bluuebunny/crossref_metadata_2025 huggingface dataset:
Three-dimensional Dynamic Finite Element Analysis of Multiple Laser Shock Peening Processes
Authors: Ding K.
Published: January 2004

Laser shock peening (LSP) is an innovative surface treatment technique successfully applied to improving fatigue performance of metallic materials. The fatigue strength and fatigue life of the laser peened material can be significantly improved by deep compressive residual stresses being introduced into the material. The compressive residual stress distribution along the depth of the material is attributed to a high amplitude stress wave induced by a high energy laser pulse. The present paper describes a finite element method for simulating the residual stress distribution in a metal alloy 35CD4 50 HRC steel in single and multiple LSP processes. The process used a three-dimensional dynamic finite element model impacted by a square laser spot. The predicted results for single LSP were well correlated with the available experimental data. Meanwhile, the effects of multiple LSP processes, pressure magnitude and duration, and laser spot sizes on the compressive stress field in the metal alloy were evaluated for the purpose of optimising the process.
Simulation of Phase Transformations and Temperature Profiles by Temperature Controlled Laser Hardening: Influence of Properties of Base Material
Authors: Obergfell K. , Schulze V. , Vöhringer O.
Published: January 2004

Simulation of laser hardening of steels was carried out, involving the finite element system ABAQUS and user defined material laws, which led to a coupled calculation of temperature, phase and stress development during heating and cooling. Additionally, the simulation allowed the phase distributions within the affected zone to be determined. Good correspondence between the results of the simulated and experimental data was obtained in respect of the influence of irradiation time and base material on the size of the hardened zone.
Sliding Abrasion Wear Assessment of Al2o3-SiC Nanocomposite Coatings
Authors: Dearnley P. A. , Panagopoulos K. , Kern E. , Weiss H.
Published: January 2004

The present work describes abrasion wear tests that were carried out on low carbon steel test wheels coated with a series of high velocity oxygen fuel (HVOF) and plasma sprayed Al2O3 - SiC nanocomposite coatings with varying SiC contents. These were compared with pure Al2O3 coatings applied by HVOF and with uncoated steel. The HVOF sprayed coatings exhibited consistently superior abrasion wear resistance compared with plasma sprayed coatings of equivalent composition and were much better than uncoated steel. Overall, the HVOF Al2O3 - 10SiC nanocompo2 site coating showed the best abrasion resistance of all the coatings tested. They were worn very slowly by a microabrasion process. The poor performance of the plasma sprayed coatings was attributed to inefficient in flight melting of the particle agglomerates during the deposition process. This resulted in coatings with a low cohesive strength, which made them particularly vulnerable to particle pull out during abrasion testing.
Formation of YSZ Films by Thermal Annealing of Y/Zr Layers in Air
Authors: Pranevičius L. , Milčius D. , Širvinskaite V. , Norby T. , Haugsrud R. , Pranevičius L. L. , Templier C.
Published: January 2004

Homogeneous yttria stabilised zirconia films were synthesised using thermal annealing of Y/Zr layers of strictly controlled thickness in air in the temperature range 600 - 1000 ° C. Intermixing and oxidation kinetics were investigated. Secondary ion mass spectrometry analysis was used to record the depth profiles of the most important elements across the thickness of the synthesised films. The characterisation of film structure was carried out by X-ray diffraction. Surface roughness and topography were monitored by atomic force microscopy and scanning electron microscopy. Results showed that there is a correlation between surface topography and mixing and oxidation kinetics. The existence of columnar boundaries and a nanocrystalline structure in the films seem to affect the oxygen penetration mechanism significantly.
Microarc Electrodeposition of Ceramic Films on Double Electrodes of AZ91D Magnesium Alloy by Symmetrical AC Pulse Method
Authors: Yuangang L. , Wei Z. , Jiuqing L.
Published: January 2004

Using the two direction symmetrical alternating current pulse method, ceramic films were successfully electrodeposited simultaneously on anodic and cathodic AZ91D magnesium specimens by microarc oxidation. This process was named double electrode microarc electrodeposition (DEME). The thickness, morphology and composition of the DEME films were studied using SEM and X-ray diffraction patterns. The rare earth element Ce was detected in both the anodic and cathodic films when CeF4·H2O was added to the film forming an electrolyte. The improvement in corrosion resistance of AZ91D after DEME treatment was shown by comparing potentiodynamic scanning polarisation curves and the electrochemical impedance spectroscopy of the specimens with and without DEME treatment. By immersing the samples with and without DEME treatment in 3.5%NaCl solution, it was found that the corrosion rate of specimens treated using the DEME process was much lower than that of untreated specimens. In order to reduce their porosity, samples with DEME films were further painted with three different kinds of coatings: sol-gel, polysilicone and epoxy lacquer. Samples coated with DEME film and epoxy coatings could sustain a 336 h neutral salt spray test.
Electroless Nickel Plating of Atomised and Sponge Iron Compacts
Authors: Bolarín A. M. , Sánchez F. , Barba A. , Coreño O. , Coreño J.
Published: January 2004

