bluuebunny/crossref_metadata_2025_split huggingface dataset:
Geochemical modelling of diagenetic reactions in a sub-arkosic sandstone
Authors: Barclay S. A. , Worden R. H. 
Published: July 2002

AbstractA reaction path model was constructed in a bid to simulate diagenesis in the Magnus Sandstone, an Upper Jurassic turbidite reservoir in the Northern North Sea, UKCS. The model, involving a flux of source rock-derived CO2 into an arkosic sandstone, successfully reproduced simultaneous dissolution of detrital K-feldspar and growth of authigenic quartz, ankerite and illite. Generation of CO2 occurred before and during the main phase of oil generation linking source rock maturation with patterns of diagenesis in arkosic sandstones and limiting this type of diagenesis to the earlier stages of oil charging. Independent corroborative evidence for the model is provided by formation water geochemical data, carbon isotope data from ankerite and produced gas phase CO2 and the presence of petroleum inclusions within the mineral cements. The model involves a closed system with respect to relatively insoluble species such as SiO2 and Al2O3 but is an open system with respect to CO2. There are up to seven possible rate-controlling steps including: influx of CO2, dissolution of K-feldspar, precipitation of quartz, ankerite and illite, diffusive transport of SiO2 and Al2O3 from the site of dissolution to the site of precipitation and possibly the rate of influx of Mg2+ and Ca2+. Given the large number of possible controls, and contrary to modern popular belief, the rate of quartz precipitation is thus not always rate limiting.
Reply to discussion of “Extracting K-Ar ages from shales: a theoretical test”
Authors: Środoń J . 
Published: July 2002

AbstractAs plots of K-Ar ages vs. percentage of the detrital component of mineral mixtures containing a detrital and a diagenetic illite (or illite-smectite) have different curved shapes, the linear extrapolation method of extracting the end-member ages is not justified. The curvature depends on the difference in K2O contents; thus it can be minimized if the percentage of detrital illite is normalized to the sum of detrital illite plus illitic fraction of diagenetic illite-smectite.
An 57Fe Mössbauer spectral study of vermiculitization in the Palabora Complex, Republic of South Africa
Authors: Badreddine R. , Grandjean F. , Vandormael D. , Fransolet A. -M. , Long G. J. 
Published: July 2002

AbstractTwo phlogopite, two mixed-layer phlogopite-vermiculite, and two vermiculite samples collected from the Palabora Complex of South Africa have been investigated at 295 K by X-ray diffraction, chemical analysis, and Mössbauer spectroscopy. In addition the temperature dependence of the Mössbauer spectra has been measured between 95 and 295 K for one phlogopite and one mixed-layer sample. The results of the chemical analyses and the Mössbauer spectra improve our knowledge of the vermiculitization process in the Palabora Complex. Both techniques indicate oxidation of the Fe ions during the sequence: phlogopite → mixed-layer → vermiculite. Further, the Mössbauer spectra indicate that Fe oxidation occurs mainly in the octahedral sites and suggest that migration and oxidation of the Fe2+ ions from the octahedral sites to the tetrahedral sites may occur during the transformation of phlogopite into a mixed-layer phase. Finally, the vermiculitization process involves both Fe oxidation and loss of K with a concomitant increase in the Mg content.
Smectite transformation in high molar KOH solutions
Authors: Bauer A. , Velde B. 
Published: July 2002

AbstractBatch reactor experiments were performed at 35°C and 80°C to determine the effect of high molar KOH solutions on the mineralogy and solution chemistry of two different smectites. The Ceca smectite is a nearly pure montmorillonite, and the Ibeco clay has a significant component of 35% beidellitic charge. Each reactor was charged with 1 g of <2 mm fraction smectite and 80, 160, 240 ml of 0.1–4 M KOH solution. In these experiments, the changes in solution composition and mineralogy were monitored as a function of time.In the experiments, at all temperatures and under all chemical conditions, the smectite appears to change in diffracting domain size, which decreases with time. This probably reflects a change in crystal shape. The structures then become more illite rich and the diffracting domain continues to decrease.
Trace element partitioning between wollastonite and silicate-carbonate melt
Authors: Law K. M. , Blundy J. D. , Wood B. J. , Ragnarsdottir K. V. 
Published: July 2002

