Modeling of in-situ crystallization processes in the Permian mafic layered intrusion of Mont Collon (Dent Blanche nappe, western Alps)

The Mont Collon mafic complex is one of the best preserved examples of the Early Permian magmatism in the Central Alps, related to the intra-continental collapse of the Variscan belt. It mostly consists (> 95 vol.%) of ol+hy-nonnative plagioclase-wehrlites, olivine- and cpx-gabbros with cumulitic structures, crosscut by acid dikes. Pegmatitic gabbros, troctolites and anorthosites outcrop locally. A well-preserved cumulative, sequence is exposed in the Dents de Bertol area (center of intrusion). PT-calculations indicate that this layered magma chamber emplaced at mid-crustal levels at about 0.5 GPa and 1100 degrees C. The Mont Collon cumulitic rocks record little magmatic differentiation, as illustrated by the restricted range of clinopyroxene mg-number (Mg#(cpx)=83-89). Whole-rock incompatible trace-element contents (e.g. Nb, Zr, Ba) vary largely and without correlation with major-element composition. These features are characteristic of an in-situ crystallization process with variable amounts of interstitial liquid L trapped between the cumulus mineral phases. LA-ICPMS measurements show that trace-element distribution in the latter is homogeneous, pointing to subsolidus re-equilibration between crystals and interstitial melts. A quantitative modeling based on Langmuir's in-situ crystallization equation successfully duplicated the REE concentrations in cumulitic minerals of all rock facies of the intrusion. The calculated amounts of interstitial liquid L vary between 0 and 35% for degrees of differentiation F of 0 to 20%, relative to the least evolved facies of the intrusion. L values are well correlated with the modal proportions of interstitial amphibole and whole-rock incompatible trace-element concentrations (e.g. Zr, Nb) of the tested samples. However, the in-situ crystallization model reaches its limitations with rock containing high modal content of REE-bearing minerals (i.e. zircon), such as pegmatitic gabbros. Dikes of anorthositic composition, locally crosscutting the layered lithologies, evidence that the Mont Collon rocks evolved in open system with mixing of intercumulus liquids of different origins and possibly contrasting compositions. The proposed model is not able to resolve these complex open systems, but migrating liquids could be partly responsible for the observed dispersion of points in some correlation diagrams. Absence of significant differentiation with recurrent lithologies in the cumulitic pile of Dents de Bertol points to an efficiently convective magma chamber, with possible periodic replenishment, (c) 2005 Elsevier B.V. All rights reserved.

Determination of chemical composition and its relationship with optical properties of Ti-N and Ti-V-N sputtered thin films

In the investigation of thin films of transition metal nitrides, an essential role is played by the accurate determination of their chemical composition. Actually the chemical composition depends on the deposition parameters and influences the optical properties. These relations are illustrated in thin films of TiNx and (Ti1-yVy)N-x deposited by reactive magnetron sputtering from composite targets of the elements. By variation of the nitrogen partial pressure and the target composition, different samples have been obtained. The chemical composition has been measured by electron probe microanalysis at low irradiation voltages. The optical properties are evaluated by ex-situ ellipsometry. Using the screened Drude model, they are correlated with the differences in composition. Adding vanadium or nitrogen in Ti-N is shown to have the same effect on the optical properties.

La régression tumorale n'est pas un facteur de risque d'atteinte du ganglion sentinelle dans les mélanomes fins (indice de Breslow < or = 1 mm) [Tumour regression is not predictive for higher risk of sentinel node involvement in thin melanomas (Breslow thickness < or = 1 mm)]

