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1Latest Papers from Table of Contents or Articles in PressO. Hen ; M. Sargsian ; L. B. Weinstein ; E. Piasetzky ; H. Hakobyan ; D. W. Higinbotham ; M. Braverman ; W. K. Brooks ; S. Gilad ; K. P. Adhikari ; J. Arrington ; G. Asryan ; H. Avakian ; J. Ball ; N. A. Baltzell ; M. Battaglieri ; A. Beck ; S. May-Tal Beck ; I. Bedlinskiy ; W. Bertozzi ; A. Biselli ; V. D. Burkert ; T. Cao ; D. S. Carman ; A. Celentano ; S. Chandavar ; L. Colaneri ; P. L. Cole ; V. Crede ; A. D'Angelo ; R. De Vita ; A. Deur ; C. Djalali ; D. Doughty ; M. Dugger ; R. Dupre ; H. Egiyan ; A. El Alaoui ; L. El Fassi ; L. Elouadrhiri ; G. Fedotov ; S. Fegan ; T. Forest ; B. Garillon ; M. Garcon ; N. Gevorgyan ; Y. Ghandilyan ; G. P. Gilfoyle ; F. X. Girod ; J. T. Goetz ; R. W. Gothe ; K. A. Griffioen ; M. Guidal ; L. Guo ; K. Hafidi ; C. Hanretty ; M. Hattawy ; K. Hicks ; M. Holtrop ; C. E. Hyde ; Y. Ilieva ; D. G. Ireland ; B. I. Ishkanov ; E. L. Isupov ; H. Jiang ; H. S. Jo ; K. Joo ; D. Keller ; M. Khandaker ; A. Kim ; W. Kim ; F. J. Klein ; S. Koirala ; I. Korover ; S. E. Kuhn ; V. Kubarovsky ; P. Lenisa ; W. I. Levine ; K. Livingston ; M. Lowry ; H. Y. Lu ; I. J. MacGregor ; N. Markov ; M. Mayer ; B. McKinnon ; T. Mineeva ; V. Mokeev ; A. Movsisyan ; C. Munoz Camacho ; B. Mustapha ; P. Nadel-Turonski ; S. Niccolai ; G. Niculescu ; I. Niculescu ; M. Osipenko ; L. L. Pappalardo ; R. Paremuzyan ; K. Park ; E. Pasyuk ; W. Phelps ; S. Pisano ; O. Pogorelko ; J. W. Price ; S. Procureur ; Y. Prok ; D. Protopopescu ; A. J. Puckett ; D. Rimal ; M. Ripani ; B. G. Ritchie ; A. Rizzo ; G. Rosner ; P. Roy ; P. Rossi ; F. Sabatie ; D. Schott ; R. A. Schumacher ; Y. G. Sharabian ; G. D. Smith ; R. Shneor ; D. Sokhan ; S. S. Stepanyan ; S. Stepanyan ; P. Stoler ; S. Strauch ; V. Sytnik ; M. Taiuti ; S. Tkachenko ; M. Ungaro ; A. V. Vlassov ; E. Voutier ; N. K. Walford ; X. Wei ; M. H. Wood ; S. A. Wood ; N. Zachariou ; L. Zana ; Z. W. Zhao ; X. Zheng ; I. Zonta
American Association for the Advancement of Science (AAAS)
Published 2014Staff ViewPublication Date: 2014-10-18Publisher: American Association for the Advancement of Science (AAAS)Print ISSN: 0036-8075Electronic ISSN: 1095-9203Topics: BiologyChemistry and PharmacologyComputer ScienceMedicineNatural Sciences in GeneralPhysicsPublished by: -
2Latest Papers from Table of Contents or Articles in PressP. A. Perez-Mancera ; A. G. Rust ; L. van der Weyden ; G. Kristiansen ; A. Li ; A. L. Sarver ; K. A. Silverstein ; R. Grutzmann ; D. Aust ; P. Rummele ; T. Knosel ; C. Herd ; D. L. Stemple ; R. Kettleborough ; J. A. Brosnan ; R. Morgan ; S. Knight ; J. Yu ; S. Stegeman ; L. S. Collier ; J. J. ten Hoeve ; J. de Ridder ; A. P. Klein ; M. Goggins ; R. H. Hruban ; D. K. Chang ; A. V. Biankin ; S. M. Grimmond ; L. F. Wessels ; S. A. Wood ; C. A. Iacobuzio-Donahue ; C. Pilarsky ; D. A. Largaespada ; D. J. Adams ; D. A. Tuveson
