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Much of our understanding of atmospheric secondary organic aerosol (SOA) formation from volatile organic compounds derives from laboratory chamber measurements, including mass yield and elemental composition. These measurements alone are insufficient to identify the chemical mechanisms of SOA production. We present here a comprehensive dataset on the molecular identity, abundance, and kinetics of α-pinene SOA, a canonical system that has received much attention owing to its importance as an organic aerosol source in the pristine atmosphere. Identified organic species account for ∼58–72% of the α-pinene SOA mass, and are characterized as semivolatile/low-volatility monomers and extremely low volatility dimers, which exhibit comparable oxidation states yet different functionalities. Features of the α-pinene SOA formation process are revealed for the first time, to our knowledge, from the dynamics of individual particle-phase components. Although monomeric products dominate the overall aerosol mass, rapid production of dimers plays a key role in initiating particle growth. Continuous production of monomers is observed after the parent α-pinene is consumed, which cannot be explained solely by gas-phase photochemical production. Additionally, distinct responses of monomers and dimers to α-pinene oxidation by ozone vs. hydroxyl radicals, temperature, and relative humidity are observed. Gas-phase radical combination reactions together with condensed phase rearrangement of labile molecules potentially explain the newly characterized SOA features, thereby opening up further avenues for understanding formation and evolution mechanisms of α-pinene SOA.

Sodium serves as one of the primary cations in the central nervous system, playing a crucial role in maintaining normal brain function. In this study, we investigated alterations in sodium concentrations in the brain and/or cerebrospinal fluid across multiple models, including an aging model, a stroke model, a nitroglycerin (NTG)-induced rat migraine model, a familial hemiplegic migraine type 2 (FHM2) mouse model, and a transgenic mouse model of Alzheimer’s disease (AD). Our results reveal that older rats exhibited higher sodium concentrations in cerebrospinal fluid (CSF), plasma, and various brain regions compared to their younger counterparts. Additionally, findings from the stroke model demonstrated a significant increase in sodium in the ischemic/reperfused region, accompanied by a decrease in potassium and an elevated sodium/potassium ratio. However, we did not detect significant changes in sodium in the NTG-induced rat migraine model or the FHM2 mouse model. Furthermore, AD transgenic mice showed no significant differences in sodium levels compared to wild-type mice in CSF, plasma, or the hippocampus. These results underscore the nuanced regulation of sodium homeostasis in various neurological conditions and aging, providing valuable insights into potential mechanisms underlying these alterations.

We describe and compare two outcrops of pyroxenite associated with Neoproterozoic ophiolite sequences in the Eastern Desert of Egypt: small masses in the Abu Samuki area of the North Eastern Desert and large belts in the Wadi El‐Mireiwa area of the South Eastern Desert. This study presents field observations, petrographic descriptions, and data on mineral and whole‐rock compositions as a basis for investigating the tectonic setting, nature, origin, and alteration history of this pyroxenite. Both pyroxenite bodies represent cumulates from the crustal sections of fragmented ophiolites, emplaced by thrusting above metasedimentary rocks and island arc assemblages, and later intruded by granite. Samples from both localities are mainly olivine clinopyroxenite. The compositions of olivine (Fo ∼ 79.7 and 0.13–0.49 wt% NiO), clinopyroxene, and fresh Cr‐spinel cores, as well as the low whole rock Mg# (average 87.6 at Abu Samuki and 85.7 at Wadi El‐Mireiwa) are all consistent with a cumulate origin for both pyroxenite suites. Moreover, the geochemical data all indicate that both pyroxenite suites are derived from fragments of oceanic lithosphere that developed in a fore‐arc supra‐subduction zone environment. The differences in mineral chemistry between the two locations suggest that the parental magma at Abu Samuki was low‐Ti fore‐arc basalt, while that at Wadi El‐Mireiwa was a high‐Ca boninite. The existence of green spinel, zoisite, Al‐amphibole, pumpellyite and Mg‐chlorite as secondary minerals in pyroxenite at Abu Samuki can be attributed to alteration and metasomatism by Al‐Mg‐Ca‐bearing hydrothermal fluids. The preservation of deformation features in clinopyroxene and the absence of K‐bearing secondary minerals suggest that this alteration was associated with circulation of seawater in fractured oceanic crust during the pre‐obduction stage of ophiolite emplacement and not with the post‐obduction granitoid intrusion. Plain Language Summary Pyroxenites are an uncommon class of rocks dominated by the pyroxene group minerals. They are known to occur both in the crust and mantle of the Earth and may be formed by several mechanisms. When their field relations, textures, and mineral compositions indicate that they formed in the oceanic crust by accumulation of crystals freezing out of magma as it cools, they are known as cumulates. In this case, they may be used to reconstruct aspects of the composition and tectonic setting of their parental liquids. Here we report two instances of cumulate pyroxenite from fragments of ancient (between 700 and 850 million years old) oceanic crust, exposed in the basement terrane of the Eastern Desert of Egypt, between the Nile and the Red Sea. We determined that both crystallized from varieties of magma that are today found almost exclusively in ocean‐ocean subduction zones, in the region between the volcanic front and the trench, that is, the fore‐arc. In one case, the igneous rocks have been overprinted by secondary minerals associated with hydrothermal alteration and we show that this occurred on the seafloor and infer details of the composition of the fluids migrating through this ancient fore‐arc crust. Key Points The pyroxenite suites represent lower‐crustal cumulate ultramafic members of the Neoproterozoic oceanic lithosphere Pyroxenites were formed in fore‐arc environment by crystallization of low‐Ti fore‐arc basaltic and high‐Ca boninitic melts A range of secondary minerals formed by seafloor infiltration of high Mg‐Al hydrothermal fluid

