Interband electron Raman scattering in a quantum wire in a transverse magnetic field

Electron Raman scattering (ERS) is investigated in a parabolic semiconductor quantum wire in a transverse magnetic field neglecting by phonon-assisted transitions. The ERS cross-section is calculated as a function of a frequency shift and magnetic field. The process involves an interband electronic transition and an intraband transition between quantized subbands. We analyze the differential cross-section for different scattering configurations. We study selection rules for the processes. Some singularities in the Raman spectra are found and interpreted. The scattering spectrum shows density-of-states peaks and interband matrix elements maximums and a strong resonance when scattered frequency equals to the "hybrid" frequency or confinement frequency depending on the light polarization. Numerical results are presented for a GaAs/AlGaAs quantum wire.Comment: 8 pages, 5 figure

Conducting polymer tattoo electrodes in clinical electro- and magneto-encephalography

Temporary tattoo electrodes are the most recent development in the field of cutaneous sensors. They have successfully demonstrated their performances in the monitoring of various electrophysiological signals on the skin. These epidermal electronic devices offer a conformal and imperceptible contact with the wearer while enabling good quality recordings over time. Evaluations of brain activity in clinical practice face multiple limitations, where such electrodes can provide realistic technological solutions and increase diagnostics efficiency. Here we present the performance of inkjet-printed conducting polymer tattoo electrodes in clinical electroencephalography and their compatibility with magnetoencephalography. The working mechanism of these dry sensors is investigated through the modeling of the skin/electrode impedance for better understanding of the biosignals transduction at this interface. Furthermore, a custom-made skin phantom platform demonstrates the feasibility of high-density recordings, which are essential in localizing neuropathological activities. These evaluations provide valuable input for the successful application of these ultrathin electronic tattoos sensors in multimodal brain monitoring and diagnosis

Long-Term Photometric and Spectral Variations of DI Cephei

We have analyzed the photometric and spectral variations of the classical T Tauri star DI Cep for the last 50 years. Currently the star is at its faintest state and possesses an emission spectrum in the visual range. Synchronous spectroscopy and UBV R photometry show that the higher the brightness, the stronger were the intensities of hydrogen Hα, Hβ emission lines and of FeII, HeI λ5876 ˚A emissions. For the first time, we detected, with a high probability, quasi-periodic variations of the star’s brightness and of its spectrum with the period P = 2020 ± 200 days

Preparation and analysis of Pr-Ga-Al alloys

Pr-Ga-Al alloys were prepared from individual metals Pr, Ga, Al purified from oxide films in an inert atmosphere of the glove box. The metals were mixed in a certain proportion in crucibles and annealed at 832.4±1.7 °C and 366.2±6.3 °C for 19 hours and 53 hours re-spectively. Three ingots were obtained with different praseodymium content. X-ray phase analysis showed that the dominant phase of these alloys is PrGa6. A formation of Pr(GaAl)2 solid solution was also detected

On a factorization of second order elliptic operators and applications

We show that given a nonvanishing particular solution of the equation (divpgrad+q)u=0 (1) the corresponding differential operator can be factorized into a product of two first order operators. The factorization allows us to reduce the equation (1) to a first order equation which in a two-dimensional case is the Vekua equation of a special form. Under quite general conditions on the coefficients p and q we obtain an algorithm which allows us to construct in explicit form the positive formal powers (solutions of the Vekua equation generalizing the usual powers of the variable z). This result means that under quite general conditions one can construct an infinite system of exact solutions of (1) explicitly, and moreover, at least when p and q are real valued this system will be complete in ker(divpgrad+q) in the sense that any solution of (1) in a simply connected domain can be represented as an infinite series of obtained exact solutions which converges uniformly on any compact subset of . Finally we give a similar factorization of the operator (divpgrad+q) in a multidimensional case and obtain a natural generalization of the Vekua equation which is related to second order operators in a similar way as its two-dimensional prototype does

Preparation and analysis of Pr-Ga-Al alloys

Pr-Ga-Al alloys were prepared from individual praseodymium, gallium and aluminum purified from oxide films in an inert atmosphere of the glove box. The Ga-Al phase diagram was used to choose the eutectic composition (2.1 mol. % Al). The metals were mixed in a certain proportion in crucibles (BeO) and annealed at 832.4±1.7 °C and 366.2±6.3 °C for 19 hours and 53 hours, respectively. Three ingots were obtained with different praseodymium content. The alloys were investigated by X-ray phase analysis, scanning electron microscopy and electron backscatter diffraction technique. A general chemical analysis was also performed. Depending on praseodymium content the alloys consisted of PrGa6 intermetallic compound phase; a mixture of PrGa6 and ϵ-PrGa2 IMCs; and ϵ-PrGa2 phase. Ternary intermetallic compounds of praseodymium were not detected. A small addition of aluminum does not affect the phase characteristics of intermetallic compounds of praseodymium in alloys. © 2019 Author(s)

PHASES High Precision Differential Astrometry of delta Equulei

delta Equulei is among the most well-studied nearby binary star systems. Results of its observation have been applied to a wide range of fundamental studies of binary systems and stellar astrophysics. It is widely used to calibrate and constrain theoretical models of the physics of stars. We report 27 high precision differential astrometry measurements of delta Equulei from the Palomar High-precision Astrometric Search for Exoplanet Systems (PHASES). The median size of the minor axes of the uncertainty ellipses for these measurements is 26 micro-arcseconds. These data are combined with previously published radial velocity data and other previously published differential astrometry measurements using other techniques to produce a combined model for the system orbit. The distance to the system is determined to within a twentieth of a parsec and the component masses are determined at the level of a percent. The constraints on masses and distance are limited by the precisions of the radial velocity data; we outline plans improve this deficiency and discuss the outlook for further study of this binary.Comment: Accepted by AJ. Complete versions of tables 2-7 now available at http://stuff.mit.edu/~matthew1/deltaEquTables/ (removed from astroph server