Magnetic properties of ferro-antiferromagnetic spin triangle chain

Frustrated spin-12model consisting of a linear chain of triangles with ferro (F)- and antiferromagnetic interactions connected by ferromagnetic interactions (triangles chain) is studied. The ground state phase diagram depending on the interaction ratios consists of ferromagnetic, two ferrimagnetic and singlet phases. The magnetic properties in these phases are analyzed both analytically and numerically. We show that in some regions of the singlet phase the magnetization curves have magnetization plateau and magnetization jumps. We study the thermodynamics and its relation to the specific structure of the excitation spectrum of the triangle chain.

Spin triangle chain with ferromagnetic and antiferromagnetic interactions on the transition line

We investigate spin-12anisotropic model of a linear chain of triangles with competing ferro- and antiferromagnetic interactions and ferromagneic Heisenberg interactions between triangles. For a certain ratio between interactions the one-magnon excitation band is dispersionless leading to an existence of localized-magnon states which form macroscopically degenerated ground states. The spectrum of excitations has a specific structure depending on the value of the triangle-triangle interaction. Such specific structure determines the low-temperature thermodynamics and, in particular, the temperature dependence of a specific heat. In the limit of strong anisotropy of interactions the spectrum has a multi-scale structure which consists of subsets rank-ordered on small parameter. Each subset is responsible for the appearance of the peak in the temperature dependence of the specific heat.

Two-dimensional spin models with macroscopic degeneracy

We consider a class of anisotropic spin-12models with competing ferro- and antiferromagnetic interactions on two-dimensional Tasaki and kagome lattices consisting of corner sharing triangles. For certain values of the interactions the ground state is macroscopically degenerated in zero magnetic field. In this case the ground state manifold consists of isolated magnons as well as the bound magnon complexes. The ground state degeneracy is estimated using a special form of exact wave function which admits arrow configuration representation on two-dimensional lattice. The comparison of this estimate with the result for some special exactly solved models shows that the used approach determines the number of the ground states with exponential accuracy. It is shown that the main contribution to the ground state degeneracy and the residual entropy is given by the bound magnon complexes.

Spectral detection of spin-polarized ultra low-energy electrons in semiconductor heterostructures

The circularly polarized cathodoluminescence (CL) technique has been used to study the free spin-polarized electron injection in semiconductor heterostructures with quantum wells (QWs). A polarized electron beam was created by the emission of optically oriented electrons from the p-GaAs(Cs,O) negative electron affinity (NEA) photocathode. The prepared beam was injected in a semiconductor QW target, which was activated by cesium and oxygen to reduce the work function. To study the spin-dependent injection, we developed a spin-detector prototype, which consists of a compact proximity focused vacuum tube with the source and target placed parallel to each other on the opposite ends of the vacuum tube (photodiode). The injection of polarized low-energy electrons into the target by varying the kinetic energy in the range of 0.5-5.0 eV and temperature in the range of 90-300 K was studied. The CL was polarized to 2 % by the injection of 20 % spin-polarized electron beam with the energy of 0.5 eV at room temperature. The asymmetry (Sherman function) of spin detection was estimated. It was shown that the dependence of the CL polarization degree on the injected electron energy is satisfactory described by the model that considers the electron spin relaxation in the heterostructure matrix and QWs. The results demonstrate that semiconductor detectors are promising for the spin-polarimetry applications based on the optical detection of free-electron spin polarization.

Heisenberg-Ising delta-chain with bond alternation

The spin-[Formula: see text] delta-chain (sawtooth chain) with antiferromagnetic Heisenberg basal chain and Ising apical-basal interactions is studied. The basal-apical interactions involve the bond alternation. The limiting cases of the model include the symmetrical delta-chain and the antiferromagnetic chain in the staggered magnetic field. We study ground state properties of the model by the exact diagonalization and density matrix renormalization group methods. The ground state phase diagram as a function of the bond alternation consists of magnetic and various non-magnetic phases. All phases excluding the ferrimagnetic phase are gapped and an origin of the gaps is cleared.

Kagome-like chains with anisotropic ferromagnetic and antiferromagnetic interactions

We consider a spin-[Formula: see text] kagome-like chain with competing ferro- and antiferromagnetic anisotropic exchange interactions. The ground state phase diagram of this model consists of the ferromagnetic and ferrimagnetic phases. We study the ground state and the low-temperature properties on the phase boundary between these phases. The ground state on this phase boundary is macroscopically degenerate and consists of localized magnon states. We calculate the ground state degeneracy and corresponding residual entropy. The spontaneous magnetization has a jump on the phase boundary confirming the first-order type of the phase transition. In the limit of a strong anisotropy, the spectrum of the low-energy excitations has multi-scale structure governing the peculiar features of the specific heat behavior.

Ferrimagnetism in delta chain with anisotropic ferromagnetic and antiferromagnetic interactions

We consider analytically and numerically an anisotropic spin-[Formula: see text] delta-chain (sawtooth chain) in which exchange interactions between apical and basal spins are ferromagnetic and those between basal spins are antiferromagnetic. In the limit of strong anisotropy of exchange interactions this model can be considered as the Ising delta chain with macroscopic degenerate ground state perturbed by transverse quantum fluctuations. These perturbations lift the ground state degeneracy and the model reduces to the basal XXZ spin chain in the magnetic field induced by static apical spins. We show that the ground state of such a model is ferrimagnetic. The excitations of the model are formed by ferrimagnetic domains separated by domain walls with a finite energy. At low temperatures the system is effectively divided into two independent subsystems, the apical subsystem described by the Ising spin-[Formula: see text] chain and the basal subsystem described by the XXZ chain with infinite zz interactions.

