Search

Undoped as well as K-doped (40%), Y-doped (40%), Zr-doped (10%), and Mo-doped (12.5%) strontium barium niobate Sr0.5Ba0.5Nb2O6 (SBN50) materials have been investigated to explore the effect of heavy doping on the structural and functional properties (thermo-power, thermal and electrical conductivities) both in the as prepared (oxidized) and reduced states. For all materials, the EXAFS spectra at the Nb – K edge can be consistently analyzed with the same model of six shells around the Nb sites. Doping mostly gives a simple size effect on the structural parameters, but doping on the Nb sites weakens the Nb–O bond regardless of dopant size and charge. Shell sizes and Debye–Waller factors are almost unaffected by temperature and oxidation state, and the disorder is of static nature. The functional effects of heavy doping do not agree with a simple model of hole or electron injection by aliovalent substitutions on a large band gap semiconductor. With respect to the undoped samples, doping with Mo depresses the thermal conductivity by ~ 30%, Y doping enhances the electrical conductivity by an order of magnitude, while Zr doping increases the Seebeck coefficient by a factor of 2–3. Globally, the ZT efficiency factor of the K-, Y-, and Zr-doped samples is enhanced at least by one order of magnitude with respect to the undoped or Mo-doped materials., This work has been supported by the “Materiali Avanzati” Program (Projet code 2012-0815) of the Cariplo foundation (Milano, Italy). BM08 (LISA)@ESRF is acknowledged for the provision of beam-time, travel and accommodation expenses (Exp. HC-1582).

In the present work, we show a successful approach to achieve stable structural and optical changes induced by pressure on bulk amounts of MAPI after pressure release. Such effects on the optical properties resemble those achieved in situ (e.g., in diamond anvil cells) but are retained and stabilized under ambient conditions thanks to a partial quenching of the high-pressure state.

We investigated the interdiffusion process in nanostructured fluoritic oxides sintered by Field Assisted or Spark Plasma Sintering (FAST/SPS). Ceria and zirconia nanopowders were surface decorated with dopants, using simple solution techniques and then sintered at temperatures of 600–900 °C for very short times, under a pressure of 575 MPa. Remarkable ionic conductivity increase and phase composition alteration were observed after only 5 min of sintering. This rapid modification cannot be justified with regular bulk diffusion models, as cationic bulk diffusivity in these oxides is very limited at these temperatures. We propose an alternative model, involving only surface diffusion processes, justifying the apparently anomalous fast interdiffusion. This model helps clarifying some fundamental aspects of diffusion at the nanoscale when fast sintering is involved. We also evidenced as surface decoration coupled with FAST/SPS represents a simple alternative approach to the doping of oxides, which can be applied when other approaches are inconvenient.

Nanostructuring has been proposed as an effective strategy for the reduction of the phonon contribution to the thermal conductivity, resulting in an increase in the figure of merit of thermoelectric materials. However, obtaining bulk samples presenting high relative density and nanometric grain size can be quite challenging, particularly in the case of ceramic phases. Only few examples have been reported and none in the case of Ca3Co4O9. In this work, we used a sol-gel synthesis coupled with ball milling to prepare powders of Ca3Co4O9 presenting a grain size as small as 4 nm. These nanopowders were then sintered at different temperature and pressures using the High-Pressure Field-Assisted Sintering Technique (HP-FAST). Relative densities up to 95 vol% where obtained while maintaining a nanometric grain size. The microstructural and electrical properties of the sintered samples have been characterized. The results show that in this oxide a reduction to the nanometric grain size produces a drastic reduction in the electrical conductivity, which cannot be compensated by the reduction in the thermal conductivity. The Seebeck effect, on the other hand, appears to be affected only marginally by the grain size and porosity.

