Properties of the emission region in pulsars with opposite subpulse drift directions in different profile components

The first Field Emission Guns (FEG) on TEM/STEM instruments were introduced by Philips in 1977. In the past decade these EM400-series microscopes have been very successful, especially in analytical electron microscopy, where the high currents in small probes are particularly suitable. In High Resolution Electron Holography, the high coherence of the FEG has made it possible to approach atomic resolution.Most of these TEM/STEM systems are based on a cold field emitter (CFE). There are, however, a number of disadvantages to CFE’s, because of their very small emission region: the maximum current is limited (a strong disadvantage for high-resolution TEM imaging) and the emission is unstable, requiring special measures to reduce the strong FEG-induced noise. Thermal field emitters (TFE), i.e. a zirconiated field emitter source operating in the thermal or Schottky mode, have been shown to be a viable and attractive alternative to CFE’s. TFE’s have larger emission regions, providing much higher maximum currents, better stability, and reduced sensitivity to vacuum conditions as well as mechanical and electrical interferences.

Download Full-text

Imaging and SERS Study of the Au Nanoparticles Interaction with HPV and Carcinogenic Cervical Tissues

Molecules ◽

10.3390/molecules26123758 ◽

2021 ◽

Vol 26 (12) ◽

pp. 3758

Author(s):

Andrea Ceja-Fdez ◽

Ramon Carriles ◽

Ana Lilia González-Yebra ◽

Juan Vivero-Escoto ◽

Elder de la Rosa ◽

...

Keyword(s):

Multiphoton Microscopy ◽

Surface Enhanced Raman Spectroscopy ◽

Rapid Screening ◽

Emission Region ◽

Sem Images ◽

Spectral Signatures ◽

Two Photon ◽

Surface Enhanced ◽

Surface Enhanced Raman ◽

Gold Nps

In this work, gold NPs were prepared by the Turkevich method, and their interaction with HPV and cancerous cervical tissues were studied by scanning electron microscopy, energy-dispersive x-ray spectroscopy, confocal and multiphoton microscopy and SERS. The SEM images confirmed the presence and localization of the gold NPs inside of the two kinds of tissues. The light absorption of the gold NPs was at 520 nm. However, it was possible to obtain two-photon imaging (red emission region) of the gold NPs inside of the tissue, exciting the samples at 900 nm, observing the morphology of the tissues. The infrared absorption was probably due to the aggregation of gold NPs inside the tissues. Therefore, through the interaction of gold nanoparticles with the HPV and cancerous cervical tissues, a surface enhanced Raman spectroscopy (SERS) was obtained. As preliminary studies, having an average of 1000 Raman spectra per tissue, SERS signals showed changes between the HPV-infected and the carcinogenic tissues; these spectral signatures occurred mainly in the DNA bands, potentially offering a tool for the rapid screening of cancer.

Download Full-text

Bacteria in the global atmosphere – Part 2: Modeling of emissions and transport between different ecosystems

Atmospheric Chemistry and Physics ◽

10.5194/acp-9-9281-2009 ◽

2009 ◽

Vol 9 (23) ◽

pp. 9281-9297 ◽

Cited By ~ 190

Author(s):

S. M. Burrows ◽

T. Butler ◽

P. Jöckel ◽

H. Tost ◽

A. Kerkweg ◽

...

Keyword(s):

Seasonal Variation ◽

Residence Time ◽

General Circulation ◽

Bacterial Species ◽

Circulation Model ◽

Cloud Condensation Nucleus ◽

Cloud Formation ◽

Emission Region ◽

Culturable Bacteria ◽

Bacterial Cells

Abstract. Bacteria are constantly being transported through the atmosphere, which may have implications for human health, agriculture, cloud formation, and the dispersal of bacterial species. We simulate the global transport of bacteria, represented as 1 μm and 3 μm diameter spherical solid particle tracers in a general circulation model. We investigate factors influencing residence time and distribution of the particles, including emission region, cloud condensation nucleus activity and removal by ice-phase precipitation. The global distribution depends strongly on the assumptions made about uptake into cloud droplets and ice. The transport is also affected, to a lesser extent, by the emission region, particulate diameter, and season. We find that the seasonal variation in atmospheric residence time is insufficient to explain by itself the observed seasonal variation in concentrations of particulate airborne culturable bacteria, indicating that this variability is mainly driven by seasonal variations in culturability and/or emission strength. We examine the potential for exchange of bacteria between ecosystems and obtain rough estimates of the flux from each ecosystem by using a maximum likelihood estimation technique, together with a new compilation of available observations described in a companion paper. Globally, we estimate the total emissions of bacteria-containing particles to the atmosphere to be 7.6×1023–3.5×1024 a−1, originating mainly from grasslands, shrubs and crops. We estimate the mass of emitted bacteria- to be 40–1800 Gg a−1, depending on the mass fraction of bacterial cells in the particles. In order to improve understanding of this topic, more measurements of the bacterial content of the air and of the rate of surface-atmosphere exchange of bacteria will be necessary. Future observations in wetlands, hot deserts, tundra, remote glacial and coastal regions and over oceans will be of particular interest.

