Mechanism of selective lesion of the cardiovascular system in psycho-emotional stress

A species predisposition to hypertensive and ischemic heart disease occurs in mammals only at the level of primates, and is associated with social regulation of biological reactions. The specific physiological mechanism giving rise to psychonerogenic pathology may be an inhibition of the motor component of the agressive-defensive response. Repeated combination of pursuit with subsequent immobilization resulted in four out of five experimental baboons developing serious arterial hypertension and ischemic lesion of the heart which lasted many years

Experimental results on mass-thickness distribution in spacecraft equipment

A technique is described for evaluating the shielding properties of spacecraft equipment with respect to cosmic radiation. A gamma-ray source is used in conjunction with a scintillation detector to determine mass-thickness distribution both in plane geometry for equipment units, and in spherical geometry for given points within the spacecraft. Equations are presented for calculating mass-thickness distribution functions, and the results are compared with experimental measurements

A gamma-ray testing technique for spacecraft

The simulated cosmic radiation effect on a spacecraft structure is evaluated by gamma ray testing in relation to structural thickness. A drawing of the test set-up is provided and measurement errors are discussed

Symplectic methods for Hamiltonian systems with additive noise

Stochastic systems, phase flows of which have integral invariants, are considered. Hamiltonian systems with additive noise being a wide class of such systems possess the property of preserving symplectic structure. For them, numerical methods preserving the symplectic structure are constructed. A special attention is paid to systems with separable Hamiltonians, to second order differential equations with additive noise, and to Hamiltonian systems with small additive noise

Mean-square symplectic methods for Hamiltonian systems with multiplicative noise

Stochastic systems with multiplicative noise, phase flows of which have integral invariants, are considered. For such systems, numerical methods preserving the integral invariants are constructed using full implicit schemes of a new type for stochastic differential equations. In these full implicit schemes increments of Wiener processes are substituted by some truncated random variables. They are important for both theory and practice of numerical integration of stochastic differential equations. A special attention is paid to systems with separable Hamiltonians and to Hamiltonian systems with small noise. Liouvillian methods for stochastic systems preserving phase volume are also proposed. Some results of numerical experiments are presented

Numerical Methods for Stochastic Systems Preserving Symplectic Structure

Stochastic Hamiltonian systems with multiplicative noise, phase flows of which preserve symplectic structure, are considered. To construct symplectic methods for such systems, sufficiently general fully implicit schemes, i.e., schemes with implicitness both in deterministic and stochastic terms, are needed. A new class of fully implicit methods for stochastic systems is proposed. Increments of Wiener processes in these fully implicit schemes are substituted by some truncated random variables. A number of symplectic integrators is constructed. Special attention is paid to systems with separable Hamiltonians. Some results of numerical experiments are presented. They demonstrate superiority of the proposed symplectic methods over very long times in comparison with nonsymplectic ones

Efficacy of sildenafil therapy in children with pulmonary hypertension secondary to congenital heart disease

Mother and Child’s Institute, Department of Cardiology, Republic of MoldovaPurpose: pulmonary hypertension (PH) resulting from congenital heart disease (CHD) remains one of the most difficult childhood illness to treat. Sildenafil, a selective inhibitor of phosphodiesterase-5, is known as an effective and promising pulmonary vasodilator, with minors and insignifi cant reverse effects. Methods: we have evaluated the efficacy and the tolerability of sildenafil in chidren with advanced PH secondary CHD with shunts (simple (14 pts), mixed (35 pts) and complex (28 pts). In this monocentric, double-blind, placebocontrolled study we randomly assigned 77 pts with advanced PH (35 with repaired shunts, 31-palliative procedure and 11 inoperable pts) to placebo or Sildenafil orally, with the dose of 1-2 mg/kg/day each 8h for 6-12 months. The Sildenafil group consisted of 38 pts (mean age 19,9±5,3 months: 16 boys/22 girls) and the placebo group – 39 pts (mean age 21,7±7,8 months: 22 boys/17 girls). The study protocol included: functional class (FC) NYHA/Ross; O2 saturation; 6-min walk test; transthoracic echocardiogram (mean PAP, tricuspid annular plane systolic excursion (TAPSE), myocardial performance index (MPI or Tei index), right cardiac catheterisation, measuring pulmonary vascular resistance (PVR). In addition a special questionnaire of evidence of adverse reactions was available. Results: at the patients treated with Sildenafil was observed an improvement of FC NYHA/Ross from 3,16±0,1 to 2,15±0,1 (p<0,001); O2 sat (+3,1±0,5%) comparing with placebo (+0,6±0,3%), (p<0,001); an effort tolerance estimated by 6-minute walk test (+152,5±17,4 m at 6 months and +184,3±21,2m at 12 months of treatment), (p<0,001); the decreasing of mean PAP, with 22,0±2,22 at 6 months and with 19,03±2,3 mmHg at 12 months (p<0,001) and PVRI had decreased with 2,45±0,19 UW·m2 (p<0,001); the improvement of the systolic function, TAPSE from 16,55±0,34 to 20,7±0,64 mm/m2 (p<0,001) and global function of RV (Tei index) with 0,15±0,01(-31%) to initial (p<0,001). In placebo group the respective signs slightly changed and only PVR diminished from 6,4±0,1 to 5,7±0,3 UW/m2 (p<0,05). There was no death in the sildenafil-treated cases, contrary to 5 in the placebo group. Conclusions: Sildenafil is efficient in treating PH secondary to congenital systemic-to-pulmonary shunts, but even more effective in corrected surgical shunts. Sildenafil improves FC, tolerability at effort, O2 sat, systolic and global function of RV, diminishing PAPm and PVRI comparing with placebo. This remedy has good tolerability, with minors and insignifi cant adverse reactions and favourable impact on the quality of life