Organophilicity of MCM-41 adsorbents studied by adsorption and temperature-programmed desorption

In this paper, the organophilic property of MCM-41 was studied and compared with hydrophobic silicalite-l using adsorption and temperature-programmed desorption (TPD) methods. The surface heterogeneity of MCM-41 was evaluated in terms of activation energy for desorption (E-d) and isosteric heat of adsorption (q(st)). Results show that MCM-41 has a higher affinity to polar organic compounds than to non-polar organics while silicalite-l has a higher affinity to non-polar organic compounds than to polar organics. This organophilic behaviour of MCM-41 is attributed to its surface heterogeneity. (C) 2001 Elsevier Science B.V. All rights reserved.

Engineering the structures of nanoporous clays with micelles of alkyl polyether surfactants

Composite clay nanostructures (CCNs) were observed in intercalating Laponite clay with alumina in the presence of alkyl polyether surfactants which contain hydrophobic alkyl chains and ether groups. Such nanostructured clays are highly porous solids consisting of randomly orientated clay platelets intercalated with alumina nanoparticles. The pores in the product solids are larger than the dimension of the surfactant molecules, ranging from 2 to 10 nm. This suggests that the micelles of the surfactant molecules, rather than the molecules, act as templates in the synthesis. Interestingly, it is found that the size of the framework pores was directly proportional to the amount of the surfactants in terms of moles, but shows no evident dependence on the size of the surfactant molecules. Broad pore size distributions were observed for the product CCNs. This study demonstrates that introducing surfactants in the pillaring process of clays is a powerful strategy for tailoring the pore structures of nanoporous clays. With this new technique, it is possible to design and engineer such composite clay nanostructures with desired pore and surface properties by the proper choice of surfactant amounts and preparation conditions.

Recent advances in the preparation and utilization of carbon nanotubes for hydrogen storage

Recent progress in the production, purification, and experimental and theoretical investigations of carbon nanotubes for hydrogen storage are reviewed. From the industrial point of view, the chemical vapor deposition process has shown advantages over laser ablation and electric-arc-discharge methods. The ultimate goal in nanotube synthesis should be to gain control over geometrical aspects of nanotubes, such as location and orientation, and the atomic structure of nanotubes, including helicity and diameter. There is currently no effective and simple purification procedure that fulfills all requirements for processing carbon nanotubes. Purification is still the bottleneck for technical applications, especially where large amounts of material are required. Although the alkali-metal-doped carbon nanotubes showed high H-2 Weight uptake, further investigations indicated that some of this uptake was due to water rather than hydrogen. This discovery indicates a potential source of error in evaluation of the storage capacity of doped carbon nanotubes. Nevertheless, currently available single-wall nanotubes yield a hydrogen uptake value near 4 wt% under moderate pressure and room temperature. A further 50% increase is needed to meet U.S. Department of Energy targets for commercial exploitation. Meeting this target will require combining experimental and theoretical efforts to achieve a full understanding of the adsorption process, so that the uptake can be rationally optimized to commercially attractive levels. Large-scale production and purification of carbon nanotubes and remarkable improvement of H-2 storage capacity in carbon nanotubes represent significant technological and theoretical challenges in the years to come.

Adsorption study of benzene in ink-bottle-like MCM-41

The pore-opening size of MCM-41 is tailored to be in the microporous region using a chemical vapor deposition technique for selective tailoring. Although the pore opening is narrowed, the internal pore body of MCM-41 remains unchanged so the pore volume retains a substantial portion (80%) of its original value. The adsorption equilibrium of nitrogen and benzene in the modified MCM-41 shows a type I isotherm, which significantly improves the adsorption performance of MCM-41 for low-concentration volatile organic compounds. The adsorption kinetics of benzene in the modified MCM-41 is also studied.

A review of animal models for the study of arsenic carcinogenesis

As inorganic arsenic is a proven human carcinogen, significant effort has been made in recent decades in an attempt to understand arsenic carcinogenesis using animal models, including rodents (rats and mice) and larger mammals such as beagles and monkeys. Transgenic animals were also used to test the carcinogenic effect of arsenicals, but until recently all models had failed to mimic satisfactorily the actual mechanism of arsenic carcinogenicity. However, within the past decade successful animal models have been developed using the most common strains of mice or rats. Thus dimethylarsinic acid (DMA), an organic arsenic compound which is the major metabolite of inorganic arsenicals in mammals, has been proven to be tumorigenic in such animals. Reports of successful cancer induction in animals by inorganic arsenic (arsenite and arsenate) have been rare, and most carcinogenetic studies have used organic arsenicals such as DMA combined with other tumor initiators. Although such experiments used high concentrations. of arsenicals for the promotion of tumors, animal models using doses of arsenicals species closed to the exposure level of humans in endemic areas are obviously the most significant. Almost all researchers have used drinking water or food as the pathway for the development of animal model test systems in order to mimic chronic arsenic poisoning in humans; such pathways seem more likely to achieve desirable results. (C) 2002 Elsevier Science Ireland Ltd. All rights reserved.

