scholarly journals Isostatic postglacial rebound over Fennoscandia with a self-gravitating spherical visco-elastic Earth model

1996 ◽  
Vol 23 ◽  
pp. 318-327 ◽  
Author(s):  
E. Le Meur
Keyword(s):  
Present Model ◽  
Short Review ◽  
Earth Model ◽  
Postglacial Rebound ◽  
Mantle Viscosity ◽  
Surface Displacements ◽  
Grounding Line ◽  
The Common ◽  
Characteristic Features ◽  
Sensitive Issues

Accounting for isostasy in glaciological models has always been a necessity but these models mostly use very simple parameterizations (Le Meur and Huybrechts, 1996). The need for more realistic isostatic parameterizations rapidly became apparent, especially in the treatment of bedrock-sensitive issues such as the grounding-line migration (Huybrechts, 1990a, b). To this end, a rather sophisticated Earth model, avoiding most of the common assumptions, has been developed and is presented here. The two key groups of parameters, to which the model is most sensitive, are the Earth properties and the rheological law used for the mantle. The aim of this paper is first to justify the use of Maxwell rheology for the mantle and then to tune the most sensitive Earth parameter, namely the mantle viscosity, in order to match the numerous present-day uplift data over Fennoscandia. So, in the first instance, a short review of the different available rheologies is presented and discussed. The visco-elastic theory, as well as the mathematical background used in the present model, is also briefly sketched. Secondly, a glacial scenario over Fennoscandia served as an input for the model in a calibration test on the mantle-viscosity values. The degree of agreement of the model outputs with the present-day measurements gives a reference set of Green functions, to which one can reasonably refer when modelling the isostatic response over areas where such a control is not possible (Le Meur and Huybrechts, 1996). Finally, a closer look to the time-dependent surface displacements will confirm the ability for the model to reproduce correctly the main postglacial rebound characteristic features.

scholarly journals Isostatic postglacial rebound over Fennoscandia with a self-gravitating spherical visco-elastic Earth model

1996 ◽  
Vol 23 ◽  
pp. 318-327 ◽  
Author(s):  
E. Le Meur
Keyword(s):  
Present Model ◽  
Short Review ◽  
Earth Model ◽  
Postglacial Rebound ◽  
Mantle Viscosity ◽  
Surface Displacements ◽  
Grounding Line ◽  
The Common ◽  
Characteristic Features ◽  
Sensitive Issues

Accounting for isostasy in glaciological models has always been a necessity but these models mostly use very simple parameterizations (Le Meur and Huybrechts, 1996). The need for more realistic isostatic parameterizations rapidly became apparent, especially in the treatment of bedrock-sensitive issues such as the grounding-line migration (Huybrechts, 1990a, b). To this end, a rather sophisticated Earth model, avoiding most of the common assumptions, has been developed and is presented here. The two key groups of parameters, to which the model is most sensitive, are the Earth properties and the rheological law used for the mantle. The aim of this paper is first to justify the use of Maxwell rheology for the mantle and then to tune the most sensitive Earth parameter, namely the mantle viscosity, in order to match the numerous present-day uplift data over Fennoscandia. So, in the first instance, a short review of the different available rheologies is presented and discussed. The visco-elastic theory, as well as the mathematical background used in the present model, is also briefly sketched. Secondly, a glacial scenario over Fennoscandia served as an input for the model in a calibration test on the mantle-viscosity values. The degree of agreement of the model outputs with the present-day measurements gives a reference set of Green functions, to which one can reasonably refer when modelling the isostatic response over areas where such a control is not possible (Le Meur and Huybrechts, 1996). Finally, a closer look to the time-dependent surface displacements will confirm the ability for the model to reproduce correctly the main postglacial rebound characteristic features.

scholarly journals Mass balance of the Antarctic ice sheet 1992–2016: reconciling results from GRACE gravimetry with ICESat, ERS1/2 and Envisat altimetry

2021 ◽  
pp. 1-27
Author(s):  
H. Jay Zwally ◽  
John W. Robbins ◽  
Scott B. Luthcke ◽  
Bryant D. Loomis ◽  
Frédérique Rémy
Keyword(s):  
Mass Balance ◽  
Antarctic Peninsula ◽  
East Antarctica ◽  
Mantle Material ◽  
West Antarctica ◽  
Mantle Viscosity ◽  
Grounding Line ◽  
The Antarctic ◽  
Total Gain

