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The Horizon 2020 project PECSYS aims to build a large area demonstrator for hydrogen production from solar energy via integrated photovoltaic (PV) and electrolysis systems of different types. In this study, Si- and CIGS-based photovoltaics are developed together with three different electrolyzer systems for use in the corresponding integrated devices. The systems are experimentally evaluated and a general model is developed to investigate the hydrogen yield under real climatic conditions for various thin film and silicon PV technologies and electrolyser combinations. PV characteristics using a Si heterojunction (SHJ), thin film CuInxGa1-xSe2, crystalline Si with passivated emitter rear totally diffused and thin film Si are used together with temperature dependent catalyst load curves from both acidic and alkaline approaches. Electrolysis data were collected from (i) a Pt-IrO2-based acidic electrolysis system, and (ii) NiMoW-NiO-based and (iii) Pt-Ni foam-based alkaline electrolysis systems. The calculations were performed for mid-European climate data from Julich, Germany, which will be the installation site. The best systems show an electricity-to-hydrogen conversion efficiency of 74% and over 12% solar-to-hydrogen (STH) efficiencies using both acidic and alkaline approaches and are validated with a smaller lab scale prototype. The results show that the lower power delivered by all the PV technologies under low irradiation is balanced by the lower demand for overpotentials for all the electrolysis approaches at these currents, with more or less retained STH efficiency over the full year if the catalyst area is the same as the PV area for the alkaline approach. The total yield of hydrogen, however, follows the irradiance, where a yearly hydrogen production of over 35 kg can be achieved for a 10 m(2) integrated PV-electrolysis system for several of the PV and electrolyser combinations that also allow a significant (100-fold) reduction in necessary electrolyser area for the acidic approach. Measuring the catalyst systems under intermittent and ramping conditions with different temperatures, a 5% lowering of the yearly hydrogen yield is extracted for some of the catalyst systems while the Pt-Ni foam-based alkaline system showed unaffected or even slightly increased yearly yield under the same conditions.

Oxygen evolution reaction (OER) is a demanding step within the water splitting process for its requirement of a high overpotential. Thus, to overcome this unfavourable kinetics, an efficient catalyst is required to expedite the process. In this context, we report on Ni foam functionalised with low cost iron (Fe) and iron hydroxide (Fe(OH)X), wet chemically synthesized as OER catalysts. The prepared catalyst based on iron hydroxide precipitate shows a promising performance, exhibiting an overpotential of 270 mV (at a current density of 10 mA cm−2 in 1 M KOH solution), an efficient Tafel slope of ∼50 mV dec−1 and stable chronopotentiometry. The promising performance of the anode was further reproduced in the overall water splitting reaction with a two electrode cell. The overall reaction requires a lower potential of 1.508 V to afford 10 mA cm−2, corresponding to 81.5% electrical to fuel efficiency.

The stochastic uncertainties affecting the models used to describe the behavior of structural/mechanical systems may give rise to unfavorable scenarios leading to failures. In this framework, the quantification of the failure probability is a recognized fundamental task for structural safety and reliability analyses. Unfortunately, the estimation of the failure probability of structural/mechanical systems is a computationally demanding task, especially when the failure is a rare event and the computer codes used to model the system response require large computational efforts. One major issue further complicates the estimation process, i.e., the parameters of the probability distributions of the random variables used to describe the uncertainties involved can, in turn, be imprecise, since they are typically estimated by means of statistical inference based on observations and engineering judgment. In this context, reliability sensitivity analysis aims at estimating the influence of this additional source of uncertainty on the system failure probability in order to assess the robustness of the system to the modeling of uncertainties. Intuitively, reliability sensitivity analyses may easily become prohibitive by standard sampling-based methods (e.g., Monte Carlo method), since a nested, second level of uncertainties is involved. To overcome this issue, in this work we embed the efficient AK-IS algorithm for estimating small failure probabilities within an original computational framework that allows to perform a Sobol-based, global sensitivity analysis of the failure probability at an affordable number of computer model evaluations. The algorithm is demonstrated with reference to two case studies of literature of structural/mechanical reliability, often used in the literature as benchmark tests.