Chronic pain (CP) represents a complex pathology profoundly involving both neural and glial compartments of the central nervous system. While most CP studies have also investigated the macroscopic brain vascular system, its microstructural architecture still remains largely unexplored. Further, the adaptive modifications of the vascular microstructure as consequence of diseases or pathological insults did not receive adequate attention. Here we show microtomographic signs of diffuse and conspicuous microvascular neogenesis in somatosensory cortex of CP animal models already peaking at 15 days from the model instantiation. Progressive fading of this microvessel neogenesis then ensued in the next six months yet maintaining higher vascular density with a preserved small fraction of them. Due to the important consequences on the neuron-glial-vessel arrangements and on the resulting metabolic and functional disorders of the local networks, novel additional scenarios of CP are thus conceivable with profound consequences of potential future CP diagnostic and therapeutic appraisals. Significance Statement Chronic pain (CP) is an excruciating condition with various clinical presentations. Major signs are characterized by a rich repertoire of pain quality, intensity and length. While neuronal and glial anomalies have been associated to CP less attention has been granted to the micro-vessel and capillary compartments of the involved brain regions. Our research illustrates how the microvessel compartments of the somatosensory cortex in experimental animals present profound and long-lasting signs of extensive neogenesis (about fourfold) early within the first two weeks from the CP start, undergoing a slow and incomplete decline within six months. These results may change the CP clinical picture with potential novel therapeutic approaches to it.

In this paper we report the influence of the absolute surface area (ASA) and aspect ratio (L/D) of hydrothermally grown ZnO nanorods (NRs) on the NO 2 and H 2 gases relative responses (RRs) in the 20 ppb − 1 ppm and 50 ppm–1000 ppm concentrations range. We used films of NRs characterized by different geometrical features, such as diameter, length, L/D and ASA, obtained using different growth times, but all showing a well-defined hexagonal shape and an alignment perpendicular to the substrate. Values of L/D up to 129 and NRs lengths up to 14 μm have been obtained; one of the highest reported for quasi-one-dimensional ZnO nanostructures obtained through solution-based one-pot syntheses. Electrical tests at 150 °C (NO 2 ) and 200 °C (H 2 ) carried out using films of NRs presenting different L/D evidenced a direct relationship between the increase of the ASA and L/D and gas RRs. The influence of geometrical and chemical characteristics, such as diameter, size and surface-defects concentration is also discussed in light of the existing literature. Cross sensitivity, investigated measuring the H 2 (target) response in the presence of NO 2 (interfering) gases as well as dynamic and cumulative NO 2 gas reproducibility test are also presented. Beside the considerable interference played by NO 2 to the H 2 response, our long NRs demonstrate an excellent reproducibility of the electrical signal and fast recovery of the base line, evidencing the absence of irreversible chemisorption or sample-surface “history-related” phenomena.

When used in prosthetic dentistry, zirconia encounters severe durability issues due to low temperature degradation: exposure to humidity results in a transition from tetragonal to monoclinic phase, associated to disruptive integrity loss. Recently it has been shown that size-induced stabilization helps maintaining zirconia in tetragonal form, when the grain size is reduced to the nano-range. Objective of this work is to demonstrate the applicability of High Pressure Field Assisted Sintering (HP-FAST) to the preparation of dense, nanostructured samples of tetragonal yttria stabilized zirconia, with yttria content between 0.5 and 3 mol% and showing resistance to low temperature degradation. The yttria stabilized zirconia nanopowders were prepared by a hydrothermal method. Sintering by HP-FAST was performed at 900 °C in 5 min, under a pressure of 620 MPa. Resistance to low temperature degradation was tested at 134 °C, under vapor pressure, for up to 40 h. Both pristine and aged samples were characterized by X-ray diffraction, high-resolution scanning electron microscopy and nanoindentation tests in continuous stiffness measurement mode. The sintered samples presented a grain size between 20 and 30 nm and low or null monoclinic content. Both parameters resulted unaffected by ageing. The best results in terms of phase composition and mechanical properties have been obtained with the material containing 1.5 mol% of yttria. These results induce to reconsider the use of yttria stabilized zirconia as material for dental prosthetic systems requiring long-term durability.

Nanostructuring has been proposed as an effective strategy for the reduction of the phonon contribution to the thermal conductivity, resulting in an increase in the figure of merit of thermoelectric materials. However, obtaining bulk samples presenting high relative density and nanometric grain size can be quite challenging, particularly in the case of ceramic phases. Only few examples have been reported and none in the case of Ca₃Co₄O₉. In this work, we used a sol–gel synthesis coupled with ball milling to prepare powders of Ca₃Co₄O₉ presenting a grain size as small as 4 nm. These nanopowders were then sintered at different temperature and pressures using the High-Pressure Field-Assisted Sintering Technique (HP-FAST). Relative densities up to 95 vol% where obtained while maintaining a nanometric grain size. The microstructural and electrical properties of the sintered samples have been characterized. The results show that in this oxide a reduction to the nanometric grain size produces a drastic reduction in the electrical conductivity, which cannot be compensated by the reduction in the thermal conductivity. The Seebeck effect, on the other hand, appears to be affected only marginally by the grain size and porosity.

