bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis of Aromatic Compounds by Catalytic CC Bond Activation of Biphenylene or Angular [3]Phenylene
Authors: Korotvička Aleš , Císařová Ivana , Roithová Jana , Kotora Martin 
Published: March 2012

AbstractSubstituted phenanthrenes and picenes were easily prepared by reaction of biphenylene or angular [3]phenylene with various alkynes in the presence of a catalytic amount of [IrCl(cod)]2/dppe (cod=1,5‐cyclooctadiene, dppe=1,2‐bis(diphenylphosphino)ethane). The reaction is based on CC bond activation of the cyclobutane ring. The reaction tolerates the presence of bulky groups on the alkyne, such as the ferrocene moiety. In addition, a catalytic system based on [RhCl(cod)]2/dppe enabled the, hitherto unreported, reaction of biphenylene with nitriles to provide phenanthridines.
Temperature Dependence of Surface Nanobubbles
Authors: Berkelaar Robin P. , Seddon James R. T. , Zandvliet Harold J. W. , Lohse Detlef 
Published: March 2012

AbstractThe temperature dependence of nanobubbles was investigated experimentally using atomic force microscopy. By scanning the same area of the surface at temperatures from 51 °C to 25 °C it was possible to track geometrical changes of individual nanobubbles as the temperature was decreased. Interestingly, nanobubbles of the same size react differently to this temperature change; some grow whilst others shrink. This effect cannot be attributed to Ostwald ripening, since the growth and shrinkage of nanobubbles appears to occur in distinct patches on the substrate. The total nanobubble volume per unit area shows a maximum around 33 °C, which is comparable with literature where experiments were carried out with increasing temperature. This underlines the stability of surface nanobubbles.
Mass Transport at Microband Electrodes: Transient, Quasi‐Steady‐State, and Convective Regimes
Authors: Amatore Christian , Pebay Cécile , Sella Catherine , Thouin Laurent 
Published: March 2012

AbstractMass transport at microband electrodes is investigated theoretically and experimentally in unstirred solutions by chronoamperometry and cyclic voltammetry. Because natural convection limits the convection‐free domain up to which diffusion layers may only expand, several regimes of mass transport are identified through simulation by means of a previous model. A zone diagram is established which allows all relative contributions to mass transport to be delineated according to the electrode dimension, timescale of experiment, and amplitude of natural convection. In opposition to the quasi‐steady‐state regime usually expected at microband electrodes under diffusion control, a steady‐state regime always occurs at long enough times. By comparison to microdisk electrodes, a greater influence of natural convection is predicted. These results are validated experimentally by monitoring current responses and mapping steady‐state concentration profiles at microband electrodes.
Engineering the Atomic Structure of Carbon Nanotubes by a Focused Electron Beam: New Morphologies at the Sub‐Nanometer Scale
Authors: Rodríguez‐Manzo Julio A. , Krasheninnikov Arkady V. , Banhart Florian 
Published: March 2012

AbstractCarbon atoms are displaced in pre‐selected locations of carbon nanotubes by using a focused electron beam in a scanning transmission electron microscope. Sub‐nanometer‐sized holes are created that change the morphology of double and triple‐walled carbon nanotubes and connect the shells in a unique way. By combining in situ transmission electron microscopy experiments with atomistic simulations, we study the bonding between defective shells in the new structures which are reminiscent of the shape of a flute. We demonstrate that in double‐walled nanotubes the shells locally merge by forming nanoarches while atoms with dangling bonds can be preserved in triple‐walled carbon nanotubes. In the latter system, nanoarches are formed between the inner‐ and outermost shells, shielding small graphenic islands with open edges between the neighboring shells. Our results indicate that arrays of quantum dots may be produced in carbon nanotubes by spatially localized electron irradiation, generating atoms with dangling bonds that may give rise to localized magnetic moments.
Benign Catalysis with Iron: Unique Selectivity in Catalytic Isomerization Reactions of Olefins
Authors: Jennerjahn Reiko , Jackstell Ralf , Piras Irene , Franke Robert , Jiao Haijun , Bauer Matthias , Beller Matthias 
Published: March 2012

