3,241 research outputs found

    Osteology and relationships of <i>Acrorhinichthys poyatoi</i> gen. et sp nov (Pycnodontiformes) from the marine Late Cretaceous of Lebanon

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    The osteology of Acrorhinichthys poyatoi gen. et sp. nov., a pycnodontid fish from the marine Cenomanian (Late Cretaceous) of Lebanon, is studied in detail. The new fossil genus belongs to the order Pycnodontiformes, but is less evolved than the Pycnodontidae. It still exhibits a few bony plates (= tesserae) in the gular region, 3 teeth on the premaxilla and 5 teeth on the dentary, and its parietal is devoid of a brush-like process. It shares a few characters with Akromystax, the most primitive taxon within Pycnodontidae, characters lost in the other members of the family

    Hygienic requirements of urban living environment in the Russian Federation and in Italy: a comparison

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    Introduzione/scopo. La pianificazione urbana tende a contenere e regolamentare la crescita urbana consentendo uno sviluppo sostenibile a livello ambientale, sociale e sanitario. Nel presente lavoro gli autori hanno confrontato i quadri normativi della Federazione Russ e dell’Italia ponendo particolare attenzione agli aspetti urbani degli spazi abitativi. Metodo. Considerando la ponderosa produzione normativa nei due paesi, il lavoro ha preso in esame le normative a livello nazionale per l’Italia e federale per la Russia, tenendo principalmente conto dei seguenti aspetti: strumenti di pianificazione urbana e protezione ambientale e sanitaria degli spazi abitativi. Risultati. I problemi relativi alla sicurezza igienico-sanitaria dell’ambiente di vita in Russia sono essenzialmente riconducibili a due sistemi normativi (SNiP e SanPiN), mentre in Italia rientrano nel D.M. 05/07/1975. I principi fondamentali della pianificazione urbana in Russia sono dettati da una norma federale, mentre in Italia sono recepiti nel Piano Regolatore Generale (PRG) comunale e nei diversi regolamenti locali, dove si riasriassume tutta la normativa sovraordinata. Gli aspetti legati alla qualità ambientale, infine, in entrambi i paesi sono disciplinati da varie leggi specifiche (federali e statali); un articolato sistema di norme che tengono conto dei potenziali impatti sulla salute e sull’ambiente Conclusioni. Gli autori ritengono che dovrebbero essere sviluppati, specialmente in Italia che si trova nettamente più indietro da questo punto di vista, strumenti normativi chiari e aggiornati aventi per oggetto l’igiene degli edifici e degli ambienti urbani, basati sulle più recenti acquisizioni di letteratura scientifica internazionale nell’intento di garantire i più alti standard in materia di tutela della Salute Pubblica.Aim. Urban planning tries to contain and regulate the uncontrolled growth of cities, encouraging their sustainable development at environmental, social and health levels. In the present work, the authors compare the regulatory frameworks of the Russian Federation and of Italy, with particular attention paid to the urban aspects of living spaces. Method. Considering the extant normative production in the two countries, the authors examine national legislation for Italy and federal legislation for Russia, mainly taking into account the following aspects: urban planning tools and environmental and sanitary protection of living spaces. Results. Hygienic-sanitary requirements regarding living environment in Russia are essentially expressed by two regulatory systems (SNiP and SanPiN), while in Italy they are regulated by the D.M. 07/05/1975. The main principles of urban planning in Russia are expressed by federal standards, while in Italy they are incorporated in the Municipal General Plan (PRG) and in the various local regulations, where all the superordinate regulations are summarized. Finally, aspects related to environmental quality in both countries are governed by various specific laws (federal and state); a complex system of rules that take into account potential impacts on health and the environment. Conclusions. The authors reckon that clear and updated regulatory tools should be developed, especially in Italy that lags behind, regarding the building and urban hygiene, relying on the most recent acquisitions of international scientific literature in order to guarantee the highest standards in Public Health safeguard

    Layered superconductors as negative-refractive-index metamaterials

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    We analyze the use of layered superconductors as anisotropic metamaterials. Layered superconductors can have a negative refraction index in a wide frequency range for arbitrary incident angles. Indeed, low-Tc (s-wave) superconductors allow to produce artificial heterostructures with low losses for T<<Tc. However, the real part of their in-plane effective permittivity is very large. Moreover, even at low temperatures, layered high-Tc superconductors have a large in-plane normal conductivity, producing large losses (due to d-wave symmetry). Therefore, it is difficult to enhance the evanescent modes in either low-Tc or high-Tc superconductors.Comment: 4 pages, 2 figure

