jablonkagroup/rise_ai_scientists huggingface dataset:
Authors: Laurence Illing Midgley | Vincent Stimper | Gregor N. C. Simm | Bernhard Schölkopf | José Miguel Hernández-Lobato
Source: arXiv (Cornell University) (preprint, 2022-08-03)
Field: Materials Science — Materials Chemistry

Flow Annealed Importance Sampling Bootstrap Normalizing flows are tractable density models that can approximate complicated target distributions, e.g. Boltzmann distributions of physical systems. However, current methods for training flows either suffer from mode-seeking behavior, use samples from the target generated beforehand by expensive MCMC methods, or use stochastic losses that have high variance. To avoid these problems, we augment flows with annealed importance sampling (AIS) and minimize the mass-covering $α$-divergence with $α=2$, which minimizes importance weight variance. Our method, Flow AIS Bootstrap (FAB), uses AIS to generate samples in regions where the flow is a poor approximation of the target, facilitating the discovery of new modes. We apply FAB to multimodal targets and show that we can approximate them very accurately where previous methods fail. To the best of our knowledge, we are the first to learn the Boltzmann distribution of the alanine dipeptide molecule using only the unnormalized target density, without access to samples generated via Molecular Dynamics (MD) simulations: FAB produces better results than training via maximum likelihood on MD samples while using 100 times fewer target evaluations. After reweighting the samples, we obtain unbiased histograms of dihedral angles that are almost identical to the ground truth. Variance (accounting) ; Sampling (signal processing) ; Histogram ; Algorithm ; Flow (mathematics) ; Computer science ; Importance sampling ; Mathematics ; Statistics ; Monte Carlo method ; Statistical physics ; Artificial intelligence ; Physics ; Image (mathematics) ; Geometry Machine Learning in Materials Science ; Protein Structure and Dynamics ; Mass Spectrometry Techniques and Applications
Authors: Wanyao Meng | Sijie Wang | Haifeng Lv | Zhenxing Wang | Xuewen Han | Zijing Zhou | Junwen Pu
Source: BioResources (article, 2022-03-21)
Field: Chemistry — Spectroscopy

Porous cellulose nanofiber (CNF)-based aerogel with the loading of zeolitic imidazolate frameworks-8 (ZIF-8) for Cu(II) removal from wastewater A novel biobased porous aerogel was synthesized using physical mixing, freeze-drying, and in-situ growth methods. Zeolitic imidazolate frameworks-8 (ZIF-8) were grafted onto the surface of the CS/CNF solid composite to form a ZIF-8@CS/CNF aerogel. The structural characteristics and the adsorption potential of the ZIF-8@CS/CNF aerogel were investigated. It was found that the specific surface area of the ZIF-8@CS/CNF aerogel was 206 m2/g, and the water stability of the CNF aerogel was enhanced by incorporating the CS. Meanwhile, the adsorption isotherm and kinetics of the composite aerogel fit the pseudo-second-order kinetic model (R2 = 0.96) and the Langmuir isotherm model (R2 = 0.97) with the copper(II) oxide (Cu(II)) theoretical adsorption capacity of 245 mg/g, respectively. Furthermore, this aerogel, which combined metal-organic frameworks (MOFs) and CNF, was easy to fabricate and it was biodegradable. These characteristics suggest it has a broad potential for wastewater treatment. Aerogel ; Zeolitic imidazolate framework ; Materials science ; Adsorption ; Imidazolate ; Chemical engineering ; Langmuir adsorption model ; Nanofiber ; Porosity ; Composite number ; Specific surface area ; Metal-organic framework ; Composite material ; Catalysis ; Organic chemistry ; Chemistry Aerogels and thermal insulation ; Advanced Cellulose Research Studies
Authors: Loredana Ferreri | Grazia M. L. Consoli | Gabriele Clarizia | Daniela Zampino | Antonia Nostro | Giuseppe Granata | Giovanna Ginestra | Maria Laura Giuffrida | Stefania Zimbone | Paola Bernardo
Source: Journal of Materials Science (article, 2022-11-01)
Field: Chemistry — Organic Chemistry

