bluuebunny/crossref_metadata_2025_split huggingface dataset:
Interactive effects of wildfire and climate on permafrost degradation in Alaskan lowland forests
Authors: Brown Dana R. N. , Jorgenson M. Torre , Douglas Thomas A. , Romanovsky Vladimir E. , Kielland Knut , Hiemstra Christopher , Euskirchen Eugenie S. , Ruess Roger W. 
Published: July 2015

AbstractWe examined the effects of fire disturbance on permafrost degradation and thaw settlement across a series of wildfires (from ~1930 to 2010) in the forested areas of collapse‐scar bog complexes in the Tanana Flats lowland of interior Alaska. Field measurements were combined with numerical modeling of soil thermal dynamics to assess the roles of fire severity and climate history in postfire permafrost dynamics. Field‐based calculations of potential thaw settlement following the loss of remaining ice‐rich permafrost averaged 0.6 m. This subsidence would cause the surface elevations of forests to drop on average 0.1 m below the surface water level of adjacent collapse‐scar features. Up to 0.5 m of thaw settlement was documented after recent fires, causing water impoundment and further thawing along forest margins. Substantial heterogeneity in soil properties (organic layer thickness, texture, moisture, and ice content) was attributed to differing site histories, which resulted in distinct soil thermal regimes by soil type. Model simulations showed increasing vulnerability of permafrost to deep thawing and thaw settlement with increased fire severity (i.e., reduced organic layer thickness). However, the thresholds of fire severity that triggered permafrost destabilization varied temporally in response to climate. Simulated permafrost dynamics underscore the importance of multiyear to multidecadal fluctuations in air temperature and snow depth in mediating the effects of fire on permafrost. Our results suggest that permafrost is becoming increasingly vulnerable to substantial thaw and collapse after moderate to high‐severity fire, and the ability of permafrost to recover is diminishing as the climate continues to warm.
Optical coherence tomography reflects brain atrophy in multiple sclerosis: A four‐year study
Authors: Saidha Shiv , Al‐Louzi Omar , Ratchford John N. , Bhargava Pavan , Oh Jiwon , Newsome Scott D. , Prince Jerry L. , Pham Dzung , Roy Snehashis , van Zijl Peter , Balcer Laura J. , Frohman Elliot M. , Reich Daniel S. , Crainiceanu Ciprian , Calabresi Peter A. 
Published: July 2015

ObjectiveThe aim of this work was to determine whether atrophy of specific retinal layers and brain substructures are associated over time, in order to further validate the utility of optical coherence tomography (OCT) as an indicator of neuronal tissue damage in patients with multiple sclerosis (MS).MethodsCirrus high‐definition OCT (including automated macular segmentation) was performed in 107 MS patients biannually (median follow‐up: 46 months). Three‐Tesla magnetic resonance imaging brain scans (including brain‐substructure volumetrics) were performed annually. Individual‐specific rates of change in retinal and brain measures (estimated with linear regression) were correlated, adjusting for age, sex, disease duration, and optic neuritis (ON) history.ResultsRates of ganglion cell + inner plexiform layer (GCIP) and whole‐brain (r = 0.45; p < 0.001), gray matter (GM; r = 0.37; p < 0.001), white matter (WM; r = 0.28; p = 0.007), and thalamic (r = 0.38; p < 0.001) atrophy were associated. GCIP and whole‐brain (as well as GM and WM) atrophy rates were more strongly associated in progressive MS (r = 0.67; p < 0.001) than relapsing‐remitting MS (RRMS; r = 0.33; p = 0.007). However, correlation between rates of GCIP and whole‐brain (and additionally GM and WM) atrophy in RRMS increased incrementally with step‐wise refinement to exclude ON effects; excluding eyes and then patients (to account for a phenotype effect), the correlation increased to 0.45 and 0.60, respectively, consistent with effect modification. In RRMS, lesion accumulation rate was associated with GCIP (r = −0.30; p = 0.02) and inner nuclear layer (r = −0.25; p = 0.04) atrophy rates.InterpretationOver time GCIP atrophy appears to mirror whole‐brain, and particularly GM, atrophy, especially in progressive MS, thereby reflecting underlying disease progression. Our findings support OCT for clinical monitoring and as an outcome in investigative trials. Ann Neurol 2015;78:Ann Neurol 2015;78:679–696
Zum Charakter der chemischen Bindung von Argonatomen mit gemischten Gold/Silber‐Trimeren
Authors: Shayeghi Armin , Johnston Roy L. , Rayner David M. , Schäfer Rolf , Fielicke André 
Published: July 2015

