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71.
G. Principi P. Polato A. Paccagnella A. Maddalena S. Lo Russo G. Battaglin 《Hyperfine Interactions》1989,46(1-4):517-526
Conversion electron Mössbauer spectroscopy (CEMS) has been used to investigate the various Fe coordination states at the interface of the Fe/SiO2 couple after irradiation with 200 keV Kr ions in the dose range from 2.5×1015 to 3.5×1016 ions/cm2. After removal of the unmixed Fe layer by a simple etching procedure, it was possible to recognize the presence of small Fe clusters, Fe-oxide and Fe-silicate phases, whose relative amount has been determined as a function of the irradiation dose. The amount of mixed Fe has been evaluated in the etched samples by means of Rutherford backscattering spectrometry (RBS). Structural changes in the interfacial region after thermal annealings for 5 h at 500 and 700°C have been detected and correlated to corre-sponding changes in optical properties. 相似文献
72.
Abstract The optical Fréedericksz transition for linearly polarized light at normal incidence is studied in mixtures of nematic E7 and cholesteric C15 in cells coated for homeotropic alignment. The reorientation process is found to be dramatically different from the case of pure nematic samples showing the phenomenon of optical phase locking and large hysteresis. These effects are ascribed to the occurrence of self-induced stimulated light scattering, which does not occur in pure nematics. 相似文献
73.
F. De Filippo C. de Lisio P. Maddalena G. Lérondel T. Yao C. Altucci 《Applied Physics A: Materials Science & Processing》2001,73(6):737-740
Porous-silicon reflectance has been determined over a large energy range, from 1 eV to 16 eV, by combining a NIR/visible/UV
spectrometer with a new VUV light source as laser-harmonic radiation. The porous-silicon dielectric function was deduced from
reflectance measurements by Kramers–Kronig analysis. We point out that, for the first time, laser harmonics have been applied
in the optical characterization of materials as a new and suitable alternative to synchrotron radiation.
Received: 9 January 2001 / Accepted: 28 April 2001 / Published online: 20 June 2001 相似文献
74.
Peter Kutschy Mojmr Suchý Aldo Andreani Milan Dzurilla Maddalena Rossi 《Tetrahedron letters》2001,42(52):9281-9283
The analogs of indole phytoalexin cyclobrassinon have been prepared in four steps from corresponding 1-substituted 2-chloroindole-3-carboxylic acids, employing a hitherto unknown photochemical cyclization of new indolyl thiocarbamates to 1,3-thiazino[6,5-b]indole-4-one derivatives as a key step. 相似文献
75.
76.
Plinio Innocenzi Massimo Esposto Amedeo Maddalena 《Journal of Sol-Gel Science and Technology》2001,20(3):293-301
Hybrid organic-inorganic materials were synthesized from acid catalysed sols of tetraethyl orthosilicate, 3-glycidoxypropyltrimethoxysilane and titanium or zirconium alkoxides. The mechanical properties of these materials were measured in different conditions of preparation. The elastic modulus E was determined by a resonance method and by Knoop microindentation. After a thermal treatment at 125°C for 120 h, E was around 3–5 and 1–2 GPa for the samples synthesized with titanium butoxide or zirconium butoxide, respectively. An increase in E in the samples cured for longer times was observed. Knoop microhardness also increased with the heating time and was larger in samples synthesized from titanium alkoxides than zirconium alkoxides. The two methods gave results in good agreement when applied to samples treated for shorter times. In the other samples Knoop microindentation gave a larger value of E compared to the resonance vibration method. Hardness to elastic modulus ratio, H/E, was evaluated by Knoop microindentation. The elastic recovery at the longest heat treatment time was similar to that of soda-lime glasses. Fracture toughness was measured by three points flexural test, a KIc in the range of 0.4–0.5 MPa m1/2 was evaluated for samples treated during 168 h. 相似文献
77.
