Geometry-Tuned Optical Absorption Spectra of the Coupled Quantum Dot-Double Quantum Ring Structure.

We investigate the energy spectra and optical absorption of a 3D quantum dot-double quantum ring structure of GaAs/Al0.3Ga0.7As with adjustable geometrical parameters. In the effective mass approximation, we perform 3D numerical computations using as height profile a superposition of three Gaussian functions. Independent variations of height and width of the dot and of the rings and also of the dot-rings distance determine particular responses, useful in practical applications. We consider that a suitable manipulation of the geometrical parameters of this type of quantum coupling offer a variety of responses and, more important, the possibility of a fine adjusting in energy spectra and in the opportunity of choosing definite absorption domains, properties required for the improvement of the performances of optoelectronic devices.

Asymmetric effects of hydroclimate extremes on eastern US tree growth: Implications on current demographic shifts and climate variability.

Forests around the world are experiencing changes due to climate variability and human land use. How these changes interact and influence the vulnerability of forests are not well understood. In the eastern United States, well-documented anthropogenic disturbances and land-use decisions, such as logging and fire suppression, have influenced forest species assemblages, leading to a demographic shift from forests dominated by xeric species to those dominated by mesic species. Contemporarily, the climate has changed and is expected to continue to warm and produce higher evaporative demand, imposing stronger drought stress on forest communities. Here, we use an extensive network of tree-ring records from common hardwood species across ~100 sites and ~1300 trees in the eastern United States to examine the magnitude of growth response to both wet and dry climate extremes. We find that growth reductions during drought exceed the positive growth response to pluvials. Mesic species such as Liriodendron tulipifera and Acer saccharum, which are becoming more dominant, are more sensitive to drought than more xeric species, such as oaks (Quercus) and hickory (Carya), especially at moderate and extreme drought intensities. Although more extreme droughts produce a larger annual growth reduction, mild droughts resulted in the largest cumulative growth decreases due to their higher frequency. When using global climate model projections, all scenarios show drought frequency increasing substantially (3-9 times more likely) by 2100. Thus, the ongoing demographic shift toward more mesic species in the eastern United States combined with drier conditions results in larger drought-induced growth declines, suggesting that drought will have an even larger impact on aboveground carbon uptake in the future in the eastern United States.

Investigating the potential of monocyclic B9N9 and C18 rings for the electrochemical sensing, and adsorption of carbazole-based anti-cancer drug derivatives: DFT-based first-principle study.

CONTEXT: For the first time, the use of monocyclic rings C18 and B9N9 as sensors for the sensing of carbazole-based anti-cancer drugs, such as tetrahydrocarbazole (THC), mukonal (MKN), murrayanine (MRY), and ellipticine (EPT), is described using DFT simulations and computational characterization. The geometries, electronic properties, stability studies, sensitivity, and adsorption capabilities of C18 and B9N9 counterparts towards the selected compounds confirm that the analytes interact through active cavities of the C18 and B9N9 rings of the complexes. METHODS: Based on the interaction energies, the sensitivity of surfaces towards EPT, MKN, MRY, and THC analytes is observed. The interaction energy of EPT@B9N9, MKN@B9N9, MRY@B9N9, and THC@B9N9 complexes are observed - 20.40, - 19.49, - 20.07, and - 18.27 kcal/mol respectively which is more exothermic than EPT@C18, MKN@C18, MRY@C18, and THC@C18 complexes are - 16.37, - 13.97, - 13.96, and - 11.39 kcal/mol respectively. According to findings from the quantum theory of atoms in molecules (QTAIM) and the reduced density gradient (RDG), dispersion forces play a significant role in maintaining the stability of these complexes. The electronic properties including FMOs, density of states (DOS), natural bond orbitals (NBO), charge transfer, and absorption studies are carried out. In comparison of B9N9 and C18, the analyte recovery time for C18 is much shorter (9.91 × 10-11 for THC@C18) than that for B9N9 shorter recovery time value of 3.75 × 10-9 for EPT@B9N9. These results suggest that our reported sensors B9N9 and C18 make it faster to detect adsorbed molecules at room temperature. The sensor response is more prominent in B9N9 due to its fine energy gap and high adsorption energy. Consequently, it is possible to think of these monocyclic systems as a potential material for sensor applications.

Multistability of segmented rings by programming natural curvature.

