Experiments of Interfacial Roughening in Hele-Shaw Flows with Weak Quenched Disorder

We have studied the kinetic roughening of an oil--air interface in a forced imbibition experiment in a horizontal Hele--Shaw cell with quenched disorder. Different disorder configurations, characterized by their persistence length in the direction of growth, have been explored by varying the average interface velocity v and the gap spacing b. Through the analysis of the rms width as a function of time, we have measured a growth exponent beta ~= 0.5 that is almost independent of the experimental parameters. The analysis of the roughness exponent alpha through the power spectrum have shown different behaviors at short (alpha_1) and long (alpha_2) length scales, separated by a crossover wavenumber q_c. The values of the measured roughness exponents depend on experimental parameters, but at large velocities we obtain alpha_1 ~= 1.3 independently of the disorder configuration. The dependence of the crossover wavenumber with the experimental parameters has also been investigated, measuring q_c ~ v^{0.47} for the shortest persistence length, in agreement with theoretical predictions.Comment: 20 pages, 22 figure

Use of hyghly reactive rice husk ash in the production of cement matrix reinforced with Green coconut fiber

[EN] This study evaluated the influence of partial replacement of Portland cement by rice husk ash (RHA) to enable the use of green coconut husk fiber as reinforcement for cementitious matrix. The use of highly reactive pozzolanic ash contributes for decreasing the alkaline attack on the vegetable fiber, originated from waste materials. The slurry dewatering technique was used for dispersion of the raw materials in aqueous solution, followed by vacuum drainage of water and pressing for the production of pad composites, as a simplified simulation of the Hatschek process for industrial manufacture. Five formulations were evaluated, two of them without any mineral additions. One of the mixtures served as a reference (without green coconut fibers) and the remaining ones were reinforced with the green coconut fibers (5% by weight of binder) and with the content of Portland cement replacement by RHA equal to 0, 30, 40 and 50%. The composites were analyzed at 28 days of age and after aging by immersion in warm wáter (65 ◦C), which lasted for 28 additional days. Physical and mechanical tests were applied for assessment of the performance of composites. Thermogravimetric analysis was used to observe the consumption of portlandite and chemically combined water content in the hydrated products for pastes presenting the same levels of Portland cement replacement by RHA (i.e., 0 50%) and with the water/binder ratio kept constant and equal to 0.5. The mechanical performance evaluated by bending test after 28 days reached the MOR of 15.7 MPa after the accelerate aging, for the composites reinforced with the green coconut fiber and with high levels of Portland cement replacement by RHA demonstrating that the use of Green coconut fiber for reinforcement can be very promising for the production of binary cement based matrix. The thermogravimetry showed that the replacement of Portland cement by the RHA helped in maintaining the mechanical behavior of the green coconut fiber in the composite subjected to the accelerated aging tests, and resulted in improved mechanical performance, providing a lightweight composite.To the Fundacao de Amparo Pesquisa do Estado de Sao Paulo (FAPESP) for financial support and ICITECH Universitat Politecnica de Valencia for facilitating the research development. To the Federal Agency CNPq, Brazil for grants provided to the USP team. Project 3018/2009 financed by Generalitat Valenciana, COMBURES project financed by Centro de Cooperacion al Desarrollo de la Universitat Politecnica de Valencia (ADSIDEO COOPERACIO) and Maicerias Espanolas DACSA S.A. for supplying RHA samples.Pereira, C.; Savastano, HJ.; Paya Bernabeu, JJ.; Santos, SF.; Borrachero Rosado, MV.; Monzó Balbuena, JM.; Soriano Martínez, L. (2013). Use of hyghly reactive rice husk ash in the production of cement matrix reinforced with Green coconut fiber. Industrial Crops and Products. 49:88-96. https://doi.org/10.1016/j.indcrop.2013.04.038S88964

Search for direct production of charginos and neutralinos in events with three leptons and missing transverse momentum in √s = 7 TeV pp collisions with the ATLAS detector

A search for the direct production of charginos and neutralinos in final states with three electrons or muons and missing transverse momentum is presented. The analysis is based on 4.7 fb−1 of proton–proton collision data delivered by the Large Hadron Collider and recorded with the ATLAS detector. Observations are consistent with Standard Model expectations in three signal regions that are either depleted or enriched in Z-boson decays. Upper limits at 95% confidence level are set in R-parity conserving phenomenological minimal supersymmetric models and in simplified models, significantly extending previous results

Jet size dependence of single jet suppression in lead-lead collisions at sqrt(s(NN)) = 2.76 TeV with the ATLAS detector at the LHC

Measurements of inclusive jet suppression in heavy ion collisions at the LHC provide direct sensitivity to the physics of jet quenching. In a sample of lead-lead collisions at sqrt(s) = 2.76 TeV corresponding to an integrated luminosity of approximately 7 inverse microbarns, ATLAS has measured jets with a calorimeter over the pseudorapidity interval |eta| < 2.1 and over the transverse momentum range 38 < pT < 210 GeV. Jets were reconstructed using the anti-kt algorithm with values for the distance parameter that determines the nominal jet radius of R = 0.2, 0.3, 0.4 and 0.5. The centrality dependence of the jet yield is characterized by the jet "central-to-peripheral ratio," Rcp. Jet production is found to be suppressed by approximately a factor of two in the 10% most central collisions relative to peripheral collisions. Rcp varies smoothly with centrality as characterized by the number of participating nucleons. The observed suppression is only weakly dependent on jet radius and transverse momentum. These results provide the first direct measurement of inclusive jet suppression in heavy ion collisions and complement previous measurements of dijet transverse energy imbalance at the LHC.Comment: 15 pages plus author list (30 pages total), 8 figures, 2 tables, submitted to Physics Letters B. All figures including auxiliary figures are available at http://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/HION-2011-02