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排序方式: 共有353条查询结果,搜索用时 31 毫秒
81.
Luciano Luciani Federico Milani Roberto Zannetti Vito Di Noto 《Macromolecular Symposia》1993,66(1):55-70
Among many precursors and catalysts for alpha-olefins polymerization, one seems to be particularly interesting, because it has not been completely clarified yet. We refer especially to precursors obtained via reaction between Mg-alkyls and SiCl4. The products of this reaction are not well known; in fact, under some operating conditions, a special form of MgCl2 is obtained, showing x-ray diffraction peaks in the angular region lower than 15° (2 theta), which corresponds to the 5.9 A interplanar spacing, characteristic of alpha-MgCl2. Under other conditions, MgCl2 is obtained in the well known and strongly disordered delta structure. By employing these precursors, some catalytic systems for alpha-olefins polymerization have been prepared. In this paper, the peculiar aspects of these precursors and catalysts are described, particularly focusing on the correlation between structure and performances in ethylene and propylene polymerization. 相似文献
82.
Priscila O. Cinto Ana Luiza Ribeiro Souza Andréa C. Lima Marco V. Chaud Maria Palmira D. Gremi?o 《Chromatographia》2009,69(Z2):213-217
Praziquantel (PZQ) is a highly lipophilic drug with low aqueous solubility. Despite this, it is well absorbed from the gastrointestinal
tract. In this study, a simple LC method was developed and validated, in order to monitor the concentration of PZQ in TC-199
buffer in vitro, in the rat everted gut sac absorption model. PZQ was analyzed by a reversed-phase LC method with an isocratic
mobile phase containing acetonitrile and water in the proportions 45:55. The flow-rate was 1 mL min−1 and PZQ was determined by measuring absorbance at 215 nm, at 25 °C. The method was found to be specific, as none of the components
of TC-199 or intestinal sac artefacts interfered with the drug peak. Recovery was within acceptable statistical limits. The
limit of detection was 0.54 μg mL−1 and the limit of quantitation was 1.63 μg mL−1. The calibration curve was found to be linear in the concentration range of 10–90 μg mL−1 PZQ. The proposed method was found to be rapid and selective and hence can be applied in the monitoring of the absorption
of PZQ in in vitro everted gut sac absorption studies. 相似文献
83.
84.
85.
M. Blomqvist G. Bongiorno A. Podestà V. Serin G. Abrasonis U. Kreissig W. Möller E. Coronel S. Wachtmeister S. Csillag V. Cassina P. Piseri P. Milani 《Applied Physics A: Materials Science & Processing》2007,87(4):767-772
We report the structural and tribological characterization of nanostructured CNx thin films produced by the deposition of a supersonic carbon cluster beam assisted by nitrogen ion bombardment. The influence
of the deposition parameters on the chemical composition and structure of the films has been systematically studied by X-ray
photoelectron spectroscopy, elastic recoil detection analysis, transmission electron microscopy and atomic force microscopy.
Depending on the deposition parameters, the films show a structure ranging from amorphous to disordered graphitic with interlinked
planes. Nitrogen content depends on the nitrogen ion kinetic energy. The films have a very low density with a high surface
roughness. Friction measurements at the nanoscale show a correlation between nitrogen content and mechanical properties of
the system.
PACS 61.46-w 相似文献
86.
E. Zilli M. O''Gorman L. Giudicotti F. Milani S. L. Prunty A. Murari A. Boboc 《International Journal of Infrared and Millimeter Waves》2000,21(10):1673-1696
This paper illustrates the realisation and testing of the multichannel far-infrared polarimeter for the RFX machine, a plasma confinement experiment with the Reversed Field Pinch configuration. The diagnostic is described and the its main sections are outlined: the laser system operating at = 118.8m, the FIR optical line, the beam splitter and the beam detection units, the signal processing electronics and the motion electronics for the calibration halfwave plates. Emphasis is placed on the work performed on the polarimeter to make it operational. We illustrate the preliminary tests of the diagnostic equipment and the activity performed to bring the diagnostic into reliable operation, in particular the reduction of the noise produced by magnetically induced mechanical vibrations during machine shots. An example of the first Faraday angle measurements performed on five chords are presented and discussed. The measured Faraday angle was also compared to a theoretically calculated value, based on a simple plasma model, with satisfactory agreement between measured and predicted data. 相似文献
87.