Nature Publishing Group (NPG)
Published 2012Staff ViewPublication Date: 2012-06-16Publisher: Nature Publishing Group (NPG)Print ISSN: 0028-0836Electronic ISSN: 1476-4687Topics: BiologyChemistry and PharmacologyMedicineNatural Sciences in GeneralPhysicsKeywords: Animals ; Anoikis/genetics ; Carcinoma, Pancreatic Ductal/*enzymology/genetics/pathology ; Cell Line, Tumor ; Disease Models, Animal ; Endopeptidases ; Gene Expression Regulation, Neoplastic ; Gene Knockdown Techniques ; Humans ; Mice ; Mice, Inbred C57BL ; Pancreatic Neoplasms/*enzymology/genetics/pathology ; U937 Cells ; Ubiquitin Thiolesterase/*genetics/*metabolismPublished by: -
3Articles: DFG German National LicensesWood, S. A. ; Smowton, P. M. ; Molloy, C. H. ; Blood, P. ; Somerford, D. J.
Woodbury, NY : American Institute of Physics (AIP)
Published 1999Staff ViewISSN: 1077-3118Source: AIP Digital ArchiveTopics: PhysicsNotes: Using specially prepared structures, we have observed emission from a layer of direct-gap "monitor" material placed between the p-contact layer and p-cladding layer of a conventional 670 nm GaInP laser diode at room temperature. This observation provides direct evidence for electron leakage through the p-cladding layer in these devices. Furthermore, although emission from the quantum well and waveguide core both pin above threshold, indicating that the Fermi levels clamp throughout the active region, the monitor emission continues to rise above threshold. This is characteristic of a drift component to the leakage current, which we have confirmed by a simulation of the carrier transport processes through the cladding layer with and without drift. © 1999 American Institute of Physics.Type of Medium: Electronic ResourceURL: -
4Articles: DFG German National LicensesWood, S. A. ; Molloy, C. H. ; Smowton, P. M. ; Blood, P. ; Somerford, D. J.
Woodbury, NY : American Institute of Physics (AIP)
Published 1999Staff ViewISSN: 1077-3118Source: AIP Digital ArchiveTopics: PhysicsNotes: By placing a direct-gap monitor layer (or collector) in the p-cladding layer of red-emitting AlGaInP laser diode structures, we have studied the transport of electrons through this layer by observation of spontaneous emission. Pulsed optical excitation superimposed on cw electrical injection has been used to determine the delay time between optical injection of carriers into the well and radiative recombination from the monitor pit. Computer simulations using measured values of minority carrier lifetime for the well and monitor layer show that the transit time for electrons through the p-cladding layer correspond to an electron mobility of 160 cm2/V s. © 1999 American Institute of Physics.Type of Medium: Electronic ResourceURL: -
5Articles: DFG German National LicensesSeale, J. V. ; Wood, S. A. ; Atkinson, H. C. ; Harbuz, M. S. ; Lightman, S. L.
