The Experts below are selected from a list of 255 Experts worldwide ranked by ideXlab platform

Pieter C. Dorrestein - One of the best experts on this subject based on the ideXlab platform.

  • Top-Down Atmospheric Ionization Mass Spectrometry Microscopy Combined With Proteogenomics.
    Analytical chemistry, 2017
    Co-Authors: Cheng-chih Hsu, Michael J. Meehan, Michael W. Baker, Terry Gaasterland, Eduardo R. Macagno, Pieter C. Dorrestein
    Abstract:

    Mass spectrometry-based protein analysis has become an important methodology for proteogenomic mapping by providing evidence for the existence of proteins predicted at the genomic level. However, screening and identification of proteins directly on tissue samples, where histological information is preserved, remain challenging. Here we demonstrate that the ambient Ionization source, nanospray desorption electrospray Ionization (nanoDESI), interfaced with light microscopy allows for protein profiling directly on animal tissues at the microscopic scale. Peptide fragments for mass spectrometry analysis were obtained directly on ganglia of the medicinal leech (Hirudo medicinalis) without in-gel digestion. We found that a hypothetical protein, which is predicted by the leech genome, is highly expressed on the specialized neural cells that are uniquely found in adult sex segmental ganglia. Via this top-down analysis, a post-translational modification (PTM) of tyrosine sulfation to this neuropeptide was resolved...

  • Top-Down Atmospheric Ionization Mass Spectrometry Microscopy Combined With Proteogenomics
    2017
    Co-Authors: Cheng-chih Hsu, Michael J. Meehan, Michael W. Baker, Terry Gaasterland, Eduardo R. Macagno, Pieter C. Dorrestein
    Abstract:

    Mass spectrometry-based protein analysis has become an important methodology for proteogenomic mapping by providing evidence for the existence of proteins predicted at the genomic level. However, screening and identification of proteins directly on tissue samples, where histological information is preserved, remain challenging. Here we demonstrate that the ambient Ionization source, nanospray desorption electrospray Ionization (nanoDESI), interfaced with light microscopy allows for protein profiling directly on animal tissues at the microscopic scale. Peptide fragments for mass spectrometry analysis were obtained directly on ganglia of the medicinal leech (Hirudo medicinalis) without in-gel digestion. We found that a hypothetical protein, which is predicted by the leech genome, is highly expressed on the specialized neural cells that are uniquely found in adult sex segmental ganglia. Via this top-down analysis, a post-translational modification (PTM) of tyrosine sulfation to this neuropeptide was resolved. This three-in-one platform, including mass spectrometry, microscopy, and genome mining, provides an effective way for mappings of proteomes under the lens of a light microscope

  • Direct detection of fungal siderophores on bats with white-nose syndrome via fluorescence microscopy-guided ambient Ionization mass spectrometry.
    PloS one, 2015
    Co-Authors: Samantha J. Mascuch, Wilna J. Moree, Cheng-chih Cheng-chih Hsu, Gregory G. Turner, Tina L. Cheng, David S. Blehert, A. Marm Kilpatrick, Winifred F. Frick, Michael J. Meehan, Pieter C. Dorrestein
    Abstract:

    White-nose syndrome (WNS) caused by the pathogenic fungus Pseudogymnoascus destructans is decimating the populations of several hibernating North American bat species. Little is known about the molecular interplay between pathogen and host in this disease. Fluorescence microscopy ambient Ionization mass spectrometry was used to generate metabolic profiles from the wings of both healthy and diseased bats of the genus Myotis. Fungal siderophores, molecules that scavenge iron from the environment, were detected on the wings of bats with WNS, but not on healthy bats. This work is among the first examples in which microbial molecules are directly detected from an infected host and highlights the ability of Atmospheric Ionization methodologies to provide direct molecular insight into infection.

