bluuebunny/crossref_metadata_2025 huggingface dataset:
The Mitochondrial Permeability Transition Pore is Modulated by Oxidative Agents Through Both Pyridine Nucleotides and Glutathione at Two Separate Sites
Authors: Chernyak Boris V. , Bernardi Paolo
Published: August 2004

We studied the modulation of the permeability transition pore (MTP), a cyclosporin‐A‐sensitive channel, in deenergized mitochondria. Rat liver mitochondria were incubated in a potassium gluconate medium and treated with uncoupler, valinomycin, oligomycin and A23187. Under these conditions the membrane and Donnan potentials are collapsed, and no ion gradients are maintained, allowing the study of the dependence of MTP opening on the Ca2+ concentration under a variety of oxidative conditions without the complexities arising from changes of the membrane potential and matrix pH, and from secondary‐ion redistribution.

Cross‐linking of mitochondrial dithiols with arsenite or phenylarsine oxide, or treatment with tert ‐butylhydroperoxide leading to complete oxidation of glutathione, increased the sensitivity of MTP opening to Ca2+. This effect could be fully prevented by prior treatment of mitochondria with monobromobimane and restored by reduction with dithiothreitol. The effect of tert‐butylhydroperoxide was not additive with that of AsO, and it was completely blocked by modification of reduced glutathione with 1‐chloro 2,4‐dinitrobenzene through glutathione‐S‐transferase, indicating that oxidized glutathione affects the pore through the AsO‐reactive and PhAsO‐reactive dithiol.

Oxidation of mitochondrial pyridine nucleotides by a variety of treatments also increased the sensitivity of MTP opening to Ca2+ under conditions where glutathione was maintained in the reduced state. This effect could be fully prevented when reduced pyridine nucleotides levels were reestablished with 2‐hydroxybutyrate but not by treatment with monobromobimane or dithiothreitol.

The effects of dithiol cross‐linking or oxidation, and of pyridine nucleotide oxidation on the MTP were additive. The contribution of each of these two oxidative events, when they were induced at the same time, could still be selectively blocked by monobromobimane and dithiothreitol, or by 2‐hydroxybutyrate, respectively. Complete oxidation of pyridine nucleotides did not affect the reactivity of the dithiol towards monobromobimane, indicating that it remained in the reduced state.

After transient opening of the MTP, sensitivity to pyridine nucleotide oxidation was lost while sensitivity to dithiol cross‐linking was retained. These data indicate that the dithiol belongs to an MTP regulatory component which is larger than the MTP cutoff of about 1500 Da, or is non‐diffusible. Taken together, these findings indicate that the MTP is influenced by oxidation‐reduction events at two separate sites that can be distinguished experimentally, and that these sites are not connected by common oxidation‐reduction intermediates other than glutathione.
Limited Plasmin Proteolysis of Vitronectin
Authors: Kost Christine , Benner Kerstin , Stockmann Antje , Linder Dietmar , Preissner Klaus T.
Published: August 2004

The adhesion protein vitronectin is associated with extracellular matrices and serves as cofactor for plasminogen‐activator inhibitor‐1. Limited proteolysis by plasmin converts vitronectin into defined fragments which are detectable at sites of inflammation and angiogenesis. The loss and gain of binding functions of vitronectin fragments for macromolecular ligands was characterized in the present study. The initially generated 61–63‐kDa vitronectin‐(1–348)‐fragment serves as typical binding component for plasminogen and binding function was lost upon carboxypeptidase B treatment indicating the importance of a C‐terminal lysine. Complementary binding sites reside in isolated plasminogen kringles 1–3 (designated angiostatin) as deduced from direct binding and ligand blotting experiments. A synthetic vitronectin‐(331–348)‐peptide from the C‐terminus of the 61–63‐kDa fragment could mimic plasminogen and angiostatin binding. Also, the immobilized peptide bound tissue plasminogen‐activator and mediated plasmin formation, comparable to fibrinogen‐derived peptides. The 61–63‐kDa vitronectin fragment was indistinguishable in its adhesive properties to intact vitronectin and bound active but not latent plasminogen‐activator inhibitor‐1. Late plasminolysis of vitronectin resulted in the processing of the N‐terminal region of the protein with the generation of 42 kDd3S‐kDa fragments that had Gly89 as new N‐terminus and that were ineffective in promoting cell adhesion. Thus, at sites of cell‐matrix interactions which become proteolytically modified by plasmin during inflammatory and angiogenic processes, vitronectin serves as plasminogen/angiostatin‐binding factor. Due to this differential change in functions particularly at sites of deposition in the vascular system or at wound sites vitronectin is considered to be an important morpho‐regulatory factor.
Electropermeabilization of Intact Maize Cells Induces an Oxidative Stress
Authors: Sabri Naïma , Pelissier Bernard , Teissié Justin
Published: August 2004

By applying electric field pulses through cell suspensions, cell membranes can be permeabilized transiently, giving free access to the cytosol. Electropulsation is now routinely used in cell biology when introducing various molecules such as proteins and nucleic acids into the cell. But the molecular and cellular bases of cell electropermeabilization are still unclear. In the present study, we observed that electropermeabilization of intact black Mexican sweet (BMS) maize cells induces a generation of oxygen species (oxidative jump). Using the chemiluminescent probe lucigenin, we have shown that the electro‐induced chemiluminescent response depends on the level of the stress factor as shown by its dependence on the electric parameters (electric field intensity, duration, and number of pulses).

