jablonkagroup/rise_ai_scientists huggingface dataset:
Authors: Tzu‐Yu Chen | Eamor M. Woo | Selvaraj Nagarajan
Source: Scientific Reports (article, 2020-03-04)
Field: Materials Science — Electronic, Optical and Magnetic Materials

Periodic Fractal-Growth Branching to Nano-Structured Grating Aggregation in Phthalic Acid Small-molecule phthalic acid (PA), confined in micrometer thin films, was crystallized in the presence of strongly interacting tannic acid (TA) to investigate crystal assembly and correlation between banded patterns and branching structures. Several compositions of the mixture of ethanol/water solutions and evaporation temperatures were also manipulated to investigate the kinetic effects on the morphology of PA crystals. With increasing evaporation rate, the morphology of PA crystals systematically changes from circular-banded spherulites to highly ordered grating-banded patterns. A unique periodic fractal-branch pattern with contrasted birefringent bands exists at intermediate evaporation rate, and this unique grating architecture has never been found in other banded crystals. Crystal assembly of these three periodic morphologies was analyzed by utilizing atomic-force microscopy (AFM) and scanning electron microscopy (SEM) to reveal the mechanisms of formation of hierarchical structures of PA. The detailed growth mechanisms of the novel fractal-branching assembly into circular- or grating-banded patterns are analyzed in this work. Branching (polymer chemistry) ; Materials science ; Grating ; Phthalic acid ; Nano- ; Evaporation ; Morphology (biology) ; Scanning electron microscope ; Birefringence ; Nanotechnology ; Crystallography ; Chemical engineering ; Chemical physics ; Optics ; Chemistry ; Composite material ; Optoelectronics Liquid Crystal Research Advancements ; Surfactants and Colloidal Systems ; nanoparticles nucleation surface interactions
Authors: Delphine Pichon | Jennifer Morvan | Christophe Crévisy | Marc Mauduit
Source: Beilstein Journal of Organic Chemistry (review, 2020-02-17)
Field: Chemistry — Organic Chemistry

Copper-catalyzed enantioselective conjugate addition of organometallic reagents to challenging Michael acceptors The copper-catalyzed enantioselective conjugate addition (ECA) of organometallic nucleophiles to electron-deficient alkenes (Michael acceptors) represents an efficient and attractive methodology for providing a wide range of relevant chiral molecules. In order to increase the attractiveness of this useful catalytic transformation, some Michael acceptors bearing challenging electron-deficient functions (i.e., aldehydes, thioesters, acylimidazoles, <i>N</i>-acyloxazolidinones, <i>N</i>-acylpyrrolidinones, amides, <i>N</i>-acylpyrroles) were recently investigated. Remarkably, only a few chiral copper-based catalytic systems have successfully achieved the conjugate addition of different organometallic reagents to these challenging Michael acceptors, with excellent regio- and enantioselectivity. Furthermore, thanks to their easy derivatization, the resulting chiral conjugated products could be converted into various natural products. The aim of this tutorial review is to summarize recent advances accomplished in this stimulating field. Michael reaction ; Enantioselective synthesis ; Chemistry ; Conjugate ; Nucleophile ; Combinatorial chemistry ; Reagent ; Catalysis ; Conjugated system ; Derivatization ; Organic chemistry Asymmetric Synthesis and Catalysis ; Synthetic Organic Chemistry Methods ; Cyclopropane Reaction Mechanisms
Authors: Ignacio Poblete‐Castro | Carla Aravena-Carrasco | Matias Orellana‐Saez | Nicolas Dos Santos Pacheco | Alex Cabrera | José Manuel Borrero‐de Acuña
Source: Frontiers in Bioengineering and Biotechnology (article, 2020-03-05)
Field: Materials Science — Biomaterials