Oxford, UK : Blackwell Science Ltd
Published 2004Staff ViewISSN: 1365-2826Source: Blackwell Publishing Journal Backfiles 1879-2005Topics: MedicineNotes: We investigated the effects of gonadal hormone replacement on the pulsatile parameters underlying basal circadian corticosterone secretion in castrated male and ovariectomized female rats using an automated sampling system. Blood was collected from freely moving, unanaesthetized rats every 10 min over a 24-h period and sampling was continued during a noise stress and after lipopolysaccharide (LPS) administration. Castrated male rats had markedly higher corticosterone levels than intact controls. This was reflected by increased number and frequency of pulses in addition to an increase in the pulse height and amplitude under both basal circadian and stress conditions. Hormone replacement with either testosterone or dihydrotestosterone returned these corticosterone levels and circadian profile to those found in intact males, confirming an androgen-mediated effect. Ovariectomized females had significantly lower basal and stress-induced corticosterone levels with lower frequency and amplitude of corticosterone pulses than intact females. 17β-oestradiol replacement returned basal levels, pulsatile measurements and stress-induced corticosterone levels to those found in intact females. Three hours post-LPS administration, castrated males demonstrated significantly higher values of parvocellular paraventricular nucleus (PVN) arginine vasopressin and corticotrophin-releasing factor and anterior pituitary pro-opiomelanocortin mRNA while ovariectomized females showed significantly lower levels of all three transcripts compared to intact controls. PVN glucocorticoid receptor mRNA levels 3 h post-LPS administration were significantly decreased in castrated males and significantly increased in ovariectomized female rats. Replacement of gonadal steroids resulted in a return to the levels found in intact controls after LPS. Gonadal steroid replacement is sufficient to reverse changes in the pulsatile characteristics of corticosterone release after gonadectomy. In addition, gonadal steroid replacement reverses stress-induced alterations in hypothalamic-pituitary-adrenal (HPA) activity. These data demonstrate a major contribution of gonadal steroids to the regulation of HPA axis activity and to the pulsatile characteristics of corticosterone release.Type of Medium: Electronic ResourceURL: -
6Articles: DFG German National LicensesSeale, J. V. ; Wood, S. A. ; Atkinson, H. C. ; Bate, E. ; Lightman, S. L. ; Ingram, C. D. ; Jessop, D. S. ; Harbuz, M. S.
Oxford, UK : Blackwell Science Ltd
Published 2004Staff ViewISSN: 1365-2826Source: Blackwell Publishing Journal Backfiles 1879-2005Topics: MedicineNotes: Enhanced corticosterone release by female compared to male rats under basal and stress conditions is well documented. The demonstration that gonadectomy enhances stress-induced corticosterone secretion in male rats, but reduces such levels in female rats, suggests a causal association between gonadal steroids and corticosterone release. The present study examined the corticosterone profile of sham gonadectomized and gonadectomized female and male rats under basal and stress conditions. An automated sampling system collected blood from each freely moving, unanaesthetized rat every 10 min (i) over a 24-h period; (ii) following noise stress; and (iii) following an immune-mediated stress (lipopolysaccharide, LPS). Plasma was analysed for corticosterone content using radioimmunoassay. Castration resulted in a significant increase in basal corticosterone release compared to the sham-castrated male rats. Pulsar analysis revealed a significant two-fold increase in the number of corticosterone pulses over 24 h. Corticosterone increases in response to noise stress and to LPS injection were enhanced following castration. Conversely, ovariectomy resulted in a two-fold reduction in the number of corticosterone pulses as well as the stress response compared to sham-ovariectomized female rats. Arginine vasopressin (AVP), corticotrophin-releasing hormone (CRH) and glucocorticoid receptor mRNAs in the paraventricular nucleus and pro-opiomelanocortin (POMC) mRNA in the anterior pituitary were analysed post-LPS administration by in situ hybridization. Significantly higher values were found for AVP, CRH and POMC mRNAs examined for sham females and castrated males compared to sham males and ovariectomized females. This study confirms previous reports concerning the influence of gonadal factors in regulating HPA axis activity and stress responsiveness. The present results extend these observations to the regulation of the dynamic pattern of corticosterone release under basal conditions and suggests that this alteration in pulsatility is important for the differences in stress responsiveness when comparing males and females.Type of Medium: Electronic ResourceURL: -
7Articles: DFG German National LicensesWindle, R. J. ; Wood, S. A. ; Kershaw, Y. M. ; Lightman, S. L. ; Ingram, C. D. ; Harbuz, M. S.
