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Aging is the major risk factor for several life‐threatening pathologies and impairs the function of multiple cellular compartments and organelles. Age‐dependent deterioration of nuclear morphology is a common feature in evolutionarily divergent organisms. Lipid droplets have been shown to localize in most nuclear compartments, where they impinge on genome architecture and integrity. However, the significance of progressive nuclear lipid accumulation and its impact on organismal homeostasis remain obscure. Here, we implement non‐linear imaging modalities to monitor and quantify age‐dependent nuclear lipid deposition in Caenorhabditis elegans. We find that lipid droplets increasingly accumulate in the nuclear envelope, during aging. Longevity‐promoting interventions, such as low insulin signaling and caloric restriction, abolish the rate of nuclear lipid accrual and decrease the size of lipid droplets. Suppression of lipotoxic lipid accumulation in hypodermal and intestinal nuclei is dependent on the transcription factor HLH‐30/TFEB and the triglyceride lipase ATGL‐1. HLH‐30 regulates the expression of ATGL‐1 to reduce nuclear lipid droplet abundance in response to lifespan‐extending conditions. Notably, ATGL‐1 localizes to the nuclear envelope and moderates lipid content in long‐lived mutant nematodes during aging. Our findings indicate that the reduced ATGL‐1 activity leads to excessive nuclear lipid accumulation, perturbing nuclear homeostasis and undermining organismal physiology, during aging. Age‐dependent deterioration of lipid metabolism and nuclear morphology are common features in evolutionary divergent organisms. Nuclear lipid droplet (nLDs) deposition and LMN‐1/LMNA accumulation lead to cellular dysfunction and, subsequently, to tissue homeostasis collapse, with age. Longevity‐promoting interventions sustain nLDs abundance and nuclear envelope integrity, via distinct, HLH‐30‐driven mechanisms, to protect cellular viability and promote organismal fitness.

AbstractWe investigate twisted electrons with a well-defined orbital angular momentum, which have been ionised via a strong laser field. By formulating a new variant of the well-known strong field approximation, we are able to derive conservation laws for the angular momenta of twisted electrons in the cases of linear and circularly polarised fields. In the case of linear fields, we demonstrate that the orbital angular momentum of the twisted electron is determined by the magnetic quantum number of the initial bound state. The condition for the circular field can be related to the famous ATI peaks, and provides a new interpretation for this fundamental feature of photoelectron spectra. We find the length of the circular pulse to be a vital factor in this selection rule and, employing an effective frequency, we show that the photoelectron OAM emission spectra are sensitive to the parity of the number of laser cycles. This work provides the basic theoretical framework with which to understand the OAM of a photoelectron undergoing strong field ionisation.Graphic Abstract

We have developed a technique to estimate the three-dimensional (3D) location of lightning optical pulses based on the stereo view of common lightning pulses from two different orbital instruments. The technique only requires the satellite position and the look vector to the lightning optical source. An example dataset of the Geostationary Lightning Mappers (GLMs) on GOES-16 and GOES-17 from 10 June 2019 is used to illustrate the technique. For this dataset, we find that the values for the stereo determination of cloud-top altitudes are on average lower by 740 m than the ones calculated from the lightning ellipsoid that is currently applied during geolocation. When we compare the locations to the Advanced Baseline Imager (ABI) Cloud Height Algorithm (ACHA), we find that our technique also produces slightly lower altitude values by 240 m. There is greater spread in our technique than either the lightning ellipsoid or the ABI cloud-top height that is likely due to the incorrect pairing of groups between the two GLMs and the 8–14-km resolution in the group locations. Based on GLM location errors derived from comparisons to ground truth sources, the uncertainty in the radial location determined by the stereo location technique is 5.2 km, while the altitude uncertainty is 4.0 km. The technique can be used to 3D map lightning or other optical sources such as bolides and other upper-atmospheric optical phenomena from any two orbital sensors with overlapping fields of view.

A deep-ultraviolet (DUV) laser diode (LD) consisting of specifically designed cladding layers involving superlattice nitride alloy has been proposed. Simulation studies of different cladding layers were carried out using Crosslight software. It was found that the proposed structure effectively suppresses the leakage of the optical field from the active region and the optical confinement coefficient is 1.45 times higher than that of the conventional structure. The proposed structure has a significant increase in laser power with a low threshold current. Moreover, the introduction of novel cladding layer suppresses the electron and hole leakage from the multiple quantum well (MQW) region, which provides an attractive solution for increasing the stimulated recombination rate in the MQW region leading to the improvement in the performance of the DUV LD.Graphical abstract

AbstractWe investigate the strong-field ion emission from the surface of isolated silica nanoparticles aerosolized from an alcoholic solution, and demonstrate the applicability of the recently reported near-field imaging at 720 nm [Rupp et al., Nat. Comm., 10(1):4655, 2019] to longer wavelength (2 μ m) and polarizations with arbitrary ellipticity. Based on the experimental observations, we discuss the validity of a previously introduced semi-classical model, which is based on near-field driven charge generation by a Monte-Carlo approach and classical propagation. We furthermore clarify the role of the solvent in the surface composition of the nanoparticles in the interaction region. We find that upon injection of the nanoparticles into the vacuum, the alcoholic solvent evaporates on millisecond time scales, and that the generated ions originate predominantly from covalent bonds with the silica surface rather than from physisorbed solvent molecules. These findings have important implications for the development of future theoretical models of the strong-field ion emission from silica nanoparticles, and the application of near-field imaging and reaction dynamics of functional groups on isolated nanoparticles.Graphical abstract

