bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mixing as a driver of temporal variations in river hydrochemistry: 2. Major and trace element concentration dynamics in the Andes‐Amazon transition
Authors: Baronas J. Jotautas , Torres Mark A. , Clark Kathryn E. , West A. Joshua 
Published: March 2017

AbstractVariations in riverine solute chemistry with changing runoff are used to interrogate catchment hydrology and to investigate chemical reactions in Earth's critical zone. This approach requires some understanding of how spatial and temporal averaging of solute‐generating reactions affect the dissolved load of rivers and streams. In this study, we investigate the concentration‐runoff (C‐Q) dynamics of a suite of major (Na, Mg, Ca, Si, K, and SO4) and trace (Al, Ba, Cd, Co, Cr, Cu, Fe, Ge, Li, Mn, Mo, Nd, Ni, Rb, Sr, U, V, and Zn) elements in nested catchments of variable size, spanning the geomorphic gradient from the Andes Mountains to the Amazon Foreland‐floodplain. The major elements exhibit various degrees of dilution with increasing runoff at all sites, whereas the concentrations of most trace elements either increase or show no relationship with increasing runoff in the three larger catchments (160–28,000 km2 area). We show that the observed main stem C‐Q dynamics are influenced by variable mixing of tributaries with distinct C‐Q relationships. Trace element C‐Q relationships are more variable among tributaries relative to major elements, which could be the result of variations in geomorphology, lithology, and hydrology of the subcatchments. Certain trace metals are also lost from solution during in‐channel processes (possibly related to colloidal size‐partitioning), which may exert an additional control on C‐Q dynamics. Overall, we suggest that tributary aggregation effects should be assessed in heterogeneous catchments before C‐Q or ratio‐Q relationships can be interpreted as reflecting catchment‐wide solute generation processes and their relationship to hydrology.
Mixing as a driver of temporal variations in river hydrochemistry: 1. Insights from conservative tracers in the Andes‐Amazon transition
Authors: Torres Mark A. , Baronas J. Jotautas , Clark Kathryn E. , Feakins Sarah J. , West A. Joshua 
Published: March 2017

AbstractThe response of hillslope processes to changes in precipitation may drive the observed changes in the solute geochemistry of rivers with discharge. This conjecture is most robust when variations in the key environmental factors that affect hillslope processes (e.g., lithology, erosion rate, and climate) are minimal across a river's catchment area. For rivers with heterogenous catchments, temporal variations in the relative contributions of different tributary subcatchments may modulate variations in solute geochemistry with runoff. In the absence of a dense network of hydrologic gauging stations, alternative approaches are required to distinguish between the different drivers of temporal variability in river solute concentrations. In this contribution, we apportion the water and solute fluxes of a reach of the Madre de Dios River (Peru) between its four major tributary subcatchments during two sampling campaigns (wet and dry seasons) using spatial variations in conservative tracers. Guided by the results of a mixing model, we identify temporal variations in solute concentrations of the main stem Madre de Dios that are due to changes in the relative contributions of each tributary. Our results suggest that variations in tributary mixing are, in part, responsible for the observed concentration‐discharge (C‐Q) relationships. The implications of these results are further explored by reanalyzing previously published C‐Q data from this region, developing a theoretical model of tributary mixing, and, in a companion paper, comparing the C‐Q behavior of a suite of major and trace elements in the Madre de Dios River system.
Modeling complex flow structures and drag around a submerged plant of varied posture
Authors: Boothroyd Richard J. , Hardy Richard J. , Warburton Jeff , Marjoribanks Timothy I. 
Published: March 2017

AbstractAlthough vegetation is present in many rivers, the bulk of past work concerned with modeling the influence of vegetation on flow has considered vegetation to be morphologically simple and has generally neglected the complexity of natural plants. Here we report on a combined flume and numerical model experiment which incorporates time‐averaged plant posture, collected through terrestrial laser scanning, into a computational fluid dynamics model to predict flow around a submerged riparian plant. For three depth‐limited flow conditions (Reynolds number = 65,000–110,000), plant dynamics were recorded through high‐definition video imagery, and the numerical model was validated against flow velocities collected with an acoustic Doppler velocimeter. The plant morphology shows an 18% reduction in plant height and a 14% increase in plant length, compressing and reducing the volumetric canopy morphology as the Reynolds number increases. Plant shear layer turbulence is dominated by Kelvin‐Helmholtz type vortices generated through shear instability, the frequency of which is estimated to be between 0.20 and 0.30 Hz, increasing with Reynolds number. These results demonstrate the significant effect that the complex morphology of natural plants has on in‐stream drag, and allow a physically determined, species‐dependent drag coefficient to be calculated. Given the importance of vegetation in river corridor management, the approach developed here demonstrates the necessity to account for plant motion when calculating vegetative resistance.
Skill of ship‐following large‐eddy simulations in reproducing MAGIC observations across the northeast Pacific stratocumulus to cumulus transition region
Authors: McGibbon J. , Bretherton C. S. 
Published: March 2017

