XANES/EPR Evidence of the Oxidation of Nickel(II) Quinolinylpropioamide and Its Application in Csp3−H Functionalization

An in situ generated oxidation species of nickel quinolinylpropioamide intermediate was produced. Characterization by X-ray absorption near edge structure (XANES) and EPR provides complementary insights into this oxidized nickel species. With aliphatic amides and isocyanides as substrates, a nickel-catalyzed facile synthesis of structurally diverse five-membered lactams could be achieved.     

Study of ferromagnetism–superconductivity interactions in Co/Nb multilayers

We investigate Co/Nb multilayers to explore the spontaneous π-phase shift between the superconducting (SC) layers, which is attributed for causing the non-monotonic change of the SC transition temperature (T_c) with the ferromagnetic (FM) layer thickness (t_FM) in several FM/SC multilayered systems. The issue of interfacial roughness is also explored by growing Co/Nb multilayers at various sputtering pressures. Transport measurements show a non-monotonic dependence of T_c on t_FM, and this dependence is insensitive to the structural variation present in the samples, as measured by X-ray scattering.     

Simulating physiological conditions to evaluate nanoparticles for magnetic fluid hyperthermia (MFH) therapy applications

Magnetite nanoparticles with high self-heating capacity and low toxicity characteristics are a promising candidate for cancer hyperthermia treatment. In order to achieve minimum dosage to a patient, magnetic nanoparticles with high heating capacity are needed. In addition, the influence of physiological factors on the heat capacity of a material should be investigated in order to determine the feasibility. In this study, magnetite nanoparticles coated with lauric acid were prepared by co-precipitation of Fe³⁺:Fe²⁺ in a ratio of 2:1, 5:3, 3:2, and 4:3, and the pH was controlled using NaOH. Structural and magnetization characterization by means of X-ray diffractometry (XRD) and a superconducting quantum interference device (SQUID) revealed that the main species was Fe₃O₄ and further showed that most of the nanoparticles exhibited superparamagnetic properties. All of the magnetic nanoparticles showed a specific absorption rate (SAR) increase that was linear with the magnetic field strength and frequency of the alternating magnetic field. Among all, the magnetic nanoparticles prepared in a 3:2 ratio showed the highest SAR. To further test the influence of physiological factors on the 3:2 ratio magnetic nanoparticles, we simulated the environment with protein (bovine serum albumin, BSA), blood sugar (dextrose), electrolytes (commercial norm-saline) and viscosity (glycerol) to examine the heating capacity under these conditions. Our results showed that the SAR value was unaffected by the protein and blood sugar environments. On the other hand, the SAR value was significantly reduced in the electrolyte environment, due to precipitation and aggregation with sodium ions. For the simulated viscous environment with glycerol, the result showed that the SAR values reduced with increasing glycerol concentration. We have further tested the heating capacity contribution from the Néel mechanism by trapping the magnetic nanoparticles in a solid form of polydimethylsiloxane (PDMS) to eliminate the heating pathway due to a Brownian motion. We measured the heating capability and determined that 47% of the total heat generated by the magnetic nanoparticles was from the Néel mechanism contribution. For evaluating magnetic nanoparticles, this method provides a fast and low cost method for determining qualitative and quantitative information measurement for the effect of physiological interference and could greatly reduce the cost and time by in vitro or animal test.     

Preparation and characterization of carbon nanotubes/epoxy resin nano-prepreg for nanocomposites

The surface carbon nanotubes (CNTs) were modified to generate functional reactors by using the sonicication method to distribute CNTs evenly among epoxy resin, which was prepared into nano-prepreg with carbon fibers. Additionally, based on various proportions of modified and unmodified CNTs, the mechanical properties and conductivities of the composite, as well as, the characteristics of material subjected to various temperature conditions were investigated. Experimental results indicate that increasing CNT content enhances the mechanical strength and electrical properties. At various temperatures, the mechanical strength drops with increase in temperature because different expansion coefficients differ between fiber and epoxy resin. Finally, the failure surface of nanocomposite was examined using scanning electron microscopy (SEM). Finally we provide a discussion of the failure mechanism of the material.     

Optimization of erbium-doped fiber MOPA laser

An erbium-doped fiber laser (EDFL) constructed in a master oscillator and power amplifier (MOPA) configuration is analyzed. The pump powers for the fiber cavity laser and the booster amplifier stages are managed properly to achieve maximal pump conversion efficiency. Our design achieves a pump conversion efficiency of 91.4%, corresponding to a quantum efficiency of 96.6%, for a 1565.8 nm MOPA laser pumped by a total power of 300 mW at 1480 nm. The optimized MOPA laser shows a 25% enhancement in the pump conversion efficiency, compared to a non-MOPA fiber laser. A side lobe suppression ratio of 48 dB for the optimized MOPA laser is observed.     

Effect of graded triple delta-doped sheets on the performance of GaAs based dual channel pseudomorphic high electron mobility transistors

The characteristics of InGaP/InGaAs/GaAs dual channel pseudomorphic high electron mobility transistors (DCPHEMTs) with different graded triple delta-doped sheets are investigated and experimentally demonstrated. Based on a two-dimensional simulator of ATLAS, the band diagrams, electron densities and DC characteristics of studied devices are comprehensively analyzed. Due to the use of properly graded triple delta-doped sheets, good pinch-off and saturation characteristics, improved transport properties and wide current swing are obtained. For comparison, a practical DCPHEMT with good device performances is fabricated as well. It is found that the simulated data are in good agreement with experimental results.     

Comparison of CALIPSO and ground-based lidar profiles over Chung-Li, Taiwan

We report the first inter-comparison of vertical profiles of aerosols and clouds derived from space (CALIPSO) and ground based lidar over Chung-Li, Taiwan. Results show that inter-comparison is closer in case of aerosols than clouds. The strength/shortcoming of the comparison has been also discussed. An iterative calculation to retrieve extinction-to-backscatter ratio (lidar ratio) by using sun-photometer and CALIPSO data is also documented. By using the mentioned method, a mean lidar ratio of 23.5±8.2 sr was found. The derived lidar ratios are lower than former studies. The possible reasons for the difference have been discussed in this paper. The discussed methodology will be helpful to reduce the uncertainty of optical parameters derived from lidar data especially near the surface where the atmosphere is inhomogeneous.