The ice arches that usually develop at the northern and southern ends of Nares Strait play an important role in modulating the export of Arctic Ocean multi-year sea ice. The Arctic Ocean is evolving ...towards an ice pack that is younger, thinner, and more mobile and the fate of its multi-year ice is becoming of increasing interest. Here, we use sea ice motion retrievals from Sentinel-1 imagery to report on the recent behavior of these ice arches and the associated ice fluxes. We show that the duration of arch formation has decreased over the past 20 years, while the ice area and volume fluxes along Nares Strait have both increased. These results suggest that a transition is underway towards a state where the formation of these arches will become atypical with a concomitant increase in the export of multi-year ice accelerating the transition towards a younger and thinner Arctic ice pack.
In this work, we quantify the effect of an unresolved companion star on the derived stellar parameters of the primary star if a blended spectrum is fit assuming the star is single. Fitting tools that ...determine stellar parameters from spectra typically fit for a single star, but we know that up to half of all exoplanet host stars may have one or more companion stars. We use high-resolution spectra of planet host stars in the Kepler field from the California-Kepler Survey to create simulated binaries; we select eight stellar pairs and vary the contribution of the secondary star, then determine stellar parameters with SpecMatch-Emp and compare them to the parameters derived for the primary star alone. We find that, in most cases, the effective temperature, surface gravity, metallicity, and stellar radius derived from the composite spectrum are within 2-3 of the values determined from the unblended spectrum, but the deviations depend on the properties of the two stars. Relatively bright companion stars that are similar to the primary star have the largest effect on the derived parameters; in these cases, the stellar radii can be overestimated by up to 60%. We find that metallicities are generally underestimated, with values up to eight times smaller than the typical uncertainty in Fe/H. Our study shows that follow-up observations are necessary to detect or set limits on stellar companions of planetary host stars so that stellar (and planet) parameters are as accurate as possible.
Climate projections of sea ice retreat under anthropogenic climate change at the regional scale and in summer months other than September have largely not been evaluated. Information at this level of ...detail is vital for future planning of safe Arctic marine activities. Here the timing of when Arctic waters will be reliably ice free across Arctic regions from June to October is presented. It is shown that during this century regions along the Northern Sea Route and Arctic Bridge will be more reliably ice free than regions along the Northwest Passage and the Transpolar Sea Route, which will retain substantial sea ice cover past midcentury. Moreover, ice‐free conditions in the Arctic will likely be confined to September for several decades to come in many regions. Projections using a selection of models that accounts for agreement of models in each region and calendar month with observations yield similar conclusions.
Key Points
Monthly mean ice‐free conditions are limited to September for decades to come in many regions
Northern Sea Route to be more reliably ice free than the Northwest Passage
Model selection marginally affects results and is not recommended
Diagnosis of superficial/cutaneous fungal infections from skin, hair and nail samples is generally achieved using microscopy and culture in a microbiology laboratory, however, any presentation that ...is unusual or subcutaneous is sampled by taking a biopsy. Using histological techniques a tissue biopsy enables a pathologist to perform a full examination of the skin structure, detect any inflammatory processes or the presence of an infectious agent or foreign body. Histopathological examination can give a presumptive diagnosis while a culture result is pending, and may provide valuable diagnostic information if culture fails. This review demonstrates how histopathology contributes to the diagnosis of fungal infections from the superficial to the life threatening.
Nares Strait, the waterway that separates northwest Greenland from Ellesmere Island, is a major pathway along which sea ice leaves the Arctic, including the planet's oldest and thickest sea ice that ...is experiencing an accelerated loss. Ice arches that develop during the winter at the Strait's northern or southern terminus can remain stable for months at a time during which the transport of sea ice ceases. The Arctic's most productive polynya, the North Water (NOW) or Pikialasorsuaq (West Greenlandic for 'great upwelling') forms at the Strait's southern end. There is evidence that a warming climate and the concomitant thinning of Arctic sea ice is weakening the arches and it has been proposed that this may impact the stability of NOW and the complex ecosystem that it sustains. Here we employ a categorization of recent winters with respect to the presence or absence of ice arches to explore their impact on sea ice along the Strait and over the NOW. We find that winters during which a southern ice arch is absent are associated with a reduced and thinner ice cover along the Strait with ice conditions over the NOW similar to that during winters with a southern arch. In winters, without a southern arch, there is also an acceleration of the winds along the Strait that contributes to the presence of reduced ice cover. Ocean color remote sensing data suggests that current levels of primary productivity over the NOW are independent of the presence or absence of an ice arch. The results suggest more research is needed to assess the stability of the NOW, with respect to reduced ice cover and primary productivity, in a future where ice arches cease to form along Nares Strait.