Multistable structures have widespread applications in the design of deployable aerospace systems, mechanical metamaterials, flexible electronics, and multimodal soft robotics due to their capability of shape reconfiguration between multiple stable states. Recently, the snap-folding of rings, often in the form of circles or polygons, has shown the capability of inducing diverse stable configurations. The natural curvature of the rod segment (curvature in its stress-free state) plays an important role in the elastic stability of these rings, determining the number and form of their stable configurations during folding. Here, we develop a general theoretical framework for the elastic stability analysis of segmented rings (e.g., polygons) based on an energy variational approach. Combining this framework with finite element simulations, we map out all planar stable configurations of various segmented rings and determine the natural curvature ranges of their multistable states. The theoretical and numerical results are validated through experiments, which demonstrate that a segmented ring with a rectangular cross-section can show up to six distinct planar stable states. The results also reveal that, by rationally designing the segment number and natural curvature of the segmented ring, its one- or multiloop configuration can store more strain energy than a circular ring of the same total length. We envision that the proposed strategy for achieving multistability in the current work will aid in the design of multifunctional, reconfigurable, and deployable structures.

Integration of ecological indicators to assess a multitemporal impact of cement industries.

The present study evaluated an integrated biomonitoring approach based on three different bioindicators: tree rings, lichens, and beetles in a complex environment (urban-industrial-forest). In Central Italy, four sampling sites were selected to assess the anthropogenic impact of cement plants taking into account (1) long-term exposure (1988-2020) through the analysis of trace elements in tree rings of Quercus pubescens; (2) medium-term exposure (2020-2021) through the analysis of trace elements in thalli (outermost portions) of the lichen Xanthoria parietina; (3) short-term exposure in spring 2021 through the bioaccumulation and evaluation of sample vitality in transplants of the lichen Evernia prunastri and a periodic survey of entomological biodiversity carried out during spring and summer 2021. Trace elements of industrial origin were found in tree rings, with different levels of accumulation between 1988 and 2020 and a maximum in 2012. Native thalli of the lichen X. parietina showed an overall low bioaccumulation of trace elements except for Cr, probably reflecting the influence of national lockdown measures. The transplants of E. prunastri showed a weak stress response in the industrial and urban sites, but not in the forest, and identified Tl and V as the main elements contributing to atmospheric contamination, with peaks at the industrial sites. Concerning the beetles, a significantly lower number of species was found at the Semonte industrial site.

New opportunities for time-resolved imaging using diffraction-limited storage rings.

The advent of diffraction-limited storage rings (DLSRs) has boosted the brilliance or coherent flux by one to two orders of magnitude with respect to the previous generation. One consequence of this brilliance enhancement is an increase in the flux density or number of photons per unit of area and time, which opens new possibilities for the spatiotemporal resolution of X-ray imaging techniques. This paper studies the time-resolved microscopy capabilities of such facilities by benchmarking the ForMAX beamline at the MAX IV storage ring. It is demonstrated that this enhanced flux density using a single harmonic of the source allows micrometre-resolution time-resolved imaging at 2000 tomograms per second and 1.1 MHz 2D acquisition rates using the full dynamic range of the detector system.

Visual Outcomes in Ectopia Lentis in Marfan Syndrome: A Study of Four Surgical Techniques in Children and Adults.

Background/Objectives: To evaluate how the surgical technique and type of implanted intraocular lens influence the postoperative visual acuity and complications in ectopia lentis associated to Marfan syndrome patients. Materials and Methods: The medical records and videos of ectopia lentis surgeries in patients (children and adults) with Marfan syndrome, were retrospectively reviewed and compared. The study included 33 eyes that underwent four different intraocular lens implantation (IOL) techniques: IOL in conjunction with a simple capsular tension ring, IOL in conjunction with a Cionni modified capsular tension ring (m-CTR), two-point scleral IOL fixation and IOL with one haptic in the bag and one haptic sutured to the sclera. Results: Vision significantly improved from a mean preoperative visual acuity of 0.1122 to a mean postoperative visual acuity of 0.4539 in both age groups (p < 0.0001), with no difference in the primary outcome between children and adults. The most common surgical technique used in both age groups was IOL in conjunction with an m-CTR. There was only one major postoperative complication requiring additional surgery. Conclusions: Zonular weakness mainly influenced by age was the most important selection criterion for the surgical approach. Regardless of the technique employed, the postoperative visual acuity was improved in both adults and children.

A dwarf conifer tree from the Triassic of Antarctica: the first fossil evidence of suppressed growth in a favorable climate?

