bluuebunny/crossref_metadata_2025_split huggingface dataset:
Experimental taphonomy: silicification of plants in Yellowstone hot-spring environments
Authors: Channing Alan , Edwards Dianne 
Published: July 2007

ABSTRACTDuring experiments conducted within the vent pool of Medusa Geyser, Norris Geyser Basin, Yellowstone National Park, USA, amorphous opaline silica (opal-A) was deposited on/within plant tissues within 30 days of immersion. Initially, deposition created inter/intra-cellular films which lined cell walls plus intercellular colloid suspensions (sols) of opal-A nano/microspheres. By 330 days, opal-A deposition created a robust external and internal matrix that stabilised tissues against collapse and replicated plant structure. Opal-A films increased to micron-order thicknesses and intracellular sols were created. Systematic variation of opal-A fabric between tissues comprising living/dead cells at the time of deposition indicate that cell function, architecture and shape influence fabric development. Heterogeneity of opal-A fabric within adjacent cells of similar structure/function indicates spatially/temporally fluctuating physicochemical conditions and the presence of intraorganic microenvironments. Early deposition of opal-A films suggests a period of low silica supersaturation and slow opal-A deposition. In contrast, intracellular sols suggest high levels of supersaturation, and rapid opal-A deposition. Shell-like microsphere growth suggests cyclic variation of silica supersaturation, and alternations between rapid and slower opal-A deposition. Microsphere growth to the upper limit of colloidal stability and colloidal crystal structures indicate prolonged sol stability, whilst floc-like microsphere networks indicate localised sol instabi
The mechanism of melt extraction from lower continental crust of orogens
Authors: Brown Michael 
Published: July 2007

ABSTRACTMelt extraction is a process with a length scale that spans many orders of magnitude. Studies of residual migmatites and granulites suggest that melt has migrated from grain boundaries to networks of leucosome-filled structures to steeply inclined cylindrical or tabular granites inferred to have infilled ascent conduits. For example, in anatectic rocks from southern Brittany, France, during decompression-induced biotite-breakdown melting, melt is inferred to have been expressed from foliation-parallel structures analogous to compaction bands to dilation and shear bands, based on location of residual leucosome, and from this network of structures to ascent conduits, preserved as dykes of granite. The leucosome-filled deformation band network is elongated parallel to a sub-horizontal lineation, suggesting that mesoscale melt flow was focused primarily in the plane of the foliation along the lineation to developing dilatant transverse structures. The leucosome network connects with petrographic continuity to granite in dykes; however, the orientation of dykes discordant to fabric anisotropy suggests that their formation was controlled by stress, which indicates that the process is a fracture phenomenon. Blunt fracture tips and zigzag propagation paths indicate that the dykes represent ductile opening-mode fractures; these are postulated to have formed by coalescence of melt pockets. The structures record a transition from accumulation to draining; quantitative volume fluxes are calculated and presented for the generalised extraction process. The anatectic system may have converged to a critical state at some combination of melt fraction and melt distribution that enabled formation of ductile opening-mode fractures, but fractal distribution of inferred mesoscale melt-filled structures has not been demonstrated; this may reflect the inherent anisotropy and/or residual nature of the drained source. Melt extraction has been modelled as a self-organised critical phenomenon, but the mechanism of extraction is not described and the relationship between these models and the spatial and temporal granularity of lower continental crust is not addressed. Self-organised critical phenomena are driven systems involving ‘avalanches’ with a fractal frequency-size distribution; thus, the distribution of melt batch sizes might be expected to be fractal, but this has not yet been demonstrated in nature.
Modelling mid-crustal migmatite terrains as feeder zones for granite plutons: the competing dynamics of melt transfer by bulk versus porous flow
Authors: Olsen Sakiko N. , Marsh Bruce D. , Baumgartner Lukas P. 
Published: July 2007

