Distinguishing among dark matter annihilation channels with neutrino telescopes

We investigate the prospects for distinguishing dark matter annihilation channels using the neutrino flux from gravitationally captured dark matter particles annihilating inside the sun. We show that, even with experimental error in energy reconstruction taken into account, the spectrum of contained muon tracks may be used to discriminate neutrino final states from the gauge boson/charged lepton final states and to determine their corresponding branching ratios. We also discuss the effect of $\nu_\tau$ regeneration inside the sun as a novel method to distinguish the flavor of final state neutrinos. This effect as evidenced in the muon spectrum becomes important for dark matter masses above 300 GeV. Distinguishing primary neutrinos and their flavor may be achieved using multi-year data from a detector with the same capability and effective volume as the IceCube/DeepCore array.Comment: 12 pages, 12 figures. v2 matches the published version, with revised figures and added references for improved clarity; results unchange

Thin supported MOF based mixed matrix membranes of Pebax® 1657 for biogas upgrade

This work shows the preparation of thin mixed matrix membranes (MMMs) with a 2-3 µm thick Pebax® 1657 layer on two different supports: a porous asymmetric polyimide P84® and dense polytrimethylsilylpropyne (PTMSP). Nanoparticles of metal-organic frameworks (MOFs) ZIF-8, MIL-101(Cr), UiO-66 and ZIF-7/8 core-shells were selected as fillers for the Pebax® 1657 based MMMs, all of them being MOFs with high CO2 adsorption capacity but different pore size distribution. All the membranes were characterized by SEM, FTIR, Raman, TGA and XRD analyses, showing in all cases a perfect compatibility of the Pebax® layer with both supports and also a good dispersion of the fillers in the polymeric matrix. These membranes were applied for the separation of equimolar CO2/CH4 mixtures at 35 °C under feed pressures between 3 and 5 bar, where an improvement in the gas separation performance with increasing pressure was noticed, thanks to the favored solubility of CO2. The synergistic compatibility between Pebax® 1657 and P84® gave rise to a 470% enhancement in CO2/CH4 selectivity, reaching a maximum value of 114 while the CO2 permeance increased by 40% up to 7.5 GPU. The addition of fillers in the Pebax® polymeric phase produced an improvement in the gas separation performance of the membranes, especially in terms of permeance, where the MMMs containing a 10 wt% loading of UiO-66 reached the optimum value of 11.5 GPU of CO2 (together with a CO2/CH4 selectivity of 55.6)

Chemocatalysis of sugars to produce lactic acid derivatives on zeolitic imidazolate frameworks

Several research studies related to biorefining have focused on developing routes for biomass conversion into biomaterials or platform molecules. In this work, the zeolitic imidazolate frameworks (ZIFs) ZIF-8 and ZIF-67 have been tested as catalysts in the conversion of sugars (sucrose, glucose and fructose) into methyl lactate. ZIF-8 and ZIF-67 have the same sodalite type zeolite structure but behaved differently in the sugar conversion in methanol due to the respective presence of Zn and Co in their structures. ZIF-8 has been found to be the most active for the conversion of sugars into methyl lactate (yield 42%) and was reused in four catalytic cycles. The chemical and physical effects caused by these cycles on the catalysts have been studied by several techniques (X-ray diffraction, thermogravimetric analyses, infrared spectroscopy, X-ray photoelectron spectroscopy, scanning electronic microscopy and nitrogen adsorption)

Synthesis and gas adsorption properties of mesoporous silica-NH2-MIL-53(Al) core-shell spheres

Ordered mesoporous silica-NH2-MIL-53(Al) core-shell spheres of about 4 µm in diameter have been synthesized by seeding the corresponding mesoporous silica spheres (MSSs) with crystals of NH2-MIL-53(Al) and subsequent secondary crystal growth into a MOF shell. The morphology of the particles was analyzed by SEM, while TGA, EDX and XRD characterizations gave information on the composition and structure of this material and the activation of the MOF. N2 adsorption analysis revealed that the NH2-MIL-53(Al) shell controlled the access of guest molecules into the hydrophilic silica mesoporous structure, while the breathing behavior of the microporous NH2-MIL-53(Al) shell was confirmed by CO2 adsorption isotherms

Nanosheets of MIL-53(Al) applied in membranes with improved CO 2 /N 2 and CO 2 /CH 4 selectivities

