Relating vesicle shapes in pyroclasts to eruption styles

Vesicles in pyroclasts provide a direct record of conduit conditions during explosive volcanic eruptions. Although their numbers and sizes are used routinely to infer aspects of eruption dynamics, vesicle shape remains an underutilized parameter. We have quantified vesicle shapes in pyroclasts from fall deposits of seven explosive eruptions of different styles, using the dimensionless shape factor , a measure of the degree of complexity of the bounding surface of an object. For each of the seven eruptions, we have also estimated the capillary number, Ca, from the magma expansion velocity through coupled diffusive bubble growth and conduit flow modeling. We find that Ω is smaller for eruptions with Ca 1 than for eruptions with Ca 1. Consistent with previous studies, we interpret these results as an expression of the relative importance of structural changes during magma decompression and bubble growth, such as coalescence and shape relaxation of bubbles by capillary stresses. Among the samples analyzed, Strombolian and Hawaiian fire-fountain eruptions have Ca 1, in contrast to Vulcanian, Plinian, and ultraplinian eruptions. Interestingly, the basaltic Plinian eruptions of Tarawera volcano, New Zealand in 1886 and Mt. Etna, Italy in 122 BC, for which the cause of intense explosive activity has been controversial, are also characterized by Ca 1 and larger values of Ω than Strombolian and Hawaiian style (fire fountain) eruptions. We interpret this to be the consequence of syn-eruptive magma crystallization, resulting in high magma viscosity and reduced rates of bubble growth. Our model results indicate that during these basaltic Plinian eruptions, buildup of bubble overpressure resulted in brittle magma fragmentation.National Science Foundation EAR-1019872National Science Foundation EAR-081033

Rapid ascent and emplacement of basaltic lava during the 2005–06 eruption of the East Pacific Rise at ca. 9°51′N as inferred from CO2 contents

© The Author(s), 2016. This is the author's version of the work and is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Earth and Planetary Science Letters 453 (2016): 152-160, doi:10.1016/j.epsl.2016.08.007.Eruption rates at the mid–ocean ridges (MORs) are believed to strongly control the morphology and length of lava flows emplaced along the ridge axis, and thus the structure and porosity of the upper oceanic crust. Eruption rate also represents one of the few tools to gain insight into the driving pressures within sub-ridge magmatic systems. As eruption rate is inferred to vary systematically along the global mid-ocean ridge, understanding of how to assess eruption rate in submarine systems and how it maps to observable features of the ridge axis would provide a powerful tool to understand Earth's largest magmatic system. Eruption rates at MORs are poorly constrained, however, because of a lack of direct observations, preventing the duration of an eruption to be quantified. This study uses decompression experiments of MORB samples and numerical modeling of CO2 degassing to reconstruct the timescales for magma ascent and lava emplacement during the 2005–06 eruption of the East Pacific Rise at ca. 9°51’N. Samples collected from the lava flow are all supersaturated in dissolved CO2 contents, but CO2 decreases with distance from the vent, presumably as a consequence of progressive CO2 diffusion into growing bubbles. Samples collected at the vent contain ~105 vesicles per cm3. Pieces of these samples were experimentally heated to 1225°C at high pressure and then decompressed at controlled rates. Results, plus those from numerical modeling of diffusive bubble growth, indicate that magma rose from the axial magma chamber to the seafloor in ≤1 hour and at a rate of ≥2–3 km hr-1. Our modeling, as validated by experimental decompression of MORB samples with ~106 vesicles cm-3, also suggests that CO2 degassed from the melt within ~10–100 minutes as the vesicular lava traveled ~ 1.7 km along the seafloor, implying a volumetric flow rate on order of 103–4 m3 s-1. Given an ascent rate of ≥0.2 m s-1, the width of a rectangular dike feeding the lava would have been ~1–2 meters wide. MORB samples from the Pacific ridge are generally more supersaturated in dissolved CO2 than those from slower spreading Atlantic and Indian ridges. Our results suggest that Pacific MORBs ascend to the seafloor faster than Atlantic or Indian MORBsThis project was partially funded by a grant to J.E.G. from the U.S. National Science Foundation (OCE-1333882).2017-08-2

Magma decompression rates during explosive eruptions of Kīlauea volcano, Hawai'i, recorded by melt embayments

The decompression rate of magma as it ascends during volcanic eruptions is an important but poorly constrained parameter that controls many of the processes that influence eruptive behaviour. In this study we quantify decompression rates for basaltic magmas using volatile diffusion in olivine-hosted melt tubes (embayments) for three contrasting eruptions of Kīlauea volcano, Hawai'i. Incomplete exsolution of H₂O, CO₂ and S from the embayment melts during eruptive ascent creates diffusion profiles that can be measured using microanalytical techniques, and then modelled to infer the average decompression rate. We obtain average rates of ~0.05-0.45 MPa s-1 for eruptions ranging from Hawaiian style fountains to basaltic subplinian, with the more intense eruptions having higher rates. The ascent timescales for these magmas vary from around ~5 to ~36 minutes from depths of ~2 to ~4 km respectively. Decompression-exsolution models based on the embayment data also allow for an estimate of the mass fraction of pre-existing exsolved volatiles within the magma body. In the eruptions studied this varies from 0.1-3.2 wt%, but does not appear to be the key control on eruptive intensity. Our results do not support a direct link between the concentration of pre-eruptive volatiles and eruptive intensity; rather they suggest that for these eruptions decompression rates are proportional to independent estimates of mass discharge rate. Although the intensity of eruptions is defined by the discharge rate, based on the currently available dataset of embayment analyses it does not appear to scale linearly with average decompression rate. This study demonstrates the utility of the embayment method for providing quantitative constraints on magma ascent during explosive basaltic eruptions

