36 research outputs found
Mirror symmetry breaking through an internal degree of freedom leading to directional motion
We analyze here the minimal conditions for directional motion (net flow in
phase space) of a molecular motor placed on a mirror-symmetric environment and
driven by a center-symmetric and time-periodic force field. The complete
characterization of the deterministic limit of the dissipative dynamics of
several realizations of this minimal model, reveals a complex structure in the
phase diagram in parameter space, with intertwined regions of pinning (closed
orbits) and directional motion. This demonstrates that the mirror-symmetry
breaking which is needed for directional motion to occur, can operate through
an internal degree of freedom coupled to the translational one.Comment: Accepted for publication in Phys. Rev.
Quantum state-dependent diffusion and multiplicative noise: a microscopic approach
The state-dependent diffusion, which concerns the Brownian motion of a
particle in inhomogeneous media has been described phenomenologically in a
number of ways. Based on a system-reservoir nonlinear coupling model we present
a microscopic approach to quantum state-dependent diffusion and multiplicative
noise in terms of a quantum Markovian Langevin description and an associated
Fokker-Planck equation in position space in the overdamped limit. We examine
the thermodynamic consistency and explore the possibility of observing a
quantum current, a generic quantum effect, as a consequence of this
state-dependent diffusion similar to one proposed by B\"{u}ttiker [Z. Phys. B
{\bf 68}, 161 (1987)] in a classical context several years ago.Comment: To be published in Journal of Statistical Physics 28 pages, 3 figure
Database of spatial distribution of non indigenous species in Spanish marine waters
Research in marine Spanish waters are focused on several actions to achieve an effectively management on protected areas, with the active participation of the stakeholders and research as basic tools for decision-making. Among these actions, there is one about the knowledge and control on NIS. One of its objectives is the creation of NIS factsheets, which are going to be added to the National Marine Biodiversity Geographical System (GIS) providing complementary information about taxonomic classification, common names, taxonomic synonyms, species illustrations, identification morphological characters, habitat in the native and introduced regions, biological and ecological traits, GenBank DNA sequences, world distribution, first record and evolution in the introduced areas, likely pathways of introduction, effects in the habitats and interaction with native species, and potential management measures to apply. The database will also provide data for (1) the European online platforms, (2) the environmental assessment for the Descriptor 2 (D2-NIS) of the EU Marine Strategy Framework Directive (MSFD), as well as (3) supporting decisions made by stakeholders. It is the result of extensive collaboration among scientist, manager’s and citizen science in the Spanish North-Atlantic, South-Atlantic, Gibraltar Strait-Alboran, Levantine-Balearic and Canary Islands marine divisions, providing an updated overview of the spatial distribution of relevant extended and invasive NIS of recent and established NIS introduced by maritime transport and aquaculture pathways, as well as on cryptogenic or native species in expansion due to the climatic water warming trend