The solubility of fluorite in H 2 O and H 2 O-NaCl at high pressure and temperature

Abstract The solubility of fluorite in H 2 O and H 2 O-NaCl has been measured at 600-1000°C, 0.5-2.0 GPa in a piston-cylinder apparatus. Fluorite dissolves congruently at all conditions investigated. The data indicate that the concentration of fluorite dissolved in H 2 O is low at 600°C and 0.5 GPa (0.0014 mol/kg H 2 O) but increases strongly with temperature (T) and pressure (P) to 0.247 mol/kg H 2 O at 1000°C, 2 GPa. The data were fit with the equation log m CaF 2 = −6.587 + 2.774P 1/2 + (2.266 × 10 − 3 − 4.699 × 10 − 4 P)T, where m CaF 2 is molality of CaF 2 , T is in Kelvin, and P is in GPa. Fluorite solubility was also measured in H 2 O-NaCl fluids at 800°C and 1.0 GPa. Results indicate a strong increase in dissolved fluorite concentration with increasing NaCl content, from 0.028 mol/kg H 2 O at X NaCl = 0 to 1.673 mol/kg H 2 O at X NaCl = 0.486, where X NaCl is the mole fraction of NaCl in the fluid. The data were fit to m CaF 2 = 0.01035 + 1.141X NaCl + 4.694X NaCl 2 . The results indicate that F mobility will be further enhanced by saline brines in high P-T igneous and metamorphic environments. High F solubility in H 2 O and H 2 O-NaCl in the deep crust and upper mantle can promote mobilization of high field-strength elements, rare earth elements, U, and Th through transport as F-bearing complexes

The compositional variation of synthetic sodic amphiboles at high and ultra-high pressures

Sodic amphiboles in high pressure and ultra-high pressure (UHP) metamorphic rocks are complex solid solutions in the system Na 2 O–MgO–Al 2 O 3 –SiO 2 –H 2 O (NMASH) whose compositions vary with pressure and temperature. We conducted piston-cylinder experiments at 20–30 kbar and 700–800 °C to investigate the stability and compositional variations of sodic amphiboles, based on the reaction glaucophane=2jadeite+talc, by using the starting assemblage of natural glaucophane, talc and quartz, with synthetic jadeite. A close approach to equilibrium was achieved by performing compositional reversals, by evaluating compositional changes with time, and by suppressing the formation of Na-phyllosilicates. STEM observations show that the abundance of wide-chain structures in the synthetic amphiboles is low. An important feature of sodic amphibole in the NMASH system is that the assemblage jadeite–talc ± quartz does not fix its composition at glaucophane. This is because other amphibole species such as cummingtonite (Cm), nyböite (Nyb), Al–Na-cummingtonite (Al–Na-Cm) and sodium anthophyllite (Na-Anth) are also buffered via the model reactions: 3cummingtonite + 4quartz + 4H 2 O=7talc, nyböite + 3quartz=3jadeite + talc, 3Al–Na-cummingtonite + 11quartz + 2H 2 O=6jadeite + 5talc, and 3 sodium anthophyllite + 13quartz + 4H 2 O=3 jadeite + 7talc. We observed that at all pressures and temperatures investigated, the compositions of newly grown amphiboles deviate significantly from stoichiometric glaucophane due to varying substitutions of Al IV for Si, Mg on the M(4) site, and Na on the A-site. The deviation can be described chiefly by two compositional vectors: [Na A Al IV ][□ A Si] (edenite) toward nyböite, and [Na (M4) Al VI ][Mg (M4) Mg VI ] toward cummingtonite. The extent of nyböite and cummingtonite substitution increases with temperature and decreases with pressure in the experiments. Similar compositional variations occur in sodic amphiboles from UHP rocks. The experimentally calibrated compositional changes therefore may prove useful for thermobarometric applications.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/42228/1/410-139-2-146_01390146.pd

Photon-pair generation in photonic crystal fibre with a 1.5 GHz modelocked VECSEL

Four-wave mixing (FWM) in optical fibre is a leading technique for generating high-quality photon pairs. We report the generation of photon pairs by spontaneous FWM in photonic crystal fibre pumped by a 1.5 GHz repetition-rate vertical-external-cavity surface-emitting laser (VECSEL). The photon pairs exhibit high count rates and a coincidence-to-accidental ratio of over 80. The VECSEL's high repetition-rate, high average power, tunability, and small footprint make this an attractive source for quantum key distribution and photonic quantum-state engineering.Comment: 17 Pages, 5 Figure

