Pd and Pd-Cu supported on different carbon materials and immobilized as flow-through catalytic membranes for the chemical reduction of NO3, NO2-and BrO3- in drinking water treatment

Powdered catalysts are commonly used in lab-scale tests for the catalytic reduction of oxoanions in drinking water, but their powder nature limits their application at full scale. In this work, Pd and Pd-Cu catalysts (5% wt.) supported on carbon materials with different structural properties, in powder form, were used to prepare catalytic membranes that were tested in a reactor with flow-through configuration (FTCMR) to study their performance in the reduction of NO3-, NO2- and BrO3-. Pd catalytic membranes showed high activity in the reduction of NO2-, being the selectivity to NH4+ lower than 2% at 80% NO2- conversion in all cases. In BrO3- reduction, they exhibited a wide range of conversions being the catalyst supported on materials with high conductivity the most active ones, which may be ascribed to the charge distribution at the metal-carbon interface. NO3- reduction using Pd-Cu catalytic membranes showed that catalysts supported on materials with small nanoparticle size and low electrical conductivity exhibited higher selectivity to NH4+. FTCMR led to a good control of H2 transfer and availability in the active sites, facilitating the tuning of H2 availability conditions to preserve the activity, while maintaining/diminishing selectivity to NH4+. In simultaneous oxoanions reduction tests, NO3- reduction was inhibited by Br species, probably by affection of the Pd-Cu redox cycle. This fact could be crucial to the future development of drinking water treatment processes, as conditions the order of the disinfection and NO3- reduction stepsThe authors greatly appreciate the support from Spanish Agencia Estatal de Investigacion ´ (AEI, RTI2018–098431-BI00). Adrian ´ Marí thanks the Spanish AEI for a research grant (PRE-2019-088601). This work was also financially supported by: LA/P/0045/2020 (ALiCE), UIDB/50020/2020 and UIDP/50020/2020 (LSRE-LCM) and funded by national funds through FCT/MCTES (PIDDAC), and project NORTE01–0145-FEDER-000069 (Healthy Waters) co-funded by European Regional Development Fund (ERDF), through North Portugal Regional Operational Program (NORTE2020), under the PORTUGAL 2020 Partnership Agreemen

Association of Structural Magnetic Resonance Imaging Measures With Psychosis Onset in Individuals at Clinical High Risk for Developing Psychosis:An ENIGMA Working Group Mega-analysis

IMPORTANCE The ENIGMA clinical high risk (CHR) for psychosis initiative, the largest pooled neuroimaging sample of individuals at CHR to date, aims to discover robust neurobiological markers of psychosis risk.OBJECTIVE To investigate baseline structural neuroimaging differences between individuals at CHR and healthy controls as well as between participants at CHR who later developed a psychotic disorder (CHR-PS+) and those who did not (CHR-PS-).DESIGN, SETTING, AND PARTICIPANTS In this case-control study, baseline T1-weighted magnetic resonance imaging (MRI) data were pooled from 31 international sites participating in the ENIGMA Clinical High Risk for Psychosis Working Group. CHR status was assessed using the Comprehensive Assessment of At-Risk Mental States or Structured Interview for Prodromal Syndromes. MRI scans were processed using harmonized protocols and analyzed within a mega-analysis and meta-analysis framework from January to October 2020.MAIN OUTCOMES AND MEASURES Measures of regional cortical thickness (CT), surface area, and subcortical volumes were extracted from T1-weighted MRI scans. Independent variables were group (CHR group vs control group) and conversion status (CHR-PS+ group vs CHR-PS- group vs control group).RESULTS Of the 3169 included participants, 1428 (45.1%) were female, and the mean (SD; range) age was 21.1 (4.9; 9.5-39.9) years. This study included 1792 individuals at CHR and 1377 healthy controls. Using longitudinal clinical information, 253 in the CHR-PS+ group, 1234 in the CHR-PS- group, and 305 at CHR without follow-up data were identified. Compared with healthy controls, individuals at CHR exhibited widespread lower CT measures (mean [range] Cohen d = -0.13 [-0.17 to -0.09]), but not surface area or subcortical volume. Lower CT measures in the fusiform, superior temporal, and paracentral regions were associated with psychosis conversion (mean Cohen d = -0.22; 95% CI, -0.35 to 0.10). Among healthy controls, compared with those in the CHR-PS+ group, age showed a stronger negative association with left fusiform CT measures (F = 9.8; P < .001; q < .001) and left paracentral CT measures (F = 5.9; P = .005; q = .02). Effect sizes representing lower CT associated with psychosis conversion resembled patterns of CT differences observed in ENIGMA studies of schizophrenia (rho = 0.35; 95% CI, 0.12 to 0.55; P = .004) and individuals with 22q11.2 microdeletion syndrome and a psychotic disorder diagnosis (rho = 0.43; 95% CI, 0.20 to 0.61; P = .001).CONCLUSIONS AND RELEVANCE This study provides evidence for widespread subtle, lower CT measures in individuals at CHR. The pattern of CT measure differences in those in the CHR-PS+ group was similar to those reported in other large-scale investigations of psychosis. Additionally, a subset of these regions displayed abnormal age associations. Widespread disruptions in CT coupled with abnormal age associations in those at CHR may point to disruptions in postnatal brain developmental processes.Question How are brain morphometric features associated with later psychosis conversion in individuals at clinical high risk (CHR) for developing psychosis?Findings In this case-control study including 3169 participants, lower cortical thickness, but not cortical surface area or subcortical volume, was more pronounced in individuals at CHR in a manner highly consistent with thinner cortex in individuals with established psychosis. Regions that displayed lower cortical thickness in individuals at CHR who later developed a psychotic disorder additionally displayed abnormal associations with age.Meaning In this study, CHR status and later transition to psychosis was robustly associated with lower cortical thickness; abnormal age associations and specificity to cortical thickness may point to aberrant postnatal brain development in individuals at CHR, including pruning and myelination.This case-control study investigates baseline structural magnetic resonance imaging (MRI) differences between individuals at clinical high risk and healthy controls as well as between participants at clinical high risk who later developed a psychotic disorder and those who did not

