53,737 research outputs found
Durability/life of fiber composites in hygrothermomechanical environments
Statistical analysis and multiple regression were used to determine and quantify the significant hygrothermomechanical variables which infuence the tensile durability/life (cycle loading, fatigue) of boron-fiber/epoxy-matrix (B/E) and high-modulus-fiber/epoxy-matrix (HMS/E) composites. The use of the multiple regression analysis reduced the variables from fifteen, assumed initially, to six or less with a probability of greater than 0.999. The reduced variables were used to derive predictive models for compression an intralaminar shear durability/life of B/E and HMS/E composites assuming isoparametric fatigue behavior. The predictive models were subsequently generalized to predict the durability/life of graphite-fiber-r generalized model is of simple form, predicts conservative values compared with measured data and should be adequate for use in preliminary designs
Electrochemistry and Spectroelectrochemistry of 1,4-Dinitrobenzene in Acetonitrile and Room-Temperature Ionic Liquids: Ion-Pairing Effects in Mixed Solvents
Room-temperature ionic liquids (RTILs) have been shown to have a significant effect on the redox potentials of compounds such as 1,4-dinitrobenzene (DNB), which can be reduced in two one-electron steps. The most noticeable effect is that the two one-electron waves in acetonitrile collapsed to a single two-electron wave in a RTIL such as butylmethyl imidazolium-BF4 (BMImBF4). In order to probe this effect over a wider range of mixed-molecular-solvent/RTIL solutions, the reduction process was studied using UVâvis spectroelectrochemistry. With the use of spectroelectrochemistry, it was possible to calculate readily the difference in E°âs between the first and second electron transfer (ÎE12° = E1° â E2°) even when the two one-electron waves collapsed into a single two-electron wave. The spectra of the radical anion and dianion in BMImPF6 were obtained using evolving factor analysis (EFA). Using these spectra, the concentrations of DNB, DNBââą, and DNB2â were calculated, and from these concentrations, the ÎE12° values were calculated. Significant differences were observed when the bis(trifluoromethylsulfonyl)imide (NTf2) anion replaced the PF6â anion, leading to an irreversible reduction of DNB in BMImNTf2. The results were consistent with the protonation of DNB2â, most likely by an ion pair between DNB2â and BMIm+, which has been proposed by Minami and Fry. The differences in reactivity between the PF6â and NTf2â ionic liquids were interpreted in terms of the tight versus loose ion pairing in RTILs. The results indicated that nanostructural domains of RTILs were present in a mixed-solvent system
CO and trans-cinnamaldehyde as corrosion inhibitors of I825, L80-13Cr and N80 alloys in concentrated HCl solutions at high pressure and temperature
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Evolutionary prisoner's dilemma games with optional participation
Competition among cooperators, defectors, and loners is studied in an
evolutionary prisoner's dilemma game with optional participation. Loners are
risk averse i.e. unwilling to participate and rather rely on small but fixed
earnings. This results in a rock-scissors-paper type cyclic dominance of the
three strategies. The players are located either on square lattices or random
regular graphs with the same connectivity. Occasionally, every player
reassesses its strategy by sampling the payoffs in its neighborhood. The loner
strategy efficiently prevents successful spreading of selfish, defective
behavior and avoids deadlocks in states of mutual defection. On square
lattices, Monte Carlo simulations reveal self-organizing patterns driven by the
cyclic dominance, whereas on random regular graphs different types of
oscillatory behavior are observed: the temptation to defect determines whether
damped, periodic or increasing oscillations occur. These results are compared
to predictions by pair approximation. Although pair approximation is incapable
of distinguishing the two scenarios because of the equal connectivity, the
average frequencies as well as the oscillations on random regular graphs are
well reproduced.Comment: 6 pages, 7 figure
Aqueous Phase C-H Bond Oxidation Reaction of Arylalkanes Catalyzed by a Water-Soluble Cationic Ru(III) Complex [(pymox-Me\u3csub\u3e2\u3c/sub\u3e)\u3csub\u3e2\u3c/sub\u3eRuCl\u3csub\u3e2\u3c/sub\u3e]\u3csup\u3e+\u3c/sup\u3eBF\u3csub\u3e4\u3c/sub\u3e\u3csup\u3e-\u3c/sup\u3e
The cationic complex [(pymox-Me2)RuCl2]+BF4â was found to be a highly effective catalyst for the CâH bond oxidation reaction of arylalkanes in water. For example, the treatment of ethylbenzene (1.0 mmol) with t-BuOOH (3.0 mmol) and 1.0 mol % of the Ru catalyst in water (3 mL) cleanly produced PhCOCH3 at room temperature. Both a large kinetic isotope effect (kH/kD = 14) and a relatively large Hammett value (Ï = â1.1) suggest a solvent-caged oxygen rebounding mechanism via a Ru(IV)-oxo intermediate species
Induction of Mutations in a Bacterial Virus
In the course of experiments designed for other purposes a paradoxical observation was made: phage λ, inactivated by UV irradiation, when adsorbed onto sensitive bacteria was reactivated when a further dose of UV was given to the phage-bacterium complexes. Among the reactivated phages a fairly large proportion were mutants. A description of these findings and a discussion of their implications will be found below
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