UPML formulation for truncating conductive media in curvilinear coordinates

This work presents a formulation based on UPML for truncating conductive media by using a local and non-orthogonal coordinate system to solve Maxwell’s equations by the FDTD method. The detailed procedure for obtaining the UPML equations for this case is shown and the complete equation set is provided.     

Crystallization of Arthrobacter sp. strain 1C N-(1-D-carboxyethyl)-L-norvaline dehydrogenase and its complex with NAD+

The novel NAD+-linked opine dehydrogenase from a soil isolate Arthrobacter sp. strain 1C belongs to an enzyme superfamily whose members exhibit quite diverse substrate specificites. Crystals of this opine dehydrogenase, obtained in the presence or absence of co-factor and substrates, have been shown to diffract to beyond 1.8 ? resolution. X-ray precession photographs have established that the crystals belong to space group P21212, with cell parameters a = 104.9, b = 80.0, c = 45.5 ? and a single subunit in the asymmetric unit. The elucidation of the three-dimensional structure of this enzyme will provide a structural framework for this novel class of dehydrogenases to enable a comparison to be made with other enzyme families and also as the basis for mutagenesis experiments directed towards the production of natural and synthetic opine-type compounds containing two chiral centres.     

Correction to: Plasma processed carbon thin films applied to dye-sensitized solar cells

Journal of Solid State Electrochemistry - The authors regret an error in the Experimental section of the published article:     

A study of defects in ultra-thin transparent coatings on polymers

2 or more). Received: 1 September 1998/Accepted: 6 October 1998     

Soliton–like pulse dynamics in add–drop optical filters based on nonlinear fiber grating couplers

The dynamics characteristics of picosecond soliton-like pulses propagating through add–drop optical filters, based on lossless uniform and Gaussian nonlinear fiber grating couplers, are numerically investigated under different power levels. To obtain the temporal profiles, the nonlinear coupled-mode equations, that model these devices, are solved numerically. These devices can perform the extraction (drop) of an optical signal, since there is the reflection of a pulse previously switched between adjacent waveguides. The extraction efficiency, recurrently better at low power levels, is subordinated to the matching between the associated spectra of the input pulses and the hybrid devices analyzed. The switching effects, as well the gratings responsiveness, impact on the outputs profiles, since diverse temporal shapes can be obtained. The results reinforce the importance and the potential of properly engineered structures for all-optical processing requirements.     

Automation of a Mass Flow Controller for Application in Time‐Multiplex SF6+CH4 Plasma Etching of Silicon

In this work is proposed the automation of a gas injection (mass flow) system in order to generate timemultiplex SF₆/CH₄ radiofrequency plasma applied for silicon (Si) etching process. The control of the gas injection system is important in order to better control the process anisotropy, i.e., the high‐aspect‐ratio of mask pattern transfer to substrate surface. In other words, this control allows the attainment of deep Si etching process. Here, the automation of the gas injection system was realized through the interface between a computer and a data acquisition board. The automation software developed allows controlling the gas flow rate switching it on and off during whole process through the use of a square waveform routine, intermittent flow, beyond the conventional condition of a fixed value for gas flow rate, continuous flow. In order to investigate the time‐multiplex SF₆/CH₄ plasma etching of Si, the residual gas analysis was performed. The investigations were made keeping the following process parameters: flow of SF₆: 10 sccm, flow of CH₄: 6 sccm, 100 W rf power, wave period: 20 sec. It were monitored the partial pressure of SF⁺ ₅ (parent neutral specie: SF₆), CH⁺₄ (CH4) and SiF+ ₃ (SiF4) species as a function of time for different gas flow switching and duty cycle. The results showed that with the generation of plasma occurs a drastic change in behavior of partial pressures of SF⁺ ₅ and CH⁺₄ species. Moreover, it is evidenced that the interactions between the SF₆ and CH₄ fragments promotes a high production rate of HF molecule and consequently a decrease of atomic fluorine, mainly when plasma is on. Finally, the behavior of partial pressure of SiF⁺ ₃ specie for alternatively intermittent SF₆ and CH₄ flow operation shows us that both the etching processes and the deposition of a polymer passivation layer are occurring alternatively, a desirable feature for multi‐step etching process (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Diffusion of Paraffins in Dealuminated Y Mesoporous Molecular Sieve

Mesoporous materials have been intensely studied recently, mainly as possible component for FCC (Fluid Catalytic Cracking) catalysts due to their large surface area and accessibility to large hydrocarbon molecules. It is thus of interest for the oil industry to understand the diffusion behavior of some standard molecules in these materials. Y Zeolites, usually employed in fluid catalytic cracking, can be modified by removal of aluminum atoms from the zeolitic framework to present a greater mesoporous contribution. Dealumination of Y zeolite framework is also known to improve the stability of the catalyst thus making it more suitable for the FCC operation. This study presents diffusion measurements performed with the ZLC (Zero-Length Column) method, developed in the late eighties by Eic and Ruthven (1988a, b). The ZLC method has been largely used for a number of systems, either in gas or in liquid phases. We have now applied the ZLC method for gas phase diffusion measurements of linear paraffins (C₇–C₁₀) in dealuminated Y zeolite (USY). Experimental data were obtained at different temperatures (150 to 240°C) and flow rates (40 to 120 ml/min) and correlated through a transient Fickian diffusion model.     

Nachweis und Bestimmung des Eisens, sowie seine Trennung von anderen Elementen

Ohne Zusammenfassung