AbstractDie vorliegende Arbeit beschäftigt sich mit der kontrovers diskutierten Natur der chemischen Bindung von Edelmetallen mit Edelgasen. Experimentelle Untersuchungen verweisen auf besonders starke Au‐Ar‐Bindungen in Argon‐Komplexen gemischter Au/Ag‐Trimere. Infrarotspektren zeigen einen enormen Einfluss des Edelgases auf die Schwingungsmoden, insbesondere in Au‐reichen Trimeren, in denen die Ar‐Atome aufgrund einer relativistisch erhöhten Kovalenz der Au‐Ar‐Bindung stark involviert sind. In Ag‐reichen Trimeren dominieren die Schwingungsmoden des Metallgerüstes, was auf einen stärkeren elektrostatischen Charakter der Ag‐Ar‐Bindung hinweist. Die Experimente werden durch Dichtefunktionaltheorie‐Rechnungen gestützt, die zeigen, wie die relativistischen Unterschiede zwischen Au und Ag zu stärkeren Au‐Ar‐Bindungen führen. Durch die Möglichkeit, die Zusammensetzung und somit die Ladungsverteilung zu variieren, erweisen sich die Trimere als ideales Modellsystem, um die chemische Natur der Wechselwirkung von Edelgasen mit geschlossenschaligen Goldverbindungen zu studieren.
Copper(I)/Copper(II)‐Assisted Tandem Catalysis: The Case Study of Ullmann/Chan–Evans–Lam N1,N3‐Diarylation of 3‐Aminopyrazole
Authors: Beyer Astrid , Castanheiro Thomas , Busca Patricia , Prestat Guillaume 
Published: July 2015

AbstractUnprecedented CuI/CuII‐assisted tandem catalysis allowing an Ullmann/Chan–Evans–Lam sequence was achieved. This three‐component, one‐pot reaction triggered by a change in the oxidation state of the metal leads to the selective N1,N3‐diarylation of 3‐aminopyrazole. This new method should be a valuable tool for small‐molecule drug discovery that requires suitable regio‐ and/or chemoselective strategies for the N‐arylation of nitrogen‐containing heterocycles.
Poisoning of Highly Porous Platinum Electrodes by Amino Acids and Tissue Fluid Constituents
Authors: Köhler Christian , Bleck Lena , Frei Maxi , Zengerle Roland , Kerzenmacher Sven 
Published: July 2015

AbstractThe first comprehensive study of the poisoning behavior of physiological amino acids and important tissue fluid constituents on porous platinum electrodes was performed. On the basis of chronoamperometry under physiological conditions, the results are highly relevant for the development of enzyme‐free implantable glucose fuel cells and possibly also glucose sensors. The strongest poisoning was exhibited by positively charged alkaline amino acids and by some of the neutral amino acids, as well as by uric acid and creatinine. In contrast to previous work, sulfur‐containing amino acids showed no poisoning effect. This was explained by the use of highly porous platinum electrodes in the current study and experimental methods that were more relevant for practical applications. Furthermore, comprehensive analysis regarding the degree of recovery in the absence of poisoning species and the extent of electrode regeneration by cyclic voltammetry was performed for each of the amino acids and physiological substances.
Rhodium‐Mediated Oxygenation of Nitriles with Dioxygen: Isolation of Rhodium Derivatives of Peroxyimidic Acids
Authors: Bittner Annemarie , Braun Thomas , Herrmann Roy , Mebs Stefan 
Published: July 2015

