Molecular Geometry and Electronic Structure of Heptalentropones and Heptalendiones

The molecular geometries of 8-H-cycloheptatropone (I), 8-H- -cycloheptatropolone (II), 2-methoxy-8-H-cycloheptatropone (III), heptalen-1,8-dione (IV), 7-methoxy-heptalen-1,8-dione (V), 9-methoxy- heptalen-1,8-dione (VI) were fully optimized at lVIINDOj3 level. Heptalen-2,3-dione was also taken into account. The electronic structures of the above molecules were studied by means of INDOjS method and the importance of doubly excited configurations was tested at CNDO/S level. In all compounds a remarkable »single« and »double« bond alternation was found. Hydroxy and methoxy substitution affects the geometry of the ring where the substitution occurs whilst the unsubstituted ring unđergoes minor 01\u27 negligible changes. The electronic transitions agree well enough with the experimentally available absorption maxima; a strong transition is predicted in the neighborood of 200 nm. Several of these transitions can be correlated with those of tropone and tropolone: on the whole they are not, 01\u27 negligibly, affected by double excitations except those Iying in the range of 5 eV and the ones at 4.29 eV and 4.82 eV of heptalen-2,3-dione

Numerical experimental analysis of hybrid double lap aluminum-CFRP joints

Due to their reliability and ease of assembly, both the adhesively bonded and the mechanical joints are commonly used in different fields of modern industrial design and manufacturing, to joint composite materials or composites with metals. As it is well known, adhesively bonded joints are characterized by high stiffness and good fatigue life, although delamination phenomena localized near the free edges may limit their use, especially for applications where corrosive environments and/or moisture can lead to premature failure of the bonding. In these cases, a possible alternative is given by the well-known mechanical joints. On the contrary, these last joints (bolted, riveted) require a preliminary drilling of the elements to be joined, that may cause localized material damage and stress concentration, especially for anisotropic laminates characterized by high stress concentration factors and easy drilling damaging, with significant decrease of the load-carrying capacity of the joined elements. In order to exploit the advantages of the bonded joints and those of the mechanical joints, both industrial manufacturing and research activity have been focused recently on the so called hybrid joints, obtained by the superposition of a mechanical joint to a simple adhesively bonded joint. In order to give a contribution to the knowledge of the mechanical behavior of hybrid bonded/riveted joints, in the present work a numerical–experimental study of bonded/riveted double-lap joints between aluminum and carbon fiber reinforced polymer (CFRP) laminates, has been carried out. It has permitted to highlight both the static and the fatigue performance of such joints obtained by using aluminum and steel rivets, as well as to known the particular damage mechanisms related also to the premature localized delamination of the CFRP laminate due to the riveting process

STUDIO NUMERICO-SPERIMENTALE DI GIUNZIONI IBRIDE A DOPPIA SOVRAPPOSIZIONE CFRP-ALLUMINIO

The adhesively bonded joints and the mechanical joints between structural components made by composite materials or between elements made by composite and metal, are commonly used in different fields of modern industrial design and manufacturing, since they are characterized by economy, reliability and ease of assembly. The bonded joints are characterized by high stiffness and fatigue life, although delamination phenomena localized near the edges of attack of the adherends may limit their use, especially in particular applications where corrosive environments and humidity can lead to premature failure. In these cases, a possible alternative is offered by the well known riveted joints. On the contrary, the riveted joints require a preliminary drilling of the elements to be joined and, consequently, may cause localized material damage, especially in presence of strongly anisotropic laminates which are characterized by high stress concentration. In the present work a numerical and experimental study of hybrid double-lap joints between aluminum and CFRP laminates, have permitted to highlight both the static and the fatigue performance of such joints, also with reference to the particular damage mechanism of the adhesive layer and to the interlaminar damage of the CFRP, due to the riveting process

Pauling’s Hybridization as a Tool of Computational Chemistry

Hybrids were introduced by Pauling within the Valence Bond method on intuitive grounds a long time ago. For the last thirty years, as a result of shift of interest towards computations based on the Molecular Orbital method, hybrids have been neglected by most theoreticians. In this paper, we show that actually they are not only deeply rooted in molecular reality (because of their connection with directed valency) but can be used to process the enormous output of sophisticated molecular computations, so as to derive from them the information needed for such research as the establishment of general rules and the description of the electronic systems of large molecules. Localization, lone pair hybrids, bent bonds, and related topics are discussed starting from ab initio computations either as single canonical orbitals or as Fock and overlap matrices. Our »maximum localization^ procedure for constructing hybrids, which is close to maximum overlap procedures, appears to yield localized orbitals as good as those obtained from other localization criteria, with the advantage that the hybrids are always directed along the bonds as much as this is allowed by valence angles. The ^straight bond« criterion for constructing a reaction path starting from a strained situation is briefly recalled as an indication that Pauling’s discovery of hybridization still has a large unexploited potential

