On minimal coverings of groups by proper normalizers

For a finite group $G$, a {\it normalizer covering} of $G$ is a set of proper normalizers of some subgroups of $G$ whose union is $G$. First we give a necessary and sufficient condition for a group having a {\it normalizer covering}. Also, we find some properties of $p$-groups ($p$ a prime) having a normalizer covering. For a group $G$ with a normalizer covering, we define $\sigma_n(G)$ the minimum cardinality amongst all the normalizer coverings of $G$. In this article, we show that if $G$ is a $p$-group with a normalizer covering, then $\sigma_n(G)=p+1$ or 5. Finally, for any prime $p$ and positive integer $k$, we construct a solvable group $G$ with $\sigma_n(G)=p^k+1$

Investigation on microstructure and oxidation behavior of Cr-modified aluminide coating on γ-TiAl alloys

Microstructure and oxidation behavior of aluminide coating has been investigated. The layers were examined by optical microscopy, scanning electron microscopy (SEM) equipped with EDS and X-ray diffraction method. The isothermal oxidation behaviors of samples were investigated at 950°C for 200 h. The results indicated that TiAl₃ were formed on substrate. In addition, aluminide coating improved the oxidation resistance of γ-TiAl alloys by forming a protective alumina scale. Moreover, during oxidation treatment the interdiffusion of TiAl₃ layer with γ-TiAl substrate results in depletion of aluminum in the TiAl₃ layer and growth of TiAl₂ layer. After oxidation treatment the coating layer maintained a microstructure with phases including TiAl₃, TiAl₂ and Al₂O₃.Досліджено мікроструктуру алюмінідного покриву та його поведінку під час високотемпературного окислення. Шари алюмінідів титану вивчали за допомогою оптичної мікроскопії, сканівної електронної мікроскопії (SЕМ) з використанням дисперсного рентгеноспектрометра (EDS) та рентгенівським дифракційним методом. Випробовування проводили при 950°C впродовж 200 h. Встановлено, що на підкладці з титанового сплаву утворився TiAl₃. Покрив з алюмініду титану покращує стійкість до окислення сплавів з γ-TiAl, утворюючи захисну плівку з оксиду алюмінію. Під час окислення дифузійна взаємодія TiAl₃ з підкладкою γ-TiAl спричиняє зменшення кількості алюмінію у шарі TiAl₃ та збільшення шару TiAl₂. Після окислення в покриві утворюється мікроструктура з фазами, що містять TiAl₃, TiAl₂ та Al₂O₃.Исследовано микроструктуру алюминидного покрытия и его поведение при высокотемпературном окислении. Слои алюминида титана изучали с помощью оптической микроскопии, сканирующей электронной микроскопии (SЕМ) с использованием дисперсного рентгеноспектрометра (EDS) и рентгеновским дифракционным методом. Испытания проводили при 950°C в течение 200 h. Установлено, что на подкладке из титанового сплава образовался TiAl₃. Покрытие из алюминида титана улучшает стойкость к окислению сплавов из γ-TiAl, образовывая защитную пленку из окисла алюминия. Во время окисления диффузионное взаимодействие TiAl₃ с подкладкой γ-TiAl влечет уменьшение количества алюминия в слое TiAl₃ и увеличение слоя TiAl₂. После окисления в покрытии образуется микроструктура с фазами, которые содержат TiAl₃, TiAl₂ и Al₂O₃

Improvement of Compressible Vorticity Confinement Method by Combining It with Vortex Feature Detection Methods

In the present study, the performance of the vorticity confinement method has been improved by combining it with the vortex feature detection methods. In the conventional vorticity confinement method, the only parameter to apply or not to apply vorticity confinement is the non-zero value of vorticity. On the other hand, the presence of vorticity in some cases, like the boundary layer and the shear layer flows, does not imply the presence of vortices. Applying the vorticity confinement at these points can lead to errors, in addition to loss of solution time. In order to solve this problem, using the combination of vorticity confinement method and four methods of vortex feature detection (nondimensional Q, nondimensional λ_2, nondimensional modified ∆, and the S-Ω correlation) the vorticity confinement term is applied only in vortex regions. In order to investigate the effects of this combination, the compressible Euler equation has been investigated for the problem of two-dimensional stationary single vortex at Mach number 0.5. The results indicate significant positive effects in reducing the solving time, decreasing the sensitivity of the solution to the amount of confinement parameter and significant elimination of the oscillation

Adiabatic dynamic causal modelling

This technical note introduces adiabatic dynamic causal modelling, a method for inferring slow changes in biophysical parameters that control fluctuations of fast neuronal states. The application domain we have in mind is inferring slow changes in variables (e.g., extracellular ion concentrations or synaptic efficacy) that underlie phase transitions in brain activity (e.g., paroxysmal seizure activity). The scheme is efficient and yet retains a biophysical interpretation, in virtue of being based on established neural mass models that are equipped with a slow dynamic on the parameters (such as synaptic rate constants or effective connectivity). In brief, we use an adiabatic approximation to summarise fast fluctuations in hidden neuronal states (and their expression in sensors) in terms of their second order statistics; namely, their complex cross spectra. This allows one to specify and compare models of slowly changing parameters (using Bayesian model reduction) that generate a sequence of empirical cross spectra of electrophysiological recordings. Crucially, we use the slow fluctuations in the spectral power of neuronal activity as empirical priors on changes in synaptic parameters. This introduces a circular causality, in which synaptic parameters underwrite fast neuronal activity that, in turn, induces activity-dependent plasticity in synaptic parameters. In this foundational paper, we describe the underlying model, establish its face validity using simulations and provide an illustrative application to a chemoconvulsant animal model of seizure activity

