Dome Morphology Research Articles

Overview of the eruptions of Sinabung Volcano, 2010 and 2013–present and details of the 2013 phreatomagmatic phase

A small phreatic eruption of Sinabung Volcano, North Sumatra on 28 August 2010, at 18:30 local time marked the first eruption in the past ~1200years. The eruption took place from two small vents in the south crater area. Explosions and ash emissions from these vents generated multiple ash plumes that reached altitudes of up to 5km during early- to mid-September. By the end of September 2010, only low level steam plumes were visible and the alert level was reduced from Level 4 (highest) to Level 3. The 2010 eruption effectively ended at this time. Beginning two days after the initial 2010 eruption, activity of the eruption has been monitored continuously by a telemetered seismic network surrounding the volcano and by remotely sensed observations. This monitoring system was supplemented with a near-field continuous GPS network, beginning in February 2011. Persistent fumarolic emissions continued for almost 3years following the 2010 eruption, before a new eruption began on 15 September 2013. This eruption continues to the present. The ongoing eruption is divided into 5 major phases: 1) phreatomagmatic phase (July 2013–18 December 2013); 2) first dome and collapse phase with pyroclastic density currents (PDCs; block-and-ash flows and related surges) to south (18 December 2013–10 January 2014); 3) lava-flow and collapse phase (10 January 2014–mid-September 2014); 4) second lava dome and collapse phase with PDCs to south (mid-September 2014–July 2015); 5) lava dome collapse and ash explosion phase with PDCs to southeast and east (August 2015–present). The volcano erupted intermittently during the early phreatomagmatic phase with small vertical ash explosions. Then the eruption became increasingly vigorous with more repetitive and intense vertical ash explosions during late October through November. The first small pyroclastic density currents (PDCs) began on November 1. These pyroclastic flows descended the southeastern flank to a distance of 2km.Swarms of volcano-tectonic (VT) earthquakes and volcanic tremor lasting hours occurred repeatedly during the phreatomagmatic phase and some of these VT-swarms were followed by explosions. In early December 2013, during the transition between phreatomagmatic and dome-collapse phases, swarms of hybrid earthquakes took place preceding and accompanying dome growth. The first lava dome was observed in satellite images on 18 December near the main crater rim. Partial collapses of the dome produced PDCs beginning on 30 December. Growth of this first lava dome continued into January and was accompanied by additional collapses and PDCs. By about 10 January, the lava had transitioned from a summit dome morphology into a lava flow morphology. The resulting lava flow descended the southeast flank of the volcano, producing flow-front and marginal collapses with associated PCDs. One such flow-flank collapse on 2 February 2014 resulted in a PCD that killed 16. The lava flow phase continued through mid-September 2014, when a second summit lava dome began to grow and collapse, producing PDCs initially to the south and southeast, and then beginning in July 2015 to the east and southeast.The eruption of Sinabung resulted in major impacts on the population of the resort and farming area near the volcano and in the Ginting and Karo Regencies of North Sumatra. Local residents, having not experienced eruptions in their lifetimes, were initially curious and eager to receive any information about the eruption regardless of its source. Various institutions provided information with little coordination, resulting in confusion. With time communications have improved and communities and the responsible governments have become better prepared in dealing with the persistent eruption. The Government of Indonesia has provided funding to support villagers who lived within a 5km radius danger zone to stay in relocation camps as a permanent relocation area is being identified. Unfortunately, on 21 May 2016, 9 additional fatalities took place in the village of Gamber, within the danger zone, when a dome collapse sent a pyroclastic density current into the area.Throughout the eruption, the volcano has been monitored by the Indonesian Center for Volcanology and Geologic Hazard Mitigation (CVGHM) in partnership with the USGS-USAID Volcano Disaster Assistance Program and the Disaster Prevention Research Institute of Kyoto University. Monitoring techniques have included seismic, geodetic, gas, satellite and field observations, as well as occasional sampling of ash and lava for geochemical analyses. In this paper, we summarize key aspects of the monitoring data, their interpretations and their use in forecasting eruptive behavior and in issuance of alerts and warnings. More detailed interpretations of the monitoring data and their use are found in other papers of this special issue.

