jablonkagroup/rise_ai_scientists huggingface dataset:
Authors: Amy Marie Jehl
Source: eScholarship (California Digital Library) (article, 2019-01-01)
Field: Chemistry — Organic Chemistry

N-Heterocyclic Silyl and Silylene Metal Complexes Within a PSiP Framework: Synthesis, Structure and Reactivity N-heterocyclic carbenes (NHC) are strong Lewis bases that have demonstrated broad utility as ligands for transition metal (TM) catalysts. Silicon analogues, N-heterocyclic silylenes (NHSi), are comparatively less well studied. The decreased π–π overlap between the Si 3p orbital and adjacent nitrogen lone pairs creates a more accessible vacant orbital on Si, resulting in increased ambiphilic character. When bound to a transition metal, this empty orbital presents an opportunity to cooperatively bind and activate substrate molecules. To increase the stability of a potential metal–silylene complex we targeted the diphosphine ligand precursor 1,2-bis(R2PCH2NCH2)C6H4 (R = alkyl or aryl), first reported by Yamashita and Nozaki in the construction of a boron-anchored pincer. Reported here are (PCy)2Si pincer ligands and their TM–silylene complexes for small molecule activation.The bimetallic dinickel disilylene complex, (PCy)4Ni2Si2, is reactive with dihydrogen, phenol, thiophenol and diphenyl disulfide, resulting in addition of the E–H or E–E bond (E = H, O, or S) across the Ni2Si2 core and the conversion of the silylene ligands to bridging silyls. We also investigated the reactivity of (PCy)4Ni2Si2 with CO2. Addition of excess CO2 to (PCy)4Ni2Si2 revealed a new product, (PCy)4Ni2(µ-CO)Si2O, featuring a bridging CO across the two Ni centers and a Si–O–Si linkage. This product corresponds to the direct deoxygenation of CO2 and the transfer of the oxygen atom to the silylene ligands. CO dissociation is observed under certain conditions to give an oxo-bridged 16 e– (PCy)4Ni2(Si2O) complex that can also be synthesized via direct O-atom transfer to (PCy)4Ni2Si2. A transient side-bound CO2 intermediate was hypothesized to initially form across one of the two Ni0–silylene interactions prior to C=O bond cleavage and the formation of (PCy)4Ni2(µ-CO)Si2O. Trapping experiments with TMSCl support this hypothesis, as an intermediate can be isolated, (PCy)4NiClNi(CO)Si2O-TMS, featuring a terminal Ni–CO and a trimethylsiloxyl moiety on one of the two Si centers, suggesting the cooperativity of the Ni–Si bond in activating CO2. This work highlights the promise of using TM–silylene interactions for the cooperative activation of small molecules. Silylene ; Chemistry ; Pincer movement ; Reductive elimination ; Reactivity (psychology) ; Lone pair ; Medicinal chemistry ; Oxidative addition ; Stereochemistry ; Aryl ; Photochemistry ; Catalysis ; Molecule ; Alkyl ; Organic chemistry ; Silicon Organoboron and organosilicon chemistry ; Synthesis and characterization of novel inorganic/organometallic compounds ; Organometallic Complex Synthesis and Catalysis
Authors: Cindy Gomes Correia
Source: Oskar-Bordeaux (Universite de Bordeaux) (preprint, 2019-12-13)
Field: Materials Science — Materials Chemistry