Support in Clinical Settings as Perceived by Nursing Students in Iran: A Qualitative Study

Background: Although support is one of the most substantial needs of nursing students during clinical education, it is not clearly defined in the literature. Objectives: The current study aimed to explore the concept of support in clinical settings as perceived by nursing students. Materials and Methods: A qualitative content analysis was used to explore the meaning of student support in clinical settings. A purposive sampling with maximum variation was used to select the participants among bachelor nursing students in the nursing school of Babol University of Medical Sciences in the north of Iran. Semi-structured interviews were conducted to gather the perceptions and experiences of seventeen nursing students. Conventional content analysis was applied to analyze the data. Results: In the current study, the main theme, nurturance, was emerged with seven subthemes of humanistic behavior with the student, respectful communication with students, accepting the student in the clinical setting, sustaining confidence, need based supervision, accepting the profession in the society and empowerment. Conclusions: Nursing students support in the clinical education requires a nurturing care; a care that leads to the sense of worthiness and respectability in students and contributes to the improvement of their clinical abilities

Effects of essential oils of Satureja bachtiarica and Nigella sativa on the efficacy of lactococcosis vaccine in rainbow trout (Oncorhynchus mykiss)

Lactococcosis has been defined as acute septicaemia, which causes economic losses in farmed fish, especially in rainbow trout. This study was done to evaluate the effects of the essential oils of Satureja bachtiarica and Nigella sativa on the efficacy of lactococcosis vaccine in rainbow trout. A total number of 270 fishes with a mean weight of 120 g were obtained; they were randomly divided into nine groups, each with three replicates, after two weeks of adaptation. The groups were: no injection group, vaccine only group, DMSO injection group, vaccine with 50, 100, and 200 micrograms Intraperitoneal injection (IP) injection. Two, four, and six weeks after vaccination, serological and haematological parameters were evaluated. In the sixth week, 1.7×10^7 cfu as LD50 96 hrs of Lactococcus garvieae were IP injected and the relative survival percentage was calculated. The results indicated that N. sativa essence is effective on the leukocyte population as the highest number of leukocytes were found in fish receiving high concentration of N. sativa. The relative survival rate of the studied fish decreased with decreasing concentrations of the N. sativa essential oil concentration, with a significant difference with control groups (p<0.05). However, using S. bachtiarica was not significantly effective on the relative survival rate of fish. The results of this study indicated that N. sativa essential oil can be used as adjuvant for L. garvieae vaccine, since it resulted in increasing leukocytes and the relative survival rate although S. bachtiarica was not effective on immune parameters of the studied fish

Fatty Acid Based Ionic Liquids: A New Antistatic Agent For Floor Coating

This research was conducted to obtain cis-oleyl imidazolinium iodide ionic liquid as an antistatic agent in ceramic and wood floor coatings. Synthesis of cis-oleyl imidazolinium iodide ionic liquid was carried out by reacting diethylenetriamine and cis-oleic acid in a ratio of 1:2 which was reacted utilizing microwave irradiation followed by quaternary methylation using methyl iodide. Then, Fourier-transform infrared spectroscopy (FTIR), proton nuclear magnetic resonance (1H NMR), and carbon-13 nuclear magnetic resonance (13C NMR) instruments were used to characterize the synthesis results. The results showed that the synthesis of cis-oleyl imidazolinium iodide ionic liquid was successful. The electrostatic effectiveness of the cis-oleyl imidazolinium iodide mixed ionic liquid floor coating is statically dissipative because the surface resistance values are in the range of 106 – 109 Ω. Optimum point-to-point resistance in coating mixture is 108 Ω (2-9 wt%), ceramic floor coating 108 Ω (7-9 wt%), and wood floor coating 108 Ω (7-9 wt%). Meanwhile, the optimum ground resistance in the coating mixture is 108 Ω (2-9 wt%), ceramic coating 109 Ω (4-9 wt%), and wood floor coating 109 Ω (1-9 wt%). The coated floor has a yellow color due to iodide which makes it unsuitable for use on white surfaces. Dust adhesion test results show that the mixed-coated floor attracts much less dust than the non-ionic liquid coating

Comparison of Various Compressible Vorticity Confinement Methods and Development Two New Confinement Parameters

In this paper, vorticity confinement parameters are successfully developed for compressible flows. The first new confinement parameter is proportional to spectral radii of the flux Jacobian matrix. Therefore, the confinement parameter implicitly contains the local conditions of the flow field. This new method is named as lambda vorticity confinement method. In order to gain confidence in the applicability of vorticity confinement, it would be ideal to completely eliminate constant coefficients from confinement parameters. Because these constant coefficients should be determined for every problem by trial and error and it takes a long time. In the next part of this paper, a suitable relation is introduced for the vorticity confinement parameter that doesn’t need any constant coefficient. This new method is named as adaptive vorticity confinement method. Then the capability of these new methods is compared with the other vorticity confinement methods for solving shock-vortex interaction and three dimensional moving vortex problems

A combined nodal and uniform pricing mechanism for congestion management in distribution power networks

We present a price-based approach for congestion management in distribution power systems with renewable generations with the final goal of maximizing a social welfare function which includes net revenues of network users as well as the cost of real power losses. Particularly, we design a combined nodal and uniform pricing mechanism for maximization of the social welfare function while maintaining voltage magnitudes in a desired bound and respecting the grid's actual capacity. Storage systems are considered in order to increase/add elasticity to generations and loads. Simulation results are provided for a modified IEEE-37 bus. A scenario is numerically simulated where the excess of generation in the absence of storage and price signals leads to deviations of voltages from a desired bound. Thereafter, it is shown that the application of the price signals is effective to maintain the voltages within the desired bound while the designed social welfare function is maximized