Magmatic degassing, lava dome extrusion, and explosions from Mount Cleveland volcano, Alaska, 2011–2015: Insight into the continuous nature of volcanic activity over multi-year timescales

Mount Cleveland volcano (1730m) is one of the most active volcanoes in the Aleutian arc, Alaska, but heightened activity is rarely accompanied by geophysical signals, which makes interpretation of the activity difficult. In this study, we combine volcanic gas emissions measured for the first time in August 2015 with longer-term measurements of thermal output and lava extrusion rates between 2011 and 2015 calculated from MODIS satellite data with the aim to develop a better understanding of the nature of volcanic activity at Mount Cleveland. Degassing measurements were made in the month following two explosive events (21 July and 7 August 2015) and during a period of new dome growth in the summit crater. SO2 emission rates ranged from 400 to 860td−1 and CO2/SO2 ratios were <3, consistent with the presence of shallow magma in the conduit and the observed growth of a new lava dome. Thermal anomalies derived from MODIS data from 2011 to 2015 had an average repose time of only 4days, pointing to the continuous nature of volcanic activity at this volcano. Rapid increases in the cumulative thermal output were often coincident with visual confirmation of dome growth or accumulations of tephra in the crater. The average rate of lava extrusion calculated for 9 periods of rapid increase in thermal output was 0.28m3s−1, and the total volume extruded from 2011 to 2015 was 1.9–5.8Mm3. The thermal output from the lava extrusion events only accounts for roughly half of the thermal budget, suggesting a continued presence of shallow magma in the upper conduit, likely driven by convection. Axisymmetric dome morphology and occasional drain back of lava into the conduit suggests low-viscosity magmas drive volcanism at Mount Cleveland. It follows also that only small overpressures can be maintained given the small domes and fluid magmas, which is consistent with the low explosivity of most of Mount Cleveland's eruptions. Changes between phases of dome growth and explosive activity are somewhat unpredictable and likely result from plugs that are related to the dome obtaining a critical dimension, or from small variations in the magma ascent rate that lead to crystallization-induced blockages in the upper conduit, thereby reducing the ability of magma to degas. We suggest the small magma volumes, slow ascent rates, and low magma viscosity lead to the overall lack of anomalous geophysical signals prior to eruptions, and that more continuous volcanic degassing measurements might lead to more successful eruption forecasting at this continuously-active open-vent volcano.

Mechanical behaviour of dacite from Mount St. Helens (USA): A link between porosity and lava dome extrusion mechanism (dome or spine)?

There is a rich diversity in lava dome morphology, from blocky domes and lobes to imposing spine and whaleback structures. The latter extrude via seismically active, gouge-rich conduit-margin faults, a manifestation of a brittle failure mode. Brittle versus ductile behaviour in volcanic rocks is known to be porosity dependent, and therefore offers a tantalising link between the properties of the material near the conduit margin and the extrusion mechanism (dome or spine). We test this hypothesis by complementing published data on the mechanical behaviour of dacites from the 2004–2008 spine-forming eruption at Mount St. Helens (MSH) with new data on dacite lavas collected from the 1980 dome. The 1980 dacite samples were deformed at room temperature under a range of pressures (i.e., depths) to investigate their mechanical behaviour and failure mode (brittle or ductile). Low-porosity dacite (porosity ~0.19) is brittle up to an effective pressure of 30MPa (depth ~1km) and is ductile at 40MPa (depth ~1.5km). High-porosity dacite (porosity~0.32) is ductile above an effective pressure of 5MPa (depth ~200m). Samples deformed in the brittle regime show well-developed (~1mm) shear fracture zones comprising broken glass and crystal fragments. Samples deformed in the ductile regime feature anastomosing bands of collapsed pores. The combined dataset is used to explore the influence of strain rate, temperature, and porosity on the mechanical behaviour and failure mode of dacite. A decrease in strain rate does not influence the strength of dacite at low temperature, but reduces strength at high temperature (850°C). Due to the extremely low glass content of these materials, such weakening is attributed to the increased efficiency of subcritical crack growth at high temperature. However, when strain rate is kept constant, temperature does not significant impact strength reflecting the highly crystallised nature of dacite from MSH. Dacite from the 2004–2008 eruption is stronger than 1980 dome material and remains brittle even at high effective pressures, a consequence of their low preserved porosities. Only the porous (porosity~0.32) 1980 dome material deformed in a ductile manner (i.e., no macroscopic shear fracture) at effective pressures relevant for edifice deformation. Spine formation typically involves the extrusion of low-porosity material along faults that envelop the magma-filled conduit (i.e., brittle deformation), suggesting that the extrusion mechanism (dome or spine) may be a consequence of slow ascent rates and efficient pre-eruptive outgassing. Well-outgassed, low-porosity (slow ascent rate) materials favour a brittle mode of failure promoting spine extrusion, while poorly-outgassed, high-porosity (fast ascent rate) materials result in blocky domes or lobes. A crystal content-porosity map for brittle (spine) versus ductile (blocky dome) behaviour demonstrates that the window for brittle deformation is small and offers an explanation as to why spine and whaleback structures are relatively rare in nature.

