Expediente v. 16, n. 55

$n$-cocoherent rings‎, ‎$n$-cosemihereditary rings and $n$-V-rings

 Let $R$ be a ring‎, ‎and let $n‎, ‎d$ be non-negative integers‎. ‎A right $R$-module $M$ is called $(n‎, ‎d)$-projective if $Ext^{d+1}_R(M‎, ‎A)=0$ for every $n$-copresented right $R$-module $A$‎. ‎$R$ is called right $n$-cocoherent if every $n$-copresented right $R$-module is $(n+1)$-coprese-nted‎, ‎it is called a right co-$(n,d)$-ring if every right $R$-module is $(n‎, ‎d)$-projective‎. ‎$R$...

Maciej Zukowski - n. 55

The intracluster iron distribution around 4 C + 55 . 16

We report on the metal distribution in the intracluster medium around the radio galaxy 4C+55.16 (z = 0.24) observed with the Chandra X-ray Observatory. The radial metallicity profile shows a dramatic change at 10 arcsec (∼ 50 kpc) in radius from half solar to twice solar at inner radii. Also found was a plume-like feature located at∼ 3 arcsec to the south-west of the centre of the galaxy, which...

$n$-cocoherent rings‎, ‎$n$-cosemihereditary rings and $n$-v-rings

let $r$ be a ring‎, ‎and let $n‎, ‎d$ be non-negative integers‎. ‎a right $r$-module $m$ is called $(n‎, ‎d)$-projective if $ext^{d+1}_r(m‎, ‎a)=0$ for every $n$-copresented right $r$-module $a$‎. ‎$r$ is called right $n$-cocoherent if every $n$-copresented right $r$-module is $(n+1)$-coprese-nted‎, ‎it is called a right co-$(n,d)$-ring if every right $r$-module is $(n‎, ‎d)$-projective‎. ‎$r$ ...

Fractionation of 14 N 15 N 16 O and 15 N 14 N 16 O During Photolysis at 213 nm

Motivated by Yung and Miller’s suggestion [1997] that N2O is isotopically fractionated during UV photolysis in the stratosphere, we have studied the photolysis rates of the NNO and NNO structural isotopomers. In this study, we follow the concentrations of these compounds with FTIR spectroscopy during photolysis at 213 nm. Our results show that, as Yung and Miller predicted, the photolysis rate ...