A System Design Methodology for Analog Feed Forward Artificial Neural Networks

Today Feed Forward Neural Networks (FFNs) use paradigms tied to mathematical frameworks more than to actual electronic devices. This fact makes analog neural integrated circuits heavy to design. Here we propose an alternative model that can use the native computational properties of the basic electronic circuits. A practical framework is described to train analog FFNs in compliance with the model. This is especially useful whenever the weight storage elements cannot be re-programmed on the fly at a high rate. To show how the capability of such framework can be applied to neural systems with non conventional architectures two cases are presented. The first one is a neural signal processor named NESP which has sigmoidal neurons and the other is an innovative architecture named N-LESS.     

Hippocampal Deletion of CB1 Receptor Impairs Social Memory and Leads to Age-Related Changes in the Hippocampus of Adult Mice

Endocannabinoid system activity declines with age in the hippocampus, along with the density of the cannabinoid receptor type-1 (CB1). This process might contribute to brain ageing, as previous studies showed that the constitutive deletion of the CB1 receptor in mice leads to early onset of memory deficits and histological signs of ageing in the hippocampus including enhanced pro-inflammatory glial activity and reduced neurogenesis. Here we asked whether the CB1 receptor exerts its activity locally, directly influencing hippocampal ageing or indirectly, accelerating systemic ageing. Thus, we deleted the CB1 receptor site-specifically in the hippocampus of 2-month-old CB1^flox/flox mice using stereotaxic injections of rAAV-Cre-Venus viruses and assessed their social recognition memory four months later. Mice with hippocampus-specific deletion of the CB1 receptor displayed a memory impairment, similarly as observed in constitutive knockouts at the same age. We next analysed neuroinflammatory changes in the hippocampus, neuronal density and cell proliferation. Site-specific mutant mice had enhanced glial cell activity, up-regulated levels of TNFα in the hippocampus and decreased cell proliferation, specifically in the subgranular zone of the dentate gyrus. Our data indicate that a local activity of the CB1 receptor in the hippocampus is required to maintain neurogenesis and to prevent neuroinflammation and cognitive decline.     

Physico-chemical properties of WO3/TiO2 systems employed for 4-nitrophenol photodegradation in aqueous medium

A series of polycrystalline WO_x/TiO₂ samples were prepared by means of a conventional impregnation method. The samples were characterized by means of X-ray diffraction, Vis-UV diffuse reflectance and Raman spectroscopies, nitrogen adsorption at 77 K for determining specific surface areas and surface texture, scanning electron microscopy, and FT-IR monitoring of pyridine adsorption for measuring the surface acidity. Catalytic activity of the samples has been assessed by carrying out as a ``probe'' reaction the photodegradation of 4- nitrophenol in aqueous medium. The results obtained indicate that incorporation of tungsten on titania leads to formation of different surface species, depending on the tungsten loading. Tungsta microcrystals were detected by X-ray diffraction when the nominal molar W/Ti ratio reached a value of 8.0%. FT-IR investigation indicated that the presence of tungsten induces formation of Brønsted and Lewis surface acid sites. The photoactivity results confirm the beneficial effect of tungsten in TiO₂ for 4-nitrophenol photodegradation in aqueous medium. The reaction rates are higher than those reported in literature for another set of samples and maximum photoactivity was achieved for a sample containing 1.96 moles of W per 100 moles of Ti.     

Photocatalytic thin films of TiO2 formed by a sol-gel process using titanium tetraisopropoxide as the precursor

Thin TiO₂ films were prepared with the dip-coating technique by using sols deriving from titanium tetraisopropoxide. TiO₂ films were formed on glass substrates previously covered by a SiO₂ layer obtained from a tetraethylortosilicate sol. The films, after a thermal treatment at 673 K, mainly consisted of TiO₂ anatase. The samples were characterised by X-ray diffraction, UV-Vis spectroscopy, scanning electron microscopy and atomic force microscopy. The photoactivity of the various films was tested by using as probe reaction the photo-oxidation of 2-propanol in gas-solid regime. The photoreactivity results indicated that the TiO₂ films were efficient for degrading 2-propanol under UV illumination, propanone being the only compound detected as intermediate product. Films prepared by using Degussa P25 appeared to be more photoactive, but the coating was easily detached by wiping.     

