. , Powles Stephen B.
Published: July 2007

In 2003, a random survey was conducted across the Western Australian wheatbelt to establish the frequency and distribution of herbicide resistance in ryegrass populations infesting crop fields. Five hundred cropping fields were visited at crop maturity, and ryegrass seed was collected in 452 of these fields. Subsequently, each crop field population was screened with herbicides of various modes of action that are commonly used for ryegrass control in Australian cropping systems. Most of these ryegrass populations were found to be resistant to the ACCase-inhibitor herbicide diclofop-methyl (68%) and the ALS-inhibitor herbicide sulfometuron (88%). A comparison of resistance levels in the same agronomic zones surveyed 5 years earlier determined that there had been an increase of 20 percentage points in the frequency of resistance over this 5-year period. This survey also determined that the majority (64%) of populations were found to be multiple resistant to both diclofop-methyl and sulfometuron. The distribution patterns of the collected populations indicated that there were higher frequencies of resistant and developing resistance populations occurring in the intensively cropped regions of the wheatbelt, which had greater herbicide selection pressure. Of concern is that 24% and 8% of populations were found to be developing resistance to trifluralin and clethodim, respectively. Currently these herbicides are heavily relied upon for control of ACCase and ALS herbicide resistant ryegrass. Nearly all populations remain susceptible to glyphosate. Ryegrass across the WA wheatbelt now exhibits multiple resistance across many but not all herbicides, posing severe management and sustainability challenges.
Increasing applications of potassium fertiliser to barley crops grown on deficient sandy soils increased grain yields while decreasing some foliar diseases
Authors: Brennan R. F. , Jayasena K. W.
Published: July 2007

Most sandy soils used for cropping in south-western Australia (SWA) have now become potassium (K) deficient due to removal of K in hay and grain, so it is now profitable to apply K fertiliser to most barley (Hordeum vulgare L.) crops in the region. Leaf diseases of barley crops in the region have increased in recent years particularly in the in medium to high (350–600 mm annual average rainfall) areas of SWA. Seventeen field experiments were undertaken to determine the effect of applications of K fertiliser, either the chloride (KCl) or sulfate source (K2SO4), on grain yield increases and on the percentage leaf area diseased (%LAD) when diseases were controlled or not controlled by fungicide sprays. Maximum grain yield of barley was achieved where adequate K fertiliser (~8–22 kg K/ha) was applied and leaf diseases were controlled by fungicide. Applying increasing amounts of applied K fertiliser (0–120 kg K/ha) to barley decreased the %LAD by powdery mildew (Blumeria graminis f. sp. hordei Syn.) and spot-type net blotch (Pyrenophora teres f. maculata (Sacc.) Shoem.) and increased grain yield. By contrast, when leaf rust (Puccinia hordei G. Otth) was present the %LAD was unaffected by K application. When powdery mildew was the major disease, larger increases in grain yields and larger reductions in %LAD were obtained when KCl was used instead of K2SO4. About twice as much K fertiliser as K2SO4 was required for 90% maximum grain yield compared with KCl where powdery mildew was present. Applying larger amounts (>40 kg K/ha) of K fertiliser than required to achieve maximum grain yields did not further reduce %LAD by powdery mildew. There were no significant differences between the 2 sources of K fertiliser on the %LAD by spot-type net blotch. Generally, the percentage protein content and hectolitre weight of grain were unaffected by K fertiliser. Potassium fertiliser decreased the percentage grain < 2.5 mm (known locally as screenings) and control of the foliar leaf diseases by applications of fungicide resulted in a decrease in protein content and screenings and increased hectolitre weight of barley grain. The concentration of K in dried shoots that was related to 90% of the maximum shoot yield (critical diagnostic K) decreased as the plant matured, and was ~41 g/kg at Z22, ~30 g/kg at Z32, ~20 g/kg at Z40, and ~15 g/kg at Z59. The concentration of K in dried shoots which was related to 90% of the grain yield (critical prognostic K) decreased as plant matured, and was similar to critical diagnostic K values. Leaf disease had little effect on critical concentrations of K at early growth stages (Z22 and Z32).
Quantitative characterization of cell synchronization in yeast
Authors: Danø Sune , Madsen Mads Find , Sørensen Preben Graae
Published: July 2007

Metabolic oscillations in baker's yeast serve as a model system for synchronization of biochemical oscillations. Despite widespread interest, the complexity of the phenomenon has been an obstacle for a quantitative understanding of the cell synchronization process. In particular, when two yeast cell populations oscillating 180° out of phase are mixed, it appears as if the synchronization dynamics is too fast to be explained. We have probed the synchronization dynamics by forcing experiments in an open-flow reactor, and we find that acetaldehyde has a very strong synchronization effect that can account quantitatively for the classical mixing experiment. The fast synchronization dynamics is explained by a general synchronization mechanism, which is dominated by a fast amplitude response as opposed to the expected slow phase change. We also show that glucose can mediate this kind of synchronization, provided that the glucose transporter is not saturated. This makes the phenomenon potentially relevant for a broad range of cell types.