A note on the necessary conditions for the algebraic Riccati equation

We derive some useful and easily computable necessary conditionsfor the existence of a positive semi-definite solution to thealgebraic Ricatti equation (ARE). A motivating example is givento highlight the usefulness of the conditions for controllerand observer designs for nonlinear systems. Further, an upperbound on the trace of the solution to the ARE is also derived.     

Generation of near transform-limited ultrashort laser pulses in kilohertz chirped-pulse amplification system by compensating high order phase distortions

The effects of gain narrowing and high order dispersions on the pulse duration in our kilohertz chirpedpulse amplification system have been compensated experimentally. Using an acousto-optic programmable dispersive filter (AOPDF), the spectral full-width at half-maximum (FWHM) is expanded from 30 to50 nm. Stable laser pulses with the duration of 30 fs (FWHM), which is 1.07 times Fourier-transformlimitation, have been acquired by pre-compensating the high order phase distortions using the phase measured by spectral phase interferometry for direct electric-field reconstruction (SPIDER).     

FT-NIR Spectroscopy of some long-chain fatty acids and alcohols

Fourier-transform (FT) near-infrared (NIR) spectroscopy has proved to be a powerful technique in investigating structure and thermodynamic properties of long-chain fatty acids and alcohols. In order to extract useful information from the NIR spectra, bands due to the second as well as first overtones of OH-stretching modes of the monomeric forms were employed. It has been also found that two-dimensional (2D) NIR correlation spectroscopy can accentuate useful information often obscured in the complicated NIR spectral data set.     

The origin of the high performance of tungsten carbides/carbon nanotubes supported Pt catalysts for methanol electrooxidation

The Pt supported on WC modified MWCNT catalysts (PtWC/MWCNT) were synthesized by the combination of organic colloidal and intermittent microwave heating (IMH) methods for the first. The results proved the better performance of the PtWC/MWCNT catalyst than that of Pt/C for methanol oxidation in terms of the onset potential and peak current density. The synergistic effect between Pt nanoparticles and WC and the structure effect of the MWCNTs could be the reasons to result in the high activity. The CO stripping test provided the evidence that the onset potential shift for methanol oxidation is consistent with the reduction in the overpotential for the CO oxidation on PtWC/MWCNT catalyst. Therefore, the mechanism of the high performance for methanol oxidation on PtWC/MWCNT catalyst is probably the easier oxidation of CO-like species which cause high overpotential for further oxidation of methanol.     

Superior energy capacity of graphene nanosheets for a nonaqueous lithium-oxygen battery

Graphene nanosheets (GNSs) were synthesized and used as cathode active materials in a nonaqueous lithium-oxygen battery. The GNSs electrode delivered an extremely high discharge capacity in comparison to carbon powders, which is attributed to its unique morphology and structure.     

Facile controlled synthesis and growth mechanisms of flower-like and tubular MnO2 nanostructures by microwave-assisted hydrothermal method

Birnessite flower-like and α-type tubular MnO(2) nanostructures were selectively synthesized through simple decomposition of KMnO(4) under hydrochloric acid condition by controlling reaction temperature using a microwave-assisted hydrothermal method. The as-prepared samples were characterized in detail by various techniques including X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, high-resolution transmission electron microscopy, Fourier transform-infrared spectroscopy, and Raman scattering spectroscopy. While the growth of flower-like birnessite-MnO(2) might follow a widely accepted Ostwald ripening process, we proposed a formation mechanism of the nanotubular α-MnO(2) based on our evidence, which was assembly of nanorods through an "oriented attachment" process.     

Total synthesis and antidepressant activities of laetispicine and its derivatives

The first total synthesis of laetispicine (1a), an amide alkaloid isolated from the stems of Piper laetispicum C.DC (Piperaceae), and the synthesis of some of its derivatives were described. Based on the evaluation of antidepressant activities in the forced swimming test, compounds 1h and 1i were identified as potent and safe antidepressant lead compounds.