High temporal and spatial resolution observations of low energy electrons by a mother-daughter rocket in the vicinity of two quiescent auroral arcs

1973 ◽  
Vol 21 (11) ◽  
pp. 1957-1967 ◽  
Author(s):  
B.N. Mæhlum ◽  
H. Moestue
Keyword(s):  
Spatial Resolution ◽  
Low Energy ◽  
Low Energy Electrons ◽  
Temporal And Spatial ◽  
Auroral Arcs

scholarly journals Luminosity variations in several parallel auroral arcs before auroral breakup

1997 ◽  
Vol 15 (8) ◽  
pp. 959-966 ◽  
Author(s):  
V. Safargaleev ◽  
W. Lyatsky ◽  
V. Tagirov
Keyword(s):  
Spatial Resolution ◽  
Characteristic Time ◽  
Auroral Breakup ◽  
Temporal And Spatial ◽  
Auroral Arcs

Abstract. Variation of the luminosity in two parallel auroral arcs before auroral breakup has been studied by using digitised TV-data with high temporal and spatial resolution. The intervals when a new arc appears near already existing one were chosen for analysis. It is shown, for all cases, that the appearance of a new arc is accompanied by fading or disappearance of another arc. We have named these events out-of-phase events, OP. Another type of luminosity variation is characterised by almost simultaneous enhancement of intensity in the both arcs (in-phase event, IP). The characteristic time of IP events is 10–20 s, whereas OP events last about one minute. Sometimes out-of-phase events begin as IP events. The possible mechanisms for OP and IP events are discussed.

High-spatial-resolution secondary and Auger imaging in a STEM

1989 ◽  
Vol 47 ◽  
pp. 208-209 ◽  
Author(s):  
J.S. Drucker ◽  
M. Krishnamurthy ◽  
G.G. Hembree ◽  
Luo Chuan Hong ◽  
J.A. Venables
Keyword(s):  
Spatial Resolution ◽  
Electron Spectroscopy ◽  
Focal Length ◽  
Surface Preparation ◽  
Low Energy ◽  
Objective Lens ◽  
Thin Sample ◽  
Electron Collection ◽  
Low Energy Electrons ◽  
Analysis System

Secondary electrons form the main signal in a standard SEM, and machines incorporating Auger electron spectroscopy and imaging have become widely commercialized. However, these approaches to low energy (0-2000eV) electron spectroscopy and imaging do not work at the highest spatial resolution, since there are geometrical and electromagnetic conflicts as the focal length of the probe forming lens is reduced. As discussed elsewhere in more detail, the solution is to make the magnetic probe forming lens of the SEM/STEM also function as the first stage of the electron collection and analysis system.A new lOOkV field emission STEM has been constructed for the NSF HREM facility, which incorporates provision for using these low energy electrons from both sides of a thin sample. The outline design has been described previously. The microscope, codenamed MIDAS, is of UHV construction throughout with ∽10−10 mbar at the sample position, and extensive surface preparation facilities. The region of the column concerned with secondary and Auger electrons is shown diagrammatically, but to scale, in fig. 1. This region consists of the objective lens, O, bounded by analyser chambers AC1 and AC2, onto which the electron detectors are mounted.

Daytime aurora observed from Spitsbergen

Polar Record ◽  
1994 ◽  
Vol 30 (173) ◽  
pp. 85-96 ◽  
Author(s):  
D. A. R. Simmons ◽  
K. Henriksen
Keyword(s):  
Interference Filter ◽  
Magnetic Activity ◽  
Low Energy ◽  
Continuous Darkness ◽  
Energy Profiles ◽  
Low Energy Electrons ◽  
The One ◽  
Auroral Arcs ◽  
Hydrogen Lines ◽  
Entry Layer

AbstractDaytime (or dayside cleft) aurora is almost a permanent feature of the midday skies over Spitsbergen during the continuous darkness of the polar night It was observed in one or other of its characteristic forms around geomagnetic noon on 58 of 59 clear day sduring the wintersof 1987/1988, 1990/1991, and 1992/1993. The three types of day time aurora were studied by visual, colour photographic, and interference-filter techniques to confirm the precise nature of the observed emissions. Prenoon aurora, which is characterised by diffuse, patchy, green aurora at 557.7 nm, was observed on 42 occasions. It is generated by low-energy electrons of less than 300 eV coming through the entry layer of the dayside cleft. Noontime aurora, which consists largely of pure red emissions at 630.0/636.4 nm, was observed on 50 occasions. It is generated by high-flux, very low-energy electrons of 10–50 eV flowing directly from the solar wind through the polar cusp. Postnoon aurora, which is characterised by discrete, green auroral arcs at 557.7 nm, was also observed on 42 occasions. Like prenoon aurora, it is generated by low-energy electrons of less than 300 eV derived from the entry layer of the cleft Occasionally, some background or diffuse aurora is also observed, generated by high fluxes of low-energy proton precipitation and characterised by the hydrogen lines Hα and Hβ. On the one exceptional day on which daytime aurora was not observed, magnetic activity was exceptionally low.These ground-based observations complement satellite studies of analogous auroral events. In particular, the visual characteristics of the different types of daytime aurora may be explained in terms of the flux rates and energy profiles of the electrons that have been mapped in the different regions of the dayside cleft by satellite-borne detectors.

