bluuebunny/crossref_metadata_2025_split huggingface dataset:
Calculation Approach for Ceramic Heat Pipe Heat Exchangers for High‐Temperature Applications
Authors: Unz Simon , Hack Nina , Beckmann Michael 
Published: July 2018

AbstractMetal materials show poor lifetime behavior under high‐temperature conditions and aggressive atmospheres. An alternative solution is the use of ceramic material, e.g., silicon carbide ceramics. These ceramics cannot be processed and joined like metal materials. For this reason, the simple geometry of a heat pipe can be used as a basic design for ceramic heat exchanger systems in the high‐temperature process technology for industrial and power plant applications. Heat pipes are hermetically sealed tubes filled with a working fluid. By transferring heat to one side and by releasing heat from the other side a two‐phase cycle is set up. For these apparatuses a numerical calculation model for a more exact determination of the working behavior of large units under high‐temperature conditions is introduced, considering both convective and radiative heat transfer.
Cereal phenolic contents as affected by variety and environment
Authors: Rao Shiwangni , Schwarz Lachlan J. , Santhakumar Abishek B. , Chinkwo Kenneth A. , Blanchard Christopher L. 
Published: July 2018

AbstractBackground and objectivesPhenolic compounds found in cereals have been shown to possess antioxidant activity that has ensured an increased interest in their health beneficial properties. This review analyzed studies investigating the phenolic content of rice, barley, oats, and sorghum grown in different geographical locations and the effect environmental factors have on them.FindingsFrom the studies reviewed, it was identified that whole grain pigmented cereals exhibited phenolic profiles with polyphenols such as anthocyanins, proanthocyanidins, and their derivatives that translated to higher total phenolic content and antioxidant activity. Variation in phenolic content was also observed in cereal species grown in different geographical locations and when subjected to variable levels of salinity, water, and temperature.ConclusionsDespite the increasing body of knowledge on the phenolic content of cereals, studies focusing on the effect of environment on cereal phenolic content are limited; hence, more research is warranted.Significance and noveltyThis review examines literature to provide a holistic understanding of how environment plays a role in the regulation of phenolic metabolites in cereals such as oats with a focus on pigmented varieties of rice, barley, and sorghum.
Hydrodynamics and Mass Transfer in a Lab‐Scale Stirred‐Pulsed Extraction Column
Authors: Soboll Sebastian , Kockmann Norbert 
Published: July 2018

AbstractAn extraction column with energy input through simultaneous stirring and pulsation allows for efficient countercurrent extraction on lab‐scale. While stirring generates small droplets with a narrow droplet size distribution, pulsation supports the axial transport of the dispersed phase, enabling countercurrent flow on this small scale. By studying the influence of several operating parameters, fundamental mechanics and characteristics of the column are revealed. Increasing the stirrer speed leads to smaller droplets and higher extraction performance as well as lower maximum throughput. The maximum throughput is increased by raising the pulsation intensity.
Effect of Isomerization on the Reversible Reaction of Hydrogenation‐Dehydrogenation of ortho‐Terphenyl on a Pt/C Catalyst
Authors: Kalenchuk Alexander N. , Bogdan Victor I. , Dunaev Sergei , Kustov Leonid M. 
Published: July 2018

AbstractReversible catalytic hydrogenation‐dehydrogenation reactions of ortho‐terphenyl (o‐terphenyl) as one of the most promising materials for hydrogen storage were investigated. The conversion of o‐terphenyl is 100 % and the selectivity to perhydro‐o‐terphenyl reaches 99 % in the first cycle of hydrogenation on a commercial Pt/C catalyst. The dehydrogenation process in a flow reactor is accompanied by the formation of isomerization products of o‐terphenyl, in particular, exhaustively and partially hydrogenated compounds formed from meta‐terphenyl (m‐terphenyl) and triphenylene. These substrates are subject to hydrogenation independently during the second hydrogenation cycle, which reduces the selectivity of recyclization of o‐terphenyl. Dodecahydrotriphenylene demonstrates a higher reactivity during the second cycle of dehydrogenation compared to perhydro‐o‐terphenyl. The amount of generated hydrogen is consistent with the kinetic data.
Emerging Considerations for the Future Development of Electrochemical Paper‐Based Analytical Devices
Authors: Paschoalino Waldemir J. , Kogikoski Sergio , Barragan José T. C. , Giarola Juliana F. , Cantelli Lory , Rabelo Thais M. , Pessanha Tatiana M. , Kubota Lauro T. 
Published: July 2018

