The global community needs to be aware of the potential psychosocial consequences that may be experienced by health care workers who are actively managing patients with coronavirus disease (COVID-19). These health care workers are at increased risk for experiencing mood and trauma-related disorders, including posttraumatic stress disorder (PTSD). In this concept article, strategies are recommended for individual health care workers and hospital leadership to aid in mitigating the risk of PTSD, as well as to build resilience in light of a potential second surge of COVID-19.

SN1991bg-like supernovae are a distinct subclass of thermonuclear Type Ia supernovae (SNe Ia). Their spectral and photometric peculiarities indicate that their progenitors and explosion mechanisms differ from ‘normal’ SNe Ia. One method of determining information about supernova progenitors we cannot directly observe is to observe the stellar population adjacent to the apparent supernova explosion site to infer the distribution of stellar population ages and metallicities. We obtain integral field observations and analyse the spectra extracted from regions of projected radius $\sim\,\text{kpc}$ about the apparent SN explosion site for 11 91bg-like SNe in both early- and late-type galaxies. We utilise full-spectrum spectral fitting to determine the ages and metallicities of the stellar population within the aperture. We find that the majority of the stellar populations that hosted 91bg-like supernovae have little recent star formation. The ages of the stellar populations suggest that that 91bg-like SN progenitors explode after delay times of >6 Gyr, much longer than the typical delay time of normal SNe Ia, which peaks at $\sim$1 Gyr.

Some picritic lavas from near the base of the volcanic succession in the Lebombo region of the Karoo Province contain phenocrysts of olivine and skeletal microphenocrysts of ilmenite, the latter indicating rapid crystallization from the magma. These ilmenite grains contain up to 6% MgO. The near-liquidus crystallization and the high MgO content of the ilmenite are highly anomalous for ilmenite in tholeiitic rocks. These features reflect the atypical nature (high MgO and TiO2) of the parental magma and/or highly reduced conditions of crystallization.

The assemblage of lagenide foraminifers in uppermost Permian rocks of the central Taurides consists of 22 species in 16 genera, including the new species Rectostipulina pentamerata, plus additional unidentified elements. Of these, only two identifiable species in “Nodosaria” and indeterminate syzraniids survived the end-Permian mass extinction. The last occurrences of most taxa fall within the upper half-meter of the Permian System, a pattern consistent with abrupt extinction when tested for the Signor-Lipps effect. Permian survivors are joined locally in the Lower Triassic and lower Middle Triassic by three additional species. Globally, lagenide species diversity remained low until latest Anisian time, and probably did not reach pre-extinction levels until Late Triassic or Early Jurassic time. The survival of the lagenide clade, in contrast to the complete elimination of fusulinoidean fusulinides, may be linked to the lagenides' comparatively greater paleoenvironmental tolerances and wider paleogeographic distribution. Evaluation of lagenide extinction and survival across the Permian–Triassic boundary in the central Taurides is complicated by a facies change from bioclastic wackestones and packstones to oolitic grainstones near the top of the Permian, and by the development of variably dolomitized and pyritic stromatolites and overlying oolites in the lowest Triassic. The stromatolitic and oolitic Lower Triassic lithologies represent a sedimentologic response to the end-Permian mass extinction and unusual Early Triassic marine environments. Stromatolites likely became established as disaster forms in an ecologically permissive period that lacked normal marine grazing and bioturbating benthos. Their calcification and preservation may have been promoted by high carbonate saturation levels. Oolites, which are found in recurring facies associations with stromatolites and other anachronistic carbonates in Lower Triassic rocks throughout the Tethyan embayment, probably also formed in response to elevated saturation levels and the absence of a skeletal sink for carbonate.

Chlorsulfuron {2-chloro-N-[[(4-methoxy-6-methyl-1,3,5-triazin-2-yl)amino]carboxyl]benzenesulfonamide} has recently been registered for the control of several broadleaf weeds in spring wheat (Triticum aestivum L.), durum wheat (Triticum durum Desf.), and barley (Hordeum vulgare L.) in western Canada. Residue carryover of this herbicide can cause injury to subsequent sensitive crops. A bioassay technique based on growth of pregerminated corn roots was used to detect levels of chlorsulfuron as low as 0.125 ppb in three Saskatchewan soils. Confidence levels of 95% were established. These confidence bands allowed the detection of chlorsulfuron levels within a minimum and maximum variation of 3.1 and 11.5% of root development.

