En el contexto de la profunda crisis civilizatoria que vive la humanidad, se da igualmente una severa crisis de las izquierdas en diferentes partes del mundo. Las propuestas alternativas que fueron ...representadas por los denominados gobiernos progresistas en América Latina, en lo fundamental, fracasaron en términos de los objetivos que se transformadores que se propusieron. La incapacidad de la izquierda »oficial« para reflexionar crítica y autocríticamente sobre estas experiencias impide aprender de éstas, con lo cual no puede sino profundizarse la crisis de dicha izquierda como alternativa al capitalismo y, más ampliamente, a civilización en crisis.
Electrocatalytic CO2 reduction has developed into a broad field, spanning fundamental studies of enzymatic ‘model’ catalysts to synthetic molecular catalysts and heterogeneous gas diffusion ...electrodes producing commercially relevant quantities of product. This diversification has resulted in apparent differences and a disconnect between seemingly related approaches when using different types of catalysts. Enzymes possess discrete and well understood active sites that can perform reactions with high selectivity and activities at their thermodynamic limit. Synthetic small molecule catalysts can be designed with desired active site composition but do not yet display enzyme‐like performance. These properties of the biological and small molecule catalysts contrast with heterogeneous materials, which can contain multiple, often poorly understood active sites with distinct reactivity and therefore introducing significant complexity in understanding their activities. As these systems are being better understood and the continuously improving performance of their heterogeneous active sites closes the gap with enzymatic activity, this performance difference between heterogeneous and enzymatic systems begins to close. This convergence removes the barriers between using different types of catalysts and future challenges can be addressed without multiple efforts as a unified picture for the biological‐synthetic catalyst spectrum emerges.
Electrochemical CO2 utilization has quickly expanded and diversified into employing a wide range of catalysts and device configurations. This mini‐review seeks to highlight the significant progress and common elements in heterogeneous, small molecule and enzymatic systems to bridge the gap between these seemingly disparate approaches and to provide a more holistic and unified strategy to develop the field of electrocatalytic CO2 reduction.
Gelatinous zooplankton play a crucial role in marine planktonic food webs. However, primarily due to methodological challenges, the in situ diet of zooplankton remains poorly investigated and little ...is known about their trophic interactions including feeding behaviour, prey selection and in situ feeding rates. This is particularly true for gelatinous zooplankton including the marine pelagic tunicate, Dolioletta gegenbauri. In this study, we applied an 18S rRNA amplicon metabarcoding approach to identify the diet of captive‐fed and wild‐caught D. gegenbauri on the midcontinental shelf of the South Atlantic Bight, USA. Sequencing‐based approaches were complimented with targeted quantitative real‐time polymerase chain reaction (PCR) analyses. Captive‐fed D. gegenbauri gut content was dominated by pico‐, nano‐ and micro‐plankton including pico‐dinoflagellates (picozoa) and diatoms. These results suggested that diatoms were concentrated by D. gegenbauri relative to their concentration in the water column. Analysis of wild‐caught doliolids by quantitative real‐time PCR utilizing a group‐specific diatom primer set confirmed that diatoms were concentrated by D. gegenbauri, particularly by the gonozooid life stage associated with actively developing blooms. Sequences derived from larger metazoans were frequently observed in wild‐caught animals but not in captive‐fed animals suggesting experimental bias associated with captive feeding. These studies revealed that the diet of D. gegenbauri is considerably more diverse than previously described, that parasites are common in wild populations, and that prey quality, quantity and parasites are likely all important factors in regulating doliolid population dynamics in continental shelf environments.