A novel material based on an antibacterial choline-calixarene nanoassembly embedded in thin films Abstract Supramolecular chemistry is one of the current strategies for producing advanced materials. With the aim to develop new Thin-Films with antibacterial activity, we embedded an amphiphilic choline-calix[4]arene possessing antibacterial properties in polymeric Thin-Films based on polyether-co-amide matrix (Pebax ® 2533). The loading of the calix[4]arene derivative in the film was performed by solution casting. The amount of calixarene additive in the films was in the range of 0.5–5 wt%. The self-supported Thin-Films were characterized by investigating phase miscibility, morphology, spectral properties, and gas transport. The release of the calixarene derivative from the films was studied in a biomimetic medium as PBS (10 mM, pH 7.4). The presence of the additive did not affect the thermal stability of the copolymer, whereas it induced an increase in crystallinity, wettability, and gas permeability of the blend films according to its concentration. The antibacterial activity of the films was evaluated in vitro against Escherichia coli and Staphylococcus aureus strains, representative of Gram-negative and Gram-positive bacteria. The developed films displayed antibacterial activity against both strains. In particular, Pebax ® − 5 wt% Chol-Calix caused within 10 h a reduction in E. coli and S. aureus of 2.57 and 2 log CFU/mL, respectively. The potential toxicity of the films was also tested on mouse embryonic fibroblasts NIH/3T3. Pebax ® 2533/calixarene derivative combination appears a promising approach for the development of novel flexible antibacterial materials. Graphical abstract Calixarene ; Materials science ; Crystallinity ; Thin film ; Antibacterial activity ; Wetting ; Chemical engineering ; Amphiphile ; Copolymer ; Organic chemistry ; Nanotechnology ; Polymer ; Bacteria ; Chemistry ; Composite material ; Molecule Antimicrobial agents and applications ; Advanced Polymer Synthesis and Characterization ; Supramolecular Chemistry and Complexes
Authors: Paula Muñoz-Flores | Po S. Poon | C. Sepúlveda | Conchi O. Ania | Juan Matos
Source: Catalysts (article, 2022-01-01)
Field: Materials Science — Materials Chemistry

Photocatalytic Performance of Carbon-Containing CuMo-Based Catalysts under Sunlight Illumination Carbon-doped nanostructured CuMo-based photocatalysts were prepared by solvothermal synthesis. Two thermal treatments—oxidative and inert atmosphere—were used for the synthesis of the catalysts, and the influence of spherical carbon structures upon the crystalline phases on the photocatalytic activity and stability was studied. XRD showed the catalysts are nanostructured and composed by a mixture of copper (Cu, Cu2O, and CuO) and molybdenum (MoO2 and MoO3) crystalline phases. The catalysts were used for the degradation of yellow 5 under solar light. A remarkable leaching of Mo both in dark and under solar irradiation was observed and quantified. This phenomenon was responsible for the loss of photocatalytic activity for the degradation of the dye on the Mo-containing series. Conversely, the Cu-based photocatalysts were stable, with no leaching observed after 6 h irradiation and with a higher conversion of yellow 5 compared with the Mo- and CuMo series. The stability of Cu-based catalysts was attributed to a protective effect of spherical carbon structures formed during the solvothermal synthesis. Regarding the catalysts’ composition, sample Cu4-800-N2 prepared by pyrolysis exhibited up to 4.4 times higher photoactivity than that of the pristine material, which is attributed to a combined effect of an enhanced surface area and micropore volume generated during the pyrolytic treatment due to the presence of the carbon component in the catalyst. Scavenger tests have revealed that the mechanism for tartrazine degradation on irradiated Cu-based catalysts involves successive attacks of •OH radicals. Catalysis ; Photocatalysis ; Materials science ; Carbon fibers ; Leaching (pedology) ; Inert gas ; Inorganic chemistry ; Chemical engineering ; Nuclear chemistry ; Chemistry ; Organic chemistry ; Composite material ; Composite number Copper-based nanomaterials and applications ; Advanced Photocatalysis Techniques ; Nanomaterials for catalytic reactions
Authors: Inge Bos | Eline F. Brink | Lucile Michels | Joris Sprakel
Source: Soft Matter (article, 2022-01-01)
Field: Materials Science — Surfaces, Coatings and Films

