A Cost-Benefit Analysis on Modulation Formats for 40-Gb/s Optical Communication Systems

This article discusses possible approaches for optical network capacity upgrade by considering the use of different modulation formats at 40 Gb/s. First, a performance evaluation is carried out regarding tolerance to three impairments: spectral narrowing due to filter cascading, chromatic dispersion, and self-phase modulation. Next, a cost-benefit analysis is conducted, considering the specific optoelectronic components required for the optical transmitter/receiver configuration of each format.

Analysis of PVC pipe-wall viscoelasticity during water hammer

This research work focuses on the analysis of hydraulic transients in polyvinyl chloride (PVC) pipes, which are characterized by a viscoelastic rheological behavior. Transient pressure data were collected in a pipe rig consisting of a set of PVC pipes. The creep function of the PVC pipes was determined by using an inverse transient model based on collected transient pressure data and compared with that obtained by carrying out mechanical tensile tests of PVC pipe specimens. The numerical results obtained from the transient solver have shown that the attenuation, dispersion, and shape of transient pressures were well described. The incorporation of the viscoelastic mechanical behavior in the hydraulic transient model has provided an excellent fitting between numerical results and observed data. Calibrated creep function based on inverse analysis fit the one determined by mechanical tests well, which emphasized the importance of pipe-wall viscoelasticity in hydraulic transients in PVC pipes.

Montmorillonite as a component of polysulfone nanocomposite membranes

Nanocomposite membranes containing polysulfone (PSI) and sodium montmorillonite from Wyoming (MMT) were prepared by a combination of solution dispersion and the immersion step of the wet-phase inversion method. The purpose was to study the MMT addition with contents of 0.5 and 3.0 mass% MMT in the preparation of nanocomposite membranes by means of morphology, thermal, mechanical and hydrophilic properties of nanocomposite membranes and to compare these properties to the pure PSf membrane ones. Small-angle X-ray diffraction patterns revealed the formation of intercalated clay mineral layers in the PSf matrix and TEM images also presented an exfoliated structure. A good dispersion of the clay mineral particles was detected by SEM images. Tensile tests showed that both elongation at break and tensile strength of the nanocomposites were improved in comparison to the pristine PSf. The thermal stability of the nanocomposite membranes, evaluated by onset and final temperatures of degradation, was also enhanced. The hydrophilicity of the nanocomposite membranes, determined by water contact angle measurements, was higher; therefore, the MMT addition was useful to produce more hydrophilic membranes. (C) 2009 Elsevier B.V. All rights reserved.

Nanostructured diamond-like carbon films characterization

In this work, we have studied the influence of the substrate surface condition on the roughness and the structure of the nanostructured DLC films deposited by high-density plasma chemical vapor deposition Four methods were used to modify the silicon wafers surface before starting the deposition processes of the nanostructured DLC films. micro-diamond powder dispersion, micro-graphite powder dispersion, and roughness generation by wet chemical etching and roughness generation by plasma etching. The reference wafer was only submitted to a chemical cleaning. It was possible to see that the final roughness and the sp(3) hybridization degree (that is related with the structure and chemical composition) strongly depend on the substrate surface conditions The surface roughness was observed by AFM and SEM and the hybridization degree of the DLC films was analyzed by Raman Spectroscopy Thus, the effects of the substrate surface on the DLC film structure were confirmed. These phenomena can be explained by the fact that the locally higher surface energy and the sharp edges may induce local defects promoting the nanostructured characteristics in the DLC films. (C) 2009 Elsevier B.V. All rights reserved.

Influence of substrate surface topography in the deposition of nanostructured diamond-like carbon films by high density plasma chemical vapor deposition

In this work, we have studied the influence of the substrate surface condition on the roughness and the structure of the nanostructured DLC films deposited by High Density Plasma Chemical Vapor Deposition. Four methods were used to modify the silicon wafers surface before starting the deposition processes of the nanostructured DLC films: micro-diamond powder dispersion, micro-graphite powder dispersion, and roughness generation by wet chemical etching and roughness generation by plasma etching. The reference wafer was only submitted to a chemical cleaning. It was possible to see that the final roughness and the sp(3) hybridization degree strongly depend on the substrate surface conditions. The surface roughness was observed by AFM and SEM and the hybridization degree of the DLC films was analyzed by Raman Spectroscopy. In these samples, the final roughness and the sp(3) hybridization quantity depend strongly on the substrate surface condition. Thus, the effects of the substrate surface on the DLC film structure were confirmed. These phenomena can be explained by the fact that the locally higher surface energy and the sharp edges may induce local defects promoting the nanostructured characteristics in the DLC films. (C) 2008 Elsevier B.V. All rights reserved.