Environmentally Friendly Photocatalytic Oxidation of Aromatic Alcohol to Aldehyde in Aqueous Suspension of Brookite TiO2

X-ray photoelectron spectroscopy (XPS) has been applied to the study pertaining to preparation and characterization of catalysts used in propylene polymerization. The analysis has indicated support/donor interaction in active support (adduct) and active support/TiCl₄ interaction during catalyst preparation process. A systematic study has been made to identify suitable adduct from a set of three adducts for catalyst synthesis. Precise binding energy of Titanium species on catalyst surface has been measured and its dispersion on support has been evaluated to correlate catalyst performance with the surface spectroscopic parameters.     

A sensitivity-enhanced field-effect chiral sensor

Organic thin-film transistor sensors have been recently attracting the attention of the plastic electronics community for their potential exploitation in novel sensing platforms. Specificity and sensitivity are however still open issues: in this respect chiral discrimination-being a scientific and technological achievement in itself--is indeed one of the most challenging sensor bench-tests. So far, conducting-polymer solid-state chiral detection has been carried out at part-per-thousand concentration levels. Here, a novel chiral bilayer organic thin-film transistor gas sensor--comprising an outermost layer with built-in enantioselective properties-is demonstrated to show field-effect amplified sensitivity that enables differential detection of optical isomers in the tens-of-parts-per-million concentration range. The ad-hoc-designed organic semiconductor endowed with chiral side groups, the bilayer structure and the thin-film transistor transducer provide a significant step forward in the development of a high-performance and versatile sensing platform compatible with flexible organic electronic technologies.     

The Material-Dependent Parameter Controlling the Universal Phase Diagram of Cuprates

The critical temperature T _c in the universal phase diagram of cuprate superconductors is a function of two variables: the hole-doping δ and a material dependent parameter. Here we focus on the behavior of T _c,max as a function of the material dependent parameter (MDP) at the optimum hole doping. We have discussed the correlation between (1) the average Cu—O (planar) distance, or the strain of the Cu—O bond, (2) the nearest-neighbor hopping t′ and (3) the Lifshitz parameter z. These Lifshitz parameter z = μ_{δ = 0.16}−E _vHs which are all material dependent parameters, where μ_{δ = 0.16} is the chemical potential at optimum doping and E_vHs is the energy of the Van Hove singularity, defines the proximity to the Fermi surface topological transition from electron-like to hole-like. The results show that the striped phases occur for z < 0, the highest T _c,max for and the drop of T _c,max for z > 75 meV.     

A Suitable Tool for Sustainable Groundwater Management

Artificial recharge is used to increase the availability of groundwater storage and reduce saltwater intrusion in coastal aquifers, where pumping and droughts have severely impaired groundwater quality. The implementation of optimal recharge methods requires knowledge of physical, chemical, and biological phenomena involving water and wastewater filtration in the subsoil, together with engineering aspects related to plant design and maintenance operations. This study uses a novel Decision Support System (DSS), which includes soil aquifer treatment (SAT) evaluation, to design an artificial recharge plant. The DSS helps users make strategic decisions on selecting the most appropriate recharge methods and water treatment technologies at specific sites. This will enable the recovery of safe water using managed aquifer recharge (MAR) practices, and result in reduced recharge costs. The DSS was built using an artificial intelligence technique and knowledge-based technology, related to both quantitative and qualitative aspects of water supply for artificial recharge. The DSS software was implemented using rules based on the cumulative experience of wastewater treatment plant engineers and groundwater modeling. Appropriate model flow simulations were performed in porous and fractured coastal aquifers to evaluate the suitability of this technique for enhancing the integrated water resources management approach. Results obtained from the AQUASTRESS integrated project and DRINKADRIA IPA CBC suggest the most effective strategies for wastewater treatments prior to recharge at specific sites.     

Heterogeneous photocatalysis: guidelines on experimental setup,catalyst characterization,interpretation, and assessment of reactivity

Soon after the publication of the first pioneering works on heterogeneous photocatalysis, the number of papers on this topic continuously increased. This intriguing field of research is very complex as it endows with an interdisciplinary overview that involves different aspects of chemistry, physics, material and environmental sciences. Even if photocatalytic applications in real processes are often difficult to be implemented and scaled-up, investigations at laboratory scale are easy to be performed, and in some cases they may give rise to misconceptions. For this reason, the present work aims to sum up most of the common experimental techniques and procedures generally used in heterogeneous photocatalysis and to highlight the guidelines and the rules that a rigorous analysis and study of a photocatalytic system must follow. The paper focuses on the importance of standardization of photocatalytic experiments with special attention on the possibility to compare results obtained under different experimental conditions.