The structures of the α‐alums RbCr(SO4)2·12H2O and CsCr(SeO4)2·12H2O at 293 and 12 K

The crystal structures of the α‐alums rubidium chromium bis(­sulfate) dodecahydrate, RbCr(SO₄)₂·12H₂O, and caesium chromium bis[tetraoxoselenate(VI)] dodecahydrate, CsCr(SeO₄)₂·12H₂O, have been determined by X‐ray diffraction at 293 and 12 K. The metal atoms lie on sites and the anions lie on threefold rotation axes. The accurate and extensive data sets lead to much more precise determinations than are available from earlier work, particularly at 12 K. The changes in the atomic displacement parameters between 293 and 12 K correspond to the respective predominances of intermolecular and intramolecular vibrational effects.     

Abstract parabolic problems with critical nonlinearities and applications to Navier-Stokes and heat equations

We prove a local existence and uniqueness theorem for abstract parabolic problems of the type when the nonlinearity satisfies certain critical conditions. We apply this abstract result to the Navier-Stokes and heat equations.

     

Inferring topological features of proteins from amino acid residue networks

Topological properties of native folds are obtained from statistical analysis of 160 low homology proteins covering the four structural classes. This is done analyzing one, two and three-vertex joint distribution of quantities related to the corresponding network of amino acid residues. Emphasis on the amino acid residue hydrophobicity leads to the definition of their center of mass as vertices in this contact network model with interactions represented by edges. The network analysis helps us to interpret experimental results such as hydrophobic scales and fraction of buried accessible surface area in terms of the network connectivity. Moreover, those networks show assortative mixing by degree. To explore the vertex-type dependent correlations, we build a network of hydrophobic and polar vertices. This procedure presents the wiring diagram of the topological structure of globular proteins leading to the following attachment probabilities between hydrophobic–hydrophobic 0.424(5), hydrophobic-polar 0.419(2) and polar–polar 0.157(3) residues.     

Coherent thermal emission by microstructured waveguides

Following Greffet et al. [Coherent emission of light by thermal sources. Nature 2002;416:61-4], we study in this article, the possibility to engineer thermal coherent sources with waveguides. The idea is to rule a grating on a waveguide made of a slice of germanium deposited on a participating media such as glass. The guided waves, thermally excited are coupled to the far field by the grating and increase the system emissivity in certain directions and wavelengths. We numerically compute the diffraction of a plane wave by the grating by a rigorous coupled waves algorithm (RCWA). The reflected, transmitted and absorbed energy calculated allows to obtain the system emissivity by means of the Kirchhoff law.     

Transition-metal nanoparticles in imidazolium ionic liquids: recyclable catalysts for biphasic hydrogenation reactions

1-n-Butyl-3-methylimidazolium hexafluorophosphate room-temperature ionic liquid is not only suitable as a medium for the preparation and stabilization of iridium nanoparticles but also ideal for the generation of recyclable biphasic catalytic systems for hydrogenation reactions. Thus, Ir(0) nanoparticles with a mean diameter of 2 nm have been prepared by reduction of Ir(I) dissolved in the ionic liquid with H2. This catalytic solution can be reused several times for the biphasic hydrogenation of olefins under mild reaction conditions.     

Polylactide (PLA)-CaSO4 composites toughened with low molecular weight and polymeric ester-like plasticizers and related performances

Large amounts of stable β-anhydrite II (AII), a specific type of dehydrated gypsum and a by-product of lactic acid production process, can be melt-blended with bio-sourced and biodegradable polylactide (PLA) to produce economically interesting novel composites with high tensile strength and thermal stability.To enhance their toughness, while preserving an optimal stiffness, selected low molecular weight plasticizers (bis(2-ethylhexyl) adipate and glyceryl triacetate) and polymeric adipates with different molecular weights have been mixed with a specific PLA (l/d isomer ratio of 96/4) and 40 wt% of AII using an internal kneader. Addition of up to 10 wt% plasticizer into these highly filled compositions can trigger a fourfold increase of the impact strength with respect to the compositions without any modifier, cold crystallization properties and a significant decrease of their glass transition temperature. Moreover, these ternary compositions (PLA-AII-plasticizer) are clearly characterized by easier processing, notable thermo-mechanical performances and good filler dispersion. This study represents a new approach in formulating novel melt-processable polyester grades with improved characteristic features using PLA as biodegradable polymer matrix.     

