Cylindrical irregularity on a half-space and equivalent radiators

Analytic expressions are constructed for the near field of a filament of electric dipoles placed near the edge of a cylindrical surface projecting from a half-space with finite conductivity. Equivalent dipole moments of radiators taking into account the effect of irregularity on the far field are obtained under the assumption of small transverse dimensions of the irregularity as compared to the wavelength.     

Mechanical Activation of Diopside in CO2

The mechanical activation (MA) of diopside in a controlled CO₂ atmosphere was studied using different grinding facilities. The results demonstrate that diopside may sorb CO₂ by two mechanisms, depending on the nature of the MA process. If grinding is not accompanied by structure breakdown, the sorption process is similar to that reported for metal oxides, and the adsorbate consists of undistorted CO₃ ^2- groups. If the MA process leads to diopside amorphization, CO₂ is sorbed in the form of distorted carbonate groups, and the IR spectrum contains a split absorption band (1433 and 1522 cm^–1) similar to the CO₃ ^2- band in the spectra of carbonate-containing silicate glasses. After ball milling in an AL-1000 mechanical activator in CO₂ for 580 min, diopside contains up to 15 wt % CO₂. Subsequent heating ensures partial or complete removal of the carbonate. Acid treatment of diopside after MA in CO₂ leads to decomposition of the carbonate and almost complete leaching of the Ca and Mg cations.     

Salvaging the Lepse tender

The basic problems of salvaging the Lepse tender of the Murmansk Shipping Company are examined. The main sources of nuclear and radiation danger are determined, the characteristics of their structural features which prevent the appearance of a spontaneous reaction are given, the consequences of long-time storage of spent fuel assemblies are described, and different variants of their removal from storage are proposed. A computational validation of the required degree of subcriticality of the spent nculear fuel and an assessment of possible accidents, including accidents accompanying sinking of the vessel at its permanent base, are given. The salvaging steps are described, the bottlenecks are determined, schemes for handling the vessel are validated, and the radiation load on the workers is estimated. __________ Translated from Atomnaya énergiya, Vol. 101, No. 1, pp. 65–69, July, 2006.     

Adaptive Identification of Nonstationary Technological Processes with Markov Parameters in Stochastic Control Problems

An adaptive approach to the identification of nonstationary technological processes with Markov parameters is put forward, which relies on the use of the local identification in the problems of stochastic control. A two-loop system of adaptive control with a group of experts (decision-makers) in the outer loop is considered, which accounts for specific features of the applied field of investigations.     

Electrostatic axially harmonic orbital trapping: a high-performance technique of mass analysis

This work describes a new type of mass analyzer which employs trapping in an electrostatic field. The potential distribution of the field can be represented as a combination of quadrupole and logarithmic potentials. In the absence of any magnetic or rf fields, ion stability is achieved only due to ions orbiting around an axial electrode. Orbiting ions also perform harmonic oscillations along the electrode with frequency proportional to (m/z)-1/2. These oscillations are detected using image current detection and are transformed into mass spectra using fast FT, similarly to FTICR. Practical aspects of the trap design are presented. High-mass resolution up to 150,000 for ions produced by laser ablation has been demonstrated, along with high-energy acceptance and wide mass range.     

Fiber-optic voltage sensor based on a Bi12TiO20 crystal

A fiber-optic voltage sensor based on the longitudinal Pockels effect in a Bi(12)TiO(20) crystal is described. The use of a special backreflecting prism as a phase-retarding element is shown to improve the sensitivity and temperature stability of the sensor. A comparison between the temperature properties of the glass backreflecting prism and that of a quarter-wave plate is derived. The sensor demonstrates temperature stability of +/-1.5% from -20 degrees C to 60 degrees C and sensitivity of 0.145% per 1 V(rms) at 850 nm without the use of an additional temperature control channel.     

Growth on urea can trigger death and peroxidation of the cyanobacterium Synechococcus sp. strain PCC 7002

Laboratory conditions have been identified that cause the rapid death of cultures of cyanobacteria producing urease. Once the death phase had initiated in the stationary growth phase, cells were rapidly bleached of all pigmentation. Null mutations in the ureC gene, encoding the alpha subunit of urease, were constructed, and these mutants were no longer sensitive to growth in the presence of urea. High levels of peroxides, including lipid peroxides, were detected in the bleaching cells. Exogenously added polyunsaturated fatty acids triggered a similar death response. Vitamin E suppressed the formation of peroxides and delayed the onset of cell bleaching. The results suggest that these cyanobacterial cells undergo a metabolic imbalance that ultimately leads to oxidative stress and lipid peroxide formation. These observations may provide insights into the mechanism of sudden cyanobacterial bloom disappearance in nature.     

Functional analysis of the DNA-packaging/terminase protein gp17 from bacteriophage T4

In bacteriophage T4, the terminase complex constituted by the large subunit gp17 (69 kDa) and the small subunit gp16 (18 kDa) is a critical component of the ATP-driven DNA-packaging pump that translocates DNA into an empty capsid shell. Evidence suggests that the large subunit gp17 is the critical component and consists of a number of the functional sites required for DNA-packaging. It exhibits a terminase activity that introduces non-specific cuts into DNA, a portal vertex binding site that allows linkage of cleaved DNA to an empty prohead, an in vitro DNA-packaging activity, and an ATPase activity. In addition, a consensus metal-binding motif and two consensus ATP-binding sites have been identified by sequence analysis. In order to understand the mechanism of action of the multifunctional gp17, we developed an expression-based selection strategy to select for mutants that are defective in terminase function. Characterization of one of the mutants revealed a unique phenotype in which a single H436R mutation resulted in a dramatic loss of both the terminase and the DNA-packaging functions. Indeed, in vivo substitution of H436 with any of the 12 amino acids for which a suppressor is available was lethal to T4 development. According to one hypothesis, H436 is part of a metal-binding motif that is essential for gp17 function. This hypothesis was tested by introducing mutations at each of the three histidine pairs, the H382-X2-H385 pair, the H411-X2-H414 pair and the H430-X5-H436 pair, which constitute the histidine-rich region near the C terminus of gp17. A mutation at either the H411 pair or the H430 pair resulted in a loss of gp17 function, whereas a mutation at the H382 pair had no effect. In addition to the putative metal-binding motif, substitutions at residue K166 within the putative N terminus-proximal ATP-binding site also resulted in a loss of gp17 function. We propose that a metal-binding motif involving the histidine residues within the sequence H411-X2-H414-X15-H430-X5-H436 is essential for gp17 function. Metal-terminase interactions may be required for structural alignment and stabilization of functional sites in phage T4 terminase and other double-stranded DNA phage terminases.     

Dynamics of the marital structure with respect to the nationality and birthplace of spouses in a modern urbanized Siberian population (as exemplified by Tomsk)

To analyze a population's marital structure with respect to the ethnicity and birthplace of the spouses and to estimate the indices of endogamy, migration, and marriage assortativeness, the records of marriages in Tomsk during two periods of time (1970-1972 and 1985-1990) were studied. The parameters of the population-genetic and demographic structure proved to change during the studied period: the endogamy index and the indices of marriage assortativeness increased, and the migration index decreased. These data suggest that the genetic structure of the Tomsk urbanized population stabilized with time and that the intrapopulation subdivision decreased (a tendency for panmixia).