ZnO sol–gel films, with and without embedded Pt nanoparticles, were used as seeding layers for the hydrothermal growth of ZnO nanorods. The morphology of the nanorods was controlled by adjusting the chemistry and processing, yielding samples with high transparencies and exposed surface areas. The prepared samples were assessed for performance as optical gas sensors in terms of absorbance variation and response time and these data were correlated with the structural properties. The nanorods grown on ZnO films containing Pt nanoparticles showed excellent H 2 -sensing properties owing to the high exposed surface areas of the ZnO nanorods and to the catalytic effect the underlying Pt nanoparticles.

ZnO nanorods present great potential for application in optical, sensing and piezoelectric devices; thanks to their nanometric diameter and large surface area. In some of these applications a probing current must flow directly through the nanorods, requiring each nanorod to be directly connected to two electrodes. To attain this architecture a few solutions have been proposed in the past, mostly involving the use of complex and time-consuming procedures, but the large-scale production of such devices represents still a major challenge. We present here a new all-solution approach that allows the fabrication of extensive self-assembled, bi-dimensional networks of ZnO nanorods. Such networks can be easily produced on interdigitated electrodes with no need for any alignment, resulting directly in the formation of very robust devices. The entire process is fast, does not require any complex experimental apparatus and involves only the use of inexpensive and environmentally friendly chemical reagents. We demonstrate the potentiality of such networks in a gas sensing application, where these networks were able to detect NO2 at trace levels, at low temperatures, using UV-visible activation.

Correction for 'Dependence of the Ce(iii)/Ce(iv) ratio on intracellular localization in ceria nanoparticles internalized by human cells' by Daniela Ferraro, et al., Nanoscale, 2017, 9, 1527-1538.

Nanopowders of pure or very lightly doped zirconia were studied by means of total scattering and pair distribution function analysis, with the aim of understanding how the size of the particles (if a size limit of about 20 nm is not exceeded) tends to stabilise the tetragonal polymorph at room temperature. Total scattering and PDF analyses, together with Rietveld refinements, showed that the tetragonal model is indeed applicable to the average structure of these nanocrystalline zirconia samples, and provided comparable results. However, all the samples, with no influence from the dopant content, showed a similar local distortion for r < 10 A. In this region, the data were fitted with two slightly different tetragonal structures, with a tetragonal distortion that decreases with the Rmax used, giving rise to a structure closer to the average tetragonal one (given by Rietveld as well as by average PDF refinements). In the first coordination shell, however, an orthorhombic distortion fits very well both in intensity and in position. This distortion may be responsible of the increased RMS strain local level, and therefore of the stabilisation of the high temperature structure at room temperature.

Thermal degradation of metal-loaded hydrogel films is a powerful tool to synthesize high-quality metal oxide thin films with nanometric grain size, but the formation mechanism is still poorly known. We exploited fluorescence X-ray absorption fine structure as a short-range probe to investigate the first stages of nucleation and the following development of ZnO nanoparticles in Zn-loaded hydrogels, annealed for 20 min at temperatures between 150 and 500 °C. The experimental results evidenced that the first nuclei of ZnO begin to form at 300 °C, whereas at 350 °C the ZnO nanoparticles are already well crystallized. By coupling the results with those obtained by thermal analysis, profilometry, HR-TEM, diffraction and μ-FTIR, a formation mechanism was suggested. The optical and electrical properties of the samples confirm that the polymer forms an insulating shell around the nanoparticles up to 450 °C: the intimate hybridization promotes stress relaxation during the annealing, yielding crack-free metal oxide ...

