Transflective liquid-crystal display using low-twisted vertically aligned mode

We present the design of a transflective and low-power LCD using a low-twist vertically aligned liquid crystal (LC) cell, achieved by blending a chiral additive with a patterned reflector in a single-domain configuration. Unlike the conventional single-domain transflective LCD, in which it is possible to optimize only one of the transmissive and reflective regions, the device suggests that it is possible to optimize both the transmission and reflection design to obtain favorable results in both reflective and transmissive light conditions by optimizing the chiral pitch and twist angle. From the parameter space diagram (PSD) method, which does not include the information on chiral pitch and the nonuniform LC director tilt angle, optimization focused on the transmissive region is performed. By analyzing the relation between the transmittance and the chiral pitch under the applied voltage, the optimized twist angle and chiral pitch are proposed. It is described that the optimized twist angle is also available for the reflective region by the dynamic PSD method by considering the average tilt angle under applied voltage.     

Some New Features in the Pseudoscalar Meson and Vector Meson Photoproductions

We investigate the role of the t-channel meson exchange in various photoproduction processes to discuss features of the respective production mechanism. For the less model-dependent analysis we work with the t-channel meson pole reggeized in the Born approximation amplitude. With the meson–baryon coupling constants chosen consistently with symmetry prediction we show that the Reggeized pole model could reproduce the experimental data to a good degree in the lower energy region. Numerical consequences show the significance of the tensor meson exchange in the γ p → K ⁺Λ, the dominance of the pseudoscalar meson exchange in the πΔ (and KΣ*) processes, and the sizable role of the vector-meson magnetic moment in the charged ρ (and K*) photoproductions, respectively. These new features from the present analyses could provide a useful guide for future study of the N* resonances in the low energy region.     

Determination of the debris produced from poly(ethylene terephthalate) during KrF excimer laser ablation

Pulsed UV laser beams, which are widely used in the processing of polymers, have many advantages because their photon energy is higher than the binding energy of polymers. Fabricating polymers with a UV laser process is faster, cleaner, and more convenient than with other processes. Nevertheless, some problems occur in the precision microprocessing of polymers. For example, the formation and deposition of surface debris, which is produced from the breakdown of either polymer chains or radical bonds.To determine the formation and origin of surface debris, a KrF excimer laser beam (248 nm) was used in the processing of poly(ethylene terephthalate) (PET). The investigation of the debris formation was facilitated by UV-vis spectroscopy, ATR FT-IR spectroscopy, and NMR spectroscopy. The UV-vis absorption peak indicates that the primary chromophore in the PET is benzoate. Furthermore, because benzoate causes the primary absorption, the absorbed energy is transferred by heat generation to an unsaturated ester. The ATR FT-IR spectrometer measurements show that the phenyl systems in the benzoate are demolished by ablation. This phenomenon indicates that the photochemical reaction causes the benzoate bonds to break down, and this breakdown in turn causes the carbonization to leave debris on the PET.     

Temperature effect on deposition rate of silicon nitride films

Temperature effects on deposition rate of silicon nitride films were characterized by building a neural network prediction model. The silicon nitride films were deposited by using a plasma enhanced chemical vapor deposition system and process parameter effects were systematically characterized by 2⁶⁻¹ fractional factorial experiment. The process parameters involved include a radio frequency power, pressure, temperature, SiH₄, N₂, and NH₃ flow rates. The prediction performance of generalized regression neural network was drastically improved by optimizing multi-valued training factors using a genetic algorithm. Several 3D plots were generated to investigate parameter effects at various temperatures. Predicted variations were experimentally validated. The temperature effect on the deposition rate was a complex function of parameters but N₂ flow rate. Larger decreases in the deposition rate with the temperature were only noticed at lower SiH₄ (or higher NH₃) flow rates. Typical effects of SiH₄ or NH₃ flow rate were only observed at higher or lower temperatures. A comparison with the refractive index model facilitated a selective choice of either SiH₄ or NH₃ for process optimization.     

