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Viral immunity: Basic mechanisms and therapeutic applications—a Keystone Symposia report
No full textViruses infect millions of people each year. Both endemic viruses circulating throughout the population as well as novel epidemic and pandemic viruses pose ongoing threats to global public health. Developing more effective tools to address viruses requires not only in-depth knowledge of the virus itself but also of our immune system's response to infection. On June 29 to July 2, 2022, researchers met for the Keystone symposium “Viral Immunity: Basic Mechanisms and Therapeutic Applications.” This report presents concise summaries from several of the symposium presenters
Quantum Gravity in the Lab. I. Teleportation by Size and Traversable Wormholes
No full textWith the long-term goal of studying models of quantum gravity in the lab, we propose holographic teleportation protocols that can be readily executed in table-top experiments. These protocols exhibit similar behavior to that seen in the recent traversable-wormhole constructions of Gao et al. [J. High Energy Phys., 2017, 151 (2017)] and Maldacena et al. [Fortschr. Phys., 65, 1700034 (2017)]: information that is scrambled into one half of an entangled system will, following a weak coupling between the two halves, unscramble into the other half. We introduce the concept of teleportation by size to capture how the physics of operator-size growth naturally leads to information transmission. The transmission of a signal through a semiclassical holographic wormhole corresponds to a rather special property of the operator-size distribution that we call size winding. For more general systems (which may not have a clean emergent geometry), we argue that imperfect size winding is a generalization of the traversable-wormhole phenomenon. In addition, a form of signaling continues to function at high temperature and at large times for generic chaotic systems, even though it does not correspond to a signal going through a geometrical wormhole but, rather, to an interference effect involving macroscopically different emergent geometries. Finally, we outline implementations that are feasible with current technology in two experimental platforms: Rydberg-atom arrays and trapped ions
Oscillating bound states in non-Markovian photonic lattices
No full textIt is known that the superposition of two bound states in the continuum (BICs) leads to the phenomenon of an oscillating bound state, where excitations mediated by the continuum modes oscillate persistently. We perform exact calculations for the oscillating BICs in a one-dimensional photonic lattice coupled to a “giant atom” at multiple points. Our work is significantly distinct from previous proposals of oscillating BICs in continuous waveguide systems due to the presence of a finite energy band contributing band-edge effects. In particular, we show that the bound states outside the energy band are detrimental to the oscillating BIC phenomenon, and can be suppressed by increasing either the number of coupling points or the separation between each coupling point. Crucially, non-Markovianity is necessary for the existence of oscillating BICs, and the oscillation amplitude increases with the characteristic delay time of the giant atom interactions. We also propose an initialization scheme in the BIC subspace. Our work be experimentally implemented on current photonic waveguide array platforms and opens up prospects in utilizing reservoir engineering for the storage of quantum information in photonic lattices
Tailored XZZX codes for biased noise
No full textQuantum error correction (QEC) for generic errors is challenging due to the demanding threshold and resource requirements. Interestingly, when physical noise is biased, we can tailor our QEC schemes to the noise to improve performance. Here we study a family of codes having XZZX-type stabilizer generators, including a set of cyclic codes generalized from the five-qubit code and a set of topological codes that we call generalized toric codes (GTCs). We show that these XZZX codes are highly qubit efficient if tailored to biased noise. To characterize the code performance, we use the notion of effective distance, which generalizes code distance to the case of biased noise and constitutes a proxy for the logical failure rate. We find that the XZZX codes can achieve a favorable resource scaling by this metric under biased noise. We also show that the XZZX codes have remarkably high thresholds that reach what is achievable by random codes, and furthermore they can be efficiently decoded using matching decoders. Finally, by adding only one flag qubit, the XZZX codes can realize fault-tolerant QEC while preserving their large effective distance. In combination, our results show that tailored XZZX codes give a resource-efficient scheme for fault-tolerant QEC against biased noise
Auditory Mondrian masks the airborne-auditory artifact of focused ultrasound stimulation in humans
No full textLow-intensity Focused Ultrasound Stimulation (FUS) can modulate neural activity in cortical, subcortical, and deep brain regions, achieving millimeter precision through transcranial ultrasound stimulation (TUS) and can affect behavior [1,2]. However, there is concern that FUS may induce an auditory effect, cortically activating the subject's auditory sensation, thus confounding behavioral and electrophysiological responses during TUS research [[3], [4], [5], [6], [7]]. Several studies have mitigated this auditory artifact through ramping [8] or audio masking [5,6], but prior research has had two main limitations. First, previous studies addressed a limited range of the total FUS parameter space: fundamental frequency (f0), pulse repetition frequency (PRF), duty cycle (DC), sonication duration (SD), and intensity (I) [1,7,[9], [10], [11]]. Second, as these studies used direct stimulation of subjects, they did not distinguish between airborne or tissue conduction effects [[5], [6], [7]]. Here, we evaluate the airborne auditory artifact over a range of FUS parameters through sonographic characterization, the human subject's response to recorded audio clips, and a two-interval forced choice (2IFC) task to test the effectiveness of three mask types: square [5,6], pulsed sine, and random multitone. The multitone random mask, or Auditory Mondrian, is inspired by the visual Mondrian used in the continuous flash suppression to mask visual targets [12].
