1,065 research outputs found
Study of Interplanetary Magnetic Field with Ground State Alignment
We demonstrate a new way of studying interplanetary magnetic field -- Ground
State Alignment (GSA). Instead of sending thousands of space probes, GSA allows
magnetic mapping with any ground telescope facilities equipped with
spectropolarimeter. The polarization of spectral lines that are pumped by the
anisotropic radiation from the Sun is influenced by the magnetic realignment,
which happens for magnetic field (<1G). As a result, the linear polarization
becomes an excellent tracer of the embedded magnetic field. The method is
illustrated by our synthetic observations of the Jupiter's Io and comet Halley.
Polarization at each point was constructed according to the local magnetic
field detected by spacecrafts. Both spatial and temporal variations of
turbulent magnetic field can be traced with this technique as well. The
influence of magnetic field on the polarization of scattered light is discussed
in detail. For remote regions like the IBEX ribbons discovered at the boundary
of interstellar medium, GSA provides a unique diagnostics of magnetic field.Comment: 11 pages, 19 figures, published in Astrophysics and Space Scienc
Transport through a quantum wire with a side quantum-dot array
A noninteracting quantum-dot array side-coupled to a quantum wire is studied.
Transport through the quantum wire is investigated by using a noninteracting
Anderson tunneling Hamiltonian. The conductance at zero temperature develops an
oscillating band with resonances and antiresonances due to constructive and
destructive interference in the ballistic channel, respectively. Moreover, we
have found an odd-even parity in the system, whose conductance vanishes for an
odd number of quantum dots while becomes for an even number. We
established an explicit relation between this odd-even parity, and the
positions of the resonances and antiresonances of the conductivity with the
spectrum of the isolated QD arrayComment: 5 pages, 4 figures, submitted to PR
Research on Primary Shielding Calculation Source Generation Codes
Primary Shielding Calculation (PSC) plays an important role in reactor shielding design and analysis. In order to facilitate PSC, a source generation code is developed to generate cumulative distribution functions (CDF) for the source particle sample code of the J Monte Carlo Transport (JMCT) code, and a source particle sample code is deveoped to sample source particle directions, types, coordinates, energy and weights from the CDFs. A source generation code is developed to transform three dimensional (3D) power distributions in xyz geometry to source distributions in r θ z geometry for the J Discrete Ordinate Transport (JSNT) code. Validation on PSC model of Qinshan No.1 nuclear power plant (NPP), CAP1400 and CAP1700 reactors are performed. Numerical results show that the theoretical model and the codes are both correct
Broad-line region geometry from multiple emission lines in a single-epoch spectrum
The broad-line region (BLR) of active galactic nuclei (AGNs) traces gas close
to the central supermassive black hole (BH). Recent reverberation mapping (RM)
and interferometric spectro-astrometry data have enabled detailed
investigations of the BLR structure and dynamics, as well as estimates of the
BH mass. These exciting developments motivate comparative investigations of BLR
structures using different broad emission lines. In this work, we have
developed a method to simultaneously model multiple broad lines of the BLR from
a single-epoch spectrum. We apply this method to the five strongest broad
emission lines (H, H, H, Pa, and He
5876) in the UV-to-NIR spectrum of NGC 3783, a nearby Type I AGN
which has been well studied by RM and interferometric observations. Fixing the
BH mass to the published value, we fit these line profiles simultaneously to
constrain the BLR structure. We find that the differences between line profiles
can be explained almost entirely as being due to different radial distributions
of the line emission. We find that using multiple lines in this way also
enables one to measure some important physical parameters, such as the
inclination angle and virial factor of the BLR. The ratios of the derived BLR
time lags are consistent with the expectation of theoretical model calculations
and RM measurements.Comment: 16 pages, 9 figures, 4 tables, accepted for publication in A&
