Mesostructured ZnO/Au nanoparticle composites with enhanced photocatalytic activity

Ease of catalyst separation from reaction mixtures represents a significant advantage in heterogeneous photocatalytic wastewater treatment. However, the activity of the catalyst strongly depends on its surface-to-volume ratio. Here, we present an approach based on cylindrical polybutadiene-block-poly(2-vinylpyridine) polymer brushes as template, which can be simultaneously loaded with zinc oxide (ZnO) and gold (Au) nanoparticles. Pyrolytic template removal of the polymer yields in mesostructured ZnO/Au composites, showing higher efficiencies in the photocatalytic degradation of ciprofloxacin and levofloxacin (generic antibiotics present in clinical wastewater) as compared to neat mesostructured ZnO. Upscaling of the presented catalyst is straightforward promising high technical relevance

Enhancing the Catalytic Activity of Palladium Nanoparticles via Sandwich-Like Confinement by Thin Titanate Nanosheets

As atomically thin oxide layers deposited on flat (noble) metal surfaces have been proven to have a significant influence on the electronic structure and thus the catalytic activity of the metal, we sought to mimic this architecture at the bulk scale. This could be achieved by intercalating small positively charged Pd nanoparticles of size 3.8 nm into a nematic liquid crystalline phase of lepidocrocite-type layered titanate. Upon intercalation the galleries collapsed and Pd nanoparticles were captured in a sandwichlike mesoporous architecture showing good accessibility to Pd nanoparticles. On the basis of X-ray photoelectron spectroscopy (XPS) and CO diffuse reflectance Fourier transform infrared spectroscopy (DRIFTS) Pd was found to be in a partially oxidized state, while a reduced Ti species indicated an electronic interaction between nanoparticles and nanosheets. The close contact of titanate sandwiching Pd nanoparticles, moreover, allows for the donation of a lattice oxygen to the noble metal (inverse spillover). Due to the metal–support interactions of this peculiar support, the catalyst exhibited the oxidation of CO with a turnover frequency as high as 0.17 s–1 at a temperature of 100 °C

Segregation by thermal diffusion of an intruder in a moderately dense granular fluid

A solution of the inelastic Enskog equation that goes beyond the weak dissipation limit and applies for moderate densities is used to determine the thermal diffusion factor of an intruder immersed in a dense granular gas under gravity. This factor provides a segregation criterion that shows the transition between the Brazil-nut effect (BNE) and the reverse Brazil-nut effect (RBNE) by varying the parameters of the system (masses, sizes, density and coefficients of restitution). The form of the phase-diagrams for the BNE/RBNE transition depends sensitively on the value of gravity relative to the thermal gradient, so that it is possible to switch between both states for given values of the parameters of the system. Two specific limits are considered with detail: (i) absence of gravity, and (ii) homogeneous temperature. In the latter case, after some approximations, our results are consistent with previous theoretical results derived from the Enskog equation. Our results also indicate that the influence of dissipation on thermal diffusion is more important in the absence of gravity than in the opposite limit. The present analysis extends previous theoretical results derived in the dilute limit case [V. Garz\'o, Europhys. Lett. {\bf 75}, 521 (2006)] and is consistent with the findings of some recent experimental results.Comment: 10 figure

Renin inhibition by substituted piperidines: A novel paradigm for the inhibition of monomeric aspartic proteinases?

BackgroundThe aspartic proteinase renin catalyses the first and rate-limiting step in the conversion of angiotensinogen to the hormone angiotensin II, and therefore plays an important physiological role in the regulation of blood pressure. Numerous potent peptidomimetic inhibitors of this important drug target have been developed, but none of these compounds have progressed past clinical phase II trials. Limited oral bioavailability or excessive production costs have prevented these inhibitors from becoming new antihypertensive drugs. We were interested in developing new nonpeptidomimetic renin inhibitors.ResultsHigh-throughput screening of the Roche compound library identified a simple 3,4-disubstituted piperidine lead compound. We determined the crystal structures of recombinant human renin complexed with two representatives of this new class. Binding of these substituted piperidine derivatives is accompanied by major induced-fit adaptations around the enzyme's active site.ConclusionsThe efficient optimisation of the piperidine inhibitors was facilitated by structural analysis of the renin active site in two renin-inhibitor complexes (some of the piperidine derivatives have picomolar affinities for renin). These structural changes provide the basis for a novel paradigm for inhibition of monomeric aspartic proteinases

On Arrangements of Orthogonal Circles

In this paper, we study arrangements of orthogonal circles, that is, arrangements of circles where every pair of circles must either be disjoint or intersect at a right angle. Using geometric arguments, we show that such arrangements have only a linear number of faces. This implies that orthogonal circle intersection graphs have only a linear number of edges. When we restrict ourselves to orthogonal unit circles, the resulting class of intersection graphs is a subclass of penny graphs (that is, contact graphs of unit circles). We show that, similarly to penny graphs, it is NP-hard to recognize orthogonal unit circle intersection graphs.Comment: Appears in the Proceedings of the 27th International Symposium on Graph Drawing and Network Visualization (GD 2019

Estableciendo una interfaz ciencia-gestión-sociedad para la conservación de la biodiversidad y el bienestar humano en la Amazonia: el caso de Madre de Dios, Perú

El objetivo de esta investigación transdisciplinaria fue establecer las bases para una interfaz ciencia-gestión-sociedad para la conservación ambiental y el desarrollo sostenible en Madre de Dios, Perú mediante: (1) la identificación y la caracterización de los actores de la conservación de la biodiversidad y el bienestar humano; (2) el análisis de los puntos de vista de los actores sobre las principales tendencias del desarrollo en la región; y (3) un proceso de involucramiento de los actores desde la academia, el gobierno y la sociedad civil. Los métodos usados incluyeron visitas de campo, entrevistas a expertos, un mapeo detallado de actores, una encuesta a actores y un taller participativo multiactor. El mapeo de partes interesadas identificó a 16 categorías de actores clave dentro de los usuarios directos de los recursos de la tierra, los usuarios indirectos de los recursos de la tierra, el sector público, la sociedad civil y las organizaciones de investigación. Según los actores encuestados, la debilidad de las instituciones gubernamentales y la corrupción son unas de las causas subyacentes a los problemas ambientales y sociales en Madre de Dios, y en particular de la minería aurífera y otras actividades extractivas ilegales e informales. El estudio resaltó también el potencial innovador que existe en la región, que ha sido el hogar de varias iniciativas exitosas para la naturaleza y la gente en las últimas décadas

How policymakers and other leaders can build a more sustainable post-COVID-19 ‘normal’

The UN 2030 Agenda’s 17 Sustainable Development Goals (SDGs) and the COVID-19 pandemic share two important characteristics. They are global challenges that if not met, pose risks to all citizens. Furthermore, responses need to be system-level, rather than sectoral. COVID-19 has illuminated three complementary, compelling actions that can address these challenges—work across silos; visibly use science in policy; and harness simultaneous global interruption to habits. This commentary describes these using worked examples and suggests actions for policymakers and other leaders. Acknowledging that the full SDG agenda is of much broader multidimensional scope than the COVID-19 pandemic, the SDG examples focus on environmental sustainability