Oxford, UK : Blackwell Science, Ltd
Published 2001Staff ViewISSN: 1365-2826Source: Blackwell Publishing Journal Backfiles 1879-2005Topics: MedicineNotes: Frequent blood sampling from males rats was used to study hypothalamic-pituitary-adrenal (HPA) axis activation during arthritis and its association with diminished responses to acute psychological stress. In control rats, corticosterone release occurred in a series of 13 ± 1 pulses per 24 h. Induction of arthritis by Mycobacterium-adjuvant injection initially increased the rate of hormone release within each pulse and, by day 14 postinjection, when hind-paw inflammation was established, caused a marked increase in pulse frequency to 22 ± 1 per 24 h leading directly to elevated circulating corticosterone levels. In both control and adjuvant-treated rats, there was a marked response to a 10-min noise stress when the stimulus coincided with a rising or interpulse phase of the endogenous corticosterone rhythm. However, when the noise stress coincided with a falling phase of this rhythm, the response was greatly diminished. Since corticosterone pulse frequency was markedly increased and hence interpulse interval decreased by day 14, there was an increased probability of the noise stress occurring during the nonstress responsive falling phase of the corticosterone secretory cycle. As a result, the group mean response to noise stress was significantly smaller in the arthritic than the controls (70.2 ± 9.2 versus 107.8 ± 13.0 ng/ml, respectively). In contrast to the differential response to noise stress, all rats showed similar responses to the acute immunological challenge with i.v. lipopolysaccharide. Thus, altered basal pulse frequency is a major factor influencing HPA activation during acute psychological stress.Type of Medium: Electronic ResourceURL: -
8Articles: DFG German National LicensesNolan, L. A. ; Windle, R. J. ; Wood, S. A. ; Kershaw, Y. M. ; Lunness, H. R. ; Lightman, S. L. ; Ingram, C. D. ; Levy, A.
Oxford, UK : Blackwell Science Ltd
Published 2000Staff ViewISSN: 1365-2826Source: Blackwell Publishing Journal Backfiles 1879-2005Topics: MedicineNotes: Many millions of people throughout the world are at risk of developing iodine deficiency-associated disorders. The underlying effects of iodine deficiency on neuroendocrine function are poorly defined. We have studied stress-induced and diurnal variation in corticosterone secretion in female rats rendered chronically hypothyroid by feeding them an iodine-free diet for 6 months. Corticosterone secretory responses in iodine deficient animals were compared to those seen in animals rendered hypothyroid with propylthiouracil and untreated controls. By using a well-validated, automated blood sampling system to collect small samples of blood over the complete daily cycle in unrestrained animals, we have demonstrated for the first time that the normal diurnal rhythm of corticosterone secretion is lost in chronic iodine deficiency and that the corticosterone secretory response to the psychological stress of 10 min exposure to white noise is attenuated. Despite restoration of circulating triiodothyronine and thyrotropin releasing hormone- and thyroid stimulating hormoneβ-transcript prevalence in the hypothalamus and pituitary, respectively, 1 month after restoration of normal iodine-containing diet both the diurnal variation in corticosterone levels and the corticosterone secretory response to the noise stress remained reduced in amplitude compared to control animals. Thus, chronic hypothyroidism induced by iodine deficiency significantly attenuates hypothalamo-pituitary-adrenal axis activity, an effect that persists after functional recovery of the thyroid axis.Type of Medium: Electronic ResourceURL: -
9Articles: DFG German National LicensesStaff View