Robust dendrite morphogenesis is a critical step in the development of reproducible neural circuits. However, little is known about the extracellular cues that pattern complex dendrite morphologies. ...In the model nematode Caenorhabditis elegans, the sensory neuron PVD establishes stereotypical, highly branched dendrite morphology. Here, we report the identification of a tripartite ligand-receptor complex of membrane adhesion molecules that is both necessary and sufficient to instruct spatially restricted growth and branching of PVD dendrites. The ligand complex SAX-7/L1CAM and MNR-1 function at defined locations in the surrounding hypodermal tissue, whereas DMA-1 acts as the cognate receptor on PVD. Mutations in this complex lead to dramatic defects in the formation, stabilization, and organization of the dendritic arbor. Ectopic expression of SAX-7 and MNR-1 generates a predictable, unnaturally patterned dendritic tree in a DMA-1-dependent manner. Both in vivo and in vitro experiments indicate that all three molecules are needed for interaction.
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•SAX-7/L1CAM acts as a spatially patterned guidance cue in the hypodermis•SAX-7/L1CAM and MNR-1 guide the outgrowth, branching, and stability of dendrites•DMA-1 acts as the neuronal receptor for SAX-7 and MNR-1
A receptor-ligand complex located at the membrane instructs the spatial morphogenesis of dendrites.
Many cells undergo symmetry-breaking polarization toward a randomly oriented “front” in the absence of spatial cues. In budding yeast, such polarization involves a positive feedback loop that enables ...amplification of stochastically arising clusters of polarity factors. Previous mathematical modeling suggested that, if more than one cluster were amplified, the clusters would compete for limiting resources and the largest would “win,” explaining why yeast cells always make one and only one bud. Here, using imaging with improved spatiotemporal resolution, we show the transient coexistence of multiple clusters during polarity establishment, as predicted by the model. Unexpectedly, we also find that initial polarity factor clustering is oscillatory, revealing the presence of a negative feedback loop that disperses the factors. Mathematical modeling predicts that negative feedback would confer robustness to the polarity circuit and make the kinetics of competition between polarity factor clusters relatively insensitive to polarity factor concentration. These predictions are confirmed experimentally.
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► Imaging at high spatiotemporal resolution shows symmetry breaking process in yeast ► Polarity factors polarize in an oscillatory manner indicative of negative feedback ► Modeling shows that negative feedback increases robustness of polarization ► Negative feedback promotes rapid competition between clusters of polarity factors
High-resolution filming of yeast polarization during bud formation, combined with modeling, shows that both positive and negative feedback loops make the polarization process robust and rapid, ensuring the selection of a single bud site.
In the first book to present the history of Baltimore school desegregation, Howell S. Baum shows how good intentions got stuck on what Gunnar Myrdal called the "American Dilemma." Immediately after ...the 1954 Brown v. Board of Education decision, the city's liberal school board voted to desegregate and adopted a free choice policy that made integration voluntary.
Baltimore's school desegregation proceeded peacefully, without the resistance or violence that occurred elsewhere. However, few whites chose to attend school with blacks, and after a few years of modest desegregation, schools resegregated and became increasingly segregated. The school board never changed its policy. Black leaders had urged the board to adopt free choice and, despite the limited desegregation, continued to support the policy and never sued the board to do anything else.
Baum finds that American liberalism is the key to explaining how this happened. Myrdal observed that many whites believed in equality in the abstract but considered blacks inferior and treated them unequally. School officials were classical liberals who saw the world in terms of individuals, not races. They adopted a desegregation policy that explicitly ignored students' race and asserted that all students were equal in freedom to choose schools, while their policy let whites who disliked blacks avoid integration. School officials' liberal thinking hindered them from understanding or talking about the city's history of racial segregation, continuing barriers to desegregation, and realistic change strategies.
From the classroom to city hall, Baum examines how Baltimore's distinct identity as a border city between North and South shaped local conversations about the national conflict over race and equality. The city's history of wrestling with the legacy of Brown reveals Americans' preferred way of dealing with racial issues: not talking about race. This avoidance, Baum concludes, allows segregation to continue.
ABSTRACT As the closest open cluster to the Sun, the Hyades is an important benchmark for many stellar properties, but its members are also scattered widely over the sky. Previous studies of stellar ...rotation in the Hyades relied on targeted observations of single stars or data from shallower all-sky variability surveys. The re-purposed Kepler mission, K2, is the first opportunity to measure rotation periods (Prot) for many Hyads simultaneously while also being sensitive to fully convective M dwarf members. We analyze K2 data for 65 Hyads and present Prot values for 48. Thirty-seven of these are new measurements, including the first Prot measurements for fully convective Hyads. For 9 of the 11 stars with Prot in the literature and this work, the measurements are consistent; we attribute the two discrepant cases to spot evolution. Nearly all stars with masses 0.3 M are rapidly rotating, indicating a change in rotation properties at the boundary to full convection. When confirmed and candidate binaries are removed from the mass-period plane, only three rapid rotators with masses 0.3 M remain. This is in contrast to previous results showing that the single-valued mass-period sequence for 600 Myr old stars ends at 0.65 M when binaries are included. We also find that models of rotational evolution predict faster rotation than is actually observed at 600 Myr for stars 0.9 M . The dearth of single rapid rotators more massive than 0.3 M indicates that magnetic braking is more efficient than previously thought, and that age-rotation studies must account for multiplicity.
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