Airborne photogrammetry and geomorphological analysis of the 2001–2012 exogenous dome growth at Molodoy Shiveluch Volcano, Kamchatka

In 2001, after a six-year pause in extrusive activity, lava dome growth resumed at Molodoy Shiveluch Volcano. The new period of dome growth (2001–present) has morphological features that were uncommon during the previous periods of the dome formation (1980–1981, 1993–1995): numerous lava lobes and crease structures. Thus, the current dome growth is mostly of an exogenous type with short periods of endogenous growth that occurred in 2003, 2005, and 2010. Geomorphological interpretation of stereo photo images has revealed elements of the dome that are hardly distinguishable in single photographs. We have made detailed descriptions of the dome morphology covering all the dates of the available images. By using photogrammetric processing of aerial photographs, we created Digital Terrain Models and topographic maps of the lava dome and defined its volumes for 2001 (0.19km3), 2003 (0.47km3), 2005 (0.48km3), 2010 (0.54km3), and 2012 (0.63km3). We also defined other morphometric characteristics: absolute and relative heights, as well as the dimensions of the dome and its elements for the investigated period. Taking into account large partial failures of the dome in 2005 (>0.11km3) and 2010 (0.28km3), we suggest that the volume of the extruded material for the whole 1980–2012 period was no less than 1.02km3. The average extrusion rate over the 2001–2012 period exceeded 225,000 m3/day. The transition from endogenous to exogenous dome growth was possibly caused by change in extruded material physical properties due to an increase of SiO2. On the basis of geomorphological analysis of the current lava dome features, we suggest the possible process of the exogenous dome formation at Molodoy Shiveluch. The crease structures detected at Molodoy Shiveluch were classified into three groups according to their shapes: radial, bilaterally symmetrical, and irregular. These crease structures are morphologically similar to those formed at Unzen Volcano during the 1990–1995 eruption. Some revealed morphological features of the crease structures show that the role of gravity is insignificant in their formation. We assume that the crease structures at Molodoy Shiveluch were formed by inner stresses due to thermal and solidification gradients.

Cardiac standstill and circulatory flow arrest in surgical treatment of intracranial aneurysms: a historical review

Since the first surgery for an intracranial aneurysm in 1931, neurological surgeons have long strived to determine the optimal methods of surgical correction. Significant challenges of aneurysm clipping include intraoperative rupture and complex dome morphology. Hypothermia, cardiopulmonary bypass, pharmacologically induced hypotension, and cardiac standstill are a few of the methodologies historically and currently employed in the management of these issues. In the 1980s, significant advances in pharmacology and anesthesiology led to the use of agents such as adenosine for chemically induced hypotension and eventually complete circulatory arrest. Since the institution of the use of these agents, the traditional methods of circulatory arrest under conditions of hypothermia and cardiopulmonary bypass have fallen out of favor. However, there still exists a subset of technically difficult aneurysms for which cardiac standstill, both chemical and hypothermic, remains a viable therapeutic option. In this paper, the authors describe the history of cardiac standstill by both hypothermic and chemically induced means as well as provide examples in which these techniques are still necessary.

Efficient Reprogramming of Naïve-Like Induced Pluripotent Stem Cells from Porcine Adipose-Derived Stem Cells with a Feeder-Independent and Serum-Free System

