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Mechanical interlocking of molecules (catenation) is a nontrivial challenge in modern synthetic chemistry and materials science 1 , 2 . One strategy to achieve catenation is the design of pre-annular molecules that are capable of both efficient cyclization and of pre-organizing another precursor to engage in subsequent interlocking 3 – 9 . This task is particularly difficult when the annular target is composed of a large ensemble of molecules, that is, when it is a supramolecular assembly. However, the construction of such unprecedented assemblies would enable the visualization of nontrivial nanotopologies through microscopy techniques, which would not only satisfy academic curiosity but also pave the way to the development of materials with nanotopology-derived properties. Here we report the synthesis of such a nanotopology using fibrous supramolecular assemblies with intrinsic curvature. Using a solvent-mixing strategy, we kinetically organized a molecule that can elongate into toroids with a radius of about 13 nanometres. Atomic force microscopy on the resulting nanoscale toroids revealed a high percentage of catenation, which is sufficient to yield ‘nanolympiadane’ 10 , a nanoscale catenane composed of five interlocked toroids. Spectroscopic and theoretical studies suggested that this unusually high degree of catenation stems from the secondary nucleation of the precursor molecules around the toroids. By modifying the self-assembly protocol to promote ring closure and secondary nucleation, a maximum catenation number of 22 was confirmed by atomic force microscopy. Nanoscale toroids with a high percentage of poly-catenation and radii of up to about 13 nm are kinetically organized using fibrous supramolecular assemblies with intrinsic curvature and a solvent-mixing strategy.

Molecular recognition to preorganize noncovalently polymerizable supramolecular complexes is a characteristic process of natural supramolecular polymers, and such recognition processes allow for dynamic self-alteration, yielding complex polymer systems with extraordinarily high efficiency in their targeted function. We herein show an example of such molecular recognition-controlled kinetic assembly/disassembly processes within artificial supramolecular polymer systems using six-membered hydrogen-bonded supramolecular complexes (rosettes). Electron-rich and poor monomers are prepared that kinetically coassemble through a temperature-controlled protocol into amorphous coaggregates comprising a diverse mixture of rosettes. Over days, the electrostatic interaction between two monomers induces an integrative self-sorting of rosettes. While the electron-rich monomer inherently forms toroidal homopolymers, the additional electrostatic interaction that can also guide rosette association allows helicoidal growth of supramolecular copolymers that are comprised of an alternating array of two monomers. Upon heating, the helicoidal copolymers undergo a catastrophic transition into amorphous coaggregates via entropy-driven randomization of the monomers in the rosette. Unlike natural supramolecular polymers, artificial counterparts do not have molecular recognition processes to preorganize the supramolecular complexes before final assembly. Here, the authors show supramolecular copolymerization driven by integrative self-sorting of two different monomers into discrete six-membered supramolecular complexes (rosettes).