MIL-68(Al) and MIL-53(Al) are carboxylate-based metal-organic frameworks (MOFs) with the same chemical composition but different structures (polymorphs). In this study, MIL-53(Al) nanosheets of ca. 150 nm in size with an average thickness of 3.5 ± 0.9 nm were obtained after immersion of a sample composed of MIL-68(Al) and MIL-53(Al) in water under different conditions (ultrasound, stirring, reflux, 60 °C and room temperature). The disaggregated MIL-53(Al) nanosheets produced under more severe conditions were suspended in a PDMS solution and then deposited on asymmetric polyimide P84® supports under vacuum filtration to form supported mixed matrix membranes (MMMs). When applied to the separation of CO 2 /CH 4 and CO 2 /N 2 mixtures, the MMM with MIL-53(Al) nanosheets improved the CO 2 /CH 4 (28.4-28.7 vs. 22.4) and CO 2 /N 2 (19.9-23.2 vs. 17.5) selectivities of the conventional MIL-53(Al) MMM with higher CO 2 permeances (20.8-29.6 GPU vs. 9.5 GPU for CO 2 /CH 4 and 17.7-26.8 GPU vs. 11.2 GPU for CO 2 /N 2 )

Outstanding aspects on the use of spent FCC catalyst in binders

4 pages, 3 fiures, 7 tables.-- En: 1st Spanish National Conference on Advances in Materials Recycling and Eco – Energy Madrid, 12-13 November 2009.-- Editors: F. A. López, F. Puertas, F. J. Alguacil and A. Guerrero.FCC is a waste material from petrochemical plants which has interesting properties for preparing binders. FCC is lightly grey in color, and white FCC-portland cements with L*≥85 can be prepared. FCC reactivity is enhanced by grinding and it is attributed to pozzolanic reaction towards lime. Stratlingite is the main hydrated product from pozzolanic reaction, and CSH and CAH are also formed. Reactivity of FCC is high, and low curing temperature does not affect this contribution to strength in hardened mixtures. Additionally, high strength concrete can be easily prepared, and compressive strength greater 100MPa can be reached. Mixtures with low w/b ratio showed good behaviour in carbonation tests.Authors thank to Ministerio de Ciencia y Tecnología of Spain and FEDER the financial support of MAT 2001-2694 and BIA 2004-0052 projects.Peer reviewe

Estudio de la velocidad de corrosión de aceros embebidos en morteros de cemento sustituidos con residuo de catalizador de craqueo catalítico (FC3R)

This paper reports on a study of the corrosion levels in steel bars embedded in mortars made with a blend of Portland cement and (0-20%) spent fluid catalytic cracking catalyst residue (FC3R), with a variable (0.3-0.7) water/binder (w/b) ratio. The specimens were stored in the following conditions: relative humidity of 40, 80 or 100% and CO2 concentrations of 5 and 100%. The steel corrosion rate was measured with polarization resistance techniques. In the absence of aggressive agents, the steel was found to remain duly passivated in mortars with an FC3R content of up to 15% under all the conditions of relative humidity tested. The reinforcement corrosion level in mortars with a w/b ratio of 0.3 and 15% FC3R subjected to accelerated carbonation was similar to the level observed in the unblended Portland cement control mortar.En este trabajo se ha estudiado el nivel de corrosión de barras de acero embebidas en morteros de cemento Portland con relación agua/material cementante (a/mc) variable (0,3-0,7), en los que parte del cemento (0-20%) se sustituyó por catalizador de craqueo usado (FC3R). Las condiciones de conservación de las probetas elaboradas fueron las siguientes: distintas humedades relativas (40, 80 y 100%) y dos concentraciones de CO2 (5 y 100%). La velocidad de corrosión de los aceros se midió mediante la técnica de resistencia de polarización. Se ha podido determinar que, bajo las distintas condiciones de humedad relativa y ausencia de agresivo, los aceros se mantuvieron correctamente pasivados en los morteros con contenidos de FC3R de hasta el 15%. El nivel de corrosión que presenta el refuerzo embebidos en morteros con sustitución de un 15% de cemento por FC3R y relación a/mc 0,3, al ser sometidos a un proceso de carbonatación acelerada, era muy similar al mostrado por el mortero patrón, sin FC3R