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Zircon shape is commonly reported during geochronology and geochemistry analyses of igneous, metamorphic, and sedimentary rocks, but the relationship of zircon shape to primary growth environmental conditions remains poorly constrained. Current models for the control on igneous zircon shape focus on the relative growth of crystal prisms and pyramids, which are not discernible in the imaging techniques used for rapid quantification of zircon shape in geochronology sample mounts. We model the relationship between whole‐rock composition and zircon 2D shape in mineral separates from 45 mafic to felsic igneous samples, representative of Archean and Proterozoic crust in Western Australia. Shape parameters are derived from semi‐automated measurement of photomicrographs of polished zircon crystals in epoxy resin mounts. Whole‐rock composition shows a statistically significant relationship to median magmatic zircon crystal area and mathematically defined "roundness." Zircon populations show reduced median area and increased median roundness as whole‐rock silica decreases. Phase equilibrium modeling based on whole‐rock composition, and automated electron microscopy mineral maps, indicates that the compositional predisposition of zircon shape is influenced by fundamentally different physical growth environments in mafic versus felsic melts. Specifically, influential factors that differ between mafic and felsic liquids include crystallization sequence and duration—which influence unconstrained growth space—and the potential for absorption/exsolution of zirconium from the accompanying mineral assemblage. We present quantitative, explanatory models for the relationship between zircon 2D shape and whole‐rock silica and demonstrate that the relationships are adhered to across a broad spectrum of whole‐rock compositions. Plain Language Summary: Zircon is a resilient mineral that can preserve chemical information over billions of years and is used to date different types of rocks. The 2D boundary shapes of polished zircon crystals are commonly reported during their analysis. However, it is challenging to interpret the geological meaning of the 2D shapes as little is known about how the crystals' growth environment affects them. Current understanding is mostly based on 3D crystal faces that are not easily interpreted from imaging techniques geared toward rapid measurements of large quantities of zircon grains, as used during typical isotopic analysis of this mineral. We investigate whether there is geological information in easily acquired 2D zircon boundary shape. We measured the 2D shapes of zircons from different rock types and model how the shape changes with rock composition. We then model how different rock types crystallize and compare the crystallization models to mineral growth relationships seen in the rocks. We find that the 2D shape of zircon is affected by growth space, growth duration, and competition for mineral components. These three factors vary with rock composition. Thus, zircon 2D shape varies with rock composition, hinting at potentially useful, currently untapped, additional information stored in zircon grains. Key Points: Parent magma silica content influences the median 2D shape of an igneous zircon populationMajor controls of median zircon 2D boundary shape appear extrinsic to the crystalPredominant zircon crystallization processes differ between mafic and felsic rocks [ABSTRACT FROM AUTHOR]

Throughout geological history, biodiversity trends have been punctuated by sharp declines coinciding with mass extinction events. Certain organisms—known as disaster forms—flourish during the extinction aftermath from a lack of ecological competition and predation. Microbialites (in particular, stromatolites) are known to increase in environmental diversity following these biotic crises. However, it remains important to identify whether individual microbialite occurrences are a result of globally driven competition reduction or favourable local conditions. Here, we reconsider stromatolites from the northern Perth Basin of Western Australia, previously reported as Smithian (late Olenekian) in age and part of a biotic rebound following the end-Permian mass extinction and re-evaluate their paleodepositional setting and age. Detailed mapping, macro-analysis and meso-analysis of the Perth Basin locality have identified a well-preserved and diverse morphological assemblage of stromatolites that are intimately associated with a coarse siliciclastic facies. The characteristics of, and relationships between the stromatolitic and coarse siliciclastic facies support a restricted aquatic paleodepositional environment with fluvial/alluvial influences. In the Perth Basin, such depositional environments occurred most commonly during the Permian (Guadalupian to Lopingian). The robustness of previous age constraints interpreted from overlying strata (Kockatea Shale) are questioned by the identification of a depositional hiatus and onlapping relationship of the Kockatea Shale on the stromatolitic sequence. Therefore, we suggest that the mid-Phanerozoic northern Perth Basin Stromatolitic Sequence cannot be unequivocally associated with the end-Permian mass extinction and may have instead thrived owing to a favourable paleodepositional setting. The mid-Phanerozoic northern Perth Basin stromatolites are not a unique case. A compilation of reported Permian and Triassic microbialite occurrences shows that stromatolites, although most common following the end-Permian mass extinction, also occur before and after the extinction event in a range of environmental settings. Ten microbialite forms were described and mapped out over 30 km in the northern Perth Basin. Perth Basin Stromatolitic Sequence formed in a restricted aquatic depositional setting with fluvial and/or alluvial influences. Stromatolites from the northern Perth Basin are unlikely to be associated with the end-Permian mass. [ABSTRACT FROM AUTHOR]

The nature and evolution of Earth's crust during the Hadean and Eoarchean is largely unknown owing to a paucity of material preserved from this period. However, clues may be found in the chemical composition of refractory minerals that initially grew in primordial material but were subsequently incorporated into younger rocks and sediment during lithospheric reworking. Here we report Hf isotopic data in 3.9 to 1.8 billion year old detrital zircon from modern stream sediment samples from West Greenland, which document successive reworking of felsic Hadean-to-Eoarchean crust during subsequent periods of magmatism. Combined with global zircon Hf data, we show a planetary shift towards, on average, more juvenile Hf values 3.2 to 3.0 billion years ago. This crustal rejuvenation was coincident with peak mantle potential temperatures that imply greater degrees of mantle melting and injection of hot mafic-ultramafic magmas into older Hadean-to-Eoarchean felsic crust at this time. Given the repeated recognition of felsic Hadean-to-Eoarchean diluted signatures, ancient crust appears to have acted as buoyant life-rafts with enhanced preservation-potential that facilitated later rapid crustal growth during the Meso-and-Neoarchean. The nature and evolution of Earth's crust during the Hadean and Eoarchean is largely unknown due to the lack of preserved material from this period. Here, the authors document a period of crustal rejuvenation between 3.2 and 3.0 Ga, coincident with peak mantle potential temperatures that imply greater degrees of mantle melting and injection of hot mafic-ultramafic magmas into older Hadean-to-Eoarchean felsic crust at this time. [ABSTRACT FROM AUTHOR]