Abstract GRACE and ICESat Antarctic mass-balance differences are resolved utilizing their dependencies on corrections for changes in mass and volume of the same underlying mantle material forced by ice-loading changes. Modeled gravimetry corrections are 5.22 times altimetry corrections over East Antarctica (EA) and 4.51 times over West Antarctica (WA), with inferred mantle densities 4.75 and 4.11 g cm−3. Derived sensitivities (Sg, Sa) to bedrock motion enable calculation of motion (δB0) needed to equalize GRACE and ICESat mass changes during 2003–08. For EA, δB0 is −2.2 mm a−1 subsidence with mass matching at 150 Gt a−1, inland WA is −3.5 mm a−1 at 66 Gt a−1, and coastal WA is only −0.35 mm a−1 at −95 Gt a−1. WA subsidence is attributed to low mantle viscosity with faster responses to post-LGM deglaciation and to ice growth during Holocene grounding-line readvance. EA subsidence is attributed to Holocene dynamic thickening. With Antarctic Peninsula loss of −26 Gt a−1, the Antarctic total gain is 95 ± 25 Gt a−1 during 2003–08, compared to 144 ± 61 Gt a−1 from ERS1/2 during 1992–2001. Beginning in 2009, large increases in coastal WA dynamic losses overcame long-term EA and inland WA gains bringing Antarctica close to balance at −12 ± 64 Gt a−1 by 2012–16.

Heart failure in an elderly population

2001 ◽  
Vol 11 (4) ◽  
pp. 311-321
Author(s):  
DN Carmichael ◽  
Michael Lye
Keyword(s):  
Heart Failure ◽  
Treatment Options ◽  
Clinical Syndrome ◽  
Point Of View ◽  
Diagnostic Challenge ◽  
The Common ◽  
Characteristic Features ◽  
The Many ◽  
Neuroendocrine Activation ◽  
Symptoms And Signs

Heart failure has been defined in many ways and definitions change over time. The multiplicity of definitions reflect the paucity of our understanding of the primary underlying physiology of heart failure and the many diseases for which heart failure is the common end-point. Fundamentally, heart failure represents a failure of the heart to meet the body’s requirement for blood supply for whatever reason. It is thus a clinical syndrome with characteristic features – not a single disease in its own right. The syndrome includes symptoms and signs of organ underperfusion, fluid retention and neuroendocrine activation. The syndrome arises from a range of possible causes of which ischaemic heart disease is the commonest. From the point of view of a clinician, the underlying pathology will determine treatment options and prognosis. The extensive range of possible aetiologies present a diagnostic challenge both to correctly identify the syndrome amongst all other causes of dyspnoea and to identify the aetiology, allowing optimization of treatment.

scholarly journals QUEER CRITICISM AS A POST-MODERNIST APPROACH

2015 ◽  
Vol 1 (1) ◽  
pp. 132
Author(s):  
Hamdi Hameed Yousif
Keyword(s):  
Literary Criticism ◽  
Literary Work ◽  
First Century ◽  
Critical Approach ◽  
The Social ◽  
Late Twentieth ◽  
The Common ◽  
Characteristic Features ◽  
The One ◽  
Late Twentieth Century

One of the post-modernist approaches to literary criticism is the queer criticism which has not been evaluated properly. Queer criticism can refer to any piece of literary criticism that interprets a text from a non-straight perspective. Therefore, it includes both lesbian and gay criticism. The aim of this paper, therefore, is to trace the social and political reasons behind the emergence of Queer criticism in the late twentieth century till it acquired momentum in the twenty-first century. After trying to define the terms related to the Queer criticism, the paper tries to examine the poetics of queer (gay and lesbian) literary works and to point out the main characteristic features of this critical approach by identifying the criteria and the textual evidence by which a literary work is labeled queer. It, also tries to shed light on the common features between queer criticism and feminism, on the one hand, and queer criticism and the deconstructuralist approach on the other hand. The final section of the study is a critique which points out the negative aspects of this approach.

scholarly journals Two independent methods for mapping the grounding line of an outlet glacier – example from the Astrolabe Glacier, Terre Adélie, Antarctica

2013 ◽  
Vol 7 (4) ◽  
pp. 3969-4014
Author(s):  
E. Le Meur ◽  
M. Sacchettini ◽  
S. Garambois ◽  
E. Berthier ◽  
A. S. Drouet ◽  
...  
Keyword(s):  
Control Points ◽  
Gps Measurements ◽  
Outlet Glacier ◽  
Ice Surface ◽  
Surface Displacements ◽  
Grounding Line ◽  
Terre Adélie ◽  
Elastic Slab ◽  
Kinematic Approach

Abstract. The grounding line is a key element acting on the dynamics of coastal outlet glaciers. Knowing its position accurately is fundamental for both modelling the glacier dynamics and establishing a benchmark to which one can later refer in case of change. Here we map the grounding line of the Astrolabe Glacier in East Antarctica (66°41´ S; 140°05´ E), using hydrostatic and tidal methods. The first method is based on new surface and ice thickness data from which the line of buoyant flotation is found. We compare this hydrostatic map with kinematic GPS measurements of the tidal response of the ice surface. By detecting the transitions where the ice starts to move vertically in response to the tidal forcing we find control points for the grounding line position along GPS profiles. %If it can be shown that the long-term viscous mechanical behaviour of the ice slab validates the hydrostatic approach, mapping the grounding line from the ice supper surface displacements conversely requires correcting for the rigid elastic slab effect that dominates at tidal frequencies. With the help of a 2-dimensional elastic plate model, rigid elastic deviations are computed and applied to these control points. Once the extent of the grounding zone, the kinematic approach is consistent with the hydrostatic map. These two approaches lead us to propose a grounding line for the Astrolabe Glacier that significantly deviates from those obtained so far from satellite imagery.

