scholarly journals Infrared and Millimeter Views of the Helix: the Nearest, Massive, Neutral Remnant of a Circumstellar Envelope

1999 ◽  
Vol 191 ◽  
pp. 425-430 ◽  
Author(s):  
P.J. Huggins ◽  
P. Cox ◽  
T. Forveille ◽  
R. Bachiller ◽  
K. Young
Keyword(s):  
Large Scale ◽  
Near Infrared ◽  
Critical Role ◽  
Ring Structure ◽  
Circumstellar Envelope ◽  
3 Dimensional ◽  
Optical Images ◽  
Formation And Evolution ◽  
Visualization Techniques

We present new, infrared and millimeter views of the Helix nebula which illustrate the critical role of remnant, neutral AGB envelopes in the formation and evolution of planetary nebulae. Large scale ∼ 1 000″ mapping of the entire nebula in the CO (J = 2 − 1) line with the CSO reveals the global structure of the envelope. The CO emission forms the familiar ring structure seen in optical images of the Helix, and indicates a massive remnant with ≳ 50% the mass of the ionized nebula. High resolution CO mapping with the IRAM 30 m telescope shows that the whole envelope is fragmented into an intricate array of small clumps, closely related to the cometary globules seen in the central, ionized cavity. 5–17 μm spectroscopy of the Helix with ISOCAM reveals a remarkable near infrared spectrum, dominated by the pure (v = 0 − 0) rotational lines of H2. The H2 lines are excited to a temperature of ∼ 900 K, and likely arise in warm, outer layers of the small clumps seen in CO. Imaging of the H2 emission with ISOCAM over the whole nebula provides a striking portrait of the fragmented neutral envelope. 3-dimensional views of the envelope are also presented, based on CO mapping and using 3-dimensional visualization techniques. Point symmetries dominate the toroidal structure, and suggest an origin for the Helix in equatorial mass-loss on the AGB, shaped by the action of bipolar outflows or jets.

scholarly journals Multicellular rosettes organize neuropil formation

2020 ◽  
Author(s):  
Christopher A. Brittin ◽  
Anthony Santella ◽  
Kristopher Barnes ◽  
Mark W. Moyle ◽  
Li Fan ◽  
...  
Keyword(s):  
Functional Organization ◽  
Critical Role ◽  
Ring Structure ◽  
Nerve Ring ◽  
Cell Behaviors ◽  
Dense Networks ◽  
C Elegans ◽  
Single Axon ◽  
Organizational Features

SummaryNeuropils are compartments in the nervous system containing dense networks of neurites and synapses which function as information processing centers. Neuropil formation requires structural and functional organization at and across different scales, achieving single-axon precision for circuits that carry out the core functions while simultaneously accommodating variability among individuals [1; 2; 3; 4]. How these organizational features emerge over development is poorly understood. The nerve ring is the primary neuropil in C. elegans, and its structure is thoroughly mapped [5; 6]. We show that prior to axon outgrowth, nerve ring neurons form a ring of multicellular rosettes with surrounding cells to organize the stratified nerve ring structure [7; 8]. Axon bundles which correspond to future nerve ring strata grow from rosette centers, travel along the ring on “bridge” cells that are simultaneously engaged in adjacent rosettes, and assemble into a topographic scaffold of the nerve ring. SAX-3/Robo is required for proper rosette formation and outgrowth from the center. Furthermore, axon contact sites that form early in development are more conserved than the later ones, indicating a temporal component in neuropil structural variability. Our results reveal an unexpected and critical role of collective cell behaviors prior to innervation to pattern a complex neuropil and orchestrate its formation across scales.

Trust in scientists in times of pandemic: Panel evidence from 12 countries

2021 ◽  
Vol 118 (40) ◽  
pp. e2108576118
Author(s):  
Yann Algan ◽  
Daniel Cohen ◽  
Eva Davoine ◽  
Martial Foucault ◽  
Stefanie Stantcheva
Keyword(s):  
Large Scale ◽  
Social Trust ◽  
Critical Role ◽  
Individual Level ◽  
Individual Support ◽  
Compliant Behavior ◽  
Paradoxical Effects ◽  
The Government ◽  
Nonpharmaceutical Interventions

This article analyzes the specific and critical role of trust in scientists on both the support for and compliance with nonpharmaceutical interventions (NPIs) during the COVID-19 pandemic. We exploit large-scale, longitudinal, and representative surveys for 12 countries over the period from March to December 2020, and we complement the analysis with experimental data. We find that trust in scientists is the key driving force behind individual support for and compliance with NPIs and for favorable attitudes toward vaccination. The effect of trust in government is more ambiguous and tends to diminish support for and compliance with NPIs in countries where the recommendations from scientists and the government were not aligned. Trust in others also has seemingly paradoxical effects: in countries where social trust is high, the support for NPIs is low due to higher expectations that others will voluntary social distance. Our individual-level longitudinal data also allows us to evaluate the effects of within-person changes in trust over the pandemic: we show that trust levels and, in particular, trust in scientists have changed dramatically for individuals and within countries, with important subsequent effects on compliant behavior and support for NPIs. Such findings point out the challenging but critical need to maintain trust in scientists during a lasting pandemic that strains citizens and governments.