We recruited 228 healthy participants for the three online auditory psychophysical experiments (See Supplementary Methods for details). In experiment 1, participants performed a detection task in which they were asked whether they detected a distinct sound while listening to audio recordings of FUS sham and stimulation trials. In experiments 2 and 3, participants performed a two-interval forced choice (2IFC) task in which they chose which interval of a pair contained the FUS stimulation embedded in an auditory mask. Audio clips from the microphone were used without volume (loudness) manipulation and confirmed by experimenters to match the sound produced from the FUS setup.
In an artificial environment, we found that the ultrasound transducer is a primary source of airborne auditory artifacts (Fig. S1 A and B). Short-time Fourier transforms (STFT) of the audio recordings of FUS revealed clear frequency bands at the PRF and harmonics, along with additional frequency bands in the human hearing range that did not fit with the corresponding PRF (Fig. 1 A). These additional frequency bands were consistent at approximately 8 and 12 kHz throughout all PRF and even seen with continuous wave US bursts (Fig. 1 A, yellow arrows) and appeared regardless of the coupling method or the cone and arm setup (Fig. 1 B). The electrical spectrum density showed no peaks at the human frequency range, so it likely did not contribute to the auditory artifact. Based on the above acoustic analyses, we concluded that the ultrasound transducer is a source of airborne auditory artifacts
Uncertainty in Early German Romanticism
No full textThis introduction explores how uncertainty was used as a poetic and philosophical tool around 1800. It first sets up the historical context for the appropriation of uncertainty by underscoring the philosophical interest in challenging the foundations of knowledge. It then focuses on German Romanticism, using the writings of Novalis and Friedrich Schlegel as its primary reference point for an analysis of the poetic and philosophical implications of uncertainty. The authors argue that the work of these two writers presents a philosophical engagement with uncertainty as a problem in its own right and a desire to connect uncertainty to important romantic concepts such as chaos and hypothesis. The introduction concludes with an emphasis on Schlegel’s contributions to the problem of uncertainty
Toward implementing autonomous adaptive data acquisition for scanning hyperspectral imaging of biological systems
No full textAutonomous experimentation is an emerging area of research, primarily related to autonomous vehicles, scientific combinatorial discovery approaches in materials science and drug discovery, and iterative research loops of planning, experimentation, and analysis. However, autonomous approaches developed in these contexts are difficult to apply to high-dimensional mapping technologies, such as scanning hyperspectral imaging of biological systems, due to sample complexity and heterogeneity. We briefly cover the history of adaptive sampling algorithms and surrogate modeling in order to define autonomous adaptive data acquisition as an objective-based, flexible building block for future biological imaging experimentation driven by intelligent infrastructure. We subsequently summarize the recent implementations of autonomous adaptive data acquisition (AADA) for scanning hyperspectral imaging, assess how these address the difficulties of autonomous approaches in hyperspectral imaging, and highlight the AADA design variation from a goal-oriented perspective. Finally, we present a modular AADA architecture that embeds AADA-driven flexible building blocks to address the challenge of time resolution for high-dimensional scanning hyperspectral imaging of nonequilibrium dynamical systems. In our example research-driven experimental design case, we propose an AADA infrastructure for time-resolved, noninvasive, and label-free scanning hyperspectral imaging of living biological systems. This AADA infrastructure can accurately target the correct state of the system for experimental workflows that utilize subsequent expensive, high-information-content analytical techniques
Lateral Erosion of Bedrock Channel Banks by Bedload and Suspended Load
