Effect of surface roughness on determination of tissue optical properties obtained by diffusion approximation

A nylon bar with different surface roughness is used as a simulation sample of biological tissue for the determination of optical properties by using the spatially resolved steady-state diffuse reflection technique. The results obtained indicate that surface roughness has some effects on the determination of the optical properties of the nylon bar. The determined reduced scattering coefficient decreases with the decrease of the surface roughness of the nylon bar and goes to a constant for the lower surface roughness, and the determined absorption coefficient increases with the decrease of the surface roughness of the nylon bar. Consequently, the optical properties of the tissues obtained by the spatially resolved steady-state diffuse reflection technique should be modified.     

Ring-opening metathesis polymerization of norbornene derivatives for multifunctionalized all-optical photorefractive polymers with a non-conjugated main chain

With the aim of multifunctionalized all-optical photorefractive polymers bearing a non-conjugated main chain (NCMC), four novel norbornene-containing monomers were synthesized by introduction of different alkyl spacers between the functional chromophore and norbornene group. The polymers were prepared via ring-opening metathesis polymerization (ROMP) and characterized by IR, UV–Vis, GPC, DSC, TG, etc. Their number average molecular weights (M_n) are higher than 1.0 × 10⁴, and their glass transition temperatures are in the range from 75 °C to 153 °C depending on the volume of functional group and spacer length. The polymers have good thermal stability up to 280 °C and excellent solubility in THF. Optically transparent films were fabricated with N-ethyl-carbazole (ECZ) as a plasticizer and C₆₀ as a charge generator. Their photorefractive performance was evaluated at 633 nm by two-beam-coupling (TBC) experiment at a zero electrical field. TBC signals were observed from these films without prepoling, indicating that the synthesized NCMC polymers bear an all-optical photorefractive property.     

Light field imaging based on a parallel SVM method for recognizing 2D fake pedestrians

It is novel to apply three-dimensional (3D) light field imaging technology to recognize two-dimensional (2D) fake pedestrians. In this paper, we propose a parallel support vector machine (SVM) method based on 3D light field imaging (light field camera) and machine learning techniques. A light field (LF) camera with robust sensors, which is able to record rich 3D information, is used as hardware equipment. Histogram of oriented gradient (HOG) feature extraction algorithm and SVM classification method are used to recognize the real and 2D fake pedestrians efficiently. Besides, we carry out an experiment on our improved LF pedestrian dataset. The experimental results of parameter optimization study show that in the case of 400 training samples (200 positive samples and 200 negative samples), 120 to 420 testing samples, and an HOG cellsize as 8×8, the best recognition accuracy with polynomial kernel function is improved by more than 2% compared with the previous method. The best accuracy is 99.17%. Otherwise, the recognition accuracy of more than 98.00% will be obtained even under other experimental conditions.     

Morphologies of GdBO3:Eu3+ one-dimensional nanomaterials

Europium doped gadolinium orthoborate nanorods and nanoribbons were morphology-controlled grown on the porous anodic aluminum oxide (AAO) template surface via a hydrothermal process combined with high-temperature calcination. The morphologies, crystal structures and luminescent properties of the as-prepared nanomaterials were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and photoluminescence (PL) spectra. The morphologies of the nanomaterials were controlled by the calcination temperature. If calcined at 1000 °C, the morphology of the GdBO₃:Eu³⁺ one-dimensional materials is nanorods; when calcined at 800 and 600 °C, the shapes of the Eu-doped GdBO₃ are nanoribbons. If treated at 900 °C, the as-prepared samples are composed of nanorods and nanoribbons.The changed morphologies of the as-prepared nanomaterials obtained from different calcination temperatures were explained according to the structural phase transition of GdBO₃. The PL spectrum shows that the characteristic emission of GdBO₃:Eu³⁺ one-dimensional nanomaterials is the ⁵D₀ → ⁷F₁ transition.     