scholarly journals MPGD2015: Low-energy electron source to characterize Micromegas/InGrid and study of dE/dx for low energy electrons

2018 ◽  
Vol 174 ◽  
pp. 02011
Author(s):  
David Attie ◽  
Sergey Barsuk ◽  
Oleg Bezshyyko ◽  
Leonid Burmistrov ◽  
Andrii Chaus ◽  
...  
Keyword(s):  
Spatial Resolution ◽  
Particle Tracking ◽  
Low Energy ◽  
Energy Electron ◽  
English Abstract ◽  
Simulation Studies ◽  
Wide Range ◽  
Low Energy Electrons ◽  
Detailed Simulation ◽  
Low Energy Electron

Insert your english abstract here.A new versatile facility LEETECH for detector R&D, tests and calibration is designed and constructed. It uses electrons produced by the photoinjector PHIL at LAL, Orsay and provides a powerful tool for wide range R&D studies of different detector concepts delivering “monochromatic” samples of low energy electrons with adjustable energy and intensity. Among other innovative instrumentation techniques, LEETECH will be used for testing various gaseous tracking detectors and studying new Micromegas/InGrid concept which has very promising characteristics of spatial resolution and can be a good candidate for particle tracking and identification. In this paper the importance and expected characteristics of such facility based on detailed simulation studies are addressed.

Transfer optics for high spatial resolution electron spectroscopy

1988 ◽  
Vol 46 ◽  
pp. 666-667
Author(s):  
G. G. Hembree ◽  
Luo Chuan Hong ◽  
P.A. Bennett ◽  
J.A. Venables
Keyword(s):  
Magnetic Field ◽  
Scanning Transmission Electron Microscope ◽  
Low Energy ◽  
Objective Lens ◽  
State University ◽  
Arizona State University ◽  
Initial Field ◽  
Resolution Electron ◽  
Scanning Transmission ◽  
Low Energy Electrons

A new field emission scanning transmission electron microscope has been constructed for the NSF HREM facility at Arizona State University. The microscope is to be used for studies of surfaces, and incorporates several surface-related features, including provision for analysis of secondary and Auger electrons; these electrons are collected through the objective lens from either side of the sample, using the parallelizing action of the magnetic field. This collimates all the low energy electrons, which spiral in the high magnetic field. Given an initial field Bi∼1T, and a final (parallelizing) field Bf∼0.01T, all electrons emerge into a cone of semi-angle θf≤6°. The main practical problem in the way of using this well collimated beam of low energy (0-2keV) electrons is that it is travelling along the path of the (100keV) probing electron beam. To collect and analyze them, they must be deflected off the beam path with minimal effect on the probe position.

Preincubation with Sn-complexes causes intensive intracellular retention of 99mTc in thyroid cells in vitro

2012 ◽  
Vol 51 (05) ◽  
pp. 179-185 ◽  
Author(s):  
M. Wendisch ◽  
D. Aurich ◽  
R. Runge ◽  
R. Freudenberg ◽  
J. Kotzerke ◽  
...  
Keyword(s):  
Cell Model ◽  
Low Energy ◽  
Thyroid Cells ◽  
Low Energy Electrons ◽  
A Cell ◽  
Vitro Model ◽  
Uptake Studies ◽  
Radiobiological Effects ◽  
Radioactivity Retention