Download Full-text

The local and remote atmospheric impacts of Africa’s 21st century aerosol emission trajectory

10.5194/egusphere-egu21-14417 ◽

2021 ◽

Author(s):

Chris Wells ◽

Apostolos Voulgarakis

Keyword(s):

Regional Climate ◽

Emission Region ◽

Anthropogenic Aerosol ◽

Remote Locations ◽

Aerosol Emission ◽

Radiation Fluxes ◽

The World ◽

Aerosol Emissions ◽

The Impact ◽

Lower Biomass

Aerosols are a major climate forcer, but their historical effect has the largest uncertainty of any forcing; their mechanisms and impacts are not well understood. Due to their short lifetime, aerosols have large impacts near their emission region, but they also have effects on the climate in remote locations. In recent years, studies have investigated the influences of regional aerosols on global and regional climate, and the mechanisms that lead to remote responses to their inhomogeneous forcing. Using the Shared Socioeconomic Pathway scenarios (SSPs), transient future experiments were performed in UKESM1, testing the effect of African emissions following the SSP3-RCP7.0 scenario as the rest of the world follows SSP1-RCP1.9, relative to a global SSP1-RCP1.9 control. SSP3 sees higher direct anthropogenic aerosol emissions, but lower biomass burning emissions, over Africa. Experiments were performed changing each of these sets of emissions, and both. A further set of experiments additionally accounted for changing future CO2 concentrations, to investigate the impact of CO2 on the responses to aerosol perturbations. Impacts on radiation fluxes, temperature, circulation and precipitation are investigated, both over the emission region (Africa), where microphysical effects dominate, and remotely, where dynamical influences become more relevant.&#160;

Download Full-text

The distance to the heliospheric VLF emission region

Advances in Space Research ◽

10.1016/0273-1177(95)00352-f ◽

1995 ◽

Vol 16 (9) ◽

pp. 303-306 ◽

Cited By ~ 4

Author(s):

R.L. McNutt ◽

A.J. Lazarus ◽

J.W. Belcher ◽

J. Lyon ◽

C.C. Goodrich ◽

...

Keyword(s):

Emission Region

Download Full-text

3.29. Radio recombination lines from starburst galaxies

Symposium - International Astronomical Union ◽

10.1017/s0074180900084424 ◽

1998 ◽

Vol 184 ◽

pp. 147-148

Author(s):

K.R. Anantharamaiah

Keyword(s):

Millimeter Wave ◽

Dynamic Range ◽

Starburst Galaxies ◽

Aperture Synthesis ◽

Emission Region ◽

Full Extent ◽

Radio Recombination Lines

Starburst activity is often heavily obscured by dust. To see through the dust and measure the full extent, power and dynamics of the starburst, we are surveying hydrogen radio recombination lines (RRLs) from famous nearby starburst galaxies. Exploiting the improved sensitivity and dynamic range of aperture synthesis arrays such as the VLA and the AT and millimeter-wave telescopes such as SEST and the IRAM-30m telescope, we have searched for RRLs in about 25 starburst galaxies. RRLs have been detected in 14 galaxies. The observations were made variously at 1.4, 4.9, 8.4, 86, 135 and 232 GHz (Anantharamaiah et al 1993, Zhao et al 1996, 1997, Phookun et al 1997). Table 1 summarizes the observations. In all the cases the detected line originates in the nuclear starburst region and the emission region is resolved with a beam of 1–3″.

Download Full-text

The MURALES survey

Astronomy and Astrophysics ◽

10.1051/0004-6361/202039062 ◽

2020 ◽

Vol 645 ◽

pp. A12

Author(s):

B. Balmaverde ◽

A. Capetti ◽

A. Marconi ◽

G. Venturi ◽

M. Chiaberge ◽

...

