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Vanadium doped indium sulfide, In2S3:V, is studied as a potential absorber material for intermediate band solar cells. Based on electronic considerations, it is usually assumed that V occupies octahedrally coordinated In sites, although geometrical considerations would favor tetrahedral In sites. In this study, we therefore combined experimental X-ray diffraction and X-ray absorption spectroscopy with ab initio theoretical calculations of both α and β phase to elucidate the incorporation of V in In2S3:V thin films grown with different V content and different growth temperatures. Comparing shape and position of the measured and calculated X-ray absorption edge of V, comparing experimentally determined and calculated V-S bond lengths, and evaluating the calculated heat of solution of V on different lattice sites all indicate that V is incorporated on octahedral rather than tetrahedral sites in the In2S3 matrix. For this material system, the electronic benefit of octahedral coordination thus outweighs the mechanical stress of the associated lattice relaxation. Finally, we studied the electronic structure of V-substituted α-In2S3 using hybrid density functional calculations and find that for a concentration of 1.9 at%, V on octahedrally coordinated In sites forms an empty intermediate band isolated from valence and conduction bands. By increasing the V content to 3.8 at%, however, the gap between intermediate band and conduction band closes, which results in a reduction of the band gap. This differs from the electronic structure calculated for β-In2S3:V and clearly demonstrates that both crystal structure and V incorporation site affect the resulting electronic material properties.

First cross-calibration of all existing Zr isotopic standards and two certified reference materials to a new commercially available standard NRC ZIRC-1, and the first report of the Zr isotopic composition of Allende chondrite.

Various chemical elements including nickel (Ni) exhibit mass-independent isotope heterogeneity on a bulk meteorite level, which is generally accepted to reflect the heterogeneous distribution of presolar carrier(s) from different nucleosynthetic sources. Thus, understanding the nature of the carriers can help decipher the origin of the observed nucleosynthetic variability, which remains elusive. In this study, we present the first high precision measurements of mass-independent and mass-dependent Ni isotope compositions for step-leaches of the CI chondrite Ivuna and Efremovka CAIs supplemented by bulk chondrite measurements. Step-leaches record highly anomalous Ni isotope signatures that can be attributed to at least four diverse nucleosynthetic sources. The most anomalous leachates show either large deficits (up to 0.1 %) in the neutron-poor 58Ni and 60Ni nuclides (L11, thought to contain mainly s-process derived Ni) or minor enrichments and deficits (∼100 ppm) in 60Ni or 64Ni (L6, L8, L9 and L10, all thought to derive mainly from supernovae). Pristine CAIs record Ni isotope compositions typified by enrichments in 58Ni of up to 400 ppm. Our new data for bulk chondrites agree with earlier work and emphasize the appropriateness of using the 62Ni/61Ni ratio for internal normalization. Based on the compositional relations between the step-leaches data, CAIs, and bulk meteorites, we show that 60Ni variability is consistent with being of nucleosynthetic origin as opposed to reflecting variable Fe/Ni ratios in the presence of live 60Fe. Finally, we infer that the observed Ni nucleosynthetic disk variability is predominantly driven by a combination of processes separating different nucleosynthetic carriers in the disk from each other, including thermal processing and size-based sorting.

Die chronisch inflammatorisch demyelinisierende Polyneuropathie (CIDP) ist eine seltene Erkrankung des peripheren Nervensystems. Im Verlauf der Erkrankung kommt es zu symmetrischer, oft proximal betonter Schwache der Extremitaten. Teilweise treten auch sensorische Ausfalle auf. Wir beschreiben einen Fall, bei dem aufgrund proximal betonter Beinschwache und erhohter Entzundungsparameter zunachst eine Polymyalgia rheumatica vermutet wurde. Letztendlich wurde nach interdisziplinarer Diagnostik eine CIDP mit gleichzeitigem Vorliegen einer Endokarditis diagnostiziert.

The terrestrial planets endured a phase of bombardment following their accretion, but the nature of this late accreted material is debated, preventing a full understanding of the origin of inner solar system volatiles. We report the discovery of nucleosynthetic chromium isotope variability (μ54Cr) in Martian meteorites that represent mantle-derived magmas intruded in the Martian crust. The μ54Cr variability, ranging from -33.1 ± 5.4 to +6.8 ± 1.5 parts per million, correlates with magma chemistry such that samples having assimilated crustal material define a positive μ54Cr endmember. This compositional endmember represents the primordial crust modified by impacting outer solar system bodies of carbonaceous composition. Late delivery of this volatile-rich material to Mars provided an exotic water inventory corresponding to a global water layer >300 meters deep, in addition to the primordial water reservoir from mantle outgassing. This carbonaceous material may also have delivered a source of biologically relevant molecules to early Mars., Science Advances, 8 (46), ISSN:2375-2548

Volatile molecules containing hydrogen, carbon, and nitrogen are key components of planetary atmospheres. In the pebble accretion model for rocky planet formation, these volatile species are accreted during the main planetary formation phase. For this study, we modelled the partitioning of volatiles within a growing planet and the outgassing to the surface. The core stores more than 90\% of the hydrogen and carbon budgets of Earth for realistic values of the partition coefficients of H and C between metal and silicate melts. The magma oceans of Earth and Venus are sufficiently deep to undergo oxidation of ferrous Fe$^{2+}$ to ferric Fe$^{3+}$. This increased oxidation state leads to the outgassing of primarily CO$_2$ and H$_2$O from the magma ocean of Earth. In contrast, the oxidation state of Mars' mantle remains low and the main outgassed hydrogen carrier is H$_2$. This hydrogen easily escapes the atmosphere due to the irradiation from the young Sun in XUV wavelengths, dragging with it the majority of the CO, CO$_2$, H$_2$O, and N$_2$ contents of the atmosphere. A small amount of surface water is maintained on Mars, in agreement with proposed ancient ocean shorelines, for moderately low values of the mantle oxidation. Nitrogen partitions relatively evenly between the core and the atmosphere due to its extremely low solubility in magma; the burial of large reservoirs of nitrogen in the core is thus not possible. The overall low N contents of Earth disagree with the high abundance of N in all chondrite classes and favours a volatile delivery by pebble snow. Our model of rapid rocky planet formation by pebble accretion displays broad consistency with the volatile contents of the Sun's terrestrial planets. The diversity of the terrestrial planets can therefore be used as benchmark cases to calibrate models of extrasolar rocky planets and their atmospheres., Comment: Version accepted for Astronomy & Astrophysics

