bluuebunny/crossref_metadata_2025_split huggingface dataset:
Short seed longevity, variable germination conditions, and infrequent establishment events provide a narrow window for Yucca brevifolia (Agavaceae) recruitment
Authors: Reynolds M. Bryant J. , DeFalco Lesley A. , Esque Todd C. 
Published: October 2012

• Premise of the Study: The future of long‐lived stand‐forming desert plants such as Yucca brevifolia (Joshua tree) has come into question in light of climate variation and landscape‐scale disturbances such as wildfire. Understanding plant establishment dynamics is important for mitigating the impacts of disturbances and promoting revegetation.• Methods: We placed Y. brevifolia seeds in shallow caches and manipulated granivore access, nurse shrub effects, and the season of cache placement to determine conditions for seed germination and seedling establishment.• Key Results: Greatest seedling emergence occurred during spring and summer, when increased soil moisture was accompanied by warm soil temperatures. Late winter–spring emergence for cached seeds was enhanced beneath shrub canopies, but seedling survival declined beneath shrubs as temperatures increased in spring. Germinability of seed remaining in the soil was reduced from 50–68% after 12 mo residence time in soil and declined to <3% after 40 mo. Following dispersal from parent plants, seeds are either removed by granivores or lose germinability, imposing substantial losses of potential germinants.• Conclusions: Specific germination and establishment requirements impose stringent limits on recruitment rates for Y. brevifolia. Coupled with infrequent seed availability, the return rates to prefire densities and demographic structure may require decades to centuries, especially in light of potential changes to regional desert climate in combination with the potential for fire recurrence. Demographic patterns are predicted to vary spatially in response to environmental variability that limits recruitment and may already be apparent among extant populations.
Metal‐Free, Visible Light‐Induced Borylation of Aryldiazonium Salts: A Simple and Green Synthetic Route to Arylboronates
Authors: Yu Jian , Zhang Ling , Yan Guobing 
Published: October 2012

AbstractThe eosin Y‐catalyzed borylation of aryldiazonium salts under irradiation with visible light has been developed. This novel protocol provides an attractive route for the preparation of arylboronates, due to its operational simplicity and practicability as well as the mild reaction conditions.
A sensitive LC‐MS/MS method for the simultaneous determination of amoxicillin and ambroxol in human plasma with segmental monitoring
Authors: Dong Xin , Ding Li , Cao Xiaomei , Jiang Liyuan , Zhong Shuisheng 
Published: October 2012

ABSTRACTAmoxicillin (AMO) degrades in plasma at room temperature and readily undergoes hydrolysis by the plasma amidase. In this paper, a novel, rapid and sensitive LC‐MS/MS method operated in segmental and multiple reaction monitoring has been developed for the simultaneous determination of amoxicillin and ambroxol in human plasma. The degradation of amoxicillin in plasma was well prevented by immediate addition of 20 μL glacial acetic acid to 200 μL aliquot of freshly collected plasma samples before storage at −80°C. The sensitivity of the method was improved with segmental monitoring of the analytes, and lower limits of quantitation of 0.5 ng/mL for ambroxol and 5 ng/mL for amoxicillin were obtained. The sensitivity of our method was five times better than those of the existing methods. Furthermore, the mass response saturation problem with amoxicillin was avoided by diluting the deproteinized plasma samples with water before injection into the LC‐MS/MS system. The method was successfully employed in a pharmacokinetic study of the compound amoxicillin and ambroxol hydrochloride tablets. Copyright © 2012 John Wiley & Sons, Ltd.
Nisin, an apoptogenic bacteriocin and food preservative, attenuates HNSCC tumorigenesis via CHAC1
Authors: Joo Nam E. , Ritchie Kathryn , Kamarajan Pachiyappan , Miao Di , Kapila Yvonne L. 
Published: October 2012