Induced pluripotent stem cells (iPSCs) are somatic cells reprogrammed by ectopic expression of transcription factors or small molecule treatment, which resemble embryonic stem cells (ESCs). They hold great promise for improving the generation of genetically modified large animals. However, few porcine iPSCs (piPSCs) lines obtained currently can support development of cloned embryos. Here, we generated iPSCs from porcine adipose-derived stem cells (pADSCs), using drug-inducible expression of defined human factors (Oct4, Sox2, c-Myc and Klf4). Reprogramming of iPSCs from pADSCs was more efficient than from fibroblasts, regardless of using feeder-independent or feeder-dependent manners. By addition of Lif-2i medium containing mouse Lif, CHIR99021 and PD0325901 (Lif-2i), naïve-like piPSCs were obtained under feeder-independent and serum-free conditions. These successfully reprogrammed piPSCs were characterized by short cell cycle intervals, alkaline phosphatase (AP) staining, expression of Oct4, Sox2, Nanog, SSEA3 and SSEA4, and normal karyotypes. The resemblance of piPSCs to naïve ESCs was confirmed by their packed dome morphology, growth after single-cell dissociation, Lif-dependency, up-regulation of Stella and Eras, low expression levels of TRA-1-60, TRA-1-81 and MHC I and activation of both X chromosomes. Full reprogramming of naïve-like piPSCs was evaluated by the significant up-regulation of Lin28, Esrrb, Utf1 and Dppa5, differentiating into cell types of all three germ layers in vitro and in vivo. Furthermore, nuclear transfer embryos from naïve-like piPSCs could develop to blastocysts with improved quality. Thus, we provided an efficient protocol for generating naïve-like piPSCs from pADSCs in a feeder-independent and serum-free system with controlled regulation of exogenous genes, which may facilitate optimization of culture media and the production of transgenic pigs.

Enhanced Differentiation of Stem Cell Derived Cardiac Myocytes by Electronic Expression of IK1 Reveals an Atrial-Specific Kv1.5-Like Current

Human induced pluripotent stem cell derived cardiac myocytes (h-iPSC-CMs) are a major advance in drug safety testing and research into human cardiac electrophysiology. However, these cells have potential limitations when used for quantitative action potential (AP) analysis. These cells are a mixture of atrial and ventricular cell types, which can be distinguished, to some extent, by action potential (AP) morphology. However, the spontaneous activity of h-iPSC-CMs results in parameter variability and anomalous pharmacological responses, leading to cell misidentification. The spontaneous behavior is largely due to the absence of an IK1 inwardly rectifying potassium channel (IK1).We examined the effect of using an in silico interface to electronically express this missing IK1. An in silico interface was developed to express synthetic IK1 in cells under whole cell voltage clamp using a variant of the dynamic clamp approach. Electronic IK1 expression resulted in a stable physiological resting potential, eliminated spontaneous activity, reduced spontaneous early and delayed after depolarizations, and decreased AP variability. Stimulated APs had a rapid upstroke and spike and dome morphology, and the readily recognizable repolarization attributes of ventricular and atrial cells. When examining the late components of outward current, we found that APs classified on the basis of AP morphology as “atrial-like” had a significantly larger sustained outward Kv1.5-like component at +50 mV than “ventricular-like” APs (in pA/pF: 1.76 ± 0.47 (n=6) vs. 0.74 ± 0.07 (n=7), p 0.4). These data indicate that h-IPSC-CM myocytes with synthetic expression of IK1 can easily be differentiated into ventricular-like and atrial-like myocytes by AP morphology, and that atrial-like cells exhibit an atrial-specific current.

Electronic “expression” of the inward rectifier in cardiocytes derived from human-induced pluripotent stem cells

Human-induced pluripotent stem cell (h-iPSC)-derived cardiac myocytes are a unique model in which human myocyte function and dysfunction are studied, especially those from patients with genetic disorders. They are also considered a major advance for drug safety testing. However, these cells have considerable unexplored potential limitations when applied to quantitative action potential (AP) analysis. One major factor is spontaneous activity and resulting variability and potentially anomalous behavior of AP parameters. To demonstrate the effect of using an in silico interface on electronically expressed I(K1), a major component lacking in h-iPSC-derived cardiac myocytes. An in silico interface was developed to express synthetic I(K1) in cells under whole-cell voltage clamp. Electronic I(K1) expression established a physiological resting potential, eliminated spontaneous activity, reduced spontaneous early and delayed afterdepolarizations, and decreased AP variability. The initiated APs had the classic rapid upstroke and spike and dome morphology consistent with data obtained with freshly isolated human myocytes as well as the readily recognizable repolarization attributes of ventricular and atrial cells. The application of 1 µM of BayK-8644 resulted in anomalous AP shortening in h-iPSC-derived cardiac myocytes. When I(K1) was electronically expressed, BayK-8644 prolonged the AP, which is consistent with the existing results on native cardiac myocytes. The electronic expression of I(K1) is a simple and robust method to significantly improve the physiological behavior of the AP and electrical profile of h-iPSC-derived cardiac myocytes. Increased stability enables the use of this preparation for a controlled quantitative analysis of AP parameters, for example, drug responsiveness, genetic disorders, and dynamic behavior restitution profiles.

