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991.
Paolo Allia Marco Co?sson Paola Tiberto Franco Vinai Oana Bretcanu 《Journal of magnetism and magnetic materials》2010,322(9-12):1286-1289
Slow fluctuations of the electrical resistance R have been systematically observed in three glass-ceramics containing aggregates of magnetite nanoparticles, in measurements where R was studied as a function of time at the magnetic remanence. These fluctuations are shown to be an intrinsic (i.e., not instrumental or spurious) feature of these materials. The associated electrical noise has been obtained by performing a numerical FFT transform of different segments of the R(t) curves after proper baseline subtraction. In this way, the spectral density has been investigated in the very low-frequency region (1×10?3<f<0.2 Hz), usually not covered in standard noise measurements. The spectral density shows a 1/fα behaviour (with α?1.6) in all cases. The results are discussed in terms of the existing models about conductance fluctuations in half-metallic oxides in the hopping regime. It is suggested that electron trapping–detrapping mechanisms (thought to be the source of electrical noise) play a relevant role in the hopping processes between adjacent nanoparticle aggregates of magnetite, which dominate the material's resistivity. 相似文献
992.
Isabel Marques Rodrigues Amaral Jo?o Felipe Moreira Neto Gustavo Borges Pereira Mariani Borges Franco Marcelo Emílio Beletti Warwick Estevam Kerr Ana Maria Bonetti Carlos Ueira-Vieira 《Micron (Oxford, England : 1993)》2010,41(2):123-129
Infection in insects stimulates a complex defensive response. Recognition of pathogens may be accomplished by plasma or hemocyte proteins that bind specifically to bacterial or fungal polysaccharides. Several morphologically distinct hemocyte cell types cooperate in the immune response. Hemocytes attach to invading organisms and then isolate them by phagocytosis, by trapping them in hemocyte aggregates called nodules, or by forming an organized multicellular capsule around large parasites. In the current investigation the cellular in the hemolymph third instar larvae of M. scutellaris has been characterized by means of light microscopy analysis and phagocytosis assays were performed in vivo by injection of 0.5 μm fluorescence beads in order to identify the hemocyte types involved in phagocytosis. Four morphotypes of circulating hemocytes were found in 3rd instar larvae: prohemocytes, plasmatocytes, granulocytes and oenocytoids. The results presented plasmatocytes and granulocytes involved in phagocytic response of foreign particles in 3rd instar larvae of M. scutellaris. 相似文献
993.
Guastello Stephen J. Orsucci Franco 《Nonlinear dynamics, psychology, and life sciences》2001,5(1):1-2
Nonlinear Dynamics, Psychology, and Life Sciences - 相似文献
994.
995.
High beam quality in a HyBrID copper laser operating with an unstable resonator made of a concave mirror and a plano-convex BK7 lens 总被引:1,自引:0,他引:1
Madalena Alice Priante Gio Walter Miyakawa Nicolau Andr Silveira Rodrigues Denise Maria Zezell Rudimar Riva Marcelo Geraldo Destro Jaime Tsutomu Watanuki Carlos Schwab 《Optics & Laser Technology》2006,38(7):523-527
This paper presents a very simple unstable resonator, made of a concave mirror (total reflector) and a bare plane–convex BK7 lens working as a convex coupling mirror, which is quite efficient for HyBrID copper laser. In addition to a good quality factor (M2=4.9), experimental results showed that it is possible to control the laser output power by introducing a variable aperture iris inside the cavity, close to the coupling lens, without spoiling beam quality. A rough theoretical model helped to explain these results as a combined effect of unstable resonator plus radial gain distribution. 相似文献
996.
We study the femtosecond filamentation in a liquid amplifying medium, sulphorhodamine 640 in a methanol solvent. In the presence of population inversion, the energy of the filament increases while its diameter expands because of peak intensity clamping. PACS 42.25.Bs; 42.65.Jx; 42.65.Re; 42.65.Sf 相似文献
997.
We generalize the classical Frobenius Theorem to distributions that are spanned by locally Lipschitz vector fields. The various versions of the involutivity conditions are extended by means of set-valued Lie derivatives—in particular, set-valued Lie brackets—and set-valued exterior derivatives. A PDEs counterpart of these Frobenius-type results is investigated as well. 相似文献
998.
999.
We investigate numerically the influence of the pressure on femtosecond filamentation in air. We show that femtosecond filamentation occurs at low pressure and compute the features of the plasma channel generated in the wake of the pulse. We discuss the influence of the pulse duration, chirp and input beam shape on the length of the plasma channels. These calculations constitute a prerequisite for laboratory experiments over short distances as well as for vertical femtosecond filamentation at high altitude on which light detection and ranging techniques or lightning protection rely. 相似文献
1000.
Olga Franco Ingo Orgzall Günter Reck Sabine Stockhause Burkhard Schulz 《Journal of Physics and Chemistry of Solids》2005,66(6):994-1003
The crystalline structures of two modifications of a compound containing the oxadiazole ring, 2,5-di-(4-aminophenyl)-1,3,4-oxadiazole (DAPO) were determined. One of these modifications contains water molecules in the crystal structure, which is observed for the first time for an oxadiazole crystal. Both crystals show an orthorhombic structure. The water free modification, DAPO I, belongs to the space group Pbca (61) and has the lattice parameters: a=13.461(5), b=7.937(3) and c=22.816(8) Å (CCDC 246608). The water containing pseudo-polymorph, DAPO II, has the space group Cmcm (63) and the lattice parameters: a=16.330(5), b=12.307(2) and c=6.9978(14) Å (CCDC 246609). To gain information on the inter molecular interactions within the crystals, X-ray experiments under compression at ambient temperature and under heating at vacuum conditions were performed. Neither DAPO I nor DAPO II undergo phase transitions in the ressure range up to 5 GPa, as could be concluded from X-ray and Raman experiments. X-ray and calorimetric studies indicate that DAPO II dehydrates into DAPO I under increasing temperature. Structural considerations suggest a two-stage process. The compression behavior of both substances is well described by the Murnaghan equation of state (MEOS) and the values of the bulk modulus and its pressure derivative are determined for these crystals. Additionally, in the case of DAPO I, also the thermal expansion coefficient α0 was measured. 相似文献