WOS:000600550100030; International audience; Chromium (Cr) isotopes play an important role in cosmochemistry and planetary science because they are powerful tools for dating (Mn-53-Cr-53 short-lived chronometry), tracing (Cr-54 nucleosynthetic anomalies) the origins of the materials, and studying the processes involved in volatile element fractionation and planetary differentiation (Cr stable isotopic fractionation). To use Cr isotopes for these purposes, it is essential to precisely know the compositions of the various chondritic reservoirs. However, the Cr isotope composition of Rumuruti (R) chondrites remains unknown. Here, we report high-precision mass-independent (average 2SE uncertainty of similar to 0.02 and similar to 0.06 for epsilon Cr-53 and epsilon Cr-54, respectively; epsilon indicates 10,000 deviation) and mass-dependent (uncertainty of average 0.03 parts per thousand for delta Cr-53; .delta indicates 1000 deviation) Cr isotope data for 12 bulk R chondrites of petrologic types 3-6 (including R chondrite breccias), and one R chondrite-like clast (MS-CH) in the Almahata Sitta polymict ureilite. All the R chondrites show homogeneous bulk epsilon Cr-54 values, -0.06 +/- 0.08 (2SD), similar only to those of the Earth-Moon system and enstatite chondrites. This first epsilon Cr-54 dataset for R chondrites provides significant addition to the epsilon Cr-54-A, Delta O-17 diagram, and positions them as a potential endmember for planetary precursors. The R chondrites possess a higher Mn-55/Cr-52 of 0.68 +/- 0.04 relative to most of carbonaceous chondrites and higher epsilon Cr-53 values 0.23 +/- 0.05 (2SD) relative to most of chondrite groups. This likely results from the lower chondrule abundance in R chondrites compared to that of ordinary and enstatite chondrites. The stable Cr isotope composition of R chondrites is homogeneous with a delta Cr-53 = -0.12 +/- 0.03%e (2SD). Combined with previous data of other groups of chondrites, we show that the stable Cr isotopic composition of all the chondrites is homogeneous with delta Cr-53 of -0.12 +/- 0.04%e (2SD, N = 42) and is independent of the petrologic type and redox conditions. The lack of mass-dependent fractionation between all groups of chondrites suggests that the average chondrite delta Cr-53 value is also representative for the initial composition of all differentiated planets in the Solar System. Finally, the MS-CH clast in Almahata Sitta has a Cr isotopic composition (epsilon Cr-53 = 0.18 +/- 0.04, epsilon Cr-54 = 0.16 +/- 0.07, and delta Cr-53 = -0.11 +/- 0.05%e) that is consistent (within error) with it being an R chondrite-like clast. (C) 2020 Elsevier Ltd. All rights reserved.

Background/Aims: Extracellular vesicles (EVs), including microvesicles and exosomes, deliver bioactive cargo mediating intercellular communication in physiological and pathological conditions. EVs are increasingly investigated as therapeutic agents and targets, but also as disease biomarkers. However, a definite consensus regarding EV isolation methods is lacking, which makes it intricate to standardize research practices and eventually reach a desirable level of data comparability. In our study, we performed an inter-laboratory comparison of EV isolation based on a differential ultracentrifugation protocol carried out in 4 laboratories in 2 independent rounds of isolation. Methods: Conditioned medium of colorectal cancer cells was prepared and pooled by 1 person and distributed to each of the participating laboratories for isolation according to a pre-defined protocol. After EV isolation in each laboratory, quantification and characterization of isolated EVs was collectively done by 1 person having the highest expertise in the respective test method: Western blot, flow cytometry (fluorescence-activated cell sorting [FACS], nanoparticle tracking analysis (NTA), and transmission electron microscopy (TEM). Results: EVs were visualized with TEM, presenting similar cup-shaped and spherical morphology and sizes ranging from 30 to 150 nm. NTA results showed similar size ranges of particles in both isolation rounds. EV preparations showed high purity by the expression of EV marker proteins CD9, CD63, CD81, Alix, and TSG101, and the lack of calnexin. FACS analysis of EVs revealed intense staining for CD63 and CD81 but lower levels for CD9 and TSG101. Preparations from 1 laboratory presented significantly lower particle numbers (p < 0.0001), most probably related to increased processing time. However, even when standardizing processing time, particle yields still differed significantly between groups, indicating inter-laboratory differences in the efficiency of EV isolation. Importantly, no relation was observed between centrifugation speed/k-factor and EV yield. Conclusions: Our findings demonstrate that quantitative differences in EV yield might be due to equipment- and operator-dependent technical variability in ultracentrifugation-based EV isolation. Furthermore, our study emphasizes the need to standardize technical parameters such as the exact run speed and k-factor in order to transfer protocols between different laboratories. This hints at substantial inter-laboratory biases that should be assessed in multi-centric studies.

We present a series of papers dedicated to modelling the accretion and differentiation of rocky planets that form by pebble accretion within the lifetime of the protoplanetary disc. In this first paper, we focus on how the accreted ice determines the distribution of iron between the mantle (oxidized FeO and FeO$_{1.5}$) and the core (metallic Fe and FeS). We find that an initial primitive composition of ice-rich material leads, upon heating by the decay of $^{26}$Al, to extensive water flow and the formation of clay minerals inside planetesimals. Metallic iron dissolves in liquid water and precipitates as oxidized magnetite Fe$_3$O$_4$. Further heating by $^{26}$Al destabilizes the clay at a temperature of around 900 K. The released supercritical water ejects the entire water content from the planetesimal. Upon reaching the silicate melting temperature of 1,700 K, planetesimals further differentiate into a core (made mainly of iron sulfide FeS) and a mantle with a high fraction of oxidized iron. We propose that the asteroid Vesta's significant FeO fraction in the mantle is a testimony of its original ice content. We consider Vesta to be a surviving member of the population of protoplanets from which Mars, Earth, and Venus grew by pebble accretion. We show that the increase in the core mass fraction and decrease in FeO contents with increasing planetary mass (in the sequence Vesta -- Mars -- Earth) is naturally explained by the growth of terrestrial planets outside of the water ice line through accretion of pebbles containing iron that was dominantly in metallic form with an intrinsically low oxidation degree., Comment: Version accepted for Astronomy & Astrophysics