Electroless coatings are obtained by means of an autocatalytic chemical reduction process for depositing different metals. Electroless nickel plating is an engineering coating, normally used for its excellent corrosion and wear resistance. Little information exists about the application of this type of coating on powder metallurgy products, compared with the large amount of data available on coatings on wrought metal products by means of the same technique. The present paper discusses the effect of the different grades (20, 15, 10, 7 and 5%) and types (irregular and regular) of porosity of iron powder metallurgy compacts, on the properties of the electroless nickel coating: thickness, composition, deposition rate, microhardness, porosity, adhesion and corrosion resistance. Sponge and atomised iron compacts with different porosities were obtained by pressing at different densities (5.5 - 7.0 g cm-3) and sintering at 1120 ° C in an N2 - H2 atmosphere. The sintered parts were successfully coated by electroless nickel deposition using a hypophosphite bath with the same composition and conditions for all the compacts, and the coating was subsequently characterised. The ferroxyl test was used to evaluate the grade of superficial porosity, and the salt spray test helped to obtain the corrosion resistance of the nickel - phosphorus deposits on the PM compacts. Electron and optic microscopy techniques were used to analyse the coating thickness quantitatively. Also, measurements were performed to determine the microhardness achieved in the coatings. Results show that, for both types of powder, levels of porosity > 12% cause coatings with deficient properties: low corrosion resistance, high levels of porosity, dispersion in microhardness and low thickness. However, the coatings obtained in the pieces made with the atomised powder have better characteristics than those elaborated with iron sponge powder.
Monitoring Stress in Thin Films during Processing
Authors: Chason E. , Sheldon B. W.
Published: January 2004

Wafer curvature measurements are a simple yet sensitive way to measure stress in thin films. A multibeam optical system designed for in situ monitoring makes it possible to monitor the evolution of thin film stress in real time in a variety of deposition and processing environments. Examples of stress measurements in epitaxial systems, polycrystalline films and hard coatings are discussed.
Chlorites: occurrence, genesis and crystal chemistry – introduction
Authors: Berger G. , Beaufort D.
Published: January 2004

The crystal chemistry and mechanisms of chlorite formation (more particularly the ferrous varieties) are currently attracting growing interest in various fields of application. In oil prospection, this interest is linked to the origin and formation of diagenetic chlorite rims that preserve the quality of sandy reservoirs down to unusual depths of burial. In the nuclear industry, the use of iron containers for the storage of radioactive waste is likely to produce ferrous chlorites by interaction with the clayey barrier within which the waste is stored. The ditrioctahedral and tri-trioctahedral chlorites are also some of the best clay mineral markers of hydrothermal activity leading to the formation of uranium deposits underlying the Proterozoic unconformity that make up the largest current economic reserves.

The high chemical and structural variability of chlorite is an obstacle in understanding its mechanism of formation, transformation and alteration. This also applies to the determination of the thermodynamic parameters that are required for digital models based on thermo-kinetic laws.
A nanopetrographic and textural study of grain-coating chlorites in sandstone reservoirs
Authors: Billault V. , Beaufort D. , Baronnet A. , Lacharpagne J. -C.
Published: January 2004

Scanning electronic microscopy (SEM) and transmission electronic microscopy (TEM) investigations of chlorite grain coatings from four different sandstone reservoirs indicate a progressive change in both texture and arrangement of chlorite particles from the contact with the detrital substratum to the centre of the pore. Such spatial distribution results from growth by geometrical selection. Geometrical selection of chlorite crystals proceeded during a single event of continuous growth which began before the consolidation of the sandy sediments, lasted through part of the subsequent mechanical compaction and ceased before the occurrence of quartz cement. Nanopetrographic investigations near the detrital quartz-chlorite coating interface demonstrate that inhibition of the quartz cement is due to the limitation of the epitaxial growth of quartz to the interparticular space at the base of the chlorite coating and not an absence of nucleation. It is suggested that these results can be applied to most of the sandstones which contain Fe-rich chlorite grain coatings.
Effect of acid treatment on the structure of sepiolite
Authors: Yebra-Rodríguez A. , Martín-Ramos J . D. , Del Rey F. , Viseras C. , López-Galindo A.
Published: January 2004

An ab initio determination of the structure of sepiolite after acid treatment (HCl 0.5 N for 24 h) was carried out using X-ray powder diffraction data. After acid treatment, the sections normal to the a and c axes presented discontinuities, ∼2.25 Å wide, parallel to the (010) plane, with no electronic density maxima, thus suggesting that adjacent planes are joined by van der Waals-like residual links. Partial dissolution was detected on both octahedral and tetrahedral sheets, beginning by breaking the ribbons not along the edges, but in the centre, thus creating a 5.20 x 66.79 Å tunnel along the a axis. By interrupting the tetrahedral sheet, this mechanism changes the phyllosilicate-like nature of the sepiolite to an inosilicate-like structure.
Firing transformations of a carbonatic clay from the High–Atlas, Morocco
Authors: Kacim S. , Hajjaji M.
Published: January 2004

The firing transformations of a Triassic calcareous clay were investigated, in the range 800 –1075ºC, by using X-ray diffraction and by measuring some ceramic properties (linear shrinkage, density and porosity). It was found that gehlenite and wollastonite are the only neoformed crystalline phases, when anorthite is also expected. The occurrence of these phases is discussed, emphasizing the role of the activity of free silica and calcite concentration. Moreover, new reaction paths for anorthite and wollastonite are envisaged.
Surface microtopography of sudoite
Authors: Jige M. , Kitagawa R. , Zaykov V. V. , Sinyakovskaya I .
Published: January 2004

The gold-decoration technique of electron microscopy is used to study the surface microtopography of natural (001) surfaces of sudoite collected from a hydrothermal vein of the Berezovsk gold deposit, Central Urals, Russia. Only closed step patterns with malformed and/or nearly circular islands were observed on the (001) growth surface of sudoite crystals, implying a twodimensional nucleation mechanism. This is in contrast to the spiral step patterns commonly recognized on growth surfaces of other clay minerals, such as illite and kaolinite, formed under hydrothermal conditions. It is inferred that the crystallization of sudoite occurred under relatively higher temperatures and/or from more highly supersaturated fluids than many other hydrothermal clay minerals so far described.
Zeolite crystal habits, compositions, and paragenesis; Blackhead Quarry, Dunedin, New Zealand
Authors: Graham I. T. , Pogson R. E. , Colchester D. M. , Baines A.
Published: January 2004