While the electroinduced cell permeabilization has a short life, the oxidative jump that is triggered by this electropermeabilization is a much longer‐lived response. The electroinduced loss in viability is linearly correlated to permeabilization. However, there is no correlation between the oxidative jump and the loss in viability. The modulation of oxygen species electroinduction by antioxidant products (dimethylsulfoxide, sodium L‐ascorbate, and glutathione) does not lead to an increase in cell viability. Such results are different to those observed with mammalian cells and indicate that even if the same phenomenon is observed when pulsing mammalian or intact plant cells, the associated metabolic response is not the same.
Characterization of Xanthine Dehydrogenase from the Anaerobic Bacterium Veillonella atypica and Identification of a Molybdopterin‐Cytosine‐Dinucleotide‐Containing Molybdenum Cofactor
Authors: Gremer Lothar , Meyer Ortwin
Published: August 2004

The molybdenum‐containing iron‐sulfur flavoprotein xanthine dehydrogenase from the anaerobic bacterium Veillonella atypica has been purified approximately 800‐fold with a yield of approximately 40% and a specific activity of approximately 70 μmol ferricyanide reduced · min−1· mg protein−1 with xanthine as electron donor, which corresponds to approximately 30 μmol xanthine oxidized · min−1· mg protein−1 with methylene blue as electron acceptor. The 129‐kDa enzyme was a non‐covalent heterotrimer with large (82.4 kDa), medium (28.5 kDa) and small (18.4 kDa) subunits. The N‐termini of the small and medium polypeptides of V. atypica xanthine dehydrogenase and the corresponding domains of eukaryotic xanthine dehydrogenases were similar, whereas the N‐terminus of the large polypeptide was unrelated to eukaryotic xanthine dehydrogenases. The enzyme contained 0.86 atoms Mo, 1.75 atoms Fe, 1.61 atoms acid‐labile sulfur and 0.68 molecules FAD/molecule, which corresponds to a 1:2.0:1.9:0.8 molar ratio. Acid hydrolysis revealed 0.95 mol CMP and 0.80 mol AMP/mol xanthine dehydrogenase. After treatment of the enzyme with iodoacetamide, di(carboxamidomethyl)molybdopterin cytosine dinucleotide was identified, which indicates that molybdopterin cytosine dinucleotide is the organic portion of the V. atypica xanthine dehydrogenase molybdenum cofactor. The enzyme and its molybdenum cofactor occurred in a 1:1 molar ratio. Xanthine dehydrogenases from eukaryotic sources are characterized by a domain structure and the presence of duplicate copies of two types of [2Fe‐2S] clusters. In contrast, the xanthine dehydrogenase from V. atypica had a heterotrimeric subunit structure and a single [2Fe‐2S] cluster. In addition, the enzyme indicates the presence of a molybdopterin dinucleotide as a constituent of a xanthine dehydrogenase molybdenum cofactor.
Photoaffinity Labeling of the Head‐Activator Receptor from Hydra
Authors: Hampe Wolfgang , Frank Rainer W. , Schulze Christian , Dehning Inga , Schaller H. Chica
Published: August 2004

A photoaffinity ligand for the head‐activator (HA) receptor from hydra was synthesized using solid‐phase peptide synthesis and coupling of two HA peptides over their ε‐amino groups of Lys7 with succinimidyl esters. The new ligand, Bpa‐HA‐HA bipeptide, contains one normal HA peptide and another where p ‐benzoylphenylalanine (Bpa) was added at the amino terminus to allow ultraviolet activation and Tyrl1 instead of Phel1 for radioiodination. The 125I‐Bpa‐HA‐HA bipeptide bound with nanomolar affinity to the HA receptor from the multiheaded mutant of Chlorohydra viridissima as measured in a filter assay. After photoaffinity labeling of the hydra membrane fraction, a 200‐kDa band was detected using reducing or non‐reducing SDS/PAGE and autoradiography. Unlabeled HA derivatives, but no other neuropeptides, inhibited the labeling. Competition experiments with HA‐HA homobipeptide in the nanomolar range indicate that predominantly the low‐affinity and not the high‐affinity HA receptor was photolabeled. Further evidence that the labeled molecule is the HA receptor‐ comes from specific photoaffinity labeling with a second ultraviolet‐activatable ligand containing p ‐nitrophenylalanine. The HA receptor could be functionally solubilized with Triton X‐100 or Chaps. In the solubilizate the 200‐kDa HA receptor was photolabeled specifically by both ligands. Liquid‐phase isoelectric focussing of the solubilizate indicated a pI of about 5.4 of the photolabeled molecule. After chemical deglycosylation with trifluoromethanesulfonic acid, the apparent molecular mass of the labeled molecule was decreased to 180 kDa, indicating that the receptor is glycosylated.
Critical reflection in social work: a response to globalisation?1
Authors: Morley Christine
Published: August 2004

This article presents a reflective theoretical deconstruction of my practice with disempowered human service workers. Specifically, it presents a case study of how critical reflection was fostered amongst a group of practitioners in Geelong, a regional Victorian town in Australia. This models how a critical postmodern analysis provided a framework for overcoming entrenched power dynamics and structural barriers in a particular context and at a particular point in time. It describes and analyses the content of this work in terms of its significance and implications for responding to the impact of globalisation on this group, which was undermining the effectiveness of their social work practice.
Changing faces: the story of two Canadian street youth shelters
Authors: Karabanow Jeff
Published: August 2004