ABSTRACTThe common association of mid-crustal migmatites with an upper-level granite pluton could indicate that the migmatites are a feeder zone for the pluton. If magma from a deeper level pervasively intrudes a high temperature metamorphic complex, most of the intruded magma would not freeze because of the prevailing temperature. The interaction between the magma and country rocks, which could include partial melting and crystallisation of the magma passing through, would modify magma to a more granitic composition, as found in the higher-level pluton.The physical aspect of the magma transport through such a hot feeder zone is modelled by introducing a dimensionless melt transport (MT) number, which is the ratio of the rate of melt movement caused by the bulk flow of the entire mass (melt+solid) to that of porous media flow of melt only through the solid framework. The MT number is strongly dependent on the melt content of the melt-rich zone (MRZ), the diameter of the MRZ and typical particle size in the MRZ.The ∼300-Ma, diatexitic, Lauterbrunnen migmatites (LM) in the Aar massif, Swiss Alps, may be such a feeder zone for the nearby 303-Ma Gastern granite (GG). The chemical and field evidence indicates that the LM formed by an intrusion of intermediate composition magma, which interacted with country rocks to produce a magma of GG composi
Lithium isotopic compositions of the New England Batholith: correlations with inferred source rock compositions
Authors: Bryant Colleen J. , Chappell Bruce W. , Bennett Victoria C. , McCulloch Malcolm T. 
Published: July 2007

ABSTRACTA strong correlation exists between the Li isotopic compositions of CarboniferousTriassic granites from the New England Batholith, and the previously inferred involvement of sedimentary and mantle/infracrustal source components. Isotopically (Nd and Sr) juvenile, low-K, Cordilleran I-type granites of the Clarence River supersuite have δ7 Li= +2·2 to +8‰ similar to those of arc magmas, the inferred source of these granites (Bryant et al. 1997). Isotopic variability within this supersuite probably arises from heterogeneity within primary mantle-derived magmas, combined with subsequent modifications through interactions with crustal materials. Oxidised, high-K granites of the Moonbi Supersuite have more homogenous and slightly lighter Li isotopic compositions (δ7 Li= +1·9 to +4·2‰). The observed range of values lies within the range of arc magmas, and is consistent with partial melting of arc shoshonites within the crust (cf. Chappell 1978) or the involvement of high-K mantle-derived magmas (cf. Shaw & Flood 1981; Landenberger & Collins 1998). S-type granites of the Bundarra (δ7 Li= −0·1 to +2·1‰; average= +1˙3‰; n=6) and Hillgrove supersuites (δ7 Li= +0·4 to +1·7‰; average= +0·8‰) define a narrow range of isotopic compositions which are, overall, lower than those observed in NEB I-type granites or generally observed in primary arc magmas. Their isotopic compositions are equivalent to those typically observed in shales (primarily δ7 Li= −3·2 to +2·0‰; Moriguti & Nakamura 1998; Teng et al. 2004). No difference is evident in the isotopic compositions of the two S-type supersuites despite inferred differences in the degree of weathering experienced by the sedimentary protolith, or differences in mineralogy of the granites. Granites of the Uralla Supersuite, which have been have formed from mixtures of local meta-igneous and meta-sedimentary components, span a broad range of values (δ7 Li= −1·3 to +3·9‰) which overlap with both the sediment-poor New England Batholith I-type intrusions of the Clarence River and Moonbi supersuites, and the S-type granites of the Bundarra and Hillgrove supersuites. Lower δ7 Li values primarily occur in lower-K plutons from the northern portion of the Uralla Supersuite.Overall, anatexis and magma differentiation do not appear to contribute to significant fractionation of Li isotopes relative to the inferred source components. However, subtly lower δ7 Li values, evident in the three leucogranites analysed herein, imply that subtle Li isotopic fractionation may occur in association with the exsolution of an aqueous fluid. Like most isotopic systems, the Li isotopic composition of rocks is not a definitive guide to source rock compositions, but given the results herein, the present authors suggest that it may play a very useful role in understanding crustal processes.
Granites, dynamic magma chamber processes and pluton construction: the Aztec Wash pluton, Eldorado Mountains, Nevada, USA
Authors: Harper Brian E. , Miller Calvin F. , Koteas G. Christopher , Cates Nicole L. , Wiebe Robert A. , Lazzareschi Daniel S. , Cribb J. Warner 
Published: July 2007