Ductile functionalized polypropylene is of great interest in multi-layer composites development. A capped-end triblock polyether diamine (H2N-PO2-TMO9-PO3-NH2) was used as a linker of two different ...maleated isotactic polypropylenes (iPP-g-MAH, at 1 and 3 wt%) by twin-screw reactive extrusion. The molecular architecture, the semi-crystalline microstructure and the mechanical properties of the resulting polymers were analysed as a function of the molar ratio of NH2:MAH (0:1, 0.33:1, 0.5:1, 0.66:1, 1:1, 1.5:1, 2:1). At the molecular scale, the chemically modified polymers were characterized by FTIR and by the determination of gel content following the ASTM D2765-84 standard method. Differential Scanning Calorimetry, Wide Angle X-rays Scattering and Self Successive Auto-nucleation techniques showed the impact of the crosslinking: a decrease of the melting temperature as compared with the unmodified iPP-g-MAH polymer, as well as a decrease of the crystallinity ratio for the iPP-g-MAH at 3 wt% of MAH. Interestingly, Dynamic Mechanical Analysis and video-controlled uniaxial tensile tests showed that the polymers obtained in stoichiometric NH2:MAH molar ratio exhibit the best mechanical properties enlightened by a switch from brittle to ductile mechanical behaviour with few differences between the two iPP-g-MAH.
A slight crosslinking enables maleated isotactic polypropylenes to switch from brittle to ductile mechanical behavior with higher resilience than the most conventional one. Display omitted
•A capped-end triblock polyetherdiamine is used as a linker of different iPP-g-MAH by twin-screw reactive extrusion.•The three-dimensional networks are characterized by FTIR and by the determination of gel content.•The semi-crystalline microstructure is thermally described applying the Self-Successive Auto nucleation technique.•A switch from brittle to ductile mechanical properties is observed studying the intrinsic true mechanical behaviours.
The pyridazine-pyridine triazole-based Rat ligand, L pydzpy 4-(4-methylphenyl)-3-(3-pyridazinyl)-5-(2-pyridinyl)-1,2,4-triazole, is potentially ditopic. Nevertheless, L pydzpy is shown herein to ...exclusively form mononuclear iron(II) complexes, FeII(L pydzpy )2(NCE)2·solvent, in the presence of coordinating NCE anions (E = S or Se). Specifically, a new family of 10 mononuclear complexes, in which L pydzpy binds in a monotopic bidentate manner, has been made: two solvent-free complexes, FeII(L pydzpy )2(NCS)2 (1) and FeII(L pydzpy )2(NCSe)2 (2); six solvatomorphs, 1·4CH3CN, 2·4CH3CN, 1·2.25CH3CN, 2·3CH3CN, 2·tetrahydrofuran, and 2·CHCl3; and a pair of desolvated polymorphs, 1′ and 2′. Seven of them are spin crossover-active, the exceptions being 1, 2, and 2′. This is confirmed by single-crystal X-ray diffraction (XRD) for 1, 2, 1·4CH3CN, and 2·4CH3CN and is consistent with variable-temperature optical microscopy observations on single crystals of 1·4CH3CN and 2·4CH3CN and on samples of 1′ and 2′. Powder XRD, thermogravimetric analysis, and solid-state magnetometry reveal that desolvated 1′ and 2′ are capable of absorbing and desorbing a range of volatile guests: CH3CN in both cases and also tetrahydrofuran and CHCl3 in the case of 2′.
A Simple Method of Predicting Spin State in Solution Rodríguez-Jiménez, Santiago; Yang, Mingrui; Stewart, Ian ...
