60 research outputs found
Subordinated Langevin Equations for Anomalous Diffusion in External Potentials - Biasing and Decoupled Forces
The role of external forces in systems exhibiting anomalous diffusion is
discussed on the basis of the describing Langevin equations. Since there exist
different possibilities to include the effect of an external field the concept
of {\it biasing} and {\it decoupled} external fields is introduced.
Complementary to the recently established Langevin equations for anomalous
diffusion in a time-dependent external force-field [{\it Magdziarz et al.,
Phys. Rev. Lett. {\bf 101}, 210601 (2008)}] the Langevin formulation of
anomalous diffusion in a decoupled time-dependent force-field is derived
Continuous Time Random Walks with Internal Dynamics and Subdiffusive Reaction-Diffusion Equations
We formulate the generalized master equation for a class of continuous time
random walks in the presence of a prescribed deterministic evolution between
successive transitions. This formulation is exemplified by means of an
advection-diffusion and a jump-diffusion scheme. Based on this master equation,
we also derive reaction-diffusion equations for subdiffusive chemical species,
using a mean field approximation
Feynman-Kac equation for anomalous processes with space-and time-dependent forces
Invited contribution to the J. Phys. A special issue Emerging Talent
Weakly non-ergodic Statistical Physics
We find a general formula for the distribution of time averaged observables
for weakly non-ergodic systems. Such type of ergodicity breaking is known to
describe certain systems which exhibit anomalous fluctuations, e.g. blinking
quantum dots and the sub-diffusive continuous time random walk model. When the
fluctuations become normal we recover usual ergodic statistical mechanics.
Examples of a particle undergoing fractional dynamics in a binding force field
are worked out in detail. We briefly discuss possible physical applications in
single particle experiments
A Glial Variant of the Vesicular Monoamine Transporter Is Required To Store Histamine in the Drosophila Visual System
Unlike other monoamine neurotransmitters, the mechanism by which the brain's histamine content is regulated remains unclear. In mammals, vesicular monoamine transporters (VMATs) are expressed exclusively in neurons and mediate the storage of histamine and other monoamines. We have studied the visual system of Drosophila melanogaster in which histamine is the primary neurotransmitter released from photoreceptor cells. We report here that a novel mRNA splice variant of Drosophila VMAT (DVMAT-B) is expressed not in neurons but rather in a small subset of glia in the lamina of the fly's optic lobe. Histamine contents are reduced by mutation of dVMAT, but can be partially restored by specifically expressing DVMAT-B in glia. Our results suggest a novel role for a monoamine transporter in glia that may be relevant to histamine homeostasis in other systems
Run and tumble particle under resetting:a renewal approach
We consider a particle undergoing run and tumble dynamics, in which its
velocity stochastically reverses, in one dimension. We study the addition of a
Poissonian resetting process occurring with rate . At a reset event the
particle's position is returned to the resetting site and the particle's
velocity is reversed with probability . The case corresponds
to position resetting and velocity randomization whereas corresponds
to position-only resetting. We show that, beginning from symmetric initial
conditions, the stationary state does not depend on i.e. it is
independent of the velocity resetting protocol. However, in the presence of an
absorbing boundary at the origin, the survival probability and mean time to
absorption do depend on the velocity resetting protocol. Using a renewal
equation approach, we show that the the mean time to absorption is always less
for velocity randomization than for position-only resetting.Comment: 16 pages, 1 figure, version accepted in Journal of Physics
The Possible Influence of Corticosteroid Therapy on the Natural Course of Pulmonary Sarcoidosis.
Intermittent chemotherapy of pulmonary tuberculosis using rifampicin and isoniazid for primary treatment: the influence of various factors on the frequency of side-effects
The level of p-amino salicylic acid, streptomycin, thiosemicarbazone and aethionamide in blood and urine following local treatment of cavernostomy cavities
- …