Quantum cascade laser-based sensor for detection of exhaled and biogenic nitric oxide

A real-time, in situ CO sensor using 2.3 μm DFB diode laser absorption, with calibration-free wavelength-modulation-spectroscopy, was demonstrated for continuous monitoring in the boiler exhaust of a pulverized-coal-fired power plant up to temperatures of 700 K. The sensor was similar to a design demonstrated earlier in laboratory conditions, now refined to accommodate the harsh conditions of utility boilers. Measurements were performed across a 3 m path in the particulate-laden economizer exhaust of the coal-fired boiler. A 0.6 ppm detection limit with 1 s averaging was estimated from the results of a continuous 7-h-long measurement with varied excess air levels. The measured CO concentration exhibited expected inverse trends with the excess O₂ concentration, which was varied between 1 and 3 %. Measured CO concentrations ranged between 6 and 200 ppm; evaluation of the data suggested a dynamic range from 6 to 10,000 ppm based on a minimum signal-to-noise ratio of ten and maximum absorbance of one. This field demonstration of a 2.3 μm laser absorption sensor for CO showed great potential for real-time combustion exhaust monitoring and control of practical combustion systems.     

New possibilities in crystal morphology

Two new morphological phenomena are predicted in crystals: meniscus disappearance and meniscus fixation. Helium crystals are the most convenient objects for their observation. The text was submitted by the authors in English.     

High-field low-frequency spin dynamics

The theory of exchange symmetry of spin ordered states is extended to the case of high magnetic fields. The low frequency spin dynamics equation for the quasi-goldstone mode is derived for two cases of collinear and noncollinear antiferromagnets. A new relation between the static and dynamic characteristics is found. The text was submitted by the authors in English.     

On the complete controllability of hybrid differential-difference systems

For time-independent hybrid differential-difference linear systems, we study the complete controllability problem, that is, the problem of complete quieting of such systems. We derive necessary and sufficient parametric conditions for strict complete controllability in various classes of admissible controls. In the case of simplest basic classes, we prove necessary and sufficient parametric conditions for the weak complete controllability and suggest a method for constructing the desired controls quieting the system by using methods of the theory of entire functions of finite degree. We discuss problems of estimating the duration of the transient process. As an example, we consider the strict complete controllability problem in various classes of functions for the case of a system of scalar differential-difference equations.     

Picosecond time of spontaneous emission in plasmonic patch nanoantennas

Level anticrossing (LAC) spectroscopy has been demonstrated on a family of uniaxially oriented spin color centers with S = 3/2 in the ground and excited states in hexagonal 4H-, 6H-, and rhombic 15R-SiC polytypes. It has been shown that these centers exhibit unique characteristics such as optical spin alignment up to the temperatures of 250°C. A sharp variation of the IR photoluminescence intensity in the vicinity of LAC with the record contrast has been observed, which can be used for a purely all-optical sensing of the magnetic field and temperature without applying radiofrequency field. A distinctive feature of the LAC signal is weak dependence on the direction of the magnetic field that allows one to monitor the LAC signals in the nonoriented systems, such as powder of SiC nanocrystals.     

Tin U ?-centers formed through nuclear transformations in vitreous arsenic sulfides and selenides

It has been shown using the M?ssbauer emission spectroscopy for isotope ¹¹⁹Sn that impurity tin atoms formed after the radioactive decay of ¹¹⁹Sb atoms in vitreous arsenic sulfide and selenide are localized in arsenic sites and play the role of two-electron centers with negative correlation energy. The most of daughter ^119m Sn atoms formed after the radioactive decay of the ^119m Te atoms in glasses are arranged in chalcogen sites; they are electrically inactive. Considerable recoil energy of daughter atoms in the case of decay of ^119m Te leads to the appearance of ^119m Sn atoms shifted from chalcogen sites.     

Identification of two-electron centers with a negative correlation energy in high-temperature superconductors

On the basis of comparison of experimental and calculated parameters of the electric field gradient tensor, it is shown that holes in the YBa₂Cu₃O₇ and YBa₂Cu₄O₈ lattices are localized on oxygen ions in the CuO₃ chains. These results agree with the model suggesting that the mechanism responsible for the high-temperature superconductivity in the YBa₂Cu₃O₇ and YBa₂Cu₄O₈ compounds is the interaction of electrons with two-atom two-electron copper centers with a negative correlation energy.     

On deviations and defects of meromorphic functions of finite lower order

We obtain estimates for the sum of deviations and sum of defects to power 1/2 in terms of the Valiron defect of the derivative at zero. In particular, the Fuchs hypothesis (1958) is verified.     

Synthesis and characterization of bismuth-containing oxyfluoroniobate glasses

New glasses are prepared in the MnNbOF₅-BaF₂-BiF₃ system. The thermal parameters of these glasses are analyzed as influenced by bismuth trifluoride. IR and Raman spectroscopy shows that the glass structures are built of Nb(O, F)₆ polyhedra, which are linked by oxygen bridges to form glass nets via. A medium-order order region in the glass includes fluoroniobate polyhedra not linked directly to bismuth trifluoride polyhedra. A Ba_0.55Bi_0.45F_2.45 crystalline phase is discovered at 320°C in a glass of composition 20MnNbOF₅-40BaF₂-40BiF₃.