Secondary organic aerosol (SOA) is ubiquitous in the atmosphere and plays a pivotal role in climate, air quality, and health. Monoterpenes, emitted in large quantities from forested regions, are a dominant source of SOA globally, with dimers having been identified as key contributors to particle formation and growth. Here, we establish the role of concerted oxidation by O 3 and OH as a significant route to dimer formation in SOA generated from β-pinene, the second-most-abundant monoterpene emitted to the atmosphere. Production of this class of dimers is found to occur through both gas- and particle-phase processes. Dimer formation via synergistic O 3 + OH oxidation could represent an appreciable source of “missing” SOA not included in current atmospheric models. Dimeric compounds contribute significantly to the formation and growth of atmospheric secondary organic aerosol (SOA) derived from monoterpene oxidation. However, the mechanisms of dimer production, in particular the relevance of gas- vs. particle-phase chemistry, remain unclear. Here, through a combination of mass spectrometric, chromatographic, and synthetic techniques, we identify a suite of dimeric compounds (C 15–19 H 24–32 O 5–11 ) formed from concerted O 3 and OH oxidation of β-pinene (i.e., accretion of O 3 - and OH-derived products/intermediates). These dimers account for an appreciable fraction (5.9–25.4%) of the β-pinene SOA mass and are designated as extremely low-volatility organic compounds. Certain dimers, characterized as covalent dimer esters, are conclusively shown to form through heterogeneous chemistry, while evidence of dimer production via gas-phase reactions is also presented. The formation of dimers through synergistic O 3 + OH oxidation represents a potentially significant, heretofore-unidentified source of low-volatility monoterpene SOA. This reactivity also suggests that the current treatment of SOA formation as a sum of products originating from the isolated oxidation of individual precursors fails to accurately reflect the complexity of oxidation pathways at play in the real atmosphere. Accounting for the role of synergistic oxidation in ambient SOA formation could help to resolve the discrepancy between the measured atmospheric burden of SOA and that predicted by regional air quality and global climate models.

Doc number: 3 Abstract Background: Cerebrospinal fluid (CSF) sodium levels have been reported to rise during episodic migraine. Since migraine frequently starts in early morning or late afternoon, we hypothesized that natural sodium chronobiology may predispose susceptible persons when extracellular CSF sodium increases. Since no mammalian brain sodium rhythms are known, we designed a study of healthy humans to test if cation rhythms exist in CSF. Methods: Lumbar CSF was collected every ten minutes at 0.1 mL/min for 24 h from six healthy participants. CSF sodium and potassium concentrations were measured by ion chromatography, total protein by fluorescent spectrometry, and osmolarity by freezing point depression. We analyzed cation and protein distributions over the 24 h period and spectral and permutation tests to identify significant rhythms. We applied the False Discovery Rate method to adjust significance levels for multiple tests and Spearman correlations to compare sodium fluctuations with potassium, protein, and osmolarity. Results: The distribution of sodium varied much more than potassium, and there were statistically significant rhythms at 12 and 1.65 h periods. Curve fitting to the average time course of the mean sodium of all six subjects revealed the lowest sodium levels at 03.20 h and highest at 08.00 h, a second nadir at 09.50 h and a second peak at 18.10 h. Sodium levels were not correlated with potassium or protein concentration, or with osmolarity. Conclusion: These CSF rhythms are the first reports of sodium chronobiology in the human nervous system. The results are consistent with our hypothesis that rising levels of extracellular sodium may contribute to the timing of migraine onset. The physiological importance of sodium in the nervous system suggests that these rhythms may have additional repercussions on ultradian functions.

