33 research outputs found
QED Effects in Heavy Few-Electron Ions
Accurate calculations of the binding energies, the hyperfine splitting, the
bound-electron g-factor, and the parity nonconservation effects in heavy
few-electron ions are considered. The calculations include the relativistic,
quantum electrodynamic (QED), electron-correlation, and nuclear effects. The
theoretical results are compared with available experimental data. A special
attention is focused on tests of QED in a strong Coulomb field.Comment: 28 pages, 6 tables, 5 figure
Hyperfine splitting in heavy ions with the nuclear magnetization distribution determined from experiments on muonic atoms
The hyperfine splitting in hydrogenlike Bi, Tl, and
Tl is calculated with the nuclear magnetization determined from
experimental data on the hyperfine splitting in the corresponding muonic atoms.
The single-particle and configuration-mixing nuclear models are considered. The
QED corrections are taken into account for both electronic and muonic atoms.
The obtained results are compared with other calculations and with experiment.Comment: 8 pages, 5 tables, accepted for publication in Nuclear Instruments
and Methods in Physics Research
State and debris of trees of afforestation belts in arid conditions of the Southern part of Central Siberia
It would be beneficial to consider ways to preserve afforestation belts in arid conditions due to climate change. It was observed that the most favorable conditions for growth were present in the extreme rows (windward and lee) in forest protection belts of Siberian larch, squat elm, and black poplar. This is reflected in the maximum tree size and density. The intensity of thinning along the rows may vary depending on the age of the plantation and the tree species
Electric field effects on optical properties of semiconductor nanorods
We studied electric field effects on optical properties of CdSe/ZnS nanorods integrated in thin films sandwiched between transparent electrodes. It was demonstrated that P-polarized component of the photoluminescence of CdSelZnS nanorods is quenched stronger by external electric field than the S-polarized component. Quantum dots are more sensitive to external electric field than the nanorods. A mechanism of external electric field influence on the luminescence spectrum of semiconductor nanorods is discussed
QED theory of the nuclear recoil effect on the atomic g factor
The quantum electrodynamic theory of the nuclear recoil effect on the atomic
g factor to all orders in \alpha Z and to first order in m/M is formulated. The
complete \alpha Z-dependence formula for the recoil correction to the
bound-electron g factor in a hydrogenlike atom is derived. This formula is used
to calculate the recoil correction to the bound-electron g factor in the order
(\alpha Z)^2 m/M for an arbitrary state of a hydrogenlike atom.Comment: 17 page
Polariton condensation and lasing in optical microcavities - the decoherence driven crossover
We explore the behaviour of a system which consists of a photon mode dipole
coupled to a medium of two-level oscillators in a microcavity in the presence
of decoherence. We consider two types of decoherence processes which are
analogous to magnetic and non-magnetic impurities in superconductors. We study
different phases of this system as the decoherence strength and the excitation
density is changed. For a low decoherence we obtain a polariton condensate with
comparable excitonic and photonic parts at low densities and a BCS-like state
with bigger photon component due to the fermionic phase space filling effect at
high densities. In both cases there is a large gap in the density of states. As
the decoherence is increased the gap is broadened and suppressed, resulting in
a gapless condensate and finally a suppression of the coherence in a low
density regime and a laser at high density limit. A crossover between these
regimes is studied in a self-consistent way analogous to the Abrikosov and
Gor'kov theory of gapless superconductivity.Comment: 17 pages, 8 figures, submitted to PR
Luminescence in quantum-confined cadmium selenide nanocrystals and nanorods in external electric fields
It is found that the absorption and luminescence spectra of CdSe nanocrystals and nanorods depend on the external electric field. It is shown that the external electric field quenches the P-polarized photoluminescence of CdSe nanorods to a degree higher than the degree of field-induced quenching of the S-polarized photoluminescence. It is established that the nanocrystals are more sensitive to the external electric field than the nanorods. The effect of the external electric field on the luminescence properties of the semiconductor nanorods is discussed. © 2009 Pleiades Publishing, Ltd
Relativistic nuclear recoil corrections to the energy levels of hydrogen-like and high lithium like atoms in all orders in
The relativistic nuclear recoil corrections to the energy levels of
low-laying states of hydrogen-like and high lithium-like atoms in all
orders in are calculated. The calculations are carried out using the
B-spline method for the Dirac equation.
For low the results of the calculation are in good agreement with the
-expansion results. It is found that the nuclear recoil
contribution, additional to the Salpeter's one, to the Lamb shift () of
hydrogen is . The total nuclear recoil correction to the energy
of the transition in lithium-like uranium
constitutes and is largely made up of QED contributions.Comment: 19 pages, latex, accepted for publication in Phys. Rev.
Connecting the data landscape of long-term ecological studies: The SPI-Birds data hub
The integration and synthesis of the data in different areas of science is drastically slowed and hindered by a lack of standards and networking programmes. Long-term studies of individually marked animals are not an exception. These studies are especially important as instrumental for understanding evolutionary and ecological processes in the wild. Furthermore, their number and global distribution provides a unique opportunity to assess the generality of patterns and to address broad-scale global issues (e.g. climate change). To solve data integration issues and enable a new scale of ecological and evolutionary research based on long-term studies of birds, we have created the SPI-Birds Network and Database (www.spibirds.org)\u2014a large-scale initiative that connects data from, and researchers working on, studies of wild populations of individually recognizable (usually ringed) birds. Within year and a half since the establishment, SPI-Birds has recruited over 120 members, and currently hosts data on almost 1.5 million individual birds collected in 80 populations over 2,000 cumulative years, and counting. SPI-Birds acts as a data hub and a catalogue of studied populations. It prevents data loss, secures easy data finding, use and integration and thus facilitates collaboration and synthesis. We provide community-derived data and meta-data standards and improve data integrity guided by the principles of Findable, Accessible, Interoperable and Reusable (FAIR), and aligned with the existing metadata languages (e.g. ecological meta-data language). The encouraging community involvement stems from SPI-Bird's decentralized approach: research groups retain full control over data use and their way of data management, while SPI-Birds creates tailored pipelines to convert each unique data format into a standard format. We outline the lessons learned, so that other communities (e.g. those working on other taxa) can adapt our successful model. Creating community-specific hubs (such as ours, COMADRE for animal demography, etc.) will aid much-needed large-scale ecological data integration