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The process of wave front reversal for nonreciprocal magnetostatic surface waves (MSSWs), propagating in ferromagnetic yttrium iron garnet films, has been studied theoretically and experimentally. The efficiency of wave front reversal for nonreciprocal MSSWs turned out to be approximately ten times smaller than for reciprocal backward volume magnetostatic waves under similar conditions.

The effect of double-wave-front reversal in the system of dipolar and dipole-exchange spin waves propagating in a ferrite film is studied experimentally and theoretically with the goal of development of a nonlinear microwave signal processor. In the proposed processor microwave signal pulse supplied to the input antenna excites in the ferrite film a long-wavelength dipolar spin wave (magnetostatic wave), which in the course of propagation is scattered on the film inhomogeneities and is transformed into short-wavelength long-lifetime dipole-exchange spin waves. Then, a sequence of two high-power double-frequency parametric pumping pulses, supplied to the film through an open dielectric resonator with a certain time delay between them, performs first, and then second, wave-front reversal for all the spin waves created by the input signal in the ferrite film. As a result of this double wave-front reversal process microwave output pulses with either reversed (input antenna) or nonreversed (output antenna) tim...

The well-known problem of the correlations between eruptive processes in the chromosphere and corona and peculiarities of the magnetic field structure in solar active regions (ARs) on the photospheric level are discussed in this paper. We study the time variations in the first four moments of distribution (over the field) of four integral parameters of the magnetic field of an AR. We used Huairou (PR China) and Solar Orbit Heliospheric Observatory, Michelson–Doppler Interferometer (SOHO/MDI) measurements of longitudinal magnetic fields for ten ARs. We study the following integral parameters of an AR: total magnetic flux F a, tilting angle A n, complexity parameter H u and relative total magnetic flux imbalance O v. The distributions of these parameters show essential differences between quiet and flare productive ARs. One can observe specific differences in the distributions before and during flares. The four first distribution moments take into account these differences and so they can be good quantitati...

The anisotropy of the absorption and electroabsorption spectra of CdP2 and CdP4, single crystals has been investigated. A number of interband gaps has been determined and specified. The energies and the type of phonons involved in direct and indirect transitions have been determined. Proceeding from group-theoretical calculations of the band structure, the transitions in CdP4 have been localised and some regularities of the phonons in CdP2 have been revealed. Die Anisotropie der Absorptions- und Elektroabsorptionsspektren von CdP2- und CdP4-Einkristallen wurde untersucht und eine Auzahl von Interbandabstanden bestimmt und spezifiziert. Die Energien und die Art der bei den direkten und indirekten Ubergangen beteiligten Phononen wurden bestimmt. Von gruppentheoretischen Berechnungen det Bandstruktur ausgehend wurden die Ubergange in CdP4 lokalisiert und einige Regelmasig-keiten der Phononen in CdP2 aufgedeckt.

In order to address the problem of characterisation of high dose rate workplace fields, unique techniques and devices have been developed and tested. The kit of devices comprises a passive spectrometric system and six-vector collimator with thermoluminiscent detectors (TLDs) inside, allowing determination of the anisotropy of the radiation field, both horizontal and vertical. The passive spectrometric system makes use of simultaneous exposure of several TLDs placed inside spherical attenuators. Deconvolution of gamma spectra is performed by solving a system of simultaneous linear equations. The problem of solving ill-defined systems of simultaneous equations was addressed by a system regularisation method. The energy resolution of the system is not high (seven to ten energy bins can be distinguished), yet is sufficient for practical needs. After several benchmark tests, the discussed experimental set-up was extensively tested in various locations within Object 'Shelter'. Results of both energy spectrum and exposure geometry characterisation demonstrated the feasibility of the proposed approach.

Between 1986 and 1990, several hundred thousand workers, called "liquidators" or "clean-up workers," took part in decontamination and recovery activities within the 30-km zone around the Chernobyl nuclear power plant in Ukraine, where a major accident occurred in April 1986. The Chernobyl liquidators were mainly exposed to external ionizing radiation levels that depended primarily on their work locations and the time after the accident when the work was performed. Because individual doses were often monitored inadequately or were not monitored at all for the majority of liquidators, a new method of photon (i.e., gamma and x rays) dose assessment, called "RADRUE" (Realistic Analytical Dose Reconstruction with Uncertainty Estimation), was developed to obtain unbiased and reasonably accurate estimates for use in three epidemiologic studies of hematological malignancies and thyroid cancer among liquidators. The RADRUE program implements a time-and-motion dose-reconstruction method that is flexible and conceptually easy to understand. It includes a large exposure rate database and interpolation and extrapolation techniques to calculate exposure rates at places where liquidators lived and worked within approximately 70 km of the destroyed reactor. The RADRUE technique relies on data collected from subjects' interviews conducted by trained interviewers, and on expert dosimetrists to interpret the information and provide supplementary information, when necessary, based upon their own Chernobyl experience. The RADRUE technique was used to estimate doses from external irradiation, as well as uncertainties, to the bone marrow for 929 subjects and to the thyroid gland for 530 subjects enrolled in epidemiologic studies. Individual bone marrow dose estimates were found to range from less than one muGy to 3,300 mGy, with an arithmetic mean of 71 mGy. Individual thyroid dose estimates were lower and ranged from 20 muGy to 507 mGy, with an arithmetic mean of 29 mGy. The uncertainties, expressed in terms of geometric standard deviations, ranged from 1.1 to 5.8, with an arithmetic mean of 1.9.