This study addresses the relationship between street youth shelters and formal child welfare systems in Toronto, Canada. Two case examples, Covenant House (CH) and Youth Without Shelter (YWS), are examined through archival material, participant observations and structured interviews with 21 front‐line and managerial shelter workers. The findings suggest that both shelters have formed reciprocal and unequal partnerships with formal child‐welfare organisations. The consequences of such an arrangement are threefold: (1) CH and YWS no longer possess an internal environment to support traditional street youths; (2) both shelters have strayed from their original intentions; and (3) many shelter workers express frustration within this dynamic. Several recommendations are put forward to support the survival of youth shelters: advocating increased government daily rates; seeking a balance between building a legitimate public image and an alternative street youth reputation; making every effort to house hard‐core street youths; and building innovative internal programmes to act as referral points.
GRID-ENABLED NON-RIGID REGISTRATION OF MEDICAL IMAGES
Authors: STEFANESCU RADU , PENNEC XAVIER , AYACHE NICHOLAS
Published: August 2004

Over recent years, non-rigid registration has become a major issue in medical imaging. It consists in recovering a dense point-to-point correspondence field between two images, and usually takes a long time. This is in contrast to the needs of a clinical environment, where usability and speed are major constraints, leading to the necessity of reducing the computation time from slightly less than an hour to just a few minutes. As financial pressure makes it hard for healthcare organizations to invest in expensive high-performance computing (HPC) solutions, cluster computing proves to be a convenient solution to our computation needs, offering a large processing power at a low cost. Among the fast and efficient non-rigid registration methods, we chose the demons algorithm for its simplicity and good performances. The parallel implementation decomposes the correspondence field into spatial blocks, each block being assigned to a node of the cluster. We obtained an acceleration of 11 by using 15 2GHz PC's connected through a 1GB/s Ethernet network and reduced the computation time from 40min to 3min30. In order to further optimize the costs and the maintenance load, we investigate in the second part the transparent use of shared computing resources, either through a graphic client or a Web one.
A NOTE ON BICRITERIA SCHEDULES WITH OPTIMAL APPROXIMATIONS RATIOS
Authors: BAILLE FABIEN , BAMPIS EVRIPIDIS , LAFOREST CHRISTIAN
Published: August 2004

We consider the problem of scheduling a set of independent tasks (with release dates and deadlines) on a set of parallel identical machines. Our objective is to find a schedule maximizing simultaneously two objectives, namely the weight of scheduled tasks and their total profit. To solve this general problem, we present a technique, FUSION, based on the composition of two mono-criteria solutions and we prove that it gives the best possible approximation ratio for both metrics.
COULOMB'S LAW MODIFICATION IN NONLINEAR AND IN NONCOMMUTATIVE ELECTRODYNAMICS
Authors: GAETE PATRICIO , SCHMIDT IVÁN
Published: August 2004

We study the lowest-order modifications of the static potential for Born–Infeld electrodynamics and for the θ-expanded version of the noncommutative U(1) gauge theory, within the framework of the gauge-invariant but path-dependent variables formalism. The calculation shows a long-range correction (1/r5-type) to the Coulomb potential in Born–Infeld electrodynamics. However, the Coulomb nature of the potential (to order e2) is preserved in noncommutative electrodynamics.
THE STUECKELBERG FIELD
Authors: RUEGG HENRI , RUIZ-ALTABA MARTÍ
Published: August 2004

In 1938, Stueckelberg introduced a scalar field which makes an Abelian gauge theory massive but preserves gauge invariance. The Stueckelberg mechanism is the introduction of new fields to reveal a symmetry of a gauge-fixed theory. We first review the Stueckelberg mechanism in the massive Abelian gauge theory. We then extend this idea to the standard model, stueckelberging the hypercharge U(1) and thus giving a mass to the physical photon. This introduces an infrared regulator for the photon in the standard electroweak theory, along with a modification of the weak mixing angle accompanied by a plethora of new effects. Notably, neutrinos couple to the photon and charged leptons have also a pseudo-vector coupling. Finally, we review the historical influence of Stueckelberg's 1938 idea, which led to applications in many areas not anticipated by the author, such as strings. We describe the numerous proposals to generalize the Stueckelberg trick to the non-Abelian case with the aim to find alternatives to the standard model. Nevertheless, the Higgs mechanism in spontaneous symmetry breaking remains the only presently known way to give masses to non-Abelian vector fields in a renormalizable and unitary theory.
Strenuous physical exercise inhibits granulocyte activation induced by high altitude
Authors: Choukèr Alexander , Demetz Florian , Martignoni André , Smith Leslie , Setzer Florian , Bauer Andreas , Hölzl Joseph , Peter Klaus , Christ Frank , Thiel Manfred
Published: August 2004

To test the hypothesis of whether strenuous physical exercise inhibits neutrophils that can get activated by hypobaric hypoxia, we analyzed the effects of both high altitude and strenuous exercise alone and in combination on potentially cytotoxic functions of granulocytes in healthy volunteers ( n = 12 men; average age 27.6 yr; range 24–38 yr). To this end, a field study was prospectively performed with an open-labeled within-subject design comprising three protocols. Protocol I (high altitude) involved a helicopter ascent, overnight stay at 3,196 m, and descent on the following day. Protocol II (physical exercise) involved hiking below an altitude of 2,100 m with repetitive ascents amounting to a total ascent to that of protocol III. Protocol III (combination of physical exercise and high altitude) involved climbing from 1,416 to 3,196 m, stay overnight, and descent on the following day. In protocol I, number of granulocytes did not change, but potentially cytotoxic functions of cells (CD18 expression and superoxide production) were early and significantly upregulated. In protocol II, subjects developed granulocytosis, but functions of cells were inhibited. In protocol III, granulocytosis occurred at higher values than those observed under protocol II. Potentially cytotoxic functions of cells, however, were strongly inhibited again. In conclusion, high altitude alone, even moderate in extent, can activate potentially cytotoxic functions of circulating granulocytes. Strenuous physical exercise strongly inhibits this activation, which may give protection from an otherwise inflammatory injury.
Regulated on Activation, Normal T Cell Expressed and Secreted (RANTES) Antagonist (Met-RANTES) Controls the Early Phase of
Trypanosoma cruzi
–Elicited Myocarditis
Authors: Marino Ana Paula M.P. , da Silva Andréa , dos Santos Paula , Pinto Luzia Maria de Oliveira , Gazzinelli Ricardo Tostes , Teixeira Mauro Martins , Lannes-Vieira Joseli
Published: August 2004

