Episodic transport of discrete magma batches beneath Aso volcano

Magma ascent, storage, and discharge in the trans-crustal magmatic system are keys to long-term volcanic output and short-term eruption dynamics. How a distinct magma batch transports from a deep reservoir(s) to a pre-eruptive storage pool with eruptible magma remains elusive. Here we show that repetitive very-long-period signals (VLPs) beneath the Aso volcano are preceded by a short-lived (~50–100 s), synchronous deformation event ~3 km apart from the VLP source. Source mechanism of a major volumetric component (~50–440 m3 per event) and a minor low-angle normal-fault component, together with petrological evidence, suggests episodic transport of discrete magma batches from an over-pressured chamber roof to a pre-eruptive storage pool near the brittle-ductile transition regime. Magma ascent velocity, decompression rate, and cumulative magma output deduced from recurrent deformation events before recent 2014 and 2016 eruptions reconcile retrospective observations of the eruption style, tephra fallouts, and plume heights, promising real-time evaluation of upcoming eruptions.

Climbing Performance in U23 and Professional Cyclists during a Multi-stage Race

The aim of this study was to analyze climbing performance across two editions of a professional multistage race, and assess the influence of climb category, prior workload, and intensity measures on climbing performance in U23 and professional cyclists. Nine U23 cyclists (age 20.8±0.9 years) and 8 professional cyclists (28.1±3.2 years) participated in this study. Data were divided into four types: overall race performance, climb category, climbing performance metrics (power output, ascent velocity, speed), and workload and intensity measures. Differences in performance metrics and workload and intensity measures between groups were investigated. Power output, ascent velocity, speed were higher in professionals than U23 cyclists for Cat 1 and Cat 2 (p≤0.001–0.016). Workload and intensity measures (Worktotal, Worktotal∙km-1, Elevationgain, eTRIMP and eTRIMP∙km-1) were higher in U23 compared to professionals (p=0.002–0.014). Climbing performance metrics were significantly predicted by prior workload and intensity measures for Cat 1 and 2 (R2=0.27–0.89, p≤0.001–0.030) but not Cat 3. These findings reveal that climbing performance in professional road cycling is influenced by climb categorization as well as prior workload and intensity measures. Combined, these findings suggest that Cat 1 and 2 climbing performance could be predicted from workload and intensity measures.

GEODYNAMIC PROCESSES DURING ASCENT OF A PLUME WITH INTERMEDIATE THERMAL POWER THROUGH THE CONTINENTAL LITHOSPHERE AND DURING ITS ERUPTION ON THE SURFACE

The study is focused on thermochemical mantle plumes with intermediate thermal power (1.15 < Ka < 1.9). Previously we have shown that these plumes are diamondiferous. Based on the laboratory modeling data, the flow structure of a melt in a plume conduit is represented. A plume melts out and ascends from the core – mantle boundary to the bottom of the continental lithosphere. The plume roof moves upwards in the lithosphere because of melting of the lithospheric matter at the plume roof and due to the effect of superlithostatic pressure on the roof, which causes motion in the lithosphere block above the plume roof. The latter manifests itself by uplifting of the ground surface above the plume. As the plume ascends through the lithosphere, the elevation of the surface increases until the plume ascends to critical level xкр, where an eruption conduit is formed. In our model, plume ascent velocity uпл is the rate of melting at the plume roof. Values of uпл and the ascent velocity of a spherical plume roof due to superlithostatic pressure U are calculated. Relationships are found between these velocities and the plume roof depth. The dependence of the velocity of the surface’s rise on the dynamic viscosity of the lithosphere block above the plume is obtained. A relationship is determined between the maximum surface elevation and the lithosphere viscosity. The elevation values are determined for different times and different lithosphere viscosities.The results of laboratory modeling of flow structure at the plume conduit/eruption conduit interface are presented. The flow was photographed (1) in the plane passing through the axes of the plume conduit and the eruption conduit; and (2) in case of the line-focus beam perpendicular to the axial plane. The photographs were used for measuring the flow velocities in the plume conduit and the eruption conduit. Corresponding Reynolds numbers and flow regimes are determined. The relation of dynamic pressure in the eruption conduit to that in the plume conduit is found for intermediate-power plumes. The melt flow velocity in the eruption conduit depends on superlithostatic pressure on the plume roof, plume diameter and kinematic viscosity of the melt. Its values are determined for different kinematic viscosities of melt.