Band gap tunable and improved microstructure characteristics of Cu2ZnSn(S1−x,Sex)4 thin films by annealing under atmosphere containing S and Se

Cu₂ZnSn(S_xS_1?x)₄ (CZTSSe) thin films were prepared by annealing a stacked precursor prepared on Mo coated glass substrates by the sputtering technique. The stacked precursor thin films were prepared from Cu, SnS₂, and ZnS targets at room temperature with stacking orders of Cu/SnS₂/ZnS. The stacked precursor thin films were annealed using a tubular two zone furnace system under a mixed N₂ (95%) + H₂S (5%) + Se vaporization atmosphere at 580 °C for 2 h. The effects of different Se vaporization temperature from 250 °C to 500 °C on the structural, morphological, chemical, and optical properties of the CZTSSe thin films were investigated. X-ray diffraction patterns, Raman spectroscopy, and X-ray photoelectron spectroscopy results showed that the annealed thin films had a single kesterite crystal structure without a secondary phase. The 2θ angle position for the peaks from the (112) plane in the annealed thin films decreased with increasing Se vaporization temperature. Energy dispersive X-ray results showed that the presence of Se in annealed thin films increased from 0 at% to 42.7 at% with increasing Se vaporization temperatures. UV–VIS spectroscopy results showed that the absorption coefficient of all the annealed thin films was over 10⁴ cm^?1 and that the optical band gap energy decreased from 1.5 eV to 1.05 eV with increasing Se vaporization temperature.     

Surface–plasmon-coupled photoluminescence from CdS nanoparticles with Au films

The enhancement of surface–plasmon-coupled photoluminescence from CdS nanoparticles was examined for various thicknesses of sputtered Au films. The improved luminescence with thickness control of Au correlated well with the increased density of surface–plasmon states, which was modified by the plasmon-dispersion relation at the planar Au/PMMA interface. By annealing the Au films to form a rough surface morphology, the emission in the CdS nanoparticles was further enhanced by the improved excitation and coupling of the surface–plasmon modes.     

Small sample properties of generalized logit model estimators with bootstrap

The generalized logit model of nominal type with random regressors is studied for bootstrapping. We assess the accuracy of some estimators for our generalized logit model, using a Monte Carlo simulation. That is, we study the finite sample properties containing the consistency and asymptotic normality of the maximum likelihood estimators. Also, we compare Newton Raphson algorithm with BHHH algorithm.     

Paradoxical high signal intensity of hepatocellular carcinoma in the hepatobiliary phase of Gd-EOB-DTPA enhanced MRI: initial experience

Purpose

To describe the paradoxical high signal intensity of hepatocellular carcinoma (HCC) in the hepatobiliary phase on gadolinium-ethoxybenzyl-diethylenetriamine pentaacetic acid (Gd-EOB-DTPA)-enhanced magnetic resonance imaging (MRI).

Materials and Methods

A database search was performed to identify cases of HCC that showed unusual prolonged enhancement in the hepatobiliary phase of Gd-EOB-DTPA MRI. All patients received 3.0-T liver MRI including precontrast T1-weighted images, T2-weighted images and a post Gd-EOB-DTPA-enhanced dynamic study. The signal intensity of HCC was measured at pre-enhanced, arterial, portal, delayed and hepatobiliary phase using regions of interest. Radiologic and pathologic correlation was performed for the paradoxically prolonged enhancing portion of HCC in the hepatobiliary phase.

Results

Four patients (all male, age range 44-70; mean 57.5 years) were included in this study. All patients showed HCC lesions that were low signal intensity (SI) on T1-WI, high SI on T2-WI, enhanced in arterial phase, and washed-out in delayed phase. All cases showed paradoxically high SI in hepatobiliary phase, which was unusual for HCC. Pathologically, they were all diagnosed as well-differentiated HCC with prominent cytoplasm and a bile secreting appearance.

Conclusion

HCC may demonstrate the prolonged high signal intensity at the hepatobiliary phase on Gd-EOB-DTPA enhanced MRI. These HCCs tended to be highly differentiated and to have prominent bile secretion.     

Electro‐optic switching with liquid crystal graphene

Graphene oxide (GO) particles in aqueous dispersions can form liquid crystal (LC) phases at extremely low concentrations due to the extremely high aspect ratio of the flakes and noticeably, they possess an extremely large Kerr coefficient attractive for low power consumption electro‐optic devices. Reduced graphene does not easily form LC phases in water due to its hydrophobic nature but here we show that stable dispersions of reduced graphene oxide can be realized with surfactants and that they exhibit birefringence upon shearing as well as under application of electric fields. The performance of the system is largely superior to GO LC possessing longer time stability and drastically improved electro‐optic properties with an induced birefringence twice as large at the same field strength thanks to the almost recovery of graphene properties upon reduction. (© 2016 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)