Wear out in the maximum power point condition of tandem microcrystalline Si/amorphous Si thin film PV modules due to extended light soaking is a well-known effect due to the Staebler–Wronski mechanism [ 1 ]. However, several studies [ [2] , [3] , [4] , [5] , [6] , [7] , [8] ] on a-Si:H single junction and tandem solar cells, have shown that, under suitable conditions of electric field in reverse bias, illumination, especially at well-defined wavelengths (700–800 nm), and temperature conditions, an improvement of the cell main electric parameters is possible. In this work, we report on new stress tests performed on tandem amorphous Silicon PV devices (both non-stabilized and stabilized), highlighting the improvement of their electrical performances, founded both in the tests performed on non-stabilized samples (essentially due to the reverse bias stresses carried out in these tests) and in the outdoor tests on stabilized samples (not subjected to reverse bias stresses) going from morning to afternoon illumination. In the latter tests, the efficiency improvement observed in the afternoon is stable overnight and observed also in the early stages of the morning outdoor test in the following day. Possible causes of such effect are discussed.

One of the most important aspects in controlling colloidal deposition is manipulating the homogeneity of the deposit by avoiding the coffee-ring effect caused by capillary flow inside the droplet during drying. After our previous work where we achieved homogeneous deposition of cellulose nanocrystals (CNCs) from a colloidal suspension by reinforcing Marangoni flow over the internal capillary flow (Gençer et al. Langmuir 2017, 33 (1), 228-234), we now set out to reduce the importance of capillary flow inside a drying droplet by inducing gelation. In this paper, we discuss the effect of gelation on the deposition pattern and on the self-assembly of CNCs during droplet drying. CNC films were obtained by drop casting CNC suspensions containing NaCl and CaCl2 salts. A mixed methodology using rheological and depolarized dynamic light scattering was applied to understand the colloidal behavior of the CNCs. In addition, analysis of the mixture's surface tension, viscosity, and yield stress of the suspensions were used to gain deeper insights into the deposition process. Finally, the understanding of the gelation behavior in the drying droplet was used to exert control over the deposit where the coffee-ring deposit can be converted to a dome-shaped deposit. ispartof: Biomacromolecules vol:19 issue:8 pages:3233-3243 ispartof: location:United States status: published

In this paper, we report on the performances of silicon photomultipliers (SiPMs) with commercial long-pass interferential and plastic filters integrated on the detector's package for environmental light rejection. Several applications, including functional near infrared (NIR) spectroscopy or light detection and ranging, would benefit from the use of highly sensitive detectors like SiPMs with optimized electro-optical characteristics in NIR wavelength range. To this purpose, it is fundamental to reduce the absorption of environmental spurious light leading in application to a decrease of the detector's sensitivity, especially for very weak photon fluxes. We will show how the use of both types of filters has a relevant impact on the electro-optical performances of the bare detectors, in terms of cross talk reduction at high overvoltage values, detection efficiency, spectral response and capability to shield effectively the devices from the absorption of stray light, at the different light wavelengths used for the measurements.

Cellulose nanofibers (CNFs) have interesting physicochemical and colloidal properties that have been recently exploited in novel drug-delivery systems for tailored release of poorly soluble drugs. The morphology and release kinetics of such drug-delivery systems heavily relied on the drug-CNF interactions; however, in-depth understanding of the interactions was lacking. Herein, the interactions between a poorly soluble model drug molecule, furosemide, and cationic cellulose nanofibers with two different degrees of substitution are studied by sorption experiments, Fourier transform infrared spectroscopy, and molecular dynamics (MD) simulation. Both MD simulations and experimental results confirmed the spontaneous sorption of drug onto CNF. Simulations further showed that adsorption occurred by the flat aryl ring of furosemide. The spontaneous sorption was commensurate with large entropy gains as a result of release of surface-bound water. Association between furosemide molecules furthermore enabled surface precipitation as indicated by both simulations and experiments. Finally, sorption was also found not to be driven by charge neutralization, between positive CNF surface charges and the furosemide negative charge, so that surface area is the single most important parameter determining the amount of sorbed drug. An optimized CNF-furosemide drug-delivery vehicle thus needs to have a maximized specific surface area irrespective of the surface charge with which it is achieved. The findings also provide important insights into the design principles of CNF-based filters suitable for removal of poorly soluble drugs from wastewater. ispartof: LANGMUIR vol:34 issue:19 pages:5464-5473 ispartof: location:United States status: published

Photoelectrochemical water splitting is a promising method to produce H 2 by making use of solar energy. In this paper we report on a photocathode made by p-type crystalline Si covered with an n-type 3C-SiC polycrystalline film, acting as protective layer and transparent emitter. The photoelectrodes exhibit a saturated photocurrent above 30 mA cm −2 . No decay is observed after 9 h under constant current stress at 1 kW m −2 with AM1.5G spectrum illumination. Improvement of the photocurrent value is achieved by covering the 3C-SiC emitter with Au or Pt nanoparticles. Under suitable metal nanoparticles deposition conditions, compared to the samples without nanoparticles, two major effects are observed: first the onset potential is considerably reduced, and second, higher saturated photocurrent is found, up to 38 mA cm −2 , i.e. with a 27% increase. Optical and micro-structural studies on the nanoparticles provide insights on the origin of the observed effects.

