Методики измерений показателей состава воздушных сред: разработка и применение

Accurate and reliable measurements of the composition of air environments (workplace air, ambient air, industrial air emissions) form a solid basis for decision making in the area of environmental quality. This article deals with the problem of developing and testing techniques for measuring air quality parameters. The disadvantages of the existing techniques are identified. A methodology for creating appropriate techniques is proposed. Procedures for developing reference materials (RMs) for internal and external quality control of measurement results are described, along with approaches to estimating the metrological characteristics of measurement techniques. The process of applying measurement techniques is specified. It is shown that techniques for measuring air quality parameters may be divided for two basic stages, i. e., the stage of analytical sampling and the stage of measuring the required indicators in this sample. This approach expands the possibilities of developing and certifying such techniques, thereby increasing the reliability of measurement results. Using the developed approach, the authors have successfully developed 12 techniques for measuring air quality parameters and four certified reference materials (CRMs). Works in this direction are continued.Обеспечение достоверности измерений показателей состава воздушных сред (воздуха рабочей зоны, атмосферного воздуха, промышленных выбросов в атмосферу) имеет важное значение для принятия управленческих решений по поддержанию качества окружающей среды. Статья посвящена разработке и применению методик измерений показателей качества воздушных сред. В работе отражены недостатки существующих методик, описана используемая авторами методология создания соответствующих методик, указаны процедуры разработки стандартных образцов, необходимых для проведения внутреннего и внешнего контроля качества результатов измерений, оценивания метрологических характеристик методик, изложена процедура применения методик. Авторы рассматривают возможность разделения методик измерений показателей состава воздушных сред на две стадии: стадию отбора аналитической пробы и стадию измерений содержаний показателей в аналитической пробе, что существенно расширяет возможности разработки и аттестации таких методик и позволяет повысить достоверность информации о качестве измерений. С использованием указанной методологии на данный момент авторами статьи разработано 12 методик измерений показателей состава воздушных сред и 4 стандартных образца утвержденного типа. Работы в данном направлении продолжаются

Electrophysiological Characterization of Uncoupled Mutants of LacY

In this study of the lactose permease of Escherichia coli (LacY), five functionally irreplaceable residues involved specifically in H+ translocation (Arg302 and Glu325) or in the coupling between protonation and sugar binding (Tyr236, Glu269, and His322) were mutated individually or together with mutant Glu325 → Ala. The wild type and each mutant were purified and reconstituted into proteoliposomes, which were then examined using solid-supported-membrane-based electrophysiology. Mutants Glu325 → Ala or Arg302 → Ala, in which H+ symport is abolished, exhibit a weakly electrogenic rapid reaction triggered by sugar binding. The reaction is essentially absent in mutant Tyr236 → Phe, Glu269 → Ala, and His322 → Ala, and each of these mutations blocks the electrogenic reaction observed in the Glu325 → Ala mutant. The findings are consistent with the interpretation that the electrogenic reaction induced by sugar binding is due to rearrangement of charged residues in LacY and that this reaction is blocked by mutation of each member of the Tyr236/Glu269/His322 triad. In addition, further support is provided for the conclusion that deprotonation is rate limiting for downhill lactose/H+ symport

Limit cycles for the Kukles system

This paper investigates the number and distributions of limit\ud cycles for the Kukles system, which also can be regarded as a\ud class of reduced Kukles system under cubic perturbation. Using\ud the techniques of bifurcation theory and qualitative analysis, we\ud have obtained three different distributions of five limit cycles\ud for the considered systems. In the first two distributions, the\ud five limit cycles are all non-small amplitude, which is very\ud different from the previous work