Science

Learning about threats is essential for survival. During threat learning, an innocuous sensory percept like a tone acquires an emotional meaning when paired with an aversive stimulus, like a mild footshock. The amygdala is critical for threat memory formation, but little is known about upstream brain areas that process aversive somatosensory information. Using optogenetic techniques in mice, we found that silencing of the posterior insula during footshock reduced acute fear behavior, and impaired one-day threat memory...

We introduce the optical ruler, an electromagnetic analog of a physical ruler, for nanoscale displacement metrology. The optical ruler is a complex electromagnetic field in which singularities serve as the marks on the scale. It is created by the diffraction of light on a metasurface, with singularity marks then revealed by high-magnification interferometric observation. Using a Pancharatnam-Berry phase metasurface, we demonstrate a displacement resolving power of better than 1 nm (λ/800) at a wavelength of 800 nm...

G protein-coupled receptors (GPCRs) in the G protein-coupled active state have higher affinity for agonists compared to when they are in the inactive state, but the molecular basis for this is unclear. We have determined four active-state structures of the β1 -adrenoceptor (β1 AR) bound to conformation-specific nanobodies in the presence of agonists of varying efficacy. Comparison with inactive-state structures of β1 AR bound to the identical ligands showed a 24-42% reduction in the volume of the orthosteric binding site...

The mammalian brain's somatosensory cortex is a topographic map of the body's sensory experience. In mice, cortical barrels reflect whisker input. We asked whether these cortical structures require sensory input to develop or are driven by intrinsic activity. Indeed, thalamocortical columns, connecting thalamus to cortex, emerge before sensory input and concur with calcium waves in the embryonic thalamus. We show here that the columnar organization of the thalamocortical somatotopic map exists in the mouse embryo before sensory input, thus linking spontaneous embryonic thalamic activity to somatosensory map formation...

Quantum walks are the quantum analogs of classical random walks, which allow simulating large-scale quantum many-body systems and realizing universal quantum computation without time-dependent control. We experimentally demonstrate quantum walks of one and two strongly correlated microwave photons in a 1D array of 12 superconducting qubits with short-range interactions. First, in one-photon quantum walks, we observed the propagation of the density and correlation of the quasi-particle excitation of the superconducting qubit, and quantum entanglement between qubit pairs...

Advances in ultrafast lasers, chirped pulse amplifiers, and frequency comb technology require fundamentally new pulse-modulation strategies capable of supporting unprecedentedly large bandwidth and high peak power while maintaining high spectral resolution. We demonstrate how dielectric metasurfaces can be leveraged to shape the temporal profile of a near-infrared femtosecond pulse. Finely tailored pulse shaping operations, including splitting, compression, chirping and higher-order distortion, are achieved using a Fourier-transform setup embedding metasurfaces able to manipulate, simultaneously and independently, the amplitude and phase of the constituent frequency components of the pulse...

Global satellite data are analyzed to determine trends in oceanic wind speed and wave height over the 33-year period 1985 to 2018. The analysis uses an extensive database obtained from a total of 31 satellite missions comprising three independent instruments-altimeters, radiometers and scatterometers. The analysis shows small increases in mean wind speed and wave height over this period, with stronger increases in extreme conditions (90th percentiles). The strongest increases occur in the Southern Ocean. Confidence in the results is strengthened because the wind speed trends are confirmed by all three satellite systems...

No abstract text is available yet for this article.

Feedbacks between glacier retreat and the solid Earth may slow ice loss from Antarctica.

The discovery of ferromagnetism in 2D van der Waals (vdW) crystals has generated widespread interest. Making further progress requires quantitative knowledge of the magnetic properties of vdW magnets on the nanoscale. We use scanning single-spin magnetometry based on diamond NV centers to image the magnetization, localized defects and magnetic domains of atomically thin crystals of the vdW magnet CrI3 We determine the magnetization of CrI3 monolayers to be ≈16μB /nm2 with comparable values in samples with odd numbers of layers, whereas the magnetization vanishes when the number of layers is even...

Neuromorphic computers could overcome efficiency bottlenecks inherent to conventional computing through parallel programming and read out of artificial neural network weights in a crossbar memory array. However, selective and linear weight updates and <10 nanoampere read currents are required for learning that surpasses conventional computing efficiency. We introduce an ionic floating-gate memory (IFG) array based upon a polymer redox transistor connected to a conductive-bridge memory (CBM). Selective and linear programming of a transistor array is executed in parallel by overcoming the bridging voltage threshold of the CBMs...