Background: Thin melanomas (Breslow thickness <= 1 mm) are considered highly curable. The aim of this study was to evaluate the correlation between histological tumour regression and sentinel lymph node (SLN) involvement in thin melanomas. Patients and methods: This was a retrospective single-centre study of 34 patients with thin melanomas undergoing SLN biopsy between April 1998 and January 2005. Results: The study included 14 women and 20 men of mean age 56.3 years. Melanomas were located on the neck (n = 3), soles (n = 4), trunk (n = 13) and extremities (n = 14). Pathological examination showed 25 SSM, four acral lentiginous melanomas, three in situ melanomas, one nodular melanoma and one unclassified melanoma with a mean Breslow thickness of 0.57 mm. Histological tumour regression was observed in 26 over 34 cases and ulceration was found in one case. Clark levels were as follows: I (n = 3), II (n = 20), III (n = 9), IV (n = 2). Growth phase was available in 15 cases (seven radial and eight vertical). Mitotic rates, available in 24 cases, were: 0 (n = 9), 1 (n = 11), 2 (n = 2), 3 (n = 1), 6 (n = 1). One patient with histological tumour regression (2.9% of cases and 3.8% of cases with regressing tumours) had a metastatic SLN. One patient negative for SLN had a lung relapse and died of the disease. Mean follow-up was 26.2 months. Conclusion: The results of the present study and the analysis of the literature show that histological regression of the primary tumour does not seem predictive of higher risk of SLN involvement in thin melanomas. This suggests that screening for SLN is not indicated in thin melanomas, even those with histological regression.

Forensic examination of ink by high-performance thin layer chromatography - The United States Secret Service Digital Ink Library

Forensic examinations of ink have been performed since the beginning of the 20th century. Since the 1960s, the International Ink Library, maintained by the United States Secret Service, has supported those analyses. Until 2009, the search and identification of inks were essentially performed manually. This paper describes the results of a project designed to improve ink samples' analytical and search processes. The project focused on the development of improved standardization procedures to ensure the best possible reproducibility between analyses run on different HPTLC plates. The successful implementation of this new calibration method enabled the development of mathematical algorithms and of a software package to complement the existing ink library.

Error and attack tolerance of layered complex networks.

Many complex systems may be described by not one but a number of complex networks mapped on each other in a multi-layer structure. Because of the interactions and dependencies between these layers, the state of a single layer does not necessarily reflect well the state of the entire system. In this paper we study the robustness of five examples of two-layer complex systems: three real-life data sets in the fields of communication (the Internet), transportation (the European railway system), and biology (the human brain), and two models based on random graphs. In order to cover the whole range of features specific to these systems, we focus on two extreme policies of system's response to failures, no rerouting and full rerouting. Our main finding is that multi-layer systems are much more vulnerable to errors and intentional attacks than they appear from a single layer perspective.

Contrasting magma types and timing of intrusion in the Permian layered mafic complex of Mont Collon (Western Alps, Valais, Switzerland): evidence from U/Pb zircon and 40Ar/39Ar amphibole dating

We have selected and dated three contrasting rock-types representative of the magmatic activity within the Permian layered mafic complex of Mont Collon, Austroalpine Dent Blanche nappe, Western Alps. A pegmatitic gabbro associated to the main cumulus sequence yields a concordant U/Pb zircon age of 284.2 +/- 0.6 Ma, whereas a pegmatitic granite dike crosscutting the latter yields a concordant age of 282.9 +/- 0.6 Ma. A Fe-Ti-rich ultrabasic lamprophyre, crosscutting all other lithologies of the complex, yields an 40Ar/39Ar plateau age of 260.2 +/- 0.7 Ma on a kaersutite concentrate. All ages are interpreted as magmatic. Sub-contemporaneous felsic dikes within the Mont Collon complex are ascribed to anatectic back-veining from the country-rock, related to the emplacement of the main gabbroic body in the continental crust, which is in accordance with new isotopic data. The lamprophyres have isotopic compositions typical of a depleted mantle, in contrast to those of the cumulate gabbros, close to values of the Bulk Silicate Earth. This indicates either contrasting sources for the two magma pulses - the subcontinental lithospheric mantle for the gabbros and the underlying asthenosphere for the lamprophyres - or a single depleted lithospheric source with variable degrees of crustal contamination of the gabbroic melts during their emplacement in the continental crust. The Mont Collon complex belongs to a series of Early Permian mafic massifs, which emplaced in a short time span about 285-280 Ma ago, in a limited sector of the post-Variscan continental crust now corresponding to the Austroalpine/ Southern Alpine domains and Corsica. This magmatic activity was controlled in space and time by crustal-scale transtensional shear zones.

Comparison of different methods for thin section EM analysis of Mycobacterium smegmatis.

