High resolution scanning tunneling spectroscopy of ultrathin Pb on Si(111)-(6x6) substrate

The electronic structure of Si(111)-(6x6)Au surface covered with submonolayer amount of Pb is investigated using scanning tunneling spectroscopy. Already in small islands of Pb with thickness of 1 ML Pb$_{(111)}$ and with the diameter of only about 2 nm we detected the quantized electronic state with energy 0.55 eV below the Fermi level. Similarly, the I(V) characteristics made for the Si(111)-(6x6)Au surface reveal a localized energy state 0.3 eV below the Fermi level. These energies result from fitting of the theoretical curves to the experimental data. The calculations are based on tight binding Hubbard model. The theoretical calculations clearly show prominent modification of the I(V) curve due to variation of electronic and topographic properties of the STM tip apex.Comment: 7 pages, 7 figures, accepted for publication in Surface Scienc

Comparative cytogenetics on eight Malagasy Mantellinae (Anura, Mantellidae) and a synthesis of the karyological data on the subfamily

We performed a molecular and cytogenetic analysis on different Mantellinae species and revised the available chromosomal data on this group to provide an updated assessment of its karyological diver sity and evolution. Using a fragment of the mitochondrial 16S rRNA, we performed a molecular taxo nomic identification of the samples that were used for cytogenetic analyses. A comparative cytogenetic analysis, with Giemsa’s staining, Ag-NOR staining and sequential C-banding + Giemsa + CMA + DAPI was performed on eight species: Gephyromantis sp. Ca19, G. striatus (Vences, Glaw, Andreone, Jesu et Schimmenti, 2002), Mantidactylus (Chonomantis) sp. Ca11, M. (Brygoomantis) alutus (Peracca, 1893), M. (Hylobatrachus) cowanii (Boulenger, 1882), Spinomantis prope aglavei “North” (Methuen et Hewitt, 1913), S. phantasticus (Glaw et Vences, 1997) and S. sp. Ca3. Gephyromantis striatus, M. (Brygoomantis) alutus and Spinomantis prope aglavei “North” have a karyotype of 2n = 24 chromosomes while the other species show 2n = 26 chromosomes. Among the analysed species we detected differences in the number and position of telocentric elements, location of NOR loci (alternatively on the 6th, 7th or 10th pair) and in the distribution of heterochromatin, which shows species-specific patterns. Merging our data with those previously available, we propose a karyotype of 2n = 26 with all biarmed elements and loci of NORs on the 6th chromosome pair as the ancestral state in the whole family Mantellidae. From this putative ancestral condition, a reduction of chromosome number through similar tandem fusions (from 2n = 26 to 2n = 24) occurred independently in Mantidactylus Boulenger, 1895 (subgenus Brygoomantis Dubois, 1992), Spinomantis Dubois, 1992 and Gephyromantis Methuen, 1920. Similarly, a relocation of NORs, from the putative primitive configuration on the 6th chromosome, occurred independently in Gephyroman tis, Blommersia Dubois, 1992, Guibemantis Dubois, 1992, Mantella Boulenger, 1882 and Spinomantis. Chromosome inversions of primitive biarmed elements likely generated a variable number of telocentric elements in Mantella nigricans Guibé, 1978 and a different number of taxa of Gephyromantis (subgenera Duboimantis Glaw et Vences, 2006 and Laurentomantis Dubois, 1980) and Mantidactylus (subgenera Brygoomantis, Chonomantis Glaw et Vences, 1994, Hylobatrachus Laurent, 1943 and Ochthomantis Glaw et Vences, 1994)

Site structure analysis and optimization

The article contains information about current situation of site development, reasons why sites are so essential for activity of organizations and why researches of their structure improvement are so important. Short analysis of previous researches is provided, with their negative features and ways for further researches being exposed. Several ways to formulate recommendations and requirements for site structure are suggested, as well as methods for its optimization. A method for implementation of research results as software product is proposed. The information about an example of such software which performs analysis of sites of educational institution is provided too

Local disorder and optical properties in V-shaped quantum wires : towards one-dimensional exciton systems