  • Visualizing life with ambient mass spectrometry.
    Current opinion in biotechnology, 2014
    Co-Authors: Cheng-chih Hsu, Pieter C. Dorrestein
    Abstract:

    Since the development of desorption electrospray Ionization (DESI), many other Ionization methods for ambient and Atmospheric pressure mass spectrometry have been developed. Ambient Ionization mass spectrometry has now been used for a wide variety of biological applications, including plant science, microbiology, neuroscience, and cancer pathology. Multimodal integration of Atmospheric Ionization sources with the other biotechnologies, as well as high performance computational methods for mass spectrometry data processing is one of the major emerging area's for ambient mass spectrometry. In this opinion article, we will highlight some of the most influential technological advances of ambient mass spectrometry in recent years and their applications to the life sciences.

  • Data-Independent Microbial Metabolomics with Ambient Ionization Mass Spectrometry
    Journal of The American Society for Mass Spectrometry, 2013
    Co-Authors: Christopher M. Rath, Jane Y. Yang, Theodore Alexandrov, Pieter C. Dorrestein
    Abstract:

    Atmospheric Ionization methods are ideally suited for prolonged MS/MS analysis. Data-independent MS/MS is a complementary technique for analysis of biological samples as compared to data-dependent analysis. Here, we pair data-independent MS/MS with the ambient Ionization method nanospray desorption electrospray Ionization (nanoDESI) for untargeted analysis of bacterial metabolites. Proof-of-principle data and analysis are illustrated by sampling Bacillus subtilis and Pseudomonas aeruginosa directly from Petri dishes. We found that this technique enables facile comparisons between strains via MS and MS/MS plots which can be translated to chemically informative molecular maps through MS/MS networking. The development of novel techniques to characterize microbial metabolites allows rapid and efficient analysis of metabolic exchange factors. This is motivated by our desire to develop novel techniques to explore the role of interspecies interactions in the environment, health, and disease. This is a contribution to honor Professor Catherine C. Fenselau in receiving the prestigious ASMS Award for a Distinguished Contribution in Mass Spectrometry for her pioneering work on microbial mass spectrometry. Figure ᅟ

Ilya Usoskin - One of the best experts on this subject based on the ideXlab platform.

  • Computation of electron precipitation Atmospheric Ionization : updated model CRAC-EPII
    Proceedings of 35th International Cosmic Ray Conference — PoS(ICRC2017), 2017
    Co-Authors: Aleksandar Mishev, Irina Mironova, Anton Artamonov, Genady Kovaltsov, Ilya Usoskin
    Abstract:

    A new model of the CRAC family, CRAC:EPII (Cosmic Ray Atmospheric Cascade: Electron Precipitation Induced Ionization) is presented. The model allows one to calculate Atmospheric Ionization induced by precipitating electrons. The model is based on pre-computed with highprecision Ionization yield functions, which are obtained using full Monte Carlo simulation of electron propagation and interaction in the Earth’s atmosphere, explicitly considering all physical processes involved in ion production. The simulations were performed using GEANT 4 simulation tool PLANETOCOSMICS with NRLMSISE 00 Atmospheric model. A quasi-analytical approach, which allows one to compute the Ionization yields for events with arbitrary incidence is also presented. It is compared with Monte Carlo simulations and good agreement between Monte Carlo simulations and quasi-analytical approach is achieved.

  • Updated model CRAC : HEPII of Atmospheric Ionization due to high energy protons
    Proceedings of 35th International Cosmic Ray Conference — PoS(ICRC2017), 2017
    Co-Authors: Alexander Mishev, Anton Artamonov, Gennady Kovalstov, Ilya Usoskin
    Abstract:

    An extension of the CRAC model - CRAC:HEPII (Cosmic Ray Atmospheric Cascade: High Energy Proton Induced Ionization) is presented. The model allows one to compute the ion production by high energy protons entering the Earth’s atmosphere. The model is an extension of the CRAC:CRII model and it is focused on the upper part of the stratosphere and mesosphere. The model is also applicable in the low termosphere. The model is based on pre-computed with high statistics Ionization yield functions. Therefore, the CRAC:HEPII model is based on a full Monte Carlo simulation of primary proton propagation and interaction with the atmosphere and explicitly considers various physical processes involved in ion production. All simulations were performed using the GEANT 4 simulation tool PLANETOCOSMICS with NRLMSISE 00 Atmospheric model. The Ionization yield function allows one to compute ion production due to various populations of primary protons in a wide energy range 100 keV –- 20 GeV/nucleon for a given altitude, from about 6.5×10$^{−9}$ g/cm$^2$ (about 200 km a.s.l.) to the sea level considering a given primary proton spectrum. The spacial and height resolution of the model is improved compared to CRAC model. An application of the model for computation of ion production during ground level enhancement events is demonstrated. A quasi-analytical approach, which allows one to compute the Ionization yields for events with arbitrary incidence is also presented.

