scholarly journals Configurational energy and the formation of mixed flowing/powder snow and ice avalanches

2016 ◽  
Vol 57 (71) ◽  
pp. 179-188 ◽  
Author(s):  
Perry Bartelt ◽  
Othmar Buser ◽  
Cesar Vera Valero ◽  
Yves Bühler
Keyword(s):  
Flow Density ◽  
Configurational Energy ◽  
The Core ◽  
Base Camp ◽  
Avalanche Flow ◽  
Particle Ensemble ◽  
Flowing Powder ◽  
Powder Avalanche ◽  
Air Compression ◽  
Snow And Ice

Abstract.A long-standing problem in avalanche dynamics is to model the flow of a mixed flowing/powder avalanche. Here we use the thermodynamic concept of configurational energy to describe the blow-out of air from the avalanche core. Configurational energy is the mean potential energy associated with the location of snow and ice particles in the avalanche core. As such, configurational energy determines the avalanche flow density. Expansion of the particle ensemble reduces the flow density and leads to the intake of air. Compression of the particle ensemble causes the blow-out of the intaken air, now laden with ice dust. Once formed, the cloud moves independently of the flowing avalanche with the initial momentum acquired in the core. Configurational energy changes in the avalanche core are therefore intimately related to the formation of the powder suspension cloud. In this paper we use the concept of configurational energy to predict the mass of air taken into and blown out of the core. This requires calculating the dispersive pressure arising from random particle movements and configuration changes related to the expansion and collapse of the flowing particle ensemble. The ice avalanche that struck the Everest base camp on 25 April 2015 is simulated using the proposed concept.

scholarly journals Avalanche Impact Pressures on Structures with Upstream Pile-Up/Accumulation Zones of Compacted Snow

2018 ◽  
Author(s):  
Perry Bartelt ◽  
Andrin Caviezel ◽  
Sandro Degonda ◽  
Othmar Buser
Keyword(s):  
Snow Avalanche ◽  
Flow Density ◽  
Accumulation Process ◽  
Pile Up ◽  
Wet Snow ◽  
Upstream Direction ◽  
Flow Deceleration ◽  
Braking Distance ◽  
Avalanche Flow

Abstract. Existing methods to calculate snow avalanche impact pressures on rigid obstacles are based on the assumption of no upslope pile-up of snow behind the structure at impact. Here we develop a method to predict avalanche impact pressures that accounts for the compaction and accumulation process. We show why this process leads to large impact pressures even at low avalanche approach velocities. The induced pressure depends on the incoming avalanche flow density relative to the ultimate compaction density because this determines the avalanche braking distance and therefore the flow deceleration in the upstream direction. The pile-up/accumulation process induces two additional pressures: (1) the static pressure of the pile-up zone and (2) the tractive stresses operating on the shear planes interfacing the accumulated and still moving avalanche snow. We demonstrate the use of the model on two theoretical examples and one real case study. Avalanche mitigation in maritime regions, or regions undergoing climate change with increasing wet snow avalanche activity, should consider the forces caused by the pile-up/accumulation process in engineering design.

scholarly journals FEATURES OF THE STONE-ICE AVALANCHE IN THE REGION OF DEVDORAK GLACER ON MAY 17, 2014 ON THE INSTRUMENTAL DATA OF THE KARMADON PARAMETRIC RANGE

2017 ◽  
Author(s):  
В.Б. Заалишвили ◽  
Д.А. Мельков
Keyword(s):  
Energy Release ◽  
Temporal Analysis ◽  
The Caucasus ◽  
Instrumental Data ◽  
Natural Processes ◽  
The Core ◽  
Observational Network ◽  
Avalanche Flow ◽  
Instrumental Monitoring ◽  
Ice Avalanche

В связи с активизацией опасных природных процессов на Кавказе и, в частности, сходом ледника Колка 20 сентября 2002 года, в сентябре 2003 года было сформировано ядро сети комплексных наблюдений «Кармадонский параметрический полигон». Главным назначением новой сети являлся инструментальный мониторинг опасных геологических природно-техногенных процессов в регионе. Сетью зарегистрирован обвал массы льда и горных пород в районе Девдоракского ледника 17 мая 2014 года и движение образовавшейся каменно-ледовой лавины. Были построены диаграммы энерговыделения и выполнен спектрально-временной анализ записей для ближайших станций Колка и Кармадон. Отмечены общие закономерности движения с событием 20 сентября 2002 года на леднике Колка, выполнен расчет возможных скоростей движения лавинообразного потока. In connection with the activation of dangerous natural processes in the Caucasus and in particular the fall of the Kolka glacier on September 20, 2002, the core of the complex observational network «Karmadon Parametric Range» was formed in September 2003. The main purpose of the new network was instrumental monitoring of dangerous geological natural and man-caused processes in the region. The network recorded a collapse of the mass of ice and rocks in the region of the Devdorak glacier on May 17, 2014 and the movement of the formed stone-ice avalanche. The diagrams of energy release were calculated and a spectral-temporal analysis of the records for the nearest Kolka and Karmadon stations was performed. The general regularities of the movement with the event on September 20, 2002 on the Kolka Glacier are noted, the possible velocities of the avalanche flow are calculated.