Directed self-assembly strategies for orientation-controlled block copolymers for advanced lithography. L’objectif de ce travail était de mettre en évidence le potentiel du PDMSBb-PS pour des applications en nanolithographie avancée. Pour cela, nous avons fourni une compréhension du comportement d’auto-assemblage du PDMSB-b-PS en masse et en film mince. Nous avons réalisé l’auto-assemblage de ce copolymère semicristallin en cylindre et gyroïde bien définis avec des périodicités inférieures à 20 nm grâce à un paramètre d’interaction de Flory-Huggins élevé (Chapitre 2). Nous avons par la suite proposé une approche pour obtenir des lamelles perpendiculaires du PDMSB-b-PS en film mince grâce à l’utilisation de sur-couches neutres réticulables. La polyvalence de cette approche a été démontrée à l’aide de CPBs de masses moléculaires différentes et s’est ensuite étendue à la formation d’empilements via un processus d’auto-assemblage itératif (chapitre 3). Enfin, nous avons réticulé la surcouche neutre à l’aide d’agents photo-sensibles ce qui nous a permis d’obtenir un motif par photolithographie au-dessus du film CPB. Ainsi, il a été possible de contrôler l’orientation du CPB à des endroits spécifiques du film (Chapitre 4). Copolymer ; Lithography ; Orientation (vector space) ; Self-assembly ; Materials science ; Block (permutation group theory) ; Nanotechnology ; Computer science ; Polymer ; Optoelectronics ; Composite material ; Mathematics ; Geometry Block Copolymer Self-Assembly ; Advanced Polymer Synthesis and Characterization ; Advancements in Photolithography Techniques
Authors: Michele Cascio | Ioannis Deretzis | Giuseppe Fisicaro | G. Falci | Giovanni Mannino | Antonino La Magna
Source:  (article, 2019-12-19)
Field: Materials Science — Materials Chemistry

Tailoring Active Defect Centers During the Growth of Group IV Crystals Defects, e.g., Vacancies (Vs) and Defect-impurity centers, e.g., Nitrogen-Vacancy complexes (NVs), in group IV materials (diamond, SiC, graphene) are unique systems for Quantum Technologies (QT). The control of their positioning is a key issue for any realistic QT application and their tailored inclusion during controlled crystal-growth processes could overcome the limitations of other incorporation methods (e.g., ion implantation causing strong lattice damage). To date, the atomistic evolution regarding the growth of group IV crystals is barely known and this missing knowledge often results in a lack of process control in terms of mesoscopic crystal quality, mainly concerning the eventual generation of local or extended defects and their space distribution. We have developed Kinetic Monte Carlo models to study the growth kinetics of materials characterized by sp 3 bonding symmetries with an atomic-level accuracy. The models can be also coupled to the continuum simulation of the gas-phase status generated in the equipment to estimate the deposition rate and reproduce a variety of growth techniques (e.g., Chemical and Physical Vapour deposition, sublimation, etc.). Evolution is characterized by nucleation and growth of ideal or defective structures and their balance depends critically on process-related parameters. Quantitative predictions of the process evolution can be obtained and readily compared with the structural characterization of the processed samples. In particular, we can describe the surface state of the crystal and the defect generation/evolution (for both point and extended defects, e.g., stacking faults) as a function of the initial substrate conditions and the process parameters (e.g., temperature, pressure, gas flow). Kinetic Monte Carlo ; Materials science ; Nucleation ; Vacancy defect ; Chemical physics ; Crystallographic defect ; Sublimation (psychology) ; Diamond ; Chemical vapor deposition ; Crystal growth ; Mesoscopic physics ; Crystallography ; Nanotechnology ; Monte Carlo method ; Chemistry ; Condensed matter physics ; Thermodynamics ; Metallurgy ; Physics Diamond and Carbon-based Materials Research ; Semiconductor materials and devices ; Thermal properties of materials
Authors: Ashley Burns
Source: Aquila Digital Community (University of Southern Mississippi) (article, 2019-01-01)
Field: Chemistry — Spectroscopy

