Russian Academy of Sciences

About: Russian Academy of Sciences is a government organization based out in Moscow, Russia. It is known for research contribution in the topics: Catalysis & Laser. The organization has 272615 authors who have published 417512 publications receiving 4538835 citations. The organization is also known as: RAS & RAN.

Adaptability of innate motor patterns and motor control mechanisms.

Abstract: The following factors underlying behavioral plasticity are discussed: (1) reflex adaptability and its role in the voluntary control of movement, (2) degrees of freedom and motor equivalence, and (3) the problem of the discrete organization of motor behavior. Our discussion concerns a variety of innate motor patterns, with emphasis on the wiping reflex in the frog.It is proposed that central regulation of stretch reflex thresholds governs voluntary control over muscle force and length. This suggestion is an integral part of the equilibrium-point hypothesis, two versions of which are compared.Kinematic analysis of the wiping reflex in the spinal frog has shown that each stimulated skin site is associated with a group of different but equally effective trajectories directed to the target site. Such phenomena reflect the principle of motor equivalence -the capacity of the neuronal structures responsible for movement to select one or another of a set of possible trajectories leading to the goal. Redundancy of degrees of freedom at the neuronal level as well as at the mechanical level of the body's joints makes motor equivalence possible. This sort of equivalence accommodates the overall flexibility of motor behavior.An integrated behavioral act or a single movement consists of dynamic components. We distinguish six components for the wiping reflex, each associated with a certain functional goal, specific body positions, and motor-equivalent movement patterns. The nervous system can combine the available components in various ways in forming integrated behavioral sequences. The significance of command neuronal organization is discussed with respect to (1) the combinatory strategy of the nervous system and (2) the relation between continuous and discrete forms of motor control. We conclude that voluntary movements are effected by the central nervous system with the help of the mechanisms that underlie the variability and modifiability of innate motor patterns.

Mitochondrial signaling in mammalian cells activated by red and near-IR radiation.

Abstract: Mitochondrial signaling is an information channel between the mitochondrial respiratory chain and the nucleus for the transduction signals regarding the functional state of the mitochondria. The present review examines the question whether radiation of visible and near-IR (IR-A) radiation can activate this retrograde-type cellular signaling pathway. Experimental data about modulation of elements of mitochondrial retrograde signaling by the irradiation (mitochondrial membrane potential DeltaPsi(m), reactive oxygen species ROS, Ca(2+), NO, pH(i), fission-fusion homeostasis of mitochondria) are reviewed. The terminal enzyme of the mitochondrial respiratory chain cytochrome c oxidase is considered as the photoacceptor. Functions of cytochrome c oxidase as a signal generator as well as a signal transducer in irradiated cells are outlined.

Mechanism of coupling of oxidative phosphorylation and the membrane potential of mitochondria.

Abstract: THE existence of an electrical potential difference at the mitochondrial membrane is one of the postulates of Mitchell's chemiosmotic theory of oxidative phosphorylation1,2. A shunting of the mitochondrial membrane leads to the uncoupling of oxidative phosphorylation. It has been demonstrated that uncoupling agents increase the proton permeability of phospholipid micelle membranes3 and artificial bimolecular membranes4–7. Mitchell and Moyle8 showed that uncouplers can operate as proton carriers in mitochondrial membranes.

Macroscopically ordered state in an exciton system

Abstract: There is a rich variety of quantum liquids—such as superconductors, liquid helium and atom Bose–Einstein condensates—that exhibit macroscopic coherence in the form of ordered arrays of vortices1,2,3,4. Experimental observation of a macroscopically ordered electronic state in semiconductors has, however, remained a challenging and relatively unexplored problem. A promising approach for the realization of such a state is to use excitons, bound pairs of electrons and holes that can form in semiconductor systems. At low densities, excitons are Bose-particles5, and at low temperatures, of the order of a few kelvin, excitons can form a quantum liquid—that is, a statistically degenerate Bose gas or even a Bose–Einstein condensate5,6,7. Here we report photoluminescence measurements of a quasi-two-dimensional exciton gas in GaAs/AlGaAs coupled quantum wells and the observation of a macroscopically ordered exciton state. Our spatially resolved measurements reveal fragmentation of the ring-shaped emission pattern into circular structures that form periodic arrays over lengths up to 1 mm.