ABSTRACTThe mid-Miocene Aztec Wash pluton is divisible into a relatively homogeneous portion entirely comprising granites (the G zone, or GZ), and an extremely heterogeneous zone (HZ) that includes the products of the mingling, mixing and fractional crystallisation of mafic and felsic magmas. Though far less variable than the HZ, the GZ nonetheless records a dynamic history characterised by cyclic deposition of the solidifying products of the felsic portion of a recharging, open-system magma chamber.Tilting has exposed a 5-km section through the GZ and adjacent portions of the HZ. A porphyry is interpreted as a remnant of a chilled roof zone that marks the first stage of felsic GZ intrusion. Subsequent recharging by felsic and mafic magma, reflected by repeated cycles of crystal accumulation and melt segregation in the GZ and emplacement of mafic flows in the HZ, rejuvenated and maintained the chamber. Kilometre-scale lobes of mafic HZ material were deposited as prograding tongues into the GZ during periods of increased mafic input. Thus, they are lateral equivalents of the cumulate GZ granites with which they interfinger. Conglomerate-like units comprising rounded, matrix-supported intermediate clasts in cumulate granite are located immediately above the lobes. These ‘conglomerates’ appear to represent debris flows shed from sloping upper surfaces of the lobes. Thus, the GZ can be viewed as comprising distal facies, remote from the site of mafic recharging in the HZ, and the HZ as comprising proximal facies.Elemental chemistry suggests that the GZ cumulate granites represent a second-stage accumulation from an already evolved melt, and that coarse, more mafic, feldspar+biotite+accessory mineral ± hornblende rocks trapped between mafic sheets in the HZ are the initial cumulates. Fractionated melt accumulated roofward and laterally, and was the direct parent of the ‘evolved’ GZ cumulates. The most highly fractionated, fluid-rich melts accumulated at the roof.
Palaeoproterozoic, rift-related, 13C-rich, lacustrine carbonates, NW Russia. Part I: Sedimentology and major element geochemistry
Authors: Melezhik V. A. , Fallick A. E. 
Published: July 2007

ABSTRACTThe 150-m-thick Kuetsjärvi Sedimentary Formation (KSF) from the Pechenga Greenstone Belt, NW Russia, is one of the key formations in the study of a positive δ13Ccarb excursion occurring globally in the Palaeoproterozoic. The KSF formed in an intracratonic rift setting and is sandwiched between two, 2-km-thick subaerially erupted volcanic units. The KSF was previously interpreted as shallow marine, but new data reported here indicate that it is a non-marine unit deposited on a deeply subaerially weathered surface mantling the underlying volcanic rocks. The lowermost part of the KSF represents an alluvial–fluvial plain, followed by a laterally and vertically variable succession of variegated to mottled fine-grained siliciclastic rocks and ‘red beds‘, dolostones containing stromatolite sheets, hydrothermal travertine deposits and abundant desiccation features (e.g.tepees, surfical silicified crusts and dissolution cavities), including probable pseudomorphed evaporites. Measured S and Corg concentrations for the carbonate and siliciclastic rocks are low. Combined, these features indicate that the carbonate rocks of the KSF accumulated in a shallow lacustrine setting. Major types of carbonate facies were formed by: (1) biologically-induced precipitation; (2) evaporitic removal of CO2 in a closed lake environment; and (3) chemical precipitation from thermal springs. Apparently, none of these carbonate facies was in full isotopic equilibrium with atmospheric CO2. This interpretation shows the importance of taking into account the interplay between global and local depositional factors when interpreting the isotopic signature of the KSF dolostones and its implication for the Palaeoproterozoic carbon isotope excursion
Agnostid trilobites from the Arenig–Llanvirn of South China
Authors: Turvey Samuel T. 
Published: July 2007