Stronger or longer: Discriminating between Hawaiian and Strombolian eruption styles

The weakest explosive volcanic eruptions globally, Strombolian explosions and Hawaiian fountaining, are also the most common. Yet, despite over a hundred years of observations, no classifications have offered a convincing, quantitative way of demarcating these two styles. New observations show that the two styles are distinct in their eruptive time scale, with the duration of Hawaiian fountaining exceeding Strombolian explosions by ∼300–10,000 s. This reflects the underlying process of whether shallow-exsolved gas remains trapped in the erupting magma or is decoupled from it. We propose here a classification scheme based on the duration of events (brief explosions versus prolonged fountains) with a cutoff at 300 s that separates transient Strombolian explosions from sustained Hawaiian fountains.The authors wish to acknowledge grants from NSF (EAR-0409303, 0810332, 1145159, 1427357) and ARRA (113153 via the Hawaiian Volcano Observatory), which funded this research.This is the accepted manuscript. The final version is available at http://dx.doi.org/10.1130/G37423.

Transient deformation associated with explosive eruption measured at Masaya volcano (Nicaragua) using Interferometric Synthetic Aperture Radar

Deformation caused by processes within a volcanic conduit are localised, transient, and therefore challenging to measure. However, observations of such deformation are important because they provide insight into conditions preceding explosive activity, and are important for hazard assessment. Here, we present measurements of low magnitude, transient deformation covering an area of ∼4 km2 at Masaya volcano spanning a period of explosive eruptions (30th April - 17th May 2012). Radial uplift of duration 24 days and peak displacements of a few millimetres occurred in the month before the eruption, but switched to subsidence ∼27 days before the onset of the explosive eruption on 30th of April. Uplift resumed during, and continued for ∼16 days after the end of the explosive eruption period. We use a finite element modelling approach to investigate a range of possible source geometries for this deformation, and find that the changes in pressurisation of a conduit 450 m below the surface vent (radius 160 m and length 700 m), surrounded by a halo of brecciated material with a Young’s modulus of 15 GPa, gave a good fit to the InSAR displacements. We propose that the pre-eruptive deformation sequence at Masaya is likely to have been caused by the movement of magma through a constriction within the shallow conduit system. Although measuring displacements associated with conduit processes remains challenging, new high resolution InSAR datasets will increasingly allow the measurement of transient and lower magnitude deformation signals, improving the method’s applicability for observing transitions between volcanic activity characterised by an open and a closed conduit system

Galektin-3 in der Interaktion von T Zellen und Tumorzellen

Galektin-3 ist ein b-Galaktosid-bindendes Protein, das je nach Lokalisation unterschiedlichste Funktionen aufweist. Eine immunsuppressive Funktion von Galektin-3 wird im Kontext der Tumorimmunologie diskutiert. Im Rahmen dieser Arbeit wurde der Einfluss von Galektin-3 in der Interaktion von Tumorzellen mit T Zellen, insbesondere den für eine Immuntherapie interessanten gammadelta T Zellen, untersucht. Insgesamt deuten die Ergebnisse dieser Arbeit darauf hin, dass Galektin-3 in der Tumorumgebung eine immunsuppressive Funktion besitzt. Die Ergebnisse legen allerdings nahe, dass die immunsuppressive Wirkung von Galektin-3 durch einen adoptiven Transfer in vitro expandierter Vgamma9Vdelta2 gammadelta T Zellen allein oder in Kombination mit bispezifischen Antikörpern überkommen werden könnte