Динамика подъема скользящей дуги в униполярной лестнице Иакова

The authors created a device with a gliding unipolar arc of the Jacob’s ladder type. This paper presents investigation results of the arc ascent dynamics. It was found that the arc motion is uniform on the major part of its way. The arc ascent has the convection nature due to the air heating by the plasma. Dependence of the arc ascent velocity on the apex angle between the electrodes is obtained. The dependence is decreasing.

Modeling the Crystallization and Emplacement Conditions of a Basaltic Trachyandesitic Sill at Mt. Etna Volcano

This study documents the compositional variations of phenocrysts from a basaltic trachyandesitic sill emplaced in the Valle del Bove at Mt. Etna volcano (Sicily, Italy). The physicochemical conditions driving the crystallization and emplacement of the sill magma have been reconstructed by barometers, oxygen barometers, thermometers and hygrometers based on clinopyroxene, feldspar (plagioclase + K-feldspar) and titanomagnetite. Clinopyroxene is the liquidus phase, recording decompression and cooling paths decreasing from 200 to 0.1 MPa and from 1050 to 940 °C, respectively. Plagioclase and K-feldspar cosaturate the melt in a lower temperature interval of ~1000–870 °C. Cation exchanges in clinopyroxene (Mg-Fe) and feldspar (Ca-Na) indicate that magma ascent is accompanied by progressive H2O exsolution (up to ~2.2 wt. %) under more oxidizing conditions (up to ΔNNO + 0.5). Geospeedometric constraints provided by Ti–Al–Mg cation redistributions in titanomagnetite indicate that the travel time (up to 23 h) and ascent velocity of magma (up to 0.78 m/s) are consistent with those inferred for other eruptions at Mt. Etna. These kinetic effects are ascribed to a degassing-induced undercooling path caused principally by H2O loss at shallow crustal conditions. Rare earth element (REE) modeling based on the lattice strain theory supports the hypothesis that the sill magma formed from primitive basaltic compositions after clinopyroxene (≤41%) and plagioclase (≤12%) fractionation. Early formation of clinopyroxene at depth is the main controlling factor for the REE signature, whereas subsequent degassing at low pressure conditions enlarges the stability field of plagioclase causing trace element enrichments during eruption towards the surface.

Magnetic resonance imaging of water ascent in embolized xylem vessels of grapevine stem segments

Wang, M., Tyree, M. T. and Wasylishen, R. E. 2013. Magnetic resonance imaging of water ascent in embolized xylem vessels of grapevine stem segments. Can. J. Plant Sci. 93: 879–893. Temporal and spatial information about water refilling of embolized xylem vessels and the rate of water ascent in these vessels is critical for understanding embolism repair in intact living vascular plants. High-resolution 1H magnetic resonance imaging (MRI) experiments have been performed on embolized grapevine stem segments while they were subjected to refilling at two different applied water pressures in order to investigate these important aspects of embolism repair. Magnetic resonance imaging difference images show that vessels located near the bark tend to refill faster than do inner ones, suggesting that vessel position within the cross section of the stem may affect the refilling process within the vessel. An MRI method for determining the water ascent velocity in each individual embolized xylem vessel is presented. At ambient pressure, the water ascent velocity ranges from 0.0090 to 0.60 mm min−1, but increases to a range of 0.016 to 0.70 mm min−1 at 9.8 kPa above ambient pressure. A steady-state bubble model that offers analytical solutions of the water ascent velocity in embolized xylem vessels is presented; model calculations show that if other parameters are held constant, water ascent velocity is influenced by vessel diameter and position.

Simulation of Ascent Rule for the Individual Escape Suit

During the individual escape, free ascent is the only way to decompression. While the men are situated in the deep pressure, the velocity of ascent, the time of getting to balance become the most important factors for escape. The paper use mathematical methods, consult the hydrodynamics parameter which educed by experiment, simulate the ascent rule while the men are in the individual escape suit, and calculate the ascent velocity, acceleration, balance time of different weight, and compare the simulation result with the experiment , which can prove the veracity of simulation.