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Dark pulse combs are formed in normal-dispersion microresonators with mode-interaction-assisted excitation, increasing freedom in microresonator design and potentially extending Kerr comb generation into the visible wavelength regime.

The shuttle effect of polysulfides in lithium sulfur batteries leads to performance degradation. Here, authors use fiber-based sensors to track and quantify the dissolved polysulfide concentration in the electrolyte during cell charge and discharge, revealing insights on stability and performance.

To measure an optical frequency, you are best off using an optical frequency comb. A radical approach shakes up how these combs are produced, and will permit their closer integration into optical-fibre technology.

Terahertz frequency combs are highly desired for applications in precision measurements, sensing, spectroscopy and metrology. Here the authors demonstrate the room-temperature chip-based THz frequency comb using nonlinear frequency generation from a mid-infrared quantum cascade laser comb.

A synthesizer that combines a fixed low-noise photonic oscillator and a direct digital synthesizer—and is based on components that can all be integrated on chip—can create microwave signals that are tunable with low noise.

Breather solitons can be found in both physical and biological nonlinear systems. Here, Yuet al. demonstrate this type of soliton in silicon and silicon nitride microresonators, which advances the understanding of soliton-based comb-generation in microresonators.

A nonlinear coherent spectroscopy that uses three slightly different repetition-rate frequency combs is demonstrated. A 2D spectrum with comb resolution is generated using only 365 milliseconds of data, almost 600 times faster than previous approaches.

By leveraging microcavity-integrated photonics and Kerr-induced optical frequency division, an integrated photonic millimetre-wave oscillator with low phase noise is demonstrated, achieving –77 dBc Hz^–1 and –121 dBc Hz^–1, respectively, at 100-Hz and 10-kHz offset frequencies, corresponding to –98 dBc Hz^–1 and –142 dBc Hz^–1 when scaled to a 10-GHz carrier.

Frequency combs are created by stabilizing the evolution of the carrier–envelope phase of a mode-locked laser. Researchers have now demonstrated a simplified method of creating frequency combs that enables trains of identical pulses to be easily produced.

Nonlinear interactions between modes with eigenfrequencies that differ by orders of magnitude occur in several physical systems. This article provides a simple conceptual model of these interactions, and uses this model to design tunable frequency combs.

An optical atomic clock operating on a magnetic-dipole transition in a highly charged argon ion is shown to improve uncertainties for the absolute transition frequency and isotope shift by several orders of magnitude.

We leverage advances in integrated photonics to generate low-noise microwaves with an optical frequency division architecture that can be low power and chip integrated.

A miniaturized optical frequency division system that could transfer the generation of microwaves, with superior spectral purity, to a complementary metal-oxide-semiconductor-compatible integrated photonic platform is demonstrated showing potential for large-volume, low-cost manufacturing for many applications.

Covalent histone modifications can affect the structure of chromatin. Expression of underlying monomethylated histone H3K27 is associated with chromocenters in Arabidopsis, but its presence is unaffected by mutations in the expected methyltransferases. Data now indicate that this modification is catalyzed by Arabidopsis ATRX5 and ATXR6 and is required for silencing, but in a pathway independent of that involving DNA methyltransferases.

Citizen science taps the efforts of non-experts. Here, authors describe Drugit, an extension of the crowdsourcing game Foldit, and its use in designing a non-peptide binder of Von Hippel Lindau E3 ligase for use with proteolysis targeting chimeras.

An ex vivo model of human colon cancer enables study of the drivers of tumor development and invasion.

Atherosclerosis results from the accumulation of lipoproteins in the vascular wall. Here, Thierer et al. report the design of a chemiluminescent reporter for atherogenic lipoproteins using fusion of apolipoprotein-B to a luciferase enzyme, and find it bears potential for the identification of regulators of lipoprotein metabolism in vivo.

Infection of mice on a selenium-deficient diet with a nonvirulent Coxsackievirus selects a stable cardiovirulent strain (pages 433–436).

Polycomb group proteins are involved in the epigenetic maintenance of repressive chromatin states, with the gene-silencing activity of the Polycomb repressive complex 2 (PRC2) dependent on its ability to trimethylate lysine 27 of histone H3. The carboxy-terminal domain of the EED subunit of the complex is now shown to specifically bind to histone tails carrying trimethyl-lysine residues associated with repressive chromatin marks, leading to activation of the methyltransferase activity of PRC2.

This protocol describes the establishment of a reversible replication barrier using plasmid templates containing a lacO array bound by LacR repressor. The method allows fine control of replication fork movement and replication fork encounter with DNA lesions.

Nucleosomes consist of two copies of each histone. H2A.Z is a variant H2A-related histone known to be enriched around transcription start sites. However, an H2A.Z-containing nucleosome could contain contain two copies of H2A.Z (homotypic) or one of H2A.Z and one of canonical H2A (heterotypic). Homotypic and heterotypic H2A.Z nucleosomes are now mapped and their distributions relative to promoters analyzed.

This review presents an overview of scenarios where van der Waals (vdW) materials provide unique advantages for nanophotonic biosensing applications. The authors discuss basic sensing principles based on vdW materials, advantages of the reduced dimensionality as well as technological challenges.

Presa, Bailey et al. assess the feasibility and efficacy of intrathecal administration of AAV9-SUMF1 gene therapy in the Sumf1-KO mouse model of Multiple Sulfatase Deficiency. They show that it provides sustained, significant improvements in survival, in the absence of neurological defects, even when given to juvenile mice.

A modeling study using case and mortality data from the first 8 months of the COVID-19 pandemic in the United States explores five potential future scenarios of social distancing mandates and mask use at the state level, with projections of the course of the epidemic through winter 2021.

Synchronization, a ubiquitous phenomenon in nature, has been extensively studied from the frequency point of view for micro- and nano-electromechanical systems, but less so when amplitude stability is concerned. The authors investigate, theoretically and experimentally, the amplitude stabilization in an externally harmonic drive synchronized noisy nonlinear oscillator, showcasing the effect of the amplitude noise reduction in these devices.