Blackhead Quarry exploits a small Miocene (~10 Ma) basanitic volcanic centre in the Dunedin Volcanic Group, New Zealand. Vesicles near the quarry top contain Ca– and Na-rich zeolites, abundant calcite and rare pyrite resulting from localized low-T hydrothermal alteration (<100°C). Mineral assemblages were characterized by EDS and laser Raman spectroscopy with the latter the most useful in determining the identity of fibrous zeolite species. Secondary mineral assemblages crystallized during final stages of lava cooling from aqueous solutions enriched in Ca, Na, K, Ba and (CO3)2–leached from surrounding calcareous rocks and basanite. Phillipsite-K (generation I) crystallized first (in some places directly on fresh basanite) followed by the Ca-rich zeolites, chabazite-Ca, calcian phillipsite–K (generation II), gismondine and thomsonite. Later Na-rich fluids crystallized gonnardite and natrolite, and finally calcite from late Ca-rich fluids. Zeolite composition is not reflected by morphology. For example, both phacolitic and pseudocubic chabazite are chabazite-Ca, and although all phillipsite crystals have a similar habit, their composition varies widely. Various lithologies comprising the Blackhead volcanic centre have unique secondary mineral paragenetic sequences controlled largely by the rock structure and solution chemistry.
Rhönite paragenesis in pyroxenite xenoliths, Mount Sidley volcano, Marie Byrd Land, West Antarctica
Authors: Grapes R. H. , Wysoczanski R. J. , Hoskin P. W. O.
Published: January 2004

Rhönite occurs in lower crustal pyroxenite xenoliths erupted in phonolite from the Mount Sidley composite volcano, Marie Byrd Land, Antarctica, as a localized breakdown product, with plagioclase, clinopyroxene, ± olivine ± Ti-magnetite + melt, of kaersutite, and as microphenocrysts (with olivine, plagioclase, clinopyroxene) in pockets of basanitic melt. Rhö nite after kaersutite has a more NaSi-rich/ CaAl-poor composition, lower Ti, and formed at higher oxidation (∼NNO) conditions than rhönite occurring as microphenocrysts in basanite. Comparison with experimentally determined rhönite stability in understaturated alkali basalt and as a reaction product after Ti-amphibole indicates that the Mount Sidley rhönite (and associated minerals) formed between 1090 and 1190°C at <0.5 kbar, presumably during temporary residence of the xenoliths in a shallow magma chamber below the volcanic edifice.
Kinetic parameters associated with self-heating of New Zealand coals under adiabatic conditions
Authors: Beamish B. B. , George J. D. St. , Barakat M. A.
Published: January 2004

Adiabatic self-heating tests were carried out on five New Zealand coal samples ranging in rank from lignite to high-volatile bituminous. Kinetic parameters of oxidation were obtained from the self-heating curves assuming Arrhenius behaviour. The activation energy E (kJ mol–1) and the pre-exponential factor A (s–1) were determined in the temperature range of 70–140°C. The activation energy exhibited a definite rank relationship with a minimum E of 55 kJ mol–1 occurring at a Suggate rank of ∼6.2 corresponding to subbituminous C. Either side of this rank there was a noticeable increase in the activation energy indicating lower reactivity of the coal. A similar rank trend was also observed in the R70 self-heating rate index values that were taken from the initial portion of the self-heating curve from 40 to 70°C. From these results it is clear that the adiabatic method is capable of providing reliable kinetic parameters of coal oxidation.
Ion exchange between aqueous fluid and spent nuclear fuel alteration products: Implications for the mobility of Cs in the probable repository at Yucca Mountain
Authors: Hoskin P. W. O. , Burns P. C.
Published: January 2004

Compreignacite, a naturally occurring potassium uranyl oxide hydrate, is an expected alteration product of spent nuclear fuel subjected to oxidative corrosion in the presence of water. Ion-exchange experiments were performed using natural crystals of compreignacite in a 2 M CsCl solution at 180°C for 24 h, and in a 100 ppm CsCl solution at 90°C for 14 days. Exchange of Cs into crystals of compreignacite was demonstrated by crystal-structure analysis for a crystal from 2 M solution and chemical analysis for crystals from both exchange experiments. The structure of Cs-exchanged compreignacite is hexagonal, space group P2m, a= 14.1014 (18) Å, c = 15.127(3) Å, V = 2605.1(7) Å2. It was solved by direct methods and refined on the basis of F2 for all unique reflections to a final R1 = 6.37%. The structure determination demonstrated almost complete exchange of Cs for K in the interlayer of the structure, as confirmed by compositional analysis of the crystals, and provided the formula Cs6[(UO2)12(OH)10O10](H2O)3.5, Z= 2. The structure of Cs-exchanged compreignacite contains α-U3O8-type sheets of uranyl pentagonal bipyramids that are topologically identical, although compositionally distinct, to those in compreignacite. Compreignacite crystals placed in 100 ppm CsCl solution also incorporated substantial Cs by ion exchange. Ion exchange experiments, using Cs-exchanged compreignacite from earlier experiments, in 2 M KCl solution at 90°C for 14 days showed that compreignacite will retain significant Cs in the presence of a solution rich in K. These experiments indicate that formation of compreignacite structure-type phases in a geological repository due to alteration of nuclear waste may significantly impact upon the mobility of Cs, either by direct incorporation of Cs into growing crystals, or by exchange of Cs into earlier-formed crystals of compreignacite when they contact Cs-bearing solutions.
Hydroxylian pseudorutile derived from picroilmenite in the Murray Basin, southeastern Australia
Authors: Grey I. E. , Li C.
Published: January 2004

