Oscillations above sunspots from the temperature minimum to the corona

Context. An analysis of the oscillations above sunspots was carried out using simultaneous ground-based and Solar Dynamics Observatory (SDO) observations (SiI 10827A, HeI 10830A, FeI 6173A, 1700A, HeII 304A, FeIX 171A). Aims. Investigation of the spatial distribution of oscillation power in the frequency range 1-8 mHz for the different height levels of the solar atmosphere. Measuring the time lags between the oscillations at the different layers. Methods. We used frequency filtration of the intensity and Doppler velocity variations with Morlet wavelet to trace the wave propagation from the photosphere to the chromosphere and the corona. Results. The 15 min oscillations are concentrated near the outer penumbra in the upper photosphere (1700 A), forming a ring, that expands in the transition zone. These oscillations propagate upward and reach the corona level, where their spatial distribution resembles a fan structure. The spatial distribution of the 5 min oscillation power looks like a circle-shape structure matching the sunspot umbra border at the photospheric level. The circle expands at the higher levels (HeII 304A and FeIX 171A). This indicates that the low-frequency oscillations propagate along the inclined magnetic tubes in the spot. We found that the inclination of the tubes reaches 50--60 degrees in the upper chromosphere and the transition zone. The main oscillation power in the 5-8 mHz range concentrates within the umbra boundaries at all the levels. The highest frequency oscillations (8 mHz) are located in the peculiar points inside the umbra. These points probably coincide with umbral dots. We deduced the propagation velocities to be 28+-15 km/s, 26+-15 km/s, and 55+-10 km/s for the SiI 10827A-HeI 10830A, 1700A-HeII 304A, and HeII 304A-FeIX 171A height levels, respectively

Phase composition and microstructure of Ti-6Al-4V alloy after hydrogen-plastic working

The influence of combination of thermohydrogen treatment and plastic working of Ti-6Al-4V (VS6 Ru) titanium alloy on its microstructure and phase composition has been investigatedyesBelgorod State Universit

Entangled-State Lithography: Tailoring any Pattern with a Single State

We demonstrate a systematic approach to Heisenberg-limited lithographic image formation using four-mode reciprocal binominal states. By controlling the exposure pattern with a simple bank of birefringent plates, any pixel pattern on a $(N+1) \times (N+1)$ grid, occupying a square with the side half a wavelength long, can be generated from a $2 N$-photon state.Comment: 4 pages, 4 figure

Quantum Imaging

We provide a brief overview of the newly born field of quantum imaging, and discuss some concepts that lie at the root of this field.Comment: 8 pages, 19 figure

Influence of magnetic field on paramagnetic-ferromagnetic transition in La1−x_{1-x}Cax_{x}MnO3_{3} (x≈0.25x\approx 0.25) crystal: ultrasonic and transport studies

The ultrasonic properties of La$_{1-x}$Ca$_{x}$MnO$_{3}$ ($x\approx 0.25$) with the Curie temperature $T_C$ about 200 K are studied. Temperature dependences of longitudinal and transverse sound velocities were measured in zero magnetic field and for different constant magnetic fields as well. The ultrasonic study is supported by magnetic, resistive, magnetoresistive, structural and other measurements of the sample that facilitate interpretation of the results obtained. The magnetic field influence on sound properties found in this study presents some new features of the interplay between the elastic and magnetic properties of these compounds. It is shown that the paramagnetic-ferromagnetic transition in the sample studied is first order, but can become second order under the influence of applied magnetic field.Comment: submitted to Phys. Rev.

Enabling Universal Memory by Overcoming the Contradictory Speed and Stability Nature of Phase-Change Materials

The quest for universal memory is driving the rapid development of memories with superior all-round capabilities in non-volatility, high speed, high endurance and low power. Phase-change materials are highly promising in this respect. However, their contradictory speed and stability properties present a key challenge towards this ambition. We reveal that as the device size decreases, the phase-change mechanism changes from the material inherent crystallization mechanism (either nucleation- or growth-dominated), to the hetero-crystallization mechanism, which resulted in a significant increase in PCRAM speeds. Reducing the grain size can further increase the speed of phase-change. Such grain size effect on speed becomes increasingly significant at smaller device sizes. Together with the nano-thermal and electrical effects, fast phase-change, good stability and high endurance can be achieved. These findings lead to a feasible solution to achieve a universal memory

Binary optical communication in single-mode and entangled quantum noisy channels

We address binary optical communication in single-mode and entangled quantum noisy channels. For single-mode we present a systematic comparison between direct photodetection and homodyne detection in realistic conditions, i.e. taking into account the noise that occurs both during the propagation and the detection of the signals. We then consider entangled channels based on twin-beam state of radiation, and show that with realistic heterodyne detection the error probability at fixed channel energy is reduced in comparison to the single-mode cases for a large range of values of quantum efficiency and noise parameters

Topological evolution of self-induced silicon nanogratings during prolonged femtosecond laser irradiation

Abstract Gradual evolution of self-induced silicon sur face topology from one-dimensional ridge-like to twodimensional spike-like nanogratings and then to isotropic sets of micro-columns was observed by evenly increasing IR and UV femtosecond laser irradiation dose. This topo logical evolution exhibits clear indications of consequent melting and vaporization processes being set up during the prolonged laser irradiation. Monotonously decreasing cumulative IR and UV femtosecond laser-nanostructuring thresholds may indicate an increase of optical absorbance of the laser-nanostructured silicon surfaces versus the increas ing laser dose, consistent with the consequent onset of the abovementioned thermal modification processes