Fossils of Columbian mammoths (Mammuthus columbi) and pygmy mammoths (Mammuthus exilis) have been reported from Channel Islands National Park, California. Most date to the last glacial period (Marine Isotope Stage [MIS] 2), but a tusk of M. exilis (or immature M. columbi) was found in the lowest marine terrace of Santa Rosa Island. Uranium-series dating of corals yielded ages from 83.8 ± 0.6 ka to 78.6 ± 0.5 ka, correlating the terrace with MIS 5.1, a time of relatively high sea level. Mammoths likely immigrated to the islands by swimming during the glacial periods MIS 6 (~ 150 ka) or MIS 8 (~ 250 ka), when sea level was low and the island–mainland distance was minimal, as during MIS 2. Earliest mammoth immigration to the islands likely occurred late enough in the Quaternary that uplift of the islands and the mainland decreased the swimming distance to a range that could be accomplished by mammoths. Results challenge the hypothesis that climate change, vegetation change, and decreased land area from sea-level rise were the causes of mammoth extinction at the Pleistocene/Holocene boundary on the Channel Islands. Pre-MIS 2 mammoth populations would have experienced similar or even more dramatic changes at the MIS 6/5.5 transition.

Results of a detailed topographic survey of Ghiacciaio del Calderone, Italy, the southernmost in Europe, are described and compared with those of surveys made in earlier years. Recession and thinning, much affected by micro-climate, have been the predominant state of health during the 20th century. Between 1916 and 1990, volume is estimated to have been reduced by about 90% and area by about 68%.

Few studies have investigated nitrogen (N) fertilizer management in no-tillage (NT) tobacco (Nicotiana tobacum L.) production systems, even though N fertilization is known to influence tobacco cured leaf yield and quality. The present study evaluated how tillage practice and N fertilizer rate affected burley tobacco agronomic performance, plant available nitrogen (PAN) supply, and leaf chemical constituents. In 2012 and 2013, three N fertilizer rates (0, 140 and 280 kg N/ha) were introduced as split-plots within a long-term NT and conventional tillage (CT) (mouldboard plough) comparison study. Results (2007–2013) showed that the effect of tillage on tobacco yield depended on seasonal weather; NT tobacco appeared to have lower yield than CT tobacco in seasons with <450 mm growing season rainfall, but similar yields when rainfall was >500 mm. In 2012 (432 mm rainfall; 84% of the long-term seasonal mean), leaf SPAD reading, leaf nitrate concentration, total nitrogen concentration at the topping day (i.e. removal of flowers/buds at the tops of the plants) and cured leaf nicotine and alkaloid content suggested that N deficiency was more pronounced in NT than CT at the lowest N fertilizer rate. The PAN supply, as measured by a modified in situ resin core method, was similar in 2012 between NT and CT, suggesting that plant factors may have had a role in N uptake efficiency. This scenario did not repeat in 2013 (706 mm rainfall; 137% of the long-term seasonal mean). Even though N fertilization rates were identical for both tillage practices in 2012 and 2013, PAN was lower, on average, in 2012. Because N uptake is largely the result of mass flow, the impact of reduced root density in NT tobacco would be expected to be more pronounced in a season such as 2012, when water was limited. Banding N close to the tobacco root system and/or side-dressing some portion of N may be recommended strategies to improve N use efficiency in NT burley tobacco production.

The stratotype for the Bashkirian Stage of the Soviet Middle Carboniferous is located on the Askyn River in Gornaya Bashkiria (western slope of south Urals). Twenty-four rock samples, mostly from the lower part of the section, yielded abundant and diverse assemblages of calcareous foraminifers which are systematically described and illustrated here for the first time.

The foraminiferal assemblage from the Siuransky Horizon at the base of the Bashkirian is essentially identical to that from the top of the underlying Lower Carboniferous Serpukhovian Stage. Thus, foraminifers do not provide a basis for identifying the Soviet Lower–Middle Carboniferous boundary. This notwithstanding, the presence of the foraminifer Globivalvulina bulloides (Brady) (=G. moderata Reitlinger) and the conodont Idiognathodus parvus (Dunn) in both the upper Serpukhovian and Bashkirian indicates that the base of the Bashkirian can be no older than medial to late Morrowan of the North American succession. The primitive fusulinid Pseudostaffella (Pseudostaffella) appears at the bases of the lower Bashkirian Akavassky Horizon and the North American Atokan Series. The base of the Akavassky is interpreted to be somewhat older than early Atokan, however, because Ps. (Pseudostaffella) appeared in the Urals in phylogenetic continuity with its immediate ancestor, whereas in most of North America it was an immigrant.