We predict a repulsive Casimir–Polder-type dispersion interaction between a single neutron and a metal or dielectric surface. We consider a scenario where a single neutron is subject to an external magnetic field. Due to its intrinsic magnetic moment, the neutron then forms a magnetisable two-level system which can exchange virtual photons with a nearby surface. The resulting dispersion interaction between a purely magnetic object (neutron) and a purely electric one (surface) is found to be repulsive, in contrast to the typical attractive interaction between electric objects. Its magnitude is considerably smaller than the standard atom–surface Casimir–Polder force due to the magnetic nature of the interaction and the smallness of the electron-to-neutron mass ratio. Nevertheless, we show that it can be comparable to the gravitational potential of the same surface and should be taken into consideration in future neutron interference experiments.

Optically Pumped Magnetometers (OPMs) have emerged as a viable and wearable alternative to cryogenic, superconducting MEG systems. This new generation of sensors has the advantage of not requiring cryogenic cooling and as a result can be flexibly placed on any part of the body. The purpose of this review is to provide a neuroscience audience with the theoretical background needed to understand the physical basis for the signal observed by OPMs. Those already familiar with the physics of MRI and NMR should note that OPMs share much of the same theory as the operation of OPMs rely on magnetic resonance. This review establishes the physical basis for the signal equation for OPMs. We re-derive the equations defining the bounds on OPM performance and highlight the important trade-offs between quantities such as bandwidth, sensor size and sensitivity. These equations lead to a direct upper bound on the gain change due to cross-talk for a multi-channel OPM system. •We review the theoretical basis of OPMs.•We re-derive the signal equations for OPMs.•We highlight the important trade-offs in sensor design.•We discuss the practical implementation of this technology.

Metasurface-based optical elements typically manipulate light waves by imparting space-variant changes in the amplitude and phase with a dense array of scattering nanostructures. The highly localized and low optical-quality-factor ( Q ) modes of nanostructures are beneficial for wavefront shaping as they afford quasi-local control over the electromagnetic fields. However, many emerging imaging, sensing, communication, display and nonlinear optics applications instead require flat, high- Q optical elements that provide substantial energy storage and a much higher degree of spectral control over the wavefront. Here, we demonstrate high- Q , non-local metasurfaces with atomically thin metasurface elements that offer notably enhanced light–matter interaction and fully decoupled optical functions at different wavelengths. We illustrate a possible use of such a flat optic in eye tracking for eyewear. Here, a metasurface patterned on a regular pair of eye glasses provides an unperturbed view of the world across the visible spectrum and redirects near-infrared light to a camera to allow imaging of the eye. High optical-quality-factor, non-local metasurfaces enable independent functions across different wavelength bands.

Miniaturized lasers are an emerging platform for generating coherent light for quantum photonics, in vivo cellular imaging, solid-state lighting and fast three-dimensional sensing in smartphones1–3. Continuous-wave lasing at room temperature is critical for integration with opto-electronic devices and optimal modulation of optical interactions4,5. Plasmonic nanocavities integrated with gain can generate coherent light at subwavelength scales6–9, beyond the diffraction limit that constrains mode volumes in dielectric cavities such as semiconducting nanowires10,11. However, insufficient gain with respect to losses and thermal instabilities in nanocavities has limited all nanoscale lasers to pulsed pump sources and/or low-temperature operation6–9,12–15. Here, we show continuous-wave upconverting lasing at room temperature with record-low thresholds and high photostability from subwavelength plasmons. We achieve selective, single-mode lasing from Yb3+/Er3+-co-doped upconverting nanoparticles conformally coated on Ag nanopillar arrays that support a single, sharp lattice plasmon cavity mode and greater than wavelength λ/20 field confinement in the vertical dimension. The intense electromagnetic near-fields localized in the vicinity of the nanopillars result in a threshold of 70 W cm−2, orders of magnitude lower than other small lasers. Our plasmon-nanoarray upconverting lasers provide directional, ultra-stable output at visible frequencies under near-infrared pumping, even after six hours of constant operation, which offers prospects in previously unrealizable applications of coherent nanoscale light.

The molecular machinery of life is founded on chiral building blocks, but no experimental technique is currently available to distinguish or monitor chiral systems in live cell bio-imaging studies. Luminescent chiral molecules encode a unique optical fingerprint within emitted circularly polarized light (CPL) carrying information about the molecular environment, conformation, and binding state. Here, we present a CPL Laser Scanning Confocal Microscope (CPL-LSCM) capable of simultaneous chiroptical contrast based live-cell imaging of endogenous and engineered CPL-active cellular probes. Further, we demonstrate that CPL-active probes can be activated using two-photon excitation, with complete CPL spectrum recovery. The combination of these two milestone results empowers the multidisciplinary imaging community, allowing the study of chiral interactions on a sub-cellular level in a new (chiral) light. Here, the authors introduce a live-cell imaging system using chiroptical contrast, enabling the study of chiral interactions. They demonstrate simultaneous imaging of enantiomeric pairs of molecular probes emitting circularly polarised light, using both single and two-photon excitation.