AbstractNisin, a bacteriocin and commonly used food preservative, may serve as a novel potential therapeutic for treating head and neck squamous cell carcinoma (HNSCC), as it induces preferential apoptosis, cell cycle arrest, and reduces cell proliferation in HNSCC cells, compared with primary keratinocytes. Nisin also reduces HNSCC tumorigenesis in vivo. Mechanistically, nisin exerts these effects on HNSCC, in part, through CHAC1, a proapoptotic cation transport regulator, and through a concomitant CHAC1‐independent influx of extracellular calcium. In addition, although CHAC1 is known as an apoptotic mediator, its effects on cancer cell apoptosis have not been examined. Our studies are the first to report CHAC1's new role in promoting cancer cell apoptosis under nisin treatment. These data support the concept that nisin decreases HNSCC tumorigenesis in vitro and in vivo by inducing increased cell apoptosis and decreased cell proliferation; effects that are mediated by activation of CHAC1, increased calcium influxes, and induction of cell cycle arrest. These findings support the use of nisin as a potentially novel therapeutic for HNSCC, and as nisin is safe for human consumption and currently used in food preservation, its translation into a clinical setting may be facilitated.
Crystal Structure Determination and Mutagenesis Analysis of the Ene Reductase NCR
Authors: Reich Sabrina , Hoeffken Hans Wolfgang , Rosche Bettina , Nestl Bettina M. , Hauer Bernhard 
Published: October 2012

AbstractThe crystal structure of the “ene” nicotinamide‐dependent cyclohexenone reductase (NCR) from Zymomonas mobilis (PDB ID: 4A3U) has been determined in complex with acetate ion, FMN, and nicotinamide, to a resolution of 1.95 Å. To study the activity and enantioselectivity of this enzyme in the bioreduction of activated α,β‐unsaturated alkenes, the rational design methods site‐ and loop‐directed mutagenesis were applied. Based on a multiple sequence alignment of various members of the Old Yellow Enzyme family, eight single‐residue variants were generated and investigated in asymmetric bioreduction. Furthermore, a structural alignment of various ene reductases predicted four surface loop regions that are located near the entrance of the active site. Four NCR loop variants, derived from loop‐swapping experiments with OYE1 from Saccharomyces pastorianus, were analysed for bioreduction. The three enzyme variants, P245Q, D337Y and F314Y, displayed increased activity compared to wild‐type NCR towards the set of substrates tested. The active‐site mutation Y177A demonstrated a clear influence on the enantioselectivity. The loop‐swapping variants retained reduction efficiency, but demonstrated decreased enzyme activity compared with the wild‐type NCR ene reductase enzyme.
Crystal Structures and Emitting Properties of Trifluoromethylaminoquinoline Derivatives: Thermal Single‐Crystal‐to‐Single‐Crystal Transformation of Polymorphic Crystals That Emit Different Colors
Authors: Abe Yuichiro , Karasawa Satoru , Koga Noboru 
Published: October 2012

Abstract2,4‐Trifluoromethylquinoline (TFMAQ) derivatives that have amine (1), methylamine (2), phenylamine (3), and dimethylamine (4) substituents at the 7‐position of the quinoline ring were prepared and crystallized. Six crystals including the crystal polymorphs of 2 (crystal GB and YG) and 3 (crystal B and G) were obtained and characterized by X‐ray crystallography. In solution, TFMAQ derivatives emitted relatively strong fluorescence (${\lambda {{{\rm f}\hfill \atop {\rm max}\hfill}}}$=418–469 nm and Φf(s)=0.23–0.60) depending on the solvent polarity. From Lippert–Mataga plots, Δμ values in the range of 7.8–14 D were obtained. In the crystalline state, TFMAQ derivatives emitted at longer wavelengths (${\lambda {{{\rm f}\hfill \atop {\rm max}\hfill}}}$=464–530 nm) with lower intensity (Φf(c)=0.01–0.28) than those in n‐hexane solution. The polymorphous crystals of 2 and 3 emitted different colors: 2, ${\lambda {{{\rm f}\hfill \atop {\rm max}\hfill}}}$=470 and 530 nm with Φf(c)=0.04 and approximately 0.01 for crystal GB and YG, respectively; and 3, ${\lambda {{{\rm f}\hfill \atop {\rm max}\hfill}}}$=464 and 506 nm with Φf(c)=0.28 and approximately 0.28 for crystal B and G, respectively. In both crystal polymorphs of 2 and 3, crystals GB and G showed emission color changes by heating/melting/cooling cycles that were representative. By following the color changes in heating at the temperature below the melting point with X‐ray diffraction measurements and X‐ray crystallography, the single‐crystal‐to‐single‐crystal transformations from crystal GB to YG for 2 and from crystal B to G for 3 were revealed.
Suzuki Coupling Reactions in Neat Water as the Solvent: Where in the Biphasic Reaction Mixture Do the Catalytic Reaction Steps Occur?
Authors: Röhlich Christoph , Wirth Andreas S. , Köhler Klaus 
Published: October 2012