Journal of the American Chemical Society,
12/2017, Letnik:
139, Številka:
50
Journal Article
Recenzirano
A simple method, using density functional theory (DFT), of predicting spin-state in advance of synthesis is reported. Specifically, an excellent correlation is observed between the switching ...temperatures (T 1/2) in CDCl3 solution of five spin-crossover (SCO)-active FeII(L azine )2(NCBH3)2 complexes and the DFT-calculated (and observed) 15N NMR chemical shift (δNA ) of the five different azine-substituted 1,2,4-triazole ligands employed, L azine = 4-(4-methylphenyl)-3-phenyl-5-(azine)-1,2,4-triazole, where azine = pyridine, pyridazine, 4-pyrimidine, pyrazine, and 2-pyrimidine. To test the generality of this finding, DFT was also employed to readily predict the δNA values for a family of 16 literature ligands, known as bpp X,Y X,Y-substituted 2,6-(pyrazol-1-yl)pyridines, which have produced 16 SCO-active FeII(bpp X,Y )2(Z)2 complexes (Z = BF4 or in one case PF6) in (CD3)2CO solution: again an excellent correlation was found between the computed δNA and the observed T 1/2. These correlations represent a key advance in the field, as they allow a simple DFT calculation on a modified ligand to be used to reliably predict, before synthesis of the ligand or complex, the T 1/2 that would result from that modification. Achieving such easily predictable tuning of T 1/2, and hence of spin-state, is a significant step forward in the field of SCO and also has big implications in many other fields in which spin-state is key, including catalysis, metallo-enzyme modeling studies, and host–guest chemistry.
Metallophilicity is an essential concept that builds upon the attraction between closed shell metal ions. We report on the M2(bisNHC)22+ (M=AuI, AgI; NHC=N‐heterocyclic carbene) systems, which ...display almost identical features in the solid state. However, in solution the Au2 cation exhibits a significantly higher degree of rigidity owed to the stronger character of the aurophilic interactions. Both Au2 and Ag2 cationic constructs are able to accommodate Ag+ ions via M–M interactions, despite their inherent Coulombic repulsion. When electrostatic repulsion between host and guest is partially diminished, M–M distances are substantially shortened. Quantum chemical calculations estimate intermetallic bond orders up to 0.2. Although at the limit of (or beyond) the van der Waals radii, metallophilic interactions are responsible for their behavior in solution.
Host‐guest systems: Although they seem to be almost identical in the solid state, Au⋅⋅⋅Au interactions in solution proved to be much stronger than Ag⋅⋅⋅Ag bonding in our unsupported system. Such interactions take place even beyond the van der Waals limits (see figure).
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The EMPA-REG OUTCOME (Empagliflozin, Cardiovascular Outcome Event Trial in patients with Type 2 Diabetes Mellitus (T2DM)) trial made evident the potentiality of pharmacological ...sodium-glucose cotransporter 2 (SGLT2) inhibition for treating patients with diabetes and cardiovascular disease. Since the effect of empagliflozin or other SGLT2 inhibitors on the whole cardiac metabolic profile was never analysed before, and with the purpose to contribute to elucidate the benefits at cardiac level of the use of empagliflozin, we explored the effect of the treatment with empagliflozin for six weeks on the cardiac metabolomic profile of Zucker diabetic fatty rats, a model of early stage T2DM, using untargeted metabolomics approach. Empagliflozin reduced significantly the cardiac content of sphingolipids (ceramides and sphingomyelins) and glycerophospholipids (major bioactive contributing factors linking insulin resistance to cardiac damage) and decreased the cardiac content of the fatty acid transporter cluster of differentiation 36 (CD36); induced significant decreases of the cardiac levels of essential glycolysis intermediaries 2,3-bisphosphoglycerate and phosphoenolpyruvate, and regulated the abundance of several amino acids of relevance as tricarboxylic acid suppliers and/or in the metabolic control of the cardiac function as glutamic acid, gamma-aminobutyric acid and sarcosine. Empagliflozin treatment activated the cardioprotective master regulator of cellular energyhomeostasis AMP-activatedproteinkinase (AMPK) and enhanced autophagy at cardiac level, while it decreased significantly the cardiac mRNA levels of the pro-inflammatory cytokines interleukin-6 (IL-6), chemerin, TNF-α and MCP-1, reinforcing the hypothesis of a direct role for empagliflozin in attenuating cardiac inflammation. Our results provide an advancement on the knowledge of the mechanisms linking the therapy with empagliflozin with protective effects on the development of cardiometabolic diseases whose course is associated with remarkable cardiac bioenergetics dysregulation and disarrangement in cardiac metabolome and lipidome.
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