Engineering the Osmotic State of Pseudomonas putida KT2440 for Efficient Cell Disruption and Downstream Processing of Poly(3-Hydroxyalkanoates) In the last decade, the development of novel programmable cell lytic systems based on different inducible genetic constructs like the holin-endolysin and lysozyme appears as a promising alternative to circumvent the use of costly enzymes and mechanical disrupters for downstream processing of intracellular microbial products. Despite the advances, upon activation of these systems the cellular disruption of the biocatalyst occurs in an extended period, thus delaying the recovery of poly(3-hydroxyalkanoate) (PHA). Herein the osmotic state of Pseudomonas putida KT2440 was engineered by inactivating the inner-membrane residing rescue valve MscL, which is responsible mainly for circumventing low-osmolarity challenges. Then the major outer membrane porin OprF and the specific porin OprE were overproduced during PHA producing conditions on decanoate-grown cells. The engineered P. putida strains carrying each porin showed no impairment on growth rate and final biomass and PHA yield after 48 h cultivation. Expression of both porins in tandem in the mutant strain KTmscL-oprFE led to a slight reduction of the biomass synthesis (10%) but higher PHA accumulation (%wt) relative to the cell dry mass. Each strain was then challenged to an osmotic upshift for 1 h and subsequently to a rapid passage to a hypotonic condition where the membrane stability of the KTmscL-oprFE suffered damage, resulting in a rapid reduction of cell viability. Cell disruption accounted for more than 95% of the cell population within 3 hours as reported by colony forming units, FACS analyses, and transmission electron microscopy. PHA recovery yielded 94.2% of the biosynthesized biopolymer displaying no significant alterations on the final monomer composition. This study can serve as an efficient genetic platform for the recovery of any microbial intracellular compound allowing less unit operation steps for cellular disruption. Pseudomonas putida ; Downstream processing ; Downstream (manufacturing) ; Chemistry ; Osmotic shock ; Chromatography ; Biochemistry ; Engineering ; Operations management biodegradable polymer synthesis and properties ; Biopolymer Synthesis and Applications ; Microplastics and Plastic Pollution
Authors: Caizhen Yao | Shizhen Xu | Xiaodong Jiang | Jiaxuan Chen | Xiaodong Yuan
Source: Journal of Chemistry (article, 2020-07-31)
Field: Materials Science — Surfaces, Coatings and Films

A Simple Way to Achieve Self-Cleaning Surfaces with Unique Antifouling Property Self-cleaning surfaces may have wide applications such as microfluidic devices, lab-on-a-chip, sensors, microreactors, air purification, and antimicrobial fields. In this article, by using a combination of femtosecond (fs) laser irradiation and fluorination technique, self-cleaning stainless steel surfaces with unique antifouling property were obtained. New insight is developed through a detailed analysis of the antifouling behavior of the self-cleaning surfaces. The surface free energy and its polar and disperse components were calculated by using the Owens–Wendt-–Rabel–Kaelble (OWRK) method. X-ray photoelectron spectroscopy was employed to analyse the surface elemental compositions and functional groups. The antifouling property of the surface was recorded by using a high speed camera. Water sliding angles (SAs) were reduced by fluorination treatment, resulting in low adhesive superhydrophobic surfaces with the self-cleaning property. The influences of micro/nanostructures, fluorination, and their combination on the surface free energy were investigated. The interaction process between water droplets and pollutants (inorganic and organic particles) on the treated surface was explored. The antifouling property of an optimized specimen (CA = 162° and SA = 1°) was tested and compared with the untreated sample. Biofouling ; Chemistry ; X-ray photoelectron spectroscopy ; Contact angle ; Surface energy ; Microreactor ; Nanotechnology ; Femtosecond ; Nanostructure ; Chemical engineering ; Laser ; Materials science ; Optics ; Organic chemistry Surface Modification and Superhydrophobicity ; Laser-induced spectroscopy and plasma ; Laser Material Processing Techniques
Authors: Ioannis Koutsamanis | Martin Spoerk | Florian Arbeiter | Rafael Johannes-Paul Eder | Eva Roblegg
Source: Polymers (article, 2020-12-10)
Field: Materials Science — Biomaterials