Earthquakes follow a well-known power-law size relation, with smaller events occurring much more often than larger events. Earthquake catalogs are thus dominated by small earthquakes, yet still missing a much larger number of even smaller events caused by signal fidelity issues. To overcome these limitations, we applied a template matching detection technique to the entire waveform archive of the regional seismic network in southern California. This effort resulted in a catalog with 1.81 million earthquakes, a factor of 10 increase, which provides important new insights into the geometry of fault zones at depth, foreshock behavior and nucleation processes, and earthquake triggering mechanisms...

All-perovskite-based polycrystalline thin-film tandem solar cells have the potential to deliver efficiencies of > 30%. However, the performance of all-perovskite-based tandem devices have been limited by the lack of high-efficiency, low-band-gap Sn-Pb mixed-perovskite solar cells (PSCs). We report on using guanidinium thiocyanate (GuaSCN) to dramatically improve the structural and optoelectronic properties of Sn-Pb mixed, low-band-gap (~1.25 electron volt) perovskite films that have 10-times lower defect density, leading to carrier lifetimes of greater than 1 microsecond and diffusion lengths of 2...

Targeted blockade of PD-1 using checkpoint inhibitor immunotherapies can activate T cells to destroy tumors. PD-1 is believed to function mainly at the effector but not in the activation phase of T cell responses, yet how PD-1 function is restricted at the activation stage is currently unknown. Here we demonstrate that CD80 interacts with PD-L1 in cis on antigen presenting cells (APCs) to disrupt PD-L1/PD-1 binding. Subsequently, PD-L1 cannot engage PD-1 to inhibit T cell activation when APCs express substantial amounts of CD80...

Eukaryotic genes are regulated by multivalent transcription factor complexes. Through cooperative self-assembly, these complexes perform non-linear regulatory operations involved in cellular decision-making and signal processing. Here, we apply this design principle to synthetic networks, testing whether engineered cooperative assemblies can program non-linear gene circuit behavior in yeast. Using a model-guided approach, we show that specifying strength and number of assembly subunits enables predictive tuning between linear and non-linear regulatory response for single- and multi-input circuits...

Electron transfer (ET) reactions slow down when they become thermodynamically very favorable, a counterintuitive interplay of kinetics and thermodynamics termed the inverted region in Marcus theory. Here we report inverted region behavior for proton-coupled electron transfer (PCET). Specifically, photochemical studies of anthracene-phenol-pyridine triads give rate constants for PCET charge recombination that are slower for the more thermodynamically favorable reactions. Photoexcitation forms an anthracene excited state that undergoes PCET to create a charge separated state...

Glutamate-gated AMPA receptors mediate the fast component of excitatory signal transduction at chemical synapses throughout all regions of the mammalian brain. AMPA receptors are tetrameric assemblies composed of four subunits, GluA1-4. Despite decades of study, the subunit composition, subunit arrangement and molecular structure of native AMPA receptors remain unknown. Here we elucidate the structures of 10 distinct native AMPA receptor complexes by single particle cryo-EM. We find that receptor subunits are arranged non stochastically, with the GluA2 subunit preferentially occupying the B and D positions of the tetramer and with triheteromeric assemblies comprising a major population of native AMPA receptors...

Outcome-based targets are needed to achieve biodiversity goals.

No abstract text is available yet for this article.

The prespliceosome, comprising U1 and U2 snRNPs bound to the pre-mRNA 5' splice site (5'SS) and branch point sequence, associates with the U4/U6.U5 tri-snRNP to form the fully-assembled precatalytic pre-B spliceosome. Here, we report cryo-EM structures of the human pre-B complex captured before U1 snRNP dissociation at 3.3 Å core resolution, and the human tri-snRNP at 2.9 Å resolution. U1 snRNP inserts the 5'SS-U1 snRNA helix between the two RecA domains of the Prp28 DEAD-box helicase. ATP-dependent closure of the Prp28 RecA domains releases the 5'SS to pair with the nearby U6 ACAGAGA-box sequence presented as a mobile loop...