1,690 research outputs found

    Report on the Second Catalog Interoperability Workshop

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    The events, resolutions, and recommendations of the Second Catalog Interoperability Workshop, held at JPL in January, 1988, are discussed. This workshop dealt with the issues of standardization and communication among directories, catalogs, and inventories in the earth and space science data management environment. The Directory Interchange Format, being constructed as a standard for the exchange of directory information among participating data systems, is discussed. Involvement in the Interoperability effort by NASA, NOAA, ISGS, and NSF is described, and plans for future interoperability considered. The NASA Master Directory prototype is presented and critiqued and options for additional capabilities debated

    The SPASE Data Model for Heliophysics Data: Is it Working?

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    The Space Physics Archive Search and Extract (SPASE) Data Model was developed to provide a metadata standard for describing Heliophysics (Space and Solar Physics) data within that science discipline. The SPASE Data Model has matured over the many years of its creation and is presently represented by Version 2.2.1. Information about SPASE can be obtained from the website group.org. The Data Model defines terms and values as well as the relationships between them in order to describe the data resources in the Heliophysics data environment. This data environment is quite complex, consisting of Virtual Observatories, Resident Archives, Data Providers, Partnering Data Centers, Services, Final Archives, and a Deep Archive. SPASE is the metadata language standard intended to permeate the complexity and provide a common method of obtaining and understanding data. Is it working in this capacity? SPASE has been used to describe a wide range of data. Examples range from ground-based magnetometer data to interplanetary satellite measurements to space weather model results. Has it achieved the goal of making the data easier to find and use? To find data of interest it is necessary that all the data of importance be described using the SPASE Data Model. Within the part of the data community associated with NASA (supported through NASA funding) there are obligations to use SPASE and (0 describe the old and new data using the SPASE XML schema. Although this pan of the community is not near 100% compliance with the mandate, there is good progress being made and the goal should be reachable in the future. Outside of the NASA data community there is still work to be done to convince the international community that SPASE descriptions are w011h the cost of their generation. Some of these groups such as Cluster, HELlO, GAIA, NOAA/NGDe. CSSDP, VSTO, SuperMAG, and IUGONET have agreed to use SPASE. but there are still other groups of importance that need (0 be reached. It is also assumed that the terminology is sufficiently broad and the descriptions are sufficiently complete that researchers needing data of a specific type or from a specific period can find and acquire what they need. A valid SPASE description can be very brief or very thorough depending on the willingness of the author to spend the time necessary to make the description useful. There is evidence that users are finding what they need through the SPASE descriptions, and this standard is a big step forward in Heliophysics data location. Does SPASE make it easier to use the data once they are found,) Thorough descriptions of data using SPASE can describe the data down to the level of individual parameters and exactly how the data are organized and stored. Should the SPASE data descriptions be written in such a way that they can be automatically ingested and understood by software tools'? Heliophysics instruments are becoming morc versatile all the time and the complexity of the data makes it tedious and time consuming to write SPASE descriptions with this level of sophistication even with the improvement of the tools used to generate the descriptions. Is it better to just write human-readable descriptions of the data at the parameter level or to refer to references that provide this information? This is a debate that is presently taking place and software is being developed to test what is possible

    Regulation of clathrin-coated vesicle nucleation

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    Clathrin-mediated endocytosis is a selective pathway for the entry of transmembrane proteins into the cell through the generation of a short-lived vesicular intermediate. Cells and tissues depend on this process for obtaining nutrients, modulation of signaling and cell migration. The clathrin-coated structure intermediate is assembled on the plasma membrane from a cohort of 20-30 distinct proteins that aid in cargo selection, scaffolding, membrane bending and scission of the vesicle. Exactly how these complex assemblies are nucleated at the plasma membrane remains unclear although the lipid phosphatidylinositol-4,5-bisphosphate (PtdIns(4,5)P2) plays an important role by anchoring many of the endocytic components. The work in this thesis helps to clarify the nucleation phase by describing the molecular details of the interaction between a PtdIns(4,5)P2-generating lipid kinase PIPKIgamma and the heterotetrameric clathrin adaptor AP-2. By engaging a subdomain on the AP-2 beta2 subunit appendage, the kinase is strategically positioned at assembly sites to generate PtdIns(4,5)P2 and drive coat assembly forward. Clathrin binds to the same subdomain on the beta2 appendage but with a higher apparent affinity. I therefore invoke a model in which PtdIns(4,5)P2 production for nucleation is negatively regulated by PIPKIgamma displacement from AP-2 by clathrin at later stages of assembly. I also demonstrate that a cargo-sorting alternate adaptor that binds to the other subsite on the AP-2 beta2 appendage is not subject to displacement by clathrin during clathrin-coated vesicle budding, ensuring non-competitive cargo incorporation into the vesicle. Finally, the PtdIns(4,5)P2-binding EFC domain proteins FCHO1 and FCHO2 have been proposed to act as dedicated nucleators of clathrin-coated structures on the plasma membrane. I demonstrate in multiple cell lines that these proteins are not invariantly required for placement of clathrin-coated assemblies on the plasma membrane despite being early arriving components themselves. FCHO1/2 are involved in the regulation of the size and number of these assemblies in some cellular contexts. My data support the model of PtdIns(4,5)P2 regulated, not protein regulated, nucleation of clathrin-coated structures; however multiple parallel pathways may contribute to initiation of endocytic buds

