Construction of calibration curves for methods of analyzing environmental samples

A formalized procedure is proposed for constructing calibration curves and evaluating their error in methods developed for the quantitative chemical analysis of environmental samples. The procedure satisfies the requirements of government metrological standards. Examples from practice are given to illustrate the construction of linear and nonlinear calibration curves and the corresponding confidence intervals. Translated from Izmeritel'naya Tekhnika, No. 3, pp. 64–68, March, 1998.     

Enhancement of the luminescence yield of Er3+ ions at λ=1.54μmm in ZBLAN glass additionally doped with Eu3+ and Tb3+ and pumped in the range λ=0.975 μm

In fluorozirconate glasses the luminescence yield of Er ₂ ³⁺ ions on the ⁴ I _13/2–⁴ I _15/2 lasing transition was increased more than tenfold by additional doping with Yb³⁺ and Tb³⁺ ions. Pis’ma Zh. Tekh. Fiz. 24, 81–85 (May 12, 1998)     

Improving the testability of switched-capacitor filters

A design-for-test methodology for SC filters is presented, based on an architecture using some additional circuitry and providing extra capabilities for both off- and on-line tests. The approach uses a comparison (voting) mechanism to indicate whether or not two copies of a filter element (a biquad, for instance) have a similar response during their actual operation. The design and implementation of a few filter examples are included to assess the potential usefulness of this new approach.     

Investigation of the behavior of platinum-group elements during vitrification of model high-level wastes in application to an induction melter with a cold crucible

Conclusions In the process of vitrification of high-level wastes the platinum-group elements form at the calcination stage phases which have a limited solubility in the glass melts. If the dissolved part of the platinum-group elements, which at 1200–1300°C does not form more than 30% of their total concentration in the melt [3], is neglected, then apparently it can be assumed that the behavior of the dispersed particles of the platinum-group elements is determined by their thermodynamic stability, interaction with one another, and sedimentation, and the melts of the phosphate and borosilicate glasses play the role of an inert medium. Ruthenium dioxide and the solid solutions based on it, which contain up to 1.5% Ru, Rh, and Pd, are stable up to 1500°C. In the temperature range 1050–1200°C rhodium oxide and the solid solutions based on it, decompose and form metallic rhodium. Metallic palladium apparently forms at 800–900°C. In ceramic melters the temperature of the glass melt is equal to the temperature of the dispersed particles and the composition of the heterogeneous phase based on the platinum-group elements will be determined by the temperature chosen for performing the vitrification process. Induction heating results in local overheating of the electrically conducting dispersed particles by the high-frequency field and, irrespective of the process temperature, in the melt it forms alloys based on platinum-group elements. In summary, the local temperature of the dispersed particles will determine their phase composition, their density, and ultimately their rate of sedimentation and accumulation at the bottom of the melters. State Science Center of the Russian Federation A. A. Bochvar All-Union Scientific-Research Institute of Standardization in Machine Engineering. Translated from Atomnaya énergiya, Vol. 79, No. 1, pp. 34–37, July, 1995.     

Ohmic contact and transport properties of II–VI Green/Blue laser diodes

The employment of the Zn(Se,Te) pseudo-graded contacting scheme to p-type ZnSe-based alloys contributes directly to the recent demonstration of room temperature continuous-wave operation of II– VI green-blue laser diodes. Contact ohmicity is maintained down to cryogenic temperatures which enabled the investigation of electrical transport properties associated with the p-type nitrogen-doped ZnSe, Zn(S,Se), and (Zn,Mg)(S,Se). The observation of both persistent photoconductivity and a metastable population of holes which are in thermodynamic equilibrium with hydrogenic acceptors having reduced activation energy suggests the presence of a DX-like behavior for holes in p-type (Zn,Mg)(S,Se).     

Effect of neutron radiation on the structure and properties of uranium monosilicide

A. A. Bochvar All-Union Scientific-Research Institute of Standardization in Machine Engineering. Moscow Engineering Physics Institute. Translated from Atomnaya énergiya, Vol. 77, No. 2, pp. 123–129, August, 1994.     

Electrocortical desynchronization after microinfusion of kainic acid into the locus coeruleus in rats

CD-1, a genetically-engineered CHO cell line, was cultivated with a Biosilon microcarrier culture system. We successfully cultivated CD-1 cells to a very high density (over 1 x 10(7) cells/ml). Prourokinase was stably secreted at about 180 IU/10(6) cells/24 h. Experiments showed that CD-1 cells growing on Biosilon microcarriers were able to spontaneously release from the microcarriers, then reattach and proliferate on fresh microcarriers. This makes it very easy to scale up production. The microcarriers could be reused several times without affecting adhesion, proliferation and prourokinase secretion. With CM-PECC membrane radial flow chromatography and MPG chromatography, the prourokinase in conditioned medium could be purified to a specific activity of 1 x 10(5) IU/mg of protein. The purification factor was about 600 fold, and approximately 90% of the biological activity was recovered.     

Experimental study of the interaction range and association rate of surface-attached cadherin 11

We describe a method allowing quantitative determination of the interaction range and association rate of individual surface-attached molecules. Spherical beads (1.4 micro(m) radius) were coated with recombinant outer domains of the newly described classical type II cadherin 11, a cell adhesion molecule. Beads were driven along cadherin-coated surfaces with a hydrodynamic force of approximately 1 pN, i.e., much less than the mechanical strength of many ligand-receptor bonds. Spheres displayed periods of slow motion interspersed with arrests of various duration. Particle position was monitored with 50 Hz frequency and 0.025 micro(m) accuracy. Nearly 1 million positions were recorded and processed. Comparison between experimental and computer-simulated trajectories suggested that velocity fluctuations might be related quantitatively to Brownian motion perpendicular to the surface. The expected amplitude of this motion was of order of 100 nm. Theoretical analysis of the relationship between sphere acceleration and velocity allowed simultaneous determination of the wall shear rate and van der Waals attraction between spheres and surface. The Hamaker constant was estimated at 2.9 x 10(-23) J. The frequency of bond formation was then determined as a function of sphere velocity. Experimental data were consistent with the view that the rate of association between a pair of adhesion molecules was approximately 1.2 x 10(-3) s-1 and the interaction range was approximately 10 nm. It is concluded that the presented methodology allows sensitive measurement of sphere-to-surface interactions (with approximately 10 fN sensitivity) as well as the effective range and rate of bond formation between individual adhesion molecules.