The interaction of bovine serum albumin (BSA) with sulfated, carboxylated, and pyridinium-grafted cellulose nanocrystals (CNCs) was studied as a function of the degree of substitution by determining the adsorption isotherm and by directly measuring the thermodynamics of interaction. The adsorption of BSA onto positively charged pyridinium-grafted cellulose nanocrystals followed Langmuirian adsorption with the maximum amount of adsorbed protein increasing linearly with increasing degree of substitution. The binding mechanism between the positively charged pyridinum-grafted cellulose nanocrystals and BSA was found to be endothermic and based on charge neutralization. A positive entropy of adsorption associated with an increase of the degree of disorder upon addition of BSA compensated for the unfavorable endothermic enthalpy and enabled formation of pyridinium-g-CNC-BSA complexes. The endothermic enthalpy of adsorption was further found to decrease as a function of increasing degree of substitution. Negatively charged cellulose nanocrystals bearing sulfate and/or carboxylic functionalities were found to not interact significantly with the BSA protein. To investigate in more detail the role of single amino acids in the adsorption of proteins onto cellulose nanocrystals, we also studied the interaction of different types of amino acids with CNCs, i.e., charged (lysine, aspartic acid), aromatic (tryptophan, tyrosine), and polar (serine) amino acids. We found that none of the single amino acids bound with CNCs irrespective of surface charge and that therefore the binding of proteins with CNCs appears to require larger amino acid sequences that induce a greater entropic contribution to stabilize binding. Single amino acids are thus not adsorbed onto cellulose nanocrystals. ispartof: Langmuir vol:33 issue:22 pages:5473-5481 ispartof: location:United States status: published

3C-SiC layers (7 and 15 μm thick), epitaxially grown on silicon, were covered with gold nanoparticles by immersion in a solution containing HF and KAuCl4. The surface of the layers played a crucial role in the morphology of the deposited metal network and large gold agglomerates developed on the pronounced antiphase domain boundaries of the thinner layer. Preferential growth was not observed on the smooth surface of the 15 μm thick layer. Rutherford backscattering spectrometry and electron microscopy outlined a progressive nucleation that takes place for less than 60 s immersion times under a kinetic control process. For longer deposition time each cluster grows under a diffusion control process, resulting in flower-like gold particles. However, the nucleation and growth processes can be strongly modified by multiple immersions in solution after rinsing in water. The adopted procedure allows the tailoring of the particles size and avoids the aggregation, therefore improving by about 1 order of magnitude t...

The Staebler-Wronski effect in amorphous silicon based photovoltaic devices is responsible for degradation of their power conversion efficiency, within approximately the first one thousand hours of light soaking. Several experimental studies led to highlight the performance instability phenomena for the mentioned devices, underling that recovery and improvement of such performance are observable, by subjecting such devices (both of single-junction and tandem types) to DC reverse bias stresses under illumination, or to operation in the Maximum Power Point (MPP) under variable conditions of temperature and illumination. In this work, we present and discuss the results of novel recent outdoor tests on stabilized specimens (i.e., exposed to 1000 h extended light soaking, before our tests) of tandem amorphous/microcrystalline Si (a-Si/&micro, c-Si) photovoltaic (PV) minimodules operating in their MPP, by analyzing the causes of the performance instability effects, systematically observed on a daily scale. During the mentioned tests, we have monitored the solar cell operating temperature and the incident solar spectrum at various times in different days to verify the effect of cell temperature and solar spectrum changes on the cell performances. The experimental results show a clear correlation between performance improvements of the photovoltaic modules and their thermal history during the outdoor tests, proving the interplay between defect build-up at a lower temperature and defect annealing at a higher temperature, taking place in the solar cells operated in MPP during conventional outdoor operation.