AbstractMany reports on water‐compatible palladium catalysts have appeared in the recent literature. For hydrophobic substrates, mixtures with pure water are biphasic, and it is widely not regarded that the elusive locality of the catalytic process (in water, the organic layer, or at the phase boundary) has an important impact on the mechanism and efficiency of the reaction. In the present work, for the first time systematic variation of reaction parameters has been performed for Suzuki coupling experiments with chloro‐ and bromoarenes in pure water. The investigations are not only aimed at the factors influencing the catalytic activity, but also at the effects that may occur particularly in water/organic biphasic media, and on the question as to in which of the two liquid phases the reaction takes place. These investigations have revealed that dilution of the base (in the aqueous layer) and the Pd species (in the organic layer) are detrimental to the reaction, and that phase‐transfer processes play a major role in the overall mechanism. A series of experiments with variation of parameters like precatalyst hydrophilicity, organic and water phase volume, additives, stirring rate, base concentration, and so forth, indicate that for the systems under study the reaction occurs in the organic layer. The water phase needs to be present to dissolve and provide polar reactants, and re‐absorb side products. The results encourage to pay more regard to the question of phase locality of coupling reactions in water in general.
Chemie und Science Fiction
Authors: Gelius Rolf 
Published: October 2012

AbstractDie moderne Science‐Fiction‐Literatur ist international zum Spiegel des wissenschaftlich‐technischen Fortschritts geworden. Sie deckt aber auch Fehlentwicklungen auf, z.B. in der Drogenszene, und gleitet nicht selten in andere literarische Bereiche ab, wie Fantasie oder Satire. Ist sie jetzt und in der Zukunft noch geeignet, junge Menschen für ein Chemiestudium zu begeistern?
Händigkeit – leben in einer chiralen Welt
Authors: Rüger Anne J. , Kramer Joshua , Seifermann Stefan , Busch Mark , Muller Thierry , Bräse Stefan 
Published: October 2012

AbstractWir leben in einer chiralen Welt, in der Bild und Spiegelbild oftmals nicht identisch sind. Da wir mit diesen Gegebenheiten aufwachsen, haben wir uns unbewusst an unsere chirale Umgebung angepasst. Tauscht man z.B. einen Korkenzieher gegen sein “Scherzartikel”‐Pendant mit entgegengesetzter Windung aus, brauchen wir etwas Zeit um uns an die ungewohnte Handhabung anzupassen. Die Chiralität oder Händigkeit spielt jedoch auch eine große Rolle in der Welt der Moleküle. Von Duft‐ und Süßstoffen, über Futtermittelzusätze bis hin zu Medikamenten, überall spielen Bild, Spiegelbild und folglich die Reinheit, mit der ein chirales Molekül hergestellt wird, eine entscheidende Rolle. Anhand sechs ausgewählter Experimente wird das faszinierende Thema der Chiralität erläutert.
Der Wittelsbacher und der Hope‐Diamant
Authors: Evers Jürgen , Möckl Leonhard , Nöth Heinrich 
Published: October 2012