Volume fraction and width of ribbon-like crystallites control the rubbery modulus of segmented block copolymers

cited By 0We discuss the origin of the plateau modulus enhancement (χ) in semi-crystalline segmented block copolymers by increasing the concentration in hard segments within the chains (XHS). The message we deliver is that the plateau modulus of these thermoplastic elastomers is greatly dominated by the volume fraction (φ) and the width (W) of crystallites according to χ-1 ~ φW in agreement with a recent topological model we have developed. We start by a quick review of literature with the aim to extract χ(φ) for different chemical structures. As we suspected, we find that most of the data falls onto a mastercurve, in line with our predictions, confirming that the reinforcement in such materials is mainly dominated by the crystallite's content. This important result is then supported by the investigation of copolymer mixtures in which φ is fixed, providing a similar reinforcement, while the chains compositions is significantly different. Finally, we show that the reinforcement can be enhanced at constant φ by increasing W for a given class of block copolymers. This can be done by changing the process route and is again in good agreement with our expectations. © 2019 Walter de Gruyter GmbH, Berlin/Boston

Bimodal Crystallization Kinetics of PBT/PTHF Segmented Block Copolymers: Impact of the Chain Rigidity

cited By 3By combining linear rheology and differential scanning calorimetry experiments performed under isothermal and nonisothermal conditions, we clarify the mechanisms of crystallization occurring in three industrially relevant PBT/PTHF segmented block copolymers. After a careful and systematic analysis of the crystallization kinetics based on "classic" Avrami-like models (1 &lt; n &lt; 2), we reveal (and quantify) the two-step nature of the PBT segments' association. Besides, we discuss the role of the hard (PBT) and soft (PTHF) segments' length by confronting our results to PBT homopolymers. As expected, while 2 kg mol -1 PTHF segments are found to delay substantially the crystallization of the PBT within the copolymers, we demonstrate that shortening them down to 1 kg mol -1 results in similar kinetics as for neat PBT lamellar crystallization. This result, raising fundamental questions on the chains' conformation, is finally discussed jointly with our rheological tests (gelation) and recent theoretical predictions with the aim to bring new insights into the topology of such complex systems. © Copyright 2019 American Chemical Society

Modeling shear-induced crystallization in startup flow: The case of segmented copolymers

cited By 0We propose to extend the well-known Doi-Edwards theory to model the viscosity divergence caused by shear-induced crystallization occurring upon startup flow experiments in segmented block copolymers (M w = 50 kg mo l - 1). Unlike models such as Convective Constraint Release in which the chain relaxation is accelerated by the shear, we propose to increase the final relaxation time of the polymer within the memory function to take into consideration the progressive association of the hard-segments. To this aim, we make use of the Avrami equation in which we parametrize the crystallization rate to depend on the shear rate in a linear way. In this context and contrary to what is generally proposed for supramolecular polymers, we consider the hard-segments aggregation as an irreversible process (infinite lifetime) due to the crystalline nature and the high-functionality of the resulting topological nodes. The exponential trend of the Avrami process is then validated by stress relaxation experiments performed at different levels of strain. Moreover, the growth mode parameter, usually assigned to the geometry of the crystallites, is found to be independent of the shear rate and in excellent agreement with a previous work in which we investigated the quiescent crystallization of the same system. We finally apply our model to fit data measured at different temperatures, well-confirming the development of hard-segments' crystallites from the very first stages of the isothermal shearing process. © 2019 The Society of Rheology