Increasing attention is now paid to bifacial PV devices since these, compared to monofacial modules, allow increased electricity production thanks to their additional radiation collection from the back side. Since accurate performance predictions are of crucial importance for PV devices to maximize the electricity production, several efforts have been made for bifacial PV modeling and related optimization [1]–[6]. In this work, we present a new analytical model, usable to any geographical position, for the performance prediction of bifacial PV modules. We compare the model predictions to experiments in which module height, ground albedo, and tilt are varied and we observe good agreement.

Aim of AMPERE is the setting-up of an European sustainable manufacturing full-scale automated industrial pilot line, to produce bifacial heterojunction technology (HJT) silicon solar cells and modules. In this work we illustrate the state of art of AMPERE project, started in May 2017, focusing on its technical results, industrial and economic sustainability and perspectives on LCOE in the frame of vertical integration along with EGP as its natural end-user. These expected outcomes will be assessed and evaluated as a solid backbone to pave the way to the GW factory scaling up. The decision to accelerate in the project timeframe, within 2019, the installation and start-up of a manufacturing line, leading to a nominal capacity of EGP Catania 3SUN site to 200 MWp, will support the demonstration of the viability of HJT solar module massive production in Europe.

Thin dielectric films are essential components of most micro- and nanoelectronic devices, and they have played a key role in the huge development that the semiconductor industry has experienced during the last 50 years. Guaranteeing the reliability of thin dielectric films has become more challenging, in light of strong demand from the market for improved performance in electronic devices. The degradation and breakdown of thin dielectrics under normal device operation has an enormous technological importance and thus it is widely investigated in traditional dielectrics (e.g., SiO2, HfO2, and Al2O3), and it should be further investigated in novel dielectric materials that might be used in future devices (e.g., layered dielectrics). Understanding not only the physical phenomena behind dielectric breakdown but also its statistics is crucial to ensure the reliability of modern and future electronic devices, and it can also be cleverly used for other applications, such as the fabrication of new-concept resistive switching devices (e.g., nonvolatile memories and electronic synapses). Here, the fundamentals of the dielectric breakdown phenomenon in traditional and future thin dielectrics are revised. The physical phenomena that trigger the onset, structural damage, breakdown statistics, device reliability, technological implications, and perspectives are described. Fil: Palumbo, Félix Roberto Mario. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Tecnológica Nacional. Facultad Regional Buenos Aires. Unidad de Investigación y Desarrollo de las Ingenierías; Argentina Fil: Wen, Chao. Soochow University; China Fil: Lombardo, Salvatore. Consiglio Nazionale delle Ricerche; Italia Fil: Pazos, Sebastián Matías. Universidad Tecnológica Nacional. Facultad Regional Buenos Aires. Unidad de Investigación y Desarrollo de las Ingenierías; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Aguirre, Fernando Leonel. Universidad Tecnológica Nacional. Facultad Regional Buenos Aires. Unidad de Investigación y Desarrollo de las Ingenierías; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Eizenberg, Moshe. Technion - Israel Institute of Technology; Israel Fil: Hui, Fei. Soochow University; China. Technion - Israel Institute of Technology; Israel Fil: Lanza, Mario. Soochow University; China

Background Brodie’s abscess is a form of chronic pyogenic osteomyelitis that usually affects the cancellous part of the long bones in children. Its treatment is represented by antibiotic therapy alone or in association with surgical procedures. Case presentation A 12-years-old male affected by a Brodie’s abscess of the tibia involving the distal growth plate was admitted to the Pediatric Department for a conservative treatment. After several attempts of antibiotic therapy interrupted for intolerance manifestations he was surgically treated with bioactive glass BAG-S53P4 (BonAlive, BonAlive Biomaterials Ltd., Biolinja, Finland), with excellent results. Conclusions In our experience BAG-S53P4 has proven to be an effective bone substitute without side effects even in the pediatric population. In our case it eradicated the infection without interfere with the growth; neither epiphysiodesis nor other disorders were found during the follow-up. For the publication of this case report we followed the CARE guidelines for good clinical case reports; the parents gave consent for publication.