Background—

Comprehension of the pathogenesis of
Trypanosoma cruzi
–elicited myocarditis is crucial to delineate strategies aimed at ameliorating the inflammation associated with heart dysfunction. The augmented expression of CC chemokines, especially CCL5/RANTES and CCL3/MIP-1α, in the hearts of infected mice suggests a role for CC chemokines and their receptors in the pathogenesis of
T cruzi
–elicited myocarditis.

Methods and Results—

We report that during the early phase of infection in C3H/HeJ mice infected with 100 blood trypomastigotes of
T cruzi
, most of the inflammatory cells invading the heart tissue were CD8
+
cells and expressed CCR5, a CCL5/RANTES, and CCL3/MIP1-α receptor. Furthermore, peripheral blood CD8
+
T lymphocytes displayed increased expression of CCR5. These findings led us to use Met-RANTES, a selective CCR1 and CCR5 antagonist, to modulate the acute
T cruzi
–elicited myocarditis. Met-RANTES treatment did not interfere with parasitism but significantly decreased the numbers of CD4
+
and CD8
+
T cells, CCR5
+
, and interleukin-4
+
cells invading the heart, paralleling the diminished deposition of fibronectin. Moreover, Met-RANTES treatment resulted in increased survival of infected animals, compared with saline treatment.

Conclusions—

These results indicate that the massive influx of CCR5
+
cells into cardiac tissue is not crucial for cell-mediated anti–
T cruzi
immunity but appears to be critical for pathogenesis of
T cruzi
–elicited myocarditis. Thus, CC chemokine receptors might become an attractive therapeutic target for further evaluation during
T cruzi
infection.
Norepinephrine Transporter–Deficient Mice Exhibit Excessive Tachycardia and Elevated Blood Pressure With Wakefulness and Activity
Authors: Keller Nancy R. , Diedrich André , Appalsamy Martin , Tuntrakool Sunti , Lonce Suzanna , Finney Charlene , Caron Marc G. , Robertson David
Published: August 2004

Background—

Norepinephrine (NE) is a primary neurotransmitter of central autonomic regulation and sympathetic nerve conduction, and the norepinephrine transporter (NET) is crucial in limiting catecholaminergic signaling. NET is sensitive to antidepressants, cocaine, and amphetamine. NET blockade often is associated with cardiovascular side effects, and NET deficiency is linked to tachycardia in familial orthostatic intolerance.

Methods and Results—

We telemetrically monitored NET-deficient (NET
−/−
) mice to determine the cardiovascular effects of reduced NE reuptake. Mean arterial pressure was elevated in resting NET
−/−
mice compared with NET
+/+
controls (103±0.6 versus 99±0.4 mm Hg;
P
<0.01), and corresponding pressures increased to 122±0.3 and 116±0.3 mm Hg (
P
<0.0001) with activity. Heart rate was also greater in resting NET
−/−
mice (565±5 versus 551±3 bpm;
P
<0.05), and genotypic differences were highly significant during the active phase (640±5 versus 607±3 bpm;
P
<0.0001). Conversely, the respiratory rate of resting NET
−/−
mice was dramatically reduced, whereas increases after the day/night shift surpassed those of controls. Plasma catecholamines in NET
−/−
and NET
+/+
mice were as follows: NE, 69±8 and 32±7; dihydroxyphenylglycol, 2+0.4 and 17±3; epinephrine, 15±3 and 4±0.6; and dopamine, 13±4 and 4±1 pmol/mL. Catechols in urine, brain, and heart also were determined.

Conclusions—

Resting mean arterial pressure and heart rate are maintained at nearly normal levels in NET-deficient mice, most likely as a result of increased central sympathoinhibition. However, sympathetic activation with wakefulness and activity apparently overwhelms central modulation, amplifying peripheral catecholaminergic signaling, particularly in the heart.
Competitive adsorption and desorption of glyphosate and phosphate on clay silicates and oxides
Authors: Gimsing A. L. , Borggaard O. K.
Published: August 2004

Competitive adsorption of glyphosate and phosphate on goethite and gibbsite and on illite, montmorillonite and two kaolinites differing in surface area was evaluated. The results show that glyphosate and phosphate are competing for the adsorption sites, but the degree of competition depends on the adsorbent. On goethite the competition is very much in favour of phosphate, on gibbsite the competition is closer, but still phosphate is favoured, while on illite, montmorillonite and kaolinite the competition is almost equal. The amounts of glyphosate and phosphate, which can be adsorbed also depends on the adsorbent: the oxides adsorb more than the clay silicates. The amount adsorbed on kaolinite was dependent on the specific surface area. Changes in the surface area did not affect the competition between glyphosate and phosphate for adsorption sites. The results indicate that differences among soils of different mineralogical composition regarding the adsorption of glyphosate and phosphate can be expected.
Mössbauer spectra of α- and γ-polymorphs of FeOOH and Fe2O3 : effects of poor crystallinity and of Al-for-Fe substitution
Authors: De Grave E. , Barrero C. A. , Da Costa G. M. , Vandenberghe R. E. , Van San E.
Published: August 2004