ABSTRACTAgnostid trilobites are relatively abundant and taxonomically diverse in outer shelf facies of the Yangtze Platform and Jiangnan Transitional Belt regions of the South China Plate. Nine Arenig and Llanvirn species, representing at least five genera or subgenera in the Agnostidae, Diplagnostidae and Metagnostidae, are treated in a taxonomic review of the South Chinese Agnostida, based on new material from the Dawan and Kuniutan formations of W Hubei and the Zitai and Jiuxi formations of N Hunan. The new genus Han is established to incorporate the globally youngest known diplagnostid species. The new species Han solo, Geragnostus (Geragnostus) balanolobus and G. (G.) waldorfstatleri are established. G. carinatus is recognised as being based on inaccurately interpreted material, and is only tentatively retained within Geragnostus. Three further taxa represented by poorly preserved material are left in open nomenclature. The geographic distributions of different agnostid species across the South China Plate, and the endemicity to the palaeoplate displayed by all Arenig–Llanvirn South Chinese species, suggest that these agnostids at least were either benthic or epibenthic.
Banffia constricta, a putative vetulicolid from the Middle Cambrian Burgess Shale
Authors: Caron Jean-Bernard 
Published: July 2007

ABSTRACTAlthough Banffia constricta was first described in 1911, the affinities of this soft-bodied fossil animal have remained unclear. Banffia is redescribed here, on the basis of over 300 specimens. Banffia has a bipartite body measuring up to 10 cm in length. The entire body is axially twisted along a spiral, clockwise as seen from the front. The anterior section consists of two fused carapace-like units with a prominent crown-like structure at the anterior end surrounding the mouth. This crown-like structure is composed of three concentric circlets. A single antenniform outgrowth lies posterior to the mouth. The posterior section of Banffia is composed of 40 to 50 lightly sclerotised segments. The anus is terminal, and situated in a caudal notch. The gut is straight. Simple serially repeated structures along the gut may represent metameric mid-gut diverticulae. Banffia is considered to have been an epibenthic gregarious animal and possibly a deposit-feeder.Banffia is putatively classified as an end-member of the phylum Vetulicolia, in a new class, the Banffozoa. If the vetulicolids represent a stem-group deuterostome, the absence of gills and a possible endostyle in Banffia is problematic. The presence of mid-gut diverticulae in Banffia may represent a link with the protostomes.
Social exclusion
Authors: Gray Anne 
Published: July 2007

Lawless, P., Martin, R. and Hardy, S. 1998: UNEMPLOYMENT AND SOCIAL EXCLUSION: LANDSCAPES OF LABOUR INEQUALITY London: Regional Studies Association with Jessica Kingsley Press, £17.95 paper Madanipour, A., Cars, G. and Allen, J. 1998: SOCIAL EXCLUSION IN EUROPEAN CITIES: PROCESSES, EXPERIENCES AND RESPONSES London: Regional Studies Association with Jessica Kingsley Press, £17.95 paper
Reviews
Authors: Aidoo Akwasi , Munslow Barry 
Published: July 2007

The Political Economy of Race and Class in South Africa,by Bernard Makhosezwe Magubane, (Monthly Review Press, New York and London, 1979), 364pp, notes, index. $18.50.
Amilcar Cabral, Unity and Struggle(Heinemann Educational Books, London 1980, pp.298, £2.25).
Structure‐Function Relationships in the Growing Hexa‐Coordinate Hemoglobin Sub‐Family
Authors: de Sanctis Daniele , Pesce Alessandra , Nardini Marco , Bolognesi Martino , Bocedi Alessio , Ascenzi Paolo 
Published: July 2007

AbstractHemoglobin and related heme proteins, generally referred to as 'globins', reversibly bind gaseous diatomic ligands (O2, NO, and CO) to a penta‐coordinate heme iron atom, the ligand filling the sixth coordination site. Over the last decade, several new globins have been reported to display a functionally‐relevant hexa‐coordinate heme iron atom, whose sixth coordination site is taken by an endogenous protein ligand. The reversible intramolecular hexa‐ to penta‐coordination process at the heme‐Fe atom modulates exogenous ligand binding properties of hexa‐coordinate globins. Here, we review current knowledge on hexa‐coordinate globins in terms of their structural and functional properties. IUBMB Life, 56: 643‐651, 2004
Solution structure of the zinc finger HIT domain in protein FON
Authors: He Fahu , Umehara Takashi , Tsuda Kengo , Inoue Makoto , Kigawa Takanori , Matsuda Takayoshi , Yabuki Takashi , Aoki Masaaki , Seki Eiko , Terada Takaho , Shirouzu Mikako , Tanaka Akiko , Sugano Sumio , Muto Yutaka , Yokoyama Shigeyuki 
Published: July 2007

