Label-free morphometry of retinal nerve fiber bundles by second-harmonic-generation microscopy

We present an application of second-harmonic generation (SHG) microscopy for label-free visualization and quantification of the morphology of nerve fibers in the retina. We show that SHG arises from the retinal nerve fiber layer and that it is specifically associated with uniformly oriented microtubules in the axons. The utility of axonal SHG is demonstrated for imaging the neuroanatomy of fresh ex vivo retina, and the three-dimensional structure of the axons of retinal ganglion cells is quantitatively analyzed.     

Unveiling the correlation between non‐diffracting tractor beam and its singularity in Poynting vector

This paper investigates the singular optics of nonparaxial light beams in the near field when the light behaves as a tractor beam. New insights into the optical pulling force, which is usually represented by integrating the stress tensor at a black box enclosing the object, are interpreted by the optical singularity of the Poynting vector. The negative nonconservative pulling force originates from the transfer of the azimuthal Poynting vector to the longitudinal component partly owing to the presence of a scatterer. The separatrice pattern and singularity shifts of the Poynting vector unanimously exhibit a differentiable near‐field distribution in the presence of optical pulling force. A new method is established to calculate the near‐field optical force using the differential Poynting vector in the far field. The results obtained provide a clear physical interpretation of the light–matter interaction and manifest the significance of singular optics in manipulating objects.

     

Multifractal detrended fluctuation analysis of derivative and spot markets

We investigate the multifractal properties of price increments in the cases of derivative and spot markets. Through the multifractal detrended fluctuation analysis, we estimate the generalized Hurst and the Renyi exponents for price fluctuations. By deriving the singularity spectrum from the above exponents, we quantify the multifractality of a financial time series and compare the multifractal properties of two different markets. The different behavior of each agent-group in transactions is also discussed. In order to identify the nature of the underlying multifractality, we apply the method of surrogate data to both sets of financial data. It is shown that multifractality due to a fat-tailed distribution is significant.     

Investigation of dibutyl phthalate as plasticizer on poly(methyl methacrylate)–lithium tetraborate based polymer electrolytes

Polymer electrolyte membranes, comprising of poly(methyl methacrylate) (PMMA), lithium tetraborate (Li₂B₄O₇) as salt and dibutyl phthalate (DBP) as plasticizer were prepared using a solution casting method. The incorporation of DBP enhanced the ionic conductivity of the polymer electrolyte. The polymer electrolyte containing 70 wt.% of poly(methyl methacrylate)–lithium tetraborate and 30 wt.% of DBP presents the highest ionic conductivity of 1.58 × 10⁻⁷ S/cm. The temperature dependence of ionic conductivity study showed that these polymer electrolytes obey Vogel–Tamman–Fulcher (VTF) type behaviour. Thermogravimetric analysis (TGA) was employed to analyse the thermal stability of the polymer electrolytes. Fourier transform infrared (FTIR) studies confirmed the complexation between poly(methyl methacrylate), lithium tetraborate and DBP.     

Enhancement of Near-Cloaking. Part II: The Helmholtz Equation

The aim of this paper is to extend the method of Ammari et al. (Commun. Math. Phys., 2012) to scattering problems. We construct very effective near-cloaking structures for the scattering problem at a fixed frequency. These new structures are, before using the transformation optics, layered structures and are designed so that their first scattering coefficients vanish. Inside the cloaking region, any target has near-zero scattering cross section for a band of frequencies. We analytically show that our new construction significantly enhances the cloaking effect for the Helmholtz equation.     

Interfacial electronic structure of molybdenum oxide on the fullerene layer,a potential hole-injecting layer in inverted top-emitting organic light-emitting diodes

The interfacial electronic structures of molybdenum oxide (MoO_x) deposited on fullerene (C₆₀) which could be used as a hole-injecting layer in inverted top-emitting organic light-emitting diodes (TE-OLEDs) were investigated by photoemission spectroscopy. The hole-injecting barrier height (Φ_B^h) at each interface investigated by an ultraviolet photoemission spectroscopy was reduced to from 1.4 to 0.1 eV as the thickness of MoO_x (Θ_MoOx) was increased from 0.1 to 5.0 nm on C₆₀. In these interface system, the sign of vacuum-level shift, highest occupied molecular orbital (HOMO)-level shift, and core-level shifts were all positive indicating that the interface mechanism is attributed to the work-function differences due to a band bending at these interfaces. Moreover, the near-edge X-ray absorption fine structure spectra at carbon K-edge did not show any structural modification as well as any chemical reaction at the MoO_x-on-C₆₀ interfaces when Θ_MoOx was changed on C₆₀. From these results, the inverted TE-OLED with C₆₀ (5.0 nm)/MoO_x (5.0 nm) showed the power efficiency of 1.7 lm/W at a luminance of about 1000 cd/m² and the maximum luminance of about 76.000 cd/m² at the bias voltage of 11.0 V. It exhibited the highest performance among the inverted TE-OLEDs fabricated as a function of MoO_x thickness from 0 to 5.0 nm.     

Defect formation of Au thin films on SiO2/Si upon annealing

We have studied structural changes of Au film surfaces grown on Si with native oxide layers. Using X-ray photoelectron spectroscopy (XPS), we found that annealing above 200°C can cause formation of defects (or cracks), which is most likely driven by interdiffusion of Au and Si accompanying strong Au–Si interactions at the interface regime. Scanning tunneling microscopy (STM) study is also in line with defect formation upon annealing. Interaction of O₂ with rough Au surfaces is discussed in connection with catalytic activities of Au surfaces.