Observations of Radio Emission of the Moon at 2.3 cm by the Pulkovo Large Radio Telescope

1962 ◽  
Vol 14 ◽  
pp. 527-532
Author(s):  
N. L. Kaydanovsky ◽  
V. N. Ihsanova ◽  
G. P. Apushkinsky ◽  
O. N. Shivris
Keyword(s):  
Brightness Temperature ◽  
Resolving Power ◽  
Variable Component ◽  
Central Meridian ◽  
Lunar Crust ◽  
Maximum Brightness ◽  
Area Efficiency ◽  
Direct Measurements ◽  
Subsolar Point ◽  
And Shifts

The measurement of the amplitude of variation of the brightness temperatureTaat the centre of the lunar disk enables, as is shown in [1], to evaluate the magnitude of the equivalent conductivity σ of the material of the lunar crust. The amplitude of variation of brightness temperatureTacan be determined with the aid of radio telescopes with high resolving power by direct measurements of the brightness temperatureTein the course of a lunation. Such measurements require that the area efficiency σ of the antenna and conditions of calibration of the receiving apparatus over the period of observations to be constant, and this is hard to ensure.Tacan also be determined by measuring the shift of the centre of gravity of radiationxu[2]†, resulting from the fact that the variable component of brightness temperature, in superimposing itself on the constant component, distorts the symmetry of the curves of equal light intensity (isophotes) relative to the central meridian, and shifts the point of maximum brightness away from the centre of the disk in the direction of the subsolar point, asTais a functionxu.

scholarly journals On a possible corrugation of the galactic plane

1970 ◽  
Vol 38 ◽  
pp. 147-150 ◽  
Author(s):  
C. M. Varsavsky ◽  
R. J. Quiroga
Keyword(s):  
Brightness Temperature ◽  
Solid Body ◽  
Rotation Curve ◽  
Galactic Plane ◽  
Maximum Temperature ◽  
Body Rotation ◽  
Maximum Brightness ◽  
Solid Body Rotation ◽  
The Galaxy ◽  
Sinusoidal Pattern

We have studied the rotation curve of the Galaxy at different heights below and above the equator. In the course of this work we noticed that the maximum brightness temperature of hydrogen oscillates around the galactic plane following a fairly sinusoidal pattern. It is further noticed that the maximum temperature of hydrogen occurs right on the plane in the regions where the rotation curve has a form indicating solid body rotation. A rotation curve based on points of maximum hydrogen temperature does not differ appreciably from a rotation curve measured on the galactic plane.

scholarly journals Strong, Variable Circular Polarization in PKS 1519–273

2001 ◽  
Vol 182 ◽  
pp. 135-138
Author(s):  
Jean-Pierre MacQuart ◽  
Lucyna Kedziora-Chudczer ◽  
David Jauncey ◽  
David Rayner
Keyword(s):  
Brightness Temperature ◽  
Frequency Dependence ◽  
Radio Source ◽  
Circular Polarization ◽  
Stokes Parameters ◽  
Variable Component ◽  
Circularly Polarized ◽  
Interstellar Scintillation ◽  
Variable Radio ◽  
Variable Radio Source

AbstractWe find strong (> 1%) circular polarization in the intraday-variable radio source PKS 1519–273. The source exhibits ~ 12 hourly variability in all four Stokes parameters at 4.8 and 8.6 GHz, and longer timescale variability at 2.5 and 1.4 GHz. The characteristics and frequency dependence of the variability suggest that it is due to interstellar scintillation. VSOP limits on the distance to the scattering screen constrain the brightness temperature to TB > 5 × 1013 K. The fluctuations in total intensity are well-correlated with those in circular polarization, implying that the variable component of the source is −3.8 ±0.4% circularly polarized at 4.8 GHz. The origin of the circular polarization is unclear.

scholarly journals A comparison between radioheliograms and optical observations of the solar corona

1959 ◽  
Vol 9 ◽  
pp. 118-122 ◽  
Author(s):  
M. Waldmeier
Keyword(s):  
Solar Activity ◽  
Radio Emission ◽  
Optical Emission ◽  
Solar Limb ◽  
Resolving Power ◽  
Optical Observations ◽  
High Solar Activity ◽  
Central Meridian ◽  
Coronal Line ◽  
The One