Towards the Synthesis of an Artificial Fluorescent Siderophore Siderophores are molecules capable of binding ferric ions with high affinity (Ka = 1052). This thesis outlines our attempts to synthesize an artificial siderophore, which incorporates a signaling group to help monitor the uptake of ferric ions. The artificial siderophore is a tripodal molecular receptor synthesized in a five-step procedure with a proposed final sixth step. Rhodamine 6G azide (95.0% yield) was formed from rhodamine 6G and the synthesis of 2-azidoethanamine was modified from the literature. The tripodal arm portion of the sensor was successfully synthesized by protecting the catechol of 2,3-dihydroxybenzaldehyde to form 3-formyl-1,2-phenylene dimethanesulfonate (98.8% yield). The reduction of the aldehyde in the previous compound to a primary alcohol formed 3-(hydroxymethyl)-1,2-phenylene dimethanesulfonate (86.6% yield), which then underwent a nucleophilic substitution to yield 3-(bromomethyl)-1,2-phenylene dimethanesulfonate (80.0% yield). The product of the nucleophilic substitution then successfully underwent a bimolecular nucleophilic substitution to yield the mesyl protected tripodal arm (76.8% yield). Siderophore ; Fluorescence ; Computer science ; Artificial intelligence ; Biology ; Bacteria ; Physics ; Genetics Molecular Sensors and Ion Detection ; Supramolecular Chemistry and Complexes ; Luminescence and Fluorescent Materials
Authors: Jianan Li
Source: D-Scholarship@Pitt (University of Pittsburgh) (article, 2019-09-27)
Field: Materials Science — Materials Chemistry

GRAPHENE-COMPLEX OXIDE HETEROSTRUCTURE Graphene and complex-oxide heterostructures are both 2D systems that have initiated numerous research areas. The two-dimensional electron gas (2DEG) in both systems differs in many ways from traditional semiconductor materials. This research is dedicated to integrating these two versatile systems. Conventionally, the transfer of graphene grown by chemical vapor deposition is assisted by poly(methyl methacrylate) (PMMA). A new transfer method is developed in this research and can protect the graphene against contaminations. The graphene transferred onto the complex-oxide heterostructure substrates using such method is atomically clean with high mobility. Conductive atomic force microscope (c-AFM) writing technique is applied to graphene-complex-oxide heterostructure to reversibly control the charge-neutrality point (CNP) with nanoscale resolution, utilizing the tunability of the complex-oxide substrate. The local electron density and conductivity of the complex-oxide heterostructure interface can be patterned with the c-AFM tip, and the CNP of the proximal graphene is shifted. With this effect, the mixing of edge state in quantum Hall regime on the edge of graphene p-n junctions can be reversibly controlled. Quantization of resistance is observed as a result of the mixing at low temperature, depending on the directions of currents and magnetic fields. Nanoscale devices such as superlattices can also be produced on various two-dimensional material heterostructure by combining these two techniques. Graphene ; Heterojunction ; Materials science ; Oxide ; Nanotechnology ; Graphene oxide paper ; Optoelectronics ; Graphene nanoribbons ; Chemical vapor deposition ; Semiconductor ; Substrate (aquarium) ; Quantum dot Graphene research and applications ; Quantum and electron transport phenomena ; Surface and Thin Film Phenomena
Authors: Jaekyung Koh
Source: eScholarship (California Digital Library) (article, 2019-01-01)
Field: Materials Science — Biomaterials