E. Barborini I. N. Kholmanov A. M. Conti P. Piseri S. Vinati P. Milani C. Ducati 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,24(1-3):277-282
Nanostructured titanium dioxide films have been deposited
by supersonic cluster beam deposition (CBD). Nanoparticles are
produced by a pulsed microplasma cluster source (PMCS) and
selected by aerodynamic separation effects. The as-deposited
film is a complex mixture where amorphous material coexists, at
the nanoscale, with anatase and rutile crystal phases. The
nanocrystalline fraction of the film is characterized by crystal
size ranging from 100 nm to less than 5 nm. We have
characterized the film structure by transmission electron
microscopy, Raman spectromicroscopy, X-ray diffraction, and
UV-visible spectroscopy showing that correlations exist between
cluster size and film properties. In particular if very small
clusters are deposited, the film shows a predominant rutile
phase whereas larger clusters form films with mainly anatase
structure. Our observations suggest that phonon confinement
effects are responsible for a significant shift and broadening
observed for the Raman peaks. In addition, optical gap tuning is
provided by mass selection: large clusters assembling generates
a film with 3.22 eV optical gap, while smallest clusters 3.52
eV. 相似文献
88.
Brunsell PR Yadikin D Gregoratto D Paccagnella R Bolzonella T Cavinato M Cecconello M Drake JR Luchetta A Manduchi G Marchiori G Marrelli L Martin P Masiello A Milani F Ortolani S Spizzo G Zanca P 《Physical review letters》2004,93(22):225001
Active feedback stabilization of multiple independent resistive wall modes is experimentally demonstrated in a reversed-field pinch plasma. A reproducible simultaneous suppression of several nonresonant resistive wall modes is achieved. Coupling of different modes due to the limited number of the feedback coils is observed in agreement with theory. The feedback stabilization of nonresonant RWMs also has an effect on tearing modes that are resonant in the central plasma, leading to a significant prolongation of the discharge pulse. 相似文献
89.
D. Batani C. Botto M. Moret M. Milani G. Lucchini K. Eidmann F. Cotelli C. Lora Lamia Donin G. Poletti T. Ford A. Stead 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,21(2):167-179
In this paper the results of an experiment on soft X-ray contact microscopy using a laser-plasma source are presented. A resolution
of 50 nm has been achieved imaging pig sperm cells, while other specimens, such as algae and yeast cells, showed internal
details, proving the technique to be a powerful tool for biological investigations. Original biological information has been
obtained and the conditions for optimal image formation have been studied.
Received 5 June 2002 Published online 24 September 2002
RID="a"
ID="a"e-mail: batani@mib.infn.it 相似文献
90.
Paul J. Robinson Julen Munarriz Michael E. Valentine Austin Granmoe Natalia Drichko Juan R. Chamorro Priscila F. Rosa Tyrel M. McQueen Anastassia N. Alexandrova 《Angewandte Chemie (International ed. in English)》2020,59(27):10996-11002
Samarium hexaboride is an anomaly, having many exotic and seemingly mutually incompatible properties. It was proposed to be a mixed‐valent semiconductor, and later a topological Kondo insulator, and yet has a Fermi surface despite being an insulator. We propose a new and unified understanding of SmB6 centered on the hitherto unrecognized dynamical bonding effect: the coexistence of two Sm?B bonding modes within SmB6, corresponding to different oxidation states of the Sm. The mixed valency arises in SmB6 from thermal population of these distinct minima enabled by motion of B. Our model simultaneously explains the thermal valence fluctuations, appearance of magnetic Fermi surface, excess entropy at low temperatures, pressure‐induced phase transitions, and related features in Raman spectra and their unexpected dependence on temperature and boron isotope. 相似文献