In this paper, we use dynamic light scattering in polarized and depolarized mode to determine the translational and rotational diffusion coefficients of concentrated rod-like cellulose nanocrystals in aqueous suspension. Within the range of studied concentrations (1 – 5 wt%), the suspension starts a phase transition from an isotropic to an anisotropic state as shown by microscopy and viscosity measurements. SANS measurements also confirmed the start of cellulose nanocrystal alignment and a decreasing distance between the cellulose nanocrystals with increasing concentration. As expected, rotational and translational diffusion coefficients generally decreased with increasing concentration. However, the translational parallel diffusion coefficient was found to show a local maximum at the onset of the isotropic-to-nematic phase transition. This is attributed to the increased available space for rods to move along their longitudinal axis upon alignment. This increased parallel diffusion coefficient thus confirms the general idea that rodlike particles gain translational entropy upon alignment while paying the price for losing rotational degrees of freedom. Once the concentration increases further, diffusion becomes more hindered even in the aligned regions due to a reduction in the rod separation distance. This leads to once again decreasing translational diffusion coefficients. Furthermore, the relaxation rate for fast mode translational diffusion (parallel to the long particle axis) exhibited two regimes of relaxation behavior at concentrations where significant alignment of the rods is measured. We attribute this unusual dispersive behavior to two length scales: one linked to the particle length (at large wavevector q), and the other to a twist fluctuation correlation length (at low wavevector q) along the CNC rods that is of a larger length when compared to the actual length of rods and could be linked to the size of aligned domains. ispartof: LANGMUIR vol:35 issue:6 pages:2289-2302 ispartof: location:United States status: published

Platinum thin films are deposited on open-cell nickel foam with porosity of 95% via spontaneous galvanic displacement. Ni foams with different morphologies and pore size are compared and characterized by electrochemical and structural analysis techniques. The effect of Pt coating on the electrochemical activity is studied by using the Pt coated foam as electrode material for hydrogen evolution reaction in an aqueous alkaline electrolyte. The electrocatalytic activity of the electrodes is evaluated using linear sweep voltammetry curves and Tafel plots as a function of deposition time. The comparison with scanning electron microscopy analyses demonstrates that the catalytic activity has a maximum when the platinum film completely covers the Ni surface. The further increase of the Pt thickness leads to mechanical instability with crack formation and delamination. The effect of the foam morphology on the Pt deposition rate has been evaluated and discussed, determining the minimum Pt amount required to achieve the maximum electrochemical activity, as well as the maximum thickness in order to assure stable characteristics before delamination occurs.

Avascular necrosis (AVN) is a disease due to the interruption of the blood supply to the bone. It is one of the most common and debilitating therapy-related sequelae of the antileukemic treatment and it may not be clinically recognized. Symptomatic AVN have been reported in 1-17% of children with acute lymphoblastic leukemia (ALL) during treatment or thereafter although an incidence of up to 72% of asymptomatic AVN has been detected with systematic screening by magnetic resonance imaging (MRI). In all cases AVN is related to ALL treatment and in particular to high-dose steroids. While the AVN of the hip is frequently reported in the literature, reports regarding AVN of the talus are lacking; moreover, there is little consensus about its incidence, diagnostic algorithm and treatment. Talus is an articular weight-bearing bone with over 60% of the surface covered by cartilage and a specific limited vascular supply. The aim of this article is to provide an up-to-date review about management of avascular necrosis of the talus highlighting the importance of early diagnosis based on ankle MRI imaging in pediatric patients affected with ALL.

The aim of this work is to evaluate the possible use of Nexar&trade, polymer, a sulfonated pentablock copolymer (s-PBC), whose structure is formed by tert-butyl styrene, hydrogenated isoprene, sulfonated styrene, hydrogenated isoprene, and tert-butyl styrene (tBS-HI-SS-HI-tBS), as a more economical and efficient alternative to Nafion&reg, membrane for proton exchange membrane (PEM) electrolysis cells. Furthermore, we have studied a new methodology for modification of gas diffusion layers (GDL) by depositing Pt and TiO2 nanoparticles at the cathode and anode side, respectively, and a protective polymeric layer on their surface, allowing the improvement of the contact with the membrane. Morphological, structural, and electrical characterization were performed on the Nexar&trade, membrane and on the modified GDLs. The use of modified GDLs positively affects the efficiency of the water electrolysis process. Furthermore, Nexar&trade, showed higher water uptake and conductivity with respect to Nafion&reg, resulting in an increased amount of current generated during water electrolysis. In conclusion, we show that Nexar&trade, is an efficient and cheaper alternative to Nafion&reg, as the proton exchange membrane in water splitting applications and we suggest a possible methodology for improving GDLs&rsquo, properties. These results meet the urgent need for low-cost materials and processes for hydrogen production.

