On the Unit Graph of a Noncommutative Ring

Let $R$ be a ring (not necessary commutative) with non-zero identity. The unit graph of $R$, denoted by $G(R)$, is a graph with elements of $R$ as its vertices and two distinct vertices $a$ and $b$ are adjacent if and only if $a+b$ is a unit element of $R$. It was proved that if $R$ is a commutative ring and \fm is a maximal ideal of $R$ such that |R/\fm|=2, then $G(R)$ is a complete bipartite graph if and only if (R, \fm) is a local ring. In this paper we generalize this result by showing that if $R$ is a ring (not necessary commutative), then $G(R)$ is a complete $r$-partite graph if and only if (R, \fm) is a local ring and $r=|R/m|=2^n$, for some $n \in \N$ or $R$ is a finite field. Among other results we show that if $R$ is a left Artinian ring, $2 \in U(R)$ and the clique number of $G(R)$ is finite, then $R$ is a finite ring.Comment: 6 pages. To appear in Algebra Colloquiu

Exploring field scale salinity using simulation modeling, example for Rudasht area, Esfahan Province, Iran

Salinity / Simulation models / Soil-water-plant relationships / Soil properties / Climate / Irrigated farming / Water quality / Iran / Esfahan Province / Rudasht Area

A typology of community and stakeholder engagement based on documented examples in the field of novel vector control.

BackgroundDespite broad consensus on the importance of community and stakeholder engagement (CSE) for guiding the development, regulation, field testing, and deployment of emerging vector control technologies (such as genetically engineered insects), the types of activities pursued have varied widely, as have the outcomes. We looked to previous CSE efforts for clarity about appropriate methods and goals. Our analysis yielded a typology of CSE, and related vocabulary, that describes distinctions that funders, organizers, and scholars should make when proposing or evaluating CSE.MethodsWe compiled available formal documentation of CSE projects, starting with projects mentioned in interviews with 17 key informants. Major features of these examples, including the initiators, target groups, timing, goals, and methods were identified using qualitative coding. Based on these examples, subcategories were developed for a subset of features and applied to the identified cases of CSE in the documents. Co-occurrence of subcategorized features was examined for patterns.ResultsWe identified 14 documented examples CSE projects, which were comprised of 28 distinct CSE activities. We found no clear patterns with respect to timing. However, we found that grouping examples according to whether initiators or targets could enact the immediate desired outcome could help to clarify relationships between goals, methods, and targets.ConclusionBased on this analysis, we propose a typology that distinguishes three categories of CSE: engagement to inquire -where initiators are empowered to act on information collected through engagement with target groups; engagement to influence -where initiators engage to affect the actions of already-empowered target groups; and engagement to involve -where initiators engage to delegate authority to target groups. The proposed typology can serve as a guide for establishing the goals, identifying appropriate methods, and evaluating and reporting CSE projects by directing attention to important questions to be asked well before determining who to engage and how

Подземная река Ужла – примечательный феномен Русской равнины

Сообщение представляет историю исследования феномена реки и источника-воклюза Ужла в Вологодской области, а также итоги спелеоподводной экспедиции, проведенной в марте 2012 г. и посвященной изучению этого источника. Результатом экспедиции явилось обнаружение на глубине 64-66 метров (от зеркала воды в источнике) подземного русла реки Ужла – протяженной подводной пещеры.Повідомлення представляє історію дослідження феномену річки та джерела-воклюзу Ужла у Вологодській області, а також підсумки спелеопідводної експедиції, проведеної у березні 2012 р. і присвяченої вивченню цього джерела. Результатом експедиції стало виявлення на глибині 64-66 метрів (від дзеркала води в джерелі) підземного русла річки Ужла - протяжної підводної печери.This communication presents history of investigations of the phenomenon of the river and Vaucluse-type resurgence Uzhla in the Vologda region results of the speleo-diving expedition conducted in March 2012, aimed in studying of the resurgence. The result of expedition was a discovery of an underground river-bed of the river Uzhla – an extensive submarine cave at depth of 64-66 meters (from the water table at the source)

Pengaruh Faktor Situasional dan Faktor Karakteristik Personal Auditor terhadap Premature Sign Off (Studi Empiris pada Kantor Akuntan Publik Pekanbaru, Padang dan Palembang)

This research are to analyze time pressure, audit risk, review procedures and quality control, materiality, locus of control, self esteem in relation to ambition and auditor turn over intention that can affect the premature sign off. The population was all the independent auditor who worked at the KAP in the city of Pekanbaru, Padang and Palembang. While the sample of this research in the KAP auditors work in Pekanbaru, Padang and Palembang with 82 sample auditors. Methods of data collection in this study is a survey method with a questionnaire instrument. Method of data analysis used to test the quality of the data that include validity, reliability testing, and hypothesis testing is the analysis of the multiple linear regression using software SmartPLS Version2 M3. Hypothesis testing using partial least square test showed that the variables time pressure, audit risk, review procedures and quality control, materiality and locus of control significantly influence the premature sign off. While the variable self esteem in relation to ambition and auditor turn over intention does not directly affect the premature sign off. Value of R-Square indicates that the variables jointly time pressure, audit risk, review procedures and quality control, materiality, locus of control, self esteem in relation to ambition and auditor turn over intention contribute to the dependent variable (premature sign off) of 44.8%, while the remaining 55.2% is explained by other variables outside the research model.Keywords: premature sign off, situational factor and personal characteristic factor auditor

Effect of different levels of dietary betaine on growth performance, food efficiency and survival rate of pike perch (Sander lucioperca) fingerlings

A 6-week feeding experiments were carried out to determine the effects of different levels of dietary betaine on growth performance, food efficiency and survival rate of pike perch which has a critical period during transition feeding. Fingerlings of pike perch were fed with live food (treatment A), without betaine added to biomar (treatment B), 1% betaine added to biomar (treatment C) and 2% betaine added to biomar (treatment D) in 1000 l concreted tanks. 200 fingerlings (1.50 g, mean weight) were stocked in each tank and fed up to 7 meals per day. Higher increment in body weight (4.99 ± 0.73 g), specific growth rate (3.90 ± 0.06) and food efficiency (104.42 ± 4.27) were obtained with treatment D (2% betaine added to biomar). This treatment also showed significant (P<0.05) decrease in food conversion ratio (0.93 ± 0.04) in comparison with other treatments. Highest survival rate was observed in treatment B (biomar without betaine) with a 34.5 % rate and greatest cannibalism (1.03 ± 0.01) was found in treatment D, respectively. It was concluded that betaine could increase the palatability and acceptability of food and could be suitable to weaning the pike perch fingerlings to artificial diet