Bacteria are generally difficult specimens to prepare for conventional resin section electron microscopy and mycobacteria, with their thick and complex cell envelope layers being especially prone to artefacts. Here we made a systematic comparison of different methods for preparing Mycobacterium smegmatis for thin section electron microscopy analysis. These methods were: (1) conventional preparation by fixatives and epoxy resins at ambient temperature. (2) Tokuyasu cryo-section of chemically fixed bacteria. (3) rapid freezing followed by freeze substitution and embedding in epoxy resin at room temperature or (4) combined with Lowicryl HM20 embedding and ultraviolet (UV) polymerization at low temperature and (5) CEMOVIS, or cryo electron microscopy of vitreous sections. The best preservation of bacteria was obtained with the cryo electron microscopy of vitreous sections method, as expected, especially with respect to the preservation of the cell envelope and lipid bodies. By comparison with cryo electron microscopy of vitreous sections both the conventional and Tokuyasu methods produced different, undesirable artefacts. The two different types of freeze-substitution protocols showed variable preservation of the cell envelope but gave acceptable preservation of the cytoplasm, but not lipid bodies, and bacterial DNA. In conclusion although cryo electron microscopy of vitreous sections must be considered the 'gold standard' among sectioning methods for electron microscopy, because it avoids solvents and stains, the use of optimally prepared freeze substitution also offers some advantages for ultrastructural analysis of bacteria.

Point defects and texture of Pd1-xInx sputtered intermetallic thin films

Pd1-xInx thin films (0.4 < x < 0.56) were prepared by radio frequency sputtering from a multi-zone target. The properties of these Hume-Rothery alloys were studied by X-ray diffractometry, electron probe microanalysis and scanning tunneling microscopy. The diffraction spectra were analyzed to obtain the intensity ratio of the (100) superlattice line to the (200) normal line, together with the variations of the lattice constant. The results ape explained quantitatively by a model based on point defects, i.e. Pd vacancies in In-rich films and Pd antisite atoms in Pd-rich films. In-rich films grow preferentially in the [100] direction while Pd-rich films grow preferentially in the [110] direction. The grains in indium-rich sputtered films appear to be enclosed in an atomically thick, indium-rich layer. The role of texture and the influence of point defects on electrical resistivity is also reported. (C) 1996 Elsevier Science Limited.

Silver-assisted laser desorption ionization for high spatial resolution imaging mass spectrometry of olefins from thin tissue sections.

Silver has been demonstrated to be a powerful cationization agent in mass spectrometry (MS) for various olefinic species such as cholesterol and fatty acids. This work explores the utility of metallic silver sputtering on tissue sections for high resolution imaging mass spectrometry (IMS) of olefins by laser desorption ionization (LDI). For this purpose, sputtered silver coating thickness was optimized on an assorted selection of mouse and rat tissues including brain, kidney, liver, and testis. For mouse brain tissue section, the thickness was adjusted to 23 ± 2 nm of silver to prevent ion suppression effects associated with a higher cholesterol and lipid content. On all other tissues, a thickness of at 16 ± 2 nm provided the best desorption/ionization efficiency. Characterization of the species by MS/MS showed a wide variety of olefinic compounds allowing the IMS of different lipid classes including cholesterol, arachidonic acid, docosahexaenoic acid, and triacylglyceride 52:3. A range of spatial resolutions for IMS were investigated from 150 μm down to the high resolution cellular range at 5 μm. The applicability of direct on-tissue silver sputtering to LDI-IMS of cholesterol and other olefinic compounds presents a novel approach to improve the amount of information that can be obtained from tissue sections. This IMS strategy is thus of interest for providing new biological insights on the role of cholesterol and other olefins in physiological pathways or disease.

Structural and electrical properties of Fe-doped TiO2 thin films

The present study discusses the effect of iron doping in TiO2 thin films deposited by rf sputtering. Iron doping induces a structural transformation from anatase to rutile and electrical measurements indicate that iron acts as an acceptor impurity. Thermoelectric power measurement shows a transition between n-type and p-type electrical conduction for an iron concentration around 0.13 at.%. The highest p-type conductivity at room temperature achieved by iron doping was 10(-6) S m(-1).