The demonstration of large operative safety margins is the fundamental requirement for the transition of new generation nuclear reactors from the early concept phase to the initial industrial design one. In order to do so, it is necessary to perform a thorough characterization of the uncertainties affecting the models used for describing the physical behavior of the reactors and to quantify their impact on the safety performances of the plant, typically in terms of the probability of occurrence of deviations from the nominal, or design, operative conditions, often referred to as failure probabilities (reliability analysis). Conceptually, this problem can be solved by framing the problem within a stochastic setting and propagating the uncertainties, represented by suitable probability distributions, by resorting to sampling-based, Monte Carlo (MC) schemes. However, the high reliability of these plants and the complexity of the computer codes used to model their behavior are such that standard MC approaches would require prohibitive computational times. Further computational issues then arise due to the fact that the stochastic models adopted, i.e., the probability distributions, are, in turn, affected by uncertainties, typically related to the inference process adopted to estimate their relevant parameters, so that the estimates of the failure probabilities also become uncertain, with potentially significant impacts on any safety-based decision making process. In this context, the objective of this work is that of providing an innovative computational tool for efficiently performing Sobol-based global reliability sensitivity analysis that allows to satisfactorily quantify the impact of these additional uncertainties on the safety performances of innovative nuclear reactors concepts. The method exploits an original adaptive surrogate modeling with MC variance based techniques, in order to reduce the computational efforts while maintaining sufficient degrees of accuracy. The resulting algorithm is demonstrated with reference to a real innovative nuclear reactor concept, i.e., the Lead Bismuth Eutectic eXperimental Accelerator Driven System (LBE-XADS) reactor. The results of the analysis show the potentiality of the method, offering important insights on the robustness of the concept reactor safety design and suggesting possible paths of improvement, at acceptable computational times.

Platinum nanostructures are of large interest because of their electrocatalytic properties, enhanced by the high surface/volume ratio, and find applications in numerous fields from fuel cells and electrolyzers, to gas biosensors and nano-biomedicine. In this work we present a simple procedure, based on spontaneous galvanic displacement, to obtain Pt nanoparticles (PtNPs) directly on Si substrate. The nucleation and growth processes involved in the deposition have been studied by Transmission Electron Microscopy and Rutherford Backscattering Spectrometry. The nucleation is quite complex and includes, first, the generation of primary non-growing clusters, with size smaller than 2 nm. Then, for longer deposition times, larger particles are formed, resulting from dynamic coalescence of primary clusters with/or single ion attachment processes. The growth of such larger particles follows the prediction of the classical diffusion limited model. Moreover, the large nanoparticles are poly-crystalline and exhibit a nano-porous structure, in agreement with a mixed aggregative-diffusion limited growth. The nano-porous structure implies a high internal surface area, therefore making these particles particularly promising as efficient catalysts.

We built a fiber-less prototype of an optical system with 156 channels each one consisting of an optode made of a silicon photomultiplier (SiPM) and a pair of light emitting diodes (LEDs) operating at 700 nm and 830 nm. The system uses functional near-infrared spectroscopy (fNIRS) and diffuse optical tomography (DOT) imaging of the cortical activity of the human brain at frequencies above 1 Hz. In this paper, we discuss testing and system optimization performed through measurements on a multi-layered optical phantom with mechanically movable parts that simulate near-infrared light scattering inhomogeneities. The baseline optical characteristics of the phantom are carefully characterized and compared to those of human tissues. Here we discuss several technical aspects of the system development, such as LED light output drift and its possible compensation, SiPM linearity, corrections of channel signal differences, and signal-to-noise ratio (SNR). We implement an imaging algorithm that investigates large phantom regions. Thanks to the use of SiPMs, very large source-to-detector distances are acquired with a high SNR and 2 Hz time resolution. The overall results demonstrate the high potentialities of a system based on SiPMs for fNIRS/DOT human brain imaging applications.