Probing the 2D kinematic structure of early-type galaxies out to three effective radii

We detail an innovative new technique for measuring the two-dimensional (2D) velocity moments (rotation velocity, velocity dispersion and Gauss-Hermite coefficients h(3) and h(4)) of the stellar populations of galaxy haloes using spectra from Keck DEIMOS (Deep Imaging Multi-Object Spectrograph) multi-object spectroscopic observations. The data are used to reconstruct 2D rotation velocity maps. Here we present data for five nearby early-type galaxies to similar to three effective radii. We provide significant insights into the global kinematic structure of these galaxies, and challenge the accepted morphological classification in several cases. We show that between one and three effective radii the velocity dispersion declines very slowly, if at all, in all five galaxies. For the two galaxies with velocity dispersion profiles available from planetary nebulae data we find very good agreement with our stellar profiles. We find a variety of rotation profiles beyond one effective radius, i.e. rotation speed remaining constant, decreasing and increasing with radius. These results are of particular importance to studies which attempt to classify galaxies by their kinematic structure within one effective radius, such as the recent definition of fast- and slow-rotator classes by the Spectrographic Areal Unit for Research on Optical Nebulae project. Our data suggest that the rotator class may change when larger galactocentric radii are probed. This has important implications for dynamical modelling of early-type galaxies. The data from this study are available on-line.

New alk genes detected in Antarctic marine sediments

Alkane monooxygenases (Alk) are the key enzymes for alkane degradation. In order to understand the dispersion and diversity of alk genes in Antarctic marine environments, this study analysed by clone libraries the presence and diversity of alk genes (alkB and alkM) in sediments from Admiralty Bay, King George Island, Peninsula Antarctica. The results show a differential distribution of alk genes between the sites, and the predominant presence of new alk genes, mainly in the pristine site. Sequences presented 53.10-69.60% nucleotide identity and 50.90-73.40% amino acid identity to alkB genes described in Silicibacter pomeroyi, Gordonia sp., Prauserella rugosa, Nocardioides sp., Rhodococcus sp., Nocardia farcinica, Pseudomonas putida, Acidisphaera sp., Alcanivorax borkumensis, and alkM described in Acinetobacter sp. This is the first time that the gene alkM was detected and described in Antarctic marine environments. The presence of a range of previously undescribed alk genes indicates the need for further studies in this environment.

The decline of the world`s energy intensity

Energy intensity of the total primary energy supply (TPES), total final energy consumption (TFC) and LOSSES in the conversion from TPES to TFC were analyzed for the World, OECD and Rest of the World (ROW) countries. LOSSES increased significantly for all groups of countries due to the increase of electricity production from coal in the period studied (1971-2008). Electricity share final consumption almost doubled, increasing from 8.8% to 17.2% in the period studied. However the energy intensity of LOSSES remained practically constant, which reflects the fact that the efficiency of electricity generation from coal (the main source of electricity) remained practically constant in that period. Despite the attractiveness of end-use devices running on electricity such as computers, which is typical of modern societies, the CO(2) emissions are bound to increase unless coal is replaced by less carbon emitting sources such as natural gas, renewables and nuclear energy. (C) 2011 Elsevier Ltd. All rights reserved.

Chemical abundance analysis of the Be star HD 171054

In this work the results of a spectroscopic study of the southern field narrow-line Be star HD 171054 are presented. High dispersion and signal-to-noise ratio spectra allowed the estimation of the fundamental photospheric parameters such as the projected rotational velocity, effective temperature and superficial gravity from non-LTE stellar atmosphere models. From these parameters and microturbulence, the abundances of He, C, N, O, Mg, Al and Si for this object are estimated. Results show that C is depleted whereas N is overabundant compared with the sun and OB stars in the solar vicinity. Oxygen and helium are close to the solar value. Magnesium is down by 0.43 dex and aluminium and silicon are overabundant. (C) 2010 Elsevier B.V. All rights reserved.

Development of a fast capillary electrophoresis method to determine inorganic cations in biodiesel samples

The aim of this study was to develop a fast capillary electrophoresis method for the determination of inorganic cations (Na(+), K(+), Ca(2+), Mg(2+)) in biodiesel samples, using barium (Ba(2+)) as the internal standard. The running electrolyte was optimized through effective mobility curves in order to select the co-ion and Peakmaster software was used to determine electromigration dispersion and buffer capacity. The optimum background electrolyte was composed of 10 mmol L(-1) imidazole and 40 mmol L(-1) of acetic acid. Separation was conducted in a fused-silica capillary (32 cm total length and 23.5 cm effective length, 50 mu m I.D.), with indirect UV detection at 214 nm. The migration time was only 36 s. In order to obtain the optimized conditions for extraction, a fractional factorial experimental design was used. The variables investigated were biodiesel mass, pH, extractant volume, agitation and sonication time. The optimum conditions were: biodiesel mass of 200 mg, extractant volume of 200 mu L. and agitation of 20 min. The method is characterized by good linearity in the concentration range of 0.5-20 mg kg(-1) (r > 0.999), limit of detection was equal to 0.3 mg kg(-1), inter-day precision was equal to 1.88% and recovery in the range of 88.0-120%. The developed method was successfully applied to the determination of cations in biodiesel samples. (c) 2010 Elsevier B.V. All rights reserved.