DNA dynamics in complex coacervate droplets and micelles Single stranded DNA (ssDNA), or another polyanion, can be mixed with polycations to form liquid-like complex coacervates. When the polycations are replaced by cationic-neutral diblock copolymers, complex coacervate core micelles (C3Ms) can be formed instead. In both complex coacervates and C3Ms, dynamics plays an important role. Yet, to date, the effect of chain length on the dynamics effect is still not fully understood. The DNA complexes provide a versatile platform to further elucidate these chain length effects because the DNA is monodisperse and its length can be easily adapted. Therefore, we study in this paper the dynamics of fluorescently labelled ssDNA in both complex coacervate droplets and micelles. The DNA dynamics in the complex coacervate droplets is probed by fluorescence recovery after photobleaching (FRAP). We observe that the DNA diffusion coefficient depends more strongly on the DNA length than predicted by the sticky Rouse model and we show that this can be partly explained by changes in complex coacervate density, but that also other factors might play a role. We measure the molecular exchange of C3Ms by making use of Förster resonance energy transfer (FRET) and complement these measurements with Langevin dynamics simulations. We conclude that chain length polydispersity is the main cause of a broad distribution of exchange rates. We hypothesise that the different exchange rates that we observe for the monodisperse DNA are mainly caused by differences in dye interactions and show that the dye can indeed have a large effect on the C3M exchange. In addition, we show that a new description of the C3M molecular exchange is required that accounts among others for the effect of the length of the oppositely charged core species. Together our findings can help to better understand the dynamics in both specific DNA systems and in complex coacervate droplets and micelles in general. Coacervate ; Micelle ; Chemistry ; DNA ; Copolymer ; Chemical engineering ; Dynamics (music) ; Nanotechnology ; Chemical physics ; Materials science ; Chromatography ; Polymer ; Organic chemistry ; Biochemistry ; Physics Polymer Surface Interaction Studies ; Block Copolymer Self-Assembly ; Nanopore and Nanochannel Transport Studies
Authors: Laura I.V. Holz | Vanessa C.D. Graça | Francisco J.A. Loureiro | Sergey M. Mikhalev | Diogo Mendes | Adélio Mendes | Duncan P. Fagg
Source: Journal of Materials Chemistry C (article, 2022-01-01)
Field: Materials Science — Materials Chemistry

Tailoring the anion stoichiometry and oxidation kinetics of vanadium (oxy)nitride by the control of ammonolysis conditions Higher N/O increases significantly the V(O,N) oxidation resistance. Vanadium ; Stoichiometry ; Kinetics ; Materials science ; Nitride ; Vanadium nitride ; Ion ; Inorganic chemistry ; Physical chemistry ; Chemistry ; Metallurgy ; Nanotechnology ; Organic chemistry Catalytic Processes in Materials Science ; Electronic and Structural Properties of Oxides ; Radioactive element chemistry and processing
Authors: Yuhang Sun | Di Cai | Yumiao Yang | Xinyang Chen | Binhui Wang | Zhitong Yao | Meiqing Jin | Jie Liu | Markus Reinmöller | José Luiz Francisco Alves
Source: Biomass and Bioenergy (article, 2022-12-29)
Field: Materials Science — Polymers and Plastics

Investigation of the thermal conversion behavior and reaction kinetics of the pyrolysis of bio-based polyurethane: A reference study In view of the global objective of carbon neutrality, using natural biomaterials to prepare bio-based polyurethane (BPU) is a significant means of reducing our heavy dependence on fossil fuels. If the utilization of these biomaterials is to increase, appropriate treatment methods after they reach the end of their life cycle are a challenge that must be addressed in advance. In the present study, thermogravimetric (TG) experiments were conducted for bio-based polyurethane (BPU) as a reference case compared to neat polyurethane (NPU) from fossil resources. The resultant generation of pyrolysis products was analyzed using coupled thermogravimetric analysis, Fourier-transformed infrared spectroscopy and gas chromatography mass spectrometry (TG-FTIR-GC/MS). The reaction kinetics were investigated using three model-free methods by Flynn–Wall–Ozawa (FWO), Kissinger–Akahira–Sunose (KAS), and Starink, in addition to the model-fitting Coats–Redfern (CR) method. The TG analysis indicated that the decomposition of BPU and NPU can be divided into three similar stages with temperature ranges of <200 °C, 220–450/500 °C and above 500 °C. Activation energies (Ea) of BPU and NPU conversion fell in the range of 149.4–221.0 kJ mol−1 and 95.6–162.6 kJ mol−1 respectively when using the model-free methods. The apparent reaction mechanism study revealed that both samples were in accordance with the reaction order models, with orders of 3 for BPU and 2.5 for NPU. Polyurethane ; Thermogravimetric analysis ; Pyrolysis ; Fourier transform infrared spectroscopy ; Kinetics ; Thermal decomposition ; Gas chromatography ; Chemistry ; Materials science ; Chemical engineering ; Nuclear chemistry ; Analytical Chemistry (journal) ; Organic chemistry ; Chromatography Polymer composites and self-healing ; biodegradable polymer synthesis and properties ; Polymer crystallization and properties
Authors: Yi Hong | Xiaowei Huo | Jinhong Gu | Wei Lei | Sun Zhenping | Fuxiang Du | Chao Dai | Xiongfei Wu | Zhiguang Liu | Jian Ren
Source: RSC Advances (article, 2022-01-01)
Field: Chemistry — Organic Chemistry