Overview of the 2006 eruption of Mt. Merapi

In the last part of the 20th century and the beginning of the 21st century, Mt. Merapi in Central-Java Indonesia erupted about every 2–5years. Most of the eruptions were low in explosivity, with VEI-3 or less. Eruptions usually involve the formation of a lava dome, either in the beginning or in the end of the eruptive episode.For the 2006 eruption, the precursory signal was first observed in the middle of the year 2005 with a decrease in EDM slope distances to points on the rim, an increase of seismicity and a possible increase of SO2 emissions. Those early events marked the beginning of a more continuous period of inflation, which led to the eruption.In total, the pre-eruption displacement of the southern rim reached at least 2.4m toward the measuring station in Kaliurang (KAL). From late April until June 2006, a lava dome grew on the summit with a volume that gradually increased until it reached about 4.1millionm3 in 38days. The total of erupted magma was about 5.3millionm3 dense-rock-equivalent (DRE). The dome subsequently collapsed in three steps from June 4 to June 14, leaving an open scar on its southeast side. In this paper we detail the changes of dome morphology that were monitored by taking successive photographs from similar positions. The eruption in 2006 marked a significant change in summit morphology, from west-southwestward opening during the 20th century to the currently southeast orientation. Also, an Mw 6.4 earthquake occurred on 26 May, midway through the eruption, which adds interesting questions about the relationship of the eruption and the earthquake.EDM data from 2006 and previous eruptions show that the summit remains inflated after each eruption, i.e., no significant deflation occurs following eruptions. The lack of post-eruption deflation suggests that magma remains in the shallow parts of the edifice after the eruption. As a result, the complex of summit lava domes and their intrusive roots grow with time and Merapi's rim and summit become progressively more unstable and prone to collapse.

Identification of structural controls in an active lava dome with high resolution DEMs: Volcán de Colima, Mexico

Monitoring the topography of active lava domes is critical for detecting changes that may trigger or influence collapse or explosive activity. Internal dome structure and conditions are more difficult to elucidate, but also play vital roles. Here, we describe the exposure (following an explosion) of significant scarps in the active dome at Volcán de Colima, Mexico, that are interpreted as evidence of brittle failure planes and a complex internal dome morphology. In the first use of automated 3D computer vision reconstruction techniques (structure‐from‐motion and multi‐view stereo, SfM‐MVS) on an active volcanic dome, we derive high resolution surface models from oblique and archive photographs taken with a consumer camera. The resulting 3D models were geo‐referenced using features identified in a web‐sourced orthoimage; no ground‐based measurements were required. In December 2010, the dome (2.14 × 106 m3) had a flat upper surface, reflecting an overall ductile emplacement regime. Between then and May 2011, a period of low explosivity was accompanied by a small volume loss (0.4 × 105 m3) and arcuate steps appeared in the dome surface, suggesting the presence of localized planes of weakness. The complex array of summit scarps was exposed following a significant explosion in June 2011, and is interpreted to be the surface expression of fault planes in the dome. The 1‐m resolution DEMs indicated that the region of greatest volume loss was not coincident with the assumed location of the conduit, and that heterogeneity within the dome may have been important during the June explosion.

Rheology of arc dacite lavas: experimental determination at low strain rates

Andesitic–dacitic volcanoes exhibit a large variety of eruption styles, including explosive eruptions, endogenous and exogenous dome growth, and kilometer-long lava flows. The rheology of these lavas can be investigated through field observations of flow and dome morphology, but this approach integrates the properties of lava over a wide range of temperatures. Another approach is through laboratory experiments; however, previous studies have used higher shear stresses and strain rates than are appropriate to lava flows. We measured the apparent viscosity of several lavas from Santiaguito and Bezymianny volcanoes by uniaxial compression, between 1,109 and 1,315 K, at low shear stress (0.085 to 0.42 MPa), low strain rate (between 1.1 × 10−8 and 1.9 × 10−5 s−1), and up to 43.7 % total deformation. The results show a strong variability of the apparent viscosity between different samples, which can be ascribed to differences in initial porosity and crystallinity. Deformation occurs primarily by compaction, with some cracking and/or vesicle coalescence. Our experiments yield apparent viscosities more than 1 order of magnitude lower than predicted by models based on experiments at higher strain rates. At lava flow conditions, no evidence of a yield strength is observed, and the apparent viscosity is best approached by a strain rate- and temperature-dependent power law equation. The best fit for Santiaguito lava, for temperatures between 1,164 and 1,226 K and strain rates lower than 1.8 × 10−4 s−1, is $$ \log {\eta_{\text{app}}} = - 0.738 + 9.24 \times {10^3}{/}T(K) - 0.654 \cdot \log \dot{\varepsilon } $$ where η app is apparent viscosity and $$ \dot{\varepsilon } $$ is strain rate. This equation also reproduced 45 data for a sample from Bezymianny with a root mean square deviation of 0.19 log unit Pa s. Applying the rheological model to lava flow conditions at Santiaguito yields calculated apparent viscosities that are in reasonable agreement with field observations and suggests that internal shear heating may be significant ongoing heat source within these flows, enabling highly viscous lava to travel long distances.