AbstractThe use of noble metal catalysts in homogeneous catalysis has been well established. Due to their price and limited availability, there is growing interest in the substitution of such precious metal complexes with readily available and bio‐relevant catalysts. In particular, iron is a “rising star” in catalysis. Herein, we present a general and selective iron‐catalyzed monoisomerization of olefins, which allows for the selective generation of 2‐olefins. Typically, common metal complexes give mixtures of various internal olefins. Both bulk‐scale terminal olefins and functionalized terminal olefins give the corresponding products under mild conditions in good to excellent yields. The proposed reaction mechanism was elucidated by in situ NMR studies and supported by DFT calculations and extended X‐ray absorption fine structure (EXAFS) measurements.
A One‐Pot Method for the Selective Conversion of Hemicellulose from Crop Waste into C5 Sugars and Furfural by Using Solid Acid Catalysts
Authors: Sahu Ramakanta , Dhepe Paresh Laxmikant 
Published: March 2012

AbstractWe present a solid‐acid catalyzed one‐pot method for the selective conversion of solid hemicellulose without its separation from other lignocellulosic components, such as cellulose and lignin. The reactions were carried out in aqueous and biphasic media to yield xylose, arabinose, and furfural. To overcome the drawbacks posed by mineral acid methods in converting hemicelllulose, we used heterogeneous catalysts that work at neutral pH. In a batch reactor, these heterogeneous catalysts, such as solid acids (zeolites, clays, metal oxides etc.), resulted in >90 % conversion of hemicellulose. It has been shown that the selectivity for the products can be tuned by changing the reaction conditions, for example, a reaction carried out in water at 170 °C for 1 h with HBeta (Si/Al=19) and HUSY (Si/Al=15) catalysts gave yields of 62 and 56 % for xylose and arabinose, respectively. With increased reaction time (6 h) and in presence of only water, HUSY resulted in yields of 30 % xylose + arabinose and 18 % furfural. However, in a biphasic reaction system (water + p‐xylene, 170 °C, 6 h) yields of 56 % furfural with 17 % xylose+arabinose could be achieved. It was shown that with the addition of organic solvent the furfural yield could be increased from 18 to 56 %. Under optimized reaction conditions, >90 % carbon balance was observed. The study revealed that catalysts were recyclable with a 20 % drop in activity for each subsequent run. It was observed that temperature, pressure, reaction time, substrate to catalyst ratio, solvent, and so forth had an effect on product formation. The catalysts were characterized by means of X‐ray diffraction, temperature‐programmed desorption of NH3, inductively coupled plasma spectroscopy, elemental analysis, and solid‐state NMR (29Si, 27Al) spectroscopy techniques.
Exploring Aligned‐Carbon‐Nanotubes@Polyaniline Arrays on Household Al as Supercapacitors
Authors: Huang Fan , Lou Fengliu , Chen De 
Published: March 2012

AbstractHerein, we demonstrate a new approach towards the construction of supercapacitors consisting of carbon nanotubes (CNTs) and conducting polymers (ECPs) with high specific power, high specific energy, and stable cycling performance through a 3D design of a thin film of polyaniline (PANI) on an aligned small carbon nanotube (ACNT) array on household Al foils. The thin‐film strategy is used to fully exploit the specific capacitance of PANI, and obtain regular pores, strong interaction between PANI and CNTs, and reduced electrical resistance for the electrodes. A facile process is developed to fabricate a highly flexible supercapacitor using this binder‐free composite on household Al foil as the current collector. It exhibits high specific energy of 18.9 Wh kg−1, high maximum specific power of 11.3 kW kg−1 of the active material in an aqueous electrolyte at 1.0 A g−1, and excellent rate performance and cycling stability. A high specific energy of 72.4 Wh kg−1, a high maximum specific power of 24.9 kW kg−1, and a good cycling performance of the active material are obtained in an organic electrolyte.
Enhanced Light Harvesting in Plasmonic Dye‐Sensitized Solar Cells by Using a Topologically Ordered Gold Light‐Trapping Layer
Authors: Yang Nailiang , Yuan Qi , Zhai Jin , Wei Tianxin , Wang Dan , Jiang Lei 
Published: March 2012

AbstractDye‐sensitized solar cells (DSSCs) are promising low‐cost, high‐efficiency devices with low environmental impact. One of the important methods to improve their efficiencies involves increasing the light‐harvesting efficiency. Earlier work has focused on varying the morphology of the photoanode. With such a hierarchical structured photoanode in hand, we modify herein the structure of the counter electrode to enhance the optical path length through the plasmonic and reflecttion effects. With the introduced topological gold layer, the photocurrent and efficiency are increased by 16 % and 18 %, respectively, due to the increased light collection. Besides, this effect is effective at both high and low levels of solar irradiation.
A novel multicarrier CDMA transmission scheme for cognitive radios with sidelobe suppression
Authors: Rajabzadeh Morteza , Khoshbin Hossein 
Published: March 2012

