Lossy data compression with random gates

We introduce a new protocol for a lossy data compression algorithm which is based on constraint satisfaction gates. We show that the theoretical capacity of algorithms built from standard parity-check gates converges exponentially fast to the Shannon's bound when the number of variables seen by each gate increases. We then generalize this approach by introducing random gates. They have theoretical performances nearly as good as parity checks, but they offer the great advantage that the encoding can be done in linear time using the Survey Inspired Decimation algorithm, a powerful algorithm for constraint satisfaction problems derived from statistical physics

Differences in uptake kinetics of ammonium and nitrate in legumes and cereals

In a greenhouse experiment, influx isotherms were obtained for nitrate and ammonium from pigeonpeas cv. ICPL 87, chickpea cv. K850, groundnut cv. NCAC 17090, sorghum cv. CSH5, Pennisetum glaucum cv. WC 75 and maize cv. Ganga 5. The transition in influx isotherms for both N sources was within the concentration range (0.05-2.5 mM) tested. There were significant differences in Km and Vmax for ammonium between legumes and cereals. The difference in the kinetic properties for nitrate uptake between the 2 groups of plants only became apparent at the highest concentration tested. Legumes translocated absorbed nitrate and ammonium to shoots more rapidly than cereal

Density limit in discharges with high internal inductance on JT-60U

High densities exceeding the Greenwald limit by a factor of 1.7 have been obtained in L-mode discharges with high internal inductances of elli as high as 2.8 in JT-60U. The internal inductance is controlled by ramping down the plasma current. In addition to the extension of the operational regime limited by disruptions, confinement performance remains as good as an H89PL factor of 1.6 even above the Greenwald limit. While an earlier high elli study has indicated core confinement improvement due to enhancement of the poloidal field, the additional improvement of the tolerance against the high density turned out to be correlated with high edge temperature. The normalized density when the detachment occurs, characterized by a decrease in the Dα signal at the divertor, is even higher in the case with no disruption than in the case with a disruption. These comparisons have indicated that the improvement in thermal and particle transport does exist in the periphery and in the edge in high elli plasmas, and the shift of the density limit towards higher densities is observed coincidently. Although the high elli discharge studied here lies outside the usual parameter space for steady-state operation of a tokamak, demonstration of a stable discharge with good confinement beyond the Greenwald limit suggests that the magnetic shear at the edge is one key parameter to uncover the physical elements of the operational density limit

One step RSB scheme for the rate distortion function

We apply statistical mechanics to an inverse problem of linear mapping to investigate the physics of the irreversible compression. We use the replica symmetry breaking (RSB) technique with a toy model to demonstrate the Shannon's result. The rate distortion function, which is widely known as the theoretical limit of the compression with a fidelity criterion, is derived using the Parisi one step RSB scheme. The bound can not be achieved in the sparsely-connected systems, where suboptimal solutions dominate the capacity.Comment: 8 pages, 2 figure

Magnetic irreversibility and Verwey transition in nano-crystalline bacterial magnetite

The magnetic properties of biologically-produced magnetite nanocrystals biomineralized by four different magnetotactic bacteria were compared to those of synthetic magnetite nanocrystals and large, high quality single crystals. The magnetic feature at the Verwey temperature, $T_{V}$, was clearly seen in all nanocrystals, although its sharpness depended on the shape of individual nanoparticles and whether or not the particles were arranged in magnetosome chains. The transition was broader in the individual superparamagnetic nanoparticles for which $T_{B}<T_{V}$, where $T_{B}$ is the superparamagnetic blocking temperature. For the nanocrystals organized in chains, the effective blocking temperature $T_{B}>T_{V}$ and the Verwey transition is sharply defined. No correlation between the particle size and $T_{V}$ was found. Furthermore, measurements of $M(H,T,time)$ suggest that magnetosome chains behave as long magnetic dipoles where the local magnetic field is directed along the chain and this result confirms that time-logarithmic magnetic relaxation is due to the collective (dipolar) nature of the barrier for magnetic moment reorientation

Appraisal of Local Farmers’ Practices on Land Management for a Guideline of Agricultural Development in the Sahel Zone of Niger

In order to bridge a gap between research results and farmers’ needs for agricultural development in the Sahel, we made a study of traditional agricultural production systems derived from what we understood about indigenous knowledge (IK) of Sahelian farmers. The study was conducted in the western part of Niger, West Africa. IK was gathered from interviews among several villages of different generations. Then impartiality was verified. We obtained detailed information on land management and topographical features of farmland and devised a thorough local classification system. Statistical results showed that the obtained information was not significantly different among villages and generations. This result brought recognition that IK was a shared knowledge among local farmers in the study area. The study classified in detail a farmland that was directly or indirectly affected by household economy, the potential of natural resources like organic matter, and the relationship between agriculturalist and pastoralist. Understanding this context for soil fertility management at the village level makes it possible to assess the situation more appropriately than simply looking at actual practices, thereby helping to identify a problematic issue that concerns local farmers

Precision Measurement of Cosmic-Ray Antiproton Spectrum

The energy spectrum of cosmic-ray antiprotons has been measured in the range 0.18 to 3.56 GeV, based on 458 antiprotons collected by BESS in recent solar-minimum period. We have detected for the first time a distinctive peak at 2 GeV of antiprotons originating from cosmic-ray interactions with the interstellar gas. The peak spectrum is reproduced by theoretical calculations, implying that the propagation models are basically correct and that different cosmic-ray species undergo a universal propagation. Future BESS flights toward the solar maximum will help us to study the solar modulation and the propagation in detail and to search for primary antiproton components.Comment: REVTeX, 4 pages including 4 eps figure

Role of the dimerized gap due to anion ordering in spin-density wave phase of (TMTSF)2_2ClO4_4 at high magnetic fields

Magnetoresistance measurements have been carried out along the highly conducting a axis in the FISDW phase of hydrogened and deuterated (TMTSF)$_2$ClO$_4$ for various cooling rates through the anion ordering temperature. With increasing the cooling rate, a) the high field phase boundary $\beta_{\rm {HI}}$, observed at 27 T in hydrogened samples for slowly cooled, is shifted towards a lower field, b) the last semimetallic SDW phase below $\beta_{\rm {HI}}$ is suppressed, and c) the FISDW insulating phase above $\beta_{\rm {HI}}$ is enhanced in both salts. The cooling rate dependence of the FISDW transition and of $\beta_{\rm {HI}}$ in both salts can be explained by taking into account the peculiar SDW nesting vector stabilized by the dimerized gap due to anion ordering.Comment: 6pages,6figures(EPS), accepted for publication in PR