A Beginner’s Guide to Molecular Identification of Seaweed

The most rapidly expanding areas for seaweed production in the world are the tropics, including Indonesia, yet these areas are also where molecular identification of local marine flora has only been sporadically employed. Furthermore, a goal for the Government of Indonesia is to diversify the types of seaweed that are being utilized, targeting valuable products and, hand in hand, to develop aquaculture techniques for these species. Morphological methods for species identification in algae are complex or unreliable, due to simple morphologies and plasticity. Therefore, it is crucial that the correct identification is made for species and varieties of commercial interest so that growth and biochemical results can be compared and contrasted between locations, across environments and over time without taxonomic ambiguity. This guide presents entry level methodologies for sample collection, DNA preservation, DNA extraction, PCR, and analyses of DNA sequence data, as a first step in the genetic characterization of both well-known cultivated species and identification of different species with potential economic properties

Genetic affinities between trans-oceanic populations of non-buoyant macroalgae in the high latitudes of the Southern Hemisphere

Marine biologists and biogeographers have long been puzzled by apparently non-dispersive coastal taxa that nonetheless have extensive transoceanic distributions. We here carried out a broad-scale phylogeographic study to test whether two widespread Southern Hemisphere species of non-buoyant littoral macroalgae are capable of long-distance dispersal. Samples were collected from along the coasts of southern Chile, New Zealand and several subAntarctic islands, with the focus on high latitude populations in the path of the Antarctic Circumpolar Current or West Wind Drift. We targeted two widespread littoral macroalgal species: the brown alga Adenocystisutricularis (Ectocarpales, Heterokontophyta) and the red alga Bostrychiaintricata (Ceramiales, Rhodophyta). Phylogenetic analyses were performed using partial mitochondrial (COI), chloroplast (rbcL) and ribosomal nuclear (LSU / 28S) DNA sequence data. Numerous deeply-divergent clades were resolved across all markers in each of the target species, but close phylogenetic relationships - even shared haplotypes - were observed among some populations separated by large oceanic distances. Despite not being particularly buoyant, both Adenocystisutricularis and Bostrychiaintricata thus show genetic signatures of recent dispersal across vast oceanic distances, presumably by attachment to floating substrata such as wood or buoyant macroalgae.This work was funded by New Zealand Marsden contract 07-UOO-099, Department of Zoology and University of Otago Research grants to JMW and CIF; a Shackleton Scholarship to CIF; an Allan Wilson Centre for Molecular Ecology and Evolution postdoctoral grant to CIF; Australian Antarctic Division AAS project #2914

Interplay between Tectonics and Mount Etna’s Volcanism: Insights into the Geometry of the Plumbing System