BACKGROUND AND AIMS: The complexity of fossil forest ecosystems is difficult to reconstruct due to the fragmentary nature of the fossil record. However, detailed morpho-anatomical studies of well-preserved individual fossils can provide key information on tree growth and ecology, including in biomes with no modern analog such as the lush forests that developed in the polar regions during past greenhouse climatic episodes. METHODS: We describe an unusual-looking stem from Middle Triassic (ca 240 Ma) deposits of Antarctica with over 100 very narrow growth-rings and conspicuous persistent vascular traces through the wood. Sections of the specimen were prepared using the cellulose acetate peel technique to determine its systematic affinities and analyse its growth. KEY RESULTS: The new fossil shows similarities with the form genus Woodworthia and with conifer stems from the Triassic of Antarctica, and is assigned to the conifers. Vascular traces are interpreted as those of small branches retained on the trunk. Growth-ring analyses reveal one of the slowest growth rates reported in the fossil record, with an average of 0.2 mm/season. While the tree was growing within the Triassic polar circle, sedimentological data and growth-ring information from other fossil trees, including from the same locality, support the presence of favorable conditions in the region. CONCLUSIONS: The specimen is interpreted as a dwarf conifer tree that grew under a generally favorable regional climate but whose growth was suppressed due to stressful local site conditions. This is the first time that a tree with suppressed growth is identified as such in the fossil record, providing new insights on the structure of polar forests under greenhouse climates and, more generally, on the complexity of tree communities in deep time.

Advances in assessing Ca, K, and Mn translocation in oak tree stems (Quercus spp.).

As a part of the biogeochemical cycle, nutrient translocation plays an important role in enhancing the capacity of perennial plants to grow in nutrient-poor soils. Although leaf translocation has been extensively studied, nutrient translocation between wood rings has received considerably less attention, primarily because of methodological constraints. This study aimed to (i) evaluate the effects of different drying techniques on Ca, K, and Mn concentrations, (ii) calibrate a semi-quantitative method for obtaining ring-to-ring nutrient concentrations along wood cores, and (iii) develop a complete calculation chain for nutrient translocation. Three pairs of cores per tree were extracted from nine oaks, and three drying methods-103 °C, 65 °C, and freeze-drying-were applied to each core pair. For each core pair, the first core was analyzed using ITRAX. The second core was analyzed using ICP-OES following the mineralization of a 20 mg wood sample. Ca, K, and Mn concentrations and wood density were not affected by the drying methods (p > 0.05 for Ca, K, and Mn). After upscaling at the stand level, the total translocation was 10.8 ± 5.5 kg ha-1, 14.8 ± 11.4 kg ha-1, and 2.6 ± 0.9 kg ha-1 for Ca, K, and Mn, respectively, after 45 growing years. The total Ca, K, and Mn translocation showed a strong tree effect, partly explained by tree diameter. The study findings suggest that similar measurements can be performed on all wood cores sampled in previous studies and stored after air-drying. These results provide a reference for future analyses of Ca, K, and Mn translocations in different species from wide geographic areas.

Generation of multimillion chemical space based on the parallel Groebke-Blackburn-Bienaymé reaction.

Parallel Groebke-Blackburn-Bienaymé reaction was evaluated as a source of multimillion chemically accessible chemical space. Two most popular classical protocols involving the use of Sc(OTf)3 and TsOH as the catalysts were tested on a broad substrate scope, and prevalence of the first method was clearly demonstrated. Furthermore, the scope and limitations of the procedure were established. A model 790-member library was obtained with 85% synthesis success rate. These results were used to generate a 271-Mln. readily accessible (REAL) heterocyclic chemical space mostly containing unique chemotypes, which was confirmed by comparative analysis with commercially available compound collections. Meanwhile, this chemical space contained 432 compounds that already showed biological activity according to the ChEMBL database.

High-resolution reconstruction of April-September precipitation and major extreme droughts in China over the past ∼530 years.