AbstractDuring the Marine ARM GPCI Investigation of Clouds (MAGIC) in October 2011 to September 2012, a container ship making periodic cruises between Los Angeles, CA, and Honolulu, HI, was instrumented with surface meteorological, aerosol and radiation instruments, a cloud radar and ceilometer, and radiosondes. Here large‐eddy simulation (LES) is performed in a ship‐following frame of reference for 13 four day transects from the MAGIC field campaign. The goal is to assess if LES can skillfully simulate the broad range of observed cloud characteristics and boundary layer structure across the subtropical stratocumulus to cumulus transition region sampled during different seasons and meteorological conditions. Results from Leg 15A, which sampled a particularly well‐defined stratocumulus to cumulus transition, demonstrate the approach. The LES reproduces the observed timing of decoupling and transition from stratocumulus to cumulus and matches the observed evolution of boundary layer structure, cloud fraction, liquid water path, and precipitation statistics remarkably well. Considering the simulations of all 13 cruises, the LES skillfully simulates the mean diurnal variation of key measured quantities, including liquid water path (LWP), cloud fraction, measures of decoupling, and cloud radar‐derived precipitation. The daily mean quantities are well represented, and daily mean LWP and cloud fraction show the expected correlation with estimated inversion strength. There is a −0.6 K low bias in LES near‐surface air temperature that results in a high bias of 5.6 W m−2 in sensible heat flux (SHF). Overall, these results build confidence in the ability of LES to represent the northeast Pacific stratocumulus to trade cumulus transition region.
Kontrolle der Freisetzungskinetik von Nanopartikeln aus 3D‐gedruckten Hydrogelgerüsten
Authors: Baumann Bernhard , Jungst Tomasz , Stichler Simone , Feineis Susanne , Wiltschka Oliver , Kuhlmann Matthias , Lindén Mika , Groll Jürgen 
Published: March 2017

AbstractDie bisher größtenteils unerforschte Kombination aus Biofabrikation und Nanotechnologie ermöglicht eine örtlich und zeitlich aufgelöste Freisetzung von Wirkstoffen aus hierarchischen, zellbeladenen Biomaterialien. Als ein erster Schritt in Richtung der Verknüpfung dieser beiden Forschungsgebiete wird hier gezeigt, dass die Einstellung der elektrostatischen Nanopartikel‐Polymer‐ und Nanopartikel‐Nanopartikel‐Wechselwirkungen verwendet werden kann, um die Freisetzungskinetik von Nanopartikeln aus gedruckten 3D Hydrogelgerüsten zu steuern. Diese grundlegende Strategie kann für die räumliche und zeitliche Kontrolle der Freisetzungskinetik von nanopartikulären Wirkstoffträgern in biofabrizierten Konstrukten verwendet werden.
HACA's Heritage: A Free‐Radical Pathway to Phenanthrene in Circumstellar Envelopes of Asymptotic Giant Branch Stars
Authors: Yang Tao , Kaiser Ralf I. , Troy Tyler P. , Xu Bo , Kostko Oleg , Ahmed Musahid , Mebel Alexander M. , Zagidullin Marsel V. , Azyazov Valeriy N. 
Published: March 2017

AbstractThe hydrogen‐abstraction/acetylene‐addition (HACA) mechanism has been central for the last decades in attempting to rationalize the formation of polycyclic aromatic hydrocarbons (PAHs) as detected in carbonaceous meteorites such as in Murchison. Nevertheless, the basic reaction mechanisms leading to the formation of even the simplest tricyclic PAHs like anthracene and phenanthrene are still elusive. Here, by exploring the previously unknown chemistry of the ortho‐biphenylyl radical with acetylene, we deliver compelling evidence on the efficient synthesis of phenanthrene in carbon‐rich circumstellar environments. However, the lack of formation of the anthracene isomer implies that HACA alone cannot be responsible for the formation of PAHs in extreme environments. Considering the overall picture, alternative pathways such as vinylacetylene‐mediated reactions are required to play a crucial role in the synthesis of complex PAHs in circumstellar envelopes of dying carbon‐rich stars.
A Strategy to Design Hyperpolarized 13C Magnetic Resonance Probes Using [1‐13C]α‐Amino Acid as a Scaffold Structure
Authors: Nishihara Tatsuya , Kameyama Yutaka , Nonaka Hiroshi , Takakusagi Yoichi , Hyodo Fuminori , Ichikawa Kazuhiro , Sando Shinsuke 
Published: March 2017