Study on the relation between the refractive index of fresh muscle tissue and its water content from 400 to 750 nm

Refractive index dispersion (RID) of fresh tissue is highly related to water content. However, there is no experimental investigation about their relationship for a wide spectral range. In this study, with the aid of a previously proposed lab-made apparatus, the RID of fresh and fully-dehydrated mutton muscle samples were measured over the continuous spectral range from 400 to 750 nm. The mass fractions and volume fractions were also measured. Results showed that the RID of fresh muscle tissue equals to the sum of fully-dehydrated tissue RID and water RID multiplied by their respective volume fractions. The results in this study also experimentally proved that the effective medium theory of refractive index is applicable for tissue analysis.     

Mid-infrared ridge waveguide in MgO:LiNbO3 crystal produced by combination of swift O5+ ion irradiation and precise diamond blade dicing

We report on the fabrication of ridge waveguide operating at mid-infrared wavelength in MgO:LiNbO₃ crystal by using O⁵⁺ ion irradiation and precise diamond blade dicing. The waveguide shows good guiding properties at the wavelength of 4 μm along the TM polarization. Thermal annealing has been implemented to improve the waveguiding performances. The propagation loss of the ridge waveguide has been reduced to be 1.0 dB/cm at 4 μm after annealing at 310 °C. The micro-Raman spectra indicate that the microstructure of the MgO:LiNbO₃ crystal has no significant change along the ion track after swift O⁵⁺ ion irradiation.     

Electronic structure of alkali-metal/alkaline-earth-metal fluorine beryllium borate NaSr3Be3B3O9F4 single crystal: DFT approach

The electronic band structure, total and angular momentum resolved projected density of states for NaSr₃Be₃B₃O₉F₄ are calculated using the all-electron full potential linearized augmented plane wave plus local orbitals (FP-LAPW + lo) method. The calculations are performed within four exchange correlations namely; local density approximation (LDA), general gradient approximation (PBE-GGA), Engel–Vosko generalized gradient approximation (EVGGA) and the recently modified Becke–Johnson potential (mBJ). Calculations suggest that NaSr₃Be₃B₃O₉F₄ is a direct wide band gap semiconductor. The exchange correlations potentials exhibit significant influence on the value of the energy gap being about 4.82 eV (LDA), 5.16 eV (GGA), 6.20 (EVGGA) and 7.20 eV (mBJ). The mBJ approach succeed by large amount in bringing the calculated energy gap closer to the experimental one (7.28 eV). The angular momentum resolved projected density of states shows the existence of a strong hybridization between the various orbitals. In additional we have calculated the electronic charge density distribution in two crystallographic planes namely (1 0 1) and (0 0 −1) to visualized the chemical bonding characters.     

The optimal design of photonic crystal optical devices with step-wise linear refractive index

In the paper, we have studied one-dimensional step-wise linear photonic crystal with and without defect layer, and analyzed the effect of defect layer position, thickness, refractive index real part and imaginary part on the transmissivity, electric field distribution and output electric field intensity. By calculation, we have obtained a set of optimal parameters, which can be optimally designed optical device, such as optical amplifier, attenuator, optical diode by the step-wise linear photonic crystal.     

Large-area high-performance SERS substrates with deep controllable sub-10-nm gap structure fabricated by depositing Au film on the cicada wing

Noble metal nanogap structure supports strong surface-enhanced Raman scattering (SERS) which can be used to detect single molecules. However, the lack of reproducible fabrication techniques with nanometer-level control over the gap size has limited practical applications. In this letter, by depositing the Au film onto the cicada wing, we engineer the ordered array of nanopillar structures on the wing to form large-area high-performance SERS substrates. Through the control of the thickness of the Au film deposited onto the cicada wing, the gap sizes between neighboring nanopillars are fine defined. SERS substrates with sub-10-nm gap sizes are obtained, which have the highest average Raman enhancement factor (EF) larger than 2 × 10⁸, about 40 times as large as that of commercial Klarite® substrates. The cicada wings used as templates are natural and environment-friendly. The depositing method is low cost and high throughput so that our large-area high-performance SERS substrates have great advantage for chemical/biological sensing applications.