Substituted pyrido[3,2-d]pyrimidines are accessible by a reaction sequence consisting of HWE-reaction, Z/E-photoisomerization, and ring closure the pyridine ring. Bis-pyridopyrimidines can be obtained from 7-amino-pyrido[3,2-d]pyrimidines.

We prove that in a ring Rwith an identity there exists an element a ∈ R and a nonzero derivation d ∈ Der R such that ad(a) 6= 0. A ring R is said to be a d-rigid ring for some derivation d ∈ Der R if d(a) = 0 or ad(a) 6= 0 for all a ∈ R. We study rings with rigid derivations and establish that a commutative Artinian ring R either has a non-rigid derivation or R = R1 ⊕ · · · ⊕ Rn is a ring direc...

Let $ m , n in mathbb{N}$, $D$ be a division ring, and $M_{m times n}(D)$ denote the bimodule of all $m times n$ matrices with entries from $D$. First, we characterize one-sided submodules of $M_{m times n}(D)$ in terms of left row reduced echelon or right column reduced echelon matrices with entries from $D$. Next, we introduce the notion of a nest module of matrices with entries from $D$. We ...

how to cite this article: shetty g, avabratha k.s, rai b.s. ring-enhancing lesions in the brain: a diagnostic dilemma. iran j child neurol. 2014 summer;8(3): 61-64. abstract the most common radiological abnormality seen in young indian patients with epilepsy is single small enhancing (ring/disc) computed tomographic (ct) lesions. the two most common differential diagnosis of this lesion in clin...

In this paper, using annular resonator we have designed an adding and dropping filter light based ontwo-dimensional photonic crystals. The shape of ring resonator filter adding and dropping that wehave proposed is Race Track. This filter has a hexagonal lattice structure of silicon bars withrefractive index 3/46 that is located in the context of air with refractive index 1. Transmissionefficien...

Phytochrome photoreceptors in plants and microorganisms switch photochromically between two states, controlling numerous important biological processes. Although this phototransformation is generally considered to involve rotation of ring D of the tetrapyrrole chromophore, Ulijasz et al. (Ulijasz, A. T., Cornilescu, G., Cornilescu, C. C., Zhang, J., Rivera, M., Markley, J. L., and Vierstra, R. ...