Design and construction of a RHEED diffractometer with energy resolution capability

In this work the author describes the set up of a UHV system to study the growth of ultra-thin metallic films on a silicon substrate under RHEED conditions. However, a new feature has been added to the normal RHEED apparatus. Because the phosphor screen acts as a high pass filter for the scattered electrons, energy filtering is normally excluded from RHEED techniques. In the experimental apparatus, a biased Faraday collector has been added to measure only the elastically scattered part of the diffracted beams. The electrical currents involved range from about 15 nA to 0.1 nA for the elastically scattered part of a diffracted beam. The (111) surface of Si has been chosen to perform RHEED, with the incident beam along the (100) direction. In order to test the performance of the RHEED set-up, the authors have performed two kinds of measurements, first, they have deposited Ag/Si(111) at different rates and have monitored the diffracted current of the specularly reflected beam with the Faraday collector unbiased, and second, they have tested the capability of the Faraday cup to measure only the elastically scattered part of the diffracted beams

The Population Decline and Extinction of Darwin's Frogs

Darwin's frogs (Rhinoderma darwinii and R. rufum) are two species of mouth-brooding frogs from Chile and Argentina. Here, we present evidence on the extent of declines, current distribution and conservation status of Rhinoderma spp.; including information on abundance, habitat and threats to extant Darwin's frog populations. All known archived Rhinoderma specimens were examined in museums in North America, Europe and South America. Extensive surveys were carried out throughout the historical ranges of R. rufum and R. darwinii from 2008 to 2012. Literature review and location data of 2,244 archived specimens were used to develop historical distribution maps for Rhinoderma spp. Based on records of sightings, optimal linear estimation was used to estimate whether R. rufum can be considered extinct. No extant R. rufum was found and our modelling inferred that this species became extinct in 1982 (95% CI, 1980-2000). Rhinoderma darwinii was found in 36 sites. All populations were within native forest and abundance was highest in Chiloé Island, when compared with Coast, Andes and South populations. Estimated population size and density (five populations) averaged 33.2 frogs/population (range, 10.2-56.3) and 14.9 frogs/100 m(2) (range, 5.3-74.1), respectively. Our results provide further evidence that R. rufum is extinct and indicate that R. darwinii has declined to a much greater degree than previously recognised. Although this species can still be found across a large part of its historical range, remaining populations are small and severely fragmented. Conservation efforts for R. darwinii should be stepped up and the species re-classified as Endangered

The Voices And Relationships Of The Chilean Frogs Eupsophus migueli And Eupsophus calcaratus (Amphibia, Anura, Leptodactylidae)

Volume: 98Start Page: 411End Page: 41

The Karyotypes Of The Chilean Frogs Eupsophus emiliopugini And E-Vertebralis (Amphibia, Anura, Leptodactylidae)

Volume: 104Start Page: 7End Page: 1

Advertisement Calls And Relationships Of Chilean Frogs Eupsophus contulmoensis And E-Insularis (Amphibia, Anura, Leptodactylidae)

Volume: 107Start Page: 391End Page: 39

Taxonomy Of Bufo venustus Anura Leptodactylidae From Central Chile

Volume: 95Start Page: 688End Page: 69

The Status Of 2 Chilean Frogs Of The Genus Eupsophus Anura Leptodactylidae

Volume: 95Start Page: 594End Page: 60

Comparative Cytogenetic Analysis Of The Chilean Leptodactylid Frog Genus Telmatobufo, With The Description Of The Chromosomes Of T-Venustus

Volume: 113Start Page: 890End Page: 89