174 research outputs found
The Solar Radius in the EUV during the Cycle XXIII
Aims. To determine the solar transition region and coronal radius at EUV
wavelengths and its time evolution during Solar Cycle XXIII.
Methods. We use daily 30.4 and 17.1 nm images obtained by the Extreme
Ultraviolet Imager (EIT) aboard the SoHO satellite and derive the solar radius
by fitting a circle to the limb brightness ring.
Results. The weighted mean of the temporal series gives (967''.56 +/- 0''.04)
and (969''.54 +/- 0''.02) at 30.4 and 17.1 nm respectively. No significant
correlation was found with the solar cycle at any of the two wavelengths.
Conclusions. Since the temperature formation of the 30.4 nm line is between
(60 - 80) 10^3 K (Transition Region), the obtained result is bigger than that
derived from present atmospheric models. On the contrary this height is
compatible with radio models.Comment: accepted for publication in Astronomy & Astrophysics minor changes
introduced during review proces
Comparison of solar radio and EUV synoptic limb charts during the present solar maximum
The present solar cycle is particular in many aspects: it had a delayed
rising phase, it is the weakest of the last 100 years, and it presents two
peaks separated by more than one year. To understand the impact of these
characteristics on the solar chromosphere and coronal dynamics, images from a
wide wavelength range are needed. In this work we use the 17~GHz radio
continuum, formed in the upper chromosphere and the EUV lines 304 and
171~{\AA}, that come from the transition region (He II) and the corona (Fe IX,
X), respectively. We analyze daily images at 304 and 171~{\AA} obtained by the
Atmospheric Imaging Assembly (AIA). The 17~GHz maps were obtained by the
Nobeyama Radioheliograph (NoRH). To construct synoptic limb charts, we
calculated the mean emission of delimited limb areas with 100" wide and angular
separation of . At the equatorial region, the results show an
hemispheric asymmetry of the solar activity. The northern hemisphere dominance
is coincident with the first sunspot number peak, whereas the second peak
occurs concurrently with the increase in the activity at the south. The polar
emission reflects the presence of coronal holes at both EUV wavelengths,
moreover, the 17~GHz polar brightenings can be associated with the coronal
holes. Until 2013, both EUV coronal holes and radio polar brightenings were
more predominant at the south pole. Since then they have not been apparent in
the north, but thus appear in the beginning of 2015 in the south as observed in
the synoptic charts. This work strengthens the association between coronal
holes and the 17~GHz polar brightenings as it is evident in the synoptic limb
charts, in agreement with previous case study papers. The enhancement of the
radio brightness in coronal holes is explained by the presence of bright
patches closely associated with the presence of intense unipolar magnetic
fields.Comment: 6 pages, 5 figures. Acccepted for publication in Astronomy &
Astrophysic
Association of radio polar cap brightening with bright patches and coronal holes
Radio-bright regions near the solar poles are frequently observed in Nobeyama
Radioheliograph (NoRH) maps at 17 GHz, and often in association with coronal
holes. However, the origin of these polar brightening has not been established
yet. We propose that small magnetic loops are the source of these bright
patches, and present modeling results that reproduce the main observational
characteristics of the polar brightening within coronal holes at 17 GHz. The
simulations were carried out by calculating the radio emission of the small
loops, with several temperature and density profiles, within a 2D coronal hole
atmospheric model. If located at high latitudes, the size of the simulated
bright patches are much smaller than the beam size and they present the
instrument beam size when observed. The larger bright patches can be generated
by a great number of small magnetic loops unresolved by the NoRH beam. Loop
models that reproduce bright patches contain denser and hotter plasma near the
upper chromosphere and lower corona. On the other hand, loops with increased
plasma density and temperature only in the corona do not contribute to the
emission at 17 GHz. This could explain the absence of a one-to-one association
between the 17 GHz bright patches and those observed in extreme ultraviolet.
