Synthesis Features of Iron Oxide Nanopowders with High Magnetic and Sorption Properties

The magnetic particles of iron oxides are promising materials for the purification of water from ions of heavy metals and radionuclides. Their advantage compared to other sorbents is the ability to extract by applied magnetic field, which greatly simplifies the task of extraction, separation and processing in cleaning technologies. The aim of this work is investigation of temperature and concentration of iron in the solution effect on the phase composition, nanoparticle size and their magnetization. Phase magnetite in the sample increases with increasing temperature and the magnetization decreases slightly with increasing the initial concentration of iron in solution. We found that regardless of the conditions of deposition formed spherical particles whose average size ranges from 7 to 15 nm. The sorptive capacity of the particles is virtually independent of the phase composition and for cobalt is about 18 mg/g. For sorption-based material magnetic particles Fe3O4 recommended to carry out the deposition process at a temperature not lower than 80°C. The concentration of iron in solution must be within 0,15–0,3M. The particles obtained contain in their composition at least 90 wt.% of magnetite phase and are characterized by a magnetization in the range of 65–70 A·m2/kg. Also in the paper is comparing efficiency of extraction and sorptioncapacity for cobalt particles by different phase of magnetite and hematite

Synthesis Features of Iron Oxide Nanopowders with High Magnetic and Sorption Properties

The magnetic particles of iron oxides are promising materials for the purification of water from ions of heavy metals and radionuclides. Their advantage compared to other sorbents is the ability to extract by applied magnetic field, which greatly simplifies the task of extraction, separation and processing in cleaning technologies. The aim of this work is investigation of temperature and concentration of iron in the solution effect on the phase composition, nanoparticle size and their magnetization. Phase magnetite in the sample increases with increasing temperature and the magnetization decreases slightly with increasing the initial concentration of iron in solution. We found that regardless of the conditions of deposition formed spherical particles whose average size ranges from 7 to 15 nm. The sorptive capacity of the particles is virtually independent of the phase composition and for cobalt is about 18 mg/g. For sorption-based material magnetic particles Fe3O4 recommended to carry out the deposition process at a temperature not lower than 80°C. The concentration of iron in solution must be within 0,15–0,3M. The particles obtained contain in their composition at least 90 wt.% of magnetite phase and are characterized by a magnetization in the range of 65–70 A·m2/kg. Also in the paper is comparing efficiency of extraction and sorptioncapacity for cobalt particles by different phase of magnetite and hematite

Optimal Exercise Strategies for Operational Risk Insurance via Multiple Stopping Times

In this paper we demonstrate how to develop analytic closed form solutions to optimal multiple stopping time problems arising in the setting in which the value function acts on a compound process that is modified by the actions taken at the stopping times. This class of problem is particularly relevant in insurance and risk management settings and we demonstrate this on an important application domain based on insurance strategies in Operational Risk management for financial institutions. In this area of risk management the most prevalent class of loss process models is the Loss Distribution Approach (LDA) framework which involves modelling annual losses via a compound process. Given an LDA model framework, we consider Operational Risk insurance products that mitigate the risk for such loss processes and may reduce capital requirements. In particular, we consider insurance products that grant the policy holder the right to insure k of its annual Operational losses in a horizon of T years. We consider two insurance product structures and two general model settings, the first are families of relevant LDA loss models that we can obtain closed form optimal stopping rules for under each generic insurance mitigation structure and then secondly classes of LDA models for which we can develop closed form approximations of the optimal stopping rules. In particular, for losses following a compound Poisson process with jump size given by an Inverse-Gaussian distribution and two generic types of insurance mitigation, we are able to derive analytic expressions for the loss process modified by the insurance application, as well as closed form solutions for the optimal multiple stopping rules in discrete time (annually). When the combination of insurance mitigation and jump size distribution does not lead to tractable stopping rules we develop a principled class of closed form approximations to the optimal decision rule. These approximations are developed based on a class of orthogonal Askey polynomial series basis expansion representations of the annual loss compound process distribution and functions of this annual loss

Dithiophosphoric and dithiophosphonic acids and their derivatives on the basis of thymol: Synthesis and antimicrobial activity

Biologically active dithiophosphoric and dithiophosphonic acids, their ammonium salts as well as S-silyl and S-plumbyl derivatives were prepared by the reaction of thymol with tetraphosphorus decasulfide and 2,4-diaryl 1,3,2,4-dithiadiphosphetane-2,4-disulfides. © 2013 Copyright Taylor and Francis Group, LLC

Impurity breakdown and terahertz luminescence in n-GaN epilayers under external electric field

We report on the observation and experimental studies of impurity breakdown and terahertz luminescence in n-GaN epilayers under external electric field. The terahertz electroluminescence is observed in a wide range of doping levels (at noncompensated donor density from 4.5×10[sup 16] to 3.4×10[sup 18] cm[sup −3]). Spectra of terahertz luminescence and photoconductivity are studied by means of Fourier transform spectrometry. Distinctive features of the spectra can be assigned to intracenter electron transitions between excited and ground states of silicon and oxygen donors and to hot electron transitions to the donor states.Peer reviewe

Исследование сорбции лекарственных веществ перфтораном

Objective: to estimate the perfluorane adsorption capacity of the drugs belonging to different pharmacological groups. Materials and methods. The binding of perfluorane to 50 drugs at concentrations of 12.5 to 100 ^M was studied in vitro using equilibrium dialysis. Results. Interactions of ligands with the particles of perfluorane emulsion were found to be of three types. Type 1 substances were characterized by negative affinity to perfluorane; type 2 ligands acted indifferently with the emulsion; type 3 compounds were reversibly adsorbed with the particles of the blood substitute by the affinity constants ( Kaff) of 104 M-1. Conclusion. The perfluorane adsorption capacity is ambiguous and seems to depend on the properties of ligands. Type 3 interactions, which may lead to an increase in blood adsorption capacity and change in the pharmacokinet-ics of drugs used in combination with perfluorane, appear to be the most important. Key words: perfluorane, binding, drugs, drug interactions.Цель исследования — оценка сорбционной способности перфторана в отношении лекарственных веществ, принадлежащих к различным фармакологическим группам. Материалы и методы. В экспериментах in vitro с помощью метода равновесного диализа исследована степень связывания с перфтораном 50 лекарственных веществ, взятых в концентрациях от 12,5 до 100 мкМ. Результаты. Выявлены три типа взаимодействия лигандов с частицами эмульсии перфторана. Вещества первого типа характеризовались негативной тропностью к перфторану; ли-ганды второго типа вели себя индифферентно по отношению к эмульсии; соединения третьего типа обратимо сорбировались частицами кровезаменителя с константами взаимодействия Kag порядка 104 М-1. Заключение. Сорбционная активность перфторана в отношении лекарственных веществ проявляется неоднозначно и, по-видимому, зависит от свойств лигандов. Наиболее значимыми представляются взаимодействия третьего типа, результатом которых может стать увеличение сорбционной емкости крови и изменение фармакокинетики лекарств, используемых совместно с перфтораном. Ключевые слова: перфторан, связывание, лекарственные вещества, лекарственные взаимодействия