Growth mechanisms and timing of emplacement of a vertically layered mafic intrusion in the feeder zone of an ocean island volcano (Fuerteventura, Canary islands)

Résumé pour le grand public L'île de Fuerteventura (Canaries) offre l'occasion rare d'observer les racines d'un volcan océanique édifié il y a 25 à 30 millions d'années et complètement érodé. On y voit de nombreux petits plutons de forme et composition variées, témoignant d'autant d'épisodes de l'activité magmatique. L'un de ces plutons, appelé PX1, présente une structure inhabituelle formée d'une alternance de bandes verticales d'épaisseur métrique à hectométrique de roches sombres de composition pyroxénilique ou gabbroïque. Les pyroxénites résultent clairement de l'accumulation de cristaux de pyroxènes et non de la simple solidification d'un magma? Se pose dès lors la question de la nature du processus qui a conduit à l'accumulation verticale de niveaux concentrés en pyroxènes. En effet, les litages pyroxénitiques classiques sont subhorizontaux, car ils résultent de l'accumulation gravitaire des cristaux séparés du magma dont ils cristalli¬sent par sédimentation. Cette étude vise à identifier et comprendre les mécanismes qui ont engendré ce Iitage minéralogique vertical et l'im¬portant volume de ces faciès cumulatifs. Nous nous sommes également intéressés aux conditions de pression et de température régnant au moment de la mise en place du pluton, ainsi qu'à sa durée de vie et à sa vitesse de refroidis¬sement. Enfin une approche géochimique nous a permis de préciser la nature de la source mantellique des magmas liés à cette activité magmatique. PX1 est en réalité un complexe filonien formé à des conditions de pression et de température de 1-2 kbar et 1050- 1100°C; sa construction a nécessité au moins 150 km3 de magma. L'alternance d'horizons gabbroïques et pyroxéniti¬ques représente des injections successives de magma sous la forme de filons verticaux, mis en place dans un contexte régional en extension. L'étude des orientations des minéraux dans ces faciès révèle que les horizons gabbroïques enregistrent l'extension régionale, alors que les pyroxénites sont générées par une compaction au sein du pluton. Ceci suggère que le régime des contraintes, qui était extensif lors de l'initiation de la mise en place de PX1, est pério¬diquement devenu compressif au sein même du pluton. Cette compression serait liée à des cycles de mise en place où la vitesse de croissance du pluton dépassait celle de l'extension régionale. La différenciation observée au sein de chaque horizon, depuis des pyroxénites riches en olivine jusqu'à des pyroxé¬nites à plagioclase interstitiel et des gabbros, ainsi que la composition géochimique des minéraux qui les constituent suggèrent que chaque filon vertical s'est mis en place à partir d'un magma de composition identique, puis a évolué indépendamment des autres en fonction du régime thermique et du régime des contraintes local. Lorsque le magma en train de cristalliser s'est trouvé en compression, le liquide résiduel a été séparé des cristaux déjà formés et extrait du système, laissant derrière lui une accumulation de cristaux dont la nature et les proportions dépendaient du stade de cristallisation atteint par le magma au moment de l'extraction. Ainsi, les niveaux de pyroxénites à olivine (premier minéral à cristalliser) ont été formés lorsque le magma correspondant était encore peu cristallisé; à l'inverse, les py¬roxénites riches en plagioclase (minéral plus tardif dans la séquence de cristallisation) et certains gabbros à caractère cumulatif résultent d'une compression tardive dans le processus de cristallisation du filon concerné. Les liquides résiduels extraits des niveaux pyroxénitiques sont rarement observés dans PX1, certaines poches et filonets de com¬position anorthositique pourraient en être les témoins. L'essentiel de ces liquides a probablement gagné des niveaux supérieurs du pluton, voire la surface du volcan. L'origine du régime compressif périodique affectant les filons en voie de cristallisation est attribuée aux injections suivantes de magma au sein du pluton, qui se sont succédées à un rythme plus rapide que la vitesse de consolidation des filons. Des datations U/Pb de haute précision sur des cristaux de zircon et de baddeleyite ainsi que40Ar/39Ar sur des cris¬taux d'amphibole révèlent une initiation de la mise en place de PX1 il y a 22.1 ± 0,7 Ma; celle-ci a duré quelque 0,48 ± 0,22 à 0,52 ± 0,29 Ma. Ce laps de temps est compatible avec celui nécessaire à la cristallisation des filons individuels, qui va de moins d'une année lors de l'initiation du magmatisme à 5 ans lors du maximum d'activité de PX1. La présence de cristaux résorbés enregistrant une cristallisation complexe suggère l'existence d'une chambre mag¬matique convective sous-jacente à PX1 et périodiquement rechargée. Les compositions isotopiques des roches étu¬diées révèlent une source mantellique profonde de type point chaud avec une contribution du manteau lithosphéri- que métasomatisé présent sous les îles Canaries. Résumé L'intrusion mafique Miocène PX1 fait partie du soubassement superficiel (0.15-0.2 GPa, 1100 °Q d'un volcan d'île océanique. La