The aim of the study is to declare the role of surgery in potentially curative malignant pancreatic neuroendocrine tumors, in term of prognosis, survival and complications after the surgical procedures. Does the surgery plays a significant role in the best patient's interest even in metastatic pancreatic neuroendocrine tumors? Clinical and pathological factors that changed the outcomes were also analyzed. It is retrospective, case series study. All patients who were undergoing surgery for malignant pancreatic neuroendocrine tumors from 2013 to 2018. Results show that, sixteen patients were recruited with a mean age at diagnosis of 49.31 years, (ranging from 19-80 years). There were 8 male and 8 female patients. Common symptoms were abdominal pain 12 (75%) of them three cases had clinical jaundice 3 (18.8%) and one case had acute pancreatitis and pancreatic necrosis. One (6.3%) patient had functional tumor, and the rest 15 (93.8%) were nonfunctional tumors; all of the patients were sporadic pancreatic neuroendocrine tumors. Overall morbidity was (43.8%) with no perioperative mortality. The median follow-up period was 23 months, ranging from 5-68 months. Recurrence occurred in four cases with a median disease-free interval of 9.5 moths with grade of differentiation (P-value 0.027), lymph node metastases (P-value 0.027) and tumor stage (P-value 0.017) were associated with recurrent disease. The overall 5 year survival was 81.2% and the disease free survival was (75%) at 5 year, with grade of tumor (Pvalue 0.001), lymph node metastases (P-value 0.001), invasion of other visceral organs(P-value 0.018) and recurrence (P-value 0.001)were associated with decreased survival. In conclusion, pancreatic neuroendocrine tumors have favorable long-term survival after surgical resections even in the presence of liver metastases depending on the grade of differentiation of tumor and lymph node metastases rather than liver metastases and other factors. [ABSTRACT FROM AUTHOR]

Detrital zircon geochronology is a powerful tool to address a range of geological questions related to sedimentary provenance. Nonetheless, non‐unique answers may result when igneous rocks of the same age are sourced from disparate locations. In an effort to resolve some of this issue in zircon provenance investigations, we explore the potential of detrital zircon grains to be linked to their original magmatic source through their grain shape. In order to develop this grain shape measure as a provenance tool, we first examine the relationships between chemistry and a range of different grain shape descriptors. We find grain shape to show a linear relationship to U‐concentration on a lithologic unit level. We interpret this relationship to be a function of crystal chemical control in igneous samples. Principal component analysis demonstrates the potential of simple grain shape descriptors (major axis, minor axis, and effective diameter) to characterize grains from particular rock units. Applying these same shape measures to sedimentary basins in the Proterozoic Albany–Fraser Orogen in southwest Australia allows us to closely replicate the findings of previous traditional U–Pb geochronological investigations in terms of grain provenance. In addition, we apply this technique to Mesozoic sediment on the southern margin of Australia and show for the first time that its detritus is more likely derived from the underlying crystalline basement rather than surrounding orogens that share similar magmatic ages. [ABSTRACT FROM AUTHOR]

A nonlinear boundary-value problem for the equilibrium of a pressurized magnetoelastic membrane acted upon by an applied magnetic field is derived from three-dimensional magnetoelasticity. The model is specified entirely by differential equations in the limit of weak material magnetization, these replacing the integro-differential equations of the general theory. The model is further specialized to axisymmetry, and several problems of technical interest are solved numerically. [ABSTRACT FROM AUTHOR]

Two morbilliviruses were isolated from carcases of Mediterranean monk seals () which had died in coastal areas of Greece and Mauritania. They were characterised as being closely related to the previously identified dolphin and porpoise morbilliviruses on the basis of their serological cross-reactivities in immunofluorescence assays, and sequence homologies in their N and P genes. The results suggest that morbilliviruses of aquatic mammals may cross barriers between species of different orders. [ABSTRACT FROM PUBLISHER]

A survey of a sample of physician group practices in Wisconsin was undertaken to determine the amounts of charity care, bad debt, and discounted Medicaid care that were provided in 1988. Overall, the physician group practices in the sample reported dollar amounts of uncompensated care and discounted Medicaid care that averaged approximately 7.6% of their total billings for the year (1.6% of charity care, 3.0% of bad debt, and 3.0% of discounted Medicaid care). From the dollar totals reported, it was calculated that the individual physicians represented by this sample of group practices were responsible for, on average, +4300 of charity care, +9100 of bad debt, and +7500 of Medicaid discounted services, for a yearly per-physician total of +20,900 of uncompensated care and discounted care provided to uninsured and indigent patients. The results indicate that a majority of the group practices provided more charity care in 1988 than they had 5 years earlier and suggest that the burden of providing uncompensated care tends to fall disproportionately on those group practices that are also providing relatively high levels of service to Medicaid recipients. [ABSTRACT FROM AUTHOR]