Structure of the Rambler Rhyolite, Baie Verte Peninsula, Newfoundland: Inversions using UBC-GIF Grav3D and Mag3D

Hosted within the Pacquet Harbour Group (PHG) on the Baie Verte Peninsula of north-central Newfoundland, the Rambler rhyolite is a 487 Ma unit of felsic tuffs , flows and subvolcanic intrusive rocks. The PHG has been affected by multiple phases of deformation with the youngest D 4 deformation event producing broad northeast plunging upright cross folds in the Rambler rhyolite. Fold culminations on the upper bounding surface of the rhyolite host Cu +/− Au volcanogenic massive sulfide deposits (e.g. Rambler and Ming mines). Geophysical inversions of recently acquired high resolution gravity and magnetic data have been implemented to determine the extent of the fold axis (dome) at depth. To direct the outcome of the inversion process towards a more geologically reasonable solution this study outlines a procedure which permits the inclusion of known geological and geophysical constraints into the input (reference) model for inversion using the MAG3D and GRAV3D algorithms provided by the University of British Columbia Geophysical Inversion Facility. Reference model constraints included surficial geological contacts as defined by aeromagnetic data , and subsurface distribution of physical property variations from a series of drill-hole logs. The output (computed) model images the surface of the rhyolite dome as dipping roughly 40° to the northeast as a series of voxels with density values ranging from 2.71 to 2.75 g/cm 3 . While previously published ore deposit models parallel this structure in the near surface, results from these inversions suggest deeper exploration may be favorable. Magnetic inversion modeling has not provided any insight into dome morphology however it outlines the distribution of gabbroic dykes surrounding the dome. ► We present geologically constrained inversion models of the Rambler mining camp. ► Known geologic bounds and physical property ranges were included in the input mesh. ► Complimentary gravity and magnetic inversions outline the main lithological units. ► The two inversions image adjacent antiformal and synformal structures. ► The ore horizon has a direct association with the locus of the fold axes.

The J Wave Syndromes and Their Role in Sudden Cardiac Death

The electrocardiographic J wave, also referred as the Osborn wave, is a deflection with a dome or hump morphology at the junction between the QRS complex and the ST segment on the body surface ECG. Earlier studies attributed the J wave to a variety of factors including hypoxia, injury current, acidosis, delayed ventricular depolarization, and early ventricular repolarization.1 Clinical and arrhythmogenic significance of the J wave abnormalities had largely been ignored until 1996 when Yan and Antzelevitch published a study elucidating the ionic and cellular basis of the J wave, indicating that a prominent Ito-mediated action potential notch in ventricular epicardium but not endocardium may produce a transmural voltage gradient during early ventricular repolarization that could register as a J wave or J point elevation in the ECG.2 Growing evidence has since been advanced indicating that J wave abnormalities, which are often accompanied by early repolarization and ST segment elevation on the ECG, are in some cases associated with a risk of sudden cardiac death. The J wave syndromes, which represent a variable spectrum of phenotypic expression with accentuation of the J wave, can be inherited or acquired.3–6 This review attempts to summarize current knowledge about J-wave syndromes- linking bench work with the bedside.