AbstractWe have performed an experimental study of the influence of varying size and charge on cation partitioning between wollastonite and silicate-carbonate melt in the system CaCO3-SiO2. The experimental conditions (3 GPa, 1420°C) lie close to the wollastonite II tc/I tc phase boundary. Results for 1+, 2+, 3+ and 4+ partitioning show parabolic dependence of partition coefficients on ionic radius, which can be fitted to the elastic strain model of Blundy and Wood (1994), wherein partitioning is described using three parameters: site radius (r0), site elasticity (apparent Young's Modulus) and the ‘strain-free’ partition coefficient (D0) for an element with radiusr0. The apparent Young's Modulus of the Ca site in wollastonite, obtained from modelling the 2+ partitioning data, is 99±3 GPa, similar to the bulk-crystal value for the polymorph wollastonite I tc.r0decreases with increasing charge on the substituent cation, whileD0also shows an approximately parabolic dependence on charge, with a maximum for 2+ cations. Partition coefficients for divalent cations Zn, Co, Fe, Cd, Mn and Pb are lower than would be predicted from their ionic radii alone, indicating a preference for the melt. This may be a consequence either of cation-carbonate complexation in the melt, or of the more distorted nature of cation co-ordination environments in melts.
Mineralogical controls on phosphorus recovery from wastewaters
Authors: Valsami-Jones E. 
Published: July 2002

AbstractThe removal of phosphorus from wastewaters is becoming very common, to meet water quality targets, and avoid environmental problems related to eutrophication. At the same time, agricultural application of P-rich sewage biosolids is diminishing for reasons of logistics and of public pressure. As a result P from wastewaters is ultimately disposed of in landfills. Over the long term, phosphate ore reserves will become depleted. Recycling of P from wastewaters may thus be a realistic prospect if scientific and technical issues can be resolved. At the centre of the scientific problems lie considerations about optimizing phosphate precipitation as Ca phosphates. A number of Ca phosphate minerals exist, although by far the most common of these is hydroxylapatite. Precipitation kinetic considerations, however, suggest that other Ca phosphates (such as brushite, octacalcium phosphate, whitlockite, monetite or amorphous Ca phosphate) may initially precipitate, and later recrystallize into the most stable hydroxylapatite. This article reviews the complex precipitation mineralogy, chemistry and kinetics of Ca phosphates.
Structural discontinuities in plagioclase and constraints on mixing properties of the low series: a computational study
Authors: Vinograd V. L. , Putnis A. , Kroll H. 
Published: July 2002

AbstractSubsolidus phase relations in the plagioclase system are investigated using an Ising-type model. The model treats ordering of Al,Si and Na,Ca cations in three dimensions using a version of the cluster variation method. The interactions within the T (Al,Si) and M (Na,Ca) sublattices and the interactions between the T and M sublattices are constrained by the available experimental information on orderdisorder transitions in the system. The paper suggests a thermodynamic explanation for the existence of two distinct structural series (high and low) and gives constraints on the thermodynamics of low plagioclases.
A detailed structural characterization of quartz on heating through the α–β phase transition
Authors: Tucker M. G. , Keen D. A. , Dove M. T. 
Published: July 2002

AbstractTotal neutron scattering measurements, analysed using a modification of the reverse Monte Carlo modelling method to account for long-range crystallographic order, have been used to describe the temperature-dependent behaviour of the structure of quartz. Two key observations are reported. First, the symmetry change associated with the displacive α–β phase transition is observed in both the long-range and short-range structural correlations. Secondly, some aspects of the structure, such as the Si–O bond length and the thermally-induced dynamic disorder, the latter of which sets in significantly below the transition, are relatively insensitive to the phase transition. These results are used to show that the α-domain model of the β-phase disorder is inappropriate and that the classical soft-mode picture of the phase transition is too simplistic. Instead, it is argued that the structural behaviour is best described in terms of its ability to respond to low-frequency, high-amplitude vibrational modes. This view is supported by additional single-crystal diffuse neutron scattering measurements.
Verbeekite, monoclinic PdSe2, a new mineral from the Musonoi Cu-Co-Mn-U mine, near Kolwezi, Shaba Province, Democratic Republic of Congo
Authors: Roberts A. C. , Paar W. H. , Cooper M. A. , Topa D. , Criddle A. J. , Jedwab J. 
Published: July 2002