To assess morbidity and mortality of parainfluenza virus (PIV) infections in immunocompromised patients, we analysed PIV infections in a hematology and stem cell transplantation (SCT) unit over the course of three years. Isolated PIV strains were characterized by sequence analysis and nosocomial transmission was assessed including phylogenetic analysis of viral strains. 109 cases of PIV infection were identified, 75 in the setting of SCT. PIV type 3 (n = 68) was the most frequent subtype. PIV lower respiratory tract infection (LRTI) was observed in 47 patients (43%) with a mortality of 19%. Severe leukopenia, prior steroid therapy and presence of co-infections were significant risk factors for development of PIV-LRTI in multivariate analysis. Prolonged viral shedding was frequently observed with a median duration of 14 days and up to 79 days, especially in patients after allogeneic SCT and with LRTI. Nosocomial transmission occurred in 47 patients. Phylogenetic analysis of isolated PIV strains and combination with clinical data enabled the identification of seven separate clusters of nosocomial transmission. In conclusion, we observed significant morbidity and mortality of PIV infection in hematology and transplant patients. The clinical impact of co-infections, the possibility of long-term viral shedding and frequent nosocomial transmission should be taken into account when designing infection control strategies.

The diagnosis of coronavirus disease 2019 (COVID-19) is mainly based on a positive severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) polymerase chain reaction (PCR) result. PCR samples are obtained from upper or lower respiratory tract specimens. However, the sensitivity of PCR is known to have some limitations. We report on a patient who was admitted to our hospital with dyspnea, fever, cough, and history of contact with a SARS-CoV-2 infected relative. The initial chest computed tomography (CT) showed only minimal changes and SARS-CoV-2 PCR from a nasopharyngeal swab sample was negative. PCR results obtained from further nasopharyngeal swabs, qualified sputum samples, and from a lower respiratory tract specimen also remained negative. At day 13 after admission, a second chest CT showed radiological findings suspicious for viral pneumonia. Finally, serologic results showed high levels of immunoglobulin G and immunoglobulin A antibodies against the S1 domain of the SARS-CoV-2 spike protein, and the patient was diagnosed with COVID-19 pneumonia.

Calcium isotope data ( δ 44 Ca , μ 42 / 44 Ca , and μ 48 / 44 Ca ) are reported for high-temperature metamorphic rocks and minerals, and compared with density-functional theory (DFT) estimates of equilibrium Ca isotope fractionation factors for plagioclase, garnet, clinopyroxene, orthopyroxene, olivine, and apatite. The data and calculations are used to evaluate equilibrium and kinetic fractionation effects that apply to high-temperature metamorphism, where extended residence at high temperature should promote equilibration, but where centimeter-to-meter scale Ca transport could produce diffusive kinetic effects. At upper-granulite facies conditions (T ≥ ∼900 °C), DFT-predicted equilibrium fractionations between minerals are ≤0.8‰, decreasing to ca. 0.6‰ at 1100 °C. We find much larger δ 44 Ca variations in both whole-rock samples (range of ∼4‰) and individual minerals (range of ∼8‰), and large variations in the Ca isotope fractionation between mineral pairs (e.g. Δ 44 Ca grt-plag from −1.5 to +1.5‰). Deviations from equilibrium tend to be larger in concert with indications of higher temperature, such as increasing whole-rock Mg#, plagioclase anorthite content, orthopyroxene Ca/Mg, and garnet Mg#. These large variations are inferred to be due to intragranular or grain-boundary diffusion during metamorphism, as this is the only mechanism that can produce such large isotopic variations. We can confirm the kinetic origin of the variations using measurements of μ 48 / 44 Ca by MC-ICP-MS to distinguish kinetic from equilibrium fractionation processes using a triple-isotope approach. A new variable ( Δ 48 Ca ′ ) quantifies deviations from the Ca-isotope equilibrium slope on a plot of 48Ca/44Ca vs. 42Ca/44Ca. Available geochronological constraints and numerical modeling indicate that observed kinetic isotope fractionations between adjacent high and low Ca rock layers require effective Ca diffusivities of 10−10 to 10−7 m2/yr, and a ratio of Ca isotope diffusivities of D 44 / D 40 ≈ 0.99. The diffusivities are consistent with Ca transport by volume- and grain-boundary diffusion. The apparent contrast in isotopic diffusivities is large and more consistent with silicate liquids than aqueous fluids. This study confirms that kinetic Ca isotope effects are abundant in nature and can overwrite small equilibrium effects, even at high temperatures and even when other techniques (such as Fe-Mg exchange and Ca-in-Opx thermometry) suggest the establishment of chemical equilibrium. Our results imply that kinetic fractionation effects may complicate the use of δ 44 Ca measurements for geothermometry or as a tracer of carbonate recycling into the mantle.

Reliably dated surficial deposits for reconstructing palaeoclimate are rare in the McMurdo Dry Valleys of Antarctica. While many tephra have been found and dated, none is well characterized. In the Wright Valley, the Hart Ash is poorly dated and described. This paper reports profiles through tephra, the chemical signature of the glass shards and new high-precision multi-crystal laser fusion of 40Ar/39Ar ages. Major and trace element analyses of glass shards indicate the tephra are phonolitic and most probably sourced from Mount Discovery in the Erebus volcanic province. Two chemically distinct and stratigraphically separate tephra layers within the Hart Ash were found in three closely spaced soil profiles. The complex stratigraphy between these profiles could not be delineated without the geochemistry of the tephra. Importantly, our data suggest that only one tephra may be an in situ fall-out deposit, which gave a robust age of 2.97 ± 0.02 Ma. This new age for the Hart Ash tephra, which is 10 cm thick and is preserved at the current surface, provides a maximum age for surface deposits in the lower Wright Valley. This study highlights that well-characterized tephra enhance stratigraphic correlations in the Dry Valleys and improve the accuracy of palaeoenvironmental interpretations.

The synthesis of pyridazinium salts was achieved from readily available phenylazosulfonates in a single reaction step. The reaction proceeds via the formation of short-lived phenyldiazenes, which-owing to the strongly acidic conditions-are partially protonated. The phenyldiazenes then undergo a rapid cycloaddition to furans to give pyridazinium salts via elimination of water. The fact that the pyridazinium synthesis shows a low sensitivity toward oxygen, although phenyldiazenes occur as intermediates, can be explained by the very fast cycloaddition step and the partial protonation of the phenyldiazene.

