750 research outputs found
A new model for the structure of the DACs and SACs regions in the Oe and Be stellar atmospheres
In this paper we present a new mathematical model for the density regions
where a specific spectral line and its SACs/DACs are created in the Oe and Be
stellar atmospheres. In the calculations of final spectral line function we
consider that the main reasons of the line broadening are the rotation of the
density regions creating the spectral line and its DACs/SACs, as well as the
random motions of the ions. This line function is able to reproduce the
spectral feature and it enables us to calculate some important physical
parameters, such as the rotational, the radial and the random velocities, the
Full Width at Half Maximum, the Gaussian deviation, the optical depth, the
column density and the absorbed or emitted energy. Additionally, we can
calculate the percentage of the contribution of the rotational velocity and the
ions' random motions of the DACs/SACs regions to the line broadening. Finally,
we present two tests and three short applications of the proposed model.Comment: 9 pages, 5 figures, accepted for publication in PAS
Embedding low loss polymer optical fibre Bragg gratings:two different approaches
In this paper, we present two different ways to embed polymer fibre Bragg gratings (FBGs) into polymer matrices. In the first experiment, we embedded the FBG into a 3D printed polymer structure, whereas in the second experiment, the coating was polymerized around the fibre. In both cases, the response of the grating was unchanged, without any loss or distortion of the FBG signal compared with the bare fibre response. The design of the polymer coating was optimised for the measurement of a single measurand. We highlighted two possible applications: surface bend deformation monitoring and improved-sensitivity temperature sensing
Cryptic breakpoint identified by whole-genome mate-pair sequencing in a rare paternally inherited complex chromosomal rearrangement
Abstract Background Precise characterization of apparently balanced complex chromosomal rearrangements in non-affected individuals is crucial as they may result in reproductive failure, recurrent miscarriages or affected offspring. Case presentation We present a family, where the non-affected father and daughter were found, using FISH and karyotyping, to be carriers of a three-way complex chromosomal rearrangement [t(6;7;10)(q16.2;q34;q26.1), de novo in the father]. The family suffered from two stillbirths, one miscarriage, and has a son with severe intellectual disability. In the present study, the family was revisited using whole-genome mate-pair sequencing. Interestingly, whole-genome mate-pair sequencing revealed a cryptic breakpoint on derivative (der) chromosome 6 rendering the rearrangement even more complex. FISH using a chromosome (chr) 6 custom-designed probe and a chr10 control probe confirmed that the interstitial chr6 segment, created by the two chr6 breakpoints, was translocated onto der(10). Breakpoints were successfully validated with Sanger sequencing, and small imbalances as well as microhomology were identified. Finally, the complex chromosomal rearrangement breakpoints disrupted the SIM1, GRIK2, CNTNAP2, and PTPRE genes without causing any phenotype development. Conclusions In contrast to the majority of maternally transmitted complex chromosomal rearrangement cases, our study investigated a rare case where a complex chromosomal rearrangement, which most probably resulted from a Type IV hexavalent during the pachytene stage of meiosis I, was stably transmitted from a fertile father to his non-affected daughter. Whole-genome mate-pair sequencing proved highly successful in identifying cryptic complexity, which consequently provided further insight into the meiotic segregation of chromosomes and the increased reproductive risk in individuals carrying the specific complex chromosomal rearrangement. We propose that such complex rearrangements should be characterized in detail using a combination of conventional cytogenetic and NGS-based approaches to aid in better prenatal preimplantation genetic diagnosis and counseling in couples with reproductive problems
Experimental Control and Characterization of Autophagy in Drosophila
Insects such as the fruit fly Drosophila melanogaster, which fundamentally reorganize their body plan during metamorphosis, make extensive use of autophagy for their normal development and physiology. In the fruit fly, the hepatic/adipose organ known as the fat body accumulates nutrient stores during the larval feeding stage. Upon entering metamorphosis, as well as in response to starvation, these nutrients are mobilized through a massive induction of autophagy, providing support to other tissues and organs during periods of nutrient deprivation. High levels of autophagy are also observed in larval tissues destined for elimination, such as the salivary glands and larval gut. Drosophila is emerging as an important system for studying the functions and regulation of autophagy in an in vivo setting. In this chapter we describe reagents and methods for monitoring autophagy in Drosophila, focusing on the larval fat body. We also describe methods for experimentally activating and inhibiting autophagy in this system and discuss the potential for genetic analysis in Drosophila to identify novel genes involved in autophagy
Relativistic many-body calculations of electric-dipole matrix elements, lifetimes and polarizabilities in rubidium
Electric-dipole matrix elements for ns-n'p, nd-n'p, and 6d-4f transitions in
Rb are calculated using a relativistic all-order method. A third-order
calculation is also carried out for these matrix elements to evaluate the
importance of the high-order many-body perturbation theory contributions. The
all-order matrix elements are used to evaluate lifetimes of ns and np levels
with n=6, 7, 8 and nd levels with n=4, 5, 6 for comparison with experiment and
to provide benchmark values for these lifetimes. The dynamic polarizabilities
are calculated for ns states of rubidium. The resulting lifetime and
polarizability values are compared with available theory and experiment.Comment: 8 pages, 2 figure
Optimizing the fast Rydberg quantum gate
The fast phase gate scheme, in which the qubits are atoms confined in sites
of an optical lattice, and gate operations are mediated by excitation of
Rydberg states, was proposed by Jaksch et al. Phys. Rev. Lett. 85, 2208 (2000).
