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141.
A novel phase-control method with application to phase-shifting interferometry is presented. The linear polarization state of an external (green) light beam is recorded on a bacteriorhodopsin film, and this polarization state is read by a circular polarized (red) laser beam. By reading the bacteriorhodopsin film, the original (red) wave reverses its circularity and becomes phase shifted by an amount that is dependent on the polarization of the external (green) beam. This method of phase control can be applied in a two-beam interferometer in which the test and reference waves are orthogonally polarized, which allows one to obtain phase modulation without moving parts inside the interferometer. 相似文献
142.
P.?SantiagoEmail author J.A.?Ascencio D.?Mendoza M.?Pérez-Alvarez A.?Espinosa C.?Reza-SanGermán P.?Schabes-Retchkiman G.A.?Camacho-Bragado M.?José-Yacamán 《Applied Physics A: Materials Science & Processing》2004,78(4):513-518
In the present work we report the synthesis of MoS2 nanotubes with diameters greater than 10 nm using a template method. The length and properties of these nanotubes are a direct result of the preparation method. High-resolution transmission electron microscopy is used to study the structure of these highly curved entities. Molecular dynamics simulations of MoS2 nanotubes reveal that one of the stable forms of the nanotubes is a twisted one. The twisting of the nanotubes produces a characteristic contrast in the images, which is also studied using simulation methods. The analysis of the local contrast close to the perpendicular orientation shows geometrical arrays of dots in domain-like structures, which are demonstrated to be a product of the atomic overlapping of irregular curvatures in the nanotubes. The configuration of some of the experimentally obtained nanotubes is demonstrated to be twisted with a behavior suggesting partial plasticity. PACS 61.16.Bg; 79.60.Jv; 61.46.+w; 61.50.Ah 相似文献
143.
Nacimiento F Alcántara R Nwokeke UG González JR Tirado JL 《Ultrasonics sonochemistry》2012,19(2):352-357
A sonochemical method has been used to prepare negative electrode materials containing intermetallic nanoparticles and polyacrylonitrile (PAN). The ultrasound irradiation is applied to achieve small particle size. After annealing at 490 °C under Ar-flow, the polymer PAN is partially carbonized and the metallic nanoparticles are surrounded by a carbonaceous matrix. The main metallic phase is CoSn2. The carbonaceous coating and the surface oxides have been explored by using XPS. The resulting CoSn2-carbonaceous phase electrode (CoSn2@C) shows improved electrochemical behavior (ca. 450 mAh/g after 50 cycles) in comparison with previous reports on pure crystalline CoSn2. The reaction between CoSn2@C and Li has been studied by using XRD and 119Sn Mössbauer spectroscopy. The formation of large grains of crystalline LixSn phases after the first discharge is discarded. The small particle size which is achieved by using ultrasonication and the carbonaceous matrix contribute to maintain the Co-Sn interactions during the electrochemical cycling. The aggregation of the nanosized metallic particles upon electrochemical cycling can be suppressed by the carbonaceous matrix (pyrolytic PAN). 相似文献
144.
Jos�� Fl��vio Marcelino Borges Marlon Luiz Hneda Andr�� Maur��cio Brinatti Jo?o Batista Marimon da Cunha Jadir Aparecido Rosa Jos�� Domingos Fabris 《Hyperfine Interactions》2011,203(1-3):9-15
A sample of the coarse sand fraction from the soil material of the A-horizon (0?C0.2 m from the soil surface) of a dusky red magnetic Oxisol was submitted to high-energy mechanical milling for different times. This assay aimed mainly at (a) monitoring the individualization of strongly aggregated mineral particles, and (b) measuring the effect of the milling pressure on the mineralogy changes of the material. These data are also intended to experimentally subside any physical model describing the mechanical behavior of the superficial soil layer that is subjected to intensive machine management, in agriculture fields. Powder X-ray data reveal that some mineralogical phases, notably gibbsite, disappear soon after the first few hours milling. The 298 K-transmission Mössbauer spectrum for the non-milled sand sample shows a qualitatively typical pattern for the sand fraction of basalt derived soils, with magnetically ordered sextets, assignable mainly to hematite and maghemite, and an intense central (super)paramagnetic Fe3?+? doublet. For the milled samples, spectra revealed progressive spectral reduction of the magnetic hyperfine structure, with concomitant increase of relative subspectral areas due to (super)paramagnetic phases, as the milling time increased. This result is consistent with the reduction of measured saturation magnetization, from 4.96(8) J T???1 kg???1, for the non-milled sample, to 3.26(7) J T???1 kg???1, for the sample milled for 8 hours. 相似文献
145.
