Throughout the present article, we understand by a ring a commutative ring with identity, and by an over-ring of a ring R a ring containing R and having the same identity with R. Let T be an over-ring of a ring R. If T is generated by a single element over R and if •v is a homomorphism of T into a ring T', then •vT is generated by a single element over •vR. In õ 1, we discuss some results relat...

[reaction: see text] A novel ring opening ring closing metathesis (ROM-RCM) was demonstrated for cyclic conjugated dienes, effecting the excision of a C(2)H(2) unit and a net ring contraction. Applying the ring contraction metathesis, new 14-membered ring macrolide antibiotics were synthesized in a single step from existing 16-membered ring macrolides. This new class of macrolide antibiotics wi...

background and objectives: one of the simplest and cheapest attachments for overdentures, is the ball-type attachment, however, keeping it during the first year of prosthesis delivery and after that is one of the main concerns of dentists. the present study aimed to assess the wear of matrix in overdentures attachment supported by one, two and three implants in the mandible. materials and metho...

We have developed a linearly-polarized Ytterbium-doped fiber ring laser with single longitudinal-mode output at 1064nm for LISA and other space applications. Single longitudinalmode selection was achieved by using a fiber Bragg grating (FBG) and a fiber Fabry-Perot (FFP). The FFP also serves as a frequency-reference within our ring laser. Our laser exhibits comparable low frequency and intensit...