A potential source of decoherence in this system derives from motional heating,
which occurs if the ground and Rydberg states of the atom move in different
optical lattice potentials. We propose to minimize this effect by choosing the
lattice photon frequency \omega so that the ground and Rydberg states have the
same frequency-dependent polarizability \alpha(omega). The results are
presented for the case of Rb.Comment: 5 pages, submitted to PR
Cascade coherence transfer and magneto-optical resonances at 455 nm excitation of Cesium
We present and experimental and theoretical study of nonlinear
magneto-optical resonances observed in the fluorescence to the ground state
from the 7P_{3/2} state of cesium, which was populated directly by laser
radiation at 455 nm, and from the 6P_{1/2} and 6P_{3/2} states, which were
populated via cascade transitions that started from the 7P_{3/2} state and
passed through various intermediate states. The laser-induced fluorescence
(LIF) was observed as the magnetic field was scanned through zero. Signals were
recorded for the two orthogonal, linearly polarized components of the LIF. We
compared the measured signals with the results of calculations from a model
that was based on the optical Bloch equations and averaged over the Doppler
profile. This model was adapted from a model that had been developed for D_1
and D_2 excitation of alkali metal atoms. The calculations agree quite well
with the measurements, especially when taking into account the fact that some
experimental parameters were only estimated in the model.Comment: small changes to text of previous version; 12 pages, 8 figure
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Identifying jumps in financial assets: A comparison between nonparametric jump tests
We perform a comprehensive Monte Carlo comparison between nine alternative procedures available in the literature to detect jumps in financial assets using high-frequency data. We evaluate size and power properties of the procedures under alternative sampling frequencies, persistence in volatility, jump size and intensity, and degree of contamination with microstructure noise. The overall best performance is shown by the Andersen, Bollerslev, and Dobrev (2007) and Lee and Mykland (2008) intraday procedures (ABD-LM), provided the price process is not very volatile. We propose two extensions to the existing battery of tests. The first regards the finite sample improvements based on simulated critical values for the ABD-LM procedure. The second regards a procedure that combines frequencies and tests able to reduce the number of spurious jumps. Finally, we report an empirical analysis using real high frequency data on five stocks listed in the New York Stock Exchange
Approximations for radiative cooling and heating in the solar chromosphere
Context. The radiative energy balance in the solar chromosphere is dominated
by strong spectral lines that are formed out of LTE. It is computationally
prohibitive to solve the full equations of radiative transfer and statistical
equilibrium in 3D time dependent MHD simulations.
Aims. To find simple recipes to compute the radiative energy balance in the
dominant lines under solar chromospheric conditions.
Methods. We use detailed calculations in time-dependent and 2D MHD snapshots
to derive empirical formulae for the radiative cooling and heating.
Results. The radiative cooling in neutral hydrogen lines and the Lyman
continuum, the H and K and intrared triplet lines of singly ionized calcium and
the h and k lines of singly ionized magnesium can be written as a product of an
optically thin emission (dependent on temperature), an escape probability
(dependent on column mass) and an ionization fraction (dependent on
temperature). In the cool pockets of the chromosphere the same transitions
contribute to the heating of the gas and similar formulae can be derived for
these processes. We finally derive a simple recipe for the radiative heating of
the chromosphere from incoming coronal radiation. We compare our recipes with
the detailed results and comment on the accuracy and applicability of the
recipes.Comment: accepted for publication in Astronomy & Astrophysic
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