Armenian National Academy of Sciences

About: Armenian National Academy of Sciences is a government organization based out in Yerevan, Armenia. It is known for research contribution in the topics: Population & Laser. The organization has 4090 authors who have published 4042 publications receiving 40828 citations. The organization is also known as: Armenian National Academy of Sciences & NAS RA.

Unstable visible mutations induced in Drosophila melanogaster by injections of oncogenic virus DNA into the polar plasm of early embryos

Abstract: When RSV DNA cloned in pBR 322 or DNA of simian adenovirus Sa7 (C8) is injected into the pole plasm of embryos of various Drosophila stocks, the progeny of 1–70% of the surviving flies display visible mutations. The mutagenesis is partially directed: the loci mutating due to retrovirus and adenovirus DNA do not everlap. The majority of resulting mutants are characterised by high instability: reversions and new mutations occur in them, which sometimes spread over the whole population(“explosive” instability). The injected sequences are revealed by dot-hybridization in the DNA of many mutant strains, but only rarely by Southern blotting procedures. The results show that the microinjection of oncovirus DNA into embryos is an approach for obtaining highly unstable strains even from wildtype stable Drosophila stocks without crosses with MR lines or the introduction of P elements. The sets of unstable mutations induced by oncovirus DNA is different from those in hybrid dysgenesis.

On the theory of surface waves in a uniaxial semiconductor slab

Abstract: The coupled optical-phonon–plasmon surface waves in a uniaxial polar semiconductor slab are investigated. A number of new surface modes are found which do not occur in cubic materials. Some properties of surface magnetoplasmons due to finite size are investigated. [Russian Text Ignored]

Amino Acid Structures

Abstract: Although this book deals with salts of amino acids, this chapter discusses the structures of pristine amino acids, since these molecular structures are also found in salts, and factors as solubility and conditions of crystal growth are important for the synthesis of amino acid salts as well as the pure form. In this context, the impact of minimal changes in conditions (such as impurities) on the growth of amino acid crystals is noted. The structural variation is very high, as not only amino acids differ from each other, but many amino acids exist in more than one form. This refers to the fact that enantiopure crystals can be grown as well as racemates (so-called dl-amino acids). Moreover, often more than one hydration state is found: Anhydrous forms are common, but many amino acids form hydrated crystals. For some amino acids (e.g., glycine, proline, methionine), more than one polymorph of the same hydration state is found. Some of these polymorphs form at ambient condition, often due to minuscule changes in conditions. For others, variation in temperature and pressure has been found to be the cause of the formation of different polymorphs. High-pressure data are available for some amino acids (e.g., alanine, serine, cysteine). Most amino acids are found to form a so-called head-to-tail motif, where acid and amino groups connect to form infinite chains. In some of the larger, nonpolar amino acids, a bilayer pattern is found, where polar groups of opposing molecules face each other, forming a layer, with the hydrophobic side chain facing outward (this motif is found in phenylalanine, methionine, leucine, or isoleucine). Not all amino acids crystallize readily, as is proved by the crystal structure of l-arginine, which could be determined only very recently, and that of lysine, which could not be solved at all to date. In addition to the standard 20, some nonstandard amino acids are discussed. Finally, notes on remarkable physical effects (such as piezoelectric data) or possible applications (as for instance the interactions of amino acids with carbon nanotubes) are presented.