Research article

Background: An increasing number of studies demonstrate that genetic differentiation and speciation in the sea occur over much smaller spatial scales than previously appreciated given the wide distribution range of many morphologically defined coral reef invertebrate species and the presumed dispersal-enhancing qualities of ocean currents. However, knowledge about the processes that lead to population divergence and speciation is often lacking despite being essential for the understanding, conservation, and management of marine biodiversity. Sponges, a highly diverse, ecologically and economically important reef-invertebrate taxon, exhibit spatial trends in the Indo-West Pacific that are not universally reflected in other marine phyla. So far, however, processes generating those unexpected patterns are not understood.Results: We unraveled the phylogeographic structure of the widespread Indo-Pacific coral reef sponge Leucetta chagosensis across its known geographic range using two nuclear markers: the rDNA internal transcribed spacers (ITS 1&2) and a fragment of the 28S gene, as well as the second intron of the ATP synthetase beta subunit-gene (ATPSb-iII). This enabled the detection of several deeply divergent clades congruent over both loci, one containing specimens from the Indian Ocean (Red Sea and Maldives), another one from the Philippines, and two other large and substructured NW Pacific and SW Pacific clades with an area of overlap in the Great Barrier Reef/Coral Sea...Conclusion: We argue that both founder and vicariance events during the late Pliocene and Pleistocene were responsible to varying degrees for generating the deep phylogeographic structure. This structure was perpetuated largely as a result of the life history of L. chagosensis, resulting in high levels of regional isolation. Reciprocally monophyletic populations constitute putative sibling (cryptic) species, while population para- and polyphyly may indicate incipient speciation processes. The genetic diversity and biodiversity of tropical Indo-Pacific sponges appears to be substantially underestimated since the high level of genetic divergence is not necessarily manifested at the morphological level.researc

Deep genetic divergences among Indo-Pacific populations of the coral reef sponge Leucetta chagosensis (Leucettidae): Founder effects, vicariance, or both?

<p>Abstract</p> <p>Background</p> <p>An increasing number of studies demonstrate that genetic differentiation and speciation in the sea occur over much smaller spatial scales than previously appreciated given the wide distribution range of many morphologically defined coral reef invertebrate species and the presumed dispersal-enhancing qualities of ocean currents. However, knowledge about the processes that lead to population divergence and speciation is often lacking despite being essential for the understanding, conservation, and management of marine biodiversity. Sponges, a highly diverse, ecologically and economically important reef-invertebrate taxon, exhibit spatial trends in the Indo-West Pacific that are not universally reflected in other marine phyla. So far, however, processes generating those unexpected patterns are not understood.</p> <p>Results</p> <p>We unraveled the phylogeographic structure of the widespread Indo-Pacific coral reef sponge <it>Leucetta chagosensis </it>across its known geographic range using two nuclear markers: the rDNA internal transcribed spacers (ITS 1&2) and a fragment of the 28S gene, as well as the second intron of the <it>ATP synthetase beta subunit</it>-gene (<it>ATPSb</it>-iII). This enabled the detection of several deeply divergent clades congruent over both loci, one containing specimens from the Indian Ocean (Red Sea and Maldives), another one from the Philippines, and two other large and substructured NW Pacific and SW Pacific clades with an area of overlap in the Great Barrier Reef/Coral Sea. Reciprocally monophyletic populations were observed from the Philippines, Red Sea, Maldives, Japan, Samoa, and Polynesia, demonstrating long-standing isolation. Populations along the South Equatorial Current in the south-western Pacific showed isolation-by-distance effects. Overall, the results pointed towards stepping-stone dispersal with some putative long-distance exchange, consistent with expectations from low dispersal capabilities.</p> <p>Conclusion</p> <p>We argue that both founder and vicariance events during the late Pliocene and Pleistocene were responsible to varying degrees for generating the deep phylogeographic structure. This structure was perpetuated largely as a result of the life history of <it>L. chagosensis</it>, resulting in high levels of regional isolation. Reciprocally monophyletic populations constitute putative sibling (cryptic) species, while population para- and polyphyly may indicate incipient speciation processes. The genetic diversity and biodiversity of tropical Indo-Pacific sponges appears to be substantially underestimated since the high level of genetic divergence is not necessarily manifested at the morphological level.</p

Angular dependence of copper surface damage induced by an intense coherent thz radiation beam

In this work, we show the damage induced by an intense coherent terahertz (THz) beam on copper surfaces. The metallic surface was irradiated by multiple picosecond THz pulses generated by the Free Electron Laser (FEL) at the ISIR facility of the Osaka University, reaching an electric field on the sample surface up to ~4 GV/m. No damage occurs at normal incidence, while images and spectroscopic analysis of the surface point out a clear dependence of the damage on the incidence angle, the electric field intensity, and polarization of the pulsed THz radiation. Ab initio analysis shows that the damage at high incidence angles could be related to the increase of the absorbance, i.e., to the increase of the temperature around or above 1000◦ C. The experimental approach we introduced with multiple fast irradiations represents a new powerful technique useful to test, in a reproducible way, the damage induced by an intense electric gradient on copper and other metallic surfaces in view of future THz-based compact particle accelerators