High-quality micropatterned SnO 2 , In 2 O 3 , ZrO 2 and TiO 2 thin films were prepared by a simple soft-lithographic process, based on the use of metal-loaded poly(ethylene glycol)-based hydrogels. The hydrogels liquid precursors have been embossed using polydimethylsiloxane molds, then rapidly photopolymerized and thermally degraded producing, despite the large volume contraction, crack-free and highly transparent ceramic patterns, with a thickness tunable between 40 nm and 1 μm. The films were characterized by a very fine nanostructure, presenting uniform, well-sintered and crystallized nanoparticles with a grain size in the range of 5–30 nm. The influence of both annealing temperature and heating rate on the thermal degradation of the precursor has been investigated: in the case of ZrO 2 and TiO 2 , size-induced stabilization of tetragonal and anatase structures, respectively, was obtained and maintained also after annealing at temperatures up to 700 °C. The typical drawbacks associated to other soft-lithographic approaches (such as the limited thickness to avoid crack formation, the uncontrolled reactivity or the need for thermal solidification with the mold in place) were overcome, thanks to the intimate hybridization between the polymer and the inorganic salts, coupled with the improved reliable solidification achieved by the photopolymerization.

The synthesis and functional characterization of dense bulk nanometric oxides are reviewed, with particular emphasis on the modifications that a grain size in the low nanometric range (10–50 nm) introduces in their physical properties. The preparation of ceramics with low porosity and extremely small grain size is particularly challenging and mostly relies on the sintering of extremely fine nanopowder. The most popular methods for the preparation of the starting nanopowders are introduced and briefly discussed as well as the most widely employed densification techniques. The role of nanostructure in controlling phase stability, electrical and thermal transport, optical and magnetic properties of nano-oxides is discussed in details. Several examples are given where bulk materials prepared with grain size equal or below 50 nm show characteristics that are either enhanced or, in some cases, completely different from those possessed by the same materials, but with larger grain sizes.

International audience; CeO2 nanoparticles (CNPs) have been investigated as promising antioxidant agents with significant activity in the therapy of diseases involving free radicals or oxidative stress. However, the exact mechanism responsible for CNP activity has not been completely elucidated. In particular, in situ evidence of modification of the oxidative state of CNPs in human cells and their evolution during cell internalization and subsequent intracellular distribution has never been presented. In this study we investigated modification of the Ce(III)/Ce(IV) ratio following internalization in human cells by X-ray absorption near edge spectroscopy (XANES). From this analysis on cell pellets, we observed that CNPs incubated for 24 h showed a significant increase in Ce(III). By coupling on individual cells synchrotron micro-X-ray fluorescence (mu XRF) with micro-XANES (mu XANES) we demonstrated that the Ce(III)/Ce(IV) ratio is also dependent on CNP intracellular localization. The regions with the highest CNP concentrations, suggested to be endolysosomes by transmission electron microscopy, were characterized by Ce atoms in the Ce(IV) oxidation state, while a higher Ce(III) content was observed in regions surrounding these areas. These observations suggest that the interaction of CNPs with cells involves a complex mechanism in which different cellular areas play different roles

The behaviour of TiO2based electrodes was investigated during the photoelectrocatalytic water splitting process. TiO2nanotubes and compact oxide structures were obtained by electrochemical oxidation of Ti foils. A subsequent hydrothermal process carried out at both the nanotubular and compact oxide structures allowed decorating the structure by TiO2nanoparticles. The synthesized TiO2samples worked as photoanodes both in a bulk three electrode cell and in a thin gap cell. The results from measurements of the photocurrent and from electrochemical impedance spectroscopy were used to highlight a combined effect of the wavelength of the incident light and the kind of cell configuration, on the global performance of the systems. The results indicate that the decoration process does not result only in a simple increase of the specific surface, but it also determines a different concentration of the bulk and superficial sites in the electrode. The different response of the sites at different wavelengths, along with the accessibility of the electrolyte to the porous structure are evocated to justify the experimental behaviour observed.

High-quality micropatterning of ZnO nanorods was obtained by combining deposition of patterned ZnO seed layers, through soft lithography of metal-loaded hydrogels, with a solution method for growth of nanorods. The embossed hydrogel was photo-polymerised and thermally degraded, providing uniform, well-sintered seed layers with low surface roughness and a film thickness tunable in the range of 50–200 nm. The films were composed of small nanoparticles (20–30 nm) that were fully crystalline and had a preferred orientation along the c axis. These films acted as ideal seed layers for the growth of nanorods, whose diameter could be controlled by the seeding grain size, in the range of 50–100 nm. The procedure yielded complex patterns of dense arrays of vertically aligned nanorods characterised by high lithographic quality, using inexpensive, environmentally-friendly chemicals and simple experimental apparatus.

