Percolative model of proton conductivity of Nafion membranes

A model is proposed for the simulation of Nafion^® proton conductivity, where it is assumed that proton conduction occurs only in the water present in the membrane pores. Water is considered to be present in the pores due to two different phenomena: adsorption and capillary condensation. In the latter case, the pore is flooded and proton conduction occurs throughout the whole pore section. The conditions under which capillary condensation occurs are simulated in the model through the Kelvin–Cohan equation for condensation. The Kelvin–Cohan equation is a function of RH, temperature and the pore radius; the larger the pore, the higher the RH for which capillary condensation takes place. If the conditions for capillary condensation are not satisfied, then water is present in the pore due to adsorption under the form of a water layer which covers the pore walls and provides a path for proton conduction. In this case, the modified Brunauer–Emmet–Teller (BET) equation has been used in the model to simulate the thickness of the water layer.     

Environmental implications of crop insurance subsidies in Southern Italy

The changing environment affects agriculture with uncertainty. On the other hand, policies to cope with risks may have strong impacts on the environment. We evaluate the effects of public risk management programmes, such as subsidized crop insurance, fertilizer use and land allocation to crops. We implement a mathematical programming model of a representative wheat–tomato farm in Puglia, a Southern Italy region. The results show that under the current crop insurance programmes, tomato production is expected to expand and will require larger amounts of fertilizer, whereas the opposite is true for wheat production. Policy and environmental implications are discussed.     

Waste gas biofiltration: advances and limitations of current approaches in microbiology

As confidence in gas biofiltration efficacy grows, ever more complex malodorant and toxic molecules are ameliorated. In parallel, for many countries, emission control legislation becomes increasingly stringent to accommodate both public health and climate change imperatives. Effective gas biofiltration in biofilters and biotrickling filters depends on three key bioreactor variables: the support medium; gas molecule solubilization; and the catabolic population. Organic and inorganic support media, singly or in combination, have been employed and their key criteria are considered by critical appraisal of one, char. Catabolic species have included fungal and bacterial monocultures and, to a lesser extent, microbial communities. In the absence of organic support medium (soil, compost, sewage sludge, etc.) inoculum provision, a targeted enrichment and isolation program must be undertaken followed, possibly, by culture efficacy improvement. Microbial community process enhancement can then be gained by comprehensive characterization of the culturable and total populations. For all species, support medium attachment is critical and this is considered prior to filtration optimization by water content, pH, temperature, loadings, and nutrients manipulation. Finally, to negate discharge of fungal spores, and/or archaeal and/or bacterial cells, capture/destruction technologies are required to enable exploitation of the mineralization product CO(2).     

Test-beds for molecular electronics: metal-molecules-metal junctions based on Hg electrodes

Junctions based on mesoscopic Hg electrodes are used to characterize the electrical properties of the organic molecules organized in self-assembled monolayers (SAMs). The junctions M-SAM//SAM-Hg are formed by one electrode based on metals (M) such as Hg, Ag, Au, covered by a SAM, and by a second electrode always formed by a Hg drop carrying also a SAM. The electrodes, brought together by using a micromanipulator, sandwich SAMs of different nature at the contact area (approximately = 0.7 microm2). The high versatility of the system allows a series of both electrical and electrochemical junctions to be assembled and characterized: (i) The compliant nature of the Hg electrodes allows incorporation into the junction and measurement of the electrical behavior of a large number of molecular systems and correlation of their electronic structure to the electrical behavior; (ii) by functionalizing both electrodes with SAMs exposing different functional groups, X and Y, it is possible to compare the rate of electron transfer through different X...Y molecular interactions; (iii) when the junction incorporates one of the electrode formed by a semitransparent film of Au, it allows electrical measurements under irradiation of the sandwiched SAMs. In this case the junction behaves as a photoswitch; iv) incorporation of redox centres with low lying, easily reachable energy levels, provides electron stations as indicated by the hopping mechanism dominating the current flow; (v) electrochemical junctions incorporating redox centres by both covalent and electrostatic interactions permit control of the potential of the electrodes with respect to that of the redox state by means of an external reference electrode. Both these junctions show an electrical behavior similar to that of conventional diodes, even though the mechanism generating the current flow is different. These systems, demonstrating high mechanical stability and reproducibility, easy assembly, and a wide variety of produced results, are convenient test-beds for molecular electronics and represent a useful complement to physics-based experimental methods.     

On the interaction between a fixed bed of solid material and the confining column wall: the Janssen approach

A general verification of the Janssen model was carried out by measuring the bottom pressure of different granular materials confined in a cylindrical column. Special effort was made in order to experimentally test all the physical parameters appearing in Janssen’s equation, especially the particle-wall friction coefficient μ and Janssen’s factor, K. The results indicate that although Janssen’s approach is capable of qualitatively reproduce the observed behavior, the physical meaning of the parameter appearing in Janssen’s equation requires further considerations.     

