Development of a State-Space Water-Level Control for an Array of Cells to be Employed as Compensator in Radiotherapy

This paperdeals with the problem of water-level control for an array ofcells by means of an hydraulic circuit. An on-off valve fillsall the cells, while each cell is drained by a single on-offvalve, so the control is intrinsically coupled. An optimal controlwith PWM (pulse width modulation) valves is carried out. At theend, simulation and experimental results are presented. The arrayof cells may find application as compensator for radiotherapy(Total Body Irradiation), by interposing the cells between thex-ray source and the patient: on-line water-level variationsin the cells allow local radiation dose control.     

The effect of connectivity on EEG rhythms, power spectral density and coherence among coupled neural populations: analysis with a neural mass model

In the present work, a neural mass model consisting of four interconnected neural groups (pyramidal neurons, excitatory interneurons, inhibitory interneurons with slow synaptic kinetics, and inhibitory interneurons with fast synaptic kinetics) is used to investigate the mechanisms which cause the appearance of multiple rhythms in EEG spectra, and to assess how these rhythms can be affected by connectivity among different populations. In particular, we analyze a circuit, composed of three interconnected populations, each with a different synaptic kinetics (hence, with a different intrinsic rhythm). Results demonstrate that a single population can exhibit many different simultaneous rhythms, provided that some of these come from external sources (for instance, from remote regions). Analysis of coherence, and of the position of peaks in power spectral density, reveals important information on the possible connections among populations, especially useful to follow temporal changes in connectivity. Subsequently, the model is validated by comparing the power spectral density simulated in one population with that computed in the controlateral cingulated cortex (a region involved in motion preparation) during a right foot movement task in four normal subjects. The model is able to simulate real spectra quite well with only moderate parameter changes within the subject. In perspective, the results may be of value for a deeper comprehension of mechanism causing EEGs rhythms, for the study of brain connectivity and for the test of neurophysiological hypotheses.     

State-of-art review of the optimization methods to design the configuration of hybrid renewable energy systems (HRESs)

The current research aims to present an inclusive review of latest research works performed with the aim of improving the efficiency of the hybrid renewable energy systems (HRESs) by employing diverse ranges of the optimization techniques, which aid the designers to achieve the minimum expected total cost, while satisfying the power demand and the reliability. For this purpose, a detailed analysis of the different classification drivers considering the design factors such as the optimization goals, utilized optimization methods, grid type as well as the investigated technology has been conducted. Initial results have indicated that among all optimization goals, load demand parameters including loss of power supply probability (LPSP) and loss of load probability (LLP), cost, sizing (configuration), energy production, and environmental emissions are the most frequent design variables which have been cited the most. Another result of this paper indicates that almost 70% of the research projects have been dedicated towards the optimization of the off-grid applications of the HRESs. Furthermore, it has been demonstrated that, integration of the PV, wind and battery is the most frequent configuration. In the next stage of the paper, a review concerning the sizing methods is also carried out to outline the most common techniques which are used to configure the components of the HRESs. In this regard, an analysis covering the optimized indicators such as the cost drivers, energy index parameters, load indicators, battery’s state of charge, PV generator area, design parameters such as the LPSP, and the wind power generation to load ratio, is also performed.     

A desalination battery

Water desalination is an important approach to provide fresh water around the world, although its high energy consumption, and thus high cost, call for new, efficient technology. Here, we demonstrate the novel concept of a "desalination battery", which operates by performing cycles in reverse on our previously reported mixing entropy battery. Rather than generating electricity from salinity differences, as in mixing entropy batteries, desalination batteries use an electrical energy input to extract sodium and chloride ions from seawater and to generate fresh water. The desalination battery is comprised by a Na(2-x)Mn(5)O(10) nanorod positive electrode and Ag/AgCl negative electrode. Here, we demonstrate an energy consumption of 0.29 Wh l(-1) for the removal of 25% salt using this novel desalination battery, which is promising when compared to reverse osmosis (~ 0.2 Wh l(-1)), the most efficient technique presently available.     

Effect of periodic feeding on substrate uptake and storage rates by a pure culture of Thiothrix (CT3 strain)

A pure culture of Thiothrix strain CT3 has been aerobically cultured under periodic acetate feeding in a Sequencing Batch Reactor (SBR) at volumetric organic load rate of 0.12gCODL(-1)d(-1). Two different culture residence times (12d or 20d) were adopted as well as two different feed frequencies (1 and 4d(-1), for each culture residence time), the volumetric organic load rate being the same under all conditions. The transient response of the microorganism to the periodic acetate feed was investigated through batch tests with biomass withdrawn from the SBR, as function of the different SBR operating conditions. In all tested conditions, a quick transient response to the acetate spike was observed with fast increase of acetate uptake rate (ranging from 71 to 247mgCODgCOD(-1)h(-1)). This transient response was mainly due to acetate storage in form of poly-hydroxybutyrate (ranging from 45% to 64% of the observed yield) whereas the growth response (i.e. increase of production rate of active biomass) generally played a minor role (ranging from 21% to 38% of the observed yield). Apart from this general trend, culture residence time as well as feed frequency had a strong impact on transient behaviour of cultured cells. The overall transient response (i.e. maximum specific substrate removal rate) increased as culture residence time decreased or as feed frequency increased. Moreover, the ratio of storage response and growth response increased as the overall transient response decreased, i.e. the storage response was preferentially maintained when cells presented a lower transient response. The ability of the cells to increase their growth rate with respect to SBR average value was the lowest under the most unfavourable conditions (residence time 20d, feed frequency 1d(-1)) and increased with the increase in maximum substrate uptake rate.     