Fully dense Sm-doped ceria powders, with doping content between 2 and 30 at.% and grain size below 20 nm, were consolidated using a High-Pressure Field Assisted Sintering (HP-FAST) apparatus. Using a uniaxial pressure of 600 MPa relative densities above 95% were achieved at temperatures as low as 600 °C with sintering times of only 5 min. Thanks to these exceptionally mild sintering conditions, grain growth during densification was very limited. The samples were characterized using impedance spectroscopy and the results showed a single semicircle, due to an overwhelming contribution of the grain boundary resistance. Thanks to the brick layer model, the present results were compared to literature data on microcrystalline materials and revealed that, contrary to what previously reported by several authors, negligible modification of the specific grain boundary conductivity can be produced through the reduction of the grain size in Sm-doped ceria in the considered doping interval.

We investigated the conductivity of high-density bulk-anatase samples with a grain size between 24 and 56 nm prepared by high pressure field-assisted sintering. When exposed to humid atmosphere, the insurgence of proton conductivity was observed for temperatures below 350 °C. Below this temperature, the samples showed a conductivity several orders of magnitude higher than that measured under dry oxygen atmosphere. The protonic conductivity strongly increased as grain size decreased, while a negligible dependence from porosity was observed when the latter ranged between 8 and 25 vol%. If compared with zirconia- and ceria-based nanomaterials with similar grain size, bulk nanometric anatase showed the highest low temperature protonic conductivity as well as the highest crossover temperature between dry and humid conduction behavior.

The densification of undoped zirconia nanopowder was performed using the High-Pressure Field Assisted Sintering technique, with the aim of preparing bulk size-stabilized tetragonal zirconia. The role played by the structural and microstructural properties of the starting powders on the characteristics of the sintered materials was investigated by exploring several different synthetic routes. Nanopowders prepared by solvothermal methods were proven to give the most satisfactory results thanks to their microstructure, particularly characterized by uniform spherical microaggregates. Using solvothermally synthesized powder as a starting material, nearly fully dense (97% relative density) samples of undoped size-stabilized tetragonal zirconia were obtained with a sintering cycle of 5 min under a uniaxial pressure of 700 MPa, at sintering temperatures as low as 900 °C.

A gold electrode modified by chemisorption of Coenzyme A (CoA-CME) has been prepared. Exploiting its complexation properties towards heavy metal ions usually present in natural waters, it was shown that CoA has a stronger interaction with Cu than with the Pb and Cd; the complexation constants of bounded CoA with these ions were calculated by a novel approach. The metal ions can be determined in natural waters at the CoA-CME by open circuit preconcentration followed by medium exchange in citrate buffer before the anodic stripping voltammetry. The presence in solution of competing ligands and important aspects regarding the complexation were investigated.

A new solution method based on inexpensive hydrogels and inorganic salts is applied to the synthesis of micropatterned ceramic oxide thin films. Poly(ethylene glycol)-based polymeric precursors, loaded with simple metal precursors, are photopolymerized and micropatterned through soft-lithographic techniques. After thermal degradation, ceramic oxide thin films are produced. The process, examined by means of thermal analysis, grazing incidence diffraction, atomic force microscopy and profilometry, leads to homogeneous nanostructured films, and exhibits great lithographic reliability, remarkably avoiding lateral shrinkage and background residual layer. The method, which permits to overcome some drawbacks related to conventional soft-lithographic and polymer-assisted deposition techniques, was applied to a large number of simple and complex oxides.

The paper describes the preparation of micropatterned zinc oxide films through a synthetic route based on the thermal degradation of metal-loaded poly(ethylene glycol)-based hydrogels. This approach requires very simple apparatuses and involves only simple, inexpensive and environmentally friendly chemicals. Highly transparent and crack free nanocrystalline films were obtained through this route. The evolution of the films during the thermal degradation and the influence of synthesis parameters on the film characteristics were investigated by thermal analysis, X-ray grazing incidence diffraction, scanning electron microscopy, atomic force microscopy and micro-Raman. The response toward reducing gasses was tested at different temperatures. Finally, the micropatterning of ZnO films through soft lithography has been characterized.