AbstractDioxygen is used as the oxygenation agent in the rhodium‐mediated conversion of nitriles into amides. The characterization of intermediate species and model compounds as well as isotope‐labeling studies provided an insight into the reaction mechanism. The conversions of rhodium hydroperoxido or methylperoxido complexes with nitriles into metallacyclic rhodium‐ κ2‐(N,O)‐peroxyimidate compounds represent essential key steps. The former are accessible from a rhodium(III) peroxido complex and the latter represent rhodium derivatives of Payne’s reagent (peroxyimidic acids).
Über Rosmarin und Rosmarinsäure
Authors: Gao Ying Ying , Siehl Hans‐Ullrich , Petzold Heike , Sicker Dieter , Zeller Klaus‐Peter , Berger Stefan 
Published: July 2015

AbstractRosmarinsäure, ein Labiatengerbstoff, kommt in Rosmarin aber auch in anderen Pflanzen wie Thymian, Buntnessel, Bohnenkraut, Salbei, Oregano oder Zitronenmelisse vor, aus der sie hier isoliert wurde. Sie ist als Ester der Kaffeesäure ein chiraler, aromatischer Naturstoff. Rosmarinsäure schmeckt bitter, was bei Rosmarin als Gewürz reizvoll sein kann. Wegen ihrer Brenzkatechin‐Substruktur ist sie ein Antioxidans. Anwendungen als Heilmittel sind aufgrund der vielfältigen physiologischen Wirkungen möglich und werden weiter untersucht. Die an der Buntnessel komplett aufgeklärte Biosynthese hat zu Versuchen geführt, Rosmarinsäure in pflanzlichen Zellkulturen biotechnologisch in hoher Ausbeute herzustellen. Die Darstellung einer spektroskopisch reinen Probe ist anspruchsvoll. Alle analytischen Spektren werden vollständig entweder im Hauptteil oder in der supporting information wiedergegeben und interpretiert.
Self‐Assembly of PEG‐Coated Ceria Nanoparticles Shows Dependence on PEG Molecular Weight and Ageing
Authors: Neal Craig J. , Das Soumen , Saraf Shashank , Tetard Laurene , Seal Sudipta 
Published: July 2015

AbstractCerium oxide (ceria) nanoparticles (CNPs) were synthesized in poly(ethylene glycol)s (PEGs) of different molecular weights (MWs; 300, 600, 1500, 3000, 4000, and 6000 Da) with water as a cosolvent, and changes in physicochemical properties, especially morphology and size, were monitored as a function of time. High‐resolution transmission electron microscopy (HRTEM) was performed for all solutions and revealed octahedral, star morphologies for CNPs coated with 1500 MW PEG. Raman and FTIR spectroscopy, HRTEM images, conductivity, and electrophoretic mobility imply the self‐assembly of small spherical particles to octahedral, star‐shaped particles by means of a fractal assembly method. Dynamic light scattering measures were used to create an empirical growth model of the observed octahedral self‐assembly. It was also determined that PEG polymer chain lengths and age‐dependent redox activities of CNPs limit or allow this assembly owing to molecular‐weight‐dependent physicochemical properties. This study highlights the significance of ageing on solution‐based nanoparticles and its implications in the use of nanoparticles over long periods of time. As PEG‐ylated nanoparticles have found extensive use in biomedical applications, we have tested the aged particles in vitro for toxicity.
Selective Oxidation of Sulfides Catalyzed by the Nanocluster Polyoxomolybdate (NH4)12[Mo36(NO)4O108(H2O)16]
Authors: Amini Mojtaba , Naslhajian Hadi , Farnia S. Morteza F. , Hołyńska Małgorzata 
Published: July 2015