Beginning in summer 1957, W. N. Christiansen and D. S. Mathewson [1] have regularly obtained two-dimensional radioheliograms at λ = 21 cm with a resolving power of 3 minutes of arc. The authors have already noticed the close connection between the regions of radio emission on the one side and the fields of spots and faculae on the other side. Considering, however, that the radio emission at the wavelength involved emerges from heights of 20,000 to 50,000, or even up to 100,000 km above the photosphere, i.e. from the inner corona, it seems to be more suitable to compare the radioheliograms with the optical emission of the corona than with the photospheric and chromospheric phenomena. Yet, as the coronal observations can be carried out at the solar limb only, it is difficult to get optical pictures of the corona in front of the sun's disk. Such a picture has to be built up from the daily limb-observations covering the period from 7 days before to 7 days after the date in question; e.g. the coronal intensities shown along the central meridian are measured 7 days before at the E-limb or 7 days later at the W-limb. Since the corona may change greatly within a few days—especially during the present high solar activity—the reliability of an optical corona-picture diminishes from the limb to the central meridian. In addition, a further uncertainty has to be considered in constructing coronal maps, in so far as no station possesses complete coronal observations; therefore, observations of different stations have to be used, which are very difficult to reduce to each other. The main difficulty of such a reduction arises from the fact that the single stations carry out their observations at different distances from the sun's limb ranging from 20,000 to 45,000 km. The coronagrams discussed in the following are based on the intensities of the green coronal line 5303 Å as published in the Quarterly Bulletin on Solar Activity [2].

scholarly journals Limiting Brightness Temperature for Synchrotron Sources

1998 ◽  
Vol 164 ◽  
pp. 135-136
Author(s):  
A. Lähteenmäki ◽  
E. Valtaoja
Keyword(s):  
Brightness Temperature ◽  
Flux Density ◽  
Temperature Limit ◽  
Total Flux ◽  
Reasonable Estimate ◽  
Maximum Brightness ◽  
X Ray ◽  
Brightness Temperatures ◽  
A Value ◽  
Inverse Compton

AbstractThe maximum brightness temperature limit for synchrotron sources derived from inverse Compton catastrophe is usually taken to be 1012 K. Readhead has argued in 1994 that the equipartition brightness temperature may be a better estimate for Tb,lim. It provides a value of 5 × 1010 K. We suggest that a reasonable estimate of the value of Tb,lim can also be achieved by comparing Doppler boosting factors from total flux density variations at 22 and 37 GHz with traditional Doppler factors from the SSC X-ray flux. We also compare our variability brightness temperatures with values calculated for individual sources observed with VLBI, obtaining other independent estimates of Tb,lim.

scholarly journals The Linear Polarization of Radiation from Jupiter at 6 cm Wavelength

1968 ◽  
Vol 21 (3) ◽  
pp. 337 ◽  
Author(s):  
D Morris ◽  
JB Whiteoak ◽  
F Tonking
Keyword(s):  
Synchrotron Radiation ◽  
Brightness Temperature ◽  
Linear Polarization ◽  
High Frequency ◽  
Central Meridian ◽  
Thermal Component ◽  
Nonthermal Radiation ◽  
Polarization Of Radiation ◽  
The Mean ◽  
Direction Of Polarization

At a wavelength of 6 cm the degree of linear polarization of the radiation from Jupiter is 0�076�0�002. The variation of the direction of polarization with longitude of the central meridian is consistent with the increased period of rotation determined by Komesaroff and McCulloch (1967). There is evidence of an asymmetricl beaming of the nonthermal radiation with longitude in addition to the latitude asymmetry that was detected previously by Roberts and Komesaroff (1965). The mean flux density normalized to a distance of 4�04 a.u. is 1O�7�0�2 f.u. The small nonthermal contribution (3'7 f.u.) is further evidence for a high frequency cutoff in the synchrotron radiation; the thermal component corresponds to a brightness temperature of about 250oK.

scholarly journals Inactivation times from 290 to 315 nm UVB in sunlight for SARS coronaviruses CoV and CoV-2 using OMI satellite data for the sunlit Earth

2020 ◽  
Author(s):  
Jay Herman ◽  
Bryan Biegel ◽  
Liang Huang
Keyword(s):  
Solar Zenith Angle ◽  
Action Spectrum ◽  
Geographic Area ◽  
Direct Sunlight ◽  
Clear Sky ◽  
Direct Measurements ◽  
Atmospheric Data ◽  
Subsolar Point ◽  
Ultraviolet Irradiance ◽  
Laboratory Exposure