Therapeutic targeting of ependymoma as informed by oncogenic enhancer profiling

Genomic sequencing has driven precision-based oncology therapy; however, the genetic drivers of many malignancies remain unknown or non-targetable, so alternative approaches to the identification of therapeutic leads are necessary. Ependymomas are chemotherapy-resistant brain tumours, which, despite genomic sequencing, lack effective molecular targets. Intracranial ependymomas are segregated on the basis of anatomical location (supratentorial region or posterior fossa) and further divided into distinct molecular subgroups that reflect differences in the age of onset, gender predominance and response to therapy1,2,3. The most common and aggressive subgroup, posterior fossa ependymoma group A (PF-EPN-A), occurs in young children and appears to lack recurrent somatic mutations2. Conversely, posterior fossa ependymoma group B (PF-EPN-B) tumours display frequent large-scale copy number gains and losses but have favourable clinical outcomes1,3. More than 70% of supratentorial ependymomas are defined by highly recurrent gene fusions in the NF-κB subunit gene RELA (ST-EPN-RELA), and a smaller number involve fusion of the gene encoding the transcriptional activator YAP1 (ST-EPN-YAP1)1,3,4. Subependymomas, a distinct histologic variant, can also be found within the supratetorial and posterior fossa compartments, and account for the majority of tumours in the molecular subgroups ST-EPN-SE and PF-EPN-SE. Here we describe mapping of active chromatin landscapes in 42 primary ependymomas in two non-overlapping primary ependymoma cohorts, with the goal of identifying essential super-enhancer-associated genes on which tumour cells depend. Enhancer regions revealed putative oncogenes, molecular targets and pathways; inhibition of these targets with small molecule inhibitors or short hairpin RNA diminished the proliferation of patient-derived neurospheres and increased survival in mouse models of ependymomas. Through profiling of transcriptional enhancers, our study provides a framework for target and drug discovery in other cancers that lack known genetic drivers and are therefore difficult to treat.This work was supported by an Alex's Lemonade Stand Young Investigator Award (S.C.M.), The CIHR Banting Fellowship (S.C.M.), The Cancer Prevention Research Institute of Texas (S.C.M., RR170023), Sibylle Assmus Award for Neurooncology (K.W.P.), the DKFZ-MOST (Ministry of Science, Technology & Space, Israel) program in cancer research (H.W.), James S. McDonnell Foundation (J.N.R.) and NIH grants: CA154130 (J.N.R.), R01 CA169117 (J.N.R.), R01 CA171652 (J.N.R.), R01 NS087913 (J.N.R.) and R01 NS089272 (J.N.R.). R.C.G. is supported by NIH grants T32GM00725 and F30CA217065. M.D.T. is supported by The Garron Family Chair in Childhood Cancer Research, and grants from the Pediatric Brain Tumour Foundation, Grand Challenge Award from CureSearch for Children’s Cancer, the National Institutes of Health (R01CA148699, R01CA159859), The Terry Fox Research Institute and Brainchild. M.D.T. is also supported by a Stand Up To Cancer St. Baldrick’s Pediatric Dream Team Translational Research Grant (SU2C-AACR-DT1113)

Experimental and field-related investigations on the metamorphic history of eclogites in the Sesia-Lanzo Zone, Western Alps (Italy).

The lack of applicable geobarometers in many eclogite facies rocks led to the evaluation of the assemblage K-feldspar-jadeite-quartz (KJQ) as a possible geobarometer in Chapter II. Use of appropriate mixing models to K-feldspar and jadeite solid solutions allowed application of the reaction albite = jadeite + quartz to the KJQ assemblage, which was used to constrain pressures and also a(H\sb2O) in eclogite facies metagranitic and metapelitic rocks from the Sesia-Lanzo Zone. Based on textural evidence and thermobarometric calculations the P-T conditions of five different stages of mineral growth in eclogites from Ianca Valley in the Sesia-Lanzo Zone were performed in Chapter III. It was possible to reconstruct a P-T-a(H\sb2O) path for these eclogites. The data show that the eclogites underwent a nearly isothermal decompressional path from 570-650\sp\circC at 21 kbar to 500-600\sp\circC at 11-13 kbar and finally to 300-500\sp\circC and 3-7 kbar. During these stages, a(H\sb2O) remained relatively high (0.7-1.0). Piston-cylinder experiments on sodic amphiboles were undertaken in Chapters IV and V. Synthetic sodic amphiboles are displaced from stoichiometric glaucophane, and the glaucophane component increases with decreasing temperature and increasing pressure. The compositions of these amphiboles are comparable to those from ultra-high pressure rocks. Additional piston-cylinder experiments on the reaction 2 glaucophane = 4 jadeite + 3 enstatite + 2 coesite + 2 H\sb2O were undertaken in Chapter V. They yielded a bracket between 37 and 38 kbar at 800\sp\circC which allowed the calculation a $\Delta$G\sp\circ\sb{\rm f,298} for glaucophane. The resulting $\Delta$G\sp\circ\sb{\rm f,298} is -11253 $\pm$ 2 kJ/mol, 5-20 kJ/mol more negative than previous estimates. An experimental investigation on the synthesis of F-Al-sphene (CaAlSiO\sb4F), which yielded Al contents of 50 to 98 mol percent, was performed in Chapter VI. No significant pressure or temperature dependency of the (Al + F) substitution could be found. Activity measurements by dilution of the reaction anorthite + rutile = sphene + kyanite with fluorite revealed only a slight non-ideality in the system CaTiSiO\sb5 CaAlSiO\sb4F at 1000\sp\circC and 1100\sp\circC. These preliminary data strongly support the use of a molecular mixing model for sphene.Ph.D.Earth SciencesGeologyUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/131559/2/9910011.pd