Extreme drought events have increased, causing serious losses and damage to the social economy under current warming conditions. However, short-term meteorological data limit our understanding and projection of these extremes. With the accumulation of proxy data, especially tree-ring data, large-scale precipitation field reconstruction has provided opportunities to explore underlying mechanisms further. Using point-by-point regression, we reconstructed the April-September precipitation field in China for the past ∼530 years on the basis of 590 proxy records, including 470 tree-ring width chronologies and 120 drought/flood indices. Our regression models explained average 50% of the variance in precipitation. In the statistical test on calibration and verification, our models passed the significance level that assured reconstruction quality. The reconstruction data performed well, showing consistency and better quality than previously reported reconstructions. The first three leading modes of variability in the reconstruction revealed the main distribution modes of precipitation over China. Wet/drought and extremely wet/drought years accounted for 12.81%/10.92% (68 years/58 years) and 1.69%/3.20% (9 years/17 years) of the past ∼530 years in China, respectively. Major extreme drought events can be identified explicitly in our reconstruction. The detailed features of the Chongzhen Great Drought (1637-1643), the Wanli Great Drought (1585-1590), and the Ding-Wu Great Famine (1874-1879), indicated the existence of potentially different underlying mechanisms that need further exploration. Although further improvements can be made for remote uninhabited areas and large deserts, our gridded reconstruction of April-September precipitation in China over the past ∼530 years can provide a solid database for studies on the attribution of climate change and the mechanism of extreme drought events.

Two- and Three-Spin Hybrid Inorganic-Organic [2]Rotaxanes Containing Metallated Salen Groups.

Mono- and bis-salen functionalised [2]rotaxanes have been synthesised from the esterification of [2]rotaxanes containing phenol-terminated threads (salen = N,N'-bis(salicylidene)ethylenediamine). The [2]rotaxanes have general formula [RH][Cr7NiF8(O2CtBu)16], where [RH]+ is a thread with a central secondary ammonium site that templates a [Cr7NiF8(O2CtBu)16]- ring. The threads are terminated at one or both ends by carboxylic acid functionalised salen groups. The {M(salen)} groups can be free-base [M = (H+)2] or metallated [M = Cu2+, Ni2+, (VO)2+]. The [2]rotaxanes have been characterised by single crystal XRD and solid- and solution-state EPR spectroscopy. Where two paramagnetic M ions are involved [M = Cu2+ and/or (VO)2+] the [2]rotaxanes contain three electron spin S = ½ centres, since the {Cr7Ni} ring has an S = ½ ground state which is well isolated at low temperatures. These three-spin [2]rotaxanes have been characterised in solution by pulsed dipolar EPR spectroscopies (DEER, also known as PELDOR, and RIDME). The M···M and M···{Cr7Ni} interactions measured are consistent with dipolar interactions and also with the distances from single crystal XRD.

Synthesis of a Library of Terpenoid Alkaloid-Like Compounds Containing Medium-Sized Rings via Reconstruction of the Humulene Skeleton.

The construction of a chemical library based on natural products is a promising method for the synthesis of natural product-like compounds. In this study, we synthesized a terpenoid alkaloid-like compound library based on the humulene skeleton. Our strategy, which enables access to diverse ring systems such as 11-membered monocyclic, oxabicyclic, and medium-sized aza ring-containing scaffolds, involves the introduction of a nitrogen atom, an intermolecular C-O bond formation via Lewis acid-mediated epoxide-opening transannulation, and a ring-reconstruction strategy based on olefin metathesis. A cheminformatics analysis based on their structural and physicochemical properties revealed that the synthesized compounds have high three-dimensionality and high natural product likeness scores but with structural novelty. The usefulness of the terpenoid alkaloid-like compound library for drug discovery and the accessibility to structure-activity relationship studies were validated by performing an assay for osteoclast-specific tartrate-resistant acid phosphatase activity, resulting in the identification of a seed compound for bone-resorptive diseases such as osteoporosis.

Unveiling dynamics of nitrogen content and selected nitrogen heterocycles in thrombin inhibitors: a ceteris paribus approach.

BACKGROUND: Despite the progress in comprehending molecular design principles and biochemical processes associated with thrombin inhibition, there is a crucial need to optimize efforts and curtail the recurrence of synthesis-testing cycles. Nitrogen and N-heterocycles are key features of many anti-thrombin drugs. Hence, a pragmatic analysis of nitrogen and N-heterocycles in thrombin inhibitors is important throughout the drug discovery pipeline. In the present work, the authors present an analysis with a specific focus on understanding the occurrence and distribution of nitrogen and selected N-heterocycles in the realm of thrombin inhibitors. RESEARCH DESIGN AND METHODS: A dataset comprising 4359 thrombin inhibitors is used to scrutinize various categories of nitrogen atoms such as ring, non-ring, aromatic, and non-aromatic. In addition, selected aromatic and aliphatic N-heterocycles have been analyzed. RESULTS: The analysis indicates that ~62% of thrombin inhibitors possess five or fewer nitrogen atoms. Substituted N-heterocycles have a high occurrence, like pyrrolidine (23.24%), pyridine (20.56%), piperidine (16.10%), thiazole (9.61%), imidazole (7.36%), etc. in thrombin inhibitors. CONCLUSIONS: The majority of active thrombin inhibitors contain nitrogen atoms close to 5 and a combination of N-heterocycles like pyrrolidine, pyridine, piperidine, etc. This analysis provides crucial insights to optimize the transformation of lead compounds into potential anti-thrombin inhibitors.