TM oxides coatings for high demanding accelerator components

Large electric gradients are required for a variety of new applications, notably including the extreme high brightness electron sources for X-ray free electron lasers (FELs), RF photoinjector, industrial and medical accelerators and linear accelerators for particle physics colliders. In the framework of a INFN-LNF, SLAC (USA), KEK (Japan), UCLA (Los Angeles) collaboration, the Laboratori Nazionali di Frascati (LNF) is involved in the modelling, development and test of RF structures devoted to acceleration with high gradient electric field of particles through metal device. In order to improve the maximum sustainable gradients in normal conducting RF accelerating structures, we had to minimize the breakdown and the dark current. To this purpose the study of new materials and manufacturing techniques is mandatory to identify solutions to such extremely demanding applications. We considered the possibility to coat copper (and other metals) with a relatively thick film to improve and optimize breakdown performances. We present here the first characterization of MoO3 films deposited on copper by pulsed-laser deposition (PLD) starting from a commercial MoO3 target

Optical properties of two-dimensional tin nanosheets epitaxially grown on graphene

Heterostacks formed by combining two-dimensional materials show novel properties which are of great interest for new applications in electronics, photonics and even twistronics, the new emerging field born after the outstanding discoveries on twisted graphene. Here, we report the direct growth of tin nanosheets at the two-dimensional limit via molecular beam epitaxy on chemical vapor deposited graphene on Al2O3(0001). The mutual interaction between the tin nanosheets and graphene is evidenced by structural and chemical investigations. On the one hand, Raman spectroscopy indicates that graphene undergoes compressive strain after the tin growth, while no charge transfer is observed. On the other hand, chemical analysis shows that tin nanosheets interaction with sapphire is mediated by graphene avoiding the tin oxidation occurring in the direct growth on this substrate. Remarkably, optical measurements show that the absorption of tin nanosheets show a graphene-like behavior with a strong absorption in the ultraviolet photon energy range, therein resulting in a different optical response compared to tin nanosheets on bare sapphire. The optical properties of tin nanosheets therefore represent an open and flexible playground for the absorption of light in a broad range of the electromagnetic spectrum and technologically relevant applications for photon harvesting and sensors.Comment: 14 pages, 7 figure

Interplay among work function, electronic structure and stoichiometry in nanostructured VO: X films

The work function is the parameter of greatest interest in many technological applications involving charge exchange mechanisms at the surface. The possibility to produce samples with a controlled work function is then particularly interesting, albeit challenging. We synthetized nanostructured vanadium oxide films by a room temperature supersonic cluster beam deposition method, obtaining samples with tunable stoichiometry and work function (3.7-7 eV). We present an investigation of the electronic structure of several vanadium oxide films as a function of the oxygen content via in situ Auger, valence-band photoemission spectroscopy and work function measurements. The experiments probed the partial 3d density of states, highlighting the presence of strong V 3d-O 2p and V 3d-V 4s hybridizations which influence 3d occupation. We show how controlling the stoichiometry of the sample implies control over work function, and that the access to nanoscale quantum confinement can be exploited to increase the work function of the sample relative to the bulk analogue. In general, the knowledge of the interplay among work function, electronic structure, and stoichiometry is strategic to match nanostructured oxides to their target applications

Dimethyl carbonate as a green alternative to acetonitrile in reversed-phase liquid chromatography. Part I: Separation of small molecules

: Nowadays, environmental problems are drawing the attention of governments and international organisations, which are therefore encouraging the transition to green industrial processes and approaches. In this context, chemists can help indicate a suitable direction. Beside the efforts focused on greening synthetic approaches, currently also analytical techniques and separations are under observation, especially those employing large volumes of organic solvents, such as reversed-phase liquid chromatography (RPLC). Acetonitrile has always been considered the best performing organic modifier for RPLC applications, due to its chemical features (complete miscibility in water, UV transparency, low viscosity etc); nevertheless, it suffers of severe shortcomings, and most importantly, it does not fully comply with Environmental, Health and Safety (EHS) requirements. For these reasons, alternative greener solvents are being investigated, especially easily available alcohols. In this work, chromatographic performance of the most common solvents used in reversed-phase chromatography, i.e., acetonitrile, ethanol and isopropanol, have been compared to a scarcely used solvent, dimethyl carbonate (DMC). The analytes of interest were two small molecules, caffeine and paracetamol, whose kinetics and retention behaviour obtained with the four solvents have been compared, and all contributions to band broadening have been assessed. Results about kinetic performance are very promising, indicating that a small amount (7&nbsp;% v/v) of DMC is able to produce the same efficiency as a 2.5-times larger ACN volume (18&nbsp;% v/v), and larger efficiency than alcohols. This paper reports, for the first time, fundamental studies concerning the mass transfer phenomena when DMC is used as an organic solvent in RPLC, and, together with the companion paper, represents the results of a research whose final aim was to discover whether DMC is suitable for chromatographic applications both in linear and preparative conditions

Not just ‘small potatoes’: Knowledge of the idiomatic meanings of collocations

© 2016, © The Author(s) 2016. This study investigated learner knowledge of the figurative meanings of 30 collocations that can be both literal and figurative. One hundred and seven Chilean Spanish-speaking university students of English were asked to complete a meaning-recall collocation test in which the target items were embedded in non-defining sentences. Results showed limited collocation knowledge, with a mean score of 33% correct. The study also examined the effects of frequency, semantic transparency, year at university, and everyday engagement with the second language (L2) outside the classroom on this collocation knowledge. Mixed-effects modelling indicated that there was no relationship between frequency and semantic transparency and the knowledge of the figurative meanings. However, a positive relationship was found between this knowledge and year at university, time spent in an English-speaking country, and time spent reading