AbstractThe (NH4)12[Mo36(NO)4O108(H2O)16]·30.84H2O ({Mo36}) catalyst has been synthesized and successfully employed in the selective oxidation of various sulfides to sulfoxides with urea hydrogen peroxide as oxidant under mild reaction conditions with 84–99 % conversion and 58–99 % selectivity, with active functional groups such as the hydroxy group and C=C bonds tolerated in the oxidation. The {Mo36} catalyst showed high catalytic activity for a high substrate/catalyst ratio (up to 30000:1) and is recyclable.
π‐Excess σ2P=C–N–Heterocycles: Catalytic P‐Arylation and Alkylation of N‐Alkyl‐1,3‐benzazaphospholes and Isolation of P,N‐Disubstituted Dihydrobenzaza­phosphole P‐Oxides
Authors: Niaz Basit , Aluri Bhaskar R. , Jones Peter G. , Heinicke Joachim W. 
Published: July 2015

Abstract2‐Unsubstituted N‐alkyl‐1,3‐benzazaphospholes, diagonally P–C related to 2,3‐unsubstituted indoles, were successfully arylated by aryl iodides and bromides or alkylated by neopentyl iodide by heating in DMF in the presence of a catalytic amount of PdCl2 or H2PtCl6 and a suitable base. In contrast to the known 2‐arylations of indoles under these conditions, the reactions led to arylation in the 3‐position and proceeded via highly moisture‐sensitive intermediates to P‐substituted 1,3‐benzazaphosphole P‐oxides. Thus, we present a novel route for the direct P‐substitution of aromatic σ2P‐heterocycles with electrophilic aryl/alkyl halides. Characteristic NMR spectroscopic data of the intermediates are consistent with –P(aryl)–C(Br/Cl)–N– species formed by metal‐mediated addition of the aryl halides at the P=C bond rather than by oxidative addition to ylidic intermediates. Benzazaphospholium salts, accessible by using triethyloxonium tetrafluoroborate at room temperature and also very sensitive to hydrolysis, display distinct NMR spectroscopic data. The structures of the products were elucidated by conclusive NMR spectroscopy and HRMS data and crystal‐structure analysis. Minor amounts of a bis(arylation) product could likewise be identified by crystal‐structure analysis.
Mechanisms and Factors Controlling Photoisomerization Equilibria, Ligand Exchange, and Water Oxidation Catalysis Capabilities of Mononuclear Ruthen­ium(II) Complexes
Authors: Hirahara Masanari , Hakamata Tomoya , League Aaron B. , Ertem Mehmed Z. , Takahashi Kosuke , Nagai Sho , Inaba Keisuke , Yamazaki Hirosato , Saito Kenji , Yui Tatsuto , Cramer Christopher J. , Yagi Masayuki 
Published: July 2015

AbstractThe photoisomerization equilibrium between distal‐ and proximal‐[Ru(tpy)(pyqu)OH2]2+ [d‐ and p‐RuH2O, tpy = 2,2′;6′,2″‐terpyridine, pyqu = 2‐(2′‐pyridyl)quinoline] is characterized. The kinetic analysis of the pD‐dependent photoisomerization reactions (monitored by 1H NMR) of d‐RuH2O and p‐RuH2O shows (1) that both hydroxo isomers, distal‐ and proximal‐[Ru(tpy)(pyqu)OH]+, are inert to photoisomerization, and (2) that the back reaction (distal to proximal) is 3.0 times faster than the forward reaction (proximal to distal). Isolation of distal‐ and proximal‐[Ru(tpy)(pyqu)Cl]+ (d‐ and p‐RuCl) as well as d‐ and p‐RuH2O isomers enabled comprehensive studies on geometric structures, ligand exchange and redox reactions, and water oxidation catalysis for these isomers. The observed aquation rate constant (9.2 × 10–2 s–1 at 40 μM) of p‐RuCl to form p‐RuH2O is 1700 times higher than that (5.4 × 10–5 s–1 at 63 μM) of d‐RuCl at 298 K owing to the steric repulsion between a chloro ligand and the 8‐proton of the quinoline moiety. The turnover frequency (TOF = 1.7 × 10–3 s–1) of p‐RuH2O for catalytic water oxidation is 1.7 times greater than that (1.0 × 10–3 s–1) for d‐RuH2O, in contrast to the [Ru(tpy)(pynp)OH2]2+ isomer system, in which the TOF of the distal isomer is higher than that of the proximal one by one order of magnitude. The mechanisms and factors controlling the photoisomerization equilibria and water oxidation catalysis of the d‐ and p‐RuH2O isomers are discussed on the basis of experimental and theoretical investigations.
Tertiary Amine Promoted Asymmetric ­Aldol Reaction of Aldehydes
Authors: Gut Bartosz , Mlynarski Jacek 
Published: July 2015

