| 1. |
- Cordoba-Jabonero, Carmen, et al.
(författare)
-
Assessments for possible habitability in Martian polar environments : Fundaments based in ice screening of UV radiation
- 2004
-
Ingår i: ESA SP. - 0379-6566 .- 1609-0438. ; 545, s. 187-188
-
Tidskriftsartikel (refereegranskat)abstract
- We present a study of the solar UV radiation in Martian high latitude environments covered by ice, where the UV propagation through the polar cover depends on the ice radiative properties (layers of H2O or CO 2 ice). But also we will investigate the changes in the subsurface UV levels induced by the seasonal variations of solar UV flux on the surface, as well as by the seasonal freezing-thawing and related CO2 sublimation processes. The biological dose relative to DNA-damage will be also estimated for biological implication assessments. All these studies will be compared with the biological dose received in the Antarctic snow-ice covered environment which is seasonally exposed to high UV radiation levels (formation of "ozone hole"), where the environmental conditions could be similar to those present on Mars
|
|
| 2. |
- Gaite, José A., et al.
(författare)
-
Nonlinear spherical gravitational downfall of gas onto a solid ball : Analytic and numerical results
- 2003
-
Ingår i: Physica D. - : Elsevier. - 0167-2789 .- 1872-8022. ; 183:1-2, s. 102-116
-
Tidskriftsartikel (refereegranskat)abstract
- The process of downfall of initially homogeneous gas onto a solid ball due to the ball's gravity (relevant in astrophysical situations) is studied with a combination of analytic and numerical methods. The initial explicit solution soon becomes discontinuous and gives rise to a shock wave. Afterwards, there is a crossover between two intermediate asymptotic similarity regimes, where the shock wave propagates outwards according to two self-similar laws, initially accelerating and eventually decelerating and vanishing, leading to a static state. The numerical study allows one to investigate in detail this dynamical problem and its time evolution, verifying and complementing the analytic results on the initial solution, intermediate self-similar laws and static long-term solution.
|
|
| 3. |
- Herr, Werner, et al.
(författare)
-
Hybrid fast multipole method applied to beam-beam collisions in the strong-strong regime
- 2001
-
Ingår i: Physical Review Special Topics - Accelerators and Beams. - 1098-4402. ; 4:5, s. 37-45
-
Tidskriftsartikel (refereegranskat)abstract
- The strong-strong interactions of two colliding beams are simulated by tracking the motion of a set of macroparticles. The field generated by each distribution is evaluated using the fast multipole method together with some elements of particle-mesh methods. This technique allows us to check the exact frequencies of the coherent modes and the frequencies of oscillations of individual particles in the beam. The agreement between the simulations and analytical calculations is largely improved. Furthermore, it is an efficient method to study the coherent modes in the case of separated beams.
|
|
| 4. |
- Zorzano, María Paz, et al.
(författare)
-
Dynamic renormalization group and noise induced transitions in a reaction diffusion model
- 2004
-
Ingår i: Physica A. - : Elsevier. - 0378-4371 .- 1873-2119. ; 334:1-2, s. 67-77
-
Tidskriftsartikel (refereegranskat)abstract
- We investigate how additive weak noise (correlated as well as uncorrelated) modifies the parameters of the Gray-scott reaction diffusion system by performing numerical simulations and applying a renormalization group (RG) analysis in the neighborhood of the spatial scale where biochemical reactions take place. One can obtain the same sequence of spatial-temporal patterns by means of two equivalent routes: (i) by increasing only the noise intensity and keeping all other model parameters fixed; or (ii) keeping the noise fixed, and adjusting certain model parameters to their running scale-dependent values as predicted by the RG. This explicit demonstration validates the dynamic RG transformation for finite scales in a two-dimensional stochastic model and provides further physical insight into the coarse-graining analysis proposed by this scheme. Through several study cases we explore the role of noise and its temporal correlation in self-organization and propose a way to drive the system into a new desired state in a controlled way.
|
|
| 5. |
- Zorzano, María Paz, et al.
(författare)
-
Emergence of synchronous oscillations in neural networks excited by noise
- 2003
-
Ingår i: Physica D. - : Elsevier. - 0167-2789 .- 1872-8022. ; 179:1-2, s. 105-114
-
Tidskriftsartikel (refereegranskat)abstract
- The presence of noise in nonlinear dynamical systems can play a constructive role, increasing the degree of order and coherence or evoking improvements in the performance of the system. An example of this positive influence in a biological system is the impulse transmission in neurons and the synchronization of a neural network. Integrating numerically the Fokker-Planck (FP) equation we show a self-induced synchronized oscillation. Such an oscillatory state appears in a neural network coupled with a feedback term, when this system is excited by noise and the noise strength is within a certain range
|
|