AbstractThe zinc finger HIT domain is a sequence motif found in many proteins, including thyroid hormone receptor interacting protein 3 (TRIP‐3), which is possibly involved in maturity‐onset diabetes of the young (MODY). Novel zinc finger motifs are suggested to play important roles in gene regulation and chromatin remodeling. Here, we determined the high‐resolution solution structure of the zinc finger HIT domain in ZNHIT2 (protein FON) from Homo sapiens, by an NMR method based on 567 upper distance limits derived from NOE intensities measured in three‐dimensional NOESY spectra. The structure yielded a backbone RMSD to the mean coordinates of 0.19 Å for the structured residues 12–48. The fold consists of two consecutive antiparallel β‐sheets and two short C‐terminal helices packed against the second β‐sheet, and binds two zinc ions. Both zinc ions are coordinated tetrahedrally via a CCCC‐CCHC motif to the ligand residues of the zf‐HIT domain in an interleaved manner. The tertiary structure of the zinc finger HIT domain closely resembles the folds of the B‐box, RING finger, and PHD domains with a cross‐brace zinc coordination mode, but is distinct from them. The unique three‐dimensional structure of the zinc finger HIT domain revealed a novel zinc‐binding fold, as a new member of the treble clef domain family. On the basis of the structural data, we discuss the possible functional roles of the zinc finger HIT domain.
The solution structure of ParD, the antidote of the ParDE toxin–antitoxin module, provides the structural basis for DNA and toxin binding
Authors: Oberer Monika , Zangger Klaus , Gruber Karl , Keller Walter 
Published: July 2007

AbstractParD is the antidote of the plasmid‐encoded toxin–antitoxin (TA) system ParD–ParE. These modules rely on differential stabilities of a highly expressed but labile antidote and a stable toxin expressed from one operon. Consequently, loss of the coding plasmid results in loss of the protective antidote and poisoning of the cell. The antidote protein usually also exhibits an autoregulatory function of the operon. In this paper, we present the solution structure of ParD. The repressor activity of ParD is mediated by the N‐terminal half of the protein, which adopts a ribbon‐helix‐helix (RHH) fold. The C‐terminal half of the protein is unstructured in the absence of its cognate binding partner ParE. Based on homology with other RHH proteins, we present a model of the ParD–DNA interaction, with the antiparallel β‐strand being inserted into the major groove of DNA. The fusion of the N‐terminal DNA‐binding RHH motif to the toxin‐binding unstructured C‐terminal domain is discussed in its evolutionary context.
Domain folding and flexibility of Escherichia coli FtsZ determined by tryptophan site‐directed mutagenesis
Authors: Díaz‐Espinoza Rodrigo , Garcés Andrea P. , Arbildua José J. , Montecinos Felipe , Brunet Juan E. , Lagos Rosalba , Monasterio Octavio 
Published: July 2007

AbstractFtsZ has two domains, the amino GTPase domain with a Rossmann fold, and the carboxyl domain that resembles the chorismate mutase fold. Bioinformatics analyses suggest that the interdomain interaction is stronger than the interaction of the protofilament longitudinal interfaces. Crystal B factor analysis of FtsZ and detected conformational changes suggest a connection between these domains. The unfolding/folding characteristics of each domain of FtsZ were tested by introducing tryptophans into the flexible region of the amino (F135W) and the carboxyl (F275W and I294W) domains. As a control, the mutation F40W was introduced in a more rigid part of the amino domain. These mutants showed a native‐like structure with denaturation and renaturation curves similar to wild type. However, the I294W mutant showed a strong loss of functionality, both in vivo and in vitro when compared to the other mutants. The functionality was recovered with the double mutant I294W/F275A, which showed full in vivo complementation with a slight increment of in vitro GTPase activity with respect to the single mutant. The formation of a stabilizing aromatic interaction involving a stacking between the tryptophan introduced at position 294 and phenylalanine 275 could account for these results. Folding/unfolding of these mutants induced by guanidinium chloride was compatible with a mechanism in which both domains within the protein show the same stability during FtsZ denaturation and renaturation, probably because of strong interface interactions.