  • Atmospheric Ionization induced by precipitating electrons: Comparison of CRAC:EPII model with a parametrization model
    Journal of Atmospheric and Solar-Terrestrial Physics, 2016
    Co-Authors: Anton Artamonov, Alexander Mishev, Ilya Usoskin
    Abstract:

    Abstract Results of a comparison of a new model CRAC:EPII (Cosmic Ray Atmospheric Cascade: Electron Precipitation Induced Ionization) with a commonly used parametric model of Atmospheric Ionization is presented. The CRAC:EPII is based on a Monte Carlo simulation of precipitating electrons propagation and interaction with matter in the Earth's atmosphere. It explicitly considers energy deposit: Ionization, pair production, Compton scattering, generation of Bremsstrahlung high energy photons, photo-Ionization and annihilation of positrons, multiple scattering as physical processes accordingly. Propagation of precipitating electrons and their interactions with air is simulated with the GEANT4 simulation tool PLANETOCOSMICS code using NRLMSISE-00 Atmospheric model. Ionization yields are computed and compared with a parametrization model for different energies of incident precipitating energetic electrons, using simulated fluxes of mono-energetic particles. A good agreement between the two models is achieved in the mesosphere but the contribution of Bremsstrahlung in the stratosphere, which is not accounted for in the parametric models, is found significant. As an example, we calculated profiles of the ion production rates in the middle and upper atmosphere (below 100 km) on the basis of balloon-born measured spectra of precipitating electrons for 30-October-2002 and 07-January-2004.

  • Ionization of the earth's atmosphere by solar and galactic cosmic rays
    Acta Geophysica, 2008
    Co-Authors: Ilya Usoskin, Peter Velinov, Laurent Desorgher, Marisa Storini, Rolf Bütikofer, Erwin Flückiger, Gennady A. Kovaltsov
    Abstract:

    A brief review of the research of Atmospheric effects of cosmic rays is presented. Numerical models are discussed, that are capable to compute the cosmic ray induced Ionization at a given location and time. Intercomparison of the models, as well as comparison with fragmentary direct measurements of the Atmospheric Ionization, validates their applicability for the entire atmosphere and the whole range of the solar activity level variations. The effect of sporadic solar energetic particle events is shown to be limited on the global scale, even for the most severe event, but can be very strong locally in polar regions, affecting the physical-chemical properties of the upper atmosphere, especially at high altitudes. Thus, a new methodology is presented to study cosmic ray induced Ionization of the atmosphere in full detail using realistic numerical models calibrated to direct observations.

  • Role of centennial geomagnetic changes in local Atmospheric Ionization
    Geophysical Research Letters, 2008
    Co-Authors: Ilya Usoskin, Monika Korte, G. A. Kovaltsov
    Abstract:

    [1] Many studies of solar-terrestrial relation are based on globally (or hemispherically) averaged quantities, including the average cosmic ray flux. However, regional effects of cosmic ray induced Ionization due to geomagnetic changes may be comparable to or even dominate over the solar signal at mid-latitudes on centennial-to-millennial time scales. We show that local changes of the tropospheric Ionization due to fast migration of the geomagnetic axis are crucial on centennial time scale, and the use of global averages may smear an important effect. We conclude that changes of the regional tropospheric Ionization at mid-latitudes are defined by both geomagnetic changes and solar activity, and none of the two processes can be neglected. This substantiates a necessity for a careful analysis of the regional, not global, indices at mid-latitudes and offers a new possibility to disentangle direct (solar radiation) and indirect (via cosmic rays) effects in the solar-terrestrial relations.

