Optical-inertia space sextant for an advanced space navigation system, phase B

Optical-inertia space sextant for advanced space navigation syste

Onset of interchange instability in a coupled core–SOL plasma

The dynamics at the edge of fusion confinement devices is driven by interchange instabilities and involves the motion of plasma across two regions—the “core region” and the scrape-off layer (SOL)—distinguished by whether field lines are, respectively, closed or connected to the wall. Motivated by this phenomenon, we present an extensive linear stability analysis of a two-layer plasma model encompassing the coupled interactions between the region with closed field lines and the SOL. We focus on the effect of varying the particle diffusivity and ion viscosity, revealing the significant variation in the spatial structure of the critical modes. In addition, we have investigated the dependence of the stability threshold on the ratio of the width of the region with closed field lines to that of the SOL; this dependence is strong when the ratio is sufficiently small, but becomes insignificant once the ratio is of order unity

Social signals regulate gonadotropin-releasing hormone neurons in the green treefrog

Animals coordinate their physiological state with external cues to appropriately time reproduction. These external cues exert effects through influences on the gonadotropin-releasing hormone neurons (GnRH), at the apex of the hypothalamus-pituitary-gonad (HPG) axis. In green treefrogs, mating calls are important regulators of reproductive behavior and physiology. Reception of mating calls causes an increase in androgen levels, and androgens promote the production of mating calls, demonstrating a mutual influence between the communication and endocrine systems. In order to investigate the central nervous system correlates of social regulation of the HPG axis in green treefrogs, we exposed males to a mating chorus or a control stimulus (tones), counted the resulting number of septo-preoptic GnRH-immunoreactive cells (GnRH-ir), and measured changes in plasma androgens. We found that reception of the mating chorus caused an increase in the number of GnRH-ir cells. As previously shown, we also found that the reception of the mating chorus resulted in higher androgen levels, suggesting that the higher GnRH-ir cell number represents increased GnRH production and release. We suggest that mating calls are an important supplementary cue that promotes GnRH production and release within the context of GnRH regulation by seasonal cues. Previous studies have proposed a neuroanatomical link between the anuran auditory system and GnRH neurons. Our results demonstrate a functional role for this proposed sensory-endocrine circuit, and show for the first time an influence of acoustic signals on GnRH neurons

Optical inertial space sextant for an advanced space navigation system

Dual field optical tracking system and television camera chain combined with two gyroscopes to form space navigation sextant

Further search for a neutral boson with a mass around 9 MeV/c2

Two dedicated experiments on internal pair conversion (IPC) of isoscalar M1 transitions were carried out in order to test a 9 MeV/c2 X-boson scenario. In the 7Li(p,e+e-)8Be reaction at 1.1 MeV proton energy to the predominantly T=0 level at 18.15 MeV, a significant deviation from IPC was observed at large pair correlation angles. In the 11B(d,n e+e-)12C reaction at 1.6 MeV, leading to the 12.71 MeV 1+ level with pure T=0 character, an anomaly was observed at 9 MeV/c2. The compatibility of the results with the scenario is discussed.Comment: 12 pages, 5 figures, 2 table

Neutron clock as a friction-meter

Fast-fission reactions in collisions of four heavy systems (well below the fusion extra-push energy threshold), for which Hinde and coworkers had measured the prescission neutron multiplicities, have been analysed in terms of the deterministic dynamic model of Feldmeier coupled to a time-dependent statistical cascade calculation. In order to reproduce the measured prescission multiplicities and the observed (nearly symmetric) mass divisions, the energy dissipation must be dramatically changed with regard to the standard one-body dissipation: In the entrance channel, in the process of forming a composite system, the energy dissipation must be reduced to at least half of the one-body dissipation strength (k(s)(in) less than or equal to 0.5), and in the exit channel (from a mononucleus shape to scission) it must be increased to about 10 times that value (k(s)(out) approximate to 10)

Discrete Laplace Cycles of Period Four

We study discrete conjugate nets whose Laplace sequence is of period four. Corresponding points of opposite nets in this cyclic sequence have equal osculating planes in different net directions, that is, they correspond in an asymptotic transformation. We show that this implies that the connecting lines of corresponding points form a discrete W-congruence. We derive some properties of discrete Laplace cycles of period four and describe two explicit methods for their construction