This work explored the influence of the citrus pectin degree and pattern of methylesterification on its interaction with Zn2+ using isothermal titration calorimetry (ITC). Pectin samples with a comparable degree of methylesterification (DM) but distinct distribution patterns of non-methylesterified carboxylic groups (absolute degree of blockiness, DBabs) were produced through enzymatic (blockwise pattern) or alkaline (random pattern) demethylesterification. The pectin-Zn2+ interaction was found to be endothermic, in which a positive entropy change compensated for the unfavorable endothermic enthalpy change, driving the interaction between pectin and Zn2+. Decreasing pectin DM or increasing DBabs promoted Zn2+ binding, with the estimated binding capacity (mol Zn2+/mol GalA) and binding constant (mM−1) being mainly determined by pectin DBabs, rather than DM. ITC was found to be a useful technique to study the pectin-cation interaction, however, low DM pectin samples are sensitive to gelling and therefore more difficult to study. ispartof: CARBOHYDRATE POLYMERS vol:197 pages:460-468 ispartof: location:England status: Published online

Negatively charged ions readily interact with the surface of positively charged pyridinium-grafted cellulose nanocrystals. In this work we investigated the thermodynamics of these interactions using isothermal titration calorimetry. We investigated the effect of the ionic charge, using carboxylate salts with different valence (1-4), and compared it with sodium sulfate as another delocalized ionic charge. Experiments performed using cellulose nanocrystals with three different degrees of substitution of pyridinium grafts showed that the number of ions adsorbed onto the surface of cellulose nanocrystals is directly linked to the number of grafted cationic functionalities. The adsorption of anions onto pyridinium-grafted nanocrystals was further found to be endothermic and driven by an increase in entropy upon adsorption of the anions due to the release of surface bound water. The association constant increased with the net charge of the anions from a low value for monovalent sodium acetate. Both entropy and enthalpy increased linearly with the net charge of the anions, demonstrating that a stronger depolarization occurred when anions of higher net charge were adsorbed. The values of the stoichiometric number determined were lower than the values relative to processes involving ions in solution, suggesting a more complex mode of interaction, involving hydrogen-bonding and bridge formation. However, the number of adsorbed ions was directly correlated with the amount of cationic surface grafts. This makes it possible to control the amount of surface interactions directly with the degree of substitution on the nanocrystal surfaces. Comparison with zeta potential measurements showed that zeta-potential measurements can be used as a direct method to determine the stoichiometry of binding between the positive surface grafts and the carboxylate salts. ispartof: PHYSICAL CHEMISTRY CHEMICAL PHYSICS vol:20 issue:26 pages:17637-17647 ispartof: location:England status: published

We have realized tandem amorphous Si / microcrystalline Si PV cells and modules with an n+ SiOx emitter heterojunction with microcrystalline Si. The SiOx films show filamentary nanostructures and high electrical conductivity. Excellent photovoltaic characteristics are demonstrated.

In this work, we investigate some major issues for the use of silicon photomultiplier (SiPM) devices in continuous wave functional near-infrared spectroscopy (CW fNIRS). We analyzed the after-pulsing effect, proposing the physical mechanism causing it, and determining its relevance for CW fNIRS. We studied the SiPM transients occurring as the SiPM device goes from the dark (LED in off state) to the illumination (LED in on state) conditions. and vice-versa. Finally, we studied the SiPM SNR in standard CW fNIRS operation. (C) 2018 Optical Society of America under the terms of the OS.A Open Access Publishing Agreement

This work explored the influence of the citrus pectin degree and pattern of methylesterification on its interaction with Zn

Ever-widespread employment of renewable energy sources, such as wind and sun, request the simultaneous use of effective energy storage systems owing to the intermittent and unpredictable energy generation by these sources. The most reliable storage systems currently under investigation are batteries and electrochemical cells for hydrogen production from water splitting. Both systems store chemical energy which can be converted on demand. The low power density is the weakness of the batteries while the high production cost limits currently the wide use of hydrogen from electrochemical water splitting. In this work, attention was focused on the use of nanostructured Ni as a cathode for electrochemical production of hydrogen from alkaline solution. The work is aimed at analysing the energy dissipation at 0.5 Acm−2, which is a value of applicative interest, for detecting one of the cause determining the high production cost. The development of electrochemical cells employing alkaline solution is currently the most promising approach in comparison with electrolysers using acidic solution which are expensive, because require precious metals as electrodes and high cost cation-selective membrane for efficiently conducting water splitting. Nanostructured Ni electrodes were fabricated through a cheap and easily scalable process, based on the Ni electrodeposition inside the pores of a commercial polycarbonate membrane acting as a template. On the contrary, a galvanic connection driving a spontaneous displacement reaction was employed for synthesising Pd nanostructured electrode which was tested for comparison purposes. Once the membrane is dissolved in an organic solution, the electrodes were initially characterized by SEM, EDS and XRD analysis. Then, electrochemical tests were performed to evaluate electrocatalytic properties of the electrodes. The tests were conducted through either cyclic or linear sweep voltammetry in 30% w/w KOH aqueous solution. Then, the nanostructured electrodes were tested under constant current density of 0.5 Acm−2. In comparison with nanostructured Pd, Ni electrodes with the same morphology and in otherwise identical conditions show a better response in terms of electrocatalytic activity. In addition, these electrodes showed satisfying stability over time through tests longer than 60 h. The analysis of energy dissipation revealed that the prevalent contribution was due to the ohmic drop)which can be reduced through a properly cell design) based on the accurate control of the parameters determining ohmic drop inside the cell.