Boron doping positively enhances the catalytic activity of carbon materials for the removal of bisphenol A Boron-doped carbon materials (BCs), low-cost and environmentally friendly carbocatalysts, were prepared for the activation of persulfate (PS) for the removal of bisphenol A (BPA). Compared with B-free carbon materials (Cs), the adsorption and catalytic activity were significantly enhanced by the boron modification. Fast and efficient removal of BPA was achieved using the BCs/PS system. The BPA removal rate constant increased linearly with the adsorption capacity of BCs. Electron paramagnetic resonance (EPR) spectroscopy and radical quenching experiments indicated that the degradation mechanisms in the BCs/PS system were different from conventional radical-based oxidation pathways. On the contrary, nonradical pathways were demonstrated to dominate the oxidation processes in the removal of BPA using the BCs/PS system. Herein, a mechanism is proposed where PS is activated by the carbon material to form a reactive electron-deficient carbocatalyst ([BCs]*) complex with a high redox potential, driving a nonradical oxidation pathway to achieve BPA removal. Through experimental investigation and the use of electrochemical techniques (cyclic voltammetry, Tafel corrosion analysis and open circuit voltages), B-doped carbon materials for the activation of PS elevate the potential of the derived nonradical [BCs]* complexes, and then accelerate the BPA removal efficiency <i>via</i> an electron transfer process. Utilizing adsorption and nonradical oxidation processes, the BCs/PS system possesses great potential for the removal of BPA in practical applications such as wastewater treatment. Boron ; Bisphenol A ; Doping ; Catalysis ; Carbon fibers ; Bisphenol ; Chemistry ; Inorganic chemistry ; Materials science ; Chemical engineering ; Organic chemistry ; Composite material ; Epoxy ; Optoelectronics Nanomaterials for catalytic reactions ; Catalytic Processes in Materials Science ; Advanced oxidation water treatment
Authors: Henrik Siegel | Alessio J. Sprockel | Matthew S. Schwenger | Jesse M. Steenhoff | Iske Achterhuis | Wiebe M. de Vos | Martin F. Haase
Source: ACS Applied Materials & Interfaces (article, 2022-09-15)
Field: Materials Science — Materials Chemistry

Synthesis and Polyelectrolyte Functionalization of Hollow Fiber Membranes Formed by Solvent Transfer Induced Phase Separation Ultrafiltration membranes are important porous materials to produce freshwater in an increasingly water-scarce world. A recent approach to generate porous membranes is solvent transfer induced phase separation (STrIPS). During STrIPS, the interplay of liquid-liquid phase separation and nanoparticle self-assembly results in hollow fibers with small surface pores, ideal structures for applications as filtration membranes. However, the underlying mechanisms of the membrane formation are still poorly understood, limiting the control over structure and properties. To address this knowledge gap, we study the nonequilibrium dynamics of hollow fiber structure evolution. Confocal microscopy reveals the distribution of nanoparticles and monomers during STrIPS. Diffusion simulations are combined with measurements of the interfacial elasticity to investigate the effect of the solvent concentration on nanoparticle stabilization. Furthermore, we demonstrate the separation performance of the membrane during ultrafiltration. To this end, polyelectrolyte multilayers are deposited on the membrane, leading to tunable pores that enable the removal of dextran molecules of different molecular weights (>360 kDa, >60 kDa, >18 kDa) from a feed water stream. The resulting understanding of STrIPS and the simplicity of the synthesis process open avenues to design novel membranes for advanced separation applications. Membrane ; Materials science ; Polyelectrolyte ; Chemical engineering ; Ultrafiltration (renal) ; Nanoparticle ; Surface modification ; Polymer ; Solvent ; Nanotechnology ; Chromatography ; Organic chemistry ; Chemistry ; Composite material Pickering emulsions and particle stabilization ; Surface Modification and Superhydrophobicity ; Membrane Separation Technologies
Authors: Jinlong Zhao | Hanchao Ma | Hong Huang | Jianping Zhang | Youliang Chen
Source: Journal of Thermal Analysis and Calorimetry (article, 2022-11-04)
Field: Materials Science — Materials Chemistry