The Growth-Climate Relationships of Three Dominant Subalpine Conifers on the Baima Snow Mountain in the Southeastern Tibetan Plateau.

The impact of climates on the radial growth of muti-species remains insufficiently understood in the climate-sensitive southeastern Tibetan Plateau, and this hampers an effective assessment of forest growth under the background of global warming. Here, we studied the growth-climate relationships of three major species (Abies georgei, Larix potaninii, and Picea likiangensis) on the Baima Snow Mountain (BSM) by using dendrochronology methods. We constructed basal area increment (BAI) residual chronologies based on the dated ring-width measurements and correlated the chronologies with four climate factors. We also calculated the contributions of each climate factor to species growth. We found that photothermal conditions played a more important role than moisture in modulating radial growth, and P. likiangensi presented the strongest sensitivity to climate change among the three species. The growing season (June and July) temperature positively affected the radial growth of three species. Winter (previous December and current January) SD negatively impacted the tree growth of A. georgei and P. likiangensis. Significant correlations between growth and precipitation were detected only in A. georgei (January and May). Warming since the beginning of the 1950s promoted the growth of A. georgei and P. likiangensis, while the same effect on L. potaninii growth was found in the recent 50 years.

Slide tracheoplasty for congenital tracheal stenosis: A systematic review.

INTRODUCTION: Slide tracheoplasty has become the gold standard surgery for congenital tracheal stenosis (CTS). This condition is rare and the surgery can be challenging and is performed by experienced surgeons in tertiary centers. A few reports involving relatively small cohorts have been published. The aim of this review is to evaluate the post-operative mortality and morbidity of pediatric slide tracheoplasty for CTS. METHODS: A systematic literature review was performed according to PRISMA guidelines. The Medline and EMBASE databases were screened using a search strategy defined in collaboration with a librarian. We included articles reporting the post-operative mortality rate of slide tracheoplasties for treatment of CTS in children, when at least 10 patients were included. RESULTS: A total of 932 articles were reviewed, and 15 studies were eligible with a total of 845 patients. The overall post-operative mortality rate was 9.3 %, and most deaths were airway related. The open revision surgery rate after surgery was 2.8 % and the endoscopic revision rate was 27.6 %. DISCUSSION: This study highlights key factors to consider before the surgery and helps anticipate post-operative follow-up considerations for children with CTS. Several factors were identified as predictors of mortality including young age, weight at the time of surgery and association with lung hypoplasia or aplasia. CONCLUSION: Although slide tracheoplasty has gained popularity in recent years due to better outcomes, it remains a major surgery with mortality risk and the need for multidisciplinary management.

Retrospective evaluation of "Rods and Rings" pattern detected in the anti-nuclear antibody (ANA) indirect immunofluorescence (IIF) test.