We present a new approach to the synthesis of inorganic coatings based on the ability of cultured cells to actively uptake large amounts of nanoparticles. The cellular matrix allows maintaining the adhesion of the nanoparticles to the substrate at temperatures high enough to allow bonding of the powders on the substrate during a subsequent thermal degradation. Exploiting different cell abilities it is possible to obtain patterning and formation of nanocomposites even on substrates characterized by complex geometries. These results suggest that cultured eukaryotic cells have good potential as a tool for the realization of inorganic coatings.

The preparation, characterization and analytical application of a chemically modified gold electrode (CME), based on thiolated α-cyclodextrin self assembled monolayer (SAM), have been described. The CME was effective for the determination of nitroaromatic explosive compounds; 2,4,6-trinitrotoluene (TNT) was determined with satisfactory results (LOQ = 30 μmolL−1). The analytical response in contaminated water and in presence of other nitroaromatic compounds, such as 2,4-dinitrotoluene (DNT) and picric acid (PA), has been evaluated.

The increasing use of engineered nanoparticles (NPs) in a wide range of commercial products raises concern about the possible risks that NPs pose to human health. Many aspects of the interaction between living cells and NPs are still unclear, and a reliable assessment of NP genotoxicity would be important. One of the most common tests used for genotoxicity is the comet assay, a sensitive method measuring DNA damage in individual cells. The assay was originally developed for soluble molecules, but it is also used in the assessment of genotoxicity of NPs. However, concerns have been raised recently about the reliability of this test in the case of NPs, but no conclusive results have been presented. Using nuclei isolated from human epithelial cells incubated with NPs, we obtained clear evidence of overestimation of NP genotoxicity by the comet assay in the case of CeO2, TiO2, SiO2, and polystyrene NPs. Removal of the NPs in the cytoplasm was effective in eliminating this genotoxicity overestimation (ex post damage) and determining the actual damage produced by the NPs during incubation with the cells (ex ante damage). This method could improve significantly the determination of NP genotoxicity in eukaryotic cells.

ZnO is one of the materials of choice as anode for lithium batteries, due to its high theoretical capacity, natural abundance, low toxicity, and low cost. At present, however, its industrial exploitation is impeded by massive capacity fading, and by cycling instability due to the drastic volume expansions during the electrochemical lithiation/delithiation process. Herein, we present a novel graphite coated-ZnO anode for LiBs based on films of nanosheets, coated with graphite. The electrode is obtained by a simple and inexpensive solution hydrothermal synthesis, whereas the graphite is deposited by thermal evaporation, which is easier to perform than a wet chemistry technique. Our approach leads to a substantial increase of the permanent specific capacity, obtaining values of 600 mAhg-1 after 100 cycles at a high specific current of 1 Ag-1. This represents the best performance for long-cycled, ZnO-based anodes obtained so far. Such result derives from the peculiar porous structure of the nanosheets film (pore diameter < 1 nm), as well as by the graphite coating that works as a dimensional buffer and preserves its morphology during cycling. This appears a very promising strategy for designing more stable ZnO-based anodes for Li batteries and microbatteries.

Diethylzinc mediates the asymmetric allylation of aldehydes through Umpolung of a π-allyl palladium complex. An investigation of the palladium source and the chiral monophosphane ligands have shown that the leaving group has a dramatic effect on the enantioselectivity of the reaction. The procedure furnished products in satisfactory yields and up to 70% ee .

Undoped and heavily doped (K, Y, Zr, Mo) strontium barium niobate Sr0.5Ba0.5Nb2O6 (SBN50) materials have been prepared by co-precipitation. X-ray diffraction shows the formation of a single-phase product and that 10% and 12.5% of the Nb sites can be occupied by Zr and Mo, respectively. K can enter 40% of the Sr sites, while the maximum Y substitution is also around 40%. The starting stoichiometry is effective in driving the substitutions to the desired sites. X-ray Absorption Spectroscopy (XAS) at the Nb-K edge shows the presence of Nb(V) independent of doping. A pre-edge 1s-4d transition surprisingly indicates the hole injection with Y doping and the electron injection with Zr doping. Chemical reduction does not affect the stability of the structure, except for a small decrease of maximum Y solubility, while the Nb(V) oxidation state and the XAS pre-edge feature are unmodified. The oxidized samples are insulators, the reduced samples show electrical conductivity, and doping significantly enhances thermop...

