Nonlinear magnetoacoustic waves in plasma with isentropic thermal instability.

Evolution of magnetoacoustic (MA) waves in the heat-releasing plasma is analyzed. Due to the temperature and density dependence of the heating and cooling processes, the dispersion properties of MA waves in the considered medium is rather specific. The dispersion of phase velocity can be either positive or negative, and waves can be further damped or amplified. The amplification of MA waves takes place in the case of isentropic instability. In order to analyze waves in such a medium, we use an approach based on an analogy between nonequilibrium relaxing gas and heat-releasing plasma. The uncompensated isentropic instability restricts the applicability of linear equations describing evolution of magnetoacoustic waves. It appears that for a stabilization of the isentropic instability to be reached, the inclusion of quadratic nonlinear terms is sufficient. In the current research, we derive the nonlinear magnetoacoustic equation (NMAE), which can describe evolution of fast and slow MA waves. The obtained nonlinear equation is different from the known analogues used for the analysis of waves in the considered type of medium, which are modifications of Korteweg-de Vries or Burgers equations. In contrast to the known analogues, it is obtained without the restrictions on wave spectrum and takes into account the main features of nonadiabatic processes that affect the formation of stationary wave structures. We describe analytical solutions of this equation in the form of shock waves including the self-sustained (autowave) pulse and investigate the dependence of these waves on the direction and magnitude of the external magnetic field. The evolutionary stability of the obtained structures is confirmed with the help of numerical solutions of the NMAE. The applicability of NMAE and the correctness of its solutions have been confirmed by the numerical solution of the initial system of magnetohydrodinamic equations. It is shown that the self-sustained (autowave) pulses, which may be realized only in the case of isentropic instability, completely recover their shape after the collision.

Reaction of Mast Cells in the Zone of Polypropylene Mesh Implantation.

Reaction of mast cells of adult male Wistar rats (n=15) in the zone of polypropylene mesh fixation was studied by histochemical, immunohistochemical, and traditional morphological methods on days 1, 5, 10, and 30 after implantation. Immediately after the intervention, mast cells stimulated the processes aimed at wound healing. Secretion of mast cells was clearly regulatory. These cells migrated to the zone of injury for subsequent activation of their function. The number of cNOS+ mast cells near the polypropylene mesh was maximum on day 1 and the number of iNOS+ mast cells peaked on day 5 of the experiment, which probably represented a compensatory reaction. Presumably, stimulation of fibrillogenesis was largely due to the activatory effect of mast cells on the fibroblast function, but not to collagen production by these mast cells.

[Cytokines in surgery for pulmonary tuberculosis]. / Tsitokiny v kollapsokhirurgii tuberkuleza legkikh.

AIM: To evaluate the effect of various methods of thoracoplasty on local production of cytokines in patients with pulmonary tuberculosis. MATERIAL AND METHODS: The main group consisted of patients after traditional thoracoplasty. Thoracoplasty was compared with endoprosthesis of polypropylene mesh 'Surgipro - SPMM-149'. TNF-α and IL-10 cytokines in exudate from surgical area were measured by using of solid-phase enzyme immunoassay (OOO 'Vector-Best', Russia). RESULTS: It was revealed that local production of pro- and anti-inflammatory cytokines is more pronounced after thoracoplasty with polypropylene mesh 'Surgipro - SPMM-149'. Local cytokine balance changes towards inflammation were more pronounced after thoracoplasty with mesh implant and did not depend on the degree of drug sensitivity.

[The role of magnetic resonance tomography in diagnosis of syringomyelia]. / Znachenie magnitno-resonansnoi tomografii v diagnostike siringomielii.

The paper presents the analysis of the results of the examination of 90 patients with syringomyelia using magnetic-resonance "Bruker" tomograph with the intensity of the magnetic field 0.23 T. The observation was carried out according to the authors' classification. Symptom complex of syringomyelia corresponding to the anatomic disorders of the spinal cord was described. The authors made a conclusion, that the magnetic-resonance tomography, as the most informative method, was a method of choice in syringomyelia. In 21% of the patients there was idiopathic syringomyelia; in 47.3% a process spread to the caudal regions of medulla oblongata. In 79% cases syringomyelia manifested as a syndrome; in 50% of the total cases it was found in Arnold--Chiari anomaly.

[Magnetic resonance tomography in the diagnosis of vertebro-neurological diseases]. / Magnitno=rezonansnaia tomografiia v diagnostike veretebronevrologicheskoi patologii.