Mt. Etna lies in front of the southeast-verging Apennine-Maghrebian fold-and-thrust belt, where the NNW-trending Malta Escarpment separates the Sicilian continental crust from the Ionian Mesozoic oceanic basin, presently subducting beneath the Calabrian arc (Selvaggi and Chiarabba, 1995). Seismic tomographic studies indicate the presence of a mantle plume beneath the volcano with a Moho transition at depth less than 20 km (Nicolich et al.,2000; Barberi et al., 2006). Geophysical and geological evidences suggest that the Mt. Etna magma ascent mechanism is related to the major NNW-trending lithospheric fault (Doglioni et al., 2001). However, the reason for the Mt. Etna mantle plume draining and channeling the magma from the upper mantle source to the surface is not yet clear. All models proposed in literature (Rittmann, 1973; Tanguy et al., 1997; Monaco et al.; 1997; Gvirtzman and Nur, 1999; Doglioni et al., 2001) do not explain why such a mantle plume has originated in this anomalous external position with respect to the arc magmatism and back-arc spreading zones associated with the Apennines subduction. Some ideas on the subduction rollback must be better developed through the comparison with new regional tomographic studies that are being released. Moreover, tomographic studies reveal a complex and large plumbing system below the volcano from -2 to -7 km a.s.l., wide up to 60 km2 that reduces itself in size down to -18 km of depth close to the apex of the mantle plume. Chiocci et al. (2011) found a large bulge on the underwater continental margin facing Mt. Etna, and suggested that the huge crystallized magma body intruded in the middle and upper continental crust was able to trigger an instability process involving the Sicilian continental margin during the last 0.1 Ma. This phenomenon induces the sliding of the volcano eastern flank observed since the 90s (Borgia et al, 1992; Lo Giudice and Rasà, 1992) because the effects of the bulge collapse are propagating upslope, and the continuous decompression at the volcano summit favors the ascent of basic magma without lengthy storage in the upper crust, as one might expect in a compressive tectonic regime. Taken together, these new evidences (tomographic, tectonic, volcanic) are concerned with the exceptional nature of Mt. Etna and raise the need to explain the origin of the mantle plume that supplies its volcanism. The lower crust and the uppermost mantle need to be better resolved in future experiments and studies. The use of regional and teleseismic events for tomography and receiver function analyses is required to explore a volume that has only marginally been investigated to date. The relation between the magma source in the mantle and the upper parts of the system, as well as the hypothesis above reported on the relation between tectonics and volcanism and the role of lithospheric faults, could be resolved only by applying seismological techniques able to better constrain broader and deeper models. Finally, although the recent tomographic inversions have progressively improved our knowledge of Etna’s shallow structure, highlighting a complex pattern of magma chambers and conduits with variable dimensions, the geometry of the conduits and the dimensions and shapes of small magmatic bodies still require greater investigation. Their precise definition is crucial to delineate a working model of this volcano in order to understand its behaviour and evolution. For this purpose, at least within the volcanic edifice, the precise locations of the seismo-volcanic signals can be considered a useful tool to constrain both the area and the depth range of magma degassing and the geometry of the shallow conduits. In this work, we furnish evidences that the tremor and LP locations allowed to track magma migration during the initial phase of the 2008-2009 eruption and in particular the initial northward dike intrusion, also confirmed by other geophysical, structural and volcanological observations (Aloisi et al., 2009; Bonaccorso et al., 2011), and the following fissure opening east of the summit area at the base of SEC. All these evidences, obtained by the marked improvement in the monitoring system together with the development of new processing techniques, allowed us to constrain both the area and the depth range of magma degassing, highlighting the geometry of the magmatic system feeding the 2008-2009 eruption

The Role of Patient-Specific Morphological Features of the Left Atrial Appendage on the Thromboembolic Risk Under Atrial Fibrillation

Background: A large majority of thrombi causing ischemic complications under atrial fibrillation (AF) originate in the left atrial appendage (LAA), an anatomical structure departing from the left atrium, characterized by a large morphological variability between individuals. This work analyses the hemodynamics simulated for different patient-specific models of LAA by means of computational fluid–structure interaction studies, modeling the effect of the changes in contractility and shape resulting from AF. Methods: Three operating conditions were analyzed: sinus rhythm, acute atrial fibrillation, and chronic atrial fibrillation. These were simulated on four patient-specific LAA morphologies, each associated with one of the main morphological variants identified from the common classification: chicken wing, cactus, windsock, and cauliflower. Active contractility of the wall muscle was calibrated on the basis of clinical evaluations of the filling and emptying volumes, and boundary conditions were imposed on the fluid to replicate physiological and pathological atrial pressures, typical of the various operating conditions. Results: The LAA volume and shear strain rates were analyzed over time and space for the different models. Globally, under AF conditions, all models were well aligned in terms of shear strain rate values and predicted levels of risk. Regions of low shear rate, typically associated with a higher risk of a clot, appeared to be promoted by sudden bends and focused at the trabecule and the lobes. These become substantially more pronounced and extended with AF, especially under acute conditions. Conclusion: This work clarifies the role of active and passive contraction on the healthy hemodynamics in the LAA, analyzing the hemodynamic effect of AF that promotes clot formation. The study indicates that local LAA topological features are more directly associated with a thromboembolic risk than the global shape of the appendage, suggesting that more effective classification criteria should be identified

Characterization of seismic signals recorded in Tethys Bay, Victoria Land (Antarctica): data from atmosphere-cryosphere-hydrosphere interaction

In this paper, we analysed 3-component seismic signals recorded during 27 November 2016 - 10 January 2017 by two stations installed in Tethys Bay (Victoria Land, Antarctica), close to Mario Zucchelli Station. Due to the low noise levels , it was possible to identify three different kinds of signals: teleseismic earthquakes, microseisms, and icequakes . We focus on the latter two. A statistically significant relationship was found between microseism amplitude and both wind speed and sea swell. Thus, we suggest that the recorded microseism data are caused by waves at the shore close to the seismic stations rather than in the deep ocean during storms. In addition, w e detected three icequakes , with dominant low frequencies (below 2 Hz), located in the David Glacier area with local magnitude of 2.4-2.6. These events were likely to have been generated at the rock–ice interface under the glacier. This work shows how seismic signals recorded in Antarctica provide insights on the interactions between the atmosphere-cryosphere-hydrosphere. Since climate patterns drive these interactions, investigations on Antarctic seismic signals could serve as a proxy indicator for estimating climate changes