No full textBedrock rivers carry large amounts of fine sediment in suspension. We developed a mechanistic model for erosion of bedrock channel banks by impacting bedload and suspended load particles that are advected laterally by turbulent eddies (advection-abrasion model). The model predicts high lateral erosion rates near the bed, with rates decreasing up to the water surface. The model also predicts greater erosion within the suspended load layer than the bedload layer for many typical sediment supply and transport conditions explored. We compared the advection-abrasion model with a previously derived model for lateral erosion of bedrock banks by bedload particles deflected by stationary bed alluvium (deflection-abrasion model). Erosion rates predicted by the deflection-abrasion model are lower, except within limited conditions where sediment is transported near the threshold of motion and the bed is near fully covered in sediment. Both processes occur in bedrock rivers at the same time, so we combined the advection-abrasion and deflection-abrasion models and found that the lateral erosion rate generally increases with increasing transport stage and relative sediment supply for a given grain size. Application of our combined-abrasion model to a natural bedrock river with a wide distribution of discharge and supply events, and mixed grain sizes, indicates that finer sediment dominates the lateral erosion on channel banks in low sediment supply environments and can be as important as coarser sediment in high sediment supply environments
Generation of laboratory nanoflares from multiple braided plasma loops
No full textSolar flares are intense bursts of electromagnetic radiation accompanied by energetic particles and hard X-rays. They occur when magnetic flux loops erupt in the solar atmosphere. Solar observations detect energetic particles and hard X-rays but cannot reveal the generating mechanism because the particle acceleration happens at a scale smaller than the observation resolution. Thus, details of the cross-scale physics that explain the generation of energetic particles and hard X-rays remain a mystery. Here, we present observations from a laboratory experiment that simulates solar coronal loop physics. Transient, localized 7.6-keV X-ray bursts and a several-kilovolt voltage spike are observed in braided magnetic flux ropes of a 2-eV plasma when the braid strand radius is choked down to be at the kinetic scale by either magnetohydrodynamic (MHD) kink or magnetic Rayleigh–Taylor instabilities. This sequence of observations reveals a cross-scale coupling from MHD to non-MHD physics that is likely responsible for generating solar energetic particles and X-ray bursts. All the essential components of this mechanism have been separately observed in the solar corona
A Luminous Dust-obscured Tidal Disruption Event Candidate in a Star-forming Galaxy at 42 Mpc
No full textWhile the vast majority of tidal disruption events (TDEs) have been identified by wide-field sky surveys in the optical and X-ray bands, recent studies indicate that a considerable fraction of TDEs may be dust obscured and thus preferentially detected in the infrared (IR) wave bands. In this Letter, we present the discovery of a luminous mid-IR nuclear flare (termed WTP14adbjsh), identified in a systematic transient search of archival images from the NEOWISE mid-IR survey. The source reached a peak luminosity of L ≃ 10⁴³ erg s⁻¹ at 4.6 μm in 2015 before fading in the IR with a TDE-like F ∝ t^(-5/3) decline, radiating a total of more than 3 × 10⁵¹ erg in the last 7 yr. The transient event took place in the nearby galaxy NGC 7392, at a distance of around 42 Mpc; yet, no optical or X-ray flare is detected. We interpret the transient as the nearest TDE candidate detected in the last decade, which was missed at other wavelengths due to dust obscuration, hinting at the existence of TDEs that have been historically overlooked. Unlike most previously detected TDEs, the transient was discovered in a star-forming galaxy, corroborating earlier suggestions that dust obscuration suppresses significantly the detection of TDEs in these environments. Our results demonstrate that the study of IR-detected TDEs is critical in order to obtain a complete understanding of the physics of TDEs and to conclude whether TDEs occur preferentially in a particular class of galaxies