José F. Cariñena Javier de Lucas Manuel F. Rañada 《International Journal of Theoretical Physics》2011,50(7):2114-2124
A geometric approach is used to study the Abel first-order differential equation of the first kind. The approach is based
on the recently developed theory of quasi-Lie systems which allows us to characterise some particular examples of integrable
Abel equations. Second order Abel equations will be discussed and the inverse problem of the Lagrangian dynamics is analysed:
the existence of two alternative Lagrangian formulations is proved, both Lagrangians being of a non-natural class. The study
is carried out by means of the Darboux polynomials and Jacobi multipliers. 相似文献
146.
The gadolinium-based manganite GdMnO3 of perovskite structure has been partially substituted at the manganese site by transition metal elements Me like Cu, Ni and Co, leading to a general formula GdMexMn1−xO3, in which different magnetic entities (e.g., Gd3+, Cu2+, Ni2+, Co2+, Co3+, Mn3+, Mn4+) can coexist, depending on charge equilibrium conditions. For divalent cations such as Cu2+ and Ni2+, the solid solution extends from x (Me)=0–0.5, with O-type orthorhombic symmetry (a<c/√2<b). When the substituting element is cobalt, the solid solution extends over the whole range [0?x ?1], changing from O′-type symmetry (c/√2<a<b) to O-type for x>0.5. In this latter case, the synthesis is performed under oxygen flow, which allows the cobalt ion to take a 3+ oxidation state. 相似文献
147.
We analyze the forces on a small dipolar particle and the electromagnetic momentum density in a configuration consisting in two perpendicular circularly polarized stationary waves. The field distribution shows regions in which the electric and magnetic fields are parallel corresponding to a null Poynting vector. Although the average value of the momentum density, proportional to the Poynting vector, is zero in these regions, there are scattering forces acting on small particles due to light's spin force. The total scattering force suggests a new definition of the average value of the momentum density for free propagating electromagnetic fields. 相似文献
148.
Magon CJ Lima JF Ribeiro RR Martins MJ 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2007,184(1):176-183
When the spin Hamiltonian is a linear function of the magnetic field intensity the resonance fields can be determined, in principle, by an eigenfield equation. In this report, we show a new technical approach to the resonance field problem where the eigenfield equation leads to a dynamic equation or, more specifically, to a first order differential equation of a variable L(x), where x is associated with the magnetic field h. Such differential equation has the property that: its stationary solution is the eigenfield equation and the spectral information contained in L(x) is directly related to the resonance spectrum. Such procedure, known as the "harmonic inversion problem" (HIP), can be solved by the "filter diagonalization method" (FDM) providing sufficient precision and resolution for the spectral analysis of the dynamic signals. Some examples are shown where the resonance fields are precisely determined in a single procedure, without the need to solve eigenvalue equations. 相似文献
149.
José P.B. Silva Koppole C. Sekhar Sofia A.S. Rodrigues Anatoli Khodorov Javier Martín-Sanchez Mário Pereira Maria J.M. Gomes 《Current Applied Physics》2012,12(4):1144-1147
The effect of pulse amplitude on the ferroelectric and switching properties of pulsed laser deposited Ba0.8Sr0.2TiO3 thin films has been studied. The structural and morphological analysis revealed that the films had a well crystallized perovskite phase and grain size of about 30–40 nm. A well saturated P–E hysteresis loop was observed with a remnant polarization (Pr) ≈ 4.8 μC/cm2 and a coercive field ≈ 100 kV/cm at a frequency of 1 kHz. The Pr has been found to be decreased only 4.3% after passing 8.0 × 108 cycles. The analysis of switching response with nucleation limited switching model reveals that characteristic switching time (t0) variance is due to the random distribution of the local electric fields. The peak value of polarization current and t0 exhibits exponential dependence on reciprocal of pulse amplitude. 相似文献