The last three eruptions at the Cordón Caulle volcanic complex, Chile, have been strikingly similar in that they have started with relatively short pre-eruptive warning and produced chemically ...homogeneous rhyolite to rhyodacite magma with glassy to aphyric texture. These characteristics collectively call for an understanding of the storage conditions leading to the rise and extraction of crystal-poor silicic magma from volcanoes. We have analyzed and experimentally reproduced the mineral assemblage and glass chemistry in rhyolite magma produced in the most recent eruption of Cordón Caulle, and we use these to infer magma storage and ascent conditions. Fe–Ti oxide mineral geothermometry suggests that the rhyolite was stored at ∼870–920 °C. At these temperatures, the phenocryst assemblage (plag∼An
37
> cpx + opx > mag + ilm) can be reproduced under H
2
O-saturated conditions of between 100 and 50 MPa, corresponding to crustal depths between about 2.5 and 5.0 km. The shallow and relatively hot magma storage conditions have implications for the rapid onset, degassing efficiency, and progression from explosive to mixed pyroclastic-effusive eruption style at Cordón Caulle.
The Surtsey Magma Series Schipper, C Ian; Jakobsson, Sveinn P; White, James D L ...
Scientific reports,
06/2015, Letnik:
5, Številka:
1
Journal Article
Recenzirano
Odprti dostop
The volcanic island of Surtsey (Vestmannaeyjar, Iceland) is the product of a 3.5-year-long eruption that began in November 1963. Observations of magma-water interaction during pyroclastic episodes ...made Surtsey the type example of shallow-to-emergent phreatomagmatic eruptions. Here, in part to mark the 50(th) anniversary of this canonical eruption, we present previously unpublished major-element whole-rock compositions, and new major and trace-element compositions of sideromelane glasses in tephra collected by observers and retrieved from the 1979 drill core. Compositions became progressively more primitive as the eruption progressed, with abrupt changes corresponding to shifts between the eruption's four edifices. Trace-element ratios indicate that the chemical variation is best explained by mixing of different proportions of depleted ridge-like basalt, with ponded, enriched alkalic basalt similar to that of Iceland's Eastern Volcanic Zone; however, the systematic offset of Surtsey compositions to lower Nb/Zr than other Vestmannaeyjar lavas indicates that these mixing end members are as-yet poorly contained by compositions in the literature. As the southwestern-most volcano in the Vestmannaeyjar, the geochemistry of the Surtsey Magma Series exemplifies processes occurring within ephemeral magma bodies on the extreme leading edge of a propagating off-axis rift in the vicinity of the Iceland plume.
Sex hormones and choice under risk Schipper, Burkhard C.
Journal of economic psychology,
June 2023, 2023-06-00, Letnik:
96
Journal Article
Recenzirano
Odprti dostop
We study the correlation of choice under risk in Holt–Laury lotteries for gains and losses with gender, the use of hormonal contraceptives, menstrual cycle information, salivary testosterone, ...estradiol, progesterone, and cortisol as well as the digit ratio (2D:4D; length of the index finger to the ring finger of the right hand) in more than 200 subjects (45% females). In males, salivary testosterone is negatively correlated with risk aversion for gains only. In females, salivary cortisol is positively correlated with risk aversion for gains only. No other significant correlations between risk preferences and salivary hormones are observed. No significant correlations between risk preferences and the menstrual cycle are observed in naturally cycling females. No significant correlations between risk preferences and the digit ratio are observed in either gender and/or race.
The main objective of the study is to determine if non-specific physical symptoms (NSPS) in people with self-declared sensitivity to radiofrequency electromagnetic fields (RF EMF) can be explained ...(across subjects) by exposure to RF EMF. Furthermore, we pioneered whether analysis at the individual level or at the group level may lead to different conclusions. By our knowledge, this is the first longitudinal study exploring the data at the individual level.
A group of 57 participants was equipped with a measurement set for five consecutive days. The measurement set consisted of a body worn exposimeter measuring the radiofrequency electromagnetic field in twelve frequency bands used for communication, a GPS logger, and an electronic diary giving cues at random intervals within a two to three hour interval. At every cue, a questionnaire on the most important health complaint and nine NSPS had to be filled out.