Enhanced stem cell niche through microporous annealed particle scaffolds Although stem cell therapy holds promises for intractable diseases, its efficacy has been limited by low retention and function of transplanted cells. Two of the key challenges for cell-based therapies are localization and cell function control once injected in a patient. Co-delivery of cells with hydrogels can mitigate these issues by localizing cells at a disease site and enhancing retention. However, the gold standard method, in situ gelation after injection with cells, confines transplanted cells and secreted therapeutic molecules within scaffolds due to the nanoporous nature of the hydrogel mesh. Confined cells are confounded from participating in regeneration, leading to poor outcomes. Moreover, it has been challenging to modulate the biophysical properties of such hydrogels independently from porosity for effective stem cell functional control.Here we show that microparticle scaffolds that can be co-injected locally with therapeutic cells and assembled in situ to generate a stem cell niche with interconnected microscale pore networks automatically formed in the void space between packed spherical particles. This approach enables enhanced migration and cell-cell connections between cells and transport of therapeutic molecules as well as higher cell proliferation in vitro and retention in vivo. Another key point is the modulation of biophysical properties independently from microporosity. Our scaffold provides a tunable porous environment by changing the physical properties of hydrogel building blocks. Using this platform technology, we demonstrated increased cell activity, such as proliferation and secretion, while the microporosity of the scaffolds induced tissue infiltration and vascularization. This approach achieves localized delivery of stem cells in a non-invasive manner creating a highly-tunable stem cell niche in situ which we envision can advance stem cell therapies as well as other cell-based therapies. Stem cell ; Self-healing hydrogels ; Scaffold ; Nanotechnology ; Cell ; Materials science ; In vivo ; Microscale chemistry ; Chemistry ; Microporous material ; Cell biology ; Biophysics ; Biomedical engineering ; Biology ; Medicine ; Composite material ; Biochemistry Electrospun Nanofibers in Biomedical Applications
Authors: Dumitru Petru Iga | Dumitru Popescu | Silvia Gitman
Source: Revista de Chimie (article, 2019-12-14)
Field: Chemistry — Organic Chemistry

Alternate Modulation of Biological Activity of Stress Molecule, b-D-glucopyranosyl-cholesterol, by Chemical Modification of Sugar Moiety. Hypotheses concerning biochemical meaning of the new glycosides We have synthesized, beside the presently consecrated stress molecule, b-D-glucopyranosyl-cholesterol, b-D-arabinopyranosyl-, a-L-arabinofuranosyl- and b- and a-D-(3-O-methyl)glucopyranosyl-cholesterol. Two types of glycosylation agents were used: peracylated sugar bromide, with CdCO3 as promotor, and peracetylated sugar in the presence of BF3·OBu2 as promoting agent, respectively. A chemical test was used for synthesis monitoring: Zemplén saponification of reaction mixture had to produce an amphiphilic glycoside migrating in the region of cerebrosides, by TLC in a suitable solvent system. All intermediates and final products have been characterized by 1H and 13C NMR spectroscopy as well as by chemical and chromatographical methods. In the virtue of the recently discovered biochemical relationships of cholesterol and cerebrosides (or glycosterols and ceramide) new biochemical hypotheses have been advanced concerning the meaning of these new glycosides. Keywords: L-arabinopyranose, L-arabinofuranose, 3-O-methyl D-glucose, cholesterol, glycosterol, NMR spectra Chemistry ; Glycoside ; Glycosylation ; Saponification ; Moiety ; Chemical structure ; Stereochemistry ; Molecule ; Bromide ; Organic chemistry ; Sugar ; Biochemistry Carbohydrate Chemistry and Synthesis ; Analytical Chemistry and Chromatography ; Diet, Metabolism, and Disease
Authors: María J. Hortigüela | Igor Bdikin | Gonzalo Otero‐Irurueta
Source: Thin Solid Films (article, 2019-10-12)
Field: Materials Science — Materials Chemistry

Thermal vapor sulfurization of molybdenum layers Molybdenum ; Thermal ; Materials science ; Mineralogy ; Metallurgy ; Thermodynamics ; Chemistry ; Physics 2D Materials and Applications ; MXene and MAX Phase Materials ; Perovskite Materials and Applications
Authors: Merlin von Soosten | Dennis Valbjørn Christensen | Chang‐Beom Eom | Thomas Sand Jespersen | Yunzhong Chen | Nini Pryds
Source: Scientific Reports (preprint, 2019-11-29)
Field: Materials Science — Materials Chemistry