AbstractVerbeekite, ideally PdSe2, monoclinic with space-group choices C2/m, C2 or Cm; a = 6.659(7), b = 4.124(5), c = 4.438(6) Å, ß = 92.76(3)°, V = 121.7(4) Å3; a:b:c = 1.6147:1:1.0761, Z = 2, is a new, very rare, primary mineral, intimately associated with secondary oosterboschite {(Pd,Cu)7Se5}, from the Musonoi Cu-Co-Mn-U mine, near Kolwezi, Shaba Province, Democratic Republic of Congo. Additional associated minerals are Cu- and Pd-bearing trogtalite {(Co,Cu,Pd)Se2}, Se-bearing digenite and Se-bearing covellite. The strongest five lines of the X-ray powder-diffraction pattern {d in Å (I) (hkl)} are: 4.423(30)(001), 3.496 (30)(110), 2.718(100)(111), 1.955(50)(310 and 1.896(50)(12). The mineral has also been identified, as a single anhedral 25 µm-sized grain, from Hope's Nose, Torquay, Devon, England where it is associated with native gold, chrisstanleyite Ag2Pd3Se4, oosterboschite(?), unnamed Pd2HgSe3 and cerussite. At Musonoi, altered verbeekite grains do not exceed 200 µm in size and are anhedral, black, with a black streak and a metallic lustre. The mineral is opaque, brittle, has an uneven fracture, and lacks discernible cleavage. The VHN5 ranges 490–610, mean 550 kp/mm2 (2 indentations), roughly approximating a Mohs' hardness of 5Ý. Dcalc. = 7.211 g/cm3 for the ideal formula. Electron-microprobe analyses (mean of 4 spot analyses) yielded Pd 39.6, Cu 0.5, Se 58.8, total 98.9 wt.%. The empirical formula is (Pd0.99Cu0.02)σ1.01Se1.99, based on Pd+Cu+Se = 3. In plane-polarized reflected light, the mineral is a nondescript grey and is neither pleochroic nor perceptibly bireflectant. Anisotropy is moderate with rotation tints in varying shades of brown. Reflectance spectra and colour values are tabulated. The name honours Dr Théodore Verbeek (1927–1991) who was the first geoscientist to study the Musonoi palladium mineralization in the Democratic Republic of Congo (1955–1967) and who co-discovered this new mineral phase.
An application of the point-dipole model to the problem of optical anomalies in grandite garnets
Authors: Shtukenberg A. G. , Popov D. Yu. , Punin Yu. O. 
Published: July 2002

AbstractThe origin of anomalous birefringence in grossular-andradite (grandite) garnets is considered. Using the point-dipole model we have calculated the anomalous optical indicatrix for four crystals (three from the paper by Takéuchi et al. (1982) and one studied previously by the present authors). The calculated indicatrix is in good agreement with the observed one. This suggests that the origin of anomalous birefringence in grandite garnets is due to Al/Fe ordering. Interrelations between the observed optical indicatrix, the structure of the growing face, the site occupancy in the crystal structure and the calculated optical indicatrix suggest a growth origin of Fe/Al ordering in grandite garnets and confirm the growth dissymmetrization hypothesis.
Fibre growth in wet salt aggregates in a temperature gradient field
Authors: den Brok Bas , Passchier Cees , Sieber Michel 
Published: July 2002

AbstractIntense fibrosity develops in wet porous NaCl crystal aggregates (grain size 250–500 µm) held in a temperature (T) gradient field (0.5–4°C/mm) at temperatures between 20 and 50–60°C. In situ microscopic observation of the process shows that fibre growth is associated with T-gradient driven motion of tiny gas (air, water vapour) bubbles present in the saturated intercrystalline aqueous NaCl solution. Gas bubbles move through the intercrystalline pore fluid into the cold direction. They only move if they are next to an NaCl crystal; bubbles that are ‘free’ do not move. Each bubble is ‘pushed’ into the cold direction by a growing crystal fibre of the same diameter as the bubble itself. Fibres apparently grow due to oversaturation of the NaCl solution at the hot side of the gas bubble. Crystals dissolve at the cold side of the gas bubbles, apparently by undersaturation of the NaCl solution there. Thus, bubbles dissolve their way through NaCl-crystals and aggregates. Intense fibrosity develops within weeks.
Fe-Mn cation ordering in fayalite–tephroite (FexMn1−x)2SiO4 olivines: a neutron diffraction study
Authors: Redfern S. A. T. , Knight K. S. , Henderson C. M. B. , Wood B. J. 
Published: July 2002

AbstractTime-of-flight neutron powder diffraction has been employed to determine precise occupancies of the M1 and M2 metal cation sites in synthetic olivines of compositions (Fe0.3Mn0.7)2SiO4, (Fe0.5Mn0.5)2−SiO4, and (Fe0.7Mn0.3)2SiO4. The distribution coefficient for Fe-Mn exchange in these samples has values of 4.864, 3.976, and 4.078, reflecting the preference of Mn2+ for the M2 site, over Fe2+. These results, and the behaviour of the difference in mean bond lengths of the two sites, indicate that, while showing a tendency towards ordering, the composition-dependence of the solid solution is near ideal.
Early Palaeolithic bone diagenesis in the Arago cave at Tautavel,
France
Authors: Quattropani L. , Charlet L. , de Lumley H. , Menu M. 
Published: July 2002