Introduction: Anti-rods and rings (anti-RR) antibodies have recently been described as a cytoplasmic pattern in IIF-based screening of autoantibodies on HEp-2 cells and ICAP has named it as AC-23. It is most frequently related to drug-induced antibody generation. This study aimed to investigate the clinical significance of AC-23 positivity and its relevance to the diagnosis and/or follow-up of the associated diseases and/or drug use. Methods: A multicenter retrospective study was conducted among 10 hospitals from six different provinces in Türkiye from January 2017 to December 2021. The laboratory data and clinical information of 600 patients with positive anti-RR antibodies out of 547.558 HEp-2 IIF ANA samples were analyzed. Results: The distribution of AC-23 positive patients by year indicated a steady increase between 2017-2021. Anti-RR prevalence in post-COVID-19 period was significantly higher than that of pre-COVID-19 period (p=0.00). Concomitant ANA positivity was detected in 56.5% of patients, the most common patterns being AC-4 and AC-5 (41.1%). The most frequent pathology among the anti-RR positive patients was an autoimmune disease (19.83%); 28.57% of which had rheumatoid arthritis and 17.65% autoimmune liver disease. Among the 600 patients, 65 (10.83%) were diagnosed as hepatitis C virus (HCV) infection. Available data for 38 of the HCV patients revealed that 71.05% of them had a history of interferon alfa+ribavirin and 28.95% of them had a history of NS3/4/5A/5B polymerase inhibitor or protease inhibitor drug use. Significant increase in the rate of anti-RR positivity was observed in the post-COVID-19 period when compared to pre-COVID-19 period (p:0.00). Discussion: This is the first multicenter study in Türkiye about the clinical association of anti-RR antibodies which may be ignored during routine HEp-2 IIF testing. Pathologies other than HCV should be taken into consideration in terms of the possible role of anti-RR in autoimmune diseases and other pathologies. The preliminary data obtained in this study suggest that anti-RR antibody development might also be associated to COVID-19, supporting the several previous data related to the potential of viruses triggering the formation of autoantibodies. Large-scale prospective studies should elucidate the clinical significance of RR pattern and determine its role in patient diagnosis and follow-up.

Design and calculation of photoelectric properties of resonance enhanced InAs/GaSb type-II superlattices photodetectors with diffraction rings structure.

The resonance enhanced InAs/GaSb type-II Superlattices (T2SLs) infrared detectors with diffraction rings is designed, and the photoelectric characteristics are calculated and studied in this paper. The diffraction rings are designed on the top surface of T2SLs detector to control the incident light inside the device by forming the resonant cavity. We designed the structure of the conventional PIN InAs/GaSb T2SLs photodetector, calculated the energy band structure of the absorption layer, and analyzed the influence of the thickness of the absorption layer on the photoelectric performance. It is proved that blindly increasing the thickness of the absorption layer cannot effectively improve the device performance. We further studied the quantum efficiency (QE) and electric field distribution of the device after adding the diffraction ring structure. The results show that the structure with diffraction rings can significantly improve the QE of the photodetector without increasing the dark current. The interaction between the diffraction ring and the metal contact layer will enhance the localization of the electric field and further increase the light absorption between the semiconductor layers.

Physiological meaning of bimodal tree growth-climate response patterns.

Correlation coefficients are widely used to identify and quantify climate signals in proxy archives. Significant relationships between tree-ring chronologies and meteorological measurements are typically applied by dendroclimatologists to distinguish between more or less relevant climate variation for ring formation. While insignificant growth-climate correlations are usually found with cold season months, we argue that weak relationships with high summer temperatures not necessarily disprove their importance for xylogenesis. Here, we use maximum latewood density records from ten treeline sites between northern Scandinavia and southern Spain to demonstrate how monthly growth-climate correlations change from narrow unimodal to wide bimodal seasons when vegetation periods become longer and warmer. Statistically meaningful relationships occur when minimum temperatures exceed 'biological zero' at around 5° C. We conclude that the absence of evidence for statistical significance between tree growth and the warmest summer temperatures at Mediterranean sites is no evidence of absence for the physiological importance of high summer temperatures for ring formation. Since correlation should never be confused with causation, statistical values require mechanistic understanding, and different interpretations are needed for insignificant correlations within and outside the growing season.

Oxygen production from dissociation of Europa's water-ice surface.

Jupiter's moon Europa has a predominantly water-ice surface that is modified by exposure to its space environment. Charged particles break molecular bonds in surface ice, thus dissociating the water to ultimately produce H2 and O2, which provides a potential oxygenation mechanism for Europa's subsurface ocean. These species are understood to form Europa's primary atmospheric constituents. Although remote observations provide important global constraints on Europa's atmosphere, the molecular O2 abundance has been inferred from atomic O emissions. Europa's atmospheric composition had never been directly sampled and model-derived oxygen production estimates ranged over several orders of magnitude. Here, we report direct observations of H2+ and O2+ pickup ions from the dissociation of Europa's water-ice surface and confirm these species are primary atmospheric constituents. In contrast to expectations, we find the H2 neutral atmosphere is dominated by a non-thermal, escaping population. We find 12 ± 6 kg s-1 (2.2 ± 1.2 × 1026 s-1) O2 are produced within Europa's surface, less than previously thought, with a narrower range to support habitability in Europa's ocean. This process is found to be Europa's dominant exogenic surface erosion mechanism over meteoroid bombardment.