William V. Boynton - One of the best experts on this subject based on the ideXlab platform.

  • solar energetic particles in near mars space
    Journal of Geophysical Research, 2007
    Co-Authors: Janet G. Luhmann, Cary Zeitlin, David A. Brain, J G Lyon, Gregory T. Delory, R. Turner, William V. Boynton
    Abstract:

    [1] The space radiation environment near Mars has taken on new interest due to the resurrection of plans to send humans to explore the red planet. In addition, solar energetic particles represent a possibly significant input of energy to the atmosphere of Mars during major events, with consequences for Atmospheric Ionization, chemistry, and possibly escape. Measurements of solar events by the MARIE and GRS experiments on Mars Odyssey illustrate how Mars affects the low-Mars-orbit fluxes of these particles, apparently blocking some particles' access to the spacecraft. The extent to which the presence of Mars reduces the fluxes in Mars orbit from their interplanetary values, and the circumstances and geometry of those reductions, is examined using a simple model and some observationally inspired assumptions about the nature of solar energetic particle events. The results suggest how Mars orbiter SEP results can be interpreted, and also how near-Mars fluxes for a particular interplanetary event can be predicted.

  • Solar energetic particles in near‐Mars space
    Journal of Geophysical Research, 2007
    Co-Authors: Janet G. Luhmann, Cary Zeitlin, David A. Brain, J G Lyon, Gregory T. Delory, R. Turner, William V. Boynton
    Abstract:

    [1] The space radiation environment near Mars has taken on new interest due to the resurrection of plans to send humans to explore the red planet. In addition, solar energetic particles represent a possibly significant input of energy to the atmosphere of Mars during major events, with consequences for Atmospheric Ionization, chemistry, and possibly escape. Measurements of solar events by the MARIE and GRS experiments on Mars Odyssey illustrate how Mars affects the low-Mars-orbit fluxes of these particles, apparently blocking some particles' access to the spacecraft. The extent to which the presence of Mars reduces the fluxes in Mars orbit from their interplanetary values, and the circumstances and geometry of those reductions, is examined using a simple model and some observationally inspired assumptions about the nature of solar energetic particle events. The results suggest how Mars orbiter SEP results can be interpreted, and also how near-Mars fluxes for a particular interplanetary event can be predicted.

Alexander Mishev - One of the best experts on this subject based on the ideXlab platform.

  • Ionization effect in the Earth’s atmosphere during the sequence of October–November 2003 Halloween GLE events
    Journal of Atmospheric and Solar-Terrestrial Physics, 2020
    Co-Authors: Alexander Mishev, Peter Velinov
    Abstract:

    Abstract The effect of precipitating high-energy particles on Atmospheric physics and chemistry is extensively studied over the last decade. In majority of the existing models, the precipitating particles induced Ionization plays an essential role. For such effects, it is necessary to possess enhanced increase in ion production, specifically during the winter period. In this study, we focus on highly penetrating particles — cosmic rays. The galactic cosmic rays are the main source of Ionization in the Earth’s stratosphere and troposphere. On the other hand, the Atmospheric Ionization may be significantly enhanced during strong solar energetic particle events, mainly over the polar caps. A specific interest is paid to the most energetic solar proton events leading to counting rate enhancement of ground-based detectors, namely the so-called ground level enhancements (GLEs). During solar cycle 23, several strong ground level enhancements were observed. A sequence of three GLEs was observed in October–November 2003, the Halloween events. Here, on the basis of 3-D Monte Carlo model, we computed the energetic particles induced Atmospheric Ionization, explicitly considering the contribution of cosmic rays with galactic and solar origin. The ion production rates were computed as a function of the altitude above sea level using reconstructed solar energetic particles spectra. The 24 h and event averaged Ionization effects relative to the average due to galactic cosmic rays were also computed.