We analysed the (time-lagged) associations between RF-EMF exposure in the included frequency bands and the total number of NSPS and self-rated severity of the most important health complaint. The manifestation of NSPS was studied during two different time lags - 0–1 h, and 1–4 h - after exposure and for different exposure metrics of RF EMF. The exposure was characterised by exposure metrics describing the central tendency and the intermittency of the signal, i.e. the time-weighted average exposure, the time above an exposure level or the rate of change metric.
At group level, there was no statistically significant and relevant (fixed effect) association between the measured personal exposure to RF EMF and NSPS.
At individual level, after correction for multiple testing and confounding, we found significant within-person associations between WiFi (the self-declared most important source) exposure metrics and the total NSPS score and severity of the most important complaint in one participant. However, it cannot be ruled out that this association is explained by residual confounding due to imperfect control for location or activities. Therefore, the outcomes have to be regarded very prudently. The significant associations were found for the short and the long time lag, but not always concurrently, so both provide complementary information. We also conclude that analyses at the individual level can lead to different findings when compared to an analysis at group level.
•No correlation of electromagnetic fields (EMF) and health effects at group level•Significant within person correlation EMF and non specific physical symptoms•Time above a level of exposure and rate of change show correlations; TWA doesn't.
Unawareness, beliefs, and speculative trade Heifetz, Aviad; Meier, Martin; Schipper, Burkhard C.
Games and economic behavior,
January 2013, 2013-1-00, 20130101, Letnik:
77, Številka:
1
Journal Article
Recenzirano
Odprti dostop
We define a generalized state-space model with interactive unawareness and probabilistic beliefs. Such models are desirable for potential applications of asymmetric unawareness. Applying our ...unawareness belief structures, we show that the common prior assumption is too weak to rule out speculative trade in all states. Yet, we prove a generalized “No-speculative-trade” theorem according to which there cannot be common certainty of strict preference to trade. Moreover, we prove a generalization of the “No-agreeing-to-disagree” theorem.
► We define a generalized state-space model with interactive unawareness and probabilistic beliefs and show that non-trivial unawareness obtains in such models. ► We show that the common prior assumption is too weak to rule out speculative trade under unawareness in all states. ► We prove a generalized “No-speculative-trade” theorem according to which there cannot be common certainty of strict preference to trade. ► We prove a generalization of the “No-agreeing-to-disagree” theorem.
We offer new insights into how an explosive eruption can transition into an effusive eruption. Magma containing >0.2 wt% dissolved water has the potential to vesiculate to a porosity in excess of 80 ...vol.% at atmospheric pressure. Thus all magmas contain volatiles at depth sufficient to form foams and explosively fragment. Yet gas is often lost passively and effusive eruptions ensue. Magmatic foams are permeable and understanding permeability in magma is crucial for models that predict eruptive style. Permeability also governs magma compaction models. Those models generally imply that a reduction in magma porosity and permeability generates an increased propensity for explosivity.
Here, our experimental results show that surface tension stresses drive densification without creating an impermeable ‘plug’, offering an additional explanation of why dense magmas can avoid explosive eruption. In both an open furnace and a closed autoclave, we subject pumice samples with initial porosity of ∼70 vol.% to a range of isostatic pressures (0.1–11 MPa) and temperatures (350–950 °C) relevant to shallow volcanic environments. Our experimental data and models constrain the viscosity, permeability, timescales, and length scales over which densification by pore-scale surface tension stresses competes with density-driven compaction. Where surface tension dominates the dynamics, densification halts at a plateau connected porosity of ∼25 vol.% for our samples. SEM, pycnometry and micro-tomography show that in this process (1) microporous networks are destroyed, (2) the relative pore network surface area decreases, and (3) a remaining crystal framework enhances the longevity of macro-pore connectivity and permeability critical for sustained outgassing. We propose that these observations are a consequence of a surface tension-driven retraction of viscous pore walls at areas of high bubble curvature (micro-vesicular network terminations), and that this process drives bulk densification and permits continued outgassing. We propose a regime diagram of the relative dominance of surface tension and gravitational compaction that illustrates the interplay between viscosity, permeability, lengthscale and timescale. We contend that surface tension-driven magma densification is an as-yet overlooked phenomenon that extends our volcanological, geothermal and hydrothermal knowledge of how gas can escape densifying volcanic plugs and why dense lavas remain permeable.