Ilmenite concentrates obtained from heavy mineral deposits in the Murray Basin, southeastern Australia contain appreciable quantities (up to 10 wt.%) of an unusual hydrated Fe titanate mineral in the form of orange to red coloured translucent grains. The grains are weakly magnetic and have a low apparent density (<3.3 g cm–3) due to microprosity, which enables them to be easily concentrated in a pure state. Samples from different deposits have similar analyses of 67–69% TiO2, 8 –9% Fe2O3, 2–3% FeO, 11 –12% H2O and 8 –9% of intra-pore impurities, mainly SiO2 and Al2O3. The powder pattern for the mineral closely matches that for pseudorutile; having a hexagonal subcell with a = 2.844 (1) Å, c = 4.575 (1) Å. The idealized composition range of the Fe titanate, calculated from analyses and structure refinements, is [FeTi6O12(OH)3].3H2O to [FeTi6O11(OH)5].2H2O. The molecular water is nonstructural, probably adsorbed on the surfaces of nano-scale domains of the mineral. Electron microprobe and scanning electron microscopy studies provide evidence for formation of the mineral by replacement reactions acting on MgO-rich ferrian ilmenite grains. The mineral represents a distinct intermediate in the chemical weathering of ilmenite, having a pseudorutile-like structure but a leucoxene-like composition. It is unusual in not having undergone any recrystallization to phases such as rutile and anatase.
Evolutionary stages of crystallization of weakly peralkaline syenites: evidence from ejecta in the plinian deposits of Agua de Pau volcano (São Miguel, Azores Islands)
Authors: Ridolfi F. , Renzulli A. , Santi P. , Upton B. G. J.
Published: January 2004

Weakly peralkaline syenite ejecta within the plinian fall deposits of Agua de Pau volcano (São Miguel, Azores Islands) are divisible into (1) silica-undersaturated and (2) silica-saturated/oversaturated groups. The first group occurs in the pre-Fogo-A pyroclastic falls (15.2 ka) whereas the second occurs in the Fogo-A pumices (5 ka). The petrography indicates that the syenites of both groups crystallized at shallow depths and whole-rock geochemistry shows that they have compositions reflecting those of the Agua de Pau trachyte magmas. The syenites are inferred to be derived from solidification zones around the margins of the parental magma chamber. Mineral parageneses in both syenite groups permit distinction of three magmatic stages of crystallization: (1) an early crystallization stage; (2) a main crystallization stage during which most of the feldspar growth occurred; and (3) a late interstitial stage. Crystallization of the trachytic magmas yielded peralkaline residuals, highly enriched in volatiles, alkalis, HFSE andREE. In the silica-undersaturated syenites, the complex Zr-Ti silicate minerals, eudialyte and a låvenite-like mineral, crystallized interstitially from the residual magmas. In contrast, the zircono-silicate dalyite, andREE-rich minerals (chevkinite-(Ce), britholite-(Ce) and pyrochlore), together with thorite, were late-stage interstitial products of the silica-saturated/oversaturated syenites.
Nickelphosphide from the Vicenice octahedrite: Rietveld crystal structure refinement of a synthetic analogue
Authors: Skála R. , M. Drábek
Published: January 2004

The original description of nickelphosphide from the Butler meteorite [(Ni1.83Fe1.21)Σ3.04P0.96 to (Ni1.71Fe1.28Co0.01)Σ3.00P1.00] lacks detailed and accurate powder data – with only 11 observed reflections down to 1.37 Å. Consequently, no crystal structure information for this phase is available. Here we present the crystal structure for a synthetic analogue of the phase found in the Vicenice IID medium octahedrite (with a mean empirical formula of (Ni1.69Fe1.31)Σ3.00P1.00) and a hypothetical Ni3P end-member. Unit-cell dimensions of the synthetic analogue of Ni1.68Fe1.33P0.99 composition from individual peak profile fitting of XRD data collected with Cu radiation are a= 9.0168(2)Å, c= 4.4491(1)Å, V= 361.72(1)Å3 and those for Ni3P composition are a= 8.9546(1)Å, c= 4.38714(8)Å, V= 351.783(8)Å3. The space group of the mineral is I4¯ and Z= 8. The crystal structure refined from powder data by the Rietveld method is consistent with that refined and published for Fe3P and Ni3P synthetic compounds as well as Fe-dominant schreibersite from single-crystal data. However, because of the similarity of the scattering of iron and nickel, we were not able to refine directly the site occupancies in the synthetic analogue of the nickelphosphide from the Vicenice iron meteorite.
On the significance of small deviations from higher symmetry
Authors: Baur W. H. , Fischer R. X.
Published: January 2004

Small deviations from higher symmetry can be established by single-crystal diffraction methods by (1) measuring the metric of the unit cell with high, non-routine precision; (2) measuring a full reflection sphere of diffraction data and testing it for the presence or absence of symmetry elements in the dataset; (3) refining the structure in both the higher and the lower symmetry and comparing the results; (4) checking the refined crystal structures for the presence or absence of hidden symmetry elements. By these criteria it is not established that the v{120} growth sector of yugawaralite really has triclinic symmetry (Tanaka et al., 2002). On the contrary, the refined metrical parameters and the atomic positions conform to monoclinic symmetry within the margins of experimental error.
Textural and spectroscopic studies on hydrothermal dumortierite from an Al-rich clay deposit, southeastern Korea
Authors: Choo C. O. , Kim Y.
Published: January 2004