scholarly journals Brief Communication: Dynamic magnification factors for tree blow-down by powder snow avalanche air blasts

2017 ◽  
Author(s):  
Perry Bartelt ◽  
Peter Bebi ◽  
Thomas Feistl ◽  
Othmar Buser ◽  
Caviezel Andrin
Keyword(s):  
Flow Velocity ◽  
Short Duration ◽  
Snow Avalanche ◽  
Blow Down ◽  
Air Blast ◽  
Magnification Factors ◽  
Avalanche Flow ◽  
Powder Avalanche ◽  
Root Plate ◽  
Air Blasts

Abstract. We study how short duration powder avalanche blasts can break and overturn tall trees. Tree blow-down is often used to back-calculate avalanche pressure and therefore constrain avalanche flow velocity and motion. We find that tall trees are susceptible to avalanche air blasts because the duration of the air blast is near to the period of vibration of tall trees, both in bending and root-plate overturning. Dynamic magnification factors for bending and overturning failures should therefore be considered when back-calculating avalanche impact pressures.

scholarly journals Dynamic magnification factors for tree blow-down by powder snow avalanche air blasts

2018 ◽  
Vol 18 (3) ◽  
pp. 759-764 ◽  
Author(s):  
Perry Bartelt ◽  
Peter Bebi ◽  
Thomas Feistl ◽  
Othmar Buser ◽  
Andrin Caviezel
Keyword(s):  
Flow Velocity ◽  
Short Duration ◽  
Snow Avalanche ◽  
Blow Down ◽  
Air Blast ◽  
Magnification Factors ◽  
Avalanche Flow ◽  
Powder Avalanche ◽  
Root Plate ◽  
Air Blasts

Abstract. We study how short duration powder avalanche blasts can break and overturn tall trees. Tree blow-down is often used to back-calculate avalanche pressure and therefore constrain avalanche flow velocity and motion. We find that tall trees are susceptible to avalanche air blasts because the duration of the air blast is near to the period of vibration of tall trees, both in bending and root-plate overturning. Dynamic magnification factors for bending and overturning failures should therefore be considered when back-calculating avalanche impact pressures.

scholarly journals Measurement of snow particle size and velocity in avalanche powder clouds

2017 ◽  
Vol 63 (238) ◽  
pp. 249-257 ◽  
Author(s):  
YOICHI ITO ◽  
FLORENCE NAAIM-BOUVET ◽  
KOUICHI NISHIMURA ◽  
HERVÉ BELLOT ◽  
EMMANUEL THIBERT ◽  
...  
Keyword(s):  
Particle Size ◽  
Settling Velocity ◽  
Test Site ◽  
The Core ◽  
Large Particles ◽  
Ultrasonic Anemometer ◽  
Particle Speed ◽  
Avalanche Flow ◽  
Surface Particle ◽  
Snow Particle

ABSTRACTParticle size, particle speed and airflow speed have been measured in the powder snow clouds of avalanches to investigate the suspension and transportation processes of snow particles. The avalanches were artificially triggered at the Lautaret full-scale avalanche test-site (French Alps) where an ultrasonic anemometer and a snow particle counter were setup in an avalanche track for measurements. Relatively large particles were observed during passage of the avalanche head and then the size of the particles slightly decreased as the core of the avalanche passed the measurement station. The particle size distribution was well fitted by a gamma distribution function. A condition for suspension of particles within the cloud based on the ratio of vertical velocity fluctuation to particle settling velocity suggests that the large particles near the avalanche head are not lifted up by turbulent diffusion, but rather ejected by a process involving collisions between the avalanche flow and the rough snow surface. Particle speeds were lower than the airflow speed when large particles were present in the powder cloud.

What face familiarity feelings say about the lateralization of specific entities within the core system

2019 ◽  
Vol 42 ◽  
Author(s):  
Guido Gainotti
Keyword(s):  
Temporal Lobe ◽  
Memory System ◽  
Core System ◽  
The Core ◽  
Memory Traces ◽  
Specific Memory ◽  
Target Article ◽  
Temporal Structures ◽  
The Right

Abstract The target article carefully describes the memory system, centered on the temporal lobe that builds specific memory traces. It does not, however, mention the laterality effects that exist within this system. This commentary briefly surveys evidence showing that clear asymmetries exist within the temporal lobe structures subserving the core system and that the right temporal structures mainly underpin face familiarity feelings.

