Characterisation of a track structure imaging detector

The spatial distribution of radiation-induced ionisations in sub-cellular structures plays an important role in the initial formation of radiation damage to biological tissues. Using the nanodosimetry approach, physical characteristics of the track structure can be measured and correlated to DNA damage. In this work, a novel nanodosimeter is presented, which detects positive ions produced by radiation interacting with a gas-sensitive volume in order to obtain a high resolution image of the radiation track structure. The characterisation of the detector prototype was performed and different configurations of the device were tested by varying the detector cathode material and the working gas. Preliminary results show that the ionisation cluster size distribution can be obtained with this approach. Further work is planned to improve the detector efficiency in order to register the complete three-dimensional track structure of ionising radiatio

Crystal structure and magnetic properties of highly-coercive Sr[1–x]Gd[x]Fe[12–x]Zn[x]O[19] ferrites

High-coercivity ferrite samples Sr[1–x]Gd[x]Fe[12–x]Zn[x]O]19] (x = 0, 0.1, 0.2, 0.3, 0.4, 0.5) with magnetoplumbite structure were prepared from oxides Fe[2]O[3], Gd[2]O[3], ZnO and carbonate SrCO[3] by solid-state ceramic method, the dependence of the unit cell parameters aand con the value of xwas determined. XRD showed that the samples with x >0.1 were not single-phase, and the samples with x > 0.2 contained not only bases phase with the structure of magnetplumbite, but also the a-Fe[2]O[3] and Gd[3]Fe[5]O[12] phases. It was found that increase of the xvalue leads to a slight decrease in the Curie temperature (from 727 K for the basic ferrite SrFe[12]O[19] to 714 K for Sr[1–x]Gd[x]Fe[12–x]Zn[x]O[19] solid solution with x = 0.5). It has been found that at 300 K values of spontaneous magnetization (no) and coercive force (?Hc) of solid solution Sr[0.9]Gd[0.1]Fe[11.9]Zn[0.1]O[19] are respectively 1.3 and 2.3% higher than for the base ferrite SrFe[12]O[19], and values of samples with x > 0.1 of these magnetic properties decreases gradually

New and old N=8 superconformal field theories in three dimensions

We show that an infinite family of N=6 d=3 superconformal Chern-Simons-matter theories has hidden N=8 superconformal symmetry and hidden parity on the quantum level. This family of theories is different from the one found by Aharony, Bergman, Jafferis and Maldacena, as well as from the theories constructed by Bagger and Lambert, and Gustavsson. We also test several conjectural dualities between BLG theories and ABJ theories by comparing superconformal indices of these theories.Comment: 16 pages, late

Electrical and magnetic properties of lead-substituted lanthanum ferrimanganites

The temperature dependences of the electrical conductivity, thermopower, and magnetoresistance for single crystals of lead-substituted lanthanum ferrimanganites are investigated. The data on the magnetic microstructure obtained by Mössbauer spectroscopy are analyzed. An inversion of the magnetoresistance sign with an increase in temperature and the giant positive magnetoresistance are found for one of the samples. The magnetoresistance quadratically depends on the field, and its temperature dependence exhibits a maximum. © 2000 MAIK "Nauka/Interperiodica"

Magnetic properties of solid solutions of BiFeO3– SmCoO3 system

Solid solutions of BiFeO3– SmCoO3were synthesized by a solid-state method. Peculiarities of the influence of isovalent substitution of Bi 3+ and Fe 3+ ions in BiFeO3by Sm 3+ , Co 3+ ions on the crystal structure and magnetic properties of Bi1–xSmxFe1–xCoxO3solid solutions are found. It is shown that the substitution 3-25% of the Bi 3+ , Fe 3+ ions in BiFe0O3by Sm 3+ , Co 3+ ions results in the gradual destruction of the antiferromagnetic and conception of ferromagnetic ordering. In this case replacing up to 10% of Sm 3+ and Co 3+ ions in SmCoO3by Bi 3+ and Fe 3+ ions leads to the stabilization of Co 3+ ions in a diamagnetic state

Mössbauer studies of sublattice magnetization curves of ferromagnets with several species of characterizing ions

The paper gives a model of a local molecular field describing the magnetization curves in iron garnets separately according to magnetic sublattices. It takes account of the relation between the ion distribution over the lattice sites as well as the values of the local magnetic field and the parameters of the superexchange interaction in such materials. The relations obtained are compared with the data of Mössbauer and NMR spectroscopy. © 1980 Plenum Publishing Corporation

Synthesis, magnetic and luminescent properties of Nd[1–x]La[x]GaO[3] (0.7 ≤ х ≤ 1.0) solid solutions

Nd[1–x]La[x]GaO[3] (0.7 < х < 1.0) solid solutions were synthesized by the ceramic method, their crystal structure, magnetic and luminescent properties were investigated. The solid solutions investigated behave as paramagnetics in temperature region of 5–300 K. Calculated values of Nd{3+} ion effective magnetic moment in solid solutions investigated are lower than theoretical. There probably exists „partial freezing” of orbital moment of Nd{3+} ions by the crystal field of the orthorhombically distorted perovskite structure of Nd[1–x]La[x]GaO[3] gallates. It is shown that Nd[0.1]La[0.9]GaO[3] is an efficient phosphor with IR-emission, so it is prospective for use in IR-LEDs

Determination of the parameters characterizing the superexchange interaction in complex ferrite-spinels

A calculation procedure is proposed here for determining the values of exchange parameters, applicable to spinels which contain three kinds of ions in tetrahedral positions and which have an arbitrary distribution of cations. The values of exchange integrals obtained here for ferrites of the manganese-zinc system provide a useful basis for a quantitative interpretation of the spread of Curie-temperature readings in experiments which involve ferrites with the same composition. © 1976 Plenum Publishing Corporation

Index for Three Dimensional Superconformal Field Theories and Its Applications

We review aspects of superconformal indices in three dimension. Three dimensional superconformal indices can be exactly computed by using localization method including monopole contribution, and can be applied to provide evidences for mirror duality, AdS_4/CFT_3 correspondence and global symmetry enhancement of strongly coupled gauge theories. After reviewing, we discuss the possibility of global symmetry enhancement in a finite rank of gauge group.Comment: 14 pages, Proceedings of the Seventh International Conference Quantum Theory and Symmetries (QTS-7) in Prague, Czech Republic, August, 2011; v2: minor modifications, discussion of supersymmetry enhancement of abelian ABJM theory by using an index were adde