SUMMARYNoncontiguous multicarrier code division multiple access (MC‐CDMA) is an effective multiple access method for cognitive radio systems that can deploy the noncontiguous vacant parts of a certain spectrum shared with the users of a primary system. However, the large spectral sidelobes of the Fourier transform based implementation of the MC‐CDMA interfere with the adjacent primary transmission. In this paper, a novel complex signature sequence set is proposed for synchronous downlink MC‐CDMA based cognitive radio networks to suppress the sidelobes. To do so, the minimization of the sidelobes power is developed as an eigen‐optimization problem that is optimally solved by using the eigenvalue decomposition method. The optimal complex signature sequences are chosen as the eigenvectors attained by the eigenvalue decomposition of a symmetric matrix that is dependent of the spectral characteristics of the primary users. Simulation results show that by a slight decrease in the maximum number of active users compared with full load, the sidelobes can be considerably suppressed. The effect of cyclic prefix length, the bandwidth of the primary system and the number of active users on the sidelobe suppression performance is analyzed through numerical simulations. Copyright © 2012 John Wiley & Sons, Ltd.
Immunophenotypic characterization of enteric neural crest cells in the developing avian colorectum
Authors: Nagy Nandor , Burns Alan J. , Goldstein Allan M. 
Published: March 2012

AbstractBackground: The enteric nervous system (ENS) develops from neural crest‐derived cells that migrate along the intestine to form two plexuses of neurons and glia. While the major features of ENS development are conserved across species, minor differences exist, especially in the colorectum. Given the embryologic and disease‐related importance of the distal ENS, the aim of this study was to characterize the migration and differentiation of enteric neural crest‐derived cells (ENCCs) in the colorectum of avian embryos. Results: Using normal chick embryos and vagal neural tube transplants from green fluorescent protein (GFP) ‐transgenic chick embryos, we find ENCCs entering the colon at embryonic day (E) 6.5, with colonization complete by E8. Undifferentiated ENCCs at the wavefront express HNK‐1, N‐cadherin, Sox10, p75, and L1CAM. By E7, differentiation begins in the proximal colon, with L1CAM and Sox10 becoming restricted to neuronal and glial lineages, respectively. By E8, multiple markers of differentiation are expressed along the entire colorectum. Conclusions: Our results establish the pattern of ENCC migration and differentiation in the chick colorectum, demonstrate the conservation of marker expression across species, highlight a range of markers, including neuronal cell adhesion molecules, which label cells at the wavefront, and provide a framework for future studies in avian ENS development. Developmental Dynamics 241:842–851, 2012. © 2012 Wiley Periodicals, Inc.
Inhibitory morphogens and monopodial branching of the embryonic chicken lung
Authors: Gleghorn Jason P. , Kwak Jiyong , Pavlovich Amira L. , Nelson Celeste M. 
Published: March 2012

AbstractBackground: Branching morphogenesis generates a diverse array of epithelial patterns, including dichotomous and monopodial geometries. Dichotomous branching can be instructed by concentration gradients of epithelial‐derived inhibitory morphogens, including transforming growth factor‐β (TGFβ), which is responsible for ramification of the pubertal mammary gland. Here, we investigated the role of autocrine inhibitory morphogens in monopodial branching morphogenesis of the embryonic chicken lung. Results: Computational modeling and experiments using cultured organ explants each separately revealed that monopodial branching patterns cannot be specified by a single epithelial‐derived autocrine morphogen gradient. Instead, signaling by means of TGFβ1 and bone morphogenetic protein‐4 (BMP4) differentially affect the rates of branching and growth of the airways. Allometric analysis revealed that development of the epithelial tree obeys power‐law dynamics; TGFβ1 and BMP4 have distinct but reversible effects on the scaling coefficient of the power law. Conclusions: These data suggest that although autocrine inhibition cannot specify monopodial branching, inhibitory morphogens define the dynamics of lung morphogenesis. Developmental Dynamics 241:852–862, 2012. © 2012 Wiley Periodicals, Inc.
Airway epithelial cell differentiation during lung organogenesis requires C/EBPα and C/EBPβ
Authors: Roos Abraham B. , Berg Tove , Barton Jenny L. , Didon Lukas , Nord Magnus 
Published: March 2012