Highly Enantioselective Synthesis of 1,2,3‐Substituted Cyclopropanes by Using α‐Iodo‐ and α‐Chloromethylzinc Carbenoids

Herein, we report the enantio‐ and diastereoselective formation of trans‐iodo‐ and trans‐chlorocyclopropanes from α‐iodo‐ and α‐chlorozinc carbenoids by using a dioxaborolane‐derived chiral ligand. The synthetically useful iodocyclopropane building blocks were derivatized by an electrophilic trapping of the corresponding cyclopropyl lithium species or a Negishi coupling to give access to a variety of enantioenriched 1,2,3‐substituted cyclopropanes. The synthetic utility of this method was demonstrated by the formal synthesis of an HIV‐1 protease inhibitor. In addition, the related stereoselective bromocyclopropanation was also investigated. New insights about the relative electrophilicity of haloiodomethylzinc carbenoids are also presented.     

Insights into the Complexity of Weak Intermolecular Interactions Interfering in Host–Guest Systems

The recognition properties of heteroditopic hemicryptophane hosts towards anions, cations, and neutral pairs, combining both cation–π and anion–π interaction sites, were investigated to probe the complexity of interfering weak intermolecular interactions. It is suggested from NMR experiments, and supported by CASSCF/CASPT2 calculations, that the binding constants of anions can be modulated by a factor of up to 100 by varying the fluorination sites on the electron‐poor aromatic rings. Interestingly, this subtle chemical modification can also reverse the sign of cooperativity in ion‐pair recognition. Wavefunction calculations highlight how short‐ and long‐range interactions interfere in this recognition process, suggesting that a disruption of anion–π interactions can occur in the presence of a co‐bound cation. Such molecules can be viewed as prototypes for examining complex processes controlled by the competition of weak interactions.     

Growth of Chlorella vulgaris on Sugarcane Vinasse: The Effect of Anaerobic Digestion Pretreatment

Microalgae farming has been identified as the most eco-sustainable solution for producing biodiesel. However, the operation of full-scale plants is still limited by costs and the utilization of industrial and/or domestic wastes can significantly improve economic profits. Several waste effluents are valuable sources of nutrients for the cultivation of microalgae. Ethanol production from sugarcane, for instance, generates significant amounts of organically rich effluent, the vinasse. After anaerobic digestion treatment, nutrient remaining in such an effluent can be used to grow microalgae. This research aimed to testing the potential of the anaerobic treated vinasse as an alternative source of nutrients for culturing microalgae with the goal of supplying the biodiesel industrial chain with algal biomass and oil. The anaerobic process treating vinasse reached a steady state at about 17 batch cycles of 24 h producing about 0.116 m³CH₄ kgCOD_vinasse ^?1. The highest productivity of Chlorella vulgaris biomass (70 mg l^?1 day^?1) was observed when using medium prepared with the anaerobic digester effluent. Lipid productivity varied from 0.5 to 17 mg l^?1 day^?1. Thus, the results show that it is possible to integrate the culturing of microalgae with the sugarcane industry by means of anaerobic digestion of the vinasse. There is also the advantageous possibility of using by-products of the anaerobic digestion such as methane and CO₂ for sustaining the system with energy and carbon source, respectively.     

Preparation of Polyfunctional Arylzinc Organometallics in Toluene by Halogen/Zinc Exchange Reactions

A wide range of polyfunctional diaryl‐ and diheteroarylzinc species were prepared in toluene within 10 min to 5 h through an I/Zn or Br/Zn exchange reaction using bimetallic reagents of the general formula R′₂Zn?2 LiOR (R′=sBu, tBu, pTol). Highly sensitive functional groups, such as a triazine, a ketone, an aldehyde, or a nitro group, were tolerated in these exchange reactions, enabling the synthesis of a plethora of functionalized (hetero)arenes after quenching with various electrophiles. Insight into the constitution and reactivity of these bimetallic mixtures revealed the formation of highly active lithium diorganodialkoxyzincates of type [R′₂Zn(OR)₂Li₂].