In recent years, an increasing progress have been observed in application of polymer science and technology in different aspects of energy including energy production, conversion, and storage. Humans have been engaged with severe air pollution of the world and its adverse effects on the all aspects of life. The most reliable solution to decrease the emission of greenhouse gases and other pollutants is complete or at least partial substitution of petroleum-based fuels with CLEAN energy. Therefore, finding renewable and/or sustainable energy resources such as sunlight, internal earth heat, hydrogen and oxygen gases, wind, and hydroelectric energy as well as extending their public usage is of vital prominence. In this regard, polymers due to their distinctive combination of desired and tailor-made properties attracted much attentions in different fields of energy production.

In this paper, we introduce the new notion of n-f-CLEAN rings as a generalization of f-CLEAN rings. Next, we investigate some properties of such rings. We prove that Mn (R) is n-f-CLEAN for any n-f-CLEAN ring R. We also, get a condition under which the definitions of n-CLEANness and n-f-CLEANness are equivalent.

A ring R with identity is called “CLEAN” if for every element a ΠR, there exist an idempotent e and a unit u in R such that a=u+e.Let C (R) denote the center of a ring R and g (x) be a polynomial in C(R) [x]. An element r Î R is called “g (x) -CLEAN” if r=u+s where g(s) =0 and u is a unit of R and R is g (x) -CLEAN if every element is g(x) -CLEAN. In this paper we define a ring to be weakly g (x) -CLEAN if each element of R can be written as either the sum or difference of a unit and a root of g (x).

Background: Omphalitis is among the most common disease of neonatal periods that could lead to septicemia and peritonitis. To compare the use of alcohol with CLEAN cord care, the present study was conducted in Fiazbakhsh hospital in Karaj, from July 1999 till February 2000.Materials and methods: A total of 548 normal neonates had entered this sequential controlled clinical trial. Participants were distributed in two groups of case (CLEAN cord care) and control (using alcohol). T-test, chi-square, and Fishers exact test were used for data analysis. Results: The study population included 265 neonates in the case group and 247 as control. The cord separation was significantly earlier in the case group (5.47 ±1.38 vs. 6.04±1.89 days). There was no significant difference considering the rate of complications (omphalitis, granuloma, and bleeding). Umbilical cord bleeding following the cord separation was seen in 23(8.7%) neonates of the case group and 25(10.1%) of the control group, however, this difference was not statistically significant.Conclusion: CLEAN cord care seems to be more practical and efficient in healthy breastfed newborns who are kept with their mothers by rooming-in.

A ring R is a strongly CLEAN ring if every element in R is the sum of an idempotent and a unit that commute. We construct some classes of strongly CLEAN rings which have stable range one. It is shown that such CLEANness of 2´2 matrices over commutative local rings is completely determined in terms of solvability of quadratic equations.

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