AbstractBackground: CCAAT/enhancer‐binding protein (C/EBP)α is crucial for lung development and differentiation of the pulmonary epithelium. Conversely, no lung defects have been observed in C/EBPβ‐deficient mice, although C/EBPβ trans‐activate pulmonary genes by binding to virtually identical DNA‐sequences as C/EBPα. Thus, the pulmonary phenotype of mice lacking C/EBPβ could be explained by functional replacement with C/EBPα. We investigated whether C/EBPα and C/EBPβ have overlapping functions in regulating lung epithelial differentiation during organogenesis. Epithelial differentiation was assessed in mice with a lung epithelial–specific (SFTPC‐Cre‐mediated) deletion of C/EBPα (CebpaΔLE), C/EBPβ (CebpbΔLE), or both genes (CebpaΔLE; CebpbΔLE). Results: Both CebpaΔLE mice and CebpaΔLE; CebpbΔLE mice demonstrated severe pulmonary immaturity compared to wild‐type littermates, while no differences in lung histology or epithelial differentiation were observed in CebpbΔLE mice. In contrast to CebpaΔLE mice, CebpaΔLE; CebpbΔLE mice also displayed undifferentiated Clara cells with markedly impaired protein and mRNA expression of Clara cell secretory protein (SCGB1A1), compared to wild‐type littermates. In addition, ectopic mucus‐producing cells were observed in the conducting airways of CebpaΔLE; CebpbΔLE mice. Conclusions: Our findings demonstrate that C/EBPα and C/EBPβ play pivotal, and partly overlapping roles in determining airway epithelial differentiation, with possible implications for tissue regeneration in lung homeostasis and disease. Developmental Dynamics 241:911–923, 2012. © 2012 Wiley Periodicals, Inc.
A Lissencephaly‐1 homologue is essential for mitotic progression in the planarian Schmidtea mediterranea
Authors: Cowles Martis W. , Hubert Amy , Zayas Ricardo M. 
Published: March 2012

AbstractBackground: Planarians are renowned for their capacity to replace lost tissues from adult pluripotent stem cells (neoblasts). Here we report that Lissencephaly‐1 (lis1), which has roles in cellular processes such as mitotic spindle apparatus orientation and in signal regulation required for stem cell self‐renewal, is required for stem cell maintenance in the planarian Schmidtea mediterranea. Results: In planarians, lis1 is expressed in differentiated tissues and stem cells. lis1 RNAi leads to head regression, ventral curling, and death by lysis. By labeling the neoblasts and proliferating cells, we found lis1 knockdown animals show a dramatic increase in the number of mitotic cells, followed by depletion of the stem cell pool. Analysis of the mitotic spindles in dividing neoblasts revealed that defective spindle positioning is correlated with cells arrested at metaphase. In addition, we show that inhibiting a planarian homologue of nudE, predicted to encode a LIS‐1 interacting protein, also leads to cell cycle progression defects. Conclusions: Our results provide evidence for a conserved role of LIS1 and NUDE in regulating the function of the mitotic spindle apparatus in a representative Lophotrochozoan and that planarians will be useful organisms in which to investigate LIS1 regulation of signaling events underlying stem cell self‐renewal. Developmental Dynamics 241:901–910, 2012. © 2012 Wiley Periodicals, Inc.
Specific inactivation ofTwist1in the mandibular arch neural crest cells affects the development of the ramus and reveals interactions with hand2
Authors: Zhang Yanping , Blackwell Evan L. , McKnight Mitchell T. , Knutsen Gregory R. , Vu Wendy T. , Ruest L. Bruno 
Published: March 2012

AbstractBackground: The basic helix‐loop‐helix (bHLH) transcription factorTwist1fulfills an essential function in neural crest cell formation, migration, and survival and is associated with the craniosynostic Saethre‐Chotzen syndrome in humans. However, its functions during mandibular development, when it may interact with other bHLH transcription factors like Hand2, are unknown because mice homozygous for theTwist1null mutation die in early embryogenesis. To determine the role ofTwist1during mandibular development, we used theHand2‐Cretransgene to conditionally inactivate the gene in the neural crest cells populating the mandibular pharyngeal arch.Results: The mutant mice exhibited a spectrum of craniofacial anomalies, including mandibular hypoplasia, altered middle ear development, and cleft palate. It appears thatTwist1is essential for the survival of the neural crest cells involved in the development of the mandibular ramal elements.Twist1plays a role in molar development and cusp formation by participating in the reciprocal signaling needed for the formation of the enamel knot. This gene is also needed to control the ossification of the mandible, a redundant role shared withHand2.Conclusion: Twist1, along with Hand2, is essential for the proximodistal patterning and development of the mandible and ossification. Developmental Dynamics, 2012. © 2012 Wiley Periodicals, Inc.
Ophthalmic changes in severe anorexia nervosa: A case series
Authors: Gaudiani Jennifer L. , Braverman Jon M. , Mascolo Margherita , Mehler Philip S. 
Published: March 2012