The type Bashkirian succession contains a seemingly complete phylogeny from advanced eostaffellids to primitive fusulinids. Plectostaffella jakhensis, immediate ancestor to the fusulinids, arose from a member of the Eostaffella postmosquensis plexus in the late Serpukhovian. Plectostaffella jakhensis, in turn, gave rise to Ps. (Semistaffella) variabilis in the early Bashkirian (late Siuransky), from which evolved Ps. (Ps.) antiqua shortly thereafter (earliest Akavassky). An as yet unidentified but advanced species of Ps. (Pseudostaffella) is the most likely ancestor to late Bashkirian Neostaffella ivanovi. The evolutionary series leading from the E. postmosquensis plexus to primitive Neostaffella apparently developed exclusively in the Eurasian–Arctic faunal realm, as Pl. jakhensis, Ps. (Semistaffella) variabilis, and Ps. (Ps.) antiqua are unknown in the Midcontinent–Andean region. Diverse Ps. (Pseudostaffella) spp. appeared in the latter area pursuant to an adaptive radiation aided by periodic interchange between faunal realms.

The Order Lagenida is a monophyletic group of calcareous foraminifers that originated in Middle Pennsylvanian time via acquisition of hyaline-radial wall structure and loss of microgranular wall structure, the latter being characteristic of the close sister group and likely ancestor, the Fusulinida. Early lagenides are delineated into subgroups on the basis of presence or absence of partitioning within their tests, and among partitioned forms, on continuous versus discontinuous growth styles. Partitioned, discontinuously growing forms may be further delineated on the basis of test symmetry and on modifications to chamber shape and apertural complexity. Early lagenides underwent rapid taxonomic differentiation during late Moscovian and early Kasimovian time. Taxonomic differentiation was accompanied by rapid dispersal from the presumed center of origin in the midcontinent-Andean area to tropical and subtropical shelves worldwide. By Early Permian time certain lagenides were adapted to cool water paleoenvironments, as evidenced by their occurrences in high paleolatitudes and even in glaciomarine basins. Early Permian lagenides do not exhibit marked provincialism, but there is evidence for paleolatitudinal control on assemblages. The midcontinent-Andean and present Arctic areas contain similar, diverse faunas from low- to mid paleolatitudes along the western margin of Pangaea. These faunas share many elements in common with faunas from the tropical and subtropical eastern margin of Pangaea (Paleotethys). In contrast, the Europe-Urals, Siberian and Australian areas are characterized by a slightly different faunal association from mid- to high paleolatitudes in both hemispheres. Panthalssan faunas are less well known, but seemingly contain only cosmopolitan taxa.

The Visean–Serpukhovian boundary is not yet defined by a Global Stratotype Section and Point (GSSP) but it is recognizable operationally by the appearance of the conodont Lochriea ziegleri in the L. nodosa–L. ziegleri chronocline. Foraminiferal successions across this boundary in the type area of the Serpukhovian Stage (Moscow Basin, Russia), elsewhere in Russia and in the central United States suggest that the appearances of Asteroarchaediscus postrugosus, Janischewskina delicata, Eolasiodiscus donbassicus, and specimens controversially referred to “Millerella tortula” are reliable, auxiliary indices to the base of the Serpukhovian. In southern Guizhou Province, China, Visean–Serpukhovian rock sequences from slope and platform settings have yielded rich associations of conodonts and foraminifers, respectively. The Nashui section is a leading candidate for the Serpukhovian GSSP because its slope deposits contain an uninterrupted record of conodont occurrences including the L. nodosa–L. ziegleri transition. Foraminifers recovered from the Nashui section are comparatively rare and include none of the basal Serpukhovian indices. In contrast, the nearby Yashui section represents a platform interior setting in which foraminifers flourished and conodonts were nearly absent. The base of the Serpukhovian at Yashui is marked approximately by the appearance of “tortula-like” specimens. Although it is not possible to correlate biostratigraphically between the Nashui and Yashui sections, the occurrence of “tortula-like” specimens at the Yashui section allows correlation with the mid-Venevian Substage of the Moscow Basin at a level coinciding with the appearance of L. ziegleri. Together, the slope and platform sections comprise an informative biostratigraphic reference area for micropaleontologic characterization of the Visean–Serpukhovian boundary in southern Guizhou.

The graphic correlation technique has been used to directly relate the stratigraphic appearances of key species in the Bashkirian Stage stratotype to those in a North American composite section. The type Bashkirian is separated from the underlying Serpukhovian Stage by an erosional unconformity and associated lacuna of undetermined, but probably minor duration. Accordingly, the base of the type Bashkirian (base of Bogdanovkian Horizon) is only slightly younger than the international mid-Carboniferous boundary. A level within the upper part of the Tashastian Horizon (Upper Bashkirian Substage) most likely correlates with the Morrowan-Atokan boundary. This level roughly coincides with a sequence boundary at the Bashkirian stratotype and with a regional unconformity in the North American midcontinent. The top of the Bashkirian Stage (top of Asatauian Horizon) is lower Atokan in North American terms. On the basis of recent 40Ar/39Ar and SHRIMP zircon geochronology studies, the age of the mid-Carboniferous boundary is estimated at 314 Ma and a horizon of early Atokan age is dated at 310.8 Ma. Accepting the present biostratigraphic correlations, these values suggest a duration for the Bashkirian Stage of slightly more than 3.2 m.y. and a duration of the Morrowan Series of slightly less than 3.2 m.y.