Abstract
Bones from level G in the Arago cave (Tautavel, Southern France, 450 ky) were
analysed using a combination of particle induced X-ray and gamma-ray emission
(PIXE and PIGME) and X-ray diffraction (XRD). Human occupation and guano
production by bats introduced a large amount of phosphate into the cave and as a
result a decarbonated pocket was formed in the sediment, characterized by the
dissolution of clay minerals, calcite and bones, and by the precipitation of
phosphate secondary minerals. The Al released by clay minerals was reprecipitated
as crandallite in the few remaining bones, and as montgomeryite with traces of
crandallite in the surrounding sediments. Bones within the pocket have very high
levels of Al, Fe, F and Zn and often have ‘diffusive’ type U-shaped concentration
profiles. These profiles show that post-mortem uptake of trace elements occurred,
and thus that trace element composition has to be used with care in
palaeonutritional studies but is indicative of local palaeoenvironment. This
uptake is complicated by a large increase in hydroxylapatite crystallinity in
Palaeolithic bones compared to modern or more recent ones, as a result of the
large P influx which occurred in the Arago cave after the sediment
deposition.
A high bone marrow plasma cell labeling index in stable plateau–phase multiple myeloma is a marker for early disease progression and death
Authors: Steensma David P. , Gertz Morie A. , Greipp Philip R. , Kyle Robert A. , Lacy Martha Q. , Lust John A. , Offord Janice R. , Plevak Matthew F. , Therneau Terry M. , Witzig Thomas E. 
Published: July 2002

Abstract
The plasma cell labeling index (PCLI) is a measure of plasma cell proliferative activity and is an important prognostic factor in newly diagnosed multiple myeloma (MM). Occasionally patients have been observed with stable, plateau phase MM with minimal numbers of residual light-chain–restricted monoclonal plasma cells, but a high PCLI. No data are available on the outcomes for such patients. Data from 57 patients with plateau phase MM and a marrow PCLI of more than 1.0% were compared with 105 matched control patients with MM with a marrow PCLI of less than 1.0%. All patients had less than 10% total plasma cells on marrow aspirate and biopsy. The median time to progression and overall survival were 8 months and 20 months, respectively, in the high PCLI group versus 39 months and 56 months, respectively, in the low PCLI group (P &lt; .0001). These findings suggest that a high PCLI in patients with apparently stable, plateau phase MM is an adverse parameter that may predict a short time to disease progression and death.
Molecular and flow cytometric analysis of the Vβ repertoire for clonality assessment in mature TCRαβ T-cell proliferations
Authors: Langerak Anton W. , van den Beemd René , Wolvers-Tettero Ingrid L. M. , Boor Patrick P. C. , van Lochem Ellen G. , Hooijkaas Herbert , van Dongen Jacques J. M. 
Published: July 2002

AbstractClonality assessment through Southern blot (SB) analysis ofTCRB genes or polymerase chain reaction (PCR) analysis ofTCRG genes is important for diagnosing suspect mature T-cell proliferations. Clonality assessment through reverse transcription (RT)–PCR analysis of Vβ-Cβ transcripts and flow cytometry with a Vβ antibody panel covering more than 65% of Vβ domains was validated using 28 SB-defined clonal T-cell receptor (TCR)αβ+ T-ALL samples and T-cell lines. Next, the diagnostic applicability of the Vβ RT-PCR and flow cytometric clonality assays was studied in 47 mature T-cell proliferations. Clonal Vβ-Cβ RT-PCR products were detected in all 47 samples, whereas single Vβ domain usage was found in 31 (66%) of 47 patients. The suspect leukemic cell populations in the other 16 patients showed a complete lack of Vβ monoclonal antibody reactivity that was confirmed by molecular data showing the usage of Vβ gene segments not covered by the applied Vβ monoclonal antibodies. Nevertheless, this could be considered indirect evidence for the “clonal” character of these cells. Remarkably, RT-PCR revealed an oligoclonal pattern in addition to dominant Vβ-Cβ products and single Vβ domain expression in many T-LGL proliferations, providing further evidence for the hypothesis raised earlier that T-LGL derive from polyclonal and oligoclonal proliferations of antigen-activated cytotoxic T cells. It is concluded that molecular Vβ analysis serves to assess clonality in suspect T-cell proliferations. However, the faster and cheaper Vβ antibody studies can be used as a powerful screening method for the detection of single Vβ domain expression, followed by molecular studies in patients with more than 20% single Vβ domain expression or large suspect T-cell populations (more than 50%-60%) without Vβ reactivity.
Intravenous injection of apoptotic leukocytes enhances bone marrow engraftment across major histocompatibility barriers
Authors: Bittencourt Marcelo de Carvalho , Perruche Sylvain , Contassot Emmanuel , Fresnay Stéphanie , Baron Marie-Hélène , Angonin Régis , Aubin François , Hervé Patrick , Tiberghien Pierre , Saas Philippe 
Published: July 2002