Development of Porous Polyurethane Implants Manufactured via Hot-Melt Extrusion Implantable drug delivery systems (IDDSs) offer good patient compliance and allow the controlled delivery of drugs over prolonged times. However, their application is limited due to the scarce material selection and the limited technological possibilities to achieve extended drug release. Porous structures are an alternative strategy that can overcome these shortcomings. The present work focuses on the development of porous IDDS based on hydrophilic (HPL) and hydrophobic (HPB) polyurethanes and chemical pore formers (PFs) manufactured by hot-melt extrusion. Different PF types and concentrations were investigated to gain a sound understanding in terms of extrudate density, porosity, compressive behavior, pore morphology and liquid uptake. Based on the rheological analyses, a stable extrusion process guaranteed porosities of up to 40% using NaHCO<sub>3</sub> as PF. The average pore diameter was between 140 and 600 µm and was indirectly proportional to the concentration of PF. The liquid uptake of HPB was determined by the open pores, while for HPL both open and closed pores influenced the uptake. In summary, through the rational selection of the polymer type, the PF type and concentration, porous carrier systems can be produced continuously via extrusion, whose properties can be adapted to the respective application site. Extrusion ; Porosity ; Materials science ; Die swell ; Polyurethane ; Rheology ; Porous medium ; Polymer ; Chemical engineering ; Drug delivery ; Composite material ; Nanotechnology Electrospun Nanofibers in Biomedical Applications ; Polymer composites and self-healing ; Polymer Foaming and Composites
Authors: Hidetoshi Miyazaki | Osman Murat Özkendir | Selen Günaydın | Kosuke Watanabe | Kazuo Soda | Yoichi Nishino
Source: Scientific Reports (article, 2020-11-13)
Field: Materials Science — Materials Chemistry

Probing local distortion around structural defects in half-Heusler thermoelectric NiZrSn alloy The half-Heusler NiZrSn (NZS) alloy is particularly interesting owing to its excellent thermoelectric properties, mechanical strength, and oxidation resistance. However, the experimentally investigated thermal conductivity of half-Heusler NZS alloys shows discrepancies when compared to the theoretical predictions. This study investigates the crystal structure around atomic defects by comparing experimental and theoretical X-ray absorption fine structure (XAFS) spectra of the crystal structure of a half-Heusler NZS alloy. The results of both Zr and Ni K-edge XAFS spectra verified the existence of atomic defects at the vacancy sites distorting the C1<sub>b</sub>-type crystal structure. We concluded that the distortion of the atoms around the interstitial Ni disorder could be the probable reason for the observed lower thermal conductivity values compared to that predicted theoretically in half-Heusler alloys. Our study makes a significant contribution to the literature because the detailed investigation of the lattice distortion around atomic defects will pave the way to further reduce the thermal conductivity by controlling this distortion. Materials science ; X-ray absorption fine structure ; Thermoelectric effect ; Alloy ; Thermal conductivity ; Crystal structure ; Crystal (programming language) ; Distortion (music) ; Condensed matter physics ; Vacancy defect ; Crystallography ; Metallurgy ; Thermodynamics ; Chemistry ; Composite material ; Spectroscopy ; Optoelectronics ; Physics Advanced Thermoelectric Materials and Devices ; Thermal properties of materials ; Machine Learning in Materials Science
Authors: Yiming Niu | Hiroshi Suzuki | Christopher J. Hosford | Thomas Walz | Joshua S. Chappie
Source: Nature Communications (article, 2020-11-20)
Field: Materials Science — Materials Chemistry

Structural asymmetry governs the assembly and GTPase activity of McrBC restriction complexes McrBC complexes are motor-driven nucleases functioning in bacterial self-defense by cleaving foreign DNA. The GTP-specific AAA + protein McrB powers translocation along DNA and its hydrolysis activity is stimulated by its partner nuclease McrC. Here, we report cryo-EM structures of Thermococcus gammatolerans McrB and McrBC, and E. coli McrBC. The McrB hexamers, containing the necessary catalytic machinery for basal GTP hydrolysis, are intrinsically asymmetric. This asymmetry directs McrC binding so that it engages a single active site, where it then uses an arginine/lysine-mediated hydrogen-bonding network to reposition the asparagine in the McrB signature motif for optimal catalytic function. While the two McrBC complexes use different DNA-binding domains, these contribute to the same general GTP-recognition mechanism employed by all G proteins. Asymmetry also induces distinct inter-subunit interactions around the ring, suggesting a coordinated and directional GTP-hydrolysis cycle. Our data provide insights into the conserved molecular mechanisms governing McrB family AAA + motors. Asymmetry ; GTPase ; Computational biology ; Biology ; Cell biology ; Physics Enzyme Structure and Function ; Microtubule and mitosis dynamics ; DNA Repair Mechanisms
Authors: А. В. Букетов | S. O. Smetankin | Eduard Lysenkov | Kyrylo Yurenin | Олександр Акімов | Serhii Yakushchenko | Iryna Lysenkova
Source: Advances in Materials Science and Engineering (article, 2020-01-01)
Field: Materials Science — Materials Chemistry