Rhyolitic phreatomagmatism explored: Tepexitl tuff ring (Eastern Mexican Volcanic Belt)

Rhyolitic Tepexitl tuff ring in the Serdán-Oriental Basin of the eastern Trans-Mexican Volcanic Belt is a young, well-preserved circular crater — a simple morphology that belies a more complex eruptive history. Field observations, ash studies (granulometry, componentry, and morphology) and volatile data (LOI and XRF) allow the broad division of the Tepexitl deposits into two sequences: a lower sequence characterized by fine-grained deposits with abundant bomb and lapilli sags, and an upper sequence of coarse-grained deposits that show little to no deformation. The early eruptions at Tepexitl are interpreted to have been dominated by discrete, highly efficient, phreatomagmatic blasts, which caused a progressive deepening of the eruptive center (lower sequence), followed by a transition to dominantly magmatic behavior in the upper sequence. Dome growth occurred at the end of the eruption, but subsequent retrogressive explosions triggered by external water destroyed all trace of the original dome morphology. Molten fuel-coolant interaction (MFCI) is commonly thought to cause the repetitive water–magma interaction in phreatomagmatic eruptions, but a process by which magma and viscous felsic magmas can mingle prior to explosive interaction has not been described. A viable mechanism for rhyolitic MFCI, based upon field work at Tepexitl and laboratory experiments, requires that fluidized sediments intrude marginal fractures in the rhyolite magma, creating enough interfacial surface area to initiate phreatomagmatic explosions from within the interior of a rising plug or dome.

Co-7% Ir Soft Magnetic Intermediate Layer for Perpendicular Media

The current perpendicular magnetic recording (PMR) media uses a non-magnetic dual Ru intermediate layer. Replacing the bottom Ru layer with a Co-7at% Ir soft magnetic crystalline interlayer is expected to enhance both the magnetic field strength and gradient. Fabrication processing parameters were varied to develop the CoIr layer with desired properties (soft magnetic properties, texture, and dome morphology) to be utilized in practical PMR media design. First, the oxide was added to create a magnetically grain-to-grain isolated structure and the well segregated microstructure was obtained. Secondly, CoIr without the oxide was deposited on amorphous Ta and confirmed to have the hcp (00.2) texture and 5 nm Ru on top develops the hcp (00.2) texture epitaxially. The recording layer properties were not deteriorated with the replacement of Ru bottom layer with CoIr. The feasibility of CoIr application in the current PMR media will be discussed based on the experimental results.

Analysis of Venusian steep‐sided domes utilizing stereo‐derived topography

The morphology and topography of 23 Venusian steep‐sided domes are analyzed to examine possible emplacement mechanisms. Stereo radargrammetric techniques are used with Magellan synthetic aperture radar image data (∼100 m resolution) to generate digital elevation models for the domes (∼1 km horizontal resolution). Heights of the domes range from 390 to 1590 m, aspect ratios (height/diameter) range from 0.01 to 0.07, and volumes range from 73 to 1790 km3. Dome morphology varies along a continuous trend that is directly related to the aspect ratio. Domes with a low aspect ratio tend to be sunken in their centers, whereas domes with higher aspect ratios have flat to convex surfaces. Domes with the highest aspect ratios have central peaks. These trends are likely due to slight variations in the thickness of the crust and, possibly, effusion rates. Episodic emplacement is also inferred to be a significant process for the formation and growth of some of the domes in this sample.

Do Mouse Epicardial Action Potentials Present Phase 2?

Mouse ventricular action potentials (AP) recorded from acute dissociated cardiac myocytes lacks of phase 2. In order to evaluate if this is always true for all the muscular layers within the ventricular wall, we decided to perform optical and electrophysiological experiments to evaluate the time course of APs in the subepicardial layer of intact perfuse mouse hearts. Epicardial APs show a typical spike and dome morphology present in other non-rodent mammalian species. The APs recorded optically by means of Pulsed Local Field Fluorescence Microscopy and the potentiometric dye Di-8-Anneps show a very similar time course when compared to the one obtained with microelectrodes. However, the phase 2 of the optically recorded APs is more depolarized in comparison with the electrically recorded one suggesting a larger contribution of the t-system to the epicardial APs. In order to evaluate the molecular mechanisms involved in the genesis of phase 2 APs in mouse epicardium we performed experiments to evaluate the role of intracellular Ca2+ release on the time course of APs. Interestingly, both ryanodine/thapsigargin treatment and perfusion with caffeine significantly decreased the contribution of phase 2 to the APs. Finally we evaluate the hypothesis that intracellular Ca2+ is traduced in AP changes by an activation of influx of Na+ through the Na Ca exchanger in the forward mode. Experiments where extracellular Na+ was replaced by increasing concentration of Li+ induce a significant decrease of the AP phase 2. Moreover, two known blockers, KB-R7943 (KBR) and SEA0400 (SEA) also dramatically decrease the contribution of phase 2 to the AP time course. Our results indicate that mouse epicardial AP displays a significant phase 2 that is generated by an influx of Na through the Na Ca exchanger. Supported by NIH R01-HL-084487 to AE.

