Acid modified bamboo‐type carbon nanotubes and cup‐stacked‐type carbon nanofibres as adsorbent materials: cadmium removal from aqueous solution

BACKGROUND: Nitrogen‐doped multi‐walled carbon nanotubes (CN_x) and cup‐stacked‐type carbon nanofibres (CST) were modified with nitric acid, at 85 °C, for 1–3 h to enhance their cation adsorption capacity, and were used for cadmium removal from aqueous solutions. These carbon nanostructures were characterized by SEM, EDX, FTIR, BET surface area, TGA and acid/base titrations. In addition, cadmium adsorption experiments were carried out at different pH values and constant temperature. RESULTS: EDX and FTIR revealed a 0.4 times increase in oxygen content after acid treatment, which was reflected in an increment of up to 1.93 mmol g^?1 of acid sites and in a shift of about two units of the zero point charge to lower pH values. The BET surface area, in general, decreased as the oxidation time increased. Finally, batch sorption experiments indicated that CN_x are more effective than CST to sequester Cd²⁺ at pH 7; the sorption capacities of these materials increased as pH rose. CONCLUSIONS: The results obtained indicate that it is feasible to modify both physical and chemical properties of the carbon nanostructures CN_x and CST by HNO₃ in such a way that they can be used to adsorb cations present in aqueous solutions. Copyright © 2008 Society of Chemical Industry     

A New Distance Measure for Model-Based Sequence Clustering

We review the existing alternatives for defining model-based distances for clustering sequences and propose a new one based on the Kullback-Leibler divergence. This distance is shown to be especially useful in combination with spectral clustering. For improved performance in real-world scenarios, a model selection scheme is also proposed.     

Dynamic vegetation model as a tool for ecological impact assessments of dam operation

This study presented the results of an application of a floodplain dynamic model to the Nakdong River, South Korea. At the Nakdong River, high flows are reduced by dams and the river bed is degraded. Both changes contribute toward the same result: the floodplain is hydraulically disconnected from the main channel and the morphology of the river has been modified. Such changes brought also to a deep modification in the riparian vegetation distribution, abundance and composition. The focus of the study is on the relationship between the hydrology alterations induced by dams and the successional changes in riparian vegetation. More in detail, the study attempts to adapt an existing dynamic floodplain vegetation model to the Nakdong ecosystem characteristics in order to single out what were the effects of the dam operations that led to a change in the riparian landscape. The dynamic model is targeted on Monsoon floodplain vegetation, it is developed upon a custom developed geoprocessing framework and supported by a standalone user interface. It simulates dynamics of floodplain vegetation communities based on different physical parameters. The general concept of the model is that a vegetation community will either undergo toward a maturation stage or will be destroyed (recycling or retrogression) if the magnitude of key physical parameters is greater than the threshold value for a specific community. The model has been calibrated using hydraulic data spanning the time period 1952–2007. The calibration results have been also used to investigate the impacts on the riparian vegetation given by dams operations. The findings of the research highlight that consecutive years of reduced maximum discharge allowed consistent vegetation colonization of riverine areas that were bare before the dam construction.     

Assigning discounts in a marketing campaign by using reinforcement learning and neural networks

In this work, RL is used to find an optimal policy for a marketing campaign. Data show a complex characterization of state and action spaces. Two approaches are proposed to circumvent this problem. The first approach is based on the self-organizing map (SOM), which is used to aggregate states. The second approach uses a multilayer perceptron (MLP) to carry out a regression of the action-value function. The results indicate that both approaches can improve a targeted marketing campaign. Moreover, the SOM approach allows an intuitive interpretation of the results, and the MLP approach yields robust results with generalization capabilities.     

Does Peer Review Predict the Performance of Research Projects in Health Sciences?

Peer review is a basic component of the scientific process, but its performance has seldom been evaluated systematically. To determine whether pre-approval characteristics of research projects predicted the performance of projects, we conducted a retrospective cohort study of all 2744 single-centre research projects financed by the Spanish Health Research Fund since 1988 and completed before 1996. Peer review scores of grant applications were significant predictors of performance of funded projects, and the likelihood of production was also higher for projects with a basic research component, longer duration, higher budget or a financed research fellow. Funding agencies should monitor their selection process and assess the performance of funded projects to design future strategies in supporting health sciences research.     

Regulation and market power in the Spanish liquefied petroleum gas industry: Progress or failure?

This paper presents a detailed study of the structure, market power and competition in the distribution sector for liquefied petroleum gas (LPG), within Spain. It is a segment of energy consumption and supply that is not often given serious attention, despite the fact that LPG is a crucial source of energy to many households, in many countries in Europe and in the rest of the world. Despite formally being an open and liberalized sector, the Spanish LPG market is characterized by high concentration within the industry; Repsol Butano, the dominant operator, practically controls the entire value chain. These structural characteristics probably justify state intervention in the form of price fixing, in order to guarantee accessible prices for final consumers. Nevertheless, applying this tool has had negative effects on the opening and liberalization process. On the one hand, it fails to encourage entry or an increase in the participation of new operators; on the other, it has considerably deteriorated the economic and financial performance of the distribution agents that are subjected to two strong forces. First, the dominant operator looks after its own interests and its income; and second, the Government tries to defend the interests of final consumers by fixing prices that inadequately remunerate the activity. This shows the contradictory regulatory actions that try to promote competition, and then establish mechanisms to regulate activity by fixing prices that act as price limits. These government set prices discourage new competitors from entering.     

A novel and efficient kinematic synthesis approach of the spherical 4R function generator for five and six precision points

This paper presents two new efficient computational methods for the exact kinematic synthesis of a spherical 4R function generator, involving five and six precision points. Several illustrative examples showing the applicability of the proposed approach are discussed and presented in detail.     

Selective enzyme-linked immunosorbent assay for triclosan. Application to wastewater treatment plant effluents

A sensitive and highly selective enzyme-linked immunosorbent assay was developed for triclosan, one of the most common bactericides in personal care products, which is also considered as an emerging contaminant, given its presence in the effluents of sewage and wastewater treatment plants. From synthesized haptens, polyclonal rabbit antibodies against triclosan were raised. The best ELISA immunoassay was based on an antibody-coated format, yielding a detection limit of 0.03 microg L(-1), an I50 of 3.85 microg L(-1), and a dynamic range from 0.22 to 42.16 microg L(-1), with little or no cross-reactivity (< 10%) to similarly structured compounds, including its metabolite methyltriclosan (CR < 6%). The assay was applied as a screening method to quantify triclosan in surface water and in wastewaters. After C18 solid-phase extraction, nanogram per liter concentrations were determined in effluents of urban wastewater treatment plants. The satisfactory recoveries achieved as well as the agreement between immunochemical and chromatographic methods (GC-MS) indicate its potential for either screening or laboratory quantification.