Background: Coronavirus-19 disease (COVID-19) is mainly affecting the respiratory tract, causing viral pneumonia with fever, hypoxemia, and cough. Commonly observed complications include acute respiratory failure, liver or kidney injury, and cardiovascular or neurologic symptoms. In some patients, inflammatory damage results in long term complications like pulmonary fibrosis, chronic pulmonary thrombotic microangiopathy, or neurologic symptoms. The developement of spontaneous pneumothorax is reported as a rare complication mainly in consequence to mechanic ventilation in the criticall ill. Case Report: We report on two cases of COVID-19 pneumonia complicated by a spontaneous pneumothorax and bullous lesions of the lung. Bilateral giant bullae were observed in one of the cases. This complication occurred after an initial resolvement of respiratory symptoms (day 16 and day 29 after COVID-19 treatment was started). Initially, both patients had shown a rather mild course of COVID-19 pneumonia and no mechanical ventilatory support had been necessary. Why Should an Emergency Physician Be Aware of This? In both cases, COVID-19 caused alveolar damage and formation of thoracic bullae with consequent spontaneous pneumothorax as a serious complication. Emergency physicans must be aware of this complication even if the initial COVID-19 symptoms have resolved.

Pebbles of millimeter sizes are abundant in protoplanetary discs around young stars. Chondrules inside primitive meteorites - formed by melting of dust aggregate pebbles or in impacts between planetesimals - have similar sizes. The role of pebble accretion for terrestrial planet formation is nevertheless unclear. Here we present a model where inwards-drifting pebbles feed the growth of terrestrial planets. The masses and orbits of Venus, Earth, Theia (which later collided with the Earth to form the Moon) and Mars are all consistent with pebble accretion onto protoplanets that formed around Mars' orbit and migrated to their final positions while growing. The isotopic compositions of Earth and Mars are matched qualitatively by accretion of two generations of pebbles, carrying distinct isotopic signatures. Finally, we show that the water and carbon budget of Earth can be delivered by pebbles from the early generation before the gas envelope became hot enough to vaporise volatiles., Comment: Science Advances, in press

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Snow depth on sea ice is an essential state variable of the polar climate system and yet one of the least known and most difficult to characterize parameters of the Arctic and Antarctic sea ice systems. Here, we present a new type of autonomous platform to measure snow depth, air temperature, and barometric pressure on drifting Arctic and Antarctic sea ice. “Snow Buoys” are designed to withstand the harshest environmental conditions and to deliver high and consistent data quality with minimal impact on the surface. Our current dataset consists of 79 time series (47 Arctic, 32 Antarctic) since 2013, many of which cover entire seasonal cycles and with individual observation periods of up to 3 years. In addition to a detailed introduction of the platform itself, we describe the processing of the publicly available (near real time) data and discuss limitations. First scientific results reveal characteristic regional differences in the annual cycle of snow depth: in the Weddell Sea, annual net snow accumulation ranged from 0.2 to 0.9 m (mean 0.34 m) with some regions accumulating snow in all months. On Arctic sea ice, the seasonal cycle was more pronounced, showing accumulation from synoptic events mostly between August and April and maxima in autumn. Strongest ablation was observed in June and July, and consistently the entire snow cover melted during summer. Arctic air temperature measurements revealed several above-freezing temperature events in winter that likely impacted snow stratigraphy and thus preconditioned the subsequent spring snow cover. The ongoing Snow Buoy program will be the basis of many future studies and is expected to significantly advance our understanding of snow on sea ice, also providing invaluable in situ validation data for numerical simulations and remote sensing techniques.

Expression of signaling proteins in bone cells depends on their embryological mesoderm-derived (e.g. tibia) or cranial neural crest (CNC)-derived (e.g. jaw) origin. Connexin 43 (Cx43) is a gap junction protein that plays an essential role in the mode of action of bisphosphonates (BP). This study aimed to investigate Cx43 expression and the influence of BP application on mesoderm- and CNC-derived bone. Using a rat model, molar extraction and tibia osteotomy with (Group 4) or without (Group 3) previous BP application was performed. Untreated (Group 1) and animals selectively treated with BPs (Group 2) served as controls. Cx43 expression was immunohistochemically determined 12 and 16 weeks postoperatively via a labeling index. Cx43 expression in CNC-derived bone was significantly higher compared with mesodermal bone. BP application decreased Cx43 expression; however, detected expression levels were still higher in jawbone (Group 2 tibia vs jaw: 5.83 ± 5.06 vs 23.52 ± 6.42; p = 0.007). During bone healing after surgical intervention (Group 3) there were no expression differences between tibia and jawbone. BP treatment prior to surgery resulted in significantly lower Cx43 expression in CNC-derived compared with tibia bone (Group 4 tibia vs jaw: 56.84 ± 15.57 vs 16.40 ± 5.66; p Increased Cx43 expression in jaw compared with tibia bone is in line with their embryological origins. A significant Cx43 suppression in jawbone after BP application and surgery might contribute to the selectively altered osseous turnover and development of MRONJ in CNC-derived bone.

Refractory inclusions [Ca-Al-rich Inclusions (CAIs) and Amoeboid Olivine Aggregates (AOAs)] in primitive meteorites are the oldest Solar System solids. They formed in the hot inner protoplanetary disk and, as such, provide insights into the earliest disk dynamics and physicochemical processing of the dust and gas that accreted to form the Sun and its planetary system. Using the short-lived 26Al to 26Mg decay system, we show that bulk refractory inclusions in CV (Vigarano-type) and CR (Renazzo-type) carbonaceous chondrites captured at least two distinct 26Al-rich (26Al/27Al ratios of ∼5 × 10−5) populations of refractory inclusions characterized by different initial 26Mg/24Mg isotope compositions (μ26Mg*0). Another 26Al-poor CAI records an even larger μ26Mg*0 deficit. This suggests that formation of refractory inclusions was punctuated and recurrent, possibly associated with episodic outbursts from the accreting proto-Sun lasting as short as 26Al enrichments and large nucleosynthetic Mg isotope effects. This suggests that refractory inclusions formed by incomplete thermal processing of presolar dust, thereby inheriting a diluted signature of their isotope systematics. As such, they record snapshots in the progressive sublimation of isotopically anomalous presolar carriers through selective thermal processing of young dust components from the proto-Solar molecular cloud. We infer that 26Al-rich refractory inclusions incorporated 26Al-rich dust which formed 26Al-poor inclusions (such as FUN- and PLAC-type CAIs) incorporated >10 Myr old dust.