In the present study, we investigated the peripheral nervous system (PNS) (both in terms of its ultrastructure and in terms of its function) of rats made cobalamin (Cbl)-deficient either through total gastrectomy or through prolonged feeding on a Cbl-deficient diet. In both these types of Cbl-deficient neuropathies we found: (a) ultrastructurally, intramyelin and endoneural edema, with no or minimal axonal damage in the PNS, in dorsal root ganglia, and the ventral and dorsal rootlets of the spinal cord; (b) electrophysiologically, a significant reduction in the nerve conduction velocity, consistent with that reported in (a); (c) morphometrically, a significant reduction in the density of myelinated fibers both in the sciatic nerve and in the peroneal nerve. All these pathological changes were reversed by chronic postoperative administration of Cbl into totally gastrectomized (TGX)-rats, hinting at the specificity of the damage itself in relation to the permanent Cbl-deficient status of the TGX-rats. No signs of segmental demyelination or remyelination were found. We also observed a turning of type I fibers into type II fibers in the soleus muscle of all our Cbl-deficient rats, however the Cbl deficiency had been induced. This muscular change was still present in TGX- and Cbl-treated rats, and it cannot be related to a malnutrition status, since it has been observed also in rats fed a Cbl-deficient diet. All these results demonstrate that Cbl deficiency strongly affects rat PNS within different parameters.

Uncovering the mechanism of low-temperature protonic conduction in highly dense nanostructured metal oxides opens the possibility to exploit the application of simple ceramic electrolytes in proton exchange fuel cells, overcoming the drawbacks related to the use of polymeric membranes. High proton conducting, highly dense (relative density 94 vol%) TiO2 samples are prepared by a fast pressure-assisted sintering method, which allows leaving behind an interconnected network of open nanoporosity. Solid-state 1H NMR is used to characterize the presence of strongly associated water confined in the nanopores and hydroxyl moieties bonded to the pores walls, providing a model to explain the unusually high protonic conductivity. At the lowest temperatures (T < 55 °C) protons hop between confined water molecules, according to a Grotthuss mechanism. The resulting conductivity values are however much higher than those of liquid water, indicating a significant increase in the charge carriers concentration. At higher temperatures (up to 450 °C) unexpected proton conduction is still present, thanks to the persistence of hydroxyl groups, derived from water chemisorption, which still produce protons by ionization. The phenomenon is strongly dependent on grain size, and not explicable by simple geometric brick-layer models, suggesting that the enhanced ionization could rely on space charge region effects

Field assisted sintering studies have produced a wealth of data about the densification behaviors of many powder systems. However, the sheer volume of work has not met with sufficient mechanistic descriptions of the processes in metal or ceramic systems. This fact has, and is, limiting the acceptance and widespread use of this promising technique in larger than laboratory scale manufacturing. We describe here the nature of the influences of electric fields and/or currents, changes in heating rate, and the effects of applied pressures upon ceramic and metal systems in context of the commonly accepted stages of sintering. As many of the specific mechanisms discussed have not been directly characterized within field assisted sintering studies we focus on the established theoretical underpinnings to better understand their influence and to enable definitive future experimentation on this area of research.

International audience; Zirconia nanopowder with doping YO contents between 0 and 1% mol. were synthesized by the Pechini method. The crystallite dimensions of the powder, around 10nm, allows for the size stabilization of the tetragonal polymorph over the thermodynamically stable monoclinic one. As the nanopowders are heated to 1200°C and subsequently cooled back to room temperature, a complex evolution of the phase composition occurs. Upon heating the tetragonal phase transforms slowly into the monoclinic one and the transition cannot be completed before entering the stability range of the tetragonal phase (above 1150°C). Upon cooling, on the other hand, the reaction is considerably faster and the complete transformation into the monoclinc phase occurs in a narrow temperature range. Rietveld analysis of the high temperature x-ray patterns revealed as, during heating, the transition is manly controlled by microstructural parameters and in particular it is triggered by the release of RMS microstrain. Upon cooling, on the other hand, the transition is kinetically controlled by the doping content.