This paper presents various aspects, revealed by Mössbauer spectroscopy, of structural and magnetic properties of Al-substituted small-particle soil-related oxides. For goethite we focus on the relations between the hyperfine fields on the one hand, and crystallinity and Al content on the other. It is argued that these relations only provide a rough estimate of the Al content in natural samples. The ferrimagnetic-like behaviour reflected in the external-field Mössbauer spectra (4.2 K, 60 kOe) of certain Al goethites is presented. The spectra obtained for lepidocrocites are not spectacular, but confirmed that up to ∼10 at.% Al can be incorporated in the structure. Three differently-made series of hematites are considered. The Morin transition and spin structures in hematite are very sensitive to crystallinity and Al content, and probably to the presence of structural OH–. Integral low-energy electron Mössbauer spectroscopy on non-substituted samples indicates that the Morin-transition temperature in the surface layers (2 to 5 nm) is not significantly shifted from the bulk value. Measurements in extremely high magnetic fields (140 kOe) have shown that a spin-flip transition is induced in highly-substituted samples which exhibit no Morin transition in zero field. The use of external fields is crucial for the characterization and precise determination of the hyperfine parameters and site occupancies for maghemites, and for phase analyses of magnetic soils.
Iron in soil kaolins from Indonesia and Western Australia
Authors: Hart R. D. , St Pierre T. G. , Gilkes R. J . , McKinley A. J. , Siradz S. , Singh Balwant
Published: August 2004

Soil kaolins from Indonesia and Western Australia and a range of reference kaolins were studied using Mössbauer spectroscopy, electron paramagnetic resonance (EPR) spectroscopy and SQUID magnetometry. Mössbauer spectra indicate that the Fe within the kaolins is in the highspin Fe3+oxidation state and that a large fraction of the Fe is present as dispersed atoms residing within the octahedral sites of the kaolinite crystal structure. The EPR spectra are typical for soil kaolins except for the absence of radiation-induced defects for the Indonesian kaolins. The Fe(I)spectra are dominant with a strong symmetric peak atg= 4.3, the presence of Fe(II) spectra is shown by a shoulder on this peak atg= 4.9 and a small phase up peak atg= 9.2.

Low-temperature (5 K) magnetization (M) measurements over large field (H) sweeps (±70 kOe) yieldedM(H) curves which are fitted well with Brillouin functions indicating the paramagnetic nature of the kaolins at temperatures down to 5 K. A very small remanent magnetization was detectable in the kaolins. Remanent magnetization to saturation magnetization ratios ranged from 10–4to 10–3for the Indonesian kaolins and were all ∼10–3for the Western Australian kaolins, indicating that at high fields the vast majority of the magnetization of the kaolins is due to paramagnetic ions.

Zero-field-cooled and field-cooled magnetization measurements in small fields (500 Oe) indicate that the Indonesian kaolins are generally free from magnetically-blocked material down to a temperature of 5 K. The magnetic susceptibility of the Indonesian kaolins shows Curie Law behaviour indicating paramagnetic behaviour over all temperatures down to 5 K. Measurements on the Western Australian kaolins indicated the presence of some magnetic material that is magnetically blocked at temperatures below ∼200 ­ 250 K. As a consequence, the magnetic susceptibility showed large deviations from Curie Law behaviour.
Prograde and retrograde diagenetic and metamorphic evolution in metapelitic rocks of Sierra Espuña (Spain)
Authors: Abad I . , Nieto F. , Peacor D. R. , Velilla N.
Published: August 2004

An unusually complete sequence of pelitic rocks ranging from diagenetic to greenschist-facies metamorphic grades occurs in southern Sierra Espun˜a, Spain. Prograde and retrograde reactions have been studied by X-ray diffraction and electron microscopy (SEM, TEM and AEM). The prograde reaction series, with reactions facilitated by tectonic stress, includes: (1) R4 interstratified illite-smectite in the diagenetic Malaguide Complex that preserves the variable orientation of original smectite packets, and has 1Md polytypism; (2) chemically heterogeneous illite and Na-K dioctahedral white micas that progressively evolve toward chemical and textural equilibrium in the anchizonal Intermediate Units; and (3) thick, defect-free packets of phengite, paragonite and clinochlore which have a typical metamorphic texture, in the Alpujarride Complex. Two superimposed retrograde episodes produced: (a) sudoite at near-peak metamorphic conditions and (b) dioctahedral smectite during low-temperature retrograde diagenesis.
Evolution of mineral assemblages and textures from sediment through hornfels in the Salton Sea Geothermal Field: Direct crystallization of phyllosilicates in a hydrothermal-metamorphic system
Authors: Giorgetti G. , Mata M. P. , Peacor D. R.
Published: August 2004

Microanalytical data on Plio-Pleistocene sediments from a Salton Sea Geothermal Field well define the evolution of textures and mineral assemblages from sediment to metamorphic rock in an open hydrothermal system.

At shallow depths detrital grains occur within a fine-grained matrix of I-S and illite. As depth and temperature increase, grains lose their detrital characteristics; they subsequently form a continuous intergrown array of irregular domains, with phyllosilicates occupying the progressively decreasing pore space.