Nearly continuous cores from a 500-meter interval of upper Moscovian through post-Artinskian carbonate strata on the Finnmark Platform have yielded rich assemblages of fusulinaceans and smaller foraminifers. The fusulinaceans provide an independent time framework for evaluating stratigraphic occurrences of associated smaller foraminifers. Information derived from this study has been integrated with that from previous investigations to produce a smaller foraminiferal biostratigraphic model for the High Arctic. Kasimovian strata are characterized by occurrences of Nodosinelloides spp., Protonodosaria spp. and Hemigordius schlumbergeri. Overlying lower Gzhelian beds are identified by the appearances of Raphconilia modificata and Amphoratheca iniqua. Tezaquina clivuli and Cribrogenerina gigas first occur in upper Gzhelian strata, and Asselian rocks contain appearances of Geinitzina postcarbonica and Pachyphloia spp. Phylogenetic reconstructions suggest that the Late Carboniferous-Early Permian pseudovidalinids (Archaediscacea) derived from the Pseudoammidiscidae, as did the older group of predominantly Early Carboniferous archaediscaceans. The repeated development of similar morphologies within the two groups of archaediscaceans includes examples of both convergence and iterative evolution. The Protonodosariidae and Syzraniidae most likely evolved from an earlandiid ancestor. The syzraniids gave rise to the Geinitzinidae, which in turn gave rise to the Pachyphloiidae. As in the archaediscaceans, evolution within and among the Earlandiidae, Protonodosariidae, Syzraniidae, Geinitzinidae and Pachyphloiidae includes multiple examples of repeated patterns. Two key phenotypic developments seemingly led to bursts of diversification in different groups throughout late Paleozoic foraminiferal evolution. The acquisition of an outer hyaline or pseudofibrous wall layer was a morphologic breakthrough followed by taxonomic radiation in both groups of archaediscaceans and in the Earlandia-Syzrania lineage. The second major event was the shift from an undivided tubular morphology to uniserial morphology in both the Earlandiidae-Protonodosariidae and Syzraniidae-Geinitzinidae lines. Nodosinelloides pinardae is proposed as a new name for Nodosaria grandis Lipina, 1949 (preoccupied).

A comprehensive, high resolution stratigraphic database of fusulinoidean foraminifers reveals that this group of protists suffered extreme losses during the Guadalupian extinction. Most species (88%) were eliminated gradually over the course of 9 myr during the Wordian and Capitanian ages. A pulse of greatly elevated per capita extinction frequency occurred during the last million years of the Capitanian (260–259 Ma). Contrary to prevailing opinion, the end-Capitanian event did not preferentially eliminate large, morphologically complex species in the families Schwagerinidae and Neoschwagerinidae, because most species in those families were already extinct. Rather, 69 percent of the species eliminated at the end of the Capitanian were small, morphologically conservative representatives of the Ozawainellidae, Schubertellidae and Staffellidae. Survivors from these families comprised the low-diversity association of Wuchiapingian fusulinoideans. Schubertellids, and to a lesser extent ozawainellids, diversified in the late Wuchiapingian and Changhsingian ages before the final demise of fusulinoideans during the end-Permian mass extinction. The Wordian–Capitanian fusulinoidean attrition might have been caused by photosymbiont loss and habitat reduction stemming from an interval of global cooling termed the Kamura event (∼265–259.5 Ma), although the onset of fusulinoidean diversity decline predates geochemical evidence for the beginning of the Kamura event by ∼3 myr. The end-Capitanian extinction pulse might reflect environmental deterioration from the combined effects of global cooling, Emeishan effusive volcanism and sea-level lowstand.

Fusulinacean foraminifera have been described from several localities and horizons within the Upper Pennsylvanian and Lower Permian of the North American midcontinent (Beede, 1916; Dunbar and Condra, 1927; Skinner, 1931; Newell, 1934; Newell and Keroher, 1937; Merchant and Keroher, 1939; Dunbar and Henbest, 1942; Burma, 1942; Thompson, 1954, 1957; Thompson et al., 1956; Douglass, 1962; King, 1988; Sanderson and Verville, 1988), but surprisingly, a comprehensive account of fusulinacean biostratigraphy of the stratotype of the Upper Pennsylvanian Virgilian Stage has never been published. This report summarizes fusulinacean biostratigraphic data from the Virgilian section in the stratotype region of southeastern Kansas. The publication of this dataset is particularly important because of the current efforts to standardize global Pennsylvanian chronostratigraphy (Metcalfe, 1997), and related efforts and debates concerning the definition and correlation of stages in the Upper Pennsylvanian and Lower Permian succession of North America.