Keyword(s):

Emission Line ◽

Large Scale ◽

Line Emission ◽

Emission Region ◽

Gas Velocity ◽

Ionized Gas ◽

Large Scale Structures ◽

Scale Structures ◽

Integral Field Spectrograph ◽

Integral Field

We present the final observations of a complete sample of 37 radio galaxies from the Third Cambridge Catalogue (3C) with redshift < 0.3 and declination < 20° obtained with the VLT/MUSE optical integral field spectrograph. These data were obtained as part of the MUse RAdio Loud Emission line Snapshot (MURALES) survey with the main goal of exploring the AGN feedback process in the most powerful radio sources. We present the data analysis and, for each source, the resulting emission line images and the 2D gas velocity field. Thanks to the unprecedented depth these observations reveal emission line regions (ELRs) extending several tens of kiloparsec in most objects. The gas velocity shows ordered rotation in 25 galaxies, but in several sources it is highly complex. We find that the 3C sources show a connection between radio morphology and emission line properties. In the ten FR I sources the line emission region is generally compact, only a few kpc in size; only in one case does it exceed the size of the host. Conversely, all but two of the FR II galaxies show large-scale structures of ionized gas. The median extent is 16 kpc with the maximum reaching a size of ∼80 kpc. There are no apparent differences in extent or strength between the ELR properties of the FR II sources of high and low gas excitation. We confirm that the previous optical identification of 3C 258 is incorrect: this radio source is likely associated with a quasi-stellar object at z ∼ 1.54.

Download Full-text

The emission properties, structure and stability of ionic liquid menisci undergoing electrically assisted ion evaporation

Journal of Fluid Mechanics ◽

10.1017/jfm.2021.988 ◽

2022 ◽

Vol 933 ◽

Author(s):

Ximo Gallud ◽

Paulo C. Lozano

Keyword(s):

Ionic Liquid ◽

Steady State ◽

Ion Source ◽

Emission Region ◽

Tension Stress ◽

Liquid Temperature ◽

Axially Symmetric ◽

Current Output ◽

Hydraulic Impedance ◽

Ion Evaporation

The properties and structure of electrically stressed ionic liquid menisci experiencing ion evaporation are simulated using an electrohydrodynamic model with field-enhanced thermionic emission in steady state for an axially symmetric geometry. Solutions are explored as a function of the external background field, meniscus dimension, hydraulic impedance and liquid temperature. Statically stable solutions for emitting menisci are found to be constrained to a set of conditions: a minimum hydraulic impedance, a maximum current output and a narrow range of background fields that maximizes at menisci sizes of 0.5–3 ${\rm \mu}{\rm m}$ in radius. Static stability is lost when the electric field adjacent to the electrode that holds the meniscus corresponds to an electric pressure that exceeds twice the surface tension stress of a sphere of the same size as the meniscus. Preliminary investigations suggest this limit to be universal, therefore, independent of most ionic liquid properties, reservoir pressure, hydraulic impedance or temperature and could explain the experimentally observed bifurcation of a steady ion source into two or more emission sites. Ohmic heating near the emission region increases the liquid temperature, which is found to be important to accurately describe stability boundaries. Temperature increase does not affect the current output when the hydraulic impedance is constant. This phenomenon is thought to be due to an improved interface charge relaxation enhanced by the higher electrical conductivity. Dissipated ohmic energy is mostly conducted to the electrode wall. The higher thermal diffusivity of the wall versus the liquid, allows the ion source to run in steady state without heating.

Download Full-text

Pulsating aurora and cosmic noise absorption associated with growth-phase arcs

Annales Geophysicae ◽

10.5194/angeo-36-59-2018 ◽

2018 ◽

Vol 36 (1) ◽

pp. 59-69 ◽

Cited By ~ 7

Author(s):

Derek McKay ◽

Noora Partamies ◽

Juha Vierinen

Keyword(s):

Growth Phase ◽

Optical Emission ◽

Border Region ◽

Emission Region ◽

Expansion Phase ◽

Phase Dynamics ◽

Noise Absorption ◽

Initial Stage ◽

Cosmic Noise

Abstract. The initial stage of a magnetospheric substorm is the growth phase, which typically lasts 1–2 h. During the growth phase, an equatorward moving, east–west extended, optical auroral arc is observed. This is called a growth-phase arc. This work aims to characterize the optical emission and riometer absorption signatures associated with growth-phase arcs of isolated substorms. This is done using simultaneous all-sky camera and imaging riometer observations. The optical and riometric observations allow determination of the location of the precipitation within growth-phase arcs of low- (<10 keV) and high- (> 10 keV) energy electrons, respectively. The observations indicate that growth-phase arcs have the following characteristics: The peak of the cosmic noise absorption (CNA) arc is equatorward of the optical emission arc. This CNA is contained within the region of diffuse aurora on the equatorward side. Optical pulsating aurora are seen in the border region between the diffuse emission region on the equatorward side and the bright growth-phase arc on the poleward side. CNA is detected in the same region. There is no evidence of pulsations in the CNA. Once the equatorward drift starts, it proceeds at constant speed, with uniform separation between the growth-phase arc and CNA of 40±10 km. Optical pulsating aurora are known to be prominent in the post-onset phase of a substorm. The fact that pulsations are also seen in a fairly localized region during the growth phase shows that the substorm expansion-phase dynamics are not required to closely precede the pulsating aurora. Keywords. Ionosphere (auroral ionosphere)

Download Full-text