Catálogo de publicaciones - revistas

<jats:p>Conventional separation technologies to separate valuable commodities are energy intensive, consuming 15% of the worldwide energy. Mixed-matrix membranes, combining processable polymers and selective adsorbents, offer the potential to deploy adsorbent distinct separation properties into processable matrix. We report the rational design and construction of a highly efficient, mixed-matrix metal-organic framework membrane based on three interlocked criteria: (i) a fluorinated metal-organic framework, AlFFIVE-1-Ni, as a molecular sieve adsorbent that selectively enhances hydrogen sulfide and carbon dioxide diffusion while excluding methane; (ii) tailoring crystal morphology into nanosheets with maximally exposed (001) facets; and (iii) in-plane alignment of (001) nanosheets in polymer matrix and attainment of [001]-oriented membrane. The membrane demonstrated exceptionally high hydrogen sulfide and carbon dioxide separation from natural gas under practical working conditions. This approach offers great potential to translate other key adsorbents into processable matrix.</jats:p>

<jats:p>Structural maintenance of chromosomes (SMC) protein complexes structure genomes by extruding DNA loops, but the molecular mechanism that underlies their activity has remained unknown. We show that the active condensin complex entraps the bases of a DNA loop transiently in two separate chambers. Single-molecule imaging and cryo–electron microscopy suggest a putative power-stroke movement at the first chamber that feeds DNA into the SMC–kleisin ring upon adenosine triphosphate binding, whereas the second chamber holds on upstream of the same DNA double helix. Unlocking the strict separation of “motor” and “anchor” chambers turns condensin from a one-sided into a bidirectional DNA loop extruder. We conclude that the orientation of two topologically bound DNA segments during the SMC reaction cycle determines the directionality of DNA loop extrusion.</jats:p>

<jats:p>Ambitious conservation efforts are needed to stop the global biodiversity crisis. In this study, we estimate the minimum land area to secure important biodiversity areas, ecologically intact areas, and optimal locations for representation of species ranges and ecoregions. We discover that at least 64 million square kilometers (44% of terrestrial area) would require conservation attention (ranging from protected areas to land-use policies) to meet this goal. More than 1.8 billion people live on these lands, so responses that promote autonomy, self-determination, equity, and sustainable management for safeguarding biodiversity are essential. Spatially explicit land-use scenarios suggest that 1.3 million square kilometers of this land is at risk of being converted for intensive human land uses by 2030, which requires immediate attention. However, a sevenfold difference exists between the amount of habitat converted in optimistic and pessimistic land-use scenarios, highlighting an opportunity to avert this crisis. Appropriate targets in the Post-2020 Global Biodiversity Framework to encourage conservation of the identified land would contribute substantially to safeguarding biodiversity.</jats:p>

<jats:p>Global policies call for connecting protected areas (PAs) to conserve the flow of animals and genes across changing landscapes, yet whether global PA networks currently support animal movement—and where connectivity conservation is most critical—remain largely unknown. In this study, we map the functional connectivity of the world’s terrestrial PAs and quantify national PA connectivity through the lens of moving mammals. We find that mitigating the human footprint may improve connectivity more than adding new PAs, although both strategies together maximize benefits. The most globally important areas of concentrated mammal movement remain unprotected, with 71% of these overlapping with global biodiversity priority areas and 6% occurring on land with moderate to high human modification. Conservation and restoration of critical connectivity areas could safeguard PA connectivity while supporting other global conservation priorities.</jats:p>

<jats:p> The design of materials and their manufacture into membranes that can handle industrial conditions and separate complex nonaqueous mixtures are challenging. We report a versatile strategy to fabricate polytriazole membranes with 10-nanometer-thin selective layers containing subnanometer channels for the separation of hydrocarbons. The process involves the use of the classical nonsolvent-induced phase separation method and thermal cross-linking. The membrane selectivity can be tuned to the lower end of the typical nanofiltration range (200 to 1000 gram mole <jats:sup>−1</jats:sup> ). The polytriazole membrane can enrich up to 80 to 95% of the hydrocarbon content with less than 10 carbon atoms (140 gram mole <jats:sup>−1</jats:sup> ). These membranes preferentially separate paraffin over aromatic components, making them suitable for integration in hybrid distillation systems for crude oil fractionation. </jats:p>

<jats:p> The rarity of parthenogenetic species is typically attributed to the reduced genetic variability that accompanies the absence of sex, yet natural parthenogens can be surprisingly successful. Ecological success is often proposed to derive from hybridization through enhanced genetic diversity from repetitive origins or enhanced phenotypic breadth from heterosis. Here, we tested and rejected both hypotheses in a classic parthenogen, the diploid grasshopper <jats:italic>Warramaba virgo</jats:italic> . Genetic data revealed a single hybrid mating origin at least 0.25 million years ago, and comparative analyses of 14 physiological and life history traits showed no evidence for altered fitness relative to its sexual progenitors. Our findings imply that the rarity of parthenogenesis is due to constraints on origin rather than to rapid extinction. </jats:p>

<jats:p>Topological insulators constitute a newly characterized state of matter that contains scatter-free edge states surrounding an insulating bulk. Conventional wisdom regards the insulating bulk as essential, because the invariants that describe the topological properties of the system are defined therein. Here, we study fractal topological insulators based on exact fractals composed exclusively of edge sites. We present experimental proof that, despite the lack of bulk bands, photonic lattices of helical waveguides support topologically protected chiral edge states. We show that light transport in our topological fractal system features increased velocities compared with the corresponding honeycomb lattice. By going beyond the confines of the bulk-boundary correspondence, our findings pave the way toward an expanded perception of topological insulators and open a new chapter of topological fractals.</jats:p>

<jats:p>Mountains are hotspots of biodiversity and ecosystem services, but they are warming about twice as fast as the global average. Climate change may reduce alpine snow cover and increase vegetation productivity, as in the Arctic. Here, we demonstrate that 77% of the European Alps above the tree line experienced greening (productivity gain) and &lt;1% browning (productivity loss) over the past four decades. Snow cover declined significantly during this time, but in &lt;10% of the area. These trends were only weakly correlated: Greening predominated in warmer areas, driven by climatic changes during summer, while snow cover recession peaked at colder temperatures, driven by precipitation changes. Greening could increase carbon sequestration, but this is unlikely to outweigh negative implications, including reduced albedo and water availability, thawing permafrost, and habitat loss.</jats:p>

<jats:p>Insects are facing a multitude of anthropogenic stressors, and the recent decline in their biodiversity is threatening ecosystems and economies across the globe. We investigated the impact of glyphosate, the most commonly used herbicide worldwide, on bumblebees. Bumblebee colonies maintain their brood at high temperatures via active thermogenesis, a prerequisite for colony growth and reproduction. Using a within-colony comparative approach to examine the effects of long-term glyphosate exposure on both individual and collective thermoregulation, we found that whereas effects are weak at the level of the individual, the collective ability to maintain the necessary high brood temperatures is decreased by more than 25% during periods of resource limitation. For pollinators in our heavily stressed ecosystems, glyphosate exposure carries hidden costs that have so far been largely overlooked.</jats:p>