The MnO 2 /carbon nanotubes (CNTs) composites were prepared through a modified one-pot reaction process, in which CNTs were coated by cross-linked MnO 2 flakes uniformly. The composition, morphology, and microstructure of the products were characterized using TG, XRD, XPS, Raman, FESEM, TEM, and STEM. It reveals that the MnO 2 layer stands on the sidewalls of the inner nanotubes uniformly about 50 nm thick, and the loading of MnO 2 on the CNTs reaches 84%. Furthermore, the supercapacitive performances were investigated by cyclic voltammogram (CV), galvanostatic charge−discharge, and electrochemical impedance spectroscopy (EIS). The experimental results indicate that the composite exhibits not only high specific capacitance of 201 F g −1 and rate capability (the specific capacitance at 20 A g −1 is 70% of that at 1 A g −1 ), but also excellent cycle stability (no obvious capacitance decay after 10 000 cycles at 1 A g −1 ). An asymmetric electrochemical capacitor was assembled by using the obtained MnO 2 /CNTs composite as positive electrode and activated carbon (AC) as negative electrode. The as-assembled AC//MnO 2 /CNTs capacitor can cycle reversibly in a voltage of 0−1.5 V and give a high energy density of 13.3 Wh kg −1 at a power density of 600 W kg −1 .

BIOSCREEN is a well-known simple tool for evaluating the transport of dissolved contaminants in groundwater, ideal for rapid screening and teaching. This work extends the BIOSCREEN model for the calculation of stable isotope ratios in contaminants. A three-dimensional exact solution of the reactive transport from a patch source, accounting for fractionation by first-order decay and/or sorption, is used. The results match those from a previously published isotope model but are much simpler to obtain. Two different isotopes may be computed, and dual isotope plots can be viewed. The dual isotope assessment is a rapidly emerging new approach for identifying process mechanisms in aquifers. Furthermore, deviations of isotope ratios at specific reactive positions with respect to "bulk" ratios in the whole compound can be simulated. This model is named BIOSCREEN-AT-ISO and will be downloadable from the journal homepage.

A systematic approach to the design of GaAs FET bandpass distributed amplifiers is presented for the first time. The graphical design procedures presented enable one to examine the trade‐offs between the design variables and arrive at the appropriate design for a specified gain and bandwidth. © 1995 John Wiley & Sons, Inc.

In this article a novel distributed amplifier configuration consisting of cascaded-transistor cells is presented. For a given transistor and total gate periphev (number of transistors) in the amplifier, the new conjiguration gives higher gain-bandwidth product than conuentional distributed amplifiers. This fact