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41.
Filippo Samperi Salvatore Battiato Concetto Puglisi Andrea Scamporrino Veronica Ambrogi Laura Ascione Cosimo Carfagna 《Journal of polymer science. Part A, Polymer chemistry》2011,49(16):3615-3630
Linear–hyperbranched hybrid poly(butylene adipate) (HPBA) copolymers were synthesized through a branching reaction between the linear tailored prepolymer terminated with methyl ester groups and different mol percents of the 1,1,1‐tris(hydroxymethyl) propane (TMP) as branching agent, using the titanium(IV) isopropoxide as catalyst, at 180 °C under vacuum for different times. All samples were characterized by NMR and matrix assisted laser desorption/ionization time of flight mass spectrometry (MALDI‐TOF MS). In particular, MALDI‐TOF mass spectra of the unfractionated and size exclusion chromatography (SEC)‐fractionated hyperbranched (HB) samples gave information on their composition, on the end groups as well as on the TMP units present in each family of HB macromolecules. HB chains containing cyclic branches and ether bonds formed by intermolecular transesterification and intramolecular and intermolecular transetherification side reactions, respectively, were also revealed by MALDI‐TOF MS analysis. All samples were also investigated by SEC. The average molar masses (MMs) evaluated by SEC calibrated with the polystyrene (PS) narrow standards were overestimated with respect to those calculated by the SEC/MALDI‐TOF MS self‐ calibration method, which gave reliable values. Moreover, it also showed that the hydrodynamic volume of the HPBA polymers was higher than that of the linear PSs with similar MMs. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011 相似文献
42.
Giuseppe Giovannelli Lucia D’Urzo Giovanna Maggiulli Stefano Natali Cosimo Pagliara Ivonne Sgura Benedetto Bozzini 《Journal of Solid State Electrochemistry》2010,14(3):479-494
This paper concentrates on a novel approach to the electrochemical treatment of bronze disease, based on the use of room-temperature ionic liquids (RTIL). In particular, we employed 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide as the electrolyte for the galvanostatic cathodic treatment of a late bronze-age artifact that had been exposed to marine environment during its history, dating back to ca. 1100 B.C. After an accurate metallographic and structural analysis of the as-found object—proving, among other findings, that bronze disease is essentially related to the presence of nantokite locked inside subsurface pits of typical equivalent diameter of several hundred micrometers, we subjected it to optimal electrochemical conditions, showing—on the basis of X-ray diffraction—that nantokite could be effectively removed and Cu(I) reduced to metallic Cu. Numerical computations in the full three-dimensional pit geometry, with realistic nonlinear electrochemical boundary conditions, provide the theoretical framework for the choice of RTIL—as opposed to aqueous solutions—and for the quantitative evaluation of Cl− removal rates. 相似文献
43.
Prof. Lucia D'Accolti Dr. Cosimo Annese Dr. Caterina Fusco 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(52):12003-12017
The successful isolation and characterization of a dioxirane species in 1988 opened up one of the most attractive methods for the efficient oxidation of simple and/or structurally complex molecules. Dioxirane today rank among the most powerful tools in organic chemistry, with numerous applications in commercially important processes. They were quickly recognized as efficient oxygen transfer agents, especially for epoxidations and for a wide range of O-insertion reactions into C−H bonds. Dioxirane possess catalytic activity and appear as highly (chemo-, regio-, and stereo-) selective oxidants, despite their reactivity under mild and strictly neutral conditions being controlled by a combination of steric and electronic factors. In this review, we discuss some of the most recent and significant developments in the selective homogeneous and heterogeneous oxyfunctionalization of non-activated C−H bonds in hydrocarbons of natural and non-natural targets by using isolated dioxirane or, more generally, by using the ketones (i.e., the dioxirane precursors) as organocatalysts. 相似文献
44.
Fuda C Hesek D Lee M Morio K Nowak T Mobashery S 《Journal of the American Chemical Society》2005,127(7):2056-2057
Methicillin-resistant Staphylococcus aureus (MRSA) has acquired a unique penicillin-binding protein (PBP), PBP 2a, which has rendered the organism resistant to the action of all available beta-lactam antibiotics. The X-ray structure of PBP 2a shows the active site in a closed conformation, consistent with resistance to inhibition by beta-lactam antibiotics. However, it is known that PBP 2a avidly cross-links the S. aureus cell wall, which is its physiological function. It is shown herein that synthetic fragments of the bacterial cell wall bind in a saturable manner to PBP 2a and cause a conformational change in the protein that makes the active site more accessible to binding to a beta-lactam antibiotic. These observations and measurements point to a novel strategy by nature to keep the active site of PBP 2a sheltered from the inhibitory activity of the antibiotics, yet it becomes available to the polymeric cell wall by a requisite conformational change for the critical cell wall cross-linking reaction. 相似文献
45.
Cosimo Bambi 《理论物理通讯》2009,(7):78-80
The possibility of stable or quasi-stable Planck mass black hole remnants as solution to the black hole information paradox is commonly believed phenomenologically unacceptable. Since we need a black hole remnant for every possible initial state, the number of remnants is expected to be infinite and that would lead to remnant pair production in any physical process with a total available energy roughly exceeding the Planck mass. In this note I point out that a positive cosmological constant of the Universe would naturally lead to an upper bound on the number of possible remnants. 相似文献
46.
