Simultaneous spectrophotometric determination of chromium (VI) and iron (III) in alloys

In this work the possibility of simultaneous spectrophotometric determination of chromium (VI) and iron (III) in alloys with help of the mixed organic reagents (diphenylcarbazide and 1,10-phenanthroline, diphenylcarbazide and sulphosalicylic acid) is studied. We have applied curve fitting method to separate individual signals of chromium (VI) and iron (III) from overlapped absorption spectrum. Peak shape analysis of pure signals of complexes of chromium (VI) with diphenylcarbazide and iron (III) with the 1,10-phenanthroline and sulphosalicylic acid is previously carried out. For adequate application of curve fitting method we chose the optimal empirical models of signals taking into account preliminary information on their shape. Correctness of determination of concentration by means of the offered technique is proved by "added-found" method for a series of mixtures with different ratios of concentration of chromium (VI) and iron (III). It is founded that the error of determination of concentration doesn't exceed 11%

Simultaneous spectrophotometric determination of chromium(VI) and iron (III) by H-point standard addition method

In this work the possibility of simultaneous spectrophotometric determination of chromium (VI) and iron (III) in alloys with help of the mixed organic reagent (diphenylcarbazide and 1,10-phenanthroline) is studied. We have applied Н-point standard addition method to determine concentrations of chromium (VI) and iron (III) from the mixture. The pure signals of complexes of chromium (VI) with diphenylcarbazide and iron (III) with the 1,10-phenanthroline and their calibration plots are previously carried out. We established the possibility of simultaneous determination of chromium (VI) and iron (III) in the different concentration ranges by Н-point standard addition method. Correctness of determination of concentration by means of the offered technique is proved by "added-found" method for a series of mixtures with different ratios of concentration of chromium (VI) and iron (III). It is founded that the error of determination of concentration doesn't exceed 33 %.

Behaviour of the Blazar CTA 102 during two giant outbursts

Blazar CTA 102 underwent exceptional optical and high-energy outbursts in 2012 and 2016-2017. We analyze its behaviour during these events, focusing on polarimetry as a tool that allows us to trace changes in the physical conditions and geometric configuration of the emission source close to the central black hole. We also use Fermi gamma-ray data in conjunction with optical photometry in an effort to localize the origin of the outbursts.AST-1615796 - Boston Universit

Use of virtual mind mapping to organise effective colaboration of students in project activities

Статья посвящена проблеме организации проектной деятельности обучающихся в электронном и дистанционном обучении. Одним из инструментов создания виртуальной среды для эффективного командного взаимодействия обучающихся и достижения поставленных целей является использование интеллект-карт как онлайн-сервисов совместного доступа для решения поставленных задач. В работе рассматриваются основы и необходимые компоненты проектной работы, принципы построения интеллект-карт, возможности и ограничения таких интернет-сервисов.The article is devoted to organization of project activities of students in electronic and distance learning. One of the tools to create a virtual environment for effective team interaction of students and achieve goals of a project is to use mind maps as online services for project task solving. The paper deals with the basics and necessary components of project work, principles of mind maps, possibilities and drawbacks of such Internet services

Temperature sensitivity of soil respiration is dependent on readily decomposable C substrate concentration

International audienceTemperature acclimation of soil organic matter (SOM) decomposition is one of the major uncertainties in predicting soil CO2 efflux by the increase in global mean temperature. A reasonable explanation for an apparent acclimation proposed by Davidson and colleagues (2006) based on Michaelis-Menten kinetics suggests that temperature sensitivity decreases when both maximal activity of respiratory enzymes (Vmax) and half- saturation constant (Ks) cancel each other upon temperature increase. We tested the hypothesis of the canceling effect by the mathematical simulation of the data obtained in the incubation experiments with forest and arable soils. Our data confirm the hypothesis and suggest that concentration of readily decomposable C substrate as glucose equivalent is an important factor controlling temperature sensitivity. The highest temperature sensitivity was observed when C substrate concentration was much lower than Ks. Increase of substrate content to the half-saturation constant resulted in temperature acclimation associated with the canceling effect. Addition of the substrate to the level providing respiration at a maximal rate Vmax leads to the acclimation of the whole microbial community as such. However, growing microbial biomass was more sensitive to the temperature alterations. This study improves our understanding of the instability of temperature sensitivity of soil respiration under field conditions, explaining this phenomenon by changes in concentration of readily decomposable C substrate. It is worth noting that this pattern works regardless of the origin of C substrate: production by SOM decomposition, release into the soil by rhizodeposition, litter fall or drying-rewetting events

The principles of the green economy in the context of agglomeration: Evidence from Big Ekaterinburg

The authors consider an urban agglomeration as a more integral informal economic subject uniting economic interests of its municipalities and expressing interests of the territory which can become a driver of the "green economy" strategy. High level of social and economic development of an agglomeration kernel, and high capabilities related to minimization of environmental risks and multiplying natural capital of the small cities allows synchronization of economic growth, optimal use of natural resources and decreasing decoupling effect. Using Big Ekaterinburg as an example of urban agglomerations the authors have shown that strategic planning documents on the municipal level require cardinal revision in the context of complex development of the territory, "green" economy principles implementation and harmonization of relations among the economy, society, and environment. © 2018 Institute of Physics Publishing. All rights reserved.The authors would like to express their deepest gratitude to the Russian Foundation for Basic Research (RFBR) for the support of the research within the project No. 17-22-07001 "The complex algorithm of culture-based regeneration of minor industrial cities in the context of agglomeration processes in Russia and Europe"

Learning analytics in massive open online courses as a tool for predicting learner performance

Learning analytics in MOOCs can be used to predict learner performance, which is critical as higher education is moving towards adaptive learning. Interdisciplinary methods used in the article allow for interpreting empirical qualitative data on performance in specific types of course assignments to predict learner performance and improve the quality of MOOCs. Learning analytics results make it possible to take the most from the data regarding the ways learners engage with information and their level of skills at entry. The article presents the results of applying the proposed learning analytics algorithm to analyze learner performance in specific MOOCs developed by Ural Federal University and offered through the National Open Education Platform. © 2018, National Research University Higher School of Economics.This study was support- ed by financial assis- tance provided under the Resolution of the Government of the Rus sian Federation No. 211, Contract No. 02. A03.21.0006. Translated from Russian by I. Zhuchkova