Dimeric compounds contribute significantly to the formation and growth of atmospheric secondary organic aerosol (SOA) derived from monoterpene oxidation. However, the mechanisms of dimer production, in particular the relevance of gas- vs. particle-phase chemistry, remain unclear. Here, through a combination of mass spectrometric, chromatographic, and synthetic techniques, we identify a suite of dimeric compounds (C15–19H24–32O5–11) formed from concerted O₃ and OH oxidation of β-pinene (i.e., accretion of O₃- and OH-derived products/intermediates). These dimers account for an appreciable fraction (5.9–25.4%) of the β-pinene SOA mass and are designated as extremely low-volatility organic compounds. Certain dimers, characterized as covalent dimer esters, are conclusively shown to form through heterogeneous chemistry, while evidence of dimer production via gas-phase reactions is also presented. The formation of dimers through synergistic O₃ + OH oxidation represents a potentially significant, heretofore-unidentified source of low-volatility monoterpene SOA. This reactivity also suggests that the current treatment of SOA formation as a sum of products originating from the isolated oxidation of individual precursors fails to accurately reflect the complexity of oxidation pathways at play in the real atmosphere. Accounting for the role of synergistic oxidation in ambient SOA formation could help to resolve the discrepancy between the measured atmospheric burden of SOA and that predicted by regional air quality and global climate models.

The rapid turnover of dimethylsulfoniopropionate (DMSP), likely the most relevant dissolved organic sulfur compound in the surface ocean, makes it pivotal to understand the cycling of organic sulfur. Dimethylsulfoniopropionate is mainly synthesized by phytoplankton, and it can be utilized as carbon and sulfur sources by marine bacteria or cleaved by bacteria or algae to produce the volatile compound dimethylsulfide (DMS), involved in the formation of sulfate aerosols. The fluxes between the consumption (i.e., demethylation) and cleavage pathways are thought to depend on community interactions and their sulfur demand. However, a quantitative assessment of the sulfur partitioning between each of these pathways is still missing. Here, we report for the first time the sulfur isotope fractionations by enzymes involved in DMSP degradation with different catalytic mechanisms, expressed heterologously in Escherichia coli. We show that the residual DMSP from the demethylation pathway is 2.7‰ enriched in δ 34S relative to the initial DMSP, and that the fractionation factor (34 ε) of the cleavage pathways varies between −1 and −9‰. The incorporation of these fractionation factors into mass balance calculations constrains the biological fates of DMSP in seawater, supports the notion that demethylation dominates over cleavage in marine environments, and could be used as a proxy for the dominant pathways of degradation of DMSP by marine microbial communities.

The immune system uses paracrine signaling to spatially confine potent responses such as inflammation. A bio-orthogonal synthetic paracrine system could enable engineering of analogous multicellular circuits in which different cell types coordinate their functions in a spatially organized fashion. Here, using the plant hormone auxin as a bio-orthogonal chemical signal, we introduce programmable paracrine circuits that distribute sensing and effector functions to different cell types to spatially restrict responses in mouse xenografts. Cells engineered to express auxin biosynthetic genes generated auxin-dense regions with tunable length scales in vivo. This localized signaling ability enabled design of a multicellular sentinel-effector system, in which THP-1 sentinel cells conditionally produce auxin in regions expressing the tumor-specific antigen EGFRvIII, and Jurkat effector cells respond by locally modulating the activity of a chimeric antigen receptor (CAR). This two-cell type system was able to achieve localized activation of engineered effector cells in vivo. These results establish a foundation for engineering multicellular therapeutic systems that focus responses in specific tissue contexts or disease sites.

Much of our understanding of atmospheric secondary organic aerosol (SOA) formation from volatile organic compounds derives from laboratory chamber measurements, including mass yield and elemental composition. These measurements alone are insufficient to identify the chemical mechanisms of SOA production. We present here a comprehensive dataset on the molecular identity, abundance, and kinetics of a-pinene SOA, a canonical system that has received much attention owing to its importance as an organic aerosol source in the pristine atmosphere. Identified organic species account for ~58-72% of the a-pinene SOA mass, and are characterized as semivolatile/low-volatility monomers and extremely low volatility dimers, which exhibit comparable oxidation states yet different functionalities. Features of the a-pinene SOA formation process are revealed for the first time, to our knowledge, from the dynamics of individual particle-phase components. Although monomeric products dominate the overall aerosol mass, rapid production of dimers plays a key role in initiating particle growth. Continuous production of monomers is observed after the parent a-pinene is consumed, which cannot be explained solely by gas-phase photochemical production. Additionally, distinct responses of monomers and dimers to a-pinene oxidation by ozone vs. hydroxyl radicals, temperature, and relative humidity are observed. Gas-phase radical combination reactions together with condensed phase rearrangement of labile molecules potentially explain the newly characterized SOA features, thereby opening up further avenues for understanding formation and evolution mechanisms of a-pinene SOA.