A novel crystalline soft magnetic intermediate layer for perpendicular recording media

In order to improve the recording efficiency in current perpendicular recording media, it is important to reduce the distance from the head to soft underlayer. In this paper, a soft magnetic intermediate layer is proposed to partially replace the presently used Ru intermediate layer. The new soft magnetic intermediate layer serves two purposes, which are as follows: (1) to decrease the thickness of the nonmagnetic Ru intermediate layer by providing a proper crystalline texture and surface morphology for the optimal crystalline grain growth of the magnetic storage layer on top and (2) to act as an additional soft magnetic underlayer that is closer to the head air bearing surface to enhance the recording performance. The prototypes of the soft magnetic intermediate layer consists of CoIr:SiO2/CoPt:SiO2/NiW multilayer structure. CoIr and CoPt were chosen because both have the hcp structure but the opposite sign for K1. A zero effective magnetoanisotropy of a composite grain is accomplished by varying the thickness ratio of each layer of CoIr and CoPt. The developed multilayer film shows the hcp (00.2) orientation with a dome morphology for facilitating the growth of the top magnetic storage layer as well as soft magnetic properties (K1=6.8×105 erg/cc).

ASTER and field observations of the 24 December 2006 eruption of Bezymianny Volcano, Russia

An explosive eruption occurred at Bezymianny Volcano (Kamchatka Peninsula, Russia) on 24 December 2006 at 09:17 (UTC). Seismicity increased three weeks prior to the large eruption, which produced a 12–15 km above sea level (ASL) ash column. We present field observations from 27 December 2006 and 2 March 2007, combined with satellite data collected from 8 October 2006 to 11 April 2007 by the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER), as part of the instrument's rapid-response program to volcanic eruptions. Pixel-integrated brightness temperatures were calculated from both ASTER 90 m/pixel thermal infrared (TIR) data as well as 30 m/pixel short-wave infrared (SWIR) data. Four days prior to the eruption, the maximum TIR temperature was 45 °C above the average background temperature (−33 °C) at the dome, which we interpret was a precursory signal, and had dropped to 8 °C above background by 18 March 2007. On 20 December 2006, there was also a clear thermal signal in the SWIR data of 128 °C using ASTER Band 7 (2.26 μm). The maximum SWIR temperature was 181 °C on the lava dome on 4 January 2007, decreasing below the detection limit of the SWIR data by 11 April 2007. On 4 January 2007 a hot linear feature was observed at the dome in the SWIR data, which produced a maximum temperature of 700 °C for the hot fraction of the pixel using the dual band technique. This suggests that magmatic temperatures were present at the dome at this time, consistent with the emplacement of a new lava lobe following the eruption. The eruption also produced a large, 6.5 km long by up to 425 m wide pyroclastic flow (PF) deposit that was channelled into a valley to the south–southeast. The PF deposit cooled over the following three months but remained elevated above the average background temperature. A second field investigation in March 2007 revealed a still-warm PF deposit that contained fumaroles. It was also observed that the upper dome morphology had changed in the past year, with a new lava lobe having in-filled the crater that formed following the 9 May 2006 eruption. These data provide further information on effusive and explosive activity at Bezymianny using quantitative remote sensing data and reinforced by field observations to assist in pre-eruption detection as well as post-eruption monitoring.

Geomorphology, Sedimentary Structures, and Genesis of Dome Dunes in Western Canada

Dome dunes in four stabilized, inland dune fields in western Canada are predominantly composed of horizontal to low-angle cross-strata, indicating that slip face development was rare. Dip angles of lee side deposits decrease upward in the dome dunes. The spread of dip directions increases with elevation in the dunes, spanning 360° for topset deposits. Sedimentary structures indicative of moisture (adhesion laminae) and vegetation (scour surfaces) occur in the dunes and denivation features are also present. Sediment adhesion is responsible for the maintenance of the dome morphology. Sediment sorting within the dome dunes is poorer than in other local dune types in the vicinity, suggesting that less reworking/ineffective selective transport occurred and that the dome dunes are more efficient in retaining sediment. The rarity of slip face and grainfall deposits and the abundance of low angle deposits indicate that preferential accumulation of sediment at the top of the lee side did not occur. Development of domal morphology is a consequence of the inhibition of slip face development. In inland, relatively moist boreal environments, the primary factor limiting or precluding sediment accumulation at the crest of the dunes is a low rate of sedimentation.