Process-Oriented Structure Tuning of PBT/PTHF Thermoplastic Elastomers

cited By 0International audienc

Mechanistic Understanding of Sticker Aggregation in Supramolecular Polymers: Quantitative Insights from the Plateau Modulus of Triblock Copolymers

Quantifying the impact of associative group aggregation on the mechanical properties of dense supramolecular networks remains a challenging problem. To address this question, we carry out coarse-grained molecular dynamics simulations of triblock copolymers consisting of a linear succession of hard (crystallizable) and soft (amorphous) segments. This molecular architecture offers the opportunity to increase the volume fraction of crystallites, serving as supramolecular aggregates, in a progressive and controlled fashion, allowing us to study its impact on the plateau modulus of the corresponding thermoplastic elastomers. By unifying these simulations with a recent mechanistic model and experimental data, we provide new quantitative insights into the microscopic origin of the mechanical reinforcement. Enhancement of the plateau modulus originates from the network’s topology at low crystallite content

Mechanistic Understanding of Sticker Aggregation in Supramolecular Polymers: Quantitative Insights from the Plateau Modulus of Triblock Copolymers

Quantifying the impact of associative group aggregation on the mechanical properties of dense supramolecular networks remains a challenging problem. To address this question, we carry out coarse-grained molecular dynamics simulations of triblock copolymers consisting of a linear succession of hard (crystallizable) and soft (amorphous) segments. This molecular architecture offers the opportunity to increase the volume fraction of crystallites, serving as supramolecular aggregates, in a progressive and controlled fashion, allowing us to study its impact on the plateau modulus of the corresponding thermoplastic elastomers. By unifying these simulations with a recent mechanistic model and experimental data, we provide new quantitative insights into the microscopic origin of the mechanical reinforcement. Enhancement of the plateau modulus originates from the network’s topology at low crystallite content

Fast scanning calorimetry clarifies the understanding of the complex melting and crystallization behavior of polyesteramide multi-block copolymers

cited By 3Fast scanning calorimetry has been applied in order to understand the phase transitions in thermoplastic elastomers (TPEs) based on well-defined multi-block copolymers made of ‘soft’ polytetrahydrofuran and ‘hard’ terephthalate ester diamides. The intrinsically complex chemical structure of TPEs leads to complex phase transitions. By changing their thermal history over a wide range of temperature (from −100 °C to 200 °C) and cooling rates (from 10 to 4000 °C s−1), we clarify the origins of the various phases present in these materials. In particular, we study the different possibilities for the hard segments to associate depending on their mobility during the quenching phase, forming either strong and stable structures or weaker and metastable ones. Besides, we demonstrate that a minimal cooling rate of 800 °C s−1 is necessary to keep these TPEs (made of short and monodisperse hard segments) amorphous leading to a subsequent cold crystallization when heating back, at around 30 °C. Finally, we validate our interpretations by varying the copolymer composition (from 10 wt% to 20 wt% hard segments), revealing the thermal invariance of poorly organized domains. Based on these data, we also discuss the importance of chain diffusion in the crystallization process. Applying fast scanning calorimetry allows us to link fundamental understanding to industrial application. © 2018 Society of Chemical Industry. © 2018 Society of Chemical Industr

Multiscale structure of super insulation nano-fumed silicas studied by SAXS, tomography and porosimetry

cited By 2We focus on describing the multi-scale structure of a fumed silica characterized by remarkably low thermal conductivity (ca. 2–5 mW m −1 K −1 ) when used as a core material in vacuum insulating panels. While such powders are known to be highly polydisperse at different lengthscales (hardly quantifiable), we propose to adapt a recent methodology based on small-angle X-ray scattering experiments with the aim of providing simple criteria for characterizing the morphology of these nanostructured silicas. Combining this technique with transmission electron microscopy, electron-tomography and mercury intrusion porosimetry then allows assigning the origin of the super-insulation to the low dimensionality of the silica aggregates at lengthscales smaller than 500 nm. Remarkably, by using independently these three techniques, we always find the compacity of the aggregates (radius of ca. 40 nm) to be equal to 0.29 ± 0.01. This study proposes therefore a robust methodology, potentially of a great interest for industrial applications. © 2019 Acta Materialia Inc