The exciton localization is studied in GaAs/GaAlAs V-shaped quantum wires (QWRs) by high spatial resolution spectroscopy. Scanning optical imaging of different generations of samples shows that the localization length has been enhanced as the growth techniques were improved. In the best samples, excitons are delocalized in islands of length of the order of 1 micron, and form a continuum of 1D states in each of them, as evidenced by the sqrt(T) dependence of the radiative lifetime. On the opposite, in the previous generation of QWRs, the localization length is typically 50 nm and the QWR behaves as a collection of quantum boxes. These localization properties are compared to structural properties and related to the progresses of the growth techniques. The presence of residual disorder is evidenced in the best samples and explained by the separation of electrons and holes due to the large in-built piezo-electric field present in the structure.Comment: 8 figure

Two new species of terrestrial microhylid frogs (Microhylidae: Cophylinae: Rhombophryne) from northeastern Madagascar

We describe two new microhylid frog species of the genus Rhombophryne from the humid forests of northeastern Madagascar: Rhombophryne botabota sp. n. and R. savaka sp. n. e former is a medium-sized species, characterised by darkened lateral sides of the head (present in only one other congener, R. laevipes) and a unique combination of morphological, osteological, and molecular characters. e latter is a rather small species, characterised by medially undivided vomerine teeth with two large lateral diastemata, and presence of inguinal spots. Rhombophryne savaka sp. n. is the first species of the genus known from Makira Natural Park, and is reported also from Marojejy National Park and Ambolokopatrika (Betaolana Forest). Although its distribution range is relatively large compared to those of congeners, its known extent of occurrence is less than 2,000 km2. As deforestation and habitat degradation persist as threats despite formal legal protection, we suggest an IUCN Red List status of Vulnerable for this species. Rhombophryne savaka sp. n. is possibly endemic to the Marojejy National Park, like several other Rhombophryne species, but is unusual in being found at a relatively low altitude. As such, it is likely to be at high risk of habitat loss and decreasing range, and we propose a status of Endangered for it. We discuss the a nities of these new species and the variability of calls in this genus

Longevidade comparada e idade da maturidade sexual em doze anuros dos gêneros Boophis, Gephyromantis e Mantidactylus (Anura: Mantellidae) da floresta tropical de Madagascar

Apresentamos aqui dados sobre a idade na maturidade sexual e longevidade para algumas espécies de Mantellidae dos gêneros Boophis, Gephyromantis e Mantidactylus que habitam a floresta tropical de baixa altitude de Masoala (nordeste de Madagascar). Contagens de linhas de crescimento (LAGs) foram utilizadas para calcular a longevidade dessas espécies; esses dados contribuem para avaliações do nível de ameaça desses anuros. Boophis inclui espécies de médio a grande porte (SVL = 30–65 mm) que atingem a maturidade sexual em 1–3 anos e vivem de 3–9 anos (i.e., longevidade média). Mantidactylus e Gephyromatis incluem espécies de pequeno a grande porte (SVL = 22–107 e 35–49 mm, respectivamente) que atingem maturidade sexual em 1–3 anos e vivem de 1–8 e 3–7 anos, respectivamenteData on the age at sexual maturity and longevity of some mantellid species of the genera Boophis, Gephyromantis, and Mantidactylus that inhabit the low altitude rainforest of Masoala (northeastern Madagascar) are presented. Counts of lines of arrested growth (LAGs) were used to calculate longevity in these species; these data contribute to assessment of the threat level of the studied anurans. Boophis includes species of mediumto large-sized frogs (SVL = 30–65 mm) that attain sexual maturity in 1–3 years and live 3–9 years (i.e., mid-longevity). Mantidactylus and Gephyromatis include small- to largesized species (SVL = 22–107 mm and 35–49 mm, respectively) that attain sexually maturity in 1–3 years and live 1–8 and 3–7 years, respectivel

A new finding of Salamandra lanzai in the Upper Sangone Valley (NW Italy) marks the species' most disjunct population (Amphibia: Urodela: Salamandridae)

