Model for the hydrogen adsorption on carbon nanostructures

The hydrogen sorption capacity of carbon nanostructures was for several years a very controversial subject. Theoretical models have been published demonstrating a great potential for a large hydrogen sorption capacity of carbon nanostructures. Here we present a simple empirical model where condensation of hydrogen as a monolayer at the surface of nanotubes as well as bulk condensation in the cavity of the tube is assumed. The maximum potential amount of hydrogen absorbed according to the model was calculated to be 2.28×10-3mass % S[m2g-1]=3.0mass % for the adsorption of a monolayer hydrogen at the surface. The condensation of hydrogen in the cavity of the tube leads to a potential absorption for single wall nanotubes starting at 1.5mass % and increasing with the diameter of the tubes. The experimentally measured hydrogen capacity of the nanotube samples correlates with the B.E.T. specific surface area. The slope of the linear relationship is 1.5×10-3mass %/m2g-1. Therefore, the extrapolated maximum discharge capacity of a carbon sample is 2mass %. Furthermore, it can be concluded, that the hydrogen sorption mechanism is related to the surface of the sample, i.e. a surface adsorption proces

Porous silica spheres as indoor air pollutant scavengers

Porous silica spheres were investigated for their effectiveness in removing typical indoor air pollutants, such as aromatic and carbonyl-containing volatile organic compounds (VOCs), and compared to the commercially available polymer styrene-divinylbenzene (XAD-4). The silica spheres and the XAD-4 resin were coated on denuder sampling devices and their adsorption efficiencies for volatile organic compounds evaluated using an indoor air simulation chamber. Real indoor sampling was also undertaken to evaluate the affinity of the silica adsorbents for a variety of indoor VOCs. The silica sphere adsorbents were found to have a high affinity for polar carbonyls and found to be more efficient than the XAD-4 resin at adsorbing carbonyls in an indoor environment

Mediation, translation and local ecologies: understanding the impact of policy levers on FE colleges

This article reports the views of managers and tutors on the role of policy ‘levers’ on teaching, learning, and inclusion in colleges of Further Education (FE) in our research project, ‘The impact of policy on learning and inclusion in the Learning and Skills Sector (LSS)’.i Using data from five research visits conducted over two years in eight FE learning sites, we explore the processes by which colleges ‘mediate’ and ‘translate’ national policy levers and how this affects their ability to respond to local need. The paper tentatively develops three related concepts/metaphors to explain the complexity of the policy/college interface – ‘the process of mediation’, ‘acts of translation’ and ‘local ecologies’. We found that policy levers interacted with a complex set of national, local and institutional factors as colleges responded to pressures from the external environment and turned these into internal plans, systems and practices. We conclude by suggesting that national policy-makers, who design national policy levers, may not be fully aware of these complexities and we make the case for the benefits of greater local control over policy levers, where these interactions are better understood

Self-Motions of General 3-RPR Planar Parallel Robots

This paper studies the kinematic geometry of general 3-RPR planar parallel robots with actuated base joints. These robots, while largely overlooked, have simple direct kinematics and large singularity-free workspace. Furthermore, their kinematic geometry is the same as that of a newly developed parallel robot with SCARA-type motions. Starting from the direct and inverse kinematic model, the expressions for the singularity loci of 3-RPR planar parallel robots are determined. Then, the global behaviour at all singularities is geometrically described by studying the degeneracy of the direct kinematic model. Special cases of self-motions are then examined and the degree of freedom gained in such special configurations is kinematically interpreted. Finally, a practical example is discussed and experimental validations performed on an actual robot prototype are presented

Time-resolved homodyne characterization of individual quadrature-entangled pulses

We describe a simple and efficient setup to generate and characterize femtosecond quadrature-entangled pulses. Quantum correlations equivalent to about 2.5 dB squeezing are efficiently and easily reached using the non-degenerate parametric amplification of femtosecond pulses through a single-pass in a thin (0.1 mm) potassium niobate crystal. The entangled pulses are then individually sampled to characterize the non-separability and the entropy of formation of the states. The complete experiment is analysed in the time-domain, from the pulsed source of quadrature entanglement to the time-resolved homodyne detection. This particularity allows for applications in quantum communication protocols using continuous-variable entanglement.Comment: 7 pages, 5 figure

Navigating through the RLATES Interface: A Web-Based Adaptive and Intelligent Educational System

10 pages, 4 figures.-- Contributed to: Workshop on Human Computer Interface for Semantic Web and Web Applications (HCI-SWWA’03). Part of the International Federated Conferences (OTM'03, Catania, Sicily, Italy, Nov 3-7, 2003).The paper shows the architecture of the RLATES system, an Adaptive and Intelligent Educational System that uses the Reinforcement Learning model (RL) in order to learn to teach each student individually, being adapted to their learning needs in each moment of the interaction. This paper is focused on the interface module of RLATES, describing how the student could navigate through the system interface and how this interface adjusts the page contents according to the user learning needs. For this adaptation, the system changes the links appearance of the page and the presentation of the system knowledge.Publicad

Faucets as a reservoir of endemic Pseudomonas aeruginosa colonization/infections in intensive care units

Objective: To evaluate the role of faucets as a reservoir for Pseudomonas aeruginosa colonization/infection of patients hospitalized in intensive care units (ICUs). Design: Prospective epidemiological investigation performed during a nonepidemic period of 1year. The inner part of the ICU faucets were swabbed for P. aeruginosa. Data were recorded on all patients with at least one culture of a clinical specimens positive for P. aeruginosa. Pulsed-field gel electrophoresis was used to characterize the strains. Setting: Five ICUs of a university hospital which are supplied by two separate water distribution networks. Patients: During a 1-year period 132 cases were investigated. Results: In 42% of cases (56/132) there were isolates identical to those found in the faucets, with a total of nine different genotypes. Among the nine genotypes isolated from both patients and faucets one of them, the most prevalent, was isolated in the two networks and in 30 cases. The other eight genotypes were recovered almost exclusively from either one (three genotypes in 12 cases) or the other (five genotypes in 12 cases) network and from the patients in the corresponding ICUs. Conclusions: These results suggest that the water system of the ICUs was the primary reservoir of patient's colonization/infection with P. aeruginosa in a substantial proportion of patients, although the exact mode of acquisition could not be determine

Biochemical and clinical response after umbilical cord blood transplant in a boy with early childhood-onset beta-mannosidosis.

BACKGROUND: Deficiency in the enzyme β-mannosidase was described over three decades ago. Although rare in occurrence, the presentation of childhood-onset β-mannosidase deficiency consists of hypotonia in the newborn period followed by global development delay, behavior problems, and intellectual disability. No effective pharmacologic treatments have been available. METHODS: We report 2-year outcomes following the first umbilical cord blood transplant in a 4-year-old boy with early childhood-onset disease. RESULTS: We show restoration of leukocyte β-mannosidase activity which remained normal at 2 years posttransplant, and a simultaneous increase in plasma β-mannosidase activity and dramatic decrease in urine-free oligosaccharides were also observed. MRI of the brain remained stable. Neurocognitive evaluation revealed test point gains, although the magnitude of improvement was less than expected for age, causing lower IQ scores that represent a wider developmental gap between the patient and unaffected peers. CONCLUSION: Our findings suggest that hematopoietic cell transplant can correct the biochemical defect in β-mannosidosis, although preservation of the neurocognitive trajectory may be a challenge