We report on the mass-independent Cr isotope compositions of 11 main group ureilites and an ureilitic trachyandesite (ALM-A). The 54Cr/52Cr ratios for main group ureilites vary from −1.06±0.04 to −0.78±0.05 and averaged at −0.91±0.15 (2SD, N=18) including the data from literature. We argue that this variation reflects primitive mantle heterogeneities within the ureilite parent body (UPB). As such, this body did not experience a global-scale magma ocean, which is consistent with heterogeneous O isotope in ureilites. Furthermore, the ε54Cr values, Mn/Cr ratios, C isotope ratios, Mg# values, and Fe/Mn ratios in the olivine cores of ureilites are correlated with each other, which suggests the mixing of ureilite precursors from at least two reservoirs, rather than a smelting process or the oxidation from ice melting. All the ureilite samples (including the ALM-A) fall on a well-defined 53Mn–53Cr isochron corresponding to a 53Mn/55Mn ratio of (6.02 ± 1.59)×10−6, which translates to an age of 4566.7±1.5 Ma (within 2 Ma after calcium-aluminum-rich inclusions; CAIs) when anchored to the U-corrected Pb–Pb age for the D’Orbigny angrite. This old age indicates early partial melting on the UPB, consistent with the early accretion of the UPB (within 1 Ma after CAIs) predicted by thermal modeling. Furthermore, there is a 4∼5 Ma age difference between the external isochron in this study and internal isochron ages for the feldspathic clasts in polymict ureilites, which likely reflects an impact history during the early evolution of the UPB.

We investigated the stable isotope fractionation of chromium (Cr) for a panorama of chondrites, including EH and EL enstatite chondrites and their chondrules and different phases (by acid leaching). We observed that chondrites have heterogeneous δ 53Cr values (per mil deviation of the 53Cr/52Cr from the NIST SRM 979 standard), which we suggest reflect different physical conditions in the different chondrite accretion regions. Chondrules from a primitive EH3 chondrite (SAH 97096) possess isotopically heavier Cr relative to their host bulk chondrite, which may be caused by Cr evaporation in a reduced chondrule-forming region of the protoplanetary disk. Enstatite chondrites show a range of bulk δ 53Cr values that likely result from variable mixing of isotopically different sulfide-silicate-metal phases. The bulk silicate Earth (δ 53Cr = –0.12 ± 0.02‰, 2SE) has a lighter Cr stable isotope composition compared to the average δ 53Cr value of enstatite chondrites (–0.05 ± 0.02‰, 2SE, when two samples out of 19 are excluded). If the bulk Earth originally had a Cr isotopic composition that was similar to the average enstatite chondrites, this Cr isotope difference may be caused by evaporation under equilibrium conditions from magma oceans on Earth or its planetesimal building blocks, as previously suggested to explain the magnesium and silicon isotope differences between Earth and enstatite chondrites. Alternatively, chemical differences between Earth and enstatite chondrite can result from thermal processes in the solar nebula and the enstatite chondrite-Earth, which would also have changed the Cr isotopic composition of Earth and enstatite chondrite parent body precursors.

Cell activation and apoptosis lead to the formation of extracellular vesicles (EVs) such as exosomes or microvesicles (MVs). EVs have been shown to modulate immune responses; recently, MVs were described to carry microRNA (miRNA) and a role for MVs in the pathogenesis of autoimmune diseases has been discussed. Here we systematically characterized MVs and exosomes according to their release stimuli. The miRNA content of viable or apoptotic human T lymphocytes and the corresponding MVs was analyzed. miRNA, protein and surface marker expression, as well as cytokine release by human monocytes was measured after EV engulfment. Finally, miRNA expression in T lymphocytes and MVs of healthy individuals was compared with those of systemic lupus erythematosus (SLE) patients. We demonstrate that, depending on the stimuli, distinct subtypes of EVs are released, differing in size and carrying a specific RNA profile. We observed an accumulation of distinct miRNAs in MVs after induction of apoptosis and the transfer of functional miRNA by MVs into human monocytes. MVs released from apoptotic cells provoke less of an inflammatory response than those released from viable cells. MiR-155*, miR-34b and miR-34a levels in T lymphocytes and corresponding MVs were deregulated in SLE when compared to healthy individuals.

The large collection of howardite-eucrite-diogenite (HED) meteorites allows us to study the initial magmatic differentiation of a planetesimal. We report Pb-Pb ages of the unequilibrated North West Africa (NWA) 4215 and Dhofar 700 diogenite meteorites and their mass-independent 26Mg isotope compositions (26Mg*) to better understand the timing of differentiation and crystallization of their source reservoir(s). NWA 4215 defines a Pb-Pb age of 4484.5 ± 7.9 Myr and has a 26Mg* excess of +2.3 ± 1.6 ppm whereas Dhofar 700 has a Pb-Pb age of 4546.4 ± 4.7 Myr and a 26Mg* excess of +25.5 ± 1.9 ppm. We interpret the young age of NWA 4215 as a thermal overprint, but the age of Dhofar 700 is interpreted to represent a primary crystallization age. Combining our new data with published Mg isotope and trace element data suggests that approximately half of the diogenites for which such data are available crystallized within the first 1–2 Myr of our solar system, consistent with a short-lived, early-formed magma ocean undergoing convective cooling. The other half of the diogenites, including both NWA 4215 and Dhofar 700, are best explained by their crystallization in slowly cooled isolated magma chambers lasting over at least ~20 Myr.

The Ninth Industrial Fluid Properties Simulation Challenge aimed to test the ability of molecular modeling approaches to predict water/oil interfacial tension (IFT) at conditions of high temperature and pressure. In particular, the challenge featured water/oil IFT where the oil was n-dodecane, toluene, or a 50:50 n-dodecane/toluene blend at 1.825 MPa and temperatures in the range of 383 K to 443 K. Seven entries were received including approaches such as molecular dynamics (MD) and Monte Carlo (MC) simulations, COSMO-RS, and iSAFT, and they were judged by comparison to pendant drop tensiometer benchmark data. The quality of predictions varied among the entries between approximately 20 % and 70 % of the total points possible with the entries based on MD and MC having the highest scores in most cases. As is often the case in molecular modeling, predictions of the relative trends tended to be reliable even if the absolute values were not.