    A Generic Model for Current Collapse in Spin Blockaded Transport

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    A decrease in current with increasing voltage, often referred to as negative differential resistance (NDR), has been observed in many electronic devices and can usually be understood within a one-electron picture. However, NDR has recently been reported in nanoscale devices with large single-electron charging energies which require a many-electron picture in Fock space. This paper presents a generic model in this transport regime leading to a simple criterion for the conditions required to observe NDR and shows that this model describes the recent observation of multiple NDR's in Spin Blockaded transport through weakly coupled-double quantum dots quite well. This model shows clearly how a delicate interplay of orbital energy offset, delocalization and Coulomb interaction lead to the observed NDR under the right conditions, and also aids in obtaining a good match with experimentally observed features. We believe the basic model could be useful in understanding other experiments in this transport regime as well.Comment: 10 pages, 10 figures. to appear in Phys Rev

    A re-description of <i>Hensodon spinosus</i>, a remarkable coccodontid fish (Actinopterygii, †Pycnodontiformes) from the Cenomanian (Late Cretaceous) of Haqel, Lebanon

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    Hensodon spinosus, a rare and very peculiar pycnodontiform fish from the Upper Cenomanian limestone of the Haqel fossils quarry (Lebanon) is re-described on the basis of four new specimens. It is the only species assigned to the genus. It shares with the family Coccodontidae (sensu Poyato-Ariza & Wenz, 2002) almost all its synapomorphies but is also characterized by several unique autapomorphies. The species exhibits a rounded general shape of the body, an enormous head, an extremely reduced snout with a minute mouth gash, a horny frontal showing modifications that we interpret as dimorphic sexual differences, styliform teeth, a giant occipital process with many spines on its margins and formed by the dermosupraoccipital, the parietal and the supratemporal, a prefrontal, an edentulous, unornamented, elongated rhomboid maxilla, a very massive spiny cleithrum, a big spiny post-coelomic bone, and a few elongated bar scales. All those characters award a unique impressive aspect to the fish. Remains of the original colour pattern add information about the external aspect of this remarkable fish

    Особливості числового розв’язання варіаційної задачі узгодження сигналу та його нейромережева інтерпретація

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    The features of numerical solution of variation problem of matching of signal with band-pass filter – determination of minimum after energy input signal at the specified value of output signal - are considered. Procedure of determination of optimum input signal is based on the method of the dynamic programming. Neural network interpretation of the problem is considered

    Orientation-dependent Casimir force arising from highly anisotropic crystals: application to Bi2Sr2CaCu2O8+delta

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    We calculate the Casimir interaction between parallel planar crystals of Au and the anisotropic cuprate superconductor Bi2Sr2CaCu2O8+delta (BSCCO), with BSCCO's optical axis either parallel or perpendicular to the crystal surface, using suitable generalizations of the Lifshitz theory. We find that the strong anisotropy of the BSCCO permittivity gives rise to a difference in the Casimir force between the two orientations of the optical axis, which depends on distance and is of order 10-20% at the experimentally accessible separations 10 to 5000 nm.Comment: 5 pages, 3 figures. Accepted for publication in Physical Review

    Hygienic and sanitary standards of housing in Europe: a comparative analysis of nine countries

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    In recent years, growing interest was devoted to housing conditions from both scientific community and public health, so they are now considered among the main environmental and social health determinants of health of the population. Aim of the study is to analyze and compare the current regulations regarding housing sanitary requirements in different Countries of the EU (Sweden, United Kingdom, Denmark, the Netherlands, France, Germany, Portugal, Spain) with the contents of the Italian Health Ministerial Decree 5th July 1975. From the websites of the official channels of the various countries the regulations have been downloaded. For the comparison, only the aspects of BCs concerning the scale of the building were examined; the comparison concerned all the requirements of the Health Ministerial Decree of 5.07.1975 and some other parameters (e.g. indoor chemical pollution, ionizing radiation, non-ionizing radiation) not provided for in the Ministerial Decree, treated in the other standards regulations, and relevant for the indoor well-being of the occupants. The authors observe a wide variability in the contents and in the formulation of the hygienic-sanitary requirements among the different Building Codes, above all as regards the dimensional data and some fundamental themes (e.g. heating systems, mechanical ventilation) whose treatment is often not it is updated with respect to the technological-scientific innovation consolidated over the past few years. A diverse approach among European Countries is also observed: from a market-oriented logic (e.g. UK), to a prescriptive one (Italy), to a functionality-oriented (the Netherlands). The comparative analysis we carried out made it possible to identify convergences and divergences in the standards analysed for the different European countries. As far as the Italian legislation on the usability of residential premises, finally, considering the health, social, environmental and economic trends, many standards contained in the MD 5th July 1975 should be reviewed and updated
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