AbstractDiamanten entstehen aus Kohlenstoff bei hohen Drücken und hohen Temperaturen im Erdinneren. Dotierung mit geringen Mengen Bor erzeugt ihre blaue Farbe. Zwei der berühmtesten blauen historischen Diamanten, der Wittelsbacher und der Hope‐Diamant, stammen aus der indischen Kollur‐Mine. Letzteren brachte der französische Diamantenhändler Tavernier im 17. Jahrhundert nach Europa. Heute ist er im Smithsonian Institute in Washington ausgestellt. Der Wittelsbacher Diamant befand sich lange Zeit im Besitz des Hauses Wittelsbach, bis er 1951 heimlich in Antwerpen verkauft wurde. 2008 ersteigerte ihn der Juwelier Graff und ließ ihn umschleifen. 2011 wurde er an einen unbekannten Besitzer weiterverkauft. Aufgrund der gemeinsamen Herkunft und Farbe der Diamanten wurde lange Zeit vermutet, die beiden Edelsteine könnten Bruchstücke eines gemeinsamen größeren Kristalles sein. Durch optische Untersuchungen konnte nun eindeutig geklärt werden, dass beide Diamanten zwar ähnliche optische Eigenschaften besitzen, in bestimmten Merkmalen jedoch so stark voneinander abweichen, dass sie nicht einem gemeinsamen größeren Kristall entstammen können.
Arsenat‐Stoffwechsel widerlegt
Authors: Groß Michael 
Published: October 2012

AbstractVor zwei Jahren erregten Forscher großes Aufsehen mit der Behauptung, ein auffallend arsenresistenter Bakterienstamm aus einem Salzsee in Kalifornien könne in seinem Stoffwechsel und womöglich gar in seiner DNA Phosphat durch Arsenat ersetzen. Zwei eingehendere Studien haben dies jetzt widerlegt.
Regioslektive meta‐Substitution von Aromaten
Authors: Jaenicke Lothar 
Published: October 2012

AbstractDie elektronenreichen aromatischen Systeme sind bekanntlich schwierig elektronegativ in meta zu substituieren. Ein vielversprechender Ansatz mag die Gaunt‐Methode sein. Diese benötigt allerdings als Erstschritt Spezialreagenzien wie übervalente Iod‐Verbindungen. Deshalb ist ein Eintopfverfahren gesucht.
Carbon Dioxide Insertion into Diamines: A Computational Study of Solvent Effects
Authors: Eger Wilhelm A. , Genest Alexander , Rieger Bernhard , Rösch Notker 
Published: October 2012

AbstractWe studied computationally, on the model compound ethylenediamine, the insertion of carbon dioxide into diamines, yielding cyclic urea compounds. Two mechanisms were elaborated, depending on the value of the dielectric constant (DC) of the solvent. Accordingly, reaction mixtures with a high DC lead to carbamates, whereas lower DC values result in the preferred product cyclic urea. Additives behaving as “proton shuttles” act as catalysts, significantly reducing the activation barriers of insertion and ring closure to surmountable values. CO2 insertion into diamines may also occur by autocatalysis, even without further additives, but under less favorable conditions, for example, lower yields. Amine reagents are most efficient at proton shuttling, followed by alcohols. The activation barrier of the rate‐limiting step is lowered in a reaction mixture with higher values of DC, up to a critical value εcr≈18. Hence, in a suitably optimized reaction mixture, ring closure is suggested to occur under milder conditions than those previously applied experimentally. The two roles of the additive, that is, acting as proton shuttling agent and adjusting the effective DC of the reaction mixture, do not have to be assigned to a single compound, possibly affording a handle on process optimization.
Amperometric Biosensor Based on Galactose Oxidase Immobilized in Clay Matrix
Authors: Charmantray Franck , Touisni Nadia , Hecquet Laurence , Mousty Christine 
Published: October 2012