The presence of Salamandra lanzai was confirmed for the Upper Sangone Valley (Turin Province, NW Italy), within the Parco Naturale Orsiera Rocciavré. The species attribution was further supported by morphological and genetic (16S) analysis and represents the north-eastern most limit of the species’ distribution. This salamander was so far known only for a few major alpine valleys of Italy (Po, Pellice, and Germanasca Valleys), and France (Guil Valley). The new finding is especially interesting since it is separated from its closest known locality by about 15 km. For such a reason this population needs to be carefully managed

Resolving a taxonomic and nomenclatural puzzle in mantellid frogs: synonymization of Gephyromantis azzurrae with G. corvus, and description of Gephyromantis kintana sp. nov. from the Isalo Massif, western Madagascar

The genus Gephyromantis belongs to the species-rich family Mantellidae and is currently divided in six subgenera. Among these is the subgenus Phylacomantis, which currently includes four described species: Gephyromantis pseudoasper, G. corvus, G. azzurrae, and G. atsingy. The latter three species are distributed in western Madagascar, and two of them (G. azzurrae and G. corvus) occur in the Isalo Massif. Based on the analysis of molecular data (a fragment of the 16S rRNA gene), morphological inspection of museum specimens, and photographic comparisons, G. azzurrae is synonymised with G. corvus and the second Phylacomantis lineage of Isalo is described as G. kintana sp. nov. This medium-sized frog species (adult snout-vent length 35–44 mm) is assigned to this subgenus according to genetic and morphological similarities to the other known species of Phylacomantis. Gephyromantis kintana sp. nov. is known only from the Isalo Massif, while new records for G. corvus extend its range to ca. 200 km off its currently known distribution. These two taxa seem to occur in syntopy in at least one locality in Isalo, and the easiest way to distinguish them is the inspection of the ventral colouration, dark in G. corvus and dirty white in G. kintana.info:eu-repo/semantics/publishedVersio

Uncovering the herpetological diversity of small forest fragments in south-eastern Madagascar (Haute Matsiatra)

Madagascar has historically suffered from high fragmentation of forested habitats, often leading to biodiversity loss. Neverthless, forest fragments still retain high levels of biological diversity. The Haute Matsiatra Region (south-eastern Madagascar) hosts the renowned Andringitra National Park and several surrounding isolated forest fragments embedded in a matrix of human-dominated landscape. During a herpetological survey conducted in the Region, we visited a total of 25 sites. We applied a molecular taxonomic approach to identify the collected material and generate new reference sequences to improve the molecular identification of Malagasy herpetofauna. We identified a total of 28 amphibian and 38 squamate taxa and provided a systematic account for each one of them. Nine of the identified taxa are candidate species, amongst which one was newly identified. We extended the known distributional range of 21 taxa (nine amphibians and 12 squamates). Although the largest forest fragments hold a higher number of species, we also detected a relatively high herpetological diversity in small patches. Our results highlight the importance of investigating small forest fragments to contribute to a better understanding of the patterns of diversity and distribution of the amphibians and reptiles of Madagascar.info:eu-repo/semantics/publishedVersio

Time-resolved cathodoluminescence of InGaAs/AlGaAs tetrahedral pyramidal quantum structures

An original time resolved cathodoluminescence set up has been used to investigate the optical properties and the carrier transport in quantum structures located in InGaAs/AlGaAs tetrahedral pyramids. An InGaAs quantum dot formed just below the top of the pyramid is connected to four types of low-dimensional barriers: InGaAs quantum wires on the edges of the pyramid, InGaAs quantum wells on the (111)A facets and segregated AlGaAs vertical quantum wire and AlGaAs vertical quantum wells formed at the centre and at the pyramid edges. Experiments were performed at a temperature of 92K, an accelerating voltage of 10kV and a beam probe current of 10pA. The cathodoluminescence spectrum shows five luminescence peaks. Rise and decay times for the different emission wavelengths provide a clear confirmation of the peak attribution (previously done with other techniques) to the different nanostructures grown in a pyramid. Moreover, experimental results suggest a scenario where carriers diffuse from the lateral quantum structures towards the central structures (the InGaAs quantum dot and the segregated AlGaAs vertical quantum wire) via the InGaAs quantum wires on the edges of the pyramid. According to this hypothesis, we have modeled the carrier diffusion along these quantum wires. An ambipolar carrier mobility of 1400cm2/V s allows to obtain a good fit to all temporal dependence