Chromatographic purification of chromium (Cr), which is required for high-precision isotope analysis, is complicated by the presence of multiple Cr-species with different effective charges in the acid digested sample aliquots. The differing ion exchange selectivity and sluggish reaction rates of these species can result in incomplete Cr recovery during chromatographic purification. Because of large mass-dependent inter-species isotope fractionation, incomplete recovery can affect the accuracy of high-precision Cr isotope analysis. Here, we demonstrate widely differing cation distribution coefficients of Cr(III)-species (Cr(3+), CrCl(2+) and CrCl2(+)) with equilibrium mass-dependent isotope fractionation spanning a range of ∼1‰/amu and consistent with theory. The heaviest isotopes partition into Cr(3+), intermediates in CrCl(2+) and the lightest in CrCl2(+)/CrCl3°. Thus, for a typical reported loss of ∼25% Cr (in the form of Cr(3+)) through chromatographic purification, this translates into 185 ppm/amu offset in the stable Cr isotope ratio of the residual sample. Depending on the validity of the mass-bias correction during isotope analysis, this further results in artificial mass-independent effects in the mass-bias corrected (53)Cr/(52)Cr (μ(53)Cr* of 5.2 ppm) and (54)Cr/(52)Cr (μ(54)Cr* of 13.5 ppm) components used to infer chronometric and nucleosynthetic information in meteorites. To mitigate these fractionation effects, we developed strategic chemical sample pre-treatment procedures that ensure high and reproducible Cr recovery. This is achieved either through 1) effective promotion of Cr(3+) by >5 days exposure to HNO3H2O2 solutions at room temperature, resulting in >∼98% Cr recovery for most types of sample matrices tested using a cationic chromatographic retention strategy, or 2) formation of Cr(III)-Cl complexes through exposure to concentrated HCl at high temperature (>120 °C) for several hours, resulting in >97.5% Cr recovery using a chromatographic elution strategy that takes advantage of the slow reaction kinetics of de-chlorination of Cr in dilute HCl at room temperature. These procedures significantly improve cation chromatographic purification of Cr over previous methods and allow for high-purity Cr isotope analysis with a total recovery of >95%.

The decay of radioactive 26Al to 26Mg (half-life of 730,000 years) is postulated to have been the main energy source promoting asteroidal melting and differentiation in the nascent solar system. High-resolution chronological information provided by the 26Al-26Mg decay system is, therefore, intrinsically linked to the thermal evolution of early-formed planetesimals. In this paper, we explore the timing and style of asteroidal differentiation by combining high-precision Mg isotope measurements of meteorites with thermal evolution models for planetesimals. In detail, we report Mg isotope data for a suite of olivine-rich [Al/Mg ~ 0] achondritic meteorites, as well as a few chondrites. Main Group, pyroxene and the Zinder pallasites as well as the lodranite all record deficits in the mass-independent component of μ26Mg (μ26Mg*) relative to chondrites and Earth. This isotope signal is expected for the retarded ingrowth of radiogenic 26Mg* in olivine-rich residues produced through partial silicate melting during 26Al decay and consistent with their marginally heavy Mg isotope composition relative to ordinary chondrites, which may reflect the early extraction of isotopically light partial melts from the source rock. We propose that their parent planetesimals started forming within ~250,000 years of solar system formation from a hot (>~500 K) inner protoplanetary disk region characterized by a reduced initial (26Al/27Al)0 abundance (~1-2 × 10-5) relative to the (26Al/27Al)0 value in CAIs of 5.25 × 10-5. This effectively reduced the total heat production and allowed for the preservation of solid residues produced through progressive silicate melting with depth within the planetesimals. These 'non-carbonaceous' planetesimals acquired their mass throughout an extended period (>3 Myr) of continuous accretion, thereby generating onion-shell structures of incompletely differentiated zones, consisting of olivine-rich residues, overlaid by metachondrites and undifferentiated chondritic crusts. In contrast, individual olivine crystals from Eagle Station pallasites record variable μ26Mg* excesses, suggesting that these crystals captured the 26Mg* evolution of a magmatic reservoir controlled by fractional crystallization processes during the lifespan of 26Al. Similar to previous suggestions based on isotopic evidence, we suggest that Eagle Station pallasites formed from precursor material similar in composition to carbonaceous chondrites from a cool outer protoplanetary disk region characterized by (26Al/27Al)0 ≥ 2.7 × 10-5. Protracted planetesimal accretion timescales at large orbital distances, with onset of accretion 0.3-1 Myr post-CAIs, may have resulted in significant radiative heat loss and thus efficient early interior cooling of slowly accreting 'carbonaceous' planetesimals.

The short-lived (26)Al radionuclide is thought to have been admixed into the initially (26)Al-poor protosolar molecular cloud before or contemporaneously with its collapse. Bulk inner Solar System reservoirs record positively correlated variability in mass-independent (54)Cr and (26)Mg*, the decay product of (26)Al. This correlation is interpreted as reflecting progressive thermal processing of in-falling (26)Al-rich molecular cloud material in the inner Solar System. The thermally unprocessed molecular cloud matter reflecting the nucleosynthetic makeup of the molecular cloud before the last addition of stellar-derived (26)Al has not been identified yet but may be preserved in planetesimals that accreted in the outer Solar System. We show that metal-rich carbonaceous chondrites and their components have a unique isotopic signature extending from an inner Solar System composition toward a (26)Mg*-depleted and (54)Cr-enriched component. This composition is consistent with that expected for thermally unprocessed primordial molecular cloud material before its pollution by stellar-derived (26)Al. The (26)Mg* and (54)Cr compositions of bulk metal-rich chondrites require significant amounts (25-50%) of primordial molecular cloud matter in their precursor material. Given that such high fractions of primordial molecular cloud material are expected to survive only in the outer Solar System, we infer that, similarly to cometary bodies, metal-rich carbonaceous chondrites are samples of planetesimals that accreted beyond the orbits of the gas giants. The lack of evidence for this material in other chondrite groups requires isolation from the outer Solar System, possibly by the opening of disk gaps from the early formation of gas giants.

