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 $\sigma_n(G)=p^k+1$

How does split announcement affect stock liquidity? Evidence from Bursa Malaysia

© 2020 by the authors. Licensee MDPI, Basel, Switzerland. This study examines the impact of stock splits on stock liquidity in Bursa Malaysia from 2004–2018. The study uses event study methodology and investigates liquidity changes, the role of liquidity, and the relationship between abnormal returns and liquidity as well. We found a significant liquidity improvement on the splits announcement, announcement of book closing date and split execution date (Ex-date), while it declined after the split Ex-date. The findings also indicate that firms with a low-level liquidity prior to split announcements experienced an increase in liquidity after Ex-date. Using panel data analysis, we find that the fixed effect model is more appropriate than the pooled OLS, and the abnormal announcement returns are driven by stock liquidity

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

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

The Effect of Experience on Recognition of Mother’s Voice in Preterm Infants

Background: According to existing theories, supportive cares provided through specific kinds of stimuli affect the growth, development and neurobehavioral functioning of preterm infants. Some of the studies indicate that the fetal heart rate response to mother’s voice begins in the week 32 of pregnancy. However, the fact that whether preterm infant is able to recognize mother’s live voice from the voice of a stranger woman is unknown. Objectives: The present study aimed to compare the effects of mother’s voice and a stranger’s voice on the heart rate of preterm infants hospitalized in a neonatal intensive care unit (NICU). Methods: In a clinical trial study, 66 preterm infants hospitalized in the NICU were randomly assigned into three groups of 22 (i.e. mother’s voice and stranger’s voice groups and a silent group). The infants’ heart rates were recorded by a monitoring system in all of the three groups each five minutes for 30 minutes overall (10 minutes before, during and after the intervention) in three consecutive days. Both one-way and repeated measures analysis of variance were used to analyze the data in terms of significant differences. Also, the chi-square test and analysis of variance were used to compare the demographic variables of the groups. Results: The heart rate of the infants in the mother’s voice group, stranger’s voice group and the silent group were 133.99 � 2.72, 134.26 � 2.43 and 137.94 � 2.92 per minutes, respectively (P > 0.588) and changed to 143.42 � 2.85, 133.22 � 2.15 and 138.28 � 2.21, respectively (P = 0.016). Moreover, the infants’ heart rates were respectively 136.87�3.38, 132.68�2.22 and 138.19�2.65 per minutes, 10 minutes after the intervention (P > 0.345). Conclusions: No significant difference was found between the mean heart rates of the three groups neither before, nor 10 minutes after the intervention. However, a significant difference was observed among the three groups during the intervention. Therefore, we can conclude that the preterm infants can recall and differentiate their mothers’ voice from the voice of a stranger. Then, an opportunity can be provided during the developmental care for the infants to hear their mothers’ voice

The effect of intra-articular meperidine and bupivacaine 0.5 on postoperative pain of arthroscopic knee surgery; a randomized double blind clinical trial

Background: Arthroscopic knee surgeries have a painful postoperative course, which often necessitates acute pain management. Among different analgesia techniques, Intra-articular injection is the technique of choice for many pain specialists, based on its confined effect to the surgical site (knee), lack of systemic effects and promotion of safe early ambulation. Objectives: The aim of this study was to compare analgesic effects of intra-articular meperidine, bupivacaine 0.5 or their combination after knee arthroscopic surgery. Patients and Methods: Sixty ASA class I-II patients� candidates for arthroscopy knee surgery enrolled in a randomized double blind study to receive either 20 mL of bupivacaine 0.5; 100 mg meperidine (diluted in normal saline) or bupivacaine 0.5 along with 100 mg meperidine. A written informed consent was obtained from all patients. Postoperative analgesia duration, VAS at 2, 6, 12 and 24 hours, the Results: The bupivacaine-meperidine group had better duration of postoperative analgesia (P = 0.001), latter first analgesic request (P � first analgesic request time, total fentanyl consumption in first 24 hours, patients� satisfaction and adverse effects were recorded. 0.001), lower total fentanyl consumption in first 24 hours after the operation (P = 0.001), less mean VAS at 2 hours (P = 0.001) and more patients� overall satisfaction (P = 0.01) compared with each medication alone. VAS at 6, 12 and 24 postoperative hours were not different between the groups of study. No adverse effects were observed. Conclusions: Although postoperative intra-articular meperidine is a better alternative for bupivacaine, their combination could improve their analgesic effects compared with each other alone. © 2015, Iranian Society of Regional Anesthesia and Pain Medicine (ISRAPM)

Minimal coverings of completely reducible groups

Let G be a group that is a set-theortic union of finitely many proper subgroups. Cohn defined σ(G) to be the least integer m such that G is the union of m proper subgroups. Determining σ is an open problem for most non-solvable groups. In this paper we give a formula for σ(G), where G is a completely reducible group

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

Thermal Management Systems and Waste Heat Recycling by Thermoelectric Generators-An Overview

With the fast evolution in greenhouse gas (GHG) emissions (e.g., CO2, N2O) caused by fossil fuel combustion and global warming, climate change has been identified as a critical threat to the sustainable development of human society, public health, and the environment. To reduce GHG emissions, besides minimizing waste heat production at the source, an integrated approach should be adopted for waste heat management, namely, waste heat collection and recycling. One solution to enable waste heat capture and conversion into useful energy forms (e.g., electricity) is employing solid-state energy converters, such as thermoelectric generators (TEGs). The simplicity of thermoelectric generators enables them to be applied in various industries, specifically those that generate heat as the primary waste product at a temperature of several hundred degrees. Nevertheless, thermoelectric generators can be used over a broad range of temperatures for various applications; for example, at low temperatures for human body heat harvesting, at mid-temperature for automobile exhaust recovery systems, and at high temperatures for cement industries, concentrated solar heat exchangers, or NASA exploration rovers. We present the trends in the development of thermoelectric devices used for thermal management and waste heat recovery. In addition, a brief account is presented on the scientific development of TE materials with the various approaches implemented to improve the conversion efficiency of thermoelectric compounds through manipulation of Figure of Merit, a unitless factor indicative of TE conversion efficiency. Finally, as a case study, work on waste heat recovery from rotary cement kiln reactors is evaluated and discussed.Sadeq Hooshmand Zaferani, Mehdi Jafarian, Daryoosh Vashaee, and Reza Ghomashch