Das Politikfeld des Straßengüterverkehrs und die besondere Bedeutung des 'Alpenquerenden Straßengütertransitverkehrs' in Österreich und der Schweiz als Spannungsfeld auf europäischer und nationaler Ebene

Die Dissertation behandelt in Form einer vergleichenden Politikfeldanalyse das Thema des Straßengüterverkehrs in Österreich und der Schweiz mit besondererer Berücksichtigung des Problemfeldes des Alpenquerenden Straßengütertransitverkehrs. Hierbei werden unterschiedliche policy-instruments auf nationaler, europäischer und intergouvernementaler Ebene beleuchtet, Entwicklungen und Lösungsansätze dargestellt, und in Form einer vergleichenden Maßnahmenanalyse untersucht. Methodisch stützt sich die Arbeit auf Quellen- und Literaturanalyse mit besonderer Berücksichtigung und Darstellung nationaler, europäischer und internationaler Rechtsnormen und Rahmenbedingungen. Sie stellt mittels empirischer Analyse dar, wie sich das Politikfeld auf diesen unterschiedlichen Ebenen und in den erwähnten Ländern entwickelt hat, welche Konfliktlinien es gibt und beschäftigt sich mit der Frage wie und ob diese gelöst werden (können)

Quantitative evaluation of mineral grains using automated SEM-EDS analysis and its application potential in optically stimulated luminescence dating

Optically stimulated luminescence (OSL) dating allows constraining the depositional age of sediments with good accuracy and precision. A fundamental requirement in OSL dating is to use purified sub-samples (i.e. mono-mineralogic aliquots composed of e.g. quartz or potassium feldspar only), because of the different OSL properties and dosimetry characteristics of each mineral phase. Where multiple mineral phases are present on an aliquot, a mixed OSL signal might be obtained, with potentially adverse effects on the robustness of the resulting optical ages. Detailed evaluation of the mineralogical composition of the hundreds or even thousands of individual mineral particles that constitute an aliquot in OSL dating has – until recently – not been reasonably feasible with current analytical techniques. Here we report on the use of an automated mineralogy system that combines scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) and facilitates ultra-fast analysis of particulate mineral phases with a spatial resolution on the micron scale. The method is applied to mono-mineralogic coarse-grained (100–250 μm) and poly-mineral fine-grained (4–11 μm) OSL samples, respectively and cross-checked with electron probe micro analysis (EPMA). It is shown that (i) some coarse-grained mineral extracts that underwent standard physico-chemical preparation to isolate quartz for OSL dating, still suffer from mineralogical contamination, mainly in the form of feldspar and mica inclusions and, that (ii) polymineral fine-grained samples reveal a complex mineralogical composition with a significant percentage of mica (mainly muscovite). Implications of these quantitative mineralogical observations for OSL dating are discussed. QEMSCAN is further used to examine the efficiency of different physico-chemical preparation strategies to isolate a restricted range of mineralogies and to optimize single preparation steps. We conclude that the clear advantage of automated SEM–EDS systems lies in the rapidity with which accurate high-resolution maps of hundreds or even thousands of mineral particles can be generated, i.e. at a level statistically representative of the bulk OSL sample. Automated SEM–EDS techniques might thus be helpful in OSL dating for quality assurance and investigation of problematic OSL samples