The movement of isolated boulders on tidal flats by ice floes

1982 ◽  
Vol 19 (4) ◽  
pp. 748-754 ◽  
Author(s):  
John J. Drake ◽  
S. B. McCann
Keyword(s):  
Coefficient Of Friction ◽  
Short Distance ◽  
Tidal Flats ◽  
Ice Thickness ◽  
Limiting Factor ◽  
Mechanism Analysis ◽  
Standard Format ◽  
Ice Roughness ◽  
Ice Floes ◽  
Distance Transport

The ability of ice floes to move isolated boulders on tidal flats by flotation and by pushing and (or) rolling them along the bed is considered in the standard format of sediment movement (entrainment, transport, and deposition). Analysis shows that flotation competence depends on ice thickness and floe size, and is sufficient to transport most of the boulders reported from eastern Canadian tidal flats. However, a limiting factor in the transportation of large boulders by this mode is likely to be the entrainment mechanism. Analysis of movement of grounded boulders by lateral ice thrust shows that, on both deformable and non-deformable beds, rolling rather than sliding will occur. Rolling competence depends on floe size, ice roughness, the ice–rock coefficient of friction, and current and (or) wind strength. Resistance to movement is a function of the embedment ratio and bed properties. Rolling could account for most of the observed short-distance transport of large boulders.

scholarly journals Sea-ice thickness and roughness in the Ross Sea, Antarctica

2001 ◽  
Vol 33 ◽  
pp. 187-193 ◽  
Author(s):  
Tina Tin ◽  
Martin O. Jeffries
Keyword(s):  
Surface Roughness ◽  
Sea Ice ◽  
Ross Sea ◽  
Geographical Location ◽  
Ice Thickness ◽  
Snow Surface ◽  
Sea Ice Thickness ◽  
Antarctic Sea Ice ◽  
Ice Roughness ◽  
Ice Floes

AbstractSea-ice thickness and roughness data collected on three cruises in the Ross Sea, Antarctica, showed interseasonal, regional and interannual variability. Variability was reduced to season, or age of ice floe, when sea-ice roughness values from around Antarctica were compared. There were statistically significant correlations between mean snow elevation and mean ice thickness; snow surface roughness and mean ice thickness; and snow surface roughness and ice bottom roughness, which appeared to be independent of season, geographical location and deformation history of ice floes. Our field data indicate that ice thickness can be predicted from snow elevation measurements with higher accuracy in summer. The feasibility of using snow surface roughness to infer ice thickness and ice bottom roughness is promising, and can provide us with a means to study the thickness and underside of Antarctic sea ice at good spatial and temporal resolution.

scholarly journals Apulo-Calabrese and Crossbreed Pigs Show Different Physiological Response and Meat Quality Traits after Short Distance Transport

Animals ◽  
2018 ◽  
Vol 8 (10) ◽  
pp. 177 ◽  
Author(s):  
Gizella Aboagye ◽  
Stefania Dall’Olio ◽  
Francesco Tassone ◽  
Martina Zappaterra ◽  
Salvatore Carpino ◽  
...  
Keyword(s):  
Meat Quality ◽  
Short Distance ◽  
Blood Parameters ◽  
Quality Traits ◽  
Large White ◽  
Meat Quality Traits ◽  
Genetic Types ◽  
Alkaline Phosphate ◽  
Distance Transport ◽  
Sodium And Potassium

Despite the increasing interest in the welfare of animals during transport, very little is known on the response of local pig breeds to the transport procedures. This study aims to compare the effect of short journey on behaviour, blood parameters, and meat quality traits in 51 Apulo-Calabrese and 52 crossbreed [Duroc × (Landrace × Large White)] pigs. All the animals were blood sampled five days before delivery (basal condition) and at exsanguination for the analysis of creatine kinase, cortisol, glucose, lactate, albumin, albumin/globulin, total protein, urea, creatinine, aspartate aminotransferase (AST), alanine aminotransferase, alkaline phosphate, sodium, and potassium. Post mortem pH, color, drip loss, cooking loss, and Warner-Bratzler shear force were measured at different times in longissimus thoracis samples. Univariate and multivariate analyses showed that glucose, albumin/globulin, urea, and AST at exsanguination were influenced by the genetic type. Apulo-Calabrese showed the highest increase in blood values of lactate, creatinine, sodium and potassium after the short distance transport. Behavioural occurrences were similar in both genetic types during unloading and lairage. Small differences were observed for meat quality although significantly higher a* and lower L* were found in Apulo-Calabrese pigs, showing meat with a deeper red colour than crossbreeds.