scholarly journals The role of haploinsufficiency of RPS14 and p53 activation in the molecular pathogenesis of the 5q- syndrome

2011 ◽  
Vol 3 (2s) ◽  
pp. 10 ◽  
Author(s):  
Jacqueline Boultwood
Keyword(s):  
Mouse Model ◽  
Large Scale ◽  
Critical Role ◽  
Ribosomal Gene ◽  
Molecular Pathogenesis ◽  
Erythroid Progenitor ◽  
Great Insight ◽  
P53 Activation ◽  
Distinct Subtype

In recent years we have gained great insight into the molecular pathogenesis of the 5q- syndrome, a distinct subtype of myelodysplasia. The demonstration of haploinsufficiency of the ribosomal gene RPS14 (mapping to the commonly deleted region) and the finding that this is the cause of the erythroid defect in the 5qsyndrome represent major advances. A mouse model of the human 5q- syndrome generated by large-scale deletion of the Cd74-Nid67 interval (containing RPS14) further supports a critical role for RPS14 haploinsufficiency. It is widely accepted that ribosomal deficiency results in p53 activation and defective erythropoiesis and the crossing of the ‘5q- mice’ with p53 deficient mice ameliorated the erythroid progenitor defect. Emerging data suggests that the p53 activation observed in the mouse model may also apply to the human 5q- syndrome.

The Carnegie Uaxactun Project and the Development of Maya Archaeology

1990 ◽  
Vol 1 (2) ◽  
pp. 257-276 ◽  
Author(s):  
Stephen L. Black
Keyword(s):  
Large Scale ◽  
Critical Role ◽  
Carnegie Institution ◽  
Field Methods ◽  
Maya Archaeology ◽  
History Of ◽  
Maya Area

AbstractThe Carnegie Institution of Washington's 1924–1937. Uaxactun Project, one of the first large-scale excavations in the Maya area, established the role of dirt archaeology in Maya studies. The archaeologists who worked on this pioneering project developed many field methods and approaches that remain in use today. A review of the project and of the careers of its participants shows the critical role the Carnegie Uaxactun Project has played in the history of Maya archaeology.

scholarly journals A Speckle Duplicity Survey of the Hyades Cluster

1992 ◽  
Vol 135 ◽  
pp. 561-563
Author(s):  
B.D. Mason ◽  
H.A. McAlister ◽  
W.I. Hartkopf
Keyword(s):  
Critical Role ◽  
Speckle Interferometry ◽  
The Sun ◽  
Hyades Cluster ◽  
Multiple Stars ◽  
Cluster Distance ◽  
Cluster Environment ◽  
Formation And Evolution ◽  
Binary And Multiple Stars

Due to its proximity to the Sun, the Hyades serves the critical role of luminosity calibration of all cluster main sequences, and hence is one of the lower rungs in the cosmic distance ladder. We attempt here to use the enhanced capabilities of speckle interferometry, in comparison with classical techniques, to add to the list of binary and multiple stars in the Hyades. New systems will not only eventually help to improve our knowledge of the cluster distance, but they will also help further our understanding of the formation and evolution of binary and multiple stars in the cluster environment.

scholarly journals Modeling the Hydroclimatology of Kuwait: The Role of Subcloud Evaporation in Semiarid Climates

2008 ◽  
Vol 21 (12) ◽  
pp. 2976-2989 ◽  
Author(s):  
Marc P. Marcella ◽  
Elfatih A. B. Eltahir
Keyword(s):  
Boundary Conditions ◽  
Interannual Variability ◽  
Large Scale ◽  
Climate Model ◽  
Regional Climate ◽  
Critical Role ◽  
Rain Gauge ◽  
Annual Rainfall ◽  
Semiarid Region

Abstract A new subcloud layer evaporation scheme is incorporated into Regional Climate Model, version 3 (RegCM3), to better simulate the rainfall distribution over a semiarid region around Kuwait. The new scheme represents subcloud layer evaporation of convective as well as large-scale rainfall. Model results are compared to observations from rain gauge data networks and satellites. The simulations show significant response to the incorporation of subcloud layer evaporation as a reduction by as much as 20% in annual rainfall occurs over the region. As a result, the new model simulations of annual rainfall are within 15% of observations. In addition, results indicate that the interannual variability of rainfall simulated by RegCM3 is sensitive to the specification of boundary conditions. For example, forcing RegCM3’s lateral boundary conditions with the 40-yr ECMWF Re-Analysis (ERA-40) data, instead of NCEP–NCAR’s Reanalysis Project 2 (NNRP2), reduces interannual variability by over 25%. Moreover, with subcloud layer evaporation incorporated and ERA-40 boundary conditions implemented, the model’s bias and root-mean-square error are significantly reduced. Therefore, the model’s ability to reproduce observed annual rainfall and the year-to-year variation of rainfall is greatly improved. Thus, these results elucidate the critical role of this natural process in simulating the hydroclimatology of semiarid climates. Last, a large discrepancy between observation datasets over the region is observed. It is believed that the inherent characteristics that are used to construct these datasets explain the differences observed in the annual and interannual variability of Kuwait’s rainfall.