International audience; Chondrules are major components of chondrites and are believed to drive the accretion of planetary embryos. As such, constraining the timing and origin of chondrules is central for understanding the early evolution of the solar system and the formation of planets. Enstatite chondrites (ECs) have isotope compositions for multiple elements that match that of the Earth and, thus, are considered to be good analogs of the precursor material from which the Earth formed. Here, we report the first high-precision mass-independent Cr isotope data of nine chondrules in one of the least-altered EH chondrites, Sahara 97096. Seven primitive chondrules show typical Cr-54/Cr-52 ratios of bulk ECs, whereas two chondrules have ratios similar to carbonaceous chondrites. The presence of two chondrules with a carbonaceous chondrite signature suggests early inward transport of material to the EC accretion region. The Mn/Cr ratios of the EC-like chondrules (except one with high Fe content) correlate with their Cr-53/Cr-52 isotope ratios, which we interpret as a fossil isochron, with a slope corresponding to a Mn-53/Mn-55 initial ratio of (5.01 0.59) x 10(-6) (2 sigma). When anchored to the D'Orbigny angrite, this Mn-53/Mn-55 ratio returns an absolute age of 4565.7 0.7 Ma for EC chondrule formation (precursor age), 1.6 0.7 Ma after solar system formation. This protracted formation of EC chondrules may suggest that the mass transfer of outer solar system material started prior to the end of planetary embryo accretion, as chondrules could represent the main building blocks of terrestrial planets.

Northwest Africa (NWA) 12379 is a new metal-rich chondrite with unique characteristics distinguishing it from all previously described meteorites. It contains high Fe,Ni-metal content (∼ 70 vol.%) and completely lacks interchondrule matrix; these characteristics are typical only for metal-rich carbonaceous (CH and CB) and G chondrites. However, chondrule sizes (60 to 1200 μm; mean = 370 μm), their predominantly porphyritic textures, nearly equilibrated chemical compositions of chondrule olivines (Fa18.1–28.3, average Fa24.9±3.2, PMD = 12.8; Cr2O3 = 0.03 ± 0.02 wt.%; FeO/MnO = 53.2 ± 6.5 (wt.-ratio); n = 28), less equilibrated compositions of low-Ca pyroxenes (Fs3.2–18.7Wo0.2–4.5; average Fs14.7±3.7Wo1.4±1.3; n = 20), oxygen-isotope compositions of chondrule olivine phenocrysts (Δ17O ∼ 0.2–1.4‰, average ∼ 0.8‰), and the presence of coarse-grained Ti-bearing chromite, Cl-apatite, and merrillite, all indicate affinity of NWA 12379 to unequilibrated (type 3.8) ordinary chondrites (OCs). Like most OCs, NWA 12379 experienced fluid-assisted thermal metamorphism that resulted in formation of secondary ferroan olivine (Fa27) that replaces low-Ca pyroxene grains in chondrules and in inclusions in Fe,Ni-metal grains. Δ17O of the ferroan olivine (∼ 4‰) is similar to those of aqueously-formed fayalite in type 3 OCs, but its δ18O is significantly higher (15–19‰, average = 17‰ vs. 3―12‰, average = 8‰, respectively). We suggest classifying NWA 12379 as the ungrouped metal-rich chondrite with affinities of its non-metal fraction to unequilibrated OCs and speculate that it may have formed by a collision between an OC-like body and a metal-rich body and subsequently experienced fluid-assisted thermal metamorphism. Trace siderophile element abundances and isotopic compositions (e.g., Mo, Ni, Fe) of the NWA 12379 metal could help to constrain its origin.

The mechanisms and timescales of accretion of 10–1000 km sized planetesimals, the building blocks of planets, are not yet well understood. With planetesimal melting predominantly driven by the decay of the short-lived radionuclide 26Al (26Al→26Mg; t1/2 = 0.73 Ma), its initial abundance determines the permissible timeframe of planetesimal-scale melting and its subsequent cooling history. Currently, precise knowledge about the initial 26Al abundance [(26Al/27Al)0] exists only for the oldest known solids, calcium aluminum-rich inclusions (CAIs) – the so-called canonical value. We have determined the 26Al/27Al of three angrite meteorites, D’Orbigny, Sahara 99555 and NWA 1670, at their time of crystallization, which corresponds to (3.98 ± 0.15)×10−7, (3.64 ± 0.18)×10−7, and (5.92 ± 0.59)×10−7, respectively. Combined with a newly determined absolute U-corrected Pb–Pb age for NWA 1670 of 4564.39 ± 0.24 Ma and published U-corrected Pb–Pb ages for the other two angrites, this allows us to calculate an initial (26Al/27Al)0 of (1.33−0.18+0.21)×10−5 for the angrite parent body (APB) precursor material at the time of CAI formation, a value four times lower than the accepted canonical value of 5.25 × 10−5. Based on their similar 54Cr/52Cr ratios, most inner solar system materials likely accreted from material containing a similar 26Al/27Al ratio as the APB precursor at the time of CAI formation. To satisfy the abundant evidence for widespread planetesimal differentiation, the subcanonical 26Al budget requires that differentiated planetesimals, and hence protoplanets, accreted rapidly within 0.25 ± 0.15 Ma of the formation of canonical CAIs.

The presence of isotope heterogeneity of nucleosynthetic origin amongst meteorites and their components provides a record of the diverse stars that contributed matter to the protosolar molecular cloud core. Understanding how and when the solar system’s nucleosynthetic heterogeneity was established and preserved within the solar protoplanetary disk is critical for unraveling the earliest formative stages of the solar system. Here, we report calcium and magnesium isotope measurements of primitive and differentiated meteorites as well as various types of refractory inclusions, including refractory inclusions (CAIs) formed with the canonical 26 Al/ 27 Al of ∼5 × 10 −5 ( 26 Al decays to 26 Mg with a half-life of ∼0.73 Ma) and CAIs that show fractionated and unidentified nuclear effects (FUN-CAIs) to understand the origin of the solar system’s nucleosynthetic heterogeneity. Bulk analyses of primitive and differentiated meteorites along with canonical and FUN-CAIs define correlated, mass-independent variations in 43 Ca, 46 Ca and 48 Ca. Moreover, sequential dissolution experiments of the Ivuna carbonaceous chondrite aimed at identifying the nature and number of presolar carriers of isotope anomalies within primitive meteorites have detected the presence of multiple carriers of the short-lived 26 Al nuclide as well as carriers of anomalous and uncorrelated 43 Ca, 46 Ca and 48 Ca compositions, which requires input from multiple and recent supernovae sources. We infer that the solar system’s correlated nucleosynthetic variability reflects unmixing of old, galactically-inherited homogeneous dust from a new, supernovae-derived dust component formed shortly prior to or during the evolution of the giant molecular cloud parental to the protosolar molecular cloud core. This implies that similarly to 43 Ca, 46 Ca and 48 Ca, the short-lived 26 Al nuclide was heterogeneously distributed in the inner solar system at the time of CAI formation.