ISSN: 1438-1168Source: Springer Online Journal Archives 1860-2000Topics: GeosciencesDescription / Table of Contents: Zusammenfassung ¶Experimentelle Bestimmung der hydrothermalen Löslichkeit von Platingruppen-Elementen unter besonderer Berücksichtigung von Porphyry Copper-Systemen Wir haben eine Reihe von Experimenten zur Löslichkeit von metallischem Osmium und Palladium in überkritischen wässrigen KCl Fluiden durchgeführt. Dabei war pH durch die Assoziation K-Feldspat-Quarz-Muskovit gepuffert, die Sauerstoff-Fugazität wurde durch verschiedene Sauerstoffpuffer bei 400 und 500°C kontrolliert. Ein wichtiges Ziel dieser sorgfältig eingegrenzten Experimente war es, die derzeit bestehenden theoretischen Modelle zur PGE-Löslichkeit zu testen. Unsere experimentellen Ergebnisse zeigen, dass die Konzentration von Osmium in einer 1,0 m KCl-Lösung mit Ni-NiO (NNO) Puffer bei 500°C ungefähr 3 ppb (≈ 1,9 × 10−8 mol/kg H2O) beträgt, wogegen die Konzentration von Osmium in einer 1,5 m KCl-Lösung, auch durch NNO bei 500°C gepuffert, bei ≈ 130 ppb (≈ 6,5 × 10−7 mol/kg H2O) liegt. Dass der pH in beiden Experimenten fast identisch ist, weist darauf hin, dass Osmium in der Lösung als Chloridkomplex vorliegt. Die Konzentration von Osmium in einer 1,5 m KCl-Lösung, aber mit einem Puffer mit höherer Sauerstoff-Fugazität (Re-ReO2) (RRO) gepuffert, ist ungefähr um eine Größenordnung höher (≈ 1705 ppb; ≈ 1 × 10−5 mol/kg H2O). Die Palladium-Konzentration in einer 0,1 m KCl-Lösung, die durch RRO bei 500°C gepuffert wird, und in einer 0,1 m KCl-Lösung, die bei 400°C durch MnO-Mn3O4 gepuffert wird, sind 40 ppb (≈ 3,8 × 10−7 mol/kg H2O) und ungefähr 15 ppb (1,4 × 10−7 mol/kg H2O). Unsere experimentellen Ergebnisse zur Löslichkeit von Palladium-Metall zeigen, zusammen mit Geländebeobachtungen, dass die theoretischen Berechnungen von Sassani und Shock (1990, 1998) die Löslichkeit von Palladium unter superkritischen Bedingungen um viele Gröβenordnungen unterschätzen. Dies lässt sich direkt auf Porphyry Copper-Systeme anwenden, weil in diesen Temperaturen, pH, Salinität und Sauerstoff-Fugazität den experimentellen Parametern weitgehend entsprechen. Die Anwendung unserer experimentellen Ergebnisse zeigt, dass ein typisches Porphyry Copper-System mindestens 40 t Palladium transportieren kann, wenn Quellen von Platingruppen-Elementen (PGE) verfügbar sind und wenn die Phase, die die Löslichkeit kontrolliert, metallisches Pd ist. In ähnlicher Weise läβt sich die Menge von Osmium, die in einem typischen Porphyry-System transportiert werden kann, mit mindestens 3 t berechnen. Porphyry-Systeme sind somit in der Lage, ausreichend PGE zu transportieren, um zumindest PGE-Lagerstätten mittlerer Gröβe zu erzeugen. Das Fehlen von bedeutendem Osmium-Mineralisation in bekannten Porphyry-Lagerstätten läβt sich entweder auf das Fehlen geeigneter Metallquellen, oder auf die Anwesenheit von Osmium in weniger löslichem Form, wie z.B. als Sulfid, zurückführen.Notes: Summary We have conducted a series of experiments on the solubility of metallic osmium and palladium in supercritical aqueous KCl fluids in which pH was buffered by the assemblage K-feldspar-quartz-muscovite and oxygen fugacity was controlled by various oxygen buffers at 400° and 500°C. An important objective of these well-constrained experiments is to evaluate current theoretical models of PGE solubility. Our experimental results indicate that the concentration of Os in a 1.0 m KCl solution buffered by the Ni-NiO (NNO) assemblage at 500°C is ∼ 3 ppb (∼1.9 × 10−8 moles/kg H2O), whereas the concentration of Os in a 1.5 m KCl solution also buffered by NNO at 500°C is ∼ 130 ppb (∼ 6.5 × 10−7 moles/kg H2O). As the pH in these two experiments is nearly the same, this finding implies that Os is present in solution as a chloride complex. The concentration of Os in a 1.5 m KCl solution but buffered by a higher oxygen fugacity buffer (Re-ReO2 assemblage) (RRO) is about one order of magnitude higher (∼ 1705 ppb; ∼ 1 × 10−5 moles/kg H2O). The palladium concentrations in a 0.1 m KCl solution buffered by RRO at 500°C and in a 0.1 m KCl solution buffered by MnO-Mn3O4 at 400°C are ∼ 40 ppb (∼ 3.8 × 10−7 moles/kg H2O) and ∼ 15 ppb (1.4 × 10−7 moles/kg H2O), respectively. Our experimental