AbstractHyperpolarization is an emerging method that dramatically enhances NMR signal intensity. As a result of their increased sensitivity, hyperpolarized (HP) NMR molecular probes can be used to perform time‐resolved spectroscopy and imaging in vitro and in vivo. It is, however, challenging to design such probes de novo. Herein, the [1‐13C]α‐amino acid is reported as a scaffold structure to design HP 13C NMR molecular probes. The [1‐13C]α‐amino acid can be converted to various HP 13C chemical probes that show sufficient chemical shift change by altering the chemical state of the α nitrogen upon interaction with the target. Several previously reported HP probes could be explained by this design principle. To demonstrate the versatility of this approach, two α‐amino‐acid‐based HP 13C chemical probes, sensitive to pH and Ca2+ ion, were developed and used to detect targets.
Covalent Crosslinking of Graphene Quantum Dots by McMurry Deoxygenation Coupling
Authors: Chen Limei , Hu Peiguang , Lu Jia En , Chen Shaowei 
Published: March 2017

AbstractGraphene quantum dots were covalently crosslinked forming ensembles of a few hundred nanometers in size by McMurry deoxygenation coupling reactions of peripheral carbonyl functional moieties catalyzed by TiCl4 and Zn powders in refluxing THF, as evidenced by TEM, AFM, FTIR, Raman and XPS measurements. Photoluminescence measurements showed that after chemical coupling, the excitation and emission peaks blue‐shifted somewhat and the emission intensity increased markedly, likely due to the removal of oxygenated species where quinone‐like species are known to be effective electron acceptors and emission quenchers.
Dasatinib inhibits actin fiber reorganization and promotes endothelial cell permeability through RhoA‐ROCK pathway
Authors: Dasgupta Swapan K. , Le Anhquyen , Vijayan K. Vinod , Thiagarajan Perumal 
Published: March 2017

AbstractTreatment with dasatinib, a tyrosine kinase inhibitor, is associated with edema, pleural effusion, and pulmonary edema. We investigated the effect of dasatinib on the barrier function of human microvascular endothelial cells‐1 (HMEC‐1) in vitro and in vivo. The permeability of HMEC‐1 to fluorescein isothiocyante (FITC)‐dextran increased in Transwell chambers within 5 min following the addition of therapeutic concentrations of dasatinib. The change in permeability was associated with increased activation of RhoA GTPase and its effector Rho‐associated coiled‐coil kinase 1(ROCK1). RhoA inhibitor C3 transferase almost completely inhibited dasatinib‐induced increase in permeability. Under similar conditions, imatinib had no effect on permeability or activation of RhoA. Since integrin‐induced cell spreading suppresses RhoA activation, we examined the effect of dasatinib on cell spreading on fibronectin substrate. Dasatinib impaired endothelial cell spreading in a concentration‐dependent manner and induced disorganization of actin fibers. Tyrosine kinases play an essential role in transmitting signals from integrins to RhoA and we examined tyrosine phosphorylation of several cytoskeletal proteins. Dasatinib markedly inhibited tyrosine phosphorylation of p130 Crk‐associated substrate (p130cas), paxillin and vinculin. These results suggest that the inhibition of tyrosine phosphorylation of the focal adhesion plaque components by dasatinib may alter the assembly of actin fibers resulting in the activation of RhoA/ROCK pathway. Consistent with these findings, dasatinib‐induced increase in the permeability was blocked by ROCK inhibitor y27632. In vivo administration of y27632, significantly inhibited the dasatinib‐induced extravasation of Evans blue in mice and dasatinib‐induced increase in microvascular permeability was attenuated in ROCK1‐deficient mice. These findings suggest that ROCK inhibitors could serve as therapeutic modalities to ameliorate the dasatinib‐induced pulmonary changes.
Dravet syndrome: a new causative SCN1A mutation?
Authors: Poryo Martin , Clasen Oriana , Oehl‐Jaschkowitz Barbara , Christmann Alexander , Gortner Ludwig , Meyer Sascha 
Published: March 2017