Wojciech Mróz Jean Philippe Bombenger Dr. Chiara Botta Dr. Alessio Orbelli Biroli Dr. Maddalena Pizzotti Prof. Filippo De Angelis Dr. Leonardo Belpassi Riccardo Tubino Prof. Francesco Meinardi Prof. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(46):12791-12798
Excimer formation in a new class of terthiophene‐based fluorophores covalently bonded to a cyclotetrasiloxane scaffold has been demonstrated and the photophysical process ruling it has been investigated in detail and modeled theoretically. In contrast to the conventional systems in which long‐living fluorophores such as pyrene are linked in the same molecule, an excimer is formed only when two terthiophene‐based branches nano‐organized on the same cyclotetrasiloxane scaffold are close enough together when excitation takes place. In such a case, excimer formation is extremely efficient, and the new bound excited states are quite stable. 相似文献
78.
New approaches in GMO detection 总被引:3,自引:0,他引:3
Maddalena Querci Marc Van den Bulcke Jana Žel Guy Van den Eede Hermann Broll 《Analytical and bioanalytical chemistry》2010,396(6):1991-2002
The steady rate of development and diffusion of genetically modified plants and their increasing diversification of characteristics,
genes and genetic control elements poses a challenge in analysis of genetically modified organisms (GMOs). It is expected
that in the near future the picture will be even more complex. Traditional approaches, mostly based on the sequential detection
of one target at a time, or on a limited multiplexing, allowing only a few targets to be analysed at once, no longer meet
the testing requirements. Along with new analytical technologies, new approaches for the detection of GMOs authorized for
commercial purposes in various countries have been developed that rely on (1) a smart and accurate strategy for target selection,
(2) the use of high-throughput systems or platforms for the detection of multiple targets and (3) algorithms that allow the
conversion of analytical results into an indication of the presence of individual GMOs potentially present in an unknown sample.
This paper reviews the latest progress made in GMO analysis, taking examples from the most recently developed strategies and
tools, and addresses some of the critical aspects related to these approaches. 相似文献
79.
We report here the main results of a successful attempt to predict some macroscopic properties of representative polymers of technological relevance both in regular and disordered forms by using first principle quantum mechanical approaches at microscopic level. Until now, the prediction of the structural and thermal properties of those polymers has been mostly a domain of molecular mechanics methods. To overcome the limits of those classical computational tools whenever physical properties are significantly influenced by stereoelectronic effects (e.g., electron rich substituents), we employed methods rooted in the Density Functional Theory (DFT). A general computational strategy including the proper choice of periodic boundary conditions (PBC), functional, basis set, and model system size, has been tested and validated for saturated polymers such as polyethylene and isotactic/syndiotactic polypropylenes. On the basis of these results, a comprehensive study of poly(tetrafluoroethylene) (PTFE) chains in both regular periodic and disordered conformations has been performed. A statistical approach has been next applied to obtain the thermal concentration of defects and to reproduce the thermal behavior of the investigated polymer. At the end, a very good agreement with experimental X-ray diffraction and IR results has been achieved, definitely reaching a good understanding of the widely studied disorder phenomenon determining the main technological properties of poly(tetrafluoroethylene) (the trade Teflon) and, at the same time, identifying the proper computational tools to investigate perfluoro-compounds and other complex polymeric systems. 相似文献
80.
The use of Brownian dynamics simulations to investigate the presence of structural (kinks) and dynamic (bulges) anomalies
in short DNA stretches is analyzed in connection with a string-of-beads model. A scaling method to choose the hydrodynamic
translational and rotational parameters of the beads is proposed and tested on straight, kinked and bulged DNA fragments 17 nm
long. The model reproduces the rigid-body rotational diffusion for the straight DNA and for the fluorescence polarization
anisotropy decay of the kinked and bulged DNAs the model predicts a different behavior which is found experimentally.
Received: 24 March 1998 / Accepted: 3 September 1998 / Published online: 23 November 1998 相似文献