314 research outputs found
Observed crustal uplift near the Southern Patagonian Icefield constrains improved viscoelastic Earth model
Thirty‒one GPS geodetic measurements of crustal uplift in southernmost South America determined extraordinarily high trend rates (> 35 mm/yr) in the north‒central part of the Southern Patagonian Icefield. These trends have a coherent pattern, motivating a refined viscoelastic glacial isostatic adjustment model to explain the observations. Two end‒member models provide good fits: both require a lithospheric thickness of 36.5 ± 5.3 km. However, one end‒member has a mantle viscosity near η =1.6 ×1018 Pa s and an ice collapse rate from the Little Ice Age (LIA) maximum comparable to a lowest recent estimate of 1995–2012 ice loss at about −11 Gt/yr. In contrast, the other end‒member has much larger viscosity: η = 8.0 ×1018 Pa s, half the post–LIA collapse rate, and a steadily rising loss rate in the twentieth century after AD 1943, reaching −25.9 Gt/yr during 1995–2012.Fil: Lange, H.. Technische Universitaet Dresden; AlemaniaFil: Casassa, G.. Centro de Estudios Cientificos; Chile. Universidad de Magallanes; ChileFil: Ivins, E. R.. Institute of Technology. Jet propulsion Laboratory; Estados UnidosFil: Schroeder, L.. Technische Universitaet Dresden; AlemaniaFil: Fritsche, M.. Technische Universitaet Dresden; AlemaniaFil: Richter, Andreas Jorg. Technische Universitaet Dresden; Alemania. Universidad Nacional de la Plata. Facultad de Ciencias Astronómicas y GeofÃsicas. Departamento de AstrometrÃa; Argentina. Consejo Nacional de Investigaciones CientÃficas y Técnicas. Centro CientÃfico Tecnológico Conicet - La Plata; ArgentinaFil: Groh, A.. Technische Universitaet Dresden; AlemaniaFil: Dietrich, R.. Technische Universitaet Dresden; Alemani
Quantifying mass balance processes on the Southern Patagonia Icefield
ArtÃculo de publicación ISIWe present surface mass balance simulations of
the Southern Patagonia Icefield (SPI) driven by downscaled
reanalysis data. The simulations were evaluated and interpreted
using geodetic mass balances, measured point balances
and a complete velocity field of the icefield for spring
2004. The high measured accumulation of snow of up to
15.4 m w.e. yr−1
(meters water equivalent per year) as well
as the high measured ablation of up to 11 m w.e. yr−1
is reproduced
by the model. The overall modeled surface mass
balance was positive and increasing during 1975–2011. Subtracting
the surface mass balance from geodetic balances,
calving fluxes were inferred. Mass losses of the SPI due to
calving were strongly increasing from 1975–2000 to 2000–
2011 and higher than losses due to surface melt. Calving
fluxes were inferred for the individual glacier catchments and
compared to fluxes estimated from velocity data. Measurements
of ice thickness and flow velocities at the glaciers’
front and spatially distributed accumulation measurements
can help to reduce the uncertainties of the different terms in
the mass balance of the Southern Patagonia Icefield.FONDECYT
3140135
European Union
22637
Diffusion of a ring polymer in good solution via the Brownian dynamics
Diffusion constants D_{R} and D_{L} of ring and linear polymers of the same
molecular weight in a good solvent, respectively, have been evaluated through
the Brownian dynamics with hydrodynamic interaction. The ratio ,
which should be universal in the context of the renormalization group, has been
estimated as for the large-N limit. It should be consistent
with that of synthetic polymers, while it is smaller than that of DNAs such as
. Furthermore, the probability of the ring polymer being a
nontrivial knot is found to be very small, while bond crossings may occur at
almost all time steps in the present simulation that realizes the good solvent
conditions.Comment: 11 pages, 4 figure
Key Role of Defects in Thermoelectric Performance of TiMSn (M = Ni, Pd, and Pt) Half-Heusler Alloys
Universality in the diffusion of knots
We have evaluated a universal ratio between diffusion constants of the ring
polymer with a given knot and a linear polymer with the same molecular
weight in solution through the Brownian dynamics under hydrodynamic
interaction. The ratio is found to be constant with respect to the number of
monomers, , and hence the estimate at some should be valid practically
over a wide range of for various polymer models. Interestingly, the ratio
is determined by the average crossing number () of an ideal
conformation of knotted curve , i.e. that of the ideal knot. The of
ideal knots should therefore be fundamental in the dynamics of knots.Comment: 8 pages, 14 figure
Stochastic control applied to the ISWEC Wave Energy System
ISWEC (Inertial Sea Wave Energy Converter) is a fl oating marine device able to harvest sea waves energy by the interaction between the pitching motion of a fl oater and a spinning fl ywheel which can drive an electric PTO. In the ISWEC the hull dynamics is governed and controlled by the gyroscopic torque. The optimal control logic results in tuning the fl oater dynamics to the incoming waves in order to maximize the power transfer from the waves to the fl oater. In this paper the control problems of the ISWEC are stated and a control scheme based on the sub-optimal stochastic control logic is presented. The control scheme here presented has been tested using real wave records acquired at the deployment location in Pantelleria Island, which is one of the most energetic sites of the Mediterranean Sea
On the Limits of Analogy Between Self-Avoidance and Topology-Driven Swelling of Polymer Loops
The work addresses the analogy between trivial knotting and excluded volume
in looped polymer chains of moderate length, , where the effects of
knotting are small. A simple expression for the swelling seen in trivially
knotted loops is described and shown to agree with simulation data. Contrast
between this expression and the well known expression for excluded volume
polymers leads to a graphical mapping of excluded volume to trivial knots,
which may be useful for understanding where the analogy between the two
physical forms is valid. The work also includes description of a new method for
the computational generation of polymer loops via conditional probability.
Although computationally intensive, this method generates loops without
statistical bias, and thus is preferable to other loop generation routines in
the region .Comment: 10 pages, 5 figures, supplementary tex file and datafil
Observed crustal uplift near the Southern Patagonian Icefield constrains improved viscoelastic Earth model
Thirty‒one GPS geodetic measurements of crustal uplift in southernmost South America determined extraordinarily high trend rates (> 35 mm/yr) in the north‒central part of the Southern Patagonian Icefield. These trends have a coherent pattern, motivating a refined viscoelastic glacial isostatic adjustment model to explain the observations. Two end‒member models provide good fits: both require a lithospheric thickness of 36.5 ± 5.3 km. However, one end‒member has a mantle viscosity near η =1.6 ×1018 Pa s and an ice collapse rate from the Little Ice Age (LIA) maximum comparable to a lowest recent estimate of 1995–2012 ice loss at about −11 Gt/yr. In contrast, the other end‒member has much larger viscosity: η = 8.0 ×1018 Pa s, half the post–LIA collapse rate, and a steadily rising loss rate in the twentieth century after AD 1943, reaching −25.9 Gt/yr during 1995–2012.Facultad de Ciencias Astronómicas y GeofÃsica
Phase separation in mixtures of colloids and long ideal polymer coils
Colloidal suspensions with free polymer coils which are larger than the
colloidal particles are considered. The polymer-colloid interaction is modeled
by an extension of the Asakura-Oosawa model. Phase separation occurs into
dilute and dense fluid phases of colloidal particles when polymer is added. The
critical density of this transition tends to zero as the size of the polymer
coils diverges.Comment: 5 pages, 3 figure
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