Electrophysical Properties of Epoxy Composite Materials Filled with Carbon Black Nanopowder The effect of carbon black (CB) nanopowder on the electrical properties of polymer composite systems based on the epoxy resin is investigated using the method of impedance spectroscopy. It is established that the electrical and dielectric properties of the studied systems significantly depend on the nanofiller content. It is found that electrical conductivity and dielectric constant exhibit percolation behavior when the filler’s content increases. In this case, the electrical conductivity increases exponentially, indicating the formation of filler electrically conductive mesh inside the polymer matrix. A small jump in electrical conductivity when reaching the percolation threshold indicates the formation of indirect contacts between the particles. The value of the percolation threshold of conductivity is 8%. It is shown that the dielectric constant of epoxy nanosystems is almost unchanged in the frequency range of 10 2 –10 5 Hz. It is related to the structural features of the filler particles, which ensure the existence of a minimal dielectric gradient between the matrix and the filler. It is found that the dielectric constant of the studied systems also shows percolation behavior. The obtained material based on the epoxy matrix is characterized by a high value of dielectric constant, which at a carbon black nanopowder content of 29% is 4680. This material is characterized by relative frequency invariance and a high value of dielectric constant, so it has great potential for practical application. Materials science ; Dielectric ; Epoxy ; Percolation threshold ; Composite material ; Carbon black ; Conductivity ; Percolation (cognitive psychology) ; Electrical resistivity and conductivity ; Composite number ; Dielectric spectroscopy ; Polymer ; Electrode Carbon Nanotubes in Composites ; Material Properties and Applications ; Dielectric materials and actuators
Authors: Anastasya Shilova | Hugo Lebrette | Oskar Aurelius | Jie Nan | M. Welin | Rebeka Kovačič | Swagatha Ghosh | Cecilia Safari | Ross J. Friel | Mirko Milas | Zdeněk Matěj | Martin Högbom | Gisela Brändén | Marco Kloos | Robert L. Shoeman | Bruce Doak | Thomas Ursby | M. Håkansson | Derek T. Logan | U. Müeller
Source: Journal of Synchrotron Radiation (article, 2020-08-21)
Field: Materials Science — Materials Chemistry

Current status and future opportunities for serial crystallography at MAX IV Laboratory Over the last decade, serial crystallography, a method to collect complete diffraction datasets from a large number of microcrystals delivered and exposed to an X-ray beam in random orientations at room temperature, has been successfully implemented at X-ray free-electron lasers and synchrotron radiation facility beamlines. This development relies on a growing variety of sample presentation methods, including different fixed target supports, injection methods using gas-dynamic virtual-nozzle injectors and high-viscosity extrusion injectors, and acoustic levitation of droplets, each with unique requirements. In comparison with X-ray free-electron lasers, increased beam time availability makes synchrotron facilities very attractive to perform serial synchrotron X-ray crystallography (SSX) experiments. Within this work, the possibilities to perform SSX at BioMAX, the first macromolecular crystallography beamline at MAX IV Laboratory in Lund, Sweden, are described, together with case studies from the SSX user program: an implementation of a high-viscosity extrusion injector to perform room temperature serial crystallography at BioMAX using two solid supports - silicon nitride membranes (Silson, UK) and XtalTool (Jena Bioscience, Germany). Future perspectives for the dedicated serial crystallography beamline MicroMAX at MAX IV Laboratory, which will provide parallel and intense micrometre-sized X-ray beams, are discussed. Beamline ; Synchrotron ; Synchrotron radiation ; Linear particle accelerator ; Diffraction ; Injector ; Materials science ; Beam (structure) ; Optics ; Mechanical engineering ; Physics ; Engineering Enzyme Structure and Function ; Biochemical and Molecular Research ; Protein Structure and Dynamics
Authors: Miguel Vega-Castellote | Dolores Pérez‐Marín | Irina Torres | José-Manuel Moreno-Rojas | María‐Teresa Sánchez
Source: Journal of Food Engineering (article, 2020-11-12)
Field: Chemistry — Analytical Chemistry