  • Spectra of high energy electron precipitation and Atmospheric Ionization rates retrieval from balloon measurements
    The Science of the total environment, 2019
    Co-Authors: Irina Mironova, G. A. Bazilevskaya, Gennady A. Kovaltsov, Anton Artamonov, Eugene Rozanov, Alexander Mishev, Vladimir Makhmutov, Arseniy Karagodin, Ksenia Golubenko
    Abstract:

    Abstract The bremsstrahlung from high and relativistic energy electron precipitation (HEEP) measured with balloon based instruments provides information on energy spectra and fluence of the precipitating energetic electrons allowing calculations of the Atmospheric Ionization. HEEP from the outer radiation belt at the subauroral region causes an increase in the Ionization rates down to about 20 km altitudes. We study the variability in the Ionization rate using the balloon observations of secondary bremsstrahlung initiated by HEEP. For the first time the changes of Atmospheric Ionization rates on an hourly and minute time scale at different altitudes was retrieved from balloon observations. These new highlights are important for Atmospheric electricity that is sensitive to the local condition in the atmosphere including the local Ionization rate.

  • Ion production and Ionization effect in the atmosphere during the Bastille day GLE 59 due to high energy SEPs
    Advances in Space Research, 2018
    Co-Authors: Alexander Mishev, Peter Velinov
    Abstract:

    Abstract The influence of high energy particles, specifically cosmic rays, on Atmospheric physics and chemistry is highly discussed. In most of the proposed models the role of Ionization in the atmosphere due to cosmic rays is not negligible. Moreover, effect(s) on minor constituents and aerosols are recently observed, specifically over the polar regions during strong solar particle events. According to the recent findings for such effects it is necessary an essential increase of ion production, specifically during the winter period. The galactic cosmic rays are the main source of Ionization in the Earth’s stratosphere and troposphere. Occasionally, the Atmospheric Ionization is significantly enhanced during strong solar energetic particles events, specifically over the polar caps. During the solar cycle 23 several strong ground level enhancements were observed. One of the strongest was the Bastille day event occurred on 14 July 2000. Using a full Monte Carlo 3-D model, we compute the Atmospheric Ionization, considering explicitly the contribution of cosmic rays with galactic and solar origin, focusing on high energy particles. The model is based on Atmospheric cascade simulation with the PLANETOCOSMICS code. The ion production rate is computed as a function of the altitude above the sea level. The ion production rate is computed on a step ranging from 10 to 30 min throughout the event, considering explicitly the spectral and angular characteristics of the high energy part of solar protons as well as their time evolution. The corresponding event averaged Ionization effect relative to the average due to galactic cosmic rays is computed in lower stratosphere and upper troposphere at various altitudes, namely 20 km, 15 km, 12 km and 8 km above the sea level in a sub-polar and polar regions. The 24h and the weekly Ionization effects are also computed in the troposphere and low stratosphere. Several applications are discussed.

  • Updated model CRAC : HEPII of Atmospheric Ionization due to high energy protons
    Proceedings of 35th International Cosmic Ray Conference — PoS(ICRC2017), 2017
    Co-Authors: Alexander Mishev, Anton Artamonov, Gennady Kovalstov, Ilya Usoskin
    Abstract:

    An extension of the CRAC model - CRAC:HEPII (Cosmic Ray Atmospheric Cascade: High Energy Proton Induced Ionization) is presented. The model allows one to compute the ion production by high energy protons entering the Earth’s atmosphere. The model is an extension of the CRAC:CRII model and it is focused on the upper part of the stratosphere and mesosphere. The model is also applicable in the low termosphere. The model is based on pre-computed with high statistics Ionization yield functions. Therefore, the CRAC:HEPII model is based on a full Monte Carlo simulation of primary proton propagation and interaction with the atmosphere and explicitly considers various physical processes involved in ion production. All simulations were performed using the GEANT 4 simulation tool PLANETOCOSMICS with NRLMSISE 00 Atmospheric model. The Ionization yield function allows one to compute ion production due to various populations of primary protons in a wide energy range 100 keV –- 20 GeV/nucleon for a given altitude, from about 6.5×10$^{−9}$ g/cm$^2$ (about 200 km a.s.l.) to the sea level considering a given primary proton spectrum. The spacial and height resolution of the model is improved compared to CRAC model. An application of the model for computation of ion production during ground level enhancement events is demonstrated. A quasi-analytical approach, which allows one to compute the Ionization yields for events with arbitrary incidence is also presented.