Аудіовізуальні особливості пейзажистики ранніх балад Т. Шевченка
(uk) У статті осмислюються аудіовізуальні особливості пейзажотворення в ранній творчості Тараса Шевченка. На матеріалі балад «Причинна», «Тополя», «Утоплена» розглядається сугестивна майстерність поета, здатність до живописання словом, створення ілюзії присутності реципієнта в художньому світі твору.(en) Audiovisual features of the landscape descriptionin the early Shevchenko’s ballads. The paper interprets audiovisual features of the landscape description in the early works of Taras Shevchenko. Suggestive poetic skill, capability of word skill, creating the illusion of recipient’s presence in the worldof the art works are considered on the material of the ballads "The Girl under a Spell", "Poplar", "A Drowned Girl"
Silencing of PTK7 in Colon Cancer Cells: Caspase-10-Dependent Apoptosis via Mitochondrial Pathway
Protein tyrosine kinase-7 (PTK7) is a catalytically inactive receptor tyrosine kinase (RTK). PTK7 is upregulated in many common human cancers, including colon cancer, lung cancer, gastric cancer and acute myeloid leukemia. The reason for this up-regulation is not yet known. To explore the functional role of PTK7, the expression of PTK7 in HCT 116 cells was examined using small interference (siRNA)-mediated gene silencing. Following transfection, the siRNA successfully suppressed PTK7 mRNA and protein expression. Knocking down of PTK7 in HCT 116 cells inhibited cell proliferation compared to control groups and induced apoptosis. Furthermore, this apoptosis was characterized by decreased mitochondrial membrane potential and activation of caspase-9 and -10. Addition of a caspase-10 inhibitor totally blocked this apoptosis, suggesting that caspase-10 may play a critical role in PTK7-knockdown-induced apoptosis, downstream of mitochondria. These observations may indicate a role for PTK7 in cell proliferation and cell apoptosis and may provide a potential therapeutic pathway for the treatment of a variety of cancers
The Mass of β Pictoris C from β Pictoris b Orbital Motion
Aims. We aim to demonstrate that the presence and mass of an exoplanet can now be effectively derived from the astrometry of another exoplanet. Methods. We combined previous astrometry of β Pictoris b with a new set of observations from the GRAVITY interferometer. The orbital motion of β Pictoris b is fit using Markov chain Monte Carlo simulations in Jacobi coordinates. The inner planet, β Pictoris c, was also reobserved at a separation of 96 mas, confirming the previous orbital estimations. Results. From the astrometry of planet b only, we can (i) detect the presence of β Pictoris c and (ii) constrain its mass to 10.04-3.10+4.53 MJup. If one adds the astrometry of β Pictoris c, the mass is narrowed down to 9.15-1.06+1.08 MJup. The inclusion of radial velocity measurements does not affect the orbital parameters significantly, but it does slightly decrease the mass estimate to 8.89-0.75+0.75 MJup. With a semimajor axis of 2.68 ± 0.02 au, a period of 1221 ± 15 days, and an eccentricity of 0.32 ± 0.02, the orbital parameters of β Pictoris c are now constrained as precisely as those of β Pictoris b. The orbital configuration is compatible with a high-order mean-motion resonance (7:1). The impact of the resonance on the planets\u27 dynamics would then be negligible with respect to the secular perturbations, which might have played an important role in the eccentricity excitation of the outer planet
Using the motion of S2 to constrain vector clouds around SgrA*
The dark compact object at the centre of the Milky Way is well established to
be a supermassive black hole with mass , but the nature of its environment is still under debate. In this
work, we used astrometric and spectroscopic measurements of the motion of the
star S2, one of the closest stars to the massive black hole, to determine an
upper limit on an extended mass composed of a massive vector field around
Sagittarius A*. For a vector with effective mass , our Markov Chain Monte Carlo analysis shows
no evidence for such a cloud, placing an upper bound at confidence level. We show that dynamical
friction exerted by the medium on S2 motion plays no role in the analysis
performed in this and previous works, and can be neglected thus.Comment: 9 pages, 5 figures, accepted to MNRA
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