AbstractObjective:We describe the diagnosis and management of lagophthalmos, or failure of eyelid closure, in five patients with severe anorexia nervosa (AN) who complained of dry, irritated eyes and photophobia.Method:Five patients with these findings are described retrospectively.Results:Examination revealed lagopthalmos in the setting of ptosis and enophthalmos, with multiple other starvation‐mediated medical complications.Discussion:These eye findings, as complications of AN, have not been described in the literature. With careful protective measures, initiation of nutritional rehabilitation, and intensively monitored early refeeding, these patients' ocular abnormalities and associated symptoms resolved completely. Recognition of this pathology and appropriate management can prevent long‐term morbidity in the form of permanent loss of visual acuity due to corneal abrasions and improve the outcomes for these patients with severe AN. © 2012 by Wiley Periodicals, Inc. Int J Eat Disord 2012.
Longitudinal stability of binge‐eating type in eating disorders
Authors: Peterson Carol B. , Swanson Sonja A. , Crow Scott J. , Mitchell James E. , Agras W. Stewart , Halmi Katherine A. , Crosby Ross D. , Wonderlich Stephen A. , Berg Kelly C. 
Published: March 2012

AbstractObjective:The purpose of this study was to examine the 2‐year longitudinal stability of objective bulimic (binge eating) episodes (OBEs) and subjective bulimic (binge eating) episodes (SBEs) in a multisite eating disorders sample.Method:Participants included 288 females with eating disorder symptoms who were assessed every 6 months using the Eating Disorder Examination.Results:Markov modeling revealed considerable longitudinal variability between types of binge eating over 6‐month time intervals with relatively higher probability estimates for consistency between OBEs and SBEs than specific transitions between types for the overall sample as well as for eating disorder diagnostic groups. Transition patterns examining all five time points indicated notable variability in binge‐eating patterns among participants.Discussion:These findings suggest that although longitudinal patterns of binge types are variable among individuals with eating disorders, consistency in OBEs and SBEs was the most common pattern observed. © 2012 by Wiley Periodicals, Inc. Int J Eat Disord 2012.
Manganese‐Enhanced MRI Contrast Agents: From Small Chelates to Nanosized Hybrids
Authors: Kueny‐Stotz Marie , Garofalo Antonio , Felder‐Flesch Delphine 
Published: March 2012

AbstractDuring the last decades, a wide range of molecular and cellular imaging techniques have been developed and optimized, resulting in important progress in the understanding of diagnostic and biological processes. Among these techniques, magnetic resonance imaging (MRI) is certainly one of the most popular, because of its high spatial resolution and the fact that it does not require the use of radioisotopes. Although gadolinium has long been the most commonly used paramagnetic metal to design efficient MRI contrast agents, the discovery of its potential toxicity has driven researchers to give priority to other paramagnetic metals, as, for example, manganese. With this microreview we would like to highlight the state of the art of manganese‐based MRI contrast agents with a particular focus on the chemical structures of these agents and on their chronological evolution from simple chelates to complex nanohybrid systems.
Towards the Sequence‐Selective Recognition of Double‐Stranded DNA Containing Pyrimidine‐Purine Interruptions by Triplex‐Forming Oligonucleotides
Authors: Hari Yoshiyuki , Obika Satoshi , Imanishi Takeshi 
Published: March 2012

AbstractTriplex formation with double‐stranded DNA (dsDNA) by oligonucleotides has potential for applications in attractive technologies such as gene therapy and genetic diagnosis. However, triplex‐forming oligonucleotides (TFOs) can only recognize homopurine strands in homopurine‐homopyrimidine regions in dsDNA, either through Hoogsteen or through reverse‐Hoogsteen hydrogen bonds. A straightforward and powerful approach to overcoming this sequence limitation is the development of artificial nucleic acids capable of recognizing specific pyrimidine‐purine interruptions (i.e., a CG or TA base pair) in triplex formation. This review describes artificial nucleic acids, especially those containing non‐natural nucleobases, developed to recognize CG or TA base pairs in dsDNA targets.