Dumortierite occurs as small nodules or thin layers along horizontal fractures in the altered volcanic rocks of the Milyang clay deposit, southeastern Korea. Textural evidence shows that dumortierite is associated with pyrophyllite, suggesting that the silica activity increased with decreasing B and Al activities during the hydrothermal alteration. Dumortierite chemistry shows a slight excess of Al, possibly due to common occurrence of Al-rich minerals in the clay deposit. The structural formula of dumortierite is recalculated as Al6.93(Fe0.03Mg0.07)B(Si2.99Al0.01)O18. An absorption peak at 1387 cm–1 in the IR spectrum indicates that B is present in three-fold coordinated sites. The 29Si MAS NMR spectrum has two peaks at –90.9 and –95.5 ppm, showing that Si in dumortierite is located in two different crystallographic sites and is linked to four octahedral Al atoms. The 27Al MAS NMR spectrum shows only one asymmetrical peak near 0 ppm, suggesting that there is no substitution of Al for Si. The 11B MAS NMR spectrum at 17.5 ppm shows a typical second order quadrupole pattern represented by the three-fold coordinated B. The 11B chemical shifts indicate that all of the B occupies such sites, indicating that the B sites are axially symmetric or nearly so in a very well defined site.
Geochemistry of biotite in metabentonites as an age discriminant, indicator of regional magma sources and potential correlating tool
Authors: Batchelor R. A.
Published: January 2004

The chemical composition of unaltered biotites extracted from 18 Lower Palaeozoic metabentonites from Sweden, Norway and Scotland was determined. Discrimination based on FeO, MgO and TiO2proved able to separate the metabentonites on the basis of their stratigraphical age. A triangular discrimination diagram using MgO, FeO and Al2O3classified the biotites as calc-alkaline. Independent support for the discriminant power of FeO, MgO and TiO2in biotite comes from Sr isotope ratios and Sr concentration data from cognate apatite crystals. Within this dataset Caradocian and Llandoverian metabentonites have unique biotite compositions, while Wenlockian samples can be characterized to a lesser degree. Biotite composition also supported the correlation of a pair of metabentonites from Norway known to form part of the same horizon. Biotite in metabentonites preserves the chemical signature of the host magmas in which it crystallized and can be used to discriminate between metabentonites of different ages and provenance.
Structural phase transitions and mixing behaviour of the Ba-aluminate (BaAl2O4)– Sr-aluminate (SrAl2O4) solid solution
Authors: Rodehorst U. , Carpenter M. A. , Marion S. , Henderson C. M. B.
Published: January 2004

Phase transitions in the BaAl2O4–SrAl2O4solid solution have been analysed as a function of temperature and composition using infrared (IR) powder absorption spectroscopy. The improper ferroelectric phase transitionP6322 →P63(2A superstructure) in the BaAl2O4end-member can be detected through a change in slope of the wavenumbers of hard modes at ∽450 K. A change in line widths at ∽520 K appears to correlate with the development of diffuse intensity ina*-b*planes of electron diffraction patterns reported elsewhere in the literature. The same shift in wavenumber of hard modes is not observed in spectra from samples with compositions corresponding to 60, 80 and 90% of BaAl2O4component, but a change in line widths at ∽500 K has been tentatively explained in terms of a different phase transition, from aP6322 parent structure to aP63(√3A superstructure) product. Strain analysis of published high-temperature lattice parameter data suggests that the hexagonal → monoclinic transition in Sr-rich members of the solid solution may consist of two discrete transitions, and a sequenceP6322 →C2 →P21is suggested. The second transition could be related to instabilities in the hexagonal solid solution. Autocorrelation analysis of the IR spectra reveals a large positive deviation from linear behaviour across the solid solution, which is interpreted in terms of microscopic strain effects. These microscopic strains are probably responsible for the different transformation behaviour shown by samples with different compositions across the solid solution.
Fahlore as a petrogenetic indicator: Keno Hill Ag-Pb-Zn District, Yukon, Canada
Authors: Sack R. O. , Lynch J. V. G. , Foit F.
Published: January 2004

Fahlores [~(Cu,Ag)10(Zn,Fe)2Sb4S13] from the Keno Hill mining district, central Yukon, Canada record virtually the entire petrogenetic history of a Cretaceous hydrothermal system extending over 40 km outward from the Mayo Lake granitic pluton. These fahlores are an essential constituent of polymetallic sulphide veins developed in a graphitic Mississippian quartzite, where they occur in association with sphalerite, pyrargyrite, galena and siderite. Fahlores exhibit pronounced east-west zoning in average Ag/(Ag+Cu) and Zn/(Zn+Fe) values, with these simultaneously increasing and decreasing from east to west over 20 km of hydrothermal activity. These zonations are coupled with average Ag/(Ag+Cu) and Zn/(Zn+Fe) values in fahlore roughly paralleling the 300°C isotherm for fahlores in equilibrium with pyrargyrite, miargyrite and sphalerite in the simple system Ag2S-Cu2S-ZnS-FeS-Sb2S3. Early high-Ag, high-Zn fahlores from the eastern and western mines have Ag/(Ag+Cu) and Zn/(Zn+Fe) values requiring temperatures ≥400°C, in agreement with temperatures established from the As-content of arsenopyrite coexisting with pyrite, pyrrhotite and sphalerite. Ag/(Ag+Cu) and Zn/(Zn + Fe) values in later, main-stage fahlores are consistent with the 250–310°C range of temperatures established for boiling of Keno Hill fluids. Finally, Ag- and Fe-rich fahlores were produced by retrograde Fe-Zn exchange with sphalerite or crystallized from late-stage epithermal fluids which produced polybasite, stephanite, acanthite and wire silver. One such fahlore exhibits unmixing into high-Ag and low-Ag varieties. This is the first reported miscibility gap for freibergite fahlores and confirms the earlier prediction of such gaps.
Redefinition of arhbarite, Cu2Mg(AsO4)(OH)3
Authors: Krause W. , Bernhardt H.-J. , Effenberger H. , Kolitsch U. , Lengauer CH.
Published: January 2004

