Current and power spectrum in a magnetic tunnel device with an atomic size spacer

Current and its noise in a ferromagnetic double tunnel barrier device with a small spacer particle were studied in the framework of the sequential tunneling approach. Analytical formulae were derived for electron tunneling through the spacer particle containing only a single energy level. It was shown that Coulomb interactions of electrons with a different spin orientation lead to an increase of the tunnel magnetoresistance. Interactions can also be responsible for the negative differential resistance. A current noise study showed, which relaxation processes can enhance or reduce fluctuations leading either to a super-Poissonian or a sub-Poissonian shot noise.Comment: 12 pages, 4 figure

Fine Splitting of Electron States in Silicon Nanocrystal with a Hydrogen-like Shallow Donor

Electron structure of a silicon quantum dot doped with a shallow hydrogen-like donor has been calculated for the electron states above the optical gap. Within the framework of the envelope-function approach we have calculated the fine splitting of the ground sixfold degenerate electron state as a function of the donor position inside the quantum dot. Also, dependence of the wave functions and energies on the dot size was obtained

Riociguat treatment in patients with chronic thromboembolic pulmonary hypertension: Final safety data from the EXPERT registry

Objective: The soluble guanylate cyclase stimulator riociguat is approved for the treatment of adult patients with pulmonary arterial hypertension (PAH) and inoperable or persistent/recurrent chronic thromboembolic pulmonary hypertension (CTEPH) following Phase

Quantification of diffuse scattering in glass and polymers by parametric power law analysis of UV to NIR light

We have developed a parametric analysis of diffuse scattering (haze) measured by integrating sphere, based on power law ('B') representation of changes in scattering intensity vs. NIR to UV wavelengths. The standard haze quantification method involves integration over the visible band, and so prevents interpreting the important B-dependency relative to its physical characteristic. Integration also removes proper interpretation of the physiological response to human vision by considering the diffuse signal as constant. Our B-modeling of diffuse scattering allows a closer connection between haze and both physical and physiological quantities, while yielding the same quantification of haze as the standard method. In particular, the measured B dependence on scattering size (a) can be related by Rayleigh-Gans (R-G) (4.0 to 2.0), and Mie (as formulated by van de Hulst, "MievdH") (2.0 to 0.0) scattering theories. While mathematically, the large size limit of R-G asymptotically equals the small size limit of MievdH, large discontinuities exist predicting B(a) between R-G and MievdH theories due to differences in the way that refractive index (n) is used, showing a need to develop a more unified scattering theory. As an intermediate fix to this problem, we find that the MievdH (n=1.3) B(a) trend matches well with the R-G B(a) trend, establishing continuity in B(a) over its entire range. This MievdH (1.3) assumption is therefore used as a parametric tool to estimate a. We find for glass, a â20nm, while for polymers, a ranges from about 10nm to over 200nm. By comparing this average size with the associated scattering efficiencies, we deduce the number of scattering centers. We thus obtain a quantitative handle on why haze differs for various glass and polymer materials

Mid-IR plasmonics and photomodification with Ag films

The optical properties of semicontinuous silver films have been studied in the mid infrared. The film extinction spectra are shown to be well tailored by the deposition conditions and post-fabrication photomodification with both nanosecond and picosecond laser pulses at 10.6 mu m. The photomodification results in a decrease of the extinction above the laser wavelength. We find that the induced changes in the optical responses of the films are both wavelength and polarization selective. This technique allows the creation of long-pass filters for the mid-IR range in accord with the earlier theory