results on the solubility of Pd metal in combination with field observations show that the theoretical calculations of Sassani and Shock (1990, 1998) on palladium underestimate the solubility of palladium by many orders of magnitude under supercritical conditions. Our experimental results are directly applicable to porphyry copper systems because in such systems temperature, pH, salinity and oxygen fugacity are similar to the experimental parameters. Application of our experimental results indicate that a typical porphyry systems can transport at least 40 tons of Pd if sources of platinum-group elements (PGE) are available and the solubility-controlling phase is metallic Pd. Similarly, the amount of osmium that can be transported in a typical porphyry system is calculated to be at least ∼ 3 tons. Consequently, porphyry systems have the capacity to transport sufficient PGE to form at least mid-sized PGE deposits. The absence of important Os mineralization in known porphyry deposits may be due to the lack of availability of source materials, or to the presence of Os in less soluble forms, such as sulfides.Type of Medium: Electronic ResourceURL: -
10Articles: DFG German National LicensesStaff View
ISSN: 1432-1106Keywords: Tendon jerk ; Fusimotor ; Reflex Muscle spindle ; CatSource: Springer Online Journal Archives 1860-2000Topics: MedicineNotes: Abstract This is a study of the tendon jerk reflex elicited by a brief stretch applied to the triceps surae muscle group in the chloralose-anaesthetised cat. The size of the recorded reflex depended on stretch parameters (optimum at 300 μm amplitude at a rate of 100 mm/s) and on how the muscle had been conditioned. A reflex elicited after a conditioning contraction at the test length was often twice as large as after a contraction carried out at a length longer than the test length. This difference was attributed to the amount of slack introduced in the intrafusal fibres of muscle spindles by conditioning. The question was posed, did ongoing fusimotor activity exert any influence on the size of the tendon jerk? Depolarization indices (DPI) were calculated from responses of muscle spindles to stretch and correlated with the level of reflex tension. Values of DPI obtained from afferent responses with and without repetitive stimulation of identified fusimotor fibres suggested that with the stretch parameters used here the main influence of fusimotor activity was that it removed any pre-existing slack in muscle spindles and thereby increased reflex tension. In the absence of intrafusal slack, stimulation of static and dynamic fusimotor fibres had little additional influence on the size of the reflex. It is concluded that much of the variability typically seen with tendon jerks is due to muscle history effects. Since in muscles which have not been deliberately conditioned there is commonly some slack present in spindles, activity in fusimotor fibres is likely to reduce slack and therefore increase reflex size.Type of Medium: Electronic ResourceURL: -
11Articles: DFG German National LicensesStaff View
ISSN: 1432-1866Source: Springer Online Journal Archives 1860-2000Topics: GeosciencesNotes: Abstract Two sets of measurements of the solubility of Pt and Pd in bisulfide solutions have been carried out at low temperatures. The first involved the equilibration of Pt metal with bisulfide solutions at 25 °C and pH = 6–12 for periods up to five years. These experiments yielded Pt concentrations on the order of tens of μg/L at sulfide concentrations as low as 0.001 molal under conditions too reducing to permit significant contributions from hydroxide complexes. The second set of experiments consisted of reacting PtS, PdS and Au with H2S-saturated solutions having pH values of 3–4 at 25°, 50° and 90 °C. These experiments showed that the solubilities of all three metals increased with temperature. The observed order of solubility was Au 〉 Pt ≈ Pd. Solubilities ranged from 10 to 75 μg/L Au, 4 to 20 μg/L Pt and 0.5 to 10 μg/L Pd. The data