Arhbarite was described in 1982 as a new copper arsenate, Cu2(OH)AsO4·6H2O, from the Arhbar mine, Morocco. Due to the very small grain size no crystallographic data other than the X-ray powder diffraction data could be given. Reinvestigation of the type material and of new finds from the El Guanaco mine, Chile, is based on Rietveld refinement of X-ray powder data, electron microprobe investigations, optical studies as well as infrared and Raman spectra. The main results are: (1) arhbarite has the ideal formula Cu2Mg(AsO4)(OH)3 with magnesium oxide as an additional constituent and (2) arhbarite is isotypic with gilmarite, Cu3(AsO4)(OH)3. Arhbarite is triclinic, space group P1 (no. 1), unit-cell parameters (type material; refined from powder data) a= 5.315(4), b= 5.978(6), c= 5.030(6)Å, α = 113.58(6), β = 97.14(7), γ = 89.30(8)°, V= 145.2(1)Å3, Z= 1. Microprobe analyses of the type material gave MgO 10.20, CuO 47.46, NiO 0.20, CoO 0.24, As2O5 33.85, SiO2 0.10, H2O 7.58 (calc.), total 99.63 wt.%. The empirical formula is Cu1.98(Mg0.88Cu0.09Ni0.01Co0.01)S0.99(AsO4)1.02(OH)2.92, based on 7 O atoms. The Chilean arhbarite shows a slightly higher Cu content than the type material; it has the formula Cu1.99(Mg0.73Cu0.25Zn0.01)∑0.99[(AsO4)1.01(SiO4)0.01]∑1.02(OH)2.92. The formal redefinition of arhbarite has been approved by the CNMMN of the IMA.
The structure of hügelite, an arsenate of the phosphuranylite group, and its relationship to dumontite
Authors: Locock A. J. , Burns P. C.
Published: January 2004

The crystal structure of hügelite, Pb2[(UO2)3O2(AsO4)2](H2O)5, monoclinic, space group P21/m, a= 31.066(3)Å, b= 17.303(2)Å, c= 7.043(1)Å, β = 96.492(2)°, V= 3761.6(1)Å3, Z= 8, Dcalc = 5.74 g/cm3, was solved by direct methods using data from a crystal twinned by pseudo-merohedry, and was refined by full-matrix least-squares techniques on the basis of F2 to agreement indices R1 of 3.3% calculated for 5519 unique observed reflections (|Fo| 5 ≥ 4σF), and wR2 of 6.7% for all data. Intensity data were collected at room temperature using Mo-Kα radiation and a CCD-based area detector. Hügelite is a member of the phosphuranylite group and is the arsenate counterpart of dumontite. The sheets of uranyl pentagonal and hexagonal bipyramids and arsenate tetrahedra in hügelite are oriented parallel to (100), and the interlayer contains four symmetrically independent Pb atoms, each of which is coordinated by two oxygen atoms from uranyl ions, two oxygen atoms from arsenate tetrahedra, and three symmetrically distinct H2O groups. The unit-cell volume is four times larger than that previously reported for hügelite, or expected by comparison to dumontite, Pb2[(UO2)3O2(PO4)2](H2O)5; the larger cell probably results from the accommodation of the larger As atoms (relative to P) in the structure, and consequent subtle variations in the coordination geometries of the U and Pb positions.
A geochemical and Sr-Nd-O isotopic study of the Proterozoic Eriksfjord Basalts, Gardar Province, South Greenland: Reconstruction of an OIB signature in crustally contaminated rift-related basalts
Authors: R. Halama  , Wenzel T. , Upton B. G. J. , Siebel W. , Markl G.
Published: January 2004

Basalts from the volcano-sedimentary Eriksfjord Formation (Gardar Province, South Greenland) were erupted at around 1.2 Ga into rift-related graben structures. The basalts have compositions transitional between tholeiite and alkaline basalt with MgO contents <7 wt.% and they displayLREE-enrichment relative to a chondritic source. Most of the trace element andREEcharacteristics are similar to those of basalts derived from OIB-like mantle sources. Initial87Sr/86Sr ratios of clinopyroxene separates range from 0.70278 to 0.70383 and initial ϵNdvalues vary from –3.2 to +2.1. The most unradiogenic samples overlap with the field defined by carbonatites of similar age and can be explained by mixing of isotopically depleted and enriched mantle components. Using AFC modelling equations, the Sr-Nd isotope data of the more radiogenic basalts can successfully be modelled by addition of <5% lower crustal granulite-facies gneisses as contaminants. δ18Ov-smowvalues of separated clinopyroxene range from +5.2 to +6.0% and fall within the range of typical mantle-derived rocks. However, up to 10% mixing with an average lower crustal component are permitted by the data.
Evolution of the North Qôroq centre nepheline syenites, South Greenland: alkali-mafic silicates and the role of metasomatism
Authors: Coulson I. M.
Published: January 2004