scholarly journals Routine Determination of Ice Thickness for Cryo-EM Grids

2018 ◽  
Author(s):  
William J. Rice ◽  
Anchi Cheng ◽  
Alex J. Noble ◽  
Edward T. Eng ◽  
Laura Y. Kim ◽  
...  
Keyword(s):  
Data Collection ◽  
Sample Preparation ◽  
Quality Data ◽  
Ice Thickness ◽  
Limiting Factor ◽  
Test Cases ◽  
Slowing Down ◽  
Routine Monitoring ◽  
The Many

AbstractRecent advances in instrumentation and automation have made cryo-EM a popular method for producing near-atomic resolution structures of a variety of proteins and complexes. Sample preparation is still a limiting factor in collecting high quality data. Thickness of the vitreous ice in which the particles are embedded is one of the many variables that need to be optimized for collection of the highest quality data. Here we present two methods, using either an energy filter or scattering outside the objective aperture, to measure ice thickness for potentially every image collected. Unlike geometrical or tomographic methods, these can be implemented directly in the single particle collection workflow without interrupting or significantly slowing down data collection. We describe the methods as implemented into the Leginon/Appion data collection workflow, along with some examples from test cases. Routine monitoring of ice thickness should prove helpful for optimizing sample preparation, data collection, and data processing.

Miniature mud volcanoes and other injection features in tidal flats, James Bay, Québec

1976 ◽  
Vol 13 (3) ◽  
pp. 422-428 ◽  
Author(s):  
Jean-Claude Dionne
Keyword(s):  
East Coast ◽  
Fine Sand ◽  
Tidal Flats ◽  
Mud Volcanoes ◽  
James Bay ◽  
Marine Clay ◽  
Ice Floes ◽  
Mud Deposit

Miniature injection features, including mud volcanoes, dikes forming polygonal patterns, and isolated patches of clay, occur in tidal flats along the east coast of James Bay. They are formed by localized upward ejection of a mixture of fluidized marine clay, silt, and fine sand through a surficial recent mud deposit. Liquefaction is related to the melting of ice in the clayey deposit. Upward flowing of clay, silt, and fine sand seems to result from overloading by the overlying sediments having a higher degree of density, and possibly also by pressures of ice floes or/and icefoot.

Variations of the Local Failure Pressure With Depth Through First-Year and Multi-Year Ice

1988 ◽  
Vol 110 (2) ◽  
pp. 159-168 ◽  
Author(s):  
D. Blanchet
Keyword(s):  
Ice Thickness ◽  
First Year ◽  
Strain Rates ◽  
Failure Pressure ◽  
Pressure Profiles ◽  
Vertical Distributions ◽  
Pressure Area ◽  
Ice Floes ◽  
Ice Pressure ◽  
The Vertical Distribution

Typical vertical distributions of the failure pressure in an ice sheet are presented. The distributions, derived for intermediate strain rates, are a function of many parameters, namely, the salinity, the temperature, the type of ice, the location of the ice pressure area through the ice thickness, the thickness of ice, the density, and the crack and flaw distributions. Two combinations of these parameters lead to “representative” summer and winter vertical ice pressure profiles for 8 and 2-m thick ice floes. The importance of the vertical distribution of the failure pressure inside an ice cover is fundamental for two reasons. The change in the eccentricity of the resultant of the load induces changes in failure mode and load transmission to the structure. This nonuniform distribution will create nonsimultaneous failure and the ice pressure on the structure will not be hydrostatically distributed over a given area.

scholarly journals A Method to Estimate Open Pack-Ice Thickness from Two-Day Sequences of Side-Lapping Satellite Images

1987 ◽  
Vol 9 ◽  
pp. 69-71 ◽  
Author(s):  
Uri Feldman
Keyword(s):  
Surface Wind ◽  
Microwave Remote Sensing ◽  
Surface Wind Speed ◽  
Ice Thickness ◽  
In Situ Observation ◽  
Pack Ice ◽  
Upper Limits ◽  
Ice Floes ◽  
Active Microwave Remote Sensing

A method to estimate open pack ice thickness drifting in a marginal ice zone (MIZ) is presented, The estimates are obtained from two-day sequences of sidelapping Landsat-1 MSS images and two-day sequences of wind field data by four steps: estimating the surface wind speed, estimating the angle of sea ice deflection, estimating three ratios between ice parameters and estimating the lower and upper limits of pack ice thickness. The method has been applied to six groups of open pack ice floes drifting in the MIZ of the Beaufort Sea during 1973–1975. In the absence of simultaneous in-situ observation, the results have not been tested, The method presented may be applied to any MIZ. Rather than using Landsat-1 MSS images, data from a high resolution active microwave remote sensing system should be employed in the future as its data will be independent of sun illumination and cloud cover.

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