On the emergence of conductivity at SrTiO3-based oxide interfaces – an in-situ study Abstract Heterostructures and crystal interfaces play a major role in state-of-the-art semiconductor devices and play a central role in the field of oxide electronics. In oxides the link between the microscopic properties of the interfaces and bulk properties of the resulting heterostructures challenge our fundamental understanding. Insights on the early growth stage of interfaces and its influence on resulting physical properties are scarce - typically the information is inferred from post growth characterization. Here, we report on real time measurements of the transport properties of SrTiO 3 -based heterostructures at room temperature, while the heterostructure is forming. Surprisingly, we detect a conducting interface already at the initial growth stage, much earlier than the well-established critical thickness limit for observing conductivity ex-situ after sample growth. We investigate how the conductivity depends on various physical processes occurring during pulsed laser depositions, including light illumination, particle bombardment by the plasma plume, interactions with the atmosphere and oxygen migration from SrTiO 3 to the thin films of varying compositions. We conclude that the conductivity in these room-temperature grown interfaces stem from oxygen vacancies with a concentration determined primarily by a balance between vacancy formation through particle bombardment and interfacial redox reaction and vacancy annihilation through oxidation. Using this approach, we propose a new design tool to control the electrical properties of interfaces in real time during their formation. Heterojunction ; Materials science ; Conductivity ; Semiconductor ; Oxide ; Optoelectronics ; Characterization (materials science) ; Nanotechnology ; Crystal (programming language) ; Chemical physics ; Chemistry ; Computer science ; Metallurgy Electronic and Structural Properties of Oxides ; Semiconductor materials and devices ; Ferroelectric and Negative Capacitance Devices
Authors: Paolo P. Mazzeo | Davide Balestri | Claudia Carraro | Roberto Perrone | Fabio Fornari | Federica Bianchi | Maria Careri | Paolo Pelagatti | Alessia Bacchi
Source: Acta Crystallographica Section A Foundations and Advances (article, 2019-08-18)
Field: Chemistry — Inorganic Chemistry

Controlled release of natural essential oils from microporous metal–organic framework Microporous material ; Metal-organic framework ; Natural (archaeology) ; Materials science ; Chemical engineering ; Metal ; Chemistry ; Organic chemistry ; Metallurgy ; Geology ; Adsorption ; Engineering Metal-Organic Frameworks: Synthesis and Applications ; Curcumin's Biomedical Applications ; Chemical Synthesis and Reactions
Authors: Dany Croteau
Source: Corpus Université Laval (Université Laval) (article, 2019-01-01)
Field: Materials Science — Biomaterials

Succession saisonnière et écophysiologie des diatomées arctiques : relation entre l'habitat, la niche lumineuse et la stratégie photoadaptative L’environnement lumineux de l’Océan Arctique est unique en raison d’interactions complexes entre la lumière et le couvert de glace de mer enneigé, et les oscillations de photopériodes extrêmes. Le succès des organismes photosynthétiques arctiques suggère donc des mécanismes de régulation flexibles qui permettent la survie lors de longues périodes d’obscurités, la capture de photons dans la pénombre sous la glace et la photoprotection rapide lors d’éclairements excessifs soudains. Les diatomées sont les producteurs primaires arctiques principaux. Elles exploitent le continuum de niches lumineuses induit par la transformation saisonnière de leur habitat au cours d’une succession de formes de vie sympagiques (glace) et planctoniques (eau). Lorsque la photosynthèse sature, les diatomées dissipent l’énergie lumineuse excessive en chaleur via le quenching non-photochimique (NPQ), principalement contrôlé par l’action du cycle des pigments xanthophylles (XC). Généralement, chez les diatomées, l’opération de ces mécanismes de photoprotection est finement adaptée à leur niche lumineuse. Cependant, peu d’études se sont intéressées aux souches arctiques, malgré les profonds contrastes de niches lumineuses qu’elles surmontent (glace, sous la glace, eaux de fontes, eaux libres). Ce manque de données entrave nos capacités à anticiper l’impact de l’intensification de l’environnement lumineux de l’océan Arctique, causée par la réduction de la superficie et de l’épaisseur du couvert neige-glace, sur l’intégrité écosystémique. Nous avons étudié les réponses à la lumière de cinq espèces de diatomées arctiques représentatives des différentes phases et habitats de leur succession saisonnière. Les espèces sympagiques ont exprimé une stratégie photoadaptative survivaliste, caractérisée par une croissance saturée à faible éclairement et un fort NPQ longuement maintenu à l’obscurité. Les espèces planctoniques ont montré une plus grande flexibilité d’exploitation de la lumière et une importante photoprotection activée par des éclairements intense et l’obscurité prolongée. Ces stratégies photoadaptatives divergentes gouverneront probablement des réponses hétérogènes à l’intensification de l’environnement lumineux arctique. Ecological succession ; Ecology ; Forestry ; Geography ; Biology Diatoms and Algae Research ; Polar Research and Ecology ; Isotope Analysis in Ecology
Authors: Muna S. Kassim | Sajeda Kareem Radhi | Ammar Fadhil Hussein Al-Maliki
Source: Thi-Qar University Journal for Engineering Sciences (article, 2019-06-01)
Field: Materials Science — Materials Chemistry

