The status of the KSS bound and its possible violations (How perfect can a fluid be?)

In this work we briefly review the Kovtun-Son-Starinet (KSS) computation of the ratio eta/s for quantum field theories with gravitational dual and the related conjecture that it is bound from below by 1/(4 pi). We discuss the validity of the bound and the nature of its possible violations, its relevance for RHIC, its connection with phase transitions and other related issues.Comment: 10 pages, 5figs, Invited talk at "10 years of AdS/CFT Correspondence", Buenos Aires, Dec. 2007, honoring Juan Maldacen

On the road to democracy /

The constitutionalist government face to face with the sanitary and educational problems of Mexico -- Revolutionary destruction and governmental reconstruction -- The understanding between the government and commerce -- The Mexican popular university -- The industrial democratic policy -- The constitutional path -- Our democratic initiation -- An interesting research concerning popular education -- Our ideal of universal solidarity -- An optimistic conclusion -- The new Control Department and administrative moralization -- Our idea of the fatherland.Mode of access: Internet

Large-Scale Continuous Flow Transformation of Oximes into Fused-Bicyclic Isoxazolidines: An Example of Process Intensification

Here, we report a continuous flow protocol for the [3 + 2] cycloaddition of nitrones, in situ generated from oximes, into bicyclic isoxazolidines. This thermal process required very high temperatures to be efficient that were not easily reached in conventional reactors. A couple of examples are presented and in both the flow process showed a greater performance than the batch mode. The process intensification study allowed the generation of 120 g/h of a key pharmaceutical intermediate

Thermochromism of Model Organic Aerosol Matter

Laboratory experiments show that the optical absorptivity of model organic matter is not an intrinsic property, but a strong function of relative humidity, temperature, and insolation. Suites of representative polyfunctional C_<i>x</i>H_<i>y</i>O_<i>z</i> oligomers in water develop intense visible absorptions upon addition of inert electrolytes. The resulting mixtures reach mass absorption cross sections σ(532 nm) ∼ 0.1 m²/gC in a few hours, absorb up to 9 times more solar radiation than the starting material, can be half-bleached by noon sunlight in ∼1 h, and can be repeatedly recycled without carbon loss. Visible absorptions red-shift and evolve increasingly faster in subsequent thermal aging cycles. Thermochromism and its strong direct dependences on ionic strength and temperature are ascribed to the dehydration of >CH−C(OH)< groups into >CC< unsaturations by a polar E1 mechanism, and bleaching to photoinduced retrohydration. These transformations are deemed to underlie the daily cycles of aerosol absorption observed in the field, and may introduce a key feedback in the earth’s radiative balance

Electrochemical Deprotection of <i>para</i>-Methoxybenzyl Ethers in a Flow Electrolysis Cell

Electrochemical deprotection of <i>p</i>-methoxybenzyl (PMB) ethers was performed in an undivided electrochemical flow reactor in MeOH solution, leading to the unmasked alcohol and <i>p</i>-methoxybenzaldehyde dimethyl acetal as a byproduct. The electrochemical method removes the need for chemical oxidants, and added electrolyte (BF₄NEt₄) can be recovered and reused. The method was applied to 17 substrates with high conversions in a single pass, yields up to 92%, and up to 7.5 g h^–1 productivity. The PMB protecting group was also selectively removed in the presence of some other common alcohol protecting groups