Synthesis and electrochemical characterization of carbon nanotubes decorated with nickel nanoparticles for use as an electrochemical capacitor

Attachment of nickel nanoparticles on multiwalled carbon nanotubes (MWCNTs) was conducted to explore the influence of Ni loading on the electrochemical capacitance of MWCNT electrodes. A chemical impregnation leaded to homogeneously disperse Ni particles onto the surface of MWCNTs, and the Ni particles were found to be an average size of 30–50 nm. The capacitive behavior of the MWCNT electrodes was investigated in 6 M KOH, by using cyclic voltammetry (CV), charge–discharge cycling, and ac electrochemical impedance spectroscopy. CV measurements showed that the Faradaic current was found to increase with the Ni coverage, indicating that the presence of Ni would enhance the pseudocapacitance through the redox process. Equivalent circuit analysis indicated that both of electrical connection and charge transfer resistances accounted for the major proportion of the overall resistance and were found to decrease with the amount of nickel. A linearity relationship between the total capacitance and the Ni population reflected that each Ni particle exhibits an identical electrochemical activity in enhancing the electrochemical capacitance. The overall electrochemical capacitance (including double layer capacitance and pseudocapacitance) of Ni-MWCNT electrode can reach a maximum of 210 F/g over 500 cycles.     

Phragmèn–Lindelöf Theorem of Minimal Surface Equations in Domains with Symmetry

Here we prove that if u satisfies the minimal surface equation with vanishing Dirichlet data, in an unbounded domain which is contained in a domain with symmetry, then the growth rate of u is determined completely by the shape of .     

Selective deprotection of acetals with Me3SiCH2MgCl. Peterson-type olefination of acetals

By employing the chelation strategy, treatment of an acetal of a contiguous diol with Me3SiCH2MgCl liberates the corresponding diol regioselectively. In addition, acetals of different structural variety are transformed upon treatment with Me3SiCH2MgCl and ZnI2 into the corresponding olefination products in good yield.     

The electronic structure of Ba1−xCaxTiO3 probed by X-ray absorption spectroscopy

We report O K-, Ca K- and L_3,2-, and Ti L_3,2-edge X-ray absorption near edge structure (XANES) spectra of Ba_1−xCa_xTiO₃ (x=0, 0.01, 0.08, and 1) and the electronic properties inferred from these XANES spectra. The spectra of O K-, Ca L_3,2- and Ti L_3,2-edges show characteristic spectral features attributable to the t_2g and e_g bands. The Ti and Ca L_3,2-edge spectra contain two sets of L₃ and L₂ features with a L₃-L₂ separation of about 5.5 and 3.4 eV, respectively. We also observe a pre-edge feature in the Ca K-edge spectra and drastically reduced t_2g features in the Ca L_3,2-edge spectra. Our XANES spectra reveal that the Ca 3d bands are low-lying and the Ca 3d t_2g bands are partially occupied.     

Moving of a nonhomogeneous, porous floc normal to a rigid plate

The boundary effect on the moving of a porous, nonhomogeneous, spherical floc normal to a rigid plate is analyzed theoretically for the case of low to medium Reynolds number. In particular, the drag force acting on the floc under various conditions is evaluated. A two-layer structure is adopted to simulate the nonhomogeneous nature of a floc. We show that if a floc is away from the plate, the streamlines surrounding the floc are distorted, but the degree of distortion becomes less significant if the floc is near the plate. The modified drag coefficient of a porous floc is orders of magnitude smaller than that of the corresponding rigid particle. For a fixed volume-averaged permeability, the effect of the presence of the plate on the behavior of a nonhomogeneous floc is more significant than that of a homogeneous floc, and this effect depends largely on the structure of a floc. The nonhomogeneous structure of a floc leads to a positive deviation from a Stokes-law-like correlation in the modified drag coefficient, and the smaller the volume-averaged permeability of a floc the greater the deviation. The presence of the plate has the effect of reducing this deviation. The nonhomogeneous structure of a floc on its modified drag coefficient is pronounced when it is close to a boundary.     

Photoelectronic properties of Cu3PS4 and Cu3PS3Se single crystals

Single crystals of Cu₃PS₄ and Cu₃PS₃Se grown by chemical vapor transport were shown to be diamagnetic p-type semiconductors. Electrical measurements showed room temperature resistivities ranging from 1 to 5 ohm-cm and carrier concentrations of 10¹⁷ cm^?3. Both materials were shown to be active as cathodes for the photoelectrolysis of water. Spectral response measurements show that substitution of selenium for sulfur lowers the optical band gap from 2.38(5) eV for Cu₃PS₄ to 2.06(4) eV for Cu₃PS₃Se.     

Fabrication of a Flexible and Disposable Microreactor Using a Dry Film Photoresist

In this paper, we demonstrate that a low‐cost flexible microreactor can be manufactured using a dry film photoresist in conjunction with photolithographic and hot roll lamination techniques. A microfluidic flow path and sample reservoir patterns were prefabricated in a dry film photoresist tape using traditional photolithographic methods. This tape was sandwiched between two plastic films ‐ wells were prepouched on the cover film — that were bonded upon passage through a hot roll laminator. A simple Plexiglas reactor holder was designed and constructed to use in evaluating the flexible microchip reactor. We demonstrate a chemical synthesis of polyaniline that was performed with this polymeric microreactor using a hydrodynamic flow control system. The fabrication of this microreactor suggests that there is great potential for designing and prototyping disposable microscale reaction systems using dry film photoresist for a range of chemical and biochemical syntheses.     

Formation Mechanisms of Sol-Gel-Derived Hydroxyapatite Using Different Thermal Processings

Sol-gel-derived hydroxyapatite (HA) precursors were calcined by two thermal processings, a rapid-thermal-calcine (RTC) heating at 100–600°C/min and a conventional-furnace-calcine (CFC) heating at 1.67°C/min, respectively. X-ray diffraction patterns revealed that the onset temperature of HA crystallization is lower in RTC, 350°C, as compared to 600°C in CFC. Pyrolytic-GC/MS programs showed that the evolved gases out of a sample subjected to RTC are mainly H₂O, N₂O and ethylamine, while those of a sample subjected to CFC are CO₂ and small organic molecules. The results leads to models that RTC can quickly remove organic portion of the gel networks, leading to a porous surface morphology and a collapse of gel networks at local areas, so that HA crystallite nucleation is facilitated due to intimate contacts among inorganic species at lower temperatures. On the other hand, slow evolution of organics during CFC leads to carbonaceous residues that isolate the inorganic species and inhibit nucleation of HA crystallites until at a higher temperature.     

Possible role of fibronectin in malignancy.

Frozen sections of tumors induced by injecting virally transformed cells into animals were stained for fibronectin by immunofluorescence. Many tumor cell lines do not express fibronectin in tumors in situ even though some of them express fibronectin in culture. Cell shape and hormones appear to influence the expression of fibronectin in culture; however, it is unclear how fibronectin expression is regulated in vivo.