Despite their crucial role in health and disease, our knowledge of immune cells within human tissues remains limited. We surveyed the immune compartment of 16 tissues from 12 adult donors by ...single-cell RNA sequencing and VDJ sequencing generating a dataset of ~360,000 cells. To systematically resolve immune cell heterogeneity across tissues, we developed CellTypist, a machine learning tool for rapid and precise cell type annotation. Using this approach, combined with detailed curation, we determined the tissue distribution of finely phenotyped immune cell types, revealing hitherto unappreciated tissue-specific features and clonal architecture of T and B cells. Our multitissue approach lays the foundation for identifying highly resolved immune cell types by leveraging a common reference dataset, tissue-integrated expression analysis, and antigen receptor sequencing.
During three of its first five orbits around the Sun, Parker Solar Probe (PSP) crossed the large-scale heliospheric current sheet (HCS) multiple times and provided unprecedented detailed plasma and ...field observations of the near-Sun HCS. We report the common detections by PSP of reconnection exhaust signatures in the HCS at heliocentric distances of 29.5–107 solar radii during encounters 1, 4, and 5. Both sunward and antisunward-directed reconnection exhausts were observed. In the sunward reconnection exhausts, PSP detected counterstreaming strahl electrons, indicating that HCS reconnection resulted in the formation of closed magnetic field lines with both ends connected to the Sun. In the antisunward exhausts, PSP observed dropouts of strahl electrons, consistent with the reconnected HCS field lines being disconnected from the Sun. The common detection of reconnection in the HCS suggests that reconnection is almost always active in the HCS near the Sun. Furthermore, the occurrence of multiple long-duration partial crossings of the HCS suggests that HCS reconnection could produce chains of large bulges with spatial dimensions of up to several solar radii. The finding of the prevalence of reconnection in the HCS is somewhat surprising since PSP has revealed that the HCS is much thicker than the kinetic scales required for reconnection onset. The observations are also in stark contrast with the apparent absence of reconnection in most of the small-scale and much more intense current sheets encountered near perihelia, many of which are associated with “switchbacks”. Thus, the PSP findings suggest that large-scale dynamics, either locally in the solar wind or within the coronal source of the HCS (at the tip of helmet streamers), plays a critical role in triggering reconnection onset.
Launched on 12 Aug. 2018, NASA’s Parker Solar Probe had completed 13 of its scheduled 24 orbits around the Sun by Nov. 2022. The mission’s primary science goal is to determine the structure and ...dynamics of the Sun’s coronal magnetic field, understand how the solar corona and wind are heated and accelerated, and determine what processes accelerate energetic particles. Parker Solar Probe returned a treasure trove of science data that far exceeded quality, significance, and quantity expectations, leading to a significant number of discoveries reported in nearly 700 peer-reviewed publications. The first four years of the 7-year primary mission duration have been mostly during solar minimum conditions with few major solar events. Starting with orbit 8 (i.e., 28 Apr. 2021), Parker flew through the magnetically dominated corona, i.e., sub-Alfvénic solar wind, which is one of the mission’s primary objectives. In this paper, we present an overview of the scientific advances made mainly during the first four years of the Parker Solar Probe mission, which go well beyond the three science objectives that are: (1) Trace the flow of energy that heats and accelerates the solar corona and solar wind; (2) Determine the structure and dynamics of the plasma and magnetic fields at the sources of the solar wind; and (3) Explore mechanisms that accelerate and transport energetic particles.
•Psilocybin rapidly reduced concentrations of the inflammatory cytokine TNF-alpha.•Psilocybin persistently reduced concentrations of interleukin 6 and C-reactive protein.•Persisting reductions in ...inflammatory markers correlated with positive increases in mood and sociability.•Systemic reductions of TNF-alpha correlated with lower hippocampal glutamate concentrations.•Psilocybin did not alter the stress response in healthy participants.