Observation of the climate and ecosystem of ice covered polar seas is a timely task for the scientific community. The goal is to assess the drastic and imminent changes of the polar sea ice cover induced by climate change. Retreating and thinning sea ice affects the planets energy budget, atmospheric, and oceanic circulation patterns as well as the ecosystem associated with this unique habitat. To increase the observational capabilities of sea ice scientists, we equipped a remotely operated vehicle (ROV) as sensor platform for interdisciplinary research at the ice water interface. Here, we present the technical details and operation scheme of the new vehicle and provide data examples from a first campaign in the Arctic in autumn 2016 to demonstrate the vehicle's capabilities. The vehicle is designed for efficient operations in the harsh polar conditions. Redundant modular design allows operation by three scientists simultaneously operating a wide variety of sensors. Sensors from physical, chemical, and biological oceanography are combined with optical and acoustic sea ice sensors to provide a comprehensive picture of the underside of sea ice. The sensor suite provides comprehensive capabilities and can be further extended as additional ports for power and communication are available. The vehicle provides full six degrees of freedom in navigation, enabling intervention, and manipulation skills despite its simple one function manipulator arm.

The mass-independent calcium isotope composition of inner-Solar-System bodies is correlated with their masses and accretion ages, indicating a rapid growth for the precursors of Earth and the Moon during the protoplanetary disk’s lifetime. Variation in the isotopic composition of material within the early inner Solar System is usually thought to reflect spatial heterogeneity in the protoplanetary disk. Martin Schiller and co-authors find that the calcium isotope composition of samples from the parent bodies of ureilite and angrite meteorites, as well as from Vesta, Mars and Earth, are correlated to the masses of their inferred parent asteroids and planets. This provides a proxy for their accretion timescales and implies a rapid 'secular' evolution of the bulk calcium isotope composition of the disk in the rocky-planet-forming region. The authors infer that this secular evolution reflects the introduction of pristine outer-Solar-System material to the thermally processed inner protoplanetary disk associated with the accretion of mass to the proto-Sun. They also conclude that the indistinguishable calcium isotope composition of the Earth and the Moon implies that the Moon-forming impact involved protoplanets that completed their accretion near the end of the disk's lifetime. Nucleosynthetic isotope variability among Solar System objects is often used to probe the genetic relationship between meteorite groups and the rocky planets (Mercury, Venus, Earth and Mars), which, in turn, may provide insights into the building blocks of the Earth–Moon system1,2,3,4,5. Using this approach, it has been inferred that no primitive meteorite matches the terrestrial composition and the protoplanetary disk material from which Earth and the Moon accreted is therefore largely unconstrained6. This conclusion, however, is based on the assumption that the observed nucleosynthetic variability of inner-Solar-System objects predominantly reflects spatial heterogeneity. Here we use the isotopic composition of the refractory element calcium to show that the nucleosynthetic variability in the inner Solar System primarily reflects a rapid change in the mass-independent calcium isotope composition of protoplanetary disk solids associated with early mass accretion to the proto-Sun. We measure the mass-independent 48Ca/44Ca ratios of samples originating from the parent bodies of ureilite and angrite meteorites, as well as from Vesta, Mars and Earth, and find that they are positively correlated with the masses of their parent asteroids and planets, which are a proxy of their accretion timescales. This correlation implies a secular evolution of the bulk calcium isotope composition of the protoplanetary disk in the terrestrial planet-forming region. Individual chondrules from ordinary chondrites formed within one million years of the collapse of the proto-Sun7 reveal the full range of inner-Solar-System mass-independent 48Ca/44Ca ratios, indicating a rapid change in the composition of the material of the protoplanetary disk. We infer that this secular evolution reflects admixing of pristine outer-Solar-System material into the thermally processed inner protoplanetary disk associated with the accretion of mass to the proto-Sun. The identical calcium isotope composition of Earth and the Moon reported here is a prediction of our model if the Moon-forming impact involved protoplanets or precursors that completed their accretion near the end of the protoplanetary disk’s lifetime.

Introduction: Medical imaging technology has revolutionized health care over the past 30 years. This is especially true for ultrasound, a modality that an increasing amount of medical personal is starting to use. Purpose: The purpose of this study was to develop and evaluate a platform for improving medical image interpretation skills regardless of time and space and without the need for expensive imaging equipment or a patient to scan. Methods, results and conclusions: A stable web application with the needed functionality for image interpretation training and evaluation has been implemented. The system has been extensively tested internally and used during an international course in ultrasound-guided neurosurgery. The web application was well received and got very good System Usability Scale (SUS) scores.

Polygonal patterned ground is a dominant geomorphic feature in the McMurdo Dry Valleys, Antarctica. In central Beacon Valley, polygons are considered to be ancient expressions of stagnant surface processes and are thought to be stable for millions of years. However, the actual rate at which these polygons form and alter is not known. We describe a detailed cross section of a polygon, make several depth profiles of meteoric 10Be along this cross section, and use optically stimulated luminescence to date a few key samples at the center of this polygon. While confirming conclusions of previous studies that the polygon shoulders are stable on a 100 k.y. time scale and experience little vertical sediment mixing, our results also give clear evidence of eolian transport to the polygon center, leading to a sediment accumulation rate of 3 cm k.y.−1 over the past 15 k.y. Moreover, the data suggest that the accumulated material is locally derived, and, hence, surface erosion of the polygon shoulders must exist that cannot be recorded by meteoric 10Be. We conclude that polygon modification and soil accumulation under the apparent frozen conditions of Beacon Valley is an active and ongoing process.

In this chapter, we summarize the evidence for high temperature Ca isotope fractionation in natural and experimental samples including minerals, igneous and metamorphic rocks and silicate melts and discuss the underlying isotope fractionation mechanisms. Furthermore, we outline the evidence for primordial nucleosynthetic variability of Ca isotopes in meteorites and their components, suggesting a diverse stellar origin of the Ca isotopes that make up our Solar System. We also present a brief synopsis of observed mass-dependent Ca stable isotope fractionation in meteoritic materials, which allow insights into the local conditions during the formative stage of our Solar System. Lastly, we provide an overview of the 40K–40Ca decay system and its use to track the evolution of Earth’s mantle, continental and oceanic crust over time as well as its potential to date igneous and sedimentary rocks.