do not permit definitive identification of the Pt and Pd species present in either set of experiments, but do strongly suggest that the species present under acidic and basic conditions are different. The measured solubility of gold at 25° and 50 °C is consistent with that measured in previous studies. Although the measured Pt and Pd solubilities are not as high as those estimated by theoretical methods, it is nevertheless evident that bisulfide complexation can lead to the remobilization of Pt and Pd over a wide range of pH under reducing conditions at geologically reasonable sulfide concentrations, at low as well as high temperatures. Such conditions are characteristic of a wide variety of geological environments where Pt and Pd have been inferred to have been affected by hydrothermal transport. In these cases, bisulfide complexation is far more effective than chloride or hydroxide complexes in transporting the PGE.Type of Medium: Electronic ResourceURL: -
12Articles: DFG German National LicensesStaff View
ISSN: 1432-1866Source: Springer Online Journal Archives 1860-2000Topics: GeosciencesNotes: Abstract An experimental study of the solubility of Pt and Pd sulfides and Au metal in aqueous bisulfide solutions was conducted at temperatures from 200° to 350 °C and at saturated vapor pressure. A 500-mL Bridgemantype pressure vessel constructed of titanium, and equipped with a motor-driven magnetic stirrer was employed. The pH and the oxidation state were buffered by the coexistence of H2S/HS−/SO inf4 sup2− . The pH at temperature was calculated to be in the range 5.91–9.43, and ∑S was 0.3–2.2 m. Under the experimental conditions, the measured solubility of gold is about two to three orders of magnitude greater than that of either platinum and palladium, and the measured solubility of platinum is, in general, approximately equal to that of palladium, in molal units. The solubilities are found to be in the range: platinum 4–800 ppb, palladium 1–400 ppb, and gold 2–300 ppm. The solubility data can be modeled adequately using the following reactions: Au+H2S+HH−=Au(HS) 2 − +1/2H2 (K14); PtS+HS−+H+=Pt (HS) 2 0 (K15); PdS+HS−+H+=Pd (HS) 2 0 (K16); PtS2+H2=Pt (HS) 2 0 (K21). With equilibrium constants determined as follows (errors represent two standard deviations): Preliminary measurements of the solubilities of metallic Pt, Pd and Au as hydroxide complexes were also conducted using a second titanium pressure vessel, at temperatures of 200° to 350 °C and vapor saturation pressure, with pH and the oxidation state controlled or buffered by adding known amounts of NaOH and H2 gas. The concentration of NaOH was in the range 0.01–1.3 m, and the partial pressure of H2 at 200 °C was 62–275 bars, initially. Under the temperature and pressure conditions of these experiments, the solubility of platinum in 1 m NaOH solution is less than 100 ppb, that of palladium is less than 10 ppb and that of gold is less than 0.2 ppm; and in 0.01 m NaOH solutions, both Pt and Pd solubilities are less than 1 ppb. These data indicate that the contributions of hydroxide complexes to the total solubilities in the bisulfide runs, where the pH was in the range of 5.9–9.4, are negligible. The concentrations of both Pt and Pd as bisulfide complexes in the Salton Sea geothermal system predicted using the stability constants determined in this work agree very well with those values measured by McKibben et al. (1990). This calculation strongly suggests that the PGE are transported in moderately reducing, near neutral hydrothermal fluids as bisulfide complexes, as is gold. However, the much lower maximum solubility of the PGE relative to gold severely constrains models of re genesis, and may explain the relative rarity of hydrothermal PGE deposits compared to the relative abundance of hydrothermal Au deposits.Type of Medium: Electronic ResourceURL: -
13Articles: DFG German National LicensesStaff View
