Every supernova so far observed has been considered to be the terminal explosion of a star. Moreover, all supernovae with absorption lines in their spectra show those lines decreasing in velocity over time, as the ejecta expand and thin, revealing slower-moving material that was previously hidden. In addition, every supernova that exhibits the absorption lines of hydrogen has one main light-curve peak, or a plateau in luminosity, lasting approximately 100 days before declining. Here we report observations of iPTF14hls, an event that has spectra identical to a hydrogen-rich core-collapse supernova, but characteristics that differ extensively from those of known supernovae. The light curve has at least five peaks and remains bright for more than 600 days; the absorption lines show little to no decrease in velocity; and the radius of the line-forming region is more than an order of magnitude bigger than the radius of the photosphere derived from the continuum emission. These characteristics are consistent with a shell of several tens of solar masses ejected by the progenitor star at supernova-level energies a few hundred days before a terminal explosion. Another possible eruption was recorded at the same position in 1954. Multiple energetic pre-supernova eruptions are expected to occur in stars of 95 to 130 solar masses, which experience the pulsational pair instability. That model, however, does not account for the continued presence of hydrogen, or the energetics observed here. Another mechanism for the violent ejection of mass in massive stars may be required.

† These authors contributed equally to this work Solution-processed organic-inorganic lead halide perovskites have recently emerged as promising gain media for tunable semiconductor lasers. However, optically pumped continuous-wave lasing at room temperature -a prerequisite for a laser diode -has not been realized so far. Here, we report lasing action in a surface emitting distributed feedback methylammonium lead iodide (MAPbI3) perovskite laser on silicon substrate, at room temperature under continuous-wave optical pumping. This outstanding performance is achieved because of the ultra-low lasing threshold of 13 W/cm 2 , which is enabled by thermal nanoimprint lithography that directly patterns perovskite into a high Q cavity with large mode confinement, while at the same time improves perovskite's emission characteristics. Our results represent a major step toward electrically pumped lasing in organic and thin-film materials, as well as the insertion of perovskite lasers into photonic integrated circuits for applications in optical computing, sensing and on-chip quantum information.Since the advent of silicon (Si) photonics, the field of photonic integrated circuit (IC) has progressed significantly over the last few decades [1]. While many photonic components have the potential to be inserted into future electronic-photonic ICs on Si, a critical component -an efficient chip-scale laser on Si -has not been realized because of Si's indirect bandgap. Although III-V/Si lasers formed via wafer bonding of III-V onto Si substrate have been the main candidate, the low yield and high manufacturing cost restrict their further development as light sources for electronic-photonic ICs [2]. An alternative gain medium that is Si compatible is solution-processed organic semiconductors. Although organic lasers cannot compete with inorganic III-V lasers in many performance metrics, they do offer several advantages such as easy wavelength tunability,

Highlights d MIWI/piRNA activates mRNA translation via imperfect basepairing interactions d HuR and eIF3f are required for MIWI/piRNA-mediated target mRNA activation d piRNA system controls the translation of a subset of mRNAs in mouse spermatids d piRNA system plays a central role in acrosome formation during spermiogenesis

We introduced a new strategy to synthesize NVP nanoparticles with a thin carbon-coating layer embedded in a three-dimensional (3D) graphene network.

Highlights d LARP7 interacts simultaneously with the U6 snRNA and U6specific C/D box snoRNAs d Depletion of LARP7 results in reduced 2 0 -O-methylation of the U6 snRNA d Changes in alternative splicing are observed in the absence of LARP7 d A LARP7 mutation causes splicing alterations in Alazami syndrome patients