Quantifying defects in graphene via Raman spectroscopy at different excitation energies

We present a Raman study of Ar(+)-bombarded graphene samples with increasing ion doses. This allows us to have a controlled, increasing, amount of defects. We find that the ratio between the D and G peak intensities, for a given defect density, strongly depends on the laser excitation energy. We quantify this effect and present a simple equation for the determination of the point defect density in graphene via Raman spectroscopy for any visible excitation energy. We note that, for all excitations, the D to G intensity ratio reaches a maximum for an interdefect distance ～3 nm. Thus, a given ratio could correspond to two different defect densities, above or below the maximum. The analysis of the G peak width and its dispersion with excitation energy solves this ambiguity.     

Static Recrystallization Kinetics and Crystallographic Texture of Nb-Stabilized Ferritic Stainless Steel Based on Orientation Imaging Microscopy

In the present study, Nb-stabilized ferritic stainless steel was prepared with annealing (430-A) and without annealing (430-NA) annealing, and the microstructure of the resulting samples was examined. The steel was then subjected to cold rolling and isothermal annealing in order to analyze its recrystallization kinetics and texture evolution. Microstructural characterization was performed by scanning and transmission electron microscopies. Recrystallization kinetics were evaluated by measuring the microhardness of the samples, and analyzing their kernel average misorientation and grain orientation spread via electron backscatter diffraction. The Avrami exponent data revealed that one-dimensional grain growth occurred owing to the migration of high-angle grain boundaries. The mean activation energies for recrystallization for 430-NA and 430-A was found to be 365 and 419 kJ mol⁻¹, respectively. The recrystallization texture was influenced by oriented nucleation and selected growth mechanisms, as well as by the Nb carbonitride distribution and grain boundary energy. The recrystallized and growing grains with the {554}〈225〉 orientation showed a dimensional advantage over the other recrystallized components. The coincident site lattice boundaries were attributed to the progression of recrystallization since the CSL numeric fraction increased as the temperature increased. The {554}〈225〉 component was associated with the ∑19a boundary, which exerted a significant control on the selective growth during the recrystallization.

     

Corrosion effects in thin‐film photovoltaic modules

Electrochemical corrosion effects can occur in thin‐film photovoltaic (PV) modules that are fabricated on tin‐oxide‐coated glass when operating at high voltages and at elevated temperatures in a humid climate. The current study shows that this corrosion is associated with a delamination of the tin oxide layer from the glass, which is caused by sodium accumulation near the interface between the tin oxide and the glass and by the ingression of moisture into the PV module from the edges. This corrosion in thin‐film PV modules can be significantly reduced by altering the growth conditions of the tin oxide or by using zinc oxide as a transparent conductive oxide electrode. Copyright © 2003 John Wiley & Sons, Ltd.     

Plasma Levels of <Emphasis Type="Italic">trans</Emphasis>-Fatty Acids are Low in Exclusively Breastfed Infants of Adolescent Mothers

The purpose of this study was to determine the levels of trans-octadecenoic acid (C18:1-trans) and trans-isomers of linoleic acid (18:2-trans), as well as long-chain polyunsaturated fatty acids (LC-PUFA), in the plasma from infants of adolescent mothers at 3 months of age, exclusively breastfed, and the relationship with the levels of the same isomers in plasma and milk of the mothers. Samples of blood and mature milk were obtained from 49 healthy adolescent mothers and their exclusively breastfed infants treated at the Instituto Fernandes Figueira-Fundação Oswaldo Cruz (IFF-FIOCRUZ) in Rio de Janeiro, Brazil. trans-Fatty acids (TFA) were analyzed by gas chromatography. The results of this study showed low levels of TFA in milk (1.53%), maternal plasma (0.50%), and plasma of infants (0.74%). The results show that, although TFA have been found in the plasma of the studied infants, the LC-PUFA levels are kept within normal limits. No association between TFA presence and parameters of nutritional status of the infants was observed, probably due to the low levels of these fatty acids found in this study.     

The Kohonen self-organizing map: an application to the study of strategic groups in the UK hotel industry

This paper examines a neural network method known as the self-organizing map (SOM). The motivation behind the SOM is to transform the data to a two-dimensional grid of nodes while preserving its 'topological' structure. In neural network terminology this involves unsupervised learning. The nearest related statistical technique is cluster analysis. We employ the SOM in the task of identifying strategic groups of companies, using data which relate to the generic strategies suggested by Porter. Following identification of different groups of hotels with certain strategic emphases, the study investigates correlations between strategies followed and hotel performance. We compare and contrast the 'feature map' generated by the SOM with the results of a standard cluster analysis using the k-means method. The data also cover performance indicators and the results indicate that performance varies between strategic groups.     

Atomic force microscopy study of FG-annealed and PECVD silicon nitride AR-coated silicon solar cells

Atomic force microscopy has been used to study the surface structure and roughness of PECVD silicon nitride coated silicon solar cells. The surface roughness increases in some areas of the solar cells after forming gas annealing. It may be one of the reasons for better light absorption on the surface of the solar cells resulting in better solar cell performance.     

Offshore decommissioning issues: Deductibility and transferability

Dealing with the decommissioning of petroleum installations is a relatively new challenge to most producer countries. It is natural to expect that industry's experience in building platforms is much greater than the one of dismantling them. Even if manifold and varied efforts are underway towards establishing international “best practices” standards in this sector, countries still enjoy rather extensive discretionary power as they practice a particular national style in the regulation of decommissioning activities in their state's jurisdiction. The present paper offers a broad panorama of this discussion, concentrating mainly on two controversial aspects. The first one analyses the ex-ante deductibility of decommissioning costs as they constitute an ex-post expense. The second discussion refers to the assignment of decommissioning responsibility in the case of transfer of exploration and production rights to new lessees during the project's life. Finally the paper applies concepts commonly used in project financing as well as structures generally used in organising pension funds to develop insights into these discussions.     

Application of GPR in the Study of a Modern Alluvial Megafan: The Case of the Taquari River in Pantanal Wetland,West-Central Brazil

A novel and timely ground penetrating radar (GPR) survey has been carried out in Pantanal from Mato Grosso State, west-central Brazil. Fieldwork was carried out on February/2001 and August/2002 in an attempt to understand avulsion processes that are occurring within Taquari alluvial megafan. The main objectives were to map channel, crevasse and floodplain morphology, as well as active sedimentary bedforms. Many GPR profiles were acquired in the medium and lower Taquari River course. Subaqueous megaripples and exposed sand bars were identified in the medium fan area. Similar features were observed in the lower fan channels, where there were many crevasses in the marginal levees. During the flooding seasons, the flow splays out on to the floodplain, where new distributary channels are being formed. GPR data show that the lower fan, Taquari channel is topographically higher than the adjacent floodplain, thus favoring avulsion as a natural process of river course shifting. GPR data obtained during the wet and dry seasons, together with sedimentology information have been very important in characterizing the fluvial dynamics, and avulsion phenomena.