Phase formation,structure and properties of light-weight aluminosilicate proppants based on clay-diabase and clay-granite binary mixes

One of the drawbacks of fusible clays is the narrow sintering interval due to a sharp increase in the amount of iron-silicate melt at a temperature of 1000–1100 °C, which hardens in the form of a glass phase upon cooling. This leads to a relatively low mechanical strength of the calcined samples and causes the danger of melting the granular material surface from such clays during the firing process. To increase the strength of samples of fusible clays, the influence of diabase and granitoid rocks was considered. It was found that the strengthening effect of diabase and granitoid rock additives in an amount of 20–50% in a mixture with fusible clay is due to an increase of total content of the crystalline phase (mullite, cristobalite and residual quartz) from 18–20% in clays without additives to 22–28 % - in mixtures with diabase and to 28–34% - with granitoid additives) at a temperature of 1050–1100 °C. This increase is due to the activation of synthesis processes of secondary mullite and crystallization from alkali-rich feldspar melt of amorphous silica, released from the structure of clay minerals. The established influence of the igneous rocks used made it possible to develop compositions and propose process flow sheet for producing aluminosilicate proppants based on fusible clays. The use of granitoid and diabase rocks in an amount of 20–70% with fusible clays produces lightweight aluminosilicate proppants with bulk density of 1.40–1.46 g/cm³ at temperature range of 1050–1100 °C, which can endure destructive pressures up to 34.5–52 MPa.     

The X<Superscript>+</Superscript> trion in a system with spatial separation of the charge carriers

A system composed of two heavy holes located in a two-dimensional (2D) quantum well (QW) and bound via mediation of an electron in a neighboring 2D QW is considered. Using a simple qualitative trial wave function, the ground-state energy of this kind of X⁺ trion is determined in the infinite-hole-mass approximation as a function of the QW spacing. Coordinate dependence of the effective potential binding the holes to each other is calculated for different values of QW spacing. In the adiabatic approximation, a set of dependences describing the X⁺ trion binding energy as a function of the electron mass to the hole mass ratio is obtained. Several estimates for the trion binding energy in GaAs-and ZnSe-based double-QW heterostructures are given.     

Radiation consequences of seawater contamination during floating storage of reactor-compartment units from salvaged nuclear-powered submarines

The storage time before salvaging of decommissioned nuclear-powered submarines and the floating storage time of reactor units from salvaged submarines can total decades. During this time, radioactive contamination of seawater occurs as a result of the corrosion of the pressure hull in the region of the reactor system and rupturing of the pressure hull - as a result of corrosion of the components of the reactor system. A computational analysis shows that under standard storage conditions the specific activity of water is 10⁵–10⁶ times lower than the intervention level. In the case when the hull and the reactor system are destroyed even with remaining fuel, the specific activity of the sea water near the point of sinking also does not exceed the intervention level because of the slow emission of fission products and transuranium nuclides.Translated from Atomnaya Énergiya, Vol. 97, No. 3, pp. 210–218, September, 2004.     

Three-dimensional structure of the cloud of a carbon pellet evaporated in plasma of Wendelstein 7-AS stellarator

Experiments performed on a Wendelstein 7-AS stellarator revealed asymmetry of the cloud of an ablating carbon pellet. The cloud is elongated in the direction of large radius toward stronger fields, that is, opposite to the direction expected due to the toroidal drift. In order to study the effect in more detail, the three-dimensional structure of the cloud was analyzed by computer tomography. The results confirmed asymmetry of the cloud. This asymmetry is related to a drift flow existing in the plasma and directed along large radius toward stronger fields. The drift velocity is numerically estimated at ～300 m/s.     

Microsomal and photochemical oxidation of aflatoxin B1

The UV irradiation (lambda = 362 nm) of aflatoxin B1 (AfB1) dissolved in water resulted in the formation of an oxidized product. The process was not inhibited by ionol, a routine inhibitor of the radical processes. The oxidized product was not found in the system where AfB1 was metabolized by the 3-methylcholanthrene-activated rat liver microsomes. It is suggested that the product is identical with 2,3-dihydrodiol of AfB1.     

Hemodynamic structure of antiorthostatic reactions: relationship of mechanical activity of the heart and arterial pressure

This paper is an update on the issue of dental student debt and provides additional data and an exploration of continued trends which were outlined by Douglass and Fein in the 1995 IOM study of The Future of Dental Education. Dental school tuitions have continued to increase at rates at or above the consumer price index. These tuition bills are increasingly being met by debt financing on the part of the students. These trends are described and then related to recent data on the future plans of dental school seniors. The second part of the paper will provide new updated date on dentists' incomes and analyze the trend in dental fees versus the consumer price index. The final section provides a summary of pay back mechanisms currently being offered to students.     

Use of liquid sealants to protect still-waste-containing tanks-settling basins from corrosion

Translated from Khimicheskoe i Neftyanoe Mashinostroenie, No. 10, pp. 29–31, October, 1992.     

Measurement of metal nanolayers optical parameters using surface plasmon resonance method

The results of experimental definition of optical parameters of silver nanolayers by the method of surface plasmon resonance (SPR) are described. The goniometric installation for measurement of angular dependences of reflection of light by layered nanosructures at the attenuated internal reflection (angular spectrum of reflection) is designed. Calculation of optical parameters of nanolayers is executed taking into account the form of a curve of tin angular spectrum of reflection. The text was submitted by the authors in English.     

Heat transfer in YBaCuO thin film/sapphire substrate system

The thermal boundary resistance at the YBaCuO thin film/Al₂O₃ substrate interface was investigated. The transparency for thermal phonons incident on the interface as well as for phonons moving from the substrate was determined. We have measured a transient voltage response of current-biased films to continuously modulated radiation. The observed knee in the modulation frequency dependence of the response reflects the crossover from the diffusion regime to the contact resistance regime of the heat transfer across the interface. The values of transparency were independently deduced both from the phonon escape time and from the time of phonon return to the film which were identified with peculiarities in the frequency dependence. The results are much more consistent with the acoustic mismatch theory than the diffuse mismatch model.We are grateful to A. Elantev for helpful discussion. We acknowledge the financial support of the Russian Scientific Council on the HTS problem (Project No. 90462).