AbstractAn amperometric galactose biosensor was developed by immobilizing galactose oxidase (GAOx) within a laponite clay film coated on a Pt electrode surface. The electrochemical assays were performed by potentiostating the GAOx/laponite bioelectrodes at +0.6 V vs. Ag/AgCl in order to oxidize the enzymatically generated hydrogen peroxide. The bioelectrochemical responses of the biosensors were optimized with regard to the buffer nature, the pH, and the GAOx/laponite ratios. Laponite provides a favorable environment to GAOx activity, since the optimized biosensor GAOx/laponite (50:25; µg:µg) shows a great sensitivity and maximum current (85 mA M−1 cm−2 and 232 µA cm−2, respectively) over a linear galactose concentration range of 1.0×10−6–1.6×10−3 M. It is also stable at least for four weeks at 4 °C.
A comparative evaluation of NB30, NB54 and PTC124 in translational read‐through efficacy for treatment of an USH1C nonsense mutation
Authors: Goldmann Tobias , Overlack Nora , Möller Fabian , Belakhov Valery , van Wyk Michiel , Baasov Timor , Wolfrum Uwe , Nagel‐Wolfrum Kerstin 
Published: October 2012

AbstractTranslational read‐through‐inducing drugs (TRIDs) promote read‐through of nonsense mutations, placing them in the spotlight of current gene‐based therapeutic research. Here, we compare for the first time the relative efficacies of new‐generation aminoglycosides NB30, NB54 and the chemical compound PTC124 on retinal toxicity and read‐through efficacy of a nonsense mutation in the USH1C gene, which encodes the scaffold protein harmonin. This mutation causes the human Usher syndrome, the most common form of inherited deaf‐blindness. We quantify read‐through efficacy of the TRIDs in cell culture and show the restoration of harmonin function. We do not observe significant differences in the read‐through efficacy of the TRIDs in retinal cultures; however, we show an excellent biocompatibility in retinal cultures with read‐through versus toxicity evidently superior for NB54 and PTC124. In addition, in vivo administration of NB54 and PTC124 induced recovery of the full‐length harmonin a1 with the same efficacy. The high biocompatibilities combined with the sustained read‐through efficacies of these drugs emphasize the potential of NB54 and PTC124 in treating nonsense mutation‐based retinal disorders.
A Novel Method for GDC Recovery During Solid Oxide Fuel Cell Manufacturing
Authors: Demir I. , Aydin F. 
Published: October 2012

AbstractThere have been a tremendous research affects in recent years for alternative routes of electricity generation using some maximum yield technologies, increased reliability, and minimum pollution. From this point of view, the solid oxide fuel cells (SOFCs) are considered as the cleanest technologies for obtaining electrical energy generation. However, an important fraction of production is wasted during the manufacturing steps. From both economical and environmental point of view, recovery of waste GDC (Gd0.1Ce0.9O3) materials is deemed important. Hence, it is the main purpose of the present study to develop a novel method to recover waste GDC materials and afterwards to produce a new SOFC (solid oxide fuel cell) from the recovered materials. The results showed that recovered GDC cell worked as efficient as the fresh materials, revealing the success of the recovery process proposed.
Carbon Oxidation With Electrically Insulated Carbon Fuel in A Coin Type Direct Carbon Fuel Cell
Authors: Lee C.‐G. , Song M.‐B. 
Published: October 2012