Electronically Stimulated Degradation of Crystalline Silicon Solar Cells

2005 ◽  
Vol 864 ◽  
Author(s):  
J. Schmidt ◽  
K. Bothe ◽  
D. Macdonald ◽  
J. Adey ◽  
R. Jones ◽  
...  
Keyword(s):  
Solar Cells ◽  
Defect Formation ◽  
Crystalline Silicon ◽  
Short Review ◽  
Current Status ◽  
Silicon Solar Cells ◽  
Cell Parameters ◽  
Crystalline Silicon Solar Cells ◽  
Characteristic Features ◽  
Oxygen Complexes

AbstractCarrier lifetime degradation in crystalline silicon solar cells under illumination with white light is a frequently observed phenomenon. Two main causes of such degradation effects have been identified in the past, both of them being electronically driven and both related to the most common acceptor element, boron, in silicon: (i) the dissociation of iron-boron pairs and (ii) the formation of recombination-active boron-oxygen complexes. While the first mechanism is particularly relevant in metal-contaminated solar-grade multicrystalline silicon materials, the latter process is important in monocrystalline Czochralski-grown silicon, rich in oxygen. This paper starts with a short review of the characteristic features of the two processes. We then briefly address the effect of iron-boron dissociation on solar cell parameters. Regarding the boron-oxygen-related degradation, the current status of the physical understanding of the defect formation process and the defect structure are presented. Finally, we discuss different strategies for effectively avoiding the degradation.

scholarly journals Flow of Rutford Ice Stream and Comparison with Carlson Inlet, Antarctica

1989 ◽  
Vol 12 ◽  
pp. 51-56 ◽  
Author(s):  
R.M. Frolich ◽  
D.G. Vaughan ◽  
C.S.M. Doake
Keyword(s):  
Surface Expression ◽  
Ice Thickness ◽  
Shear Stresses ◽  
Lateral Shear ◽  
Ice Stream ◽  
Grounding Line ◽  
Subglacial Topography ◽  
Characteristic Features ◽  
Basal Shear ◽  
Thickness Measurements

Results from movement surveys on Rutford Ice Stream are presented with complementary surface-elevation and ice-thickness measurements. Surface velocities of 300 m a−1 occur at least 130 km up-stream of the grounding line and contrast strongly with the neighbouring Carlson Inlet, where a velocity of 7 m a−1 has been measured. This contrast in velocity is not topographically controlled but appears to be due instead to differences in basal conditions, with Carlson Inlet probably being frozen to its bed. Concentration of lateral shear close to the margins and surface expression of subglacial topography both support a view of significant basal shear stresses in the central part of Rutford Ice Stream. The pattern of principal strain-rate trajectories shows a small number of characteristic features which can be compared with results from future modelling of the glacier's flow.

The Productivity of Labour in Roman Agriculture

Antiquity ◽  
1965 ◽  
Vol 39 (154) ◽  
pp. 102-107 ◽  
Author(s):  
K. D. White
Keyword(s):  
Economic History ◽  
Crop Yields ◽  
Short Review ◽  
Precise Information ◽  
De Re ◽  
Ancient Agriculture ◽  
Agricultural Efficiency ◽  
Average Return ◽  
General Average ◽  
The Common

Some years ago, in a short review of some of the major questions concerning agricultural efficiency in Roman times, I pointed out that we do not possess the materials on which to base an accurate computation. In attempting to make an assessment of agricultural efficiency we should require as a minimum basis a body of statistical information on the following points: first, the numbers of persons engaged; second, average yields per acre of certain crops for comparison with average yields in other producing countries; and third, statistics of output measured in man-hours according to recognized methods of determining the productivity of labour. The type of dficulty mentioned here is not confined to research in ancient agriculture; lack of records, and paucity of precise information, make investigation difficult in almost every department of ancient economic history. But lack of precise information has not deterred historians from making rough analyses and generalizations. The evidence on wheat-yields showed, inter alia, that it is not legitimate to use Columella’s general average return on Italian wheat of four-fold as evidence of a generally low standard of productivity in cereals (De Re Rust., III, iii, 4). So far as crop-yields are concerned, the common postulate of a low level of agricultural technique cannot be upheld.

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