    The Heliophysics Data Environment, Virtual Observatories, NSSDC, and SPASE

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    Heliophysics (the study of the Sun and its effects on the Solar System, especially the Earth) has an interesting data environment in that the data are often to be found in relatively small data sets widely scattered in archives around the world. Within the last decade there have been more concentrated efforts to organize the data access methods and create a Heliophysics Data and Model Consortium (HDMC). To provide data search and access capability a number of Virtual Observatories (VO's) have been established both via funding from the U.S. National Aeronautics and Space Administration (NASA) and through other funding agencies in the U.S. and worldwide. At least 15 systems can be labeled as Heliophysics Virtual Observatories, 9 of them funded by NASA. Other parts of this data environment include Resident Archives, and the final, or "deep" archive at the National Space Science Data Center (NSSDC). The problem is that different data search and access approaches are used by all of these elements of the HDMC and a search for data relevant to a particular research question can involve consulting with multiple VO's - needing to learn a different approach for finding and acquiring data for each. The Space Physics Archive Search and Extract (SPASE) project is intended to provide a common data model for Heliophysics data and therefore a common set of metadata for searches of the VO's and other data environment elements. The SPASE Data Model has been developed through the common efforts of the HDMC representatives over a number of years. We currently have released Version 2.1. of the Data Model. The advantages and disadvantages of the Data Model will be discussed along with the plans for the future. Recent changes requested by new members of the SPASE community indicate some of the directions for further development

    SPASE: The Connection Among Solar and Space Physics Data Centers

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    The Space Physics Archive Search and Extract (SPASE) project is an international collaboration among Heliophysics (solar and space physics) groups concerned with data acquisition and archiving. Within this community there are a variety of old and new data centers, resident archives, "virtual observatories", etc. acquiring, holding, and distributing data. A researcher interested in finding data of value for his or her study faces a complex data environment. The SPASE group has simplified the search for data through the development of the SPASE Data Model as a common method to describe data sets in the various archives. The data model is an XML-based schema and is now in operational use. There are both positives and negatives to this approach. The advantage is the common metadata language enabling wide-ranging searches across the archives, but it is difficult to inspire the data holders to spend the time necessary to describe their data using the Model. Software tools have helped, but the main motivational factor is wide-ranging use of the standard by the community. The use is expanding, but there are still other groups who could benefit from adopting SPASE. The SPASE Data Model is also being expanded in the sense of providing the means for more detailed description of data sets with the aim of enabling more automated ingestion and use of the data through detailed format descriptions. We will discuss the present state of SPASE usage and how we foresee development in the future. The evolution is based on a number of lessons learned - some unique to Heliophysics, but many common to the various data disciplines