Illite and chlorite are authigenic phyllosilicates down to 2500 m, where biotite occurs. Authigenic phyllosilicates occur as subhedral crystals (200 –600 Å thick). Alkali feldspar has end-member compositions, implying exchange of alkalis with convected fluids. Changes in texture imply dissolution of detrital phases and neocrystallization of authigenic phyllosilicates directly from pore fluids. Changes with depth are not time-dependent for phyllosilicates: they formed simultaneously at all depths as a result of a single hydrothermal event in an open system.
Structural heterogeneity of alkylammonium-exchanged, synthetic fluorotetrasilicic mica
Authors: Kłapyta Z. , GaweŁ A. , Fujita T. , Iyi N.
Published: August 2004

A series of organo-silicates was obtained from synthetic Na-fluorotetrasilicic mica (Na-TSM) by ion exchange with dodecyl-, tetradecyl-, hexadecyl- and octadecyltrimethylammonium (C12, C14, C16 and C18) bromides. When the concentration of the alkylammonium ions has varied from 0.43 to 3.4 mmol/g of the silicate, the maximum amount adsorbed on the mica was 0.92 mmol/g. As shown by 23Na MAS NMR, ∼0.30 mmol/g of Na+ ions were non-exchangeable, even if a large excess of the organic ions was used. The XRD patterns of all the samples obtained show that alkylammonium ions are distributed inhomogeneously within the mica interlayers. As a consequence, the organo-micas contain several phases consisting of randomly and regularly interstratified layers differing in terms of the amount of alkylammonium ions adsorbed. These different layers swell in ethylene glycol in the same manner and form new interlayers with identical spacings. The d001 values of individual organo-TSMs after glycolation suggest that the alkylammonium ions are oriented perpendicular or almost perpendicular to the mica layers. The Na-TSM layers were not detected in organo-TSMs by XRD. The presence of organic and inorganic (Na) mixed-ion interlayers with spacings controlled by the arrangements of the organic ions is consistent with the results obtained. These data also suggest that the alkylammonium/Na+ ion ratios vary in alternate interlayers.
A new way of assessing clay cation adsorption using normalized salt concentration
Authors: Bersillon J . -L. , Villiéras F. , Michot L. , Cases J. -M.
Published: August 2004

Kaolinite cation adsorption data are processed using recent gas adsorption concepts such as the undersaturation ∆m = ln (C/Cs) and the monolayer coverage y. This process shows that using the proper reference phase through its solubilityCs, it is possible to characterize adsorption sites that have the same adsorption energy regardless of the nature of the cation. Under mildly acidic conditions, a single ‘Langmuirian’ site category fits cation adsorption data whereas another family of sites is revealed in mildly alkaline conditions. These results suggest that at mildly acidic pH, only silanol sites are available to ion exchange and adsorption whereas at higher pH, a wider range of sites is made available, some of them displaying the same average adsorption energy and the others constituting a different category of sites with a much lower adsorption energy. This latter category is attributed to the aluminol sites.
Effects of clay-rich river-dam sediments on downstream fish and plant life
Authors: Tazaki K. , Sato M. , Van Der Gaast S. , Morikawa T.
Published: August 2004

In 1985, Dashidaira Dam, equipped with a flushing gate, was built on the Kurobe River in Toyama, Japan. Since the dam sediments were first flushed out in December 1991, benthic fish counts have decreased year by year due to repeated flushing of clay-rich dam sediments.

In June 2001, the flushed dam water contained a low oxygen concentration (1 to 2 mg/l) and high concentrations of smectite and vermiculite. To establish the cause of the death of the benthic fish, living flatfish were collected from Toyama Bay in order to examine their gills, which showed tissue damage and chemical changes caused by adherent expandable clays, derived from the flushed dam sediments. For comparison, exposure experiments on rainbow trout were carried out using smectite suspensions. Examination by optical microscopy revealed that the gills had shrunk because of the smectite concentrations. Low oxygen concentrations and large amounts of expanding clays have a significant effect on downstream benthic life.
Mobilization of heavy metals from historical smelting slag dumps, north Queensland, Australia
Authors: Lottermoser B. G.
Published: August 2004

Slag dumps occur at several historical smelting sites in north Queensland, Australia. The microcrystalline slags contain primary slag phases, relict flux, ore and furnace materials and secondary weathering related minerals. Common primary slag phases are glass, Zn-rich fayalite (± Zn-rich kirschsteinite) and Zn-rich hedenbergite. Other minor minerals include wollastonite, Zn-rich melilite, Zn-rich iscorite (Fe7SiO10), magnetite as well as a number of sulphides (pyrrhotite, galena, bornite, sphalerite, wurtzite), metallic phases (Ag, Cu, Pb, Sb), alloys (Cu3Sn), and unknown metal compounds. The slag materials contain wt.% concentrations of Zn and elevated levels of Ag, As, Cd, Cu, Ni, Pb, Sb and W. Glass, hedenbergite and fayalite/kirschsteinite are the main repositories of Zn, whereas much of the Cu and Pb is hosted by glass, sulphides, Cu3Sn alloys, metallic Cu and Pb, and unknown CuSb, AsSnPb and FeAsCu compounds. The slags are undergoing contemporaneous reaction with air and rainwater. The weathering results in the release of metals and metalloids from primary slag phases, particularly from glass, and the partial immobilization of these metals in secondary soluble and insoluble minerals in the slag heaps. Zinc exhibits pronounced chemical mobility and reports together with elevated Ca and sulphate into surface seepages (up to 10.2 mg l−1 Zn at pH 6.97). The slag dumps represent long-term sources of metal pollutants, particularly of Zn, to local ground and surface waters.
Extension of the melilite-carbonatite province in the Apennines of Italy: the kamafugite of Grotta del Cervo, Abruzzo
Authors: Stoppa F. , Woolley A. R. , Cundari A.
Published: August 2004