The North Qôroq centre comprises a series of concentric nepheline syenite intrusions and forms part of the Igaliko Nepheline Syenite Complex, in the rift-related Gardar Province of South Greenland. The North Qôroq syenites range from mildly undersaturated augite syenite to strongly peralkaline agpaitic nepheline syenite. Extensivein situfractional crystallization has been postulated for the chemical variation both within units and throughout the centre. Many of the rocks have been affected by metasomatic fluids associated with the emplacement of younger syenite units, and this complicates their interpretation. In this study, the trends and compositions exhibited by pyroxene and amphibole from North Qôroq are examined and related to either primary crystallization or metasomatic activity (e.g. controls offO2, peralkalinity). Implications thus drawn are used to interpret the chemical processes inherent in the chemical and fluid evolution of alkaline magmas, and, in particular, the transition from miaskitic to agpaitic magmatism. In general, the major phases of the North Qôroq syenites records the increasing evolution of the units by crystal fractionation, towards peralkaline compositions. The composition of olivine, in the least evolved syenites, also points to a relatively high state of fractionation of the parent magma, whilst pyroxene and amphibole record an overall decrease in Mg/Mg+Fe), and a general increase in Fe3+and alkali content, with increased fractionation. The increasing peralkalinity of the magma also governs the evolution of pyroxene and, to a lesser degree, amphibole towards higher Zr and Ti contents in the more Na-rich compositions. The trends for pyroxene from metasomatized syenite show similar patterns, but lower Fe2+enrichment, suggesting the source of the metasomatic fluids is similar to the evolving syenites. The presence of amphiboles in metasomatic rocks, and high F contents attest to the F-rich nature of the metasomatic fluids, which is in agreement with results previously reported for metasomatic fluorapatite.
Dysregulated NK receptor expression in patients with lymphoproliferative disease of granular lymphocytes
Authors: Epling-Burnette Pearlie Kay , Painter Jeffrey S. , Chaurasia Pratima , Bai Fanqi , Wei Sheng , Djeu Julie Y. , Loughran Thomas P.
Published: January 2004

The natural killer (NK) type of lymphoproliferative disease of granular lymphocytes (LDGL) is associated with the expansion of CD3-, CD16+, and/or CD56+ lymphocytes. We have examined the repertoire of NK receptors expressed on these cells and delineated the functional activity. We found skewed NK receptor expression on patient NK cells. Reactivity to a single anti-killer cell immunoglobulin-like receptor (anti-KIR) antibody was noted in 7 of 13 patients. LDGL patients variably expressed NKp30, NKp44, and NKp46 RNA. In contrast, CD94 and its inhibitory heterodimerization partner NKG2A were homogenously expressed at high levels on these NK cells. Interestingly, these patients expressed a large number of activating KIR receptors by genotype analysis. Semiquantitative reverse transcriptase-polymerase chain reaction (RT-PCR) demonstrated that lower than normal levels of RNA of the inhibitory KIR was present in some patients in contrast to normal NK cells. Consistent with a high level of activating receptors, we found the NK-LDGL cells have potent cytolytic function in both direct and redirected cytotoxicity assays. These results demonstrate that patients with NK-LDGL have an increased activating-to-inhibitory KIR ratio. This altered ratio might induce inappropriate lysis or cytokine production and impact the disease pathogenesis. (Blood. 2004;103:3431-3439)
Internal and external autocrine VEGF/KDR loops regulate survival of subsets of acute leukemia through distinct signaling pathways
Authors: Santos Susana Constantino Rosa , Dias Sérgio
Published: January 2004

Besides being expressed on endothelial cells, vascular endothelial growth factor receptors (VEGFRs) are also functional on subsets of leukemias, resulting in autocrine loops that sustain leukemia migration and proliferation. While recent evidence suggests that VEGF supports hematopoietic stem cell survival via an internal loop, the molecular mechanisms whereby autocrine stimulation of VEGFR-2 (KDR) promotes leukemia growth are not well understood. Here we show on acute myeloid primary leukemias and cell lines that VEGF/KDR autocrine loops operate both internally and externally. First, we demonstrate that KDR is constitutively phosphorylated and located at the nucleus of VEGF-producing leukemias. Treatment with anti-VEGF antibody, which acts externally, blocked KDR nuclear translocation and inhibited nuclear factor κ B (NF-κB; p65 and c-rel) activation. In contrast, a KDR-specific intracellular inhibitor failed to block KDR nuclear translocation, but inhibited the constitutive activation of mitogen activated protein kinase (MAPK)/Erk and the phosphatidylinositol 3-kinase/AKT pathways. Notably, treatment with the anti-VEGF antibody alone had little effect on cell survival, while the internal inhibitor induced leukemia apoptosis, and the 2 drugs produced synergistic effects, together and with chemotherapy, reducing cell survival to a larger extent than either agent alone. Our results demonstrate that internal and external VEGF/KDR autocrine loops regulate leukemia survival via different mechanisms, and suggest that blocking both may have therapeutic potential.
Efficacy and safety of imatinib in adult patients with c-kit–positive acute myeloid leukemia
Authors: Kindler Thomas , Breitenbuecher Frank , Marx Andreas , Beck Joachim , Hess Georg , Weinkauf Birgit , Duyster Justus , Peschel Christian , Kirkpatrick Charles J. , Theobald Matthias , Gschaidmeier Harald , Huber Christoph , Fischer Thomas
Published: January 2004

This phase 2 pilot study was conducted to determine the efficacy and safety of imatinib mesylate in patients with c-kit–positive acute myeloid leukemia (AML) refractory to or not eligible for chemotherapy. Twenty-one patients were enrolled and received imatinib 600 mg orally once daily. Five responses were seen primarily in patients, starting with relatively low blast counts in bone marrow (BM) and peripheral blood (PB): 2 patients who were considered refractory on chemotherapy on the basis of persistence of blasts in PB and BM met the criteria for complete hematologic remission, 1 patient had no evidence of leukemia, and 2 patients achieved a minor response. Treatment with imatinib demonstrated a good safety profile and was well tolerated. Western blot analysis and immunohistochemistry demonstrated c-Kit activation in primary AML cells. Further, imatinib treatment of primary AML cells inhibited c-Kit tyrosine-phosphorylation. Genomic DNA-sequencing of c-KIT showed no mutations in exons 2, 8, 10, 11, 12, and 17. Although some of the responses derived from relatively small reductions in leukemic blasts and may be attributable, in part, to prior chemotherapy, these cases suggest that imatinib has interesting clinical activity in a subset of patients with c-kit–positive AML. Further clinical trials are warranted to explore the clinical potential of imatinib in AML and to identify the underlying molecular mechanism.
Use of recombinant human growth hormone (rhGH) plus recombinant human granulocyte colony-stimulating factor (rhG-CSF) for the mobilization and collection of CD34+ cells in poor mobilizers
Authors: Carlo-Stella Carmelo , Di Nicola Massimo , Milani Raffaella , Guidetti Anna , Magni Michele , Milanesi Marco , Longoni Paolo , Matteucci Paola , Formelli Franca , Ravagnani Fernando , Corradini Paolo , Gianni Alessandro M.
Published: January 2004