AbstractMeeting the current needs for easier, more precise and faster analyses that also follow the principles of green analytical chemistry requires novel analytical chemistry strategies. Since the appearance in this century of the first device based on a paper platform, many studies have been presented in the literature, providing a wide range of designs and possibilities for the application of paper platforms to electroanalytical systems. This Review gives an overview of the field and can pave the way for the future development of electrochemical paper‐based analytical devices. We also present a critical point of view regarding what has been investigated and developed and what is still missing. This Review discusses the efforts made in the field related to important topics such as the choice of the paper substrate, the device construction process, the characterization of the device, and applications in different areas. In this way, we indicate some steps necessary for optimizing the design of the devices, with a focus on multidisciplinary collaborations that could move entire systems from the bench of the laboratory to the field.
Electron Transfer between the Gram‐Positive Enterococcus faecalis Bacterium and Electrode Surface through Osmium Redox Polymers
Authors: Pankratova Galina , Szypulska Ewelina , Pankratov Dmitry , Leech Dónal , Gorton Lo 
Published: July 2018

AbstractThe interaction between microorganisms that contain thick cell walls, such as the Gram‐positive bacterium Enterococcus faecalis, and conductive surfaces can be improved by using redox polymers as mediators. Herein, we report a detailed electrochemical characterization of the communication between E. faecalis cells and a series of osmium redox polymers with different redox potentials. The current generated from glucose oxidation by films containing osmium redox polymers and E. faecalis cells increase over time (28 h), owing to a decrease in charge‐transfer resistance within the films, possibly owing to improved penetration of the redox polymer within the bacterial cell wall.
Structure and Catalyst Effects on the Electrochemical Performance of Air Electrodes in Lithium‐Oxygen Batteries
Authors: Li Liangyu , Chen Chunguang , Chen Xiang , Zhang Xiuhui , Huang Tao , Yu Aishui 
Published: July 2018

AbstractThe lack of systematic understanding of the effects of architecture and catalysts on the electrochemical performance of lithium‐oxygen (Li−O2) batteries hinders the rational design of air electrodes. In this work, we design and synthesize two honeycomb‐like carbon‐based architectures (HCC‐100 and HCC‐500) using a hard template method. With the same amount of Mo2C catalyst loading, the electrochemical performance is compared. At a current density of 100 uA m−2, the discharge capacity of HCC‐100@Mo2C is approximately four times higher than that of HCC‐500@Mo2C m−2. This is attributed to a higher surface area and wider mesopore distribution. Compared to HCC‐100, the material without catalyst loading, the HCC‐100@Mo2C electrode shows a considerable improvement in terms of discharge capacities, cycling stability and capacity retention. The stability of the electrode is tested with IR and SEM analysis after cycling. The SEM micrographs show that discharge products of HCC‐100@Mo2C tend to form on the catalytic site, while the discharge products of HCC‐100 tend to form a thicker layer which could lead to the increased impedance. The results of IR indicate less Li2CO3 by‐product formation with HCC‐100@Mo2C.
Domino Insertion–Coupling Synthesis of Solid‐State Luminescent Propynylidene Indolones
Authors: Schönhaber Jan , D'Souza Daniel M. , Glißmann Tobias , Mayer Bernhard , Janiak Christoph , Rominger Frank , Frank Walter , Müller Thomas J. J. 
Published: July 2018

AbstractThe compound class of 3‐arylpropynylidene indolones, key intermediates in consecutive three‐component syntheses of various indole‐based chromophores with peculiar emission characteristics, are readily synthesized by a domino insertion–coupling synthesis with an electronically diverse substitution pattern in moderate to excellent yields. The title compounds are formed in E/Z‐ratios from 100:0 to 0:100. Besides structure elucidation by NMR‐spectroscopy and X‐ray structure analysis, DFT calculations have been employed to rationalize the observed stereoselectivity. The photophysical properties of 3‐arylpropynylidene indolones are characterized by intense, tunable, solid‐state emission of N‐substituted derivatives as quantified for drop‐cast films. The electronic ground state structure was corroborated by DFT and TD‐DFT calculations, showing that gradient‐corrected exchange and correlation PBE (Perdew–Burke–Ernzerhof) functionals can be successfully employed to correctly reproduce the observed absorption characteristics of merocyanine derivatives. The huge Stokes shifts strongly depend on the electronic substitution pattern as supported by Hammett–Taft correlations.
Highly Efficient Encapsulation and Phase Separation of Apolar Molecules by Magnetic Shell‐by‐Shell‐Coated Nanocarriers in Water
Authors: Luchs Tobias , Sarcletti Marco , Zeininger Lukas , Portilla Luis , Fischer Christian , Harder Sjoerd , Halik Marcus , Hirsch Andreas 
Published: July 2018