  • Calculation of Atmospheric Ionization induced by electrons with non-vertical precipitation: Updated model CRAC-EPII
    Advances in Space Research, 2017
    Co-Authors: Anton Artamonov, Irina Mironova, Gennady A. Kovaltsov, Alexander Mishev, Evgenii Plotnikov, Natalia Konstantinova
    Abstract:

    Abstract In this paper we present a method to compute Ionization rates induced by relativistic electron precipitation with arbitrary incidence. Atmospheric Ionization for monoenergetic ( > 100 keV) relativistic electron precipitation including explicitly Ionization by Bremsstrahlung radiation is considered. Two peaks of energy deposition in the atmosphere can be identified. The first Ionization peak is related to direct Ionization of primary relativistic electrons, while the second corresponds to Bremsstrahlung radiation. The Ionization rates are presented us Look-up Tables for vertical, isotropic and angular distributions for 15 ° , 30 ° and 45 ° angles of electron incidence. A computation algorithm is provided to compute Ionization for an arbitrary angular distribution of precipitation electrons.

Jan Kazil - One of the best experts on this subject based on the ideXlab platform.

  • The present-day decadal solar cycle modulation of Earth's radiative forcing via charged H2SO4/H2O aerosol nucleation
    Geophysical Research Letters, 2012
    Co-Authors: Jan Kazil, Kai Zhang, Philip Stier, Johann Feichter, Ulrike Lohmann, K. O'brien
    Abstract:

    [1] The decadal solar cycle modulation of Earth's radiative forcing via Ionization of the atmosphere by galactic cosmic rays, aerosol formation from the gas phase, and the response of clouds to aerosol is quantified for the first time with a climate model that represents and couples the relevant processes. Simulations are conducted for solar maximum and minimum conditions, with present-day anthropogenic aerosol and aerosol precursor gas emissions, and contemporary large-scale meteorology. The solar cycle signal appears in Atmospheric Ionization, aerosol formation from the gas phase, aerosol concentrations, aerosol optical depth, and in cloud properties, and is most pronounced at mid- and high latitudes. The resulting solar cycle modulation of Earth's radiative forcing exhibits a distinct hemispheric asymmetry, with peak values of −0.14 W m−2 in the southern and −0.06 W m−2in the northern mid-latitudes. Globally and annually averaged, the solar cycle modulation of Earth's radiative forcing, arising from the increase in Atmospheric Ionization by galactic cosmic rays from solar maximum to minimum, via charged nucleation of aerosol, the direct aerosol effect, and the cloud albedo effect, amounts to −0.05 W m−2. A limited relevance of this variation for the Earth's atmosphere and climate can be inferred, given that Earth's radiative forcing changes by −0.24 W m−2 from solar maximum to minimum because of a decrease in total solar irradiance.

  • Tropospheric New Particle Formation and the Role of Ions
    Space Science Reviews, 2008
    Co-Authors: Jan Kazil, R. Giles Harrison, Edward R. Lovejoy
    Abstract:

    Aerosol particles play an important role in the Earth’s troposphere and in the climate system: They scatter and absorb solar radiation, facilitate chemical processes, and serve as condensation nuclei for the formation of clouds. Tropospheric aerosol particles are emitted from surface sources or form in situ from the gas phase. Formation from the gas phase requires concentrations of aerosol precursor molecules aggregating to form molecular clusters able to grow faster than they evaporate. This process is called nucleation. Gas phase ions can reduce the concentration of aerosol precursor molecules required for nucleation, as they greatly stabilize molecular clusters with respect to evaporation. Therefore, ions are a potential source of aerosol particles. Since Atmospheric Ionization carries the signal of the decadal solar cycle due to the modulation of the galactic cosmic ray intensity by solar activity, a possible connection between the solar cycle, galactic cosmic rays, aerosols, and clouds has been a long-standing focus of interest. In this paper, we provide an overview of theoretical, modeling, laboratory, and field work on the role and relevance of ions for the formation of tropospheric aerosol particles, and on subsequent effects on clouds, and discuss briefly related research needs.