The activity of recombinant human growth hormone (rhGH) in enhancing CD34+ cell mobilization elicited by chemotherapy plus recombinant human granulocyte colony-stimulating factor (rhG-CSF) was evaluated in 16 hard-to-mobilize patients, that is, those achieving a peak of circulating CD34+ cells 10/μL or less, or a collection of CD34+ cells equal to or less than 2 × 106/kg. Patients who had failed a first mobilization attempt with chemotherapy plus rhG-CSF (5 μg/kg/d) were remobilized with chemotherapy plus rhG-CSF and rhGH (100 μg/kg/d). As compared with rhG-CSF, the combined rhGH/rhG-CSF treatment induced significantly higher (P ≤ .05) median peak values for CD34+ cells/μL (7 versus 29), colony-forming cells (CFCs)/mL (2154 versus 28 510), and long-term culture-initiating cells (LTC-ICs)/mL (25 versus 511). Following rhG-CSF and rhGH/rhG-CSF, the median yields of CD34+ cells per leukapheresis were 1.1 × 106/kg and 2.3 × 106/kg (P ≤ .008), respectively; the median total collections of CD34+ cells were 1.1 × 106/kg and 6 × 106/kg (P ≤ .008), respectively. No specific side effect could be ascribed to rhGH, except a transient hyperglycemia occurring in 2 patients. Reinfusion of rhGH/rhG-CSF-mobilized cells following myeloablative therapy resulted in prompt hematopoietic recovery. In conclusion, our data demonstrate that in poor mobilizers addition of rhGH to rhG-CSF allows the patients to efficiently mobilize and collect CD34+ cells with maintained functional properties. (Blood. 2004;103: 3287-3295)
Congenital disorder of oxygen sensing: association of the homozygous Chuvash polycythemia VHL mutation with thrombosis and vascular abnormalities but not tumors
Authors: Gordeuk Victor R. , Sergueeva Adelina I. , Miasnikova Galina Y. , Okhotin Daniel , Voloshin Yaroslav , Choyke Peter L. , Butman John A. , Jedlickova Katerina , Prchal Josef T. , Polyakova Lydia A.
Published: January 2004

Adaptation to hypoxia is critical for survival and regulates multiple processes, including erythropoiesis and vasculogenesis. Chuvash polycythemia is a hypoxia-sensing disorder characterized by homozygous mutation (598C>T) of von Hippel-Lindau gene (VHL), a negative regulator of hypoxia sensing. Although endemic to the Chuvash population of Russia, this mutation occurs worldwide and originates from a single ancient event. That VHL 598C>T homozygosity causes elevated normoxic levels of the transcription factor hypoxia inducible factor-1α (HIF-1α), serum erythropoietin and hemoglobin is known, but the disease phenotype has not been documented in a controlled manner. In this matched cohort study, VHL 598C>T homozygosity was associated with vertebral hemangiomas, varicose veins, lower blood pressures, and elevated serum vascular endothelial growth factor (VEGF) concentrations (P < .0005), as well as premature mortality related to cerebral vascular events and peripheral thrombosis. Spinocerebellar hemangioblastomas, renal carcinomas, and pheochromocytomas typical of classical VHL syndrome were not found, suggesting that overexpression of HIF-1α and VEGF is not sufficient for tumorigenesis. Although hemoglobin-adjusted serum erythropoietin concentrations were approximately 10-fold higher in VHL 598C>T homozygotes than in controls, erythropoietin response to hypoxia was identical. Thus, Chuvash polycythemia is a distinct VHL syndrome manifested by thrombosis, vascular abnormalities, and intact hypoxic regulation despite increased basal expression of hypoxia-regulated genes.
Reversal of bone marrow angiogenesis in chronic myeloid leukemia following imatinib mesylate (STI571) therapy
Authors: Kvasnicka Hans Michael , Thiele Juergen , Staib Peter , Schmitt-Graeff Annette , Griesshammer Martin , Klose Jens , Engels Knut , Kriener Susanne
Published: January 2004

The effect of imatinib mesylate (imatinib) therapy on angiogenesis and myelofibrosis was investigated and compared with interferon (IFN) and hydroxyurea (HU) in 98 patients with newly diagnosed Philadelphia chromosome-positive/BCR-ABL+ (Ph+/BCR-ABL+) chronic myeloid leukemia in first chronic phase and no other pretreatment. By means of immunostaining (CD34) and morphometry, a relationship between microvessel frequency and fiber density was detectable in initial bone marrow (BM) biopsies and sequential examinations after at least 8 months of therapy. First-line monotherapy with imatinib induced a significant reduction (normalization in comparison with controls) of microvessels and reticulin fibers. In most patients, decrease in BM vascularity was associated with a complete cytogenetic response. A significant anti-angiogenic effect was also observed after HU treatment, contrasting with IFN administration or combination regimens (IFN plus HU). In conclusion, our data support the anti-angiogenic capacity of imatinib by normalization of vascularity. In contrast, hematologic response following IFN treatment is independent from BM angiogenesis. (Blood. 2004;103:3549-3551)