Fiber transmission and generation of ultrawideband pulses by direct current modulation of semiconductor lasers and chirp-to-intensity conversion

Optical pulses generated by current modulation of semiconductor lasers are strongly frequency chirped. This effect has been considered pernicious for optical communications. We take advantage of this effect for the generation of ultrawideband microwave signals by using an optical filter to achieve chirp-to-intensity conversion. We also experimentally achieve propagation through a 20 km nonzero dispersion shifted fiber with no degradation of the signal at the receiver. Our method constitutes a prospective low-cost solution and offers integration capabilities with fiber-to-the-customer-premise systems.     

Application of selected ion flow tube mass spectrometry to real‐time atmospheric monitoring

Data are presented for real‐time atmospheric monitoring of volatile organic chemicals (VOCs) in air using selected ion flow tube mass spectrometry (SIFT‐MS) technology. These measurements were made by one of the new generation of SIFT‐MS instruments. Results are shown for five VOCs that were continually monitored from a stationary sampling point over a 4‐day period: ethene, ethanol, 1,3‐butadiene, benzene and toluene. All analytes except ethene in the study have at least two simultaneous and independent measures of concentration. These results demonstrate the great advances in SIFT‐MS that have been made in recent years. 1,3‐Butadiene is measured at a concentration of 9 pptv with a precision of 44%. For a 1‐s integration time, a detection limit of 50 pptv is achieved. Instrument sensitivities are reported for all five analytes. Copyright © 2010 John Wiley & Sons, Ltd.     

Biomass Oxidation: Formyl CH Bond Activation by the Surface Lattice Oxygen of Regenerative CuO Nanoleaves

An integrated experimental and computational investigation reveals that surface lattice oxygen of copper oxide (CuO) nanoleaves activates the formyl C? H bond in glucose and incorporates itself into the glucose molecule to oxidize it to gluconic acid. The reduced CuO catalyst regains its structure, morphology, and activity upon reoxidation. The activity of lattice oxygen is shown to be superior to that of the chemisorbed oxygen on the metal surface and the hydrogen abstraction ability of the catalyst is correlated with the adsorption energy. Based on the present investigation, it is suggested that surface lattice oxygen is critical for the oxidation of glucose to gluconic acid, without further breaking down the glucose molecule into smaller fragments, because of C? C cleavage. Using CuO nanoleaves as catalyst, an excellent yield of gluconic acid is also obtained for the direct oxidation of cellobiose and polymeric cellulose, as biomass substrates.     

Generalized Weighted Morrey Estimates for Marcinkiewicz Integrals with Rough Kernel Associated with Schrödinger Operator and Their Commutators

Let L =-?+V(x) be a Schr?dinger operator, where ? is the Laplacian on ■~n,while nonnegative potential V(x) belonging to the reverse H?lder class. The aim of this paper is to give generalized weighted Morrey estimates for the boundedness of Marcinkiewicz integrals with rough kernel associated with Schr?dinger operator and their commutators.Moreover, the boundedness of the commutator operators formed by BMO functions and Marcinkiewicz integrals with rough kernel associated with Schr?dinger operators is discussed on the generalized weighted Morrey spaces. As its special cases, the corresponding results of Marcinkiewicz integrals with rough kernel associated with Schr?dinger operator and their commutators have been deduced, respectively. Also, Marcinkiewicz integral operators, rough Hardy-Littlewood(H-L for short) maximal operators, Bochner-Riesz means and parametric Marcinkiewicz integral operators which satisfy the conditions of our main results can be considered as some examples.     

Flag-Transitive Affine Planes of Order 64

We determine all the flag-transitive affine planes of order 64. There are three: the Desarguesian plane, the Lüneburg plane and the plane given by a construction due to Kantor.     

Facile synthesis of solar light active spinel nickel manganite (NiMn2O4) by co-precipitation route for photocatalytic application

Research on Chemical Intermediates - The spinel nickel manganite (NiMn2O4) nanoparticles (NPs) were successfully synthesized through simple co-precipitation method, and their structural, optical,...     

Synchrotron radiation photoelectron spectroscopy studies of self-organization in As40Se60 nanolayers stored under ambient conditions and after laser irradiation

The influence of air and near bandgap laser irradiation on the surface structure of As₄₀Se₆₀ nanolayers has been investigated by synchrotron radiation photoelectron spectroscopy (SRPES). The As 3d and Se 3d photoemission peaks of the irradiated sample show significant differences in shapes and positions in comparison with those obtained for non-irradiated amorphous films. The experimental data processing and quantification were performed by analyzing As 3d, Se 3d, C 1s and O 1s core-level components obtained by curve fitting. The relative contribution of the As, Se, C and O atoms in different chemical states to the whole As 3d, Se 3d, C 1s and O 1s signals, its structural origins as well as their relation to the As₄₀Se₆₀ surface and subsurface nanolayers structure before and after laser irradiation is analyzed and discussed in detail. An atomic model of induced structural changes on the surface of As₄₀Se₆₀ nanolayers under ambient conditions and after laser irradiation in air is proposed.     

In situ growth of epitaxial cerium tungstate (100) thin films

The deposition of ceria on a preoxidized W(110) crystal at 870 K has been studied in situ by photoelectron spectroscopy and low-energy electron diffraction. Formation of an epitaxial layer of crystalline cerium tungstate Ce(6)WO(12)(100), with the metals in the Ce(3+) and W(6+) chemical states, has been observed. The interface between the tungsten substrate and the tungstate film consists of WO suboxide. At thicknesses above 0.89 nm, cerium dioxide grows on the surface of Ce(6)WO(12), favoured by the limited diffusion of tungsten from the substrate.