Influence of the charge carrier tunneling processes on the recombination dynamics in single lateral quantum dot molecules

We report on the charge carrier dynamics in single lateral quantum dot molecules and the effect of an applied electric field on the molecular states. Controllable electron tunneling manifests itself in a deviation from the typical excitonic decay behavior which is strongly influenced by the tuning electric field and inter-molecular Coulomb energies. A rate equation model is developed to gain more insight into the charge transfer and tunneling mechanisms. Non-resonant (phonon-mediated) electron tunneling which changes the molecular exciton character from direct to indirect, and vice versa, is found to be the dominant tunable decay mechanism of excitons besides radiative recombination.Comment: 4 pages, 4 figure

POPULATION NUMBERS OF FUR SEALS AT PRINCE EDWARD ISLAND, SOUTHERN OCEAN

During the period 17–22 December 2001, the onshore distribution and the abundance of Antarctic fur seals Arctocephalus gazella and Subantarctic fur seals A. tropicalis were determined for Prince Edward Island. Two breeding colonies of Antarctic fur seals were located on the south-east coast of the island; the first a mixed (with Subantarctic fur seals) breeding colony with an estimated 24 pups on a vegetated promontory on the northern section of Boggel Beach, and the second, a presumably pure Antarctic fur seal breeding colony with an estimated 380 pups, at Penguin Beach. At a mean intrinsic rate of natural increase of 16.2&#37 per year, Antarctic fur seals appear to be in the rapid recolonization phase of population growth. Breeding colonies of Subantarctic fur seals, largely found on the entire east coast, produced an estimated 15 000 pups, and the population had maintained a mean intrinsic rate of natural increase of some 9.5&#37 per year since 1987/88.Afr. J. mar. Sci. 25: 549–55

Evidence for density dependent population regulation in southern elephant seals in the southern Indian Ocean

The means by which populations are regulated form a central theme in conservation biology, and much debate has revolved around density dependence as a mechanism driving population change. Marion Island (46o54'S, 37o45'E) is host to a relatively small breeding population of southern elephant seals, which like its counterparts in the southern Indian and southern Pacific Oceans, have declined precipitously over the past few decades. An intensive mark-recapture study, which commenced in 1983, has yielded a long time-series of resight data on this population. We used the program MARK to estimate adult female survival in this population from resight data collected over the period 1986-1999. Including concurrent population counts as covariates significantly improved our mark-recapture models and suggests density dependent population regulation to be operational in the population. Although predation may have been involved, it is far more likely that density dependent regulation has been based on a limited food supply. A significant increase in adult female survival was evident which is likely to have given rise to recent changes in population growth

Experimental imaging and atomistic modeling of electron and hole quasiparticle wave functions in InAs/GaAs quantum dots

We present experimental magnetotunneling results and atomistic pseudopotential calculations of quasiparticle electron and hole wave functions of self-assembled InAs/GaAs quantum dots. The combination of a predictive theory along with the experimental results allows us to gain direct insight into the quantum states. We monitor the effects of (i) correlations, (ii) atomistic symmetry and (iii) piezoelectricity on the confined carriers and (iv) observe a peculiar charging sequence of holes that violates the Aufbau principle.Comment: Submitted to Physical Review B. A version of this paper with figures can be found at http://www.sst.nrel.gov/nano_pub/mts_preprint.pd

COUNTS OF SURFACE-NESTING SEABIRDS BREEDING AT PRINCE EDWARD ISLAND, SUMMER 2001/02

The first midsummer survey of surface-nesting seabirds at Prince Edward Island was conducted during December 2001. It was also the first census for most species since the early 1980s. Despite concerns about the impacts of longline fishing mortality on various albatrosses and giant petrels, there was no evidence that populations of these species had decreased. Indeed, the estimate of wandering albatrosses Diomedea exulans (Vulnerable) has increased significantly, making Prince Edward Island equal with Marion Island as supporting the largest single-island populations of this species. Species that underwent significant decreases were macaroni penguins Eudyptes chrysolophus (Vulnerable), Crozet shags Phalacrocorax [atriceps] melanogenis and Kerguelen terns Sterna virgata (Near-Threatened). The reasons for these decreases are unclear, but for macaroni penguins may be partly a consequence of competition for space with the burgeoning population of fur seals Arctocephalus spp. The 2001 survey increased the population estimates for Subantarctic skuas Catharacta antarctica, lightmantled sooty albatrosses Phoebetria palpebrata (Vulnerable) and southern giant petrels Macronectes giganteus (Vulnerable), mostly as a result of greater coverage than for previous counts. The 2001 survey confirms that Prince Edward Island remains a globally important breeding site for seabirds.Afr. J. mar. Sci. 25: 441–45

Haulout site selection by southern elephant seals at Marion Island

Using data from an ongoing mark-resight programme at Marion Island, we tested empirically whether southern elephant seals prefer certain terrestrial sites to others during the breeding, moulting and winter haulouts, and whether the pattern of site use is the same for different age and sex groups. Southern elephant seals preferred some sites, while discriminating against other sites, with different age and sex classes using different sites for certain haulout events. Wintering young animals did not show strong site selection. Some popular sites were used for all haulouts by all age and sex groups, and apparently have all the requirements of a good site for terrestrial haulout by southern elephant seals. Site selection becomes more apparent with age, suggesting the role of haulout experience in site selection

Rates of species introduction to a remote oceanic island

The introduction of species to areas beyond the limits of their natural distributions has a major homogenizing influence, making previously distinct biotas more similar. The scale of introductions has frequently been commented on, but their rate and spatial pervasiveness have been less well quantified. Here, we report the findings of a detailed study of pterygote insect introductions to Gough Island, one of the most remote and supposedly pristine temperate oceanic islands, and estimate the rate at which introduced species have successfully established. Out of 99 species recorded from Gough Island, 71 are established introductions, the highest proportion documented for any Southern Ocean island. Estimating a total of approximately 233 landings on Gough Island since first human landfall, this equates to one successful establishment for every three to four landings. Generalizations drawn from other areas suggest that this may be only one-tenth of the number of pterygote species that have arrived at the island, implying that most landings may lead to the arrival of at least one alien. These rates of introduction of new species are estimated to be two to three orders of magnitude greater than background levels for Gough Island, an increase comparable to that estimated for global species extinctions (many of which occur on islands) as a consequence of human activities