Reduction of Models in the Presence of Nuisance Parameters

In many statistical inference problems, there is interest in estimation of only some elements of the parameter vector that defines the adopted model. In general, such elements are associated to measures of location and the additional terms, known as nuisance parameters, to control the dispersion and asymmetry of the underlying distributions. To estimate all the parameters of the model and to draw inferences only on the parameters of interest. Depending on the adopted model, this procedure can be both algebraically is common and computationally very costly and thus it is convenient to reduce it, so that it depends only on the parameters of interest. This article reviews estimation methods in the presence of nuisance parameters and consider some applications in models recently discussed in the literature.

Hydrogen purification for fuel cell using CuO/CeO(2)-Al(2)O(3) catalyst

CuO/CeO(2), CuO/Al(2)O(3) and CuO/CeO(2)-Al(2)O(3) catalysts, with CuO loading varying from 1 to 5 wt.%, were prepared by the citrate method and applied to the preferential oxidation of carbon monoxide in a reaction medium containing large amounts of hydrogen (PROX-CO). The compounds were characterized ex situ by X-ray diffraction, specific surface area measurements, temperature-programmed reduction and temperature-programmed reduction of oxidized surfaces; XANES-PROX in situ experiments were also carried out to study the copper oxidation state under PROX-CO conditions. These analyses showed that in the reaction medium the Cu(0) is present as dispersed particles. On the ceria, these metallic particles are smaller and more finely dispersed, resulting in a stronger metal-support interaction than in CuO/Al(2)O(3) or CuO/CeO(2)-Al(2)O(3) catalysts, providing higher PROX-CO activity and better selectivity in the conversion of CO to CO(2) despite the greater BET area presented by samples supported on alumina. It is also shown that the lower CuO content, the higher metal dispersion and consequently the catalytic activity. The redox properties of the ceria support also contributed to catalytic performance. (C) 2010 Elsevier B.V. All rights reserved.

Evaluation of a simple hyphenated system for flow injection solid-phase pre-concentration and capillary electrophoresis

In this work, the development and evaluation of a hyphenated flow injection-capillary electrophoresis system with on-line pre-concentration is described. Preliminary tests were performed to investigate the influence of flow rates over the analytical signals. Results revealed losses in terms of sensitivity of the FIA-CE system when compared to the conventional CE system. To overcome signal decrease and to make the system more efficient, a lower flow rate was set and an anionic resin column was added to the flow manifold in order to pre-concentrate the analyte. The pre-concentration FIA-CE system presented a sensitivity improvement of about 660% and there was only a small increase of 8% in total peak dispersion. These results have confirmed the great potential of the proposed system for many analytical tasks especially for low concentration samples.

Numerical comparison between conventional dispersion compensating fibers and photonic crystal fibers as lumped Raman amplifiers

In this paper we discuss the use of photonic crystal fibers (PCFs) as discrete devices for simultaneous wideband dispersion compensation and Raman amplification. The performance of the PCFs in terms of gain, ripple, optical signal-to-noise ratio (OSNR) and required fiber length for complete dispersion compensation is compared with conventional dispersion compensating fibers (DCFs). The main goal is to determine the minimum PCF loss beyond which its performance surpasses a state-of-the-art DCF and justifies practical use in telecommunication systems. (C) 2009 Optical Society of America

Characterization of new IS elements and studies of their dispersion in two subspecies of Leifsonia xyli

Background: Leifsonia xyli is a xylem-inhabiting bacterial species comprised of two subspecies: L. xyli subsp. xyli (Lxx) and L. xyli subsp. cynodontis (Lxc). Lxx is the causal agent of ratoon stunting disease in sugarcane commercial fields and Lxc colonizes the xylem of several grasses causing either mild or no symptoms of disease. The completely sequenced genome of Lxx provided insights into its biology and pathogenicity. Since IS elements are largely reported as an important source of bacterial genome diversification and nothing is known about their role in chromosome architecture of L. xyli, a comparative analysis of Lxc and Lxx elements was performed. Results: Sample sequencing of Lxc genome and comparative analysis with Lxx complete DNA sequence revealed a variable number of IS transposable elements acting upon genomic diversity. A detailed characterization of Lxc IS elements and a comparative review with IS elements of Lxx are presented. Each genome showed a unique set of elements although related to same IS families when considering features such as similarity among transposases, inverted and direct repeats, and element size. Most of the Lxc and Lxx IS families assigned were reported to maintain transposition at low levels using translation regulatory mechanisms, consistent with our in silico analysis. Some of the IS elements were found associated with rearrangements and specific regions of each genome. Differences were also found in the effect of IS elements upon insertion, although none of the elements were preferentially associated with gene disruption. A survey of transposases among genomes of Actinobacteria showed no correlation between phylogenetic relatedness and distribution of IS families. By using Southern hybridization, we suggested that diversification of Lxc isolates is also mediated by insertion sequences in probably recent events. Conclusion: Collectively our data indicate that transposable elements are involved in genome diversification of Lxc and Lxx. The IS elements were probably acquired after the divergence of the two subspecies and are associated with genome organization and gene contents. In addition to enhancing understanding of IS element dynamics in general, these data will contribute to our ongoing comparative analyses aimed at understanding the biological differences of the Lxc and Lxx.