Abstract UVB in sunlight, 290–315 nm, can inactivate SARS CoV and SARS CoV-2 viruses on surfaces and in the air. Laboratory exposure to ultraviolet irradiance in the UVC range inactivates many viruses and bacteria in times less than 30 min. Estimated UVB inactivation doses from sunlight in J/m2 are obtained from UVC measurements and radiative transfer calculations, weighted by a virus inactivation action spectrum, using OMI satellite atmospheric data for ozone, clouds, and aerosols. For SARS CoV, using an assumed UVC dose near the mid-range of measured values, D90 = 40 J/m2, 90% inactivation times T90 are estimated for exposure to midday 10:00–14:00 direct plus diffuse sunlight and for nearby locations in the shade (diffuse UVB only). For the assumed D90 = 40 J/m2 model applicable to SARS CoV viruses, calculated estimates show that near noon 11:00–13:00 clear-sky direct sunlight gives values of T90 < 90 min for mid-latitude sites between March and September and less than 60 min for many equatorial sites for 12 months of the year. Recent direct measurements of UVB sunlight inactivation of the SARS CoV-2 virus that causes COVID-19 show shorter T90 inactivation times less than 10 min depending on latitude, season, and hour. The equivalent UVC 254 nm D90 dose for SARS CoV-2 is estimated as 3.2 ± 0.7 J/m2 for viruses on a steel mesh surface and 6.5 ± 1.4 J/m2 for viruses in a growth medium. For SARS CoV-2 clear-sky T90 on a surface ranges from 4 min in the equatorial zone to less than 30 min in a geographic area forming a near circle with solar zenith angle < 60O centered on the subsolar point for local solar times from 09:00 to 15:00 h.

scholarly journals Probing primordial 3He from hyperfine line afterglows around supercritical black holes

2019 ◽  
Author(s):  
Evgenii O Vasiliev ◽  
Shiv K Sethi ◽  
Yuri A Shchekinov
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Brightness Temperature ◽  
Angular Size ◽  
Band Width ◽  
Hyperfine Line ◽  
Maximum Brightness ◽  
Peak Value

Abstract We consider the possibility of the detection of 3HeII hyperfine line (rest frequency, $8.67 \, \rm GHz$) emission from ionized zones around accreting black holes (BHs) formed at high redshifts, z = 15–30. We show that the brightness temperature in 8.67GHz line increases and reaches a peak value after the accretion onto the BH exhausts and HeIII recombines into HeII. This period of brightening last up to 40 million years. We find that during this period the maximum brightness temperature reaches ≃ 0.2–0.5μK, depending on the epoch when such a black hole starts growing. The maximum angular size of the region emitting in the hyperfine line is around 0.5′. The flux from such a region ($\simeq 0.3 \, \rm nJy$) is too small to be detected by SKA1-MID. The RMS of the collective flux from many emitting regions from a volume bounded by the synthesized beam and the band-width of SKA1-MID might reach 100 nJy, which is potentially detectable by SKA1-MID.

Preparatory Procedures for Electron Microscopic Analysis at the Molecular Level of Resolution

1978 ◽  
Vol 36 (3) ◽  
pp. 516-520
Author(s):  
F.J. Sjostrand
Keyword(s):  
Electron Microscope ◽  
Molecular Level ◽  
Microscopic Analysis ◽  
Resolving Power ◽  
Cellular Structures ◽  
Electron Microscopic ◽  
Systematic Analysis ◽  
Technical Developments ◽  
Thin Sectioning ◽  
Obvious Reason

In the 1940's and 1950's electron microscopy conferences were attended with everybody interested in learning about the latest technical developments for one very obvious reason. There was the electron microscope with its outstanding performance but nobody could make very much use of it because we were lacking proper techniques to prepare biological specimens. The development of the thin sectioning technique with its perfectioning in 1952 changed the situation and systematic analysis of the structure of cells could now be pursued. Since then electron microscopists have in general become satisfied with the level of resolution at which cellular structures can be analyzed when applying this technique. There has been little interest in trying to push the limit of resolution closer to that determined by the resolving power of the electron microscope.

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