AbstractWe report on the development of a supramolecular nanocarrier concept that allows for the encapsulation and separation of small apolar molecules from water. The nanocarriers consist of shell‐by‐shell‐coated nanoparticles such as TiO2 and ferromagnetic Fe3O4. The first ligand shell is provided by covalently bound hexadecyl phosphonic acid (PAC16) and the second shell by noncovalently assembled amphiphiles rendering the hybrid architecture soluble in water. Agitation of these constructs with water containing the hydrocarbons G1–G4, the fluorescent marker G5, the polychlorinated biphenyl PCB 77, or crude oil leads to a very efficient uptake (up to 411 %) of the apolar contaminant. In case of the hybrids containing a Fe3O4 core, straightforward phase separation by the action of an external magnet is provided. The load can easily be released by a final treatment with an organic solvent.
Selective Synthesis of Tetrasubstituted Olefins by Copper‐Mediated Acetoxythiolation of Internal Alkynes: Scope and Mechanistic Studies
Authors: Villuendas Pedro , Ruiz Sara , Vidossich Pietro , Lledós Agustí , Urriolabeitia Esteban P. 
Published: July 2018

AbstractThe Cu‐mediated synthesis of tetrasubstituted olefins by the addition of an acetate group and a thiolate to an unactivated internal alkyne is described. The reaction is fully stereoselective, because only the E alkene is obtained. If the alkyne is asymmetric, the reaction also shows a very high degree of regioselectivity. The mechanism of the reaction is elucidated by DFT methods, which show that it takes place through Cu‐stabilized radical species. Calculations highlight the crucial role of the dimeric copper(II) diacetate in the process, as it generates the active species in which the sulfur center has an incipient thiyl radical character and accepting, through a series of changes in the oxidation states of the two copper centers, the two electrons released in the addition of two nucleophiles to the alkyne.
Thorium Oxo‐Clusters as Building Blocks for Open Frameworks
Authors: Falaise Clément , Kozma Karoly , Nyman May 
Published: July 2018

AbstractFundamental understanding of tetravalent actinide chemistry is essential to optimize many steps of the nuclear fuel cycle, as well as to predict actinide speciation in the environment. Herein, we report synthesis and structure of three open inorganic frameworks composed of Th4+‐oligomers and sulfate anions. The compounds [Th10O4(OH)8(SO4)12(H2O)18]⋅28 H2O (1), [Th9O4(OH)5(SO4)12(H2O)18]⋅ 1 TMA⋅18 H2O (2), and [Th8.5O4(OH)4(SO4)12(H2O)18]⋅2 TMA⋅n H2O (3) were obtained by slow evaporation of aqueous Th4+‐SO42− solutions, with variable SO42−:Th4+ ratios (SO42−:Th4+=1:1, 1.5:1 and 2:1 for 1, 2, and 3; TMA=tetramethylammonium). The structure of 1 features a neutral open framework architecture with two interpenetrating networks, built from Th6O4(OH)412+ hexamers and Th2(OH)26+ dimers, linked by sulfate anions. The complex anionic framework of 2 is built from hexamers, dimers, and monomers, with charge‐balancing TMA cations. Compound 3 is very similar to 2, but it is constructed only from hexamers and monomers. Small angle X‐ray scattering (SAXS) of the reaction solutions reveals pre‐assembled hexamer building units in the presence of sulfate, and underlines the key role of the sulfate‐oxoanion ligand on thorium polymerization processes.
Real‐Time Imaging of Ultrafast Charge Dynamics in Tetrafluoromethane from Attosecond Pump‐Probe Photoelectron Spectroscopy
Authors: Plésiat Etienne , Lara‐Astiaso Manuel , Decleva Piero , Palacios Alicia , Martín Fernando 
Published: July 2018