A new occurrence of a rare kamafugite near L'Aquila, Abruzzo, is described in detail to characterize its paragenesis and to establish possible genetic links with similar alkaline mafic igneous rocks from the Oricola-Camerata Nuova (OC) volcanic field, ˜20 km to the west. Both occurrences belong to the Umbria-Latium-Ultralkaline-District (ULUD), an igneous district represented by rare kamafugites and carbonatites and distinct from the much more voluminous Roman Region (RR) rocks. The new kamafugite was found in a cave known as Grotta del Cervo (GC), associated with epiclastic and pyroclastic rocks. In the latter, lapilli ash tuff, welded lapilli, ultramafic xenoliths, cognate lithics and pelletal lapilli have been identified. The mineralogy of the welded lapilli comprises, in order of decreasing abundance, diopside, leucite, haüyne, Mg-mica, andraditic garnet, apatite, magnetite, kalsilite and olivine. The rock is carbonate-free. Based on bulk-rock chemistry it is classified as a kamafugite, closely approaching the composition of ULUD kamafugites, according to Sahama's (1974) criteria. Separate lapilli ash tuff, characterized by the same silicate mineralogy as that of the welded lapilli, plus modal carbonate exceeding 10 wt.%, is classified as a carbonatitic kamafugite. Bulk-rock and trace-element compositions confirm that the Grotta del Cervo rocks closely approach the ULUD analogues.

The Grotta del Cervo occurrence partially fills the geographical and compositional gap between ULUD rocks and the rocks from the Vulture Complex, also a carbonatite and melilitite locality ˜200 km south of GC, and adds considerably to the bulk of kamafugitic and related rocks lying along the Italian Apennines. The petrogenesis of these kamafugites rocks is discussed and possible mineralogical similarities with the Roman Region rocks are highlighted.
Unusual Fe-Ti-Cr spinels from discordant bodies of iron-rich ultramafic pegmatite at the Amandelbult Platinum mine, northwestern Bushveld Complex
Authors: Scoon R. N. , Eales H. V.
Published: August 2004

Spinels associated with discordant bodies of iron-rich ultramafic pegmatite are described from the Amandelbult Platinum mine in the northwestern part of the Bushveld Complex. The spinels are divided into three groups, disseminated Ti-magnetite, disseminated Fe-Ti-Cr spinel and massive Fe-Ti-Cr spinel. The Fe-Ti-Cr spinels show a range of unusual compositions intermediate between chromite and Ti-magnetite. A relationship was found between stratigraphic height and spinel-type, with the Fe-Ti-Cr spinels restricted to pegmatites from the Upper Critical zone and Ti-magnetite to pegmatites from the Lower Main zone. Ilmenite is a ubiquitous component of all of the pegmatites examined here. The massive Fe-Ti-Cr oxide pegmatites are found only where earlier-formed chromitite layers are juxtaposed with sheet-like bodies of olivine-clinopyroxene pegmatite. A distinct thickening of the original chromitite layers in this situation, and compositional gradients within them, points to accretion of Fe-Ti-Cr spinels onto them prior to partial sub-solidus re-equilibration. Analytical data are presented for these spinels and for the Ti-magnetite.

The composition of the Fe-Ti-Cr spinels is not duplicated by cumulus spinels in the Bushveld Complex, but the compositions and microtextures of the disseminated Ti-magnetite are very similar to cumulus Ti-magnetite from the Upper zone. Accordingly, it is deduced that the Ti-magnetite in the pegmatites from the Lower Main zone, together with the ilmenite, crystallized at magmatic temperatures from a suitable Fe-Ti-rich silicate-oxide melt. No evidence has been found to link the pegmatites to hydrothermal fluids. The Cr-rich nature of the disseminated spinels in pegmatites from the Upper Critical zone suggests that the pegmatite melt was richer in chromium at this stratigraphic height, although re-equilibration with earlier-formed cumulus chromite also occurred. Formation of the Fe-Ti-Cr oxide pegmatites reflects a complex process that is incompletely understood and why new oxides plate onto pre-existing chromitite layers that are juxtaposed with Fe-rich ultramafic pegmatites is a matter of conjecture.
Iron-rich ultramafic pegmatite replacement bodies within the Upper Critical Zone, Rustenburg Layered Suite, Northam Platinum Mine, South Africa
Authors: Reid D. L. , Basson I. J.
Published: August 2004

Discordant veins, pipes and occasionally subconcordant sheets of iron-rich ultramafic pegmatite disrupt the layered cumulate sequence of the Upper Critical Zone, Rustenburg Layered Suite, Bushveld Complex. These pegmatite bodies have been studied where they replace the Merensky Reef footwall at Northam Platinum Mine, situated in the Swartklip Facies of the western lobe of the Rustenburg Layered Suite. Composed chiefly of ferroaugite and fayalitic olivine, the pegmatites appear to be formed by the preferential replacement of plagioclase-rich cumulates within the layered sequence. Fe-Ti oxides, sulphide (pyrrhotite and chalcopyrite) and plagioclase also occur in variable quantities. Differentiation within the pegmatite is observed where it has spread laterally beneath the impervious Merensky chromitite layer, with the development of subparallel cm-scale layers of massive magnetitite, massive sulphide and sulphide pegmatite. While some Fe-rich mobile phase must have been responsible for the pegmatites, it is concluded that the pegmatite bulk composition does not represent the original liquid. Furthermore the mode of occurrence precludes the injection of a crystal mush. Rather it is argued, mainlyon geochemical and isotopic grounds, that Fe-rich residual melts derived from the Upper Zone in the downward crosscutting gap areas migrated laterallyand upwards into the adjacent Upper Critical Zone. Variable reaction with the layered cumulates produced the anastomosing pegmatite bodies.
Graftonite in phosphatic iron formations associated with the mid-Proterozoic Gamsberg Zn-Pb deposit, Namaqua Province, South Africa
Authors: Stalder M. , Rozendaal A.
Published: August 2004