A mammographic evaluation of the morphostructural variations of the breast during hormone-replacement therapy in the postmenopause

OBJECTIVE: To compare i.v. ketorolac with i.v. prochlorperazine as the initial treatment of migraine headaches in the ED. METHODS: A prospective, double-blind comparison study was performed, using a convenience sample of 64 patients suffering from migraine headaches presenting to the ED at a tertiary care university teaching hospital. Patients were randomly assigned to receive either 10 mg of prochlorperazine i.v. or 30 mg of ketorolac i.v.. Patients scored the severity of their headaches using a 10-cm visual analog pain scale. An initial mark was made on the scale at the time of entry into the study and later another mark was made on a new unmarked pain scale 1 hour after medication administration. Changes in pain scores within each treatment group and between groups were analyzed using the Wilcoxon rank sum test. RESULTS: Prior to treatment, the patients assigned to receive prochlorperazine had a median score of 9.2 cm (mean +/- SD pain score of 8.3 cm +/- 2.1 cm), while the patients receiving ketorolac had a median score of 9.0 (mean pain score of 8.4 cm +/- 1.7 cm). There was no significant difference between the pain scores of the participants in the 2 groups prior to treatment (p = 0.80). One hour after medication administration, the patients in the prochlorperazine group had a median score of 0.5 cm (mean 2.1 +/- 3.2 cm), while those patients receiving ketorolac had a median pain score of 3.9 (mean 4.0 +/- 3.3 cm). The decrease in pain score was significant for both groups of patients (p = 0.0001). The change in pain score for the patients in the prochlorperazine group (median 7.1) was significantly greater than the change in pain score for the patients in the ketorolac group (median 4.0; p = 0.04). CONCLUSION: Although both drugs were associated with a significant reduction in pain scores, benefit over a placebo agent was not tested. Furthermore, the patients who received prochlorperazine i.v. for migraine headaches had a statistically significant greater decrease in their pain scores than did those receiving ketorolac i.v.     

EFFECTS OF SOLID FRICTIONAL INTERACTIONS ON THE APPLICABILITY OF THE FLUID-DYNAMIC SCALING RULES FOR FLUIDISATION

Experimental results are reported which confirm the validity of the fluid dynamic scaling rules for gas-solid fluidised beds operated in the bubbling regime, regardless of the particle and wall roughness. These rules still apply for shallow beds operated in the slugging regime for cases in which the ratio (H_mt/D_t) of inital bed height to bed diameter is less than the tangent of the angle of internal friction of the particles; however, for higher values of H_mt/D_t, which permit the formation of fully developed dense-phase slugs, the scaling rules become invalid. This is considered to be due to particle-particle and particle-wall interactions, and evidence is reported for both these effects in the slugging regime.     

A two-dimensional protein map of human amniotic fluid at 17 weeks' gestation

Using updated technical procedures (immobilized pH gradients for isoelectric focusing followed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis: IPG/SDS-PAGE) we provide a two-dimensional (2-D) map of amniotic fluid (AF) proteins. This map comprises over 800 silver-stained spots. Over 150 spots have been identified by matching on the net with human plasma and cerebrospinal fluid maps available from SWISS 2DPAGE database; several additional spots were assigned by immunoblotting and/or microanalytical techniques. This report details our investigation on AF proteins focusing on the 17th week of gestation, when AF is most commonly used for clinical evaluation of fetal disorders. As a whole, the map displays a number of potential markers for fetal development and for gestation abnormalities. The 2-D electrophoretic technique allows the monitoring of all these proteins at the same time along with additional spots that may prove of diagnostic significance.     

Group communication on highways: An evaluation study of geocast protocols and applications

Nowadays, most of the applications proposed for Vehicular Ad Hoc Networks (VANETs) rely on geocasting, i.e. on the possibility to identify the end-points of the communication through their geographic coordinates instead of their network addresses. At the same time, each vehicular application has its own set of Quality-of-Service (QoS) requirements which must be guaranteed by the underlying dissemination protocol. This has lead to a proliferation of geocast protocols proposed in the literature of VANETs, usually based on reactive or proactive approaches. However, most of these solutions are tailored for a specific application (e.g. active-safety applications), and thus might not be suitable for generic deployments of VANETs. In this paper, we propose a Dynamic Backbone Assisted (DBA) MAC protocol as a general solution to support geocast communication on highway scenarios for different classes of vehicular applications. DBA-MAC combines the benefits of proactive and reactive schemes through a cross-layer architecture which includes: (i) a novel distributed clustering algorithm and (ii) a fast information dissemination mechanism. First, DBA-MAC creates and maintains a virtual backbone of vehicles inside the highway scenario. Then, it provides fast dissemination of geocast messages through a combination of contention-free and contention-based forwarding mechanisms at the link layer. We provide a complete and exhaustive evaluation of the DBA-MAC scheme under different application requirements and network load conditions. We propose three metrics for the selection of backbone members which provide different characteristics in terms of delivery delay and ratio, and we analyze their performance with both analytical models and simulation studies. Then, we evaluate the performance of DBA-MAC compared to traditional geocast schemes for three classes of vehicular applications: active-safety applications, traffic-information applications, multimedia streaming (audio/video) applications. The simulation results confirm that DBA-MAC is able to greatly reduce the delivery delay for active-safety applications, and to adequately meet the requirements of multimedia applications for VANETs.