2,044 research outputs found
Topological Phenomena in Normal Metals
This paper is devoted to topological phenomena in normal metals with rather
complicated Fermi surface. The results of the article are based on the deep
topological theorems concerning the geometry of non-compact plane sections of
level surfaces of periodic function in 3-dimensional Euclidean space which are
the quasi-classical electron orbits in the presence of homogeneous magnetic
field. The main result is that the observation of electrical conductivity in
strong magnetic fields can reveal such nontrivial topological characteristics
of Fermi surface as integral planes, connected with conductivity tensor and
locally stable under small rotations of magnetic field. This planes are
connected with generic non-closed orbits on the Fermi surface. Some non-generic
situations are also discussed.Comment: 21 pages, 9 Encapsulated Postscript figure
Dynamical Systems, Topology and Conductivity in Normal Metals
New observable integer-valued numbers of the topological origin were revealed
by the present authors studying the conductivity theory of single crystal 3D
normal metals in the reasonably strong magnetic field (). Our
investigation is based on the study of dynamical systems on Fermi surfaces for
the motion of semi-classical electron in magnetic field. All possible
asymptotic regimes are also found for based on the topological
classification of trajectories.Comment: Latex, 51 pages, 14 eps figure
Elementary Intracellular Ca Signals approximated as a Transition of Release Channel System from a Metastable State
Cardiac muscle contraction is initiated by an elementary Ca signal (called Ca spark) which is achieved by collective action of Ca release channels in a cluster. The mechanism of this synchronization remains uncertain. We approached Ca spark activation as an emergent phenomenon of an interactive system of release channels. We constructed a weakly lumped Markov chain that applies an Ising model formalism to such release channel clusters and probable open channel configurations and demonstrated that spark activation is described as a system transition from a metastable to an absorbing state, analogous to the pressure required to overcome surface tension in bubble formation. This yielded quantitative estimates of the spark generation probability as a function of various system parameters. We performed numerical simulations to find spark probabilities as a function of sarcoplasmic reticulum Ca concentration, obtaining similar values for spark activation threshold as our analytic model, as well as those reported in experimental studies. Our parametric sensitivity analyses also showed that the spark activation threshold decreased as Ca sensitivity of RyR activation and RyR cluster size increased
Open level lines of a superposition of periodic potentials on a plane
We consider here open level lines of potentials resulting from the
superposition of two different periodic potentials on the plane. This problem
can be considered as a particular case of the Novikov problem on the behavior
of open level lines of quasi-periodic potentials on the plane with four
quasi-periods. At the same time, the formulation of this problem may have many
additional features that arise in important physical systems related to it.
Here we will try to give a general description of the emerging picture both in
the most general case and in the presence of additional restrictions. The main
approach to describing the possible behavior of the open level lines will be
based on their division into topologically regular and chaotic level lines.Comment: 8 pages, 5 figures, revte
Recommended from our members
Microvesicles and intercellular communication in the context of parasitism
There is a rapidly growing body of evidence that production of microvesicles (MVs) is a universal feature of cellular life. MVs can incorporate microRNA (miRNA), mRNA, mtDNA, DNA and retrotransposons, camouflage viruses/viral components from immune surveillance, and transfer cargo between cells. These properties make MVs an essential player in intercellular communication. Increasing evidence supports the notion that MVs can also act as long-distance vehicles for RNA molecules and participate in metabolic synchronization and reprogramming eukaryotic cells including stem and germinal cells. MV ability to carry on DNA and their general distribution makes them attractive candidates for horizontal gene transfer, particularly between multi-cellular organisms and their parasites; this suggests important implications for the co-evolution of parasites and their hosts. In this review, we provide current understanding of the roles played by MVs in intracellular pathogens and parasitic infections. We also discuss the possible role of MVs in co-infection and host shifting
Geometry of quasiperiodic functions on the plane
The present article proposes a review of the most recent results obtained in
the study of Novikov's problem on the description of the geometry of the level
lines of quasi-periodic functions in the plane. Most of the paper is devoted to
the results obtained for functions with three quasi-periods, which play a very
important role in the theory of transport phenomena in metals. In this part,
along with previously known results, a number of new results are presented that
significantly refine the general description of the picture that arises in this
case. New statements are also presented for the case of functions with more
than three quasi-periods, which open up approaches to the further study of
Novikov's problem in the most general formulation. The role of Novikov's
problem in various fields of mathematical and theoretical physics is also
discussed.Comment: 24 pages, 17 figures, late
- …