Patients characterized by stress-related disorders such as depression display elevated circulating concentrations of pro-inflammatory cytokines and a hyperactive HPA axis. Psychedelics are demonstrating promising results in treatment of such disorders, however the mechanisms of their therapeutic effects are still unknown. To date the evidence of acute and persisting effects of psychedelics on immune functioning, HPA axis activity in response to stress, and associated psychological outcomes is preliminary. To address this, we conducted a placebo-controlled, parallel group design comprising of 60 healthy participants who received either placebo (n = 30) or 0.17 mg/kg psilocybin (n = 30). Blood samples were taken to assess acute and persisting (7 day) changes in immune status. Seven days’ post-administration, participants in each treatment group were further subdivided: 15 underwent a stress induction protocol, and 15 underwent a control protocol. Ultra-high field (7-Tesla) magnetic resonance spectroscopy was used to assess whether acute changes in glutamate or glial activity were associated with changes in immune functioning. Finally, questionnaires assessed persisting self-report changes in mood and social behavior. Psilocybin immediately reduced concentrations of the pro-inflammatory cytokine tumor necrosis factor-α (TNF-α), while other inflammatory markers (interleukin (IL)- 1β, IL-6, and C-reactive protein (CRP)) remained unchanged. Seven days later, TNF-α concentrations returned to baseline, while IL-6 and CRP concentrations were persistently reduced in the psilocybin group. Changes in the immune profile were related to acute neurometabolic activity as acute reductions in TNF-α were linked to lower concentrations of glutamate in the hippocampus. Additionally, the more of a reduction in IL-6 and CRP seven days after psilocybin, the more persisting positive mood and social effects participants reported. Regarding the stress response, after a psychosocial stressor, psilocybin did not significantly alter the stress response. Results are discussed in regards to the psychological and therapeutic effects of psilocybin demonstrated in ongoing patient trials.
Images of the solar corona obtained by the Solar-Terrestrial Relations Observatory (STEREO) provide high-cadence, high-resolution observations of a compression wave forming ahead of a fast (940 km ...s--1) coronal mass ejection (CME) that erupted at ~9:00 UT on 2010 April 03. The passage of this wave at 1 AU is detected in situ by the Advanced Composition Explorer and Wind spacecraft at 08:00 UT on April 05 as a shock followed by a turbulent and heated sheath. These unprecedented and complementary observations of a shock-sheath region from the Sun to 1 AU are used to investigate the onset of a Solar Energetic Particle (SEP) event measured at the first Lagrange point (L1) and at STEREO-Behind (STB). The spatial extent, radial coordinates, and speed of the ejection are measured from STEREO observations and used as inputs to a numerical simulation of the CME propagation in the background solar wind. The simulated magnetic and plasma properties of the shock and sheath region at L1 agree very well with the in situ measurements. These simulation results reveal that L1 and STB are magnetically connected to the western and eastern edges of the driven shock, respectively. They also show that the 12 hr delay between the eruption time of the ejection and the SEP onset at L1 corresponds to the time required for the bow shock to reach the magnetic field lines connected with L1. The simulated shock compression ratio increases along these magnetic field lines until the maximum flux of high-energy particles is observed.
We report observations of reconnection exhausts in the Heliospheric Current Sheet (HCS) during Parker Solar Probe Encounters 08 and 07, at 16 Rs and 20 Rs, respectively. Heliospheric current sheet ...(HCS) reconnection accelerated protons to almost twice the solar wind speed and increased the proton core energy by a factor of ∼3, due to the Alfvén speed being comparable to the solar wind flow speed at these near‐Sun distances. Furthermore, protons were energized to super‐thermal energies. During E08, energized protons were found to have leaked out of the exhaust along separatrix field lines, appearing as field‐aligned energetic proton beams in a broad region outside the HCS. Concurrent dropouts of strahl electrons, indicating disconnection from the Sun, provide further evidence for the HCS being the source of the beams. Around the HCS in E07, there were also proton beams but without electron strahl dropouts, indicating that their origin was not the local HCS reconnection exhaust.
Plain Language Summary
Magnetic reconnection in current sheets is a universal plasma process that converts magnetic energy into particle energy. The process is important in many laboratory, solar, and astrophysical plasmas. The heliospheric current sheet (HCS), which originates from the Sun and extends throughout the heliosphere, is the largest current sheet in the solar system. One of the surprises of the Parker Solar Probe mission is the finding that magnetic reconnection is almost always active in the near‐Sun HCS, despite its enormous scales. In this paper, we report direct evidence showing that reconnection in the HCS close to the Sun can be a source of energetic protons observed in the solar wind. The reason protons can be accelerated to high energies (to tens of kilo‐electronvolts) is because the available magnetic energy per particle is high close to the Sun. This finding is important because the source of energetic protons in the heliosphere is unknown.