Plasmonic lasers advance To push the physical limitations of lasers to the nanoscale regime it is necessary to tackle the fundamental challenge of surpassing the diffraction limit. It has been suggested that surface plasmons — light–matter waves trapped on the surface of a conductor — can be used to tightly confine light on very short length scales, but such approaches have been previously hampered by severe losses. Oulton et al . now demonstrate that it is possible to circumvent this problem by utilizing a hybrid between a dielectric waveguide and a conducting surface supporting a plasmon mode, thereby showing the experimental realization of a nanoscale plasmonic laser with an optical mode a hundred times smaller than the diffraction limit. Such hybrid plasmonic coherent light sources offer the possibility to explore extreme interactions between light and matter, and may open important new avenues in optoelectronics. A key challenge is to realize ultracompact lasers that can directly generate coherent optical fields at the nanometre scale, far beyond the diffraction limit. Surface plasmons could be used to tightly confine light on very short lengthscales, but so far this approach has been hampered by ohmic losses at optical frequencies. The experimental demonstration of nanometre-scale plasmonic lasers is now reported, realized using a hybrid plasmonic waveguide — these lasers can generate optical modes a hundred times smaller than the diffraction limit. Laser science has been successful in producing increasingly high-powered, faster and smaller coherent light sources 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 . Examples of recent advances are microscopic lasers that can reach the diffraction limit, based on photonic crystals 3 , metal-clad cavities 4 and nanowires 5 , 6 , 7 . However, such lasers are restricted, both in optical mode size and physical device dimension, to being larger than half the wavelength of the optical field, and it remains a key fundamental challenge to realize ultracompact lasers that can directly generate coherent optical fields at the nanometre scale, far beyond the diffraction limit 10 , 11 . A way of addressing this issue is to make use of surface plasmons 12 , 13 , which are capable of tightly localizing light, but so far ohmic losses at optical frequencies have inhibited the realization of truly nanometre-scale lasers based on such approaches 14 , 15 . A recent theoretical work predicted that such losses could be significantly reduced while maintaining ultrasmall modes in a hybrid plasmonic waveguide 16 . Here we report the experimental demonstration of nanometre-scale plasmonic lasers, generating optical modes a hundred times smaller than the diffraction limit. We realize such lasers using a hybrid plasmonic waveguide consisting of a high-gain cadmium sulphide semiconductor nanowire, separated from a silver surface by a 5-nm-thick insulating gap. Direct measurements of the emission lifetime reveal a broad-band enhancement of the nanowire’s exciton spontaneous emission rate by up to six times owing to the strong mode confinement 17 and the signature of apparently threshold-less lasing. Because plasmonic modes have no cutoff, we are able to demonstrate downscaling of the lateral dimensions of both the device and the optical mode. Plasmonic lasers thus offer the possibility of exploring extreme interactions between light and matter, opening up new avenues in the fields of active photonic circuits 18 , bio-sensing 19 and quantum information technology 20 .

Magnetic fields in galaxies are produced via the amplification of seed magnetic fields of unknown nature. The seed fields, which might exist in their initial form in the intergalactic medium, were never detected. We report a lower bound B ≥ 3 x 10⁻¹⁶ gauss on the strength of intergalactic magnetic fields, which stems from the nonobservation of GeV gamma-ray emission from electromagnetic cascade initiated by tera-electron volt gamma rays in intergalactic medium. The bound improves as λB⁻¹/² if magnetic field correlation length, λB, is much smaller than a megaparsec. This lower bound constrains models for the origin of cosmic magnetic fields.

A durable molecular catalyst for water oxidation has been made from readily available and relatively inexpensive materials. Roughly three-fourths of the power generated globally comes from burning fossil fuels. For solar energy to compete directly as a replacement, technologies are needed to capture this energy in a chemical form—as a fuel—so it can be used when sunlight is not available. One bottleneck in the development of practical solar fuels is the water oxidation reaction. Water is the only potential source of electrons capable of reducing protons to H 2 or CO 2 to carbonaceous fuels on a global scale. Thus, while there may be many options for reduction catalysts, redox cycling inevitably requires the coupling of reduction reactions to water oxidation (see the figure, panel A). On page 342 of this issue, Yin et al. ( 1 ) report on a water-soluble water oxidation catalyst that has a reaction center containing four cobalt (Co) atoms. Its surrounding ligands are not organic groups but are polyoxotungstate (PW 9 O 34 9− ) anions that resemble the solid oxide supports of heterogeneous catalysts. This catalyst weds the best features of extant heterogeneous and homogeneous catalysts while remedying many of their respective disadvantages.

Flexible, stretchable, and spanning microelectrodes that carry signals from one circuit element to another are needed for many emerging forms of electronic and optoelectronic devices. We have patterned silver microelectrodes by omnidirectional printing of concentrated nanoparticle inks in both uniform and high-aspect ratio motifs with minimum widths of approximately 2 micrometers onto semiconductor, plastic, and glass substrates. The patterned microelectrodes can withstand repeated bending and stretching to large levels of strain with minimal degradation of their electrical properties. With this approach, wire bonding to fragile three-dimensional devices and spanning interconnects for solar cell and light-emitting diode arrays are demonstrated.

