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41.
P. Calvani A. Bellucci M. Girolami S. Orlando V. Valentini A. Lettino D. M. Trucchi 《Applied Physics A: Materials Science & Processing》2014,115(1):25-29
Coupling effect in spiral-shaped metamaterials composed of four half rings at different sizes is investigated to achieve tunability in THz range. This novel spiral-shaped structure was fabricated on flexible substrate with laser micro-lens array (MLA) lithography and measured by THz time domain spectroscopy (THz-TDS). The experimental results suggest that mutual capacitance and inductance coupling in the spiral-shaped structure would result in frequency shifts of the four resonances. The observed shifting trends of the four resonant frequencies are in good agreement with simulation and are further explained by the electric field distribution. By varying the gap sizes among the half rings, four resonant frequencies can be tuned flexibly. Such a spiral-shaped design has potential applications in multi-band tunable THz MEMS devices. 相似文献
42.
Christine Wallace Jeremy J. Bellucci Antonio Simonetti Tim Hainley Elizabeth C. Koeman Peter C. Burns 《Journal of Radioanalytical and Nuclear Chemistry》2013,298(2):993-1003
The spatial distribution of radiation within trinitite thin sections have been mapped using alpha track radiography and beta autoradiography in combination with optical microscopy and scanning electron microscopy. Alpha and beta maps have identified areas of higher activity, and these are concentrated predominantly within the surficial glassy component of trinitite. Laser ablation-inductively coupled plasma mass spectrometry (LA-ICP-MS) analyses conducted at high spatial resolution yield weighted average 235U/238U and 240Pu/239Pu ratios of 0.00718 ± 0.00018 (2σ) and 0.0208 ± 0.0012 (2σ), respectively, and also reveal the presence of some fission (137Cs) and activation products (152,154Eu). The LA-ICP-MS results indicate positive correlations between Pu ion signal intensities and abundances of Fe, Ca, U and 137Cs. These trends suggest that Pu in trinitite is associated with remnants of certain chemical components from the device and surrounding Trinity test-related structures at ground zero. In contrast, negative correlations between Pu ion signals and SiO2 and K2O contents were observed within the glassy matrix of trinitite. This LA-ICP-MS result was corroborated by combined back-scattered electron imaging and alpha radiography, and indicates that Pu was not incorporated into unmelted crystalline grains of precursor minerals (i.e., quartz-SiO2 and K-feldspar-KAlSi3O8) present within the desert sand at the Trinity site. The results from this study indicate that the device-related radionuclides were preferentially incorporated into the glassy matrix in trinitite. 相似文献
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S. Bellucci C. Balasubramanian A. Grilli F. Micciulla A. Raco A. Popov V. Baranov V. Biryukov Yu. Chesnokov V. Maisheev 《JETP Letters》2006,83(3):95-97
We observe positron bending by a crystal lattice, presumably being guided by a channeling phenomenon, deflecting the beam
by about 10 milliradian over a length of 1 mm of silicon. This technique may lead to the use of the channeling effect for
steering particle beams at energies below 1 GeV, for the purpose of producing beams of low emittance with enhanced stability
for medical and biological applications.
The text was submitted by the authors in English. 相似文献
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U. Costantino A. Gallipoli M. Nocchetti G. Camino F. Bellucci A. Frache 《Polymer Degradation and Stability》2005,90(3):586-590
The thermal properties and combustion behaviour of new PE–hydrotalcites nanocomposites are described. Hydrotalcites were synthesized and then intercalated with stearate anion, because of the compatibility of long alkyl chain with polyethylene chains. The presence of inorganic filler shields PE from thermal oxidation, shifting the temperature range of volatilisation towards that of thermal degradation in nitrogen, and brings to a reduction of 55% in heat release rate during combustion. 相似文献
47.
S. Bellucci 《Zeitschrift fur Physik C Particles and Fields》1987,34(2):249-254
The calculation of the one-loop effective potential of the Wess-Zumino model is carried out using Green functions which propagate fields inn-dimensional anti-de Sitter space. The divergent parts of the amplitudes are independent of the choice of boundary conditions. The finite counterterms can be adjusted in such a way that the renormalized action be supersymmetric invariant. Addressing the question of the survival of the supersymmetry invariance of the vacuum state, we derive the result of the persistence of supersymmetry in the semiclassical approximation. 相似文献
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Attention has been recently called upon the fact that the weak and null energy conditions are violated in wormhole solutions of Einstein's theory with classical, nonminimally coupled, scalar fields as material source. It is shown that the discussion is only meaningful when ambiguities in the definitions of stress-energy tensor and energy density of a nonminimally coupled scalar are resolved. The three possible approaches are discussed with emphasis on the positivity of the respective energy densities and covariant conservation laws. The root of the ambiguities is traced to the energy localization problem for the gravitational field. 相似文献
50.