Adoption and maintenance of contour bunds and hedgerows in a dynamic environment - Experience in the Philippine uplands

The widespread adoption of soil conservation technologies by farmers (notably contour hedgerows) observed in Guba, Cebu City, Philippines, is not often observed elsewhere In the country. Adoption of these technologies was because of the interaction of such phenomena as site-specific factors, appropriate extension systems, and technologies. However, lack of hedgerow maintenance, decreasing hedgerow quality, and disappearance of hedgerows raised concerns about sustainability. The dynamic nature of upland farming systems suggests the need for a location-specific farming system development framework, which provides farmers with ongoing extension for continual promotion of appropriate conservation practices.

The rhetoric of sector-wide approaches for health development

The past decade has witnessed an increasing concerns over the effectiveness of project-based development assistance and the promotion of sector-wide approaches (SWAps) to health as a means to increase donor collaboration, consolidate local management of resources and undertake the policy and systems reform necessary to achieve a greater impact on health issues. The concept has gained the support of both the World Bank and the World Health Organisation, as well as key bilateral donors, and dominates current initiatives in development assistance for health. This paper examines the proposal of SWAps as rhetoric, and seeks to understand how that rhetoric functions, despite the variable application of its constituent elements and the range of contexts in which it operates. (C) 2002 Elsevier Science Ltd. All rights reserved.

Effects of physical activity on emotional well-being among older Australian women - Cross-sectional and longitudinal analyses

Objective: To explore relationships between physical activity and mental health cross-sectionally and longitudinally in a large cohort of older Australian women. Method: Women in their 70s participating in the Australian Longitudinal Study on Women's Health responded in 1996 (aged 70-75) and in 1999 (aged 73-78). Cross-sectional data were analyzed for 10,063 women and longitudinal data for 6472. Self-reports were used to categorize women into four categories of physical activity at each time point as well as to define four physical activity transition categories across the 3-year period. Outcome variables for the cross-sectional analyses were the mental health component score (MCS) and mental health subscales of the Medical Outcomes Study Short Form (SF-36). The longitudinal analyses focused on changes in these variables. Confounders included the physical health component scale (PCS) of the SF-36, marital status, body mass index (BMI) and life events. Adjustment for baseline scores was included for the longitudinal analyses. Results: Cross-sectionally, higher levels of physical activity were associated with higher scores on all dependent variables, both with and without adjustment for confounders. Longitudinally, the effects were weaker, but women who had made a transition from some physical activity to none generally showed more negative changes in emotional well-being than those who had always been sedentary, while those who maintained or adopted physical activity had better outcomes. Conclusion: Physical activity is associated with emotional well-being among a population cohort of older women both cross-sectionally and longitudinally, supporting the need for the promotion of appropriate physical activity in this age group. (C) 2003 Elsevier Science Inc. All rights reserved.

Protein film voltammetry of Rhodobacter capsulatus xanthine dehydrogenase

Xanthine dehydrogenase (XDH) from the bacterium Rhodobacter capsulatus catalyzes the hydroxylation of xanthine to uric acid with NAD(+) as the electron acceptor. R. capsulatus XDH forms an (alphabeta)(2) heterotetramer and is highly homologous to homodimeric eukaryotic XDHs. The crystal structures of bovine XDH and R. capsulatus XDH showed that the two proteins have highly similar folds; however, R. capsulatus XDH is at least 5 times more active than bovine XDH and, unlike mammalian XDH, does not undergo the conversion to the oxidase form. Here we demonstrate electrocatalytic activity of the recombinant enzyme, expressed in Escherichia coli, while immobilized on an edge plane pyrolytic graphite working electrode. Furthermore, we have determined all redox potentials of the four cofactors (Mo-VI/V, Mo-V/IV, FAD/FADH, FADH/FADH(2) and two distinct [2Fe-2S](2+/+) clusters) using a combination of potentiometric and voltammetric methods. A novel feature identified in catalytic voltammetry of XDH concerns the potential for the onset of catalysis (ca. 400 mV), which is at least 600 mV more positive than that of the highest potential cofactor. This unusual observation is explained on the basis of a pterin-associated oxidative switch during voltammetry that precedes catalysis.