OBJECTIVE This study aimed at investigating radiation exposure of hippocampus in interventional medical profes sionals irradiated in the operating room, and to compare doses in the hippocampus with the effective dose (protec tion quantity), as well as with the doses measured by individual dosimeter, in order to estimate probability of reach ing levels of radiation induced cognitive and other neuropsychiatric alterations during their working career, through a Monte Carlo simulation. MATERIALS AND METHODS A Monte Carlo simulation of hippocampal exposure was used by means of a hybrid voxel mathematical phantom of a doctor irradiated in typical angiographic projections and energy spectra inherent to interventional cardiology procedures. RESULTS The results showed that cranial irradiation was very heterogeneous and depended on the projection: doses of left and right hippocampi may be different up to a factor of 2.5; under certain conditions, the dose of the left hippocampus may be twice the effective dose, estimated by conventional double dosimetry algorithm. CONCLUSIONS The professional span doses of the irradiated hippocampus may overcome the threshold able to pro voke possible cognitive and emotional behavioral impairment. Therefore, in depth studies of the effects of brain irradiation in occupationally exposed interventional medical personnel appear urgently needed and crucial.

Relaxation of linear magnetization dynamics is well described by the viscous Gilbert damping processes. However, for strong excitations, nonlinear damping processes such as the decay via magnon-magnon interactions emerge and trigger additional relaxation channels. Here, we use space- and time-resolved microfocused Brillouin light scattering spectroscopy and micromagnetic simulations to investigate the nonlinear relaxation of strongly driven propagating spin waves in yttrium iron garnet nanoconduits. We show that the nonlinear magnon relaxation in this highly quantized system possesses intermodal features, i.e., magnons scatter to higher-order quantized modes through a cascade of scattering events. We further show how to control such intermodal dissipation processes by quantization of the magnon band in single-mode devices, where this phenomenon approaches its fundamental limit. Our study extends the knowledge about nonlinear propagating spin waves in nanostructures which is essential for the construction of advanced spin-wave elements as well as the realization of Bose-Einstein condensates in scaled systems., Comment: 8 pages, 4 figures

Evacuees from the 30 km zone and liquidators are likely to have received the highest Chemobyl exposures. Doses to the majority of them remained unknown, calling for dose reconstruction. This need prompted development of new techniques of retrospective dosimetry. Application of state-of-art stochastic dosimetric models and determination of site-specific location factors allowed the determination of individual doses and uncertainty ranges for a significant part of the evacuated population. A number of approaches were used to recover existing gaps in dosimetric information related to liquidators. EPR dosimetry with teeth is useful for high precision retrospective dosimetry of liquidators; now teeth from liquidators are being collected systematically in Ukraine. Analytical dose reconstruction was conducted for about 2000 Chemobyl workers. Reconstruction of doses to the rest of the liquidators requires application of a different methodology based on analysis of regularities of exposure and assignment of dose intervals according to attributes of the liquidators.

A nano-scale reconfigurable magnonic crystal is designed using voltage-controlled perpendicular magnetic anisotropy (PMA) in ferromagnetic-dielectric hetero-structures. A periodic array of gate metallic stripes is placed on top of a MgO/Co structure in order to apply a periodic electric field and to modify the PMA in Co. It is numerically demonstrated that the application of the voltage to the gate stripes modifies the spin-wave propagation and leads to the formation of band gaps in the spin-wave spectrum. The band gaps are dynamically controllable, i.e. it is possible to switch band gaps on and off within a few nanoseconds. The width and the center frequency of the band gaps is defined by the applied voltage. At last, it is shown that the application of the voltage to selected, rather than to all gate stripes allows for a pre-defined modification of the band gap spectra. The proposed voltage-controlled reconfigurable magnonic crystal opens a new way to low power consumption magnonic applications., 13 pages, 5 figures

The design and fabrication technology for integrated arrays for vertical-cavity surface-emitting lasers with bottom AlGaAs/GaAs semiconductor and top AlGaO/GaAs distributed Bragg reflectors is suggested. Arrays containing 8×8 lasers with an active region based on two InGaAs quantum wells were produced. Individual emitters with an oxidized aperture of 8–10 μm in diameter demonstrate cw lasing at 960–965 nm at room temperature, with a threshold current of 1.0–2.5 mA, external efficiency of up to 0.4 mW/mA, and a maximum output power of over 2 mW.

Spin waves (SW) are the excitation of the spin system in a ferromagnetic condensed matter body. They are collective excitations of the electron system and, from a quasi-classical point of view, can be understood as a coherent precession of the electrons' spins. Analogous to photons, they are also referred to as magnons indicating their quasi-particle character. The collective nature of SWs is established by the short-range exchange interaction as well as the non-local magnetic dipolar interaction, resulting in coherence of SWs from mesoscopic to even macroscopic length scales. As one consequence of this collective interaction, SWs are "charge current free" and, therefore, less subject to dissipation caused by scattering with impurities on the atomic level. This is a clear advantage over diffusive transport in spintronics that not only uses the charge of an electron but also its spin degree of freedom. Any (spin) current naturally involves motion and, thus, scattering of electrons leading to excessive heating as well as losses. This renders SWs a promising alternative to electric (spin) currents for the transport of spin information - one of the grand challenges of condensed matter physics., Editorial foreword, 5 pages, 1 figure