particularité de ce pluton est l'existence d'alternances d'unités de gabbros et de pyroxénites qui met¬tent en évidence un litage magmatique vertical (NNE-SSW). Les horizons gabbroiques et pyroxénitiques sont constitués d'unités de différenciation métriques qui suggèrent tine mise en place par injections périodiques de filons verticaux de magma formant un complexe filonien. Chaque filon vertical a subi une différenciation parallèle à un front de solidification sub-vertical parallèle aux bords du filon. Les pyroxénites résultent du fractionnement et de l'accumulation d'olivine ± clinopyroxene ± plagioclase à partir d'un magma basaltique faiblement alcalin et sont interprétées comme étant des imités de différenciation tronquées dont le liquide interstitiel a été extrait par compaction. L'orientation préférentielle des clinopyroxènes dans ces pyroxe- nites (obtenues par analyse EBSD et micro-tomographique) révèle une composante de cisaillement simple dans la genèse de ces roches, ce qui confirme cette interprétation. La compaction des pyroxénites est probablement causée par a mise en place de filons de magma suivants. Le liquide interstitiel expulsé est probablement par ces derniers. Les clinopyroxènes des gabbros, montrent une composante de cisaillement pure suggérant qu'ils sont affectés par une déformation syn-magmatique parallèle aux zones de cisaillement NNE-SSW observées autour de PX1 et liées au contexte tectonique Miocène d'extension régionale. Ceci suggère que les gabbros sont liés à des taux de mise en place faibles à la fin de cycles d'activité magmatique et sont peu ou pas affectés par la compaction. L'initiation et la géométrie de PX1 sont donc contrôlées par le contexte tectonique régional d'extension alors que les taux et les volumes de magma dépendent de facteurs liés à la source. Des taux d'injection élevés résultent probable¬ment en une croissance du pluton supérieure à la place crée par cette extension. Dans ce cas de figure, la propagation des nouveaux dykes et l'inaptitude du magma à circuler à travers les anciens dykes cristallisés pourrait causer une augmentation de la pression non-lithostatique sur ces derniers, exprimée par un cisaillement simple et l'expulsion du liquide interstitiel qu'ils contiennent (documenté par les zones de collecte anorthositiques). Les compositions en éléments majeurs et traces des gabbros et pyroxenites de PX1 sont globalement homogènes et dépendent de la nature cumulative des échantillons. Cependant, de petites variations des concentrations en éléments traces ainsi que les teneurs en éléments traces des bordures de clinopyroxenes suggèrent que ces derniers ont subi un processus de rééquilibrage et de cristallisation in situ. L'homogénéité des compositions chimiques des échantillons, ainsi que la présence de grains de clinopyroxene résorbés suggère que le complexe filonien PX1 s'est mis en place au dessus d'une chambre magmatique périodiquement rechargée dans laquelle la convection est efficace. Chaque filon est donc issu d'un même magma, mais a subi une différenciation par cristallisation in situ (jusqu'à 70% de fraction¬nement) indépendamment des autres. Dans ces filons cristallisés, les minéraux cumulatifs subissent un rééquilibrage partiel avec les liquide interstitiel avant que ce dernier ne soit expulsé lors de la compaction (mettant ainsi un terme à la différenciation). Ce modèle de mise en place signifie qu'un minimum de 150Km3 de magma est nécessaire à la genèse de PX1, une partie de ce volume ayant été émis par le 'Central Volcanic Complex' de Fuerteventura. Les rapports isotopiques radiogéniques mesurés révèlent la contribution de trois pôles mantelliques dans la genèse du magma formant PX1. Le mélange de ces pôles HIMU, DMM et EM1 refléterai l'interaction du point chaud Cana¬rien avec un manteau lithosphérique hétérogène métasomatisé. Les petites variations de ces rapports et des teneurs en éléments traces au sein des faciès pourrait refléter des taux de fusion partielle variable de la source, résultant en un échantillonnage variable du manteau lithosphérique métasomatisé lors de son interaction avec le point chaud. Des datations U/Pb de haute précision (TIMS) sur des cristaux de zircon et de baddeleyite extraits de gabbros de PX1 révèlent que l'initiation de la cristallisation du magma a eu lieu il y a 22.10±0.07 Ma et que l'activité magmatique a duré un minimum de 0.48 à 0.52 Ma. Des âges 40Ar/39Ar obtenus sur amphibole sont de 21.9 ± 0.6 à 21.8 ± 0.3 Ma, identiques aux âges U/Pb. La combinaison de ces méthodes de datations, suggère que le temps maximum nécessaire à PX1 pour se refroidir en dessous de la température de fermeture de l'amphibole est de 0.8Ma. Ceci signifie que la durée de vie de PX1 est de 520 000 à 800 000 ans. La coexistence de cristaux de baddeleyite et de zircon dans un gabbro est attribuée à son interaction avec un fluide riche en C02 relâché par les carbonatites encaissantes lors du métamorphisme de contact généré par la mise en place de PX1 environ 160 000 ans après le début de sa mise en place. Les durées de vie obtenue sont en accord avec le modèle de mise en place suggérant une durée de cristallisation poux chaque filon allant de 