Trichloroethene dechlorination and H2 evolution are alternative biological pathways of electric charge utilization by a dechlorinating culture in a bioelectrochemical system

Recently,the proof-of-principle of an innovative bioelectrochemical process fortrichloroethene (TCE) bioremediation was presented. In this newly developed process, a solid-state electrode polarized to -450 mV (vs SHE), in the presence of a low-potential redox mediator (methyl viologen), is employed as an electron donor for the microbial reductive dechlorination of TCE to lower or nonchlorinated end products. In the present study, we investigated the influence of methyl viologen and TCE concentrations on process performance. Using a highly enriched hydrogenotrophic dechlorinating culture, as a source culture in batch experiments, we found that TCE dechlorination and H2 evolution were the two main biological reactions which were stimulated. The relative contribution of the two reactions appeared to be strongly dependent on the mediator concentration. At the lowest methyl viologen (MV) concentrations (25-750 microM), only TCE dechlorination was stimulated, and no H2 was produced; at higher MV concentrations, both reactions occurred simultaneously, although they showed distinct kinetic features. In batch experiments in which TCE was omitted from the system, the rate of H2 production was remarkably increased (up to 80 times), suggesting that protons represented an alternative electron sink in the absence of the more energetically favorable TCE. Clearly, optimization of the process for TCE dechlorination requires H2 evolution to be minimized by, for instance, operating the system at low mediator concentrations, and this can be possibly achieved through proper physical immobilization of the mediator at the electrode surface. On the other hand, the observed bioelectrocatalytic H2 production occurred at virtually no overpotentials with respect to the thermodynamic 2H+/H2 potential. This finding revealed that the dechlorinating culture employed represented quite an exceptional and previously unrecognized biocatalytic system for H2 production.     

AF-ABLE in the multi agent contest 2009

This is the second year in which a team from University College Dublin has participated in the Multi Agent Contest (http://www.multiagentcontest.org/2009). This paper describes the system that was created to participate in the contest, along with observations of the team’s experiences in the contest. The system itself was built using the AFAPL agent programming language running on the Agent Factory platform. A hybrid control architecture inspired by the SoSAA strategy aided in the separation of concerns between low-level behaviours (such as movement and obstacle evasion) and higher-level planning and strategy.     

Synthesis of biodiesel from edible,non-edible and waste cooking oils via supercritical methyl acetate transesterification

The use of methyl acetate instead of methanol for supercritical synthesis of glycerol-free biodiesel from vegetable oils is a new process and its study is very limited in the literature. In this work, it has been tested for the first time on three edible and non-edible oils with different fatty acid composition. The process was also applied to waste oil with higher free fatty acid (FFA) content. The results demonstrate that the oil composition does not significantly influence the biodiesel yield.The influence of temperature, pressure and molar ratio of reactants was studied. All the oils achieved complete conversion after 50 min at 345 °C, 20 MPa with methyl acetate:oil molar ratio equal to 42:1. The obtained data also allowed calculating the apparent rate coefficients and activation energies.Eventually, some new information on the process was obtained. Thermal degradation of triacetin, which substitutes glycerol as the by-product of the transesterification reaction, was observed. Some indicative experiments were performed to understand the role of the acetic acid produced by FFA esterification.     

Microwave Absorbing Coatings Based on a Blend of Nitrile Rubber, EPDM Rubber and Polyaniline

Summary The mechanical and microwave radiation absorbing properties of conductive ternary blends based on nitrile rubber, EPDM rubber and polyaniline, doped with dodecylbenzene sulfonic acid, have been investigated with special interest in the concentrations of nitrile rubber and conductive polymer in the blend. The ternary blends were prepared by melt blending using an internal mixer. Mechanical properties and soluble fraction analyses show that crosslinking occurs during blending, and that the crosslinking degree depends on the concentrations of doped polyaniline and nitrile rubber in the blend. The crosslinking reaction involves the doping acid (dodecylbenzene sulfonic acid) of polyaniline and the -C≡N group in the nitrile rubber. The ternary blends can be used for microwave absorption in the frequency range of 8–12 GHz. This property depends on the concentration of the conductive polymer and film thickness.     

Obtaining hydrocarbons from ethanol over iron-modified ZSM-5 zeolites

The search for new energy sources has impulsed hydrocarbon production from methanol and ethanol over ZSM-5 zeolites. Iron incorporation by different methods has led to a variety of chemical applications. Thus, hydrocarbon production from ethanol was studied over a ZSM-5 zeolite modified by ion exchange and impregnation with iron. XRD, FTIR, TPR, nitrogen adsorption, Mössbauer and photoacoustic spectroscopies were used for the samples characterization. The highest yield of liquid hydrocarbons was obtained with the low iron-exchanged zeolite, especially co-feeding hydrogen. The calcination procedure led to a migration of the iron species, probably forming iron oxide particles.