AbstractElectrically insulated carbon fuel, called cartridge fuel here, was employed in a coin type direct carbon fuel cell, which was assembled using molten carbonate fuel cell technology. The cartridge fuel was comprised of solid carbon and carbonate mixtures filling an alumina tube. Both ends of the tube were sealed with Ni mesh through which gas was able to penetrate. However, the meshes were installed inside the tube, forming an electrically insulated fuel cartridge. The cartridge fuel showed very similar performance to normal powder fuel, indicating that carbon oxidation took place through the intermediate gas species of carbon monoxide. Also, solid carbons were manufactured from oak at 400, 800, and 1,200 °C. The carbon that was carbonized at lower temperature showed higher open circuit voltage and performance. The difference between the carbon species results in a performance variation due to varying generation of CO.
Korean practice of conventional tunnelling, NATM / Koreanische Praxis beim konventionellen Tunnelbau/NÖT
Authors: Lee In‐Mo , Park Kwang‐Joon 
Published: October 2012

AbstractSince the conventional tunnelling method or NATM was introduced in 1982, it has always remained more popular in Korea than the mechanized tunnelling method. More than 90 % of the total length of tunnels in the Korean peninsula have been designed and constructed according to the NATM. The Korean practice of utilization of the NATM will be discussed in this paper, focusing on the main characteristics of Korean practice and technical issues.Seit die konventionelle Tunnelbaumethode bzw. NÖT 1982 in Korea eingeführt wurde, ist sie immer noch beliebter als der maschinelle Tunnelbau. Mehr als 90 % der gesamten Tunnellänge auf der koreanischen Halbinsel wurden nach der NÖT geplant und ausgeführt. In diesem Beitrag wird die Anwendung der NÖT in Korea vorgestellt und auf die wesentlichen lokalen Anwendungsmerkmale und auf technische Fragen eingegangen.
The base area of Zillergründl Dam / Der Aufstandsbereich der Sperre Zillergründl
Authors: Obernhuber Pius 
Published: October 2012

AbstractIn high arch dams situated in wide valleys, the water load has the effect that the vertical forces from the self‐weight are redistributed from the centre of the dam toward its flanks. As a consequence, the normal force in the foundation area of the central dam blocks is reduced and a gap may open in the base joint, which widens even further due to uplift pressure.Taking the Zillergründl Dam as an example, such behaviour can be demonstrated both by static calculations and measurements. The base joint gap, as it has been calculated and measured, would lead to sealing problems if no upstream apron is provided. Due to the upstream apron, however, the uplift pressures will be limited and correct behaviour is ensured. In the left‐hand flank, directly on the downstream side, there is a fault zone. To bridge this zone, a concrete support element was constructed there. Due to loosening down to a considerable depth in the zone of the right‐hand flank, the dam was provided with exceptionally deep foundations in that area. Measuring and monitoring results have shown that both measures have proved worthwhile and ensure high bearing capacity.Bei hohen Gewölbemauern in weiten Tälern kommt es zufolge Wasserlast zu einer Umlagerung der Vertikalkräfte aus dem Eigengewicht von der Sperrenmitte zu den Flanken. Dadurch kommt es im Aufstandsbereich der mittleren Sperrenblöcke zu einer Verringerung der Normalkraft und damit verbunden allenfalls auch zu einer Klaffung der Bodenfuge, die durch den Sohlwasserdruck noch verstärkt wird.Dieses Verhalten kann am Beispiel der Sperre Zillergründl sowohl durch statische Berechnungen als auch durch Messungen veranschaulicht werden. Die errechnete und auch gemessene Klaffung der Bodenfuge würde ohne Vorboden vermutlich zu Problemen bei der Abdichtung führen. Durch den Vorboden werden jedoch die Sohlwasserdrücke begrenzt und ein einwandfreies Verhalten gewährleistet. Im Bereich der linken Flanke befindet sich unmittelbar an der Sperrenluftseite eine Störungszone. Zur Überbrückung dieser Zone wurde dort ein Stützkörper angeordnet. Im Bereich der rechten Flanke wurde die Sperre aufgrund einer tiefreichenden Auflockerung außergewöhnlich tief eingebunden. Beide Maßnahmen haben sich, wie die Mess‐ und Beobachtungsergebnisse zeigen, bewährt und gewährleisten eine hohe Tragsicherheit.