Roberto Grisorio Claudia Piliego Paola Fini Pinalysa Cosma Piero Mastrorilli Giuseppe Gigli Gian Paolo Suranna Cosimo Francesco Nobile 《Journal of polymer science. Part A, Polymer chemistry》2008,46(18):6051-6063
The synthesis of new random poly(2,7‐fluorenylene‐vinylene)s was achieved by a Suzuki–Heck cascade polymerization reaction. The poly(fluorenylene‐vinylene) base structure was modified by the regio‐random incorporation of 1‐cyano‐2,5‐phenylene as electron withdrawing unit ( CN‐PFV1 ) and its properties were compared with terpolymers also embodying 1,4‐dioctyloxy‐2,5‐phenylene ( CN‐PFV2 ) or 3,6‐N‐octylcarbazole ( CN‐PFV3 ) as electron‐donating moieties. Thermal analysis revealed a high thermal stability (Td > 389 °C) and the absence of glass transitions for all polymers. Cyclic voltammetry indicated a high electron affinity of the materials (2.96–3.21 eV) attributed to the presence of the cyano‐containing comonomer. In dilute solutions, the copolymers showed a broad green fluorescence with quantum yields ranging from 0.42 to 0.79, while in the solid state, a relatively narrow emission centered at ~ 560 nm, governed by the low‐energy segments within the π‐conjugated backbone, was observed. The electroluminescence properties of the materials were tested in OLED devices of ITO/PEDOT‐PSS/ CN‐PFV1‐3 /Ca/Al or ITO/PEDOT‐PSS/ CN‐PFV1‐3 /Alq3/Ca/Al configurations, showing a bright green‐yellow emission that, in the case of CN‐PFV2 , reached 1403 cd/m2 with efficiencies as high as 0.13 cd/A. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6051–6063, 2008 相似文献
47.
The Arnowitt–Deser–Misner (ADM) evolution equations for the induced metric and the extrinsic-curvature tensor of the spacelike surfaces which foliate the space-time manifold in canonical general relativity are a first-order system of quasi-linear partial differential equations, supplemented by the constraint equations. Such equations are here mapped into another first-order system. In particular, an evolution equation for the trace of the extrinsic-curvature tensor K is obtained whose solution is related to a discrete spectral resolution of a three-dimensional elliptic operator
of Laplace type. Interestingly, all nonlinearities of the original equations give rise to the potential term in
. An example of this construction is given in the case of a closed Friedmann–Lemaitre–Robertson–Walker universe. Eventually, the ADM equations are re-expressed as a coupled first-order system for the induced metric and the trace-free part of K. Such a system is written in a form which clarifies how a set of first-order differential operators and their inverses, jointly with spectral resolutions of operators of Laplace type, contribute to solving, at least in principle, the original ADM system. 相似文献
48.
Cosimo Cardellicchio Francesco Naso Maria Annunziata M. Capozzi 《Phosphorus, sulfur, and silicon and the related elements》2013,188(5-6):1161-1170
Abstract Grignard reagents were found to displace carbanionic leaving groups from suitable sulfinyl compounds. Because the process occurred with full inversion at the sulfinyl group, it was possible to set up an easy and straightforward route to chiral nonracemic sulfoxides. The starting compounds were easily produced, mainly by enantioselective oxidation of prochiral sulfides, and then the carbon-for-carbon displacement was effected with formation of a variety of new enantiopure sulfoxides. 相似文献
49.
Spin Hall Magnetoresistance and Spin Nernst Magnetothermopower in a Rashba System: Role of the Inverse Spin Galvanic Effect 下载免费PDF全文
In ferromagnet/normal‐metal bilayers, the sensitivity of the spin Hall magnetoresistance and the spin Nernst magnetothermopower to the boundary conditions at the interface is of central importance. In general, such boundary conditions can be substantially affected by current‐induced spin polarizations. In order to quantify the role of the latter, we consider a Rashba two‐dimensional electron gas with a ferromagnet attached to one side of the system. The geometry of such a system maximizes the effect of current‐induced spin polarization on the boundary conditions, and the spin Hall magnetoresistance is shown to acquire a non‐trivial and asymmetric dependence on the magnetization direction of the ferromagnet. 相似文献
50.
Roberto Grisorio Pinalysa Cosma Piero Mastrorilli Gian Paolo Suranna Cosimo Francesco Nobile 《Tetrahedron》2008,64(37):8738-8745
The preparation and properties of the first spirocyclohexane-functionalized bifluorene-based monodispersed molecular materials is described. The obtained compounds were characterized by 1H NMR, 13C{1H} NMR, IR, DSC, UV-vis and photoluminescence both in solution and in the solid state. The molecules show emissions ranging from the blue to the blue-green region, and higher glass transition temperatures and spectral stability with respect to the analogous compounds containing 9,9,9′,9′-tetrahexyl-[2,2′]-bifluorene core. The materials were used as active layers in electroluminescent devices with ITO/PEDOT-PSS/SB1-4/Ca/Al and ITO/PEDOT-PSS/SB1-4/BCP/Ca/Al configurations. 相似文献