AbstractThe direct asymmetric self‐aldol reactions of various α‐oxyaldehydes catalyzed by tertiary amines have been demonstrated. By using 10 mol‐% of quinine catalyst, dimerization products have been prepared in high yields, with good anti‐diastereocontrol, and up to 80 % ee. The presented enolate‐mediated synthesis of protected tetrose sugars has never been accomplished before by chiral tertiary amine organocatalysts.
A Non‐Aldol Preparation of Enantiopure Propionate‐Derived Motifs with the Assistance of Chiral Sulfoxides: Application to a Convergent Synthesis of the Lactone Core of Octalactins
Authors: Bauder Claude 
Published: July 2015

AbstractPropionate‐derived fragments were prepared by a non‐aldol method using chiral sulfoxide chemistry. A methacrylate ester, assisted by a chiral sulfoxide as an auxiliary agent, was easily transformed into an optically pure allylic alcohol, which was then subjected to diastereoselective hydroboration with the bulky dialkylborane 9‐BBN. The diastereofacial selectivity was governed by a preferred spatial arrangement of a staggered conformation model, as suggested by Houk, taking into account of the various A(1,2) allylic strains. Thus, the the two adjacent stereocentres in the enantiopure allylic alcohol were installed with an anti configuration. As an application of this work, we have described an enantioselective synthesis of the unusual eight‐membered lactone ring of the octalactins. Two propionate‐derived fragments were coupled to give precursor 18, which was subjected to Yamaguchi's macrolactonisation to give the required lactone ring.
Undecorated Cu(OAc)2‐Catalyzed C(sp3)–C(sp3) Bond Formation through para‐Hydroxy Group Triggered Remote Benzylic C(sp3)–H Bond Functionalization
Authors: Huang Jian‐Gang , Guo Ying , Li Yu‐Dan , Liu Hong‐Wei , Liao Dao‐Hua , Ji Ya‐Fei 
Published: July 2015

AbstractThe undecorated Cu(OAc)2‐catalyzed para‐hydroxy group triggered oxidative coupling of 2,6‐disubstituted 4‐cresols with fluorinated β‐keto esters or malonates leading to benzylic C(sp3)–C(sp3) bond formation was investigated. This formal double C(sp3)–H coupling method features mild conditions, atom economy, ligand‐ and additive‐free catalysis, and ambient air as the terminal oxidant. This ecofriendly method allows rapid access to highly functionalized 3‐phenylpropanoate derivatives containing fluorinated quaternary carbon‐like centers. On the basis of active p‐benzoquinone methide intermediates, a plausible mechanism was proposed.
The role of starvation in biomass harvesting and lipid accumulation: Co‐culture of microalgae–bacteria in synthetic wastewater
Authors: Xu Yanjia , Wang Yao , Yang Yang , Zhou Dandan 
Published: July 2015

In this study, the microalgae–bacterial culture, composed of Chlorella vulgaris and activated sludge, was cultivated under starvation condition by controlling synthetic wastewater concentrations. After 8‐day culturing, nutrients such as organic carbon, ammonium nitrogen and phosphate were basically removed. The dynamic formation phases of the microalgae–bacterial consortium were identified to microalgae adsorbed by sludge flocs, new bacteria adhesion on microalgae and bacteria uniformly distributed and attachment and detachment of biomass in balance. The consortiums had much better settle‐ability than pure microalgae, and this phenomenon was particularly obvious in starvation term. Lipid accumulation of microalgae was also critically influenced by starvation cultivation, lipid content and lipid productivity of bioreactor with 5% initial wastewater (IW) were 17.1% and 0.045 g (L day−1)−1. This study gave a new insight into formation processes of microalgae–bacterial consortium, and confirmed that starvation term was an effective strategy to enhance the consortium settle‐ability and lipid accumulation capability. © 2015 American Institute of Chemical Engineers Environ Prog, 35: 103–109, 2016
Particulate flow at the mouth of the Soummam watershed (Algeria)
Authors: Allili‐Ailane Chafika , Laignel Benoît , Adjeroud Nawel , Bir Hassiba , Madani Khodir 
Published: July 2015