Zirconia-based materials, with very low or null doping contents (YO1.5 between 0% and 4% mol), were prepared in the form of bulk nanostructured materials through a two-step process. Nanometric powders of size-stabilized tetragonal zirconia were synthesized by the Pechini method and subsequently densified using the high-pressure field-assisted rapid sintering method at temperatures around 850°–900°C for 5 min under a pressure of ∼800 MPa. By this method, theoretical densities of ∼98% were achieved while retaining the grain size in the final product between 40 and 50 nm. The transition to the thermodynamically stable monoclinic phase was consequently prevented, allowing for the first time the synthesis of size-stabilized zirconia in a high-density bulk form.

The preparation and application of a humic acids modified gold electrode (HA-CME) have been described. Derivatization of HAs as β-thioesters caused their partial fragmentation and, thus, a consequent separation by size exclusion chromatography (SEC) was necessary. The CME prepared with functionalized HAs having an average MW of 52000 demonstrated to be effective for trace As(III) determination (LOQ = 0.3 μg L −1 ). This CME has been characterized both by electrochemical techniques and atomic force microscopy (AFM). The HA-CME provided reliable measurements in natural waters at different salinity with no need of desalting the sample. Total inorganic arsenic could be determined after reduction of As(V) with SO 2 . Under these conditions, organic arsenic species were not mineralized and did not interfere.

Alcohol is noxious to the brain and peripheral nervous system. However, wine contains substances that may have positive biological and pharmacological effects. Resveratrol is the most studied and probably the most active of these substances. This naturally occurring compound, which is present in wine and grapes, reduces oxidative stress in neuronal-like cell cultures. We have shown that resveratrol induces phosphorylation of the mitogen-activated protein (MAP) kinase family members, extracellular regulated kinase 1 (ERK1) and ERK2, in the human neuroblastoma SH-SY5Y cells in vitro at much lower concentrations than those found in the plasma of rats after oral wine administration. MAP kinases are involved in numerous different aspects of signal transduction in the cells. In particular, phosphorylation of ERK2 has been related to the synaptic changes at the basis of memory and learning processes. These findings, together with our own, on resveratrol-induced activation of MAP kinases in human neuronal-like cells, and previously published epidemiological studies which have demonstrated an inverse relationship between moderate wine intake and dementia, suggest that wine (not alcohol) may have a positive effect on nervous cells.

To evaluate whether retinoic acid (RA) differentiated human neuroblastoma (HN) SH-SY5Y cells are a suitable and reliable model to test the neurotoxicity of chemotherapic drugs without the confusing effects of the neurotrophic factors commonly used to induce neuronal differentiation.Cultures of the SH-SY5Y cell line were exposed to RA to induce neuronal differentiation which was assessed by measuring the neurite length. The effect of increasing concentrations of cisplatin (CDDP) on neurite outgrowth was determined. Cyclophosphamide (CTX) was used as negative control.CDDP induced a significant reduction in the mean neurite length in a dose dependent manner. The neurotoxic effect of CDDP was reversible. Cyclophosphamide did not induce changes in RA differentiated HN cells.RA differentiated HN cells are sensitive to the neurotoxic effect of CDDP and the course of the changes is similar to that observed in clinical practice and in in vivo experimental models. Therefore, this model is proposed as a screening method to test the neurotoxicity of chemotherapy drugs and the possible effect of neuroprotectant molecules and drugs.

Peripheral nervous system alterations were induced in adult rats by administration of cisplatin (CDDP) 2 mg/kg twice weekly for 4.5 weeks. Dorsal root ganglion neurons showed pathological changes. Morphometric determinations demonstrated a reduction in size of the somatic, nuclear and nucleolar area. The nucleoli were the most involved subcellular structures. Nerve conduction velocity and the tail-flick test for pain were both significantly altered in CDDP treated rats, whereas the rota-rod test for coordination revealed no changes in either treated or control rats. Analytical determinations demonstrated platinum accumulation in the DRG of CDDP treated rats. Spontaneous recovery, demonstrated by morphometric, electrophysiological, functional and analytical determinations, occurred after treatment discontinuation within about 7 weeks. A pilot study of the possible neuroprotective action of retinoic acid (RA) was also performed with this model of cisplatin neuronopathy. The rationale for using RA was based on its assumed antioxidant and neurotrophic effect. However, RA failed to prevent morphometric, electrophysiological, functional and analytical alterations induced by CDDP on DRG neurons. RA induced only a mild generalized protective effect.