Vertebral osteochondrosis is one of the most prevalent diseases of man. The principal method for its diagnosis is x-ray examination that shows the major changes in the spine and, only indirectly, in the cord. The details are revealed by computer-aided tomography. Magnetic resonance tomography (MRT) is the most informative for the purpose, for it permits the assessment of the fine shifts in the brain and adjacent tissues, as well as the status of the vertebral disks by a noninvasive method. A total of 453 patients with various diseases of the spine and cord were examined with the TOMIKON BMT 1100 T tomographer with different pulsed sequences SPIN-echo and GRADIENT-echo, that helped differentiate between the lesions with similar clinical symptoms, such as vertebral disk hernias, extramedullary tumors, cicatricial deformations compressing the dural space and the cord, costal changes, etc. Traumatic injuries of the spinal cord, compressions of the cord with subsequent posttraumatic syringomyelia could be well differentiated. These results evidence the efficacy of MRT as a method for the diagnosis of vertebro-neurologic diseases, particularly those lacking clear-cut symptoms. MRT advantages are the possibility of imaging in many projections and visualisation of soft-tissue structures without resorting to invasive methods.

[Magnetic resonance tomography in late sequelae of spinal and spinal cord injuries]. / Magnitno-rezonansnaia tomografiia pri otdalennykh posledstviiakh pozvonochno-spinnomozgovoi travmy.

Magnetic-resonance tomography (MRT) helped obtain a high-resolution image characterized by high sensitivity in respect of soft tissue contrast visualization and providing direct imaging of the spinal cord and its radicles. This method is useful in the diagnosis of injuries to the spine and cord. A total of 64 patients of both sexes aged 6 to 67 were examined. The primary diagnosis of traumatic changes in the spine and cord was confirmed by MRT in only 62% of cases. Two groups of patients were singled out: with acute and chronic injuries, subdivided into subgroups with and without spinal cord dysfunction. The detected changes were divided into extramedullary (traumatic disk hernias, compression of the cord or radicles with a dislocated bone fragment, epidural hematoma) and intramedullary (edema, hemorrhages, spinal cord disruption); MRT diagnosis of intramedullary changes is particularly important, more so in the absence of bone injuries. In remote periods after the trauma the clinical picture was determined by spinal canal stenosis, cicatricial atrophic and adhesive changes eventually blocking the liquor space. Intramedullary changes presented as spinal cord cysts or syringomyelia. A classification of the detected changes by the types of injuries and their aftereffects is presented in the paper. The authors emphasize the desirability of MRT in spinal injuries with signs of cord dysfunction.

[Nuclear magnetic tomography in the differential diagnosis of syringobulbia and craniospinal tumors]. / Iaderno-magnitnaia tomografiia v differentsial'noi diagnostike siringobul'bii i kraniospinal'nykh opukholei.

Though syringobulbia is a rare condition, the problem of its differentiation from other craniospinal abnormalities is a pressing one. This problem may be considered solved due to introduction of nuclear magnetic tomography (NMT). Studies carried out in 43 patients helped distinguish the NMT symptoms most characteristic of syringobulbia: a centrally located echo signal zone in the medulla oblongata and the cord, the echo signal in this zone being equivalent to that of the cerebrospinal fluid or gliosis, increased transverse size of the medulla oblongata and the spinal cord, dilated volumes of the basal cysterns. A craniospinal condition resultant from a tumor process is characterized by detection of a bulky formation with a heterologous structure in the medulla oblongata, involving the cervical portion of the cord and the cerebellar structures. It is associated with a perifocal edema and IVth ventricle deformation; this latter condition is often undetectable, and occlusive hydrocephalus develops. Since NMT often permits a differential diagnosis between syringobulbia and craniospinal tumors, it must become the method of choice in patients with these conditions.

[The place of radiotherapy in the treatment of pituitary adenomas]. / Mesto luchevoi terapii v lechenii adenom gipofiza.

The paper is devoted to an analysis of the present-day role of radiotherapy of pituitary adenomas with relation to tumor spreading and the patient's neuroendocrine status. The authors made use of data obtained from the N. N. Burdenko Research Institute of Neurosurgery, USSR Academy of Medical Sciences. They analyzed the results of gamma-beam therapy, proton-beam therapy and radiosurgical implantation of 90Y granules used alone as well as in combination with surgical intervention. Based on the analysis of the clinical data on 320 patients, a conclusion is made on the indications for one or another method depending on the stage and course of the disease.

[Mathematical model of normal tissue involvement in gamma teletherapy]. / Matematicheskaia model' porazheniia normal'nykh tkanei pri distantsionnoi gamma-terapii.

A model of normal tissue injury as a result of exposure to ionizing radiation is based on an assumption that the degree of tissue injury is determined by the degree of destruction by certain critical cells. The dependence of the number of lethal injuries on a single dose is expressed by a trinomial - linear and quadratic parts and a constant, obtained as a result of the processing of experimental data. Quantitative correlations have been obtained for the skin and brain. They have been tested using clinical and experimental material. The results of the testing point out to the absence of time dependence on a single up to 6-week irradiation courses. Correlation with an irradiation field has been obtained for the skin. A conclusion has been made as to, first, time lag blurring time dependence within a certain range of courses, second, the presence of a component of true regeneration of which the degree depends on the volume irradiated. Proceeding from such an understanding of injury-regeneration processes a conclusion has been made that the concept of isoefficacy of irradiation courses is conditional. Volume-time fractionation is a promising direction in the development of radiation therapy.