[The role of early enteral nutrition in multimodal program "fast track" surgery in children]

Early enteral nutrition - in terms up to 6 h after operation - secures success of the program "fast track" surgery, together for small and large operations. Application of enteral nutrition after operation have promoted rapid elimination of intestinal paresis, early activation of its motor function, the mucosal regeneration improvement, early activation of absorptive function of underlying intestinal parts, reduction of the infection complications rate as well as the patients hosoital stay duration.

The Investigation of Intermediate Stage of Template Etching with Metal Droplets by Wetting Angle Analysis on (001) GaAs Surface

In this work, we study metal droplets on a semiconductor surface that are the initial stage for both droplet epitaxy and local droplet etching. The distributions of droplet geometrical parameters such as height, radius and volume help to understand the droplet formation that strongly influences subsequent nanohole etching. To investigate the etching and intermixing processes, we offer a new method of wetting angle analysis. The aspect ratio that is defined as the ratio of the height to radius was used as an estimation of wetting angle which depends on the droplet material. The investigation of the wetting angle and the estimation of indium content revealed significant materials intermixing during the deposition time. AFM measurements reveal the presence of two droplet groups that is in agreement with nanohole investigations. To explain this observation, we consider arsenic evaporation and consequent change in the initial substrate. On the basis of our analysis, we suggest the model of droplet evolution and the formation of two droplet groups.

[Various mechanisms of the depriming effect of bacterial endotoxin on drug metabolism]

The effect of an endotoxin from Sh. Boydii on the biotransformation of amidopyrine and acetanilide, the activity of microsomal monooxygenases, hemoxygenase, and xanthine oxidase, the lipid peroxidation (LPO) intensity, the phospholipid spectrum, and the solubilization of microsomal membrane components was studied by intraperitoneal injections (2.5 mg/kg) in rats. It was found that the endotoxin inhibits the reactions of C- and N-acetanilide hydroxylation, N-amidopyrine demethylation, acetanilide hydrolysis at the amide bond, conjugation of aminophenol metabolites with glucuronic acid and sulfate, and 4-aminoantipyrine binding to acetate. The endotoxin effect reached maximum 24 h after injection and was observed for 96 h. The inhibition of metabolism of the test preparations is related to a decrease in the content of cytochrome P-450 and in the activity of 1A2, its 2B, 2C, 3A, and 2E1 isoforms. This is obviously caused by activated LPO and enhanced nitric oxide synthesis, as evidenced by a tenfold increase in the content of NO metabolites (nitrites and nitrates) in the blood of test animals. In clinical practice, it is necessary to take into account the possibility of a significant biotransformation of drugs in the acute period of bacterial infection, which may lead to changes in the pharmacological effect and toxicity of some drugs.

[Rates of necrotic focus formation as a factor of prognosis of changes in indicators of central hemodynamics and microcirculation]

The study was undertaken to examine 89 patients with acute myocardial infarction whose pulmonary pressures were measured under monitoring. The findings were compared with the time course of necrotic focal formation. The rate of the latter was found to determine central hemodynamic changes. High necrotization rates were ascertained to be directly related to the rate of pressure elevation in the pulmonary artery and the changes in stroke volume.

[Erythrocyte deformability in patients with acute myocardial infarction]

A change in filterability of erythrocytes through a cellulose filter with pores 7 microns in diameter was examined in 67 patients with acute myocardial infarction. Dynamic evaluation of the filterability was compared with a process of necrotic focus development in time. The filterability was ascertained to have various phases coinciding with the development phases of a necrotic focus and to be an early prognostic indicator of myocardial infarction.

[The rate of formation of necrotic focus and the severity of clinical picture in the acute period of myocardial infarction]

The relationship between necrotic focus characteristics (weight and rate of necrotization) and the clinical pattern of myocardial infarction was examined. Necrosis weight was shown to have no significant effect on the course of myocardial infarction, while maximum necrotization rate was found to be a valuable predictive factor: the higher the necrotization rate, the higher the risk of fatal outcome and various complications. Prognosis, based on necrotization rate and patient's age, can be made, using an equation, derived for early prediction of myocardial infarction outcome.

[Determining the size of myocardial necrosis by a time-related biochemical method]

A mathematical procedure is proposed for quantitative assessment of necrosis weight, which is based on the processing of serial measurements of peripheral MB CPK activity in patients who died of acute myocardial infarction. The method is based on statistical treatment of biochemical findings and the results of postmortem determination of necrosis weight. A formula is derived for the biochemical equivalent of necrosis weight, which can be used a real-time intravital test.

[Determination of the mass and rate of formation of a myocardial infarct in a posterior location on a real-time scale]

A mathematical quantitative assessment technique for real-time estimation of posterior myocardial infarction weight and rate of spread is described. It is based on the variation of abdominal mapping data. A formula is derived for the calculation of necrosis weight and rate of spread.

[Determining the mass and rate of the development of myocardial infarction using the real time scale]

A quantitative mathematical procedure, based on precordial mapping variation, for real-time determination of myocardial infarction weight and rate of progress is described. Formulas have been derived for the calculation of necrosis weight and rate of formation.