In Algeria, the particulate flow in rivers is poorly quantified in the wadi due to the absence and the non‐standardization of the acquisition of measurement data. Most studies on particulate flows are quantified from time series of hydrometric stations. The present study is based on weekly sampling of water at the mouth of the Soummam watershed for the hydrological year 2011/2012. The sediment flux is analyzed from measurements of suspended solids (SS). The determination coefficients between the annual and seasonal “ liquid flow–solid flow‐” relationships vary from 75% to 82%, respectively. During this period, the watershed of 9125 km2 has provided a solid input estimated to 4.9 × 106 t yr−1, hence a specific flow of 538 t km−2 yr−1. In general, autumn floods were characterized by high concentrations of SS, which varies from 820 to 1275 mg L−1. The most important sediment transport volumes were observed during the period of December to February, this period is characterized by strong turbulence, due to extreme flows, favoring the largest volumes of solid transport. © 2015 American Institute of Chemical Engineers Environ Prog, 35: 204–211, 2016
Modeling river dune development and dune transition to upper stage plane bed
Authors: Naqshband Suleyman , van Duin Olav , Ribberink Jan , Hulscher Suzanne 
Published: July 2015

AbstractLarge asymmetric bedforms known as dunes commonly dominate the bed of sand rivers. Due to the turbulence generation over their stoss and lee sides, dunes are of central importance in predicting hydraulic roughness and water levels. During floods in steep alluvial rivers, dunes are observed to grow rapidly as flow strength increases, undergoing an unstable transition regime, after which they are washed out in what is called upper stage plane bed. This transition of dunes to upper stage plane bed is associated with high transport of bed sediment in suspension and large decrease in bedform roughness. In the present study, we aim to improve the prediction of dune development and dune transition to upper stage plane bed by introducing the transport of suspended sediment in an existing dune evolution model. In addition, flume experiments are carried out to investigate dune development under bed load and suspended load dominated transport regimes, and to get insight in the time scales related to the transition of dunes to upper stage plane bed. Simulations with the extended model including the transport of suspended sediment show significant improvement in the prediction of equilibrium dune parameters (e.g. dune height, dune length, dune steepness, dune migration rate, dune lee side slope) both under bed load dominant and suspended load dominant transport regimes. The chosen modeling approach also allows us to model the transition of dunes to upper stage plane bed which was not possible with the original dune evolution model. The extended model predicts change in the dune shapes as was observed in the flume experiments with decreasing dune heights and dune lee slopes. Furthermore, the time scale of dune transition to upper stage plane bed was quite well predicted by the extended model. Copyright © 2015 John Wiley & Sons, Ltd.
The stingless bee species, Scaptotrigona aff. depilis, as a potential indicator of environmental pesticide contamination
Authors: de Souza Rosa Annelise , I'Anson Price Robbie , Ferreira Caliman Maria Juliana , Pereira Queiroz Elisa , Blochtein Betina , Sílvia Soares Pires Carmen , Imperatriz-Fonseca Vera Lucia 
Published: July 2015

Abstract

Neonicotinoids have the potential to enter the diet of pollinators that collect resources from contaminated plants. The species Scaptotrigona aff. depilis (Moure, 1942) can be a useful indicator of the prevalence of these chemicals in the environment. Using high-performance liquid chromatography–mass spectrometry, the authors devised a protocol for neonicotinoid residue extraction and detected the presence of neonicotinoids in the bee bodies. Thus, the authors consider this species to be a potential indicator of environmental contamination. Environ Toxicol Chem 2015;34:1851–1853. © 2015 SETAC