Design of hierarchical porous aluminas by using one-pot synthesis and different calcination temperatures

Hierarchical aluminas with pore sizes ranging from a few nanometers to micrometers were obtained using an one-pot sol?Cgel synthesis. The aluminas were synthesized under acid conditions from aluminum isopropoxide in presence of poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymer template and decahydronaphthalene as emulsifier agent. High-resolution transmission electron microscopy, small-angle X-ray scattering, nitrogen physisorption isotherms and mercury intrusion porosimetry provided evidences of porous structure at different hierarchical levels. The produced aluminas possess hierarchical structure composed of different family of pores that coexist in form of cylinders, pyramids and stacking of platelets. The morphology observed by electron microscopy suggests that the cylindrical pores result from the stacking platelets and that the cylinders and pyramidal pores form the walls of macropores of circular section. These aluminas with hierarchical porous architecture present large surface areas (ca. 435?m² g^?1) and pore volumes (ca. 2.1?cm³ g^?1), tunable pore-size distributions and good thermal stability.     

Stress distribution in a transversely isotropic body with a thermally insulating parabolic crack subjected to a uniform heat flux

An explicit static thermoelastic solution is constructed for an infinite transversely isotropic body containing a thermally insulating parabolic crack in the plane of isotropy. The surface of the crack is free of stress. A uniform thermal flux is incident on the crack perpendicular to its surface. Formulas are obtained for the stress intensity factors near the tip of the crack. Institute of Mechanics, National Academy of Sciences of Ukraine, Kiev; Catholic University, Portugal. Translated from Teoreticheskaya i Prikladnaya Mekhanika, No. 30, pp. 54–66, 1999.     

Nucleate boiling of FC-87/FC-72 zeotropic mixtures on a horizontal copper disc

This paper presents nucleate boiling experimental results, at atmospheric pressure, for heat fluxes q ≤ 40 kW/m², for FC-87/FC-72 binary mixtures in molar fractions of 0/100, 25/75, 50/50, 75/25, 85/15 and 100/0, at saturation temperatures for pure fluids and bubble points for mixtures. The test section was an upward facing copper disc of 12 mm diameter and 1 mm thickness. The experimental heat transfer coefficient was compared with the correlations of Rohsenow (1952), as reported by Rohsenow et al. (Handbook of heat transfer, McGraw-Hill, New York, 1998), Stephan and Abdelsalam (Int J Heat Mass Transfer 23;73–78, 1978) and Cooper (Int Chem Eng Symp Ser 86:785–792, 1984) for pure fluids and the semi-empirical models of Stephan and Körner (Chem Ing Tech Jahrg 7:409–484, 1969), Thome (J Heat Transfer 104:474–478, 1982), Fujita et al. (1996), as reported by Rohsenow et al. (Handbook of heat transfer, McGraw-Hill, New York, 1998), Fujita and Tsutsui (Int J Heat Mass Transfer 37(1):291–302, 1994) and Calus and Leonidopoulos (Int J Heat Mass Transfer 17:249–256, 1973) for mixtures.     

Carried by History: Cesar Lattes,Nuclear Emulsions,and the Discovery of the Pi-meson

We analyze the role played by the Brazilian physicist Cesar Lattes (1924–2005) in the historical development of the nuclear emulsion technique and in the co-discovery of the pion. His works influenced and gave impetus to the development of experimental physics in Brazil, the foundation of a national center dedicated to physics research, the beginnings of Brazilian “Big Science,” and the inauguration of a long-lasting collaboration between Brazil and Japan in the field of comic ray physics.     

Understanding electrochemical performance of Ni(OH)2 films: a study contributions to energy storage

Journal of Solid State Electrochemistry - Nanostructured Ni(OH)2 was grown on the surface of a Ti plate via electrodeposition method. Analytical methods were employed to characterize the structure,...     

Nanoparticle-based assays in automated flow systems: A review

Nanoparticles (NPs) exhibit a number of distinctive and entrancing properties that explain their ever increasing application in analytical chemistry, mainly as chemosensors, signaling tags, catalysts, analytical signal enhancers, reactive species generators, analyte recognition and scavenging/separation entities.     

Mapping C−H⋅⋅⋅M Interactions in Confined Spaces: (α-ICyDMe)Au,Ag, Cu Complexes Reveal “Contra-electrostatic H Bonds” Masquerading as Anagostic Interactions**

What happens when a C−H bond is forced to interact with unpaired pairs of electrons at a positively charged metal? Such interactions can be considered as “contra-electrostatic” H-bonds, which combine the familiar orbital interaction pattern characteristic for the covalent contribution to the conventional H-bonding with an unusual contra-electrostatic component. While electrostatics is strongly stabilizing component in the conventional C−H⋅⋅⋅X bonds where X is an electronegative main group element, it is destabilizing in the C−H⋅⋅⋅M contacts when M is Au(I), Ag(I), or Cu(I) of NHC−M−Cl systems. Such remarkable C−H⋅⋅⋅M interaction became experimentally accessible within (α-ICyD^Me)MCl, NHC-Metal complexes embedded into cyclodextrins. Computational analysis of the model systems suggests that the overall interaction energies are relatively insensitive to moderate variations in the directionality of interaction between a C−H bond and the metal center, indicating stereoelectronic promiscuity of fully filled set of d-orbitals. A combination of experimental and computational data demonstrates that metal encapsulation inside the cyclodextrin cavity forces the C−H bond to point toward the metal, and reveals a still attractive “contra-electrostatic” H-bonding interaction.