    The AP-2 adaptor ÎČ2 appendage scaffolds alternate cargo endocytosis

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    The independently folded appendages of the large α and ÎČ2 subunits of the endocytic adaptor protein (AP)-2 complex coordinate proper assembly and operation of endocytic components during clathrin-mediated endocytosis. The ÎČ2 subunit appendage contains a common binding site for ÎČ-arrestin or the autosomal recessive hypercholesterolemia (ARH) protein. To determine the importance of this interaction surface in living cells, we used small interfering RNA-based gene silencing. The effect of extinguishing ÎČ2 subunit expression on the internalization of transferrin is considerably weaker than an AP-2 α subunit knockdown. We show the mild sorting defect is due to fortuitous substitution of the ÎČ2 chain with the closely related endogenous ÎČ1 subunit of the AP-1 adaptor complex. Simultaneous silencing of both ÎČ1 and ÎČ2 subunit transcripts recapitulates the strong α subunit RNA interference (RNAi) phenotype and results in loss of ARH from endocytic clathrin coats. An RNAi-insensitive ÎČ2-yellow fluorescent protein (YFP) expressed in the ÎČ1 + ÎČ2-silenced background restores cellular AP-2 levels, robust transferrin internalization, and ARH colocalization with cell surface clathrin. The importance of the ÎČ appendage platform subdomain over clathrin for precise deposition of ARH at clathrin assembly zones is revealed by a ÎČ2-YFP with a disrupted ARH binding interface, which does not restore ARH colocalization with clathrin. We also show a ÎČ-arrestin 1 mutant, which engages coated structures in the absence of any G protein-coupled receptor stimulation, colocalizes with ÎČ2-YFP and clathrin even in the absence of an operational clathrin binding sequence. These findings argue against ARH and ÎČ-arrestin binding to a site upon the ÎČ2 appendage platform that is later obstructed by polymerized clathrin. We conclude that ARH and ÎČ-arrestin depend on a privileged ÎČ2 appendage site for proper cargo recruitment to clathrin bud sites

    Combined searches for the production of supersymmetric top quark partners in proton-proton collisions at root s=13 TeV

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    A combination of searches for top squark pair production using proton-proton collision data at a center-of-mass energy of 13 TeV at the CERN LHC, corresponding to an integrated luminosity of 137 fb(-1) collected by the CMS experiment, is presented. Signatures with at least 2 jets and large missing transverse momentum are categorized into events with 0, 1, or 2 leptons. New results for regions of parameter space where the kinematical properties of top squark pair production and top quark pair production are very similar are presented. Depending on themodel, the combined result excludes a top squarkmass up to 1325 GeV for amassless neutralino, and a neutralinomass up to 700 GeV for a top squarkmass of 1150 GeV. Top squarks with masses from 145 to 295 GeV, for neutralino masses from 0 to 100 GeV, with a mass difference between the top squark and the neutralino in a window of 30 GeV around the mass of the top quark, are excluded for the first time with CMS data. The results of theses searches are also interpreted in an alternative signal model of dark matter production via a spin-0 mediator in association with a top quark pair. Upper limits are set on the cross section for mediator particle masses of up to 420 GeV

    Measurement of the W gamma Production Cross Section in Proton-Proton Collisions at root s=13 TeV and Constraints on Effective Field Theory Coefficients

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    A fiducial cross section for W gamma production in proton-proton collisions is measured at a center-of-mass energy of 13 TeV in 137 fb(-1) of data collected using the CMS detector at the LHC. The W -> e nu and mu nu decay modes are used in a maximum-likelihood fit to the lepton-photon invariant mass distribution to extract the combined cross section. The measured cross section is compared with theoretical expectations at next-to-leading order in quantum chromodynamics. In addition, 95% confidence level intervals are reported for anomalous triple-gauge couplings within the framework of effective field theory.Peer reviewe

    Search for new particles in events with energetic jets and large missing transverse momentum in proton-proton collisions at root s=13 TeV

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    A search is presented for new particles produced at the LHC in proton-proton collisions at root s = 13 TeV, using events with energetic jets and large missing transverse momentum. The analysis is based on a data sample corresponding to an integrated luminosity of 101 fb(-1), collected in 2017-2018 with the CMS detector. Machine learning techniques are used to define separate categories for events with narrow jets from initial-state radiation and events with large-radius jets consistent with a hadronic decay of a W or Z boson. A statistical combination is made with an earlier search based on a data sample of 36 fb(-1), collected in 2016. No significant excess of events is observed with respect to the standard model background expectation determined from control samples in data. The results are interpreted in terms of limits on the branching fraction of an invisible decay of the Higgs boson, as well as constraints on simplified models of dark matter, on first-generation scalar leptoquarks decaying to quarks and neutrinos, and on models with large extra dimensions. Several of the new limits, specifically for spin-1 dark matter mediators, pseudoscalar mediators, colored mediators, and leptoquarks, are the most restrictive to date.Peer reviewe
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