Experimental Study of Thermal Effect on Performance of PVC Pipes Using ANOVA Analysis In this study thermal effect at high pressure on Chlorinated Polyvinyl Chloride (CPVC) pipes studied where a test rig is built and the pipe has a diameter (d=0.5 in). The temperatures of water are varied (40, 60 and 80 cº) and the pressure is raised by using tester to reach (700 psi). The relationship between pressure and Reynolds number is discussed for the pipe used in this study with another pipe has a dimension (d= 0.75 in). ANOVA Analysis used to find the correlation of parameters effect the performance of CPVC pipes. The experimental results showed that the pressure drop increases with discharge increased at different values of temperature, when the pressure increased at constant temperature the friction losses is increased, where the values of friction losses were 4.8 ×10-4 , 8×10-4 and 2.4×10-3 mm at 100, 300 and 500 psi respectively. Thus the pipe is damage at pressure (500 psi) and temperature (80 Cº) when the thickness is (3.1 mm). Analysis of variance ; Thermal analysis ; Materials science ; Statistics ; Thermal ; Mathematics ; Thermodynamics ; Physics High voltage insulation and dielectric phenomena ; Intravenous Infusion Technology and Safety
Authors: Kevin Ramkissoon
Source: Carolina Digital Repository (University of North Carolina at Chapel Hill) (article, 2019-08-08)
Field: Chemistry — Spectroscopy

Integrated top-down and bottom-up mass spectrometry characterization of Escherichia coli ribosomal protein heterogeneity: identification of protein isoforms and post-translational modifications The bacterial genome exhibits notable plasticity but is relatively static when compared to the proteome. Protein expression can vary significantly depending on environmental factors, growth stage or stochastic processes within cells. This highly variable character, coupled with the large dynamic range of protein expression levels and the complexity achieved through processes such as post-translational modification (PTM), necessitate accurate, sensitive and high-throughput methods of analysis. The primary aim of this research was to develop an integrated experimental and analysis workflow that combines the analytical power of top-down and bottom-up mass spectrometry towards protein isoform and PTM characterization. We apply this approach to a comprehensive characterization of Escherichia coli ribosomal protein isoform heterogeneity. Our findings uncovered a significant level of heterogeneity in the post-translational modification of a number of ribosomal proteins, revealing a possible mechanism for the regulation of ribosomal protein function both within and beyond the ribosome. Escherichia coli ; Ribosomal protein ; Mass spectrometry ; Chemistry ; Gene isoform ; Ribosomal RNA ; Identification (biology) ; Ribosome ; Characterization (materials science) ; Biochemistry ; Computational biology ; Biology ; Chromatography ; Materials science ; Gene ; RNA ; Nanotechnology Mass Spectrometry Techniques and Applications ; RNA and protein synthesis mechanisms ; Advanced Proteomics Techniques and Applications