ISSN: 1432-1866Source: Springer Online Journal Archives 1860-2000Topics: GeosciencesNotes: Abstract Mo-Bi mineralization occurs in subvertical and subhorizontal quartz-muscovite-± K-feldspar veins surrounded by early albitic and later K-feldspathic alteration halos in monzogranite of the Archean Preissac pluton, Abitibi region, Québec, Canada. Molybdenite is intergrown with muscovite in the veins or associated with K-feldspar in the alteration halos. Mineralized veins contain five main types of fluid inclusions: aqueous liquid and liquid-vapor inclusions, aqueous carbonic liquid-liquid-vapor inclusions, carbonic liquid and vapor inclusions, halite-bearing aqueous liquid and liquid-vapor inclusions, trapped mineral-bearing aqueous liquid and liquid-vapor inclusions. The carbonic solid in frozen carbonic and aqueous-carbonic inclusions melts in most cases at −56.7 ± 0.1 °C indicating that the carbonic fluid consists largely of CO2. All aqueous inclusion types and the aqueous phase in carbonic inclusions have low initial melting temperatures (≥70 °C), requiring the presence of salts other than NaCl. Leachate analyses show that the bulk fluid contains variable proportions of Na, K, Ca, Cl, and traces of Mg and Li. The following solids were identified in the fluid inclusions by SEM-EDS analysis: halite, calcite, muscovite, millerite (NiS), barite and antarcticite (CaCl2 · 6H2O). All are interpreted to be trapped phases except halite which is a daughter mineral, and antarcticite which formed during sample preparation (freezing). Aqueous inclusions homogenize to liquid at temperatures between 75 °C and 400 °C; the mode is 375 °C. Aqueous-carbonic inclusions homogenize to liquid or vapor between 210 °C and 400 °C. Halite-bearing aqueous inclusions homogenize by halite dissolution at approximately 170 °C. Aqueous inclusions containing trapped solids exhibit liquid-vapor homogenization at temperatures similar to those of halite-bearing aqueous inclusions. Temperatures of vein formation, based on oxygen isotopic fractionation between quartz and muscovite, range from 342 °C to 584 °C. The corresponding oxygen isotope composition of the aqueous fluid in equilibrium with these minerals ranges from 1.2 to 5.5 per mil with a mean of 3.9 per mil, suggesting that the liquid had a significant meteoric component. Isochores for aqueous fluid inclusions intersect the modal isotopic isotherm of 425 °C at pressures between 590 and 1900 bar. A model is proposed in which molybdenite was deposited owing to decreasing temperature and/or pressure from CO2-bearing, moderate to high salinity fluids of mixed magmatic-meteoric origin that were in equilibrium with K-feldspar and muscovite. These fluids resulted from the degassing of a monzogranitic magma and evolved through interaction with volcanic (komatiitic) and sedimentary country rocks.Type of Medium: Electronic ResourceURL: -
14Articles: DFG German National LicensesWood, S. A. ; Lemons, J. E. ; Prasad, K. U. ; Urry, D. W.
Hoboken, NJ : Wiley-Blackwell
Published 1986Staff ViewISSN: 0021-9304Keywords: Chemistry ; Polymer and Materials ScienceSource: Wiley InterScience Backfile Collection 1832-2000Topics: MedicineTechnologyNotes: The in vitro calcifiability and molecular weight dependence of calcification of the polypentapeptide, (L · Val1-L· Pro2-Gly3-L · Val4-Gly5)n, which had been γ-irradiation cross-linked have been determined when exposed to dialyzates of normal, nonaugmented fetal bovine serum. The material was found to calcify: calcifiability was found to be highly molecular weight dependent and to be most favored when the highest molecular weight polymers (n ≈240) had been used for cross-linking. The in vivo biocompatibility, biodegradability, and calcifiability of the γ-irradiation cross-linked polypentapeptide were examined in rabbits in both soft and hard tissue sites. The material was found to be biocompatible irrespective of its physical form and to be biodegradable but with n of 200 or less it was not shown to calcify or ossify in the rabbit tibial nonunion model.Additional Material: 12 Ill.Type of Medium: Electronic ResourceURL: