Influence of W doping on the structure, magnetism and exchange bias in Ni47Mn40Sn13-xWxHeusler alloys.

The influence of the W-doping on the martensitic transformation, magnetic properties and exchange bias (EB) effect in the Ni47Mn40Sn13-xWx(x= 0, 0.5, 1, 1.25 at.%) magnetic shape memory alloys has been investigated. It is found that the W-doping causes a simultaneous reduction of both the ferromagnetic (FM) exchange coupling and enhancement of the magnetic anisotropy, leading to a decrease of the magnetic moment of the low-temperature phase and to a higher attainable EB. The magnetic memory measurements reveal the presence of a glassy magnetic ground state, which can significantly impact the reduction of magnetization and enhancement of EB in the studied bulk alloys. It is argued that the glassy magnetic ground state originates from the partial magnetic disorder resulting from the correlation between the antiferromagnetic and FM states. The results demonstrate that the doping by W instead of Sn is an efficient tool to tailor the EB effect in the Ni-Mn-Sn-based Heusler alloys, whereby they are promising for spintronic applications.

Magnetism of nanotwinned martensite in magnetic shape memory alloys.

Heusler-type magnetic shape memory alloys (MSMAs) exhibit a martensitic transformation (MT) accompanied by a complex magnetic reordering, strongly affected by an intricate martensitic microstructure. The hierarchic twin structure of martensite, formed as a result of minimization of elastic energy down to atomic scale, is under intensive study nowadays. On the other hand, the much more sophisticated problem of the relationship between nanoscale twin structure and the magnetism in MSMAs has being tackled only recently. It will be shown in this topical review that the nanotwin structure affects not only the basic magnetic parameters of MSMAs, but also can change qualitatively its magnetic nature and related magnetodynamic and magnetoresistance properties. This will be primarily illustrated, both theoretically and experimentally, on the prototype Ni-Mn-Ga and Ni(Co)-Mn-Sn MSMAs in the form of epitaxial thin films, but the conclusions are also valid for other Heusler-type MSMAs, both in the form of thin films, ribbons and bulk single crystals and polycrystals. The following new and remarkable phenomena will be highlighted. (i) A strong ferromagnetic exchange coupling is observed between the submicron twin components in Ni-Mn-Ga ferromagnetic martensite. It results in the modification of the average magnetic anisotropy and the formation of a non-collinear magnetic structure, whereby a negative magnetoresistance appears in a wide temperature range. (ii) Weak antiferromagnetic coupling occurs between the ferromagnetically ordered twin components in Ni(Co)-Mn-Sn martensite. This coupling enabled to explain the exchange bias and magnetic resonance spectra in the same terms as for artificial antiferromagnetically coupled multilayered structures.

Magnetic field-induced rubber-like behavior in Ni-Mn-Ga particles/polymer composite.

Single crystalline Ni-Mn-Ga is well known as a prototype ferromagnetic shape memory alloy (FSMA) exhibiting a giant magnetic field-induced strain (MFIS), up to 12%, due to the magnetically driven twin boundary rearrangement. The large stroke and fast magnetomechanical response make it important for actuators and sensors. Polycrystalline Ni-Mn-Ga is inexpensive and technologically easy accessible, but constrains from the grain boundaries inhibit the twin boundary motion, whereby a very low MFIS is observed. Here, we have shown for the first time that a polycrystalline Ni-Mn-Ga can be split into the magnetostrain-active single grains which, being specially assembled in a silicone polymer matrix, caused large and fully reversible MFIS of the resulting composite. We termed the unique reversibility of a large MFIS of the composite as the magnetic field-induced rubber-like behavior. The magnetostrain of individual particles was explored by the X-ray µCT 3D imaging. The results suggest novel solutions for development of the low cost magnetic actuators and sensors for haptic applications.

Negative Magnetoresistance in Nanotwinned NiMnGa Epitaxial Films.

Magnetic shape memory alloys are under intensive investigation due to their unusual physical properties, such as magnetic shape memory effect, magnetic field induced superelasticity, direct and inverse magnetocaloric effect etc., promising for novel applications. One of the intriguing properties of these materials in a single phase state is a giant magnetoresistance. Here we report the remarkable results about the magnetoresistive properties of epitaxial films of Ni52.3Mn26.8Ga20.9 magnetic shape memory alloy in the temperature range of 100-370 K, well below the martensitic transformation temperature. It was found that the formation of non-collinear magnetic structure due to a nanotwinning of the film results in electron scattering on such a structure and noticeable negative magnetoresistance in the entire investigated temperature range.

[COMPARATIVE MORPHOLOGICAL STUDY OF GUIDED BONE TISSUE REGENERATION USING XENOGENIC OSTEOPLASTIC MATERIAL BIOPLAST-DENT AND CERABONE].

The purpose of the work is the modeling in the experiment of guided regeneration of bone tissue with the use of osteoplastic materials Bioplast and Cerabone with the subsequent morphological study of their influence on the course of osteoreparation. The experimental-morphological part of the work was performed on 90 mature rats of the Wistar line. The animals were divided into 3 experimental groups. In the first group (30 rats), the osteoplastic material Bioplast-Dent was used; in the second group (30 rats), the osteoplastic material Cerabone was used. The third (30 rats) group was the control group. A defect in the bone region was formed in rats, a titanium screw (BT1-00) was implanted, then the bone defects were filled with osteoplastic material. In the control group, the osteoplastic material was not used. The animals were removed from the experiment by decapitation under ether anesthesia in 30, 60 and 90 days. For morphological examination the resection of the central part of the femur shaft was carried out, including a defect site with a regenerator and a titanium screw. Each studied case was subjected to a microscopy survey in which the general character of the bone structure was assessed, as well as the presence or absence of changes and their nature in the zone of implant and osteoplastic material, as well as in dependent bone areas. The result of the comparative morphological study of xenogeneic osteoplastic materials Bioplast-Dent and Cerabone resulted in the recommended use of one of the materials in this implantation technique. Regeneration time of bone structures and qualitative characteristics of the newly formed bone did not differ fundamentally, however, when using Bioplast-Dent material, osteoreparation proceeded more actively and with more optimal morphological characteristics; there were no inflammatory changes, rejections or allergic reactions in response to implantation at all stages of the experiment.

Magnetic and structural properties of glass-coated Heusler-type microwires exhibiting martensitic transformation.

We have studied magnetic and structural properties of the Heusler-type Ni-Mn-Ga glass-coated microwires prepared by Tailor-Ulitovsky technique. As-prepared sample presents magnetoresistance effect and considerable dependence of magnetization curves (particularly magnetization values) on magnetic field attributed to the magnetic and atomic disorder. Annealing strongly affects the temperature dependence of magnetization and Curie temperature of microwires. After annealing of the microwires at 973 K, the Curie temperature was enhanced to about 280 K which is beneficial for the magnetic solid state refrigeration. The observed hysteretic anomalies on the temperature dependences of resistance and magnetization in the as-prepared and annealed samples are produced by the martensitic transformation. The magnetoresistance and magnetocaloric effects have been investigated to illustrate a potential technological capability of studied microwires.

Polarized Neutron Study of Ni-Mn-Ga Alloys: Site-Specific Spin Density Affected by Martensitic Transformation.

Polarized neutron scattering has been used to obtain the magnetic moment at specific crystallographic sites of the austenitic and martensitic phases of two nonstoichiometric Ni-Mn-Ga single crystals with close composition. These alloys have been chosen because they exhibit different structures in the paramagnetic state and inverse positions of the respective martensitic transformation and Curie temperature. The diffraction analysis revealed a remarkable result: Despite the similar alloy composition, the magnetic moments of Mn are quite different for the two alloys at the same crystallographic position. Furthermore, such a difference enabled us to assess that the exchange coupling between Mn atoms switches from ferro- to antiferromagnetic at a distance between 2.92 and 3.32 Å in the martensite. These results are of great importance to guide first principles calculations that, up to now, have not been contrasted with experiments at the atomic level.

[EXPERIENCE OF TREATMENT OF PREGNANT WOMEN WITH ACUTE SURGICAL DISEASES OF THE ABDOMINAL CAVITY].

This article describes a generalized experience in the treatment of pregnant women with acute surgical diseases of the abdominal cavity.

Magnetic field and atomic order effect on the martensitic transformation of a metamagnetic alloy.

The martensitic transformation (MT) of metamagnetic shape memory alloys is very sensitive to the applied magnetic field and atomic order. We analyze the alloy Ni50Mn34.5In15.5 in magnetic fields up to 13 T. The alloy has been prepared both in an ordered state by slow cooling, and in a disordered state by rapid quenching. In both cases the dependence of the martensitic transition temperature on the field is highly nonlinear. Such departure from linearity is due to a decrease of the entropy change at the transition, ΔS, with the applied field. This can be explained by the ordering effect of the magnetic field on the frustrated magnetic structure of the alloy in the martensitic phase. Compliance with a recent model, relying on the strong magnetoelastic interactions in these compounds, is very satisfactory.

[Differential approach to the diagnosis of acute appendicitis and acute gynecological pathology in pregnant women].

This article discusses the differential diagnosis of acute appendicitis and acute gynecological pathology in different terms of the gestation.

Transformation behavior of Ni-Mn-Ga in the low-temperature limit.

The magnetic, magnetocaloric and thermal characteristics have been studied in a Ni(50.3)Mn(20.8)Ga(27.6)V(1.3) ferromagnetic shape memory alloy (FSMA) transforming martensitically at around 40 K. The alloy shows first a transformation from austenite to an intermediate phase and then a partial transformation to an orthorhombic martensite, all the phases being ferromagnetically ordered. The thermomagnetization dependences enabled observation of the magnetocaloric effect in the vicinity of the martensitic transformation (MT). The Debye temperature and the density of states at the Fermi level are equal to θ(D) = (276 ± 4) K and 1.3 states/atom eV , respectively, and scarcely dependent on the magnetic field. The MT exhibited by Ni-Mn-Ga FSMAs at very low temperatures is distinctive in the sense that it is accompanied by a hardly detectable entropy change as a sign of a small driving force. The enhanced stability of the cubic phase and the low driving force of the MT stem from the reduced density of states near the Fermi level.

Effect of atomic order on the martensitic and magnetic transformations in Ni-Mn-Ga ferromagnetic shape memory alloys.

The influence of long-range L2(1) atomic order on the martensitic and magnetic transformations of Ni-Mn-Ga shape memory alloys has been investigated. In order to correlate the structural and magnetic transformation temperatures with the atomic order, calorimetric, magnetic and neutron diffraction measurements have been performed on polycrystalline and single-crystalline alloys subjected to different thermal treatments. It is found that both transformation temperatures increase with increasing atomic order, showing exactly the same linear dependence on the degree of L2(1) atomic order. A quantitative correlation between atomic order and transformation temperatures has been established, from which the effect of atomic order on the relative stability between the structural phases has been quantified. On the other hand, the kinetics of the post-quench ordering process taking place in these alloys has been studied. It is shown that the activation energy of the ordering process agrees quite well with the activation energy of the Mn self-diffusion process.

Temperature and time dependent magnetic phenomena in a nearly stoichiometric Ni(2)MnGa alloy.

In this work, the temperature and time dependence of the magnetic properties of a polycrystalline Ni(49.7)Mn(24.1)Ga(26.2) alloy is analysed. The law of approach to magnetic saturation has been employed to estimate the magnetic anisotropy in the three structural phases of the alloy (martensitic, pre-martensitic and austenitic). The temperature dependences of magnetic parameters, such as the magnetic susceptibility and coercive field, are interpreted in terms of the changes in the magnetic anisotropy taking place with the structural transformations. The strong magnetocrystalline anisotropy is confirmed to mainly control the magnetic response of the low temperature martensitic phase. Furthermore, magnetic relaxation studies (magnetic after-effect) have been employed to analyse the main differences between the magnetization processes in the three characteristic structural phases. The time decay of the magnetization displays a distinctive response in the pre-martensitic state. The results (logarithmic time decay of the remanent magnetization and field dependence of the magnetic viscosity) indicate the thermally activated nature of the relaxation process.

[The loss of work fitness and the course of invalidism in patients with limb vessel lesions].

The growth of the sick rate of limb peripheral vessels associated with a severe outcome (trophic ulcers, amputation) exerts an appreciable effect on the lowering of quality of life in patients. This manifests by the prolonged loss of work fitness, change of the habitual occupation and disability establishment. Objective analytical information on this problem will be of help in the delineation of the tendencies in this direction and potential approaches to the prevention of social losses. The present work is based on an analysis of 2115 statements of medicosocial expert evaluation (MSEE) of invalids suffering from diseases of limb vessels, performed over recent 8 years in the Altai region. The decisions made by the MSEE were based on the results of the clinical examination of patients using the current diagnostic modalities (ultrasonography, duplex scanning, angiography, etc). It has been established that among persons who had undergone MSEE, over the half (64.1%) were under 60 years, i.e. in the age of work fitness. It is noteworthy that the overwhelming number of invalids were men (83%) and workers (84.2%). As for special vascular pathologies, the majority of patients presented with obliterative arterial diseases (OAD) of the lower limbs, accounting for 76.3% whereas patients with venous pathology ranked second in number (15.9%). The highest severity of invalidism (groups I and II) was also recorded in OAD (77.5%), especially in atherosclerosis obliterans (AO) which accounted for 84%. Of note, these diseases were marked by no tendency toward reduction of their incidence. The time of temporary disability (from 3 to 9 months) was also most frequently recorded in OAD of the limbs. In OAD, the temporary or persistent loss of work fitness were caused by critical ischemia and amputations whereas in venous pathology, namely in varicosity and post-thrombophlebotic syndrome, the cause was progressing CVI complicated by trophic ulcers. On the whole, the lack of changes in the lowering of the number of invalids due to the given pathology evidences the unsatisfactory results of these patients' rehabilitation and the high socioeconomic tension determined by considerable treatment expenses and the high number of the disabled. Approaches to the escape from such a situation should be looked for in the early mass screening diagnosis of vascular lesions, early drug and surgical treatment and in the refinement of the system of rehabilitation prophylactic medical examination.

[Using method of DNA microelectrophoresis for the assessment of genotoxic effects of mutagens in cultured human hemopoietic cells]. / Primenenie metoda mikroélektroforeza DNK dlia otsenki genotoksicheskikh éffektov mutagenov v kul'ture gemopoéticheskikh kletok cheloveka.

Formation of single- and double strand breaks in DNA which may be discovered by microelectrophoresis in agarose gel is one of the criterion of genetical lesions in cells as a result of apoptosis or of genotoxic agent action. Genotoxic action of nickel chloride at the level of DNA of the individual cells in the initial culture of human embryonic haemopoietic cells was studied. It has been shown that about 2% cells in the studied in vitro populations were in the apoptosis state. Nickel chloride induced increasing of the frequency of formation of electrophoretic tracks of "comet" type with destroyed DNA.

[Cytoprotective properties of smecta on the intestinal mucosa of the alimentary canal]. / Vliianie smetky na tsitoprotektivnye svoistva slizistoi obolochki pishchevaritel'nogo kanala.

The chief factors of aggression are discussed together with mechanisms of protection of gastric and duodenal mucosa. Results of treatment of 30 patients with gastritis (Helicobacter pylori negative) with a cytoprotective drug smecta are presented.

[Current approaches to the diagnosis and treatment of irritable bowel syndrome]. / Sovremennye podkhody k diagnostike i lecheniiu sindroma razdrazhennogo kishechnika.

Modern definition, classifications, diagnosis and treatment of irritable bowel syndrome (IBS) are presented together with results of treatment of 30 patients with irritable bowel syndrome with the new selective calcium-channel blocker dicetel.

[Pathogenetic characteristics of trigger mechanisms of preterm birth]. / Patohenetychna obumovlenist' puskovykh mekhanizmiv nedonoshuvannia vahitnosti.

A study was made into the immune factors capability to induce labour in physiologic delivery and in threat of preterm birth. The immune response reactivity was proved to be the case immediately before the physiological labour and in premature delivery. The studies made showed that a rise in the level of lymphocytes and in the subpopulations ratios is a matter of principle in the diagnosis and prognosis of the contractile activity of the uterus. Preclinical diagnosis of pregnancy suspension permit performing a rational drug correction to secure a positive effect on indices for perinatal pathology.