Nonlinear dynamics of a spin-Hall nano-oscillator based on the canted antiferromagnet.

The theory of the nonlinear dynamics of a canted antiferromagnet-based (AFM) spin-Hall oscillator with weak ferromagnetism caused by the strong Dzyaloshinskii-Moriya interaction between magnetic sublattices is rigorously studied. The AFM oscillator's frequency tuning is carried out both due to a DC spin-polarized current flowing through the normal metal layer and an external permanent magnetic field. A feature of the operation of this oscillator is the presence of a hysteresis region between the subcritical (damping) and overcritical (self-oscillating) regimes. We show that it is necessary to reduce an effective easy-plane anisotropy field of the AFM or choose antiferromagnetic material with a smaller exchange field between magnetic sublattices to get a smaller hysteresis region. The action of an external permanent magnetic field on an antiferromagnet leads to the presence of two stable equilibrium states, and the self-oscillating regime is characterized by two-mode generation. We find the conditions for the absence of two-mode generation on the "current density-magnetic field strength" plane. We believe that our results can be helpful for the practical development of a sub-THz frequency tunable oscillator based on the AFM with weak ferromagnetism.

[Fecal microbiota transplantation: donor selection criteria, storage and preparation of biomaterials (review of current recommendations)].

Fecal microbiota transplantation is a treatment method based on the introduction of donated fecal material to the recipient in order to restore the damaged composition of the intestinal microbiota. This review summarizes existing data on indications for fecal microbiota transplantation, recommendations for donor selection, processing and storage of donor biomaterial.

[The actual condition of laboratory diagnostic of Clostridium difficile-associated diarrhea; the methods of detection of toxigenic strains (review of publications).]

The Clostridium difficile-associated infection (CDI) is one of the main causes of nosocomial diarrhea. The complicacy of laboratory diagnostic results in progression of disease bringing on extensive inflammatory alterations in the wall of large intestine and characterizing by superficial necrosis of mucous membrane with development of "pseudo-membranes" resulting in development of toxic megacolon, perforation of intestinal wall, peritonitis and sepsis. The main role in diagnosing plays indication of agent and detection of its toxins. None of laboratory tests can be applied as an independent technique of laboratory diagnostic of CDI. The multi-step diagnostic can become an appropriate strategy for quick and full detection of antibiotic-associated diarrhea.

[Specific features of cerebral blood flow changes after surgical removal of chiasmatic-sellar region tumors using data of transcranial duplex sonography].

Aim of the study was to discover specific features of linear blood velocity in early postoperative period in patients with tumors of chiasmatic-sellar region. Measurement of linear blood velocity using transcranial duplex sonography was performed in 294 patients with tumors of hypothalamo-hypophyseal area (149 suprasellar pituitary adenomas, 145 endosuprasellar, hypophyseal and ventricular craniopharyngiomas). It was found that vasospasm of different severity was present in 62% cases after surgical removal of chiasmatic-sellar region tumors. This "primary vasospasm" was associated with intraoperative damage to a vessel. Delayed angiospasm was caused by subarachnoid hemorrhage into basal cisterns due to hyperactivation of neuroendocrine systems of adenohypophysis and aldosterone. Persistent vasospasm with linear blood velocity over 200 cm/s results in irreversible ischemic damage of subcortical and hypothalamic structures.

[Cerebral circulatory disorders in varying brain injury, as evidenced by transcranial Doppler study].

The investigation was undertaken to elucidate the specific features of cerebral blood flow in acute brain injury (BI) in relation to its severity. Cerebral circulation (CC) was studied in 83 patients aged 5 to 64 years in the acute period of BI. The authors estimated the consciousness by the Glasgow coma scale and CC from the mean linear blood flow velocity (LBFV) in both middle cerebral arteries (MCA). To calculate the hemispheric index (HI), blood flow was examined in the extracranial portion of the ipsilateral internal carotid artery. The traumatic lesion substrate was verified by computed tomography and magnetic resonance imaging. Intracranial and cerebral perfusion pressures were continuously monitored in 39 patients. The outcomes of BI were assessed by means of the Glasgow outcome scale. In accordance with the values of LBFV, all the patients were divided into 3 groups: 1) patients in whom MCA LBFV throughout the acute period of BI remained within the range of normal or low values (30-70 cm/sec); 2) those in whom MCA LBFV ranged from 80 to 120 cm/sec at a HI of less than 3.0; 3) those with vasospasm in whom MCA LBFV was more than 120 cm/sec at a HI of more than 3.0. Analysis of the studies revealed that despite the same consciousness impairments, the magnitude of CC disorders was appropriate to the severity of brain lesions in all three groups. At the same time severe and mixed brain lesions as intracranial hematomas, type 3 contusion foci, and profuse subarachnoidal hemorrhages were attended by the development of unilateral or bilateral vasospasm of MCA. In addition, the low CC values mainly associated with prehospital overall cerebral hypoxia were ascertained to be a poor factor of the outcome of BI. The best results of treatment for BI are achieved in moderate CC disorders as a moderate LBFV increase.