AbstractCross-tolerization of T lymphocytes after apoptotic cell uptake by dendritic cells may be involved in self-tolerance maintenance. Furthermore, immunosuppressive properties are attributed to apoptotic cells. This study evaluated the consequences of apoptotic leukocyte administration in a restrictive engraftment model of murine bone marrow (BM) transplantation. Sublethally irradiated recipients received a limited number of allogeneic BM, with or without irradiated apoptotic leukocytes of different origins. No graft-versus-host disease was observed. Whereas only a low proportion of mice receiving BM cells alone engrafted, addition of apoptotic irradiated leukocytes, independently of the origin (donor, recipient, third-party mice, as well as xenogeneic peripheral blood mononuclear cells), significantly enhanced engraftment. Similar results were obtained after infusion of leukocytes rendered apoptotic by UVB irradiation or by anti-Fas monoclonal antibody stimulation, thus confirming the role of apoptotic cells in engraftment facilitation. Overall, these results suggest that apoptotic leukocytes can nonspecifically facilitate allogeneic BM engraftment. Such a simple approach could be of interest in BM transplantation settings involving an important HLA donor/recipient disparity, a T-cell–depleted graft, or reduced conditioning regimen intensity.
The association of the glycophorin C exon 3 deletion with ovalocytosis and malaria susceptibility in the Wosera, Papua New Guinea
Authors: Patel Sheral S. , Mehlotra Rajeev K. , Kastens William , Mgone Charles S. , Kazura James W. , Zimmerman Peter A. 
Published: July 2002

AbstractErythrocyte polymorphisms, including ovalocytosis, have been associated with protection against malaria. This study in the Wosera, a malaria holoendemic region of Papua New Guinea, examined the genetic basis of ovalocytosis and its influence on susceptibility to malaria infection. Whereas previous studies showed significant associations between Southeast Asian ovalocytosis (caused by a 27– base pair deletion in the anion exchanger 1 protein gene) and protection from cerebral malaria, this mutation was observed in only 1 of 1019 individuals in the Wosera. Polymerase chain reaction strategies were developed to genotype individuals for the glycophorin C exon 3 deletion associated with Melanesian Gerbich negativity (GPCΔex3). This polymorphism was commonly observed in the study population (GPCΔex3 frequency = 0.465, n = 742). Although GPCΔex3 was significantly associated with increased ovalocytosis, it was not associated with differences in either Plasmodium falciparumor P vivax infection measured over the 7-month study period. Future case-control studies will determine if GPCΔex3 reduces susceptibility to malaria morbidity.
DUB-2A, a new member of the DUB subfamily of hematopoietic deubiquitinating enzymes
Authors: Baek Kwang-Hyun , Mondoux Michelle A. , Jaster Robert , Fire-Levin Ella , D'Andrea Alan D. 
Published: July 2002

AbstractProtein ubiquitination is an important regulator of cytokine-activated signal transduction pathways and hematopoietic cell growth. Protein ubiquitination is controlled by the coordinate action of ubiquitin-conjugating enzymes and deubiquitinating enzymes. Recently a novel family of genes encoding growth-regulatory deubiquitinating enzymes (DUB-1 and DUB-2) has been identified.DUBs are immediate-early genes and are induced rapidly and transiently in response to cytokine stimuli. By means of polymerase chain reaction amplification with degenerate primers for theDUB-2 complementary DNA, 3 murine bacterial artificial chromosome (BAC) clones that contain DUB gene sequences were isolated. One BAC contained a novel DUB gene(DUB-2A) with extensive homology to DUB-2. LikeDUB-1 and DUB-2, the DUB-2A gene consists of 2 exons. The predicted DUB-2A protein is highly related to other DUBs throughout the primary amino acid sequence, with a hypervariable region at its C-terminus. In vitro, DUB-2Ahad functional deubiquitinating activity; mutation of its conserved amino acid residues abolished this activity. The 5′ flanking sequence of the DUB-2A gene has a hematopoietic-specific functional enhancer sequence. It is proposed that there are at least 3 members of the DUB subfamily (DUB-1, DUB-2,and DUB-2A) and that different hematopoietic cytokines induce specific DUB genes, thereby initiating a cytokine-specific growth response.