Modified multipulse technique for the effective detection of pure nuclear quadrupole resonance

Modification of the steady-state free precession (SSFP) multipulse technique for the effective detection of nuclear quadrupole resonance (NQR) signals was studied. This modification is based on the use of the preparatory pulse in the SSFP pulse sequences. It was shown that under certain conditions the total intensity of accumulated NQR signal can be increased. Experimental results of applying the proposed technique to nitrogen-14 NQR in the sample of sodium nitrite (NaNO₂) are presented and convincingly demonstrate the technique’s effectiveness.     

Slow motion of a permeable sphere in a viscous fluid

Flow of a viscous fluid past a permeable sphere is investigated in the Stokes approximation. An example of such a flow is flow past a perforated or meshed spherical surface. The elements of the sphere contain rigid impermeable sections and openings through which the fluid can flow. The interaction of the sphere with the flow is described by two drag coefficients, which established the connection between the flow velocity of the fluid at the sphere and the stress tensor on it. The dependence of the flow pattern and also the drag and flow rate of the fluid on these coefficients is investigated. In special cases, the obtained solution describes flow past solid and liquid spheres.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 5, pp. 165–167, September–October, 1982.     

Convective instability of a horizontal layer of fluid between permeable membranes

The equilibrium stability is investigated of a system consisting of two semi-infinite isothermal masses of fluid divided by a horizontal layer of finite thickness of the same fluid with a vertical temperature gradient directed downwards. The transition layer is separated by thin permeable membranes. Neutral stability curves are constructed for different membrane resistances. In the case of high permeability, the equilibrium is absolutely unstable with respect to monotonic-type longwave perturbations. For low permeability membranes, instability with respect to monotonic finite-wavelength perturbations is characteristic.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 4, pp. 171–173, July–August, 1985.     

Thermal decomposition of tetraalkylammonium iodides

A number of tetramethylammonium (TMA) iodides, including mono-, tri-, and pentaiodide, were synthesized. Thermal decomposition of samples was investigated by simultaneous TG–DSC analysis accompanied by gaseous IR- and mass-spectrometry analyses. Two different reaction pathways have been observed for TMA pentaiodide at different heating rates. At low heating rates (1–5 K min^?1), a gradual mass loss takes place and a stability plateau due to monoiodide formation exists on TG curve. At high heating rates (10, 15 and 7 K min^?1 as the in-between stage), there are only two peaks on DTG curve (instead of three for lower heating rates) and no monoiodide formation is observed as the sample decomposes completely before 350 °C.     

Intellectual power supply and control system on the phasotron of the joint institute for nuclear research laboratory of nuclear problems implemented from one source at different currents in electromagnetic lenses

The intellectual power supply and control system is presented for the group of electromagnetic lenses in the phasotron-beam transport channel supplied from one power supply source. An intellectual power supply and control system is proposed to minimize power consumption upon the redistribution of the lens currents between the main power supply and additional local regulation power supply sources.     

Periodic solutions of a quasilinear wave equation with homogeneous boundary conditions

In this paper, we prove the existence of time-periodic weak solutions for the wave equation with homogeneous boundary conditions. This paper deals with the cases where a nonlinear term has a superlinear and sublinear growth. __________ Translated from Fundamentalnaya i Prikladnaya Matematika, Vol. 12, No. 5, pp. 189–201, 2005.     

The LEPTA diagnostics and control system

The Low Energy Particle Toroidal Accumulator (LEPTA) is expected to provide experiments with intense flux of positronium. The diagnostics and control system of LEPTA consists of PCs and electronic equipment grouped in accordance with their applications. Devices in CAMAC standard, instrumentation and specially designed control cards imbedded in the LEPTA equipment are used.     

Use of infrared spectroscopy for controlling protein concentration in lacrimal fluid and diagnosing corneal diseases

It was shown that changes in the absorption band intensities of peptide groups in infrared spectra of proteins contained in lacrimal fluid can be used for controlling their concentrations and diagnosing corneal diseases.     

On time-periodic solutions of a quasilinear wave equation

Existence and regularization theorems are obtained for generalized solutions of a quasilinear wave equation with variable coefficients and homogeneous Dirichlet boundary conditions. The nonlinear term either exhibits a power growth or satisfies a nonresonance condition.     

Calculations of the thermodynamic properties of dimethylsulfoxide-water solutions on the basis of the cluster solvation model

The thermodynamic functions of dimethylsulfoxide mixtures with water were analyzed over the whole composition range using the cluster solvation model taking into account the distribution of clusters over solvation numbers. The equations of the model were shown to correctly describe the concentration dependences of saturated vapor pressure and excess enthalpy and volume on the assumption of dimethylsulfoxide hydration. The hydration numbers of dimethylsulfoxide and the variance of the distribution of hydrates over stoichiometric numbers were shown to increase as the temperature decreased.