AbstractA pump‐probe experiment in the tetrafluoro‐methane (CF4) molecule has been theoretically simulated, allowing one to access electron dynamics in its natural time scale: the attosecond. The chosen pump and probe pulses can be currently produced in most attosecond laboratories. In this scheme, CF4 is first ionized by an extreme UV (XUV) attosecond pulse and the charge dynamics induced in the corresponding cation is probed with a few‐femtosecond visible light (VIS) pulse. We demonstrate that modulations in the calculated photoelectron spectra with the pump‐probe delay reflect the dynamics of the XUV‐induced electronic wave packet. In particular, from the analysis of these modulations in the interval of time delays where the pump and probe pulses do not overlap any more, one has access to the amplitudes and phases of the different components of the electronic wave packet generated by the attosecond pulse. These reflect a complex dynamics that basically consists of very fast charge fluctuations occurring all over the molecule without any preference for a particular molecular site.
Picturing the Membrane‐assisted Choreography of Cytochrome P450 with Lipid Nanodiscs
Authors: Barnaba Carlo , Ramamoorthy Ayyalusamy 
Published: July 2018

AbstractCytochrome P450, a family of monooxygenase enzymes, is organized as a catalytic metabolon, and requires enzymatic partners as well as environmental factors that tune its complex dynamic activity. P450 and its reducing counterparts are membrane‐bound proteins which are believed to dynamically interact to form functional complexes. Increasing experimental evidence signifies the role (s) of protein‐lipid interactions in P450’s catalytic function and efficiency. The challenges posed by the membrane have severely limited high‐resolution understanding of the molecular interfaces of these interactions. Nevertheless, recent NMR studies have provided piercing insights into the dynamic structural interactions that enable the function of P450. In this review, we will discuss different biomimetic approaches relevant to unveil molecular interplays at the membrane, focusing on our recent work on lipid‐nanodiscs. We also highlight the need to expand the use of nanodiscs, and the power of a combination of cutting‐edge solution and solid‐state NMR techniques, to study the dynamic structures of P450 as well as other membrane‐proteins.
Mechanical Cooperativity in DNA Cruciform Structures
Authors: Mandal Shankar , Selvam Sangeetha , Cui Yunxi , Hoque Mohammed Enamul , Mao Hanbin 
Published: July 2018

AbstractUnlike short‐range chemical bonds that maintain chemical properties of a biological molecule, long‐range mechanical interactions determine mechanochemical properties of molecules. Limited by experimental approaches, however, direct quantification of such mechanical interactions is challenging. Using magneto‐optical tweezers, herein we found torque can change the topology and mechanochemical property of DNA cruciform, a naturally occurring structure consisting of two opposing hairpin arms. Both mechanical and thermodynamic stabilities of DNA cruciforms increase with positive torque, which have been attributed to the topological coupling between DNA template and the cruciform. The coupling exists simultaneously in both arms of a cruciform, which coordinates the folding and unfolding of the cruciform, leading to a mechanical cooperativity not observed previously. As DNA torque readily varies during transcriptions, our finding suggests that DNA cruciforms can modulate transcriptions by adjusting their properties according to the torque.
Common raven movement and space use: influence of anthropogenic subsidies within greater sage‐grouse nesting habitat
Authors: Harju Seth M. , Olson Chad V. , Hess Jennifer E. , Bedrosian Bryan 
Published: July 2018

AbstractCommon raven (Corvus corax; hereafter “raven”) populations have increased dramatically in the western United States in recent years. Ravens benefit from human resources and are known predators of other avian species. We developed a raven study to determine how primary (large‐scale, high food density, and temporally consistent) anthropogenic subsidies influenced raven movement and space use during the raven and greater sage‐grouse (Centrocercus urophasianus) breeding season and within sagebrush habitat that is commonly used by greater sage‐grouse. We also examined how movement, space use, and anthropogenic subsidization differed among ravens in different breeding statuses. We hypothesized that breeding ravens would use small areas around their nest and that nonbreeding ravens would range widely in search of food. We expected that breeding ravens would frequently use anthropogenic structures and that both breeding and nonbreeding ravens would regularly visit primary point‐source subsidies (e.g., landfills and transfer stations). Twenty ravens were captured and GPS‐tagged between 2012 and 2014. We found that breeding ravens overwhelmingly built nests on anthropogenic structures (96–100%) and subsequently used small portions of the landscape intensively. Movement of nonbreeding ravens (distance average = 2783 m/h) and ravens who had failed nests (distance average = 1357 m/h) ranged widely. Breeding ravens visited highways and railroads inversely proportional to the distance between the nest and the nearest highway/railroad. Nonbreeding ravens regularly visited landfills and transfer stations, but breeding ravens did not (<0.1% of locations). We found that nonbreeding ravens travel widely to utilize primary point‐source subsidies, breeding ravens focus on areas near the nest, and ravens with failed nests switch to movement behaviors and space use similar to wide‐ranging nonbreeding ravens. These findings have implications for the management of ravens and anthropogenic subsidies in sagebrush landscapes to potentially reduce depredation of greater sage‐grouse nests.
Electrochemically Inspired Copper(II) Complex on Disposable Graphite Pencil Electrode for Effective Simultaneous Detection of Hypoxanthine, Xanthine, and Uric Acid
Authors: Odewunmi Nurudeen A. , Kawde Abdel‐Nasser , Ibrahim Mohamed 
Published: July 2018