Granular aggregates of fine-grained graftonite (Fe,Mn,Ca)3(PO4)2and intergrown wolfeite (Fe,Mn)2(PO4)(OH) occur in amphibolite-facies metamorphosed iron formations associated with the Gamsberg Zn-Pb deposit, South Africa. To date, these minerals were believed to have limited parageneses, being essentially restricted to granitic pegmatites and iron meteorites. This paper is the first report of the occurrence of graftonite and wolfeite in a regionally metamorphosed, iron formation-hosted setting. The aggregates are found together with Mn- and Pb-rich apatite and calcian pyromorphite in a pristine unit of almost pure chemical precipitates, the origin of which is intimately linked to the base-metal mineralizing process. Evidence from Gamsberg supports previous studies conducted on pegmatite-hosted graftonites that a simple host rock mineralogy and geochemical prerequisites, such as high activities of Fe, Mn, Ca and a deficiency in F, exert a dominant control on the stabilization of these minerals. However, in a marine sedimentary environment, significant concentrations of phosphorus have to be precipitated to prevent stabilization of all the phosphorus as fluorapatite. The paucity of graftonite in such settings suggests that the combination of these requirements is only rarely achieved.
Disequilibrium textures in the Leinster Granite Complex, SE Ireland: evidence for acid-acid magma mixing
Authors: Grogan S. E. , Reavy R. J.
Published: August 2004

The LGC (Leinster Granite Complex) in SE Ireland consists of five plutons or Units. Units 1 and 3 display complex magmatic disequilibrium textures described here for the first time. The textures indicative of disequilibrium include boxy cellular plagioclase, oscillatory zoning, calcic spike zones and combinations of these within individual plagioclase feldspar crystals. The textures are interpreted as having formed in a dynamic magmatic environment which facilitated acid-acid mixing on a variety of scales and at a variety of stages between source to emplacement. It is proposed that the restricted distribution of disequilibrium textures was a result of the complex strain regime operating within the crust during assembly of Units 1 and 3.
Raman and infrared spectroscopic study of the vivianite-group phosphates vivianite, baricite and bobierrite
Authors: Frost R. L. , Martens W. , Williams P. A. , Kloprogge J. T.
Published: August 2004

The molecular structure of the three vivianite-structure, compositionally related phosphate minerals vivianite, baricite and bobierrite of formula M32+(PO4)2.8H2O where M is Fe or Mg, has been assessed using a combination of Raman and infrared (IR) spectroscopy. The Raman spectra of the hydroxyl-stretching region are complex with overlapping broad bands. Hydroxyl stretching vibrations are identified at 3460, 3281, 3104 and 3012 cm−1 for vivianite. The high wavenumber band is attributed to the presence of FeOH groups. This complexity is reflected in the water HOH-bending modes where a strong IR band centred around 1660 cm−1 is found. Such a band reflects the strong hydrogen bonding of the water molecules to the phosphate anions in adjacent layers. Spectra show three distinct OH-bending bands fromstrongly hydrogen-bonded, weakly hydrogen bonded water and non-hydrogen bonded water. The Raman phosphate PO-stretching region shows strong similarity between the three minerals. In the IR spectra, complexity exists with multiple antisymmetric stretching vibrations observed, due to the reduced tetrahedral symmetry. This loss of degeneracy is also reflected in the bending modes. Strong IR bands around 800 cm−1 are attributed to water librational modes. The spectra of the three minerals display similarities due to their compositions and crystal structures, but sufficient subtle differences exist for the spectra to be useful in distinguishing the species.
Seasonal changes in the mineral compositions of tropospheric dust in the industrial region of Upper Silesia, Poland
Authors: Jablonska M. , Janeczek J. , Rietmeijer F. J. M.
Published: August 2004

The tropospheric dust loading in Upper Silesia (Poland) shows a steady, annually averaged supply of minerals from natural and anthropogenic sources, industrial dust emitters, domestic heating, transportation, but with superimposed seasonal changes for some dust types. Samples of airborne and deposited particles were collected at monthly intervals between 1996 and 2001 in several cities of Upper Silesia. Dust samples were examined by X-ray powder diffraction, analytical transmission electron microscopy, analytical scanning electron microscopy, and electron microprobe microanalysis. The most common dust included quartz, gypsum, coke, soot, hematite, magnetite, wüstite, bassanite, graphite and various K-, Fe- and Mg-bearing aluminosilicates, in order of decreasing abundance. Minor phases included α-iron, sulphur, sphalerite, halite, sylvite, hercynite, franklinite, baryte, dolomite, ankerite, apatite, olivine and feldspars. Quartz, and specific industrial minerals, e.g. spinels, sphalerite, olivine and iron, occurred throughout the year in almost constant abundances. The amounts of all other dust components show seasonal variations; gypsum, baryte and other sulphates are particularly abundant in winter. In general, minerals related to low-emission sources are abundant in the winter time, while both natural dusts and dust from high-emission sources are predominant during the summer.