1 an à 5 ans. Abstract The Miocene PX1 gabbro-pyroxenite intrusion (Fuerteventura, Canary Islands), is interpreted as the shallow-level feeder-zone (0.15-0.2 GPa and 1100-1120°C), to an ocean island volcano. The particularity of PX1 is that it displays a NNE-SSW trending vertical magmatic banding expressed by alternating gabbro and pyroxeriite sequences. The gabbro and pyroxenite sequences consist of metre-thick differentiation units, which suggest emplacement by pe¬riodic injection of magma pulses as vertical dykes that amalgamated, similarly to a sub-volcanic sheeted dyke com¬plex. Individual dykes underwent internal differentiation following a solidification front (favoured by a significant lateral/horizontal thermal gradient) parallel to the dyke edges. Pyroxenitic layers result from the fractionation and accumulation of clinopyroxene ± olivine ± plagioclase crystals from a mildly alkaline basaltic liquid and are interpre¬ted as truncated differentiation sequences, from which residual melts were extracted by compaction. Clinopyroxene mineral orientation in pyroxenites (evidenced by EBSD and micro X-ray tomography analysis) display a marked pure shear component, supporting this interpretation. Compaction and squeezing of the crystal mush is ascribed to the incoming and inflating magma pulses. The resulting expelled interstitial liquid was likely collected and erupted along with the magma flowing through the newly injected dykes. Gabbro sequences represent crystallised coalesced magma batches, emplaced at lower rates at the end of eruptive cycles, and underwent minor melt extraction as evi¬denced by clinopyroxene orientations that record a simple shear component suggesting syn-magmatic deformation parallel to observed NNF.-SSW trending shear-zones induced by the regional tensional Miocene stress-field. The initiation and geometry of PX1 is controlled by the regional extensional tectonic regime whereas rates and vo¬lumes of magma depend on source-related factors. High injection rates are likely to induce intrusion growth rates larger than could be accommodated by the regional extension. In this case, dyke tip geometry and the inability of magma to circulate through previously emplaced and crystallised dykes could result in an increase of non-lithostatic pressure on previously emplaced mushy dyke walls; generating strong pure-shear compaction and interstitial melt expulsion within the feeder-zone as recorded by the cumulitic pyroxenite bands and anorthositic collection zones. The whole-rock major and trace-element chemistry of PX1 gabbros and pyroxenites is globally homogeneous and controlled by the cumulate nature of the samples (i.e. on the modal proportions of olivine, pyroxene, plagioclase and oxides). However, small variations of whole-rock trace-element contents as well as trace-element contents of clinopyroxene rims suggest that in-situ re-equilibration and crystallisation has occurred. Additionally, the global homogeneity and presence of complex zoning of rare resorbed clinopyroxene crystals suggest that the PX1 feeder- zone overlies a periodically replenished and efficiently mixed magma chamber. Each individual dyke of magma thus originated from a compositionally constant mildly alkaline magma and differentiated independently from the others reaching up to 70% fractionation. Following dyke arrest these are affected by interaction with the trapped interstitial liquid prior to its compaction-linked expulsion (thus stopping the differentiation process). This emplacement model implies that minimum amount of approximately 150 km3 of magma is needed to generate PX1, part of it having been erupted through the overlying Central Volcanic Complex of Fuerteventura. The radiogenic isotope ratios of PX1 samples reveal the contribution on three end-members during magma genesis. This mixing of the H1MU, EMI and DMM end-members could reflect the interaction of the deep-seated Canarian mantle plume with a heterogeneous metasomatic and sepentininsed lithospheric mantle. Additionally, the observed trace-element and isotopic variations within the same fades groups could reflect varying degrees of partial melting of the source region, thus tapping more or less large areas of the metasomatised lithospheric mantle during interac¬tion with the plume. High precision ID-TIMS U/Pb zircon and baddeleyite ages from the PX1 gabbro samples, indicate initiation of magma crystallisation at 22.10 ± 0.07 Ma. The magmatic activity lasted a minimum of 0.48 to 0.52 Ma. 40Ar/39Ar amphibole ages are of 21.9 ± 0.6 to 21.8 ± 0.3, identical within errors to the U/Pb ages. The combination of the 40Ar/39Ar and U/Pb datasets imply that the maximum amount of time PX1 took to cool below amphibole Tc is 0.8 Ma, suggesting PX1 lifetime of 520 000 to 800 000 years. On top of this, the coexistence of baddeleyite and zircon in a single sample is ascribed to the interaction of PX1 with C02-rich carbonatite-derived fluids released from the host-rock carbonatites during contact metamorphism 160 000 years after PX1 initiation. These ages are in agreement with the emplacement model, implying a crystallisation time of less than 1 to 5 years for individual dykes.