Key Clinical MessageDravet syndrome is often caused by SCN1A mutations and has a wide variation in clinical appearance. Indication for genetic analysis should be an epileptic encephalopathy or severe clinical course of seizures in infants with episodes of fever before the first year of life.
Concerted Catalysis in Tight Spaces: Palladium‐Catalyzed Allylation Reactions Accelerated by Accumulated Active Sites in Mesoporous Silica
Authors: Motokura Ken , Ikeda Marika , Nambo Masayuki , Chun Wang‐Jae , Nakajima Kiyotaka , Tanaka Shinji 
Published: March 2017

AbstractThe surface of mesoporous silica was modified with a Pd–bisphosphine complex and/or a tertiary amine group for concerted acceleration of allylation reactions. Mesoporous‐silica‐supported catalysts with a 1.6 nm pore diameter showed higher performance than nonporous or larger mesoporous silica‐supported catalysts owing to the accumulation of active sites into a confined space. For the case in which allyl alcohol was used in the reaction, the presence of a silanol group on the surface was quite effective: the turnover number of Pd was nine times greater than that of the homogeneous Pd complex.
A Fluorine‐18 Radiolabeling Method Enabled by Rhenium(I) Complexation Circumvents the Requirement of Anhydrous Conditions
Authors: Klenner Mitchell A. , Pascali Giancarlo , Zhang Bo , Sia Tiffany R. , Spare Lawson K. , Krause‐Heuer Anwen M. , Aldrich‐Wright Janice R. , Greguric Ivan , Guastella Adam J. , Massi Massimiliano , Fraser Benjamin H. 
Published: March 2017

AbstractAzeotropic distillation is typically required to achieve fluorine‐18 radiolabeling during the production of positron emission tomography (PET) imaging agents. However, this time‐consuming process also limits fluorine‐18 incorporation, due to radioactive decay of the isotope and its adsorption to the drying vessel. In addressing these limitations, the fluorine‐18 radiolabeling of one model rhenium(I) complex is reported here, which is significantly improved under conditions that do not require azeotropic drying. This work could open a route towards the investigation of a simplified metal‐mediated late‐stage radiofluorination method, which would expand upon the accessibility of new PET and PET‐optical probes.
Synthesis of ortho‐Azophenols by Formal Dehydrogenative Coupling of Phenols and Hydrazines or Hydrazides
Authors: Esguerra Kenneth Virgel N. , Lumb Jean‐Philip 
Published: March 2017

AbstractAzophenols are important chromophores and reagents in organic synthesis, with applications as pigments and molecular switches. Here, we describe a catalytic aerobic process that couples phenols and hydrazines or hydrazides for their synthesis. The key aromatic C−N bond is formed by condensation between the hydrazine or hydrazide and an ortho‐quinone, which triggers a redox‐isomerization to install the azo‐functionality. Notable features include rapid access to highly functionalized azophenols with a range of electronic configurations, including “push–pull” systems, conditions that employ simple, unactivated substrates, occurrence at room temperature using an earth‐abundant and commercially available copper catalyst, and production of water as the only stoichiometric byproduct.
Chiral exploration of 6,12‐diphenyldibenzo[b,f][1,5]diazocine with stable conformation
Authors: Li Zheng‐Yi , Pan Yong , Jin Lin‐Lin , Yin Yue , Yang Bao‐Zhu , Sun Xiao‐Qiang 
Published: March 2017

AbstractA first optical resolution of 6,12‐diphenyldibenzo[b,f][1,5]diazocine with stable boat conformation was achieved by chiral supercritical fluid chromatography (SFC). The absolute configurations of enantiomers were first assigned and determined by X‐ray crystal structure based on CIP‐rules. The high optical rotation and circular dichroism spectrum were well explained by electronic helix theory. Owing to the high stabilization of boat conformation, the chiral configuration could be maintained at very high temperature, more than 200 °C, which was proved by Density Functional Theory calculations.
Operational Criteria for the Separation of Alkanes by Zeolite Membranes
Authors: Dragomirova Radostina , Jorabchi Majid Namayandeh , Paschek Dietmar , Wohlrab Sebastian 
Published: March 2017

AbstractOperational criteria for the adsorption based separation of alkanes by MFI zeolite membranes were evaluated using the model system n‐butane in methane. The influence of operation parameters is rather case sensitive and the separation is determined by the interplay between mobility of adsorbed molecules across the membrane and the depletion of the preferred adsorptive agent, n‐butane, along the membrane. Different aspects in the operational design for the separation of alkanes by zeolite membranes were illuminated, namely separation task, stationarity, and membrane surface.
Über den Technologiewandel in der Propylenoxid‐Herstellung
Authors: Bernhard Maik , Anton Johan , Schmidt Franz , Sandkaulen Florian , Pascaly Matthias 
Published: March 2017

