Improved Combinatorial Group Testing Algorithms for Real-World Problem Sizes

We study practically efficient methods for performing combinatorial group testing. We present efficient non-adaptive and two-stage combinatorial group testing algorithms, which identify the at most d items out of a given set of n items that are defective, using fewer tests for all practical set sizes. For example, our two-stage algorithm matches the information theoretic lower bound for the number of tests in a combinatorial group testing regimen.Comment: 18 pages; an abbreviated version of this paper is to appear at the 9th Worksh. Algorithms and Data Structure

Cosmological perturbations in a gravity with quadratic order curvature couplings

We present a set of equations describing the evolution of the scalar-type cosmological perturbation in a gravity with general quadratic order curvature coupling terms. Equations are presented in a gauge ready form, thus are ready to implement various temporal gauge conditions depending on the problems. The Ricci-curvature square term leads to a fourth-order differential equation for describing the spacetime fluctuations in a spatially homogeneous and isotropic cosmological background.Comment: 5 pages, no figure, To appear in Phys. Rev.

The infrared conductivity of Nax_xCoO2_2: evidence of gapped states

We present infrared ab-plane conductivity data for the layered cobaltate Na$_x$CoO$_2$ at three different doping levels ($x=0.25, 0.50$, and 0.75). The Drude weight increases monotonically with hole doping, $1-x$. At the lowest hole doping level $x$=0.75 the system resembles the normal state of underdoped cuprate superconductors with a scattering rate that varies linearly with frequency and temperature and there is an onset of scattering by a bosonic mode at 600 \cm. Two higher hole doped samples ($x=0.50$ and 0.25) show two different-size gaps (110 \cm and 200 \cm, respectively) in the optical conductivities at low temperatures and become insulators. The spectral weights lost in the gap region of 0.50 and 0.25 samples are shifted to prominent peaks at 200 \cm and 800 \cm, respectively. We propose that the two gapped states of the two higher hole doped samples ($x$=0.50 and 0.25) are pinned charge ordered states.Comment: 4 pages, 3 figure

The effect of two ectomycorrhizal fungi, Paxillus involutus and Suillus tomentosus, and of Bacillus subtilis on Fusarium damping-off in jack pine seedlings

On a testé l'effet de deux espèces de champignons ectomycorhiziens, le Paxillus involutus et le Suillus tomentosus, et une lignée de la bactérie Bacillus subtilis sur le Fusarium moniliforme, agent pathogène de la fonte des semis du pin gris (Pinus banksiana). Le P. involutus et B. subtilis ont tous les deux inhibé la croissance in vitro du F moniliforme. Les filtrats de culture de P. involutus et de B. subtilis ont été toxiques pour le F moniliforme, mais la formation de chlamydospores par le F moniliforme a été observée. Une meilleure survie des plantules a été observée lorsqu'elles étaient co-inoculées avec le P. involutus et le B. subtilis plutôt qu'avec le F moniliforme seulement. Le S. tomentosus n'a pas inhibé la croissance in vitro du F. moniliforme ni accru la survie des plantules de pin gris en présence de F moniliforme. Ce dernier a réduit la formation d'ectomycorhizes sur le pin gris par le P. involutus et le S. tomentosus. Le nombre d’unités formatrices de colonies du F. monoliforme a été significativement réduit quand les plantules ont été inoculées avec le P. involotus ou le B. subtilis seul ou en combinaison. D’autre part, le S. tomentosus n’a pas réduit le nombre d’unités formatrices de colonies du F. monoliforme. La suppression de la croissance du F. monoliforme par le P. involutus et le B. subtilis a entraîné la production de composés antifongiques.Two species of ectomycorrhizal fungi, Paxillus involutus and Suillus tomentosus, and a bacterial strain of Bacillus subtilis, were tested against Fusarium moniliforme, the causal agent of damping-off in jack pine (Pinus banksiana) seedlings. Both P. involutus and B. subtilis inhibited in vitro growth of F moniliforme. The culture filtrates of P. involutus and B. subtilis were toxic to F moniliforme, but chlamydospore formation of F moniliforme was observed. Greater jack pine seedling survival was observed when co-inoculated with P. involutus and B. subtilis than with F moniliforme alone. S. tomentosus neither inhibited in vitro growth of F moniliforme nor increased survival of jack pine seedlings against F moniliforme. F moniliforme reduced ectomycorrhiza formation on jack pine seedlings by P. involutus and S. tomentosus. The number of colony forming units of F moniliforme was significantly reduced when seedlings were inoculated with P. involutus and B. subtilis alone or in combination. S. tomentosus, on the other hand, did not reduce the number of colony forming units of F moniliforme. The suppression of F moniliforme growth by P. involutus and B. subtilis involved production of antifungal compounds

