Existence and uniqueness of stabilized propagating wave segments in wave front interaction model

Recent experimental studies of photosensitive Belousov–Zhabotinskii reaction have revealed the existence of propagating wave segments. The propagating wave segments are unstable, but can be stabilized by using a feedback control to continually adjust the excitability of the medium. Experimental studies also indicate that the locus of the size of a stabilized wave segment as a function of the excitability of the medium gives the excitability boundary for the existence of 2D wave patterns with free ends in excitable media. To study the properties of this boundary curve, we use the wave front interaction model proposed by Zykov and Showalter. This is equivalent to study a first order system of three ordinary differential equations which includes a singular nonlinearity. Using two different reduced first order systems of two ordinary differential equations, we first show the existence of wave segments for any given propagating velocity. Then the wave profiles can be classified into two types, namely, convex and non-convex types. More precisely, when the normalized propagating velocity is small, we show that the wave profile is of convex type, while the wave profile is of non-convex type when the normalized velocity is close to 1.     

Design and construction of a compact end-station at NSRRC for circular-dichroism spectra in the vacuum-ultraviolet region

A synchrotron‐radiation‐based circular‐dichroism end‐station has been implemented at beamline BL04B at the National Synchrotron Radiation Research Center (NSRRC) in Taiwan for biological research. The design and performance of this compact end‐station for measuring circular‐dichroism spectra in the vacuum‐ultraviolet region are described. The linearly polarized light from the beamline is converted to modulated circularly polarized light with a LiF photoelastic modulator to provide a usable wavelength region of 130–330 nm. The light spot at the sample position is 5 mm × 5 mm at a slit width of 300 µm and provides a flux greater than 1 × 10¹¹ photons s^?1 (0.1% bandwidth)^?1. A vacuum‐compatible cell made of two CaF₂ windows has a variable path length from 1.3 µm to 1 mm and a temperature range of 253–363 K. Measured CD spectra of (1S)‐(+)‐10‐camphorsulfonic acid and proteins demonstrated the ability of this system to extend the wavelength down to 172 nm in aqueous solution and 153 nm in hexafluoro‐2‐propanol.     

Aggregation induced polyelectrolyte multilayer film containing cubic silsesquioxane nanoparticles

Polyelectrolyte multilayer (PEM) films offer a method to functionalize substrates with specific properties that enable the films to be used for a variety of purposes. Desirable qualities of PEM films can include mechanical strengths, ease of preparations, flexibility, and their abilities to have their properties tailored to suit a particular process. We present a simple method to fabricate a class of PEM films that incorporate cubic silsesquioxane nanoparticles (CSSQ). Through a spin self-assembly (SSA) process, a hybrid multilayered film with two-components, namely, poly(styrene sulfonate) (PSS) and octaammonium cubic silsesquioxane (CSSQ) nanoparticle have been fabricated. The formation of this multilayer film is further verified by ellipsometry, contact angle studies, and atomic force microscopy (AFM). The water contact angle and ellipsometric measurements exhibit that the (PSS/OA-CSSQ) films are deposited onto the substrate. The surface topography of the deposited bilayers of PSS/OA-CSSQ film appears to be uniformly distributed with extremely small granules but the film uniformity of the granular surface is diminished and clusters of granules are observed at above 5 bilayers due to the aggregation of the OA-CSSQ nanoparticles.     

Tip-induced local anodic oxidation on p-GaAs surface with non-contact atomic force microscopy

Nano-sized oxide structures resulted from localized electrochemical oxidation induced by a negatively biased atomic force microscopy (AFM) tip operated with the non-contact mode were fabricated on p-GaAs(1 0 0) surface. The geometrical characteristics of the oxide patterns and their dependences on various fabrication parameters, e.g., the anodization time, the biased voltages, the tip scanning rates, as well as the formation mechanism and relevant growth kinetics are investigated. Results indicate that the height of the protruded oxide dots grow exponentially as a function of time in the initial stage of oxidation and soon reaches a maximum height depending linearly with the anodized voltages, in according with the behaviors predicted by space charge limited local oxidation mechanism. In addition, selective micro-Auger analysis of the anodized region reveals the formation of Ga(As)O_x, indicating the prominent role played by the field-induced nanometer-size water meniscus in producing the nanometer-scale oxide dots and bumps on p-GaAs(1 0 0) surface.     

An identification of the connections of Quillen and Beilinson-Schechtman

Given a family of Riemann surfaces and a holomorphic vector bundle Beilinson and Schechtman construct a canonical connection on the associated determinant bundle. We prove the conjecture which states that their connection coincides with the Quillen connection. This is done by reducing to the case where along fibers are invertible. Both connection forms become more accessible in this case.Supported in part by N.S.F. Grant No. DMS-9201022Supported in part by National Science Council of Republic of China Grant No. NSC 82-0208-M-002-125-T, and NSERC of Canada Grant No. OGP 0121883     

A bidirectional hybrid DWDM-PON employing optical injection locking technique and data comparators

A bidirectional hybrid dense-wavelength-division-multiplexing (DWDM)-passive optical network (PON) employing optical injection locking technique on vertical-cavity surface-emitting lasers (VCSELs) and data comparator, as well as optical injection locking technique on distributed feedback laser diodes (DFB LDs) and amplitude/phase compensator is proposed and demonstrated. Improved performances of bit error rate (BER) and carrier-to-noise ratio/composite second order/composite triple beat (CNR/CSO/CTB) were observed in our proposed bidirectional hybrid DWDM-PON. Bidirectional transmission in bidirectional hybrid DWDM-PON architecture is a very attractive option, the capacity of the optical network can be expanded relatively easily by bidirectional transmission technology.     

