Absence of room temperature ferromagnetism in bulk Mn-doped ZnO

Structural and magnetic properties have been studied for polycrystalline Zn_1-xMn_xO (x=0.02, 0.03, 0.05). Low-temperature (~500 oC) synthesis leaves unreacted starting ZnO and manganese oxides. Contrary to a recent report, no bulk ferromagnetism was observed for single-phase materials synthesized in air at temperatures above 900 oC. Single-phase samples show paramagnetic Curie-Weiss behavior.Comment: Accepted for publication in J. Appl. Phys., RevTeX, 3 pages, 4 figure

Absence of ferromagnetism in Co and Mn substituted polycrystalline ZnO

We discuss the properties of semiconducting bulk ZnO when substituted with the magnetic transition metal ions Mn and Co, with substituent fraction ranging from $x$ = 0.02 to $x$ = 0.15. The magnetic properties were measured as a function of magnetic field and temperature and we find no evidence for magnetic ordering in these systems down to $T$ = 2 K. The magnetization can be fit by the sum of a Curie-Weiss term with a Weiss temperature of $\Theta\gg$100 K and a Curie term. We attribute this behavior to contributions from both \textit{t}M ions with \textit{t}M nearest neighbors and from isolated spins. This particular functional form for the susceptibility is used to explain why no ordering is observed in \textit{t}M substituted ZnO samples despite the large values of the Weiss temperature. We also discuss in detail the methods we used to minimize any impurity contributions to the magnetic signal.Comment: 6 pages, 4 figures (revised

Structural and physical properties of SrMn1−xRuxO3SrMn_{1-x}Ru_xO_3 perovskites

We combine the results of magnetic and transport measurements with neutron diffraction data to construct the structural and magnetic phase diagram of the entire family of SrMn$_{1-x}$Ru$_{x}$O$_3$ ($0 \leqslant x \leqslant 1$) perovskites. We have found antiferromagnetic ordering of the C type for lightly Ru-substituted materials ($0.06 \leqslant x \leqslant 0.5$) in a similar manner to $R_{y}$Sr$_{1-y}$MnO$_3$ ($R$=La, Pr), due to the generation of Mn$^{3+}$ in both families of manganite perovskites by either $B$-site substitution of Ru$^{5+}$ for Mn$^{4+}$ or $A$-site substitution of $R^{3+}$ for Sr$^{2+}$. This similarity is driven by the same ratio of $d^4$ / $d^3$ ions in both classes of materials for equivalent substitution level. In both cases, a tetragonal lattice distortion is observed, which for some compositions ($0.06 \leqslant x \leqslant 0.2$) is coupled to a C-type AF transition and results in a first order magnetic and resistive transition. Heavily substituted SrMn$_{1-x}$Ru$_{x}$O$_3$ materials are ferromagnetic due to dominating exchange interactions between the Ru$^{4+}$ ions. Intermediate substitution ($0.6 \leqslant x \leqslant 0.7$) leads to a spin-glass behavior instead of a quantum critical point reported previously in single crystals, due to enhanced disorder.Comment: 9 pages, 10 figures, accepted for publication in Physical Review

Prognosis of recurrent myocardial infarction based on shortliffe fuzzy models using the electrical characteristics of biologically active points

This report discusses the employment of the electrical characteristics of biologically active points (BAP) in the meridian of the heart to solve the task of prognosticating recurrence of myocardial infarctions during the rehabilitation period using fuzzy decision rule

ANATOMICAL AND TOPOGRAPHICAL FEATURES OF ANTERIOR VITREOUS CORTEX

Introduction. The vitreous body (VB) is limited  by anterior cortex (AC) layers, consisting of densely interconnected collagen fibers. There is no consensus regarding the structural AC organization and its relationship with the structures of the eyeball.Purpose. To study the anatomical and topographical features of the anterior cortical layers of VB.Material  and  methods.  We  developed an  original method  for contrasting the VB structures  using an ultra-fine Vitreokontrast suspension based on a water-insoluble inorganic salt of barium sulfate in the isotonic solution. The study was performed in 20 cadaveric donor eyes. the  original technology.  Dissection was carried  out  according to a proposed original technology. The scleral incision was made at a 4mm distance from the limbus along the circumference. Then we cut the sclera between the rectus muscles, then the petals of choroid and retina were formed, and also they were cut off. Then we cut the sclera between the rectus muscles, then the petals of choroid and retina were formed, and also cut them off. We stained the vitreous structures using the Vitreokontrast suspension with a sequential removal of the anterior cortex up to the posterior lens capsule.Results. After the cortex removal in the cadaveric donor eyes several membranous structures  (on an average of four) were detected with a covering the retrolental space with an ability to exfoliate, with sites of the attachment to the Wieger ligament and fibers of ciliary zonula and pars plana. After the removal of the membranous structures and their restaining a layer of vitreous fibers was contrasted on the posterior capsule of the lens in the area of Berger space projection. Conclusion. The study revealed no case of a true full anterior cortex detachment. The anterior cortex exfoliation occurred with the formation of a multilayer membranous structure, covering the posterior surface of lens and ciliary body.The presence of vitreous fibers closely associated with the posterior capsule of the lens in the projection area  of Berger space, allows to suppose a possibility of retrolental bag existence, one of walls of which is associated with the posterior lens capsule

Dilute ferrimagnetic semiconductors in Fe-substituted spinel ZnGa2_2O4_4

Solid solutions of nominal composition [ZnGa$_2$O$_4$]$_{1-x}$[Fe$_3$O$_4$]$_x$, of the semiconducting spinel ZnGa$_2$O$_4$ with the ferrimagnetic spinel Fe$_3$O$_4$ have been prepared with $x$ = 0.05, 0.10, and 0.15. All samples show evidence for long-range magnetic ordering with ferromagnetic hysteresis at low temperatures. Magnetization as a function of field for the $x$ = 0.15 sample is S-shaped at temperatures as high as 200 K. M\"ossbauer spectroscopy on the $x$ = 0.15 sample confirms the presence of Fe$^{3+}$, and spontaneous magnetization at 4.2 K. The magnetic behavior is obtained without greatly affecting the semiconducting properties of the host; diffuse reflectance optical spectroscopy indicates that Fe substitution up to $x$ = 0.15 does not affect the position of the band edge absorption. These promising results motivate the possibility of dilute ferrimagnetic semiconductors which do not require carrier mediation of the magnetic moment.Comment: 9 pages and 6 figure

The features of the structural organization of spinal ganglia in a subphylum of vertebtates

Fig. 6. Fragment of microscopic structure of spinal ganglion of domestic bull: a — neurocytes; b — cores if glial cells; c — nerval fibers. Hematoxilin and eosin. ×120.Published as part of Goralskiy, L. P., Guralska, S. V., Kolesnik, N. L. & Sokulskiy, I. M., 2018, The Features Of The Structural Organization Of Spinal Ganglia In A Subphylum Of Vertebtates, pp. 501-508 in Vestnik Zoologii 52 (6) on page 506, DOI: 10.2478/vzoo-2018-0051, http://zenodo.org/record/645498