Reliability and validity of nonverbal thin slices in social interactions

Four studies investigated the reliability and validity of thin slices of nonverbal behavior from social interactions including (1) how well individual slices of a given behavior predict other slices in the same interaction; (2) how well a slice of a given behavior represents the entirety of that behavior within an interaction; (3) how long a slice is necessary to sufficiently represent the entirety of a behavior within an interaction; (4) which slices best capture the entirety of behavior, across different behaviors; and (5) which behaviors (of six measured behaviors) are best captured by slices. Notable findings included strong reliability and validity for thin slices of gaze and nods, and that a 1.5 min slice from the start of an interaction may adequately represent some behaviors. Results provide useful information to researchers making decisions about slice measurement of behavior.

Speciation and Bioavailability Measurements of Environmental Plutonium Using Diffusion in Thin Films.

The biological uptake of plutonium (Pu) in aquatic ecosystems is of particular concern since it is an alpha-particle emitter with long half-life which can potentially contribute to the exposure of biota and humans. The diffusive gradients in thin films technique is introduced here for in-situ measurements of Pu bioavailability and speciation. A diffusion cell constructed for laboratory experiments with Pu and the newly developed protocol make it possible to simulate the environmental behavior of Pu in model solutions of various chemical compositions. Adjustment of the oxidation states to Pu(IV) and Pu(V) described in this protocol is essential in order to investigate the complex redox chemistry of plutonium in the environment. The calibration of this technique and the results obtained in the laboratory experiments enable to develop a specific DGT device for in-situ Pu measurements in freshwaters. Accelerator-based mass-spectrometry measurements of Pu accumulated by DGTs in a karst spring allowed determining the bioavailability of Pu in a mineral freshwater environment. Application of this protocol for Pu measurements using DGT devices has a large potential to improve our understanding of the speciation and the biological transfer of Pu in aquatic ecosystems.