Although grain boundaries can serve as effective sinks for radiation-induced defects such as interstitials and vacancies, the atomistic mechanisms leading to this enhanced tolerance are still not well understood. With the use of three atomistic simulation methods, we investigated defect-grain boundary interaction mechanisms in copper from picosecond to microsecond time scales. We found that grain boundaries have a surprising \"loading-unloading\" effect. Upon irradiation, interstitials are loaded into the boundary, which then acts as a source, emitting interstitials to annihilate vacancies in the bulk. This unexpected recombination mechanism has a much lower energy barrier than conventional vacancy diffusion and is efficient for annihilating immobile vacancies in the nearby bulk, resulting in self-healing of the radiation-induced damage.

The Kirsten rat sarcoma viral oncogene homolog (KRAS) is mutated in approximately 25% of all human cancers and is known to be a major player promoting and maintaining tumorigenesis through the RAS/MAPK pathway. Over the years, a large number of studies have identified strategies at different regulatory levels to tackle this ‘difficult-to-target’ oncoprotein. Yet, the most ideal strategy to overcome KRAS and its downstream effects has yet to be uncovered. This review summarizes the role of KRAS activating mutations in multiple cancer types as well as the key findings for potential strategies inhibiting its oncogenic behavior. A comprehensive analysis of the different pathways and mechanisms associated with KRAS activity in tumors will ultimately pave the way for promising future work that will identify optimum therapeutic strategies.

Systems approaches to disease are grounded in the idea that disease-perturbed protein and gene regulatory networks differ from their normal counterparts; we have been pursuing the possibility that these differences may be reflected by multiparameter measurements of the blood. Such concepts are transforming current diagnostic and therapeutic approaches to medicine and, together with new technologies, will enable a predictive and preventive medicine that will lead to personalized medicine.Systems approaches to disease are grounded in the idea that disease-perturbed protein and gene regulatory networks differ from their normal counterparts; we have been pursuing the possibility that these differences may be reflected by multiparameter measurements of the blood. Such concepts are transforming current diagnostic and therapeutic approaches to medicine and, together with new technologies, will enable a predictive and preventive medicine that will lead to personalized medicine.

Children nowadays, particularly in urban areas, are more disconnected from nature than ever before, leading to a large-scale \"extinction of experience\" with the natural world. Yet there are many potential benefits from children interacting with nature first-hand, including via outdoor learning opportunities. Urban environmental education programmes typically aim to increase awareness and knowledge of local biodiversity and to promote positive attitudes and behaviour towards the environment. However, limited research has been conducted evaluating to what extent these interventions achieve their goals. Here, we explore and assess the influence of a six-week bird-feeding and monitoring project conducted within school grounds (\"Bird Buddies\") on individual awareness, knowledge and attitudes towards birds by primary school children. This initiative was conducted across eight (sub-)urban primary schools within Brighton and Hove (UK), with 220 participating children (aged 7 to 10). Via pre- and post-project questionnaires, we found evidence for enhanced awareness of local biodiversity, alongside significant gains in both bird identification knowledge and attitudes, which were greatest for children with little prior exposure to nature. Many children expressed a keenness to continue improving the environmental value of their school grounds and to apply elements of the project at home. Student project evaluation scores were consistently positive. Mirroring this, participating teachers endorsed the project as a positive learning experience for their students. One year after the project, several schools were continuing to feed and watch birds. Collectively, the findings from this study highlight the multiple benefits that can be derived from engagement with a relatively short outdoor environmental activity. We therefore believe that such interventions, if repeated locally/longer term, could enhance children's experience with nature in urban settings with combined positive environmental impact.