A conserved variable in the perturbed hydrodynamic world model

We introduce a scalar-type perturbation variable $\Phi$ which is conserved in the large-scale limit considering general sign of three-space curvature ($K$), the cosmological constant ($\Lambda$), and time varying equation of state. In a pressureless medium $\Phi$ is {\it exactly conserved} in all scales.Comment: 4 pages, no figure, To appear in Phys. Rev.

Field evaluation of the CATT/Trypanosoma brucei gambiense on blood-impregnated filter papers for diagnosis of human African trypanosomiasis in southern Sudan.

Most Human African Trypanosomiasis (HAT) control programmes in areas endemic for Trypanosoma brucei gambiense rely on a strategy of active mass screening with the Card Agglutination Test for Trypanosomiasis (CATT)/T. b. gambiense. We evaluated the performance, stability and reproducibility of the CATT/T. b. gambiense on blood-impregnated filter papers (CATT-FP) in Kajo-Keji County, South-Sudan, where some areas are inaccessible to mobile teams. The CATT-FP was performed with a group of 100 people with a positive CATT on whole blood including 17 confirmed HAT patients and the results were compared with the CATT on plasma (CATT-P). The CATT-FP was repeated on impregnated filter papers stored at ambient and refrigerated temperature for 1, 3, 7 and 14 days. Another 82 patients with HAT, including 78 with a positive parasitology, were tested with the CATT-FP and duplicate filter paper samples were sent to a reference laboratory to assess reproducibility. The CATT-FP was positive in 90 of 99 patients with HAT (sensitivity: 91%). It was less sensitive than the CATT-P (mean dilution difference: -2.5). There was no significant loss of sensitivity after storage for up to 14 days both at ambient and cool temperature. Reproducibility of the CATT-FP was found to be excellent (kappa: 0.84). The CATT-FP can therefore be recommended as a screening test for HAT in areas where the use of CATT-P is not possible. Further studies on larger population samples in different endemic foci are still needed before the CATT-FP can be recommended for universal use

Supermetallic conductivity in bromine-intercalated graphite

Exposure of highly oriented pyrolytic graphite to bromine vapor gives rise to in-plane charge conductivities which increase monotonically with intercalation time toward values (for ~6 at% Br) that are significantly higher than Cu at temperatures down to 5 K. Magnetotransport, optical reflectivity and magnetic susceptibility measurements confirm that the Br dopes the graphene sheets with holes while simultaneously increasing the interplanar separation. The increase of mobility (~ 5E4 cm^2/Vs at T=300 K) and resistance anisotropy together with the reduced diamagnetic susceptibility of the intercalated samples suggests that the observed supermetallic conductivity derives from a parallel combination of weakly-coupled hole-doped graphene sheets.Comment: 5 pages, 4 figure

Multitasking associative networks

We introduce a bipartite, diluted and frustrated, network as a sparse restricted Boltzman machine and we show its thermodynamical equivalence to an associative working memory able to retrieve multiple patterns in parallel without falling into spurious states typical of classical neural networks. We focus on systems processing in parallel a finite (up to logarithmic growth in the volume) amount of patterns, mirroring the low-level storage of standard Amit-Gutfreund-Sompolinsky theory. Results obtained trough statistical mechanics, signal-to-noise technique and Monte Carlo simulations are overall in perfect agreement and carry interesting biological insights. Indeed, these associative networks pave new perspectives in the understanding of multitasking features expressed by complex systems, e.g. neural and immune networks.Comment: to appear on Phys.Rev.Let