Search

Phenylacetylene was inserted and polymerized in 5 nm diameter silica nanotubes under high pressure-high temperature conditions of 0.5 GPa and 437 K in an inert gas. The resulting nanocomposite was characterized by infrared and Raman spectroscopy and scanning and transmission electron microscopy. The vibrational spectroscopic data confirmed the formation of [pi]-conjugated polyphenylacetylene and the absence of crystallization of the amorphous nanotubes. Scanning transmission electron microscopy coupled with energy dispersive X-ray spectroscopy, STEM-EDX, measurements confirmed the insertion of the polymer in the channels of the nanotubes and electron diffraction confirmed the amorphous nature of both the polymer and the host Si[O.sub.2] nanotubes. The obtained nanocomposite is a candidate material for gas sensing applications. Key words: silica nanotubes, polymer, high pressure, transmission electron microscopy, Raman spectroscopy. Du phenylacetylene a ete insere puis polymerise dans des nanotubes de silice de diametre 5 nm dans de conditions de haute pression 0,5 GPa et haute temperature 437 K. Le nanocomposite obtenu a ete caracterise par spectroscopies infrarouge et Raman et par microscopies electronique a balayage et en transmission. Les donnees de spectroscopie vibrationnelle ont confirme la formation de polyphenylacetylene n-conjugue ainsi que l'absence de cristallisation des nanotubes amorphes. La microscopie electronique en transmission a balayage, couplee a la spectroscopie des rayons X en dispersion d'energie a confirme Tinsertion du polymere a l'interieur des canaux des nanotubes. La diffraction electronique a confirme la nature amorphe du polymere et des nanotubes de Si[O.sub.2] hote. Le nanocomposite est un candidat comme materiau pour les capteurs de gaz. Mots-cles: nanotubes de silice, polymere, haute pression, microscopie electronique en transmission, spectroscopie Raman., Introduction Polyphenyacetylene (1-10)has attracted particular attention over the past decades as a p-conjugated system, which can be used as a conducting polymer. Conducting polymers present a considerable interest for applications [...]

While it is widely recognized that purely organic molecular systems with multiple bonds undergo chemical condensation at sufficiently high pressures (from tenths to tens of GPa), the fate of organometallics at extreme conditions remains largely underexplored. We have investigated the high pressure (up to 41 GPa) chemical transformations in a simple molecular system known as nickelocene, (C5H5)2Ni, which serves as a representative example of a class of organometallics called sandwich compounds. Nickelocene decomposed above 13 GPa, at room temperature, while lower pressure thresholds have been observed at higher temperatures (295–573 K). The products were identified as nanocomposite materials, primarily composed of disordered, nickel-rich nanoparticles segregated within an extended, amorphous matrix of hydrogenated carbon (a-C:H). The investigation was conducted by means of diamond anvil cells in combination with optical spectroscopies and microscopy, synchrotron x-ray absorption spectroscopy and diffraction, as well as transmission electron microscopy. Our findings have the potential to stimulate further research into the high-pressure chemical reactivity of organometallics and open up new synthesis routes for the production of metal-based nanoparticles, which find a wide range of applications. [ABSTRACT FROM AUTHOR]

While polymeric carbon monoxide (pCO) has been experimentally found to remain amorphous and undecomposed at room temperature up to 50 GPa, the question of whether crystalline counterparts of it can be obtained naturally raises. From different computational studies, it can be inferred that either the crystallization of amorphous pCO (a-pCO) or its decomposition into a mixture of CxOy suboxides (x > y) or carbon and CO2 may occur. In this study, we report experimental investigations of the high temperature (700–4000 K) transformation of a-pCO in the 47–120 GPa pressure range, conducted by x-ray diffraction in laser heated diamond anvil cells. Our results show the formation of no crystalline phases other than CO2 phase V, thus indicating the decomposition of the pristine a-pCO into CO2 and, likely, a mixture of amorphous CxOy suboxides and amorphous carbon hardly detectable at extreme conditions. These results support the theoretical picture of the pCO decomposition. We also show that the pressure-temperature kinetic border for this decomposition is very steep, thus indicating a strongly pressure-dependent kinetic barrier. [ABSTRACT FROM AUTHOR]

Here, we focus on the problem of minimizing complex classical cost functions associated with prototypical discrete neural networks, specifically the paradigmatic Hopfield model and binary perceptron. We show that the adiabatic time evolution of QA can be efficiently represented as a suitable Tensor Network. This representation allows for simple classical simulations, well-beyond small sizes amenable to exact diagonalization techniques. We show that the optimized state, expressed as a Matrix Product State (MPS), can be recast into a Quantum Circuit, whose depth scales only linearly with the system size and quadratically with the MPS bond dimension. This may represent a valuable starting point allowing for further circuit optimization on near-term quantum devices.