Moreover, the emission arising from small magnetic loops located close to the
limb may merge with the usual limb brightening profile, increasing its
brightness temperature and width.Comment: 8 pages, 6 figures, 1 table. Accepted for publication in The
Astrophysical Journa
Maternal immunity against rabies in raccoon dogs
The objective of the study was to examine possible maternally transferred antibodies (maAb) against rabies in raccoon dogs. Ten cubs born from a rabiesimmune animal were bled on days 31, 36, 43, 50, 57 and 64 post partum. The geometric mean titres of the cubs were 1.19, 1.18, 0.45, 0.25, 0.25 and 0.16 IU/ml, respectively. Up to 36 days post partum maAb were detected in all cubs at levels ≥ 0.5 IU/ml and at day 56 post partum all animals had maAb levels < 0.5 IU/ml. Based on the results of this study, it is suggested that vaccine baits should not be distributed before July if the vaccination campaign is aimed at immunizing young raccoon dogs as well
Investigating strain between phase-segregated domains in Cu-deficient CuInP2S6
CuInP2S6 (CIPS) is an emerging layered ferroelectric material with a TC above
room temperature. When synthesized with Cu deficiencies (i.e.,
Cu1-xIn1+x/3P2S6), the material segregates into CIPS and In4/3P2S6 (IPS)
self-assembled heterostructures within the same single crystal. This
segregation results in significant in-plane and out-of-plane strains between
the CIPS and IPS phases as the volume fraction of CIPS (IPS) domains shrink
(grow) with decreasing Cu fraction. Here, we synthesized CIPS with varying
amounts of Cu (x = 0, 0.2, 0.3, 0.4, 0.5, 0.7, 0.8 and 1) and measured the
strains between the CIPS and IPS phases through the evolution of the respective
Raman, infrared, and optical reflectance spectra. Density functional theory
calculations revealed vibrational modes unique to the CIPS and IPS phases,
which can be used to distinguish between the two phases through two-dimensional
Raman mapping. A comparison of the composition-dependent frequencies and
intensities of the CIPS and IPS Raman peaks showed interesting trends with
decreasing CIPS phase fraction (i.e., Cu/In ratio). Our data reveal red- and
blue-shifted Raman and infrared peak frequencies that we correlate to lattice
strains arising from the segregation of the material into CIPS and IPS chemical
domains. The strain is highest for a Cu/In ratio of 0.33 (Cu0.4In1.2P2S6),
which we attribute to equal and opposite strains exerted by the CIPS and IPS
phases on each other. In addition, bandgaps extracted from the optical
reflectance spectra revealed a decrease in values, with the lowest value (~ 2.3
eV) for Cu0.4In1.2P2S6.Comment: 12 pages, 6 figure
ALMA small-scale features in the quiet Sun and active regions
Aims. The main aim of the present analysis is to decipher (i) the small-scale
bright features in solar images of the quiet Sun and active regions obtained
with the Atacama Large Millimeter/submillimeter Array (ALMA) and (ii) the ALMA
correspondence of various known chromospheric structures visible in the H-alpha
images of the Sun. Methods. Small-scale ALMA bright features in the quiet Sun
region were analyzed using single-dish ALMA observations (1.21 mm, 248 GHz) and
in an active region using interferometric ALMA measurements (3 mm, 100 GHz).
With the single-dish observations, a full-disk solar image is produced, while
interferometric measurements enable the high-resolution reconstruction of part
of the solar disk, including the active region. The selected quiet Sun and
active regions are compared with the H-alpha (core and wing sum), EUV, and soft
X-ray images and with the magnetograms. Results. In the quiet Sun region,
enhanced emission seen in the ALMA is almost always associated with a strong
line-of-sight (LOS) magnetic field. Four coronal bright points were identified,
while other small-scale ALMA bright features are most likely associated with
magnetic network elements and plages. In the active region, in 14 small-scale
ALMA bright features randomly selected and compared with other images, we found
five good candidates for coronal bright points, two for plages, and five for
fibrils. Two unclear cases remain: a fibril or a jet, and a coronal bright
point or a plage. A comparison of the H-alpha core image and the 3 mm ALMA
image of the analyzed active region showed that the sunspot appears dark in
both images (with a local ALMA radiation enhancement in sunspot umbra), the
four plage areas are bright in both images and dark small H-alpha filaments are
clearly recognized as dark structures of the same shape also in ALMA.Comment: 12 pages, 4 figures, to be published in Astronomy and Astrophysic
Comparative immunogenicity and efficacy studies with oral rabies virus vaccine SAD P5/88 in raccoon dogs and red foxes
A comparative study of immunogenicity and efficacy of the oral rabies virus vaccine SAD P5/88 in raccoon dogs and foxes was conducted. The raccoon dogs received 10 (n = 6), 106.3 (n = 6) or 105.7 FFU SAD P5/88 (n = 5) by direct oral application, and subsequently all animals seroconverted. The foxes received 107.2 (n = 4), 106.2 (n = 4), 105.2 (n = 4) and 104.2 FFU SAD P5/88 (n = 5) by the same route. On days 106 and 196 post vaccination 10 raccoon dogs and 16 foxes were challenged with a relevant street virus, respectively. All 10 raccoon dogs vaccinated with 106.3 (n = 5) or 105.7 FFU SAD P5/88 (n = 5) survived the challenge, whereas all control animals (n = 5) died of rabies. Two foxes vaccinated with 104.2 FFU and one fox vaccinated with 105.2 FFU died of rabies on day 7, 17 and 12 post infection, respectively. Also all control foxes succumbed to rabies. Our findings demonstrate that SAD P5/88 is not only an effective vaccine for oral vaccination of foxes but also for that of raccoon dogs
- …