SummaryTechnetium radiopharmaceuticals are well established in nuclear medicine. Besides its well-known gamma radiation, 99mTc emits an average of five Auger and internal conversion electrons per decay. The biological toxicity of these low-energy, high-LET (linear energy transfer) emissions is a controversial subject. One aim of this study was to estimate in a cell model how much 99mTc can be present in exposed cells and which radiobiological effects could be estimated in 99mTc-overloaded cells. Methods: Sodium iodine symporter (NIS)- positive thyroid cells were used. 99mTc-uptake studies were performed after preincubation with a non-radioactive (cold) stannous pyro - phosphate kit solution or as a standard 99mTc pyrophosphate kit preparation or with pure pertechnetate solution. Survival curves were analyzed from colony-forming assays. Results: Preincubation with stannous complexes causes irreversible intracellular radioactivity retention of 99mTc and is followed by further pertechnetate influx to an unexpectedly high 99mTc level. The uptake of 99mTc pertechnetate in NIS-positive cells can be modified using stannous pyrophosphate from 3–5% to >80%. The maximum possible cellular uptake of 99mTc was 90 Bq/cell. Compared with nearly pure extracellular irradiation from routine 99mTc complexes, cell survival was reduced by 3–4 orders of magnitude after preincubation with stannous pyrophosphate. Conclusions: Intra cellular 99mTc retention is related to reduced survival, which is most likely mediated by the emission of low-energy electrons. Our findings show that the described experiments constitute a simple and useful in vitro model for radiobiological investigations in a cell model.

scholarly journals Semi-automated classification of colonial Microcystis by FlowCAM imaging flow cytometry in mesocosm experiment reveals high heterogeneity during seasonal bloom

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Yersultan Mirasbekov ◽  
Adina Zhumakhanova ◽  
Almira Zhantuyakova ◽  
Kuanysh Sarkytbayev ◽  
Dmitry V. Malashenkov ◽  
...  
Keyword(s):  
Machine Learning ◽  
Flow Cytometry ◽  
Spatial Resolution ◽  
Mesocosm Experiment ◽  
Imaging Flow Cytometry ◽  
Leibler Divergence ◽  
Temporal And Spatial ◽  
High Level ◽  
Training Sets

AbstractA machine learning approach was employed to detect and quantify Microcystis colonial morphospecies using FlowCAM-based imaging flow cytometry. The system was trained and tested using samples from a long-term mesocosm experiment (LMWE, Central Jutland, Denmark). The statistical validation of the classification approaches was performed using Hellinger distances, Bray–Curtis dissimilarity, and Kullback–Leibler divergence. The semi-automatic classification based on well-balanced training sets from Microcystis seasonal bloom provided a high level of intergeneric accuracy (96–100%) but relatively low intrageneric accuracy (67–78%). Our results provide a proof-of-concept of how machine learning approaches can be applied to analyze the colonial microalgae. This approach allowed to evaluate Microcystis seasonal bloom in individual mesocosms with high level of temporal and spatial resolution. The observation that some Microcystis morphotypes completely disappeared and re-appeared along the mesocosm experiment timeline supports the hypothesis of the main transition pathways of colonial Microcystis morphoforms. We demonstrated that significant changes in the training sets with colonial images required for accurate classification of Microcystis spp. from time points differed by only two weeks due to Microcystis high phenotypic heterogeneity during the bloom. We conclude that automatic methods not only allow a performance level of human taxonomist, and thus be a valuable time-saving tool in the routine-like identification of colonial phytoplankton taxa, but also can be applied to increase temporal and spatial resolution of the study.

Potential of Arabic documentary sources for reconstructing past climate in the western Mediterranean region from AD 680 to 1815

The Holocene ◽  
2021 ◽  
pp. 095968362110332
Author(s):  
Yassin Meklach ◽  
Chantal Camenisch ◽  
Abderrahmane Merzouki ◽  
Ricardo Garcia Herrera
Keyword(s):  
Spatial Resolution ◽  
Mediterranean Region ◽  
Climate Extremes ◽  
Western Mediterranean ◽  
Historical Documents ◽  
Atmospheric Conditions ◽  
Documentary Sources ◽  
Drought Conditions ◽  
Temporal And Spatial ◽  
Climate Proxies

Archival records and historical documents offer direct observation of weather and atmospheric conditions and have the highest temporal and spatial resolution, and precise dating, of the available climate proxies. They also provide information about variables such as temperature, precipitation and climate extremes, as well as floods, droughts and storms. The present work studied Arab-Islamic documentary sources covering the western Mediterranean region (documents written by Arab-Islamic historians that narrate social, political and religious history) available for the period AD 680–1815. They mostly provide information on hydrometeorological events. In Iberia the most intense droughts were reported during AD 747–753, AD 814–822, AD 846–847, AD 867–874 and AD 914–915 and in the Maghreb AD 867–873, AD 898–915, AD 1104–1147, AD 1280–1340 and AD 1720–1815 had prevalent drought conditions. Intense rain episodes are also reported.

Sign in / Sign up

Export Citation Format

Share Document