Probabilistic Evaluation of the Dynamics and Predictability of the Mesoscale Convective Vortex of 10–13 June 2003

2007 ◽  
Vol 135 (4) ◽  
pp. 1544-1563 ◽  
Author(s):  
Daniel P. Hawblitzel ◽  
Fuqing Zhang ◽  
Zhiyong Meng ◽  
Christopher A. Davis
Keyword(s):  
Large Scale ◽  
Mesoscale Model ◽  
Critical Role ◽  
Probabilistic Evaluation ◽  
Mesoscale Convective ◽  
Upper Level ◽  
Mesoscale Convective Vortex ◽  
Horizontal Grid ◽  
Development And Evolution

Abstract This study examines the dynamics and predictability of the mesoscale convective vortex (MCV) of 10–13 June 2003 through ensemble forecasting. The MCV of interest developed from a preexisting upper-level disturbance over the southwest United States on 10 June and matured as it traveled northeastward. This event is of particular interest given the anomalously strong and long-lived nature of the circulation. An ensemble of 20 forecasts using a 2-way nested mesoscale model with horizontal grid increments of 30 and 10 km are employed to probabilistically evaluate the dynamics and predictability of the MCV. Ensemble mean and spread as well as correlations between different forecast variables at different forecast times are examined. It is shown that small-amplitude large-scale balanced initial perturbations may result in very large ensemble spread, with individual solutions ranging from a very strong MCV to no MCV at all. Despite similar synoptic-scale conditions, the ensemble MCV forecasts vary greatly depending on intensity and coverage of simulated convection, illustrating the critical role of convection in the development and evolution of this MCV. Correlation analyses reveal the importance of a preexisting disturbance to the eventual development of the MCV. It is also found that convection near the center of the MCV the day after its formation may be an important factor in determining the eventual growth of a surface vortex and that a stronger midlevel vortex is more conducive to convection, especially on the downshear side, consistent with the findings of previous MCV studies.

scholarly journals Geodynamic modeling of the process of formation and evolution of lithospheric structures: experience of Schmidt institute of physics of the earth RAS

2019 ◽  
pp. 122-133
Author(s):  
V. O. Mikhailov ◽  
E. P. Timoshkina
Keyword(s):  
Large Scale ◽  
Sedimentary Basins ◽  
Geophysical Data ◽  
Small Scale ◽  
Tectonic Structures ◽  
The Earth ◽  
Basin Formation ◽  
Formation And Evolution ◽  
Geodynamic Models

Key results of numerical geodynamic modeling of the structures of the lithosphere at the Institute of Physics of the Earth of the Russian Academy of Sciences are presented. Even in the very first models, the aim of these studies was to describe the time evolution of the boundaries of the layers composing the geological structures which is required for correlating the modeling results to the geological and geophysical data. In 1983, the equation of motion for the upper boundary of the model was complemented by the allowance of sedimentation and erosion. This equation provided the basis for building the geodynamic models of the formation of various types of sedimentary basins and made it possible to mathematically analyze the problem of estimating the rates of paleotectonic movements from thickness, age, and facies composition of sedimentary layers. New data on the formation and evolution processes of large-scale tectonic structures are obtained in the model of a rheologically stratified Earth’s boundary layer, asymptotically linked to mantle convection model. In particular, the role of the small-scale convection in the formation of lithospheric structures in the tectonic settings of extension and compression has been explored. The numerical results clearly demonstrate the key role of the small-scale asthenospheric convection in sedimentary basin formation (post-rift, on passive continental margins, in foredeep basins). The constructed models served as the basis for interpretation of heterogeneous geological and geophysical data in the context of geodynamic models. The examples of statement of inverse problems are presented and the relevant bibliography is provided.

Conceptualizing the Challenge and Moving to Solutions

2018 ◽  
pp. 237-266
Author(s):  
Alan E. Kazdin
Keyword(s):  
Public Health ◽  
Mental Illness ◽  
Substance Use ◽  
Mental Disorders ◽  
Physical Health ◽  
Large Scale ◽  
Critical Role ◽  
Grand Challenges ◽  
Substance Use And Abuse

This chapter places the challenge of reducing the burdens of mental illness in broader contexts and progresses from these to concrete recommendations on how to proceed toward next steps. The notions of wicked problems and grand challenges provide two contexts for understanding the challenge. From broad concepts, the chapter moves to means of addressing challenges and making progress in concrete ways to reduce the burdents of mental illness. Illustrations are provided of promising efforts in relation to physical health, mental disorders, and substance use and abuse. The critical role of assessment, especially large-scale surveillance measures from public health, is also discussed.

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