This work presents a preliminary study on the electrical characterization of high efficiency bifacial solar cells. An opening discussion on the state-of-the-art of such advanced technology is initially proposed and the experimental characterization of some prototypes is described. From this analysis, it can be stated that the bifacial silicon solar cells can be a very promising technology with high electrical performances and efficiency.

The Staebler and Wronski light soaking effect [1-3] in hydrogenated amorphous silicon (a-Si:H) results as a worsening of solar cell performances under light soaking which results in a substantial loss of cell power conversion efficiency compared to time zero performance. In this work, comparing the behavior of single a-Si:H p-i-n devices with that of tandem a-Si:H / microcrystalline Si solar cells, we report on the performance improvement of the solar cells under prolonged exposure to reverse bias DC electric fields and illumination. In the paper we discuss about the radical differences between the forward and reverse bias stress and on the spectroscopic signature of the defects responsible for the instability / improvement effect. In addition, we determine the range of wavelengths where the photons are effective to improve the lifetime and cell efficiency. Finally, examples of reverse bias practical use in solar cell application are shown.

Hydrogen is potentially a reliable, affordable and sustainable energy carrier. Unfortunately hydrogen gas must be usually be generated from other compounds: 96% of Hydrogen is still extracted from fossil fuels, such as natural gas, oil and coal. The generation by electrolysis using the solar energy is a promising carbon free approach but it needs to be improved in terms of efficiency and durability to become economically appealing. A crucial factor is represented by the electrode and catalyst materials. The catalysts with highest activity and stability are noble or rare materials. In particular, IrO2 represents the best compromise for an active and stable oxygen evolution reaction catalyst. In order to minimize the amount of rare material, an affordable technique consists in depositing the catalyst on the surface of a less noble metal, such as nickel or steel. The deposition of IrO2 usually requires high temperature (200-1000°C), high purity precursors and complex experimental set up. In this paper we propose the use of electroless deposition through spontaneous galvanic displacement as a promising and simple deposition technique to produce interconnected IrO2 nanoparticles on nickel foam electrodes (figure 1). The deposition process of Ir on Ni has been studied as a function of time, pH and temperature. The formation of the iridium oxide has been achieved by thermal annealing in air. The experimental conditions have been optimized in order to improve the catalytic activity during water splitting measurements in 1M KOH, using a saturated calomel electrode (SCE) as reference and a Pt wire as counter. Scanning Electron Microscopy (SEM) analyses, coupled with X-ray Energy Dispersive Spectroscopy (EDX) and X-Rays Photoelectron Spectroscopy (XPS) show that, under proper deposition conditions, we can overcome the limits of other deposition techniques, achieving a uniform IrO2 coverage throughout the 3D structure of the Ni foam. Such a condition is crucial for the long term stability of the electrodes under constant current stress. The amount of Ir on the Ni foam has been experimentally evaluated, obtaining optimal results with 8 mg cm−2 of noble metal in a 0.16 cm thick electrode. Such a value is more than two orders of magnitude lower than typical values employed in the PEM electrolyzers, therefore making the present approach very promising. Figure 1

We study resistive switching memories with Hf or Ti metal oxygen exchange layers.STEM dark field and EELS are used to observe the conductive filament.The filament is a cone-shaped metal-rich region in the HfO2 dielectric layer.Composition of the metallic filament is dominated by Hf or Ti depending on the OEL. A detailed physical analysis of the conductive filament electrically formed in HfO2-based resistive switching memory devices with both Hf and Ti metal oxygen exchange layers is presented. The filament, observed by applying transmission electron microscopy (TEM), scanning TEM (STEM), and electron energy loss spectroscopy (EELS) techniques to 50i?50nm2 cells, is a cone-shaped metal-rich region in the HfO2 dielectric of the resistive switching device.