AbstractA facile electrochemical method was developed by in‐situ electrochemical complexation of Cu(II) ions with uric acid (UA), xanthine (XA) and hypoxanthine (HXA) on the disposable graphite pencil electrode (DGPE) surface for sensitive and selective simultaneous determination of UA, XA and HXA in phosphate buffer solution (PBS, pH 7.00±0.20). Raman Spectroscopy revealed the fluorescence nature of the corresponding Cu(II) – complexes of phosphate ions, UA, XA and HXA on DGPE while Density Function Theory (DFT) calculation was used to estimate their binding energies which are responsible for the enhanced peaks of UA, XA, and HXA as a result of their stronger interaction with copper atoms than phosphate ions. Square wave voltammetry was used in the analytical part. The calculated limits of detections were 14.42 nM, 5.04 nM and 4.93 nM for UA, XA and HXA, respectively. Potential interferences showed almost no significant effect on the peaks of UA, XA, and HXA, and the developed method was successfully utilized for simultaneous determination of the three analytes on human serum and urine with impressive percentage recovery.
Study of prebiotic potential and antioxidant activity in Plantago spp. leaves after enzymatic hydrolysis with hemicellulase and xylanase
Authors: Lukova Paolina , Karcheva‐Bahchevanska Diana , Mollova Daniela , Nikolova Mariana , Mladenov Rumen , Iliev Ilia 
Published: July 2018

AbstractThe leaves of Plantago species have been known as a rich source of polysaccharides, polyphenols, and iridoids. In the recent years, some authors have examined the relative influence of carbohydrate compositions and polyphenols on their antioxidant and prebiotic activity. In this study enzymatic hydrolysis of Plantago major, Plantago lanceolata, and Plantago media leaves with hemicellulase and xylanase was carried out. The chemical composition of the enzyme‐derived hydrolysis products was determined. Their antioxidant activity was evaluated using 2,2‐diphenyl‐2‐picryl‐hydrazyl‐hydrate, ferric reducing antioxidant power, and cupric reducing antioxidant capacity assays. The utilization of the carbohydrate complex from the obtained hydrolysates to stimulate the production of certain glycohydrolases from Lactobacillus plantarum probiotic strains was investigated. The HPLC analysis of the hydrolysis products showed the presence of galactose and arabinose in 1:3 and 1:4 ratios. The highest concentration of total sugars was determined in P. major hydrolysates with hemicellulase (386.71 mg/g dry weight). The antioxidant activity according to the three methods was the highest in P. media hydrolysates, which correlated with their total phenolic concentration. L. plantarum S27 showed the highest values of α‐galactosidase activity at the 24‐h fermentation process when it was cultivated in a broth with the presence of P. major hydrolysates with hemicellulase and xylanase (0.129 U/mg and 0.133 U/mg, respectively).
Noise Phenomena in Electrochemical Impedance Spectroscopy of Polymer Electrolyte Membrane Electrolysis Cells
Authors: Elsøe K. , Kraglund M. R. , Grahl‐Madsen L. , Scherer G. G. , Hjelm J. , Jensen S. H. , Jacobsen T. , Mogensen M. B. 
Published: July 2018

AbstractIn this study, the origin of noise in electrochemical impedance spectroscopy (EIS) spectra measured on a variety of polymer electrolyte membrane electrolysis cells (PEMECs) has been investigated. EIS was measured during operation at various current densities of seven different PEMECs divided in five different cell types including both acidic PEMECs and alkaline PEMECs. The noise pattern differed between various types of cells and between cells of the same cell type. Integration time had no influence on the EIS noise level, whereas the AC amplitude seems to influence the EIS noise level. Other electrical noise sources influencing the EIS measurements have been studied with oscilloscope. No noise was observed at DC. A hypothesis explaining the relation between bubble formation during electrolysis and EIS noise is proposed based on the experimental findings.