Using high resolution and dynamic reaction cell for the improvement of the sensitivity of direct silicon determination in uranium materials by inductively coupled plasma mass spectrometry

The paper describes solving the problem of direct silicon determination at low levels in uranium materials, caused by the spectral interferences of polyatomic ions and the high value of blank levels, using inductively coupled plasma mass spectrometry (ICP MS). To overcome the interference problem, two primary techniques have been applied: double focusing high-resolution ICP MS and dynamic reaction cell (DRC) filled with highly reactive ammonia gas. All measurements were performed at high resolution (m/Δm = 4000) on an Element-2 mass spectrometer and pressurized mode of a dynamic reaction cell on an Elan DRC II mass spectrometer. The ways to reducing background levels are investigated. The effects of operating conditions, such as plasma parameters, DRC system original parameters, and uranium matrix influence on the analytical signals of silicon at m/z = 28 have been observed for different mass spectrometer types. The detection limits and the random error characteristics (relative standard deviation) of silicon determination in uranium materials were estimated. © 2013 Pleiades Publishing, Ltd

Validation of a face image assessment technology to study the dynamics of human functional states in the EEG resting-state paradigm

The article presents the results of a study aimed at finding covariates to account for the activity of implicit cognitive processes in conditions of functional rest of the subjects and during them being presented their own or someone else’s face in a joint analysis of EEG experiment data. The proposed approach is based on the analysis of the dynamics of the facial muscles of the subject recorded on video. The pilot study involved 18 healthy volunteers. In the experiment, the subjects were sitting in front of a computer screen and performed the following task: sequentially closed their eyes (three trials of 2 minutes each) and opened them (three trials of the same duration between periods of closed eyes) when the screen was either empty or when it was showing a video recording of their own face or the face of an unfamiliar person of the same gender as the participant. EEG, ECG and a video of the face were recorded for all subjects. In the work a separate subtask of the study was also addressed: validating a technique for assessing the dynamics of the subjects’ facial muscle activity using the recorded videos of the “eyes open” trials to obtain covariates that can be included in subsequent processing along with EEG correlates in neurocognitive experiments with a paradigm that does not involve the performance of active cognitive tasks (“resting-state conditions”). It was shown that the subject’s gender, stimulus type (screen empty or showing own/other face), trial number are accompanied by differences in facial activity and can be used as study-specific covariates. It was concluded that the analysis of the dynamics of facial activity based on video recording of “eyes open” trials can be used as an additional method in neurocognitive research to study implicit cognitive processes associated with the perception of oneself and other, in the functional rest paradigm

РАЗРАБОТКА КОМПЛЕКСА МАСС-СПЕКТРОМЕТРИЧЕСКИХ С ИНДУКТИВНО СВЯЗАННОЙ ПЛАЗМОЙ МЕТОДИК ОПРЕДЕЛЕНИЯ СОДЕРЖАНИЯ ИЗОТОПА ТЕХНЕЦИЙ-99 В УРАНОВЫХ МАТЕРИАЛАХ

The methods for the quantitative determination of technetium isotope (99Tc) in uranium materials based on inductively coupled plasma mass-spectrometry are described. The results of the investigation of uranium matrix effect on the analytical signal of 99Tc for two mass-spectrometer models are presented. Different approaches for the quantification of 99Tc in uranium materials are investigated including direct analysis and analysis with preliminary uranium separation. The methods for the quantification of 99Tc consisting of chromatographic separation of uranium and 99Tc using UTEVA and TEVA resins with consequent ICP-MS detection were developed. The detection limits of the developed methods are within the range of 0.0006 to 0.02 ng/g U. The choice of optimum conditions for quantitative determination of 99Tc by direct ICP-MS analysis allowed avoiding «tough» ICP-MS operating conditions which consist in high forward power equal to 1600 W. The developed methods require much less time and effort compared to radiometry methods. The introduction of the developed methods allow improving the existing standards for the quality control of the uranium materials in nuclear industry.Keywords: Inductively coupled plasma mass-spectrometry, technetium isotope, uranium fluorides, uranium oxides, chromatographic separation(Russian)DOI: http://dx.doi.org/10.15826/analitika.2013.17.4.005S.L. Ivanov1, N.V. Kuzmina1, A.Yu. Leykin2, A.V. Prosviryakova1, A.V. Saprygin1,3 1Open Joint Stock Company «Ural Electochemical Integrated Plant (JSC «UEIP»), Novouralsk, Russian Federation2Moscow representative office INTERTECH Corporation, Moscow, Russian Federation3FSAEI HPE «Ural Federal University named after the first President of Russia B.N. Yeltsin», Ekaterinburg, Russian FederationОписан комплекс методик определения содержания изотопа технеций-99 (99Тс) в урановых материалах, основанный на методе масс-спектрометрии с индуктивно связанной плазмой. Приведены результаты исследования матричного влияния урана на аналитический сигнал 99Тс для двух моделей масс-спектрометров. Исследованы возможности метода для определения содержания 99Тс в различных вариантах: с предварительным отделением урана и прямого анализа. Разработанные масс-спектрометрические методики, основанные на экстракционно-хроматографическом разделении урана и 99Тс на смолах UTEVA и TEVA (Eichrom Technologies), отличаются низкими пределами обнаружения (0.0006-0.02 нг/г). Предлагаемые условия прямого масс-спектрометрического определения содержания 99Тс позволяют отказаться от «жестких» условий работы масс-спектрометров, требующих установления высокой мощности высокочастотного генератора (1600 Вт). Основными достоинствами разработанного комплекса являются значительное сокращение длительности и трудоемкости выполнения анализа по сравнению с радиометрическими методиками. Внедрение разработанных методик позволит усовершенствовать комплекс методик, используемых в системе контроля качества урановых материалов, действующих на предприятиях атомной отрасли.Ключевые слова:масс-спектрометрия с индуктивно связанной плазмой, изотоп технеций-99, фториды урана, оксиды урана, экстракционно-хроматографическое разделениеDOI: http://dx.doi.org/10.15826/analitika.2013.17.4.00

EEG Correlates of Trait and Mathematical Anxiety during Lexical and Numerical Error-Recognition Tasks.