Intracellular parasites of the genus Glugea Thélohan, 1891 (Microsporidia) comprise about 34 putative species capable of causing high morbidity and mortality in freshwater and marine teleost fishes. In this study, we report on the first mass mortality event associated with Glugea sp. infecting free‐ranging round sardinella Sardinella aurita in the southern Tyrrhenian Sea (Italy). Here, we describe the ultrastructure of mature spores of this microsporidian and characterize it molecularly, as well as report its phylogenetic position. Most of the affected fish showed an irregular swelling of its abdomen. At necropsy, a variable number of xenomas, spherical to ellipsoidal in shape, were found in the peritoneal cavity strongly attached to the viscera of all fish. Histological analysis revealed varying severity of chronic inflammation along with occasional necrosis in visceral organs associated with multiple xenoma proliferation. These pathological findings were considered the main cause of this mass mortality event. Morphologically, the present material was closely related to G. sardinellesis and G. thunni. The phylogenetically closest taxa to the newly SSU rDNA sequence were G. thunni and an erroneusly identified G. plecoglossi, which were very closely related to each other, also suggesting that all these sequences might belong to the same species. [ABSTRACT FROM AUTHOR]

The cestode family Gymnorhynchidae (Trypanorhyncha) comprises three genera and six valid species that, as adults, are all intestinal parasites of large pelagic sharks. Their life cycle has not been elucidated yet, but it has been proposed that copepods serve as first, pelagic euphausiids or schooling fish as second, and larger predatory fishes as third intermediate hosts. Molidae fish have been proposed as intermediate hosts for at least two gymnorhynchid species (i.e., Molicola horridus and M. uncinatus). During a parasitological survey of fish from the coast of Kerala (India), some individuals of a gymnorhynchid species were found in a sharptail mola Masturus lanceolatus. Parasites were located on the subcapsular tissue of liver showing a serpiginous route. Based on 28S rDNA molecular and phylogenetic analysis, parasites were identified as Gymnorhynchus isuri, which resulted genetically identical to G. isuri obtained from the liver of a sun fish Mola mola in the Mediterranean Sea. [ABSTRACT FROM AUTHOR]

Appropriate diagnoses of parasites of apex marine predators are crucial to understand their biodiversity, host specificity, biogeography, and life cycles. Such diagnoses are also informative of ecological and biological characteristics of both host and environment in which the hosts and their parasites live. We here (i) investigate the parasite fauna of a bluntnose sixgill shark Hexanchus griseus (Bonnaterre, 1788) obtained from the Gulf of Naples (Tyrrhenian Sea), (ii) characterize molecularly all its metazoan parasites, and (iii) resurrect and report the main morphological features and phylogenetic position of Grillotia acanthoscolex, a cestode species previously synonymized with Grillotia adenoplusia. A rich parasite fauna represented by eight different taxa was found, including two monogeneans (Protocotyle grisea and Protocotyle taschenbergi), one digenean (Otodistomum veliporum), four cestodes (Crossobothrium dohrnii, Clistobothrium sp., G. acanthoscolex, and G. adenoplusia), and one copepod (Protodactylina pamelae). Sequencing of these samples accounts for an important molecular baseline to widen the knowledge on the parasitic fauna of bluntnose sixgill sharks worldwide and to reconstruct their correct food chains. The bluntnose sixgill shark was found to be a definitive host for all endoparasites found here, confirming that it occupies an apex trophic level in the Mediterranean Sea. The taxa composition of the trophic parasite fauna confirms that the bluntnose sixgill shark mostly feeds on teleost fish species. However, the occurrence of two phillobothrid cestodes (C. dohrnii and Clistobothrium sp.) suggests that it also feeds on squids. Finally, we emphasize the importance of using integrative taxonomic approaches in the study of parasites from definitive and intermediate hosts to elucidate biology and ecology of taxa generally understudied in the Mediterranean Sea. [ABSTRACT FROM AUTHOR]