Der Interleukin-1-Genkomplex in der Schizophrenie

Es gilt heute als gesichert, dass eine starke genetische Komponente in der Ätiologie der Schizophrenie vorliegt. In der vorliegenden Arbeit wurden in einer Fall-Kontroll-Assoziationsstudie drei genetische Polymorphismen in Genen des Interleukin-1-Genkomplexes auf eine mögliche Assoziation mit Schizophrenie untersucht: die Gene, die für die proinflammatorischen Interleukine Interleukin-1 alpha und Interleukin-1 beta kodieren, sowie das Gen, welches für den antiinflammatorischen Interleukin-1-Rezeptorantagonist kodiert. Dieser ist der natürlich vorkommende, endogene Gegenspieler von Interleukin-1. Seine biologische Funktion scheint in der Kontrolle des Ausmaßes der proinflammatorischen Interleukine zu liegen. Die in der vorliegenden Arbeit untersuchten Gene liegen innerhalb einer Genregion auf Chromosom 2p12-q22.1, die in einer groß angelegten Meta-Analyse als einziger Genabschnitt eine genomweite signifikante Kopplung erreichte (Lewis et al. 2003). Daher sind die Gene des Interleukin-1-Genkomplexes positionelle Kandidatengene in der Pathogenese der Schizophrenie. Außerdem sind die Interleukine deswegen sehr interessante Proteine für die Schizophrenie, da sie den Metabolismus von Neurotransmittern und die Hirnentwicklung beeinflussen sowie Informationen zwischen Zellen des peripheren Immunsystems und des zentralen Nervensystems vermitteln können. Im Blut, in der Zerebrospinalflüssigkeit sowie im präfrontalen Cortex schizophrener Patienten konnten veränderte Konzentrationen von IL-1 und IL-1RA im Vergleich zu Kontrollen beobachtet werden. Dies weist auf eine Dysregulation der Interleukine in der Schizophrenie hin. Da Anomalien bei der Hirnentwicklung, den Neurotransmittersystemen und dem Immunsystem als mögliche Pathomechanismen der Schizophrenie betrachtet werden, ist es durchaus vorstellbar, dass eine genetisch bedingte Störung in dem sensitiven Gleichgewicht zwischen pro- und antiinflammatorischen Interleukinen in der Schizophrenie zumindest teilweise krankheitsauslösend oder -beeinflussend sein kann. Für diese Fragestellung wurden Allel- und Genotypfrequenzen eines C-889T-Basenaustauschpolymorphismus im Promotor des Interleukin-1 alpha-Gens, eines C-511T-Basenaustauschpolymorphismus im Promotor des Interleukin-1 beta-Gens sowie eines variable number of tandem repeats (VNTR) -Polymorphismus im zweiten Intron des Interleukin-1-Rezeptorantagonist-Gens untersucht. In der vorliegenden Arbeit konnte keine Assoziation zwischen den untersuchten Polymorphismen der Gene des Interleukin-1 alpha und beta mit der Diagnose Schizophrenie festgestellt werden. Bei dem untersuchten Polymorphismus des IL-1RN konnte ein Trend in Richtung einer selteneren Häufigkeit des Allels 2 bei Schizophrenen nachgewiesen werden. Die Analyse von Haplotypen des IL-1-Genkomplexes auf Assoziation mit Schizophrenie ergab keinen Zusammenhang. Die vorliegenden Ergebnisse sprechen dafür, dass das seltenere Vorkommen des Allels 2 des IL-1RA bei den Schizophrenen einen Einfluss auf das Entstehungsrisiko der Schizophrenie haben könnte, indem es zu einer Verschiebung der sensitiven Balance des Interleukin-1-Genkomplexes zwischen pro- und antiinflammatorischen Interleukinen zugunsten der proinflammatorischen Interleukine führt. Dieser Befund bekräftigt die Hypothese, dass eine überschießende Aktivierung des Immunsystems in der Pathogenese der Schizophrenie eine Rolle spielen könnte. Außerdem weist er darauf hin, dass die Dysregulation der Interleukine bei den Schizophrenen zumindest teilweise genetisch bedingt sein könnte. Die Ergebnisse sprechen somit für eine mögliche schützende Rolle des Allels 2 des Interleukin-1-Rezeptorantgonisten vor der Entstehung der Schizophrenie. Dieser Befund wurde durch neuste Studien von Zanardini et al. (2003) und Bocchio-Chiavetto et al. (2002), in denen die Träger des IL-1RN Allel 2 signifikant seltener bei den Schizophrenen vertreten waren, unterstützt

To What Extent Can Individualisation in Terms of Different Types of Mode Improve Learning Outcomes and Learner Satisfaction? A Pre-study

With the latest technological developments and associated new possibilities in teaching, the personalisation of learning is gaining more and more importance. It assumes that individual learning experiences and results could generally be improved when personal learning preferences are considered. To do justice to the complexity of the personalisation possibilities of teaching and learning processes, we illustrate the components of learning and teaching in the digital environment and their interdependencies in an initial model. Furthermore, in a pre-study, we investigate the relationships between the learner\u27s ability to (digital) self-organise, the learner’s prior- knowledge learning in different variants of mode and learning outcomes as one part of this model. With this pre-study, we are taking the first step towards a holistic model of teaching and learning in digital environments

To What Extent Can Individualisation in Terms of Different Types of Mode Improve Learning Outcomes and Learner Satisfaction? A Pre-study

With the latest technological developments and associated new possibilities in teaching, the personalisation of learning is gaining more and more importance. It assumes that individual learning experiences and results could generally be improved when personal learning preferences are considered. To do justice to the complexity of the personalisation possibilities of teaching and learning processes, we illustrate the components of learning and teaching in the digital environment and their interdependencies in an initial model. Furthermore, in a pre-study, we investigate the relationships between the learner's ability to (digital) self-organise, the learner’s prior- knowledge learning in different variants of mode and learning outcomes as one part of this model. With this pre-study, we are taking the first step towards a holistic model of teaching and learning in digital environments