Exploring the potential of NIRS technology for the in situ prediction of amygdalin content and classification by bitterness of in-shell and shelled intact almonds Amygdalin ; Partial least squares regression ; Linear discriminant analysis ; Chemistry ; Receiver operating characteristic ; Mathematics ; Food science ; Artificial intelligence ; Pattern recognition (psychology) ; Statistics ; Computer science Spectroscopy and Chemometric Analyses ; Cassava research and cyanide ; Isotope Analysis in Ecology
Authors: Zhijin Zhang | Tian Liang | Chen Li | Xingliang Jiang | Jian Wu | Bin Wu
Source: Polymers (article, 2020-02-04)
Field: Materials Science — Materials Chemistry

Electrical Strength and Physicochemical Performances of HTV Silicone Rubber under Salt-Fog Environment with DC Energized In recent years, the performances of rubber composite insulators, which operate in the coastal foggy regions, have attracted researchers' concern because of the observation of their degradation. In this paper, salt-fog experiments with DC test voltage of high-temperature vulcanized (HTV) silicone rubber (SR) have been conducted. The electrical strength and material performances of samples with salt-fog treatment were focused on. The DC flashover voltage, hydrophobicity, scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and dielectric parameter were investigated. It was found that the samples' performances deteriorated after salt-fog treatment. The DC flashover voltage of HTV SR decreased in the salt-fog environment. The hydrophobicity of the material deteriorated and the static contact angle (CA) became small. Under the action of electric and thermal stress, the surface of samples after salt-fog treatment became rough and porous. The absorption peak of the hydrophobic groups decreased, indicating that the molecular chain of SR material was broken, and the filler was consumed, bringing down the arc resistance of the sample. The absorption of moisture further led to insulation performance loss and then reduced the electrical strength of the material. Degradation of physicochemical properties will eventually lead to a decline in electrical strength. Materials science ; Composite material ; Vulcanization ; Silicone rubber ; Contact angle ; Fourier transform infrared spectroscopy ; Arc flash ; Absorption of water ; Scanning electron microscope ; Electrolyte ; Natural rubber ; Chemical engineering ; Chemistry ; Insulator (electricity) High voltage insulation and dielectric phenomena ; Power Transformer Diagnostics and Insulation ; Dielectric materials and actuators
Authors: Philippe Schwaller | Alain C. Vaucher | Teodoro Laino | Jean‐Louis Reymond
Source: ChemRxiv (preprint, 2020-10-11)
Field: Materials Science — Materials Chemistry

Prediction of Chemical Reaction Yields using Deep Learning Artificial intelligence is driving one of the most important revolutions in organic chemistry. Multiple platforms, including tools for reaction prediction and synthesis planning based on machine learning, successfully became part of the organic chemists' daily laboratory, assisting in domain-specific synthetic problems. Unlike reaction prediction and retrosynthetic models, the prediction of reaction yields has received less attention in spite of the enormous potential of accurately predicting reaction conversion rates. Reaction yields models, describing the percentage of the reactants converted to the desired products, could guide chemists and help them select high-yielding reactions and score synthesis routes, reducing the number of attempts. So far, yield predictions have been predominantly performed for high-throughput experiments using a categorical (one-hot) encoding of reactants, concatenated molecular fingerprints, or computed chemical descriptors. Here, we extend the application of natural language processing architectures to predict reaction properties given a text-based representation of the reaction, using an encoder transformer model combined with a regression layer. We demonstrate outstanding prediction performance on two high-throughput experiment reactions sets. An analysis of the yields reported in the open-source USPTO data set shows that their distribution differs depending on the mass scale, limiting the dataset applicability in reaction yields predictions. Computer science ; Categorical variable ; Artificial intelligence ; Yield (engineering) ; Machine learning ; Chemistry ; Biological system ; Materials science Machine Learning in Materials Science ; Computational Drug Discovery Methods ; Advanced Text Analysis Techniques