•We offer an additional explanation as to how bubbly magma densifies to become lava.•Magmas can have the same permeability and different porosity, without necessitating cracking.•Our data demonstrates that surface tension can densify and deform magma.•Micro-tomography tracks and quantifies change in pore structure following experimentation.
The proximity of the major city of Arequipa to El Misti has focused attention on the hazards posed by the active volcano. Since its last major eruption in the fifteenth century, El Misti has ...experienced a series of modest phreatic eruptions and fluctuating fumarolic activity. Here, we present the first measurements of the compositions of gas emitted from the lava dome in the summit crater. The gas composition is found to be fairly dry with a H
2
O/SO
2
molar ratio of 32 ± 3, a CO
2
/SO
2
molar ratio of 2.7 ± 0.2, a H
2
S/SO
2
molar ratio of 0.23 ± 0.02 and a H
2
/SO
2
molar ratio of 0.012 ± 0.002. This magmatic gas signature with minimal evidence of hydrothermal or wall rock interaction points to a shallow magma source that is efficiently outgassing through a permeable conduit and lava dome. Field and satellite observations show no evolution of the lava dome over the last decade, indicating sustained outgassing through an established fracture network. This stability could be disrupted if dome permeability were to be reduced by annealing or occlusion of outgassing pathways. Continued monitoring of gas composition and flux at El Misti will be essential to determine the evolution of hazard potential at this dangerous volcano.
Unbeatable imitation Duersch, Peter; Oechssler, Jörg; Schipper, Burkhard C.
Games and economic behavior,
09/2012, Letnik:
76, Številka:
1
Journal Article
Recenzirano
Odprti dostop
We show that for many classes of symmetric two-player games, the simple decision rule “imitate-if-better” can hardly be beaten by any strategy. We provide necessary and sufficient conditions for ...imitation to be unbeatable in the sense that there is no strategy that can exploit imitation as a money pump. In particular, imitation is subject to a money pump if and only if the relative payoff function of the game is of the rock–scissors–paper variety. We also show that a sufficient condition for imitation not being subject to a money pump is that the relative payoff game is a generalized ordinal potential game or a quasiconcave game. Our results apply to many interesting examples of symmetric games including 2×2 games, Cournot duopoly, price competition, public goods games, common pool resource games, and minimum effort coordination games.
► We show that the simple decision rule “imitate-if-better” can hardly be beaten by any other strategy. ► This results holds for a large class of games. ► We provide necessary and sufficient conditions for imitation to be unbeatable.
Studies have demonstrated a higher risk of adverse outcomes among infants born or admitted during off-hours, as compared to office hours, leading to questions about quality of care provide during ...off-hours (weekend, evening or night). We aim to determine the relationship between off-hours delivery and adverse perinatal outcomes for subgroups of hospital births.
This retrospective cohort study was based on data from the Netherlands Perinatal Registry, a countrywide registry that covers 99% of all hospital births in the Netherlands. Data of 449,714 infants, born at 28 completed weeks or later, in the period 2003 through 2007 were used. Infants with a high a priori risk of morbidity or mortality were excluded. Outcome measures were intrapartum and early neonatal mortality, a low Apgar score (5 minute score of 0-6), and a composite adverse perinatal outcome measure (mortality, low Apgar score, severe birth trauma, admission to a neonatal intensive care unit).
Evening and night-time deliveries that involved induction or augmentation of labour, or an emergency caesarean section, were associated with an increased risk of an adverse perinatal outcome when compared to similar daytime deliveries. Weekend deliveries were not associated with an increased risk when compared to weekday deliveries. It was estimated that each year, between 126 and 141 cases with an adverse perinatal outcomes could be attributed to this evening and night effect. Of these, 21 (15-16%) are intrapartum or early neonatal death. Among the 3100 infants in the study population who experience an adverse outcome each year, death accounted for only 5% (165) of these outcomes.
This study shows that for infants whose mothers require obstetric interventions during labour and delivery, birth in the evening or at night, are at an increased risk of an adverse perinatal outcomes.
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