Present and Future Gamma-Ray Probes of the Cygnus OB2 Environment

The MAGIC Collaboration has provided new observational data pertaining to the TeV J2032+4130 gamma-ray source (within the Cygnus OB2 region), for energies E_gamma >400 GeV. It is then appropriate to update the impact of these data on gamma-ray production mechanisms in stellar associations. We consider two mechanisms of gamma-ray emission, pion production and decay (PION) and photo-excitation of high-energy nuclei followed by prompt photo-emission from the daughter nuclei (A*). We find that while the data can be accommodated with either scenario, the A* features a spectral bump, corresponding to the threshold for exciting the Giant Dipole Resonance, which can serve to discriminate between them. We comment on neutrino emission and detection from the region if the PION and/or A* processes are operative. We also touch on the implications for this analysis of future Fermi and Cerenkov Telescope Array data.Comment: 6 pp, 2 figs. Matching version publihed in Phys. Rev.

Retinal tubulin binds macular carotenoids

Journal ArticlePURPOSE: To investigate the biochemical mechanisms responsible for the specific uptake, concentration, and stabilization of the carotenoids lutein and zeaxanthin in the macula. METHODS: Soluble extracts of bovine retina mixed with radioactive carotenoids were purified by hydrophobic interaction, ion exchange, and gel filtration chromatography. Carotenoid-associated proteins in these purified preparations were identified through photoaffinity labeling and protein microsequencing. Similar purifications on human macular tissue without the addition of exogenous carotenoids also were performed. RESULTS: Experiments on bovine retinal tissue demonstrated that tubulin is the major soluble carotenoid-binding protein. When soluble extracts of human macular protein were examined, the endogenous carotenoids lutein and zeaxanthin were found to copurify with tubulin. CONCLUSIONS: Tubulin is found in abundance in the receptor axon layer of the fovea, where it can serve as a locus for the deposition of the high concentrations of macular carotenoids found there. The binding interaction of carotenoids and tubulin in the Henle's fiber layer could play an important role in the photoprotective effects of the macular carotenoids against the progression of age-related macular degeneration. The association of carotenoids with tubulin, a protein that can form highly ordered linear arrays, may provide an explanation for the dichroic phenomenon of Haidinger's brushes

Retinal tubulin binds macular carotenoids

Journal ArticlePURPOSE: To investigate the biochemical mechanisms responsible for the specific uptake, concentration, and stabilization of the carotenoids lutein and zeaxanthin in the macula. METHODS: Soluble extracts of bovine retina mixed with radioactive carotenoids were purified by hydrophobic interaction, ion exchange, and gel filtration chromatography. Carotenoid-associated proteins in these purified preparations were identified through photoaffinity labeling and protein microsequencing. Similar purifications on human macular tissue without the addition of exogenous carotenoids also were performed. RESULTS: Experiments on bovine retinal tissue demonstrated that tubulin is the major soluble carotenoid-binding protein. When soluble extracts of human macular protein were examined, the endogenous carotenoids lutein and zeaxanthin were found to copurify with tubulin. CONCLUSIONS: Tubulin is found in abundance in the receptor axon layer of the fovea, where it can serve as a locus for the deposition of the high concentrations of macular carotenoids found there. The binding interaction of carotenoids and tubulin in the Henle's fiber layer could play an important role in the photoprotective effects of the macular carotenoids against the progression of age-related macular degeneration. The association of carotenoids with tubulin, a protein that can form highly ordered linear arrays, may provide an explanation for the dichroic phenomenon of Haidinger's brushes

Tunnel electron-vibrational spectroscopy of adsorbed complexes on the surface of ultra-small metal nanoparticles

This work was supported by the Russian Foundation for Basic Research (the project no. 18-03-00453) and into frameworks of the state task for ICP RAS 0082-2018-0003 (the state registration number АААА-А18-118012390045-2)

Deep-well ultrafast manipulation of a SQUID flux qubit

Superconducting devices based on the Josephson effect are effectively used for the implementation of qubits and quantum gates. The manipulation of superconducting qubits is generally performed by using microwave pulses with frequencies from 5 to 15 GHz, obtaining a typical operating clock from 100MHz to 1GHz. A manipulation based on simple pulses in the absence of microwaves is also possible. In our system a magnetic flux pulse modifies the potential of a double SQUID qubit from a symmetric double well to a single deep well condition. By using this scheme with a Nb/AlOx/Nb system we obtained coherent oscillations with sub-nanosecond period (tunable from 50ps to 200ps), very fast with respect to other manipulating procedures, and with a coherence time up to 10ns, of the order of what obtained with similar devices and technologies but using microwave manipulation. We introduce the ultrafast manipulation presenting experimental results, new issues related to this approach (such as the use of a feedback procedure for cancelling the effect of "slow" fluctuations), and open perspectives, such as the possible use of RSFQ logic for the qubit control.Comment: 9 pages, 7 figure

Parametrization of the angular correlation and degree of linear polarization in two-photon decays of hydrogen-like ions

The two-photon decay in hydrogen-like ions is investigated within the framework of second order perturbation theory and Dirac's relativistic equation. Special attention is paid to the angular correlation of the emitted photons as well as to the degree of linear polarization of one of the two photons, if the second is just observed under given angles. Expressions for the angular correlation and the degree of linear polarization are expanded in terms of $\cos\theta$-polynomials, whose coefficients depend on the atomic number and the energy sharing of the emitted photons. The effects of including higher (electric and magnetic) multipoles upon the emitted photon pairs beyond the electric-dipole approximation are also discussed. Calculations of the coefficients are performed for the transitions $2s_{1/2}\rightarrow1s_{1/2}$, $3d_{3/2}\rightarrow1s_{1/2}$ and $3d_{5/2}\rightarrow1s_{1/2}$, along the entire hydrogen isoelectronic sequence ($1\le Z \le 100$)

Correlated Electrons Step-by-Step: Itinerant-to-Localized Transition of Fe Impurities in Free-Electron Metal Hosts

High-resolution photoemission spectroscopy and realistic ab-initio calculations have been employed to analyze the onset and progression of d-sp hybridization in Fe impurities deposited on alkali metal films. The interplay between delocalization, mediated by the free-electron environment, and Coulomb interaction among d-electrons gives rise to complex electronic configurations. The multiplet structure of a single Fe atom evolves and gradually dissolves into a quasiparticle peak near the Fermi level with increasing the host electron density. The effective multi-orbital impurity problem within the exact diagonalization scheme describes the whole range of hybridizations.Comment: 10 pages, 4 figure