Key Points
Large available magnetic energy per particle led to significant proton acceleration by reconnection in the near‐Sun heliospheric current sheet (HCS) at 16 and 20 Rs
Proton beams and strahl electron dropouts in separatrices are evidence for HCS being a source of energetic protons seen outside the HCS
Energetic protons beams outside the HCS also exist without strahl electron dropouts. Their origin is unlikely to be the local HCS exhaust
We present heliospheric current sheet (HCS) and plasma sheet (HPS) observations during Parker Solar Probe's (PSP) first orbit around the Sun. We focus on the eight intervals that display a true ...sector boundary (TSB; based on suprathermal electron pitch angle distributions) with one or several associated current sheets. The analysis shows that (1) the main density enhancements in the vicinity of the TSB and HCS are typically associated with electron strahl dropouts, implying magnetic disconnection from the Sun, (2) the density enhancements are just about twice that in the surrounding regions, suggesting mixing of plasmas from each side of the HCS, (3) the velocity changes at the main boundaries are either correlated or anticorrelated with magnetic field changes, consistent with magnetic reconnection, (4) there often exists a layer of disconnected magnetic field just outside the high-density regions, in agreement with a reconnected topology, (5) while a few cases consist of short-lived density and velocity changes, compatible with short-duration reconnection exhausts, most events are much longer and show the presence of flux ropes interleaved with higher-β regions. These findings are consistent with the transient release of density blobs and flux ropes through sequential magnetic reconnection at the tip of the helmet streamer. The data also demonstrate that, at least during PSP's first orbit, the only structure that may be defined as the HPS is the density structure that results from magnetic reconnection, and its byproducts, likely released near the tip of the helmet streamer.
A detailed analysis is presented of 33 RR Lyrae stars in Pisces observed with the Kepler space telescope over the 8.9-d long K2 Two-Wheel Concept Engineering Test. The sample includes not only ...fundamental-mode and first-overtone (RRab and RRc) stars but the first two double-mode (RRd) stars that Kepler detected and the only modulated first-overtone star ever observed from space so far. The precision of the extracted K2 light curves made it possible to detect low-amplitude additional modes in all subtypes. All RRd and non-modulated RRc stars show the additional mode at P
X
/P
1 ∼ 0.61 that was detected in previous space-based photometric measurements. A periodicity longer than the fundamental mode was tentatively identified in one RRab star that might belong to a gravity mode. We determined the photometric Fe/H values for all fundamental-mode stars and provide the preliminary results of our efforts to fit the double-mode stars with non-linear hydrodynamic pulsation models. The results from this short test run indicate that the K2 mission will be, and has started to be, an ideal tool to expand our knowledge about RR Lyrae stars. As a by-product of the target search and analysis, we identified 165 bona fide double-mode RR Lyrae stars from the Catalina Sky Survey observations throughout the sky, 130 of which are new discoveries.
The GBAR project (Gravitational Behaviour of Anti hydrogen at Rest) at CERN, aims to measure the free fall acceleration of ultracold neutral anti hydrogen atoms in the terrestrial gravitational ...field. The experiment consists preparing anti hydrogen ions (one antiproton and two positrons) and sympathetically cooling them with B
e
+
ions to less than 10
μ
K. The ultracold ions will then be photo-ionized just above threshold, and the free fall time over a known distance measured. We will describe the project, the accuracy that can be reached by standard techniques, and discuss a possible improvement to reduce the vertical velocity spread.
ABSTRACT
In this paper, we present evidence for magnetic transients with small radial extents ranging from 0.025 to 0.118 AU measured in situ by the
Solar-Terrestrial Relations Observatory
(
STEREO
) ...and the near-Earth
Advanced Composition Explorer
(
ACE
) and
Wind
spacecraft. The transients considered in this study are much smaller (<0.12 AU) than the typical sizes of magnetic clouds measured near 1 AU (∼0.23 AU). They are marked by low plasma beta values, generally lower magnetic field variance, short timescale magnetic field rotations, and are all entrained by high-speed streams by the time they reach 1 AU. We use this entrainment to trace the origin of these small interplanetary transients in coronagraph images. We demonstrate that these magnetic field structures originate as either small or large mass ejecta. The small mass ejecta often appear from the tip of helmet streamers as arch-like structures and other poorly defined white-light features (the so-called blobs). However, we have found a case of a small magnetic transient tracing back to a small and narrow mass ejection erupting from below helmet streamers. Surprisingly, one of the small magnetic structures traces back to a large mass ejection; in this case, we show that the central axis of the coronal mass ejection is along a different latitude and longitude to that of the in situ spacecraft. The small size of the transient is related to the in situ measurements being taken on the edges or periphery of a larger magnetic structure. In the last part of the paper, an ejection with an arch-like aspect is tracked continuously to 1 AU in the
STEREO
images. The associated in situ signature is not that of a magnetic field rotation but rather of a temporary reversal of the magnetic field direction. Due to its “open-field topology,” we speculate that this structure is partly formed near helmet streamers due to reconnection between closed and open magnetic field lines. The implications of these observations for our understanding of the variability of the slow solar wind are discussed.
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