A scanning electron microscopic study on dissolving process of cholesterol gallstones by chenodeoxycholic acid (CDCA)

1978 ◽  
Vol 36 (2) ◽  
pp. 522-523
Author(s):  
T. Kanetaka ◽  
M. Cho ◽  
S. Kawamura ◽  
T. Sado ◽  
K. Hara
Keyword(s):  
Electron Microscope ◽  
Chenodeoxycholic Acid ◽  
Outer Surface ◽  
Electron Microscopic ◽  
Cholesterol Gallstones ◽  
The Core ◽  
Scanning Electron Microscopic Study ◽  
Scanning Electron Microscopic ◽  
Acceleration Voltage ◽  
Scanning Electron

The authors have investigated the dissolution process of human cholesterol gallstones using a scanning electron microscope(SEM). This study was carried out by comparing control gallstones incubated in beagle bile with gallstones obtained from patients who were treated with chenodeoxycholic acid(CDCA).The cholesterol gallstones for this study were obtained from 14 patients. Three control patients were treated without CDCA and eleven patients were treated with CDCA 300-600 mg/day for periods ranging from four to twenty five months. It was confirmed through chemical analysis that these gallstones contained more than 80% cholesterol in both the outer surface and the core.The specimen were obtained from the outer surface and the core of the gallstones. Each specimen was attached to alminum sheet and coated with carbon to 100Å thickness. The SEM observation was made by Hitachi S-550 with 20 kV acceleration voltage and with 60-20, 000X magnification.

The Structure and Development of Microbodies in the Fat Body and other Tissues of an Insect (Calpodes Ethlius)

1970 ◽  
Vol 28 ◽  
pp. 148-149
Author(s):  
M. Locke ◽  
J. T. McMahon
Keyword(s):  
Electron Microscopy ◽  
Liquid Crystals ◽  
Fat Body ◽  
Competitive Inhibitor ◽  
Dense Core ◽  
Urate Oxidase ◽  
Blood Proteins ◽  
Free Base ◽  
The Core ◽  
The Matrix

The fat body of insects has always been compared functionally to the liver of vertebrates. Both synthesize and store glycogen and lipid and are concerned with the formation of blood proteins. The comparison becomes even more apt with the discovery of microbodies and the localization of urate oxidase and catalase in insect fat body.The microbodies are oval to spherical bodies about 1μ across with a depression and dense core on one side. The core is made of coiled tubules together with dense material close to the depressed membrane. The tubules may appear loose or densely packed but always intertwined like liquid crystals, never straight as in solid crystals (Fig. 1). When fat body is reacted with diaminobenzidine free base and H2O2 at pH 9.0 to determine the distribution of catalase, electron microscopy shows the enzyme in the matrix of the microbodies (Fig. 2). The reaction is abolished by 3-amino-1, 2, 4-triazole, a competitive inhibitor of catalase. The fat body is the only tissue which consistantly reacts positively for urate oxidase. The reaction product is sharply localized in granules of about the same size and distribution as the microbodies. The reaction is inhibited by 2, 6, 8-trichloropurine, a competitive inhibitor of urate oxidase.

Exsolution and inversion in pigeonite from the Whin Sill, Northern England

1978 ◽  
Vol 36 (1) ◽  
pp. 474-475
Author(s):  
P.P.K. Smith
Keyword(s):  
High Temperature ◽  
Low Temperature ◽  
Homogeneous Nucleation ◽  
Silicate Mineral ◽  
Antiphase Boundaries ◽  
Two Phase ◽  
Primitive Form ◽  
The Core ◽  
Nucleation Mechanisms ◽  
And Inversion

Grains of pigeonite, a calcium-poor silicate mineral of the pyroxene group, from the Whin Sill dolerite have been ion-thinned and examined by TEM. The pigeonite is strongly zoned chemically from the composition Wo8En64FS28 in the core to Wo13En34FS53 at the rim. Two phase transformations have occurred during the cooling of this pigeonite:- exsolution of augite, a more calcic pyroxene, and inversion of the pigeonite from the high- temperature C face-centred form to the low-temperature primitive form, with the formation of antiphase boundaries (APB's). Different sequences of these exsolution and inversion reactions, together with different nucleation mechanisms of the augite, have created three distinct microstructures depending on the position in the grain.In the core of the grains small platelets of augite about 0.02μm thick have farmed parallel to the (001) plane (Fig. 1). These are thought to have exsolved by homogeneous nucleation. Subsequently the inversion of the pigeonite has led to the creation of APB's.

Intramitochondrial Viruses of Reptilian Cell Origin

1972 ◽  
Vol 30 ◽  
pp. 318-319
Author(s):  
Philip D. Lunger ◽  
H. Fred Clark
Keyword(s):  
Particle Production ◽  
Outer Zone ◽  
Density Variation ◽  
Core Region ◽  
Mitochondrial Membranes ◽  
Virus Particles ◽  
The Core ◽  
Vipera Russelli ◽  
Maturation Stages ◽  
Type Particle

In the course of fine structure studies of spontaneous “C-type” particle production in a viper (Vipera russelli) spleen cell line, designated VSW, virus particles were frequently observed within mitochondria. The latter were usually enlarged or swollen, compared to virus-free mitochondria, and displayed a considerable degree of cristae disorganization.Intramitochondrial viruses measure 90 to 100 mμ in diameter, and consist of a nucleoid or core region of varying density and measuring approximately 45 mμ in diameter. Nucleoid density variation is presumed to reflect varying degrees of condensation, and hence maturation stages. The core region is surrounded by a less-dense outer zone presumably representing viral capsid.Particles are usually situated in peripheral regions of the mitochondrion. In most instances they appear to be lodged between loosely apposed inner and outer mitochondrial membranes.

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