Experimental investigation and numerical modeling of oxidative pyrolysis mechanism of mining PVC cable sheath Abstract Cables modified with flame retardants are widely used in the coal mining process to enhance their fire safety performance. This paper investigates experimentally and numerically the thermo-oxidative degradation process of PVC-based mining cable sheath, which consists of PVC resin and plasticizers (Phthalate esters), fillers (Calcium carbonate), and flame retardant (Antimony trioxide) as additives. Thermogravimetry coupled with Fourier transform infrared spectroscopy (TG-FTIR) experiments were performed at different heating rates in an air atmosphere. TG results showed that the decomposition processes of mining PVC cable sheath are more complicated than those of pure PVC with additional degradation steps, which was further confirmed by FTIR gas analysis. A deconvolution method was used to distinguish the independent reactions from the overlapped derivative thermogravimetric (DTG) peaks. It was found that the whole degradation process can be divided into seven steps, based on which an oxidative pyrolysis model was developed: pyrolysis of plasticizers (steps 1 and 2), dehydrogenation (step 3), emission and combustion of volatile fraction (step 4), carbon combustion (step 5), oxidative pyrolysis of complicated additives (step 6), and decomposition of residues (step 7). The kinetic triplets (activation energy, pre-exponential factor, and reaction model function) for each reaction were firstly calculated using three commonly used model-free methods and then further optimized using the genetic algorithm (GA). Based on the optimized parameters, the reaction mechanisms and their associated kinetic parameters were determined. The findings of this study are important in understanding the oxidative pyrolysis process of PVC cable sheath, and the obtained kinetic parameters can also be used for its pyrolysis and fire modeling, waste recycling, and risk assessment. Pyrolysis ; Thermogravimetric analysis ; Thermogravimetry ; Combustion ; Materials science ; Fourier transform infrared spectroscopy ; Plasticizer ; Chemical engineering ; Decomposition ; Thermal decomposition ; Chemistry ; Organic chemistry ; Composite material Thermal and Kinetic Analysis ; Polymer Science and PVC ; Flame retardant materials and properties
Authors: Emilio Mateev
Source: FARMACIA (article, 2022-04-25)
Field: Chemistry — Organic Chemistry

DESIGN, SYNTHESIS, BIOLOGICAL EVALUATION AND MOLECULAR DOCKING OF PYRROLE-BASED COMPOUNDS AS ANTIOXIDANT AND MAO-B INHIBITORY AGENTS Alzheimer's disease (AD) is the most widespread neurodegenerative disorder with a significant impact on health systems. Considering the lack of efficient treatment, compounds with multi-target activities are usually designed as promising options to fill the evident gap. In this study, two novel N-pyrrolyl carboxylic acids (4a and 5a) and eight corresponding amide derivatives (4a1-4a3 and 5a1-5a5) were synthesized and fully elucidated by 1 H NMR, FT-IR and HRMS (high resolution mass spectrometry). All reported compounds were assessed for their radical (DPPH and ABTS + ) scavenging properties and MAO-B blocking potential. The results indicated that compound 5a2 could serve as a prominent lead compound for a future optimization as a MAO-B inhibitor. In addition, the DPPH and ABTS + assays demonstrated significant antioxidant capacity. A possible binding conformation of 5a2 in the active site of MAO-B was also identified through molecular docking simulations. The analysis of the major interactions indicated the establishment of several unfavourable steric clashes. Thus, reducing the size of the core structure could drastically increase the MAO-B antagonizing potency of the pyrrole-based compounds. Docking (animal) ; Antioxidant ; Inhibitory postsynaptic potential ; Combinatorial chemistry ; Chemistry ; Computational biology ; Stereochemistry ; Biochemistry ; Biology ; Medicine Synthesis and biological activity