The Drosophila ananassae species complex: Evolutionary relationships among different members

Information about genetic structure and historical demography of natural populations is central to understanding how natural selection changes genomes. Drosophila ananassae is a widespread species occurring in geographically isolated or partially isolated populations and provides a unique opportunity to investigate population structure and molecular variation. D. ananassae and its closely related species serve as a widely used model in population and evolutionary genetics. The ananassae subgroup belongs to the melanogaster species group. This subgroup contains 22 described species distributed mainly throughout Southeast Asia, with some species expanding into northeastern Australia, South Pacific and Indian subcontinent and Africa. Within the ananassae subgroup, three species complexes-ananassae, bipectinata and ercepeae have been recognized based on male genital morphology. D. ananassae and its relatives have many advantages as a model of genetic differentiation and speciation. In this review, distribution, phylogenies, hybridization, sexual isolation among D. ananassae complex have been discussed. The complex of several cryptic island species provides a useful model for evolutionary studies dealing with the mechanisms of speciation

Ionoluminescence studies of combustion synthesized Dy3+ doped nano crystalline forsterite

Ionoluminescence (IL) of nano crystalline Mg2SiO4:Dy3+ pellet samples bombarded with 100 MeV Si+8 ions with fluences in the range (1.124–22.480) × 1012 ions cm−2 have been studied. Two prominent IL bands with peaks at ∼480 nm and ∼580 nm and a weak band with peak at ∼670 nm are recorded. The characteristic peaks are attributed to luminescence center activated by Dy3+ ions due to the transitions 4F9/2→6H15/2,6H13/2 and 6H11/2. It is found that IL intensity initially decreases rapidly and then continuous to decrease slowly with further increase in ion fluence. The reduction in the Ionoluminescence intensity with increase of ion fluence might be attributed to degradation of Si–O ( 2ν3) bonds present on the surface of the sample and/or due to lattice disorder produced by dense electronic excitation under heavy ion irradiation

Luminescence studies in swift heavy ion irradiated aluminum silicates

Thermoluminescence (TL) of kyanite single crystals bombarded with 100 MeV swift Ag8+ and Si8+ ions with fluences in the range 1 à 1011-5 à 1014 ions/cm2 has been studied at room temperature (RT). Two TL glows with peaks one at â¼445 K and another one at â¼550 K are recorded in Si8+ ion bombarded kyanite single crystals at a warming rate of 20 K min-1. It is observed that the TL peak intensity increases with increase of ion fluence. This may be attributed to the creation of new traps during bombardment process. However, in the case of Ag8+ ion bombarded samples, a single well resolved glow with peak at â¼520 K is observed in all the samples. Also, photoluminescence (PL) of Ag8+ ion irradiated kyanite single crystals have been studied and it is observed that a pair of sharp as well as strong PL emission bands with peaks at â¼688 and 706 nm along with a broad emission band in the region 710-800 nm at an excitation of 442 nm laser beam. It is found that PL intensity decreases with increase of ion fluence. The decrease in intensity with increase of ion fluence is attributed to amorphization of the sample. © 2005 Elsevier B.V. All rights reserved