The perceived potential of business social networking sites

Business social networking is a facilitator of several business activities, such as market studies, communication with clients, and identification of business partners. This paper traduces the results of a study undertaken with the purpose of getting to know how the potential of networking is perceived in the promotion of business by participants of the LinkedIn network, and presents two main contributions: (1) to disseminate within the business community which is the relevance given to social networking; and (2) which are the social networks best suitable to the promotion of business, to support the definition of strategies and approaches accordingly. The results confirm that LinkedIn is the most suitable network to answer the needs of those that look for professional contacts and for the promotion of business, while innovation is the most recognized factor in the promotion of business through social networking. This study contributes to a better understanding of the potential of different business social networking sites, to support organizations and professionals to align their strategies with the perceived potential of each network.

Integration of management systems: towards a sustained success and development of organizations

Effective environmental management within companies, integrated with other management areas like quality and occupational health and safety, is nowadays assumed to be a strategic way to implement and improve lean and cleaner production. Also, sustainable development (SD) and business sustainability can be achieved through a better coordinated management of processes versus associated resources. This paper presents an in depth discussion regarding the promotion of integrated management systems, their benefits and major contribution towards the sustainable development of cleaner production related features. It addresses issues regarding the contributions resulting from the integration of standardized Management System (MS) from both internal and external perspectives. Complementing the overall review of aspects to the development of integrated management systems a survey was conducted in order to better understand the relevance of the identified success factors. The main findings in this paper are as follows: a contextualization model of sustainable development and integrated management systems considering the Triple Bottom Line: economic, social and environmental; and, a method and associated model to support the development of integrated management systems as well as general guidelines to support integration. It can be concluded that a proactive approach and commitment to cleaner production, supported by an integrated management system, brings relevant savings for organizations as well as providing value to the relevant interested parties.

Improving the learning experience and learning environment of adults in Higher Education – Project LIHE: the Portuguese case

Project LIHE: the Portuguese Case. ESREA Fourth Access Network Conference – “Equity, Access and Participation: Research, Policy and Practice”. Edinburgh (Scotland), 11 – 13 December, 2003.

Fabrication of Three-Dimensional Dendritic Ni-Co Films By Electrodeposition on Stainless Steel Substrates

Co-deposition of nickel and cobalt was carried out on austenitic stainless steel (AISI 304) substrates by imposing a square waveform current in the cathodic region. The innovative procedure applied in this work allows creating a stable, fully developed, and open porous three-dimensional (3D) dendritic structure, which can be used as electrode for redox supercapacitors. This study investigates in detail the influence of the applied current density on the morphology, mass, and chemical composition of the deposited Ni-Co films and the resulting 3D porous network dendritic structure. The morphology and the physicochemical composition were studied by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (W). The electrochemical behavior of the materials was evaluated by cyclic voltammetry (CV). The results highlight the mechanism involved in the coelectrodeposition process and how the lower limit current density tailors the film composition and morphology, as well as its electrochemical activity.

Trends in properties of para-substituted 3-(phenylhydrazo)pentane-2,4-diones

Trends between the Hammett's sigma(p) and related normal sigma(n)(p), inductive sigma(I), resonance sigma(R), negative sigma(-)(p) and positive sigma(+)(p) polar conjugation and Taft's sigma(o)(p) substituent constants and the N-H center dot center dot center dot O distance, delta(N-H) NMR chemical shift, oxidation potential (E-p/2(ox), measured in this study by cyclic voltammetry (CV)) and thermodynamic parameters (pK, Delta G(0), Delta H-0 and Delta S-0) of the dissociation process of unsubstituted 3-(phenylhydrazo)pentane-2,4-dione (HL1) and its para-substituted chloro (HL2), carboxy (HL3), fluoro (HL4) and nitro (HL5) derivatives were recognized. The best fits were found for sigma(p) and/or sigma(-)(p) in the cases of d(N center dot center dot center dot O), delta(N-H) and E-p/2(ox), showing the importance of resonance and conjugation effects in such properties, whereas for the above thermodynamic properties the inductive effects (sigma(I)) are dominant. HL2 exists in the hydrazo form in DMSO solution and in the solid state and contains an intramolecular H-bond with the N center dot center dot center dot O distance of 2.588(3)angstrom. It was also established that the dissociation process of HL1-5 is non-spontaneous, endothermic and entropically unfavourable, and that the increase in the inductive effect (sigma(I)) of para-substitutents (-H < -Cl < -COOH < -F < -NO2) leads to the corresponding growth of the N center dot center dot center dot O distance and decrease of the pK and of the changes of Gibbs free energy, of enthalpy and of entropy for the HL1-5 acid dissociation process. The electrochemical behaviour of HL1-5 was interpreted using theoretical calculations at the DFT/HF hybrid level, namely in terms of HOMO and LUMO compositions, and of reactivities induced by anodic and cathodic electron-transfers. Copyright (C) 2010 John Wiley & Sons, Ltd.