Decoherence of flux qubits due to 1/f flux noise

We have investigated decoherence in Josephson-junction flux qubits. Based on the measurements of decoherence at various bias conditions, we discriminate contributions of different noise sources. We present a Gaussian decay function extracted from the echo signal as evidence of dephasing due to 1/f flux noise whose spectral density is evaluated to be about (10(-6)Phi0)2/Hz at 1 Hz. We also demonstrate that, at an optimal bias condition where the noise sources are well decoupled, the coherence observed in the echo measurement is limited mainly by energy relaxation of the qubit.     

Prominin‐1‐Specific Binding Peptide‐Modified Apoferritin Nanoparticle Carrying Irinotecan as a Novel Radiosensitizer for Colorectal Cancer Stem‐Like Cells

Resistance of cancer stem cells to radiotherapy remains a major obstacle to successful cancer management. Prominin‐1 (PROM1) is a cancer stem cell marker. Nanoparticle (NP) chemotherapeutics preferentially accumulate in tumors and are able to target cancer and cancer stem‐like cells through cancer cell‐specific ligands, making them uniquely suited as radiosensitizers for chemoradiation therapy. Using a biocompatible apoferritin NP, a PROM1‐targeted NP carrying irinotecan (PROM1‐NP) is engineered. The synergistic effect of the NP and irradiation is evaluated in PROM1‐overexpressing HCT‐116 colorectal cancer cell lines in vitro and in vivo. PROM1‐NP has a size of 17.2 ± 0.2 nm and surface charge of ?13.5 ± 0.2 mV. It demonstrates higher intracellular uptake than nontargeted NP or irinotecan alone. Treatment with PROM1‐NPs decreases HCT‐116 cell proliferation in a dose‐ and time‐dependent manner. In vitro radiosensitization reveals that PROM1‐NP is significantly more effective as a radiosensitizer than nontargeted NP or irinotecan. HCT‐116 tumor xenograft growth is markedly slower following treatment with PROM1‐NP plus irradiation, suggesting that PROM1‐NP is more effective as a radiosensitizer than irinotecan and nontargeted NP in vivo. This study provides the first preclinical evidence of the effectiveness of PROM1‐targeted NP formulation of irinotecan as a radiosensitizer.     

Optimization of microcrystalline silicon thin film solar cell isolation processing parameters using ultraviolet laser

This study used ultraviolet laser to perform the microcrystalline silicon thin film solar cell isolation scribing process, and applied the Taguchi method and an L₁₈ orthogonal array to plan the experiment. The isolation scribing materials included ZnO:Al, AZO transparent conductive film with a thickness of 200 nm, microcrystalline silicon thin film at 38% crystallinity and of thickness of 500 nm, and the aluminum back contact layer with a thickness of 300 nm. The main objective was to ensure the success of isolation scribing. After laser scribing isolation, using the minimum scribing line width, the flattest trough bottom, and the minimum processing edge surface bumps as the quality characteristics, this study performed main effect analysis and applied the ANOVA (analysis of variance) theory of the Taguchi method to identify the single quality optimal parameter. It then employed the hierarchical structure of the AHP (analytic hierarchy process) theory to establish the positive contrast matrix. After consistency verification, global weight calculation, and priority sequencing, the optimal multi-attribute parameters were obtained. Finally, the experimental results were verified by a Taguchi confirmation experiment and confidence interval calculation. The minimum scribing line width of AZO (200 nm) was 45.6 μm, the minimum scribing line width of the microcrystalline silicon (at 38% crystallinity) was 50.63 μm and the minimum line width of the aluminum thin film (300 nm) was 30.96 μm. The confirmation experiment results were within the 95% confidence interval, verifying that using ultraviolet laser in the isolation scribing process for microcrystalline silicon thin film solar cell has high reproducibility.     

Determination of 129I in cement-solidified radwastes using neutron activation

The purpose of this study is to develop a neutron activation method to determine trace amounts of ¹²⁹I in cement-solidified radwastes. The radwaste samples were alkaline fused using KOH and then ¹²⁹I and iodine carrier were chemically separated by solvent extraction before and after neutron irradiation. Both stable iodine (¹²⁷I) and ¹²⁹I can be activated by neutrons through ¹²⁷I (n, 2n) ¹²⁶I and ¹²⁹I (n, γ) ¹³⁰I reactions; their activated radionuclides were counted together with a high-purity germanium detector. The chemical recovery yields ranged from 30 to 60 %, and it was found that more than 99.9 % of interfering radionuclides can be removed using solvent extraction after neutron irradiation. The minimum detectable amounts can be lowered to less than 1 mBq g^?1, which is superior to low energy γ-ray spectrometry by a factor of >10², on average. The established technique can be applied to re-evaluation of ¹²⁹I content in radwastes that can be re-classified to lower classes, and the cost for designing a final disposal facility can be significantly reduced.