ZusammenfassungPropylenoxid (PO) ist eines der industriell wichtigsten chemischen Zwischenprodukte. Es dient als Ausgangsverbindung für die Herstellung von Schaumstoffen, Lösungsmitteln oder Enteisungsmitteln und leistet damit einen wichtigen Beitrag für das moderne Leben. Traditionell erfolgt die Herstellung von PO nach dem Chlorhydrin‐Verfahren, das noch heute die größte Bedeutung besitzt. Die umweltfreundlichere und chlorfreie Herstellung von PO erlauben die Koppelproduktverfahren SM‐PO und MTBE‐PO, bei denen Styrol und MTBE als Folgeprodukte anfallen. Die Wirtschaftlichkeit dieser Verfahren wird demnach nicht nur durch das PO sondern auch durch die Nachfrage der Folgeprodukte bestimmt. Eine Weiterentwicklung des SM‐PO‐Verfahrens ist das CU‐PO‐Verfahren, bei dem kein Folgeprodukt anfällt. Die Entwicklung des hochselektiven Katalysators Titansilikalit‐1 (TS‐1) gepaart mit der verbesserten Verfügbarkeit großer Mengen von Wasserstoffperoxid ermöglichte die großtechnische Realisierung der koppelproduktfreien HPPO‐Technologie an mehreren Standorten weltweit. Dieses neue Verfahren ermöglicht die Herstellung von PO mit ausgezeichneten Ausbeuten und Selektivitäten, wobei ausschließlich Wasser als umweltfreundliches Nebenprodukt anfällt. Der Einsatz homogener Katalysatoren sowie die einstufige Direktoxidation von Propylen mit Luft bzw. Sauerstoff sind bislang nur von akademischer Bedeutung.
Development of model systems for in vitro investigation of transdermal transport pathways
Authors: Liuzzi Roberta , Preziosi Valentina , Caserta Sergio , Guido Stefano 
Published: March 2017

AbstractSkin is a complex structured system primarily involved in Transdermal Drug Delivery (TDD). The outer stratum corneum represents the main barrier to the entrance of external molecules. Nowadays, none of the recognized methods, used for the investigation of penetration processes, is able to give a complete overview of the transport mechanisms involved. Standard protocols are based on the use of human or animal skin samples, which are difficult and expensive to obtain. Here, we present a novel experimental setup to investigate TDD by using Confocal Laser Scanning Microscopy and image analysis. The methodology is based on diffusion experiments of fluorescent‐labelled fluids (water, oil, and oil‐in‐water emulsions), in a model matrix. Using an agarose gel as model for a proof of concept, different penetration efficiencies were observed, suggesting an important role of both chemical composition and fluid microstructure on the transport mechanism. An adequate model system should be used to better mimic the stratum corneum morphology and properties. To this aim, several bicontinuous emulsion gels, obtained from an emulsification process, were preliminary formulated and suggested as model systems to mimic the stratum corneum. In this work, we define the key directions for the development of an innovative approach to study the penetration of formulations through the skin.
Salinity tolerance, adsorption, and emulsification properties of nonylphenol alkyl sulphonates derived from bi‐component linear alpha olefin
Authors: Niu Ruixia , Wang Daqiang , Long Biao , Song Hua , Wang Chao , Wang Jingling , He Junyao 
Published: March 2017

ABSTRACTA series of bi‐component nonylphenol alkyl sulphonate surfactants with different alkyl chains (C12/n‐NPAS, n = 8, 10, 14, 16) were synthesized through sulphonation‐alkylation‐neutralization, using a mixture of linear alpha olefins as raw materials. The chemical structures were characterized by FTIR and ESI‐MS. The purity values measured by the two‐phase titration method were all higher than 0.96 g/g (96 wt%). The effects of the raw materials composition on salinity tolerance, adsorption, and emulsification properties were also investigated. There is marked adsorption amount variation for bi‐component surfactants with a strong difference of carbon number of alkyl groups. The salinity tolerance of C12/n‐NPAS is about 40 g · L−1 of NaCl, and 0.65 g · L−1 of CaCl2. Compared with petroleum sulphonates (14 g · L−1 of NaCl, 0.08 g · L−1 of CaCl2) and LAS (22 g · L−1 of NaCl, 0.37 g · L−1 of CaCl2), NPAS surfactants show a low adsorption, excellent salinity tolerance, and emulsion stability.