EEG correlates of mathematical and trait anxiety level were studied in 52 healthy Russian-speakers during execution of error-recognition tasks with lexical, arithmetic and algebraic conditions. Event-related spectral perturbations were used as a measure of brain activity. The ERSP plots revealed alpha/beta desynchronizations within a 500-3000 ms interval after task onset and slow-wave synchronization within an interval of 150-350 ms. Amplitudes of these intervals reflected the accuracy of error recognition, and were differently associated with the three conditions. The correlates of anxiety were found in theta (4-8 Hz) and beta2 (16-20 Hz) frequency bands. In theta band the effects of mathematical anxiety were stronger expressed inlexical, than in arithmetic and algebraic condition. The mathematicalanxiety effects in theta band were associated with differences between anterior and posterior cortical areas, whereas the effects of trait anxiety were associated with inter-hemispherical differences. In beta1 and beta2 bands effects of trait and mathematical anxiety were directed oppositely. The trait anxiety was associated with increase of amplitude of desynchronization, whereas the mathematical anxiety was associated with decrease of this amplitude. The effect of mathematical anxiety in beta2 band was insignificant for lexical condition but was the strongest in algebraic condition. EEG correlates of anxiety in theta band could be interpreted as indexes of task emotionality, whereas the reaction in beta2 band is related to tension of intellectual resources

Development of a neural network for diagnosing the risk of depression according to the experimental data of the stop signal paradigm

These days, the ability to predict the result of the development of the system is the guarantee of the successful functioning of the system. Improving the quality and volume of information, complicating its presentation, the need to detect hidden connections makes it ineffective, and most often impossible, to use classical statistical forecasting methods. Among the various forecasting methods, methods based on the use of artificial neural networks occupy a special place. The main objective of our work is to create a neural network that predicts the risk of depression in a person using data obtained using a motor control performance testing system. The stop-signal paradigm (SSP) is an experimental technique to assess a person’s ability to activate deliberate movements or inhibit movements that have become inadequate to external conditions. In modern medicine, the SSP is most commonly used to diagnose movement disorders such as Parkinson’s disease or the effects of stroke. We hypothesized that SSP could serve as a basis for detecting the risk of affective diseases, including depression. The neural network we are developing is supposed to combine such behavioral indicators as: the amount of missed responses, amount of correct responses, average time, the amount of correct inhibition of movements after stopsignal onset. Such a combination of indicators will provide increased accuracy in predicting the presence of depression in a person. The artificial neural network implemented in the work allows diagnosing the risk of depression on the basis of the data obtained in the stop-signal task. An architecture was developed and a system was implemented for testing motor control indicators in humans, then it was tested in real experiments. A comparison of neural network technologies and methods of mathematical statistics was carried out. A neural network was implemented to diagnose the risk of depression using stop-signal paradigm data. The efficiency of the neural network (in terms of accuracy) was demonstrated on data with an expert assessment for the presence of depression and data from the motor control testing system

Comprehensive analysis of the 5-HTTLPR allelic polymorphism effect on behavioral and neurophysiological indicators of executive control in people from different ethnic groups in Siberia

The allelic polymorphism of the serotonin transporter’s gene 5-HTTLPR is considered as one of the factors determining an individual genetic predisposition to the development of a wide range of affective disorders, including depression. Many studies have shown that the climatic and social conditions of people’s life can have a significant impact on the connections of 5-HTTLPR with the risk of depression. The stop-signal paradigm (SSP) is an experimental method allowing evaluating an individual ability to the self-control of behavior in a changing environment. In the SSP experiment, a subject should either press one of several buttons quickly after the appearance of the target stimuli or suppress the already started movement if an inhibitory signal follows the target stimulus. The aim of this study is a research of associations between the allelic the 5-HTTLPR polymorphism and the individual scores of the personal anxiety level, as well as the behavioral and neurophysiological indicators of the ability to self-control over motor reactions in the SSP. The study was conducted among people from three ethno-regional groups: healthy Caucasoids from Novosibirsk, the Mongoloid groups of the indigenous population of the Tuva Republic and Sakha Republic (Yakutia). Genetic, ethnographic, and psychological influences on an individual’s ability to control motor responses were compared. The amplitude of the premotor peak of the evoked brain potential was used as a neurophysiological marker of the person’s readiness to the execution of target-directed activity. It was revealed that the frequency of the S-allele polymorphism 5-HTTLPR was significantly higher for both mongoloid groups compared to the Caucasoids. The S/S genotype was associated with an increased level of personal anxiety and at the same time with a better ability to the self-control of behavior in the SSP experiment. Anxiety level, participants’ sex, ethnicity, and allelic polymorphism 5-HTTLPR had a statistically significant effect on the amplitude of the premotor readiness potential recorded under the SSP conditions in the frontal and parietal-occipital cortical regions. Our data support the hypothesis that the S/S genotype of the 5-HTTLPR polymorphism may be associated with more success in adapting to the climatic conditions connected with high life risk in comparison to L/L and L/S genotypes